Showing papers in "Measurement Science and Technology in 2013"
TL;DR: In this article, the authors present the basis for each technique, recent developments in methods and performance limitations, and present a performance comparison of different techniques, taking data reported over the preceding decade, and draw conclusions from this benchmarking.
Abstract: The detection and measurement of gas concentrations using the characteristic optical absorption of the gas species is important for both understanding and monitoring a variety of phenomena from industrial processes to environmental change. This study reviews the field, covering several individual gas detection techniques including non-dispersive infrared, spectrophotometry, tunable diode laser spectroscopy and photoacoustic spectroscopy. We present the basis for each technique, recent developments in methods and performance limitations. The technology available to support this field, in terms of key components such as light sources and gas cells, has advanced rapidly in recent years and we discuss these new developments. Finally, we present a performance comparison of different techniques, taking data reported over the preceding decade, and draw conclusions from this benchmarking.
1,293 citations
TL;DR: A survey of the major developments in 3D velocity field measurements using the tomographic particle image velocimetry (PIV) technique is given in this article, where the fundamental aspects of the technique are discussed beginning from hardware considerations for volume illumination, imaging systems, their configurations and system calibration.
Abstract: A survey is given of the major developments in three-dimensional velocity field measurements using the tomographic particle image velocimetry (PIV) technique. The appearance of tomo-PIV dates back seven years from the present review (Elsinga et al 2005a 6th Int. Symp. PIV (Pasadena, CA)) and this approach has rapidly spread as a versatile, robust and accurate technique to investigate three-dimensional flows (Arroyo and Hinsch 2008 Topics in Applied Physics vol 112 ed A Schroder and C E Willert (Berlin: Springer) pp 127–54) and turbulence physics in particular. A considerable number of applications have been achieved over a wide range of flow problems, which requires the current status and capabilities of tomographic PIV to be reviewed. The fundamental aspects of the technique are discussed beginning from hardware considerations for volume illumination, imaging systems, their configurations and system calibration. The data processing aspects are of uppermost importance: image pre-processing, 3D object reconstruction and particle motion analysis are presented with their fundamental aspects along with the most advanced approaches. Reconstruction and cross-correlation algorithms, attaining higher measurement precision, spatial resolution or higher computational efficiency, are also discussed. The exploitation of 3D and time-resolved (4D) tomographic PIV data includes the evaluation of flow field pressure on the basis of the flow governing equation. The discussion also covers a-posteriori error analysis techniques. The most relevant applications of tomo-PIV in fluid mechanics are surveyed, covering experiments in air and water flows. In measurements in flow regimes from low-speed to supersonic, most emphasis is given to the complex 3D organization of turbulent coherent structures.
620 citations
TL;DR: In this paper, a distributed optical fiber sensor is introduced which is capable of quantifying multiple dynamic strain perturbations along 1 km of a sensing fiber simultaneously using a standard telecommunication single-mode optical fiber.
Abstract: A distributed optical fibre sensor is introduced which is capable of quantifying multiple dynamic strain perturbations along 1 km of a sensing fibre simultaneously using a standard telecommunication single-mode optical fibre The technique is based on measuring the phase between the Rayleigh scattered light from two sections of the fibre which define the gauge length The phase is spatially determined along the entire length of the fibre with a single pulse This allows multiple moving strain perturbation to be tracked and quantified along the entire length of the fibre The demonstrated setup has a spatial resolution of 2 m with a frequency range of 500-5000 Hz The minimum detectable strain perturbation of the sensor was measured to be 80 ne
373 citations
TL;DR: A review of the approach to extract pressure fields from flow velocity field data, typically obtained with particle image velocimetry (PIV), by combining the experimental data with the governing equations is presented in this article.
Abstract: The topic of this article is a review of the approach to extract pressure fields from flow velocity field data, typically obtained with particle image velocimetry (PIV), by combining the experimental data with the governing equations. Although the basic working principles on which this procedure relies have been known for quite some time, the recent expansion of PIV capabilities has greatly increased its practical potential, up to the extent that nowadays a time-resolved volumetric pressure determination has become feasible. This has led to a novel diagnostic methodology for determining the instantaneous flow field pressure in a non-intrusive way, which is rapidly finding acceptance in an increasing variety of application areas. The current review describes the operating principles, illustrating how the flow-governing equations, in particular the equation of momentum, are employed to compute the pressure from the material acceleration of the flow. Accuracy aspects are discussed in relation to the most dominating experimental influences, notably the accuracy of the velocity source data, the temporal and spatial resolution and the method invoked to estimate the material derivative. In view of its nature of an emerging technique, recently published dedicated validation studies will be given specific attention. Different application areas are addressed, including turbulent flows, aeroacoustics, unsteady wing aerodynamics and other aeronautical applications.
337 citations
TL;DR: An overview of the state of the art concerning the fundamental properties of electrode polarization of interest in the measurement of high conductivity samples and its implications for both dielectric (DS) and impedance spectroscopy (IS) can be found in this article.
Abstract: In this review, we present an overview of the state of the art concerning the fundamental properties of electrode polarization (EP) of interest in the measurement of high conductivity samples and its implications for both dielectric (DS) and impedance spectroscopy (IS). Initially a detailed description of what constitutes EP is provided and the problems that it induces. Then, we review some of the more popular models that have been used to describe the physical phenomena behind the formation of the ionic double layer. Following this we shall enumerate the common strategies used historically to correct its influence on the measured signals in DS or in IS. Finally we also review recent attempts to employ fractal electrodes to bypass the effects of EP and to offer some physical explanation as to the limitations of their use.
294 citations
TL;DR: Why three-phase flow measurement is still important and why it remains a difficult problem to solve are discussed.
Abstract: The problem of how to accurately measure the flowrate of oil–gas–water mixtures in a pipeline remains one of the key challenges in the petroleum industry. This paper discusses why three-phase flow measurement is still important and why it remains a difficult problem to solve. The measurement strategies and principal base technologies currently used by commercial manufacturers are described, and research developments that could influence future flowmeter design are considered. Finally, future issues, which will need to be addressed by manufacturers and users of three-phase flowmeters, are discussed.
273 citations
TL;DR: Sciacchitano et al. as discussed by the authors presented a method to quantify the uncertainty of PIV data, i.e., the unknown actual error of the measured velocity field is estimated using the velocity field itself as input along with the original images.
Abstract: A novel method is presented to quantify the uncertainty of PIV data. The approach is a posteriori, i.e. the unknown actual error of the measured velocity field is estimated using the velocity field itself as input along with the original images. The principle of the method relies on the concept of super-resolution: the image pair is matched according to the cross-correlation analysis and the residual distance between matched particle image pairs (particle disparity vector) due to incomplete match between the two exposures is measured. The ensemble of disparity vectors within the interrogation window is analyzed statistically. The dispersion of the disparity vector returns the estimate of the random error, whereas the mean value of the disparity indicates the occurrence of a systematic error. The validity of the working principle is first demonstrated via Monte Carlo simulations. Two different interrogation algorithms are considered, namely the cross-correlation with discrete window offset and the multi-pass with window deformation. In the simulated recordings, the effects of particle image displacement, its gradient, out-of-plane motion, seeding density and particle image diameter are considered. In all cases good agreement is retrieved, indicating that the error estimator is able to follow the trend of the actual error with satisfactory precision. Experiments where time-resolved PIV data are available are used to prove the concept under realistic measurement conditions. In this case the ‘exact’ velocity field is unknown; however a high accuracy estimate is obtained with an advanced interrogation algorithm that exploits the redundant information of highly temporally oversampled data (pyramid correlation, Sciacchitano et al (2012 Exp. Fluids 53 1087–105)). The image-matching estimator returns the instantaneous distribution of the estimated velocity measurement error. The spatial distribution compares very well with that of the actual error with maxima in the highly sheared regions and in the 3D turbulent regions. The high level of correlation between the estimated error and the actual error indicates that this new approach can be utilized to directly infer the measurement uncertainty from PIV data. A procedure is shown where the results of the error estimation are employed to minimize the measurement uncertainty by selecting the optimal interrogation window size.
238 citations
TL;DR: In this paper, the cross-correlation peak ratio, the ratio of primary to secondary peak height, is shown to correlate strongly with the range of observed error values for a given measurement, regardless of flow condition or image quality.
Abstract: Numerous studies have established firmly that particle image velocimetry (PIV) is a robust method for non-invasive, quantitative measurements of fluid velocity, and that when carefully conducted, typical measurements can accurately detect displacements in digital images with a resolution well below a single pixel (in some cases well below a hundredth of a pixel). However, to date, these estimates have only been able to provide guidance on the expected error for an average measurement under specific image quality and flow conditions. This paper demonstrates a new method for estimating the uncertainty bounds to within a given confidence interval for a specific, individual measurement. Here, cross-correlation peak ratio, the ratio of primary to secondary peak height, is shown to correlate strongly with the range of observed error values for a given measurement, regardless of flow condition or image quality. This relationship is significantly stronger for phase-only generalized cross-correlation PIV processing, while the standard correlation approach showed weaker performance. Using an analytical model of the relationship derived from synthetic data sets, the uncertainty bounds at a 95% confidence interval are then computed for several artificial and experimental flow fields, and the resulting errors are shown to match closely to the predicted uncertainties. While this method stops short of being able to predict the true error for a given measurement, knowledge of the uncertainty level for a PIV experiment should provide great benefits when applying the results of PIV analysis to engineering design studies and computational fluid dynamics validation efforts. Moreover, this approach is exceptionally simple to implement and requires negligible additional computational cost.
214 citations
TL;DR: In this paper, a hybrid algorithm is proposed that similar to MART iteratively reconstructs 3D-particle locations by comparing the recorded images with the projections calculated from the particle distribution in the volume.
Abstract: For tracking the motion of illuminated particles in space and time several volumetric flow measurement techniques are available like 3D-particle tracking velocimetry (3D-PTV) recording images from typically three to four viewing directions. For higher seeding densities and the same experimental setup, tomographic PIV (Tomo-PIV) reconstructs voxel intensities using an iterative tomographic reconstruction algorithm (e.g. multiplicative algebraic reconstruction technique, MART) followed by cross-correlation of sub-volumes computing instantaneous 3D flow fields on a regular grid. A novel hybrid algorithm is proposed here that similar to MART iteratively reconstructs 3D-particle locations by comparing the recorded images with the projections calculated from the particle distribution in the volume. But like 3D-PTV, particles are represented by 3D-positions instead of voxel-based intensity blobs as in MART. Detailed knowledge of the optical transfer function and the particle image shape is mandatory, which may differ for different positions in the volume and for each camera. Using synthetic data it is shown that this method is capable of reconstructing densely seeded flows up to about 0.05 ppp with similar accuracy as Tomo-PIV. Finally the method is validated with experimental data.
200 citations
TL;DR: In this paper, a novel strategy has been developed for analysis of wavelength-scanned, wavelength modulation spectroscopy (WMS) with tunable diode lasers (TDLs).
Abstract: A novel strategy has been developed for analysis of wavelength-scanned, wavelength modulation spectroscopy (WMS) with tunable diode lasers (TDLs). The method simulates WMS signals to compare with measurements to determine gas properties (e.g., temperature, pressure and concentration of the absorbing species). Injection-current-tuned TDLs have simultaneous wavelength and intensity variation, which severely complicates the Fourier expansion of the simulated WMS signal into harmonics of the modulation frequency (fm). The new method differs from previous WMS analysis strategies in two significant ways: (1) the measured laser intensity is used to simulate the transmitted laser intensity and (2) digital lock-in and low-pass filter software is used to expand both simulated and measured transmitted laser intensities into harmonics of the modulation frequency, WMS-nfm (n = 1, 2, 3,...), avoiding the need for an analytic model of intensity modulation or Fourier expansion of the simulated WMS harmonics. This analysis scheme is valid at any optical depth, modulation index, and at all values of scanned-laser wavelength. The method is demonstrated and validated with WMS of H2O dilute in air (1 atm, 296 K, near 1392 nm). WMS-nfm harmonics for n = 1 to 6 are extracted and the simulation and measurements are found in good agreement for the entire WMS lineshape. The use of 1f-normalization strategies to realize calibration-free wavelength-scanned WMS is also discussed.
177 citations
TL;DR: In this article, a variable optical transfer function (OTF) is proposed to reduce the negative effects of optical distortions on the reconstruction of particle images. But, the OTF is not suitable for the case of 3D particle tracking.
Abstract: A new approach to the weighting function, which describes particle imaging in tomographic reconstruction, is introduced. Instead of assuming a spatially homogeneous mapping function of voxels to the images, a variable optical transfer function (OTF) is applied. By this method, the negative effects of optical distortions on the reconstruction can be reduced considerably. The effects of these improvements in reconstruction quality on the methods of tomographic particle imaging velocimetry, as well as 3D particle tracking are investigated. A method to calibrate the OTF to experimental circumstances is proposed as an additional step to the volume self-calibration. It is shown that this kind of calibration is able to capture the predominant particle imaging both for simulated as well as experimental data. The most common distortions of particle imaging are blurring due to a small depth of field and astigmatism due to imaging optics. The effects of both of these distortions on reconstruction and correlation quality are investigated via simulated data. In both cases, a strong influence on relevant parameters can be seen. Reconstructions using a spatially varying OTF, calibrated to the imaging conditions, show a significant improvement in reconstruction quality and the accuracy of the particle peak position, as well as in the accuracy of the gained displacement vector field when using two time steps. Evaluation of experimental data by PTV methods shows a reduction in ghost particle intensity and improvements in peak position accuracy. A computationally efficient method of applying the OTF to tomographic reconstruction is introduced.
TL;DR: The pulse burst laser system as mentioned in this paper produces high repetition rate output by slicing the output of a low power continuous wave laser and passing the resulting burst of pulses through a series of pulsed Nd:YAG amplifiers.
Abstract: Recent advances in ultra-high repetition rate (100?kHz and above) laser diagnostics for fluid dynamic measurements are reviewed. The development of the pulse burst laser system, which enabled several of these advances, is described. The pulse burst laser system produces high repetition rate output by slicing the output of a low power continuous wave laser and passing the resulting burst of pulses through a series of pulsed Nd:YAG amplifiers. Several systems have been built with output approaching 1.0 J/pulse over bursts of up to 100 pulses generated at between 50 and 1000?kHz. Combined with the capabilities of several types of commercially available high-speed cameras, these systems have been used to make a wide variety of high repetition rate and 3D flow measurements. Several examples of various high repetition rate laser diagnostics are described, including flow visualization, filtered Rayleigh scattering, planar Doppler velocimetry, particle image velocimetry, planar laser induced fluorescence, molecular tagging velocimetry and 3D flow visualization.
TL;DR: In this article, the authors compared hot-wire and particle image velocimetry (PIV) measurements with velocity fields computed using two different PIV algorithms and found that the difference in uncertainty between the two methods can be estimated using the uncertainty surface method.
Abstract: Particle image velocimetry is a powerful and flexible fluid velocity measurement tool. In spite of its widespread use, the uncertainty of PIV measurements has not been sufficiently addressed to date. The calculation and propagation of local, instantaneous uncertainties on PIV results into the measured mean and Reynolds stresses are demonstrated for four PIV error sources that impact uncertainty through the vector computation: particle image density, diameter, displacement and velocity gradients. For the purpose of this demonstration, velocity data are acquired in a rectangular jet. Hot-wire measurements are compared to PIV measurements with velocity fields computed using two PIV algorithms. Local uncertainty on the velocity mean and Reynolds stress for these algorithms are automatically estimated using a previously published method. Previous work has shown that PIV measurements can become ‘noisy’ in regions of high shear as well as regions of small displacement. This paper also demonstrates the impact of these effects by comparing PIV data to data acquired using hot-wire anemometry, which does not suffer from the same issues. It is confirmed that flow gradients, large particle images and insufficient particle image displacements can result in elevated measurements of turbulence levels. The uncertainty surface method accurately estimates the difference between hot-wire and PIV measurements for most cases. The uncertainty based on each algorithm is found to be unique, motivating the use of algorithm-specific uncertainty estimates.
TL;DR: A look at the history of this journal reveals some significant trends in the evolution of measurement science and shows how key papers published in the journal have influenced these developments as discussed by the authors, which can be found in the references therein.
Abstract: A look at the history of this journal reveals some significant trends in the evolution of measurement science and shows how key papers published in the journal have influenced these developments.
TL;DR: In this article, the authors applied an inductance-capacitance (LC) resonance method to an inductive pulse debris sensor to increase the sensitivity of small metallic wear debris.
Abstract: Detection of small metallic wear debris is critical to identify abnormal wear conditions for prognosis of pending machinery failure. In this paper we applied an inductance–capacitance (LC) resonance method to an inductive pulse debris sensor to increase the sensitivity. By adding an external capacitor to the sensing coil of the sensor, a parallel LC resonance circuit is formed that has a unique resonant frequency. At an excitation frequency close to the resonant frequency, impedance change (and thus change in voltage output) of the LC circuit caused by the passage of a debris particle is amplified due to sharp change in impedance at the resonant peak; thus signal-to-noise ratio and sensitivity are significantly improved. Using an optimized measurement circuit, iron particles ranging from 32 to 96 µm and copper particles ranging from 75 to 172 µm were tested. Results showed that the parallel LC resonance method is capable of detecting a 20 µm iron particle and a 55 µm copper particle while detection limits for the non-resonance method are 45 and 125 µm, respectively. In contrast to the non-resonant method, the sensitivity of the resonance method has been significantly improved.
TL;DR: In this paper, a multi-camera digital imaging system comprising eight optical imaging fibres and two RGB charged-couple device (CCD) cameras is used to acquire two-dimensional (2D) images of the flame simultaneously from eight equiangular directions.
Abstract: This paper presents an experimental investigation, visualization and validation in the three-dimensional (3D) reconstruction of flame temperature and emissivity distributions by using optical tomographic and two-colour pyrometric techniques. A multi-camera digital imaging system comprising eight optical imaging fibres and two RGB charged-couple device (CCD) cameras are used to acquire two-dimensional (2D) images of the flame simultaneously from eight equiangular directions. A combined logical filtered back-projection (LFBP) and simultaneous iterative reconstruction and algebraic reconstruction technique (SART) algorithm is utilized to reconstruct the grey-level intensity of the flame for the two primary colour (red and green) images. The temperature distribution of the flame is then determined from the ratio of the reconstructed grey-level intensities and the emissivity is estimated from the ratio of the grey level of a primary colour image to that of a blackbody source at the same temperature. The temperature measurement of the system was calibrated using a blackbody furnace as a standard temperature source. Experimental work was undertaken to validate the flame temperature obtained by the imaging system against that obtained using high-precision thermocouples. The difference between the two measurements is found no greater than ±9%. Experimental results obtained on a laboratory-scale propane fired combustion test rig demonstrate that the imaging system and applied technical approach perform well in the reconstruction of the 3D temperature and emissivity distributions of the sooty flame.
TL;DR: In this article, a 3D capacitance tomography measurement system was proposed for non-invasive void fraction calculation and flow structure identification in vertical and horizontal pipelines, which includes the 3D ECT sensor structure optimization process, the metrological evaluation of the image reconstruction accuracy and the developed liquid void fractions calculation method efficiency, in comparison with other common techniques.
Abstract: The industrial diagnostic and monitoring systems still require new methods offering new possibilities of non-invasive observation and analysis of the two-phase gas–liquid mixture flows. This paper demonstrates a new measurement system dedicated for non-invasive void fraction calculation and flow structure identification in vertical and horizontal pipelines. The study of the metrological validation of the designed three-dimensional capacitance tomography measurement system is discussed here. This research includes the 3D ECT sensor structure optimization process, the metrological evaluation of the image reconstruction accuracy and the developed liquid void fraction calculation method efficiency, in comparison with other common techniques. As a result of the performed analysis the advantages of the designed 3D ECT measurement system for non-invasive real-time dynamic flow process identification were discussed.
TL;DR: In this paper, a tomographic reconstruction of 3D vortex-flame interactions was performed on two interacting turbulent premixed bluff-body stabilized flames under steady flow conditions and acoustic excitation.
Abstract: The tomographic reconstruction of OH ∗ chemiluminescence was performed on two interacting turbulent premixed bluff-body stabilized flames under steady flow conditions and acoustic excitation. These measurements elucidate the complex three-dimensional (3D) vortex‐flame interactions which have previously not been accessible. The experiment was performed using a single camera and intensifier, with multiple views acquired by repositioning the camera, permitting calculation of the mean and phase-averaged volumetric OH ∗ distributions. The reconstructed flame structure and phase-averaged dynamics are compared with OH planar laser-induced fluorescence and flame surface density measurements for the first time. The volumetric data revealed that the large-scale vortex‐flame structures formed along the shear layers of each flame collide when the two flames meet, resulting in complex 3D flame structures in between the two flames. With a fairly simple experimental setup, it is shown that the tomographic reconstruction of OH ∗ chemiluminescence in forced flames is a powerful tool that can yield important physical insights into large-scale 3D flame dynamics that are important in combustion instability.
TL;DR: The development of methods for measuring the dielectric properties of materials is reviewed with a special view to the background of the past 90 years in this article, where the close correlation between progress in measurement methods and scientific and technological advances is shown.
Abstract: The development of methods for measuring the dielectric properties of materials is reviewed with a special view to the background of the past 90 years. The close correlation between progress in measurement methods and scientific and technological advances is shown. The current state of techniques for the broadband dielectric spectroscopy of materials, covering the enormous range from about 10−5–1013 Hz, is reported. Also briefly presented are currently discussed methods for the scanning microwave microscopy as well as electrical tomography of objects. Reference to a wide spectrum of applications demonstrates the broad and diverse usability of dielectric measurement methods.
TL;DR: In this paper, a low-cost ozone sensor based on conductivity changes of heated tungstic oxide is presented, which is capable of accurately measuring ambient concentrations of ozone, using a combination of temperature steps and air flow-rate steps.
Abstract: This paper presents a novel low-cost instrument that uses a sensor based on conductivity changes of heated tungstic oxide, which is capable of accurately measuring ambient concentrations of ozone. A combination of temperature steps and air flow-rate steps is used to continually reset and re-zero the sensor. A two-stage calibration procedure is presented, in which a nonlinear transformation converts sensor resistance to a signal linear in ozone concentration, then a linear correlation is used to align the calibration with a reference instrument. The required calibration functions specific for the sensor, and control system for air flow rate and sensor temperature, are housed with the sensor in a compact, simple-to-exchange assembly. The instrument can be operated on solar power and uses cell phone technology to enable monitoring in remote locations. Data from field trials are presented here to demonstrate that both the accuracy and the stability of the instrument over periods of months are within a few parts-per-billion by volume. We show that common failure modes can be detected through measurement of signals available from the instrument. The combination of long-term stability, self-diagnosis, and simple, inexpensive repair means that the cost of operation and calibration of the instruments is significantly reduced in comparison with traditional reference instrumentation. These instruments enable the economical construction and operation of ozone monitoring networks of accuracy, time resolution and spatial density sufficient to resolve the local gradients that are characteristic of urban air pollution.
TL;DR: The Journal of Scientific Instruments (JSI) was the first scientific instrument journal published by the Institute of Physics (IOP) in 1923 as mentioned in this paper and has been published for 90 years since then.
Abstract: Dear authors, reviewers and readers of Measurement Science and Technology, As a New Year dawns I would like to thank all those who have published papers with us in 2012, and offer a special thanks go to those of you who have given up much of your precious time and kindly reviewed articles for the journal. I would also like to take this opportunity to update you all on some of the developments on the journal as we look ahead to a 2013 that will be a very special year for MST. Something that many readers may not be aware of is that Measurement Science and Technology was the world's first scientific instrument journal, and in 2013 we will be celebrating 90 years since the journal was first published. In 1923 the Institute of Physics launched the Journal of Scientific Instruments in order to capture the essential information regarding the design and performance of instruments, which was then often unobtainable from books or articles focused on results. The journal has moved with the times over the 90 years since its first publication, changing its name and scope to ensure it reflects the community it serves, but the dissemination of useful measurement knowledge has always been its core purpose. In 2013 we will be celebrating the sustained success of the journal with a series of articles and events throughout the year. These include a one-day 'Frontiers of Measurement' meeting to be held at the Institute of Physics, London, on 21 March. We do hope you can join us and leading speakers for this exciting event. We also think you will enjoy reading the articles in this special reviews issue which will showcase some of the best research in the journal's scope as well as look back over the past 90 years with a historical perspective by Richard Dewhurst and a historical review of the measurement of dielectric properties of materials by Udo Kaatze. Regular readers will already be familiar with our special issue programme, collecting original research papers in areas of interest to our readers. We can look forward in 2013 to the publication of special issues on 3D velocimetry and optical fibre sensors, areas where we have a long history of publishing articles from the some of the best researchers in the field. In my first year as Editor, I have enjoyed gaining an overview of other fields, in particular through the review articles. Multidisciplinarity, bound by the common language of measurement, is a hallmark of Measurement Science and Technology. It still impresses me that I can be reading about the measurement of protein dynamics [1] in one issue and measuring the interior of volcanoes [2] in another! As is so often the case, translating methods across research fields can break through the limits of traditional approaches and produce a real game-changer. By signing up to receive table of contents alerts, one can browse the journal and pick out topics of interest as well as experience the serendipity that comes from seeing things from the perspective of another research field. This seldom happens when looking at more narrowly focused journals or subject alerts. As this is a special year for the journal we are planning to publish several perspectives articles from members of our Editorial Board. Those published already have proved very popular so far as they give a personal view on a topic of current interest and help express the unique character of the journal. When speaking to young researchers I am particularly aware that having their articles published in a timely fashion is important, and I am pleased that our publication times are highly competitive, with most authors receiving a publication decision within six weeks and most articles being published a month after acceptance. Looking forward to 2013, we will continue to rely on our esteemed reviewers, for their help in determining which articles make a significant contribution to the field of measurement. Their work is highly valued, not only by those of us who work directly on the journal, but also by the readers who can continue to refer to MST knowing that only work of a high standard is published here. Finally I wish to thank the Institute of Physics Publishing team and the whole Editorial Board of Measurement Science and Technology. Their professionalism, expertise and dedication have, together with the fine work of authors and reviewers, led directly to the journal's impact factor (a measure of the average number of times recent papers are referenced by others) rising to its all-time high of 1.494. Impact factor is often taken as an indication of the quality and relevance of recently published research, and although as researchers we develop our own instinct for recognizing journals of high quality, it is gratifying as an Editor to see the data from an independent organization (Thomson ISI) agreeing with my own assessment. In research, as in commerce, competition raises quality and it is especially encouraging that our impact factor is now, for the first time, the highest in the sector of wide-ranging instrumentation and techniques. There simply remains for me to say thank you again for your contribution to Measurement Science and Technology in 2012, and wish you all the very best for a successful 2013! References [1] Adamczyk K et al 2012 Measuring protein dynamics with ultrafast two-dimensional infrared spectroscopy Meas. Sci. Technol. 23 062001 [2] Okubo S and Tanaka H K M 2012 Imaging the density profile of a volcano interior with cosmic-ray muon radiography combined with classical gravimetry Meas. Sci. Technol. 23 042001
TL;DR: In this paper, a method for determining the lateral resolution of areal surface topography measuring instruments using a type ASP (star-shaped) material measure is presented. And the resolution of a phase shifting interferometer was determined based on the ISO definition of the lateral period limit.
Abstract: Calibration of the scales of areal surface topography measuring instruments requires testing of the resolution. Several designs of artefact that allow testing of the resolution of such instruments are currently available; however, analysis methods need to be developed to provide comparable results. A novel method for determining the lateral resolution of areal surface topography measuring instruments is presented. The method uses a type ASP (star-shaped) material measure. To demonstrate the validity of the method, the resolution of a phase shifting interferometer was determined based on the ISO definition of the lateral period limit. Using the proposed method, the type ASP material measure, which is often used to judge qualitatively an instrument's resolution, can be used to quantitatively estimate the resolution of instruments using the topography data.
TL;DR: In this paper, a dual-comb interferometric method was proposed to eliminate the dead zones in the measurement range by separating the measurement pulses from the reference pulses using orthogonal polarization.
Abstract: Absolute distances were measured using two femtosecond lasers of different pulse repetition rates by revisiting the dual-comb interferometric method proposed by Coddington et al (2009 Nature Photon. 3 351–6). The apparatus built for experiments was designed to eliminate the dead zones in the measurement range by separating the measurement pulses from the reference pulses using orthogonal polarization. In addition, the pulse repetition rate of the signal laser was made tunable in order to extend the non-ambiguity range (NAR) by adaptively adjusting the synthetic wavelength in consideration of the de facto measurement stability in the air. Actual tests performed in the open air proved that a target distance of 69.3 m is measured without interruptions at a 200 µs update rate in the presence of a ~170 µm drift of the optical path length caused by the fluctuation of the refractive index of air. The proposed hardware system design for effective NAR extension will facilitate the use of dual-comb interferometry for various terrestrial applications.
TL;DR: This review identifies gaps in the literature which require attention for the realization of both truly portable and in-situ CE systems and emphasizes the importance of a holistic approach.
Abstract: Capillary electrophoresis (CE) is a technique which uses an electric field to separate a mixed sample into its constituents. Portable CE systems enable this powerful analysis technique to be used in the field. Many of the challenges for portable systems are similar to those of autonomous in-situ analysis and therefore portable systems may be considered a stepping stone towards autonomous in-situ analysis. CE is widely used for biological and chemical analysis and example applications include: water quality analysis; drug development and quality control; proteomics and DNA analysis; counter-terrorism (explosive material identification) and corrosion monitoring. The technique is often limited to laboratory use, since it requires large electric fields, sensitive detection systems and fluidic control systems. All of these place restrictions in terms of: size, weight, cost, choice of operating solutions, choice of fabrication materials, electrical power and lifetime. In this review we bring together and critique the work by researchers addressing these issues. We emphasize the importance of a holistic approach for portable and in-situ CE systems and discuss all the aspects of the design. We identify gaps in the literature which require attention for the realization of both truly portable and in-situ CE systems.
TL;DR: The positioning algorithms implemented in goGPS are presented, emphasizing the modularity of the software design; two specific strategies to support the navigation with low-cost receivers are also proposed and discussed, namely an empirical observation weighting function calibrated on the receiver signal-to-noise ratio and the inclusion of height information from a digital terrain model as an additional observation in the Kalman filter.
Abstract: goGPS is a free and open source satellite positioning software package aiming to provide a collaborative platform for research and teaching purposes. It was first published in 2009 and since then several related projects are on-going. Its objective is the investigation of strategies for enhancing the accuracy of low-cost single-frequency GPS receivers, mainly by relative positioning with respect to a base station and by a tailored extended Kalman filter working directly on code and phase observations. In this paper, the positioning algorithms implemented in goGPS are presented, emphasizing the modularity of the software design; two specific strategies to support the navigation with low-cost receivers are also proposed and discussed, namely an empirical observation weighting function calibrated on the receiver signal-to-noise ratio and the inclusion of height information from a digital terrain model as an additional observation in the Kalman filter. The former is crucial when working with high-sensitivity receivers, while the latter can significantly improve the positioning in the vertical direction. The overall goGPS positioning accuracy is assessed by comparison with a dual-frequency receiver and with the positioning computed by a standard low-cost receiver. The benefits of the calibrated weighting function and the digital terrain model are investigated by an experiment in a dense urban environment. It comes out that the use of goGPS and low-cost receivers leads to results comparable with those obtained by higher level receivers; goGPS has good performances also in a dense urban environment, where its additional features play an important role.
TL;DR: In this paper, the theory of optical transfer functions in 3D imaging is presented, with a focus on suitable methods for the establishment of calibration standards for 3D images and surface topography measurements.
Abstract: A significant number of areal surface topography measuring instruments, largely based on optical techniques, are commercially available. However,implementation of optical instrumentation into production is currently difficult dueto the lack of understanding of the complex interaction between the light and the component surface. Studying the optical transfer function of the instrument can help address this issue. Herea review is given of techniques for the measurement of optical transfer functions. Starting from the basis of a spatially coherent, monochromatic confocal scanning imaging system, the theory of optical transfer functions in three-dimensional (3D) imaging is presented. Further generalizations are reviewed allowing the extension of the theory to the description of conventional and interferometric 3D imaging systems. Polychromatic transfer functions and surface topography measurements are also discussed. Following presentation of theoretical results, experimental methods to measure the optical transfer function of each class of system are presented, with a focus on suitable methods for the establishment of calibration standards in 3D imaging and surface topography measurements.
TL;DR: In this article, an experimental apparatus for gas/oil/water flow measurement based on a flow-conditioning device and electrical capacitance tomography (ECT) and microwave sensors was developed.
Abstract: In the oil industry, it is important to measure gas/oil/water flows produced from oil wells. To determine oil production, it is necessary to measure the water-in-liquid ratio (WLR), liquid fraction and some other parameters, which are related to multiphase flow rates. A research team from the University of Manchester and Schlumberger Gould Research have developed an experimental apparatus for gas/oil/water flow measurement based on a flow-conditioning device and electrical capacitance tomography (ECT) and microwave sensors. This paper presents the ECT part of the developed apparatus, including the re-engineering of an ECT sensor and a model-based image reconstruction algorithm, which is used to derive the WLR and the thickness of the liquid layer in oil-continuous annular flows formed by the flow-conditioning device. The ECT sensor was tested both at Schlumberger and on TUV-NEL's Multiphase Flow Facility. The experimental results are promising.
TL;DR: In this article, a method for increasing the accuracy and extending the dynamic range of time-resolved particle image velocimetry (PIV) is introduced. But the method is based on tracking the patterned fluid element, within a chosen interrogation window, along its individual trajectory throughout an image sequence.
Abstract: A novel method is introduced for increasing the accuracy and extending the dynamic range of time-resolved particle image velocimetry (PIV). The approach extends the concept of particle tracking velocimetry by multiple frames to the pattern tracking by cross-correlation analysis as employed in PIV. The working principle is based on tracking the patterned fluid element, within a chosen interrogation window, along its individual trajectory throughout an image sequence. In contrast to image-pair interrogation methods, the fluid trajectory correlation concept deals with variable velocity along curved trajectories and non-zero tangential acceleration during the observed time interval. As a result, the velocity magnitude and its direction are allowed to evolve in a nonlinear fashion along the fluid element trajectory. The continuum deformation (namely spatial derivatives of the velocity vector) is accounted for by adopting local image deformation. The principle offers important reductions of the measurement error based on three main points: by enlarging the temporal measurement interval, the relative error becomes reduced; secondly, the random and peak-locking errors are reduced by the use of least-squares polynomial fits to individual trajectories; finally, the introduction of high-order (nonlinear) fitting functions provides the basis for reducing the truncation error. Lastly, the instantaneous velocity is evaluated as the temporal derivative of the polynomial representation of the fluid parcel position in time. The principal features of this algorithm are compared with a single-pair iterative image deformation method. Synthetic image sequences are considered with steady flow (translation, shear and rotation) illustrating the increase of measurement precision. An experimental data set obtained by time-resolved PIV measurements of a circular jet is used to verify the robustness of the method on image sequences affected by camera noise and three-dimensional motions. In both cases, it is demonstrated that the measurement time interval can be significantly extended without compromising the correlation signal-to-noise ratio and with no increase of the truncation error. The increase of velocity dynamic range scales more than linearly with the number of frames included for the analysis, which supersedes by one order of magnitude the pair correlation by window deformation. The main factors influencing the performance of the method are discussed, namely the number of images composing the sequence and the polynomial order chosen to represent the motion throughout the trajectory.
TL;DR: In this paper, the trajectories, the translation and rotation of finite-size inertial particles together with turbulent flow are measured simultaneously in three dimensions by tracking the temporal evolution of small fluorescent tracer particles.
Abstract: We report a novel experimental technique that measures simultaneously in three dimensions the trajectories, the translation and the rotation of finite-size inertial particles together with the turbulent flow. The flow field is analyzed by tracking the temporal evolution of small fluorescent tracer particles. The inertial particles consist of a super-absorbent polymer that renders them index and density matched with water and thus invisible. The particles are marked by inserting at various locations tracer particles into the polymer. Translation and rotation, as well as the flow field around the particle are recovered dynamically from the analysis of the marker and tracer particle trajectories. We apply this technique to study the dynamics of inertial particles much larger in size (Rp/η ≈ 100) than the Kolmogorov length scale η in a von Karman swirling water flow (Rλ ≈ 400). We show, using the mixed (particle/fluid) Eulerian second-order velocity structure function, that the interaction zone between the particle and the flow develops in a spherical shell of width 2Rp around the particle of radius Rp. This we interpret as an indication of a wake induced by the particle. This measurement technique has many additional advantages that will make it useful to address other problems such as particle collisions, dynamics of non-spherical solid objects, or even of wet granular matter.
TL;DR: In this article, a passive vision-sensing system, comprising two cameras and composite filtering techniques, was proposed for real-time detection of the bead height and width through deposition of thin walls.
Abstract: Additive manufacturing based on gas metal arc welding is an advanced technique for depositing fully dense components with low cost. Despite this fact, techniques to achieve accurate control and automation of the process have not yet been perfectly developed. The online measurement of the deposited bead geometry is a key problem for reliable control. In this work a passive vision-sensing system, comprising two cameras and composite filtering techniques, was proposed for real-time detection of the bead height and width through deposition of thin walls. The nozzle to the top surface distance was monitored for eliminating accumulated height errors during the multi-layer deposition process. Various image processing algorithms were applied and discussed for extracting feature parameters. A calibration procedure was presented for the monitoring system. Validation experiments confirmed the effectiveness of the online measurement system for bead geometry in layered additive manufacturing.