水样中亚铁及总铁含量连续测定方法探讨

文章研究了在同一样品溶液中连续测定亚铁和总铁的分析方法,对同一标准样品溶液和实际样品进行了单独测定亚铁和总铁含量的实验,同时在完成亚铁含量测定后加入试剂,进行了总铁含量的连续测定,并对实验数据进行相对误差分析。结果表明:单独和连续测定的总铁含量数据无显著性差异,方法切实可行。     

TFM实时成像技术在缺陷检测中的应用

在压力容器的超声检测中,为解决传统相控阵（PA）二维成像存在缺陷图像畸变,难以准确定性等问题,采用1种基于全聚焦法（TFM）的实时超声成像技术,使用一维线阵和二维面阵分别对孔等典型实际缺陷进行扫查,获得缺陷的二维和三维图像,从定量角度对比分析2者的准确度。结果表明:该方法获得的三维图像测量误差在8%以内,具有更高的精确度和检出率,对于孔类缺陷的还原度更高,这对于缺陷检测与评估以及和特种设备的安全生产具有重要意义。     

玻璃量器滴定管容量示值误差对分析结果的影响

介绍了玻璃量器滴定管的用途、分类和容量示值误差的检定,分析和探讨了容量示值误差和流液口最后一滴水珠示值的大小对分析结果的影响。容量示值误差的大小能够影响分析结果的准确性,使被测样品的含量偏离其真实结果,选择合格、合适的滴定管,可以减少分析过程带来的误差,提高分析结果的准确度。     

供电企业操作岗位员工安全胜任力模型的构建

为给供电企业的安全管理工作提供胜任力方面的理论依据和实践指导,通过采用系统编制的供电企业操作岗位员工安全胜任力调查问卷,对供电企业操作岗位员工进行整群随机抽样的问卷调查。对346份有效数据进行探索性因素分析,初步构建供电企业操作岗位员工安全胜任力的5因素模型;重新发放问卷,对141份有效数据进行的验证性因素分析支持了该模型因素结构的合理性;再次重新取样,对120份有效数据进行独立样本t检验和多层回归分析,检验5个安全胜任力因素对违章行为的影响。供电企业操作岗位员工安全胜任力模型以职业素养、安全意识、职业技能、身心健康和情绪稳定性5个因素为基本结构,其中,职业素养、安全意识、身心健康和情绪稳定性4个安全胜任力因素对违章行为具有显著负向影响。     

基于粗神经网络的管制员工作差错风险预警模型

针对空中交通管制员工作差错风险类型,指出指标体系建构过程的动态性特征,从个人、团队、设备、环境及管理几个方面,建构预警指标体系,运用粗糙集在数据挖掘方面的优势,通过基于属性重要度的启发式约简算法,提取关键指标,剔除冗余指标,可以实现在不丢失关键预警监控对象的情况下,结合BP人工神经网络构建实时预警模型,既有利于加快运算速度,又有利于进行重点监控.经过实例仿真,粗糙集与BP网络结合建构的预警模型,能有效针对管制员工作差错风险进行实时预警监控.     

五孔测针标定曲线数学模型的计算机控制

由于三维流场测试工作及计算量繁重 ,采用传感技术实现三维流场的自动测试 ,计算机选出最优拟合曲线与实测数据相比较 ,因而达到测试三维流场风流目的。利用回归分析原理 ,将感压元件五孔测针的一系列标定曲线建立了相应的数学模型 ,采用MATLAB语言 ,实现了对标定曲线的拟合 ,用PLOT函数实现了对拟合标定曲线的自动绘制。同时考虑高次多项式 (拟合次数n >10 )易出现振荡的特点 ,故在拟合次数n从 1～ 10可能拟合多项式中 ,选出最优多项式。通过数学模型的应用实现了由计算机控制 ,从而为有效利用传感技术对三维流场的自动化测试提供了可能性。     

Quantitative assessments of municipal waste management systems: Using different indicators to compare and rank programs in New York State

The primary objective of waste management technologies and policies in the United States is to reduce the harmful environmental impacts of waste, particularly those relating to energy consumption and climate change. Performance indicators are frequently used to evaluate the environmental quality of municipal waste systems, as well as to compare and rank programs relative to each other in terms of environmental performance. However, there currently is no consensus on the best indicator for performing these environmental evaluations. The purpose of this study is to examine the common performance indicators used to assess the environmental benefits of municipal waste systems to determine if there is agreement between them regarding which system performs best environmentally. Focus is placed on how indicator selection influences comparisons between municipal waste management programs and subsequent system rankings. The waste systems of ten municipalities in the state of New York, USA, were evaluated using each common performance indicator and Spearman correlations were calculated to see if there was a significant association between system rank orderings. Analyses showed that rank orders of waste systems differ substantially when different indicators are used. Therefore, comparative system assessments based on indicators should be considered carefully, especially those intended to gauge environmental quality. Insight was also gained into specific factors which may lead to one system achieving higher rankings than another. However, despite the insufficiencies of indicators for comparative quality assessments, they do provide important information for waste managers and they can assist in evaluating internal programmatic performance and progress. To enhance these types of assessments, a framework for scoring indicators based on criteria that evaluate their utility and value for system evaluations was developed. This framework was used to construct an improved model for waste system performance assessments.     

Reducing over-reporting of deterministic co-occurrence patterns in biotic communities

Null models of species co-occurrence are widely used to infer the existence of various ecological processes. Here we investigate the susceptibility of the most commonly used of these models (the C-score in conjunction with the sequential swap algorithm) to type 1 and type 2 errors. To do this we use simulated datasets with a range of numbers of sites, species and coefficients of variation (CV) in species abundance. We find that this model is particularly susceptible to type 1 errors when applied to large matrices and those with low CV in species abundance. As expected, type 2 error rates decrease with increasing numbers of sites and species, although they increase with increasing CV in species abundance. Despite this, power remains acceptable over a wide range of parameter combinations. The susceptibility of this analytical method to type 1 errors indicates that many previous studies may have incorrectly reported the existence of deterministic patterns of species co-occurrence. We demonstrate that in order to overcome the problem of high type 1 error rates, the number of swaps used to generate null distributions for smaller matrices needs to be increased to over 50,000 swaps (well beyond the 5000 commonly used in published analyses and the 30,000 suggested by Lehsten and Harmand, 2006). We also show that this approach reduces type 1 error rates in real datasets. However, even using this solution, larger datasets still suffer from high type 1 error rates. Such datasets therefore require the use of very large numbers of swaps, which calls for improvements in the most commonly used software. In general, users of this powerful analytical method must be aware that they need surprisingly large numbers of swaps to obtain unbiased estimates of structuring in biotic communities.