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201.
针对目前R502主流替代工质R507和R404A存在的温室效应指数高、与矿物油互溶性差等缺点,提出了环保性能更好的三组近共沸混合工质R134a/R290、R134a/R1270和R134a/R290/R1270作为R502新型替代工质;并对其热物性、循环性能、安全性能和溶油性进行了计算分析。结果表明:除了压缩机排气温度偏高,这三组R134a/HCs混合工质的其它主要循环性能参数如压缩机压力比、容积制冷量和系统性能系数COP都优于R507和R404A,并且从理论上讲不存在可燃可爆的危险,同时可以与矿物油互溶,在替代R502方面更具有优势,其中R134a/R290/R1270在高热负荷下的综合性能最优良。 相似文献
202.
203.
Xiangming He Weihua Pu Jianguo Ren Li Wang Jiulin Wang Changyin Jiang Chunrong Wan 《Ionics》2008,14(4):335-337
The charge/discharge characteristics of the sulfur composite cathodes were investigated at different temperatures and different
current densities. The composite presented the discharge capacities of 854 and 632 mAh g−1 at 60 and −20 °C, respectively, while it had the discharge capacities of 792 mAh g−1 at 25 °C. The composite presented the discharge capacities of 792 and 604 mAh g−1 at 55.6 and 667 mA g−1, respectively, at room temperature. The results showed that the sulfur composite cathodes presented good charge/discharge
characteristics between 60 and −20 °C and at a high c-rate up to 667 mA g−1. 相似文献
204.
Microscopic phonon theory of semiconductor nanocrystals (NCs) is reviewed in this paper. Phonon modes of Si and Ge NCs with
various sizes of up to 7 nm are investigated by valence force field theory. Phonon modes in spherical SiGe alloy NCs approximately
3.6 nm (containing 1147 atoms) in size have been investigated as a function of the Si concentration. Phonon density-of-states,
quantum confinement effects, as well as Raman intensities are discussed.
相似文献
205.
对双向抽运拉曼光纤放大器(RFA)的噪声特性、增益饱和及抽运功率转换效率进行了详细研究。结果表明,双向抽运拉曼光纤放大器的噪声特性介于前向抽运与后向抽运之间,但主要取决于前向抽运方式所导致的噪声特性;双向抽运方式的饱和功率低于单向抽运方式的饱和功率,同前向抽运与后向抽运提供的增益比例有关;双向抽运方式的抽运功率转换效率同信号光功率及前、后向抽运提供的增益有关,当信号光功率较低时,增加前向抽运的比例可取得较高的抽运功率转换效率,而信号光功率较高时,增加后向抽运的比例可取得较高的抽运功率转换效率。研究一种配置(情况3)的双向抽运拉曼光纤放大器,可以完全补偿100km传输线路的损耗(包括无源器件的损耗),最低光信噪比为30.21dB。 相似文献
206.
ZHU Yabin ZHOU Yueliang LIU Zhen WANG Shufang CHEN Zhenghao U Huibin YANG Guozhen XlAO Ling Ren Hongtao JIAO Yulei Zheng Minghui 《中国科学G辑(英文版)》2004,47(2):165-172
The irreversibility field (Hirr) of Y-based superconductor is much higher than that of Bi-based superconductor. Y-based superconductor is capable of maintaining stable electrical currents in high magnetic field and electric field, so it is a better suited mate-rial for electric-current applications. Commonly, the Y-based tapes comprise a YBCO thick film deposited on a flexible substrate, typically with an intermediate buffer layer, and an overcoat of noble metal. In this process, the interm… 相似文献
207.
Improving the membrane model by which the entropy of the black hole is studied, we study the entropy of the black hole in the non-thermal equilibrium state. To give the problem stated here widespread meaning, we discuss the (n 2)-dimensional de Sitter spacetime. Through discussion, we obtain that the black hole‘s entropy which contains two horizons (a black hole‘s horizon and a cosmological horizon) in the non-thermal equilibrium state comprises the entropy corresponding to the black hole‘s horizon and the entropy corresponding to the cosmological horizon. Furthermore, the entropy of the black hole is a natural property of the black hole. The entropy is irrelevant to the radiation field out of the horizon. This deepens the understanding of the relationship between black hole‘s entropy and horizon‘s area. A way to study the bosonic and fermionic entropy of the black hole in high non-thermal equilibrium spacetime is given. 相似文献
208.
ZHANG Li-Chun WU Yue-Qin LI Huai-Fan ZHAO Ren 《理论物理通讯》2008,50(7):97-100
Recently, there has been much attention devoted to resolving the quantum corrections to the Bekenstein- Hawking black hole entropy. The different correction leading terms are obtained by the different methods. In this paper, we calculate the correction to SAdS5 black hole thermodynamic quantity due to the generalized uncertainty principle. Furthermore we derive that the black hole entropy obeys Bekenstein Hawking area theorem. The entropy has infinite correction terms. And every term is finite and calculable. The corrected Cardy-Vedinde formula is derived. In our calculation, Bekenstein Hawking area theorem still holds after considering the generalized uncertainty principle. We have not introduced any hypothesis. The calculation is simple. Physics meaning is clear. We note that our results are quite general. It is not only valid for four-dimensional spacetime but also for higher-dimensional SAdS spacetime. 相似文献
209.
You-Cun Chen Guang-Xiang Liu Xiao-Ming Ren You Song 《Journal of Physics and Chemistry of Solids》2008,69(10):2445-2452
Four molecular solids consisting of the 7,7,8,8-tetracyanoquinodimethane (TCNQ) radical and benzylpyridinium or benzylquinolinium derivatives with molar ratios of 1:1 (1-3) and 2:1 (4) have been prepared and characterized. In the crystals of 1 and 3, TCNQ− monoanions and the corresponding cations form segregated stacks, which are regular in 1 but irregular in 3. Instead of segregated stacks, TCNQ− monoanions in 2 form isolated π-dimers. In the crystals of 4, two crystallographic independent TCNQ species possess almost equal fractional negative charge (ca. −0.5). Two types of TCNQ species form a tetrad, these tetrads make a TCNQ stack with the pattern …BAAB…BAAB… along the crystallographic a-b direction. The magnetisms for 1-4 can be simply explained by the formation of singlet spin state. A broken symmetry approach in a density functional theory framework at the ub3lyp/6-31 g level was used to calculate the magnetic exchange constants in 1-4. The results qualitatively demonstrate the observed magnetic properties. 相似文献
210.
Influence of atmospheric pressure plasma treatment time on penetration depth of surface modification into fabric 总被引:1,自引:0,他引:1
In order to determine the relationship between the treatment duration of atmospheric pressure plasma jet (APPJ) and the penetration depth of the surface modification into textile structures, a four-layer stack of polyester woven fabrics was exposed to helium/oxygen APPJ for different treatment durations. The water-absorption time for the top and the bottom sides of each fabric layer was reduced from 200 s to almost 0 s. The capillary flow height for all fabric layers in the stack increased linearly with the treatment duration but the rate of increasing reduced linearly with the fabric layer number. A model for the capillary flow height as a function of treatment duration and the layer number was established based on the experimental data and the maximum penetration depth of the APPJ was predicted for the polyester fabric. The improved wettability of the fabrics was attributed to the enhanced surface roughness due to plasma etching and the surface chemical composition change due to plasma-induced chemical reaction as detected by scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. The surface roughness and the surface chemical composition change diminished as the fabric layer number increased. 相似文献