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原位聚合法制备连续玻璃纤维增强尼龙6复合材料的改性和性能 被引量:1
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作者 冯冰涛 王晓珂 +6 位作者 张萌 殷茂峰 张信 孙国华 马劲松 李鹏鹏 侯连龙 《高分子材料科学与工程》 EI CAS CSCD 北大核心 2024年第1期25-33,共9页
尼龙6(PA6)树脂具有优异的性能,其连续纤维复合材料在汽车、航空航天领域具有广泛应用。但是PA6树脂熔融后黏度较高,不易对连续纤维充分浸渍,并且连续纤维与PA6的复合材料界面黏附性较差,限制了其复合材料的性能和应用。针对这些问题,... 尼龙6(PA6)树脂具有优异的性能,其连续纤维复合材料在汽车、航空航天领域具有广泛应用。但是PA6树脂熔融后黏度较高,不易对连续纤维充分浸渍,并且连续纤维与PA6的复合材料界面黏附性较差,限制了其复合材料的性能和应用。针对这些问题,文中对连续玻璃纤维增强尼龙6(CGF/PA6)复合材料开展了研究。首先,采用阴离子开环聚合制备PA6,确定了其最佳制备工艺;其次,用硅烷偶联剂KH550(AP)对连续玻璃纤维(CGF)进行改性,并对其进行了红外光谱表征;最后,通过原位聚合法制备了CGF/PA6复合材料,研究了AP改性对CGF/PA6复合材料力学性能的影响,并对CGF/PA6复合材料的拉伸断口进行了扫描电镜分析。结果表明,AP被键合到了CGF表面,AP改性可以增强CGF/PA6复合材料的界面黏附性,从而使CGF/PA6复合材料的拉伸强度得到改善,当AP用量为2%时,CGF/PA6复合材料的拉伸强度高达88.52 MPa,此时,复合材料的断裂伸长率最低,为4.90%。CGF/PA6复合材料的冲击强度变化不大,均在50 k J/m2左右,说明复合材料的韧性受CGF表面改性影响较小。 展开更多
关键词 原位聚合 连续玻璃纤维 尼龙6 硅烷偶联剂KH550 力学性能
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Reversible solid-liquid conversion enabled by self-capture effect for stable non-flow zinc-bromine batteries 被引量:1
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作者 Xixi Zhang xiaoke wang +7 位作者 Guangmeng Qu Tairan wang Xiliang Zhao Jun Fan Cuiping Han Xijin Xu Chunyi Zhi Hongfei Li 《Green Energy & Environment》 SCIE EI CAS CSCD 2024年第6期1035-1044,共10页
Non-flow aqueous zinc-bromine batteries without auxiliary components(e.g.,pumps,pipes,storage tanks)and ion-selective membranes represent a cost-effective and promising technology for large-scale energy storage.Unfort... Non-flow aqueous zinc-bromine batteries without auxiliary components(e.g.,pumps,pipes,storage tanks)and ion-selective membranes represent a cost-effective and promising technology for large-scale energy storage.Unfortunately,they generally suffer from serious diffusion and shuttle of polybromide(Br^(-),Br^(3-))due to the weak physical adsorption between soluble polybromide and host carbon materials,which results in low energy efficiency and poor cycling stability.Here,we develop a novel self-capture organic bromine material(1,10-bis[3-(trimethylammonio)propyl]-4,4'-bipyridinium bromine,NVBr4)to successfully realize reversible solid complexation of bromide components for stable non-flow zinc-bromine battery applications.The quaternary ammonium groups(NV^(4+)ions)can effectively capture the soluble polybromide species based on strong chemical interaction and realize reversible solid complexation confined within the porous electrodes,which transforms the conventional“liquid-liquid”conversion of soluble bromide components into“liquid-solid”model and effectively suppresses the shuttle effect.Thereby,the developed non-flow zinc-bromide battery provides an outstanding voltage platform at 1.7 V with a notable specific capacity of 325 mAh g^(-1)NVBr4(1 A g^(-1)),excellent rate capability(200 mAh g^(-1)NVBr4 at 20 A g^(-1)),outstanding energy density of 469.6 Wh kg^(-1)and super-stable cycle life(20,000 cycles with 100%Coulombic efficiency),which outperforms most of reported zinc-halogen batteries.Further mechanism analysis and DFT calculations demonstrate that the chemical interaction of quaternary ammonium groups and bromide species is the main reason for suppressing the shuttle effect.The developed strategy can be extended to other halogen batteries to obtain stable charge storage. 展开更多
关键词 Solid-liquid conversion Self-capture Non-flow zinc-bromine batteries Quaternary ammonium
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High-performance magnesium/sodium hybrid ion battery based on sodium vanadate oxide for reversible storage of Na^(+)and Mg^(2+)
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作者 xiaoke wang Titi Li +5 位作者 Xixi Zhang Yaxin wang Hongfei Li Hai-Feng Li Gang Zhao Cuiping Han 《Journal of Energy Chemistry》 SCIE EI CAS CSCD 2024年第9期79-88,共10页
Magnesium ion batteries(MIBs)are a potential field for the energy storage of the future but are restricted by insufficient rate capability and rapid capacity degradation.Magnesium-sodium hybrid ion batteries(MSHBs)are... Magnesium ion batteries(MIBs)are a potential field for the energy storage of the future but are restricted by insufficient rate capability and rapid capacity degradation.Magnesium-sodium hybrid ion batteries(MSHBs)are an effective way to address these problems.Here,we report a new type of MSHBs that use layered sodium vanadate((Na,Mn)V_(8)O_(20)·5H_(2)O,Mn-NVO)cathodes coupled with an organic 3,4,9,10-perylenetetracarboxylic diimide(PTCDI)anode in Mg^(2+)/Na^(+)hybrid electrolytes.During electrochemical cycling,Mg^(2+)and Na^(+)co-participate in the cathode reactions,and the introduction of Na^(+)promotes the structural stability of the Mn-NVO cathode,as cleared by several ex-situ characterizations.Consequently,the Mn-NVO cathode presents great specific capacity(249.9 mA h g^(−1)at 300 mA g^(−1))and cycling(1500 cycles at 1500 mA g^(−1))in the Mg^(2+)/Na^(+)hybrid electrolytes.Besides,full battery displays long lifespan with 10,000 cycles at 1000 mA g^(−1).The rate performance and cycling stability of MSHBs have been improved by an economical and scalable method,and the mechanism for these improvements is discussed. 展开更多
关键词 Aqueous battery Hybrid ion battery Mg^(2+)/Na^(+)co-intercalation High-rate performance Organic-water hybrid electrolyte
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Synergistic enhancement of cathode/anode interfaces with high water-retentive organohydrogel enabling highly stable zinc ion batteries
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作者 Xixi Zhang Qingxiu Yu +8 位作者 Guangmeng Qu xiaoke wang Chuanlin Li Chenggang wang Na Li Jinzhao Huang Cuiping Han Hongfei Li Xijin Xu 《Journal of Energy Chemistry》 SCIE EI CAS CSCD 2024年第11期670-679,共10页
Current aqueous battery electrolytes,including conve ntional hydrogel electrolytes,exhibit unsatisfactory water retention capabilities.The sustained water loss will lead to subsequent polarization and increased intern... Current aqueous battery electrolytes,including conve ntional hydrogel electrolytes,exhibit unsatisfactory water retention capabilities.The sustained water loss will lead to subsequent polarization and increased internal resistance,ultimately resulting in battery failure.Herein,a double network(DN) orga no hydrogel electrolyte based on dimethyl sulfoxide(DMSO)/H_(2)O binary solvent was proposed.Through directionally reconstructing hydrogen bonds and reducing active H_(2)O molecules,the water retention ability and cathode/anode interfaces were synergistic enhanced.As a result,the synthesized DN organohydrogel demonstrates exceptional water retention capabilities,retaining approximately 75% of its original weight even after the exposure to air for 20 days.The Zn MnO_(2) battery delivers an outstanding specific capacity of275 mA h g^(-1) at 1 C,impressive rate performance with 85 mA h g^(-1) at 30 C,and excellent cyclic stability(95% retention after 6000 cycles at 5 C).Zn‖Zn symmetric battery can cycle more than 5000 h at 1 mA cm^(-2) and 1 mA h cm^(-2) without short circuiting.This study will encourage the further development of functional organohydrogel electrolytes for advanced energy storage devices. 展开更多
关键词 Enhanced water-retentive Organohydrogel electrolyte Stable Zn||MnO+2 batteries Enhancement of cathode/anode interfaces
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A Fusion Localization Method Based on Target Measurement Error Feature Complementarity and Its Application
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作者 Xin Yang Hongming Liu +3 位作者 xiaoke wang Wen Yu Jingqiu Liu Sipei Zhang 《Journal of Beijing Institute of Technology》 EI CAS 2024年第1期75-88,共14页
In the multi-radar networking system,aiming at the problem of locating long-distance targets synergistically with difficulty and low accuracy,a dual-station joint positioning method based on the target measurement err... In the multi-radar networking system,aiming at the problem of locating long-distance targets synergistically with difficulty and low accuracy,a dual-station joint positioning method based on the target measurement error feature complementarity is proposed.For dual-station joint positioning,by constructing the target positioning error distribution model and using the complementarity of spatial measurement errors of the same long-distance target,the area with high probability of target existence can be obtained.Then,based on the target distance information,the midpoint of the intersection between the target positioning sphere and the positioning tangent plane can be solved to acquire the target's optimal positioning result.The simulation demonstrates that this method greatly improves the positioning accuracy of target in azimuth direction.Compared with the traditional the dynamic weighted fusion(DWF)algorithm and the filter-based dynamic weighted fusion(FBDWF)algorithm,it not only effectively eliminates the influence of systematic error in the azimuth direction,but also has low computational complexity.Furthermore,for the application scenarios of multi-radar collaborative positioning and multi-sensor data compression filtering in centralized information fusion,it is recommended that using radar with higher ranging accuracy and the lengths of baseline between radars are 20–100 km. 展开更多
关键词 dual-station positioning feature complementarity information fusion engineering applicability
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Location Distribution Characteristics in Leaf Lateral Asymmetry of Hybrid Indica Rice
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作者 Jie Li Yuehua Feng +3 位作者 Jinfeng Peng xiaoke wang Dinghua Yang Guiling Xu 《Phyton-International Journal of Experimental Botany》 SCIE 2020年第3期657-666,共10页
Rice leaves show lateral asymmetry.Differences in width,thickness,chlorophyll meter readings,nitrogen content,density,and yield on each asymmetrical have been reported.However,limited information is available on the d... Rice leaves show lateral asymmetry.Differences in width,thickness,chlorophyll meter readings,nitrogen content,density,and yield on each asymmetrical have been reported.However,limited information is available on the distribution characteristics of the smooth side(SS)and rough side(RS)of rice leaves.The SS of rice leaves can be divided into two types according to its location in leaf:one is the smooth side appearing on the left(SSAL)of the leaf,while the smooth side of the other type appears on the right(SSAR).Through the investigation of four rice varieties,we identified that the proportion of SSAL or SSAR of flag leaves on main stems or tillers was close to 0.50 in the rice population.On the same tiller stem,SSAL and SSAR present alternately,and the SS always stretches ahead of the RS in the curled state.Among the tiller flag leaves of a single rice plant,the proportion of tiller flag leaves with SSAL or SSAR to the total number of tillers is a discrete random variable.Frequency distribution analysis of these proportions showed that the percent of frequency of some class limits was close to each other,and the ratios of percent of frequency of SSAL to SSAR were close to 1:1.To our knowledge,this is a novel finding in rice canopy morphology.According to this study,we can divide rice population into two groups in four hybrid rice varieties. 展开更多
关键词 Hybrid rice leaf lateral asymmetry rough side smooth side
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Research on Construction Monitoring of Large-Span Steel Pipe Truss Structure
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作者 Kongliang Chen Guoqing Yuan +2 位作者 Liankun wang Wenzhi Zhang xiaoke wang 《Open Journal of Civil Engineering》 2019年第4期255-267,共13页
The steel roof of Jiangmen gymnasium is the large-span spatial pipe truss structure, which is composed of main truss, secondary truss and stable truss. This paper systematically expounds the construction simulation an... The steel roof of Jiangmen gymnasium is the large-span spatial pipe truss structure, which is composed of main truss, secondary truss and stable truss. This paper systematically expounds the construction simulation analysis, the composition of the construction monitoring system, the monitoring method, and the arrangement of measuring points. The construction simulation analysis simulates the whole process of the main truss cumulative lifting installation, the secondary truss and auxiliary structure hoisting, and then the main truss for overall unloading, which is the difficulty of the whole project. The results of the structural construction monitoring show that the roof structure is in a safe state, and the fine construction simulation analysis provides a theoretical basis for the construction process, and the theoretical value of the simulation analysis is in good agreement with the measured data. In addition, vertical displacement and stress are obvious mutations in the unloading stage of roof support, but the stress of each measuring point is in elastic working condition, which meets the design requirements, indicating the correctness of the model and method in construction simulation analysis and calculation, and also provides reference for the design and construction of related projects in the future. 展开更多
关键词 GYMNASIUM PIPE TRUSS MONITORING STRESS DISPLACEMENT
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Phosphorylation of the LCB1 subunit of Arabidopsis serine palmitoyltransferase stimulates its activity and modulates sphingolipid biosynthesis
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作者 Yuan Li Hanwei Cao +6 位作者 Tingting Dong xiaoke wang Liang Ma Kun Li Huiqiang Lou Chun-Peng Song Dongtao Ren 《Journal of Integrative Plant Biology》 SCIE CAS CSCD 2023年第6期1585-1601,共17页
Sphingolipids are the structural components of membrane lipid bilayers and act as signaling molecules in many cellular processes.Serine palmitoyltransferase(SPT)is the first committed and rate-limiting enzyme in the d... Sphingolipids are the structural components of membrane lipid bilayers and act as signaling molecules in many cellular processes.Serine palmitoyltransferase(SPT)is the first committed and rate-limiting enzyme in the de novo sphingolipids biosynthetic pathway.The core SPT enzyme is a heterodimer consisting of LONG-CHAIN BASE1(LCB1)and LCB2 subunits.SPT activity is inhibited by orosomucoid proteins and stimulated by small subunits of SPT(ssSPTs).However,whether LCB1 is modified and how such modification might regulate SPT activity have to date been unclear.Here,we show that activation of MITOGEN-ACTIVATED PROTEIN KINASE 3(MPK3)and MPK6 by upstream MKK9 and treatment with Flg22(a pathogen-associated molecular pattern)increases SPT activity and induces the accumulation of sphingosine long-chain base t18:0 in Arabidopsis thaliana,with activated MPK3and MPK6 phosphorylating AtLCB1.Phosphorylation of AtLCB1 strengthened its binding with AtLCB2b,promoted its binding with ssSPTs,and stimulated the formation of higher order oligomeric and active SPT complexes.Our findings therefore suggest a novel regulatory mechanism for SPT activity. 展开更多
关键词 ARABIDOPSIS MAPK PHOSPHORYLATION SPHINGOLIPIDS
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Self-water-absorption-type two-dimensional composite photocatalyst with high-efficiency water absorption and overall water-splitting performance
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作者 Gang Zhao Wenxuan Ma +3 位作者 xiaoke wang Yupeng Xing Shuhua Hao Xijin Xu 《Advanced Powder Materials》 2022年第2期9-18,共10页
Photocatalytic overall water splitting is an interesting research topic in the field of energy and outer space exploration.Here,we designed a P/MoS_(2) composite photocatalyst with self-water-absorption performance by... Photocatalytic overall water splitting is an interesting research topic in the field of energy and outer space exploration.Here,we designed a P/MoS_(2) composite photocatalyst with self-water-absorption performance by compositing MoS_(2) nanosheets and polycrystalline black phosphorus nanosheets.The composite photocatalyst produced a sufficient amount of hydrogen in the absence of any precious metal.This also demonstrated photocatalytic overall water-splitting ability in the absence of any sacrificial agent.More interestingly,it effectively absorbed water and demonstrated good overall water-splitting performance under the simulated Mars conditions;the average hydrogen production rate was 17.68μmol h^(-1) g^(-1),and the oxygen production rate was 7.61μmol h^(-1) g^(-1) over a period of 70 h.A comprehensive investigation of the ability of the composite photocatalyst to absorb water and produce hydrogen was performed. 展开更多
关键词 Self-water-absorption-type photocatalyst Two-dimensional materials P/MoS_(2) Water absorption Overall water splitting
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Response of runoff and soil loss to reforestation and rainfall type in red soil region of southern China 被引量:20
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作者 Zhigang Huang Zhiyun Ouyang +2 位作者 Fengrui Li Hua Zheng xiaoke wang 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2010年第11期1765-1773,共9页
To evaluate the long-term effects of reforestation types on soil erosion on degraded land, vegetation and soil properties under conventional sloping farmland (CSF) and three different reforestation types including a... To evaluate the long-term effects of reforestation types on soil erosion on degraded land, vegetation and soil properties under conventional sloping farmland (CSF) and three different reforestation types including a Pinus massoniana secondary forest (PSF), an Eucommia ulmoides artificial economic forest (EEF) and a natural succession type forest (NST), were investigated at runoff plot scale over a six-year period in a red soil region of southern China. One hundred and thirty erosive rainfall events generating runoff in plots were grouped into four rainfall types by means of K-mean clustering method. Erosive rainfall type I is the dominant rainfall type. The amount of runoff and the soil loss under erosive rainfall type III were the most, followed by rain-fall type II, IV and I. Compared with CSF treatment, reforestation treatments decreased the average annual runoff depth and the soil loss by 25.5%–61.8% and 93.9%– 96.2% during the study period respectively. Meanwhile, runoff depth at PSF and EEF treatments was significantly lower than that in NST treatment, but no significant difference existed in soil erosion modulus among the three reforestation treatments. This is mainly due to the improved vegetation properties (i.e., vegetation coverage, biomass of above- and below-ground and litter-fall mass) and soil properties (i.e., bulk density, total porosity, infiltration rate and organic carbon content) in the three reforestation treatments compared to CSF treatment. The PSF and EEF are recommended as the preferred reforestation types to control runoff and soil erosion in the red soil region of southern China, with the NST potentially being used as an important supplement. 展开更多
关键词 reforestation type rainfall type vegetation and soil property soil erosion red soil region
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Preliminary report on methane emissions from the Three Gorges Reservoir in the summer drainage period 被引量:13
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作者 Fei Lu Le Yang +10 位作者 xiaoke wang Xiaonan Duan Yujing Mu Wenzhi Song Feixiang Zheng Junfeng Niu Lei Tong Hua Zheng Yongjuan Zhou Jiangxiao Qiu Zhiyun Ouyang 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2011年第12期2029-2033,共5页
Recently reported summertime methane (CH4) emissions (6.7 ± 13.3 mg CH4/(m2·hr)) from newly created marshes in the drawdown area of the Three Gorges Reservoir (TGR), China have triggered broad concer... Recently reported summertime methane (CH4) emissions (6.7 ± 13.3 mg CH4/(m2·hr)) from newly created marshes in the drawdown area of the Three Gorges Reservoir (TGR), China have triggered broad concern in academic circles and among the public. The CH4 emissions from TGR water surfaces and drawdown areas were monitored from 3rd June to 16th October 2010 with floating and static chambers and gas chromatography. The average CH4 emission flux from permanently flooded areas in Zigui, Wushan and Yunyang Counties was (0.33 ± 0.09) mg CH4/(m2·hr). In half of these hottest months of the year, the wilderness, cropland and deforested drawdown sites were aerobic and located above water level, and the CH4 emissions were very small, ranging from a sink at 0.12 mg CH4/(m2·hr) to a source at 0.08 mg CH4/(m2·hr) except for one mud-covered site after flood. Mean CH4 emission in flooded drawdown sites was 0.34 mg CH4/(m2·hr). The emissions from the rice paddy sites in the drawdown area were averaged at (4.86 ± 2.31) mg CH4/(m2·hr). Excepting the rice-paddy sites, these results show much lower emission levels than previously reported. Our results indicated considerable spatial and temporal variation in CH4 emissions from the TGR. Human activities and occasional events, such as flood, may also affect emission levels. Long-term CH4 measurements and modeling in a large region are necessary to accurately estimate greenhouse gas emissions from the TGR. 展开更多
关键词 METHANE the Three Gorges Reservoir drawdown area SUMMER drainage uncertainty FLOOD
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Effects of land use, climate, topography and soil properties on regional soil organic carbon and total nitrogen in the Upstream Watershed of Miyun Reservoir, North China 被引量:19
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作者 Shufang wang xiaoke wang Zhiyun Ouyang 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2012年第3期387-395,共9页
Soil organic carbon (SOC) and total nitrogen (TN) contents as well as their relationships with site characteristics are of profound importance in assessing current regional, continental and global soil C and N sto... Soil organic carbon (SOC) and total nitrogen (TN) contents as well as their relationships with site characteristics are of profound importance in assessing current regional, continental and global soil C and N stocks and potentials for C sequestration and N conservation to offset anthropogenic emissions of greenhouse gases. This study investigated contents and distribution of SOC and TN under different land uses, and the quantitative relationships between SOC or TN and site characteristics in the Upstream Watershed of Miyun Reservoir, North China. Overall, both SOC and TN contents in natural secondary forests and grasslands were much higher than in plantations and croplands. Land use alone explained 37.2% and 38.4% of variations in SOC and TN contents, respectively. The optimal models for SOC and TN, achieved by multiple regression analysis combined with principal component analysis (PCA) to remove the multicollinearity among site variables, showed that elevation, slope, soil clay and water contents were the most significant factors controlling SOC and TN contents, jointly explaining 70.3% of SOC and 67.1% of TN contents variability. Only does additional 1.9% and 3% increase in the interpretations of SOC and TN contents variability respectively when land use was added to regressions, probably due to environment factors determine land use. Therefore, environmental variables were more important for SOC and TN variability than land use in the study area, and should be taken into consideration in properly evaluating effects of future land use changes on SOC and TN on a regional scale. 展开更多
关键词 soil organic carbon soil total nitrogen principal component analysis multiple regression analysis
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Recent advances in the improvement of g-C_(3)N_(4) based photocatalytic materials 被引量:15
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作者 Yupeng Xing xiaoke wang +5 位作者 Shuhua Hao Xueli Zhang Xiao wang Wenxuan Ma Gang Zhao Xijin Xu 《Chinese Chemical Letters》 SCIE CAS CSCD 2021年第1期13-20,共8页
g-C_(3)N_(4) have been widely used in the fields of photocatalytic hydrogen production,photocatalytic degradation of dyes and oxidative degradation of toxic gases due to their excellent performance.It has attracted ex... g-C_(3)N_(4) have been widely used in the fields of photocatalytic hydrogen production,photocatalytic degradation of dyes and oxidative degradation of toxic gases due to their excellent performance.It has attracted extensive attention in recent years due to its highly efficient photocatalytic capacity of hydrogen generation,water oxidation,carbon dioxide reduction and degradation of organic pollutants.Because of the abundant carbon and nitrogen composition of the earth,large-scale production and industrial applications of this material are possible.The modification of this material makes its performance more excellent so that this new material can obtain a steady stream of vitality.These outstanding works have become important materials and milestones on the road to mankind's photocatalytic hydrogen production.This review will begin with the basic idea of designing,synthesizing and improving g-C_(3)N_(4) based photocatalytic materials,and introduce the latest development of g-C_(3)N_(4) photocatalysts in hydrogen production from four aspects of controlling the carbon/nitrogen ratio,morphology,element doping and heterojunction structure of g-C_(3)N_(4) materials. 展开更多
关键词 Carbon nitride MODIFICATION ENHANCEMENT PHOTOCATALYST Hydrogen evolution reaction
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Spatial and seasonal variability of CO_2 flux at the air-water interface of the Three Gorges Reservoir 被引量:9
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作者 Le Yang Fei Lu +4 位作者 xiaoke wang Xiaonan Duan Lei Tong Zhiyun Ouyang Hepeng Li 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2013年第11期2229-2238,共10页
Diffusive carbon dioxide (CO2) emissions from the water surface of the Three Gorges Reservoir, currently the largest hydroelectric reservoir in the world, were measured using floating static chambers over the course... Diffusive carbon dioxide (CO2) emissions from the water surface of the Three Gorges Reservoir, currently the largest hydroelectric reservoir in the world, were measured using floating static chambers over the course of a yearlong survey. The results showed that the average,annual CO2 flux was (163.3 ± 117.4) mg CO2/(m^2.hr) at the reservoir surface, which was larger than the CO2 flux in most boreal and temperate reservoirs but lower than that in tropical reservoirs. Significant spatial variations in CO2 flux were observed at four measured sites, with the largest flux measured at Wushan (221.9 mg CO2/(m^2.hr)) and the smallest flux measured at Zigui (88.6 mg CO2/(m^2.hr)); these differences were probably related to the average water velocities at different sites. Seasonal variations in CO2 flux were also observed at four sites, starting to increase in January, continuously rising until peaking in the summer (June-August) and gradually decreasing thereafter. Seasonal variations in CO2 flux could reflect seasonal dynamics in pH, water velocity, and temperature. Since the spatial and temporal variations in CO2 flux were significant and dependent on multiple physical, chemical, and hydrological factors, it is suggested that long-term measurements should be made on a large spatial scale to assess the climatic influence of hydropower in China, as well as the rest of the world. 展开更多
关键词 CO2 emission spatial variation seasonal variation water velocity TEMPERATURE PH
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Soil temperature and moisture sensitivities of soil CO_2 efflux before and after tillage in a wheat field of Loess Plateau,China 被引量:7
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作者 Hongxing Zhang xiaoke wang +6 位作者 Zongwei Feng Junzhu Pang Fei Lu Zhiyun Ouyang Hua Zheng Wenzhao Liu Dafeng Hui 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2011年第1期79-86,共8页
As a conventional farming practice, tillage has lasted for thousands of years in Loess Plateau, China. Although recent studies show that tillage is a prominent culprit to soil carbon loss in croplands, few studies hav... As a conventional farming practice, tillage has lasted for thousands of years in Loess Plateau, China. Although recent studies show that tillage is a prominent culprit to soil carbon loss in croplands, few studies have investigated the influences of tillage on the responses of soil CO2 efflux (SCE) to soil temperature and moisture. Using a multi-channel automated CO2 efflux chamber system, we measured SCE in situ continuously before and after the conventional tillage in a rain fed wheat field of Loess Plateau, China. The changes in soil temperature and moisture sensitivities of SCE, denoted by the Q10 value and linear regression slope respectively, were compared in the same range of soil temperature and moisture before and after the tillage. The results showed that, after the tillage, SCE increased by 1.2-2.2 times; the soil temperature sensitivity increased by 36.1%-37.5%; and the soil moisture sensitivity increased by 140%-166%. Thus, the tillage-induced increase in SCE might partially be attributed to the increases in temperature and moisture sensitivity of SCE. 展开更多
关键词 soil CO2 efflux Loess Plateau moisture sensitivity temperature sensitivity TILLAGE wheat field
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Changes in nitrogen budget and potential risk to the environment over 20 years(1990–2010) in the agroecosystems of the Haihe Basin, China 被引量:6
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作者 Mengmeng Zheng Hua Zheng +6 位作者 Yingxia Wu Yi Xiao Yihua Du Weihua Xu Fei Lu xiaoke wang Zhiyun Ouyang 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2015年第2期195-202,共8页
The nitrogen balance can serve as an indicator of the risk to the environment of nitrogen loss from agricultural land. To investigate the temporal and spatial changes in agricultural nitrogen application and its poten... The nitrogen balance can serve as an indicator of the risk to the environment of nitrogen loss from agricultural land. To investigate the temporal and spatial changes in agricultural nitrogen application and its potential threat to the environment of the Haihe Basin in China, we used a database of county-level agricultural statistics to calculate agricultural nitrogen input, output,surplus intensity, and use efficiency. Chemical fertilizer nitrogen input increased by 51.7% from1990 to 2000 and by 37.2% from 2000 to 2010, concomitant with increasing crop yields.Simultaneously, the nitrogen surplus intensity increased by 53.5% from 1990 to 2000 and by16.5% from 2000 to 2010, presenting a continuously increased environmental risk. Nitrogen use efficiency decreased from 0.46 in 1990 to 0.42 in 2000 and remained constant at 0.42 in 2010,partly due to fertilizer composition and type improvement. This level indicates that more than half of nitrogen inputs are lost in agroecosystems. Our results suggest that although the improvement in fertilizer composition and types has partially offset the decrease in nitrogen use efficiency, the environmental risk has still increased gradually over the past 20 years, along with the increase in crop yields and nitrogen application. It is important to achieve a better nitrogen balance through more effective management to significantly reduce the environmental risk,decrease nitrogen surplus intensity, and increase nitrogen use efficiency without sacrificing crop yields. 展开更多
关键词 Nitrogen budget Nitrogen surplus intensity Nitrogen use efficiency Environmental risk AGROECOSYSTEM Haihe Basin
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Nitrogen pollution and source identification of urban ecosystem surface water in Beijing 被引量:7
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作者 Yufen REN Zhiwei XU +4 位作者 Xinyu ZHANG xiaoke wang Xiaomin SUN D. J. BALLANTINE Shengzhong wang 《Frontiers of Environmental Science & Engineering》 SCIE EI CAS CSCD 2014年第1期106-116,共11页
Nitrogen contamination of surface water is a worldwide environmental problem with intensive agricul- ture and high population densities. We assessed the spatial and seasonal variation in concentrations of total nitrog... Nitrogen contamination of surface water is a worldwide environmental problem with intensive agricul- ture and high population densities. We assessed the spatial and seasonal variation in concentrations of total nitrogen and different nitrogen species present in surface-water in Beijing, China. Also, chemical (NO3-N/C1-) and isotopic (615Nnitrate) indicators were used to identify nitrate sources. The results showed that, during 2009 and 2010, nitrate nitrogen concentrations ranged from 0.7 to 7.6 mg· L^-1, ammonium nitrogen from 0. I to 3.4 mg· L^-1, and total nitrogen from 2.4 to 17.0mg· L^-1. Inorganic nitrogen accounted for between 60 and 100% of total nitrogen at the ten monitoring sites. Nitrate nitrogen, ammonium nitrogen, and total nitrogen concentrations at the 2 downstream monitoring sites in south-eastern Beijing were significantly higher than those at the other eight upstream monitoring sites (P 〈 0.01). Examination of seasonal variation showed that there was a significant inverse relationship between nitrate nitrogen concentrations and precipitation, and that nitrate nitrogen concentrations peaked in the dry seasons. The information given by the 15Nnitrate values and nitrate nitrogen concentrations, combined with the NO3-N/C1- ratio distribution, showed that domestic sewage was the major source of nitrate in Beijing. Methods to control and reduce sewage pollution are urgently needed to help manage surface water quality in Beijing. 展开更多
关键词 nitrogen concentration spatial and seasonalvariation stable nitrogen isotope urban ecosystem source
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Arbuscular mycorrhizal fungi alter the response of growth and nutrient uptake of snap bean(Phaseolus vulgaris L.) to O_3 被引量:6
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作者 Shuguang wang Zhaozhong Feng +1 位作者 xiaoke wang Wenliang Gong 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2011年第6期968-974,共7页
The effects of arbuscular mycorrhizal fungi(AMF) Glomus mosseae on the responses to elevated O3 in growth and nutrition of snap bean(Phaseolus vulgaris L.cv Guangzhouyuan) were investigated.Exposure was conducted ... The effects of arbuscular mycorrhizal fungi(AMF) Glomus mosseae on the responses to elevated O3 in growth and nutrition of snap bean(Phaseolus vulgaris L.cv Guangzhouyuan) were investigated.Exposure was conducted in growth chambers by using three O3 concentrations(20(CF),80(CFO1) and 120 nL/L(CFO2);8 hr/day for 75 days).Results showed that elevated O3 slightly impacted overall mycorrhizal colonization,but significantly decreased the proportional frequency of hypha and increased the proportional frequency of spores and vesicles,suggesting that O3 had significant effects on mycorrhizal structure.Elevated O3 significantly decreased yield,dry mass and nutrient contents(N,P,K,Ca and Mg) in both non-mycorrhizal and mycorrhizal plants.However,significant interactive effects were found in most variables due to that the reduction by O3 in the mycorrhizal plants was less than that in the non-mycorrhizal plants.Additionally,AMF increased the concentrations of N,P,Ca,and Mg in shoot and root.It can be concluded that AMF alleviated detrimental effects of increasing O3 on host plant through improving plant nutrition and growth. 展开更多
关键词 arbuscular mycorrhizal fungi nutrition status mycorrhizal colonization elevated 03 snap bean
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Soil warming effect on net ecosystem exchange of carbon dioxide during the transition from winter carbon source to spring carbon sink in a temperate urban lawn 被引量:6
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作者 Xiaoping Zhou xiaoke wang +6 位作者 Lei Tong Hongxing Zhang Fei Lu Feixiang Zheng Peiqiang Hou WenzhiSong Zhiyun Ouyang 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2012年第12期2104-2112,共9页
The significant warming in urban environment caused by the combined effects of global warming and heat island has stimulated widely development of urban vegetations. However, it is less known of the climate feedback o... The significant warming in urban environment caused by the combined effects of global warming and heat island has stimulated widely development of urban vegetations. However, it is less known of the climate feedback of urban lawn in warmed environment. Soil warming effect on net ecosystem exchange (NEE) of carbon dioxide during the transition period from winter to spring was investigated in a temperate urban lawn in Beijing, China. The NEE (negative for uptake) under soil warming treatment (temperature was about 5~C higher than the ambient treatment as a control) was -0.71 ~mol/(m2.sec), the ecosytem was a CO2 sink under soil warming treatment, the lawn ecosystem under the control was a CO2 source (0.13 Ixmol/(mE.sec)), indicating that the lawn ecosystem would provide a negative feedback to global warming. There was no significant effect of soil warming on nocturnal NEE (i.e., ecosystem respiration), although the soil temperature sensitivity (Q10) of ecosystem respiration under soil warming treatment was 3.86, much lower than that in the control (7.03). The CO2 uptake was significantly increased by soil warming treatment that was attributed to about 100% increase of ct (apparent quantum yield) and Amax (maximum rate of photosynthesis). Our results indicated that the response of photosynthesis in urban lawn is much more sensitive to global warming than respiration in the transition period. 展开更多
关键词 soil warming urban lawn C02 uptake ecosystem respiration
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Climate extremes and ozone pollution:a growing threat to China’s food security 被引量:5
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作者 Hanqin Tian Wei Ren +9 位作者 Bo Tao Ge Sun Art Chappelka xiaoke wang Shufen Pan Jia Yang Jiyuan Liu Ben SFelzer Jerry MMelillo John Reilly 《Ecosystem Health and Sustainability》 SCIE 2016年第1期2-11,共10页
Ensuring global food security requires a sound understanding of climate and environmental controls on crop productivity.The majority of existing assessments have focused on physical climate vari-ables(i.e.,mean temper... Ensuring global food security requires a sound understanding of climate and environmental controls on crop productivity.The majority of existing assessments have focused on physical climate vari-ables(i.e.,mean temperature and precipitation),but less on the increasing climate extremes(e.g.,drought)and their interactions with increasing levels of tropospheric ozone(O3).Here we quantify the combined impacts of drought and O3 on China’s crop yield using a comprehensive,process-based agricultural eco-system model in conjunction with observational data.Our results indicate that climate change/variability and O3 together led to an annual mean reduction of crop yield by 10.0%or 55 million tons per year at the national level during 1981-2010.Crop yield shows a growing threat from severe episodic droughts and in-creasing O3 concentrations since 2000,with the largest crop yield losses occurring in northern China,causing serious concerns in food supply security in China.Our results imply that reducing tropospheric O3 levels is critical for securing crop production in coping with increasing frequency and severity of extreme climate events such as droughts.Improving air quality should be a core component of climate adaptation strategies. 展开更多
关键词 China food security climate change crop yield DROUGHT tropospheric ozone(O3).
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