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951.
Ravi Sood Sean Farrell Paul ONeill Ravi Manchanda N.M. Ashok 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2006,38(12):2779-2781
We have analysed 9 years of data from the All Sky Monitor on the Rossi X-ray Timing Explorer for 2S 0114+650 to study the evolution of its spin, binary, and super-orbital periods. The spin history of the neutron star in this system exhibits torque reversals lasting 1 year. The newly discovered super-orbital period has remained stable over the 9-year span, making 2S 0114+650 the fourth known system to exhibit stable super-orbital modulation. We compare its super-orbital period evolution with those of the other three such systems. 相似文献
952.
953.
长期受粒子辐照、紫外辐照等因素的影响,地球同步卫星的太阳电池阵输出功率会出现较为明显的衰减。这里选取某地球同步卫星使用的背表面反射(BSR)硅太阳电池阵为研究对象,采用光强因子和温度因子修正太阳电池阵的输出功率,使用局部加权回归散点平滑法(LOWESS)分析了其在设计寿命期间的输出功率衰减规律;同时基于LOWESS建立了预测模型,用于硅太阳电池阵超寿运行期间的功率预测。实测数据表明:本文构建的预测模型可以满足超寿地球同步卫星在轨管理使用需求。 相似文献
954.
Multi-sensor image matching based on salient edges has broad prospect in applications, but it is difficult to extract salient edges of real multi-sensor images with noises fast and accurately by using common algorithms. According to the analysis of the features of salient edges, a novel salient edges detection algorithm and its rapid calculation are proposed based on possibility fuzzy C-means (PFCM) kernel clustering using two-dimensional vectors composed of the values of gray and texture. PFCM clustering can overcome the shortcomings that fuzzy C-means (FCM) cluster- ing is sensitive to noises and possibility C-means (PCM) clustering tends to find identical clusters. On this basis, a method is proposed to improve real-time performance by compressing data sets based on the idea of data reduction in the field of mathematical analysis. In addition, the idea that kernel-space is linearly separable is used to enhance robustness further. Experimental results show that this method extracts salient edges for real multi-sensor images with noises more accurately than the algorithm based on force fields and the FCM algorithm; and the proposed method is on average about 56 times faster than the PFCM algorithm in real time and has better robustness. 相似文献
955.
A system impulse response with low sidelobes is critical in synthetic aperture radar(SAR) images because sidelobes contribute to noise and interfere with nearby scatterers. However,the conventional tricks of sidelobe suppression are unable to be exactly applied to the case of spaceborne sliding spotlight SAR due to great azimuth shifts in both time and frequency domains. In this paper, an extended chirp scaling algorithm is presented for spaceborne sliding spotlight SAR data imaging. The proposed algorithm firstly uses the spectral analysis(SPECAN) technique to avoid the azimuth spectrum folding effect and then employs the chirp scaling(CS) algorithm to achieve data focusing, i.e., the so-called two-step approach. To suppress the sidelobe level, an efficient strategy for the azimuth spectral weighting which only involves matrix multiplications and short fast Fourier transformations(FFTs) is proposed, which is a post-process executed on the focused SAR image and particularly simple to be implemented. The SAR image processed by the proposed extended CS algorithm is very precise and perfectly phase-preserving. In the end, computer simulation results verify the analysis and confirm the validity of the proposed algorithm. 相似文献
956.
For high-efficiency grinding of difficult-to-cut materials such as titanium and nickel alloys, a high porosity is expected and also a sufficient mechanical strength to satisfy the function.However, the porosity increase is a disadvantage to the mechanical strength. As a promising pore forming agent, alumina bubbles are firstly induced into the abrasive layer to fabricate porous cubic boron nitride(CBN) wheels. When the wheel porosity reaches 45%, the bending strength is still high up to 50 MPa with modified orderly pore distribution. A porous CBN wheel was fabricated with a total porosity around 30%. The grinding performance of the porous composite-bonded CBN wheel was evaluated in terms of specific force, specific grinding energy, and grinding temperature, which were better than those of the vitrified one under the same grinding conditions. Compared to the vitrified CBN wheel, clear straight cutting grooves and less chip adhesion are observed on the ground surface and there is also no extensive loading on the wheel surface after grinding. 相似文献
957.
为了研究三维内转式进气道对飞行器力矩特性的影响规律,对一系列设计状态为Ma=6.5的内转式进气道展开力矩特性研究。对不同布局形式,进气形式以及基准流场中心体的内转式进气道对飞行器力矩特性的影响展开分析研究。研究结果表明,对于内转式进气道而言,有连接板的水滴型进气道双侧布局力矩特性较优,且容易满足飞行器总体需求;布局形式对进气道的力矩特性影响最显著,进气形式对侧滑力矩的影响比基准流场中心体影响更明显,而抬头力矩和滚转力矩受基准流场中心体影响更加突出;中心体在0~0.1Rs(Rs为基准流场入口半径)变化时,抬头力矩变化不大,而在0.1~0.2Rs抬头力矩变化明显。 相似文献
958.
短距起飞/垂直降落(STOVL)飞机由于其优越的作战性能,受到了世界航空大国的高度重视。通过借鉴目前最先进的 STOVL 动力 F135- PW -600发动机技术发展思路,研究了基于国内某型发动机改 STOVL 动力方案时,主发动机与升力风扇之间的匹配和约束关系。研究结果表明:随着升力风扇压比和流量的增加,主发动机升力减小,升力风扇升力增加;同一主发动机状态下,升力风扇流量越大,发动机前后升力平衡的升力风扇压比越小,总升力越大;主发动机性能越高,发动机前后升力平衡的升力风扇压比和流量越大,发动机总升力也越大。 相似文献
959.
张维方 《民用飞机设计与研究》2014,(3):81-84
介绍了头部损伤判据HIC的概念、适航要求及影响运输类飞机客舱头排旅客座椅HIC的相关参数;叙述了旅客座椅头排距、头部撞击壁板的刚度、安全带织带伸长率、乘坐摩擦系数等参数的影响和重要程度;对如何设计符合HIC要求的经济舱头排旅客座椅和壁板提出了建议。 相似文献
960.
周烨斐刘艳涛 《民用飞机设计与研究》2014,(3):88-91
对比航电传统系统架构,分析了综合模块化航电系统(Integrated Modular Avionics,简称IMA)架构的优点;针对IMA系统功能的高集成度带来的资源分配难度和安全性要求,提出了IMA系统分区和资源分配策略,并给出了具体方法,对民用飞机IMA系统设计具有一定的指导意义和实用价值。 相似文献