Coral reef limestone(CRL)constitutes a distinctive marine carbonate formation with complex mechanical properties.This study investigates the multiscale damage and fracture mechanisms of CRL through integrated experime...Coral reef limestone(CRL)constitutes a distinctive marine carbonate formation with complex mechanical properties.This study investigates the multiscale damage and fracture mechanisms of CRL through integrated experimental testing,digital core technology,and theoretical modelling.Two CRL types with contrasting mesostructures were characterized across three scales.Macroscopically,CRL-I and CRL-II exhibited mean compressive strengths of 8.46 and 5.17 MPa,respectively.Mesoscopically,CRL-I featured small-scale highly interconnected pores,whilst CRL-II developed larger stratified pores with diminished connectivity.Microscopically,both CRL matrices demonstrated remarkable similarity in mineral composition and mechanical properties.A novel voxel average-based digital core scaling methodology was developed to facilitate numerical simulation of cross-scale damage processes,revealing network-progressive failure in CRL-I versus directional-brittle failure in CRL-II.Furthermore,a damage statistical constitutive model based on digital core technology and mesoscopic homogenisation theory established quantitative relationships between microelement strength distribution and macroscopic mechanical behavior.These findings illuminate the fundamental mechanisms through which mesoscopic structure governs the macroscopic mechanical properties of CRL.展开更多
The gasification behaviors of coke were investigated under conditions simulating a hydrogen-rich blast furnace atmosphere,composed of N_(2),CO,CO_(2),H_(2),and H_(2)O.Systematic experimental studies were conducted to ...The gasification behaviors of coke were investigated under conditions simulating a hydrogen-rich blast furnace atmosphere,composed of N_(2),CO,CO_(2),H_(2),and H_(2)O.Systematic experimental studies were conducted to examine the effects of gasification temperature and H_(2)O content on the microstructural and macroscopic properties of coke.The results indicated that increasing temperature and H_(2)O content enhanced the gasification and dissolution loss of coke,with temperature having a more significant impact.Pore structure analysis of the gasified coke revealed that small pores and micropores predominated at 900 and 1000℃.However,at gasification temperatures above 1100℃,oversized holes formed,some of which extended into the coke's interior.The compressive strength of the coke was also assessed,showing that higher gasification temperatures or increased H_(2)O content reduced this property.This reduction is primarily due to the increased coke porosity and the degradation of the pore wall structure.X-ray diffraction analysis results suggested that higher gasification temperatures and H2O content could improve the degree of order in the carbon microcrystals of the gasified coke.展开更多
This research presents an advanced study on the modeling and stability analysis of electro-hydraulic control modules used in intelligent chassis systems.Firstly,a comprehensive nonlinear mathematical model of the elec...This research presents an advanced study on the modeling and stability analysis of electro-hydraulic control modules used in intelligent chassis systems.Firstly,a comprehensive nonlinear mathematical model of the electro-hydraulic power-shift system is developed,incorporating pipeline characteristics through impedance analysis and examining coupling effects between the pilot solenoid valve,main valve,and pipeline.Then,the model’s accuracy is validated through experimental testing,demonstrating high precision and minimal model errors.A comparative analysis between simulation data(both with and without pipeline characteristics)and experimental results reveals that the model considering pipeline parameters aligns more closely with experimental data,highlighting its superior accuracy.The research further explores the influence of key factors on system stability,including damping coefficient,feedback cavity orifice diameter,spring stiffness,pipeline length,and pipeline diameter.Significant findings include the critical impact of damping coefficient,orifice diameter,and pipeline length on stability,while spring stiffness has a minimal effect.These findings provide valuable insights for optimizing electro-hydraulic control modules in intelligent chassis systems,with practical implications for automotive and construction machinery applications.展开更多
Iron ore pellets,as one of the main charges of blast furnaces,have a greater impact on the CO_(2)emission reduction and stable operation of blast furnaces.The isothermal reduction behavior of the pellets obtained from...Iron ore pellets,as one of the main charges of blast furnaces,have a greater impact on the CO_(2)emission reduction and stable operation of blast furnaces.The isothermal reduction behavior of the pellets obtained from a Chinese steel plant was studied in the gas mixtures of CO and N_(2).The results showed the reduction process is divided into two stages.The reduction in the initial stage(time t≤40 min)is cooperatively controlled by internal diffusion and interface chemical reactions with the activation energy of 30.19 and 16.67 kJ/mol,respectively.The controlling step of the reduction in the final stage(t>40 min)is internal diffusion with the activation energy of 34.60 kJ/mol.The reduction process can be described by two equations obtained from kinetic calculations.The reduction degree can be predicted under different temperatures and time,and the predicted results showed an excellent correlation with the experimental results.The reduction mechanisms were confirmed by the analysis of the scanning electron microscope equipped with an energy dispersive spectrometer and optical microscope.展开更多
In a hydrogen-rich blast furnace,an increased coke load accentuates the support skeleton role of coke,particularly in the cohesive and dripping zones following partial dissolution with slag.To investigate the dissolut...In a hydrogen-rich blast furnace,an increased coke load accentuates the support skeleton role of coke,particularly in the cohesive and dripping zones following partial dissolution with slag.To investigate the dissolution behaviours of coke in these regions,coke samples were gasified in a N2-CO-CO_(2)-H_(2)-H_(2)O atmosphere,simulating hydrogen-rich blast furnace conditions.Subsequently,the dissolution of gasified coke with slag containing FeO was analysed.The influence of coke gasification degree and FeO concentration in slag on coke dissolution was examined.The results showed that both higher coke gasification degrees and increased FeO content accelerate coke mass loss and exacerbate surface degradation upon dissolution,while effects on the internal structure of coke remain relatively minor,especially regarding FeO concentration.Additionally,hydrogen-rich gasification raised the graphitisation level of coke,with dissolution further enhancing the graphitisation of gasified coke.展开更多
The problem of disturbance rejection in humanoid robots has been properly studied,with most prior work focusing on hip-ankle-stepping compliance control strategies or whole-body inverse dynamics control.This paper pre...The problem of disturbance rejection in humanoid robots has been properly studied,with most prior work focusing on hip-ankle-stepping compliance control strategies or whole-body inverse dynamics control.This paper presents an adaptive disturbance rejection balance controller based on a Variable-inertia Centroidal Model Predictive Control(ViC-MPC)approach,designed to address both minor disturbances that affect standing balance and major disturbances requiring stepping adjustments.The controller also facilitates reliable balance recovery after stepping adjustments.The humanoid robot is modeled as a spatial variable-inertia ellipsoid,representing the distribution of centroidal dynamics,with the contact wrenches optimized in real-time through a customized MPC formulation.Inspired by capturability-based constraints,we propose an adaptive dynamic stability transition strategy.This strategy is activated based on the Retrospective Horizon Average Centroidal Velocity(RHACV)and the Capture Point(CP),ensuring effective stepping adjustments and disturbance rejection.With the torque-controlled humanoid robot BHR8P,extensive simulation and experimental results demonstrate the effectiveness of the proposed method,highlighting its capability to adapt to and recover from various disturbances with improved stability.展开更多
Two^(87)Sr optical lattice clocks(OLCs)are being developed and operated at the National Institute of Metrology(NIM),located on different campuses that are 40km apart.In order to compare the optical frequencies of thes...Two^(87)Sr optical lattice clocks(OLCs)are being developed and operated at the National Institute of Metrology(NIM),located on different campuses that are 40km apart.In order to compare the optical frequencies of these two Sr OLCs,a 58-km noise canceled fiber link is built to transfer both a 1542-nm transfer laser and a microwave reference from Changping campus to Hepingli campus.Two commercial optical frequency combs(OFCs)with adapted single-branch 698/1542nm outputs coherently unite the two 698-nm clock lasers and the 1542-nm transfer laser.The fractional instability of the comparison yields 3.1×10^(−17)at 10000 s averaging time.The measured fractional frequency difference between these two Sr OLCs was evaluated to be 1.9(3.2)×10^(−17),which is within their claimed uncertainties.This result demonstrates the consistency of their frequencies when they serve as optical frequency standards.Our remote comparison demonstrates the feasibility of optical clock comparison through a long-distance fiber link and contributes to the progress of redefinition of the SI second.展开更多
AIM: To investigate whether 7-d triple therapies are still valid in populations with low levels of resistance.METHODS: A total of 1106 Helicobacter pylori(H. pylori)-positive patients were divided into three groups,ea...AIM: To investigate whether 7-d triple therapies are still valid in populations with low levels of resistance.METHODS: A total of 1106 Helicobacter pylori(H. pylori)-positive patients were divided into three groups,each of which received one type of 7-d triple therapy. Therapeutic outcomes of the patients were assessed by the 13C-urea breath test at 8 wk after treatment. The susceptibility of H. pylori to antibiotics was determined by an agar-dilution method. Data analysis was performed by χ2 tests.RESULTS: The eradication rates in groups A,B and C were 90.71%(332/366),90.46%(313/346) and 90.87%(189/208),respectively(P = 0.986). The resistance rates were 8.91% for clarithromycin,14.78% for levofloxacin and 0% for amoxicillin. The eradication rate was significantly different between clarithromycin-and levofloxacin-resistant patients(P < 0.05) in group A. Patients whose treatment failed in group A also had a higher clarithromycin resistance rate than did successive patients(P = 0.034). However,levofloxacin resistance had no obvious influence on the eradication rate. Furthermore,three main antibiotics(clarithromycin,levofloxacin and amoxicillin) had lower DID(defined daily dose per 1000 inhabitants per day) in this city.CONCLUSION: Clarithromycin resistance is the main reason for the failure of 7-d triple therapy. In populations with low levels of resistance,a 7-d triple therapy is a viable choice. The choice of therapy should not be influenced by conditions in high antibiotic resistance regions.展开更多
AIM To investigate alterations in the fecal microbiome using 16 S r RNA amplicon sequencing in couples in the same cohabitation environment.METHODS Fecal samples were collected from eight ulcerative colitis(UC) patien...AIM To investigate alterations in the fecal microbiome using 16 S r RNA amplicon sequencing in couples in the same cohabitation environment.METHODS Fecal samples were collected from eight ulcerative colitis(UC) patients and their healthy partners at Lishui People's Hospital, Zhejiang Province, China. DNA was extracted and the variable regions V3 and V4 of the 16 S r RNA genes were PCR amplified using a two-step protocol. Clear reads were clustered into operational taxonomic units(OTUs) at the 97% sequence similarity level using UCLUST v1.2.22. The Wilcoxon rank-sumtest(R v3.1.2) was used to compare inter-individual differences. Differences with a P value < 0.05 were considered statistically significant.RESULTS Fecal microbial communities were more similar among UC patients than their healthy partners(P = 0.024). UC individuals had a lower relative abundance of bacteria belonging to the Firmicutes, especially Blautia, Clostridium, Coprococcus and Roseburia(P < 0.05). Microbiota dysbiosis was detected in UC patients and their healthy partners. Relevant genera included Akkermansiam, Bacteroides, Escherichia, Lactobacillales, Klebsiella and Parabacteroides. The enriched pathways in fecal samples of UC patients were related to lipid and nucleotide metabolism. Additionally, the pathways involved in membrane transport and metabolism of cofactors and vitamins were more abundant in the healthy partners.CONCLUSION Our results suggested that the microbial composition might be affected in healthy partners cohabiting with UC patients, especially in terms of microbiota dysbiosis.展开更多
Residual thermal stress in the system is a serious problem that affects the application of tritium permeation barrier coatings in fusion reactors. The stress not only determines the adhesion between coating and substr...Residual thermal stress in the system is a serious problem that affects the application of tritium permeation barrier coatings in fusion reactors. The stress not only determines the adhesion between coating and substrate, but also changes the properties of the material. In this study,finite element analysis was used to investigate the relationship between the residual thermal stress and the mechanical properties of Al_2O_3 tritium penetration barrier systems. Moreover, the residual thermal stress influenced by factors such as different substrates, temperature, and substrate roughness was also analyzed. The calculation showed that the hardness and elastic modulus increased with increasing compressive stress. However, the hardness and elastic modulus decreased with increasing tensile stress. The systems composed of Al_2O_3 coatings and different substrates exhibited different trends in mechanical properties. As the temperature increased, the hardness and the elastic modulus increased in an Al_2O_3/316 L stainless steel system; the trend was opposite in an Al_2O_3/Si system.Apart from this, the roughness of the substrate surface in the system could magnify the change in hardness and elastic modulus of the coating. Results showed that all these factors led to variation in the mechanical properties of Al_2O_3 tritium permeation barrier systems. Thus, thedetailed reasons for the changes in mechanical properties of these materials need to be analyzed.展开更多
BACKGROUND The resistance rate to antibacterial drugs is the key inhibitor of Helicobacter pylori(H.pylori)eradication treatment.AIM To evaluate the prevalence and drug resistance of H.pylori based on big data.METHODS...BACKGROUND The resistance rate to antibacterial drugs is the key inhibitor of Helicobacter pylori(H.pylori)eradication treatment.AIM To evaluate the prevalence and drug resistance of H.pylori based on big data.METHODS Gastric mucosal specimens were collected from naive patients undergoing upper gastrointestinal endoscopy for H.pylori culture and antimicrobial susceptibility testing(AST),including clarithromycin,levofloxacin,metronidazole and amoxicillin.Every 10 years of age was grouped as an age group.The H.pylori infection and resistance were explored based on the age group and gender.RESULTS The number of H.pylori-positive specimen was 94509 in 283823 gastric mucosal specimens,with an infection rate of 33.30%.The infection rate increased with age,and males had a higher infection rate than females.The average resistance rate of H.pylori to amoxicillin and metronidazole was 0.21%and 93.72%,which remained stable.The average resistance rate to clarithromycin was 23.99%with an increasing trend from 14.43%to 38.24%.The average resistance rate to levofloxacin was 30.29%,which increased from 17.07%to 39.42%and mostly stabilized after 2017.The resistance rate of H.pylori increased with age,except amoxicillin.H.pylori in females are at higher risk of resistance to metronidazole but not to amoxicillin,regardless of the age group.Meanwhile,H.pylori in females are at higher risk of resistance to levofloxacin and clarithromycin in the 21-50 age group.The single,dual,triple and quadruple-drug resistance rate was 54.59%,29.03%,11.71%and 0.11%,respectively.CONCLUSION The resistance of H.pylori in Taizhou city is serious.Guided by the consensus report,individualized treatment based on AST is recommended.展开更多
NIM-Sr2 optical lattice clock has been developed on the Changping campus of National Institute of Metrology(NIM).Considering the limitations in NIM-Sr1,several improved parts have been designed including a differentia...NIM-Sr2 optical lattice clock has been developed on the Changping campus of National Institute of Metrology(NIM).Considering the limitations in NIM-Sr1,several improved parts have been designed including a differential pumping stage in the vacuum system,a permanent magnet Zeeman slower,water-cooled anti-Helmholtz coils,an extended viewport for Zeeman slower,etc.A clock laser with a short-time stability better than 3×10^(-16)is realized based on a self-designed 30-cm-long ultra-low expansion cavity.The systematic frequency shift has been evaluated to an uncertainty of 7.2×10^(-18),with the uncertainty of BBR shift and the collisional frequency shift being an order of magnitude lower than the last evaluation of NIM-Sr1.展开更多
Unmanned systems such as legged robots require fast-motion responses for operation in complex envi-ronments.These systems therefore require explosive actuators that can provide high peak speed or high peak torque at s...Unmanned systems such as legged robots require fast-motion responses for operation in complex envi-ronments.These systems therefore require explosive actuators that can provide high peak speed or high peak torque at specific moments during dynamic motion.Although hydraulic actuators can provide a large force,they are relatively inefficient,large,and heavy.Industrial electric actuators are incapable of providing instant high power.In addition,the constant reduction ratio of the reducer makes it difficult to eliminate the tradeoff between high speed and high torque in a given system.This study proposes an explosive electric actuator and an associated control method for legged robots.First,a high-power-density variable transmission is designed to enable continuous adjustment of the output speed to torque ratio.A heat-dissipating structure based on a composite phase-change material(PCM)is used.An integral torque control method is used to achieve periodic and controllable explosive power output.Jumping experiments are conducted with typical legged robots to verify the effectiveness of the proposed actuator and control method.Single-legged,quadruped,and humanoid robots jumped to heights of 1.5,0.8,and 0.5 m,respectively.These are the highest values reported to date for legged robots powered by electric actuators.展开更多
AIM To analyze the bacterial community structure and distribution of intestinal microflora in people with and without metabolic syndrome and combined these data with clinical indicators to determine relationships betw...AIM To analyze the bacterial community structure and distribution of intestinal microflora in people with and without metabolic syndrome and combined these data with clinical indicators to determine relationships between selected bacteria and metabolic diseases. METHODS Faecal samples were collected from 20 patients with metabolic syndrome and 16 controls at Cangnan People's Hospital, Zhejiang Province, China. DNA was extracted and the V3-V4 regions of the 16 S rRNA genes were amplified for high throughput sequencing. Clear reads were clustered at the 97% sequence similarity level. α and β diversity were used to describe the bacterial community structure and distribution in patients. Combined with the clinical indicators, further analysis was performed.RESULTS Bacteroidetes, Firmicutes, Actinobacteria, Proteobacteria, Fusobacteria were the dominant phyla, and Prevotella, Bacteroides and Faecalibacterium was the top three genera in faecal samples. α diversity analysis showed that the species richness of metabolic syndrome samples(group D) was significantly higher than the control(group C)(P < 0.05), and the microbial diversity of group C was greater than that of group D. According to the principal co-ordinates analysis, the samples of group C clustered more tightly, indicating that the distribution of bacteria in healthy patients was similar. The correlation analysis showed that alkaline phosphatase was negatively correlated with the abundance of Prevotella(P < 0.05). There was a negative correlation between low-density lipoprotein and the abundance of Ruminococcus(P < 0.05) and a positive correlation between the high-density lipoprotein and the abundance of Ruminococcus(P < 0.05). The total protein and the alanine aminotransferase was positively correlated with the abundance of Peptostreptococcus(P < 0.05). CONCLUSION The changes microbial communities can be used as an indicator of metabolic syndrome, and Prevotella may be a target microorganism in patients with metabolic syndrome.展开更多
To improve the efficiency of iron recovery from steel slag and reduce the wear-and-tear on facilities, a new method was proposed by adding a secondary screen sizer to the magnetic separation process according to grain...To improve the efficiency of iron recovery from steel slag and reduce the wear-and-tear on facilities, a new method was proposed by adding a secondary screen sizer to the magnetic separation process according to grain size distribution of magnetic iron （M-Fe） in the slag. The final recycling efficiency was evaluated by calculating the percentage of recycled M-Fe to the maximum amount of M-Fe that could be recovered. Three types of slags, namely basic oxygen furnace slag, desul- furization slag, and iron ladle slag, were studied, and the results showed that the optimized re- covery efficieneies were 93.20%, 92. 48%, and 85.82% respectively, and the recycling efficien eies were improved by 9.58%, 7.11%, and 6.24% respectively. Furthermore, the abrasion between the mill equipment and the remaining slags was significantly reduced owing to the efficient recovery of larger M-Fe particles. In addition, the using amount of grinding balls was reduced by 0. 46 kg when every 1 t steel slag was processed.展开更多
Rock slopes are usually reinforced by a number of rock bolts due to the high efficiency and low price.However,where should the rock bolts be installed is still a troublesome issue.For anti-dip bedding rock slopes(ABRS...Rock slopes are usually reinforced by a number of rock bolts due to the high efficiency and low price.However,where should the rock bolts be installed is still a troublesome issue.For anti-dip bedding rock slopes(ABRSs),the installation position of rock bolts is a controlling factor that determines the reinforcement effect.In this work,a theoretical method is firstly proposed for assessing the stability of ABRSs reinforced by rock bolts using a limit equilibrium model.A comparison of theoretical calculations and numerical results was conducted to test the correctness of the theoretical method.Based on the stability assessment of ABRSs,we introduce adaptive moment estimation method(Adam)to optimize the installation location of rock bolts.Using Adam optimizer,the optimal layout of rock bolts with the maximum factor of safety can be determined,and the factor of safety of the slope increases by about 25%using the same amount of rock bolts but with different installation locations.The proposed method enables the fast stability analysis and supporting design for reinforced ABRSs,which paves the way to smart supporting design of slopes.展开更多
Whole-body control is beneficial for improving the disturbance adaptation of humanoid robots,since it can simultaneously optimize desired joint torque,joint acceleration,and contact force while considering whole-body ...Whole-body control is beneficial for improving the disturbance adaptation of humanoid robots,since it can simultaneously optimize desired joint torque,joint acceleration,and contact force while considering whole-body dynamics and other physical limits.However,the lack of torque feedback information prevents the position-controlled humanoids from utilizing whole-body control directly,because it enhances the difficulty of guaranteeing desired contact force which is important for maintaining stability.In this paper,a whole-body control that integrates task-space inverse dynamics and variable contact force control is proposed for position-controlled humanoids to enhance the robot’s adaptability toward the unknown disturbance.The task-space inverse dynamics generates the desired joint acceleration and contact force with the consideration of whole-body dynamics and other limits to track the references.The variable contact force control modifies references related to Center of Mass(CoM)and end effectors to ensure reasonable contact force tracking performance,thereby assuring good tracking performance of CoM and momentum to maintain robot stability.Simulations and experiments of balancing and walking under unknown disturbance have been successfully conducted on a position-controlled humanoid robot,BHR-7P3,with the proposed method.展开更多
基金National Key Research and Development Program of China (No.2021YFC3100800)the National Natural Science Foundation of China (Nos.42407235 and 42271026)+1 种基金the Project of Sanya Yazhou Bay Science and Technology City (No.SCKJ-JYRC-2023-54)supported by the Hefei advanced computing center
文摘Coral reef limestone(CRL)constitutes a distinctive marine carbonate formation with complex mechanical properties.This study investigates the multiscale damage and fracture mechanisms of CRL through integrated experimental testing,digital core technology,and theoretical modelling.Two CRL types with contrasting mesostructures were characterized across three scales.Macroscopically,CRL-I and CRL-II exhibited mean compressive strengths of 8.46 and 5.17 MPa,respectively.Mesoscopically,CRL-I featured small-scale highly interconnected pores,whilst CRL-II developed larger stratified pores with diminished connectivity.Microscopically,both CRL matrices demonstrated remarkable similarity in mineral composition and mechanical properties.A novel voxel average-based digital core scaling methodology was developed to facilitate numerical simulation of cross-scale damage processes,revealing network-progressive failure in CRL-I versus directional-brittle failure in CRL-II.Furthermore,a damage statistical constitutive model based on digital core technology and mesoscopic homogenisation theory established quantitative relationships between microelement strength distribution and macroscopic mechanical behavior.These findings illuminate the fundamental mechanisms through which mesoscopic structure governs the macroscopic mechanical properties of CRL.
基金the financial support provided by the National Natural Science Foundation of China(Nos.52174300 and 52404340)Natural Science Foundation of Chongqing,China(No.cstc2020jcyj-msxmX0583)+2 种基金Research Foundation of Chongqing University of Science and Technology(No.ckrc20240612)Chongqing Talent Plan Project(cstc2021ycjh-bgzxm0211)Chongqing Doctoral“Through Train”Project(No.sl202100000343).
文摘The gasification behaviors of coke were investigated under conditions simulating a hydrogen-rich blast furnace atmosphere,composed of N_(2),CO,CO_(2),H_(2),and H_(2)O.Systematic experimental studies were conducted to examine the effects of gasification temperature and H_(2)O content on the microstructural and macroscopic properties of coke.The results indicated that increasing temperature and H_(2)O content enhanced the gasification and dissolution loss of coke,with temperature having a more significant impact.Pore structure analysis of the gasified coke revealed that small pores and micropores predominated at 900 and 1000℃.However,at gasification temperatures above 1100℃,oversized holes formed,some of which extended into the coke's interior.The compressive strength of the coke was also assessed,showing that higher gasification temperatures or increased H_(2)O content reduced this property.This reduction is primarily due to the increased coke porosity and the degradation of the pore wall structure.X-ray diffraction analysis results suggested that higher gasification temperatures and H2O content could improve the degree of order in the carbon microcrystals of the gasified coke.
基金Supported by the Basic Product Innovation Plan for Vehicle Power Scientific Research Project(Grant No.JCCPCX201704).
文摘This research presents an advanced study on the modeling and stability analysis of electro-hydraulic control modules used in intelligent chassis systems.Firstly,a comprehensive nonlinear mathematical model of the electro-hydraulic power-shift system is developed,incorporating pipeline characteristics through impedance analysis and examining coupling effects between the pilot solenoid valve,main valve,and pipeline.Then,the model’s accuracy is validated through experimental testing,demonstrating high precision and minimal model errors.A comparative analysis between simulation data(both with and without pipeline characteristics)and experimental results reveals that the model considering pipeline parameters aligns more closely with experimental data,highlighting its superior accuracy.The research further explores the influence of key factors on system stability,including damping coefficient,feedback cavity orifice diameter,spring stiffness,pipeline length,and pipeline diameter.Significant findings include the critical impact of damping coefficient,orifice diameter,and pipeline length on stability,while spring stiffness has a minimal effect.These findings provide valuable insights for optimizing electro-hydraulic control modules in intelligent chassis systems,with practical implications for automotive and construction machinery applications.
基金support from the National Natural Science Foundation of China(No.52174300)Natural Science Foundation of Chongqing,China(Nos.cstc2020jcyj-msxmX0583 and cstc2021jcyj-msxmX1004)+1 种基金Chongqing Talent Plan Project(No.cstc2021ycjh-bgzxm0211)Chongqing Doctoral"Through Train"Project(No.sl202100000343).T。
文摘Iron ore pellets,as one of the main charges of blast furnaces,have a greater impact on the CO_(2)emission reduction and stable operation of blast furnaces.The isothermal reduction behavior of the pellets obtained from a Chinese steel plant was studied in the gas mixtures of CO and N_(2).The results showed the reduction process is divided into two stages.The reduction in the initial stage(time t≤40 min)is cooperatively controlled by internal diffusion and interface chemical reactions with the activation energy of 30.19 and 16.67 kJ/mol,respectively.The controlling step of the reduction in the final stage(t>40 min)is internal diffusion with the activation energy of 34.60 kJ/mol.The reduction process can be described by two equations obtained from kinetic calculations.The reduction degree can be predicted under different temperatures and time,and the predicted results showed an excellent correlation with the experimental results.The reduction mechanisms were confirmed by the analysis of the scanning electron microscope equipped with an energy dispersive spectrometer and optical microscope.
基金the financial support provided by the National Natural Science Foundation of China(Nos.52174300 and 52404340)Science and Technology Innovation Key R&D Program of Chongqing,China(No.CSTB2024TIAD-STX0009)+3 种基金The Science and Technology Research Program of Chongqing Municipal Education Commission(No.KJQN202401507)Chongqing Talent Plan Project(cstc2021ycjh-bgzxm0211)Natural Science Foundation of Chongqing,China(No.CSTB2024NSCQ-LZX0052)Chongqing Doctoral“Through Train”Project(No.sl202100000343).
文摘In a hydrogen-rich blast furnace,an increased coke load accentuates the support skeleton role of coke,particularly in the cohesive and dripping zones following partial dissolution with slag.To investigate the dissolution behaviours of coke in these regions,coke samples were gasified in a N2-CO-CO_(2)-H_(2)-H_(2)O atmosphere,simulating hydrogen-rich blast furnace conditions.Subsequently,the dissolution of gasified coke with slag containing FeO was analysed.The influence of coke gasification degree and FeO concentration in slag on coke dissolution was examined.The results showed that both higher coke gasification degrees and increased FeO content accelerate coke mass loss and exacerbate surface degradation upon dissolution,while effects on the internal structure of coke remain relatively minor,especially regarding FeO concentration.Additionally,hydrogen-rich gasification raised the graphitisation level of coke,with dissolution further enhancing the graphitisation of gasified coke.
基金supported in part by the National Natural Science Foundation of China under Grant 52575004the Beijing Natural Science Foundation under Grant L243004the National Natural Science Foundation of China under Grant 62403060.
文摘The problem of disturbance rejection in humanoid robots has been properly studied,with most prior work focusing on hip-ankle-stepping compliance control strategies or whole-body inverse dynamics control.This paper presents an adaptive disturbance rejection balance controller based on a Variable-inertia Centroidal Model Predictive Control(ViC-MPC)approach,designed to address both minor disturbances that affect standing balance and major disturbances requiring stepping adjustments.The controller also facilitates reliable balance recovery after stepping adjustments.The humanoid robot is modeled as a spatial variable-inertia ellipsoid,representing the distribution of centroidal dynamics,with the contact wrenches optimized in real-time through a customized MPC formulation.Inspired by capturability-based constraints,we propose an adaptive dynamic stability transition strategy.This strategy is activated based on the Retrospective Horizon Average Centroidal Velocity(RHACV)and the Capture Point(CP),ensuring effective stepping adjustments and disturbance rejection.With the torque-controlled humanoid robot BHR8P,extensive simulation and experimental results demonstrate the effectiveness of the proposed method,highlighting its capability to adapt to and recover from various disturbances with improved stability.
基金supported by the National Key R&D Program of China(Grant No.2021YFF0603802)the National Natural Science Foundation of China(Grant No.61905231)+1 种基金the State Administration for Market Regulation(Grant No.CXTD202301)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0300902)。
文摘Two^(87)Sr optical lattice clocks(OLCs)are being developed and operated at the National Institute of Metrology(NIM),located on different campuses that are 40km apart.In order to compare the optical frequencies of these two Sr OLCs,a 58-km noise canceled fiber link is built to transfer both a 1542-nm transfer laser and a microwave reference from Changping campus to Hepingli campus.Two commercial optical frequency combs(OFCs)with adapted single-branch 698/1542nm outputs coherently unite the two 698-nm clock lasers and the 1542-nm transfer laser.The fractional instability of the comparison yields 3.1×10^(−17)at 10000 s averaging time.The measured fractional frequency difference between these two Sr OLCs was evaluated to be 1.9(3.2)×10^(−17),which is within their claimed uncertainties.This result demonstrates the consistency of their frequencies when they serve as optical frequency standards.Our remote comparison demonstrates the feasibility of optical clock comparison through a long-distance fiber link and contributes to the progress of redefinition of the SI second.
文摘目的了解Wnt/β-catenin信号转导通路在瘢痕疙瘩原代成纤维细胞中关键蛋白和m RNA水平,探讨其在瘢痕疙瘩形机制中的作用。方法采用组织块培养法进行原代成纤维细胞培养,通过Western Blot和RT-PCR法分别检测正常皮肤以及瘢痕疙瘩成纤维细胞中Wnt/β-catenin信号转导通路中相关信号分子Wnt5a、β-catenin、GSK-3β、p-GSK-3β蛋白和Wnt5a、β-catenin、GSK-3βm RNA水平,比较两者之间差异。结果与正常皮肤相比,瘢痕疙瘩成纤维细胞中Wnt5a、β-catenin、p-GSK-3β蛋白及Wnt5a、β-catenin m RAN水平增高(P<0.05),GSK-3β蛋白及m RNA表达水平无明显变化。结论在瘢痕疙瘩形成过程中,Wnt5a、β-catenin m RAN上调并导致Wnt5a、β-catenin蛋白水平增高以及GSK-3β蛋白磷酸化导致p-GSK-3β增高可能在瘢痕疙瘩的形成机制中起着重要作用。
基金Supported by Science and Technology Program of Zhejiang Province,China,No.2001C23140National Technology R and D Program in the 12th Five-Year Plan of China,No.2012BAI06B02+2 种基金Major Technology Project as part of"Prevention and Control of Major Infectious Diseases including AIDS and Viral Hepatitis",No.2013ZX10004216-002National Key Scientific Instrument and Equipment Development ProjectNo.2012YQ180117
文摘AIM: To investigate whether 7-d triple therapies are still valid in populations with low levels of resistance.METHODS: A total of 1106 Helicobacter pylori(H. pylori)-positive patients were divided into three groups,each of which received one type of 7-d triple therapy. Therapeutic outcomes of the patients were assessed by the 13C-urea breath test at 8 wk after treatment. The susceptibility of H. pylori to antibiotics was determined by an agar-dilution method. Data analysis was performed by χ2 tests.RESULTS: The eradication rates in groups A,B and C were 90.71%(332/366),90.46%(313/346) and 90.87%(189/208),respectively(P = 0.986). The resistance rates were 8.91% for clarithromycin,14.78% for levofloxacin and 0% for amoxicillin. The eradication rate was significantly different between clarithromycin-and levofloxacin-resistant patients(P < 0.05) in group A. Patients whose treatment failed in group A also had a higher clarithromycin resistance rate than did successive patients(P = 0.034). However,levofloxacin resistance had no obvious influence on the eradication rate. Furthermore,three main antibiotics(clarithromycin,levofloxacin and amoxicillin) had lower DID(defined daily dose per 1000 inhabitants per day) in this city.CONCLUSION: Clarithromycin resistance is the main reason for the failure of 7-d triple therapy. In populations with low levels of resistance,a 7-d triple therapy is a viable choice. The choice of therapy should not be influenced by conditions in high antibiotic resistance regions.
基金Supported by Lishui Science and Technology Bureau Research Fund,No.2013JYZB43Medical and Health Science and Technology Plan Project of Zhejiang Province,No.2015KYB371
文摘AIM To investigate alterations in the fecal microbiome using 16 S r RNA amplicon sequencing in couples in the same cohabitation environment.METHODS Fecal samples were collected from eight ulcerative colitis(UC) patients and their healthy partners at Lishui People's Hospital, Zhejiang Province, China. DNA was extracted and the variable regions V3 and V4 of the 16 S r RNA genes were PCR amplified using a two-step protocol. Clear reads were clustered into operational taxonomic units(OTUs) at the 97% sequence similarity level using UCLUST v1.2.22. The Wilcoxon rank-sumtest(R v3.1.2) was used to compare inter-individual differences. Differences with a P value < 0.05 were considered statistically significant.RESULTS Fecal microbial communities were more similar among UC patients than their healthy partners(P = 0.024). UC individuals had a lower relative abundance of bacteria belonging to the Firmicutes, especially Blautia, Clostridium, Coprococcus and Roseburia(P < 0.05). Microbiota dysbiosis was detected in UC patients and their healthy partners. Relevant genera included Akkermansiam, Bacteroides, Escherichia, Lactobacillales, Klebsiella and Parabacteroides. The enriched pathways in fecal samples of UC patients were related to lipid and nucleotide metabolism. Additionally, the pathways involved in membrane transport and metabolism of cofactors and vitamins were more abundant in the healthy partners.CONCLUSION Our results suggested that the microbial composition might be affected in healthy partners cohabiting with UC patients, especially in terms of microbiota dysbiosis.
文摘Residual thermal stress in the system is a serious problem that affects the application of tritium permeation barrier coatings in fusion reactors. The stress not only determines the adhesion between coating and substrate, but also changes the properties of the material. In this study,finite element analysis was used to investigate the relationship between the residual thermal stress and the mechanical properties of Al_2O_3 tritium penetration barrier systems. Moreover, the residual thermal stress influenced by factors such as different substrates, temperature, and substrate roughness was also analyzed. The calculation showed that the hardness and elastic modulus increased with increasing compressive stress. However, the hardness and elastic modulus decreased with increasing tensile stress. The systems composed of Al_2O_3 coatings and different substrates exhibited different trends in mechanical properties. As the temperature increased, the hardness and the elastic modulus increased in an Al_2O_3/316 L stainless steel system; the trend was opposite in an Al_2O_3/Si system.Apart from this, the roughness of the substrate surface in the system could magnify the change in hardness and elastic modulus of the coating. Results showed that all these factors led to variation in the mechanical properties of Al_2O_3 tritium permeation barrier systems. Thus, thedetailed reasons for the changes in mechanical properties of these materials need to be analyzed.
基金Taizhou Science and Technology Plan Project,No.1701KY20.
文摘BACKGROUND The resistance rate to antibacterial drugs is the key inhibitor of Helicobacter pylori(H.pylori)eradication treatment.AIM To evaluate the prevalence and drug resistance of H.pylori based on big data.METHODS Gastric mucosal specimens were collected from naive patients undergoing upper gastrointestinal endoscopy for H.pylori culture and antimicrobial susceptibility testing(AST),including clarithromycin,levofloxacin,metronidazole and amoxicillin.Every 10 years of age was grouped as an age group.The H.pylori infection and resistance were explored based on the age group and gender.RESULTS The number of H.pylori-positive specimen was 94509 in 283823 gastric mucosal specimens,with an infection rate of 33.30%.The infection rate increased with age,and males had a higher infection rate than females.The average resistance rate of H.pylori to amoxicillin and metronidazole was 0.21%and 93.72%,which remained stable.The average resistance rate to clarithromycin was 23.99%with an increasing trend from 14.43%to 38.24%.The average resistance rate to levofloxacin was 30.29%,which increased from 17.07%to 39.42%and mostly stabilized after 2017.The resistance rate of H.pylori increased with age,except amoxicillin.H.pylori in females are at higher risk of resistance to metronidazole but not to amoxicillin,regardless of the age group.Meanwhile,H.pylori in females are at higher risk of resistance to levofloxacin and clarithromycin in the 21-50 age group.The single,dual,triple and quadruple-drug resistance rate was 54.59%,29.03%,11.71%and 0.11%,respectively.CONCLUSION The resistance of H.pylori in Taizhou city is serious.Guided by the consensus report,individualized treatment based on AST is recommended.
基金supported by the National Key R&D Program of China(Grant Nos.2021YFF0603802 and 2016YFF0200201)。
文摘NIM-Sr2 optical lattice clock has been developed on the Changping campus of National Institute of Metrology(NIM).Considering the limitations in NIM-Sr1,several improved parts have been designed including a differential pumping stage in the vacuum system,a permanent magnet Zeeman slower,water-cooled anti-Helmholtz coils,an extended viewport for Zeeman slower,etc.A clock laser with a short-time stability better than 3×10^(-16)is realized based on a self-designed 30-cm-long ultra-low expansion cavity.The systematic frequency shift has been evaluated to an uncertainty of 7.2×10^(-18),with the uncertainty of BBR shift and the collisional frequency shift being an order of magnitude lower than the last evaluation of NIM-Sr1.
基金supported by the National Key Research Program of China (2018YFB1304500)the National Natural Science Foundation of China (91748202 and 62073041)
文摘Unmanned systems such as legged robots require fast-motion responses for operation in complex envi-ronments.These systems therefore require explosive actuators that can provide high peak speed or high peak torque at specific moments during dynamic motion.Although hydraulic actuators can provide a large force,they are relatively inefficient,large,and heavy.Industrial electric actuators are incapable of providing instant high power.In addition,the constant reduction ratio of the reducer makes it difficult to eliminate the tradeoff between high speed and high torque in a given system.This study proposes an explosive electric actuator and an associated control method for legged robots.First,a high-power-density variable transmission is designed to enable continuous adjustment of the output speed to torque ratio.A heat-dissipating structure based on a composite phase-change material(PCM)is used.An integral torque control method is used to achieve periodic and controllable explosive power output.Jumping experiments are conducted with typical legged robots to verify the effectiveness of the proposed actuator and control method.Single-legged,quadruped,and humanoid robots jumped to heights of 1.5,0.8,and 0.5 m,respectively.These are the highest values reported to date for legged robots powered by electric actuators.
基金Supported by the Medical and Health Science and Technology Plan Project of Zhejiang Province,No.2015KY371the Public Technology Application Research of Zhejiang Province Science and Technology Hall,No.2016C33242
文摘AIM To analyze the bacterial community structure and distribution of intestinal microflora in people with and without metabolic syndrome and combined these data with clinical indicators to determine relationships between selected bacteria and metabolic diseases. METHODS Faecal samples were collected from 20 patients with metabolic syndrome and 16 controls at Cangnan People's Hospital, Zhejiang Province, China. DNA was extracted and the V3-V4 regions of the 16 S rRNA genes were amplified for high throughput sequencing. Clear reads were clustered at the 97% sequence similarity level. α and β diversity were used to describe the bacterial community structure and distribution in patients. Combined with the clinical indicators, further analysis was performed.RESULTS Bacteroidetes, Firmicutes, Actinobacteria, Proteobacteria, Fusobacteria were the dominant phyla, and Prevotella, Bacteroides and Faecalibacterium was the top three genera in faecal samples. α diversity analysis showed that the species richness of metabolic syndrome samples(group D) was significantly higher than the control(group C)(P < 0.05), and the microbial diversity of group C was greater than that of group D. According to the principal co-ordinates analysis, the samples of group C clustered more tightly, indicating that the distribution of bacteria in healthy patients was similar. The correlation analysis showed that alkaline phosphatase was negatively correlated with the abundance of Prevotella(P < 0.05). There was a negative correlation between low-density lipoprotein and the abundance of Ruminococcus(P < 0.05) and a positive correlation between the high-density lipoprotein and the abundance of Ruminococcus(P < 0.05). The total protein and the alanine aminotransferase was positively correlated with the abundance of Peptostreptococcus(P < 0.05). CONCLUSION The changes microbial communities can be used as an indicator of metabolic syndrome, and Prevotella may be a target microorganism in patients with metabolic syndrome.
基金the funding of Chongqing Application and Development Project of China(cstc2014yykfB100007)
文摘To improve the efficiency of iron recovery from steel slag and reduce the wear-and-tear on facilities, a new method was proposed by adding a secondary screen sizer to the magnetic separation process according to grain size distribution of magnetic iron （M-Fe） in the slag. The final recycling efficiency was evaluated by calculating the percentage of recycled M-Fe to the maximum amount of M-Fe that could be recovered. Three types of slags, namely basic oxygen furnace slag, desul- furization slag, and iron ladle slag, were studied, and the results showed that the optimized re- covery efficieneies were 93.20%, 92. 48%, and 85.82% respectively, and the recycling efficien eies were improved by 9.58%, 7.11%, and 6.24% respectively. Furthermore, the abrasion between the mill equipment and the remaining slags was significantly reduced owing to the efficient recovery of larger M-Fe particles. In addition, the using amount of grinding balls was reduced by 0. 46 kg when every 1 t steel slag was processed.
基金supported by National Natural Science Foundation of China(Grant No.12072358)Youth Innovation Promotion Association,Chinese Academy of Sciences(Grant No.2022333)Key Laboratory of Roads and Railway Safety Control(Shijiazhuang Tiedao University),the Ministry of Education(Grant No.STDTKF202103).
文摘Rock slopes are usually reinforced by a number of rock bolts due to the high efficiency and low price.However,where should the rock bolts be installed is still a troublesome issue.For anti-dip bedding rock slopes(ABRSs),the installation position of rock bolts is a controlling factor that determines the reinforcement effect.In this work,a theoretical method is firstly proposed for assessing the stability of ABRSs reinforced by rock bolts using a limit equilibrium model.A comparison of theoretical calculations and numerical results was conducted to test the correctness of the theoretical method.Based on the stability assessment of ABRSs,we introduce adaptive moment estimation method(Adam)to optimize the installation location of rock bolts.Using Adam optimizer,the optimal layout of rock bolts with the maximum factor of safety can be determined,and the factor of safety of the slope increases by about 25%using the same amount of rock bolts but with different installation locations.The proposed method enables the fast stability analysis and supporting design for reinforced ABRSs,which paves the way to smart supporting design of slopes.
基金This work was supported in part by the National Natural Science Foundation of China under Grant 62073041 and 61973039in part by the Beijing Municipal Science and Technology Project under Grant Z221100000222013in part by the“111”Project under Grant B08043.
文摘Whole-body control is beneficial for improving the disturbance adaptation of humanoid robots,since it can simultaneously optimize desired joint torque,joint acceleration,and contact force while considering whole-body dynamics and other physical limits.However,the lack of torque feedback information prevents the position-controlled humanoids from utilizing whole-body control directly,because it enhances the difficulty of guaranteeing desired contact force which is important for maintaining stability.In this paper,a whole-body control that integrates task-space inverse dynamics and variable contact force control is proposed for position-controlled humanoids to enhance the robot’s adaptability toward the unknown disturbance.The task-space inverse dynamics generates the desired joint acceleration and contact force with the consideration of whole-body dynamics and other limits to track the references.The variable contact force control modifies references related to Center of Mass(CoM)and end effectors to ensure reasonable contact force tracking performance,thereby assuring good tracking performance of CoM and momentum to maintain robot stability.Simulations and experiments of balancing and walking under unknown disturbance have been successfully conducted on a position-controlled humanoid robot,BHR-7P3,with the proposed method.
