Surface Texture

... MU-WEI JIAN1, JUN-YU DONG1, JIA-HUA (JERRY) WU 2 ... 2 Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton Cambridge, United Kingdom E-MAIL: dongjunyu@ouc.edu.cn, jianmuwei@sohu.com, jerry.wu@sanger ... [5] Jian, Muwei; Dong, Junyu; ...

A numerical simulation has been carried out to investigate the buoyancy induced flow and heat transfer characteristics inside a wavy walled enclosure. The enclosure consists of two parallel wavy and two straight walls. The top and the bottom walls are wavy and kept isothermal. Two straight-vertical sidewalls are considered adiabatic. Governing equations are discretized using the control volume based Finite-Volume method with collocated variable arrangement. Simulation was carried out for a range of surface waviness ratios, =0.00-0.25; aspect ratios, A=0.25-0.5; and Rayleigh numbers Ra=100-107 for a fluid having Prandtl number equal to 1.0. Results are presented in the form of local and global Nusselt number distributions, streamlines, and isothermal lines for different values of surface waviness and aspect ratios. For a special case of =0 and A=1.0, the average Nusselt number distribution is compared with available reference. The results suggest that natural convection heat transfer is changed considerably when surface waviness changes and also depends on the aspect ratio of the domain. In addition to the heat transfer results, the heat transfer irreversibility (HTI) in terms of Bejan number (Be) was measured. For a set of selected values of the parameters (, A, and Ra), a contour of the Bejan number is presented at the end of this paper.

The process conditions for a high-efficiency and low cost crystalline silicon solar cell were optimized. Novel approaches such as wafer cleaning and saw -damage removal using 0.5wt% of 2,4,6-trichloro-1,3,5-triazine, silicon surface texturing with optimized pyramid heights (∼5μm), and a third step of drive-in after phosphosilicate glass (PSG) removal followed by oxide removal were investigated. A simple method of chemical etching adopted for edge isolation was optimized with edge etching of 5–10μm, without any penetration of chemicals between the stacked wafers. The conversion efficiency, open-circuit voltage, short-circuit current, and fill factor of the cell fabricated with the optimized process were a maximum of 17.12%, 618.4mV, 5.32A, and 77% under AM1.5 conditions, respectively.

Rate laws have been determined for the aqueous oxidation of pyrite by ferric ion, dissolved oxygen and hydrogen peroxide at 30°C in dilute, acidic chloride solutions. Fresh, smooth pyrite grain surfaces were prepared by cleaning prior to experiments. Initial specific surface areas were measured by the multipoint BET technique. Surface textures before and after oxidation were examined by SEM. The initial rate method was used to derive rate laws. The specific initial rates of oxidation (moles pyrite cm -2 min -1) are given by the following rate laws (concentrations in molar units): rsp, Fe3+ = -10 -9.74M0.5Fe3+ M-0.5H+ ( pH 1-2) rsp, o2 = -10 -6.77M0.5O2 ( pH 2-4) rsp, h2o2 = -10 -1.43MH2O2 ( pH 2-4) An activation energy of 56.9 ± 7.5 kJ mole -1 was determined for the oxidation of pyrite by dissolved oxygen from 20-40°C. HPLC analyses indicated that only minor amounts of polythionates are detectable as products of oxidation by oxygen below pH 4; the major sulfur product is sulfate. Ferric ion and sulfate are the only detectable products of pyrite oxidation by hydrogen peroxide. Hydrogen peroxide is consumed by catalytic decomposition nearly as fast as it is by pyrite oxidation. SEM photomicrographs of cleaned pyrite surfaces indicate that prior to oxidation, substantial intergranular variations in surface texture exist. Reactive surface area is substantially different than total surface area. Oxidation is centered on reactive sites of high excess surface energy such as grain edges and corners, defects, solid and fluid inclusion pits, cleavages and fractures. These reactive sites are both inherited from mineral growth history and applied by grain preparation techniques. The geometry and variation of reactive sites suggests that the common assumption of a first-order, reproducible dependence of oxidation rates on surface area needs to be tested.

A B S T R A C T Textured surfaces have been shown to provide enhanced tribological performance in a variety of contacts. Numerical analysis and optimisation methods are combined for application-oriented texture optimisation. However, an analytical approach is advantageous in providing more generic in-depth understanding of the nature of the relationships between texture parameters and objective functions, such as enhanced load carrying capacity and reduced friction. The paper outlines such an approach to obtain a set of global optimum design parameters for partially textured surfaces. The optimised results are expressed in dimensionless form, which enables their use for a variety of applications. The performance of optimised partially textured sliding surfaces is compared with the other conventional bearing geometries in their optimum state.

The study of textured surface performance is one of the highly researched topics in recent times. This is mainly due to the advantages that such surfaces can potentially provide in practice, in mitigating adverse tribological conditions, such as friction and wear. However, considering the complexities found in practice, a methodological analysis and evaluation procedure is essential in order to gain an understanding of the benefits from utilising such features in a given contact. The current study provides a combined analytical and experimental approach towards an enhanced understanding of the behaviour of textured surfaces relative to their untextured counterparts. The developed analytical models are invaluable in providing an insight into the relationship between the many parameters involved in defining even simple surface texture feature geometry and the expected outcomes in practice, when corroborated with experimental results. The current study reports on such an endeavour. With the studied texture configuration, the results have shown the possibility of reducing friction by as much as 25%.

This article examines materiality as a surface condition and as inscribed in the texture of photographic and filmic images. First, it discusses examples where surface textures become striking due to various, frequently combined factors, such as image transfer, enlargement, the exigencies of the machinery involved and the properties of the film stock. Here, image resolution is the main focus. Second, it deals with the case of camera-less photography and film, where apparent surfaces are caused by directly acting upon the photo paper or the film stock. The third part offers close-readings of three exemplary artworks to be apprehended as poignant and exciting examples of how a photograph’s or film’s materiality determines its meaning, how textuality and texturality match. These readings include Steven Pippin’s series of photographs Laundromat-Locomotion (1997), Alison Rossiter’s works with expired silver gelatine photo papers (2007-ongoing) and David Gatten’s film Secret History of the Dividing Line (2002). Finally, in my concluding remarks, I will briefly address the critical potential of textures that foreground their materiality.

With the more precise demands of modern engineering products, the control of surface texture together with dimensional accuracy has become more important. This paper outlines the Taguchi optimization methodology, which is applied to optimize cutting parameters in end milling operation. The study was conducted in machining operation in hardened steel DIN GX40CRMOV5-1. The processing of the job was done by TiN coated carbide inserted end-mill tool under semi-finishing and finishing conditions of high-speed cutting. The milling parameters evaluated were cutting speed, feed rate and depth of cut. The experiments were conducted by using L-27 (313) orthogonal array as suggested by Taguchi. Signal-to- Noise (S/N) ratio and Pareto Analysis of Variance (ANOVA) are employed to analyze the effect of milling parameters on surface roughness. Main effects of process parameters on the quality characteristics have been analyzed. The results show that the optimum parameters of machining by CNC Milli...