排序方式： 共有16条查询结果，搜索用时 226 毫秒
1.
A rigorous theoretical investigation on the characteristics of dust-ion-acoustic (DIA) shock waves in an unmagnetized multi component electron-positron-ion dusty plasma (consisting of inertial ions, electrons of two distinct temperatures referred to as low and high temperature superthermal electrons where superthermality is introduced via the κ-type of nonthermal distribution, Boltzmann distributed positrons, and negatively charged immobile dust grains) has been made both theoretically and analytically. The hydrodynamic equation for inertial ions has been used to derive the Burgers equation. The influence of superthermal electrons, Maxwellian positrons and ion kinematic viscosity, which are found in this investigation, significantly modify the basic features of DIA shock waves, are briefly discussed. The present investigation can be very effective for studying and understanding the basic characteristics of shock wave propagation through different astrophysical situations where distinct temperature superthermal electrons dominate the wave dynamics. 相似文献
2.
3.
Mohammad Hossein Sowlat Kazem Naddafi Masud Yunesian Peter L. Jackson Saeedeh Lotfi Abbas Shahsavani 《洁净——土壤、空气、水》2013,41(12):1143-1151
Source apportionment of particulate matter <10 µm in diameter (PM10), having considerable impacts on human health and the environment, is of high priority in air quality management. The present study, therefore, aimed at identifying the potential sources of PM10 in an arid area of Ahvaz located in southwest of Iran. For this purpose, we collected 24‐h PM10 samples by a high volume air sampler. The samples were then analyzed for their elemental (Al, As, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Na, Ni, Pb, Se, Si, Sn, Sr, Li, Ti, V, Zn, Mo, and Sb) and ionic (NH, Cl?, NO, and SO) components using inductively coupled plasma optical emission spectrometry and ion chromatography instruments, respectively. Eight factors were identified by positive matrix factorization: crustal dust (41.5%), road dust (5.5%), motor vehicles (11.5%), marine aerosol (8.0%), secondary aerosol (9.5%), metallurgical plants (6.0%), petrochemical industries and fossil fuel combustion (13.0%), and vegetative burning (5.0%). Result of this study suggested that the natural sources contribute most to PM10 particles in the area, followed closely by the anthropogenic sources. 相似文献
4.
Understanding the variability in monthly rainfall amounts is important for the management of water resources. We use entropy, a measure of variability, to quantify the rainfall variability in Australia. We define the entropy of stable rainfall (ESR) to measure the long‐term average rainfall variability across the months of the year. The stations in northern Australia observe substantially more variability in rainfall distributions and stations in southern Australia observe less variability in rainfall distribution across the months of the year. We also define the consistency index (CI) to compare the distribution of the monthly rainfall for a given year with the long‐term average monthly rainfall distribution. Higher value of the CI indicates the rainfall in the year is consistent with the overall long‐term average rainfall distribution. Areas close to the coastline in northern, southern and eastern Australia observe more consistent rainfall distribution in individual years with the long‐term average rainfall distribution. For the studied stations, we categorize the years into different potential water resource availability on the basis of annual rainfall amount and CI. For almost all Australian rainfall stations, El Niño years have a greater risk of having below median and relatively inconsistent rainfall distribution than La Niña years. The results may be helpful for developing area‐specific water usage strategies. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
5.
6.
A rigorous theoretical investigation is carried out in analyzing the excitation of electrostatic ion acoustic (IA) solitary wave (SW) structures in two dimensional negative ion magneto-plasmas with superthermal electrons (following κ type distribution). The Zakharov-Kuznetsov (ZK) equation is derived by employing the well known reductive perturbation method, and the analytical solution of ZK equation assists to find out the SW profiles along with their properties. The consequences of different plasma parameters (regarding our considered plasma system) variation on SW structures has been studied. It is found that magnetic field intensity, superthermal parameter κ and temperature of positive and negative ions as well as their densities significantly modify the basic characteristics (amplitude, width, etc.) of the SW waves. A comparison of the SW structures is also presented when the electrons are Maxwellian to when they are superthermal. The relevance of the findings of this work with astrophysical plasmas is briefly pointed out. 相似文献
7.
8.
Nicholas Williamson Atsuki Komiya Shigenao Maruyama Masud Behnia Steve W. Armfield 《Journal of Oceanography》2009,65(3):349-359
The transport of nutrient-rich, deep sea water from an artificial upwelling pipe has been simulated. A numerical model has
been built within a commercial Computational Fluid Dynamics (CFD) package. The model considers the flow of the deep sea water
after it is ejected from the pipe outlet in a negatively buoyant plume (densimetric Froude number = −2.6), within a stably
stratified ocean environment subject to strong ocean current cross flow. Two cross-flow profiles were tested with momentum
flux ratios equal to 0.92 and 3.7. The standard k-ε turbulence model has been employed and a range of turbulent Schmidt and Prandtl numbers tested. In all cases the results
show that the rapid diffusion of heat and salinity at the pipe outlet causes the plume to attain neutral buoyancy very rapidly,
preventing strong fountain-like behavior. At the higher momentum flux ratio fountain-like behavior is more pronounced close
to the pipe outlet. The strong cross-current makes horizontal advection the dominant transport process downstream. The nutrient
plume trajectory remains largely within one relatively thin stratified layer, making any ocean cross-flow profile less important.
Very little unsteady behavior was observed. The results show that the nutrient is reduced to less than 2% of its inlet concentration
10 meters downstream of the inlet and this result is largely independent of turbulent Prandtl or Schmidt number. Initial results
would suggest that if such an artificial upwelling were to be viable for an ocean farming project, a large number of upwelling
pipes would be necessary. Further work will have to determine the minimum nutrient concentration required to sustain a viable
phytoplankton population and the required spacing between upwelling pipes. 相似文献
9.
A rigorous theoretical investigation has been made on the obliquely propagating dust-acoustic (DA) waves in a magnetized dusty plasmas consisting of distinct temperature q-distributed electrons with distinct strength of nonextensivities, nonthermal ions and negatively charged mobile dust grains, and analyzed by deriving the Zakharov-Kuznetsov equation. It is found that the characteristics and the properties of the DA solitary waves (DASWs) are significantly modified by the external magnetic field, relative temperature ratio of ions, relative number densities of electrons as well as ions, the nonextensivity of electrons, nonthermality of ions and the obliqueness of the system. The possible implications of the results obtained from this analysis in space and laboratory dusty plasmas are briefly addressed. 相似文献
10.
Xinrong Zhang Shigenao Maruyama Koutaro Tsubaki Seigo Sakai Masud Behnia 《Journal of Oceanography》2006,62(2):133-142
The mechanism of enhanced diffusivity occurring in the deep-sea perpetual salt fountain has been investigated experimentally
and numerically. Some factors which possibly contribute to the enhanced diffusivity were found to be the pipe oscillation
with ocean waves and its baffled wall surface. Field experiments in the ocean (Onagawa Bay of Miyagi, Japan) and numerical
simulations were performed to study and confirm the dynamics of the flow and heat transport with enhanced diffusivity occurring
in upwelling deep-sea water. The agreement between the field experimental data and the numerical solutions of an oscillating-wall
boundary condition imposed on the baffled pipe is encouraging, and it indicates the baffled pipe surface subject to the oscillatory
motion leads to the enhanced diffusivity. The buoyancy force and then upwelling velocity can be greatly increased by the enhanced
diffusivity. The dominant mechanism is the occurrence of complicated vortices and vortex shedding leading to efficient mixing
and enhanced diffusion. 相似文献