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Search Results: 1 - 10 of 4717 matches for " Guan Liangzhi "
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Simultaneous Determination of Alkali Metal ,Ammonium Ions and Amines by Single-Column Ion Chromatography
单柱离子色谱法同时测定碱金属、铵离子和胺类

Guan Liangzhi,Yu Hong,
关良智
,于泓

色谱 , 1995,
Abstract: imultaneous determination of alkali metal,ammonium ions and amines by single-column ion chromatogra-phy is described,A cation-exchange column was employed for separation with conductivity detection.Oxalicacid was used as eluent and the optimum eluent concentration was 4.0mmol/L. The detection limits,relativestandarddeviations and calibration curves for alkali metal.ammonium ions and amines were oblained. Themethod was applied for determining tap water.well water.soda water and snow with satisfactory results.
Determination of Fe, Mg and Ca in Superheater Tube Scale and Boiler Scale by Single Column Ion Chromatography
单柱离子色谱法测定过热器管垢和锅炉垢中铁、镁和钙的含量

Li Ping,Yu Hong,Cui Lingfei,Guan Liangzhi,Liu Shuangquan,
李萍
,于泓,崔凌飞,关良智,刘双全

色谱 , 1998,
Abstract: 首先用碱熔融法分解试样,然后加抗坏血酸将试液中的Fe3+还原为Fe2+,再用离子色谱法测定试液中的Fe2+,Mg2+和Ca2+。采用Shim-packIC-Cl阳离子交换柱分离样品离子,以0.25mmol/L乙二胺-0.50mmol/L柠檬酸(pH4.50)为流动相,以CDD-6A电导检测器检测,使被测组分得到满意的分离和检测。Fe,Mg和Ca的加标回收率均在90%以上。测定结果与原子吸收光谱法测定结果相近。
SPATIAL PATTERNS OF CROP YIELDS IN LATIN AMERICA AND THE CARIBBEAN
Wood,Stanley; You,Liangzhi; Zhang,Xiaobo;
Cuadernos de economía , 2004, DOI: 10.4067/S0717-68212004012400003
Abstract: because of the apparent slowdown in the growth of crop yield potential, the increasing share of farmers already using modern crop varieties, and the accelerating flow of knowledge on agricultural technology, one would expect to find gradual convergence in observed crop yields. instead, using a new, sub-national yield database, we find a divergence. we illustrate how technology generation has been biased towards more-favored production systems, leaving persistent pockets of low yields in more marginal lands. rainfall patterns appear to have changed in ways that exacerbate yield divergence. cross-border barriers to technology spillover appear larger among than within countries
SPATIAL PATTERNS OF CROP YIELDS IN LATIN AMERICA AND THE CARIBBEAN
Stanley Wood,Liangzhi You,Xiaobo Zhang
Cuadernos de Economía , 2004,
Abstract: Because of the apparent slowdown in the growth of crop yield potential, the increasing share of farmers already using modern crop varieties, and the accelerating flow of knowledge on agricultural technology, one would expect to find gradual convergence in observed crop yields. Instead, using a new, sub-national yield database, we find a divergence. We illustrate how technology generation has been biased towards more-favored production systems, leaving persistent pockets of low yields in more marginal lands. Rainfall patterns appear to have changed in ways that exacerbate yield divergence. Cross-border barriers to technology spillover appear larger among than within countries La aparente disminución del crecimiento en el potencial del rendimiento de los cultivos, la creciente proporción de agricultores que utilizan variedades de alto rendimiento (HYV), y el flujo de conocimiento sobre tecnología agropecuaria sugieren convergencia en los rendimientos de los cultivos. En cambio, utilizando una base de datos nueva sobre rendimiento de cultivos a nivel subnacional, vemos una divergencia. La generación de tecnología ha estado sesgada hacia sistemas de producción más favorecida, dejando atrás nichos de baja producción persistentes en las tierras marginales. Los patrones de pluviosidad cambiaron en formas que exacerban la divergencia de rendimiento. Los obstáculos al flujo de conocimiento y tecnología parecen mayores entre diferentes países que dentro de ellos mismos
Controllable magnetic correlation between two impurities by spin-orbit coupling in graphene
F. M. Hu,Liangzhi Kou,Thomas Frauenheim
Physics , 2015,
Abstract: Two magnetic impurities on the edge of a zigzag graphene nanoribbon strongly interact with each other via indirect coupling, which can be mediated by conducting carriers. By means of Quantum Monte Carlo (QMC) simulations, we find that the spin-orbit coupling $\lambda$ and the chemical potential $\mu$ in system can be used to drive the transition of local-spin exchange from ferromagnetism to anti-ferromagnetism. Since the tunable ranges for $\lambda$ and $\mu$ in graphene are experimentally reachable, we thus open the possibilities for its device application. The symmetry in spatial distribution is broken by the vertical and the transversal spin-spin correlations due to the effect of spin-orbit coupling, leading to the spatial anisotropy of spin exchange, which distinguish our findings from the case in normal Fermi liquid.
Phosphorene: Fabrication, Properties and Applications
Liangzhi Kou,Changfeng Chen,Sean C. Smith
Physics , 2015,
Abstract: Phosphorene, the single- or few-layer form of black phosphorus, was recently rediscovered as a twodimensional layered material holding great promise for applications in electronics and optoelectronics. Research into its fundamental properties and device applications has since seen exponential growth. In this Perspective, we review recent progress in phosphorene research, touching upon topics on fabrication, properties, and applications; we also discuss challenges and future research directions. We highlight the intrinsically anisotropic electronic, transport, optoelectronic, thermoelectric, and mechanical properties of phosphorene resulting from its puckered structure in contrast to those of graphene and transition-metal dichalcogenides. The facile fabrication and novel properties of phosphorene have inspired design and demonstration of new nanodevices; however, further progress hinges on resolutions to technical obstructions like surface degradation effects and non-scalable fabrication techniques. We also briefly describe the latest developments of more sophisticated design concepts and implementation schemes that address some of the challenges in phosphorene research. It is expected that this fascinating material will continue to offer tremendous opportunities for research and development for the foreseeable future.
Phosphorene as a superior gas sensor: Selective adsorption and distinct I-V response
Liangzhi Kou,Thomas Frauenheim,Changfeng Chen
Physics , 2014,
Abstract: Recent reports on the fabrication of phosphorene, i.e., mono- or few-layer black phosphorus, have raised exciting prospects of an outstanding two-dimensional (2D) material that exhibits excellent properties for nanodevice applications. Here we study by first-principles calculations the adsorption of CO, CO2, NH3, NO and NO2 gas molecules on a mono-layer phosphorene. Our results predict superior sensing performance of phosphorene that rivals or even surpasses other 2D materials such as graphene and MoS2. We determine the optimal adsorption positions of these molecules on the phosphorene and identify molecular doping, i.e., charge transfer between the molecules and phosphorene, as the driving mechanism for the high adsorption strength. We further calculated the current-voltage (I-V) relation using a non-equilibrium Greens function (NEGF) formalism. The transport features show large (one to two orders of magnitude) anisotropy along different (armchair or zigzag) directions, which is consistent with the anisotropic electronic band structure of phosphorene. Remarkably, the I-V relation exhibits distinct responses with a marked change of the I-V relation along either the armchair or the zigzag directions depending on the type of molecules. Such selectivity and sensitivity to adsorption makes phosphorene a superior gas sensor that promises wide-ranging applications.
Adaptive Motion Segmentation for Changing Background  [PDF]
Yepeng Guan
Journal of Software Engineering and Applications (JSEA) , 2009, DOI: 10.4236/jsea.2009.22014
Abstract: Segmentation of moving objects efficiently from video sequence is very important for many applications. Background subtraction is a common method typically used to segment moving objects in image sequences taken from a statistic camera. Some existing algorithms cannot adapt to changing circumstances and require manual calibration in terms of specification of parameters or some hypotheses for changing background. An adaptive motion segmentation method is developed according to motion variation and chromatic characteristics, which prevents undesired corruption of the background model and does not consider the adaptation coefficient. RGB color space is selected instead of introducing complex color models to segment moving objects and suppress shadows. A color ratio for 4-connected neighbors of a pixel and multi-scale wavelet transformation are combined to suppress shadows. The mentioned approach is scene-independent and high correct segmentation. It has been shown that the approach is robust and efficient to detect moving objects by experiments.
Moved Score Confidence Intervals for Means of Discrete Distributions  [PDF]
Yu Guan
Open Journal of Statistics (OJS) , 2011, DOI: 10.4236/ojs.2011.12009
Abstract: Let X denote a discrete distribution as Poisson, binomial or negative binomial variable. The score confidence interval for the mean of X is obtained based on inverting the hypothesis test and the central limit theorem is discussed and recommended widely. But it has sharp downward spikes for small means. This paper proposes to move the score interval left a little (about 0.04 unit), called by moved score confidence interval. Numerical computation and Edgeworth expansion show that the moved score interval is analogous to the score interval completely and behaves better for moderate means; for small means the moved interval raises the infimum of the coverage probability and improves the sharp spikes significantly. Especially, it has unified explicit formulations to compute easily.
Ethnic Difference of Disease Prevalence in Rural China: Examples and Explanations  [PDF]
Ming Guan
Health (Health) , 2015, DOI: 10.4236/health.2015.74052
Abstract: Ethnic difference of disease prevalence has attracted great attentions in recent years in China, but few researches have summarized analysis available on ethnic difference of disease prevalence in rural China. The PubMed Central, Wiley Inter science, Science direct, Biomed central, CNKI and Springer-link were searched to identify studies published between January 1984 and October 2014 on ethnic inequality of health status in rural China. Distinct ethnic differences of disease prevalence exist in rural China. Results across disciplines put different explanations on the ethnic differences from ethnicity, infant feeding, and inequality in maternal health services utilization angles. The ethnic inequality of health status in rural China can be reduced by policy makers to allocate more resources towards health service in ethnic rural China.
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