螺杆泵内部滑失与泵外漏失机理研究

为了认清螺杆泵的漏失机理,还原其井下实际生产条件下的工作状况,根据流体传压特性,将螺杆泵漏失细分为泵内滑失和泵外漏失。在确定泵内压力分布的基础上计算了螺杆泵各腔室的滑失速度,研究了不同泵吸入口空隙率和排出口压力下的漏失规律。结果表明:泵内压力变化导致泵内流体滑失,滑失又会影响泵内压力分布,泵外漏失是泵内滑失达到一定程度时出现的现象;气相存在一个较小的滑失区间,随着泵排出口压力增加,滑失区间向吸入口偏移;泵吸入口空隙率的增加改变了泵内流体的可压缩性,使得液相滑失速度曲线由线性进化为抛物线型,气相滑失区间向排出口扩散。研究结果为螺杆泵漏失量的计算提供了依据。

痔疮治疗机的研制

一、概述痔疮是一种常见病、多发病,尤其是脑力劳动者和长时间采取坐势工作者,由于臀部的血液不能顺利返流,形成了痔疮(有内、外和混合痔),影响了人们的正常生活、工作和学习,严重时需住院治疗。目前常用的治疗方法是手术切除缝合。此法对患者的痛苦较大,术后排便困难,疼痛严重;若经多次缝合容易形成肛门狭窄而带来新的问题。由于排便困难增加了对血管的压迫,使形成痔疮的机会增多。此外,尚有药物治疗手段,一般见效较慢。我科研制的新型治疗机是利用在安全范围内的恒定直流电,通过电极送入痔疮,由于在痔疮根部的电流密度最大,在几分钟的时间内即产生血栓、阻塞或切断供应痔核的营养通道,使痔核内的细胞无营养而坏死,从而使整个痔疮逐渐萎缩。

主恩实在是多

神对我的恩典太多了,这恩典像珍珠一样,一个一个赐给我。十余年来这恩典汇成了一个珍珠海,我沐浴在这海里多幸福。但我有时却身在福中不知是福,还在犯罪,不知道亲近神,也不知道主爱的宝贵。他的爱是圣洁的,超过世上一切的爱。神对我的爱有下面几个见证来说明: 一、神的拣选,从小蒙召 主耶稣说:“神救了我们,以圣召召我们,不是按我们的行为,乃是按他的旨意和恩典。这恩典是万古之先基督耶稣里赐给我们的。”我年轻时体质就很差。

车胎打滑别慌张

每当下雨路滑时,驾驶员都会打起十二分精神,假如车速过高的话,在转弯及制动时,便很容易产生打滑现象。不过,只要你有正确的驾驶知识,事故是可以避免的。 不少驾驶员遇上路面湿滑时,往往以为只要把行车的速度略微降低就安全了。事实却远非如此,这也正是雨天发生交通意外事故特别多的因素之一。到底为什么汽车在湿滑路面上会有打滑失控的现象产生?怎样才能预防与解决?

Wear behavior of high strength and high conductivity Cu alloys under dry sliding

In order to study the wear behavior of different kinds of contact wires,the dry sliding wear behaviors of Cu-Sn,Cu-Ag and Cu-Mg alloys prepared by up-drawn continuous casting and followed continuous extrusion were studied.The research was tested on a block-on-ring wear tester.The results indicate that the friction coefficient is remarkably influenced by the formation of a continuous tribofilm,which consists of oxidation film.The abrasion,adhesion,oxidation and plastic deformation are observed.Oxidation and abrasion wear mechanisms dominate at the lower sliding velocity and load.The combination of oxidation and adhesion play leading roles with the increasing load and velocity.Plastic deformation is detected under higher applied load and sliding velocities.

Stability of roof structure and its control in steeply inclined coal seams

To improve the effectiveness of control of surrounding rock and the stability of supports on longwall topcoal caving faces in steeply inclined coal seams, the stability of the roof structure and hydraulic supports was studied with physical simulation and theoretical analysis. The results show that roof strata in the vicinity of the tail gate subside extensively with small cutting height, while roof subsidence near the main gate is relatively assuasive. With increase of the mining space, the caving angle of the roof strata above the main gate increases. The characteristics of the vertical and horizontal displacement of the roof strata demonstrate that caved blocks rotate around the lower hinged point of the roof structure, which may lead to sliding instability. Large dip angle of the coal seam makes sliding instability of the roof structure easier.A three-hinged arch can be easily formed above both the tail and main gates in steeply inclined coal seams. With the growth in the dip angle, subsidence of the arch foot formed above the main gate decreases significantly, which reduces the probability of the roof structure becoming unstable as a result of large deformation, while the potential of the roof structure's sliding instability above the tail gate increases dramatically.

Effects of crankpin bearing speed and dimension on engine power

A new method combining the slider-crank mechanism dynamic(SCM)and crankpin bearing(CB)lubrication models is proposed to analyze the effects of CB dimensions and engine speed on the lubrication efficiency and friction power loss(LE-FPL)of an engine.The dynamic and lubrication equations are then solved on the basis of the combined model via an algorithm developed in MATLAB.To enhance the reliability of the research results,the experimental data of combustion gas pressure is applied for simulation.The load bearing capacity(or oil film pressure),friction force,friction coefficient,and eccentricity ratio of the CB are selected as objective functions to evaluate the LE-FPL.The effects of engine speed,bearing width,and bearing radius on the LE-FPL are then evaluated.Results show that reductions in engine speed,bearing width,or bearing radius can decrease the FPL but reduce the LE of the engine and vice versa.In particular,the LE-FPL can effectively be improved by slightly reducing the bearing width and bearing radius or maintaining engine speed at 2000 r/min.

Experimental Study of Heat Transfer Enhancement and Friction Loss Induced by Inserted Rotor-assembled Strand （II） Lubricant Oil 22

The paper described experimental investigation of heat transfer and single-phase pressure drop through tubes with different rotor-assembled strands inserted in the Reynolds number range of 800-9000 with lubricant as working fluid. In the experiment, fixed mounts were employed to eliminate the entrance effect. The experimental results showed that the employment of fixed mounts led to a visible bias of friction factor in the laminar regime while it could not affect the Nusselt numbers significantly. Experiment for the tube inserted with rotors-assembled strand showed remarkable improvement for heat transfer with the Nusselt number increased by 200%-225% in the laminar regime and 125%-160% in the transitional regime. Meanwhile, the friction factor increased inevitably by 200%-300% within the same range of Reynolds number. The comparison of different rotor-assembled strands in-serted tubes and plain tube showed that the heat transfer benefited from the increase of the diameter of rotor-assembled strand with the same lead and the decrease of the lead of rotor-assembled strand, so does the friction factor. Based on experimental data and thorough multivariant linear normal regression method, the correlations of average Nusselt number and friction factor are established.

A discussion of the risks and benefits of using rock terracing to limit soil erosion in Guizhou Province

The construction of stone terraces to minimise soil erosion is common throughout Guizhou. This technique, however, has high inherent risk. Stone terraces are usually much higher than those with earth risers. While they trap a greater thickness of soil on the slope they increase the risk of slope failures, reduce moisture and nutrient availability to plants, and thin more soil up slope. The stone risers also threaten long-term productivity. When a riser collapses debris is deposited over the terrace below making farming difficult. These breaches in the terrace focus surface runoff leading to gully formation and increased sediment transport down slope. Artificial drainage systems, often used in conjunction with terracing, compound the risk. These channels prevent precipitation from soaking into the soil. This limits groundwater and soil moisture recharge which reduces the availability of water for crops and the length of the growing season. The rapid drainage of water from the slope reduces the time of concentration of the catchment resulting in an increase in flood activity. Floods are caused by smaller rainstorm events. They arrive faster and peak quicker and higher than before the channels were constructed. Engineering solutions to soil erosion must therefore be used in conjunction with, and are not as a substitute for, good land management strategies. Furthermore, despite changes in land use practices, and the application of new technologies, there is a maximum amount of production that can be obtained from this land on a sustainable basis.

Precision loss of ball screw mechanism under sliding-rolling mixed motion behavior

The sliding-rolling mixed motion behavior degrades the ball screw’s precision at different levels.Based on the sliding-rolling mixed motion between ball and screw/nut raceway,the ball screw’s precision loss considering different given axial loading and rotational speed working conditions was investigated.Since creep and lubrication relate to sliding and rolling motion wear,the creep and lubrication characteristics are analyzed under different working conditions.Besides,the precision loss was calculated considering the sole influence of sliding behavior between ball and screw and compared with the results from other current models.Finally,research on precision loss owing to the sliding-rolling mixed motion behavior was realized under given working conditions,and suitable wear tests were carried out.The analytical results of precision loss are in good agreement with the experimental test conclusions,which is conducive to better predicting the law of precision loss in stable wear period.

Geospatial susceptibility mapping of earthquake-induced landslides in Nuweiba area, Gulf of Aqaba, Egypt

Earthquake induced landslides are one of the most severe geo-environmental hazards that cause enormous damage to infrastructure, property, and loss of life in Nuweiba area. This study developed a model for mapping the earthquake-induced landslide susceptibility in Nuweiba area in Egypt with considerations of geological, geomorphological, topographical, and seismological factors. An integrated approach of remote sensing and GIS technologies were applied for that target. Several data sources including Terra SAR-X and SPOT 5 satellite imagery, topographic maps, field data, and other geospatial resources were used to model landslide susceptibility. These data were used specifically to produce important thematic layers contributing to landslide occurrences in the region. A rating scheme was developed to assign ranks for the thematic layers and weights for their classes based on their contribution in landslide susceptibility. The ranks and weights were defined based on the knowledge from field survey and authors experiences related to the study area. The landslide susceptibility map delineates the hazard zones to three relative classes of susceptibility: high, moderate, and low. Therefore, the current approach provides a way to assess landslide hazards and serves for geo-hazard planning and prediction in Nuweiba area.

A polynomial smooth epsilon-support vector regression based on cubic spline interpolation

Regression analysis is often formulated as an optimization problem with squared loss functions. Facing the challenge of the selection of the proper function class with polynomial smooth techniques applied to support vector regression models, this study takes cubic spline interpolation to generate a new polynomial smooth function ｜×｜ε^ 2, in g-insensitive support vector regression. Theoretical analysis shows that Sε^2 -function is better than pε^2 -function in properties, and the approximation accuracy of the proposed smoothing function is two order higher than that of classical pε^2 -function. The experimental data shows the efficiency of the new approach.

A simple theoretical approach for analysis of slide-toe-toppling failure

A prevalent kind of failure of rock slopes is toppling instability.In secondary toppling failures,these instabilities are stimulated through some external factors.A type of secondary toppling failure is"slide-toe-toppling failure".In this instability,the upper and toe parts of the slope have the potential of sliding and toppling failures,respectively.This failure has been investigated by an analytical method and experimental tests.In the present study,at first,the literature review of toppling failure is presented.Then a simple theoretical solution is suggested for evaluating this failure.The recommended method is compared with the approach of AMINI et al through a typical example and three physical models.The results indicate that the proposed method is in good agreement with the results of AMINI et al’s approach and experimental models.Therefore,this suggested methodology can be applied to examining the stability of slide-toe-toppling failure.

Numerical Modeling of Giant Badu Landslide Reactivated by Excavation in China

In southwest of China, landslide reactivation caused by excavation has caused huge property and human losses, and posed severely threaten to the construction and operation of the man-made linear structures. A reactivated landslide is a complex process. The engineering practices have shown that a correct understanding of the reactivated mechanism of an ancient giant landslide is significant for the landslide mitigation. In this paper, a case study of the ancient Badu landslide that underwent multiple reactivations during the construction of Nanning-Kunming railway was discussed. The landslide characteristics are described and the reactivated features and progressive failure of the landslide are revealed. The reactivated mechanism of the landslide is analyzed by use of geological process analysis method and is simulated using the 3D FEM （finite element method）. At last, the reactivated mechanism mode of Badu giant landslide is put forward, namely ＂creeping-tensile cracking-shear breaking with zoning and grading features＂. The understanding of this kind of reactivated mechanism had helped engineers to take efficient and economic mitigation measures to stabilize the landslide.

Research on Stability Calculation Methods for Grillage Supporting Structure with Pre-stressed Anchor

Aiming at prestressed anchor cable frame in the presence of reinforcement landslide problem, through the selection of test points, the paper study and tested soil pressure, frame internal force and prestress losses under prestressed anchor cable frame beam, reveal the law of internal force distribution, and provides a theory basis for the rational design of prestressed anchor cable in landslide.

A Class of Smoothing-regularization Methods to Mathematical Programs with Vanishing Constraints

this paper,we propose a class of smoothing-regularization methods for solving the mathematical programming with vanishing constraints.These methods include the smoothing-regularization method proposed by Kanzow et al.in[Comput.Optim.Appl.,2013,55(3):733-767]as a special case.Under the weaker conditions than the ones that have been used by Kanzow et al.in 2013,we prove that the Mangasarian-Fromovitz constraint qualification holds at the feasible points of smoothing-regularization problem.We also analyze that the convergence behavior of the proposed smoothing-regularization method under mild conditions,i.e.,any accumulation point of the stationary point sequence for the smoothing-regularization problem is a strong stationary point.Finally,numerical experiments are given to show the efficiency of the proposed methods.

人际关系漫谈

一段时间以来,人际关系曾经成为人们茶余饭后的一个话题,人们对当前的人际关系众说纷纭,褒贬不一,各有各的看法。从总的情况看,满意的要比不满意的少。为什么人们对人际关系议论纷纷,为什么有比较多的同志对当前的人际关系不大满意?怎样才能建立和谐、融洽的社会主义人际关系?这是很值得探讨的问题。

Research on Wet Steam Spontaneous Condensing Flows Considering Phase Transition and Slip

A new dual-fluid model considering phase ansition and velocity slip was proposed in this paper and the Cunningham correction was used in the droplet resistance calculation. This dual-fluid model was applied to the numerical simulations of wet steam flow in a 2D LAVAL nozzle and in the White cascade respectively. The results of two simulations demonstrate that the model is reliable. Meanwhile, the spontaneous condensing flow in White cascade was analyzed and it infers that the irreversible loss caused by condensation accounts for the largest share （about 8.78% of inlet total pressure） in total pressure loss while the loss caused by velocity slip takes the smallest share （nearly 0.42%）, and another part of total pressure loss caused by pneumatic factors contributes a less share than condensation, i.e. almost 3.95% of inlet total pressure.