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bouncing scenario of general relativistic hydrodynamics in extended gravity

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Communications in Theoretical Physics 2021年第2期73卷 96-101页

作者： A y Shaikh b Mishra Department of Mathematics Indira Gandhi MahavidyalayaRalgaon-445402India Department of Mathematics Birla Institute of Technology and Science PilaniHyderabad CampusHyderabud-500078India

In this paper,we have framed bouncing cosmological model of the Universe in the presence of general relativistic hydrodynamics in an extended theory of *** metric assumed here is the flat Friedmann–Robertson–Walker space–time and the stress energy tensor is of perfect *** general relativity(GR)has certain issues with late time cosmic speed up phenomena,here we have introduced an additional matter geometry coupling that described the extended gravity to *** dynamical parameters are derived and *** dynamical behavior of the equation of state parameter has been *** have observed that the bouncing behavior is mostly controlled by the coupling parameter.

关键词： FRW metric extended gravity bouncing scenario energy conditions

Giant magnetocaloric effect in Tb_5Ge_(2-x)Si_(2-x)Mn_(2x) compounds

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Chinese Physics b 2010年第5期19卷 542-548页

作者： e.yzak b.emre y.elerman A.ycel Department of engineering Physics Faculty of EngineeringAnkara University06100 BesevlerAnkaraTurkey Faculty of Science and Letters Physics DepartmentMugla UniversityKtekli 48000 MuglaTurkey

The crystal structure, magnetic and magnetocaloric characteristics of the pseduo ternary compounds of TbsGe2-xSi2-xMn2x （0 ≤ 2x ≤ 0.1） were investigated by x-ray powder diffraction and magnetization measurements. The x-ray powder diffraction results show that all compounds preserve the monoclinic phase as the majority phase and all the synthesized compounds were observed to be ferromagnetic from magnetization measurements. Magnetic phase transitions were interpreted in terms of Landau theory. Maximum isothermal magnetic entropy change value （20.84 J-kg-1 -K-1） was found for Tb5Ge1.95Si1.95Mn0.1 at around 123 K in the magnetic field change of 5T.

关键词： magnetic properties magnetocaloric effect isothermal magnetic entropy change

Processing and characterization of the microstructure and mechanical properties of Al6061–Tib_(2) composite

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International Journal of Minerals,Metallurgy and Materials 2021年第6期28卷 1080-1089页

作者： y.Pazhuhanfar b.eghbali Faculty of Materials Science and engineering Sahand University of TechnologyTabrizIran

In the present research,aluminum metal matrix composites were processed by the stir casting *** effects of Tib2 reinforcement particles,severe plastic deformation through accumulative roll bonding(ARb),and aging treatment on the microstructural characteristics and mechanical properties were also *** tensile tests and microhardness measurements were conducted,and the microstructural characteristics were ***,the important problems associated with cast samples,including nonuniformity of the reinforcement particles and high porosity content,were solved through the ARb *** the initial stage,particle-free zones,as well as particle clusters,were observed on the microstructure of the ***,after the ARb process,fracturing phenomena occurred in brittle ceramic particles,followed by breaking down of the fragments into fine particles as the number of rolling cycles ***,composites with a uniform distribution of particles were ***,the tensile strength and microhardness of the ARb-processed composites increased with the increase in the reinforcement mass ***,their ductility exhibited a different *** post-deformation aging treatment(T6),the mechanical properties of composites were improved because of the formation of fine Mg2Si precipitates.

关键词： stir casting accumulative roll bonding aging treatment mechanical properties microstructural characteristics Tib2 ceramic particle

Solid Desiccant Dehumidification Techniques Inspired from Natural electroosmosis Phenomena

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Journal of bionic engineering 2011年第1期8卷 90-97页

作者： b. Li y. y. yan Faculty of engineering University of Nottingham Lenton Firs Building University Park Nottingham NG7 2RD UK

electroosmosis has been shown to be an effective means of different applications in various fields such as Micro-electro-Mechanical systems （MeMS） and biomimetics applications. This paper aims to prove the concept that the electroosmosis phenomena can also be cooperated into larger scale applications in the building service industry like dehumidification or damping proof. The electroosmotic flow inside a porous medium is validated experimentally to further understand the dehumidification mechanism of combined techniques. An experimental test validates that the condensation from the porous medium can be obtained by electroosmotic force generated by external electric field, especially for specific desiccant powders like zeolite and diatomaceous earth. With a range of volts from 5 V to 20 V applying between the testing plates, the maximum flow rate through the cross section in the testing plate achieved during the peak period is 1.35 laL＇min 1. These promising phenomena can act as an alternative way for energy choice in dehumidification industrial field. Further researches on new regeneration methods for solid desiccant dehumidification are required to make the system simple, energy-saving and suitable for small air conditioning units.

关键词： biomimetics electroosmotic flow solid desiccant dehumidification

effects of Impurity on the Ground—State Transitions of a Quantum Dot in Strong Magnetic Field

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Communications in Theoretical Physics 2001年第6期35卷 735-739页

作者： K.S.CHAN e.y.b.PUN 等 DepartmentofPhysicsandMaterialsScience CityuniversityofHongKongHongKongChina Departmentofelectronic

The low-lying spectra of parabolic quantum dots with or without an impurity at the center are investigated.While it has been known that the electron-electron interaction leads to ground-state transitions on magic values of angular momentum in a magnetic field. We show, in this paper, that the implantation of an impurity ion at the center can either enhance or suppress such transitions, depending on whether it is an acceptor or a donor ion.

关键词： impurity states quantum dots

Theoretical and numerical investigation of HF elastic wave propagation in two-dimensional periodic beam lattices

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Acta Mechanica Sinica 2013年第6期29卷 783-798页

作者： b.Tie b.y.Tian D.Aubry Laboratory MSSMat(UMR-CNRS 8579) Ecole Centrale ParisGrande Voie des Vignes92295 Chatenay-Malabry CedexFrance

The elastic wave propagation phenomena in two-dimensional periodic beam lattices are studied by using the bloch wave transform. The numerical modeling is applied to the hexagonal and the rectangular beam lattices, in which, both the in-plane （with respect to the lattice plane） and out-of-plane waves are considered. The dispersion relations are obtained by calculating the bloch eigenfrequencies and eigenmodes. The frequency bandgaps are observed and the influence of the elastic and geometric properties of the primitive cell on the bandgaps is studied. by analyzing the phase and the group velocities of the bloch wave modes, the anisotropic behaviors and the dispersive characteristics of the hexagonal beam lattice with respect to the wave prop- agation are highlighted in high frequency domains. One im- portant result presented herein is the comparison between the first bloch wave modes to the membrane and bend- ing/transverse shear wave modes of the classical equivalent homogenized orthotropic plate model of the hexagonal beam lattice. It is shown that, in low frequency ranges, the homog- enized plate model can correctly represent both the in-plane and out-of-plane dynamic behaviors of the beam lattice, its frequency validity domain can be precisely evaluated thanks to the bloch modal analysis. As another important and original result, we have highlighted the existence of the retro- propagating bloch wave modes with a negative group veloc- ity, and of the corresponding ＂retro-propagating＂ frequency bands.

关键词： elastic wave propagation Periodic beam lattice bloch wave theory bandgaps Anisotropy Disper- sion relation

Adaptation of real earthquake records for their reproduction by a shaking table with limited stroke

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earthquake engineering and engineering Vibration 2010年第4期9卷 493-502页

作者： b blostotsky y Ribakov G Agranovich Ariel University Center of Samaria

Shaking tables with moving platforms are widely used in laboratory testing of structural models and full-sized devices. In most cases, the platform＇s movement should reproduce real ground acceleration records. However, the stroke of the platform, required for reproduction of real records, is usually rather large. This limitation does not allow an accurate realization of the ground motion by the shaking table. Commonly, in order to overcome this problem, original records are modified, which causes a significant change in the acceleration records＇ spectra. That is why structural responses to the original and to the modified records are different. A new method for modification of original acceleration records is proposed, in which the original record is corrected by an additional artificial one that changes the shaking platform＇s displacement. The corrected record is obtained as a sequence of impulses, The magnitude and duration of each impulse, as well as their location on the time scale, are obtained by an optimization procedure. The optimization is implemented according to a performance index, aimed to minimize the influence of the correcting acceleration record on the specmam of the original one. The proposed method has higher reproduction accuracy, compared to other known methods. Its effectiveness is demonstrated by comparison of response spectra and dynamic behaviors of three multi-story structures subjected to natural and modified seismic excitations.

关键词： shaking table platform stroke earthquake record reproduction scaling optimization

The Log-Concavity of Kazhdan-Lusztig Polynomials of Uniform Matroids

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Journal of Systems Science & Complexity 2023年第1期36卷 117-128页

作者： XIe Matthew H y ZHANG Philip b College of Science Tianjin University of TechnologyTianjin 300384China College of Mathematical Science Tianjin Normal UniversityTianjin 300387China

elias,et al.(2016)conjectured that the Kazhdan-Lusztig polynomial of any matroid is *** by a computer proof of Moll’s log-concavity conjecture given by Kauers and Paule,the authors use a computer algebra system to pr... 详细信息

关键词： HolonomicFunctions Kazhdan-Lusztig polynomial log-concavity uniform matroid

Impact analysis of compressor rotor blades of an aircraft engine

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Frontiers of Structural and Civil engineering 2019年第3期13卷 505-514页

作者： y b SUDHIR SASTRy b G KIROS F HAILU R bUDARAPU Department of Aeronautical engineering Institute of Aeronautical EngineeringDundigalHyderabad 500043India Department of Aeronautical engineering College of EngineeringDefense UniversityBishoftu 1041Ethiopia School of Mechanical Sciences Indian Institute of Technology BhubaneswarBhubaneswar 752050India

Frequent failures due to foreign particle impacts are observed in compressor blades of the interceptor fighter MIG-23 aircraft engines in the ethiopian air force,supplied by the Dejen Aviation *** this paper,we made an attempt to identify the causes of failure and hence recommend the suitable materials to withstand the foreign particle *** and stress analysis of one of the recently failed MIG-23 gas turbine compressor blades made up of the following Aluminum based alloys:6061-T6,7075-T6,and 2024-T4,has been performed,apart from the impact analysis of the rotor blades hit by a granite *** numerical results are correlated to the practical *** on the modal,stress and impact analysis and the material properties of the three considered alloys,alloy 7075-T6 has been recommended as the blade material.

关键词： axial flow compressor rotor and stator blades aircraft engine stress and impact analysis aluminum alloys