1990年以来长江三角洲耕地资源变化及驱动因子研究

长江三角洲地区是中国经济发展最为快速的地区之一,虽耕地资源秉赋较好,但在经济快速发展的背景下,耕地问题显得十分严峻。以长江三角洲地区16个地级市为研究对象,利用1990~2012年相关数据,以市域为单元分析了耕地资源变化和实际利用强度的时空演变过程。结果表明:(1)1990~2012年,长三角地区的耕地总面积和人均耕地面积呈现周期性的下降趋势,以"快-慢-快-慢-慢"的循环模式逐步降低;(2)长三角地区耕地实际利用强度大体呈现"北强南弱"分布规律,在空间表现上,原来集中连片的 "高-高"、"低-低"格局正逐渐破碎化,开始出现斑点镶嵌式格局;(3)长三角地区的人口、二三产业比重和城市化水平均对耕地面积变化起到显著作用,其弹性系数分别为-0.216、-0.194和-0.203,而人均GDP与耕地面积则没有显著相关性。     

基于CI指数的祁东县干旱特征分析

利用衡阳市祁东县气象站1960~2013年逐日平均气温、降水观测数据,计算综合气象干旱指数。以国家标准《气象干旱等级GB/T20481~2006》为依据划分不同干旱等级、计算干旱日数、干旱强度等,在此基础上统计干旱日的年、年代际统计并作了线性分析,并为应对干旱提出了自己的建议:祁东县干旱日每年均有出现,但不同强度干旱日发生频率不同,在全球变暖大背景下,干旱日等级越高,其增幅愈明显;祁东县的平均干旱过程数为2.5次/a,一年出现2次干旱过程几率最大,无旱过程的几率为9.3%;在统计年干旱强度时,选用持续时间最长的一次有较好代表性。近54a来,干旱强度年变化可分为三高两低,目前处于干旱强度较高期;祁东县大部分年份有季节性干旱,单季旱以秋旱为主,在双季干旱中,夏秋连旱居多,历史上夏秋冬连旱出现了三次;为了应对日趋严重的干旱,需增强人们的防旱抗灾意识、加大水利设置投入、推广节水农业和提高干旱监测预警能力。     

Experimental study on fire suppression performance of the high pressure water mist in the engine room of an offshore platform

The total flooding application water mist system is a new type of environmentally-friendly fixed extinguishing system. The optimizing design can improve its fire extinguishing performance. At present, the water mist fire extinguishing system in the engine room of the offshore deepwater semi-submersible support platform has not attracted sufficient attention. In this paper, the water mist in the engine room of a deepwater semi-submersible support platform was studied. It contains the effect of water mist on the heat absorption and oxygen insulation of diesel pool fires. The applicable parameters of the water mist fire extinguishing system were also determined. Moreover, based on the shielding of the fire source in the engine room and the different requirements for water mist extinguishing parameters, a hierarchical multi-parameter combined high-pressure water mist fire extinguishing system was proposed. In the full-scale experimental engine room model, according to the fire extinguishing experiments for diesel pool fires with different areas, this kind of hierarchical multi-parameter water mist system is very effective on shielded and non-shielded fires. In addition, it is still effective even in a non-closed environment coupled with smoke exhausting.     

Experimental investigation of the performance of modified expanded graphite powder doped with zinc borate in extinguishing sodium fires

Sodium is the main cooling medium in the circuit of fourth-generation nuclear reactors, and its leakage constitutes a severe fire hazard because of its high chemical activity. In this study, expandable graphite (EG), which is a traditional sodium fire-extinguishing agent, was modified with zinc borate (ZB) as an intercalator, and the modified EG_ZB was characterized. Moreover, the effectiveness of the modified EG_ZB in extinguishing sodium fires was tested using a self-developed fire-extinguishing experimental device. This study's results indicated that EG, EG_ZB had a smaller particle size, higher thermal stability, higher fire-extinguishing speed, and lower powder mass consumption than EG. During the fire-extinguishing process, ZnO decomposed by ZB captured free radicals and inhibited the combustion reaction. Furthermore, B₂O₃ was adsorbed on the surface of the EG layer, which strengthened covering and asphyxiation. The findings of this study provide crucial information for effectively controlling fires caused by active metals and metallo-organic compounds.     

基于缓冲区重采样的LSTM林火预测模型*

为提高林火风险预测精度,挖掘地图上隐含的空间信息、时间序列上隐含的长期趋势和循环波动,提出1种基于缓冲区重采样的长短期记忆（LSTM）林火预测模型,选取15个与林火相关的影响因素,以方差膨胀因子为评价指标对其进行多重共线性检验,方差膨胀因子大于10的因素具有共线性,并采用信息增益率验证筛选结果的合理性。考虑到火灾的空间聚集特性,采用缓冲区分析与过采样相结合方法减少样本不均衡现象的影响,最终得到176 732条样本。对12个影响因素和研究时间段的火点建立LSTM预测模型,对森林火灾发生风险进行预测。研究结果表明:基于缓冲区重采样的LSTM林火预测模型有效考虑时空上隐含的信息,预测模型准确率为87.06%,特异性为97.99%,敏感度为76.12%,阳性预测率为97.43%,阴性预测率为80.41%,ROC曲线与AUC值均优于随机森林（RF）和支持向量机（SVM）这2种基准算法。维尔克松秩和检验发现,本文提出的模型与基准算法结果具有显著性差异。研究结果可为提高林火风险预测精度提供参考。     

Influences on stakeholder support for a wildfire early warning system in a UK protected area

Projected increases in wildfire risk and impacts to human populations in the UK have prompted the installation of expanded management approaches such as early warning systems (EWSs). Newer iterations of wildfire EWSs help mitigate risk through rapid detection, often using high-resolution monitoring technology and instantaneous information collection. While existing research suggests that local social context plays an important role in the effective application of EWSs, little is known about factors that contribute to stakeholder support for these technocratic systems and their successful implementation in protected areas. This study examines support for an EWS in Northumberland National Park, UK, using focus groups with a broad range of local stakeholders. We found that diverse stakeholder understandings of wildfire, different perceptions of wildfire risk, and varied identification of values at risk collectively help explain mixed support for the EWS. Mixed support also was an outgrowth of distrust between several stakeholder groups, indicating a need for improved communication regarding wildfire risk management across stakeholder groups. Results suggest that EWSs adopted in multi-use protected areas shared by a range of stakeholder are most likely to be successful when stakeholders have shared understandings of the hazard and opportunities for collective planning to address its risks. We conclude that EWSs are a viable approach to wildfire risk reduction, but there needs to be a critical consideration of pre-existing stakeholder dynamics for effective EWS implementation.     

It’s All in the Numbers: Acreage Tallies and Environmental Program Evaluation

Increasingly, performance measurement is being used to hold federal agencies accountable, represent environmental progress, and evaluate the effectiveness of environmental programs. The need to track measurable outputs has created a tendency to present programmatic progress solely by quantifiable data, despite the inherent complexity of natural resource management. Wetlands and fire management programs are two specific environmental arenas that have come to overemphasize the tracking of acreage numbers to validate existing policy direction. In both of these arenas, we find the definition and categorization of "countable" acres to be inconsistent and unreliable. We explore this systemic flaw for both wetlands and fire programs and describe its implications for environmental policy and natural resource management more broadly. We conclude with recommendations for improved performance measurement in these arenas.     

陕西绥德地区黄土-古土壤序列地球化学特征及其环境指示意义

黄土高原北部的绥德地区处于干旱-半干旱地区,对环境变化的响应十分敏感,通过对黄土-古土壤的研究对比可以探索该区的古环境气候特征、环境变化信息等相关问题.本文对绥德黄土-古土壤进行常量、微量、稀土元素测试分析,并与其他地区黄土的地球化学特征进行了对比.结果 表明:绥德地区黄土-古土壤的主要化学成分以SiO2、Al2O3、...     

变电站与输电线路的电磁环境影响水平分析与测试评估——以部分220kV及110kV输变电设施为例

通过对220kV及110kV户内布置、户外布置方式的变电站,架空输电线路以及地下电缆线的工频电场强度、工频磁场强度的监测,分析比较了变电站及输电线路对环境的贡献水平以及衰减规律。结果表明输变电设施对环境的贡献值非常有限,且随与之距离的增加而明显衰减。     

共模阻抗稳定网络的研制

为了消除辐射测试场地供电端口阻抗的差异,本文设计制作了一种共模阻抗稳定网络,可以在供电端口处提供稳定的共模阻抗。文中对该网络的技术参数、元件规格及分布参数控制提出设计方案.经实际制作与量测验证后,该稳定网络可以在30~300MHz的频段内提供稳定的阻抗(50±5?),符合设计方案的目标,利用此网络可有效消除供电端口阻抗差异引起的测试误差。