Characteristics of wheel-rail vibration of the vertical section in high-speed railways

In order to analyze the characteristics of wheel-rail vibration of the vertical section in a high-speed railway, a vehicle-line dynamics model is established using the dynamics software SIMPACK. Through this model, the paper analyzes the influence of vertical section parameters, including vertical section slope and vertical curve radius, on wheel-rail dynamics interaction and the acting region of wheel-rail vibration. In addition, the characteristics of wheel- rail vibration of the vertical section under different velocities are investigated. The results show that the variation of wheel load is not sensitive to the vertical section slope but is greatly affected by the vertical curve radius. It was also observed that the smaller the vertical curve radius is, the more severe the interaction between the wheel and rail be- comes. Furthermore, the acting region of wheel-rail vibration expands with the vertical curve radius increasing. On another note, it is necessary to match the slope and vertical curve radius reasonably, on account of the influence of operation speed on the characteristics of wheel-rail vibration. This is especially important at the design stage of vertical sec- tions for lines of different grades.

Dynamic responses of bridge-approach embankment transition section of high-speed rail

Based on the vehicle track coupling dynamics theory, a new spatial dynamic numerical model of vehicle track subgrade coupling system was established considering the interaction among different structural layers in the subgrade system. The dynamic responses of the coupled system were analyzed when the speed of train was 350 km/h and the transition was filled with graded broken stones mixed with 5% cement. The results indicate that the setting form of bridge-approach embankment section has little effect on the dynamic responses, thus designers can choose it on account of the practical circumstances. Because the location about 5 m from the bridge abutment has the greatest deformation, the stiffness within 0 5 m zone behind the abutment should be specially designed. The results of the study from vehicle track dynamics show that the maximum allowable track deflection angle should be 0.09% and the coefficient of subgrade reaction(K30) is greater than 190 MPa within the 0 5 m zone behind the abutment and greater than 150 MPa in other zones.

Tomography for Q of the Eastern Section of the Tianshan Area from High-frequency Attenuation of S-wave

Based on the waveform data of 5,076 local earthquakes recorded at 25 stations in Xinjiang during the period from 2009 to 2014 and the observation reports provided by the Xinjiang Digital Seismic Network,a data set of 19,140 attenuation factors t*is obtained by fitting the high-frequency attenuation of S-wave spectra with a genetic algorithm. The spatial distribution of Q_S is determined by inverting the t*data with seismic tomography. The results show that the average Q0 in eastern Tianshan is 520,and there is a significant correlation between the Q_S value distribution or attenuation characteristics it disclosed and the surface structure of the study area. The Q_S value is lower in the intersection area of the mountain basin which is located on the north and south sides of the Tianshan Mountains,and the high Q_S distribution is more concentrated inside the Tianshan orogenic belt. The M≥6. 0 earthquakes have been basically located in the Low-Q_S region since 1900. 24 high heat flow points in eastern Tianshan are located at the north and south of Tianshan Mountains where low Q_S exists,indicating a negative correlation. In addition,there is a positive correlation between the velocity structure and the attenuation structure in the study area,which reflects the consistency of the 2-D attenuation structure with the velocity structure and the two-dimensional density structure.

High-Resolution Geochemical Significance of Lowest Triassic at Majiashan Section, Chaohu, Anhui Province, China

The Permian Triassic boundary (PTB) and the lowest Triassic in the Yangtze region are considered to be the sediments of dysaeroxic and even anoxic environments, due to the dark thin bedded fine deposits, the highly developed parallel beddings with pyrites, the suppression of bio disturbance, and the monotonous fossils. However, the trace fossils there show a rather weak effect of the anoxic event. Meanwhile, the high resolution geochemical data are analyzed with 2 cm interval in the PTB and the lowest Triassic at the Majiashan Section, Chaohu, Anhui Province. The results show that the water depth of Chaohu region in the earliest Triassic was shallow, which might be a feature of the neritic environment. The high resolution geochemical proxies for anoxia have some contrary results. The geochemical data often indicate the dysaeroxic and even anoxic environments during that time, whereas other proxies (such as w (V)/ w (Cr), w (Ni)/ w (Co)) denote that they are normal marine sediments.

Influence of Axial Feeding on Hydroforming of Aluminum Alloy Tubular Part with Rectangular Section

The hydroforming experiment of aluminum tubular part with rectangular section was carried out to investigate influence of axial feeding on thickness distribution and calibration pressure of the corner.Thickness distribution and relation between corner radius and internal pressure were analyzed.The influence of lubricant was discussed.Microstructure and hardness of different region were observed.It is shown that thickness reduction in the transition region between the corner and center region is the biggest.Friction condition has influence both on the thickness distribution and calibration pressure of the corner.As the increase of the axial feeding,the calibration pressure is decreased.There is only little change for the microstructure,but the hardness is increased by 23.3% for the transition region.

Psychotic due to bath salts and methamphetamines:emergency cesarean section under general anesthesia

The use of ＂bath salts＂ or other new psychoactive substances,otherwise known as ＂legal highs＂,is increasing.Illicit drug use during pregnancy is not uncommon.Nevertheless,literature reporting bath salts and their effect on pregnancy is scant.Besides,there seems to be no literature about bath salts and conduct of general anesthesia.This case report describes a general anesthetic for the surgical delivery of an infant to a woman under the acute influence of bath salts and methamphetamines.

Stall Flutter Analysis of High-Aspect-Ratio Composite Wing

The stall flutter characters of high-aspect-ratio composite wing are investigated, and the effects of structure geometric nonlinearity and stiffness couple created by composite anisotropy on them also are discussed. Firstly, the high-aspect-ratio wing is modeled as a composite thin-walled closed section Euler beam whose displacement and rotation both could be of finite value, and the nonlinear dynamic equations is build up on it with all the effects of geometric nonlinearity, aerodynamic nonlinearity and anisotropy of material being considered. Then vibration equations are deduced through perturbing the dynamic equations at wing＇s equilibrium position, and coupled with unsteady stall aerodynamic model and ONERA model, to obtain the nonlinear stall flutter analysis equations of wing. Finally, the flutter stabilities with various wind speeds are determined by the harmonic balance method. With several exampies, the validity of the stall flutter model is proved, and the significant effects of geometric nonlinearity on the stall flutter various characters as wall as the effects of ply angle on the stall flutter speed and frequency also are discussed.

型钢高强自密实混凝土黏结滑移性能试验研究

为研究型钢与高强自密实混凝土界面黏结滑移性能,以混凝土保护层厚度和型钢埋置长度作为变化参数,设计9个型钢高强自密实混凝土试件进行推出试验.观察试件破坏过程、破坏形态和裂缝发展形式,获取了试件加载端的荷载-滑移全过程曲线,研究不同变量对其黏结性能的影响规律.结果表明:型钢高强自密实混凝土组合结构界面极限黏结强度随着混凝土保护层厚度的增加而增大,最大增幅94.9%;随着型钢埋置长度的增加而减小,最大削减为38.1%.界面黏结抗剪刚度随着型钢保护层厚度的增加先增大后减小,最大增幅85.1%;随着型钢埋置长度的增加而增大,最大增幅为30%.界面耗能能力与其变量相关性较弱;随保护层厚度的增加,界面损伤发展越晚;随型钢埋置深度的增加,界面损伤速度减缓.提出了型钢高强自密实混凝土黏结强度的计算公式,能较好地预测型钢高强自密实混凝土黏结强度.

基于可拓理论的隧道洞口段动力响应规律研究

隧道洞口段存在偏压浅埋、围岩破碎等情况,为探究隧道洞口段在地震作用下的动力响应规律并给出安全性定量评估指标,以雅万高铁6号隧道为依托建立数值模型,分别输入雅万人工合成波、EI波、KB波以及WL波4个地震波,基于可拓理论,建立可拓物元模型,对采用数值模拟方法得出的隧道洞口段在最不利地震波作用下的弯矩、轴力、相对位移、加速度4个安全评估指标结果创建分区,以综合定量指标对雅万高铁6号隧道洞口段进行安全性评估,并提出了抗震设防长度。同时,分析了在不同地震波作用下的雅万高铁6号隧道洞口段的动力响应规律。结果表明:(1)在雅万人工波作用下,隧道各评估点动力响应程度约为其余3种天然波作用下动力响应程度的1.2倍;(2)各地震波计算所得4个评估指标沿纵向方向变化规律基本相同,轴力及弯矩峰值均出现在拱肩拱脚位置,相对位移峰值均发生在洞口处仰拱至拱顶测线,评估指标峰值发生时刻略微滞后于地震波峰值加速度对应时刻;(3)在雅万人工合成波作用下,雅万高铁六号隧道洞口段抗震设防长度为45~55 m,为隧道洞径的3.5~4倍。研究成果可为通过综合定量指标对隧道洞口段进行抗震安全性评估提供参考。

高频彩色多普勒超声诊断剖宫产术后腹壁子宫内膜异位症的临床价值分析

目的 分析高频彩色多普勒超声诊断剖宫产术后腹壁子宫内膜异位症(AWE)的临床价值。方法 选取2019年5月至2022年5月我院收治的90例疑似剖宫产术后AWE患者,均接受常规超声及高频彩色多普勒超声诊断,以病理诊断结果作为“金标准”,比较以上两种方式诊断AWE的敏感性、特异性及准确率。结果 病理诊断结果显示,90例疑似剖宫产术后AWE患者中72例确诊为阳性,18例为阴性,常规超声及高频彩色多普勒超声检出阳性例数分别为60例、 70例,阴性例数分别为10例、 16例;高频彩色多普勒超声诊断剖宫产术后AWE的敏感性、特异性及准确率分别为97.22%、 88.89%、 95.56%,均显著高于常规超声(P <0.05)。结论 高频彩色多普勒超声诊断剖宫产术后AWE的敏感性、特异性、准确性较高,值得临床推广应用。

回收式自体输血在高出血风险产妇剖宫产术中的应用研究

目的探究回收式自体输血在高出血风险产妇剖宫产术中的应用效果。方法选取行剖宫产手术产妇100例,术前被诊断为具有高危出血风险,包括凶险性前置胎盘、胎盘植入、胎盘早剥、先兆子宫破裂以及疤痕子宫。依据输血方式不同,自体输血50例为观察组,异体输血50例为对照组。比较2组患者临床指标、血常规、凝血功能、炎症因子及术后不良反应。结果观察组术中失血量、术中输血量、血费、总费用、手术时间及住院时间少于或短于对照组,差异有统计学意义(P<0.05)。开始输血即刻(T_(1))时,2组产妇血常规指标比较差异均无统计学意义(P>0.05);输血结束(T_(2))及术后24 h(T_(3))时,2组红细胞压积(Hct)比较差异无统计学意义(P>0.05),观察组血红蛋白(Hb)、血小板(Plt)均高于对照组,差异有统计学意义(P<0.05)。T_(1)时,2组产妇凝血功能指标比较差异均无统计学意义(P>0.05);T_(2)、T_(3)时,2组D-二聚体(D-D)比较差异无统计学意义(P>0.05),观察组凝血酶原时间(PT)、凝血酶时间(TT)、活化部分凝血活酶时间(APTT)均短于对照组,纤维蛋白原(Fib)高于对照组,差异有统计学意义(P<0.05)。输血后48 h,观察组血清降钙素原(PCT)、白细胞介素-6(IL-6)均低于对照组,差异有统计学意义(P<0.05);观察组过敏反应、感染及低血压发生人数均低于对照组,但2组产妇总不良反应发生率比较差异无统计学意义(P>0.05)。结论回收式自体输血在高出血风险产妇剖宫产术中的临床应用效果显著。

黄河下游花园口至孙口河段高效输沙洪水阈值研究

河流能量耗散率变化反映了河道水沙输移能力以及河床形态的调整规律。本文研究区域为黄河下游花园口至孙口河段,从能量耗散角度出发,结合对实测资料的统计分析,探究了河流边界阻力能耗率与来水来沙、断面形态以及河床稳定性之间的定量关系,并基于边界阻力能耗率与河床稳定性双重指标,确定了花园口至孙口河段的高效输沙洪水阈值。研究结果表明:流量是影响边界阻力能耗率的主要因素,并与边界阻力能耗率的幂次呈线性相关;随着流量增大到2000 m^(3)/s以上,边界阻力能耗率随含沙量增加呈先减弱后增强的趋势。大流量条件下边界阻力能耗率与宽深比呈负相关关系,花园口与夹河滩断面形态复杂,相关性较弱;相比之下高村与孙口断面形态简单,相关性增强。非恒定水沙条件下的河床大多处于失稳状态,在综合考虑河床形态稳定及边界阻力能耗率最低的前提下,计算得出花园口至孙口河段的洪水高效输沙临界流量约为1500 m^(3)/s,含沙量约为23 kg/m^(3)。

嵌套加强的LQ550高强冷弯薄壁C型钢连续檩条受力性能研究

为提高LQ550级高强冷弯薄壁C型钢连续檩条的承载能力,采用在支座处嵌套的方法来加强连续檩条。对未加强和采用两种嵌套方式加强的檩条共7组试件进行三点受弯试验,得到了试件的承载性能和破坏形态,试验结果表明加强后的试件出现跨中局部屈曲和嵌套端部局部屈曲两种破坏形态。采用ABAQUS软件建立了非线性有限元模型对嵌套加强的檩条进行数值模拟,有限元分析得到的承载力和破坏形态与试验结果吻合良好,验证了有限元模型的准确性。基于验证的有限元模型,分析了两种嵌套方式和不同嵌套长度对檩条承载力的提升,且表明嵌套檩条的长度宜取为连续檩条跨度的1/5~1/4。

UHPC湿接缝浇筑的质量控制技术研究

污水处理厂生物反应池预制拼装施工复杂,超高性能混凝土(UHPC)湿接缝连接部位施工不当可能产生裂缝。结合工程实例,针对现场施工空间受限、湿接缝浇筑长度超过25 m等难点,采用UHPC搅拌泵送智能化一体机、分段连续浇筑、分阶段多重养护等措施,确保了UHPC湿接缝浇筑施工的顺利进行,有效解决了超长湿接缝开裂风险,提升了湿接缝浇筑质量。

First order sea clutter cross section for bistatic shipborne HFSWR

This paper studies the development on the first order sea clutter cross section for bistatic high frequency surface wave radar (HFSWR). Based on the received first order electric field expression, a closed-form of cross sections is derived to account for the case of receiving antenna array being mounted on the shipborne platform. The uniform linear motion and sway motion components are assumed to be responsible for the observed differences in comparison with the bistatic fixed antenna case. Correspondingly, simulations are conducted to study the sea clutter spectral characteristics for these two cases versus different system parameters and sea state conditions. It is shown numerically that the forward motion component will spread the Bragg lines severely and the influence triggered by the sway motion can be explained as the Bessel function modulation of the ordinary sea clutter spectra. The obtained results have important implications in the application of shipborne HFSWR technology to ocean remote sensing and target detection.

钢筋混凝土薄壁空心高墩塑性铰长度计算方法

针对我国现行抗震设计规范尚未明确给出钢筋混凝土(RC)薄壁空心高墩塑性铰长度计算方法的问题,首先收集整理了既有RC桥墩塑性铰长度计算方法以及试验数据,分析影响塑性铰计算长度的主要因素;同时对实际桥梁工程采用的RC薄壁空心墩构造参数进行统计归纳.在验证有限元建模方法准确性后,采用ABAQUS软件建立了高度为40~120 m的8种典型RC薄壁空心高墩的精细化有限元模型,并开展非线性推覆分析,得到不同高度桥墩的等效塑性铰长度.最后讨论不同塑性铰长度计算方法的适用性,发现Eurocode 8规范的计算公式精度最高,可用于计算RC薄壁空心高墩的塑性铰长度.

高强度聚焦超声治疗剖宫产瘢痕妊娠的临床价值

目的分析高强度聚焦超声治疗剖宫产瘢痕妊娠的临床价值。方法选取40例剖宫产瘢痕妊娠患者,根据随机数字表法分为研究组和对照组,各20例。对照组采取子宫动脉栓塞术治疗,研究组采取高强度聚焦超声治疗。对比两组临床指标、β-人绒毛膜促性腺激素(β-HCG)转阴情况、并发症和术后疼痛评分及治疗成功率。结果两组的术中出血量、β-HCG降至正常时间、平均住院费用、住院时间、并发症发生率、治疗成功率、2周、4周的β-HCG转阴率及术后36h疼痛评分对比,差异无统计学意义(P>0.05);研究组术后12h、24h疼痛评分明显低于对照组(P<0.05)。结论高强度聚焦超声治疗剖宫产瘢痕妊娠患者,具有较高的治疗价值,安全性较好,值得临床应用。

基于大中衔接的金割效应物理摆教学设计

利用自制仪器“金割效应物理摆”,基于大中衔接理念,对大学物理复摆实验进行了教学设计.从高中物理单摆知识过渡到大学物理复摆知识,建立了大学与中学物理实验之间的联系.该研究重点关注学生综合能力的培养,有利于学生构建知识框架、提高解决问题的能力,并且可以有效促进中学和大学物理实验教育的衔接.

高强度金属棒料精密剪切分离技术研究进展

金属棒料切断分离的下料工序是大多数机械零件成形制造的第1道工序。传统冲床剪切和带锯锯切的工艺方法由于存在不同程度的切断力大、断面质量差、生产效率低和材料浪费等问题,难以适用于中大直径的高强度金属棒料的高效精密切断。依据剪切下料的锻压设备类型及加载速度,将处于研究及推广状态的高强度金属棒料的精密剪切分离技术分为低速和高速两类,从工艺原理、设备类型、断面质量以及剪切效率等方面对不同精密剪切分离技术进行了探讨。相比于传统下料技术,高速精密剪切分离技术切断效率及断面精度更高,并提出了该技术进一步的研究方向。

胡家河地面水平井压裂防治冲击地压管理实践

胡家河矿为解决回采工作面高位坚硬顶板难以及时垮落的问题,引进地面“L”型水平井分段压裂技术,采取井上和井下联合监测压裂施工的方法,对压裂效果进行分析。胡家河矿在施工开展期间为规范压裂技术实施、合理分配人员和及时解决现场问题,构建了以“地面水平井分段压裂”为中心,“五+”协作统筹推进工作,做到六项反馈与确认,七大环节优化,最终形成了“156677”地面水力压裂管理体系。为推动同类矿井冲击地压防治技术研究工作提供新思路。