Stochastic diffusion in inverse square fields: General formulation for interplanetary gas     

M.H.A. Hassan  Max K. Wallis 《Planetary and Space Science》1983,31(1):1-10

The Fokker-Planck equation for small stochastic changes to particles in Kepler orbits has to be formulated in terms of the integrals of motion. We generalize the modelling of proton and electron collisional perturbations to gas particles on trajectories through the solar system in order to include both spatial and velocity diffusion. The general solution is obtained in terms of a 4-dimensional normal distribution. Treatment of the singularity in the Fokker-Planck operator reduces the dimensionality by one. In addition to extending earlier results for anisotropic collisional heating in the thermal approximation, the present formulation gives the changes in density due to the mean repulsive force and to perturbations of trajectories (spatial diffusion). The net diffusion is almost everywhere towards the sun and the density increase is significant in the downstream hydrogen wake, particularly where destructive depletion is strong and gravitational focussing weak.  相似文献   

Contribution of oceans' sensible heating to the atmospheric available potential energy     

Dr. Hassan El-Sayed 《Meteorology and Atmospheric Physics》1973,22(2-3):257-284

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Hydrogeology, Log Analysis, and Hydrochemistry of Unconsolidated Aquifers South of El-Sadat City, Egypt     

M.G. Atwia  A.A. Hassan  S.A. Ibrahim 《Hydrogeology Journal》1997,5(2):27-38

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Horizontal distribution of the rotifer plankton of Lake Aydat (France)   总被引：2，自引：0，他引：2  

Nicole Lair  Hassan Taleb  Patricia Reyes-Marchant 《Aquatic Sciences - Research Across Boundaries》1996,58(3):253-268

We investigated the causes of the shift which occurs in the horizontal distribution of planktonic rotifers of Lake Aydat. A normalised PCA was used to analyse the spatio-temporal distribution of 18 rotifer species. They are more numerous in the littoral zone, but seasonal changes remain higher than spatial changes. Results illustrate the capability of rotifers to take efficiently advantage of available space and food. The digestive tracts of fry and juvenile roach was also analysed and the index of Ivlev was used to determine prey selection. Fish predation occurs in the nearshore zone and the interactions between invertebrate predators and their prey are illustrated by the quantitative changes in community dynamics. Among the complex cascade of events varying in the course of the year, and despite of resource partitioning, predator-prey interactions as well as the exploitative competition between rotifers and crustaceans produce gradients exhibited in the horizontal distribution of rotifers in Lake Aydat.  相似文献   

Behavioural responses of the bivalve Scrobicularia plana (da Costa) subjected to short-term copper (Cu II) concentrations     

Hassan B. Akberali  Julia E. Black 《Marine environmental research》1980,4(2):97-107

Short-term (6 h) behavioural responses and mortality of Scrobicularia exposed to low concentrations of copper in sea water (31%, S) have been investigated.Scrobicularia can detect copper at a concentration of 0·01 ppm. The initial response is valve closure resulting in a rapid drop in heart rate. In concentrations of 0·05, 0·01 and, to a lesser extent, 0·1 ppm copper added to sea water, the clams begin to interact with the polluted water after 2–3 h. In 0·5 ppm, the valves remain closed and the heart rate is maintained at a low level over the 6-h exposure period.Mortality increases with time in 0·5 ppm copper concentration, reaching 50% in 5–7 days. In 0·05 and 0·01 ppm, no mortality was recorded over this period.There is an increase in mantle cavity water calcium concentration after 6 h in 0·5 ppm, in contrast to 0·1, 0·05 and 0·01 ppm. Aspects of anaerobiosis, accumulation of heavy metals and survival are discussed in relation to the behaviour of Scrobicularia exposed to various copper concentrations.  相似文献   

Geochemistry of lamprophyres associated with uranium mineralization, Southeastern Desert, Egypt     

Mohamed E. Ibrahim Mohamed M. El-Tokhi Gehad M. Saleh Mamdouh A. Hassan 《中国地球化学学报》2007,26(4):356-365

Two brecciated shear zones (NNW-SSE) are found crosscutting cataclastic rocks. The cataclastic rocks (3.0 km2) occupy the core of the granitic pluton and enclose a roof pendant of mafic-ultramafic rocks. The NNW-SSE-extending lamprophyre dykes vary in thickness from 0.5 m to 1 m and up to 800 m long, cutting the cataclastic rocks and are composed mainly of plagioclases, amphiboles, relics of pyroxenes and K-feldspar phenocrysts embedded in fine-grained groundmass. They are characterized as being peraluminous, calc-alkaline in composition (chemical trap) and enriched in calcite, sulfide and P2O5. The lamprophyres were affected by hydrothermal alteration (chlorite-carbonate alteration) while the cataclastic rocks were affected by diagenetic alteration (K-feldspar-albite alteration). Uranium mineralization is the product of hydrothermal events and has been investigated by X-ray diffraction (XRD) and environmental scanning electron microscopy (ESEM), involving primary uranium minerals (U3O8) and secondary uranium minerals (uranophane and beta-uranophane, kasolite, torbernite, autonite and meta-autonite) in addition to U- bearing minerals (astrocyanite, betafite and fergusonite). The presence of different mineral parageneses associated with clay minerals indicates that the lamprophyres were subjected to acidic and alkaline mineralizing solutions. Moreover, the U-Zr/U, U-Ce/U values show negative correlations, confirming U-enrichment in both cataclastic rocks and shear zones while the Th-eU/eTh, Th-Zr/Th and Th-Ce/Th values show negative correlations, indicating that the U-bearing solutions are rich in Th in the cataclastic rocks only.  相似文献   

Simulation of tropical cyclone Vamei (2001) using the PSU/NCAR MM5 model     

L. Juneng  F. T. Tangang  C. J. C. Reason  S. Moten  W. A. W. Hassan 《Meteorology and Atmospheric Physics》2007,97(1-4):273-290

Summary In this study, a rare tropical cyclone Vamei was simulated using the non-hydrostatic version 3.6 of the Penn State University (PSU) – National Center for Atmospheric Research (NCAR) mesoscale model MM5. This unusual cyclone was generated on 26 December 2001 in an area close to the equator in the southern part of the South China Sea. The model was integrated for 80 h from 0000 UTC 26 December 2001 to 1800 UTC 29 December 2001. To examine the model performance, several important simulated fields including sea-level pressure, surface wind speed and precipitation were compared to observations. The model simulated track of the cyclone was also compared to the best track provided by the Joint Typhoon Warning Center (JWTC). Overall, the model performed reasonably well, particularly in simulating the cyclone track and precipitation amount and spatial distribution. The analysis of the model output indicated the important role of the latent heat flux in the genesis and intensification of tropical cyclone Vamei.  相似文献   

Geological Controls of Variograms in a Complex Carbonate Reservoir, Eastern Province, Saudi Arabia     

A. Sahin  S. G. Ghori  A. Z. Ali  H. F. El-Sahn  H. M. Hassan  A. Al-Sanounah 《Mathematical Geology》1998,30(3):309-322

To derive meaningful results from a geostatistical study, it is extremely important to establish the relationship between geology and variograms. However, it is not always easy to establish such a relationship, mainly because of the inadequacy of quantitative or qualitative information. Large amounts of reliable well-log porosity data and the detailed geological information from a complex carbonate reservoir located in the Eastern Province of Saudi Arabia provided an ideal case study of the relationships between geology and variograms. The reservoir under consideration is in the form of a gently dipping, elongated anticline and consists of three productive zones which have been subdivided into several lithologically distinct layers. Results, which indicate an excellent match between geology and porosity variograms, are summarized as follows: (1) use of stratigraphic distances resulted in considerable improvement in the behavior of variograms, (2) structurally controlled geometrical anisotropy is the most obvious feature of variograms, and (3) layers consisting of more complex lithologic framework provided variograms with relatively greater nugget variances and shorter ranges. These results provide further insight into geology and form a meaningful basis for estimation and simulation of the reservoir. They also could be used as a general guide in the geostatistical study of similar carbonate reservoirs.  相似文献   

ODONATE COMMUNITIES （ODONATA： INSECTA） IN A TROPICAL RIVER BASIN, MALAYSIA     

CheSalmahMR AbuHassanA AmeiliaZS 《湿地科学》2004,2(1):1-9

Odonata larvae were sampled from 16 tributaries of Kerian River in the Kerian River Basin (KRB) using a kick samphng technique from September 1998 to May 1999 encompassing both rainy and dry seasons. The distribution of odonate genera was significantly different ( F15.16 = 3.99) among rivers in both seasons ( F15.16 = 4.70) at P = 0.05. However, no seasonal influence was detected. Protoneuridae and Libellulidae were the most dominant families in this basin. Other families Gomphidae, Coenagrionidae, Macromiidae, Chlorocyphidae and Calopterygidae, were common but Aeshnidae and Eupheidae were rare. Several common species, Prodasineura autumnalis, Brachythemis contaminata, Macromia gerstaeckeri, Paragomphus, Orthetrum brunneum, Rhinocypha quadrimaculata and Copera marginipes were identified. The calculated values of biological indices ( H‘, D, E, R1 and R2) showed that the dragonfly fauna in this river basin was slightly poor. Varied physieo- chemical parameters of the river possibly as a result of human activities in surrounding areas were found to influence the distribution of the dragonfly larvae in the KRB. This study showed that the KRB provided favorable habitats for Protoneuridae and 1Libellulidae. Two most dominant species Prodasineura autumnalis and Brachythemis contaminata were obviously favoured slightly acidic water of the Kerian river tributaries.  相似文献   

Facies and sequence stratigraphy of a Late Barremian wave-dominated deltaic deposit, Agadir Basin, Morocco     

Mohammed Nouidar  El Hassan Chellaï 《Sedimentary Geology》2002,150(3-4):375-384

The late Barremian succession in the Agadir Basin of the Moroccan Western High Atlas represents wave-dominated deltaic deposits. The succession is represented by stacked thickening and coarsening upwards parasequences 5–15 m thick formed during fifth- or fourth-order regression and building a third-order highstand systems tract. Vertical facies transitions in parasequences reflect flooding followed by shoaling of diverse shelf environments ranging from offshore transition interbedded mudstones, siltstones and thin sandstones, lower shoreface/lower delta front hummocky bedforms to upper shoreface/upper delta front cross-bedded sandstones. The regional configuration reflects the progradation of wave-dominated deltas over an offshore setting. The maximum sea-level fall led to the development of a sequence boundary that is an unconformity. The subsequent early Aptian relative sea-level rise contributes to the development of an extensive conglomerate lagged transgressive surface of erosion. The latter and the sequence boundary are amalgamated forming a composite surface.  相似文献