检索结果-南通市图书馆

Comparative study on aerodynamic heating under perfect and nonequilibrium hypersonic flows

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2016年第2期59卷 78-84页

作者： Qiu Wang jin ping li Wei Zhao Zong lin Jiang State Key Laboratory of High Temperature Gas Dynamics Institute of Mechanics Chinese Academy of Sciences

In this study, comparative heat flux measurements for a sharp cone model were conducted by utilizing a high enthalpy shock tunnel JF-10 and a large-scale shock tunnel JF-12, responsible for providing nonequilibrium and perfect gas flows, respectively. Experiments were performed at the Key Laboratory of High Temperature Gas Dynamics(LHD), Institute of Mechanics, Chinese Academy of Sciences. Corresponding numerical simulations were also conducted in effort to better understand the phenomena accompanying in these experiments. By assessing the consistency and accuracy of all the data gathered during this study, a detailed comparison of sharp cone heat transfer under a totally different kind of freestream conditions was build and analyzed. One specific parameter, defined as the product of the Stanton number and the square root of the Reynold number, was found to be more characteristic for the aerodynamic heating phenomena encountered in hypersonic flight. Adequate use of said parameter practically eliminates the variability caused by the deferent flow conditions, regardless of whether the flow is in dissociation or the boundary condition is catalytic. Essentially, the parameter identified in this study reduces the amount of ground experimental data necessary and eases data extrapolation to flight.

关键词： aerodynamic heating hypersonic shock tunnel Stanton number sharp cone

Effects of Cyclic Electron Flow Inhibitor(Antimycin A)on Photosystem Photoinhibition of Sweet Pepper Leaves upon Exposure to Chilling Stress Under Low Irradiance

在线全文

学校读者我要写书评

暂无评论

Agricultural Sciences in China 2006年第7期5卷 506-511页

作者： li Xin-guo ZHAO jin-ping XU ping-li MENG jing-jing HE Qi-wei High-Tech Center Shandong Academy of Agricultural Sciences Ji＇nan 250100 P.R.China

In chloroplast, there were two pathways involved in the cyclic electron flow around photosystem 1 （PS 1）. One was the NADH dehydrogenase （NDH）-dependent flow and the other was the ferredoxin quinone reductase-dependent flow. It was proposed that the NDH-dependent cyclic electron flow around PSI was related to the xanthophyll cycle-dependent non-photochemical quenching （NPQ） at chilling temperature under low irradiance （CL）. The function of the chloroplastic cyclic electron flow around PS 1 was examined by comparing sweet pepper （Capsicum annuum L.） control with its antimycin A （AA）-fed leaves upon exposure to CL stress. During CL stress, the maximum photochemical efficiency of PS2 （Fv/Fm） decreased markedly in both controls and AA-fed leaves, and P700＋ was also lower in AA-fed leaves than in controls. These results implied that cyclic electron flow around PS 1 functioned to protect the photosynthetic apparatus from CL stress. Under such stress, NPQ and PS2-driven electron transport rate were different between AA-fed leaves and controls. The lower NPQ in AA-fed leaves might be related to an inefficient proton gradient across thylakoid membranes （ApH） because of inhibiting cyclic electron flow around PS 1 under CL stress.

关键词： sweet pepper chilling stress cyclic electron flow non-photochemical quenching the xanthophyll cycle

To improve robustness of mechanical properties of semi-solid cast A356 alloy using taguchi design method

在线全文

学校读者我要写书评

暂无评论

China Foundry 2024年第2期21卷 175-184页

作者： Yi-wu Xu Hong-yi Zhan Wei Tong jin-ping li Le-peng Zhang De-jiang li Xiao-qin Zeng School of Materials Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China China Science Lab General Motors Global Research&DevelopmentShanghai 201206China General Motors(China)Investment Co. Ltd.Shanghai 201206China China International Intellectech Corporation(CIIC) Beijing 100004China

Mechanical properties of semi-solid casting are dependent on multiple processing parameters,and improper processing parameters will not only reduce mean data but also increase *** present study investigated the impact of parameters in slurry preparation and heat treatment on the yield strength and ductility of T6 heat-treated A356 Al-Si alloy using rapid slurry forming(RSF)semi-solid *** focus was primarily on the robustness of mechanical properties based on Taguchi design *** analyzing signal-to-noise ratio and minimum value calculated from-3S,the optimum slurry preparation parameters and heat treatment parameters were determined to be no quench,enthalpy exchange material(EEM)temperature of 140℃,EEM-to-melt ratio of 6mass%,stirring time of 18 s,solution heat treated at 520℃ for 2 h,and ageing heat treated at 190℃ for 6 *** a small batch validation,the-3S yield strength and-3S elongation reach 256.1 MPa and 5.03% respectively,showing a satisfactory *** hardness and microstructure of heat-treated samples with the best and worst properties were characterized to gain insight into the underlying mechanisms affecting the mean value and variations of mechanical properties.

关键词： semi-solid casting taguchi design method signal-to-noise ratio mechanical property microstructure

Effects of magnesium and copper additions on tensile properties of Al-Si-Cr die casting alloy under as-cast and T5 conditions

在线全文

学校读者我要写书评

暂无评论

China Foundry 2023年第1期20卷 12-22页

作者： Hong-yi Zhan Yi-wu Xu Pan Wang Jian-feng Wang jin-ping li Le-peng Zhang General Motors Global Research&Development China Science LaboratoryShanghai 201206China School of Materials Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China General Motors(China)Investment Co. Ltd.Shanghai 201206China China International Intellectech Corporation(CIIC) Beijing 100004China

Aluminum high pressure die casting(HPDC)technology has evolved in the past decades,enabling stronger and larger one-piece casting with significant part *** also offers a higher design freedom for more mass-efficient thin-walled body *** body structures that require excellent ductility and fracture toughness to be joined with steel sheet via self-piercing riveting(for instance,shock towers and hinge pillars,etc.),a costly T7 heat treatment comprising a solution heat treatment at elevated temperatures(450℃-500℃)followed by an over-ageing heat treatment is needed to optimize microstructure for meeting product *** enable cost-efficient mass production of HPDC body structures,it is important to eliminate the expensive T7 heat treatment without sacrificing mechanical *** die cast alloy chemistry is a potential solution to improve fracture toughness and ductility of the HPDC *** present study intends to tailor the Mg and Cu additions for a new Al-Si-Cr type die casting alloy(registered as A379 with The Aluminum Association,USA)to achieve the desired tensile properties without using T7 heat *** was found that Cu addition should be avoided,as it is not effective in enhancing strength while degrades tensile *** addition is very effective in improving strength and has minor impact on tensile *** investigated Al-Si-Cr alloy with a nominal composition of Al-8.5wt.%Si-0.3wt.%Cr-0.2wt.%Fe shows comparable tensile properties with the T7 treated AlSi10MnMg alloy which is currently used for manufacturing shock towers and hinge pillars.

关键词： Al-Si alloy intermetallics high pressure die casting tensile property T7 heat treatment

Photodetectors based on two-dimensional MoS_(2) and its assembled heterostructures

在线全文

学校读者我要写书评

暂无评论

Chip 2022年第3期1卷 8-27页

作者： Tao Hu Rui Zhang jin-ping li Jian-Yun Cao Feng Qiu National Center for International Research on Photoelectric and Energy Materials Yunnan Key Laboratory for Micro/Nano Materials&TechnologySchool of Materials and EnergyYunnan UniversityKunming 650500China

Photodetectors are finding various potential applications in sensing and detection,information communication,light-emitting diode,optical modulators,ultrafast laser,*** disulfide(MoS_(2))has sparked great interest given its unique crystal phase,flexible preparation,structural stability,and regulable photoelectronic ***,the MoS_(2)-based photodetector is demonstrated to be an excellent device fabrication platform to explore underlying sen-sitive detection,broadband optical detection,high-speed response,low-power consumption,two-dimensional integrated circuit,and its synergetic mechanism,which is also proved to be an excellent candidate for next-generation *** review summarizes the structural,optical,and transport features of MoS_(2).Then the working mechanisms and figures of merit are explored for the MoS_(2)***,the detector modulation strategies are introduced in detail about layer-number engineering and chemical doping ***,the recent heterostructure assembling strategies(MoS_(2)/nD,n=0,1,2,3)of detector architectures are classified based on flexible van der Waals ***,the future direction of MoS_(2)photodetectors is discussed,which can be delivered as a feasible guideline in two-dimensional photodetector and integrated circuit fields.

关键词： MoS_(2) Synthetic strategy Figures of merit Heterostructure photodetector

Development of High Strength and Toughness Non-Heated Al–Mg–Si Alloys for High-Pressure Die-Casting

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2021年第6期34卷 845-860页

作者： ling-Yang Yuan Pan-Wen Han Ghulam Asghar Bao-liang liu jin-ping li Bin Hu Peng-Huai Fu li-Ming Peng National Engineering Research Center of light Alloy Net Forming and Key State Laboratory of Metal Matrix Composites School of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai 200240China Shanghai light Alloy Net Forming National Engineering Research Center Co. LtdShanghai 201615China General Motors China Science Laboratory Shanghai 201206China

Based on the 3 factors and 3 levels orthogonal experiment method,compositional effects of Mg,Si,and Ti addition on the microstructures,tensile properties,and fracture behaviors of the high-pressure die-casting Al-x Mg-y Si-z Ti alloys have been *** analysis of variance shows that both Mg and Si apparently infl uence the tensile properties of the alloys,while Ti does *** tensile mechanical properties are comprehensively infl uenced by the amount of eutectic phase(α-Al+Mg2Si),the average grain size,and the content of Mg dissolved intoα-Al *** optimized alloy is Al-7.49 Mg-3.08 Si-0.01 Ti(wt%),which exhibits tensile yield strength of 219 MPa,ultimate tensile strength of 401 MPa,and elongation of 10.5%.Furthermore,contour maps,showing the relationship among compositions,microstructure characteristics,and the tensile properties are constructed,which provide guidelines for developing high strength and toughness Al–Mg–Si–Ti alloys for high-pressure die-casting.

关键词： Al–Mg–Si–Ti alloy Microstructure Tensile properties High strength and toughness Contour maps

Detection and differentiation of early hepatocellular carcinoma from cirrhosis using CT perfusion in a rat liver model

在线全文

学校读者我要写书评

暂无评论

Hepatobiliary & Pancreatic Diseases International 2016年第6期15卷 612-618页

作者： jin-ping li Guang-Long Feng Da-Qing li Hai-Bo Wang De-li Zhao Yong Wan Hui-Jie Jiang Department of Radiology Second Affiliated HospitalHarbin Medical University Harbin 150086 China

BACKGROUND： Functional imaging such as CT perfusion can detect morphological and hemodynamic changes in he- patocellular carcinoma （HCC）. Pre-carcinoma and early HCC nodules are difficult to differentiate by observing only their hemodynamics changes. The present study aimed to investi- gate hemodynamic parameters and evaluate their differential diagnostic cut-off between pre-carcinoma and early HCC nodules using CT perfusion and receiver operating characteristic （ROC） curves. METHODS： Male Wistar rats were randomly divided into control （n=20） and experimental （n=70） groups. Diethylnitrosamine （DEN） was used to induce pre-carcinoma and early HCC nodules in the experimental group. Perfusion scanning was carried out on all survival rats discontinuously from 8 to 16 weeks. Hepatic portal perfusion （HPP）, hepatic arterial fraction （HAF）, hepatic arterial perfusion （HAP）, hepatic blood volume （HBV）, hepatic blood flow （HBF）, mean transit time （MTT） and permeability of capillary vessel surface （PS） data were provided by mathematical deconvolution model. The perfusion parameters were compared among the three groups of rats （control, pre-carcinoma and early HCC groups） using the Kruskal-Wallis test and analyzed with ROC curves. Histological examination of the liver tissues with hematoxylin and eosin staining was performed after CT ***： For HPP, HAF, HBV, HBF and MTT, there were significant differences among the three groups （P〈0.05）. HAF had the highest areas under the ROC curves： 0.80 （control vs pre-carcinoma groups） and 0.95 （control vs early HCC groups） with corresponding optimal cut-offs of 0.37 and 0.42, respectively. The areas under the ROC curves for HPP was 0.79 （control vs pre-carcinoma groups） and 0.92 （control vs early HCC groups） with corresponding optimal cut-offs of 136.60 mL/min/100 mg and 108.47 mL/min/100 mg, respectively. CONCLUSIONS： CT perfusion combined with ROC curve analysis is a new diagnosis model for distinguishing between pre-carcinoma an

关键词： liver neoplasms computed tomography perfusion imaging rat model

First-principles study on the mechanics, optical, and phonon properties of carbon chains

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2018年第11期27卷 559-567页

作者： jin-ping li Song-He Meng Han-Tao Lu Takami Tohyama National Key Laboratory of Science and Technology on Advanced Composites in Special Environments Center for Composite Materials and StructureHarbin Institute of TechnologyHarbin 150080China Center for Interdisciplinary Studies&Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education Lanzhou UniversityLanzhou 730000China Department of Applied Physics Tokyo University of ScienceTokyo 125-8585Japan

Besides graphite,diamond,graphene,carbon nanotubes,and fullerenes,there is another allotrope of carbon,carbyne,existing in the form of a one-dimensional chain of carbon *** has been theoretically predicted that carbyne would be stronger,stiffer,and more exotic than other materials that have been synthesized *** this article,two kinds of carbyne,i.e.,cumulene and polyyne are investigated by the first principles,where the mechanical properties,electronic structure,optical and phonon properties of the carbynes are *** results on the crystal binding energy and the formation energy show that though both are difficult to be synthesized from diamond or graphite,polyyne is more stable and harder than *** tensile stiffness,bond stiffness,and Young's modulus of cumulene are 94.669 eV/Å,90.334 GPa,and 60.62 GPa,respectively,while the corresponding values of polyyne are 94.939 eV/Å,101.42 GPa,and60.06 *** supercell calculation shows that carbyne is most stable at N=5,where N is the supercell number,which indicates that the carbon chain with 10 atoms is most *** calculation on the electronic band structure shows that cumulene is a conductor and polyyne is a semiconductor with a band gap of 0.37 *** dielectric function of carbynes varies along different directions,consistent with the one-dimensional nature of the carbon *** the phonon dispersion of cumulene,there are imaginary frequencies with the lowest value down to-3.817 THz,which indicates that cumulene could be unstable at room temperature and normal pressure.

关键词： carbyne first-principles calculation electronic structure physical properties

An Improved Mumford-Shah Model and Its Applications to Image Processing with the Piecewise Constant Level Set Method

在线全文

学校读者我要写书评

暂无评论

自动化学报 2007年第12期33卷 1259-1262页

作者： SONG jin-ping li Shuai-Jie Institute of Applied Mathematics College of Mathematics and Information ScienceHenan UniversityKaifeng 475004P.R.China

为快分割并且降噪，提高 penalization 学期的古典 Mumford-Shah (MS ) 模型需要，即增加 penalization 参数，它导致目标的渐渐的消失。在这份报纸，我们建议一个改进 Mumford-Shah (IMS ) 模型避免现象，并且采用 piecewise 常数水平... 详细信息

为快分割并且降噪，提高 penalization 学期的古典 Mumford-Shah (MS ) 模型需要，即增加 penalization 参数，它导致目标的渐渐的消失。在这份报纸，我们建议一个改进 Mumford-Shah (IMS ) 模型避免现象，并且采用 piecewise 常数水平集合方法(PCLSM ) 和坡度降下方法解决最小化问题。数字实验被给显示出新模型和算法的效率和优点。

关键词：分段持续水平集方法分割降噪经典MS模型最小化算法