混凝土仿古坡屋盖施工的难点及解决方式

以太原某饭店改扩建工程为例,结合其仿古建筑屋盖为钢筋混凝土结构坡屋面形式的工程概况,针对施工中存在的多项施工难点,提出了具体的应对措施,并探讨了措施的效果,为今后的类似工程提供了参考借鉴。     

喷丸加工的工艺特性及参数控制研究

提出了喷丸加工新算法,该算法是模拟喷丸过程中零件表面层的塑性变化,从而控制能量参数。在喷丸加工时,表面层塑性变形积聚了大量压缩能量,通过进行能量参数优化,得到零件的最大疲劳强度并绘出曲率参数曲线。     

小曲率拱型支架支护系统理论与试验分析

针对煤层顺槽梯形支架存在的问题,提出一种新型结构的小曲率拱型支架。采用曲梁模型进行了支架系统的受力分析,得到其最大承载能力;通过与直梁支架承载能力相比较,得到了小曲率拱型支架承载能力系数与曲梁跨度和半径的影响关系。同时进行了地面试压和井下支护工程实验。结果证明:小曲率拱型支架力学性能远优于梯形支架,支撑能力大,自身稳定性良好,有效解决了近距离和下分层煤层巷道不可锚且在强压下难支护的问题。     

非强制平面转弯带式输送机曲率半径影响因素分析

从力平衡角度分析参数变化对非强制平面转弯带式输送机曲率半径的影响。张力的变化对曲率半径的影响最大,成槽角及抬高角的变化对曲率半径的影响也较大。     

Underactuated miniature bending joint composed of serial pulleyless rolling joints

This paper proposes a miniature bending joint composed of serial rolling joints; it refers to the classification of small joints of other products and studies on surgical applications according to the structures and transmissions. To achieve this, a pulleyless rolling joint is introduced as a unit component and the basic design principle is established for the joint. A simple mechanism guarantees a smooth rolling contact using elastic fixtures. Underactuation, which prevents S-shaped curvature similar to buckling, is applied to drive the bending joint with a limited number of wire cables. Using a 1-DOF real-sized prototype, experiments were performed to measure the motion accuracy and payload capacity from various angles to evaluate the efficacy of an improved design that enhances the payload on the distal end. This novel joint is applicable to a wider variety of surgical tools and catheters relative to other candidates owing to its small constant curvature, reasonable payload capacity, and miniature size.     

Using the genetic algorithm to enhance nonnegative matrix factorization initialization

Nonnegative matrix factorization (NMF) algorithms have been utilized in a wide range of real applications; however, the performance of NMF is highly dependent on three factors including: (1) choosing a problem dependent cost function; (2) using an effective initialization method to start the updating procedure from a near‐optimal point; and (3) determining the rank of factorized matrices prior to decomposition. Due to the nonconvex nature of the NMF cost function, finding an analytical‐based optimal solution is impossible. This paper is aimed at proposing an efficient initialization method to modify the NMF performance. To widely explore the search space for initializing the factorized matrices in NMF, the island genetic algorithm (IGA) is employed as a diverse multiagent search scheme. To adapt IGA for NMF initialization, we present a specific mutation operator. To assess how the proposed IGA initialization method efficiently enhances NMF performance, we have implemented state‐of‐the‐art initialization methods and applied to the Japanese Female Facial Expression dataset to recognize the facial expression states. Experimental results demonstrate the superiority of the proposed approach to the compared methods in terms of relative error and fast convergence.     

楔形环管片纵向接头对施工荷载力学响应研究

楔形环管片是盾构隧道曲线段的重要组成部分。以珠海-澳门轻轨某急弯隧道为例,利用ANSYS有限元软件计算了楔形环管片在不同管片幅宽、楔形量、隧道曲率半径、千斤顶压力等条件下管片纵向接头的受力情况,重点分析了管片环间接头的最大正负弯矩。研究结果表明:随着盾构隧道曲线半径减小,正负最大弯矩均增大,不同隧道转弯半径下,管片最大正负弯矩均随接头抗弯刚度的增大而增大;不论正负弯矩,均有管片幅宽越小最大弯矩越大的现象。不同管片幅宽下,管片最大正负弯矩均随接头抗弯刚度的增大而增大;曲线半径为150 m时,最大正弯矩基本随着千斤顶压力呈线性增大的趋势,最大约为1 180 k N·m。研究结果对今后的急弯盾构隧道管片设计有一定的指导意义。     

基于多核学习的投影非负矩阵分解算法

非负矩阵分解(NMF)把给定的数据矩阵分解成低维的非负基矩阵和对应的系数矩阵,两者之间存在必然联系。为此,研究者将基矩阵转换为系数矩阵的投影,进一步提高分解效率。但是该方法无法处理非线性数据,核函数的引入部分解决了此问题,却同时导致核函数参数选择的问题。基于多核学习理论,提出了一种多核学习的投影非负矩阵分解(MKPNMF)算法,该算法有效地避免了核函数参数选择的问题,同时提高了学习性能。在实际人脸数据上的实验结果表明,MKPNMF较已有的NMF类方法具备明显的性能优势。     

涡旋曲面铣削加工工艺改进

涡旋线是一种曲率在时刻变化的复杂曲线,涡旋面铣削加工中,动态前后角、切削层厚度(切深)以及切削力都随之变化,如果切削用量设计不当,将使动态切削状态恶化,严重降低刀具寿命,影响加工效率,这些影响切削性能的因素都与进给量直接有关。当曲率增大,切深加大,动态后角变小,以及切削力增加,这种现象明显地表现在涡旋曲线接近中心的部位,往往导致刀具急剧磨损以致断裂,严重影响生产率。因此涡旋曲面铣削加工进给率计算必须考虑其曲率的变化,但通常是根据经验按曲率的变化分段安排进给率,不是以精确计算为依据。为了改进涡旋曲面铣削加工工艺,本文工作结合涡旋压缩机主体涡旋盘常用的涡旋线建立数学模型,计算单位时间进给的切削层厚度,提出进给率优化方法,并利用Weilenmann方法计算相应的切削力,参照工艺性和经济性的要求、改善现行的涡旋加工工艺。     

Detonation Shock Dynamics Relations for RDX-TNT Based Cast Explosives

RDX and TNT based explosives are very useful in performing research and development works especially when complex shaping of an assembly is required due to their molding capability and the range of ratios in which they can be mixed. In this paper, for these compositions, detonation shock dynamics (DSD) relations between normal detonation velocity Dn and detonation wave curvature κ are determined for RDX∶TNT explosives in weight ratios 40∶60, 50∶50 and 60∶40. Experiments are performed with 50 mm diameter rate sticks of approximately 200 mm length using high speed rotating mirror camera and time measurement probes. The results show that first order DSD relation is indeed representative of these explosives. The slope of this relation increases by increasing TNT contents in these explosives. Going from 40% to 60% TNT, the data show an increase of more than 100% in negative slope of Dn-κ relation.