Low-temperature thermodynamic properties of disordered zeolites of the natrolite group     

I. E. Paukov  N. K. Moroz  Yu. A. Kovalevskaya  I. A. Belitsky 《Physics and Chemistry of Minerals》2002,29(4):300-306

 The heat capacity of paranatrolite and tetranatrolite with a disordered distribution of Al and Si atoms has been measured in the temperature range of 6–309 K using the adiabatic calorimetry technique. The composition of the samples is represented with the formula (Na_1.90K_0.22Ca_0.06)[Al_2.24Si_2.76O₁₀]·nH₂O, where n=3.10 for paranatrolite and n=2.31 for tetranatrolite. For both zeolites, thermodynamic functions (vibrational entropy, enthalpy, and free energy function) have been calculated. At T=298.15 K, the values of the heat capacity and entropy are 425.1 ± 0.8 and 419.1 ±0.8 J K⁻¹ mol⁻¹ for paranatrolite and 381.0 ± 0.7 and 383.2 ± 0.7 J K⁻¹ mol⁻¹ for tetranatrolite. Thermodynamic functions for tetranatrolite and paranatrolite with compositions corrected for the amount of extraframework cations and water molecules have also been calculated. The calculation for tetranatrolite with two water molecules and two extraframework cations per formula yields: C _p (298.15)=359.1 J K⁻¹ mol⁻¹, S(298.15) −S(0)=362.8 J K⁻¹ mol⁻¹. Comparing these values with the literature data for the (Al,Si)-ordered natrolite, we can conclude that the order in tetrahedral atoms does not affect the heat capacity. The analysis of derivatives dC/dT for natrolite, paranatrolite, and tetranatrolite has indicated that the water- cations subsystem within the highly hydrated zeolite may become unstable at temperatures above 200 K. Received: 30 July 2001 / Accepted: 15 November 2001  相似文献   

Agricultural land use in the coastal area of the Alexander von Humboldt National Park, Cuba and its implication for conservation and sustainability     

A. Wezel  S. Bender 《GeoJournal》2002,57(4):241-249

In the Alexander von Humboldt National Park in eastern Cuba many endemic animals and plants are found in various different natural habitats, which are considered to be the most important ones for in-situ conservation in the entire Insular Caribbean. In some areas of the National Park agriculture is practised. Thus, the objective of this study was to document and analyse the different land use activities and their consequences for local resource management and conservation of biodiversity in two village areas. A particular question was: what has changed since the foundation of the National Park in 1996? As time series data for land use and aerial photographs were not available for this part of Cuba, a qualitative evaluation was carried out. For this, six different land use units were mapped in 2001 and additional information gathered for areas with special interest related to sustainable land use and resource conservation. Although most parts of the study area are influenced to various degrees by human impact, the different types of land use seem presently not to have a crucial or detrimental impact on the land resources of the Alexander von Humboldt National Park. However, exploitation of the natural resources in certain areas could be improved with different management options to reach sustainability as well as to meet the conservation objectives of the National Park. This includes reduced or abandoned agricultural use of steep slopes to reduce erosion risk as well as a facilitated regeneration of natural vegetation in many parts of the study area to be able to conserve the high valuable biodiversity of the Park. Environmental education seems to have played an important and successful role since the foundation of the Park in 1996. Since then, cropping on steep slopes as well as illegal logging and poaching could be reduced.  相似文献   

关于水资源承载力理论与方法的研究   总被引：119，自引：3，他引：119  

朱一中  夏军  谈戈 《地理科学进展》2002,21(2):180-188

本文首先明确了水资源承载力的基本概念 ,指出可持续发展理论、水 -生态 -社会经济复合系统理论、二元模式下的水文循环机制和过程是水资源承载力研究的理论基础 ,对水资源承载力研究的基本内容、评价指标体系的建立和评价方法进行了较全面的概括和总结。  相似文献   

资源环境与社会经济协调发展探析   总被引：15，自引：2，他引：15  

李胜芬  刘斐 《地域研究与开发》2002,21(1):78-80

文章首先回顾了资源环境与社会经济发展的理论，提出资源环境与社会经济协调发展内涵：一方面，要在资源环境承载力范围内发展社会经济，追求社会经济发展的最大化，另一方面，环境承载力是动态的，要依靠社会经济发展不断提高，这两个方面是相互作用、相互制约的。在此基础上，详细论述了资源环境与社会经济协调发展的内容,并从社会经济发展、资源环境管理等角度探讨了资源环境与社会经济协调发展的政策调控，通过建立节约型国民经济体系、深化资源环境管理，实现区域一体化，以保证资源环境与社会经济协调发展的实现。  相似文献   

旅游心理容量的测定——以武陵源黄石寨景区为例   总被引：19，自引：0，他引：19  

周年兴 《地理与地理信息科学》2003,19(2):102-104

旅游容量是旅游规划和管理中的重要工具之一。该文引入边际满意度的概念,提出了旅游心理容量的满意度模型,并且以武陵源黄石寨景区为实证研究,进行了旅游心理容量的测定。  相似文献   

旅游生态环境容量的经济学探讨   总被引：10，自引：4，他引：10  

吴志才  彭华 《云南地理环境研究》2003,15(1):69-74

在总结旅游环境容量研究进展的基础上，提出了研究旅游环境容量意义及其概念体系，并就影响旅游环境容量的关键性因子－旅游生态环境容量进行了分析，运用经济学的理论和方法，提出了引起旅游生态环境容量的深层原因是外部不经济性，最后就为了实现资源环境的可持续发展，应该从法律、行政，经济、社会等角度对社会各利益加以协调，构建了有效的制度平台和相应的措施，使外部成本内部化，并提出了解决这些问题的具体对策和建议。  相似文献   

软土地基上静压预制桩承载力的工后增大效应     

肖军华  韩爱民 《江苏地质》2003,27(4):233-236

分析了软土地基上预制桩承载力的时效性机理，介绍了几种研究承载力时效性的经验回归公式，结合工程说明应充分认识承载力时效性的科学性和利用这种规律潜在的巨大经济效益。  相似文献   

抗拔桩设计方法     

李垚  李峰 《中国煤田地质》2003,15(1):48-50

当地下水位较高时,地下车库等附属建筑物不得不对抗浮问题进行考虑,抗拔桩被越来越多的应用于工程中。依据工程实例对抗拔桩设计荷载条件、抗浮桩单桩承载力设计、抗浮桩桩身结构设计、群桩地基整体稳定性、单位面积抗浮力、抗拔桩抗裂分别进行了阐述,以及抗拔桩设计中应考虑的问题进行了论述。  相似文献   

桩承载力时效对桩土相互作用及沉降的影响分析   总被引：2，自引：2，他引：2  

郑刚  任彦华 《岩土力学》2003,24(1):65-69

对软土中两根47 m长灌注桩分别在成桩28 d和1 750 d后进行了承载力试验，其极限承载力提高幅度达到30％左右。分析了单桩承载力随时间提高(称为时效)的机理，提出了单桩承载力时效对桩筏基础桩土相互作用影响的分析方法，并结合工程实例进行了分析。  相似文献   

振动沉模大直径现浇薄壁管桩技术及其应用 (Ⅰ):开发研制与设计   总被引：54，自引：25，他引：54  

刘汉龙  费康  马晓辉  高玉峰 《岩土力学》2003,24(2):164-168

振动沉模现浇混凝土薄壁管桩（PCC桩）技术是河海大学自主开发研制的用于地基加固处理的专利技术，是一种适合于软土地区的新型高效优质桩型，可有效地提高地基承载力和减小地基沉降。笔者介绍了振动沉模现浇混凝土薄壁管桩的技术原理、加固机理、施工设备、施工工艺及其设计与质量检测方法。该桩型具有承载力高、质量可靠和工程造价低等优点，具有较大的推广应用价值。  相似文献