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WAVELET-BASED FAIRING OF B-SPLINE SURFACES 总被引:2,自引:0,他引:2
Inrecentyears,waveletanalysisgetsmoreandmoreapplicationsincomputergraphics[1],includingradiositycomputation[2],curveandsurfac... 相似文献
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超音速时修正空速与马赫数的换算及加速度因子的计算 总被引:2,自引:0,他引:2
傅职忠 《中国民航学院学报》1996,14(3):10-20
给出了超音速飞行时修正空速与马赫数的换算公式,并根据导出的公式计算了0—32000m各高度上的修正空速与马赫数、真空速对应的数值表,该表与文献[2]中给出的数值表(表25)完全一致。此外,也给出了在超音速时等表速爬升的加速度因子的计算公式。 相似文献
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Fiberreinforcedmetallaminates(FRMLs)areagroupofmaterialsbybondingthinmetalsheetswithfibercomposites[13],typicalywith2/1layup... 相似文献
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高分辨率有限差分—有限元混合方法及其在气动热计算中的应用 总被引:3,自引:6,他引:3
在文献[1]结合NND格式思想^[2]提出的有限元格式基础上,给出一种有限差分-有限元混合方法。通过求解完全Navier-Stokes方程,得到了高超声速情况下钝头体轴对称绕流的较满意结果,同时讨论了网格Re数对驻点热流的影响。 相似文献
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本文将文献[1]中提出的方法推广应用于三维可压缩N-S方程,文中给出了钝锥超声速三维粘性绕流的结果。得到了背风面分离的流动图画,计算结果与实验相吻合。 相似文献
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本文成功地将二阶迎风TVD数值格式运用到弱电离、化学非平衡斜激波反射流场的数值计算中,气体力学方程与组元质量守恒方程组全耦合求解是目前非平衡流场数值计算中的新方向。文中详细给出了气体力学方程和组元质量守恒方程组全耦合求解过程,最后给出了三种不同情况斜激波反射流场数值结果并进行了详细讨论,本文所得结果与文献[4]提供的实验结果和文献[1]提供的数值结果相符合。 相似文献
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对用搅拌法制备的Al-6wt%Cu基SiC颗粒复合材料熔体的流变行为、流变模型、颗粒含量及温度对各流变参数的影响进行了研究。认为其流变模型为[H1]-[S|N1]-[H2|N2]。在不同温度下填加不同成分含量的SiC颗粒,其流变参数值受到不同程度的影响。 相似文献
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《中国航空学报》2016,(5):1378-1384
It is difficult to build accurate model for measurement noise covariance in complex back-grounds. For the scenarios of unknown sensor noise variances, an adaptive multi-target tracking algorithm based on labeled random finite set and variational Bayesian (VB) approximation is pro-posed. The variational approximation technique is introduced to the labeled multi-Bernoulli (LMB) filter to jointly estimate the states of targets and sensor noise variances. Simulation results show that the proposed method can give unbiased estimation of cardinality and has better performance than the VB probability hypothesis density (VB-PHD) filter and the VB cardinality balanced multi-target multi-Bernoulli (VB-CBMeMBer) filter in harsh situations. The simulations also confirm the robustness of the proposed method against the time-varying noise variances. The computational complexity of proposed method is higher than the VB-PHD and VB-CBMeMBer in extreme cases, while the mean execution times of the three methods are close when targets are well separated. 相似文献
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In this paper, a cardinality compensation method based on Information-weighted Consensus Filter(ICF) using data clustering is proposed in order to accurately estimate the cardinality of the Cardinalized Probability Hypothesis Density(CPHD) filter. Although the joint propagation of the intensity and the cardinality distribution in the CPHD filter process allows for more reliable estimation of the cardinality(target number) than the PHD filter, tracking loss may occur when noise and clutter are high in the measurements in a practical situation. For that reason, the cardinality compensation process is included in the CPHD filter, which is based on information fusion step using estimated cardinality obtained from the CPHD filter and measured cardinality obtained through data clustering. Here, the ICF is used for information fusion. To verify the performance of the proposed method, simulations were carried out and it was confirmed that the tracking performance of the multi-target was improved because the cardinality was estimated more accurately as compared to the existing techniques. 相似文献
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《中国航空学报》2016,(3):704-713
In the theory of belief functions, the measure of uncertainty is an important concept, which is used for representing some types of uncertainty incorporated in bodies of evidence such as the discord and the non-specificity. For the non-specificity part, some traditional measures use for reference the Hartley measure in classical set theory;other traditional measures use the simple and heuristic function for joint use of mass assignments and the cardinality of focal elements. In this paper, a new non-specificity measure is proposed using lengths of belief intervals, which represent the degree of imprecision. Therefore, it has more intuitive physical meaning. It can be proved that our new measure can be rewritten in a general form for the non-specificity. Our new measure is also proved to be a strict non-specificity measure with some desired properties. Numerical examples, simulations, the related analyses and proofs are provided to show the characteristics and good properties of the new non-specificity definition. An example of an application of the new non-specificity measure is also presented. 相似文献
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Belief functions theory is an important tool in the field of information fusion. However, when the cardinality of the frame of discernment becomes large, the high computational cost of evidence combination will become the bottleneck of belief functions theory in real applications. The basic probability assignment (BPA) approximations, which can reduce the complexity of the BPAs, are always used to reduce the computational cost of evidence combination. In this paper, both the cardinalities and the mass assignment values of focal elements are used as the criteria of reduction. The two criteria are jointly used by using rank-level fusion. Some experiments and related analyses are provided to illustrate and justify the proposed new BPA approximation approach. 相似文献
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It is understood that the forward-backward probability hypothesis density (PHD) smoothing algorithms proposed recently can significantly improve state estimation of targets. However, our analyses in this paper show that they cannot give a good cardinality (i.e., the number of targets) estimate. This is because backward smoothing ignores the effect of temporary track drop- ping caused by forward filtering and/or anomalous smoothing resulted from deaths of targets. To cope with such a problem, a novel PHD smoothing algorithm, called the variable-lag PHD smoother, in which a detection process used to identify whether the filtered cardinality varies within the smooth lag is added before backward smoothing, is developed here. The analytical results show that the proposed smoother can almost eliminate the influences of temporary track dropping and anomalous smoothing, while both the cardinality and the state estimations can significantly be improved. Simulation results on two multi-target tracking scenarios verify the effectiveness of the proposed smoother. 相似文献
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建立以宏观电中性、不同种类粒子间滑移流动为基本假设的一维多流体简化模型,构造了相应的数值计算方法,用于分析霍尔推力器(亦称稳态等离子体推力器,简称SPT)的加速器通道内部物理过程。在适当边界条件以及适当模型常数条件下,能够获得无论在定性还是定量上都与实际比较接近的收敛的稳态解。结果显示,电势降落集中在出口附近,离子加速过程与该电势降落一致;在通道前半段电离比较剧烈,而在出口附近趋于平缓,出口电离度接近80%;由于焦耳加热作用,电子从出口截面向阳极漂移过程中,其温度由初始的约10eV首先提升到接近60eV的峰值,该峰值出现在离出口约1/3通道长度位置上;随后,由于越来越多的能量损耗于电离过程,到阳极附近电子温度降至约25eV。受其中的一些假设所限,本模型不能反映一些特殊区域和某些比较重要的物理过程,同时能够收敛的条件也受到了限制。 相似文献
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