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91.
A. S. Saad 《Astronomische Nachrichten》2004,325(9):733-739
In this paper, accelerated power series solutions are developed for N‐dimensional symmetric radially polytropes. The solutions are valid for any geometric and polytropic index. The implementation of Padé technique and changing of the independent variable give us identical polytrope solutions to the numerical one. Physical parameters are presented for Ndimensional radially polytropes. In case of the isothermal sphere, the density profile is accurate to 10–5 per cent whatever the value of ξ is. All the computations are performed using Mathematica software. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
92.
Nadia A. Saad 《Astrophysics and Space Science》2003,284(3):1001-1012
The stellar problem of three bodies is studied. A Lie transform is used to eliminate the short and intermediate periodic terms
from Harrington's Hamiltonian. The resulting system is a one of two degrees of freedom whose further reduction requires recourse
to numerical procedures.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
93.
S. A. El Wakil M. H. Haggag H. M. Machali E. A. Saad 《Astrophysics and Space Science》1983,91(1):125-131
The Padé approximants is used to estimate the albedo for an inhomogeneous semi-infinite medium. The single-scattering albedo is assumed to fall off exponentially with optical depth. 相似文献
94.
The best way of reducing roll motion is by increasing roll damping. Bilge keels are the most common devices for increasing roll damping. If more control is required, anti-roll tanks and fins are used. Tanks have the advantage of being able to function when the ship is not underway. Our objective is to develop design procedures for passive tanks for roll reduction in rough seas. This paper focuses on the design of passive U-tube tanks. The tank-liquid equation of motion is integrated simultaneously with the six-degree-of-freedom (6DOF) equations of the ship motion. The coupled set of equations is solved by using the Large Amplitude Motion Program ‘LAMP’, which is a three-dimensional time-domain simulation of the motion of ships in waves. The unstabilized and stabilized roll motions of a S60-70 ship with forward speed and beam waves have been analyzed. For high-amplitude waves, the unstabilized roll angle exhibits typical nonlinear phenomena: a shift in the resonance frequency, multi-valued responses, and jumps. The performance of a S60-70 ship with a passive tank is investigated in various sea states with different encounter wave directions. It is found that passive anti-roll tanks tuned in the linear or nonlinear ranges are very effective in reducing the roll motion in the nonlinear range. The effect of the tank damping, frequency, and mass on the tank performance is studied. Also, it is found that passive anti-roll tanks are very effective in reducing the roll motion for ships having a pitch frequency that is nearly twice the roll frequency in sea states 5 and 6. 相似文献
95.
Christian Amblard Télesphore Sime-Ngando Saad Rachiq Gilles Bourdier 《Aquatic Sciences - Research Across Boundaries》1993,55(1):1-9
The abundance and the biomass of bacterial, phytoplanktonic, and ciliate communities were estimated at different depths during the spring planktonic development in an oligo-mesotrophic lake (the Pavin lake).The bacterial population, which consists mainly of free bacteria (94% of the total bacterial abundance), displays only low cell densities (0.6 to 7 × 105 cells · ml–1) and represents low biomass values (0.9 to 11.5 µgC·l–1) The bacteria represent from 0.9 to 23.8% (M = 9.7%) of the microplanktonic biomass (with the exclusion of heterotrophic nanoflagellates, i.e. bacteria + phytoplankton + ciliates, size range 0.2–160 µm). The abundance of the phytoplankton varies between 0.5 and 1.8 × 106 cells·l–1, and the biomass values between 12 and 118 µC·l–1. The phytoplankton population constitutes the largest part of the microplanktonic biomass (51.9 to 96.6%, M = 80.6%), and the diatomMelosira italica subsp.subarctica is the largely dominant species of this community. The population of ciliates, essentiallyOligotrichida andScuticociliatida, displays densities between 1.3 and 38.3 × 103 cells·l–1 (M = 6.7 × 103 cells·l–1), and biomass values vary from 0.10 to 16.30 µgC·l–1 (M = 6.01 µgC·l–1). The ciliates constitute thus from 0.1 to 26.4% (M = 9.8%) of the microplanktonic biomass. Whereas the oligotrichs are best represented in the euphotic zone, the small-sized scuticociliates dominate in the hypolimnion. Besides, species having symbionts and considered to be mixotrophic (Strobilidium gyrans, Strombidium viride, Stokesia vernalis) develop preferentially in the epilimnion and constitute more than 50% of the total ciliate biomass. 相似文献
96.
Mohammed‐Osama J. Azzam Kamal Al‐Malah Ziad Al‐Gazzawi Saad A. Al‐Omari 《洁净——土壤、空气、水》2010,38(9):822-830
Olive mills wastewater (OMW) is a critical environmental problem in the Mediterranean area due to its extremely high levels of COD and phenols. In this study, a group of adsorption experiments were conducted to investigate the dynamic response of the pH, COD, phenols, TSS, TDS, and TS concentrations of pretreated OMW, using different concentrations of activated carbon as adsorbent. The pretreatment included sedimentation and filtration of OMW. The pretreated OMW was then subjected to adsorption. A series of adsorption steps in stirred batch vessels were studied, namely, one stage, two‐stage countercurrent, and three‐stage countercurrent adsorption systems. A combined two‐ two‐stage countercurrent adsorption steps were also studied. Experimental results showed that such treatment protocols were promising. For example, a treatment protocol composed of a three‐stage countercurrent adsorption process using activated carbon of concentration of 24 g/L of OMW was able to reduce the COD from 60 000 mg/L down to 22 300 mg/L, while phenols were reduced from 450 to 15 mg/L. 相似文献
97.
Rock water interactions play an important role in the flow of groundwater. Groundwater samples were collected from deep production wells with depths ranging from 120 to 230 m. Complete chemical analysis of 40 groundwater samples was collected from the fractured limestone aquifer including major cations (Na+, K+, Ca2+, Mg2+) and major anions (Cl?, SO4 2?, HCO3 ?, CO3 2?). A geochemical modeling (NETPATH Software) was applied for environmental simulate net geochemical mass-balance reactions between initial and final waters along a hydrologic flow path. This program simulates selected evolutionary waters for every possible combination of the plausible phases that account for the composition of a selected set of chemical constraints in the system. The groundwater of the Eocene aquifer mainly belongs to fairly fresh water with salinity contents ranging from 228 to 3595 ppm. The measured groundwater levels range between 8 and 25 m near the river Nile to the limestone plateau (eastwards). Consequently, groundwater flows from east to westward toward the river Nile. Groundwater aquifer in the study area is mainly composed of fractured limestone; the saturated states of the PCO2, calcite, aragonite, dolomite, siderite, gypsum, anhydrite, hematite, and goethite in addition to H2 gas were estimated. The undersaturated state of carbon dioxide reflects closed conditions and very low probability of recent recharge, and it reveals also the high tendency of water to precipitates carbonate species. Undersaturation by carbonate minerals is only restricted to some pockets distributed on the different places of the aquifer in the study area. The majority of groundwater samples of Eocene aquifer in the study area indicated that groundwater is not suitable for irrigation with treatment and requires good drainage. 相似文献
98.
Maher Aldahri Saad mogren Kamal Abdelrahman Hani Zahran Sherif El Hady Mahmoud El-Hadidy 《Journal of the Geological Society of India》2017,89(4):435-443
Ten boreholes drilled in Ubhur area up to the depth of bedrock indicted the shallow depth of bedrock where the average depth ranges between 10 and 15 m. The standard penetration test N-values of these boreholes were measured and averaged. Based on N-values to the depth of bedrock, Ubhur area can be classified as site class C and D. Multichannel analysis of surface waves technique has been applied along seventy six profiles using 24-channel geophone array and 4.5Hz vertical geophones with 1m geophone spacing and sledgehammer and/or weight drop as seismic energy sources. Values of shear wave velocity to 30 m are calculated and then averaged (Vs30) where it ranges between 310.08 m/s and 1139.8 m/s. Therefore, Ubhur area can be classified into site class B, C and D based on site classification of the national earthquake hazards reduction program (NEHRP) recommendations. Accordingly, the greatest part of the study area falls in site class C while class B and D covered limited areas in the western and the eastern parts respectively. Depending on the shallow depth of bedrock in the study area, the Vs30 parameter is not applicable in the study area so the average values of Vs for the soil thickness, excluding the bedrock, have been calculated and mapped for site class C and D only. So Vs30 approach is not applicable for areas with shallow depth of bedrock which gives higher classification. 相似文献
99.
In this paper, relation was developed for Hyades stars between a function of the right ascensions and the angular distances from the vertex. The precision criteria of this relation are very satisfactory and a correlation coefficient value of ? 1 was found which proves that the attributes are completely related linearly. The importance of this relation was illustrated through its usages as: ?a criterion for membership of the cluster, ?a generating function for evaluating some parameters of the cluster, ?a generating function for the initial values of the vertex equatorial coordinates which could then be improved iteratively using the procedure of differential corrections. 相似文献
100.
S. A. El Wakil H. Machali M. T. Attia E. A. Saad 《Astrophysics and Space Science》1987,137(2):239-250
Radiation transfer problem in the slowing-down region is solved for a spherical geometry. Modelled kernels are used to represent the slowing-down kernel. Calculations are performed for the radiation flux at the boundary of the sphere for two cases: (i) in the presence of internal source, (ii) if the radiation is incident on the sphere. Numerical results are obtained by using the Padé approximant technique. 相似文献