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  • 201.
    Ali Soomro, Razium
    et al.
    University of Bristol, England; University of Sindh, Pakistan.
    Richard Hallam, Keith
    University of Bristol, England.
    Hussain Ibupoto, Zafar
    University of Sindh, Pakistan.
    Tahira, Aneela
    University of Sindh, Pakistan.
    Tufail Hussain Sherazi, Syed
    University of Sindh, Pakistan.
    Sanam Sirajjuddin; Memon, Safia
    University of Sindh, Pakistan.
    Willander, Magnus
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Amino acid assisted growth of CuO nanostructures and their potential application in electrochemical sensing of organophosphate pesticide2016Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 190, s. 972-979Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This work reports a highly sensitive electrochemical sensor for organophosphate pesticide (malathion) based on unique and attractive CuO nanostructures. The discussed nanostructures were synthesized using low temperature hydrothermal growth method utilizing green amino acids such as glycine, serine, threonine and histidine as effective bio-compatible templates. The morphological evaluation demonstrated formation of unique and attractive 1-D nanostructures reflecting the effective growth controlling and directing capabilities of the utilized amino acids. The as-synthesized CuO nanostructures were noted to possess high affinity towards malathion which enabled their application as electrode material for the development of affinity based electrochemical sensor. Although, the as-synthesized morphologies were all sensitive towards malathion but the glycine directed triangular flake-like nanostructures exhibited greater sensitivity compared to other competitors. The electrochemical behaviour of the modified electrodes was studied using cyclic voltammetry (CV) whereas, differential pulse voltammetry (DPV) was utilized for the analytical evaluation of the sensor. The developed sensor demonstrated high reproducibility, stability, wide detection window (1-12 nM), and sensitivity to detect malathion up to 0.1 nM based on suppressive signal measurement. In addition, the sensor system exhibited high anti-interference capability in the presence of common co-existing pesticides like lindane, carbendazim, and trichlorfon. The developed sensor provides an effective measure for detecting extremely low concentration of malathion with wide applicability in various fields. (C) 2015 Elsevier Ltd. All rights reserved.

  • 202.
    Ali, Zaheer
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för kardiovaskulär medicin. Linköpings universitet, Medicinska fakulteten.
    Islam, Anik
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för kardiovaskulär medicin. Linköpings universitet, Medicinska fakulteten.
    Sherrell, Peter
    Imperial Coll London, England.
    Le-Moine, Mark
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Lolas, Georgios
    Univ Athens, Greece.
    Syrigos, Konstantinos
    Univ Athens, Greece.
    Rafat, Mehrdad
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Jensen, Lasse
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för kardiovaskulär medicin. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Diagnostikcentrum, Klinisk farmakologi.
    Adjustable delivery of pro-angiogenic FGF-2 by alginate: collagen microspheres2018Inngår i: BIOLOGY OPEN, ISSN 2046-6390, Vol. 7, nr 3, artikkel-id UNSP bio027060Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Therapeutic induction of blood vessel growth (angiogenesis) in ischemic tissues holds great potential for treatment of myocardial infarction and stroke. Achieving sustained angiogenesis and vascular maturation has, however, been highly challenging. Here, we demonstrate that alginate: collagen hydrogels containing therapeutic, pro-angiogenic FGF-2, and formulated as microspheres, is a promising and clinically relevant vehicle for therapeutic angiogenesis. By titrating the amount of readily dissolvable and degradable collagen with more slowly degradable alginate in the hydrogel mixture, the degradation rates of the biomaterial controlling the release kinetics of embedded proangiogenic FGF-2 can be adjusted. Furthermore, we elaborate a microsphere synthesis protocol allowing accurate control over sphere size, also a critical determinant of degradation/release rate. As expected, alginate: collagen microspheres were completely biocompatible and did not cause any adverse reactions when injected in mice. Importantly, the amount of pro-angiogenic FGF-2 released from such microspheres led to robust induction of angiogenesis in zebrafish embryos similar to that achieved by injecting FGF-2-releasing cells. These findings highlight the use of microspheres constructed from alginate: collagen hydrogels as a promising and clinically relevant delivery system for pro-angiogenic therapy.

  • 203.
    Alici, Gursel
    et al.
    School of Mechanical, Materials, and Mechatronic Engineering, ARC Centre of Excellence for Electromaterials Science, University of Wollongong, Wollongong, Australia.
    Mutlu, Rahim
    School of Mechanical, Materials, and Mechatronic Engineering, ARC Centre of Excellence for Electromaterials Science, University of Wollongong, Wollongong, Australia.
    Melling, Daniel
    Institute for Medical Science and Technology, University of Dundee, Dundee, UK.
    Jager, Edwin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Sensor- och aktuatorsystem. Linköpings universitet, Tekniska fakulteten.
    Kaneto, Keiichi
    Kyushu Institute of Technology, Eamex Co. Ltd, Chuoku, Fukuoka, Japan.
    Conducting Polymers as EAPs: Device Configurations2016Inngår i: Electromechanically Active Polymers: A Concise Reference / [ed] Federico Carpi, Cham: Springer, 2016, s. 257-292Kapittel i bok, del av antologi (Annet vitenskapelig)
    Abstract [en]

    This chapter focuses on device configurations based on conjugated polymer transducers. After the actuation and sensing configurations in the literature are presented, some successful device configurations are reviewed, and a detailed account of their operation principles is described. The chapter is concluded with critical research issues. With reference to the significant progress made in the field of EAP transducers in the last two decades, there is an increasing need to change our approach to the establishment of new device configurations, novel device concepts, and cutting-edge applications. To this aim, we should start from the performance specifications and end up with the material synthesis conditions and properties which will meet the performance specifications (top-to-down approach). The question should be “what electroactive material or materials can be used for a specific purpose or application,” rather than looking for an application or a device concept suitable to the unique properties of the EAPs and transducers already made of these materials. The field is mature enough to undertake this paradigm change.

  • 204.
    Alickovic, Emina
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Kevric, Jasmin
    Int Burch University, Bosnia and Herceg.
    Subasi, Abdulhamit
    Effat University, Saudi Arabia.
    Performance evaluation of empirical mode decomposition, discrete wavelet transform, and wavelet packed decomposition for automated epileptic seizure detection and prediction2018Inngår i: Biomedical Signal Processing and Control, ISSN 1746-8094, E-ISSN 1746-8108, Vol. 39, s. 94-102Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study proposes a new model which is fully specified for automated seizure onset detection and seizure onset prediction based on electroencephalography (EEG) measurements. We processed two archetypal EEG databases, Freiburg (intracranial EEG) and CHB-MIT (scalp EEG), to find if our model could outperform the state-of-the art models. Four key components define our model: (1) multiscale principal component analysis for EEG de-noising, (2) EEG signal decomposition using either empirical mode decomposition, discrete wavelet transform or wavelet packet decomposition, (3) statistical measures to extract relevant features, (4) machine learning algorithms. Our model achieved overall accuracy of 100% in ictal vs. inter-ictal EEG for both databases. In seizure onset prediction, it could discriminate between inter-ictal, pre-ictal, and ictal EEG with the accuracy of 99.77%, and between inter-ictal and pre-ictal EEG states with the accuracy of 99.70%. The proposed model is general and should prove applicable to other classification tasks including detection and prediction regarding bio-signals such as EMG and ECG. (C) 2017 Elsevier Ltd. All rights reserved.

  • 205.
    Alickovic, Emina
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Lunner, Thomas
    Linköpings universitet, Institutet för handikappvetenskap (IHV). Linköpings universitet, Institutionen för klinisk och experimentell medicin, Avdelningen för neuro- och inflammationsvetenskap. Linköpings universitet, Medicinska fakulteten. Eriksholm Research Centre, Oticon A/S, 20 Rortangvej, Snekkersten, Denmark.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    A System Identification Approach to Determining Listening Attention from EEG Signals2016Inngår i: 2016 24TH EUROPEAN SIGNAL PROCESSING CONFERENCE (EUSIPCO), IEEE , 2016, s. 31-35Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We still have very little knowledge about how ourbrains decouple different sound sources, which is known assolving the cocktail party problem. Several approaches; includingERP, time-frequency analysis and, more recently, regression andstimulus reconstruction approaches; have been suggested forsolving this problem. In this work, we study the problem ofcorrelating of EEG signals to different sets of sound sources withthe goal of identifying the single source to which the listener isattending. Here, we propose a method for finding the number ofparameters needed in a regression model to avoid overlearning,which is necessary for determining the attended sound sourcewith high confidence in order to solve the cocktail party problem.

  • 206.
    Alickovic, Emina
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten. Oticon AS, Denmark.
    Lunner, Thomas
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutet för handikappvetenskap (IHV). Oticon AS, Denmark; Tech Univ Denmark, Denmark.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Ljung, Lennart
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    A Tutorial on Auditory Attention Identification Methods2019Inngår i: Frontiers in Neuroscience, ISSN 1662-4548, E-ISSN 1662-453X, Vol. 13, artikkel-id 153Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Auditory attention identification methods attempt to identify the sound source of a listeners interest by analyzing measurements of electrophysiological data. We present a tutorial on the numerous techniques that have been developed in recent decades, and we present an overview of current trends in multivariate correlation-based and model-based learning frameworks. The focus is on the use of linear relations between electrophysiological and audio data. The way in which these relations are computed differs. For example, canonical correlation analysis (CCA) finds a linear subset of electrophysiological data that best correlates to audio data and a similar subset of audio data that best correlates to electrophysiological data. Model-based (encoding and decoding) approaches focus on either of these two sets. We investigate the similarities and differences between these linear model philosophies. We focus on (1) correlation-based approaches (CCA), (2) encoding/decoding models based on dense estimation, and (3) (adaptive) encoding/decoding models based on sparse estimation. The specific focus is on sparsity-driven adaptive encoding models and comparing the methodology in state-of-the-art models found in the auditory literature. Furthermore, we outline the main signal processing pipeline for how to identify the attended sound source in a cocktail party environment from the raw electrophysiological data with all the necessary steps, complemented with the necessary MATLAB code and the relevant references for each step. Our main aim is to compare the methodology of the available methods, and provide numerical illustrations to some of them to get a feeling for their potential. A thorough performance comparison is outside the scope of this tutorial.

  • 207.
    Alickovic, Emina
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Subasi, Abdulhamit
    Effat Univ, Saudi Arabia.
    Automatic Detection of Alzheimer Disease Based on Histogram and Random Forest2020Inngår i: PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON MEDICAL AND BIOLOGICAL ENGINEERING, CMBEBIH 2019, SPRINGER , 2020, Vol. 73, s. 91-96Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Alzheimer disease is one of the most prevalent dementia types affecting elder population. On-time detection of the Alzheimer disease (AD) is valuable for finding new approaches for the AD treatment. Our primary interest lies in obtaining a reliable, but simple and fast model for automatic AD detection. The approach we introduced in the present contribution to identify AD is based on the application of machine learning (ML) techniques. For the first step, we use histogram to transform brain images to feature vectors, containing the relevant "brain" features, which will later serve as the inputs in the classification step. Next, we use the ML algorithms in the classification task to identify AD. The model presented and elaborated in the present contribution demonstrated satisfactory performances. Experimental results suggested that the Random Forest classifier can discriminate the AD subjects from the control subjects. The presented modeling approach, consisting of the histogram as the feature extractor and Random Forest as the classifier, yielded to the sufficiently high overall accuracy rate of 85.77%.

  • 208.
    Alickovic, Emina
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Subasi, Abdulhamit
    Effat Univ, Saudi Arabia.
    Ensemble SVM Method for Automatic Sleep Stage Classification2018Inngår i: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 67, nr 6, s. 1258-1265Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sleep scoring is used as a diagnostic technique in the diagnosis and treatment of sleep disorders. Automated sleep scoring is crucial, since the large volume of data should be analyzed visually by the sleep specialists which is burdensome, time-consuming tedious, subjective, and error prone. Therefore, automated sleep stage classification is a crucial step in sleep research and sleep disorder diagnosis. In this paper, a robust system, consisting of three modules, is proposed for automated classification of sleep stages from the single-channel electroencephalogram (EEG). In the first module, signals taken from Pz-Oz electrode were denoised using multiscale principal component analysis. In the second module, the most informative features are extracted using discrete wavelet transform (DWT), and then, statistical values of DWT subbands are calculated. In the third module, extracted features were fed into an ensemble classifier, which can be called as rotational support vector machine (RotSVM). The proposed classifier combines advantages of the principal component analysis and SVM to improve classification performances of the traditional SVM. The sensitivity and accuracy values across all subjects were 84.46% and 91.1%, respectively, for the five-stage sleep classification with Cohens kappa coefficient of 0.88. Obtained classification performance results indicate that, it is possible to have an efficient sleep monitoring system with a single-channel EEG, and can be used effectively in medical and home-care applications.

  • 209.
    Alickovic, Emina
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Subasi, Abdulhamit
    Effat University, Saudi Arabia.
    Medical Decision Support System for Diagnosis of Heart Arrhythmia using DWT and Random Forests Classifier2016Inngår i: Journal of medical systems, ISSN 0148-5598, E-ISSN 1573-689X, Vol. 40, nr 4, s. 108-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, Random Forests (RF) classifier is proposed for ECG heartbeat signal classification in diagnosis of heart arrhythmia. Discrete wavelet transform (DWT) is used to decompose ECG signals into different successive frequency bands. A set of different statistical features were extracted from the obtained frequency bands to denote the distribution of wavelet coefficients. This study shows that RF classifier achieves superior performances compared to other decision tree methods using 10-fold cross-validation for the ECG datasets and the obtained results suggest that further significant improvements in terms of classification accuracy can be accomplished by the proposed classification system. Accurate ECG signal classification is the major requirement for detection of all arrhythmia types. Performances of the proposed system have been evaluated on two different databases, namely MIT-BIH database and St. -Petersburg Institute of Cardiological Technics 12-lead Arrhythmia Database. For MIT-BIH database, RF classifier yielded an overall accuracy 99.33 % against 98.44 and 98.67 % for the C4.5 and CART classifiers, respectively. For St. -Petersburg Institute of Cardiological Technics 12-lead Arrhythmia Database, RF classifier yielded an overall accuracy 99.95 % against 99.80 % for both C4.5 and CART classifiers, respectively. The combined model with multiscale principal component analysis (MSPCA) de-noising, discrete wavelet transform (DWT) and RF classifier also achieves better performance with the area under the receiver operating characteristic (ROC) curve (AUC) and F- measure equal to 0.999 and 0.993 for MIT-BIH database and 1 and 0.999 for and St. Petersburg Institute of Cardiological Technics 12-lead Arrhythmia Database, respectively. Obtained results demonstrate that the proposed system has capacity for reliable classification of ECG signals, and to assist the clinicians for making an accurate diagnosis of cardiovascular disorders (CVDs).

  • 210.
    Alickovic, Emina
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Subasi, Abdulhamit
    Effat Univ, Saudi Arabia.
    Normalized Neural Networks for Breast Cancer Classification2020Inngår i: PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON MEDICAL AND BIOLOGICAL ENGINEERING, CMBEBIH 2019, SPRINGER , 2020, Vol. 73, s. 519-524Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In almost all parts of the world, breast cancer is one of the major causes of death among women. But at the same time, it is one of the most curable cancers if it is diagnosed at early stage. This paper tries to find a model that diagnose and classify breast cancer with high accuracy and help to both patients and doctors in the future. Here we develop a model using Normalized Multi Layer Perceptron Neural Network to classify breast cancer with high accuracy. The results achieved is very good (accuracy is 99.27%). It is very promising result compared to previous researches where Artificial Neural Networks were used. As benchmark test, Breast Cancer Wisconsin (Original) was used.

  • 211.
    Alimadadi, Majid
    et al.
    Department of Natural Sciences, Mid Sweden University, Sweden.
    Lindström, Stefan B
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Kulachenko, Artem
    Department of Solid Mechanics, Royal Institute of Technology (KTH), Stockholm, Sweden.
    Role of microstructures in the compression response of three-dimensional foam-formed wood fiber networks2018Inngår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 14, s. 8945-8955Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High-porosity, three-dimensional wood fiber networks made by foam forming present experimentally accessible instances of hierarchically structured, athermal fiber networks. We investigate the large deformation compression behavior of these networks using fiber-resolved finite element analyses to elucidate the role of microstructures in the mechanical response to compression. Three-dimensional network structures are acquired using micro-computed tomography and subsequent skeletonization into a Euclidean graph representation. By using a fitting procedure to the geometrical graph data, weare able to identify nine independent statistical parameters needed for the regeneration of artificial networks with the observed statistics. The compression response of these artificially generated networks and the physical network is then investigated using implicit finite element analysis. A direct comparison of the simulation results from the reconstructed and artificial network reveals remarkable differences already in the elastic region. These can neither be fully explained by density scaling, the size effect nor the boundary conditions. The only factor which provides the consistent explanation of the observed difference is the density and fiber orientation nonuniformities; these contribute to strain-localization so that the network becomes more compliant than expected for statistically uniform microstructures. We also demonstrate that the experimentally manifested strain-stiffening of such networks is due to development of new inter-fiber contacts during compression.

  • 212.
    Alirezaie, Marjan
    et al.
    Institutionen för naturvetenskap och teknik , Örebro Universitet.
    Hammar, Karl
    Högskolan i Jönköping, JTH, Datateknik och informatik.
    Blomqvist, Eva
    Linköpings universitet, Institutionen för datavetenskap, Interaktiva och kognitiva system. Linköpings universitet, Tekniska fakulteten.
    Nyström, Mikael
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Ivanova, Valentina
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    SmartEnv Ontology in E-care@home2018Inngår i: SSN 2018 - Semantic Sensor Networks Workshop: Proceedings of the 9th International Semantic Sensor Networks Workshopco-located with 17th International Semantic Web Conference (ISWC 2018) / [ed] Maxime Lefrançois, Raúl Garcia Castro, Amélie Gyrard, Kerry Taylor, CEUR-WS , 2018, Vol. 2213, s. 72-79Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this position paper we briefly introduce SmartEnv ontology which relies on SEmantic Sensor Network (SSN) ontology and is used to represent different aspects of smart and sensorized environments. We will also talk about E-carehome project aiming at providing an IoT-based health-care system for elderly people at their homes. Furthermore, we refer to the role of SmartEnv in Ecarehome and how it needs to be further extended to achieve semantic interoperability as one of the challenges in development of autonomous health care systems at home.

  • 213.
    Alling, Björn
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Högberg, Hans
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Armiento, Rickard
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    A theoretical investigation of mixing thermodynamics, age-hardening potential, and electronic structure of ternary (M1-xMxB2)-M-1-B-2 alloys with AlB2 type structure2015Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Transition metal diborides are ceramic materials with potential applications as hard protective thin films and electrical contact materials. We investigate the possibility to obtain age hardening through isostructural clustering, including spinodal decomposition, or ordering-induced precipitation in ternary diboride alloys. By means of first-principles mixing thermodynamics calculations, 45 ternary (M1-xMxB2)-M-1-B-2 alloys comprising (MB2)-B-i (M-i = Mg, Al, Sc, Y, Ti, Zr, Hf, V, Nb, Ta) with AlB2 type structure are studied. In particular Al1-xTixB2 is found to be of interest for coherent isostructural decomposition with a strong driving force for phase separation, while having almost concentration independent a and c lattice parameters. The results are explained by revealing the nature of the electronic structure in these alloys, and in particular, the origin of the pseudogap at E-F in TiB2, ZrB2, and HfB2.

  • 214.
    Alling, Björn
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten. Max Planck Institute Eisenforsch GmbH, Germany.
    Koermann, F.
    Max Planck Institute Eisenforsch GmbH, Germany; Delft University of Technology, Netherlands.
    Grabowski, B.
    Max Planck Institute Eisenforsch GmbH, Germany.
    Glensk, A.
    Max Planck Institute Eisenforsch GmbH, Germany.
    Abrikosov, Igor
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten. National University of Science and Technology MISIS, Russia.
    Neugebauer, J.
    Max Planck Institute Eisenforsch GmbH, Germany.
    Strong impact of lattice vibrations on electronic and magnetic properties of paramagnetic Fe revealed by disordered local moments molecular dynamics2016Inngår i: PHYSICAL REVIEW B, ISSN 2469-9950, Vol. 93, nr 22, artikkel-id 224411Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study the impact of lattice vibrations on magnetic and electronic properties of paramagnetic bcc and fcc iron at finite temperature, employing the disordered local moments molecular dynamics (DLM-MD) method. Vibrations strongly affect the distribution of local magnetic moments at finite temperature, which in turn correlates with the local atomic volumes. Without the explicit consideration of atomic vibrations, the mean local magnetic moment and mean field derived magnetic entropy of paramagnetic bcc Fe are larger compared to paramagnetic fcc Fe, which would indicate that the magnetic contribution stabilizes the bcc phase at high temperatures. In the present study we show that this assumption is not valid when the coupling between vibrations and magnetism is taken into account. At the gamma-delta transition temperature (1662 K), the lattice distortions cause very similar magnetic moments of both bcc and fcc structures and hence magnetic entropy contributions. This finding can be traced back to the electronic densities of states, which also become increasingly similar between bcc and fcc Fe with increasing temperature. Given the sensitive interplay of the different physical excitation mechanisms, our results illustrate the need for an explicit consideration of vibrational disorder and its impact on electronic and magnetic properties to understand paramagnetic Fe. Furthermore, they suggest that at the gamma-delta transition temperature electronic and magnetic contributions to the Gibbs free energy are extremely similar in bcc and fcc Fe.

  • 215.
    Allström, Andreas
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Highway Traffic State Estimation and Short-term Prediction2016Licentiatavhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    Traffic congestion is increasing in almost all large cities, leading to a number of negative effects such as pollution and delays. However, building new roads is not a feasible solution. Instead, the use of the existing road network has to be optimized, together with a shift towards more sustainable transport modes. In order to achieve this there are several challenges that needs to be addressed. One challenge is the ability to provide accurate information about the current and future traffic state. This information is an essential input to the traffic management center and can be used to influence the choices made by the travelers. Accurate information about the traffic state on highways, where the potential to manage and control the traffic in general is very high, would be of great significance for the traffic managers. It would help the traffic managers to take action before the system reaches congestion and limit the effects of it. At the same time, the collection of traffic data is slowly shifting from fixed sensors to more probe based data collection. This requires an adaptation and further development of the traditional traffic models in order for them to handle and take advantage of the characteristics of all types of data, not just data from the traditionally used fixed sensors.

    The objective of this thesis is to contribute to the development and implementation of a model for estimation and prediction of the current and future traffic state and to facilitate an adaptation of the model to the conditions of the highway in Stockholm. The model used is a version of the Cell Transmission Model (CTM-v) where the velocity is used as the state variable. Thus, together with an Ensemble Kalman Filter (EnKF) it can be used to fuse different types of point speed measurements. The model is developed to run in real-time for a large network. Furthermore, a two-stage process used to calibrate the model is implemented. The results from the calibration and validation show that once the model is calibrated, the estimated travel times corresponds well with the ground truth travel times collected from Bluetooth sensors.

    In order to produce accurate short-term predictions for various networks and conditions it is vital to combine different methods. We have implemented and evaluated a hybrid prediction approach that assimilates parametric and non-parametric short-term traffic state prediction. To predict mainline sensor data we use a neural network, while the CTM-v is ran forward in time in order to predict future traffic states. The results show that both the hybrid approach and the CTM-v prediction without the additional predicted mainline sensor data is superior to a naïve prediction method for longer prediction horizons.

  • 216.
    Allström, Andreas
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Barceló, Jaume
    Department of Statistics and Operations Research, Universitat Politècnica de Catalunya.
    Ekström, Joakim
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Grumert, Ellen
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Gundlegård, David
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Rydergren, Clas
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Traffic management for smart cities2017Inngår i: Designing, developing, and facilitating smart cities: urban design to IoT solutions. Part III / [ed] Vangelis Angelakis, Elias Tragos, Henrich C. Pöhls, Adam Kapovits and Alessandro Bassi, Switzerland: Springer, 2017, s. 211-240Kapittel i bok, del av antologi (Annet vitenskapelig)
    Abstract [en]

    Smart cities, participatory sensing as well as location data available in communication systems and social networks generates a vast amount of heterogeneous mobility data that can be used for traffic management. This chapter gives an overview of the different data sources and their characteristics and describes a framework for utilizing the various sources efficiently in the context of traffic management. Furthermore, different types of traffic models and algorithms are related to both the different data sources as well as some key functionalities of active traffic management, for example short-term prediction and control.

  • 217.
    Allström, Andreas
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Ekström, Joakim
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Gundlegård, David
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Ringdahl, Rasmus
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem.
    Rydergren, Clas
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Bayen, Alexandre M.
    Department of Civil and Environmental Engineering, University of California.
    Patire, Anthony D.
    Department of Civil and Environmental Engineering, University of California.
    A hybrid approach for short-term traffic state and travel time prediction on highways2016Inngår i: TRB 95th annual meeting compendium of papers, 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Traffic management and traffic information are essential in urban areas, and require a good knowledge about both the current and the future traffic state. Both parametric and non-parametric traffic state prediction techniques have previously been developed, with different advantages and shortcomings. While non-parametric prediction has shown good results for predicting the traffic state during recurrent traffic conditions, parametric traffic state prediction can be used during non-recurring traffic conditions such as incidents and events. Hybrid approaches, combining the two prediction paradigms have previously been proposed by using non-parametric methods for predicting boundary conditions used in a parametric method. In this paper we instead combine parametric and non-parametric traffic state prediction techniques through assimilation in an Ensemble Kalman filter. As non-parametric prediction method a neural network method is adopted, and the parametric prediction is carried out using a cell transmission model with velocity as state. The results show that our hybrid approach can improve travel time prediction of journeys planned to commence 15 to 30 minutes into the future, using a prediction horizon of up to 50 minutes ahead in time to allow the journey to be completed.

  • 218.
    Allström, Andreas
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Ekström, Joakim
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Gundlegård, David
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Ringdahl, Rasmus
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Rydergren, Clas
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Bayen, Alexandre M.
    Department of Civil and Environmental Engineering, University of California, Berkeley, CA, USA.
    Patire, Anthony D.
    Department of Civil and Environmental Engineering, University of California, Berkeley, CA, USA.
    Hybrid Approach for Short-Term Traffic State and Travel Time Prediction on Highways2016Inngår i: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, Vol. 2554, s. 60-68Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Traffic management and traffic information are essential in urban areas and require reliable knowledge about the current and future traffic state. Parametric and nonparametric traffic state prediction techniques have previously been developed with different advantages and shortcomings. While nonparametric prediction has shown good results for predicting the traffic state during recurrent traffic conditions, parametric traffic state prediction can be used during nonrecurring traffic conditions, such as incidents and events. Hybrid approaches have previously been proposed; these approaches combine the two prediction paradigms by using nonparametric methods for predicting boundary conditions used in a parametric method. In this paper, parametric and nonparametric traffic state prediction techniques are instead combined through assimilation in an ensemble Kalman filter. For nonparametric prediction, a neural network method is adopted; the parametric prediction is carried out with a cell transmission model with velocity as state. The results show that the hybrid approach can improve travel time prediction of journeys planned to commence 15 to 30 min into the future, with a prediction horizon of up to 50 min ahead in time to allow the journey to be completed

  • 219.
    Alm Grundström, Henrik
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Developments in Topology Optimization in the ADDMAN Project2018Rapport (Annet vitenskapelig)
    Abstract [en]

    This document gives an account of some of the work done so far on topology optimization (TO) in the ADDMAN project. As well as the mathematical formulations and implementations details, short discussions are presented on some of the nuances of the different formulations and how they should be used efficiently

  • 220.
    Alm Grundström, Henrik
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Trinitas Topology Optimization Tutorial Document2018Rapport (Annet vitenskapelig)
  • 221.
    Alm, Therese
    Linköpings universitet, Institutionen för datavetenskap, Interaktiva och kognitiva system. Linköpings universitet, Tekniska fakulteten.
    Design av en användarvänlig Androidapplikation för trådlös kommunikation med Electronic Control Unit för bil eller testmiljö2015Independent thesis Basic level (university diploma), 10,5 poäng / 16 hpOppgave
    Abstract [sv]

    Det här examensarbetet har utförts inom programmet högskoleingenjör datateknik vid Linköpings Universitet under våren 2015 och utförts på begäran av ArcCore i Linköping. Syftet med det här examensarbetet är att skapa och designa en användarvänlig Androidapplikation som trådlöst kan kommunicera med electronic control units i bil eller testmiljö.

    Androidapplikationen består av fem huvudskärmar, fyra vars uppgift är att skriva ut informationen som åker över CAN bussen. De fem skärmarna är start, felkoder, sensorer, ECU extract och overview. Start tar dig vidare till de andra skärmarna, felkoder skriver ut alla felkoder, sensorer skriver ut alla sensorvärden, ECU extract skriver ut all information och overview visar en virtuell instrumentbräda. Användarutvärderingar har utförts för att ta fram både designen och layouten på applikationen. Utvecklingsprocessen för att få fram applikationen har genomförts med hjälp av utvecklingsmetoden extreme programming och utvärderingar har utförts med traditional usability tests och binary success. Utvärderingarnas feedback har använts för att utveckla både designen och användarvänligheten på applikationen.

    Androidapplikationen har utvecklats i Android Studio och kommunicerar med ECU:erna med hjälp av en PEAK PCAN wireless gateway som kopplats upp mot Hercules Development Kit TMS570 MCU.

    Resultatet är att vi tydligt kan se att användarvänligheten har ökat under utvecklingsprocessen och att vi nu med hjälp av utvärderingar har en snygg och lättanvändarvänlig Android applikation som kommer kunna användas av alla som vill ta del av informationen som finns på CAN bussen.

  • 222.
    Almgren, Magnus
    et al.
    Department of computer science and engineering, Chalmers university of technology, Gothenburg.
    Andersson, Peter
    FOI, Swedish Defence Research Agency, Linköping, Sweden.
    Björkman, Gunnar
    Stockholms stad / Kungliga Tekniska Högskolan, KTH, Stockholm.
    Ekstedt, Mathias
    Industrial Information and Control Systems, Royal Institute of Technology, KTH, Stockholm.
    Hallberg, Jonas
    FOI, Swedish Defence Research Agency, Linköping, Sweden.
    Nadjm-Tehrani, Simin
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Westring, Eric
    FOI, Swedish Defence Research Agency, Linköping, Sweden.
    RICS-el: Building a National Testbed for Research and Training on SCADA Security2019Inngår i: Critical Information Infrastructures Security: 13th International Conference, CRITIS 2018, Kaunas, Lithuania, September 24-26, 2018, Revised Selected Papers / [ed] Eric Luiijf, Inga Žutautaitė and Bernhard Hämmerli, Springer, 2019, s. 219-225Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    Trends show that cyber attacks targeting critical infrastructures are increasing, but security research for protecting such systems are challenging. There is a gap between the somewhat simplified models researchers at universities can sustain contra the complex systems at infrastructure owners that seldom can be used for direct research. There is also a lack of common datasets for research benchmarking. This paper presents a national experimental testbed for security research within supervisory control and data acquisition systems (SCADA), accessible for both research training and experiments. The virtualized testbed has been designed and implemented with both vendor experts and security researchers to balance the goals of realism with specific research needs. It includes a real SCADA product for energy management, a number of network zones, substation nodes, and a simulated power system. This environment enables creation of scenarios similar to real world utility scenarios, attack generation, development of defence mechanisms, and perhaps just as important: generating open datasets for comparative research evaluation.

  • 223.
    Almgren, Richard
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling. Linköpings universitet, Tekniska fakulteten. Green Business AB.
    Näringslivets insatser på miljöområdet: För Naturvårdsverket2015Rapport (Annet vitenskapelig)
    Abstract [sv]

    Uppdraget för denna rapport har varit att beskriva näringslivets insatser på miljöområdet med avseende på vilka miljöfrågor som näringslivet prioriterar, hur företagen organiserar sina insatser och vilka verktyg de använder för att förbättra sin miljöprestanda, hur de ser på några vanliga statliga styrmedel, vilka som är de viktigaste drivkrafterna och hindren till förbättrad miljöprestanda samt att även blicka utanför Sveriges gränser.

    Generationsperspektivet, ungefär 3-års cykler, på miljöfrågorna innebär att det ofta tar lång tid innan ett miljöproblem uppenbarar sig som ett problem. Likaså tar det ofta lång tid att åtgärda upptäckta problem med hänsyn till att de ofta kräver omställningar med nya tekniska lösningar, som inte alltid finns till hands, och som också behöver inför as brett i näringslivet.

    När det gäller den första frågan om vilka de viktigaste miljöfrågorna är för näringslivets del visar denna studie att det främst gäller klimatfrågan och produkternas miljöaspekter i ett värdekedjeperspektiv. Båda frågorna är globala till sin karaktär. De studerade företagen har hög beredskap och har redan påbörjat arbetet att för svensk del bidra till att minska klimatpåverkan. Innebörden av de antagna målen hos de 50 studerade företagen är att företag som verkar i Sverige enligt denna studie ska kunna medverka till att nå den nivå på insatser som IPCC indikerat för år 2050. Det är den tidpunkt som IPCC siktar på i sina senaste utvärderingar. Flera företag har vardera skisserat en trovärdig färdplan för att göra verksamheten koldioxidsnål eller koldioxidneutral till nämnda tidpunkt. Det är känt från andra liknande studier att det f rån näringslivets perspektiv dock också behövs ett politiskt mål av flera skäl, bl a för att regeringar och näringsliv i alla länder ska dra åt samma håll. Det som emellertid är intressant nu är att näringslivet i Sverige enligt denna studie har påbörjat arbetet med att finna lösningar för att nå ett ev kommande politiskt globalt mål. De studerade företagen i Sverige har även i stor utsträckning upprättat egna mål och genomför åtgärder på de områden som de nationella miljökvalitetsmålen täcker, bl a med inriktning på att begränsa förorening av luft- och vattenområden men även på att värna den biologiska mångfalden i jord- och skogsbruk samt att värna och utveckla naturvärden i den bebyggda miljön. Resultaten i form av utsläppsminskningar på de föroreningsanknutna områdena är goda även om det på flera områden återstår insatser att göra. Miljökvaliteten i Sverige på dessa områden påverkas dock främst av verksamhet i länder utanför Sveriges gränser. Den miljöpåverkan som uppstår som följd av den ökade handeln mellan länder är idag svår av kvantifiera på grund brister i lämplig statistik och mätetal. Inriktningen av handeln pekar emellertid på att Sverige exporterar mer varor med goda miljöprestanda, räknat i hela värdekedjan, än importerar varor med dåliga. Utöver nämnda områden har företagen ofta mål för användning av resurser och utveckling av förnybara energikällor.

    När det gäller den andra frågan om företagens egna insatser visar studien att det i rapporten studerade delen av näringslivet i Sverige i betydande omfattning på frivillig väg har infört egna verktyg för att effektivt kunna hantera sina miljöfrågor. Den viktigaste förändringen är att begreppet hållbar utveckling nu har slagit rot. Det medför att miljöfrågorna nu fått en tydligare plats i företagens ledningar i samverkan med andra frågor inom begreppet hållbarhet. De viktiga förebilderna för innebörden av hållbar utveckling är UN Global Compact, OECDs vägledning för multinationella företag och den internationella standarden ISO 26000 om socialt ansvarstagande. Rapporteringen av studerade företagens insatser på hållbarhetsområdet sker i stor utsträckning enligt den modell som utarbetats av GRI (Global Reporting Initiative). Den egna målstyrda verksamheten baseras väsentligen på miljöledningssystem som upprättats med stöd av den internationella miljöledningsstandarden ISO 14001, inom vilken även lagstyrda insatser hanteras internt . Syftet med sådana miljöledningssystem är att bidra med en effektiv metod att hantera miljöfrågorna i ett företag. Den logik som denna standard har byggt upp, m ed målstyrning som viktigaste komponent, lyser igenom i alla företagens hållbarhetsredovisningar. Det är alltså tydligt att ISO 14001 har fått stort genomslag i den praktiska hanteringen av miljöfrågorna. Vidare är det tydligt att företagen idag fäster sto r vikt vid att värna och utveckla den biologiska mångfalden i skogen. Mer än 70 procent av den produktiva skogsmarken i Sverige är certifierad enligt något av de stora förekommande certifieringssystemen (FSC/PEFC). Det innebär omfattande åtaganden för skog sägarna att värna om den biologiska mångfalden och att sätta av marker för naturvårdsändamål.

    När det gäller den tredje frågan om näringslivets förhållningssätt till statliga styrmedel har näringslivet i Sverige generellt sett en positiv syn på det regel verk som reglerar deras verksamhet. Efterlevnaden synes vara god av gällande regler. Den statliga individuella, integrerade tillståndsprövningen anses av berörda företag vara ett bra styrmedel. Det gäller även den europeiska kemikalielagstiftningen REACH. Däremot framgår det tydligt av studien att den nuvarande utformningen av tillståndsprövningen enligt berörda företag efter hand har blivit alldeles för omständlig och tidsmässigt utdragen. Idag tar tillståndsprocessen över tre år i genomsnitt. Det bör tydliggöras att inget företag har yrkat på att sänka miljökraven i sig utan framförallt att få tillståndsprocessen att gå fortare. Studien visar att det finns flera sådana möjligheter utan att varken göra avkall på kraven i direktiv från EU eller hänsyn till miljön. Avgiften på kväveoxider har mer eller mindre förlorat sin roll som styrmedel och fungerar numera mest som subvention av energisektorn på bekostnad av skogsindustrin. Det är framförallt skogsindustrin som framför kritik på denna punkt. Vidare ans er berörda företag att handeln med utsläppsrätter enligt EU ETS bör utvidgas till ett globalt system för att kunna bli verkningsfullt.

    När det gäller den fjärde frågan om drivkrafter och hinder för förbättrad miljöprestanda var lagstiftningen den stora drivkraften under 1970- och 1980-talen. Olika marknadsbaserade krav har numera fått en betydligt större roll än tidigare. Kraften i dessa krav skiftar från bransch till bransch och från miljöfråga till miljöfråga. En notering som stödjer tesen om att marknad en tagit över är det faktum att även de i denna undersökning utvalda företag, som inte i någon påtaglig utsträckning styrs av lagstiftning, också har ambitiösa program och planer. En annan bild av samma utveckling är relationen till kunder och andra intressenter. Det framkommer av företagen i studien att de knappast idag kan verka på marknaden samtidigt som förtroendet för företaget sviktar hos kunder och andra intressenter. En viss reservation kan dock vara befogad. Bakom olika marknadsrelaterade krav står ofta myndighetskrav eller lagstiftning. Det motsatta gäller naturligtvis också, dvs bakom lagstiftningskrav finns ofta ytterst ett krav på marknaden. Vidare är det tydligt från studien att d en värdegrund som idag omfattar de flesta svenskar, att värna om miljön, gäller också för företag. Sverige är ett relativt homogent land med en i stora delar gemensam värdegrund. En betydande del av alla insatser för miljön görs därför på helt frivillig väg av ren omtanke om miljön. Också detta bekräftas av det faktum att även de företag som inte omfattas av statliga krav på tillstånd, anmälan eller andra ”skarpa krav” också vidtar åtgärder för att skydda miljön med liknande inriktning och omfattning som de med sådana krav.

    Genomgången av olika verktyg och styrmedel får konsekvenser för de statliga och kommunala myndigheterna. Olika statliga regelverk är inte längre är det enda svaret på förbättrad miljöprestanda hos näringslivet. Det innebär att miljöpolitiken för regering och myndigheter snarare bör vara att skaffa sig ett rimligt förhållningssätt till de olika initiativen på marknaden med innebörd att staten underlättar för och stödjer företag, snarare än reglerar. Efter genomgången i denna rapport är svaret entydigt nej på frågan om det behövs kompletterande styrmedel. Det saknas i varje fall miljömotiv för det.

    Informationen för att besvara frågorna i denna undersökning har främst hämtats från en grupp av 50 stora företag med verksamhet i Sverige. Därutöver har information inhämtat s från intervjuer (11 företag, varav 6 från gruppen av 50), andra tillgängliga undersökningar och litteratur. De 55 företagen utgör inte ett representativt urval av näringslivet idag. Däremot vet vi från tidigare undersökningar att den värdegrund och de insatser som de stora företagen gör efter hand verkar som inspiration för de mindre företagen. Många av de mindre företagen är också leverantörer till de stora och har krav fr ån kunden att förhålla sig till. Det de stora företagen gör idag förmodas vara giltiga för en större del av näringslivet om några år.

  • 224.
    Almquist, Mathias
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Almquist, Viktor
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Krishnamoorthi, Vengatanathan
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Carlsson, Niklas
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Eager, Derek
    Univ Saskatchewan, Canada.
    The Prefetch Aggressiveness Tradeof in 360 degrees Video Streaming2018Inngår i: PROCEEDINGS OF THE 9TH ACM MULTIMEDIA SYSTEMS CONFERENCE (MMSYS18), ASSOC COMPUTING MACHINERY , 2018, s. 258-269Konferansepaper (Fagfellevurdert)
    Abstract [en]

    With 360 degrees video, only a limited fraction of the full view is displayed at each point in time. This has prompted the design of streaming delivery techniques that allow alternative playback qualities to be delivered for each candidate viewing direction. However, while prefetching based on the users expected viewing direction is best done close to playback deadlines, large buffers are needed to protect against shortfalls in future available bandwidth. This results in conflicting goals and an important prefetch aggressiveness tradeoff problem regarding how far ahead in time from the current playpoint prefetching should be done. This paper presents the first characterization of this tradeoff. The main contributions include an empirical characterization of head movement behavior based on data from viewing sessions of four different categories of 360 degrees video, an optimization-based comparison of the prefetch aggressiveness tradeoffs seen for these video categories, and a data-driven discussion of further optimizations, which include a novel system design that allows both tradeoff objectives to be targeted simultaneously. By qualitatively and quantitatively analyzing the above tradeoffs, we provide insights into how to best design tomorrows delivery systems for 360 degrees videos, allowing content providers to reduce bandwidth costs and improve users playback experiences.

  • 225.
    Almquist, Mathias
    et al.
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska fakulteten.
    Almquist, Viktor
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska fakulteten.
    Vergara Alonso, Ekhiotz Jon
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Nadjm-Tehrani, Simin
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Communication Energy Overhead of Mobiles Games2015Inngår i: MobiGames '15: Proceedings of the 2nd Workshop on Mobile Gaming, Association for Computing Machinery (ACM), 2015, s. 1-6Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Although a significant proportion of the mobile apps are games there has been little attention paid to their specific characteristics with respect to communication energy. In this paper we select 20 mobile games among the top 100 free Android games, and study their data patterns and communication energy use over a total of 25 hours of playing. The analysis of the energy for communication over 3G networks indicates that there is a wide variation among the games, the largest footprint being 8 times higher than the lowest one. The results also indicates both app-specific and category-specific relations between data pattern and energy use, as well as variations in CPU utilisation.

  • 226.
    Almqvist, Roland M.
    et al.
    Företagsekonomiska institutionen, Stockholms universitet.
    Graaf, Johan
    Företagsekonomiska institutionen, Stockholms universitet.
    Jannesson, Erik
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Industriell ekonomi. Linköpings universitet, Tekniska fakulteten.
    Parment, Anders
    Företagsekonomiska institutionen, Stockholms universitet.
    Skoog, Matti
    Företagsekonomi, Åbo akademi / Företagsekonomiska institutionen, Stockholms universitet.
    Boken om ekonomistyrning2016 (oppl. 1)Bok (Annet vitenskapelig)
    Abstract [sv]

    Denna bok ger en bred introduktion till ämnet ekonomistyrning. Boken speglar ekonomistyrningens relevans för dagens organisationer inom näringsliv, offentlig sektor och civilsamhälle. Författarna går igenom de grundläggande modeller, verktyg och processer som traditionell ekonomistyrning erbjuder. Här märks ekonomiska ansvarsenheter, resultat- och balansräkning, kassaflödesanalys, nyckeltal, belöningssystem, budgetering, kalkylering på kort och lång sikt, internpriser samt avvikelseanalys.

    Boken om ekonomistyrning utgår från att ekonomistyrningen har en central roll i att skapa mer hållbara organisationer och lägger betydande vikt vid aspekter som sociala och miljömässiga kostnader, projektstyrning, miljöinvesteringar och humankapital. Boken har därmed ett tydligt hållbarhets- och samhällsperspektiv.

    Författarna betonar även vikten av att ekonomistyrningen utgör en välavvägd helhet genom den så kallade styrmixen. En genomtänkt styrmix ger verktyg för att motivera medarbetare att arbeta mot gemensamma mål och skapa konkurrenskraftiga organisationer. Till boken finns ett rikt övningsmaterial i form av en övningsbok.

  • 227.
    Almyras, Georgios
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Nanodesign. Linköpings universitet, Tekniska fakulteten.
    Sangiovanni, Davide Giuseppe
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten. Ruhr Univ Bochum, Germany.
    Sarakinos, Kostas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Nanodesign. Linköpings universitet, Tekniska fakulteten.
    Semi-Empirical Force-Field Model For The Ti1-XAlXN (0 ≤ x ≤ 1) System2019Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 2, artikkel-id 215Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a modified embedded atom method (MEAM) semi-empirical force-field model for the Ti1-xAlxN (0 x 1) alloy system. The MEAM parameters, determined via an adaptive simulated-annealing (ASA) minimization scheme, optimize the models predictions with respect to 0 K equilibrium volumes, elastic constants, cohesive energies, enthalpies of mixing, and point-defect formation energies, for a set of approximate to 40 elemental, binary, and ternary Ti-Al-N structures and configurations. Subsequently, the reliability of the model is thoroughly verified against known finite-temperature thermodynamic and kinetic properties of key binary Ti-N and Al-N phases, as well as properties of Ti1-xAlxN (0 amp;lt; x amp;lt; 1) alloys. The successful outcome of the validation underscores the transferability of our model, opening the way for large-scale molecular dynamics simulations of, e.g., phase evolution, interfacial processes, and mechanical response in Ti-Al-N-based alloys, superlattices, and nanostructures.

  • 228.
    Alnoor, Hatim
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Toward the Optimization of Low-temperature Solution-based Synthesis of ZnO Nanostructures for Device Applications2017Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    One-dimensional (1D) nanostructures (NSs) of Zinc Oxide (ZnO) such as nanorods (NRs) have recently attracted considerable research attention due to their potential for the development of optoelectronic devices such as ultraviolet (UV) photodetectors and light-emitting diodes (LEDs). The potential of ZnO NRs in all these applications, however, would require synthesis of high crystal quality ZnO NRs with precise control over the optical and electronic properties. It is known that the optical and electronic properties of ZnO NRs are mostly influenced by the presence of native (intrinsic) and impurities (extrinsic) defects. Therefore, understanding the nature of these intrinsic and extrinsic defects and their spatial distribution is critical for optimizing the optical and electronic properties of ZnO NRs. However, identifying the origin of such defects is a complicated matter, especially for NSs, where the information on anisotropy is usually lost due to the lack of coherent orientation.

    Thus, the aim of this thesis is towards the optimization of the lowtemperature solution-based synthesis of ZnO NRs for device applications. In this connection, we first started with investigating the effect of the precursor solution stirring durations on the deep level defects concentration and their spatial distribution along the ZnO NRs. Then, by choosing the optimal stirring time, we studied the influence of ZnO seeding layer precursor’s types, and its molar ratios on the density of interface defects. The findings of these investigations were used to demonstrate ZnO NRs-based heterojunction LEDs. The ability to tune the point defects along the NRs enabled us further to incorporate cobalt (Co) ions into the ZnO NRs crystal lattice, where these ions could occupy the vacancies or interstitial defects through substitutional or interstitial doping. Following this, high crystal quality vertically welloriented ZnO NRs have been demonstrated by incorporating a small amount of Co into the ZnO crystal lattice. Finally, the influence of Co ions incorporation on the reduction of core-defects (CDs) in ZnO NRs was systematically examined using electron paramagnetic resonance (EPR).

  • 229.
    Alnoor, Hatim
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska fakulteten.
    Chey, Chan Oeurn
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska högskolan.
    Pozina, Galia
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Liu, Xianjie
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten.
    Khranovskyy, Volodymyr
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Willander, Magnus
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Nour, Omer
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Effect of precursor solutions stirring on deep level defects concentration and spatial distribution in low temperature aqueous chemical synthesis of zinc oxide nanorods2015Inngår i: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 5, nr 8, artikkel-id 087180Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hexagonal c-axis oriented zinc oxide (ZnO) nanorods (NRs) with 120-300 nm diameters are synthesized via the low temperature aqueous chemical route at 80 degrees C on silver-coated glass substrates. The influence of varying the precursor solutions stirring durations on the concentration and spatial distributions of deep level defects in ZnO NRs is investigated. Room temperature micro-photoluminesnce (mu-PL) spectra were collected for all samples. Cathodoluminescence (CL) spectra of the as-synthesized NRs reveal a significant change in the intensity ratio of the near band edge emission (NBE) to the deep-level emission (DLE) peaks with increasing stirring durations. This is attributed to the variation in the concentration of the oxygen-deficiency with increasing stirring durations as suggested from the X-ray photoelectron spectroscopy analysis. Spatially resolved CL spectra taken along individual NRs revealed that stirring the precursor solutions for relatively short duration (1-3 h), which likely induced high super saturation under thermodynamic equilibrium during the synthesis process, is observed to favor the formation of point defects moving towards the tip of the NRs. In contrary, stirring for longer duration (5-15 h) will induce low super saturation favoring the formation of point defects located at the bottom of the NRs. These findings demonstrate that it is possible to control the concentration and spatial distribution of deep level defects in ZnO NRs by varying the stirring durations of the precursor solutions.

  • 230.
    Alnoor, Hatim
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska fakulteten.
    Pozina, Galia
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Khranovskyy, Volodymyr
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Liu, Xianjie
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten.
    Iandolo, Donata
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Willander, Magnus
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Nur, Omer
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Influence of ZnO seed layer precursor molar ratio on the density of interface defects in low temperature aqueous chemically synthesized ZnO nanorods/GaN light-emitting diodes2016Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 119, nr 16, s. 165702-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Low temperature aqueous chemical synthesis (LT-ACS) of zinc oxide (ZnO) nanorods (NRs) has been attracting considerable research interest due to its great potential in the development of light-emitting diodes (LEDs). The influence of the molar ratio of the zinc acetate (ZnAc): KOH as a ZnO seed layer precursor on the density of interface defects and hence the presence of non-radiative recombination centers in LT-ACS of ZnO NRs/GaN LEDs has been systematically investigated. The material quality of the as-prepared seed layer as quantitatively deduced by the X-ray photoelectron spectroscopy is found to be influenced by the molar ratio. It is revealed by spatially resolved cathodoluminescence that the seed layer molar ratio plays a significant role in the formation and the density of defects at the n-ZnO NRs/p-GaN heterostructure interface. Consequently, LED devices processed using ZnO NRs synthesized with molar ratio of 1:5M exhibit stronger yellow emission (similar to 575 nm) compared to those based on 1:1 and 1:3M ratios as measured by the electroluminescence. Furthermore, seed layer molar ratio shows a quantitative dependence of the non-radiative defect densities as deduced from light-output current characteristics analysis. These results have implications on the development of high-efficiency ZnO-based LEDs and may also be helpful in understanding the effects of the ZnO seed layer on defect-related non-radiative recombination. Published by AIP Publishing.

  • 231.
    Alnoor, Hatim
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska fakulteten.
    Pozina, Galia
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Willander, Magnus
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Nur, Omer
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Seed layer synthesis effect on the concentration of interface defects and emission spectra of ZnO nanorods/p-GaN light-emitting diode2017Inngår i: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 214, nr 1, artikkel-id 1600333Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    As the low-temperature aqueous chemical synthesis (LT-ACS), holds great promises for the synthesis of one-dimensional (1D) ZnO nanostructure-based light-emitting diodes (LEDs) and hence require parameter tuning for optimal performance. N-ZnO nanorods (NRs)/p-GaN heterojunction LEDs have been synthesized by the LT-ACS using ZnO nanoparticle (NPs) seed layers prepared with different precursor solutions. The effect of these seed layers on the interface defect properties and emission intensity of the as-synthesized n-Zn/p-GaN heterojunction LEDs has been demonstrated by spatially resolved cathodoluminescence (CL) and electroluminescence (EL) measurements, respectively. A significant reduction of the interface defects in the n-ZnO NRs/p-GaN heterostructure synthesized from a seed layer prepared from zinc acetate (ZnAc) with a mixture of potassium hydroxide (KOH) and hexamethylenetetramine (HMTA) (donated as ZKH seed) compared with those prepared from ZnAc and KOH (donated as ZK seed) is observed as revealed by spatially resolved CL. Consequently, the LEDs based on n-ZnO NRs/p-GaN prepared from ZKH seed show an improvement in the yellow emission (approximate to 578nm) compared to that based on the ZK seed as deduced from the electroluminescence measurements. The improvement in the yellow EL emission on the ZKH LED probably attributed to the low presence of the non-radiative defect as deduced by light-output current (L-I) characteristics analysis.

  • 232.
    Alnoor, Hatim
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska fakulteten.
    Savoyant, Adrien
    Aix Marseille University, France.
    Liu, Xianjie
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten.
    Pozina, Galia
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Willander, Magnus
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Nur, Omer
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    An effective low-temperature solution synthesis of Co-doped [0001]-oriented ZnO nanorods2017Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 121, nr 21, artikkel-id 215102Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We demonstrate an efficient possibility to synthesize vertically aligned pure zinc oxide (ZnO) and Co-doped ZnO nanorods (NRs) using the low-temperature aqueous chemical synthesis (90 degrees C). Two different mixing methods of the synthesis solutions were investigated for the Co-doped samples. The synthesized samples were compared to pure ZnO NRs regarding the Co incorporation and crystal quality. Electron paramagnetic resonance (EPR) measurements confirmed the substitution of Co2+ inside the ZnO NRs, giving a highly anisotropic magnetic Co2+ signal. The substitution of Zn2+ by Co2+ was observed to be combined with a drastic reduction in the core-defect (CD) signal (g similar to 1.956) which is seen in pure ZnO NRs. As revealed by the cathodoluminescence (CL), the incorporation of Co causes a slight red-shift of the UV peak position combined with an enhancement in the intensity of the defect-related yellow-orange emission compared to pure ZnO NRs. Furthermore, the EPR and the CL measurements allow a possible model of the defect configuration in the samples. It is proposed that the as-synthesized pure ZnO NRs likely contain Zn interstitial (Zn-i(+)) as CDs and oxygen vacancy (V-O) or oxygen interstitial (O-i) as surface defects. As a result, Co was found to likely occupy the Zn-i(+), leading to the observed CDs reduction and hence enhancing the crystal quality. These results open the possibility of synthesis of highly crystalline quality ZnO NRs-based diluted magnetic semiconductors using the low-temperature aqueous chemical method. Published by AIP Publishing.

  • 233.
    Alodeh, Maha
    et al.
    Univ Luxembourg, Luxembourg.
    Spano, Danilo
    Univ Luxembourg, Luxembourg.
    Kalantari, Ashkan
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten. Univ Luxembourg, Luxembourg.
    Tsinos, Christos G.
    Univ Luxembourg, Luxembourg.
    Christopoulos, Dimitrios
    Newtec Satcom, Belgium.
    Chatzinotas, Symeon
    Univ Luxembourg, Luxembourg.
    Ottersten, Bjorn
    Univ Luxembourg, Luxembourg.
    Symbol-Level and Multicast Precoding for Multiuser Multiantenna Downlink: A State-of-the-Art, Classification, and Challenges2018Inngår i: IEEE Communications Surveys and Tutorials, ISSN 1553-877X, E-ISSN 1553-877X, Vol. 20, nr 3, s. 1733-1757Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Precoding has been conventionally considered as an effective means of mitigating or exploiting the interference in the multiantenna downlink channel, where multiple users are simultaneously served with independent information over the same channel resources. The early works in this area were focused on transmitting an individual information stream to each user by constructing weighted linear combinations of symbol blocks (codewords). However, more recent works have moved beyond this traditional view by: 1) transmitting distinct data streams to groups of users and 2) applying precoding on a symbol-persymbol basis. In this context, the current survey presents a unified view and classification of precoding techniques with respect to two main axes: 1) the switching rate of the precoding weights, leading to the classes of block-level and symbol-level precoding and 2) the number of users that each stream is addressed to, hence unicast, multicast, and broadcast precoding. Furthermore, the classified techniques are compared through representative numerical results to demonstrate their relative performance and uncover fundamental insights. Finally, a list of open theoretical problems and practical challenges are presented to inspire further research in this area.(1)

  • 234.
    Al-Omaishe, Allaa
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten. 860418-9061.
    The impacts of adopting large touch screens and tablets with access  to electronic healthcare records2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In the last decade modern information technology systems have been introduced to healthcare in order to improve it. The aim of this study is to present the impact of such information system’s adoption on patient safety and efficiency within healthcare.

    Interviews, observations along with literature study were conducted in order to study the impact of the adoption on patient safety and efficiency at hospital’s wards where a new information system is implemented.

    The conclusion of this study is that such information technology systems can improve patient safety. However it is believed that the information technology system can improve efficiency in some aspects such as the communication among medical care personnel while other aspects within efficiency can be achieved if some improvements are made. Moreover the ability to access Electronic Healthcare Records is considered to be important to improve the medical care, which can increase patient safety. 

  • 235.
    Alonso, Fabiola
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Deep brain stimulation: Patient-specific modelling, simulation and visualization of  DBS electric field2019Konferansepaper (Annet (populærvitenskap, debatt, mm))
  • 236.
    Alonso, Fabiola
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Models and Simulations of the Electric Field in Deep Brain Stimulation: Comparison of Lead Designs, Operating Modes and Tissue Conductivity2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Deep brain stimulation (DBS) is an established surgical therapy for movement disorders such as Parkinson’s disease (PD) and essential tremor (ET). A thin electrode is implanted in a predefined area of the brain with the use of stereotactic neurosurgery. In the last few years new DBS electrodes and systems have been developed with possibilities for using more parameters for control of the stimulation volume.

    In this thesis, simulations using the finite element method (FEM) have been developed and used for investigation of the electric field (EF) extension around different types of DBS lead designs (symmetric, steering) and stimulation modes (voltage, current). The electrode surrounding was represented either with a homogeneous model or a patient-specific model based on individual preoperative magnetic resonance imaging (MRI). The EF was visualized and compared for different lead designs and operating modes.

    In Paper I, the EF was quantitatively investigated around two lead designs (3389 and 6148) simulated to operate in voltage and current mode under acute and chronic time points following implantation.Simulations showed a major impact on the EF extension between postoperative time points which may explain the clinical decisions to change the stimulation amplitude weeks after implantation. In Paper II, the simulations were expanded to include two leads having steering function (6180, Surestim1) and patient-specific FEM simulations in the zona incerta. It was found that both the heterogeneity of the tissue and the operating mode, influence the EF distribution and that equivalent contact configurations of the leads result in similar EF. The steering mode presented larger volumes in current mode when using equivalent amplitudes. Simulations comparing DBS and intraoperative stimulation test using a microelectrode recording (MER) system (Paper III), showed that several parallel MER leads and the presence of the non-active DBS contacts influence the EF distribution and that the DBS EF volume can cover, but also extend to, other anatomical areas.

    Paper IV introduces a method for an objective exploitation of intraoperative stimulation test data in order to identify the optimal implant position in the thalamus of the chronic DBS lead. Patient-specific EF simulations were related to the anatomy with the help of brain atlases and the clinical effects which were quantified by accelerometers. The first results indicate that the good clinical effect in ET is due to several structures around the ventral intermediate nucleus of the thalamus.

  • 237.
    Alonso, Fabiola
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten.
    Hemm-Ode, Simone
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan. University of Applied Sciences and Arts Northwestern Switzerland.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten.
    Influence on Deep Brain Stimulation from Lead Design, Operating Mode and Tissue Impedance Changes – A Simulation Study2015Inngår i: Brain Disorders and Therapy, ISSN 2168-975X, Vol. 4, nr 3, artikkel-id 1000169Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: Deep brain stimulation (DBS) systems in current mode and new lead designs are recently available. To switch between DBS-systems remains complicated as clinicians may lose their reference for programming. Simulations can help increase the understanding.

    Objective: To quantitatively investigate the electric field (EF) around two lead designs simulated to operate in voltage and current mode under two time points following implantation.

    Methods: The finite element method was used to model Lead 3389 (Medtronic) and 6148 (St Jude) with homogenous surrounding grey matter and a peri-electrode space (PES) of 250 μm. The PES-impedance mimicked the acute (extracellular fluid) and chronic (fibrous tissue) time-point. Simulations at different amplitudes of voltage and current (n=236) were performed using two different contacts. Equivalent current amplitudes were extracted by matching the shape and maximum EF of the 0.2 V/mm isolevel.

    Results: The maximum EF extension at 0.2 V/mm varied between 2-5 mm with a small difference between the leads. In voltage mode EF increased about 1 mm at acute compared to the chronic PES. Current mode presented the opposite relationship. Equivalent EFs for lead 3389 at 3 V were found for 7 mA (acute) and 2.2 mA (chronic).

    Conclusions: Simulations showed a major impact on the electric field extension between postoperative time points. This may explain the clinical decisions to reprogram the amplitude weeks after implantation. Neither the EF extension nor intensity is considerably influenced by the lead design.

  • 238.
    Alonso, Fabiola
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten.
    Latorre, Malcolm
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten.
    Göransson, Nathanael
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten. Region Östergötland, Sinnescentrum, Neurokirurgiska kliniken US.
    Zsigmond, Peter
    Region Östergötland, Sinnescentrum, Neurokirurgiska kliniken US. Linköpings universitet, Institutionen för klinisk och experimentell medicin, Avdelningen för neuro- och inflammationsvetenskap. Linköpings universitet, Medicinska fakulteten.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten.
    Investigation into Deep Brain Stimulation Lead Designs: A Patient-Specific Simulation Study2016Inngår i: Brain Sciences, ISSN 2076-3425, E-ISSN 2076-3425, Vol. 6, nr 3, s. 1-16Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    New deep brain stimulation (DBS) electrode designs offer operation in voltage and current mode and capability to steer the electric field (EF). The aim of the study was to compare the EF distributions of four DBS leads at equivalent amplitudes (3 V and 3.4 mA). Finite element method (FEM) simulations (n = 38) around cylindrical contacts (leads 3389, 6148) or equivalent contact configurations (leads 6180, SureStim1) were performed using homogeneous and patient-specific (heterogeneous) brain tissue models. Steering effects of 6180 and SureStim1 were compared with symmetric stimulation fields. To make relative comparisons between simulations, an EF isolevel of 0.2 V/mm was chosen based on neuron model simulations (n = 832) applied before EF visualization and comparisons. The simulations show that the EF distribution is largely influenced by the heterogeneity of the tissue, and the operating mode. Equivalent contact configurations result in similar EF distributions. In steering configurations, larger EF volumes were achieved in current mode using equivalent amplitudes. The methodology was demonstrated in a patient-specific simulation around the zona incerta and a “virtual” ventral intermediate nucleus target. In conclusion, lead design differences are enhanced when using patient-specific tissue models and current stimulation mode.

  • 239.
    Alonso, Fabiola
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Vogel, Dorian
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten. University of Applied Sciences and Arts Northwestern Switzerland FHNW, 4132 Muttenz, Switzerland.
    Johansson, Johannes
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Hemm, Simone
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten. rthwestern Switzerland FHNW, 4132 Muttenz, Switzerland.
    Electric Field Comparison between Microelectrode Recording and Deep Brain Stimulation Systems: A Simulation Study2018Inngår i: Brain Sciences, ISSN 2076-3425, E-ISSN 2076-3425, Vol. 8, nr 2Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The success of deep brain stimulation (DBS) relies primarily on the localization of the implanted electrode. Its final position can be chosen based on the results of intraoperative microelectrode recording (MER) and stimulation tests. The optimal position often differs from the final one selected for chronic stimulation with the DBS electrode. The aim of the study was to investigate, using finite element method (FEM) modeling and simulations, whether lead design, electrical setup, and operating modes induce differences in electric field (EF) distribution and in consequence, the clinical outcome. Finite element models of a MER system and a chronic DBS lead were developed. Simulations of the EF were performed for homogenous and patient-specific brain models to evaluate the influence of grounding (guide tube vs. stimulator case), parallel MER leads, and non-active DBS contacts. Results showed that the EF is deformed depending on the distance between the guide tube and stimulating contact. Several parallel MER leads and the presence of the non-active DBS contacts influence the EF distribution. The DBS EF volume can cover the intraoperatively produced EF, but can also extend to other anatomical areas. In conclusion, EF deformations between stimulation tests and DBS should be taken into consideration as they can alter the clinical outcome

  • 240.
    Alonso, Fabiola
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Vogel, Dorian
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Hemm-Ode, Simone
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten. Institute for Medical and Analytical Technologies and Department of Biomedical Engineering, University of Applied Sciences and Art Northwestern Switzerland.
    Comparison between intraoperative and chronic and deep brain stimulation2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    INTRODUCTION

    The success of the deep brain stimulation (DBS) therapy relies primarily in the localization of the implanted electrode, implying the need of utmost accuracy in the targeting process. Intraoperative microelectrode recording and stimulation tests are a common procedure before implanting the permanent DBS lead to determine the optimal position with a large therapeutic window where side effects are avoided and the best improvement of the symptoms is achieved. Differences in dimensions and operating modes exist between the exploration and the permanent DBS electrode which might lead to different stimulation fields, even when ideal placement is achieved. The aim of this investigation is to compare the electric field (EF) distribution around the intraoperative and the chronic electrode, assuming that both have exactly the same position.

    METHODS

    3D models of the intraoperative exploration electrode and the chronically implanted DBS lead 3389 (Medtronic Inc., USA) were developed using COMSOL 5.2 (COMSOL AB, Sweden). Patient-specific MR images were used to determine the conductive medium around the electrode. The exploration electrode and the first DBS contact were set to current and voltage respectively (0.2mA(V) - 3 mA(V) in 0.1 mA(V) steps). The intraoperative model included the grounded guide tube used to introduce the exploration electrode; for the chronic DBS model, the outer boundaries were grounded and the inactive contacts were set to floating potential considering a monopolar configuration. The localization of the exploration and the chronic electrode was set according to the planned trajectory. The EF was visualized and compared in terms of volume and extension using a fixed isocontour of 0.2 V/mm.

    RESULTS

    The EF distribution simulated for the exploration electrode showed the influence of the parallel trajectory and the grounded guide tube. For an amplitude of e.g. 2 mA/2 V, the EF extension of the intraoperative was 0.6 mm larger than the chronic electrode at the target level; the corresponding difference in volume was 76.1 mm3.

    CONCLUSION

    Differences in the EF shape between the exploration and the chronic DBS electrode have been observed using patient-specific models. The larger EF extension obtained for the exploration electrode responds to its higher impedance and the use of current controlled stimulation. The presence of EF around the guide tube and the influence of the parallel trajectory require further experimental and clinical evaluation.

  • 241.
    Alonso, Fabiola
    et al.
    Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten.
    Electric Field Comparison of Deep Brain Stimulation Lead Designs - a Stimulation Study2016Konferansepaper (Fagfellevurdert)
  • 242.
    Alonso, Fabiola
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten.
    Latorre, Malcolm
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten.
    Comparison of Three Deep Brain Stimulation Lead Designs under Voltage and Current Modes2015Inngår i: WORLD CONGRESS ON MEDICAL PHYSICS AND BIOMEDICAL ENGINEERING, 2015, VOLS 1 AND 2 / [ed] David A. Jaffray, Springer, 2015, Vol. 51, s. 1196-1199Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Since the introduction of deep brain stimulation (DBS) the technique has been dominated by Medtronic sys-tems. In recent years, new DBS systems have become available for patients, and some are in clinical trials. The present study aims to evaluate three DBS leads operated in either voltage or current mode. 3D finite element method (FEM) models were built in combination with a neuron model for this purpose. The axon diameter was set to D = 5 μm and simulations performed in both voltage (0.5-5 V) and current (0.5-5 mA) mode. The evaluation was achieved based on the distance from the lead for neural activation and the electric field (EF) extension at 0.1 V/mm. The results showed that the neural activation distance agrees well between the leads with an activation distance dif-ference less than 0.5 mm. The shape of the field at the 0.1 V/mm isopotential surface in 3D is mostly spherical in shape around the activated section of the steering lead.

  • 243.
    Alonso, Fabiola
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten.
    Latorre, Malcolm
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten.
    Neural Activation Compared to Electric Field Extension of Three DBS Lead Designs2015Konferansepaper (Fagfellevurdert)
    Abstract [en]

    SINCE the introduction of deep brain stimulation (DBS) about 20 years ago, the stimulation technique has been dominated by Medtronic DBS-system setup. In recent years, new DBS systems have become available, of which some are in clinical trials or available to patients [1]. In the present study three different lead designs are investigated via computer simulation:

    Medtronic 3389, St. Jude 6148 and Sapiens SureStim. The aim was to compare the neural activation distance and the electric field (EF) maximum spatial extension for each lead.

    A 3D finite element method model was built using COMSOL Multiphysics 4.4a (COMSOL AB, Stockholm, Sweden) to simulate the electric potential around the DBS lead. Brain tissue was modelled as a homogeneous volume of grey matter (electric conductivity of 0.09 S/m). The electrode-tissue interface was modelled with a 250μm thick peri-electrode space mimicking the fibrous tissue which covers the lead at the chronic stimulation stage (σ = 0.06S/m, equivalent to white matter electric conductivity). The stimulation amplitude was set to 1V in monopolar configuration using C1 electrode or equivalent in all cases. Each simulated electric potential distribution was exported to MatLab (The MathWorks, USA) and used as input to a cable neuron simulation.

    An axon cable model with 21 nodes based on the concept by Åström et al., [2] was set up in MatLab and combined with the exported field distributions. The model considered a 5 μm thick neuron, a pulse width of 60 μs and a drive potential ranging from 0.5 V to 5 V in 0.5 V steps.

    The SureStim lead results showed a shorter neural activation distance and EF extension. The distance to the isolevel of 0.2 V/mm is close to the neural activation distance at each stimulation amplitude, and we conclude that the electric field is a suitable predictor to visualize the stimulated regions.

  • 244.
    Alonso, Fabiola
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Zsigmond, Peter
    Region Östergötland, Centrum för kirurgi, ortopedi och cancervård, Kirurgiska kliniken US. Linköpings universitet, Institutionen för klinisk och experimentell medicin, Avdelningen för neuro- och inflammationsvetenskap. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Sinnescentrum, Neurokirurgiska kliniken US.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Influence of Virchow-Robin spaces in the Electric Field Distribution in Subthalamic Nucleus Deep Brain Stimulation2019Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Objectives: Previous investigations have shown the appearance of cysts i.e. Virchow-Robin spaces (VR) in the basal ganglia and their relationship with parkinsonian symptoms [1-3]. Simulations [4]using the finite element method (FEM) suggests that VR affects the electric field around deep brain stimulation (DBS) electrodes. The aim of the study was to evaluate how the electric field is modified by the presence of cysts in the STN. Methods: The effect of cysts on the electric field around the DBS lead placed in the STN was evaluated using FEM. 3D patient-specific brain models were built with COMSOL 5.2 (COMSOL AB, Sweden) and an in-house developed software [5] to convert a T2 weighted MRI of Parkinsonian patients (ethics approval no: 2012/434-3) into electrical conductivity matrix readable by FEM software. VR was classified as CSF [6]assigning a high electrical conductivity (2.0 S/m). The stimulation amplitudes were set to the clinically programmed values. Depending on the lead used, the stimulation was set to voltage control (3389) or current control (6180, ring mode). The coordinates corresponding to the lowest (first) electrode and the third higher up in the lead, taken from the postoperative CT electrode artefact, were used to localize the leads in the brain model [7]. The electric field was visualized with a 0.2V/mm isosurface. Results: Simulations showed that the electric field distribution is affected by the cysts. The higher conductivity at these regions in the vicinity of the electrode redistributes the electric field pushing it away from the cyst. The same effect occurs regardless of the operating mode or the lead design as long as the directional lead is configured in ring mode. Conclusions: The use of patient-specific models has shown the importance of considering nuances of the patients’ anatomy in the STN. This information can be used to determine the stimulation parameter and to support the analysis of side effects induced by the stimulation. The potential advantage of directional leads can also be assessed by including in the model patient-specific data.

  • 245.
    Alonso-Magdalena, Paloma
    et al.
    Departamento de Biología Aplicada, Universidad Miguel Hernández.
    Rivera, Fransisco J.
    Laboratory of Stem Cells and Neurogeneration, Institute of Anatomy, Histology and Pathology, Facultu of Medicine and Center for INterdiciplinary Studies on the Nervous System (CISNe), Universitad Austral de Chile; Institute for Molecular Regenerative MEdicine and Spinal Cord Injury and Tissue Regeneration Center Salzburg (SCI-TReCS), Paracelsus University, Salzburg, Austira.
    Guerrero Bosagna, Carlos
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biologi. Linköpings universitet, Tekniska fakulteten.
    Bisphenol-A and metabolic diseases: epigenetic developmental and transgenerational basis2016Inngår i: Environmental Epigenetics, ISSN 2058-5888, Vol. 2, nr 3, s. 1-10Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Exposure to environmental toxicants is now accepted as a factor contributing to the increasing incidence of obesity and metabolic diseases around the world. Such environmental compounds are known as ‘obesogens’. Among them, bisphenol-A (BPA) is the most widespread and ubiquitous compound affecting humans and animals. Laboratory animal work has provided conclusive evidence that early-life exposure to BPA is particularly effective in predisposing individuals to weight gain. Embryonic exposure to BPA is reported to generate metabolic disturbances later in life, such as obesity and diabetes. When BPA administration is combined with a high-fat diet, there is an exacerbation in the development of metabolic disorders. Remarkably, upon BPA exposure of gestating females, metabolic disturbances have been found both in the offspring and later in life in the mothers themselves. When considering the metabolic effects generated by an early developmental exposure to BPA, one of the questions that arises is the role of precursor cells in the etiology of metabolic disorders. Current evidence shows that BPA and other endocrine disruptors have the ability to alter fat tissue development and growth by affecting the capacity to generate functional adipocytes, as well as their rate of differentiation to specific cell types. Epigenetic mechanisms seem to be involved in the BPA-induced effects related to obesity, as they have been described in both in vitro and in vivo models. Moreover, recent reports also show that developmental exposure to BPA generates abnormalities that can be transmitted to future generations, in a process called as transgenerational epigenetic inheritance.

  • 246.
    Alpat, B.
    et al.
    Ist Nazl Fis Nucl, Italy; Sabanci Univ, Turkey.
    Gulgun, M.A.
    Sabanci Univ, Turkey.
    Corapcioglu, G.
    Sabanci Univ, Turkey.
    Yildizhan Özyar, Melike
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Di Lazzaro, P.
    ENEA, Italy.
    Murra, D.
    ENEA, Italy.
    Kaplanoglu, T.
    Maprad Srl, Italy.
    Postolache, V
    Maprad Srl, Italy.
    Mengali, S.
    Consorzio CREO, Italy.
    Simeoni, M.
    Consorzio CREO, Italy.
    Urbani, A.
    Consorzio CREO, Italy.
    Testing of substrates for flexible optical solar reflectors: irradiations of nano-hybrid coatings of polyimide films with 20 keV electrons and with 200-400 nm ultraviolet radiation2019Inngår i: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 14, artikkel-id T06003Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the frame of a project aimed at developing a new type of optical solar reflectors we present the scientific and technological issues addressed during irradiations of nano-hybrid coatings on polyimide films by using 20 keV electron beam from a modified use of Scanning Electron Microscope (SEM) and with ultraviolet (UV) dose equal to 300 space-equivalent Sun hours. Details of a new approach to use SEM for low energy electron irradiations and of a new UV irradiation setup are given.

  • 247.
    Al-Sader, Mohamed
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Gaze-driven interaction in video games2018Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The introduction of input devices with natural user interfaces in gaming hardware has changed the way we interact with games. Hardware with motion-sensing and gesture recognizing capabilities remove the constraint of interacting with games through typical traditional devices like mouse-keyboard and gamepads. This changes the way we approach games and how the game communicates back to us as the player opening new levels of interactivity. This thesis covers how eye tracker technology can be used to affect rendering effects in games.

  • 248.
    AlSalhi, M S.
    et al.
    King Saud University, Saudi Arabia .
    Atif, M
    King Saud University, Saudi Arabia; National Institute of Laser and Optronics, Nilore, Islamabad, Pakistan.
    Ansari, A A.
    King Saud University, Saudi Arabia .
    Khun, Kimleang
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Hussain Ibupoto, Zafar
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Willander, Magnus
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska högskolan. King Saud University, Riyadh, Saudi Arabia.
    Growth and characterization of ZnO nanowires for optical applications2013Inngår i: Laser physics, ISSN 1054-660X, E-ISSN 1555-6611, Vol. 23, nr 6, artikkel-id 065602Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present work, cerium oxide CeO2 nanoparticles were synthesized by the sol-gel method and used for the growth of ZnO nanorods. The synthesized nanoparticles were studied by x-ray diffraction (XRD) and Raman spectroscopic techniques. Furthermore, these nanoparticles were used as the seed layer for the growth of ZnO nanorods by following the hydrothermal growth method. The structural study of ZnO nanorods was carried out by means of field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM) and XRD techniques. This study demonstrated that the grown ZnO nanorods are well aligned, uniform, of good crystal quality and have diameters of less than 200 nm. Energy dispersive x-ray (EDX) analysis revealed that the ZnO nanorods are composed only of zinc, cerium as the seed atom, and oxygen atoms, with no other impurities in the grown nanorods. Moreover, a photoluminescence (PL) approach was applied for the optical characterization, and it was observed that the near-band-edge (NBE) emission was the same as that of the zinc acetate seed layer, however the green and orange/red emission peaks were slightly raised due to possibly higher levels of defects in the cerium oxide seeded ZnO nanorods. This study provides an alternative approach for the controlled synthesis of ZnO nanorods using cerium oxide nanoparticles as the seed nucleation layer, improving both the morphology of the nanorods and the performance of devices based upon them.

  • 249.
    Al-Salihi, Hayder
    et al.
    The Department of Informatics, King’s College London, UK.
    Van Chien, Trinh
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Le, Tuan Anh
    The Department of Design Engineering and Mathematics, Middlesex University, London, UK.
    Nakhai, Mohammad Reza
    The Department of Informatics, King’s College London, London, UK.
    A Successive Optimization Approach to Pilot Design for Multi-Cell Massive MIMO Systems2018Inngår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 22, nr 5, s. 1086-1089Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this letter, we introduce a novel pilot designapproach that minimizes the total mean square errors of theminimum mean square error estimators of all base stations (BSs)subject to the transmit power constraints of individual users inthe network, while tackling the pilot contamination in multicellmassive MIMO systems. First, we decompose the originalnon-convex problem into distributed optimization sub-problemsat individual BSs, where each BS can optimize its own pilotsignals given the knowledge of pilot signals from the remainingBSs. We then introduce a successive optimization approach totransform each optimization sub-problem into a linear matrixinequality form, which is convex and can be solved by availableoptimization packages. Simulation results confirm the fast convergenceof the proposed approach and prevails a benchmarkscheme in terms of providing higher accuracy.

  • 250.
    Alsegård, Adam
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Interactive out-of-core rendering and filtering of one billion stars measured by the ESA Gaia mission2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The purpose of this thesis was to visualize the 1.7 billion stars released by the European Space Agency, as the second data release (DR2) of their Gaia mission, in the open source software OpenSpace with interactive framerates and also to be able to filter the data in real-time. An additional implementation goal was to streamline the data pipeline so that astronomers could use OpenSpace as a visualization tool in their research.

    An out-of-core rendering technique has been implemented where the data is streamed from disk during runtime. To be able to stream the data it first has to be read, sorted into an octree structure and then stored as binary files in a preprocess. The results of this report show that the entire DR2 dataset can be read from multiple files in a folder and stored as binary values in about seven hours. This step determines what values the user will be able to filter by and only has to be done once for a specific dataset. Then an octree can be created in about 5 to 60 minutes where the user can define if the stars should be filtered by any of the previously stored values. Only values used in the rendering will be stored in the octree. If the created octree can fit in the computer’s working memory then the entire octree will be loaded asynchronously on start-up otherwise only a binary file with the structure of the octree will be read during start-up while the actual star data will be streamed from disk during runtime.

    When the data have been loaded it is streamed to the GPU. Only stars that are visible are uploaded and the application also keeps track of which nodes that already have been uploaded to eliminate redundant updates. The inner nodes of the octree store the brightest stars in all its descendants as a level-of-detail cache that can be used when the nodes are small enough in screen space.

    The previous star rendering in OpenSpace has been improved by dividing the rendering phase into two passes. The first pass renders into a framebuffer object while the second pass then performs a tonemapping of the values. The rendering can be done either with billboard instancing or point splatting. The latter is generally the faster alternative. The user can also switch between using VBOs or SSBOs when updating the buffers. The latter is faster but requires OpenGL 4.3, which Apple products do not currently support.

    The rendering runs with interactive framerates for both flat and curved screen, such as domes/planetariums. The user can also switch dataset during render as well as render technique, buffer objects, color settings and many other properties. It is also possible to turn time on and see the stars move with their calculated space velocity, or transverse velocity if the star lacks radial velocity measurements. The calculations omits the gravitational rotation. The purpose of the thesis has been fulfilled as it is possible to fly through the entire DR2 dataset on a moderate desktop computer and filter the data in real-time. However, the main contribution of the project may be that the ground work has been laid in OpenSpace for astronomers to actually use it as a tool when visualizing their own datasets and also for continuing to explore the coming Gaia releases.

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