Photogalvanic generation of dihydrogen by water splitting using MoS 4 2− as catalyst

A 4% solar energy efficiency has been achieved for photogeneration of dihydrogen (H₂) using MoS ₄ ²⁻ as catalyst, when the anode compartment of a photogalvanic cell is illuminated. The generated photocurrent rises slowly with time and reaches a limiting value. Ten hours after the reaction starts, a secondary dark reaction sets in which produces H₂ and photocurrent even when the light is switched off. Possible mechanisms in both cases have been suggested.     

Robust control with structure perturbations

The problem of making a given stabilizing controller robust so that the closed-loop system remains stable for prescribed ranges of variations of a set of physical parameters in the plant. The problem is treated in the state-space and transfer-function domains. In the state-space domain a stability hypersphere is determined in the parameter space using Lyapunov theory. The radius of this hypersphere is iteratively increased by adjusting the controller parameters until the prescribed perturbation ranges are contained in the stability hypersphere. In the transfer-function domain a corresponding stability margin is defined and optimized on the basis of the recently introduced concept of the largest stability hypersphere in the space of coefficients of the closed-loop characteristic polynomial. The design algorithms are illustrated by examples     

Finite element analysis of fluid-structure interaction effect on liquid retaining structures due to sloshing

Fluid-structure interaction problems, which may be categorized into different types, have attracted the attention of engineers because of their numerous practical applications. Sloshing of liquid in a liquid filled container subjected to external excitations and coupled interaction between the liquid and container wall due to sloshing is one such problem. The focus of the present paper is on the development of a numerical scheme using finite element technique to calculate the sloshing displacement of liquid and pressure developed due to such sloshing. The scheme is extended to study the coupled effect of sloshing and container wall movement due to change in the liquid pressure.     

Development and study of an automatic AC bridge for impedancemeasurement

An automatic ac bridge method employing the principle of balancing by means of a stochastic gradient search algorithm is presented. Among the various gradient search techniques, the Widrow-Hoff least mean square (LMS) technique has been chosen as it involves a low computational burden. The LMS algorithm has been used by the authors for the operation of an ac bridge operating with continuous variables. The relevant operation has been verified by simulation; it can also measure negative impedance. A relation has been established between parameters to be used in the LMS algorithm for discrete and continuous versions of the bridge. The balance convergence time for a relatively simple form of the LMS bridge, namely, the R-R type bridge, has been theoretically established and experimentally verified both by simulation and real-time implementation. The frequency response of the LMS algorithm has also been determined     

Electromagnetic scattering from a flat plate with rim loading andRAM saving

The problem of electromagnetic scattering from a plate with a rim loading for transverse electric (TE) and transverse magnetic (TM) polarizations is investigated. The analysis is based on the work of R. Tiberio et al. (ibid., vol.AP-33, no.8, p.867-73, 1985) on the uniform geometrical theory of diffraction analysis of a wedge with two face impedances. The two-dimensional field is converted into three-dimensional field using Siegel's 2-D to 3-D conversion formula. The corner effects are neglected. The width of the coating around the edges which gives the same result as a uniformly coated plate of the same size is estimated. Hence, the percentage of saving of radar-absorbing material (RAM) can also be estimated for practical application in radar cross-section (RCS) reduction problems     

Properties of continuous analog estimators for a discretereliability-growth model

A discrete reliability-growth model (appropriate for success-failure data) whose derivation parallels that of a popular nonhomogeneous Poisson process model (appropriate for continuous failure time data) is considered.,Following J. M. Finkelstein (ibid. vol.R-32, p.508-11, Dec. 1983) continuous analog estimators are defined for use with the discrete model when there is a constant prespecified number of test trials between system configuration changes. The large-sample properties of these estimators, including consistency and normality, are established. Large-sample standard-error formulas and confidence interval procedures are developed     

Effect of substrate temperature on the adhesion properties of magnetron sputtered nano-composite Si-C-N hard thin films

The adhesion and film failure studies on nano-composite SiCN thin films on silicon, glass and steel have been carried out. It was observed that both coating as well as the substrate has an influence on the adhesion of film. The films on hard substrate Si failed adhesively whereas on softer substrate, steel, cohesive failure was observed. The measured critical load was around 18 N and 24 N for SiCN film on silicon and steel substrate respectively. A decrease in critical load and interface toughness with the increase of substrate temperature during deposition for glass and steel substrate was observed.     

Rotational molding cycle time reduction through surface enhanced molds: Part A—Theoretical study

Rotational molding has been regarded as a plastic molding method with great potential. The process offers virtually stress‐free products having no weld lines or material wastage, and utilizes relatively inexpensive molds. Yet its widespread growth is hindered due to long production cycle times, which are limited by the time required to heat up and cool down the mold and the product. To address this issue, efforts have been made to enhance heat transfer to and from molds, ultimately reducing cycle times. The application of extended and rough surfaces to molds is investigated here. The aim of this study is to predict reductions in cycle time due to the enhancement of mold surfaces (i.e. roughness‐enhanced and pin‐enhanced molds). By utilizing a combination of heat transfer correlations, numerical analysis, and an existing rotational molding process simulation, cycle time predictions were made. The average predicted cycle time reductions were ～21 and 32% for the roughness‐enhanced and pin‐enhanced molds considered, under a variety of conditions. POLYM. ENG. SCI., 47:1406–1419, 2007. © 2007 Society of Plastics Engineers