Showing papers by "University of Bahrain published in 1997"
TL;DR: In this paper, the energy absorption characteristics of corrugated tubes are experimentally studied, where corrugations are introduced in the tube to force the plastic deformation to occur at predetermined intervals along the tube generator.
154 citations
TL;DR: In this paper, the authors describe the results of a feasibility study into the use of mid-infrared spectroscopy for addressing certain authenticity problems with selected fresh meats, including the detection of frozen-thawed meats and semi-quantitative analysis of mixtures.
134 citations
TL;DR: The cross product is studied as a method for generating and analyzing interconnection network topologies for multiprocessor systems and is given a new tool for further studying some of the known interconnection topologies, such as the hypercube and the mesh.
Abstract: We study the cross product as a method for generating and analyzing interconnection network topologies for multiprocessor systems. Consider two interconnection graphs G/sub 1/ and G/sub 2/ each with some established properties such as symmetry, low degree and diameter, scalability, simple optimal routing, recursive structure (partitionability), fault tolerance, existence of node-disjoint paths, low cost embedding, and efficient broadcasting. We investigate and evaluate the corresponding properties for the cross product of G/sub 1/ and G/sub 2/ based on the properties of G/sub 1/ and those of G/sub 2/. We also give a mathematical characterization of product families of graphs which are closed under the cross product operation. This investigation is useful in two ways. On one hand, it gives a new tool for further studying some of the known interconnection topologies, such as the hypercube and the mesh, which can be defined using the cross product operation. On the other hand, it can be used in defining and evaluating new interconnection graphs using the cross product operation on known topologies.
107 citations
TL;DR: In this paper, the authors defined the range of principal forms the climate of Bahrain has taken during the past six decades, particularly through the temperature and rainfall trends, and evaluated the consequent degree of aridity on the Islands.
64 citations
TL;DR: In this paper, the variations of molar conductivity of various surfactants such as sodium caprylate, sodium laurate, sodium palmitate, salt stearate, etc.
55 citations
TL;DR: A fourth-order block method based on the composite Simpson rule is developed for the parallel solution of ordinary differential equations, its principal error term is linear in the block size while the increased order and stability allow a modest increase in parallelism without further computational complexity.
Abstract: A fourth-order block method based on the composite Simpson rule is developed for the parallel solution of ordinary differential equations. Like the block scheme based on the composite Trapezoidal Rule, its principal error term is linear in the block size while the increased order and stability allow a modest increase in parallelism without further computational complexity. Numerical results confirm the enhanced properties of the higher-order method.
36 citations
TL;DR: In this article, a new set of controller tuning relations is developed by explicitly considering the characteristics of the closed-loop behavior, and the proposed relations overcome the main disadvantage of existing tuning methods is that they may lead to closedloop performance results which are quite different from those desired.
Abstract: In this contribution, a new set of controller tuning relations is developed. The main disadvantage of the existing tuning methods is that they may lead to closed-loop performance results which are quite different from those desired. The proposed relations overcome this disadvantage by explicitly considering the characteristics of the closed-loop behavior. These expressions related the parameters of the controller to the parameters of a first-order plus time delay (FOPTD) model of the plant as well as the overshoot of the closed-loop response to a step change in the setpoint.
30 citations
TL;DR: Urgent measures are needed to eliminate lead from gasoline, paint and other sources in the environment to reduce lead exposure among children in Bahrain.
Abstract: SummaryTo determine lead exposure among children in Bahrain, a total of 280 shed deciduous whole teeth were collected from 269 children. Teeth were analyzed for lead concentrations using atomic absorption spectrophotometry with electrothermal atomization. Children were between 5 and 15 years old. The study period extended from July 1993 to April 1994. The study showed that the overall mean tooth-lead level was 4.3 μg/g dry weight with a range of 0.1–60.8 μg/g dry weight. The cumulative frequency distribution revealed that 35% of the teeth had a lead concentration of more than 4 μg/g dry weight. The tooth-lead concentrations differed according to the tooth type and age. The child's sex, nationality, area of residence and socio-economic status had no impact on tooth-lead level. In conclusion, lead is present in toxic concentrations in 35% of the teeth of the children studied. Urgent measures are needed to eliminate lead from gasoline, paint and other sources in the environment.
29 citations
TL;DR: An experimental investigation into the microbial contamination of cutting fluids is presented and confirms the laboratory based results of the fluid biocontamination by culture and identification of the micro-organisms, and their ability to survive in the workshop fluid systems.
27 citations
01 Jan 1997
TL;DR: Fifteen species from the family Chenopodiaceae have been analysed for their chemical constituents: alkaloids, anthraquinones, coumarins, flavonoids, saponins, sterols and/or terepenes and tannins.
Abstract: Fifteen species from the family Chenopodiaceae have been analysed for their chemical constituents: alkaloids, anthraquinones, coumarins, flavonoids, saponins, sterols and/or terepenes and tannins. The antimicrobial activity of these plants was tested in two concentrations against Gram-negative Escherichia coli and Pseudomonas aeruginosa, and Gram-positive Staphylococcus aureus and Bacillus subtilis.
26 citations
TL;DR: In this article, an algorithm is developed for the optimum design of steel frames composed of prismatic and/or tapered members, where the width of an I-section is taken as constant, together with the thickness of web and flange, while the depth is considered to be varying linearly between joints.
TL;DR: In this paper, the authors investigated the effect of traditional and modern education on the creativity of students in the Sudan, and found that the traditional education performed significantly better than the modern education, but with equal performance on one test.
Abstract: This study investigated the differing effect upon creativity of traditional and modern education in the Sudan. The salient characteristics of the two types are presented, with a brief discussion of their likely effects. Four creativity tests, suitably modified for local conditions, were administered to 264 male and female students, with an age range of 15–20 years. The results indicated that the group receiving modern education performed significantly better than the traditionally educated group on two of the four creativity tests, but with equal performance on one test. The traditionally educated group performed significantly better on the fourth test. The discussion suggests there are a number of factors, both sociocultural and methodological, which may account for these findings.
01 Dec 1997
TL;DR: Intensive simulations based on SPICE3 indicate that the proposed circuit can realise different activation functions including step, linear threshold, and sigmoid functions.
Abstract: In on-chip learning feedforward and feedback neural networks, different nonlinear activation functions are required. To date, these different functions are realised by physically changing the activation circuits. A novel CMOS analogue circuit suitable for modelling neurons with programmable activation functions is introduced. The proposed circuit is realised by optimising the second-order components of MOS transistors. Programmability of the activation function is achieved using an external controlling signal. Intensive simulations based on SPICE3 indicate that the proposed circuit can realise different activation functions including step, linear threshold, and sigmoid functions.
TL;DR: The structural and optoelectronic properties of intrinsic amorphous silicon (a-Si:H) and micro-crystalline silicon ( µc-Si-H) deposited using electron cyclotron resonance plasmaenhanced chemical vapor deposition (ECR-PECVD) with a microwave power of 150 W were studied as a function of the ECR source-to-substrate distance, d ss, process pressure, hydrogen dilution and substrate temperature.
Abstract: The structural and optoelectronic properties of intrinsic amorphous silicon (a-Si:H) and microcrystalline silicon ( µc-Si:H) deposited using electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD) with a microwave power of 150 W were studied as a function of the ECR source-to-substrate distance, d ss, process pressure, hydrogen dilution and substrate temperature. Hydrogen was used as the excitation gas and silane was injected into the main chamber. Deposition rates show a maximum as a function of the deposition pressure. For d ss=6 cm this maximum occurs between 5 and 10 mTorr. ECR-deposited a-Si:H films show a high Tauc bandgap (~1.9 eV), low dark conductivity (~10-11 Ω-1 cm-1), relatively high Urbach energy (≥55 meV) and high defect density (≥5×1015 cm-3) compared with a-Si:H grown by RF glow discharge. Hydrogen evolution and infrared spectroscopy reveal the presence of voids and/or columnar structure. The transition from amorphous to microcrystalline silicon occurs under conditions of high hydrogen dilution, low deposition pressure, and low d ss. The higher the hydrogen dilution, the lower the substrate temperature needed to achieve µc-Si:H. Raman spectra of the µc-Si:H suggest small grain size ( ~4 nm) and crystalline fraction (~60%). A growth model is proposed that includes silane excitation both by the ECR electrons and by the excited hydrogen species.
TL;DR: This work develops and analyse routing, multi-node broadcasting, single-node scattering and total exchange algorithms in the k-ary n-cube interconnection network that are optimal if one-port I/O communication.
TL;DR: In this article, the authors investigated the effect of ageing on the performance of an industrial steam reforming catalyst and found that the changes in the surface properties and the chemical content of the catalyst reduced the catalyst activity.
TL;DR: In this article, a procedure for solving the Navier-Stokes equations for the steady, one-dimensional flow of a binary water-based lubricant within an infinite breadth hydrodynamic journal bearing is described.
TL;DR: Most bacteria were isolated from the pelagic waters and oyster samples, and they were highest during the warmer months, while in seawater, coliforms were isolated in high numbers during September‐October at both sites.
Abstract: Concentrations of four bacterial groups namely coliforms, Vibrio cholerae, V. parahaemolyticus and Faecal streptococci in sea water and oyster (Pinctada radiata) were investigated from March 1991 to March 1992 at nearshore site and a pelagic site. In seawater, coliforms were isolated in high numbers during September‐October at both sites, while in oyster coliforms were higher than those in water all through the study period, with no definite pattern. Both V. cholerae and V. parahaemolyticus were present in seawater and oysters during the warmer months (June, July, September and October). In oysters, V. cholerae was more prominent than V. parahaemolyticus. Faecal streptococci were detected mainly in waters of both sites during September and October. Peak counts in oysters at both sites occurred in July; and they were five times greater at the pelagic site. In general, most bacteria were isolated from the pelagic waters and oyster samples, and they were highest during the warmer months. Some disappeared tot...
TL;DR: In this article, electrical conductivity and surface tension measurements on various surfactants, such as sodium caprylate, sodium laurate and sodium palmitate, were carried out in molten acetamide at 90 °C.
TL;DR: The average annual ratio was found to be 3.87% with a lowest value of 3.3% and a highest value of 4.35% in each year as discussed by the authors.
TL;DR: The synthesis of highly substituted cyclohexane derivatives has been carried out in a single one-pot reaction of aceteophenones and trans-dibenzoylethylene (1:2) using sodium ethoxide in anhydrous diethyl ether at room temperature to give 4-aroyl 2,3,5-tribenzoyl-1-phenylcyclohexanols.
TL;DR: In this paper, the authors proved a Korovkin type approximation theorem for positive linear operators on weighted spaces of continuous real-valued functions on a compact Hausdorff space X.
Abstract: We prove a Korovkin type approximation theorem for positive linear operators on weighted spaces of continuous real-valued functions on a compact Hausdorff space X . These spaces comprise a variety of subspaces of C ( X ) with suitable locally convex topologies and were introduced by Nachbin 1967 and Prolla 1977. Some early Korovkin type results on the weighted approximation of real-valued functions in one and several variables with a single weight function are due to Gadzhiev 1976 and 1980.
TL;DR: New block methods of order two and three for the numerical solution of initial value problems are derived such that low powers of the blocksize appear in the principal local truncation errors.
Abstract: New block methods of order two and three for the numerical solution of initial value problems are derived. The matrix coefficients of these methods are chosen such that low powers of the blocksize appear in the principal local truncation errors.
TL;DR: This paper shows the applicability of the SPICE circuit analysis computer program for studying the behaviour of multi-state desribed by Markov models by comparing those obtained by the Laplace transform and the flow graph methods.
TL;DR: The authors analyzes the problems associated with the renegotiation of debt contracts involving a bank (the lender) and a firm (the borrower) when the latter is operated by a risk averse manager.
Abstract: This paper analyzes the problems associated with the renegotiation of debt contracts involving a bank (the lender) and a firm (the borrower) when the latter is operated by a risk averse manager Firms undertake risky projects with loan capital borrowed from the bank When a firm cannot pay off a loan it is technically bankrupt Both the borrower and the lender may however experience a Pareto-improvement in their positions by renegotiating the loan By renegotiating the terms of the debt the financially distressed firm can avoid the stigmatization of bankruptcy and the bank can avoid the costs of seizing the borrower's assets However, our main finding is that, from the bank's point of view, renegotiating as a policy of recovering loan payments may be inefficient in practice because of false bankruptcy claims and moral hazard problems associated with exposure of the borrowing firm to the risk of default We present a solution to the false bankruptcy claim problem that involves a mixe d strategy between asset seizure by the bank and debt renegotiation
TL;DR: Karyological analysis was carried out on three separate populations of the Water Frog Rana cf.
Abstract: Karyological analysis was carried out on three separate populations of the Water Frog Rana cf. ridibunda from Bahrain, Saudi Arabia, and Egypt. Chromosome preparations made from bone marrow cells showed that the three populations possess a karyotype of 26 chromosomes. Variation in the relative arm lengths of the chromosomes 3, 5 and 11 among the three populations was recorded. No cytological evidence of sex dimorphism was recorded in the three populations. The present study failed to recognise any secondary constriction in the karyotypes of the three populations. The karyological studies do not indicate that the three populations belong to different species.
TL;DR: In this paper, a model is presented to predict the magnetization relaxation behavior below T c measured in NMR experiments on YBa 2 Cu 3 O 7 thin films, and the model provides evidence that vortex diffusion plays an important role in producing local magnetic field gradients which affect the line shapes of the NMR signals.
Abstract: A model is presented to predict the magnetization relaxation behavior below T c measured in NMR experiments on YBa 2 Cu 3 O 7 thin films. The model provides evidence that vortex diffusion plays an important role in producing local magnetic field gradients which affect the line shapes of the NMR signals. In the long time limit, the diffusion coefficient D of the local vortex lines as a function of the temperature takes the form D = e e − σ / T , where e and σ are constants. This form is remarkably consistent with that used to fit the measured data. This behavior of the vortex lines is expected in high temperature superconductors since the flux lines diffuse large distances helped by the large thermal energies and high anisotropy of these materials.
TL;DR: A time domain analysis of an optically controlled digital microstrip switch for microwave integrated circuits on Si substrates is studied and a new model for high-frequency pulse propagation on a microstrip optical switch for different optical parameters is presented.
Abstract: A time domain analysis of an optically controlled digital microstrip switch for microwave integrated circuits on Si substrates is studied A new model for high-frequency pulse propagation on a microstrip optical switch for different optical parameters is presented A frequency-dependent macromodel for a microstrip line with a gap is implemented in spice3, taking into consideration high-frequency pulse dispersion, conductor and dielectric losses, metallization thickness, gap length, and different optical parameters such as optical energy, surface recombination velocities, and diffusion of generated carriers In addition, the developed model has been used to optimize the switching frequency, gap length, level of optical power, and suitable substrate material parameters
TL;DR: In this paper, a four-fingered physically built robot hand is used to manipulate an object with a cooperative action of fingers using a Cartesian-based motion, where the hand dexterity measure based on individual finger measurements is used.