Moment quantization of inhomogeneous spin ensembles

Robust excitation of a large spin ensemble is a long-standing problem in the field of quantum information science and engineering and presents a grand challenge in quantum control. A formal theoretical treatment of this task is to formulate it as an ensemble control problem defined on an infinite-dimensional space. In this paper, we present a distinct perspective to understand and control quantum ensemble systems. Instead of directly analyzing spin ensemble systems defined on a Hilbert space, we transform them to a space where the systems have reduced dimensions with distinctive network structures through the introduction of moment representations. In particular, we illustrate the idea of moment quantization for a spin ensemble and illuminate how this technique leads to a dynamically equivalent control system of moments. This equivalence enables the control of spin ensembles through the control of their moment systems, which in turn creates a new control analysis and design paradigm for quantum ensemble systems based on the use of truncated moment systems.     

磁悬浮控制力矩陀螺高速转子的高精度位置控制

在受到陀螺效应、动框架效应等影响后产生的磁力非线性问题是磁悬浮控制力矩陀螺(MSCMG)高速转子位置精度下降的主要因素。为解决以上问题,提高转子位置精度,本文分析了转子所受磁力的特性,建立了转子系统非线性动力学模型,提出了神经网络滑模控制方法。设计滑模控制律,采用径向基函数神经网络逼近控制律中的非线性模型,自适应算法根据误差在线调整神经网络的权值,同时可以保证整个系统的稳定性。仿真和实验结果表明,所提出方法的转子位置精度达到99%,稳态误差为0.000 2 mm。神经网络滑模控制可以实现MSCMG转子系统的高精度位置控制。     

Ultimate strength of continuous composite box-girder bridges with precast decks

In order to apply precast decks to continuous composite bridges, several experiments and analytical studies were performed. From many previous studies, design criteria for crack controls in transverse joints of prefabricated slabs were confirmed. These considerations were needed for serviceability. The bridges which satisfy service limit states, also, should be evaluated for ultimate strengths to define limit states. In this paper, experimental and analytical studies of two-span continuous composite bridges with open box girder section were conducted. Cracking, yielding and ultimate loads were evaluated and compared with the test results for design of continuous composite bridges with precast decks. To evaluate yielding loads of continuous bridges, an uncracked section method considering moment redistribution which is defined in EUROCODE 4, was considered. In calculation of ultimate strengths, full or partial shear connection and sectional classes which were defined in EUROCODE or AASHTO LRFD specifications were considered. Also, through numerical analysis considering material nonlinearities, moment-curvature relationship and moment redistributions were estimated.     

栓焊刚性节点先拧后焊施工性能的试验研究

本文研究了焊接对栓焊混用节点连接性能的影响!通过依靠摩擦传递外力板的有限元分析,得出 了焊接作用下栓焊节点域的应力分布。并通过试验测定了焊接时节点域的温度分布,高强度螺栓预拉力变 化和节点板的收缩变形。最后即对高强度螺栓预拉力影响问题提出了施工建议。     

Further study on the flexural behaviour of concrete-filled steel tubes

This paper is a further study on the flexural behaviour of concrete-filled steel tubes based on the former work presented by Han [Han LH. Flexural behaviour of concrete-filled steel tubes. Journal of Constructional Steel Research 2004;60(2):313-37]. A total of 36 composite beam specimens filled with self-consolidating concrete (SCC) were tested. The main parameters varied in the tests are: (1) sectional types (circular and square); (2) steel yielding strength (from 235 to 282 MPa); (3) the ratio of tube diameter (or width) to wall thickness, D/t (from 47 to 105), and (4) the ratio of shear span to depth (from 1.25 to 6). Comparisons are made with predicted beam capacities using the existing methods, such as AIJ-1997 [Architectural Institute of Japan (AIJ). Recommendations for design and construction of concrete filled steel tubular structures. 1997], AISC-LRFD-1999 [AISC. Load and resistance factor design specification for structural steel buildings. Chicago: American Institute of Steel Construction, Inc.; 1999], BS5400-1979 [British Standard Institute: BS5400, Part 5, Concrete and composite bridges. 1979], EC4-1994 [Eurocode 4. Design of composite steel and concrete structures, Part 1.1: General rules and rules for buildings (together with United Kingdom National Application Document). DD ENV 1994-1-1:1994. London W1A2BS: British Standards Institution; 1994] and the method proposed by Han [Han LH. Flexural behaviour of concrete-filled steel tubes. Journal of Constructional Steel Research 2004;60(2):313-37].Applied calculation formulae of moment versus curvature curves and the flexural stiffness of concrete-filled steel tubular (CFST) beams are presented, based on the mechanics model of Han [Han LH. Flexural behaviour of concrete-filled steel tubes. Journal of Constructional Steel Research 2004;60(2):313-37]. Comparisons are made with predicted beam flexural stiffness using different methods, such as AIJ-1997, AISC-LRFD-1999, BS5400-1979, EC4-1994 and the method proposed in this paper. Comparisons are also made between the simplified model and the mechanics model, and generally good agreement is achieved.     

Discussion on: moment methods for structural reliability

A few comments on moment method for reliability analysis advocated by Zhao and Ono are presented in the paper. It is demonstrated using a number of numerical examples that the first four moments of a distribution, particularly when they are crudely estimated, do not always allow good estimates of tail probabilities, and that some different equivalent forms of performance function that describe the same structural problem may give totally incorrect values for the reliability when the Zhao and Ono methodology is applied to them. Furthermore, the computation method for the first four moments proposed by the same authors may be incorrect so that the reliability result is unreasonable accordingly.     

Structural analysis of greenhouses: A case study in Turkey

This study was carried out to determine the structural and functional characteristics of the greenhouses in greenhouse enterprises of Turkey. Greenhouse enterprises are widely common along the Marmara, Aegean and Mediterranean cost lines. Marmara region was selected as the study area since it is the pioneering region and has large areas allocated to greenhouses, and has various greenhouse types. Information about greenhouse types, material properties, placement, and arrangement of greenhouses in the study area was gathered by a questionnaire; then greenhouses in enterprises were divided into groups based on cover material, load bearing materials and directional placement. A total of four types of greenhouse with the most economic cross-section, one from each group, were selected and load acting on structural members of greenhouses were calculated. Loads acting on beams of each greenhouse were analysed by Force Method and Moment Distribution Method. The results obtained were compared statistically to determine the best methodology for structural analysis of greenhouses. As a result, no statistical difference was found between moments and shear forces obtained from both methods. However, a difference occurred based on greenhouse types and it was determined that the values obtained for trussed block greenhouse were higher than the other ones.     

ACI规范中关于轴向力、力矩对纵向钢筋按圆形排列截面的作用

对纵向钢筋按圆形排列的截面杆件推导了钢筋和混凝土部分所分担的轴向力和力矩的计算公式。最终的计算程序用来绘制轴向力、力矩作用下的影响曲线 ,列于ACI委员会 340设计手册[2 ] 。     

Effect of the moment transfer efficiency of a beam web on deformation capacity at box column-to-H beam connections

This paper investigates the effect of moment transfer efficiency of a beam web on deformation capacity at beam-to-column connections. Non-linear finite element analysis of five connection models was conducted. Analytical results showed that the moment transfer efficiency of the connection with a box column was poor when compared to a connection with an H-column; this was due to the out-of-plane deformation of the column flange. Based on previous test data, analytical results were compared with experimental results. Analytical and experimental results showed that the deformation capacity of the connection with a box column decreased due to the poor moment transfer efficiency of a beam web, followed by strain concentration at the beam flange.     

基于不变矩和SVM的圆形交通标志识别方法研究

针对道路交通标志的自动识别问题,通过不变矩和支持向量机(SVM)方法对圆形标志图像识别方法进行研究。首先根据交通标志的颜色和形状信息对采集到的原始图像进行颜色分割、形态学去噪和形状检测等处理,获得图像中包含交通标志的区域。然后分别对标志图像进行Hu矩和Zernike矩的特征值提取,将特征值输入SVM中进行训练并采用网格搜索法对SVM进行参数优化,最后使用优化后的支持向量机方法实现交通标志的识别。实验表明,与现有的其他交通标志识别算法相比,采用高阶Zernike矩与优化后SVM的识别方法有更好的识别效果。