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FE SImULATION OF CENTER CRACK OCCURRENCE IN TUBE ROUNDS DURING TWO-ROLL ROTARY ROLLING PROCESS

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Acta metallurgica Sinica(English Letters) 2007年第3期20卷 225-234页

作者： S.Z. Li j. Xu Y.D. Yin j.G. Xue F. Pan j.m. Zheng j.H. Yoon Department of materials Forming and Control Engineering Anhui University of Technology Ma＇anshan 243002 China Provincial Key Laboratory of metals and Processing Ma＇anshan 243002 China Steel Tube ＆ Pipe Company of Bao Steel Co. Ltd. Shanghai 200941 China Department of metallurgy and materials Science Changwon National University Changwon 641-773 Korea

With the aid of FE （finite element） code *** 2005, 2-D coupled thermo-mechanical simulation of center-crack occurrence in round billet during 2-roll rotary rolling process was presented using Oyane ductile fracture criteria. A simple modeling is put forward based on the spiral motion of the workpiece as an essential characteristic in movement. The influence of the feed angle and the entry cone angle of the main roll on the process was taken into account in the modeling. The soundness for simplifying the 3-D rotary rolling into a 2-D problem was discussed. By adopting the parameters of Diescher piercer in 140mm mandrel mill of Bao Steel, the distribution and development of strain/stress were analyzed, and the eigen value of ductile fracture as well. The critical percentage of diameter reduction was obtained from the simulation. The result showed a good agreement with the experimental value, and therefore was of widely guiding significance to the practical process for rationally formulating the deformation parameters of steel tube piercing.

关键词： numerical simulation inside crack, tube piercing rotary rolling seamless tube deformation

ON THE EXISTENCE OF ZERO POINTS OF A CONTINUOUS FUNCTION

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Acta mathematica Scientia 2002年第2期22卷 171-177页

作者： j.m. SorianoDepartamento de Andlisis matematico, Facultad de matemdticas, Universidad de Sevilla, Aptdo. 1160, Sevilla 41080, Spain Univ Sevilla Fac Matemat Dept Anal Matemat E-41080 Seville Spain

A sufficient condition is given to assert that a continuous mapping between Rm and Rn has a zero. The constructive proof of the result is based upon continuation methods and supplies the existence of a path leading to... 详细信息

关键词： Zero point continuation methods Banach fixed point theorem homotopy topological direct sum isomorphism k-contractive mapping

Arctic sea-ice extent: No record minimum in 2023 or recent years

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Atmospheric and Oceanic Science Letters 2025年第1期18卷 52-55页

作者： Ola m.johannessen Tor I.Olaussen Nansen Scientific Society BergenNorway Nansen Environmental and Remote Sensing Center BergenNorway

Arctic sea-ice extent reaches its minimum each year in September. On 11 September 2023 the minimum was 4.969 million square kilometers(***^(2)). This was not a record low, which occurred in 2012, when the minimum was 4.175 ***^(2), 0.794 ***^(2) less than the minimum in 2023. However, the ice extent had decreased by 0.432 ***^(2) compared with 2022. Nevertheless, the summer melting in 2023 was remarkably less than expected when considering the strong heat waves in the atmosphere and ocean, with record temperatures set around the world. In general, there is a high correlation between the long-term decrease in sea-ice extent and the increasing CO_(2) in the atmosphere, where the increase of CO_(2) in recent decades explains about 80% of the decrease in sea ice in September, while the remainder is caused by natural variability.

关键词： Sea ice Arctic minimum ice Climate

Unconstrained methods for Generalized Complementarity Problems

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journal of Computational mathematics 1997年第3期15卷 253-264页

作者： j.m. Peng Y. Yuan(State Key Laboratory of Scientific and Engineering Conputing, ICmSEC, Chinese Academy of Sciences, Beijing, China) CHINESE ACAD SCI ICMSECSTATE KEY LAB SCI & ENGNBEIJINGPEOPLES R CHINA

In this paper, the generalized complementarity problem is formulated as an unconstrained optimization problem. Our results generalize the results of [9]. The dimensionality of the unconstrained problem is the same as that of the original problem. If the mapping of generalized complementarity problem is differentiable, the objective function of the unconstrained problem is also differentiable. All the solutions of the original problem are global minimizers of the optimization problem. A generalized strict complementarity condition is given. Under certain assumptions, local properties of the correspondent unconstrained optimization problem are studied. Limited numerical tests are also reported.

关键词： In PX math

A new physical simulation tool to predict the interface of dissimilar aluminum to steel welds performed by friction melt bonding

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journal of materials Science & Technology 2019年第9期35卷 2048-2057页

作者： T.Sapanathan N. j.m.nez-mena I. Sabirov m.A. monclus j.m. molina-Aldaregui P. Xia L. Zhao A. Simar Institute of mechanics Materials and Civil EngineeringUCLouvain1348 Louvain-la-NeuveBelgium ImDEA materials Institute Calle Eric Kandel 228906 GetafeMadridSpain Universidad Politicnica de madrid E.T.S. de Ingenieros de Caminos28040 MadridSpain

Optimization of the intermetallic layer thickness and the suppression of interfacial defects are key elements to improve the load bearing capacity of dissimilar joints. However, till date we do not have a systematic tool to investigate the dissimilar joints and the intermetallic properties produced by a welding condition. Friction melt Bonding (FmB) is a recently developed technique for joining dissimilar metals that also does not exempt to these challenges. The FmB of DP980 and A16061-T6 was investigated using a new physical simulation tool, based on Gleeble thermo-mechanical simulator, to understand the effect of individual parameter on the intermetallic formation. The proposed method demonstrates its capability in reproducing the intermetallic characteristics, including the thickness of intermetallic bonding layer, the morphology and texture of its constituents (Fe2AU and Fe4Ali3), as well as their nanohardness and reduced modulus. The advantages of physical simulation tool can enable novel developing routes for the development of dissimilar metal joining processes and facilitate to reach the requiring load bearing capacity of the joints.

关键词： Physical simulation Interface Intermetallics Nanoindentation joining

A LOWER BOUND OF STABLE STATIONARY TRAjECTORIES

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Acta mathematica Scientia 2007年第3期27卷 535-540页

作者： j.m. Soriano C. Ding Departamento de Andlisis matemdtico Facultad de Matematicas Universidad de Sevilla Aptdo. 1160 Sevilla 41080 Spain Department of Applied mathematics Zhejiang University of Technology Hangzhou 310032 China

It is proven that an autonomous system verifying some conditions has at least one stable stationary trajectory and it is also given a lower bound to the number of unstable stationary trajectorlies.

关键词： Autonomous system continuation methods trajectory nondegenerate critical point zero point stationary trajectory stable trajectory asymptotically stable morse inequalities

Analytical Solution of Boundary Integral Equations for 2-D Steady Linear Wave Problems

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journal of Ocean University of China 2005年第4期4卷 357-365页

作者： j.m. Chuang Naval Architecture and marine Engineering Program Dalhouse University P.O. Box 1000 Halifax Nava Scotia B3J2X4 Canada

Based on the Fourier transform, the analytical solution of boundary integral equations formulated for the complex velocity of a 2-D steady linear surface flow is derived. It has been found that before the radiation condition is imposed,free waves appear both far upstream and downstream. In order to cancel the free waves in far upstream regions, the eigensolution of a specific eigenvalue, which satisfies the homogeneous boundary integral equation, is found and superposed to the analytical solution. An example, a submerged vortex, is used to demonstrate the derived analytical solution. Furthermore,an analytical approach to imposing the radiation condition in the numerical solution of boundary integral equations for 2-D steady linear wave problems is proposed.

关键词： boundary integral equation Cauchy's formula Rankine source method Fourier transform radiation condition

The Effect of Water Hyacinth （Eichhornia Crassipes） Infestation on Phytoplankton Productivity in Lake Naivasha and the Status of Control

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journal of Environmental Science and Engineering 2011年第10期5卷 1252-1260页

作者： j.m. mironga j.m. mathooko S.m. Onywere Department of Geography Egerton University Egerton 20115 Kenya Department of Zoology Egerton University Egerton 20115 Kenya Department of Environmental Planning and management School of Environmental Studies Kenyatta University Nairobi 00100 Kenya

The paper presents data collected in an assessment of the effects of water hyacinth （Eichhornia crassipes） infestation on phytoplankton productivity in Lake Naivasha. A summary of the status of control and strategies used is given. The ecological effects of water hyacinth on the lake have received little attention compared to the large body of work available on the weed＇s socioeconomic impact. This study was conducted to determine the effect of hyacinth infestation on the phytoplankton productivity. Several sampling stations were set up in the lake at sites containing floating mats of the weed and at sites where the weed was absent. Phytoplankton chlorophyll-a concentration and dissolved oxygen were measured at each station and used as proxies for phytoplankton productivity. The findings show that phytoplankton productivity in weed covered areas is reduced with significant change in species composition and biodiversity suggesting that water hyacinth can alter the ecology of the lake. Although water hyacinth has continued posing serious ecological consequences, the control strategies already adopted will continue to reduce deleterious impacts and allow sustained development in the Lake Naivasha Basin. There is need however to undertake research to quantify the level of ecological damage and the costs of control. There are other effects such as livelihood loss, diseases, and disruption of normal operations that also need to be quantified.

关键词： Water hyacinth ecological effects phytoplankton.

magnetic Behaviour of Tb/Si Nanoscale multilayers with Small Thickness of Rare Earth Layers

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Chinese Physics Letters 2007年第6期24卷 1717-1719页

作者： A.V. Svalov V.O. Vas'kovskiy G.V. Kurlyandskaya j.m. Barandiaran N.N. Schegoleva A.N. Sorokin Ural State University Lenin Avenue 51 620083 Ekaterinburg Russia Universidad del Pals Vasco UPV-EHU Facultad de Ciencias Depto Electricidad yVElectr6nica Apdo. 644'48080 Bilbao Spain Institute of metal Physics Ural Branch of RAS Kovalevskaya str. 18 620219 Ekaterinburg Russia

We report the magnetic properties of Tb/Si multilayers obtained by rf-sputtering at the Tb layer thickness LTb = 3 nm. Analysis of the magnetization processes indicates more complex behaviour than canonical spinglass transition. It is more probable that these multilayers contain both Tb superparamagnetic particles and Tb-Si spin-glass alloys.

关键词： SPIN-GLASS TRANSITION GD/W mULTILAYERS TERBIUm FILmS NANOPARTICLES