Virtually coupled train set control subject to space-time separation:A distributed economic MPC approach with emergency braking configuration

The emerging virtual coupling technology aims to operate multiple train units in a Virtually Coupled Train Set(VCTS)at a minimal but safe distance.To guarantee collision avoidance,the safety distance should be calculated using the state-of-the-art space-time separation principle that separates the Emergency Braking(EB)trajectories of two successive units during the whole EB process.In this case,the minimal safety distance is usually numerically calculated without an analytic formulation.Thus,the constrained VCTS control problem is hard to address with space-time separation,which is still a gap in the existing literature.To solve this problem,we propose a Distributed Economic Model Predictive Control(DEMPC)approach with computation efficiency and theoretical guarantee.Specifically,to alleviate the computation burden,we transform implicit safety constraints into explicitly linear ones,such that the optimal control problem in DEMPC is a quadratic programming problem that can be solved efficiently.For theoretical analysis,sufficient conditions are derived to guarantee the recursive feasibility and stability of DEMPC,employing compatibility constraints,tube techniques and terminal ingredient tuning.Moreover,we extend our approach with globally optimal and distributed online EB configuration methods to shorten the minimal distance among VCTS.Finally,experimental results demonstrate the performance and advantages of the proposed approaches.

Framework of Distributed Coupled Atmosphere-Ocean-Wave Modeling System

In order to research the interactions between the atmosphere and ocean as well as their important role in the intensive weather systems of coastal areas, and to improve the forecasting ability of the hazardous weather processes of coastal areas, a coupled atmosphere-ocean-wave modeling system has been developed. The agent-based environment framework for linking models allows flexible and dynamic information exchange between models. For the purpose of flexibility, portability and scalability, the framework of the whole system takes a multi-layer architecture that includes a user interface layer, computational layer and service-enabling layer. The numerical experiment presented in this paper demonstrates the performance of the distributed coupled modeling system.

Fully Coupled Fluid-Structure Interaction Model Based on Distributed Lagrange Multiplier/Fictitious Domain Method

This paper, with a finite element method, studies the interaction of a coupled incompressible fluid-rigid structure system with a free surface subjected to external wave excitations. With this fully coupled model, the rigid structure is taken as ＂fictitious＂ fluid with zero strain rate. Both fluid and structure are described by velocity and pressure. The whole domain, including fluid region and structure region, is modeled by the incompressible Navier-Stokes equations which are discretized with fixed Eulerian mesh. However, to keep the structure＇ s rigid body shape and behavior, a rigid body constraint is enforced on the ＂fictitious＂ fluid domain by use of the Distributed Lagrange Multipher/Fictitious Domain （DLM/ FD） method which is originally introduced to solve particulate flow problems by Glowinski et al. For the verification of the model presented herein, a 2D numerical wave tank is established to simulate small amplitude wave propagations, and then numerical results are compared with analytical solutions. Finally, a 2D example of fluid-structure interaction under wave dynamic forces provides convincing evidences for the method excellent solution quality and fidelity.

Preliminary analysis of the zonal distribution of ENSO-related SSTA in three CMIP5 coupled models

The simulated sea surface temperature anomaly(SSTA)over the tropical Pacific during El Ni?o–Southern Oscillation(ENSO)is investigated in three representative coupled models:CESM1-CAM5,FGOALS-s2,and FGOALS-g2.It is found that there is a significant westward shift bias in reproducing the zonal distribution(ZD)of the ENSO-related SSTA in CESM1-CAM5 and FGOALS-s2,whereas the SSTA-ZD simulated by FGOALS-g2 is relatively realistic.Through examining the SSTA-ZD during both warm and cold phases of ENSO separately,the authors reveal that the SSTA-ZD simulation bias during the ENSO cycle mainly lies in the bias during the warm phase.It is noted that both the simulated zonal wind stress anomaly(τ’_x)and shortwave heat flux(SW)anomaly exhibit westward shift biases in CESM1-CAM5 and FGOALS-s2,while the counterparts in FGOALS-g2 are relatively reasonable.The westward shift biases in representingτ’_x and the SW anomaly(SWA)are attributed to the westward-shifted precipitation anomaly(PrA).It is suggested that the mean SST cold bias over the cold tongue region is the key factor behind the westward-shift bias in simulating the El Ni?o-related PrA,which leads to the westward-shiftedτ’_x and SWA.Collectively,the aforementioned anomaly fields,including the dynamic part(τ’_x)and thermodynamic part(SWA),contribute to the westward-shift bias in simulating the El Ni?o-related SSTA.This study provides clues for understanding the ZD simulation biases of ENSO-related fields;however,further in-depth investigation with more model simulations,especially the incoming CMIP6 simulations,is still needed to fully understand the ENSO SSTA-ZD simulation bias in coupled models.

Natural Frequency of the Bridge—Vehicle Coupled System Considering Uniform Distributed Moving Load

Natural frequencies of the bridge—vehicle coupling system considering uniform distributed load varying with position is investigated in this work.An analytic model of a simply supported beam bridge with constant section is introduced to establish the frequency equations of the coupled system.Comparisons with the results between analytic model and FEM indicate that the present research is correct and reasonable.In view of an example bridge,natural frequencies are studied on the bridge subjected to uniform distributed moving loads in cases of different weight and span,by which some regular phenomenon are obtained.The present study can apply in the engineering problem of interaction between bridges and moving loads such as trains and tracked vehicles.

Fluid Flow and Solidification Simulation in Beam Blank Continuous Casting Process With 3D Coupled Model

Based on turbulent theory, a 3D coupled model of fluid flow and solidification was built using finite difference method and used to study the influence of superheating degree and casting speed on fluid flow and solidification, analyze the interaction between shell and molten steel, and compare the temperature distribution under different technological conditions. The results indicate that high superheating degree can lengthen the liquid-core depth and make the crack and breakout possible, so suitable superheating should be controlled within 35℃ according to the simulation results. Casting speed which is one of the most important technological parameters of improving production rate, should be controlled between 0. 85 m/min and 1.05 m/min and the caster has great potential in the improvement of blank quality.

Model of coupled gas flow and deformation process in heterogeneous coal seams and its application

The heterogeneity of coal was studied by mechanical tests. Probability plots of experimental data show that the mechanical parameters of heterogeneous coal follow a Weibull distribution. Based on elasto-plastic mechanics and gas dynamics, the model of coupled gas flow＇ and deformation process of heterogeneous coal was presented and the effects of heterogeneity of coal on gas flow and failure of coal wcrc investigated. Major findings include： The effect of the heterogeneity of coal on gas flow and mechanical thilure of coal can be considered by the model in this paper. Failure of coal has a great effect on gas flow.

Assimilation of ASAR Data with a Hydrologic and Semi-empirical Backscattering Coupled Model to Estimate Soil Moisture

The most promising approach for studying soil moisture is the assimilation of observation data and computational modeling. However, there is much uncertainty in the assimilation process, which affects the assimilation results. This research developed a one-dimensional soil moisture assimilation scheme based on the Ensemble Kalman Filter (EnKF) and Genetic Algorithm (GA). A two-dimensional hydrologic model-Distributed Hydrology-Soil-Vegetation Model (DHSVM) was coupled with a semi-empirical backscattering model (Oh). The Advanced Synthetic Aperture Radar (ASAR) data were assimilated with this coupled model and the field observation data were used to validate this scheme in the soil moisture assimilation experiment. In order to improve the assimilation results, a cost function was set up based on the distance between the simulated backscattering coefficient from the coupled model and the observed backscattering coefficient from ASAR. The EnKF and GA were used to re-initialize and re-parameterize the simulation process, respectively. The assimilation results were compared with the free-run simulations from hydrologic model and the field observation data. The results obtained indicate that this assimilation scheme is practical and it can improve the accuracy of soil moisture estimation significantly.

Assessment of earthquake-induced landslide hazard zoning using the physics-environmental coupled Model

In order to prevent and mitigate disasters,it is crucial to immediately and properly assess the spatial distribution of landslide hazards in the earthquake-affected area.Currently,there are primarily two categories of assessment techniques:the physical mechanism-based method(PMBM),which considers the landslide dynamics and has the advantages of effectiveness and proactivity;the environmental factor-based method(EFBM),which integrates the environmental conditions and has high accuracy.In order to obtain the spatial distribution of landslide hazards in the affected area with near realtime and high accuracy,this study proposed to combine the PMBM based on Newmark method with EFBM to form Newmark-Information value model(N-IV),Newmark-Logic regression model(N-LR)and Newmark-Support Vector Machine model(N-SVM)for seismic landslide hazard assessment on the Ludian Mw 6.2 earthquake in Yunnan.The predicted spatial hazard distribution was compared with the actual cataloged landslide inventory,and frequency ratio(FR),and area under the curve(AUC)metrics were used to verify the model's plausibility,performance,and accuracy.According to the findings,the model's accuracy is ranked as follows:N-SVM>N-LR>N-IV>Newmark.With an AUC value of 0.937,the linked N-SVM was discovered to have the best performance.The research results indicate that the physics-environmental coupled model(PECM)exhibits accuracy gains of 46.406%(N-SVM),30.625%(N-LR),and 22.816%(N-IV)when compared to the conventional Newmark technique.It shows varied degrees of improvement from 2.577%to 12.446%when compared to the single EFBM.The study also uses the Ms 6.8 Luding earthquake to evaluate the model,showcasing its trustworthy in forecasting power and steady generalization.Since the suggested PECM in this study can adapt to complicated earthquake-induced landslides situations,it aims to serve as a reference for future research in a similar field,as well as to help with emergency planning and response in earthquakeprone regions with landslides.

Analytical solution of vacuum preloading technology combined with electroosmosis coupling considering impacts of distribution of soil’s electrical potential

Combining vacuum preloading technology and electroosmosis can improve the treatment effect of soft soil foundation by utilizing the advantages of both methods.Many studies indicate that the soil electrical potential is non-linearly distributed in the treatment process by the combined method.However,in the previous theoretical study,the non-linear-distribution impacts of soil’s electrical potential on soft soil foundation treatment have not been considered.It is always assumed to be linear distribution,which is different from the experimental results.In this paper,the coupling consolidation model of this technology under the two-dimensional plane strain condition is initially established;and the well resistance effect,the vacuum load decreasing along the soil depth and the non-linear variation of electrical potential in the soil are considered.Then,the analytical solutions of the average excess pore water pressure and soil’s consolidation degree in the anode affected area are acquired based on the soil’s electrical potential distribution.Finally,the rationality of the analytical solution is testified by conducting an experimental model test,which proves the scientificity of the analytical solution.The analytical solution is adopted to better predict the dissipation of excess pore water pressure and soil consolidation degree when using the combined technology.This study can provide a reference with more accuracy for the engineering practices of this combined technology in the future.

Thermo-mechanical coupled analysis of hot ring rolling process

A 3D rigid-plastic and coupled thermo-mechanical FE model for hot ring rolling(HRR) was developed based on DEFORM 3D software,then coupled heat transferring,material flow and temperature distribution of the ring in HRR were simulated and the effects of process parameters on them were analyzed.The results show that the deformation nonuniformity of ring blank increases with the increase of the rotational speed of driver roll and friction factor or the decrease of the feed rate of idle roll and initial temperature of ring blank.The temperature nonuniformity of ring blank decreases with the increase of the feed rate of idle roll or the decrease of initial temperature of ring blank and friction factor.There is an optimum rotational speed of driver roll under which the temperature distribution of ring blank is the most uniform.The results obtained can provide a guide for forming parameters optimization and quality control.

Coupling effects of influence factors on probability of corrosion initiation time of reinforced concrete

The coupling model of major influence factors such state affecting the chloride diffusion process in concrete is as environmental relative humidity, load-induced crack and stress discussed. The probability distributions of the critical chloride concentration Cc, the chloride diffusion coefficient D, and the surface chloride concentration Cs were determined based on the collected natural exposure data. And the estimation of probability of corrosion initiation considering the coupling effects of influence factors is presented. It is found that the relative humidity and curing time are the most effective factors affecting the probability of corrosion initiation before and after 10 years of exposure time. At the same exposure time, the influence of load-induced crack and stress state on the probability of corrosion initiation is obvious, in which the effect of crack is the most one

Breakup Effect of Weakly Bound Projectile on the Barrier Distribution Around Coulomb Barrier

The excitation function of quasi-elastic （QEL） scattering at a backward angle has been measured for 9^Be＋208^Pb. The barrier distribution was extracted by means of the first derivative of the measured excitation function and calculated with the coupled-channel model. The present work shows that the experimental barrier distribution extracted from QEL scattering is shifted to the low energy side by 1.5 MeV as compared with the theoretical one. This energy discrepancy indicates that breakup is important in the colliding processes of the weakly bound nucleus system.

基于CAS法的核电工程异形水箱分布质量计算模型

对于形状复杂的大型核电工程储液结构,Housner弹簧-质量模型适用性较差,基于有限元法的流-固耦合数值分析模型复杂、计算和存储量大,难以满足工程设计要求。该文基于声学-结构耦合法(CAS)提出了一种兼顾精度和效率的分布质量模型,通过理论推导从CAS计算结果中剥离得到的器壁动水压强脉冲分量,进而提出器壁单元各节点位置的分布式脉冲附加质量计算公式,精确地考虑了储液容器的形状对液体晃动的影响,同时实现了流-固耦合分析的解耦,有效解决了复杂大型核电工程储液结构的动力分析的难题。以矩形刚性水箱为例,将该文模型的结果与Housner分布模型比较,验证了该模型的合理性和可靠性。针对顶部具有复杂形状水箱的AP1000安全壳结构进行地震动分析,将该文模型与精细的流-固耦合模型进行比较,结果显示:两种模型计算结果吻合性好,该文模型前处理简便且在计算时间效率具有明显优势。该文模型可为核电工程考虑结构-地基、流-固耦合的多因素耦合高效分析奠定基础。

风浪联合作用下分布式调谐质量阻尼器对海上半潜漂浮式风机的减振控制

海上半潜漂浮式风机在复杂深海环境下产生有害振动会威胁风机的安全性和耐久性,针对该问题并结合美国NREL的5 MW样机的漂浮平台几何结构构造,提出利用分布式调谐质量阻尼器(Tuned Mass Dampers,TMDs),即分别在漂浮平台的3根浮筒中布置TMD,形成等边三角形布置,对随机风浪联合作用下海上半潜漂浮式风机的平台纵摇振动进行控制。为了更好地描述分布式TMDs对海上半潜漂浮式风机的减振效果,基于拉格朗日方程和模态叠加法,对海上半潜漂浮式风机-TMDs耦合系统提出并建立了9自由度多体动力学模型。基于H_(∞)算法,即以平台纵摇频响函数的峰值为优化目标,对分布式TMDs的参数进行优化设计,优化设计中考虑了3个TMDs之间的耦合关系。对风机-TMDs耦合系统开展了风浪联合作用下的数值模拟,分析了分布式TMDs对平台纵摇响应的减振效果。结果表明:最优设计下的分布式TMDs对海上半潜漂浮式风机平台纵摇振动具有良好的减振性能;在三种不同工况的随机风浪荷载作用下,分布式TMDs对平台纵摇固有频率附近的功率谱密度曲线峰值减振率和标准差减振率能分别达到39%和52%以上。

核电工程异形水箱流固耦合分布式参数模型与效用研究

在流固耦合动力分析领域,传统的Housner模型在工程设计中发挥重要作用。但其理论推导仅适用于规则水箱,采用集中质量总体模型描述液体晃动的整体效应,难以有效模拟异形水箱储液结构的局部精细响应,亟须建立适用于不规则水体晃荡的分布式附加质量模型。基于势流理论推导了一种模态综合法模型,实现了分布质量与储液器壁激振加速度的解耦。该模型能够有效剥离分布式的脉冲质量与对流质量;同时,实体网格的振型分析适用于任意形状水体的动力分析。通过算例的形式将该模型与精细声学-结构耦合(Acoustic-Structural coupling,CAS)模拟法进行了比较,验证了模型的精确性与可靠性。最后,基于本文的模型研究了核电异形的安全水箱在不同水位和减晃格栅分布下的动力响应规律,并检验了其在工程中的适用性。

路轨协同下地铁配送网络抗毁性分析与关键节点识别

为研究路轨(道路-轨道)协同城市配送中地铁网络的抗毁性和关键节点,支撑路轨协同下城市配送的组网模式以及配送网络的可靠性提升,首先,以相对网络效率、相对负载熵为抗毁性测度指标,基于改进的耦合映像格子(CML)模型,研究不同攻击模式下的网络抗毁性变化;其次,选取反映网络运输效率的中心性指标和反映网络承载能力的现实性指标,构建网络关键节点综合识别模型;然后,通过分析不同指标权重下的网络抗毁性水平,得到最优权重取值下的关键节点集合;最后,以成都市地铁网络为例进行实证分析,验证该模型的有效性和实用性。研究结果表明:在同等扰动强度下,地铁网络面对随机攻击时抗毁能力更强;当面临外部扰动时,相对网络效率与相对负载熵损失在20%以上的节点占比分别为6.3%与6.8%,其中相对网络效率损失最大可达56.3%,相对负载熵损失最大可达50.2%;同时,考虑现实性指标与中心性指标,平均每个关键节点造成的相对网络效率损失与相对负载熵最大损失分别为8.99%与4.38%,需予以重点关注。

细长桁架臂卸载反弹动应力分布规律及试验

为研究细长桁架臂在卸载冲击下的动态响应变化规律,提出了基于等效梁振型函数的桁架臂动应力分布计算模型。根据等效梁振型函数,探讨了卸载后桁架臂动应力分布假设,分析了影响桁架臂卸载反弹动响应的相关参数。以装备细长桁架臂的动臂塔机为对象,建立了桁架臂精细化有限元模型和起重机刚柔耦合模型,通过仿真辨识了应力分布模型的关键参数。实施了动臂塔机系列载荷卸载冲击试验,桁架臂上主弦杆的动应力试验值与理论计算结果误差小于7%,表明动应力分布理论模型与实际相符。通过理论模型预测了极限工况下桁架臂上主弦杆动应力分布状态,发现在最大载荷卸载条件下起重臂动应力峰值超过结构承载极限,为卸载条件下起重机关键结构的优化设计提供依据。

基于绿色城轨的北京地铁车辆基地分布式耦合供热方案研究

结合北京地铁既有车辆基地的供热能耗特点,建立了新建车辆基地的供热模型,从绿色低碳角度分析了分布式耦合供热方案的节能降碳潜力。该供热方案满足北京市的相关供热政策,且达到了《中国城市轨道交通绿色城轨发展行动方案》规定的绿色能源利用指标要求,是未来寒冷地区车辆基地低碳供热发展的方向之一。

氨燃料管状SOFCs中热冲击影响与性能的模拟研究

研究氨燃料固体氧化物燃料电池(solidoxidefuel cells,SOFCs)热冲击的产生机理将会给电池的温度管理、可靠性管理及电池的性能优化提供更多可能性。但由于化学、电化学的反应过程复杂、模型仿真所涉物理场较多,鲜有关于氨燃料SOFCs的仿真研究。为此,该文通过建立耦合了吸热的氨气裂解反应、电化学反应、局部电流分布、温度分布以及物质流动的仿真模型,分析了单个阴极支撑的管状直接氨气裂解SOFCs的热冲击(热应力和热对流)形成机理。研究得出,过快且不均衡的氨气裂解反应是电池局部低温产生的主要原因,这会直接造成电池整体出现376K的温差。通过采用氨气预重整的方法能使氨SOFCs在相同操作电压下温度分布更均匀,平均温度更高,在800℃的环境温度下96%预重整的氨SOFCs能将阳极的温度极值差从62.16 K降为1.0 K,电池内部的温度分布得到显著改善。该研究可为氨燃料SOFCs的热管理优化提供重要理论依据,此外,该文详细展示的氨燃料SOFCs耦合模型的建模方法可以为用其他富氢气体做燃料的SOFCs的模拟仿真研究提供思路。