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871.
872.
热传导终端反问题是典型的不适定问题,应用基于全变差的正则化方法来获得它的稳定数值解,将近似解的求解范围由连续函数空间扩大到了有界变差函数空间,并将固定点迭代法用于求解非线性的Euler方程,并进行了理论分析和数值实验。结果表明:该方法与算法具有高效稳定全局收敛等优点。 相似文献
873.
874.
Karel Kudela Ronald Langer 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
Lomnický Štít (LS, situated at High Tatra mountain, 2634 m above sea level, in the direction of 49.40°N, 20.22°E; geomagnetic vertical cut-off rigidity for cosmic rays ∼4 GV) is a relevant place for cosmic ray studies. After a brief review of the LS research history we present a selection of the results based on the measurements performed by the neutron monitor located at that site. In particular, the characteristics of quasi-periodicities and the diurnal variability amplitude and phase obtained from those data are discussed. 相似文献
875.
N. Pierdicca C. Bignami M. Roca P. Féménias M. Fascetti M. Mazzetta C.N. Loddo A. Martini S. Pinori 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
Although the history of spaceborne altimeters goes back to the early seventies, the absolute calibration of the backscattering coefficient has never been deeply investigated. This information has been primarily used to infer the wind speed via an empirical model, and the intercalibration among different satellite altimeters has revealed to be suitable for this purpose, being the wind retrieval based on an empirical relationship. As far as Ku band system is concerned, the sigma naught absolute calibration of the Envisat altimeter (RA-2) has been performed using an active reference target provided by a transponder. This has been exploited during the 6-month Commissioning phase to generate early calibration results. In order to monitor the RA-2 backscatter calibration during the Envisat lifetime, a continuous calibration effort has been carried out by operating the transponder as much as possible. This paper aims to review the entire effort for calibrating the RA-2 sigma naught measurements, which lasted for almost seven years. It presents in detail the adopted methodology and the final outcome of the activity, providing the users with the correction (bias) to get the calibrated sigma naught and analyzing its stability during almost the entire Envisat lifetime. Specifically, it is concluded that the RA-2 backscatter measurements were quite stable, even if a bias of about 1 dB should be considered with respect to the actually released product. Some small changes in the bias as function of time can be identified during most of the Envisat lifetime, consisting in a slight increase in the first two years, followed by a more stable period and a final drop observed at the end of 2009, until the conclusion of the calibration activity (corresponding to the change in Envisat orbit). 相似文献
876.
蔡靖 《中国民航学院学报》2008,26(6):32-36
为了更好地解决基桩缺陷量化分析问题,从建立成层土中缺陷桩桩土系统模型入手,引入矩阵递推法,求解出成层土中多缺陷桩桩顶和桩身任意点的瞬态响应解析解,并应用此解对缺陷桩瞬态响应影响参数进行分析,得出在利用幅值比进行缺陷量化分析方法中的关键影响因素为桩侧土阻尼系数,为成层土中基桩缺陷量化分析和承载力评价奠定了理论基础。 相似文献
877.
导弹飞行试验时制导系统误差系数(工具误差)与地面试验的误差系数是否一致(或部分一致),这是人们比较关心的问题,本文从理论上介绍了线性模型假设检验方法,应用这种方法检验制导系统工具误差天地因子的一致性,若一致(或部分一致)则验前信息可被充分利用以提高制导系统误差系数分离的效果。 相似文献
878.
879.
为了研究微小通道结构在航空发动机涡轮叶片中应用的前景和可行性,以空气为冷却介质,在Re=1000~3000、转速为0~500 r/min、Ro=0~3.5×10-3条件下,对水力直径为1 mm的旋转微小通道组的流动和换热特性进行试验研究。结果表明:微小通道流阻系数呈现粗糙壁通道特征,通道临界Re≈2350,流阻系数以及临界Re随转速增加未见明显改变。在静止状态下,通道组综合换热系数随Re增大而增大,换热系数分布沿流动方向逐渐减小;在旋转状态下,通道组平均综合换热系数略有增大,旋转对换热特性的影响随着流动的发展而增大 相似文献
880.
Turbulence affects both combustion and NO formation. Fluctuation correlations are ideally used for quantitative analysis. From the instantaneous chemical reaction rate expression,ignoring the third-order correlation terms, the averaged reaction rate will have four terms, including the term of averaged-variable product, a concentration fluctuation correlation term, and temperature-concentration fluctuation correlation term. If the reaction-rate coefficient is denoted as K, the temperature fluctuation would be included in the K fluctuation. In order to quantitatively study the effect of turbulence on NO formation in methane-air swirling combustion, various turbulencechemistry models are tested. The magnitudes of various correlations and their effects on the time-averaged reaction rate are calculated and analyzed, and the simulation results are compared with the experimental measurement data. The results show that among various correlation moments, the correlation between the reaction-rate coefficient K fluctuation with the concentration fluctuation is most important and is a strong nonlinear term. 相似文献