AIM: To investigate the relationship between the expression levels of nm23 mRNA, CD44s, and CD44v6,and oncogenesis, development and metastasis of human gastric adenocarcinoma, colorectal adenocarcinoma,intraductal car...AIM: To investigate the relationship between the expression levels of nm23 mRNA, CD44s, and CD44v6,and oncogenesis, development and metastasis of human gastric adenocarcinoma, colorectal adenocarcinoma,intraductal carcinoma of breast, and lung cancer.METHODS: Using tissue microarray by immuhistochemical (IHC) staining and in situ hybri-dization (ISH), we examined the expression levels of nm23mRNA, CD44s, and CD44v6 in 62 specimens of human gastric adenocarcinoma and 62 specimens of colorectal adenocarcinoma; the expression of CD44s and CD44v6in 120 specimens of intraductal carcinoma of breast and 20 specimens of normal breast tissue; the expression of nm23 mRNA in 72 specimens of human lung cancer and 23 specimens of normal tissue adjacent to cancer.RESULTS: The expression of nm23 mRNA in the tissues of gastric and colorectal adenocarcinoma was not significantly different from that in the normal tissues adjacent to cancer (P＞0.05), and was not associated with the invasion of tumor and the pathology grade of adenocarcinoma (P＞0.05). However, the expression of nm23 mRNA was correlated negatively to the lymph node metastasis of gastric and colorectal adenocarcinoma (r = -0.49, P＜0.01; r = -4.93, P＜0.01). The expression of CD44s in the tissues of gastric and colorectal adenocarcinoma was significantly different from that in the normal tissues adjacent to cancer (P＜0.05;P＜0.01). CD44v6 was expressed in the tissues of gastric and colorectal adenocarcinoma only, the expression of CD44v6 was significantly associated with the lymph node metastasis, invasion and pathological grade of the tumor (r = 0.47, P＜0.01; r = 5.04, P＜0.01). CD44sand CD44v6 were expressed in intraductal carcinoma of breast, the expression of CD44s and CD44v6 was significantly associated with lymph node metastases and invasion (P＜0.01). However, neither of them was expressed in the normal breast tissue. In addition, the expression of CD44v6 was closely related to the degree of cell differentiation of intraductal carcinoma of breast (展开更多
Detailed high-resolution emission inventories of primary particles(PM2.5,BC and OC) and pollutant gases(SO2,NOx,NH3,CO and VOCs) for China in 2007 were constructed on the basis of the latest fuel consumption data,most...Detailed high-resolution emission inventories of primary particles(PM2.5,BC and OC) and pollutant gases(SO2,NOx,NH3,CO and VOCs) for China in 2007 were constructed on the basis of the latest fuel consumption data,mostly at the county level,and from socio-economic statistics and data on fossil and biomass fuels obtained from government agencies.New emission factors reflecting local features were also used.The calculated emissions were 13.212 Mt PM2.5,1.4 Mt BC,2.946 Mt OC,31.584 Mt SO2,23.248 Mt NOx,16.017 Mt NH3,164.856 Mt CO and 35.464 Mt VOCs.The national and regional emissions were gridded with 0.5°× 0.5° resolution for use in air quality models.Larger emissions were found in eastern and central China than in western China.The emissions estimated here are roughly equal to those obtained in previous studies,but with different contributions from because of seasonal changes in residential heating and biomass combustion.Finally,uncertainties in inventories were analyzed.展开更多
Emission factors of particulate matter （PM）, element carbon （EC）, organic carbon （OC）, SO2, NOx, CO, CO2, and ten ions （Na^＋, NH4^＋, K^＋, Mg^2＋, Ca^2＋, Fˉ, Clˉ, NO2ˉ, NO3ˉ, SO42ˉ） were estimated from...Emission factors of particulate matter （PM）, element carbon （EC）, organic carbon （OC）, SO2, NOx, CO, CO2, and ten ions （Na^＋, NH4^＋, K^＋, Mg^2＋, Ca^2＋, Fˉ, Clˉ, NO2ˉ, NO3ˉ, SO42ˉ） were estimated from the domestic burning of four types of commonly produced crop residues in rural China： rice straw, wheat straw, corn stover, and cotton stalk, which were collected from the representative regions across China. A combustion tower was designed to simulate the cooking conditions under which the peasants burned their crop residues in rural China, to measure the emission factors. Results showed that wheat straw had the highest emission factor for the total PM （8.75 g/kg） among the four crop residues, whereas, corn stover and wheat straw have the highest emission factor for EC （0.95 g/kg） and OC （3.46 g/kg）, respectively. Corn stover also presents as having the highest emission factors of NO, NOx, and CO2, whereas, wheat straw, rice straw, and cotton stalk had the highest emission factors of NO2, SO2, and CO, respectively. The water-soluble ions, K^＋ and Clˉ, had the highest emission factors from all the crops. Wheat straw had a relatively higher emission factor of cation species and Fˉ, Clˉ, NO2ˉ than other residues.展开更多
Emissions resulting from crop straw field burning in China, which have caused serious environmental problems in China, are estimated in this paper. From the county-level data of crop production in 2000― 2003 from the...Emissions resulting from crop straw field burning in China, which have caused serious environmental problems in China, are estimated in this paper. From the county-level data of crop production in 2000― 2003 from the government statistics, taking into account the ratio of residue and grain, the total amount of crop straw production is estimated to be about 600 Tg per year, 76% of which are rice, wheat and corn straw. With reference to the data of living standards, the percentage of crop straw burnt in fields for counties are obtained and consequently the total amount of burnt straws is approximately 140 Tg/year. With the emission factors from literature and experiments, appropriate emission factors have been obtained. The total amounts of PM, SO_2, NO_x, NH_3, CH_4, BC, OC, VOC, CO, CO_2 emissions from field burning of crop straw in China are estimated. All emissions are presented at county level. Some pollutants, such as BC, VOC, OC, CO and CO_2, are contributing a major portion to the total emissions of China. This paper uses a map with resolution of 0.2°×0.2° to present the PM emissions distribution from crop straw burnt in 2003. The results show a significant regional unevenness of emissions, with larger amounts of pollutions coming from the provinces in eastern and northeast China. The regions with higher emissions per unit area are located as a belt stretching from northeast China to eastern China.展开更多
To investigate the influence of tempering process on microstructural evolutions and mechanical properties of 00Cr13Ni4Mo supermartensitic stainless steel（SMSS）,specimens were tempered in the temperature range of 520...To investigate the influence of tempering process on microstructural evolutions and mechanical properties of 00Cr13Ni4Mo supermartensitic stainless steel（SMSS）,specimens were tempered in the temperature range of 520-720 ℃ for 3 h followed by air cooling and an optimized tempering temperature was chosen to prolong holding time from 3 to 12 h.After heat treatments,microstructure examination was conducted by scanning electron microscope,X-ray diffraction examinations,hardness measurements and tensile tests.The results revealed that the superior mechanical properties were achieved by quenching at 1040 ℃ for 1 h＋water cooling and tempering at 600 ℃ for 3 h＋air cooling.Increasing isothermal tempering time could improve the toughness notably.It was believed that the property was correlated with the microstructure of tempered lath martensite and retained austenite.More retained austenite content is beneficial to the higher toughness of the SMSS.展开更多
Asthma,rhinitis and eczema(allergic or non-allergic)have increased throughout the world during the last decades,especially among children.Changes in the indoor environment are suspected to be important causes.China ha...Asthma,rhinitis and eczema(allergic or non-allergic)have increased throughout the world during the last decades,especially among children.Changes in the indoor environment are suspected to be important causes.China has experienced a dramatic change in indoor environmental exposures during the past two decades.However,such changes and their associations with children’s asthma and other health aspects have not been thoroughly studied.China,Children,Homes,Health(CCHH),Phase I,was a cross-sectional questionnaire survey of 48219 children 1–8 years old in 10 Chinese cities during 2010–2012.The questionnaire includes the International Study of Asthma and Allergies in Childhood(ISAAC)core health questions and additional questions regarding housing,life habits and outdoor environment.In health analyses,children aged 3–6 years old were included.The prevalences of doctor diagnosed asthma varied from 1.7%to 9.8%(mean 6.8%),a large increase from 0.91%in 1999 and 1.50%in2000.The prevalence of wheeze,rhinitis and atopic eczema(last 12 months)varied from 13.9%to 23.7%,24.0%to 50.8%and4.8%to 15.8%,respectively.Taiyuan had the lowest prevalences of all illnesses and Shanghai the highest,except for wheezewhere the highest value was for Urumqi.We found(1)no obvious association between disease prevalences and ambient PM10concentrations and(2)higher prevalences of disease in humid climates with hot summers and cold winters,but with no centrally heated buildings.Associations between the diseases and economic status as indexed by Gross Domestic Product(GDP)requires further study.展开更多
Sustainable and resilient pavement infrastructure is critical for current economic and environmental challenges.In the past 10 years,the pavement infrastructure strongly supports the rapid development of the global so...Sustainable and resilient pavement infrastructure is critical for current economic and environmental challenges.In the past 10 years,the pavement infrastructure strongly supports the rapid development of the global social economy.New theories,new methods,new technologies and new materials related to pavement engineering are emerging.Deterioration of pavement infrastructure is a typical multi-physics problem.Because of actual coupled behaviors of traffic and environmental conditions,predictions of pavement service life become more and more complicated and require a deep knowledge of pavement material analysis.In order to summarize the current and determine the future research of pavement engineering,Journal of Traffic and Transportation Engineering(English Edition)has launched a review paper on the topic of"New innovations in pavement materials and engineering:A review on pavement engineering research 2021".Based on the joint-effort of 43 scholars from 24 well-known universities in highway engineering,this review paper systematically analyzes the research status and future development direction of 5 major fields of pavement engineering in the world.The content includes asphalt binder performance and modeling,mixture performance and modeling of pavement materials,multi-scale mechanics,green and sustainable pavement,and intelligent pavement.Overall,this review paper is able to provide references and insights for researchers and engineers in the field of pavement engineering.展开更多
Using GIS, GPS and GPRS, a dynamic management system of ore blending in an open pit mine has been designed and developed. A linear program was established in a practical application. The system is very good at automat...Using GIS, GPS and GPRS, a dynamic management system of ore blending in an open pit mine has been designed and developed. A linear program was established in a practical application. The system is very good at automatically drawing up a daily production plan of ore blending and monitors and controls the process of mining production in real time. Experiments under real conditions show that the performance of this system is stable and can satisfy production standards of ore blending in open pit mines.展开更多
Magnesium(Mg)alloys have been extensively used in various fields,such as aerospace,automobile,electronics,and biomedical industries,due to their high specific strength and stiff ness,excellent vibration absorption,ele...Magnesium(Mg)alloys have been extensively used in various fields,such as aerospace,automobile,electronics,and biomedical industries,due to their high specific strength and stiff ness,excellent vibration absorption,electromagnetic shielding eff ect,good machinability,and recyclability.Friction stir processing(FSP)is a severe plastic deformation technique,based on the principle of friction stir welding.In addition to introducing the basic principle and advantages of FSP,this paper reviews the studies of FSP in the modification of the cast structure,superplastic deformation behavior,preparation of finegrained Mg alloys and Mg-based surface composites,and additive manufacturing.FSP not only refines,homogenizes,and densifies the microstructure,but also eliminates the cast microstructure defects,breaks up the brittle and network-like phases,and prepares fine-grained,ultrafine-,and nano-grained Mg alloys.Indeed,FSP significantly improves the comprehensive mechanical properties of the alloys and achieves low-temperature and/or high strain rate superplasticity.Furthermore,FSP can produce particle-and fiber-reinforced Mg-based surface composites.As a promising additive manufacturing technique of light metals,FSP enables the additive manufacturing of Mg alloys.Finally,we prospect the future research direction and application with friction stir processed Mg alloys.展开更多
Aerobic composting is a method for the sanitary disposal of human feces as is used in bio-toilet systems.As the products of composting can be utilized as a fertilizer,it would be beneficial if the composting condition...Aerobic composting is a method for the sanitary disposal of human feces as is used in bio-toilet systems.As the products of composting can be utilized as a fertilizer,it would be beneficial if the composting conditions could be more precisely controlled for the retention of fecal nitrogen as long as possible in the compost.In this study,batch experiments were conducted using a closed aerobic thermophilic composting reactor with sawdust as the bulk matrix to simulate the condition of a bio-toilet for the sanitary disposal of human feces.Attention was paid to the characteristics of nitrogen transformation.Under the controlled conditions of temperature at 60°C,moisture content at 60%,and a continuous air supply,more than 70%fecal organic removal was obtained,while merely 17%fecal nitrogen loss was observed over a two-week composting period.The nitrogen loss was found to occur mainly in the first 24 h with the rapid depletion of inorganic nitrogen but with an almost unchanged organic nitrogen content.The fecal NH4-N which was the main component of the inorganic nitrogen(>90%)decreased rapidly in the first day,decreased at a slower rate over the following days,and finally disappeared entirely.The depletion of NH4-N was accompanied by the accumulation of NH3 gas in the ammonia absorber connected to the reactor.A mass balance between the exhausted NH3 gas and the fecal NH4-N content in the first 24 hours indicated that the conversion of ammonium into gaseous ammonia was the main reason for nitrogen loss.Thermophilic composting could be considered as a way to keep a high organic nitrogen content in the compost for better utilization as a fertilizer.展开更多
Graded modified Fenton’s （MF） oxidation is a strategy in which H 2 O 2 is added intermittently to prevent a sharp temperature increase and undesired soil sterilization at soil circumneutral pH versus adding the sam...Graded modified Fenton’s （MF） oxidation is a strategy in which H 2 O 2 is added intermittently to prevent a sharp temperature increase and undesired soil sterilization at soil circumneutral pH versus adding the same amount of H 2 O 2 continuously.The primary objective of the present study was to investigate whether a mild MF pre-oxidation such as a stepwise addition of H 2 O 2 can prevent sterilization and achieve a maximum degradation of tank oil in soil.Optimization experiments of graded MF oxidation were conducted using citric acid,oxalic acid and SOLV-X as iron chelators under different frequencies of H 2 O 2 addition.The results indicated that the activity order of iron chelates decreased as：citric acid （51%） SOLV-X （44%） oxalic acid （9%）,and citric acid was found to be an optimized iron chelating agent of graded MF oxidation.Three-time addition of H 2 O 2 was found to be favorable and economical due to decreasing total petroleum hydrocarbon removal from three time addition （51%） to five time addition （59%）.Biological experiments were conducted after graded MF oxidation of tank oil completed under optimum conditions mentioned above.After graded oxidation,substantially higher increase （31%） in microbial activity was observed with excessive H 2 O 2 （1470 mmol/L,the mol ratio of H 2 O 2：Fe 2＋ was 210：1） than that of non-oxidized soil.Removal efficiency of tank oil was up to 93% after four weeks.Especially,the oil fraction （C 10 –C 40 ） became more biodagradable after graded MF oxidation than its absence.Therefore,graded MF oxidation is a mild pretreatment to achieve an effective bioremediation of oil contaminated soil.展开更多
Using GIS,GPS and GPRS,an intelligent monitoring and dispatch system of trucks and shovels in an open pit has been designed and developed.The system can monitor and dispatch open-pit trucks and shovels and play back t...Using GIS,GPS and GPRS,an intelligent monitoring and dispatch system of trucks and shovels in an open pit has been designed and developed.The system can monitor and dispatch open-pit trucks and shovels and play back their historical paths.An intelligent data algorithm is proposed in a practical application.The algorithm can count the times of deliveries of trucks and load- ings of shovels.Experiments on real scenes show that the performance of this system is stable and can satisfy production standards in open pits.展开更多
The effects of phase transformation on mechanical properties and pitting corrosion of 2205 duplex stainless steel were investigated. The amount of a phase in the test specimen varied up to a maximum of 6 % by thermal ...The effects of phase transformation on mechanical properties and pitting corrosion of 2205 duplex stainless steel were investigated. The amount of a phase in the test specimen varied up to a maximum of 6 % by thermal treatment at 850 ℃ for up to 60 min. The results showed that ~ phase markedly increased the hardness and decreased the impact toughness of the test steel. But the increasing tendency of the ultimate tensile strength and the yield strength was not obvious, while the total elongation abruptly decreased with the aging time from 5 to 60 min. SEM impact microfractograph analysis revealed that the types of impact fracture changed from ductile mode to transcrystalline mode when the specimens were aged for 5-60 min. Furthermore, the extent of pitting potential reducing was found to be strongly temperature dependent, more pronounced at the higher temperature. During the incubation period of σ phase nucleation, the pitting corrosion test temperature and the aging time had collaborative effects on evidently displacing the pitting potential towards less noble values. After 15 min, the higher temperature contributed more to decreasing the pitting potential than the aging time.展开更多
Developing sustainable and clean electrochemical energy conversion technologies is a crucial step in addressing the challenges of energy shortage and environmental pollution. Exploring and developing new electrocataly...Developing sustainable and clean electrochemical energy conversion technologies is a crucial step in addressing the challenges of energy shortage and environmental pollution. Exploring and developing new electrocatalysts with excellent performance and low cost will facilitate the commercial use of these energy conversion technologies. Recently, dual-atom catalysts(DACs) have attracted considerable research interest since they exhibit higher metal atom loading and more flexible active sites compared to single-atom catalysts(SACs). In this paper, the latest preparation methods and characterization techniques of DACs are systematically reviewed. The advantages of homonuclear and heteronuclear DACs and the catalytic mechanism and identification technologies between the two DACs are highlighted. The current applications of DACs in the field of electrocatalysis are summarized. The development opportunities and challenges of DACs in the future are prospected. The ultimate goal is to provide new ideas for the preparation of new catalysts with excellent properties by customizing diatomic catalysts for electrochemical applications.展开更多
In order to analyze the effect of voltage during micro-arc oxidation(MAO)on corrosion and wear properties of Ti6Al4V(TC4),the MAO technology was employed to treat TC4 samples fabricated by selective electron beam melt...In order to analyze the effect of voltage during micro-arc oxidation(MAO)on corrosion and wear properties of Ti6Al4V(TC4),the MAO technology was employed to treat TC4 samples fabricated by selective electron beam melting(SEBM)at the voltages of 400,420 and 450 V.The results show that the metastable anatase phase gradually transforms to rutile phase with oxidation time and temperature increasing.The surface morphology of coating contains numerous micropores with uniform size distribution.Cracks and pores over 10μm are found on MAO-TC4 sample with applied voltage of 450 V.The thickness of MAO coating is positively correlated with the voltage.The corrosion resistance and wear resistance are related to phase composition,micropore size distribution on the surface and film thickness.When the voltage is 420 V,the coating shows the smallest corrosion current density(0.960×10^-7 A/cm^2)and the largest resistance(7.17×10^5Ω·cm^2).Under the same load condition,the coating exhibits larger friction coefficient and wear loss than the TC4 substrate.With the increase of voltage,the wear mechanism of the coating changes from abrasive wear to adhesive wear,and the adhesive wear is intensified at applied voltage of 450 V,with a maximum friction coefficient of 0.821.展开更多
Urban lake ecosystems are significant for social development,but currently we know little about the geographical distribution of algal community in urban lakes at a large-scale.In this study,we investigated the algal ...Urban lake ecosystems are significant for social development,but currently we know little about the geographical distribution of algal community in urban lakes at a large-scale.In this study,we investigated the algal community structure in different areas of urban lakes in China and evaluated the influence of water quality parameters and geographical location on the algal community.The results showed that obvious differences in water quality and algal communities were observed among urban lakes in different geographical areas.Chlorophyta was the dominant phylum,followed by cyanobacteria in all areas.The network analysis indicated that algal community composition in urban lakes of the western and southern area showed more variations than the eastern and northern areas,respectively.Redundancy analysis and structural equation model revealed that nutrients and p H were dominant environmental factors that affected the algal community,and they showed higher influence than that of iron,manganese and COD Mn concentration.Importantly,algal community and density exhibited longitude and latitude relationship.In general,these results provided an ecological insight into large-scale geographical distributions of algal community in urban lakes,thereby having potential applications for management of the lakes.展开更多
Elevated arsenic（As） in groundwater poses a great threat to human health. Coagulation using mono- and poly-Fe salts is becoming one of the most cost-effective processes for groundwater As removal. However, a limitat...Elevated arsenic（As） in groundwater poses a great threat to human health. Coagulation using mono- and poly-Fe salts is becoming one of the most cost-effective processes for groundwater As removal. However, a limitation comes from insufficient understanding of the As removal mechanism from groundwater matrices in the coagulation process, which is critical for groundwater treatment and residual solid disposal. Here, we overcame this hurdle by utilizing microscopic techniques to explore molecular As surface complexes on the freshly formed Fe flocs and compared ferric（III） sulfate（FS） and polyferric sulfate（PFS）performance, and finally provided a practical solution in As-geogenic areas. FS and PFS exhibited a similar As removal efficiency in coagulation and coagulation/filtration in a two-bucket system using 5 mg/L Ca（ClO）_2. By using the two-bucket system combining coagulation and sand filtration, 500 L of As-safe water（〈 10 μg/L） was achieved during five treatment cycles by washing the sand layer after each cycle. Fe k-edge X-ray absorption near-edge structure（XANES） and As k-edge extended X-ray absorption fine structure（EXAFS） analysis of the solid residue indicated that As formed a bidentate binuclear complex on ferrihydrite, with no observation of scorodite or poorly-crystalline ferric arsenate. Such a stable surface complex is beneficial for As immobilization in the solid residue, as confirmed by the achievement of much lower leachate As（0.9 μg/L-0.487 mg/L）than the US EPA regulatory limit（5 mg/L）. Finally, PFS is superior to FS because of its lower dose, much lower solid residue, and lower cost for As-safe drinking water.展开更多
The seasonal changes in leaf particulate matter （PM） accumulation, surface wettability and micromor- phology in urban tree species, including Sophorajaponica （S. japonica）, Platanus acerifolia （P. acerifolia） an...The seasonal changes in leaf particulate matter （PM） accumulation, surface wettability and micromor- phology in urban tree species, including Sophorajaponica （S. japonica）, Platanus acerifolia （P. acerifolia） and Cedrus deodara （C. deodara）, were studied during a single growing season. The three species showed distinct seasonal trends in PM accumulation, increasing from spring to autumn （or winter） even during the rainy season, but at different rates. During the study, the leaf PM retention amount ofP acerifolia, a species with ridged leaf surfaces, was significantly higher than that of S. japonica and C. deodara, species with waxy leaf surfaces. The contact angles of water droplets on leaves decreased with leafage except on the abaxial surface orS.japonica, which remained non-wettable or highly non-wettable throughout the growing season; the decrease in the contact angle on adaxial surface of S. japonica was greater when compared with P acerifolia and C. deodara. A significant and negative relationship existed between leaf PM retention amounts and contact angles on adaxial surface of leaves of all three species. The increase in wettability, probably caused when epicuticular wax was destroyed by mechan- ical and chemical abrasion, seemed to be the main factor leading to seasonal variations in leaf PM accumulation.展开更多
A novel Cu-Mn-Ce/cordierite honeycomb catalyst was prepared by an incipient wetness method and the catalyst was characterized. The active ingredients were present as various spinel species of Cu, Mn and Ce oxides with...A novel Cu-Mn-Ce/cordierite honeycomb catalyst was prepared by an incipient wetness method and the catalyst was characterized. The active ingredients were present as various spinel species of Cu, Mn and Ce oxides with different valences and they were unevenly dispersed over the surface of the catalyst. The catalytic oxidation of gaseous toluene was primarily investigated using a fixed bed reactor under microwave heating in the continuous flow mode. Under the optimal conditions of 6.7 wt-% loading of the active component, a bed temperature of 200℃, a flow rate of 0.12 m^3 · h^-1 and an initial concentration of toluene of 1000 mg·m^-3, the removal and mineralization efficiencies of toluene were 98% and 70%, respectively. Thus the use of the microwave effectively improved the oxidation of toluene and this is attributed to dipole polarization and hotspot effects. After four consecutive cycles (a total of 1980 min), the Cu-Mn- Ce/cordierite catalyst still exhibited excellent catalytic activity and structural stability, and the toluene removal was higher than 90%. This work demonstrates the possibility of treating volatile organic compounds in exhaust gases by microwave-assisted catalytic oxidation.展开更多
A high-manganese austenitic steel matrix （Mn13） composite reinforced with TiN ceramic particles was synthesized by means of Vacuum-Evaporation Pattern Casting （V-EPC）. The composite microstructure and interface bo...A high-manganese austenitic steel matrix （Mn13） composite reinforced with TiN ceramic particles was synthesized by means of Vacuum-Evaporation Pattern Casting （V-EPC）. The composite microstructure and interface bonding of TiN/matrix were analyzed utilizing optical microscope （OM） and X-ray diffraction （XRD）. The effects of different volume fraction of TiN on impact wear resistance were evaluated by MLD-10 impact wear test. The results showed that TiN was evenly distributed in composite layer and had a good interface bonding with matrix when the volume fractions of TiN were 27% and 36% respectively. However, cast defects and TiN agglomeration occurred when the TiN volume fraction increased to 48~. Compared with high-manganese austenitic steel （Mnl3）, the im- pact wear resistance of the TiN-reinforced composite is better. In small impact load conditions, composite layer can effectively resist abrasives wear and TiN particles played an important role in determining impact wear resistance of composite layer. In large impact load, the synergistic roles of spalling of TiN particles and the increase of work hardening of Mn13 based material are responsible for impact wear resistance.展开更多
基金Supported by the National Key Development Programs of West China during the 10th Five-Year Plan Period, No. 2001BA901A44
文摘AIM: To investigate the relationship between the expression levels of nm23 mRNA, CD44s, and CD44v6,and oncogenesis, development and metastasis of human gastric adenocarcinoma, colorectal adenocarcinoma,intraductal carcinoma of breast, and lung cancer.METHODS: Using tissue microarray by immuhistochemical (IHC) staining and in situ hybri-dization (ISH), we examined the expression levels of nm23mRNA, CD44s, and CD44v6 in 62 specimens of human gastric adenocarcinoma and 62 specimens of colorectal adenocarcinoma; the expression of CD44s and CD44v6in 120 specimens of intraductal carcinoma of breast and 20 specimens of normal breast tissue; the expression of nm23 mRNA in 72 specimens of human lung cancer and 23 specimens of normal tissue adjacent to cancer.RESULTS: The expression of nm23 mRNA in the tissues of gastric and colorectal adenocarcinoma was not significantly different from that in the normal tissues adjacent to cancer (P＞0.05), and was not associated with the invasion of tumor and the pathology grade of adenocarcinoma (P＞0.05). However, the expression of nm23 mRNA was correlated negatively to the lymph node metastasis of gastric and colorectal adenocarcinoma (r = -0.49, P＜0.01; r = -4.93, P＜0.01). The expression of CD44s in the tissues of gastric and colorectal adenocarcinoma was significantly different from that in the normal tissues adjacent to cancer (P＜0.05;P＜0.01). CD44v6 was expressed in the tissues of gastric and colorectal adenocarcinoma only, the expression of CD44v6 was significantly associated with the lymph node metastasis, invasion and pathological grade of the tumor (r = 0.47, P＜0.01; r = 5.04, P＜0.01). CD44sand CD44v6 were expressed in intraductal carcinoma of breast, the expression of CD44s and CD44v6 was significantly associated with lymph node metastases and invasion (P＜0.01). However, neither of them was expressed in the normal breast tissue. In addition, the expression of CD44v6 was closely related to the degree of cell differentiation of intraductal carcinoma of breast (
基金supported by the National Basic Research Program of China (2011CB403404)the National R&D Special Fund (Meteorology) for Public Welfare Industry (GYHY200706036)
文摘Detailed high-resolution emission inventories of primary particles(PM2.5,BC and OC) and pollutant gases(SO2,NOx,NH3,CO and VOCs) for China in 2007 were constructed on the basis of the latest fuel consumption data,mostly at the county level,and from socio-economic statistics and data on fossil and biomass fuels obtained from government agencies.New emission factors reflecting local features were also used.The calculated emissions were 13.212 Mt PM2.5,1.4 Mt BC,2.946 Mt OC,31.584 Mt SO2,23.248 Mt NOx,16.017 Mt NH3,164.856 Mt CO and 35.464 Mt VOCs.The national and regional emissions were gridded with 0.5°× 0.5° resolution for use in air quality models.Larger emissions were found in eastern and central China than in western China.The emissions estimated here are roughly equal to those obtained in previous studies,but with different contributions from because of seasonal changes in residential heating and biomass combustion.Finally,uncertainties in inventories were analyzed.
文摘Emission factors of particulate matter （PM）, element carbon （EC）, organic carbon （OC）, SO2, NOx, CO, CO2, and ten ions （Na^＋, NH4^＋, K^＋, Mg^2＋, Ca^2＋, Fˉ, Clˉ, NO2ˉ, NO3ˉ, SO42ˉ） were estimated from the domestic burning of four types of commonly produced crop residues in rural China： rice straw, wheat straw, corn stover, and cotton stalk, which were collected from the representative regions across China. A combustion tower was designed to simulate the cooking conditions under which the peasants burned their crop residues in rural China, to measure the emission factors. Results showed that wheat straw had the highest emission factor for the total PM （8.75 g/kg） among the four crop residues, whereas, corn stover and wheat straw have the highest emission factor for EC （0.95 g/kg） and OC （3.46 g/kg）, respectively. Corn stover also presents as having the highest emission factors of NO, NOx, and CO2, whereas, wheat straw, rice straw, and cotton stalk had the highest emission factors of NO2, SO2, and CO, respectively. The water-soluble ions, K^＋ and Clˉ, had the highest emission factors from all the crops. Wheat straw had a relatively higher emission factor of cation species and Fˉ, Clˉ, NO2ˉ than other residues.
基金Supported by the National Key Basic Research Project of China (Grant No. 2006CB403700)
文摘Emissions resulting from crop straw field burning in China, which have caused serious environmental problems in China, are estimated in this paper. From the county-level data of crop production in 2000― 2003 from the government statistics, taking into account the ratio of residue and grain, the total amount of crop straw production is estimated to be about 600 Tg per year, 76% of which are rice, wheat and corn straw. With reference to the data of living standards, the percentage of crop straw burnt in fields for counties are obtained and consequently the total amount of burnt straws is approximately 140 Tg/year. With the emission factors from literature and experiments, appropriate emission factors have been obtained. The total amounts of PM, SO_2, NO_x, NH_3, CH_4, BC, OC, VOC, CO, CO_2 emissions from field burning of crop straw in China are estimated. All emissions are presented at county level. Some pollutants, such as BC, VOC, OC, CO and CO_2, are contributing a major portion to the total emissions of China. This paper uses a map with resolution of 0.2°×0.2° to present the PM emissions distribution from crop straw burnt in 2003. The results show a significant regional unevenness of emissions, with larger amounts of pollutions coming from the provinces in eastern and northeast China. The regions with higher emissions per unit area are located as a belt stretching from northeast China to eastern China.
基金Item Sponsored by Special Project of Shaanxi Education Department of China(07JK309)Xi'an University of Architecture and Technology of China(JC0714)
文摘To investigate the influence of tempering process on microstructural evolutions and mechanical properties of 00Cr13Ni4Mo supermartensitic stainless steel（SMSS）,specimens were tempered in the temperature range of 520-720 ℃ for 3 h followed by air cooling and an optimized tempering temperature was chosen to prolong holding time from 3 to 12 h.After heat treatments,microstructure examination was conducted by scanning electron microscope,X-ray diffraction examinations,hardness measurements and tensile tests.The results revealed that the superior mechanical properties were achieved by quenching at 1040 ℃ for 1 h＋water cooling and tempering at 600 ℃ for 3 h＋air cooling.Increasing isothermal tempering time could improve the toughness notably.It was believed that the property was correlated with the microstructure of tempered lath martensite and retained austenite.More retained austenite content is beneficial to the higher toughness of the SMSS.
基金supported by the National Natural Science Foundation of China(51136002,51076079,51006057)Ministry of Science and Technology of China(2012BAJ02B03)National High Technology Research and Development Program of China(2010AA064903)
文摘Asthma,rhinitis and eczema(allergic or non-allergic)have increased throughout the world during the last decades,especially among children.Changes in the indoor environment are suspected to be important causes.China has experienced a dramatic change in indoor environmental exposures during the past two decades.However,such changes and their associations with children’s asthma and other health aspects have not been thoroughly studied.China,Children,Homes,Health(CCHH),Phase I,was a cross-sectional questionnaire survey of 48219 children 1–8 years old in 10 Chinese cities during 2010–2012.The questionnaire includes the International Study of Asthma and Allergies in Childhood(ISAAC)core health questions and additional questions regarding housing,life habits and outdoor environment.In health analyses,children aged 3–6 years old were included.The prevalences of doctor diagnosed asthma varied from 1.7%to 9.8%(mean 6.8%),a large increase from 0.91%in 1999 and 1.50%in2000.The prevalence of wheeze,rhinitis and atopic eczema(last 12 months)varied from 13.9%to 23.7%,24.0%to 50.8%and4.8%to 15.8%,respectively.Taiyuan had the lowest prevalences of all illnesses and Shanghai the highest,except for wheezewhere the highest value was for Urumqi.We found(1)no obvious association between disease prevalences and ambient PM10concentrations and(2)higher prevalences of disease in humid climates with hot summers and cold winters,but with no centrally heated buildings.Associations between the diseases and economic status as indexed by Gross Domestic Product(GDP)requires further study.
基金National Key R&D Program of China(No.2018YFB1600200,2021YFB1600200)National Natural Science Foundation of China(No.51608457,51778038,51808016,51808403,51908057,51908072,51908165,51908331,52008029,52008069,52078018,52078025,52078049,52078209,52108403,52122809,52178417)+9 种基金Marie Sk?odowska-Curie Individual Fellowships of the European Commission’s Horizon 2020 programme(No.101024139)Natural Science Foundation of Heilongjiang Province(No.JJ2020ZD0015)China Postdoctoral Science Foundation funded project(No.BX20180088)Research Capability Enhancement Program for Young Professors of Beijing University of Civil Engineering and Architecture(No.02080921021)Young Scholars of Beijing Talent Program(No.02082721009)Beijing Municipal Natural Science Foundation and Beijing Municipal Education Commission(No.KZ201910016017)German Research Foundation(No.OE 514/15-1(459436571))Fundamental Research Funds for the Central Universities(No.2020kfyXJJS127)Marie Sk?odowska-Curie Individual Fellowships of the European Commission’s Horizon 2020 Programme(No.101030767)Research Fund for High Level Talent Program(No.22120210108)。
文摘Sustainable and resilient pavement infrastructure is critical for current economic and environmental challenges.In the past 10 years,the pavement infrastructure strongly supports the rapid development of the global social economy.New theories,new methods,new technologies and new materials related to pavement engineering are emerging.Deterioration of pavement infrastructure is a typical multi-physics problem.Because of actual coupled behaviors of traffic and environmental conditions,predictions of pavement service life become more and more complicated and require a deep knowledge of pavement material analysis.In order to summarize the current and determine the future research of pavement engineering,Journal of Traffic and Transportation Engineering(English Edition)has launched a review paper on the topic of"New innovations in pavement materials and engineering:A review on pavement engineering research 2021".Based on the joint-effort of 43 scholars from 24 well-known universities in highway engineering,this review paper systematically analyzes the research status and future development direction of 5 major fields of pavement engineering in the world.The content includes asphalt binder performance and modeling,mixture performance and modeling of pavement materials,multi-scale mechanics,green and sustainable pavement,and intelligent pavement.Overall,this review paper is able to provide references and insights for researchers and engineers in the field of pavement engineering.
文摘Using GIS, GPS and GPRS, a dynamic management system of ore blending in an open pit mine has been designed and developed. A linear program was established in a practical application. The system is very good at automatically drawing up a daily production plan of ore blending and monitors and controls the process of mining production in real time. Experiments under real conditions show that the performance of this system is stable and can satisfy production standards of ore blending in open pit mines.
基金sponsorship from the National Natural Science Foundation of China(Nos.51574192,51404180,51974220,and U1760201)the Key Industrial Research Program of Shaanxi Province,China(No.2017ZDXMGY-037)+1 种基金the National Key Research and Development Program of China(No.Z20180407)the Youth Innovation Team of Shaanxi Universities(No.2019-2022).
文摘Magnesium(Mg)alloys have been extensively used in various fields,such as aerospace,automobile,electronics,and biomedical industries,due to their high specific strength and stiff ness,excellent vibration absorption,electromagnetic shielding eff ect,good machinability,and recyclability.Friction stir processing(FSP)is a severe plastic deformation technique,based on the principle of friction stir welding.In addition to introducing the basic principle and advantages of FSP,this paper reviews the studies of FSP in the modification of the cast structure,superplastic deformation behavior,preparation of finegrained Mg alloys and Mg-based surface composites,and additive manufacturing.FSP not only refines,homogenizes,and densifies the microstructure,but also eliminates the cast microstructure defects,breaks up the brittle and network-like phases,and prepares fine-grained,ultrafine-,and nano-grained Mg alloys.Indeed,FSP significantly improves the comprehensive mechanical properties of the alloys and achieves low-temperature and/or high strain rate superplasticity.Furthermore,FSP can produce particle-and fiber-reinforced Mg-based surface composites.As a promising additive manufacturing technique of light metals,FSP enables the additive manufacturing of Mg alloys.Finally,we prospect the future research direction and application with friction stir processed Mg alloys.
基金the National Natural Science Foundation of China(Grant No.51021140002)the National Program of Water Pollution Control(No.2008ZX07317-004)the Program for Changjiang Scholars and Innovative Research Team in University(No.IRT0853)。
文摘Aerobic composting is a method for the sanitary disposal of human feces as is used in bio-toilet systems.As the products of composting can be utilized as a fertilizer,it would be beneficial if the composting conditions could be more precisely controlled for the retention of fecal nitrogen as long as possible in the compost.In this study,batch experiments were conducted using a closed aerobic thermophilic composting reactor with sawdust as the bulk matrix to simulate the condition of a bio-toilet for the sanitary disposal of human feces.Attention was paid to the characteristics of nitrogen transformation.Under the controlled conditions of temperature at 60°C,moisture content at 60%,and a continuous air supply,more than 70%fecal organic removal was obtained,while merely 17%fecal nitrogen loss was observed over a two-week composting period.The nitrogen loss was found to occur mainly in the first 24 h with the rapid depletion of inorganic nitrogen but with an almost unchanged organic nitrogen content.The fecal NH4-N which was the main component of the inorganic nitrogen(>90%)decreased rapidly in the first day,decreased at a slower rate over the following days,and finally disappeared entirely.The depletion of NH4-N was accompanied by the accumulation of NH3 gas in the ammonia absorber connected to the reactor.A mass balance between the exhausted NH3 gas and the fecal NH4-N content in the first 24 hours indicated that the conversion of ammonium into gaseous ammonia was the main reason for nitrogen loss.Thermophilic composting could be considered as a way to keep a high organic nitrogen content in the compost for better utilization as a fertilizer.
基金supported by the Program of In-ternational S&T Cooperation(No.2010 DFA 94550,2010KW-24-1)the National Natural Science Founda-tion of China(No.50830303)+1 种基金the Major Science and Technology Program for Water Pollution Control and Treatment(No.2009ZX07317-007-001)the Program for Changjiang Scholars and Innovative Research Team in University(No.IRT0853)
文摘Graded modified Fenton’s （MF） oxidation is a strategy in which H 2 O 2 is added intermittently to prevent a sharp temperature increase and undesired soil sterilization at soil circumneutral pH versus adding the same amount of H 2 O 2 continuously.The primary objective of the present study was to investigate whether a mild MF pre-oxidation such as a stepwise addition of H 2 O 2 can prevent sterilization and achieve a maximum degradation of tank oil in soil.Optimization experiments of graded MF oxidation were conducted using citric acid,oxalic acid and SOLV-X as iron chelators under different frequencies of H 2 O 2 addition.The results indicated that the activity order of iron chelates decreased as：citric acid （51%） SOLV-X （44%） oxalic acid （9%）,and citric acid was found to be an optimized iron chelating agent of graded MF oxidation.Three-time addition of H 2 O 2 was found to be favorable and economical due to decreasing total petroleum hydrocarbon removal from three time addition （51%） to five time addition （59%）.Biological experiments were conducted after graded MF oxidation of tank oil completed under optimum conditions mentioned above.After graded oxidation,substantially higher increase （31%） in microbial activity was observed with excessive H 2 O 2 （1470 mmol/L,the mol ratio of H 2 O 2：Fe 2＋ was 210：1） than that of non-oxidized soil.Removal efficiency of tank oil was up to 93% after four weeks.Especially,the oil fraction （C 10 –C 40 ） became more biodagradable after graded MF oxidation than its absence.Therefore,graded MF oxidation is a mild pretreatment to achieve an effective bioremediation of oil contaminated soil.
文摘Using GIS,GPS and GPRS,an intelligent monitoring and dispatch system of trucks and shovels in an open pit has been designed and developed.The system can monitor and dispatch open-pit trucks and shovels and play back their historical paths.An intelligent data algorithm is proposed in a practical application.The algorithm can count the times of deliveries of trucks and load- ings of shovels.Experiments on real scenes show that the performance of this system is stable and can satisfy production standards in open pits.
基金Item Sponsored by Special Project of Education Depart ment of Shaanxi Province of China (07JK309)Project of Science andTechnology Research and Development Program of Shaanxi Province of China (2010K10-13)
文摘The effects of phase transformation on mechanical properties and pitting corrosion of 2205 duplex stainless steel were investigated. The amount of a phase in the test specimen varied up to a maximum of 6 % by thermal treatment at 850 ℃ for up to 60 min. The results showed that ~ phase markedly increased the hardness and decreased the impact toughness of the test steel. But the increasing tendency of the ultimate tensile strength and the yield strength was not obvious, while the total elongation abruptly decreased with the aging time from 5 to 60 min. SEM impact microfractograph analysis revealed that the types of impact fracture changed from ductile mode to transcrystalline mode when the specimens were aged for 5-60 min. Furthermore, the extent of pitting potential reducing was found to be strongly temperature dependent, more pronounced at the higher temperature. During the incubation period of σ phase nucleation, the pitting corrosion test temperature and the aging time had collaborative effects on evidently displacing the pitting potential towards less noble values. After 15 min, the higher temperature contributed more to decreasing the pitting potential than the aging time.
文摘Developing sustainable and clean electrochemical energy conversion technologies is a crucial step in addressing the challenges of energy shortage and environmental pollution. Exploring and developing new electrocatalysts with excellent performance and low cost will facilitate the commercial use of these energy conversion technologies. Recently, dual-atom catalysts(DACs) have attracted considerable research interest since they exhibit higher metal atom loading and more flexible active sites compared to single-atom catalysts(SACs). In this paper, the latest preparation methods and characterization techniques of DACs are systematically reviewed. The advantages of homonuclear and heteronuclear DACs and the catalytic mechanism and identification technologies between the two DACs are highlighted. The current applications of DACs in the field of electrocatalysis are summarized. The development opportunities and challenges of DACs in the future are prospected. The ultimate goal is to provide new ideas for the preparation of new catalysts with excellent properties by customizing diatomic catalysts for electrochemical applications.
基金Projects(51504191,51671152,51874225)supported by the National Natural Science Foundation of ChinaProject supported by the Fund of State Key Laboratory of Porous Metal Materials,China。
文摘In order to analyze the effect of voltage during micro-arc oxidation(MAO)on corrosion and wear properties of Ti6Al4V(TC4),the MAO technology was employed to treat TC4 samples fabricated by selective electron beam melting(SEBM)at the voltages of 400,420 and 450 V.The results show that the metastable anatase phase gradually transforms to rutile phase with oxidation time and temperature increasing.The surface morphology of coating contains numerous micropores with uniform size distribution.Cracks and pores over 10μm are found on MAO-TC4 sample with applied voltage of 450 V.The thickness of MAO coating is positively correlated with the voltage.The corrosion resistance and wear resistance are related to phase composition,micropore size distribution on the surface and film thickness.When the voltage is 420 V,the coating shows the smallest corrosion current density(0.960×10^-7 A/cm^2)and the largest resistance(7.17×10^5Ω·cm^2).Under the same load condition,the coating exhibits larger friction coefficient and wear loss than the TC4 substrate.With the increase of voltage,the wear mechanism of the coating changes from abrasive wear to adhesive wear,and the adhesive wear is intensified at applied voltage of 450 V,with a maximum friction coefficient of 0.821.
基金the National Natural Science Foundation of China(No.51978561)the International Science and Technology Cooperation Program in Shaanxi Province(No.2018kw-011)Shaanxi Provincial Key Research and Development Projects(Nos.2019ZDLSF06-01 and 2019ZDLSF06-02).
文摘Urban lake ecosystems are significant for social development,but currently we know little about the geographical distribution of algal community in urban lakes at a large-scale.In this study,we investigated the algal community structure in different areas of urban lakes in China and evaluated the influence of water quality parameters and geographical location on the algal community.The results showed that obvious differences in water quality and algal communities were observed among urban lakes in different geographical areas.Chlorophyta was the dominant phylum,followed by cyanobacteria in all areas.The network analysis indicated that algal community composition in urban lakes of the western and southern area showed more variations than the eastern and northern areas,respectively.Redundancy analysis and structural equation model revealed that nutrients and p H were dominant environmental factors that affected the algal community,and they showed higher influence than that of iron,manganese and COD Mn concentration.Importantly,algal community and density exhibited longitude and latitude relationship.In general,these results provided an ecological insight into large-scale geographical distributions of algal community in urban lakes,thereby having potential applications for management of the lakes.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (No. XDB14020201)the National Natural Science Foundation of China (Nos. 41373123, 21337004)the Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences (No. YSW2013A01)
文摘Elevated arsenic（As） in groundwater poses a great threat to human health. Coagulation using mono- and poly-Fe salts is becoming one of the most cost-effective processes for groundwater As removal. However, a limitation comes from insufficient understanding of the As removal mechanism from groundwater matrices in the coagulation process, which is critical for groundwater treatment and residual solid disposal. Here, we overcame this hurdle by utilizing microscopic techniques to explore molecular As surface complexes on the freshly formed Fe flocs and compared ferric（III） sulfate（FS） and polyferric sulfate（PFS）performance, and finally provided a practical solution in As-geogenic areas. FS and PFS exhibited a similar As removal efficiency in coagulation and coagulation/filtration in a two-bucket system using 5 mg/L Ca（ClO）_2. By using the two-bucket system combining coagulation and sand filtration, 500 L of As-safe water（〈 10 μg/L） was achieved during five treatment cycles by washing the sand layer after each cycle. Fe k-edge X-ray absorption near-edge structure（XANES） and As k-edge extended X-ray absorption fine structure（EXAFS） analysis of the solid residue indicated that As formed a bidentate binuclear complex on ferrihydrite, with no observation of scorodite or poorly-crystalline ferric arsenate. Such a stable surface complex is beneficial for As immobilization in the solid residue, as confirmed by the achievement of much lower leachate As（0.9 μg/L-0.487 mg/L）than the US EPA regulatory limit（5 mg/L）. Finally, PFS is superior to FS because of its lower dose, much lower solid residue, and lower cost for As-safe drinking water.
文摘The seasonal changes in leaf particulate matter （PM） accumulation, surface wettability and micromor- phology in urban tree species, including Sophorajaponica （S. japonica）, Platanus acerifolia （P. acerifolia） and Cedrus deodara （C. deodara）, were studied during a single growing season. The three species showed distinct seasonal trends in PM accumulation, increasing from spring to autumn （or winter） even during the rainy season, but at different rates. During the study, the leaf PM retention amount ofP acerifolia, a species with ridged leaf surfaces, was significantly higher than that of S. japonica and C. deodara, species with waxy leaf surfaces. The contact angles of water droplets on leaves decreased with leafage except on the abaxial surface orS.japonica, which remained non-wettable or highly non-wettable throughout the growing season; the decrease in the contact angle on adaxial surface of S. japonica was greater when compared with P acerifolia and C. deodara. A significant and negative relationship existed between leaf PM retention amounts and contact angles on adaxial surface of leaves of all three species. The increase in wettability, probably caused when epicuticular wax was destroyed by mechan- ical and chemical abrasion, seemed to be the main factor leading to seasonal variations in leaf PM accumulation.
文摘A novel Cu-Mn-Ce/cordierite honeycomb catalyst was prepared by an incipient wetness method and the catalyst was characterized. The active ingredients were present as various spinel species of Cu, Mn and Ce oxides with different valences and they were unevenly dispersed over the surface of the catalyst. The catalytic oxidation of gaseous toluene was primarily investigated using a fixed bed reactor under microwave heating in the continuous flow mode. Under the optimal conditions of 6.7 wt-% loading of the active component, a bed temperature of 200℃, a flow rate of 0.12 m^3 · h^-1 and an initial concentration of toluene of 1000 mg·m^-3, the removal and mineralization efficiencies of toluene were 98% and 70%, respectively. Thus the use of the microwave effectively improved the oxidation of toluene and this is attributed to dipole polarization and hotspot effects. After four consecutive cycles (a total of 1980 min), the Cu-Mn- Ce/cordierite catalyst still exhibited excellent catalytic activity and structural stability, and the toluene removal was higher than 90%. This work demonstrates the possibility of treating volatile organic compounds in exhaust gases by microwave-assisted catalytic oxidation.
基金Item Sponsored by Office of Education of Shaanxi Province of China(08JK345)Programs for Industry Development of Shaanxi Province of China(2008K06-18)
文摘A high-manganese austenitic steel matrix （Mn13） composite reinforced with TiN ceramic particles was synthesized by means of Vacuum-Evaporation Pattern Casting （V-EPC）. The composite microstructure and interface bonding of TiN/matrix were analyzed utilizing optical microscope （OM） and X-ray diffraction （XRD）. The effects of different volume fraction of TiN on impact wear resistance were evaluated by MLD-10 impact wear test. The results showed that TiN was evenly distributed in composite layer and had a good interface bonding with matrix when the volume fractions of TiN were 27% and 36% respectively. However, cast defects and TiN agglomeration occurred when the TiN volume fraction increased to 48~. Compared with high-manganese austenitic steel （Mnl3）, the im- pact wear resistance of the TiN-reinforced composite is better. In small impact load conditions, composite layer can effectively resist abrasives wear and TiN particles played an important role in determining impact wear resistance of composite layer. In large impact load, the synergistic roles of spalling of TiN particles and the increase of work hardening of Mn13 based material are responsible for impact wear resistance.
