基于LinuxPPS的高精度校时系统实现

为了实现南极天文观测设备的精确校时,采用搭建高精度网络时间协议NTP（Network Time Protoc01）服务器的方法实现。基本思路是从NMEA0183数据中提取时间信息,通过PPS信号保证高精度。具体实现方法：主要采用GPS接收芯片G591构造硬件电路,软件部分需要LinuxPPS（Linux Pulse Per Second）和NTP服务器软件的正确安装和配置。对照实验表明基于LinuxPPS的NTP服务器是精确、稳定而可靠的。     

Comparative analysis of land use/cover change trajectories and their driving forces in two small watersheds in the western Loess Plateau of China

To prevent soil loss and achieve better ecological environments, soil conservation measures have been taken during the past decades in the western Loess Plateau of China. In this paper, a case study was taken in Luoyu valley and Lver valley, two sub-watersheds of Xihe watershed and comparison was carried out between them. The main object of this study is to monitor land use/cover changes in the two similar small watersheds utilizing SPOT5 imageries by object-oriented human–computer interactive classification method, further develop the method of spatio-temporal analysis of land use/cover change by using pattern metrics of change trajectories and relative land use suitability index (R) in smaller watersheds, and make comparisons between the two similar small watersheds, taking water and soil conservation measures into consideration. Results show that combining GIS and RS, this method can be perfectly applied to make comparisons between different small watersheds with similar geographical backgrounds. And land use/cover spatiotemporal dynamic change characteristics can be preferably expressed by pattern metrics of change trajectories and R values based on topographical data. Different emphases have been laid according to their own geological backgrounds in the two watersheds and human activities have different effects on the landscapes of the two watersheds. The main change pattern is from slope farmland to terrace (322, the largest in Luoyu valley) or to economic fruit forest (344, the largest in Lver valley). R value of every slope grade in both of the two watersheds drops with the rising of slope degree on the whole and it shows that there is still much to do for people in the two watersheds in consideration that all the R values are still lower than 0.7.     

高分辨率遥感影像在核电站厂址普选中的应用初探

国家核电正处于新的发展时期,核电站厂址普选正在全国范围内展开。本文针对目前核电站厂址普选过程中所采用方式方法,探讨了一种利用高分辨率遥感影像进行核电站厂址普选的方法,并简要分析了这种方法的可行性及优点。     

全球地震柱的地震层析成像证据

依据地震地热说原理,搜集国内外地震层析成像研究的成果．揭示了地震柱的物理属性。得出全球24个地震柱中已有资料的20个地震柱的深部地幔圆锥体均具有P波高速异常体特征,相反,只有火山和浅源地震活动而无中、深源地震活动的地区,比如冰岛和夏威夷,其地幔深部则为P波低速异常体。为解释这个重要的物理现象和构造现象,引入空化理论解释并提出了3个假设。地震柱概念是地震地热说赖以生存的物质基础和构造基础,是与当今流行的地质学派板块构造、地质力学和地幔柱理论的最大区别。深入解读地震柱的物理属性及其构造学意义．或许能为构造地质学和地球动力学带来革命性的大讨论。     

The importance of being reliable – Local ecological knowledge and management of forage plants in a dryland pastoral system (Morocco)

In dryland rangelands with their high environmental variability, local ecological knowledge of forage plants is essential for management decisions. Ecological apparency hypothesis (EAH) predicts plants' availability and visibility to be important criteria for local valuation. However, EAH has mainly been tested in low-variability systems. We ask whether EAH is valid for forage plants in drylands; which other local criteria exist; and how criteria are connected to management decisions.In a Moroccan pastoral system, we applied a novel ethnobotanical method by calculating the Cognitive Salience Index (CSI) for plants' valuation (CSI_antro) and availability (CSI_eco). To evaluate explicit criteria, we correlated palatability and nutritive value to CSI_anthro. ANCOVAs related CSI_anthro to EAH criteria (CSI_eco and lifetime) and to plant occurrence on pasture types. We found EAH criteria to better predict CSI_antro than explicit criteria. Apparent plants from semi-arid pastures were more valued than those from arid pastures (HSD; p < 0.05). We introduce the criterion of reliability into EAH to explain this, and demonstrate how pastoralists adjust management decisions to resource reliability. Linking resource valuation to management decisions can thus improve our understanding of resilience mechanisms. Our study also confirms the validity of EAH for forage species and dryland environments.     

INFLUENCE OF SUBARCTIC VEGETATION COVER ON SNOWMELT

An examination of the three major components of the energy balance has shown that subarctic vegetation cover markedly alters the relative importance of these components for the snowmelt. It has been found that the contribution of net radiation decreases as forest cover decreases while sensible and latent heat contributions to the snowmelt increase with decreasing forest cover. The decrease in the importance of net radiation with decreasing forest cover is due to the effect of the forest cover on albedo and the effects of the forest cover on the long-wave radiation component of the radiation balance. This situation seems to be typical for open canopy forests. The increase in importance of sensible and latent heat in the open is due to the increase in wind speed from the forest to open sites.     

高纯碳酸锶清洁生产国内外研究进展

高纯碳酸锶是一种高附加价值的重要锶化合物,由于它具有独特的物理化学性能,因而被广泛应用于电子、化工、材料等领域。但高纯碳酸锶的生产仍存在环境污染严重、产品质量难以稳定控制、生产成本高等问题。综述了国内外高纯碳酸锶清洁生产工艺研究与应用进展,详细介绍了天青石碳还原法、天青石复分解法、粗碳酸锶酸溶碱析法、粗碳酸锶焙烧分解法、硝酸锶法、氯化锶法等高纯碳酸锶主要生产工艺的研究与应用进展,评述了各生产工艺产生的污染物的净化处理方法与技术改进,剖析了各工艺的优点和存在的问题。结合我国目前高纯碳酸锶的生产现状及与国外生产技术存在的差距,并对我国高纯碳酸锶生产技术的发展方向进行了展望。     

The Growth and Location of High Order Services in the Canadian Urban System, 1971–1991

In spite of the considerable economic importance of high order (intermediate demand) services, research on the growth and location of these activities has remained at a fairly aggregate level. The behavior of the individual elements of this group has rarely been documented in detail. In this paper, we seek to determine if individual high order service activities are becoming spatially more concentrated or dispersed across the Canadian urban system, and to determine if differential rates of growth may be observed by region and by urban size category. These issues are of considerable importance in the ongoing debate concerning the impact of the tertiarization of the economy on uneven spatial development. We examine the performance and location of 17 individual high order service activities over a set of 152 Canadian urban areas with populations greater than 10,000 inhabitants. Most of these activities are highly concentrated in a small number of very large urban areas, and their level of concentration declined only very slightly over the period 1971–1991. We conclude with an examination of the factors underlying the geographic concentration of high order services at the upper end of the urban hierarchy.     

基于ANSYS的黄土高边坡开挖卸荷稳定性分析

基于ANSYS软件的岩土分析模块,利用强度折减模拟边坡由稳定状态到不稳定,得到安全系数;利用网格划分后杀死单元模拟边坡开挖卸荷状态,分析其稳定性的变化,其边坡位移与监测结果基本一致。     

滇西云龙混合岩化高温热液锡矿床

矿床产于区域性主干断裂旁侧、向斜轴部发育的断裂带中,严格受构造控制。混合岩化花岗岩与锡的形成、富集关系密切,是成矿的母岩。