Fractionation of Bolti fish tissue lipids into classes and within the triglyceride class with TLC

By utilising TLC with a developing system of petroleum ether-diethylether-acetic acid (70:30:2 v/v) and allowing the front to travel 18 cm, the best conditions for the fractionation of Bolti tissue lipids were achieved. Four distinct classes—triglycerides, free fatty acids, sterols and phospholipids—were detected. In addition, two other faint classes—hydrocarbons and diglycerides—were identified.Silica gel impregnated with silver nitrate has been employed for the fractionation of the triglycerides into groups. Seven groups were found when 1·5% of ethanol was added to the developing system of chloroform-acetic acid (99·5:0·5 v/v). Raising the ethanol content to 2% resulted in the detection of eight groups.     

Application of Response Surface Methodology to the Selection of Machining Variables

This paper presents the use of Response Surface Methodology for analysis of material removal processes. Mathematical models of tool life, surface finish and cutting force are developed in terms of cutting speed, feed, and depth of cut. The models were then used to select the levels of the machining variables such that certain criteria could be achieved. Specific examples include increasing the rate of metal removal without sacrificing surface finish and with a minimum loss in tool life.     

A Fourier Series Generalized Geometry-Based Analytical Model of Switched Reluctance Machines

A novel invertible generalized flux/current switched reluctance machine (SRM) model based on the Fourier series expansion is presented. This model, which is derived from machine geometry and materials properties, is accurate enough to be used for actual machine representation and can also be simplified for real-time controller applications. Simulation and experimental results illustrate that the proposed modeling approach provides better representation of the SRM than other existing techniques     

Evaluation of Some Starch Derivatives Containing Amide Groups as Flocculants

Three types of starch derivatives namely poly(acrylamide)‐starch graft copolymer, carbamoylethylated starch, and starch carbamate were prepared and evaluated as flocculants. Native and hydrolyzed maize starches were used as parent materials for these derivatives. The flocculation was followed by monitoring transmission % and weight removal %. The different factors affecting flocculation were studied. These factors include: (a) flocculant dose, (b) pH of the flocculation medium and (c) starch derivatives type, molar mass and nitrogen content. The flocculation efficiency of the three starch derivatives follows the order: poIy(acryIamide)‐starch graft copoIymer > carbamoylethylated starch > starch carbamate. The flocculation efficiency increases on increasing the nitrogen content and/or decreasing the molar mass of the flocculant. The flocculation efficiency of various flocculants at pH 6 is higher than at pH 8. The poIy(acryIamide)‐ starch graft copoIymer based on H₃‐starch has a higher flocculation efficiency than polyacryIamide.     

HYDROMAGNETIC NATURAL CONVECTION FROM AN INCLINED POROUS SQUARE ENCLOSURE WITH HEAT GENERATION

The problem of unsteady, laminar, two-dimensional hydromagnetic natural convection heat transfer in an inclined square enclosure filled with a fluid-saturated porous medium in the presence of a transverse magnetic field and fluid heat generation effects is studied numerically. The walls of the enclosure are maintained at constant temperatures. The flow in the porous region is modeled using the Brinkman-extended Darcy's law to account for the no-slip conditions at the walls. The control volume method is used to solve the governing balance equations for different values of the Darcy number, Hartmann number, and the inclination angle. Favorable comparisons with previously published work are performed. These comparisons confirmed the correctness of the numerical results. The obtained numerical results are presented graphically in terms of streamlines and isotherms as well as velocity and temperature profiles at midsections of the cavity to illustrate interesting features of the solution.     

Parallelization of the Scale‐Changing Technique in Grid Computing environment for the electronmagnetic simulation of multi‐scale structures

A parallel computing approach to run fast and full‐wave electromagnetic simulation of complex structures in Grid Computing environment is presented. In this study, we show how Grid Computing improves speed and/or reliability over that provided by a single computer, while typically being much more cost‐effective than single computers of comparable speed or reliability. An efficient monolithic (unique) formulation for the electromagnetic modelling of complex (multi‐scale) structures, i.e. structures that exhibit multiple metallic patterns whose sizes cover a large range of scales, is used here. This approach, named the Scale‐Changing Technique, is based on the cascade of multi‐modal Scale‐Changing Networks, each network modelling the electromagnetic coupling between two successive scale levels. These networks can be first computed separately, in an adaptive use of Grid Computing architecture nature, and then cascaded for the global electromagnetic simulation. Based on this technique, a fast computer algorithm was developed and tested in the Grid‐Computing environment. For illustration purposes, the electromagnetic analysis of multi‐scale structures, applied to phase‐shifter elements and an example of infinite passive reflectarray, was carried out. The obtained results have confirmed the effectiveness of such an approach compared with sequential computing. This approach shows very good computation performance while keeping the same accuracy. Besides, this method is very promising for optimizing circuit with multiple design parameters to handle and for the global electromagnetic simulation of multi‐scale and/or oer‐sized structures. Copyright © 2010 John Wiley & Sons, Ltd.     

A passivity‐based simple adaptive synergetic control for a class of nonlinear systems

For a class of nonlinear systems with the representation {A(x), B(x), C} and where the system parameters and dynamics are unknown, a simple adaptive synergetic controller ensuring the asymptotic convergence of the system to a desired manifold is proposed based on the technique of simple adaptive control (SAC). It is well known that the design of the synergetic control (SC) law requires a thorough knowledge of the system parameters and dynamics. Such problem obstructs the synthesis of the SC law and the designer is prompted to pass through the estimation methods, which, in turn, poses a problem of increasing the computation time of the control algorithm. To cope with this problem, a solution is proposed by modifying the original SC law to develop an SAC‐like adaptive SC law without the need of prior knowledge of the system. The stability of the proposed adaptive controller is formally proven via the Lyapunov approach. Experimental application to a quadrotor system is given to validate the theoretical results.     

A compact CMOS DC-DC buck converter based on a novel complement value leaping PWM technique

A very compact ultra-low power DC-DC buck converter is presented. The proposed buck converter employs a novel complement value leaping pulse-width modulation (PWM) technique to realize the desired DC mean-value for various loads. Incorporating just two counters with a simple digital controller to load the repeatedly complemented value of the 4bit up/down counter as the initial value of the least significant bits of the 5bit up counter, a PWM pulse is created to manage the charge/recharge period. The realized PWM signal maintains the same desired output voltage mean value for any load resistance between 80 and 140 Ω. The switching frequency is 160 kHz, and the overall power consumption is 26.9 nW, while the efficiency is 93.4% for current range of 1.7 to 3 mA. The performance of the proposed converter is validated by Cadence post-layout simulations utilizing TSMC180nm CMOS technology for 1-V supply voltage providing the output voltage mean value of 0.24 V.