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排序方式: 共有403条查询结果,搜索用时 15 毫秒
1.
2.
Hemant K. Badola Jitendra S. Butola 《山地科学学报》2005,2(2):173-180
This paper examines the effect of ploughing depths (A -- 60 cm, B -- 45 cm and C -- 30 cm) on the growth and yield of Heracleum candicans Wall (Apiaceae), a threatened medicinal herb of the Himalayan region. This less-explored plant is being suggested as a potential crop for the mountain agriculture. The study was carried out in an orchard in Himachal Pradesh, India at 2500 m altitude, for two successive growth years. During the first year, all plants remained in juvenile state; in the second year, nearly 65 % plants produced flowers only under 60cm ploughing depth. Among its morphological traits, plant height, collar diameter and aboveground flesh weight were found to be strongly correlated (P 〈 0.01) with the belowground biomass during the first year (r =0.968, 0.925 and 0.973, respectively) and during the second year (r=0.945, 0.928 and 0.775, respectively). Increase in the ploughing depth was significantly correlated (P〈0.01) with all growth parameters, including the belowground dry weight, marketable portion of the produce. The belowground biomass (commercial yield; 16.28 Qt/hec) at depth A was about 2.6 and 4.7 times higher than those recorded at depths B and C, respectively. The results clearly justify the importance of deep ploughing and this paper strongly recommends it for economically sustainable cropping. 相似文献
3.
4.
The mean state of the tropical atmosphere is important as the nature of the coupling between the ocean and the atmosphere
depends nonlinearly on the basic state of the coupled system. The simulation of the annual cycle of the tropical surface wind
stress by 17 atmospheric general circulation models (AGCMs) is examined and intercompared. The models considered were part
of the Atmospheric Model Intercomparison Project (AMIP) and were integrated with observed sea surface temperature (SST) for
the decade 1979–1988. Several measures have been devised to intercompare the performance of the 17 models on global tropical
as well as regional scales. Within the limits of observational uncertainties, the models under examination simulate realistic
tropical area-averaged zonal and meridional annual mean stresses. This is a noteworthy improvement over older generation low
resolution models which were noted for their simulation of surface stresses considerably weaker than the observations. The
models also simulate realistic magnitudes of the spatial distribution of the annual mean surface stress field and are seen
to reproduce realistically its observed spatial pattern. Similar features are observed in the simulations of the annual variance
field. The models perform well over almost all the tropical regions apart from a few. Of these, the simulations over Somali
are interesting. Over this region, the models are seen to underestimate the annual mean zonal and meridional stresses. There
is also wide variance between the different models in simulating these quantities. Large model-to-model variations were also
seen in the simulations of the annual mean meridional stress field over equatorial Indian Ocean, south central Pacific, north
east Pacific and equatorial eastern Pacific oceans. It is shown that the systematic errors in simulating the surface winds
are related to the systematic errors in simulating the Inter-Tropical Convergence Zone (ITCZ) in its location and intensity.
Weaker than observed annual mean southwesterlies simulated by most models over Somali is due to weaker than observed southwesterlies
during the Northern Hemisphere summer. This is related to the weaker than observed land precipitation simulated by most models
during the Northern Hemisphere summer. The diversity in simulation of the surface wind over Somali and equatorial Indian ocean
is related to the diversity of AGCMs in simulating the precipitation zones in these regions.
Received: 2 August 1996 / Accepted: 7 February 1997 相似文献
5.
6.
Tapendra Nath Maulik 《Pure and Applied Geophysics》1965,60(1):42-50
Summary Propagation of surface wave in heterogeneous media with various laws of variation of elastic properties have been discussed previously by several authors. There the laws of variations were taken on the considerations that the solutions might be had in terms of known functions. Here the approximate solutions for polynomial law of variations of elastic properties have been obtained. 相似文献
7.
We have sampled particles of native aluminium (Al°) in two sediment cores from the Central Indian Basin (CIB). The cores are geographically separated but are located at the base of two seamounts. The native Al° particles occurring as grains and spherules, have an average Al content of 95% and are associated with volcanogenic–hydrothermal material. Morphologically and compositionally, the specimens are similar to those reported from the East Pacific Rise. After ruling out several processes for the presence of the native Al°, we hypothesize that during progressive melting of magma, a basaltic magma is produced which has high contents of reductants such as methane and hydrogen, and a low oxygen fugacity. During the upward migration of such magma, reduction to metallic aluminium and the formation of native Al° particles takes place. 相似文献
8.
A unified ionospheric electron collision frequency model profile 〈νg〉 has been calculated in the height range 50–500 km. The computed profile accounts for the electron collisions with the neutral particles as well as the ions. Experimental values of momentum transfer cross-sections have been used for electron collisions with N2, O2 and Ar and theoretical values for N, O, He and H. It is observed that the electron-ion collisions 〈νei〉 dominate over the electron-neutral collisions 〈νen〉 above 170 km. However, 〈νe?N〉 is of the same order of magnitude as 〈νe?O〉 in the height range 170–210 km. Above 360 km 〈νe?O〉 becomes more important among the neutrals. The temporal, seasonal and solar epoch variations of 〈νei〉 are also shown. A typical electron collision frequency profile 〈νg〉 corresponding to the exospheric temperature of 1100 K has been compared with the available experimental results for D, E and F-regions obtained from different experimental techniques. This profile has been used to determine the electrical, thermal, heat flow and current flow conductivities, the mobility and the diffusivity of electrons. The results so obtained are found to be in good agreement with the earlier results. 相似文献
9.
S. K. Nath N. N. Biswas M. Dravinski A. S. Papageorgiou 《Pure and Applied Geophysics》2002,159(11-12):2673-2698
—?Site response was estimated at 19 sites in the Anchorage basin in south-central Alaska, using 15 local earthquakes recorded with good signal-to-noise ratio by a temporary weak motion network. The receiver-function-type horizontal-to-vertical spectral ratios (HVSR) were computed at 1–9 Hz frequency band and the resulting HVSR contour maps at 1, 5 and 9 Hz are presented here. The spatial site response distribution shows considerable variation from the foothills of the Chugach Mountains in the east to the western part of Anchorage. The site response increases by a factor of 3 and 3.5 at 1 and 5 Hz, respectively, from the area of older glacial deposits in the eastern part of the city to the area occupied by the Bootlegger Cove formation, particularly in the section adjoining Knik Arm. At 9 Hz, the variation of HVSR from the east to the west is smaller, approximately by a factor of 2. Moreover, the trend of the HVSR variation at 1 and 5 Hz shows good correlation with that of the soil class obtained from surface measurements of S-wave velocity in the 0–30?m depth range and available results on ground failure susceptibility of Anchorage. 相似文献
10.
We present some preliminary results from a multi-layer soil temperature finite-difference model using the data set obtained
during the pilot experiment on land surface processes at Anand. We hope that the present results will prove useful during
the final field experiments scheduled for the coming monsoon season. 相似文献