Gettering by heat thermal processing: application in crystalline silicon solar cells

The aim of this work is to getter unwanted impurities from solar grade crystalline silicon (Si) wafers and then to enhance their electronic properties. This was done by forming a sacrificial porous silicon (PS) layer on both sides of the Si wafers and by performing infrared (IR) thermal annealing treatments (at around 950 °C) in a SiCl₄/N₂ controlled atmosphere. The process allows concentrating unwanted impurities in the PS layer and near the PS/silicon interface. These treatments reduce the resistivity by about two orders of magnitude at a depth of about 40 μm and improve the minority carrier diffusion length from 75 to 210 μm. This gettering method was also tested on silicon wafers where grooved fingers and back contacts were achieved using a chemical vapor etching (CVE) method. Front buried metallic contacts and small holes for local back surface field were then achieved after the gettering stage in order to realize silicon solar cells. It was shown that the photovoltaic parameters of gettered silicon solar cells were improved as regard to ungettered ones.     

Multi-criteria decision making in workforce choice using AHP,WSM and WPM

This paper focuses on the implementation of Multi-Criteria Decision Making (MCDM) methods to evaluate the workforce competence in apparel industry. In this study, the Analytic Hierarchy Process (AHP), the Weighted Sum Model (WSM) and the Weighted Product Model (WPM) are suggested to solve workforce selection problem. The use of these methods is expected to help choose the best operator among several alternatives. Based on three criteria, each worker is evaluated in each executed operation. The criteria are a Quality Index ‘QI’, an Activity ‘A’ and an Attendance Rate ‘AR’. Thanks to the MCDM methods, scores allowing an objective classification of operators are obtained. Experimental results on AHP, WSM and WPM methods show the same decisions with the same workers’ classification from the best to the worst alternative. The resulting database contributes to the line balancing optimization by choosing for each operation, and as far as possible, the most competent operator.     

Improvement of thermal performance of spiral heat exchanger on hydrogen storage by adding copper fins

The reaction time of hydrogen in metal-hydride vessels (MHVs for short) is strongly influenced by the heat transfer from/to the hydride bed. In the present work an experimental study of the geometric and the operating parameters of a finned spiral heat exchanger has been carried out to identify their influence on the performance of the charging process of the MHV. The experimental results show that the charge time of the reactor is considerably reduced, when finned spiral heat exchanger is used. In addition, the effect of different parameters (flow mass and temperature of the cooling fluid, applied pressure of hydrogen in the case of absorption and desorption) has been discussed and obtained results show that a good choice of these parameters is important.     

A new approach to predict the fabric shrinkage in denim garments after finishing treatments

The principal purpose of this work is to develop a new approach to model and predict the fabric shrinkage in denim garments after finishing treatments. This study was carried out on denim blue jeans fabrics of different structures which are transformed into pants. The shrinkage 056 measured at different parts of the pant (waist, hem and knees). A factorial design analysis with 960 experiments conducted under industrial conditions and repeated three times was applied to study the garment shrinkage behaviour. A standard method was modified to characterize the potential shrinkage of the denim garment fabrics and to model their intrinsic shrinkage parameters. Relevant models calculating the fabric shrinkage of the denim garments in the different treated zones of pants according to the finishing treatments are identified and validated in three industrial orders. The obtained results, statistically and industrially validated, show very well the accuracy of the established shrinkage prediction models and their reliability to be applied in industrial scale.     

Silicon Seed Priming Enhances Salt Tolerance of Barley Seedlings through Early ROS Detoxification and Stimulation of Antioxidant Defence

Silicon - Seed priming has recently gained considerable attention to induce salt tolerance in several crop plants. In the present study, we evaluated the effect of seed priming with silicon (Si)...     

Determination of a sewing quality index of denim fabrics

This paper reports a determination of a sewing quality index in order to assist the industry in providing quality clothing before production. The particularity of this work lies in the fact that it encompasses various sewing quality parameters (efficiency, slippage, and puckering) into a single overall quality index. Moreover, a program was investigated, to determine the quality index, so that the manufacturer has only to enter the available data. In fact, by entering the input parameters which are blend composition, seam direction, fabric mass, stitch density, and seam thread linear density, an overall quality index will be given and the seam quality as well as the defect sources will be displayed. To reach this aim, regression models were determined to predict seam quality. In this work, 18 denim fabrics were sewn with two commercial sewing threads. Their influences, ranked according to the seam quality, were also determined. The seam efficiency was calculated by determining both the seam and the fabric's tensile strength. The seam slippage was determined by calculating the difference between the elongation at the break of the seam and the elongation at the break of the fabric. Seam puckering was determined by measuring both the fabric and seam’s thickness.     

Influence of some sewing parameters upon the sewing efficiency of denim fabrics

This paper reports an experimental investigation of the effect of the seam threads linear density, the stitch density and some fabric properties on the seam efficiency. Furthermore, on the basis of the seam quality parameters, regression models were determined in order to predict seam efficiency. In this work, 18 denim fabrics, having different compositions and masses, were sewn with two commercial sewing threads. Their performances, ranked according to the seam quality, were also determined. The seam efficiency was calculated by determining of the seam tensile strength and the fabric tensile strength. It was concluded that the increase in the seam thread linear density increases the seam efficiency, as well as the stitch density. However, the fabric mass has a random effect on seam efficiency. About the composition, we conclude that the seam efficiency decreases with polyester but increases with elastane. According to the seam direction, it was found that, in the weft direction, the seam efficiency was more important than in the warp direction.     

Media handling for multimedia conferencing in multihop cellular networks

This article addresses the media-handling aspects of multimedia conferencing in multihop cellular networks. Participation in multimedia conferences in MCNs may be confined to either the conventional cellular network or the MANET. Participation also can span both networks. However, neither the media-handling architectures currently in use in conventional cellular networks, nor the ones in use in MANETs are appropriate. When they are used, either the participants in the conventional cellular network, or the ones in the MANETs, might experience long and potentially unacceptable end-to-end stream delays. Furthermore, these architectures are the antipodes of each other. Reconciling them is not an easy task. We evaluate the architectures currently in use in cellular networks and MANETs, show that none is suitable, and propose a new architecture that bridges the two worlds. The new architecture uses the MANET media-handling architectures as a starting point. It is based on media mediators. A media mediator is composed of two functional entities: the media gateway controller mediator and the media gateway mediator. A proof-of-concept prototype was implemented, and extensive simulations were conducted to evaluate performance.     

The oxidation of sulfide to sulfoxide on Ti-complex/MCM-41 catalyst

The heterogeneous Kagan-type catalyst was prepared by an in situ method using MCM-41 as support. The influence of the incorporation process on the structure of MCM-41 was studied using XRD, FT-IR, UV-vis, ²⁹Si-MAS-NMR and N₂ adsorption–desorption. The obtained materials showed a definite catalytic activity on the oxidation of sulfide to sulfoxide in the medium containing dichloromethane (solvent) and H₂O₂ or TBHP (oxidant).