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应用波束形成法研究51CrV4梯度功能钢的微观结构

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冶金分析 2009年第4期29卷 7-13页

作者： J.Gken m.maikranz-valentin J.Timmerberg S.Luker D.Fuβ J.Feierabend K.Steinhoff Institute of maritime Studies University of Applied Sciences Chair of metal Forming Technology University of Kassel Department of Electrical Engineering University of Applied Sciences Agency of Computer-Generated Imagery Gfai Tech GmbH

对组分梯度功能范围的调整要求已提出,通常通过不同材料组合得以解决。但是这种生产方式一方面需要一系列的工序,另一方面也需要具体的知识,包括所用材料的独特物理及机械特性,尤其是它们的形变及热行为。因此,为了降低能耗,考虑到生态... 详细信息

对组分梯度功能范围的调整要求已提出,通常通过不同材料组合得以解决。但是这种生产方式一方面需要一系列的工序,另一方面也需要具体的知识,包括所用材料的独特物理及机械特性,尤其是它们的形变及热行为。因此,为了降低能耗,考虑到生态需求,一个组分的现代工业设计程序只应包括一种操作程序和一种具有优化性能的范围大的材料。同时对同质的工件初样进行热处理及机械处理保证了控制材料能够具有最终元件性能的梯度功能。第一步,研究不同热处理对CrV-合金热处理矩形条钢(51CrV4)微观结构演化的影响。生产出只具有铁素体-珠光体、铁素体-珠光体-贝氏体和马氏体结构的条钢。与振动的振幅衰减相关的时间由声学照相机测定。这种声学照相机可以产生彩码声音图谱,显示覆盖于已记录样品图像上噪音的强度和来源。基于作为常规信号处理方法的波束形成概念,该声音分析用来控制换能器阵列上信号的接收或传播方向。条钢的独特微观结构状况造成了振动特性的显著变化。

关键词：钢梯度功能内耗波束形成法

ASSESSING THE LINK BETWEEN PUBLIC OPINION AND SOCIAL SUSTAINABILITY IN BUILDING AND INFRASTRUCTURE PROJECTS

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Journal of Green Building 2015年第3期10卷 177-190页

作者： Vanessa valentin Susan m.Bogus Department of Civil Engineering University of New MexicoAlbuquerqueNM 87131USA

Increasing the use of social sustainability in the decision-making process for build-ing and infrastructure projects requires that it be defined such that it can be evaluated *** potential indicator of social sustainability in infrastruc-ture projects is public opinion,which can provide a means to evaluate the level of social sustainability on a project based on personal *** opinion includes both support and opposition for a *** this study,the causes or triggers for public opposition to a construction project are identified and then compared to principles of social sustainability to determine if they are *** case study projects were used to identify common triggers of public *** results suggest that common triggers of public opposition are related to land acquisition,escalating construction costs and the presence of endangered species on the project *** of the twelve principles of social sustainability that were identified were determined to be related to public *** results of this study suggest that public opposition could be used as a measure for some elements of social sus-tainability but that further research into other measures for social sustainability is necessary.

关键词： social sustainability public opinion triggers of public opposition to building and infrastructure projects

Real Submanifolds in Complex Spaces

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Acta mathematica Sinica,English Series 2017年第1期33卷 1-20页

作者： valentin BURCEA The Departament of mathematics The Federal University of Santa Catarina Brazil

Let （Zll, . . . , Z1N,... , Zml,. . . , ZmN, Wll,. . . , Wmm） be the coordinates in C^mN＋m2. In this note we prove the analogue of the Theorem of moser in the case of the real-analytic submanifold m defined as follows W=zz-t＋O（3）,where W ={wij}1≤ i,j≤ m and Z ={Zij}1≤i≤ m,1≤j≤N We prove that m is biholomorphically equiva-lent to the model W =zz-tif and only if is formally equivalent to it.

关键词： Real submanifold equivalence problem fischer decomposition

Load dependent microstructural evolution in an as-cast 26%Cr high chromium cast iron during unlubricated sliding

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Friction 2022年第8期10卷 1258-1275页

作者： U.Pranav NAYAK Sebastian SUÁREZ valentin PESNEL Frank mÜCKLICH maría Agustina GUITAR Department of materials Science Saarland UniversitySaarbrücken 66123Germany materials Engineering Center Saarland Saarbrücken 66123Germany Ecole Européenne d’ingénieurs en Génie des matériaux Universitéde LorraineNancy 54000France

In the current study,an as-cast 26%Cr high chromium cast iron(HCCI)alloy was subjected to dry-sliding linear wear tests,under different *** loads were selected based on analytically computing the critical load(PC)i.e.,the load necessary to induce plastic *** PC was calculated to be 15 N and accordingly,a sub-critical load(5 N)and an over-critical load(20 N)were *** influence of increasing the load during the wear test was investigated in terms of the matrix microstructural behaviour and its ability to support the surrounding *** morphological aspects of the wear tracks,and the deformed matrix microstructure adjacent and underneath the track was analysed by confocal laser scanning microscope(CLSm)and scanning electron microscope(SEm),*** evidence of plastic deformation of the matrix was observed below *** the contrary,at loads equal to and higher than PC,the austenitic matrix plastically deformed as evidenced by the presence of slip *** backscattered diffraction(EBSD)measurements in terms of grain reference orientation deviation,and micro-Vickers hardness of the austenitic matrix indicated a deformation depth of about 40μm at the maximum applied load of 20 *** active wear mechanisms during sliding were a combination of both adhesive and abrasive wear,although increasing the load shifted the dominant mechanism towards *** was primarily attributable to the increased propensity for carbide cracking and fracturing,combined with the inability of the hardened austenitic matrix surface and sub-surface to adequately support the broken carbide ***,the shift in the dominant wear mechanism was also reflected in the wear volume and subsequently,the wear rate.

关键词： high chromium cast iron unlubricated sliding plastic deformation wear resistance carbide spallation matrix hardness

Transient Charge Trapping in Eu^(3+)-Doped Nanocomposites by Ultrafast Laser Excitation

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Journal of Rare Earths 2006年第6期24卷 663-667页

作者： Sergie Lysenko Jose Jimenez valentin Vikhnin Department of Physics University of Puerto Rico Mayaguez PR 00681USA

Eu^3＋ was incorporated as probe ions into nanocomposite glasses, such as metal silver doped phosphate glass and crystalline nanocomposites Si-enriched SiO2 glass. Luminescence studies show that the doped europium ions are present as trivalent Eu^3＋ , and are distributed in the matrix on the boundary surface of nanoparticles. The valence switching from Eu^3＋ to Eu^2＋ was observed in Si-SiO2 nanocomposites when ultrafast laser excitation was applied. In silver metal nan-oparticles embedded aluminophosphate glass, a time-resolved ultrafast degenerate-four-wave-mixing （DFWm） experiment shows enhanced third-order nonlinearity at zero-delay time, followed by a bell-like signal buildup. It is attributed to the creation of electronic polaron and vibronic Wannier-mott exciton （WmE）. In europium codoped sample, however, the bell-like signal is depressed. All the above observations are interpreted as the result of a strong Coulomb interaction between conduction electrons produced inside the nanoparticles by laser excitation and Eu^3＋ ions residing near the surface. The trivalent europium ions play the role as positive boundary charges attracting electrons. This results in temporary formation of Eu^2＋ , and blocks the resonant tunneling transition in the silver-glass system to avoid creating large radius polaron.

关键词： nanocomposite europium ultrafast excitation rare earths

Application of machine learning to assess the influence of microstructure on twin nucleation in mg alloys

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npj Computational materials 2024年第1期10卷 2988-3001页

作者： Biaobiao Yang valentin Vassilev-Galindo Javier Llorca ImDEA materials Institute C/Eric Kandel 2Getafe28906 MadridSpain Department of materials Science Polytechnic University of Madrid/Universidad Politécnica de MadridE.T.S.de Ingenieros de Caminos28040 MadridSpain

Twin nucleation in textured mg alloys was studied by means of electron back-scattered diffraction in samples deformed in tension along different orientations in more than 3000 *** addition,28 relevant parameters,categorized in four different groups(loading condition,grain shape,apparent Schmid factors,and grain boundary features)were also recorded for each *** information was used to train supervised machine learning classification models to analyze the influence of the microstructural features on the nucleation of extension twins in mg *** was found twin nucleation is favored in larger grains and in grains with high twinning Schmid factors,but also that twins may form in the grains with very low or even negative Schmid factors for twinning if they have at least one smaller neighboring grain and another one(or the same)that is more ***,twinning of small grains with high twinning Schmid factors is favored if they have low basal slip Schmid factors and have at least one neighboring grain with a high basal slip Schmid factor that will deform *** results reveal the role of many-body relationships,such as differences in stiffness and size between a given grain and its neighbors,to assess extension twin nucleation in grains unfavorably oriented for twinning.

关键词： grain alloys microstructure

Design and fabrication of crack-junctions

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microsystems & Nanoengineering 2017年第1期3卷 71-79页

作者： valentin Dubois Frank Niklaus Göran Stemme KTH Royal Institute of Technology Micro and NanosystemOsquldas väg 10Stockholm 10044Sweden

Nanogap electrodes consist of pairs of electrically conducting tips that exhibit nanoscale *** are building blocks for a variety of applications in quantum electronics,nanophotonics,plasmonics,nanopore sequencing,molecular electronics,and molecular ***-junctions(CJs)constitute a new class of nanogap electrodes that are formed by controlled fracture of suspended bridge structures fabricated in an electrically conducting thin film under residual tensile *** advantages of the CJ methodology over alternative technologies are that CJs can be fabricated with wafer-scale processes,and that the width of each individual nanogap can be precisely controlled in a range from o2 to 4100 *** the realization of CJs has been demonstrated in initial experiments,the impact of the different design parameters on the resulting CJs has not yet been *** we investigate the influence of design parameters such as the dimensions and shape of the notches,the length of the electrode-bridge and the design of the anchors,on the formation and propagation of cracks and on the resulting features of the *** verify that the design criteria yields accurate prediction of crack formation in electrode-bridges featuring a beam width of 280 nm and beam lengths ranging from 1 to 1.8μ*** further present design as well as experimental guidelines for the fabrication of CJs and propose an approach to initiate crack formation after release etching of the suspended electrode-bridge,thereby enabling the realization of CJs with pristine electrode surfaces.

关键词： arrays crack-junctions lithography nanofabrication nanogap electrodes notches optimization tunneling junctions

Busting the efficiency of SAPO-34 catalysts for the methanol-to-olefin conversion by post-synthesis methods

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Chinese Journal of Chemical Engineering 2020年第8期28卷 2022-2027页

作者： Guoju Yang Ji Han Yujun Huang Xiaoxin Chen valentin Valtchev State Key Laboratory of Inorganic Synthesis and Preparative Chemistry College of ChemistryJilin University2699 Qianjin StreetChangchun 130012China International Center of Future Science Jilin University2699 Qianjin StreetChangchun 130012China Normandie Univ ENSICAENUNICAENCNRSLaboratoire Catalyse et Spectrochimie6 Marechal Juin14050 CaenFrance

As an effective non-petroleum based process for producing light olefins, the methanol-to-olefin(mTO) route has become an indispensable alternative to the industrial production of light olefins. The silicoaluminophosphate SAPO-34 zeolite(CHA-type structure) has proven to be an efficient industrial catalyst for the production of ethylene and propylene by the mTO reaction. However, the inherent structure and related diffusion limitations of SAPO-34 limit the mass transport and thus cause rapid deactivation of the catalyst. Fabrication of hierarchical SAPO-34 zeolite is one of the most effective strategies to address the intrinsic diffusion limitation. As simple, inexpensive, and efficient approach, the post-synthetic route has attracted considerable attention and widely used to introduce secondary meso-/macropores into the microporous SAPO-34 material. Significant effort has been dedicated to the development of post-synthesis strategies to prepare hierarchical SAPO-34 zeolite, thereby enhancing its catalytic performance in the mTO process. This mini-review addresses the post-synthesis preparation of hierarchical SAPO-34 catalysts and their mTO performance. Furthermore, some current problems and prospects of the post-synthesis route to hierarchical SAPO-34 catalysts are also revised. We expect this minireview to inspire the more efficient preparation of hierarchical SAPO-34 catalysts for the mTO process.

关键词： Zeolites SAPO-34 Post-synthesis treatment Hierarchical mTO

Abundance and spatial dynamics of bacterioplankton in the Seven Rila Lakes,Bulgaria

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Chinese Journal of Oceanology and Limnology 2010年第3期28卷 451-458页

作者： Silvena BOTEVA Ivan TRAYKOV Anelia KENAROVA valentin BOGOEV Biology Faculty Sofia University"St. Kliment Ohridski"8 Dragan Tzankov Blvd. 1611 Sofia Bulgaria

In the high mountain oligotrophic Seven Rila Lakes (2 095–2 535 m a.s.l.) bacterial abundance was recorded in July and September 2006. In July, bacterial abundance (average (3.32±2.5)×105 cell/ml) in the lakes correlated negatively with elevation, while in September (average (26.39±7.1)×105 cell/ml) this pattern was altered and the greatest abundance of bacteria occurred at the highest ((39.05±1.5)×105 cell/ml) and the lowest ((30.63±6.0)×105 cell/ml) elevated lakes. Regression analyses suggested that the principal factor controlling bacterial abundance, in both July and September, was inorganic nitrogen (NO3-N and NH4-N; R2=0.70, Pmajor regulating factors were temperature (R2=0.66, Pmber. All factors, except NO3-N, had a positive effect on bacterial abundance.

关键词： bacterial abundance high mountain lake Rila mountain environmental factor bottom-up control