双块式无砟轨道枕上压力监测标定方法

为探寻双块式无砟轨道枕上压力的长期监测方法,以CRTSⅠ型双块式轨枕为研究对象,首次利用埋入式光纤光栅传感器研究了双块式轨枕内部应变值和枕上压力的线性关系.首先,在轨枕制造阶段埋入FRP-OF光纤光栅应变传感器,用于测试轨枕内部应变变化;其次,通过反力架和千斤顶对轨枕进行静力加载标定,分析轨枕表面加载力和轨枕内部应变的线性关系;最后,通过有限元仿真进行验证和修正.结果表明:在轨枕表面施加的载荷和轨枕内部光纤光栅应变传感器的测试值具有良好线性关系,将此线性斜率确定为标定系数(4.90~5.28 kN/με),仿真数据与实测数据的误差在5%以内;对比轨枕在反力架约束和在道床板约束两种不同边界条件工况下的枕内应变,修正了枕上压力计算式,提出了一种基于双块式轨枕内部应变的枕上压力计算方法,并在高速铁路运营线路上测得枕上压力约为30~42 kN;该方法为高速铁路轮轨荷载传递研究、无砟轨道结构的强度计算理论和方法的完善以及列车轮对状态监测提供重要依据.

康复新液联合氦氖激光治疗Ⅱ期及以上压力性皮肤溃疡32例

目的：对于Ⅱ期及以上压力性皮肤溃疡的治疗，应用康复新液联合氦氖激光的临床疗效进行探讨和观察。方法：选取2012年1月~2014年1月，我院收治的Ⅱ期及以上压力性溃疡患者62例，随机分成2组，采用康复新液联合氦氖激光治疗的32例患者，设为观察组；给予雷佛奴尔纱条、0．1％浓度，进行填塞引流的30例患者，设为比对组。观察2组患者的治疗效果，并进行比较分析。结果：经治疗，观察组的32例患者，治愈22例，治愈率68．75％；有效6例，占18．75％；无效4例，占12．50％；平均治愈时间15．48±1．35天；比对组的30例患者，治愈7例，治愈率23．33％；有效7例，占23．33％；无效16例，占53．34％；平均治愈时间21．32±1．43天。2组相比较差异显著，且P〈0．05，具有统计学意义。结论：在Ⅱ期及以上压力性溃疡的治疗时，应用康复新液联合氦氖激光方法，能够有效提高患者治疗有效率，加快康复时间，具有临床应用和推广价值。

轨距1067mm铁路预应力PC轨枕枕上压力检算

本文综述了安哥拉共和国本格扛铁路预应力混凝土轨枕枕土压力捡算的过程，从预应力混凝土轨枕静态枕上压力和准静态枕上压力上分别进行检算。并结合对预应力PC轨枕检算的结果，阐述了轨距1067mm PC轨枕在不同时速，相同轴重，静态和准静态下每公里铺设轨枕数量的区别，为本格拉铁路采用预应力PC轨枕提供了可靠依据。

持续封闭式负压吸引联合银离子敷料在3期以上压力性损伤的应用

目的:探讨持续封闭式负压吸引联合银离子敷料在3期以上压力性损伤中的应用价值。方法:选取我院2014年5月至2016年5月收治的3期以上压力性损伤患者80例,依据随机数字表法将患者分为持续封闭式负压吸引联合银离子敷料护理组(实验组,n=40)和单纯银离子敷料护理组(对照组,n=40)两组,对两组患者的临床疗效、换药次数、肉芽组织生长时间、创面愈合时间、换药费用进行统计分析。结果:实验组组患者护理的总有效率显著高于对照组(95.0%vs 62.5%,P<0.05),换药次数显著少于对照组(P<0.05),肉芽组织生长时间、创面愈合时间均显著短于对照组(P<0.05),疼痛程度评分、换药费用均显著低于对照组(P<0.05)。结论:持续封闭式负压吸引联合银离子敷料较单纯银离子敷料在3期以上压力性损伤中具有较高的应用价值。

土坡上压力水管抗滑稳定性及对镇墩作用力的计算

本文主要论述土坡上压力水管抗滑稳定性及对下面镇墩作用力的计算,对下面镇墩作用力计算分柔性管及钢管,钢管又分管道抗滑稳定及不稳定两种情况。解决上述问题具有实际意义,因为这些问题在工程中经常遇到。

心理护理干预在负压引流联合骑跨椅治疗3期以上压力性损伤中的临床应用及对患者的影响

目的探究心理护理干预在负压引流(VSD)联合骑跨椅治疗3期以上压力性损伤中的临床应用及对患者的影响。方法选取2017年7月至2018年12月东莞市第三人民医院住院3期以上的压力性损伤患者60例,采用随机数字分为对照组和实验组,各30例。全部患者均给予VSD联合骑跨椅治疗。对照组采用常规护理。实验组在常规护理基础之上给予心理护理干预。对比两组患者心理情绪、治疗依从性等指标。结果两组治疗总有效率比较,差异有统计学意义(P<0.05)。护理前,两组焦虑自评量表(SAS)、抑郁自评量表(SDS)评分比较,差异无统计学意义(P>0.05);护理2 w后,两组SAS、SDS评分明显低于护理前,实验组SAS、SDS评分低于对照组,差异均有统计学意义(均P<0.05)。两组依从率比较差异有统计学意义(P<0.05)。结论心理护理干预能缓解VSD联合骑跨椅治疗3期以上压力性损伤患者的不良情绪,提高其治疗依从性,使其积极配合治疗,能够提高压力性损伤治疗效果,改善其创面。

基于土拱效应的刚性挡墙墙后主动土压力

考虑平移模式下刚性挡土墙墙后填土中的土拱效应,采用中心圆弧拱迹线法得到了不同填土内摩擦角和墙土摩擦条件下,挡土墙的滑裂面倾角和侧向主动土压力系数。在此基础上,采用水平微分层法求解得到了作用在挡土墙上的主动土压力、主动土压力合力及其作用点的解析式。与前人理论研究成果及试验监测结果的对比分析表明:本文理论得到的平移模式下刚性挡墙墙后主动土压力合力略小于Paik和应宏伟计算结果,大于章瑞文计算值;土压力合力作用点高于Paik理论解和应宏伟计算结果;侧向主动土压力系数与Paik理论解和应宏伟理论解基本相等。相较于其它方法,本文理论得到的刚性挡墙墙后主动土压力分布与模型试验结果吻合得更好。

复合式围护结构中搅拌桩土压力分担的计算

本论文结合工程实例 ,采用有限元程序分析了开挖过程中 ,灌注桩—搅拌桩复合式围护结构中搅拌桩的土压力分担情况。并通过土参数的改变 ,讨论了影响搅拌桩土压力分担的因素。对灌注桩—搅拌桩这种复合式围护结构的机理进行了进一步研究。

北京地铁17号线南段混凝土道床承载力分析

北京地铁17号线南段地下轨道部分主要道床形式为普通长枕式整体道床,施工工序中包含轨道车和平板车运送轨排、钢筋和混凝土等。为了缩短轨道车运送工序时间,减少卸车点至作业面距离,对普通长枕式整体道床进行混凝土浇筑后24 h道床承载力分析。检算结果表明:最不利情况下的枕上动压力为14.25 kN;轨枕弯曲强度(轨下截面正弯矩和枕中截面负弯矩)在允许范围之内;道床强度符合要求;混凝土抗剪强度符合要求。

“浮力”的教学初探

本文通过教材分析,对“浮力”教学结构中的几个问题进行初步的探讨,主要是就本章的教学内容、教学方法、学生学习“浮力”时的心理障碍三个方面进行分析,为搞好本章教学和学生学习提供参考意见。

Numerical simulation of residual stress field in green power metallurgy compacts by modified Drucker-Prager Cap model

Compaction process simulation and residual stress prediction of green PM compact were carried out with elasto-plastic 3D FEA based on the modified Drueker-Prager Cap model in Abaqus. The model parameters of the investigated powder Distaloy AE were determined as functions of relative density through typical mechanical property tests of powder. The model was implemented as a user subroutine USDFLD. Single sided compaction of a d20 ram^5 mm disk green compact of Distaloy AE was simulated, and the residual stress of the disk after ejection was predicted with FEA. The FEA results of the compaction process and the residual stress of the disk show good agreement with compaction experiments and X-ray diffraction measurements, which validates the model and its parameters. The results indicate that the compressive residual stresses exist mainly in a thin layer on the side surface, but the residual stresses are very small on the top and bottom surfaces.

Comparative experimental study on inhibiting gas explosion using ABC dry powder and diatomite powder

Using a 20 L spherical explosion suppressing test system, the largest gas explosion pressure and maximum pressure rising rate with additives of ultra-fine ABC dry powder and diatomite powder were tested and compared, and the explosion suppression effect of the two kinds of powder was analyzed. Experimental results show that both powders can suppress gas ex- plosion and ABC dry powder is superior to diatomite powder. Adding two powders under the same experimental conditions, when methane concentration is 7.0%, the maximum explosion pressure decreased 39% and 4%, respectively, while the rising rate of the maximum pressure decreased 80% and 53%, respectively. When methane concentration is 9.5%, the maximum ex- plosion pressure decreased 14% and 12%, respectively, the rising rate of maximum pressure decreased 62% and 27%, respec- tively, the maximum explosion pressure decreased 23% and 18%, respectively, while the rising rate of the maximum pressure decreased 77% and 70%, respectively. When methane concentration is 12.0%, the explosion suppression effect of ultra-fine ABC dry powder is not affected by the methane concentration, and the explosion suppression effect of diatomite powder under high methane concentrations is more obvious.

A new failure mechanism for deep cavity and upper bound solution of supporting pressure

The investigation of supporting pressure is of great significance to the design of underground structures.Based on the kinematical approach of limit analysis,an improved failure mechanism is proposed,and the supporting pressure is investigated for deep buried cavity.Three failure mechanisms are first introduced according to the existing failure mechanisms of geotechnical structures of limit analysis.A comparison with respect to the optimal failure mechanisms and the upper bound solutions provided among these three mechanisms are then conducted in an attempt to obtain the improved failure mechanism.The results provided by the improved failure mechanism are in good agreement with those by the existing method,the numerical solution and field monitoring,which demonstrates that the proposed failure mechanism is effective for the upper bound analysis of supporting pressure.

Effect of particle size of coal dust on explosion pressure

The effect of the particle size of coal dust on explosion pressure and the rising rate of explosion pressure is studied. Three coal dusts from Lingan Coal Mine in Canada and Datong Coal Mine in China are selected to test. The influence of particle size on the maximum explosion pressure P max and maximum pressure rising rate (d p /d t ) max of each coal dust was tested experimentally. The results indicate that with the decrease of particle size of coal dusts, explosion pressure increases on condition of the same concentration. If the concentration of coal dust is different, the maximum explosion pressure appears at the concentration of 500 g/m^3. The smaller the particle size of coal dusts, the larger the rising rate of explosion pressure of coal dust. When the concentration of coal dust is 500 g/m^3, the rising rate of explosion pressure of each coal dust is the maximum.

Upper bound analytical solution for surrounding rock pressure of shallow unsymmetrical loading tunnels

By combining the results of laboratory model tests with relevant flow rules, the failure mode of shallow unsymmetrical loading tunnels and the corresponding velocity field were established. According to the principle of virtual power, the upper bound solution for surrounding rock pressure of shallow unsymmetrical loading tunnel was derived and verified by an example. The results indicate that the calculated results of the derived upper bound method for surrounding rock pressure of shallow unsymmetrical loading tunnels are relatively close to those of the existing "code method" and test results, which means that the proposed method is feasible. The current code method underestimates the unsymmetrical loading feature of surrounding rock pressure of shallow unsymmetrical loading tunnels, so it is unsafe; when the burial depth is less or greater than two times of the tunnel span and the unsymmetrical loading angle is less than 45°, the upper bound method or the average value of the results calculated by the upper bound method and code method respectively, is comparatively reasonable. When the burial depth is greater than two times of the tunnel span and the unsymmetrical loading angle is greater than 45°, the code method is more suitable.

Endoscopic Effects on Peristaltic Flow of a Nanofluid

In the present investigation we have studied the peristaltic flow of a nanofluid in an endoscope. The flow is investigated in a wave frame of reference moving with velocity of the wave c. Analytical solutions have been calculated using Homotopy perturbation method （HPM） for temperature and nanoparticle equation while exact solutions have been calculated for velocity and pressure gradient. Numerical integration have been used to obtain the graphical results for pressure rise and frictional forces. The effects of various emerging parameters are investigated for five different peristaltic waves. Streamlines have been plotted at the end of the article.

Comparative study on pullout behaviour of pressure grouted soil nails from field and laboratory tests

Pullout resistance of a soil nail is a critical parameter in design and analysis for geotechnical engineers. Due to the complexity of field conditions, the pullout behaviour of cement grouted soil nail in field is not well investigated. In this work, a number of field pullout tests of pressure grouted soil nails were conducted to estimate the pullout resistance of soil nails. The effective bond lengths of field soil nails were accurately controlled by a new grouting packer system. Typical field test results and the related comparison with typical laboratory test results reveal that the apparent coefficient of friction （ACF） decreases with the increase of overburden soil pressure when grouting pressure is constant, but increases almost linearly with the increase of grouting pressure when overburden pressure （soil depth） is unchanged. Water contents of soil samples at soil nail surfaces show obvious reductions compared with the results of soil samples from drillholes. After soil nails were completely pulled out of the ground, surface conditions of the soil nails and surrounding soil were examined. It is found that the water content values of the soil at the soil/nail interfaces decrease substantially compared with those of soil samples extracted from drillholes. In addition, all soil nails expand significantly in the diametrical direction after being pulled out of ground, indicating that the pressurized cement grout compacts the soil and penetrates into soil voids, leading to a corresponding shift of failure surface into surrounding soil mass significantly.