In this paper we study three popular on-line disk scheduling algorithms, FCFS, SSTF, and LOOK, using competitive analysis. Our results show that, in a competitive sense, the performance of LOOK is better than those of...
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In this paper we study three popular on-line disk scheduling algorithms, FCFS, SSTF, and LOOK, using competitive analysis. Our results show that, in a competitive sense, the performance of LOOK is better than those of SSTF and FCFS. As a by-product, our analysis also reveals quantitatively the role played by the size of the window, which in our model is a waiting buffer that holds a fixed number of requests waiting to be serviced next. The window, in some sense, offers the lookahead ability which is mentioned in several on-line problems.
This paper presents a method to verify the correctness of protocols and distributed algorithms. The method compares a state graph of the implementation with a specification which is a state graph representing the desi...
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This paper presents a method to verify the correctness of protocols and distributed algorithms. The method compares a state graph of the implementation with a specification which is a state graph representing the desired abstract behavior. The steps in the specification correspond to atomic transactions, which are not atomic in the implementation. The method relies on an aggregation function, which is a type of abstraction function that aggregates the steps of each transaction in the implementation into a single atomic transaction in the specification. The key idea in defining the aggregation function is that it must complete atomic transactions which have committed but are not finished. This paper illustrates the method on a directory-based cache coherence protocol developed for the Stanford FLASH multiprocessor. The coherence protocol consisting of more than a hundred different kinds of implementation steps has been reduced to a specification with six kinds of atomic transactions. Based on the reduced behavior, it is very easy to prove crucial properties of the protocol including data consistency of cached copies at the user level. This is the first correctness proof verified by a theorem-prover for a cache coherence protocol of this complexity. The aggregation method is also used to prove that the reduced protocol satisfies a desired memory consistency model.
This paper describes the original research and development of an Electronic Load Governor which Is microprocessor based and incorporates three-phase balancing. The combined study and testing of the transient behaviour...
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This paper describes the original research and development of an Electronic Load Governor which Is microprocessor based and incorporates three-phase balancing. The combined study and testing of the transient behaviour of the governor indicated the need for an improved control algorithm. The results of the implementation of the advanced algorithm me presented and compared with the original algorithm.
Adaptive linear filtering can improve effective speech-to-noise ratios by attenuating spectral regions with intense noise components to reduce the noise's spread of masking onto speech in neighboring regions, This...
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Adaptive linear filtering can improve effective speech-to-noise ratios by attenuating spectral regions with intense noise components to reduce the noise's spread of masking onto speech in neighboring regions, This mechanism was examined in static listening conditions for seven individuals with sensorineural hearing loss. Subjects were presented with nonsense syllables in an intense octave-band noise centered on 0.5, 1, or 2 kHz. The nonsense syllables were amplified to maximize the articulation index;the noises were the same for all subjects. The processing consisted of applying frequency-selective attenuation to the speech-plus-noise with the goal of attenuating the frequency region containing the noise by various amounts. Consonant recognition scores and noise masking patterns were collected in all listening conditions. When compared with masking patterns obtained from normal-hearing subjects, all hearing-impaired subjects had higher masked thresholds at frequencies below, within, and above the masker band except for one subject who demonstrated additional masking above the masker only. Frequency-selective attenuation resulted in both increases and decreases in consonant recognition scores. Increases were associated with a release from upward spread of masking. Decreases were associated with applying too much attenuation such that speech energy within the masker band that was audible before processing was partially below threshold after processing. Fletcher's [Speech and Hearing in Communication (Van Nostrand, New York, 1953)] version of articulation theory (without modification) accounted for individual subject differences within the range of variability associated with the consonant recognition test in almost every instance. Hence, primary factors influencing speech reception benefits are characterized by articulation theory. Fletcher's theory appears well-suited to guide the design of control algorithms that will maximize speech recognition for individual liste
This article presents a technical opinion in the case of collaborative programming for a large, complex system, in which two programmers are working jointly on the same algorithm and code. A field experiment was condu...
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This article presents a technical opinion in the case of collaborative programming for a large, complex system, in which two programmers are working jointly on the same algorithm and code. A field experiment was conducted using experienced programmers who worked on a challenging problem important to their organization, in their own environments, and with their own equipment. Findings revealed that all the teams outperformed the individual programmers, enjoyed the problem-solving process more, and had greater confidence in their solutions. Several aspects of this experiment make the results significant. First, there may be a tendency to dismiss results using small groups. Questions may arise at the value of these results if the collaborators do not perform twice as well as individuals, at least in the amount of time spent. The article concludes that the crunch-time information systems development will demand innovative ways to produce high-quality systems in a short time, with companies increasingly introducing new products. This rare experimental research is phenomenon considering the luxury of using collaborative programming while many companies are experiencing shortages of experienced programmer/analysts.
The erection of large hydroelectric power stations leads to appreciable changes in hydrothermal and ice river regimes both above and below the hydroscheme. The river regime change affects the adjacent areas ecology. T...
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The erection of large hydroelectric power stations leads to appreciable changes in hydrothermal and ice river regimes both above and below the hydroscheme. The river regime change affects the adjacent areas ecology. To estimate completely the ecologic effect of designed and already constructed hydroelectric power stations, it is necessary to determine the hydrothermal and ice river regime changes. As a methodical basis for the construction of a set of computer algorithms, a method of splitting by physical processes and the module principle has been used. Among the hydro-ice-thermics problems of rivers and water reservoirs are the following: the determination of the temperature regime of a water reservoir, an investigation of stratified flows in a weakly-running water reservoir;an investigation of a hydrothermal river regime;an investigation of ice cover edge dynamics in the downstream of a river. For every problem, mathematical models of different levels of complication and computer programs have been worked out.
We propose an accurate collision detection algorithm for use in virtual reality applications, The algorithm works for three-dimensional graphical environments where multiple objects, represented as polyhedra (boundary...
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We propose an accurate collision detection algorithm for use in virtual reality applications, The algorithm works for three-dimensional graphical environments where multiple objects, represented as polyhedra (boundary representation), are undergoing arbitrary motion (translation and rotation). The algorithm can be used directly for both convex and concave objects and objects can be deformed (nonrigid) during motion. The algorithm works efficiently by first reducing the number of face pairs that need to be checked accurately for interference, by first localizing possible collision regions using bounding box and spatial subdivision techniques, Face pairs that remain after this pruning stage are then accurately checked for interference. The algorithm is efficient, simple to implement, and does not, require any memory-intensive auxiliary data structures to be precomputed and updated,The performance of the proposed algorithm is compared directly against other existing algorithms, e.g., the separating plane algorithm, octree update method, and distance-based method. Results are given to show the efficiency of the proposed method in a general environment.
Cooperative micro-robotic scent tracking vehicles are designed to collectively "sniff out" locations of high scent concentrations in unknown, geometrically complex environments. These vehicles are programed ...
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Cooperative micro-robotic scent tracking vehicles are designed to collectively "sniff out" locations of high scent concentrations in unknown, geometrically complex environments. These vehicles are programed with guidance and control algorithms that allow inter cooperation among vehicles. In this paper, a cooperative guidance and control algorithm for scent tracking micro-robotic vehicles is presented. This algorithm is comprised of a sensory compensation sub-algorithm using point source cancellation, a guidance sub-algorithm using gradient descent tracking, and a control sub-algorithm using proportional feedback. The concepts of social rank and point source cancellation are new concepts introduced within. Simulation results for cooperative vehicles swarms are given. Limitations are discussed.
A new method for the control of chaos is presented. The procedure is based on proportional feedback and is very simple to implement. The presentation is pedagogical, and in order to illustrate the method, we apply it ...
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A new method for the control of chaos is presented. The procedure is based on proportional feedback and is very simple to implement. The presentation is pedagogical, and in order to illustrate the method, we apply it to the Henon map and to the Lorenz equations. Finally, we look at the stability of the control algorithm in the presence of noise. (C) 1998 American Association of Physics Teachers.
The main purposes of this paper are to illustrate several key issues in the implementation of a conventional Nonlinear Model Predictive Control algorithm on a reasonably large industrial process and to test the effect...
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ISBN:
(纸本)0780345304
The main purposes of this paper are to illustrate several key issues in the implementation of a conventional Nonlinear Model Predictive Control algorithm on a reasonably large industrial process and to test the effectiveness of the Nonlinear Model Predictive Control algorithm recently proposed by Zheng for control of large nonlinear systems with constraints. We show why a conventional Nonlinear Model Predictive Control algorithm may fail to provide integral control under very reasonable conditions (i.e., integral control is guaranteed if and only if a global solution is implemented and the output horizon is infinite) and illustrate this undesirable behavior through simulations on the Tennessee East man process. In addition to computational advantage, we argue that Zheng's algorithm may be preferred based on robust performance consideration.
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