水泥中三氧化硫检测不确定度评定

通过对水泥三氧化硫检测过程中不确定度分量的分析,探讨了水泥三氧化硫检测的不确定度评定方法,并通过评定发现在检测过程中称量过程带入的不确定度占有量,提醒广大检测人员注意称量的准确性,并定期计量称量仪器。     

钢筋保护层厚度测量不确定度的评定

根据JGJ/T 152-2019《混凝土中钢筋检测技术规程》中的检测技术要求,对同一点混凝土剪力墙钢筋保护层厚度进行10次重复性检测,综合分析相关标准检验检测过程以及日常检测过程,建立数学模型,进行不确定度分量的确定.依据JJF 1059.1-2012《测量不确定度评定与表示》进行A类不确定度和B类不确定度计算,最终得...     

基于质控数据计算土壤中铜检测的不确定度

利用ICP-MS（电感耦合等离子体质谱）法对土壤中的铜含量进行检测,以国家标准物质作为质控样品,进行多次测定。基于top-down方法利用质控数据对其进行Anderson-Darling检验（拟合优度检验）,以判断过程是否达到统计受控。计算期间精密度的不确定度分量μR＇和偏倚的不确定度分量μb,合成不确定度分量,得到检测方法测量不确定度。此方法计算思路清晰,方法简洁易行、考虑因素全面,且与实际检测过程保持一致,具有较高的可靠性和可信度。     

校准曲线随机不确定度的估计

在水质分之中，标准曲线的准确度对水质样品测验结果至关重要，本文通过对校准曲线标准差的统计检验、校准曲线截距随机不确定度的估计等不确定因素进行分析，介绍了在不同置信水平下校准曲线随机不确定度进行检验的原理和方法。在实际工作中，通过对校准曲线的检验，可提高检测精度，避免系统误差。校准曲线的检验在水质质量控制中发挥着重要作用。     

预应力混凝土用钢绞线抗拉强度测量不确定度的评定

拉伸强度性能对混凝土用钢绞线极为重要。通过预应力混凝土用钢绞线拉伸强度试验过程建立数学模型,对钢绞线抗拉强度进行不确定度评定,结果表明影响抗拉强度结果的主要因素是重复性试验。因此,在实际检验检测活动中,应提高检验检测人员素质,以保证检测的准确性。     

工业废水中化学需氧量检测的不确定度评定

文章通过对工业废水中化学需氧量检测过程中不确定度来源进行详细的分析和鉴别,确定出影响因素的不确定度分量,从而计算出合成标准不确定度和扩展不确定度。不确定度的评定有利于分析人员在分析过程中对可能产生误差的环节加以特别的关注。     

混凝土外加剂中测定硫酸钠含量的不确定度评定

通过对标准检测方法外加剂中硫酸钠含量检测过程的模型分析,检测结果的不确定度主要来源于仪器、检测环境条件和人员等。对外加剂硫酸钠含量测定的不确定度的各个分量进行了计算和评定,得出外加剂中硫酸钠含量检测的扩展不确定度,并分析实验过程的注意事项以提高实验的准确性。     

混凝土外加剂中硫酸钠含量测定的不确定度评定

通过对标准检测方法外加剂中硫酸钠含量检测过程的模型分析,检测结果的不确定度主要来源于仪器、检测环境条件、人员等。对外加剂硫酸钠含量测定的不确定度的各个分量进行了计算和评定,得出外加剂中硫酸钠含量检测的扩展不确定度。并分析实验过程的注意事项以提高实验的准确性。     

水泥中三氧化硫含量检测结果测量不确定度评定

本文通过对水泥中三氧化硫含量的检测过程进行分析.寻找该检测过程的测量不确定度的各个来源,对各分量进行了分析、合成,对测定结果的不确定度进行了评定和表述。     

建筑材料放射性检测不确定度评定研究

根据《建筑材料放射性核素限量》(GB 6566—2010)中对建筑材料的放射性检测不确定度的相关要求,通过理论以及试验,具体介绍了放射性检测不确定度评定的过程和方法,通过建立数学模型,并且针对影响不确定度测量结果的各种不确定度来源进行具体的分析以及评定,找出并分析不确定度分量,最后合成得到建筑材料样品中内照射指数以及外照射指数的不确定度。     

散热器热工性能检测不确定度评定实例分析

建立了散热器热工性能检测的数学模型,分析了检测过程中不确定度来源.计算了直接测量参数(铂电阻值、热水质量流量)的不确定度,对间接求得参数(温度、散热器热流量)进行不确定度的传递计算,得出散热器热工性能检测主要参数的扩展不确定度评定结果.     

Characterization of extracellular polymeric substances produced by mixed microorganisms in activated sludge with gel-permeating chromatography, excitation-emission matrix fluorescence spectroscopy measurement and kinetic modeling

In this work the extracellular polymeric substances (EPS) produced by mixed microbial community in activated sludge are characterized using gel-permeating chromatography (GPC), 3-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy measurement and mathematical modeling. Chromatograms of extracted EPS exhibit seven peaks, among which proteins have four peaks and polysaccharides have three peaks. Evolution of the chromatogram area indicates that the quantity of produced EPS increases significantly in the substrate utilization process. With the parallel factor analysis (PARAFAC) approach, two components of the polymer matrix are identified by the EEM analysis, one as EPS proteins at Ex/Em 280/340 nm and one matrix associated as fulvic-acid-like substances at 320/400 nm. The proteins and fulvic-acid-like substances in the EPS increase in the substrate utilization phase, but decrease in the endogenous phase. To have a better insight into EPS production, the kinetic modeling of EPS is performed with regard to their molecular weight distribution and chemical natures identified by GPC and EEM. In this way, the dynamics of these important microbial products are better understood.     

Characteristic dynamic traffic load effects in bridges

When formulating an approach to assess bridge traffic loading with allowance for Vehicle-Bridge Interaction (VBI), a trade-off is necessary between the limited accuracy and computational demands of numerical models and the limited time periods for which experimental data is available. Numerical modelling can simulate sufficient numbers of loading scenarios to determine characteristic total load effects, including an allowance for VBI. However, simulating VBI for years of traffic is computationally expensive, often excessively so. Furthermore, there are a great many uncertainties associated with numerical models such as the road surface profile and the model parameter values (e.g., spring stiffnesses) for the heavy vehicle fleet. On site measurement of total load effect, including the influence of VBI, overcomes many of these uncertainties as measurements are the result of actual loading scenarios as they occur on the bridge. However, it is often impractical to monitor bridges for extended periods of time which raises questions about the accuracy of calculated characteristic load effects.Soft Load Testing, as opposed to Proof Load or Diagnostic Load Testing, is the direct measurement of load effects on bridges subject to random traffic. This paper considers the influence of measurement periods on the accuracy of soft load testing predictions of characteristic load effects, including VBI, for bridges with two lanes of opposing traffic. It concludes that, even for relatively short time periods, the estimates are reasonably accurate and tend to be conservative. Provided the data is representative, Soft Load Testing is shown to be a useful tool for calculating characteristic total load effect.     

石膏复合防水剂对石膏晶体形成的影响

利用SEM,EPS等现代测试手段,从掺加石膏防水剂后石膏晶体形成的变化角度,分析了石膏防水剂对石膏制品晶体形成的影响原因及防水机理.     

Fire Performance of External Thermal Insulation Composite System (ETICS) Facades with Expanded Polystyrene (EPS) Insulation and Thin Rendering

External Thermal Insulation Composite System (ETICS) facades with expanded polystyrene (EPS) insulation and thin rendering are applied frequently in buildings. Considering high combustibility of EPS, with these facades concerns also arise regarding spread of a possible fire between neighbouring compartments of high-rise buildings. Fire tests of two large-scale facades were performed to study two parameters presumably influencing significantly the fires of such facades in real-life settings, i.e. incident heat flux upon the facade’s surface (IHFFS) and damage of the facade’s render (the latter being a consequence of poor or unfinished construction work, ageing or fire-induced thermal strain). The first facade was rendered fully and was exposed to moderately-fast increasing IHFFS. In the second (partially unrendered) facade case the IHFFS progressed faster. The facade flame body (temperatures and shape) was monitored by thermocouples, photo and video cameras. For detection of melting of EPS and internal burning, thermocameras were used within the facades areas outside the visible plume. In the plume zone, however, a group of thermocouples was embedded inside EPS and the shapes (plateaus and slopes) of the collected time-temperature graphs were observed for these purposes. The IHFFS imposed on the facades during fire testing were estimated by numerical calculations. In both cases the first pronounced render crack was evolved at the estimated average between-windows IHFFS of around 30 kW/m\(^2\) and was followed by internal burning of EPS. While the latter did not seem to spread across the facade for the fully-rendered facade, a fast fire spread was detected for the second specimen.     

Investigation of soil-geosynthetic-structure interaction associated with induced trench installation

The design of subsurface structures associated with transportation and other underground facilities, such as buried pipes and culverts, requires an understanding of soil-structure interaction. Earth loads on these structures are known to be dependent on the installation conditions. To reduce earth pressures acting on buried structures installed under high embankments, the induced trench method has been recommended and applied in practice for several decades. It involves the installation of a compressible material (e.g. EPS geofoam blocks) immediately above the buried structure to mobilize shear strength in the backfill material. A first step towards understanding this complex soil-geosynthetic-structure interaction and accurately modeling the load transfer mechanism is choosing a suitable material model for the geofoam that is capable of simulating compressive testing results. In this study, an experimental investigation is conducted to measure the changes in contact pressure on the walls of a rigid structure buried in granular backfill with an overlying geofoam layer. Validated using the experimental results, finite element analysis is then performed and used to study the role of geofoam density, thickness and location on the load transferred to the buried structure. Conclusions are made regarding the effect of modeling EPS inclusion as a non-linear material and the role of EPS configuration on the earth pressure distribution around the buried structure.     

Uncertainties in heat-pump coefficient of performance (COP) and exergy efficiency based on standardized testing

The uncertainties allowed in testing following international (ISO) and European (CEN) standards for testing of residential heat pumps (HPs) were investigated and quantified. For air/air HPs, the relative uncertainties of COP and exergy efficiency allowed by the CEN standard were found to be from 7% to 9%. For the ISO standard the figures were from 5% to 10%. For air/water HPs, the CEN standard allowed up to 9% relative uncertainty in the COP and 7% in the exergy efficiency. In addition to the uncertainties described in the standards, it was also shown how to estimate the uncertainty of COP due to uncertainties in the levels of temperature where the heat transfer occurs. For air/air HPs at standard rating conditions, this contributed 3% to the relative uncertainty of the COP and the exergy efficiency. Exemplary calculations based on published test data showed that very few HPs had performance clearly above or below those with the median results. The exergy efficiency of the air/air HPs, with some exceptions, showed a decrease with increasing outdoor temperature. A similar, but weaker tendency was observed for air/water HPs. The exergy efficiencies for air/water HPs were typically found in the range from 0.3 to 0.4.     

Fusion of redundant measurements for enhancing the reliability of total cooling load based chiller sequencing control

Total cooling load based chiller sequence in multiple-chiller plants is essentially the best approach to stage a chiller on or off in order to satisfy thermal comfort requirement and achieve energy efficiency simultaneously. In practice, however, this approach cannot be reliably implemented. The reason is the measurement of the cooling load of multiple-chiller plants is not always consistent enough for staging chillers on or off appropriately. Measurement uncertainties, including noises, outliers and biases, have a significant influence on the performance of the sequencing operation. This paper develops a strategy of fusing available redundant measurements to reduce the measurement uncertainties. With a moving window, the proposed strategy can (i) remove measurement outliers according to a calibrated Moffat distance between redundant measurements; (ii) reduce the influence of measurement noises by merging redundant measurements; and (iii) calibrate the bias of the merged measurements. Simulation studies are represented to show the merits of the proposed strategy for improving the reliability of the total cooling load based chiller sequencing control.     

EPS混凝土单轴冲击压缩试验及破坏形态分析

为研究EPS颗粒体积掺量对混凝土单轴动态抗压强度和破坏形态的影响,采用直径74 mm的分离式霍普金森压杆装置,对4种EPS颗粒体积掺量的EPS混凝土进行单轴冲击压缩试验,分析了应变率和EPS颗粒体积掺量对EPS混凝土单轴动态抗压强度和破坏形态的影响。试验结果表明,EPS混凝土单轴动态抗压强度随应变率的增加而增大,随EPS颗粒体积掺量的增加而降低,当EPS颗粒体积掺量在20%~30%之间,EPS混凝土单轴动态抗压强度降低幅度较小;EPS混凝土试件破坏形态具有明显的高掺量低应变率效应;当EPS颗粒体积掺量达到30%之后,EPS混凝土试件裂而不碎。     

Influence of shear on the production of extracellular polymeric substances in membrane bioreactors

Shear is used to control fouling in membrane bioreactor (MBR) systems. However, shear also influences the physicochemical and biological properties of MBR biomass. The current study examines the relationship between the level of shear and extracellular polymeric substance (EPS) production in MBRs. Two identical MBRs were operated in parallel where the biomass in one reactor was exposed to seven times greater shear forces. The concentrations of floc-associated and soluble EPS were monitored for the duration of the experiment. The stickiness of extracted floc-associated EPS from each reactor was also characterized using atomic force microscopy. A mathematical model of floc-associated and soluble EPS production was applied to quantitatively describe changes in EPS production with shear. Biomass grown in a high shear environment has lower floc-associated EPS production compared to biomass grown in a lower shear environment. This decrease in floc-associated EPS production also corresponds to a decrease in soluble EPS production, which can be explained by both the lower concentration of floc-associated EPS and the production of stickier floc-associated EPS that is more erosion resistant in the high shear reactor. This research suggests that mechanical stresses can have a significant impact on the production rates of floc-associated and soluble EPS—key parameters governing membrane fouling in MBRs.