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Control Method for Steel Strip Roughness in Two-stand Temper Mill Rolling 被引量:8
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作者 LI Rui ZHANG Qingdong +2 位作者 ZHANG Xiaofeng YU Meng WANG Bo 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2015年第3期573-579,共7页
How to control surface roughness of steel strip in a narrow range for a long time has become an important question because surface roughness would significantly influence the appearance of the products. However, there... How to control surface roughness of steel strip in a narrow range for a long time has become an important question because surface roughness would significantly influence the appearance of the products. However, there are few effective solutions to solve the problem currently. In this paper, considering both asperities of work roll pressing in and squeezing the steel strip, two asperity contact models including squeezing model and pressing in model in a two-stand temper mill rolling are established by using finite element method(FEM). The simulation investigates the influences of multiple process parameters, such as work roll surface roughness, roll radius and roll force on the surface roughness of steel strip. The simulation results indicate that work rolls surface roughness and roll force play important roles in the products; furthermore, the effect of roll force in the first stand is opposite to the second. According to the analysis, a control method for steel strip surface roughness in a narrow range for a long time is proposed, which applies higher work roll roughness in the first stand and lower roll roughness in the second to make the steel strip roughness in a required narrow range. In the later stage of the production, decreasing the roll force in the first stand and increasing the roll force in the second stand guarantee the steel strip roughness relatively stable in a long time. The following experimental measurements on the surface topography and roughness of the steel strips during the whole process are also conducted. The results validate the simulation conclusions and prove the effect of the control method. The application of the proposed method in the steel strip production shows excellent performance including long service life of work roll and high finished product rate. 展开更多
关键词 temper mill rolling surface roughness interface contact
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Improvement on strip flatness of cold temper mills by modifying roll contour shape 被引量:3
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作者 Xiaoyan Li Jie Zhang +2 位作者 Xianlin Chen Jianguo Cao Haixia Li Mechanical Engineering School, University of Science and Technology Beijing, Beijing 100083, China 《Journal of University of Science and Technology Beijing》 CSCD 2004年第3期251-255,共5页
A study on roll gap profile (strip profile) control was accomplished in a1700 mm single-stand temper mill. Some critical problems such as the deviation of work roll contourcaused by grinding and wear, the effectivenes... A study on roll gap profile (strip profile) control was accomplished in a1700 mm single-stand temper mill. Some critical problems such as the deviation of work roll contourcaused by grinding and wear, the effectiveness of work roll bending were discussed. Using a finiteelement model, the effects of roll contours (ground and wear) on strip profile were investigated.The roll bending effect on strip thickness was also analyzed. It is pointed out that there are somespecial features of flatness control in the temper mill: during temper rolling, roll deformation isslight due to small rolling load, and the loaded roll gap profile mainly depends on work rollcontour, while the backup roll has a little effect on gap crown; the effect of bending force ongauge can not be ignored due to the coupling between flatness control and gauge control. A new rollcontour arrangement adaptable to the mill was presented and has been put into practical production.The application of the new set of rolls showed some good results: larger crown control range of workroll bender, higher rolling stability, better strip profile and flatness quality. 展开更多
关键词 cold rolling temper mill strip shape control roll contour arrangement BENDING
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Harmonic Current′s Coupling Effect on the Main Motion of Temper Mill Set 被引量:6
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作者 HE Jian-jun YU Shou-yi ZHONG Jue 《Journal of Central South University》 SCIE EI CAS 2000年第3期162-164,共3页
The paper probes into a probable condition that causes temper mill chatter from aspect of electromechanical coupling of complex electromechanical system, and mainly studies the effect of temper mill electrical driving... The paper probes into a probable condition that causes temper mill chatter from aspect of electromechanical coupling of complex electromechanical system, and mainly studies the effect of temper mill electrical driving system harmonic current on the main motion of temper mill set. Aiming at the electrical driving system of CM04 temper mill, the effect of harmonic current is analyzed and evaluated according to different load. Combining the features of CM04 temper mill′s structure and its working state, the paper discusses in every detail how the harmonic current in main circuit, which can be regarded as a disturbance via feedback control circuit , influences main motion of temper mill set. 展开更多
关键词 ELECTROMECHANICAL coupling temper mill HARMONIC current ROLLING mill chatter
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Development of Roller Ends Forced-Contact Model and Cambering Technology for UCM Temper Mill (II)——Development of cambering technology for UCM temper mill
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作者 Zhenhua Bai Xiaodong Shi +5 位作者 Hongxin Si Linfang Han Ruibing Long Shoumin Wu Xiujun Li Dongdong Zhang 《Engineering(科研)》 2011年第7期743-749,共7页
Roller ends forced-contact and overmuch roll consumption are the widespread problems in temper rolling process of thin strip for two-stand UCM temper mill. Fully thinking the equipment and technology characteristics o... Roller ends forced-contact and overmuch roll consumption are the widespread problems in temper rolling process of thin strip for two-stand UCM temper mill. Fully thinking the equipment and technology characteristics of UCM temper mill, we took the newly-built 1220 UCM temper mill of Baosteel as the research object in this paper. A model of roller ends forced-contact and a calculation model of flatness for UCM temper mill are established after a great deal of site tracing and theoretical researches. On this basis, an optimal mathematical model of roll shape which is suited for UCM temper mill is developed. Working roll curve is the combination of cosine curve and high order curve. The cosine subentry is used to control edge wave, the high order curve subentry is used to control roller ends forced-contact. Furthermore, the chamfering curve of middle roller end is optimized. Those are the innovations. Through the above-mentioned technology, pressure distribution between rollers caused by the shift of middle roll becomes more homogeneous, pressure peak disappeared, working life of roll is improved effectively as well. Relevant technologies have been used to the practice of 1220 UCM temper mill of Baosteel and have achieved good use effects, which is of further extending application value. 展开更多
关键词 UCM temper mill Forced-Contact ROLL Shape ROLL Consumption
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Development of Roller Ends Forced-Contact Model and Cambering Technology for UCM Temper Mill (I)——Development of Roller Ends Forced-Contact Model and the Computational Model of Flatness for UCM temper mill
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作者 Zhenhua Bai Hongxin Si +5 位作者 Xiaodong Shi Linfang Han Ruibing Long Shoumin Wu Xiujun Li Dongdong Zhang 《Engineering(科研)》 2011年第7期736-742,共7页
Roller ends forced-contact and overmuch roll consumption are the widespread problems in temper rolling process of thin strip for two-stand UCM temper mill. Fully thinking the equipment and technology characteristics o... Roller ends forced-contact and overmuch roll consumption are the widespread problems in temper rolling process of thin strip for two-stand UCM temper mill. Fully thinking the equipment and technology characteristics of UCM temper mill, we took the newly-built 1220 UCM temper mill of Baosteel as the research object in this paper. A model of roller ends forced-contact and a calculation model of flatness for UCM temper mill are established after a great deal of site tracing and theoretical researches. On this basis, an optimal mathematical model of roll shape which is suited for UCM temper mill is developed. Working roll curve is the combination of cosine curve and high order curve. The cosine subentry is used to control edge wave, the high order curve subentry is used to control roller ends forced-contact. Furthermore, the chamfering curve of middle roller end is optimized. Those are the innovations. Through the above-mentioned technology, pressure distribution between rollers caused by the shift of middle roll becomes more homogeneous, pressure peak disappeared, working life of roll is improved effectively as well. Relevant technologies have been used to the practice of 1220 UCM temper mill of Baosteel and have achieved good use effects, which is of further extending application value [1]. 展开更多
关键词 UCM temper mill Forced-Contact ROLL Shape ROLL Consumption
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Modeling and identification of HAGC system of temper rolling mill 被引量:5
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作者 贺尚红 钟掘 《Journal of Central South University of Technology》 EI 2005年第6期699-704,共6页
Including servo valve, hydraulic cylinder, mill and sensor and ignoring nonlinear factors, the linear dynamic model of hydraulic automatic gage control(HAGC) system of a temper rolling mill was theoretically derived. ... Including servo valve, hydraulic cylinder, mill and sensor and ignoring nonlinear factors, the linear dynamic model of hydraulic automatic gage control(HAGC) system of a temper rolling mill was theoretically derived. The order of the model is 4/4, and can be reduced to 2/2. Based on modulating functions method, utilizing numerical integration, we constructed the equivalent identification model of HAGC, and the least square estimation algorithm was established. The input and output data were acquired on line at temper rolling mill in Shangshai Baosteel Group Corporation, and the continuous time model of HAGC system was estimated with the proposed method. At different modulating window intervals, the estimated parameters changed remarkably. When the frequency bandwidth of modulating filter matches that of estimated system, the parameters can be estimated accurately. Finally, the dynamic model of the HAGC was obtained and validated based on the spectral analysis result. 展开更多
关键词 hydraulic automatic gage control MODELING IDENTIFICATION temper rolling mill
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Temperate Stutzerimonas Phage Encoding Toxin-Antitoxin System Genes Represents a Novel Genus
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作者 ZHANG Hong GUO Ruizhe +14 位作者 GAO Chen ZHENG Kaiyang XIONG Yao DONG Yue LIU Yundan WANG Ziyue CHEN Ying WANG Hongmin SHAO Hongbing SUNG Yeong Yik MOK Wen Jye WONG Li Lian MCMINN Andrew WANG Min LIANG Yantao 《Journal of Ocean University of China》 SCIE CAS CSCD 2024年第4期1087-1101,共15页
Stutzerimonas have been extensively studied due to their remarkable metabolic and physiological diversity.However,research on its phages is currently limited.In this study,we isolated a novel double-stranded DNA(dsDNA... Stutzerimonas have been extensively studied due to their remarkable metabolic and physiological diversity.However,research on its phages is currently limited.In this study,we isolated a novel double-stranded DNA(dsDNA)phage,vB_SstM-PG1,from the marine environment that infects Stutzerimonas stutzeri G1.Its dsDNA genome is 37204 bp long with a G/C content of 64.14%and encodes 54 open reading frames.The phage possesses a tail packaging structure that is different from known Stutzerimonas stutzeri phages and exhibits structural protein characteristics similar to those of temperate phages.In addition,two genes of toxin-antitoxin system,including YdaS_antitoxin and HEPN_SAV_6107,were found in the vB_SstM-PG1 genome and play important roles in regulating host growth and metabolism.With phylogenetic tree and comparative genomic analysis,it has been determined that vB_SstM-PG1 is not closely related to any phages previously identified in the GenBank database.Instead,it has a connection with enigmatic,uncultured viruses.Specifically,the vB_SstM-PG1 virus exhibits an average nucleotide identity of over 70%with six uncultivated viruses identified in the IMG/VR v4 database.This significant finding has resulted in the identification of a novel viral genus known as Metabovirus. 展开更多
关键词 Stutzerimonas vB_SstM-PG1 Metabovirus temperate phage genomic and phylogenetic analysis
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Variations and determinants of tissue carbon concentration of 32 sympatric temperate tree species
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作者 Jun Pan Jing Zhang +8 位作者 Xingchang Wang Xiuwei Wang Qi Wang Yankun Liu Yulong Liu Yunfei Diao Xiankui Quan Chuankuan Wang Xiaochun Wang 《Journal of Forestry Research》 SCIE EI CAS CSCD 2024年第6期62-72,共11页
Plant carbon(C)concentration is a fundamental trait for estimating C storage and nutrient utilization.However,the mechanisms of C concentration variations among different tree tissues and across species remains poorly... Plant carbon(C)concentration is a fundamental trait for estimating C storage and nutrient utilization.However,the mechanisms of C concentration variations among different tree tissues and across species remains poorly understood.In this study,we explored the variations and determinants of C concentration of nine tissues from 216 individuals of 32 tree species,with particular attention on the effect of wood porosity(i.e.,non-porous wood,diffuse-porous wood,and ring-porous wood).The inter-tissue pattern of C concentration diverged across the three porosity types;metabolically active tissues(foliage and fine roots,except for the foliage of ring-porous species)generally had higher C levels compared with inactive wood.The poor inter-correlations between tissue C concentrations indicated a necessity of measuring tissue-and specific-C concentrations.Carbon concentration for almost all tissues generally decreased from non-porous,to diffuse-porous and to ring-porous.Tissue C was often positively correlated with tissue(foliage and wood)density and tree size,while negatively correlated with growth rate,depending on wood porosity.Our results highlight the mediating effect of type of wood porosity on the variation in tissue C among temperate species.The variations among tissues were more important than that among species.These findings provided insights on tissue C concentration variability of temperate forest species. 展开更多
关键词 Carbon fraction Growth rate temperate tree species Tissue density Wood porosity
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Instrumented oscillographic study on impact toughness of an axle steel DZ2 with different tempering temperatures
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作者 Shuo Liu Peng Zhang +6 位作者 Bin Wang Kaizhong Wang Zikuan Xu Fangzhong Hu Xin Bai Qiqiang Duan Zhefeng Zhang 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2024年第7期1590-1598,共9页
Compared with the conventional Charpy impact test method,the oscillographic impact test can help in the behavioral analysis of materials during the fracture process.In this study,the trade-off relationship between the... Compared with the conventional Charpy impact test method,the oscillographic impact test can help in the behavioral analysis of materials during the fracture process.In this study,the trade-off relationship between the strength and toughness of a DZ2 axle steel at various tempering temperatures and the cause of the improvement in impact toughness was evaluated.The tempering process dramatically influenced carbide precipitation behavior,which resulted in different aspect ratios of carbides.Impact toughness improved along with the rise in tempering temperature mainly due to the increase in energy required in impact crack propagation.The characteristics of the impact crack propagation process were studied through a comprehensive analysis of stress distribution,oscilloscopic impact statistics,fracture morphology,and carbide morphology.The poor impact toughness of low-tempering-temperature specimens was attributed to the increased number of stress concentration points caused by carbide morphology in the small plastic zone during the propagation process,which resulted in a mixed distribution of brittle and ductile fractures on the fracture surface. 展开更多
关键词 axle steel DZ2 tempering process impact toughness oscillographic impact test impact crack propagation carbides
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Grouping tree species to estimate basal area increment in temperate multispecies forests in Durango,Mexico
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作者 Jaime Roberto Padilla-Martínez Carola Paul +2 位作者 Kai Husmann Jose Javier Corral-Rivas Klaus von Gadow 《Forest Ecosystems》 SCIE CSCD 2024年第1期1-13,共13页
Multispecies forests have received increased scientific attention,driven by the hypothesis that biodiversity improves ecological resilience.However,a greater species diversity presents challenges for forest management... Multispecies forests have received increased scientific attention,driven by the hypothesis that biodiversity improves ecological resilience.However,a greater species diversity presents challenges for forest management and research.Our study aims to develop basal area growth models for tree species cohorts.The analysis is based on a dataset of 423 permanent plots(2,500 m^(2))located in temperate forests in Durango,Mexico.First,we define tree species cohorts based on individual and neighborhood-based variables using a combination of principal component and cluster analyses.Then,we estimate the basal area increment of each cohort through the generalized additive model to describe the effect of tree size,competition,stand density and site quality.The principal component and cluster analyses assign a total of 37 tree species to eight cohorts that differed primarily with regard to the distribution of tree size and vertical position within the community.The generalized additive models provide satisfactory estimates of tree growth for the species cohorts,explaining between 19 and 53 percent of the total variation of basal area increment,and highlight the following results:i)most cohorts show a"rise-and-fall"effect of tree size on tree growth;ii)surprisingly,the competition index"basal area of larger trees"had showed a positive effect in four of the eight cohorts;iii)stand density had a negative effect on basal area increment,though the effect was minor in medium-and high-density stands,and iv)basal area growth was positively correlated with site quality except for an oak cohort.The developed species cohorts and growth models provide insight into their particular ecological features and growth patterns that may support the development of sustainable management strategies for temperate multispecies forests. 展开更多
关键词 temperate multispecies forests Cluster analysis Basal area increment Generalized additive models
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Self tempering effect of near eutectic Al-Si casting with different wall thickness solidified and cooled in permanent die 被引量:1
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作者 胡心平 谢玲 张娟 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2011年第12期2576-2583,共8页
In order to study the self tempering effect on the solidification of Al-Si alloy, a setup was designed to conduct experiments. The characters of β phases in different thicknesses of Al-Si samples were investigated. T... In order to study the self tempering effect on the solidification of Al-Si alloy, a setup was designed to conduct experiments. The characters of β phases in different thicknesses of Al-Si samples were investigated. The results show that the size distributions of β phases obey the logarithmic normal distribution. The Brinell hardness tests were also carried out. The tested hardness results show that the hardness distribution of the casting cooled in water is evener than that cooled in air, and its averaged value is higher than that cooled in air. 展开更多
关键词 β phase Al-Si alloy self tempering effect Brinell hardness
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CHANGES OF ATMOSPHERIC CO_2, PHOTOSYNTHESIS OF THE GRASS LAYER AND SOIL CO_2 EVOLUTION IN A TYPICAL TEMPERATE DECIDUOUS FOREST STAND IN THE MOUNTAINOUS AREAS OF BEIJING 被引量:2
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作者 蒋高明 韩兴国 周广胜 《Acta Botanica Sinica》 CSCD 1997年第7期653-660,共8页
Middle-sized chambers (40cmx40cmx20 cm) and an infrared gas analyzer (IRGA) were used for the measurement of net photosynthesis of the grass layer and soil CO2 evolution, in Quercus liaotungensis Koidz. forest, which ... Middle-sized chambers (40cmx40cmx20 cm) and an infrared gas analyzer (IRGA) were used for the measurement of net photosynthesis of the grass layer and soil CO2 evolution, in Quercus liaotungensis Koidz. forest, which is a typical temperate forest ecosystem in the mountainous areas of Beijing. Changes of CO2 concentrations in both the atmosphere (2m above canopy) and the forest canopy (2m below the top of the canopy) together with those of net photosynthesis and soil CO2 evolution were also examined, in order to find the characteristics of CO2 exchange between the different components of the temperate forest ecosystem and the atmosphere. Atmospheric CO2 averaged (323+10) and (330+1) mol mol-1 respectively in summer and autumn. During the 24-hour measurements, large differences as much as -46 and -61 mol mol-1 respectively in the atmosphere and forest were found. Net photosynthesis of the grass layer in summer was (2. 59 9+ 1.05) mol CO2 m-2 S-1, two times of that in autumn, (1.31+0.39) mol CO2 s-1 In summer, there was much more CO2 evolved from soil than in autumn, averaging (5.18+0.75) mol CO2 m-2 s-1 and (1.96 + 0.57) (mol CO2 m-2 s-1, respectively. A significant correlation was found between soil CO2 evolution and ground temperature, with F =-0.864 2+0.310 1X,r=0.7164, P<0.001 (n=117). Both the minimal atmospheric CO2 level and the maximum net photosynthesis occurred around 14:00; and an increase in atmospheric CO2 and of soil CO2 evolution during night times were also found to be remarkable. 展开更多
关键词 Gas exchange PHOTOSYNTHESIS Soil CO2 evolution CO2 temperate forest
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Landscape patterns of overstory litterfall and related nutrient fluxes in a cool-temperate forest watershed in northern Hokkaido,Japan 被引量:1
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作者 徐小牛 柴田英昭 《Journal of Forestry Research》 SCIE CAS CSCD 2007年第4期249-254,共6页
Within a forested watershed at the Uryu Experimental Forest of Hokkaido University in northern Hokkaido, overstory litterfall and related nutrient fluxes were measured at different landscape zones over two years. The ... Within a forested watershed at the Uryu Experimental Forest of Hokkaido University in northern Hokkaido, overstory litterfall and related nutrient fluxes were measured at different landscape zones over two years. The wetland zone covered with Picea glehnii pure stand. The riparian zone was deciduous broad-leaved stand dominated by Alnus hirsuta and Salix spp., while the mixture of deciduous broadleaf and evergreen conifer dominated by Betula platyphylla, Quercus crispula and Abies sachalinensis distributed on the upland zone. Annual litterfall averaged 1444, 5122, and 4123 kg.hm^-2·a^-1 in the wetland, riparian and upland zones, respectively. Litterfall production peaked in September-October, and foliage litter contributed the greatest amount (73.4%-87.6 %) of the annual total litterfall. Concentrations of nutrients analyzed in foliage litter of the dominant species showed a similar seasonal variation over the year except for N in P glehnii and A. hirsuta. The nutrient fluxes for all elements analyzed were greatest on riparian zone and lowest in wetland zone. Nutrient fluxes via litterfall followed the decreasing sequence: N (11-129 kg.hm-2.aq) 〉 Ca (9-69) 〉 K (5-20) 〉 Mg (3-15) 〉 P (0.4-4.7) for all stands. Significant differences were found in litterfall production and nutrient fluxes among the different landscape components. There existed significant differences in soil chemistry between the different landscape zones. The consistently low soil C:N ratios at the riparian zone might be due to the higher-quality litter inputs (largely N-fixing alder). 展开更多
关键词 Landscape LITTERFALL Nutrient cycling Soil chemistry temperate forest
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Abiotic and biotic drivers of species diversity in understory layers of cold temperate coniferous forests in North China 被引量:10
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作者 Hui Wang Mengtao Zhang Hongwei Nan 《Journal of Forestry Research》 SCIE CAS CSCD 2019年第6期2213-2225,共13页
Understory plants are important components of forest ecosystems and play a crucial role in regulating community structures,function realization,and community succession.However,little is known about how abiotic and bi... Understory plants are important components of forest ecosystems and play a crucial role in regulating community structures,function realization,and community succession.However,little is known about how abiotic and biotic drivers affect the diversity of understory species in cold temperate coniferous forests in the semiarid climate region of North China.We hypothesized that(1)topographic factors are important environmental factors affecting the distribution and variation of understory strata,and(2)different understory strata respond differently to environmental factors;shrubs may be significantly affected by the overstory stratum,and herbs may be more affected by surface soil conditions.To test these hypotheses,we used the boosted regression tree method to analyze abiotic and biotic environmental factors that influence understory species diversity,using data from 280 subplots across 56 sites in cold temperate coniferous forests of North China.Elevation and slope aspect were the dominant and indirect abiotic drivers affecting understory species diversity,and individual tree size inequality(DBH variation)was the dominant biotic driver of understory species diversity;soil water content was the main edaphic factors affecting herb layers.Elevation,slope aspect,and DBH variation accounted for 36.4,14.5,and 12.1%,respectively,of shrub stratum diversity.Shrub diversity decreased with elevation within the range of altitude of this study,but increased with DBH variation;shrub diversity was highest on north-oriented slopes.The strongest factor affecting herb stratum species diversity was slope aspect,accounting for 25.9%of the diversity,followed by elevation(15.7%),slope(12.2%),and soil water content(10.3%).The highest herb diversity was found on southeast-oriented slopes and the lowest on northeast-oriented slopes;herb diversity decreased with elevation and soil water content,but increased with slope.The results of the study provide a reference for scientific management and biodiversity protection in cold temperate coniferous forests of North China. 展开更多
关键词 ABIOTIC and biotic DRIVERS Cold temperATE CONIFEROUS forests North China SEMI-ARID region UNDERSTORY species diversity
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Litter decomposition and C and N dynamics as affected by N additions in a semi-arid temperate steppe, Inner Mongolia of China 被引量:17
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作者 Qin PENG YuChun QI +7 位作者 YunShe DONG YaTing HE ShengSheng XIAO XinChao LIU LiangJie SUN JunQiang JIA ShuFang GUO CongCong CAO 《Journal of Arid Land》 SCIE CSCD 2014年第4期432-444,共13页
Litter decomposition is the fundamental process in nutrient cycling and soil carbon(C) sequestration in terrestrial ecosystems. The global-wide increase in nitrogen(N) inputs is expected to alter litter decomposit... Litter decomposition is the fundamental process in nutrient cycling and soil carbon(C) sequestration in terrestrial ecosystems. The global-wide increase in nitrogen(N) inputs is expected to alter litter decomposition and,ultimately, affect ecosystem C storage and nutrient status. Temperate grassland ecosystems in China are usually N-deficient and particularly sensitive to the changes in exogenous N additions. In this paper, we conducted a 1,200-day in situ experiment in a typical semi-arid temperate steppe in Inner Mongolia to investigate the litter decomposition as well as the dynamics of litter C and N concentrations under three N addition levels(low N with 50 kg N/(hm2?a)(LN), medium N with 100 kg N/(hm2?a)(MN), and high N with 200 kg N/(hm2?a)(HN)) and three N addition forms(ammonium-N-based with 100 kg N/(hm2?a) as ammonium sulfate(AS), nitrate-N-based with 100 kg N/(hm2?a) as sodium nitrate(SN), and mixed-N-based with 100 kg N/(hm2?a) as calcium ammonium nitrate(CAN)) compared to control with no N addition(CK). The results indicated that the litter mass remaining in all N treatments exhibited a similar decomposition pattern: fast decomposition within the initial 120 days, followed by a relatively slow decomposition in the remaining observation period(120–1,200 days). The decomposition pattern in each treatment was fitted well in two split-phase models, namely, a single exponential decay model in phase I(〈398 days) and a linear decay function in phase II(≥398 days). The three N addition levels exerted insignificant effects on litter decomposition in the early stages(〈398 days, phase I; P〉0.05). However, MN and HN treatments inhibited litter mass loss after 398 and 746 days, respectively(P〈0.05). AS and SN treatments exerted similar effects on litter mass remaining during the entire decomposition period(P〉0.05). The effects of these two N addition forms differed greatly from those of CAN after 746 and 1,053 days, respectively(P〈0.05). During the decomposition period, N concentrations in the decomposing litter increased whereas C concentrations decreased, which also led to an exponential decrease in litter C:N ratios in all treatments. No significant effects were induced by N addition levels and forms on litter C and N concentrations(P〉0.05). Our results indicated that exogenous N additions could exhibit neutral or inhibitory effects on litter decomposition, and the inhibitory effects of N additions on litter decomposition in the final decay stages are not caused by the changes in the chemical qualities of the litter, such as endogenous N and C concentrations. These results will provide an important data basis for the simulation and prediction of C cycle processes in future N-deposition scenarios. 展开更多
关键词 litter decomposition N deposition N level N form C sequestration semi-arid temperate grassland
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Effects of Si on the stability of retained austenite and temper embrittlement of ultrahigh strength steels 被引量:9
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作者 Li-jun Wang Qing-wu Cai Hui-bin Wu Wei Yu 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2011年第5期543-550,共8页
Effects of silicon (Si) content on the stability of retained austenite and temper embrittlement of ultrahigh strength steels were investigated using X-ray diffraction (XRD),transmission electron microscopy (TEM)... Effects of silicon (Si) content on the stability of retained austenite and temper embrittlement of ultrahigh strength steels were investigated using X-ray diffraction (XRD),transmission electron microscopy (TEM),and other experimental methods.The results show that Si can suppress temper embrittlement,improve temper resistance,and hinder the decomposition of retained austenite.Reversed austenite appears gradually with the increase of Si content during tempering.Si has a significant effect on enhancing carbon (C) partitioning and improving the stability of retained austenite.Si and C atoms are mutually exclusive in lath bainite,while they attract each other in austenite.ε-carbides are found in 1.8wt% Si steel tempered at 250℃,and they get coarsened obviously when tempered at 400℃,leading to temper embrittlement.Not ε-carbides but acicular or lath carbides lead to temper embrittlement in 0.4wt% Si steel,which can be inferred as cementites and composite compounds.Temper embrittlement is closely related to the decomposition of retained austenite and the formation of reversed austenite. 展开更多
关键词 SILICON ultrahigh strength steel retained austenite temper embrittlement reversed austenite
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Impact of nitrogen addition on plant community in a semi-arid temperate steppe in China 被引量:20
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作者 Ling SONG XueMei BAO +1 位作者 XueJun LIU FuSuo ZHANG 《Journal of Arid Land》 SCIE 2012年第1期3-10,共8页
Increased nitrogen (N) deposition will often lead to a decline in species richness in grassland ecosystems but the shifts in functional groups and plant traits are still poorly understood in China. A field experimen... Increased nitrogen (N) deposition will often lead to a decline in species richness in grassland ecosystems but the shifts in functional groups and plant traits are still poorly understood in China. A field experiment was conducted at Duolun, Inner Mongolia, China, to investigate the effects of N addition on a temperate steppe ecosystem. Six N levels (0, 3, 6, 12, 24, and 48 g N/(m2-a)) were added as three applications per year from 2005 to 2010. Enhanced N deposition, even as little as 3 g N/(m2.a) above ambient N deposition (1.2 g N/(m2.a)), led to a decline in species richness of the whole community. Increasing N addition can significantly stimulate aboveground biomass of perennial bunchgrasses (PB) but decrease perennial forbs (PF), and induce a slight change in the biomass of shrubs and semi-shrubs (SS). The biomass of annuals (AS) and perennial rhizome grasses (PR) accounts for only a small part of the total biomass. Species richness of PF decreased significantly with increasing N addition rate but there was a little change in the other functional groups. PB, as the dominant functional group, has a relatively higher height than others. Differences in the response of each functional group to N addition have site-specific and species-specific characteristics. We initially infer that N enrichment stimulated the growth of PB, which further suppressed the growth of other functional groups. 展开更多
关键词 nitrogen addition species richness BIOMASS functional group temperate steppe Duolun Inner Mongolia
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Precipitation behavior and martensite lath coarsening during tempering of T/P92 ferritic heat-resistant steel 被引量:7
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作者 Lin-qing Xu Dan-tian Zhang +4 位作者 Yong-chang Liu Bao-qun Ning Zhi-xia Qiao Ze-sheng Yan Hui-jun Li 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2014年第5期438-447,共10页
Tempering is an important process for T/P92 ferritic heat-resistant steel from the viewpoint of microstructure control, as it facili- tates the formation of final tempered martensite under serving conditions. In this ... Tempering is an important process for T/P92 ferritic heat-resistant steel from the viewpoint of microstructure control, as it facili- tates the formation of final tempered martensite under serving conditions. In this study, we have gained deeper insights on the mechanism underlying the microstructural evolution during tempering treatment, including the precipitation of carbides and the coarsening of martensite laths, as systematically analyzed by optical microscopy, transmission electron microscopy, and high-resolution transmission electron mi- croscopy. The chemical composition of the precipitates was analyzed using energy dispersive X-ray spectroscopy. Results indicate the for- mation of M3C (cementite) precipitates under normalized conditions. However, they tend to dissolve within a short time of tempering, owing to their low thermal stability. This phenomenon was substantiated by X-ray diffraction analysis. Besides, we could observe the precipitation of fine carbonitrides (MX) along the dislocations. The mechanism of carbon diffusion controlled growth of M23C6 can be expressed by the Zener's equation. The movement of Y-junctions was determined to be the fundamental mechanism underlying the martensite lath coarsening process. Vickers hardness was estimated to determine their mechanical properties. Based on the comprehensive analysis of both the micro- structural evolution and hardness variation, the process of tempering can be separated into three steps. 展开更多
关键词 ferritic steel heat resisting temperING PRECIPITATION MARTENSITE COARSENING
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Effect of tempering temperature on microstructure and mechanical properties of high boron white cast iron 被引量:10
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作者 Liu Zhongli Li Yanxiang Chen Xiang 《China Foundry》 SCIE CAS 2012年第4期313-317,共5页
The effect of different tempering temperatures on the microstructure and mechanical properties of airquenched high boron white cast iron was studied.The results indicate that the high boron white cast iron comprises d... The effect of different tempering temperatures on the microstructure and mechanical properties of airquenched high boron white cast iron was studied.The results indicate that the high boron white cast iron comprises dendritic matrix and inter-dendritic M 2 B boride;and the matrix comprises martensite and pearlite.After quenching in the air,the matrix is changed into lath martensite;but only 1-μm-size second phase exists in the matrix.After tempering,another second phase of several tens of nanometers is found in the matrix,and the size and quantity increase with an increase in tempering temperature.The two kinds of second precipitation phase with different sizes in the matrix have the same chemical formula,but their forming stages are different.The precipitation phase with larger size forms during the austenitizing process,while the precipitation phase with smaller size forms during the tempering process.When tempered at different temperatures after quenching,the hardness decreases with an increase in the tempering temperature,but it increases a little at 450 ℃ due to the precipitation strengthening effect of the second phase,and it decreases greatly due to the martensite decomposition above 450 ℃.The impact toughness increases a little when tempered below 300 ℃,but it then decreases continuously owing to the increase in size and quantity of the secondary precipitate above 300 ℃.Considered comprehensively,the optimum tempering temperature is suggested at 300 ℃ to obtain a good combination of hardness and toughness. 展开更多
关键词 high boron white cast iron BORIDE QUENCHING temperING
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Influence of climate warming and nitrogen deposition on soil phosphorus composition and phosphorus availability in a temperate grassland,China 被引量:13
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作者 GuangNa ZHANG ZhenHua CHEN +2 位作者 AiMing ZHANG LiJun CHEN ZhiJie WU 《Journal of Arid Land》 SCIE CSCD 2014年第2期156-163,共8页
Climate warming and nitrogen (N) deposition change ecosystem processes, structure, and functioning whereas the phosphorus (P) composition and availability directly influence the ecosystem structure under condi- ti... Climate warming and nitrogen (N) deposition change ecosystem processes, structure, and functioning whereas the phosphorus (P) composition and availability directly influence the ecosystem structure under condi- tions of N deposition. In our study, four treatments were designed, including a control, diurnal warming (DW), N deposition (ND), and combined warming and N deposition (WN). The effects of DW, ND, and WN on P composition were studied by 3~p nuclear magnetic resonance (3~p NMR) spectroscopy in a temperate grassland region of China. The results showed that the N deposition decreased the soil pH and total N (TN) concentration but increased the soil OIsen-P concentration. The solution-state 31p NMR analysis showed that the DW, ND and WN treatments slightly decreased the proportion of orthophosphate and increased that of the monoesters. An absence of myo-inositol phosphate in the DW, ND and WN treatments was observed compared with the control. Furthermore, the DW, ND and WN treatments significantly decreased the recovery of soil P in the NaOH-EDTA solution by 17%-20%. The principal component analysis found that the soil pH was positively correlated with the P recovery in the NaOH-EDTA solution. Therefore, the decreased soil P recovery in the DW and ND treatments might be caused by an indirect influence on the soil pH. Additionally, the soil moisture content was the key factor limiting the available P. The positive correlation of total carbon (TC) and TN with the soil P composition indicated the influence of climate warming and N deposition on the biological processes in the soil P cycling. 展开更多
关键词 climate warming nitrogen deposition temperate grassland 31p nuclear magnetic resonance spectroscopy
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