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1.
GP. Horedt 《Celestial Mechanics and Dynamical Astronomy》1972,6(2):232-241
We consider a large massM and two small massesm
1 andm
2 (m
1 m
2;m
1,m
2M). The orbit ofm
1 is initially circular and the motion ofm
2 hyperbolic with respect toM. The orbital elements of the small masses are strongly modified after a close, single encounter betweenm
1 andm
2.An approximative method, similar to the theory of stellar encounters, is used to determine the probabilities of collisions, hyperbolas, direct and retrograde ellipses, as well as the mean values of the semimajor axes and their root mean square deviation after the encounter.The results are close to those which are obtained if the massm
2 is negligibly small, (Mm
1m
2;m
2 0), as should be also expected on general grounds. 相似文献
2.
Sediment resuspension during and after mechanical excavation of macrophytes may have a significant impact on resident fish populations. Unfortunately, little is known about the influence of this sediment on the respiratory performance and feeding abilities of fishes in New Zealand waterways. We examined the effects of suspended sediment (SS) concentrations previously observed after a large-scale macrophyte removal operation on oxygen consumption (MO2) and feeding rates of brown trout (Salmo trutta). MO2 at 0 mg L?1, 150 mg L?1, 300 mg L?1, 450 mg L?1 and 600 mg L?1 of SS was measured using semi-closed respirometry. Feeding rates at the same SS concentrations were also measured using laboratory tank experiments. Results suggest that SS concentrations up to 600 mg L?1 have no effect on MO2. Conversely, feeding rates were significantly reduced at 450 mg L?1 (22% reduction) and 600 mg L?1 (31% reduction), indicating that sediment concentrations above 450 mg L?1 may negatively affect brown trout populations. 相似文献
3.
Somenath Mondal G.P. Padmakumar V. Sharma Maryam Shojaei Baghini 《Geomechanics and Geoengineering》2016,11(1):73-85
Determination of thermal properties of soils (viz., thermal resistivity, thermal conductivity, thermal diffusivity and heat capacity), which primarily influence heat migration through the soil mass, is essential in situations where geomaterials are relentlessly subjected to higher temperatures and temperature variations. These properties of the soil mainly depend upon its type, mineralogy, particle size and gradational characteristics, density and water content. In this context, earlier researchers have determined thermal conductivity of soils by employing a thermal probe (a line heat source), which works on the principle of transient method (TM) of heat conduction. However, this methodology cannot be employed for establishing the heat flow (read thermal regime) through the soil. Hence, development of an alternate technique, which facilitates quantification of temporal and spatial variation of the heat flux and temperature in the soil mass, becomes essential. With this in mind, a methodology to determine thermal conductivity of soils by employing the concept of thermal flux measurement (TFM) has been developed and its details are presented in this paper. Results obtained from the TM and TFM have also been critically evaluated for the sake of validation and generating more confidence in the proposed methodology. 相似文献
4.
GP. Horedt 《Earth, Moon, and Planets》1976,15(3-4):439-443
If the mass of the Earth was not considerably larger than at present, the pre-capture orbit of the Moon was in the range 0.9–1.1 A.U. Capture occurred within several 108 years after formation of the Moon. 相似文献
5.
GP Jones 《新西兰海洋与淡水研究杂志》2013,47(3):334-359
Abstract This review examines the history and current understanding of the ecology of rocky reef fishes in northeastern New Zealand, marking the fiftieth anniversary of the Leigh Marine Laboratory. The cumulative number of publications increased steadily to c. 180 by 2012. Most attention has been on the snapper (Pagrus auratus, f. Sparidae), the largest in size and economically most important species, and on triplefins (Tripterygiidae), the smallest in size and most diverse family. A strong quantitative school emerged in the 1980s, a period when there was little research on temperate reef fishes elsewhere. A ‘bottom-up’ view of the effects of habitat structure on fish emerged, identifying the key roles of depth, topography and macroalgae. By 2000, attention shifted to using marine reserves as laboratories for ecological research. A ‘top-down’ view of fish as predators emerged, documenting cascading effects on prey communities and habitats. The two different viewpoints have not yet been integrated. Research gaps, including population connectivity and climate change, represent major challenges for the next 50 years. 相似文献
6.
Quantitative recruitment of ichthyofauna into a South African temporarily open/closed estuary (TOCE) was investigated during three distinct hydrological phases: closed overwash, open outflow and tidal mouth conditions. Maximum recruitment densities occurred during outflow conditions and declined when the system became tidally inundated. Recruitment densities were lowest during overwash events. Selective diel variation was evident, with higher night-time densities for each phase. This study highlights the importance of seasonal timing and duration of open conditions and overwash events for structuring ichthyofaunal community composition of southern African TOCEs. 相似文献
7.
K. B. Padmakumar B. R. Smitha Lathika Cicily Thomas C. L. Fanimol G. SreeRenjima N. R. Menon V. N. Sanjeevan 《Ocean Science Journal》2010,45(3):151-157
This study presents in situ evidence for the blooms of Trichodesmium erythraeum observed in the shelf waters of the South Eastern Arabian Sea (SEAS) during the onset of the southwest monsoon in June 2009. Evidence showed that water surface discoloration was caused by the accumulation of T. erythraeum, and that the water column contained a colony of T. thiebautii. The surface water color in the bloom region varied from pale brown to pinkish red. Pale brown indicated healthy algae at the peak of its photosynthetic activity, while pinkish red indicated the presence of photosynthetically less active filaments. Zooplankton abundance, especially copepodites, in the bloom area substantiated the theory that Trichodesmium filaments are excellent epiphytes to which the copepodites cling. The bloom area was very fertile with copious quantities of dissolved oxygen (6.85 ml L?1), PO4-P (0.108 μmol L?1) and SiO4 (1.29 μmol L?1). Lower NO3-N (0.028 μmol L?1) values in the bloom area did not appear to affect Trichodesmium growth from molecular nitrogen fixation. However, lower NO3-N values altered the normal phytoplankton composition of this area. 相似文献
8.
华南西部地区晚中生代与W-Sn矿有关花岗岩的年代学格架及地质意义 总被引：10，自引：3，他引：7
华南西部地区是我国重要的大型-超大型锡多金属矿床分布区。本文根据近年来新获得的花岗岩LA-ICP-MS锆石U-Pb数据,结合近几年以来新报道的高精度成岩成矿年代学资料和地球动力学研究进展,总结发现华南西部地区中生代岩浆-成矿作用的时代主要集中在晚白垩世(76～98Ma)。通过分别总结华南东、西部地区晚白垩岩浆作用及相应的成矿作用的特征,发现华南东、西部的成岩成矿作用特征表现出明显的差异,但是这两地内部各自却表现出高度的一致性;且东部地区明显要比西部地区更为复杂,但二者之间的共同点在于该时期均处于岩石圈伸展的环境和壳幔间的相互作用明显。晚白垩世华南西部地区主要受控于华南陆块陆内背景下岩石圈伸展而导致的岩浆-成矿作用这一因素,而东部地区除此之外还受到太平洋古板块北北东向走滑带来的影响。 相似文献
9.
In the present study, an attempt has been made to characterize the biophysical land units in Kanholi bara river basin of sub-humid
tropical ecosystem of central India using remotely sensed data, field surveys and GIS based multi-criteria overlay analysis.
The geo-spatial database on elevation, slope, landforms, soil depth, soil erosion, land use/land cover and hydrogeomorphological
parameters has been generated using IRS-ID LISS-III satellite data coupled with soil survey data in GIS. The methodology followed
in characterization of biophysical land units in GIS includes assigning scores for different classes of the layers and weighatges
for different layers based on their characteristics and degree of influence on desired output. GIS based ‘multi criteria overlay’
analysis reveals seventeen distinct biophysical land units in the river basin. Severe (50.5-59.5) to very severe (59.5) biophysical
stress units are found in plateau spurs, isolated mounds, linear ridges, dissected plateau and escarpments. These zones are
associated with severe to very severe erosion, steep to very steep, extremely shallow soils, poor to very poor groundwater
prospects, wastelands and scrublands. The characterization of biophysical land units helps in analysis of their potentials,
problems and stress environment to plan and execute site-specific landscape management practices and maximize the productivity
from each biophysical land unit. The present study demonstrates that generation of geo-spatial database based on remotely
sensed data and field surveys in GIS and their analysis helps great extent in characterization of biophysical land units and
analysis of their stress environment for management. 相似文献
10.
SHARE Asia自动气象站网络：喜马拉雅山—喀喇昆仑山地区气候研究的一个必要组成部分 总被引：1，自引：0，他引：1
E. Vuillermoz L. Bertolani C. Smiraglia GP. Verza G. Tartari A. Marinoni P. Bonasoni 《地球科学进展》2006,21(12):1244-1253
Ev K2 CNR SHARE Asia计划的目标就是建立一个沿喜马拉雅山—喀喇昆仑山脉的监测网络，为气象学和气候研究提供参数，特别是为季风变化、大气化学、冰川学、高海拔湖沼学和古湖沼学等研究，同时也为准确地确定地球表面坐标。SHARE Asia 计划的一个特殊的目的是发展一套完整的测量系统，以满足不断进步的环境与地球科学；促进当地的技术升级和建设的能力。
就像WMO CEOP 和UNEP ABC一样，SHARE Asia 气象—气候及大气化学观测站已经成为重要的国际科学计划的一部分。 相似文献