Accurate knowledge of mesospheric winds and waves is essential for studying the dynamics and climate in the mesosphere and lower thermosphere(MLT)region.In this study,we conduct a comparative analysis of the mesospher...Accurate knowledge of mesospheric winds and waves is essential for studying the dynamics and climate in the mesosphere and lower thermosphere(MLT)region.In this study,we conduct a comparative analysis of the mesosphere tidal results obtained from two adjacent meteor radars at low latitudes in Kunming,China,from November 2013 to December 2014.These two radars operate at different frequencies of 37.5 MHz and 53.1 MHz,respectively.However,overall good agreement is observed between the two radars in terms of horizontal winds and tide observations.The results show that the dominant tidal waves of the zonal and meridional winds are diurnal and semidiurnal tides.Moreover,we conduct an exhaustive statistical analysis to compare the tidal amplitudes and vertical wavelengths recorded by the dual radar systems,which reveals a high degree of alignment in tidal dynamics.The investigation includes variances and covariances of tidal amplitudes,which demonstrate remarkable consistency across measurements from both radars.This finding highlights clear uniformity in the mesospheric tidal patterns observed at low latitudes by the two neighboring meteor radars.Results of the comparative analysis specifically underscore the significant correlation in vertical wavelength measurements,validating the robustness of radar observations for tidal research.展开更多
During gas extraction from deep coal,the rock endures high effective stress,with both the time-dependent deformation and anisotropic structure of the rock controlling the permeability evolution.To reveal this phenomen...During gas extraction from deep coal,the rock endures high effective stress,with both the time-dependent deformation and anisotropic structure of the rock controlling the permeability evolution.To reveal this phenomenon,a numerical simulation framework of the finite volume method and transient embedded discrete fracture model is proposed to establish a new constitutive model that links poroelastoplastic deformation,adsorption-induced swelling,and aperture compression.From this model,anisotropic permeability tensors were derived to further achieve the simulation of coevolution.Meanwhile,our permeability model was verified against the measured permeability data,and the history match of the numerical model showed better results where the mismatch was less than 5%.The results indicate that(1)the long-term permeability evolution clearly showed the competitive effects of multiple deformation mechanisms,which involves three stages:compaction-dominated decline,adsorption-dominated rebound,and creep-controlled loss.(2)The increased number of compressible cleats/fractures accelerated the initial permeability decline,while the increased desorption-induced strain promoted faster rebound and enhancement and higher viscosity coefficients enhanced the creep effect,which led to significant long-term permeability loss.(3)Massive hydraulic fracturing created a larger drainage area,accelerating methane desorption and causing sharp permeability rebound with reduced residual gas,which shows that the permeability remained higher than the initial values even after the extensive extraction via the fractured horizontal wells.The permeability evolution mechanisms displayed varying properties,such as coal rank and burial depth,and distinct characteristics.A precise understanding of multiple competitive stress effects is crucial for optimizing coalbed methane extraction techniques and improving recovery efficiency.展开更多
The rapid development of magnetic materials provides the possibility for the application of permanent magnet stirring(PMS).Numerical and experimental investigations were employed with respect to the solidification pro...The rapid development of magnetic materials provides the possibility for the application of permanent magnet stirring(PMS).Numerical and experimental investigations were employed with respect to the solidification process of the Al—2Sc alloy controlled by a novel PMS using NdFeB permanent magnets under various rotation speeds(0,50,100 and 150 r/min).The simulated results reveal that the maximum electromagnetic force increases proportionally from 4.14 to 12.39 kN/m^(3)and the maximum tangential velocity increases from 0.13 to 0.36 m/s when the rotation speed of PMS enhances from 50 to 150 r/min in the ingot melt.Besides,the experimental results demonstrate that PMS can achieve a uniform distribution of blocky Al_(3)Sc precipitated phase in the longitudinal direction under the impact of a forced fluid flow.Moreover,increasing rotation speed of PMS is beneficial to refining aluminum grain size significantly and decreasing the texture intensity in the alloy.In addition,the Brinell hardness of Al-2Sc alloy is increased by 33%to 27.8 HB and the tensile strength is enhanced by 34%-128.2 MPa,due to the improved distribution of the strengthening Al_(3)SC phase and the grain refinement of Al matrix under the impact of PMS.This work provides an effective application of NdFeB permanent magnets in the metal cast field.展开更多
The demand for oil casing steel with ultra-high strength and excellent impact toughness for safe application in ultra-deep wells is pressing.In improving the combination of strength,ductility,and impact toughness,the ...The demand for oil casing steel with ultra-high strength and excellent impact toughness for safe application in ultra-deep wells is pressing.In improving the combination of strength,ductility,and impact toughness,the designed Cr-Mo-V micro-alloyed oil casing steel was quenched at 800,900,and 1000℃,followed by tempering at 600,680,and 760℃,respectively,to obtain distinct microstruc-tures.The results showed that the microstructure of the samples quenched at 800℃ followed by tempering comprised untransformed ferrite and large undissolved carbides,which considerably deteriorated tensile strength and impact toughness.For other conditions,the nuc-leated carbides and the boundaries are key factors that balance the tensile strength from 1226 to 971 MPa and the impact toughness from 65 to 236 J.From the perspective of carbide,optimal precipitation strengthening is achieved with a smaller carbide size obtained by a low tempering temperature of 600℃,while larger-sized carbides would remarkably soften the matrix to improve the toughness but deteriorate the tensile strength.Additionally,an increase in prior austenite grain size with the corresponding enlarged sub-boundaries obtained by high quenching temperatures substantially diminishes grain refinement strengthening,dislocation strengthening,and the energy absorbed in the crack propagation process,which is unfavorable to strength and toughness.展开更多
Battery safety has emerged as a critical challenge for achieving carbon neutrality,driven by the increasing frequency of thermal runaway incidents in electric vehicles(EVs)and stationary energy storage systems(ESSs).C...Battery safety has emerged as a critical challenge for achieving carbon neutrality,driven by the increasing frequency of thermal runaway incidents in electric vehicles(EVs)and stationary energy storage systems(ESSs).Conventional battery monitoring technologies struggle to track multiple physicochemical parameters in real time,hindering early hazard detection.Embedded optical fiber sensors have gained prominence as a transformative solution for next-generation smart battery sensing,owing to their micrometer size,multiplexing capability,and electromagnetic immunity.However,comprehensive reviews focusing on their advancements in operando multi-parameter monitoring remain scarce,despite their critical importance for ensuring battery safety.To address this gap,this review first introduces a classification and the fundamental principles of advanced battery-oriented optical fiber sensors.Subsequently,it summarizes recent developments in single-parameter battery monitoring using optical fiber sensors.Building on this foundation,this review presents the first comprehensive analysis of multifunctional optical fiber sensing platforms capable of simultaneously tracking temperature,strain,pressure,refractive index,and monitoring battery aging.Targeted strategies are proposed to facilitate the practical development of this technology,including optimization of sensor integration techniques,minimizing sensor invasiveness,resolving the cross-sensitivity of fiber Bragg grating(FBG)through structural innovation,enhancing techno-economics,and combining with artificial intelligence(AI).By aligning academic research with industry requirements,this review provides a methodological roadmap for developing robust optical sensing systems to ensure battery safety in decarbonization-driven applications.展开更多
P3-type manganese-iron-based cathodes with high specific capacity and abundant resource have attracted considerable attention for sodium-ion batteries.However,the long-term cycle stability of P3-type cathodes is still...P3-type manganese-iron-based cathodes with high specific capacity and abundant resource have attracted considerable attention for sodium-ion batteries.However,the long-term cycle stability of P3-type cathodes is still not satisfactory.In this work,we design a new quaternary manganese-iron-based cathode material(P3-Na_(0.54)Mn_(0.64)Fe_(_(0.1)6)Mg_(0.1)Cu_(0.1)O_(2))by Cu substitution.The strong covalent Cu-O bonds improve the structural stability and the reversibility of O redox during charge and discharge processes.Cu substitution also mitigates the structure change with less unit cell volume variation,and improves the Na-ion transport kinetics effectively.As a result,NMFMC delivers much improved cycling stability and rate capability compared with NMFM.It reveals that the charge compensation of NMFMC is mainly contributed by Mn^(3+/4+),Fe^(3+/3.5+)and O_(2-/-)during the charge and discharge processes,and Cu substitution can also enhance the activity and reversibility of Fe redox.This strategy provides a new pathway toward improving the stability and O redox reversibility of P3-type cathode materials for sodium-ion batteries.展开更多
Betula alnoides is a fast-growing hardwood species grown in large plantations in Southeast Asia and South China.Nitrogen requirements for producing robus seedlings,growth and nutrient dynamics were investigated using ...Betula alnoides is a fast-growing hardwood species grown in large plantations in Southeast Asia and South China.Nitrogen requirements for producing robus seedlings,growth and nutrient dynamics were investigated using exponential fertilization treatments.Root collar diameter,height,dry mass and nutrient contents of seedlings increased exponentially in all fertilization treatments as time progressed.Moreover,with water soluble fertilizer（Plant Products plus microelements N–P2O5–K2O：20–20–20）,300 mg N seedling-1was adequate.Vector analysis revealed that P was the most responsive nutrient element followed by N and K.Dilutions of N and K were evident in the plants without N addition,which induced initial P sufficiency and then luxury consumption probably due to the antagonistic interaction between N and P.However deficiencies of N,P and K were mostly observed in al exponential regimes during the experiment because seedling growth rate exceeded nutrient uptake rate,inferring that further study on improving the nutrient uptake efficiency is needed.Analysis of relationships among nutrient supply,dry mass,N content and N concentration demonstrated that 100–400 mg N seedling-1induced sufficiency to luxury consumption of nitrogen without significant change in dry mass,and 400 mg N seedling-1is recommended to apply for nutrient loading of seedlings before outplanting.The findings will help improve seedling quality and enhance the production of robust seedlings for plantation forestry of this species.展开更多
Salvo attacking a surface target by multiple missiles is an effective tactic to enhance the lethality and penetrate the defense system. However, existing cooperative guidance laws in the midcourse or terminal course a...Salvo attacking a surface target by multiple missiles is an effective tactic to enhance the lethality and penetrate the defense system. However, existing cooperative guidance laws in the midcourse or terminal course are not suitable for long-and medium-range missiles or stand-off attacking. Because the initial conditions of cooperative terminal guidance that are generally generated from the mid-course flight may not lead to a successful cooperative terminal guidance without proper mid-course flight adjustment. Meanwhile, cooperative guidance in the mid-course cannot solely guarantee the accuracy of a simultaneous arrival of multiple missiles. Therefore, a joint mid-course and terminal course cooperative guidance law is developed. By building a distinct leader-follower framework, this paper proposes an efficient coordinated Dubins path planning method to synchronize the arrival time of all engaged missiles in the mid-course flight. The planned flight can generate proper initial conditions for cooperative terminal guidance, and also benefit an earliest simultaneous arrival. In the terminal course, an existing cooperative proportional navigation guidance law guides all the engaged missiles to arrive at a target accurately and simultaneously.The integrated guidance law for an intuitive application is summarized. Simulations demonstrate that the proposed method can generate fast and accurate salvo attack.展开更多
With the increasing maritime activities and the rapidly developing maritime economy, the fifth-generation(5G) mobile communication system is expected to be deployed at the ocean. New technologies need to be explored t...With the increasing maritime activities and the rapidly developing maritime economy, the fifth-generation(5G) mobile communication system is expected to be deployed at the ocean. New technologies need to be explored to meet the requirements of ultra-reliable and low latency communications(URLLC) in the maritime communication network(MCN). Mobile edge computing(MEC) can achieve high energy efficiency in MCN at the cost of suffering from high control plane latency and low reliability. In terms of this issue, the mobile edge communications, computing, and caching(MEC3) technology is proposed to sink mobile computing, network control, and storage to the edge of the network. New methods that enable resource-efficient configurations and reduce redundant data transmissions can enable the reliable implementation of computing-intension and latency-sensitive applications. The key technologies of MEC3 to enable URLLC are analyzed and optimized in MCN. The best response-based offloading algorithm(BROA) is adopted to optimize task offloading. The simulation results show that the task latency can be decreased by 26.5’ ms, and the energy consumption in terminal users can be reduced to 66.6%.展开更多
NMR serves as an important technique for probing rock pore space,such as pore structure characterization,fluid identification,and petrophysical property testing,due to the reusability of cores,convenience in sample pr...NMR serves as an important technique for probing rock pore space,such as pore structure characterization,fluid identification,and petrophysical property testing,due to the reusability of cores,convenience in sample processing,and time efficiency in laboratory tests.In practice,NMR signal collection is normally achieved through polarized nuclei relaxation which releases crucial relaxation messages for result interpretation.The impetus of this work is to help engineers and researchers with petroleum background obtain new insights into NMR principals and extend existing methodologies for characterization of unconventional formations.This article first gives a brief description of the development history of relaxation theories and models for porous media.Then,the widely used NMR techniques for characterizing petrophysical properties and pore structures are presented.Meanwhile,limitations and deficiencies of them are summarized.Finally,future work on improving these insufficiencies and approaches of enhancement applicability for NMR technologies are discussed.展开更多
AIM To determine the diagnostic accuracy of two-dimensional shear wave elastography(2D-SWE) for the noninvasive assessment of liver fibrosis in patients with autoimmune liver diseases(AILD) using liver biopsy as the r...AIM To determine the diagnostic accuracy of two-dimensional shear wave elastography(2D-SWE) for the noninvasive assessment of liver fibrosis in patients with autoimmune liver diseases(AILD) using liver biopsy as the reference standard.METHODS Patients with AILD who underwent liver biopsy and 2D-SWE were consecutively enrolled. Receiver operating characteristic(ROC) curves were constructed to assess the overall accuracy and to identify optimal cut-off values.RESULTS The characteristics of the diagnostic performance were determined for 114 patients with AILD. The areas under the ROC curves for significant fibrosis, severe fibrosis, and cirrhosis were 0.85, 0.85, and 0.86, respectively, and the optimal cut-off values associated with significant fibrosis(≥ F2), severe fibrosis(≥ F3), and cirrhosis(F4) were 9.7 k Pa, 13.2 k Pa and 16.3 k Pa, respectively. 2D-SWE showed sensitivity values of 81.7% for significant fibrosis, 83.0% for severe fibrosis,and 87.0% for cirrhosis, and the respective specificity values were 81.3%, 74.6%, and 80.2%. The overall concordance rate of the liver stiffness measurements obtained using 2D-SWE vs fibrosis stages was 53.5%.CONCLUSION2D-SWE showed promising diagnostic performance for assessing liver fibrosis stages and exhibited high cut-off values in patients with AILD. Low overall concordance rate was observed in the liver stiffness measurements obtained using 2D-SWE vs fibrosis stages.展开更多
Hepatocellular carcinoma(HCC)is a highly heterogeneous,invasive,and conventional chemotherapy-insensitive tumor with unique biological characteristics.The main methods for the radical treatment of HCC are surgical res...Hepatocellular carcinoma(HCC)is a highly heterogeneous,invasive,and conventional chemotherapy-insensitive tumor with unique biological characteristics.The main methods for the radical treatment of HCC are surgical resection or liver transplantation.However,recurrence rates are as high as 50%and 70%at 3 and 5 years after liver resection,respectively,and even in Milan-eligible recipients,the recurrence rate is approximately 20%at 5 years after liver transplantation.Therefore,reducing the postoperative recurrence rate is key to improving the overall outcome of liver cancer.This review discusses the risk factors for recurrence in patients with HCC radical surgical resection and adjuvant treatment options that may reduce the risk of recurrence and improve overall survival,including local adjuvant therapy(e.g.,transcatheter arterial chemoembolization),adjuvant systemic therapy(e.g.,molecular targeted agents and immunotherapy),and other adjuvant therapies(e.g.,antiviral and herbal therapy).Finally,potential research directions that may change the paradigm of adjuvant therapy for HCC are analyzed.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 42125402 and 42174183)the National Key Technologies R&D Program of China (Grant No.2022YFF0503703)+2 种基金the B-type Strategic Priority Program of the Chinese Academy of Sciences (Grant No. XDB41000000)the foundation of the National Key Laboratory of Electromagnetic Environment and the Fundamental Research Funds for the Central Universitiesthe Chinese Meridian Project
文摘Accurate knowledge of mesospheric winds and waves is essential for studying the dynamics and climate in the mesosphere and lower thermosphere(MLT)region.In this study,we conduct a comparative analysis of the mesosphere tidal results obtained from two adjacent meteor radars at low latitudes in Kunming,China,from November 2013 to December 2014.These two radars operate at different frequencies of 37.5 MHz and 53.1 MHz,respectively.However,overall good agreement is observed between the two radars in terms of horizontal winds and tide observations.The results show that the dominant tidal waves of the zonal and meridional winds are diurnal and semidiurnal tides.Moreover,we conduct an exhaustive statistical analysis to compare the tidal amplitudes and vertical wavelengths recorded by the dual radar systems,which reveals a high degree of alignment in tidal dynamics.The investigation includes variances and covariances of tidal amplitudes,which demonstrate remarkable consistency across measurements from both radars.This finding highlights clear uniformity in the mesospheric tidal patterns observed at low latitudes by the two neighboring meteor radars.Results of the comparative analysis specifically underscore the significant correlation in vertical wavelength measurements,validating the robustness of radar observations for tidal research.
基金support of the National Natural Science Foundation of China(U23B6004 and 52404045)the CAST Young Talent Support Program,Doctoral Student Special Project.
文摘During gas extraction from deep coal,the rock endures high effective stress,with both the time-dependent deformation and anisotropic structure of the rock controlling the permeability evolution.To reveal this phenomenon,a numerical simulation framework of the finite volume method and transient embedded discrete fracture model is proposed to establish a new constitutive model that links poroelastoplastic deformation,adsorption-induced swelling,and aperture compression.From this model,anisotropic permeability tensors were derived to further achieve the simulation of coevolution.Meanwhile,our permeability model was verified against the measured permeability data,and the history match of the numerical model showed better results where the mismatch was less than 5%.The results indicate that(1)the long-term permeability evolution clearly showed the competitive effects of multiple deformation mechanisms,which involves three stages:compaction-dominated decline,adsorption-dominated rebound,and creep-controlled loss.(2)The increased number of compressible cleats/fractures accelerated the initial permeability decline,while the increased desorption-induced strain promoted faster rebound and enhancement and higher viscosity coefficients enhanced the creep effect,which led to significant long-term permeability loss.(3)Massive hydraulic fracturing created a larger drainage area,accelerating methane desorption and causing sharp permeability rebound with reduced residual gas,which shows that the permeability remained higher than the initial values even after the extensive extraction via the fractured horizontal wells.The permeability evolution mechanisms displayed varying properties,such as coal rank and burial depth,and distinct characteristics.A precise understanding of multiple competitive stress effects is crucial for optimizing coalbed methane extraction techniques and improving recovery efficiency.
基金Project supported by the Natural Science Foundation of Hunan Province(2024JJ4056)the Key Project of Guangxi Zhuang Autonomous Region(AB22080089)the Government of Chongzuo,Guangxi Zhuang Autonomous Region(FA20210716)。
文摘The rapid development of magnetic materials provides the possibility for the application of permanent magnet stirring(PMS).Numerical and experimental investigations were employed with respect to the solidification process of the Al—2Sc alloy controlled by a novel PMS using NdFeB permanent magnets under various rotation speeds(0,50,100 and 150 r/min).The simulated results reveal that the maximum electromagnetic force increases proportionally from 4.14 to 12.39 kN/m^(3)and the maximum tangential velocity increases from 0.13 to 0.36 m/s when the rotation speed of PMS enhances from 50 to 150 r/min in the ingot melt.Besides,the experimental results demonstrate that PMS can achieve a uniform distribution of blocky Al_(3)Sc precipitated phase in the longitudinal direction under the impact of a forced fluid flow.Moreover,increasing rotation speed of PMS is beneficial to refining aluminum grain size significantly and decreasing the texture intensity in the alloy.In addition,the Brinell hardness of Al-2Sc alloy is increased by 33%to 27.8 HB and the tensile strength is enhanced by 34%-128.2 MPa,due to the improved distribution of the strengthening Al_(3)SC phase and the grain refinement of Al matrix under the impact of PMS.This work provides an effective application of NdFeB permanent magnets in the metal cast field.
基金supported from the National Nat-ural Science Foundation of China(Nos.52274342 and 52130408)the Fundamental Research Funds for the Central Universities of Central South University,China(No.1053320213826).
文摘The demand for oil casing steel with ultra-high strength and excellent impact toughness for safe application in ultra-deep wells is pressing.In improving the combination of strength,ductility,and impact toughness,the designed Cr-Mo-V micro-alloyed oil casing steel was quenched at 800,900,and 1000℃,followed by tempering at 600,680,and 760℃,respectively,to obtain distinct microstruc-tures.The results showed that the microstructure of the samples quenched at 800℃ followed by tempering comprised untransformed ferrite and large undissolved carbides,which considerably deteriorated tensile strength and impact toughness.For other conditions,the nuc-leated carbides and the boundaries are key factors that balance the tensile strength from 1226 to 971 MPa and the impact toughness from 65 to 236 J.From the perspective of carbide,optimal precipitation strengthening is achieved with a smaller carbide size obtained by a low tempering temperature of 600℃,while larger-sized carbides would remarkably soften the matrix to improve the toughness but deteriorate the tensile strength.Additionally,an increase in prior austenite grain size with the corresponding enlarged sub-boundaries obtained by high quenching temperatures substantially diminishes grain refinement strengthening,dislocation strengthening,and the energy absorbed in the crack propagation process,which is unfavorable to strength and toughness.
基金the financial supports of the National Natural Science Foundation of China(No.52372200)a project supported by the State Key Laboratory of Mechanics and Control for Aerospace Structures(No.MCAS-S-0324G01)。
文摘Battery safety has emerged as a critical challenge for achieving carbon neutrality,driven by the increasing frequency of thermal runaway incidents in electric vehicles(EVs)and stationary energy storage systems(ESSs).Conventional battery monitoring technologies struggle to track multiple physicochemical parameters in real time,hindering early hazard detection.Embedded optical fiber sensors have gained prominence as a transformative solution for next-generation smart battery sensing,owing to their micrometer size,multiplexing capability,and electromagnetic immunity.However,comprehensive reviews focusing on their advancements in operando multi-parameter monitoring remain scarce,despite their critical importance for ensuring battery safety.To address this gap,this review first introduces a classification and the fundamental principles of advanced battery-oriented optical fiber sensors.Subsequently,it summarizes recent developments in single-parameter battery monitoring using optical fiber sensors.Building on this foundation,this review presents the first comprehensive analysis of multifunctional optical fiber sensing platforms capable of simultaneously tracking temperature,strain,pressure,refractive index,and monitoring battery aging.Targeted strategies are proposed to facilitate the practical development of this technology,including optimization of sensor integration techniques,minimizing sensor invasiveness,resolving the cross-sensitivity of fiber Bragg grating(FBG)through structural innovation,enhancing techno-economics,and combining with artificial intelligence(AI).By aligning academic research with industry requirements,this review provides a methodological roadmap for developing robust optical sensing systems to ensure battery safety in decarbonization-driven applications.
基金supported by the National Key Scientific Research Project(No.2022YFB2502300)the National Natural Science Foundation of China(No.52071085).
文摘P3-type manganese-iron-based cathodes with high specific capacity and abundant resource have attracted considerable attention for sodium-ion batteries.However,the long-term cycle stability of P3-type cathodes is still not satisfactory.In this work,we design a new quaternary manganese-iron-based cathode material(P3-Na_(0.54)Mn_(0.64)Fe_(_(0.1)6)Mg_(0.1)Cu_(0.1)O_(2))by Cu substitution.The strong covalent Cu-O bonds improve the structural stability and the reversibility of O redox during charge and discharge processes.Cu substitution also mitigates the structure change with less unit cell volume variation,and improves the Na-ion transport kinetics effectively.As a result,NMFMC delivers much improved cycling stability and rate capability compared with NMFM.It reveals that the charge compensation of NMFMC is mainly contributed by Mn^(3+/4+),Fe^(3+/3.5+)and O_(2-/-)during the charge and discharge processes,and Cu substitution can also enhance the activity and reversibility of Fe redox.This strategy provides a new pathway toward improving the stability and O redox reversibility of P3-type cathode materials for sodium-ion batteries.
基金financially supported by The Ministry of Science and Technology,China(2012BAD21B0102)
文摘Betula alnoides is a fast-growing hardwood species grown in large plantations in Southeast Asia and South China.Nitrogen requirements for producing robus seedlings,growth and nutrient dynamics were investigated using exponential fertilization treatments.Root collar diameter,height,dry mass and nutrient contents of seedlings increased exponentially in all fertilization treatments as time progressed.Moreover,with water soluble fertilizer（Plant Products plus microelements N–P2O5–K2O：20–20–20）,300 mg N seedling-1was adequate.Vector analysis revealed that P was the most responsive nutrient element followed by N and K.Dilutions of N and K were evident in the plants without N addition,which induced initial P sufficiency and then luxury consumption probably due to the antagonistic interaction between N and P.However deficiencies of N,P and K were mostly observed in al exponential regimes during the experiment because seedling growth rate exceeded nutrient uptake rate,inferring that further study on improving the nutrient uptake efficiency is needed.Analysis of relationships among nutrient supply,dry mass,N content and N concentration demonstrated that 100–400 mg N seedling-1induced sufficiency to luxury consumption of nitrogen without significant change in dry mass,and 400 mg N seedling-1is recommended to apply for nutrient loading of seedlings before outplanting.The findings will help improve seedling quality and enhance the production of robust seedlings for plantation forestry of this species.
基金supported by the National Natural Science Foundation of China (No.61304215)supported by the Beijing Education Committee Cooperation Building Foundation Project (CSYS100070417)
文摘Salvo attacking a surface target by multiple missiles is an effective tactic to enhance the lethality and penetrate the defense system. However, existing cooperative guidance laws in the midcourse or terminal course are not suitable for long-and medium-range missiles or stand-off attacking. Because the initial conditions of cooperative terminal guidance that are generally generated from the mid-course flight may not lead to a successful cooperative terminal guidance without proper mid-course flight adjustment. Meanwhile, cooperative guidance in the mid-course cannot solely guarantee the accuracy of a simultaneous arrival of multiple missiles. Therefore, a joint mid-course and terminal course cooperative guidance law is developed. By building a distinct leader-follower framework, this paper proposes an efficient coordinated Dubins path planning method to synchronize the arrival time of all engaged missiles in the mid-course flight. The planned flight can generate proper initial conditions for cooperative terminal guidance, and also benefit an earliest simultaneous arrival. In the terminal course, an existing cooperative proportional navigation guidance law guides all the engaged missiles to arrive at a target accurately and simultaneously.The integrated guidance law for an intuitive application is summarized. Simulations demonstrate that the proposed method can generate fast and accurate salvo attack.
基金the National S&T Major Project (No. 2018ZX03001011)the National Key R&D Program(No.2018YFB1801102)+1 种基金the National Natural Science Foundation of China (No. 61671072)the Beijing Natural Science Foundation (No. L192025)
文摘With the increasing maritime activities and the rapidly developing maritime economy, the fifth-generation(5G) mobile communication system is expected to be deployed at the ocean. New technologies need to be explored to meet the requirements of ultra-reliable and low latency communications(URLLC) in the maritime communication network(MCN). Mobile edge computing(MEC) can achieve high energy efficiency in MCN at the cost of suffering from high control plane latency and low reliability. In terms of this issue, the mobile edge communications, computing, and caching(MEC3) technology is proposed to sink mobile computing, network control, and storage to the edge of the network. New methods that enable resource-efficient configurations and reduce redundant data transmissions can enable the reliable implementation of computing-intension and latency-sensitive applications. The key technologies of MEC3 to enable URLLC are analyzed and optimized in MCN. The best response-based offloading algorithm(BROA) is adopted to optimize task offloading. The simulation results show that the task latency can be decreased by 26.5’ ms, and the energy consumption in terminal users can be reduced to 66.6%.
基金financially supported by the National Science Foundation for Distinguished Young Scholars(51525404)the National Science and Technology Major Project(No.2016ZX05002002)the National Science and Technology Major Project(2016ZX05048-004-006)。
文摘NMR serves as an important technique for probing rock pore space,such as pore structure characterization,fluid identification,and petrophysical property testing,due to the reusability of cores,convenience in sample processing,and time efficiency in laboratory tests.In practice,NMR signal collection is normally achieved through polarized nuclei relaxation which releases crucial relaxation messages for result interpretation.The impetus of this work is to help engineers and researchers with petroleum background obtain new insights into NMR principals and extend existing methodologies for characterization of unconventional formations.This article first gives a brief description of the development history of relaxation theories and models for porous media.Then,the widely used NMR techniques for characterizing petrophysical properties and pore structures are presented.Meanwhile,limitations and deficiencies of them are summarized.Finally,future work on improving these insufficiencies and approaches of enhancement applicability for NMR technologies are discussed.
文摘AIM To determine the diagnostic accuracy of two-dimensional shear wave elastography(2D-SWE) for the noninvasive assessment of liver fibrosis in patients with autoimmune liver diseases(AILD) using liver biopsy as the reference standard.METHODS Patients with AILD who underwent liver biopsy and 2D-SWE were consecutively enrolled. Receiver operating characteristic(ROC) curves were constructed to assess the overall accuracy and to identify optimal cut-off values.RESULTS The characteristics of the diagnostic performance were determined for 114 patients with AILD. The areas under the ROC curves for significant fibrosis, severe fibrosis, and cirrhosis were 0.85, 0.85, and 0.86, respectively, and the optimal cut-off values associated with significant fibrosis(≥ F2), severe fibrosis(≥ F3), and cirrhosis(F4) were 9.7 k Pa, 13.2 k Pa and 16.3 k Pa, respectively. 2D-SWE showed sensitivity values of 81.7% for significant fibrosis, 83.0% for severe fibrosis,and 87.0% for cirrhosis, and the respective specificity values were 81.3%, 74.6%, and 80.2%. The overall concordance rate of the liver stiffness measurements obtained using 2D-SWE vs fibrosis stages was 53.5%.CONCLUSION2D-SWE showed promising diagnostic performance for assessing liver fibrosis stages and exhibited high cut-off values in patients with AILD. Low overall concordance rate was observed in the liver stiffness measurements obtained using 2D-SWE vs fibrosis stages.
文摘Hepatocellular carcinoma(HCC)is a highly heterogeneous,invasive,and conventional chemotherapy-insensitive tumor with unique biological characteristics.The main methods for the radical treatment of HCC are surgical resection or liver transplantation.However,recurrence rates are as high as 50%and 70%at 3 and 5 years after liver resection,respectively,and even in Milan-eligible recipients,the recurrence rate is approximately 20%at 5 years after liver transplantation.Therefore,reducing the postoperative recurrence rate is key to improving the overall outcome of liver cancer.This review discusses the risk factors for recurrence in patients with HCC radical surgical resection and adjuvant treatment options that may reduce the risk of recurrence and improve overall survival,including local adjuvant therapy(e.g.,transcatheter arterial chemoembolization),adjuvant systemic therapy(e.g.,molecular targeted agents and immunotherapy),and other adjuvant therapies(e.g.,antiviral and herbal therapy).Finally,potential research directions that may change the paradigm of adjuvant therapy for HCC are analyzed.
基金supported by the USTC Research Funds of the Double First-Class Initiative(YD3420002004)the National Natural Science Foundation of China(42125402,41974174,42188101,41831071,42174183,and 41904135)+4 种基金the B-type Strategic Priority Program of CAS(XDB41000000)the Project of Stable Support for Youth Team in Basic Research Field,CAS(YSBR-018)the Fundamental Research Funds for the Central Universitiesthe Anhui Provincial Natural Science Foundation(2008085MD113)the Joint Open Fund of Mengcheng National Geophysical Observatory(MENGO202209).
