Texture formation in the cold rolling of pseudo-alloys

The formation of metallographic and crystallographic textures and the properties of the composite materials W - Cu, W - Ni - Fe, and Ag - Ni with a metal matrix were studied after 5–85% squcezing by rolling. It was established that crystallographic texture tended to be suppressed by the localization of deformation and formation of cracks along interfaces, the type of which, as well as the character of the structure-sensitive properties depended on the nature of the material and its processing history. Translated from Poroshkovaya Metallurgiya, Nos. 1–2(411), pp. 88–96, January–February, 2000.     

Phase behavior of gelatin in the presence of pectin in water-acid medium

Summary Phase separation of alkaline gelatin in water-acid solutions in the presence of low etherified pectin (ED 38%) were investigated. The effects of the pectin weight fraction in pectin/gelatin mixture (q_o) as well as two conditions of complex formation, namely, mixing of the binary biopolymer-solvent systems at pH 3.5 (‘mixing conditions’), or preparation of the ternary gelatin-pectin-water systems at pH 7.5 and their subsequent acidification up to pH 3.5 (‘titration conditions’), on phase equilibrium and macrostructure of the concentrated complex phase were established using phase analysis, and optical microscopy. At q_o<0.5 the aggregative phase separation was observed in both conditions of complex formation leading to the almost complete concentration of both biopolymers in the bottom phase at q_o=0.3 (‘mixing conditions’) and at q_o=0.5 (‘titration conditions’). At q_o>0.5 unusual three phase separation took place in the ‘mixing conditions’, leading to formation of supernatant (phase 1), complex coacervate (phase 2) and concentrated pectin solution (phase 3). Possible mechanism of such phenomenon was discussed in term of segregative and aggregative phase separations.     

Thermal analysis and solidification pathways of Mg–Al–Ca system alloys

Mg–Al–Ca alloys are creep resistant magnesium alloys with high application potentials. The solidification pathways and microstructure formation in this alloy system are still under discussion. In this paper, the solidification behavior of AZ91 and AM50 with Ca addition (AZC91x and AMC50x alloys) was investigated by a computer-aided cooling curve analysis (CA-CCA) system. Microstructure and phase identification were carried out by SEM and EDX analysis. The results show that the Ca-containing phase formation mainly depends on Ca content and Ca/Al ratio. With increasing the Ca/Al ratio these phases transform from Al₂Ca to (Mg, Al)₂Ca and Mg₂Ca. Moreover, Ca addition decreases the liquidus temperature of Mg–Al alloys, but influences the solidus temperature in a more complex way. Increasing the Ca content also decreases the solid fraction at which dendrite coherency occurs. The relationship between solidification interval, dendrite coherency point, formation of Ca-containing phases and hot tearing is also discussed.     

Application of ultrasonic treating to degassing of metal ingots

The relations between porosity in the ingot and the effecting factors such as the ultrasonic power and the time of ultrasonic vibration (UV) treating to melt were investigated. Moreover, the mechanism of the porosity formation and the prevention method was studied. The results indicate that the effect of degasification was better when the intensity of UV is above threshold value. On the contrary, the intensity of UV below the value resulted in the increase of the gas content in the ingot and the decrease of density. It could be confirmed that there is an appropriate time on degasification by UV treating. When treating time is over the time, the density of the ingot tended to decrease. By using UV to degas with constraint cooling in the bottom of the ingot, the value of porosity volume (PV) can be decreased below 0.1 cm³/100 g and the η_deg is near to 97%.     

A clustering approach for minimizing intercell trips in cell formation

Excessive intercell trips in a cellular manufacturing system may minimize the benefits that the system can provide. Hence, this research develops a non-linear integer formula to reduce intercell trips in a cell type system design. A clustering algorithm is then developed to obtain a satisfactory solution to the proposed cell formulation problem. To determine the performance of the proposed clustering algorithm, comparisons are made with an Exhaustive Search (ES) algorithm to show the relative optimality.     

Ultra-stability of gas hydrates at 1 atm and 268.2 K

This paper details creation of methane sI hydrates that are much more stable at 1 atm and 268.2 K than any previously reported. Extraordinarily stable natural gas sII hydrates at 1 atm and 268.2-270.2 K are reported for the first time. Test innovations that achieved ultra-stabilities give insight into hydrate self-preservation mechanisms. Water-surfactant liquid solutions were used to nucleate hydrate crystals that adsorbed as extremely small particles on surfaces of high thermal conductivity. The small hydrate particles packed and consolidated symmetrically upon Al or Cu cylindrical surfaces, minimizing internal void spaces and fractures in the accumulated 250-400 g hydrate mass. Resulting hydrate stability window is 268.2-270.2 K at 1 atm. Methane sI, as well as natural gas sII, hydrates exhibit only minimal decomposition upon reducing confining system pressure to 1 atm in the 268.2-270.2 K stability window. Total gas that evolved after 24 h at 1 atm in the stability window typically amounted to less than 0.5% of originally stored gas, and this ultra-stability was shown to persist when the test was allowed to run 256 h before terminating. The entire methane sI or natural gas sII hydrate mass remains stable during pressure reduction to 1 atm, whereas previous reports defined hydrate anomalous stability for only about 50% of fractional hydrate remnants.     

Crack patterns in brittle thin films

The physical system studied is a brittle elastic film bonded to an elastic substrate with different elastic properties; a residual tensile stress is presumed to exist in the film. The focus of the study is the influence of the mismatch in elastic properties on patterns of crack formation in the film. The stress intensity factor and crack driving force for growth of a periodic array of cracks in the direction normal to the interface under two-dimensional conditions are determined for any crack depth and any mismatch in elastic parameters. It is found that, even for a relatively stiff film material, the stress intensity factor of each crack as a function of crack depth exhibits a local maximum. The driving force for crack extension in the direction parallel to the interface is then determined on the basis of these two-dimensional results, and the equilibrium spacing of crack arrays is estimated for given residual stress. The results of the calculations are used as a basis for qualitative arguments to explain the crack patterns which have been observed in GaN films on Si substrates.     

基于电缆地层测试的储层产能预测方法研究

通过对电缆地层压力测试资料和采集流体样品的PVT组分分析,提出了电缆地层测试储层产能预测的方法,为部分替代DST测试提供了理论基础。首先,利用曲线拟合方法精确求取地层有效渗透率和表皮系数等产能参数;利用采集流体样品的PVT组分分析,确定原油黏度、体积系数和溶解气油比等流体参数,结合电缆地层测试的产能方程,从而计算出储层的采油指数(PI)或单层日产量。     

天然气成藏过程的地球化学示踪研究现状

天然气成藏过程的地球化学示踪研究,即利用天然气残留的地球化学信息,反演其生成、运移、聚集和保存的动态过程,以确定其来源、资源前景和分布规律,并提供有利的勘探目标.通过数十年的研究,中外地球化学家提出了多种类型的示踪指标,并对各类指标在天然气生成、运移、聚集及保存等成藏过程中的行为有了一定的认识:天然气烷烃组分、稳定同位素、轻烃及稀有气体是天然气源对比、重塑运聚成藏过程的有效指标,它们共同构成了天然气成藏示踪的指标体系;初步揭示了天然气组分组成、同位素组成等指标在不同阶段成藏的动力学变化规律,成为利用指标重塑天然气成藏过程的依据.在总结已有成果的基础上,结合目前研究中与地质背景结合少、机理与定量化研究程度低、混源成藏及散失过程研究薄弱等问题,认为天然气成藏过程的地球化学示踪应加强地质条件分析、物理模拟与数理模型建立、混源成藏及散失过程示踪方面的研究.     

Loss of the thalamic nuclei for "head direction" impairs performance on spatial memory tasks in rats.

This study sought to characterize the effects of removing the nuclei of primary importance in relaying the thalamic head direction signal to the hippocampal formation (the anterior dorsal [AD] and lateral dorsal [LD] nuclei) on the performance of a variety of spatial and nonspatial tasks. The results indicate that combined excitotoxic lesions of the AD and LD nuclei produce marked deficits on a variety of spatial tasks. These tasks included T-maze alternation and the ability to locate a hidden platform set at a fixed distance and fixed direction from a beacon in a Morris water maze. Although object recognition appeared unaffected, marked impairments were found in the ability to detect when an object was placed in a novel position (object-in-place memory). (PsycINFO Database Record (c) 2010 APA, all rights reserved)