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  • 46501.
    Velupillai, Sumithra
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Mowery, Danielle L.
    South, Brett R.
    Kvist, Maria
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences. Karolinska Institutet, Sweden.
    Dalianis, Hercules
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Recent Advances in Clinical Natural Language Processing in Support of Semantic Analysis2015In: IMIA Yearbook of Medical Informatics, ISSN 0943-4747, Vol. 10, no 1, p. 183-193Article in journal (Refereed)
    Abstract [en]

    Objectives

    We present a review of recent advances in clinical Natural Language Processing (NLP), with a focus on semantic analysis and key subtasks that support such analysis.

    Methods

    We conducted a literature review of clinical NLP research from 2008 to 2014, emphasizing recent publications (2012-2014), based on PubMed and ACL proceedings as well as relevant referenced publications from the included papers.

    Results

    Significant articles published within this time-span were included and are discussed from the perspective of semantic analysis. Three key clinical NLP subtasks that enable such analysis were identified: 1) developing more efficient methods for corpus creation (annotation and de-identification), 2) generating building blocks for extracting meaning (morphological, syntactic, and semantic subtasks), and 3) leveraging NLP for clinical utility (NLP applications and infrastructure for clinical use cases). Finally, we provide a reflection upon most recent developments and potential areas of future NLP development and applications.

    Conclusions

    There has been an increase of advances within key NLP subtasks that support semantic analysis. Performance of NLP semantic analysis is, in many cases, close to that of agreement between humans. The creation and release of corpora annotated with complex semantic information models has greatly supported the development of new tools and approaches. Research on non-English languages is continuously growing. NLP methods have sometimes been successfully employed in real-world clinical tasks. However, there is still a gap between the development of advanced resources and their utilization in clinical settings. A plethora of new clinical use cases are emerging due to established health care initiatives and additional patient-generated sources through the extensive use of social media and other devices.

  • 46502.
    Velupillai, Sumithra
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Skeppstedt, Maria
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Kvist, Maria
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences. Karolinska Institutet, Sweden.
    Mowery, Danielle
    Chapman, Brian E.
    Dalianis, Hercules
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Chapman, Wendy W.
    Cue-based assertion classification for Swedish clinical text-Developing a lexicon for pyConTextSwe2014In: Artificial Intelligence in Medicine, ISSN 0933-3657, E-ISSN 1873-2860, Vol. 61, no 3, p. 137-144Article in journal (Refereed)
    Abstract [en]

    Objective: The ability of a cue-based system to accurately assert whether a disorder is affirmed, negated, or uncertain is dependent, in part, on its cue lexicon. In this paper, we continue our study of porting an assertion system (pyConTextNLP) from English to Swedish (pyConTextSwe) by creating an optimized assertion lexicon for clinical Swedish. Methods and material: We integrated cues from four external lexicons, along with generated inflections and combinations. We used subsets of a clinical corpus in Swedish. We applied four assertion classes (definite existence, probable existence, probable negated existence and definite negated existence) and two binary classes (existence yes/no and uncertainty yes/no) to pyConTextSwe. We compared pyConTextSwe's performance with and without the added cues on a development set, and improved the lexicon further after an error analysis. On a separate evaluation set, we calculated the system's final performance. Results: Following integration steps, we added 454 cues to pyConTextSwe. The optimized lexicon developed after an error analysis resulted in statistically significant improvements on the development set (83%F-score, overall). The system's final F-scores on an evaluation set were 81% (overall). For the individual assertion classes, F-score results were 88% (definite existence), 81% (probable existence), 55% (probable negated existence), and 63% (definite negated existence). For the binary classifications existence yes/no and uncertainty yes/no, final system performance was 97%/87% and 78%/86% F-score, respectively. Conclusions: We have successfully ported pyConTextNLP to Swedish (pyConTextSwe). We have created an extensive and useful assertion lexicon for Swedish clinical text, which could form a valuable resource for similar studies, and which is publicly available.

  • 46503.
    Velupillai, Sumithra
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Skeppstedt, Maria
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Kvist, Maria
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences. Karolinska University Hospital.
    Mowery, Danielle
    Chapman, Brian E.
    Dalianis, Hercules
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Chapman, Wendy W.
    Porting a Rule-based Assertion Classifier for Clinical Text from English to Swedish2013In: Proceedings of the 4th International Louhi Workshop on Health Document Text Mining and Information Analysis - Louhi 2013 / [ed] Hanna Suominen, NICTA, Australia's ICT Research Centre of Excellence , 2013Conference paper (Refereed)
    Abstract [en]

    An existing rule-based assertion classier is ported from En- glish to Swedish: pyConTextSwe. Evaluation on Swedish clinical texts shows that the English lexical resources are useful, but that there are assertion cues not obtainable in existing resources. Iterative error cor- rection of cue lexicons improves results for the ported classier. Overall nal results are 82% F-score on a development set and 74% on a test set.

  • 46504.
    Velupillai, Sumithra
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Weegar, Rebecka
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Kvist, Maria
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Temporal Annotation of Swedish Intensive Care Notes2016Conference paper (Refereed)
    Abstract [en]

    We describe the creation of a corpus of Swedish intensive care unit (ICU) notes annotated for temporal expressions. Clinical notes from an ICU in Stockholm, Sweden were used. The HeidelTime system was adapted to develop Swedish clinical time expression (TIMEX3) resources. Overall micro-average Inter-Annotator Agreement is high (86% F1). We have created Swedish lexical resources with clinically specific time expressions that will be useful for the development of a Swedish clinical text temporal reasoning system.

  • 46505.
    Vemmenby, Mikael
    et al.
    University of Kalmar, School of Communication and Design.
    Helenius, Jessica
    University of Kalmar, School of Communication and Design.
    Användning av virtuella mötesplatser2009Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Internet is used today as a traditional medium for information exchange and social interaction. One of these is virtual meeting places where people meet and exchange information, socialize and exchange knowledge with each other. The group has chosen to examine the factors affecting the use of web forums, one of the virtual meeting places that exist on the Internet today. And look at how people use the web forum today in the current situation and how to design a web forum.

    A survey was conducted to find out how people look at web forums today, 80 people participated, and they got to talk about what they think about different web forums regarding how and why the use these them. Guidelines on how a web forum should be designed were also developed. An interview was also carried out to a specific audience to see if there were special needs and interests that they had, so that we could take that into account in the development of the guidelines that are to be used in the design for this web forum. The group carried out a user tests on a mockup designed to investigate how people would respond and use the web forums of different age groups.

    The results showed that many users of web forums today are different between users, depending on gender and age. The use of various web forums depends on that they have different needs and interests. This dose so the layout of the web forum must be directed so as to be adapted for any specific audience. Mainly people used web forums as an information source where you can find answers and ask questions to others. Two factors must be fulfilled for a page to be able to grow, and that is trust and credibility. This can be fulfilled by its members if they can create an identity for them self in the virtual meeting place. It is also important for lurkers on a virtual meeting place that they show commitment, support and encourage members to be active participant. The lurker’s role is an important one when the site goes throw its state of maturity and growth.

     

    Keywords: Web Forum, virtual meeting places, user study.

  • 46506.
    Vemulapalli, Revanth
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Mada, Ravi Kumar
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Performance of Disk I/O operations during the Live Migration of a Virtual Machine over WAN2014Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Virtualization is a technique that allows several virtual machines (VMs) to run on a single physical machine (PM) by adding a virtualization layer above the physical host's hardware. Many virtualization products allow a VM be migrated from one PM to other PM without interrupting the services running on the VM. This is called live migration and offers many potential advantages like server consolidation, reduced energy consumption, disaster recovery, reliability, and efficient workflows such as "Follow-the-Sun''. At present, the advantages of VM live migration are limited to Local Area Networks (LANs) as migrations over Wide Area Networks (WAN) offer lower performance due to IP address changes in the migrating VMs and also due to large network latency. For scenarios which require migrations, shared storage solutions like iSCSI (block storage) and NFS (file storage) are used to store the VM's disk to avoid the high latencies associated with disk state migration when private storage is used. When using iSCSI or NFS, all the disk I/O operations generated by the VM are encapsulated and carried to the shared storage over the IP network. The underlying latency in WAN will effect the performance of application requesting the disk I/O from the VM. In this thesis our objective was to determine the performance of shared and private storage when VMs are live migrated in networks with high latency, with WANs as the typical case. To achieve this objective, we used Iometer, a disk benchmarking tool, to investigate the I/O performance of iSCSI and NFS when used as shared storage for live migrating Xen VMs over emulated WANs. In addition, we have configured the Distributed Replicated Block Device (DRBD) system to provide private storage for our VMs through incremental disk replication. Then, we have studied the I/O performance of the private storage solution in the context of live disk migration and compared it to the performance of shared storage based on iSCSI and NFS. The results from our testbed indicate that the DRBD-based solution should be preferred over the considered shared storage solutions because DRBD consumed less network bandwidth and has a lower maximum I/O response time.

  • 46507. Venica, Stefano
    et al.
    Driussi, Francesco
    Vaziri, Sam
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Palestri, Pierpaolo
    Selmi, Luca
    Graphene Base Transistors With Bilayer Tunnel Barriers: Performance Evaluation and Design Guidelines2017In: IEEE Transactions on Electron Devices, ISSN 0018-9383, E-ISSN 1557-9646, Vol. 64, no 2, p. 593-598Article in journal (Refereed)
    Abstract [en]

    Graphene-based capacitors and Graphene base transistors (GBTs) featuring innovative engineered tunnel barriers are characterized in DC and the data are thoroughly analyzed by means of an electrical model and a Monte Carlo transport simulator. Followingmodel calibra-tion on experiments, we then propose strategies to improve the DC common-base current gain and the cutoff frequency of GBTs. The DC and RF performance of optimized GBT structures based on realistic technology data are analyzed in detail to highlight advantages and potential limits of this device concept.

  • 46508.
    Venigalla, Thejaswi
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Akkapaka, Raj Kiran
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Teletraffic Models for Mobile Network Connectivity.2013Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    We are in an era marked by tremendous global growth in mobile traffic and subscribers due to change in the mobile communication technology from second generation to third and fourth generations. Especially usage of packet-data applications has recorded remarkable growth. The need for mobile communication networks capable of providing an ever increasing spectrum of services calls for efficient techniques for the analysis, monitoring and design of networks. To meet the ever increasing demands of the user and to ensure on reliability and affordability, system models that can capture the characteristics of actual network load and yield acceptable precise predictions of performance in a reasonable amount of time must be developed. This can be achieved using teletraffic models as they capture the behaviour of system through interpret-able functions and parameters. Past years have seen extremely numerous teletraffic models for different purposes. Nevertheless there is no model that provides a proper frame work to analyse the mobile networks. This report attempts to provide a frame work to analyse the mobile traffic and based on the analysis we design teletraffic models that represent the realistic mobile networks and calculate the buffer under-flow probability.

  • 46509.
    Venson, José Eduardo
    et al.
    Instituto de Informática, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil.
    Bevilacqua, Fernando
    University of Skövde, School of Informatics. University of Skövde, The Informatics Research Centre. Universidade Federal da Fronteira Sul, Chapecó, Brazil.
    Berni, Jean
    Animati Computação Aplicada à Saúde, Santa Maria, Brazi.
    Onuki, Fabio
    Medvia Diagnóstico, Porto Alegre, Brazi.
    Maciel, Anderson
    Instituto de Informática, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil.
    Diagnostic concordance between mobile interfaces and conventional workstations for emergency imaging assessment2018In: International Journal of Medical Informatics, ISSN 1386-5056, E-ISSN 1872-8243, Vol. 113, p. 1-8Article in journal (Refereed)
    Abstract [en]

    Introduction

    Mobile devices and software are now available with sufficient computing power, speed and complexity to allow for real-time interpretation of radiology exams. In this paper, we perform a multivariable user study that investigates concordance of image-based diagnoses provided using mobile devices on the one hand and conventional workstations on the other hand.

    Methods

    We performed a between-subjects task-analysis using CT, MRI and radiography datasets. Moreover, we investigated the adequacy of the screen size, image quality, usability and the availability of the tools necessary for the analysis. Radiologists, members of several teams, participated in the experiment under real work conditions. A total of 64 studies with 93 main diagnoses were analyzed.

    Results

    Our results showed that 56 cases were classified with complete concordance (87.69%), 5 cases with almost complete concordance (7.69%) and 1 case (1.56%) with partial concordance. Only 2 studies presented discordance between the reports (3.07%). The main reason to explain the cause of those disagreements was the lack of multiplanar reconstruction tool in the mobile viewer. Screen size and image quality had no direct impact on the mobile diagnosis process.

    Conclusion

    We concluded that for images from emergency modalities, a mobile interface provides accurate interpretation and swift response, which could benefit patients' healthcare.

  • 46510.
    Ventocilla, Elio
    et al.
    University of Skövde, School of Informatics. University of Skövde, The Informatics Research Centre.
    Riveiro, Maria
    University of Skövde, School of Informatics. University of Skövde, The Informatics Research Centre.
    Visual Analytics Solutions as 'off-the-shelf' Libraries2017In: 2017 21st International Conference Information Visualisation (IV): Computer Graphics, Imaging and Visualisation. Biomedical Visualization, Visualisation on Built and Rural Environments & Geometric Modelling and Imaging, IEETeL2017 / [ed] Ebad Banissi, Mark W. McK. Bannatyne, Fatma Bouali, Nuno Miguel Soares Datia, Georges Grinstein, Dennis Groth, Weidong Huang, Malinka Ivanova, Sarah Kenderdine, Minoru Nakayama, Joao Moura Pires, Muhammad Sarfraz, Marco Temperini, Anna Ursyn, Gilles Venturini, Theodor G. Wyeld, Jian J. Zhang, IEEE Computer Society, 2017, p. 281-287Conference paper (Refereed)
    Abstract [en]

    Visual Analytics has brought forward many solutions to different tasks such as exploring topics, understanding user and customer behavior, comparing genomes, or detecting anomalies. Many of these solutions, if not most, are standalone applications with technological contributions which cannot be easily taken for: reuse in other domains, further improvement, benchmarking, or integration and deployment alongside other solutions. The latter can prove specially helpful for exploratory data analysis. This often leads researchers to re-implement solutions and thus to a suboptimal use of skills and resources. This paper discusses further the lack of off-the-shelf libraries for Visual Analytics, and proposes the creation of pluggable libraries on top of existing technologies such as Spark and Zeppelin. We provide an illustrative example of a pluggable, Visual Analytics library using these technologies.

  • 46511.
    Ventura, Håkan
    Linköping University, Department of Electrical Engineering.
    Diameter: Next generations AAA protocol2001Independent thesis Basic level (professional degree)Student thesis
    Abstract [en]

    The need for AAA protocols in the world are increasing and todays most common protocols RADIUS and TACACS+, cannot cope with the fast advances in fields benefiting from the use of AAA protocols. This is why IETF has developed the protocol Diameter as a next generations AAA protocol. The objective of this thesis is to account for the work conducted with Diameter as well as to determine if it is going to become the major AAA protocol of the next generation. In this thesis, I describe what Diameter is, its close integration with the Mobile IP protocol and its other uses. As Diameter is based on RADIUS an introduction to AAA and RADIUS is given in order to comprehend where we are today and where we are going as well as to why. I also compare today’s protocols (RADIUS, TACACS+, Kerberos and COPS) against the next generations AAA protocol Diameter. From this comparison, the Mobile IP integration capabilities and an analysis of the support of the Diameter protocol I have come to the conclusion that Diameter is going to become the major AAA protocol of the next generation.

  • 46512.
    Vera, Alejandro
    KTH, School of Information and Communication Technology (ICT).
    Stream Processing and Deep Learning for Localization in Cellular Networks2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Nowadays, telecommunication operators have access to a vast amount of mobile devices that could be tracked. The location information of all their subscribers could be aggregated and used to extract useful insights through population analytics. However, currently operators are only capable of performing location on-demand for a small amount a devices. The reason for such limitation is the use of Location Servers that implement analytical location methods. Most of these methods are very demanding for the network because they require some kind of synchronization or orchestration between the network components. Furthermore, for many of those location methods, the accuracy of predictions is not satisfactory due to the noise added by the environment and measurements.

    This thesis proposes a solution capable of performing location for all the devices in the operator’s network while improving the accuracy of predictions. It consists in using a passive listener for network events (GPEH in this implementation, but could be other) to gather the required data for location and use it as input for a neural network (better suited for handling noisy data) that predicts the location. It has been designed as a modular stream processing architecture that allows to easily implement new data sources and is highly scalable.

    Results show that this new approach outperforms the predictions of the operator’s Location Server having a 56.86% better accuracy (mean error distance). Furthermore, thanks to its scalable design and the optimizations done, the system implemented in production is capable of processing in a small cluster the 15 minute events files produced in the whole 3G network of the operator in just 12 minutes, which means it could also be used with real time data sources.

  • 46513.
    Vera Contreras, Vanessa
    et al.
    Jönköping University, School of Engineering, JTH, Computer Science and Informatics.
    Carlsson, Rebecca
    Jönköping University, School of Engineering, JTH, Computer Science and Informatics.
    Följ strömmen eller drunkna: En kvalitativ intervjustudie av hur livsstilsbudskap på Facebook påverkar unga kvinnor2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This study is about whether lifestyle message on Facebook affects young women. The purpose has been to reinforce previous research that shows that people are influenced by advertising. Moreover, has been to the depths to find out how this contributes to the young women affected by lifestyle message.

    In order to fulfill the purpose of the study and answer the question empirical data has been collected by using Small-N-studies. It included interviews with six participating young women, where it was taken out how they experienced advertising on Facebook, thoughts about the norms and interaction with Facebook. It was also prepared some basis for the interviews and it was to obtain an overview of the advertising that appeared on the respondents news feeds on Facebook.

    The findings of the study on the basis of theory and empirical evidence shows that lifestyle messages on Facebook affects young women. However, it is difficult to measure how and to what extent lifestyle message on Facebook influence because there are so many other factors that affect people. But one can say that this is an alternate reality for young people today and that they spend much of their time there. Businesses and friends are the ones who create the content on Facebook and that they can interact with each other is a factor that makes this a channel where advertising affect some extra.

    The limitations of the study was the relationship to the respondents because it can interfere with the distancing. It would have been desirable to do more of in-depth interviews to analyze more data and enhance the study even more, but because of time and lack of resources it was not possible. It would also have been desirable to study more in depth in the various theories that have been raised in the study, and also spend more time on the search for information within digital media and young people's use of Facebook, because it was difficult to find relevant research and theories. 

  • 46514.
    Vera, Xavier
    Mälardalen University, Department of Computer Science and Electronics.
    Cache and Compiler Interaction: How to analyze, optimize and time cache behavior2003Doctoral thesis, monograph (Other scientific)
  • 46515.
    Verenzuela, Daniel
    KTH, School of Information and Communication Technology (ICT).
    Scalability of Device-to-Device Communications in Cellular Networks2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In current cellular networks the demand of traffic is rapidly increasing and new techniques need to be developed to accommodate future service requirements. Device-to-Device (D2D) communications is one technique that has been proposed to improve the performance of the system by allowing devices to communicate directly without routing traffic through the base station. This technique has the means to improved performance and support new proximity based services.  

    Nowadays new applications based on geographical proximity are becoming more and more popular suggesting that D2D communications will have a high de- mand in the near future. Thus the study of the scalability of D2D communications is of paramount importance.  

    We define the scalability of D2D communications underlay cellular networks as the maximum number of D2D links that can share the cellular resources while assuring QoS to both D2D links and cellular users.

    In this thesis we study the scalability of D2D communication underlay cellu- lar networks in a multi-cell environment. We propose interference coordination schemes to maximize the number of D2D links while assuring QoS to D2D links and cellular users.  

    Three interference coordination schemes have been proposed considering dif- ferent levels of available channel state information (CSI). The first scheme is called no CSI centralized (N-CSIC) scheme and it is based on a centralized solution where no CSI is needed. The second is partial CSI distributed (P-CSID) scheme and it is based on a distributed solution where partial CSI is available. The last scheme is named full CSI optimal (F-CSIOp) scheme and it is achieved by formulating an optimization problem considering full CSI to be available.  

    Extensive mathematical and numerical analysis is conducted to develop and evaluate the proposed schemes. The results show that F-CSIOp scheme offers the best performance followed by the P-CSID and finally N-CSIC, thus a clear relationship is found between complexity and performance.  

    The P-CSID offers a practical solution for a low complexity interference co- ordination scheme that achieves good scalability and capacity for a wide range of strict QoS requirements. Moreover the results show that further improvement can be achieved if proper selection of the involved parameters is done along with the implementations of closed loop power control (CLPC) schemes.  

    The N-CSIC scheme provides a good solution for low SINR values of D2D links when the QoS of cellular users is low. Thus it is a good candidate for applications like sensor networks or M2M communications where the SINR requirements are rather low and there are no primary users to impose more interference constraints.  

    Finally we conclude that good scalability and capacity can be achieved with the proposed low complexity interference coordination schemes for D2D communications and provide interesting topics for future research.

  • 46516.
    Vergara, Alexander
    et al.
    University of California, San Diego, USA.
    Fonollosa, Jordi
    University of California, San Diego, USA.
    Mahiques, Jonas
    University of California, San Diego, USA.
    Trincavelli, Marco
    Örebro University, School of Science and Technology.
    Rulkov, Nikolai
    University of California, San Diego, USA.
    Huerta, Ramon
    University of California, San Diego, USA.
    On the performance of gas sensor arrays in open sampling systems using inhibitory support vector machines2013In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 185, no August 2013, p. 462-477Article in journal (Refereed)
    Abstract [en]

    Chemo-resistive transduction presents practical advantages for capturing the spatio-temporal and structural organization of chemical compounds dispersed in different human habitats. In an open sampling system, however, where the chemo-sensory elements are directly exposed to the environment being monitored, the identification and monitoring of chemical substances present a more difficult challenge due to the dispersion mechanisms of gaseous chemical analytes, namely diffusion, turbulence, and advection. The success of such actively changeable practice is influenced by the adequate implementation of algorithmically driven formalisms combined with the appropriate design of experimental protocols. On the basis of this functional joint-formulation, in this study we examine an innovative methodology based on the inhibitory processing mechanisms encountered in the structural assembly of the insect's brain, namely Inhibitory Support Vector Machine (ISVM) applied to training a sensor array platform and evaluate its capabilities relevant to odor detection and identification under complex environmental conditions. We generated - and made publicly available - an extensive and unique dataset with a chemical detection platform consisting of 72 conductometric metal-oxide based chemical sensors in a custom-designed wind tunnel test-bed facility to test our methodology. Our findings suggest that the aforementioned methodology can be a valuable tool to guide the decision of choosing the training conditions for a cost-efficient system calibration as well as an important step toward the understanding of the degradation level of the sensory system when the environmental conditions change.

  • 46517.
    Vergara Alonso, Ekhiotz Jon
    Linköping University, Department of Computer and Information Science, RTSLAB - Real-Time Systems Laboratory.
    Implementation of a manycast protocol for intermittently connected mobile ad hoc networks in disaster areas2010Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    Nowadays, the use of mobile phones and other wireless devices has become an indispensable part of daily life. However, the focus of wireless communication is on infrastructure-based networks, making them prone to service outage if for any reason the infrastructure is overloaded or there is no network coverage. This is the case in a disaster area, where the infrastructure that supports the communication may be destroyed or could become useless.

    Different approaches to complement the exchange of information in these scenarios are emerging as research results. This thesis concerns Random-Walk Gossip (RWG), which is a protocol to disseminate information in disaster areas. RWG is a many-cast protocol for intermittently connected mobile ad hoc networks. The more people can communicate, the more chances of success there are. Therefore, it is useful to investigate the possibility of implementing such protocols on commodity devices. Since Symbian is currently the most widespread mobile phone operating system, this master's thesis presents the implementation of the protocol in that platform. The protocol is also implemented in Linux and Mac OS X in order to provide heterogeneity. Finally, some aspects of the performance of the protocol in different devices are analyzed, studying the CPU load, memory consumption, radio range, energy consumption and response time of different devices using the protocol. The studies show that the use of the RWG protocol in both laptops and handheld devices is viable.

  • 46518.
    Vergara Alonso, Ekhiotz Jon
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Fairness and Incentive Considerations in Energy Apportionment Policies2016In: ACM Transactions on Modeling and Performance Evaluation of Computing Systems, ISSN 2376-3639, Vol. 2, no 1Article in journal (Refereed)
    Abstract [en]

    The energy consumption of a system is determined by the system component usage patterns and interactions between the coexisting entities and resources. Energy accounting plays an essential role to reveal the contribution of each entity to the total consumption and for energy management. Unfortunately, energy accounting inherits the apportionment problem of accounting in general, which does not have a general single best solution. In this paper we leverage cooperative game theory commonly used in cost allocation problems to study the energy apportionment problem, i.e., the problem of prescribing the actual energy consumption of a system to the consuming entities (e.g., applications, processes or users of the system).

    We identify five relevant fairness properties for energy apportionment and present a detailed categorisation and analysis of eight previously proposed energy apportionment policies from different fields in computer and communication systems. In addition, we propose two novel energy apportionment policies based on cooperative game theory which provide strong fairness notion and a rich incentive structure. Our comparative analysis in terms of the identified five fairness properties as well as information requirement and computational complexity shows that there is a trade-off between fairness and the other evaluation criteria. We provide guidelines to select an energy apportionment policy depending on the purpose of the apportionment and the characteristics of the system.

  • 46519.
    Vergara Alonso, Ekhiotz Jon
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Asplund, Mikael
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Sharing the Cost of Lunch: Energy Apportionment Policies2015In: Proceedings of the 11th ACM Symposium on QoS and Security for Wireless and Mobile Networks, ACM Digital Library, 2015, p. 91-97Conference paper (Refereed)
    Abstract [en]

    Energy consumption has become a hot topic in computer and communication technologies pinpointing the need to carefully analyse system efficiency. The energy consumption of a system is determined by the usage patterns of system components and complex interactions between the coexisting entities and resources. Providing transparency of a system’s consumption by breaking down the total consumption is vital to evaluate and provide energy-efficient design and operation.

    In this paper we survey the apportionment problem in different fields such as computer systems, wireless sensor networks, mobile devices and energy-efficient buildings. The challenge lies in how to attribute a share of the total energy consumption to the responsible entities (e.g., applications, processes or users of the system). Our analysis identifies that energy apportionment is a common problem in different fields and reviews five previously applied energy apportionment policies. Also, the work identifies relevant further research.

  • 46520.
    Vergara, Ekhiotz Jon
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Energy-aware Cross-layer Burst Buffering for Wireless Communication2012In: e-Energy '12 Proceedings of the 3rd International Conference on Future Energy Systems: Where Energy, Computing and Communication Meet, ACM , 2012Conference paper (Other academic)
    Abstract [en]

    The massive explosion of mobile applications with the ensuing data exchange over the cellular infrastructure is not only a blessing to the mobile user but also has a price in terms of regular discharging of the device battery. A big contributor to this energy consumption is the power hungry wireless network interface. We leverage a measurement kit to perform accurate physical energy consumption measurements in a third generation (3G) telecommunication modem thus isolating the energy footprint of data transfers as opposed to other mobile phone-based measurement studies. Using the measurement kit we show how the statically configured network parameters, i.e., channel switch timers, and buffer thresholds, in addition to the transfer data pattern and the radio coverage, impact the communication energy footprint. We then demonstrate that being aware of static network parameters creates room for energy savings. This is done by devising a set of algorithms that (a) infer the network parameters efficiently, and (b) use the parameters in a new packet scheduler in the device. The combined regime is shown to transfer background uplink data, from real world traces of Facebook and Skype, with significant energy saving compared to the state-of-the-art.

  • 46521.
    Vergori, Giuseppe
    et al.
    Politecnico di Milano, Italy.
    Tamburri, Damian A
    Politecnico di Milano, Italy.
    Perez-Palacin, Diego
    Univeristy of Zaragoza, Spain.
    Mirandola, Raffaela
    Politecnico di Milano, Italy.
    DevOps Performance Engineering: A Quasi-Ethnographical Study2017In: Proceedings of the 8th ACM/SPEC on International Conference on Performance Engineering Companion, New York, USA: ACM Press, 2017, p. 127-132Conference paper (Refereed)
    Abstract [en]

    DevOps is a software engineering strategy to reduce software changes' rollout times by adopting any set of tactics that reduce friction in software lifecycles and their organisational variables, for example: coordination, communication, product evolution, deployment, operation, continuous architecting, continuous integration and more. Going DevOps is increasingly demanding that software engineering disciplines which were typically product-oriented such as software performance engineering to rethink their typical comfort zone, enlarging their scope from product, to process or even further to ecosystem and organisational levels of abstraction. This article makes an attempt at understanding what are the dimensions in DevOps organisational scenarios that can be addressed with a performance engineering lens. To do this, we performed a quasi-ethnographical study featuring a real-life industrial DevOps scenario. Discussing our results we conclude that many synergies exist between DevOps and performance engineering each with peculiarities, limitations and challenges - more research is needed to offer a full-spectrum performance-engineering support for DevOps practitioners.

  • 46522.
    Verhagen, Harko
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    de Azevedo, Razera
    Cerratto-Pargman, Teresa
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Ramberg, Robert
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Plagiarism awareness, perception, and attitudes among students and teachers in Swedish higher education – a case study2010Conference paper (Other academic)
    Abstract [en]
    The objective of the empirical study presented in this paper was to investigate students’ and teachers attitudes towards the issue of plagiarism. The study was conducted at the department of Computer and Systems Sciences (DSV) at Stockholm University (SU) in Sweden in 2009. For the purpose of the investigation, we chose to make a comparison between results obtained by Uppsala University in a previously survey focused on the study of prevention of plagiarism in student work in 2005 (Henriksson, 2008). The goal with the comparison was twofold: i) to point at similarities and differences found on the issue of how plagiarism is perceived and faced by teachers and students at both universities as well as to summarize teachers’ and students’ attitudes towards plagiarism at DSV-Stockholm University and Ii) to develop a strategy to prevent plagiarism at DSV- Stockholm University. The survey which was in English and was sent by e-mail to teachers and students at the master level at DSV and was answered by 47 students and 24 teachers. Results obtained can be organized into the following topics: Awareness of plagiarism (consisting of a comparison between students and teachers); attitudes towards plagiarism(consisting of a comparison between students and teachers and European and non-European students studying at DSV); perception of plagiarism (consisting of a comparison between students and teachers and European and non-European students studying at DSV) and, comparison of results obtained by Uppsala and Stockholm University.
  • 46523.
    Verhagen, Harko
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Is there an I in We? Combining individual and collective modes of decision making2013In: Normative Multi-Agent Systems: NorMAS 2013, 2013Conference paper (Other academic)
    Abstract [en]

    Social simulation is one of the main areas for agent-based model use with norms being one of the mostly used and studied social mechanisms. The focus has been on inter-agent mechanisms through which individuals are influenced by social norms, resulting in dynamics of norms such as emergence and diffusion. What is lacking is an integration of models of collectiveness such as we-intentionality to transcend the atomistic models such as rational choice, game theory, and social choice theory. We will start with Webers Weber distinction between four types of actions resulting from instrumental, normative, emotional or affectual and traditional motivations for actions. Then we present social norms in the light of the growing literature on collective reasoning/intentionality/rationality and outline a model in which social norms are modelled based on an agent’s collective capacity. This will be connected to the Consumat agent architecture that integrates the social and individual aspects of automatic, instrumental and normative decision making.

  • 46524.
    Verhagen, Harko
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Multiagent systems research and social science theory2006In: Handbook of research on nature inspired computing for economics and management / [ed] Jean-Philippe Rennard, Hershey, Pa.: Idea Group Reference , 2006, p. 101-110Chapter in book (Other academic)
    Abstract [en]

    This chapter describes the possible relationships between multiagent systems research and social science research, more particularly sociology. It gives examples of the consequences and possibilities of these relationships and describes some of the important issues and concepts in each of these areas. It finally points out some future directions for a bidirectional relationship between the social sciences and multiagent systems research which hopefully will help researchers in both research areas as well as researchers in management and organisation theory.

  • 46525.
    Verhagen, Harko
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Norms, individualist and collectivist perspectives (on decision making)2014Conference paper (Other academic)
  • 46526.
    Verhagen, Harko
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Eladhari, Mirjam
    Gotland University, , .
    Johansson, Magnus
    Stockholm University, , .
    Constructing autonomous social characters for games2011Conference paper (Refereed)
  • 46527.
    Verhagen, Harko
    et al.
    DSV, Stockholm University.
    Eladhari, Mirjam P
    Gotland University, School of Game Design, Technology and Learning Processes.
    Johansson, Magnus
    DSV, Stockholm University.
    Social believable NPCs: a conceptual model and analysis of current NPC models2011Conference paper (Refereed)
  • 46528.
    Verhagen, Harko
    et al.
    Stockholm University.
    Eladhari, Mirjam P
    Högskolan på Gotland.
    Johansson, Magnus
    Stockholm University.
    Social believable NPCs: a conceptual model and analysis of current NPC models2011Conference paper (Refereed)
  • 46529.
    Verhagen, Harko
    et al.
    Stockholms universitet.
    Eladhari, Mirjam Palosaari
    Malta University, Malta.
    Johansson, Magnus
    Stockholms universitet.
    McCoy, Josh
    University of Southern California, USA.
    Social Believability in Games2013In: Advances in Computer Entertainment: 10th International Conference. Proceedings / [ed] Dennis Reidsma, Haruhiro Katayose, Anton Nijholt, Springer International Publishing , 2013, p. 649-652Conference paper (Refereed)
    Abstract [en]

    The Social Believability in Games Workshop intends to be a point of interaction for researchers and game developers interested in different aspects of modelling, discussing, and developing believable social agents and Non-Player Characters (NPCs). This can include discussions around behaviour based on social and behavioural science theories and models, social affordances when interacting with game worlds and more. The intention is to invite participants from a multitude of disciplines in order to create a broad spectrum of approaches to the area.

  • 46530.
    Verhagen, Harko
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Elsenbroich, Corinna
    Surrey University, , .
    Computational Social Science and the Search for Mechanisms2013Other (Other (popular science, discussion, etc.))
  • 46531.
    Verhagen, Harko
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Elsenbroich, Corinna
    Putting the agent back together again: needs for integrating social and behavioural sciences for agent-based social simulation2012In: Report from Dagstuhl Seminar 12111: Normative Multi-Agent Systems / [ed] Giulia Andrighetto, Guido Governatori, Pablo Noriega, and Leon van der Torre, 2012, p. 46-Conference paper (Other academic)
  • 46532.
    Verhagen, Harko
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Elsenbroich, Corinna
    Fällström, Kurt
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Modelling Contextual Decision-Making in Dilemma Games2017In: Advances in Social Simulation 2015 / [ed] Wander Jager, Rineke Verbrugge, Andreas Flache, Gert de Roo, Lex Hoogduin, Charlotte Hemelrijk, Cham, Switzerland: Springer, 2017, p. 121-127Chapter in book (Refereed)
    Abstract [en]

    Social dilemmas such as the Prisoner’s Dilemma and the Tragedy of the Commons have attracted widespread interest in several social sciences and humanities including economics, sociology and philosophy. Different frameworks of human decision-making produce different answers to these dilemmas. Common for most real-world analyses of the dilemmas is finding that behaviour and choices depend on the decision context. Thus an all-in-one solution such as the rational choice model is untenable. Rather, a framework for agent-based social simulation of real-world behaviour should start by recognising different modes of decisionmaking. This paper presents such a framework and an initial evaluation of its results in two cases, (1) a repeated prisoner’s dilemma tournament playing against a set of well-known base models, and (2) a Tragedy of the Commons simulation.

  • 46533.
    Verhagen, Harko
    et al.
    Stockholms universitet, Institutionen för data- och systemvetenskap.
    Johansson, Magnus
    Stockholms universitet, Institutionen för data- och systemvetenskap.
    Demystifying guilds: MMORPG-playing and norms2009In: Breaking New Ground: Innovation in Games, Play, Practice and Theory, 2009Conference paper (Refereed)
  • 46534.
    Verhagen, Harko
    et al.
    Stockholms universitet, Institutionen för data- och systemvetenskap.
    Johansson, Magnus
    Stockholms universitet, Institutionen för data- och systemvetenskap.
    Demystifying guilds: MMORPG-playing and norms2009In: Breaking New Ground: Innovation in Games, Play, Practice and Theory, 2009Conference paper (Refereed)
  • 46535.
    Verhagen, Harko
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Johansson, Magnus
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Demystifying guilds: MMORPG-playing and norms2009In: Breaking New Ground: Innovation in Games, Play, Practice and Theory, 2009Conference paper (Refereed)
  • 46536.
    Verhagen, Harko
    et al.
    DSV, Stockholm University.
    Johansson, Magnus
    DSV, Stockholm University.
    Eladhari, Mirjam P
    Gotland University, School of Game Design, Technology and Learning Processes.
    Model of Social Believable NPCs for Teacher Training2011In: Proceedingsof the 5th European Conference on Games Based Learning / [ed] Dimitris Gouscos and Michalis Meimaris, Athens, Greece: The National and Kapodistrian University of Athens , 2011, p. 771-774Conference paper (Refereed)
    Abstract [en]

    This paper proposes a conceptual model for non-player characters for use in a serious game application. The game is aimed for teacher training with a focus on training of social skills related to conflict handling. Conflict handling is difficult to emulate in a realistic way and appears not frequent enough in the practical training part of teacher education to enable sufficient training. Also, training in a real world situation may be ethically less sound. To develop a serious game for conflict handling training, we need to create non-player characters that can emulate conflicts in a realistic way. For this, we need to extend current models with social and emotional aspects. We present previously developed meta-models that enable us to propose such a model and combine these and recent game research to a Model Social Game Agent.

  • 46537.
    Verhagen, Harko
    et al.
    Stockholm University.
    Johansson, Magnus
    Stockholm University.
    Eladhari, Mirjam P
    Högskolan på Gotland.
    Model of Social Believable NPCs for Teacher Training2011In: Proceedings of the 5th European Conference on Games Based Learning / [ed] Dimitris Gouscos and Michalis Meimaris, Athens, Greece: The National and Kapodistrian University of Athens , 2011, p. 771-774Conference paper (Refereed)
    Abstract [en]

    This paper proposes a conceptual model for non-player characters for use in a serious game application. The game is aimed for teacher training with a focus on training of social skills related to conflict handling. Conflict handling is difficult to emulate in a realistic way and appears not frequent enough in the practical training part of teacher education to enable sufficient training. Also, training in a real world situation may be ethically less sound. To develop a serious game for conflict handling training, we need to create non-player characters that can emulate conflicts in a realistic way. For this, we need to extend current models with social and emotional aspects. We present previously developed meta-models that enable us to propose such a model and combine these and recent game research to a Model Social Game Agent.

  • 46538.
    Verhagen, Harko
    et al.
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Arts, Department of Game Design. Stockholms universitet, Institutionen för data- och systemvetenskap.
    Johansson, Magnus
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Arts, Department of Game Design. Stockholms universitet, Institutionen för data- och systemvetenskap.
    Eladhari, Mirjam P.
    The Need for Socially Believable NPCs: Game Designers' View2012In: ECREA’s Pre-Conference: Experiencing Digital Games: Use, Effects & Culture of Gaming, 2012Conference paper (Refereed)
  • 46539.
    Verhagen, Harko
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Johansson, Magnus
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Eladhari, Mirjam P.
    The Need for Socially Believable NPCs: Game Designers' View2012In: ECREA’s Pre-Conference: Experiencing Digital Games: Use, Effects & Culture of Gaming, 2012Conference paper (Refereed)
  • 46540.
    Verhagen, Harko
    et al.
    Stockholms universitet.
    Johansson, Magnus
    Stockholms universitet.
    Eladhari, Mirjam P
    The Need for Socially Believable NPCs: Game Designers' View2012In: ECREA’s Pre-Conference: Experiencing Digital Games: Use, Effects & Culture of Gaming, 2012Conference paper (Refereed)
  • 46541.
    Verhagen, Harko
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Johansson, Magnus
    Jager, Wander
    Games and Online Research Methods2017In: The SAGE Handbook of Online Research Methods / [ed] Nigel Fielding, Raymond M. Lee, Grant Blank, Los Angeles: Sage Publications, 2017, no 2, p. 295-306Chapter in book (Refereed)
  • 46542.
    Verhagen, Harko
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Noriega, PabloConsejo Superior de Investigaciones Científicas, , Institut d'Investigació en Intelligència Artificial.Balke, TinaSurrey University.De Vos, MarinaBath University .
    Social coordination: principles, artefacts and theories (SOCIAL.PATH).2013Conference proceedings (editor) (Other (popular science, discussion, etc.))
  • 46543.
    Verhagen, Harko
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Noriega, Pablo
    d’Inverno, Mark
    Towards a Design Framework for Controlled Hybrid Social Games2013In: Social Coordination: Principles, Artefacts and Theories (SOCIAL.PATH): AISB Convention 2013 / [ed] Harko Verhagen, Pablo Noriega, Tina Balke, Marina de Vos, 2013, p. 83-87Conference paper (Refereed)
    Abstract [en]

    We propose a framework for designing and deploying games where social behaviour is kept under control. This framework may also be used for designing other dynamic coordinated social spaces.

  • 46544.
    Verhagen, Harko
    et al.
    Stockholms universitet, Institutionen för data- och systemvetenskap.
    Palosaari Eladhari, Mirjam
    Johansson, Magnus
    Stockholms universitet, Institutionen för data- och systemvetenskap.
    McCoy, Josh
    Social Believability in Games2013In: Advances in Computer Entertainment: 10th International Conference. Proceedings / [ed] Dennis Reidsma, Haruhiro Katayose, Anton Nijholt, Springer International Publishing , 2013, p. 649-652Conference paper (Refereed)
    Abstract [en]

    The Social Believability in Games Workshop intends to be a point of interaction for researchers and game developers interested in different aspects of modelling, discussing, and developing believable social agents and Non-Player Characters (NPCs). This can include discussions around behaviour based on social and behavioural science theories and models, social affordances when interacting with game worlds and more. The intention is to invite participants from a multitude of disciplines in order to create a broad spectrum of approaches to the area.

  • 46545.
    Verhagen, Harko
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Palosaari Eladhari, Mirjam
    Johansson, Magnus
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    McCoy, Josh
    Social Believability in Games2013In: Advances in Computer Entertainment: 10th International Conference. Proceedings / [ed] Dennis Reidsma, Haruhiro Katayose, Anton Nijholt, Springer International Publishing , 2013, p. 649-652Conference paper (Refereed)
    Abstract [en]

    The Social Believability in Games Workshop intends to be a point of interaction for researchers and game developers interested in different aspects of modelling, discussing, and developing believable social agents and Non-Player Characters (NPCs). This can include discussions around behaviour based on social and behavioural science theories and models, social affordances when interacting with game worlds and more. The intention is to invite participants from a multitude of disciplines in order to create a broad spectrum of approaches to the area.

  • 46546.
    Verhagen, Henricus
    KTH, Superseded Departments, Computer and Systems Sciences, DSV.
    Autonomy and reasoning for natural and artificial agents2004In: Agents And Computational Autonomy: Potential, Risks, And Solutions / [ed] Nickles, M; Rovatsos, M; Weiss, G, 2004, Vol. 2969, p. 83-94Conference paper (Refereed)
    Abstract [en]

    In this article, I will present recent thoughts and theories on autonomy for natural and artificial agents. Even though the recent work on autonomy for artificial agents has interesting aspects, it excels in being unsystematic and a lack of references to theories outside of agent research supporting one or the other. Embedding these discussions in a broader framework of discussions in philosophy and sociology will enable us to sketch a broader yet more detailed picture. It will also enable us to discuss the reasoning of artificial agents.

  • 46547.
    Verhagen, Henricus
    Stockholm University.
    Norm autonomous agents2000Doctoral thesis, monograph (Other academic)
  • 46548.
    Verhulsdonck, Tijmen
    KTH, School of Information and Communication Technology (ICT).
    One Shot Object Detection: For Tracking Purposes2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    One of the things augmented reality depends on is object tracking, which is a problem classically found in cinematography and security. However, the algorithms designed for the classical application are often too expensive computationally or too complex to run on simpler mobile hardware. One of the methods to do object tracking is with a trained neural network, this has already led to great results but is unfortunately still running into some of the same problems as the classical algorithms. For this reason a neural network designed specifically for object tracking on mobile hardware needs to be developed. This thesis will propose two di erent neural networks designed for object tracking on mobile hardware. Both are based on a siamese network structure and methods to improve their accuracy using filtering are also introduced. The first network is a modified version of “CNN architecture for geometric matching” that utilizes an a ne regression to perform object tracking. This network was shown to underperform in the MOT benchmark as-well as the VOT benchmark and therefore not further developed. The second network is an object detector based on “SqueezeDet” in a siamese network structure utilizing the performance optimized layers of “MobileNets”. The accuracy of the object detector network is shown to be competitive in the VOT benchmark, placing at the 16th place compared to trackers from the 2016 challenge. It was also shown to run in real-time on mobile hardware. Thus the one shot object detection network used for a tracking application can improve the experience of augmented reality applications on mobile hardware. 

  • 46549.
    Verikas, Antanas
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    Bacauskiene, M.
    Department of Applied Electronics, Kaunas University of Technology, Kaunas, Lithuania.
    Using artificial neural networks for process and system modelling2003In: Chemometrics and Intelligent Laboratory Systems, ISSN 0169-7439, E-ISSN 1873-3239, Vol. 67, no 2, p. 187-191Article in journal (Refereed)
    Abstract [en]

    This letter concerns several papers, devoted to neural network-based process and system modelling, recently published in the Chemometrics and Intelligent Laboratory Systems journal. Artificial neural networks have proved themselves to be very useful in various modelling applications, because they can represent complex mapping functions and discover the representations using powerful learning algorithms. An optimal set of parameters for defining the functions is learned from examples by minimizing an error functional. In various practical applications, the number of examples available for estimating parameters of the models is rather limited. Moreover, to discover the best model, numerous candidate models must be trained and evaluated. In such thin-data situations, special precautions are to be taken to avoid erroneous conclusions. In this letter, we discuss three important issues, namely network initialization, over-fitting, and model selection, the right consideration of which can be of tremendous help in successful network design and can make neural modelling results more valuable.

  • 46550.
    Verikas, Antanas
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Intelligent systems (IS-lab).
    Bacauskiene, M.
    Department of Applied Electronics, Kaunas University of Technology, Kaunas, Lithuania.
    Dosinas, A.
    Department of Applied Electronics, Kaunas University of Technology, Kaunas, Lithuania.
    Bartkevicius, V.
    Department of Applied Electronics, Kaunas University of Technology, Kaunas, Lithuania.
    Gelzinis, A.
    Department of Applied Electronics, Kaunas University of Technology, Kaunas, Lithuania.
    Vaitkunas, M.
    Department of Applied Electronics, Kaunas University of Technology, Kaunas, Lithuania.
    Lipnickas, A.
    Department of Applied Electronics, Kaunas University of Technology, Kaunas, Lithuania.
    An intelligent system for tuning magnetic field of a cathode ray tube deflection yoke2003In: Knowledge-Based Systems, ISSN 0950-7051, E-ISSN 1872-7409, Vol. 16, no 3, p. 161-164Article in journal (Refereed)
    Abstract [en]

    This short communication concerns identification of the number of magnetic correction shunts and their positions for deflection yoke tuning to correct the misconvergence of colours of a cathode ray tube. The misconvergence of colours is characterised by the distances measured between the traces of red and blue beams. The method proposed consists of two phases, namely, learning and optimisation. In the learning phase, the radial basis function neural network is trained to learn a mapping: correction shunt position→changes in misconvergence. In the optimisation phase, the trained neural network is used to predict changes in misconvergence depending on a correction shunt position. An optimisation procedure based on the predictions returned by the neural net is then executed in order to find the minimal number of correction shunts needed and their positions. During the experimental investigations, 98% of the deflection yokes analysed have been tuned successfully using the technique proposed.

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