北石顶驱WinCC趋势画面在故障分析中的应用

北石顶驱采用Win CC系统作为上位机监控系统,西门子S7-300型PLC作为控制器,通过Win CC与PLC之间的MPI通讯,实现了对顶驱参数的图形显示,实时监测,数据记录。在出现问题时,可以通过趋势画面查看数据记录,帮助分析问题。通过实例,介绍了如何分析趋势画面的数据,了解、判断顶驱出现的问题。     

Performance analysis of switch‐and‐stay combining in two‐way relay systems with analog network coding and time‐division broadcast protocols

In this paper, we consider switch‐and‐stay combining (SSC) in two‐way relay systems with two amplify‐and‐forward relays, one of which is activated to assist the information exchange between the two sources. The system operates in either analog network coding (ANC) protocol where the communication is only achieved with the help of the active relay or time‐division broadcast (TDBC) protocol where the direct link between two sources can be utilized to exploit more diversity gain. In both cases, we study the outage probability and bit error rate (BER) for Rayleigh fading channels. In particular, we derive closed‐form lower bounds for the outage probability and the average BER, which remain tight for different fading conditions. We also present asymptotic analysis for both the outage probability and the average BER at high signal‐to‐noise ratio. It is shown that SSC can achieve the full diversity order in two‐way relay systems for both ANC and TDBC protocols with proper switching thresholds. Copyright © 2014 John Wiley & Sons, Ltd.     

轮胎定型硫化机氮气硫化喷头角度设计与实验

轮胎氮气硫化工艺因节能效果显著而备受推崇,此项技术在国外已得到广泛应用。近年来,国内轮胎生产企业陆续投入资金进行轮胎氮气硫化工艺技术改造,逐渐淘汰传统、高能耗的过热水硫化工艺。本工作提出通过改变蒸汽进入轮胎型腔内部的喷射角度的设想,并进行试验验证,试图解决氮气硫化工艺轮胎上下胎侧温差大的问题。     

Locking‐free discontinuous finite elements for the upper bound yield design of thick plates

This work investigates the formulation of finite elements dedicated to the upper bound kinematic approach of yield design or limit analysis of Reissner–Mindlin thick plates in shear‐bending interaction. The main novelty of this paper is to take full advantage of the fundamental difference between limit analysis and elasticity problems as regards the class of admissible virtual velocity fields. In particular, it has been demonstrated for 2D plane stress, plane strain or 3D limit analysis problems that the use of discontinuous velocity fields presents a lot of advantages when seeking for accurate upper bound estimates. For this reason, discontinuous interpolations of the transverse velocity and the rotation fields for Reissner–Mindlin plates are proposed. The subsequent discrete minimization problem is formulated as a second‐order cone programming problem and is solved using the industrial software package MOSEK . A comprehensive study of the shear‐locking phenomenon is also conducted, and it is shown that discontinuous elements avoid such a phenomenon quite naturally whereas continuous elements cannot without any specific treatment. This particular aspect is confirmed through numerical examples on classical benchmark problems and the so‐obtained upper bound estimates are confronted to recently developed lower bound equilibrium finite elements for thick plates. Copyright © 2015 John Wiley & Sons, Ltd.     

铝型材分流模上模带凸台模坯的锻造

材料的选择和模坯的锻造对于铝型材挤压模具是十分重要和关键的。通过例子介绍了挤压模具中的分流模上模带凸台的模坯的锻造方法,包括材料的选择、工艺方案、锻造过程的控制及镦挤胎模的设计,同时介绍了锻件的后处理退火工艺。上模采用带凸台的锻件,提高了模具强度,同时又降低了成本。这些已经应用于实际生产中,并经实践证明是行之有效的。     

复合地层中盾构刀具磨损超前控制研究

通过分析国内土压平衡式盾构隧道典型工程案例,对上软下硬地层近年来的施工问题和采取的主要措施统计分析,总结出土压平衡盾构在上软下硬地层中施工关键问题及其规律。结合地层特性,针对滚刀磨损问题,提出评估上软下硬地层分布情况及盾构施工地质适应性问题的方法;同时,对盾构机掘进过程中的盾构推力、刀盘扭矩、贯入度变化监测统计,通过比推力及比扭矩指标变化实现对地质变化的预判,提出调整措施。结合实际工程,当盾构在上软下硬地层掘进时,通过评估地层分布,进行针对性的施工预判调整,能有效降低滚刀受冲击荷载的影响,避免盾构产生过快磨损,延长滚刀正常工作时的掘进距离,显著提高上软下硬地层中盾构施工效率。     

硫酸钠溶液腐蚀对固化态氯离子稳定性的影响

采用质量分数为5%的Na_2SO_4溶液浸泡内掺NaCl水泥净浆的方法,研究了水泥净浆中固化态氯离子数量的变化特征,并借助X射线衍射(XRD)、红外光谱(FTIR)和热分析(DTG)等测试技术对该条件下固化态氯离子的失稳机理进行分析.结果表明:固化态氯离子在Na_2SO_4溶液腐蚀环境下易失去稳定性,并重新转变为游离态;Na_2SO_4溶液中硫酸根离子与Friedel盐中氯离子的置换是Friedel盐分解的主要原因,置换过程中所形成的单硫型硫铝酸钙(AFm)转变为钙矾石(AFt),促进了二次AFt的形成;Na_2SO_4溶液腐蚀对Friedel盐的分解作用是混凝土内部固化态氯离子失稳的主要原因,其对C-S-H凝胶固化氯离子稳定性的影响并不显著.     

消防设备电源监控系统设计

对消防设备电源监控系统相关规范及标准进行分析及梳理,分析归纳消防设备电源、消防设备电源监控系统的定义及作用,结合某大型城市综合体工程,介绍消防设备电源监控系统的设置场所、范围、部位、布线等设计。     

改性沥青同步碎石上封层在 G109 线兰州段的应用

结合SBS改性沥青同步碎石在G109国道上的实际应用,得出SBS改性沥青同步碎石上封层可提高路面抵抗反射裂缝的能力,对路面裂缝、龟网裂有很好的修复作用,具备良好的防水性能和粘结性能,使路面抗滑,有施工速度快、成本支出小、施工简便等优点。     

一类新的能够渐进达到Gilbert-Varshamov界的Alternant子类码

本文基于Maximum Distance Separable(MDS)码的Hamming重量分布提出一类新的二元Alternant子类码.分析表明这类新的子类码包含整个BCH码类,并且可以渐进达到Gilbert-Varshamov(GV)界.