Additive manufacturing(AM)technology has emerged as a viable solution for manufacturing complexshaped WC−Co cemented carbide products,thereby expanding their applications in industries such as resource mining,equipmen...Additive manufacturing(AM)technology has emerged as a viable solution for manufacturing complexshaped WC−Co cemented carbide products,thereby expanding their applications in industries such as resource mining,equipment manufacturing,and electronic information.This review provides a comprehensive summary of the progress of AM technology in WC−Co cemented carbides.The fundamental principles and classification of AM techniques are introduced,followed by a categorization and evaluation of the AM techniques for WC−Co cemented carbides.These techniques are classified as either direct AM technology(DAM)or indirect AM technology(IDAM),depending on their inclusion of post-processes like de-binding and sintering.Through an analysis of microstructure features,the most suitable AM route for WC−Co cemented carbide products with controllable microstructure is identified as the indirect AM technology,such as binder jet printing(BJP),which integrates AM with conventional powder metallurgy.展开更多
Low-density superalloys often exhibit low yield strength in the intermediate temperature range(300−650℃).To enhance yield performance in this range,the CALPHAD method was used to design a new Co-based superalloy.The ...Low-density superalloys often exhibit low yield strength in the intermediate temperature range(300−650℃).To enhance yield performance in this range,the CALPHAD method was used to design a new Co-based superalloy.The Co−30Ni−10Al−3V−6Ti−2Ta alloy,designed based onγʹphase dissolution temperature and phase fraction,was synthesized via arc melting and heat treatment.Phase transition temperatures,microstructure evolution,and hightemperature mechanical properties were characterized by differential scanning calorimetry,scanning electron microscopy,dual-beam TEM,and compression tests.Results show that the alloy has low density(8.15 g/cm^(3))and highγʹdissolution temperature(1234℃),along with unique yield strength retention from room temperature to 650℃.The yield strength anomaly(YSA)is attributed to high stacking fault energy and activation of the Kear−Wilsdorf locking mechanism,contributing to superior high-temperature stability of the alloy.The yield strength of this alloy outperforms other lowdensity Co-based superalloys in the temperature range of 23−650℃.展开更多
A thoroughly mechanistic understanding of the electrochemical CO reduction reaction(eCORR)at the interface is significant for guiding the design of high-performance electrocatalysts.However,unintentionally ignored fac...A thoroughly mechanistic understanding of the electrochemical CO reduction reaction(eCORR)at the interface is significant for guiding the design of high-performance electrocatalysts.However,unintentionally ignored factors or unreasonable settings during mechanism simulations will result in false positive results between theory and experiment.Herein,we computationally identified the dynamic site preference change of CO adsorption with potentials on Cu(100),which was a previously unnoticed factor but significant to potential-dependent mechanistic studies.Combined with the different lateral interactions among adsorbates,we proposed a new C–C coupling mechanism on Cu(100),better explaining the product distribution at different potentials in experimental eCORR.At low potentials(from–0.4 to–0.6 V_(RHE)),the CO forms dominant adsorption on the bridge site,which couples with another attractively aggregated CO to form a C–C bond.At medium potentials(from–0.6 to–0.8 VRHE),the hollow-bound CO becomes dominant but tends to isolate with another adsorbate due to the repulsion,thereby blocking the coupling process.At high potentials(above–0.8 VRHE),the CHO intermediate is produced from the electroreduction of hollow-CO and favors the attraction with another bridge-CO to trigger C–C coupling,making CHO the major common intermediate for C–C bond formation and methane production.We anticipate that our computationally identified dynamic change in site preference of adsorbates with potentials will bring new opportunities for a better understanding of the potential-dependent electrochemical processes.展开更多
Community-based ecotourism (CBET) aims to empower local communities through engagement and participation. Cambodia serves as a prime example of a developing country where the local community necessitates sustained sta...Community-based ecotourism (CBET) aims to empower local communities through engagement and participation. Cambodia serves as a prime example of a developing country where the local community necessitates sustained stakeholder support to foster empowerment and promote local economic development. Ecotourism and conservation are among the major issues of concern in the study of community development. This study used the main five eco-tourism areas in Cambodia as examples. It looks at the connections between eco-innovations in tourism products, community engagement, co-creation experiences, support for CBET, perceived impact likelihood outcomes, community economic benefits, environmentally responsible behavior in ecotourism sites, and biodiversity conservation. The study employed a quantitative research approach to investigate and parameterize the dynamic ecotourism components as well as to explore key factors that influence the CBET. We collected the data using a self-administered survey on 398 local eco-based tourism communities that sell services and products to tourists. We also asked for structured questionnaire items of local communities that provide tourism services to visitors in eco-tourism destination sites in 2022-2023. The SEM results showed that this study significantly impacted and confirmed all relationships among research variables, as proposed in the conceptual model. We also discuss in detail the research findings of this study.展开更多
Background: Mycoplasma pneumoniae (MP) is the primary causative agent of community-acquired pneumonia, which has increasingly become resistant to macrolides, complicating treatment regimens, especially with the co-inf...Background: Mycoplasma pneumoniae (MP) is the primary causative agent of community-acquired pneumonia, which has increasingly become resistant to macrolides, complicating treatment regimens, especially with the co-infection factor. Its worldwide prevalence has fluctuated due to the influence of the COVID-19 pandemic. The study investigated co-infection patterns in children diagnosed with Mycoplasma pneumoniae pneumonia (MPP). Methods: From June 2022 to December 2023, we retrospectively analyzed the clinical data for hospitalized children with Mycoplasma pneumoniae pneumonia in Wuhan, China. We collected data on age, sex, clinical information, and pathogenic results. We also collected sputum or bronchoalveolar lavage fluid (BALF) samples to test respiratory pathogens and macrolide resistance using targeted microbial next-generation sequencing (tNGS). We analyzed the data using SPSS. Results: The study involved 417 patients diagnosed with MPP, of whom 86.33% had co-infections. Co-infections were notably linked to lobar pneumonia, prominent imaging shadows and higher macrolide resistance rate. Key bacterial pathogens were Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus, rhinoviruses, and human adenoviruses (HADV). In MPP cases, Candida albicans was the fungal pathogen related to co-infections. The co-infection with HADV and human bocavirus 1 (HBoV1) correlated with prolonged fever, whereas Bordetella pertussis was linked to prolonged cough. In contrast, Candida albicans exhibited a weaker association with diffuse large-area infiltration on chest imaging, and its co-infection was less likely to result in severe disease. Conclusion: These results offer valuable insight into Mycoplasma pneumoniae pneumonia in children, highlighting the impact of co-infections on the disease’s clinical outcomes.展开更多
One of the challenging tasks in cognitive radio(CR) networks is to agree on a common control channel to exchange control information. This paper presents a novel medium access control(MAC) protocol for CR network whic...One of the challenging tasks in cognitive radio(CR) networks is to agree on a common control channel to exchange control information. This paper presents a novel medium access control(MAC) protocol for CR network which efficiently and intelligently establishes a common control channel between CR nodes. The proposed protocol is the first CR MAC protocol which is hybrid in nature and lies between global common control channel(GCCC) and non-GCCC family of MAC protocols. The dynamic nature of the protocol makes the CR nodes converge on a newly found control channel quicker whenever the interference from a licensed user is sensed. The analytical results show that the dynamic, hybrid and adaptive nature of proposed protocol yields higher throughputs when compared with other CR MAC protocols.展开更多
The Co-Ni-Ti-V quaternary phase diagrams within the Co-Ni-rich region were investigated using the electron probe X-ray micro-analyzer(EPMA)and X-ray diffraction(XRD).Three isothermal sections corresponding to the Co-1...The Co-Ni-Ti-V quaternary phase diagrams within the Co-Ni-rich region were investigated using the electron probe X-ray micro-analyzer(EPMA)and X-ray diffraction(XRD).Three isothermal sections corresponding to the Co-10Ni-Ti-V,Co-15Ni-Ti-V,and Co-20Ni-Ti-V quaternary systems at 1000°C were experimentally established.The results indicate that increasing Ni content markedly broadens theγ(α-Co)andγ′(Co3Ti)two-phase regions.Based on the Co-Ni-Ti-V phase diagram,alloys with highγ′solvus temperature were designed,and their comprehensive properties,includingγ′coarsening behavior and mechanical properties,were thoroughly investigated.Compared to Co-Ti-based superalloys,the Co-20Ni-10Ti-10V alloy exhibits lower coarsening rates ofγ′precipitates andγ/γ′lattice mismatch.Notably,it possesses exceptional high-temperature mechanical properties,with a yield strength of 508 MPa at 1000°C.This superior performance is primarily attributed to the presence of a high density of stacking fault shear.展开更多
Electrochemical reduction of carbon dioxide(CO_(2)RR)is a promising approach to complete the carbon cycle and potentially convert CO_(2)into valuable chemicals and fuels.Cu is unique among transition metals in its abi...Electrochemical reduction of carbon dioxide(CO_(2)RR)is a promising approach to complete the carbon cycle and potentially convert CO_(2)into valuable chemicals and fuels.Cu is unique among transition metals in its ability to catalyze the CO_(2)RR and produce multi-carbon products.However,achieving high selectivity for C2+products is challenging for copper-based catalysts,as C–C coupling reactions proceed slowly.Herein,a surface modification strategy involving grafting long alkyl chains onto copper nanowires(Cu NWs)has been proposed to regulate the electronic structure of Cu surface,which facilitates*CO-*CO coupling in the CO_(2)RR.The hydrophobicity of the catalysts increases greatly after the introduction of long alkyl chains,therefore the hydrogen evolution reaction(HER)has been inhibited effectively.Such surface modification approach proves to be highly efficient and universal,with the Faradaic efficiency(FE)of C_(2)H_(4) up to 53%for the optimized Cu–SH catalyst,representing a significant enhancement compared to the pristine Cu NWs(30%).In-situ characterizations and theoretical calculations demonstrate that the different terminal groups of the grafted octadecyl chains can effectively regulate the charge density of Cu NWs interface and change the adsorption configuration of*CO intermediate.The top-adsorbed*CO intermediates(*COtop)on Cu–SH catalytic interface endow Cu–SH with the highest charge density,which effectively lowers the reaction energy barrier for*CO-*CO coupling,promoting the formation of the*OCCO intermediate,thereby enhancing the selectivity towards C_(2)H_(4).This study provides a promising method for designing efficient Cu-based catalysts with high catalytic activity and selectivity towards C2H4.展开更多
基金supported by Major Science and Technology Projects in Fujian Province,China(No.2023HZ021005)State Key Laboratory of Powder Metallurgy,Central South University,ChinaFujian Key Laboratory of Rare-earth Functional Materials,China。
文摘Additive manufacturing(AM)technology has emerged as a viable solution for manufacturing complexshaped WC−Co cemented carbide products,thereby expanding their applications in industries such as resource mining,equipment manufacturing,and electronic information.This review provides a comprehensive summary of the progress of AM technology in WC−Co cemented carbides.The fundamental principles and classification of AM techniques are introduced,followed by a categorization and evaluation of the AM techniques for WC−Co cemented carbides.These techniques are classified as either direct AM technology(DAM)or indirect AM technology(IDAM),depending on their inclusion of post-processes like de-binding and sintering.Through an analysis of microstructure features,the most suitable AM route for WC−Co cemented carbide products with controllable microstructure is identified as the indirect AM technology,such as binder jet printing(BJP),which integrates AM with conventional powder metallurgy.
基金supported by the National Natural Science Foundation of China(Nos.51831007,52101135)the Shenzhen Science and Technology Program,China(No.SGDX20210823104002016)the Guangdong Basic and Applied Basic Research Foundation,China(Nos.2021B1515120071,JCYJ20220531095217039)。
文摘Low-density superalloys often exhibit low yield strength in the intermediate temperature range(300−650℃).To enhance yield performance in this range,the CALPHAD method was used to design a new Co-based superalloy.The Co−30Ni−10Al−3V−6Ti−2Ta alloy,designed based onγʹphase dissolution temperature and phase fraction,was synthesized via arc melting and heat treatment.Phase transition temperatures,microstructure evolution,and hightemperature mechanical properties were characterized by differential scanning calorimetry,scanning electron microscopy,dual-beam TEM,and compression tests.Results show that the alloy has low density(8.15 g/cm^(3))and highγʹdissolution temperature(1234℃),along with unique yield strength retention from room temperature to 650℃.The yield strength anomaly(YSA)is attributed to high stacking fault energy and activation of the Kear−Wilsdorf locking mechanism,contributing to superior high-temperature stability of the alloy.The yield strength of this alloy outperforms other lowdensity Co-based superalloys in the temperature range of 23−650℃.
文摘A thoroughly mechanistic understanding of the electrochemical CO reduction reaction(eCORR)at the interface is significant for guiding the design of high-performance electrocatalysts.However,unintentionally ignored factors or unreasonable settings during mechanism simulations will result in false positive results between theory and experiment.Herein,we computationally identified the dynamic site preference change of CO adsorption with potentials on Cu(100),which was a previously unnoticed factor but significant to potential-dependent mechanistic studies.Combined with the different lateral interactions among adsorbates,we proposed a new C–C coupling mechanism on Cu(100),better explaining the product distribution at different potentials in experimental eCORR.At low potentials(from–0.4 to–0.6 V_(RHE)),the CO forms dominant adsorption on the bridge site,which couples with another attractively aggregated CO to form a C–C bond.At medium potentials(from–0.6 to–0.8 VRHE),the hollow-bound CO becomes dominant but tends to isolate with another adsorbate due to the repulsion,thereby blocking the coupling process.At high potentials(above–0.8 VRHE),the CHO intermediate is produced from the electroreduction of hollow-CO and favors the attraction with another bridge-CO to trigger C–C coupling,making CHO the major common intermediate for C–C bond formation and methane production.We anticipate that our computationally identified dynamic change in site preference of adsorbates with potentials will bring new opportunities for a better understanding of the potential-dependent electrochemical processes.
文摘Community-based ecotourism (CBET) aims to empower local communities through engagement and participation. Cambodia serves as a prime example of a developing country where the local community necessitates sustained stakeholder support to foster empowerment and promote local economic development. Ecotourism and conservation are among the major issues of concern in the study of community development. This study used the main five eco-tourism areas in Cambodia as examples. It looks at the connections between eco-innovations in tourism products, community engagement, co-creation experiences, support for CBET, perceived impact likelihood outcomes, community economic benefits, environmentally responsible behavior in ecotourism sites, and biodiversity conservation. The study employed a quantitative research approach to investigate and parameterize the dynamic ecotourism components as well as to explore key factors that influence the CBET. We collected the data using a self-administered survey on 398 local eco-based tourism communities that sell services and products to tourists. We also asked for structured questionnaire items of local communities that provide tourism services to visitors in eco-tourism destination sites in 2022-2023. The SEM results showed that this study significantly impacted and confirmed all relationships among research variables, as proposed in the conceptual model. We also discuss in detail the research findings of this study.
文摘Background: Mycoplasma pneumoniae (MP) is the primary causative agent of community-acquired pneumonia, which has increasingly become resistant to macrolides, complicating treatment regimens, especially with the co-infection factor. Its worldwide prevalence has fluctuated due to the influence of the COVID-19 pandemic. The study investigated co-infection patterns in children diagnosed with Mycoplasma pneumoniae pneumonia (MPP). Methods: From June 2022 to December 2023, we retrospectively analyzed the clinical data for hospitalized children with Mycoplasma pneumoniae pneumonia in Wuhan, China. We collected data on age, sex, clinical information, and pathogenic results. We also collected sputum or bronchoalveolar lavage fluid (BALF) samples to test respiratory pathogens and macrolide resistance using targeted microbial next-generation sequencing (tNGS). We analyzed the data using SPSS. Results: The study involved 417 patients diagnosed with MPP, of whom 86.33% had co-infections. Co-infections were notably linked to lobar pneumonia, prominent imaging shadows and higher macrolide resistance rate. Key bacterial pathogens were Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus, rhinoviruses, and human adenoviruses (HADV). In MPP cases, Candida albicans was the fungal pathogen related to co-infections. The co-infection with HADV and human bocavirus 1 (HBoV1) correlated with prolonged fever, whereas Bordetella pertussis was linked to prolonged cough. In contrast, Candida albicans exhibited a weaker association with diffuse large-area infiltration on chest imaging, and its co-infection was less likely to result in severe disease. Conclusion: These results offer valuable insight into Mycoplasma pneumoniae pneumonia in children, highlighting the impact of co-infections on the disease’s clinical outcomes.
文摘One of the challenging tasks in cognitive radio(CR) networks is to agree on a common control channel to exchange control information. This paper presents a novel medium access control(MAC) protocol for CR network which efficiently and intelligently establishes a common control channel between CR nodes. The proposed protocol is the first CR MAC protocol which is hybrid in nature and lies between global common control channel(GCCC) and non-GCCC family of MAC protocols. The dynamic nature of the protocol makes the CR nodes converge on a newly found control channel quicker whenever the interference from a licensed user is sensed. The analytical results show that the dynamic, hybrid and adaptive nature of proposed protocol yields higher throughputs when compared with other CR MAC protocols.
基金supported by the National Natural Science Foundation of China(Nos.51831007,52371007)the Shenzhen Science and Technology Program,China(No.SGDX20210823104002016)the Guangdong Basic and Applied Basic Research Foundation,China(No.2021B1515120071).
文摘The Co-Ni-Ti-V quaternary phase diagrams within the Co-Ni-rich region were investigated using the electron probe X-ray micro-analyzer(EPMA)and X-ray diffraction(XRD).Three isothermal sections corresponding to the Co-10Ni-Ti-V,Co-15Ni-Ti-V,and Co-20Ni-Ti-V quaternary systems at 1000°C were experimentally established.The results indicate that increasing Ni content markedly broadens theγ(α-Co)andγ′(Co3Ti)two-phase regions.Based on the Co-Ni-Ti-V phase diagram,alloys with highγ′solvus temperature were designed,and their comprehensive properties,includingγ′coarsening behavior and mechanical properties,were thoroughly investigated.Compared to Co-Ti-based superalloys,the Co-20Ni-10Ti-10V alloy exhibits lower coarsening rates ofγ′precipitates andγ/γ′lattice mismatch.Notably,it possesses exceptional high-temperature mechanical properties,with a yield strength of 508 MPa at 1000°C.This superior performance is primarily attributed to the presence of a high density of stacking fault shear.
文摘Electrochemical reduction of carbon dioxide(CO_(2)RR)is a promising approach to complete the carbon cycle and potentially convert CO_(2)into valuable chemicals and fuels.Cu is unique among transition metals in its ability to catalyze the CO_(2)RR and produce multi-carbon products.However,achieving high selectivity for C2+products is challenging for copper-based catalysts,as C–C coupling reactions proceed slowly.Herein,a surface modification strategy involving grafting long alkyl chains onto copper nanowires(Cu NWs)has been proposed to regulate the electronic structure of Cu surface,which facilitates*CO-*CO coupling in the CO_(2)RR.The hydrophobicity of the catalysts increases greatly after the introduction of long alkyl chains,therefore the hydrogen evolution reaction(HER)has been inhibited effectively.Such surface modification approach proves to be highly efficient and universal,with the Faradaic efficiency(FE)of C_(2)H_(4) up to 53%for the optimized Cu–SH catalyst,representing a significant enhancement compared to the pristine Cu NWs(30%).In-situ characterizations and theoretical calculations demonstrate that the different terminal groups of the grafted octadecyl chains can effectively regulate the charge density of Cu NWs interface and change the adsorption configuration of*CO intermediate.The top-adsorbed*CO intermediates(*COtop)on Cu–SH catalytic interface endow Cu–SH with the highest charge density,which effectively lowers the reaction energy barrier for*CO-*CO coupling,promoting the formation of the*OCCO intermediate,thereby enhancing the selectivity towards C_(2)H_(4).This study provides a promising method for designing efficient Cu-based catalysts with high catalytic activity and selectivity towards C2H4.
