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991.
The behaviors of concentric-double inclusions dispersed in continuous media are investigated theoretically to find some possibilities
of improving toughness of composite materials by dispersing double-inc’usions instead of single-inclusions. The general solutions
of the Stokes equation, expressed in terms of the spherical harmonics, are used for analyzing the problems that are related
to the concentric-double inclusions. From the analysis, it is found that the pressure and stress fields inside and outside
the inclusion can be modified by changing the modulus ratios and the thickness of shell layer. Especially, the positions of
the minimum pressure points and the maximum stress points turn out to be controllable with some degree of freedom. 相似文献
992.
993.
SH Cho JY Seo DC Choi HJ Yoon YJ Cho KU Min GK Lee JW Seo YY Kim 《Canadian Metallurgical Quarterly》1996,26(10):1210-1219
BACKGROUND: There have been many studies concerning pathological changes in bronchial mucosa from asthmatics; however, few studies has been carried out to evaluate pathological changes according to the severity of asthma. OBJECTIVE: This study was designed to evaluate the cellular components in bronchoalveolar lavage fluid (BALF) and histological abnormalities in asthmatics according to the severity of asthma. METHODS: Bronchoalveolar lavages, bronchoscopic biopsies and ultrastructural examinations were performed in 13 asthmatics and 11 (BAL) or four (biopsies) non-asthmatic controls. The proportions of epithelial cells and correlations with PC20Meth which reflects bronchial hyperresponsiveness. Light microscopic examination revealed loss of epithelium, inflammatory cell infiltrations and thickening of the basement membrane which also showed significant correlation with PC20Meth. Hypertrophy of airway smooth muscles and hyperplasia of mucous glands were prominent in asthmatics but there was no difference according to the severity of asthma. Ultrastructural examination revealed that basement membrane thickening on light microscopic examination is due to the increased subepithelial collagen deposition with normal thickness of basal lamina. CONCLUSION: These data suggest that loss of epithelial cells, infiltration of inflammatory cells, especially eosinophils, and increased deposition of subepithelial collagen play major roles in determining the severity of asthma and non-specific bronchial hyperresponsiveness. 相似文献
994.
Ketones react with primary amines in dioxane at 180 °C in the presence of a catalytic amount of a ruthenium catalyst to give the corresponding α-alkylated ketones in moderate to good yields. With alkyl(methyl) ketones, the alkylation takes place exclusively at less-hindered methyl position over α-methylene. 相似文献
995.
Young-Gyu Kim Seok-Beom Cho Pil-Jong Kim Boo-Kil Kwon 《Journal of Mechanical Science and Technology》2006,20(3):329-334
This paper presents the evaluation of LPG (Liquefied petroleum gas) regulators for home use. For the evaluation, several properties
of the regulators were experimentally analyzed, such as the operation of safety device, the adjusting and lock-up pressure,
the adjusting spring and the diaphragm, with respect to the used time of the regulators. Experimental results showed that
the initial operation performances of regulators were degraded with increase of the service time and also showed that the
degradation of the performance and material property could become serious after about six-year-use of the regulators. 相似文献
996.
Cho K.J. Kim W.J. Stapleton S.P. Kim J.H. Lee B. Choi J.J. Kim J.Y. 《Electronics letters》2006,42(12):704-705
A 40 W gallium-nitride microwave Doherty power amplifier for WCDMA repeater applications is presented. The main amplifier and peaking amplifier are implemented using two 20 W PEP GaN HEMTs. Performance is evaluated for broadband gain, power efficiency and adjacent-channel-power-ratio (ACPR). Experimental results of the GaN Doherty amplifier yielded a power gain of over 11 dB from 1.8 to 2.5 GHz, 68% power added efficiency at 40 W peak power. Good linearity performance of -48 dBc ACPR is obtained at a peak-to-average ratio of 9.8 dB. 相似文献
997.
J. R. Cho K. W. Kim J. K. Lee T. H. Park W. Y. Lee 《International journal for numerical methods in engineering》2002,55(6):733-752
In this paper, we address analytical and numerical studies on the free vibration of fluid–structure interaction problems considering the fluid compressibility. According to the separation of variables together with the boundary condition enforcement, we first derive a compressible‐fluid velocity potential function. Next, we split the structure region into the wet and dry parts, for which we apply the Novozhilov thin shell theory. Combining two dynamic displacement fields, for two split structure parts, using the displacement compatibility conditions, we finally obtain a simultaneous equation system for computing natural frequencies and modes. According to the derived analytical formulae, we compute natural frequencies and modes, stress resultants, together with the comparison with the FEM analysis and the incompressible case. Numerical results show, compared to the incompressible case, that the compressible case produces lower natural frequencies and, furthermore, the relative difference is influenced by the slenderness of tanks and the relative liquid fill height. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
998.
999.
Chang Seo Park Byung Jin Cho 《Electron Device Letters, IEEE》2005,26(11):796-798
High work function (4.9 eV) on high-/spl kappa/ gate dielectric, which is suitable for bulk p-MOSFET, has been achieved using fully silicided (FUSI) Pt/sub x/Si gate without boron predoping of polysilicon. High concentration of Pt in FUSI Pt/sub x/Si using Ti capping layer on Pt in the FUSI process is a key to achieving high work function and reduced Fermi-level pinning on high-/spl kappa/ dielectric. By combining with substituted Al (SA) gate for nMOSFET, a wide range of work function difference (0.65 eV) between n and pMOSFETs is demonstrated, without any adverse effects of polysilicon predoping. 相似文献
1000.
Faist J. Sirtori C. Capasso F. Sivco D.L. Baillargeon J.N. Hutchinson A.L. Cho A.Y. 《Photonics Technology Letters, IEEE》1998,10(8):1100-1102
High-temperature operation (T=320 K) of quantum cascade lasers has been extended to 11.5-μm wavelengths with high performances. Peak-pulsed optical power of 55 mW is obtained at 300 K with a high T 0=172 K, in good agreement with our theoretical model 相似文献