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Acoustic band gaps in two-dimensional square arrays of semi-hollow circular cylinders

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Science China(technological Sciences) 2009年第2期52卷 303-312页

作者： t. Kim MOE Key Laboratory for Strength and Vibration School of Aerospace Xi'an Jiaotong University

Concave surfaces focus sound while convex surfaces disperse sound. It is therefore interesting to know if it is possible to make use of these two opposite characteristics to enhance the band gap performance of periodic arrays of solid cylinders in air. In this paper, the band gap characteristics of a 2-D square array of semi-hollow circular cylinders embedded in air are investigated, both experimentally and theoretically. In comparison with the types of inclusion studied by previous researchers, a semi-hollow circular cylinder is unique in the sense that it has concave inner surfaces and convex outer surfaces. the finite difference time domain (FDtD) method is employed to study the propagation behavior of sound across the new phononic crystal of finite extent, and the influences of sample size and inclusion orientation on band gap characteristics are quantified in order to obtain the maximum band gap. For reference, the band gap behaviors of solid circular cylinder/air and hollow circular cylinder/air systems are considered and compared with those of semi-hollow circular cylinder/air systems. In addition to semi-hollow circular cylinders, other inclusion topologies such as semi-hollow triangular and square cylinders are also investigated. to validate the theoretical predictions, experimental measurements on square arrays of hollow Al cylinders in air and semi-hollow Al cylinders in air are carried out. the results demonstrate that the semi-hollow circular cylinder/air system has the best overall band gap performance.

关键词： phononic crystals PDtD semi-hollow circular cylinders band gaps experimental verification

Hollow dimension of modules

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2005年第10期6卷 1055-1057页

作者： ORHAN Nil KESKiN tütüNCü Derya Department of Mathematics University of HacettepeBeytepe 06532 AnkaraTurkeyDepartment of Mathematics University of Hacettepe Beytepe 06532 AnkaraTurkey

In this paper, we are interested in the following general question： Given a module Mwhich has finite hollow dimension and which has a finite collection of submodules Ki （ 1≤i≤n） such that M=K1 ＋... ＋Kn can we find an expression for the hollow dimension of Min terms of hollow dimensions of modules built up in some way from Kt… ,Kn？ We prove the following theorem： Let Mbe an amply supplemented module having finite hollow dimension and let Ki （ 1 ≤i≤n） be a finite collection of submodules of M such that M=K1 ＋... ＋Kn. then the hollow dimension h（M） of M is the sum of the hollow dimensions of Ki （1≤i≤n） if and only if Ki is a supplement of K1＋...＋K（i-1）＋K（i＋1）＋...＋Kn in M for each 1≤i≤n.

关键词： Hollow dimension Supplement submodule

Numerical damage evaluation of perforated steel columns subjected to blast loading

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Defence technology（防务技术） 2022年第5期18卷 735-746页

作者： Mahmoud t.Nawar Ibrahim t.Arafa Osama M.Elhosseiny Structural Engineering Department Zagazig UniversityZagazig44519Egypt

the structural performance of perforated steel columns(PSCs)is significantly more complex than the one of solid web I-shaped elements under the diversity of blast loading *** damage criterion of PSCs is not only related to initial deformation response during the blast but also the residual axial load capacity and it can be considered as a reliable index after the blast ***,the PSCs damages will be studied in two stages;direct and post blast *** the present study,the dynamic response of PSCs was numerically evaluated under different levels of blast threats using LS-DYNA *** explicit finite element(FE)analyses are carried out to investigate the effect of various parameters,such as web opening shapes,boundary conditions and strengthening details on the damage index and toughness of the PSCs compared to the parent steel *** results of the comparative study show that the damage and toughness decrease when the support condition changes from pinned to fixed ends through the two stages of *** give high toughness compared to its parent sections during blast shock stage while,a remarkable decrease in toughness is observed during the application of axial gravity after blast ***,the web opening shapes have slight effects on the global dynamic behavior of PSCs,particularly in terms of residual *** the contrary,the retrofitting strategy using both closed holes at end and vertical stiffeners have an effective enhancement to get higher toughness in case of the extreme blasts.

关键词： Perforated steel columns Blast load Damage criterion Numerical modeling Explicit finite element analysis Web-opening shapes

Indium antimonide based HEMt for RF applications

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Journal of Semiconductors 2014年第11期35卷 20-22页

作者： t.D.Subash t.Gnanasekaran K.N.S.K College of Engineering Nagercoil-629901India RMK College of Engineering and technology Tamil Nadu601206India

We report on an indium antimonide high electron mobility transistor with record cut-off frequency characteristics. For high frequency response it is important to minimize parasitic resistance and capacitance to improve short-channel effects. For analog applications adequate pinch-off behavior is demonstrated. For proper device scaling we need high electron mobility and high electron density. toward this end, the device design features and simulation are carried out by the Synopsys tCAD tool. A 30 nm InSb HEMt exhibits an excellent cut-off frequency of 586 GHz. to the knowledge of the authors, the obtained cut-off frequency is the highest ever reported in any FEt on any material system.

关键词： HEMt InSb gate length cut-off frequency short-channel effects

Effect of Injection Position on In-Flight Melting Behavior of Granular Alkali-Free Glass Raw Material in 12-Phase AC Arc Plasma

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Plasma Science and technology 2009年第6期11卷 699-703页

作者：姚耀春 K.YAtSUDA t.WAtANABE t.YANO National Engineering Laboratory of Vacuum Metallurgy Kunming University of Science and Technology Department of Environmental Chemistry and Engineering Tokyo Institute of TechnologyYokohama 226-8502Japan Department of Chemistry and Materials Science Tokyo Institute of TechnologyTokyo 152-8550Japan

An innovative in-flight glass melting technology with a multi-phase AC arc plasma was developed to save energy and reduce emissions for the glass industry. the effect of the injection position on the in-flight melting behavior of granulated powders was investigated. Results show that the injection position has a strong effect on the melting behavior of alkali-free glass raw material. With the increase in injection distance, the vitrification, decomposition, and particle shrinkage of initial powders are improved. Longer injection distance causes much energy to transfer to particles due to a longer residence time of powder in the high temperature zone. the high vitrification and decomposition degrees indicate that the new in-flight melting technology with 12-phase AC arc can substantially reduce the melting and refining time for glass production.

关键词： 12-phase AC arc plasma in-flight melting technology heat transfer glass production

Microstructural Evolution of Pearlite in Eutectoid Fe-C Alloys during Severe Cold Rolling

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Journal of Materials Science & technology 2005年第1期21卷 25-27页

作者： WantangFU YiXIONG JunZHAO YongLI t.Furuhara t.Maki KeyLab.ofMetastableMater.Sci.&tech.YanshanUniversity Qiuhuangdao066004China//Dept.ofMater.Sci.andEng.KyotoUuiversityKyoto606-8501Japan KeyLab.ofMetastableMater.Sci.&tech.YanshanUniversity Qiuhuangdao066004China Dept.ofMater.Sci.andEng. KyotoUuiversityKyoto606-8501Japan

the microstructural evolution of pearlite during severe cold rolling in Fe-0.8C binary alloy and Fe-1Mn-0.8C ternary alloys was investigated by using SEM, tEM and XRD etc. the results show that the deformed pearlite consists of irregularly bent lamella, coarse lamella with shear-band and fine lamella. As the rolling reduction increases, the proportion of fine lamella increases. the strong plastic deformation, amorphization and dissolution of cementite take place during the severe cold rolling. the maximum carbon content in ferrite reaches 0.15 mass% after 90% cold rolling.

关键词： Pearlite Severe cold rolling Microstructural evolution Dissolution Amorphization Fe-C alloy

Processing and Performance of Alumina Fiber Reinforced Alumina Composites

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Journal of Materials Science & technology 2003年第4期19卷 337-340页

作者： P.Y.Leet t.Uchijima t.Yano Research Laboratory for Nuclear Reactors Tokyo Institute of Technology2-12-1O-okayamaMeguro-kuTokyo152-8550JapanResearch Laboratory for Nuclear ReactorsTokyo Institute of Technology2-12-1O-okayamaMeguro-kuTokyo152-8550JapanResearch Laboratory for Nuclear ReactorsTokyo Institute of Technology2-12-1O-okayamaMeguro-kuTokyo152-8550Japan

Processing of alumina fiber-reinforced alumina matrix composites by hot-pressing was described. the mechanical properties of the composites fabricated by different sintering conditions including temperature and pressure have been investigated. the results indicated that the higher sintering temperature and pressure corresponded to the higher bulk density and higher maximum strength of the composite, whereas the pseudo-ductility of the composite was lower. the preliminary results of the composite with monazite-coated fibers showed that maximum strength could be improved up to 35% compared with the noncoated fiber composite in the same sintering condition. Moreover, the fracture behavior of the composite changed from completely brittle fracture to non-brittle fracture under the suitable sintering conditions. SEM observation of the fracture surface indicated that the coating worked as a protective barrier and avoided sintering of the fibers together even at high temperature and pressure during densification process.

关键词： Al2O3/Al2O3 composites Mechanical properties Hot-pressing Fiber reinforced composites

Potential recovery of precious metals from waste laptops in Jordan

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Rare Metals 2015年第7期34卷 517-521页

作者： Mohammad A.t.Alsheyab Program Manager of Civil and Environmental Engineering Qatar Foundation

to achieve a sustainable development in the electronic and electrical equipment(EEE) industry, it is necessary to protect the available natural *** addition, to satisfy the increasing demand on EEE, it is necessary to provide alternative sources of raw *** this paper, laptops were imported to Jordan in 2011 as an example to show the potential recovery of metals and precious metals from high grade waste electronic and electrical equipment by conducting a mass flow rate analysis using the StAN *** results show that considerable amounts of gold, silver, cobalt, palladium,and copper could be *** will reduce the amounts needed from primary natural resources and offset the CO2 emissions produced from mining the primary raw material resources.

关键词： Precious metals Laptops Waste of electronic and el

A　Possible　Origin　of　Dark　Energy

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Chinese Physics Letters 2004年第6期21卷 1187-1188页

作者： t.D.Lee PhysicsDepartment ColumbiaUniversityNewYorkNY10027USA

We discuss the possibility that the existence of dark energy may be due to the presence of a spin zero field φ(x), either elementary or composite. In the presence of other matter field, the transformation φ(x)→φ(x) + constant can generate a negative pressure, like the cosmological constant. In this picture, our universe can be thought as a very large bag, similar to the much smaller MIt bag model for a single nucleon.

关键词： Gravitation and cosmology Particle physics and field theory Astrophysics and astroparticles