Monitoring Longitudinal Vehicular Velocity by Using Driving Wheels Information

In order to enhance the accuracy and overcome the limitation of representing the vehicular velocity with non driving wheel speed signals, which is commonly used in researching on automotive dynamic control systems at present, the dynamic and kinematics models of running vehicles and wheels are established. The concept that expresses vehicle velocity using only the driving wheel speed information with adjustable weight factors is described and an algorithm is proposed. A Matlab program with the algorithm embedded is made to simulate the vehicle’s accelerating under different road conditions, and it’s simulation results coincide well with the experimental results, which demonstrates the validity of the algorithm.

Zero group velocity longitudinal modes in an isotropic cylinder

Zero group velocity （ZGV） modes are studied in an isotropic cylinder. The L （0, 2） mode behaves anomalously for the materials with a value of the bulk velocity ratio, to, in the range √2 〈 κ 〈 2.64 and normally otherwise. All higher modes, except the first few, have no ZGV point for all isotropic materials. This is explained analytically by finding the slope of phase velocity dispersion curves of modes first when the phase velocity equals κ and then at their initial state.

The effect of electron initial longitudinal velocity on the non-sequential double ionization process in an elliptically polarized laser field

The effect of initial longitudinal velocity of the tunnelled electron on the non-sequential double ionization （NSDI） process in an elliptically polarized laser field is studied by a semiclassical model. We find that the non-zero initial longitudinal velocity has a suppressing effect on single-return collision （SRC） events in the double ionization process, more specifically, it results in an obvious reduction in the center part of the correlation momentum distributions in the direction of the major polarization axis （z axis） and makes the distribution of single-return collision in the minor polarization axis （x axis） become narrower.

Longitudinal Variability of the Vertical Drift Velocity Inferred from Ground-Based Magnetometers and C/NOFS Observations in Africa

This study aims at discussing longitudinal effects on the variability of the vertical E × B drift velocity at low latitudes, specifically over African sector. To this effect, observations from ground-based magnetometers and the Ion Velocity Meter experiment onboard C/NOFS satellite are analyzed in conjunction with equatorial electric field and neutral wind model estimates under geomagnetically quiet conditions in the years 2012-2013. Notwithstanding the limitation in data over Africa, the combination of ground-based and in-situ observations confirmed the existence of longitudinal differences in the E × B between the Atlantic, Western and Eastern African sectors. This was well reproduced by the equatorial electric field model (EEFM) which showed that during noon, the peak of the equatorial electric field (EEF) was the lowest in the Atlantic sector, with an increasing trend towards the Eastern longitude. The Horizontal Wind Model 14 (HWM14) showed that the eastward zonal (poleward meridional) wind velocity was the lowest (highest) in the Eastern sector. Furthermore, the zonal (meridional) wind increased (decreased) from the Eastern to the Atlantic sector. These results highlight the contribution of the neutral wind velocity in driving the longitudinal difference in the vertical drift velocity over Africa.

Longitudinal dynamic response of pile in layered soil based on virtual soil pile model

Taking the effect of finite soil layers below pile end into account,the longitudinal dynamic response of pile undergoing dynamic loading in layered soil was theoretically investigated.Firstly,finite soil layers below pile end are modeled as virtual soil pile whose cross-section area is the same as that of the pile and the soil layers surrounding the pile are described by the plane strain model.Then,by virtue of Laplace transform and impedance function transfer method,the analytical solution of longitudinal dynamic response at the pile head in frequency domain is yielded.Also,the semi-analytical solution in time domain undergoing half-cycle sine pulse at the pile head is obtained by means of inverse Laplace transform.Based on these solutions,a parametric study is conducted to analyze emphatically the effects of parameters of soil below pile end on velocity admittance and reflected wave signals at the pile head.Additionally,a comparison with other models with different supporting conditions from soil below pile end is performed to verify the model presented.

Influence of Collective Boulder Array on the Surrounding Time-averaged and Turbulent Flow Fields

Arrays of large immobile boulders,which are often encountered in steep mountain streams,affect the timing and magnitude of sediment transport events through their interactions with the approach flow.Despite their importance in the quantification of the bedload rate,the collective influence of a boulder array on the approach timeaveraged and turbulent flow field has to date been overlooked.The overarching objective is,thus,to assess the collective effects of a boulder array on the time-averaged and turbulent flow fields surrounding an individual boulder within the array,placing particular emphasis on highlighting the bed shear stress spatial variability.The objective of this study is pursued by resolving and comparing the timeaveraged and turbulent flow fields developing around a boulder,with and without an array of isolated boulders being present.The results show that the effects of an individual boulder on the time-averaged streamwise velocity and turbulence intensity were limited to the boulder's immediate vicinity in the streamwise(x/d c < 2-3) and vertical(z/d c < 1) directions.Outside of the boulder's immediate vicinity,the time-averaged streamwise velocity was found to be globally decelerated.This global deceleration was attributed to the form drag generated collectively by the boulder array.More importantly,the boulder array reduced the applied shear stress exerted on theindividual boulders found within the array,by absorbing a portion of the total applied shear.Furthermore,the array was found to have a "homogenizing" effect on the near-bed turbulence thus significantly reducing the turbulence intensity in the near-bed region.The findings of this study suggest that the collective boulder array bears a portion of the total applied bed shear stress as form drag,hence reducing the available bed shear stress for transporting incoming mobile sediment.Thus,the effects of the boulder array should not be ignored in sediment transport predictions.These effects are encapsulated in this study by Equation(6).

Structural features of crust-mantle assemblage in the lithosphere along the Longitudinal Seismic Belt of China and their tectonic effect

The 1°×1° distribution map of crustmantle structural ratio R for the lithosphere along the Longitudinal Seismic Belt of China has been compiled using computer based on the results of geophysical prospecting by previous researchers, and the latest results by the present authors. Based on this map, an insight into the structural features of the crustmantle assemblage along the Longitudinal Seismic Belt has been gained, while their relation to seismic activity and the distributions of geothermal flux and intracrustal high conductivitylow velocity layers, as well as their tectonic effect to seismicity have been discussed.

Comparison Analysis of Longitudinal Electrical Conductivity Distribution and Seismic Tomography Velocity Models for the Central Tien Shan Region

The paper is dedicated to consider the approach of longitudinal electrical conductivity maps construction for Central Tien Shan region and to complete the comparison analysis of these maps with related seismic tomography data.The results of joint analysis of longitudinal electrical conductivity distribution and seismic tomography velocity models with respect to geological and geophysical senses allow to confirm the already known and to establish the new patterns of structure and geodynamics of the Tien Shan segment of Central Asia such as the manifestation of characteristic structural ensembles,reflection of the longitudinal and transverse segmentation of the Tien Shan,the existence within the framework of a“single”orogen of segments with different near-surface and deep structure and morphological expression.As well,the correlation between the velocity characteristics and geoelectric properties was found.This correlation allows to identify signs of reflection of fault structures in geophysical fields and to clarify the territorial and structural position of both visible and hidden faults.Additionally,in the paper,the geological interpretation of geophysical anomalies is considered.

隧道火灾临界风速模型的差异与适用性分析

临界风速是纵向通风隧道防排烟设计的重要指标,目前广泛采用的临界风速模型分为临界弗洛德数模型(世界道路协会PIARC推荐)和分段函数模型(美国消防协会NFPA推荐)两类,但两种公式的计算结果差异显著,给隧道防火设计造成了困扰。本文分析了PIARC公式和NFPA公式在不同火源功率、隧道宽度、隧道高度下计算临界风速的差异及成因,同时结合隧道火灾全尺寸试验、数值模拟对比了两种公式计算结果的控烟效果,并与已有的全尺寸和比尺模型试验数据比较论证了两公式的适用性。结果表明,受临界弗洛德数取值和均匀混合假定的制约,PIARC公式无法准确反映临界风速随火源功率的变化规律,公式计算结果明显偏小,且误差随着宽高比的增大而增大;而NFPA公式更加全面地考虑了火羽流状态与隧道断面尺寸之间的相对关系对临界风速的影响,计算结果具有更好的烟气控制效果,且与试验数据更为吻合;NFPA公式可以适用于大部分隧道断面和火源功率条件下的临界风速计算,而PIARC公式仅适用于断面宽高比较小(AR≤1)和火源功率较大(HRR≥15MW)时的临界风速计算。

隧道防火门分流对端部临界送风风速的影响

在单洞双线轨道交通隧道发生火灾时,人员从火源上游防火门疏散,防火门的分流作用将影响端部送风风速。采用理论计算与数值模拟相结合的方法探究其影响关系,首先通过理论分析推导出了端部临界送风风速公式;随后,利用PyroSim软件建立了全尺寸模型,并针对不同数量防火门、火源热释放速率、隧道高度的分流情况进行了研究。结果表明:在相同火源热释放速率下,防火门的分流流速随着防火门开启数量的增多而减少;相同位置防火门的分流流速随火源热释放速率的增大呈指数增长的关系;防火门总分流量随防火门开启数量与热释放速率的0.3次方之积呈线性增长的关系,而受隧道高度的影响较小;结合理论推导,建立了端部临界送风风速的数学模型。研究结果为隧道火灾情况下的人员疏散和通风设计提供了科学依据。

融冰沿气槽结构超疏水斜面下滑的解析数值分析

文章提出了融冰沿气槽结构超疏水表面顺向下滑过程的物理几何模型.对融冰层液膜微剪切流进行分析,利用超疏水壁面“黏-滑”边界条件建立了微剪切流场的双Fourier级数方程,求得解析数值解,在此基础上研究了融冰层液膜微剪切流的速度分布及冰层下滑速度与超疏水表面气槽占比(a)、斜面倾角(α)以及融冰层液膜厚度(δ)之间的定量规律.研究结果表明,融冰层越薄或空气槽占比越大,融冰层微剪切流场偏离平板剪切流越显著;三相接触线处滑移速度梯度发生突变并达到峰值;a,α与δ的增大均会导致冰层超滑速度非线性增加,融冰层厚度增大到1之后超滑速度趋于渐近解析解函数.基于所取的参数值,a=0.95,δ=0.2以及a=0.9,δ=0.1时,由超疏水壁面结构导致的冰层下滑速度增量相对于总下滑速度的占比超过60%,此时冰层下滑速度主要来自超滑速度的贡献.文章的研究为当前超疏水除冰应用中的相关流体物理过程提供了参考.

自旋翼无人机纵向解耦控制技术研究

针对对象自旋翼无人机,提出在干扰下如何实现解耦控制。由于对象无人机空中段飞行过程中对外界干扰十分敏感,很容易在干扰下激发高度和速度间的耦合,现有控制策略优先考虑了速度控制,而牺牲了高度控制性能,所以导致高度控制鲁棒性较差。针对此特性,提出升降速率指令内回路控制结构以增加系统对高度差的反应能力,并且在桨盘控制通道加入高度反馈以弥补油门控制的不足。通过仿真测试改进策略的解耦性能以及鲁棒性,验证了该策略是合理且可行的。

地下立交互通匝道集中排烟效果研究

针对两端连接主隧道的互通匝道火灾烟气控制问题,依托南京建宁西路曲线A匝道工程,借助数值模拟软件FDS,研究HRR为30 MW下纵向诱导风速、排烟口尺寸及火源位置对顶部集中排烟效果的影响。结果表明:火源位于匝道中部,诱导风速为1.0 m/s时恰好保证烟气不发生“跨区蔓延”,诱导风速为1.5 m/s、排烟量为150 m^(3)/s时,控烟效果更好;匝道内烟气蔓延范围随排烟口尺寸增大而减小,当排烟口长宽比为4、面积为6 m^(2)时,匝道内烟气控制效果较好,系统整体排烟效率大于98%;排烟口长宽比不变时,拱顶最高温度随排烟口面积增大而降低;排烟口面积不变时,拱顶最高温度随排烟口长宽比增大而升高。火源位于匝道上游或下游时,排烟风量至少需增大至210 m^(3)/s,诱导风速需作针对性优化。

冻融循环下秸秆纤维混凝土损伤特性及动态力学性能研究

为研究冻融循环对不同纤维掺量的秸秆纤维混凝土动态力学性能的影响,采用非金属超声波检测仪测量不同冻融循环次数下秸秆纤维混凝土试件纵波波速,利用直径74 mm变截面分离式霍普金森压杆试验装置对试件开展动态单轴压缩试验,分析试件纵波波速、峰值应力、劣化度、韧性及破碎耗能密度与冻融循环次数及秸秆纤维掺量间的关系。结果表明:纤维的掺入能够提高混凝土材料的纵波波速及整体性,随着冻融循环次数的增加,秸秆纤维混凝土纵波波速随之降低,冻融循环会对试件造成损伤;秸秆纤维的掺入会增强混凝土材料的力学性能,掺量为0.2%时效果最佳,冻融循环作用试件峰值应力不断降低,劣化度不断增加,相较于冻融循环0次素混凝土试件,冻融循环30、60、90、120次试件峰值应力分别降低6.96%、19.4%、34.2%、53.3%,冻融循环后期应力降幅显著增加,纤维的掺入在一定程度上减缓了冻融作用下试件劣化程度;纤维掺量为0.2%时试件的韧性与破碎耗能密度提升最大,冻融循环会对试件造成劣化,降低其韧性及吸能效果。秸秆纤维的掺入使混凝土材料力学性能大幅增加,秸秆纤维的绿色可再生性对秸秆纤维混凝土的推广具有重大意义。

漂浮植被作用下水流纵向流速的垂向分布及离散特性研究

为探究漂浮植被影响下明渠水流流速及纵向离散系数的沿程变化特性,采用Fluent软件中的k-ε模型进行三维数值模拟并与水槽试验结果进行对比分析,在模型验证合理的基础上,对漂浮植被不同根系下探深度及覆盖率下水流纵向时均流速的垂向分布特性进行研究,并基于改进的分区模型分析了含漂浮植被明渠的纵向离散系数。结果表明:漂浮植被水流垂向上可分为含植被水流层、无植被水流层与近河床层。纵向流速最大值出现在无植被水流层,其大小与植被下探深度及覆盖率呈正相关。含植被水流层的纵向流速随植被根系下探深度和覆盖率的增加而减小,无植被水流层及近河床层的纵向流速随着下探深度和覆盖率的增大而增大,且植被覆盖率及下探深度越大含植被水流层与无植被水流层的流速差异越大。纵向离散系数沿程表现出先增大后减小的趋势,在植被区中下游离散最为剧烈,且与植被下探深度和覆盖率呈正相关。

一种列车制动信号无线传输通讯系统设计

在铁路运输趋于高速和重载的背景下,重载列车传统空气制动系统仅能适用于单元式重载列车,并且后期维护相对不便,且在制动时会带来过大的车钩纵向力,影响行车安全,因此具有高带宽、低延迟、维护便捷等优点的无线制动系统应运而生。为了解决上述问题,立足于制动系统制动信号的无线传输,基于嵌入式技术设计了一套制动信号无线传输通讯系统。硬件方面,以STC8H8K64U作为主控芯片完成通讯系统的原理图设计,主要包括电源模块、CAN(Controller Area Network,控制器局域网)网络模块、GPRS(General Packet Radio Service,通用分组无线服务技术)模块、无线网络LoRa(Long Range Radio,远距离无线电)模块等,并且对硬件进行抗干扰处理。软件方面,完成STC8的外设驱动程序设计、LoRa无线网络模块的程序设计以及装置与系统之间通讯协议的自定义。基于以上设计,完成通讯系统的调试与测试工作,对无线网络模块LoRa的通讯距离进行测试,通过建立动力学模型和线路试验来对比使用传统空气制动方案制动与使用制动信号无线传输通讯系统制动方案下的制动波速以及车钩纵向力。测试和试验结果表明:系统各模块功能正常,能有效完成与车辆控制装置和远程控制平台之间的数据交互;有行人、树木、建筑等遮挡物时,无线网络模块LoRa的通讯距离为400 m;使用制动信号无线传输通讯系统在列车制动时可有效提升制动波速,减小车钩纵向力。研究结果可为重载列车的制动系统设计提供参考。

基于矿物溶解理论的砂岩化学损伤动态模型

酸腐蚀环境下岩石物理力学性质的劣化本质上由岩石矿物的溶解引发的孔隙微裂隙的扩展贯通所致。为研究酸性环境下砂岩矿物的溶解特性,选择pH=1、3的盐酸溶液为腐蚀环境,借助X射线衍射试验鉴定砂岩矿物成分及含量,测试不同浸泡周期下溶液的pH值、阳离子浓度、岩样的质量及其纵波波速,并通过矿物溶解理论与化学动力学原理,建立反映整个腐蚀过程的砂岩化学损伤动态模型。研究结果表明:酸性环境下砂岩的损伤主要由长石和方解石的溶解所致,矿物溶解反应分为界面吸附、界面交换、解吸附三个步骤,且步骤最慢者对整个反应起控制作用。矿物溶解速率与H+浓度的n次幂成正比,且0<n≤1,其数值与矿物自身特性和溶液pH值有关。酸-岩反应具有较强的时间依赖性,其速率随腐蚀时间的延长逐渐减小而后趋于稳定,且溶液pH值越小,腐蚀时间越长,砂岩劣化越严重。pH=1、3的盐酸溶液作用下,通过化学损伤模型得到的砂岩孔隙度与通过纵波波速得到的孔隙度随腐蚀时间的变化规律具有较好的一致性,验证了模型的有效性与合理性。研究结果可为酸化学环境下岩体工程的安全性评估与灾害防治提供理论参考。

冻融循环作用下的花岗岩边坡岩体强度研究

以伊春鹿鸣钼矿发育的花岗岩边坡岩体为例,开展不同风化程度的花岗岩岩石样品的冻融循环单轴抗压强度试验和纵波波速试验,得到不同风化程度的花岗岩冻融循环单轴抗压强度和纵波波速损失程度不同,风化程度高的花岗岩冻融系数较低;冻融循环作用下的花岗岩单轴抗压强度冻融系数与纵波波速损伤变量之间为线性关系,对于不同风化类型的花岗岩,其线性关系高度相近。从边坡稳定性分析的角度出发,提出了2种获取冻融循环花岗岩边坡岩体强度参数的方法,并进行了计算验证。结果显示:采用单轴抗压强度冻融系数直接折减抗剪强度,或采用纵波波速冻融系数折减RMR值后推导抗剪强度,所得结果均可进行边坡稳定性计算;相对来讲,后者计算的安全系数与边坡体实际稳定状态更为接近。

基于深度强化学习CLPER-DDPG的车辆纵向速度规划

为了解决车辆纵向速度规划任务中规划器不易收敛以及在多场景之间切换时稳定性差的问题,基于多层感知机设计了车辆纵向速度规划器,构建了结合优先经验回放机制和课程学习机制的深度确定性策略梯度算法。该文设计了仿真场景进行模型的训练和测试,并对深度确定性策略梯度(DDPG)、结合优先经验回放机制的深度确定性策略梯度(PER-DDPG)、结合优先经验回放机制和课程学习机制的深度确定性策略梯度(CLPER-DDPG)3种算法进行对比实验,并在园区内的真实道路上进行实车实验。结果表明:相比于DDPG算法,CLPER-DDPG算法使规划器的收敛速度提高了56.45%,距离差均值降低了16.61%,速度差均值降低了15.25%,冲击度均值降低了18.96%。此外,当实验场景的环境气候和传感器硬件等参数发生改变时,模型能保证在安全的情况下完成纵向速度规划任务。

纵向通风作用下隧道内氢泄漏爆炸隐患分析

为研究纵向通风能否有效控制隧道中泄漏氢气的扩散以及降低可燃氢云的超压危害,本文以一长100 m的方形隧道为研究对象,利用FLUENT软件对隧道内氢气泄漏扩散现象进行数值模拟,基于可燃氢云爆炸超压对人和建筑物的危害分级,分析纵向通风降低隧道内氢气泄漏爆炸危害性的作用效果.研究结果表明:计算工况下,隧道内发生氢气射流火灾时的纵向风速范围为6.5~8.0 m/s;纵向通风能够有效控制隧道内氢气的泄漏和扩散,但不能完全消除隧道氢泄漏爆炸的可能性和危害性.