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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

Anisotropic Inter-granular Corrosion Behaviors and Microstructures of AlMgsiCu Alloy sheets Made by Thermal–Mechanical Treatments

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Acta Metallurgica sinica(English letters) 2022年第2期35卷 275-284页

作者： l.M.liu Y.X.lai C.l.Wu z.zhang j.H.Chen Center for High-Resolution Electron Microscopy College of Materials Science and EngineeringHunan UniversityChangsha 410082China

This study investigates the microstructure and local corrosion behavior of an Al-Mg-si-Cu alloy,which has been subjected to cold-rolling with different deformation strain ratios(DsRs)and followed by artificial *** corrosion tests show that peak-aged samples with a small DsR(5-10%)are sensitive to inter-granular corrosion(IGC)along both the normal and rolling *** the DsR increases to medium strength(20-40%),IGC sensitivity decreases along both directions and corrosion propagates *** the DsR is 60-80%,IGC sensitivity along the normal direction continues to decrease,but increases along the rolling direction,indicating pronounced corrosion *** characterization reveals the decreased IGC sensitivity is mainly attributed to a reduction in element segregation at high-angle grain boundaries and the kinked and discontinuous grain boundary corrosion *** increased IGC sensitivity along the rolling direction could be related to the significantly flattened grains.

关键词： Al alloys local corrosion Anisotropy Transmission electron microscopy(TEM) Electron backscattering diffraction(EBsD)

High mechanical strengths and ductility of stainless steel 304l fabricated using selective laser melting

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journal of Materials science & Technology 2019年第2期35卷 388-394页

作者： Q.B.Nguyen z.zhu F.l.Ng B.W.Chua s.M.l.Nai j.Wei singapore Institute of Manufacturing Technology Institute of Research and Development Duy Tan University

Achieving not only high mechanical strengths but also high ductility is recently established using an additive manufacturing technique called selective laser melting. In the present study, stainless steel 304 l fully dense samples were successfully printed using the 3 D systems – ProX 300 printing machine. The ductility and tensile yield strength were almost two and three times higher compared to those of AsTM cast's alloy. Honey comb like nano-cellular structure with different orientation was observed in the fine grains(~4μm) due to fast cooling rate. In addition, the formation of martensite phase in random grains is also a contributor to the strengths. Furthermore, negative residual stresses in the build and horizontal directions were detected and assisted further increase in the tensile strength. Fractography revealed the ductile feature of plastic deformation and the crack openings at unmelted particles or pores.

关键词： Additive manufacturing stainless steel Powder selective laser melting

Chemical characteristics of aerosols at coastal station in Hong Kong.Ⅱ. Environmental behavior of trace elements during the April 1995 to April 1996

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journal of Environmental sciences 2004年第2期16卷 212-221页

作者： K.s.lam z.l.Cheng s.C.Kot C.W.Tsang Department of Civil and structural Engineering the Hong Kong Polytechnic UniversityResearch Center for Eco-Environmental Sciences Chinese Academy of SciencesDepartment of Mechanical Engineering The Hong Kong University of Science & Technology Clear Water BayDepartment of Applied Biology and Chemical Technology the Hong Kong Polytechnic University Hung Hom Hong Kong ChinaBeijing 100085 ChinaHong Kong ChinaHung Hom Hong Kong China

An one-year of sampling aerosol program was carried out during the period of April 1995 to April 1996 at coastal region, Cape D′Aguilar, in Hong Kong. The trace element composition of aerosol particles(TsP and PM 10 ) were measured and anal.zed by using the Instrumental Neutron Activation Analysis(INAA) and Inductive Couple Plasma-Mass spectrometry(ICP-Ms) techniques. The results showed that the polluted elements such as: V, zn, As, Pb, Cd, sb, I, se, Bi, with high enrichment factor(E.F) values, are derived from anthropogenic sources, while sc, Al, Fe, Mn, sm, la, sr are less than 10 in E.F, these elements are related the crust and soil. The concentration of the trace elements are present seasonal variation i.e. summer low and winter high, whereas the V or noncrustal V(V *) present summer high and winter low, this phenomenon might be explained by local or regional oil combustion sources. Use three type of elemental ratio, e.g. la/sm, Mn */V * and Bi/Al indicate that both TsP and PM 10 of la/sm ratios are mainly related to soil and dust, Mn */V * are probably represent fossil combustion and Bi/Al are possibly associated with refuse incineration, ferromanganese alloys and aluminum production. The varimax rotation factor analysis for trace elements was performed. By means of the absolute principal component analysis(APCA) and multiple regression, the contribution of trace elements to possible sources and overall means of trace elements were estimated. The results showed that the present station is impacted by the anthropogenic species, although the quantities are different during the summertime and wintertime.

关键词： TsP PM 10 trace elements enhancement factor element ratios seasonal variation factor analysis

New method for oblique impact dynamics research of a flexible beam with large overall motion considering impact friction force

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Acta Mechanica sinica 2016年第4期32卷 720-730页

作者： W.Yuan l.li D.G.zhang j.z.Hong school of science Nanjing University of Science and Technology Department of Engineering Mechanics Shanghai Jiao Tong University

A flexible beam with large overall rotating motion impacting with a rigid slope is studied in this paper. The tangential friction force caused by the oblique impact is anal.zed. The tangential motion of the system is divided into a stick state and a slip state. The contact constraint model and Coulomb friction model are used respectively to deal with the two states. Based on this hybrid modeling method, dynamic equations of the system, which include all states（before, during, and after the collision）are obtained. simulation results of a concrete example are compared with the results obtained from two other models： a nontangential friction model and a modified Coulomb model. Differences in the results from the three models are discussed. The tangential friction force cannot be ignored when an oblique impact occurs. In addition, the results obtained from the model proposed in this paper are more consistent with real movement.

关键词： collision oblique friction stick tangential considering Coulomb constraint coordinate rotating

Cleaning Radio Frequency Interference in Pulsar-Folded Data Based on the Conditional Random Fields with an Adaptive Prior

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Research in Astronomy and Astrophysics 2023年第10期23卷 184-191页

作者： Xue Chen j.l.Han W.Q.su z.l.Yang D.j.zhou National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China school of Astronomy and space science University of Chinese Academy of SciencesBeijing 100049China CAs Key laboratory of FAsT NAOCChinese Academy of SciencesBeijing 100101China

Radio astronomy observations are frequently impacted by radio frequency interference(RFI).We propose a novel method,named 2σCRF,for cleaning RFI in the folded data of pulsar observations,util.zing a Bayesian-based model called conditional random fields(CRFs).This algorithm minimizes the“energy”of every pixel given an initial *** standard deviations(i.e.,rms values)of the folded pulsar data are util.zed as pixels for all subintegrations and ***-RFI data without obvious interference is treated as“background noise,”while RFI-affected data have different classes due to their exceptional rms *** initial labeling can be automated and is adaptive to the actual *** CRF algorithm optimizes the label category for each pixel of the image with the prior initial *** demonstrate the efficacy of the proposed method on pulsar folded data obtained from Five-hundred-meter Aperture spherical radio Telescope *** can effectively recognize and tag various categories of RFIs,including broadband or narrowband,constant or instantaneous,and even weak RFIs that are unrecognizable in some pixels but picked out based on their *** results are comparable to those obtained via manual labeling but without the need for human intervention,saving time and effort.

关键词： methods:data analysis techniques:image processing (stars:)pulsars:general

Tensile strength and Electrical Conductivity of Carbon Nanotube Reinforced Aluminum Matrix Composites Fabricated by Powder Metallurgy Combined with Friction stir Processing

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journal of Materials science & Technology 2014年第7期30卷 649-655页

作者： z.Y.liu B.l.Xiao W.G.Wang z.Y.Ma shenyang National laboratory for Materials science Institute of Metal ResearchChinese Academy of Sciences Dalian University of Technology liaoning shihua University

A route combining powder metallurgy and subsequent friction stir processing was util.zed to fabricate carbon nanotube （CNT） reinforced AI （CNT/AI） and 6061AI （CNT/6061AI） composites. Microstructural observations indicated that CNTs were uniformly dispersed in the matrix in both CNT/AI and CNT/6061AI composites. Mg and si elements tended to segregate at CNT-AI interfaces in the CNT/6061AI composite during artificial aging treatment. The tensile properties of both the AI and 6061AI were increased by CNT incorporation. The electrical conductivity of CNT/AI was decreased by CNT addition, while CNT/6061AI exhibited an increase in electrical conductivity due to the Mg and si segregation.

关键词： Carbon nanotubes Metal matrix composites Mechanical properties Electrical properties Friction stir processing

NUMERICAl sTUDY OF TURBUlENT IMPINGING jET WITH A REFINED k-ε MODEl

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journal of Hydrodynamics 2000年第4期12卷 8-15页

作者： Xu, j.l. Xu, z. Huang, s.j. zhang, K.Y. Xiao, M. 2nd Dep. Nanjing Univ. of Aeron. and Astron. Nanjing 210016 China

A refined k-Ε model re-considering the fluctuating pressure diffusion term in the dissipation rate equation (Ε-equation) is provided and used in the numerical study of circular semi-confined turbulent impinging jet. The results are compared with those of the standard k-Ε model and show that the predicting ability of the refined k-Ε model is much improved, especially for the turbulent kinetic energy k. so it is necessary to consider the effect of the fluctuating pressure diffusion term and to model this term correctly and exactly in the near wall region with the great adverse pressure gradient, where the effect of the pressure fluctuating is important. Therefore we can conclude that the new modeling idea expressed in this paper is correct and effective.

关键词： Computer simulation jets Mathematical models Turbulence

Effect of silver Content on Microstructure and Properties of Brass/steel Induction Brazing joint Using Ag-Cu-zn-sn Filler Metal

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journal of Materials science & Technology 2011年第4期27卷 377-381页

作者： j. Cao l.X. zhang H.Q. Wang l.z. Wu j.C. Feng state Keylab of AdvanCed Welding Production Technology Harbin Instituteof Technology Harbin 150001 China Center for Composite Materials and structures Harbin Institute of Technology Harbin 150001 China

The induction brazing of brass to steel using Ag-Cu-zn-sn filler metal was investigated in this study. The influence of A8 content on the microstructure and properties were anal.zed by means of optical microscopy, scanning electron microscopy and electron probe microanalysis. Defect free joint was achieved using Ag- Cu-zn-sn filler metal. The microstructure of the joint was mainly composed of Ag-based solid solution and Cu-based solid solution. The increase of A8 content and the cooling rate both led to the increase of the needle like eutectic structure. The tensile strength decreased with the increase of Ag content. The tensile strength at room temperature using Ag25Cuznsn filler metal reached 445 MPa. All fractures using Ag-Cu-zn-sn filler metal presented ductile characteristic.

关键词： Induction brazing Brass steel Microstructure Tensile strength