Swedish Institute of Computer Science Publications Database
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Representation and similarity evaluation of symbolic time series in uncertain environments
No full textFault Diagnosis of Heavy Duty Machines: Automatic Transmission Clutches
No full textThis paper presents a generic approach to fault diagnosis of heavy duty machines that combines signal processing, statistics, machine learning, and case-based reasoning for on-board and off-board analysis. The used methods complement each other in that the on-board methods are fast and light-weight, while case-based reasoning is used off-board for fault diagnosis and for retrieving cases as support in manual decision making. Three major contributions are novel approaches to detecting clutch slippage, anomaly detection, and case-based diagnosis that is closely integrated with the anomaly detection model. As example application, the proposed approach has been applied to diagnosing the root cause of clutch slippage in automatic transmissions
Conventions for Coordinating Large Agile Projects
No full textThere is no universal way to coordinate Agile teams in large development projects because they have unique challenges. This suggests that the best way to coordinate the teams is to ask them how they want to be managed given a set of constraints. This requires particular communication and negotiation skills in the leadership team, which we discuss in this article. We describe the skills as a set of conventions, founded on the argument that every organization is a complex adaptive system and should therefore be analyzed from multiple system perspectives. We investigate scientific models for managing complexity and evaluate their usefulness through qualitative interviews with 14 managers in large private and public organizations in Saudi Arabia. We conclude that a set of proposed conventions could facilitate coordination by functioning as a supportive context enabling managers to apply various system perspectives simultaneously
Hitting time in Erlang loss systems with moving boundaries
No full textWhen the boundary—the total number of servers—in an Erlang loss system is a function of time, customers may also be lost due to boundary variations. On condition that these customers are selected independently of their history, we solve for the hitting-time distribution and transient distribution of busy servers. We derive concise asymptotic expressions in the time domain for normal loads in the heavy-traffic limit, i.e., when the offered load ρ is high, and the number of servers scales as ρ+O(√ρ). The solutions are computationally efficient, and simulations confirm the theoretical results
On the global solution of a fuzzy linear system
No full textThe global solution of a fuzzy linear system contains the crisp vector solution of a real linear system. So discussion about the global solution of a n × n fuzzy linear system Ax˜ = b˜ with a fuzzy number vector b in the right hand side and crisp a coefficient matrix A is considered. The advantage of the paper is developing a new algorithm to find the solution of such system by considering a global solution based upon the concept of a convex fuzzy numbers. At first the existence and uniqueness of the solution are introduced and then the related theorems and properties about the solution are proved in details. Finally the method is illustrated by solving some numerical examples.
Keywords: Fuzzy linear system, Algebraic solution, Fuzzy number
Integrated Register Allocation and Instruction Scheduling with Constraint Programming
No full textThis dissertation proposes a combinatorial model, program representations, and constraint solving techniques for integrated register allocation and instruction scheduling in compiler back-ends. In contrast to traditional compilers based on heuristics, the proposed approach generates potentially optimal code by considering all trade-offs between interdependent decisions as a single optimization problem.
The combinatorial model is the first to handle a wide array of global register allocation subtasks, including spill code optimization, ultimate coalescing, register packing, and register bank assignment, as well as instruction scheduling for Very Long Instruction Word (VLIW) processors. The model is based on three novel, complementary program representations: Linear Static Single Assignment for global register allocation; copy extension for spilling, basic coalescing, and register bank assignment; and alternative temporaries for spill code optimization and ultimate coalescing. Solving techniques are proposed that exploit the program representation properties for scalability.
The model, program representations, and solving techniques are implemented in Unison, a code generator that delivers potentially optimal code while scaling to medium-size functions. Thorough experiments show that Unison: generates faster code (up to 41% with a mean improvement of 7%) than LLVM (a state-of-the-art compiler) for Hexagon (a challenging VLIW processor), generates code that is competitive with LLVM for MIPS32 (a simpler RISC processor), is robust across different benchmarks such as MediaBench and SPECint 2006, scales up to medium-size functions of up to 1000 instructions, and adapts easily to different optimization criteria.
The contributions of this dissertation are significant. They lead to a combinatorial approach for integrated register allocation and instruction scheduling that is, for the first time, practical (it robustly scales to medium-size functions) and effective (it yields better code than traditional heuristic approaches)
Access Control in the Internet of Things
No full textThe new generation of Wireless Sensor Networks, that is known as the Internet of Things enables the direct connection of physical objects to the Internet using microcontrollers. In most cases these microcontrollers have
very limited computational resources. The global connectivity provides great opportunities for data collection and analysis as well as for interaction of
objects that cannot be connected to the same local area network. Many of application scenarios have high requirements to security and privacy of transmitted data. At the same time security solutions that are utilized for
general purpose computers are not always applicable for constrained devices.
That leaves a room for new solutions that takes into account the technological aspects of the Internet of Things.
In this thesis we investigate the access control solution for the IETF standard draft Constrained Application Protocol, using the Datagram Transport Layer Security protocol for transport security. We use the centralized approach to save access control information in the framework. Since the public key cryptography operations might be computationally too expensive for constrained devices we build our solution based on symmetric cryptography.
Evaluation results show that the access control framework increases computational effort of the handshake by 6.0%, increases the code footprint of the Datagram Transport Layer Security implementation by 7.9% and has no effect on the overall handshake time. Our novel protocol is not vulnerable to Denial of Service or Drain Battery Attack
The Lord of the Sense: A Privacy Preserving Reputation System for Participatory Sensing Applications
No full textElectronic devices we use on a daily basis collect sensitive information without preserving user's privacy. In this paper, we propose the lord of the sense (LotS), a privacy preserving reputation system for participatory sensing applications. Our system maintains the privacy and anonymity of information with the use of cryptographic techniques and combines voting approaches to support users' reputation. Furthermore, LotS maintains accountability by tracing back a misbehaving user while maintaining k-anonymity. A detailed security analysis is presented with the current advantages and disadvantages of our system
Jogging with Technology
No full textThere has been a significant increase of interactive technologies to support sports activities. Examples are heart rate monitors for cyclists, jogging apps on mobile phones and GPS sports watches for extreme sports. Despite consumer popularity, there is little knowledge about how they should be designed in order to support the exertion activity. Based on CHI’13’s success of conducting a special interest group outdoors, we propose jogging with technology to discuss sports support interactive systems and investigate what future
opportunities and challenges exist
A Simulation Tool for Evaluating Attack Impact in Cyber Physical Systems
No full textSecurity is getting an ever increasingly important issue in cyber-physical systems comprising autonomous systems. However, it is not possible to defend from all possible attacks for cost and performance reasons. An attack ranking is thus necessary. We propose a simulative framework that makes it possible to rank attacks according to their impact. We also describe a case study to assert its usefulness and effectiveness