Optimisation study of large‐scale enzymatic synthesis of oleyl oleate,a liquid wax ester,by response surface methodology

An optimisation study of the large‐scale enzymatic synthesis of a liquid wax ester from oleic acid and oleyl alcohol using Novozym 435 was carried out. Investigations were performed in batch mode with a stirred tank reactor (STR) with one multi‐bladed impeller. Response surface methodology (RSM) based on a five‐level, three‐variable central composite rotatable design (CCRD) was used to evaluate the interactive effects of various parameters. The parameters are amount of enzyme (A) (90–120 g), impeller speed (B) (100–400 rpm) and temperature (C) (40–60 °C). The optimum conditions derived via RSM at a fixed reaction time of 1 h were successfully optimised as A = 104 g, B = 388.0 rpm and C = 49.7 °C. The actual experimental yield was 96.7% under the optimum conditions, which compared well with the maximum predicted value of 97.6%. Copyright © 2005 Society of Chemical Industry     

Ion-exchange kinetics and electrical conductivity studies of polyaniline Sn(IV) tungstoarsenate; (SnO2)(WO3)(As2O5)4(C6H5NH)2·nH2O: a new semi-crystalline ‘polymeric-inorganic’ composite cation-exchange material

A new and novel electrically conducting ‘polymeric-inorganic’ composite cation-exchange material; polyaniline Sn(IV) tungstoarsenate was prepared by incorporating polyaniline into inorganic ion-exchanger material. It possessed improved ion-exchange capacity, high chemical and thermal stabilities, reproducibility and selectivity for some specific metal ions. Kinetic study of exchange for some divalent metal ions of alkaline earths and transition metals was carried out under the conditions favoring a particle diffusion-controlled ion-exchange phenomenon and some physical parameters such as self diffusion coefficient D₀, energy of activation E_a and entropy of activation ΔS* were determined. The temperature dependence of electrical conductivity of this composite material with increasing temperatures was measured by using 4-in-line-probe DC electrical conductivity measuring-technique. The conductivity values lie in the semiconductor region, i.e. in the range of 10⁻³ S cm⁻¹ that follow the Arrhenius equation. The energy of activation of electrical conduction for the composite was also calculated.     

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     

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.     

Nonlinear analysis, design, and implementation of a VCO in S frequency band

A VCO in S frequency band is designed by using nonlinear technique based on large signal model of semiconductor devices. The nonlinear circuit of the VCO is analyzed by a novel analytical approach of harmonic balance method as an autonomous circuit, and with fulfilling the stability condition of the network, the output specifications are determined. This proposed nonlinear approach for determining of the frequency and amplitude stability is also based on harmonic balance method. The results of the analysis are compared with those of measurements. The comparison shows good agreement between results of this analytical approach and the measurements. Zahra Ghanian was born in Tehran, Iran, in 1975. She received the B.Sc. degree in electrical engineering from Sharif University of Technology, Tehran, Iran, in 1998, and the M.Sc. degree from the Amirkabir University of Technology, Tehran, Iran, in 2001. Since 2000, she has been involved in several research and engineering projects at the Amirkabir University of Technology, Iran Telecommunications Research Center (ITRC) and Niroo Research Institute (NRI). Her main areas of interest are design, simulation and analysis of circuits for Microwave, Millimeter wave and Wireless applications. Abdolali Abdipour was born in Iran in 1966. He obtained his B.Sc. in Electrical Engineering from Tehran University, Tehran, Iran in 1989, and the M.Sc. in Electronics from Limoges University, Limoges, France in 1992. Then he achieved his PhD degree in Electronic Engineering from Paris XI University, Paris, France in March 1996. His research areas include wireless communication systems (RF Technology and Transceivers), RF/Microwave/mm-wave circuit and system design, E & M modeling of active devices and circuits, high frequency electronics (signal and noise), nonlinear modeling and analysis of microwave devices and circuits. He has published over 80 papers in the refereed journals and international conferences. He authored two books “Noise in Electronic Communication: Modeling, Analysis and measurement” and “Transmission Lines” (in Persian). He is currently an associate professor of Electrical Engineering Department at Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran. Ayaz Ghorbani received PG diploma, m. Phiel and PhD degrees from the university of Bradford U.K. in 1984, 1985 and 1987 respectively in the area of electrical and communication engineering. From 1987 up to now he has been teaching various courses in the department of electrical engineering at university of Amirkabir (Tehran poly technique) Tehran, Iran. In 1987 he was awarded John Robertshaw Travel Award to visit a number of research establishments in the United States of America from Bradford University, and in 1990 he was also awarded U.R.S.I. Young Scientists Award at general assembly of the URSI, Prague, Czech Republic. In 2004 he was in Bradford University for one year as a research visitor where he obtained post doctorate degree. Dr. Ghorbani is author and coauthor of more than seventy papers in conferences as well as scientific journals.     

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.     

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.