Enhancement of photocatalytic activity by metal deposition: characterisation and photonic efficiency of Pt, Au and Pd deposited on TiO2 catalyst

Pt, Au and Pd deposited TiO2 have been prepared and characterised by surface analytical methods such as surface area, XRD, and scanning electron micrograph and photophysical characterisation by diffuse reflectance spectroscopy. The photocatalytic activity of the doped catalysts was ascertained by the photo-oxidation of leather dye, acid green 16 in aqueous solution illuminated with low-pressure mercury lamp ( approximately 254 nm). The effect of metal contents on the photocatalytic activity was investigated. The highest photonic efficiency was observed with metal deposition level of less than 1 wt%.     

Low-Resistance Cu-Sn Electroplated–Evaporated Microbumps for 3D Chip Stacking

Low-resistance copper-tin (Cu-Sn) microbumps, with sizes varying from 5 μm × 5 μm to 20 μm × 20 μm and formed by electroplating–evaporation bumping (EEB) technology for three-dimensional integration of large-scale integrated chips, have been evaluated for their microstructure and electrical resistance. It was inferred from x-ray diffraction data that the formation of low-resistance Cu₃Sn intermetallic compound (IMC) is facilitated at higher bonding temperature. Electron probe microanalysis mapping showed that, even before bonding, Cu-Sn IMCs were formed at the interface between Cu and Sn, whereas they were sandwiched between the Cu of the upper and lower microbumps after bonding. Electron backscatter diffraction analysis revealed that the crystal orientation of Sn grains was sharply localized in the (100) orientation for physical vapor deposited (PVD) sample, while electroplated Sn film exhibited a mixed crystal orientation in all (100), (110), and (001) axes. A resistance value of ~35 mΩ per bump was obtained for Cu-Sn microbumps with area of 400 μm², which is several times lower than the resistance value reported for Cu-Sn microbumps fabricated by a pure electroplating method. The low resistance value obtained for EEB-formed Cu-Sn microbumps after bonding is explained by (i) the reduced surface roughness for evaporated Sn, (ii) the high degree of crystal grain orientation resulting from layer-by-layer growth in the PVD Sn, despite their smaller grain size, and (iii) the absence of impurity segregation at grain boundaries.     

Optimization of Training and Scheduling in the Non-Coherent SIMO Multiple Access Channel

Channel state information (CSI) is important for achieving large rates in MIMO channels. However, in time-varying MIMO channels, there is a tradeoff between the time/energy spent acquiring channel state information (CSI) and the time/energy remaining for data transmission. This tradeoff is accentuated in the MIMO multiple access channel (MAC), since the number of channel vectors to be estimated increases with the number of users. Furthermore, the problem of acquiring CSI is tightly coupled with the problem of exploiting CSI through multiuser scheduling. This paper considers a block-fading MAC with coherence time T, n uncoordinated users-each with one transmit antenna and the same average power constraint, and a base station with M receive antennas and no a priori CSI. For this scenario, a training-based communication scheme is proposed and the training and multiuser-scheduling aspects of the scheme are jointly optimized. In the high-SNR regime, the sum capacity of the non-coherent SIMO MAC is characterized and used to establish the SNR-scaling-law optimality of the proposed scheme. In the low-SNR regime, the sum-rate of the proposed scheme is found to decay linearly with vanishing SNR when flash signaling is incorporated. Furthermore, this linear decay is shown to be order-optimal through comparison to the low-SNR sum capacity of the non-coherent SIMO MAC. A by product of these SNR-asymptotic analyses is the observation that non-trivial scheduling (i.e., scheduling a strict subset of trained users) is advantageous at low SNR, but not at high SNR. The sum-rate and per-user throughput are also explored in the large-n and large-M regimes. Non-coherent capacity, training, multiple access channel, multiuser scheduling, opportunistic scheduling.     

Web engineering: an introduction

Within a short period, the Internet and World Wide Web have become ubiquitous, surpassing all other technological developments in our history. They've also grown rapidly in their scope and extent of use, significantly affecting all aspects of our lives. Industries such as manufacturing, travel and hospitality, banking, education, and government are Web-enabled to improve and enhance their operations. E-commerce has expanded quickly, cutting across national boundaries. Even traditional legacy information and database systems have migrated to the Web. Advances in wireless technologies and Web-enabled appliances are triggering a new wave of mobile Web applications. As a result, we increasingly depend on a range of Web applications. Now that many of us rely on Web based systems and applications, they need to be reliable and perform well. To build these systems and applications, Web developers need a sound methodology, a disciplined and repeatable process, better development tools, and a set of good guidelines. The emerging field of Web engineering fulfils these needs. It uses scientific, engineering, and management principles and systematic approaches to successfully develop, deploy, and maintain high-quality Web systems and applications. It aims to bring the current chaos in Web based system development under control, minimize risks, and enhance Web site maintainability and quality     

Study of shrinkage stresses for drying of brick as a conjugate problem

Drying induced shrinkage stresses of a two‐dimensional rectangular brick of aspect ratio 2 is studied numerically. The drying of brick is analysed as a conjugate problem. The conservation equations for the solid are obtained using continuum approach and the Navier–Stokes equations have been solved for the flow field. An elastic model has been used to calculate the shrinkage stresses. The present unified model predicts the stress concentration at the leading edge where it is expected to be maximum due to large shrinkage. Copyright © 2000 John Wiley & Sons, Ltd.     

Electrochemical bromination and oxidation of alkyl aromatic compounds by two-phase electrolysis

A simple, regioselective, environmentally clean and economical method for the preparation of side chain/ ring brominated aromatic compounds is reported in 70–98% yield by an electrochemical method using two phase electrolysis technique. Electrochemical reactions were carried out using aqueous 25–50 wt% sodium bromide containing catalytic amount (5 wt%) of hydrobromic acid as an aqueous phase and chloroform containing alkyl aromatic compounds as an organic phase, at a temperature of 0–30 °C in an undivided cell. The same two-phase electrolytic system can be used for the oxidation of benzylic alcohols to the corresponding benzaldehydes in 80–94% yield without over oxidation to carboxylic acids. The advantage of this very mild procedure is a room temperature reaction used with an undivided cell. Excellent conversions are observed. After completion of alcohol oxidation the electrolyte can be reused for a number of times, demonstrating “spent reagent” free electro organic reaction as an attractive one. In the case of side chain/ring bromination of alkyl aromatic compounds, the electrolyte can be reused after making up the concentration of the electrolyte with 47 wt% HBr solution. In some cases homogeneous electrolysis is applied, where the two-phase electrolysis did not work. Styrene epoxidation and α-bromination of ketones underwent homogeneous electrolysis at room temperature without any catalyst. The reaction was performed in CH₃CN-water (3: 2) using equimolar amount of NaBr as an electrolyte to get 68% of styrene epoxide. Use of an ionic liquid 1-butyl 3-methyl imidazolium bromide (Bmim) Br, instead of NaBr improved the yield and current efficiency of styrene epoxide to 86%.     

Electrical properties of chemical solution deposited (Bi0.9RE0.1)(Fe0.975Cu0.025)O3−δ (RE=Ho and Tb) thin films

Pure BiFeO₃ (BFO) and (Bi_0.9RE_0.1)(Fe_0.975Cu_0.025)O_3?δ (RE=Ho and Tb, denoted by BHFCu and BTFCu) thin films were prepared on Pt(111)/Ti/SiO₂/Si(100) substrates by using a chemical solution deposition method. The BHFCu and BTFCu thin films showed improved electrical and ferroelectric properties compared to pure BFO thin film. Among them, the BTFCu thin film exhibited large remnant polarization (2P_r), low coercive field (2E_c) and reduced leakage current density, which are 89.15 C/cm² and 345 kV/cm at 1000 kV/cm and 5.38×10^?5 A/cm² at 100 kV/cm, respectively.     

Experimental study of solar assisted ground source heat pump system during space heating operation from morning to evening

Journal of Mechanical Science and Technology - Experimental investigation of solar assisted ground source heat pump system has been carried out to understand performance variation during space...     

Comparison of Microtexture Evolution During Cryo and Room Temperature Rolling of Ti–5Ta–2Nb Alloy

An α + β Ti–5Ta–2Nb alloy has been developed for applications under severe oxidizing conditions of boiling concentrated nitric acid in spent fuel reprocessing plant. The formation of nanocrystalline grains has been observed in the cryo-rolled sample accompanied by a significant improvement in yield strength whereas the grain refinement is not significant in case of room temperature rolled sample. Suppression of dynamic recovery plays a major role in the formation of nanostructured material. The evolution of micro-texture during room temperature rolling and cryo-rolling has been compared in this study. The rolling texture of room temperature and cryo-rolled samples are similar to the rolling texture predicted for hexagonal materials with c/a <1.6. XRD analysis indicates peaks shift to lower 2θ with increase in rolling strains indicating the presence of tensile residual strains. Peak broadening is also observed indicating an increase in defect density and decrease in grain size.     

Failure Analysis of AISI 304 Stainless Steel Sleeve Used in High-Pressure Hose Assembly of Actuation System of a Satellite Launch Vehicle

Hydraulic control actuation systems in launch vehicles use flexible hoses for transmission of forces to actuators at different locations. The hose ends are connected to the interface adapters by AISI 304 stainless steel sleeves. These sleeves are assembled to nipple end fittings of the high-pressure hose by a swaging operation to obtain leak-proof hose assemblies. The swaging operation is carried out at room temperature by a hydraulically operated swaging machine. Performance of the system as a whole requires strict adherence to the quality standards maintaining the critical interface dimensions within specified tolerances and ensuring the compression given to the swaged joint through the sleeve. If the joining forces are less, this can result in loose joints and gross leakage, whereas excessive compression can cause damage to the parts of the system namely the sleeve, stainless steel braid, PTFE or the adapter. The swaged joint is a single-point failure mode, indicating that a failure in the joint can lead to mission failure. It has to withstand harsh environments such as high pressure, low and high temperature extremes, fatigue loading due to pressure cycling as well as vibration. Therefore, as part of design verification, a detailed qualification plan has been prepared and the hoses were tested as per the plan. As per the test plan, these hoses undergo acceptance tests which include pneumatic and hydraulic pressure testing. During acceptance testing of hoses, one of the hose sleeves was found to be cracked. The cracking was observed after carrying out the pneumatic test when the assembly was being prepared for hydraulic pressure set-up. This paper describes the detailed metallurgical investigation carried out to understand the cause of failure and actions taken to avoid similar failures.