Three-dimensional(3D)printing technology has been widely used to create artificial rock samples in rock mechanics.While 3D printing can create complex fractures,the material still lacks sufficient similarity to natura...Three-dimensional(3D)printing technology has been widely used to create artificial rock samples in rock mechanics.While 3D printing can create complex fractures,the material still lacks sufficient similarity to natural rock.Extrusion free forming(EFF)is a 3D printing technique that uses clay as the printing material and cures the specimens through high-temperature sintering.In this study,we attempted to use the EFF technology to fabricate artificial rock specimens.The results show the physico-mechanical properties of the specimens are significantly affected by the sintering temperature,while the nozzle diameter and layer thickness also have a certain impact.The specimens are primarily composed of SiO_(2),with mineral compositions similar to that of natural rocks.The density,uniaxial compressive strength(UCS),elastic modulus,and tensile strength of the printed specimens fall in the range of 1.65–2.54 g/cm3,16.46–50.49 MPa,2.17–13.35 GPa,and 0.82–17.18 MPa,respectively.It is capable of simulating different types of rocks,especially mudstone,sandstone,limestone,and gneiss.However,the simulation of hard rocks with UCS exceeding 50 MPa still requires validation.展开更多
Climate change can intensify drought in many regions of the world and lead to more frequent drought events or altered cycles of soil water status.Therefore,it is important to enhance the tolerance to drought and thus ...Climate change can intensify drought in many regions of the world and lead to more frequent drought events or altered cycles of soil water status.Therefore,it is important to enhance the tolerance to drought and thus health,vigor,and success of transplantation seedlings used in the forestry by modifying fertilization and promoting mycorrhization.Here,we sowed seeds of Japanese larch(Larix kaempferi)in 0.2-L containers with 0.5 g(low fertilization;LF)or 2 g(high fertilization;HF)of slow-release fertilizer early in the growing season.One month later,we irrigated seedlings with non-sterilized ectomycorrhizal inoculum(ECM)or sterilized solution(non-ECM),and after about 2 months,plants were either kept well watered(WW;500 mL water/plant/week)or subjected to drought(DR;50 mL water per plant/week)until the end of the growing season.HF largely stimulated plant growth and above-and belowground biomass production,eff ects that are of practical signifi cance,but caused a small decrease in stomatal conductance(Gs 390)and transpiration rate(E 390),which in practice is insignifi cant.ECM treatment resulted in moderate inhibition of seedling growth and biomass and largely canceled out the enhancement of biomass and foliar K content by HF.DR caused a large decrease in CO 2 assimilation,and enhanced stomatal closure and induced senescence.DR also largely depleted foliar Mg and enriched foliar K.Although DR caused a large decrease in foliar P content in LF,it moderately increased P in HF.Likewise,DR increased foliar K in HF but not in LF,and decreased foliar P in ECM plants but not in non-ECM plants.Conversely,ECM plants exhibited a large enrichment in foliar P under WW and had a lower water potential under DR when grown in LF.These results indicate that the drought tolerance and health and vigor of Japanese larch seedlings can be modifi ed by soil fertility and soil microorganisms.This study provides a basis for new multifactorial research programs aimed at producing seedlings of superior quality for forestation under climate change.展开更多
Inventory data were available from 96 plots of even-aged,monoculture,tall-open forests of Eucalyptus pilularis Smith,aged 2-63 years,growing in sub-tropical regions along the east coast of Australia.A model was develo...Inventory data were available from 96 plots of even-aged,monoculture,tall-open forests of Eucalyptus pilularis Smith,aged 2-63 years,growing in sub-tropical regions along the east coast of Australia.A model was developed relating the maximum possible stem basal area growth rate of individual trees to their stem basal area.For any tree size,this maximum increased as site productivity increased.However,the size at which this maximum occurred decreased as productivity increased.Much research has shown that,at any stand age,trees of a particular stem basal area are taller on more productive sites than on less productive ones.Taller trees incur greater respiratory costs to ensure maintenance of the photo synthetic capacity of their canopies;this reduces their growth rates.It was concluded that trees with larger basal areas will have the maximum possible growth rate on a less productive site,whilst trees with smaller basal areas will have the maximum possible on a more productive site.The model developed may constitute the first stage of a complete individual tree growth model system to predict wood yields from these forests.展开更多
P values based on standard hypothesis testing are commonly reported in articles published by the Journal of Forestry Research(JFR).However,effect sizes are barely used and reported,even if they are of direct relevance...P values based on standard hypothesis testing are commonly reported in articles published by the Journal of Forestry Research(JFR).However,effect sizes are barely used and reported,even if they are of direct relevance to the primary questions of many of the published studies.The incorporation of effect sizes in studies published by JFR should be encouraged and promoted.Inclusion of effect sizes as a requirement in the journal guidelines will facilitate a major change in the way data are tested and interpreted,with the ultimate goal to exempt researchers from the custom of drawing conclusions merely based upon a dichotomous statistical result(P value).Such a policy can also lead to more informed decisions of whether identified effects are of practical relevance to the forestry.展开更多
核数据不确定性分析影响着反应堆安全,在反应堆堆芯物理计算过程中具有重要意义。利用SCALE6.1程序包中KENO模块建立反应堆模拟评估和验证基准BEAVRS(Benchmark for Evaluation and Validation of Reactor Simulations)第一循环热态零...核数据不确定性分析影响着反应堆安全,在反应堆堆芯物理计算过程中具有重要意义。利用SCALE6.1程序包中KENO模块建立反应堆模拟评估和验证基准BEAVRS(Benchmark for Evaluation and Validation of Reactor Simulations)第一循环热态零功率堆芯物理模型,采用TSUNAMI-3D模块开展k_(eff)的敏感性与不确定性分析,分析了不同燃料富集度、不同温度对k_(eff)敏感性与不确定性的影响。结果表明:核数据不确定性导致BEAVRS模型的k_(eff)总的不确定性为0.5016%;^(235)U的平均裂变中子数敏感性导致k_(eff)的敏感性系数最大(0.92658);对k_(eff)不确定性贡献最大的是238U(n,γ)反应截面,为0.29814%;在燃料富集度降低、温度上升时,238U(n,γ)反应截面不确定性会导致k_(eff)的不确定性增大。因此,在开展反应堆堆芯物理计算过程中,应重点关注238U(n,γ)反应截面信息。展开更多
Objective:To observe the protective effect of breviscapineon mice with cisplatin-induced nephrotoxicity.Methods:Mice were given a single injection of cisplalin(8 mg/kg,up.);then,breviscapine was given to mice at 25 mg...Objective:To observe the protective effect of breviscapineon mice with cisplatin-induced nephrotoxicity.Methods:Mice were given a single injection of cisplalin(8 mg/kg,up.);then,breviscapine was given to mice at 25 mg/kg and 50 mg/kg doses,respectively,once a day for seven days.Renal tissue structure was observed after animals were sacrificed.Blood urea nitrogen(BUN),serum creatinine(Scr),lipid peroxide(MDA) and superoxide dismutase(SOD) serum levels were detected;and MDA,glutathione peroxidase,and SOD levels in the renal cortex were detected.Results:Compared with the blank control group(BCG),the kidney pathological damage of mice in the model control group(MCG) was more severe.After applying different doses of breviscapine,different degrees of renal injury improvement appeared.Compared with the BCG,the serum levels of Scr and BUN in the MCG increased to(89.92±6.78) μmoL/L and(15.32±4.53) mmoL/L.The differences were statistical significant(P<0.01).Compared with the MCG,the serum levels of Scr and BUN in the Bre low-dose groups and Bre high-dose groups decreased significantly(P<0.05).Compared with the BCG,the MDA levels in serum and in the renal cortex in the MCG significantly increased,while the SOD levels significantly decreased.Both the differences were statistically significant(P<0.01).In the Bre low-dose groups and Bre high-dose groups,MDA levels in serum and in the renal cortex significantly decreased,while SOD and glutathione peroxidase levels in the renal cortex significantly increased,compared with the MCG;and the differences were statistically significant(P<0.05).Conclusions:Breviscapine can reduce cisplatin induced renal toxicity in mice and it's possible through inhibition of renal tubule cell lipid peroxidation and reduces the nephrotoxicity of cisplatin.展开更多
Topography can have signifi cant eff ects on seismic ground response during an earthquake because topographic irregularities cause considerable diff erences between the seismic waves emitted by the source and the wave...Topography can have signifi cant eff ects on seismic ground response during an earthquake because topographic irregularities cause considerable diff erences between the seismic waves emitted by the source and the waves reaching the ground surface. When a seismic motion happens in a topographically irregular area, seismic waves are trapped and refl ected between the topographic features. Therefore, the interaction between topographies can amplify seismic ground response. In order to reveal how interaction between topographies infl uences seismic response, several numerical fi nite element studies have been performed by using the ABAQUS program. The results show that topographic features a greater distance between the seismic source and the site would cause greater seismic motion amplifi cation and is perceptible for the hills far away from the source and the ridges. Also, site acceleration response is impacted by surrounding topography further than site velocity and displacement response.展开更多
The available models for eff ective periods of site and structure are reviewed in context of frequency tuning in the inelastic seismic response of soil-structure system. The eff ect of seismic intensity and ductility ...The available models for eff ective periods of site and structure are reviewed in context of frequency tuning in the inelastic seismic response of soil-structure system. The eff ect of seismic intensity and ductility demand, on the eff ective periods, is investigated, and inelastic site amplifi cation is shown to be strongly correlated to the normalized eff ective period. Two non-dimensional parameters, analogous to the conventional site amplifi cation factors in codes, are defi ned to quantify the inelastic site amplifi cation. It is shown that the inelastic site amplifi cation factor (i.e. ratio of constant ductility spectral ordinates at soil site to those at rock outcrop) is able to represent the site eff ects more clearly, as compared to the inelastic site amplifi cation ratio (i.e. ratio of inelastic spectral ordinates at soil site to the corresponding elastic spectral ordinates at rock outcrop). Further, the peak in the amplifi cation factor corresponding to the eff ective site period diminishes rapidly with increasing ductility demand.展开更多
In the fine-grain TL dating the full o dose must be converted into the equivalent P dose. The conversion is finished by Keff-value, which is an effective or effectiveness. But the Keff can not be measured directly for...In the fine-grain TL dating the full o dose must be converted into the equivalent P dose. The conversion is finished by Keff-value, which is an effective or effectiveness. But the Keff can not be measured directly for each sample and only the external radiative efficiency K3.7 can be measured. In order to obtain the Keff a special study for the conversion factor of Keff to K3.t has been made using the ultrathin TLD. The results show that the conversion factor of tile TLD for archaeological samples is 0.847, which is in agreement with calculated value 0.85.展开更多
The metal oxide/nitrogen-doped carbon(NC)compounds zirconium oxide/NC(ZrO_(2)/NC)and cerium oxide/NC(CeO_(2)/NC)were synthesized via the pyrolysis of polyaniline on the metal oxide surface.The characterization of the ...The metal oxide/nitrogen-doped carbon(NC)compounds zirconium oxide/NC(ZrO_(2)/NC)and cerium oxide/NC(CeO_(2)/NC)were synthesized via the pyrolysis of polyaniline on the metal oxide surface.The characterization of the ZrO_(2)/NC and CeO_(2)/NC catalysts showed more active CO_(2) reduction reaction activity than that of NC catalyst without metal oxide.Gas chromatography analysis revealed that CO and H_(2)were the primary products,and no liquid-phase products were detected via proton nuclear magnetic resonance spectroscopy or high-performance liquid chromatography.The maximum Faraday effi ciency of ZrO_(2)/NC reached 90%at−0.73 V(vs.RHE),with the current density of CO at 5.5 mA/cm^(2);this Faraday effi ciency value was higher than that of NC(41%),with the current density of CO at 3.1 mA/cm^(2).The interaction between the metal oxide and carbon allowed the effi cient formation of defect sites,especially imine-type nitrogen,strengthening the adsorption of the key reaction intermediate CO_(2)^(•−) and thus promoting the CO_(2) reduction reaction.展开更多
In order to implement cost-effective machining of gr anite materials with diamond impregnated tools, we should realize low tool w ear, low energy consumption, and high cutting efficiency, while the accuracy of the wor...In order to implement cost-effective machining of gr anite materials with diamond impregnated tools, we should realize low tool w ear, low energy consumption, and high cutting efficiency, while the accuracy of the workpiece surfaces are maintained to be satisfactory. It is understood that the main factors affecting the tool wear, the energy, and the efficiency during the machining process are related to the tribological interactions that occur at the interface between the diamond tool surface and the workpiece. Based on this consideration, we propose a new machining method to machine granite materia ls to achieve improved cost effectiveness. In the proposed method, the tribologi cal interactions are maintained to a minimum. Based on the analyses of the experimental results, the following conclusions can be drawn: The wear performance is greatly dependent on the machining parameters and their combination. Therefore, optimum machining parameters must be set up at first in order to optimize the tribological characteristics of segments and thereby sawbl ade performance. These may be realized by balancing the energy expended by frict ion and the mechanical load on diamond crystal. The geometry and structure of diamond segments are another important criterion f or the diamond saw blade. Using a seven-layer structure for multi-blades sawin g and applying segments with side slots for trimming application had greatly red uced the frictions in the sawing processes. The wetting and bonding between diamonds and matrix alloys have been considered as the prerequisite for high wear performance of the segments. Diamonds coated w ith Ti-Cr alloy by a unique technique can effectively improve its wetting c apability and provide more storage space for debris, thereby reducing friction i nteractions.展开更多
Quantitative analysis of time scale effects is conducive to further understanding of vegetation water and soil conservation mechanism.Based on the observation data of the grass covered and bare soil( control) experime...Quantitative analysis of time scale effects is conducive to further understanding of vegetation water and soil conservation mechanism.Based on the observation data of the grass covered and bare soil( control) experimental plots located in Hetian Town,Changting County of Fujian Province from 2007 to 2010,the characteristics of 4 parameters( precipitation,vegetation,RE and SE) were analyzed at precipitation event,month,season,and annual scales,and then the linear regression models were established to describe the relationships between RE( SE)and its influencing factors of precipitation and vegetation. RE( SE) means the ratio of runoff depth( soil loss) of grass covered plot to that of the control plot. Results show that these 4 parameters presented different magnitude and variation on different time scales. RE and SE were relatively stable either within or among different time scales due to their ratios reducing the influence of other factors. The coupling of precipitation and vegetation led to better water conservation effect at lower RE( < 0. 3) at precipitation event scale as well as at season scale,while the water conservation effect was dominated by precipitation at slightly higher( 0. 3- 0. 4) and higher( > 0. 7) REs at precipitation event scale as well as at annual scale( R2> 0. 78). For the soil conservation effect,precipitation or / and vegetation was / were the dominated influence factor( s) at precipitation event and annual scales,and the grass LAI could basically describe the positive conservation effect( SE <1,R2> 0. 55),while the maximum 30 min intensity( I30) could describe the negative conservation effect more accurately( SE >1,R2> 0. 79). More uncertainties( R2≈0. 4) exist in the models of both RE and SE at two moderate time scales( month and season). Consequently,factors influencing water and soil conservation effect of grass present different variation and coupling characteristics on different time scales,indicating the importance of time scale at the study on water and soil conservation.展开更多
基金financially supported by the Beijing Natural Science Foundation for Young Scientists(Grant No.8214052)the Talent Fund of Beijing Jiaotong University(Grant No.2021RC226)the State Key Laboratory for GeoMechanics and Deep Underground Engineering,China University of Mining and Technology(Grant No.SKLGDUEK2115).
文摘Three-dimensional(3D)printing technology has been widely used to create artificial rock samples in rock mechanics.While 3D printing can create complex fractures,the material still lacks sufficient similarity to natural rock.Extrusion free forming(EFF)is a 3D printing technique that uses clay as the printing material and cures the specimens through high-temperature sintering.In this study,we attempted to use the EFF technology to fabricate artificial rock specimens.The results show the physico-mechanical properties of the specimens are significantly affected by the sintering temperature,while the nozzle diameter and layer thickness also have a certain impact.The specimens are primarily composed of SiO_(2),with mineral compositions similar to that of natural rocks.The density,uniaxial compressive strength(UCS),elastic modulus,and tensile strength of the printed specimens fall in the range of 1.65–2.54 g/cm3,16.46–50.49 MPa,2.17–13.35 GPa,and 0.82–17.18 MPa,respectively.It is capable of simulating different types of rocks,especially mudstone,sandstone,limestone,and gneiss.However,the simulation of hard rocks with UCS exceeding 50 MPa still requires validation.
基金supported by JSPS KAKENHI Grant Number JP17F17102 (to EA and MK)Startup Foundation for Introducing Talent of Nanjing University of Information Science and Technology (NUIST)(No. 003080)the Jiangsu Distinguished Professor program of the People’s Government of Jiangsu Province
文摘Climate change can intensify drought in many regions of the world and lead to more frequent drought events or altered cycles of soil water status.Therefore,it is important to enhance the tolerance to drought and thus health,vigor,and success of transplantation seedlings used in the forestry by modifying fertilization and promoting mycorrhization.Here,we sowed seeds of Japanese larch(Larix kaempferi)in 0.2-L containers with 0.5 g(low fertilization;LF)or 2 g(high fertilization;HF)of slow-release fertilizer early in the growing season.One month later,we irrigated seedlings with non-sterilized ectomycorrhizal inoculum(ECM)or sterilized solution(non-ECM),and after about 2 months,plants were either kept well watered(WW;500 mL water/plant/week)or subjected to drought(DR;50 mL water per plant/week)until the end of the growing season.HF largely stimulated plant growth and above-and belowground biomass production,eff ects that are of practical signifi cance,but caused a small decrease in stomatal conductance(Gs 390)and transpiration rate(E 390),which in practice is insignifi cant.ECM treatment resulted in moderate inhibition of seedling growth and biomass and largely canceled out the enhancement of biomass and foliar K content by HF.DR caused a large decrease in CO 2 assimilation,and enhanced stomatal closure and induced senescence.DR also largely depleted foliar Mg and enriched foliar K.Although DR caused a large decrease in foliar P content in LF,it moderately increased P in HF.Likewise,DR increased foliar K in HF but not in LF,and decreased foliar P in ECM plants but not in non-ECM plants.Conversely,ECM plants exhibited a large enrichment in foliar P under WW and had a lower water potential under DR when grown in LF.These results indicate that the drought tolerance and health and vigor of Japanese larch seedlings can be modifi ed by soil fertility and soil microorganisms.This study provides a basis for new multifactorial research programs aimed at producing seedlings of superior quality for forestation under climate change.
文摘Inventory data were available from 96 plots of even-aged,monoculture,tall-open forests of Eucalyptus pilularis Smith,aged 2-63 years,growing in sub-tropical regions along the east coast of Australia.A model was developed relating the maximum possible stem basal area growth rate of individual trees to their stem basal area.For any tree size,this maximum increased as site productivity increased.However,the size at which this maximum occurred decreased as productivity increased.Much research has shown that,at any stand age,trees of a particular stem basal area are taller on more productive sites than on less productive ones.Taller trees incur greater respiratory costs to ensure maintenance of the photo synthetic capacity of their canopies;this reduces their growth rates.It was concluded that trees with larger basal areas will have the maximum possible growth rate on a less productive site,whilst trees with smaller basal areas will have the maximum possible on a more productive site.The model developed may constitute the first stage of a complete individual tree growth model system to predict wood yields from these forests.
基金co-supported by the Outstanding Action Plan of Chinese Sci-tech Journals(Grant No.OAP–C–077)the Startup Foundation for Introducing Talent of Nanjing University of Information Science&Technology(NUIST),Nanjing,China(Grant No.003080)the Jiangsu Distinguished Professor Program of the People’s Government of Jiangsu Province。
文摘P values based on standard hypothesis testing are commonly reported in articles published by the Journal of Forestry Research(JFR).However,effect sizes are barely used and reported,even if they are of direct relevance to the primary questions of many of the published studies.The incorporation of effect sizes in studies published by JFR should be encouraged and promoted.Inclusion of effect sizes as a requirement in the journal guidelines will facilitate a major change in the way data are tested and interpreted,with the ultimate goal to exempt researchers from the custom of drawing conclusions merely based upon a dichotomous statistical result(P value).Such a policy can also lead to more informed decisions of whether identified effects are of practical relevance to the forestry.
文摘核数据不确定性分析影响着反应堆安全,在反应堆堆芯物理计算过程中具有重要意义。利用SCALE6.1程序包中KENO模块建立反应堆模拟评估和验证基准BEAVRS(Benchmark for Evaluation and Validation of Reactor Simulations)第一循环热态零功率堆芯物理模型,采用TSUNAMI-3D模块开展k_(eff)的敏感性与不确定性分析,分析了不同燃料富集度、不同温度对k_(eff)敏感性与不确定性的影响。结果表明:核数据不确定性导致BEAVRS模型的k_(eff)总的不确定性为0.5016%;^(235)U的平均裂变中子数敏感性导致k_(eff)的敏感性系数最大(0.92658);对k_(eff)不确定性贡献最大的是238U(n,γ)反应截面,为0.29814%;在燃料富集度降低、温度上升时,238U(n,γ)反应截面不确定性会导致k_(eff)的不确定性增大。因此,在开展反应堆堆芯物理计算过程中,应重点关注238U(n,γ)反应截面信息。
基金supported by the National Natural Science Foundation of China(No.81401428)
文摘Objective:To observe the protective effect of breviscapineon mice with cisplatin-induced nephrotoxicity.Methods:Mice were given a single injection of cisplalin(8 mg/kg,up.);then,breviscapine was given to mice at 25 mg/kg and 50 mg/kg doses,respectively,once a day for seven days.Renal tissue structure was observed after animals were sacrificed.Blood urea nitrogen(BUN),serum creatinine(Scr),lipid peroxide(MDA) and superoxide dismutase(SOD) serum levels were detected;and MDA,glutathione peroxidase,and SOD levels in the renal cortex were detected.Results:Compared with the blank control group(BCG),the kidney pathological damage of mice in the model control group(MCG) was more severe.After applying different doses of breviscapine,different degrees of renal injury improvement appeared.Compared with the BCG,the serum levels of Scr and BUN in the MCG increased to(89.92±6.78) μmoL/L and(15.32±4.53) mmoL/L.The differences were statistical significant(P<0.01).Compared with the MCG,the serum levels of Scr and BUN in the Bre low-dose groups and Bre high-dose groups decreased significantly(P<0.05).Compared with the BCG,the MDA levels in serum and in the renal cortex in the MCG significantly increased,while the SOD levels significantly decreased.Both the differences were statistically significant(P<0.01).In the Bre low-dose groups and Bre high-dose groups,MDA levels in serum and in the renal cortex significantly decreased,while SOD and glutathione peroxidase levels in the renal cortex significantly increased,compared with the MCG;and the differences were statistically significant(P<0.05).Conclusions:Breviscapine can reduce cisplatin induced renal toxicity in mice and it's possible through inhibition of renal tubule cell lipid peroxidation and reduces the nephrotoxicity of cisplatin.
文摘Topography can have signifi cant eff ects on seismic ground response during an earthquake because topographic irregularities cause considerable diff erences between the seismic waves emitted by the source and the waves reaching the ground surface. When a seismic motion happens in a topographically irregular area, seismic waves are trapped and refl ected between the topographic features. Therefore, the interaction between topographies can amplify seismic ground response. In order to reveal how interaction between topographies infl uences seismic response, several numerical fi nite element studies have been performed by using the ABAQUS program. The results show that topographic features a greater distance between the seismic source and the site would cause greater seismic motion amplifi cation and is perceptible for the hills far away from the source and the ridges. Also, site acceleration response is impacted by surrounding topography further than site velocity and displacement response.
文摘The available models for eff ective periods of site and structure are reviewed in context of frequency tuning in the inelastic seismic response of soil-structure system. The eff ect of seismic intensity and ductility demand, on the eff ective periods, is investigated, and inelastic site amplifi cation is shown to be strongly correlated to the normalized eff ective period. Two non-dimensional parameters, analogous to the conventional site amplifi cation factors in codes, are defi ned to quantify the inelastic site amplifi cation. It is shown that the inelastic site amplifi cation factor (i.e. ratio of constant ductility spectral ordinates at soil site to those at rock outcrop) is able to represent the site eff ects more clearly, as compared to the inelastic site amplifi cation ratio (i.e. ratio of inelastic spectral ordinates at soil site to the corresponding elastic spectral ordinates at rock outcrop). Further, the peak in the amplifi cation factor corresponding to the eff ective site period diminishes rapidly with increasing ductility demand.
文摘In the fine-grain TL dating the full o dose must be converted into the equivalent P dose. The conversion is finished by Keff-value, which is an effective or effectiveness. But the Keff can not be measured directly for each sample and only the external radiative efficiency K3.7 can be measured. In order to obtain the Keff a special study for the conversion factor of Keff to K3.t has been made using the ultrathin TLD. The results show that the conversion factor of tile TLD for archaeological samples is 0.847, which is in agreement with calculated value 0.85.
基金The work was supported by the National Key R&D Program of China(No.2016YFB0600901)Changyi Hydrogen Industrial Technology Fund.
文摘The metal oxide/nitrogen-doped carbon(NC)compounds zirconium oxide/NC(ZrO_(2)/NC)and cerium oxide/NC(CeO_(2)/NC)were synthesized via the pyrolysis of polyaniline on the metal oxide surface.The characterization of the ZrO_(2)/NC and CeO_(2)/NC catalysts showed more active CO_(2) reduction reaction activity than that of NC catalyst without metal oxide.Gas chromatography analysis revealed that CO and H_(2)were the primary products,and no liquid-phase products were detected via proton nuclear magnetic resonance spectroscopy or high-performance liquid chromatography.The maximum Faraday effi ciency of ZrO_(2)/NC reached 90%at−0.73 V(vs.RHE),with the current density of CO at 5.5 mA/cm^(2);this Faraday effi ciency value was higher than that of NC(41%),with the current density of CO at 3.1 mA/cm^(2).The interaction between the metal oxide and carbon allowed the effi cient formation of defect sites,especially imine-type nitrogen,strengthening the adsorption of the key reaction intermediate CO_(2)^(•−) and thus promoting the CO_(2) reduction reaction.
文摘In order to implement cost-effective machining of gr anite materials with diamond impregnated tools, we should realize low tool w ear, low energy consumption, and high cutting efficiency, while the accuracy of the workpiece surfaces are maintained to be satisfactory. It is understood that the main factors affecting the tool wear, the energy, and the efficiency during the machining process are related to the tribological interactions that occur at the interface between the diamond tool surface and the workpiece. Based on this consideration, we propose a new machining method to machine granite materia ls to achieve improved cost effectiveness. In the proposed method, the tribologi cal interactions are maintained to a minimum. Based on the analyses of the experimental results, the following conclusions can be drawn: The wear performance is greatly dependent on the machining parameters and their combination. Therefore, optimum machining parameters must be set up at first in order to optimize the tribological characteristics of segments and thereby sawbl ade performance. These may be realized by balancing the energy expended by frict ion and the mechanical load on diamond crystal. The geometry and structure of diamond segments are another important criterion f or the diamond saw blade. Using a seven-layer structure for multi-blades sawin g and applying segments with side slots for trimming application had greatly red uced the frictions in the sawing processes. The wetting and bonding between diamonds and matrix alloys have been considered as the prerequisite for high wear performance of the segments. Diamonds coated w ith Ti-Cr alloy by a unique technique can effectively improve its wetting c apability and provide more storage space for debris, thereby reducing friction i nteractions.
基金Supported by National Natural Science Foundation Project(41071281)Natural Science Foundation of Jiangsu Province(BK20131078)"Qing Lan Project" of Jiangsu Provincial Department of Education
文摘Quantitative analysis of time scale effects is conducive to further understanding of vegetation water and soil conservation mechanism.Based on the observation data of the grass covered and bare soil( control) experimental plots located in Hetian Town,Changting County of Fujian Province from 2007 to 2010,the characteristics of 4 parameters( precipitation,vegetation,RE and SE) were analyzed at precipitation event,month,season,and annual scales,and then the linear regression models were established to describe the relationships between RE( SE)and its influencing factors of precipitation and vegetation. RE( SE) means the ratio of runoff depth( soil loss) of grass covered plot to that of the control plot. Results show that these 4 parameters presented different magnitude and variation on different time scales. RE and SE were relatively stable either within or among different time scales due to their ratios reducing the influence of other factors. The coupling of precipitation and vegetation led to better water conservation effect at lower RE( < 0. 3) at precipitation event scale as well as at season scale,while the water conservation effect was dominated by precipitation at slightly higher( 0. 3- 0. 4) and higher( > 0. 7) REs at precipitation event scale as well as at annual scale( R2> 0. 78). For the soil conservation effect,precipitation or / and vegetation was / were the dominated influence factor( s) at precipitation event and annual scales,and the grass LAI could basically describe the positive conservation effect( SE <1,R2> 0. 55),while the maximum 30 min intensity( I30) could describe the negative conservation effect more accurately( SE >1,R2> 0. 79). More uncertainties( R2≈0. 4) exist in the models of both RE and SE at two moderate time scales( month and season). Consequently,factors influencing water and soil conservation effect of grass present different variation and coupling characteristics on different time scales,indicating the importance of time scale at the study on water and soil conservation.
