灰色马尔可夫理论在地震预测方面的研究

以陕南地区汶川地震余震资料数据为实例,提出灰色马尔可夫模型对地震进行预测.利用传统的GM(1,1)模型对数据进行拟合和初步预测,运用马尔可夫模型的状态区间和状态转移矩阵对初步预测值进行修正,并对下一组地震数据进行预测.结果表明,模型预测精度高,预测值与实际值接近,可以作为今后地震预报的辅助手段.     

“Forever Hmong”: Ethnic Minority Livelihoods and Agrarian Transition in Upland Northern Vietnam

This article examines how ethnic minority Hmong farmers have adapted to, circumnavigated, or resisted state-sponsored agrarian change and other interventions in the northern Vietnam uplands over the past twenty years. Based on longitudinal research with Hmong informants, I examine to what extent their livelihood strategies have led to wealth creation or differentiation. The article highlights the most important transformations, as farmers conceive and voice them, to Hmong agrarian livelihoods over this period, the importance of longitudinal fieldwork to help unravel endogenous wealth definitions, and the complex impacts of state interventions on ethnic minority ways of making a living.     

Spatiotemporal index for analyzing controls on snow climatology: application in the Colorado Front Range

Mountain snowpacks are important water supplies that are susceptible to climate change, yet snow measurements are sparse relative to snowpack heterogeneity. We used remote sensing to derive a spatiotemporal index of snow climatology that reveals patterns in snow accumulation, persistence, and ablation. Then we examined how this index relates to climate, terrain, and vegetation. Analyses were based on Moderate Resolution Imaging Spectroradiometer eight-day snow cover from 2000 to 2010 for a mountain watershed in the Colorado Front Range, USA. The Snow Cover Index (SCI) was calculated as the fraction of years that were snow covered for each pixel. The proportion of SCI variability explained by independent variables was evaluated using regression analysis. Independent variables included elevation, northing, easting, slope, aspect, northness, solar radiation, precipitation, temperature, and vegetation cover. Elevation was the dominant control on SCI patterns, due to its influence on both temperature and precipitation. Grouping SCI values by elevation, we identified three distinct snow zones in the basin: persistent, transitional, and intermittent. The transitional snow zone represents an area that is sensitive to losing winter snowpack. The SCI can be applied to other basins or regions to identify dominant controls on snow cover patterns and areas sensitive to snow loss.     

转型期社区医疗服务多元供给模式——以广州市天河区为例

以广州市统计局提供的第六次人口普查数据作为人口统计数据源,以天河区卫生局提供的社区医疗机构数据作为社区医疗服务研究数据源,以广州市天河区作为研究案例,总结出社区医疗服务存在政府供给、单位制供给、集体经济供给、社会力量供给4种模式。各供给模式均具有受卫生局领导、政府部门监管和作为城市医疗体系的基础等一系列共性,同时在供给主体、服务对象、筹资与财务管理和人事管理等方面存在差异性,形成相互补充的多元模式共存体系,社区医疗服务的准公共物品属性、社会经济体制转型与城乡二元体制、居民的多元化需求和不同供给主体的利益诉求综合作用是多元模式共存的机制。只有充分利用多元模式供给主体、全方位协调机制要素、进行合理的制度设计,才能更好地促进社区医疗服务均等化,同时为其他城市公共服务供给提供参考借鉴。     

泰安市设施农用地的时空格局演变与影响因素

设施农用地是农副产品重要的空间载体。在土地利用转型视角下,区域耕地、非农建设用地规模对设施农用地规模的作用机制及其空间效应尚不明确。论文基于第二、三次全国土地利用调查数据(简称为“二调”和“三调”),运用空间自相关分析、土地利用转移矩阵等方法,系统分析泰安市设施农用地的空间演变特征及其关键影响因素。研究发现：(1)二调至三调期间,泰安市设施农用地规模总量相对稳定,但净变化剧烈,耕地、非农建设用地分别是设施农用地主要的转入来源、退出去向;(2)泰安市设施农用地呈现出从县城中心向外围推移的规律性,远城区集聚趋势不断加强;(3)二调时期,耕地规模促进设施农用地扩张,而三调时期,耕地规模抑制设施农用地增长,并且在远离县城的乡镇表现更为显著;(4)二调、三调时期非农建设用地均稳定促进设施农用地扩张,这一作用在空间上普遍存在。研究结论可为耕地“非粮化”“非农化”治理以及设施农用地的空间布局调整提供理论支撑。     

Evolution of a Coronal Loop System

The temporal variation of a loop system that appears to be changing rapidly is examined. The analyzed data were obtained on 15 May 1999, with the Transition Region and Coronal Explorer (TRACE) during an observing campaign and consist of observations in the Fe ix/Fe x 171?Å and Fe xii 195?Å passbands taken at a cadence of ～10 min. The special interest in this loop system is that it looks like one expanding loop; however, careful examination reveals that the loop consists of several strands and that new loop strands become visible successively at higher altitudes and lower loop strands fade out during the one hour of our observations. These strands have different widths, densities, and temperatures and are most probably consisting of, at least, a few unresolved thinner threads. Several geometric and physical parameters are derived for two of the strands and an effort is made to determine their 3D structure based on the extrapolation of the magnetic field lines. Electron density estimates allow us to derive radiative and conductive cooling times and to conclude that these loop strands are cooling by radiation.     

International wood trade and forest change: A global analysis

Throughout history, humans have transformed natural forests into agricultural land, settlement areas and managed forests. Studies on the dynamics of forest change are one of the mainstays in land change science. The forest transition theory offers a powerful tool to analyze changes in human interference with forests. At the national level, a range of factors have been found to influence a country's forest change. The role of international wood product trade has, however, rarely been studied based on empirical data. We offer a global assessment of how this trade helps shape observed forest change, by relating forest stock change to net trade of wood products for the period 1997-2007 and by localizing the origin of wood consumed in a given nation. For many nations, traded wood products have a relevant impact on the course of ongoing forest transitions. We develop a general typology of how wood product trade can influence forest change and place various nations within this framework. We find that many wealthy nations with returning forests seem to accelerate this return by importing wood products. These imports appear to be provided by two main types of wood exporters: (a) by wealthy countries with low population densities and stable forests and (b) by relatively poor countries with declining forests, employing increasing population and welfare levels. We discuss these findings in the light of general theories on land use transitions and forest change and conclude by highlighting implications for national forest policies and global environmental governance, aiming at reducing negative impacts of wood products and enhancing the positive role they can play in replacing more fossil fuel intensive products.     

The Campanian Ignimbrite (Y5) tephra at Crvena Stijena Rockshelter, Montenegro

Clearly defined distal tephras are rare in rockshelter sediment records. Crvena Stijena, a Palaeolithic site in Montenegro, contains one of the longest (> 20 m) rockshelter sediment records in Europe with deposits ranging in age from Middle Pleistocene to mid-Holocene. A distinctive tephra is clearly exposed within the well stratified record approximately 6.5 m below the present land surface. We present geochemical data to confirm that this tephra is a distal equivalent of the Campanian Ignimbrite deposits and a product of the largest Late Pleistocene eruption in Europe. Originating in the Campanian volcanic province of southwest Italy, this tephra has been independently dated to 39.3 ka. It is a highly significant chronostratigraphic marker for southern Europe. Macrostratigraphic and microstratigraphic observations, allied with detailed particle size data, show that the tephra layer is in a primary depositional context and was transported into the rockshelter by aeolian processes. This site is unique because the tephra forms an abrupt boundary between the Middle and Upper Palaeolithic records. Before they can be used as chronostratigraphic markers in rockshelter and cave-mouth environments, it is essential to establish the stratigraphic integrity of distal tephras and the mechanisms and pathways involved in their transport and deposition.     

A new approach for phase transitions in miscible multi-phase flow in porous media

The tightly coupled, strongly nonlinear nature of non-isothermal multi-phase flow in porous media poses a tough challenge for numerical simulation. This trait is even more pronounced, if miscibility is also considered. A primary reason why inclusion of miscibility tends to be problematic are the difficulties stemming from phase transitions: on the one hand, phase transitions need to be included since the presence or absence of fluid phases has a major impact on the flow behavior; on the other hand, convergence of the nonlinear solver may be severely affected if they are not handled robustly.In this work, we present a mathematically sound approach to include phase transitions in the nonlinear system of equations: first, the transition conditions are formulated as a set of local inequality constraints, which are then directly integrated into the nonlinear solver using a nonlinear complementarity function. Under this scheme, Newton-Raphson solvers exhibit considerably more robust convergence behaviour compared to some previous approaches, which is then illustrated by several numerical examples.