The interrupted aging mechanisms were applied to Ni75Al2.9V22.1 alloy by using the microscopic phase-field simulation method. For the single phase region existing at high temperature, the low content alloy was used as...The interrupted aging mechanisms were applied to Ni75Al2.9V22.1 alloy by using the microscopic phase-field simulation method. For the single phase region existing at high temperature, the low content alloy was used as the study object. With the progressive aging mechanisms, the metastable phase γ′ of high temperature can be obtained from the low temperature two phase regions, and the quantity of γ′ phase reduces with increasing temperature. The θ single phase morphology at high temperature regions will turn to be the γ′＋θ two phase morphology at low temperature with the interrupted aging method. Despite of the different precipitation paths of γ′ phase, the precipitation mechanisms are the same for the low temperature aging and high temperature interrupted aging.展开更多
Most conventional ceramic based aluminum metal matrix composites(MMCs) are either heavy,costly or combination of both. In order to reduce cost and weight,while at the same time maintaining quality,cow horn particles(C...Most conventional ceramic based aluminum metal matrix composites(MMCs) are either heavy,costly or combination of both. In order to reduce cost and weight,while at the same time maintaining quality,cow horn particles(CHp) was used with aluminum alloy A356 to produce MMC for brake drum application and other engineering uses. The aim of this research is to model the age hardening process of the produced composite using response surface methodology(RSM) and artificial neural network(ANN),and to use the developed ANN as fitness function for a simulated annealing optimization algorithm(SA-NN system) for optimization of age hardening process parameters. The results show that ANN modeled the age hardening data excellently and better than RSM with a correlation coefficient of experimental response with ANN predictions being 0.9921 as against 0.9583 for the RSM. The SA-NN system optimized process parameters were in very close agreement with the experimental values with the maximum relative error of 1.2%,minimum of 0.35% and average of 0.71%.展开更多
In order to investigate the effect of sintering temperature on aging properties and mechanical properties of 3Y-TZP dental ceramic in simulated oral environment, 3Y-TZP nanopowder compacts were pressurelessly sintered...In order to investigate the effect of sintering temperature on aging properties and mechanical properties of 3Y-TZP dental ceramic in simulated oral environment, 3Y-TZP nanopowder compacts were pressurelessly sintered at 1 350℃, 1 400 ℃, 1 450 ℃,1 500 ℃, respectively, then were treated by soaking in artificial saliva （65 ℃, pH=7） for two months. The treated specimens sintered at 1 350 ℃ showed there was no phase transformation but whose strength and toughnesswere significantly improved （P〈0.05）, while those sintered at 1 400 ℃- 1 500 ℃ revealed a small amount of phase transformation and insignificant mechanical reinforcement （P〉0.05）. No microcracks were detected but increment in lattice volume was found in all specimens. Lowering sintering temperature favors aging resistance and mechanical reinforcement of 3Y-TZP in a simulated oral environment.展开更多
Mathematical models have been widely employed for the simulation of growth dynamics of annual crops,thereby performing yield prediction,but not for fruit tree species such as jujube tree(Zizyphus jujuba).The objective...Mathematical models have been widely employed for the simulation of growth dynamics of annual crops,thereby performing yield prediction,but not for fruit tree species such as jujube tree(Zizyphus jujuba).The objectives of this study were to investigate the potential use of a modified WOFOST model for predicting jujube yield by introducing tree age as a key parameter.The model was established using data collected from dedicated field experiments performed in 2016-2018.Simulated growth dynamics of dry weights of leaves,stems,fruits,total biomass and leaf area index(LAI) agreed well with measured values,showing root mean square error(RMSE) values of 0.143,0.333,0.366,0.624 t ha^-1 and 0.19,and R2 values of 0.947,0.976,0.985,0.986 and 0.95,respectively.Simulated phenological development stages for emergence,anthesis and maturity were 2,3 and 3 days earlier than the observed values,respectively.In addition,in order to predict the yields of trees with different ages,the weight of new organs(initial buds and roots) in each growing season was introduced as the initial total dry weight(TDWI),which was calculated as averaged,fitted and optimized values of trees with the same age.The results showed the evolution of the simulated LAI and yields profiled in response to the changes in TDWI.The modelling performance was significantly improved when it considered TDWI integrated with tree age,showing good global(R2≥0.856,RMSE≤0.68 t ha^-1) and local accuracies(mean R2≥0.43,RMSE≤0.70 t ha^-1).Furthermore,the optimized TDWI exhibited the highest precision,with globally validated R2 of 0.891 and RMSE of 0.591 t ha^-1,and local mean R2 of 0.57 and RMSE of 0.66 t ha^-1,respectively.The proposed model was not only verified with the confidence to accurately predict yields of jujube,but it can also provide a fundamental strategy for simulating the growth of other fruit trees.展开更多
As-cast HK40 steel was aged at 700, 800, or 900℃ for times as long as 2000 h. Microstructural characterization showed that the primary M_7C_3 carbide network contained a substantial content of manganese, in agreement...As-cast HK40 steel was aged at 700, 800, or 900℃ for times as long as 2000 h. Microstructural characterization showed that the primary M_7C_3 carbide network contained a substantial content of manganese, in agreement with the microsegregation of manganese calculated by Thermo-Calc using the Scheil–Gulliver module. The dissolution of primary carbides caused the solute supersaturation of austenite and subsequent precipitation of fine M_(23)C_6 carbides in the austenite matrix for aged specimens. During prolonged aging, the carbide size increased with increasing time because of the coarsening process. A time–temperature–precipitation diagram for M_(23)C_6 carbides was calculated using the Thermo-CalcPRISMA software; this diagram showed good agreement with the experimental growth kinetics of precipitation. The fine carbide precipitation caused an increase in hardness; however, the coarsening process of carbides promoted a decrease in hardness. Nanoindentation tests of the austenite matrix indicated an increase in ductility with increasing aging time.展开更多
Ag nanowires(AgNWs)have shown great application value in the field of flexible electronics due to their excellent optical and electrical properties,and the quality of its joints of AgNWs in the thin film network direc...Ag nanowires(AgNWs)have shown great application value in the field of flexible electronics due to their excellent optical and electrical properties,and the quality of its joints of AgNWs in the thin film network directly plays a key role in its performance.In order to further improve the joint quality of AgNWs under thermal excitation,the thermal welding process and atomic evolution behavior of AgNWs were investigated through a combination of in situ experimental and molecular dynamics simulations.The influence of processing time,temperature,and stress distribution due to spatial arrangement on nanojoints was systematically explored.What is more,the failure mechanisms and their atomic interface behavior of the nanojoints were also investigated.展开更多
By means of constant temperature and constant pressure molecular dynamic simulation technique, a series of simulations of the glass transition and crystallization processes of Ag 50Au 50 were performed. The atoms inte...By means of constant temperature and constant pressure molecular dynamic simulation technique, a series of simulations of the glass transition and crystallization processes of Ag 50Au 50 were performed. The atoms interact via EAM potential function. Pair correlation functions of liquid Ag 50Au 50 during different cooling rates and temperatures were simulated to reveal the structural features of liquid, super-cooled liquid, glass state and crystal. The thermodynamics and kinetics of structure transition of Ag 50Au 50 during cooling processes were performed.展开更多
This paper studied a structured model by age of tuberculosis. A population divided into two parts was considered for the study. Each subpopulation is submitted to a program of vaccination. It was allowed the migration...This paper studied a structured model by age of tuberculosis. A population divided into two parts was considered for the study. Each subpopulation is submitted to a program of vaccination. It was allowed the migration of vaccinated people only between the two patches. After the determination of and , the local and global stability of the disease-free equilibrium was studied. It showed the existence of three endemic equilibrium points. The theoretical results were illustrated by a numeric simulation.展开更多
[Objectives] To study the protective effect of Space Ginseng Yeast on human primary fibroblasts. [Methods] Multiple indicators were used to simulate the microgravity effect,so as to study the protective effect of Spac...[Objectives] To study the protective effect of Space Ginseng Yeast on human primary fibroblasts. [Methods] Multiple indicators were used to simulate the microgravity effect,so as to study the protective effect of Space Ginseng Yeast on human primary fibroblasts under simulated microgravity condition. [Results]Space Ginseng Yeast could improve changes of cell morphology and decline of the survival rate caused by microgravity,restore the expression and effective arrangement of cytoskeletal protein Tubulin,extracellular matrix proteins Integrin and Fibronectin,and can inhibit the abnormal expression of MMP-1. The protective effect of Space Ginseng Yeast diluted 20-500 times is better,and the protective effect of Space Ginseng Yeast diluted 100 times is the most obvious. [Conclusions] Space Ginseng Yeast can protect damage of human primary fibroblasts caused by simulated microgravity.展开更多
基金supported by the National Natural Science Foundation of China(No.50671084)the Doctoral Foundation of Northwestern Polytechnical University(No.CX200507).
文摘The interrupted aging mechanisms were applied to Ni75Al2.9V22.1 alloy by using the microscopic phase-field simulation method. For the single phase region existing at high temperature, the low content alloy was used as the study object. With the progressive aging mechanisms, the metastable phase γ′ of high temperature can be obtained from the low temperature two phase regions, and the quantity of γ′ phase reduces with increasing temperature. The θ single phase morphology at high temperature regions will turn to be the γ′＋θ two phase morphology at low temperature with the interrupted aging method. Despite of the different precipitation paths of γ′ phase, the precipitation mechanisms are the same for the low temperature aging and high temperature interrupted aging.
文摘Most conventional ceramic based aluminum metal matrix composites(MMCs) are either heavy,costly or combination of both. In order to reduce cost and weight,while at the same time maintaining quality,cow horn particles(CHp) was used with aluminum alloy A356 to produce MMC for brake drum application and other engineering uses. The aim of this research is to model the age hardening process of the produced composite using response surface methodology(RSM) and artificial neural network(ANN),and to use the developed ANN as fitness function for a simulated annealing optimization algorithm(SA-NN system) for optimization of age hardening process parameters. The results show that ANN modeled the age hardening data excellently and better than RSM with a correlation coefficient of experimental response with ANN predictions being 0.9921 as against 0.9583 for the RSM. The SA-NN system optimized process parameters were in very close agreement with the experimental values with the maximum relative error of 1.2%,minimum of 0.35% and average of 0.71%.
基金Funded by the National High Technology Research and Development Program of China (No.2006AA03Z440)
文摘In order to investigate the effect of sintering temperature on aging properties and mechanical properties of 3Y-TZP dental ceramic in simulated oral environment, 3Y-TZP nanopowder compacts were pressurelessly sintered at 1 350℃, 1 400 ℃, 1 450 ℃,1 500 ℃, respectively, then were treated by soaking in artificial saliva （65 ℃, pH=7） for two months. The treated specimens sintered at 1 350 ℃ showed there was no phase transformation but whose strength and toughnesswere significantly improved （P〈0.05）, while those sintered at 1 400 ℃- 1 500 ℃ revealed a small amount of phase transformation and insignificant mechanical reinforcement （P〉0.05）. No microcracks were detected but increment in lattice volume was found in all specimens. Lowering sintering temperature favors aging resistance and mechanical reinforcement of 3Y-TZP in a simulated oral environment.
基金supported by the National Natural Science Foundation of China(41561088 and 61501314)the Science&Technology Nova Program of Xinjiang Production and Construction Corps,China(2018CB020)
文摘Mathematical models have been widely employed for the simulation of growth dynamics of annual crops,thereby performing yield prediction,but not for fruit tree species such as jujube tree(Zizyphus jujuba).The objectives of this study were to investigate the potential use of a modified WOFOST model for predicting jujube yield by introducing tree age as a key parameter.The model was established using data collected from dedicated field experiments performed in 2016-2018.Simulated growth dynamics of dry weights of leaves,stems,fruits,total biomass and leaf area index(LAI) agreed well with measured values,showing root mean square error(RMSE) values of 0.143,0.333,0.366,0.624 t ha^-1 and 0.19,and R2 values of 0.947,0.976,0.985,0.986 and 0.95,respectively.Simulated phenological development stages for emergence,anthesis and maturity were 2,3 and 3 days earlier than the observed values,respectively.In addition,in order to predict the yields of trees with different ages,the weight of new organs(initial buds and roots) in each growing season was introduced as the initial total dry weight(TDWI),which was calculated as averaged,fitted and optimized values of trees with the same age.The results showed the evolution of the simulated LAI and yields profiled in response to the changes in TDWI.The modelling performance was significantly improved when it considered TDWI integrated with tree age,showing good global(R2≥0.856,RMSE≤0.68 t ha^-1) and local accuracies(mean R2≥0.43,RMSE≤0.70 t ha^-1).Furthermore,the optimized TDWI exhibited the highest precision,with globally validated R2 of 0.891 and RMSE of 0.591 t ha^-1,and local mean R2 of 0.57 and RMSE of 0.66 t ha^-1,respectively.The proposed model was not only verified with the confidence to accurately predict yields of jujube,but it can also provide a fundamental strategy for simulating the growth of other fruit trees.
基金financial support from SIP-BEIFI-IPN and CONACYT
文摘As-cast HK40 steel was aged at 700, 800, or 900℃ for times as long as 2000 h. Microstructural characterization showed that the primary M_7C_3 carbide network contained a substantial content of manganese, in agreement with the microsegregation of manganese calculated by Thermo-Calc using the Scheil–Gulliver module. The dissolution of primary carbides caused the solute supersaturation of austenite and subsequent precipitation of fine M_(23)C_6 carbides in the austenite matrix for aged specimens. During prolonged aging, the carbide size increased with increasing time because of the coarsening process. A time–temperature–precipitation diagram for M_(23)C_6 carbides was calculated using the Thermo-CalcPRISMA software; this diagram showed good agreement with the experimental growth kinetics of precipitation. The fine carbide precipitation caused an increase in hardness; however, the coarsening process of carbides promoted a decrease in hardness. Nanoindentation tests of the austenite matrix indicated an increase in ductility with increasing aging time.
基金supported by the Major Science and Technology Project of Precious Metal Materials Genetic Engineering in Yunnan Province,China(No.202002AB080001)the National Natural Science Foundation of China(No.52071002)the Natural Science Foundation of Anhui Province,China(No.2008085QE200)。
基金supported by National Natural Science Foundation of China(Grant Nos.52022078 and 51875450)Shaanxi Provincial Key Research and Development Program(Grant No.2021ZDLGY10-02)the fund of the State Key Laboratory of Solidification Processing in NPU,(Grant No.SKLSP202203)。
文摘Ag nanowires(AgNWs)have shown great application value in the field of flexible electronics due to their excellent optical and electrical properties,and the quality of its joints of AgNWs in the thin film network directly plays a key role in its performance.In order to further improve the joint quality of AgNWs under thermal excitation,the thermal welding process and atomic evolution behavior of AgNWs were investigated through a combination of in situ experimental and molecular dynamics simulations.The influence of processing time,temperature,and stress distribution due to spatial arrangement on nanojoints was systematically explored.What is more,the failure mechanisms and their atomic interface behavior of the nanojoints were also investigated.
文摘By means of constant temperature and constant pressure molecular dynamic simulation technique, a series of simulations of the glass transition and crystallization processes of Ag 50Au 50 were performed. The atoms interact via EAM potential function. Pair correlation functions of liquid Ag 50Au 50 during different cooling rates and temperatures were simulated to reveal the structural features of liquid, super-cooled liquid, glass state and crystal. The thermodynamics and kinetics of structure transition of Ag 50Au 50 during cooling processes were performed.
文摘This paper studied a structured model by age of tuberculosis. A population divided into two parts was considered for the study. Each subpopulation is submitted to a program of vaccination. It was allowed the migration of vaccinated people only between the two patches. After the determination of and , the local and global stability of the disease-free equilibrium was studied. It showed the existence of three endemic equilibrium points. The theoretical results were illustrated by a numeric simulation.
文摘[Objectives] To study the protective effect of Space Ginseng Yeast on human primary fibroblasts. [Methods] Multiple indicators were used to simulate the microgravity effect,so as to study the protective effect of Space Ginseng Yeast on human primary fibroblasts under simulated microgravity condition. [Results]Space Ginseng Yeast could improve changes of cell morphology and decline of the survival rate caused by microgravity,restore the expression and effective arrangement of cytoskeletal protein Tubulin,extracellular matrix proteins Integrin and Fibronectin,and can inhibit the abnormal expression of MMP-1. The protective effect of Space Ginseng Yeast diluted 20-500 times is better,and the protective effect of Space Ginseng Yeast diluted 100 times is the most obvious. [Conclusions] Space Ginseng Yeast can protect damage of human primary fibroblasts caused by simulated microgravity.
