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排序方式: 共有663条查询结果,搜索用时 15 毫秒
1.
Nonlinear Alfvén wave in a hot rotating and strongly magnetized electron-positron plasma is considered. Using relativistic two fluid equations, the dispersion relation for Alfvén wave in the rotating plasma is obtained. Large amplitude Alfvén solitons are found to exist in the rotating pulsar plasma. Rotational effects on solitons are discussed. 相似文献
2.
Rashid Umar M. Muqtada A. Khan Izrar Ahmed Shakeel Ahmed 《Journal of Earth System Science》2008,117(1):69-78
The Kali-Hindon inter-stream region extends over an area of 395 km2 within the Ganga-Yamuna interfluve. It is a fertile tract for sugarcane cultivation. Groundwater is a primary resource for
irrigation and industrial purposes. In recent years, over-exploitation has resulted in an adverse impact on the groundwater
regime. In this study, an attempt has been made to calculate a water balance for the Kali-Hindon inter-stream region. Various
inflows and outflows to and from the aquifer have been calculated. The recharge due to rainfall and other recharge parameters
such as horizontal inflow, irrigation return flow and canal seepage were also evaluated. Groundwater withdrawals, evaporation
from the water table, discharge from the aquifer to rivers and horizontal subsurface outflows were also estimated. The results
show that total recharge into the system is 148.72 million cubic metres (Mcum), whereas the total discharge is 161.06 Mcum,
leaving a deficit balance of −12.34 Mcum. Similarly, the groundwater balance was evaluated for the successive four years.
The result shows that the groundwater balance is highly sensitive to variation in rainfall followed by draft through pumpage.
The depths to water level are shallow in the canal-irrigated northern part of the basin and deeper in the southern part. The
pre-monsoon and post-monsoon water levels range from 4.6 to 17.7 m below ground level (bgl) and from 3.5 to 16.5 m bgl respectively.
It is concluded that the groundwater may be pumped in the canal-irrigated northern part, while withdrawals may be restricted
to the southern portion of the basin, where intense abstraction has led to rapidly falling water table levels. 相似文献
3.
Hydrogeologic assessment of escalating groundwater exploitation in the Indus Basin, Pakistan 总被引:1,自引:1,他引:0
Groundwater development has contributed significantly to food security and reduction in poverty in Pakistan. Due to rapid population growth there has been a dramatic increase in the intensity of groundwater exploitation leading to declining water tables and deteriorating groundwater quality. In such prevailing conditions, the hydrogeological appraisal of escalating groundwater exploitation has become of paramount importance. Keeping this in view, a surface water–groundwater quantity and quality model was developed to assess future groundwater trends in the Rechna Doab (RD), a sub-catchment of the Indus River Basin. Scenario analysis shows that if dry conditions persist, there will be an overall decline in groundwater levels of around 10 m for the whole of RD during the next 25 years. The lower parts of RD with limited surface water supplies will undergo the highest decline in groundwater levels (10 to 20 m), which will make groundwater pumping very expensive for farmers. There is a high risk of groundwater salinization due to vertical upconing and lateral movement of highly saline groundwater into the fresh shallow aquifers in the upper parts of RD. If groundwater pumping is allowed to increase at the current rate, there will be an overall decline in groundwater salinity for the lower and middle parts of RD because of enhanced river leakage. 相似文献
4.
Sawant SB Khan YS 《Population geography : a journal of the Association of Population Geographers of India》1982,4(1-2):67-75
This paper analyzes the impact of various factors on variations in the rate of natural increase of population in Western Maharashtra, India. By using district level data, coefficients of correlation have been calculated between the rate of natural increase, the birth rate and the death rate on the 1 hand and different factors affecting them on the other. The analysis shows that in Western Maharashtra the birth rate is high in response to the high death rate and the high infant mortality rate. It is also revealed that the rate of natural increase of the population declines with an increase in the proportion of working females as well as the proportion of educated males. All this signifies that the region under study is in the 2nd stage of the "demographic transition." 相似文献
5.
Summary Analytical transmission electron microscopy has been used to investigate two zincian dolomites occurring as overgrowths on calcite from the oxidized zone of the ore bodies at Broken Hill, New South Wales. Particular attention has been focussed on the nature of the microstructures, and any correlations between microstructure and local composition, especially zinc content. The possible occurrence of tiny amounts of the zinc dolomite, minrecordite, has also been explored.The most notable features in the zincian dolomite are fine-scale distributions of ribbonlike calcitic second phase, growth bands, and modulated microstructures (strong modulations in diffraction contrast). Their occurrence is correlated with calcium in excess of stoichiometric requirements, but is not directly influenced by zinc content. The associated calcites are low in zinc, but they also exhibit carbonate second phase, which is thought to be dolomitic although giving no detectable order (b-type) reflections. Long-exposure electron diffraction patterns, however, revealed the presence of diffuse c-type superstructure reflections, which are thought to arise from smaller volumes in which Ca and Mg cations are ordered, for which a model is proposed.
With 10 Figures 相似文献
Zusammensetzungsabhängige Mikrogefüge in Zn-haltigen Karbonat-Vergesellschaftungen von Broken Hill, New South Wales
Zusammenfassung Analytische Transmissionselektronenmikroskopie wurde benutzt um zwei Zn-haltige Dolomite zu untersuchen, die als Überzüge von Calcit aus der Oxidationszone der Erzkörper von Broken Hill, New South Wales, auftraten. Besondere Aufmerksamkeit wurde der Art der Mikrogefüge und möglichen Korrelationen zwischen Mikrogefüge und der lokalen Zusammensetzung, vor allem dem Zn-Gehalt, gewidmet. Dem möglichen Auftreten von geringen Mengen des Zn-Dolomit, Minrecordit, wurde ebenfalls nachgegangen.Die bemerkenswertesten Erscheinungen im Zn-haltigen Dolomit sind feine bandartige Verteilung einer calcitischen Phase, Wachstumsbänder und modulierte Strukturen (starke Modulationen im Beugungskontrast sichtbar). Ihr Auftreten ist mit über das stöchiometrische Verhältnis hinaus vorhandenem Ca korreliert; es ist aber vom Zn-Gehalt nicht direkt beeinflußt. Die mitvergesellschafteten Calcite haben einen niedrigen Zn-Gehalt, zeigen aber eine weitere Karbonatphase. Diese wird für dolomitsch gehalten, obwohl keine entsprechenden Ordnungsreflexe (b-Reflexè) nachweisbar waren. Sehr lange belichtete Elektronenbeugungs-Aufnahmen zeigen jedoch diffuse c-Typ-Über-struktur-Reflexe. Diese sind wahrscheinlich auf kleine Bereiche beschränkt, in dener die Ca und Mg Kationen geordnet sind, wofür ein Modell vorgeschlagen wird.
With 10 Figures 相似文献
6.
M. Hassan M. A. Haq M. Aslam M. Saleem K. P. Akhtar S. Sarwar Alam 《International Journal of Environmental Science and Technology》2006,2(4):319-325
Twenty four new strains were tested for their yield, quality and Leaf Curl Virus (ClCuV) resistance. NIAB-111/S, NIAB-98 and NIAB-999 were significantly high fruit bearing varieties at 90 days completing 59.54, 48.26 and 46.00% fruiting respectively. Seed cotton yield of VH-142 was highest with 5417 kgha?1 and 52 per plant boll bearing, DNH-57 and NIAB-999 remained second and third with 5234 and 5095 kg ha?1 seed cotton yield, respectively. BH-160 and CRIS-467 were found to be second and third highest boll bearing varieties with 50.97 and 40.20 per plant average bolls respectively. Plant height in CRIS-467, MNH-642 and SLH-224 was significantly higher in comparison to other varieties.NIAB-98, CIM-499 and CIM-506 were found short stature varieties in comparison with other but out of these NIAB-98 and CIM-506 were in high yielding position and CIM-499 was found medium yielder variety. GOT% of MNH-642 remained highest having value of 45.00%. While GOT%. of NIBGE-1, CRIS-168 and CRIS-467 was at lowest position with 35.73, 35.89 and 36.62% respectively. NIAB-111, CIM-499 and BH-160 were at first position in terms of fibre fineness with micronaire values 3.98, 4.00 and 4.07 ìg/inch having fibre length 28.53, 31.38 and 30.23 mm respectively. Out of 26 varieties, 16 varieties resulted maturity index in the range of 85.03% and 90.30% with highest maturity index in case of NIBGE-1 (i.e. 90.30%) followed by NIAB-999 and MNH-642 with 89.55 and 85.5% respectively.CRIS-168, CRIS-468 and CRIS-467 were found viral susceptible. 相似文献
7.
M. M. Uddin A. K. M. Harun-Ar-Rashid S. M. Hossain M. A. Hafiz K. Nahar S. H. Mubin 《International Journal of Environmental Science and Technology》2006,3(4):447-453
This paper gives impact of Arsenic contaminated water on human health as well as overview of the extent and severity of groundwater arsenic contamination in Bangladesh. Scalp hair is the most important part of the human body to monitor the accumulation of this type of poison. Therefore, an experiment has been carried out by Neutron Activation Analysis (NAA) at Atomic Energy Research Establishment (AERE), Savar, Dhaka, Bangladesh on human hair of corresponding tube well water users of these areas to determine the total accumulation of arsenic to their body. Hair samples collected from the region where the groundwater was found highly contaminated with arsenic. The obtained results of arsenic concentration in the lower age (Hb) categories of users (below 12 years of age users) is in the range of 0.33 to 3.29 /gmg/g (ppm) and that in the Hu categories (upper 12 years of age users) is 0.47 to 6.64 μg/g (ppm). Where as maximum permissible range is 1 ppm certified from WHO. Results show that the peoples are highly affected where the groundwater is highly contaminated with arsenic and acts as the primary source of arsenic poisoning among the peoples of those areas. The results indicate that human population is affected with arsenic locally using the contaminated water for a long time. 相似文献
8.
Ahmad Shlash Alawneh Osama K. Nusier Ahmed Abdul-Ezel Al-Mufty 《Geotechnical and Geological Engineering》2006,24(3):637-660
A reliability based method was used to design and analyse shallow foundations using first-order Taylor series approximation.
The computer program Mathcad was used to facilitate all mathematical and computional efforts. This method is an effective
tool to assist the foundation designers and analyists to investigate how reliable their designs or analyses are in relation
to the ultimate bearing capacity of the foundations. The approach presented in this paper provides a reliable alternative
for design and analysis of shallow foundations, rather than the conventional design methods, which employs the assumptions
of a specified saftey factor. Several examples were presented for design and analysis of strip footings embedded in sandy
soil, and rectangular and square footings analysis embedded in clayey soils. The program input and output of each example
are also presented and discussed. 相似文献
9.
The impact of Southern Oscillation on thecyclogenesis over the Bay of Bengal duringthe summer monsoon has been investigated.The analysis of correlation coefficients(CCs) between the frequency of monsoondepressions and the Southern OscillationIndex (SOI) reveals that more depressionsform during July and August of El Niñoyears. Due to this, the seasonal frequencyof monsoon depressions remains little higherduring El Niño epochs even though thecorrelations for June and September are notsignificant. The CCs for July and August aresignificant at the 99% level.The El Niño-Southern Oscillation (ENSO)is known to affect Indian MonsoonRainfall (IMR) adversely. The enhancedcyclogenesis over the Bay of Bengal duringJuly and August is an impact of ENSO whichneeds to be examined closely. Increasedcyclogenesis over the Bay of Bengal may bereducing the deficiency in IMR duringEl Niño years by producing more rainfallover the eastern parts of India duringJuly and August. Thus there is a considerablespatial variation in the impact of ENSOon the monsoon rainfall over India and El Niñoneed not necessarily imply a monsoonfailure everywhere in India.The area of formation of monsoon depressionsshifts eastward during El Niño years.Warmer sea surface temperature (SST) anomaliesprevail over northwest and adjoiningwestcentral Bay of Bengal during premonsoon andmonsoon seasons of El Niño years.May minus March SOI can provide useful predictionsof monsoon depression frequencyduring July and August. 相似文献
10.
Major biological parameters of four permanent (Lake Colac, Modewarre, Bolac and Tooliorook), shallow and slightly saline lakes in the volcanic plains of western Victoria, Australia recorded bi-monthly between November 1999–September 2001 are described. Chlorophyll a concentration ranged from 3–29 μg l−1 with peaks in autumn. Phytoplankton taxa recorded were diverse, with Chlorophyta and Bacillariophyta being common. Cyanobacterial blooms were recorded mostly in summer. Zooplankton abundance in the lakes ranged from 12–368 individuals per litre. Rotifera dominated Lake Bolac, Copepoda dominated Lake Modewarre and they co-dominated Lake Colac and Tooliorook. Zooplankton interactions with phytoplankton suggest that simple predator-prey relationships cannot fully explain the trends exhibited and that a more complex model was acting to regulate algal biomass. A decline in the abundance of zooplankton in summer in Lake Modewarre was attributed to predation by high number of exotic larval carp at that time of the year. A total of 25 benthic macroinvertebrate taxa were recorded from Lake Colac, 30 from Modewarre, 22 from Bolac and 35 from Tooliorook. Twenty-one of the 45 taxa identified occurred in at least three lakes. Nine of the 12 taxa that occurred in only one lake were from Lake Tooliorook. Simpson's diversity index was low in Lake Bolac when compared to other three lakes. Lake Modewarre had more benthic individuals (3246 Ind m−2) than other three lakes (range 624–1397 Ind m−2). The combined contribution of Ostracoda, Amphipoda and Gastropoda dominated the benthos in all the lakes throughout the study period. Macroinvertebrate taxa richness was higher in the present study lakes than recorded from the lakes in the region. Frequency of sampling and number of sampling sites seemed more important in determining species richness than the size and shallowness of the lakes. 相似文献