In view of different compressor adding ways in the ammonia-water absorption/compression combined refrigeration AWA /CCR cycle combining the Schulz state equation of the ammonia-water solution the theoretical analysis ...In view of different compressor adding ways in the ammonia-water absorption/compression combined refrigeration AWA /CCR cycle combining the Schulz state equation of the ammonia-water solution the theoretical analysis and calculations on two combination ways by adding the compressor in the high-pressure area and in the low-pressure area are conducted respectively.The effects of several factors including the evaporation temperature Te heat-source temperature Th as well as the cooling water temperature Tw on the equivalent heat consumption in compression qCW heat consumption in absorption qG and the system coefficient of performance COP are analyzed under the two combination configurations.The results show that the effect of the equivalent heat consumption in compression on the COP is less than that of the heat consumption in absorption.Besides the compressor set in the high-pressure area uses more energy than that in the low-pressure area. Moreover the compressor in the low-pressure area is superior to that in the high-pressure area with respect to the COP. Under the given intermediate pressure there is an optimum heat-source temperature corresponding to the maximum COP of the AWA/CCR cycle.展开更多
Liquefied natural gas(LNG) is the most economical way of transporting natural gas(NG) over long distances. Liquefaction of NG using vapor compression refrigeration system requires high operating and capital cost. Due ...Liquefied natural gas(LNG) is the most economical way of transporting natural gas(NG) over long distances. Liquefaction of NG using vapor compression refrigeration system requires high operating and capital cost. Due to lack of systematic design methods for multistage refrigeration cycles, conventional approaches to determine optimal cycle are largely trial-and-error. In this paper a novel mixed integer non-linear programming(MINLP)model is introduced to select optimal synthesis of refrigeration systems to reduce both operating and capital costs of an LNG plant. Better conceptual understanding of design improvement is illustrated on composite curve(CC) and exergetic grand composite curve(EGCC) of pinch analysis diagrams. In this method a superstructure representation of complex refrigeration system is developed to select and optimize key decision variables in refrigeration cycles(i.e. partition temperature, compression configuration, refrigeration features, refrigerant flow rate and economic trade-off). Based on this method a program(LNG-Pro) is developed which integrates VBA,Refprop and Excel MINLP Solver to automate the methodology. Design procedure is applied on a sample LNG plant to illustrate advantages of using this method which shows a 3.3% reduction in total shaft work consumption.展开更多
With COP and dynamic characteristics in refrigeration cycle as criteria,a new metal hydride couple——LaNi 4.61 Mn 0.26 Al 0.13 /La 0.6 Y 0.4 Ni 4.8 Mn 0.2 was selected by establishing calculation procedure and metal ...With COP and dynamic characteristics in refrigeration cycle as criteria,a new metal hydride couple——LaNi 4.61 Mn 0.26 Al 0.13 /La 0.6 Y 0.4 Ni 4.8 Mn 0.2 was selected by establishing calculation procedure and metal hydride selection model.The experimental results show that the refigeration cycle of the selected couple is good in the performance.The recovered waste heat and refrigeration power from exhaust gas of several kinds of automobile are calculated by waste-heat formula,coefficient R Q and COP.Refrigeration cycle of the new couple can satisfy the air-conditioning requirement of truck and car and is not enough in passenger car,according to the respective cooling load.展开更多
Progression of cells from G2 phase of the cell cycle to mitosis is a tightly regulated cellular process that requires activation of the Cdc2 kinase, which determines onset of mitosis in all eukaryotic cells. In both h...Progression of cells from G2 phase of the cell cycle to mitosis is a tightly regulated cellular process that requires activation of the Cdc2 kinase, which determines onset of mitosis in all eukaryotic cells. In both human and fission yeast (Schizosaccharomyces pombe) cells, the activity of Cdc2 is regulated in part by the phosphorylation status of tyrosine 15 (Tyr15) on Cdc2, which is phosphorylated by Wee1 kinase during late G2 and is rapidly dephosphorylated by the Cdc25 tyrosine phosphatase to trigger entry into mitosis. These Cdc2 regulators are the downstream targets of two well- characterized G2/M checkpoint pathways which prevent cells from entering mitosis when cellular DNA is damaged or when DNA replication is inhibited. Increasing evidence suggests that Cdc2 is also commonly targeted by viral proteins, which modulate host cell cycle machinery to benefit viral survival or replication. In this review, we describe the effect of viral protein R (Vpr) encoded by human immunodeficiency virus type 1 (HIV-1) on cell cycle G2/M regulation. Based on our current knowledge about this viral effect, we hypothesize that Vpr induces cell cycle G2 arrest through a mechanism that is to some extent different from the classic G2/M checkpoints. One the unique features distinguishing Vpr-induced G2 arrest from the classic checkpoints is the role of phosphatase 2A (PP2A) in Vpr-induced G2 arrest. Interestingly, PP2A is targeted by a number of other viral proteins including SV40 small T antigen, polyomavirus T antigen, HTLV Tax and adenovirus E4orf4. Thus an in-depth understanding of the molecular mechanisms underlying Vpr-induced G2 arrest will provide additional insights into the basic biology of cell cycle G2/M regulation and into the biological significance of this effect during host-pathogen interactions.展开更多
Nano-sized LiFePO_4·Li_3V_2（PO_4）_3/C was synthesized via a sol-gel route combining with freeze-drying. X-ray diffraction results show that this composite mainly consists of olivine Li Fe PO4 and monoclinic Li3...Nano-sized LiFePO_4·Li_3V_2（PO_4）_3/C was synthesized via a sol-gel route combining with freeze-drying. X-ray diffraction results show that this composite mainly consists of olivine Li Fe PO4 and monoclinic Li3 V2（PO4）3 phases with small amounts of V-doped LiFePO_4 and Fe-doped Li_3V_2（PO_4）_3. The magnetic properties of LiFePO_4·Li_3V_2（PO_4）_3/C are significantly different from LiFePO_4/C. Trace quantities of ferromagnetic impurities and Fe_2P are verified in LiFePO_4/C and LiFePO_4·Li_3V_2（PO_4）_3/C by magnetic tests, respectively. LiFePO_4·Li_3 V_2（PO_4）_3/C possesses relatively better rate capacities and cyclic stabilities, especially at high charge-discharge rates.The initial discharge capacities are 136.4 and 130.0 mA h g^（-1）,and the capacity retentions are more than 98% after 100 cycles at 2C and 5C, respectively, remarkably better than those of LiFePO_4/C. The excellent electrochemical performances are ascribed to the mutual doping of V^（3＋）and Fe^（2＋）, complementary advantages of LiFePO_4 and Li_3V_2（PO_4）_3 phases, the residual high-ordered carbon and Fe_2P with outstanding electric conductivity in the nanocomposite.展开更多
基金The National Natural Science Foundation of China(No.51176029)
文摘In view of different compressor adding ways in the ammonia-water absorption/compression combined refrigeration AWA /CCR cycle combining the Schulz state equation of the ammonia-water solution the theoretical analysis and calculations on two combination ways by adding the compressor in the high-pressure area and in the low-pressure area are conducted respectively.The effects of several factors including the evaporation temperature Te heat-source temperature Th as well as the cooling water temperature Tw on the equivalent heat consumption in compression qCW heat consumption in absorption qG and the system coefficient of performance COP are analyzed under the two combination configurations.The results show that the effect of the equivalent heat consumption in compression on the COP is less than that of the heat consumption in absorption.Besides the compressor set in the high-pressure area uses more energy than that in the low-pressure area. Moreover the compressor in the low-pressure area is superior to that in the high-pressure area with respect to the COP. Under the given intermediate pressure there is an optimum heat-source temperature corresponding to the maximum COP of the AWA/CCR cycle.
文摘Liquefied natural gas(LNG) is the most economical way of transporting natural gas(NG) over long distances. Liquefaction of NG using vapor compression refrigeration system requires high operating and capital cost. Due to lack of systematic design methods for multistage refrigeration cycles, conventional approaches to determine optimal cycle are largely trial-and-error. In this paper a novel mixed integer non-linear programming(MINLP)model is introduced to select optimal synthesis of refrigeration systems to reduce both operating and capital costs of an LNG plant. Better conceptual understanding of design improvement is illustrated on composite curve(CC) and exergetic grand composite curve(EGCC) of pinch analysis diagrams. In this method a superstructure representation of complex refrigeration system is developed to select and optimize key decision variables in refrigeration cycles(i.e. partition temperature, compression configuration, refrigeration features, refrigerant flow rate and economic trade-off). Based on this method a program(LNG-Pro) is developed which integrates VBA,Refprop and Excel MINLP Solver to automate the methodology. Design procedure is applied on a sample LNG plant to illustrate advantages of using this method which shows a 3.3% reduction in total shaft work consumption.
基金National Natural Science Foundation ofChina(No.5 0 2 760 63 )
文摘With COP and dynamic characteristics in refrigeration cycle as criteria,a new metal hydride couple——LaNi 4.61 Mn 0.26 Al 0.13 /La 0.6 Y 0.4 Ni 4.8 Mn 0.2 was selected by establishing calculation procedure and metal hydride selection model.The experimental results show that the refigeration cycle of the selected couple is good in the performance.The recovered waste heat and refrigeration power from exhaust gas of several kinds of automobile are calculated by waste-heat formula,coefficient R Q and COP.Refrigeration cycle of the new couple can satisfy the air-conditioning requirement of truck and car and is not enough in passenger car,according to the respective cooling load.
基金supported in part by grants from the National Institute of Health GM89630 and AI63080an endowed Research Scholar Chair by the Medical Research Institute Councilby an internal grant of the University of Maryland Medical Center(RYZ).
文摘Progression of cells from G2 phase of the cell cycle to mitosis is a tightly regulated cellular process that requires activation of the Cdc2 kinase, which determines onset of mitosis in all eukaryotic cells. In both human and fission yeast (Schizosaccharomyces pombe) cells, the activity of Cdc2 is regulated in part by the phosphorylation status of tyrosine 15 (Tyr15) on Cdc2, which is phosphorylated by Wee1 kinase during late G2 and is rapidly dephosphorylated by the Cdc25 tyrosine phosphatase to trigger entry into mitosis. These Cdc2 regulators are the downstream targets of two well- characterized G2/M checkpoint pathways which prevent cells from entering mitosis when cellular DNA is damaged or when DNA replication is inhibited. Increasing evidence suggests that Cdc2 is also commonly targeted by viral proteins, which modulate host cell cycle machinery to benefit viral survival or replication. In this review, we describe the effect of viral protein R (Vpr) encoded by human immunodeficiency virus type 1 (HIV-1) on cell cycle G2/M regulation. Based on our current knowledge about this viral effect, we hypothesize that Vpr induces cell cycle G2 arrest through a mechanism that is to some extent different from the classic G2/M checkpoints. One the unique features distinguishing Vpr-induced G2 arrest from the classic checkpoints is the role of phosphatase 2A (PP2A) in Vpr-induced G2 arrest. Interestingly, PP2A is targeted by a number of other viral proteins including SV40 small T antigen, polyomavirus T antigen, HTLV Tax and adenovirus E4orf4. Thus an in-depth understanding of the molecular mechanisms underlying Vpr-induced G2 arrest will provide additional insights into the basic biology of cell cycle G2/M regulation and into the biological significance of this effect during host-pathogen interactions.
基金supported by the National Natural Science Foundation of China (21673051)Guangdong Province Science & Technology Bureau (2014A010106029, 2014B010106005 and 2016A010104015)+3 种基金Guangzhou Science & Innovative Committee (201604030037)the Youth Foundation of Guangdong University of Technology (252151038)the link project of the National Natural Science Foundation of China and Guangdong Province (U1401246)the Science and Technology Program of Guangzhou City of China (201508030018)
文摘Nano-sized LiFePO_4·Li_3V_2（PO_4）_3/C was synthesized via a sol-gel route combining with freeze-drying. X-ray diffraction results show that this composite mainly consists of olivine Li Fe PO4 and monoclinic Li3 V2（PO4）3 phases with small amounts of V-doped LiFePO_4 and Fe-doped Li_3V_2（PO_4）_3. The magnetic properties of LiFePO_4·Li_3V_2（PO_4）_3/C are significantly different from LiFePO_4/C. Trace quantities of ferromagnetic impurities and Fe_2P are verified in LiFePO_4/C and LiFePO_4·Li_3V_2（PO_4）_3/C by magnetic tests, respectively. LiFePO_4·Li_3 V_2（PO_4）_3/C possesses relatively better rate capacities and cyclic stabilities, especially at high charge-discharge rates.The initial discharge capacities are 136.4 and 130.0 mA h g^（-1）,and the capacity retentions are more than 98% after 100 cycles at 2C and 5C, respectively, remarkably better than those of LiFePO_4/C. The excellent electrochemical performances are ascribed to the mutual doping of V^（3＋）and Fe^（2＋）, complementary advantages of LiFePO_4 and Li_3V_2（PO_4）_3 phases, the residual high-ordered carbon and Fe_2P with outstanding electric conductivity in the nanocomposite.
