Effects of load modeling in security constrained OPF studies

Results of computational experiments carried out on an adaptation of the AEP/IEEE 30 bus test system are reported. Some selected buses were modeled using an exponential type of load model. Three cases are considered. In the first case it is assumed that the specified load at modeled buses is obtained with unity voltage. In the second case it is assumed that the transformer taps have been adjusted to give all industrial-type consumers one per unit at the low-voltage panel when the high-side voltage corresponds to the standard optimal power flow (OPF) solution. The third case differs from the second in that the specified power demand is assumed to take place when the high-side voltages correspond to the intact case of the standard security constrained OPF solution. It is concluded that a decrease in fuel cost can be obtained in some instances when load models are incorporated in security constrained OPF studies during contingencies only. In situations where a decrease in fuel cost is obtained in this manner, the magnitude of decrease depends on the total percentage of load fed by fixed tap transformers and the sensitivity of these loads to modeling     

Volume and thermal studies for tellurite glasses

Binary tellurite glass systems of the forms TeO₂(100 − x) − xA _n O _m where A _n O _m  = La₂O₃ or V₂O₅ and x = 5, 7.5, 10, 12.5, 15, 17.5, and 20 mol% for La₂O₃ and 10, 20, 25, 30, 35, 40, 45, and 50 mol% for V₂O₅ were prepared. Density and molar volume of each glass were measured and calculated. The compressibility model has been used to find the difference volume V _d due to the exchange of one formula unit between Te and both of La and V in the binary glass system and the mean volume V _A per formula unit in the present binary glass in order to check whether or not it is independent of the percentage of the modifier for a glass series and also different from series to another. Differential scanning calorimetric at different heating rates was used to gain some insight into the thermal stability and calorimetric behavior of the present binary transition metal and rare-earth tellurite glasses. The glass transformation temperature T _g and glass crystallization temperature T _c were recorded at different heating rates to calculate both of the glass transition activation and the glass crystallization activation energies by using different methods.     

Evaluation of Some Nonionic Surfactants Derived From Vanillin as Corrosion Inhibitors for Carbon Steel During Drilling Processes

Four eco‐friendly nonionic surfactants based on vanillin were investigated as corrosion inhibitors against carbon steel dissolution during the drilling process in the oil field. The corrosion inhibition efficiencies of the tested compounds were determined using weight loss, electrochemical polarization, and electrochemical impedance techniques. The data obtained show that the nonionic surfactants prevent the corrosion of drilling tools and their inhibition efficiency increased with an increase in their concentration. Tafel curves revealed that the surfactants under study act as mixed inhibitors. The adsorption of the inhibitors on carbon steel surface decreases the double‐layer capacitance. The inhibition efficiencies of the surfactants were influenced by their chemical structure and surface activity.     

Egyptian Mango Juice. Experiment on Storage Experience

In this study processed mango juice was packed in four types of containers and stored at different temperatures for 16 weeks through which furfural level determination and organoleptic assessment were conducted. The experiment revealed an evident relationship to exist among furfural level, storage temperature and type of packing material. Furfural level failed to closely parallel flavour difference; therefore it could be regarded as one of the features concomitant juice aging rather than accepted as a satisfactory criterion of off flavour. The study relates flavour deterioration to the changes in the lipid fraction of the juice.     

A transformation for necessary optimality conditions for systems with polynomial nonlinearities

This work shows a new formulation means to obtain the optimal control for systems having polynomial nonlinearities by using functional analytic methods. The polynomic system is reduced to a quadratic form by introducing a set of pseudostate variables and the structure of the system is characterized by a set of matrices. A new set of optimizing equations is obtained and the necessary and sufficient conditions are met by the positive definiteness requirement on the system matrix.     

Online algorithm for removal of decaying DC-offset from fault currents

This paper presents an efficient method for removing exponentially decaying DC offset from fault currents. Instantaneous value of the actual exponentially decaying DC offset is calculated by integrating the input signal. The DC component is removed by subtracting the DC value at each sampling instant. The Discrete Fourier Transform (DFT) is applied to the result to extract the phasor of the fundamental component. Different transient signals are investigated. The results show that the proposed method is accurate and easy to implement.     

Synthesis, Surface, Thermodynamic Properties of Some Biodegradable Vanillin-Modified Polyoxyethylene Surfactants

Four water-soluble non-ionic ethoxylated surfactants based on vanillin were synthesized (VE₁₅, VE₂₀, VE₄₀, and VE₆₀). The chemical structures of these surfactants were confirmed using FT-IR and ¹H-NMR spectra. The molecular weights of the compounds were determined using viscosity measurements and gel permeation chromatography. Surface tension as a function of the concentration of the surfactant in aqueous solution was measured at 25, 40 and 55?°C. From these measurements, the critical micelle concentration (CMC), effectiveness (??_cmc), efficiency (pC₂₀), maximum surface (??_max) excess and minimum surface area (A _min), were calculated. The surface activity measurements showed their high tendency towards adsorption and micellization and their good surface tension reduction, and low interfacial tension. The emulsion stability measurements showed the applicability of these surfactants as emulsifying agents. The thermodynamic parameters of micellization (??G _mic, ??H _mic, ??S _mic) and adsorption (??G _ads, ??G _ads, ?S _ads) showed their tendency towards adsorption at the interfaces and also micellization in the bulk of their solutions. The biodegradability of the prepared surfactants was tested in river water using die-away method and showed their readily biodegradation in the open environment.     

A Digital Estimation Algorithm for Impedance Measurements

This paper presents a new digital algorithm for measuring an unknown impedance. The proposed algorithm is based on the minimization of the least absolute value of the error. The algorithm developed in [5] is used to solve the resulting optimization problem. The proposed algorithm is general enough to implement for measuring impedance. The effects of critical parameters on the accuracy of the measured unknown impedance are discussed. Results from simulated data are given to form our conclusions.