氧弹量热仪测定物质燃烧热值的误差分析

从两方面研究了环境恒温式氧弹量热仪在测定物质燃烧热值过程中可能出现的误差,讨论了误差的产生机理和校正方式,给出了计算方法,并进行了试验分析.     

Comparison of self-organizing maps classification approach with cluster and principal components analysis for large environmental data sets

Three classification techniques (loading and score projections based on principal components analysis (PCA), cluster analysis (CA) and self-organizing maps (SOM)) were applied to a large environmental data set of chemical indicators of river water quality. The study was carried out by using long-term water quality monitoring data. The advantages of SOM algorithm and its classification and visualization ability for large environmental data sets are stressed. The results obtained allowed detecting natural clusters of monitoring locations with similar water quality type and identifying important discriminant variables responsible for the clustering. SOM clustering allows simultaneous observation of both spatial and temporal changes in water quality. The chemometric approach revealed different patterns of monitoring sites conditionally named "tributary", "urban", "rural" or "background". This objective separation could lead to an optimization of river monitoring nets and to a better tracing natural and anthropogenic changes along the river stream.     

Structural form-finding of bending components in buildings by using parametric tools and principal stress lines

This paper aims to provide an efficient and straightforward structural form-finding method for designers to extrapolate component forms during the conceptual stage. The core idea is to optimize the classical method of structural form-finding based on principal stress lines by using parametric tools. The traditional operating process of this method relies excessively on the designer's engineering experience and lacks precision. Meanwhile, the current optimization work for this method is overly complicated for architects, and limitations in component type and final result exist. Therefore, to facilitate an architect's conceptual work, the optimization metrics of the method in this paper are set as simplicity, practicality, freedom, and rapid feedback. For that reason, this paper optimizes the method from three aspects: modeling strategy for continuum structures, classification processing of data by using the k-nearest neighbor algorithm, and topological form-finding process based on stress lines. Eventually, it allows architects to create structural texture with formal aesthetics and modify it in real time on the basis of structural analysis results. This paper also explores a comprehensive application strategy with internal force analysis diagramming to form-finding. The finite element analysis tool Karamba3D verifies the structural performance of the form-finding method. The performance is compared with that of the conventional form, and the comparison results show the practicality and potential of the strategy in this paper.     

后张法预应力束筋伸长量误差分析

结合后张法预应力的施工体会,详细分析了对束筋伸长量影响较大的物理参数,提出了相应的修正方法,并通过具体算例予以验证,为后张法预应力混凝土结构的设计和施工提供了有意义的指导。     

r建筑物的定位放样方法及其误差分析

鉴于建筑物定位的点位放样精度和放样方案的选择在整个建筑工程的施工过程中占有重要的地位,首先分析了建筑物定位放样的精度要求,然后讨论了极坐标法和角度交会法放样的误差问题,从而为建筑工程进行定位放样时合理的选择放样方案奠定了基础。     

A-posteriori analysis of the relevance of a multicriteria decision-aid method for best management practice choice in urban storm drainage

The problem of the choice of best storm drainage management scenarios led to the development of a multicriteria decision-aid method based on twenty seven criteria defined in partnership with a group of experts. A validation study of the methodology showed its relevance on real cases but also that the large number of criteria hindered its use. An a-posteriori analysis of the results obtained by our methodology from three real projects was carried out in order to try to extract non-discriminating criteria, to identify those that could be removed, combined or re-formulated, and to try to understand the reasons why they failed to prove relevant. The work is based on two reduction methods: one empirical and one based on entropy calculations.     

Source apportionment of PM2.5 in Beijing using principal component analysis/absolute principal component scores and UNMIX

Source apportionment of fine particulate matter (PM2.5, i.e., particles with an aerodynamic diameter of 2.5 microm or less) in Beijing, China, was determined using two eigenvector models, principal component analysis/absolute principal component scores (PCA/APCS) and UNMIX. The data used in this study were from the chemical analysis of 24-h samples, which were collected at 6-day intervals in January, April, July, and October 2000 in the Beijing metropolitan area. Both models identified five sources of PM2.5: secondary sulfate and secondary nitrate, a mixed source of coal combustion and biomass burning, industrial emission, motor vehicles exhaust, and road dust. On average, the PCA/APCS and UNMIX models resolved 73% and 85% of the PM2.5 mass concentrations, respectively. The results were comparable to previous estimate using the positive matrix factorization (PMF) and chemical mass balance (CMB) receptor models. Secondary products and the emissions from coal combustion and biomass burning dominated PM2.5. Such comparison among various receptor models, which contain different physical constraints, is important for better understanding PM2.5 sources.     

索杆预张力结构杆件长度误差敏感性的理论分析与试验研究

针对索杆预张力结构施工中存在的杆件长度误差,基于随机理论建立符合正态分布的随机误差模型,推导了结构预张力偏差与索长偏差的基本关系,并根据数理统计方法得到随机预张力偏差的统计特性,得到各杆件长度误差敏感性评价方法.通过设计跨度为5m的空腹索桁架结构模型,并在其上调整索杆长度来模拟施工过程中产生的长度误差.分析了引入误差后体系预张力变化及结合ANSYS软件数值分析来考察验证各杆件的误差敏感性.结果表明:预张力结构不同杆件具有不同长度误差敏感性.空腹索桁架结构中环索误差敏感性最明显,脊索、斜索次之,桅杆最弱;试验结果与理论分析基本一致,表明理论分析和模型设计加工的有效性和正确性.     

水质分析中误差的控制

针对水质分析的重要性,研究了水质分析中误差的产生原因,并提出了误差的控制措施,强调了克服水质分析误差还应注意的几点问题,指出只有对整个分析过程进行严格控制,才能确保分析结果的准确性和可靠性.     

浅述地面三维激光扫描技术及其点云误差分析

近年来,地面三维激光扫描技术的快速发展,使空间数据的获取能力得到了显著提高。地面三维激光扫描技术将使传统的工程测量从静态的单点测量发展到动态的跟踪测量和三维立体测量领域。地面三维激光扫描在土木工程、地形测量、路桥设计、地理数据采集、建筑物变形监测等诸多领域都获得了成功的应用,为城市规划及数字城市等宏观领域的广泛应用提供了条件。本文简单阐述了地面三维激光扫描技术的基本工作原理、点云误差分析及国内外的工程应用实例。     

高精度大型轨道梁制作过程中的测量误差分析

详细介绍了大型轨道梁制作过程中产生的测量误差种类,对水准仪、经纬仪测量、卷尺测量和光电测量中产生的偶然误差进行了分析,提出了减小测量误差的建议,从而提高高精度轨道梁的制作质量。     

转体施工拱桥合龙误差对全桥影响可靠度分析

探讨了转体施工拱桥合龙误差的成因,深入研究了转动轴的定位误差分析,推导出转动轴定位偏差产生跨中合龙偏差的计算公式。通过结构力学方法和平面有限元模型相结合分析了合龙误差对钢箱拱肋的力学性能影响。     

大跨度T构连续梁振动模态分析

指出模态分析是进行抗震分析所必需的前期分析过程,建立了T构连续梁系统的振动分析模型,并对该系统进行了模态分析,得到了该系统的振动动力特性（固有频率、振型）,为该结构的抗震分析提供一定的理论依据。     

经验模式分解与小波分解在变形分析应用中的对比分析

经验模式分解和小波分解是当前有效处理非平稳信号的两种时频分析方法,它们各具有其优缺点,适用于不同的应用。信号突变性检测、趋势检测和频率检测的对比实验表明,在突变检测方面小波分解优于经验模式分解;但经验模式分解在低频信号检测及趋势检测方面优于小波分解,从对实际GPS动态位移监测分析的结果可以看出,经验模式分解更有利于缓慢变形趋势的提取和无噪声干扰下的低频变形信号检测。     

建筑物混凝土结构中钢筋位置检测方法及误差分析

基于理论模型、实物模型和案例测试结果发现,电磁感应法与地质雷达法都可用于钢筋配置检测。经测试结果误差分析,电磁感应法的精度优于地质雷达法,但二者测试结果都满足相关规范要求。不同之处在于,电磁感应法仅能够检测钢筋位置,而地质雷达法在检测钢筋位置的同时兼顾检测混凝土基材质量。地质雷达法检测混凝土中钢筋的映像特征为有规律的连续小月牙形强反射信号,月牙波幅较窄,月牙顶部为钢筋的上部,到混凝土面的距离为保护层厚度;完整的混凝土基材映像特征为反射较弱,波形均匀,同相轴连续。     

平面体系机动分析模式及其应用

平面体系的机动分析是结构力学课程教学中的重点和难点之一,是学习结构力学后续内容的基础和前提。针对机动分析时学生遇到的实际问题,经过对大量习题的分析、归纳和总结,提出平面体系"2+2+3+4"机动分析模式,使平面体系机动分析过程可以按照一定的模式和步骤进行,让看似无从下手的分析变得有章可循。针对三种不同机动分析方法,分别辅以例题对分析步骤进行详细说明,为结构力学平面体系机动分析教学提供新的模式和参考。     

桥面防水层电动剪切仪测试技术与误差分析

防水层的抗剪性能是决定铺装结构稳定性和长期防水功效是否能得以发挥的重要因素 ,然而 ,国内外均没有用于防水层与桥面混凝土和沥青面层层间抗剪强度现场检测的仪器。研制了可对实验数据进行实时采集处理的桥面防水层专用电动剪切仪 ,详细介绍了电动剪切仪的结构功能、操作步骤、技术指标、数据处理方法 ,并对仪器设计和使用过程中可能存在的误差进行分析 ,认为所研发仪器可有效地检测桥面沥青铺装和沥青路面结构的层间抗剪强度。     

炼铁高炉风口中心测定方法及误差分析

根据炼铁高炉炉壳施工中风口中心定位精度要求高的情况,介绍了两种常用的定位方法,即经纬仪分度法和圆周等分法,并对其误差作了简要分析,通过严格控制炉体施工误差,从而择优选用风口定位方法。     

表面式换热器实验台水侧换热量测试误差分析

介绍了实验系统误差分析的基本原理，给出了换热器水侧换热量测试误差的表达式，研究了水侧换热量测试仪表最大允许误差的影响因素，分析了水温测试误差和压差测试误差对水侧换热量测试误差的影响，指出换热器进出口水温测试误差是影响换热器水侧换热量测试误差的主要因素。