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Characterization of Operators on the Dual of Hypergroups which Commute with Translations and Convolutions

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Acta Mathematica Sinica,English Series 2004年第2期20卷 201-208页

作者： Ali Ghaffari Alireza Medghalchi Department of Mathematics Semnan UniversityP.O.Box 35195-363SemnanIran Department of Mathematics Teacher Training UniversityTehranIran.

For a locally compact group G, L 1(G) is its group algebra and L ∞(G) is the dual of L 1(G). Lau has studied the bounded linear operators T : L ∞(G) → L ∞(G) which commute with convolutions and translations. For a subspace H of L ∞(G), we know that M(L ∞(G),H), the Banach algebra of all bounded linear operators on L ∞(G) into H which commute with convolutions, has been studied by Pym and Lau. In this paper, we generalize these problems to L(K)*, the dual of a hypergroup algebra L(K) in a very general setting, i. e. we do not assume that K admits a Haar measure. It should be noted that these algebras include not only the group algebra L 1(G) but also most of the semigroup algebras. Compact hypergroups have a Haar measure, however, in general it is not known that every hypergroup has a Haar measure. The lack of the Haar measure and involution presents many difficulties; however, we succeed in getting some interesting results.

关键词： Hypergroup algebras Group algebras Operators Translations Convolutions Invariant

Effects of solution treatment on high temperature deformation behavior of extruded Mg-0.35Y-2.17Nd-0.36Zr biomedical alloy

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Transactions of Nonferrous Metals Society of China 2019年第9期29卷 1842-1853页

作者： Sh.ALIYARI S.M.FATEMI S.M.MIRESMAEILI Department of Metallurgy and Materials Engineering Shahid Rajaee Teacher Training University

The high temperature deformation behavior of an extruded Mg-0.35 Y-2.17 Nd-0.36 Zr(wt.%) alloy was investigated for biomedical application by employing compression tests in temperature range of 225-525 ℃ and strain rate range of 0.0003-0.03 s-1. To study the significance of solute elements, the material was solution-treated before deformation. The low temperature yield strength of the as-extruded material significantly decreased after solutionizing process. A drastic change in the strength of solutionized alloy was recorded as the temperature was raised to 450 ℃, which was attributed to the promotion of grain boundary sliding(GBS). It was evidently shown that the slip-to-twinning transition temperature did not necessarily coincide with the strength-drop temperature. Based on constitutive equations, deformation parameters and related activation energy for the experimental alloy have been determined, incorporating the strain-dependent material constants. The verification of predictability of the developed models indicates a good agreement between experimental and predicted data.

关键词： Mg alloy hot deformation constitutive model twinning

Effects of wollastonite nanofibers on fluid flow in medium-density fiberboard

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Journal of Forestry Research 2016年第1期27卷 209-217页

作者： Hamid R.Taghiyari Younes Sarvari Samadi Wood Science and Technology Department Faculty of Civil Engineering Shahid Rajaee Teacher Training University Faculty of Wood Technology and Construction Rosenheim University of Applied Sciences

We studied the effect of wollastonite nanofibers on fluid flow in medium-density fiberboard （MDF）. Nanowollastonite （NW） was applied in MDF at 10 %, based on the dry weight of wood fibers. We also tested chicken feathers as an additive to the matrix at 5 and 10 % by weight. The weight of feathers was reduced from the wood fibers to keep the density of the panels constant （0.66 g cm-3）. Wollastonite nanofibers acted as filler in the matrix and significantly decreased gas and liquid perme- ability. Higher thermal conductivity of the N-W-treated MDF-mats resulted in a better cure of resin, and conse- quently more integrity in the composite-matrix and lower permeability. The water-repellant property of wollastonite also contributed to the decrease in liquid permeability. Feathers reduced gas and liquid permeability due to the hydrophobic nature of keratin, as well as its formation as a physical barrier towards passing of fluids. Ten percent feather content proved too high and some checks and cracks occurred in the core of the panels after hot-pressing. Panels with 5 %-feather content resulted in both lower fluid flow and adequate physical integrity in the core sec- tion of the MDF-matrix.

关键词： Chicken feather Composite board Mineralmaterials Thermal conductivity coefficient Wollastonitenanofibers Wood fiber

Characterization of semisolid deformation behavior of a high Zr-containing WE magnesium alloy

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Rare Metals 2022年第12期41卷 4201-4208页

作者： Masoud Moradjoy-Hamedani Abbas Zarei-Hanzaki Seyed Mahmood Fatemi School of Metallurgy and Materials Engineering College of EngineeringUniversity of TehranTehran 515-14395Iran School of Mechanical Engineering Shahid Rajaee Teacher Training UniversityTehran 136-16785Iran

The effects of temperature and strain rate on the semisolid deformation behavior of a high Zr WE54 magnesium alloys were studied at temperatures of 570,595 and 620℃.A flow stress peak was appeared during deformation of the feedstock experimental material at deformation conditions of 570℃,0.010 and 0.100 s-1,and 595℃,0.100 *** latter results were connected to the occurrence of dynamic recrystallization in solid ***,these conditions were gauged to be able to activate"lubricated flow"*** 570℃and strain rate of 0.001 s-1as well as 595℃and rates of 0.010 and 0.001 s^(-1),the flow stress increases and reaches a plateau,where dynamic recovery is considered as the dominant ***,at 620℃under all the strain rates,the flow stress drops for a limited strain range and then increases *** results show that as the liquid removes from the boundaries between the solid parts,the densification of the globules occurs at higher strains,causing an increase in the flow *** analysis points out that the feedstock material exhibits a lower flow stress than as-cast alloy associating with a modified morphology of Zr particles after deformation.

关键词： Mg-RE alloy Feedstock Semisolid deformation Liquid flow

Effect of Ca addition on microstructure and impression creep behavior of cast AZ61 magnesium alloy

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Transactions of Nonferrous Metals Society of China 2019年第10期29卷 2056-2065页

作者： B.NAMI S.M.MIRESMAEILI F.JAMSHIDI I.KHOUBROU Department of Materials Engineering and New Technologies Shahid Rajaee Teacher Training University

Microstructure and creep properties of AZ61 alloy containing 1 and 3 wt.% Ca were investigated. The creep properties were examined using impression method under different stresses between 200 and 500 MPa at the temperature ranging from 423 to 491 K. The microstructure of AZ61 alloy contains α(Mg) matrix and Mg17 Al12 intermetallic phases. It is shown that adding Ca to AZ61 alloy reduces the amount of Mg17 Al12 phase via forming(Mg,Al)2 Ca phase;furthermore, increasing the Ca content to 3 wt.% leads to the formation of(Mg,Al)2 Ca phase, as well as the elimination of the Mg17 Al12 phase. Creep properties of AZ61 alloy are improved with the Ca addition. The improvement in creep properties is attributed to the reduction in the amount of Mg17 Al12 phase and the formation of(Mg,Al)2 Ca phase with high thermal stability. According to the obtained creep data, it is concluded that the pipe diffusion-climb controlled dislocation creep is the dominant creep mechanism and Ca addition has no influence on this mechanism. The effect of pre-deformation on the creep properties of AZ61+3%Ca alloy reveals that the creep resistance of the alloy depends on the continuity of(Mg,Al)2 Ca phase. It is decreased by reducing the phase continuity.

关键词： impression creep magnesium alloy Ca addition dislocation creep phase continuity

Determination of Critical Temperatures in Hot Rolling of a Nb-Microalloyed Steel Sheet

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Journal of Iron and Steel Research International 2011年第S1期18卷 585-589页

作者： Daavood Mirahmadi Khaki Vahid Alizaadeh Otaaghvar Department of Materials Engineering Shahid Rajaee Teacher Training UniversityTehranIran School of Mechanical Engineering Islamic Azad UniversityTehranIran

To design the controlled hot rolling and thermomechanical processes of microalloyed steels,it is essential to know the various critical transformation temperatures like the grain coarsening temperature (T gc),the non-recrystallization temperature (T nr),the start of austenite-to-ferrite transformation (A r3),and the finish of the austenite-to-ferrite transformation (A r1).In this work,the heat treatment and continuous cooling compression (CCC) testing were performed to determine the critical temperatures of a Nb-microalloyed *** obtained from the CCC testing on the strain-stress curves were confirmed by metallographic *** carry out the CCC testing,T nr equals 960℃;A r3 equals 830℃ and A r1 equals 665℃ were *** addition,to specify the grain coarsening temperature that it usually occurs during reheating the slabs,seven different reheating temperatures between 1000 to 1300℃ with 50℃ increments for the soaking treatment were *** soaking the specimens in furnace,the grain coarsening temperature (T gc) was obtained about the temperature of 1250 ℃.Moreover,it was observed that increasing the reheating temperatures causes more decline of the precipitates ***,the temperature range of 1200 to 1250℃ is recommended to reheat these types of steels.

关键词： Nb-microalloyed steel continuous cooling compression testing critical temperatures microstructure

Quasi-Local Energy Distribution and Thermodynamics of Reissner-Nordstrom Black Hole Surrounded by Quintessence

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Communications in Theoretical Physics 2011年第2期55卷 291-295页

作者： Mahamat Saleh Bouetou Bouetou Thomas Timoleon Crepin Kofane Department of Physics Faculty of Science University of Yaounde Dpartment of Physics Higher Teacher's Training College University of Maroua Ecole Nationale Superieure Polytechnique University of Yaounde

We investigate quasi-local energy distribution and thermodynamics of the Reissner-Nordstr6m black hole space-time surrounded by quintessence. We use the quasi-local energy distribution from Einstein energy-momentum complex. We plot the variation of the energies, temperature and heat capacity with the state parameter related to the quintessence ωq. We show that due to the presence of quintessence, the total energy of the outer region as well as the temperature and heat capacity decreases with the increase of the density of quintessence, while the total energy of the black hole region increases.

关键词： quasi-local energy distribution thermodynamics Reissner-NordstrSm black hole quintessence

Design of electronic sections for nano-displacement measuring system

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Frontiers of Optoelectronics 2010年第4期3卷 376-381页

作者： Saeed OLYAEE Samaneh HAMEDI Zahra DASHTBAN Nano-Photonics and Optoelectronics Research Laboratory Faculty of Electrical and Computer Engineering Shahid Rajaee Teacher Training University (SRTTU)

Noncontact displacement measurement is generally based on the interferometry method. In the semiconductor industry, a technique for measuring small features is required as circuit integration becomes denser and the wafer size becomes larger. An interferometric system known as a three-longitudinal-mode heterodyne interferometer(TLMI) is made of two main parts: optical setup and electronic sections. In the optical part, the base and measurement signals having 500-MHz frequency are produced, resulting from interfering three longitudinal modes. The secondary beat frequency to measure the displacement in the TLMI is about 300 k Hz. To extract the secondary beat frequency, wide-band amplifiers, doublebalanced mixers(DBMs), band-pass filters(BPFs), and low-pass filters(LPFs) are used. In this paper, we design the integrated circuit of a super-heterodyne interferometer with total gain of 56.9 dB in size of 1030 μm×1030 μm.

关键词： nano-displacement double-balanced mixer (DBM) integrated circuit three-longitudinal-mode interferometer

Effects of densification on untreated and nano-aluminum-oxide impregnated poplar wood

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Journal of Forestry Research 2017年第2期28卷 403-410页

作者： Hamid R.Taghiyari Ghonche Rassam Kazem Ahmadi-DavazdahEmam Wood Science&Technology Department The Faculty of Civil EngineeringShahid Rajaee Teacher Training UniversityTehranIran Zelam Ltd A Lonza CompanyNew PlymouthNew Zealand

Effects of densification of poplar wood（Populus nigra） impregnated with nano-aluminum oxide（NA） and pre-treated with water vapor for 4 and 6 h were investigated in the present study. Physical and mechanical properties of treated poplar wood were measured according to the ASTM D-143 standard specifications, and then compared with the untreated specimens. Results showed significant improvement in all properties as a result of densification. A 4-h vapor pre-treatment improved effects on both physical and mechanical properties. When the duration of vapor-treatment increased to 6 h, wood polymers degraded to the extent that the improvements due to the vapor pre-treatment decreased substantially, though the final results were still significant improvements compared with the control specimens. High thermal conductivity coefficient of NA slightly but not significantly improved properties. Due to the high spring-back after 15 days,densified poplar is not recommended for applications in which densified wood will be exposed for long periods to high humidity or to direct water.

关键词： poplar untreated nigra degraded specifications exposed pretreatment modulus Heidelberg swelling