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21.
Si-Woong Lee Jae Gark Choi Byoung-Ju Yun 《Electronics letters》2003,39(9):712-714
An adaptive contour smoothing algorithm designed as a preprocessor for shape coders is presented. In the method, the degree of the adaptive smoothing is controlled based on the significance of each contour point, which is quantified according to inter-region contrast in an intensity image. The actual smoothing consists of an expansion operator and a thinning algorithm. 相似文献
22.
G Stoll S Müller B Schmidt P van der Meide S Jung KV Toyka HP Hartung 《Canadian Metallurgical Quarterly》1993,142(6):1866-1875
This study reports the cellular localization of interferon-gamma (IFN-gamma) and MHC class II antigen (Ia) in the spinal cord of rats with experimental autoimmune encephalomyelitis induced by adoptive transfer of myelin basic protein-specific T cells. Numerous IFN-gamma-positive cells, stained with two different monoclonal antibodies against IFN-gamma, were present from days 3 to 7 after cell transfer. Their number was greatly reduced on day 10. A subpopulation of T cells was IFN-gamma positive. Moreover, a large number of ED1-positive macrophages contained IFN-gamma immunoreactivity. The transient presence of immune cells containing IFN-gamma immunoreactivity in experimental autoimmune encephalomyelitis suggests a pathogenic role of this cytokine in immune-mediated demyelination of the central nervous system. 相似文献
23.
A study on the prediction of heat transfer coefficient (HTC) and pressure drop of refrigerant mixtures is reported. HTCs and pressure drops of prospective mixtures to replace R12 and R22 are predicted on the same cooling capacity basis. Results indicate that nucleate boiling is suppressed at qualities greater than 20.0% for all mixtures and evaporation becomes the main heat transfer mechanism. For the same capacity, some mixtures containing R32 and R152a show 8.0–10.0% increase in HTCs. Some mixtures with large volatility difference exhibit as much as 55.0% reduction compared with R12 and R22, caused by mass transfer resistance and property degradation due to mixing (32.0%) and reduced mass flow rates (23.0%). Other mixtures with moderate volatility difference exhibit 20.0–30.0% degradation due mainly to reduced mass flow rates. The overall impact of heat transfer degradation, however, is insignificant if major heat transfer resistance exists in the heat transfer fluid side (air system). If the resistance in the heat transfer fluid side is of the same order of magnitude as that on the refrigerant side (water system), considerable reduction in overall HTC of up to 20% is expected. A study of the effect of uncertainties in transport properties on heat transfer shows that transport properties of liquid affect heat transfer more than other properties. Uncertainty of 10.0% in transport properties causes a change of less than 6% in heat transfer prediction. 相似文献
24.
Synthesis of ultrafine LiCoO2 powders by the sol-gel method 总被引:8,自引:0,他引:8
Ultrafine high-temperature (HT) LiCoO2 powders were synthesized by the sol-gel method using polyacrylic acid (PAA) as a chelating agent. The decomposition process of the gel precursor was examined to determine the crystallization temperature and the dependence of the physicochemical properties of HT-LiCoO2 powders on the PAA quantity was extensively investigated. Polycrystalline HT-LiCoO2 powders, composed of very uniformly sized ultrafine particulates with an average particle size of 30–50 nm and a specific surface area of 2.3–17 m2g–1, could be obtained at the lower calcination temperature of 550 °C and the shorter calcination time of 1 h compared to the solid-state reaction. 相似文献
25.
In Europe, the challenge of the design of third-generation cellular mobile radio systems has been taken numerous research and development activities in this field have been started. The authors try to give an overview of the European activities in this field. The article is organized in two parts. In the first part, the requirements for third-generation cellular mobile radio systems such as Universal Mobile Telecommunications System (UMTS) and Future Public Land Mobile Telecommunications System (FPLMTS), which has been named International Mobile Telecommunications after the year 2000 (IMT-2000) are presented concisely. Also, the importance and challenge of the multiple access design for such third-generation cellular mobile radio systems is explained. In the second part, numerous European research activities with focus on the multiple access design for third-generation cellular mobile radio systems are reviewed 相似文献
26.
The energy release rate, which is the total derivative of the energy with respect to crack length, is recognized as corresponding to the shape sensitivity analysis with the crack length change represented by the tangential component of design velocity. In this paper the sensitivity formula recently developed for a changing boundary condition has been further extended to cover crack kinking under mixed mode loading. Due to difficulty in defining the velocity field at the corner, the energy release rate at the onset of crack kinking is obtained by extrapolating the energy release rates for finite length kinked cracks. A rectangular plate with a single edge slant crack under uniform tension is taken as a numerical example. The multi-region technique in the numerical implementation of the boundary integral equation is adopted to consider the asymmetry of the problem. Excellent accuracy is observed as compared with reference analytic solutions. 相似文献
27.
Joon Sik LeeIn Sung Jung 《International Journal of Heat and Mass Transfer》2002,45(1):113-123
Experiments are conducted to investigate the effects of bulk flow pulsations on film cooling with compound angle holes. A row of five film cooling holes is considered with orientation angles of 0°, 30°, 60°, and 90° at a fixed inclination angle of 35°. Static pressure pulsations are produced by an array of six rotating shutter blades, which extend across the span of the exit of the wind tunnel test section. The pulsation frequency is fixed at 36 Hz, but changes in the time-averaged blowing ratios of 0.5, 1.0 and 2.0 produce three different coolant Strouhal numbers, 3.6, 1.8 and 0.9, respectively. Detailed film cooled boundary layer temperature distributions are measured by a cold wire and the adiabatic film cooling effectiveness by thermochromic liquid crystal (TLC). The boundary layer temperature surveys show that pulsations induce large disruptions to the boundary layer temperature distribution and the film coverage. As the orientation angle increases, the injectant concentration spreads further into the spanwise direction because of pulsations than the steady case. With pulsations the adiabatic film cooling effectiveness value decreases regardless of the orientation angle. The amount of reduction, however, depends on the orientation angle in such a way that the larger the orientation angle is, the smaller the reduction is. 相似文献
28.
介绍了高频等参数感应的基本原理。以胜利油田比较典型的 3口井为例 ,详细分析了高频感应资料在划分薄夹层、确定储层流体饱和类型、评价储层电阻率空间分布等方面的应用。研究结果表明 ,高频感应具有极高的纵向分辨率和较好的径向探测特性 ,能够准确计算地层真电阻率、侵入带电阻率及侵入半径 ,通过与常规感应及薄层测井资料的对比 ,论证了高频等参数感应在测井技术应用上的优越性 相似文献
29.
Han-Sam Cho Hyun-Kyo Jung 《Energy Conversion, IEEE Transaction on》2002,17(4):492-499
The force equation of a synchronous permanent-magnet planar motor (SPMPM) was investigated. The flux density distribution of a two-dimensional (2-D) magnet array for a SPMPM was obtained by solving the equations of the scalar magnetic potential. The expressions of the force and back-EMF constant were derived and examined. Using these expressions, the conditions for normal operation of the SPMPM were found and the optimal design was determined in order to maximize the force of the SPMPM. 相似文献
30.
An existing extensive database on the isothermal and thermomechanical fatigue behaviour of high-temperature titanium alloy
EVII 834 and dispersoid-strengthened aluminum alloy X8019 in SiC particle-reinforced as well as unreinv conditions was used
to evaluate both the adaptability of fracture mechanics approaches to TMF and the resulting predictive capabilities of determining
material life by crack propagation consideration. Selection of the correct microstructural concepts was emphasised and these
concepts were, then adjusted by using data from independent experiments in order to avoid any sort of fitting. It is shown
that the cyclic /-integral (δJeff concept) is suitable to predict the cyclic lifetime for conditions where the total crack propagation rate is approximately
identical to pure fatigue crack growth velocity. In the case that crack propagation is strongly affected by creep, the creep-fatigue
damage parameter δCF introduced by Riedel can be successfully applied. If environmental effects are very pronounced, the accelerating influence
of corrosion on fatigue crack propagation can no longer implicitly be taken into account in the fatigue crack growth law.
Instead, a linear combination of the crack growth rate contributions from plain fatigue (determined in vacuum) and from environmental
attack is assumed and found to yield a satisfactory prediction, if the relevant corrosion process is taken into account. 相似文献