Actor-Critic Reinforcement Learning and Application in Developing Computer-Vision-Based Interface Tracking

This paper synchronizes control theory with computer vision by formalizing object tracking as a sequential decision-making process.A reinforcement learning(RL)agent successfully tracks an interface between two liquids,which is often a critical variable to track in many chemical,petrochemical,metallurgical,and oil industries.This method utilizes less than 100 images for creating an environment,from which the agent generates its own data without the need for expert knowledge.Unlike supervised learning(SL)methods that rely on a huge number of parameters,this approach requires far fewer parameters,which naturally reduces its maintenance cost.Besides its frugal nature,the agent is robust to environmental uncertainties such as occlusion,intensity changes,and excessive noise.From a closed-loop control context,an interface location-based deviation is chosen as the optimization goal during training.The methodology showcases RL for real-time object-tracking applications in the oil sands industry.Along with a presentation of the interface tracking problem,this paper provides a detailed review of one of the most effective RL methodologies:actor–critic policy.

Measurement of Liquid Concentration Fields Near Interface with Cocurrent Gas-Liquid Flow Absorption Using Holographic Interferometry

Real-time laser holographic interferometry was applied to measure liquid concentrations of CO2 in the vicinity of gas-liquid free interface under the conditions of cocurrent gas-liquid flow for absorption of CO2 by ethanol. The influences of the Reynolds number on the measurable interface concentration and on the film thickness were discussed. The results show that CO2 concentration decreases exponentially along the mass transfer direction, and the concentration gradient increases as Reynolds number of either liquid or gas increases. CO2 concentrations fluctuate slightly along the direction of flow; on the whole, there is an increase in CO2 concentration. The investiga- tion also demonstrated that film thickness decreases with the increase of Reynolds number of either of the two phases. Sherwood number representing the mass transfer coefficient was finally correlated as a function of the hy- drodynamic parameters and the physical properties.

Growth and aggregation micromorphology of natural gas hydrate particles near gas-liquid interface under stirring condition

To investigate the morphological evolution of the whole growth and aggregation processes of hydrate crystals near the gas–liquid interface,we used a high-pressure visual reactor with high-speed camera to capture the micromorphology of hydrate particles in a natural gas+pure water system with pressure from 2.6 to 3.6 MPa and sub-cooling from 4.7 to 6.23C.The results showed that under low sub-cooling conditions,the amount and size of particles increased first and then decreased in the range of 0–330 lm,and the small particles always dominated.These particles can be roughly classified into two categories:planar flake particles and polyhedral solid particles.Then,the concept of maximum growth dominant particle size was proposed to distinguish the morphological boundary of growth and aggregation.In addition,the micro model was established to better reflect the effects of particle formation process and evolution mechanism near the gas–liquid interface under stirring condition.The results of this study can provide a guidance for flow assurance in multiphase pipeline.

AN EMBEDDED BOUNDARY METHOD FOR ELLIPTIC AND PARABOLIC PROBLEMS WITH INTERFACES AND APPLICATION TO MULTI-MATERIAL SYSTEMS WITH PHASE TRANSITIONS

The embedded boundary method for solving elliptic and parabolic problems in geometrically complex domains using Cartesian meshes by Johansen and Colella （1998, J. Comput. Phys. 147, 60） has been extended for elliptic and parabolic problems with interior boundaries or interfaces of discontinuities of material properties or solutions. Second order accuracy is achieved in space and time for both stationary and moving interface problems. The method is conservative for elliptic and parabolic problems with fixed interfaces. Based on this method, a front tracking algorithm for the Stefan problem has been developed. The accuracy of the method is measured through comparison with exact solution to a two-dimensional Stefan problem. The algorithm has been used for the study of melting and solidification problems.

A NEW FRONT TRACKING METHOD FOR COMPRESSIBLE FLOWS

In this paper, a new FCT VOF method is developed and applied to the study of the evolution of substance interfaces in compressible flows.

Multi-Deme Parallel FGAs-Based Algorithm for Multitarget Tracking

For data association in multisensor and multitarget tracking, a novel parallel algorithm is developed to improve the efficiency and real-time performance of FGAs-based algorithm. One Cluster of Workstation （COW） with Message Passing Interface （MPI） is built. The proposed Multi-Deme Parallel FGA （MDPFGA） is run on the platform. A serial of special MDPFGAs are used to determine the static and the dynamic solutions of generalized m-best S-D assignment problem respectively, as well as target states estimation in track management. Such an assignment-based parallel algorithm is demonstrated on simulated passive sensor track formation and maintenance problem. While illustrating the feasibility of the proposed algorithm in multisensor multitarget tracking, simulation results indicate that the MDPFGAs-based algorithm has greater efficiency and speed than the FGAs-based algorithm.

Hand Motion Tracking Using Simulated Annealing Method in a Discrete Space

Hand tracking is a challenging problem due to the complexity of searching in a 20 ＋ degrees of freedom （DOF） space for an optimal estimation of hand configuration. The feasible hand configurations are represented as a discrete space, which avoids learning to find parameters as general configuration space representations do. Then, an extended simulated annealing method with particle filtering to search for optimal hand configuration in the proposed discrete space, in which simplex search running in multi-processor is designed to predict the hand motion instead of initializing the simulated annealing randomly, and particle filtering is employed to represent the state of the tracker at each layer for searching in high dimensional configuration space. Experimental results show that the proposed method makes the hand tracking more efficient and robust.

基于认知差异的点餐界面可用性评价

近年来,线上点餐的中年用户数量激增,但其界面设计的普适性相对欠缺,存在较大的优化空间。运用设计学科方法对中年用户点餐体验进行优化,能提高点餐效率,产生更高的经济价值。本文先通过感性问卷调研,得出中、青年用户对点餐界面的感性认知差异评价。再利用眼动实验得出点餐界面可用性评价。最后,综合分析总结两项评价结果,找出点餐界面中待解决问题,并根据这些问题提出普适设计建议:其一,加大导航栏字号、采用通俗词语、利用色彩加强视觉引导来帮助中年用户理解界面信息;其二,将界面中的装饰性图片替换为功能性图片,可以有效提高中年用户点餐效率;其三,增加切换控件部分在界面的占比,加入自动播放功能,引导中年用户使用该功能。

Tracking the atomic pathways of Pt3Ni-Ni(OH)2 core-shell structures at the gas-liquid interface by in-situ liquid cell TEM

Using the in-situ liquid cell transmission electron microscopy, the three-stage growth of Pt3Ni-Ni(OH)2 core-shell structures at the gas-liquid interfaces was clearly observed, which consists of(1) a thermodynamically driven Pt3Ni alloy core by the monomer attachment,(2) a nickel(Ni) shell formation due to the depletion of the Pt salt precursor, and(3) the oxidation and of the Ni shell into Ni(OH)2 flakes. We also further observed the nucleation and growth of the Ni(OH)2 flakes on an existing layer either at the middle part or at the step edge. More interestingly, the dynamic transformation among a Pt3Ni alloy, Ni clusters and Ni(OH)2 flakes was also imaged even at a high electron dose rate.

基于眼动追踪技术的数字界面人机交互效能评价研究综述

数字界面是人机交互的主要平台,科学合理的界面设计能够促进高效和谐的人机交互,开展数字界面人机交互效能评价能够有效节省时间资源和开发成本,为界面的设计定型奠定坚实基础。利用眼动追踪技术对该效能进行评价能够客观反映用户的视觉心理及认知思维过程。结合该技术在人机界面交互中的评价机理,归纳梳理了目前的研究现状,并指出其未来的应用和发展趋势将围绕算法优化、模型计算、多元融合和无感交互等方面展开。

温度荷载作用下高铁纵连无砟轨道板间接缝界面损伤研究

高铁纵连板式无砟轨道的板间接缝作为一种后浇结构,在极端温度荷载作用下易出现界面脱黏等病害,不仅影响轨道结构整体纵向刚度及连接稳定性,同时对列车运行安全造成威胁。为探究温度荷载作用下板间接缝的界面损伤分布规律,首先,在无砟轨道内部布设温度传感器获取轨道板的温度场,基于实测数据制定轨道板温度分析工况;然后,基于双线性内聚力理论,建立同时考虑预应力钢筋作用及板间接缝界面损伤的纵连板式无砟轨道模型,并从垂直和水平方向分析实际温度场作用下接缝界面的损伤规律及分布差异;最后,将仿真结果与现场接缝损伤情况进行对比,确定接缝界面最不利受力位置,为指导工务部门精细化检修作业提供参考。结果表明:轨道板实际温度梯度存在超过高速铁路设计规范的情况;整体降温与负温度梯度耦合作用为最不利加载工况,垂直方向上宽接缝与轨道板垂直接触界面以及窄接缝与砂浆层接触界面损伤尤为严重;水平方向上接缝界面在邻近预应力钢筋区域可能存在隐蔽病害,在平均升温18.92℃时接缝界面在该区域均出现损伤,工务部门应加强关注接缝界面在预应力钢筋布置区域的损伤发展。

基于眼动追踪和触觉反馈的人-多机器人班组交互系统

针对在动态复杂、非结构化的场景中缺乏自然、高效人机交互方式的问题,提出了一种基于眼动追踪和触觉反馈的人多机器人班组交互系统,用于管理由多机器人和人组成的团队。该系统利用混合现实头盔在现实世界中叠加虚拟交互界面,操作员通过基于凝视信号的非语言注意力感知的输入方法进行人机交互指令的输入,进而控制多机器人进行协同运动,同时操作员通过振动和挤压2种触觉反馈模态来感知多机器人系统编队队形的尺寸变化与编队完成状态。为了验证人机交互系统的有效性与可行性,设计了触觉反馈实验与人多机器人班组交互系统实验,实验结果表明:所提出的基于眼动追踪和触觉反馈的人机交互系统能有效控制多机器人系统进行编队,指令执行成功率达93.3%,与仅通过视觉反馈相比,在有触觉反馈的情况下操作员可以使用更少的时间完成多机器人状态感知,交互效率提高了14.55%。

导视地图界面维度差异下的视觉搜索效率研究

图像的维度差异会对用户的信息获取及视觉交互效率产生一定程度的影响,以导视地图界面设计为例,建立三种不同维度的地图样本,利用眼动追踪实验收集用户搜索指定目标时的眼动数据进行分析,同时基于SUS系统可用性量表收集用户主观感受数据。结合定性与定量方法,比较分析了不同维度的地图呈现下用户的视觉搜索效率高低与规律差异,结果表明:在2D的呈现方式下,用户的综合搜索效率最高,而随着界面维度的升高,用户的搜索行为因受到透视因素干扰,综合搜索效率逐渐降低。

山西古城商业街界面要素研究

许多城市大肆推进传统风貌古城的修复和重建,导致古城商业街面貌同质化严重,微观尺度下商业街界面要素的保护和更新缺乏更加科学的指导。文章以平遥古城明清一条街和太原古县城十字街为研究对象,采用层次分析法(AHP)与眼动追踪实验分别得出古城商业街界面各要素的主观权重,以及人眼观察商业街界面各要素的客观眼动指标,并且将两者进行了相关性分析。研究表明,只有个别主观权重和客观眼动指标具有相关性,其余大多数具有独立性,所以在古城商业街的建设、保护和更新研究过程中,应综合考虑游客的心理和生理感受,有效提升商业街界面空间品质。

基于多模态感知的儿童有声读物APP导航界面设计

为优化儿童有声读物APP导航界面中元素过于复杂和缺乏引导性所导致的操作不协调、认知负荷增加的问题,文章通过对界面进行重新筹划布局,综合色彩运用、语音交互和触觉反馈因素,提出基于多模态感知体验的儿童有声读物APP界面交互系统。使用穿戴式眼动仪进行眼动实验测试,将眼动数据进行配对样本t检验对比分析,得到适用于儿童操作的界面元素组合方式,进而优化导航界面,以期为相关设计提供一定的参考。

高速铁路解锁后纵连式无砟轨道纵向温度应力及界面损伤研究

针对持续高温作用下纵连板式无砟轨道结构因温度应力过大而产生严重病害的问题,提出部分解锁方案以释放其温度应力。为量化解锁后轨道结构温度应力的释放效果并探究其释放原理,建立部分解锁后CRTSⅡ板式无砟轨道数值计算模型,分析整体温升作用下层间界面损伤的演化规律和部分解锁后轨道结构对温度应力的释放效果。研究表明:整体温升作用下,由于解锁后轨道板和底座板纵向位移差较大,导致轨道结构层间损伤、离缝产生的临界整体温升较低;解锁后轨道结构层间离缝产生的临界整体温升为13℃。由于纵连板式无砟轨道结构体系的转变,且层间黏结强度随整体温升的升高而降低,解锁后轨道板和宽窄接缝的温度应力得到了部分释放;当整体温升为50℃时,轨道板纵向应力最大释放量可达17.5 MPa,相比于解锁前下降了95.5%;宽窄接缝纵向应力释放量最大可达17.35 MPa,相比于解锁前下降了95.3%。随整体温升的不断升高,层间界面损伤不断扩展,轨道板纵向约束减弱,故纵向应力反而降低;解锁后宽窄接缝温度应力随整体温升的变化规律受层间离缝面积影响,其随着整体温升升高呈先增大后减小再增加趋势。

Mechanical characteristic variation of ballastless track in highspeed railway:effect of train–track interaction and environment loads

Due to the fact that ballastless tracks in highspeed railways are not only subjected to repeated train–track dynamic interaction loads,but also suffer from complex environmental loads,the fundamental understanding of mechanical performance of ballastless tracks under sophisticated service conditions is an increasingly demanding and challenging issue in high-speed railway networks.This work aims to reveal the effect of train–track interaction and environment loads on the mechanical characteristic variation of ballastless tracks in high-speed railways,particularly focusing on the typical interface damage evolution between track layers.To this end,a finite element model of a double-block ballastless track involving the cohesive zone model for the track interface is first established to analyze the mechanical properties of the track interface under the loading–unloading processes of the negative temperature gradient load(TGL)followed by the same cycle of the positive TGL.Subsequently,the effect of wheel–rail longitudinal interactions on the nonlinear dynamic characteristics of the track interface is investigated by using a vehicle-slab track vertical-longitudinal coupled dynamics model.Finally,the influence of dynamic water pressure induced by vehicle dynamic load on the mechanical characteristics and damage evolution of the track interface is elucidated using a fluid–solid coupling method.Results show that the loading history of the positive and negative TGLs has a great impact on the nonlinear development and distribution of the track interface stress and damage;the interface damage could be induced by the wheel–rail longitudinal vibrations at a high vehicle running speed owing to the dynamic amplification effect caused by short wave irregularities;the vehicle dynamic load could produce considerable water pressure that presents nonlinear spatial–temporal characteristics at the track interface,which would lead to the interface failure under a certain condition due to the coupled dynamic effect of vehicle load and water pressure.

AN ADAPTIVE FAST INTERFACE TRACKING METHOD

An adaptive numerical scheme is developed for the propagation of an interface in a velocity field based on the fast interface tracking method proposed in [2]. A multiresolution stategy to represent the interface instead of point values, allows local grid refinement while controlling the approximation error on the interface. For time integration, we use an explicit Runge-Kutta scheme of second-order with a multiseale time step, which takes longer time steps for finer spatial scales. The implementation of the algorithm uses a dynamic tree data structure to represent data in the computer memory. We briefly review first the main algorithm, describe the essential data structures, highlight the adaptive scheme, and illustrate the computational efficiency by some numerical examples.

Horizontal Push Plate Test and Simulation of CRTS II Slab Ballastless Track

Good interlayer interface performance is the key to maintaining the stability of CRTSⅡslab ballastless track structure.In a project,the tangential cohesion parameters of CRTSⅡslab ballastless track structure are generally measured by horizontal push plate test,so as to measure the interlayer interface performance.Horizontal push plate contraction scale and full scale tests of CRTSⅡslab ballastless track structure are carried out to obtain the tangential force-displacement relation curve of the interlayer interface,thus obtaining the parameters of cohesion model.A threedimensional progressive damage analysis model for CRTSⅡslab ballastless track structure is established,the whole process inversion of the horizontal push plate test is carried out,and the reliability of the contraction scale test results is verified by means of simulation and comparative analysis of test results.The results show that the greater the tangential stiffness of the interlayer interface of the track structure,the weaker the interlayer deformation coordination capability;the more significant the non-uniformity of the interface damage,the more likely the stress concentration;the greater the fracture toughness,the less likely the disjoint in the interlayer interface of the track structure.

温度荷载作用下高铁无砟轨道界面性能演变规律研究

植筋锚固修复是当前高速铁路工务部门针对CRTSⅡ型板式无砟轨道高温上拱病害采用的最常用整治方案。为研究温度循环荷载作用下植筋锚固修复对轨道结构层间界面服役性能的影响,制作复合试件并进行温度循环试验和界面剪切试验。试验发现,轨道结构植筋修复能够提高轨道板与CA砂浆层界面抗剪性能,增强界面服役稳定性。在试验的基础上建立CRTSⅡ型板式无砟轨道植筋修复后界面-结构空间精细化损伤模型,研究界面在温度循环荷载作用下损伤演变规律。研究结果表明:相较于未植筋结构,植筋修复后无砟轨道层间脱黏面积和脱黏速率均得到有效抑制;考虑到植筋锚固后易诱发植筋孔周围界面应力集中和刚度退化等开裂风险,建议工务部门严格控制植筋数量,加强轨道板植筋孔处巡检工作。