卫星光学相机MTF在轨检测方法研究

调制传递函数是反映卫星光学相机成像性能的重要参数,针对调制传递函数多种在轨检测方法,本文在分析了可利用地面景物的基础上,结合目前卫星光学相机分辨率不断提高的现状,着重从原理和方法上介绍了利用不同亮度地块接壤的地面靶标进行检验的刃边法,同时依据实验研究成果,介绍了对原始刃边数据拟合和调制传递函数的频谱增密技术,这些技术对提高调制传递函数获取精度具有重要的作用。     

Turbulent intensity and its similarity function over an Inner Mongolian grassland during spring

Macroscopic reason for the development of turbulences in fluid is the conjunction action of velocity and temperature shears. We use the 2008 spring flux observations in the surface layer over Inner Mongolian grassland, obtain the similarity functions of turbulent intensity under different stratification stability conditions, and calculate the clear day turbulent intensity in the spring, which is then analyzed and compared with the observed values of turbulent intensity. The results show that in the Inner Mo...     

均匀导电半空间中频率域和时间域三维电张量格林函数及应用

从电张量格林函数的物理意义出发,在频率域和时间域研究了均匀导电半空间中的电张量格林函数,并基于Ｆｒｅｄｈｏｌｍ方程分析了三维电磁散射的数值模拟方法。作者还根据实际情况,首次模拟出三维瞬变电磁激电异常的相位剖面图,其结果与直流情况类似并与实际资料相吻合。     

海洋岩石圈板块有效弹性厚度研究

本文在前人研究大陆岩石圈板块有效弹性厚度的基础上,建立研究海洋岩石圈板块有效弹性厚度的理论模型,推导出与大陆岩石圈不同的海洋岩石圈板块响应函数 Z(k,Te) 理论计算公式.并分析海洋岩石圈板块响应函数 Z(k,Te) 的特点.文中对实际的海洋测量数据的响应函数 Z(k,Te) 进行计算和分析,估算我国南海南沙海域和南海中央海盆岩石圈板块有效弹性厚度分别约为10 km和6~7 km.     

基于三维应变格林函数反演中小震震源机制

随着复杂速度结构反演的发展和高性能计算能力的提升,基于高精度3D介质模型计算格林函数反演震源机制更具可行性。中小地震因具有更好的覆盖和近似点源效应,在区域结构成像中有着广泛的应用。基于波形类的反演方法如波动方程层析成像\,全波形反演都需要震源机制解,而传统的震源机制反演方法不能很好地应用于中小地震。采用有限差分法构建应变格林张量(Strain Green Tensor,SGT)数据库,将合成波形和实际波形按震相截窗并滤波到不同的频带范围,先通过最小化互相关走时差来进行震源重定位,再通过最小化波形残差反演震源机制。通过合成数据测试验证方法的正确性,随后将该方法应用于青藏高原东部边缘龙门山地区,反演一系列M_W3.4～5.7的中小地震震源机制。由于应变格林张量数据库可预先构建,该方法可以应用于(近)实时震源机制解反演。     

CT能谱成像对肝脏微小转移瘤的诊断价值

目的：探讨肝脏微小转移瘤患者应用CT能谱成像诊断的效果及对患者肝功能的影响。方法：回顾性分析2015年5月至2017年5月我院收治的肝脏微小转移瘤患者80例的临床资料,根据诊断方法不同分成对照组和研究组两组。对照组常规的CT诊断,研究组应用CT能谱成像的诊断方法,对比诊断结果。结果：对比诊断结果,研究组诊断出的病灶个数以及检出率显著高于对照组（&;lt;i&;lt;P&;lt;/i&;lt;&;lt;0.05）,同时漏检率以及误检率均低于对照组（&;lt;i&;lt;P&;lt;/i&;lt;&;lt;0.05）;研究组应用诊断方法的诊断敏感度、阳性预测值以及特异性都高于对照组（&;lt;i&;lt;P&;lt;/i&;lt;&;lt;0.05）;对比治疗效果,研究组的疗效显著优于对照组（&;lt;i&;lt;P&;lt;/i&;lt;&;lt;0.05）。结论：应用CT能谱成像诊断肝脏微小转移瘤患者,有助于疾病早发现、早治疗,有更高的诊断价值,利于患者改善肝功能,值得在临床上推广应用。     

四种湍流模型对空化流动模拟的比较

采用四种湍流模型对NACA66水翼空化流动进行模拟,分析了不同湍流模型和壁面函数对空化流动模拟结果的影响.分析结果表明:ASM模型和RNG k-ε模型对空化数不敏感,且计算精度较高;Realizable k-ε模型对空化数的变化很敏感,对不同的空化数计算精度相差很大;标准k-ε模型对空化数不敏感,但精度不高.增强壁面函数法对空化数不敏感,计算精度较高;标准壁面函数法和非平衡壁面函数法对空化数有一定的敏感性,但计算结果差异不大.     

An integrated wavelet concept of physical geodesy

For the determination of the earth's gravity field many types of observations are nowadays available, including terrestrial gravimetry, airborne gravimetry, satellite-to-satellite tracking, satellite gradio-metry, etc. The mathematical connection between these observables on the one hand and gravity field and shape of the earth on the other is called the integrated concept of physical geodesy. In this paper harmonic wavelets are introduced by which the gravitational part of the gravity field can be approximated progressively better and better, reflecting an increasing flow of observations. An integrated concept of physical geodesy in terms of harmonic wavelets is presented. Essential tools for approximation are integration formulas relating an integral over an internal sphere to suitable linear combinations of observation functionals, i.e. linear functionals representing the geodetic observables. A scale discrete version of multiresolution is described for approximating the gravitational potential outside and on the earth's surface. Furthermore, an exact fully discrete wavelet approximation is developed for the case of band-limited wavelets. A method for combined global outer harmonic and local harmonic wavelet modelling is proposed corresponding to realistic earth's models. As examples, the role of wavelets is discussed for the classical Stokes problem, the oblique derivative problem, satellite-to-satellite tracking, satellite gravity gradiometry and combined satellite-to-satellite tracking and gradiometry. Received: 28 February 1997 / Accepted: 17 November 1997     

A determination of source properties of large intraplate earthquakes in Alaska

Historically, large and potentially hazardous earthquakes have occurred within the interior of Alaska. However, most have not been adequately studied using modern methods of waveform modeling. The 22 July 1937, 16 October 1947, and 7 April 1958 earthquakes are three of the largest events known to have occurred within central Alaska (M _s =7.3,M _s =7.2 andM _s =7.3, respectively). We analyzed teleseismic body waves to gain information about the focal parameters of these events. In order to deconvolve the source time functions from teleseismic records, we first attempted to improve upon the published focal mechanisms for each event. Synthetic seismograms were computed for different source parameters, using the reflectivity method. A search was completed which compared the hand-digitized data with a suite of synthetic traces covering the complete parameter space of strike, dip, and slip direction. In this way, the focal mechanism showing the maximum correlation between the observed and calculated traces was found. Source time functions, i.e., the moment release as a function of time, were then deconvolved from teleseismic records for the three historical earthquakes, using the focal mechanisms which best fit the data. From these deconvolutions, we also recovered the depth of the events and their seismic moments. The earthquakes were all found to have a shallow foci, with depths of less than 10 km.The 1937 earthquake occurred within a northeast-southwest band of seismicity termed the Salcha seismic zone (SSZ). We confirm the previously published focal mechanism, indicating strike-slip faulting, with one focal plane parallel to the SSZ which was interpreted as the fault plane. Assuming a unilateral fault model and a reasonable rupture velocity of between 2 and 3 km/s, the 21 second rupture duration for this event indicates that all of the 65 km long SSZ may have ruptured during this event. The 1947 event, located to the south of the northwest-southeast trending Fairbanks seismic zone, was found to have a duration of about 11 seconds, thus indicating a rupture length of up to 30 km. The rupture duration of the 1958 earthquake, which occurred near the town of Huslia, approximately 400 km ENE of Fairbanks, was found to be about 9 seconds. This gives a rupture length consistent with the observed damage, an area of 16 km by 64 km.