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Material and structural instabilities of single-wall carbon nanotubes

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Acta Mechanica Sinica 2008年第3期24卷 285-288页

作者： j.Wu k.C.hwang j.Song Y.Huang FML Department of Engineering MechanicsTsinghua UniversityBeijing 100084China Department of Mechanical Science and Engineering University of Illinois1206 W.Green StreetUrbanaIL 61801USA Department of Civil and Environmental Engineering and Department of Mechanical Engineering Northwestern UniversityEvanstonIL 60208USA

The nonlinear atomistic interactions usually involve softening behavior. Instability resulting directly from this softening are called the material instability, while those unrelated to this softening are called the structural instability. We use the finite-deformation shell theory based on the interatomic potential to show that the tension instability of single-wall carbon nanotubes is the material instability, while the compression and torsion instabilities are structural instability.

关键词： Carbon nanotubes Instability

Small Zeros of Additive Forms in Several Variables

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Acta Mathematica Sinica,English Series 1998年第1期14卷 57-66页

作者： j. S. hwang Institute of Mathematics Academia Sinica Taipei Taiwan 11529 China

Let f（X） be an additive form defined by f（X）=f（x1. x2,…,xs）=σ1α1x1k+σα2x2k+…+σsαsxsk, where αo≠0 is integer, i=1, 2,…, s. In 1979, Schmidt proved that if ε>0 then there is a large constant C（k, ε） such that for s≥C（k, ε） the equation f（X）=0 has a nontrivial integer solution in σ1. σ2,…σs, x1, x2…,xs satisfying σi=±1 and |xi|≤Aε, i=1, 2.…,s where A=max|ai|. Schmidt did not estimate this constant C（k. ε） since it would be extremely large. In this paper, we prove the following result: Theorem 1 If log A≤1/ε,then C（k,ε）≤max （2/ε,20）; if log A>1/ε,A is sufficiently larye and 1/2A≤5≤|ai|≤A,i=1. 2,…, s, then C（k,ε）≤c1c2p and if the last condition is omitted, then C（k. ε）≤[4/ε]c1c2,where c1={2k+1 for≤k≤11 [5k2log k] for k≥12, c2=100c1k22k+c12 and p=2[log 2c1/ε]. We note that the inequality in the first case is sharp but not in the second case.

关键词： Additive form Subset sums Small zeros

Fabrication and Properties of SiB6-B4C with Phenolic Resin as a Carbon Source

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journal of Materials Science & Technology 2008年第1期24卷 102-104页

作者： G. C.hwang j.Matsushita United Graduate School of Science and Engineering Tokai University 1117 Kitakaname Hiratsuka 259-12921 Japan

Si-B-C ceramic composites were synthesized using SiB-6,B-4C,and phenolic resin as a carbon source by pressureless sintering in an Ar ***,the Si-B-C ceramic composites were fabricated to determine their potential for applications as high hardness and high temperature *** X-ray diffraction patterns of sintered bodies of SiB-6-B-4C with carbonized phenolic resin can be seen that SiB-6 and C changed to B-4C and *** this study,it is obtained that carbonized phenolic resin is good addition material as a reaction material comparing to carbon powder at 1683 k for 1 h by pressureless sintering in an Ar atmosphere.

关键词： Silicon boride Boron carbide Phenolic resin

In vitro production of functional sperm in mice

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Asian journal of Andrology 2011年第6期13卷 791-792页

作者： kathleen hwang Dolores j Lamb Scott Department of Urology Baylor College of Medicine Houston TX 77030 USA Scott Department of Urology and Molecular and Cellular Biology Baylor College of Medicine Houston TX 77030 USA Laboratory for Male Reproductive Research and Testing Baylor College of Medicine Houston TX 77030 USA

Spermatogenesis refers to the process by which the production and development of the spermatozoa （the mature male gamete of most sexually reproducing species） occurs. It is a complex, stepwise process of sperm development, taking more than a month depending upon the species involving three specific functional phases： spermatogonial proliferation, meiosis and metamorphosis.1 Investigators have been successful in recreating this process in some species of fish; however, this whole process has never been reproduced in vitro in mammals.

关键词： Spermatogenesis refers production the spermatozoa

Eradication of Solenopsis invicta by pyriproxyfen at the Shihmen Reservoir in northern Taiwan

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Insect Science 2009年第6期16卷 493-501页

作者： ji-Sen hwang Department of Natural Science Graduate School of Environmental Education and Resources Taipei Municipal University of EducationTaiwan China

The aim of this study was to investigate the possibility of eradicating the red imported fire ant, Solenopsis invicta Buren, in the hot, humid and rainy conditions of northern Taiwan. Thirteen hectares of the Shihmen Reservoir have been infected with these ants, with a total of 1 578 mounds. Pyriproxyfen was applied at a rate of 2 kg/hectare each season, for a total of four seasons. Surveys using visual examination, bait traps, as well as the population index method showed that the brood, the reproductive ants, and the worker ants within the nests were all significantly reduced 1 month after the first application of pyriproxyfen. Four months after the initial application there were no more brood or reproductive ants. After 8 months there were no longer any active mounds left, and 12 months later there were no more worker ants. After monitoring for 1 more year, it was ascertained that the red imported fire ants were eradicated. The percentages of decrease after 2, 4 and 6 months of treatment were 57.4%, 80.5%, and 98.2%, respectively.

关键词： eradication insect growth regulator pyriproxyfen red imported fire ant,Solenopsis invicta

Design Features and Commissioning of the Versatile Experiment Spherical Torus (VEST) at Seoul National University

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Plasma Science and Technology 2013年第3期15卷 244-251页

作者： k.j.CHUNG Y.H.AN B.k.jUNG H.Y.LEE C.SUNG Y.S.NA T.S.HAHM Y.S.hwang Department of Nuclear Engineering Seoul National University

A new spherical torus called VEST （Versatile Experiment Spherical Torus） is designed, constructed and successfully commissioned at Seoul National University. A unique design feature of the VEST is two partial solenoid coils installed at both vertical ends of a center stack, which can provide sufficient magnetic fluxes to initiate tokamak plasmas while keeping a low aspect ratio configuration in the central region. According to initial double null merging start-up scenario using the partial solenoid coils, apprdpriate p6wer supplies for driving a toroidal field coil, outer poloidal field coils, and the partial solenoid Coils are fabricated and successfully commissioned. For reliable start-up, a pre-ionization system with two cost-effective homemade magnetron power supplies is also prepared. In addition, magnetic and spectroscopic diagnostics with appropriate data acquisition and control systems are well prepared for initial operation of the device. The VEST is ready for tokamak plasma operation by completing and commissioning most of the designed components.

关键词： spherical torus partial solenoids double null merging start-up

Seismic health monitoring of RC frame structures using smart aggregates

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Earthquake Engineering and Engineering Vibration 2013年第1期12卷 25-32页

作者： Wen-I Liao C.H.Lin j.S.hwang G.Song Department of Civil Engineering Taipei University of Techology (NTUT) Department of Construction Engineering Taiwan University of Science and Technology Department of Mechanical Engineering University of Houston

Structural health monitoring of RC structures under seismic loads has recently attracted much attention in the earthquake engineering research community. In this study, a piezoceramic-based device called ＂smart aggregate＂ was used for the health monitoring of RC frame structures under earthquake excitations. Three RC moment frames instrumented with smart aggregates were tested using a shaketable with different ground excitation intensities. Distributed piezoceramic- based smart aggregates were embedded in the RC structures and used to monitor their health condition during the tests. The sensitivity and effectiveness of the proposed piezoceramic-based approach were investigated and evaluated by analyzing the measured responses. The displacement ductility demand of the structural members was calculated and compared with the damage index determined from the health monitoring system. The comparison shows that the damage index is compatible with the calculated ductility demand.

关键词： smart aggregate health monitoring RC frame shaketable piezoceramic

Gamma Vibrational Bands and Chiral Doublet Bands in A≈100 Neutron-rich Nuclei

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原子核物理评论 2009年第S1期26卷 64-69页

作者： j.H.Hamilton A.V.Ramayya j.k.hwang j.O.Rasmussen S.Frauendorf V.Dimitrov Department of Physics Vanderbilt University Lawrence Berkeley National Laboratory Physics Department Notre Dame University

The level structures of neutron-rich 105Mo,106Mo,108Mo and 110Ru nuclei in A ≈ 100 region have been carefully investigated by coincidence measurements of the prompt γ-rays populated in the spontaneous fission of 252Cf with the Gammasphere detector array. In 105Mo,one-phonon k=9/2 and two-phonon k=13/2 γ-vibrational bands have been identified. In 108Mo,one-phonon γ-vibrational band is expanded and two-phonon γ-vibrational band has been identified. Two similar sets of bands in 106Mo and 110Ru are observed to high spins,which have been proposed as the soft chiral γ-vibrational bands. The characteristics for these γ-vibrational bands and chiral doublet bands have been discussed.

关键词： high spin state neutron-rich nucleus γ-vibrational band chiral doublet band

Collective Band Structures in Neutron-Rich ^108Mo Nucleus

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Chinese Physics Letters 2007年第6期24卷 1517-1520页

作者：丁怀博朱胜江 j.H.Hamilton A.V.Ramayya j.k.hwang Y.X.Luo j.0.Rasmussen I.Y.Lee 车兴来王建国徐强 Department of Physics Tsinghua University Beijing 100084 Department of Physics Vanderbilt University Nashville Tennessee 37235 USA Lawrence Berkeley National Laboratory Berkeley California 94720 USA

High spin states in the neutron-rich ^108Mo nucleus are studied by measuring prompt γ-rays following the spontaneous fission of 252Cf with a Gammasphere detector array. The ground-state band is confirmed, and the one-phonon γ-vibrational band is updated with spin up to 12h. A new collective band with the band head level at 1422.4keV is suggested as a two-phonon γ-vibrational band. Another new band is proposed as a two-quasi- proton excitation band. Systematic characteristics of the collective bands are discussed.

关键词： Collective Structures Neutron-Rich