The kinetics of the oxidation of aluminum-zinc alloys in oxygen at high temperature

The oxidation behavior of high-purity aluminum-zinc alloys has been studied at temperatures from 475 to 575°C in dry oxygen at a pressure of 76 Torr. The oxidation product is duplex in nature consisting of both amorphous and crystalline -Al₂O₃. The crystalline -Al₂O₃ grows as roughly cylindrical crystals of constant thickness at any given temperature and alloy content; the crystals grow into the metal from the amorphous oxide-metal interface by inward diffusion of oxygen through the overlying amorphous film. The amorphous oxide film existing between the crystals of -Al₂O₃ grows with accurately parabolic kinetics throughout the temperature and alloy composition range. The amorphous oxide existing above the crystalline phase grows at a lower rate because of the additional resistance to cation diffusion conferred by the underlying crystalline phase. Increasing the zinc content of the alloy from 0.1 to 1.0% causes a reduction in the crystal nucleation density and an increase in the radial growth rate. The presence of Zn has no effect on the growth kinetics of the amorphous oxide between the crystals of -Al₂O₃.     

快速凝固Cu_(71)Cr_(29)合金的显微组织及性能

研究了氩气保护熔炼和单辊旋铸Cu_(71)Cr_(29)合金的显微组织和性能.结果表明,氩气保护熔炼Cu_(71)Cr_(29)合金的显微组织主要以初生的富Cr枝晶形式存在于Cu基体中,而单辊旋铸Cu_(71)Cr_(29)合金的显微组织呈现出球状富Cr相,且富Cr球的大小随着条带厚度的变化而变化,靠近自由面的富Cr球直径比接触面要大,分析表明合金快速凝固过程中发生了亚稳态的液相分离.与氩气保护熔炼Cu_(71)Cr_(29)合金相比,单辊旋铸Cu_(71)Cr_(29)合金的显微硬度增加了100%,主要是由于固溶度增加和晶粒细小的缘故.     

汽车自动变速系统的能源效益及可靠性

本文通过探讨汽车自动变速系统的工作流程,分析了如何提升汽车变速系统的可靠性及能源效率等问题.     

高含水稀油油藏蒸汽驱过程中原油组成性质的变化

在大庆葡Ⅰ组非均质砂岩油藏的葡71-75井区进行了稀油(地下粘度4.9 mPa.s)蒸汽驱试验。试验区水驱采出程度22.62%,综合含水82.87%,包含1口注入井和分属不同井网的7口采油井。取3口典型采油井,测定注汽前、注汽78天和120天时采出原油组成、性质的变化。结果表明,在汽驱过程中采出原油的密度、凝固点、含蜡、含胶质沥青质及运动粘度下降;初馏点显著降低(120℃→84℃→75℃),总馏量和300℃前各馏分量增多;50~90℃动力粘度在汽驱120天时最低,汽驱78天时略高于汽驱前;气油比增大;全烃分析表明汽驱后采出油轻质馏分增多,成熟度提高。基于前人关于蒸汽驱中产生热水蒸馏混合带的见解,利用所得分析测试数据,讨论了稀油蒸汽驱油机理:初期以热膨胀为主,中期为热膨胀、蒸汽蒸馏和降粘,后期为蒸汽蒸馏。图5表3参6。     

低剂量X射线全身照射诱导脾淋巴细胞内[Ca2+]i及CD71表达的适应性反应

为了观察低剂量X射线全身照射诱导脾淋巴细胞内[Ca2+]i及CD71表达的适应性反应.采用Fura-2负载,双波长荧光测定法检测细胞内[Ca2+]i浓度.采用单克隆抗体免疫荧光标记,流式细胞术检测淋巴细胞CD71表达.发现0.075Gy低剂量预照射能明显减轻其后2.0Gy攻击剂量照射对细胞内[Ca2+]i及CD71的抑制作用.低剂量辐射能诱导脾淋巴细胞[Ca2+]i及CD71表达的适应性反应.此变化可能是低剂量辐射诱导T淋巴细胞免疫适应性反应的重要机制之一.     

Corrigendum to “Exponential state estimation for recurrent neural networks with distributed delays” [Neurocomputing 71(1–3) (2007) 428–438]

In the letter [Neurocomputing 71(1–3) (2007) 428–438], there exists one minor error in computing the derivative of V₂((t)) and thus, the proof of Theorem 1 needs some improvement.     

也门69、71区块油气勘探前景展望

也门69、71区块为中原油田2004年通过选区评价在中东地区获得的新的油气勘探合同区块,它们分别位于也门境内富含油气的马里卜-夏布瓦盆地和塞云-马西拉盆地.初步的石油地质评价认为两区块内生、储、盖层及圈闭发育比较好,资源落实;区内钻井见良好油气显示,周边邻区均发现了规模较大的油气田或商业产层,因此两区块均具有较好的油气勘探前景.     

FANUC与华中HNC-21/22T系统G71指令格式和应用的区别

FANUC 0 i系统的数控车床和华中HNC-21/22T系统的数控车床都具有复合车削循环功能,能简化程序编制,但2种系统的指令使用时存在着不同,以示例方式介绍G71指令在编程格式、编程要求及应用上的不同。     

Depth of interaction detection for -ray imaging

A novel design for an inexpensive depth of interaction capable detector for γ-ray imaging has been developed. The design takes advantage of the strong correlation between the width of the scintillation light distribution in monolithic crystals and the interaction depth of γ-rays. We present in this work an inexpensive modification of the commonly used charge dividing circuits which enables the instantaneous and simultaneous computation of the second order moment of light distribution. This measure provides a good estimate for the depth of interaction and does not affect the determination of the position centroids and the energy release of γ-ray impact. The method has been tested with a detector consisting of a monolithic LSO block sized and a position-sensitive photomultiplier tube H8500 from Hamamatsu. The mean spatial resolution of the detector was found to be for the position centroids and for the DOI. The best spatial resolutions were observed at the center of the detector and yielded for the position centroids and for the DOI.