The aramid fiber-reinforced composites(AFRC)can increase the durability of corresponding applications such as aerospace,automobile and other large structural parts,due to the improvement in hardness,heat build-up,wear...The aramid fiber-reinforced composites(AFRC)can increase the durability of corresponding applications such as aerospace,automobile and other large structural parts,due to the improvement in hardness,heat build-up,wear properties and green environmental protection.However,because of its complex multiphase structure and unique heterogeneity and anisotropy,the poor compression fatigue resistance and the incident surface fibrillation are inevitable.To improve the assembly precision of AFRC,mechanical processing is necessary to meet the dimensional accuracy.This paper focuses on the influence of contour milling parameters on delamination defects during milling of AFRC laminates.A series of milling experiments are conducted and two different kinds of delamination defects including tearing delamination and uncut-off delamination are investigated.A computing method and model based on brittle fracture for the two different types of delamination are established.The results can be used for explaining the mechanism and regularity of delamination defects.The control strategy of delamination defects and evaluation method of finished surface integrity are further discussed.The results are meaningful to optimize cutting parameters,and provide a clear understanding of surface defects control.展开更多
The identification of the imperfection originating from finite-temperature-difference heat transfer is an indispensable step for both the performance analysis and the better design of a heat exchanger network （HEN） ...The identification of the imperfection originating from finite-temperature-difference heat transfer is an indispensable step for both the performance analysis and the better design of a heat exchanger network （HEN） with the aim of energy saving. This study develops a convenient area method for visualizing the heat-transfer imperfection of a HEN in terms of temperature-heat flow diagrams （ T-Q diagrams） by combining the composite curves that have already been used in pinch analysis and the re- cently developed entransy analysis. It is shown that the area between the hot and cold composite curves and the hot and cold utility lines on a T-Q diagram is just equal to the total entransy dissipation rate during the multi-stream heat transfer process occurred in a HEN, and this area can be used to graphically represent the total heat-transfer imperfection of the HEN. The increase in heat recovery or decrease in energy requirements with decreasing the minimum temperature difference, ATmin, of a HEN can then be attributed to a lower entransy dissipation rate, quantitatively represented by the decrease of the area between the composite curves and the utility lines. In addition, the differences between the T-Q diagram and the pre-existing energy level-enthalpy flow diagram （12-H diagram） in the roles of visualizing process imperfection and designing HENs are dis- cussed.展开更多
Energy crisis and environmental problems urgently drive the proposal of new strategies to improve human wellbeing and assist sustainable development.To this end,scientists have explored many metal oxides-based photoca...Energy crisis and environmental problems urgently drive the proposal of new strategies to improve human wellbeing and assist sustainable development.To this end,scientists have explored many metal oxides-based photocatalysts with high stability,low cost,earth abundance,and potentially high catalytic activity relevant for key applications such as H2O splitting,CO2 reduction,N2 fixation,and advanced oxidation of pollutants.In these metal oxides,oxygen vacancies(OVs)are ubiquitous and intrinsic defects with pronounced impacts on the physicochemical properties of the catalysts,which may open new opportunities for obtaining efficient metal oxides.The thorough understanding of the structural and electronic nature of OVs is necessary to determine how they serve as catalytically active sites.In this review,we summarize the origin of OVs,the strategies to introduce OVs,as well as the fundamental structure-activity relationships to relate these crystal defects to catalyst properties including light absorption,charge separation,etc.We emphasize the mechanism of OVs formation and their effects on the intrinsic catalytic characteristics of the metal oxides.We also present some multicomponent catalytic platforms where OVs contribute to catalysis via synergy.Finally,opportunities and challenges on engineering defects in photocatalysts are summarized to highlight the future directions of this research field.展开更多
Intrinsic and extrinsic ion migration is a very large threat to the operational stability of perovskite solar cells and is difficult to completely eliminate due to the low activation energy of ion migration and the ex...Intrinsic and extrinsic ion migration is a very large threat to the operational stability of perovskite solar cells and is difficult to completely eliminate due to the low activation energy of ion migration and the existence of internal electric field.We propose a heterojunction route to help suppress ion migration,thus improving the operational stability of the cell from the perspective of eliminating the electric field response in the perovskite absorber.A heavily doped p-type(p^(+))thin layer semiconductor is introduced between the electron transporting layer(ETL)and perovskite absorber.The heterojunction charge depletion and electric field are limited to the ETL and p^(+)layers,while the perovskite absorber and hole transporting layer remain neutral.The p^(+)layer has a variety of candidate materials and is tolerant of defect density and carrier mobility,which makes this heterojunction route highly feasible and promising for use in practical applications.展开更多
A transmission bottleneck occurs during each human immunodeficiency virus(HIV) transmission event, which allows only a few viruses to establish new infection. However, the genetic characteristics of the transmitted vi...A transmission bottleneck occurs during each human immunodeficiency virus(HIV) transmission event, which allows only a few viruses to establish new infection. However, the genetic characteristics of the transmitted viruses that are preferentially selected have not been fully elucidated. Here, we analyzed amino acids changes in the envelope protein during simian immunodeficiency virus(SIV)/HIV deep transmission history and current HIV evolution within the last 15–20 years. Our results confirmed that the V1V2 region of gp120 protein, particularly V1, was preferentially selected. A shorter V1 region was preferred during transmission history, while during epidemic, HIV may evolve to an expanded V1 region gradually and thus escape immune recognition. We then constructed different HIV-1 V1 mutants using different HIV-1 subtypes to elucidate the role of the V1 region in envelope function. We found that the V1 region, although highly variable, was indispensable for virus entry and infection, probably because V1 deletion mutants exhibited impaired processing of gp160 into mature gp120 and gp41. Additionally, the V1 region affected Env incorporation. These results indicated that the V1 region played a critical role in HIV transmission and infection.展开更多
We analyze a Markov cellular automaton that models the spread of viruses that often progress to a chronic condition, such as human immunodeficiency virus （HIV） or hep- atitis C virus （HCV）. We show that the comple...We analyze a Markov cellular automaton that models the spread of viruses that often progress to a chronic condition, such as human immunodeficiency virus （HIV） or hep- atitis C virus （HCV）. We show that the complex dynamical system produces a Markov process at the later stages, whose eigenvectors corresponding to the eigenvalue 1 have physical significance for the long-term prognosis of the virus. Moreover we show that drug treatment leads to chronic conditions that can be modeled by Markov shifts with more optimal eigenveetors.展开更多
基金supported by the National Natural Science Foundation of China(No.51975334)Key R&D Project of Shandong Province(No.2019JMRH0407)the Fundamental Research Funds of Shandong University Grant。
文摘The aramid fiber-reinforced composites(AFRC)can increase the durability of corresponding applications such as aerospace,automobile and other large structural parts,due to the improvement in hardness,heat build-up,wear properties and green environmental protection.However,because of its complex multiphase structure and unique heterogeneity and anisotropy,the poor compression fatigue resistance and the incident surface fibrillation are inevitable.To improve the assembly precision of AFRC,mechanical processing is necessary to meet the dimensional accuracy.This paper focuses on the influence of contour milling parameters on delamination defects during milling of AFRC laminates.A series of milling experiments are conducted and two different kinds of delamination defects including tearing delamination and uncut-off delamination are investigated.A computing method and model based on brittle fracture for the two different types of delamination are established.The results can be used for explaining the mechanism and regularity of delamination defects.The control strategy of delamination defects and evaluation method of finished surface integrity are further discussed.The results are meaningful to optimize cutting parameters,and provide a clear understanding of surface defects control.
基金supported by the National Natural Science Foundation of China(Grant Nos.51206079,51356001)
文摘The identification of the imperfection originating from finite-temperature-difference heat transfer is an indispensable step for both the performance analysis and the better design of a heat exchanger network （HEN） with the aim of energy saving. This study develops a convenient area method for visualizing the heat-transfer imperfection of a HEN in terms of temperature-heat flow diagrams （ T-Q diagrams） by combining the composite curves that have already been used in pinch analysis and the re- cently developed entransy analysis. It is shown that the area between the hot and cold composite curves and the hot and cold utility lines on a T-Q diagram is just equal to the total entransy dissipation rate during the multi-stream heat transfer process occurred in a HEN, and this area can be used to graphically represent the total heat-transfer imperfection of the HEN. The increase in heat recovery or decrease in energy requirements with decreasing the minimum temperature difference, ATmin, of a HEN can then be attributed to a lower entransy dissipation rate, quantitatively represented by the decrease of the area between the composite curves and the utility lines. In addition, the differences between the T-Q diagram and the pre-existing energy level-enthalpy flow diagram （12-H diagram） in the roles of visualizing process imperfection and designing HENs are dis- cussed.
基金financially supported by the National Natural Science Foundation of China(U1905215,51772053 and 51672046)。
文摘Energy crisis and environmental problems urgently drive the proposal of new strategies to improve human wellbeing and assist sustainable development.To this end,scientists have explored many metal oxides-based photocatalysts with high stability,low cost,earth abundance,and potentially high catalytic activity relevant for key applications such as H2O splitting,CO2 reduction,N2 fixation,and advanced oxidation of pollutants.In these metal oxides,oxygen vacancies(OVs)are ubiquitous and intrinsic defects with pronounced impacts on the physicochemical properties of the catalysts,which may open new opportunities for obtaining efficient metal oxides.The thorough understanding of the structural and electronic nature of OVs is necessary to determine how they serve as catalytically active sites.In this review,we summarize the origin of OVs,the strategies to introduce OVs,as well as the fundamental structure-activity relationships to relate these crystal defects to catalyst properties including light absorption,charge separation,etc.We emphasize the mechanism of OVs formation and their effects on the intrinsic catalytic characteristics of the metal oxides.We also present some multicomponent catalytic platforms where OVs contribute to catalysis via synergy.Finally,opportunities and challenges on engineering defects in photocatalysts are summarized to highlight the future directions of this research field.
基金supported by the National Natural Science Foundation of China(52072402,11874402,51627803,51421002,91733301,51761145042,and 51872321)the International Partnership Program of Chinese Academy of Sciences(112111KYSB20170089)。
文摘Intrinsic and extrinsic ion migration is a very large threat to the operational stability of perovskite solar cells and is difficult to completely eliminate due to the low activation energy of ion migration and the existence of internal electric field.We propose a heterojunction route to help suppress ion migration,thus improving the operational stability of the cell from the perspective of eliminating the electric field response in the perovskite absorber.A heavily doped p-type(p^(+))thin layer semiconductor is introduced between the electron transporting layer(ETL)and perovskite absorber.The heterojunction charge depletion and electric field are limited to the ETL and p^(+)layers,while the perovskite absorber and hole transporting layer remain neutral.The p^(+)layer has a variety of candidate materials and is tolerant of defect density and carrier mobility,which makes this heterojunction route highly feasible and promising for use in practical applications.
基金supported by the International Science & Technology Cooperation Program of China (2011DFA31030)Deutsche Forschungsgemeinschaft (Transregio TRR60),National Natural Science Foundation of China (No.81461130019)
文摘A transmission bottleneck occurs during each human immunodeficiency virus(HIV) transmission event, which allows only a few viruses to establish new infection. However, the genetic characteristics of the transmitted viruses that are preferentially selected have not been fully elucidated. Here, we analyzed amino acids changes in the envelope protein during simian immunodeficiency virus(SIV)/HIV deep transmission history and current HIV evolution within the last 15–20 years. Our results confirmed that the V1V2 region of gp120 protein, particularly V1, was preferentially selected. A shorter V1 region was preferred during transmission history, while during epidemic, HIV may evolve to an expanded V1 region gradually and thus escape immune recognition. We then constructed different HIV-1 V1 mutants using different HIV-1 subtypes to elucidate the role of the V1 region in envelope function. We found that the V1 region, although highly variable, was indispensable for virus entry and infection, probably because V1 deletion mutants exhibited impaired processing of gp160 into mature gp120 and gp41. Additionally, the V1 region affected Env incorporation. These results indicated that the V1 region played a critical role in HIV transmission and infection.
文摘We analyze a Markov cellular automaton that models the spread of viruses that often progress to a chronic condition, such as human immunodeficiency virus （HIV） or hep- atitis C virus （HCV）. We show that the complex dynamical system produces a Markov process at the later stages, whose eigenvectors corresponding to the eigenvalue 1 have physical significance for the long-term prognosis of the virus. Moreover we show that drug treatment leads to chronic conditions that can be modeled by Markov shifts with more optimal eigenveetors.
