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NORMAL STATE OPTIMAL LOAD ALLOCATION IN DISTRIBUTION-SYSTEMS

IEEE TRANSACTIONS ON POWER DELIVERY 1987年第1期2卷 147-155页

作者： AOKI, K ICHIMORI, T KANEZASHI, M AICHI INST TECHNOL TOYOTAJAPAN

This paper addresses a subproblem related to distribution automation. It outlines an algorithm and presents computer results for minimizing the losses in a loop distribution system based on the remote operation of sectionalizing switches on feeders interconnecting different substations. The minimization is carried out subject to the voltage-drop, line-capacity and substation-capacity constraints. Computational experience with a system of realistic size indicates that the procedure proposed here is valid and effective in practical operations.

关键词： Switches Voltage Substation automation distributed computing Mathematical programming Cities and towns Power system interconnection Fault detection Power supplies Constraint optimization

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Numerically Stable Polynomially Coded computing

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IEEE TRANSACTIONS ON INFORMATION THEORY 2021年第5期67卷 2758-2785页

作者： Fahim, Mohammad Cadambe, Viveck R. Penn State Univ Dept Elect Engn University Pk PA 16802 USA Qualcomm Technol Inc San Diego CA 92121 USA

We study the numerical stability of polynomial based encoding methods, which has emerged to be a powerful class of techniques for providing straggler and fault tolerance in the area of coded computing. Our contributions are as follows: 1) We construct new codes for matrix multiplication that achieve the same fault/straggler tolerance as the previously constructed MatDot Codes and Polynomial Codes. 2) We show that the condition number of every m x m sub-matrix of an m x n, n >= m Chebyshev-Vandermonde matrix, evaluated on the n-point Chebyshev grid, grows as O(n(2(n-m))) for n > m. 3) By specializing our orthogonal polynomial based constructions to Chebyshev polynomials, and using our condition number bound for Chebyshev-Vandermonde matrices, we construct new numerically stable techniques for coded matrix multiplication. We empirically demonstrate that our constructions have significantly lower numerical errors compared to previous approaches which involve inversion of Vandermonde matrices. We generalize our constructions to explore the trade-off between computation/communication and fault-tolerance. 4) We propose a numerically stable specialization of Lagrange coded computing. Our approach involves the choice of evaluation points and a suitable decoding procedure. Our approach is demonstrated empirically to have lower numerical errors as compared to standard methods.

关键词： distributed computing coded computing fault tolerance stragglers numerical stability

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Computations of SAR distributions for two anatomically based models of the human head using CAD files of commercial telephones and the parallelized FDTD code

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IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION 1998年第6期46卷 829-833页

作者： Tinniswood, AD Furse, CM Gandhi, OP Univ Utah Dept Elect Engn Salt Lake City UT 84112 USA

A method for importing data from computer-aided design (CAD) files for a mobile telephone into finite-difference time-domain (FDTD) simulation software is described. Although the FDTD method is well suited for the bio-electromagnetic simulations and has become the method of choice for most researchers in this area, there may be some limitations to its use. Limitations include, the description of the source (e.g., the mobile telephone) and the fact that the FDTD method requires large amounts of memory and computational power. The size of the computational space is dependent upon both the physical size of the model and its resolution. Higher frequencies of operation require higher resolutions. This could place the solution of some problems outside the capabilities of the technique. Often the telephone has to be represented by a plastic covered metal box, which approximates the shape of the actual device. The paper addresses these problems, Wires and circuit boards inside the telephone can act as resonant elements if they are not shielded, This potential problem is also considered. The large problem size associated with high-resolution FDTD simulations is accommodated by the use of a parallel implementation of the FDTD method (run on an IBM SP-2), The techniques developed here are used for two anatomically based head models that have been developed from magnetic resonance imaging (MRI) of two human subjects, The usefulness of the techniques developed and comparisons of the specific absorption rates (SAR's) in the two models are discussed.

关键词： distributed computing Finite difference methods Telephony Time domain analysis Design automation Mobile computing Computational modeling Magnetic resonance imaging Computer simulation Physics computing

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Service discovery strategies in ubiquitous communication environments

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IEEE COMMUNICATIONS MAGAZINE 2006年第9期44卷 106-113页

作者： Sivavakeesar, Siva Gonzalez, Oscar F. Pavlou, George Univ Surrey Networks Res Grp Ctr Commun Syst Res Guildford GU2 5XH Surrey England

Past communication and computing trends are inadequate to deal with today's complex, distributed, and diverse network environments. With the recent development of small-size tetherless communication/computing devices and the increasing diversity in their capabilities, autonomic ubiquitous communication environments are emerging. In such environments, the execution of a complex task does not necessarily make use of prconfigured devices or networks, but requires instead the selection of suitable computing elements on-the-fly, based on the task requirements and device characteristics (i.e., networking-on-demand or task-centric networking). Research is currently being carried out in various dimensions in this emerging domain, including, among other approaches for context awareness, service discovery and self-management. In this article we concentrate on proposing a distributed mechanism for discovering suitable service elements on-the-fly.

关键词： UBIQUITOUS computing COMPUTER programming distributed computing EMBEDDED computer systems COMPUTER networks WIDE area networks (Computer networks) distributed shared memory COMPUTERS SYSTEMS development EMBEDDED computer systems -- Programming

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Transparently obtaining scalability for Java applications on a cluster

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JOURNAL OF PARALLEL AND distributed computing 2000年第10期60卷 1159-1193页

作者： Aridor, Y Factor, M Teperman, A Eilam, T Schuster, A IBM Haifa Res Lab Ctr Adv Technol Matam IL-31905 Haifa Israel Technion Israel Inst Technol IL-32000 Haifa Israel

cJVM is a Java virtual machine (JVM) which provides a single system image of a traditional JVM while executing in a distributed fashion on the nodes of a cluster. cJVM virtualizes the cluster. transparently distributing the objects and threads of any pure Java application. The aim of cJVM is to obtain improved scalability Tor Java server applications by distributing the application's work among the cluster's computing resources, cJVM's architecture, its unique object model, thread, and memory models, were described by Y. Aridor et al. (1999. in "International Conference on Parallel Processing, September 21-24) and at http://***/projects/systech/***. In this article, we focus on the optimization techniques employed in cJVM to achieve high scalability. In particular, we focus on the techniques used to enhance locality, thereby reducing the amount of communication generated by cJVM. Our optimization techniques are based on three principles. First, we employ a large number of mostly simple optimizations which address caching, locality of execution, and object migration. Second, we take advantage of the Java semantics and of common usage patterns in implementing the optimizations. Third, we use speculative optimizations. taking advantage of the fact that the cJVM run-time environment can correct false speculations. We have demonstrated the usefulness of these techniques on a large 110 Kloc), real. Java application where we demonstrate an 80% efficiency on a four-node cluster. This paper discusses the various techniques used and reports our results. (C) 2000 Academic Press.

关键词： cluster Java Java virtual machine distributed computing scalability high performance computing

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DeFTA: A plug-and-play peer-to-peer decentralized federated learning framework

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INFORMATION SCIENCES 2024年 670卷

作者： Zhou, Yuhao Shi, Minjia Tian, Yuxin Ye, Qing Lv, Jiancheng Sichuan Univ Coll Comp Sci 24 South Sect 1Yihuan Rd Chengdu 610064 Sichuan Peoples R China Engn Res Ctr Machine Learning & Ind Intelligence Chengdu 610065 Sichuan Peoples R China

Federated learning (FL) is a pivotal catalyst for enabling large-scale privacy-preserving distributed machine learning (ML). By eliminating the need for local raw dataset sharing, FL substantially reduces privacy concerns and alleviates the isolated data problem. However, in reality, the success of FL is predominantly attributed to a centralized framework called FedAvg [1], in which workers are responsible for model training, and servers are in control of model aggregation. Nevertheless, FedAvg's centralized worker-server architecture has raised new concerns, including low scalability of the cluster, risk of data leakage, and central server failure or even defection. To overcome these challenges, we propose De centralized F ederated T rusted A veraging (DeFTA), a decentralized FL framework that serves as a plug-and-play replacement for FedAvg , bringing instant improvements to security, scalability, and fault-tolerance in the federated learning process. In essence, it primarily consists of a novel model aggregating formula with theoretical performance analysis, and a decentralized trust system (DTS) to significantly enhance system robustness. Extensive experiments conducted on six datasets and six basic models suggest that DeFTA not only exhibits comparable performance with FedAvg in a more realistic setting, but also achieves remarkable resilience even when 67% of workers are malicious.

关键词： distributed computing Federated learning Decentralization Peer-to-peer Framework

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On minimal connectivity requirements for secure message transmission in directed networks

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INFORMATION PROCESSING LETTERS 2018年 131卷 1-6页

作者： Kishore, Ravi Vanarasa, Chiranjeevi Kannan, Srinathan Int Inst Informat Technol Hyderabad 500032 Telangana India IIIT H C STAR A3-107 Hyderabad 500032 Telangana India

In a synchronous distributed network of n nodes, the goal of a Secure Message Transmission (SMT) protocol is to securely deliver the sender's message at the receiver's end in the presence of a computationally unbounded adversary that can partially control the network by corrupting some of its nodes (except the sender and the receiver). In a network modelled as a directed graph, to achieve unconditional security tolerating t(b) Byzantine faults, it is known that: (1) if all the paths are one-way connected from the sender to the receiver - called as forward channels - then 2t(b) +1 vertex-disjoint forward channels are necessary and sufficient (2) for 1 <= u <= tb, if there exist 2t(b) + 1 u vertex-disjoint forward channels then u vertex-disjoint paths from the receiver to the sender - known as feedback channels - are necessary and sufficient. Moreover, similar characterization exists for tolerating mixed faults - up to t(f) fail-stop faults in addition to t(p) passive faults. We notice that these results characterized the networks by studying the required number of extra vertex-disjoint feedback channels, conditioned on the existence of a certain number of forward channels. In this work, we give a generic characterization without attaching any such if condition. Specifically, we answer the following questions. In a given directed graph, that is abstracted as a collection of strong paths from S to R and R to S, under what conditions is SMT (im)possible tolerating: (1) up to t(p) passive faults?, (2) mixed faults - up to t(f) fail-stop faults in addition to tp passive faults?, and (3) up to t(b) Byzantine faults? Also, for each of these three problems, we explicitly show that there are networks in which SMT protocols exist whereas the existing results do not characterize such networks. (C) 2017 Elsevier B.V. All rights reserved.

关键词： distributed computing Fault tolerance Secure communication Information theoretic security distributed computing

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Shadow/Puppet Synthesis: A Stepwise Method for the Design of Self-Stabilization

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IEEE TRANSACTIONS ON PARALLEL AND distributed SYSTEMS 2016年第11期27卷 3338-3350页

作者： Klinkhamer, Alex Ebnenasir, Ali Michigan Technol Univ Dept Comp Sci Houghton MI 49931 USA

This paper presents a novel two-step method for automated design of self-stabilization. The first step enables the specification of legitimate states and an intuitive (but imprecise) specification of the desired functional behaviors in the set of legitimate states (hence the term "shadow"). After creating the shadow specifications, we systematically introduce the main variables and the topology of the desired self-stabilizing system. Subsequently, we devise a parallel and complete backtracking search towards finding a self-stabilizing solution that implements a precise version of the shadow behaviors, and guarantees recovery to legitimate states from any state. To the best of our knowledge, the shadow/puppet synthesis is the first sound and complete method that exploits parallelism and randomization along with the expansion of the state space towards generating self-stabilizing systems that cannot be synthesized with existing methods. We have validated the proposed method by creating both a sequential and a parallel implementation in the context of a software tool, called Protocon. Moreover, we have used Protocon to automatically design three new self-stabilizing protocols that we conjecture to require the minimal number of states per process to achieve stabilization (when processes are deterministic): 2-state maximal matching on bidirectional rings, 5-state token passing on unidirectional rings, and 3-state token passing on bidirectional chains.

关键词： Self-stabilization distributed computing program synthesis

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DIRECT COMPUTATION OF ULTRASOUND PHASED-ARRAY DRIVING SIGNALS FROM A SPECIFIED TEMPERATURE DISTRIBUTION FOR HYPERTHERMIA

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IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING 1992年第8期39卷 825-835页

作者： MCGOUGH, RJ EBBINI, ES CAIN, CA Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

This paper presents a new method which obtains ultrasound hyperthermia applicator phased-array element driving signals from a desired temperature distribution. The approach combines a technique which computes array element driving signals from focal point locations and intensities with a new technique which calculates focal point locations and power deposition values from temperature requirements. Temperature specifications appear here as upper and lower bounds within the tumor volume, and a focal point placement algorithm chooses focal patterns capable of achieving the temperature range objective. The linear algebraic structure of the method allows rapid calculation of both the phased-array driving signals and an approximate temperature field response. Computer simulations verify the method with a spherical section array (SSA) for a variety of temperature specifications and blood perfusion values. This scheme, which applies to any phased-array geometry, completes an essential step in both treatment planning and feedback for hyperthermia with ultrasound phased-array applicators.

关键词： distributed computing Ultrasonic imaging Phased arrays Temperature distribution Hyperthermia Acoustic arrays Applicators Neoplasms Geometry Power generation

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SYSTEM SUPPORT FOR TIME-CRITICAL APPLICATIONS

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COMPUTER COMMUNICATIONS 1993年第10期16卷 619-636页

作者： NORTHCUTT, JD KUERNER, EM [a]Sun Microsystems Labs Inc. 2550 Garcia Avenue Building 29 Mountain View CA 94043 USA

A number of interesting applications have time constraints associated with them - most notably those in the area of multimedia. Today's workstations do not provide adequate support for applications whose definition of correctness is a function of time. This paper presents a set of system-level mechanisms that permit the incorporation of multiple streams of sustained, high-bandwidth, time-critical information into the distributed workstation computing environment. The goal of this work is to enable programmers to write applications that manipulate (i.e. acquire, transport, process, store and present) and synchronize time-critical information streams, and do so with an ease comparable to that of manipulating text or graphics on a workstation today. This paper provides a description of the different types of temporal relationships required by time-critical applications, and provides a means of expressing these relationships to the underlying system in a minimally constraining fashion (i.e. through a technique called 'loose synchronization'). The central concept behind the mechanisms described here is the notion of time-regulated transport of time-critical information being provided by means of mechanisms that are software analogues to Phase-Locked Loops (PLL).

关键词： distributed computing SYSTEM SUPPORT TIME-CRITICAL

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