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Adaptation of Nitraria sphaerocarpa to wind-blown sand environments at the edge of a desert oasis

Journal of Environmental Sciences 2007年第4期19卷 482-487页

作者： LI Qiu-yan zhao wen-zhi FANG Hai-yan Chinese Ecosystem Network Research Linze Inland River Basin Research Station Laboratory of Hydrology and Applied Ecology Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China. Institute of Geographical Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China

This study addresses the adaptation of Nitraria sphaerocarpa to blown sand at the edge of a desert oasis with regard to the aspects of soil seed banks, seedlings, and population. Horizontally, the total number of seeds per unit area decreased from the shrub canopy center to intershrub areas, and most seeds were found under shrub canopies. Vertically, the highest proportion of seeds was found at depths of 5-10 cm. The emergence percentage, seedling mass, and seedling height, which were significantly affected by both burial depth and seed size, were highest at the optimal burial depth of 2 cm, and decreased with increasing burial depth in each seed size-class. Although seedling mass was usually greatest for large seeds and least for small seeds at each burial depth, little difference was observed in seedling height at shallow burial depths of 0-3 cm. The population shows a patchy and discontinuous distribution pattern. Population height increases with increasing sand depth. Also the density increases with increasing depth of sand in the desert; however, there is a steady decrease when the depth of sand is more than 100 cm. This result indicates that the depth of sand that is most suitable for the growth of Nitraria sphaerocarpa is 100 cm. The size of the population is significantly correlated with the sand depth, which increases with increasing depth in the desert.

关键词： Nitraria sphaerocarpa soil seed bank seedling growth sand burial adaptation

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Empirical likelihood for first-order mixed integer-valued autoregressive model

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Applied Mathematics(A Journal of Chinese Universities) 2018年第3期33卷 313-322页

作者： YANG Yan-qiu WANG De-hui zhao zhi-wen Department of Mathematics Jilin University Department of Mathematics Jilin Normal University

In this paper, we not only construct the confidence region for parameters in a mixed integer-valued autoregressive process using the empirical likelihood method, but also establish the empirical log-likelihood ratio statistic and obtain its limiting distribution. And then, via simulation studies we give coverage probabilities for the parameters of interest. The results show that the empirical likelihood method performs very well.

关键词： mixed integer-valued autoregressive model empirical likelihood asymptotic distribution confidence region

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Possible Superconductivity at 37K in Graphite-Sulphur Composite

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Chinese Physics Letters 2001年第12期18卷 1648-1650页

作者： YANG Hai-Peng wen Hai-Hu zhao zhi-wen LI Shi-Liang zhao Zhong-Xian National Laboratory for Superconductivity Institute of Physics and Center for Condensed Matter PhysicsChinese Academy of SciencesP.O.Box 603Beijing 100080

Sulphur intercalated graphite composites with diamagnetic transitions at 6.7 and 37K are prepared. The magnetization hysteresis loops (MHL), x-ray diffraction (XRD) patterns, and resistance have been measured. From the MHL, a slight superconducting-like penetration process is observed at 15K in the low field region. The XRD shows no large difference from the mixture of graphite and sulphur indicating that the volume of the superconducting phase (if any) is very small. The temperature dependence of resistance shows a typical semi-conducting behaviour with a saturation in the low-temperature region. This saturation is either induced by the delocalization of conducting electrons or by possible superconductivity in this system.

关键词： composites saturation conducting

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Strong Quantum Fluctuation of Vortices in Bulk Samples of the New Superconductor MgB_(2)

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Chinese Physics Letters 2001年第6期18卷 816-819页

作者： wen Hai-Hu LI Shi-Liang zhao zhi-wen NI Yong-Ming REN zhi-An CHE Guang-Can YANG Hai-Peng LIU zhi-Yong zhao Zhong-Xian National Laboratory for Superconductivity Institute of Physics and Center for Condensed Matter PhysicsChinese Academy of SciencesBeijing 100080

By using transport and magnetic measurement,the upper critical field H_(c2)(T)and the irreversibility line Hirr(T)has been determined.A big separation between H_(c2)(0)and Hirr(0)has been found showing the existence of a quantum vortex liquid state induced by quantum fluctuation of vortices in the new superconductor MgB_(2).Further investigation on the magnetic relaxation shows that both the quantum tunneling and the thermally activated flux creep depends weakly on ***,when the melting field Hirr is approached,a drastic rise of the relaxation rate is *** may indicate that the melting of the vortex matter at a finite temperature is also induced by the quantum fluctuation of vortices.

关键词： temperature. quantum relaxation

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Upper Critical Field and Irreversibility Line Determined by Transport Measurement of the New Superconductor MgB_(2)

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Chinese Physics Letters 2001年第6期18卷 823-825页

作者： JIN Hao wen Hai-Hu LI Shi-Liang zhao zhi-wen NI Yong-Ming REN zhi-An CHE Guang-Can YANG Hai-Peng LIU zhi-Yong ZHENG Dong-Ning zhao Zhong-Xian National Laboratory for Superconductivity Institute of Physics and Center for Condensed Matter PhysicsChinese Academy of SciencesBeijing 100080

Resistive transitions of the new superconductor MgB_(2) are carried out under magnetic fields from 0 to 8 *** is found that the irreversibility field Hirr(T)and the upper critical field Hc2(T)obtained are very close to those determined in the magnetic *** using the Arrhenius activation lawρ=ρ0exp(-U/kBT),the activation barrier U has been determined by the low dissipation part of R(T)*** is found that U■kBT manifests a very weak thermal activation and thermal fluctuation *** may further indicate that the flux dynamics near Hirr(T)is induced by strong quantum fluctuation and tunneling of vortices.

关键词： activation Upper thermal

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Statistical Inference for the Parameter of Rayleigh Distribution Based on Progressively Type-I Interval Censored Sample

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Communications in Mathematical Research 2015年第2期31卷 108-118页

作者： Abdalroof M S zhao zhi-wen Wang De-hui School of Mathematics Jilin University College of Mathematics Jilin Normal University

In this paper, the estimation of parameters based on a progressively type-I interval censored sample from a Rayleigh distribution is studied. Different methods of estimation are discussed. They include mid-point approximation estima- tor, the maximum likelihood estimator, moment estimator, Bayes estimator, sampling adjustment moment estimator, sampling adjustment maximum likelihood estimator and estimator based on percentile. The estimation procedures are discussed in details and compared via Monte Carlo simulations in terms of their biases.

关键词： EM algorithm maximum likelihood estimation moment method Bayesestimation Rayleigh distribution

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Analysis of Water Resources Supply and Demand and Security of Water Resources Development in Irrigation Regions of the Middle Reaches of the Heihe River Basin, Northwest China

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Agricultural Sciences in China 2006年第2期5卷 130-140页

作者： JI Xi-bin KANG Er-si CHEN Ren-sheng zhao wen-zhi XlAO Sheng-chun JIN Bo-wen Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 P.R.China Linze Inland River Basin Comprehensive Research Station Chinese Ecosystem Network Research Linze 734200 P.R.China

Based on the data for meteorology, hydrology, soil, planting, vegetation, and socio-economic development of the irrigation region in the middle reaches of the Heihe River basin, Northwest China, the model of balance of water supply and demand in the region was established, and the security of water resource was assessed, from which the results that the effects of unified management of water resources in the Heihe River basin between Gansu Province and Inner Mongolia on regional hydrology are significant with a decrease in water supply diverted from Heihe River and an increase in groundwater extracted. In addition, it was found that the groundwater level has been steadily decreasing due to over pumping and decrease in recharges. In present year （2003）, the volume of potential groundwater in the irrigation districts is far small because of the groundwater overdraft; even in the particular regions, there is no availability of groundwater resources for use. By 2003, water supply is not sufficient to meet the water demand in the different irrigation districts, the sustainable development and utilization of water resources are not secured, and the water supply crisis occurs in Pingchuan irrigation district. Achieving water security for the sustainable development of society, agriculture, economy, industry, and livelihoods while maintaining or improving the abilities of the management and planning of water resources, determining of the reasonable percentage between water supply and groundwater utilization and water saving in agricultural irrigation are taken into account. If this does not occur, it is feared that the present performance of water development and planning may further aggravate the problem of scarcities of water resources and further damage the fragile ecological system.

关键词： middle reaches of Heihe River irrigation region water resources supply and demand balance evaluation of the security of water resources

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Statistical Inference for the Parameter of Pareto Distribution Based on Progressively Type-I Interval Censored Sample

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Communications in Mathematical Research 2014年第4期30卷 345-357页

作者： Abdalroof M.S. zhao zhi-wen Wang De-hui College of Mathematics Jilin University College of Mathematics Jilin Normal University

In this paper, the estimation of parameters based on a progressively typeI interval censored sample from a Pareto distribution is studied. Different methods of estimation are discussed, which include mid-point approximation estimator, the maximum likelihood estimator and moment estimator. The estimation procedures are discussed in details and compared via Monte Carlo simulations in terms of their biases.

关键词： EM-algorithm maximum likelihood estimation method of moment Bayes estimation

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Photosynthetic characteristics of intercropped winter wheat under limited supplemental irrigation in the semiarid northwestern China

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Journal of Agricultural Science and Technology 2009年第4期3卷 51-57页

作者： ZHANG Heng-jia zhao wen-zhi Linze National Field Station for Farmland Ecosystem Hydrology and Ecology Laboratory of Watershed CAREERI CAS Lanzhou 730000 Water Resources Engineering Department School of Engineering Gansu Agricultural University Lanzhou 730070 China

A field experiment was conducted for intercropped winter wheat （Triticum aestivum） in 2002/2003 to evaluate the effects of limited supplemental irrigation on photosynthetic characteristics of intercropped winter wheat in semiarid environment. The result indicated that significances occurred in grain yield between the intercropped wheat treatments and sole wheat control （CKW）, and in yield between the irrigated intercropped wheat plots （WC2W, WC3W, WC5W） and not irrigated （WC1W） except for WC4W plots with nearly the same yield as WC1W. In comparison with CKW, 11.8%, 18.5%, 23.6%, 11.5%, and 30.7% of yield increase in the intercropped wheat plots were obtained in WCIW, WC2W, WC3W, WC4W, and WC5W respectively. Compared to the intercropped wheat plots without irrigation, yields in WC2W, WC3W, and WC5W were improved by 5.9%, 10.5%, and 16.9%, respectively. The dynamics of CGR and NAR in both intercropped （WC1W-WC5W） and solely cropped wheat （CKW） showed a type of ＂single peak＂ curves, with both the maximum CGR and NAR occurred during jointing to heading （14/4-6/5） of wheat. In addition, soil water potential （SWP） fluctuated as a function of the precipitation and limited supplemental irrigation.

关键词： limited supplemental irrigation grain yield cropgrowth rate net assimilation rate soil water potential intercropped winter wheat

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The SCUSUM Estimation of Variance Change Point in Linear Process

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Chinese Quarterly Journal of Mathematics 2011年第2期26卷 170-173页

作者： zhao wen-zhi XIA zhi-ming School of Science Xi＇an Polytechnic University Xi＇an 710048 China Department of Mathematics Northwest University Xi＇an 710069 China

This paper considers the estimation problem of a variance change-point in linear *** of a SCUSUM type change-point estimator is proved and its rate of convergence is *** mean-unknown case is also considered.

关键词： variance change point linear process rate of convergence

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