| 1. |
- Seoane Martinez, Fernando, 1976, et al.
(författare)
-
Simple voltage-controlled current source for wideband electrical bioimpedance spectroscopy: circuit dependences and limitations
- 2011
-
Ingår i: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 22:11
-
Tidskriftsartikel (refereegranskat)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.
(författare)
-
Emissivity compensated spectral pyrometry-algorithm and sensitivity analysis
- 2014
-
Ingår i: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 25:2
-
Tidskriftsartikel (refereegranskat)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.
(författare)
-
Emissivity compensated spectral pyrometry for varying emissivity metallic measurands
- 2014
-
Ingår i: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 25:2
-
Tidskriftsartikel (refereegranskat)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.
(författare)
-
Monitoring the osmotic response of single yeast cells through force measurement in the environmental scanning electron microscope
- 2014
-
Ingår i: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 25:2
-
Tidskriftsartikel (refereegranskat)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.
(författare)
-
Enhanced color ratio calibration approach for two-dimensional surface thermometry using laser-induced phosphorescence
- 2013
-
Ingår i: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 24:8
-
Tidskriftsartikel (refereegranskat)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.
(författare)
-
Experimental Validation of a Method for Removing the Capacitive Leakage Artifact from Electrical Bioimpedance Spectroscopy Measurements
- 2010
-
Ingår i: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 21:11, s. 115802-
-
Tidskriftsartikel (refereegranskat)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.
(författare)
-
TomoBank : A tomographic data repository for computational x-ray science
- 2018
-
Ingår i: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 29:3
-
Tidskriftsartikel (refereegranskat)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.
(författare)
-
Automated Phosphor Thermometry Lifetime Calibration of Multiple Phosphors and Emission Lines to above 1900 K
- 2022
-
Ingår i: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 33:12
-
Tidskriftsartikel (refereegranskat)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.
(författare)
-
Sources of error for single-shot PMT-based phosphor thermometry in harsh conditions
- 2021
-
Ingår i: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 32:8
-
Tidskriftsartikel (refereegranskat)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.
(författare)
-
Upconversion phosphor thermometry for use in thermal barrier coatings
- 2023
-
Ingår i: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 34:6
-
Tidskriftsartikel (refereegranskat)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.
(författare)
-
Clustering-based particle detection method for digital holography to detect the three-dimensional location and in-plane size of particles
- 2021
-
Ingår i: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 32:5
-
Tidskriftsartikel (refereegranskat)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.
(författare)
-
Roadmap on signal processing for next generation measurement systems
- 2022
-
Ingår i: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 33:1
-
Forskningsöversikt (refereegranskat)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.
(författare)
-
Instrumented platform for assessment of isometric hand muscles contractions
- 2019
-
Ingår i: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 30:6
-
Tidskriftsartikel (refereegranskat)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.
(författare)
-
Quantitative laser diagnostics on trimethylindium pyrolysis and photolysis for functional nanoparticle growth
- 2022
-
Ingår i: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 33:5
-
Tidskriftsartikel (refereegranskat)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.
(författare)
-
Arbitrary position 3D tomography for practical application in combustion diagnostics
- 2022
-
Ingår i: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 33:12
-
Tidskriftsartikel (refereegranskat)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.
(författare)
-
Multiple scattering reduction in instantaneous gas phase phosphor thermometry : Applications with dispersed seeding
- 2019
-
Ingår i: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 30:5
-
Tidskriftsartikel (refereegranskat)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.
(författare)
-
An extension of digital volume correlation for multimodality image registration
- 2017
-
Ingår i: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 28:9
-
Tidskriftsartikel (refereegranskat)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
(författare)
-
Assuring measurement quality in person-centred healthcare
- 2018
-
Ingår i: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 29:3, s. 034003-
-
Tidskriftsartikel (refereegranskat)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.
(författare)
-
Neutron spectroscopy measurements of 14 MeV neutrons at unprecedented energy resolution and implications for deuterium-tritium fusion plasma diagnostics
- 2018
-
Ingår i: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 29:4, s. 045502-
-
Tidskriftsartikel (refereegranskat)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.
(författare)
-
Characterization of the microstructures of specialty optical fibers for electric-field sensing by propagation-based x-ray phase-contrast microtomography
- 2021
-
Ingår i: Measurement science and technology. - : IOP Publishing Ltd. - 0957-0233 .- 1361-6501. ; 32:6
-
Tidskriftsartikel (refereegranskat)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.
(författare)
-
Development of an automatic routine for calibration of thermographic phosphors
- 2014
-
Ingår i: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 25:2
-
Tidskriftsartikel (refereegranskat)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.
(författare)
-
Evolution in boron-based GEM detectors for diffraction measurements : From planar to 3D converters
- 2016
-
Ingår i: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 27:11
-
Tidskriftsartikel (refereegranskat)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.
(författare)
-
Flame propagation visualization in a spark-ignition engine using laser-induced fluorescence of cool-flame species
- 2005
-
Ingår i: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 16:5, s. 1083-1091
-
Tidskriftsartikel (refereegranskat)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.
(författare)
-
Surface topography of microstructures in lithium niobate by digital holographic microscopy
- 2004
-
Ingår i: Measument science and technology15. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 15:5, s. 961-
-
Tidskriftsartikel (refereegranskat)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.
(författare)
-
Picosecond-lidar thermometry in a measurement volume surrounded by highly scattering media
- 2011
-
Ingår i: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 22:12
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 26. |
- Kiefer, Johannes, et al.
(författare)
-
Laser-induced breakdown spectroscopy in a partially premixed turbulent jet flame
- 2013
-
Ingår i: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 24:7
-
Tidskriftsartikel (refereegranskat)abstract
- A new approach for studying mixing and combustion phenomena in turbulent partially premixed flames using laser-induced breakdown spectroscopy (LIBS) is demonstrated. Setting the laser pulse energy just above the breakdown threshold in the cold gas allows statistical data to be obtained concerning the probability of finding cold or hot gas inside the measurement volume. Moreover, a compositional analysis utilizing the LIBS spectra allows the mixing of the different cold gas flows to be studied. A proof-of-concept experiment is carried out in a turbulent jet flame stabilized on a coaxial burner. The LIBS data agree well with results obtained by planar laser-induced fluorescence of OH radicals.
|
|
| 27. |
- Kiefer, J., et al.
(författare)
-
Laser-induced breakdown spectroscopy in gases using ungated detection in combination with polarization filtering and online background correction
- 2010
-
Ingår i: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 21:6
-
Tidskriftsartikel (refereegranskat)abstract
- Quantitative and fast analysis of gas mixtures is an important task in the field of chemical, security and environmental analysis. In this paper we present a diagnostic approach based on laser-induced breakdown spectroscopy (LIBS). A polarization filter in the signal collection system enables sufficient suppression of elastically scattered light which otherwise reduces the dynamic range of the measurement. Running the detector with a doubled repetition rate as compared to the laser online background correction is obtained. Quantitative measurements of molecular air components in synthetic, ambient and expiration air are performed and demonstrate the potential of the method. The detection limits for elemental oxygen and hydrogen are in the order of 15 ppm and 10 ppm, respectively.
|
|
| 28. |
- Larsson, Jörgen
(författare)
-
Laser and synchrotron radiation pump-probe x-ray diffraction experiments
- 2001
-
Ingår i: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 12:11, s. 1835-1840
-
Tidskriftsartikel (refereegranskat)abstract
- Recent developments have allowed x-ray diffraction techniques at synchrotron radiation facilities to be employed with a temporal resolution of around 1 ps. These developments are the availability of firstly, high brightness third-generation x-ray sources, secondly, passively mode-locked lasers with 100 fs temporal duration and thirdly, averaging streak cameras with sub-picosecond temporal resolution. In this paper, we discuss how these novel devices are combined in time-resolved x-ray diffraction experiments at synchrotron radiation facilities.
|
|
| 29. |
- Lindén, Johannes, et al.
(författare)
-
Limitations of ICCD detectors and optimized 2D phosphor thermometry
- 2012
-
Ingår i: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 23:3
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents investigations on the limitations of intensified CCD (ICCD) cameras when performing quantitative 2D temperature measurements using thermographic phosphors. The temperature is evaluated using a two-color ratio technique, which demands high signal linearity of the detector. However, this work shows that the ICCD cameras used suffer from nonlinearity at levels of irradiance that do not necessarily produce particularly high count levels, i.e. well below the saturation limit of the A/D converter. For the phosphor thermometry, this results in false absolute temperature readings and decreased measurement precision. The results show that there is a useful workspace in the irradiance/camera gain combination where the detector should preferably be used. A response function for the ICCD camera used is constructed. Furthermore, in order to perform quantitative measurements, there is an upper limit of counts that should not be exceeded. This limit must be investigated for each experimental configuration since it depends on the characteristics of the specific light source and also varies between different cameras.
|
|
| 30. |
- Lindén, Johannes, et al.
(författare)
-
Precision in 2D temperature measurements using the thermographic phosphor BAM
- 2012
-
Ingår i: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 23:8
-
Tidskriftsartikel (refereegranskat)abstract
- Investigation of optimized spatial precision for surface temperature measurements is performed. The temperature is measured by means of two-color ratio imaging with ICCD cameras, using the thermographic phosphor BAM. The precision in temperature is put in relation to the spatial resolution, two quantities which involve a trade-off in this case: the more spatial smoothing the better precision, but also the worse spatial resolution. Two different setups are used in order to investigate the influence of laser shot-to-shot variations, the flat-field correction and image registration process on the precision. In order to achieve high precision it is crucial to operate the ICCD cameras with a gain setting that does not introduce nonlinearity effects at the present level of irradiance. The results provide guidance on the precision to be expected from surface temperature measurements using the two-color ratio technique in combination with thermographic phosphors and also confirm the importance of highly stable and linear ICCD detectors. At room temperature and low spatial resolution the precision is evaluated to 0.4%.
|
|
| 31. |
- Naylor, G. A, et al.
(författare)
-
A sub-picosecond accumulating streak camera for x-rays
- 2001
-
Ingår i: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 12:11, s. 1858-1864
-
Tidskriftsartikel (refereegranskat)abstract
- An x-ray streak camera system uses a laser triggered photo-conductive switch to synchronize the high voltage ramp applied to its sweep plates to the photo-excitation of a sample. This technique allows the jitter. between successive sweeps to be kept below 100 fs compared to over 1 ps:using classical methods. By accumulating a stable pulsed x-ray signal over many sweeps, a very high dynamic range can be achieved whilst maintaining a sub-picosecond time resolution. The ultimate time resolution is limited by the dispersion of electrons in the streak tube. Whilst triggering with a laser at 900 Hz we have achieved a time resolution (FWHM) of 640 fs at a detection wavelength of 267 nm for a 60 s accumulation period, corresponding to over 50 000 sweeps.
|
|
| 32. |
- Petrov, P. K., et al.
(författare)
-
Techniques for microwave measurements of ferroelectric thin films and their associated error and limitations
- 2005
-
Ingår i: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 16:2, s. 583-589
-
Tidskriftsartikel (refereegranskat)abstract
- This paper examines the problem of evaluating the microwave properties of thin ferroelectric films patterned as planar capacitors. Two types of microwave measurements of ferroelectric thin films are considered: reflection- and resonance-type measurements. Algorithms are presented for evaluation of capacitance-permittivity and dielectric loss. Using sensitivity analysis, the error and limitations associated with these measurements are estimated. The end result is a series of formulae that use the network analyser's measurement data to calculate the capacitance-permittivity, the dielectric loss and the associated error.
|
|
| 33. |
- Risman, PO, 1943, et al.
(författare)
-
Retro-modelling of a dual resonant applicator and accurate dielectric properties of liquid water from −20 °C to +100 °C
- 2007
-
Ingår i: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 18, s. 959-966
-
Tidskriftsartikel (refereegranskat)abstract
- A critical analysis is made of literature reports on the dielectric properties of pure water from liquid water supercooled at −20 ◦C, to +100 ◦C, in principle in the frequency range 0 to 3 GHz. Measurements using completemulti-step numerical modelling of a dual resonant cavity at about 920 MHz and 2230 MHz are presented. The measured data at about +20 ◦C are used as reference for the calculation of data at other temperatures. Due to the high resolution and considerations of various error sources, the resultingaccuracy becomes high and allows the construction of improved empiricalformulae for the Debye relaxation behaviour.
|
|
| 34. |
- Sjöholm, Johan, et al.
(författare)
-
Ultra-high-speed pumping of an optical parametric oscillator (OPO) for high-speed laser-induced fluorescence measurements
- 2009
-
Ingår i: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 20:2
-
Tidskriftsartikel (refereegranskat)abstract
- The feasibility of pumping an optical parametric oscillator (OPO) with an ultra-high repetition rate multi:YAG laser system, producing a burst of up to eight high-energy pulses, has been investigated. For this investigation an OPO with a bandwidth around 5 cm(-1), together with a frequency doubling crystal, was selected. In some laser-induced fluorescence measurements the large linewidth from the OPO can be advantageous as several lines can be excited simultaneously avoiding the saturation effects of individual lines. The energy output from the OPO as a function of pulse separation was measured down to pulse separations of 400 ns and was found to be completely independent of the pulse separation. The efficiency of the OPO unit, when optimized for single-pulse operation, was measured to be around 25% for all pulses, giving over 80 mJ at 585 nm output when pumped with similar to 350 mJ at 355 nm. This is similar to the specified efficiency for the OPO. The system was found to give a slightly lower efficiency when double pulsing the Nd:YAG lasers. This is attributed to a somewhat elongated pulse length from the Nd:YAG lasers giving a lower pump energy density. The system was applied for measuring high-speed planar laser-induced fluorescence images of OH radicals in a Bunsen burner.
|
|
| 35. |
- Svanberg, Sune
(författare)
-
Some applications of ultrashort laser pulses in biology and medicine
- 2001
-
Ingår i: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 12:11, s. 1777-1783
-
Tidskriftsartikel (refereegranskat)abstract
- Ultrashort laser pulses are finding increasing applications in biology and medicine. Such pulses can be used directly or after non-linear modification. Direct utilization includes propagation studies in scattering media with applications in optical mammography, dosimetry for photodynamic therapy and species concentration assessment. Intense continua of electromagnetic radiation of very brief duration are formed in the interaction of focused ultrashort and intense laser pulses with matter. Two different kinds of experiment using such radiation are described, employing visible radiation and x-rays, respectively. Focusing into water leads to the generation of a light continuum through self-phase modulation. The propagation of the light through tissue was studied, addressing questions related to specific tissue chromophore absorption. When terawatt laser pulses are focused onto a solid target with high nuclear charge Z, intense x-ray radiation of few ps duration and with energies exceeding hundreds of keV is emitted. Biomedical applications of this radiation are described, including differential absorption and gated-viewing imaging.
|
|
| 36. |
- Särner, Gustaf, et al.
(författare)
-
Investigations of blue emitting phosphors for thermometry
- 2008
-
Ingår i: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 19:12
-
Tidskriftsartikel (refereegranskat)abstract
- Blue emitting phosphors are investigated and reported for possible use in thermometry. Currently reported thermographic phosphors in general have the drawback of long emission lifetimes obstructing the possibility to time gate for background discrimination. An additional problem is that many thermographic phosphors have emission in the red spectral region, making them vulnerable for black body radiation at high temperatures. This work reports the temperature sensitivity for nine phosphors considered suitable for accurate temperature measurements in harsh conditions both in single points and in two dimensions (2D).
|
|
| 37. |
- Särner, Gustaf, et al.
(författare)
-
Using oxygen-quenched pressure-sensitive paint for oxygen concentration measurements in low-temperature combustion environments
- 2008
-
Ingår i: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 19:8
-
Tidskriftsartikel (refereegranskat)abstract
- The feasibility of using pressure-sensitive paint for oxygen concentration measurements in low-temperature combustion environments has been investigated and applied to slow combustion processes. In addition, the temperature limitation for this application was studied. A Nd:YAG laser system, a PMT and fiber-optics were used for developing a compact probe for oxygen measurements. The lifetime sensitivity to oxygen concentration and temperature of a commercially available pressure-sensitive paint has been investigated with regard to possible abilities and limitations. After calibrations with regard to temperature, measurements in slow combustion environments showed that the technique is capable of accurately measuring oxygen concentration in environments up to 180 degrees C. The measurements indicate usability also in the combustion area despite issues of thermal quenching and quenching from NO. The compact design of the system makes it a useful tool for oxygen measurements in situations where suction probes and other oxygen measurement techniques are too intrusive.
|
|
| 38. |
- Tenishev, Vladimir, et al.
(författare)
-
On-line diagnostic tool for measurement of the time delay between two ultrashort light pulses
- 2004
-
Ingår i: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 15:9, s. 1762-1767
-
Tidskriftsartikel (refereegranskat)abstract
- Ultrafast accelerator-based sources combined with synchronized femtosecond lasers are currently being developed. The method described here is intended as a jitter monitor at such facilities. We report on the possibility of extracting a time-offset signal between two different synchronized ultrashort light pulses. The method is based on sum-frequency generation in a nonlinear crystal. Aiming at extracting the time-difference from visible pulsed radiation from an x-ray undulator and femtosecond laser pulses we are investigating the possibility of obtaining timing information when one of the two pulses is very weak (10(6) photons/pulse). This will enable on-line monitoring of the relative timing of an accelerator-based free-electron laser and a synchronized visible laser. The spatial position of the sum-frequency mixed region is registered using a position sensitive detector (PSD). We show that for an 80 fs light source the described electronic equipment is capable of delivering a signal proportional to the temporal shift of different ultrashort light pulses with an accuracy of approximately 30 fs in a time interval of several ps.
|
|
| 39. |
- Wellander, Rikard, et al.
(författare)
-
Three-dimensional measurement of the local extinction coefficient in a dense spray
- 2011
-
Ingår i: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 22:12
-
Tidskriftsartikel (refereegranskat)abstract
- Laser extinction, signal attenuation and multiple scattering are the three main phenomena limiting qualitative and quantitative measurements in planar laser imaging of sprays. In this paper, a method is presented where structured laser illumination planar imaging is used to remove the signal contribution from multiply scattered light. Based on this technique, data from side scattering and transmission measurements are obtained simultaneously. An algorithm, compensating for signal attenuation and laser extinction, is further applied to calculate the local extinction coefficient. The method is first demonstrated on a cuvette containing a homogeneous solution of scattering particles with an extinction coefficient (mu) over bar (e) = 0.13 mm(-1). Finally the procedure is applied on an air-assisted water spray with a maximum optical depth of OD similar to 3, where the position-dependent extinction coefficient is extracted within the probed volume. To the best of our knowledge, this paper demonstrates for the first time a method to measure the local (mu) over bar (e) within the three dimensions of an inhomogeneous scattering medium using laser sheet illumination, after suppression of the multiple light scattering intensity.
|
|
| 40. |
- Xiaohong, Zhou, et al.
(författare)
-
The thermal insulation difference of clothing ensembles on the dry and perspiration manikins
- 2010
-
Ingår i: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 21:8
-
Tidskriftsartikel (refereegranskat)abstract
- There are about a hundred manikin users around the world. Some of them use the manikin such as 'Walter' and 'Tore' to evaluate the comfort of clothing ensembles according to their thermal insulation and moisture resistance. A 'Walter' manikin is made of water and waterproof breathable fabric 'skin', which simulates the characteristics of human perspiration. So evaporation, condensation or sorption and desorption are always accompanied by heat transfer. A 'Tore' manikin only has dry heat exchange by conduction, radiation and convection from the manikin through clothing ensembles to environments. It is an ideal apparatus to measure the thermal insulation of the clothing ensemble and allows evaluation of thermal comfort. This paper compares thermal insulation measured with dry 'Tore' and sweating 'Walter' manikins. Clothing ensembles consisted of permeable and impermeable clothes. The results showed that the clothes covering the 'Walter' manikin absorbed the moisture evaporated from the manikin. When the moisture transferred through the permeable clothing ensembles, heat of condensation could be neglected. But it was observed that heavy condensation occurred if impermeable clothes were tested on the 'Walter' manikin. This resulted in a thermal insulation difference of clothing ensembles on the dry and perspiration manikins. The thermal insulation obtained from the 'Walter' manikin has to be modified when heavy condensation occurs. The modified equation is obtained in this study.
|
|
| 41. |
- Yu, M., et al.
(författare)
-
Survivability of thermographic phosphors (YAG:Dy) in a combustion environment
- 2010
-
Ingår i: Measurement Science & Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 21:3
-
Tidskriftsartikel (refereegranskat)abstract
- The feasibility of applying laser-induced phosphorescence in a combustion environment was shown by testing the consistency of the emission-temperature relations of thermographic phosphor particles (YAG:Dy). The relations were calibrated before and after the phosphor particles had passed a flame front. The calibrations were performed in air and in pure oxygen. The emission-temperature relation prevails from around 300 K to 1300 K. The difference in emission-temperature relation for the two different cases is less than the experimental precision (3%).
|
|
| 42. |
- Kontturi, V, et al.
(författare)
-
Simultaneous detection of absorption spectrum and refractive index ratio with a spectrophotometer : monitoring contaminants in bioethanol
- 2011
-
Ingår i: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 22:5, s. 6-
-
Tidskriftsartikel (refereegranskat)abstract
- The optical properties of a biofuel resulting from the fungi-treated lignocellulosic biomass in an ethanol matrix were studied. The matrix simulates the case that the bioethanol is contaminated by sugars, water and colour pigments that reduce the quality of the biofuel and compromise the combustion process. It is suggested that by applying a spectrophotometer only, it is possible to obtain valid information, i.e. the spectral features of the contaminants as well as the refractive index ratio of bioethanol. This allows for simultaneous purity and density detection of biomass-derived liquids or liquid biofuels, in comparison to a reference representing an ideal bioethanol (pure ethyl alcohol, ethanol of 99.5% purity (v/v)).
|
|
| 43. |
|
|
| 44. |
- Karlsson, Erik B., et al.
(författare)
-
The hydrogen anomaly in neutron Compton scattering : new experiments and a quantitative theoretical explanation
- 2016
-
Ingår i: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 27:8
-
Tidskriftsartikel (refereegranskat)abstract
- No consensus has been reached so far about the hydrogen anomaly problem in Compton scattering of neutrons, although strongly reduced H cross-sections were first reported almost 20 years ago. Over the years, this phenomenon has been observed in many different hydrogen-containing materials. Here, we use yttrium hydrides as test objects, YH2, YH3, YD2 and YD3, Y(HxD1-x)(2) and Y(HxD1-x)(3), for which we observe H anomalies increasing with transferred momentum q. We also observe reduced deuteron cross-sections in YD2 and YD3 and have followed those up to scattering angles of 140 degrees corresponding to high momentum transfers. In addition to data taken using the standard Au-197 foils for neutron energy selection, the present work includes experiments with Rh-103 foils and comparisons were also made with data from different detector setups. The H and D anomalies are discussed in terms of the different models proposed for their interpretation. The 'electron loss model' (which assumes energy transfer to excited electrons) is contradicted by the present data, but it is shown here that exchange effects in scattering from two or more protons (or deuterons) in the presence of large zero-point vibrations, can explain quantitatively the reduction of the cross-sections as well as their q-dependence. Decoherence processes also play an essential role. In a scattering time representation, shake-up processes can be followed on the attosecond scale. The theory also shows that large anomalies can appear only when the neutron coherence lengths (determined by energy selection and detector geometry) are about the same size as the distance between the scatterers.
|
|
| 45. |
- Sanchez, B., et al.
(författare)
-
On the calculation of the D-optimal multisine excitation power spectrum for broadband impedance spectroscopy measurements
- 2012
-
Ingår i: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 23:8, s. 085702-
-
Tidskriftsartikel (refereegranskat)abstract
- The successful application of impedance spectroscopy in daily practice requires accurate measurements for modeling complex physiological or electrochemical phenomena in a single frequency or several frequencies at different (or simultaneous) time instants. Nowadays, two approaches are possible for frequency domain impedance spectroscopy measurements: (1) using the classical technique of frequency sweep and (2) using (non-)periodic broadband signals, i.e. multisine excitations. Both techniques share the common problem of how to design the experimental conditions, e.g. the excitation power spectrum, in order to achieve accuracy of maximum impedance model parameters from the impedance data modeling process. The original contribution of this paper is the calculation and design of the D-optimal multisine excitation power spectrum for measuring impedance systems modeled as 2R-1C equivalent electrical circuits. The extension of the results presented for more complex impedance models is also discussed. The influence of the multisine power spectrum on the accuracy of the impedance model parameters is analyzed based on the Fisher information matrix. Furthermore, the optimal measuring frequency range is given based on the properties of the covariance matrix. Finally, simulations and experimental results are provided to validate the theoretical aspects presented.
|
|
| 46. |
|
|
| 47. |
- Anyangwe Nwaboh, Javis, et al.
(författare)
-
Metrological quantification of CO in biogas using laser absorption spectroscopy and gas chromatography
- 2018
-
Ingår i: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 29:9
-
Tidskriftsartikel (refereegranskat)abstract
- Biogas has a vital role in the future market of renewable energy. When upgraded to biomethane, it can be injected into natural gas grids if the level of certain impurities complies with the specifications in EN16723. For some of these impurities, suitable measurement methods are lacking which hampers the quality control of biomethane to be injected into natural gas networks. Here, we report the evaluation of three detection methods suitable for carbon monoxide (CO) in biogas and biomethane applications for which EN16723 specifies an upper limit of 0.1% (1000 µmol/mol). Two of these methods are based on laser absorption spectroscopy (LAS) and one on gas chromatography (GC). Both LAS spectrometers are employing direct absorption spectroscopy and operating at 4.6µm, probing a single CO absorption line in the fundamental CO band: One – called dTDLAS (direct tunable diode laser absorption spectroscopy)- is based on a new Interband Cascade Laser specially designed for biogas and biomethane applications, while the other is based on Quantum Cascade Laser Absorption Spectroscopy (QCLAS). The GC is equipped with two packed columns (Hayesep Q and Molecular Sieve 5A) and a thermal conductivity detector. Carbon monoxide amount fraction results in biogas matrices derived using these three measurement methods are compared to amount fraction values of different, gravimetrically prepared reference gas standards of CO in biogas. These were used to validate the measurement capabilities. The measured CO amount fraction results from LAS and GC covered 10 µmol/mol to 30000 µmol/mol (system measurement ranges, LAS: 3 µmol/mol - 1000 µmol/mol, GC: 500 µmol/mol - 30000 µmol/mol) and were in excellent agreement with the gravimetric values of the gas standards. At 400 µmol/mol, the guide to the expression of uncertainty in measurement (GUM) compliant relative standard uncertainties of our calibration-free dTDLAS and the gas-calibrated QCLAS systems are estimated to be 1.4 % vs 0.5 %, respectively. The relative standard uncertainty of the GC CO measurements at 5075 µmol/mol is 1.3 %. This work demonstrates that, by means of GC and LAS, relative standard uncertainties of 1.4 % and below can be reached for CO measurements in biogas and that cost-optimized calibration-free approaches not requiring frequent use of gas standards have become available.
|
|
| 48. |
- Arrhenius, Karine, et al.
(författare)
-
Comparison of optical feedback cavity enhanced absorption spectroscopy and gas chromatography for the measurement of the main components and impurities in biogas, landfill gas, biomethane and carbon dioxide streams
- 2023
-
Ingår i: Measurement science and technology. - : Institute of Physics. - 0957-0233 .- 1361-6501. ; 34:9
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, we evaluated the performances of a custom-built optical feedback cavity enhanced absorption spectroscopy (OFCEAS) instrument for the determination of the composition of energy gases, focusing on methane and carbon dioxide as main components, and carbon monoxide as impurities, in comparison with the well-established, validated, and traceable gas chromatographic method. A total of 115 real sample gases collected in biogas plants or landfills were analyzed using with both techniques over a period of 12 months. The comparison of the techniques showed that the virtual model which allows the measurement, needs to be optimized using real samples of varied compositions. The OFCEAS measurement technique was found to be capable of measuring both the main components and a trace component in different matrices; to within a 2% measurement uncertainty (higher than the gas chromatograph/thermal conductivity detector (GC/TCD) method). The OFCEAS method exhibits a very fast response, does not require daily calibration, and can be implemented online. The agreements between the OFCEAS technique and the GC/TCD method show that the drift of the OFCEAS instruments remains acceptable in the long term as long as no change is made to the virtual model. Matrix effects were observed, and those need to be taken into consideration when analyzing different types of samples. © 2023 The Author(s). Published by IOP Publishing Ltd.
|
|
| 49. |
- Arrhenius, Karine, et al.
(författare)
-
Development and evaluation of a novel analyser for ISO14687 hydrogen purity analysis
- 2020
-
Ingår i: Measurement science and technology. - : Institute of Physics Publishing. - 0957-0233 .- 1361-6501. ; 31:7
-
Tidskriftsartikel (refereegranskat)abstract
- Standards ISO14687 and EN17124 set stringent limits for numerous gaseous impurities and particulates that may damage the fuel cell system in a hydrogen vehicle, as it is highly sensitive to the presence of even very low levels of impurities. However, performing the whole set of analyses is both technically challenging and time-consuming for any laboratory and will require a combination of several analytical techniques or instruments. In this study, we discussed the selection of analytical techniques for hydrogen purity testing in order to optimize the CAPEX (capital expenditure) and OPEX (operational expenditure), while ensuring the quality of the results and the compliance of the analytical methods with ISO21087. Among the individual impurities to be analysed in ISO14687, spectroscopy techniques are suitable for ammonia, carbon dioxide, carbon monoxide, formaldehyde, formic acid, oxygen and water. Spectroscopy techniques are even suitable for some impurities belonging to the three total species such as hydrogen sulphide, hydrogen chloride and methane. However, helium and argon, which are monoatomic, do not exhibit response in the infrared region. Therefore, any spectroscopic analysis method must be completed by another method in order to simultaneously analyse all individual gaseous impurities from ISO14687. In this study, we constructed and demonstrated the feasibility of an instrument composed of a gas chromatograph having three columns (two packed columns and a PLOT (Porous Layer Open Tubular) column and two detectors (FID and TCD) coupled in parallel to two OFCEAS instruments using reference gas mixtures. Finally, we also proposed an extended configuration that will allow performing the whole set of analyses for gaseous species from ISO14687
|
|
| 50. |
- Ayoub, M. W. Ben, et al.
(författare)
-
Quantitative determination of bound water in cardboard by measurement of dielectric permittivity
- 2018
-
Ingår i: Measurement science and technology. - : Institute of Physics Publishing (IOPP). - 0957-0233 .- 1361-6501. ; 29:2
-
Tidskriftsartikel (refereegranskat)abstract
- In this study we investigated the complex dielectric permittivity of cardboard with different water contents using a coaxial transmission/reflection technique from 10 MHz to 1.5 GHz. A relaxation process was analyzed to identify the bonding forms that exist in cardboard; this analysis was accompanied by a selective direct thermo-coulometric method. Two different types of bonding of water are found in cardboard (free and bound water) and both can be eliminated at 105 degrees C. The novelty of this work is the experimental correlation between the relaxation frequency situated in the radio-frequency band and the fraction of bound water in cardboard with a low water content.
|
|
