Critical evaluation of the thermodynamic properties of cobalt

The thermodynamic properties and the pressure-temperature phase diagram of Co have been evaluated from experimental information using thermodynamic models for the Gibbs energy of the various phases. For hcp and fcc Co the model describes the magnetic contribution to the molar volume, expansivity, and compressibility and the efect of pressure upon the Curie temperature. Experimental data of many different types are satisfactorily described by the evaluated model parameters.This work was supported by the Swedish Board for Technical Development, and by Sandvik Hard Materials, Stockholm, Sweden.     

Evaluating Alloy Composition Using The Gibbs Triangle

Ingot quality is characterized by SPC evaluations; meaning Structure (S), Property (P), and Composition (C). Structure-property studies are classified as “sensitive” attributes while composition is considered to be an “insensitive” parameter. For example, it is common to hear the phrase that global composition is “insensitive” to structure and property values. For superalloys, structural analyses are applied using the scanning electron microscope (SEM) to determine both size, shape and distribution effects for the gamma prime phase. Examination of properties requires mechanical tests for strength, hardness, toughness and, so forth. However, for investigations on composition, the scientific community still depends on optical emission spectroscopy (OES) for measurements of global results using arc burns to represent bulk volume. This leads to the obvious question…. What needs to be done to better quantify the OES results? Further…. How can the controlling microconstituents of a superalloy be better related to the overall composition results for an improved qualification of ingots? This article addresses these needs and priorities. And, the said article is offered as a contribution to the sum of total knowledge.     

The effects of air pollution and climatic factors on atmospheric corrosion of marble under field exposure

The atmospheric corrosion of marble was evaluated in terms of SO₂ concentration as air pollution and climatic factors such as rainfall, relative humidity, temperature and so on under the field exposure. Marble of calcite type (CaCO₃) was exposed to outdoor atmospheric environment with and without a rain shelter at four test sites in the southern part of Vietnam for 3-month, 1- and 2-year periods from July 2001 to September 2003. The thickness loss of marble was investigated gravimetrically. X-ray diffraction and X-ray fluorescent methods were applied to study corrosion products on marble. The corrosion product of marble was only gypsum (CaSO₄ · 2H₂O) and was washed out by rain under the unsheltered exposure condition. It was found that the most substantial factors influencing the corrosion of marble were rainfall, SO₂ concentration in the air and relative humidity. Based on the results obtained, we estimated the dose-response functions for the atmospheric corrosion of marble in the southern part of Vietnam.     

深部动压巷道非对称变形力学机制及控制对策

为解决深部动压巷道支护的技术难题,以鹤煤九矿东总回风巷为研究背景,针对东总回风巷非对称变形量大且难支护的问题,采用现场调研、工程地质分析、物理相似模拟和现场试验相结合的方法,对巷道变形破坏机理和控制对策进行了研究。研究结果表明:巷道变形破坏受围岩岩性、构造应力、采动应力、重力、地质构造等多种因素影响,其变形力学机制确定为IABIIABDIIIABC型;采动应力造成巷道围岩应力场的大小和方向发生了改变,是巷道产生非对称变形的主要因素。通过选取针对性的控制对策将复合型变形力学机制转化为单一型,提出了"锚网索喷+底角锚杆+全断面注浆+反底拱"非对称耦合控制对策,并在现场进行了应用。相似模拟和现场监测结果显示:该控制对策有效控制了围岩非对称变形,现场应用效果良好。     

爆生气体对邻近硐室背爆侧预制裂纹影响机理

采用动态焦散线实验方法,研究爆炸荷载作用下邻近硐室背爆侧裂纹扩展规律时发现,伴随爆生气体释放出现的弧线型应力集中区是爆生气体引起的主应力差峰值位置,与背爆侧裂纹的扩展有较大的关联。实验研究表明:炸药爆炸后,产生的应力波首先作用于硐室背爆侧裂纹,随后爆生气体产生的准静态应力作用于裂纹,对裂纹的扩展起主要作用,而卸载波主要作用于裂纹扩展后期,使裂纹出现翘曲现象。当弧线型应力集中区接近扩展中的裂纹时,裂纹扩展速度达到峰值,约等于弧线型应力集中区的移动速度,之后,裂纹尖端与弧线型应力集中区的相对距离基本不变,当该应力集中区越过裂纹尖端,裂纹扩展速度逐渐减小,最终止裂。裂纹尖端动态应力强度因子与裂纹扩展速度具有相似的变化规律,峰值动态应力强度因子出现在弧线型应力集中区越过裂纹尖端之前。基于该发现进行的研究证实了爆生气体对邻近巷道裂纹扩展的主导作用,深化了爆炸荷载对邻近巷道影响机理的研究。     

地下煤火土壤典型重金属分布特征

通过采集乌鲁木齐大泉湖火区土壤样及实验室测定,研究了火区土壤理化性质与重金属Hg,As,Cu,Pb,Cr,Zn,Ni空间分布特征。结果表明:温度正常区土壤温度随采样深度增加的幅度较温度异常区小;温度正常、温度异常区土壤有机质含量随深度的增加均减少,温度正常区I,II,III,IV层土壤有机质含量大于温度异常区相应土层有机质含量;温度异常区土壤层I重金属Cu,Pb,Cr,Zn,Ni含量均小于温度正常区土壤层I相应重金属含量,II层则有增加的趋势并大于温度正常区相应土层重金属含量;温度正常区、温度异常区土壤Hg,As,Cu,Ni重金属含量随深度变化幅度及波动幅度较小,而温度异常区土壤Pb,Cr,Zn重金属含量随深度变化波动幅度较温度正常区大;火区热效应、地形、土壤及气象因子是影响土壤重金属分布的主要原因。土壤典型重金属砷形态分析表明:残留态砷含量最高,水溶态砷含量最低;水溶态砷在火区取样区域内I,II,III,IV土壤层区域富集特征与各层土壤碳酸钙富集特征趋于一致;温度正常区土壤残留态砷、铁形砷含量随深度变化的趋势与土壤碳酸钙含量随深度变化趋势一致;温度异常区残留态砷含量随深度增加波动趋势与土壤有机质含量波动趋势有较强关联性;温度正常区、温度异常区均值水溶态砷含量基本稳定,表明其与温度、土壤特性等无明显相关性。     

1.25～3.125 Gb/s连续数据速率CDR设计

设计了一款工作速率为1.25～3.125 Gb/s的连续可调时钟数据恢复(CDR)电路,可以满足多种通信标准的设计需求.CDR采用相位插值型双环路结构,使系统可以根据应用需求对抖动抑制和相位跟踪能力独立进行优化.针对低功耗和低噪声的需求,提出一种新型半速率采样判决电路,利用电流共享和节点电容充放电技术,数据速率为3.125 Gb/s时,仅需要消耗50 μA电流.芯片采用0.13 μm工艺流片验证,面积0.42 m㎡,功耗98 mw,测试结果表明,时钟数据恢复电路接收PRBS7序列时,误码率小于10-12.     

Numerical simulation and experimental research on the wheel brush sampling process of an asteroid sampler

To examine the environmental characteristics of the microgravity force and the weathered layer on an asteroid surface, a symmetric wheel brush asteroid sampler is proposed for the collection of particles on the asteroid surface. To study the influence of the wheel brush rotation speed on the sampling efficiency and the driving torque required for the wheel brush, the contact dynamics model between particles and sampling wheel brushes is established and a simulation and experimental verification of the sampling process are conducted. The parameter calibration of the sampled particles is studied first, and the calibrated particle parameters are used in the numerical simulation of the sampling process. The sampling results and the particle stream curves are obtained for the working conditions of different rotation speeds, and the effects of different parameter settings on the sampling efficiency are analyzed. In addition, a set of rotating symmetrical sampling wheel brush devices is built for the ground test, and the dynamic torque sensor is used to test the torque change of the wheel brush during the sampling process. The relationship between the speed of the wheel brush and the driving torque of the wheel brush motor is determined by comparing the simulation results with the test results. Results indicate that when the rotating speed of the wheel brush is faster, the sampling efficiency is higher, and the driving torque required for the sampling wheel brush is greater. Moreover, a numerical simulation analysis of the sampling process of the wheel brush sampler in a microgravity environment is conducted to determine the optimal speed condition, and the brushing test of the wheel brush sampler in the microgravity environment is verified with the drop tower method. This research proposes the structural optimization design and motor selection of a wheel brush asteroid sampler, which provides important reference value and engineering significance.