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Facet-dependent electro-optical properties of cholesteric liquid crystals doped with Cu2O nanocrystals

Nano Research 2018年第9期11卷 4836-4845页

作者： Dongyu Zhao lihong xu Yang Shang Xiaoxia Li Lin Guo Key Laboratory of Bio-lnspired Smart Interfacial Science and Technology Ministry of Education School of Chemistry Beijing Advanced Innovation Center for Biomedical Engineering Beihang University Beijing 100191 China Key Laboratory of Micro-Nano Measurement-Manipulation and Physics Ministry of Education School of Physics and Nuclear Energy Engineering Beihang University Beijing 100191 China

Excellent electro-optical （E-O） performances are essential for high-quality reflective cholesteric liquid crystal （LC） displays, but are often limited by the high driving voltages required by these displays. Dispersing functional nanomaterials into the LCs has emerged as a promising approach to achieve outstanding E-O properties. In this work, we report the facet-controlled E-O properties of a chiral nematic LC （N＊LC） doped with cubic, octahedral, and rhornbic dodecahedral Cu20. The outstanding E-O properties of the doped systems are related to the interaction between the liquid crystals and Cu20 dopants with different exposed crystal planes. Doping with octahedral and rhombic dodecahedral Cu20 reduces the stability of the planar state, as a result of both the surface abundance of active Cu atoms that interact with the polarized LC molecules, and the large amounts of vertexes and edges on the crystal surfaces, which accelerate the transition from the planar to the focal conic state under an applied electric field. Rhombic Cu20 is the most effective dopant for improving the E-O properties of the present LCs, resulting in a 65.31% reduction of the threshold voltage. The facet and morphology effects highlighted in this work provide a new pathway to develop excellent energy-saving meso-materials with exposed high-reactivity facets, improving their potential applications in electro-optical technologies and information displays.

关键词： Cu2O nanocrystals liquid crystals electro-optical properties host-guest systems facet-dependence

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Effects of impregnation sequence on the microstructure and performances of Cu-Co based catalysts for the synthesis of higher alcohols

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Journal of Natural Gas Chemistry 2008年第4期17卷 369-373页

作者： Siyu Deng Wei Chu Huiyuan xu Limin Shi lihong Huang Department of Chemical Engineering Sichuan University Chengdu 610065 Sichuan China

Silica-supported CuCo catalysts were prepared by impregnation method with different impregnation sequence for higher alcohols synthesis. These catalysts were characterized by H2-TPR, XRD, N2 adsorption, XPS techniques and CO selective hydrogenation reaction measurement. The effects of impregnation sequence on the structure and performance of catalysts were investigated, and there were important influences on the selectivity to higher alcohols. There was a strong synergistic effect between copper and cobalt for the co-impregnated sample. The CuCo/SiO2 catalyst prepared by co- impregnation showed a better yield of total alcohols, and a higher selectivity to total alcohols which reached 51.5%.

关键词： copper cobalt impregnation sequence synergistic effect selective hydrogenation carbon monoxide

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Chemical synthesis and characterization of manganese oxide coated Ni particles

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Science China(Physics,Mechanics & Astronomy) 2013年第8期56卷 1508-1513页

作者： AN Jing xu lihong HE Jun ZHAO DongLiang LIU ZhongYuan Department of Functional Material Research Central Iron and Steel Research Institute State Key Lab of Metastable Materials Science and Technology Yanshan University

Nanosized Ni particles with an average diameter of about 8 nm were prepared by reducing of NiCl 2 with sodium borohydride (NaBH 4 ) in aqueous solution. By moderate annealing in protective atmosphere, the composite grew up to be 15-20 nm particles. Both of the as-prepared and annealed Ni particles were coated by a layer of manganese oxide via decomposition reaction in aqueous KMnO4 solution. Hysteresis loops of as-prepared samples show a large increase in the magnetization with decreasing temperature and an unsaturated component at high magnetic field. In contrast, the ferromagnetic characteristics of annealed one are much stronger with large magnetization and coercivity. The thermomagnetic curves verified the coexistence of ferromagnetic Ni and antiferromangetic Mn oxide phases. But there exists no exchange bias behavior in the samples, even though the interface structure between the ferromagnetic Ni core and the antiferromagnetic manganese oxides has been distinctly formed. The absence of exchange bias probably originates from the weak ferromagnetic characteristic of Ni cores.

关键词： nanoparticles chemical reduction core-shell structure magnetic property

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Study on magnetic memory signals of medium carbon steel specimens with surface crack precut during loading process

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Rare Metals 2006年第z1期25卷 431-435页

作者： DONG lihong xu Binshi DONG Shiyun YE Minghui CHEN Qunzhi Basic Department Ordnance Engineering College Shijiazhuang 050003 China National Key Laboratory for Remanufacturing of Armored Force Engineering Institute Beijing 100072 China National Key Laboratory for Remanufacturing of Armored Force Engineering Institute Beijing 100072 China National Key Laboratory for Remanufacturing of Armored Force Engineering Institute Beijing 100072 China Basic Department Ordnance Engineering College Shijiazhuang 050003 China Beijing Aeronautical Technology Research Center Beijing 100076 China

Static tensile test and tensile-tensile fatigue test of medium carbon steel sheet specimens with surface crack precut were performed on MTS810 hydraulic testing machine to clear the meaning of the point of Hp(y) value zero. Magnetic memory signals were measured during the test process. The results show that only one point of Hp(y) zero value exists in all measured magnetic signal curves during the loading process, which should be a sign of intersection of positive-negative magnetic poles after magnetic ordered state appears and does not indicate the position of surface crack precut. The analysis shows that the surface crack precut can not interrupt the magnetic ordered state occurred during the test completely, hence its Hp(y) value is not zero. However, the crack extending to a penetrated defect at the instant of specimen′s fracture leads to the discontinuance of magnetic ordered state.

关键词： metal magnetic memory ferromagnetic materials surface crack precut Hp(y) zero value magnetic ordered state

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Environmental and canopy conditions regulate the forest floor evapotranspiration of larch plantations

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Forest Ecosystems 2022年第5期9卷 606-616页

作者： Zebin Liu Yanhui Wang Pengtao Yu lihong xu Songping Yu Key Laboratory of Forest Ecology and Environment of National Forestry and Grassland Administration Ecology and Nature Conservation InstituteChinese Academy of ForestryBeijing100091China School of Soil and Water Conservation Beijing Forestry UniversityBeijing100083China

Background:Integrated forest-water management focusing on forest-water coordination is an important way to alleviate water use conflicts among forests and other sectors in vast dryland *** floor evapotranspiration(FE),which is an important component of forest evapotranspiration,accounts for a large proportion of the water consumed in arid *** how environmental and canopy conditions impact FE has important significance for guiding integrated forest-water management in a changing ***:The microlysimeter(ML)-measured evapotranspiration(FE_(ML)),reference evapotranspiration(ET_(o)),volumetric soil moisture(VSM),and canopy leaf area index(LAI)were monitored in a Larix principis-rupprechtii plantation located in the semi-humid Liupan Mountains of Northwest China in 2019(June–September)and 2021(May–September).The response functions of the FE coefficient(the ratio of daily FEML to ET_(o))to the individual factors of VSM and LAI were determined using upper boundary lines of scatter diagrams of measured *** framework of the daily FE(FE_(ML))model was established by multiplying the response functions to individual factors and then calibrated and validated using measured data to assess the FE response to environmental and canopy ***:(1)The FE coefficient increased first rapidly and then slowly with rising VSM but decreased slowly with rising LAI.(2)The simple daily FE(FE_(ML))model developed by coupling the impacts of ET_(o),LAI,and VSM in this study performed well for predicting FE.(3)The impacts of ET_(o),LAI,and VSM were quantified using the FE(FE_(ML))model,e.g.,at a given VSM,the impact of ETo on FE increased obviously with decreasing LAI;at a given ET_(o),the impact of LAI on FE increased with rising VSM.(4)In the two study years,when directly using the microlysimeter measurement,the real FE on the forest floor was overestimated when the VSM in microlysimeters was above 0.215 but underestimated below 0.215 due

关键词： Larch plantation Forest floor evapotranspiration Reference evapotranspiration Soil water content Canopy structure

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A method for modelling greenhouse temperature using gradient boost decision tree

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Information Processing in Agriculture 2022年第3期9卷 343-354页

作者： Wentao Cai Ruihua Wei lihong xu Xiaotao Ding College of Electronics and Information Engineering TongJi UniversityShanghai 201804PR China Shanghai Dushi Green Engineering Co. LtdHorticultural Research InstituteShanghai Academy of Agricultural SciencesShanghai 201106PR China

y consumption efficiency and to increase the crop *** the increase of agri-cultural data generated by the Internet of Things(IoT),more feasible models are necessary to get full usage of such *** this research,a Gradient Boost Decision Tree(GBDT)model based on the newly-developed Light Gradient Boosting Machine algorithm(LightGBM or LGBM)was proposed to model the internal temperature of a ***-tures including climate variables,control variables and additional temporal information collected within five years were used to construct a suitable dataset to train and validate the LGBM *** adaptive cross-validation method was developed as a novelty to improve the LGBM model performance and self-adaptive *** comparison of the pre-dictive accuracy,a Back-Propagation(BP)Neural Network model and a Recurrent Neural Network(RNN)model were built under the same *** two GBDT algorithms,Extreme Gradient Boosting(Xgboost)and Stochastic Gradient Boosting(SGB),were also introduced to compare the predictive accuracy with LGBM *** suggest that the LGBM has best fitting ability for the temperature curves with RMSE value at 0.645℃,as well as the fastest training speed among all algorithms with 60 times faster than the other two neural network *** LGBM has strongly potential application pro-spect on both greenhouse environment prediction and real-time predictive control.

关键词： Gradient boost decision tree Light gradient boosting machine Temperature prediction model Neural network

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Impacts of environmental and canopy conditions on the nighttime sap flow of larch plantations in the Liupan Mountains,China

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Journal of Forestry Research 2023年第6期34卷 1927-1940页

作者： Songping Yu Jianbin Guo Zebin Liu Yanhui Wang lihong xu Pengtao Yu Liang He School of Soil and Water Conservation Beijing Forestry UniversityBeijing 100083People’s Republic of China Key Laboratory of Forest Ecology and Environment of National Forestry and Grassland Administration Ecology and Nature Conservation InstituteChinese Academy of ForestryBeijing 100091People’s Republic of China

Nighttime sap flow(Q_(n))is an important physiological activity under which trees manage drought *** in-depth understanding of the characteristics of Q_(n)and its response to environmental and canopy conditions are of significance for arid area forest and water *** study measured daily sap flow(Q_(s))of a Larix principis-rupprechtii plantation in the Liupan Mountains,northwest China during the 2017-2019 growing seasons,and separated Q_(s)into daytime sap flow(Qd)and Q_(n).Meteorological conditions(reference evapotranspiration,ETref),canopy structure(leaf area index,LAI),and soil moisture(relative soil water content,RSWC)were considered as the main biophysical factors affecting Q_(n).The structural equation model and upper boundary line method determined the effects of compound and single factors on Q_(n)The daily mean Q_(n)values during the growing seasons in 2017,2018,and 2019 were 0.024,0.026,and 0.030 mm d-1,accounting for 6.2,11.2,and 10.1%of Q_(s),respectively.Q_(n)at different canopy development phases(leaf expanding,LG;leaf expanded,LD;and defoliation,DF)over three years was LD>LG>DF.Q_(n)increased with increasing ETref,whereas the ratio of Q_(n)to Q_(s)decreased.Q_(n)did not show regular variation in the three-year growing seasons under different soil moisture *** LAI mainly controlled Q_(n)by affecting Qd,whereas RSWC had no significant effect on Q_(n).Q_(n)had a positive and linear relationship with LAI and a quadratic relationship with *** explained 40%of variation in Q_(n)Meteorological and canopy conditions are important factors affecting Q_(n)on the semi-humid study *** application of the Q_(n)model coupled with the impact of ETrefand LAI furthers understanding of the impacts of climate and forest structure change on Q_(n).

关键词： Nighttime sap flow Reference evapotranspiration Leaf area index Soil moisture Multifactor impact

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Effects of morphology and concentration of CuS nanoparticles on alignment and electro-optic properties of nematic liquid crystal

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Nano Research 2017年第2期10卷 618-625页

作者： Bin Liu Yiran Ma Dongyu Zhao lihong xu Fashun Liu Wei Zhou Lin Guo Key Laboratory of Bio-lnspired Smart Interfacial Science and Technology Ministry of Education School of Chemistry and EnvironmentBeihang University Beijing 100191 China

Nanoparticles （NPs） with flower-like and frame morphologies were synthesized from CuS, a remarkable transition-metal sulfide. We introduced two kinds of CuS NPs into a nematic liquid crystal （LC） 4-cyano-4＇-n-pentylbiphenyl （5CB） and investigated the morphology- and concentration-dependent alignment and electro-optic （E-O） effects of CuS NPs on 5CB. A trace amount of flower-like CuS NPs induced a uniform homeotropic orientation of LC molecules; this is attributable to the obtained desirable compact nanosheet structure. Moreover, both flower-like and frame CuS NPs induced a remarkable improvement in the E-O properties of 5CB, and the flower-like CuS/5CB system exhibited a better performance. The doped CuS NPs in the LC host suppressed the shielding effect and strengthened the electric field, resulting in outstanding E-O properties. At a doping concentration of 0.05 wt.%, CuS NPs were well-dispersed and achieved the optimum E-O performance. This study provides a novel method for inducing a uniform orientation and enhanced E-O properties of LC molecules by doping with extraordinary CuS NPs, leading to potential applications in establishing flexible LC displays.

关键词： liquid crystal CuS nanoparticles vertical alignment electro-optic properties

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Learning to Teach in Secondary College

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校园英语 2016年第9期 52-53页

作者： xu lihong Luojia College Wuhan University

English teaching in secondary colleges is quite different from the others. The individuality of the students and the vocational oriented training goal are the chief features. The key issues for the teachers in secondary colleges are learning to teach and make it a collaborative effort, reflective process, situated experience and theorizing opportunity.

关键词： collaborative effort reflective process situated experience theorizing opportunity

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Characteristics of canopy interception and its simulation with a revised Gash model for a larch plantation in the Liupan Mountains, China

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Journal of Forestry Research 2018年第1期29卷 187-198页

作者： Zebin Liu Yanhui Wang Ao Tian Yu Liu Ashley A.Webb Yarui Wang Haijun Zuo Pengtao Yu Wei Xiong lihong xu Institute of Forest Ecology Environment and ProtectionChinese Academy of Forestry Key Laboratory of Forestry Ecology and Environment of State Forestry Administration College of Soil and Water Conservation Beijing Forestry University NSW Department of Primary Industries Tamworth Agricultural Institute

Canopy interception is a significant proportion of incident rainfall and evapotranspiration of forest ecosystems. Hence, identifying its magnitude is vital for studies of eco-hydrological processes and hydrological impact evaluation. In this study, throughfall, stemflow and interception were measured in a pure Larix principis-rupprechtii Mayr.（larch） plantation in the Liupan Mountains of northwestern China during the growing season（May–October） of 2015, and simulated using a revised Gash model. During the study period, the total precipitation was 499.0 mm; corresponding total throughfall, stemflow and canopy interception were 410.3, 2.0 and 86.7 mm,accounting for 82.2, 0.4 and 17.4% of the total precipitation, respectively. With increasing rainfall, the canopy interception ratio of individual rainfall events decreased initially and then tended to stabilize. Within the study period, the simulated total canopy interception, throughfall and stemflow were 2.2 mm lower, 2.5 mm higher and 0.3 mm lower than their measured values, with a relative error of 2.5, 0.6 and 15.0%, respectively. As quantified by the model, canopy interception loss（79%） mainly consisted of interception caused by canopy adsorption, while the proportions of additional interception and trunk interception were small. The revised Gash model was highly sensitive to the parameter of canopy storage capacity,followed by the parameters of canopy density and mean rainfall intensity, but less sensitive to the parameters of mean evaporation rate, trunk storage capacity, and stemflow ratio. The revised Gash model satisfactorily simulated the total canopy interception of the larch plantation within the growing season but was less accurate for some individual rainfall events, indicating that some flaws exist in the model structure. Further measures to improve the model’s ability in simulating the interception of individual rainfall events were suggested.

关键词： Canopy interception Larch plantation Revised Gash model Stemflow Throughfall

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