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51.
Because of the global warming impact of hydro fluorocarbons, the uses of natural refrigerants in automotive and HVAC industries have received worldwide attention. CO2 is the most promising refrigerant in these industries, especially the transcritical CO2 refrigeration cycle. The objective of this work is to identify the main factors that affect two‐stage compression transcritical CO2 system efficiency. A second law of thermodynamic analysis on the entire two‐stage CO2 cycle is conducted so that the exergy destruction of each system component can be deduced and ranked, allowing future efforts to focus on improving the components that have the highest potential for advancement. The inter‐stage pressure is used as a variable parameter in the analysis study. The second law efficiency, coefficient of cooling performance and total exergy destruction of the system variations with the inter‐stage pressure are presented graphically. It was concluded that there is an optimum inter‐stage pressure that maximizes both first law and second law efficiencies. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
52.
Akin Mustafa Günsel Armağan Bilgiçli Ahmet T. Tüzün Burak Arabaci Gulnur Şaki Neslihan Yarasir M. Nilüfer 《Protection of Metals and Physical Chemistry of Surfaces》2020,56(3):609-618
Protection of Metals and Physical Chemistry of Surfaces - Corrosion inhibition effects of water-soluble peripheral substituted cobalt, copper and zinc metallophthalocyanines (CoPc (1), CuPc (2) and... 相似文献
53.
Ipek Akin Mikinori Hotta Filiz Cinar Sahin Onuralp Yucel Gultekin Goller Takashi Goto 《Journal of the European Ceramic Society》2009,29(11):2379-2385
ZrB2–SiC composites were prepared by spark plasma sintering (SPS) at temperatures of 1800–2100 °C for 180–300 s under a pressure of 20 MPa and at higher temperatures of above 2100 °C without a holding time under 10 MPa. Densification, microstructure and mechanical properties of ZrB2–SiC composites were investigated. Fully dense ZrB2–SiC composites containing 20–60 mass% SiC with a relative density of more than 99% were obtained at 2000 and 2100 °C for 180 s. Below 2120 °C, microstructures consisted of equiaxed ZrB2 grains with a size of 2–5 μm and α-SiC grains with a size of 2–4 μm. Morphological change from equiaxed to elongated α-SiC grains was observed at higher temperatures. Vickers hardness of ZrB2–SiC composites increased with increasing sintering temperature and SiC content up to 60 mass%, and ZrB2–SiC composite containing 60 mass% SiC sintered at 2100 °C for 180 s had the highest value of 26.8 GPa. The highest fracture toughness was observed for ZrB2–SiC composites containing 50 mass% SiC independent of sintering temperatures. 相似文献
54.
This research investigates current practices in Operations and Maintenance (O&M), from the initial phase of assigning maintenance requests through the completion of the requests, in order to identify types of inefficiency and their causes. Fifty-eight real maintenance cases have been shadowed; and maintenance activities performed by the tradespeople have been recorded with time data corresponding to each activity. O&M inefficiencies categorized into two groups, Structural and Individual, are demonstrated through specific cases. A statistical analysis is used to show how O&M tasks, activities, and categories impact overall O&M performance. The results show that tradespeople vastly underutilize maintenance data in the field due to problems with data accessibility and reliability. Based on the shadowing activity results, we observed 12+% potential for improvement in maintenance time efficiency by providing proper information support. 相似文献
55.
Mehmet Murat Karaoğlu Halis Gürbüz Kotancilar Kamil Emre Gerçekaslan 《International Journal of Food Science & Technology》2008,43(10):1778-1785
The effects of frozen storage and initial baking time of par‐baked cake on baking loss, volume, moisture, colour and textural properties of cake obtained after thawing and rebaking were investigated. Cakes, par‐baked at 175 °C for 15, 20 and 25 min, were stored at ?18 °C for 3, 6 and 9 months. After storage, par‐baked cakes were thawed and rebaked at 175 °C for 10, 15 and 20 min. Baking loss, moisture content, L and +b colour values, firmness, gumminess and chewiness of the resulting full‐baked cakes were significantly affected by both par‐baking and frozen storage time, while specific volume, cohesiveness, springiness and resilience values were significantly affected by frozen storage time. The increase in the time of frozen storage of the par‐baked cake leads to a decrease in the quality of the rebaked cake, namely an increase of baking loss and cake crumb firmness, and a loss in the moisture content and specific volume. Moisture of cake crumb, L and +b colour values, firmness, gumminess and chewiness significantly increased as the par‐baking time increased. However, regarding baking loss, specific volume, moisture content and textural properties, 3‐month intermediate storage at ?18 °C and 20‐min initial baking time gave the best result among the cakes produced by using the two‐step baking procedure. 相似文献
56.
57.
Volodymyr V. Oberemok Refat Z. Useinov Oleksii A. Skorokhod Nikita V. Galchinsky Ilya A. Novikov Tatyana P. Makalish Ekaterina V. Yatskova Alexander K. Sharmagiy Ilya O. Golovkin Yuri I. Gninenko Yelizaveta V. Puzanova Oksana A. Andreeva Edie E. Alieva Emre Eken Kateryna V. Laikova Yuri V. Plugatar 《International journal of molecular sciences》2022,23(24)
Insects vastly outnumber us in terms of species and total biomass, and are among the most efficient and voracious consumers of plants on the planet. As a result, to preserve crops, one of the primary tasks in agriculture has always been the need to control and reduce the number of insect pests. The current use of chemical insecticides leads to the accumulation of xenobiotics in ecosystems and a decreased number of species in those ecosystems, including insects. Sustainable development of human society is impossible without useful insects, so the control of insect pests must be effective and selective at the same time. In this article, we show for the first time a natural way to regulate the number of insect pests based on the use of extracellular double-stranded DNA secreted by the plant Pittosporum tobira. Using a principle similar to one found in nature, we show that the topical application of artificially synthesized short antisense oligonucleotide insecticides (olinscides, DNA insecticides) is an effective and selective way to control the insect Coccus hesperidum. Using contact oligonucleotide insecticide Coccus-11 at a concentration of 100 ng/μL on C. hesperidum larvae resulted in a mortality of 95.59 ± 1.63% within 12 days. Green oligonucleotide insecticides, created by nature and later discovered by humans, demonstrate a new method to control insect pests that is beneficial and safe for macromolecular insect pest management. 相似文献
58.
This article extends a procedure that has been used to discretize the static physical system following the assumption that a continuous flexible beam can be replaced by a system of rigid bars and joints which resists relative rotation of the attached bars. We call this procedure the “discrete element response of beams”. The object of this article is to present and formulate a new simple, practical and inexpensive approximate technique for determining the time response of beams, with different boundary conditions, carrying a moving mass. To verify the results, other solutions are obtained by continuous simulation systems, CSMP, and dynamic finite element, PAFEC. This algorithm is shown to be much more efficient computationally. 相似文献
59.
Edgar Rangel-German Serhat Akin Louis Castanier 《Journal of Petroleum Science and Engineering》2006,51(3-4):197-213
Water–air imbibition and oil–water drainage displacements were conducted using a laboratory flow apparatus in fractured sandstone systems. During the experiments, porosity and saturation were measured along the core using a Computerized Tomography (CT) scanner. 3-D saturation images were reconstructed to observe matrix–fracture interactions. Differences in fluid saturations and relative permeabilities caused by changes of fracture width have also been analyzed. In the case of water–air imbibition, narrower fracture apertures showed more stable fronts and delayed water breakthrough compared to the wide fracture systems. However, the final water saturation was higher in wide fracture systems, thus showing that capillary pressure in the narrow fracture has more effect on fluid distribution in the matrix. During oil–water drainage, oil saturations were higher in the blocks near the thin fracture, again showing the effect of fracture capillary pressure. Oil fingering was observed in the wide fracture. Fine-grid simulations of the experiments using a commercial reservoir simulator were performed. Relative permeability and capillary pressure curves were obtained by history matching the experiments. The results showed that the assumption of fracture relative permeability equal to phase saturation is incorrect. It was found that both capillary and viscous forces affect the process. The matrix capillary pressure obtained by matching an experiment showed lower values than those reported in the literature. 相似文献
60.