薄壁离心钢管混凝土扭转全过程简化计算研究

通过对22根薄壁离心钢管混凝土构件抗扭性能试验数据的研究，提出了该结构受扭破坏的三个阶段的概念；在钢管和混凝土现有规范计算方法的基础上，建立了组合构件弹性扭矩、塑性扭矩的简化公式；以钢管的空心率、含钢率、长细比为参数，提出了构件组合模量表达式，并且采用与国际有关研究、国内相关规范相一致的直接双直线法，建立了组合刚度及组合构件抗扭各阶段的变形计算方法，并进行了扭转全过程简化计算，结果与试验结果吻合良好。     

基于滞后磁化参数变化的扭矩检测模型研究

通过对在扭矩和磁场作用情况下,铁磁性钢轴中滞后参数的变化,构造了一磁-力滞后模型。借助于此模型,可以确定与扭应力有关的矫顽磁场、剩磁以及相对磁导率等磁性参数的变化。得出了检测扭矩的最好磁参数是在饱和或接近于饱和时的Hc结论。     

基于CMPCA的化工生产过程性能监测与故障诊断

根据化工生产过程的间歇反应特点,提出了一种基于一致多方向主元分析(CMPCA)的过程性能监测与故障诊断方法.首先基于动态时间规整DTW(Dynamic Time Warping)技术对批次数据进行同步化,􀁯从而使得用于建模和诊断的数据均具一致性,保证了过程性能监测与故障诊断的.     

Exact static element stiffness matrices of non‐symmetric thin‐walled curved beams

An evaluation procedure of exact static stiffness matrices for curved beams with non‐symmetric thin‐walled cross section are rigorously presented for the static analysis. Higher‐order differential equations for a uniform curved beam element are first transformed into a set of the first‐order simultaneous ordinary differential equations by introducing 14 displacement parameters where displacement modes corresponding to zero eigenvalues are suitably taken into account. This numerical technique is then accomplished via a generalized linear eigenvalue problem with non‐symmetric matrices. Next, the displacement functions of displacement parameters are exactly calculated by determining general solutions of simultaneous non‐homogeneous differential equations. Finally an exact stiffness matrix is evaluated using force–deformation relationships. In order to demonstrate the validity and effectiveness of this method, displacements and normal stresses of cantilever thin‐walled curved beams subjected to tip loads are evaluated and compared with those by thin‐walled curved beam elements as well as shell elements. Copyright © 2004 John Wiley & Sons, Ltd.     

变截面筒中筒结构受扭分析

在开口薄壁杆件的扭转理论的基础上加以修正，推导出变截面筒体在扭转荷载作用下的扭角微分方程．提出筒中筒结构在纯扭矩作用下的力学简便分析方法，即利用连续化假定，分析了变截面处的边界条件，求出了在两种常用荷载(顶端集中扭矩、均布扭矩)作用下的协调传递矩阵．利用连续化条件求出任意截面的参数，然后推广到多个变截面求出任意楼层的扭转角及内力．该法适用于n阶变截面的筒中筒结构的受扭计算分析，并适用于计算机计算，思路清晰，计算量小，简便易掌握，是一种合理适用的简便计算方法．     

有挠时空引力场的Newman-Penrose方程

考虑具有局部Lorentz度规gμν和非对称联络Гμν^λ。的四维微分流形U4，给出U4时空的标架分量和旋系数，引入新的Ricci张量和曲率张量的无迹部分的标架分量．导出挠率的Bianchi恒等式。将旋系数表述的Newman-Penrose方程推广到包含任何非对称联络的时空，得到U4空间的Newman-Penrose方程。所得到的方程较之无挠时空的方程更长且方程数更多，由于联络的非对称性，这是必然的，方程的复杂性也是不可避免的。但认为在时空有挠的U4空间求解引力场问题，这一方程组将是相对便利的形式。     

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介绍了一种全新设计的材料扭转试验机,主要采用了液压回转式夹具装夹试样,通过伺服电机—滚珠丝杆—传感器方式对长线材试样施加恒定的拉紧力,以及伺服电机—减速机构驱控夹头双向旋转,可针对Ф7 mm~Ф14 mm、2 000 MPa级长线材试样开展各类扭转以及低成本的慢速拉扭复合疲劳试验。基于对试样扭矩变化的实时跟踪,可实现0.000 5~30 r/min的变速扭转以及在扭矩陡降(即最大扭转塑性)瞬时临界采样,供后续试样内部组织与外表面形貌评价分析。     

SIMULATION OF FILLING AND EMPTYING IN A HEXAGONAL-SHAPE SOLAR GRAIN SILO

ABSTRACT

A new silo design for grain-storage is examined using a numerical procedure to model its 3D granular flows during the filling and emptying processes. The authors in Hemández-Cordero, et al. Korea-Australia Rheol. J. 12(1)269-281(2000)] have previously presented the design of the new silo and its observed flow behavior. Its main characteristic is the almost complete elimination of excessive dynamics stresses. Since the required computational resources to model the transient phenomena in these experiments are enormous, here, we present basic numerical results related to packing and dynamics of grains considering this complex design. Especial emphasis is given to simulate in great detail collisions of spherical grains with the walls, between themselves, as well as the complex geometry of the new silo, such as filling and unloading openings, inclined walls, etc. The interactions include compressive normal forces between grains as well as tangential forces involved in sliding and rolling between two kernels. Virtual contact mechanics valid in the vicinity of the symmetry plane of the silo are also prescribed, permitting predictions closer to experimentally observed behavior. In spite of the complexity of interactions, steady flow patterns results obtained with reasonable computational times are presented.     

How many reference patterns can improve profitability for real-time trading in futures market?

Investors in futures market used to employ trading system which depends on reference pattern (template) to detect real-time buy or sell signal from the market. Indeed they prepare in advance a number of reference patterns that market movement might follow, and then match the current market with one of reference patterns. One popular way to prepare templates is to fix a relatively small number of them which represent possible market movements efficiently. The underlying assumption of this approach is of course that the current market movement is close enough to one of the templates. However, there is always a calculated risk that the current market is close to none of them sufficiently. In this article we investigate the issue of appropriate number of templates (or template cardinality I) in terms of profitability. We will show that one may improve profitability by increasing I and that random pattern sampling plays a key role in such case. An empirical study is done on the Korean futures market.     

Interfacial microstructures and properties of aluminum alloys/galvanized low-carbon steel under high-pressure torsion

A new composite processing technology characterized by hot-dip Zn–Al alloy process was developed to achieve a sound metallurgical bonding between Al–7 wt% Si alloy (or pure Al) castings and low-carbon steel inserts, and the variations of microstructure and property of the bonding zone were investigated under high-pressure torsion (HPT). During hot-dipping in a Zn–2.2 wt% Al alloy bath, a thick Al₅Fe₂Zn_x phase layer was formed on the steel surface and retarded the formation of Fe–Zn compound layers, resulting in the formation of a dispersed Al₃FeZn_x phase in zinc coating. During the composite casting process, complex interface reactions were observed for the Al–Fe–Si–Zn (or Al–Fe–Zn) phases formation in the interfacial bonding zone of Al–Si alloy (or Al)/galvanized steel reaction couple. In addition, the results show that the HPT process generates a number of cracks in the Al–Fe phase layers (consisting of Al₅Fe₂ and Al₃Fe phases) of the Al/aluminized steel interface. Unexpectedly, the Al/galvanized steel interface zone shows a good plastic property. Beside the Al/galvanized steel interface zone, the microhardnesses of both the interface zone and substrates increased after the HPT process.