This study investigated the physicochemical properties,enzyme activities,volatile flavor components,microbial communities,and sensory evaluation of high-temperature Daqu(HTD)during the maturation process,and a standar...This study investigated the physicochemical properties,enzyme activities,volatile flavor components,microbial communities,and sensory evaluation of high-temperature Daqu(HTD)during the maturation process,and a standard system was established for comprehensive quality evaluation of HTD.There were obvious changes in the physicochemical properties,enzyme activities,and volatile flavor components at different storage periods,which affected the sensory evaluation of HTD to a certain extent.The results of high-throughput sequencing revealed significant microbial diversity,and showed that the bacterial community changed significantly more than did the fungal community.During the storage process,the dominant bacterial genera were Kroppenstedtia and Thermoascus.The correlation between dominant microorganisms and quality indicators highlighted their role in HTD quality.Lactococcus,Candida,Pichia,Paecilomyces,and protease activity played a crucial role in the formation of isovaleraldehyde.Acidic protease activity had the greatest impact on the microbial community.Moisture promoted isobutyric acid generation.Furthermore,the comprehensive quality evaluation standard system was established by the entropy weight method combined with multi-factor fuzzy mathematics.Consequently,this study provides innovative insights for comprehensive quality evaluation of HTD during storage and establishes a groundwork for scientific and rational storage of HTD and quality control of sauce-flavor Baijiu.展开更多
This study investigates the corrosion-assisted fatigue crack growth rate(FCGR)of 16 mm thick AA 7075-T651 friction stir welded(FSW)joints.Compact tension(CT)specimens were extracted from both the base material and FSW...This study investigates the corrosion-assisted fatigue crack growth rate(FCGR)of 16 mm thick AA 7075-T651 friction stir welded(FSW)joints.Compact tension(CT)specimens were extracted from both the base material and FSW joints to evaluate FCGR under varying corrosion exposure durations(0,7,30,60,and 90 days)at a constant stress ratio of 0.5.Microstructural analysis of the welds was conducted using optical and transmission electron microscopy(TEM).Results indicate that the critical stress intensity factor range(ΔK_(cr))of FSW joints is lower than that of the base material,primarily due to precipitate dissolution in the weld zone during the FSW process,as confirmed by TEM analysis.The fatigue life of FSW joints was significantly lower than that of the base material,but with prolonged exposure to seawater corrosion,the gap in fatigue life narrowed.Specimens exposed to seawater for more than 60days exhibited minimal differences in fatigue life between the base material and the FSW joints.This was attributed to the higher corrosion rate of the base material compared to the weld nugget,resulting in the formation of deeper pits that facilitated crack initiation and accelerated fatigue failure.The findings conclude that extended corrosion exposure leads to similar fatigue life and crack growth behaviour in both the base material and FSW joints.SEM and EDX analysis of AA7075-T651 revealed corrosion pits and rust products in initiation zones,ductile striations in growth regions,and secondary cracks with micro voids in fracture zones.FSW joints exhibited ultra-fine grains,smooth ductile fracture in initiation and growth regions,and brittle fracture in the fracture zones under both corroded and uncorroded conditions.展开更多
This study examines the effects of friction stir welding(FSW)and post-weld heat treatment(PWHT)on the grain boundary character distribution and corrosion resistance of cross sectional(top and bottom)regions of nickel-...This study examines the effects of friction stir welding(FSW)and post-weld heat treatment(PWHT)on the grain boundary character distribution and corrosion resistance of cross sectional(top and bottom)regions of nickel-and molybdenum-free high-nitrogen austenitic stainless steel(HNASS).FSW at 400 rpm and 30 mm/min resulted in finer grains(4.18μm)and higher coincident site lattice(CSL)boundaries(32.3%)at the top of the stir zone(SZ)due to dynamic recrystallization(DRX).PWHT at 900℃for 1 h led to grain coarsening(12.91μm the bottom SZ)but enhanced CSL boundaries from 24.6%to 30.2%,improving grain boundary stability.PWHT reduced the kernel average misorientation(KAM)by 14.9%in the SZ-top layer and 20.4%in the SZ-bottom layer,accompanied by a 25%decrease in hardness in the SZ-top layer and 26.7%in the SZ-bottom layer,indicating strain recovery and reduced dislocation density.Potentiodynamic polarization tests(PDP)showed a 18%increase in pitting potential and a 76%reduction in corrosion rate after PWHT.The improvement in corrosion resistance is attributed to the increase inΣ3 twin boundaries,which enhance grain boundary stability and reduce susceptibility to localized corrosion.These findings highlight the role of PWHT in refining the microstructure and strengthening corrosion resistance,making HNASS a promising material for demanding applications.展开更多
To investigate the influence of temperature on the physical,mechanical and acoustic emission characteristics of granites,uniaxial compression test,variable-angle shear test,acoustic emission signal monitoring and the ...To investigate the influence of temperature on the physical,mechanical and acoustic emission characteristics of granites,uniaxial compression test,variable-angle shear test,acoustic emission signal monitoring and the measurement of physical parameters including mass,size and P-wave velocity were carried out on granite samples treated at temperatures T ranging from 25 to 900℃.The results show that the density and P-wave velocity decrease gradually with increasing T.As the temperature increases,the peak compressive stress decreases while the peak strain increases,due to the fact that a high temperature induces the escaping of waters within granites,the expanding of mineral grains and the generations of fractures.With the increment of T,both the peak shear stress and the cohesion decrease,whereas the frictional angle increases.During the compressing and shearing tests,the maximum acoustic emission counts show a decreasing trend when T increases from 25 to 900℃.When T exceeds 573℃,the crystal lattice structure of quartz changes fromα-phase toβ-phase,decreasing the mechanical behavior of granites to a great extent.In addition,the results also indicate that T=500−600℃ is the critical temperature ramge to characterize the influence of temperature on the physical,mechanical and acoustic emission characteristics of granites.展开更多
Two new binary near-azeotropic mixtures named M1 and M2 were developed as the refrigerants of the high-temperature heat pump(HTHP).The experimental research was used to analyze and compare the performance of M1 and M2...Two new binary near-azeotropic mixtures named M1 and M2 were developed as the refrigerants of the high-temperature heat pump(HTHP).The experimental research was used to analyze and compare the performance of M1 and M2-based in the HTHP in different running conditions.The results demonstrated the feasibility and reliability of M1 and M2 as new high-temperature refrigerants.Additionally,the exploration and analyses of the support vector machine(SVM)and back propagation(BP)neural network models were made to find a practical way to predict the performance of HTHP system.The results showed that SVM-Linear,SVM-RBF and BP models shared the similar ability to predict the heat capacity and power input with high accuracy.SVM-RBF demonstrated better stability for coefficient of performance prediction.Finally,the proposed SVM model was used to assess the potential of the M1 and M2.The results indicated that the HTHP system using M1 could produce heat at the temperature of 130°C with good performance.展开更多
To understand the response characteristics of soybean seedling resistance systems to high-temperature stress,the spring soybean varieties HN44 and HN65 were selected in this study as the experimental materials,as they...To understand the response characteristics of soybean seedling resistance systems to high-temperature stress,the spring soybean varieties HN44 and HN65 were selected in this study as the experimental materials,as they had substantial differences in stress resistance.Soybean physiological status was studied under high-temperature stress.Sand culture was used in the experiment,and soybeans at the seedling stage were treated with high-temperature stress.The results showed that the activity of antioxidases and osmotic regulatory substance contents in soybean increased under high-temperature treatment for a certain period of time,the activity of antioxidases and osmotic regulatory substance contents decreased after continuous treatment,and high temperatures continuously increased malondialdehyde contents in the two varieties.At high temperatures,the antioxidant activity and osmotic regulator contents of HN44 were higher than those of HN65,and the malondialdehyde contents of HN44 were higher than those of HN65.The above results showed that HN44 soybeans exhibited significantly higher resistance to high-temperature stress than HN65 variety.展开更多
This study investigated the effect of pre-friction surfacing heat treatment of consumable rods and heat input during friction surfacing on the microstructure,mechanical properties,and wear resistance of hypereutectic ...This study investigated the effect of pre-friction surfacing heat treatment of consumable rods and heat input during friction surfacing on the microstructure,mechanical properties,and wear resistance of hypereutectic Al-Si alloy deposited on a commercially pure aluminum substrate.The results show that regardless of the consumable rod’s heat treatment conditions,the coating’s efficiency has increased with the increase in heat input,so the coating efficiency increases by 20%and 30%in the solid solution-treated rod and the artificially aged rod,respectively.By increasing the heat input,the average grain size in the coating fabricated by solid solution-treated rod and artificially aged rod increased from 0.1 to 0.9μm and from 0.2 to 1.3μm,respectively.At constant heat input,the average hardness and wear resistance of the coating created in the solid solution-treated rod are lower than those of the artificially aged rod.By decreasing heat input,the wear loss in the coating fabricated by solid solution-treated rod and artificially aged rod decreased by 10%and 20%,respectively,reaching 0.1 and 0.03μg/m.展开更多
文摘This study investigated the physicochemical properties,enzyme activities,volatile flavor components,microbial communities,and sensory evaluation of high-temperature Daqu(HTD)during the maturation process,and a standard system was established for comprehensive quality evaluation of HTD.There were obvious changes in the physicochemical properties,enzyme activities,and volatile flavor components at different storage periods,which affected the sensory evaluation of HTD to a certain extent.The results of high-throughput sequencing revealed significant microbial diversity,and showed that the bacterial community changed significantly more than did the fungal community.During the storage process,the dominant bacterial genera were Kroppenstedtia and Thermoascus.The correlation between dominant microorganisms and quality indicators highlighted their role in HTD quality.Lactococcus,Candida,Pichia,Paecilomyces,and protease activity played a crucial role in the formation of isovaleraldehyde.Acidic protease activity had the greatest impact on the microbial community.Moisture promoted isobutyric acid generation.Furthermore,the comprehensive quality evaluation standard system was established by the entropy weight method combined with multi-factor fuzzy mathematics.Consequently,this study provides innovative insights for comprehensive quality evaluation of HTD during storage and establishes a groundwork for scientific and rational storage of HTD and quality control of sauce-flavor Baijiu.
文摘This study investigates the corrosion-assisted fatigue crack growth rate(FCGR)of 16 mm thick AA 7075-T651 friction stir welded(FSW)joints.Compact tension(CT)specimens were extracted from both the base material and FSW joints to evaluate FCGR under varying corrosion exposure durations(0,7,30,60,and 90 days)at a constant stress ratio of 0.5.Microstructural analysis of the welds was conducted using optical and transmission electron microscopy(TEM).Results indicate that the critical stress intensity factor range(ΔK_(cr))of FSW joints is lower than that of the base material,primarily due to precipitate dissolution in the weld zone during the FSW process,as confirmed by TEM analysis.The fatigue life of FSW joints was significantly lower than that of the base material,but with prolonged exposure to seawater corrosion,the gap in fatigue life narrowed.Specimens exposed to seawater for more than 60days exhibited minimal differences in fatigue life between the base material and the FSW joints.This was attributed to the higher corrosion rate of the base material compared to the weld nugget,resulting in the formation of deeper pits that facilitated crack initiation and accelerated fatigue failure.The findings conclude that extended corrosion exposure leads to similar fatigue life and crack growth behaviour in both the base material and FSW joints.SEM and EDX analysis of AA7075-T651 revealed corrosion pits and rust products in initiation zones,ductile striations in growth regions,and secondary cracks with micro voids in fracture zones.FSW joints exhibited ultra-fine grains,smooth ductile fracture in initiation and growth regions,and brittle fracture in the fracture zones under both corroded and uncorroded conditions.
文摘This study examines the effects of friction stir welding(FSW)and post-weld heat treatment(PWHT)on the grain boundary character distribution and corrosion resistance of cross sectional(top and bottom)regions of nickel-and molybdenum-free high-nitrogen austenitic stainless steel(HNASS).FSW at 400 rpm and 30 mm/min resulted in finer grains(4.18μm)and higher coincident site lattice(CSL)boundaries(32.3%)at the top of the stir zone(SZ)due to dynamic recrystallization(DRX).PWHT at 900℃for 1 h led to grain coarsening(12.91μm the bottom SZ)but enhanced CSL boundaries from 24.6%to 30.2%,improving grain boundary stability.PWHT reduced the kernel average misorientation(KAM)by 14.9%in the SZ-top layer and 20.4%in the SZ-bottom layer,accompanied by a 25%decrease in hardness in the SZ-top layer and 26.7%in the SZ-bottom layer,indicating strain recovery and reduced dislocation density.Potentiodynamic polarization tests(PDP)showed a 18%increase in pitting potential and a 76%reduction in corrosion rate after PWHT.The improvement in corrosion resistance is attributed to the increase inΣ3 twin boundaries,which enhance grain boundary stability and reduce susceptibility to localized corrosion.These findings highlight the role of PWHT in refining the microstructure and strengthening corrosion resistance,making HNASS a promising material for demanding applications.
基金Projects(51979272,BZ2020066)supported by the National Natural Science Foundation of ChinaProjet supported by the Department of Science and Technology of Jiangsu Province,China。
文摘To investigate the influence of temperature on the physical,mechanical and acoustic emission characteristics of granites,uniaxial compression test,variable-angle shear test,acoustic emission signal monitoring and the measurement of physical parameters including mass,size and P-wave velocity were carried out on granite samples treated at temperatures T ranging from 25 to 900℃.The results show that the density and P-wave velocity decrease gradually with increasing T.As the temperature increases,the peak compressive stress decreases while the peak strain increases,due to the fact that a high temperature induces the escaping of waters within granites,the expanding of mineral grains and the generations of fractures.With the increment of T,both the peak shear stress and the cohesion decrease,whereas the frictional angle increases.During the compressing and shearing tests,the maximum acoustic emission counts show a decreasing trend when T increases from 25 to 900℃.When T exceeds 573℃,the crystal lattice structure of quartz changes fromα-phase toβ-phase,decreasing the mechanical behavior of granites to a great extent.In addition,the results also indicate that T=500−600℃ is the critical temperature ramge to characterize the influence of temperature on the physical,mechanical and acoustic emission characteristics of granites.
基金Project (2015CB251403) supported by the National Key Basic Research Program of China(973)
文摘Two new binary near-azeotropic mixtures named M1 and M2 were developed as the refrigerants of the high-temperature heat pump(HTHP).The experimental research was used to analyze and compare the performance of M1 and M2-based in the HTHP in different running conditions.The results demonstrated the feasibility and reliability of M1 and M2 as new high-temperature refrigerants.Additionally,the exploration and analyses of the support vector machine(SVM)and back propagation(BP)neural network models were made to find a practical way to predict the performance of HTHP system.The results showed that SVM-Linear,SVM-RBF and BP models shared the similar ability to predict the heat capacity and power input with high accuracy.SVM-RBF demonstrated better stability for coefficient of performance prediction.Finally,the proposed SVM model was used to assess the potential of the M1 and M2.The results indicated that the HTHP system using M1 could produce heat at the temperature of 130°C with good performance.
基金Supported by the National Key Research and Development Program(2018YFD1000903)。
文摘To understand the response characteristics of soybean seedling resistance systems to high-temperature stress,the spring soybean varieties HN44 and HN65 were selected in this study as the experimental materials,as they had substantial differences in stress resistance.Soybean physiological status was studied under high-temperature stress.Sand culture was used in the experiment,and soybeans at the seedling stage were treated with high-temperature stress.The results showed that the activity of antioxidases and osmotic regulatory substance contents in soybean increased under high-temperature treatment for a certain period of time,the activity of antioxidases and osmotic regulatory substance contents decreased after continuous treatment,and high temperatures continuously increased malondialdehyde contents in the two varieties.At high temperatures,the antioxidant activity and osmotic regulator contents of HN44 were higher than those of HN65,and the malondialdehyde contents of HN44 were higher than those of HN65.The above results showed that HN44 soybeans exhibited significantly higher resistance to high-temperature stress than HN65 variety.
文摘This study investigated the effect of pre-friction surfacing heat treatment of consumable rods and heat input during friction surfacing on the microstructure,mechanical properties,and wear resistance of hypereutectic Al-Si alloy deposited on a commercially pure aluminum substrate.The results show that regardless of the consumable rod’s heat treatment conditions,the coating’s efficiency has increased with the increase in heat input,so the coating efficiency increases by 20%and 30%in the solid solution-treated rod and the artificially aged rod,respectively.By increasing the heat input,the average grain size in the coating fabricated by solid solution-treated rod and artificially aged rod increased from 0.1 to 0.9μm and from 0.2 to 1.3μm,respectively.At constant heat input,the average hardness and wear resistance of the coating created in the solid solution-treated rod are lower than those of the artificially aged rod.By decreasing heat input,the wear loss in the coating fabricated by solid solution-treated rod and artificially aged rod decreased by 10%and 20%,respectively,reaching 0.1 and 0.03μg/m.
