OALib Journal期刊

ISSN: 2333-9721




2018 ( 240 )

2017 ( 228 )

2016 ( 294 )

2015 ( 3581 )


匹配条件: “XU Guo-yu” ,找到相关结果约118774条。
Menthyl 2-oxo-2H-chromene-3-carboxylate
Cui-Lian Xu,Shan-Yu Liu,Gang Chen,Guo-Yu Yang
Acta Crystallographica Section E , 2009, DOI: 10.1107/s1600536809035995
Abstract: The title compound, C20H24O4, was synthesized from the reaction of 2-oxo-2H-chromene-3-acyl chloride and menthol. The mean plane of the ester group and that of the four essentially planar (maximum deviation 0.0112 ) C atoms of the chair-form cyclohexyl ring form dihedral angles of 43.8 (3) ° and 81.8 (1)°, respectively, with the mean plane of the coumarin ring system. In the crystal structure, weak intermolecular C—H...O hydrogen bonds connect the molecules into a two-dimensional network.
Cinnamyl 2-oxo-2H-chromene-3-carboxylate
Cui-Lian Xu,Nan Yang,Guo-Yu Yang,Su-Fang Fan
Acta Crystallographica Section E , 2009, DOI: 10.1107/s1600536809045644
Abstract: The title compound, C19H14O4, was prepared by the reaction of 2-oxo-2H-chromene-3-acyl chloride with cinnamic alcohol. The whole molecule is not planar, the dihedral angle between the planes of coumarin and benzene rings being 13.94 (4)°, but the plane of the coumarin ring and that of the ester group are almost coplanar, making a dihedral angle of 2.9 (1)°. In the crystal structure, weak intermolecular C—H...O hydrogen bonds link two molecules into dimers, and π–π stacking interactions between inversion-related rings of the coumarin groups [centroid–centroid distance 3.8380 (15) with a slippage of 1.535 ], which connect the dimers into columns extending along [010].
High precision measurement method of parameters of plane circle based on stereo vision

LIN Guo-yu,CHEN Xu,ZHANG Wei-gong,

计算机应用研究 , 2010,
Abstract: This paper proposed a high precision measurement method of plane circle parameters based on stereo vision to solve the certain deficiency which existed in current method of measuring the center and radius parameter of plane circle.Firstly,using the edge grouped algorithm and ellipse fitting algorithm,extracted the ellipse shape in stereo image.Secondly,acquired the 3D coordinate of points in the circle shape by the grouping stereo matching algorithm. Lastly through the three-dimension plane fitting algorithm, transformation of coordinates algorithm, circle fitting algorithm and transformation of coordinates inversely,calculated the plane circle parameters.The experiment shows that the method can decrease the distortion caused by perspective projection and can improve the measurement accuracy.
Strong Neutral Spatial Effects Shape Tree Species Distributions across Life Stages at Multiple Scales
Yue-Hua Hu, Guo-Yu Lan, Li-Qing Sha, Min Cao, Yong Tang, Yi-De Li, Da-Ping Xu
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0038247
Abstract: Traditionally, ecologists use lattice (regional summary) count data to simulate tree species distributions to explore species coexistence. However, no previous study has explicitly compared the difference between using lattice count and basal area data and analyzed species distributions at both individual species and community levels while simultaneously considering the combined scenarios of life stage and scale. In this study, we hypothesized that basal area data are more closely related to environmental variables than are count data because of strong environmental filtering effects. We also address the contribution of niche and the neutral (i.e., solely dependent on distance) factors to species distributions. Specifically, we separately modeled count data and basal area data while considering life stage and scale effects at the two levels with simultaneous autoregressive models and variation partitioning. A principal coordinates of neighbor matrix (PCNM) was used to model neutral spatial effects at the community level. The explained variations of species distribution data did not differ significantly between the two types of data at either the individual species level or the community level, indicating that the two types of data can be used nearly identically to model species distributions. Neutral spatial effects represented by spatial autoregressive parameters and the PCNM eigenfunctions drove species distributions on multiple scales, different life stages and individual species and community levels in this plot. We concluded that strong neutral spatial effects are the principal mechanisms underlying the species distributions and thus shape biodiversity spatial patterns.
Genetic Projection Pursuit Evaluation Method of Network Attack Resistance Ability

WANG Hui-mei,LI Xu,XIAN Ming,WANG Guo-yu,

计算机科学 , 2010,
Abstract: Attack Resistance best (ART) is an important security evaluation method and evaluating the system's attack resistance ability becomes a new domain of ART. Based on the security properties of the network, the network's attack resistance evaluation indexes were established from views of the goal system' s attack effect and the hacker' s cost. A projection pursuit evaluation model based on real coding based accelerating genetic algorithm was presented, and it was used in attack resistance ability evaluation for the first time. A simulation example was given,which showed that the approach was brief and effective. The approach can be used to evaluate the attack resistance ability, as well as to compare like kind attack's effect.
New Near Space Security Handoff Scheme Based on Context Transfer

XU Guo-yu,CHEN Xing-yuan,DU Xue-hui,

计算机科学 , 2013,
Abstract: 针对临近空间中安全切换问题,提出一种新的基于上下文传递的安全切换机制。首先,设计了一种面向临近空间浮空器的切换基站预测算法,以基于多普勒频移技术计算飞行器发生切换的时间与位置,确定切换基站;其次,利用上下文传递机制预先将认证信息发送给切换基站,保证切换过程中通信的可靠性。性能分析与仿真实验表明,该机制通信与计算开销小,强制中断概率低,能够满足临近空间的应用需求。
Evaluation of a Filter-Based Model for Computations of Cavitating Flows


中国物理快报 , 2011,
Optical and Magnetic Properties of Fe-Doped GaN Diluted Magnetic Semiconductors Prepared by MOCVD Method

TAO Zhi-Kuo,ZHANG Rong,CUI Xu-Gao,XIU Xiang-Qian,ZHANG Guo-Yu,XIE Zi-Li,GU Shu-Lin,SHI Yi,ZHENG You-Dou,

中国物理快报 , 2008,
Abstract: Fe-doped GaN thin films are grown on c-sapphires by metal organic chemical vapour deposition method (MOCVD). Crystalline quality and phase purity are characterized by x-ray diffraction and Raman scattering measurements. There are no detectable second phases formed during growth and no significantdegradation in crystalline quality as Fe ions are doped. Fe-related optical transitions are observed in photoluminescence spectra. Magnetic measurements reveal that the films show room-temperature ferromagnetic behaviour. The ferromagnetism may originate from carrier-mediated Fe-doped GaN diluted magnetic semiconductors or nanoscale iron clusters and Fe--N compounds which we have not detected.
Attribution of the 20th Century Climate Warming in China

ZHAO Zong-Ci,WANG Shao-Wu,XU Ying,REN Guo-Yu,LUO Yong,GAO Xue-Jie,

气候与环境研究 , 2005,
Abstract: 多套观测资料检测表明,近百年来中国气候明显变暖,变暖趋势达到0.2~0.8℃/100a,近50年变暖趋势更达到0.6~1.1℃/50 a.气候代用资料研究表明,中国20世纪的变暖在近千年中属于明显的,但对于20世纪是否为近千年中最暖的百年,还有待更多的观测研究验证.气候模式归因分析表明,20世纪中国的变暖与太阳活动、火山活动和人类活动有关,近50年的明显变暖可能与人类排放引起的大气中温室气体浓度增加有一定联系.但是,目前这一结论仍然存在着不确定性,尚需更多的研究工作.由于中国区域辽阔,不同区域气候差异较大,而且20世纪前50年观测资料匮乏,近千年的代用资料分布不广,因此,应该进一步考证中国20世纪的气温变化和在近千年中的地位.
章伊华,林丹益,YANG Guo-yu
兵工学报 , 2015, DOI: 10.3969/j.issn.1000-1093.2015.05.027
Abstract: ?运用多微凸体粗糙接触表面由弹性、弹塑性至塑性变形转化过程的连续光滑可导原理,论证了载荷作用下接触面接触强度及实际接触面之间的连续性和区域性。用混合单元法创建实际螺栓结构接触压力模型,求解出螺栓结构的实际接触面积与接触压应力分布。对比超声波实验数据,有限元分析(FEA)结果与超声波实验结果相吻合,验证了模型的正确性和有效性。通过系列模型,分析压应力沿螺栓方向的传递作用,证明螺栓联接结构接触应力在环形区域内分布的连续性,并探讨了改变预紧力和结构几何参数对螺栓联接接触强度、接触应力范围的影响规律。

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