Author
Wolfgang A. Halang
Other affiliations: FernUniversität Hagen
Bio: Wolfgang A. Halang is an academic researcher from Rolf C. Hagen Group. The author has contributed to research in topics: Software & Unified Modeling Language. The author has an hindex of 23, co-authored 248 publications receiving 2010 citations. Previous affiliations of Wolfgang A. Halang include FernUniversität Hagen.
Papers published on a yearly basis
Papers
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Book•
31 Aug 1991
TL;DR: This paper focuses on the development of Real Time Languages and their applications, and on the proposed extension of PEARL, which aims to provide a real-time version of English as a programming language.
Abstract: 1 Introduction.- 1.1 Motivation.- 1.1.1 A Chemical Process Application.- 1.1.2 A Power Plant Application.- 1.1.3 A Fighter Aircraft Application.- 1.1.4 Real Time System Requirements.- 1.2 Predictability and Simplicity.- 1.3 Constructing Predictable Real Time SystemsNew Thinking Categories and Optimality Criteria.- 1.4 Guiding Principles for Predictable, Verifiable Real Time Software and Hardware.- 1.4.1 Language Assumptions.- 1.4.2 System Software and Hardware Assumptions.- 1.5 Book Outline.- 2 Real Time Features of High Level Languages.- 2.1 A Representative Real Time Application Design.- 2.2 Historical Development of Real Time Languages.- 2.3 Requirements of a Real Time Language.- 2.4 Review of Existing Languages.- 2.4.1 Pseudocodes and Assembly Languages.- 2.4.2 FORTRAN.- 2.4.3 JOVIAL.- 2.4.4 RTL/1 and RTL/2.- 2.4.5 PEARL.- 2.4.6 ILIAD.- 2.4.7 Modula and Modula-2.- 2.4.8 PORTAL.- 2.4.9 Ada.- 2.4.10 Forth.- 2.4.11 Languages for Programmable Logic Controllers.- 2.4.12 Experimental Hard Real Time Languages.- 2.4.13 Survey Summary.- 2.5 Taking a Closer Look at Real-Time Euclid.- 2.5.1 Language Structure.- 2.5.2 Real Time Units and Time Functions.- 2.5.3 Absence of Dynamic Data Structures.- 2.5.4 Time-Bounded Loops.- 2.5.5 Absence of Recursion.- 2.5.6 Processes.- 2.5.7 Condition Variables.- 2.5.8 Monitors, Signals, Waits and Broadcasts.- 2.5.9 Exception Handling.- 2.5.10 Summary.- 2.6 A Second Review - Focusing on Real Time Features.- 2.6.1 Selection of Reviewed Languages.- 2.6.2 A Survey of Real Time Features Supported.- 2.6.3 A Discussion of Additional Real Time FeaturesNeeded.- 2.6.4 Summary.- 2.7 Taking a Closer Look at Ada.- 2.7.1 Ada's Limitations.- 2.7.2 Changing Ada.- 2.8 Taking a Closer Look at PEARL.- 2.8.1 An Overview of Basic PEARL.- 2.8.2 PEARL's Limitations.- 2.8.3 An Overview of Distributed PEARL.- 2.9 Proposal for an Extension of PEARL.- 2.9.1 Locks and Timeouts.- 2.9.2 Timed Synchronisation.- 2.9.3 Time-Bounded Loops.- 2.9.4 Status Operators.- 2.9.5 Surveillance of Event Occurrences.- 2.9.6 Parallel Processing and Precedence Relations of Tasks Sets.- 2.9.7 Expressing Timing Constraints.- 2.9.8 Overload Detection and Handling.- 2.9.9 Hierarchical Deadlock Prevention.- 2.9.10 Support of Task-Oriented Hierarchical Storage Management.- 2.9.11 Exact Timing of Operations.- 2.9.12 Tracing and Event Recording.- 2.9.13 Restriction to Static Language Features.- 2.9.14 Application-Oriented Simulation.- 2.9.15 Graceful System Degradation Using the Conceptof Imprecise Results.- 2.9.15.1 Transient Overloads.- 2.9.15.2 Diversity Based Error Detection and Handling.- 2.9.16 Synopsis of PEARL Language Extensions.- 2.9.17 Summary.- 3 Language-Independent Schedulability Analysis of Real Time Programs.- 3.1 Front End of the Schedulability Analyser.- 3.1.1 Front End Segment Trees.- 3.1.2 Condition, Bracket, Subprogram and Process Records.- 3.1.3 Front End Statistics.- 3.2 Back End of the Schedulability Analyser.- 3.2.1 Resolving Segment Trees.- 3.2.2 Converting Process Trees.- 3.2.3 A Real Time Model.- 3.2.3.1 A High Level Model Description.- 3.2.3.2 A Survey of Real Time Modeling.- 3.2.3.3 Frame Superimposition Our Solutionof the Model.- 3.2.3.4 Delays.- 3.2.3.5 Interruptible Slow-downs.- 3.2.3.6 Overall Solution Algorithm.- 3.3 Schedulability Analysis of Real-Time Euclid and Ex-tended PEARL.- 3.4 Summary.- 4 A Real Time Hardware Architecture.- 4.1 Useful Analogies.- 4.2 Properties and Architectural Implications of Comprehen-sive Deadline-Driven Scheduling.- 4.2.1 Implications of Employing Earliest DeadlineScheduling.- 4.2.2 Sufficient Conditions for Feasible Task Executabil-ity under Resource Constraints.- 4.2.3 Non-pre-emptive Deadline Scheduling.- 4.2.4 Avoiding Context-Switches Without Violation ofFeasibility.- 4.3 The Layered Structure of Real Time Operating Systems.- 4.4 Outline of the Architecture.- 4.5 Comparison with other Architectures.- 4.6 Task-Oriented and Predictable Storage Management.- 4.7 Direct Memory Access Without Cycle Stealing.- 4.7.1 Synchronous Direct Memory Access.- 4.7.2 Dynamic Bus Subdivision.- 4.7.3 Integration of a DMA Facility into Dynamic RAM Chips.- 4.8 Precisely Timed Peripherals.- 4.8.1 Required Functions and their Invocation in PEARL.- 4.8.2 Implementation of Hardware Support.- 4.8.3 Operating System Support.- 4.8.4 Clock Synchronisation in a Distributed System.- 4.9 Summary.- 5 An Operating System Kernel and its Dedicated Processor.- 5.1 Hardware Organisation.- 5.1.1 Time-Dependent Elements.- 5.1.2 Event Recognition Modules.- 5.2 Primary Event Reaction.- 5.2.1 Representation of Time Schedules.- 5.2.2 Algorithms and Data Structures of the Time Management.- 5.2.3 Algorithms and Data Structures of the Event Management.- 5.2.4 Implementation of Other Features.- 5.3 Secondary Event Reaction.- 5.3.1 Functions.- 5.3.2 Control Programs.- 5.3.3 Task Control Blocks.- 5.3.4 Kernel Algorithms.- 5.4 Summary.- 6 Implementation.- 6.1 Real-Time Euclid.- 6.1.1 Compiler.- 6.1.1.1 Kernel.- 6.1.1.2 Schedulability Analyser.- 6.1.1.3 Hardware.- 6.2 Extended PEARL.- 6.2.1 Compiler Functions.- 6.2.2 Run-Time Features.- 6.3 Summary.- 7 Evaluation.- 7.1 Real-Time Euclid and its Schedulability Analyser.- 7.1.1 Applications.- 7.1.1.1 A Simulated Power Station.- 7.1.1.2 A Simulated Packet-Level Handshakingin X.25.- 7.1.1.3 Schedulability Analyser Evaluation.- 7.2 Qualitative Evaluation of the Co-processor Architecture..- 7.3 Summary.- 8 Outlook.- 8.1 Summary of Contributions.- 8.2 Directions for Future Research.
163 citations
TL;DR: The security of the proposed image encryption scheme is studied and the following problems are found: a differential chosen-plaintext attack can break the scheme with only three chosen plain-images; there is a number of weak keys and some equivalent keys for encryption; the scheme is not sensitive to the changes of plain- images.
131 citations
TL;DR: The development of power electronics in the past century and the current state-of-the-art power electronics converters are briefly reviewed, before giving an insight into the deficiencies of the conventional current-source and voltage-source converters and, then, proposing a design methodology for impedance source converters aimed to replace the traditional tedious, manual and experience dependent design methods.
Abstract: The development of power electronics in the past century and the current state of the art of power electronics converters are briefly reviewed, before giving an insight into the deficiencies of the conventional current-source and voltage-source converters and into the superiority of impedance-source converters and, then, proposing a design methodology for impedance-source converters aimed to replace the traditional tedious, manual and experience-dependent design methods. Some examples for their deployment in renewable-energy applications are discussed, and the direction into which power electronic converters will develop in the future is indicated.
110 citations
TL;DR: Some defects of the proposed new image encryption schemes are discussed and how to break them with a chosen-plaintext attack.
Abstract: Chaotic systems have been broadly exploited through the last two decades to build encryption methods. Recently, two new image encryption schemes have been proposed, where the encryption process involves a permutation operation and an XOR-like transformation of the shuffled pixels, which are controlled by three chaotic systems. This paper discusses some defects of the schemes and how to break them with a chosen-plaintext attack.
98 citations
TL;DR: An approach to generate multiple pseudorandom-bit sequences from a single spatiotemporal chaotic system is proposed and it is observed from simulation results that the CML–MPRBG has good cryptographic properties.
86 citations
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Journal Article•
9,185 citations
01 Apr 1997
TL;DR: The objective of this paper is to give a comprehensive introduction to applied cryptography with an engineer or computer scientist in mind on the knowledge needed to create practical systems which supports integrity, confidentiality, or authenticity.
Abstract: The objective of this paper is to give a comprehensive introduction to applied cryptography with an engineer or computer scientist in mind. The emphasis is on the knowledge needed to create practical systems which supports integrity, confidentiality, or authenticity. Topics covered includes an introduction to the concepts in cryptography, attacks against cryptographic systems, key use and handling, random bit generation, encryption modes, and message authentication codes. Recommendations on algorithms and further reading is given in the end of the paper. This paper should make the reader able to build, understand and evaluate system descriptions and designs based on the cryptographic components described in the paper.
2,188 citations
TL;DR: It is proved that consensus tracking in the closed-loop multi-agent systems with a fixed topology having a directed spanning tree can be achieved if the feedback gain matrix and the coupling strength are suitably selected.
Abstract: Distributed consensus tracking is addressed in this paper for multi-agent systems with Lipschitz-type node dynamics. The main contribution of this work is solving the consensus tracking problem without the assumption that the topology among followers is strongly connected and fixed. By using tools from M-matrix theory, a class of consensus tracking protocols based only on the relative states among neighboring agents is designed. By appropriately constructing Lyapunov function, it is proved that consensus tracking in the closed-loop multi-agent systems with a fixed topology having a directed spanning tree can be achieved if the feedback gain matrix and the coupling strength are suitably selected. Furthermore, with the assumption that each possible topology contains a directed spanning tree, it is theoretically shown that consensus tracking under switching directed topologies can be achieved if the control parameters are suitably selected and the dwell time is larger than a positive threshold. The results are then extended to the case where the communication topology contains a directed spanning tree only frequently as the system evolves with time. Finally, some numerical simulations are given to verify the theoretical analysis.
705 citations