Experimental investigations into triplex hybrid process of GA-RDECDM during subtractive processing of MMC’s

The use of Al-6063 SiCp metal matrix composites (MMCs) in electronic packaging applications, heat sinks for printed circuit boards and for microwave housings necessitates certain degree of machining operations to meet the specifications of the product. The various conventional and non-conventional machining processes had been used to machine the MMCs. But all such processes have their limitations in providing the desired outcomes. Therefore, the present research endeavor, a new process variant of ECDM for the machining of Al-6063 SiCp MMCs. The developed grinding assisted rotary disk electrochemical discharge machining (GA-RDECDM) process integrates the concept of triplex hybridization. In GA-RDECDM, an abrasive coated rotary disk was used as a tool electrode. The abrasive coated disk provides micro gaps between the tool electrode and work material surface and thereby it results in thin and stable gas film formation. The breakdown of thin and stable gas films produce high frequency, low intensity discharges and consequently improves the machining performance. The additional abrasion action imparted by rotating disk ensures the continuation of ECDM process. The influence of various process parameters including applied voltage, pulse on time, electrolyte concentration and the disk rotation rate on width over cut (WOC) and depth were experimentally investigated. Multi criteria optimization using desirability approach predicts the parametric combination of applied voltage of 99V, pulse on time of 3 ms, electrolyte concentration of 17%wt./vol. and disk rotation rate of 30 rpm as the optimum setting for fabrication of slits on the MMCs. The underlying process mechanism is also investigated and presented with appropriate illustrations. The major contribution of the present research work is the development of a novel method for the fabrication of the slits on MMCs.     

An effusive molecular beam technique for studies of polyatomic gas-surface reactivity and energy transfer

An effusive molecular beam technique is described to measure alkane dissociative sticking coefficients, S(T(g), T(s); ?), on metal surfaces for which the impinging gas temperature, T(g), and surface temperature, T(s), can be independently varied, along with the angle of incidence, ?, of the impinging gas. Effusive beam experiments with T(g) = T(s) = T allow for determination of angle-resolved dissociative sticking coefficients, S(T; ?), which when averaged over the cos?(?)/π angular distribution appropriate to the impinging flux from a thermal ambient gas yield the thermal dissociative sticking coefficient, S(T). Nonequilibrium S(T(g), T(s); ?) measurements for which T(g) ≠ T(s) provide additional opportunities to characterize the transition state and gas-surface energy transfer at reactive energies. A resistively heated effusive molecular beam doser controls the T(g) of the impinging gas striking the surface. The flux of molecules striking the surface from the effusive beam is determined from knowledge of the dosing geometry, chamber pressure, and pumping speed. Separate experiments with a calibrated leak serve to fix the chamber pumping speed. Postdosing Auger electron spectroscopy is used to measure the carbon of the alkyl radical reaction product that is deposited on the surface as a result of alkane dissociative sticking. As implemented in a typical ultrahigh vacuum chamber for surface analysis, the technique has provided access to a dynamic range of roughly 6 orders of magnitude in the initial dissociative sticking coefficient for small alkanes on Pt(111).     

Automatic Parallelization of Recursive Procedures

Parallelizing compilers have traditionally focussed mainly on parallelizing loops. This paper presents a new framework for automatically parallelizing recursive procedures that typically appear in divide-and-conquer algorithms. We present compile-time analysis, using powerful, symbolic array section analysis, to detect the independence of multiple recursive calls in a procedure. This allows exploitation of a scalable form of nested parallelism, where each parallel task can further spawn off parallel work in subsequent recursive calls. We describe a runtime system which efficiently supports this kind of nested parallelism without unnecessarily blocking tasks. We have implemented this framework in a parallelizing compiler, which is able to automatically parallelize programs like quicksort and mergesort, written in C. For cases where even the advanced compile-time analysis we describe is not able to prove the independence of procedure calls, we propose novel techniques for speculative runtime parallelization, which are more efficient and powerful in this context than analogous techniques proposed previously for speculatively parallelizing loops. Our experimental results on an IBM G30 SMP machine show good speedups obtained by following our approach.     

Aqueous lubricating properties of charged (ABC) and neutral (ABA) triblock copolymer chains

Application of charged polymer chains as additives for lubricating neutral surfaces in aqueous environment, especially via polymer physisorption, is generally impeded by the electrostatic repulsion between adjacent polymers on the surface. In this study, we have investigated the adsorption and aqueous lubricating properties of an amphiphilic triblock copolymer, comprised of a neutral poly(ethylene glycol) (PEG) block, a hydrophobic poly(2-methoxyethyl acrylate) (PMEA) block, and a charged poly(methacrylic acid) (PMAA) block, namely PEG-b-PMEA-b-PMAA. After adsorption onto a nonpolar hydrophobic surface from aqueous solution, an equal and homogeneous mixture of neutral PEG and charged PMAA chains is formed on the surface, with an adsorbed polymer mass comparable to its fully neutral counterpart, PEG-b-PMEA-b-PEG. The lubricity of PEG-b-PMEA-b-PMAA showed significant improvement compared to fully charged polymer chains, e.g. poly(acrylic acid)-block-poly(2-methoxyethyl acrylate) (PAA-b-PMEA), which is attributed to dilution of charged moieties on the surface and subsequent improvement of the lubricating film stability.     

Nucleus-nucleus potential in the range -2

S Kailas  A Navin 《Canadian Metallurgical Quarterly》1992,46(2):809-810

Road safety engineering: an effective tool in the fight against whiplash injuries

Road safety engineering can play an integral part in the prevention of whiplash injuries. While improvements to vehicle design can reduce the severity of whiplash injuries when a crash occurs, improvements to road safety can prevent whiplash-inducing crashes from occurring in the first place. Whiplash injuries are most commonly associated with rear end crashes. Unfortunately, rear end crashes are also the most common type of crash at urban signalized intersections, where the majority of crashes occur in British Columbia, Canada. The Insurance Corporation of British Columbia (ICBC), through the road improvement program, has been funding road improvements in order to reduce the frequency of collisions at high crash locations in British Columbia. Several road safety engineering countermeasures specifically targeted at rear end collisions have been researched and deployed. These countermeasures include simple and affordable solutions such as signal visibility enhancements, as well as complex and expensive solutions such as intersection geometric upgrades. When appropriately used, these countermeasures have proven to be extremely cost-effective in reducing the frequency of rear end collisions. Widespread application of signal visibility enhancements is now being pursued to further decrease the risk of rear end collisions and whiplash injuries. Costs are the direct cost of the ICBC portion of the investment and benefits are only those associated with reduced insurance claims over a 2-year period.     

A new cubic equation of state for fluids and fluid mixtures

A new cubic equation of state for pure fluids is presented in this work. The new equation requires the critical temperature and pressure, as well as two additional parameters to characterize each particular fluid. These parameters have been evaluated by minimizing deviations in saturated liquid densities while simultaneously satisfying the equality of fugacities along the saturation curve. Thus, good predictions of volumetric properties in the liquid region are obtained, while accuracy in vapour—liquid equilibrium calculations is maintained. Parameters for polar as well as nonpolar fluids are presented in this paper. In the case of nonpolar fluids, the two parameters required can be correlated with the acentric factor. No such relationship with independently measured quantities could be found for polar fluids. It is shown that the new equation reproduces many of the good features of the Soave and Peng—Robinson equations of state for nonpolar fluids, whilst overcoming some of the limitations of these equations for polar fluids. Applications of the equation of state to the correlation of phase equilibria are demonstrated.     

Influence of fiber orientation on high stress wear behavior of sisal fiber‐reinforced epoxy composites

Sisal fiber‐reinforced epoxy composites having three different fiber orientations, namely LL, LT, TT mentioned in the text were prepared and tested for their high stress abrasive wear behavior. Effect of fiber orientation, sliding distance, and load on abrasive wear of sisal–epoxy composites have been determined. Wear data of composites have been compared with the pure epoxy. Incorporation of fibers decreases the wear rate of epoxy resin, which varies with the fiber orientation. Wear rate in case of TT composite is found minimum as compared to other two composites. Wear rate follows the following trend, W_TT < W_LT < W_LL. Owing to minimum exposed area of fiber to the sliding asperities, lowest wear rate occurs in the case of TT composite. Increase of load and sliding distance increases the wear volume in all the composites, because of the progressive loss of material. Wear mechanism has been discussed by using SEM micrographs of the worn surfaces. POLYM. COMPOS., 28:437–441, 2007. © 2007 Society of Plastics Engineers.     

Development, structure and strength properties of PP/PMMA/FA blends

A new type of flyash filled PP/PMMA blend has been developed. Structural and thermal properties of flyash (FA) filled polypropylene (PP)/polymethyl methacrylate (PMMA) blend system have been determined and analysed. Filled polymer blends were developed on a single screw extruder. Strength and thermal properties of FA filled and unfilled PP/PMMA blends were determined. Addition of flyash imparted dimensional and thermal stability, which has been observed in scanning electron micrographs and in TGA plot. Increase of flyash concentration increased the initial degradation temperature of PP/PMMA blend. The increase of thermal stability has been explained based on increased mechanical interlocking of PP/PMMA chains inside the hollow structure of flyash.     

Effect of Selected Pretreatments on Impregnation of Curcuminoids and Their Influence on Physico-chemical Properties of Raw Banana Slices

The effect of pretreatments, namely, blanching, ultrasound, vacuum and their combinations on curcuminoid impregnation in raw banana slices, was studied in conjunction with treatments in pure water as well as in 10 % NaCl solution. The treatments such as ultrasound, vacuum and combination of vacuum and blanching with ultrasound resulted in higher curcuminoid infusion compared to control for both pure water and 10 % NaCl osmotic treatments. The blanching treatment resulted in lower infusion of curcuminoids as compared to that of control due to the gelatinisation of starch present in banana. Further, the increase in surrounding solution concentration from pure water to 10 % NaCl resulted in enhanced curcuminoid infusion (e.g. from 85 to 95 mg/100 g for combined vacuum and sonication treatment). However, the direction of the mass transfer of water as well as solid was reversed. The samples subjected to combined vacuum and sonication treatment resulted in lowest compressive force, highest infusion of curcuminoids and highest total colour difference compared to other treatments. Besides, the dehydration of such product also resulted in the highest retention of curcuminoids compared to the individual treatments. The present study concluded that osmotic treatment can be a feasible technology for the infusion of functional ingredients into foods without altering its matrix. The extent of infusion can be significantly enhanced by the application of combined treatment such as vacuum and ultrasound.