A novel approach for predetermination of magnetization characteristics of transformers including hysteresis

A new method has been suggested for determining an analytical expression for the hysteresis loop of the transformers and non-linear reactors from the manufacturer's data giving the conventional RMS saturation curve and no load loss. The accuracy of the technique is verified by the experimental results. The analytical expression thus proposed also exhibits the hysteretic property of increasing the loop area with increase of frequency of operation. Furthermore the energy loss expression associated with the hysteresis loop is derived from the suggested expression.     

A replenishment policy for items with price-dependent demand,time-proportional deterioration and no shortages

In this article, an order-level inventory system for deteriorating items has been developed with demand rate as a function of selling price. The demand and the deterioration rate are price dependent and time proportional, respectively. We have considered a perishable item that follows a three-parameter Weibull distribution deterioration. Shortages are not permitted in our model. The optimal solution is illustrated with a numerical example and the sensitivity analysis of parameters is carried out.     

Cooperative formation control of autonomous underwater vehicles: An overview

Formation control is a cooperative control concept in which multiple autonomous underwater mobile robots are deployed for a group motion and/or control mission. This paper presents a brief review on various cooperative search and formation control strategies for multiple autonomous underwater vehicles (AUV) based on literature reported till date. Various cooperative and formation control schemes for collecting huge amount of data based on formation regulation control and formation tracking control are discussed. To address the challenge of detecting AUV failure in the fleet, communication issues, collision and obstacle avoidance are also taken into attention. Stability analysis of the feasible formation is also presented. This paper may be intended to serve as a convenient reference for the further research on formation control of multiple underwater mobile robots.     

Effects of velocity slip,anisotropy and tilt on the steady state performance of aerostatic porous annular thrust bearings

The analysis predicts the steady state performance characteristics of externally pressurized annular porous gas thrust bearings of finite pad thickness. The modified Reynolds equation, governing the flow in the bearing clearance, is derived from the Navier-Stokes equations using the Beavers-Joseph slip velocity condition at the porous interface. The anisotropy of the porous matrix and the tilt of the bearing are also taken into account. The dimensionless load capacity, the mass rate of flow and the static stiffness are computed numerically and presented in the form of charts for various operating parameters and bearing dimensions. The effect of slip is to reduce the load capacity and to increase the mass rate of flow for all values of the feeding parameter.     

Self-healable,Eu~(3+)-based polymeric gels containing terpyridyl groups with tunable luminescence based on ion recognition

Novel luminescent materials that change their emission colors in responding to external stimuli have attracted increasing attentions in the past decades.Herein,we report the preparation of a novel kind of Eu~(3+)-based polymeric organogel with three networks.With dynamic coordination interactions,the organogel shows fast self-healing and adjustable fluorescent emission properties in the presence of different metal ions via coordination interaction competition effect.Dynamic coordination interaction also endows the gel with multiple stimuli-responsive properties such as water,base and acid.The multistimuli responsive fluorochromic organogel demonstrates a new way of preparing optical materials and bio-relevant sensors.     

Differential evolutionary algorithm for TCSC-based controller design

In this paper, a systematic procedure for modelling, simulation and optimal tuning the parameters of a thyristor controlled series compensator (TCSC) controller, for the power system stability enhancement is presented. The design problem of the proposed controller is formulated as an optimization problem and differential evolution (DE) is employed to search for optimal controller parameters. A detailed analysis on the selection of objective function and controller structure on the effectiveness of the TCSC controller is carried out and simulation results are presented. The dynamic performance TCSC controller under various loading and disturbance conditions are analyzed and compared. Finally, the proposed design approach is extended to a multi-machine power system for simultaneous design of multiple and multi-type controllers.     

Tribological Behavior of Acrylic Acid–Modified Date Palm Leaf–Reinforced Polyvinyl Alcohol Composite

Most machine components are frequently exposed to tribological loadings during their service life. Hence, the tribological performance of materials is an essential element to be considered in the design of mechanical parts in addition to mechanical properties. Previously, authors have studied the mechanical properties of date palm leaf–reinforced polyvinyl alcohol composite. In the present investigation, an attempt has been made to investigate the tribological behavior of the composite under a multipass abrasion condition. The composite was prepared by reinforcing randomly oriented acrylic acid–modified date palm leaf fibers with varying weight percentages of 10, 20, 28, and 30%. The performances of the specific wear rate and wear weight loss were investigated as a function of applied loads and abrading distances. It was observed that 28 wt% is the optimum fiber loading to achieve maximum tribological properties similar to mechanical properties obtained from previous work. Scanning electron microscopy was used to understand the wear mechanisms of the composite at optimum fiber loading.     

Numerical simulation of GaAs MESFETS including velocity overshoot

An effective procedure considering the velocity overshoot effect in numerical simulation of GaAs MESFETs is presented. The results of the corresponding routine SEMICO II are compared with results of Monte-Carlo simulations and with results of the routine SEMICO I without overshoot.Implanted MESFETs have been simulated with and without including the overshoot effect, and from these data equivalent circuits have been derived. From circuit calculations of E/D inverter ring oscillators it is concluded that the velocity overshoot effect leads to a twofold decrease of the gate propagation delay time for 0.25 μm gate length.     

The Future of Electric Transmission

Transmission sector problems require a new business and regulatory paradigm if electric power restructuring is to succeed. Performance-based regulation of for-profit transmission seems to be the best alternative.