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Application of Diffusion Brazing in Stockage of Vacuum Electronic Devices

稀有金属材料与工程 2011年第S3期40卷 19-22页

作者： Li Haitao, Qu Wenqing, Zhuang Hongshou Beijing University of aeron. & Astro., Beijing 300072, China Beijing Univ aeron & Astro Beijing 300072 Peoples R China

The vacuum electronic device is the key components widely used in the fields of radar, navigation, electronic warfare and so on. Multi-brazing process is adopted in the manufacturing, and the leakage is easy to happen at many parts, such as brazed seams and base materials of tube shell, leading breakage of the devices. But now the brazing filler metal used in the stockage of vacuum electronic devices is very seldom. For the safe of vacuum electronic devices, stockage temperature must be lower than the brazing temperature. Gallium is liquid at room temperature, and has a lower vapor pressure. The Ga-based alloy can diffuse with the high melting point metal, and then form heat-resistance and a good sealing performance of solid-state alloys. In this study three kinds of Ga-based alloys used for the stockage were developed. The diffusion brazing for the stockage on three materials with defect, such as OFHC, kovar and Ag-Cu brazed seams was carried out. The influence factors such as parent materials, brazing filler metal and brazing temperature on the stockage quality were discussed. The results indicated that parent materials, brazing filler metals and brazing temperature had obvious influences on stockage. For OFHC and Ag-Cu filler with defects, the stockage effects were better than kovar. The effect of Ga-In-Cu alloy was the best because the compact diffusion layer was formed between the stockage brazing materials and base materials. As the brazing temperature went up, the diffusion layer formed between stockage material and OFHC, kovar became obviously thicker, the stockage effect got better. For Ag-Cu brazing seams, the stockage effect was satisfactory at 500 ℃, erosion will happen at the higher temperature.

关键词： vacuum electronic devices vacuum brazing stockage diffusion brazing

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CHARACTERISATION OF RATIONAL AND NURBS DEVELOPABLE SURFACES IN COMPUTER AIDED DESIGN

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Journal of Computational Mathematics 2021年第4期39卷 556-573页

作者： Leonardo Fernandez-Jambrina etsi Navales Universidad Politecnica de Madrid28040-MadridSpain

In this paper we provide a characterisation of rational developable surfaces in terms of the blossoms of the bounding curves and three rational functions∧,M,ν.Properties of developable surfaces are revised in this *** particular,a closed algebraic formula for the edge of regression of the surface is obtained in terms of the functions∧,M,ν,which are closely related to the ones that appear in the standard decomposition of the derivative of the parametrisation of one of the bounding curves in terms of the director vector of the rulings and its *** is also shown that all rational developable surfaces can be described as the set of developable surfaces which can be constructed with a constant∧,M,ν.The results are readily extended to rational spline developable surfaces.

关键词： NURBS Bezier Rational Spline NURBS Developable surfaces

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DEVELOPABLE SURFACE PATCHES BOUNDED BY NURBS CURVES

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Journal of Computational Mathematics 2020年第5期38卷 715-731页

作者： Leonardo Fernandez-Jambrina Francisco Perez-Arribas etsi Navales Universidad Polit´ecnica de Madrid28040-MadridSpain

In this paper we construct developable surface patches which are bounded by two rational or NURBS curves,though the resulting patch is not a rational or NURBS surface in *** is accomplished by reparameterizing one of the boundary *** reparameterization function is the solution of an algebraic *** the relevant case of cubic or cubic spline curves,this equation is quartic at most,quadratic if the curves are B´ezier or splines and lie on parallel planes,and hence it may be solved either by standard analytical or numerical methods.

关键词： NURBS B´ezier Rational,Spline NURBS Developable surfaces

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Ignition　and　Extinction　of　Monopropellant　Droplet　with　Lewis　Number　Different　from　Unity

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Journal of Thermal Science 1994年第1期3卷 53-60页

作者： Fernando F. Fachini(Instituto Nacional de Pesquisas Espaciais-INPE, Rodovia Presidente Dutra Km 40, 12630-000 Cachoeira Paulista-SP, Brasil)Amable M. Linan 1. Instituto Nacional de Pesquisas Espaciais-INPE Rodovia Presidente Dutra Km 40 12630-000 Cachoeira Paulista-SP Brasil 2. E.T.S.I. aeronáuticos Univ. Ploitécnica de Madrid Plaza Cardenal Cisneros 3 28400 Madrid Espa?a

E.T.S.I. aeronauticos, Univ. Ploitecnica de Madrid, Plaza Cardenal Cisneros 3, 28400-Madrid, Espana

关键词： ignition extinction monopropellant Lewis number effects

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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

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Optimal laser intensity profiles for a uniform target illumination in direct-drive inertial confinement fusion

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High Power Laser Science and Engineering 2014年第4期2卷 62-67页

作者： Mauro Temporal Benoit Canaud Warren J.Garbett Rafael Ramis Centre de Mathématiques et de Leurs Applications ENS Cachan and CNRS 61 Av.du President WilsonF-94235 Cachan Cedex France CEA DIF F-91297 Arpajon Cedex France AWE plc Aldermaston ReadingBerkshire RG7 4PR United Kingdom etsi aeronuticos Universidad Polit'ecnica de Madrid28040 Madrid Spain

A numerical method providing the optimal laser intensity profiles for a direct-drive inertial confinement fusion scheme has been developed. The method provides an alternative approach to phase-space optimization studies, which can prove computationally expensive. The method applies to a generic irradiation configuration characterized by an arbitrary number NBof laser beams provided that they irradiate the whole target surface, and thus goes beyond previous analyses limited to symmetric configurations. The calculated laser intensity profiles optimize the illumination of a spherical *** paper focuses on description of the method, which uses two steps: first, the target irradiation is calculated for initial trial laser intensities, and then in a second step the optimal laser intensities are obtained by correcting the trial intensities using the calculated illumination. A limited number of example applications to direct drive on the Laser Mega Joule(LMJ) are described.

关键词： direct drive inertial confinement fusion laser system

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Rock mass structural recognition from drill monitoring technology in underground mining using discontinuity index and machine learning techniques

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International Journal of Mining Science and Technology 2023年第5期33卷 555-571页

作者： Alberto Fernández JoséA.Sanchidrián Pablo Segarra Santiago Gómez Enming Li Rafael Navarro Universidad Politécnica de Madrid–etsi Minas y Energía Spain Universidad de Salamanca–GIR Charrock Spain

A procedure to recognize individual discontinuities in rock mass from measurement while drilling(MWD)technology is developed,using the binary pattern of structural rock characteristics obtained from in-hole images for *** from two underground operations with different drilling technology and different rock mass characteristics are considered,which generalizes the application of the methodology to different sites and ensures the full operational integration of MWD data *** approaches are followed for site-specific structural model building:a discontinuity index(DI)built from variations in MWD parameters,and a machine learning(ML)classifier as function of the drilling parameters and their *** prediction ability of the models is quantitatively assessed as the rate of recognition of discontinuities observed in borehole *** between the parameters involved in the models for each site,and differences in their weights,highlight the site-dependence of the resulting *** ML approach offers better performance than the classical DI,with recognition rates in the range 89%to 96%.However,the simpler DI still yields fairly accurate results,with recognition rates 70%to 90%.These results validate the adaptive MWD-based methodology as an engineering solution to predict rock structural condition in underground mining operations.

关键词： Drill monitoring technology Rock mass characterization Underground mining Similarity metrics of binary vectors Structural rock factor Machine learning

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Electron Beam Curing of Advanced Composites

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Journal of Materials Science & Technology 2000年第6期16卷 627-630页

作者： Gang SUI, Weihong ZHONG Dep. of Materials Sci. and Eng. Beijing Univ. of Aeron. and Astron. Beijing 100083 China

The fundamental concept of electron beam method and the application in cure of composites are elaborated in this paper. The components of electron beam curing system are introduced. The mechanisms of interaction between electron beam and polymer matrix composites are presented. Recent studies reported including work of authors themselves on electron beam curing of composites are also discussed. Moreover, the authors believe that it is necessary to do the basic research about understanding how electron beam affects cured network and the mechanical/physical properties of the composites, for establishing a quantitative or semi-quantitative formulation.

关键词： Electron Beam Curing of Advanced Composites EB

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Depth of closure:New calculation method based on sediment data

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International Journal of Sediment Research 2018年第2期33卷 198-207页

作者： Luis Aragonés Jose Ignacio Pagán Isabel López José C.Serra Department of civil engineering University of Alicante Department of transportation ETSI Caminos Polytechnic University of Valencia

Obtaining depth of closure(DoC) in an accurate manner is a fundamental issue for coastal engineering,since good results for coastal structures and beach nourishment depend mainly on DoC. Currently, there are two methods for obtaining the DoC, mathematical formulations and profile surveys. However, these methods can incur important errors if one does not take into account the characteristics and morphology of the area, or if one does not have a sufficiently long time series. In this work the DoC is obtained from the break in the trend of the sediment with the depth, that is, in general with the increase of the depth a decrease in the size of the sediment takes place. However, at one point this tendency changes and the size increases, and then decreases again. When comparing the point where the minimum sediment size occurs before the increase, it is observed that the error incurred is small compared to other methods. If the Standard Deviation of Depth Change(SDDC) method is considered as the most accurate method, the error incurred by the proposed method is less than 7%. In addition, it can be seen that the dispersion of the sediment method always occurs outside the zone of bar movement. Whereas in the methods of profiles survey(using 2 cm precision profiles), sometimes the DoC is obtained within the active zone of bar movement. In addition, where the relative minimum of the median sediment size is found, and the sizes of 0.063 and 0.125 mm predominate in the composition of the sample. Therefore, this new method allows the precise location of the DoC to be obtained in a fast and simple way. Furthermore, this method has the advantage that it is not affected by the modifications that may be experienced by both the study area and the cross-shore beach profile.

关键词： Depth of Closure Median sediment size Profile surveys Profile change GIS

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Study on the Compatibility of SMA and Composite Materials by Holographic Interferometry

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Chinese Journal of Lasers 2000年第6期9卷 66-71页

作者： ZHAO Zhimin (Applied Optics Research Section, Nanjing University of aeronautics & Astronautics, Nanjing 210016, China) Applied Opt. Res. Section Nanjing Univ. of Aeron. and Astron. Nanjing 210016 China

With the help of holographic interferometry a study is conducted on the compatibility of SMA (shape memory alloy) and epoxy resin composite material. The paper gives experiment results and analysis which show that after coupling SMA with the composite material, the flexural rigidity of composite material is somewhat reinforced. Under certain conditions, SMA and the epoxy resin composite material are compatible.

关键词： SMA composite material compatibili?

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