Quantative and qualitive identification of the fatty acids in the mullet (Liza aurata), sever juga (Acipenser stellatus) and Persian sturgeon (A. persicus), considering of cold storing effects on them

At the fishing season, in 2000, samples of species persian sturgeon (A. persicus), Severjuga (A. stellatus) and Mullet (L. aurata), were caught from the southern coasts of Caspian Sea and were freezes and preserved in the cold storage for one year They have also become biometery. The tissue's fillet were identified in order to determined the Fatty Acids. This was done during one year, frequently, fresh, two weeks after freezing and then monthly, respectively. So, after the extraction of lipids from the tissues and methylation, was injected to the gas-liquid Chromatography. After calibration, identified Fatty Acids were compared with standards according to their Retention Times. Peroxid value, lipid content and humidity were controlled. The unsaturated Fatty acids had The most amount, and a plenty of Polyunsaturated Fatty acids (PUFA) were observed, so that linoleic (C18:2), a-linolenic (C18:3), Arashidonic (C20:4), EPA (C20:5) and DHA (C22:6) Fatty acids had high amounts. The w-3, PUFA were more in comparison with w-6. The effects of freezing and cold storing on the fish fatty acids , were evaluated by the statistical tests , like SPSS, Tukey, Homogenous and Anova, and showed that in some species, a group of Fatty acids, specially PUFA, had some variation. The peroxide value that indicates the lipid deterioration, increased during toring. So, the best term if preserving in the cold storage, were determined and their Nutrition value and Medical applications due to their consumption were investigated.

Deformation and fracture of impulsively loaded sandwich panels

Light metal sandwich panel structures with cellular cores have attracted interest for multifunctional applications which exploit their high bend strength and impact energy absorption. This concept has been explored here using a model 6061-T6 aluminum alloy system fabricated by friction stir weld joining extruded sandwich panels with a triangular corrugated core. Micro-hardness and miniature tensile coupon testing revealed that friction stir welding reduced the strength and ductility in the welds and a narrow heat affected zone on either side of the weld by approximately 30%. Square, edge clamped sandwich panels and solid plates of equal mass per unit area were subjected to localized impulsive loading by the impact of explosively accelerated, water saturated, sand shells. The hydrodynamic load and impulse applied by the sand were gradually increased by reducing the stand-off distance between the test charge and panel surfaces. The sandwich panels suffered global bending and stretching, and localized core crushing. As the pressure applied by the sand increased, face sheet fracture by a combination of tensile stretching and shear-off occurred first at the two clamped edges of the panels that were parallel with the corrugation and weld direction. The plane of these fractures always lay within the heat affected zone of the longitudinal welds. For the most intensively loaded panels additional cracks occurred at the other clamped boundaries and in the center of the panel. To investigate the dynamic deformation and fracture processes, a particle-based method has been used to simulate the impulsive loading of the panels. This has been combined with a finite element analysis utilizing a modified Johnson-Cook constitutive relation and a Cockcroft-Latham fracture criterion that accounted for local variation in material properties. The fully coupled simulation approach enabled the relationships between the soil-explosive test charge design, panel geometry, spatially varying material properties and the panel's deformation and dynamic failure responses to be explored. This comprehensive study reveals the existence of a strong instability in the loading that results from changes in sand particle reflection during dynamic evolution of the panel's surface topology. Significant fluid-structure interaction effects are also discovered at the sample sides and corners due to changes of the sand reflection angle by the edge clamping system. © 2012 Elsevier Ltd. All rights reserved.

The challenges ahead for bio-inspired 'soft' robotics

THERE ARE MANY different kinds of robots: factory automation systems that weld and assemble car engines; machines that place chocolates into boxes; medical devices that support surgeons in operations requiring high-precision manipulation; cars that drive automatically over long distances; vehicles for planetary exploration; mechanisms for powerline or oil platform inspection; toys and educational toolkits for schools and universities; service robots that deliver meals, clean floors, or mow lawns; and "companion robots" that are real partners for humans and share our daily lives. In a sense, all these robots are inspired by biological systems; it's just a matter of degree. A driverless vehicle imitates animals moving autonomously in the world.© 2012 ACM.

42CrMo激光焊焊缝组织

42CrMo合金钢C含量高、合金元素含量多、淬硬倾向大,焊接性能差。激光焊接具有功率密度高、焊接变形小等优点,适合焊接传统工艺难焊的同种或异种金属。通过额定功率为3kW的Nd∶YAG固体激光器焊接42CrMo,采用光学显微镜(OM)、扫描电镜(SEM)、X衍射、硬度仪分析了焊缝区域组织、成分和硬度变化。研究结果表明:焊缝区域组织为马氏体,热影响完全淬火区的组织为马氏体+贝氏体组织,热影响不完全淬火区的组织为贝氏体。从焊缝正面到焊缝背面的硬度分布表明:由于焊缝正面有保护气体的作用提高了焊缝正面熔池的冷却速度,使焊缝背面的硬度低于焊缝正面的硬度。

Corrosion fatigue of welded joints of steel for marine platform

Experiments on the corrosion fatigue behaviour of welded joints of the steel for marine platform in air and seawater, and of the joints in seawater with cathodic protection, yielded data for linear regression to obtain fatigue life curves (Delta S-N-f). The laws of corrosion fatigue in welded joints of test steel are discussed with reference to those of A(587) and A(131) steel. In these experiments, the fatigue damage occurring at all welded joints around the weld interface resulted in the cracks and fractures. The fatigue life of the specimens in seawater with cathodic protection is longer than that in seawater Without protection.

基于人工神经网络的钛合金焊接接头机械性能预测

采用多层前向反馈神经网络模型,对钛合金钨极氩弧焊的焊接接头机械性能进行了模拟和预测。其中,输入参数包括钛合金成分、冷却速度和热处理参数;输出参数包括5个重要的机械性能,即极限抗拉强度、延伸率、断面收缩率、屈服强度和硬度。详细分析了铝和钒这2种元素对机械性能的影响。

大型激光叠焊系统研究与开发

介绍一种新型激光叠焊系统,利用该系统可将尺寸范围为12.0m×1.5m厚度不等的两块不锈钢板重叠焊接在一起。针对大尺寸不锈钢板尺寸大、易变形等特点提出了主—辅式压紧机构,有效地控制了焊接过程中大尺寸板材的变形并消除了板材间隙;设计了ufxyz型四轴联动方案:u轴与x轴同向,u轴驱动钢板进行大范围运动,x轴驱动激光头小范围运动。u轴与x轴的复合运动提高系统精度的同时提高了系统焊接动态响应速度。对实际焊接板材进行试验验证,结果表明使用该系统进行焊接的钢板可承受压强最大能达到6.1MPa。

结构光视觉传感器误差分析与结构分析

结构光视觉传感器是视觉焊缝跟踪系统获得焊缝信息的重要组成部分,其测量误差与性能对焊缝跟踪系统的总体测量精度及可靠性有着直接影响。本文对应用于焊缝跟踪的结构光视觉传感器进行误差分析,包括传感器硬件系统结构误差、激光散斑噪声误差及镜头畸变误差等,并对不同结构方式下的视觉传感器建立了数学模型,具体分析了结构参数对其误差的影响,提出结构光视觉焊缝跟踪传感器优化设计方法,并依据仿真结果给出结构优化设计参数,最后通过实验验证了该优化设计方法的正确性。

基于数学形态学的激光拼焊熔池图像处理研究

基于拼板激光焊接工程中的实时检测系统,应用数学形态学中的相关图像处理技术,提出了一种新的熔池图像处理流程模型,并通过实验得到了三种清晰的熔池边缘图像,同时验证了该模型的正确性。将算法与经典算法进行比较,证明了该算法对于激光拼焊的适用性和鲁棒性。

焊缝图像处理技术在激光拼焊中的应用

基于拼板激光焊接工程中的视觉跟踪系统,应用相关图像处理技术,建立了一种焊缝跟踪的图像处理流程模型,并通过实验验证了该模型的正确性。

Theories of Comparative Analysis

Comparative analysis is the problem of predicting how a system will react to perturbations in its parameters, and why. For example, comparative analysis could be asked to explain why the period of an oscillating spring/block system would increase if the mass of the block were larger. This thesis formalizes the task of comparative analysis and presents two solution techniques: differential qualitative (DQ) analysis and exaggeration. Both techniques solve many comparative analysis problems, providing explanations suitable for use by design systems, automated diagnosis, intelligent tutoring systems, and explanation based generalization. This thesis explains the theoretical basis for each technique, describes how they are implemented, and discusses the difference between the two. DQ analysis is sound; it never generates an incorrect answer to a comparative analysis question. Although exaggeration does occasionally produce misleading answers, it solves a larger class of problems than DQ analysis and frequently results in simpler explanations.

Switching Between Discrete and Continuous Process Models to Predict Molecular Genetic Activity

Two kinds of process models have been used in programs that reason about change: Discrete and continuous models. We describe the design and implementation of a qualitative simulator, PEPTIDE, which uses both kinds of process models to predict the behavior of molecular energetic systems. The program uses a discrete process model to simulate both situations involving abrupt changes in quantities and the actions of small numbers of molecules. It uses a continuous process model to predict gradual changes in quantities. A novel technique, called aggregation, allows the simulator to switch between theses models through the recognition and summary of cycles. The flexibility of PEPTIDE's aggregator allows the program to detect cycles within cycles and predict the behavior of complex situations.

Selective defect of anti-pneumococcal IgG in a patient with persistent polyclonal B cell lymphocytosis.

BACKGROUND: Persistent polyclonal B cell lymphocytosis (PPBL) is a rare condition characterized by increased IgM and large excess of B cells with an IgD(+) CD27(+) phenotype. In normal individuals, these cells play a central role in the defense against pneumococcal infection. So far, few studies have characterized humoral immune responses in PPBL patients. We therefore measured IgG directed against S. pneumoniae antigens in a 51 yr-old woman with PPBL before and after vaccination with a pneumococcal 23-valent polysaccharide vaccine. METHODS: Antibodies against pneumococcal antigens were measured first with an overall immunoassay using microplates coated with the 23-valent pneumococcal vaccine. A serotype-specific test was also performed according to the WHO consensus protocol. RESULTS: Despite a large number of IgD(+) CD27(+) cells, our patient had low baseline titers of IgG directed against pneumococcal antigens and did not significantly respond to a 23-valent polysaccharide vaccine against S. pneumoniae. On the contrary, she had good titers of IgG directed against tetanus toxoid. CONCLUSION: IgM(+) IgD(+) CD27(+) cells which accumulate in this patient with typical PPBL patient failed to perform IgG isotype switch after a polysaccharide vaccine. The potential mechanisms and relationships with the main features of PPBL are discussed. Further studies on a larger number of similar patients are needed.

Finite volume methods applied to the computational modelling of welding phenomena

This paper presents the computational modelling of welding phenomena within a versatile numerical framework. The framework embraces models from both the fields of computational fluid dynamics (CFD) and computational solid mechanics (CSM). With regard to the CFD modelling of the weld pool fluid dynamics, heat transfer and phase change, cell-centred finite volume (FV) methods are employed. Additionally, novel vertex-based FV methods are employed with regard to the elasto-plastic deformation associated with the CSM. The FV methods are included within an integrated modelling framework, PHYSICA, which can be readily applied to unstructured meshes. The modelling techniques are validated against a variety of reference solutions.