滚石碰撞冲击数值模拟分析

随着山区道路与隧道的发展与广泛应用,隧道进出口上部岩体发生掉块、落石的情形时有发生。该类落石对隧道进出口与道路安全的影响日益成为严重安全问题。然后现有关于落石冲击的研究中,冲击计算主要以半经验半理论为主,然而各类算法的适宜性、合理性一直未能得到充分验证。文中通过理论分析结合三维数值模拟对落石的冲击力算法及其落石尺寸、自由落高和缓冲土层厚度等指标的相关性进行了研究,得到了关于落石冲击力计算的有益结果。     

Catalytic Combustion of Lean Methane Assisted by Electric Field over Pd/Co<Subscript>3</Subscript>O<Subscript>4</Subscript> Catalysts at Low Temperature

A series of Pd/Co₃O₄ catalysts were prepared by Self-Propagating High-Temperature Synthesis (SHS) method in this study, and electric field was applied for catalytic combustion of lean methane over Pd/Co₃O₄ catalysts at low temperature. When electric field was applied, the catalytic combustion performance of Pd/Co₃O₄ catalysts was greatly improved, and the application of electric field could reduce the load of active element Pd to some extent while maintaining the same efficiency. Based on experimental tests and the analysis results of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), H₂-temperature-programmed reduction (H₂-TPR) and in-situ diffuse reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS), the mechanism of catalytic oxidation of CH₄ over Pd/Co₃O₄ catalysts in electric field was proposed. The catalytic combustion of CH₄ occurs only when the temperature is higher than 250 °C normally, but when electric field was applied, the whole process of CH₄ oxidation was promoted significantly and the reaction temperature was reduced. Electric field could promote the reduction of the support Co₃O₄ to release the lattice oxygen, resulting in the increase of PdO_x and the surface chemisorbed oxygen, which could provide more active sites for the low-temperature oxidation of CH₄. Furthermore, electric field could accelerate the dehydroxylation of CoOOH to further enhance the activity of the catalysts.     

TRAFFIC-BASED SCHEDULING MECHANISM IN AN IP/ATM ROUTER

Introduction　　 In recentyears,ATM has been installed com-prehensively,especially in the backbone of cam-puses and cities. On account of the differencesamong ATM,IP and other networks[1,2 ] ,how toeffectively integrate them is a very important andcritical issue to ATM and other networks.An IP/ATM router which can interconnect1 55M ATM,1 0 0 M Ethernet,2 M ATM,PPP,2 B D ISDN and X.2 5is under developing in ourlab.In prior work,we have designed its softwarearchitecture[3] .We als…     

加筋材料地基处理在改扩建高速公路中的应用研究

高速公路扩建工程对于提升交通运输效率、促进区域经济发展具有至关重要的作用。针对高速公路扩建施工中差异沉降和不协调变形问题,提出了一种基于添加加筋材料地基处理技术的施工方法,该方法分为材料选取和地基、土基处理两部分。通过颗粒及物质组成试验、液限和塑限试验、击实试验、浸水承载比试验对施工材料进行选取,按埋深高度区间段进行软土地基处理,再使用加筋材料进行土基处理。选取山东某段高速公路扩建工程进行实验对研究方法有效性进行验证,结果表明：研究方法在进行地基沉降测试时,4个测点平均沉降量为4.915 mm;在1 000 m含弯道路段扩建施工时工期为359 d。综上说明提出的研究方法能够有效提升扩建道路的强度,同时具有更好的施工实施效果。     

安乐死的内涵与外延

从1986年陕西的第一例安乐死到现在,已经过去了20年,要求安乐死的呼声也几经起落,直到今年初,借着两会的召开,这一话题又热了起来。笔者认为多年争论的胶着状态也许是大家对安乐死并没有形成统一的看法,大家对安乐死的本质还认识不清,所以笔者认为有必要对安乐死的内涵与外延做一个梳理,让大家对安乐死的概念有进一步的认识。     

梦回草原——蒙古国探秘

贴平车贴,分发手台,我们的车队又要出发。习惯了清晨、朝阳,以及大多熟悉的笑容,一起去蒙古国探寻戈壁的神奇、发现沙漠的秘密、体味草原的细腻、感受异乡都市的古朴。     

臭氧协同Fe/SSZ-13分子筛催化氧化低浓度甲烷的性能研究

当前低浓度甲烷催化氧化存在起燃温度高、贵金属用量大等问题,为探索低成本、清洁高效的甲烷去除技术,基于臭氧的强氧化性和Fe/SSZ-13分子筛优异的吸附性,探究了在臭氧(O₃)气氛下Fe负载量、n(CH₄)∶n(O₃)以及空速对甲烷催化氧化性能的影响。研究结果表明,在Fe负载量为1%,n(CH₄)∶n(O₃)为1∶6,温度为200℃的条件下,甲烷的转化率可达80.8%。通过BET,XRD,NH₃-TPD,H₂-TPR,UV-Vis以及XPS表征手段,证明了适量的Fe负载可以提高催化剂比表面积,促进更多酸性位点的形成,调节催化剂表面铁元素的价态分布和种类,从而促进甲烷催化臭氧化反应。基于原位红外试验发现O₃可以活化活性位点,进而促进甲烷吸附和催化氧化反应。     

为TDCS提供2Mb/s通道的注意事项

为使铁路运输向信息化迈进,沈阳铁路局将大面积开通TDCS（列车调度指挥系统）.根据以往对沈山线TDCS的维护经验,在提供2Mb/s通道时应注意以下问题.     

装卸设备点检制在二连站的应用实践

二连站装卸作业所根据本所装卸设备多、口岸换装作业量大的实际,在装卸设备的运用维护管理中试行点检制,制定出点检作业标准及运行管理制度,对设备运行状态进行动态分析,提高了设备管理水平。