一种新型的COD在线自动监测仪

本文介绍了一种采用羟基自由基（OH）氧化水中有机物,通过电流变化计算出COD值,并与国标方法进行线性回归比对校正后,仪器测量值与标准方法CODCr值具有较好一致性的新型COD在线自动监测仪。     

一种新型 COD在线自动监测仪

介绍了Elox100A COD在线自动监测仪的测量原理、分析流程和主要特点。仪器采用羟基自由基（OH）氧化水中有机物，通过计算电流变化测得水中化学需氧量（COD值）。与国标方法进行线性回归校正后，仪器测量值与国际方法测得的CODcr值具有较好的一致性。     

机房温度对医用回旋加速器束流损失率的影响

目的探讨医用回旋加速器粒子加速环境温度对束流损失的影响;确定不同温度条件下加速器磁场系统工作时的最佳励磁电流,实现最大程度降低束流损失。方法在励磁电流值恒定条件下,分别在不同的温度条件下(15-25℃)测量加速粒子自粒子源至剥离碳膜的束流损失情况,计算束流损失率;根据不同加速环境的温度适度调整磁场励磁电流值,使束流损失率最小。结果励磁电流值恒定时,束流在低温条件下束流损失率较大,在15-23℃温度范围随温度升高束流损失呈递减趋势,当温度超过23℃时,束流损失又有增大趋势;在温度相对较低时励磁电流需适度下调、温度升高时适度上调才能实现束流损失尽量小的目的。结论回旋加速器运行环境的温度对束流损失影响较大,通过励磁电流校正可以有效"弥补"束流损失。     

放宽长度量精密测量环境温度条件的探讨

在长度精密测量中,测量环境温度因素引起的热变形误差,在仪器总误差中占很大比重,必须加以修正。在传统的方法中,一般是提出较为严格苛刻的测量环境温度控制条件来减轻或消除温度误差的影响。但这在很大程度上局限了仪器的使用范围,给用户很多不便。近几年国外很多精密测长仪器都将测量环境温度放宽到+15℃～+25℃、+15℃～+35℃甚至+10℃～+40℃。文中探讨温度误差修正的理论依据,提出一套在特定条件下可行的环境温度控制条件及温度误差修正方法。     

COD在线测量中温度影响的消除方法研究

针对吸收光谱法测量溶液化学需氧量过程中发现环境温度对测量结果影响较大的问题,对温度在测量过程中可能造成的干扰因素进行理论推理,通过实验对发光二极光工作特性和反应液吸光度受温度变化的影响加以讨论。提出在高温下进行比色测量的方法以减小环境温度变化对测量结果的影响,并通过大量实验证明在高温消解后,冷却至60℃时对反应液进行比色测量结果一致性好、标定结果可靠,可以避免实际应用中环境温度变化对测量结果的干扰。     

固体进样原子荧光用于测量农产品中的镉

本文用固体进样原子荧光（AFS）对农产品样品进行了镉含量的分析测定。本工作使用配备多孔石墨管（PGT）电热蒸发器和钨丝（TC）作为镉的捕获器的固体进样原子荧光测镉仪,通过基体处理、标准曲线策略、干扰、标样测量、比对实验及实际样品测量,考察了该仪器在农产品检测领域中的应用。该仪器最大的特点是不需要任何样品消解,可直接固体进样进行测定,测量一个样品耗时不超过5min。测量结果表明,仪器的检出限为30 ng L-1（0.3 pg）;相对标准偏差小于5%。基于其捕获、二次释放式的方式可完全分离几乎所有基体干扰,有机物、无机物对此方法无显著干扰,对多种标物测试值也都在标物的不确定度范围。用实际样品和其它仪器如电感耦合等离子体质谱（ICPMS）、石墨炉原子吸收（GFAAS）、阳极溶出（PDV）测定结果相比,固体进样检测方法与这些方法测得的数据没有显著性差异;用固体进样检测方法对实际农产品样品测定,样品的加标回收率均在90%～105%之间。该仪器检测方法操作简便、耗时短,非常适用于农产品中Cd的现场测定。     

EA-Conflo-IRMS联机系统的燃烧转化率漂移及其对氮、碳同位素比值测定的影响

本文给出了元素分析仪-同位素比值质谱（EA-Conflo-IRMS）联机系统的燃烧转化率随测量样品次数的变化规律，以及样品的氮、碳同位素测量值与其燃烧转化率的关系。在测量前356个样品时仪器的燃烧转化率几乎不变，测量接下来的127个样品时燃烧转化率逐渐递减，而最后65个样品的燃烧转化率保持在另一个显著降低的水平。当燃烧转化率显著降低时，还原管的填料被大量氧化，氧化管上部的氧化能力下降。尽管由于受多种因素的影响同位素测定值的变化表现出一定的复杂性，但是样品的氮、碳同位素值总体上随着燃烧转化率的降低而变负。为了校正仪器漂移的状态，采用反标定方法对EA Conflo IRMS联机系统在状态漂移时的CO₂参考气同位素值进行了重新设定，并再次测量了几个标准样的碳同位素值，其结果的准确度在0.1‰以内且测量精度好于0.15‰。可见，定期通过反标定来消除燃烧转化率漂移对同位素值产生的影响是可行的。     

基于双光束光路系统在线监测COD的稳定性研究

针对光度法测定COD的在线监测仪受环境温度影响较大、测定结果稳定性差的问题,对光路和信号采集条件等因素进行验证与探讨,提出优化光纤结构和信号采集、处理方式,以提高系统的稳定性,降低系统受环境温度等因素的影响程度。结果表明,采用特殊结构双光束光纤传导光信号,在信号采集温度为50℃,信号采集时间为1s的条件下,测定结果稳定,受环境温度影响小。根据标准HJ 377-2019要求,对仪器的检出限、示值误差、重复性、低浓度漂移等指标进行测试,其结果均优于仪器测试指标要求,该装置及监测方法可用于水质COD的在线监测。     

基于RBF神经网络算法在重金属浓度测量中的应用

针对在线重金属检测仪器其测量数据精度较低的问题进行研究,同时考虑电化学传感器随温度变化易产生误差,提出了采用多传感器数据融合方法,将RBF(Radial Basis Function Neural Network)算法应用到检测中。研究结果表明此方法可使重金属浓度检测系统的输出结果更加准确,实现了温度补偿,减轻了环境温度对传感器测量精度和稳定性带来的不利影响。     

固溶处理对Fe-Cr-Mo阻尼合金内耗影响的研究

研究了固溶处理温度对新型铁磁型Fe-Cr-Mo阻尼合金内耗的影响。结果表明,经加热FeCr-Mo合金到900~1 200℃保温1h,并随炉冷固溶处理后,合金内耗随应变幅值的增大呈现先增加后减小的规律,且在900~1 100℃固溶处理温度范围内,内耗对应变幅值的敏感性随固溶温度升高而增大。经1 100℃固溶处理的合金,因其晶粒较大,第二相颗粒较少,残余内应力较小,并形成了有利于提升内耗的大尺寸、宽畴壁的片状磁畴,故而具有最高的内耗峰值。     

SIMULTANEOUS MEASUREMENT OF STRAIN AND TEMPERATURE WITH POLARIZATION MAINTAINING FIBER BRAGG GRATING LOOP MIRROR

□ A novel simultaneous method of strain and temperature measurement based on a polarization maintaining fiber Bragg grating loop mirror is proposed and demonstrated. The sensing head was composed of a fiber loop mirror and a section of fiber Bragg grating made of a polarization maintaining fiber. The Bragg wavelengths of the fiber grating in the polarization maintaining fiber were along slow and fast axis showing different sensitivities to strain and temperature with the interferometric peak wavelength of the fiber loop mirror. By monitoring the shifts of the Bragg wavelength and interferometric peak of the fiber loop mirror, with its temperature sensitivity of 0.1167 nm/°C and strain sensitivity of 0.0093 nm/μ?, a temperature measurement resolution about 0.009°C and a strain measurement resolution of 1.08 μ? was achieved theoretically and experimentally.     

A MEMS‐based heating holder for the direct imaging of simultaneous in‐situ heating and biasing experiments in scanning/transmission electron microscopes

The introduction of scanning/transmission electron microscopes (S/TEM) with sub‐Angstrom resolution as well as fast and sensitive detection solutions support direct observation of dynamic phenomena in‐situ at the atomic scale. Thereby, in‐situ specimen holders play a crucial role: accurate control of the applied in‐situ stimulus on the nanostructure combined with the overall system stability to assure atomic resolution are paramount for a successful in‐situ S/TEM experiment. For those reasons, MEMS‐based TEM sample holders are becoming one of the preferred choices, also enabling a high precision in measurements of the in‐situ parameter for more reproducible data. A newly developed MEMS‐based microheater is presented in combination with the new NanoEx?‐i/v TEM sample holder. The concept is built on a four‐point probe temperature measurement approach allowing active, accurate local temperature control as well as calorimetry. In this paper, it is shown that it provides high temperature stability up to 1,300°C with a peak temperature of 1,500°C (also working accurately in gaseous environments), high temperature measurement accuracy (<4%) and uniform temperature distribution over the heated specimen area (<1%), enabling not only in‐situ S/TEM imaging experiments, but also elemental mapping at elevated temperatures using energy‐dispersive X‐ray spectroscopy (EDS). Moreover, it has the unique capability to enable simultaneous heating and biasing experiments. Microsc. Res. Tech. 79:239–250, 2016. © 2016 Wiley Periodicals, Inc.     

Calibration of an ultrasonic flow meter for hot water

If we want to keep the number of necessary characterisation measurements within acceptable limits, we need to be confident that a flow instrument design reacts in a predictable and straightforward way to systematic influences. In this paper, the important systematic influences for an ultrasonic flow meter (UFM) for feed water flow are identified to decide which characterisations have to be carried out in addition to a typical baseline calibration with water at 20 °C. In heat metering applications where there are temperatures up to 120 °C it is for example known that the temperature influence on the flow instrument is important and this also applies to higher temperatures such as in the feed water control of power plants. One of the critical systematic temperature influences that affects most flow instruments is the thermal expansion of the meter body. From June 2009 to March 2010, the “Heat and Vacuum” department of the Physikalisch-Technische Bundesanstalt conducted a measurement campaign to characterise the influence of thermal expansion of a meter body on the calibration of an 8 inch (DN 200) five chord UFM for feed water application in the temperature range from 4 °C to 85 °C and flow range from 50 m³ h⁻¹ to 900 m³ h⁻¹. An overview of the procedures and facility used for the calibration is given and the measurement conditions under which the calibrations were performed are detailed. It is shown that a linear model of the thermal expansion effect is appropriate for the investigated conditions.     

High temperature and force measurements using a type II cascaded regenerated fiber Bragg grating (RFBG)

Abstract

A Type II-IR (infrared) grating cascaded with a regenerated fiber Bragg grating (RFBG) is described for force measurements at high temperature. The sensor was fabricated by fusion splicing a Type II grating with a Type I seed grating that was subjected to isothermal annealing in order to obtain the RFBG. Due to the different responses to temperature and force, these parameters were determined by measuring the reflection peak of the Type II grating and RFBG. The experimental results indicate that the sensor may be used for simultaneous measurement of temperature and force from 250?°C to 500?°C and 0.003?N to 0.797?N.     

FY-3C/可见光红外扫描辐射计中红外通道太阳污染的识别和修正

基于风云-3C/可见光红外扫描辐射计(FY-3/CVIRR)的中红外通道(3.7μm)的太阳污染现象和发生规律,分析了太阳污染出现的时空特征,提出了初步判识并修正北半球太阳污染数据的方法,并就太阳污染对定标系数和黑体亮温的影响做了定量的评估。结果表明,对于FY-3C/VIRR的中红外通道,太阳光线照射到定标黑体时所形成的北半球高纬度太阳污染主要出现在太阳天顶角在85°~118°之间的位置时;由太阳污染导致的该区域地球观测亮温日平均偏差为4.5K左右,最大偏差达到15K左右。通过对逐日太阳污染数据进行识别,并采用污染前后定标系数进行线性求差值,可以初步修正太阳污染对定标系数带来的异常影响。     

Temperature and refractive index sensor using a high-birefringence fiber loop mirror and single mode-coreless-single mode fiber structure

A novel fiber optic sensor for the simultaneous measurement of refractive index and temperature is reported. The sensor consists of a high-birefringence fiber loop mirror and a section of single mode-coreless-single mode fiber structure. The single mode-coreless-single mode fiber structure served as a refractometer while the high-birefringence fiber loop mirror was used to measure temperature. The multimode interference valley of the single mode-coreless-single mode fiber structure was sensitive to the surrounding refractive index of liquids (96.42 nm/refractive index unit) and had almost no response to temperature fluctuations. The high-birefringence fiber loop mirror was highly sensitive to temperature (1.98 nm/°C) but was insensitive to changes in refractive index. The theoretical and experimental results demonstrated simultaneous measurement of temperature and refractive index. The optimum resolution was 2.07 × 10^?4 refractive index units and 0.01°C.     

A comparison of specimen stage surface temperature and the GA-1 control unit reading in Balzer's Freeze fracture microtome cold stage

The cold stage specimen surface in our Balzer's 300 Freeze-etch instrument, averages 29–43°C warmer than the reading on the GA-1 stage temperature control unit. By introduction of Indium foil seals above and below the stainless steel plug in the stage tower, the specimen cold stage surface temperatures were still 9–10°C warmer than the GA-1 reading. After replacing the stainless steel plug with a copper plug and using Indium seals, the cold stage specimen surface was brought within 2.6°C of the GA-1 temperature reading. In addition, the copper plug, Indium seal modified stage cools about two times faster in going from –100°C to –150°C than the normal stainless steel stage modified with Indium seals.     

Simultaneous measurement of humidity and temperature using a polyvinyl alcohol tapered fiber bragg grating

An optical fiber sensor based on a multimode tapered fiber cascading fiber Bragg grating has been proposed and experimentally demonstrated for the simultaneous measurement of humidity and temperature. The sensor was constructed using a tapered fiber that was coated with polyvinyl alcohol and a fiber Bragg grating with high reflectivity. The measurement of humidity and temperature was achieved by monitoring changes in reflective optical power and spectral shift, respectively. Due to the different measurement methods, the effect of temperature on humidity measurement may be ignored. The theoretical analysis and experimental results show that the highest sensitivities of 0.33 µW/%RH and 10.9?pm/°C were achieved when the diameter of the taper waist was 26?µm and the thickness of coating was 3.3?µm. Due to the advantages of good linearity, low cost of fabrication and convenient operation, the proposed sensor is promising for simultaneously measuring humidity and temperature.     

DETERMINATION OF CONCENTRATION AND TEMPERATURE BY A FABRY-PEROT CAVITY FORMED BY TWO FIBER BRAGG GRATINGS

A sensing system based on a Fabry-Perot cavity formed by two fiber Bragg gratings for simultaneous measurements of temperature and liquid concentration is reported. Detailed analysis and discussion of the spectral transmission characteristics of the device are provided based on Coupled-Mode Theory. Through numerical simulation of spectral transmission, reflection spectra are shown to be influenced by the grating and Fabry-Perot cavity lengths, and sensing properties of temperature and liquid concentration are studied. A fast Fourier transform based demodulation method that simultaneously demodulates temperature and liquid concentration signals of the device was studied. The use of the fast Fourier transform provides absolute measurements with high sensitivity. The temperature sensitivity was 0.0104 nm/°C, the resolution was 1°C, the error of repeatability was 4%, the hysteresis was less than 0.010 nm, and the sensitivity of the measurement on liquid reflection was 0.01%.     

The Annealing Behavior of the Subsurface Zone Induced by Friction in Bismuth Detected by Positron Lifetime Technique

The annealing behavior of the subsurface zone (SZ) in pure bismuth induced by dry sliding was studied using the positron lifetime measurement. This measurement allows us to detect the SZ and its recovery, and recrystallization processes. The comparative measurements of the sample exposed to compression revealed the thermal stability of the SZ. The compressed sample rebuilt its structure due to the recovery and recrystallization processes at the temperature of 60 °C, whereas the sample exposed to dry sliding does it at higher temperature of 260 °C, which is close to the melting point. The isothermal annealing at the temperature of 100 °C confirmed these results. The defect depth profile induced by dry sliding evolves with the annealing temperature in such a way that the concentration of defects at the worn surface gradually decreases, but at the depth between 50 and 170 μm, the generation of new defects takes place at the temperature of 75, 100 and even at 175 °C. At the temperature of 175 °C, the defects still are extended up to the depth of about 60 μm from the worn surface. The results were qualitatively confirmed by the measurements of the Vickers microhardness depth profile. Similar annealing behavior of the SZ was observed in pure magnesium.