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The statistical nature of gate delays in current day technologies necessitates the use of measures, such as path criticality and node/edge criticality for timing optimization. Node criticalities are typically computed using the complementary path delay. An alternative approach to compute the criticality using the circuit delay has been recently proposed. In this paper, we discuss in detail, the use of circuit delay to compute node criticalities and show that the criticality thus found is not equal to the conventional measure found using complementary path delay. However, there is a monotonic relationship between them and the two measures can be used interchangeably. We derive new bounds for the global criticality and propose a pruning algorithm based on these bounds to improve the accuracy and speed of computation. The use of this pruning technique results in a significant speedup in criticality computations. We obtain an order of magnitude average speedup for ISCAS benchmarks.

Security evaluation is a major concern in real time operation of electric power networks, exhibiting behavioral patterns under abnormal conditions. Security assessment and evaluation can be viewed as a pattern analysis task identifying abnormal patterns of the power system behavior under highly loaded conditions. Traditional method of security evaluation are highly time consuming and infeasible for direct on-line implementation. This paper presents application of pattern directed inference system for static and transient security evaluation and classification. A straightforward and quick procedure called Sequential Forward Selection method is used for feature selection process. The classifier model in the pattern directed inference system is designed using different pattern classifier algorithms, viz., conventional, neural network and machine learning classifiers. Support Vector Machine (SVM), one of the popular machine learning classifier, is recognized as a suitable pattern classifier for security evaluation problem. The generalization performance of SVM classifier is greatly influenced by the proper setting of its parameters. This paper also addresses different heuristic optimization techniques used in the selection of SVM parameters. The design, development and performance of different classifiers for power system security classification are presented in detail. Simulation work is performed on standard New England 39-bus benchmark system and the feasibility of implementation of the proposed SVM based classifier system for on-line security evaluation is also discussed. � 2012 Elsevier Ltd. All rights reserved.

Novel polymer nanocomposites comprising of MnO2 nanotubes (MNTs), functionalized multiwalled carbon nanotubes (f-MWCNTs), and polyvinylidene fluoride (PVDF) were synthesized. Homogeneous distribution of f-MWCNTs and MNTs in PVDF matrix were confirmed by field emission scanning electron microscopy. Electrical conductivity measurements were performed on these polymer composites using four probe technique. The addition of 2 wt.% of MNTs (2 wt.%, f-MWCNTs) to PVDF matrix results in an increase in the electrical conductivity from 10-16S/m to 4.5 × 10-5S/m (3.2 × 10-1S/m). Electromagnetic interference shielding effectiveness (EMI SE) was measured with vector network analyzer using waveguide sample holder in X-band frequency range. EMI SE of approximately 20 dB has been obtained with the addition of 5 wt.% MNTs-1 wt.% f-MWCNTs to PVDF in comparison with EMI SE of approximately 18 dB for 7 wt.% of f-MWCNTs indicating the potential use of the present MNT/f-MWCNT/PVDF composite as low-cost EMI shielding materials in X-band region.

Thermopower measurements in a range of 300-650 K along with room temperature optical absorption and electrical resistivity studies were performed on indium oxide (IO) and indium tin oxide (ITO) thin films grown by reactive dc sputtering. The thermopower of as-grown and oxygen-annealed IO and ITO films measured in Ar ambient displayed characteristics attributable to oxygen loss. The observations were substantiated with optical absorption and electrical resistivity results. � 2009 IOP Publishing Ltd.

A novel current control strategy called user-defined constant switching frequency method for a four-leg voltage source inverter is presented. This scheme allows the user to directly set the switching frequency of all the legs. Unlike the hysteresis current control where the switching frequency is variable and the fourth leg operates at a very high frequency, the proposed method ensures a constant and reduced switching frequency for all the switches of the inverter. This is achieved by exercising an indirect control on the occurrence and duration of the uncontrollable (zero vector) states. The three legs of the inverter are operated in hysteresis current tracking mode and the switches of the fourth leg are controlled with a square pulse of fixed user-defined frequency. The above advantages supplemented with the simplicity, fast response and robustness make this an attractive scheme. The feasibility of the proposed strategy is verified through extensive simulation and experimental studies on a distribution static compensator to compensate for unbalanced and non-linear loads in a distribution power network. � 2009 The Institution of Engineering and Technology.

A detailed theoretical analysis has been carried out to study the role of ceramic supports (alumina and SiC) and pulsed microwave heating of polymer (Natural Rubber, NR, and Nylon 66) slabs due to various distributions of microwave incidences. Ceramic plates are typical representations as they withstand high temperature without any deformation. It is found that ceramic plates influence the heating processes significantly and local hot spots within samples are governed by specific type of ceramic plates for various sample thicknesses and distributions of microwave incidence (one side or both sides). Optimized pulsing of microwave incidence has been employed to minimize the thermal runaway or hot spots in order to achieve uniform temperature distribution and pulsing is introduced based on two parameters: setpoint ( Δ T S ) and on–off constraint ( T ′ ) . Detailed spatial distributions of power and temperature are illustrated for a few representative length scales to demonstrate the role of local maxima in power and temperature on heating rate as well as thermal runaway with or without pulsing. Pulsing ratio (PR) has been defined as PR = t off / t p , where t off is power-off time and t p is the total processing time such that smaller PR denotes large processing rates. It is found that one side incidence gives smaller values of PR for both the ceramic plates whereas SiC plate may be suitable for both sides incidence with large sample thicknesses of NR samples. It is also found that larger values of setpoints also minimize PR. The setpoints along with the on–off constraint play critical role to select the heating strategy as a function of ceramic plates and types of incidence. Pulsing may not be important for smaller thicknesses of Nylon samples and SiC or alumina plates may be recommended for processing larger thicknesses of Nylon samples in presence of pulsing. Current study recommends the efficient microwave heating methodologies for polymer processing attached with ceramic plates by means of optimized pulsing for the first time.

Water distribution network that includes supply reservoirs, overhead tanks, consumer demand nodes, interconnecting pipes, lifting pumps, and control valves is the main mode of water supply for majority of the communities especially in urban areas. Supply of required quantity of water and at right time is the primary objective of water distribution network analysis. The analysis of water distribution networks can be broadly classified into design and operation problems and both problems have been the focus of many researchers over the past three decades. In the water distribution network design problems, the target is attaining the cost effective configuration that satisfies the minimum hydraulic head requirement at the demand nodes. In this paper, a new algorithm for design of water distribution network namely "heuristics-based algorithm" which completely utilizes the implicit information associated with the water distribution network to be designed has been proposed and validated with two water distribution networks. It is found that the proposed algorithm performs well for the least-cost design of water distribution networks. � 2009 ASCE.

This paper presents differential evolutionary algorithm for optimal dispatch for reactive power and voltage control in power system operation studies. The problem is formulated as a mixed integer, nonlinear optimization problem taking into account both continuous and discrete control variables. The optimal setting of control variables such as generator voltages, tap positions of tap changing transformers and the number of shunt reactive compensation devices to be switched for real power loss minimization in the transmission system are determined. In the proposed method, the inequality operational constraints were handled by "penalty parameterless" approach. This helps in avoiding the time-consuming trial and error process for fixing the penalty parameter and makes the process system independent. The algorithm was tested on standard IEEE 14,30,57 and 118-Bus systems and the results compared with conventional method. � 2008 Elsevier Ltd. All rights reserved.

The theory of instantaneous symmetrical components is used for the detection of insulation faults in a three-phase induction motor. Based on the experimental data of motor intake currents and the system voltages, the loci of positive- and negative-sequence components of currents are plotted. These loci overlap with each other under healthy winding conditions as their major and minor axes coincides. When an inter-turn short circuit occurs, these axes do not coincide with each other and displacement angle ϕ appears between two major axes. Thereby, the non-overlapping area comes into existence. The proposed system considers the effects due to unbalance in voltages, asymmetry in stator winding design, and measurement errors. Experimental results are reported to demonstrate the effectiveness of the proposed technique at different load conditions.

This paper presents a differential evolution (DE) based optimal power flow (OPF) for reactive power dispatch in power system planning studies. DE is a simple population-based search algorithm for global optimization and has a minimum number of control parameters. The problem is formulated as a mixed integer non-linear optimization problem taking into account both continuous and discrete control variables. The proposed method determines control variable settings such as generator voltages (continuous), tap positions (discrete) and the number of shunt reactive compensation devices to be switched (discrete) for real power loss minimization in the transmission system using DE algorithm. Most of the evolutionary algorithm applications to optimization problems apply penalty function approach to handle the inequality constraints, involving penalty coefficients. The correct combination of these coefficients can be determined only by a trial and error basis. In the proposed approach, the inequality constraints are handled by penalty parameterless scheme. Voltage security margin was evaluated using continuation power flow (CPF), to ensure the feasibility of the optimal control variable setting. The suitability of the method was tested on IEEE 14 and IEEE RTS 24-bus systems and results compared with sequential quadratic programming (SQP) method. The DE provides near global solutions comparable to that obtained using SQP. � 2007 Elsevier B.V. All rights reserved.

In this paper, the theory of instantaneous symmetrical components is applied to explore various control strategies of load compensation, under different supply voltages. When the supply voltages are balanced and sinusoidal, all of these strategies converge to the same compensation characteristics. However, when the supply voltages are not balanced sinusoids, these control strategies result in different degrees of compensation in harmonics, power factor, neutral current, and compensator ratings. These control strategies are discussed in detail and a comparative study of their performance in terms of the rms value, total harmonic distortion, power factor of source currents, and compensator ratings is presented. Based on this study, it is possible to select the best strategy to meet the required load compensation characteristics for available supply voltages. A three-phase four-wire distribution system supplying an unbalanced and nonlinear load is considered for simulation study. The detailed simulation results using MATLAB are presented to support the proposed compensation strategies. � 2008 IEEE.

In this study, we present a high-level testability analysis technique that evaluates the testability of a design based on the proposed controllability and observability measures. The control-data flow graph (CDFG) constructed from the VHDL description of a design is first analyzed to identify hard-to-control conditional branches and hard-to-control/observe register transfer statements. After the hard-to-test areas of the design are identified, the proposed testability enhancement methods can be applied to improve the testability of the circuit. Unlike many recent studies in the area of high-level test synthesis (HLTS) that focus on improving the testability of data paths, our approach also improves the testability of synthesized circuits by enhancing the controllability of the control flow. Experimental results on several high-level synthesis benchmarks show that when this approach is used prior to logic synthesis, the test generation complexities are reduced while better fault coverage and ATPG efficiency are often achieved. Implementation of this technique requires minimal logic and performance overheads and allows test vectors to be applied at clock-speed.

The division multiplier technique proposed by Tomota, Sugiyama and Yamaguchi, is implemented in a simple way with minimum number of components. However the multiplier realised is of the two quadrant type.

The all-bidirectional-edges problem is to find an edge-labeling of an undirected network G=(V, E), with a source and a sink, such that an edge e=uv in E is labeled ?u, v? or ?u, u? (or both) depending on the existence of a (simple) path from the source to the sink traversing e, that visits the vertices u and v in the order u, v or v, u respectively. The best-known algorithm for this problem requires O(|V|�|E|) time [5]. We show that the problem is solvable optimally on a planar graph. ? 1993 Springer-Verlag New York Inc.

A new four-constant curve fit is proposed for the R-T characteristic of a thermistor. That it provides a better fit than the two-constant law R = AeB/Tis demonstrated by taking the examples of two standard commercial thermistors. A simple numerical method is suggested for determining the constants of the new fit. Compared to other empirical relationships, the present equation lends itself to easy hardware linearization. A temperature-to-frequency converter that has been developed employing the proposed fit is described. The converter is free from any error due to thermistor lead resistances, and provides an accuracy better than 0.2 K over a temperature range from 300 K to 390 K. ? 1993 IEEE