Spatial and orientational distribution of cracks in crystalline photovoltaic modules generated by mechanical load tests

Cracks in crystalline silicon solar cells influence the photovoltaic (PV) module power output in accelerated aging tests. A detailed insight into the formation of cracks offers the potential to optimize the PV module design in order to reduce the risk of power degradation in its lifetime. In this paper we present a statistical analysis on the crack formation in 27 crystalline silicon PV modules caused by a standard mechanical load test according to IEC 61215 10.16. The criticality of cracks depends strongly on the crack orientation, therefore we analyze both the spatial distribution of cracks and its dependence on the orientation of the cracks in the tested PV modules. We find that 50% of the damaged cells are cracked parallel to the busbars, which is a crack orientation with high potential impact on the power output of the PV module. A simplified numerical analysis is used to give an explanation for the statistical data and we propose a strategy for the reduction of the crack criticality.     

Experimental studies on damage detection of beam structures with wavelet transform

Experimental studies are reported for crack detection of a beam structure under a static displacement with the spatial wavelet transform. An invisible perturbation in the deflection profile of the beam at the crack position due to its existence would be induced. Such a small perturbation will be discerned or amplified through a wavelet transform such that a detection of crack location becomes possible practically. To realize this, the static profile of a cracked cantilever aluminum beam subjected to a static displacement at its free end is analyzed with Gabor wavelet to identify the crack. The damage detection of the beam with different crack depths is conducted. The spatial wavelet transform is proven to be effective in identifying the damage area even when the crack depth is around 26% of the thickness of the beam.     

Improvement of the storage process for cracked table olives

The aim of this work was to improve the storage method for cracked table olives. First, a study was carried out of the washing phase in 5% (wt/vol) NaCl brine with ascorbic acid and sodium metabisulphite added to it. Its use removed half the proportion of the initial sugar content in the flesh and markedly decreased the content of polyphenols in the fruits, confirming the effectiveness of this treatment. Washing with 5% NaCl and sodium metabisulphite was selected and applied in storage phase which follows. Storage of the washed cracked olives produced an additional decrease in sugars and polyphenols in the flesh, although the product still retained a fairly high concentration of residual sugars at the end of the storage period. The growth of lactic acid bacteria in this phase was prevented by the high NaCl level (10–13% at the equilibrium) but yeast growth, followed by a decline phase, was found in all storage systems studied. The use of a CO₂ atmosphere led to a partial inactivation of yeasts for about 300 h and showed a protective effect on polyphenols. Application of ozone had a favourable effect on initial solubilisation of sugars and polyphenols but caused a negative effect on fresh appearance, colour retention and polyphenol degradation. CaCl₂ + MgCl₂ treatment led to a significantly faster decline phase of yeasts. A tentative improved process for cracked olive storage may consist of a previous washing of olives for 24 h with a 5% NaCl solution (optionally added with 0.1% sodium metabisulphite), and a subsequent brining in a 15% NaCl solution with 0.25% CaCl₂ + 0.20% MgCl₂ or in a 15% NaCl brine under CO₂ atmosphere.     

国外裂解碳五馏分的分离状况

介绍了国外裂解碳五馏分的分离技术。     

Crack tip stress fields for thin,cracked plates in bending,shear and twisting: A comparison of plate theory and three-dimensional elasticity theory solutions

A three-dimensional finite element study of crack tip fields in thin plates under bending, shearing, and twisting loads is carried out to study the relation of the plate theory crack tip fields to the actual, three dimensional crack tip fields. In the region r>0.5h the Kirchhoff theory is a good approximation of the three dimensional stress fields for symmetric plate bending. The Reissner theory gives a good approximation in the region r<0.1h. Similar results are found for the shear and twisting problems, although for pure shear loading, the Kirchhoff theory is a good approximation somewhat farther r>h from the crack tip than in the bending problem. In the case of shear loading the near tip out-of-plane shear stresses do not vary quadratically through the thickness as in plate theory, but are nearly constant, except in the neighborhood of the free surface. Quadratic variation, as predicted by plate theory, is observed for r>h. Energy release rates based on the Kirchhoff and Reissner theories agree well with those computed by means of three dimensional finite element analyses.     

R圆角细节原始疲劳质量探索研究

总结了Ｒ圆角细节原始疲劳质量研究的探索工作。通过对所设计的典型Ｒ圆角细节试件的耐久性试验,证实了这种新细节（主要考虑Ｒ圆角过渡区对寿命的影响）可以获得断口的ａ～ｔ曲线（ａ为裂纹长度;ｔ为试验的飞行小时数）,并通过断口反推得到其原始疲劳质量,为这种新细节的耐久性设计和分析提供了技术基础。     

基于有限元模型单一开裂纹转子的振动分析与无损估计

基于局部柔度理论和传递矩阵分析,给出一种简化的裂纹转子有限元模型。数值仿真研究了转子的长径比、裂纹位置以及裂纹深度对停机状态单一开裂纹转子的特征频率和振型的影响。提出一种借助裂纹转子前两阶特征频率和一阶振型对转子进行无损估计的新方法,仿真算例验证了该方法的有效性和可行性。     

隔膜泵隔膜破裂自动报警系统的设计与实现

为往复式隔膜泵开发了一套分布式隔膜破裂自动报警系统,该系统用下位机检测隔膜腔隔膜是否破裂,用上位机显示隔膜泵运行时隔膜工作状态的平面图、隔膜破裂的具体位置,并具有各种管理功能。系统运行可靠,造价低,功能强,提高了生产效率。     

破碎围岩注浆加固数值模拟分析与工程应用

介绍了注浆技术在破碎回采煤巷中的运用。分析了注浆加固机理：注浆液通过充填、压密等作用提高破碎围岩的强度,改变围岩的破坏机理,提高围岩的稳定性。通过UDEC数值模拟和高河煤矿现场实测数据得到：模拟巷道顶底板相对最大位移量为307 mm,两帮相对位移量为229 mm;实测顶底板相对最大位移量为359 mm,两帮相对位移量为262 mm,模拟与实测数据基本一致,巷道变形量得到有效控制,为矿井的安全、高效生产提供了有力的技术保障。该注浆加固技术可为破碎围岩支护提供指导意义。     

APPLICATION OF WAVELET TIME-FR EQUENCY ANALYSIS TO IDENTIFICATION OF CRACKED ROTOR

Based on the simple hinge crack model and the local flexibility theorem, the corresponding dynamic equation of the cracked rotor is modelled, the numerical simulation solutions of the cracked rotor and the uncracked rotor are obtained. By the continuous wavelet time-frequency transform, the wavelet time-frequency properties of the uncracked rotor and the cracked rotor are discussed. A new detection algorithm that uses the wavelet time-frequency transform to identify the crack is proposed. The influence of the sampling frequency on the wavelet time-frequency transform is analyzed by the numerical simulation research. The valid sampling frequency is suggested. Experiments demonstrate the validity and availability of the proposed algorithm in identification of the cracked rotor for engineering practices.