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Contamination by Organochlorine Pesticides in the Estuaries of Southeast China

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Chemical Research in Chinese Universities 2002年第2期18卷 153-160页

作者： Z.l.Zhang h.S.hong J.l.Zhou M.h.Dai K.Maskaouib W.Q.Chen Department of Environmental Science and Engineering Tsinghua POPs Research CentreTsinghua UniversityBeijing 100084China Key laboratory of Marine Environmental Science of Ministry of Education Environmental Science Research CentreXiamen Universi-tyXiamen 361005China School of Chemistry Physics and Environmental ScienceUniversity of SussexFalmerBrighton BN19QJUK

Persistent organic pollutants(POPs) such as organochlorine pesticides are of global concern due to their widespread occurrence and persistence. This paper reports recent research studying the distribution and fate of organochlorine pesticides in the Jiulong River, the Minjiang River and the Pearl River estuaries in Southeast China. Eighteen organochlorine pesticides were extracted from water, pore water and sediment samples, followed by analysis by GC ECD. The results showed that the contamination levels were similar in these three estuaries. The levels of the total organochlorine pesticides in porewater were significantly higher than those in surface water, due to the high affinity of these hydrophobic compounds for sediment phase. Among the hexachlorocyclohexane(hCh) compounds, β hCh was found to be the most important isomer. The analysis of 1,1,1 trichloro 2,2 bis chlorophenyl ethane(DDT) and its metabolites showed that 1,1 dichloro 2[ o chlorophenyl] 2[ p chlorophenyl] ethylene(DDE) was dominant in the group.

关键词： Organochlorine insecticides DDT lindane Jiulong River Estuary Minjiang River Estuary Pearl River Estuary Water Sediment

Oxidation,Mechanical and Tribological Behaviors of the Ni/cBN Abrasive Coating-Coated Titanium Alloys

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Acta Metallurgica Sinica(English letters) 2021年第7期34卷 1007-1020页

作者： Y.D.liu J.h.liu W.S.Gu h.l.li W.h.li Z.l.Pei J.Gong C.Sun School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China Institute of Metal Research Chinese Academy of SciencesShenyang 110016China

In order to improve the oxidation and wear resistance of blades tip of titanium alloys as well as the sealing performance of the gas turbine engine,a Ni/cBN abrasive coating was prepared on titanium alloys through composite ***,mechanical and tribological properties of the abrasive coating were ***,the effect of the oxidation on the mechanical and tribological properties was also *** results revealed that the abrasive coating underwent slight oxidation within 700℃.Meanwhile,some intermetallic compounds,Ni3Ti,NiTi and NiTi2,were formed at the coating/substrate interface during *** to the pinning effect of cBN particles and the different thermal expansion coefficients of the coating and substrate,the coating/substrate interface was cracked after oxidation at 700℃.Tensile results showed that the presence of coating reduced the strength of the alloy significantly at room temperature,while only marginal variations of the strength of the coated and uncoated specimens at elevated ***,the wear tests indicated that the coating had the excellent cutting ability and wear resistance,which can effectively protect the blades tip of titanium *** the temperature increased,the wear resistance decreased due to the decrease in the mechanical properties of the Ni/cBN coating.

关键词： Abrasive coating Oxidation Mechanical properties Wear Titanium alloy

Effect of radiative loss mechanisms on FIR thermometric parameters of Nd^(3+)-doped lithium tellurite glasses

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Journal of Rare Earths 2024年第7期42卷 1250-1257,I0002页

作者： C.Y.Morassuti A.P.l Silva l.A.O.Nunes S.M.lima l.h.C.Andrade Optical and Photothermal Spectroscopy Group(GEOF) Center for Studies in Natural Resources(CERNA)State University of Mato Grosso do Sul(UEMS)C.P.351DouradosMSBrazil Renato Archer Information Technology Center Dom Pedro I Highway(SP-65)Km 1436-Chácaras Campos dos AmaraisCampinasSPBrazil Institute of Physics of São Carlos University of São PauloSão CarlosSPBrazil

Nd^(3+)-doped tellurite glasses are promising materials for thermometers based on the fluorescence intensity ratio(FIR)***,at high Nd^(3+)concentrations,energy transfer(ET)processes such as optical reabsorption and cross-relaxation can affect the Nd^(3+)emission,which has been little explored in the ***,the present work investigated the use of Nd^(3+)-doped tellurite glass(samples doped with Nd^(3+)at 0.2 mol%,0.5 mol%,2.0 mol%,and 4.0 mol%)in fluorescence thermometers,in the temperature range from 299 to 371 *** results indicate a strong dependence of the FIR parameters on the Nd^(3+)concentration,due to changes in the emission band profiles caused by optical reabsorption of the Nd^(3+)emissions and cross-relaxation processes.A decrease of the relative sensitivity of the ratio^(4)F_(5/2)→^(4)I_(9/2)/^(4)F_(3/2)→^(4)I_(9/2)is observed for samples doped with higher amounts of Nd^(3+).The maximum relative sensitivity at 299 K is 3.00%/K,which is the highest value among the reported Nd^(3+)ions.

关键词： Nd^(3+)-doped tellurite glass Fluorescence intensity ratio Optical thermometry Judd-Ofelt Rare earths

ON FATIGUE CRACK PATh DEVIATION AT ElEVATED TEMPERATURE IN ElECTRON BEAM REPAIRED WElDMENTS OF TURBINE DISK

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Acta Metallurgica Sinica(English letters) 2004年第4期17卷 584-590页

作者： h.Q.Zhang h.Y.Zhao Y.h.Zhang l.h.li X.A.Zhang Department of Mechanical Engineering Tsinghua University Beijing 100084 ChinaDepartment of Mechanical Engineering Tsinghua University Beijing 100084 ChinaSchool of Mechanical Engineering and Automation Beijing University of Aeronautics and AstronauticsBeijing 100083 ChinaSchool of Mechanical Engineering and Automation Beijing University of Aeronautics and AstronauticsBeijing 100083 ChinaBeijing Institute of Aeronautical Materials Beijing 100095 China

Fatigue crack growth behaviors in electron beam weldments of a nickel-base superalloy are studied. The objective of this paper is to discuss effects of the inhomogeneity of mechanical performance on fatigue crack growth (FCG) rate and crack path deviation (CPD). The base metal served in a turbine disk of aerospace engine was selected to fabricate bead-on-plate weldments by using electron beam welding. Some wedge-type opening loading specimens, notched in three different zone of weld metal, hAZ and base metal, were employed and performed fatigue crack growth tests at 650℃. The results show that the fatigue crack growth of electron beam welded joints is instable due to the influence of mechanical heterogeneities. Owing to the crack deviation at the weld metal and heat-affected-zone (hAZ), the effective growth driving force at the tip of fatigue crack was reduced with the reduction of the effective stress intensity factor (SIF) which finally causes fatigue crack rate decrease. Fatigue crack was strongly affected by size and the symmetrical characteristics of the plastic zone at the crack tip, which means that the integrity of the welded structure containing the fatigue crack mainly depended on the toughness of the low strength zone.

关键词： fatigue crack growth crack path deviation electron beam welding inhomogeneity of mechanical performance

Efficient heuristic Replication Techniques for high Data Availability in Cloud

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Computer Systems Science & Engineering 2023年第6期45卷 3151-3164页

作者： h.l.Chandrakala R.loganathan Department of Computer Science and Engineering School of EngineeringPresidency UniversityIndia Department of Computer Science and Engineering HKBK College of EngineeringIndia

Most social networks allow connections amongst many people based on shared *** networks have to offer shared data like videos,photos with minimum latency to the group,which could be challenging as the storage cost has to be minimized and hence entire data replication is not a *** replication of data across a network of read-intensive can potentially lead to increased savings in cost and energy and reduce the end-user’s response *** simple and adaptive replication strategies exist,the solution is non-deter-ministic;the replicas of the data need to be optimized to the data usability,perfor-mance,and stability of the application *** resolve the non-deterministic issue of replication,metaheuristics are *** this work,harmony Search and Tabu Search algorithms are used optimizing the replication process.A novel har-mony-Tabu search is proposed for effective placement and replication of *** on large datasets show the effectiveness of the proposed *** is seen that the bandwidth saving for proposed harmony-Tabu replication per-forms better in the range of 3.57%to 18.18%for varying number of cloud data-centers when compared to simple replication,Tabu replication and harmony replication algorithm.

关键词： Cloud computing data replication bandwidth saving Tabu search harmony search hybrid harmony-Tabu search

A continuum traffic flow model with the consideration of coupling effect for two-lane freeways

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Acta Mechanica Sinica 2011年第2期27卷 228-236页

作者： D.-h. Sun G.-h. Peng l.-P. Fu h.-P. he College of Automation Chongqing University400030 Chongqing China Department of Civil & Environmental Engineering University of Waterloo Waterloo Ontario N2L 3G 1 Canada College of Automation Chongqing University 400030 Chongqing China

A new higher-order continuum model is proposed by considering the coupling and lane changing effects of the vehicles on two adjacent lanes. A stability analysis of the proposed model provides the conditions that ensure its linear stability. Issues related to lane changing, shock waves and rarefaction waves, local clustering and phase transition are also investigated with numerical experiments. The simulation results show that the proposed model is capable of providing explanations to some particular traffic phenomena commonly observable in real traffic flows.

关键词： Two-lane traffic Two delay time scales model Numerical simulation Coupling effect Phase transition

MICRO-DESCRIPTION OF ThE SOlUTE-FIElD AND ThE PhASE-FIElD MODEl FOR ISOThERMAl PhASE TRANSITION IN BINARY AllOYS

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Acta Metallurgica Sinica(English letters) 2004年第6期17卷 835-839页

作者： h.M.Ding l.l.Chen R.X.liu ResearchStudioofSolidificationSimulation CollegeofMaterialsScienceandEngineeringHuazhongUniversityofScienceandTechnologyWuhan430074China

A new phase field method for two-dimensional simulations of binary alloy solidification was studied. A model basing on solute conservative in every unit was developed for solving the solute diffusion equation during solidification. Two-dimensional computations were performed for ideal solutions and Ni-Cu dendritic growth into an isothermal and highly supersaturated liquid phase.

关键词： phase field isothermal phase field model diffusion

STABlE SOlUTION OF TIME DOMAIN INTEGRAl EQUATION METhODS USING QUADRATIC B-SPlINE TEMPORAl BASIS FUNCTIONS

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Journal of Computational Mathematics 2007年第3期25卷 374-384页

作者： M.Y.Xia G.h.Zhang G.l.Dai C.h.Chan School of Electronics Engineering and Computer Science Peking UniversityBeijing 100871China Department of Electronic Engineering City University of Hong KongKowloonHong KongChina

This paper is concerned with stable solutions of time domain integral equation （TDIE） methods for transient scattering problems with 3D conducting objects. We use the quadratic B-spline function as temporal basis functions, which permits both the induced currents and induced charges to be properly approximated in terms of completeness. Because the B-spline function has the least support width among all polynomial basis functions of the same order, the resulting system matrices seem to be the sparsest. The TDIE formula-tions using induced electric polarizations as unknown function are adopted and justified. Numerical results demonstrate that the proposed approach is accurate and efficient, and no late-time instability is observed.

关键词： TDIE methods B-spline temporal basis functions Transient scattering prob-lems.

Reactivity of Nanostructured MnO_2 in Alkaline Medium Studied with a Microcavity Electrode: Effect of Oxidizing Agent

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Journal of Materials Science & Technology 2011年第7期27卷 585-593页

作者： l.Benhaddad l.Makhloufi B.Messaoudi1 K.Rahmouni h.Takenouti laboratoire de Technologie des Matériaux et Génie des Procédés (lTMGP) Département de Génie des Procédés. Université A. MiraRoute de Targa Ouzemmour06000 BéjaiaAlgeria UPR 15 du CNRS lISE-laboratoire Interfaces et Systèmes Electrochimiques UPMC University Paris 06Case 133 4 place Jussieu 75252 Paris Cedex 05 France UPR 15 du CNRS lISE-laboratoire Interfaces et Systèmes Electrochimiques UPMC University Paris 06Case 1334 place Jussieu 75252 Paris Cedex 05France

The synthesis of MnO2 powders by hydrothermal method with different oxidizing agents has been successfully achieved. The characterizations by scanning electron microscopy, energy-dispersive X-ray analyses, transmission electron microscopy, and X-ray diffraction techniques confirm the synthesis of nanostructured γ-MnO2 powders. The electrochemical reactivity of these powders in 1 mol/l KOh is investigated by cyclic voltammetry and electrochemical impedance spectroscopy （EIS） by using microcavity electrode. The results reveal that the MnO2 synthesized with Na2S2O8 shows the highest electrochemical reactivity in the test medium. This is due both to its large expanded surface area and its crystallographic variety γ-MnO2 formed in the matrix of ramsdellite, which is largely used as cathodic material for primary batteries. however, the presence of pyrolusite in the structure of γ-MnO2 synthesized with （Nh4）2S2O8 decreases its electrochemical reactivity due to its narrow 1×1 size tunnel, which hinders the protons insertion.

关键词： hydrothermal processing Electrochemical impedance spectroscopy (EIS) Cyclic voltammetry X-ray diffraction γ-MnO2