Intensity Calibration Research Articles

A method for the quantitative analysis of gaseous mixtures by online mass spectrometry

Online mass spectrometry is a widely used technique in tracking composition changes of gas mixture during the reaction. This paper reports a quantification analysis method of gas mixtures detected by an online mass spectrometry. In this analysis, a mass spectrum correction coefficient matrix is generated based on the calibration of mass spectrometry intensities of premixed calibration gas mixtures, and then the concentrations of gas components are calculated from this matrix by subtracting the interferences of other components with overlapped peaks. The accuracy of obtained results were verified by online gas chromatography in the meanwhile. The detailed error analysis was supplied in a separate supplement document. This method can be applied on the online detection of gas phase reactions with promising advantages to analysis of online gas chromatography, which is suitable for analysis of spectra overlaps (a given m/z signal contributed from two or multiple components) and kinetic studies.

Study of spatiotemporally resolved temperature field and heat transfer in liquid film using PLIF

The liquid film is extensively used in various industrial production processes due to its excellent heat transfer efficiency, especially in the evaporating and cooling process, but little experimental data are acquired to represent the temperature field and heat transfer parameters with high spatiotemporal resolution. In this paper, planar laser-induced fluorescence (PLIF) technique was first described for the investigation of the temperature field of the liquid film in pipeline. An extraction method of fluorescence intensity based on the optimized average gray values, and a temperature field measurement method based on the two-dimensional planar laser intensity calibration were proposed, which effectively improved the temperature measurement accuracy of PLIF. The convective heat transfer coefficient of liquid film was calculated from the temperature field with high spatiotemporal resolution based on the heat transfer theory. In addition, the accuracy of PLIF temperature measurement was analyzed, and the relationships between the heat transfer coefficient and Reynolds number as well as heat transfer temperature difference were investigated experimentally.

Quantitative SERS by electromagnetic enhancement normalization with carbon nanotube as an internal standard.

Quantitative surface-enhanced Raman scattering (SERS) in practical applications still remain unresolved, mainly due to low reproducibility relying on the quality of the SERS substrates. In this paper, a carbon nanotube and Ag nanoparticles composite (CNT/AgNPs) is reported, and the carbon nanotube is as an internal standard for the calibration of SERS intensity of analyte molecules. The quantification of analyte molecules rhodamine 6G (R6G) is demonstrated in an aqueous solution with the concentration of 10-9 to 10-7 M. Raman mapping is used to investigate the stability of SERS spectra in a large scanning area, and the corresponding relative standard deviation (RSD) is calculated. SERS mapping reveals that the uniformity of Raman enhancement is improved through the build-in calibration with 2D Raman peak of CNT. Meanwhile, CNT/AgNPs samples are used to detect N2 in natural air, indicating that such self-calibration method can improve the reliability of the SERS analysis.

Glassy carbon, NIST Standard Reference Material (SRM 3600): hydrogen content, neutron vibrational density of states and heat capacity.

Commercial glassy carbon plates being used as absolute intensity calibration standards in small-angle X-ray scattering applications (NIST SRM 3600) have been characterized in several recent publications. This contribution adds to the characterization by measuring the hydrogen content of a plate to be (4.8 ± 0.2)× 10-4 (mol H)/(mol C), and by measuring the vibrational spectrum by neutron inelastic scattering. The spectrum bears a strong resemblance to published measurements on graphite, allowing the identification of several spectral features. The measured spectrum is used to calculate the heat capacity of low-hydrogen-content glassy carbon for comparison with measurements reported here from 20 to 295 K.

Using XRF and ICP-OES in Biosorption Studies

In this work, a method of recalculation of results of X-ray fluorescence (XRF) technique to Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) method was elaborated for biosorption studies. Equations that calibrate XRF to ICP-OES were determined, as a biosorbent strawberry, blackcurrant and raspberry seeds after supercritical CO2 extraction were used. ICP-OES showed a better precision and lower detection limits than XRF. The latter technique is cheaper, requires minimal sample preparation and gives faster results. Linear regression of the data gave almost 1:1 correlations without additional correction (for Cu r2 = 0.9998, Mn r2 = 0.807, Zn r2 = 0.979). Calibration and quantification of intensities of XRF was obtained using ICP-OES measurements after samples digestion with HNO3 in a microwave system. High positive correlations were estimated for Cu, Mn, Zn. It was demonstrated that XRF technique can be used together with other well established techniques (ICP-OES) to produce quantitative data from biosorption studies. Elaboration of cheap and quick analytical methodology is an important aspect in development of new processes and products based on biosorption process.

Radiometer for Real-time Calibration of the Xenon Arc Lamps

A standard radiometer which can be used for real-time calibration of the irradiance of Artificial Accelerated Weathering Apparatus of Xenon Arc Lamps is developed. In the paper we study the zero error, relative measurement error, cosine response, nonlinearity and fatigue property of the standard radiometer. The instrument performance should meet the requirements of real-time calibration of radiation intensity of Xenon Arc Lamps. The measured results of the real-time radiometer coincide with standard radiometers.

Spherical target-based calibration of terrestrial laser scanner intensity. Application to colour information computation

Terrestrial Laser Scanning (TLS) acquires for each scanned point its position and an intensity. Intensity of TLS is based on a measure of the electronic signal strength which is obtained by converting and amplifying the backscattered optical power of the emitted signal. In this paper, theoretical radar equation is established and particular attention is given to the necessary assumptions. A low-cost intensity calibration method is proposed that provides measurements insensitive to range and incidence angle. This process is data driven without simplifying assumption about radiometrical properties of the spherical calibration target. For the commercial device considered, the laser wavelength is 532 nm. It enables us to measure green levels. Intensity is interpreted for each point of 3D clouds in terms of green level in sRGB colour space viewed under CIE standard illuminant D65. Applications are realized on a data set acquired at Amiens cathedral. There is no more shading or multi-exposure effects compared with high-resolution camera colourisation.

Absolute intensity calibration and application at BSRF SAXS station

Small Angle X-ray Scattering (SAXS) is a common physical method to characterize the structure of materials on the nanoscale. The absolute scattering intensity contains quantitative information related to the mass and density of materials. We studied the absolute scattering intensity calibration method on the 1W2A SAXS station at Beijing Synchrotron Radiation Facility (BSRF) with standards such as glassy carbon and water, and further applied the method to determine the molecular weight of ovalbumin and the porosity of anthracite coal during pyrolysis.

Investigation on heat transfer characteristics of falling liquid film by planar laser-induced fluorescence

Falling liquid film evaporation is widely used in many industrial applications due to its efficient heat transfer characteristics. In this paper, a quantitative thermometry technique based on planar laser-induced fluorescence (PLIF) was applied to analyze the heat transfer characteristics of falling liquid film with high spatiotemporal resolution. The optimal gray values extraction method was proposed for the calibration of temperature-fluorescence intensity. The quantitative calculation of convective heat transfer coefficient and Nusselt number were conducted based on the liquid film temperature field distribution which was measured by PLIF and the trends of them were shown in different range of temperature and Reynolds number. Finally, the heat transfer correlation was proposed and the heat transfer characteristics of falling liquid film was analyzed. The quantitative correlations analysis shows that most of the correlations are more suitable for the liquid film with low Prandtl number, and the Nusselt number tends to decrease when the temperature of the liquid film increases at the constant flow rate.

AUTOMATIC EXTRACTION OF ROAD MARKINGS FROM MOBILE LASER-POINT CLOUD USING INTENSITY DATA

Abstract. With the development of intelligent transportation, road’s high precision information data has been widely applied in many fields. This paper proposes a concise and practical way to extract road marking information from point cloud data collected by mobile mapping system (MMS). The method contains three steps. Firstly, road surface is segmented through edge detection from scan lines. Then the intensity image is generated by inverse distance weighted (IDW) interpolation and the road marking is extracted by using adaptive threshold segmentation based on integral image without intensity calibration. Moreover, the noise is reduced by removing a small number of plaque pixels from binary image. Finally, point cloud mapped from binary image is clustered into marking objects according to Euclidean distance, and using a series of algorithms including template matching and feature attribute filtering for the classification of linear markings, arrow markings and guidelines. Through processing the point cloud data collected by RIEGL VUX-1 in case area, the results show that the F-score of marking extraction is 0.83, and the average classification rate is 0.9.

Local thermodynamic equilibrium in a laser-induced plasma evidenced by blackbody radiation

We show that the plasma produced by laser ablation of solid materials in specific conditions has an emission spectrum that is characterized by the saturation of the most intense spectral lines at the blackbody radiance. The blackbody temperature equals the excitation temperature of atoms and ions, proving directly and unambiguously a plasma in local thermodynamic equilibrium. The present investigations take benefit from the very rich and intense emission spectrum generated by ablation of a nickel-chromium-molybdenum alloy. This alternative and direct proof of the plasma equilibrium state re-opens the perspectives of quantitative material analyses via calibration-free laser-induced breakdown spectroscopy. Moreover, the unique properties of this laser-produced plasma promote its use as radiation standard for intensity calibration of spectroscopic instruments.

Sub-millisecond electron density profile measurement at the JET tokamak with the fast lithium beam emission spectroscopy system.

Diagnostic alkali atom (e.g., lithium) beams are routinely used to diagnose magnetically confined plasmas, namely, to measure the plasma electron density profile in the edge and the scrape off layer region. A light splitting optics system was installed into the observation system of the lithium beam emission spectroscopy diagnostic at the Joint European Torus (JET) tokamak, which allows simultaneous measurement of the beam light emission with a spectrometer and a fast avalanche photodiode (APD) camera. The spectrometer measurement allows density profile reconstruction with ∼10 ms time resolution, absolute position calculation from the Doppler shift, spectral background subtraction as well as relative intensity calibration of the channels for each discharge. The APD system is capable of measuring light intensities on the microsecond time scale. However ∼100 μs integration is needed to have an acceptable signal to noise ratio due to moderate light levels. Fast modulation of the beam up to 30 kHz is implemented which allows background subtraction on the 100 μs time scale. The measurement covers the 0.9 < ρpol < 1.1 range with 6-10 mm optical resolution at the measurement location which translates to 3-5 mm radial resolution at the midplane due to flux expansion. An automated routine has been developed which performs the background subtraction, the relative calibration, and the comprehensive error calculation, runs a Bayesian density reconstruction code, and loads results to the JET database. The paper demonstrates the capability of the APD system by analyzing fast phenomena like pellet injection and edge localized modes.

Quantitative analysis of image quality for acceptance and commissioning of an MRI simulator with a semiautomatic method.

Magnetic Resonance Imaging (MRI) simulation differs from diagnostic MRI in purpose, technical requirements, and implementation. We propose a semiautomatic method for image acceptance and commissioning for the scanner, the radiofrequency (RF) coils, and pulse sequences for an MRI simulator. The ACR MRI accreditation large phantom was used for image quality analysis with seven parameters. Standard ACR sequences with a split head coil were adopted to examine the scanner's basic performance. The performance of simulation RF coils were measured and compared using the standard sequence with different clinical diagnostic coils. We used simulation sequences with simulation coils to test the quality of image and advanced performance of the scanner. Codes and procedures were developed for semiautomatic image quality analysis. When using standard ACR sequences with a split head coil, image quality passed all ACR recommended criteria. The image intensity uniformity with a simulation RF coil decreased about 34% compared with the eight‐channel diagnostic head coil, while the other six image quality parameters were acceptable. Those two image quality parameters could be improved to more than 85% by built‐in intensity calibration methods. In the simulation sequences test, the contrast resolution was sensitive to the FOV and matrix settings. The geometric distortion of simulation sequences such as T1‐weighted and T2‐weighted images was well‐controlled in the isocenter and 10 cm off‐center within a range of ±1% (2 mm). We developed a semiautomatic image quality analysis method for quantitative evaluation of images and commissioning of an MRI simulator. The baseline performances of simulation RF coils and pulse sequences have been established for routine QA.

Multiplexed direct-frequency-comb Vernier spectroscopy of carbon dioxide 2ν1 + ν3 ro-vibrational combination band.

We investigated a set of nineteen 12C16O2 transitions of the 2ν1 + ν3 ro-vibrational band in the spectral region from 5064 to 5126 cm-1 at different pressures, using frequency-comb Vernier spectroscopy. Our spectrometer enabled the systematic acquisition of molecular absorption profiles with high precision. Spectroscopic parameters, namely, transition frequency, linestrength, and self-pressure broadening coefficient, have been accurately determined by using a global fit procedure. These data are in agreement with theoretical values contained in HITRAN2016 database [I. E. Gordon et al., J. Quant. Spectrosc. Radiat. Transfer 203, 3-69 (2017)] at the same precision level. A moderate improvement of the line intensity determinations, by a factor 1.5 in the best case [P(10) transition at 5091.6 cm-1], should be noticed, projecting direct-comb-Vernier-spectroscopy as an adequate tool for spectral intensity calibration.

Absolute laser-intensity measurement and online monitor calibration using a calorimeter at a soft X-ray free-electron laser beamline in SACLA

This paper reports measurement of the absolute intensity of free-electron laser (FEL) and calibration of online intensity monitors for a brand-new FEL beamline BL1 at SPring-8 Angstrom Compact free-electron LAser (SACLA) in Japan. To measure the absolute intensity of FEL, we used a room-temperature calorimeter originally developed for FELs in the hard X-ray range. By using the calorimeter, we calibrated online intensity monitors of BL1, gas monitors (GMs), based on the photoionization of argon gas, in the photon energy range from 25 eV to 150 eV. A good correlation between signals obtained from the calorimeter and GMs was observed in the pulse energy range from 1 μJ to 100 μJ, where the upper limit is nearly equal to the maximum pulse energy at BL1. Moreover, the calibration result of the GMs, measured in terms of the spectral responsivity, demonstrates a characteristic photon-energy dependence owing to the occurrence of the Cooper minimum in the total ionization cross-section of argon gas. These results validate the feasibility of employing the room-temperature calorimeter in the measurement of absolute intensity of FELs over the specified photon energy range.

Development and characterization of an inexpensive single-particle fluorescence spectrometer for bioaerosol monitoring

Laser-induced fluorescence (LIF) techniques to analyze atmospheric aerosols are commonly applied for research and human exposure monitoring, but are very expensive or offer poor spectral resolution. Here, we discuss how a recently proposed instrument can acquire resolved fluorescence spectra from many individual particles in a single camera image using four excitation wavelengths matched with common biological fluorophores for particle discrimination at lower cost. We discuss emission intensity calibration and demonstrate spectral differentiation among four species of pollen. These data provide context for how the instrument could be developed for pollen and mold-spore detection or for use by citizen scientists.

Optimizing Data Reduction Procedures in Spatial Heterodyne Raman Spectroscopy with Applications to Planetary Surface Analogs.

A spatial heterodyne Raman spectrometer (SHRS) is a variant of a Michelson interferometer in which the mirrors of a Michelson are replaced with two stationary diffraction gratings. When light enters the SHRS, it is reflected off of diffraction gratings at frequency-dependent angles that produce crossed wavefronts in space that can be imaged using a plane array detector. The crossed wavefronts, which represent a superposition of interference fringes, are converted to a Raman spectrum upon applying a Fourier transform. In this work, a new approach to intensity calibration is discussed that originates from modeling the shot noise produced by the SHRS and converting the real noise to idealized white noise as predicted by theory. This procedure has two effects. First, the technique produces Raman spectra with white noise. Second, when the mean of the noise is normalized to one, the technique produces Raman spectra where the intensity axis is equivalent to signal-to-noise ratio. The data reduction technique is then applied to the measurement of materials of interest to the planetary science community, including minerals and inorganic salts, at a distance of 5 m from the collecting optic.

Automated image quality assessment for chest CT scans.

Medical image quality needs to be maintained at standards sufficient for effective clinical reading. Automated computer analytic methods may be applied to medical images for quality assessment. For chest CT scans in a lung cancer screening context, an automated quality assessment method is presented that characterizes image noise and image intensity calibration. This is achieved by image measurements in three automatically segmented homogeneous regions of the scan: external air, trachea lumen air, and descending aorta blood. Profiles of CT scanner behavior are also computed. The method has been evaluated on both phantom and real low-dose chest CT scans and results show that repeatable noise and calibration measures may be realized by automated computer algorithms. Noise and calibration profiles show relevant differences between different scanners and protocols. Automated image quality assessment may be useful for quality control for lung cancer screening and may enable performance improvements to automated computer analysis methods.

光学三维扫描仪光强传递函数的测量和校正

光学三维扫描仪光强传递函数的测量和校正

Direct intensity calibration of X-ray grazing-incidence microscopes with home-lab source.

Direct intensity calibration of X-ray grazing-incidence microscopes is urgently needed in quantitative studies of X-ray emission from laser plasma sources in inertial confinement fusion. The existing calibration methods for single reflecting mirrors, crystals, gratings, filters, and X-ray detectors are not applicable for such X-ray microscopes due to the specific optical structure and the restrictions of object-image relation. This article presents a reliable and efficient method that can be performed using a divergent X-ray source and an energy dispersive Si-PIN (silicon positive-intrinsic-negative) detector in an ordinary X-ray laboratory. The transmission theory of X-ray flux in imaging diagnostics is introduced, and the quantities to be measured are defined. The calibration method is verified by a W/Si multilayer-coated Kirkpatrick-Baez microscope with a field of view of ∼95 μm at 17.48 keV. The mirror reflectance curve in the 1D coordinate is drawn with a peak value of 20.9% and an uncertainty of ∼6.0%.