Measurement of the heat of fusion of titanium and a titanium alloy (90Ti-6Al-4V) by a microsecond-resolution transient technique

A microsecond-resolution pulse heating technique was used for the measurement of the heat of fusion of titanium and a titanium alloy (90Ti-6Al-4V). The method is based on rapid (50- to 100-s) resistive self-heating of the specimen by a high-current pulse from a capacitor discharge system and measuring, as functions of time, current through the specimen, voltage across the specimen, and radiance of the specimen. Melting of the specimen is manifested by a plateau in the measured radiance. The time integral of the net power absorbed by the specimen during melting yields the heat of fusion. The values obtained for heat of fusion were 272 J · g^–1 (13.0 kJ · mol^–1) for titanium and 286 J · g^–1 for the alloy 90Ti-6Al-4V, with an estimated maximum uncertainty of ±6% in each value.Paper presented at the Second Workshop on Subsecond Thermophysics, September 20–21, 1990, Torino, Italy.     

氧化钒制取碳化钒的热力学分析

采用热力学的方法对以五氧化二钒为原料制取碳化钒的工艺过程进行了分析,分析表明:钒氧化物的转化过程中遵守逐级还原理论。钒氧化物碳化过程中,不转化为金属钒,直接转化为碳化钒。在钒氧化物的转化过程中,应尽可能使其转化为二氧化钒。若采用气相还原碳化的方法,可通过调节气体的流量、配比、还原与碳化工艺参数进行质量控制。     

非故意发射超高次谐波发生机理及影响因素分析

随着接入电网的半导体器件开关频率的提高,换流器注入电网的谐波向着高频化方向延伸。超高次谐波是配电网电力电子化必然带来的电能质量新问题之一。本文针对非故意发射超高次谐波,从PWM脉宽调制的原理出发,分析了非故意发射超高次谐波产生原因及频率分布特征,并给出了一种能够反映超高次谐波典型特征的优选聚合频带方法,进一步分析了不同因素对超高次谐波发射的影响,为超高次谐波的检测与识别、相关标准的制定以及治理方法提供理论依据。     

Frequency band synthesis STAP-GMTI system architecture with the reciprocal transceiver

The reduction of the signal bandwidth and sampling frequency is conducive to the realization of antenna array thinness based on the micro system so as to improve the adaptability of the large aperture antenna on the ultra-high speed platform.However,the high-resolution range profile of the ground moving target is required for accurate tracking and recognition of the ground moving target.In order to solve this problem,a system architecture and processing method based on the low instantaneous bandwidth digital array of transceiver reciprocity is proposed,which can realize high resolution ground moving target display(GMTI) by frequency band synthesis.Because the array transceiver reciprocity can realize the coincidence of the equivalent phase center,the phase difference of the target deviated from the beam center does not need to be compensated in the process of bandwidth synthesis,and the precise synthesis of large bandwidth signals can be realized.After the synthesis of the wideband signal,the clutter is suppressed by space-time adaptive processing(STAP) to realize the detection of ground moving targets.Simulation results verify the correctness of the system architecture and processing method.     

V2O5/g⁃C3N4催化剂的制备及其模拟油中硫化物的脱除

以三聚氰胺、偏钒酸铵、硼酸为前驱体,通过煅烧法制备V₂O₅/g⁃C₃N₄催化剂。采用XRD、FT⁃IR、XPS、SEM和BET等技术对催化剂的结构与形貌进行表征。以V₂O₅/g⁃C₃N₄为催化剂,乙腈为萃取剂,H₂O₂为氧化剂对模拟油中二苯并噻吩（DBT）的脱除进行考察。探究了反应温度、催化剂质量、萃取剂体积、n(H₂O₂)/n(S)以及不同硫化物等因素对脱硫效果的影响。在模拟油体积为5.0 mL、萃取剂乙腈体积为3.0 mL、n(H₂O₂)/n(S)=8、催化剂质量为0.02 g、反应温度为30 ℃和反应时间为60 min的最佳条件下,DBT的脱除率达到91.9%,经过5次催化剂再生后脱硫率仍可以达到85.7%。     

基于剪切带扩展法的海底斜坡稳定性分析

简介剪切带扩展法（SBP）的原理及其在海底滑坡稳定性分析的应用;以舟山六横岛典型海底斜坡为分析案例,开展基于高斯函数的SBP和极限平衡法（LEM）斜坡稳定性对比分析研究;进行SBP输入参数对剪切带扩展系数R的敏感度分析. 研究结果显示,对于斜坡剪切带破坏长度,当剪切带扩展系数R不大于1时,LEM与SBP得到的滑坡滑裂面区域一致,当R大于1时,SBP计算得到的最终滑动区域比LEM计算得到的区域大;在斜坡发生滑动破坏区域SBP比LEM计算得到的安全系数低;地震影响因素和土体特征位移对R的影响较大.     

3Cr2W8V钢强韧化处理研究

本文从强韧化机制方面，研究了用于铝合金型材挤压模具的３Ｃｒ２Ｗ８Ｖ钢在不同热处理工艺条件下的金相组织，显微结构与断口，常温与高温下的力学性能。结果表明，采用１２５０℃以上超高温淬火加４００－５００℃中温回火的强韧化处理工艺，可使该钢同时获得具有良好力学性能和较好韧性、热强性、热稳定性、热疲劳性、耐磨性等相结合的综合性能。     

CYCLIC DEFORMATION BEHAVIOUR OF Cu SINGLE CRYSTALS ORIENTED FORDOUBLE SLIP Ⅱ. Persistent Slip Bands and Deformation Bands

用光学显微镜和扫描电镜研究了双滑移取向（［０３４］，［１１７］）Ｃｕ单晶循环饱和后的表面形貌，塑性分切应变幅（γｐｌ）低于１０~（－３）时，［０３４］晶体表面上要为主滑移系的驻留滑移带（ＰＳＢｓ）占据，次滑移只在边缘区域启动，其ＰＳＢｓ细窄（＜１μｍ），体积百分数在１％以下．γｐｌ＞１０~（－３）时，次滑移开始在试样的中部启动，同时，表面出现二种贯穿晶体的宏观形变带（ＤＢＩ，ＤＢＩＩ），滑移带在形变带内集中．［１１７］晶体在γｐｌ＝４．４×１０~（－４）时，双滑移现象已十分明显．γｐｌ＞１０~（－３）时，表面也形成与前者相似的形变带．ＤＢＩ的惯习面与主滑移面平行（［０３４］晶体）或接近（［１１７］晶体），ＤＢＩＩ的惯习面则与前者垂直，文章讨论了形变带形成的可能原因．     

水轮机下环铸件凝固过程热应力模拟分析

采用数值模拟方法对水轮机下环铸件凝固过程中的应力场进行了模拟和分析。模拟中采用接触单元法处理铸件与砂芯之间力的作用,改进了传统的铸件/铸型边界条件处理方法。文中重点分析了下环凝固过程中准固相区的受力情况,根据准固相区受力特点建立了适当的热裂判据,对下环凝固过程热裂倾向性进行预测。实际生产结果与预测结果相符合。     

巨型水轮发电机组高可靠性电源冗余控制技术应用与研究

针对某巨型水电站巨型水轮发电机组电气盘柜DC 24V电源冗余控制系统,通过对不同种类DC 24V电源冗余控制方式及电气元件性能的分析,研究一种适用于巨型水电机组电气盘柜各类工况、电气元件表现良好、稳定、可靠且利于维护的DC 24V电源冗余供电控制系统,并将研究成果应用于现场设备.