The work presents new methods for selecting adaptive artificial viscosity(AAV)in iterative algorithms of completely conservative difference schemes(CCDS)used to solve gas dynamics equations in Euler variables.These me...The work presents new methods for selecting adaptive artificial viscosity(AAV)in iterative algorithms of completely conservative difference schemes(CCDS)used to solve gas dynamics equations in Euler variables.These methods allow to effectively suppress oscillations,including in velocity profiles,as well as computational instabilities in modeling gas-dynamic processes described by hyperbolic equations.The methods can be applied both in explicit and implicit(method of separate sweeps)iterative processes in numerical modeling of gas dynamics in the presence of heat and mass transfer,as well as in solving problems of magnetohydrodynamics and computational astrophysics.In order to avoid loss of solution accuracy on spatially non-uniform grids,in this work an algorithm of grid embeddings is developed,which is applied near transition points between cells of different sizes.The developed algorithms of CCDS using the methods for AAV selection and the algorithm of grid embeddings are implemented for various iterative processes.Calculations are performed for the classical problem of decay of an arbitrary discontinuity(Sod’s problem)and the problem of propagation of two symmetric rarefaction waves in opposite directions(Einfeldt’s problem).In the case of using different methods for selecting the AAV,a comparison of the solutions of the Sod’s problem on uniform and non-uniform grids and a comparison of the solutions of the Einfeldt’s problem on a uniform grid are performed.As a result of the comparative analysis,the applicability of these methods is shown in the spatially one-dimensional case(explicit and implicit iterative processes).The obtained results are compared with the data from the literature.The results coincide with analytical solutions with high accuracy,where the relative error does not exceed 0.1%,which demonstrates the effectiveness of the developed algorithms and methods.展开更多
The consistency of the dynamic behavior of the mechanical equivalent model of high-speed pantographs with that of actual high-speed pantographs under service conditions is crucial for the correctness and accuracy of t...The consistency of the dynamic behavior of the mechanical equivalent model of high-speed pantographs with that of actual high-speed pantographs under service conditions is crucial for the correctness and accuracy of the numerical simulation results of the pantograph-catenary interaction.Firstly,based on experimental data and the finite element method,models of a mass-point frame and reduced pan head were established,which can simulate the rolling and pitching motion characteristics of the dual-strip pan head.The correctness of the finite element numerical simulation of the pantograph-catenary system based on the model was verified through an industry standard and line tests.Then,the variation law of the standard deviation of the contact force(SDCF)in the speed range of 240-450 km/h was studied,and the mechanism of large fluctuation in SDCF was explained from the perspective of pantograph-catenary resonance.Finally,the influence of pan head degree of freedom and low-pass filtering frequency of the contact force time-domain signal on SDCF was studied,and the applicable speed level of the traditional three-mass model and 20 Hz filtering were provided.展开更多
In this work,we design and fabricate a deep ultraviolet(DUV)light-emitting array consisting of 10×10 micro-LEDs(μ-LEDs)with each device having 20μm in diameter.Strikingly,the array demonstrates a significant en...In this work,we design and fabricate a deep ultraviolet(DUV)light-emitting array consisting of 10×10 micro-LEDs(μ-LEDs)with each device having 20μm in diameter.Strikingly,the array demonstrates a significant enhancement of total light output power by nearly 52%at the injection current of 100 mA,in comparison to a conventional large LED chip whose emitting area is the same as the array.A much higher(~22%)peak external quantum efficiency,as well as a smaller efficiency droop forμ-LED array,was also achieved.The numerical calculation reveals that the performance boost can be attributed to the higher light extraction efficiency at the edge of eachμ-LED.Additionally,the far-field pattern measurement shows that theμ-LED array possesses a better forward directionality of emission.These findings shed light on the enhancement of the DUV LEDs performance and provide new insights in controlling the light behavior of theμ-LEDs.展开更多
Objective:Mutant KRAS,the principal isoform of RAS,plays a pivotal role in the oncogenesis of colorectal cancer by constitutively activating the RAF/MEK/ERK and PI3K/AKT pathways.Effective targeted therapies are urgen...Objective:Mutant KRAS,the principal isoform of RAS,plays a pivotal role in the oncogenesis of colorectal cancer by constitutively activating the RAF/MEK/ERK and PI3K/AKT pathways.Effective targeted therapies are urgently needed.We investigated whether rigosertib,a benzyl styryl sulfone RAS signaling disruptor,could selectively kill KRAS-mutant colorectal cancer cells.Methods:CCK-8 was used to determine the cell viability.Patient-derived tumor and cancer cell xenograft models were used to detect the inhibitory efficacy of rigosertib.Flow cytometry was used to evaluate the apoptosis and cell cycle progression.Apoptosis and cell cycle arrest markers were detected by Western blot.DCFH-DA was used to determine the reactive oxygen species.Immunohistochemistry staining and Western blot were performed to characterize RAS signaling markers in colorectal cancer tissues and cells.Results:Rigosertib(RGS)exhibited a cytotoxic effect against colorectal cancer cells,which was greater in KRAS-mutant cells.Furthermore,RGS induced mitotic arrest and oxidative stress-dependent apoptosis in KRAS-mutant DLD1 and HCT116 cells.Besides,RGS disrupted RAS signaling,and the inhibition of RAS/MEK/ERK was independent of cellular oxidative stress.Using patient-derived xenograft models,the response and tumor inhibition of RGS were significantly higher in the KRAS-mutant subgroup,while p-MEK,p-ERK,and p-AKT levels of RGS-treated tumors were significantly decreased.Finally,in a KRAS-mutant,chemotherapy-resistant patient-derived xenograft model,RGS showed a stronger therapeutic effect than the combination standard therapy involving fluoropyrimidine+oxaliplatin/irinotecan+bevacizumab.Conclusions:These data showed that targeting RAS signaling using RGS could be a therapeutic treatment for KRAS-mutant colorectal cancer patients.展开更多
Opportunistic Mobile Social Networks(OMSNs)are kind of Delay Tolerant Networks(DTNs)that leverage characteristics of Mobile Ad Hoc Networks(MANETs)and Social Networks,particularly the social features,to boost performa...Opportunistic Mobile Social Networks(OMSNs)are kind of Delay Tolerant Networks(DTNs)that leverage characteristics of Mobile Ad Hoc Networks(MANETs)and Social Networks,particularly the social features,to boost performance of routing algorithms.Users in OMSNs communicate to share and disseminate data to meet needs for variety of applications.Such networks have attracted tremendous attention lately due to the data transmission requirement from emerging applications such as IoT and smart city initiatives.Devices carried by human is the carrier of message transmission,so the social features of human can be used to improve the ability of data transmission.In this paper,we conduct a comparative survey on routing algorithms in OMSNs.We first analyze routing algorithms based on three social features.Since node selfishness is not really considered previously in aforementioned routing algorithms,but has significant impact on network performance,we treat node selfishness as another social feature,classify and elaborate routing algorithms based on incentive mechanism.To assess the impact of social features on routing algorithms,we conducted simulation for six routing algorithms and analyzed the simulation result.Finally,we conclude the paper with challenges on design of routing in OMSNs and point out some future research directions.展开更多
In view of the limited theoretical research on the load model of initial support for horseshoe-shaped prefabrication,this study focuses on the Luochuan Tunnel on the Xi'an-Yan'an newly built railway as the res...In view of the limited theoretical research on the load model of initial support for horseshoe-shaped prefabrication,this study focuses on the Luochuan Tunnel on the Xi'an-Yan'an newly built railway as the research object to explore its load model,load characteristic curve,plastic zone,deformation,and critical thickness.Theoretical research and numerical analysis were conducted.The results indicate that under the same boundary conditions,the ultimate bearing capacity of the prefabricated assembly initial support is higher than that of the shotcrete initial support,resulting in larger ultimate deformation capacity of the prefabricated assembly initial support.Based on numerical calculations,the ultimate deformation and critical thickness of the prefabricated initial lining for single-and double-track railway tunnels are obtained when buried at depths of 200,500,and 900 m in rock masses of classes Ⅲ,Ⅳ,and Ⅴ.展开更多
Background The risk of transmission of respiratory infectious diseases in emergency rooms is high,posing a severe threat to the health of healthcare workers(HCWs).Methods The study was conducted in an emergency room o...Background The risk of transmission of respiratory infectious diseases in emergency rooms is high,posing a severe threat to the health of healthcare workers(HCWs).Methods The study was conducted in an emergency room of a medical school at a university in Hong Kong during a clinical skills competition.A total of 19,246 s of video surveillance data were collected,recording the treatment of three types of patients(P1:infusion patient,P2:critically ill patient,P3:agitated patient).Taking coronavirus disease 2019(COVID-19)as an example,a multi-route transmission model was established to assess the infection risk for HCWs and the effectiveness of various interventions.Results The average distances between HCWs and patients during the treatment of P1,P2,and P3 were 0.8(25–75 percentile:0.6,1.1)m,1.0(0.8,1.2)m,and 0.5(0.4,0.7)m,respectively.When treating P2,due to intubation procedures,the hourly risk of infection was highest at 43.4%if no HCWs wore masks,which was 5.1 and 3.1 times higher than it during treatment of P1(8.5%)and P3(13.9%),respectively.During the treatment,without mask protection,the average hourly infection risk for nurses was 11.0%(P1),41.2%(P2),and 16.8%(P3),which was 1.8 times(P1),0.9 times(P2),and 1.5 times(P3)that of doctors.If HCWs wear N95 respirators and surgical masks throughout,the total infection risk can be reduced by 94.7%and 53.9%,respectively.Increasing the ventilation rate from 1 ACH to 6 ACH reduced the infection risk through long-range airborne transmission by 43.8%(P1),36.1%(P2),and 31.6%(P3),with a total infection risk reduction of 2.4%(P1),5.6%(P2),and 1.6%(P3),respectively.Conclusions The findings of the study provide a scientific support for the precise prevention and control of respiratory infectious diseases under different treatments in emergency rooms.展开更多
The Al Ga N-based deep ultraviolet(DUV)light-emitting diode(LED)is an alternative DUV light source to replace traditional mercury-based lamps.However,the state-of-the-art DUV LEDs currently exhibit poor wall-plug effi...The Al Ga N-based deep ultraviolet(DUV)light-emitting diode(LED)is an alternative DUV light source to replace traditional mercury-based lamps.However,the state-of-the-art DUV LEDs currently exhibit poor wall-plug efficiency and low light output power,which seriously hinder their commercialization.In this work,we design and report a tunnel-junctioncascaded(TJC)DUV LED,which enables multiple radiative recombinations within the active regions.Therefore,the light output power of the TJC-DUV LEDs is more than doubled compared to the conventional DUV LED.Correspondingly,the wall-plug efficiency of the TJC-DUV LED is also significantly boosted by 25%at 60 m A.展开更多
Ⅱ-Ⅴsemiconductor nanowires are indispensable building blocks for nanoscale electronic and optoelectronic devices.However,solely relying on their intrinsic physical and material properties sometimes limits device fun...Ⅱ-Ⅴsemiconductor nanowires are indispensable building blocks for nanoscale electronic and optoelectronic devices.However,solely relying on their intrinsic physical and material properties sometimes limits device functionalities to meet the increasing demands in versatile and complex electronic world.By leveraging the distinctive nature of the one-dimensional geometry and large surface-to-volume ratio of the nanowires,new properties can be attained through monolithic integration of conventional nanowires with other easy-synthesized functional materials.Herein,we combine high-crystal-quality lInitridle nanowires with amorphous molybdenum sulfides(a-MoS)to construct II.nitride/a-MoS_(x) core-shell nanostructures.Upon light ilumination,such nanostructures exhibit striking spectrally distinctive photodetection characteristic in photoelectrochemical environment,demonstrating a negative photoresponsivity of-100.42 mA W^(-1)under 254 nm ilumination,and a positive photoresponsivity of 29.5 mA W^(-1)under 365 nm ilumination.Density functional theory calculations reveal that the successful surface modifcation of the nanowires via a-MoS_(x)decoration accelerates the reaction process at the electrolyte/nanowire interface,leading to the generation of opposite photocurrent signals under different photon ilumination.Most importantly,such polarity-switchable photoconductivity can be further tuned for multiple wavelength bands photodetection by simply adjusting the surrounding environment and/or tailoring the nanowire composition,showing great promise to build light-wavelength controllable sensing devices in the future.展开更多
An emerging method for effectively improving the catalytic activity of metal oxide hybrids involves the creation of metal oxide interfaces for facilitating the activation of reagents. Here, we demonstrate that bilayer...An emerging method for effectively improving the catalytic activity of metal oxide hybrids involves the creation of metal oxide interfaces for facilitating the activation of reagents. Here, we demonstrate that bilayer vesicles formed from a hexavanadate cluster functionalized with two alkyl chains are highly efficient catalysts for the oxidation of 3,3＇,5,5＇-tetramethylbenzidine （TMB） with H2O2 at room temperature, a widely used model reaction mimicking the activity of peroxidase in biological catalytic oxidation processes. Driven by hydrophobic interactions, the double-tailed hexavanadate-headed amphiphiles can self-assemble into bilayer vesicles and create hydrophobic domains that segregate the TMB chromogenic substrate. The reaction of TMB with H2O2 takes place at the interface of the hydrophilic and hydrophobic domains, where the reagents also make contact with the catalytic hexavanadate clusters, and it is approximately two times more efficient compared with the reactions carried out with the corresponding unassembled systems. Moreover, the assembled vesicular system possesses affinity for TMB comparable to that of reported noble metal mimic nanomaterials, as well as a higher maximum reaction rate.展开更多
In this study,a robust model predictive controller is designed for the trajectory tracking problem of non-holonomic constrained wheeled mobile robot based on an elliptic invariant set approach.The controller is based ...In this study,a robust model predictive controller is designed for the trajectory tracking problem of non-holonomic constrained wheeled mobile robot based on an elliptic invariant set approach.The controller is based on a time-varying error model of robot kinematics and uses linear matrix inequalities to solve the robust tracking problem taking uncertainties into account.The uncertainties are modelled by linear fractional transform form to contain both parameter perturbations and external disturbances.The control strategy consists of a feedforward term that drives the centre of the ellipse to the reference point and a feedback term that converges the uncertain system state error to the equilibrium point.The strategy stabilises the nominal system and ensures that all states of the uncertain system remain within the ellipsoid at each step,thus achieving robust stability of the uncertain system.Finally,the robustness of the algorithm and its resistance to disturbances are verified by simulation and experiment.展开更多
Metal–semiconductor contacts play a pivotal role in controlling carrier transport in the fabrication of modern electronic devices.The exploration of van der Waals(vdW)metal contacts in semiconductor devices can poten...Metal–semiconductor contacts play a pivotal role in controlling carrier transport in the fabrication of modern electronic devices.The exploration of van der Waals(vdW)metal contacts in semiconductor devices can potentially mitigate Fermi-level pinning at the metal–semiconductor interface,with particular success in two-dimensional layered semiconductors,triggering unprecedented electrical and optical characteristics.In this work,for the first time,we report the direct integration of vdW metal contacts with bulk wide bandgap gallium nitride(GaN)by employing a dry transfer technique.High-angle annular dark-field scanning transmission electron microscopy explicitly illustrates the existence of a vdW gap between the metal electrode and GaN.Strikingly,compared with devices fabricated with electron beam-evaporated metal contacts,the vdW contact device exhibits a responsivity two orders of magnitude higher with a significantly suppressed dark current in the nanoampere range.Furthermore,by leveraging the high responsivity and persistent photoconductivity obtained from vdW contact devices,we demonstrate imaging,wireless optical communication,and neuromorphic computing functionality.The integration of vdW contacts with bulk semiconductors offers a promising architecture to overcome device fabrication challenges,forming nearly ideal metal–semiconductor contacts for future integrated electronics and optoelectronics.展开更多
基金carried out within the framework of the state assignment of KIAM RAS(No.125020701776-0).
文摘The work presents new methods for selecting adaptive artificial viscosity(AAV)in iterative algorithms of completely conservative difference schemes(CCDS)used to solve gas dynamics equations in Euler variables.These methods allow to effectively suppress oscillations,including in velocity profiles,as well as computational instabilities in modeling gas-dynamic processes described by hyperbolic equations.The methods can be applied both in explicit and implicit(method of separate sweeps)iterative processes in numerical modeling of gas dynamics in the presence of heat and mass transfer,as well as in solving problems of magnetohydrodynamics and computational astrophysics.In order to avoid loss of solution accuracy on spatially non-uniform grids,in this work an algorithm of grid embeddings is developed,which is applied near transition points between cells of different sizes.The developed algorithms of CCDS using the methods for AAV selection and the algorithm of grid embeddings are implemented for various iterative processes.Calculations are performed for the classical problem of decay of an arbitrary discontinuity(Sod’s problem)and the problem of propagation of two symmetric rarefaction waves in opposite directions(Einfeldt’s problem).In the case of using different methods for selecting the AAV,a comparison of the solutions of the Sod’s problem on uniform and non-uniform grids and a comparison of the solutions of the Einfeldt’s problem on a uniform grid are performed.As a result of the comparative analysis,the applicability of these methods is shown in the spatially one-dimensional case(explicit and implicit iterative processes).The obtained results are compared with the data from the literature.The results coincide with analytical solutions with high accuracy,where the relative error does not exceed 0.1%,which demonstrates the effectiveness of the developed algorithms and methods.
基金supported by the Major Project of China Railway Co.,Ltd.(Grant No.K2021J004-A)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB22020201)。
文摘The consistency of the dynamic behavior of the mechanical equivalent model of high-speed pantographs with that of actual high-speed pantographs under service conditions is crucial for the correctness and accuracy of the numerical simulation results of the pantograph-catenary interaction.Firstly,based on experimental data and the finite element method,models of a mass-point frame and reduced pan head were established,which can simulate the rolling and pitching motion characteristics of the dual-strip pan head.The correctness of the finite element numerical simulation of the pantograph-catenary system based on the model was verified through an industry standard and line tests.Then,the variation law of the standard deviation of the contact force(SDCF)in the speed range of 240-450 km/h was studied,and the mechanism of large fluctuation in SDCF was explained from the perspective of pantograph-catenary resonance.Finally,the influence of pan head degree of freedom and low-pass filtering frequency of the contact force time-domain signal on SDCF was studied,and the applicable speed level of the traditional three-mass model and 20 Hz filtering were provided.
基金funded by the National Natural Science Foundation of China (Grant Nos. 52161145404, 61905236, 51961145110)the Fundamental Research Funds for the Central Universities (Grant No. WK2100230020)USTC Research Funds of the Double First-Class Initiative (Grant No. YD3480002002)
文摘In this work,we design and fabricate a deep ultraviolet(DUV)light-emitting array consisting of 10×10 micro-LEDs(μ-LEDs)with each device having 20μm in diameter.Strikingly,the array demonstrates a significant enhancement of total light output power by nearly 52%at the injection current of 100 mA,in comparison to a conventional large LED chip whose emitting area is the same as the array.A much higher(~22%)peak external quantum efficiency,as well as a smaller efficiency droop forμ-LED array,was also achieved.The numerical calculation reveals that the performance boost can be attributed to the higher light extraction efficiency at the edge of eachμ-LED.Additionally,the far-field pattern measurement shows that theμ-LED array possesses a better forward directionality of emission.These findings shed light on the enhancement of the DUV LEDs performance and provide new insights in controlling the light behavior of theμ-LEDs.
基金This study was funded by grants from the National Key R&D Program of China(Grant No.2017YFC0908200 to KF Ding)the Key Technology Research and Development Program of Zhejiang Province(Grant No.2017C03017 to KF Ding)the National Natural Science Foundation of China(Grant No.81702331 to Q.Xiao,Grant No.81872481 to Y.Yuan,and Grant No.81772545 to KF Ding).
文摘Objective:Mutant KRAS,the principal isoform of RAS,plays a pivotal role in the oncogenesis of colorectal cancer by constitutively activating the RAF/MEK/ERK and PI3K/AKT pathways.Effective targeted therapies are urgently needed.We investigated whether rigosertib,a benzyl styryl sulfone RAS signaling disruptor,could selectively kill KRAS-mutant colorectal cancer cells.Methods:CCK-8 was used to determine the cell viability.Patient-derived tumor and cancer cell xenograft models were used to detect the inhibitory efficacy of rigosertib.Flow cytometry was used to evaluate the apoptosis and cell cycle progression.Apoptosis and cell cycle arrest markers were detected by Western blot.DCFH-DA was used to determine the reactive oxygen species.Immunohistochemistry staining and Western blot were performed to characterize RAS signaling markers in colorectal cancer tissues and cells.Results:Rigosertib(RGS)exhibited a cytotoxic effect against colorectal cancer cells,which was greater in KRAS-mutant cells.Furthermore,RGS induced mitotic arrest and oxidative stress-dependent apoptosis in KRAS-mutant DLD1 and HCT116 cells.Besides,RGS disrupted RAS signaling,and the inhibition of RAS/MEK/ERK was independent of cellular oxidative stress.Using patient-derived xenograft models,the response and tumor inhibition of RGS were significantly higher in the KRAS-mutant subgroup,while p-MEK,p-ERK,and p-AKT levels of RGS-treated tumors were significantly decreased.Finally,in a KRAS-mutant,chemotherapy-resistant patient-derived xenograft model,RGS showed a stronger therapeutic effect than the combination standard therapy involving fluoropyrimidine+oxaliplatin/irinotecan+bevacizumab.Conclusions:These data showed that targeting RAS signaling using RGS could be a therapeutic treatment for KRAS-mutant colorectal cancer patients.
基金This work was supported by National Natural Science Foundation of China(No.61672106)Natural Science Foundation of Beijing,China(L192023).
文摘Opportunistic Mobile Social Networks(OMSNs)are kind of Delay Tolerant Networks(DTNs)that leverage characteristics of Mobile Ad Hoc Networks(MANETs)and Social Networks,particularly the social features,to boost performance of routing algorithms.Users in OMSNs communicate to share and disseminate data to meet needs for variety of applications.Such networks have attracted tremendous attention lately due to the data transmission requirement from emerging applications such as IoT and smart city initiatives.Devices carried by human is the carrier of message transmission,so the social features of human can be used to improve the ability of data transmission.In this paper,we conduct a comparative survey on routing algorithms in OMSNs.We first analyze routing algorithms based on three social features.Since node selfishness is not really considered previously in aforementioned routing algorithms,but has significant impact on network performance,we treat node selfishness as another social feature,classify and elaborate routing algorithms based on incentive mechanism.To assess the impact of social features on routing algorithms,we conducted simulation for six routing algorithms and analyzed the simulation result.Finally,we conclude the paper with challenges on design of routing in OMSNs and point out some future research directions.
基金Research Project of China Railway Engineering Equipment Group Co.,Ltd.,Grant/Award Number:Equipment Research Cooperation 2019-14Postdoctoral Science Fund,Grant/Award Number:043201027。
文摘In view of the limited theoretical research on the load model of initial support for horseshoe-shaped prefabrication,this study focuses on the Luochuan Tunnel on the Xi'an-Yan'an newly built railway as the research object to explore its load model,load characteristic curve,plastic zone,deformation,and critical thickness.Theoretical research and numerical analysis were conducted.The results indicate that under the same boundary conditions,the ultimate bearing capacity of the prefabricated assembly initial support is higher than that of the shotcrete initial support,resulting in larger ultimate deformation capacity of the prefabricated assembly initial support.Based on numerical calculations,the ultimate deformation and critical thickness of the prefabricated initial lining for single-and double-track railway tunnels are obtained when buried at depths of 200,500,and 900 m in rock masses of classes Ⅲ,Ⅳ,and Ⅴ.
基金funded by the National Natural Science Foundation of China(grant number 52478074).
文摘Background The risk of transmission of respiratory infectious diseases in emergency rooms is high,posing a severe threat to the health of healthcare workers(HCWs).Methods The study was conducted in an emergency room of a medical school at a university in Hong Kong during a clinical skills competition.A total of 19,246 s of video surveillance data were collected,recording the treatment of three types of patients(P1:infusion patient,P2:critically ill patient,P3:agitated patient).Taking coronavirus disease 2019(COVID-19)as an example,a multi-route transmission model was established to assess the infection risk for HCWs and the effectiveness of various interventions.Results The average distances between HCWs and patients during the treatment of P1,P2,and P3 were 0.8(25–75 percentile:0.6,1.1)m,1.0(0.8,1.2)m,and 0.5(0.4,0.7)m,respectively.When treating P2,due to intubation procedures,the hourly risk of infection was highest at 43.4%if no HCWs wore masks,which was 5.1 and 3.1 times higher than it during treatment of P1(8.5%)and P3(13.9%),respectively.During the treatment,without mask protection,the average hourly infection risk for nurses was 11.0%(P1),41.2%(P2),and 16.8%(P3),which was 1.8 times(P1),0.9 times(P2),and 1.5 times(P3)that of doctors.If HCWs wear N95 respirators and surgical masks throughout,the total infection risk can be reduced by 94.7%and 53.9%,respectively.Increasing the ventilation rate from 1 ACH to 6 ACH reduced the infection risk through long-range airborne transmission by 43.8%(P1),36.1%(P2),and 31.6%(P3),with a total infection risk reduction of 2.4%(P1),5.6%(P2),and 1.6%(P3),respectively.Conclusions The findings of the study provide a scientific support for the precise prevention and control of respiratory infectious diseases under different treatments in emergency rooms.
基金supported by the National Natural Science Foundation of China(No.61905236)the University of Science and Technology of China(No.KY2100000081)+2 种基金the Chinese Academy of Sciences(No.KJ2100230003)the Fundamental Research Funds for the Central Universities(No.WK2100230020)the USTC Research Funds of the Double First-Class Initiative(No.YD3480002002)。
文摘The Al Ga N-based deep ultraviolet(DUV)light-emitting diode(LED)is an alternative DUV light source to replace traditional mercury-based lamps.However,the state-of-the-art DUV LEDs currently exhibit poor wall-plug efficiency and low light output power,which seriously hinder their commercialization.In this work,we design and report a tunnel-junctioncascaded(TJC)DUV LED,which enables multiple radiative recombinations within the active regions.Therefore,the light output power of the TJC-DUV LEDs is more than doubled compared to the conventional DUV LED.Correspondingly,the wall-plug efficiency of the TJC-DUV LED is also significantly boosted by 25%at 60 m A.
基金National Natural Science Foundation of China(Grant Nos.51727901,52161145404,61905236,51961145110)the Fundamental Research Funds for the Central Universities(Grant Nos.WK300000009,WK2100230020)。
文摘Ⅱ-Ⅴsemiconductor nanowires are indispensable building blocks for nanoscale electronic and optoelectronic devices.However,solely relying on their intrinsic physical and material properties sometimes limits device functionalities to meet the increasing demands in versatile and complex electronic world.By leveraging the distinctive nature of the one-dimensional geometry and large surface-to-volume ratio of the nanowires,new properties can be attained through monolithic integration of conventional nanowires with other easy-synthesized functional materials.Herein,we combine high-crystal-quality lInitridle nanowires with amorphous molybdenum sulfides(a-MoS)to construct II.nitride/a-MoS_(x) core-shell nanostructures.Upon light ilumination,such nanostructures exhibit striking spectrally distinctive photodetection characteristic in photoelectrochemical environment,demonstrating a negative photoresponsivity of-100.42 mA W^(-1)under 254 nm ilumination,and a positive photoresponsivity of 29.5 mA W^(-1)under 365 nm ilumination.Density functional theory calculations reveal that the successful surface modifcation of the nanowires via a-MoS_(x)decoration accelerates the reaction process at the electrolyte/nanowire interface,leading to the generation of opposite photocurrent signals under different photon ilumination.Most importantly,such polarity-switchable photoconductivity can be further tuned for multiple wavelength bands photodetection by simply adjusting the surrounding environment and/or tailoring the nanowire composition,showing great promise to build light-wavelength controllable sensing devices in the future.
基金We gratefully acknowledge the financially support by the National Natural Science Foundation of China （Nos. 21631007, 21401050, 21471087 and 21271068）, Beijing Natural Science Foundation （No. 2164063）, China Postdoctoral Science Foundation （No. 2014M560948）, the State Key Laboratory of Natural and Biomimetic Drugs （No. K20160202）, the National Natural Science Foundation of Hubei Province （No. 2015CFA131） and Wuhan Applied Basic Research Program （No. 2014010101010020）. T. B. L. acknowledges support from the National Science Foundation （No. CHE1607138） and the University of Akron.
文摘An emerging method for effectively improving the catalytic activity of metal oxide hybrids involves the creation of metal oxide interfaces for facilitating the activation of reagents. Here, we demonstrate that bilayer vesicles formed from a hexavanadate cluster functionalized with two alkyl chains are highly efficient catalysts for the oxidation of 3,3＇,5,5＇-tetramethylbenzidine （TMB） with H2O2 at room temperature, a widely used model reaction mimicking the activity of peroxidase in biological catalytic oxidation processes. Driven by hydrophobic interactions, the double-tailed hexavanadate-headed amphiphiles can self-assemble into bilayer vesicles and create hydrophobic domains that segregate the TMB chromogenic substrate. The reaction of TMB with H2O2 takes place at the interface of the hydrophilic and hydrophobic domains, where the reagents also make contact with the catalytic hexavanadate clusters, and it is approximately two times more efficient compared with the reactions carried out with the corresponding unassembled systems. Moreover, the assembled vesicular system possesses affinity for TMB comparable to that of reported noble metal mimic nanomaterials, as well as a higher maximum reaction rate.
文摘In this study,a robust model predictive controller is designed for the trajectory tracking problem of non-holonomic constrained wheeled mobile robot based on an elliptic invariant set approach.The controller is based on a time-varying error model of robot kinematics and uses linear matrix inequalities to solve the robust tracking problem taking uncertainties into account.The uncertainties are modelled by linear fractional transform form to contain both parameter perturbations and external disturbances.The control strategy consists of a feedforward term that drives the centre of the ellipse to the reference point and a feedback term that converges the uncertain system state error to the equilibrium point.The strategy stabilises the nominal system and ensures that all states of the uncertain system remain within the ellipsoid at each step,thus achieving robust stability of the uncertain system.Finally,the robustness of the algorithm and its resistance to disturbances are verified by simulation and experiment.
基金funded by the National Natural Science Foundation of China(62322410,52272168,and 52161145404)。
文摘Metal–semiconductor contacts play a pivotal role in controlling carrier transport in the fabrication of modern electronic devices.The exploration of van der Waals(vdW)metal contacts in semiconductor devices can potentially mitigate Fermi-level pinning at the metal–semiconductor interface,with particular success in two-dimensional layered semiconductors,triggering unprecedented electrical and optical characteristics.In this work,for the first time,we report the direct integration of vdW metal contacts with bulk wide bandgap gallium nitride(GaN)by employing a dry transfer technique.High-angle annular dark-field scanning transmission electron microscopy explicitly illustrates the existence of a vdW gap between the metal electrode and GaN.Strikingly,compared with devices fabricated with electron beam-evaporated metal contacts,the vdW contact device exhibits a responsivity two orders of magnitude higher with a significantly suppressed dark current in the nanoampere range.Furthermore,by leveraging the high responsivity and persistent photoconductivity obtained from vdW contact devices,we demonstrate imaging,wireless optical communication,and neuromorphic computing functionality.The integration of vdW contacts with bulk semiconductors offers a promising architecture to overcome device fabrication challenges,forming nearly ideal metal–semiconductor contacts for future integrated electronics and optoelectronics.
