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Cui C.,Beijing Spacecrafts | Guo T.,Beijing University of Technology | Wang Y.,Beijing University of Technology | Dai Q.,Beijing University of Technology
AIP Conference Proceedings | Year: 2017

Hydrostatic slideway is a key part in the heavy-duty gantry CNC machine, which supports the total weight of the gantry and moves smoothly along the table. Therefore, the oil film between sliding rails plays an important role on the carrying capacity and precision of machine. In this paper, the oil film in no friction is simulated with three-dimensional CFD. The carrying capacity of heavy hydrostatic slideway, pressure and velocity characteristic of the flow field are analyzed. The simulation result is verified through comparing with the experimental data obtained from the heavy-duty gantry machine. For the requirement of engineering, the oil film carrying capacity is analyzed with simplified theoretical method. The precision of the simplified method is evaluated and the effectiveness is verified with the experimental data. The simplified calculation method is provided for designing oil pad on heavy-duty gantry CNC machine hydrostatic slideway. © 2017 Author(s).


Rong A.,Beihang University | Pang L.,Beihang University | Liu M.,Beihang University | Yang D.,Beijing Spacecrafts
Entropy | Year: 2017

Carbon Dioxide Removal Assembly (CDRA) is one of the most important systems in the Environmental Control and Life Support System (ECLSS) for a manned spacecraft. With the development of adsorbent and CDRA technology, solid amine is increasingly paid attention due to its obvious advantages. However, a manned spacecraft is launched far from the Earth, and its resources and energy are restricted seriously. These limitations increase the design difficulty of solid amine CDRA. The purpose of this paper is to seek optimal design parameters for the solid amine CDRA. Based on a preliminary structure of solid amine CDRA, its heat and mass transfer models are built to reflect some features of the special solid amine adsorbent, Polyethylenepolyamine adsorbent. A multi-objective optimization for the design of solid amine CDRA is discussed further in this paper. In this study, the cabin CO2 concentration, system power consumption and entropy production are chosen as the optimization objectives. The optimization variables consist of adsorption cycle time, solid amine loading mass, adsorption bed length, power consumption and system entropy production. The Improved Non-dominated Sorting Genetic Algorithm (NSGA-II) is used to solve this multi-objective optimization and to obtain optimal solution set. A design example of solid amine CDRA in a manned space station is used to show the optimal procedure. The optimal combinations of design parameters can be located on the Pareto Optimal Front (POF). Finally, Design 971 is selected as the best combination of design parameters. The optimal results indicate that the multi-objective optimization plays a significant role in the design of solid amine CDRA. The final optimal design parameters for the solid amine CDRA can guarantee the cabin CO2 concentration within the specified range, and also satisfy the requirements of lightweight and minimum energy consumption. © 2017 by the authors.


Hu H.,Beijing Spacecrafts | Hu H.,China Aerospace Science and Technology Corporation | Pan B.,China Aerospace Science and Technology Corporation | Sun J.,China Aerospace Science and Technology Corporation
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2017

Based on the contact mechanics, tribology and the pseudo static theory of angular contact bearing, the theoretical computational formulae of the friction torque of solid lubrication angular contact ball bearings are obtained. Based on this, the relationship between the friction torque of spacecraft driving mechanism shafting is studied and the theoretical analysis and experimental verification for the friction torque are presented after fully considering the boundary conditions on the shafting. The result shows that the friction torque of the angular contact coated solid lubricating film increases with the increase of axial preload and the friction torque of shafting increases with the increase of tightening torque after it reaches the critical value. Furthermore the theoretical and experimental values keep consistent. So theoretical computational formulae of friction torque based on pseudo static theory is suitable for the solid lubrication angular contact bearing and spacecraft driving mechanism shafting at low speed. © 2017 Journal of Mechanical Engineering.


Wu H.,Jiangsu Key Laboratory of New Energy Generation and Power Conversion | Wan C.,Beijing Spacecrafts | Sun K.,Tsinghua University | Xing Y.,Jiangsu Key Laboratory of New Energy Generation and Power Conversion
IEEE Transactions on Power Electronics | Year: 2015

In this letter, a quasi two-stage architecture is proposed for wide input voltage range (voltage ranges ≈ 1:2) and high step-down multiple output conversion. A dc-DCX, which operates as a dc-dc converter with regulated output when the input voltage is low and as a dc-dc transformer with unregulated output when the input voltage is high, is adopted in the first stage to provide optimized intermediate dc-bus voltages for the second-stage point-of-load converters. The input and output of the dc-DCX are in series and connected to the total input voltage. Hence, part of the input power is directly transferred to the intermediate bus without conversion. The devices' voltage stresses and the transformer turns ratio of the dc-DCX are reduced by using the proposed quasi two-stage architecture. Thus, the conversion efficiency is improved significantly. Furthermore, a dual-output LLC resonant converter with hybrid center-tapped and full-bridge rectifier is proposed for the dc-DCX to achieve high efficiency and high power density. A 100-W prototype with three outputs is built and tested to verify the analysis. © 2014 IEEE.


Zhang Y.,Taiyuan University of Technology | Zhang B.,Beijing Spacecrafts
Journal of Materials Science: Materials in Electronics | Year: 2014

The effect of grain size on the dielectric properties of MgO-TiO 2-ZnO-CaO ceramics is investigated. Attrition milling is chosen to obtain nanometre particle size from micrometre particle size powders. Additionally, the present study is focused on the effect of the nature of milling balls on εr, tanδ, and the temperature coefficient of capacitance (abbreviated as TCC). For that, three kinds of balls are tested: A1, A2 or A5 mm stabilised zirconia balls. For the samples milled by A2 mm balls for 10 h, the ceramics sintered at 1,270 °C showed favorable dielectric properties with εr = 22.6, tanδ = 1.3 × 10-5, and TCC = 19.1 ppm/°C. © 2014 Springer Science+Business Media New York.


Chen X.,University of Electronic Science and Technology of China | Jia C.,University of Electronic Science and Technology of China | Wan Z.,University of Electronic Science and Technology of China | Zhang J.,Beijing Spacecrafts | Yao X.,Lanzhou University
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2014

Three phenothiazine-triphenylamine-based organic dyes (CD-1, CD-2 and CD-3) are designed based on the dye WD-8. The geometries, electronic structures, and electronic absorption spectra of these dyes before and after binding to TiO 2 are studied by density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The calculated geometries indicate that these dyes show good steric hindrance effect which is advantage to inhibit the close intermolecular π-π aggregation effectively. The lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) energy levels of these dyes could ensure positive effect on the process of electron injection and dye regeneration. The simulated spectra of CD-1∼3 show better absorption than that of WD-8 in the low energy zone. All the calculated results demonstrate that these dyes could be used as potential sensitizers for DSSCs and show better performances than WD-8. © 2013 Elsevier B.V. All rights reserved.


Jia C.,University of Electronic Science and Technology of China | Zhang J.,University of Electronic Science and Technology of China | Zhang L.,Beijing Spacecrafts | Yao X.,Lanzhou University
New Journal of Chemistry | Year: 2011

The properties of two donor-acceptor compounds tetrathiafulvalene- acenaphtho[1,2-b] quinoxaline (1) and tetrathiafulvalene-3-nitro-acenaphtho[1,2- b]quinoxaline (2) have been investigated by solution-state studies (electrochemistry, absorption, self-assembly) and theoretical calculations (DFT, TD-DFT). The electrochemical studies indicate the nitro-substituted effect on their redox properties is negligible. Both compounds show effective intramolecular charge transfer (ICT) transitions in the UV-Visible range in solution. Compared with compound 1, compound 2 has a bathochromic shift in the absorption spectra, the λ max-ICT has been extended from 20800 cm -1 to 19700 cm -1 (480 nm to 507 nm). In addition, when the nitro group is employed, the self-assembly characteristics of the two compounds are substantially changed from ribbon-like nanostructures to root-like nanostructures. Density functional theory (DFT) calculations provide insights into their molecular geometries, electronic structures, and physico-chemical properties. © 2011 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.


Zhang Y.,Taiyuan University of Technology | Wu S.,Tianjin University | Zhang B.,Beijing Spacecrafts | Wu X.,Taiyuan University of Technology
Journal of Materials Science: Materials in Electronics | Year: 2014

The effect of Li2O3-B2O 3-SiO2 (LBS) liquid-phase additives on the sintering, microstructures, and dielectric properties of MgO-TiO2-ZnO-CaO (MTZC) ceramics was investigated. It was found that the sintering temperature could be lowered easily, and the dielectric properties of MTZC ceramics could be greatly improved by adding a small amount of LBS solution additives. With the addition of 10 wt% LBS, the ceramics sintered at 900 °C showed favorable dielectric properties with εr = 21.7, Qf = 5.0 × 104 GHz, and TCF = -21.6 ppm/ °C. The distructive physical analysis showed an excellent co-firing interfacial behavior between the MTZC ceramic and the Ag electrode. It indicated that MTZC ceramics with LBS solution additives have a number of potential applications on passive integrated devices based on the low-temperature co-fired ceramics technology. © 2014 Springer Science+Business Media New York.


Wan Z.,University of Electronic Science and Technology of China | Jia C.,University of Electronic Science and Technology of China | Zhang J.,Beijing Spacecrafts | Yao X.,Lanzhou University | Shi Y.,University of Electronic Science and Technology of China
Dyes and Pigments | Year: 2012

A novel and highly conjugated donor-acceptor dyad consisting of tetrathiafulvalene unit covalently attached to a porphyrin unit has been synthesized and characterized. As compared to tetraphenylporphyrin, the fluorescence intensity and lifetime of the dyad was decreased owing to photoinduced electron transfer between the tetrathiafulvalene and porphyrin units in the excited state. The fluorescence intensity of the dyad was recovered dramatically upon the addition of Fe(ClO 4) 3· 6H 2O to a solution of the dyad, and the fluorescence intensity grows with an increasing amount of Fe(ClO 4) 3·6H 2O. More importantly, the fluorescence intensity of the dyad can be reversibly modulated by the sequential electrochemical oxidation and reduction of the tetrathiafulvalene unit, thus a new redox fluorescence switch based on this dyad has been constructed. © 2011 Elsevier Ltd. All rights reserved.


Zhang L.,Central South University | Gong W.,Beijing Spacecrafts | Chen J.,Central South University | Du Y.,Central South University
Calphad: Computer Coupling of Phase Diagrams and Thermochemistry | Year: 2014

Based on the first-principles computed activation energy, the frequency prefactor for impurity diffusivity of Pt in fcc Al was calculated by means of the Swalin correlation. The Vignes-Birchenall correlation originally developed for binary solutions with unlimited solubility was simplified to evaluate the interdiffusivities in binary terminal solutions with limited solubility. The simplified correlation was validated in fcc Ni-Al alloys, and then applied to evaluate interdiffusivities in fcc Pt-Al alloys, showing a reasonable agreement with the limited experimental data. On the basis of the limited experimental diffusivities in the literature and the presently evaluated interdiffusivities, a set of reasonable atomic mobilities in fcc Pt-Al alloys was established. This combinational approach by utilizing the limited experimental data, first-principles results, semi-empirical/empirical correlations and DIffusion Controlled TRAnsformation (DICTRA) software package is of general validity and applicable in other binary alloys with limited diffusivity information. © 2014 Elsevier Ltd. All rights reserved.

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