共查询到20条相似文献,搜索用时 328 毫秒
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The results of experimental investigations of annular diffuser channels of various configurations at different types of inlet
swirling are presented. A formula for loss calculations in such channels is proposed and experimental and calculation data
are compared. 相似文献
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A. V. Kretinin Yu. A. Bulygin V. Yu. Klimov P. A. Dronov 《Russian Aeronautics (Iz VUZ)》2009,52(4):440-443
The results of calculating the fuel component distribution along the cooling path channels in the liquid rocket engine (LRE)
based on the Monte-Carlo method with regard for a random scatter of the hydraulic resistance coefficient values in the individual
channels are presented. 相似文献
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卫星导航接收机矢量跟踪环路的核心就是用一个Kalman滤波器将标量接收机的信号跟踪和导航解算一起完成,优点是能够形成通道之间的相互辅助,缺点是也会相互影响。尤其在部分卫星信号被遮挡或者部分通道信号质量较差的环境下,问题通道会影响其他通道,甚至导致矢量跟踪环路滤波器发散,常规的方法是检测故障通道然后将故障通道剔除,这样需要对导航滤波器进行变维操作。针对此问题,提出了一种新的消除问题通道对其他通道影响的方法,同时不需要对导航滤波器进行变维。首先给出了一种标度因子,用来判断通道是否存在故障通道,然后给出一种利用模糊控制的导航滤波器自适应调整方法。仿真表明,在通道卫星信号被频繁遮挡的极端情况,矢量接收机依旧能保持正常的导航精度,并没有明显受到误差通道的影响,同时避免了对导航滤波器进行变维操作。 相似文献
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Efficient fault tolerant estimation using the IMM methodology 总被引:2,自引:0,他引:2
Space systems are characterized by a low-intensity process noise resulting from uncertain forces and moments. In many cases, their scalar measurement channels can be assumed to be independent, with one-dimensional internal dynamics. The nominal operation of these systems can be severely damaged by faults in the sensors. A natural method that can be used to yield fault tolerant estimates of such systems is the interacting multiple model (IMM) filtering algorithm, which is known to provide very accurate results. However, having been derived for a general class of systems with switching parameters, the IMM filter does not utilize the independence of the measurement errors in different channels, nor does it exploit the fact that the process noise is of low intensity. Thus, the implementation of the IMM in this case is computationally expensive. A new estimation technique is proposed herein, that explicitly utilizes the aforementioned properties. In the resulting estimation scheme separate measurement channels are handled separately, thus reducing the computational complexity. It is shown that, whereas the IMM complexity is exponential in the number of fault-prone measurements, the complexity of the proposed technique is polynomial. A simulation study involving spacecraft attitude estimation is carried out. This study shows that the proposed technique closely approximates the full-blown IMM algorithm, while requiring only a modest fraction of the computational cost. 相似文献
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为了研究浮升力效应对超燃冲压发动机燃烧室不同位置冷却通道传热特性的影响,对超临界压力下正癸烷在水平矩形冷却通道内的流动传热-固体导热耦合过程展开了详细的数值模拟研究。重点考察了燃烧室不同位置的冷却通道中浮升力对温度以及热流分配的影响及其机理。结果表明:由浮升力引起的二次流动使燃烧室不同位置的冷却通道温度分布和热流分配呈现显著的差异;浮升力提升了燃烧室不同位置冷却通道的换热效果,其中受热方向和重力作用方向相同的冷却通道换热性能提升得最多;修正的Jackson&Hall经验公式不能预测浮升力对冷却通道壁面对流换热的影响,需要寻找其他的经验公式或使用CFD手段进行计算分析来解决这一问题。 相似文献
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本文首先描述了一种有记忆删除信道模型,然后提出了分组码在该信道上的性能的迭代算法。最后以Golay(23,12,7)码为例给出了多种信道参数之下的性能曲线。 相似文献
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The laws of lateral motion control without data on the roll angle are proposed for aircraft with a single plane of symmetry. A procedure for analytical selection of the optimal gain in the aileron and rudder channels is proposed. The results of simulating the aircraft-autopilot system are presented. 相似文献
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Groves G.W. Blair W.D. Chow W.C. 《IEEE transactions on aerospace and electronic systems》1997,33(4):1345-1350
The joint distribution of the real and imaginary parts of the monopulse ratio (MR) is obtained for a monopulse radar with arbitrarily correlated Gaussian noise and non-zero means in the sum and difference channels. The general result is used to consider thresholding and to develop the marginal density for the real part of the MR for the special case of real correlation between the channels. 相似文献
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Statistical analyses of zero-crossing sampling first- and second order digital phase-locked loops in fading channls (DPLFC) are presented. A DPLFC is defined as one where the incoming signal is not only corrupted by additive Gaussian noise channel (AGN) but also by a fading communication channel. The three fading channels considered are the log-normal, Rayleigh, and Rician channels. The performance degradation of the DPLFC operation is characterized by the steady-state phase-error process probability density function and phase-error variance. Approximate analytic expressions for the phase-error statistics of a first-order DPLFC for both phase-step and frequency-step inputs are obtained by solving the Chapman-Kolmogorov equation associated with the phase-error process. The second-order DPLFC is analyzed for a frequency-step input. Numerical and simulation results are provided confirming the analyses presented for the three fading channels considered. 相似文献
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A model, constructed on the basis of modern concepts, for thermohydraulic calculation of the heat exchanger channels with the heat exchange intensifiers is proposed. Urgent problems of the further investigations in this field are formulated. 相似文献
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K. B. Panfilovich 《Russian Aeronautics (Iz VUZ)》2014,57(1):71-74
In this paper, a physical model of gas flows through the channels is refined. The influence of gas absorbed by the walls of a channel on its conductance is shown. The experimentally obtained minimum on the channel conductance-pressure dependence (as the Knudsen paradox) is interpreted. 相似文献
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This paper presents a composite model of a flight simulator. This simulator is intended for carrying out investigative tests of flight dynamics imitation models of a hingeless rotor helicopter. A schematic diagram, composition and operation channels of the flight simulator software are presented. A possibility of applying the control lag is estimated. 相似文献
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利用动态压力传感器对一低速轴流压气机转子的叶顶间隙流场进行详细的试验测量,通过对信号特征的分析,对压气机节流过程中叶顶间隙的非定常流动发展演变规律进行了研究。结果表明:压气机完全失速时,叶尖存在一以46.5%转子转速周向传播的失速团;节流过程中,叶尖前缘处的动态压力信号中存在非定常波动的特征频率带,其变化规律与叶顶流场压力非定常波动的能量迁移有关;随着压气机流量减小,叶顶泄漏流影响区域向前缘移动,失速团在叶顶前缘附近产生,并向尾缘方向扩展,最终覆盖叶片全部弦长;近失速工况时,叶顶间隙相邻通道内泄漏流相互作用,造成通道中的低压区“一前一后”交替分布从而形成一个空间上周期约2个叶片通道的扰动波。 相似文献