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On the Relationship between Climatic Variables and Pressure Systems over Saudi Arabia in the Winter Season

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Advances in Atmospheric Sciences 2015年第5期32卷 690-703页

作者： h.m.hASANEAN h.Abdel BASSET m.A.A.hUSSEIN Department of meteorology Faculty of Meteorology Environment and Arid Land AgricultureKing Abdulaziz University Department of meteorology and Astronomy Faculty of Science Al-Azhar University

The synoptic circulation over Saudi Arabia is complicated and frequently governed by the effect of large-scale pressure systems. In this work, we used NCEP–NCAR global data to illustrate the relationship between climatic variables and the main pressure systems that affect the weather and climate of Saudi Arabia, and also to investigate the influence of these pressure systems on surface air temperature（SAT） and rainfall over the region in the winter season. It was found that there are two primary patterns of pressure that influence the weather and climate of Saudi Arabia. The first occurs in cases of a strengthening Subtropical high（Sub h）, a weakening Siberian high（Sib h）, a deepening of the Icelandic Low（Ice L）, or a weakening of the Sudanese Low（Sud L）. During this pattern, the Sub h combines with the Sib h and an obvious increase of sea level pressure（SLP） occurs over southern European, the mediterranean, North Africa, and the middle East. This belt of high pressure prevents interaction between midlatitude and extratropical systems, which leads to a decrease in the SAT,relative humidity（Rh） and rainfall over Saudi Arabia. The second pattern occurs in association with a weakening of the Sub h, a strengthening of the Sib h, a weakening of the Ice L, or a deepening of the Sud L. The pattern arising in this case leads to an interaction between two different air masses： the first（cold moist） air mass is associated with the mediterranean depression travelling from west to east, while the second（warm moist） air mass is associated with the northward oscillation of the Sud L and its inverted V-shape trough. The interaction between these two air masses increases the SAT, Rh and the probability of rainfall over Saudi Arabia, especially over the northwest and northeast regions.

关键词： climatic variables pressure system surface air temperature rainfall relative humidity Saudi Arabia

Barut-Girardello and Gilmore-Perelomov coherent states for pseudoharmonic oscillators and their nonclassical properties: Factorization method

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Chinese Physics B 2013年第8期22卷 421-428页

作者： m K Tavassoly h R Jalali Atomic and molecular Group Faculty of Physics Yazd UniversityYazd Iran Photonics Research Group Engineering Research Center Yazd UniversityYazd Iran The Laboratory of Quantum Information Processing Yazd UniversityYazd Iran

In this paper we try to introduce the ladder operators associated with the pseudoharmonic oscillator, after solving the corresponding Schrrdinger equation by using the factorization method. The obtained generalized raising and lowering operators naturally lead us to the Dirac representation space of the system which is much easier to work with, in comparison to the functional hilbert space. The SU（1, 1） dynamical symmetry group associated with the considered system is exactly established through investigating the fact that the deduced operators satisfy appropriate commutation relations. This result enables us to construct two important and distinct classes of Barut-Girardello and Gilmore-Perelomov coherent states associated with the system. Finally, their identities as the most important task are exactly resolved and some of their nonclassical properties are illustrated, numerically.

关键词： pseudoharmonic oscillator factorization method Barut-Girardello coherent states Gilmore-Perelomov coherent states nonclassical properties

Dynamic Analysis for the Global Performance of An SPm-Feeder-Cage System Under Waves and Currents

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China Ocean Engineering 2015年第3期29卷 415-430页

作者： Cristian CIFUENTES m.h.KIm Ocean Engineering Program Department of Civil Engineering Texas A&M University College Station

In the present study, the dynamic response of a coupled SPm-feeder-cage system under irregular waves and shear currents is analyzed. A numerical model is developed by using the commercial software Orca Flex. hydrodynamics coefficients of the vessel are calculated by using a 3D diffraction/radiation panel program. First- and second-order wave forces are included in the calculations. morison equation is used to compute the drag force on line elements representing the net. Drag coefficients are determined at every time step in the simulation considering the relative normal velocity between the structural elements and the fluid flow. The dynamic response of the coupled system is analyzed for various environments and net materials. The results of the study show the effects of solidity ratio of the net and vertical positions of the cage on the overall dynamic response of the system, confirming the viability of this type of configuration for future development of offshore aquaculture in deep waters.

关键词： offshore aquaculture SPm(single point mooring) feeder vessel connecting lines operational/survival environment drag force equivalent net cage grouping net modeling line tensions solidity ratio

Influence of Welding Parameters on microstructure and mechanical Performance of Resistance Spot Welded high Strength Steels

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Acta metallurgica Sinica(English Letters) 2013年第5期26卷 635-640页

作者： h.Ghazanfari m.Naderi Department of mining and metallurgical Engineering Amirkabir University of Technology (Tehran Polytechnic)

This paper presents an experimental study on physical and mechanical properties of high strength steel plates（AISI 4130） joined by resistance spot welding by means of hardness mapping technique. Welding current and electrode force were selected as experimental parameters. The welded joints were exposed to tensile-shearing tests in order to determine the strength of the welded zones. hardness and microstructural examinations were carried out in order to examine the influence of welding parameters on the welded joints. hardness mapping test was conducted on the large area of weld zone, including the heat afected zone and base plate. hardness map was used to investigate the efects of current on hardness and microstructure in diferent regions of weld. Low electrode force and high welding current, used during the welding, increased the expulsion. An optimum weld quality was obtained by using 6.5 kA weld current. It was found that mechanical performance of resistance spot welded samples is controlled by nugget diameter and expulsion. Results revealed that hardness mapping technique provides one of the best methods for the physical and mechanical understanding of heterogeneous microstructures using hardness criterion.

关键词： Welding current microstructure hardness map Expulsion martensite

Validation of the Wiedemann–Franz law in a granular s-wave superconductor in the nanometer scale

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Chinese Physics B 2017年第3期26卷 506-514页

作者： A Yousefvand h Salehi m Zargar Shoushtari Department of Physics Shahid Chamran University of Ahvaz Ahvaz Iran

The present study tries to evaluate the validity of the Wiedemann-Franz law in a granular s-wave superconductor in the presence of concentrated impurities. By using Green＇s function method and the Kubo formula technique, three distinct contributions of the Aslamazov-Larkin, the maid-Thompson and, the density of states are calculated for both the electrical conductivity and the thermal conductivity in a granular s-wave superconductor. It is demonstrated that these different con- tributions to the fluctuation conductivity depend differently on the tunneling because of their different natures. This study examines the transport in a granular superconductor system in three dimensions in the limit of large tunneling conductance, which makes it possible to ignore all localization effects and the Coulomb interaction. We find that the tunneling is efficient near the critical temperature and that there is a crossover to the characteristic behavior of a homogeneous system. When it is far from the critical temperature, the tunneling is not effective and the system behaves as an ensemble of real zero-dimensional grains. The results show that the Wiedemann-Franz law is violated in both temperature regions.

关键词： granular superconductor s-wave impurity vertex fluctuation propagator

Electrical and dielectric properties of Na_(1/2)La_(1/2)Cu_3Ti_4O_(12) ceramics prepared by high energy ball-milling and conventional sintering

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Chinese Physics B 2016年第12期25卷 474-480页

作者： h mahfoz Kotb mohamad m Ahmad Department of Physics College of ScienceKing Faisal University Department of Physics Faculty of ScienceAssiut University

We report on the measurements of the electrical and dielectric properties of Na1/2La1/2Cu3Ti4O12 （NLCTO） ce- ramics prepared by high energy ball-milling and conventional sintering without any calcination steps. The x-ray powder diffraction analysis shows that pure perovskite-like CCTO phase is obtained after sintering at 1025 ℃-1075 ℃. higher sintering temperatures result in multi-phase ceramics due to thermal decomposition. Scanning electron microscope observations reveal that the grain size is in a range of - 3 μm-5 μm for these ceramics. Impedance spectroscopy measurements performed in a wide frequency range （1 hz-10 mhz） and at various temperatures （120 K-470 K） are used to study the dielectric and electrical properties of NLCTO ceramics. A good compromise between high ε′ （5.7 ×10^3 and 4.1 × 10^3 at 1.1 khz and 96 khz, respectively） and low tan δ （0.161 and 0.126 at 1.1 khz and 96 khz, respectively） is obtained for the ceramic sintered at 1050 ℃. The observed high dielectric constant behavior is explained in terms of the internal barrier layer capacitance effect.

关键词： ceramics sintering dielectric loss and relaxation electrical

monte-Carlo based cascade control approach with focus on real overactuated space systems

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Journal of Central South University 2016年第12期23卷 3171-3182页

作者： m.Shahi A.h.mazinan Department of Electrical Engineering Birjand BranchIslamic Azad University (IAU) Department of Control Engineering Faculty of Electrical EngineeringSouth Tehran BranchIslamic Azad University (IAU)

The present research relies on a cascade control approach through the monte-Carlo based method in the presence of uncertainties to evaluate the performance of the real overactuated space systems.A number of potential investigations in this area are first considered to prepare an idea with respect to *** insight proposed here is organized to present attitude cascade control approach including the low thrust in connection with the high thrust to be implemented,while the aforementioned monte-Carlo based method is carried out to guarantee the approach *** is noted that the investigated outcomes are efficient to handle a class of space systems presented via the center of mass and the moments of *** also a number of profiles for the thrust vector and the misalignments as the disturbances all vary in its span of nominal *** acquired results are finally analyzed in line with some well-known benchmarks to verify the approach *** key core of finding in the research is to propose a novel 3-axis control approach to deal with all the mentioned uncertainties of space systems under control,in a synchronous manner,as long as the appropriate models in the low-high thrusts are realized.

关键词： monte-Carlo based method cascade control approach overactuated space systems low-high thrusts models

Physicochemical Properties of Nanocrystallite Copper Ferrite Prepared by a Novel Self Flash Combustion of Acetate Precursors

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Journal of materials Science & Technology 2005年第5期21卷 675-680页

作者： m.h.Khedr A.A.Farghali Chemistry Department Faculty of Science(Beni-Suef Branch)Cairo UniversityBeni-Suef EgyptChemistry DepartmentFaculty of Science(Beni-Suef Branch)Cairo UniversityBeni-Suef Egypt

Copper ferrite, CuFe2O4, one of the important ferrites due to its interesting electrical, magnetic and structural properties, is obtained by a novel self flash combustion of a homogeneous mixture of one mole copper acetate monohydrate, Cu（Ch3COO）2·h2O, and two moles of iron （Ⅲ） acetate basic, Fe（ChCOO）2·Oh. Nanocrystalite （89 nm） Copper ferrite （less than 100%） is obtained at lower temperatures, whereas 100% copper ferrite is obtained after calcination at 1000℃. Thermal analysis （TG and DTA）, X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FTIR）, photo microscopy, magnetic and porosity obtained after calcinations at 700, 800, 900 and 1000℃ to measurements have been carried out for the specimens characterize the conversion efficiency of the powder precursors to copper ferrite. It was found that increasing temperature leads to great improvement in the magnetic properties. By increasing calcination temperature from 700～1000℃saturation magnetic flux density （Bs） increased from 17.8 to 40.8 emu/g, while remnant magnetic flux density （Br） increased from 10.1 to 17.11 emu/g.

关键词： Copper ferrite Flash combustion Synthesis Characterization magnetic properties microstructure

Fallopian tube assessment of the peristaltic-ciliary flow of a linearly viscous fluid in a finite narrow tube

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Applied mathematics and mechanics(English Edition) 2018年第3期39卷 437-454页

作者： h.AShRAF A.m.SIDDIQUI m.A.RANA Department of mathematics and Statistics Riphah International University Department of mathematics York CampusPennsylvania State University

The present theoretical assessment deals with the peristaltic-ciliary trans- port of a developing embryo within a fallopian tubal fluid in the human fallopian tube. A mathematical model of peristalsis-cilia induced flow of a linearly viscous fluid within a fallopian tubal fluid in a finite two-dimensional narrow tube is developed. The lubrica- tion approximation theory is used to solve the resulting partial differential equation. The expressions for axial and radial velocities, pressure gradient, stream function, volume flow rate, and time mean volume flow rate are derived. Numerical integration is performed for the appropriate residue time over the wavelength and the pressure difference over the wavelength. moreover, the plots of axial velocity, the appropriate residue time over wavelength, the vector, the pressure difference over wavelength, and the streamlines are displayed and discussed for emerging parameters and constants. Salient features of the pumping characteristics and the trapping phenomenon are discussed in detail. Yhrther- more, a comparison between the peristaltic flow and the peristaltic-ciliary flow is made as the special case. Relevance of the current results to the transport of a developing embryo within a fallopian tubal fluid from ampulla to the intramural in the fallopian tube is also explored. It reveals the fact that cilia along with peristalsis helps to complete the required mitotic divisions while transporting the developing embryo within a fallopian tubal fluid in the human fallopian tube.

关键词： peristaltic-ciliary flow linearly viscous fluid analytic solution human fal-lopian tube