Multidimensional augmented current equation including velocityovershoot

The augmented drift-diffusion current equation, which includes velocity overshoot effects through the space derivatives of the electric field, cannot be directly extended beyond one dimension. A new formalism is developed which considers the carrier heating and the distribution relaxation effects to obtain a multidimensional augmented drift diffusion current equation. The equivalent mobility containing the velocity overshoot correction is derived from the perturbation analysis on the carrier temperature using the energy balance equation. The issues related to the numerical implementation of this generalized model and the validity of the assumptions are also discussed     

On the RLSA antenna optimum design for DBS reception

An optimal design for the RLSA (radial line slot array) antenna useful for DBS reception is presented. Classical geometries and structures given in the literature are first used. It is found that in some cases these are not suitable. So, optimization techniques by using the right objective functions have been applied. Two different methods were developed and three antennas were designed. Numerical results and comparisons with other similar antennas give the advantages of our design     

Measurement and prediction of pressure drop in two-phase flow

Experimental data for air–water two-phase co-current flow in two different pipe diameters were used to test the prediction of pressure drop by a number of existing theories and correlations. Several models are shown to be useful for prediction, particularly with the stratified regimes which have proved difficult to handle in the past. The model suggested by Olujic proved to be of particular value.     

Transient and dynamic average-value modeling of synchronous machinefed load-commutated converters

A new average-value model of a synchronous machine fed load-commutated converter is set forth in which the stator dynamics are combined with the DC link dynamics. This model is shown to he extremely accurate in predicting system transients and in predicting frequency-domain characteristics such as the impedance looking into the synchronous machine fed load-commutated converter. The model is verified against a detailed computer simulation and against a hardware test system, thus providing a three-way comparison. The proposed model is shown to be much more accurate than models in which the stator dynamics are neglected     

Antibacterial activity of sourdough lactic acid bacteria: isolation of a bacteriocin-like inhibitory substance fromLactobacillus sanfranciscoC57

A total of 232 strains from nine species ofLactobacillusisolated from sourdoughs were screened for antagonistic activity against sourdough-related micro-organisms. Seventy-seven strains on agar medium and 52 in culture supernatants, re-adjusted to pH 6.5 and catalase-treated, showed antagonistic activity. The activities were species and strain specific showing different spectra of inhibition against sourdough lactobacilli. All the strains were inhibitory toBacillus subtilisbut not against sourdough yeasts and moulds.Lactobacillus sanfranciscoandLactobacillus plantarumstrains had the largest inhibitory spectrum. All the antimicrobial compounds produced from strains of different species contained a protein moiety and were differently sensitive to different proteinases. A bacteriocin-like inhibitory substance, which was heat-stable (100°C for 20 min), insensitive to lipase and α-amylase, of a protein nature, with an inhibitory spectrum centred about lactic acid bacteria and a bactericidal or bacteriolytic mode of action was isolated fromLb. sanfranciscoC57. The antimicrobial substance also inhibitedListeria monocytogenes, and was mainly produced in the stationary phase of growth and at pH 4.0–5.0.Lb. sanfranciscoC57 variants, which did not contain the nativec. 17 kbp plasmid, maintained their antagonistic activity, therefore, the gene encoding for the bacteriocin-like inhibitory substance fromLb. sanfranciscoC57 is chromosomally located.     

Power engineering industry interaction at Clemson University

The authors present a successful model of industry/university cooperation in establishing a strong power system curriculum in both the graduate and undergraduate level. Numerous long-term and short-term research projects have been developed to satisfy the university mission and to tackle challenging problems facing the power industry. A unique structure for the Clemson University Electric Power Research Association (CUEPRA) has been established to promote electric power system research and to meet the need for a working communication link between the power industry and the academic community. The power industries involvements in the power program at Clemson University and the strategic improvements that have been accomplished in research and education are outlined     

Development of improved methods for type testing present day mediumvoltage circuit breakers for outdoor service

Type testing for fault currents for medium-voltage circuit breakers rated at 15 kV to 72.5 kV is addressed. The ANSI designation of a new class of definite-purpose circuit breakers capable of switching transformer secondary faults and the introduction of the requirement for short-line-fault tests for breakers rated 72.5 kV and below have increased the difficulty of performing type tests in a testing laboratory. It is concluded that synthetic testing using the parallel current injection circuit is described in ANSI C37.081 provides the best available method for proving these complex requirements for medium-voltage circuit breakers     

Developing maintainable expert systems using case-based reasoning

Abstract: Maintainability problems associated with traditional software systems are exacerbated in rule-based systems. The very nature of that approach — separation of control knowledge and data-driven execution — hampers maintenance. While there are widely accepted techniques for maintaining conventional software, the same is not true for rule-based systems. In most situations, both a knowledge engineer and a domain expert are necessary to update the rules of a rule-based system. This paper presents, first, an overview of the software engineering techniques and object-oriented methods used in maintaining rule-based systems. It then discusses alternate paradigms for expert system development. The benefits of using case-based reasoning (from the maintenance point of view) are illustrated through the implementation of a case-based scheduler. The main value of the scheduler is that its knowledge base can be modified by the expert without the assistance of a knowledge engineer. Since changes in application requirements can be given directly to the system by the expert, the effort of maintaining the knowledge base is greatly reduced.     

On Toroidal Azulenoids and Other Shapes of Fullerene Cage

The possibility of toroidal cages of carbon with repeating five and seven membered ring pairs (azulene units) upon their surfaces is briefly discussed. Some of the difficulties in recognising possible fullerene cage shapes are pointed out.