A non-stationary stochastic model for periodic excitation with random phase modulation

The paper presents a non-stationary stochastic model for periodic excitation with random phase modulation, where the phase modulation is modeled as a modulated stationary. Gaussian process. Applications of the model are demonstrated by analysis of response of a single-degree-of-freedom (SDOF) system under such an excitation. The response is, in general, non-Gaussian. Cases of step, rectangular, and exponential envelopes are considered in the present study. The nonstationary second and fourth order moments are calculated by numerically solving the transient moment equations. Non-Gaussianity of the response is studied in terms of the non-stationary excess factor. Some numerical results are presented. The influences of system parameters, build-up and decay rates as well as duration of random phase modulation on the moment response of the SDOF system are discussed.     

The Einstein relation for degenerate semiconductors with nonuniformband structures

Modification of the Einstein equation for semiconductors with nonparabolic energy bands and doped nonuniformly with impurity atoms is suggested. The suggestion is based on a new approximation of the Fermi-Dirac integral of order 1/2, namely, F_1/2(η_n), where η_n is the reduced Fermi level for electrons. The relation reduces to that for semiconductors with parabolic energy bands and doped uniformly with impurity atoms under appropriate boundary conditions. A comparison of the calculated and exact results for F_1/2(η) is found to be very encouraging     

Remedial measures to control seepage problems in the Kafrein dam, Jordan

The Kafrein dam, 480 m long and 30 m high, is located on the Wadi Kafrein, a few kilometres from the active Jordan Valley fault. The Jordan Valley Authority proposed raising the crest of the existing dam by approximately 7 m and extending the length of the embankment to 554 m, in order to increase its storage capacity by 6 million m³ to a total of 8.5 million m³. The paper discusses the likelihood that existing seepage problems will be exacerbated when the dam is raised and proposes some remedial actions to increase the safety of the dam and minimise both the amount of seepage and any adverse effects. Electronic Publication     

Fractal model to predict the crack roughness effect on the local bending compliance of circular shafts

In this paper the local compliance due to a transverse fractal crack in a shaft under pure bending is investigated. In a fractal crack, the surface is considered irregular and it is characterized by the presence of nonuniformities at different scales. Therefore, the crack surface can be modeled as a fractal surface with fractal dimension D. An analytical model for the compliance coefficient is presented with and without the effect of the surface roughness. The results obtained shows that as the dimension of the fractal surface increases the compliance increases as well. It is shown that this behavior conforms well with existing experimental results.     

Grid computing: a STOPE view

Grid computing is emerging as the foundation upon which virtual organizations can be built. Such organizations are becoming of increasing importance for tackling various projects, both in academic and in business fields. This paper is concerned with presenting an integrated view of the grid to readers interested in understanding it, or perhaps in developing it further or making use of it in the future. The target view is based on the STOPE (strategy/technology/organization/people/environment) framework that has previously been used to integrate the issues of various information technology problems over its well‐defined domains. For strategy, the view considers the reasons associated with the need for the grid, including grid services and grid benefits. For technology, the technical components of the grid and their functions are taken into account. For organization, the organizations concerned with the development, technology production, service provisioning and use of the grid are considered. For people, those associated with the grid in the related organizations are taken into account. For the environment, rules, practices and support associated with the grid are discussed. Finally, the paper emphasizes questions that need to be answered in order to contribute to the future development of the grid. Copyright © 2006 John Wiley & Sons, Ltd.     

Tables of a Truncated Standard Normal Distribution: A Doubly Truncated Case

As an extension to the singly truncated case, this article further examines a doubly truncated normal distribution. In this article, we consider both symmetric and asymmetric cases with two truncation points on the left and the right, and develop the tables of a truncated mean, a truncated variance, and a cumulative probability.     

Novel Route to Propylene Carbonate: Selective Synthesis from Propylene Glycol and Carbon Dioxide

High surface area zirconium phosphate in an amorphous phase exhibits high activities for water-related reactions such as hydrolysis of ethyl acetate and esterification of acetic acid with ethanol. The zirconium phosphate is insoluble during the reaction, is recoverable by simple filtration, and can be reused at least five times without any treatment.     

Passivation of silicon by silicon nitride films

It is shown by contactless transient photoconductivity measurements in the microwave frequency range that Si₃N₄ films are an outstanding passivation of the n-type c-Si surface. Si₃N₄ on n-type Si forms an accumulation layer, which acts as an ideally reflecting potential barrier for minority carriers (holes). Due to the small space charge layer capacitance, minority carrier storage at this interface is very limited.In contrast to the latter measurements on p-type Si wafers covered with Si₃N₄ are characterized by storage of excess charge carriers in the surface depletion layer. The stored charge carriers decay slowly. The minority carriers (electrons) collected at the surface show a reduced mobility.     

Volume contraction behaviour of binary solid-liquid fluidized beds

Contrary to the widely held notion that the total bed height of a binary solid fluidized bed will be the sum of heights of the two individual mono-component beds fluidized at the same velocity, significant negative deviations have been observed in our experimental investigation. The negative deviations, signifying a contraction of the total volume of the binary solid fluidized bed, could sometimes be as high as 25% of the actual volume. The volume contraction has been found to depend mainly upon the degree of solids mixing prevailing in the bed irrespective of whether it is fully fluidized or not. The composition of the binary solid fluidized was another important factor that influenced the contraction behaviour of the bed besides the size ratio of the two constituent solid species of the binary present in the bed.     

The effects of aqueous extraction on the performance of wheat bran in bread

Wheat bran was sieved into coarse, medium and fine fractions prior to extraction with tap water. Bran, bran extract and bran residue were analysed for moisture, protein, fat, ash, pentosan and phytic acid. Farinograph measurements and baking tests showed maximum dough resistance and loaf volume of a white flour were both increased by the addition of the residue. Both these parameters were substantially decreased by bran extract and, to a lesser degree, by the bran itself. These findings were common amongst the size fractions although the residue from the coarse bran had the greatest effect on loaf volume and dough properties.