Combined analytical and FEM methods for parameters calculation of detailed model for dry-type transformer

Non-flammable characteristic of cast-resin dry-type transformers make them suitable for different kind of usages. This paper presents a method of how to obtain high frequency model of these transformers. For this purpose a detailed model is used and parameters of the model including inductances, capacitances and resistances are calculated using FEM (finite elements method). The effect of the frequency is considered in the inductance calculation using FEM. In order to validate the model, a setup was constructed for testing on high-voltage winding of dry-type transformer. The simulation results were compared with the experimental data measured from FRA (frequency response analysis) and impulse tests.     

A feedback glucose control strategy for type II diabetes mellitus based on fuzzy logic

Most patients with severe Type II diabetes mellitus, characterised by both insulin resistance and β‐cell failure, eventually require insulin therapy. According to the nonlinear dynamics of homeostasis of blood glucose, proportional‐integral (PI) controller, modified by penalising the feedback error using a fuzzy inference system has been developed to maintain normoglycaemia in a simulated patient using a closed‐loop insulin infusion pump. The simulation employs a compartment model proposed by Vahidi et al. [Vahidi et al., Biochem. Eng. J. 2011, 55(1), 7–16]. The results demonstrate that the fuzzy‐based PI controller is superior to a conventional PI controller for the regulation of blood glucose by insulin infusion for Type II diabetic patients. © 2012 Canadian Society for Chemical Engineering     

Recovery of zinc from an industrial zinc leach residue by solvent extraction using D2EHPA

A hydrometallurgical treatment involving solvent extraction of zinc using di-2-ethylhexyl phosphoric acid (D2EHPA) has been investigated to recover zinc from an industrial leach residue. The residue was leached with sulfuric acid producing leach liquor which was subjected to solvent extraction for enrichment of zinc and removal of impurities. Operating variables, such as pH, D2EHPA concentration, temperature, aqueous/organic (A/O) phase ratio, tri-butyl phosphate (TBP) concentration and sodium sulfate (Na₂SO₄) concentration in aqueous phase were studied. Practically, all zinc was extracted from the aqueous solution at pH 2.5 with 20% w/w D2EHPA in kerosene. Increasing either TBP concentration up to 5%, or Na₂SO₄ concentration up to 0.2 M, increased the zinc extraction. Zinc could be extracted at one theoretical stage at A/O of 1/1, as calculated by McCabe–Thiele method.     

Predictive Model of Hydrogen Sulfide Absorption by Chelate Solution in a Venturi Scrubber

In the present study, a simple model was used to predict the removal efficiency of a venturi scrubber for H₂S absorption into a ferric chelate solution. From momentum and mass balances in the scrubber, a set of first‐order, nonlinear ordinary differential equations relating predominantly the liquid velocity with the H₂S concentration in the liquid along the axial direction in the scrubber were formulated. These relationships were numerically solved to give performance profiles. The validity of the model was examined by comparing the results of the model with experimental data from the working laboratory scale. The results predicted from the model are in good agreement with the experimental data obtained in different sizes of the venturi scrubber and operating variables.     

Effect of applied voltage on surface and volume charge density of the jet in electrospinning of polyacrylonitrile solutions

To investigate the effect of applied voltage on jet charge density, one must investigate its effect on the jet electric current and flow rate. However, there are some difficulties in measuring the jet flow rate. Here, the electrospinning jet flow rate is calculated by applying a new method and the effects of applied voltage and feed rate on jet charge density are investigated. The jet flow rate was independent of the feed rate and increased on increasing the applied voltage. By defining an experimental equation for dependence of jet flow rate on jet current, a relation between jet volume charge density and jet current could be defined. By measuring the electrospun fiber diameter, surface charge density of the jet could be estimated. On increasing the voltage, the jet volume charge density decreased whereas the jet surface charge density remained unchanged. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

OVRP_GELS: solving open vehicle routing problem using the gravitational emulation local search algorithm

In open vehicle routing problem (OVRP), after delivering service to the last customer, the vehicle does not necessarily return to the initial depot. This type of problem originally defined about thirty years ago and still is an open issue. In real life, the OVRP is similar to the delivering newspapers and consignments. The problem of service delivering to a set of customers is a particular open VRP with an identical fleet for transporting vehicles that do not necessarily return to the initial depot. Contractors which are not the employee of the delivery company use their own vehicles and do not return to the depot. Solving the OVRP means to optimize the number of vehicles, the traveling distance and the traveling time of a vehicle. In time, several algorithms such as tabu search, deterministic annealing and neighborhood search were used for solving the OVRP. In this paper, a new combinatorial algorithm named OVRP_GELS based on gravitational emulation local search algorithm for solving the OVRP is proposed. We also used record-to-record algorithm to improve the results of the GELS. Several numerical experiments show a good performance of the proposed method for solving the OVRP when compared with existing techniques.

     

Time domain single-phase reclosure scheme for transmission lines based on dual-Gaussian mixture models

The basic principle of new adaptive reclosures are to first identify whether a fault is transient or permanent and consequently to determine the reclosing moment. In this paper a novel method to enhance self-adaptive single phase autoreclosure of transmission lines is presented. Using Gaussian Mixture Models (GMM) the redundancy of setting the threshold is omitted. The proposed algorithm could prevent closing command in permanent faults and adapt dead time in temporary events. The method is derived by processing line terminal voltage around the period of dead time. The proposed scheme uses two sampled windows from the inception of the fault and two groups of GMM. Simulations performed in EMTP/ATP environment advocate the validity of the proposed algorithm convergence speed as well as fast and accurate protection scheme for reclosing relaying. The design of GMM is easy and the relative factors of the structure elements can be regulated due to the desirable effects. Since the discrimination method is done with stochastic characteristics of signals in time domain without application of any deterministic index, more reliable and accurate classification is achieved.     

Using PSpice in teaching impulse Voltage testing of power transformers to senior undergraduate students

This paper describes an efficient method of teaching impulse voltage testing of power transformers to undergraduate students of power system groups in electrical engineering departments, as a part of a high-voltage course for senior undergraduate students. The paper shows how to simulate the power transformer and impulse generator to teach students the basics of impulse voltage testing of power transformers and to practice analyzing the test results. In the first part of the paper, the effect of wave shaping of the voltage waveform is simulated to teach the behavior of the impulse generator, and in the second part, impulse voltage testing of a transformer is simulated. Evaluation of the simulation over several semesters with more than 80 students is very positive in terms of their developing confidence in an understanding of this test.     

Effect of applied voltage on jet electric current and flow rate in electrospinning of polyacrylonitrile solutions

BACKGROUND: In the electrospinning process, through subjecting a pendent drop of a polymer solution to a high electric field, a fluid jet is ejected from the drop. To have a stable process, the rate at which the fluid is forced into the drop and the rate at which the fluid is carried away by the jet must be equal. A method is reported to find the point at which the flow into the drop is equal to the flow out of the drop. RESULTS: In the electrospinning of polyacrylonitrile solutions, by applying different voltages at a constant solution feed rate, two jet regimes were observed: stable jet and fluctuating jet regimes. The stable jet regime occurred at low voltages where the jet flow rate was lower than the feed rate, and the fluctuating jet regime occurred at higher voltages where the jet flow rate exceeded the feed rate. The highest voltage in the stable jet regime was the point where the jet flow rate was equal to the feed rate. This point was determined for different feed rates. CONCLUSION: By applying various voltages at different feed rates, and investigating the jet current, a curve showing stable processing points can be obtained. Copyright © 2008 Society of Chemical Industry     

Adaptive model predictive control for co‐ordination of compression and friction brakes in heavy duty vehicles

In this paper, an adaptive model predictive control scheme is designed for speed control of heavy vehicles. The controller co‐ordinates use of compression brakes and friction brakes on downhill slopes. Moreover, the model predictive controller takes the actuator constraints into account. A recursive least square scheme with forgetting is used in parallel with the controller to update the estimates of vehicle mass and road grade. The adaptation improved the model predictive controller. Also online estimation of the road grade enhanced the closed‐loop performance further by contributing through feedforward control. Simulations of realistic driving scenarios with a validated longitudinal vehicle model are used throughout this paper to illustrate the benefits of co‐ordinating the two braking mechanisms and influence of unknown vehicle mass and road grade. Copyright © 2006 John Wiley & Sons, Ltd.