Fundamental Ideas and Basic Concepts of HSR Route Selection in Complicated Urban Areas

Up till now,no systematic studies on railway route selection in urban areas,HSR route selection in particular,have been taken in China.Based on the Shenzhen Railway Terminal Project and the Shenzhen-Shanwei Railway Project,research on HSR route selection in complicated urban areas has been conducted.An optimal route selection plan is determined after studying the local geological and environmental conditions and the complexity of tunnel construction.The research concludes that there are four major concerns in HSR route selection:the match between the new route and the urban planning,the potential economic return for the massive investment,the likely impacts of land expropriation on social stability,and the best synthesis of multiple controlling factors to meet the HSR standard.Moreover,six principles should be followed in railway route selection in complicated urban areas:the new route should be in alignment with the railway deployment;the route should align with the existing passage as much as possible;extensive analysis and in-depth demonstrations should be done to find the most appropriate combination of open and hidden excavation in tunnel construction;geological conditions and tunnel construction complexities are among the priorities;environmental sensitive sites and environmental vibration noise should be avoided as much as possible;special attention should be paid to the relocation of the power supply,television and communication facilities and the rearrangement of tubes and wires.

Investigating Jet Appearance in Different Background Lights with High-Speed Frame Photography

Shaped charge jet formation process is studied under the conditions of different background lights by means of high speed frame photography. In order to shoot true jet appearance, the glass tube in which jet moves is vacuumized. The experiment results show that observing jet appearance with the double reflecting mirrors system is feasible as long as the vacuum of the glass tube can meet the requirement of experiment.

Simulation of shape variation of projectile nose during high-speed penetration into concrete

A formula is developed to estimate the total mass loss of projectile, based on the assump- tions that the peeling of molten surface layer in projectile nose is the primary cause of mass loss, and the frictional heat is totally absorbed by the projectile. Extrapolating this formula to predict the mass loss of local area of projectile, the receding displacement on projectile surface is obtained, which is vertical to the symmetry axis of projectile. Thereby, a finite difference method model is constructed to simulate the variation of projectile shape. The shape of residual projectile, depth of penetration of projectile and its mass loss obtained by calculation are found in good consistency with respective experimental data.

Effects of electrode configuration on electroslag remelting process of M2 high-speed steel ingot

The electrode configuration determines the thermophysical field during the electroslag remelting(ESR) process and affects the final microstructure of the ingot. In this work, ingot with a diameter of 400 mm was prepared with two electrode configuration modes of single power ESR process, namely one electrode(OE) and two series-connected electrodes(TSCE). Finite element simulation was employed to calculate the electromagnetic field, flow field and temperature field of the ESR system. The results show that the temperature of the slag pool and the metal pool of the TSCE process is lower and more uniform than that of the OE process.The calculated temperature distribution of the ingot could be indirectly verified from the shape of the metal pool by the experiment. The experimental results show that the depth of the metal pool in the OE ingot is about 160 mm, while the depth of the TSCE ingot is nearly 40 mm shallower than that of the OE ingot. Microstructural comparisons indicate that coarse eutectic carbides are formed in the center of the OE ingot, whereas more even eutectic carbides appear in the center of the TSCE ingot. In general, compared with the OE process, the TSCE process is preferred to remelt high speed steel ingots.

Influence of Ramjets’ Water Inflow on Supercavity Shape and Cavitator Drag Characteristics

Water ramjets using outer water as an oxidizer have been demonstrated as a potential propulsion mode for underwater High Speed Supercavitating Vehicles (HSSVs) because of their higher energy density, power density, and specific impulse, but water flux changes the shapes of supercavity. To uncover the cavitator drag characteristics and the supercavity shape of HSSVs with water inflow for ramjets, supercavitation flows around a disk cavitator with inlet hole are studied using the homogenous model. By changing the water inflow in the range of 0-10 L/s through cavitators having different water inlet areas, a series of numerical simulations of supercavitation flows was performed. The water inflow flux of ramjets significantly influences the drag features of disk cavitators and the supercavity shape, but it has little influence on the slender ratio of supercavitaty. Furthermore, as the water inlet area increases, the drag coefficient of the cavitators' front face decreases, but this increase does not influence the diameter of the supercavity's maximum cross section and the drag coefficient of the entire cavitator significantly. In addition, with increasing waterflux of the ramjet, both the drag coefficient of cavitators and the maximum diameter of supercavities decrease stably. This research will be helpful for layout optimization and supercavitaty scheme design of HSSVs with water inflow for ramjets.

Model tests on XCC-piled embankment under dynamic train load of high-speed railways

Piled embankments,which offer many advantages,are increasingly popular in construction of high-speed railways in China.Although the performance of piled embankment under static loading is well-known,the behavior under the dynamic train load of a high-speed railway is not yet understood.In light of this,a heavily instrumented piled embankment model was set up,and a model test was carried out,in which a servo-hydraulic actuator outputting M-shaped waves was adopted to simulate the process of a running train.Earth pressure,settlement,strain in the geogrid and pile and excess pore water pressure were measured.The results show that the soil arching height under the dynamic train load of a high-speed railway is shorter than under static loading.The growth trend for accumulated settlement slowed down after long-term vibration although there was still a tendency for it to increase.Accumulated geogrid strain has an increasing tendency after long-term vibration.The closer the embankment edge,the greater the geogrid strain over the subsoil.Strains in the pile were smaller under dynamic train loads,and their distribution was different from that under static loading.At the same elevation,excess pore water pressure under the track slab was greater than that under the embankment shoulder.

High-speed railway channel measurements and characterizations: a review

Wireless communication for high-speed railways （HSRs） that provides reliable and high data rate communi- cation between the train and trackside networks is a challenging task. It is estimated that the wireless communication traffic could be as high as 65 Mbps per high-speed train. The development of such HSR communications systems and standards requires, in turn, accurate models for the HSR propagation channel. This article provides an overview of ex- isting HSR channel measurement campaigns in recent years. Particularly, some important measurement and modeling results in various HSR scenarios, such as viaduct and U-shaped groove （USG）, are briefly described and analyzed. In addition, we review a novel channel sounding method, which can highly improve the measurement efficiency in HSR environment.

Surface Modification of Parts Material Shape Memory TiNiCo with a View to Providing a Functional and Mechanical Property as a Factor in Resource

The paper presents a complex method of forming the surface-modified layers of materials with shape memory effect, including high-speed flame spraying of powders based on TiNiCo;subsequent thermal and thermomechanical treatment allows the formation of surface layers of nano-sized state that have a high level of functional, mechanical and performance properties;it is shown that the complex processing with a layer of TiNiCo allows a reduction of the porosity of the coatings and increases the strength of the coating’s adhesion to the substrate. It is found that, after treatment with high-speed flame spraying powder shape memory TiNiCo, steel has an increase in cycle life by 30% - 40% in a cycle fatigue and 3 - 3.5 times durability. Based on comprehensive research into the metallophysical surface-modified layer, new information is obtained about the nanoscale composition.

The Richtmyer–Meshkov instability of a 'V' shaped air/helium interface subjected to a weak shock

The Richtmyer-Meshkov instability ofa ‘V＇ shaped air/helium gaseous interface subjected to a weak shock wave is experimentally studied. A soap film technique is adopted to create a ‘V＇ shaped interface with accurate initial conditions. Five kinds of ‘V＇ shaped interfaces with different vertex angles are formed to highlight the effects of initial conditions on the flow characteristics. The results show that a spike is generated after the shock impact, and grows constantly with time. As the vertex angle increases, vortices generated on the interface become less noticeable, and the spike develops less pronouncedly. The linear growth rate of interface width after compression phase is estimated by a linear model and a revised linear model, and the latter is proven to be more effective for the interface with high initial amplitudes. The linear growth rate of interface width is, for the first time in a heavy/light interface configuration, found to be a non-monotonous function of the initial perturbation amplitude-wavelength ratio.

离心式高速玉米精量排种器T形槽型孔设计与试验

针对离心式高速玉米精量排种器双粒种子并排填充导致重播严重的问题,该研究提出利用型孔槽对称凸台结构降低玉米种子并排填充概率的方法,设计了一种T形槽型孔。通过构建充种阶段玉米种子的力学模型,并结合玉米种子的形状特征确定了T形槽型孔基本结构参数。借助EDEM离散元仿真软件,以型孔槽前端长度、型孔槽后端面倾斜角以及型孔槽底部倾斜角为因素,以合格指数、重播指数与漏播指数为评价指标,设计二次正交旋转回归组合仿真试验。仿真试验结果表明:在作业速度18 km/h条件下,型孔槽前端长度为9.31 mm,型孔槽后端面倾斜角为43.37°与型孔槽底部倾斜角为70.5°时,排种质量最优,排种合格指数、重播指数与漏播指数分别为94.03%、1.72%与4.25%。台架验证试验结果表明:作业速度为15 km/h时,T形槽型孔的合格指数最高为95.16%,在此作业速度下,排种器的重播指数为1.42%,漏播指数为3.42%,满足高速精量播种要求;作业速度在12~21 km/h内时,T形槽型孔的平均合格指数为94.77%,相较于矩形槽型孔提升了3.13个百分点,相较于蹄型槽型孔提升了1.80个百分点,T形槽型孔的平均重播指数为2.06%,相较于矩形槽型孔降低了3.41个百分点,相较于蹄型槽型孔降低了2.49个百分点。该研究可为离心式高速玉米精量排种器优化提供参考。

Mindlin方法在桩承式U形路基沉降分析中的应用

为解决桩承式悬臂U形路基的沉降分析问题,将Mindlin理论应用于桩承路基引起的地基附加应力分布与地基沉降变形计算。通过对复合地基、桩基两种承载方式的U形路基和放坡式路基地基深层附加应力以及沉降位移的对比分析,系统提出基于Mindlin点荷载附加应力叠加的桩承式U形路基沉降分析方法。分析结果表明:承载桩体桩侧摩阻同桩端阻的荷载分配应满足竖向力平衡条件,桩侧摩阻根据地层应为非线性分布;Mindlin理论能够满足桩承式U形路基的沉降计算需求,有效反映出桩体承载对加固区及桩端下卧层附加应力分布的影响;相同条件下,桩承式U形路基中心沉降分别为复合地基加固U形路基中心沉降量的22%和放坡式路基中心沉降量的15.4%,其在沉降位移控制方面优势突出。

双层永磁体结构高速永磁电机转子涡流损耗解析模型

对于采用低电导率护套高电导率永磁体的表贴式高速永磁电机,在永磁体和保护套之间增加一层低电导率的永磁体,可有效降低永磁体上的涡流损耗。目前,对于双层永磁体转子结构的电机在使用有限元软件进行转子涡流损耗计算时,因为需要寻求两种永磁体不同厚度配比下的最优方案,所以要进行大量参数化,导致计算时间长、效率低。针对这一问题,该文基于精确子域法,建立了一个考虑定子开槽以及涡流反作用影响的双层永磁体结构转子涡流损耗解析模型,可同时对电枢磁场和负载磁场下双层永磁体结构转子涡流损耗进行求解,并且该模型可扩展至多层永磁体复合结构的转子涡流损耗计算。在此基础上分析了双层永磁体结构下外层永磁体不同厚度和不同材料对转子涡流损耗和内层永磁体消耗量的影响。最后通过有限元仿真和C型铁心实验验证了该解析模型的有效性。

局部外形参数对高速飞行器的RCS影响

为了降低高速飞行器的雷达散射截面(radar cross section,RCS),采用多层快速多极子算法和物理光学法研究局部外形参数对飞行器雷达散射特性的影响。在此基础上,提出一种变半径弧形的边缘钝化形式,以提高飞行器仰视对抗能力。所提出的变半径弧形钝化外形具有良好的RCS减缩能力,与传统圆弧钝化外形相比,在前向重点角域内,RCS对数均值降低了22.88%;随着仰角的增大,变半径弧形钝化形式还具备全向RCS减缩能力,在全向角域内RCS对数均值降低了13.37%。最后,研究所提出的变半径弧形钝化方式在不同雷达波频段下的RCS特性,结果表明这种钝化方式对于频率较高时仰视对抗能力更好。

考虑长细比的岩土颗粒系统非稳态流动特征研究

砂土等常见岩土颗粒系统在高速流动状态下具有显著的非稳态特征,其剪切速度分布与速度波动特征等均表现出显著的随机性。但目前颗粒系统细观特征对其宏观流动参数的影响尚不明确,针对岩土颗粒流动过程随机性特征参数的研究亟待加强。本文通过离散元环剪单元实验模拟,捕捉不同形状颗粒系统高速剪切流动过程中的宏微观特征。研究结果表明:(1)颗粒形状对系统宏观剪应力有较为显著的影响。颗粒长细比越大,其残余剪应力越大;(2)颗粒系统速度波动的空间分布同时受到剪切速度与边界效应两方面的影响。剪切速度越大,速度波动越大。边界对于颗粒速度波动具有一定的约束效应;(3)颗粒形状对系统速度波动大小有显著影响。颗粒越细长,微观速度波动越小;(4)形状特征对颗粒系统细观接触特征有显著影响。颗粒越细长,其平均配位数越大,出现较大粒间接触力的概率越小。

预制孪晶对AZ31镁合金绝热剪切敏感性的影响

为了分析不同孪晶体积分数对材料绝热剪切敏感性的影响,预制具有不同孪晶体积分数的AZ31镁合金。采用分离式霍普金森压杆在200℃、944 s^(-1)条件下对AZ31镁合金帽状试样进行高速冲击试验,采用电子背散射衍射仪和光学显微镜对试样在高应变速率变形前后的微观组织进行观察,计算了试样发生绝热剪切时的吸收能量,比较了绝热剪切带内外的显微硬度。结果表明:不同孪晶体积分数试样内均产生了绝热剪切带,随着孪晶体积分数的增加,绝热剪切带宽度和吸收能量减小,而绝热剪切敏感性增大。

考虑摩擦块形状及轮轨蠕滑的列车制动黏滑振动行为分析

制动盘与摩擦块之间相互摩擦引起的黏滑振动直接影响高速列车制动系统的稳定性并威胁车辆安全运行.为探明摩擦块形状对高速列车制动系统黏滑振动的影响,本文中针对高速列车制动系统常用的五边形和六边形摩擦块,在相对低速条件下开展了盘-块黏滑振动试验,辨识了盘-块界面的Stribeck摩擦参数,揭示了摩擦块形状、摩擦系数和盘-块界面黏滑振动之间的关系.进一步,建立了考虑盘-块摩擦、轮-轨黏着及轮-盘扭转的高速列车制动系统动力学模型,并将辨识的Stribeck摩擦参数集成到该动力学模型中,构建了盘-块界面摩擦特征与制动系统动态响应之间的关联.基于此,研究了摩擦块形状对高速列车制动系统黏滑振动的影响.结果表明,摩擦块形状通过改变盘-块界面摩擦特征,影响制动系统的黏滑振动响应及稳定性.此外,相比五边形摩擦块,采用六边形摩擦块制动系统的黏滑振动强度更低.

常德高铁站房结构设计

常德高铁站是常益长正线线路上的重要站点,站房分为下部混凝土结构和上部钢屋盖。屋盖采用Γ形刚架作为主要支撑结构,一方面斜柱有效地增加了结构的抗侧刚度,另一方面也与桃花盛开的建筑意象相契合,其结构形式经历了立体三角形桁架、箱桁结合实腹梁、箱形实腹梁3轮方案的推敲演变。针对天窗区域连系桁架拱形下弦的矢高取值,采用Grasshopper+SAP2000联动程序进行自动化参数找形,得到结构受力性能和建筑空间效果均优的平衡点。通过ABAQUS壳单元模型与SAP2000杆单元模型的对比分析,验证了利用SAP2000截面设计器对变截面的异形截面构件分析的准确性,同时对Γ形刚架进行了弹塑性极限承载力分析,结果满足要求。Γ形刚架形态舒张有力,结构受力合理,实现了建筑与结构的完美结合。

强风沙环境下高速列车车体冲蚀特性研究

为研究高速列车在不同车速下受到强风沙的冲蚀效应,基于欧拉-拉格朗日体系,利用DPM模型将风和空气设为连续相,将沙子颗粒设为离散相,对不同车速、沙粒粒径和风速下的高速列车的冲蚀效应进行了数值模拟。结果表明:随着列车车速的增加,冲蚀率开始的增速较缓,后来急剧增加;随着颗粒直径的增加,冲蚀率开始时增长较快,后面增长较为平缓。随着风速的增加,列车的冲蚀率开始时增长较缓慢,同时随车速的增大,列车的冲蚀率也逐渐增大。为研究高速列车车体处实际的冲蚀效应,在忽略涂层的情况下,采用冲蚀磨损实验机与数值模拟结合的方法,研究颗粒形状与质量流量对冲蚀效应的影响。结果表明:当颗粒形状因子增加时,车体的侵蚀率下降,而决定车体的冲蚀磨损主要是微切削磨损,当质量流速增加时,磨损率先增加后下降。

手术刀片铝箔包装纸配合金属吸唾管在阻生齿拔除术中的临床应用

目的观察手术刀片铝箔包装纸配合金属吸唾管在下颌阻生齿的拔除中的临床应用。方法纳入2023年3月至2024年3月于葫芦岛市中心医院口腔科就诊的60例下颌阻生智齿拔除患者,将此60个患者随机分为实验和对照两组,两组均应用高速涡轮手机拔除,其中实验组使用手术刀片铝箔包装纸联合金属吸唾管配合高速涡轮手机,铝箔纸盖住掀起的黏骨膜瓣,保护黏骨膜瓣及周围软组织,金属吸唾管侧方压住铝箔纸,防止铝箔纸移位同时进行吸引。对照组使用传统金属拉钩配合高速涡轮手机。两组患者于术后第7日进行拆线,比较两组患者临床疗效及不良反应的发生率。结果实验组软组织损伤率低于对照组,差异有统计学意义(P<0.05);实验组手术时间短于对照组,差异有统计学意义(P<0.05);实验组术后肿胀程度轻于对照组,差异有统计学意义(P<0.05)。结论手术刀片铝箔包装纸配合金属吸唾管的应用能有效减少周围软组织损伤,缩短手术时间,减轻术后并发症。

InP微透镜的设计与制作

高速光电探测器采用芯片背面带微透镜的背入射结构,利用微透镜对光的汇聚提高芯片与光纤的耦合效率。软件模拟发现,光敏面直径为30μm的芯片采用背入射结构时,其等效光敏面直径大于50μm,并且透镜拱高为8～15μm时,能更好实现对光的汇聚。对于InP微透镜的制作,首先要制作出透镜形状的光刻胶胶型,然后通过电感耦合等离子体（ICP）刻蚀将光刻胶图形转移到InP衬底上。光刻胶坚膜温度与坚膜时间对光刻胶形成透镜形状有很大影响。通过优化条件,150℃坚膜3 min的光刻胶呈规则透镜形状,并且表面光滑无褶皱。通过调节反应离子刻蚀（RIE）功率和ICP功率找到了合适的InP刻蚀速率,调节Cl2和BCl3的体积流量比改变了InP和光刻胶的刻蚀选择比,从而制作出不同拱高的微透镜。