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991.
The nonlinear propagation of ion-acoustic waves is studied in an unmagnetized collissionless electronegative plasma, whose constituents are the inertial warm positive/negative ions and q-distributed nonextensive electrons. The latter have strong impact on the linear dispersion relation. However, for nonlinear analysis, a reductive perturbation technique is employed to derive a Korteweg-de Vries (KdV) equation accounting for nonthermal electrons in nonplanar geometries. Numerically, the effects of various plasma parameters, such as, the nonextensive parameter (q), the negative-to-positive ion mass ratio (α), the electron-to-positive ion number density ratio (μ), the positive ion-to-electron temperature ratio (θ i ) and negative ion-to-electron temperature ratio (θ n ), have been examined on the nonplanar compressive/rarefactive fast ion-acoustic solitons (where the wave phase speed is taken as λ>1). The relevance of our findings involving plasma wave excitations should be useful both for space and laboratory plasmas, where two distinct groups of ions besides the electrons, are present. 相似文献
992.
Recombinant eel GH and yeast containing chinook salmon growth hormone (reGHand rcsGH) were incorporated into gelatin and sodium alginate (reGH-GS and rcsGH-GS) or polymer ma-trix (reGH-HP55) to protect the hormone from proteolytic cleavage in the stomach. The diets containin greGH-GS, rcsGH-GS, reGH-HP55 and free-reGH or uncoated-rcsGH were administered to red sea bream. Feeding of reGH-GS, reGH-HP55 and rcsGH-GS diets resulted in significant increases in body weight and fork length over those of controls. These results strongly suggest that gelatin and sodium algi-nate as well as polymer matrix protected the hormone from proteolytic enzymes in the gastrointestinal tract to allow the bioactive hormone to enter the circulation and eventually stimulato fish growth. 相似文献
993.
在总结二台子金矿成矿规律的基础上,采用信息量和特征分析方法对矿区及外围进行了综合预测.之后,运用地球化学与构造应力分析相结合方法,对已知矿体进行了深部预测并定位. 相似文献
994.
The classical 1-D vertical advection-diffusion model was improved in this work.The main advantages of the improved model over the previous one are:1) The applicable condition of the 1-D model is made clear in the improved model,in that it is substantively applicable only to a vertical domain on which two end-member water masses are mixing.2) The substitution of parameter f(z) in the equation of the classical 1-D model with end-member fraction f1^z makes the model more precisely and easily solved.3) All the terms in the improved model equation have specific physical meanings,which makes the model easily understood.Practical application of the improved model to predict the vertical profiles of dissovled oxygen and micronutrients in abyssal ocean water of the North Pacific proved that the improvement of the 1-D advection-diffusion model is successful and practicable. 相似文献
995.
996.
一种基于差分投影的汽车牌照自动识别方法 总被引:2,自引:0,他引:2
针对汽车牌照的特点,利用差分投影法对汽车图像进行处理,确定出牌照的准确位置并将其整体切割下来;然后利用差分投影法对牌照进行切分,切分出待识别的车牌字符;再利用模板匹配的方法对切分出的车牌字符进行识别.实践证明该方法对汽车牌照的自动识别非常有效. 相似文献
997.
Pei-sheng Chen Hong-guang Shan Pin Zhang Yi-fei Gao 《Astrophysics and Space Science》2006,302(1-4):17-25
The 2MASS observation of the infrared quasars (IR QSOs) known so far is presented in this paper. Compared with the optical
selected quasars, infrared quasars are more dust-enshrouded and have redder colors and steeper spectral indices in the near
infrared. In consequence, they are much younger than the optical selected quasars. The result may be helpful to the suggestion
that the evolution links could be the ULIRGs - > the IR QSOs - > the optical selected quasars.
This publication makes use of data products from the Two Micron All Sky Survey (2MASS), which is a joint project of the University
of Massachusetts and the Infrared Processing and Analysis Center, funded by the National Aeronautics and Space Administration
and the National Science Foundation of the United States. 相似文献
998.
A comparative modelling of two catchments of similar sizes in Taiwan and England is described. In the study, despite its success in many Taiwanese catchments, including the Yan‐Shui Creek catchment in this study, the distributed model GBDM was initially found unsuitable when applied to the Brue catchment in South West England. However, the simulations are much better after revising the infiltration capacity. Further exploration reveals several interesting findings. (1) The infiltration computation based on soil characteristics and classifications is unreliable in the model. Other factors, such as climate, farming practice and vegetation cover, could have a much more significant impact. (2) The application of the GBDM far away from its ‘home country’ unveils a possible weakness of such a model for being ‘underfitting’. The fact that an ‘adjustment factor’ added in the model could improve both its calibration and validation may indicate that there is a room to improve the GBDM structure for catchments outside Taiwan. (3) The study illustrates the difficulty in creating a universal distributed model that could suit all possible hydrological environments, under the constraint of model parameter parsimony to minimize the ‘equifinality’ problem. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
999.
1000.
Nd Isotopes and Geochemistry of Phanerozoic Clastic Sedimentary Rocks from the Yangtze Block and Their Tectonic Implications 总被引:1,自引:1,他引:0
This article presents Sm-Nd and geochemical data on fine-grained sediments of the northern margin from the Yangtze block, China, to understand the variations of Nd isotopic compositions and crustal evolution history in this area. The results are as follows: (1) Nd isotopic compositions for clastic sedimentary rocks of the Middle-Late Proterozoic have relatively positive Nd(t) values ( 2.72 to 0.69), with Nd model ages from 1.38 Ga to 1.55 Ga, corresponding to the contemporaneous volcanic rocks from the Xixiang (西乡) Group. This indicates that the arc-related materials from Middle-Late Proterozoic dominate the provenances of the Middle-Late Proterozoic periods. (2) The gradual decrease in εNd(t) during the Cambrian-Carboniferous periods is likely to reflect the progressively increasing proportion of erosion materials from the Foping (佛坪) and Qinling (秦岭) complexes, corresponding to a gradually decreasing trend in the La/Th ratios. (3) A prominent increase in the εNd(t) value of the Late Permian strata probably reflects the significant incorporation of the mantle-derived materials. The trace element data are compared with data of the Emeishan (峨嵋山) flood basalts. These data indicate that the volcanic dust has been added to the Late Permian strata during the Late Permian, represented by periods of extremely high Emeishan flood basalt activity in the south-eastern margin of the Yangtze block. 相似文献