COMPUTER SIMULATION OF EARLY STAGE OF DISLOCATION STRUCTURES IN A FATIGUED COPPER SINGLE CRYSTAL

The dislocation evolution wassimulated by using positiveand negative parallelstraightedgedislocationsrandomly distributing on the primary slip planes astheinitialconditions. Thevein and wallstructuresof dynamicequilibrium have been obtained. Abig dipolestructure wasfound inthesimulation.

Computer simulation of strain-induced morphological transformation of coherent precipitates

The coherent elastic strain-induced morphological transformation of a binarycubic model alloy was simulated with different strain energy parameters. The microscopic diffusionequation was combined with the theory of microscopic elasticity. The results show that when thestrain energy is neglected, the randomly distributed equiaxed particles are obtained with isotropiccharacteristic. It is coarsening that follows the Ostwald ripening mechanism: smaller particlesdwindle and larger particles grow; when the elastic strain is considered, plate precipitates tend toalign along the elastically soft directions <01> with anisotropic characteristic. The particlesgrow in the soft directions and coarsen further; particles dwindle in out of the soft directions.While the coarsening of the particles localized in the same row or column follows the rule: smallerparticles shrink and larger ones grow.

Dynamic response to road roughness on a tractor-semitrailer system with driver body model

A linear mass-spring system model of a tractor-semitrailer together withdriver body parts and sprung seat is presented. Natural frequencies of the system are calculated andresponse of components in the system to road roughness is completed by means of computer simulationand power spectral density (PSD) approach in all of road conditions and loading cases. The resultsshow that the severest situation of response of the system occurs when the road in rough conditionand vehicle unladen. The most sensitive frequency to human body parts is around 0.9 Hz, and modeltypes of a human body seem to be not significant to the response of a heavy tractor-semitrailersystem, including to the response of the driver himself.

Quiet environment： Acoustics of vertical green wall systems of the Islamic urban form

The development of sustainability has made the application of green concepts to cityscapes and urban design mandatory and has popularized the installation of vegetation on external street walls. Introducing greenery on external building elements is beneficial to the environment, reducing the heat impact experienced in ＂urban heat islands＂ and enhancing an area＇s visual effect. The popularity of such green systems has necessitated the assessment of their acoustic characteristics and their impact on long-distance noise propagation. These effects become important in hot climates, where the topology of the dense urban texture gives building walls larger areas than exposed streets, thereby amplifying the effects of the former＇s acoustic characteristics on noise levels. Considering the resultant sound level at a particular location between buildings as the contribution of several remote sources, a simplified computer model based on energy exchange is developed in this study. Owing to the complexity of the urban landscape, buildings are assumed to be an array of rectangular blocks. The computer model is used to investigate the effects of the installation of street vertical ve^letation on long-distance noise propagation, as well as those of the geometric parameters of the dense Islamic urban texture on the resultant noise levels.

A parametric investigation of the acoustical performance of contemporary mosques

Acoustics is an important factor in mosque prayer halls that had not been given extensive concern during the architectural design stages. Eventually, the importance of speech intelligibility became more important, given the integration of other activities into the prayer halls, such as the holy Quran recitation, speeches, and lectures. Early attempts have been made to control the propagation of sound and to maintain good acoustic quality within the prayer spaces. Architects during the conceptual design stage had barely paid attention to the design issues that affect the acoustic environment inside the prayer zones, which is either due to lack of time during the project development or, in most cases, a lack of simple design guidelines to overcome any drastic acoustical defects arising from the incorrect design, shape, or material selection. The basic guidelines for designers to select the appropriate shape, geometry, size, and finishing materials are an essential design tool. This work examines the three common design topologies of mosques, which differ in size, shape, and finishing materials. In this study, a geometric and material parametric analysis was conducted based on the shape, surface area, volume, and finishing materials of each of the three designs. For the geometric acoustics, a computer model employing the ray tracing theory was employed to investigate the three configurations. Different acoustic treatments were tested relative to the geometric disposition of each design. Finally, basic recommendations and design guidelines were presented.