检索结果-南通市图书馆

EFFEcTS OF ce ON cORROSION RESISTANcE OF Az91D MAGNESIUM ALLOY

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) 2005年第2期18卷 129-136页

作者： z.H.Huang X.F.Guo z.M.z.ang c.J.Xu SchoolofMaterialsScienceandEngineering Xi＇anUniversityofTechnologyXi＇an710048China

As-cast and corrosive microstructures of Az91D alloy containing various ce contents were observed by optical microscope (OM). The phase compositions of the alloys before and after the corrosion were analyzed by X-ray diffraction (XRD). Meanwhile, the corrosion resistance of the alloys was tested by weight loss and potentiodynamic polarization curve methods respectively. The results show that rod-like Al4ce phase is formed in Az91D alloy containing certain ce content and as-cast microstructures are refined. Az91D-0.7%ce alloy has good grain refinement effect. The addition of ce can reduce the corrosion rate and corrosion current density of Az91D alloy and those of Az91D-0.1%ce alloy reach the minimum, which are 0.35mg/(cm2·d) and 2.761μA/cm2 with 75% and 86% reduction, respectively. The increasing volume fraction and reticular degree of β phase can improve the corrosion resistance of the alloys.

关键词： Az91D magnesium alloy ce modification microstructure corrosion resistance

REcIPROcATING EXTRUSION OF IN SITU Mg_2Si REINFORcED Mg-Al BASED cOMPOSITE

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2008年第3期21卷 169-177页

作者： z.M. z.ang c.J. Xu X.F. Guo S.z. Jia School of Materials Science ＆ Engineering Xi＇an University of Technology Xi＇an 710048 China

M92Si reinforced Mg-Al based composite with high amount o/silicon was prepared by permanent mould casting, and then extruded by reciprocating extrusion （RE） after the composite was processed by homogenization heat treatment. The effect of RE processing on the morphology and size of M92Si and the mechanical properties of the com- posite were investigated, to develop new ways to refine the M928i phase and improve its shape. The result showed that RE was very useful in refining the M92Si phase. The more the RE processing passes, the better the refining effect would be. Moreover, the uniform distribution of M928i phases would be more in the composite. After the composite was processed by RE for 12 passes, most M92Si phases were equiaxed, with granular diameter below 20 μm, and distributed uniformly in the matrix of the composite. The mechanical properties of the composite could be increased prominently by RE processing, and were much higher than that in the as-cast state. As the temperature rises, the tensile strength is reduced. For the composite RE processed for 12 passes, the tensile strength, yield strength, and elongation are 325.9 MPa, 211.4 MPa, and 3.3% at room temperature, whereas, 288.2 MPa, ,207.7 MPa, and 7.8%, respectively, at 150℃. In comparison with the properties at room temperature, the tensile strength and yield strength are high and only decrease by 11.6% and 1.8% at 150℃. The M928i reinforced Mg-Al based composite possesses good heat resistance at 150℃. The excellent resistance to effect of heat is attributed to the high melting tempera- ture and good thermal stability of fine Mg2Si phases, which are distributed uniformly in the composite, and effectively hinder the grain boundary gliding and dislocation movement.

关键词： Reciprocating extrusion Magnesium alloy In situ composite Elevated temperature property

Spectral measurements of hypervelocity flow in an expansion tunnel

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2019年第1期35卷 24-31,I0002页

作者： c.K.Yuan K.zhou Y.F.Liu z.M.Hu z.L.Jiang State Key Laboratory of High-Temperature Gas Dynamic Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Sciences. University of chinese Academy of Sciences Beijing 100049China china Academy of Aerospace Aerodynamics Beijing 100074China

Atmospheric reentry vehicles and planetary probes fly through the atmosphere at hypervelocity speed. At such speed, there is a significant proportion of heat load to the vehicle surface due to radiative heating. Accurate prediction needs a good knowledge of the radiation spectrum properties. In this paper, a high-speed camera and spectrograph coupled to an intensified charge-coupled device have bee n impleme nted to inv estigate the rad i at io n flow over a semi-cylinder model. The experiments were carried out in the JF16 expansi on timnel with secondary shock velocity of 7.9 km·s^-1. Results show that the emissio n spectrum comprises several atomic lines and molecular band systems. We give detailed data of the radiation spectrum, shock shape, shock detached distance and radiation intensity varying with space and wavelength. This valuable experimental dataset will be helpful to validate computational fluid dynamics codes and radiation models, which equates to increased prediction accuracy of radiation heating. Also, some suggestions for spectral measurement in hypervelocity flow field were list in the end.

关键词： Spectral measurement Hypervelocity flow Radiation Expansion tunnel

Optical coherence tomography angiography in diabetic retinopathy: a review of current applications

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Eye and Vision 2019年第1期6卷 312-321页

作者： Kai Yuan Tey Kelvin Teo Anna c.S.Tan Kavya Devarajan Bingyao Tan Jacqueline Tan Leopold Schmetterer Marcus ang Hobart clinical School Level 343 Collins StreetHobartTAS 7000Australia Singapore National Eye centre 11 Third Hospital AveSingapore 168751Singapore Singapore Eye Research Institute 20 College Road Discovery TowerLevel 6 The AcademiaSingapore 169856Singapore Singapore National Eye centre 11 Third Hospital AveSingapore 168751Duke-NUS Medical School8 College RdSingapore 169857Singapore

Background:Diabetic retinopathy(DR)is a leading cause of vision loss in ***,the standard imaging technique to monitor and prognosticate DR and diabetic maculopathy is dye-based *** the introduction of optical coherence tomography angiography(OcTA),it may serve as a potential rapid,non-invasive imaging modality as an *** text:Recent studies on the role of OcTA in DR include the use of vascular parameters e.g.,vessel density,intercapillary spacing,vessel diameter index,length of vessels based on skeletonised OcTA,the total length of vessels,vascular architecture and area of the foveal avascular *** quantitative measures may be able to detect changes with the severity and progress of DR for clinical *** may also serve as a non-invasive imaging method to detect diabetic macula ischemia,which may help predict visual ***,there are many limitations of OcTA in DR,such as difficulty in segmentation between superficial and deep capillary plexus;and its use in diabetic macula edema where the presence of cystic spaces may affect image *** applications of OcTA in the anterior segment include detection of anterior segment ischemia and iris neovascularisation associated with proliferative DR and risk of neovascular ***:OcTA may potentially serve as a useful non-invasive imaging tool in the diagnosis and monitoring of diabetic retinopathy and maculopathy in the *** studies may demonstrate how quantitative OcTA measures may have a role in detecting early retinal changes in patients with diabetes.

关键词： Optical coherence tomography angiography Fluorescein angiography Diabetic retinopathy Screening Monitoring

Influence of a liquid-filled compartment structure on the incoming shaped charge jet stability

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2021年第2期17卷 571-582页

作者： X.D.zu z.X.Huang z.W.Guan X.c.Yin Y.M.zheng School of Mechanical Engineering Nanjing University of Science and TechnologyXiaolingwei 200Nanjing 210094China School of Engineering University of LiverpoolLiverpoolL693GQUK Department of Mechanics and Engineering Science Nanjing University of Science and TechnologyNanjing 210094China

Liquid-filled compartment structure consists of a bulk steel plate with matrix blind holes which are filled with liquid and a steel front plate to seal up the liquid with rings and *** liquid-filled compartment structure can resist the shaped charge warhead *** paper presents experimental and theoretical investigations of the penetration ability of the residual shaped charge jet emerging from the liquid-filled compartment structure after the penetration process at different impact *** the basis of shock wave propagation theory,the influence of the liquid-filled compartment structure on jet stability is *** interferences of the liquid backflow caused by a reflected shock wave and a back plate on jet stability under different impact angles are also *** addition,the range of the disturbed velocity segments of the jet at different impact angles and the penetration ability of the residual jet are obtained.A theoretical model is validated against the experimental penetration depths.

关键词： compartment structure Shaped charge jet Shock wave Disturbance Stability

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

在线全文

学校读者我要写书评

暂无评论

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 analyzed 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

EVOLUTION OF THE ELEcTROcHEMIcAL cHARAcTERISTIcS DURING PITTING cORROSION OF PURE ALUMINUM IN SODIUM cHLORIDE SOLUTION

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2005年第4期18卷 525-532页

作者： z. z.ang c. cai F.H. cao z.N. Gao J.Q. z.ang c.N. cao Department of chemistry Zhejiang University Hangzhou 310027 China Department of chemistry Ningxia University Yinchuan 750021 China State Key Laboratory for corrosion and Protection of Metals Institute of Metal Research The Chinese

The corrosion behavior of pure aluminum in neutral 3.0% （mass fraction） sodium chloride （Na-cl） solution has been studied using electrochemical impedance spectroscopy （EIS） measurement in conjunction with the scanning electron microscopy （SEM） technique. EIS information on the evolution of pitting corrosion over a period of 15 days has been obtained and analyzed with equivalent circuit technique. The results shown that, during the ensemble constant immersion time, two time constants involved, the high frequency one originated from the protective layer on the corroding surface while the low frequenO, one from the diffusion process or the corrosion reaction and so on. And there existed a period for oxide film to growth and thickening prior to the of the attacking of chloride ions to the substrate. Meanwhile, good relationship between EIS and the material corrosion type/severity has been obtained, which has been interpreted according to the characteristics of corrosion process such as auto acceleration of pitting corrosion and the protection of local anodic reaction to the area around them.

关键词： pure aluminum pitting corrosion electrochemical impedance spectroscopy pit-rnorphology

Energy flexibility characteristics of centralized hot water system in university dormitories

在线全文

学校读者我要写书评

暂无评论

Building Simulation 2023年第4期16卷 641-662页

作者： zhiqin Rao Shuqin chen Isaac Lun Lizhi Shen ang Yu Huijun Fu college of civil Engineering and Architecture Zhejiang UniversityHangzhou 310012China center for Balance Architecture Zhejiang UniversityHangzhou 310012China Department of Architecture and Built Environment University of Nottingham Ningbo ChinaNingbo 315100China Department of General Affairs Zhejiang UniversityHangzhou 310012China

The large-scale application of renewable energy is an important strategy to achieve the goal of carbon neutrality in the building *** flexibility is essential for ensuring balance between energy demand and supply when targeting the maximum penetration rate of renewable energy during the operation of regional integrated energy *** the energy flexibility characteristics of centralized hot water systems,which are an important source of such flexibility,is of great significance to the optimal operation of regional integrated energy ***,in this study,based on the annual real-time monitoring data,the energy flexibility of the centralized hot water system in university dormitories is evaluated from the perspective of available storage capacity(c_(ADR)),recovery time(t_(recovery)),and storage efficiency(η_(ADR)),by the data-driven simulation *** factors influencing the energy flexibility of the centralized hot water system are also *** storage capacity has a strong positive correlation with daily water consumption and a strong negative correlation with daily mean outdoor *** associations indicate that increased water use on the energy flexibility of the centralized hot water system is conducive to optimal *** contrast,higher outdoor temperature is *** hourly mean value of the available storage capacity in spring and winter is found to be around 80 kWh in the daytime,and about twice that in summer and *** time is evenly distributed throughout the year,while t_(recovery)/c_(ADR)in spring and winter is about half that in *** storage efficiency was significantly higher in spring,summer,and winter than in *** hourly mean storage efficiency was found to be about 40%in the *** benefits of activating energy flexibility in spring and winter are the best,because these two seasons have higher available storage capacity and storage efficiency,while the benefit

关键词： energy flexibility centralized hot water system university dormitory back propagation(BP)neural network

An Inverse Approach for Extracting Elastic-plastic Properties of Thin Films from Small Scale Sharp Indentation

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2012年第7期28卷 626-635页

作者： z.S. Ma Y.c. zhou S.G. Long c.S. Lu Key Laboratory of Low Dimensional Materials ~ Application Technology of Ministry of Education Xiangtan Uni-versity Xiangtan 411105 China Faculty of Materials Optoelectronics and Physics Xiangtan University Xiangtan 411105 China Department of Mechanical Engineering Curtin University of Technology Perth WA 6845 Australia

An inverse method for extracting the elastic-plastic properties of metallic thin films from instrumented sharp indentation has been proposed in terms of dimensional analysis and finite element modeling. A wide range of materials with different elastic modulus, yield strength, and strain-hardening exponent were *** to the Nix-Gao model for the depth dependence of hardness H,the relationship between elastic modulus E and indentation depth h can be expressed as By combiningthese two formulas, we find that there is a relationship between yield stress and indentation depth h：where σyO is the yield strength associated with the strain-hardening exponent n, the true hardness Ho and the true elastic modulus *** constant, whichis only related to n, and hH and hE are characteristic lengths for hardness and elastic modulus. The results obtained from inverse analysis show that the elastic-plastic properties of thin films can be uniquely extracted from the solution of this relationship when the indentation size effect has to be taken into account.

关键词： Indentation Elastic-plastic properties Metal thin films Inverse analysis