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Enumeration	Reference	Cover	Find
1.	Seoane Martinez, Fernando, 1976, et al. (author) Simple voltage-controlled current source for wideband electrical bioimpedance spectroscopy: circuit dependences and limitations 2011 In: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 22:11 Journal article (peer-reviewed)abstract In this work, the single Op-Amp with load-in-the-loop topology as a current source is revisited. This circuit topology was already used as a voltage-controlled current source (VCCS) in the 1960s but was left unused when the requirements for higher frequency arose among the applications of electrical bioimpedance (EBI). The aim of the authors is not only limited to show that with the currently available electronic devices it is perfectly viable to use this simple VCCS topology as a working current source for wideband spectroscopy applications of EBI, but also to identify the limitations and the role of each of the circuit components in the most important parameter of a current for wideband applications: the output impedance. The study includes the eventual presence of a stray capacitance and also an original enhancement, driving with current the VCCS. Based on the theoretical analysis and experimental measurements, an accurate model of the output impedance is provided, explaining the role of the main constitutive elements of the circuit in the source's output impedance. Using the topologies presented in this work and the proposed model, any electronic designer can easily implement a simple and efficient current source for wideband EBI spectroscopy applications, e. g. in this study, values above 150 k Omega at 1 MHz have been obtained, which to the knowledge of the authors are the largest values experimentally measured and reported for a current source in EBI at this frequency.
2.	Hagqvist, Petter, 1986, et al. (author) Emissivity compensated spectral pyrometry-algorithm and sensitivity analysis 2014 In: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 25:2 Journal article (peer-reviewed)abstract In order to solve the problem of non-contact temperature measurements on an object with varying emissivity, a new method is herein described and evaluated. The method uses spectral radiance measurements and converts them to temperature readings. It proves to be resilient towards changes in spectral emissivity and tolerates noisy spectral measurements. It is based on an assumption of smooth changes in emissivity and uses historical values of spectral emissivity and temperature for estimating current spectral emissivity. The algorithm, its constituent steps and accompanying parameters are described and discussed. A thorough sensitivity analysis of the method is carried out through simulations. No rigorous instrument calibration is needed for the presented method and it is therefore industrially tractable.
3.	Hagqvist, Petter, 1986-, et al. (author) Emissivity compensated spectral pyrometry for varying emissivity metallic measurands 2014 In: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 25:2 Journal article (peer-reviewed)abstract A novel method for converting electromagnetic spectral radiance information into temperature measurements is presented. It allows for varying spectral emissivity of the metallic measurand during the course of the measurement. Such variations are due to, e. g., thermal oxidation or temperature dependent emissivity. Based on a requirement that emissivity changes with time and temperature are smooth, it is assumed that an emissivity estimate at one sample instance can be derived from the estimated emissivity found at the previous samples together with updated spectral information. This leads to successive recalculations of spectral emissivity together with corresponding temperature values. The proposed algorithm has been proven to give accurate temperature estimates from a measurement based on the data captured by a standard UV-Vis spectrophotometer even for an oxidizing Ti-6Al-4V specimen in a temperature range between 900 and 1400 K. The method however, is not limited to these wavelength or temperature ranges.
4.	Jansson, Anna, 1985, et al. (author) Monitoring the osmotic response of single yeast cells through force measurement in the environmental scanning electron microscope 2014 In: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 25:2 Journal article (peer-reviewed)abstract We present a measurement system that combines an environmental scanning electron microscope (ESEM) and an atomic force microscope (AFM). This combination enables studies of static and dynamic mechanical properties of hydrated specimens, such as individual living cells. The integrated AFM sensor provides direct and continuous force measurement based on piezoresistive force transduction, allowing the recording of events in the millisecond range. The in situ ESEM-AFM setup was used to study Pichia pastoris wild-type yeast cells. For the first time, a quantified measure of the osmotic response of an individual yeast cell inside an ESEM is presented. With this technique, cell size changes due to humidity variations can be monitored with nanometre accuracy. In addition, mechanical properties were extracted from load-displacement curves. A Young's modulus of 13-15 MPa was obtained for the P. pastoris yeast cells. The developed method is highly interesting as a complementary tool for the screening of drugs directed towards cellular water transport activity and provides new possibilities of studying mechanosensitive regulation of aquaporins.
5.	Knappe, Christoph, et al. (author) Enhanced color ratio calibration approach for two-dimensional surface thermometry using laser-induced phosphorescence 2013 In: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 24:8 Journal article (peer-reviewed)abstract An alternative concept for calibrating spectral image intensity ratios is described, which provides simple, but effective means of compensation for systematic errors, caused by nonlinearities in signal detection. The method relies on image segmentation by means of signal thresholds, where pixels are organized into different subgroups according to their corresponding signal count value. Instead of deﬁning one global spectral ratio per calibration temperature, the phosphor-coated target surface is illuminated inhomogeneously and resulting image ratios are calibrated individually for each pixel intensity subgroup. This allows the exploitation of high intensity regions on the camera chip which offer great precision advantages, but suffer from systematic errors caused by signal nonlinearities. Temperature calibration data of BaMg2Al16O27:Eu in the temperature range between 270 and 470 K was used to assess and compare the potential of both calibration approaches. In comparison to the conventional, e.g. global calibration approach, accuracy improvements of up to 39% were gained even while keeping average signal intensities below 15% of the detector’s full dynamic range. Image ratio evaluations, based on segregated pixel subgroups, could help improve measurement accuracy also for other techniques, relying on the calibration of measured quantities. In two-dimensional phosphor thermometry, it helps bridge the current precision gap between two-color ratio methods and more elaborate lifetime-imaging approaches.
6.	Buendia, Ruben, 1982, et al. (author) Experimental Validation of a Method for Removing the Capacitive Leakage Artifact from Electrical Bioimpedance Spectroscopy Measurements 2010 In: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 21:11, s. 115802- Journal article (peer-reviewed)abstract Often when performing electrical bioimpedance (EBI) spectroscopy measurements, the obtained EBI data present a hook-like deviation, which is most noticeable at high frequencies in the impedance plane. The deviation is due to a capacitive leakage effect caused by the presence of stray capacitances. In addition to the data deviation being remarkably noticeable at high frequencies in the phase and the reactance spectra, the measured EBI is also altered in the resistance and the modulus. If this EBI data deviation is not properly removed, it interferes with subsequent data analysis processes, especially with Cole model-based analyses. In other words, to perform any accurate analysis of the EBI spectroscopy data, the hook deviation mustbe properly removed. Td compensation is a method used to compensate the hook deviation present in EBI data; it consists of multiplying the obtained spectrum, Zmeas(ω), by a complex exponential in the form of exp(–jωTd). Although the method is well known and accepted, Td compensation cannot entirely correct the hook-like deviation; moreover, it lacks solid scientific grounds. In this work, the Td compensation method is revisited, and it is shown that it should not be used to correct the effect of a capacitive leakage; furthermore, a more developed approach for correcting the hook deviation caused by the capacitive leakage is proposed. The method includes a novel correcting expression and a process for selecting the proper values of expressions that are complex and frequency dependent. The correctness of the novel method is validated with the experimental data obtained from measurements from three different EBI applications. The obtained results confirm the sufficiency and feasibility of the correcting method.
7.	De Carlo, Francesco, et al. (author) TomoBank : A tomographic data repository for computational x-ray science 2018 In: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 29:3 Journal article (peer-reviewed)abstract There is a widening gap between the fast advancement of computational methods for tomographic reconstruction and their successful implementation in production software at various synchrotron facilities. This is due in part to the lack of readily available instrument datasets and phantoms representative of real materials for validation and comparison of new numerical methods. Recent advancements in detector technology have made sub-second and multi-energy tomographic data collection possible (Gibbs et al 2015 Sci. Rep. 5 11824), but have also increased the demand to develop new reconstruction methods able to handle in situ (Pelt and Batenburg 2013 IEEE Trans. Image Process. 22 5238-51) and dynamic systems (Mohan et al 2015 IEEE Trans. Comput. Imaging 1 96-111) that can be quickly incorporated in beamline production software (Gürsoy et al 2014 J. Synchrotron Radiat. 21 1188-93). The x-ray tomography data bank, tomoBank, provides a repository of experimental and simulated datasets with the aim to foster collaboration among computational scientists, beamline scientists, and experimentalists and to accelerate the development and implementation of tomographic reconstruction methods for synchrotron facility production software by providing easy access to challenging datasets and their descriptors.
8.	Feuk, Henrik, et al. (author) Automated Phosphor Thermometry Lifetime Calibration of Multiple Phosphors and Emission Lines to above 1900 K 2022 In: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 33:12 Journal article (peer-reviewed)abstract A method is specified which enables lifetime calibration of multiple phosphors and emission lines at the same time to temperatures above 1900 K. The experimental setup and algorithm used for data collection and experimental equipment control are described. The phosphors were coated on an alumina oxide disc and the reference temperature was measured using three type B thermocouples. The algorithm automates the data collection process such that no input from an operator is required during operation. The potential systematic error in calibration temperature was evaluated and was less than 1% around 1400 K.
9.	Feuk, Henrik, et al. (author) Sources of error for single-shot PMT-based phosphor thermometry in harsh conditions 2021 In: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 32:8 Journal article (peer-reviewed)abstract This study investigates photomultiplier tube (PMT) nonlinearities, relevant for lifetime phosphor thermometry, at various decay times to assess and minimize the impact on temperature measurement accuracy. The focus is single-shot measurements performed in harsh environments where phosphor signal attenuation often is a concern. The sensitivity of decay time measurements to changing phosphorescence intensity is therefore investigated. The experimental results show that for the studied phosphors and detectors, shorter decay times between 20 ns and 6 µs, saturation effects in the PMTs decreased the measured decay time with increasing signal attenuation. For longer phosphorescence decay times, in the millisecond regime, nonlinearity effects led to an increase in the measured decay time with increasing signal attenuation. The specific detector nonlinearity response will vary among detectors, but the introduced methodology for detector analysis is a useful resource for assessing and improving accuracy in lifetime phosphor thermometry measurements.
10.	Feuk, Henrik, et al. (author) Upconversion phosphor thermometry for use in thermal barrier coatings 2023 In: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 34:6 Journal article (peer-reviewed)abstract Measuring the temperature below the surface of a thermal barrier coating (TBC) using a thin phosphor layer is challenging primarily due to the absorption and scattering of laser excitation light and phosphor luminescence as they propagate through the coating. One way to increase phosphor luminescence could be to use upconversion phosphor thermometry, which is investigated in the current study. It is attractive because using longer excitation wavelengths reduces the absorption and scattering in TBCs as 8% wt. yttria-stabilize zirconia (8YSZ) generally has lower scattering and absorption coefficients around 1000 nm than at 532 and 355 nm. Therefore, the viability of upconversion to measure the temperature at the bottom of a TBC was evaluated for the first time and was compared with the more conventional downconversion phosphor thermometry. The current work involved an experimental study of several phosphors with lanthanides doped in the 8YSZ host, which were excited through downconversion by pulsed 355 nm and 532 nm laser light and through upconversion with 965 nm laser light. The YSZ:Er,Yb and YSZ:Ho,Yb phosphors show promise for upconversion phosphor thermometry. The experimentally acquired optical phosphor characteristics were used to simulate laser light and phosphor luminescence propagation in TBCs using Kubelka–Munk theory. This was to evaluate the signal strength with upconversion excitation compared to downconversion excitation. Upconversion excitation resulted greater signal strength from an embedded phosphor layer than 532 nm excitation and much higher than 355 nm excitation. Upconversion lifetime phosphor thermometry also resulted in improved phosphor lifetime temperature sensitivity. Coupled with reduced interference from background luminescence from impurities in TBCs with upconversion, it is a promising method for temperature measurements with the thermographic phosphor embedded in or underneath a TBC.
11.	Huang, Jianqing, et al. (author) Clustering-based particle detection method for digital holography to detect the three-dimensional location and in-plane size of particles 2021 In: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 32:5 Journal article (peer-reviewed)abstract Digital holography (DH) has been extensively applied in particle field measurements due to its promising ability to simultaneously provide the three-dimensional location and in-plane size of particles. Particle detection methods are crucial in hologram data processing to determine particle size and particle in-focus depth, which directly affect the measurement accuracy and robustness of DH. In this work, inspired by clustering algorithms, a new clustering-based particle detection (CBPD) method was proposed for DH. To the best of our knowledge this is the first time that clustering algorithms have been applied in processing holograms for particle detection. The results of both simulations and experiments confirmed the feasibility of our proposed method. This data-driven method features automatic recognition of particles, particle edges and background, and accurate separation of overlapping particles. Compared with seven conventional particle detection methods, the CBPD method has improved accuracy in measuring particle positions and displacements.
12.	Iakovidis, Dimitris K., et al. (author) Roadmap on signal processing for next generation measurement systems 2022 In: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 33:1 Research review (peer-reviewed)abstract Signal processing is a fundamental component of almost any sensor-enabled system, with a wide range of applications across different scientific disciplines. Time series data, images, and video sequences comprise representative forms of signals that can be enhanced and analysed for information extraction and quantification. The recent advances in artificial intelligence and machine learning are shifting the research attention towards intelligent, data-driven, signal processing. This roadmap presents a critical overview of the state-of-the-art methods and applications aiming to highlight future challenges and research opportunities towards next generation measurement systems. It covers a broad spectrum of topics ranging from basic to industrial research, organized in concise thematic sections that reflect the trends and the impacts of current and future developments per research field. Furthermore, it offers guidance to researchers and funding agencies in identifying new prospects.
13.	Malešević, Nebojša, et al. (author) Instrumented platform for assessment of isometric hand muscles contractions 2019 In: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 30:6 Journal article (peer-reviewed)abstract Measurement of forces exerted by a human hand while performing common gestures is a highly valuable task for assessment of neurorehabilitation and neurological disorders, but also, for control of movement that could be directly transferred to assistive devices. Even though accurate and selective multi-joint measurement of hand forces is desirable in both clinical and research applications there is no commercially available device able to perform such measurements. Moreover, the custom-made systems used in research commonly impose limitations, such as availability of only single, predefined hand aperture. Furthermore, there is no consensus on design requirements for custom made measurement systems that would enable comparison of results obtained during research or clinical hand function studies. In an attempt to provide a possible solution for a device capable of multi-joint hand forces measurement and disseminate it to the research community, this paper presents the mechanical and electronic design of an instrumented platform for assessment of isometric hand muscles contractions. Some of the key features related to the developed system are: flexibility in placing the hand/fingers, fast and easy hand fitting, adjustability to different lengths, circumferences and postures of the digits, and the possibility to register individual bidirectional forces from the digits and the wrist. The accuracy of isometric force measurements was evaluated in a controlled test with the reference high accuracy force gauge device during which the developed system showed high linearity (R 2 = 0.9999). As the more realistic test, the device was evaluated when force was applied to individual sensors but also during the intramuscular electromyography (iEMG) study. The data gathered during the iEMG measurements was thoroughly assessed to obtain three appropriate metrics; the first estimating crosstalk between individual force sensors; the second evaluating agreement between measured forces and forces estimated through iEMG; and the third providing qualitative evaluation of hand force in respect to activations of individual muscle units. The results of these analyses performed on multiple joint forces show agreement with previously published results, but with the difference that in that case, the measurement was performed with a single degree of freedom device.
14.	Samuelsson, Per, et al. (author) Quantitative laser diagnostics on trimethylindium pyrolysis and photolysis for functional nanoparticle growth 2022 In: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 33:5 Journal article (peer-reviewed)abstract We report on an optical investigation of the pyrolysis and photolysis of trimethylindium (TMIn) as a typical metalorganic precursor for functional nanowire growth, aiming at an in-depth understanding of the governing chemistry and optimization of aerosol-based (aerotaxy) and epitaxial growth processes. A flow reactor with special consideration given to optical access was built to provide the chemical environment for in situ optical measurements on the pyrolysis and photolysis of TMIn. By probing a resonant transition of the indium atom, high-resolution laser absorption and laser-induced fluorescence spectroscopy were applied to obtain the atomic indium concentration at different chosen conditions in a spatially and temporally resolved manner. The results indicate that quantitative measurements of indium atoms under growth conditions are feasible. A 213 nm pulsed laser was employed to induce photolytic dissociation of TMIn vapor under chosen conditions. The photolytic dissociation of TMIn vapor with an ultraviolet laser turns out to be a promising method in generating substantial chemical effects, indicated by the generation of visible clouds of indium particles, and high concentrations of indium atoms far beyond the pyrolytically generated amount.
15.	Sanned, David, et al. (author) Arbitrary position 3D tomography for practical application in combustion diagnostics 2022 In: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 33:12 Journal article (peer-reviewed)abstract This work aims to make three-dimensional (3D) tomographic techniques more flexible and accessible to in-situ measurements in practical apparatus by allowing arbitrary camera placements that benefit applications with more restrictive optical access. A highly customizable, in-house developed tomographic method is presented, applying smoothness priors through Laplacian matrices and hull constraints based on 3D space carving. The goal of this paper is to showcase a reconstruction method with full user control that can be adopted to various 3D field reconstructions. Simulations and experimental measurements of unsteady premixed CH4/air and ethanol (C2H5OH) diffusion pool flames were evaluated, comparing arbitrarily placed cameras around the probed domain to the more commonly used in-plane-half-circle camera arrangement. Reconstructions reproduced expected topological field features for both flame types. Results showed slight decrease in reconstruction quality for arbitrarily placed cameras compared to in-plane-half-circle arrangement. However, at lower numbers of camera views (N q ⩽ 6) arbitrary placement showed better results. The introduced methodology will be useful for optically limited setups in terms of handling a priori information, camera placement and 3D field evaluation.
16.	Stephan, Michael, et al. (author) Multiple scattering reduction in instantaneous gas phase phosphor thermometry : Applications with dispersed seeding 2019 In: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 30:5 Journal article (peer-reviewed)abstract In this study the structured laser illumination planar imaging (SLIPI) technique is combined with gas phase phosphor thermometry to measure quasi-instantaneously two-dimensional temperature fields with reduced bias from multiple scattering. Different reconstruction strategies are implemented, evaluated and compared, including a two-pulse and one-pulse SLIPI approach. A gradient-based threshold algorithm for particle detection is applied to conventional planar light sheet imaging as an alternative to reduce the bias caused by multiple scattering in seeding-free regions. As a demonstration, measurements are performed in a canonical flow configuration, consisting of a heated, turbulent, air jet surrounded by an ambient co-flow. Both air flows are seeded with the thermographic phosphor BaMgAl10O17:Eu2+. Conventional light sheet imaging in the context of gas phase phosphor thermometry suffers from multiple scattering causing a significant temperature bias and low temperature sensitivity. Applying the gradient threshold algorithm removes areas without any seeding particles which improves accuracy, precision and temperature sensitivity. However, multiple scattering influences are still present and may cause an increasing bias particularly for higher seeding density. One pulse (1p) SLIPI exhibits high accuracy at intermediate precision. Multiply scattered luminescence is not fully removed and spatial resolution is lowered. Two pulse (2p) SLIPI is recommended for high temperature sensitivity and accuracy, removing impact of multiple scattering furthermost. However, 2p-SLIPI exhibits reduced temperature precision.
17.	Tudisco, E., et al. (author) An extension of digital volume correlation for multimodality image registration 2017 In: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 28:9 Journal article (peer-reviewed)abstract The question of registering two images (or image volumes) acquired with different modalities, and thus exhibiting different contrast, at different positions is addressed based on an extension of global digital image (or volume) correlation. A specific comparison metric is introduced allowing the signature of the different phases to be related. A first solution consists of a Gaussian mixture to describe the joint distribution of gray levels, which not only provides a matching of both images, but also offers a natural segmentation indicator. A second 'self-adapting' solution does not include any postulated a priori model for the joint histogram and leads to a registration of the images based on their initial histograms. The algorithm is implemented with a pyramidal multiscale framework for the sake of robustness. The proposed multiscale technique is tested on two 3D images obtained from x-ray and neutron tomography respectively. The proposed approach brings the two images to coincidence with a sub-pixel accuracy and allows for a 'natural' segmentation of the different phases.
18.	Pendrill, Leslie (author) Assuring measurement quality in person-centred healthcare 2018 In: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 29:3, s. 034003- Journal article (peer-reviewed)abstract Is it realistic to aspire to the same kind of quality-assurance of measurement in person-centred care, currently being implemented in healthcare globally, as is established in the physical sciences and engineering? Ensuring metrological comparability (‘traceability’) and reliably declaring measurement uncertainty when assessing patient ability or increased social capital are however challenging for subjective measurements often characterised by large dispersion. Drawing simple analogies between ‘instruments’ in the social sciences – questionnaires, ability tests, etc.– and engineering instruments such as thermometers does not go far enough. A possible way forward apparently equally applicable to both physical and social measurement, seems to be to model inferences in terms performance metrics of a measurement system. Person-centred care needs person-centred measurement and a full picture of the measurement process when Man acts as a measurement instrument is given in the present paper. This complements previous work by presenting the process, step by step, from the observed indication (e.g. probability of success, Psuccess, of achieving atask), through restitution with Rasch Measurement Theory, to the measurand (e.g. task difficulty). Rasch invariant measure theory can yield quantities –‘latent’ (or ‘explanatory’) variables such as task challenge or person ability – with characteristics akin to those of physical quantities. Metrological references for comparability via traceability and reliable estimates ofuncertainty and decision risks are then in reach even for perceptive measurements (and other qualitative properties). As a case study, the person-centred measurement of cognitive ability is examined, as part of the EUproject EMPIR 15HLT04 NeuroMet, for Alzheimer’s, where better analysis of correlations with brain atrophy is enabled thanks to the Rasch metrological approach.
19.	Rigamonti, D., et al. (author) Neutron spectroscopy measurements of 14 MeV neutrons at unprecedented energy resolution and implications for deuterium-tritium fusion plasma diagnostics 2018 In: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 29:4, s. 045502- Journal article (peer-reviewed)abstract An accurate calibration of the JET neutron diagnostics with a 14 MeV neutron generator was performed in the first half of 2017 in order to provide a reliable measurement of the fusion power during the next JET deuterium-tritium (DT) campaign. In order to meet the target accuracy, the chosen neutron generator has been fully characterized at the Neutron Metrology Laboratory of the National Physical Laboratory (NPL), Teddington, United Kingdom. The present paper describes the measurements of the neutron energy spectra obtained using a high-resolution single-crystal diamond detector (SCD). The measurements, together with a new neutron source routine 'ad hoc' developed for the MCNP code, allowed the complex features of the neutron energy spectra resulting from the mixed D/T beam ions interacting with the T/D target nuclei to be resolved for the first time. From the spectral analysis a quantitative estimation of the beam ion composition has been made. The unprecedented intrinsic energy resolution (<1% full width at half maximum (FWHM) at 14 MeV) of diamond detectors opens up new prospects for diagnosing DT plasmas, such as, for instance, the possibility to study non-classical slowing down of the beam ions by neutron spectroscopy on ITER.
20.	Colaço, Marcos, et al. (author) Characterization of the microstructures of specialty optical fibers for electric-field sensing by propagation-based x-ray phase-contrast microtomography 2021 In: Measurement science and technology. - : IOP Publishing Ltd. - 0957-0233 .- 1361-6501. ; 32:6 Journal article (peer-reviewed)abstract In this work, we present a quantitative (statistical) 3D morphological characterization of optical fibers used in electric-field sensing. The characterization technique employs propagation-based x-ray phase-contrast microcomputed tomography (micro-CT). In particular, we investigate specialty optical fibers that contain microstructured holes that are electro-optically modified by thermal poling to induce second-order nonlinear effects (SONE). The efficiency of the SONE is reflected in the characterization parameter, Vπ, which is highly dependent on the dimensions of the fiber. The fiber microstructures must be uniform to support the fabrication of reproducible devices. The results obtained using the micro-CT technique show that uncertainty of ±1.7% arises in the determination of the expected value of the voltage that causes a change in the phase of the electromagnetic wave equal to π rad (Vπ ), demonstrating a great advantage, compared with other techniques e.g. SEM, which would need at least 1000 images of the cross-section of an optical fiber, taken at different points, making the process more expensive and time-consuming.
21.	Abou Nada, Fahd Jouda, et al. (author) Development of an automatic routine for calibration of thermographic phosphors 2014 In: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 25:2 Journal article (peer-reviewed)abstract An automated routine for the continuous calibration of thermographic phosphors was developed as a replacement for the conventional calibration scheme that relied on fixed temperature points. The automated calibration routine was validated using Mg 3 F 2 GeO 4 :Mn as a calibration phosphor. Hardware and software aspects of the calibration process were addressed in this development. The hardware aspect included a new substrate design using a high performance alloy, the Hastelloy-C alloy, whereas the software aspect included an automated acquisition system which was capable of acquiring simultaneous thermocouple temperatures and phosphor decay waveform in real time. The design of the calibration process eliminates the need for a system in thermal equilibrium during a phosphor calibration measurement. Temperature ramping rates of up to 4 K min −1 were employed in the oven without a delay in the temperature response being measured between the phosphor and the thermocouples involved. In addition, the automated calibration setup allowed for detailed investigations on the effect of heat being delivered to the phosphor coating by the laser. These findings were confirmed by a simple heat transfer model, based on lumped system analysis. In comparison to the data acquisition performed at several fixed points with the conventional calibration scheme, the experiment duration was shortened by a factor of 4 with the overall accuracy improved by 1–2 K.
22.	Albani, Giorgia, et al. (author) Evolution in boron-based GEM detectors for diffraction measurements : From planar to 3D converters 2016 In: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 27:11 Journal article (peer-reviewed)abstract The so-called '3He-crisis' has motivated the neutron detector community to undertake an intense R&D programme in order to develop technologies alternative to standard 3He tubes and suitable for neutron detection systems in future spallation sources such as the European spallation source (ESS). Boron-based GEM (gas electron multiplier) detectors are a promising '3He-free' technology for thermal neutron detection in neutron scattering experiments. In this paper the evolution of boron-based GEM detectors from planar to 3D converters with an application in diffraction measurements is presented. The use of 3D converters coupled with GEMs allows for an optimization of the detector performances. Three different detectors were used for diffraction measurements on the INES instrument at the ISIS spallation source. The performances of the GEM-detectors are compared with those of conventional 3He tubes installed on the INES instrument. The conceptual detector with the 3D converter used in this paper reached a count rate per unit area of about 25% relative to the currently installed 3He tube. Its timing resolution is similar and the signal-to-background ratio (S/B) is 2 times lower.
23.	Bladh, Henrik, et al. (author) Flame propagation visualization in a spark-ignition engine using laser-induced fluorescence of cool-flame species 2005 In: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 16:5, s. 1083-1091 Journal article (peer-reviewed)abstract The flame propagation in a spark-ignition engine has been studied using laser-induced fluorescence (LIF) of species formed during the first ignition stage of hydrocarbon combustion. The detected two-dimensional LIF images showed the distribution of unburned regions. For the excitation, two Nd:YAG lasers operating at 355 mn were used for two consecutive measurements within the same engine cycle with adjustable time separation between the pulses. Two ICCD cameras that were synchronized to each of the laser pulses recorded pairs of fluorescence images, i.e. the movement of the flame front could be tracked. It is well known that formaldehyde is excited using a wavelength of 355 nm and a spectral signature of this species was also identified in engine LIF spectra. Programme routines were developed and used for evaluation of the flame propagation velocity from the fluorescence images. This paper presents the potential and the characteristics of the experimental technique as well as the evaluation procedure. The measurements of cool-flame intermediates have also been compared with measurements of fuel-tracer as an indicator of unburned fuel-air mixture. A good agreement between position and shape of the signal areas was obtained at crank angles where both fluorescence signal from cool-flame species excited at 355 nm and added 3-pentanone excited at 266 nm could be detected.
24.	Ferraro, P., et al. (author) Surface topography of microstructures in lithium niobate by digital holographic microscopy 2004 In: Measument science and technology15. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 15:5, s. 961- Journal article (peer-reviewed)abstract We report here on the application of digital holographic microscopy as a metrological tool for the inspection and the micro-topography reconstruction of different microstructures fabricated in bulk lithium niobate by differential etching of reversed ferroelectric domain patterned crystals. These structures have a range of applications in optical ridge waveguides, alignment structures, V-grooves, micro-tips and micro-cantilever beams and precise control of the surface quality and topography is required. The technique allows us to obtain digitally a high-fidelity surface topography description of the specimen with only one image acquisition allowing us to have relatively simple and compact set-ups able to give quantitative information on object morphology. The advantages of this technique compared to traditional microscopy are discussed.
25.	Kaldvee, Billy, et al. (author) Picosecond-lidar thermometry in a measurement volume surrounded by highly scattering media 2011 In: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 22:12 Journal article (peer-reviewed)abstract In this work, a picosecond-lidar system, using a Nd:YAG picosecond laser, a Newtonian telescope and a streak camera, was used for single-ended furnace diagnostics. The optical access of the furnace was obstructed by a sooty diffusion ethylene flame. It was demonstrated that, with proper optical arrangement, the elastic scattering of the flame can be mapped in one dimension simultaneously as temperatures, up to 1200 K, are measured in the furnace using Rayleigh thermometry. Accumulated point temperature measurements as well as one-and two-dimensional measurements were conducted. A discussion about noise influence on accuracy and precision shows that measurements allowing a resolution of similar to 6 cm are possible with a single-pixel temperature standard deviation of 91 K, while mapping soot scattering from the flame within the dynamic range of the streak camera, using 30 mJ pulse energy.

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