Tracking of cracks in sheet steel specimens under cyclic loading

In this report a non-contact gauging system based on eddy current technology is presented which permits unproblematic detection and tracking of cracks initiated by cyclic loading in sheet steel specimens. In comparison with other measuring methods the automatic pilot unit developed displays distinct advantages thanks to its highly accurate measuring results. This measuring unit is suitable for the examination of thin sheet steels (< 2 mm) and has been successfully used for studying ductile materials. Some results of such investigations are therefore illustrated.     

Facile chemical synthesis of W-Ag and W-Cu nanocomposites at low temperature

W-Ag (80.2W-19.8Ag, 70.4W-29.6Ag and 60.5W-39.5Ag) and W-Cu (79.7W-20.3Cu, 70.5W-29.5Cu and 59.8W-40.2Cu) nanocomposites in the size range of 24-30 nm have been synthesized by thermal decomposition of W(CO)6/CH3COOAg and W(CO)6/Cu(acac)2 in diphenyl ether as solvent at 220 degrees C in presence of oleic acid and hexadecyl amine and characterized. FTIR spectra have been used to explain the role of oleic acid and hexadecyl amine in the synthesis of W-Ag and W-Cu composite powders. XRD studies show that the tungsten phase is amorphous, whereas both Ag and Cu crystallize in fcc for as-synthesized W-Ag and W-Cu nanocomposites. These composite powders when annealed at 700 degrees C results in the formation of bcc tungsten and peaks corresponding to fcc silver and copper still persists. The particle size, shape and distribution of these nanocomposites of various compositions have been studied by SAXS, ESEM and TEM and found to be nearly spherical with the average diameters below 30 nm.     

Tribological characteristics of electroless Ni–B coating and optimization of coating parameters using Taguchi based grey relational analysis

Electroless nickel coating is an autocatalytic coating whose characteristics are very much dependent on the composition of electroless bath. The present study is an attempt to minimize the friction and wear characteristics of electroless Ni–B coatings simultaneously by optimizing the three coating parameters viz. bath temperature, concentration of reducing agent and concentration of nickel source together with the annealing temperature. Taguchi based grey relational analysis is employed for the optimization of this multiple response problem using an L₂₇ orthogonal array. Analysis of variance reveals that concentration of reducing agent has the maximum contribution in controlling the friction and wear behaviour of Ni–B coating. The interaction between bath temperature and nickel source concentration is also found to possess significant contribution in controlling the friction and wear characteristics. The surface morphology, composition and phase structure analysis are done with the help of scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffraction analysis (XRD), respectively. Moreover the wear mechanism is studied and found to be in general abrasive in nature.     

Removal of fluoride from drinking water using aluminum hydroxide coated rice husk ash

Fluoride content in groundwater that is greater than the WHO limit of 1.5mg/L, causes dental and skeletal fluorosis. In India, several states are affected with excess fluoride in groundwater. The problem is aggravated due to the lack of appropriate and user friendly defluoridation technology. Several fluoride removal techniques are reported in the literature amongst which the Nalgonda technique and use of activated alumina have been studied extensively. However a simple, efficient and cost effective technology is not available for widespread use in many affected regions. In this paper, we present a novel cost effective defluoridation method that is based on surface modification of rice husk ash (RHA) by coating aluminum hydroxide. RHA is obtained by burning rice/paddy husk which is an abundantly available and is an inexpensive raw material. The results showed excellent fluoride removal efficiency and the adsorption capacity was found to be between 9 and 10mg/g.     

化学机械抛光中的颗粒技术

多层金属化是集成芯片以摩尔定律的速度更替的重要工艺手段.在多层金属化中,平坦的晶圆表面对每道工序的成功完成都是非常必要的,而化学机械抛光工艺能在每道工序之前将晶圆表面抛光.化学机械抛光主要是通过使用颗粒研浆去除材料来实现晶圆抛光.除了研浆本身的化学性质外,研浆的效果也受研磨颗粒性质的影响.如果我们能够更好的理解研磨颗粒...     

Novel vibration-based technique for detecting water pipeline leakage

Exacerbating the imbalance between demand for freshwater and available water resources is the sub-optimal performance of water distribution systems, which are plagued with leaks that cause significant losses of treated freshwater. This paper presents an approach for leak detection that involves continuous monitoring of the changes in the correlation between surface acceleration measured at discrete locations along the pipeline length. A metric called leak detection index is formulated based on cross-spectral density of measured pipe surface accelerations for detecting the onset and assessing the severity of leaks. The proposed non-invasive approach requires minimal human intervention and works under normal operating conditions of the pipeline system without causing any operational disturbances. The approach is demonstrated on a 76 mm diameter polyvinyl chloride pipeline test system considering varying leak severities. The preliminary results presented in this paper seem promising and lead to several interesting questions that will require further research.     

An asymmetric FRP laminate with a circular precrack to determine impact‐induced damage

An asymmetric laminate is employed to study impact‐induced damage of subpenetration experiments. The configuration of the asymmetric laminate is chosen to have its stiffness characteristics almost identical to those of a symmetric laminate. The impact is made with a mild steel striker to have impact energy close to 12 J and impact velocity close to 50 m/s. A circular precrack is also introduced to facilitate failure on the midplane of a laminate. Due to material discontinuity at the midplane the damage area extension (DAE) of the precrack is found to be 1.83 cm² on asymmetric laminates against 0.73 cm² on symmetric laminates. Impact experiments are also conducted on bonded GFRP specimen with Epibond 1590 A/B adhesive using asymmetric laminates. DAE of adhesive interface is found to be substantially smaller than DAE of interlaminar failure. DAE of adhesive interface is further reduced when the adhesive is modified with 7.5% XNBR. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Diffusion,membrane selectivity,and nonequilibrium effects in rapid membrane osmometry

Rapid membrane osmometry, narrow distribution polystyrenes in the range 4000–700,000, and three membrane types of different porosity were used to study the effects of diffusion and of Staverman membrane selection in osmometry. It was found that equilibrium was not obtained in the rapid measurement with the two densest membranes which led to grossly low values for the high molecular weight sample but had small effect at low molecular weights. Because of membrane selectivity effects at lower, and of nonequilibrium effects at higher molecular weights, the effective range was about 4000–350,000 for the densest membrane, 90,000–500,000 for the medium porosity membrane and from 145,000 to an unrestricted upper limit for the grossest membrane. A unique characteristic of the Mechrolab 501 instrument used in the study is the small constant volume on the solvent side of the membrane which allows determination of the osmotic pressure of the diffused material and its concentration when the molecular weight is known. Diffusion can be avoided if the pressure reading is taken quickly enough but membrane selectivity effects cannot be avoided if diffusible solute is present. Enormous selectivity effects were found when mixtures of diffusible and nondiffusible molecules were measured. Experimental values of the selectivity coefficient S_n of the mixtures were found to agree closely with those calculated from the Staverman equations. Estimates of the coil size of the polymers are given to provide an estimate of the effective porosities of the membranes.     

A New Affine Arithmetic-Based Optimal Network Reconfiguration to Minimize Losses in a Distribution System Considering Uncertainty Using Binary Particle Swarm Optimization

Abstract

In the present work, Binary Particle Swarm Optimization (BPSO) based optimal re-configuration for balanced and unbalanced radial distribution networks using Affine Arithmetic (AA), with uncertainty in generation and load, is proposed to minimize the system losses. An expression for three phase real affine power loss is derived with partial deviations of real power loss in lines with respect to power injections in other buses and also with respect to power injections in other phases in case of unbalanced distribution systems. The major contribution of the present work is the application of AA based optimal network reconfiguration, to both balanced and unbalanced radial distribution networks with uncertainty. The proposed method is tested on IEEE 16, 33, 85 and 119 bus balanced distribution systems and an unbalanced 123 bus system with Distributed Generation (DG) connected at some buses. The optimal loss intervals obtained by the proposed method are compared with that obtained by Interval Arithmetic (IA) and Monte Carlo (MC) simulations based methods. The simulation results show that proposed AA based analysis gives an optimal reconfiguration, for both balanced and unbalanced radial distribution systems with uncertainty as compared to existing IA based method.