Temperature measurements of high-temperature semi-transparent infrared material using multi-wavelength pyrometry

Temperature measurements inside semi-transparent materials are important in many fields. This study investigates the measurements of interior temperature distributions in a one-dimensional semi-transparent material using multi-wavelength pyrometry based on the Levenberg–Marquardt method (LMM). The investigated material is semi-transparent Zinc Sulfide (ZnS), an infrared-transmitting optical material operating at long wavelengths. The radiation properties of the one-dimensional semi-transparent ZnS plate, including the effective spectral–directional radiation intensity and the proportion of emitted radiation, are numerically discussed at different wavelengths (8.0–14.0 μm) and temperature distributions (400–800 K) to provide the basic data for the temperature inversion problem. Multi-wavelength pyrometry was combined with the Levenberg–Marquardt method to resolve the temperature distribution along the radiative transfer direction based on the line-of-sight spectral radiation intensities at multiple wavelengths in the optimized spectral range of (11.0–14.0 μm) for the semi-transparent ZnS plate. The analyses of the non-linear inverse problem show that with less than 5.0% noise, the inversion temperature results using the Levenberg–Marquardt method are satisfactory for linear or Gaussian temperature distributions in actual applications. The analysis provides valuable guidelines for applications using multi-wavelength pyrometry for temperature measurements of semi-transparent materials.     

FTIR光谱遥测红外药剂的燃烧温度

本文利用遥感FTIR光谱，对红外药剂的燃烧特性进行了研究。在分辨率为4cm^-1时，收集4700－740cm^-1波段的光谱。从HF等燃烧产物发射的分子振转基带精细结构的谱线强度分布，可以对燃烧温度进行遥感测定，并给出了燃烧温度随时间的变化关系，实验结果表明燃烧表面附近温度梯度很大，存在着急剧的变化温度场，同时也说明，在不干扰火焰温度场的情况下，利用遥感FTIR光谱对剧烈的、非稳态快速燃烧的火焰温度进行连续实时的遥感测量，是一种快速、准确、灵敏度高的测温方法，显示了它在燃烧温度测量、产物浓度测试以及燃烧机理研究等方面的应用前景。     

Inverse analysis of non-uniform temperature distributions using multispectral pyrometry

Optical diagnostics can be used to obtain sub-pixel temperature information in remote sensing. A multispectral pyrometry method was developed using multiple spectral radiation intensities to deduce the temperature area distribution in the measurement region. The method transforms a spot multispectral pyrometer with a fixed field of view into a pyrometer with enhanced spatial resolution that can give sub-pixel temperature information from a “one pixel” measurement region. A temperature area fraction function was defined to represent the spatial temperature distribution in the measurement region. The method is illustrated by simulations of a multispectral pyrometer with a spectral range of 8.0–13.0 μm measuring a non-isothermal region with a temperature range of 500–800 K in the spot pyrometer field of view. The inverse algorithm for the sub-pixel temperature distribution (temperature area fractions) in the “one pixel” verifies this multispectral pyrometry method. The results show that an improved Levenberg–Marquardt algorithm is effective for this ill-posed inverse problem with relative errors in the temperature area fractions of (–3%, 3%) for most of the temperatures. The analysis provides a valuable reference for the use of spot multispectral pyrometers for sub-pixel temperature distributions in remote sensing measurements.     

Temperature measurements of Al containing nano-thermite reactions using multi-wavelength pyrometry

Thermite reactions with nano-scale particles have attracted much study due to their high flame temperatures and combustion velocities. The mechanism by which the reaction propagates is not well understood. The reaction temperature, the heating rate, and the reaction zone thickness are critical parameters to understanding the mechanism. Measurements of the reaction temperature for the Al/CuO, Al/MoO₃, and Al/Fe₂O₃ nano-thermite systems were made using multi-wavelength pyrometry for two experimental configurations. In one experiment, the radiative emission from the reaction of a small, unconfined pile (∼10 mg) of reacting nano-thermite is collected over a 50 ms integration time and the temperature is measured. In a second experiment, the radiative emission was collected from a single spot, with a diameter of 1.5 mm, on a transparent tube filled with the nano-thermite as the combustion wave passes and the spectrum is temporally resolved using a streak tube and detected using an intensified CCD camera. Temperature traces from these experiments show a temperature ramping period followed by a plateau in temperature. For Al/CuO, the average temperature from the unconfined pile experiment was 2390 ± 150 K, and the average plateau temperature for the temporally resolved measurements was approximately 2250 ± 100 K. For Al/MoO₃, the unconfined pile experiment yielded an average temperature of 2150 ± 100 K, and the average plateau temperature was the same. The temperature measured from the Al/Fe₂O₃ unconfined pile experiment was 1735 ± 50 K. The measured temperatures suggest that the gases generated during the reactions are primarily from the decomposition or vaporization of the various metal oxides. Furthermore, for Al/CuO and Al/MoO₃, which can be classified as ‘fast’ nano-thermites, it was shown that the length scale associated with the temperature rise is much longer than classical conduction driven reactions.     

Analysis of multi-band pyrometry for emissivity and temperature measurements of gray surfaces at ambient temperature

A multi-band pyrometry model is developed to evaluate the potential of measuring temperature and emissivity of assumably gray target surfaces at 300 K. Twelve wavelength bands between 2 and 60 μm are selected to define the spectral characteristics of the pyrometers. The pyrometers are surrounded by an enclosure with known background temperature. Multi-band pyrometry modeling results in an overdetermined system of equations, in which the solution for temperature and emissivity is obtained through an optimization procedure that minimizes the sum of the squared residuals of each system equation. The Monte Carlo technique is applied to estimate the uncertainties of temperature and emissivity, resulting from the propagation of the uncertainties of the pyrometers. Maximum reduction in temperature uncertainty is obtained from dual-band to tri-band systems, a small reduction is obtained from tri-band to quad-band, with a negligible reduction above quad-band systems (a reduction between 6.5% and 12.9% is obtained from dual-band to quad-band systems). However, increasing the number of bands does not always reduce uncertainty, and uncertainty reduction depends on the specific band arrangement, indicating the importance of choosing the most appropriate multi-band spectral arrangement if uncertainty is to be reduced. A reduction in emissivity uncertainty is achieved when the number of spectral bands is increased (a reduction between 6.3% and 12.1% is obtained from dual-band to penta-band systems). Besides, emissivity uncertainty increases for pyrometers with high wavelength spectral arrangements. Temperature and emissivity uncertainties are strongly dependent on the difference between target and background temperatures: uncertainties are low when the background temperature is far from the target temperature, tending to very high values as the background temperature approaches the target temperature.     

FTIR遥测固体推进剂燃烧温度

应用遥感FTIR对固体推进剂燃烧火焰的温度进行了研究。遥感FTIR光谱仪在光谱分辨率为4cm^-1时,连续收集燃烧火焰的发射光谱。分别利用分子基带转振光谱测温法,以及分子发射光谱最大强度谱线测温法,对燃烧温度进行了遥感实时测定。文中列出了两种方法测得的各时刻的火焰温度。结果表明。两种方法在测量快速、剧烈燃烧的火焰温度时,都是很可靠的方法,当火焰的燃烧比较稳定时,分子发射光谱最大强度谱线测温法更为简便、快速。     

农田作物光谱特征及其应用

研究了没程序烧伤小鼠淋巴细胞白介素２ｍＲＮＡ及ＩＬ－２受体αｍＲＮＡ的变化，并观察人参茎叶皂甙的体内外调节作用。结果显示，烧伤后ＩＬ－２ｍＲＮＡ及ＩＬ－２Ｒα ｍＲＮＡ水平均降低，且同伤情变化关系密切。伤后ＩＬ－２及ＩＬ－２Ｒα的变化分别同ＩＬ－２ｍＲＮＡ，ＩＬ－２Ｒα ｍＲＮＡ的变化呈非常显著的正相关。     

A specialized fast cross-correlation for acoustical measurements using coded sequences

In acoustics applications, binary maximal-length sequences and related sequences are increasingly used for acoustics system identification tasks. A number of coded sequences, such as binary maximal-length related sequences and ternary sequences possess two-valued or pulselike autocorrelation functions. It is this correlation property that is exploited in most of acoustical applications. However, the length of some of these sequences is not directly suitable for FFT-based cross-correlation algorithms. This paper explores using standard FFTs to calculate the cross-correlation between two periodic finite-length sequences of equal length, where the lengths of the sequences are not a power of 2. We apply our specialized correlation algorithm to analyze data collected in a room-acoustic environment to simultaneously obtain impulse responses between multiple sources and multiple receivers.     

A pseudo-inverse algorithm for simultaneous measurements using multiple acoustical sources

Simultaneous multiple acoustical sources measurement (SMASM) has been proposed for more effective and reliable identification of acoustical systems under critical conditions [N. Xiang and M. R. Schroeder, J. Acoust. Soc. Am. 113, 2754-2761 (2003); N. Xiang, J. N. Daigle, and M. Kleiner, J. Acoust. Soc. Am. 117, 1889-1894 (2005)]. This paper presents a pseudo-inverse algorithm for the SMASM correlation technique as an alternative way of extracting impulse responses of acoustical channels. Simulations and room acoustics experiments are carried out and the results prove the feasibility of the proposed algorithm.     

低温装置中温度测量的热沉问题

文中讨论了低温装置中的热沉问题。为减少因电引线导热对温度计的热负荷 ,提高温度测量的精度 ,在温度计的引线中加入热沉将是非常必要而且有效的手段。文中解决了不同边界条件下所需的热沉长度的求解问题 ,并讨论了其实际应用     

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应用商业软件ANSYS CFX计算了等离子体热通量和液态锂流速对自由流动液态锂温度分布的影响。计算结果表明,导向槽中心附近液态锂温度较高,冷却水入口和出口对应位置液态锂温度最低。液态锂出口温度随着等离子体热通量的增大而线性升高,冷却水流速为1.5m·s-1,热通量分别为0.1MW·m-2和1MW·m-2时,液态锂在出口处对应的温度分别为255.3°C和458.6°C。增大液态锂流速,导向槽内液态锂的温度逐渐降低,但温度变化的幅度较小。计算结果对液态锂回路安全稳定运行提供了一定参考。     

Guidelines for acoustical measurements in churches

The acoustics of churches is a cultural heritage to be preserved as carefully as the artistic and architectural aspects of this particular category of buildings. The acoustic characteristics of an environment could be measured according to different techniques varying from the numerical quantification, by means of acoustical parameters, to the recording of the binaural or ambisonic impulse responses of several combinations of source-receiver locations. The complexity of this kind of buildings can lead different researchers to choose dissimilar source-receiver arrangements, that yield incomparable results. To prevent different approaches to the problem and to assist in obtaining comparable data, the results of experimental measurements deriving from previous acoustical surveys are statistically analysed in order to better understand the spatial variation of acoustical parameters leading to the definition of a set of guidelines to standardize the choice of sources and receivers locations. In addition, suitable hardware combinations depending on the purpose of the measurement are finally suggested.     

The principle of primary spectrum pyrometry

1 Introduction Planck Law[1] is the fundamental of radiation temperature measurements, which in- dicates the quantitative relationship between the radiation intensity and the temperature of ideal blackbody.wherewhere C1 is Planck first constant, C2 Planck second constant, λ the wavelength, ε the spectral emissivity of an actual surface, I = ε (λ, T, θ, φ, β), Ib(λ, T) the radiation distri- bution of the real surface, λ1 the lower limit wavelength, λ2 the higher limit wavelength, d…     

热通量和液态锂流速对自由流动液态锂温度分布的影响

应用商业软件ANSYS CFX 计算了等离子体热通量和液态锂流速对自由流动液态锂温度分布的影响。计算结果表明,导向槽中心附近液态锂温度较高,冷却水入口和出口对应位置液态锂温度最低。液态锂出口温度随着等离子体热通量的增大而线性升高,冷却水流速为1.5m·s⁻¹,热通量分别为0.1MW·m⁻² 和1MW·m⁻² 时,液态锂在出口处对应的温度分别为255.3°C 和458.6°C。增大液态锂流速,导向槽内液态锂的温度逐渐降低,但温度变化的幅度较小。计算结果对液态锂回路安全稳定运行提供了一定参考。     

Polarised bidirectional reflectance factor measurements from vegetated land surfaces

This study measured the spectral bidirectional reflectance factors of selected vegetated land surfaces in two linear polarisation directions. It was observed that the degree of linear polarisation is usually weakest near nadir, turning 1-5% negative in the backward direction, and growing larger in the forward and Brewster directions. Polarisation was found to be inversely but non-linearly proportional to reflectance. In addition, a wavelength-dependent trend was found to exist in some data, but in general, the wavelength dependence was smooth. In most of the practical applications, a few well-selected channels would give all the available information.The authors conclude that polarisation observations may be useful in land surface remote sensing, but that only far-forward angles (60-70^°) contain a strong enough signal for easy interpretation. Polarisation near nadir is low for all known samples, and can thus be safely ignored. Despite a strong theoretical interest, no clearly discriminating signal was found in the negative polarisation branch near backward direction, providing few opportunities for quantitative analysis. There must be a better understanding of the directional effects in all applications.     

An improved high-resolution solar reference spectrum for earth's atmosphere measurements in the ultraviolet, visible, and near infrared

We have developed an improved solar reference spectrum for use in the analysis of atmospheric spectra from vacuum wavelengths of 200.07 through 1000.99 nm. The spectrum is developed by combining high spectral resolution ground-based and balloon-based solar measurements with lower spectral resolution but higher accuracy irradiance information. The new reference spectrum replaces our previous reference spectrum, and its derivatives, for use in a number of physical applications for analysis of atmospheric spectra, including: wavelength calibration; determination of instrument transfer (slit) functions; Ring effect (Raman scattering) correction; and correction for spectral undersampling of atmospheric spectra, particularly those that are dilute in absorbers. The applicability includes measurements from the GOME, SCIAMACHY, OMI, and OMPS satellite instruments as well as aircraft-, balloon-, and ground-based measurements.     

Improvements for ground-based remote sensing of atmospheric aerosol properties by additional polarimetric measurements

We discuss the improvements in the aerosol properties characterization resulting from the additional multi-wavelength polarization measurements measured by a new CIMEL polarized sun/sky-photometer, CE318-DP. In order to process direct-sun, sky and polarization measurements in a wide spectral range (340–1640 nm), we developed new calibration methods and strategies, e.g. using the Langley plot method to calibrate both direct-sun irradiance and sky radiance, as well as combining laboratory facilities with a vicarious method to calibrate the polarized sky measurements. For studying the impact of new polarimetric measurements on the retrievals of aerosol properties, we have processed an extensive record of field measurements using an updated Dubovik and King retrieval algorithm [Dubovik O, Sinyuk A, Lapyonok T, Holben BN, Mishchenko MI, et al. Application of spheroid models to account for aerosol particle nonsphericity in remote sensing of desert dust. J Geophys Res 2006;111:D11208.]. A preliminary analysis shows that adding polarization in the inversion can reduce possible errors (notably for about 30% of our field cases) in the fine mode size distribution, real part of refractive index and particle shape parameter retrievals, especially for small particles.     

Long-term trend in CHF2Cl (HCFC-22) from high spectral resolution infrared solar absorption measurements and comparison with in situ measurements

The average tropospheric volume mixing ratio of CHF₂Cl (HCFC-22) has been retrieved from a time series of high spectral resolution ground-based infrared solar absorption spectra recorded with the McMath Fourier transform spectrometer located at the U.S. National Solar Observatory facility on Kitt Peak in southern Arizona (31.9°N, 111.6°W, 2.09 km altitude) for the time period October 1987–November 2002. The retrievals are based on fits to the well-isolated, unresolved 2ν₆ Q branch at 829.05 cm⁻¹ and the SFIT2 retrieval algorithm. The measured daily averages show a near linear rise per year in the mean tropospheric volume mixing ratio as a function of time with a best fit yielding an average increase rate of (5.66±0.15) parts per trillion (10⁻¹²) by volume per year, corresponding to (6.47±0.17)%yr⁻¹, 1 sigma, at the beginning of the time series. The tropospheric mixing ratios retrieved from the solar spectra have been compared with monthly average surface flask sampling measurements from the Climate Monitoring and Diagnostic Laboratory (CMDL) station at Niwot Ridge, Colorado (40.0°N, 105.5°W, 3013 m altitude), archived measurement from the same location, and early CMDL northern hemisphere Pacific cruise measurements. The average ratio of the retrieved tropospheric mixing ratio relative to the CMDL surface mixing ratio is 1.053 for the overlapping 1987 to 2002 time period. The retrieved mean tropospheric mixing ratio is consistent with the surface measurements within the errors estimated for the remote sensing observations.     

Multispectral pyrometry for surface temperature measurement of oxidized Zircaloy claddings

Non-contact temperature measurement in a nuclear reactor is still a huge challenge because of the numerous constraints to consider, such as the high temperature, the steam atmosphere, and irradiation. A device is currently developed at CEA to study the nuclear fuel claddings behavior during a Loss-of-Coolant Accident. As a first step of development, we designed and tested an optical pyrometry procedure to measure the surface temperature of nuclear fuel claddings without any contact, under air, in the temperature range 700–850 °C. The temperature of Zircaloy-4 cladding samples was retrieved at various temperature levels. We used Multispectral Radiation Thermometry with the hypothesis of a constant emissivity profile in the spectral ranges 1–1.3 µm and 1.45–1.6 µm. To allow for comparisons, a reference temperature was provided by a thermocouple welded on the cladding surface. Because of thermal losses induced by the presence of the thermocouple, a heat transfer simulation was also performed to estimate the bias. We found a good agreement between the pyrometry measurement and the temperature reference, validating the constant emissivity profile hypothesis used in the MRT estimation. The expanded measurement uncertainty (k = 2) of the temperature obtained by the pyrometry method was ±4 °C, for temperatures between 700 and 850 °C. Emissivity values, between 0.86 and 0.91 were obtained.     

Development of methods of precise ultrasonic measurements in small volumes of liquids

The application of ultrasonic methods to investigation of problems of molecular physics and molecular biology is greatly limited by the necessity of precise measurements of ultrasound velocity and absorption in small volumes of liquids. Fixed path interferometric methods are the most adequate for such measurements in the low MHz region.In this paper disadvantages of the present interferometric methods of ultrasonic measurements are considered and new resonator cells and a simple device for such measurements are described. Accuracies of 10^?4% for the velocity change and to better than 1% for the attenuation change, at frequencies of about 7 MHz, are obtained by the device described. The volumes of the resonator cells vary within 0.1 to 0.8 ml depending on the purpose of investigation.