摘要 :
Uncertainties in design variables and problem parameters are often inevitable and must be considered in an optimization task if reliable optimal solutions are sought. Besides a number of sampling techniques, there exist several m...
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Uncertainties in design variables and problem parameters are often inevitable and must be considered in an optimization task if reliable optimal solutions are sought. Besides a number of sampling techniques, there exist several mathematical approximations of a solution's reliability. These techniques are coupled in various ways with optimization in the classical reliability-based optimization field. This paper demonstrates how classical reliability-based concepts can be borrowed and modified and, with integrated single and multiobjective evolutionary algorithms, used to enhance their scope in handling uncertainties involved among decision variables and problem parameters. Three different optimization tasks are discussed in which classical reliability-based optimization procedures usually have difficulties, namely 1) reliability-based optimization problems having multiple local optima, 2) finding and revealing reliable solutions for different reliability indices simultaneously by means of a bi-criterion optimization approach, and 3) multiobjective optimization with uncertainty and specified system or component reliability values. Each of these optimization tasks is illustrated by solving a number of test problems and a well-studied automobile design problem. Results are also compared with a classical reliability-based methodology.
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We introduce a new measure of image similarity called the complex wavelet structural similarity (CW-SSIM) index and show its applicability as a general purpose image similarity index. The key idea behind CW-SSIM is that certain im...
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We introduce a new measure of image similarity called the complex wavelet structural similarity (CW-SSIM) index and show its applicability as a general purpose image similarity index. The key idea behind CW-SSIM is that certain image distortions lead to consistent phase changes in the local wavelet coefficients, and that a consistent phase shift of the coefficients does not change the structural content of the image. By conducting four case studies, we have demonstrated the superiority of the CW-SSIM index against other indices (e.g., Dice, Hausdorff distance) commonly used for assessing the similarity of a given pair of images. In addition, we show that the CW-SSIM index has a number of advantages. It is robust to small rotations and translations. It provides useful comparisons even without a preprocessing image registration step, which is essential for other indices. Moreover, it is computationally less expensive.
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Assessment of classifier performance is critical for fair comparison of methods, including considering alternative models or parameters during system design. The assessment must not only provide meaningful data on the classifier e...
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Assessment of classifier performance is critical for fair comparison of methods, including considering alternative models or parameters during system design. The assessment must not only provide meaningful data on the classifier efficacy, but it must do so in a concise and clear manner. For two-class classification problems, receiver operating characteristic analysis provides a clear and concise assessment methodology for reporting performance and comparing competing systems. However, many other important biomedical questions cannot be posed as ldquotwo-classrdquo classification tasks and more than two classes are often necessary. While several methods have been proposed for assessing the performance of classifiers for such multiclass problems, none has been widely accepted. The purpose of this paper is to critically review methods that have been proposed for assessing multiclass classifiers. A number of these methods provide a classifier performance index called the volume under surface (VUS). Empirical comparisons are carried out using 4 three-class case studies, in which three popular classification techniques are evaluated with these methods. Since the same classifier was assessed using multiple performance indexes, it is possible to gain insight into the relative strengths and weakness of the measures. We conclude that: 1) the method proposed by Scurfield provides the most detailed description of classifier performance and insight about the sources of error in a given classification task and 2) the methods proposed by He and Nakas also have great practical utility as they provide both the VUS and an estimate of the variance of the VUS. These estimates can be used to statistically compare two classification algorithms.
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摘要 :
A numerical method is proposed for the analysis of highly dispersive linear and non-linear metamaterial structures. Firstly, pulse propagation along non-linear composite right/left-handed (CRLH) transmission line (TL) is studied. ...
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A numerical method is proposed for the analysis of highly dispersive linear and non-linear metamaterial structures. Firstly, pulse propagation along non-linear composite right/left-handed (CRLH) transmission line (TL) is studied. The dispersive CRLH line is loaded with hyper-abrupt diodes to achieve non-linearity. The characteristic impedance and propagation constant of each unit-cell of the CRLH TL is varied at each time-step, and the nonuniform line is then analysed. A novel interpolation scheme, based on the smooth behaviour of the propagation constant with small variations of the shunt capacitor is proposed. Numerical results show that high accuracy and up to 80% reduction of the computational cost is achieved. A general example which combines dispersion and nonlinearity is presented, validated and discussed. Secondly, the impulse-regime radiation of a leaky-wave antenna is analysed and used to describe a real-time spectrogram analyser (RTSA). A new calibration method for the system, which takes into account the directivity variation of the antenna with frequency, is proposed. This method provides an extremely fast and accurate tool to characterise the behaviour of leaky-wave-based RTSA systems.
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This paper demonstrates a simple electricity generating system that can supply electricity in remote areas such as seashores, hilly regions, etc. Many coastal areas have layers of rock under the sea with considerable petroleum re...
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This paper demonstrates a simple electricity generating system that can supply electricity in remote areas such as seashores, hilly regions, etc. Many coastal areas have layers of rock under the sea with considerable petroleum reserves. To extract the petroleum products, electricity is required. In such situations, stand-alone power generating system is preferred. The proposed electricity generating system consists of self-excited induction generator (SEIG) and STATic COMpensator (STATCOM)-based voltage regulator. The STATCOM supplies variable reactive power to the SEIG and acts as a voltage regulator. Apart from voltage regulation of SEIG, the STATCOM balances the generating system under unbalanced loading conditions and filters the harmonics of the loads, thereby acting both as balancer and harmonic eliminator. It also enhances the loadability, even to start and run dynamic loads such as induction motors.
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This paper describes the various common converters and illustrates the working principle of single phase matrix converter that shows a single topology capable of performing all function required in basic converter. An algorithm is...
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This paper describes the various common converters and illustrates the working principle of single phase matrix converter that shows a single topology capable of performing all function required in basic converter. An algorithm is developed that enables a single-phase matrix converter (SPMC) to perform functions of a generalised single phase power electronics converter such as acting as a frequency changer, rectifier, inverter and chopper. This reduces the need for new converter hardware. The algorithm is implemented on computer simulation software Orcad Capture CIS version 9.1. Simulation results are presented for all five types of converters with a control input variable that decides the 1) type of converter and 2) type of output waveform. The simulated results verify the working and operation of a generalised converter based on SPMC.
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The desire to provide universal connectivity for mobile computers and communication devices is fueling a growing interest in wireless packet networks. To satisfy the needs of wireless data networking, Study Group 802.11 was formed...
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The desire to provide universal connectivity for mobile computers and communication devices is fueling a growing interest in wireless packet networks. To satisfy the needs of wireless data networking, Study Group 802.11 was formed under IEEE project 802 to recommend an international standard for WLANs. A key part of the standard is the MAC protocol needed to support asynchronous and time-bounded delivery of data frames. It has been proposed that unslotted CSMA/CA be the basis for the IEEE 802.11 WLAN MAC protocols. We conduct a performance evaluation of the asynchronous data transfer protocols that are a part of the proposed IEEE 802.11 standard, taking into account the decentralized nature of communication between stations, the possibility of "capture", and presence of "hidden" stations. We compute the system throughput and evaluate fairness properties of the proposed MAC protocols. Further, the impact of spatial characteristics on the performance of the system and that observed by individual stations is determined. A comprehensive comparison of the access methods provided by the 802.11 MAC protocol is done and observations are made as to when each should be employed.
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摘要 :
The goal of distribution system reliability assessment is to predict the availability of power at each customer's service entrance. Existing methods predict the interruption frequency and duration each customer can expect, but omi...
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The goal of distribution system reliability assessment is to predict the availability of power at each customer's service entrance. Existing methods predict the interruption frequency and duration each customer can expect, but omit two major contributing factors: momentary interruptions and storms. This paper presents methods to determine the impact of each phenomena. These methods are then used to assess the reliability of an existing utility distribution system and to explore the reliability impact of distribution automation.
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摘要 :
Experimental verification of analytic formulas for the dispersion and the attenuation of electrical transient signals propagating on coplanar transmission lines is presented. The verification is done in the frequency domain over a...
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Experimental verification of analytic formulas for the dispersion and the attenuation of electrical transient signals propagating on coplanar transmission lines is presented. The verification is done in the frequency domain over a terahertz range although the experiments are in the time domain. The analytic formulas are obtained from fits to the full-wave analysis results. It is quantitatively verified that the full-wave steady-state solutions can be directly applied to the transient time-domain propagation experiments. Subpicosecond electrical pulses and an external electrooptic sampling technique are used to obtain the time-domain propagation data. From the Fourier transforms of the time-domain data both the attenuation and the phase information as a function of frequency are extracted. The dispersion and the attenuation characteristics are investigated for both coplanar waveguide and coplanar strip transmission lines. The investigation is carried out on both semiinsulating semiconductor and dielectric substrate materials. No observable losses caused by the semiconductor material are indicated.
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摘要 :
After the routing of a primary distribution system has been established, the system needs to be designed in detail-switches and protection devices must be placed, automation schemes must be decided upon, etc. This design stage has...
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After the routing of a primary distribution system has been established, the system needs to be designed in detail-switches and protection devices must be placed, automation schemes must be decided upon, etc. This design stage has a critical impact on the reliability and cost of a distribution system. This paper proposes an economic criterion for this design stage, compares several automated design methods, and identifies the algorithm best suited for distribution system reliability and cost optimization. This method is then applied to an existing utility distribution feeder and the results are discussed.
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