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排序方式: 共有1733条查询结果,搜索用时 15 毫秒
11.
The extended Aharonov-Bohm period test, recently proposed by the present authors, is used to study the electron pairing transition in the t-J ladders. The critical point is detected as a gap opening in the extended spectral flow. The result suggests a pairing prior to the onset of a phase separation, which is consistent with a recent Tomonaga-Luttinger analysis. 相似文献
12.
Toshiji Mukai Koichi Ishikawa Kenji Higashi 《Metallurgical and Materials Transactions A》1995,26(10):2521-2526
Three IN905XL aluminum alloys with fine grain (1 μm), intermediate grain (3 μm), and coarse grain (5 μm) have been developed
by a combination of mechanical alloying (MA) and conventional extrusion in order to investigate their mechanical properties
at dynamic strain rates of 1 × 103 and 2 × 103 s−1 and a quasi-static strain rate of 10-3 s−1. Flow stresses are found to increase with decreasing grain size for all the strain rates tested. Negative strain-rate sensitivity
of flow stress is observed up to 1 × 103 s−1 in both intermediate- and coarse-grained IN905XL. At the highest strain rate of 2 × 103 s−1 however, all samples showed a positive strain-rate sensitivity of strength. Total elongation at high strain rates is generally
larger than that at low strain rates. Total elongation also decreases with grain size for all the strain rates. This decrease
in elongation results from an initiation of microcracks at interfaces between the matrix and particles finely dispersed near
grain boundary regions, introduced during MA processing; then, this initiation leads elongation of alloys to small limited
values.
Formerly with the Department of Mechanical Systems Engineering, University of Osaka Prefecture.
This article is based on a presentation made in the symposium “Dynamic Behavior of Materials,” presented at the 1994 Fall
Meeting of TMS/ASM in Rosemont, Illinois, October 3-5, 1994, under the auspices of the TMS-SMD Mechanical Metallurgy Committee
and the ASM-MSD Flow and Fracture Committee. 相似文献
13.
Mr.KoichiChujo 《国外电子测量技术》2003,22(6):2-3,6
本文着重论述了波形测量技术的最新发展趋势。 相似文献
14.
Makoto Hino Minoru Hiramatsu Koichi Akiyama Hitoshi Kawasaki Masato Tsujikawa Makoto Kawamoto 《Materials and Manufacturing Processes》1997,12(1):37-46
A high powered YAG laser with kaleidoscope for surface modification was applied to the surface hardening of carbon steels containing 0. 18-0.54 wt% C without the absorbents, and the relationships between laser processing and surface hardening were investigated by hardness and microstructure. The structure of the hardened zone underwent complete martensitic transformation in all of the carbon steels tested, and its hardness increased with greater carbon content. Under identical irradiated conditions, the hardened zone expanded with increasing carbon content. A hardened zone extending from the surface to a depth of 1.0 mm was obtained at a laser power of 1.0 kW and a scanning speed of 1 mm/sec. It was found that in the surface hardening of carbon steels, a high powered YAG laser can be used to control the hardened zone by selecting the appropriate irradiation conditions, however, the hardened zone was affected by the assistant gas and the flow rate. 相似文献
15.
Far-infrared reflection spectra of dielectric ceramics, BaSm2 Ti5 O14 , BaTi4 O9 , and some pcrovskites such as Ba(Zn1/3 Nb2/3 )O3 , have been measured at room temperature using a Fourier transform infrared spectrometer in order to investigate the effect of the crystal structure on the dielectric properties. As for perovskites, Sr(Zn1/3 Nb2/3 )O3 and Sr(Mg1/3 Nb2/3 )O3 , in which B site ions are ordered, were also measured. Reflectance data were analyzed by means of a factorized form of dielectric functions instead of the classical dispersion theory, and all of the spectra were well fitted. The values of dielectric constants and tan δ calculated from the reflectance data were in good agreement with resonant cavity measurements at 5 GHz. Furthermore, results of this study have shown that the main contribution to the microwave dielectric properties is caused by low-frequency optically active modes located at 50 to about 300 cm−1 , and for perovskite structures it is suggested that the ordering of B site ions is significant in obtaining low dielectric losses. 相似文献
16.
H Wakita Y Tokura H Yagi K Nishimura F Furukawa M Takigawa 《Canadian Metallurgical Quarterly》1994,286(6):350-354
Antibody titres against Plasmodium falciparum and P. vivax were examined using the indirect fluorescent antibody test (IFAT) for 183 Gidra-speaking adults and adolescents in four ecologically different villages of lowland Papua New Guinea. The findings highlight that 1) in Gidraland P. falciparum was more prevalent than P. vivax, 2) the proportion of antibody titres of 1:64 or higher markedly differed among the villages, ranging from 35.3% to 100% for males and from 31.6% to 100% for females, and 3) in the two villages with high prevalences, these were higher among males than females. The inter-village and sex differences can be largely explained by microenvironmental conditions and behavioural patterns of the population. The population-based analyses of this study intend to contribute to a better understanding of the prevalence of malaria in human-environment settings and thus to the planning of malaria prevention. 相似文献
17.
Takanori Inoue Keiichiro Hoashi Koichi Eguchi Hiromichi Arai 《Journal of Materials Science》1993,28(6):1532-1536
The electrode characteristics of perovskite-type oxides, La0.6Sr0.4CoO3 and La0.6Sr0.4MnO3, on ceria-based oxide and stabilized zirconia were analysed by the a.c. impedance method. The ionic conductivities of the electrolyte and electrode conductivities from the a.c. impedance analysis agreed with those obtained from the current interruption and d.c. four-probe methods. Two semicircles from the charge transfer and diffusion processes appeared as the electrode resistance. The relative contribution of these two processes to the overall electrode resistance strongly depended on the microstructure of the electrode. The electrode microstructure could be controlled by the dispersion medium used for the electrode slurry. The La0.6Sr0.4MnO3 electrode coated with n-butyl acetate slurry exhibited the smallest electrode resistance. 相似文献
18.
Stable optical pulse trains with repetition rates as high as 20-30 GHz have been successfully generated at 1.55 mu m from an InGaAs/InAlAs multiquantum well electroabsorption modulator for the first time.<> 相似文献
19.
Summary Polymerization of methyl methacrylate (MMA) withtert-butyllithium (t-C4H9Li) in toluene in the presence of aluminum alkoxides such as ethoxide,tert-butoxide and 2,6-di-tert-butylphenoxide, were examined at various Al/Li ratios. In the cases of ethoxide andtert-butoxide, predominantly isotactic polymers with broad molecular weight distribution were obtained. Combinations oft-C4H9Li and bis(2,6-ditert-butylphenoxy)methylaluminum [MeAl(ODBP)2] were found to be an efficient initiating system for heterotactic polymerization of MMA, which gives PMMA rich in heterotactic triads up to 68% with narrow molecular weight distribution (Mw/Mn=1.09–1.17). End group analysis by1H NMR indicated thatt-C4H9Li initiates the polymerization and MeAl(ODBP)2 works as a stereospecific modifier. From stereosequence analysis of the heterotactic PMMA by13C NMR, it was found that the calculated pentad fractions from the first-order Markovian statistics (Pm/r=0.742, Pr/m=0.627) fitted the observed ones better than those from Bernoullian statistics. The glass transition temperature of the heterotactic PMMA was 13°C lower than that of syndiotactic PMMA, and the intrinsic viscosity in tetrahydrofuran was close to that of isotactic PMMA with a similar molecular weight but higher than that of syndiotactic PMMA. 相似文献
20.
A population protocol is one of distributed computing models for passively-mobile systems, where a number of agents change
their states by pairwise interactions between two agents. In this paper, we investigate the solvability of the self-stabilizing
leader election in population protocols without any kind of oracles. We identify the necessary and sufficient conditions to
solve the self-stabilizing leader election in population protocols from the aspects of local memory complexity and fairness
assumptions. This paper shows that under the assumption of global fairness, no protocol using only n−1 states can solve the self-stabilizing leader election in complete interaction graphs, where n is the number of agents in the system. To prove this impossibility, we introduce a novel proof technique, called closed-set
argument. In addition, we propose a self-stabilizing leader election protocol using n states that works even under the unfairness assumption. This protocol requires the exact knowledge about the number of agents
in the system. We also show that such knowledge is necessary to construct any self-stabilizing leader election protocol. 相似文献