Analysis of vertical pressure on buried pipeline with case study

This paper introduces a formula for the vertical pressure on a buried pipeline by using a modification of the basic assumptions of Marston’s theory. The fill’s cohesion is considered. The included angle between the slide surface above the pipeline and the horizontal surface is assumed to be equal to the fill’s angle of friction. The friction is calculated by multiplying the active earth pressure on the outer column and the coefficient of the friction on the slide planes It was found that the fill’s cohesion had important influence on the vertical pressure, whose vertical pressureC _c decreases with increase of the fill depth, a relationship according with that observed in practice. At the end of the paper, the formula is employed to analyze a practical case. Project (No. RC9609) supported by Natural Science Foundation of China (NSFC)     

新型摩擦实验装置的研制与应用

介绍了一种新型摩擦实验装置的工作原理、性能和实验结果。该装置设计为滑板转动的传动机构,由转动轴带动滑板转动来调节滑板的倾角,倾角达0°~50°的任意角度。滑板倾角调整分为电动机带动的快速调整和用手动微调2种。该实验装置可以用来测定2种材料之间的静、动摩擦系数,并可以进行一定角度滑板上的物体滑动、翻倒、滚动的演示。实验结果表明,所研制的实验装置具有较好的实验性和可靠性。     

Study on determination of the stable slope configuration for deep open pit mine

The space effects of deep pit slope are analyzed by an elastic mechanics principle. The interaction among the critical slide angle, the friction coefficient, the cohesion, and the horizontal radius of the deep pits is derived in this paper. It indicates that the deeper the pit is excavated, the greater the critical slide angle is. Both the theory for reducing stripping waste rock in deep pit and the approach to determining the configuration of the stable slope are developed from the interaction. The theory in this paper comprises the preceding principles of stability analysis of slopes and is suitable for analyzing that of deep pit.     

Analysis of tensioned membrane structures considering cable sliding

INTRODUCTIONTensionedmembranestructuresaremostsuitableforuseasroofstructureforavarietyofbuildingtypes,astheyprovidealight,elegant,andefficientstructurespanningoveralargeclearspace (Otto,1 973 ) .Examplesincludegymnasi ums,exhibitioncenters ,concertpavilio…     

滑板运动和冲浪运动中的动力学模型的特性

研究了滑板运动和冲浪运动中动力学模型的特性,即在光滑四滚线上和粉植圆滚线上的滑板,在竖直平面内,同一水平线上经过一个最低点的任意两点所有光滑连接线中;物体无初速度滑动时,所需时间最短的曲线是圆滚线（最速降线）这一特性对目前国际上滑板运动和冲浪运动具有指导性的意义．     

Analysis of tensioned membrane structures considering cable sliding

In routine design of tensioned membrane st ructures, the membrane is gen erally modeled using space membrane elements and the cables by space cable eleme nts, with no sliding allowed between the membrane and the cables. On the other h and, large deflections are expected and sliding between the membrane and the cab les is inevitable. In the present paper, the general finite element code ABAQUS was employed to investigate the influence of cable sliding on membrane surface o n the structural behavior. Three analysis models were devised to fulfill this pu rpose: (1) The membrane element shares nodes with the cable element; (2) The cab le can slide on the membrane surface freely (without friction) and (3) The cable can slide on the membrane surface, but with friction between the cable and the membrane. The sliding problem is modeled using a surface-based contact algorithm . The results from three analysis models are compared, showing that cable slidin g has only little influence on the structure shape and on the stress distributio ns in the membrane. The main influence of cable sliding may be its effect on the dynamic behavior of tensioned membrane structures.     

Calculation method for effect of silt sediment on lifting force of hydraulic gate

In this paper, silt sediment is considered to be Bingham body, which is made up of coarse and fine particles in front of a hydraulic gate. The coarse and fine particles provide friction and shear stress in the course of opening the gate. They constitute together the adhesion force of the sediment. Based on this viewpoint, this paper puts forward a formula for the effect of silt sediment on the lifting force. The formula includes gate weight, down-suction force, sealing rubber friction, plus-weight, water-column pressure, plus-silted-sediment weight and rolling (or sliding)-bearing friction. Finally, the verification results show that the formula has certain reliability and the calculation accuracy can meet the need of practical engineering.     

管道减振技术中的孔板压力降公式及其应用

在石油、化工等工矿企业,广泛使用管道输送流体.在一定压力和流速的作用下,这些管道壁上均会产生流体压力.当脉动的气流沿管道输送时,遇到弯头、异径管、盲板、气阀等元件时将产生激振力,受此激振力的作用,管道将会产生振动.压力脉动是引起管道及其附属设备振动的主要原因.而压力脉动是由于气流的脉动引起的,所以,控制压力脉动主要是消减气流的脉动.本文通过流体力学的柏努利公式推导出加孔板后的压力降公式.     

管外爬行机器人及其控制系统设计

主要介绍了一种管道外爬行机器人结构和控制系统的设计。机器人本体结构采用的是关节式,不仅能够攀爬直行管道,而且能够越过T型管道、十字型管道等。针对各个关节的电机的驱动方式选取c8051f020单片机为控制系统核心器件,通过压力传感器检测机器人与管道表面的压力来实现机器人的固定,采用max485多机通信模式实现对多个关节舵机的控制。通过实验室测试,该机器人基本能够实现在直行、十字交叉管道上前进、后退、上升、下降等功能。从而可以为各种工业管道、民用管道、大桥斜拉索、电缆等圆柱形体的质量检测、维护修复等作业提供一种新型的管外行走装置。     

气垫导轨装置在碰撞实验中的改进

在气垫导轨上做碰撞实验,最大限度地减少了摩擦阻力的影响,但在实际的实验过程中,仍发现滑块的初速度不同时,粘滞性摩擦阻力对测量结果有不同程度的影响,为此在气垫导轨上增加了电子发射装置,较好地控制滑块的初速度和测量滑块的加速度,从而减小粘滞性摩擦阻力对测量结果的影响。     

微量调速系统的低速摩擦特性

微量调速系统的摩擦特性是影响低速稳定性的主要原因之一，目前人们在10mm/min速度下，对单一类型的液压缸密封装置、导轨与滑台摩擦特性已有了较深的认识，但还未对该系统在5mm/min的速度下进行摩擦特性的研究。本文对此条件下该系统低速磨擦特性进行了研究分析。     

Design and experimental verification of a new multi-functional bridge seismic isolation bearing

A new multi-functional bridge seismic isolation bearing (MFBSIB) is designed and its mechanical model is developed in this paper. Combining an upper sliding device and a lower energy dispassion isolation device effectively, the new MFBSIB can adjust the deformation caused by temperature, vehicle breaks, and concrete creep, etc., in addition to dissipating energy. The switch of ??slide-isolation?? is achieved and the efficiency of both upper and lower parts is validated through experiment with a model. The shear performance curve established in this paper is verified to be efficient in describing the mechanical characteristics of the bearing through experiment. It is proved through both numerical calculation and experimental analysis that the new MFBSIB is endowed with enough vertical rigidity, good energy dissipation ability, stable overall performance, and good realization in expected goals. Its performance is slightly influenced by shear stress, while affected by vertical pressure, loading frequency, slide limit, etc., diversely. The results could provide reference for study and application of the new MFBSIB.     

考虑土拱效应绕墙顶转动刚性挡墙土压力分布

基于库仑土压力理论,通过研究刚性挡墙绕墙顶转动极限状态土体内主应力拱形状,推导了侧土压力系数和水平微分单元间摩擦系数的理论公式,进而得到改进的主、被动土压力计算公式,并用模型试验结果验证。研究表明:考虑土拱效应计算结果与模型试验结果吻合比较好,墙土摩擦角越大,土拱效应越显著,主动土压力合力作用点越往上移,被动土压力合力作用点越往下移。     

埋设管线穿过不同介质时的地震反应研究

本文应用表面波理论计算埋设管线穿过不均匀场地时的地震反应。用带竖直断面的分层介质模拟不均匀场地。从断面两侧的变形、应力连续条件近似确定两侧由表面波引起的场地运动,将所得的场地运动输入到以弹性地基梁模拟的管线上,得出管线的地震反应。最后通过计算实例对结果进行了比较分析。     

Transitions in Wear and Friction of Carbon Fiber Reinforced Copper Matrix Composite Sliding Against AISI-1045 Steel

Carbon fiber reinforced copper matrix composite is anewtype of material that can be used in an unlubricatedfriction pair because it has a good self-lubricating perfor-mance in dry sliding against the steel[1 ,2].The wear char-acteristics of composites int…     

一个改进的计算饱和烷烃回转半径的经验公式

本文以Wiener拓扑指数为基础，结合分子密堆积信息指数P3，分子支化度参量P2；提出了一个新的计算饱和烷烃回转半径的经验公式，计算结果显示，其相关性优于任碧野文经验式。     

High-order lateral buckling analysis of submarine pipeline under thermal stress

It is of importance to study and predict the possible buckling of submarine pipeline under thermal stress in pipeline design.Since soil resistance is not strong enough to restrain the large deformation of pipeline,high-order buckling modes occur very easily.Analytical solutions to high-order buckling modes were obtained in this paper.The relationships between buckling temperature and the amplitude or the wavelength of buckling modes were established.Analytical solutions were obtained to predict the occurrence and consequence of in-service buckling of a heated pipeline in an oil field.The effects of temperature difference and properties of subsoil on buckling modes were investigated.The results show that buckling will occur once temperature difference exceeds safe temperature;high-order pipeline buckling occurs very easily;the larger the friction coefficients are,the safer the submarine pipeline will be.     

蜗杆步进机构理论研究

本文介绍了蜗杆步进机构中蜗形凸轮啮合的几个理论问题。主要有轮廓曲线要求分析。啮合曲面方程及曲率半径方程推导。曲面任意点压力角精确解和坐标方程。该理论已由实践证明是正确的。     

Improving the sensitivity of protein microarray by evanescent-field-induced fluorescence

To improve the sensitivity of protein microarray, a prism surface replaces the surface of the common microscope slide. The protein targets arrayed on the surface are hybridized and labelled by fluorescent probes. Evanescent excitation occurs when the convergent laser reaches the surface, and a photomultiplier tube detects the emitted fluorescent signal. A two-dimensional actuator scans the whole surface to achieve planar laser excitation and fluorescence collection. The penetration depth of the evanescent field into the protein targets is only some hundred nanometers and can be controlled by different incident angle of the laser beam, so the undesired background signals are reduced dramatically and the detection sensitivity is improved by a factor of 50 to 100 comparing to confocal excitation. This approach can detect low abundance analytes without signal amplification.     

Vertical distribution of sediment concentration

A simple formula is proposed to predict the vertical distribution of a suspended load concentration in a 2D steady turbulent flow. The proposed formula significantly improves the well-known Rouse formula where sediment concentration has an infinitely large value at the channel bottom and a zero value at the water surface. Based on this formula and the logarithmic velocity profile, a theoretical elementary function for the transport rate of a suspended load is developed. This equation improves the Einstein equation in which the unit-width suspended sediment discharge must be solved by numerical integration and a contradiction between the lower limit of the integral and that of velocity distribution exists.