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Pu Q.,North University of China | Zhen Y.,North University of China | Rui S.,Avic Aerospace Life Support Industries Ltd
Journal of Information and Computational Science | Year: 2015

A numerical simulation model for the airbags landing system is developed by using control volume method to research the cushioning performance of the airbag landing system and analysis the affect of the typical external factors on the buffer characteristics. A series of experiments were conducted to verify the validity of the simulation model by comparing the calculation results and test data. By analyzing the simulation results, the influence of external factors on cushioning buffer are obtained. From the results we can see that the affect of the important factors such as the weight of airdropped loads, landing velocity and the altitude of landing site are significant. Based on the simulation model, the environmental adaptability of the airbags buffer system was analyzed too. Some suggestions for the adaptability of the airbags buffer system are provided and its cushioning characteristics are estimated. Copyright © 2015 Binary Information Press. Source

Zhu E.,Nankai University | Sun Q.,Nankai University | Tan P.,Nankai University | Chen Z.,Nankai University | And 2 more authors.
Nonlinear Dynamics | Year: 2014

Powered parafoil is a kind of flexible wing vehicle, which is composed of traditional parafoil system and power plant. Considering the relative motion of canopy and payload, two coordinates are built separately to analyze the motion properties of canopy and payload. According to the Kirchhoff motion equation, eight degrees of freedom (DOF) dynamic model of powered parafoil is built, including six DOF motion of canopy and relative yaw and relative pitch motion of payload. The simulation focuses on the basic motions of gliding, turning, flare landing and the responses to the wind and power. The simulation results verify the validity of dynamic model of powered parafoil. © 2014, Springer Science+Business Media Dordrecht. Source

Chen X.-S.,Beijing University of Chemical Technology | Xu G.-Z.,Beijing University of Chemical Technology | Xu G.-Z.,Beijing Technology and Business University | Zhang S.,Beijing University of Chemical Technology | And 6 more authors.
Journal of Applied Polymer Science | Year: 2013

Our previous study showed that aramid fibers (AFs) could significantly enhance the mechanical properties of polypropylene (PP) composites; for example, the tensile strength of PP/AF composites with 30 wt % AF increased by 65.6%, whereas the Izod notched impact strength was almost five times that of pure PP. However, the fire performance of the PP/AF composites was not ideal. In this study, decabromodiphenyl ethane and antimony trioxide [Sb 2O 3; decabromodiphenyl ethane-antimony trioxide (D-S)] were introduced to improve the flame retardancy of PP/D-S/AF composites. Fourier transform infrared spectroscopy and scanning electron microscopy techniques were used to investigate the possible chemical reaction between the phosphate coupling agent and AFs. The mechanical properties of the PP composites were evaluated by tensile, flexural, and impact tests. The flame retardancy was characterized by limiting oxygen index and UL-94 burning tests. The thermal properties of the PP composites was also investigated by combined thermogravimetry-differential thermal analysis. The results show that good interfacial adhesion between the fibers and the PP matrix was formed in the presence of the phosphate coupling agent. The flame retardancy and mechanical properties of the PP/D-S/AF composites were significantly improved by the incorporation of AFs and D-S. The sample containing 30 wt % D-S and 20 wt % AF reached V-0 in the UL-94 test. The maximal char residue of PP/D-S/AF was up to 15.5%, which was 115% higher than that of PP/D-S. A possible synergism of the flame retardancy between the AFs and D-S is proposed and discussed. Copyright © 2012 Wiley Periodicals, Inc. Source

Zhao Y.,Beihang University | Hu C.,Avic Aerospace Life Support Industries Ltd | Shen H.,Beihang University | Ma D.,Beihang University | And 2 more authors.
Earth Science Informatics | Year: 2012

With the rapid development of the World Wide Web, remote sensing (RS) data have become available to a wider range of public/professional users than ever before. Web Map Services (WMSs) provide a simple Web interface for requesting RS data from distributed geospatial databases. RS data providers typically expect to provide lightweight WMSs. They have a low construction cost, and can be easily managed and deployed on standard hardware/software platforms. However, existing systems for WMSs are often heavyweight and inherently hard to manage, due to their improper usage of databases or data storage. That is, they are not suitable for public data services on the Web. In addition, RS data are moving toward the multi-dimensional paradigm, which is characterized by multi-sensor, multi-spectral, multi-temporal and high resolution. Therefore, an efficient organization and storage approach of multi-dimensional RS data is needed for lightweight WMSs, and the efficient WMSs must support multi-dimensional Web browsing. In this paper, we propose a Global Remote Sensing Data Hierarchical Model (GRHM) based on the image pyramid and tiling techniques. GRHM is a logical model that is independent upon physical storage. To support lightweight WMSs, we propose a physical storage structure, and deploy multi-dimensional RS data on Web servers. To further improve the performance of WMSs, a data declustering method based on Hilbert space-filling curve is adopted for the distributed storage. We also provide an Open Geospatial Consortium (OGC) WMS and a Web map system in Web browsers. Experiments conducted on real RS datasets show promising performance of the proposed lightweight WMSs. © 2012 Springer-Verlag. Source

Wang C.,Nanjing University of Aeronautics and Astronautics | Sun J.,Nanjing University of Aeronautics and Astronautics | Yu D.,Avic Aerospace Life Support Industries Ltd
Nanjing Hangkong Hangtian Daxue Xuebao/Journal of Nanjing University of Aeronautics and Astronautics | Year: 2013

The mass-spring damper model is used to analyze the effect factors on drag parachute deployment, including resistance area, elastic modulus and diameter of the parachute system, etc. Results show that drag parachute duration and the maximum falling distance decrease with the increase of deploy velocity. But system tension becomes larger by increasing the deploy velocity (200-300 km/h). Both the increase of pilot chute resistance area and the decrease of parachute system linear density can decrease the deployment duration and the maximum falling distances obviously. The effects on the trajectory of deployment, caused by elastic modulus and diameter of parachute system are insignificant. The key factors affecting drag parachute deployment are resistance area of pilot chute, deploy velocity and linear density of parachute system. Results provide analytical basis for engineering design of drag parachute system in aerospace industry. Source

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