A new nonlinear directional overcurrent relay coordination technique, and banes and boons of near-end faults based approach

Considerations of weight factors and far-end faults in the directional overcurrent relay coordination problem formulation do not affect the optimal solution. This paper investigates this viewpoint and verifies that indeed by such an approach the optimality is not lost. But, this study reveals that in doing so, the coordination quality is sacrificed to some extent. It is also observed that if all remaining valid constraints (after relaxing few constraints based on the back-up coordination philosophy and strength of fault level generated) are considered and if the objective function is changed to running sum of all violating constraints, all valid considered constraints are satisfied. This study is done by simultaneously optimizing all settings in nonlinear environment by Sequential Quadratic Programming method using Matlab Toolbox. The results of the analysis on a sample 6-bus and IEEE 30-bus systems are presented in this paper.     

Solubility of fatty acids in supercritical carbon dioxide

The solubilities of lauric, linoleic, myristic, oleic, palmitic and stearic acid in supercritical carbon dioxide (SC-CO₂) at different pressures and temperatures were measured. The solubility values obtained in this work were compared with previously published data, and possible causes for observed discrepancies were discussed. The solubilities of the six fatty acids were modeled by Chrastil’s equation, and estimated model parameters were used to plot the solubility isotherms of fatty acids at 313, 323 and 333°K (40, 50 and 60°C) as a function of SC-CO₂ density. The comparison of solubility isotherms of fatty acids and vegetable oil suggests that separation of fatty acids from triglycerides might be possible by using SC-CO₂ at densities less than 700 kg/m³. From the effect of temperature on fatty-acid and vegetable-oil solubility, it seems that the extraction yield could be increased without sacrificing the selectivity of SC-CO₂ for fatty acids by choosing a higher operating temperature. The data also suggest that fractionation of certain fatty acids might be possible by manipulating the processing conditions. Given the values of the constants, Chrastil’s equation could serve as a guideline for choosing appropriate processing conditions and predicting the effect of pressure and temperature of SC-CO₂ on solute solubility.     

Evaluation of elastic moduli of composite materials by linear programming

A method of applying linear programming to evaluate the elastic moduli of unidirectionally fiber-reinforced composite materials is presented. Based on the theory of elasticity, the stresses and displacements of the fiber and of the resin are expressed in terms of harmonic series. The coefficients of the series are determined by the simplex algorithm to minimize the deviations which occur when the stresses and displacements are matched at the fiberresin interface and at the outer boundary of the representative element of the composite. By applying the energy principle, the Young's modulus in the fiber direction and the major Poisson's ratio of the E-glass/resin composite are found to be in good agreement with existing results, while the gap of the bounds for its bulk modulus is considerably narrowed in comparison to earlier results.     

Particulate pollution from biomass combustion in three cookstoves

The release of suspended particulate matter (SPM) in the indoor environment from the combustion of fuelwood, agri-residue, dung cakes and a mixture of fuelwood and dung cakes in traditional as well as improved biomass cookstoves is studied. The SPM emission is monitored at two positions in the kitchen and also at the centre of the living room. A comparative performance evaluation of several biofuel-cookstove combinations is undertaken. Some important results are plotted graphically and briefly discussed.     

A high-precision contrast injector for small animal x-ray digital subtraction angiography

The availability of genetically altered animal models of human disease for basic research has generated great interest in new imaging methodologies. Digital subtraction angiography (DSA) offers an appealing approach to functional imaging in small animals because of the high spatial and temporal resolution, and the ability to visualize and measure blood flow. The micro-injector described here meets crucial performance parameters to ensure optimal vessel enhancement without significantly increasing the total blood volume or producing overlap of enhanced structures. The micro-injector can inject small, reproducible volumes of contrast agent at high flow rates with computer-controlled timing synchronized to cardiopulmonary activity. Iterative bench-top and live animal experiments with both rat and mouse have been conducted to evaluate the performance of this computer-controlled micro-injector, a first demonstration of a new device designed explicitly for the unique requirements of DSA in small animals. Injection protocols were optimized and screened for potential physiological impact. For the optimized protocols, we found that changes in the time-density curves for representative regions of interest in the thorax were due primarily to physiological changes, independent of micro-injector parameters.     

Combined Wavelet-SVM Technique for Fault Zone Detection in a Series Compensated Transmission Line

This paper presents a combined wavelet-support vector machine (SVM) technique for fault zone identification in a series compensated transmission line. The proposed method uses the samples of three line currents for one cycle duration to accomplish this task. Initially, the features of the line currents are extracted by first level decomposition of the current samples using discrete wavelet transform (DWT). Subsequently, the extracted features are applied as inputs to a SVM for determining the fault zone (whether the fault is before or after the series capacitor, as observed from the relay point). The feasibility of the proposed algorithm has been tested on a 300-km, 400-kV series compensated transmission line for all the ten types of faults through detailed digital simulation using PSCAD/EMTDC. Upon testing on more than 25000 fault cases with varying fault resistance, fault inception angle, prefault power transfer level, percentage compensation level, and source impedances, the performance of the developed method has been found to be quite promising.     

Pretest in forced circulation molten salt heat transfer loop: Studies with thermia‐B

Molten salts have potential application as an efficient heat transfer medium in a primary and secondary heat exchanger in high temperature next‐generation nuclear power plant. Thermal hydraulic studies are vital for reliable and cost‐effective design of the nuclear power plant. Therefore heat transfer study of molten salts will play a vital role in this area. In this work, an experimental system was designed to study thermal hydraulics of the molten salt system up to 700°C. This work describes the pretest results of the experimental facility for extremely corrosive molten fluoride salts with a simulant thermia‐B as the working fluid. In the present work, the details of the system are discussed and thermal‐hydraulic data for heat transfer fluid thermia‐B has been presented. Experiments were carried out at Reynolds number in the range of 4500 to 40 500 and Prandtl number in the range of 34 to 144. Effect of Reynolds number, melting tank temperature, and heat input to test section on forced convective heat transfer was studied under turbulent conditions. Comparison of the experimental data with different empirical correlations has been presented.