Microstructural evolution and phase transformation induced by different heat treatments of the hypereutectic aluminium-silicon alloy, Al-25Si-5Fe-3Cu （wt%, signed as 3C）, fabricated by traditional cast （TC） and sp...Microstructural evolution and phase transformation induced by different heat treatments of the hypereutectic aluminium-silicon alloy, Al-25Si-5Fe-3Cu （wt%, signed as 3C）, fabricated by traditional cast （TC） and spray forming （SF） processes, were investigated by differential scanning calorimetry （DSC） and scanning electron microscopy （SEM） combined with energy dispersive X-ray spectroscopy and X-ray diffraction techniques. The results show that A17Cu2Fe phase can be formed and transformed in TC- and SF-3C alloys between 802-813 K and 800-815 K, respectively. The transformation from β-Al5FeSi to δ-Al4FeSi2 phase via peritectic reaction can occur at around 858-870 K and 876-890 K in TC- and SF-3C alloys, respectively. The starting precipitation temperature of δ-Al4FeSi2 phase as the dominant Fe-bearing phase in the TC-3C alloy is 997 K and the exothermic peak about the peritectic transformation of δ-Al4FeSi2→β-Al5FeSi is not detected in the present DSC experiments. Also, the mechanisms of the microstructural evolution and phase transformation are discussed.展开更多
Objectives To investigate the overall prevalence of cardiovascular disease （CVD） in subjects hospitalized for chronic obstructive pulmonary disease （COPD）,and explore the prevalence of the major CVD complications ...Objectives To investigate the overall prevalence of cardiovascular disease （CVD） in subjects hospitalized for chronic obstructive pulmonary disease （COPD）,and explore the prevalence of the major CVD complications and trends in patients with COPD over a 10-year period.Methods Medical records in the PLA General Hospital,Beijing Union Medical College Hospital,and Beijing Hospital from 2000/01/01 to 2010/03/03 were retrospectively reviewed.A total of 4960 patients with COPD were reviewed in the study （3570 males,mean age,72.2 ± 10.5 years; 1390 females,mean age,72.0 ± 10.4 years）.Results The prevalence of CVD in COPD patients was 51.7％.The three most prevalent CVDs were ischemic heart disease （28.9％）,heart failure （19.6％）,and arrhythmia （12.6％）.During the 10-year study period,the prevalence of various CVDs in COPD patients showed a gradual increasing trend with increasing age.There was higher morbidity due to ischemic heart disease （P ＜ 0.01） in male COPD patients than in the female counterparts.However,heart failure （P ＜ 0.01）and hypertension （P ＜ 0.01） occurred less frequently in male COPD patients than in female COPD patients.Furthermore,the prevalence of ischemic heart disease decreased year by year.In addition to heart failure,various types of CVD complications in COPD patients tended to occur in younger subjects.The prevalence of all major types of CVD in women tended to increase year by year.Conclusions The prevalence of CVD in patients hospitalized for COPD in Beijing was high.Age,sex and CVD trends,as well as life style changes,should be considered when prevention and control strategies are formulated.展开更多
The microstructural evolution and phase transformations of a high-alloyed Al-Zn-Mg-Cu alloy （Al-8.59Zn-2.00Mg-2.44Cu,wt%） during homogenization were investigated. The results show that the as-cast microstructure mai...The microstructural evolution and phase transformations of a high-alloyed Al-Zn-Mg-Cu alloy （Al-8.59Zn-2.00Mg-2.44Cu,wt%） during homogenization were investigated. The results show that the as-cast microstructure mainly contains dendritic α（Al）, non-equilibrium eutectics （α（Al） ＋ Mg（Zn,Al,Cu）2）, and the θ （Al2Cu） phase. Neither the T （Al2Mg3Zn3） phase nor the S （Al2CuMg） phase was found in the as-cast alloy. The calculated phase components according to the Scheil model are in agreement with experimental results. During homogenization at 460℃, all of the θ phase and most of the Mg（Zn,Al,Cu）2 phase were dissolved, whereas a portion of the Mg（Zn,Al,Cu）2 phase was transformed into the S phase. The type and amount of residual phases remaining after homogenization at 460℃ for 168 h and by a two-step homogenization process conducted at 460℃ for 24 h and 475℃ for 24 h （460℃/24 h ＋ 475℃/24 h） are in good accord with the calculated phase diagrams. It is concluded that the Al-8.59Zn-2.00Mg-2.44Cu alloy can be homogenized adequately under the 460℃/24 h ＋ 475℃/24 h treatment.展开更多
Nanocrystalline NiCrC alloy powders with a qualified particle size distribution for thermal spraying were synthesized using the cryogenic ball milling （cryomilling） method. The morphology, microstructure, size distr...Nanocrystalline NiCrC alloy powders with a qualified particle size distribution for thermal spraying were synthesized using the cryogenic ball milling （cryomilling） method. The morphology, microstructure, size distribution, and phase transformation of the powders were characterized by scanning electron microscopy （SEM）, laser scattering for particle size analysis, X-ray diffraction （XRD）, and transmission electron microscopy （TEM）. After cryomilling for 20 h, the average grain size of the as-milled powders approached a constant value of 30 nm by XRD measurement. The average particle size slightly increased from 17.5 to 20.3 μm during the 20-h milling. About 90vol% of the powders satisfied the requirement for thermal spraying with the particle dimension of 10-50 μm, and most of the powders exhibited spherical morphology, which were expected to have good fluidity during thermal spraying. The Cr2O3 phase formed during the cryornilling process as revealed in the XRD spectra, which was expected to enhance the thermal stability of the as-milled powders during the followed thermal spraying or other heat treatment.展开更多
The cylindrical billets of a Mg-3Al-1Zn （AZ31） alloy were synthesized by spray deposition processing. The microstructure evolution and mechanical properties of the alloy were investigated. The results reveal that th...The cylindrical billets of a Mg-3Al-1Zn （AZ31） alloy were synthesized by spray deposition processing. The microstructure evolution and mechanical properties of the alloy were investigated. The results reveal that the microstructure of the AZ31 alloy is refined significantly by spray deposition processing. A homogeneous and equiaxial-grain structure with an average grain size of 17 μm is obtained. Further grain refinement with an average grain size of 5 μm is attributed to dynamic recrystallization during extrusion processing. The great increase in the density of grain boundary nucleation sites by the finer initial grain sizes makes the dislocation pile-ups near subgrain boundaries being absorbed easily by the boundaries, resulting in an accelerated recrystallization process. The average tensile ultimate and yield strengths of the extruded rods are 321 MPa and 237 MPa, respectively, with an elongation of 15.2% at room temperature, which are remarkably higher than those of the conventional as-cast AZ31 alloy.展开更多
Bulk nanocrystalline Al was fabricated by mechanically milling at cryogenic temperature （cryomilling） and then by hot pressing in vacuum. By using X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and...Bulk nanocrystalline Al was fabricated by mechanically milling at cryogenic temperature （cryomilling） and then by hot pressing in vacuum. By using X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM）, the microstructure evolution of the material during cryomilling and consolidation was investigated. With increasing the milling time, the grain size decreased sharply and reduced to 42 nm when cryomilled for 12 h. The grains had grown up, and the columnar grain was formed under the hot pressing and extrusion compared with the cryomilled powders. The grain size of as-extruded specimen was approximately 300-500 nm. The reason of high thermal stability of this bulk was attributed primarily to the Zener pinning from the grain boundary of the AlN arising from cryomilling and the solute drag of the impurity. Tensile tests show that the strength of nanocrystalline Al is enhanced with decreasing grain size. The ultimate tensile strength and tensile elongation were 173 MPa and 17.5%, respectively. It appears that the measured high strength in the cryomilled Al is related to a grain-size effect, dispersion strengthening, and dislocation strengthening.展开更多
Hot deformation behavior of a new type of M3∶ 2 high speed steel with niobium addition made by spray forming was investigated based on compression tests in the temperature range of 950-1 150 ℃ and strain rate of 0. ...Hot deformation behavior of a new type of M3∶ 2 high speed steel with niobium addition made by spray forming was investigated based on compression tests in the temperature range of 950-1 150 ℃ and strain rate of 0. 001-10 s^（-1）. A comprehensive constitutive equation was obtained,which could be used to predict the flow stress at different strains. Processing map was developed on the basis of the flow stress data using the principles of dynamic material model. The results showed that the flow curves were in fair agreement with the dynamic recrystallization model. The flow stresses,which were calculated by the comprehensive constitutive equation,agreed well with the test data at low strain rates（ ≤1 s^（-1））. The material constant（ α）,stress exponent（ n） and the hot deformation activation energy（ Q_（HW）） of the new steel were 0. 006 15 MPa^（-1）,4. 81 and 546 kJ·mol^（-1）,respectively. Analysis of the processing map with an observation of microstructures revealed that hot working processes of the steel could be carried out safely in the domain（ T = 1 050-1 150 ℃,ε = 0. 01- 0. 1 s^（-1））with about 33% peak efficiency of power dissipation（ η）. Cracks was expected in two domains at either lower temperatures（ 〈 1 000 ℃） or low strain rates（ 0. 001 s^（-1）） with different cracking mechanisms. Flow localization occurred when the strain rates exceeded 1 s^（-1） at all testing temperatures.展开更多
探究土地利用多功能性的变化情况及障碍影响因素,是优化区域土地合理开发、提高土地利用效率的方式,对实现区域土地的可持续利用具有重要意义。文章以广西作为研究对象,构建经济、社会和生态三维指标体系,结合熵权TOPSIS(Technique for ...探究土地利用多功能性的变化情况及障碍影响因素,是优化区域土地合理开发、提高土地利用效率的方式,对实现区域土地的可持续利用具有重要意义。文章以广西作为研究对象,构建经济、社会和生态三维指标体系,结合熵权TOPSIS(Technique for Order Preference by Similarity to Ideal Solution)模型和障碍度模型,综合评价分析广西2010-2021年土地利用多功能性变化状况和障碍影响因素。研究表明:广西土地利用综合功能呈上升趋势,综合功能整体在不断优化。经济功能和社会功能呈现逐年上升的趋势,发展至良好阶段,生态功能在研究期间呈波动下降的趋势。经济功能和社会功能障碍度逐年降低,生态功能障碍度波动上升,从发展阶段特征来看,影响广西土地利用多功能性发挥的因素逐渐由经济社会型向经济生态型转变。展开更多
Objectives To investigate clinical characteristics, target organ damage, and the associated risk factors of the patients aged ≥ 80 yearswith true resistant hypertension （RH）. Methods Patients aged ≥ 80 years with ...Objectives To investigate clinical characteristics, target organ damage, and the associated risk factors of the patients aged ≥ 80 yearswith true resistant hypertension （RH）. Methods Patients aged ≥ 80 years with hypertension （n = 1163） were included in this study. Theincluded participants attended a structured clinical examination and an evaluation of RH was carried out. The prevalence, clinical characteristicsand target organ damage of patients with RH were assessed. The associated clinical risk factors were analyzed by using logistic regression.Results The prevalence of RH diagnosis by 24-h ambulatory blood pressure monitoring assessment was 21.15%. End-diastolic left ven-tricular internal dimension, left ventricular mass index as well as prevalence of left ventricular hypertrophy were significantly greater in pa-tients with RH than in control group. The common carotid artery intimal media thickness, carotid walls thickness, common carotid arterydiameter and relative wall thickness were significant greater in RH group than in control. A relatively higher level of creatinine, estimatedglomerular filtration rate, microalbuminuria and retinal changes was found in RIt group than in control. A multivariate analysis showed thatpatients with a history of diabetes, higher body mass index （BMI） and lipid profiles were independent risk factors of RH. Conclusions Theprevalence of RH in patients aged ≥ 80 years was within the range of reported rates of the general population. Subjects with RH diagnosisshowed a higher occurrence of target organ damage than patients with well controlled blood pressure. Patients with diabetes, higher BMI andserum lipid profiles were independent risk factors for RH in patients aged ≥ 80 years.展开更多
The influence of InAs deposition thickness on the structural and optical properties of InAs/InA1As quantum wires （QWR） superlattices （SLS） was studied. The transmission electron microscopy （TEM） results show tha...The influence of InAs deposition thickness on the structural and optical properties of InAs/InA1As quantum wires （QWR） superlattices （SLS） was studied. The transmission electron microscopy （TEM） results show that with increasing the InAs deposited thickness, the size uniformity and spatial ordering of InAs QWR SLS was greatly improved, but threading dislocations initiated from InAs nanowires for the sample with 6 monolayers （MLs） InAs deposition. In addition, the zig-zag features along the extending direc- tion and lateral interlink of InAs nanowires were also observed. The InAs nanowires, especially for the first period, were laterally compact. These structural features may result in easy tunneling and coupling of charge carders between InAs nanowires and will hamper their device applications to some extent. Some suggestions are put forward for further improving the uniformity of the stacked InAs QWRs, and for suppressing the formation of the threading dislocations in InAs QWR SLS.展开更多
The main agronomic traits,economic traits,appearance quality,main chemical components,gas composition and physical parameters of 10 flue cured tobacco varieties were investigated in the experiment.And the field natura...The main agronomic traits,economic traits,appearance quality,main chemical components,gas composition and physical parameters of 10 flue cured tobacco varieties were investigated in the experiment.And the field natural incidence of the main diseases was investigated.The results showed that main agronomic characters of the 10 varieties were in line with the breeding objectives,among which 5 varieties have good economic characters;5 varieties have good appearance quality;6 varieties have coordinated chemical composition and high potassium content;9 varieties have good smoke components and physical indicators.展开更多
Owing to their limited accuracy and narrow applicability,current antimicrobial peptide(AMP)prediction models face obstacles in industrial application.To address these limitations,we developed and improved an AMP predi...Owing to their limited accuracy and narrow applicability,current antimicrobial peptide(AMP)prediction models face obstacles in industrial application.To address these limitations,we developed and improved an AMP prediction model using Comparing and Optimizing Multiple DEep Learning(COMDEL)algorithms,coupled with high-throughput AMP screening method,finally reaching an accuracy of 94.8%in test and 88%in experiment verification,surpassing other state-of-the-art models.In conjunction with COMDEL,we employed the phage-assisted evolution method to screen Sortase in vivo and developed a cell-free AMP synthesis system in vitro,ultimately increasing AMPs yields to a range of 0.5-2.1 g/L within hours.Moreover,by multi-omics analysis using COMDEL,we identified Lactobacillus plantarum as the most promising candidate for AMP generation among 35 edible probiotics.Following this,we developed a microdroplet sorting approach and successfully screened three L.plantarum mutants,each showing a twofold increase in antimicrobial ability,underscoring their substantial industrial application values.展开更多
Acute myocardial infarction(AMI)represents a leading cause of death globally.Key to AMI recovery is timely diagnosis and initiation of treatment,ideally within 3 h of symptom onset.Cardiac troponin T(cTnT)is the gold ...Acute myocardial infarction(AMI)represents a leading cause of death globally.Key to AMI recovery is timely diagnosis and initiation of treatment,ideally within 3 h of symptom onset.Cardiac troponin T(cTnT)is the gold standard yet a low cTnT result cannot rule out AMI at early times.Here,we develop a three-biomarker joint strategy for early and accurate diagnosis of AMI via an electrochemiluminescence(ECL)immunoarray coupled with robust machine learning.The ECL immunoarray is based on an array microchip with a singleelectrode and chemiluminescent immuno-Gold(ciGold)nanoassemblies.The ciGold immunoarray was obtained by successively assembling nanocomposites of Cu^(2+)/cysteine complexes and N-(aminobutyl)-N-(ethylisoluminol)bifunctionalized gold nanoparticles combined with chitosan and antibody conjugated gold nanoparticles on the surface of a microchip.Three biomarkers,including cardiac troponin I,heart type fatty acid binding protein,and copeptin,were simultaneously detected in 260 serum samples from patients presenting with chest pain by an innovative multiplexed ECL immunoarray,and classified via the three-biomarker joint assessment model using support vector machines.The model achieved perfect discrimination(100%sensitivity and specificity)for AMI vs non-AMI patients,substantially higher than cTnT alone.Within 12 h of symptom onset,high-sensitivity cardiac troponin T(hs-cTnT)misclassified>20%of patients,while the joint biomarker assessment model retained perfect accuracy.As the time between symptom onset and testing became shorter,the degree to which the joint assessment model outperformed hs-cTnT increased.The proposed threebiomarker joint strategy is obviously superior to hs-cTnT for early and accurate diagnosis of AMI,hopefully reducing AMI mortality and saving limited medical resources.展开更多
Purpose:This article was intended to share and reflect on experiences concerning the education for sustainable development(ESD)project at Hongqiao Kindergarten in Shanghai.The project aimed to explore how ESD could be...Purpose:This article was intended to share and reflect on experiences concerning the education for sustainable development(ESD)project at Hongqiao Kindergarten in Shanghai.The project aimed to explore how ESD could be implemented in a current curriculum and to provide useful examples of educational activities and experiences.Design/Approach/Methods:The action research included two cycles with four steps.The first cycle involved the integration of ESD into a traditional science curriculum.The second cycle involved the validation and optimization of the ESD objectives.The implementation strategies were reviewed and refined.Findings:First,a variety of strategies can be used to identify the theme and choose the content.Second,the objectives should be developed on children’s life experiences and interests.Third,the idea of ESD can be implemented in multiple ways.Fourth,a reasonable objective system involving ESD was constructed for children by ages.Fifth,there were many effective ways to integrate ESD activities into other domains of curriculum.The challenges and implications were also discussed.Originality/Value:The study had a positive effect on teachers’ability to practice ESD.This was a pioneer project in early childhood education in China,which provided valuable information for those aiming to implement ESD practices in Chinese kindergartens.展开更多
In this work,highly chemiluminescent magnetic mesoporous carbon with yolk-shell structure was synthesized by encapsulating N-(4-aminobutyl)-N-ethylisoluminol(ABEI)and Co^(2+)into the magnetic mesoporous carbon composi...In this work,highly chemiluminescent magnetic mesoporous carbon with yolk-shell structure was synthesized by encapsulating N-(4-aminobutyl)-N-ethylisoluminol(ABEI)and Co^(2+)into the magnetic mesoporous carbon composites(Co^(2+)-ABEI-Fe_3O_4@void@C).The synthetic Co^(2+)-ABEI-Fe_3O_4@void@C showed a good magnetic separation property,which could remove residual ABEI molecules and Co^(2+)in less than 3 min under an external magnet.Moreover,the synthetic Co^(2+)-ABEI-Fe_3O_4@void@C demonstrated good chemiluminescence(CL)property and good stability when interacted with alkaline H_2O_2solution.The CL intensity of such Co^(2+)-ABEI-Fe_3O_4@void@C was about 120 times higher than that of ABEI-Fe_3O_4@void@C.The Co^(2+)-ABEI-Fe_3O_4@void@C also exhibited good electrochemiluminescence(ECL)property in alkaline solution.The outstanding CL/ECL performance of the Co^(2+)-ABEI-Fe_3O_4@void@C was attributed to the Co^(2+)immobilized in the Co^(2+)-ABEI-Fe_3O_4@void@C,which catalyzed the decomposition of H_2O_2to generate O_2^(·-)and HO~·,expediting the CL/ECL reaction.The synthetic Co^(2+)-ABEI-Fe_3O_4@void@C may be of great application for the development of new methodologies in bioanalysis.展开更多
基金supported by the Major State Basic Research & Development Program of China (No2006CB605204)
文摘Microstructural evolution and phase transformation induced by different heat treatments of the hypereutectic aluminium-silicon alloy, Al-25Si-5Fe-3Cu （wt%, signed as 3C）, fabricated by traditional cast （TC） and spray forming （SF） processes, were investigated by differential scanning calorimetry （DSC） and scanning electron microscopy （SEM） combined with energy dispersive X-ray spectroscopy and X-ray diffraction techniques. The results show that A17Cu2Fe phase can be formed and transformed in TC- and SF-3C alloys between 802-813 K and 800-815 K, respectively. The transformation from β-Al5FeSi to δ-Al4FeSi2 phase via peritectic reaction can occur at around 858-870 K and 876-890 K in TC- and SF-3C alloys, respectively. The starting precipitation temperature of δ-Al4FeSi2 phase as the dominant Fe-bearing phase in the TC-3C alloy is 997 K and the exothermic peak about the peritectic transformation of δ-Al4FeSi2→β-Al5FeSi is not detected in the present DSC experiments. Also, the mechanisms of the microstructural evolution and phase transformation are discussed.
文摘Objectives To investigate the overall prevalence of cardiovascular disease （CVD） in subjects hospitalized for chronic obstructive pulmonary disease （COPD）,and explore the prevalence of the major CVD complications and trends in patients with COPD over a 10-year period.Methods Medical records in the PLA General Hospital,Beijing Union Medical College Hospital,and Beijing Hospital from 2000/01/01 to 2010/03/03 were retrospectively reviewed.A total of 4960 patients with COPD were reviewed in the study （3570 males,mean age,72.2 ± 10.5 years; 1390 females,mean age,72.0 ± 10.4 years）.Results The prevalence of CVD in COPD patients was 51.7％.The three most prevalent CVDs were ischemic heart disease （28.9％）,heart failure （19.6％）,and arrhythmia （12.6％）.During the 10-year study period,the prevalence of various CVDs in COPD patients showed a gradual increasing trend with increasing age.There was higher morbidity due to ischemic heart disease （P ＜ 0.01） in male COPD patients than in the female counterparts.However,heart failure （P ＜ 0.01）and hypertension （P ＜ 0.01） occurred less frequently in male COPD patients than in female COPD patients.Furthermore,the prevalence of ischemic heart disease decreased year by year.In addition to heart failure,various types of CVD complications in COPD patients tended to occur in younger subjects.The prevalence of all major types of CVD in women tended to increase year by year.Conclusions The prevalence of CVD in patients hospitalized for COPD in Beijing was high.Age,sex and CVD trends,as well as life style changes,should be considered when prevention and control strategies are formulated.
基金supported by the Fundamental Research Funds for the Central Universities of China (No. FRF-TD-12-001)the Beijing Laboratory of Modern Traffic Metal Materials and Processing Technology
文摘The microstructural evolution and phase transformations of a high-alloyed Al-Zn-Mg-Cu alloy （Al-8.59Zn-2.00Mg-2.44Cu,wt%） during homogenization were investigated. The results show that the as-cast microstructure mainly contains dendritic α（Al）, non-equilibrium eutectics （α（Al） ＋ Mg（Zn,Al,Cu）2）, and the θ （Al2Cu） phase. Neither the T （Al2Mg3Zn3） phase nor the S （Al2CuMg） phase was found in the as-cast alloy. The calculated phase components according to the Scheil model are in agreement with experimental results. During homogenization at 460℃, all of the θ phase and most of the Mg（Zn,Al,Cu）2 phase were dissolved, whereas a portion of the Mg（Zn,Al,Cu）2 phase was transformed into the S phase. The type and amount of residual phases remaining after homogenization at 460℃ for 168 h and by a two-step homogenization process conducted at 460℃ for 24 h and 475℃ for 24 h （460℃/24 h ＋ 475℃/24 h） are in good accord with the calculated phase diagrams. It is concluded that the Al-8.59Zn-2.00Mg-2.44Cu alloy can be homogenized adequately under the 460℃/24 h ＋ 475℃/24 h treatment.
基金supported by the National High-Tech Research and Development Program of China (No.2002AA331080)
文摘Nanocrystalline NiCrC alloy powders with a qualified particle size distribution for thermal spraying were synthesized using the cryogenic ball milling （cryomilling） method. The morphology, microstructure, size distribution, and phase transformation of the powders were characterized by scanning electron microscopy （SEM）, laser scattering for particle size analysis, X-ray diffraction （XRD）, and transmission electron microscopy （TEM）. After cryomilling for 20 h, the average grain size of the as-milled powders approached a constant value of 30 nm by XRD measurement. The average particle size slightly increased from 17.5 to 20.3 μm during the 20-h milling. About 90vol% of the powders satisfied the requirement for thermal spraying with the particle dimension of 10-50 μm, and most of the powders exhibited spherical morphology, which were expected to have good fluidity during thermal spraying. The Cr2O3 phase formed during the cryornilling process as revealed in the XRD spectra, which was expected to enhance the thermal stability of the as-milled powders during the followed thermal spraying or other heat treatment.
基金supported by the Cultivation Fund of the Key Scientific and Technical Innovation Project, the Ministry of Education of China
文摘The cylindrical billets of a Mg-3Al-1Zn （AZ31） alloy were synthesized by spray deposition processing. The microstructure evolution and mechanical properties of the alloy were investigated. The results reveal that the microstructure of the AZ31 alloy is refined significantly by spray deposition processing. A homogeneous and equiaxial-grain structure with an average grain size of 17 μm is obtained. Further grain refinement with an average grain size of 5 μm is attributed to dynamic recrystallization during extrusion processing. The great increase in the density of grain boundary nucleation sites by the finer initial grain sizes makes the dislocation pile-ups near subgrain boundaries being absorbed easily by the boundaries, resulting in an accelerated recrystallization process. The average tensile ultimate and yield strengths of the extruded rods are 321 MPa and 237 MPa, respectively, with an elongation of 15.2% at room temperature, which are remarkably higher than those of the conventional as-cast AZ31 alloy.
基金This work was financially supported by the National High-Tech Research and Development Program of China ("863" Program) (No.2002AA302502)
文摘Bulk nanocrystalline Al was fabricated by mechanically milling at cryogenic temperature （cryomilling） and then by hot pressing in vacuum. By using X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM）, the microstructure evolution of the material during cryomilling and consolidation was investigated. With increasing the milling time, the grain size decreased sharply and reduced to 42 nm when cryomilled for 12 h. The grains had grown up, and the columnar grain was formed under the hot pressing and extrusion compared with the cryomilled powders. The grain size of as-extruded specimen was approximately 300-500 nm. The reason of high thermal stability of this bulk was attributed primarily to the Zener pinning from the grain boundary of the AlN arising from cryomilling and the solute drag of the impurity. Tensile tests show that the strength of nanocrystalline Al is enhanced with decreasing grain size. The ultimate tensile strength and tensile elongation were 173 MPa and 17.5%, respectively. It appears that the measured high strength in the cryomilled Al is related to a grain-size effect, dispersion strengthening, and dislocation strengthening.
基金Item Sponsored by National Basic Research Program of China(2011CB606303)Constructed Project for Key Laboratory of Beijing of China
文摘Hot deformation behavior of a new type of M3∶ 2 high speed steel with niobium addition made by spray forming was investigated based on compression tests in the temperature range of 950-1 150 ℃ and strain rate of 0. 001-10 s^（-1）. A comprehensive constitutive equation was obtained,which could be used to predict the flow stress at different strains. Processing map was developed on the basis of the flow stress data using the principles of dynamic material model. The results showed that the flow curves were in fair agreement with the dynamic recrystallization model. The flow stresses,which were calculated by the comprehensive constitutive equation,agreed well with the test data at low strain rates（ ≤1 s^（-1））. The material constant（ α）,stress exponent（ n） and the hot deformation activation energy（ Q_（HW）） of the new steel were 0. 006 15 MPa^（-1）,4. 81 and 546 kJ·mol^（-1）,respectively. Analysis of the processing map with an observation of microstructures revealed that hot working processes of the steel could be carried out safely in the domain（ T = 1 050-1 150 ℃,ε = 0. 01- 0. 1 s^（-1））with about 33% peak efficiency of power dissipation（ η）. Cracks was expected in two domains at either lower temperatures（ 〈 1 000 ℃） or low strain rates（ 0. 001 s^（-1）） with different cracking mechanisms. Flow localization occurred when the strain rates exceeded 1 s^（-1） at all testing temperatures.
文摘探究土地利用多功能性的变化情况及障碍影响因素,是优化区域土地合理开发、提高土地利用效率的方式,对实现区域土地的可持续利用具有重要意义。文章以广西作为研究对象,构建经济、社会和生态三维指标体系,结合熵权TOPSIS(Technique for Order Preference by Similarity to Ideal Solution)模型和障碍度模型,综合评价分析广西2010-2021年土地利用多功能性变化状况和障碍影响因素。研究表明:广西土地利用综合功能呈上升趋势,综合功能整体在不断优化。经济功能和社会功能呈现逐年上升的趋势,发展至良好阶段,生态功能在研究期间呈波动下降的趋势。经济功能和社会功能障碍度逐年降低,生态功能障碍度波动上升,从发展阶段特征来看,影响广西土地利用多功能性发挥的因素逐渐由经济社会型向经济生态型转变。
文摘Objectives To investigate clinical characteristics, target organ damage, and the associated risk factors of the patients aged ≥ 80 yearswith true resistant hypertension （RH）. Methods Patients aged ≥ 80 years with hypertension （n = 1163） were included in this study. Theincluded participants attended a structured clinical examination and an evaluation of RH was carried out. The prevalence, clinical characteristicsand target organ damage of patients with RH were assessed. The associated clinical risk factors were analyzed by using logistic regression.Results The prevalence of RH diagnosis by 24-h ambulatory blood pressure monitoring assessment was 21.15%. End-diastolic left ven-tricular internal dimension, left ventricular mass index as well as prevalence of left ventricular hypertrophy were significantly greater in pa-tients with RH than in control group. The common carotid artery intimal media thickness, carotid walls thickness, common carotid arterydiameter and relative wall thickness were significant greater in RH group than in control. A relatively higher level of creatinine, estimatedglomerular filtration rate, microalbuminuria and retinal changes was found in RIt group than in control. A multivariate analysis showed thatpatients with a history of diabetes, higher body mass index （BMI） and lipid profiles were independent risk factors of RH. Conclusions Theprevalence of RH in patients aged ≥ 80 years was within the range of reported rates of the general population. Subjects with RH diagnosisshowed a higher occurrence of target organ damage than patients with well controlled blood pressure. Patients with diabetes, higher BMI andserum lipid profiles were independent risk factors for RH in patients aged ≥ 80 years.
基金Special Funds for Major State Basic Research Project of China (No.G2000068303)Na-tional Natural Science Foundation of China (No.60390074, 60390071, 90101004)National High-Tech Research and Develop-ment Program of China (No.2002AA311070).
文摘The influence of InAs deposition thickness on the structural and optical properties of InAs/InA1As quantum wires （QWR） superlattices （SLS） was studied. The transmission electron microscopy （TEM） results show that with increasing the InAs deposited thickness, the size uniformity and spatial ordering of InAs QWR SLS was greatly improved, but threading dislocations initiated from InAs nanowires for the sample with 6 monolayers （MLs） InAs deposition. In addition, the zig-zag features along the extending direc- tion and lateral interlink of InAs nanowires were also observed. The InAs nanowires, especially for the first period, were laterally compact. These structural features may result in easy tunneling and coupling of charge carders between InAs nanowires and will hamper their device applications to some extent. Some suggestions are put forward for further improving the uniformity of the stacked InAs QWRs, and for suppressing the formation of the threading dislocations in InAs QWR SLS.
文摘The main agronomic traits,economic traits,appearance quality,main chemical components,gas composition and physical parameters of 10 flue cured tobacco varieties were investigated in the experiment.And the field natural incidence of the main diseases was investigated.The results showed that main agronomic characters of the 10 varieties were in line with the breeding objectives,among which 5 varieties have good economic characters;5 varieties have good appearance quality;6 varieties have coordinated chemical composition and high potassium content;9 varieties have good smoke components and physical indicators.
基金supported by a grant from the Hubei University of Science and Technology Program(No.BK202417,China)Doctoral Special Research Fund Launch Project of Jiamusi University(JMSUBZ2021-12,China)Youth Innovative Talent Cultivation Support Plan of Jiamusi University(JMSUQP2022016,China)。
文摘Owing to their limited accuracy and narrow applicability,current antimicrobial peptide(AMP)prediction models face obstacles in industrial application.To address these limitations,we developed and improved an AMP prediction model using Comparing and Optimizing Multiple DEep Learning(COMDEL)algorithms,coupled with high-throughput AMP screening method,finally reaching an accuracy of 94.8%in test and 88%in experiment verification,surpassing other state-of-the-art models.In conjunction with COMDEL,we employed the phage-assisted evolution method to screen Sortase in vivo and developed a cell-free AMP synthesis system in vitro,ultimately increasing AMPs yields to a range of 0.5-2.1 g/L within hours.Moreover,by multi-omics analysis using COMDEL,we identified Lactobacillus plantarum as the most promising candidate for AMP generation among 35 edible probiotics.Following this,we developed a microdroplet sorting approach and successfully screened three L.plantarum mutants,each showing a twofold increase in antimicrobial ability,underscoring their substantial industrial application values.
基金support of this research by the National Key Research and Development Program of China(Grant No.2016YFA0201300)the National Natural Science Foundation of China(Grant Nos.21874122 and 21527807)are gratefully acknowledged.
文摘Acute myocardial infarction(AMI)represents a leading cause of death globally.Key to AMI recovery is timely diagnosis and initiation of treatment,ideally within 3 h of symptom onset.Cardiac troponin T(cTnT)is the gold standard yet a low cTnT result cannot rule out AMI at early times.Here,we develop a three-biomarker joint strategy for early and accurate diagnosis of AMI via an electrochemiluminescence(ECL)immunoarray coupled with robust machine learning.The ECL immunoarray is based on an array microchip with a singleelectrode and chemiluminescent immuno-Gold(ciGold)nanoassemblies.The ciGold immunoarray was obtained by successively assembling nanocomposites of Cu^(2+)/cysteine complexes and N-(aminobutyl)-N-(ethylisoluminol)bifunctionalized gold nanoparticles combined with chitosan and antibody conjugated gold nanoparticles on the surface of a microchip.Three biomarkers,including cardiac troponin I,heart type fatty acid binding protein,and copeptin,were simultaneously detected in 260 serum samples from patients presenting with chest pain by an innovative multiplexed ECL immunoarray,and classified via the three-biomarker joint assessment model using support vector machines.The model achieved perfect discrimination(100%sensitivity and specificity)for AMI vs non-AMI patients,substantially higher than cTnT alone.Within 12 h of symptom onset,high-sensitivity cardiac troponin T(hs-cTnT)misclassified>20%of patients,while the joint biomarker assessment model retained perfect accuracy.As the time between symptom onset and testing became shorter,the degree to which the joint assessment model outperformed hs-cTnT increased.The proposed threebiomarker joint strategy is obviously superior to hs-cTnT for early and accurate diagnosis of AMI,hopefully reducing AMI mortality and saving limited medical resources.
文摘Purpose:This article was intended to share and reflect on experiences concerning the education for sustainable development(ESD)project at Hongqiao Kindergarten in Shanghai.The project aimed to explore how ESD could be implemented in a current curriculum and to provide useful examples of educational activities and experiences.Design/Approach/Methods:The action research included two cycles with four steps.The first cycle involved the integration of ESD into a traditional science curriculum.The second cycle involved the validation and optimization of the ESD objectives.The implementation strategies were reviewed and refined.Findings:First,a variety of strategies can be used to identify the theme and choose the content.Second,the objectives should be developed on children’s life experiences and interests.Third,the idea of ESD can be implemented in multiple ways.Fourth,a reasonable objective system involving ESD was constructed for children by ages.Fifth,there were many effective ways to integrate ESD activities into other domains of curriculum.The challenges and implications were also discussed.Originality/Value:The study had a positive effect on teachers’ability to practice ESD.This was a pioneer project in early childhood education in China,which provided valuable information for those aiming to implement ESD practices in Chinese kindergartens.
基金supported by the National Natural Science Foundation of China (21475120, 21527807)the National Key Research and Development Program of China (2016YFA0201300)
文摘In this work,highly chemiluminescent magnetic mesoporous carbon with yolk-shell structure was synthesized by encapsulating N-(4-aminobutyl)-N-ethylisoluminol(ABEI)and Co^(2+)into the magnetic mesoporous carbon composites(Co^(2+)-ABEI-Fe_3O_4@void@C).The synthetic Co^(2+)-ABEI-Fe_3O_4@void@C showed a good magnetic separation property,which could remove residual ABEI molecules and Co^(2+)in less than 3 min under an external magnet.Moreover,the synthetic Co^(2+)-ABEI-Fe_3O_4@void@C demonstrated good chemiluminescence(CL)property and good stability when interacted with alkaline H_2O_2solution.The CL intensity of such Co^(2+)-ABEI-Fe_3O_4@void@C was about 120 times higher than that of ABEI-Fe_3O_4@void@C.The Co^(2+)-ABEI-Fe_3O_4@void@C also exhibited good electrochemiluminescence(ECL)property in alkaline solution.The outstanding CL/ECL performance of the Co^(2+)-ABEI-Fe_3O_4@void@C was attributed to the Co^(2+)immobilized in the Co^(2+)-ABEI-Fe_3O_4@void@C,which catalyzed the decomposition of H_2O_2to generate O_2^(·-)and HO~·,expediting the CL/ECL reaction.The synthetic Co^(2+)-ABEI-Fe_3O_4@void@C may be of great application for the development of new methodologies in bioanalysis.
