Analysis on the stability of triangular points in the perturbed photogravitational restricted three-body problem with variable masses     

Jagadish Singh  Oni Leke  Umar Aishetu 《Astrophysics and Space Science》2010,327(2):299-308

This paper examines the effect of a constant κ of a particular integral of the Gylden-Meshcherskii problem on the stability of the triangular points in the restricted three-body problem under the influence of small perturbations in the Coriolis and centrifugal forces, together with the effects of radiation pressure of the bigger primary, when the masses of the primaries vary in accordance with the unified Meshcherskii law. The triangular points of the autonomized system are found to be conditionally stable due to κ. We observed further that the stabilizing or destabilizing tendency of the Coriolis and centrifugal forces is controlled by κ, while the destabilizing effects of the radiation pressure remain unchanged but can be made strong or weak due to κ. The condition that the region of stability is increasing, decreasing or does not exist depend on this constant. The motion around the triangular points L _4,5 varying with time is studied using the Lyapunov Characteristic Numbers, and are found to be generally unstable.  相似文献   

Hydrochemical characteristics and seasonal variations in groundwater quality of an alluvial aquifer in parts of Central Ganga Plain,Western Uttar Pradesh,India   总被引：1，自引：0，他引：1  

Rashid Umar  Izrar Ahmed  Fakhre Alam  Mohammad Muqtada Khan 《Environmental Geology》2009,58(6):1295-1300

The present study was undertaken to assess major ion chemistry of groundwater in parts of the Central Ganga Plain and observe seasonal variations in its chemical quality. Systematic sampling was carried out during November 2005 and June 2006. The major ion chemistry of groundwater shows large variations, so much so that at times the meteoric signature seems to be completely obliterated. In many samples the concentrations of SO₄, NO₃ and F are above the permissible limit for human consumption. The graphical treatment of major ion chemistry helps in identifying four types of groundwater. All possible ionic species such as NaCl, KCl, NaHCO₃, NaSO₄, KNO₃, NaNO₃, CaHCO₃, MgHCO₃, MgSO₄ are likely to occur in groundwater system. The observed chemical variations may be attributed to sediment water interaction, ion exchange, dissolution mechanisms and anthropogenic influences such as application of fertilizers and effluents from sugar factories and paper mills. A general increase in TDS is observed in samples during June 2006. The increase in salinity is attributed to evaporation from water table, irrigation return flows, anthropogenic activities and below average rainfall in 2005 and 2006. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

Estimation of static earth pressures for a sloping cohesive backfill using extended Rankine theory with a composite log-spiral failure surface     

Xu  Shi-Yu  Lawal  Abiodun Ismail  Shamsabadi  Anoosh  Taciroglu  Ertugrul 《Acta Geotechnica》2019,14(2):579-594

The Rankine earth pressure theory is extended herein to an inclined c–? backfill. An analytical approach is then proposed to compute the static passive and active lateral earth pressures for a sloping cohesive backfill retained by a vertical wall, with the presence of wall–soil interface adhesion. The proposed method is based on a limit equilibrium analysis coupled with the method of slices wherein the assumed profile of the backfill failure surface is a composite of log-spiral and linear segments. The geometry of the failure surface is determined using the stress states of the soil at the two boundaries of the mobilized soil mass. The resultant lateral earth thrust, the point of application, and the induced moment on the wall are computed considering global and local equilibrium of forces and moments. Results of the proposed approach are compared with those predicted by a number of analytical models currently adopted in the design practice for various combinations of soil’s frictional angles, wall–soil interface frictional angles, inclined angles of backfill and soil cohesions. The predicted results are also verified against those obtained from finite element analyses for several scenarios under the passive condition. It is found that the magnitude of earth thrust increases with the backfill inclination angle under both the passive and active conditions.

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Hydrogeological and hydrochemical framework of regional aquifer system in Kali-Ganga sub-basin, India   总被引：5，自引：0，他引：5  

Asad Umar  R. Umar  M. S. Ahmad 《Environmental Geology》2001,40(4-5):602-611

 The central Ganga Basin is one of the major groundwater reservoirs in India. The Kali-Ganga sub-basin is a micro watershed of the central Ganga Basin, containing a number of productive aquifers. A detailed hydrogeological investigation was carried out, which reveals the occurrence of a single-tier aquifer system down to 163 m bgl (metres below ground level), but at places it is interleaved with clay layers; thus imparting it a two-to three-tier aquifer system. These aquifers are unconfined to confined in disposition. The transmissivity, storage coefficient and hydraulic conductivity are determined as 2178 m²/day, 1.12×10^–5 and 120 m/day, respectively. The groundwater of the basin is fresh, of an alkali-bicarbonate type and is suitable for irrigation and domestic use. However, in certain areas, extensive agricultural activities, and domestic and industrial effluents have caused some deterioration of groundwater quality. This study contains data of where the concentration of Fe, Pb, Cd, Cr and Ni are higher than the permissible limits, which may be hazardous to public health. Received: 2 March 2000 · Accepted: 3 July 2000  相似文献   

A stochastic model of low flows     

S. A. Lawal  W. E. Watt  D. G. Watts 《Stochastic Hydrology and Hydraulics》1997,11(4):303-321

A model is developed for annual low flow hydrographs. Its two primary components reflect the fact that hydrologic processes during streamflow rise (function of water input) and recession (function of basin storage) are different. Durations of periods of rise (wet intervals) and recession (dry intervals) are modelled by discrete probability distributions — negative binomial for dry intervals and negative binomial or modified logarithmic series for wet intervals depending on goodness of fit. During wet intervals, the total inflow is modelled by the lognormal distribution and daily amounts are allocated according to a pattern-averaged model. During dry intervals, the flow recedes according to a deterministic-stochastic recession model. The model was applied to three Canadian basins with drainage area ranging from 2210 to 22000 km² to generate 50 realizations of low flow hydrographs. The resulting two standard-error confidence band for the simulated probability distribution of annual minimum 7-day flows enclosed the probability distribution estimated from the observed record. A sensitivity analysis for the three basins revealed that in addition to the recession submodel, the most important submodel is that describing seasonality. The state of the basin at the beginning of the low flow period is of marginal importance and the daily distribution of input is unimportant.  相似文献   

Estimation of Anthropogenic Influences in Groundwater Quality of Shallow Aquifers of Moradabad City,Western Uttar Pradesh     

Naseemus Saba  Rashid Umar  Ahsan Absar 《Journal of the Geological Society of India》2018,91(6):711-716

The present work has been carried out in Moradabad, one of the important cities in the state of Uttar Pradesh. The main focus of the study is to estimate the extent of anthropogenic contamination in shallow groundwater of the area. For this purpose, total 188 groundwater samples collected from handpumps in pre- and post monsoon period of 2012 and 2013 (47 in each season) were analyzed for physico-chemical parameters such as pH, EC, TDS, major cations (Ca, Mg, Na, and K) and anions (Cl, HCO₃, SO₄, NO₃ and F). The results of the analysis suggested that groundwater is slightly alkaline, hard to very hard in nature, average TDS values were found to be more than 1000 mg/l, which gives a clear evidence of anthropogenic influences. To estimate the extent of contamination, the information on relatively unpolluted groundwater systems occurring in different terrains including Ganga plain where the groundwater was relatively unaffected by anthropogenic activities is used. The estimated pristine chemical composition of groundwater of different terrains used in the present study was compared with the groundwater of Moradabad city. This comparison showed that Moradabad city with the highest Na, K, Cl, SO₄ and NO₃ values being 440 mg/l, 96 mg/l, 537 mg/l, 537 mg/ l and 244 mg/l, respectively, is one of the most polluted urban centres within the Ganga plain. It may be suggested that values of > 50 mg/l for Na, > 10 mg/l for K, > 25 mg/l for Cl, > 50 mg/l for SO₄ and > 10 mg/l for NO₃ have their respective sources in anthropogenic activities such as agricultural in the peripheral region, human and animal wastes, leakages from drains and septic tanks, landfill leachates and industrial effluents.  相似文献   

Quaternary sedimentation and active faulting along the Ecuadorian shelf: preliminary results of the ATACAMES Cruise (2012)     

F. Michaud  J. N. Proust  J. Y. Collot  J. F. Lebrun  C. Witt  G. Ratzov  H. Pouderoux  C. Martillo  M. J. Hernández  G. Loayza  L. Penafiel  L. Schenini  A. Dano  M. Gonzalez  D. Barba  L. De Min  G. Ponce  A. Urresta  M. Calderon 《Marine Geophysical Researches》2015,36(1):81-98

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Book reviews     

Daniel W. Gade  Manfred Domrös  Konrad Schliephake  G. Kunkel  M.O. Lawal  Andreas Grotewold  Bernd-M. Schulze  Alexander Zaporozec  Karel Bayer  Günter Borchert  Wolf Tietze 《GeoJournal》1987,14(3):390-323

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Rapid analysis with energy-dispersive X-ray fluorescence spectrometry for bauxite investigation on the Mambilla Plateau, North Eastern Nigeria     

Y. Idris  I. I. Funtua  I. M. Umar 《Chemie der Erde / Geochemistry》2004,64(4):385-398

Bauxite exploration involves routine analysis of a large number of samples for a wide range of elements. In Nigeria, though geological field exploration for bauxite started almost three decades ago very little has been achieved, mainly due to the non-availability of facilities for evaluating the dozens of suspected bauxite deposits scattered around the country. In this regard, a procedure for the rapid, accurate and precise measurement of a number of important elements in bauxite has been developed based on the newly acquired radioisotope based EDXRF spectrometer. Elements and oxides analyzed are Al₂O₃, SiO₂, TiO₂, Fe₂O₃, K₂O, Mn, Co, Cu, Zn, Ga, Rb, Sr, Y, Zr, Nb and Pb. The richest bauxite sample has concentrations of 48.08, 18.90, 1.26, 7.71 and 1.93 wt% for Al₂O₃, SiO₂, TiO₂, Fe₂O₃, and K₂O, respectively. The other values in ppm are Mn (3 0 2), Co (5 3 2), Cu (45), Zn (51), Ga (41), Rb (32), Sr (2 2 2), Y (32), Zr (8 4 9), Nb (89) and Pb (72). The measurement errors in terms of accuracy and precision are less than 5% and 10% and 5% and 15% for major and trace elements, respectively. Statistical correlation analysis carried out on the results shows the most significant relationships to be the negative correlations of alumina with silica, iron oxide and titanium. This is believed to be related to the processes of formation of bauxite, with the Si and Fe–Ti being removed as Al was being enriched.  相似文献   

Prediction of Mechanical Properties of Coal from Non-destructive Properties: A Comparative Application of MARS,ANN, and GA     

Lawal  Abiodun Ismail  Oniyide  Gafar O.  Kwon  Sangki  Onifade  Moshood  Köken  Ekin  Ogunsola  Nafiu O. 《Natural Resources Research》2021,30(6):4547-4563

Natural Resources Research - Rock properties are useful for safe operation and design of both surface and underground mines including civil engineering projects. However, the cost and time required...  相似文献