小波支持向量机在大气污染物浓度预测中的应用

用小波分解重构和支持向量机相结合的方法,建立大气污染物浓度预测模型。通过小波分解,将大气污染物浓度序列分解为不同频段的小波系数序列,再对各层的小波系数序列重构到原尺度上。利用相关分析的方法构建出低频小波系数a3和中频小波系数d3的支持向量机模型输入因子为前一天小波系数a3和7个气象因子;高频小波系数d2和d1以前三日的小波系数为输入因子,然后对各小波系数序列采用相应的支持向量机模型进行预测,各小波系数均使用ν-支持向量回归机(ν-SVR)算法和径向基函数,最后通过小波重构合成大气污染物浓度序列的最终预测结果。通过对大气SO2浓度预测实例证明,该大气污染物浓度预测模型具有推广能力较强、预测精度较高、训练速度快、便于建模等优点,具有良好的应用前景。     

Social media and mobility landscape: Uncovering spatial patterns of urban human mobility with multi source data

In this paper, we present a three-step methodological framework, including location identification, bias modification, and out-of-sample validation, so as to promote human mobility analysis with social media data. More specifically, we propose ways of identifying personal activity-specific places and commuting patterns in Beijing, China, based on Weibo (China’s Twitter) check-in records, as well as modifying sample bias of check-in data with population synthesis technique. An independent citywide travel logistic survey is used as the benchmark for validating the results. Obvious differences are discerned from Weibo users’ and survey respondents’ activity-mobility patterns, while there is a large variation of population representativeness between data from the two sources. After bias modification, the similarity coefficient between commuting distance distributions of Weibo data and survey observations increases substantially from 23% to 63%. Synthetic data proves to be a satisfactory cost-effective alternative source of mobility information. The proposed framework can inform many applications related to human mobility, ranging from transportation, through urban planning to transport emission modeling.

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Variations in Environmental Tritium Dose Estimates Due to Meteorological Data Averaging and Uncertainties in Pathway Model Parameters

The large amounts of tritium produced at the Savannah River Site (SRS) coupled with the current dose reconstruction study at the facility emphasize the importance of ensuring accurate and efficient prediction of tritium doses to the public. Presently, dose estimates to the general population in the site vicinity are calculated annually using a five year meteorological database. Determining whether detailed monthly dose estimates are necessary or whether annual averaged data is sufficient offers the potential for more efficient dose prediction. In this study, off site collective committed doses and maximum individual doses due to atmospheric tritium releases were calculated according to the methods outlined in the U.S. Nuclear Regulatory Commission's Regulatory Guide 1.109 and compared using monthly versus five-year meteorological data and source terms. Site-specific variables not currently utilized at SRS for annual dose estimates also have been included. In addition, the range of predicted doses, based on the distribution in model parameters given in the literature, were estimated. Finally, a sensitivity analysis was performed in order to determine the influence of model inputs on dose estimates. Results corroborate previous studies by indicating that the primary contributor to infant tritium dose is the ingestion of milk, while for all other age groups, the most important pathway is the ingestion of vegetation. These relative pathway contributions remain constant throughout the year for infants; for children, teenagers, and adults, however, inhalation and absorption of tritium through the skin increases in relative importance in the months of June to September. It was found that the model utilized was most sensitive to dose factors, the ratio of the specific activity of tritium oxide in vegetation to the specific activity of atmospheric tritium oxide, and breathing rates. Most importantly, it was found that over a five-year period, the use of averaged meteorological data results in total individual doses that are only 2 to 6% higher than doses determined monthly, depending on the pathway of interest.     

华南地区水库消涨带生态重建的植物筛选

水库消涨带水旱交替、坡度陡、土壤贫瘠,适生植物的选择一直是其生态重建的难题.在对华南地区多类型水体消涨区调查的基础上,通过在多个水库消涨带进行植物栽植试验,根据各水库水位的变化定期观测试验植物对淹水的反应和适应性,测定试验植物半淹水、全淹水与末淹水状态下叶片的光合能力、SOD活性、POD活性、可溶性蛋白质含量、MDA含量、脯氨酸含量等指标,观测试验植物出露期间的耐旱耐瘠性,同时利用松子坑水库蓄水验收的机会对设计常水位以下6 m内的野生陆生植物进行耐淹性调查评价.结果表明,铺地黍(Panicum repens)长期在陆生岸坡上生长良好,在浅淹、半淹至接近全淹时正常生长,在全淹10个月以上退水后仍能成活;榕(Ficus sp.)持续淹水11个月以上(水深0.5～2.89 m波动)仍生长正常;赤桉(Eucalyptus camaldulensis)持续淹水13个月以上(水深0.8～6.71 m波动)仍生长正常;白千层(Melaleucaleucadendron)持续淹水4个月(淹水最深2m)仍长势良好、整齐.铺地黍、榕、赤桉、白干层耐淹耐旱耐瘠,是水库消涨带生境的适生植物.     

污泥回流对流化床生物膜—A/O活性污泥耦合工艺的影响研究

设计一套流化床生物膜(MBBR)—A/O活性污泥耦合装置处理城镇污水,考察了污泥回流对耦合工艺处理效率的影响,研究了系统中生物膜相和悬浮相微生物在有机物降解和脱氮反应中的活性差异。实验结果表明,当系统进水COD在200~400mg/L,进水氨氮在8.0~32.0mg/L,污泥回流比为1/8时,水力停留时间为12.4h,系统COD去除率平均值达81.4%,TN去除率平均值达70.6%,系统对较难降解城镇污水的处理具有明显的技术优势。污泥回流降低了生物膜相微生物的活性,而提高了悬浮相微生物活性,但生物膜相微生物活性速率仍高于悬浮相微生物活性。与传统活性污泥工艺相比,MBBR—A/O活性污泥耦合工艺将高活性生物膜引入,使悬浮污泥浓度极大降低,有助于减少污泥回流能耗与处理成本,具有明显应用价值。     

灾后重建土地利用规划管理机制与实施对策研究

分析评价了灾后重建土地利用规划的管理机制与实施对策。研究结果表明,为了确保减灾防灾目标的实现,有效抗御地震灾害,灾后重建应对土地利用进行科学的管理和规划,建立预防机制,从源头上消除安全隐患;提高工程建设安全标准,加强建筑质量安全监管;要有切实可行的规划实施对策和措施,确保规划目标的贯彻落实。国家应给予灾后重建特殊的政策支持,以人为本,科学规划,切实加强与灾后重建各相关规划相协调;从严控制新增建设用地,严格保护耕地,节约和集约利用耕地,搞好灾毁土地的整理与复垦。     

Assessment of Tree Rings as a Hydrologic Record in a Humid Subtropical Environment1

Crockett, Kris, Jonathan B. Martin, Henri D. Grissino-Mayer, Evan R. Larson, and Thomas Mirti, 2010. Assessment of Tree Rings as a Hydrologic Record in a Humid Subtropical Environment. Journal of the American Water Resources Association (JAWRA) 1-13. DOI: 10.1111/j.1752-1688.2010.00464.x Abstract: Information about long-term variability of streamflow is important to allocate water resources, but few historical records extend more than 75 years into the past, requiring proxy records to evaluate flow prior to that time. Flow proxies have been found in tree-ring widths in temperate regions, but have rarely been used in humid subtropical environments because the relationship between tree growth and climate was believed to be weakened by limited seasonality and stress on tree growth from drought conditions. Tree-ring residual chronologies from two forests sampled from northern Florida correlate well with historical annual discharge (r² values as high as 0.47) from 3 of 15 river-gauging stations that were used to compare with the tree-ring chronologies. The best correlations occur where streamflow has little contribution from spring discharge or continuous flow from lakes and wetlands. Streams lack correlations with the tree-ring residual chronologies (r² values as low as 0.0002) where springs and continuous discharge from lakes mute variations in their flow. Tree-ring chronologies appear to be useful for reconstruction of prehistorical variations of some streamflow in humid subtropical regions, but interpretations of the reconstructions must consider the local hydrologic conditions.     

干热河谷区生态系统退化及恢复与重建途径：以云南金沙江典型区为例

云南金沙江干热河谷典型区具有北热带温度条件和长达半年以上的干季时间,植被生态系统具有破坏容易难的特点。在人为干扰下,以硬叶阔叶栎类为主的原始植被类型已基本消失,而出现大面积以禾草草类为主的退化生态系统类型。植被生态系统的退化引起严重的环境问题,表现为：（１）河谷区干旱化程度加剧,土壤凋萎湿度（ＰＷＰ）长达７～８个月,使许多植物无法生长;（２）河流泌沙量呈明显增加的趋势,如元谋龙海上江中游不文站６０     

防灾减灾规划与灾后重建规划的反思——由舟曲泥石流灾害想到的

通过对灾后重建规划的反思,强调坚持安全第一的灾后重建选址原则,强化灾害评估机制的程序,提倡坚持科学发展观,树立与自然和谐共生的规划理念;针对我国人地矛盾突出的特点,提出了城镇发展要规模适度及实施迁村并点的具体措施等预防和减轻灾害的规划途径;并提出了建设高效的应急体系,以应对超标准自然灾害的建议。     

纸面石膏板受热痕迹的数值重构研究

利用锥形量热仪实验测定了纸面石膏板暴露在不同辐射热通量、不同暴露时间下的烧损程度,基于火灾烈度理论对实验数据进行拟合,建立石膏板受热痕迹的半经验模型。通过修改FDS(Fire Dynamics Simulator)的源代码,将模型嵌入到软件中,与自身功能相结合,实现重现石膏板受热痕迹的功能。同时进行了石膏板受热痕迹的实体实验,研究了不同油盘面积、受热时间和相对位置对石膏板受热痕迹形成过程和结果的影响。利用增加了新功能的FDS软件对实体实验进行了数值重构,对比实验和模拟的结果,证明了该模型可用于石膏板受热痕迹的重现。该技术完善了火灾的数值重构技术,作为火灾调查的一种新兴的技术手段,对于完善事故调查的证据链,辅助火灾调查工作具有重要意义。