区域二氧化硫控制优化模型研究

传统的区域二氧化硫控制优化都是基于损害函数法和环境标准化法的。本文在分析比较了传统二氧化硫污染控制战略优化中的损害函数法和环境标准化法各自的优点与局限的基础上。建立了基于时间序列决策的整数规划优化模型。这一理论模型更好地描述了控制战略实施的过程。把时间作为模型优化的一个因子。这种基于时间序列的过程充分考虑了货币的时间价值。并能分析这些时间价值对二氧化硫污染控制战略的动态过程影响。本文的模型是更加符合现实的情况。它对于区域二氧化硫控制的中长期决策优化显得更为有效和准确。     

影响退耕还林农户返耕决策的因素识别与分析

可持续收入能力是西部贫困地区退耕还林农户返耕决策的关键。而可持续收入能力又可以表征为收入水平、途径和结构。以及决定其实现的各种条件。理论分析与调研结果发现．农户可持续收入能力受制于自身资本积累。当地自然条件和经济条件三方面。其中．人力和物资等资本存量不足限制了农户在可能的收入途径问的选择；自然条件影响农户依靠自然资源所获得的收入；基础设施落后、产业结构单一、就业机会缺乏等经济条件制约了退耕还林后短期内农户形成较稳定的收入途径和结构。本文提出政策调整的方向应该是消除这些限制因素的影响。为退耕还林农户可持续收入能力的提高创造条件。以确保退耕还林的长期生态效果的巩固和实现。     

Where artisanal mines and forest meet: Socio‐economic and environmental impacts in the Congo Basin

While mineral exploitation can provide significant income and employment, it may negatively impact the environment, being ultimately detrimental to livelihoods in the long term. The consequences of mining are of concern in high value forest ecosystems such as the Sangha Tri‐National (TNS) landscape covering Cameroon, the Central African Republic and Republic of the Congo. This paper captures the socio‐economic and environmental impacts of small‐scale mining in the TNS. Using structured questionnaires, consultations and observation, diamonds and gold were found to contribute directly to the livelihoods of at least 5% of the landscape's population. Although up to eight income‐generating strategies are used, mining contributes on average to 65% of total income and is used mainly to meet basic needs. A gold miner's average income is US$ 3.10 a day, and a diamond miner earns US$ 3.08, making them slightly wealthier than an average Cameroonian and three times wealthier than an average non‐miner in the TNS. Environmental impacts were temporary, low impact and of limited scale. However, with mining likely to increase in the near future, an increasing population and miners' low environmental awareness, measures are needed to ensure and reinforce the positive impact of artisanal mining on livelihoods and maintain its low environmental footprint in the TNS landscape.     

Are soil conservation technologies “win‐win?” A case study of Anjeni in the north‐western Ethiopian highlands

This study measures the impact of fanya juu terraces on the net value of crop income in a high‐rainfall area in the Ethiopian highlands using cross‐sectional multiple plot observations. Using propensity score matching methods we find that the net value of crop income for plots with fanya juu terraces is lower than for plots without fanya juu terraces. This finding makes it difficult to avoid concluding that while the technologies might reduce soil erosion and associated off‐site effects, they do so at the expense of poor farmers in the Ethiopian highlands. Therefore, fanya juu terraces cannot be characterized as a “win‐win” measure to reduce soil erosion. New agricultural technologies need to be profitable to the farmer if they are to be adopted and sustained.     

Diameter growth models for mixed-species stands of Coastal British Columbia including thinning and fertilization effects

In this study, diameter growth models for three species growing in mixed-stands of Coastal British Columbia (BC), Canada, under a variety of silvicultural treatments were developed. The three species were: Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco), western hemlock (Tsuga heterophylla (Raf.) Sarg.), and western redcedar (Thuja plicata Donn). A Box and Lucas model (1959) was initially fitted to the diameter growth series for each tree, as this model is very flexible and was based on processes reflective of the metabolic processes governing tree growth. Next, a random coefficients modelling approach (i.e., parameter prediction approach) was used to modify the estimated parameters for each species using functions of tree size and stage of development, site productivity, and inter-tree competition variables, while accounting for temporal correlation within trees. Impacts of fertilization on diameter growth were estimated by including the time since fertilization as an additional variable. Since state variables that are changed as a result of thinning were already in the model, accurate results post-thinning were obtained with no changes to the model. For the combined effects of thinning and fertilization, a two-step additive approach was used, where the state variables were changed following thinning and the diameter increment was modified for fertilization using the time since fertilization variable. Results indicated that multiple treatments sustain a change in growth for a longer time period following treatment than thinning or fertilization alone.     

刍议医疗设备管理的方法与实践应用

针对现代医疗仪器设备管理的新形势,从医疗器械的购置、验收、使用、维修保养、报废及计量检测六个方面阐述了完善医疗设备管理的方法与实践,以达到医疗设备科学化管理的目的.     

湘江沉积物镉和汞质量基准的建立及其应用

沉积物质量基准是保护底栖生物免受污染物危害的保护性临界水平,可用来评估与沉积物结合的污染物的影响,并为底栖生物保护和沉积物的科学管理提供依据.分析了湘江43个采样点沉积物、上覆水、间隙水和植物中Cd和Hg含量,选取钩虾做沉积物毒理实验,利用相平衡分配法、加标毒理实验法和背景值法确定湘江沉积物Cd和Hg质量基准低值(SQC-L)分别为1.89 mg·kg-1和0.13 mg·kg-1,基准高值(SQC-H)分别为28.32 mg·kg-1和0.79 mg·kg-1.经与国内外基准值比较,并与底栖生物监测数据和植物监测数据对比分析,表明确定的基准值合理.应用该基准值评价湘江沉积物质量现状发现,湘江沉积物Cd和Hg含量低于SQC-L和高于SQC-H的采样点所占比例较低,74.4%和76.7%的采样点沉积物Cd和Hg含量在SQC-L和SQC-H之间.     

Tidal river management in the south west Ganges-Brahmaputra delta in Bangladesh: Moving towards a transdisciplinary approach?

Due to both natural and anthropogenic forces, the south west part of the Ganges-Brahmaputra coastal area is facing diverse problems such as waterlogging, salinity, and loss of biodiversity. In order to address these challenges, local people have identified ‘tidal river management (TRM)’ as a comprehensive approach for sustainably managing this part of the Ganges-Brahmaputra Basin. However, due to institutional limitations, mismanagement and social conflicts, application of the TRM approach is not straightforward. In order to identify existing implementation barriers and to effectively apply the TRM approach, a transdisciplinary approach is examined for its potential to inform the re-shaping of TRM governing values and actions. It is argued that a thorough application of a transdisciplinary framework is essential, supported by the active involvement of key agencies and local stakeholders. The proposed transdisciplinary framework can potentially be applied to TRM projects for solving waterlogging and associated problems in order to achieve greater sustainability of the area.     

双二元经济结构下的生态建设补偿机制

双二元经济是我国生态建设补偿机制面临的根本约束条件。首先简要回顾了我国双二元经济的形成逻辑同环境污染现状之间的内在联系。指出我国政府在建国初期所采取的赶超战略和改革开放后的地区不平衡发展战略是联系二者的历史渊源。在此基础上构建的博弈模型表明。在双二元经济结构的约束条件下。生态建设供给的博弈均衡应是由东部发达地区和城市先进部门承担绝大部分甚至是全部的生态建设成本。因此。我国生态建设补偿机制的构建方向就应该是构建一个有效完善的跨区域、跨部门的生态建设补偿机制。以平衡生态建设者和生态建设收益者之间的成本和收益，这是保障生态建设可持续发展的关键。     

中国农地流转与农民收入的时空耦合关系及空间效应

基于中国省域2003—2018年面板数据,通过构建耦合协调发展模型,分析农地流转与农民收入耦合协调发展时空演变特征,并运用空间杜宾模型剖析农地流转对不同类型农民收入的空间效应。结果表明：（1）在时间维度上,农地流转与农民收入的耦合协调发展程度趋于优化,但农地流转一直以滞后于农业收入为主,农地流转由同步于非农收入转为超前于非农收入。（2）在空间维度上,农地流转与不同类型农民收入的耦合协调发展程度在不同省区之间差异明显。（3）农地流转显著促进了本地区农业收入与非农收入的提高,且农地流转对农民人均收入产生直接效应与溢出效应;虽然户均农地规模增加并没有显著提高非农收入,但农地的规模经济使得户均农地规模增加,显著促进了农业收入提高。