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101.
We investigate electromagnetic buoyancy instabilities of the electron-ion plasma with the heat flux based on not the magnetohydrodynamic
(MHD) equations, but using the multicomponent plasma approach when the momentum equations are solved for each species. We
consider a geometry in which the background magnetic field, gravity, and stratification are directed along one axis. The nonzero
background electron thermal flux is taken into account. Collisions between electrons and ions are included in the momentum
equations. No simplifications usual for the one-fluid MHD-approach in studying these instabilities are used. We derive a simple
dispersion relation, which shows that the thermal flux perturbation generally stabilizes an instability for the geometry under
consideration. This result contradicts to conclusion obtained in the MHD-approach. We show that the reason of this contradiction
is the simplified assumptions used in the MHD analysis of buoyancy instabilities and the role of the longitudinal electric
field perturbation which is not captured by the ideal MHD equations. Our dispersion relation also shows that the medium with
the electron thermal flux can be unstable, if the temperature gradients of ions and electrons have the opposite signs. The
results obtained can be applied to the weakly collisional magnetized plasma objects in laboratory and astrophysics. 相似文献
102.
This research developed an approach to enable the discrimination of lithological units and detection of host rock of chromitite bodies within ophiolitic complexes using the advanced spaceborne thermal emission and reflection radiometer (ASTER) and Landsat thematic mapper (TM) satellite data. Three main ophiolite complexes located in southern Iran were selected for the study. A specialized band ratio (4/1, 4/5, 4/7) of ASTER, minimum noise fraction (MNF) components and spectral angle mapper (SAM) on ASTER and Landsat TM data were used to distinguish ophiolitic rock units. Results show that the specialized band ratio was able to identify different rock units and serpentinized dunite as host rock of chromitites within ophiolitic complexes. Minimum noise fraction components of ASTER and Landsat TM data are suitable for distinguishing ophiolitic rock complexes at a regional scale. The integration of SAM and feature level fusion used in this investigation discriminated the ophiolitic rock units and provided geological map for the study area, including identification of high potential areas (serpentinite dunite) for chromite exploration targets. 相似文献
103.
Water resources in Egypt are becoming scarce and the demand for clean drinking water supply is one of the most important priorities of the Egyptian government in recent years. Analyzing water use and future demand forecasting is a primitive clue for water demand management. Water in Luxor is used for agricultural, residential, institutional, commercial, and touristic purposes. The results of water use analysis indicated that for the time period from 1983 to 2012, agriculture is the highest consumer of water which reached about 94.76–97.38 % followed by residential water consumption (1.90–3.05 %), institutional water consumption (0.71–1.75 %), and touristic water consumption (0.02–0.43 %), respectively. The future demand forecasting results revealed that the present situation may continue to rise in the next 50 years which will increase the water demand with a water deficit ranging between 15 and 114 MCM/year. To fill the gap between the present water consumption and future residential, institutional, commercial, and touristic water demand, additional municipal facilities, and improvement and management of water supply/demand are needed. To cope with the predicted future water demand, it is recommended to improve the on-farm irrigation, reduce the demand for irrigation water, rationalize the irrigation water use, and enhance the integrated role of water users in integrated water resources management. 相似文献
104.
Alireza Owji Isa Esfandiarpour Boroujeni Ardavan Kamali Seyed Javad Hosseinifard Mohsen Bagheri Bodaghabadi 《Arabian Journal of Geosciences》2014,7(4):1491-1499
Soil texture is an important physical soil property that may contribute to variations in many soil functions as well as nutrient storage and availability, water retention, and soil erosion. Although several methods for determining the texture classes of soil particles have been proposed, differences among hydrometer reading times have presented challenges in determining the precise soil texture classes. Therefore, this study was conducted to evaluate the effects of hydrometer reading time on the spatial variability of soil textures in the Rafsanjan area, southeast Iran. To accomplish this, 77 soil samples were collected on a 500-m square sampling grid from depths of 0–40, 40–80, and 80–120 cm, and their particle sizes were determined through analysis for 40 s, 2 h, 6.5 h, and 8 h using the Bouyoucos hydrometer method. The results showed a strong spatial correlation in the soil particles among sampling soil layers and across the study area. Moreover, the differences among hydrometer reading times did not have a significant impact on determination of coarse soil texture classes, although they did influence determination of the finer classes. Although the 8 h reading time provided the most accurate response with respect to mechanical analysis of a soil, after 6.5 h the hydrometer could also largely (more than 80.0 %, on average) achieve this goal. Additionally, the 2 h hydrometer reading time could also be useful for the initial assessment or general overview of the soil texture in a certain region; however, it is not recommended for precision agriculture or site-specific management. 相似文献
105.
Ahmad Nicknam Reza Abbasnia Yasser Eslamian Mohsen Bozorgnasab Ehsan Adeli Mosabbeb 《Journal of Earth System Science》2010,119(3):383-396
We determine the source parameters for 2003 (Mw 6.5) Bam, Iran, earthquake using an empirical Green’s function summation approach
to model ground motions recorded by two strong motion stations at approximately 45 km epicentral distance. We introduce a
genetic algorithm technique to optimize the fit to observed elastic response spectra. The proposed genetic algorithm technique
allows us to explore the sensitivity of the results to multiple source parameters, including hypocenter location, focal mechanism
(Strike and Dip), P-wave velocity in depth, fault dimension and rupture and healing velocities. 相似文献
106.
Ocean Science Journal - A practical method for the calibration of the ocean circulation model is introduced using measured water levels along the Persian Gulf coastlines. Dimensional analysis is... 相似文献
107.
Modeling in situ benzene bioremediation in the contaminated Liwa aquifer (UAE) using the slow-release oxygen source technique 总被引:5,自引:4,他引:1
Mohamed Mostafa Ahmed Mohamed Nawal E. Saleh Mohsen M. Sherif 《Environmental Earth Sciences》2010,61(7):1385-1399
Dissolved benzene was detected in the shallow unconfined Liwa aquifer, UAE, which represents the main freshwater source for
the nearby residence Bu Hasa camp area. The main source of this contamination is believed to be the rejected water released
from Bu Hasa liquid recovery plant. In this paper, a finite element model (METABIOTRANS) is used to simulate the fate and
transport of the dissolved benzene plume in Liwa aquifer. Different remediation scenarios were simulated in which the slow-release
oxygen source (SOS) technique is utilized to minimize benzene concentrations at the nearest camp supply wells downstream of
the contamination zone. Results of the remediation scenarios show that the highest biodegradation rates occur when the oxygen
source is placed near the plume center; where higher benzene concentrations exist. The nearest oxygen release source to the
contamination zone caused higher stimulation to bacterial growth than further down-gradient oxygen sources. It also exhibited
longer resident time of oxygen in the aquifer; and therefore, yielded higher reductions in benzene concentrations. However,
using one central SOS proved to be insufficient as contaminant escaped laterally. Additional four transverse oxygen sources
were necessary to capture benzene that laterally spread away from the contamination zone. These lateral SOSs were essential
to reduce benzene concentrations at the supply wells that are located at the plume fringes. Finally, it was found that increasing
oxygen release from one source did not always improve remediation; and that using several SOSs with lower release rates could
be a more practical approach to enhance benzene biodegradation in the aquifer. 相似文献
108.
This paper presents three new approaches for solving eigenvalue problems of non‐classically damped linear dynamics systems with fewer calculations than the conventional state vector approach. In the latter, the second‐order differential equation of motion is converted into a first‐order system by doubling the size of the matrices. The new approaches simplify the approach and reduce the number of calculations. The mathematical formulations for the proposed approaches are presented and the numerical results compared with the existing method by solving a sample problem with different damping properties. Of the three proposed approaches, the expansion approach was found to be the simplest and fastest to compute. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
109.
The purpose of this paper is to explore the effect of magnetic fields on the dynamics of magnetized filamentary molecular clouds.We suppose there is a filament with cylindrical symmetry and two components of axial and toroidal magnetic fields.In comparison to previous works,the novelty in the present work involves a similarity solution that does not define a function of the magnetic fields or density.We consider the effect of the magnetic field on the collapse of the filament in both axial and toroidal directions and show that the magnetic field has a braking effect,which means that the increasing intensity of the magnetic field reduces the velocity of collapse.This is consistent with other studies.We find that the magnetic field in the central region tends to be aligned with the filament axis.Also,the magnitude and the direction of the magnetic field depend on the magnitude and direction of the initial magnetic field in the outer region.Moreover,we show that more energy dissipation from the filament causes a rise in the infall velocity. 相似文献
110.
Shafiee Ali Kamalian Mohsen Jafari Mohammad Kazem Hamzehloo Hossein 《Natural Hazards》2011,59(1):481-505
An important step in effectively reducing seismic risk and the vulnerability of a city located in an earthquake prone area
is to conduct a ground motion microzonation study for the desired return period. The International Institute of Earthquake
Engineering and Seismology (IIEES) initiated a number of seismic microzonation projects for Iran. This paper presents the
steps followed by IIEES in ground motion microzonation. IIEES performs both probabilistic and deterministic seismic hazard
analysis. IIEES uses his own fault map for seismotectonic studies and develops modulus and damping curves for the soils in
the study area. The experience of ground motion microzonation shows that in almost all cases, the estimated 475-year peak
ground acceleration (PGA) values are higher than the PGA proposed by the Iranian seismic code. Although ground motion microzonation
in Iran has some shortcomings, IIEES is making new improvement. This includes development in deterministic seismic hazard
analysis, two-dimensional and three-dimensional modelling of basin and topographical effects, using microtremor measurements
to find shear-wave velocity profiles in high-density urban areas and providing maps for spectral acceleration in the study
area. 相似文献