金川矿区深部巷道支护效果评价及参数优化研究

巷道支护问题一直是矿业工程中的难题,特别是在深部软岩巷道中,能否提供持久、有效的支护直接影响着矿山的安全生产和可持续发展。“双层网锚喷+U型钢拱架”联合支护是目前金川矿区在深部巷道支护中较常用的支护方案,为了解该方案的支护效果,在二矿区814 m分斜坡道上设立试验段,采用现场监测与数值模拟计算相结合的方法,对该试验段巷道的支护效果进行评价,并针对支护的薄弱部分提出改进措施。研究结果表明：（1）在当前支护条件下,巷道顶板和两帮围岩得到了较好的控制,但底鼓问题严重,最大位移可达110 cm;（2）针对当前支护方案的薄弱环节,提出增加锚杆长度、提高锚杆强度和增加底板支护等补强措施;（3）设计了一组参数优化方案,并对其支护效果进行了数值模拟分析,认为该优化支护方案能够有效地控制巷道围岩变形,并弥补原支护方案的缺陷。     

国外自升式悬臂梁钻井平台结构特点

系统阐述了悬臂梁底座自升式钻井平台的结构形式,并对比分析了各种悬臂梁结构形式的特点:常规悬臂梁形式应用普遍,制造水平要求低;X-Y型悬臂梁结构布置更为紧凑,覆盖范围广,但其应用专利保护,造价昂贵;旋转型悬臂梁及增强改进型悬臂梁结构形式复杂,对移动导轨及滑动块制造技术要求高,未获得广泛推广。对比了各种常规悬臂梁底座的三种滑移方式:棘爪滑移、销轴滑移及齿条滑移方案。其中,销轴步进推移的方式由于其结构简单、实现功能方便而被推崇。最后给出了当前悬臂梁选型的目标。     

草舍油田CO2驱采油井注缓蚀剂高效防腐技术

草舍油田泰州组油藏于1981年发现并投入开发,石油地质储量为142×104t,1990年8月转入注水开发阶段,水驱采收率24%,可采储量34.1×104t。该油藏于2005年7月开始气水交替注CO2驱油试验,至2011年12月,采油井日产CO2气量为12000m3,综合含水率为51%,CO2对井下套管、生产管柱及井下工具的腐蚀十分剧烈,必须加以解决。根据该油藏采油井高含CO2气体防腐的要求,复配出4种HS系列高效CO2缓蚀剂,通过室内实验,评价出HS-20型CO2高效缓蚀剂,并在现场CO2驱试验区采油井中添加,其浓度为50～200μL/L。采用油管内、外监测挂环监测油管腐蚀速率,结果表明,井下油管腐蚀速率仅为0.01～0.001mm/a,具有良好的防腐效果,满足CO2驱采油井的防腐要求,保证了采油井的正常生产。相比于其他防CO2腐蚀措施,本方法简便有效,可供国内其他油田CO2驱油时借鉴。     

Alginate hydrogel as a promising scaffold for dental-derived stem cells: an in vitro study

The objectives of this study were to: (1) develop an injectable and biodegradable scaffold based on oxidized alginate microbeads encapsulating periodontal ligament (PDLSCs) and gingival mesenchymal stem cells (GMSCs); and (2) investigate the stem cell viability, and osteogenic differentiation of the stem cells in vitro. Stem cells were encapsulated using alginate hydrogel. The stem cell viability, proliferation and differentiation to adipogenic and osteogenic tissues were studied. To investigate the expression of both adipogenesis and ontogenesis related genes, the RNA was extracted and RT-PCR was performed. The degradation behavior of hydrogel based on oxidized sodium alginate with different degrees of oxidation was studied in PBS at 37?°C as a function of time by monitoring the changes in weight loss. The swelling kinetics of alginate hydrogel was also investigated. The results showed that alginate is a promising candidate as a non-toxic scaffold for PDLSCs and GMSCs. It also has the ability to direct the differentiation of these stem cells to osteogenic and adipogenic tissues as compared to the control group in vitro. The encapsulated stem cells remained viable in vitro and both osteo-differentiated and adipo-differentiated after 4?weeks of culturing in the induction media. It was found that the degradation profile and swelling kinetics of alginate hydrogel strongly depends on the degree of oxidation showing its tunable chemistry and degradation rate. These findings demonstrate for the first time that immobilization of PDLSCs and GMSCs in the alginate microspheres provides a promising strategy for bone tissue engineering.     

Light and Electron Microscopy Studies of the Visible Diffusion Zone of Mild Steel Pack Cyanided in Processed Cassava Leaves

This study investigates the microstructure of the processed cassava leaves. Standard parts machined from low visible diffusion zone formed in low carbon steel pack cyanided using carbon steel were pack cyanided by high temperature in-situ diffusion of nascent carbon and nitrogen into austenite. Formation of a visible diffusion zone was confirmed after observation with a Reichert-Jung Polyval optical microscope coupled with Zeiss AxioCam ICc 1 camera. High magnification Scanning Electron Microscope （SEM） imaging of the visible diffusion zone was done with a CamScan Series 2 scanning electron microscope. The zone was found variable in depth as measured from a representative position. The structure of all samples consists of ferrite and pearlite as determined by optical and SEM examination. Resulting products were thus both tough and hard suitable for service environments requiring high resistance to both wear and impact failure.     

Teen driver crash risk and associations with smoking and drowsy driving

Motor vehicle crashes are the leading cause of death for young people in the United States. The goal of this study was to identify risk factor profiles of teen and young adult drivers involved in crashes. General demographic and behavioral as well as driving-related factors were considered. Analysis of a nationally representative telephone survey of U.S. young drivers ages 14 to 22 (N = 900) conducted in 2005 was restricted to 506 licensed drivers (learners excluded). Statistically significant univariate associations between factors of interest and the primary outcome, crash involvement (ever) as a driver, were identified and included within a multivariate logistic regression model, controlling for potential demographic confounders. Aside from length of licensure, only driving alone while drowsy and being a current smoker were associated with having been in a crash. Gaining a better understanding of these behaviors could enhance the development of more customized interventions for new drivers.     

Model development and validation of a solar cooling plant

This paper describes the dynamic model of a solar cooling plant that has been built for demonstration purposes using market-available technology and has been successfully operational since 2001. The plant uses hot water coming from a field of solar flat collectors which feed a single-effect absorption chiller of 35 kW nominal cooling capacity. The work includes model development based on first principles and model validation with a set of experiments carried out on the real plant. The simulation model has been done in a modular way, and can be adapted to other solar cooling-plants since the main modules (solar field, absorption machine, accumulators and auxiliary heater) can be easily replaced. This simulator is a powerful tool for solar cooling systems both during the design phase, when it can be used for component selection, and also for the development and testing of control strategies.     

Monodisperse droplet formation through a continuous jet break‐up using glass nozzles operated with piezoelectric pulsation

In this article, a glass nozzle driven by piezoceramics is used to experimentally study the continuous generation of a stream of monodisperse droplets from the breakup of a liquid jet. The approach is demonstrated by examining the breakup dynamics of three distinct liquids. The droplet formation process has been found to be highly controllable and reproducible. The dependence of nozzle performance on liquid properties, flow rate, and disturbance frequency has been investigated. The ratio between the actual disturbance frequency and Reynolds number, ω, is employed at first to represent the operating range that facilitates monodisperse droplet formation. Then, the dimensionless quantity ω*, obtained by multiplying ω by the viscous characteristic time, r/(μ/ρ), has been shown to collapse the data for the lower and higher bounds of the actual disturbance frequency ranges that secure monodispersity of the droplets of all the samples tested. The impacts of liquid flow rate and disturbance frequency on the monodisperse droplet size and spacing between two neighboring droplets have been investigated and discussed. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Numerical modeling of energy balance equations in quantum well AlxGa1-xAs/GaAs p-i-n photodiodes

The energy balance equations coupled with drift diffusion transport equations in heterojunction semiconductor devices are solved modeling hot electron effects in single quantum well p-i-n photodiodes. The transports across the heterojunction boundary and through quantum wells are modeled by thermionic emission theory. The simulation and experimental current-voltage characteristics of a single p-i-n GaAs/Al _xGa_1-xAs quantum well agree over a wide range of current and voltage, The GaAs/Al_xGa_1-xAs p-i-n structures with multi quantum wells are simulated and the dark current voltage characteristics, short circuit current, and open circuit voltage results are compared with the available experimental data, In agreement with the experimental data, simulated results show that by adding GaAs quantum wells to the conventional cell made of wider bandgap Al_x Ga_1-xAs, short circuit current is improved, but there is a loss of the voltage of the host cell, In the limit of radiative recombination, the maximum power point of an Al_0.35Ga_0.65As/GaAs p-i-n photodiode with 30-quantum-well periods is higher than the maximum power point of similar conventional bulk p-i-n cells made out of either host Al_0.35Ga_0.65As or bulk GaAs material     

±800kV特高压换流阀运行试验系统研发

根据特高压直流输电工程发展的需要,研发了6500A/50kV特高压换流阀运行试验系统。参照云广±800kV直流输电工程的系统设计,介绍特高压工程运行试验的预期参数和论述试验系统原理;依据IEC60700-1和GB/T20990.1高压直流输电换流阀电气试验标准,在新研发的运行试验系统上实现了能够满足特高压换流阀要求的全套运行试验项目。