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NUmERICAL INVESTIGATION OF STRAIGHT-LINE LASER FORmING UNDER THE TEmPERATURE GRADIENT mECHANISm

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Acta metallurgica Sinica(English Letters) 2006年第2期19卷 144-150页

作者： Y.J. Shi H. Shen z.Q. yao J. Hu School of mechanical and Power Engineering Shanghai Jiaotong University Shanghai 200030 China

Laser forraing is a new flexible and dieless forming technique. To achieve the high accuracy forming, the temperature gradient mechanism （TGm） is studied. In the analysis of TGm, the plate bends about x-axis and about y-axis as well. To understand the deformation trend, the numerical simulation of deformation of plate is conducted by choosing different laser powers, laser spot diameters, scanning speeds, lengths, widths and thicknesses. From the results of simulation, it can be seen that the laser spot diameter, the scanning speed, laser power and thickness of plate play dominant roles in the laser forming process. However, the bending angles αx and αy show different trends with the variation of parameters. In addition, in comparison with above four parameters, the effect of length and width of plate on the beading angle may be neglected, but their effects are significant for the bending radius R.

关键词： laser forming temperature gradient mechanism metal plate

Distribution Patterns of major and Trace Elements and Provenance of Surface Sediments on the Continental Shelf off Western Guangdong Province and Northeastern Hainan Island

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Journal of Ocean University of China 2019年第4期18卷 849-858页

作者： GE Qian XUE z. George YE Liming XU Dong yao zhigang CHU Fengyou Key Laboratory of Submarine Geosciences State Oceanic Administration Hangzhou 310012 China Second Institute of Oceanography Ministry of Natural Resources Hangzhou 310012 China Department of Oceanography and Coastal Sciences Louisiana State University Baton Rouge LA 70803 USA Center for Computation and Technology Louisiana State University Baton Rouge LA 70803 USA Coastal Studies Institute Louisiana State University Baton Rouge LA 70803 USA Key Laboratory of Physical Oceanography Ocean University of China Qingdao 266100 China

A coupled approach based on grain size and geochemical elements is used to trace the provenance of surface sediments and to confirm the distribution patterns of grain size and elements on the continental shelf off western Guangdong Province and northeastern Hainan Island. The mean grain size ranges from 0.05 φ to 7.28 φ with a mean value of 5.60 φ. The average concentra- tions of major elements descend in the order of SiO2 > Al2O3 > CaO > Fe2O3 > K2O > mgO > Na2O > TiO2 > P2O5 > mnO, while those of trace elements exhibit a descending order of Sr > Rb > zn > V > Cr > Pb > Ni > Cu > As > Cd. On the basis of the distribution patterns of elements and results of statistical analysis, the study area is classified into three zones. zone I locates on the continental shelf off western Guangdong Province, and the sediments are mainly from Pearl River, Taiwan Residents rivers, and small rivers nearby. zone II locates in the eastern exit of Qiongzhou Strait and the coastal area off Leizhou Peninsula, and the sediments are mainly from the ero- sion products of Qiongzhou Strait and Hainan Island. zone III locates off the eastern Hainan Island and the continental shelf deeper than 50 m isobaths, and the sediments are mainly from Hainan Island and coral reef. The influence from open water should also be considered. Results indicate that the grain size is the main controlling factor for major and trace element contents and that anthropo- genic impact and biological activity also play an important role in the distribution of these elements.

关键词： grain size geochemical elements western Guangdong Province northeastern Hainan Island controlling factor

Non-alcoholic fatty liver disease: a narrative review of genetics

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The Journal of Biomedical Research 2018年第6期32卷 389-400页

作者： Christopher J.Danford zemin yao z.Gordon Jiang Division of Gastroenterology and Hepatology Beth Israel Deaconess Medical Center Department of Biochemistry Microbiology and Immunology Ottawa Institute of Systems Biology University of Ottawa

Non-alcoholic fatty liver disease(NAFLD) is now the most common cause of chronic liver diseases worldwide. It encompasses a spectrum of disorders ranging from isolated hepatic steatosis to nonalcoholic steatohepatitis(NASH),fibrosis, cirrhosis, and hepatocellular carcinoma. One of the key challenges in NAFLD is identifying which patients will progress. Epidemiological and genetic studies indicate a strong pattern of heritability that may explain some of the variability in NAFLD phenotype and risk of progression. To date, at least three common genetic variants in the PNPLA3, Tm6 SF2, and GCKR genes have been robustly linked to NAFLD in the population. The function of these genes revealed novel pathways implicated in both the development and progression of NAFLD. In addition,candidate genes previously implicated in NAFLD pathogenesis have also been identified as determinants or modulators of NAFLD phenotype including genes involved in hepatocellular lipid handling, insulin resistance,inflammation, and fibrogenesis. This article will review the current understanding of the genetics underpinning the development of hepatic steatosis and the progression of NASH. These newly acquired insights may transform our strategy to risk-stratify patients with NAFLD and to identify new potential therapeutic targets.

关键词： NAFLD NASH genetics PNPLA3 Tm6SF2 GCKR mBOAT7

Shearfree Spherically Symmetric Fluid models

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Chinese Physics Letters 2012年第5期29卷 41-44页

作者： m.Sharif z.Yousaf Department of mathematics University of the PunjabQuaid-e-Azam CampusLahore-54590Pakistan

We attempt to discover some exact analytical models of the spherically symmetric spacetime of collapsing fluid under shearfree *** types of solution are considered:one is to impose a condition on the mass function,while the other is to restrict the *** obtain five exact models in total,and some of them satisfy the Darmoie conditions.

关键词： conditions. exact satisfy

Antioxidative Responses and metal Accumulation in Invasive Plant Species Growing on mine Tailings in zanjan, Iran

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Pedosphere 2011年第6期21卷 802-812页

作者： m.m.A.BOOJAR z.TAVAKKOLI Department of Biology Tarbiat Moalem University

Tailings of a Pb and zn mine as a metal-contaminated area （zone 1） with two pioneer plant species, Peganum harmala and zygophyllum fabago, were investigated and compared with a non-contaminated area （zone 2） in the vicinity. Total concentrations of Pb, zn, and Cu in the soil of zone 1 were 1 416, 2 217, and 426 mg kg-1, respectively, and all exceeded their ranges in the normal soils. The soil pH was in the neutral range and most of the physical and chemical characteristics of the soils from both zones were almost similar. The species z. fabago accumulated higher Cu and zn in its aerial part and roots than the normal plants. On the other hand, their concentrations did not reach the criteria that the species could be considered as a metal hyperaccumulator. The species P. harmala did not absorb metals in its roots; accordingly, the accumulation factor values of these metals were lower than 1. The contents of chlorophyll, biomass, malondialdehyde, and dityrosine in these two species did not vary significantly between the two zones studied. In zone 1, leaf vacuoles of z. fabago stored 35.6% and 43.2% of the total leaf Cu and zn, respectively. However, in this species, the levels of phytochelatins （PCs） and glutathione （GSH） and antioxidant enzyme activities were significantly higher in zone 1 than in zone 2. In conclusion, metal exclusion in P. harmala and metal accumulation in z. fabago were the basic strategies in the two studied pioneer species growing on the metal-contaminated zone. In response to metal stress, elevation in antioxidant enzyme activities, increases in the PCs and GSH levels in the aerial parts, and metal storage within vacuoles counteracted each other in the invasion mechanism of z. ]abago.

关键词： accumulation factor antioxidant enzymes glutathione metal stress phytochelatins

Computation of the Fractal Pattern in manganese Dendrites

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Chinese Physics Letters 2005年第8期22卷 2112-2115页

作者： z.merdan m.Bayirli DepartmentofPhysics GaziosmanpasaUniversityTokatTurkey

The images of manganese flowers (clusters) on the surface of the natural magnesium silicate substance are scanned and the pictures of them are transferred to computer atmosphere. By using these scanning parameters, the exponents of density correlation function and fractal dimension values are calculated. For all different groups between the least and the most dense in the samples, the correlation function exponents may range from 0.141 to 0.178 and the fractal dimension values may vary between 1.61 and 1.88. In addition, the manganese flowers are divided into seven different groups according to their smallest- and largest-density features. The formation of the natural manganese clusters (flowers, dendrites) on the surface of the magnesium silicate substance can be defined by using the deposition, diffusion and aggregation model.

关键词： DDA CO Pattern

A theoretical analysis of the electromigration-induced void morphological evolution under high current density

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Acta mechanica Sinica 2017年第5期33卷 868-878页

作者： Yuexing Wang yao yao School of mechanics and Civil Engineering Northwestern Polytechnical University

In this work, analysis of electromigration-induced void morphological evolution in solder interconnects is performed based on mass diffusion theory. The analysis is conducted for three typical experimentally observed void shapes: circular, ellipse, and cardioid. Void morphological evolution is governed by the competition between the electric field and surface capillary force. In the developed model, both the electric field and capillary force on the void's surface are solved analytically. Based on the mass conversation principle, the normal velocity on the void surface during diffusion is obtained. The void morphological evolution behavior is investigated, and a physical model is developed to predict void collapse to a crack or to split into sub-voids under electric current. It is noted that when the electric current is being applied from the horizontal direction, a circular void may either move stably along the electric current direction or collapse to a finger shape, depending on the relative magnitude of the electric current and surface capillary force. However, the elliptical-shaped void will elongate along the electric current direction and finally collapse to the finger shape. On the other hand, the cardioid-shaped void could bifurcate into two sub-voids when the electric current reaches a critical value. The theoretical predictions agree well with the experimental observations.

关键词： Electromigration Analytical solution Void evolution High current density mass diffusion

A prediction model for the effective thermal conductivity of nanofluids considering agglomeration and the radial distribution function of nanoparticles

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Acta mechanica Sinica 2018年第3期34卷 507-514页

作者： z.m.zheng B.Wang School of Physics Sun Yat-Sen UniversityGuangzhou 510275China Instimt Franco-Chinois de l'Energie Nucleaire Sun Yat-Sen UniversityZhuhai 519000China

Conventional heat transfer fluids usually have low thermal conductivity, limiting their efficiency in many applications. many experiments have shown that adding nanosize solid particles to conventional fluids can greatly enhance their thermal conductivity. To explain this anomalous phenomenon, many theoretical investigations have been conducted in recent years. Some of this research has indicated that the particle agglomeration effect that commonly occurs in nanofluids should play an important role in such enhancement of the thermal conductivity, while some have shown that the enhancement of the effective thermal conductivity might be accounted for by the structure of nanofluids, which can be described using the radial distribution function of particles. However, theoretical predictions from these studies are not in very good agreement with experimental results. This paper proposes a prediction model for the effective thermal conductivity of nanofluids, considering both the agglomeration effect and the radial distribution function of nanoparticles. The resulting theoretical predictions for several sets of nanofluids are highly consistent with experimental data.

关键词： Nanofluid Thermal conductivity modeling Agglomeration Radial distribution function

Predicting the response of continuous RC deep beams under varying levels of differential settlement

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Frontiers of Structural and Civil Engineering 2019年第3期13卷 686-700页

作者： m.z.NASER R.A.HAWILEH Glenn Department of Civil Engineering Clemson UniversityClemsonSC 29634USA Department of Civil Engineering American University of SharjahSharjahUnited Arab Emirates materials Science and Engineering Research Institute American University of SharjahSharjahUnited Arab Emirates

This paper investigates the effect of differential support settlement on shear strength and behavior of continuous reinforced concrete(RC)deep beams.A total of twenty three-dimensional nonlinear finite element models were developed taking into account various constitutive laws for concrete material in compression(crushing)and tension(cracking),steel plasticity(i.e.,yielding and strain hardening),bond-slip at the concrete and steel reinforcement interface as well as unique behavior of spring-like support *** models are first validated by comparing numerical predictions in terms of load-deflection response,crack propagation,reaction distribution,and failure mode against that of measured experimental data reported in *** the developed models were successfully validated,a parametric study was designed and *** parametric study examined number of critical parameters such as ratio and spacing of the longitudinal and vertical reinforcement,compressive and tensile strength of concrete,as well as degree(stiffness)and location of support stiffness to induce varying levels of differential *** study also aims at presenting a numerical approach using finite element simulation,supplemented with coherent assumptions,such that engineers,practitioners,and researchers can carry out simple,but yet effective and realistic analysis of RC structural members undergoing differential settlements due to variety of load actions.

关键词： concrete continuous beams deep beams finite element modeling support settlement