用"3S"技术在低湿地区域提取高精度水灾信息--若干问题讨论

低湿地区域因其经济发达,财富密度大,故对于水灾损失评估,水灾信息的高精度提取显得尤为重要.作为水灾信息表征的两个重要方面:淹没范围和水深,是我们研究的重点.首先,论述了研究低湿地区域水灾的重要性;提出了研究应用“3S“技术提取高精度水灾信息的必要性,然后,综述了“3S“技术在水灾信息提取中的研究进展,指出了目前研究存在的问题;最后,阐明了今后在低湿地水灾信息高精度提取中应优先开展的研究课题.     

A Comparison of Protocols and Observer Precision for Measuring Physical Stream Attributes1

Abstract: Stream monitoring programs commonly measure physical attributes to assess the effect of land management on stream habitat. Variability associated with the measurement of these attributes has been linked to a number of factors, but few studies have evaluated variability due to differences in protocols. We compared six protocols, five used by the U.S. Department of Agriculture Forest Service and one by the U.S. Environmental Protection Agency, on six streams in Oregon and Idaho to determine whether differences in protocol affect values for 10 physical stream attributes. Results from Oregon and Idaho were combined for groups participating in both states, with significant differences in attribute means for 9 out of the 10 stream attributes. Significant differences occurred in 5 of 10 in Idaho, and 10 of 10 in Oregon. Coefficients of variation, signal‐to‐noise ratio, and root mean square error were used to evaluate measurement precision. There were differences among protocols for all attributes when states were analyzed separately and as a combined dataset. Measurement differences were influenced by choice of instruments, measurement method, measurement location, attribute definitions, and training approach. Comparison of data gathered by observers using different protocols will be difficult unless a core set of protocols for commonly measured stream attributes can be standardized among monitoring programs.     

土壤空间变异性研究评述

在研究方法上，土壤空间变异性研究经历了由定性描述到传统统计学、再到地统计学的不断改进过程，而研究内容也由对单一特性的研究逐渐转向多特性的研究。土壤空间变异性研究虽取得了明显的进展，但也存在地统计学方法在实际应用中主观性太强，土壤综合特性的空间变异性研究、时空结合的变异性研究以及与数学模型有机结合研究不够深入等问题。文章在分析国内外研究现状的基础上，提出了亟待深入研究的若干问题，对这些问题的研究有助于“数字土壤”、“精准农业”和生态环境建设的实施。     

Evaluation of Metric Precision for a Riparian Forest Survey

This article evaluates the performance of a protocol to monitor riparian forests in western Oregon, United States based on thequality of the data obtained from a field survey. Precision isthe criteria used to determine the quality of 19 field and 6 derived metrics. The derived metrics were calculated from thefield data. The survey consisted of 110 riparian sites on publicand private lands that were sampled during the summers of 1996 and 1997. In order to calculate metric precision, some of the field plots were re-measured. Metric precision was defined in terms of the coefficient of variability (CV) and standard deviation and then compared with a pre-defined data quality objective (DQO). A metric was considered precise if the CV met or exceeded the DQO. The geomorphology metrics were not precisewhile the forest stand inventory metrics and forest cover metrics, with some exceptions, were precise. The precision formany of the field and derived metrics compared favorably withthe level of precision for similar metrics reported in the literature. Recommendations are made to improve the precision for some metrics and they include changing the way precision is calculated, re-defining the field protocol, or improving field training.     

对影响测定水中矿物油结果相关因素的研究

在紫外分光光度法测定水中矿物油中 ,存在着标准油品、石油醚纯度、石油醚萃取液体积定容等相关因素影响测定结果的准确度。本研究对上述因素进行实验对比 ,明确影响因素 ,提出改进建议     

氯化亚锡还原光度法测定总磷的改进

用氯化亚锡还原光度法测定总磷时, 实验条件要求比较苛刻。克拉玛依市环境科研中心监测站对延长SnCl2、KH2PO4试剂的使用保存期、提高显色的稳定度、降低空白值的方法做了大量试验。试验表明:SnCl2-40%丙三醇溶液、KH2PO4使用液均有很好的稳定性,使用期达到2个月;钼酸铵溶液中,加入酒石酸锑钾钼蓝显色有良好的稳定性。用本方法和标准方法测定水样的结果无显著差异,其准确度与精密度均能达到要求。     

拟协克里格法在地下水水砷空间分布特征调查研究中的应用

本文以砷超标的典型地区为例,应用拟协克里格法探讨了当地潜水及两层承压水砷的空间变异特性。该方法建立于线性无偏估值理论的基础上,考虑不同变量间的相关性,引入拟协变异函数,利用已掌握的资料合理补充待研究的样本数据。应用结果表明,当地各层地下水中砷含量变异系数值分别为24.2%、26.02%、41.4%,块金值与基台值之比(C0/C0+C)分别为14.5%、3.9%、31.9%,体现了不同层位地下水砷含量的空间变异性除了受含水层结构差异的影响外,还与含水层中氧化还原条件有关。采用拟协克里格法,以潜水测试数据作为补充样本,校正两层承压水样本的估值结果,将白土山组及新近系承压水砷含量估计精度分别提高了38.1%和31.6%。该方法为大尺度、小样本情况下,开展随机变量的空间变异特征及分布规律研究提供了有效的途径。     

精确空投缓冲气囊材料研究

介绍了精确空投着陆缓冲的作用原理以及对气囊材料的要求,分析了聚酰胺、聚酯纤维2种气囊织物材料和氯丁橡胶、硅酮2种涂层材料的结构性能及发展,总结了当前主要的新材料技术,提出了着陆缓冲气囊材料的发展趋势.     

晃动平台下ADCP测流误差分析与校正

测量不稳定流和受潮汐影响的流量一直是水文工作者所面临的难题。对于工作在海水中的走航式ADCP(声学多普勒流速剖面仪),在测量流速时,受风浪影响,往往引起测量平台的晃动,通过外接光纤陀螺,对平台的姿态进行修正,从而提高ADCP的测量精度。针对典型四波束ADCP建立了在考虑到平台晃动情况下的误差修正模型,仿真结果表明该方法可明显提高测流精度。     

民航事故征候的灰色马尔可夫预测

民航事故征候的分析和预测是民航安全研究的重要内容.掌握民航事故征候的发展状况并据此提出相应的安全措施,可减少民航事故的发生.在民航事故征候灰色预测基础上,引入马尔可夫链(Markov Chains)预测理论,建立事故征候的灰色马尔可夫预测模型.该模型具有灰色预测和马尔可夫链预测的优点,不仅提高了对波动性较大的随机变量的预测精度,同时还拓宽了灰色预测的应用范围.对某一航空公司过载大事件的灰色马尔可夫预测和检验分析表明,事故征候的灰色马尔可夫预测模型精度高于GM(1,1)模型预测精度.研究表明,灰色马尔可夫预测模型可用于民航事故征候的预测.