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  • 251.
    Buckwalter, Claes
    Linköpings universitet, Institutionen för teknik och naturvetenskap.
    INFLOW: Structured Print Job Delivery2003Independent thesis Basic level (professional degree)Oppgave
    Abstract [en]

    More and more print jobs are delivered from customer to printer digitally over the Internet. Although Internet-based job delivery can be highly efficient, companies in the graphic arts and printing industry often suffer unnecessary costs related to this type of inflow of print jobs to their production workflows. One of the reasons for this is the lack of a well-defined infrastructure for delivering print jobs digitally over the Internet.

    This thesis presents INFLOW - a prototype for a print job delivery system for the graphic arts and printing industry. INFLOW is a web-based job delivery system that is hosted on an Internet-connected server by the organization receiving the print jobs. Focus has been on creating a system that is easy to use, highly customizable, secure, and easy to integrate with existing and future systems from third-party vendors. INFLOW has been implemented using open standards, such as XML and JDF (Job Definition Format).

    The requirements for ease-of-use, high customizability and security are met by choosing a web-based architecture. The client side is implemented using standard web technologies such as HTML, CSS and JavaScript while the serverside is based on J2EE, Java Servlets and Java Server Pages (JSP). Using a web browser as a job delivery client provides a highly customizable user interface and built in support for encrypted file transfers using HTTPS (HTTP over SSL).

    Process automation and easy integration with other print production systems is facilitated with CIP4’s JDF (Job Definition Format). INFLOW also supports"hot folder workflows"for integration with older preflight software and other hot folder-based software common in prepress workflows.

  • 252.
    Burghout, Wilco
    KTH, Tidigare Institutioner                               , Infrastruktur.
    Hybrid microscopic-mesoscopic traffic simulation2004Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    Traffic simulation is an important tool for modelling the operations of dynamic traffic systems and helps analyse the causes and potential solutions of traffic problems such as congestion and traffic safety. Microscopic simulation models provide a detailed representation of the traffic process, which makes them most suitable for evaluation of complicated traffic facilities and Intelligent Transportation Systems that often consist of complex traffic management, safety and information systems. Macroscopic and mesoscopic models on the other hand, capture traffic dynamics in lesser detail, but are faster and easier to apply and calibrate than microscopic models. Therefore they are most suitable for modelling large networks, while microscopic models are usually applied to smaller areas.

    The objective of this thesis is to combine the strengths of both modelling approaches and diminish their individual weaknesses by constructing a hybrid mesoscopic-microscopic model that applies microscopic simulation to areas of specific interest, while simulating a surrounding network in lesser detail with a mesoscopic model.

    Earlier attempts at hybrid modelling have concentrated on integrating macroscopic and microscopic models and have proved difficult due to the large difference between the continuous-flow representation of traffic in macroscopic models and the detailed vehicle-and driver-behaviour represented in microscopic models. These problems are solved in this thesis by developing a mesoscopic vehicle-based and event-based model that avoids the (dis)aggregation problems of traffic flows at the inter-model boundaries. In addition, this thesis focuses on the general problems of consistency across the entire hybrid model.

    The requirements are identified that are important for a hybrid model to be consistent across the models at different levels of detail. These requirements vary from network and route-choice consistency to consistency of traffic dynamics across the boundaries of the micro- and mesoscopic submodels. An integration framework is proposed that satisfies these requirements. This integration framework has been implemented in a prototype hybrid model, MiMe, which is used to demonstrate the correctness of the solutions to the various integration issues. The hybrid model integrates MITSIMLab, a microscopic traffic simulation model, and Mezzo, the newly developed mesoscopic model. Both the hybrid model and the new Mezzo model are applied in a number of case studies, including a network in the North of Stockholm, which show their validity and applicability. The results are promising and support both the proposed integration architecture and the importance of integrating microscopic and mesoscopic models.

  • 253.
    Burman, Erik
    et al.
    Department of Mathematics, University College London, London, United Kingdom.
    Hansbo, Peter
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Larson, Mats G.
    Department of Mathematics and Mathematical Statistics, Umeå University, Umeå, Sweden.
    A simple finite element method for elliptic bulk problems with embedded surfaces2018Inngår i: Computational Geosciences, ISSN 1420-0597, E-ISSN 1573-1499Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we develop a simple finite element method for simulation of embedded layers of high permeability in a matrix of lower permeability using a basic model of Darcy flow in embedded cracks. The cracks are allowed to cut through the mesh in arbitrary fashion and we take the flow in the crack into account by superposition. The fact that we use continuous elements leads to suboptimal convergence due to the loss of regularity across the crack. We therefore refine the mesh in the vicinity of the crack in order to recover optimal order convergence in terms of the global mesh parameter. The proper degree of refinement is determined based on an a priori error estimate and can thus be performed before the actual finite element computation is started. Numerical examples showing this effect and confirming the theoretical results are provided. The approach is easy to implement and beneficial for rapid assessment of the effect of crack orientation and may for example be used in an optimization loop. 

  • 254.
    Bustos, Sebastian
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Data- och elektroteknik.
    Grek, Niklas
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Data- och elektroteknik.
    Säkerhetsklassificering av IT-system på Fläkt Woods AB2006Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    This report presents a method for modelling a computer system from a security perspective. The questions that are going to be treated are:

    • What defines a secure system and how does the company relate to these factors?

    • What are the threats today based on hardware/software, human factors and company routines/policies?

    • What measures should be taken for the organisation to reach a higher level of security for their systems?

    • How do we develop a method for classification of security and what components should it contain?

    • What changes are reasonable and necessary with the respect to the company’s resources?

    The report has been done through interviews and analysis of existing systems on Fläkt Woods AB. From analysis of material, the aspects judged relevant to the subject and to the company’s needs, have been compiled to a document. It is a model for guidelines to work with security classification of IT-systems.

    The combination of the method for information and the security classification has been clear through the work on the rapport. The method that has been developed for work with security classification of IT systems can therefore not be used as an isolated occurrence to reach the wanted results but should be integrated with the existing classification of information.

    Our conclusions are reflected by the complexity of the project together with the fact that computer security is a topic that includes all parts in an IT- supported organisation. The analyses have given us a good picture of the threats to an organisation. It has clearly been shown, that much security related problems are based on direct organisational problems such as the lack of resources and requirements of system specific guidelines and policies.

  • 255.
    Butun, Ismail
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informationssystem och -teknologi.
    Pereira, Nuno
    Polytechnic Institute of Porto, Porto, Portugal .
    Gidlund, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informationssystem och -teknologi.
    Analysis of LoRaWAN V1.1 Security2018Inngår i: Proceedings of the 4th ACM MobiHoc Workshop on Experiences with the Design and Implementation of Smart Objects (SMARTOBJECTS '18)., ACM Digital Library, 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    LoRa and the LoRaWAN specification is a technology for Low Power Wide Area Networks (LPWAN) designed to allow connectivity for connected objects, such as remote sensors. Several previous works revealed various weaknesses regarding the security of LoRaWAN v1.0 (the official 1st draft) and these led to improvements included in LoRaWAN v1.1, released on Oct 11, 2017. In this work, we provide the first look into the security of LoRaWAN v1.1. We present an overview of the protocol and, importantly, present several threats to this new version of the protocol. Besides, we propose our own ramification strategies for the mentioned threats, to be used in developing next version of LoRaWAN. The threats presented were not previously discussed, they are possible even within the security assumptions of the specification and are relevant for practitioners implementing LoRa-based applications as well researchers and the future evolution of the LoRaWAN specification.

  • 256.
    Bygdeson, Andreas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Cartographer: En kartbaserad friluftsapplikation2016Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Målet med det här arbetet har varit att utveckla en friluftsapplikation för människor som rör sig i skog och mark antingen i arbetet eller i privatlivet. Med syfte att låta de skapa och placera ut markörer på en karta med aktivt uppdaterande gps positionering. För att uppnå detta har Google Maps använts som gränssnitt för att hämta och hantera kartinformation och en applikation har designats i flödesscheman utefter kravspecifikationen och i enlighet med Jacob Nielsens användbarhetsprinciper. Hallway test metoden har använts för att utvärdera hur väl användbarhetsdesignen har uppnått sina mål. Applikationen har sedan konstruerats i Java och Android Studio mot Androids mobila plattform. Utvecklingen har följt den planerade designen och uppnått samtliga konkreta mål som specificerades och i synnerhet användbarhetsmålen. Flera funktionella mål har identifierats att kunna optimeras ytterligare och en rad förslag på vidareutveckling av applikationen har tagits fram för eventuella framtida arbeten.

  • 257.
    Bäckstedt, Dennis
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informationssystem och -teknologi.
    Felsökning och optimering av trådlöst nätverk IEEE 802.11ac2017Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Trådlösa nätverk växer sig allt starkare och normen är nu mera att man i ett kontorslandskap eller

    hem skall kunna slå sig ner med sin laptop och jobba utan att behöva oroa sig om nätverksuttag

    eller sladdar. Även IP-telefoni och surfplattor är nu en naturlig del i flera användares dagliga liv,

    och just IP-telefoni ställer höga krav på det nätverk som denna är ansluten till. Därför har jag

    valt att i denna denna rapport titta närmare på den trådlösa tekniken 802.11 som är framtagen av

    standardiseringsorganisationen IEEE. Metoden jag valt att använda för att åstadkomma detta är

    att genomföra en mätning av ett befintligt trådlöst nät. Jag kommer därefter att undersöka denna

    data för att förhoppningsvis kunna lämna ett förslag på en bättre nätverksdesign. Som hjälpmedel

    för att genomföra denna mätning har jag utrustning från Ekahau, ett finsk företag vars huvudsyssla

    är just mätning, optimering och felsökning av trådlösa nät. Det jag kom fram till var att det tråd-

    lösa nätverket hade stora brister. Framförallt var täckning det stora bekymret, inte bara bristen på

    täckning utan ibland även för bra täckning vilket resulterat i sticky clients. Jag har därefter presen-

    terat en design som för att minimera kostnaderna och miljöpåverkan använder befintlig utrustning,

    dock kräver denna att det kompletteras med 9 stycken nya accesspunkter.

  • 258.
    Bäckström, David
    Linköpings universitet, Institutionen för datavetenskap.
    Boundary-Scan in the ATCA standard2005Independent thesis Basic level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Larger systems today, like telephone and optical switches, are usually based on a multiboard architecture where a set of printed-circuit boards are connected to a backplane board. These systems are also equipped with Boundary-Scan to enable testing, however, the backplane in a multi-board system has a limited wiring capability, which makes the additional backplane Boundary-Scan wiring highly costly. The problem is to access the Boundary-Scan enabled boards with the Boundary-Scan controller located at a central board. In this MSc. thesis project we propose an approach suitable for the Advanced Telecommunication Computing Architecture (ATCA) standard where we make use of the existing Intelligent Platform Management Bus (IPMB) and expands its protocol for application of Boundary-Scan tests. We have also defined a command set as well as a test data format for storing embedded test data on the boards to support the remote execution of Boundary-Scan tests. For validation of the proposed approach we have developed demonstrator.

  • 259.
    Bäckström, David
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Matematiska och systemtekniska institutionen.
    Pulstågsmodul2006Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
  • 260.
    Bäckström, Jonas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Limitations of Azure in GIS Scalability: A performance and migration study2012Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In this study, the cloud platform Windows Azure has been targeted for test implementations of Geographical Information System (GIS) software in the form of map servers and tile caches. The map servers included were GeoServer, MapNik, MapServer and SharpMap, which together with the tile caches, GeoWebCache, MapCache and TileCache, were installed on Windows Azures three different virtual machine roles (Web, Worker and VM). Furthermore, different techniques for scalingapplications and internal role communication are presented, followed by four sets of performance tests. The performance tests attempt to highlight the differences in request times, how the different role sizes handle the load from the incoming requests, how the different role sizes handle many concurrent TCP-connections and how well the incoming requests are load balanced in between the worker roles. The test implementations showed that all map servers and tile caches were successfully installed in Azure, which leads to the conclusion that Windows Azure is suitable for hosting GIS software with similar installation requirements to the previously mentioned software. Four different approaches (Direct mapping, Public Internal Endpoints, Queue and Worker Role Request Broker) are presented showing how Azure allows different methods in order to scale the internal role communication as well as the external client requests. The performance tests provided somewhat inconclusive test results due to hardware limitations in the test setup. This made it difficult to draw concluding parallels between the final results and the expected values. Minor tendencies in performance gain can be seen when scaling the VM size as well as the number of VMs.

  • 261.
    Böhm, Annette
    et al.
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Inbyggda system (CERES).
    Jonsson, Magnus
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Inbyggda system (CERES).
    Handover in IEEE 802.11p-based delay-sensitive vehicle-to-infrastructure communication2009Rapport (Annet vitenskapelig)
    Abstract [en]

    Based on communication and cooperation between vehicles and roadside infrastructure, Intelligent Transport Systems (ITS) safety applications offer great potential to avoid traffic accidents or at least reduce their impact. As these applications usually are delay-sensitive, the delay introduced by waiting for access to the wireless communication channel should both be reduced and provided with an upper bound. The proposed IEEE 802.11p standard for short to medium range vehicular communication does not offer these guarantees. In previous work, we presented a MAC (Medium Access Control) enhancement supporting delay-sensitive, safety-critical V2I (Vehicle-to-Infrastructure) applications. Since the proposed enhancement requires a deterministic and fast mechanism to associate a vehicle to a roadside unit (RSU) so that it can be integrated into the centralized polling schedule, we now target the handover and connection setup between a vehicle and an RSU. Although the first connection setup with an RSU still underlies the randomness of the original 802.11p MAC method, we provide a deterministic solution to further enhance the handover procedures by introducing a fast, proactive handover mechanism. We show that the overhead of our solution is limited and still allows our MAC protocol to support safety-critical V2I applications in a densely trafficked highway scenario.

  • 262.
    Böhm, Annette
    et al.
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Centrum för forskning om inbyggda system (CERES).
    Jonsson, Magnus
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Centrum för forskning om inbyggda system (CERES).
    Position-based data traffic prioritization in safety-critical, real-time vehicle-to-infrastructure communication2009Inngår i: IEEE International Conference on Communications Workshops, 2009. ICC Workshops 2009 / [ed] IEEE, Piscataway, N.J.: IEEE Press, 2009, s. 205-210Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Future active-safety applications in vehicular networks rely heavily on the support for real-time inter-vehicle communication. The Medium Access Control (MAC) mechanism proposed for the upcoming IEEE 802.11p standard intended for Intelligent Transport Systems (ITS) applications does not offer deterministic real-time support, i.e., the channel access delay is not upper bounded. We therefore propose a vehicle-to-infrastructure (V2I) communication solution extending IEEE 802.11p, by introducing a collision-free MAC phase with an enhanced prioritization mechanism based on vehicle positions and the overall road traffic density. A road side unit using a polling mechanism is then able to provide real-time support such that it can guarantee collision-free channel access within its transmission range. Part of the bandwidth remains unchanged such that best-effort services like ongoing vehicle-to-vehicle (V2V) applications may continue. Our solution guarantees that all communication deadlines of the V2I applications are met, while minimizing the required length of the collision-free phase. This in turn maximizes the amount of bandwidth available for best-effort services and ongoing V2V applications. The position-based prioritization mechanism further improves the throughput of both real-time and best-effort data traffic by focusing the communication resources to the most hazardous areas. The concept is evaluated analytically based on a realistic task set from a V2I merge assistance scenario.

  • 263.
    Böhm, Annette
    et al.
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    Jonsson, Magnus
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    Kunert, Kristina
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    A fibre-optic AWG-based real-time network for high-performance embedded computing2004Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, an architecture and a Medium Access Control (MAC) protocol for a multiwavelength optical communication network, applicable in short range communication systems like System Area Networks (SANs), are proposed. The main focus lies on guaranteed support for hard and soft real-time traffic. The network is based upon a single-hop star topology with an Arrayed Waveguide Grating (AWG) at its center. Traffic scheduling is centralized in one node (residing together with the AWG in a hub), which communicates through a physical control channel. The AWG’s property of spatial wavelength reuse and the combination of fixedtuned and tunable transceivers in the nodes enable simultaneous control and data transmission. A case study with defined real-time communication requirements in the field of Radar Signal Processing (RSP) was carried out and indicates that the proposed system is very suitable for this kind of application.

  • 264.
    Böhm, Annette
    et al.
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Centrum för forskning om inbyggda system (CERES).
    Kunert, Kristina
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Centrum för forskning om inbyggda system (CERES).
    Data age based MAC scheme for fast and reliable communication within and between platoons of vehicles2016Inngår i: International Conference on Wireless and Mobile Computing, Networking and Communications, Piscataway: IEEE, 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Heavy vehicles driving as platoon with highly reduced inter-vehicle gaps has shown considerable fuel saving potential, but put high timing and reliability requirements on the underlying control data exchange. The recently standardized IEEE 802.11p protocol suite for Vehicular Ad-Hoc Networks (VANETs) and its message types do neither support the demands of a platooning application nor take advantage of its properties. We therefore propose a framework for centralized channel access with retransmission capabilities for safety critical control data exchange based on the data age of earlier received messages, DA-RE (Data Age based REtransmission scheme). A simulation comparison to the 802.11p random access Medium Access Control (MAC) protocol shows that the intelligent assignment of retransmission opportunities considerably improves the reliability of platooning control data. We also propose a power control based scheme for early platoon detection allowing several platoons to temporarily share a channel and show that the safe and reliable operation of their vehicles is not compromised. © 2016 IEEE.

  • 265. Calandriello, Giorgio
    et al.
    Papadimitratos, Panos
    Hubaux, Jean-Pierre
    Lioy, Antonio
    Efficient and Robust Pseudonymous Authentication in VANET2007Inngår i: VANET'07: PROCEEDINGS OF THE FOURTH ACM INTERNATIONAL WORKSHOP ON VEHICULAR AD HOC NETWORKS, 2007, s. 19-27Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Effective and robust operations, as well as security and privacy are critical for the deployment of vehicular ad hoc networks (VANETs). Efficient and easy-to-manage security and privacy-enhancing mechanisms axe essential for the wide-spread adoption of the VANET technology. In this paper, we are concerned with this problem; and in particular, how to achieve efficient and robust pseudonym-based authentication. We design mechanisms that reduce the security overhead for safety beaconing, and retain robustness for transportation safety, even in adverse network settings. Moreover, we show how to enhance the availability and usability of privacy-enhancing VANET mechanisms: Our proposal enables vehicle on-board units to generate their own pseudonyms, without affecting the system security.

  • 266.
    Carbone, Marco
    et al.
    IT Univ Copenhagen, Rued Langgaards Vej 7, DK-2300 Copenhagen, Denmark..
    Hildebrandt, Thomas
    IT Univ Copenhagen, Rued Langgaards Vej 7, DK-2300 Copenhagen, Denmark..
    Parrow, Joachim
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Weidlich, Matthias
    Humboldt Univ, Unter Linden 6, D-10099 Berlin, Germany..
    Extended versions of papers presented at WS-FM 2014 and Beat 20142016Inngår i: Formal Aspects of Computing, ISSN 0934-5043, E-ISSN 1433-299X, Vol. 28, nr 4, s. 529-530Artikkel i tidsskrift (Annet vitenskapelig)
  • 267.
    Carlos, Perez Penichet
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Noda, Claro
    Mid-Sweden University, Sweden.
    Varshney, Ambuj
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Voigt, Thiemo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Battery-free 802.15. 4 Receiver2018Inngår i: 7th ACM/IEEE International Conference on Information Processing in Sensor Networks (IPSN), IEEE, 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We present the architecture of an 802.15.4 receiver that, for the first time, operates at a few hundred microwatts, enabling new battery-free applications. To reach the required micro-power consumption, the architecture diverges from that of commodity receivers in two important ways. First, it offloads the power-hungry local oscillator to an external device, much like backscatter transmitters do. Second, we avoid the energy cost of demodulating a phase-modulated signal by treating 802.15.4 as a frequency-modulated one, which allows us to receive with a simple passive detector and an energy-efficient thresholding circuit. We describe a prototype that can receive 802.15.4 frames with a power consumption of 361 μW. Our receiver prototype achieves sufficient communication range to integrate with deployed wireless sensor networks (WSNs). We illustrate this integration by pairing the prototype with an 802.15.4 backscatter transmitter and integrating it with unmodified 802.15.4 sensor nodes running the TSCH and Glossy protocols.

  • 268.
    Carlos, Perez Penichet
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Noda, Claro
    Mid-Sweden University, Sweden.
    Varshney, Ambuj
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Voigt, Thiemo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Demo Abstract: Battery-Free 802.15.4 Receiver2018Inngår i: 17th ACM/IEEE International Conference on Information Processing in Sensor Networks (IPSN), IEEE, 2018, s. 130-131Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We present the architecture for an 802.15.4 receiver that enables battery-free operation. To reach micro-power consumption, the architecture diverges from that of commodity receivers in the following ways: First, similar to backscatter transmitters, it offloads the power-hungry local oscillator to an external device. Second, we avoid the energy cost of demodulating a phase-modulated signal by treating 802.15.4 as a frequency-modulated one, allowing us to receive with a simple passive detector and an energy-efficient thresholding circuit. We demonstrate an off-the-shelf prototype of our receiver receives 802.15.4 from a distance of 470 cm with the carrier generator 30 cm away. This range is sufficient to integrate with deployed wireless sensor networks (WSNs). We demonstrate this integration by pairing our receiver with a 802.15.4 backscatter transmitter and integrating it with unmodified commodity sensor nodes running the TSCH protocol.

  • 269.
    Carlson, Trevor E.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Heirman, Wim
    Intel, ExaSci Lab, Santa Clara, CA USA..
    Allam, Osman
    Univ Ghent, B-9000 Ghent, Belgium..
    Kaxiras, Stefanos
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Eeckhout, Lieven
    Univ Ghent, B-9000 Ghent, Belgium..
    The Load Slice Core Microarchitecture2015Inngår i: 2015 ACM/IEEE 42Nd Annual International Symposium On Computer Architecture (ISCA), 2015, s. 272-284Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Driven by the motivation to expose instruction-level parallelism (ILP), microprocessor cores have evolved from simple, in-order pipelines into complex, superscalar out-of-order designs. By extracting ILP, these processors also enable parallel cache and memory operations as a useful side-effect. Today, however, the growing off-chip memory wall and complex cache hierarchies of many-core processors make cache and memory accesses ever more costly. This increases the importance of extracting memory hierarchy parallelism (MHP), while reducing the net impact of more general, yet complex and power-hungry ILP-extraction techniques. In addition, for multi-core processors operating in power- and energy-constrained environments, energy-efficiency has largely replaced single-thread performance as the primary concern. Based on this observation, we propose a core microarchitecture that is aimed squarely at generating parallel accesses to the memory hierarchy while maximizing energy efficiency. The Load Slice Core extends the efficient in-order, stall-on-use core with a second in-order pipeline that enables memory accesses and address-generating instructions to bypass stalled instructions in the main pipeline. Backward program slices containing address-generating instructions leading up to loads and stores are extracted automatically by the hardware, using a novel iterative algorithm that requires no software support or recompilation. On average, the Load Slice Core improves performance over a baseline in-order processor by 53% with overheads of only 15% in area and 22% in power, leading to an increase in energy efficiency (MIPS/Watt) over in-order and out-of-order designs by 43% and over 4.7x, respectively. In addition, for a power- and area-constrained many-core design, the Load Slice Core outperforms both in-order and out-of-order designs, achieving a 53% and 95% higher performance, respectively, thus providing an alternative direction for future many-core processors.

  • 270.
    Carlsson, Arthur
    Linköpings universitet, Institutionen för datavetenskap.
    Integration av AJAX i JDP: En studie i hur WM-data kan utveckla modelleringsstödet i ett webbramverk2008Independent thesis Advanced level (degree of Magister), 20 poäng / 30 hpOppgave
    Abstract [sv]

    På WM-data har man utvecklat ett ramverk som heter Java Development Platform med avsikt att modellera större delar av ett system och därmed minska mängden kod som måste skrivas för hand. Ramverket baseras helt på existerande öppna lösningar och används vid utveckling av webbaserade system och skapar en skiktat lösning med en webbapplikation som presentationslager. Problemet är att webbapplikationen har kommit att bli väldigt svår att modellera i enhet med resten av systemet framför allt på grund av den hårda kopplingen till Struts-ramverket. Samtidigt har man börjat få upp ögonen för AJAX och vad det skulle kunna tillföra ramverket.

    Examensarbetet fokuserar på att utreda de problem som existerar i ramverket samt undersöka integrationen av AJAX ur en synvinkel som gynnar dagens lösning. Detta görs genom litteraturstudier, laborationer och genom att undersöka existerande ramverk och plattformar som löser liknande problem. Fokus ligger även på hur AJAX kan användas för att lösa problemen i modelleringen.

    Resultatet av arbetet mynnar ut i en analys som behandlar de aspekter som krävs för att AJAX ska kunna bli en del av JDP-ramverket. Analysen innefattar också synen på hur AJAX skulle kunna användas för att underlätta modelleringen av webbapplikationen utan att införa något nytt modelleringsverktyg, det vill säga att UML fortfarande kan användas.

  • 271.
    Carlsson, Jonas
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan. Dept. of Electrical Engineering, Univ.,.
    Studies on asynchronous communication ports for GALS systems2005Licentiatavhandling, monografi (Annet vitenskapelig)
  • 272.
    Carlzon, Malin
    KTH, Skolan för datavetenskap och kommunikation (CSC), Numerisk Analys och Datalogi, NADA.
    BGP oscillations when peering with loopback addresses2006Inngår i: 20th International Conference on Advanced Information Networking and Applications, Vol 2, Proceedings / [ed] Martin DC, LOS ALAMITOS, USA: IEEE COMPUTER SOC , 2006, s. 712-716Konferansepaper (Fagfellevurdert)
    Abstract [en]

    An oscillating routing protocol will result in increased protocol activity and may lead to increased router CPU activity and memory consumption.  This case study shows that BGP peering using loopback addresses when peering EBGP between two dualhomed ASes will cause BGP to oscillate. It includes a detailed lab report in which several possible setups that will cause BGP to oscillate are presented. It also includes an oscillation event from one of the world's largest production networks that was caused by such a setup.

  • 273.
    Carlzon, Malin
    KTH, Skolan för datavetenskap och kommunikation (CSC), Numerisk Analys och Datalogi, NADA.
    Improving BGP convergence properties and web content blocking using BGP2006Licentiatavhandling, med artikler (Annet vitenskapelig)
  • 274.
    Carlzon, Malin
    KTH, Skolan för datavetenskap och kommunikation (CSC), Numerisk Analys och Datalogi, NADA.
    Perceived problems with BGP: a survey2006Rapport (Annet vitenskapelig)
  • 275.
    Carlzon, Malin
    KTH, Skolan för datavetenskap och kommunikation (CSC), Numerisk Analys och Datalogi, NADA.
    Resetting a damped out route in BGP2006Rapport (Annet vitenskapelig)
  • 276.
    Carlzon, Malin
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC), Numerisk Analys och Datalogi, NADA.
    Hagsand, Olof
    KTH, Skolan för datavetenskap och kommunikation (CSC), Numerisk Analys och Datalogi, NADA.
    Widell, Fredrik
    KTH, Skolan för datavetenskap och kommunikation (CSC), Numerisk Analys och Datalogi, NADA.
    Danielsson, Björn
    KTH, Skolan för datavetenskap och kommunikation (CSC), Numerisk Analys och Datalogi, NADA.
    Blocking web contents using BGP: measurements and observations2006Rapport (Annet vitenskapelig)
  • 277. Casoni, E.
    et al.
    Jerusalem, A.
    Samaniego, C.
    Eguzkitza, B.
    Lafortune, P.
    Tjahjanto, Denny
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.). IMDEA Materials Institute, Spain .
    Saez, X.
    Houzeaux, G.
    Vazquez, M.
    Alya: Computational Solid Mechanics for Supercomputers2015Inngår i: Archives of Computational Methods in Engineering, ISSN 1134-3060, E-ISSN 1886-1784, Vol. 22, nr 4, s. 557-576Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    While solid mechanics codes are now conventional tools both in industry and research, the increasingly more exigent requirements of both sectors are fuelling the need for more computational power and more advanced algorithms. For obvious reasons, commercial codes are lagging behind academic codes often dedicated either to the implementation of one new technique, or the upscaling of current conventional codes to tackle massively large scale computational problems. Only in a few cases, both approaches have been followed simultaneously. In this article, a solid mechanics simulation strategy for parallel supercomputers based on a hybrid approach is presented. Hybrid parallelization exploits the thread-level parallelism of multicore architectures, combining MPI tasks with OpenMP threads. This paper describes the proposed strategy, programmed in Alya, a parallel multi-physics code. Hybrid parallelization is specially well suited for the current trend of supercomputers, namely large clusters of multicores. The strategy is assessed through transient non-linear solid mechanics problems, both for explicit and implicit schemes, running on thousands of cores. In order to demonstrate the flexibility of the proposed strategy under advance algorithmic evolution of computational mechanics, a non-local parallel overset meshes method (Chimera-like) is implemented and the conservation of the scalability is demonstrated.

  • 278.
    Castberg, Miro
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Adaptor Development: An insight to interfacing with electrical energy meters2011Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [en]

    Since energy meters became more advanced and able to send data remotely, energy suppliers have had a need to keep their data managed. This gave birth to energy management systems which gather data from energy meters. However, for every type of meter there needs to be a specialization in the management system.

    Smart Metering Language (SML) is a protocol which was created to transfer meter data in as simple way as possible. Implementing the protocol would result in simpler and less vendor-specific solutions for energy management systems.

    This report follows the process of developing an adaptor between a device using the SML protocol and a system that manages energy meters. The thesis uses different parts of the development process in able to show specializations which were needed by the test device and its vendor. 

    The result sums up the experience of developing an adaptor and the specializations which are needed in the SML protocol.

  • 279. Catalan Rivas, Victoria
    et al.
    Fröjd, Emil
    Homberg, Tobias
    Ragnarsson, Felix
    Rick, Elsa
    Corneo, Lorenzo
    Varshney, Ambuj
    Rohner, Christian
    Voigt, Thiemo
    Gunningberg, Per
    Environmental Control at the Edge2018Konferansepaper (Annet vitenskapelig)
  • 280.
    Ceballos, Germán
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Grass, Thomas
    Hugo, Andra
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Black-Schaffer, David
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Analyzing performance variation of task schedulers with TaskInsight2018Inngår i: Parallel Computing, ISSN 0167-8191, E-ISSN 1872-7336, Vol. 75, s. 11-27Artikkel i tidsskrift (Fagfellevurdert)
  • 281.
    Ceballos, Germán
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Grass, Thomas
    Hugo, Andra
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Black-Schaffer, David
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    TaskInsight: Understanding task schedules effects on memory and performance2017Inngår i: Proc. 8th International Workshop on Programming Models and Applications for Multicores and Manycores, New York: ACM Press, 2017, s. 11-20Konferansepaper (Fagfellevurdert)
  • 282.
    Ceballos, Germán
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Sembrant, Andreas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Carlson, Trevor E.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Black-Schaffer, David
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Analyzing Graphics Workloads on Tile-based GPUs2017Inngår i: Proc. 20th International Symposium on Workload Characterization, IEEE, 2017, s. 108-109Konferansepaper (Fagfellevurdert)
  • 283. Cebrian, Juan M.
    et al.
    Sanchez, Daniel
    Aragon, Juan L.
    Kaxiras, Stefanos
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Efficient inter-core power and thermal balancing for multicore processors2013Inngår i: Computing, ISSN 0010-485X, E-ISSN 1436-5057, Vol. 95, nr 7, s. 537-566Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nowadays the market is dominated by processor architectures that employ multiple cores per chip. These architectures have different behavior depending on the applications running on the processor (parallel, multiprogrammed, sequential), but all happen to meet what is called the power and temperature wall. For future technologies (less than 22 nm) and a fixed die size, it is still uncertain the percentage of processor that can be simultaneously powered on. Power saving and power budget mechanisms can be useful to precisely control the amount of power been dissipated by the processor. After an initial analysis we discover that legacy power saving techniques work properly for matching a power budget in thread-independent and multi-programmed workloads, but not in parallel workloads. When running parallel shared-memory applications sacrificing some performance in a single core (thread) in order to be more energy-efficient can unintentionally delay the rest of cores (threads) due to synchronization points (locks/barriers), having a negative impact on global performance. In order to solve this problem we propose power token balancing (PTB) aimed at accurately matching an external power constraint by balancing the power consumed among the different cores. Experimental results show that PTB matches more accurately a predefined power budget (50 % of the original peak power) than other mechanisms like DVFS. The total energy consumed over the budget is reduced to only 8 % for a 16-core CMP with only a 3 % energy increase (overhead). We also introduce a novel mechanism named "Nitro". Nitro will overclock the core that enters a critical section (delimited by locks) in order to free the lock as soon as possible. Experimental results have shown that Nitro is able to reduce the execution time of lock-intensive applications in more than 4 % by overclocking the frequency by 15 % in selected program phases over a period of time that represents a 22 % of the total execution time. We conclude the work with an analysis of the thermal effects of PTB in different CMP configurations using realistic power numbers and heatsink/fan configurations. Results show how PTB not only balances temperature between the different cores, reducing temperature gradient and increasing signal reliability, but also allows a reduction of 28-30 % of both average and peak temperatures for the studied benchmarks when a peak power budget of 50 % is exceeded.

  • 284. Cebrian, Juan M.
    et al.
    Sanchez, Daniel
    Aragon, Juan L.
    Kaxiras, Stefanos
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Managing power constraints in a single-core scenario through power tokens2014Inngår i: Journal of Supercomputing, ISSN 0920-8542, E-ISSN 1573-0484, Vol. 68, nr 1, s. 414-442Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Current microprocessors face constant thermal and power-related problems during their everyday use, usually solved by applying a power budget to the processor/core. Dynamic voltage and frequency scaling (DVFS) has been an effective technique that allowed microprocessors to match a predefined power budget. However, the continuous increase of leakage power due to technology scaling along with low resolution of DVFS makes it less attractive as a technique to match a predefined power budget as technology goes to deep-submicron. In this paper, we propose the use of microarchitectural techniques to accurately match a power constraint while maximizing the energy-efficiency of the processor. We will predict the processor power dissipation at cycle level (power token throttling) or at a basic block level (basic block level mechanism), using the dissipated power translated into tokens to select between different power-saving microarchitectural techniques. We also introduce a two-level approach in which DVFS acts as a coarse-grain technique to lower the average power dissipation towards the power budget, while microarchitectural techniques focus on removing the numerous power spikes. Experimental results show that the use of power-saving microarchitectural techniques in conjunction with DVFS is up to six times more precise, in terms of total energy consumed over the power budget, than only using DVFS to match a predefined power budget.

  • 285. Cebrián, Juan M.
    et al.
    Aragón, Juan L.
    García, José M.
    Kaxiras, Stefanos
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Leakage-efficient design of value predictors through state and non-state preserving techniques2011Inngår i: Journal of Supercomputing, ISSN 0920-8542, E-ISSN 1573-0484, Vol. 55, nr 1, s. 28-50Artikkel i tidsskrift (Fagfellevurdert)
  • 286. Cebrián, Juan M.
    et al.
    Aragón, Juan L.
    Kaxiras, Stefanos
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Power Token Balancing: Adapting CMPs to power constraints for parallel multithreaded workloads2011Inngår i: Proc. 25th International Parallel and Distributed Processing Symposium, Piscataway, NJ: IEEE , 2011, s. 431-442Konferansepaper (Fagfellevurdert)
  • 287. Cebrián, Juan M.
    et al.
    Fernández-Pascual, Ricardo
    Jimborean, Alexandra
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Acacio, Manuel E.
    Ros, Alberto
    A dedicated private-shared cache design for scalable multiprocessors2017Inngår i: Concurrency and Computation, ISSN 1532-0626, E-ISSN 1532-0634, Vol. 29, nr 2, artikkel-id e3871Artikkel i tidsskrift (Fagfellevurdert)
  • 288.
    Cenanovic, Mirza
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Produktutveckling. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Produktutveckling - Simulering och optimering.
    Finite element methods for surface problems2017Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The purpose of this thesis is to further develop numerical methods for solving surface problems by utilizing tangential calculus and the trace finite element method. Direct computation on the surface is possible by the use of tangential calculus, in contrast to the classical approach of mapping 2D parametric surfaces to 3D surfaces by means of differential geometry operators. Using tangential calculus, the problem formulation is only dependent on the position and normal vectors of the 3D surface. Tangential calculus thus enables a clean, simple and inexpensive formulation and implementation of finite element methods for surface problems. Meshing techniques are greatly simplified from the end-user perspective by utilizing an unfitted finite element method called the Trace Finite Element Method, in which the basic idea is to embed the surface in a higher dimensional mesh and use the shape functions of this background mesh for the discretization of the partial differential equation. This method makes it possible to model surfaces implicitly and solve surface problems without the need for expensive meshing/re-meshing techniques especially for moving surfaces or surfaces embedded in 3D solids, so called embedded interface problems. Using these two approaches, numerical methods for solving three surface problems are proposed: 1) minimal surface problems, in which the form that minimizes the mean curvature was computed by iterative update of a level-set function discretized using TraceFEM and driven by advection, for which the velocity field was given by the mean curvature flow, 2) elastic membrane problems discretized using linear and higher order TraceFEM, which makes it straightforward to embed complex geometries of membrane models into an elastic bulk for reinforcement and 3) stabilized, accurate vertex normal and mean curvature estimation with local refinement on triangulated surfaces. In this thesis the basics of the two main approaches are presented, some aspects such as stabilization and surface reconstruction are further developed, evaluated and numerically analyzed, details on implementations are provided and the current state of work is presented.

  • 289.
    Cenanovic, Mirza
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Produktutveckling - Simulering och optimering.
    Finite element methods on surfaces2015Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The purpose of this thesis is to improve numerical simulations of surface problems. Two novel computational concepts are analyzed and applied on two surface problems; minimal surface problems and elastic membrane problems. The concept of tangential projection implies that direct computation on the surface is made possible compared to the classical approach of mapping 2D parametric surfaces to 3D surfaces by means of differential geometry operators. The second concept presented is the cut finite element method, in which the basic idea of discretization is to embed the d- 1-dimensional surface in a d-dimensional mesh and use the basis functions of a higher dimensional mesh but integrate over the surface. The aim of this thesis is to present the basics of the two main approaches and to provide details on the implementation.

  • 290.
    Cenanovic, Mirza
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Produktutveckling. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Produktutveckling - Simulering och optimering.
    Numerical error estimation for a TraceFEM membrane and distance function on P1 and P2 tetrahedraManuskript (preprint) (Annet vitenskapelig)
  • 291.
    Cenanovic, Mirza
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Produktutveckling - Simulering och optimering.
    Hansbo, Peter
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Produktutveckling. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Produktutveckling - Simulering och optimering.
    Larsson, Mats G.
    Umeå University.
    Cut finite element modeling of linear membranes2016Inngår i: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 310, s. 98-111Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We construct a cut finite element method for the membrane elasticity problem on an embedded mesh using tangential differential calculus, i.e., with the equilibrium equations pointwise projected onto the tangent plane of the surface to create a pointwise planar problem in the tangential direction. Both free membranes and membranes coupled to 3D elasticity are considered. The discretization of the membrane comes from a Galerkin method using the restriction of 3D basis functions (linear or trilinear) to the surface representing the membrane. In the case of coupling to 3D elasticity, we view the membrane as giving additional stiffness contributions to the standard stiffness matrix resulting from the discretization of the three-dimensional continuum.

  • 292.
    Cenanovic, Mirza
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Produktutveckling. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Produktutveckling - Simulering och optimering.
    Hansbo, Peter
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Produktutveckling. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Produktutveckling - Simulering och optimering.
    Larsson, Mats G.
    Finite element procedures for computing normals and mean curvature on triangulated surfaces and their use for mesh refinementManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    In this paper we consider finite element approaches to computing the mean curvature vector and normal at the vertices of piecewise linear triangulated surfaces. In particular, we adopt a stabilization technique which allows for first order L2-convergence of the mean curvature vector and apply this stabilization technique also to the computation of continuous, recovered, normals using L2-projections of the piecewise constant face normals. Finally, we use our projected normals to define an adaptive mesh refinement approach to geometry resolution where we also employ spline techniques to reconstruct the surface before refinement. We compare or results to previously proposed approaches.

  • 293.
    Chabloz, Jean-Michel
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektroniksystem.
    Hemani, Ahmed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektroniksystem.
    Lowering the Latency of Interfaces for Rationally-Related Frequencies2010Inngår i: 2010 IEEE INTERNATIONAL CONFERENCE ON COMPUTER DESIGN, 2010, s. 23-30Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We have introduced the Globally-Ratiochronous, Locally-Synchronous (GRLS) design paradigm, a design style based on rationally-related frequencies, with the objective to overcome the limitations of traditional multi-frequency systems by providing a flexibility close that of Globally-Asynchronous, Locally-Synchronous (GALS) systems but introducing performance penalties and overheads close to those of mesochronous systems. In this paper we focus on performances and improve the latency figures of our original GRLS interfaces by introducing two new interfaces, called GRLS-F and GRLS-noF, the first suitable for blocks with long computation time and the second for blocks with short computation time. The latency figures of the original GRLS interfaces are improved up to 50% without increasing complexity. The average latency figures of the resulting interfaces are lower than 1 Receiver clock cycle, the latency of a synchronous interface.

  • 294.
    Chavez Alcarraz, Erick
    et al.
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Data- och elektroteknik.
    Moraga, Manuel
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Data- och elektroteknik.
    Linked data performance in different databases: Comparison between SQL and NoSQL databases2014Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [en]

    Meepo AB was investigating the possibility of developing a social rating and recommendation service. In a recommendation service, the user ratings are collected in a database, this data is then used in recommendation algorithms to create individual user recommendations.

    The purpose of this study was to find out which  demands are put on a DBMS, database management system, powering a recommendation service, what impact the NoSQL databases have on the performance of recommendation services compared to traditional relational databases, and which DBMS is most suited for storing the data needed to host a recommendation service.

    Five distinct NoSQL and Relational DBMS were examined, from these three candidates were chosen for a closer comparison.

    Following a study of recommendation algorithms and services, a test suite was created to compare DBMS performance in different areas using a data set of 100 million ratings.

    The results show that MongoDB had the best performance in most use cases, while Neo4j and MySQL struggled with queries spanning the whole data set.

    This paper however never compared performance for real production code. To get a better comparison, more research is needed. We recommend new performance tests for MongoDB and Neo4j using implementations of recommendation algorithms, a larger data set, and more powerful hardware.

  • 295.
    Cheema, Ansar Zaman
    et al.
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE).
    Saqib, Imran Ullah
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE).
    Collaborating ISPs Supporting Various Real-Time Services2010Independent thesis Advanced level (degree of Master (One Year)), 15 poäng / 22,5 hpOppgave
    Abstract [en]

    These days, internet service providers (ISPs) face the challenge about how to increase profitability while hey must ensure a good quality service at the same time and scale up their network. The study involves previous research papers. On the bases of those papers,the comparison is made between different alternatives. The purpose on this study is to find a solution that combines different methods and configurations about how several ISPs could cooperate. Its implementation includes how different ISPs can configure their networks to cooperate on service provision supporting various real-time services.

  • 296.
    Chehrazi, Golriz
    Linköpings universitet, Institutionen för systemteknik.
    Workflow management systems, their security and access control mechanisms2007Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This paper gives an overview of workflow management systems (WfMSs) and their security requirements with focus on access mechanisms. It is a descriptive paper in which we examine the state of the art of workflow systems, describe what security risks affect WfMSs in particular, and how these can be diminiuished.

    WfMSs manage, illustrate and support business processes. They contribute to the performance, automation and optimization of processes, which is important in the global economy today. The security of process flows is important, since the sensitive business data need to be protected to inhibit illegal activities, such as blackmailing, imitation and fraud and to provide for good customer service.

    This paper focuses on access mechanisms, because they are basic security mechanisms used by WfMSs assuring that only authorized users are provided access to data and resources. Also because of the unsecurity of the Internet, which is commonly used as infrastructure of Workflow systems, additional security mechanisms, such as PKIs, digital signatures and SSL have to be used to provide secure workflows.

    Depending on the particular requirements in workflow systems, different extensional access control (AC) mechanisms have been developed to maintain security. But when it comes to commercially used WfMSs, the availability of the system is of utmost importance. It is the prerequisite for the system to be employed by companies. The problem is that there is always a trade-off between availability of the system and security. Because this trade off is generally solved in favor of availability, a major part of the developed AC mechanisms are not used in commercially used WfMS.

    After the first part of this paper which is rather theoretical, we examine a commercial WfMS, namely IBM's MQ Workflow , and its security mechanisms. We show vulnerabilities of the system that could be abused by attackers. Afterwards, we show which security mechanisms, in particular, AC mechanisms are provided to secure against threats. We conclude with a summary, which highlights the difference between security concepts developed in the research area and those really implemented by the commercially used WfMS.

  • 297.
    Chen, Guang
    et al.
    Tongji Univ, Coll Automot Engn, Shanghai, Peoples R China.;Tech Univ Munich, Robot & Embedded Syst, Munich, Germany..
    Cao, Hu
    Hunan Univ, State Key Lab Adv Design & Mfg Vehicle Body, Changsha, Hunan, Peoples R China..
    Aafaque, Muhammad
    Tech Univ Munich, Robot & Embedded Syst, Munich, Germany..
    Chen, Jieneng
    Tongji Univ, Coll Elect & Informat Engn, Shanghai, Peoples R China..
    Ye, Canbo
    Tongji Univ, Coll Automot Engn, Shanghai, Peoples R China..
    Roehrbein, Florian
    Tech Univ Munich, Robot & Embedded Syst, Munich, Germany..
    Conradt, Jörg
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Beräkningsvetenskap och beräkningsteknik (CST).
    Chen, Kai
    Tongji Univ, Coll Automot Engn, Shanghai, Peoples R China..
    Bing, Zhenshan
    Tech Univ Munich, Robot & Embedded Syst, Munich, Germany..
    Liu, Xingbo
    Tongji Univ, Coll Automot Engn, Shanghai, Peoples R China..
    Hinz, Gereon
    Tech Univ Munich, Robot & Embedded Syst, Munich, Germany..
    Stechele, Walter
    Tech Univ Munich, Integrated Syst, Munich, Germany..
    Knoll, Alois
    Tech Univ Munich, Robot & Embedded Syst, Munich, Germany..
    Neuromorphic Vision Based Multivehicle Detection and Tracking for Intelligent Transportation System2018Inngår i: Journal of Advanced Transportation, ISSN 0197-6729, E-ISSN 2042-3195, artikkel-id 4815383Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Neuromorphic vision sensor is a new passive sensing modality and a frameless sensor with a number of advantages over traditional cameras. Instead of wastefully sending entire images at fixed frame rate, neuromorphic vision sensor only transmits the local pixel-level changes caused by the movement in a scene at the time they occur. This results in advantageous characteristics, in terms of low energy consumption, high dynamic range, sparse event stream, and low response latency, which can be very useful in intelligent perception systems for modern intelligent transportation system (ITS) that requires efficient wireless data communication and low power embedded computing resources. In this paper, we propose the first neuromorphic vision based multivehicle detection and tracking system in ITS. The performance of the system is evaluated with a dataset recorded by a neuromorphic vision sensor mounted on a highway bridge. We performed a preliminary multivehicle tracking-by-clustering study using three classical clustering approaches and four tracking approaches. Our experiment results indicate that, by making full use of the low latency and sparse event stream, we could easily integrate an online tracking-by-clustering system running at a high frame rate, which far exceeds the real-time capabilities of traditional frame-based cameras. If the accuracy is prioritized, the tracking task can also be performed robustly at a relatively high rate with different combinations of algorithms. We also provide our dataset and evaluation approaches serving as the first neuromorphic benchmark in ITS and hopefully can motivate further research on neuromorphic vision sensors for ITS solutions.

  • 298.
    Chen, Kairang
    Linköpings universitet, Institutionen för systemteknik, Elektroniska Kretsar och System. Linköpings universitet, Tekniska fakulteten.
    Energy-Efficient Data Converters for Low-Power Sensors2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Wireless sensor networks (WSNs) are employed in many applications, such as for monitoring bio-potential signals and environmental information. These applications require high-resolution (> 12-bit) analog-to-digital converters (ADCs) at low-sampling rates (several kS/s). Such sensor nodes are usually powered by batteries or energy-harvesting sources hence low power consumption is primary for such ADCs. Normally, tens or hundreds of autonomously powered sensor nodes are utilized to capture and transmit data to the central processor. Hence it is profitable to fabricate the relevant electronics, such as the ADCs, in a low-cost standard complementary metal-oxide-semiconductor (CMOS) process. The two-stage pipelined successive approximation register (SAR) ADC has shown to be an energy-efficient architecture for high resolution. This thesis further studies and explores the design limitations of the pipelined SAR ADC for high-resolution and low-speed applications.

    The first work is a 15-bit, 1 kS/s two-stage pipelined SAR ADC that has been implemented in 0.35-μm CMOS process. The use of aggressive gain reduction in the residue amplifier combined with a suitable capacitive array digital-to-analog converter (DAC) topology in the second-stage simplifies the design of the operational transconductance amplifier (OTA) while eliminating excessive capacitive load and consequent power consumption. A comprehensive power consumption analysis of the entire ADC is performed to determine the number of bits in each stage of the pipeline. Choice of a segmented capacitive array DAC and attenuation capacitorbased DAC for the first and second stages respectively enable significant reduction in power consumption and area. Fabricated in a low-cost 0.35-μm CMOS process, the prototype ADC achieves a peak signal-to-noise-and-distortion ratio (SNDR) of 78.9 dB corresponding to an effective number of bits (ENOB) of 12.8-bit at a sampling frequency of 1 kS/s and provides a Schreier figure-of-merit (FoM) of 157.6 dB. Without any form of calibration, the ADC maintains an ENOB > 12.1-bit up to the Nyquist bandwidth of 500 Hz while consuming 6.7 μW. Core area of the ADC is 0.679 mm2.

    The second work is a 14-bit, tunable bandwidth two-stage pipelined SAR ADC which is suitable for low-power, cost-effective sensor readout circuits. To overcome the high open-loop DC gain requirement of the OTA in the gain-stage, a 3-stage capacitive charge pump (CCP) is utilized to achieve the gain-stage instead of using the switch capacitor (SC) amplifier. Unity-gain OTAs have been used as the analog buffers to prevent the charge sharing between the CCP stages. The detailed design considerations are given in this work. The prototype ADC, designed and fabricated in a low-cost 0.35-μm CMOS process, achieves a peak SNDR of 75.6 dB at a sampling rate of 20 kS/s and 76.1 dB at 200 kS/s while consuming 7.68 μW and 96 μW, respectively. The corresponding Schreier FoM are 166.7 dB and 166.3 dB. Since the bandwidth of CCP is tunable, the ADC maintains a SNDR > 75 dB up

    to 260 kHz. The core area occupied by the ADC is 0.589 mm2.

    As the low-power sensors might be active only for very short time triggered by an external pulse to acquire the data, the third work is a 14-bit asynchronous two-stage pipelined SAR ADC which has been designed and simulated in 0.18-μm CMOS process. A self-synchronous loop based on an edge detector is utilized to generate an internal clock with variable phase. A tunable delay element enables to allocate the available time for the switch capacitor DACs and the gain-stage. Three separate asynchronous clock generators are implemented to create the control signals for two sub-ADCs and the gain-stage between. Aiming to reduce the power consumption of the gain-stage, simple source followers as the analog buffers are implemented in the 3-stage CCP gain-stage. Post-layout simulation results show that the ADC achieves a SNDR of 83.5 dB while consuming 2.39 μW with a sampling rate of 10 kS/s. The corresponding Schreier FoM is 176.7 dB.

  • 299.
    Chen, Kairang
    et al.
    Linköpings universitet, Institutionen för systemteknik, Elektroniska Kretsar och System. Linköpings universitet, Tekniska fakulteten.
    Alvandpour, Atila
    Linköpings universitet, Institutionen för systemteknik, Elektroniska Kretsar och System. Linköpings universitet, Tekniska fakulteten.
    A pipelined SAR ADC with gain-stage based on capacitive charge pump2017Inngår i: Analog Integrated Circuits and Signal Processing, ISSN 0925-1030, E-ISSN 1573-1979, Vol. 90, nr 1, s. 43-53Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents a 14-bit, tunable bandwidth two-stage pipelined successive approximation analog to digital converter which is suitable for low-power, cost-effective sensor readout circuits. To overcome the high DC gain requirement of operational transconductance amplifier in the gain-stage, the multi-stage capacitive charge pump (CCP) was utilized to achieve the gain-stage instead of using the switch capacitor integrator. The detailed design considerations are given in this work. Thereafter, the 14-bit ADC was designed and fabricated in a low-cost 0.35-µm CMOS process. The prototype ADC achieves a peak SNDR of 75.6 dB at a sampling rate of 20 kS/s and 76.1 dB at 200 kS/s while consuming 7.68 and 96 µW, respectively. The corresponding FoM are 166.7 and 166.3 dB. Since the bandwidth of CCP is tunable, the ADC maintains a SNDR >75 dB upto 260 kHz. The core area occupied by the ADC is 0.589 mm2.

  • 300.
    Chen, Nan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    An IEEE 802.15.4 Packet Error Classification Algorithm: Discriminating Between Multipath Fading and Attenuation and WLAN2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In wireless sensor networks, communications are usually destroyed by signal attenuation, multipath fading and different kinds of interferences like WLAN and microwave oven interference. In order to build a stable wireless communication system, reactions like retransmission mechanisms are necessary. Since the way we must react to interference is different from the way we react to multipathfading and attenuation, the retransmission mechanism should be adjusted in different ways under those different cicumstances. Under this condition, channel diagnostics for discriminating the causes that corrupt the packets between multipath fading and attenuation (MFA) and WLAN interference are imperative. This paper presents a frame bit error rate (F-BER) regulated algorithm based on a joint RSSI-LQI classifier that may correctly diagnose the channel status. This discriminator is implemented on MicaZ sensor devices equipped with CC2420 transceivers. This discriminator is able to improve the accuracy to 91%. Although we need to wait for 2 or 3 necessary packets to make a decision, higher stability and reliability are presented when operating this discriminator.

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