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1.
In the present paper we have studied the resonance problem arising for critical mass values following Birkhoff's method of normalisation. It has been shown that for both the critical values the motion will remain unstable whether the critical terms are left in the Hamiltonian or carried to the coordinates in the process of normalisation. 相似文献
2.
M. Gamo P. Goyal Manju Kumari U. C. Mohanty M. P. Singh 《Boundary-Layer Meteorology》1994,67(3):213-227
Annual variations of mixed-layer characteristics at New Delhi, India have been studied for a weak monsoon (1987) and a strong monsoon (1988) year. In the weak monsoon year (1987), the maximum mixing depthh
max was found to have a value of around 3000 m during the pre-monsoon, less than 2000 m during the summer monsoon, around 2000 m during the post-monsoon, and less than 1000 m in the winter season. For the strong monsoon year (1988),h
max values were less than 1987 values for comparable periods throughout the year. The seasonal and yearly differences ofh
max were explained by the surface energy balance and potential temperature gradient at a time close to sunrise. According to the spatial patterns of obtained by an objective analysis of the 850 to 700 hPa layers. mixed-layer characteristics obtained at New Delhi are representative of the north and central regions of India. 相似文献
3.
S. V. N. Rao Sudhir Kumar Shashank Shekhar S. K. Sinha S. Manju 《Hydrogeology Journal》2007,15(6):1157-1167
This report examines the problem involving the pumping of groundwater from a group of 90 existing wells along the banks of the Yamuna River, northwest of Delhi (India), underlain with geologically occurring saline water. It is known that unregulated pumping will lead to upconing of saline water and therefore it is necessary to determine optimal rates and associated well locations (from an existing group of candidate wells that supply drinking water to the city of Delhi) that will minimize the total salinity. The nonlinear, non-convex problem is solved by embedding the calibrated groundwater model within a simulation-optimisation (S/O) framework. Optimisation is accomplished by using simulated annealing (SA), a search algorithm. The computational burden is primarily managed by replacing the numerical model with a surrogate simulator-artificial neural network (ANN). The model is applied to the real system to determine the optimal pumping schedule. The results of the operational model suggest that the skimming wells must be operated from optimal locations such that they are staggered in space and time to obtain the least saline water. 相似文献
4.
Spacecraft and their subsystem components are subject to a very hazardous radiation environment in both near-Earth and deep space orbits. Knowledge of the effects of this high energy particle and electromagnetic radiation is essential in designing sensors, electronic circuits and living habitats for humans in near Earth orbit, en route to and on the Moon and Mars. This paper discusses the use of Monte Carlo simulations to optimize system design, radiation source modeling, and determination of background in sensors due to galactic cosmic rays and radiation from the Moon. The results demonstrate the use of Monte Carlo particle transport toolkits to predict secondary production, determine dose rates in space and design required shielding geometry. 相似文献
5.
K. R. Renjith Manju Mary Joseph Prosenjit Ghosh K. Habeeb Rahman C. S. Ratheesh Kumar N. Chandramohanakumar 《Environmental Earth Sciences》2013,70(2):729-742
Seasonal studies were carried out from 21 stations, comprising of three zones, of Cochin Estuary, to assess the organic matter quality and trophic status. The hydographical parameters showed significant seasonal variations and nutrients and chlorophylls were generally higher during the monsoon season. However, chemical contamination along with the seasonal limitations of light and nitrogen imposed restrictions on the primary production and as a result, mesotrophic conditions generally prevailed in the water column. The nutrient stoichometries and δ 13C values of surficial sediments indicated significant allochthonous contribution of organic matter. Irrespective of the higher content of total organic matter, the labile organic matter was very low. Dominance of carbohydrates over lipids and proteins indicated the lower nutritive aspect of the organic matter, and their aged and refractory nature. This, along with higher amount of phytodetritus and the low algal contribution to the biopolymeric carbon corroborated the dominance of allochthonous organic matter and the heterotrophic nature. The spatial and seasonal variations of labile organic components could effectively substantiate the observed shift in the productivity pattern. An alternative ratio, lipids to tannins and lignins, was proposed to ascertain the relative contribution of allochthonous organic matter in the estuary. This study confirmed the efficiency of an integrated biogeochemical approach to establish zones with distinct benthic trophic status associated with different degrees of natural and anthropogenic input. Nevertheless, our results also suggest that the biochemical composition alone could lead to erroneous conclusions in the case of regions that receive enormous amounts of anthropogenic inputs. 相似文献
6.
Arecanut is one of the predominant plantation crop grown in India. Yield of this crop depends upon age of the crop and there is no information on the spectral behaviour of arecanut crops across its ages. In this study popular supervised classification algorithms were utilized for age discrimination of arecanut crops using Hyperion imagery. Arecanut plantations selected for the study are located in Channagiri Taluk, Davanagere district of Karnataka state, India. Ground truth information collected involves: (i) GPS coordinates of selected plots, (ii) spectral reflectance of arecanut crops with age ranging from 1 to 50 years, using handheld spectroradiometer with 1 nm spectral resolution. These spectral measurements were made close in time to the acquisition of Hyperion imagery to build age-based spectral library. It is observed from the analysis that crops of ages below 3, 3–7, 8–15 and above 15 years were showing distinct spectral behaviour. Accordingly, crops age ranging from 1 to 50 were grouped into four classes. Classification of arecanut crops based on age groups was performed using methods like spectral angle mapper, support vector machine and minimum distance classifier, and were compared to find the most suitable method. Among the classification methods adopted, support vector machine with linear kernel function resulted in most accurate classification method with overall accuracy of 72% for within class seperability. Individual age group classification producer’s accuracy varied minimum of 12.5% for 3–7 years age group and maximum of 86.25% for above 15 years age group. It may be concluded that, not only age- based arecanut crop classification is possible, but also it is possible to develop age-based spectral library for plantation crop like arecanut. 相似文献
7.
Manju Mary Joseph C. S. Ratheesh Kumar K. R. Renjith T. R. Gireesh Kumar N. Chandramohanakumar 《Environmental Earth Sciences》2011,62(6):1209-1218
The phosphorus fractions in three tropical mangrove systems of Cochin region were analysed by sequential extraction method.
Iron-bound phosphorus was the major fraction in the first two stations, while station 3 was exclusively dominated by calcium-bound
phosphorus. Compared to other stations, about tenfold increase in total phosphorus content was observed at station 3. This
station is a congregation of communally breeding birds, and there is accumulation of bird guano. Mineralogical analysis showed
the presence of monetite, a thermodynamically metastable calcium phosphate mineral, in this unique system. The excreta and
carcass of the birds in this sanctuary seems to be the reason for the formation of monetite, which is favoured by periodic
fluctuations in redox potential. The high mass percentages of calcium and phosphorus by XRF and SEM–EDS analysis confirm the
existence of calcium phosphate mineral at station 3. First two stations did not show any noticeable difference in phosphorus
fractions and inorganic fractions constituted to about 65% of total phosphorus. But at station 3, inorganic fractions were
about 92%. Low C:P ratios and low organic phosphorus content indicated active mineralisation of phosphorus at station 3. Bioavailable
fractions of phosphorus at stations 1 and 2 were about 75%, whereas 98% of the total phosphorus was bioavailable at station
3. Since the bulk of the total phosphorus is bioavailable, these mangrove sediments have the potential to act as source of
phosphorus to the overlying waters. 相似文献
8.
G. Manju V. M. Chowdary Y. K. Srivastava S. Selvamani A. Jeyaram S. Adiga 《Journal of the Indian Society of Remote Sensing》2005,33(1):51-61
Sustainable management of wetland ecosystem is necessary as it serves the important functions such as food storage, water
quality maintenance and providing habitat for different species of wildlife. Hence, an inventory of wetlands in any given
area is a pre-requisite for their conservation and management. A study has been carried out to delineate the wetlands of east
Champaran district of Bihar, India, using IRS ID LISS III data. The data for the pre and post monsoon seasons have been analysed
and the wetlands have been qualitatively characterized based on the turbidity and aquatic vegetation status. The extent of
water logging problem in the study area was inferred from the seasonal variation of waterspread during both the seasons. The
three categories of wetlands (ponds/lakes, water logged areas and oxbow lakes) have been identified. From the analysis, it
has been observed that the inland wetlands constitute 2.7% of the study area, of which 1.8% is subjected to water logging.
Thus, this study highlights the usefulness of remotely sensed data for wetland mapping, seasonal monitoring and characterization. 相似文献
9.
Abdul Azeez S Revichandran C Muraleedharan K. R John Sebin Seena G Nair Ravikumar C. Manju K. G 《Ocean Dynamics》2021,71(9):923-933
Ocean Dynamics - We investigated the vertical and horizontal variation of the sound speed using the Thermodynamic Equation Of Seawater-2010 (TEOS-10) and monthly CTD observations at Cochin estuary... 相似文献
10.