The impact-abrasive wear behavior of high-C martensitic steel was investigated,taking into account varying carbon(C)contents and different tempering temperatures.The evaluation was done through comprehensive microstru...The impact-abrasive wear behavior of high-C martensitic steel was investigated,taking into account varying carbon(C)contents and different tempering temperatures.The evaluation was done through comprehensive microstructural characterization,analysis of worn surface morphology,and measurement of key performance like impact toughness and surface hardening.The findings demonstrate that increasing C content and tempering temperature both has a positive effect on wear resistance,with C content exhibiting a more pronounced influence compared to the tempering temperature.The improved wear resistance of the steel with higher C content and tempering at a higher temperature can be attributed to its enhanced impact toughness.This increase in impact toughness is primarily a result of microstructural refinement and alterations in carbide morphology.Moreover,cyclic impact loading induces surface hardening due to dislocation strengthening within the martensite and the retained austenite,leading to an increase in surface hardness.The combination of surface hardening and excellent impact toughness synergistically contributes to the overall improved wear resistance observed in the experimental steel with higher C content after tempering at a higher temperature.Additionally,the dominant features observed on the worn surface are scratches and substrate delamination,indicative of a wear mechanism of the experimental steels characterized by micro-cutting/ploughing and fatigue wear.展开更多
The microstructure evolution and properties of medium-carbon cast steel alloyed with different Ni contents after tempering at various temperatures have been investigated.The addition of 0.47-1.59 wt.%Ni content result...The microstructure evolution and properties of medium-carbon cast steel alloyed with different Ni contents after tempering at various temperatures have been investigated.The addition of 0.47-1.59 wt.%Ni content results in the formation of 16%-36% retained austenite(RA).The blocky and irregular-polygonal RA mainly forms along the prior austenite grain boundaries,and the tempering temperature does not affect the RA content.The hardness of medium-carbon cast steel is affected by the precipitation of carbides and the hardness of martensite.Excessive RA content is the main cause of intergranular impact rupture and low impact energy.The long-strip carbides formed after tempering at 320℃ would further reduce the impact energy of medium-carbon cast steel.When tempering at 220 and 380℃,the increase in impact energy is attributed to the formation of rod-like and spherical carbides and the low-carbon martensite.For the medium-carbon cast steel with high impact energy,its impact-abrasive wear resistance is more excellent.Micro-cutting and delamination are the primary wear mechanisms.展开更多
Objective:This cross-sectional study aimed to determine the epidemiology of olfactory and gustatory dysfunctions related to COVID-19 in China.Methods:This study was conducted by 45 tertiary Grade-A hospitals in China....Objective:This cross-sectional study aimed to determine the epidemiology of olfactory and gustatory dysfunctions related to COVID-19 in China.Methods:This study was conducted by 45 tertiary Grade-A hospitals in China.Online and offline questionnaire data were obtained from patients infected with COVID-19 between December 28,2022,and February 21,2023.The collected information included basic demographics,medical history,smoking and drinking history,vaccination history,changes in olfactory and gustatory functions before and after infection,and other postinfection symptoms,as well as the duration and improvement status of olfactory and gustatory disorders.Results:Complete questionnaires were obtained from 35,566 subjects.The overall incidence of olfactory and taste dysfunction was 67.75%.Being female or being a cigarette smoker increased the likelihood of developing olfactory and taste dysfunction.Having received four doses of the vaccine or having good oral health or being a alcohol drinker decreased the risk of such dysfunction.Before infection,the average olfactory and taste VAS scores were 8.41 and 8.51,respectively;after infection,they decreased to 3.69 and 4.29 and recovered to 5.83 and 6.55 by the time of the survey.The median duration of dysosmia and dysgeusia was 15 and 12 days,respectively,with 0.5%of patients having symptoms lasting for more than 28 days.The overall self-reported improvement rate was 59.16%.Recovery was higher in males,never smokers,those who received two or three vaccine doses,and those that had never experienced dental health issues,or chronic accompanying symptoms.Conclusions:The incidence of dysosmia and dysgeusia following infection with the SARS-CoV-2 virus is high in China.Incidence and prognosis are influenced by several factors,including sex,SARS-CoV-2 vaccination,history of head-facial trauma,nasal and oral health status,smoking and drinking history,and the persistence of accompanying symptoms.展开更多
基金supported by Science and Technology Project of Guangzhou(2023A04J0297)Guangdong Basic and Applied Basic Research Foundation(2024A1515011622)+3 种基金National Natural Science Foundation of China(52301040)GDAS’Project of Science and Technology Development(2023GDASQNRC-0205 and 2022GDASZH-2022010107)Evaluation Project of Guangdong Provincial Key Laboratory(2023B1212060043)Young Elite Scientists Sponsorship Program by CAST(2022QNRC001).
文摘The impact-abrasive wear behavior of high-C martensitic steel was investigated,taking into account varying carbon(C)contents and different tempering temperatures.The evaluation was done through comprehensive microstructural characterization,analysis of worn surface morphology,and measurement of key performance like impact toughness and surface hardening.The findings demonstrate that increasing C content and tempering temperature both has a positive effect on wear resistance,with C content exhibiting a more pronounced influence compared to the tempering temperature.The improved wear resistance of the steel with higher C content and tempering at a higher temperature can be attributed to its enhanced impact toughness.This increase in impact toughness is primarily a result of microstructural refinement and alterations in carbide morphology.Moreover,cyclic impact loading induces surface hardening due to dislocation strengthening within the martensite and the retained austenite,leading to an increase in surface hardness.The combination of surface hardening and excellent impact toughness synergistically contributes to the overall improved wear resistance observed in the experimental steel with higher C content after tempering at a higher temperature.Additionally,the dominant features observed on the worn surface are scratches and substrate delamination,indicative of a wear mechanism of the experimental steels characterized by micro-cutting/ploughing and fatigue wear.
基金supported by the National Key Research and Development Program of China(2021YFB3701204)National Natural Science Foundation of China(52001072)+3 种基金National High-End Foreign Expert Project(G2022030064L)Guangdong Province Key Area R&D Program(2020B0101340004)GDAS'Project of Science and Technology Development(2022GDASZH-2022010103)Double Thousand Plan of Jiangxi Province(S2020CXTD0356)。
文摘The microstructure evolution and properties of medium-carbon cast steel alloyed with different Ni contents after tempering at various temperatures have been investigated.The addition of 0.47-1.59 wt.%Ni content results in the formation of 16%-36% retained austenite(RA).The blocky and irregular-polygonal RA mainly forms along the prior austenite grain boundaries,and the tempering temperature does not affect the RA content.The hardness of medium-carbon cast steel is affected by the precipitation of carbides and the hardness of martensite.Excessive RA content is the main cause of intergranular impact rupture and low impact energy.The long-strip carbides formed after tempering at 320℃ would further reduce the impact energy of medium-carbon cast steel.When tempering at 220 and 380℃,the increase in impact energy is attributed to the formation of rod-like and spherical carbides and the low-carbon martensite.For the medium-carbon cast steel with high impact energy,its impact-abrasive wear resistance is more excellent.Micro-cutting and delamination are the primary wear mechanisms.
基金National High Level Hospital Clinical Research Funding,Grant/Award Number:2022-NHLHCRF-YGJE-02Natural Science Foundation of Beijing Municipality,Grant/Award Number:7212090。
文摘Objective:This cross-sectional study aimed to determine the epidemiology of olfactory and gustatory dysfunctions related to COVID-19 in China.Methods:This study was conducted by 45 tertiary Grade-A hospitals in China.Online and offline questionnaire data were obtained from patients infected with COVID-19 between December 28,2022,and February 21,2023.The collected information included basic demographics,medical history,smoking and drinking history,vaccination history,changes in olfactory and gustatory functions before and after infection,and other postinfection symptoms,as well as the duration and improvement status of olfactory and gustatory disorders.Results:Complete questionnaires were obtained from 35,566 subjects.The overall incidence of olfactory and taste dysfunction was 67.75%.Being female or being a cigarette smoker increased the likelihood of developing olfactory and taste dysfunction.Having received four doses of the vaccine or having good oral health or being a alcohol drinker decreased the risk of such dysfunction.Before infection,the average olfactory and taste VAS scores were 8.41 and 8.51,respectively;after infection,they decreased to 3.69 and 4.29 and recovered to 5.83 and 6.55 by the time of the survey.The median duration of dysosmia and dysgeusia was 15 and 12 days,respectively,with 0.5%of patients having symptoms lasting for more than 28 days.The overall self-reported improvement rate was 59.16%.Recovery was higher in males,never smokers,those who received two or three vaccine doses,and those that had never experienced dental health issues,or chronic accompanying symptoms.Conclusions:The incidence of dysosmia and dysgeusia following infection with the SARS-CoV-2 virus is high in China.Incidence and prognosis are influenced by several factors,including sex,SARS-CoV-2 vaccination,history of head-facial trauma,nasal and oral health status,smoking and drinking history,and the persistence of accompanying symptoms.
