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  • 46501.
    Xu, Changqiao
    et al.
    State Key Laboratory of Networking and Switching Technology, Beijing University of Posts and Telecommunications, Beijing.
    Quan, Wei
    National Engineering Laboratory for Next Generation Internet Technologies, School of Electronic and Information Engineering, Beijing Jiaotong University, Beijing.
    Vasilakos, Athanasios
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Zhang, Hongke
    National Engineering Laboratory for Next Generation Internet Technologies, School of Electronic and Information Engineering, Beijing Jiaotong University, Beijing.
    Muntean, Gabriel-Miro
    School of Electronic Engineering, Network Innovations Centre, Rince Institute, Dublin City University.
    Information-centric cost-efficient optimization for multimedia content delivery in mobile vehicular networks2017Inngår i: Computer Communications, ISSN 0140-3664, E-ISSN 1873-703X, Vol. 99, s. 93-106Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Providing high-quality multimedia services is a challenging and high-cost task in mobile vehicular networks due to intermittent connectivity, highly dynamic capacity, mostly associated to heterogeneous hosts distribution and their high mobility. Information-centric networking (ICN), which adopts novel content-based dissemination instead of the traditional host-based one, has great potential to accomplish cost-efficient quality-oriented multimedia delivery. This paper proposes a novel cost-Efficient Multimedia content Delivery approach (EcoMD) in vehicular networks leveraging the ICN features. In EcoMD, two essential factors are first analyzed and modeled: content mobility and supply-demand balance, and then, a mixed integer programming (MIP) optimization is formulated to minimize the economic cost associated to guaranteed the quality level of multimedia services. To resolve this NP-hard problem, heuristic mechanisms are proposed covering three aspects: priority-based path selection, least-required source maintaining and on-demand caching enhancement. By comparison with existing state-of-the-art solutions, simulation results demonstrate how EcoMD provides an improved performance in terms of start-up delay, jitter, playback continuity, and Quality of Experience (QoE) while particularly reduces the economic cost.

  • 46502.
    Xu, Chenfan
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Impact of a Decision Support System on Obstetricians in the Pregnancy Nutrition Guidance2012Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Background: Pregnancy Nutrition (PN) guidance is an issue of great concern worldwide because of its direct relevance to the maternal healthcare and the healthy prenatal development (Li et al., 2004, p. 11). Providing an effective guidance on PN is an onerous and time-consuming task. Extensive experience, knowledge, and continuous and actual calculations are required for the obstetricians. Consequently, the PN guidance is often faced with difficulties and hurdles. It is, however, dramatically changed with the emergence of a Decision Support System (DSS) for PN guidance based on the computer information management technique. This DSS has been applied for the clinic guidance of PN in obstetrics departments or hospitals in China. Its impacts on obstetricians are investigated in this thesis.

    Objectives: This thesis investigates the consequences and intrinsic correlations of relevant factors during the application of the DSS, so that its effects on obstetricians can be clearly identified and the usefulness of this system for pregnancy nutrition guidance can be effectively established. It also lays a foundation for an effective communication between system developers and the end users of this system. At the meantime, this work proposes the concepts and methods that allow proper utility of such an information management system.

    Methods: A number of research methods have been applied for data acquisitions and analyses, including direct observations of the obstetrics department in the hospital in study, conversational interviews with the participating obstetricians, and distance communications. These approaches enable us to prepare the resources to construct the model based on these case studies. As a parallel approach, quantitative methods based on questionnaires have been conducted which reach out a large number of obstetricians in different locations. This allows a statistical analysis that permits the impact analysis and correlation of the intrinsic factors, so that the conclusions of this study can be consolidated.

    Results: Positive impacts will be measured by five factors including convenience, acceptability, generality, concreteness, and effectiveness, while negative impacts by three factors including verbosity, rigidity, and expensiveness.

    Conclusions: The DSS has successfully enhanced the application of correct PN guidance. Both positive and negative impacts have been generated on obstetricians by the DSS. These impacts are mainly related to the seniority of obstetricians and their familiarity with the PN guidance and the DSS. The development, utilization, and operation management of the DSS in PN guidance has generated impacts and functions. This study might provide resources and foundation of the systematic management of the DSS together with its development. The DSS and the related Chief Information Officers and Specialists will benefit from this study and therefore provide improved support and assistance for the end users to complete information system management successfully.

  • 46503.
    Xu, Cheng
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för datalogi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Scalable Validation of Data Streams2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In manufacturing industries, sensors are often installed on industrial equipment generating high volumes of data in real-time. For shortening the machine downtime and reducing maintenance costs, it is critical to analyze efficiently this kind of streams in order to detect abnormal behavior of equipment.

    For validating data streams to detect anomalies, a data stream management system called SVALI is developed. Based on requirements by the application domain, different stream window semantics are explored and an extensible set of window forming functions are implemented, where dynamic registration of window aggregations allow incremental evaluation of aggregate functions over windows.

    To facilitate stream validation on a high level, the system provides two second order system validation functions, model-and-validate and learn-and-validate. Model-and-validate allows the user to define mathematical models based on physical properties of the monitored equipment, while learn-and-validate builds statistical models by sampling the stream in real-time as it flows.

    To validate geographically distributed equipment with short response time, SVALI is a distributed system where many SVALI instances can be started and run in parallel on-board the equipment. Central analyses are made at a monitoring center where streams of detected anomalies are combined and analyzed on a cluster computer.

    SVALI is an extensible system where functions can be implemented using external libraries written in C, Java, and Python without any modifications of the original code.

    The system and the developed functionality have been applied on several applications, both industrial and for sports analytics.

  • 46504.
    Xu, Cheng
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Källström, Elisabeth
    Volvo Construction Equipment, Eskilstuna, Sweden.
    Risch, Tore
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Lindström, John
    ProcessIT Innovations, Luleå University of Technology, Luleå, Sweden.
    Håkansson, Lars
    Department of Applied Signal Processing, Blekinge Institute of Technology, Karlskrona, Sweden.
    Larsson, Jonas
    Volvo Construction Equipment, Eskilstuna, Sweden.
    Scalable validation of industrial equipment using a functional DSMS2017Inngår i: Journal of Intelligent Information Systems, ISSN 0925-9902, E-ISSN 1573-7675, Vol. 48, nr 3, s. 553-577Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A stream validation system called SVALI is developed in order to continuously validate correct behavior of industrial equipment. A functional data model allows the user to define meta-data, analyses, and queries about the monitored equipment in terms of types and functions. Two different approaches to validate that sensor readings in a data stream indicate correct equipment behavior are supported: with the model-and-validate approach anomalies are detected based on a physical model, while with learn-and-validate anomalies are detected by comparing streaming data with a model of normal behavior learnt during a training period. Both models are expressed on a high level using the functional data model and query language. The experiments show that parallel stream processing enables SVALI to scale very well with respect to system throughput and response time. The paper is based on a real world application for wheel loader slippage detection at Volvo Construction Equipment implemented in SVALI.

  • 46505.
    Xu, Cheng
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Wedlund, Daniel
    Helgoson, Martin
    Risch, Tore
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Model-based validation of streaming data2013Inngår i: Proc. 7th ACM International Conference on Distributed Event-Based Systems, New York: ACM Press, 2013, s. 107-113Konferansepaper (Fagfellevurdert)
  • 46506.
    Xu, Dan
    et al.
    University of California, Davis.
    Liu, Xin
    University of California, Davis.
    Vasilakos, Athanasios
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Traffic-aware resource provisioning for distributed clouds2015Inngår i: I E E E Cloud Computing, ISSN 2325-6095, Vol. 2, nr 1, s. 30-39, artikkel-id 7091770Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cloud computing's aim is to provide prompt, reliable, diverse, and yet cost-effective Internet services. To achieve this goal, existing work has considered traffic-aware resource provisioning to reduce cloud energy costs. However, much room remains for achieving a fine-grained traffic-awareness. In this article, the authors examine important cloud traffic characteristics and discuss optimization solutions to reduce energy costs while maintaining service quality. Their solution improves traffic-awareness and efficiently reduces energy costs for distributed clouds with dynamic and diverse traffic

  • 46507.
    Xu, Derek
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Kittichokechai, Kittipong
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Oechtering, Tobias J.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Secure Successive Refinement with Degraded Side Information2014Inngår i: 2014 IEEE International Symposium on Information Theory (ISIT), IEEE , 2014, s. 2674-2678Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we investigate the problem of successive refinement with side information (SI) under secrecy constraint. In particular, under classical successive refinement coding scheme, there are degraded SI sequences Y-n and Z(n) at two decoders and E-n at the eavesdropper. Based on the status of two switches, three different cases are investigated. In case 1 and 3, the eavesdropper only observes output of encoder 1 and 2, respectively, while in case 2, the eavesdropper observes outputs of both encoder 1 and 2. The Markov chain X - Y - (Z, E) holds in all cases. The equivocation is measured by the normalized entropy of source sequence conditioned on the observation of eavesdropper. We completely characterize the rate-distortion-equivocation regions for all three cases, and show that layered coding is optimal. Finally, a binary source example is given.

  • 46508. Xu, Gang
    et al.
    Ngai, Edith C.-H.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Liu, Jiangchuan
    Information-centric collaborative data collection for mobile devices in wireless sensor networks2014Inngår i: Proc. International Conference on Communications: ICC 2014, IEEE Communications Society, 2014, s. 36-41Konferansepaper (Fagfellevurdert)
  • 46509.
    Xu, Henrik
    Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik.
    Tablet application GUI usability checklist: Creation of a user interface usability checklist for tablet applications2013Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Since the beginning of the 21st century, the world has seen a changing trend in computing power thanks to advancements in technology. One peculiar platform in the field of usability is the tablet. Due to its recent introduction, it has had a relatively short life span with few established methodologies. The tablet is gaining market share at a tremendous speed and thus there has been a big demand of the appropriate evaluation methods. This comprehensive study intention is to; through a literature survey and transformation of collected material identify what usability requisites there are when developing a user interface for a tablet application. Existing user interface guidelines from various companies involving the development of tablet software are examined and paired up with usability principles in the creation of the usability checklist. The usability checklist practical effectiveness is tested on various tablet applications and the results are compared to the results of a usability user test  valuation. The majority of the usability problems found by the user test evaluation are codiscovered, in addition, there were a greater number of undiscovered usability problems that was identified with the checklist evaluation.

  • 46510.
    Xu, Jiang
    et al.
    Department of Electrical and Computer Engineering, University of Auckland.
    Yang, Chenwei
    Department of Electrical and Computer Engineering, University of Auckland.
    Zhabelova, Gulnara
    Department of Electrical and Computer Engineering, University of Auckland.
    Berber, Stevan Mirko
    Department of Electrical and Computer Engineering, University of Auckland.
    Vyatkin, Valeriy
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Towards implementation of IEC 61850 GOOSE messaging in IEC 61499 environment2013Inngår i: 2013 11th IEEE International Conference on Industrial Informatics (INDIN 2012): Bochum, Germany 29 July - 31 July 2013, Piscataway, NJ: IEEE Communications Society, 2013, s. 464-470Konferansepaper (Fagfellevurdert)
    Abstract [en]

    IEC 61850 is the new standard for substation automation. One of the IEC 61850 communication services, designed specifically for protection within the substation automation system is GOOSE messaging. GOOSE messaging is a peer to peer communication protocol aiming to satisfy the stringent communication requirements within protection systems operating over the Ethernet communication framework. One of the on-going research topics in this area is extending capabilities of IEC 61850 to represent control logic by combining it with component software architecture of the IEC 61499 standard. The Intelligent Logical Nodes (iLN) architecture is one such solution which combines the two standards. This development led to the need to implement communication services of IEC 61850 by means of IEC 61499. This paper presents such an implementation of IEC 61850 GOOSE messaging using IEC 61499 Service Interface Function Blocks implemented by means of the WinPCap library.

  • 46511.
    Xu, Jie
    et al.
    Högskolan i Borås, Akademin för bibliotek, information, pedagogik och IT.
    Yang Yang, Dan
    Högskolan i Borås, Akademin för bibliotek, information, pedagogik och IT.
    Undergraduates’ learning management by the usage of Social Media2015Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    With the rapid revolution within networks as well as social media, today people face areal well-rounded and colorful high-tech world. Indeed, the technology of socialmedia changes the way that people socialize and communicate. What is more, thepotential of the social media is limitless, because we can see the combination betweenthe classroom and networks for the communication within a group chatting on acourse discussion. This is really used in our life, especially in western countries. Bycomparison, the model or pattern of learning by using social media in China is quitedifferent. This is why this paper focuses on the perspective of undergraduates’attitudes as well as behaviors when they use Hatcheck during their studying life.Hatcheck is the biggest application for socializing in China and is seen as a ChineseFacebook. How can it change Chinese students’ manners to learn and how canstudents manage their learning process self-regulatory? This will be discussed withinthis paper.

  • 46512.
    Xu, Junjie
    et al.
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE).
    Su, Wenhui
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE).
    Performance Evaluations of Cisco ASA and Linux iptables Firewall Solutions2013Independent thesis Advanced level (degree of Master (One Year)), 10 poäng / 15 hpOppgave
    Abstract [en]

    A firewall is an essential component to provide network security and traffic control. It is widely used to prevent illegal accesses to private or corporate networks from external unsafe source like Internet. Firewalls are basically classified into two types, hardware firewalls and software firewalls. Hardware-based is a single external hardware to a system, but software-based is installed on a computer inside a system. Two such firewalls, Cisco ASA 5505 and Linux iptables are implemented and practical evaluated theirs performance. The performance test in this paper work primarily focuses on Network layer, and the main parameters include Throughput, Latency, and Concurrent Sessions. Different performance monitoring tools are also introduced in this paper.

    As a network layer firewall, the most impressive feature is through inspecting the packets to manage the traffic from the higher Layer 4-7 of OSI (Open Systems Interconnection) model, which inevitably has a certain impact on the performance. The bottleneck of the whole network is determined by what extent the impact is. The primary objective of this thesis is through analyzing the test reports to evaluate the two type firewalls’ performance. Thus the results reported in this paper gives some ideas to new firewall customers about what aspects should be considered before selecting a suitable firewall product. 

  • 46513. Xu, L
    et al.
    Stoica, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för systemteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Reglerteknik.
    Li, Jian
    Bressler, S
    Shao, X
    Ding, M
    ASEO: a method for the simultaneous estimation of single-trial event-related potentials and ongoing brain activities2009Inngår i: IEEE Transactions on Biomedical Engineering, ISSN 0018-9294, E-ISSN 1558-2531, Vol. 56, nr 1, s. 111-121Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cognitive functions are often studied by recording electric potentials from the brain over repeated presentations of a sensory stimulus or repeated performance of a motor action. Each repetition is called a trial. Recent work has demonstrated that contrary to the traditional view, the event-related potential (ERP) can vary from trial to trial and the background ongoing activity often contains rich information about the cognitive state of the brain. Based on such a variable signal plus ongoing activity model, an iterative parameter estimation method is proposed in which both the single-trial parameters of the ERP and the autoregressive representation of the ongoing activity are obtained simultaneously. This technique, referred to as the analysis of single-trial ERP and ongoing activities method, is first tested on simulation examples, and then applied to the local field potential recordings from monkeys performing a visuomotor task.

  • 46514.
    Xu, Lei
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Elmroth, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    A time interval-based credit reservation approach for prepaid composite services in cloud environments2011Inngår i: Web Services (ECOWS), 2011 Ninth IEEE European Conference on, 2011, s. 158-165Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A typical business model in cloud environments for service providers is the provision of composite services built from resources and services offered by other providers. Customers of these composite services can make an advance payment before consumption. In this scenario, accounting systems will supervise each service comprising given composite services individually. As the number of constituent services and requests submitted by customers increase dramatically, scalability issues arise. To tackle this problem, we present an approach that estimates the highest cost of a given composite service composed of multiple pre-paid services, and then calculates the duration of a time interval based on which accounting systems access and update target customers' account. It is intended to reduce overhead imposed by supervising services individually in real-time. Commercial agreements between involved business partners and potential economic compensations due to the violation of Service Level Agreement (SLA) are mirrored in the cost estimation.

  • 46515.
    Xu, Lei
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Jennings, Brendan
    Automating the generation, deployment and application of charging schemes for composed communications services2012Inngår i: 2012 IEEE Network operations and management symposium (NOMS), 2012, s. 853-859Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Creating composed services dynamically to meet the demand of every individual customer can be an inexpensive way for a service provider to differentiate itself from its competitors. Charging and billing systems are one of the key components supporting this business model. However, many existing charging and billing systems suffer from their time-consuming scheme 1 configuration process. This limits the flexibility of service providers to offer composed services. This paper proposes a framework named Accounting Logic Generator (ALG) that automates the generation and deployment of charging schemes for composed services. It processes a two-part charging scheme which contains rules that can be used to govern how the usage of a service is charged for when it is executed standalone, used in the context of a composed service, invoked within specific time intervals of interest or completed successfully in the context of composed service invocations where one or more other services fail. Furthermore, an approach that estimates service cost for the selection process of service composition is presented.

  • 46516.
    Xu, Lei
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Lakew, Ewnetu Bayuh
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Hernandez-Rodriguez, Francisco
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Elmroth, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    A Scalable Accounting Solution for Prepaid Services in Cloud Systems2012Inngår i: Proceedings of the 2012 IEEE Ninth International Conference on Services Computing, 2012, s. 81-89Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Prepaid charging, an essential option for the accounting of cloud services, provides effective financial control for both service providers and customers. However, it has to be supported by real-time credit checking and cost calculation. These real-time actions consume resources of the providers' network and impose high overhead. To tackle this issue, we present a scalable accounting solution in which an accounting component is hosted in every cluster constituting a cloud system. Each of our accounting component supervises service consumptions based on a calculated interval of a service bundle that is composed of all services hosted in a cluster and consumed by one customer simultaneously. Credit will be re-allocated when a customer's credit in one cluster is not enough to compensate further usage, and the allocation is performed based on service consumptions. This work is intended to reduce the cost of prepaid services and to ensure service provision is not hampered by the charging part. Additionally, we perform theoretical and experimental analyses that indicate this work can provide an inexpensive accounting solution for the long-lived services in storage clouds.

  • 46517.
    Xu, Lei
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Shi, Lei
    Wang, Runxin
    Jennings, Brendan
    A multiple criteria service composition selection algorithm supporting time-sensitive rules2011Inngår i: Proceedings of the12th IFIP/IEEE International Symposium on Integrated Network Management (IM 2011): Dublin, Ireland, 23—27 May 2011 / [ed] Nazim Agoulmine, Claudio Bartolini, Tom Pfeifer, Declan O'Sullivan, Institute of Electrical and Electronics Engineers (IEEE) , 2011, s. 718-721Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Constructing composite services by using of services offered by third parties is an attractive and inexpensive way for service brokers and aggregators to enhance differentiation from their competitors. When multiple services provide the same or similar functionalities, selecting those that satisfy users' non-functional requirements is crucial. In many cases, non-functional properties of services are heavily dependent on the activity of the network delivering those services whilst the network activity follows certain time-sensitive rules. We present a service selection algorithm that takes into account time-sensitive variations of non-functional propensities of services to identify a service combination offering the highest quality within a specified time interval.

  • 46518.
    Xu, Linlin
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Wireless Hybrid Bio-Sensing withMobile based Monitoring System2013Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Personal telehealth plays a crucial role in addressing global challenges of aging population and rising cost for health care. Tiny and wirelessly connected medical sensors, for example embedded in clothes or on the body, will be an integrated part of lifestyle, and will allow hospitals to remotely diagnose patients in their home.  In this thesis, a wireless bio-sensing with smart phone based monitoring system is proposed to provide a home based telehealth care for continuous monitoring. The system consists of two main parts: a wireless sensor and a health application on the smart phone. This thesis is to design the first part of the system - a wireless temperature and electrocardiography (ECG) sensor. The sensor integrates ECG front-end analog block, a micro-controller and a Bluetooth low energy (BLE) connectivity IC on a single board. To achieve the miniaturization of the sensor and users’ comfort in mind, the sensor is designed as a miniaturized hybrid system utilizing flexible batteries and printed electrodes. This can efficiently detect ECG signals and transfer them to a smart phone through BLE link.

     

  • 46519. Xu, Luzhou
    et al.
    Stoica, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Reglerteknik.
    Li, Jian
    A block-diagonal growth curve model2006Inngår i: Digital signal processing (Print), ISSN 1051-2004, E-ISSN 1095-4333, Vol. 16, nr 6, s. 902-912Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We consider a variation of the growth curve (GC) model, referred to as the block-diagonal growth curve (BDGC) model, where the unknown regression coefficient matrix is constrained to be block-diagonal. A closed-form approximate maximum likelihood (AML) estimator for this model is derived based on the maximum likelihood principle. We analyze the statistical properties of this method theoretically and show that the AML estimate is unbiased and asymptotically statistically efficient for a large snapshot number. Via numerical examples in wireless communications, we also show that the proposed AML estimator can achieve excellent estimation accuracy.

  • 46520.
    Xu, Shangjin
    Linköpings universitet, Institutionen för datavetenskap.
    Design and Implementation of the Ephemerizer System2007Independent thesis Advanced level (degree of Magister), 20 poäng / 30 hpOppgave
    Abstract [en]

    This thesis describes the system design and implementation of the secure Ephemerizer System that was first introduced by Radia Perlman in 2005. The system is designed to enable users to keep data for a finite period of time before making the data unrecoverable by destroying the keys with which the data was encrypted. The task of the Ephemerizer System service is to create, advertise, and destroy keys required for the Ephemerizer System's functionalities.

    We designed the Ephemerizer System Service's security by placing the sensitive key management modules into a Trusted Computing Base (TCB). Our compartmentalized approach distributes security requirements at different sensitivity levels into different protection domains. In our approach, we implement the trusted protection domain (our TCB) on a tamper-resistant Javacard.

    We placed the key storage database into the partly trusted protection domain to improve scalability and availability of the Ephemerizer System. The partly trusted protection domain requires memory isolation and other security mechanisms provided by the underlying operating system. We implemented several mechanisms on the TCB, such as the signature engine, cryptographic modules, the on-card expiration validator, and on-card time verification. We make the Ephemerizer System available to users as a web service and expose it though a uniform API. This approach enables the seamless integration of the Ephemerizer System into business processes on heterogeneous platforms.

  • 46521.
    Xu, Shuiai
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad.
    Automatic location of number plates at night time2014Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    In transport information area, in order to improve control system, identifying vehicle plates is very important. For that reason we are focusing on recognizing the vehicle plate from an image. To distinguish one car from others, one should remove all area except the vehicle plate. Due to the extra difficulties, like limited light, distances, moving etc., it can be hard to detect the final vehicle plate. In this work, we have solved the location of vehicle plate at night time, by separating the objects from the background by using morphological processing and analyzing the characteristics of vehicle plates by using removal of noise and mathematical calculations. According to some characteristics of cars and vehicle plates we developed an algorithm to detect the number of final vehicle plate. This algorithm works fine, and the detected result is accurate.

  • 46522. Xu, T
    et al.
    Jacobsen, G
    RISE., Swedish ICT, Acreo.
    Popov, S
    Forzati, M
    RISE., Swedish ICT, Acreo.
    Mårtensson, J
    RISE., Swedish ICT, Acreo.
    Mussolin, M
    Li, J
    RISE., Swedish ICT, Acreo.
    Wang, K
    Zhang, Y
    RISE., Swedish ICT, Acreo.
    Friberg, AT
    Frequency-domain Chromatic Dispersion Equalization using Overlap-add Methods in Coherent Optical System2011Inngår i: Journal of optical communications, ISSN 0173-4911, E-ISSN 2191-6322, Vol. 21, s. 131-5Artikkel i tidsskrift (Fagfellevurdert)
  • 46523. Xu, T
    et al.
    Jacobsen, G
    RISE., Swedish ICT, Acreo.
    Popov, S
    Li, J
    RISE., Swedish ICT, Acreo.
    Friberg, AT
    Zhang, Y
    RISE., Swedish ICT, Acreo.
    Analytical estimation of phase noise influence in coherent transmission system with digital dispersion equalization2011Inngår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 19, nr 8, s. 7756-68Artikkel i tidsskrift (Fagfellevurdert)
  • 46524. Xu, T
    et al.
    Jacobsen, G
    RISE., Swedish ICT, Acreo.
    Popov, S
    Li, J
    RISE., Swedish ICT, Acreo.
    Sergeyev, S
    Friberg, AT
    Zhang, Y
    RISE., Swedish ICT, Acreo.
    Analytical BER performance in differential n-PSK coherent transmission system influenced by equalization enhanced phase noise2015Inngår i: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 334, s. 222-Artikkel i tidsskrift (Fagfellevurdert)
  • 46525. Xu, T
    et al.
    Jacobsen, G
    RISE., Swedish ICT, Acreo.
    Popov, S
    Li, J
    RISE., Swedish ICT, Acreo.
    Vanin, E
    RISE., Swedish ICT, Acreo.
    Wang, K
    Friberg, AT
    Zhang, Y
    RISE., Swedish ICT, Acreo.
    Chromatic dispersion compensation in coherent transmission system using digital filters2010Inngår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 18, s. 16243-57Artikkel i tidsskrift (Fagfellevurdert)
  • 46526. Xu, T
    et al.
    Jacobsen, G
    RISE., Swedish ICT, Acreo.
    Popov, S
    Li, J
    RISE., Swedish ICT, Acreo.
    Wang, K
    Friberg, A T
    Normalized LMS digital filter for chromatic dispersion equalization in 112-Gbit/s, PDM-QPSK coherent optical transmission system2010Inngår i: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 283, s. 963-7Artikkel i tidsskrift (Fagfellevurdert)
  • 46527. Xu, T.
    et al.
    Jacobsen, Gunnar
    RISE., Swedish ICT, Acreo.
    Popov, S.
    Li, J.
    Liu, T.
    Zhang, Y.
    Close-form expression of one-tap normalized LMS carrier phase recovery in optical communication systems2016Inngår i: Proceedings of SPIE - The International Society for Optical Engineering, 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The performance of long-haul high speed coherent optical fiber communication systems is significantly degraded by the laser phase noise and the equalization enhanced phase noise (EEPN). In this paper, the analysis of the one-tap normalized least-mean-square (LMS) carrier phase recovery (CPR) is carried out and the close-form expression is investigated for quadrature phase shift keying (QPSK) coherent optical fiber communication systems, in compensating both laser phase noise and equalization enhanced phase noise. Numerical simulations have also been implemented to verify the theoretical analysis. It is found that the one-tap normalized least-mean-square algorithm gives the same analytical expression for predicting CPR bit-error-rate (BER) floors as the traditional differential carrier phase recovery, when both the laser phase noise and the equalization enhanced phase noise are taken into account.

  • 46528. Xu, T.
    et al.
    Jacobsen, Gunnar
    RISE., Swedish ICT, Acreo.
    Popov, S.
    Li, Jie
    RISE., Swedish ICT, Acreo.
    Liu, T.
    Zhang, Y.
    Bayvel, P.
    Analytical investigations on carrier phase recovery in dispersion-unmanaged n-PSK coherent optical communication systems2016Inngår i: Photonics, ISSN 2304-6732, Vol. 3, nr 4, artikkel-id 51Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Using coherent optical detection and digital signal processing, laser phase noise and equalization enhanced phase noise can be effectively mitigated using the feed-forward and feed-back carrier phase recovery approaches. In this paper, theoretical analyses of feed-back and feed-forward carrier phase recovery methods have been carried out in the long-haul high-speed n-level phase shift keying (n-PSK) optical fiber communication systems, involving a one-tap normalized least-mean-square (LMS) algorithm, a block-wise average algorithm, and a Viterbi-Viterbi algorithm. The analytical expressions for evaluating the estimated carrier phase and for predicting the bit-error-rate (BER) performance (such as the BER floors) have been presented and discussed in the n-PSK coherent optical transmission systems by considering both the laser phase noise and the equalization enhanced phase noise. The results indicate that the Viterbi-Viterbi carrier phase recovery algorithm outperforms the one-tap normalized LMS and the block-wise average algorithms for small phase noise variance (or effective phase noise variance), while the one-tap normalized LMS algorithm shows a better performance than the other two algorithms for large phase noise variance (or effective phase noise variance). In addition, the one-tap normalized LMS algorithm is more sensitive to the level of modulation formats.

  • 46529. Xu, T.
    et al.
    Jacobsen, Gunnar
    RISE., Swedish ICT, Acreo.
    Popov, S.
    Liu, T.
    Zhang, Y.
    Bayvel, P.
    Analytical estimation in differential optical transmission systems influenced by equalization enhanced phase noise2016Inngår i: 2016 Progress In Electromagnetics Research Symposium, PIERS 2016 - Proceedings, 2016, s. 4844-4848Konferansepaper (Fagfellevurdert)
    Abstract [en]

    An analytical model is presented for assessing the performance of the bit-error-rate (BER) in the differential m-level phase shift keying (m-PSK) transmission systems, where the influence of equalization enhanced phase noise (EEPN) has been considered. Theoretical analysis has been carried out in differential quadrature phase shift keying (DQPSK), differential 8-PSK (D8PSK), and differential 16-PSK (D16PSK) optical transmission systems. The influence of EEPN on the BER performance, in term of signal-to-noise ratio (SNR), are investigated for different fiber dispersion, LO laser linewidths, symbol rates, and modulation formats. Our analytical model achieves a good agreement with previously reported EEPN induced BER floors, and can give an accurate prediction for the DQPSK system, and a leading-order approximation for the D8PSK and the D16PSK systems.

  • 46530. Xu, T
    et al.
    Li, J
    RISE., Swedish ICT, Acreo.
    Jacobsen, G
    RISE., Swedish ICT, Acreo.
    Popov, S
    Djupsjöbacka, A
    RISE., Swedish ICT, Acreo.
    Schatz, R
    Zhang, Y
    RISE., Swedish ICT, Acreo.
    Bayvel, P
    Field trial over 820km installed SSMF its potential Terabit/s super channel application with up to 57.5-Gbaud DP-QPSK transmission2015Inngår i: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 353, s. 133-Artikkel i tidsskrift (Fagfellevurdert)
  • 46531. Xu, T.
    et al.
    Liu, T.
    Zhang, Yafan
    RISE., Swedish ICT, Acreo.
    Jacobsen, Gunnar
    RISE., Swedish ICT, Acreo.
    Li, J.
    Popov, S.
    Digital Adaptive Carrier Phase Estimation in Multi-level Phase Shift Keying Coherent Optical Communication Systems2016Inngår i: Proceedings - 2016 3rd International Conference on Information Science and Control Engineering, ICISCE 2016, 2016, s. 1293-1297Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The analysis of adaptive carrier phase estimation is investigated in long-haul high speed n-level phase shift keying (n-PSK) optical fiber communication systems based on the one-tap normalized least-mean-square (LMS) algorithm. The close-form expressions for the estimated carrier phase and the bit-error-rate floor have been derived in the n-PSK coherent optical transmission systems. The results show that the one-tap normalized LMS algorithm performs pretty well in the carrier phase estimation, but will be less effective with the increment of modulation levels, in the compensation of both intrinsic laser phase noise and equalization enhanced phase noise.

  • 46532.
    Xu, Ting
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informationssystem och -teknologi.
    Integration and Evaluation of IoT Hardware and Software platforms2017Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    The Internet of Things (IoT) is growing rapidly these years and the influence of IoT on everyday life and behavior are also increasing. It is a network that connects physical devices, vehicles, buildings, and other items and embedded with electronics, software, sensors, actuators, and network connectivity so that these objects can collect and exchange data. It has been utilized in lots of domains, such as transportation and logistics domain, healthcare domain, smart environment domain, personal and social domain. It is estimated that the IoT will consist of almost 50 billion objects by 2020. IoT Gateway is really important in IoT, which can bridge traditional communication networks with sensor networks to make the network communication easier. IoT communication is of vital importance in today’s life. This study has the aim of integrating and evaluating of IoT gateways and IoT communication systems. It proposes a scenario where the IoT gateway connects to an actuator in order to control the actuator and transmit the data via the IoT communication system, creates a demonstrator by setting up the communication between the IoT gateway platform and the IoT communication system, measures and evaluates the performance in terms of latency and throughput using the implemented scenario, and at last draws the conclusion.

  • 46533.
    Xu, Wei
    Linköpings universitet, Institutionen för datavetenskap.
    SVM-based algorithms for aligning ontologies using literature2008Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Ontologies is one of the key techniques used in Semantic Web establishment. Nowadays,many ontologies have been developed and it is critical to understand the relationships between the terms of the ontologies, i.e. we need to align the ontologies.

    This thesis deals with an approach for finding relationships between ontologies using literature by classifying documents related to terms in the ontologies.

     

    In this project the general method from [1] is used, but in the classifier generation part, a brand new classifier based on SVMs algorithm is implemented by LPU and SVMlight. We evaluate our approach and compare it to previous approaches.

  • 46534.
    Xu, Xiaoji
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik.
    Zhi, Huanyu
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik.
    Study Of Game Elements Impacting On SE Course Completion Rate In MOOCs2017Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Context. SE is a growing field in both academia and industry, online SE education becomes more and more prevalent recent years. Massive Open Online Courses, as an emerging type of open educational resource, provide SE courses a much wider development space. But on the other hand, MOOCs limit SE courses because its low completion rate. Game elements are used to address this issue, but the impact of game elements on completion rate of specific MOOCs and SE courses in MOOCs are not clear. It is necessary to find whether and how game elements could help students finish SE courses. Explore the method and idea of improving SE courses in MOOCs through game elements.

    Objectives. In this study authors investigate what game elements are applied in SE courses in MOOCs platforms, evaluate the impact of MOOCs game elements on SE courses completion situation. Based on the analysis and summary of the data and result, propose suggestion to improve SE courses.

    Methods. Authors conduct a systematic literature to find the game elements used in SE courses in MOOCs. Conducting the survey to get the data of the MOOCs game elements on completion situation in general and data of survey is analyzed by mathematical statistics. The interview is used to find how the game elements of MOOC and SE education simulation impact on learning SE courses on MOOCs by inductive content analysis.

    Results. In systematic literature review, 23 studies are selected from 358 papers of six databases. Forty-one responses of questionnaires are received and twenty interviewees take part in this study. Authors find that game elements have been applied in MOOCs in various ways and research results about effort of game elements are positive. In this study, the results of analyzing the received data in survey show that there is no significant impact of game elements on course completion rate. The interview shows that specific game element is necessary for students finishing their courses and some game elements are not well designed in students’ perspective. Two specific suggestions to improve SE courses are proposed according to survey and interview result.

    Conclusions. This research collects data through SLR, survey and interview, and evaluates the impact of game elements on SE course completion situation through analysis, comparison and summary. The result is helpful to people who design and develop the game elements in MOOCs platform. Focusing on the character of SE education and SE courses, some suggestion of designing and modifying the game elements are provided. This enables the game elements designer to target designing and arranging game elements better.

  • 46535.
    Xu, Xun
    et al.
    Univ Auckland, Dept Mech Engn, Sch Engn, Auckland 1142, New Zealand.
    Wang, Lihui
    Högskolan i Skövde, Forskningscentrum för Virtuella system. Högskolan i Skövde, Institutionen för teknik och samhälle.
    Newman, Stephen T.
    Univ Bath, Dept Mech Engn, Bath BA2 7AY, Avon, England.
    Computer-aided process planning: A critical review of recent developments and future trends2011Inngår i: International journal of computer integrated manufacturing (Print), ISSN 0951-192X, E-ISSN 1362-3052, Vol. 24, nr 1, s. 1-31Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    For the past three decades, computer-aided process planning (CAPP) has attracted a large amount of research interest. A huge volume of literature has been published on this subject. Today, CAPP research faces new challenges owing to the dynamic markets and business globalisation. Thus, there is an urgent need to ascertain the current status and identify future trends of CAPP. Covering articles published on the subjects of CAPP in the past 10 years or so, this article aims to provide an up-to-date review of the CAPP research works, a critical analysis of journals that publish CAPP research works, and an understanding of the future direction in the field. First, general information is provided on CAPP. The past reviews are summarised. Discussions about the recent CAPP research are presented in a number of categories, i.e. feature-based technologies, knowledge-based systems, artificial neural networks, genetic algorithms, fuzzy set theory and fuzzy logic, Petri nets, agent-based technology, Internet-based technology, STEP-compliant CAPP and other emerging technologies. Research on some specific aspects of CAPP is also provided. Discussions and analysis of the methods are then presented based on the data gathered from the Elsevier’s Scopus abstract and citation database. The concepts of ‘Subject Strength’ of a journal and ‘technology impact factor’ are introduced and used for discussions based on the publication data. The former is used to gauge the level of focus of a journal on a particular research subject/domain, whereas the latter is used to assess the level of impact of a particular technology, in terms of citation counts. Finally, a discussion on the future development is presented.

  • 46536.
    Xu, Yang
    et al.
    Lund University, Sweden.
    Årzen, Karl-Erik
    Lund University, Sweden.
    Cervin, Anton
    Lund University, Sweden.
    Bini, Enrico
    Scuola Superiore Sant’Anna, Italy.
    Tanasa, Bogdan
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Exploiting Job Response-Time Information in the Co-Design of Real-Time Control Systems2015Inngår i: 2015 IEEE 21ST INTERNATIONAL CONFERENCE ON EMBEDDED AND REAL-TIME COMPUTING SYSTEMS AND APPLICATIONS, Institute of Electrical and Electronics Engineers (IEEE), 2015, s. 247-256Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We consider a real-time system of multiple tasks, each task having a plant to control. The overall quadratic control cost is to be optimized. We exploit the periodicity of the task response time, which corresponds to a periodic delay pattern in the feedback control loop. Perturbed periods are used as a tool to find a finite hyper period. We present an analytical procedure to design a periodic linear-quadratic-Gaussian (LQG) controller for tasks with fixed execution times as well as a numerical solution to the periodic -- stochastic LQG problem for tasks with variable execution times. The controllers are evaluated using simulations in real-time scheduling and control co-design examples.

  • 46537.
    Xu, Yinglai
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Fluid Interactive Information Visualization: A Visualization Tool for Book Recommendation2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The accuracy of recommender systems has been largely discussed and the user experience of the recommended systems is now becoming a new focus. Combining recommendations with information visualization (InfoVis) can be a way to improve the acceptance of the system. This thesis investigates how InfoVis can support the recommended systems, aiming at improving the enjoyment and engagement of the user experience. Three prototypes are designed to evaluate the impact of using InfoVis and fluid interactive InfoVis on user engagement and enjoyment with exploratory of recommended books. The methods of product reaction card and Likert questionnaire are used during the evaluation. Results suggest that InfoVis is a viable way to improve the engagement and enjoyment of the book recommended system and it should be further researched. 

  • 46538.
    Xu, Youshi
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Zhang, Tingting
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    A VLSI Design for Universal Reed-Solomon Erasure Decoder2002Inngår i: International Conference on Signal Processing Proceedings, ICSP, IEEE conference proceedings, 2002, s. 398-401, artikkel-id 1181074Konferansepaper (Fagfellevurdert)
  • 46539.
    Xu, Youshi
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Zhang, Tingting
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    An implementation of coding scheme for packet loss protection2001Inngår i: Proceedings of the 11th International Packet Video Workshop, 2001Konferansepaper (Annet vitenskapelig)
  • 46540.
    Xu, Youshi
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Zhang, Tingting
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Variable shortened-and-punctured Reed-Solomon codes for packet loss protection2002Inngår i: IEEE Transactions On Broadcasting, ISSN 0018-9316, Vol. 48, nr 3, s. 237-245Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, techniques of Reed-Solomon (RS) codes to recover lost packets in digital video/audio broadcasting and packet switched network communications are reviewed. Usually, different RS codes and their corresponding encoders/decoders are designed and utilized to meet different requirements for different systems and applications. We incorporate these techniques into a variable RS code and present an encoding and decoding algorithm suitable for the variable RS code. A mother RS code can be used to produce a variety of RS codes and the same encoder/decoder can be used for all the derivative codes with adding/detecting zeros, removing a part of parity symbols, and adding erasures. A VLSI implementation for erasure decoding of the proposed variable RS code is described and the achievable performance is quantitatively analyzed. A typical example shows that the signal processing speed is up to 2.5 Gbits/second and the processing delay is less than one millisecond, when integrating the decoder on a single chip. Therefore, the proposed algorithm and the encoder/decoder can universally be utilized for different applications with various requirements, such as transmission data rate, packet length, packet loss protection capacity, as well as layered protection and adaptive redundancy protection in DVB/DAB broadcasting, Internet and mobile Internet communications.

  • 46541.
    Xu, Youzhi
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Zhang, Tingting
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    An adaptive redundancy technique for wireless indoor multicasting2000Inngår i: IEEE Symposium on Computers and Communications - Proceedings, Los Alamitos, Calif: IEEE Computer Society , 2000, s. 607-614Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we present an adaptive technique that combines forward error correction (FEC) with channel state estimation (CSE) and automatic repeat request (ARQ) for packet loss recovery in wireless indoor multicast systems. The novel aspect of the technique is its ability to achieve significant packet throughput with high data reliability, to avoid feedback acknowledgement (ACK) implosion, as well as to reduce and flexibly to limit delay for real-time applications. We suggest a set of criteria to measure the multicast performance and simulate a simple two-state indoor channel model. The simulation results show that the proposed technique significantly improves the communication quality and channel efficiency, to compare with traditional FEC and ARQ techniques.

  • 46542.
    Xu, Yuan
    Linköpings universitet, Institutionen för datavetenskap.
    A Study of Scalability and Performance of Solaris Zones2007Independent thesis Basic level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    This thesis presents a quantitative evaluation of an operating system virtualization technology known as Solaris Containers or Solaris Zones, with a special emphasis on measuring the influence of a security technology known as Solaris Trusted Extensions. Solaris Zones is an operating system-level (OS-level) virtualization technology embedded in the Solaris OS that primarily provides containment of processes within the abstraction of a complete operating system environment. Solaris Trusted Extensions presents a specific configuration of the Solaris operating system that is designed to offer multi-level security functionality.

    Firstly, we examine the scalability of the OS with respect to an increasing number of zones. Secondly, we evaluate the performance of zones in three scenarios. In the first scenario we measure - as a baseline - the performance of Solaris Zones on a 2-CPU core machine in the standard configuration that is distributed as part of the Solaris OS. In the second scenario we investigate the influence of the number of CPU cores. In the third scenario we evaluate the performance in the presence of a security configuration known as Solaris Trusted Extensions. To evaluate performance, we calculate a number of metrics using the AIM benchmark. We calculate these benchmarks for the global zone, a non-global zone, and increasing numbers of concurrently running non-global zones. We aggregate the results of the latter to compare aggregate system performance against single zone performance.

    The results of this study demonstrate the scalability and performance impact of Solaris Zones in the Solaris OS. On our chosen hardware platform, Solaris Zones scales to about 110 zones within a short creation time (i.e., less than 13 minutes per zone for installation, configuration, and boot.) As the number of zones increases, the measured overhead of virtualization shows less than 2% of performance decrease for most measured benchmarks, with one exception: the benchmarks for memory and process management show that performance decreases of 5-12% (depending on the sub-benchmark) are typical. When evaluating the Trusted Extensions-based security configuration, additional small performance penalties were measured in the areas of Disk/Filesystem I/O and Inter Process Communication. Most benchmarks show that aggregate system performance is higher when distributing system load across multiple zones compared to running the same load in a single zone.

  • 46543.
    Xu, Zhengyan
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad.
    Zhou, Yibing
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad.
    Specific Handwritten Chinese Character Recognition Based on Artificial Intelligence2013Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    As internet techniques are developing more and more quickly, internet becomes the

    main way to communicate with the outside world. In this case, written information

    on paper needs to be converted to digital information urgently, increasing the need

    for handwritten character recognition. The aim of this work is to discuss methods

    that can be used to recognize handwritten Chinese characters. We study geometric

    features and clustering of handwritten Chinese characters from three aspects, which

    are handwritten character preprocessing, feature extraction and clustering. To test

    the correctness of our method, an application was built that could learn to recognize

    five medium-hard handwritten Chinese characters by using a neural network.

  • 46544. Xuan, Y
    et al.
    Sandberg, M
    RISE., Swedish ICT, Acreo.
    Berggren, M
    Crispin, X
    An all-polymer-air PEDOT battery2012Inngår i: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 13, s. 623-7Artikkel i tidsskrift (Fagfellevurdert)
  • 46545.
    XUE, RUI
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Human Computer Interaction Study: Designing a Mobile Web-based Vaccination Service System Interface for Uganda in Low Resource Settings2013Independent thesis Advanced level (degree of Master (Two Years))Oppgave
    Abstract [en]

    Recently, the coverage rating of child vaccination services in developing countries, like Uganda, is lower than developed countries. The low resource setting is the reason that causes the poor vaccination performance. Health workers suffer from the heavy workload, low budget supplement and bad traffic condition, etc. Which constrains the quality of vaccination services. In this thesis, the author designs a mobile web-based vaccination service system, to improve the quality of vaccination service, within the low resource setting. A study in HCI is carried out to design a vaccination service system in the low resource settings of Uganda. Through theoretical study, the author collects the knowledge about how to apply HCI theory to system interface design. A related work study is carried out to help the author to choose the design solution. Through comparing the design with related works, the strength of using the author’s design solution in low resource of Uganda is verified. A field study helps to collect information about the user’s characteristics, which is used for designing a user-friendly system interface. An internal focus group helps to improve the design quality. The author delivers a case study example which could be evaluated and borrowed by other researchers who design a similar system. Additionally, findings from the qualitative research could be used for further research.

  • 46546.
    Xue, Ruidong
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Improved association rule mining to sensor time series2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 46547.
    Xue, Ruidong
    et al.
    Donghua Univ, Sch Comp Sci & Technol, Shanghai, Peoples R China.
    Zhang, Tingting
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Chen, Dehua
    Donghua Univ, Sch Comp Sci & Technol, Shanghai, Peoples R China.
    Le, Jiajin
    Donghua Univ, Sch Comp Sci & Technol, Shanghai, Peoples R China.
    Lavassani, Mehrzad
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Sensor Time Series Association Rule Discovery Based on Modified Discretization Method2016Inngår i: 2016 FIRST IEEE INTERNATIONAL CONFERENCE ON COMPUTER COMMUNICATION AND THE INTERNET (ICCCI 2016), IEEE, 2016, s. 196-202, artikkel-id 7778907Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Association rule discovery from sensor time series is a challenge. Because the time series has high dimensional, numerical and continuous nature. However the general association methods can only deal with data which are symbolic and discrete. And the general association methods have high processing time consumption when the data have high dimension. So a useful framework is proposed, which is pre-processing, representation, discretization and temporal association mining. In the discretization section, a modified discretization method is proposed which can combine the advantages of other methods, such as piecewise aggregate approximation (PAA), knee point selection, symbolic aggregate approximation (SAX) and monotonicity feature extraction. In the association section, a modified Apriori algorithm is proposed to discover special patterns and normal rules.

  • 46548.
    Xue, Shang
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Xu, Youzhi
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Oelmann, Bengt
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Hybrid Golomb codes for a group of quantised GG sources2003Inngår i: IEE Proceedings - Vision Image and Signal Processing, ISSN 1350-245X, E-ISSN 1359-7108, Vol. 150, nr 4, s. 256-260Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The authors develop a class of codes for quantised generalised Gaussian (GG) sources. This new class of codes, that are called hybrid Golomb (HG) codes, are hybrids of Golomb-Rice (GR) codes and exp-Golomb (EG) codes. They integrate the properties of both GR and EG codes, which makes their performance more robust under variable source parameters. The efficiencies of the three classes of codes are compared and it is shown that the set of HG codes have efficiencies of approximately 70% or greater for a wide range of parameter values, whereas GR and EG codes can have efficiencies lower than 20%. The efficiencies of the set of HG codes are also compared with the set of EG codes that have the best performance under parameter scaling. It is shown that. this set of HG codes still achieve a higher efficiency.

  • 46549. Xumin, Zhu
    et al.
    Li, Jian
    Stoica, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Reglerteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för systemteknik.
    Knowledge-aided adaptive beamforming2008Inngår i: Proceedings of the 2008 IEEE International Conference on Acoustics, Speech, and Signal Processing: March 30 - April 4, 2008, Las Vegas, Nevada, USA, 2008, s. 2337-2340Konferansepaper (Fagfellevurdert)
  • 46550.
    XuXiao, Ma
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Eliminating the latency using different Kalman filters: for a virtual reality based teleoperation system2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Latency has always been one of the essential problems within Virtual Reality (VR) domain since VR is inherently an interactive paradigm which performs the real-time estimation of human motions. From the user's point of view, the latency extremely reduces the presence experience of VR systems, especially when user won’t able to perform interactions accurately. To compensate the excessive latency, different prediction methods on human motion were studied in recent years. Among them, Kalman Filter was the most popular choice. However, the effectiveness of using Kalman Filter to eliminate the latency for VR systems is not always satisfactory in practice since the accuracy of the estimation of the users’ motion depends on several factors: the linearity of the motion, the prediction time, the computational time, and the algorithm’s limitation.Therefore, this thesis presents a VR-based haptic teleoperation system to study how to effectively eliminate the latency effectively using Kalman Filter. For investigating the performances of different prediction methods for VR systems with several factors considered, two types of Kalman Filter: Linear Kalman Filter (LKF) and Unscented Kalman Filter (UKF) have been used to predict the haptic motion dataset, under different amount of simulated latencies.The result shows, both LKF and UKF provide a good performance at compensating the latency. For 200ms latency, both filters satisfactorily eliminate the latency and improve the interaction effectiveness. The comparative study shows, LKF provides better performance since the linear rotational motion dataset captured by haptic device was used; both filters show a reduced performance when the prediction time is increased. Besides, UKF requires more computational time than LKF.

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