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  • 1.
    A. M. Naiini, Maziar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Horizontal Slot Waveguides for Silicon Photonics Back-End Integration2014Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This thesis presents the development of integrated silicon photonic devices. These devices are compatible with the present and near future CMOS technology. High-khorizontal grating couplers and waveguides are proposed. This work consists of simulations and device design, as well as the layout for the fabrication process, device fabrication, process development, characterization instrument development and electro-optical characterizations.

    The work demonstrates an alternative solution to costly silicon-on-insulator photonics. The proposed solution uses bulk silicon wafers and thin film deposited waveguides. Back-end deposited horizontal slot grating couplers and waveguides are realized by multi-layers of amorphous silicon and high-k materials.

    The achievements of this work include: A theoretical study of fully etched slot grating couplers with Al2O3, HfO2 and AIN, an optical study of the high-k films with spectroscopic ellipsometry, an experimental demonstration of fully etched SiO2 single slot grating couplers and double slot Al2O3 grating couplers, a practical demonstration of horizontal double slot high-k waveguides, partially etched Al2O3 single slot grating couplers, a study of a scheme for integration of the double slot Al2O3  waveguides with selectively grown germanium PIN photodetectors, realization of test chips for the integrated germanium photodetectors, and study of integration with graphene photodetectors through embedding the graphene into a high-k slot layer.

    From an application point of view, these high-k slot waveguides add more functionality to the current silicon photonics. The presented devices can be used for low cost photonics applications. Also alternative optical materials can be used in the context of this photonics platform.

    With the robust design, the grating couplers result in improved yield and a more cost effective solution is realized for integration of the waveguides with the germanium and graphene photodetectors.

     

     

     

     

  • 2.
    Aalto, Alve
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Jafari, Ali
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Automatic Probing System for PCB: Analysis of an automatic probing system for design verification of printed circuit boards2015Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Målet med detta examensarbete är att göra en analys av huruvida Ericssons kretskort kan testas med hjälp av ett automatiskt probe system eller om det kräver stora förändringar i designdelen av kretskorten och om, vad för förändringar det i sådant fall kan vara. Till hjälp att analysera kretskorten har vi haft oscilloskop för att få ut rådata om skillnaderna mellan de teoretiska och verkliga signalerna. För att kunna tyda oscilloskopets samplade signaler har olika programmeringsspråk som Python, Matlab samt Excel använts. En extra via i signalens väg har även simulerats i HFSS och ADS med olika sorts probar för att se hur signalens beteende påverkas. Resultaten extraherades sedan in i olika Excel ark för att få en lätt överskådlig bild av resultaten. Resultatet vi fick visade att utformningen av ett kretskort med ändringarna skulle vara lättare att göra med en ny design istället för en redan existerande då större delar av kortet skulle behöva göras om. Vissa stora komponenter behöver antingen göras om, hitta mindre men likvärdiga eller sättas på ena sidan av kortet där de inte är i vägen för proben. Kretskorten som kommer använda flygande probesystem kommer antagligen bli lite större då viornas placering är mer begränsade än tidigare. Det mest tidskrävande arbetet var att simulera olika placeringar av en extra via i signalens väg. Detta visade att på en single ended signal under två gigahertz så gör det ingen större skillnad vart i signalens väg som den extra vian placeras. Då en högre frekvens används så är själva signalens karaktär det viktigaste än placeringen av en via, men om man inte vet den exakta karaktären så är fyra millimeter bort från mottagarens sida att rekommendera då närmare placering av viorna gör att signalerna börjar störa varandra.

  • 3.
    Abad Caballero, Israel Manuel
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Secure Mobile Voice over IP2003Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Voice over IP (VoIP) kan defineras som förmågan att göra ett telefonsamtal och att skicka fax (eller att göraallting som man idag kan göra över det publika telefonnätet) över ett IP−baserat nätverk med en passande kvalitet och till lägre kostnad, alternativt större nytta.

    VoIP måste tillhandahållas med nödvändiga säkerhetstjänster utan att teknikens prestanta påverkas. Detta blir allt viktigare när VoIP används över trådlösa länktekniker (såsom trådlösa lokala nätverk, WLAN), givet dessa länkars begränsade bandbredd och den bearbetningkraft som krävs för att exekvera säkerhetsmekanismerna. Vi måste tänka på VoIPs säkerhet likt en kedja där inte någon länk, från säker uppkoppling till säker nedkoppling, får fallera för att erhålla en säker process. I detta dokument presenteras en lösning på detta problem och innefattar en säker modell för Mobile VoIP som minimerar bearbetningskostnaderna och bandbreddsutnyttjandet. Detta erhålls huvudsakligen genom utnyttjande av säkerhetsprotokoll med hög genomströmning och låg paketexpansion, såsom "Secure Real− time Protocol" (SRTP), och av krypteringsprotokoll med hög hastighet, såsom "Advanced Encryption Standard" (AES).

    I detta dokument beskriver jag problemet och dess alternativa lösningar. Jag beskriver också den valda lösningen och dess protokoll och mekanismer mer detaljerat, till exempel "Transport Layer Security" (TLS) för att säkra "Session Initiation Protocol" (SIP), SRTP för att skydda transporten av data och "Multimedia Internet KEYing" (MIKEY) för nyckelhantering. En implementation av SRTP, kallad MINIsrtp, finns också beskriven.

    Beträffande praktiskt arbete och tester av lösningsmodellen har detta projekt fokuserats på skyddandet av datatransporten (SRTP), dess implementation och prestanda. Emellertid har en grundlig teoretisk undersökning genomförts, vilken innefattar andra aspekter såsom telefonsamtalets uppkoppling och nedkoppling (med hjälp av SIP) och valet av passande nyckelhanteringsprotokoll (MIKEY) för att stödja SRTP.

  • 4. Abadal, Sergi
    et al.
    Alarcon, Eduard
    Cabellos-Aparicio, Albert
    Lemme, Max C.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Nemirovsky, Mario
    Graphene-Enabled Wireless Communication for Massive Multicore Architectures2013Ingår i: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 51, nr 11, 137-143 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Current trends in microprocessor architecture design are leading towards a dramatic increase of core-level parallelization, wherein a given number of independent processors or cores are interconnected. Since the main bottleneck is foreseen to migrate from computation to communication, efficient and scalable means of inter-core communication are crucial for guaranteeing steady performance improvements in many-core processors. As the number of cores grows, it remains unclear whether initial proposals, such as the Network-on-Chip (NoC) paradigm, will meet the stringent requirements of this scenario. This position paper presents a new research area where massive multicore architectures have wireless communication capabilities at the core level. This goal is feasible by using graphene-based planar antennas, which can radiate signals at the Terahertz band while utilizing lower chip area than its metallic counterparts. To the best of our knowledge, this is the first work that discusses the utilization of graphene-enabled wireless communication for massive multicore processors. Such wireless systems enable broadcasting, multicasting, all-to-all communication, as well as significantly reduce many of the issues present in massively multicore environments, such as data coherency, consistency, synchronization and communication problems. Several open research challenges are pointed out related to implementation, communications and multicore architectures, which pave the way for future research in this multidisciplinary area.

  • 5. Abascal, Isabel Sainz
    et al.
    Björk, Gunnar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Bipartite entanglement measure based on covariance2007Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 75, nr 6Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We propose an entanglement measure for two quNits based on the covariances of a set of generators of the su(N) algebra. In particular, we represent this measure in terms of the mutually unbiased projectors for N prime. For pure states this measure quantifies entanglement, we obtain an explicit expression which relates it to the concurrence hierarchy, specifically the I-concurrence and the three-concurrence. For mixed states we propose a separability criterion.

  • 6.
    Abbas, Haider
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektroniksystem.
    Options-Based Security-Oriented Framework for Addressing Uncerainty Issues in IT Security2010Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    Continuous development and innovation in Information Technology introduces novel configuration methods, software development tools and hardware components. This steady state of flux is very desirable as it improves productivity and the overall quality of life in societies. However, the same phenomenon also gives rise to unseen threats, vulnerabilities and security concerns that are becoming more critical with the passage of time. As an implication, technological progress strongly impacts organizations’ existing information security methods, policies and techniques, making obsolete existing security measures and mandating reevaluation, which results in an uncertain IT infrastructure. In order to address these critical concerns, an options-based reasoning borrowed from corporate finance is proposed and adapted for evaluation of security architecture and decision- making to handle them at organizational level. Options theory has provided significant guidance for uncertainty management in several domains, such as Oil & Gas, government R&D and IT security investment projects. We have applied options valuation technique in a different context to formalize optimal solutions in uncertain situations for three specific and identified uncertainty issues in IT security. In the research process, we formulated an adaptation model for expressing options theory in terms useful for IT security which provided knowledge to formulate and propose a framework for addressing uncertainty issues in information security. To validate the efficacy of this proposed framework, we have applied this approach to the SHS (Spridnings- och Hämtningssystem) and ESAM (E-Society) systems used in Sweden. As an ultimate objective of this research, we intend to develop a solution that is amenable to automation for the three main problem areas caused by technological uncertainty in information security: i) dynamically changing security requirements, ii) externalities caused by a security system, iii) obsoleteness of evaluation. The framework is general and capable of dealing with other uncertainty management issues and their solutions, but in this work we primarily deal with the three aforementioned uncertainty problems. The thesis presents an in-depth background and analysis study for a proposed options-based security-oriented framework with case studies for SHS and ESAM systems. It has also been assured that the framework formulation follows the guidelines from industry best practices criteria/metrics. We have also proposed how the whole process can be automated as the next step in development.

  • 7.
    Abbas, Haider
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Data- och systemvetenskap, DSV.
    Threats and Security Measures Involved in VoIP-Telephony2006Självständigt arbete på avancerad nivå (magisterexamen), 30 poäng / 45 hpStudentuppsats (Examensarbete)
  • 8.
    Abbas, Haider
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektroniksystem.
    Magnusson, Christer
    Department of Computer and System Sciences, Stockholm University, Sweden.
    Yngström, Louise
    Department of Computer and System Sciences, Stockholm University, Sweden.
    Hemani, Ahmed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektroniksystem.
    Addressing Dynamic Issues in Information Security Management2011Ingår i: Information Management & Computer Security, ISSN 0968-5227, Vol. 19, nr 1, 5-24 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Purpose – The paper addresses three main problems resulting from uncertainty in information securitymanagement: i) dynamically changing security requirements of an organization ii) externalities caused by a securitysystem and iii) obsolete evaluation of security concerns.

    Design/methodology/approach – In order to address these critical concerns, a framework based on optionsreasoning borrowed from corporate finance is proposed and adapted to evaluation of security architecture anddecision-making for handling these issues at organizational level. The adaptation as a methodology is demonstrated by a large case study validating its efficacy.

    Findings – The paper shows through three examples that it is possible to have a coherent methodology, buildingon options theory to deal with uncertainty issues in information security at an organizational level.

    Practical implications – To validate the efficacy of the methodology proposed in this paper, it was applied tothe SHS (Spridnings- och Hämtningssystem: Dissemination and Retrieval System) system. The paper introduces themethodology, presents its application to the SHS system in detail and compares it to the current practice.

    Originality/value – This research is relevant to information security management in organizations, particularlyissues on changing requirements and evaluation in uncertain circumstances created by progress in technology.

  • 9.
    Abbas, Haider
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektroniksystem.
    Magnusson, Christer
    Department of Computer and System Sciences, Stockholm University, Sweden.
    Yngström, Louise
    Department of Computer and System Sciences, Stockholm University, Sweden.
    Hemani, Ahmed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektroniksystem.
    Architectural Description of an Automated System for Uncertainty Issues Management in Information Security2010Ingår i: International Journal of Computer Science and Information Security, ISSN 1947-5500, Vol. 8, nr 3, 89-67 s.Artikel i tidskrift (Refereegranskat)
  • 10.
    Abbas, Haider
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik- och datorsystem, ECS.
    Magnusson, Christer
    Yngström, Louise
    Hemani, Ahmed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik- och datorsystem, ECS.
    A Structured Approach for Internalizing Externalities Caused by IT Security Mechanisms2010Ingår i: IEEE ETCS 2010, Wuhan, China, 2010, 149-153 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    Organizations relying on Information Technology for their business processes have to employ various Security Mechanisms (Authentication, Authorization, Hashing, Encryption etc) to achieve their organizational security objectives of data confidentiality, integrity and availability. These security mechanisms except from their intended role of increased security level for this organization may also affect other systems outside the organization in a positive or negative manner called externalities. Externalities emerge in several ways i.e. direct cost, direct benefit, indirect cost and indirect benefit. Organizations barely consider positive externalities although they can be beneficial and the negative externalities that could create vulnerabilities are simply ignored. In this paper, we will present an infrastructure to streamline information security externalities that appear dynamically for an organization

  • 11.
    Abbas, Haider
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Magnusson, Christer
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Data- och systemvetenskap, DSV.
    Yngström, Louise
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Data- och systemvetenskap, DSV.
    Hemani, Ahmed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Analyzing IT Security Evaluation needs for Developing Countries2009Ingår i: IPID Annual Workshop 2009, Orebro, Sweden, 2009Konferensbidrag (Övrigt vetenskapligt)
  • 12.
    Abbas, Haider
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik- och datorsystem, ECS.
    Sundkvist, Stefan
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Increasing the Performance of Crab Linux Router Simulation Package Using XEN2006Ingår i: IEEE International Conference on Industrial and Information Systems, Kandy, Sri Lanka, 2006, 459-462 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    Nowadays hardware components are very expensive, especially if the prime purpose is to perform some routing related lab exercises. Physically connected network resources are required to get the desired results. Configuration of network resources in a lab exercise consumes much time of the students and scientists. The router simulation package Crab(1), based on KnoppW, Quagga' and User Mode Linux (UML) is designed for the students to facilitate them in performing lab exercises on a standalone computer where no real network equipment is needed. In addition to that it provides the facility of connection with the real network equipments. Crab also handles the pre configuration of different parts of the simulated networks like automatic IT addressing etc. This paper will describe the performance enhancing of Crab by replacing User Mode Linux virtual machine with XEN capable of providing ten virtual sessions concurrently using a standalone computer.

  • 13.
    Abbas, Haider
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik- och datorsystem, ECS.
    Yngström, Louise
    Hemani, Ahmed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik- och datorsystem, ECS.
    Adaptability Infrastructure for Bridging IT Security Evaluation and Options Theory2009Ingår i: ACM- IEEE SIN 2009 International Conference on Security of Information and Networks, North Cyprus, 2009Konferensbidrag (Refereegranskat)
    Abstract [en]

    The constantly rising threats in IT infrastructure raise many concerns for an organization, altering security requirements according to dynamically changing environment, need of midcourse decision management and deliberate evaluation of security measures are most striking. Common Criteria for IT security evaluation has long been considered to be victimized by uncertain IT infrastructure and considered resource hungry, complex and time consuming process. Considering this aspect we have continued our research quest for analyzing the opportunities to empower IT security evaluation process using Real Options thinking. The focus of our research is not only the applicability of real options analysis in IT security evaluation but also observing its implications in various domains including IT security investments and risk management. We find it motivating and worth doing to use an established method from corporate finance i.e. real options and utilize its rule of thumb technique as a road map to counter uncertainty issues for evaluation of IT products. We believe employing options theory in security evaluation will provide the intended benefits. i.e. i) manage dynamically changing security requirements ii) accelerating evaluation process iii) midcourse decision management. Having all the capabilities of effective uncertainty management, options theory follows work procedures based on mathematical calculations quite different from information security work processes. In this paper, we will address the diversities between the work processes of security evaluation and real options analysis. We present an adaptability infrastructure to bridge the gap and make them coherent with each other. This liaison will transform real options concepts into a compatible mode that provides grounds to target IT security evaluation and common criteria issues. We will address ESAM system as an example for illustrations and applicability of the concepts.

  • 14.
    Abbas, Haider
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektroniksystem.
    Yngström, Louise
    Hemani, Ahmed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektroniksystem.
    Empowering Security Evaluation of IT Products with Options Theory2009Ingår i: 30th IEEE Symposium on Security & Privacy, Oakland, USA, 2009Konferensbidrag (Refereegranskat)
  • 15.
    Abbas, Haider
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik- och datorsystem, ECS.
    Yngström, Louise
    Hemani, Ahmed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik- och datorsystem, ECS.
    Option Based Evaluation: Security Evaluation of IT Products Based on Options Theory2009Ingår i: IEEE  ECBS-EERC 2009, New York: IEEE , 2009, 134-141 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    Reliability of IT systems and infrastructure is a critical need for organizations to trust their business processes. This makes security evaluation of IT systems a prime concern for these organizations. Common Criteria is an elaborate, globally accepted security evaluation process that fulfills this need. However CC rigidly follows the initial specification and security threats and takes too long to evaluate and as such is also very expensive. Rapid development in technology and with it the new security threats further aggravates the long evaluation time problem of CC to the extent that by the time a CC evaluation is done, it may no longer be valid because new security threats have emerged that have not been factored in. To address these problems, we propose a novel Option Based Evaluation methodology for security of IT systems that can also be considered as an enhancement to the CC process. The objective is to address uncertainty issues in IT environment and speed up the slow CC based evaluation processes. OBE will follow incremental evaluation model and address the following main concerns based on options theory i.e. i) managing dynamic security requirement with mid-course decision management ii) devising evaluation as an improvement process iii) reducing cost and time for evaluation of an IT product.

  • 16.
    Abbas, Haider
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik- och datorsystem, ECS.
    Yngström, Louise
    Hemani, Ahmed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik- och datorsystem, ECS.
    ROA Based Agile Security Evaluation of IT Products for Developing Countries2009Ingår i: IPID 4th Annual Conference 2009, London, UK, 2009Konferensbidrag (Övrigt vetenskapligt)
  • 17.
    Abbas, Haider
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik- och datorsystem, ECS.
    Yngström, Louise
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Data- och systemvetenskap, DSV.
    Hemani, Ahmed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik- och datorsystem, ECS.
    Security Evaluation of IT Products: Bridging the Gap between Common Criteria (CC) and Real Option Thinking2008Ingår i: WCECS 2008: WORLD CONGRESS ON ENGINEERING AND COMPUTER SCIENCE, 2008, 530-533 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    Information security has long been considered as a key concern for organizations benefiting from the electronic era. Rapid technological developments have been observed in the last decade which has given rise to novel security threats, making IT, an uncertain infrastructure. For this reason, the business organizations have an acute need to evaluate the security aspects of their IT infrastructure. Since many years, CC (Common Criteria) has been widely used and accepted for evaluating the security of IT products. It does not impose predefined security rules that a product should exhibit but a language for security evaluation. CC has certain advantages over ITSEC1, CTCPEC2 and TCSEC3 due to its ability to address all the three dimensions: a) it provides opportunity for users to specify their security requirements, b) an implementation guide for the developers and c) provides comprehensive criteria to evaluate the security requirements. Among the few notable shortcomings of CC is the amount of resources and a lot of time consumption. Another drawback of CC is that the security requirements in this uncertain IT environment must be defined before the project starts. ROA is a well known modern methodology used to make investment decisions for the projects under uncertainty. It is based on options theory that provides not only strategic flexibility but also helps to consider hidden options during uncertainty. ROA comes in two flavors: first for the financial option pricing and second for the more uncertain real world problems where the end results are not deterministic. Information security is one of the core areas under consideration where researchers are employing ROA to take security investment decisions. In this paper, we give a brief introduction of ROA and its use in various domains. We will evaluate the use of Real options based methods to enhance the Common Criteria evaluation methodology to manage the dynamic security requirement specification and reducing required time and resources. We will analyze the possibilities to overcome CC limitations from the perspective of the end user, developer and evaluator. We believe that with the ROA enhanced capabilities will potentially be able to stop and possibly reverse this trend and strengthen the CC usage with a more effective and responsive evaluation methodology.

  • 18.
    Abbas, Naeem
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik- och datorsystem, ECS.
    Runtime Parallelisation Switching for MPEG4 Encoder on MPSoC2008Självständigt arbete på avancerad nivå (masterexamen), 80 poäng / 120 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The recent development for multimedia applications on mobile terminals raised the need for flexible and scalable computing platforms that are capable of providing considerable (application specific) computational performance within a low cost and a low energy budget. The MPSoC with multi-disciplinary approach, resolving application mapping, platform architecture and runtime management issues, provides such multiple heterogeneous, flexible processing elements. In MPSoC, the run-time manager takes the design time exploration information as an input and selects an active Pareto point based on quality requirement and available platform resources, where a Pareto point corresponds to a particular parallelization possibility of target application. To use system’s scalability at best and enhance application’s flexibility a step further, the resource management and Pareto point selection decisions need to be adjustable at run-time. This thesis work experiments run-time Pareto point switching for MPEG-4 encoder. The work involves design time exploration and then embedding of two parallelization possibilities of MPEG-4 encoder into one single component and enabling run-time switching between parallelizations, to give run-time control over adjusting performance-cost criteria and allocation de-allocation of hardware resources at run-time. The newer system has the capability to encode each video frame with different parallelization. The obtained results offer a number of operating points on Pareto curve in between the previous ones at sequence encoding level. The run-time manager can improve application performance up to 50% or can save memory bandwidth up to 15%, according to quality request.

  • 19.
    Abbas, Sahib
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Lösning till mobilitetsproblem samt tillgänglighet till hemsidan för Iraks ambassad2014Självständigt arbete på avancerad nivå (masterexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Att använda internet nuförtiden har blivit en del av vardagen. Det känns som att Internet har delat världen i många delar där varje del delar med sig information i många olika former som placeras i olika kategorier. Vi delar information på många olika sätt, men det snabbaste och lättaste sättet är att sprida information med internet.

    Tekniken kommer med nya ideer kontinuerligt och vi utvecklar nya metoder som gör det ännu lättare för oss människor att få in information som vi forsöker att nå via internet. Två av de mest kända sätten där man kan dela med sig information är hemsidor och med "native" applikationer.

    Jag utförde exjobbet på lrakiska ambassaden. Det är en statlig irakisk organisation som ligger pa Baldersgatan 6A Stockholm. Huvuduppgift på ambassaden är att hjälpa irakisk- ­och icke irakiska medborgare som är bosatta i Sverige med vissa uppgifter.

    Ambassaden har mycket information som de försöker att dela med sig så mycket som möjligt av via hemsidan så att de minskar av det strulet de har. Hemsidan som ambassaden hade var ostrukturerad, och hade en tråkig design som ledde till att användaren fick svårigbeter med att lätt hitta det man söker.

    Detta examensarbete presenterar min lösning av problemen till ambassaden. Den är att bygga en helt ny hemsida som är mobilanpassad, som har bättre design ocb är mer strukturerad hemsida än den gamla hemsidan de hade. På så sätt så blir det mycket lättare för användaren att använda hemsidan. Samtidigt löser den mobilitetsproblemet, eftersom ambassaden började med att utveckla en native app till Iphone men projektet avbröts halvvägs för att det kostade för mycket och man insåg att det skulle uppstå ännu mer kostnader for att utveckla native appar till android ocb övriga operativ systemen. Detta examensarbete beskriver också hur man skulle kunna utveckla en mobilanpassad hemsida, vilka metoder ocb modeller som jag har använt mig av till utvecklingen av hemsidan, samt resultaten jag hade fått av de metoder som användes till utveckling av detta projekt.

  • 20. Abbas, Syed Sohail
    et al.
    Popov, Sergei Yu
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik (Stängd 20120101), Optik (Stängd 20120101).
    Compact Er 3+-doped ZBLAN green upconversion fibre laser2011Ingår i: World Academy of Science, Engineering and Technology: An International Journal of Science, Engineering and Technology, ISSN 2010-376X, E-ISSN 2070-3740, Vol. 78, 756-758 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, a fibre laser at 546 nm has been studied for a signal power of -30 dB. Er 3+-doped ZBLAN fibre has been used by upconversion pumping of a 980 nm laser diode. Gain saturation effect has been investigated in detail. Laser performance has also been discussed. An efficiency of 35% has been calculated with a length of 5 mm fibre laser. Results show that Er 3+-doped ZBLAN is a promising candidate for optical amplification at 546 nm.

  • 21.
    Abbas, Zainab
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Streaming Graph Partitioning: Degree Project in Distributed Computing at KTH Information and Communication Technology2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Graph partitioning is considered to be a standard solution to process huge graphs efficiently when processing them on a single machine becomes inefficient due to its limited computation power and storage space. In graph partitioning, the whole graph is divided among different computing nodes that process the graph in parallel. During the early stages of research done on graph partitioning, different offline partitioning methods were introduced; these methods create high computation cost as they process the whole graph prior to partitioning. Therefore, an online graph partitioning method called as streaming graph partitioning was introduced later to reduce the computation cost by assigning the edges or vertices on-the-fly to the computing nodes without processing the graph before partitioning. In our thesis, we presented an experimental study of different streaming graph partitioning methods that use two partitioning techniques: vertex partitioning and edge partitioning. Edge partitioning has proved good for partitioning highly skewed graphs. After implementing different partitioning methods, we have proposed a partitioning algorithm that uses degree information of the vertices. Furthermore, we measured the effect of different partitioning methods on the graph stream processing algorithms. Our results show that for vertex partitioning Fennel has performed better than Linear Greedy as it shows lower edge-cuts and better load balancing. Moreover, for edge partitioning, the Degree based partitioner has performed better than Least Cost Incremental and Least Cost Incremental Advanced in reducing the replication factor, but the Degree based partitioner does not do well in load balancing. In the end, we show that the custom partitioning methods, compared to default hash partitioning, save the memory space by reducing the size of aggregate states during execution of different graph processing algorithms on the resulting partitions. The Degree based partitioner performed well by reducing the size of aggregate states on average up to 50%. Other algorithms include: Fennel, Linear Greedy, Least Cost Incremental and Least Cost Incremental Advanced, they reduced the size of aggregate states on average up to 21%, 10%, 27% and 48%.

  • 22. Abbasi, A. G.
    et al.
    Muftic, Sead
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster (Stängd 20120101), Kommunikationssystem, CoS (stängd 2012-01-01).
    Schmölzer, Gernot
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster (Stängd 20120101), Kommunikationssystem, CoS (stängd 2012-01-01).
    A model and design of a security provider for Java applications2009Ingår i: International Conference for Internet Technology and Secured Transactions, ICITST 2009, 2009, 5402592- s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    The model and design of a generic security provider provides a comprehensive set of security services, mechanisms, encapsulation methods, and security protocols for Java applications. The model is structured in four layers; each layer provides services to the upper layer and the top layer provide services to applications. The services reflect security requirements derived from a wide range of applications; from small desktop applications to large distributed enterprise environments. Based on the abstract model, this paper describes design and implementation of an instance of the provider comprising various generic security modules: symmetric key cryptography, asymmetric key cryptography, hashing, encapsulation, certificates management, creation and verification of signatures, and various network security protocols. This paper also describes the properties extensibility, flexibility, abstraction, and compatibility of the Java Security Provider.

  • 23. Abbasi, A. G.
    et al.
    Muftic, Sead
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster (Stängd 20120101), Kommunikationssystem, CoS (stängd 2012-01-01).
    Schmölzer, Gernot
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster (Stängd 20120101), Kommunikationssystem, CoS (stängd 2012-01-01).
    CryptoNET: A model of generic security provider2010Ingår i: International Journal of Internet Technology and Secured Transactions, ISSN 1748-569X, E-ISSN 1748-5703, Vol. 2, nr 3-4, 321-335 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The model and design of a generic security provider provides a comprehensive set of security services, mechanisms, encapsulation methods, and security protocols for Java applications. The model is structured in four layers; each layer provides services to the upper layer and the top layer provide services to applications. The services reflect security requirements derived from a wide range of applications; from small desktop applications to large distributed enterprise environments. Based on the abstract model, this paper describes design and implementation of an instance of the provider comprising various generic security modules: symmetric key cryptography, asymmetric key cryptography, hashing, encapsulation, certificates management, creation and verification of signatures, and various network security protocols. This paper also describes the properties for extensibility, flexibility, abstraction, and compatibility of the Java security provider.

  • 24. Abbasi, A. G.
    et al.
    Muftic, Sead
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Data- och systemvetenskap, DSV.
    Schmölzer, Gernot
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Data- och systemvetenskap, DSV.
    CryptoNET: Secure federation protocol and authorization policies for SMI2009Ingår i: Post-Proceedings of the 4th International Conference on Risks and Security of Internet and Systems, CRiSIS 2009, 2009, 19-25 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    The paper describes a protocol for Secure E-Mail Infrastructure for establishing trust between different domains in order to protect mail servers from spam messages. The protocol uses messages for trusted interactions between intra and inter E-mail domain components, Secure E-mail (SEM) servers and Secure Mail Infrastructure (SMI) servers. In addition, the protocol validates E-mail addresses thus guaranteeing to the recipient that the E-mail is coming from a trusted domain. We also use XACML-based authorization policies at the sending and receiving servers, enforced by associated Policy Enforcement Point (PEP) servers at SEM servers, in order to provide a complete protection against spam.

  • 25.
    Abbasi, Abdul Ghafoor
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    CryptoNET: Generic Security Framework for Cloud Computing Environments2011Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    The area of this research is security in distributed environment such as cloud computing and network applications. Specific focus was design and implementation of high assurance network environment, comprising various secure and security-enhanced applications. “High Assurance” means that

    -               our system is guaranteed to be secure,

    -               it is verifiable to provide the complete set of security services,

    -               we prove that it always functions correctly, and

    -               we justify our claim that it can not be compromised without user neglect and/or consent.

     

    We do not know of any equivalent research results or even commercial security systems with such properties. Based on that, we claim several significant research and also development contributions to the state–of–art of computer networks security.

    In the last two decades there were many activities and contributions to protect data, messages and other resources in computer networks, to provide privacy of users, reliability, availability and integrity of resources, and to provide other security properties for network environments and applications. Governments, international organizations, private companies and individuals are investing a great deal of time, efforts and budgets to install and use various security products and solutions. However, in spite of all these needs, activities, on-going efforts, and all current solutions, it is general belief that the security in today networks and applications is not adequate.

    At the moment there are two general approaches to network application’s security. One approach is to enforce isolation of users, network resources, and applications. In this category we have solutions like firewalls, intrusion–detection systems, port scanners, spam filters, virus detection and elimination tools, etc. The goal is to protect resources and applications by isolation after their installation in the operational environment. The second approach is to apply methodology, tools and security solutions already in the process of creating network applications. This approach includes methodologies for secure software design, ready–made security modules and libraries, rules for software development process, and formal and strict testing procedures. The goal is to create secure applications even before their operational deployment. Current experience clearly shows that both approaches failed to provide an adequate level of security, where users would be guaranteed to deploy and use secure, reliable and trusted network applications.

    Therefore, in the current situation, it is obvious that a new approach and a new thinking towards creating strongly protected and guaranteed secure network environments and applications are needed. Therefore, in our research we have taken an approach completely different from the two mentioned above. Our first principle is to use cryptographic protection of all application resources. Based on this principle, in our system data in local files and database tables are encrypted, messages and control parameters are encrypted, and even software modules are encrypted. The principle is that if all resources of an application are always encrypted, i.e. “enveloped in a cryptographic shield”, then

    -               its software modules are not vulnerable to malware and viruses,

    -               its data are not vulnerable to illegal reading and theft,

    -               all messages exchanged in a networking environment are strongly protected, and

    -               all other resources of an application are also strongly protected.

     

    Thus, we strongly protect applications and their resources before they are installed, after they are deployed, and also all the time during their use.

    Furthermore, our methodology to create such systems and to apply total cryptographic protection was based on the design of security components in the form of generic security objects. First, each of those objects – data object or functional object, is itself encrypted. If an object is a data object, representing a file, database table, communication message, etc., its encryption means that its data are protected all the time. If an object is a functional object, like cryptographic mechanisms, encapsulation module, etc., this principle means that its code cannot be damaged by malware. Protected functional objects are decrypted only on the fly, before being loaded into main memory for execution. Each of our objects is complete in terms of its content (data objects) and its functionality (functional objects), each supports multiple functional alternatives, they all provide transparent handling of security credentials and management of security attributes, and they are easy to integrate with individual applications. In addition, each object is designed and implemented using well-established security standards and technologies, so the complete system, created as a combination of those objects, is itself compliant with security standards and, therefore, interoperable with exiting security systems.

    By applying our methodology, we first designed enabling components for our security system. They are collections of simple and composite objects that also mutually interact in order to provide various security services. The enabling components of our system are:  Security Provider, Security Protocols, Generic Security Server, Security SDKs, and Secure Execution Environment. They are all mainly engine components of our security system and they provide the same set of cryptographic and network security services to all other security–enhanced applications.

    Furthermore, for our individual security objects and also for larger security systems, in order to prove their structural and functional correctness, we applied deductive scheme for verification and validation of security systems. We used the following principle: “if individual objects are verified and proven to be secure, if their instantiation, combination and operations are secure, and if protocols between them are secure, then the complete system, created from such objects, is also verifiably secure”. Data and attributes of each object are protected and secure, and they can only be accessed by authenticated and authorized users in a secure way. This means that structural security properties of objects, upon their installation, can be verified. In addition, each object is maintained and manipulated within our secure environment so each object is protected and secure in all its states, even after its closing state, because the original objects are encrypted and their data and states stored in a database or in files are also protected.

    Formal validation of our approach and our methodology is performed using Threat Model. We analyzed our generic security objects individually and identified various potential threats for their data, attributes, actions, and various states. We also evaluated behavior of each object against potential threats and established that our approach provides better protection than some alternative solutions against various threats mentioned. In addition, we applied threat model to our composite generic security objects and secure network applications and we proved that deductive approach provides better methodology for designing and developing secure network applications. We also quantitatively evaluated the performance of our generic security objects and found that the system developed using our methodology performs cryptographic functions efficiently.

    We have also solved some additional important aspects required for the full scope of security services for network applications and cloud environment: manipulation and management of cryptographic keys, execution of encrypted software, and even secure and controlled collaboration of our encrypted applications in cloud computing environments. During our research we have created the set of development tools and also a development methodology which can be used to create cryptographically protected applications. The same resources and tools are also used as a run–time supporting environment for execution of our secure applications. Such total cryptographic protection system for design, development and run–time of secure network applications we call CryptoNET system. CrytpoNET security system is structured in the form of components categorized in three groups: Integrated Secure Workstation, Secure Application Servers, and Security Management Infrastructure Servers. Furthermore, our enabling components provide the same set of security services to all components of the CryptoNET system.

    Integrated Secure Workstation is designed and implemented in the form of a collaborative secure environment for users. It protects local IT resources, messages and operations for multiple applications. It comprises four most commonly used PC applications as client components: Secure Station Manager (equivalent to Windows Explorer), Secure E-Mail Client, Secure Web Browser, and Secure Documents Manager. These four client components for their security extensions use functions and credentials of the enabling components in order to provide standard security services (authentication, confidentiality, integrity and access control) and also additional, extended security services, such as transparent handling of certificates, use of smart cards, Strong Authentication protocol, Security Assertion Markup Language (SAML) based Single-Sign-On protocol, secure sessions, and other security functions.

    Secure Application Servers are components of our secure network applications: Secure E-Mail Server, Secure Web Server, Secure Library Server, and Secure Software Distribution Server. These servers provide application-specific services to client components. Some of the common security services provided by Secure Application Servers to client components are Single-Sign-On protocol, secure communication, and user authorization. In our system application servers are installed in a domain but it can be installed in a cloud environment as services. Secure Application Servers are designed and implemented using the concept and implementation of the Generic Security Server. It provides extended security functions using our engine components. So by adopting this approach, the same sets of security services are available to each application server.

    Security Management Infrastructure Servers provide domain level and infrastructure level services to the components of the CryptoNET architecture. They are standard security servers, known as cloud security infrastructure, deployed as services in our domain level could environment.

    CryptoNET system is complete in terms of functions and security services that it provides. It is internally integrated, so that the same cryptographic engines are used by all applications. And finally, it is completely transparent to users – it applies its security services without expecting any special interventions by users. In this thesis, we developed and evaluated secure network applications of our CryptoNET system and applied Threat Model to their validation and analysis. We found that deductive scheme of using our generic security objects is effective for verification and testing of secure, protected and verifiable secure network applications.

    Based on all these theoretical research and practical development results, we believe that our CryptoNET system is completely and verifiably secure and, therefore, represents a significant contribution to the current state-of-the-art of computer network security.

  • 26.
    Abbasi, Abdul Ghafoor
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Muftic, Sead
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    CryptoNET: Security Management Protocols2010Ingår i: ADVANCES IN DATA NETWORKS, COMMUNICATIONS, COMPUTERS / [ed] Mastorakis, NE; Mladenov, V, ATHENS: WORLD SCIENTIFIC AND ENGINEERING ACAD AND SOC , 2010, 15-20 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper we describe several network security protocols used by various components of CryptoNET architecture. The protocols are based on the concept of generic security objects and on well-established security standards and technologies. Distinctive features of our security protocols are: (1) they are complete in terms of their functionality, (2) they are easy to integrate with applications, (3) they transparently handle security credentials and protocol-specific attributes using FIPS 201 (PIV) smart cards, and (4) they are based on generic security objects. These protocols are: remote user authentication protocol, single-sign-on protocol, SAML authorization protocol, and secure sessions protocol. Security protocols use our Security Provider as a collection of cryptographic engines implemented either in software or using FIPS 201 (NV) smart cards. It also manages protocols' attributes using security applets stored in Ply smart card.

  • 27.
    Abbasi, Abdul Ghafoor
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster (Stängd 20120101), Kommunikationssystem, CoS (stängd 2012-01-01).
    Muftic, Sead
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster (Stängd 20120101), Kommunikationssystem, CoS (stängd 2012-01-01).
    Hotamov, I.
    Web contents protection, secure execution and authorized distribution2010Ingår i: Proceedings - 5th International Multi-Conference on Computing in the Global Information Technology, ICCGI 2010, 2010, 157-162 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper describes the design and implementation of a comprehensive system for protection of Web contents. In this design, new security components and extended security features are introduced in order to protect Web contents ageist various Web attacks. Components and extended security features are: protection of Web pages using strong encryption techniques, encapsulation of Web contents and resources in PKCS#7, extended secure execution environment for Java Web Server, eXtensible Access Control Markup Language (XACML) based authorization policies, and secure Web proxy. Design and implementation of our system is based on the concepts of generic security objects and component-based architecture that makes it compatible with exiting Web infrastructures without any modification.

  • 28.
    Abbasi, Abdul Ghafoor
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster (Stängd 20120101), Kommunikationssystem, CoS (stängd 2012-01-01).
    Muftic, Sead
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster (Stängd 20120101), Kommunikationssystem, CoS (stängd 2012-01-01).
    Mumtaz, Shahzad Ahmed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster (Stängd 20120101), Kommunikationssystem, CoS (stängd 2012-01-01).
    Security extensions of windows environment based on FIPS 201 (PIV) smart card2011Ingår i: World Congr. Internet Secur., WorldCIS, 2011, 86-92 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper describes security extensions of various Windows components based on usage of FIPS 201 (PIV) smart cards. Compared to some other similar solutions, this system has two significant advantages: first, smart cards are based on FIPS 201 standard and not on some proprietary technology; second, smart card security extensions represent an integrated solution, so the same card is used for security of several Microsoft products. Furthermore, our smart card system uses FIPS 201 applet and middleware with smart card APIs, so it can also be used by other developers to extend their own applications with smart card functions in a Windows environment. We support the following security features with smart cards: start-up authentication (based on PIN and/or fingerprint), certificate-based domain authentication, strong authentication, and protection of local resources. We also integrated our middleware and smart cards with MS Outlook and MS Internet Explorer.

  • 29. Abd El Ghany, M. A.
    et al.
    El-Moursy, M. A.
    Ismail, Mohammed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektroniksystem.
    High throughput architecture for CLICHÉ network on chip2009Ingår i: Proceedings - IEEE International SOC Conference, SOCC 2009, 2009, 155-158 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    High Throughput Chip-Level Integration of Communicating Heterogeneous Elements (CLICHÉ) architecture to achieve high performance Networks on Chip (NoC) is proposed. The architecture increases the throughput of the network by 40% while preserving the average latency. The area of High Throughput CLICHÉ switch is decreased by 18% as compared to CLICHÉ switch. The total metal resources required to implement High Throughput CLICHÉ design is increased by 7% as compared to the total metal resources required to implement CLICHÉ design. The extra power consumption required to achieve the proposed architecture is 8% of the total power consumption of the CLICHÉ architecture.

  • 30. Abd El Ghany, M. A.
    et al.
    El-Moursy, M. A.
    Ismail, Mohammed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektroniksystem. Ohio State University, Columbus, United States .
    High throughput architecture for high performance NoC2009Ingår i: ISCAS: 2009 IEEE International Symposium on Circuits and Systems, IEEE , 2009, 2241-2244 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    High Throughput Butterfly Fat Tree (HTBFT) architecture to achieve high performance Networks on Chip (NoC) is proposed. The architecture increases the throughput of the network by 38% while preserving the average latency. The area of HTBFT switch is decreased by 18% as compared to Butterfly Fat Tree switch. The total metal resources required to implement HTBFT design is increased by 5% as compared to the total metal resources required to implement BFT design. The extra power consumption required to achieve the proposed architecture is 3% of the total power consumption of the BFT architecture.

  • 31. Abd El Ghany, M. A.
    et al.
    El-Moursy, M. A.
    Korzec, D.
    Ismail, Mohammed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar. Ohio State University, Columbus, OH, United States .
    Asynchronous BFT for low power networks on chip2010Ingår i: ISCAS 2010 - 2010 IEEE International Symposium on Circuits and Systems: Nano-Bio Circuit Fabrics and Systems, IEEE , 2010, 3240-3243 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    Asynchronous Butterfly Fat Tree (BFT) architecture is proposed to achieve low power Network on Chip (NoC). Asynchronous design could reduce the power dissipation of the network if the activity factor of the data transfer between two switches (αdata satisfies a certain condition. The area of Asynchronous BFT switch is increased by 25% as compared to Synchronous switch. However, the power dissipation of the Asynchronous architecture could be decreased by up to 33% as compared to the power dissipation of the conventional Synchronous architecture when the αdata equals 0.2 and the activity factor of the control signals is equal to 1/64 of the αdata. The total metal resources required to implement Asynchronous design is decreased by 12%.

  • 32. Abd El Ghany, M. A.
    et al.
    El-Moursy, M. A.
    Korzec, D.
    Ismail, Mohammed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar. Ohio State University, Columbus, OH, United States .
    Power characteristics of networks on chip2010Ingår i: ISCAS 2010 - 2010 IEEE International Symposium on Circuits and Systems: Nano-Bio Circuit Fabrics and Systems, IEEE , 2010, 3721-3724 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    Power characteristics of different Network on Chip (NoC) topologies are developed. Among different NoC topologies, the Butterfly Fat Tree (BFT) dissipates the minimum power. With the advance in technology, the relative power consumption of the interconnects and the associate repeaters of the BFT decreases as compared to the power consumption of the network switches. The power dissipation of interswitch links and repeaters for BFT represents only 1% of the total power dissipation of the network. In addition of providing high throughput, the BFT is a power efficient topology for NoCs.

  • 33. Abd El Ghany, M. A.
    et al.
    El-Moursy, M. A.
    Korzec, D.
    Ismail, Mohammed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Power efficient networks on chip2009Ingår i: 2009 16th IEEE International Conference on Electronics, Circuits and Systems, ICECS 2009, 2009, 105-108 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    a low power switch design is proposed to achieve power-efficient Network on Chip (NoC). The proposed NoC switch reduce. The power consumption oy the Butterfly Fat Tree (BFT) architecture by 28 % as compared to the conventional BFT switch. Moreover. The power reduction technique is applied to different NoC architectures. The technique reduce. The power consumption oy the network by up to 41%. Whe. The power consumption oy the whole network includin. The interswich links and repeaters is taken into account. The overall power consumption is decreased by up to 33% at the maximum operating frequency oy the switch. The BFT architecture consume. The minimum power as compared to other NoC architectures.

  • 34. Abd Elghany, M. A.
    et al.
    El-Moursy, M. A.
    Korzec, D.
    Ismail, Mohammed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar. Ohio State University, United States .
    High throughput architecture for OCTAGON network on chip2009Ingår i: 2009 16th IEEE International Conference on Electronics, Circuits and Systems, ICECS 2009, IEEE , 2009, 101-104 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    High Throughput Octagon architecture to achieve high performance Networks on Chip (NoC) is proposed. The architecture increase. The throughput oy the network by 17% while preservin. The average latency. The area of High Throughput OCTAGON switch is decreased by 18% as compared to OCTAGON switch. The total metal resources required to implement High Throughput OCTAGON design is increased by 8% as compared to the total metal resources required to implement OCTAGON design. The extra power consumption required to achiev. The proposed architecture is 2% oy the total power consumption oy the OCTAGON architecture.

  • 35.
    ABDALMAHMOODABADI, MAHBOOBEH
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    The value of downstream information sharing in two-level supply chain: AN APPROACH TO AGENT-BASED MODELING2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Många försörjningskedjan företag har tagit initiativ för att underlätta efterfrågan informationsutbyte mellan nedströms och uppströms enheter. Informationsutbyte är en nyckelfaktor för samarbete inom supply chain management (SCM). Under de senaste decennierna har många ansträngningar gjorts för att modellera distributionskedjan matematiskt. Matematiska modeller är oförmögna att fånga den dynamiska karaktären i systemet. Det är nödvändigt att studera flerdimensionell försörjningskedjan modell där inte bara det finns kommunikation mellan leverantör och återförsäljare men även kommunikation mellan återförsäljare måste övervägas. Matematiska modeller kan ses som en enkel beslutsfattande optimering mellan två enheter där effekten av samarbete med andra enheter är helt ignoreras. Dessa modeller är långt ifrån verkliga system. Syftet med denna avhandling är att skapa en agentbaserad modell, som ersättning för matematisk modellering, för att bedöma vikten av att dela information om leverantörssidan när det finns samband mellan återförsäljare genom aktiedelning. Den konceptuella modellen av två-Echelon leveranskedjan utformas och genomförs i Java med hjälp Repast kostym. Modellen omfattar fyra typer av agenter nämligen leveranskedjan, leverantörs, återförsäljare och förmedlar medel som interagerar med varandra i en diskret händelsebaserad simulering. Multi faktornivå används för att utvärdera resultatet av leveranskedjan, när det gäller den totala kostnadsbesparingar, under olika efterfrågemönster. Den stora skillnaden mellan experimentella inställningar testas statistiskt med hjälp av ANOVA, Parvis, och Univariata tester. Dataanalys visar att betydelsen av informationsutbyte kan vara ganska hög, i synnerhet när slutkundernas krav avsevärt korrelerade. En sådan kostnadsbesparingar som uppnås genom att dela information beror på att minska lagernivån och på bekostnad av att öka mängden av rest.

  • 36.
    Abdel-Karim, R.
    et al.
    Department of Metallurgy, Faculty of Engineering, Cairo University.
    Reda, Y.
    Department of Metallurgy, Faculty of Engineering, Cairo University.
    Muhammed, Mamoun A.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    El-Raghy, S.
    Department of Metallurgy, Faculty of Engineering, Cairo University.
    Shoeib, M.
    Metals Technology Department Central Metallurgical Research and Development Institute.
    Ahmed, H.
    Department of Metallurgy, Faculty of Engineering, Cairo University.
    Electrodeposition and Characterization of Nanocrystalline Ni-Fe Alloys2011Ingår i: Journal of Nanomaterials, ISSN 1687-4110, 519274- s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nanocrystalline Ni-Fe deposits with different composition and grain sizes were fabricated by electrodeposition. Deposits with iron contents in the range from 7 to 31% were obtained by changing the Ni(2+)/Fe(2+) mass ratio in the electrolyte. The deposits were found to be nanocrystalline with average grain size in the range 20-30 nm. The surface morphology was found to be dependent on Ni(2+)/Fe(2+) mass ratio as well as electroplating time. The grains size decreased with increasing the iron content, especially in case of short time electroplating. Increasing the electroplating time had no significant effect on grain size. The microhardness of the materials followed the regular Hall-Petch relationship with amaximum value (762 Hv) when applying Ni(2+)/Fe(2+) mass ratio equal to 9.8.

  • 37. Abderrazek, K.
    et al.
    Uheida, Abdusalam
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Seffen, M.
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Srasra, N. Frini
    Srasra, E.
    Photocatalytic degradation of indigo carmine using [Zn-Al] LDH supported on PAN nanofibres2015Ingår i: Clay minerals, ISSN 0009-8558, E-ISSN 1471-8030, Vol. 50, nr 2, 185-197 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Zn-Al layered double hydroxides (LDH), before and after calcination, were tested for the removal of indigo carmine (IC) dye from solution. These LDH photocatalysts were characterized by powder x-ray diffraction (PXRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetry/differential thermogravimetry (TG/DTG), nitrogen physisorption at -196 degrees C, scanning electron microscopy (SEM) and diffuse reflectance spectrophotometry (DRS). The different photocatalysts were supported on polyacrylonitrile (PAN) nanofibres, so that filtration was unnecessary. The PXRD and FTIR analyses showed that the IC adsorption on c-Zn-Al-3-500 (LDH calcined at 500 degrees C) was enhanced by construction of the hydrotalcite matrix intercalated with the dye. The intercalation was clearly evidenced by the appearance of a peak at low degrees 2 theta values. All of the materials prepared exhibited photocatalytic activity, which for the c-Zn-Al-3-500 was comparable to that of commercial PAN-supported ZnO nanoparticles (100% degradation after 180 min). Kinetic studies showed that the degradation of the IC followed a pseudo-first order rate. The high activity and the ease of both synthesis and separation processes rendered this photocatalyst a promising candidate for environmental remediation.

  • 38. Abdi, Y.
    et al.
    Derakhshandeh, J.
    Hashemi, P.
    Mohajerzadeh, S.
    Karbassian, F.
    Nayeri, F.
    Arzi, E.
    Robertson, M. D.
    Radamson, Henry H.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Light-emitting nano-porous silicon structures fabricated using a plasma hydrogenation technique2005Ingår i: Materials Science and Engineering B: Solid-State Materials for Advanced Technology, ISSN 0921-5107, Vol. 124-125, nr SUPPL., 483-487 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The preparation of porous silicon films by DC-plasma hydrogenation and subsequent annealing of amorphous silicon films on silicon and glass substrates is reported for the first time. The effects of varying plasma power and annealing temperatures have been investigated and characterized by scanning-electron microscopy, transmission-electron microscopy, and photoluminescence. A plasma density of about 5.5 W/m2 and hydrogenation-annealing temperatures of about 400 °C was found to be suitable for the formation of nano-crystalline silicon films with grain diameters of the order of 3-10 nm. The intensity and wavelength of the emitted visible light were found to depend on the hydrogenation and annealing conditions, and patterning of the silicon films using standard lithography allowed the creation of light-emitting patterns.

  • 39.
    Abdulla, Mohammad
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Modeling of Thermal Stresses and Analysis of Micro-Crack Formations in PCB Laminates2016Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Detta examensarbete har gett mig en möjlighet att studera var, när och varför sprickbildningar sker i mönsterkortslaminaten. Sannolikheten att sprickor bildas påverkas av designen. Simulering på tre olika platser i ett mönsterkort gjordes och resultaten analyserades. En termisk simulering gjordes där resultaten visade en knapp värmegradient i brädan. Temperaturen på ytan var nästan lika stor som inuti brädan, därav slutsatsen att det inte behövs en kopplad termisk och strukturell simulering. I laminaten var det mest stress runt viorna, det var även mest kompression i laminaten kring viorna.

  • 40.
    Abdulla, Muntazar
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Cu-tråd som elektrisk ledare i CIGS-tunnfilmssolceller för att sänka silvermängden utan att förlora verkningsgrad2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Solcellsbranschen är större än någonsin tidigare och fortsätter växa samtidigt som konkurrensen mellan solcellstillverkare ökar, detta är något som pressar ner priserna på solceller och minskar lönsamheten för tillverkarna. Därför fokuserar detta projekt på hur man kan sänka mängden silver i solcellen utan att förlora verkningsgrad. Detta genomförs genom att arbeta som en problemlösare ihop med egna idéer. Genom att dra nytta av fördelarna med koppartrådar och skapa ett nytt solcellsmönster är detta möjligt då silver utgör 1/5 av tillverkningskostnaden. Projektet domineras av praktiskt arbete med fokus på innovation av standardsolcellen. Resultatet visade att man kan sänka silverpasta mängden med upp till 70 % i varje solcell genom att ta fram ett nytt silvertryck med mycket mindre silver ihop med koppartrådar. Det användes silver-belagda koppartrådar som ledare för att leda ut ström från ytan med fördelarna att det är tunna och blockerar därför solljuset mindre. Resultaten gav en verkningsgrad på 10-11% vilket är i nivå med produktionssolcellsmodulerna på Midsummer. Systemet bevisades även stabilt.

  • 41.
    Abdullah, Nazri
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Håkansson, Anne
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Moradian, E.
    Blockchain based approach to enhance big data authentication in distributed environment2017Ingår i: 2017 Ninth International Conference on Ubiquitous and Future Networks (ICUFN), IEEE Computer Society, 2017, 887-892 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    Existing authentication protocols for Big Data system such as Apache Hadoop is based on Kerberos. In the Kerberos protocol, there are numerous security issues that have remained unsolved; replay attacks, DDoS and single point of failure are some examples. These indicate potential security vulnerabilities and Big Data risks in using Hadoop. This paper presents drawbacks of Kerberos implementations and identifies authentication requirements that can enhance the security of Big Data in distributed environments. The enhancement proposed is based on the rising technology of blockchain that overcomes shortcomings of Kerberos.

  • 42.
    Abdullah, Nazri
    et al.
    Universiti Tun Hussien Onn Malaysia, Malaysia .
    Kounelis, Ioannis
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Muftic, Sead
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Security Extensions for Mobile Commerce Objects2014Ingår i: SECURWARE 2014, The Eighth International Conference on Emerging Security Information, Systems and Technologies, 2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    Electronic commerce and its variance mobile commerce have tremendously increased their popularity in the last several years. As mobile devices have become the most popular mean to access and use the Internet, mobile commerce and its security are timely and very hot topics. Yet, today there is still no consistent model of various m–commerce applications and transactions, even less clear specification of their security. In order to address and solve those issues, in this paper, we first establish the concept of mobile commerce objects, an equivalent of virtual currencies, used for m–commerce transactions. We describe functionalities and unique characteristics of these objects; we follow with security requirements, and then offer some solutions – security extensions of these objects. All solutions are treated within the complete lifecycle of creation and use of the m–commerce objects.

  • 43.
    Abedin, Ahmad
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik, Integrerade komponenter och kretsar.
    Asadollahi, Ali
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik, Integrerade komponenter och kretsar.
    Garidis, Konstantinos
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Hellström, Per-Erik
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik.
    Epitaxial growth of Ge strain relaxed buffer on Si with low threading dislocation density2016Ingår i: ECS Transactions, Electrochemical Society, 2016, nr 8, 615-621 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    Epitaxial Ge with low dislocation density is grown on a low temperature grown Ge seed layer on Si substrate by reduced pressure chemical vapor deposition. The surface topography measured by AFM shows that the strain relaxation occurred through pit formation which resulted in freezing the defects at Ge/Si interface. Moreover a lower threading dislocation density compared to conventional strain relaxed Ge buffers on Si was observed. We show that by growing the first layer at temperatures below 300 °C a surface roughness below 1 nm can be achieved together with carrier mobility enhancement. The different defects densities revealed from SECCO and Iodine etching shows that the defects types have been changed and SECCO is not always trustable.

  • 44.
    Abedin, Ahmad
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Moeen, Mahdi
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Cappetta, Carmine
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Radamson, Henry H.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Sensitivity of the crystal quality of SiGe layers grown at low temperatures by trisilane and germane2016Ingår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 613, 38-42 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This work investigates the crystal quality of SiGe layers grown at low temperatures using trisilane, and germane precursors. The crystal quality sensitivity was monitored for hydrogen chloride and/or minor oxygen amount during SiGe epitaxy or at the interface of SiGe/Si layers. The quality of the epi-layerswas examined by quantifying noise parameter, K-1/f obtained from the power spectral density vs. 1/f curves. The results indicate that while it is difficult to detect small defect densities in SiGe layers by physical material characterization, the noise measurement could reveal the effects of oxygen contamination as low as 0.16mPa inside and in the interface of the layers.

  • 45.
    Abedin, Ahmad
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Noroozi, Mohammad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Primetzhofer, Daniel
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Radamson, Henry.H
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    GeSnSi CVD Epitaxy using Silane, Germane, Digermane, and Tin tetrachlorideArtikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, strain relaxed and compressive strained Ge1-x-ySnxSiy (0.015≤x≤0.15 and 0≤y≤0.15) layers were epitaxially grown on Si substrate in a chemical vapor deposition reactor at atmospheric pressure. Digermane (Ge2H6) and germane (GeH4) were used as Ge precursors and tin tetrachloride (SnCl4) was used as Sn precursor. The growth temperature was kept below 400ᵒC to suppress Sn out diffusion. The layers crystal quality and strain were characterized using XRD, high resolution reciprocal lattice mapping and transmission electron microscopy and the surface morphology was investigated by atomic force microscopy (AFM). Furthermore, the low temperature epitaxial growth up to 15% Si atoms incorporation in Ge0.94Sn0.06 was demonstrated by adding silane (SiH4) as Si precursor. Sn contents calculated from high resolution XRD patterns were confirmed by Rutherford backscattering spectroscopy which shows that Sn atoms are mostly positioned in substitutional sites. AFM analysis showed below 1nm surface roughness for both strained and strain relaxed GeSn layers which make the promising materials for photonics and electronics applications.

  • 46.
    Abefelt, Fredrik
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Synchronized audio playback over WIFI and Ethernet: A proof of concept multi-room audio playback system2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Huvuduppgift med detta examensarbete har varit att utveckla ett synkroniserat ljuduppspelningssystem, vilket kan spela upp ljud samtidigt på flera enheter, enheterna är anslutna med antingen med Wi-Fi eller Ethernet. Två olika tillvägagångsätt har undersökts för att utveckla systemet, ett redan färdigt system och ett system baserat på ett ramverk med öppen källkod.

    Det utvecklade systemet kan utföra synkroniserad uppspelning på fem olika enheter och kan använda Blueetooth enheter och olika mediaspelare som ljudkälla.

  • 47. Aberer, Karl
    et al.
    Alima, Luc Onana
    Ghodsi, Ali
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik- och datorsystem, ECS.
    Girdzijauskas, Sarunas
    Ecole Polytechnique Fédérale de Lausanne.
    Haridi, Seif
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik- och datorsystem, ECS.
    Hauswirth, Manfred
    The Essence of P2P: A Reference Architecture for Overlay Networks2005Ingår i: Fifth IEEE International Conference on Peer-to-Peer Computing, Proceedings / [ed] Caronni, G; Weiler, N; Waldvogel, M; Shahmehri, N, 2005, 11-20 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    The success of the P2P idea has created a huge diversity of approaches, among which overlay networks, for example, Gnutella, Kazaa, Chord, Pastry, Tapestry, P-Grid, or DKS, have received specific attention from both developers and researchers. A wide variety of algorithms, data structures, and architectures have been proposed. The terminologies and abstractions used, however have become quite inconsistent since the P2P paradigm has attracted people from many different communities, e.g., networking, databases, distributed systems, graph theory, complexity theory, biology, etc. In this paper we propose a reference model for overlay networks which is capable of modeling different approaches in this domain in a generic manner It is intended to allow researchers and users to assess the properties of concrete systems, to establish a common vocabulary for scientific discussion, to facilitate the qualitative comparison of the systems, and to serve as the basis for defining a standardized API to make overlay networks interoperable.

  • 48. Aberg, D
    et al.
    Hallberg, T
    Svensson, B G
    Lindstrom, J L
    Linnarsson, M K
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Ultra-shallow thermal donor formation in oxygen-containing ambient1998Ingår i: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 210, 527-532 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Czochralski-grown phosphorus-doped (approximate to 2 x 10(14) cm(-3)) silicon wafers have been annealed in nitrogen, wet nitrogen, argon, oxygen, and vacuum ambients at 470 degrees C for times up to 500 h. Sample characterization was made with capacitance-voltage, four-point probe, DLTS, thermally stimulated capacitance, admittance spectroscopy, secondary ion-mass spectrometry, and Fourier transform infrared spectroscopy. This study finds a strong relation between the previously reported ultra-shallow thermal donors (USTDs) and shallow thermal donors (STDs), and it is shown that the net concentration of thermally formed donors is independent on annealing ambient within the experimental accuracy. It was found that the majority of formed donors for long anneals consisted of either STDs or USTDs, however, it was found that oxygen-containing ambient is indispensable for forming USTDs.

  • 49. Aberg, D
    et al.
    Linnarsson, M K
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Svensson, B G
    Hallberg, T
    Lindstrom, J L
    Ultrashallow thermal donor formation in silicon by annealing in ambient oxygen1999Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 85, 8054-8059 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Czochralski-grown silicon wafers doped with phosphorus (similar to 10(14) cm(-3)) have been annealed in nitrogen, wet nitrogen, oxygen, argon, and vacuum ambients at 470 degrees C for times up to 500 h. Sample characterization was made using predominantly electrical techniques such as admittance spectroscopy and thermally stimulated capacitance measurements but also secondary ion mass spectrometry (SIMS) and Fourier transform infrared spectroscopy were employed. In all samples, an increasing concentration of free carrier electrons is observed with increasing annealing time, reaching a maximum of similar to 10(16) cm(-3) at 100 h. For durations in excess of 100 h gradual decrease of the free electron concentration takes place except for the samples treated in wet nitrogen and oxygen atmospheres, which display donors stable even after 200 h. These stable centers are found to have shallower donor level positions in the energy band gap (similar to 25 meV below the conduction band edge E-c) than those of the centers formed in vacuum, argon, and nitrogen atmospheres (similar to 35 meV below E-c). The latter centers are associated with the well-established shallow thermal donors (STDs) while the origin of the former ones, which are labeled ultrashallow thermal donors (USTDs) is less known. However, on the basis of a wealth of experimental results we show that the USTDs are most likely perturbated STDs modified through interaction with fast-in diffusing oxygen species, possibly oxygen dimers. Further, comparison between the electrical data and the SIMS measurements reveals unambiguously that neither the STD nor the USTD centers involve nitrogen, in contrast to recent suggestions in the literature. (C) 1999 American Institute of Physics. [S0021-8979(99)06512-3].

  • 50. Abeywickrama, S.
    et al.
    Furdek, Marija
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab). University of Zagreb, Faculty of Electrical Engineering and Computing, Dept. of Telecommunications, Croatia.
    Monti, Paolo
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Nag, A.
    Wong, E.
    Dual-homing based protection for enhanced network availability and resource efficiency2014Ingår i: Asia Communications and Photonics Conference, ACP, 2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    An approach to enhance core network survivability by utilizing dual-homing capabilities of the access network. Results reveal significant improvements in core network resource utilization and connection availability, suggesting benefits to network operators and service providers.

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