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Chinese Annals of Mathematics,Series b 2021年第1期42卷 135-150页

作者： geng LAI Sisi XIE Department of Mathematics Shanghai UniversityShanghai 200444China

In order to construct global solutions to two-dimensional(2 D for short)Riemann problems for nonlinear hyperbolic systems of conservation laws,it is important to study various types of wave *** paper deals with two types of wave interactions for a 2 D nonlinear wave system with a nonconvex equation of state:Rarefaction wave interaction and shock-rarefaction composite wave *** order to construct solutions to these wave interactions,the authors consider two types of Goursat problems,including standard Goursat problem and discontinuous Goursat problem,for a 2 D selfsimilar nonlinear wave *** classical solutions to these Goursat problems are obtained by the method of *** solutions constructed in the paper may be used as building blocks of solutions of 2 D Riemann problems.

关键词： Nonlinear wave system Rarefaction wave Shock-rarefaction composite wave Wave interaction Characteristic decomposition

Mechanical and Magnetic Properties of New(Fe,Co,Ni)–b–Si–Ta bulk Glassy Alloys

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Acta Metallurgica Sinica(English Letters) 2017年第7期30卷 659-664页

作者： Yao-Xiang geng Xin Lin Yu-Xin Wang Jian-bing qiang Ying-Min Wang Chuang Dong School of Materials Science and Engineering Jiangsu University of Science and Technology State Key Laboratory of Solidification Processing Northwestern Polytechnical University Key Laboratory of Materials Modification (Ministry of Education) Dalian University of Technology

The alloying effects of the like-atom substitution of Ni and Co for Fe on the various properties of Fe_（70）b_（16.7）Si_（8.3）Ta_5 metallic glass are investigated in this present work. New Fe-based bulk glassy alloys, namely Fe_（60–x）Co_xNi_（10）b_（16.7）Si_（8.3）Ta_5（at.%;x = 10, 20 and 30） with critical diameters up to 1.5 mm, were made by means of copper mold casting.A new glass-forming ability indicator, viz., the enthalpy of supercooled liquid, has been introduced for assessment of the glass-forming abilities（GFAs） of these Fe-based multi-component alloys. Nano-indentation results indicate that the calculated elastic modulus and hardness of the bulk glassy alloys are lower than those of the Fe_（70）b_（16.7）Si_（8.3）Ta_5 *** these bulk glassy alloys, Fe_（70）b_（16.7）Si_（8.3）Ta_5 exhibits the large elastic modulus and hardness with values of 178 ± 1GPa and 12.9 ± 0.1 GPa, respectively. All the bulk glassy alloys exhibit good soft magnetic properties with high saturation magnetization bs^0.75–1.04 T but low coercive force Hc^0.2–5.2 A/m.

关键词： (Fe Co Ni)–b–Si–Ta bulk glass alloys Glass-forming ability Mechanical property Magnetic property

Nanoscale Reciprocating Sliding Contacts of Textured Surfaces:Influence of Structure Parameters and Indentation Depth

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Chinese Journal of Mechanical Engineering 2018年第4期31卷 168-181页

作者： Rui-Ting Tong geng Liu Shaanxi Engineering Laboratory for Transmissions and Controls Northwestern Polytechnical University

Textured surfaces are widely used in engineering components as they can improve tribological properties of sliding contacts, while the detailed behaviors of nanoscale reciprocating sliding contacts of textured surfaces are still lack of study. by using multiscale method, two dimensional nanoscale reciprocating sliding contacts of textured surfaces are investigated. The influence of indentation depth, texture shape, texture spacing, and tip radius on the average friction forces and the running-in stages is studied. The results show that the lowest indentation depth can make all the four textured surfaces reach steady state. Surfaces with right-angled trapezoid textures on the right side are better for reducing the running-in stage, and surfaces with right-angled trapezoid textures on the left side are better to reduce wear. Compared with other textured surfaces, the total average friction forces can be reduced by 82.94%–91.49% for the case of the contact between the tip with radius R = 60rand the isosceles trapezoid textured surface. besides,the total average friction forces increase with the tip radii due to that bigger tip will induce higher contact areas. This research proposes a detailed study on nanoscale reciprocating sliding contacts of textured surfaces, to contribute to design textured surfaces, reduce friction and wear.

关键词： Nanoscale Reciprocating sliding contacts Textured surface Structure parameters Indentation depth

The Serum Exosome Derived MicroRNA-135a,-193b, and-384 Were Potential Alzheimer's Disease biomarkers

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biomedical and Environmental Sciences 2018年第2期31卷 87-96页

作者： YANG Ting Ting LIU Chen geng GAO Shi Chao ZHANG Yi WANG Pei Chang Department of Clinical Laboratory Xuanwu Hospital Capital Medical University

Objective MicroRNAs （miRs） are attractive molecules to be considered as one of the blood-based biomarkers for neurodegenerative disorders such as Alzheimer＇s disease （AD）. The goal of this study was to explore their potential value as biomarkers for the diagnosis of *** The expression levels of exosomal miR-135a, -193b, and -384 in the serum from mild cognitive impairment （MCI）, dementia of Alzheimer-type （DAT）, Parkinson＇s disease with dementia （PDD）, and vascular dementia （VaD） patients were measured with a real-time quantitative reverse transcriptase PCR （qRT-PCR） *** both serum exosome miR-135a and miR-384 were up-regulated while miR-193b was down-regulated in serum of AD patients compared with that of normal controls. Exosome miR-384 was the best among the three miRs to discriminate AD, VaD, and PDD. Using the cut-off value could better interpret these laboratory test results than reference intervals in the AD diagnosis. ROC curve showed that the combination of miR-135a, -193b, and -384 was proved to be better than a particular one for early AD *** Our results indicated that the exosomal miRs in the serum were not only potential biomarker of AD early diagnosis, but might also provide novel insights into the screen and prevention of the disease.

关键词： Alzheimer's disease Exosome MicroRNA biomarker

THERMAL STRUCTURAL DISORDER AND MELTING TRANSITION IN HIGH-ANGLE GRAIN-bOUNDARY: A MOLECULAR-DYNAMICS STUDY

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Acta Metallurgica Sinica(English Letters) 1998年第5期11卷 365-375页

作者： S.J.Zhao Y.C.Wang J.q.You q.b.Yang L.G.Zhou H.q.Ye Xiangtan Univ Xiangtan China

A structural transition in the fcc ∑=5 (120)/[001] high-angle tilt grain-boundary(Gb)is investigated by molecular-dynamics simulation. The calculations have been performed at various temperutures and the thermodynamic melting point Tm of the model system is determined by using a many-body potential fitted to copper. A thermal disorder transition in the Gb region occurs well below the melting point. Our results indicate that such a transition is a continuous process and there is no evidence of premelting, which is entirely in accord with experiment results and theoretical *** we also observed that melting initiated at the interface and then propagated into the bulk quickly at or above Tm.

关键词： moleculandynamics grainboundary structural transition

NOx Emission Reduction Technology for Marine Engine based on Tier-Ⅲ:A Review

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Journal of Thermal Science 2020年第5期29卷 1242-1268页

作者： LU Xiuwei geng Peng CHEN Yunyue Merchant Marine College Shanghai Maritime UniversityShanghai 201306China Tianjin Research Institute of Water Transport Engineering Tianjin 300456China

The development of maritime trade has greatly promoted the development of diesel ***,with the increasingly serious environmental problems,more and more attention has been paid to the exhaust emissions of high-power marine diesel *** restrictions on SOx have been implemented globally,and the limitation of the NO,will be the next *** paper illustrates(a)Principle and research progress of NOx emissions-reduction technology of marine diesel engine;(b)Summary of advantages and disadvantages among various reduction technologies and their reduction effects;(c)The application effect of mainstream technology on ***,since exhaust gas recirculation(EGR)can achieve Tier-Ⅲ directly from Tier-Ⅰ without considering the increased fuel *** is deemed as the most promising technology to reduce emissions by controlling combustion ***,EGR has shortcomings of excessive increase in ftiel consumption and generation of waste water,which need to be solved ***,selective catalytic reduction(SCR)is the most effective and straightforward means to achieve Tier-Ⅲ.Despite of the continuous optimization of SCR unit volume,the problem of scrap catalyst seriously limits its wide *** to match the supercharger more efficiently is a key factor in choosing between high and low pressure ***,nature gas(NG)engines are capable of achieving a reduction in NOx,but in order to meet the requirements of Tier-Ⅲ,it still needs to be assisted by other *** emissions of hydrocarbon(HC)and CO in NG engines are huge defects that must be ***,technologies such as the Miller cycle,Two-stage supercharging and mixed-water combustion can also reduce emissions but were rarely used *** technologies can be combined with EGR,SCR and NG engines to optimize the enginesJ economy and emission characteristics.

关键词： marine engine NOx emission Tier-Ill exhaust gas recirculation(EGR) selective catalytic reduction(SCR) dual-fuel

Search for T-violating Effects

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Search for T-violating Effects

Local Smooth Solutions to the 3-Dimensional Isentropic Relativistic Euler equations

CCAST“CP破坏与新物理”研讨会

作者： C.q.geng Department of Physics National Tsing Hua UniversityHsinchuTaiwan

＜正＞We study the time-reversal odd lepton spin involved correlations in kaon and b-meson decays. The T violation as well as the final state interaction effects arediscussed. The predictions on these effects in vario...

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Chinese Annals of Mathematics,Series b 2014年第2期35卷 301-318页

作者： Yongcai geng Yachun LI School of Science Shanghai Institute of Technology Department of Mathematics Shanghai Jiao Tong University

The authors consider the local smooth solutions to the isentropic relativistic Euler equations in(3+1)-dimensional space-time for both non-vacuum and vacuum *** local existence is proved by symmetrizing the system and applying the FriedrichsLax-Kato theory of symmetric hyperbolic *** the non-vacuum case,according to Godunov,firstly a strictly convex entropy function is solved out,then a suitable symmetrizer to symmetrize the system is *** the vacuum case,since the coefficient matrix blows-up near the vacuum,the authors use another symmetrization which is based on the generalized Riemann invariants and the normalized velocity.

关键词： Isentropic relativistic Euler equations local-in-time smooth solutions Strictly convex entropy Generalized Riemann invariants

FATIGUE PROPERTIES OF AUSTEMPERED DUCTILE IRON(ADI)IN WATER ENVIRONMENT

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Acta Metallurgica Sinica(English Letters) 2004年第2期17卷 122-130页

作者： q.Z.Cai b.K.Wei Y.Tanaka StateKeyLabofPlasticFormingSimulation＆Dies／MouldTechnology FacultyofMaterialsScienceandEngineeringHuazhongUniversityofScienceandTechnologyWuhan430074China DepartmentofMechanicalSystemsEngineering MuroranInstituteofTechnologyMuroran050-8585Japan

The acicular ferrite in austempered ductile iron (ADI) matrix around graphite wascorroded preferentially in wet condition, promoting crack origination and propagationand resulting in the disappearance of ADI fatigue limit. ADI fatigue strength wasgradually reduced with increasing the time of test and was reduced by 50% in wetcondition at 10~7 cycles compared with the fatigue limit in dry condition. The fatiguestrength variation of ferritic ductile iron in wet condition was similar to that of ADI.The ferritic ductile iron, however, has better corrosion resistance so that the fatiguestrength was lowered only by 10% in wet condition at 10~7 cycles compared with thefatigue limit in dry condition. On the other hand, the fatigue limits of ADI and ferriticductile iron were dropped by 32% and 25% in tap water dipping 480h/dry conditionrespectively compared with those in dry condition. The reduction of fatigue limit wasattributed to corrosion pits formation correlated with stress concentration, resultingin origination and propagation of fatigue crack.

关键词： anstempered ductile iron water environment corrosion fatigue crack fatigue strength

Experimental study of the effect of wear parameters on the wear behavior of A356 alloy/cow horn particulate composites

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Defence Technology（防务技术） 2018年第1期14卷 77-82页

作者： b.q.Ochieze C.C.Nwobi-Okoye P.N.Atamuo Lafarge Africa Plc Mfamosing Plant Department of Mechanical Engineering Chukwuemeka Odumegwu Ojukwu University

Experimental study of the effect of wear parameters on the wear behaviour of A356 alloy reinforced with cow horn particles(CHp) produced by spark plasma sintering was investigated. Experiments were conducted based on the plan of experiments generated through Taguchi's(L9) technique. Tribometer was used for the wear test and Scanning electron microscope was used to analyse the worn scar of the samples. The results shows that, A356 alloy reinforced with CHp exhibited better dry sliding wear resistance than the unreinforced alloy. Wear rate decreased as the amount of CHp reinforcement increased in the matrix. It was found that, the optimum level of the factors with minimized the wear loss were obtained at: wt%CHp(20%), applied load(10 N), sliding velocity(3 m/s) and sliding distance(2000 m). It can be seen that the wear track of the sample are(D ? 0.81 and L = 42.85 mm) and(D ? 0.54 and L= 27.03 mm) for A356 alloy and composites at optimum condition respectively. The results showed that the addition of cow horn particles as reinforcing materials in A356 alloy composites increased the wear resistance of the composites greatly.

关键词： A356alloy Cow horn particles Microstructure Analysis of variance and wear behaviour