Three‑dimensional numerical simulation of dynamic strength and failure mode of a rock mass with cross joints

To study the dynamic mechanical properties and failure characteristics of intersecting jointed rock masses with different joint distributions under confining pressure,considering the cross angleαand joint persistence ratioη,a numerical model of the biaxial Hopkinson bar test system was established using the finite element method–discrete-element model coupling method.The validity of the model was verified by comparing and analyzing it in conjunction with laboratory test results.Dynamics-static combined impact tests were conducted on specimens under various conditions to investigate the strength characteristics and patterns of crack initiation and expansion.The study revealed the predominant factors influencing intersecting joints with different angles and penetrations under impact loading.The results show that the peak stress of the specimens decreases first and then increases with the increase of the cross angle.Whenα<60°,regardless of the value ofη,the dynamic stress of the specimens is controlled by the main joint.Whenα≥60°,the peak stress borne by the specimens decreases with increasingη.Whenα<60°,the initiation and propagation of cracks in the cross-jointed specimens are mainly controlled by the main joint,and the final failure surface of the specimens is composed of the main joint and wing cracks.Whenα≥60°orη≥0.67,the secondary joint guides the expansion of the wing cracks,and multiple failure surfaces composed of main and secondary joints,wing cracks,and co-planar cracks are formed.Increasing lateral confinement significantly increases the dynamic peak stress able to be borne by the specimens.Under triaxial conditions,the degree of failure of the intersecting jointed specimens is much lower than that under uniaxial and biaxial conditions.

End-to-End Joint Multi-Object Detection and Tracking for Intelligent Transportation Systems

Environment perception is one of the most critical technology of intelligent transportation systems(ITS).Motion interaction between multiple vehicles in ITS makes it important to perform multi-object tracking(MOT).However,most existing MOT algorithms follow the tracking-by-detection framework,which separates detection and tracking into two independent segments and limit the global efciency.Recently,a few algorithms have combined feature extraction into one network;however,the tracking portion continues to rely on data association,and requires com‑plex post-processing for life cycle management.Those methods do not combine detection and tracking efciently.This paper presents a novel network to realize joint multi-object detection and tracking in an end-to-end manner for ITS,named as global correlation network(GCNet).Unlike most object detection methods,GCNet introduces a global correlation layer for regression of absolute size and coordinates of bounding boxes,instead of ofsetting predictions.The pipeline of detection and tracking in GCNet is conceptually simple,and does not require compli‑cated tracking strategies such as non-maximum suppression and data association.GCNet was evaluated on a multivehicle tracking dataset,UA-DETRAC,demonstrating promising performance compared to state-of-the-art detectors and trackers.

Computer Aided Simulation on Precision Cold Forging of Universal Joint Cross

The 3D FEM numerical simulation on multi-action precision cold forging technology of universal joint cross and differential spider is done in this article using DEFORM Software, a commercial computer aided engineering software specializing in forming and heat treatment simulation technology, and suitable for cold, warm and hot forging process. The material flow properties, the dynamic variation of stress and strain in the process of deformation and the load-stroke curve have also been achieved. A good consistency is exhibited between simulation results and practical data. Based on the DEFORM simulation results, the optimized procedure has been found for forging a universal joint cross. What should be emphasized here is that a better understanding of practical forging characters and the environmental factors can greatly improve the simulation accuracy thus make the simulation results more reliable.

Digital image processing-based automatic detection algorithm of cross joint trace and its application in mining roadway excavation practice

This paper proposes a digital image processing-based detection algorithm for cross joint traces of coal roadway heading face.Initially,the acquired images were preprocessed,i.e.,adaptive correction was conducted for non-uniform illumination images based on the 2D gamma function.The edge detection algorithm was then applied to extract the edges of the structural plane,followed by the filtration of the non-structural plane noises.Moreover,the Hough transform algorithm was applied to extract the linear edges;finally,the edges were locally connected in accordance with the angle and distance criteria.The experimental results show that this algorithm can be used to reduce the noise caused by non-uniform illumination and avoid the mutual interference of multi-scale edges,so as to effectively extract the traces of the cross joint.Furthermore,Q-system and rock mass rating(RMR),were applied to conduct a quantitative evaluation on the stand-up time of unsupported roof in the four test images.The Q-system quality scores are 26.7,43.3,3.1,and 6.7,and the RMR quality scores are 56.84,58.73,48.42,and 51.42,respectively.The stand-up time of unsupported roofs with a span of 4.6 m are 30,36,7.7 and 14 d,respectively.

Numerical simulation and experimental study on constant amplitude fatigue behavior of welded cross plate-hollow sphere joints

In order to reveal the constant-fatigue fracture form and mechanism of the welded cross plate-hollow sphere joints(WCPHSJs)and establish its formula,the WCPHSJs were fatigue tested.A total of 19 specimens were tested under constant amplitude fatigue loads using a specially designed test rig.The joint was analyzed statically by t e finite element analysis(F3A),and metallographic analysis of fatigue fracture was done by the electron scanning microscope.Numerical simulation and experimental results show that the hot-spot of WCPHSJ lies at the weld toe location where severe stress is concentrated.Fatigue cracks initiate at the weld toe and then propagate circumferentially around the sphere with a diameter equivalent to the width of the cross plate up to the fatigue facture.The initial welding defects and constructional detail constitute the main factor of fatigue failure.The S-N curves for the joints were developed through a linear regession analysis of fatigue data.A formula for calculating constant amplitude fatigue,base on the concept of the hot spot stress amplitude,is proposed.

An autonomic joint radio resource management algorithm in end-to-end reconfigurable system

This paper presents the multi-step Q-learning(MQL)algorithm as an autonomic approach to thejoint radio resource management(JRRM)among heterogeneous radio access technologies(RATs)in theB3G environment.Through the'trial-and-error'on-line learning process,the JRRM controller can con-verge to the optimized admission control policy.The JRRM controller learns to give the best allocation foreach session in terms of both the access RAT and the service bandwidth.Simulation results show that theproposed algorithm realizes the autonomy of JRRM and achieves well trade-off between the spectrum utilityand the blocking probability comparing to the load-balancing algorithm and the utility-maximizing algo-rithm.Besides,the proposed algorithm has better online performances and convergence speed than theone-step Q-learning(QL)algorithm.Therefore,the user statisfaction degree could be improved also.

Joint Source-Channel Bit Allocation Based on Expected End-to-End Distortion Model

An adaptive joint source channel bit allocation method for video communications over error-prone channel is proposed.To protect the bit-streams from the channel bit errors,the rate compatible punctured convolution(RCPC)code is used to produce coding rates varying from 4/5 to 1/2 using the same encoder and the Viterbi decoder.An expected end-to-end distortion model was presented to estimate the distortion introduced in compressed source coding due to quantization and channel bit errors jointly.Based on the proposed end-to-end distortion model,an adaptive joint source-channel bit allocation method was proposed under time-varying error-prone channel conditions.Simulated results show that the proposed methods could utilize the available channel capacity more efficiently and achieve better video quality than the other fixed coding-based bit allocation methods when transmitting over error-prone channels.

A MATLAB-Based Numerical and GUI Implementation of Cross-Gradients Joint Inversion of Gravity and Magnetic Data

The cross-gradients joint inversion technique has been applied to multiple geophysical data with a significant improvement on compatibility, but its numerical implementation for practical use is rarely discussed in the literature. We present a MATLAB-based three-dimensional cross-gradients joint inversion program with application to gravity and magnetic data. The input and output information was examined with care to create a rational, independent design of a graphical user interface (GUI) and computing kernel. For 3D visualization and data file operations, UBC-GIF tools are invoked using a series of I/O functions. Some key issues regarding the iterative joint inversion algorithm are also discussed: for instance, the forward difference of cross gradients, and matrix pseudo inverse computation. A synthetic example is employed to illustrate the whole process. Joint and separate inversions can be performed flexibly by switching the inversion mode. The resulting density model and susceptibility model demonstrate the correctness of the proposed program.

Research on Angular Output Velocity of a Drive Shaft with Double Cross Universal Joints

The study object is the angular output velocity of the drive shaft which is made up of two series-wound cross universal joints. We have deduced the function relation between the angular output velocity and initiative input angle of the drive shaft with double cross universal joints that is based on the calculation formula of the angular output velocity of a single cross universal joint, and by analyzing the relation between the two input angles. By using this function relation, the constant velocity condition of the drive shaft with double cross universal joints＂ is verified. The step-by-step searching algorithm is adopted to obtain the optimal phase angle that leads to the minimum fluctuate index of the angular output velocity in the vary velocity condition. At the same time, we worked out the maximal and minimum value of the angular output velocity, and their initiative input angle. The correctness of the function of the angular output velocity and the step-by-step search algorithm are verified by an ADAMS simulation example.

深化职业教育产教融合的关键是实现跨界组织实体化运作

深化产教融合是职业教育实现高质量发展的核心举措。改革开放以来,我国职业教育产教融合在政策牵引和实践演绎的相互作用下,展现了由松散到紧密、由浅层次到深层次的演变历程。但长期以来,产教“融而不合”、校企“跨而不实”的现实困境始终难以破题。伴随市域产教联合体、行业产教融合共同体等新型产教跨界组织的产生与发展,以制度突破为基本前提,推进跨界组织的实体化运作成为深化职业教育产教融合的关键。而实现这一点,需要跨界组织具有符合实际的组织结构、发挥实效的主导权力、约束有力的职责分工、稳定的利益共享机制、有效的激励保障政策,也需要多方主体协同有效的共建共治。

新建隧道近接上穿对既有盾构隧道纵向变形的影响

新建隧道近接上穿将诱发下卧盾构隧道隆起变形,预测既有盾构隧道位移发展对近接上穿施工控制和既有盾构隧道保护具有重要意义。基于两阶段法,提出新建隧道近接上穿引发既有盾构隧道纵向位移解析解;通过可考虑环间接头弱化的非连续盾构隧道模型模拟既有盾构隧道,采用Riftin地基考虑盾构隧道-土层相互作用,同时通过Mindlin经典解得到新建隧道开挖卸载应力,并作用于既有盾构隧道之上,建立新建隧道上穿作用下既有盾构隧道纵向变形解答;通过将杭州圆形顶管隧道上穿既有地铁1号线、上海地铁8号线隧道上穿既有地铁2号线两个工程案例实测值与本文方法和常用Euler-Bernoulli(EB)等效连续梁模型计算结果进行对比,验证本文方法的合理性。研究结果表明:本文方法和EB连续梁模型预测的隧道纵向位移均接近实测值;本文方法预测的隧道弯矩和接头张开量均大于EB连续梁模型;但EB等效连续梁模型预测的纵向位移曲线整体呈现为光滑连续,而本文方法预测的位移曲线是由一系列短直线连接而成,在接头处存在“尖点”。

早期应用跨关节外固定支架对胫骨平台骨折患者膝关节软组织的保护效果

目的 探讨早期应用跨关节外固定支架治疗,对Ⅵ型胫骨平台骨折患者膝关节软组织的保护效果。方法 选取2019年1月至2020年12月收治的Ⅵ型胫骨平台骨折患者122例为研究对象,以信封法进行随机分成研究组和对照组,每组61例。研究组患者给予早期(收治12 h内)跨关节外固定支架联合内固定手术;对照组患者给予延期(收治24~72 h内)跨关节外固定支架联合内固定手术。观察和比较2组患者的手术情况指标、术后恢复指标、膝关节疗效、膝关节功能评分、膝关节软组织损伤指标。结果 研究组外固定手术时间和内固定手术时间均短于对照组,外固定术后VAS评分低于对照组,内固定术中出血少于对照组;研究组康复时间和骨折愈合时间均短于对照组,差异均有统计学意义(P<0.05);2组并发症发生率和膝关键治疗优良率比较,差异无统计学意义(P>0.05);术后,2组患者各项膝关节功能评分均降低,且研究组低于对照组,差异均有统计学意义(P<0.05);研究组外固定术后水疱发生率低于对照组,外固定术后肿胀程度小于对照组,水疱痂皮愈合时间早于对照组,差异均有统计学意义(P<0.05)。结论 与延期时机相比,给予Ⅵ型胫骨平台骨折患者早期跨关节外固定支架联合内固定手术治疗,能够缩短手术时间,提升患者骨折愈合和术后康复进程,促进患者膝关节功能和膝关节软组织损伤的恢复。

考虑衬砌截面协调变形约束的既有隧道受盾构下穿施工影响的Fourier能量变分解

目前关于新建盾构开挖诱发既有地铁隧道变形的理论研究,大多将既有隧道简化为不含接头的Euler-Bernoulli梁,而忽视了衬砌截面的剪切变形与管片接头的局部刚度削弱。此外,既有地基模型理论较少考虑衬砌管片与接触土体的协调变形约束。首先,采用Loganathan-Polous公式计算盾构开挖诱发的土体自由位移场,并将既有隧道视为考虑剪切变形的Timoshenko梁,基于沿轴线变化的抗弯与剪切刚度函数来描述管片接头的局部削弱作用;然后,结合能量变分原理与连续弹性体Mindlin解,建立考虑衬砌截面协同变形约束的隧道位移控制方程,将盾构开挖诱发的附加荷载施加于既有隧道,并使用Fourier级数方法求解既有隧道纵向变形;最后,将Fourier能量变分解与3组工程实测数据进行对比验证,取得了较好的一致性。此外,考虑隧道抗弯刚度、剪切刚度、接头刚度削弱作用、土体参数与隧道空间位置等因素的共同影响,使用抗弯系数、剪切系数及接头系数进行敏感性分析。结果表明,考虑截面变形协调约束的理论解更为符合实际,不考虑变形协调约束所得隧道位移结果偏大;衬砌接头局部刚度的削弱作用将造成隧道弯矩沿轴线在接头处发生明显锯齿状突变;抗弯系数与剪切系数的增长均导致隧道结构所受弯矩降低;剪切系数由低到高的增长将导致隧道变形模式发生“弯曲控制-弯剪混合-剪切控制”三阶段变化;隧道变形模式进入“剪切控制”阶段的过程中,抗弯刚度的变化对隧道内力影响逐渐降低;接头系数的增长将造成隧道所受弯矩降低,但隧道抗弯刚度较大时其影响逐渐减弱。

面向深部矿产资源勘探的井中重磁三维交叉梯度联合反演

单一井中重磁方法解决问题有限,其三维反演具有严重的多解性。开展面向深部矿产资源勘探的井中重磁三维交叉梯度联合反演,采用交叉梯度函数对密度和磁化率进行耦合,综合井中重磁多参数信息进行联合反演,减少反解的多解性,提高深部矿体识别的准确性。通过理论模型和实际资料进行反演分析。结果表明:井中重磁交叉梯度联合反演具有较高的纵向分辨能力,可以显著提高深部矿体识别的准确性,特别是能有效识别深部隐伏矿体。

浅析手游IP计中的应用研究

本文从手游IP在新式茶饮联名设计中的现状入手,分析手游IP在新式茶饮联名设计中的应用基础,对手游IP在新式茶饮联名设计中的应用规则进行细致的阐述,旨在更好地了解手游IP在新式茶饮联名设计中的未来发展趋势,认清IP联名的现状,归纳与总结IP联名的缺憾,实现跨圈双赢。

中哈跨界河流合作:进程、机遇与深化路径

中哈跨界河流合作机制以联合委员会为平台,在水文信息交换、水质保护、水量分配、水利工程合作等方面取得突出成果,中哈两国政治关系的提升、环委会的积极配合及“一带一路”倡议相关政策的支持是推进中哈跨界河流合作的主要因素;同时,中哈跨界河流合作机制也面临一系列挑战;制定切实有效的水资源分配规则,深化跨界河流环保合作,重视跨界含水层条约的签订,构建系统的跨界水合作制度以及多元化的水争端解决方法体系,并提升国际话语权引导国际舆论等是应对挑战,实现中哈跨界水资源可持续利用的关键。

大跨度装配式单层网壳十字形半刚性螺栓连接节点抗弯性能研究

装配式连接节点是大跨度装配式单层空间网壳结构体系的关键。提出一种适用于大跨度单层网壳结构的十字形板装配式节点。该节点由圆钢管、十字形钢板、角钢、矩形连接盖板、圆盖板和高强螺栓组成,其中圆钢管、盖板、十字形钢板在工厂焊接,现场将十字形板和角钢、矩形盖板用高强螺栓连接。该节点通过设置角钢、矩形连接盖板和十字形钢板螺栓连接,在节点受到弯曲荷载时,角钢和矩形连接盖板可以首先承受弯曲荷载,从而减少节点内侧的十字形钢板塑性损伤,并且提高节点的抗弯性能。利用有限元模拟方法,构建新型连接节点有限元模型,分析了十字形钢板和角钢厚度等变量如何影响节点在平面内外的抗弯性能。通过对各组成部分尺寸的参数化研究,得到了这些因素对所提出的连接节点平面内外抗弯性能的影响规律。研究结果表明,采用角钢与矩形盖板相连接形成的十字形节点,在抗弯刚度和承载力方面表现出了优异的性能。通过调节十字形板厚度、螺栓个数、角钢和盖板厚度可调控节点的初始抗弯刚度和抗弯承载力。基于刚性节点设计方法,对该半刚性节点进行尺寸理论设计,结果表明该方法可以保证节点弯矩设计值基本达到圆钢管的屈服弯矩,满足设计要求,提高节点安全。

细微特征增强的多级联合聚类跨模态行人重识别算法

目前跨模态行人重识别研究注重于通过身份标签在全局特征或局部特征上提取模态共享特征来减少模态差异,但却忽视了具有辨别力的细微特征。为此提出了一种基于特征增强的聚类学习网络,该网络通过全局和局部特征来挖掘并增强不同模态的细微特征,并结合多级联合聚类学习策略,最小化模态差异和类内变化。针对训练数据设计了随机颜色转换模块,在图像输入端增加模态之间的交互,以克服颜色偏差的影响。通过在公共数据集上进行实验,验证了所提方法的有效性,其中在SYSU-MM01数据集的全搜索模式下Rank-1和mAP分别达到了70.52%和64.02%;在RegDB数据集的V2I检索模式下Rank-1和mAP分别达到了88.88%和80.93%。

DCFF-Net:基于人体骨骼点的双流跨级特征融合动作识别网络

在基于骨骼的动作识别任务中,骨骼点特征对于动作识别来说至关重要。针对现有方法存在输入特征不足、特征融合策略粗糙、参数量大等问题,提出一种基于人体骨骼点的双流跨级特征融合网络。首先,针对特征输入,用欧氏距离骨架特征(EDSF)和余弦角度骨架特征(CASF)两种局部关节特征来表征人体骨骼序列,帮助网络识别不同体态和体态相似的人体动作;其次,考虑到部分动作类别的运动轨迹与全局运动的相关性,引入全局运动特征(GMF)弥补局部关节特征在此类动作上识别精度不足的问题;此外,为了加强不同特征之间的信息交互,提出一种跨级特征融合模块(CLFF),对不同特征层、不同属性的动作特征进行特征互补,丰富了网络的特征形式;最后,网络采用一维卷积(Conv1D)进行搭建,减轻了模型的计算负担。实验结果表明,所提模型在JHMDB身体动作数据集上获得了84.1%的识别准确率,在SHREC手势动作数据集上分别获得了97.4%(粗糙数据集)和95%(精确数据集)的识别准确率,取得了与先进方法相当的性能。

基于DEMATEL方法的科学基金项目绩效关键影响因素识别及实证研究——以促进海峡两岸科技合作联合基金项目为例

基础研究是应用研究和重大创新之源,联合基金作为国家基金委联合地方政府支持基础研究的主渠道之一,对提升地区原始创新能力、促进人才队伍建设发挥重要作用。为了真实反映促进海峡两岸科技合作联合基金资助项目的学术水平,从创新成果、人才培养、合作交流、项目延伸和间接影响等5个维度构建结题项目绩效评价指标体系,运用DEMATEL法分析15个二级指标之间的关联影响,结合多层次模糊综合评价法构建模型,并以某大学承担的重点支持项目为案例对影响项目绩效的关键因素进行实证分析,确定这个项目绩效评价等级。实证结果表明:DEMATEL法可以识别影响项目绩效的关键指标;模糊综合评价模型既考虑了评价对象的模糊性,也兼顾了指标体系的层次性,综合评价结果更具科学性。