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1
Sum, Stephen T., and Steven D. Brown. "Standardization of Fiber-Optic Probes for Near-Infrared Multivariate Calibrations." Applied Spectroscopy 52, no. 6 (June 1998): 869–77. http://dx.doi.org/10.1366/0003702981944418.
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The standardization of Fourier transform near-infrared (FT-NIR) spectrometers equipped with fiber-optic probes was investigated. FT-NIR spectra of caustic brines for an industrial process were measured on two different instruments. Calibration transfer across the instruments and probes was studied by employing calibration models built on one instrument to predict properties from spectra measured on the other. The transfer was examined by using spectra without and with preprocessing. The preprocessing methods included a Savitzky–Golay (SG) derivative polynomial filter, a procedure based on a finite impulse response (FIR) filter, and a combination of both. In addition to being a preprocessing technique, the FIR filter is also a standardization method that transforms the instrument response function of one instrument to match that of another. The transformation is performed over a moving processing window without the use of transfer standards. In this study, application of the FIR filter to first-derivative spectra provided the best multivariate calibration models and led to the successful transfer of calibration across different probes and spectrometers.
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Hillmer, Hartmut, Carsten Woidt, André Istock, Aliaksei Kobylinskiy, Duc Toan Nguyen, Naureen Ahmed, Robert Brunner, and Thomas Kusserow. "Role of Nanoimprint Lithography for Strongly Miniaturized Optical Spectrometers." Nanomaterials 11, no. 1 (January 11, 2021): 164. http://dx.doi.org/10.3390/nano11010164.
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Optical spectrometers and sensors have gained enormous importance in metrology and information technology, frequently involving the question of size, resolution, sensitivity, spectral range, efficiency, reliability, and cost. Nanomaterials and nanotechnological fabrication technologies have huge potential to enable an optimization between these demands, which in some cases are counteracting each other. This paper focuses on the visible and near infrared spectral range and on five types of optical sensors (optical spectrometers): classical grating-based miniaturized spectrometers, arrayed waveguide grating devices, static Fabry–Pérot (FP) filter arrays on sensor arrays, tunable microelectromechanical systems (MEMS) FP filter arrays, and MEMS tunable photonic crystal filters. The comparison between this selection of concepts concentrates on (i) linewidth and resolution, (ii) required space for a selected spectral range, (iii) efficiency in using available light, and (iv) potential of nanoimprint for cost reduction and yield increase. The main part of this review deals with our own results in the field of static FP filter arrays and MEMS tunable FP filter arrays. In addition, technology for efficiency boosting to get more of the available light is demonstrated.
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Hillmer, Hartmut, Carsten Woidt, André Istock, Aliaksei Kobylinskiy, Duc Toan Nguyen, Naureen Ahmed, Robert Brunner, and Thomas Kusserow. "Role of Nanoimprint Lithography for Strongly Miniaturized Optical Spectrometers." Nanomaterials 11, no. 1 (January 11, 2021): 164. http://dx.doi.org/10.3390/nano11010164.
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Optical spectrometers and sensors have gained enormous importance in metrology and information technology, frequently involving the question of size, resolution, sensitivity, spectral range, efficiency, reliability, and cost. Nanomaterials and nanotechnological fabrication technologies have huge potential to enable an optimization between these demands, which in some cases are counteracting each other. This paper focuses on the visible and near infrared spectral range and on five types of optical sensors (optical spectrometers): classical grating-based miniaturized spectrometers, arrayed waveguide grating devices, static Fabry–Pérot (FP) filter arrays on sensor arrays, tunable microelectromechanical systems (MEMS) FP filter arrays, and MEMS tunable photonic crystal filters. The comparison between this selection of concepts concentrates on (i) linewidth and resolution, (ii) required space for a selected spectral range, (iii) efficiency in using available light, and (iv) potential of nanoimprint for cost reduction and yield increase. The main part of this review deals with our own results in the field of static FP filter arrays and MEMS tunable FP filter arrays. In addition, technology for efficiency boosting to get more of the available light is demonstrated.
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Anderson, Mark S. "Infrared Spectroscopy with an Atomic Force Microscope." Applied Spectroscopy 54, no. 3 (March 2000): 349–52. http://dx.doi.org/10.1366/0003702001949618.
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An atomic force microscope (AFM) has been used to measure the modulated photothermal displacement of a surface, thus acting as a local detector. This was demonstrated with Fourier transform infrared (FT-IR) and filter spectrometers focused on various samples. Similarly, surface layers were removed by an AFM and analyzed by the photothermal deformation of the coated cantilever. This work shows that the AFM can function as both an infrared detector and a precise surface separation device for spectroscopic analysis. The AFM combined with an FT-IR has the potential to enhance the sensitivity, selectivity, and spatial resolution of infrared spectroscopy.
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Kilgus, Jakob, Kristina Duswald, Gregor Langer, and Markus Brandstetter. "Mid-Infrared Standoff Spectroscopy Using a Supercontinuum Laser with Compact Fabry–Pérot Filter Spectrometers." Applied Spectroscopy 72, no. 4 (January 12, 2018): 634–42. http://dx.doi.org/10.1177/0003702817746696.
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Mid-infrared (MIR) supercontinuum (SC) lasers are an attractive new option in the field of IR spectroscopy, especially for standoff detection. Supercontinuum radiation unites high brightness, high spatial coherence, and broadband spectral coverage, thereby surpassing thermal IR sources and challenging quantum cascade lasers. The employed SC source operates in the spectral region of 1.2–4.6 µm, filling the spectral gap where quantum cascade lasers lack broader availability. In this work, the SC radiation was recorded by compact Fabry–Pérot filter spectrometers ideally suited for sensitive standoff detection with real-time capability. The noise performance of the setup and measurements of different substances at standoff distances are presented, e.g., of different paints on a metal surface and an explosive precursor. Furthermore, the real-time capability of the setup is demonstrated by monitoring the evaporation of liquid 2-propanol.
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Ayasse, Alana K., Philip E. Dennison, Markus Foote, Andrew K. Thorpe, Sarang Joshi, Robert O. Green, Riley M. Duren, David R. Thompson, and Dar A. Roberts. "Methane Mapping with Future Satellite Imaging Spectrometers." Remote Sensing 11, no. 24 (December 17, 2019): 3054. http://dx.doi.org/10.3390/rs11243054.
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This study evaluates a new generation of satellite imaging spectrometers to measure point source methane emissions from anthropogenic sources. We used the Airborne Visible and Infrared Imaging Spectrometer Next Generation(AVIRIS-NG) images with known methane plumes to create two simulated satellite products. One simulation had a 30 m spatial resolution with ~200 Signal-to-Noise Ratio (SNR) in the Shortwave Infrared (SWIR) and the other had a 60 m spatial resolution with ~400 SNR in the SWIR; both products had a 7.5 nm spectral spacing. We applied a linear matched filter with a sparsity prior and an albedo correction to detect and quantify the methane emission in the original AVIRIS-NG images and in both satellite simulations. We also calculated an emission flux for all images. We found that all methane plumes were detectable in all satellite simulations. The flux calculations for the simulated satellite images correlated well with the calculated flux for the original AVIRIS-NG images. We also found that coarsening spatial resolution had the largest impact on the sensitivity of the results. These results suggest that methane detection and quantification of point sources will be possible with the next generation of satellite imaging spectrometers.
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Cadusch, Jasper J., Jiajun Meng, Benjamin J. Craig, Vivek Raj Shrestha, and Kenneth B. Crozier. "Visible to long-wave infrared chip-scale spectrometers based on photodetectors with tailored responsivities and multispectral filters." Nanophotonics 9, no. 10 (June 23, 2020): 3197–208. http://dx.doi.org/10.1515/nanoph-2020-0114.
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AbstractChip-scale microspectrometers, operational across the visible to long-wave infrared spectral region will enable many remote sensing spectroscopy applications in a variety of fields including consumer electronics, process control in manufacturing, as well as environmental and agricultural monitoring. The low weight and small device footprint of such spectrometers could allow for integration into handheld, unattended vehicles or wearable-electronics based systems. This review will focus on recent developments in nanophotonic microspectrometer designs, which fall into two design categories: (i) planar filter-arrays used in conjunction with visible or IR detector arrays and (ii) microspectrometers using filter-free detector designs with tailored responsivities, where spectral filtering and photocurrent generation occur within the same nanostructure.
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Levine, Steven P., Ying Li-Shi, Christopher R. Strang, and Xiao Hong-Kui. "Advantages and Disadvantages in the Use of Fourier Transform Infrared (FTIR) and Filter Infrared (FIR) Spectrometers for Monitoring Airborne Gases and Vapors of Industrial Hygiene Concern." Applied Industrial Hygiene 4, no. 7 (July 1989): 180–87. http://dx.doi.org/10.1080/08828032.1989.10390419.
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Zhang, Z. M., C. J. Zhu, and L. M. Hanssen. "Absolute Detector Calibration Applied to Nonlinearity Error Correction in FT-IR Measurements." Applied Spectroscopy 51, no. 4 (April 1997): 576–79. http://dx.doi.org/10.1366/0003702971940639.
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A method for correcting the effects of detector nonlinearity in Fourier transform infrared (FT-IR) spectrometers has been developed. The method incorporates directly measured results. No adjustable parameters are used. The absolute responsivity of two HgCdTe (MCT) detector/preamplifier systems as a function of incident photon flux was calibrated against a transfer-standard Ge detector with a diode laser source at 1.32 μm. With the use of the MCT detector, preliminary measurements were made on an FT-IR spectrometer in both the near- and mid-infrared spectral regions. The measured nonlinear interferograms were corrected by using the detector response curve and the measured dc output of the preamplifier. In the resultant spectra, the nonzero values in the spectral region below the detector cutoff frequency were significantly reduced when the corrected interferograms were used. The transmittance spectra of a Si wafer and a neutral-density filter were measured with an MCT detector and a deuterated triglycine sulfate (DTGS) detector. Errors in transmittance caused by detector nonlinearity were greatly reduced with the use of the correction method.
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HARTKE, JOHN, NATHAN HAGAN, BRIAN A. KINDER, and EUSTACE L. DERENIAK. "COMPUTED TOMOGRAPHIC IMAGING SPECTROMETER (CTIS) AND A SNAPSHOT HYPERSPECTRAL IMAGER AND POLARIMETER." International Journal of High Speed Electronics and Systems 18, no. 03 (September 2008): 505–17. http://dx.doi.org/10.1142/s0129156408005527.
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A Computed Tomographic Imagining Spectrometer (CTIS) is an imaging spectrometer system that acquires all the information required to reconstruct the data cube in a single integration time. This is compared to conventional systems such as whiskbroom systems, pushbroom systems, and filter wheel systems that requiring scanning in one or more coordinate direction. CTIS systems have been designed and tested in several different singular spectral bands as well as a dual band system. In addition to hyperspectral imaging spectrometers, CTIS systems have been used as an imaging spectropolarimeter and as a ranging imaging spectrometer. An imaging spectropolarimeter not only reconstructs the spectral content at every point in the scene of interest, but also provides the Stokes parameters at every point. So instead of just one data cube, we get four data cubes, one for each element of the Stokes vector. The ranging CTIS incorporates a LADAR system with the CTIS to provide the range information to targets in scene as well as the reconstructed data cube. The physical principles behind the CTIS system are presented as well as some of representative data from single band systems, the dual band proof of concept, the spectropolarimeter, and the ranging imaging spectrometer.
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Debus, Bruno, Satoshi Takahama, Andrew T. Weakley, Kelsey Seibert, and Ann M. Dillner. "Long-Term Strategy for Assessing Carbonaceous Particulate Matter Concentrations from Multiple Fourier Transform Infrared (FT-IR) Instruments: Influence of Spectral Dissimilarities on Multivariate Calibration Performance." Applied Spectroscopy 73, no. 3 (November 13, 2018): 271–83. http://dx.doi.org/10.1177/0003702818804574.
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Matching the spectral response between multiple spectrometers is a mandatory procedure when developing robust calibrations whose prediction is independent of instrument-related signal variations. A viable alternative to complex calibration transfer methods consists of matching the instrument spectral response by controlling a set of key instrumental and environmental parameters. This paper discusses the applicability of such an approach to three Fourier transform infrared (FT-IR) spectrometers used for the routine assessment of carbonaceous particulate matter concentrations in the Interagency Monitoring of PROtected Visual Environments (IMPROVE) speciation network. The effectiveness of the proposed matching procedure is evaluated by comparing the spectral response for each individual instrument in order to characterize the extent, and nature, of the remaining inter-instrument spectral dissimilarities. Instrument-related contributions to the signal were determined to be small compared with the spectral variability induced by the filter type used for sample collection. The impact of spectral differences on prediction was addressed through the comparison of model performance derived from multiple calibration scenarios. A hybrid model yielding accurate and homogeneous prediction regardless of the instrument was proposed for organic carbon (OC) and elemental carbon (EC), two major constituents of atmospheric particulate matter. Coefficients of determination of 0.98 (OC) and 0.90 (EC) with median biases not exceeding 0.20 µg (OC) and 0.07 µg (EC) are reported. The long-term stability, assessed from weekly measurements of reference samples, shows a deviation in predicted concentrations of less than ±5% over a 2.5-year period for most of the data collected. Extending OC and EC hybrid models to the prediction of ambient samples collected during the two subsequent years provides satisfactory performance. The proposed instrument matching procedure coupled with the relative simplicity of the hybrid model is an alternative to computationally advanced calibration transfer methodologies for the characterization of carbonaceous particulate matter using multiple FT-IR instruments.
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Abbasi, Behrooz, Xiaoliang Wang, Judith C. Chow, John G. Watson, Bijan Peik, Vahid Nasiri, Kyle B. Riemenschnitter, and Mohammadreza Elahifard. "Review of Respirable Coal Mine Dust Characterization for Mass Concentration, Size Distribution and Chemical Composition." Minerals 11, no. 4 (April 16, 2021): 426. http://dx.doi.org/10.3390/min11040426.
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Respirable coal mine dust (RCMD) exposure is associated with black lung and silicosis diseases in underground miners. Although only RCMD mass and silica concentrations are regulated, it is possible that particle size, surface area, and other chemical constituents also contribute to its adverse health effects. This review summarizes measurement technologies for RCMD mass concentrations, morphology, size distributions, and chemical compositions, with examples from published efforts where these methods have been applied. Some state-of-the-art technologies presented in this paper have not been certified as intrinsically safe, and caution should be exerted for their use in explosive environments. RCMD mass concentrations are most often obtained by filter sampling followed by gravimetric analysis, but recent requirements for real-time monitoring by continuous personal dust monitors (CPDM) enable quicker exposure risk assessments. Emerging low-cost photometers provide an opportunity for a wider deployment of real-time exposure assessment. Particle size distributions can be determined by microscopy, cascade impactors, aerodynamic spectrometers, optical particle counters, and electrical mobility analyzers, each with unique advantages and limitations. Different filter media are required to collect integrated samples over working shifts for comprehensive chemical analysis. Teflon membrane filters are used for mass by gravimetry, elements by energy dispersive X-ray fluorescence, rare-earth elements by inductively coupled plasma-mass spectrometry and mineralogy by X-ray diffraction. Quartz fiber filters are analyzed for organic, elemental, and brown carbon by thermal/optical methods and non-polar organics by thermal desorption-gas chromatography-mass spectrometry. Polycarbonate-membrane filters are analyzed for morphology and elements by scanning electron microscopy (SEM) with energy dispersive X-ray, and quartz content by Fourier-transform infrared spectroscopy and Raman spectroscopy.
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Libois, Quentin, Christian Proulx, Liviu Ivanescu, Laurence Coursol, Ludovick S. Pelletier, Yacine Bouzid, Francesco Barbero, Éric Girard, and Jean-Pierre Blanchet. "A microbolometer-based far infrared radiometer to study thin ice clouds in the Arctic." Atmospheric Measurement Techniques 9, no. 4 (April 27, 2016): 1817–32. http://dx.doi.org/10.5194/amt-9-1817-2016.
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Abstract. A far infrared radiometer (FIRR) dedicated to measuring radiation emitted by clear and cloudy atmospheres was developed in the framework of the Thin Ice Clouds in Far InfraRed Experiment (TICFIRE) technology demonstration satellite project. The FIRR detector is an array of 80 × 60 uncooled microbolometers coated with gold black to enhance the absorptivity and responsivity. A filter wheel is used to select atmospheric radiation in nine spectral bands ranging from 8 to 50 µm. Calibrated radiances are obtained using two well-calibrated blackbodies. Images are acquired at a frame rate of 120 Hz, and temporally averaged to reduce electronic noise. A complete measurement sequence takes about 120 s. With a field of view of 6°, the FIRR is not intended to be an imager. Hence spatial average is computed over 193 illuminated pixels to increase the signal-to-noise ratio and consequently the detector resolution. This results in an improvement by a factor of 5 compared to individual pixel measurements. Another threefold increase in resolution is obtained using 193 non-illuminated pixels to remove correlated electronic noise, leading an overall resolution of approximately 0.015 W m−2 sr−1. Laboratory measurements performed on well-known targets suggest an absolute accuracy close to 0.02 W m−2 sr−1, which ensures atmospheric radiance is retrieved with an accuracy better than 1 %. Preliminary in situ experiments performed from the ground in winter and in summer on clear and cloudy atmospheres are compared to radiative transfer simulations. They point out the FIRR ability to detect clouds and changes in relative humidity of a few percent in various atmospheric conditions, paving the way for the development of new algorithms dedicated to ice cloud characterization and water vapor retrieval.
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Wang, Likun, Changyong Cao, and Pubu Ciren. "Assessing NOAA-16 HIRS Radiance Accuracy Using Simultaneous Nadir Overpass Observations from AIRS." Journal of Atmospheric and Oceanic Technology 24, no. 9 (September 1, 2007): 1546–61. http://dx.doi.org/10.1175/jtech2073.1.
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Abstract The High-Resolution Infrared Radiation Sounder (HIRS) has been carried on NOAA satellites for more than two decades, and the HIRS data have been widely used for geophysical retrievals, climate studies, and radiance assimilation for numerical weather prediction models. However, given the legacy of the filter-wheel radiometer originally designed in the 1970s, the HIRS measurement accuracy is neither well documented nor well understood, despite the importance of this information for data users, instrument manufacturers, and calibration scientists. The advent of hyperspectral sounders, such as the Atmospheric Infrared Sounder (AIRS), and intersatellite calibration techniques makes it possible to independently assess the accuracy of the HIRS radiances. This study independently assesses the data quality and calibration accuracy of HIRS by comparing the radiances between HIRS on NOAA-16 and AIRS on Aqua with simultaneous nadir overpass (SNO) observations for the year 2004. The results suggest that the HIRS radiometric bias relative to the AIRS-convolved HIRS radiance is on the order of ∼0.5 K, except channel 16, which has a bias of 0.8 K. For all eight spectrally overlapped channels, the observations by HIRS are warmer than the corresponding AIRS-convolved HIRS channel. Other than channel 16, the biases are temperature dependent. The root causes of the bias can be traced to a combination of the HIRS blackbody emissivity, nonlinearity, and spectral uncertainties. This study further demonstrates the utility of high-spectral-resolution radiance measurements for high-accuracy assessments of broadband radiometer calibration with the SNO observations.
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Jitsufuchi, Tetsuya. "Development of an Optical Multispectral Remote Sensing System for Measuring Volcanic Surface Phenomena – Promotion Project for Next Generation Volcano Research B2 (Subtopic 2-2)." Journal of Disaster Research 14, no. 5 (August 1, 2019): 728–43. http://dx.doi.org/10.20965/jdr.2019.p0728.
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In 2016, we launched the “Promotion Project for Next Generation Volcano Research B2 (Theme B: Development of Cutting-edge Volcano Observation Technology, subtheme 2: Development of Remote Sensing Techniques for Volcano Observation), subtopic 2-2 (Development of Remote Sensing Techniques for Surface Phenomena of Volcano)” under the “Integrated Program for Next Generation Volcano Research and Human Resources Development” [1], aiming at the development of an optical multispectral remote sensing system for measuring volcanic surface phenomena. With subtopic 2-2, we are planning to develop a new observation device called a surface phenomena imaging camera (SPIC), which is technically superior to current remote sensing techniques, i.e., optical remote observation techniques used to observe volcanic surface phenomena from aircrafts or ground. We are also aiming at applying the developed observation system to quantify volcanic activities and determine volcanic eruption potentials (degrees of urgency) or branching of event trees for volcanic crises with high accuracy, contributing to better predictions of volcanic eruption transitions. To achieve the above-mentioned aims, we started the development of the SPIC by equipping it with camera-type sensors, based on preliminary analyses of the experimental observations made with the airborne spectral imaging system ARTS-SE, which consists of a pushbroom scanner and a camera system, developed by the National Research Institute for Earth Science and Disaster Resilience in FY 2015. We have already developed its components, such as the prototype filter-type multiband cameras SPIC-UC, a prototype uncooled infrared camera, SPIC-C, a cooled camera, and SPIC-SS, a visible-light camera. The SPIC-UC is a two-band camera with the function of visualizing temperature and SO2 gas concentration distributions. The SPIC-C has the function of measuring temperatures between 2 and 1075◦C with high accuracy (noise equivalent temperature difference, NETD: 16 mK); it is equipped with a sensor and a filter wheel that work in the middle wave infrared region (MWIR). The SPIC-SS is a six-lens multiband camera system that estimates the measured images from multiband spectra (6 bands) to hyper spectra (300 bands). Further, we studied a method to estimate digital surface model with a ∼30-m error. As our plan has progressed as scheduled, we intend to complete the prototype SPIC by 2020.
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Gholizadeh, Asa, João A. Coblinski, Mohammadmehdi Saberioon, Eyal Ben-Dor, Ondřej Drábek, José A. M. Demattê, Luboš Borůvka, Karel Němeček, Sabine Chabrillat, and Julie Dajčl. "vis–NIR and XRF Data Fusion and Feature Selection to Estimate Potentially Toxic Elements in Soil." Sensors 21, no. 7 (March 30, 2021): 2386. http://dx.doi.org/10.3390/s21072386.
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Soil contamination by potentially toxic elements (PTEs) is intensifying under increasing industrialization. Thus, the ability to efficiently delineate contaminated sites is crucial. Visible–near infrared (vis–NIR: 350–2500 nm) and X-ray fluorescence (XRF: 0.02–41.08 keV) spectroscopic techniques have attracted tremendous attention for the assessment of PTEs. Recently, the application of fused vis–NIR and XRF spectroscopy, which is based on the complementary effect of data fusion, is also increasing. Moreover, different data manipulation methods, including feature selection approaches, affect the prediction performance. This study investigated the feasibility of using single and fused vis–NIR and XRF spectra while exploring feature selection algorithms for the assessment of key soil PTEs. The soil samples were collected from one of the most heavily polluted areas of the Czech Republic and scanned using laboratory vis–NIR and XRF spectrometers. Univariate filter (UF) and genetic algorithm (GA) were used to select the bands of greater importance for the PTE prediction. Support vector machine (SVM) was then used to train the models using the full-range and feature-selected spectra of single sensors and their fusion. It was found that XRF spectra alone (primarily GA-selected) performed better than single vis–NIR and fused spectral data for predictions of PTEs. Moreover, the prediction models that were derived from the fused data set (particularly the GA-selected) enhanced the models’ accuracies as compared with the single vis–NIR spectra. In general, the results suggest that the GA-selected spectra obtained from the single XRF spectrometer (for As and Pb) and from the fusion of vis–NIR and XRF (for Pb) are promising for accurate quantitative estimation detection of the mentioned PTEs.
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Dong, Chengli, Michael D. O'Keefe, Hani Elshahawi, Mohamed Hashem, Stephen M. Williams, Dag Stensland, Peter S. Hegeman, et al. "New Downhole-Fluid-Analysis Tool for Improved Reservoir Characterization." SPE Reservoir Evaluation & Engineering 11, no. 06 (December 1, 2008): 1107–16. http://dx.doi.org/10.2118/108566-pa.
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Summary Downhole fluid analysis (DFA) has emerged as a key technique for characterizing the distribution of reservoir-fluid properties and determining zonal connectivity across the reservoir. Information from profiling the reservoir fluids enables sealing barriers to be proved and compositional grading to be quantified; this information cannot be obtained from conventional wireline logs. The DFA technique has been based largely on optical spectroscopy, which can provide estimates of filtrate contamination, gas/oil ratio (GOR), pH of formation water, and a hydrocarbon composition in four groups: methane (C1), ethane to pentane (C2-5), hexane and heavier hydrocarbons (C6+), and carbon dioxide (CO2). For single-phase assurance, it is possible to detect gas liberation (bubblepoint) or liquid dropout (dewpoint) while pumping reservoir fluid to the wellbore, before filling a sample bottle. In this paper, a new DFA tool is introduced that substantially increases the accuracy of these measurements. The tool uses a grating spectrometer in combination with a filter-array spectrometer. The range of compositional information is extended from four groups to five groups: C1, ethane (C2), propane to pentane (C3-5), C6+, and CO2. These spectrometers, together with improved compositional algorithms, now make possible a quantitative analysis of reservoir fluid with greater accuracy and repeatability. This accuracy enables comparison of fluid properties between wells for the first time, thus extending the application of fluid profiling from a single-well to a multiwall basis. Field-based fluid characterization is now possible. In addition, a new measurement is introduced--in-situ density of reservoir fluid. Measuring this property downhole at reservoir conditions of pressure and temperature provides important advantages over surface measurements. The density sensor is combined in a package that includes the optical spectrometers and measurements of fluid resistivity, pressure, temperature, and fluorescence that all play a vital role in determining the exact nature of the reservoir fluid. Extensive tests at a pressure/volume/temperature (PVT) laboratory are presented to illustrate sensor response in a large number of live-fluid samples. These tests of known fluid compositions were conducted under pressurized and heated conditions to simulate reservoir conditions. In addition, several field examples are presented to illustrate applicability in different environments. Introduction Reservoir-fluid samples collected at the early stage of exploration and development provide vital information for reservoir evaluation and management. Reservoir-fluid properties, such as hydrocarbon composition, GOR, CO2 content, pH, density, viscosity, and PVT behavior are key inputs for surface-facility design and optimization of production strategies. Formation-tester tools have proved to be an effective way to obtain reservoir-fluid samples for PVT analysis. Conventional reservoir-fluid analysis is conducted in a PVT laboratory, and it usually takes a long time (months) before the results become available. Also, miscible contamination of a fluid sample by drilling-mud filtrate reduces the utility of the sample for subsequent fluid analyses. However, the amount of filtrate contamination can be reduced substantially by use of focused-sampling cleanup introduced recently in the next-generation wireline formation testers (O'Keefe et al. 2008). DFA tools provide results in real time and at reservoir conditions. Current DFA techniques use absorption spectroscopy of reservoir fluids in the visible-to-near-infrared (NIR) range. The formation-fluid spectra are obtained in real time, and fluid composition is derived from the spectra on the basis of C1, C2-5, C6+, and CO2; then, GOR of the fluid is estimated from the derived composition (Betancourt et al. 2004; Fujisawa et al. 2002; Dong et al. 2006; Elshahawi et al. 2004; Fujisawa et al. 2008; Mullins et al. 2001; Smits et al. 1995). Additionally, from the differences in absorption spectrum between reservoir fluid and filtrate of oil-based mud (OBM) or water-based mud (WBM), fluid-sample contamination from the drilling fluid is estimated (Mullins et al. 2000; Fadnes et al. 2001). With the DFA technique, reservoir-fluid samples are analyzed before they are taken, and the quality of fluid samples is improved substantially. The sampling process is optimized in terms of where and when to sample and how many samples to take. Reservoir-fluid characterization from fluid-profiling methods often reveals fluid compositional grading in different zones, and it also helps to identify reservoir compartmentalization (Venkataramanan et al. 2008). A next-generation tool has been developed to improve the DFA technique. This DFA tool includes new hardware that provides more-accurate and -detailed spectra, compared to the current DFA tools, and includes new methods of deriving fluid composition and GOR from optical spectroscopy. Furthermore, the new DFA tool includes a vibrating sensor for direct measurement of fluid density and, in certain environments, viscosity. The new DFA tool provides reservoir-fluid characterization that is significantly more accurate and comprehensive compared to the current DFA technology.
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Lee, Hwa-Seub, Gyu-Weon Hwang, Tae-Yeon Seong, Jongkil Park, Jae Wook Kim, Won Mok Kim, Inho Kim, and Kyeong-Seok Lee. "Design of mid-infrared filter array based on plasmonic metal nanodiscs array and its application to on-chip spectrometer." Scientific Reports 11, no. 1 (June 9, 2021). http://dx.doi.org/10.1038/s41598-021-91762-7.
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AbstractMid-infrared wavelengths are called the molecular fingerprint region because it contains the fundamental vibrational modes inherent to the substances of interest. Since the mid-infrared spectrum can provide non-destructive identification and quantitative analysis of unknown substances, miniaturized mid-infrared spectrometers for on-site diagnosis have attained great concern. Filter-array based on-chip spectrometer has been regarded as a promising alternative. In this study, we explore a way of applying a pillar-type plasmonic nanodiscs array, which is advantageous not only for excellent tunability of resonance wavelength but also for 2-dimensional integration through a single layer process, to the multispectral filter array for the on-chip spectrometer. We theoretically and experimentally investigated the optical properties of multi-periodic triangular lattices of metal nanodiscs array that act as stopband filters in the mid-infrared region. Soft-mold reverse nanoimprint lithography with a subsequent lift-off process was employed to fabricate the multispectral filter array and its filter function was successfully extracted using a Fourier transform infrared microscope. With the measured filter function, we tested the feasibility of target spectrum reconstruction using a Tikhonov regularization method for an ill-posed linear problem and evaluated its applicability to the infrared spectroscopic sensor that monitors an oil condition. These results not only verify that the multispectral filter array composed of stopband filters based on the metal nanodiscs array when combined with the spectrum reconstruction technique, has great potential for use to a miniaturized mid-infrared on-chip spectrometer, but also provide effective guidance for the filter design.
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Richter, Daniel, Andreas Richter, and Kay Dornich. "Lexsyg smart — a luminescence detection system for dosimetry, material research and dating application." Geochronometria 42, no. 1 (December 4, 2015). http://dx.doi.org/10.1515/geochr-2015-0022.
Full textAbstract:
Abstract Following the luminescence system lexsyg research, which was designed for research, the luminescence reader lexsyg smart for the application of luminescence detection was developed by Freiberg Instruments. It is suited for routine measurements of luminescence (thermoluminescence, photoluminescence, photon-stimulated, optically stimulated and infrared stimulated luminescence) for a wide range of materials because of the availability of several stimulation sources. The possibility for user definition and change of most parameters provides a great deal of flexibility and also allows re-search applications. While detection is limited to a single unit and sample storage to 40 positions, the lexsyg smart is much faster in aliquot transportation compared to the lexsyg research, and allows fast mass measurements in luminescence dating, retrospective and personal dosimetry, etc. Cross talk of optical stimulation is absent and cross-irradiation is negligible from the single radioactive source (α, β or x-ray) because of a disconnected sample storage wheel from the measurement chamber, which has a small volume and therefore gas consumption is small. Thermoluminescence measure-ments and pre-heatings are possible with a versatile heater, which can be programmed for linear/non-linear heating at varying rates and durations for an almost unlimited number of steps. Optical excita-tion for up to three wavelength bands (violet, blue, green, yellow, infrared) is provided from high power LEDs or laser diodes, with an optional filter wheel to vary detection wavelength bands accord-ing the material specific requirements. Either can be programmed to change at almost any time within measurement sequences.