International Journal of Engineering
Volume:12 Issue: 1, Feb 1999

An experiment investigating the elastic local buckling response of trough girders composed of thin profiled steel sheeting has been undertaken Beam tests were performed to promote initial local buckling in a region of constant moment in the elastic range of structural response. The results of the experiments were compared with an elastic complex semi-analytical finite strip method of analysis, and acceptable correlation was obtained. The post-local buckling behavior was monitored in the experiments, and this response showed good agreement with a nonlinear finite strip method developed elsewhere.

A numerical solution for heave prediction is developed within the context theories for both saturated and unsaturated soil behaviors. Basically, lowering the potential level of compressing on a saturated layer will cause heaving due to water absorption. This water absorption is in an opposite way, similar to water dissipation as what happens during unloading in consolidation process. However, in unsaturated layers any change of the stability of potential energy level wilt cause the tendency of change in particle interconnection forces. So, any change by either distressing or the variation of moisture ratio will lead to soil heave. In this paper a finite element solution is employed for predicting the heave in saturated soil similar to unloading in consolidation. Also, in the case of unsaturated soil, equivalent soil suction as negative pore water pressures is applied to soil elements as equivalent nodal forces. To show the potential of this method, test results were compared with those obtained from computations. These comparisons show that the presented method is capable of predicting the heave phenomenon quite well.

This paper reports a study on a single server queue with bulk arrival and bulk service patterns wherein the incoming traffic depends on the state of the server which may be in operating or breakdown state. The repair of the breakdown server is performed in two phases. The operating duration of server, repair duration of both phases of repairing as well as job''s inter-arrival times and service times are exponentially distributed. By using generating function approach, the transient analysis for the queue size distribution has been carried out. For steady state, the stability condition and average queue length for various states have been derived. By taking a numerical illustration, the effect of various parameters on the average queue length has been depicted graphically.

A new gamma camera based on hydrogenated amorphous silicon (a-Si:H) pixel arrays to be used in nuclear medicine is introduced. Various performance characteristics of a-Si:H imagers are reviewed and compared with those of currently used equipment. An important component in the a-Si:H imager is the scintillator screen. A new approach for fabrication of high resolution CsI(Tl) scintillator layers, appropriate for coupling with a-Si:H arrays, are presented. Using Monte Carlo Simulation, the performance of the new a-Si:H based gamma camera is evaluated.

The theory presented in this paper differs from previous ones in that no arbitrary loop shape is assumed. Rather a strophoid curve, that is similar to knitted fabric Loop shape, has been assumed as the basic mathematical function. Additionally, the theory is improved by adapting buckled elastic rod theory, leading to a new equation from a certain mathematical curve. This loop model is assumed to be two- dimensional initially, but is applicable to three-dimensional analysis as well. The geometry of the fabric structure is obtained from these models. The results show good agreement between the theoretical and experimental suggestions reported by other scholars.

The range distributions of low-energy nitrogen and oxygen (2-3 keV) ions is silicon are measured and compared with these available in theories. The nitrogen distribution is very close to a Gaussian distribution as predicted by theory. The oxygen profile however, indicates a surface localized peak along with a shoulder and a long tail into the sample. The surface peak is beleived to he the result of radiation induced segregation and the position of the shoulder corresponds to the peak of the theoretical distribution, The peak position in both profiles is very close to those obtained from the theories.

This paper surveys the literature of the brushless DC motor speed control techniques. The paper should prove useful to both researchers as well as practising engineers as a signpost to the current state of the art. Based on the review some further studies are suggested.