Three-dimensional modelling of wood fracture in mode I, perpendicular to the grain direction at fibre level

A coupled experimental and numerical modelling approach was used to investigate the mechanism of softwood fracture at the fibre level. First, a three-dimensional mixed lattice-continuum fracture model was developed to investigate the mechanism of wood fracture, taking into account the porosity of its structure and its heterogeneities at the fibre level. The critical volumes in the specimen where crack propagation was more probable were modelled by a lattice that could show the alternation of earlywood and latewood fibres, and the other regions were considered as the continuum medium. The proposed model was used to investigate the mode I fracture of a small softwood sample in RL orientation. Secondly, a method was developed for microscopic observation of the crack trajectory and investigating the mechanism of initiation and propagation of cracks. This approach was used for microscopic investigation of the fracture behaviour of spruce specimens in mode I and RL orientation. The results of the numerical study were compared with the experimental results. The prepeak and postpeak behaviour of the obtained stress-displacement curve and also the crack opening trajectory in cross-section and longitudinal section in the model and experiments were in good agreement. Both the model and the microscopic observation showed that in mode I fracture and RL orientation, the main trajectory of the crack propagates in the earlywood ring.     

Predicting the unevenness of polyester/viscose blended open-end rotor spun yarns using artificial neural network and statistical models

In this study, an artificial neural network (ANN) and a statistical model are developed to predict the unevenness of polyester/viscose blended open-end rotor spun yarns. Seven different blend ratios of polyester/viscose slivers are produced and these slivers are manufactured with four different rotor speed and four different yarn counts in rotor spinning machine. A back propagation multi layer perceptron (MLP) network and a mixture process crossed regression model (simplex lattice design) with two mixture components (polyester and viscose blend ratios) and two process variables (yarn count and rotor speed) are developed to predict the unevenness of polyester/viscose blended open-end rotor spun yarns. Both ANN and simplex lattice design have given satisfactory predictions, however, the predictions of statistical models gave more reliable results than ANN.     

信息物理系统(cyber-physical system)时空建模方法及在温室控制中的应用

传统农业采用人工方式对温室进行控制,但是随着现代农业的快速发展,这种人工投入大、精度低的控制方式已不能满足现代农业需要。该文基于分层有限状态机和事件晶格的概念,建立3层的信息物理系统模型,并提出一种基于分层有限状态机的信息物理系统时空建模方法,同时利用该建模方法开发了新的温室控制系统。该系统能够将物理层传感器感知到的温室物理环境数据通过物理-信息层汇聚节点融合后上报信息层决策节点得到决策信息,物理-信息层控制节点分析决策信息得到控制信息后下传物理层执行器进行控制。由于该系统模型考虑了各层状态机中事件的时空属性,能够将温室控制的正确率由传统基于物联网的温室控制方法的80.20%提高到87.20%,错误肯定率和错误否定率由7.50%和12.30%下降到3.60%和9.20%,保障温室环境满足作物生长对温度、湿度和光照的要求。     

关于有限布尔代数的原子的性质

本文研究了有限布尔代数的原子问题，给出了关于有限布尔代数的原子的一些性质。     

Experimental Study on Plannar Representative Connections Used in Obliquely Crossing Lattice of One Super Highrise Building

One Super Highrise Building is adopted to a new structural pattern of a reinforced concrete core tube enclosed by an outer lattice tube made of obliquely crossing concrete filled rectangular steel tubular columns.In order to understand the stress state of plannar representative connections used in obliquely crossing lattice and verify the rationality of the details,two 1:3 scale models were respectively applied symmetrical and asymmetrical axial force,and experiment processes were numerical simulated by ABAQUS.The results indicate that the connections are validated to meet the design requirement of the building,with sufficient loading capacity.     

泵站前池水沙流的数值模拟

针对泵站前池内的水沙流动,基于格子Boltzmann方法和大涡模拟思想,建立了二维浅水LBM-BGK模型和泥沙数学模型的联合计算模式,进行了水沙流的数值模拟研究.介观LBM-BGK模型采用了LES的亚格子尺度应力SGS模式模拟二维浅水方程,宏观二维平面泥沙数学模型包括悬沙输运方程、河床变形方程、水流的挟沙力公式等.水流与悬沙之间的求解方法采用非耦合解模式,即先求解出水流运动控制方程,再求解泥沙输运方程,推求前池底部的冲淤变化.最后,成功地模拟了泵站前池水沙流的流速分布、水深变化和旋涡的位置和尺寸,以及泥沙的冲淤变化,流速计算结果与试验结果比较吻合.计算结果表明：此联合计算模式在一定程度上客观地、较好地重演了前池内水流的基本流态以及泥沙的冲淤变化.     

Box-Cox变换的黄金分割法实现

提出可以使用黄金分割法确定 Box- Cox变换中的参数 ,给出了一种计算步骤。提出了通过多搜索几个区间和回归诊断来更大限度地保证所确定出的参数是合用的。并从理论分析和实例检验两方面说明了与一维格点搜索法相比 ,使用黄金分割法确定 Box- Cox变换中的参数计算量较小 ,容易使计算结果达到较高的精确度 ,且易用性也有所提高。     

On the use of multiple lattice designs and α-designs in plant breeding trials

Plant breeders in Germany often use multiple lattice designs to test a large number of entries that are to be directly compared for selection. Comparison among entries from different lattices is accommodated by the use of checks. While this design has some practical merits, it is statistically expected to be less efficient than alternative designs for a large number of entries. In this note a study is made of the gain in efficiency by using a single large α‐design in place of multiple lattices. The comparison for a number of settings shows that the efficiency gain in terms of sample size or variance may be appreciable. It is concluded that plant breeders should seriously consider using α‐designs in place of multiple lattices. A simple method is described which allows breeders to study the potential gain for their particular design. Practical considerations leading to a preference of multiple lattices are critically discussed.     

广义连续格II

基于ｗａｙ－ｂｅｌｏｗ关系引进广义连续格的强连续性、代数性以及可加性，并用最大子集系对它们加以刻划．     

模态理论在空间网格结构无损探伤的应用

空间网格结构体系整体刚度好，能够满足多种建筑结构形式的要求。但在长期服役期间，结构可能产生各种损伤。这些损伤可能导致结构整体的破坏，因此，必须及时进行结构无损探伤。本文比较详细地介绍了基于模态理论的无损探伤方法间网，即频率法、能量法、柔度矩阵法等。同时，介绍了国内外基于模态理论的空格结构无损探伤的研究进展。