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141.
准确的磁场模型对于辐射带粒子环境研究至关重要.本文利用美国Van Allen Probes（VAP）在2012至2018年期间测量的磁场数据和GOES15在2011至2017年期间测量的磁场数据,定量地评估了三个较新的外磁场经验模型（TS05、TA15和TA16）对外辐射带区域（3~6.6RE）磁场的描述性能.本文选择预测效率（Prediction Efficiency,PE）作为评估指标,定量分析各模型在不同空间范围（Lm值）、不同地磁活动水平（Kp）以及不同磁地方时（MLT）下的性能表现,并且计算了观测磁场与模型磁场的夹角θ,以评估模型的磁场方向预测能力.结果表明：PE随Lm值增大,随地磁扰动增强而下降;θ随Lm值增大,随地磁扰动增强而增大.在Lm=5~6.5RE范围内,PE呈现晨昏不对称性,MLT=12-21时的PE值小于MLT=0-9时的值,说明三个磁场模型可以较好地描述晨侧磁场的强度,但它们并不能很好地反映下午至昏侧磁场的大小;在地球同步轨道附近（Lm~6.6RE）,PE呈现昼夜不对称性,MLT=9-15时的PE值大于其他时区的值,说明三个磁场模型可以很好地反映昼侧磁场大小,但在夜侧可能存在较大的误差.θ在MLT=6-12时的值小于其他时区的值,呈现昼夜不对称性,说明三个磁场模型可以较好地描述昼侧磁力线的分布位型,但在夜侧存在较大的方向描述误差.在外辐射带3~6.5RE内,TA16模型与VAP磁场观测数据最为接近,PE均大于0.7,θ均小于3°;在地球同步轨道高度（6.6RE）,TS05模型与GOES15卫星磁场观测数据最为接近,PE约为0.75,θ约为7°.相关的研究结果可以为我国星载高能粒子探测器探测数据的在轨交叉定标、辐射带高能粒子动态模型研究和相关的磁层环境理论/应用研究提供地磁场模型选择方面的参考. 相似文献
142.
The empirical orthogonal functions have been obtained for the individual summer monsoon (June through September) months using
the grid point values of monthly 700 mb geopotential heights over Indian region. The data for 21 summer monsoon months for
the years 1958 to 1978 have been used in the present computation.
The major variance reduction is due to the first three dominant functions accounting over 80% of the total variance in each
month. The variance reduction only due to the first function ranges from 45 to 65%.
The first function has in-pbase oscillation throughout the area indicating that the area under study is homogeneous and the
centre of the oscillation lies over northwest India. The amplitudes of the first function also show generally quasipers stence
in their sign within a season. The second function has two centres of action over the region of monsoon trough which are in
phase. The third function has also two centres oriented in the east-west direction but they are in the opposite phase.
Fairly large values of correlation coefficients between the patterns of the different monsoon months suggest that the patterns
for these months corresponding to the first and the second functions respectively are quite similar. The patterns for these
months also evolve with time in a related way. The spectrum analysis to the time series of amplitudes indicates the presence
of the quasi-periodicity of 3 years during these monsoon months. The amplitudes corresponding to the dominant functions are
found to be significantly related with the rainfall of central and western parts of India 相似文献
143.
《国际泥沙研究》2020,35(1):79-90
Flash floods are the highest sediment transporting agent,but are inaccessible for in-situ sampling and have rarely been analyzed by remote sensing technology.Laboratory and field experiments were done to develop linear spectral unmixing(LSU) remote sensing model and evaluate its performance in simulating the suspended sediment concentration(SSC) in flash floods.The models were developed from continuous monitoring in the laboratory and the onsite spectral signature of river bed sediment deposits and flash floods in the Tekeze River and in its tributary,the Tsirare River.The Pearson correlation coefficient was used to determine the variability of correlations between reflectance and SSCs.The coefficient of determination(R2) and root mean square of error(RMSE) were used to evaluate the performance of the generated models.The results found that the Pearson correlation coefficient between SSCs and reflectance varied based on the level of the SSCs,geological colors,and grain sizes.The performance of the LSU model and empirical remote sensing approaches were computed to be R2=0.92,and RMSE=±0.76 g/1 in the Tsirare River and R2=0.91,and RMSE=±0.73 g/1 in the Tekeze River and R2=0.81,RMSE=±2.65 g/l in the Tsirare river and R2=0.76,RMSE=±10.87 g/l in the Tekeze River,respectively.Hence,the LSU approach of remote sensing was found to be relatively accurate in monitoring and modeling the variability of SSCs that could be applied to the upper Tekeze River basin. 相似文献
144.
The moment method is a well known technique, which uses a time series ofthe first 3 moments of a spectral line, to estimate the (discrete) modeparameters and m. The method, contrary to Doppler imaging,also yields other interesting(real-valued) parameters such as the inclination angle i, or v sin i,during its identification procedure.In this paper, we are not only interested in the estimation of thesereal-valued parameters themselves but also inreliable estimates for their uncertainty.We designed a statistical formalism for the moment method based on theso-called generalized estimating equations (GEE). This formalismaims to estimate the uncertainty of the real-valued parameters taking intoaccount that the different moments of a line profile are correlated and –more importantly – that the uncertainty of the observed moments depends onthe pulsation parameters. The latter property of the moment method makesthe least-squares technique a poor choice to estimate the uncertainty ofthe real-valued parameters. We implemented the GEE method and presentan application to a high-resolution spectroscopic dataset of the slowly pulsating B star HD181558. 相似文献
145.
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147.
层积云覆盖的海洋边界层云详细微物理过程的数值模拟 总被引：1，自引：0，他引：1
文中建立了一个含显式分档的云微物理模式和辐射传输模式的一维 3阶湍流闭合模式 ,该模式可用于研究海洋边界层云中气溶胶和云的相互作用过程 ,同时提出了一种新的动力模式和微物理模式耦合方法 ,该方法可使动力模式中液态水相关项可以直接由微物理模式变量计算得到。作为模式的初步应用模拟了 2 0 0 1年APEX/ACE Asia在西太平洋上所观测到的一个个例。模拟结果和观测资料比较表明该模式基本上模拟出层积云覆盖的海洋边界层的基本结构 相似文献
148.
用2002年3月31日台湾Ms7．5地震时上海地区软土地表和基岩记录的加速度资料讨论了地表软土覆盖层面波的地震动反应，并用经验格林函数法合成了台湾未来8级大地震在上海基岩和土层处的面波加速度时程，初步估计了其对高层建筑的影响。其结果对上海的工程抗震设计有参考价值。 相似文献
149.
150.
Fracture toughness measurements under static loading conditions have been carried out in Barre and Lac du Bonnet granites.
An advanced AE technique has been adopted to monitor real-time crack initiation and propagation around the principal crack
in these tests to understand the processes of brittle failure under tension and related characteristics of the resulting fracture
process zone. The anisotropy of Mode I fracture toughness has been investigated along specific directions. Microcrack density
and orientation analysis from thin section studies have shown these characteristics to be the primary cause of the observed
variation in fracture toughness, which is seen to vary between 1.14 MPa.(m)1/2 and 1.89 MPa.(m)1/2 in Barre granite. The latter value represents the case in which the crack is propagated at right angles to the main set of
microcracks. The creation of a significant fracture process zone surrounding the propagating main crack has been confirmed.
Real-time imaging of the fracture process and formation of fracture process zone by AE techniques yielded results in very
good agreement with those obtained by direct optical analysis. 相似文献