世界政治新形势下的中国经济安全观

当前，世界政治形势处于动荡催生调整，调整蕴含机遇，在单极与多极矛盾的碰撞与互动中，正在形成某种更有效的机制，培育更为成熟、理性竞争的意识，促使各主要大国为世界的持久和平与繁荣共同担负起应有的责任。因此，国家经济安全是世界各国都普遍关注的战略问题。本文首先总结了就当今世界政治发展的四个特点，并在分析国际形势新变化对中国经济安全影响的基础上，提出了维护我国经济安全的六点思考。     

日本国内旅游业的发展及其地域特征

日本旅游业已成为国民经济的重要部门，据2002年日本交通省的统计表明，观光产业GDP已占国内生产总值的2．2％，这一数字与美国相近。但与西方国家显著不同的是，在美、英、法、意等旅游业发达国家中，国际旅游业占据举足轻重地位，而日本的旅游业却以国内旅游为主体。据日本最大旅行社JTB的统计，2002年日本旅游出行人数为34013万人次(其中出国旅游1664万人次)，而同年日本接待的外国入境游客刚刚超过500万人次。本文旨在介绍和分析日本国内旅游业的发生、发展的变化特征，以及国民不同的旅游方式和旅游地域差异。     

概率神经网络与BP网络模型在遥感图像分类中的对比研究

通过分析概率神经网络(以下称PNN)的基本结构及其训练算法,建立了卫星图像分类的概率神经网络模型,并通过实例对比分析了概率神经网络与BP网络分类模型的分类效果。实验表明,PNN图像分类方法在分类精度上优于误差反向传播神经网络模型,且分类时间相当,是一种有效的图像分类方法。     

一种组合优化的多边形化简方法

以多边形轮廓为目标 ,依据曲线特征点将其分解为一系列的弯曲特征 ,并对此弯曲特征集实施组合优化 ,将入围弯曲首尾相连 ,即可得到最终的化简结果     

民乐、山丹6.1级地震异常及台站实现短临预报的思考

在综合分析了民乐-山丹6.1级地震前张掖中心台范围内震兆异常特征的基础上,总结了本次地震前该台的短临预报过程及存在的问题,对今后台站如何搞好地震短临预报工作进行了探讨.     

Cause of winter gravity wave spectrum saturation

Gravity waves play a significant role in establishing the large-scale circulation and structure of the middle atmosphere. Through gravity wave saturation proc-esses, such motions are believed to cause turbulence, resulting in divergence of momentum flux and the diffusion of heat and constituents in the meso-sphere[1,2]. The mechanisms that contribute signifi-cantly to the gravity wave saturation are thought to be the dynamical and convective instabilities[3]. However, it is difficult to distin…     

Study on simulating strong ground motion by fractal stochastic method

The time history of strong ground motion can be synthesized by empirical Green's function (EGF) method.Firstly a large seismic event is discretized into a series of subevents; secondly recordings of earthquakes with proper size and spatial distribution are chosen as time history (EGF) of those subevents; finally the EGFs are summated to get the time history of ground motion caused by the large event.     

Experimental study on reduction of U (Ⅵ) by an anaerobic bacterium, Shewanella putrefaciens: Application to sandstone-hosted interlayer oxidation-zone type uranium deposits, China

An experimental study on reduction of U (Ⅵ) by anaerobic bacteria, Shewane//a putrefaciens, is first reported here in China. The experimental conditions were: 35℃ and pH =7.0-7.4, corresponding to a physicochemical environments in which the sandstone-hosted interlayer oxidation-zone type uranium deposit formed in Northwest China's Xinjiang. Bacteria adopted in the present experiment, Shewanella putrefaciens, occur extensively in natural environment. Our study shows that nano-crystal precipitates of uraninite quickly occurred on the surface of the cells within one week. It was found that the pitchblende was characterized by a random arrangement of uraninite nanocrystals (2-4 nm) in it, significantly different from natural pitchblende in which uraninite nanocrystals are arranged in order. Finally, a possible mechanism of uranium biomineralization by microorganisms in the deposits is discussed. Our investigation may supply a technical train of thoughts for bioremediation of nuclear-contaminated water environments and for underground dissolving extraction of the sandstone-hosted uranium ores.     

Establishment of apparent quantum yield and maximum ecosystem assimilation on Tibetan Plateau alpine meadow ecosystem

The alpine meadow is widely distributed on the Tibetan Plateau with an area of about 1.2×106kn2. Damxung County, located in the hinterland of the Tibetan Plateau, is the place covered with this typical vegetation. An open-path eddy covariance system was set up in Damxung rangeland station to measure the carbon flux of alpine meadow from July to October,2003. The continuous carbon flux data were used to analyze the relationship between net ecosystem carbon dioxide exchange (NEE) and photosynthetically active radiation (PAR), as well as the seasonal patterns of apparent quantum yield (α) and maximum ecosystem assimilation (Pmax).Results showed that the daytime NEE fitted fairly well with the PAR in a rectangular hyperbola function, with α declining in the order of peak growth period (0.0244 μmolCO2 · μmol-1pAR) ＞early growth period ＞ seed maturing period ＞ withering period (0.0098 μmolCO2 · μmol-1pAR).The Pmax did not change greatly during the first three periods, with an average of 0.433mgCO2· m-2· s-1, i.e. 9.829 μmolCO2· m-2· s-1. However, during the withering period, Pmax was only 0.35 mgCO2 · m-2 · s-1, i.e. 7.945 μmolCO2 · m-2 · s-1. Compared with other grassland ecosystems, the α of the Tibetan Plateau alpine meadow ecosystem was much lower.