Review on dynamic analysis of road pavements under moving vehicles and plane strain conditions

This paper reviews works on the dynamic analysis of flexible and rigid pavements under moving vehicles on the basis of continuum-based plane strain models and linear theories.The purpose of this review is to provide in-formation about the existing works on the subject,critically discuss them and make suggestions for further research.The reviewed papers are presented on the basis of the various models for pavement-vehicle systems and the various methods for dynamically analyzing these systems.Flexible pavements are modeled by a homogeneous or layered half-plane with isotropic or anisotropic and linear elastic,viscoelastic or poroelastic material behavior.Rigid pavements are modeled by a beam or plate on a homogeneous or layered half-plane with material properties like the ones for flexible pavements.The vehicles are modeled as concentrated or distributed over a finite area loads moving with constant or time dependent speed.The above pavement-vehicle models are dynamically analyzed by analytical,analytical/numerical or purely numerical methods working in the time or frequency domain.Representative examples are presented to illustrate the models and methods of analysis,demonstrate their merits and assess the effects of the various parameters on pavement response.The paper closes with con-clusions and suggestions for further research in the area.The significance of this research effort has to do with the presentation of the existing literature on the subject in a critical and easy to understand way with the aid of representative examples and the identification of new research areas.

Study and application of monitoring plane displacement of a similarity model based on time-series images

In order to compensate for the deficiency of present methods of monitoring plane displacement in similarity model tests,such as inadequate real-time monitoring and more manual intervention,an effective monitoring method was proposed in this study,and the major steps of the monitoring method include:firstly,time-series images of the similarity model in the test were obtained by a camera,and secondly,measuring points marked as artificial targets were automatically tracked and recognized from time-series images.Finally,the real-time plane displacement field was calculated by the fixed magnification between objects and images under the specific conditions.And then the application device of the method was designed and tested.At the same time,a sub-pixel location method and a distortion error model were used to improve the measuring accuracy.The results indicate that this method may record the entire test,especially the detailed non-uniform deformation and sudden deformation.Compared with traditional methods this method has a number of advantages,such as greater measurement accuracy and reliability,less manual intervention,higher automation,strong practical properties,much more measurement information and so on.

IN-PLANE WAVE MOTION IN FINITE ELEMENT MODEL

The analysis method of lattice dynamics in classical physics is extended to study the properties of in-plane wave motion in the hybrid-mass finite element model in this paper. The dispersion equations of P and SV waves in the discrete model are first obtained by means of separating the characteristic equation of the motion equation, and then used to analyse the properties of P-and SV-homogeneous, inhomogeneous waves and other types of motion in the model. The dispersion characters, cut-off frequencies of P and SV waves, the polarization drift and appendent anisotropic property of wave motion caused by the discretization are finally discussed.

Anisotropic Plane Symmetric Two-Fluid Cosmological Model with Time-Varying G and A

We investigate a two-fluid anisotropic plane symmetric cosmological model with variable gravitational constant G（t） and cosmological term A（t）. In the two-fluid model, one fluid is chosen to be that of the radiation field modeling the cosmic microwave background and the other one a perfect fluid modeling the material content of the universe. Exact solutions of the field equations are obtained by using a special form for the average scale factor which corresponds to a specific time-varying deceleration parameter. The model obtained presents a cosmological scenario which describes an early acceleration and late-time deceleration. The gravitation constant increases with the cosmic time whereas the cosmological term decreases and asymptotically tends to zero. The physical and kinematical behaviors of the associated fluid parameters are discussed.

The use of the greater trochanter marker in the thigh segment model:Implications for hip and knee frontal and transverse plane motion

Background:The greater trochanter marker is commonly used in 3-dimensional(3D) models;however,its influence on hip and knee kinematics during gait is unclear.Understanding the influence of the greater trochanter marker is important when quantifying frontal and transverse plane hip and knee kinematics,parameters which are particularly relevant to investigate in individuals with conditions such as patellofemoral pain,knee osteoarthritis,anterior cruciate ligament(ACL) injury,and hip pain.The aim of this study was to evaluate the effect of including the greater trochanter in the construction of the thigh segment on hip and knee kinematics during gait.Methods:3D kinematics were collected in 19 healthy subjects during walking using a surface marker system.Hip and knee angles were compared across two thigh segment definitions(with and without greater trochanter) at two time points during stance:peak knee flexion(PKF) and minimum knee flexion(Min KF).Results:Hip and knee angles differed in magnitude and direction in the transverse plane at both time points.In the thigh model with the greater trochanter the hip was more externally rotated than in the thigh model without the greater trochanter(PKF:-9.34°± 5.21° vs.1.40°± 5.22°,Min KF:-5.68°± 4.24° vs.5.01°± 4.86°;p < 0.001).In the thigh model with the greater trochanter,the knee angle was more internally rotated compared to the knee angle calculated using the thigh definition without the greater trochanter(PKF:14.67°± 6.78° vs.4.33°± 4.18°,Min KF:10.54°± 6.71° vs.-0.01°± 2.69°;p < 0.001).Small but significant differences were detected in the sagittal and frontal plane angles at both time points(p < 0.001).Conclusion:Hip and knee kinematics differed across different segment definitions including or excluding the greater trochanter marker,especially in the transverse plane.Therefore when considering whether to include the greater trochanter in the thigh segment model when using a surface markers to calculate 3D kinematics for movement assessment,it is important to have a clear understanding of the effect of different marker sets and segment models in use.

Exploration of Water Resource and Multiple Model for Water Resource Development in Karst Areas with the Preferred Plane Theory

According to the theory of preferred plane, preferred planes (faults) alwayscontrol the distribution of bedrock fissure water and hold abundant groundwater. Thus, theexploration of fissure or karst water can be converted into searching for the watery preferred plane(WPP). In the paper, the characteristic of watery preferred planes is analyzed and a series ofsuperior indices has been set up. It is introduced that WPPs are determined by the methods ofgeological analysis, superior index and complex geophysical analysis. Meanwhile, new multiple modelfor water resource development in the water-scarce areas of karst mountainous regions are advanced.

Numerical study on turbulent mixed convection in a vertical plane channel using hybrid RANS/LES and LES models

Two Delayed-Detached Eddy Simulation(DDES) models, and a Large-Eddy Simulation(LES) model are used to investigate the turbulent flows and mixed convection between a hot plate and a cold plate via the software FLUENT. The two DDES models include Production-limited DDES(PL-DDES) and Improved DDES(IDDES) models.The Wall-Adapting Local Eddy-Viscosity(WALE) model is the used LES model. The numerical computations are performed at Reynolds number Reb= 4494 and different Richardson numbers Ri = 0.025, 0.048, 0.1. The comparing data is from the Direct Numerical Simulation(DNS) at Reb= 4494 and Ri = 0.048. The comparison reveals that the two DDES models have better performance in predicting time-averaged parameters than the WALE model in the aiding flow. The best predicted time-averaged results are obtained by the PL-DDES model in the opposing flow. Furthermore, the results of different Ri obtained by the PL-DDES model agree well with the DNS data.

Modeling Walking with an Inverted Pendulum Not Constrained to the Sagittal Plane. Numerical Simulations and Asymptotic Expansions

Inverted pendulum models are commonly used to study the bio-mechanics of biped walkers. In its simplest form, the inverted pendulum consists of a point mass attached to two straight mass-less legs. Most works constrain the motion of the mass to the sagittal plane, i.e. the plane perpendicular to the ground that contains the direction toward the biped is walking. In this article, we remove this constrain to study the oscillations, the mass experiences in the direction perpendicular to the sagittal plane as the biped walks. While small, these lateral oscillations are unavoidable and of importance in the understanding of balance and stability of walkers, as well as walkers induced oscillations in pedestrian bridges.

Modeling of Plane Arrays Using a Variational Approach

The variational statement of synthesis problem is generalized in order to account the additional requirements to the synthesized radiation pattern (RP) and field distribution in the specified points of near zone. For this aim, the minimizing functional is supplemented by term providing the possibility to minimize the values of field in these points;creating the deep zeros in the RP for the certain angular coordinates is realized too. The approach foresees reduction of an explicit formula for field values in a near zone. The results of computational modeling testify the possibility to create zeros in the given RP and to minimize the values of field in a near zone of plane arrays in a great extent.

基于服装造型设计的变形与转换探究

文章通过借助众多创新、前沿的服装造型设计实例为依据,从服装外形方面出发,对服装造型的内部构造及外部轮廓的变形与转换原理进行深入探究。以平面裁剪为视角,结合具体案例分析对服装版型的变换与解构,并针对设计师在规则与不规则的几何服装造型中的廓型转换与结构工艺进行探讨,探究在人-服装-环境概念下,设计师如何通过改变服装基础结构向功能性方向变换,增加服装的附加价值。通过梳理服装造型变换所包含的各种设计形态,详尽剖析各种变形手法,预见服装产业的造型设计发展方向。

单镜头倾斜摄影测量技术的应用及精度分析

针对5镜头无人机摄影测量技术在水利工程中的限制,提出一种单镜头无人机采用5航线倾斜测量法,对水利工程进行多角度拍摄,快速建立水利工程实景三维模型的方法。通过对三维模型的平面精度、高度精度进行误差分析,证明消费级无人机在多航线飞行方案下建立的水利工程实景三维模型满足现行《水利水电工程测量规范》和《三维地理信息模型数据产品规范》。

基于灰色模型的装配式建筑施工偏差预测研究

利用灰色预测模型GM(1,1)对装配式建筑施工偏差进行了分析和预测,选择预制板的平面度偏差数据作为研究对象,通过数据的预处理、模型的建立、模型参数的估计、模型的求解、模型的还原和模型的检验等步骤,得到了预测值与实测值的对比图,以及预测误差和后验差比等指标,评价了模型的预测精度和适用性。结果表明:模型能够反映出预制板的平面度偏差的变化规律,后验差比小于模型的预测精度,可应用于装配式建筑施工中。

城市实景模型结构化线面特征重构方法

为了改善城市实景模型边缘模糊,提出了一种曲率引导的结构化线面特征重构方法。根据曲率特征将网格分割为平面、可展凹、可展凸以及不可展曲面4类,在平面分割结果内提取平面,在可展凹和可展凸分割结果内提取直线,对过度弯曲的不可展区域进行保留,最终形成包含几何特征的复合网格模型。结果表明,结合曲率信息预先设置几何特征的潜在范围,使得结构化线面特征更可靠,同时保证城市实景中复杂的树结构不被错误地提取为平面。

P型橡胶卡箍的拉压疲劳性能测试和寿命预测

P型橡胶卡箍是航空发动机外部管路系统中连接管路与支架、机匣之间的重要连接件,其主要的失效形式为机体振动和管内高压液体脉动共同作用下的疲劳断裂。卡箍的疲劳性能极大地制约了管路系统的性能,因此对于卡箍的疲劳性能研究具有重要意义。本文首先设计并进行了卡箍的拉压疲劳试验,得到了不同加载位移下的疲劳寿命。后续的断口分析表明卡箍疲劳破坏呈现出两种不同的形式:一是卡箍的金属箍带发生由外侧向内侧扩展的疲劳断裂,二是卡箍的橡胶垫圈严重的磨损现象。其次,结合卡箍疲劳试验的加载过程,建立了对应的有限元模型,并通过与贴片位置的应变对比验证了构建模型的预测精度。针对卡箍箍带疲劳断裂的失效形式,通过卡箍箍带所采用的不锈钢材料的疲劳试验结果,建立了卡箍的SWT(Smith-Watson-Topper)、FS(Fatemi-Socie)以及WB(Wang-Brown)临界平面疲劳寿命模型。最后,结合有限元分析得到的最大应力应变以及卡箍拉压疲劳试验得到的疲劳寿命结果,验证了提出的寿命模型均处于3倍分散带内,对于卡箍的疲劳寿命具有良好的估计精度。

倾角变化条件下反倾层状斜坡倾倒变形演化研究

倾倒变形是反倾层状岩质边坡的一种典型破坏模式,为了研究不同岩层倾角对反倾层状岩质边坡倾倒变形的影响,以澜沧江上游古水水电站坝前倾倒变形体为原型,从岩层倾角变化的角度出发,利用大型土工离心机试验分析了反倾层状岩质边坡的失稳破坏过程、变形演化特征与最终失稳模式等。结果表明:①反倾层状斜坡的变形演化过程基本概括为岩层压密-坡脚压裂阶段、弯折面形成-部分失稳阶段和弯折面贯通-彻底失稳3个阶段,岩层倾角的改变并不会影响斜坡阶段性演化过程;②岩层倾角越大的斜坡,斜坡形成弯折面所需时间越短,失稳破坏发生后坡体贯通性倾倒破坏深度更大,对应的变形范围越大,折断岩层的破坏程度越剧烈;③岩层倾角变化会导致斜坡的倾倒变形过程与最终失稳模式存在一定差异。倾角较小的55°和70°模型斜坡前部岩层在重力作用下发生明显弯曲倾倒变形,最终以“倾倒-弯曲-滑移”的失稳模式发生破坏;倾角最大的85°斜坡岩层发生的弯曲变形较小,最终以“倾倒-折断-崩塌”的模式发生破坏。研究结果对大型工程项目的顺利开展具有一定指导意义。

Rowe剪胀方程及一种新的推导方法

剪胀性是岩土材料的重要特性之一。Rowe剪胀方程是一种经典的剪胀方程,它形式简单,所需假定较少,能够反映粗粒土、岩石乃至混凝土的剪胀性。在国内外受到广泛关注,且有很多的改进和发展。但在通常的Rowe剪胀方程的推导中,有一些概念尚需要商榷,所引入的锯齿面也容易引起误导。本文对Rowe剪胀方程及其发展改进进行梳理,提出了参考面的概念,并给出了一种新的推导方法。新的推导方法比传统方法在概念上更为严密,对两种推导方法的探讨也有助于加深对Rowe剪胀方程的理解。

双块式无砟轨道轨枕与道床板界面脱空损伤识别

为准确识别双块式无砟轨道轨枕与道床板连接面脱空损伤,建立了双块式无砟轨道冲击回波有限元模型,分析界面损伤对弹性波传播规律的影响。在室内浇筑含有不同损伤位置和不同损伤程度的混凝土复合试件,采用冲击回波法进行损伤识别。研究结果表明:脱空损伤会显著影响弹性波在界面处的传播,基于回波信号分析可识别损伤;弹性波频率主要受激振锤大小的影响,应结合结构易损位置和理论计算选取合适的激振锤;混凝土复合试件的试验厚度值与理论厚度值相差仅为1 cm,测试结果合理,可用于判断脱空损伤程度,但不能确定损伤区域;利用平面成像技术可准确识别轨枕与道床板界面脱空范围,为双块式无砟轨道结构养护维修提供一定参考,试验结果验证了冲击回波法用于双块式轨道层间脱空识别的可行性和合理性。

云南开远市吉德金矿地质特征及成矿模式

吉德金矿矿体主要呈似层状、透镜状产于峨眉山玄武岩与下伏灰岩岩溶不整合面、玄武质火山碎屑岩夹层及次级构造破碎带中,有红土型和岩溶角砾岩型两种类型,金以微粒自然金为主,目前矿床规模较小、地质研究程度较低。通过总结成矿规律、构建成矿模式,对矿区及外围寻找红土型和岩溶角砾岩型金矿具有指导作用。

红外系统对战机的探测性能仿真分析

通过新建战机尾焰的红外辐射椭圆体模型,改进了战机红外辐射的计算方法,并得到了战机在3~5μm波段红外辐射的空间分布曲线。通过对该曲线的分析,发现该战机的红外辐射在机尾和机头各有4个辐射强度相同的极值方向。考虑到臭氧在3~5μm波段内的吸收、地面遮挡红外辐射传输和探测大气层外目标等因素,引入红外辐射大气传输距离概念进一步完善3~5μm波段红外辐射大气传输模型。以归一化探测度不同的2种红外探测器构建的红外系统为例,仿真得到战机的作用距离随探测方向变化的曲线。计算结果表明,红外系统对战机的作用距离极值并不在战机红外辐射极值方向上,且当系统作用距离较远时,大气衰减对作用距离的影响将超过战机红外辐射的影响。

HYPERSTATIC STRUCTURE MAPPING MODEL BUILDING AND OPTIMIZING DESIGN

Hyperstatic structure plane model being built by structural mechanics is studied. Space model precisely reflected in real stress of the structure is built by finite element method （FEM） analysis commerce software. Mapping model of complex structure system is set up, with convenient calculation just as in plane model and comprehensive information as in space model. Plane model and space model are calculated under the same working condition. Plane model modular construction inner force is considered as input data; Space model modular construction inner force is considered as output data. Thus specimen is built on input data and output dam. Character and affiliation are extracted through training specimen, with the employment of nonlinear mapping capability of the artificial neural network. Mapping model with interpolation and extrpolation is gained, laying the foundation for optimum design. The steel structure of high-layer parking system （SSHLPS） is calculated as an instance. A three-layer back-propagation （BP） net including one hidden layer is constructed with nine input nodes and eight output nodes for a five-layer SSHLPS. The three-layer structure optimization result through the mapping model interpolation contrasts with integrity re-analysis, and seven layers structure through the mapping model extrpulation contrasts with integrity re-analysis. Any layer SSHLPS among 1-8 can be calculated with much accuracy. Amount of calculation can also be reduced if it is appfied into the same topological structure, with reduced distortion and assured precision.