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151.
Since its discovery in 1946, NMR has become a valuable tool in physics, chemistry, biology, and medicine. With the invention of NMR logging tools that take the medical MRI or laboratory NMR equipment and turn it inside-out, the application of sophisticated laboratory techniques to determine formation properties in situ is now available. The capability has opened a new era in formation evaluation just as the introduction of NMR has revolutionized the other scientific areas. 相似文献
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Nghiem S.V. Kwok R. Yueh S.H. Gow A.J. Perovich D.K. Chih-Chien Hsu Kung-Han Ding Jin Au Kong Grenfell T.C. 《Geoscience and Remote Sensing, IEEE Transactions on》1998,36(1):111-124
To investigate effects of diurnal thermal cycles on C-band polarimetric backscatter and millimeter-wave emission from sea ice, the authors carried out a winter experiment at the outdoor geophysical research facility (GRF) in the cold regions research and engineering laboratory (CRREL), the ice sheet grew from open sea water to a thickness of 10 cm in 2.5 days, during which they took polarimetric backscatter data with a C-band scatterometer, interlaced with brightness temperature measurements at 90 GHz in conjunction with meteorological and sea ice characterizations. The initial ice growth in the late morning was slow due to high insolation. As the air temperature dropped during the night, the growth rate increased significantly. Air temperature changed drastically from about -12 to -36°C between day and night, the diurnal thermal cycle repeated itself the next day and the growth rate varied in the same manner. Ice temperature profiles clearly show the diurnal response in the ice sheet with a lag of 2.5 h behind the time of the maximum short-wave incident solar radiation. The diurnal cycles are also evident in the millimeter-wave brightness temperature data, measured sea ice backscatter revealed substantial diurnal variations up to 6 dB with repeatable cycles in synchronization with the temperature cycles and the brightness temperature modulations, the diurnal cycles in backscatter indicate that the dominant scattering mechanism related to thermodynamic processes in sea ice is reversible, a diurnal backscatter model based on sea ice electrodynamics and thermodynamics explains the observed diurnal signature. This work shows that diurnal effects are important for inversion algorithms to retrieve sea ice geophysical parameters from remote sensing data acquired with a satellite synthetic aperture radar (SAR) or scatterometer on Sun-synchronous orbits 相似文献
155.
With different amounts of KCl added in the PNBA(p- nitro benzoic acid) aqueous solution, the factors affecting the SERS (Surface Enhanced Raman Scattering) are studied systematically on the surface of Copper. The results show that in PNBA aqueous solution the occurrence of SERS effect stongly depends on the existence of Cl-. The amount of KCl added affects not only the emergence and the intensity of SERS effect, but also the adsorption properties such as the adsorption manner,etc. 相似文献
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复杂目标近场电磁散射的可视化计算方法 总被引:9,自引:1,他引:8
首次介绍了复杂目标近场散射计算的可视化方法。采用非均匀有理B样条曲面(NURBS)精确构造任意形状散射体,结合几何体近场透视变换和Z-Buffer技术实现了基于Windows平台的近场散射计算。提出广义雷达散射截面的概念并给出的若干算例。该方法充分利用了计算机3D图形设备的几何运算能力,运算速度快,严谨高,可扩展性好。 相似文献
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本文介绍了用于DPSK调制的DS扩频信号非相干检测的一种SAW器件的设计方法。对所研究的差分延迟功能均集于单一器件中。因为没有采用独立的延迟线,故消除了带限影响,DPSK解调器延迟支路无插入损耗。 相似文献
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以噻吩为单体,在等离子体环境中聚合成致密的有机膜。利用Rutherford背散射(RB2S)和质子弹性反冲(ERD)、傅里叶红外谱(FTIR)测定了膜的成分和结构;从近红外-可见-紫外光的反射和透射谱,运用传递矩阵方法研究了膜的光学性质;此外,还探讨了24keV的I+离子束的注入对等离子体噻吩聚合膜的掺杂效应。结果表明,注入层内电荷载流子的输运机理可用Mott的可变自由程跳跃(VRH)理论给以解释。
关键词: 相似文献
160.
The problem of joint estimation of time delay and Doppler shift is considered from the point of view of the Wigner distribution of the signal. A very efficient method of obtaining the optimum signal with minimum estimation error based on the convexity of the design region is developed. Practical applications, however, require the signal to satisfy other constraints which present complications in acquiring the optimum signal. A design approach based on the method of simulated annealing is suggested to solve for the optimum signal under constraints. The performance of the signals so obtained is evaluated and compared with that of signals obtained by synthesis 相似文献