Papers by Keyword: Rearrangement

Abstract: In view of the phenomenon that the curved duct in anchorage zone of cable-stayed bridges result in non-uniformity of each of steel strand, we analyzed the position change law of the prestressed steel strand in curved duct. Simulating real bridge design, a simple method was proposed to compute non-uniformity level of prestressed steel strand in the process of tensioning. Results showed that the rearrangement caused the additional length difference result in stress non-uniformity of each steel strand. Because each of steel strand cannot participate in force at the same time, the actual elongation value of the tendon is greater than theoretical value.

Abstract: Вefore the statement of the problem analysis of the financial , economic and ecological effectiveness of the implementation of the city target program management of construction and demolition waste (CDW) was necessary, which are based on the existing rules scientific and planning activities, to formulate and solve the problem of the establishment and adoption of standards (giving them status of legitimacy and obligation to fulfill) the whole range of parameters, evaluating CDW recycling activities (including foreign experience and national specificity).

Abstract: Reorganization processes is base of social development. In every field of knowledge necessary have and use adequate models proper process and so its components. Consider base model of cycle reorganization, intercommunications between its components and expediency use procedure «illumination» of cycle.

Abstract: Treatment of 3β-cholesteryl methanesulfonate with tetrabutylammonium halides in the presence of BF₃·Et₂O provides a mild and efficient method for the preparation of 3β-cholesteryl halides via i-steroid and retro-i-steroid rearrangements. The utilization of tetrabutylammonium halides avoided the moisture sensitivity and lowered the cost of reagents for the reported method based on trimethylsilyl halides.

Abstract: A twin boundary model was established to describe the multi-variant interface in the martensitic materials. The modified semi-implicit Fourier-spectral method was proposed to solve the 3-D phase-field equation. Self-accommodation plays an important role in the micro-structural evolution during the loading and unloading. The external compressive stress can cause the rearrangement of martensites from three variants to one variant. After releasing the loading, another variant can nucleate and grow in one variant at the twin boundary. Cyclic stress may lead to the redistribution of martensite variants besides the rearrangement.

Abstract: GaN nanopowders were synthesized by ammoniating pure Ga2O3 powders at 1000°C for different soaking time. The results show that the growth of GaN at this temperature is based on vapor-solid mechanism. The ammoniating reaction finished and the rearrangement process started when the soaking time is 0.5 h. When the soaking time is 1.5 h, the process of high-temperature aggradation transformed to thermal decomposition-re-crystallization process. Further increasing of soaking time, the fabricated GaN particles with large size aggregated by directional fixed nanorods are substituted by self-governed particles, which agglomerate as honeycomb. Photolumine- scence measurement (PL) test reveals that as prepared sample with 1.5 h possesses the best luminescent property.

Abstract: Understanding porosity coarsening is essential for controlling the properties of sintered materials and for producing high density or near net shape parts. As porosity is interconnected up to relative densities in excess of 80% or even 95%, measuring, monitoring and modelling of the growth of individual pores is relevant only at very high relative densities. This paper tries to convey two essentials of porosity coarsening: (i) characterization of the geometry of the pore space in the lower range of densities is possible by using stereological parameters, and (ii) coarsening of porosity takes place during all sintering stages by various mechanisms. Porosity coarsening has been reported in metals, ceramics and glasses. Recent and classical approaches, experimental results with two dimensional model arrangements as well as computer simulations of formation and opening of particle contacts are discussed. The effect of porosity dimensions on the properties of sintered materials and measures for preventing and provoking porosity coarsening are briefly addressed.

Abstract: Numerical modeling of sintering by continuum mechanical simulations is successfully applied today to predict e.g. the distortions developing during sintering. Several examples that demonstrate the possibilities of such simulations especially for industrial applications have been published recently. However, there are still open questions regarding the influence of grain rearrangement, crack formation and anisotropic starting configurations (e.g. due to prior compaction). By using the Discrete Element Method the sintering process can be investigated on a more fundamental mesoscopic scale. This method also considers effects due to particle rearrangement or anisotropic configurations as well as crack developments automatically. Their influence on various macroscopic properties like densification rate and viscosities is studied. Suggestions how to use these insights to improve existing continuum mechanical models are given.