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排序方式: 共有2836条查询结果,搜索用时 31 毫秒
41.
《International Journal of Hydrogen Energy》2019,44(51):27726-27740
A system based a fluidized bed gasifier with steam as a gasifying agent is investigated in details. Comparing the synthesis of gas compositions with experimental data available in the literature is used to validate the model. The synthesis of gas composition and efficiencies of the system is investigated respect to different biomasses considered as gasification fuels. The results indicate that the molar fractions of hydrogen and carbon dioxide are increased and the molar fraction of carbon monoxide is reduced with steam to biomass ratio (STBR). The hydrogen and cold gas efficiencies are improved with decreasing STBR. Hydrogen, cold gas, and exergy efficiencies are enhanced with temperature. The results illuminate that pine sawdust and straw have the highest hydrogen production and legume straw produces the lowest CO molar fraction. Straw has the highest hydrogen efficiency, eucalyptus and straw have the highest cold gas efficiency, and eucalyptus has the highest exergy efficiency. A systematical analytical hierarchy process (AHP)/technique for order preferences by similarity to ideal solution (TOPSIS) couple method are utilized to select the best alternative. The results illuminate that eucalyptus, straw, and pine sawdust are the best candidates, respectively as gasification fuel based on the considered criteria. 相似文献
42.
A new configuration of solar energy-driven integrated system for ammonia synthesis and power generation is proposed in this study. A detailed dynamic analysis is conducted on the designed system to investigate its performance under different radiation intensities. The solar heliostat field is integrated to generate steam that is provided to the steam Rankine cycle for power generation. The significant amount of power produced is fed to the PEM electrolyser for hydrogen production after covering the system requirements. A pressure swing adsorption system is integrated with the system that separates nitrogen from the air. The produced hydrogen and nitrogen are employed to the cascaded ammonia production system to establish increased fractional conversions. Numerous parametric studies are conducted to investigate the significant parameters namely; incoming beam irradiance, power production using steam Rankine cycle, hydrogen and ammonia production and power production using TEGs and ORC. The maximum hydrogen and ammonia production flowrates are revealed in June for 17th hour as 5.85 mol/s and 1.38 mol/s and the maximum energetic and exergetic efficiencies are depicted by the month of November as 25.4% and 28.6% respectively. Moreover, the key findings using the comprehensive dynamic analysis are presented and discussed. 相似文献
43.
44.
This paper analyses the relationship between productive efficiency and online-social-networks (OSN) in Spanish telecommunications firms. A data-envelopment-analysis (DEA) is used and several indicators of business “social Media” activities are incorporated. A super-efficiency analysis and bootstrapping techniques are performed to increase the model's robustness and accuracy. Then, a logistic regression model is applied to characterise factors and drivers of good performance in OSN. Results reveal the company's ability to absorb and utilise OSNs as a key factor in improving the productive efficiency. This paper presents a model for assessing the strategic performance of the presence and activity in OSN. 相似文献
45.
This work presents large-scale dye-sensitized solar cells and methods for their manufacture. A dye-sensitized solar cell device contains a photosensitive dye adsorbed on a large surface of the anode, and a transparent conductive cathode disposed opposite the anode, wherein platinum nano-catalytic particles adhere to its surface, and an electrolytic solution is sealed between the anode and the transparent conductive cathode. A titania nanotube film was fabricated by thermo-spraying titanium film on 304 stainless-steel substrate. The photo-current conversion efficiency was tested under an AM 1.5 solar simulator. The dye-sensitized solar cell device has a short current density of 8.22 mA cm–2, open voltage of 0.71 V, fill factor of 0.59, and conversion efficiency of 3.4%. The internal impedance of the dye-sensitized solar cell was detected and simulated using an electrical impedance spectra technique with inductance, resistance, and capacitance characteristics. The stainless-steel/titania, titania/electrolyte, electrolyte, and electrolyte/(platinum/indium tin oxide) interfaces were simulated using an resistor–capacitor parallel circuit, and bulk materials such as stainless steel, tin doped indium oxide, and conducting wire were simulated by using a series of resistors and inductance. 相似文献
46.
在集团公司不断提高客户服务满意度的要求下,提高投诉处理的及时率,提高投诉处理的效率,减少每万用户投诉比成为越来越紧迫的任务。在完成这个任务的过程中,有一个关键的步骤就是如何提高公告信息发布的效率。这个网络类公告信息包括工程信息和故障信息。发布是指在EOMS上发布并在BOSS系统上呈现给客服人员查询使用。这个效率包括公告信息的及时率、准确率和有效率。 相似文献
47.
In continuation of the authors' tables of significance tests (1963), the power function of this exact test for the 2 × 3 contingency table using the Freeman & Halton principle is derived and evaluated numerically in the form of contours of constant power for the cases: A = 5(5) 15, where A is the total number in each of the three groups observed according to the numbers of ‘Successes’ (= a i ) in each. Comparisons are also made with the exact significance points of the competing X 2 and (?2 log λ) tests under the null hypothesis H 0 and also alternatives to H 0. 相似文献
48.
Organic light-emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) have emerged as promising alternatives to phosphorescent OLEDs for harvesting both singlet and triplet excitons. However, the development of TADF-OLEDs meets a thorny problem of serious efficiency roll-off at high luminance. Here, we demonstrate an approach to suppress the efficiency roll-off characteristics in TADF-OLEDs by localized surface plasmon resonance (LSPR) effect of easy-fabricated Ag-island nanostructures. Compared with the common TADF-OLEDs at a high current density of 100 mA cm−2, the efficiency roll-off ratio of the TADF-OLEDs with Ag-island nanostructures decreases from 49.75% to 35.76% significantly, and the maximum current efficiency is increased by 10.5%. The performance enhancement is mainly attributed to the coupling between excitons and localized surface plasmons (LSPs), which could alter the excited state kinetic characteristics of TADF molecules. 相似文献
49.
O. L. Davies 《技术计量学》2013,55(1):49-61
In establishing an economical testing program the costs of routine analytical tests must be weighed against losses due to shipping material which is either above or below stated specifications. A method for obtaining an optimum sampling and testing procedure is described and examples given. 相似文献
50.
Abdelkarim Ammar Abdelhamid Benakcha Amor Bourek 《International Journal of Hydrogen Energy》2017,42(28):17940-17952
This paper presents a space vector modulation (SVM) based Direct Torque Control strategy (DTC) for induction motor (IM) in order to overcome the drawbacks of the classical DTC. SVM can reduce the high torque and flux ripples by preserving a fixed switching frequency. This technique is known by the closed loop torque SVM-DTC. Moreover, the control scheme performance is improved by inserting a second order sliding mode super twisting controller in the outer loop for speed regulation. This nonlinear technique ensures a good dynamic and high robustness against external disturbance. Furthermore, the IM energy optimization is treated in the second objective of this paper. A proposed model based loss minimization strategy is presented for efficiency optimization. This strategy chooses an optimal flux magnitude for each applied load torque. The proposed optimized SVM-DTC algorithm will be investigated by simulation and real time implementation using Matlab/Simulink with real time interface based on dSpace 1104 signal card. 相似文献