包埋法制备NiAl涂层NiCrW基高温合金的抗氧化性能

以CaCl₂为活化剂,采用包埋法在NiCrW基高温合金表面制备了NiAl涂层。采用X射线衍射、扫描电子显微镜和能谱仪对涂层表面和横截面进行了分析。结果表明,CaCl₂可以替代NH₄Cl,是一种有效的活化剂。在950 ℃下,通过4 h的包埋渗铝,制备出几乎为单相、厚度为30 μm的NiAl涂层,涂层与基体之间为富铬中间层。当包埋渗剂填充率小于100%时,NiAl层表面生成针状θ-Al₂O₃。在1000 ℃恒温空气氧化试验中,NiAl涂层开始时被高速氧化,然后逐渐变为缓慢氧化,完成了亚稳态针状θ-Al₂O₃向稳态不规则颗粒状α-Al₂O₃的转变,最终稳定的α-Al₂O₃为基体提供了良好的抗氧化保护。     

Influence of adding various rare earths on microstructures and corrosion resistance of chromizing coatings prepared via pack cementation on P110 steel

In order to improve the corrosion resistance and increase the service lifetime of P110 steel during operation,four chromizing coatings were formed onto its surface with/without addition of rare earths via pack cementation process.The surface morphologies and microstructures of the chromizing coatings were observed using scanning electron microscopy(SEM),and the phase constitutions were investigated by X-ray diffraction(XRD).Electrochemical corrosion behavior of the chromizing coatings in simulated oilfield ...     

基于SNMP网络性能管理的研究

网络管理软件设计的目的就是实现网络管理,国际标准化组织(ISO)定义了网络管理的5个功能域：失效管理、配置管理、安全管理、性能管理和计费管理。本文基于SNMP获取网络管理数据库中MIB-Ⅱ的对象信息,提出了网络性能管理的评定指标和计算方法,并对交换机上网络RMON模块进行了网络性能测试和理论分析,从而实现网络管理。     

自适应狼群算法优化ELM的模拟电路故障诊断

为了能够更加高效地检测和诊断模拟电路中的故障元件,提出了自适应狼群算法优化极限学习机的方法。该方法采用自适应遗传算法对特征参数进行选择,从而生成最优特征子集,然后利用最优特征子集构造样本输入极限学习机ELM网络对故障进行分类。针对极限学习机的输入层和隐含层之间的连接权值、隐含层的偏差都将会使其学习速度和分类正确率受到影响的问题,采用本文方法对它们进行优化并选择相应的最优值,提高了极限学习机网络训练的稳定性与故障诊断的成功率。通过2个典型模拟电路的诊断实例,给出了这些方法的具体实现过程,故障诊断率均在99%以上。仿真结果表明使用该方法进行模拟电路故障诊断时具有良好的正确率和稳定性。     

Coaxial damping series elastic actuator for improved performance of transmissibility

There are many flexible joint designs that are delivering torque and absorbing shocks simultaneously. One of the most active areas of the research is the Series Elastic Actuator (SEA), which connects the motor and load by lowering the stiffness. The problem, however, is that the non-rigid stiffness causes the system to have a lower bandwidth, thereby slowing down the system’s response. On the other hand, the high stiffness of SEA adversely affects energy efficiency and performance of impact relief. In other words, concerning the application of conventional SEAs, it is important to determine the joint stiffness. Therefore, other researchers have developed Variable Stiffness Actuators (VSAs) that can control the stiffness in the system. To improve further the controllability and transmissibility of SEAs, Variable Physical Damping Actuators (VPDAs) that can change the damping element of the system has been developed. Although previous studies have provided valuable findings, VSAs and VPDAs make the system complex so that complicated control theories are required. In this paper, a new Coaxial Damping SEA (CODSEA) that can efficiently adjust the stiffness and dynamic damping is designed. The biggest advantage of CODSEA is that it can change the stiffness and damping efficiently by converting the geometry of the driving shaft and particle materials inside the driving shaft without additional systems. In other words, only the driving shaft becomes the SEA and physical damping system.     

A graphical model for evaluating the status of series‐connected lithium‐ion battery pack

State evaluation of battery pack is essential for battery management but laborious when dealing with massive information of cells within the pack. A graphical model for evaluating the status of series‐connected Li‐ion battery pack is established to release the burden. The model is founded by a 2D diagram, with the electric quantity “E” and the capacity “Q” as its axes, therefore called by the “E‐Q diagram.” The new graphical diagram presents the dynamics of cell variations in a linear way, thereby benefiting the design and management of battery pack, including (1) quantifying the cell variations by region, (2) illustrating the evolution of cell variations during aging, (3) guiding the estimation of pack states considering algorithm error in cell states, and (4) solving the balancing problem. The experimental results conform to the theoretical analysis, indicating that the E‐Q diagram will be pervasively applied in the design and management of series‐connected battery pack. Moreover, the E‐Q diagram is suitable for education on the basics of a battery pack, because it is a graphical model.     

南京第二邮政枢纽生产主楼结构设计

在南京第二邮政枢纽生产主楼结构设计中,针对场地的地质特点,选用人工挖孔扩底灌注桩;对大面积软弱地基,采用了一种特别的换填法;根据结构单元大大超长的特点,计算了混凝土收缩和温度变化在结构内引起的内力,并在设计、施工和维护上采取了一系列措施;对由于室外回填土施工方案失误造成的地下室底板隆起开裂,采用袋装砂井与堆载联合法进行处理。上述做法效果良好,经济效益显著。     

锚网喷、钢带、锚索联合支护在装架站施工中的应用

中泰公司北井底装架站特点是断面大、服务年限长,为了保证其能长期为液压支架安装服务,为此采用锚网喷、W钢带、锚索联合支护。采用联合支护有效的控制了围岩,取得良好的效果。     

新型钻机动力头的研制

动力头是工程钻机的核心部件,钻机的回转驱动动力源、加压提升和压气排渣的枢纽。文章介绍该机构的关键问题解决方法和应用实际效果。     

Modeling the elution of organic chemicals from a melting homogeneous snow pack

Organic chemicals are often released in peak concentrations from melting snow packs. A simple, mechanistic snowmelt model was developed to simulate and predict the elution of organic substances from melting, homogeneous snow, as influenced by chemical properties and snow pack characteristics. The model calculates stepwise the chemical transport along with the melt water flow in a multi-layered snow pack, based on chemical equilibrium partitioning between the individual bulk snow phases. The model succeeds in reproducing the elution behavior of several organic contaminants observed in previously conducted cold room experiments. The model aided in identifying four different types of enrichment of organic substances during snowmelt. Water soluble substances experience peak releases early during a melt period (type 1), whereas chemicals that strongly sorb to particulate matter (PM) or snow grain surfaces elute at the end of melting (type 2). Substances that are somewhat water soluble and at the same time have a high affinity for snow grain surfaces may exhibit increasing concentrations in the melt water (type 3). Finally, elution sequences involving peak loads both at the beginning and the end of melting are simulated for chemicals that are partially dissolved in the aqueous melt water phase and partially sorbed to PM (type 4). The extent of type 1 enrichment mainly depends on the snow depth, whereby deeper snow generates more pronounced concentration peaks. PM influences the elution behavior of organic chemicals strongly because of the very large natural variability in the type and amount of particles present in snow. Urban and road-side snow rich in PM can generate type 2 concentration peaks at the end of the melt period for even relatively water soluble substances. From a clean, melting snow pack typical for remote regions, even fairly hydrophobic chemicals can be released in type 1 mode while being almost completely dissolved in the aqueous melt water phase. The model provides a mechanistic understanding of the processes that lead to chemical peak releases during snowmelt.