近百年北半球冬季大气活动中心的长期变化及其与中国气候变化的关系

研究了近１１０ａ北半球冬季６个主要大气活动中心的长期变化，检测其突变年份，划分了各自的阶段性。同时分析了大气活动中心与中国气候的关系，发现西伯利亚高压强度与中国冬季气温存在明显的负相关，北太平洋高压强度与中国冬季降水有较好的正相关。     

我国城市经济影响区域系统的初步分析

城市经济影响能力取决于城市投资集聚能力、市场集聚规模和技术、经济的水平状况。对15个经济变量所作的主因子分析表明:我国城市经济活动的差异主要受城市经济活动规模的制约。技术、经济水平差异有一定的影响,但影响不大。目前我国已形成5级区域经济影响中心,七个一级城市经济影响区域。     

Color centers in topaz: comparison between neutron and gamma irradiation

Neutron- and gamma irradiation-induced paramagnetic centers in natural colorless topaz from four different Brazilian localities were studied by electron paramagnetic resonance (EPR) and optical absorption as a function of irradiation dose and thermal treatment. Gamma irradiation doses were applied up to 1,000 kGy with a dose rate of 15 kGy h⁻¹. For the neutron irradiation experiments, a neutron flux of 4 × 10¹² cm⁻² s⁻¹ was used with an integrated flux of up to 1 × 10¹⁸ cm⁻². From the experiments, it is concluded that brownish colors are induced by gamma-rays and may be associated with a single broad isotropic EPR line with g = 2.015(2). Both the EPR line and the related optical absorption band at 460 nm (2.7 eV) are lost during thermal treatments between 150 and 200°C. Fast neutrons create the paramagnetic peroxyl radicals O₂ ⁻ and the paramagnetic O⁻ hole centers. The O⁻ centers have the same thermal stability as the optical absorption band at 620 nm (2.0 eV). It is confirmed that the absorption due to the O⁻ center is responsible for the blue color in topaz. Both color centers and their absorption bands are discussed in the context of O⁻ bound small polarons.     

北京市公共服务设施集聚中心识别分析

公共服务设施集聚中心不仅是多样化公共服务设施分布的集中区,也是公共服务设施消费的热点区和城市活力的窗口区。已有城市多中心研究主要关注就业和人口多中心,却较少关注公共服务设施多中心特征。基于北京市公共服务设施空间点要素数据,结合不同类型和等级公共服务设施的服务半径与质量特征,采用加权核密度与等值线分析等方法对北京市公共服务设施集聚中心进行了识别。研究发现：不同类型公共服务设施热点区分布的空间模式有所差异,但均存在一定程度的中心边缘结构;公共服务设施集聚强度和混合度分别呈现出“一心五片”与“一核多点”的空间特征;根据公共服务设施集聚强度和混合度的等值线分布综合判定,研究区范围共识别出136个公共服务设施集聚中心,其集聚强度与距市中心距离呈现出U型变化规律,与所在街道的人口密度存在指数分布规律;多元回归模型验证,最近公共服务设施集聚中心距离对北京城市居民公共服务设施满意度具有显著的负向影响,且其相对影响强度超过“市中心距离”区位变量;北京市公共服务设施集聚中心的形成机制包括自然历史因素的基础作用、经济发展因素的主导作用、社会需求因素的调节作用和规划政策因素的引导作用。研究认为应加强北京城市公共服务设施集聚中心的空间均衡化建设,适度增加城市边缘郊区公共服务设施集聚中心的数量和服务能级,有助于引导和疏解非首都功能产业和人口向城市郊区转移。     

STUDY OF NORTHERN WINTER ATMOSPHERIC ACTIVE CENTERS (AAC) CLIMATE BASE-STATE WITH ITS CLIMATE VARIABILITY AND EFFECTS

The study of low-frequency oscillations is an important part of climate variability research. In view of insufficient efforts spent on multidecadal and ENSO-scale changes of the climate, the present paper undertakes study of > 30 year slowly-varying means, called climate base state (CBS), of northern winter AAC's in the past 100 years and more, with the CBS variability and its temporal evolution investigated, indicating that Aleutian low and Icelandic low (North Pacific high and North American high) experience maximum (minimum) variation in the CBS. The CBS exhibits two modes for its variation. The positive (negative) phase of mode Ⅰ presents a weak (strong) NAO (North Atlantic Oscillation), a weaker (stronger) NPO (North Pacific Oscillation), a robust (feeble) Siberian high and a quite weak (vigorous) Aleutian low whilst the positive (negative) phase of mode Ⅱ reveals a feeble (strong) Aleutian low and a weak (robust) Siberian high. Also, the research shows that the recent CBS of northern circulations is in a remarkably negative phase of mode Ⅰ and a noticeably positive phase of mode Ⅱ, viz., in the background of slowly-varying circulations of an exceptionally weak Siberian high, an extremely vigorous Aleutian low and an intense NAO. The background field is likely to persist for a matter of 30 years such that northern winter temperature is expected to be in such a warm situation for a long period to follow.     

1985-2010年福建省耕地重心时空变化研究

本研究运用重心分析模型,从移动方向、移动距离、空间相关性等层面,阐述了福建省1985-2010年耕地重心的动态演变规律;通过与同期人口和经济重心移动轨迹的对比分析,探讨了耕地重心时空变化与经济发展、人口增长的空间关系。研究表明,福建省耕地、人口与经济重心均偏于几何中心东南,耕地重心更靠近几何中心,人口及经济重心则偏离显著;耕地重心呈东南-西北方向移动,并渐趋接近于几何中心,与人口、经济重心的空间演变轨迹完全相反。即改革开放以来,福建省人口增长、经济发展重心的南移、东移,是导致耕地重心呈现反向变化的主要推动力;耕地重心与人口重心的移动速度更为吻合,说明人口增长对耕地占用的影响更为直接,人口增长所带来的城镇化过程对耕地的占用,是当前耕地资源所面临的最大的威胁。     

云南地区稻作品种多样性的分布中心及其与生态、文化因素之间的联系

生态和文化因素对农作物品种的选育和分布起着十分重要的影响。本研究利用稻作品种的空间分布数据库,探讨了云南地区稻作品种多样性的分布中心及其与生态、文化因素之间的联系。研究结果表明,云南地区稻作品种多样性的分布中心主要集中在滇南、滇西南和滇东南地区。这可能与当地温暖、湿润的气候和特有的稻作文化有关。对滇南多样性分布中心而言,傣族和哈尼族的稻作文化起着重要影响;对滇西南多样性分布中心而言,起重要影响的稻作文化主要来自傣族,景颇族和拉祜族;而对滇东南分布中心而言,苗族、瑶族和壮族的稻作文化则起着相对更为重要的影响。传统文化不仅促进了稻作品种的选育,同时,丰富的稻作品种也有利于稻作文化的保存和延续。     

The Two Fixed Centers: An Exceptional Integrable System

It is usually believed that we know everything to be known for any separable Hamiltonian system, i.e. an integrable system in which we can separate the variables in some coordinate system (e.g. see Lichtenberg and Lieberman 1992, Regular and Chaotic Dynamics, Springer). However this is not always true, since through the separation the solutions may be found only up to quadratures, a form that might not be particularly useful. A good example is the two-fixed-centers problem. Although its integrability was discovered by Euler in the 18th century, the problem was far from being considered as completely understood. This apparent contradiction stems from the fact that the solutions of the equations of motion in the confocal ellipsoidal coordinates, in which the variables separate, are written in terms of elliptic integrals, so that their properties are not obvious at first sight. In this paper we classify the trajectories according to an exhaustive scheme, comprising both periodic and quasi-periodic ones. We identify the collision orbits (both direct and asymptotic) and find that collision orbits are of complete measure in a 3-D submanifold of the phase space while asymptotically collision orbits are of complete measure in the 4-D phase space. We use a transformation, which regularizes the close approaches and, therefore, enables the numerical integration of collision trajectories (both direct and asymptotic). Finally we give the ratio of oscillation period along the two axes (the ‘rotation number’) as a function of the two integrals of motion. This revised version was published online in July 2006 with corrections to the Cover Date.     

ATLANTA'S ROLE AS AN INFORMATION CENTER: INTERMETROPOLITAN SPATIAL LINKS

Atlanta has emerged in the 1980s as a major second-order command and control center within the US economy and demonstrates considerable dominance within the Southeast. Federal Express Corporation data permit examination of Atlanta's national and regional command and control functions. The concepts of information genesis, hierarchy of control, and spatial independence of information receipt clarify Atlanta's place within the specialized information network. Atlanta occupies an advantageous position within the intermetropolitan information network from which much of the Southeast's economic activity is organized.     

PETROCHEMICALS AND ECONOMIC DEVELOPMENT: THE IMPLICATIONS OF THE PUERTO RICAN EXPERIENCE*

The oil refining and petrochemical industries have occupied an important role in Puerto Rico's development strategy since the early 1960s. However, the hopes epitomized in various planning models of highly integrated and diversified oil-based industrial complexes have not been fulfilled. This paper attempts to account for the discrepancy between official expectations and subsequent events in Puerto Rico and indicates some of the lessons for other developing countries.