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991.
Calculation methods for comparing the performance of pure and mixed working fluids in heat pump applications 总被引:2,自引:0,他引:2
Three methods for comparing cycle performance of working fluids, pure as well as non-azeotropic mixtures, are investigated for two applications and for two mixture pairs, HCFC22-CFC114 and HCFC22-HCFC142b, and their pure components. The methods differ in the way of calculating the heat exchange processes. They assume, respectively, equal minimum approach temperatures, equal mean temperature differences and equal heat transfer areas. Changes of coefficient of performance (COP) with composition are explained for all methods. It is shown that transport properties must be taken into account when making rigorous comparisons between working fluids. To predict the relations between fluids with high accuracy, one must use the method with equal heat transfer areas. By the method with equal mean temperature differences, the COP can be estimated with the same accuracy for mixtures as for pure fluids, and can be used for rough estimations of the COP level with different fluids. The method of equal minimum approach temperatures should be avoided for non-azeotropic mixtures. 相似文献
992.
汤炳谦 《固体电子学研究与进展》1996,16(1):48-55
叙述了Ba(Zn1/3Ta2/3)O3介质谐振器材料的制备、结构、微波性能及典型应用。Ba(Zn1/3Ta2/3)O3介质材料介电常数εr为29.5,频率温度系数τ≈0(-55~+85℃),10GHz下最大无载Q值14700,在28GHz测得Q值约为4800。这种材料具有高Q值,特别适用于X以上波段作为振荡器电路中频率稳定元件。用这种介质谐振器已研制出8mm介质稳频微带耿氏振荡器,频率稳定度小于10×10-6/℃,最大输出功率达180mW。 相似文献
993.
Existence results for the LQG-controller are investigated. An infimal Riccati equation based controller may potentially give closed loop eigenvalues on the unit circle. Assuming left and right invertibility it is shown that there exists an optimal controller if and only if the Riccati equation based controller stabilizes the closed loop system after removal of all its unobservable and uncontrollable modes. Furthermore this reduced controller is the optimal controller, and its transfer function is unique. This existence condition is a considerable simplification of the more general geometric condition recently derived by Trentelman and Stoorvogel. 相似文献
994.
995.
激光扫描三角法是近十年发展起来的三维传感新技术,其实现扫描测量的方法可分为两类:一是采用阵列器件,用相应的同步扫描机构实现;另一则采用单通道器件,由扫描装置进行步进扫描实现。虽然这种技术在陆地及空气系统中已得到广泛应用,但在水下却存在着许多问题。本文提出了一种新型空间差频扫描测量方式,并对扫描测量原理、测量周期、分辨率及速率进行了深入讨论,最后的应用结果显示了这种新型方式用于水下三维传感的特殊优越性。 相似文献
996.
TheCubooctahedronShape──ASuboptimalCellShapefor3-DimensionalCellularSystemChaGuangming;LiZhengmao;LuFan(UniversityofElectroni... 相似文献
997.
998.
The influence of different alkali halides (LiF, LiCl. LiBr, NaF, NaCl, NaBr, KF, KCl and KBr) on α-chymotrypsin-catalysed plastein synthesis has been studied in aqueous medium at different substrate concentrations. The results showed an enhancing effect on the plastein synthesis enzyme action by the presence of salts, proportional to salt concentration, which was decreased when the substrate concentration was increased. Additionally, these facts allowed the ions to be classified as a function of their activation power (F? > Cl? > Br?: K+ > Na+ > Li+), which was in agreement with the interpretation of the Hofmeister lyotropic series. The influence of the several phenomena produced by the presence of salts in the plastein reaction, such as, salt-substrate interactions and water activity, as well as the presence of deactivated enzyme was also analysed. The obtained results showed that the substrate concentration is the most important factor, and the activating effect of salts could be simultaneously involved with both a structural change on the substrate conformation and a reduction of water activity into the reaction media, enhancing the catalytic capability of the α-chymotrypsin towards a peptide synthesis action. 相似文献
999.
Mikhail Yu. Sinev Yurii P. Tulenin Olga V. Kalashnikova Viktor Yu. Bychkov Vladimir N. Korchak 《Catalysis Today》1996,32(1-4):157-162
The analysis of methane oxidation in a wide range of pressures (0.05–10 atm) demonstrates that the efficiency of CH3 radicals recombination is of great importance for high selectivity of C2 hydrocarbons formation. The relative efficiency of different “colliders” assisting the stabilization of exited C2H*6 molecules increases in the series: solid surface> Ar> He. The increase of the overall reaction rate upon increasing pressure of the inert gases in the case of catalysts having a higher surface area and more developed pore structure is likely due to the contribution of the surface-induced chain reaction in the volume of pores. 相似文献
1000.
一种弧焊机器人实时激光扫描视觉系统 总被引:2,自引:0,他引:2
研制了一种小型高精度弧焊机器人实时激光扫描视觉系统,对其各项性能进行了测试,并进行了抗电弧光干扰试验,结果表明,此系统精度高,抗干扰能力强,检测范围宽,能广泛地应秀于机器人和自动化焊接中。 相似文献