宇生核素26Al/10Be埋藏测年法铝化学分析程序的改进

原地宇生核素26Al/10Be埋藏测年法是最近十多年涌现的测年新技术之一,广泛应用于地貌演化、古人类等研究领域,Al回收率及其纯度很大程度上决定着年代结果的精度.美国Purdue大学现用Al分离纯化程序有一些步骤尚待完善.本文通过条件实验,对该程序提出如下修改建议:①用38 ～ 75 μm阴离子交换树脂取代原用的75 ～ 150 μm树脂,以减少淋洗液(0.05 mol/L草酸-0.5 mol/L盐酸)体积并实现Al与主要干扰元素Fe、Ti的定量分离;②用阳离子交换法从草酸-盐酸中提取Al,以规避较为冗长的化学法破坏草酸.模拟样品的分析结果表明,经改进的两步骤可实现Al近于定量的回收,全流程Al回收率达91％-+5％,纯度为98％.     

Recursive calculation of hansen coefficients

Hansen coefficients are used in expansions of the elliptic motion. Three methods for calculating the coefficients are studied: Tisserand's method, the Von Zeipel-Andoyer (VZA) method with explicit representation of the polynomials required to compute the Hansen coefficients, and the VZA method with the values of the polynomials calculated recursively. The VZA method with explicit polynomials is by far the most rapid, but the tabulation of the polynomials only extends to 12th order in powers of the eccentricity, and unless one has access to the polynomials in machine-readable form their entry is laborious and error-prone. The recursive calculation of the VZA polynomials, needed to compute the Hansen coefficients, while slower, is faster than the calculation of the Hansen coefficients by Tisserand's method, up to 10th order in the eccentricity and is still relatively efficient for higher orders. The main advantages of the recursive calculation are the simplicity of the program and one's being able to extend the expansions to any order of the eccentricity with ease. Because FORTRAN does not implement recursive procedures, this paper used C for all of the calculations. The most important conclusion is recursion's genuine usefulness in scientific computing.     

Situated justice in environmental decision-making: Lessons from river management in Southeastern Australia

The practical application of environmental justice in natural resource management depends upon moving beyond generic principles to situated understanding. This understanding in turn requires knowledge of both historical and geographical contexts, including how decision-making frameworks develop and the nature of the biophysical environment itself. This paper examines these requirements based on case material from the Hunter Valley, New South Wales. In the Hunter Valley, the colonial history of river management was one of the creation, and subsequent inclusion and exclusion, of particular ‘stakes’ from the decision-making process, resulting in a narrowly defined ‘community of justice’ that became institutionalised at the catchment scale. However, even within this restricted community, distributive injustices occurred due to a failure of policy to engage with environmental variability at both spatial and temporal scales. This combination of procedural injustice and environmental variability also resulted in ecological injustice - that is a disconnected or even antagonistic human-nature relationship that restricted the opportunity to redress the severe degradation of riverine ecosystems that had occurred since European settlement. In the light of these examples, broader challenges in the application of environmental justice to river management are explored in terms of ecological complexity and contested perceptions of environmental health. Based on this material, a historically and geographically situated, ecologically informed vision of environmental justice is proposed as an essential part of sustainable river management.     

An environmental justice assessment of public beach access in Miami,Florida

The scope of empirical environmental justice (EJ) research has expanded beyond hazards exposure to scrutinize social inequities in access to amenities, but no prior study has examined the EJ implications of public beach access. Furthermore, quantitative research on white privilege is very scarce. To address these knowledge gaps, our study examines racial/ethnic and socioeconomic inequities in access to public beaches in the Miami metropolitan statistical area, Florida. Public beach accessibility is modeled with an innovative geospatial approach that involves population weighted distances to beach access sites. To assess EJ implications of public beach access for various racial/ethnic and socioeconomically vulnerable groups, spatial regression models are estimated using census tract-level data. Results indicate that beaches are more accessible to neighborhoods with a higher proportion of non-Hispanic Whites, while neighborhoods with higher percentages of Hispanics and socioeconomically disadvantaged residents have limited access. This study demonstrates the importance of assessing white privilege and access to environmental amenities in EJ research to better understand social inequities.     

时空行为视角下的实时空气污染暴露对居民日常活动满意度的影响研究——以北京市美和园社区为例

已有关于空气污染与幸福感的文献主要使用空气质量监测点的数据探讨基于居住地的静态污染暴露与居民长期幸福感的关系,缺乏考虑时空行为视角下的实时动态空气污染暴露对日常活动满意度的影响机理。根据2017年北京居民日常活动与环境健康调查数据,探讨不同活动属性的主客观空气污染暴露及活动满意度的时空差异,分析基于实时空气污染暴露的社会分异,并利用结构方程模型挖掘个人社会经济属性、居民日常活动特征、以及不同活动地点实时测度和主观感知的空气污染水平对活动满意度的影响机制及作用路径。结果表明：不同社会经济属性群体由于日常活动所处的微观环境不同,承受的实时空气污染暴露存在显著的社会分异;客观空气污染对活动满意度的直接影响并不显著,但能显著影响主观空气污染评价,而主观空气污染评价则能显著降低活动满意度,因此客观空气污染主要通过影响主观污染评价进而对活动满意度产生显著的间接效应。此外,空气污染会调节社会经济属性对活动满意度的影响效应。     

资本循环视角下的中国城乡转型思考

城市化的快速推进和市场经济的迅速发展使得资本循环周期缩短,城市空间的过度开发为资本积累再生产提供了场所,导致城市空间蔓延式增长的矛盾突出。在新型城镇化的背景下,增量主义的城乡发展已不再适应当前的社会环境,中国城乡转型发展迫在眉睫。以新马克思主义资本循环理论为切入点,分析了城乡发展与资本的逻辑关系。首先探究资本循环理论在中国城乡转型背景下的适用性,运用该理论剖析中国城乡转型发展的作用机制;然后从当前面临的各类空间矛盾出发,探讨在新型城镇化过程中政府、规划师、公众三方主体的角色变化,力求引发相关主体对城乡规划转型中的规划思路、管理方式以及制度的思考;最后提出以空间正义为核心,使中国城乡转型发展逐步走向社会公平的价值体系,推动城乡社会空间的相对公正发展。     

地质勘探工程索赔探析

工程索赔是工程承包合同履行过程中的一项重要管理活动,也是地质勘探工作的薄弱环节。通过阐明索赔在地质勘探工程中的必要性,对索赔进行了分类,并对各类索赔进行了详细说明。全面介绍了索赔应收集证据的内容以及证据的保全方法,给出了索赔的程序,特别强调了28d是索赔的最佳时机。详细介绍了索赔报告的编写内容和编写中的具体要求,对今后地质勘探行业进行索赔活动有一定的借鉴意义。     

On the determination of a set of material constants for a high‐cycle accumulation model for non‐cohesive soils

The paper discusses the determination of a set of constants for the high‐cycle accumulation model (HCA) proposed by the authors. The HCA model predicts permanent strains or excess pore water pressures in non‐cohesive soils due to a cyclic loading with a large number of cycles and with small to intermediate strain amplitudes. The laboratory tests necessary for the determination of the material constants and their analysis are explained in detail in this paper. Copyright © 2009 John Wiley & Sons, Ltd.     

The Excess of Modernity: Garbage Politics in Oaxaca,Mexico

In the last several decades, garbage strikes have taken place around the world. In this article, I examine the case of garbage strikes in Oaxaca, Mexico, a rapidly growing city. Here, garbage, which is normally considered a hazard, is revealed also to be an effective political tool for people demanding “rights to the city.” Processes of modernization that have produced an expectation of cleanliness in modern cities have, at the same time, relied on production and consumption patterns that create more and more garbage. It is this inherent contradiction that provides a space for marginalized people to use garbage as a political tool.