Dynamic performance is important to the controlling and monitoring of the organic Rankine cycle(ORC) system so to avoid the occurrence of unwanted conditions. A small scale waste heat recovery system with organic Rank...Dynamic performance is important to the controlling and monitoring of the organic Rankine cycle(ORC) system so to avoid the occurrence of unwanted conditions. A small scale waste heat recovery system with organic Rankine cycle was constructed and the dynamic behavior was presented. In the dynamic test, the pump was stopped and then started. In addition, there was a step change of the flue gas volume flow rate and the converter frequency of multistage pump, respectively. The results indicate that the working fluid flow rate has the shortest response time, followed by the expander inlet pressure and the expander inlet temperature.The operation frequency of pump is a key parameter for the ORC system. Due to a step change of pump frequency(39.49-35.24 Hz),the expander efficiency and thermal efficiency drop by 16% and 21% within 2 min, respectively. Besides, the saturated mixture can lead to an increase of the expander rotation speed.展开更多
The paper studied the relationship between microstructure and shape recovery characteristics by using colored microstructure analysis under polarized light on the thermomechanical cycled CuAlNi single crystals. The tw...The paper studied the relationship between microstructure and shape recovery characteristics by using colored microstructure analysis under polarized light on the thermomechanical cycled CuAlNi single crystals. The two-way shape memory effect in quenched thin bar resulted from the preferential formation/extinction of martensite variant due to the internal quench stress, and the variant was formed at an angle of about 45 deg. with the tension direction ([001] of the βphase). Initial thermomechanical cycling under relatively low stress single variant stress-induced martensite was formed at an angle of 45 deg. with the tension and its morphology was a lath of parallel twins. More than one group of variants were formed after several training cycles and such variants also caused tilting of some thermally formed accommodated martensite. By overheating the trained sample containing stabilized multi-variants of stress-induced martensite, very coarse martensite structure with a strong asymmetry was produced, which caused the reverse two-way shape memory effect.展开更多
The proton exchange membrane electrolysis cells(PEMECs)are electrochemical devices that efficiently produce high-purity hydrogen via electrical energy conversion,making them widely applicable in renewable energy stora...The proton exchange membrane electrolysis cells(PEMECs)are electrochemical devices that efficiently produce high-purity hydrogen via electrical energy conversion,making them widely applicable in renewable energy storage and hydrogen infrastructure development.However,the external sodium ion(Na^(+))contamination can severely damage the catalyst layer and membrane in PEMEC,causing significant performance degradation.Therefore,a segmented diagnostic platform for PEMEC is developed to analyze the poisoning effects of Na^(+)contamination on a large scale PEMEC under various operating conditions.The results demonstrate that during the cycle test,the Na^(+)poisoning process is defined as three distinct stages of initial,sustained and stable contamination stages.An increased Na^(+)concentration enhances the occupations of active sites on the catalyst layer,resulting in significant voltage spike,dynamic voltage fluctuations,non-uniformity distributions of current density and temperature.Both the low water flow rate and high operating temperature improve the chemical reaction and PEMEC performance at high current density.The deionized water flushing will dissolve Na^(+)on the catalyst layer surface and realize 2.17%decrease in voltage at 2.0 A cm^(-2) after three cycles.This study is beneficial to consolidate the understanding of poisoning effects of sodium ion contamination in PEMEC under various operating conditions,thereby overcoming the obstacles for commercial application of green hydrogen production technology.展开更多
Background Paroxysmal kinesigenic dyskinesia （PKD） is characterized by recurrent brief episodes of chorea and dystonia induced by sudden movement. Whether the central nervous system is hyper- or hypoexcitable in PKD...Background Paroxysmal kinesigenic dyskinesia （PKD） is characterized by recurrent brief episodes of chorea and dystonia induced by sudden movement. Whether the central nervous system is hyper- or hypoexcitable in PKD remains undetermined. The aim of our study was to compare the somatosensory evoked potential （SEP） recovery cycle, a marker of somatosensory system excitability, in PKD patients and controls.展开更多
基金Project(2009Gk2009)supported by the Science and Technology Department Funds of Hunan Province,ChinaProject(12C0379)supported by the Scientific Research Fund of Hunan Province,ChinaProject(13QDZ04)supported by the Scientific Research Foundation for Doctors of Xiang Tan University,China
文摘Dynamic performance is important to the controlling and monitoring of the organic Rankine cycle(ORC) system so to avoid the occurrence of unwanted conditions. A small scale waste heat recovery system with organic Rankine cycle was constructed and the dynamic behavior was presented. In the dynamic test, the pump was stopped and then started. In addition, there was a step change of the flue gas volume flow rate and the converter frequency of multistage pump, respectively. The results indicate that the working fluid flow rate has the shortest response time, followed by the expander inlet pressure and the expander inlet temperature.The operation frequency of pump is a key parameter for the ORC system. Due to a step change of pump frequency(39.49-35.24 Hz),the expander efficiency and thermal efficiency drop by 16% and 21% within 2 min, respectively. Besides, the saturated mixture can lead to an increase of the expander rotation speed.
文摘The paper studied the relationship between microstructure and shape recovery characteristics by using colored microstructure analysis under polarized light on the thermomechanical cycled CuAlNi single crystals. The two-way shape memory effect in quenched thin bar resulted from the preferential formation/extinction of martensite variant due to the internal quench stress, and the variant was formed at an angle of about 45 deg. with the tension direction ([001] of the βphase). Initial thermomechanical cycling under relatively low stress single variant stress-induced martensite was formed at an angle of 45 deg. with the tension and its morphology was a lath of parallel twins. More than one group of variants were formed after several training cycles and such variants also caused tilting of some thermally formed accommodated martensite. By overheating the trained sample containing stabilized multi-variants of stress-induced martensite, very coarse martensite structure with a strong asymmetry was produced, which caused the reverse two-way shape memory effect.
基金supported by the National Key R&D Program of China(Grant No.2023YFB4006301-1)the National Natural Science Foundation of China(Grant No.52476217 and Grant No.52311530069).
文摘The proton exchange membrane electrolysis cells(PEMECs)are electrochemical devices that efficiently produce high-purity hydrogen via electrical energy conversion,making them widely applicable in renewable energy storage and hydrogen infrastructure development.However,the external sodium ion(Na^(+))contamination can severely damage the catalyst layer and membrane in PEMEC,causing significant performance degradation.Therefore,a segmented diagnostic platform for PEMEC is developed to analyze the poisoning effects of Na^(+)contamination on a large scale PEMEC under various operating conditions.The results demonstrate that during the cycle test,the Na^(+)poisoning process is defined as three distinct stages of initial,sustained and stable contamination stages.An increased Na^(+)concentration enhances the occupations of active sites on the catalyst layer,resulting in significant voltage spike,dynamic voltage fluctuations,non-uniformity distributions of current density and temperature.Both the low water flow rate and high operating temperature improve the chemical reaction and PEMEC performance at high current density.The deionized water flushing will dissolve Na^(+)on the catalyst layer surface and realize 2.17%decrease in voltage at 2.0 A cm^(-2) after three cycles.This study is beneficial to consolidate the understanding of poisoning effects of sodium ion contamination in PEMEC under various operating conditions,thereby overcoming the obstacles for commercial application of green hydrogen production technology.
文摘Background Paroxysmal kinesigenic dyskinesia （PKD） is characterized by recurrent brief episodes of chorea and dystonia induced by sudden movement. Whether the central nervous system is hyper- or hypoexcitable in PKD remains undetermined. The aim of our study was to compare the somatosensory evoked potential （SEP） recovery cycle, a marker of somatosensory system excitability, in PKD patients and controls.
