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991.
本研究采用了主成分分析法对31个旅游网站的综合竞争力进行定量评价,计算出旅游网站的标准化综合竞争力得分,结合扩散断裂点理论对其信息辐射范围进行界定,应用ArcGIS软件生成辐射范围图,并对旅游网站的辐射范围进行分析。研究表明:①旅游网站信息的辐射范围大小不仅取决于该网站的标准化综合竞争力,还取决于与相邻竞争网站的欧氏距离。②全国旅游网站信息辐射范围分布不均匀,体现了旅游网站布设的不均衡性。我国的中部及东部沿海地区,旅游网站密集,竞争比较激烈,信息辐射范围较小。而西部、东北等其他地区网站之间距离较远,竞争环境比较宽松,信息辐射范围较广。③每个旅游网站的辐射范围的边界可以确定为唯一。从而为旅游网站企业制定新的旅游产品、营销策划、目标市场等提供依据。
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992.
为了了解科学教育专业本科生的专业满意程度,以便有针对性地改进人才培养模式,笔者通过自编问卷和访谈方法调查了4所师范院校大一至大四科学教育专业589名本科生。结果发现:大多数学生是被动选择本专业,对专业平均了解度不高;学生专业满意度低,但多数学生对专业发展前景有信心;择业意向选择小学科学教师的学生比例低。本文认为,当前科学教育专业严峻的就业形势、培养模式存在的缺陷、学生自身的因素等影响了学生的专业满意度。为此,建议教育行政部门采取相应的政策,学校采用3+2或3+3的科学教师教育模式等措施。
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993.
蕴含幂零性与谱任意符号模式矩阵是近几年组合数学中比较热门的一个研究方向。本文主要运用幂零-中心化子方法来证明谱任意。首先揭示了蕴含幂零及幂零指数与谱任意之间的关系,即:蕴含幂零的符号模式矩阵是谱任意的必要非充分条件且幂零指数为n的符号模式矩阵既非谱任意的必要条件也非充分条件。然后通过几类低阶的幂零矩阵构造了几类高阶的蕴含幂零符号模式矩阵和谱任意符号模式矩阵。最后给出了谱任意符号模式矩阵的直和仍为谱任意符号模式矩阵的一个新的条件。本文对构造幂零矩阵与谱任意符号模式矩阵有一定的应用价值。
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994.
在三维空间的有界区域上考虑不可压缩MHD方程弱解的正则性准则。利用能量估计的方法证明了一些新的涉及压力项商的正则性准则。具体地,证明了若MHD方程的弱解 u,( b) 满足 * 上唯一的强解,其中w+=u+b;w-=u-b。(注:*表示公式,见正文 )
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995.
对一类边界条件是非线性的Laplace方程的Signorini问题,提出了基于投影不动点方程的边界元迭代算法。由于Signorini边界条件 * 等价于的不动点问题 *,因此可以通过投影迭代格式 * 来满足Signorini边界条件,从而每一次迭代只需要求解一个标准的椭圆型混合边值问题。由于该算法是在Signorini边界上进行迭代,因此边界元方法很适合用于数值求解。然后利用投影性质和Green公式证明了算法的收敛性。最后,算例的数值结果表明了该算法的可行性和有效性。(注:*表示公式,见正文) )
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996.
FY-3 satellite Ultraviolet Total Ozone Unit 总被引:4,自引:0,他引:4
WANG YongMei WANG YingJian WANG WeiHe ZHANG ZhongMou Lü JianGong FU LiPing JIANG Fang CHEN Ji WANG JiHong GUAN FengJun HUANG FuXiang & ZHANG XingYingCenter for Space Science Applied Research Chinese Academy of Sciences Beijing China National Satellite Meteorological Center Beijing 《科学通报(英文版)》2010,55(1):84-89
FY-3 satellites are Chinese second-generation polar orbit meteorological satellite series. Ultraviolet Total Ozone Unit (TOU) is one of the main payloads on FY-3 satellite and the first instrument for daily global coverage of total ozone monitoring in China. The main purpose of TOU is to measure the Earth backscatter ultraviolet radiation for retrieving daily global map of atmospheric ozone. TOU will provide the important parameters for environmental monitoring, climate forecasting and global climate changi... 相似文献
997.
YU Huan WANG PuCai ZONG XueMei LI Xin & Lü DaRen LAGEO Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China Graduate University of Chinese Academy of Sciences Beijing Beijing Municipal Environmental Protection Bureau Beijing 《科学通报(英文版)》2010,55(3):308-313
The effect of the air quality ensuring measures for the Beijing 2008 Olympic Games in reducing air pollution during the game period is assessed using the tropospheric NO2 column density retrieved from Ozone Monitoring Instrument onboard AURA satellite. The basic method of the assessment is the comparison of the NO2 column densities during the game period with that during the corresponding period of 2005−2007 for the Beijing area, and the comparison among Beijing and neighbouring cities Tianjin and Tangshan, which are of similar situation in air pollution of NO2 in recent years. The images of tropospheric NO2 column densities over Northern China during the Beijing 2008 Olympic Games show the remarkable effect of the air quality ensuring measures in reducing NO2 pollution: the tropospheric NO2 column density in Beijing is much lower than that in Tianjin and Tangshan, while there were very similar values in the three large cities during the same period of the last three years. About 40% reduction in tropospheric NO2 column density over the Beijing area is obtained from the assessment during July to August, 2008, a key period of air quality ensuring measures for the Beijing 2008 Olympic Games. 相似文献
998.
WANG ShanShan LI Qin Lü XueFei LIU Tong ZHANG WeiBo GENG LiNa & DENG YuLin School of Life Science Technology Beijing Institute of Technology Beijing China Analysis Test Center Sh ong Academy of Sciences Jinan 《科学通报(英文版)》2010,55(10):910-914
In the present study,a new enzymatic microreactor is developed by immobilizing trypsin on the matrix-HILIC (hydrophilic interaction chromatography).The influences of different types of buffer solutions (borate,Tris·HCl,and phosphate),their concentrations and pH values on the immobilizing rate and the activity of immobilized trypsin were investigated.The optimal condition for off-line immobilization of trypsin on matix-HILIC was Tris·HCl buffer (20 mmol/L,pH 8.0),and then,under the optimal condition,an enzym... 相似文献
999.
YAO ZhengQuan XIAO GuoQiao & LIANG MeiYan State Key Laboratory of Loess Quaternary Geology Institute of Earth Environment Chinese Academy of Sciences Xi’an China Graduate University of the Chinese Academy of Sciences Beijing Institute of Geology Geophysics Beijing 《科学通报(英文版)》2010,55(9):787-790
Major element concentrations were analyzed on the sediments of a 203.6-m core from the North China Plain near Tianjin. The chemical index of alteration (CIA), Al2O3-(CaO+Na2O)-K2O diagram and elemental ratios, such as Al/K and Ti/Na, were used to reveal information of chemical weathering in the source regions since the late Pliocene. Results show that the fluvial materials in the North China Plain were derived from vast regions, which were in the early Na and Ca removal stage and underwent numerous upper-crustal recycling processes. Proxies of chemical weathering show a decreasing trend, in parallel with the global cooling since the late Pliocene, suggesting a strong role of the global cooing in controlling the continental chemical weathering intensity. 相似文献
1000.
ZHENG JianJun ZHANG ZhiYuan HUANG ZuoHua HU ErJiang TANG ChengLong & WANG JinHua State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an China 《科学通报(英文版)》2010,55(9):882-889
The effect of nitrogen dilution on the premixed combustion characteristics and flame structure of laminar premixed methanol-air-nitrogen mixtures are analyzed numerically based on an extended methanol oxidation mechanism. The laminar burning velocities, the mass burning fluxes, the adiabatic flame temperature, the global activation temperature, the Zeldovich number, the effective Lewis number and the laminar flame structure of the methanol-air-nitrogen mixtures are obtained under different nitrogen dilution ratios. Comparison between experiments and numerical simulations show that the extended methanol oxidation mechanism can well reproduce the laminar burning velocities for lean and near stoichiometric methanol-air-nitrogen mixtures. The laminar burning velocities and the mass burning fluxes decrease with the increase of nitrogen dilution ratio and the effect is more obvious for the lean mixture. The effective Lewis number of the mixture increases with the increase of nitrogen dilution ratio, and the diffusive-thermal instability of the flame front is decreased by the nitrogen addition. Nitrogen addition can suppress the hydrodynamic instability of methanol-air-nitrogen flames. The decrease of the mole fraction of OH and H is mainly responsible for the suppressed effect of nitrogen diluent on the chemical reaction in the methanol-air-nitrogen laminar premixed flames, and the NOx and formaldehyde emissions are decreased by the nitrogen addition. 相似文献