The electric submersible pump(ESP) is a crucial apparatus utilized for lifting in the oil extraction process.Its lifting capacity is enhanced by the multi-stage tandem structure, but variations in energy characteristi...The electric submersible pump(ESP) is a crucial apparatus utilized for lifting in the oil extraction process.Its lifting capacity is enhanced by the multi-stage tandem structure, but variations in energy characteristics and internal flow across stages are also introduced. In this study, the inter-stage variability of energy characteristics in ESP hydraulic systems is investigated through entropy production(EP) analysis,which incorporates numerical simulations and experimental validation. The EP theory facilitates the quantification of energy loss in each computational subdomain at all ESP stages, establishing a correlation between microscopic flow structure and energy dissipation within the system. Furthermore, the underlying causes of inter-stage variability in ESP hydraulic systems are examined, and the advantages and disadvantages of applying the EP theory in this context are evaluated. Consistent energy characteristics within the ESP, aligned with the distribution of internal flow structure, are provided by the EP theory, as demonstrated by our results. The EP theory also enables the quantitative analysis of internal flow losses and complements existing performance analysis methods to map the internal flow structure to hydraulic losses. Nonetheless, an inconsistency between the energy characterization based on EP theory and the traditional efficiency index when reflecting inter-stage differences is identified. This inconsistency arises from the exclusive focus of the EP theory on flow losses within the flow field, disregarding the quantification of external energy input to the flow field. This study provides a reference for the optimization of EP theory in rotating machinery while deeply investigating the energy dissipation characteristics of multistage hydraulic system, which has certain theoretical and practical significance.展开更多
Purpose:Ischemia and hypoxia are the main factors limiting limb replantation and transplantation.Static cold storage(SCS),a common preservation method for tissues and organs,can only prolong limb ischemia time to 4-6 ...Purpose:Ischemia and hypoxia are the main factors limiting limb replantation and transplantation.Static cold storage(SCS),a common preservation method for tissues and organs,can only prolong limb ischemia time to 4-6 h.The normothermic machine perfusion(NMP)is a promising method for the preservation of tissues and organs,which can extend the preservation time in vitro by providing continuous oxygen and nutrients.This study aimed to evaluate the difference in the efficacy of the 2 limb preservation methods.Methods:The 6 forelimbs from beagle dogs were divided into 2 groups.In the SCS group(n=3),the limbs were preserved in a sterile refrigerator at 4°C for 24 h,and in the NMP group(n=3),the perfusate prepared with autologous blood was used for the oxygenated machine perfusion at physiological temperature for 24 h,and the solution was changed every 6 h.The effects of limb storage were evaluated by weight gain,perfusate biochemical analysis,enzyme-linked immunosorbent assay,and histological analysis.All statistical analyses and graphs were performed using GraphPad Prism 9.0 one-way or two-way analysis of variance.The p value of less than 0.05 was considered to indicate statistical significance.Results:In the NMP group,the weight gained percentage was 11.72%±4.06%;the hypoxia-inducible factor-1αcontents showed no significant changes;the shape of muscle fibers was normal;the gap between muscle fibers slightly increased,showing the intercellular distance of(30.19±2.83)μm;and the vascularα-smooth muscle actin(α-SMA)contents were lower than those in the normal blood vessels.The creatine kinase level in the perfusate of the NMP group increased from the beginning of perfusion,decreased after each perfusate change,and remained stable at the end of perfusion showing a peak level of 4097.6 U/L.The lactate dehydrogenase level of the NMP group increased near the end of perfusion and reached the peak level of 374.4 U/L.In the SCS group,the percentage of weight gain was 0.18%±0.10%,and the contents of hypoxia-inducible factor-1αincreased gradually and reached the maximum level of(164.85±20.75)pg/mL at the end of the experiment.The muscle fibers lost their normal shape and the gap between muscle fibers increased,showing an intercellular distance of(41.66±5.38)μm.The contents of vascularα-SMA were much lower in the SCS group as compared to normal blood vessels.Conclusions:NMP caused lesser muscle damage and contained more vascularα-SMA as compared to SCS.This study demonstrated that NMP of the amputated limb with perfusate solution based on autologous blood could maintain the physiological activities of the limb for at least 24 h.展开更多
Having highly tunable molecular topology is one of the most important characteristics of polymers that provides these materials with a wide range of interesting and unique properties.In particular,ring polymers exhibi...Having highly tunable molecular topology is one of the most important characteristics of polymers that provides these materials with a wide range of interesting and unique properties.In particular,ring polymers exhibit a number of properties that are markedly distinct from their linear counterparts.Here,we compare and contrast the glass formation of unknotted,nonconcatenated ring and linear polymer melts having variable molecular mass based on molecular dynamics simulations of a coarse-grained model.After revealing an unusual property in the structure of small rings,we discuss the mass dependence of the structural relaxation time determined from the self-intermediate scattering function over a wide range of temperatures in both ring and linear polymers.As a general trend,we find that the characteristic temperatures(e.g.,the glass transition temperature)and fragility of glass formation increase with increasing molecular mass in linear polymers,but the mass dependences of these properties are rather weak in the family of ring polymer models considered,in broad accord with experimental measurements.Importantly,we show that the glass formation of ring polymers can quantitatively be described by the string model,a model that is broadly consistent with the entropy theory of glass formation and that takes the mass of string-like clusters as a molecular realization of the abstract cooperatively rearranging regions.This opens the possibility of applying the configurational entropy-based theories to describe the glass formation of ring polymers,once the ring topology is taken into account.展开更多
基金financially supported by the China Postdoctoral Science Foundation(Grant No.2023M732979 and No.2022TQ0127)the Cooperative Research Project of the Ministry of Education's "Chunhui Program"(Grant No.HZKY20220117)+1 种基金the Natural Science Foundation of Jiangsu Province(Grant No.BK20220587)the National Natural Science Foundation of China(Grant No.52309112)。
文摘The electric submersible pump(ESP) is a crucial apparatus utilized for lifting in the oil extraction process.Its lifting capacity is enhanced by the multi-stage tandem structure, but variations in energy characteristics and internal flow across stages are also introduced. In this study, the inter-stage variability of energy characteristics in ESP hydraulic systems is investigated through entropy production(EP) analysis,which incorporates numerical simulations and experimental validation. The EP theory facilitates the quantification of energy loss in each computational subdomain at all ESP stages, establishing a correlation between microscopic flow structure and energy dissipation within the system. Furthermore, the underlying causes of inter-stage variability in ESP hydraulic systems are examined, and the advantages and disadvantages of applying the EP theory in this context are evaluated. Consistent energy characteristics within the ESP, aligned with the distribution of internal flow structure, are provided by the EP theory, as demonstrated by our results. The EP theory also enables the quantitative analysis of internal flow losses and complements existing performance analysis methods to map the internal flow structure to hydraulic losses. Nonetheless, an inconsistency between the energy characterization based on EP theory and the traditional efficiency index when reflecting inter-stage differences is identified. This inconsistency arises from the exclusive focus of the EP theory on flow losses within the flow field, disregarding the quantification of external energy input to the flow field. This study provides a reference for the optimization of EP theory in rotating machinery while deeply investigating the energy dissipation characteristics of multistage hydraulic system, which has certain theoretical and practical significance.
基金supported by the National Key R&D Program of China(2019YFA0110704)the Military Logistic(s)Scientific Research Program of China(BHJ20J002).
文摘Purpose:Ischemia and hypoxia are the main factors limiting limb replantation and transplantation.Static cold storage(SCS),a common preservation method for tissues and organs,can only prolong limb ischemia time to 4-6 h.The normothermic machine perfusion(NMP)is a promising method for the preservation of tissues and organs,which can extend the preservation time in vitro by providing continuous oxygen and nutrients.This study aimed to evaluate the difference in the efficacy of the 2 limb preservation methods.Methods:The 6 forelimbs from beagle dogs were divided into 2 groups.In the SCS group(n=3),the limbs were preserved in a sterile refrigerator at 4°C for 24 h,and in the NMP group(n=3),the perfusate prepared with autologous blood was used for the oxygenated machine perfusion at physiological temperature for 24 h,and the solution was changed every 6 h.The effects of limb storage were evaluated by weight gain,perfusate biochemical analysis,enzyme-linked immunosorbent assay,and histological analysis.All statistical analyses and graphs were performed using GraphPad Prism 9.0 one-way or two-way analysis of variance.The p value of less than 0.05 was considered to indicate statistical significance.Results:In the NMP group,the weight gained percentage was 11.72%±4.06%;the hypoxia-inducible factor-1αcontents showed no significant changes;the shape of muscle fibers was normal;the gap between muscle fibers slightly increased,showing the intercellular distance of(30.19±2.83)μm;and the vascularα-smooth muscle actin(α-SMA)contents were lower than those in the normal blood vessels.The creatine kinase level in the perfusate of the NMP group increased from the beginning of perfusion,decreased after each perfusate change,and remained stable at the end of perfusion showing a peak level of 4097.6 U/L.The lactate dehydrogenase level of the NMP group increased near the end of perfusion and reached the peak level of 374.4 U/L.In the SCS group,the percentage of weight gain was 0.18%±0.10%,and the contents of hypoxia-inducible factor-1αincreased gradually and reached the maximum level of(164.85±20.75)pg/mL at the end of the experiment.The muscle fibers lost their normal shape and the gap between muscle fibers increased,showing an intercellular distance of(41.66±5.38)μm.The contents of vascularα-SMA were much lower in the SCS group as compared to normal blood vessels.Conclusions:NMP caused lesser muscle damage and contained more vascularα-SMA as compared to SCS.This study demonstrated that NMP of the amputated limb with perfusate solution based on autologous blood could maintain the physiological activities of the limb for at least 24 h.
基金financially supported by the National Natural Science Foundation of China(Nos.22222307 and 21973089)。
文摘Having highly tunable molecular topology is one of the most important characteristics of polymers that provides these materials with a wide range of interesting and unique properties.In particular,ring polymers exhibit a number of properties that are markedly distinct from their linear counterparts.Here,we compare and contrast the glass formation of unknotted,nonconcatenated ring and linear polymer melts having variable molecular mass based on molecular dynamics simulations of a coarse-grained model.After revealing an unusual property in the structure of small rings,we discuss the mass dependence of the structural relaxation time determined from the self-intermediate scattering function over a wide range of temperatures in both ring and linear polymers.As a general trend,we find that the characteristic temperatures(e.g.,the glass transition temperature)and fragility of glass formation increase with increasing molecular mass in linear polymers,but the mass dependences of these properties are rather weak in the family of ring polymer models considered,in broad accord with experimental measurements.Importantly,we show that the glass formation of ring polymers can quantitatively be described by the string model,a model that is broadly consistent with the entropy theory of glass formation and that takes the mass of string-like clusters as a molecular realization of the abstract cooperatively rearranging regions.This opens the possibility of applying the configurational entropy-based theories to describe the glass formation of ring polymers,once the ring topology is taken into account.