覆膜电极溶解氧测定仪检定装置及仪器示值误差检定结果的不确定度评定

本文根据JJG 291-2008覆膜电极溶解氧测定仪检定规程中计量标准器的主要计量性能指标,评定了覆膜电极溶解氧测定仪检定装置和仪器示值误差检定结果的不确定度.     

现行覆膜电极溶解氧测定仪检定规程存在的不足--忽略了空气湿度的影响

本文简要地分析了现行覆膜电极溶解氧测定仪检定规程中出现的一个不足之处,即在水中饱和溶解氧的计算公式中忽略了空气湿度的影响.而这个忽略会对检定结果产生较大的影响,关系到我国溶解氧测量的准确可靠性,故应尽快对现行的覆膜电极溶解氧测定仪检定规程进行修订.     

覆膜电极溶解氧测定仪示值误差的不确定度评定

对覆膜电极溶解氧测定仪示值误差的不确定度进行了评定.分析了各个分量的标准不确定度,覆膜电极溶解氧测定仪示值误差的扩展不确定度U95=2.01×0.069=0.14 mg/L.     

覆膜电极溶解氧测定仪10℃时的溶解氧浓度的示值误差测量结果不确定度评定

根据检定规程所规定的检定条件与检定方法,对覆膜电极溶解氧测定仪溶解氧浓度的示值误差测量结果进行不确定度评定。     

覆膜电极溶解氧测定仪示值误差测量值的不确定评定

本文依据JJG 291-2008《覆膜电极溶解氧测定仪检定规程》,对溶解氧测定仪测量结果的不确定度评定进行分析。     

溶解氧测定仪示值误差检定结果的不确定度评定

本文主要介绍了溶解氧测定仪分析测量水中溶解氧浓度的方法、原理。依据2018年更新的检定规程JJG 291-2018《溶解氧测定仪》,采用内插法计算溶解氧浓度参考值。通过计算由重复性、温度和大气压力引入的不确定度分量,从而分析溶解氧测定仪示值误差检定结果的测量不确定度。     

从溶解氧测定仪原理解读其校准和检定

覆膜电极溶解氧测定仪(溶氧仪)由于使用方便、便于携带而越来越受到人们的欢迎。但是人们对其测量原理和校准原理不甚了解,给使用和检定工作带来了一定的困难。对此,JJG291-2008《覆膜电极溶解氧测定仪》检定规程没有进行说明。为此,本文对溶氧仪测量原理的三个特征进行详细阐述,希望有助于大家     

JJG291-2018《溶解氧测定仪检定规程》解读

正一、规程修订背景溶解氧是判断水质污染程度的重要指标之一。环境监测领域所使用的溶解氧测定仪属于强制检定工作计量器具。目前,市场上的溶解氧测定仪主要有覆膜电极溶解氧测定仪和荧光法溶解氧测定仪两种,而JJG291-2008《覆膜电极溶解氧测定仪》(以下简称"旧规程")适用范围仅限于覆膜电极溶解氧测定仪的检定,且规程制定依据的国家标准、国际标准已对部分参数、试验方法进行了调整。为统一     

覆膜电极溶解氧测定仪新旧检定规程的差异

覆膜电极溶解氧测定仪检定规程JJG291-1999替代了JJG291-1982。经过修订的新规程与原规程相比，其检定程序更科学、合理，可满足现场检定的要求，极大地简化了检定过程，缩短了检定时间，提高了工作效率。     

《溶解氧测定仪检定规程》修订之差异探讨

正一、概述JJG291-2018《溶解氧测定仪检定规程》(以下简称"新规程")替代了JJG291-2008《覆膜电极溶解氧测定仪检定规程》(以下简称"旧规程")。新规程与旧规程相比,检定范围涵盖更广,检定方法更加清晰科学,能更好满足目前检定的要求,提高了检定工作效率。旧规程的适用范围仅限于覆膜电极溶解氧测定     

高灵敏数字显示溶氧监测仪的研制

论述了高灵敏度数字显示溶氧监测仪的电路设计、温度补偿、数模转换以及该仪表的性能。经实验和实际使用表明，该仪器运行可靠、精度高、操作简单。实现了溶氧监测仪的升级换代的目标。     

铁－氧联合监测仪（Ⅱ型）的研制

铁－氧联合监测仪是用于油田注水的、自动化程度高的在线监测仪表。铁离子的测量采用程序分析法；溶氧的测量采用薄膜式极谱型氧电极。可进行连续或定时监测，自动打印结果。在研制中，重点解决了比色计微型化、电磁阀的耐化学腐蚀、单片机的软件开发和硬件设计以及软、硬件的抗干扰等问题。针对油田注水的特点，仪器还设计了微型加热装置。     

溶胶—凝胶法制备基于荧光猝灭原理的光纤氧传感器在线监测水中溶解氧

利用氧分子对金属钌化合物的荧光具有猝灭作用的特性,构造出基于荧光猝灭原理的光纤氧传感器。就用于水中溶解氧在线监测的光纤光谱仪的搭建、传感器探头的设制及传感膜的制作过程进行探索,并对传感器的响应性能进行考察。结果表明以联吡啶钌等作为荧光指示剂以溶胶-凝胶法制备的传感膜对溶解氧的响应具有良好的可逆性,稳定性,较快的响应时间和较长的使用寿命。与标准法相对照,用本仪器系统测定了不同盐度的人工海水中的溶解氧浓度,两种方法在不同浓度水平下的溶解氧测定值均无显著性差异。本法的日内和日间RSD在1.7％～5.0％之间。     

Estimating the electrochemical reactivity of pyrite ores-their impact on pulp chemistry and chalcopyrite flotation behaviour

Prudent control of ore pulp chemistry via parameters such as redox potential (Eh), dissolved oxygen (DO) and pH, can markedly improve the flotation recovery, grade and selectivity of sulphide minerals. In this paper, the electrochemical reactivities of two pyrite minerals and their impact on chalcopyrite flotation are investigated using oxygen demand test and froth flotation. Changes in the surface chemistry/speciation are also investigated using X-ray photoelectron spectroscopy (XPS) and EDTA extraction technique. The oxygen demand test shows that the different pyrite ores display significantly different electrochemical reactivity. Furthermore, continuous aeration of the pulp reduces the reactivity of the pyrite ores. Solution and surface analysis results suggest the formation of hydroxide surface coatings on the pyrite surface as aeration progresses, preventing or minimising further oxidative reactions from taking place in the pulp. Flotation results showed that the flotation response of chalcopyrite is influenced by the pulp DO/Eh, and therefore the type and reactivity of the pyrite associated with it.     

Sol-gel synthesized Sr4Al14O25:Eu2+/Dy3+ blue–green phosphorous as oxygen sensing materials

In this study, we utilized newly synthesized Sr₄Al₁₄O₂₅:Eu²⁺/Dy³⁺ blue–green phosphors along with silver nanoparticles (AgNPs) for fabrication of oxygen sensitive materials. To the best of our knowledge oxygen sensing mechanism of the offered design is totally different from the previously published works. One-component silicone: poly (1-trimethylsilyl-1-propyne), two component phenyl bearing silicone, plasticized polymethylmethacrylate, and ethylcellulose (EC) were tested as matrix materials. Electrospun fibers, porous and smooth thin films were produced by electrospinning or knife coating technique. Oxygen induced luminescence of the phosphors at 544 nm was followed as the analytical signal. Utilization of silver nanoparticles in silicone along with phosphors resulted with a 7.14 fold enhancement in the signal intensity and significant spectral response towards oxygen competing with the signals of the oxygen sensors utilizing metalloporphyrins or ruthenium complexes. We observed high sensitivity and stability, increased surface area and an enhancement in all sensor dynamics. Linearity of the calibration plots was superior for the pO₂ range of 0.0–20.0% with respect to the previously reported ones. When stored at the ambient air of the laboratory there was no significant drift in signal intensity after 12 months. Our sensitivity and stability tests are still in progress.     

Effect of dissolved oxygen on electrochemical corrosion behavior of 2205 duplex stainless steel in hot concentrated seawater

The corrosion behavior of 2205 duplex stainless steel was investigated in hot concentrated seawater with different dissolved oxygen(DO) concentration by electrochemical measurement techniques and surface analysis methods. DO obviously enhances the cathodic reaction process, the formation of passive film and polarization resistance. With increasing the DO concentration from 0.34 to 3.06 mg L^-1, the relative contents of Fe₂O₃ and Cr₂O₃ and the Cr-enrichment gradually enlarge in the passive film. The higher DO concentrations result in lower defect densities and thicker of space charge layers in the passive films,whichmayeffectively inhibit the intrusion of aggressive chloride ions. The increment inDOconcentration clearly increases the pitting potential, but decreases the repassivation potential. It may weaken both the occurrence and repassviation tendencies of stable pitting corrosion.     

Effect of dissolved oxygen concentration on nitrate removal from groundwater using a denitrifying submerged filter

A unidirectional submerged filter system was employed to purify groundwater contaminated with nitrate by biological denitrification. The influence of the concentration of dissolved oxygen (DO) in the process was tested using ethanol, methanol and sucrose as carbon sources. Inorganic-nitrogen removal, growth of the biofilm, platable denitrifying bacteria and nitrate reducing bacteria in biofilm were studied. With regard to the type of electron donor used, the presence of oxygen decreased the removal efficiency of inorganic nitrogen and caused an increase of nitrite concentration in the treated water. These negative effects depended on utilised carbon source. Biological denitrification with alcohols such as ethanol and methanol was less affected by DO than with sucrose. The development of the biofilm was also influenced by the DO concentration as excess O₂ caused reduced biofilm growth. These biofilms developed in oxygen presence had a smaller bacterial density and a lower denitrifying bacteria versus nitrate reducing bacteria ratio, which led to an unfavorable inorganic nitrogen removal and presence of nitrite in the treated water. All these effects are more pronounced when sucrose is used as carbon source.     

Tertiary treatment of textile wastewater with combined media biological aerated filter (CMBAF) at different hydraulic loadings and dissolved oxygen concentrations

An up-flow biological aerated filter packed with two layers media was employed for tertiary treatment of textile wastewater secondary effluent. Under steady state conditions, good performance of the reactor was achieved and the average COD, NH(4)(+)-N and total nitrogen (TN) in the effluent were 31, 2 and 8mg/L, respectively. For a fixed dissolved oxygen (DO) concentration, an increase of hydraulic loading resulted in a decrease in substrate removal. With the increase of hydraulic loadings from 0.13 to 0.78m(3)/(m(2)h), the removal efficiencies of COD, NH(4)(+)-N and TN all decreased, which dropped from 52 to 38%, from 90 to 68% and from 45 to 33%, respectively. In addition, the results also confirmed that the increase of COD and NH(4)(+)-N removal efficiencies resulted from the increase of DO concentrations, but this variation trend was not observed for TN removal. With the increase of DO concentrations from 2.4 to 6.1mg/L, the removal efficiencies of COD and NH(4)(+)-N were 39-53% and 64-88%, whenas TN removal efficiencies increased from 39 to 42% and then dropped to 35%.     

Corrosion properties of a novel bulk Cu0.5NiAlCoCrFeSi glassy alloy in 288 °C high-purity water

Corrosion properties of a bulk Cu_0.5NiAlCoCrFeSi glassy alloy such as electrochemical corrosion potential (ECP), potentiodynamic polarization, and weight loss measurements were carried out for the first time in 288 °C high-purity (outlet conductivity < 0.07 μS cm^− 1) water. The change of ECP with dissolved oxygen (DO) showed a sigmoid curve. In addition, the Cu_0.5NiAlCoCrFeSi alloy exhibited a wide passive region and the passive current density was ∼ 2 × 10^− 4 A cm^− 2 in deaerated water containing 0.01 N sodium sulfate (Na₂SO₄) at 288 °C. A very low weight loss of ∼ 4.5 μg mm^− 1 was also found for the Cu_0.5NiAlCoCrFeSi alloy after immersion in deaerated 288 °C water for 12 weeks.     

A Hybrid Neural Network Model for Marine Dissolved Oxygen Concentrations Time-Series Forecasting Based on Multi-Factor Analysis and a Multi-Model Ensemble

Dissolved oxygen (DO) is an important indicator of aquaculture, and its accurate forecasting can effectively improve the quality of aquatic products. In this paper, a new DO hybrid forecasting model is proposed that includes three stages: multi-factor analysis, adaptive decomposition, and an optimization-based ensemble. First, considering the complex factors affecting DO, the grey relational (GR) degree method is used to screen out the environmental factors most closely related to DO. The consideration of multiple factors makes model fusion more effective. Second, the series of DO, water temperature, salinity, and oxygen saturation are decomposed adaptively into sub-series by means of the empirical wavelet transform (EWT) method. Then, five benchmark models are utilized to forecast the sub-series of EWT decomposition. The ensemble weights of these five sub-forecasting models are calculated by particle swarm optimization and gravitational search algorithm (PSOGSA). Finally, a multi-factor ensemble model for DO is obtained by weighted allocation. The performance of the proposed model is verified by time-series data collected by the pacific islands ocean observing system (PacIOOS) from the WQB04 station at Hilo. The evaluation indicators involved in the experiment include the Nash–Sutcliffe efficiency (NSE), Kling–Gupta efficiency (KGE), mean absolute percent error (MAPE), standard deviation of error (SDE), and coefficient of determination (R²). Example analysis demonstrates that: ① The proposed model can obtain excellent DO forecasting results; ② the proposed model is superior to other comparison models; and ③ the forecasting model can be used to analyze the trend of DO and enable managers to make better management decisions.