一种双功能谐振传感器──谐振式质量流量／密度传感器

详细地讨论了一种双功能谐振式质量流量/密度传感器的测量原理,为我国迅速研制成这种新型的谐振传感器提供了一定的理论依据。     

用经验模式参数研究电离层发电机效应

本文利用MSIS-86和IRI-86模式的基本参数,求得热层风系和电导率的三维分布;继而从发电机理论得到了电离层电位及层电流密度在北半球的分布和变化。本研究将大量数据统计平均的大气模式参数与热层、电离层理论研究联系了起来。     

P—平稳过程的最大ch熵谱估计

研究少平稳随机序列在Chrestenson变换意义下的功率谱密度及其最大熵估计问题,得到了功率谱密度函数与熵率的关系公式及最大熵谱估计的正规方程。在采样数据个数为p~m的情况下,最大熵谱估计可直接由已知的有限自相关数据表示。这些结果与Fourier意义下的功率谱密度估计有很大的不同。     

动态彩色纹影流动显示

对动态彩色纹影技术作了深入细致的阐述，并把此项技术广泛应用于超音速流场中捕捉激波等试验研究中，提供了一些实际应用的典型的流场彩色纹影照片，为波动理论研究提供了重要的实验图像（如波阵面的包波结构等）。     

泵试验的水温和水密度修正

介绍了泵闭式试验系统和相关标准对试验介质的要求,论述了泵试验对水温的控制要求,给出了常温清水的密度和饱和蒸汽压依随温度的拟合公式,对正确应用泵相似换算定律和水密度修正做了详细地阐述,结合发动机泵试验的特点,提出了经济的水温控制建议。     

对锐钛矿相TiO2的第一原理计算

用TiO₂作为阳极的光电化学电池的工作以来,对TiO₂的光催化机理的研究已发展成为一个热门研究领域.从第一原理计算的角度,用基于密度泛函理论的全电势线性缀加平面波法,对锐钛矿相TiO₂的晶格结构和电子结构作了比较系统的计算.通过使总能量和原子受力达到最低,得到晶格的优化结构,结果与实验符合得很好.由晶格优化结构得到电子结构,包括能带结构、X射线吸收谱等.其中能带结构间接跃迁能隙为2.12?eV,价带的较高态宽度与X射线衍射谱(XPS)实验值完全一致.     

Comparison of the CHAMP radio occultation data with the Canadian advanced digital ionosonde in the Polar Regions

In this paper we present the results of the comparison of the retrieved electron density profiles of the Ionospheric Radio Occultation (IRO) experiment on board CHAMP (CHAllenging Minisatellite Payload), with the ground ionosonde profiles for the Polar Regions. IRO retrieved electron density profiles from CHAMP are compared with Canadian Advanced Digital Ionosonde (CADI) measurements at two vertical sounding stations well within the Polar Cap, Eureka (geog. 80°13′ N; 86°11′ W) and Resolute Bay (geog. 74°41′ N; 94°54′ W). We compared the ionospheric parameters such as the peak electron density of the F-layer (NmF₂) and the peak height of the F-layer (h_mF₂) for a 3-year period, 2004–2006. CHAMP derived NmF₂ shows reasonable agreement with the ionosonde retrieved NmF₂ for both the stations (0.76 and 0.71 correlation coefficient, for Eureka and Resolute Bay, respectively) whereas the h_mF₂ agreement is not that acceptable (0.25 and 0.37 correlation coefficient, respectively). The h_mF₂ from vertical sounding showed less spread than the CHAMP h_mF₂.     

Evaluation of the IRI-2007 model options for the topside electron density

The International Reference Ionosphere (IRI) 2007 provides two new options for the topside electron density profile: (a) a correction of the IRI-2001 model, and (b) the NeQuick topside formula. We use the large volume of Alouette 1, 2 and ISIS 1, 2 topside sounder data to evaluate these two new options with special emphasis on the uppermost topside where IRI-2001 showed the largest discrepancies. We will also study the accurate representation of profiles in the equatorial anomaly region where the profile function has to accommodate two latitudinal maxima (crests) at lower altitudes but only a single maximum (at the equator) higher up. In addition to IRI-2001 and the two new IRI-2007 options we also include the Intercosmos-based topside model of Triskova, Truhlik, and Smilauer [Triskova, L., Truhlik, V., Smilauer, J. An empirical topside electron density model for calculation of absolute ion densities in IRI. Adv. Space Res. 37 (5), 928–934, 2006] (TTS model) in our analysis. We find that overall IRI-2007-NeQ gives the best results but IRI-2007-corrected provides a more realistic representation of the altitudinal–latitudinal structure in the equatorial anomaly region. The applicability of the TTS model is limited by the fact that it is not normalized to the F2 peak density and height.     

A generalised methodology for estimating land surface temperature for non-urban areas of Greece through the combined use of NOAA–AVHRR data and ancillary information

The purpose of this study was twofold: to develop a methodology for the estimation of land surface temperature for non-urban areas and to analyze the sensitivity of the methodology. The key element of the methodology was the development of emissivity maps based on CORINE Land Cover and the ASTER spectral library. Land surface temperatures were derived from NOAA/AVHRR data and the methodology was applied at a national scale in Greece, with emphasis given to non-urban areas. A sensitivity analysis was performed in order to determine the variables that mainly affect the estimation of land surface temperature. A varying propagation error was identified depending on the temperature and humidity of the atmosphere, as well as the land cover type. The methodology was applied to a series of 25 AVHRR images and the results were compared to in-situ measurements from representative stations.     

Wavelet modelling in support of IRI

The slant total electron content (STEC) of the ionosphere is defined as the integral of the electron density along the ray-path of the signal between the transmitter and the receiver. So-called geometry free GPS measurements provide information on the electron density, which is basically a four-dimensional function depending on spatial position and time. Since ground-based measurements are not very sensitive to the vertical structure within the atmosphere, the ionosphere is often represented by a spherical layer, where all electrons are concentrated. Then the STEC is transformed into the vertical total electron content (VTEC), which is a three-dimensional function depending on longitude, latitude and time.In our approach, we decompose an ionospheric function, i.e. the electron density or the VTEC, into a reference part computed from a given model like the International Reference Ionosphere (IRI) and an unknown correction term expanded in a multi-dimensional series in terms of localizing base functions. The corresponding series coefficients are calculable from GPS measurements applying parameter estimation procedures. Since the GPS receivers are located rather unbalanced, finer structures are modelable just in regions with a sufficient number of observation sites. Due to the localizing feature of B-spline functions we apply a tensor product spline expansion to model the correction term regionally. Furthermore, the multi-resolution representation derived from wavelet analysis allows monitoring the ionosphere at different resolutions levels. We demonstrate the advantages of this procedure by representing a simulated VTEC data set over South America.