Improvement and Application of Immune Genetic Algorithm in Structural Damage Identification

In order to solve structural multi-damage identification problem, a two-stage method based on Bayesian theory and immune genetic algorithm (IGA) is presented. Firstly, structural modal strain energy and frequency are considered as two kinds of information sources, and Bayesian theory is utilized to integrate the two information sources and preliminarily detect structural damage locations. Then, immune genetic algorithm is used to identify structural damage extents. Considering the convergence rate of basic IGA is still not very good, some improved strategies, such as culture vaccine, two termination conditions, are presented. It is shown that the two-stage method can precisely identify structural damage locations and extent, and the calculated results of the proposed improved IGA are obviously better than those of both the basic IGA and simple genetic algorithm.     

地震作用下框架整体与局部损伤的相关性

根据框架结构耗散塑性变形能与存储弹性变形能能力的损失界定结构的整体损伤，根据塑性铰耗散塑性变形能能力的损失来界定局部损伤，并以拟力法为基础推导了局部损伤与整体损伤的解析表达式，进而讨论框架结构局部损伤与整体损伤的相关性。研究表明，控制框架结构整体损伤的手段有：减小局部损伤区域的强度衰减、提高局部损伤区域的极限转动能力和减小局部损伤区域的残余变形。其机理是通过提高局部损伤区域的耗能能力与约束能力来提高整个结构耗散与存储地震能量的能力；框架结构整体损伤与局部损伤的加权值较为接近，可以采用框架局部损伤的加权值来近似估计结构的整体损伤值。     

模式识别的斜拉桥损伤诊断动力指纹与识别算法

为有效并准确诊断出斜拉桥损伤,对基于模式识别的斜拉桥损伤诊断方法进行了研究。选取易于测试出的低阶模态频率和部分关键点竖向振型数据为动力指纹,无需模态扩展或模型缩聚。研究并采用全因子设计进行动力指纹库的创建,可精确评估设定的损伤因子及其交互作用对损伤识别结果的影响。设计并增加了带随机误差的动力指纹库样本集。编制了基于Matlab的模式识别的多种算法,重点研究了精确度高的多层感知器识别算法及其提高该算法预测准确率的装袋集成算法。最后给出一座单塔双跨双索面斜拉桥的多种识别算法的损伤诊断过程和结果,得到一种可包容测试随机误差的高精确度斜拉桥损伤诊断评估模型。     

Study on constant current control of inductive power transfer with parameter identification

Aiminy at magnetic exciting current (resonant current) control, a constant current control method based on dynamic parameter identification is put forward. With energy conversion analysis, the energy storage, supply and dissipation functions of the system resonant network are constructed. The reflecting impedance identification functions are obtained by constructing the energy equilibrium relations in a period and among several periods. Furthermore, a constant current control strategy by regulating the system input voltage with Buck converter is presented. Combining the relations among system input voltage, the envelope of resonant current and the input of Buck converter, the constant current control law is proposed. The control law is verified with experiments. For the proposed method, in parameter identification, only the data of zero crossing point of resonant voltage and current are required, which reduces the complexity and costs of sampling system. Also, the constant current control law does not need complex computation and is easy to implement.     

Least-square-based Optimization of Frequency Response Function Estimation in Modal Parameters Identification

The accuracy of modal parameters identification has the influence on the quality of dynamic characteristics analysis of mechanical structure directly. And the precision of the frequency response function estimation has the great influence on the accuracy of modal parameters identification. In the engineering the frequency response function can be estimated by the average power spectrum and cross-power spectrum with the hel Pof FFT. As the result of limited frequency resolution in the course of FFT and the noise, the accuracy of modal parameters identification is influenced by the frequency response function estimation. This paper has put forward a least-square-based optimization of frequency response function estimation in modal parameters identification. According to the optimized frequency response function, the peak value can be searched to identify the damped natural frequencies and damping ratio directly. An experiment has been made to validate the proposed method. The result indicates that the damped natural frequencies and damping ratio identified by the optimized frequency response function are closer to the true results than which without the optimized frequency response function. So the accuracy of modal parameters identification can be improved by adopting the proposed method.     

Mode-Superposition Method for Passive Energy Dissipation Structures

The methods of equivalent linearization of different energy dissipation devices are different in analyzing passive energy dissipation structure including different type of energy dissipation device by using of mode-superposition response spectrum method based on equivalent linearization, which results in the differences in computing accuracy and cost in dynamic analysis. For structures separately installed different energy dissipation devices, authors utilize relatively uncoupled mode-superposition method and complex mode-superposition method for contrast analysis, and probe into the suitability of the two methods in the dynamic analysis of passive energy dissipation structure. Numerical results show that complex mode-superposition method could be better for structure with viscous dampers in order to guarantee accuracy, and relatively uncoupled mode-superposition method is recommended for structure with viscoelastic, metallic or frictional ones.     

Comparative study on the identification of structural modal parameter using different methods

Chongqing Chaotianmen Yangtze River Bridge is the world's longest-span arch bridge. The node connections on its main truss’s lower chords are to bear millions of large-amplitude stress cycles caused by automobile and light-rail train loads. However, there exists no referential designing and testing experience in such detailing on long-span steel bridges at home and abroad as yet. High-cycle fatigue behavior testing on a detailing model has been conducted to study the fatigue reliability of the bridge’s critical node connections. The testing cycling load on the model is determined according to conventional specifications and the expected traffic flow on the Bridge. The 1/2-scale detailing model is carefully fabricated to simulate the node prototype and undergo the 2 million-cycle testing with the design load. Through testing, fatigue reliability of Chaotianmen Yangtze River Bridge’s main-truss lower-chord node connections during the design service life is verified. In addition, static test data are compared with those calculated by finite element analysis to prove the validity of the node model. In the end, fatigue destruction test of the model was carried out to get the fatigue failure law of the node connection and provide necessary parameters and reference for designing and monitoring of this bridge in the future.     

Modal parameters identification for short data sequences based on stratified sampling and optimism complex Morlet wavelet

A novel modal parameter identification method based on stratified sampling and optimism complex Morlet wavelet is proposed for short data sequences. Stratified sampling is applied to divide the structure response signal into different layers which called sub samples with different thresholds, and then free decrement response signal of each layer is extracted by random decrement technique. The optimism complex Morlet wavelet transform is applied to identify modal parameter of each layer, and the weight of the layer is also determined based on the sample standard deviation. The modal parameter of the structure can be obtained by weighted calculation.The engineering application shows that the proposed method has the ability to identify modal parameter accurately, decouple low frequency intensive modal composition and restrain high frequency fake modal effectively.     

Mechanical Performance Tests of a Novel Three-dimensional Isolation Bearing

A novel three-dimensional isolation bearing (3DIB) was proposed, based on respective mechanical characteristic of lead rubber bearing, combined disc springs and rhombic steel plated damper. Firstly, the configuration department and mechanical design methodology was introduced; the horizontal and vertical stiffness and energy dissipation performance test was performed on a full scale three-dimensional isolation bearing, respectively. The results indicated that the proposed three-dimensional isolation bearing has reasonable configuration and explicit mechanical transmission mechanism; appropriate stiffness and energy dissipation performance can be achieved by reasonable design, keeping favorable holistic stability at plentiful horizontal shear displacement.     

Application of Improved Multi-population Genetic Algorithm to Damage Identification of Soil-wall System

The method of damage identification in soil-wall system was studied; a new approach based on improved multi-population genetic algorithm (IMGA) was developed. First, the simplified dynamic-detection model of soil-wall system was established, meanwhile, the theoretical analysis of characteristic equations in soil-wall system was conducted when soil in damage status. The objective function based on characteristic equations was established. Then, the improvements of multi-population genetic algorithm, including the adoption of real-valued representation, adaptive cross operator and adaptive mutation operator, were conducted. Finally, the localization and quantification of the soil-wall system damage were performed by IMGA with and without the consideration of noise, respectively. The results indicate that damage location and damage extent can be detected efficiently, and anti-noise performance is better.     

The Diagnostic Model of Cotton Aphids Based on Leaf Textural Features

[Objective] The aim of this research is to explore the possibility of rapid identification of aphid damage to cotton leaves by identifying the hyperspectral image about healthy and aphid damage cotton leaves. [Method] Taking Xinluzao 45 as material, hyperspectral images of healthy and damaged cotton leaves by aphids were obtained, and hyperspectral image information was extracted from interested regions of different cotton samples. Then three descending dimension methods were used to extract hyperspectral feature, and Gray-Level Co-occurrence Matrix to extract image texture feature. Finally a cotton aphids damage diagnostic model was built up. [Result] The prediction accuracy based on all textural samples input Random frog-partial least-square-linear discriminant Function (RF-PLS-LDA) model was 91.49%. The prediction accuracy based on energy data input principal component analysis-loading partial least-square-linear discriminant function (PCA-Loading-PLS-LDA) model was 92.55%. [Conclusion] The second-order statistics (energy) of gray co-occurrence matrix can be used to simplify the model, reduce the computation and improve the stability of prediction. Based on the texture feature vector, the identification of aphid cotton leaves can be realized effectively, which provides a method for the rapid identification of insect pests.     

田间小麦叶片光合作用的光抑制和光呼吸的防御作用

小麦叶片在晴天的表观量子效率（ＡＱＹ）和光系统Ⅱ光化学效率有明显的日变化，中香前后降低，表明小麦叶片在田间条件下发生了光抑制。ＡＱＹ和Ｆｖ／Ｆｍ在下午光照减弱后很快恢复的事实说明，光抑制发生的主要机理可能是非辐射能量耗散的增加，中有后光呼吸速率（Ｐｒ）的增加，既削弱了净光合，也降低了光合效率。在强光下连续抑制光呼吸３小时，会明显地降低净光合速率，加重光合净光合，也降低了光合效率，在强光下连续抑制光     

Numerical Simulation Analysis on Ductility Performance of High Strength RC Frame Structure

High-strength concrete has been widely used in civil structures for advantages of higher-strength, earlier curing strength and smaller deformation in applications. However, relatively weak ductility in structures in seismic zones prevented it from further application. The ductility of the structure can be improved by reinforcing reasonably rebars in correct details. A high strength RC frame model with twelve floors and two bays is numerically analyzed by using DRAIN-2DX program. It was shown that this worked fairly well in simulation of the process of structural damage and energy dissipation capacity. It also showed that this kind of frame structure has good ductility and dissipation capacity as well as great seismic performance. The proposed method can be applied in high-strength concrete structures in seismic zone.     

Experimental Investigation and Finite Element Analysis on the Hysteretic Behavior of New Steel Beam-to-Column Connections

By the hysteretic experiments and the finite element analysis of the proof-of-concept connections, the mechanical properties and energy dissipation capacity of the new steel beam-to-column connections are investigated. These connections are semi-rigid ones improved by adding threaded rods into the angle connections and can be designed to limit the structural damage only to the angles and threaded rods. It is found, by the comparative analysis of six connections tested with the same loading sequence, that the performance degradation of the connections may be resulted from the plastic damage, crack propagation of the angles and the buckling and fatigue crack of the rods. The rotation capacity and failure modes of the connections with threaded rods depend on the ability of anti-fatigue crack of the rods, and the better ductility the rods have, the better energy dissipation capacity the connections have. In addition, the hysteretic behavior and the deformation modes of the connections prior to the significant strength degradation or the fracture of the rods could be well simulated by the finite element method. Meanwhile, the stiffening effect from pre-stressing the angles, the plastic distribution of the angles and the degradation induced by the rod buckling were strongly verified by the FEA. Finally, the advantages and disadvantages of such new beam-to-column dissipative connections were analyzed, and the proposal for further connection improvement and in-depth study was made.     

Design Method of a Metal V-belt CVT Hydraulic System

The design method on the hydraulic control system is one of the key technologies of a metal V-belt continuously variable transmission(CVT).It can change the ratio of the transmission system by adjusting the pushing force of the pulley.By analyzing the structure characteristics and force relations,the design method of an important parameter of the CVT hydraulic system and the rate of transmission ratio,are put forward by simulating to the emblematical driving models.The structure parameters of the hydraulic system is gotten and validated by simulation on specific driving model.An effective design method is provided to develop the continuously variable transmission system.     

氟节胺抑制枇杷嫁接成苗砧木萌蘖相关机理初探

为寻找更长效、无害的化学控蘖剂以减轻田间管理劳动强度,以枇杷(Eriobotrya japonica)嫁接成苗为材料,喷施有效成分浓度为0.050%,0.071%和0.125%的氟节胺,于不同时期取样观察控蘖效果,并尝试探究相关机理。结果表明,氟节胺减少了叶片单位面积光能的吸收量、抑制了光化学转换,但叶片的热耗散量并无明显变化。进一步测定植株氧化还原状态发现,氟节胺能够快速促进细胞内超氧阴离子(O₂^.-)积累并延缓或抑制H₂O₂的转化,从而诱发氧化胁迫。由此可见,氟节胺可能通过抑制叶片光化学转换和热耗散来破坏新生萌蘖的光合性能,进而抑制其萌发生长,而成熟叶片则通过提升自身抗氧化系统活性耐受氟节胺造成的轻度胁迫。在本试验中,各浓度的氟节胺对控制砧木萌蘖有不同程度的效果,其中浓度为0.125%的氟节胺控蘖效果相对最佳,且基本不会对砧木和嫁接成苗造成持续伤害,其作为化学控蘖剂有一定的应用潜力。     

Experimental study on seismic behavior of beam-column sandwich joints with big beam-column eccentricity

Three specimens of sandwich joints with eccentricity being larger than a quarter of the column width in middle floor of frame are designed and loaded under cyclic loading. Their shear capacity, failure modes, and ductility, as well as energy dissipation are analyzed. The results show that the performance of sandwich joints with big eccentricity is good under cyclic loading. X-type reinforcements can be used to substitute for stirrups in the joint to bear shear forces. But the anchorage of longitudinal bars of beams in eccentric sandwich joints is relatively weak. Comparing to sandwich joints without eccentricity, the column longitudinal bars near the sandwich joints with big eccentricity are vulnerable to sudden change of strain.     

Human Face Location Based on Motion Information in a Complex Background

This paper proposes an improvement for the traditional Optical Algorithm, and presents a new way to image segmentation in a complex background. In addition, combined with the neural network, the system can locate the possible human faces successfully by means of two-step location model. In our system, the searching and locating of the human face is the most important stage. According to this, the authors adopt the two-step way to run, firstly they take up the segmentation of the candidate human face areas and then the accurate face locating based on the neural network is used. This algorithm is fast and robust. Experimental results with real scene images are given out there, and all these prove that two-step method gains many advantages in the course of human face location with motion information, such as real-time, robustness and practicality. In addition, the proposed system is also the fundamental and important part of the perfect human face recognition system.     

Optimization of Energy Dissipation Braces in Frame Structures

In this paper, the complex method of the nonlinear programming is used to optimize the parameters of energy dissipation bracing in energy dissipation braced frame. This method is realized with computer program and proved to be efficient. A 6-story reinforced concrete frame is used as a demonstrative example.     

Fatigue Life Analysis of Gussasphalt Concrete Based on Energy Method

The fatigue resistance of Gussasphalt mixture was analyzed with energy method after four point flexural fatigue test under multiple strain levels. Through the fatigue test under multiple strain levels, the linear relationship was obtained between fatigue life and cumulative dissipated energy in log log plot. And the equation for fatigue life prediction under different strain levels was also regressed. Besides, the relation between fatigue damage and dissipated energy of Gussasphalt mixture was analyzed with Maxwell model. And with the conceptions of hysteresis loop and phase angle, it is found that the mixture with bigger phase angle has better fatigue resistance.