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We have carried out photoacoustic measurements of the thermal diffusivity on samples of laboratory produced chemically bleached wood pulps, as well as on samples of several commercially available papers. Our results for bleached pulps indicate that the thermal diffusivity is correlated to each of the chemical bleaching controlling parameters (the kappa number, viscosity and brightness) measured during distinct phases of the bleaching processes. Also, the values of the thermal diffusivities for the commercial papers were found to be adequate for their end uses. It turned out that photoacoustic measurements can be a valuable research laboratory and/or industrial plant tool for comparing and controlling the properties of pulp and paper and for evaluating the effects of processing parameters upon these properties.

Understanding of wetting processes for papers of various qualities is important for the analysis and the adjustment of paper-production processes as well as for designing properties of paper for printing. In this investigation, papers of one kind with three different sizing-content values were examined by time-dependent attenuation of ultrasound transmission in mixtures of isopropanol and water. The attenuation depends on the stage of absorption of liquid into the paper sample, which furnishes the signature of the paper type and quality. Papers that have contact angles of 40° (without size), 70° (low size content) and 110° (high size content) were tested and a measurement procedure was developed. The measurement results showed that the development of attenuation with time differs at different frequencies, indicating the possibility of detecting various phases of wetting phenomena.

Softness is one of the major properties of tissue paper. Tissue softness can be divided into bulk and surface softness. The bulk softness can be measured quite reliably by measuring the thickness and elasticity of a sheet. However, the measurement of surface softness is not straightforward. One significant factor influencing surface softness is the fibers extending from the surface of the tissue paper. This paper presents a novel imaging method to detect the amount of such fibers on the tissue paper. The method is based on the detection of shadows caused by the free fiber ends. The shadows cannot be detected as such from the reflectance image of the sheet because of the wavy surface of tissue paper. Thus, the 3D information of the surface was estimated based on the photometric stereo, and the intensity variations caused by the wavy surface were filtered out. The method has the advantages over previous methods of improved accuracy and the possibility of implementation in a running paper machine.

This study proposes a new method for the characterization of paper surface and bulk structure: optical coherence tomography (OCT). Although having been used in medicine for years, this technique is still relatively unknown in the paper-making industry. First, we provide a brief description of a conventional PC-controlled measurement system for the OCT imaging of paper. In this set-up, a powerful superluminescent diode is used to illuminate a Michelson interferometer with a free-space configuration, and a piezo-transducer is placed in the optical delay line to modulate the measurement signal for optical heterodyne detection. The set-up is then applied to demonstrate the ability of the technique to visualize the surface structures of widely disparate paper samples using a single device. Next, the paper provides 3D images of a fibre network and of typical copy paper. The results prove that OCT is applicable not only to the 3D imaging of simple wood fibre networks, but also to the imaging of complex commercial paper, provided that an appropriate clearing agent is used. Finally, the effect of filler on the OCT signal slope calculated by averaging several A-scans from the sample is demonstrated, showing that increasing filler content produces a corresponding decrease of decay of the A-scan in depth.

We introduce a method to measure paper wetting based on the measurement of monochromatic (670 nm) light transmission through paper. The samples were 49.8–51.7 g m−2 handsheets, the hydrophobicity of which was tuned by the fibre content of the furnish. In addition, one of the samples was internally sized. Impact wetting with isopropanol and water mist pulses was applied. The duration of a pulse was 100 ms, and the amount of liquid per pulse was 12.6 ± 1.2 g m−2. Optical changes in a paper sample were detected by measuring the average intensity of transmitted light through a selected area. The results showed that different wetting processes (pure capillary and combined capillary and diffusion wetting) could be distinguished from each other. With the presented method, differences in the individual behaviour of the samples during wetting could also be seen.

New methods for measuring barrier properties against solvents, acids and bases on dispersion coated paper were developed and investigated. Usability, reliability and repeatability were compared both between the new methods and with the standardized method for measuring barrier properties against water vapor. Barrier properties could be measured with all methods and the results obtained by the different methods were in correlation with each other. A qualitative method based on a trace color provided an indicative result, whereas further developed methods also took into account the durability. The effective barrier lifetime could be measured by measuring the conductivity through the substrate as a function of time, or by utilizing a glass prism where the change in refractive index caused by penetrated liquid was monitored, also as a function of time. Barrier properties against water and humidity were also measured and were found not to be predictors for barrier properties against either solvents, or acids or bases, which supports the need to develop new methods.

This paper reports use of a nondestructive, miniaturized, microwave microstrip ring resonator for moisture sensing application in papers. Advantages offered by this sensor over the prevailing sensors are room-temperature operation, response time in milliseconds, measurements unaffected by dusty environment and ionic conductivity of samples. Samples of eleven types were tested, with grammage (grams per square metre) and thickness varying from 21 to 70 g m−2 and 24 to 80 µm respectively. The wet basis moisture normalization (with respect to instantaneous moisture content in the sample) was established to remove scatter and to bring out clearly grammage dependence, thus avoiding error in moisture prediction due to density variations, using only scalar measurements. A single equation for fr variations is realized in terms of grammage and normalized percentage moisture (Mww) which is valid for all types of tested paper. A model of the wet paper is suggested mainly based on water–dry paper interaction, also considering parameters like thickness and surface roughness, to explain trends of the sensitivity curves. The estimated %Mww shows an error of ±0.9% in the estimated value as compared to the actual value.

In the first part of this work ultrasonic thickness resonances were measured with offset paper samples, 80-240 g m-2 in grammage. The resonance frequency was found to be linearly dependent on the grammage of the samples. In the second part of this investigation 240 g m-2 offset paper samples were wetted with a mist pulse of either water or isopropanol. This pulse, 61±4 ms in duration, was generated by a high-power ultrasonic actuator. The change in resonance frequency, initially 660±5 kHz, was monitored during the wetting of the paper sample. An ultrasonic burst, frequency swept from 500 to 900, 600 to 1000 and 1300 to 1700 kHz, was transmitted through the sample at a 10 Hz repetition rate. This made it possible to follow the wetting of the sample at several frequencies by the same measurement. It was also possible to follow the temporal development of the apparent absorption coefficient of the sample. The shape of the transmission curves suggests that two different processes, capillary wetting and diffusion wetting, can be distinguished.

We investigated the change in surface roughness of paper during wetting. Four kinds of paper were examined by time-dependent attenuation of focused 1.2 MHz airborne ultrasound reflected from a paper sample. The samples were wetted with fog from mixtures of water and isopropanol and the transmitted ultrasonic signal was measured at 15 ms intervals for 16 s after the application of the mixture. The results showed that the attenuation of the reflected sound by time differs for various kinds of paper, indicating that there are differences in the development of wetting.

The quality of the optical surface of commercial paper after laser printing was investigated using a sensor based on a diffractive element. Using a new sensor set-up, it was possible to gain image information about reflection and transmission of light, at normal light incidence, from paper simultaneously. These two parameters were measured before and after laser printing. Image data revealed information about the gloss and surface roughness of paper as well as the influence of the black ink used in printing.

Paper–oil insulation in power transformers is degraded and gradually damaged due to electrical, chemical, mechanical and moisture factors. It is well established from several studies that moisture is a major source of insulation failure in high voltage power transformers. Measurement and monitoring of moisture is essential to predict life and operation condition for power transformers. This paper presents direct optical measurement of water content at paper insulation immersed in transformer oil inside a test cell, which contains a water source, and a capillary paper bridge to transfer water to the paper inside an oil reservoir. Optical measurement of water content was carried out in the near infrared from 900 to 1500 nm band. Experimental studies of light transmission in transformer oil and water are discussed. The criteria to establish the best optical bands for maximum sensitivities are given. The measurement limitations, calibration procedures and an error analysis are presented. The resulting technique can be used for on-line measurements in electrical apparatus that use oil–paper insulation under large electrical field gradients. The presented method has advantages, since it is a direct and fast technique to measure the water transfer to paper immersed in oil, and it could be applied in compact portable equipment at a low cost.

Surface topography, surface roughness, and surface conductivity of oil-impregnated insulation paper were studied during the damage process caused by partial discharge within the cavity of the paper. Products generated on the surface during this process were studied, as well. According to phase-resolved partial discharge patterns, the damage process can be divided into five stages. At each of the stages, surface conditions of insulation were analyzed by optical microscopy, scanning electron microscopy, atomic force microscopy and high-resistance meter. 'Ablating', 'peeling', 'cracking in silk', 'pitting' and 'electrical treeing' appear on insulation surfaces one after another during the five stages of the damage process, along with sequential generation of droplets and crystalline solids. Surface roughness initially decreases, then increases. Finally, surface conductivity exhibits a general increasing trend, before it eventually stabilizes. However, its growth rate varies in different stages of damage.

The demand for high-quality recycled pulp products has increased the need for an efficient deinking process. Assessing process efficiency via residual ink on test sheets has so far been limited to the sheet surface due to the poor transparency of paper. A refractive index matching method was studied to obtain a quantitative measure of particles within the volume of a paper sheet. In actual measurements a glass plate with etched lines from 8.5 ?m to 281.1 ?m wide was placed beneath the layers of cleared paper, and visible lines were counted with a microscope. Three different paper grades were tested with transparentizing agents. A diffusion theory-based regression model was used to find a correlation between transparency, paper grammage and paper thickness. These equations enable the determination of the size of an object detectable from a paper with a certain transparentizing agent or the parameters of a test sheet needed to detect objects of a known size. Anise oil was found to be the better of the two agents used, and they both had better transparentizing ability than air or water. The transparent paper grammage of the paper grades was determined for all the tested media. Paper's transparency was found to depend more on paper's thickness than grammage.

The consistency of fibres and concentration of fines need to be controlled during the production process in the paper industry. In paper pulp, fibre lengths range from less than a millimetre to several millimetres whereas fines particles have sizes of a few tens of micrometres. Therefore, the two fractions have different properties of optical scattering and acoustic attenuation, i.e., fibres produce more forward optical scattering and acoustic attenuation, while fines produce larger and more homogeneous scattering but less acoustic attenuation. Based on these facts, we specifically develop a new method, a scattering photoacoustic technique, to measure the consistency of fibres and concentration of fines simultaneously. It employs near-infrared light (1064 nm wavelength) to produce three acoustic waves with MHz frequencies. One piezoelectric transducer detects these waves, which are used to measure optical scattering and acoustic attenuation of pulp samples. The results indicate that our current apparatus successfully discerned the pure fibre and fines samples. It also proved capable of extracting the consistencies of fines and fibres in the studied samples that consisted of mixtures of fibre and fines. Finally, the scattering photoacoustic technique has a potential ability in online measurement of fibre and fines consistencies in pulp suspensions.

In this study, methods based on ultrasonic attenuation and optical time-of-flight measurements are used simultaneously in determining both the fibres and fines mass fractions, respectively, of a cellulose pulp fibre suspension. The optical measurements are done by a laser radar and the acoustical measurements are based on ultrasonic attenuation measurements in a pulse-echo set-up. Two kinds of long-fibre fractions are studied, thermo-mechanical pulp and chemical softwood pulp. Fibre and fines mass fraction ranges are 0.25–1.0% and 0–0.75%, respectively. The results show that the fibres are the predominant source for absorption and scattering of ultrasonic waves and are thus mainly contributing to the attenuation of ultrasound in the pulp. It is also found that the fines are the predominant source for optical scattering and fines are thus mainly contributing to the propagation delay of the light pulse in the laser radar set-up. By combining the ultrasonic attenuation and the optical time-of-flight measurements, it is shown that the mass fraction of fines and the mass fraction of fibres in a pulp sample could be determined, respectively. Validerad; 2006; 20060913 (ysko)

An optical method based on light extinction was used in measuring pulp quantity in the plate gap of a 10 MW thermomechanical pulping refiner for the first time. The relationship between pulp quantity and light extinction was determined by empirical laboratory experiments. The empirical relationship was then applied to interpret the image data obtained from field measurements. The results show the local distribution of pulp in the refiner plate gap for different rotor plate positions and refiner operation points. The maximum relative uncertainty in the measured pulp quantity was 50%. Relative pulp distributions were measured at higher accuracy. The measurements have influenced the development of a laser-based optical diagnostic method that can be applied to the quantitative visualization of technically demanding industrial processes.

A graphene oxide (GO), reduced graphene oxide (RGO) and poly(3,4-ethylenedioxytiophene)-reduced graphene oxide (PEDOT-RGO composite) gas sensors were successfully fabricated using an electrodeposition method. The electrodeposition was carried out in aqueous GO dispersions. In order to obtain RGO and PEDOT-RGO, the electrochemical reduction of GO and PEDOT-GO was carried out in 0.1 M KCl at constant potential of −0.85 V. The GO, RGO and PEDOT-RGO composites were characterized by scanning and high resolution transmission electron microscopies with electron energy loss spectroscopy, Fourier-transform infrared and Raman spectroscopies. In this work the effect of GO electrochemical reduction process was discussed. The effects of the humidity and sensing response of GO, RGO and PEDOT-RGO to different gases were investigated. It was found out the PEDOT-RGO response to NO2 was much higher than to the other analyzed gases. The influence of the operating temperature on the gas sensing response was compared. The role of the polymer and RGO in PEDOT-RGO composite has been indicated. The results are discussed in light of recent literature on graphene sensors.

In this paper we introduce a novel photoacoustic sensing technique that captures a photoacoustic signal excited by a laser light pulse after the light has propagated through a turbid medium. Simultaneously, the ultrasonic sound wave is captured after it has propagated through the same turbid medium. By combining the two signals, more information on the investigated medium can be obtained. Applications can be found in the pulp and paper industry where monitoring wood pulp compositions is of interest. Depending on its origin, pulp suspension contains different compositions of fibres and fibre fragments (fines). Poor control of the pulp composition leads to an unstable process that compromises the production, quality and energy efficiency in the pulp mill. The result shows the feasibility of the photoacoustic sensor in monitoring the mass fractions of fibres and fines in a pulp suspension. The first received echo, corresponding to the light interaction with the sample, showed a stronger correlation to the fines mass fraction compared to fibre mass fraction. The second echo, corresponding to the sound wave interaction with the sample, showed a much stronger correlation to fibre mass fraction than to fines mass fraction. Hence, it is proposed that by combining these two echoes, more information about the pulp suspension could be extracted than from any other sensor built on a single sensing principle.

Cystic fibrosis (CF) is a life-threatening genetic disease. At present, the common method for diagnosis of CF is to detect the chloride concentration in sweat using ion-selective electrodes. However, the current sweat testing methods require a relatively large quantity of sweat sample, at least 25 μL, which is very difficult to obtain, especially for newborns. This paper presents a new method and a new device for rapid detection of the chloride concentration from a small volume of solution. In this method, the chloride concentration is determined quantitatively by the fluorescence intensity of MQAE, a chloride ion fluorescent indicator. In this device, the sample is carried by a small piece of filter paper on a cover glass exposed to an UV LED light source. The resulting fluorescent signals are detected by a Si photodiode. Data acquisition and processing are accomplished by LabVIEW software in a PDA. Based on the Stern–Volmer relationship, the effects of different parameters on the fluorescence intensity were analyzed. The observed significant difference between 40 and 60 mM (the borderline of chloride concentration for CF) is discussed in this paper. The results show that detection can be completed within 10 s. The minimum detectable volume of the chloride solution is 1 μL. The novel method and the device are of great potential for CF diagnosis.

An innovative backward-mode photoacoustic transducer was developed, consisting of an optical fibre, a composite absorber, piezoelectric film and high impedance preamplifier. By receiving scattering light from a turbid suspension, the transducer produces a photoacoustic source in it. This source emits two photoacoustic waves travelling in opposite directions. The waves' amplitudes relate to the optical scattering properties of the suspension, and the echo of a wave returning from the suspension carries information of acoustic attenuation. By assessing the optical scattering and acoustic attenuation, fraction consistencies in a two-fractional suspension can be determined if one fraction dominantly scatters light and the other mainly attenuates ultrasound. This technique is used in this paper to investigate paper pulp suspensions. Pulp consists of wood celluloses and wood fines (or extra-added fillers in some cases), where cellulose lengths range from a few sub-millimetres to millimetres and fines/filler sizes are a few tens of micrometres or smaller. Due to their different size and shape, celluloses and fines (or fillers) have different optical scattering and acoustic attenuation properties. Experimental results showed that the transducer can measure pulp consistency with good linearity at least in the range from 0.5% to 3%, and that it can distinguish pulp cellulose from fines or fillers (TiO2 particles). Needless to say, this technique is also suitable for determining other suspensions in the food, pharmaceutical and mineral industries.

A non-destructive ultrasonic tester was developed to measure the stiffness of pulp bundles. The mechanical properties of pulp are important when estimating the behaviour of paper under stress. Currently available pulp tests are tedious and alter the fibres structurally and mechanically. The developed tester employs (933 ± 15) kHz tweezer-like ultrasonic transducers and time-of-flight measurement through (9.0 ± 2.5) mm long and (0.8 ± 0.1) mm thick fibre bundles kept at (19.1 ± 0.4) °C and (62 ± 1)% RH. We determined the stiffness of soft wood pulps produced by three kraft pulping modifications: standard kraft pulp, (5.2 ± 0.4) GPa, prehydrolysis kraft pulp, (4.3 ± 0.4) GPa, and alkali extracted prehydrolysis kraft pulp, (3.3 ± 0.4) GPa. Prehydrolysis and alkali extraction processes mainly lowered the hemicellulose content of the pulps, which essentially decreased the fibre-wall stiffness hence impairing the stiffness of the fibre networks. Our results indicate that the method allows ranking of pulps according to their stiffness determined from bundle-like samples taken at an early phase of the papermaking process.

Defects over a highly reflective rotary surface (HRRS) may change the service performance, lifespan and safety properties of products. Therefore, defect detection is very important for surface quality assurance. In this paper, the attributes of HRRS defect detection are described. Then, a comparative overview in terms of key parameters in the HRRS defect detection systems is elaborated. Finally, this paper reviews various detection technologies for HRRS defect detection and categorizes the previous literature by their detection technologies, which can provide a reference for further implementation and improvements in this field. This study provides guidelines for selecting which scheme is the most suitable when designing new HRRS defect detection systems.

Lab-on-chip (LOC) is recognised as one of the most affordable solutions for integrating electronics and fluidics devices. In this field, bonding plays a vital role because it provides the means for attaching multiple components onto a substrate, transforming them into a microfluidic circuit. Bonding is an integral step, especially when designing a device that is free from leakage and eventual clogging. A comprehensive review of the latest irreversible bonding technologies is discussed in this paper, in which the focus is on the layered microfluidic systems with large sensor arrays. This review covers microfluidic devices fabricated from a rigid-type glass–fibre-printed circuit board and a thermoplastic flexible printed circuit with 186 references whose development date back three decades ago. The bonding techniques are organised into the following four groups: (a) adhesive bonding, (b) thermal and solvent bonding, (c) surface modification and dry bonding and (d) photoresist groups. Other techniques are available beyond these groupings, but they can be classified into the nearest group to facilitate the discussion. This paper will benefit researchers and practitioners aiming to develop polymer-based LOC devices.

This paper presents a method for the calibration of contact heat flow sensors and the measures taken to improve the overall standard uncertainty of the measurements. This may be particularly relevant for applications such as the thermal characterization of Li-ion battery cells, where small amounts of transferred heat must be measured. The designed calibration set-up is based on the measurement of temperature gradients within a reference object, which is a common and well known approach. However, certain aspects must be considered in order to obtain accurate results. In this paper all steps taken to improve the overall measurement uncertainty are described. One of the most important characteristics of the presented methodology is the experimental determination of an equivalent thermal conductivity of the used reference object. To do so, a single-sided guarded hot plate apparatus is integrated into the calibration set-up to generate a precisely known heat flow. This approach is comparable to the determination of the ‘energy equivalent’ in calorimeters. The measured equivalent thermal conductivity agrees well to literature values, but the achieved standard uncertainty is significantly lower. By way of example, the calibration method is applied on a thermoelectric generator, where the temperature dependent sensitivity and the Seebeck coefficient are determined and compared to literature values. The average standard uncertainty of the sensor sensitivity is ±1.86%, which is lower than most results published in the literature. At 20 °C the absolute value of the determined Seebeck coefficient of the examined thermoelectric element is only 2.7% higher than the value expected for the used material ( B i 2 T e 3 ).

Acoustic tomography (AT) is considered to be a non-intrusive and effective method of obtaining temperature distribution information. The reconstruction method is crucial to obtaining reliable results of AT measurement. This paper presents a new method of reconstructing the temperature field in a measuring domain. Numerical simulations and experimental studies are conducted in this paper to validate the performance and robustness of the proposed method. In addition, it is compared to the other acknowledged regularization methods in inverse problems. The reconstruction time is also discussed to explore the feasibility of performing the construction procedure in real time. The numerical results indicate that the proposed method has better performance than other regularization methods for different temperature distributions. Moreover, it shows better anti-noise ability in the condition that the time-of-flight is contaminated by noise. The experimental reconstruction results of these reconstruction methods are compared against thermocouple measurements, showing that the proposed method has superior reconstruction performance in most cases. Therefore it may serve as a promising reference for quality improvement of temperature distribution reconstruction in AT.

In recent years, ultrasonic Lamb waves have been widely applied to the field of non-destructive testing of plate-like structures as they have outstanding advantages, such as low attenuation, high sensitivity, and wide detection range. Current studies about defect-detection of plate-like structures using Lamb waves mostly focus on non-weld plate-like structures, and defect-detection methods are based on baseline data. This paper proposes a novel baseline-free damage inspection method of welded plate-like structures, which is based on the principle of reciprocity loss and combines the OPTICS and K-means intelligent clustering algorithms to achieve accurate defect localization. In order to verify the location accuracy of the clustering defect localization algorithm, this paper performs comparative experiments between the ellipse imaging algorithm and the clustering algorithm, which use baseline data as health signals. The comparative experimental results show that the single-defect location accuracy of the clustering algorithm is greatly improved compared with the traditional ellipse algorithm. Moreover, in order to verify the validity and feasibility of the baseline-free method, this paper applies this method to obtain characteristic signals and combines the clustering algorithm to locate both single-defect and double-defects. The experimental result of baseline-free method shows that this method can successfully detect and locate multiple defects, which gets rid of the dependence of baseline data.

Pressures are often measured in fast transient regimes, even if the transducers are not calibrated in dynamic regimes. If the solutions proposed for primary calibration of the dynamic response of pressure sensors must be fully recognised, secondary methods are also needed to disseminate the standard to final users. A method for assessing measurement uncertainty, carried out by comparison with a reference transducer, traceable to primary standard, is proposed here. A typical application is gas pressure measurement. This paper follows and supplements the work done on the Mach number method in 2018. For this work the reference transducer is calibrated by the ‘collective standard method’ currently used in the ‘Laboratoire de Métrologie Dynamique’( LNE/ENSAM). This primary standard uses steps of pressure as inputs for dynamic pressure calibration that are generated by shock tubes (STs) and fast-opening devices (FODs). The uncertainty on dynamic sensitivity is evaluated from the quasi-static to the low, medium and high-frequency range (up to 10 kHz) using bandwidth comparisons. To calibrate a secondary standard transducer in gas, the method also requires one or two step generators: an ST for high-frequency range calibration and a FOD for the low-frequency range. Concerning the main results of this paper, the transducer to be calibrated and the reference transducer are placed symmetrically on the endplate of an ST. The amplitude of the pressure step generated by the tube is used to excite the transducers. Finally, the uncertainty on the sensitivity in dynamic conditions is determined by comparison with a model expected to be exhaustive. The results are provided as an uncertainty budget assigned frequency by frequency. The question asked in this work concerns the measurand used in secondary calibration: can a pressure step generated by a non-ideal ST be used in the process of calibration by comparison, i.e. for a secondary dynamic calibration? A method is proposed. Since the secondary method is derived directly from the primary one, this paper recaps the primary dynamic calibration method in gas and the budget of the associated uncertainty. Then the paper presents a secondary method and options to overcome the principal default identified in the ST frequency range, namely the non-uniform pressure fields existing in the tube.

The friction force during the scanning of a three-dimensional (3D) probe inevitably leads to undesired tangential displacement, the processing of which is challenging, especially for probes with unequal stiffness. In this paper, a new friction-coupled measurement model of the probe is deduced based on the principle of mechanics so as to realize the positioning and tracking of any friction force between the stylus ball and the sample surface. Considering the two features of the time-varying normal displacement in the scanning and the 3D unequal stiffness of the probe, this paper reveals the nonlinear bidirectional conversion between the 3D resultant force and the resultant displacement at the measuring end. The measurement deviations and the geometric relationship among the frictional force, equivalent force, normal contact force and friction-coupled force are theoretically analyzed. In addition, the finite element analysis (FEA) and calibration experiment analyze the force characteristics and sensitivity of the probe, and obtain the friction-coupled measurement model for actual measurement. The designed measurement experiment on the scanning trajectory compares the calculation difference of the displacement and azimuth angles with and without friction, and obtains a conclusion consistent with the theory and simulation.

This paper proposes a new approach for processing measured data from active Infra Red (IR) thermography, where a soft sensing algorithm is exploited for in depth defect reconstruction. This is achieved by propagating the information gathered at the wall surface to the inner layers. Correlating the experimental 2D measurements to a Finite Element (FE) model of the tested specimen it is possible to update the model with the measured data and change the geometry of the simulated inner defect, until the surface temperature distribution calculated corresponds to the measured one. Following that strategy, the unknown defect geometry can be determined. The method developed and presented in this paper consists of an optimization problem based on the minimization of the difference between the surface temperature distribution measured on the sample subjected to an active thermography test and the one resulting from the FE model. The optimization variables are the geometrical parameters (depth, width, thickness and position) characterizing the defect which will be fully determined at the complete convergence, within a given tolerance, of the optimization problem. The method includes also a preprocessing algorithm, based on the same experimental data and FE model, which allows to determine thermal and mechanical properties of the object under test, like surface emissivity, heat capacity and material conductivity and density, which are often unknown especially in the case of works of art. This soft-sensing procedure has been applied to a virtual experiment to estimate the accuracy of the reconstructed geometry and to a simulacrum of ancient fresco including defects realized on purpose.

A magnetic catalyst could be applied in a fluidized bed to improve the catalytic efficiency in the methanation and selective hydrogenation processes. Its distributions play an important role in accelerating the reactions. Electromagnetic tomography (EMT) provides an effective solution for online monitoring of the distribution of a magnetic catalyst. However, most of the EMT systems were developed to investigate the conductivity distribution. A novel EMT for the reconstruction of permeability distribution is presented in this paper. The coils, of which the sensitivity are related to frequency and coil size, were used as receivers in conventional EMT systems. In this paper, a tunneling magnetoresistance (TMR) sensor is applied to take the place of the coil. Compared with coils, the advantages of a TMR sensor on the frequency-independence and spatial resolution were investigated. A coil-TMR array was designed, in which the coil geometry was optimized and the TMR sensor was selected. The sensitivity matrix of the novel system was calculated by the perturbation method in a 3D simulation model. A FPGA-based system was designed. The reconstruction results of the magnetic catalyst validated the practicability of the permeability EMT based on TMR sensors.

It is essential to measure the shear strength of soils and interface parameters between soils and geosynthetics for the safety design and stability analysis of geosynthetic-reinforced soil structures. These parameters recommended for engineering projects are normally measured by laboratory single-stage direct/interface shear and pull-out tests. The conventional single-stage tests are carried out on at least three representative specimens under three different normal stresses. However, a large quantity of specimens will be required for large-scale tests, with tedious sample preparation procedures, so large-scale single-stage testing will be very labour intensive, time consuming and expensive. Given that the multi-stage testing method is able to measure the shear strength parameters by testing only one representative specimen, this paper investigates the feasibility, reliability and applicability of the multi-stage testing method in large-scale direct/interface shear and pull-out tests. Two compacted soils and a geogrid were tested using both single-stage and multi-stage tests. It was found that the shear strengths obtained from the multi-stage tests were slightly lower that those obtained from the single-stage tests, and the inferred apparent cohesion and friction angle matched closely. In addition, the limitations of the multi-stage testing method were highlighted, and the measured direct shear strength of the soils, the interface shear strength and pull-out shear strength between the soils and the geogrid were also compared and discussed in this paper.

As dynamic loading experiments such as a shock compression test are usually characterized by short duration, unrepeatability and high costs, high temporal resolution and precise accuracy of the measurements is required. Due to high temporal resolution up to a ten-nanosecond-scale, a Stokes polarimeter with six parallel channels has been developed to capture such instantaneous changes in optical properties in this paper. Since the measurement accuracy heavily depends on the configuration of the probing beam incident angle and the polarizer azimuth angle, it is important to select an optimal combination from the numerous options. In this paper, a systematic error propagation-based measurement configuration optimization method corresponding to the Stokes polarimeter was proposed. The maximal Frobenius norm of the combinatorial matrix of the configuration error propagating matrix and the intrinsic error propagating matrix is introduced to assess the measurement accuracy. The optimal configuration for thickness measurement of a SiO2 thin film deposited on a Si substrate has been achieved by minimizing the merit function. Simulation and experimental results show a good agreement between the optimal measurement configuration achieved experimentally using the polarimeter and the theoretical prediction. In particular, the experimental result shows that the relative error in the thickness measurement can be reduced from 6% to 1% by using the optimal polarizer azimuth angle when the incident angle is 45°. Furthermore, the optimal configuration for the dynamic metrology of a nickel foil under quasi-dynamic loading is investigated using the proposed optimization method.

The main content dealt with in this paper is to present a new apparatus and a new method that can measure multiple mechanical properties through a single test in principle, which can be used for handle evaluation for textile materials. The comprehensive handle evaluation system for fabrics and yarns (CHES-FY) is a kind of apparatus that is capable of measuring mass, bending, friction and tensile behavior just through one pulling-out test, and is able to characterize the handle of fabrics, whose measurement principle and structure of the CHES-FY system in mass and bending steps are analyzed in the present paper. The shape of a hung fabric was captured by a digital camera, and its weight was calculated. Then, a three-point bending in principle was utilized to model and analyze the bending properties of the fabric, and the corresponding formula was obtained for calculating the bending rigidity of the fabric. The comparisons of mass and bending rigidity based on 17 fabrics have been conducted by using CHES-FY, electronic balance and KES-FB2, respectively. The measured results show that there are high correlations between the three measuring systems for fabrics. It indicates that the approach using CHES-FY is feasible and accurate in measuring and characterizing mass and bending rigidity.

Complex permittivity measurement of low permittivity thin films is necessary to understand the fundamental properties and to implement these materials in devices. A new technique has been developed employing split-post dielectric resonators at operating frequencies of 10 GHz and 20 GHz to measure relative permittivity and loss tangent of low permittivity materials, respectively. The results have been confirmed by comparing the measurements with those of thick films fabricated on a quartz substrate. This paper substantiates the validity of performing non-destructive measurements of the complex permittivity of thin polymer films which was not previously possible with the split-post dielectric resonator technique. A detailed error analysis of the measurement procedure is also reported in this paper.

In order to perform gas impurity analysis on operating lamps, a mass spectrometer based in situ fracture stage has been built (Boroczki et al 2006 Meas. Sci. Technol. 17 79). The main problem of the elevated temperature measurements is the rapid condensation of the constituents after fracturing the lamp. There are two available options to record more spectra before the thermal equilibrium is reached. The first option is to increase the speed of the recording, but this is limited by the QMS unit. The second option is to introduce a buffer gas before fracturing, which slows down the diffusion process and thus increases the diffusion time (i.e. elapsed average time between the fracturing of the lamp and the impact of the particles with the wall) because the mercury atoms cannot travel in a straight line to the wall but rather suffer multiple collisions with the atoms of the buffer gas. In the present paper the authors investigated the second option by developing an improved measuring system. The speed of the recording can be investigated through the condensation phenomenon after fracturing the lamp. In order to observe the condensation phenomenon, the partial pressure of the mercury additive at different background pressures in the fracture chamber has been studied. The results of these measurements are reported in the present paper.

A technique for measuring the refractive index of a lens is described in this paper. In the present paper, an innovative technique has been proposed in which acousto-optics is involved. A new formula for evaluating the refractive index of a lens glass material is reported which is independent of lens parameters. A rectangular glass cell filled with liquid has been used as a photo-sonar device, which also has a piezoelectric crystal for generating ultrasonic waves. The test lens is immersed inside the ultrasonic cell. The focal length of the test lens has been varied by immersing it inside the ultrasonic cell filled with known liquid. The laser light travelling through the lens inside the glass cell gets diffracted when the ultrasonic waves are generated. Thus an interaction between sound and light wave occurs, resulting in a grating-like action, and the diffraction dots are displayed on a screen. A relation between the refractive index of liquids and the velocity of ultrasonic waves has been derived which also involves the separation of diffraction dots.

This paper reports on a novel instrument for measuring the water transport behaviour of fabric or paper materials in the transplanar direction. The instrument is unique in that it can not only measure the initial water absorption of the fabric in the transplanar direction, but also the rate of evaporation from the fabric surface after fully saturated with water, with the temperatures of water controlled at different levels simulating the end use conditions of the fabric. Compared with existing instruments for the water transport behaviour of fabrics or papers, the new instrument has a unique mechanism to control the water level underneath the fabric sample at a constant level (i.e. the water level is not reduced with the water transport into or through the fabric sample); as a result, the measurements are not affected by the changes of hydrostatic water pressure during testing. Repeated tests on various fabric samples showed that the measurements from the instrument are accurate, sensitive and reproducible.

Coaxial sensors are used in applications that require accurate and traceable measurements of complex permittivity. For example, coaxial sensors are often used for measurement of the complex permittivity of tissue equivalent materials (TEMs) used in specific absorption rate (SAR) measurements of exposure to RF fields. It is therefore important that well-founded metrological techniques for their use are developed and published. Although there are many published papers on coaxial sensors, few discuss the experimental techniques required to obtain the most accurate results. In this paper experimental approaches for obtaining the most accurate measurements are described. Common pitfalls with the technique are discussed. A Monte Carlo modelling (MCM) technique is used to provide estimates of uncertainty which are compared to those of measurements on reference liquids made with 3.5 mm, 7 mm and 15.1 mm diameter sensors. The MCM technique allows uncertainties to be estimated when measuring dielectrics for which there are no reference materials that have comparable properties, for example for TEMs at frequencies below 100 MHz.

A theoretical predictive model of acoustic attenuation in gas mixtures is necessary for analysing the composition of a gas mixture. A signal-processing framework applied to a direct simulation Monte Carlo (DSMC) method was developed for this purpose. As the DSMC system was proved to be an externally linear and time-invariant system in this paper, the acoustic attenuation of certain frequencies could be estimated by nonlinearly curve fitting on the basis of the data from the Fourier transform of the output signal. Two benefits could be gained from our work. First, if the simulation lasts enough time steps, the data from Fourier transform for one DSMC simulation could theoretically include every point of the attenuation spectrum. Second, the nonlinear curve-fitting method could reduce simulation time without losing predictive precision. Hence the signal processing method developed in this paper makes the DSMC simulation more efficient in analysing the relation between acoustic intensity attenuation and wave frequency. The result of our signal-processing framework based DSMC shows that the acoustic attenuation spectrum is dependent upon the composition of the gas mixture. Gas mixtures of nitrogen with variable additions of oxygen and carbon dioxide were considered in this paper. The frequency range of interest is from 8 MHz to 232 MHz in our predictive model.

The paper presents the application of temperature acquisition systems integrating thermocouples, a thermographic camera and fibre Bragg grating (FBG) sensors in gas metal arc welding (GMAW) process, MIG (metal inert gas) welding type. Efficient procedures to use FBG sensors and thermocouples were developed. The paper presents and compares measurements made in welded plates of aluminium alloy 6082-T6. Tests were performed in both plate surfaces and good agreement between the three techniques was found.

The paper presents implementation and validation of a method for accurate imaging of three-dimensional surface topographies, developed for AFM metrology but in principle applicable to the whole family of scanning probe microscopes. The method provides correction of the vertical drift, and can be applied to any AFM scanner system, without need for modification of the instrument hardware. Surface correction is performed based on two topographies taken with mutually orthogonal scanning directions. Reconstruction is rapidly achieved through the use of an automatic routine developed for the purpose. The proposed method has been tested by using an optical and a silicon flat and a high precision cylindrical artefact. Examples of successful reconstructions on different samples are also reported within the paper.

Nanoscience promises to transform today's world in the same way that integrated semiconductor devices transformed the world of electronics and computation. In the post-genomic era, the greatest challenge is to make connections between the structures and functions of biomolecules at the nanometre-scale level in order to underpin the understanding of larger scale systems in the fields of human biology and physiology. To achieve this, instruments with new capabilities need to be researched and developed, with particular emphasis on new levels of sensitivity, precision and resolution for biomolecular analysis. This paper describes an instrument able to analyse structures that range from tenths of a nanometre (proteins, DNA) to micron-scale structures (living cells), which can be investigated non-destructively in their normal state and subsequently in chemical- or biochemical-modified conditions. The high-resolution scanning Kelvin nanoprobe (SKN) measures the work-function changes at molecular level, instigated by local charge reconfiguration due to translational motion of mobile charges, dipolar relaxation of bound charges, interfacial polarization and structural and conformational modifications. In addition to detecting surface electrical properties, the instrument offers, in parallel, the surface topographic image, with nanometre resolution. The instrument can also be used to investigate subtle work function/topography variations which occur in, for example, corrosion, contamination, adsorption and desorption of molecules, crystallographic studies, mechanical stress studies, surface photovoltaic studies, material science, biocompatibility studies, microelectronic characterization in semiconductor technology, oxide and thin films, surface processing and treatments, surfaces and interfaces characterization. This paper presents the design and development of the instrument, the basic principles of the method and the challenges involved to achieve nanometric resolution and sub-millivolt sensitivity, for both the topographic imaging of surface micromorphology and surface potential and work-function determination.

In this paper, the columnar structure of TiO2 and HfO2 thin films prepared on silicon wafers is studied using two modifications of atomic force microscopy (AFM), i.e., by standard AFM and micro-hardness modification of AFM. These methods are applied to the cross-sections of the films created by fracturing samples consisting of substrates covered with the films under investigation. It is shown that the edge of the film in the cross-section does not cause an obstacle for scanning the AFM images corresponding to both the AFM modifications mentioned above. In this paper it is also shown that the micro-hardness contrast mode of AFM is the more useful technique for imaging the columnar structure of films than standard AFM when film cross-sections exhibit artificial defects originated as a consequence of fracturing the films.

This paper describes the failure analysis of an uncooled infrared focal plane array (IRFPA) under a high-g inertial load system using finite element simulation and experimental validation methods. The uncooled IRFPA, responding to a source of infrared (IR) radiation with spectral range from 8 µ mt o 14µm, is a cantilever array, which consists of two materials with mismatched thermal expansion coefficients. The radiance distribution of the IR source could be obtained by measuring the thermal–mechanical rotation angle distribution of every pixel in the cantilever array using a visible optical readout method. Based on this principle, room-temperature infrared imaging was developed under a static gravity environment, as described in our previous paper (Li C et al 2006 Meas. Sci. Technol. 17 1981–6). But under a dynamic inertial load, the rotation angle of every pixel includes not only the thermal–mechanical part but also a part induced by the inertial load. In the elastic deformation range, with a linearly increasing acceleration, the deformation angle induced by the inertial load increases linearly, which is validated by finite element simulation. This linear change in deformation, which can be subtracted from the total rotation angle in the optical readout using certain arithmetic, will not influence the imaging result. It is noteworthy that failure stress will occur when the deformation angle induced by the inertial load moves into the plastic deformation range, and the optical readout cannot image the IR object. Through finite element simulation the critical load resulting in IRFPA failure is 2715g, and this can be validated through impact using a Hopkinson bar after the IRFPA is placed in vacuum. By finite element simulation, the initial IRFPA surface profile without IR radiance after the 2715g load showed a conicoid characteristic. Simulation of the failure analysis of the uncooled IRFPA under 2715g acceleration predicts the military application of IRFPAs for an uncooled infrared imaging system in the high-g tactical range.

Radio-frequency (RF) coils are designed such that they induce homogeneous magnetic fields within some region of interest within a magnetic resonance imaging (MRI) scanner. Loading the scanner with a patient disrupts the homogeneity of these fields and can lead to a considerable degradation of the quality of the acquired image. In this paper, an inverse method is presented for designing RF coils, in which the presence of a load (patient) within the MRI scanner is accounted for in the model. To approximate the finite length of the coil, a Fourier series expansion is considered for the coil current density and for the induced fields. Regularization is used to solve this ill-conditioned inverse problem for the unknown Fourier coefficients. That is, the error between the induced and homogeneous target fields is minimized along with an additional constraint, chosen in this paper to represent the curvature of the coil windings. Smooth winding patterns are obtained for both unloaded and loaded coils. RF fields with a high level of homogeneity are obtained in the unloaded case and a limit to the level of homogeneity attainable is observed in the loaded case.

The design and experimental characterization of a burner is described, which has favourable characteristics for the accurate calibration of a range of optical thermometry techniques. The burner supports stable laminar flames and combines many of the advantages of several widely used burner designs without their disadvantages. It permits the application of point measurement techniques, line-of-sight techniques and planar imaging techniques; trace species, such as metal atoms, can be easily introduced into the flame. The implementation of the burner is described, followed by the presentation of data obtained from coherent anti-Stokes Raman scattering (CARS) measurements and numerical simulations. Spatially resolved measurements were performed over the entire flame profile at three different stoichiometries and factors causing systematic and random errors are described in detail. Measurement errors on mean temperatures were determined to be less than 1%. The shot-to-shot measurement precision was determined to be 3.5–4.0% (FWHM of temperature probability density function). The burner design together with the data presented in this paper can be used for the validation and calibration, respectively, of a variety of combustion thermometry techniques. Complete details of the burner design together with the obtained temperature data will be provided on the World Wide Web. Other researchers intending to validate and calibrate their own laser-based thermometry techniques will be able to cost-effectively reconstruct this burner and adopt the characterization presented here, thus being able to apply it without the need of their own basic validation. The authors are confident that a reconstructed burner, which is applied under the same conditions, will yield the same high level of accuracy and precision as that presented in this paper.

This paper describes a new and practical method to estimate the size of a crack on a rotating beam in a laboratory setting. The paper consists of selecting and validating a sensor and a measurement variable, devising a signal processing method for crack size estimation and carrying out experimental validations. The study employed a microphone to measure the pressure wave excited by the vibration of the rotating beam, validated the microphone signal, utilized chirp z-transform to extract the first and second vibration mode frequencies and established a diagnostic neural network to map the frequencies to crack size. Four fatigue tests were conducted to initiate and then propagate a crack. Microphone outputs and crack sizes were periodically recorded during the four tests. Data of test no. 1 were used to calibrate the neural net and data of the other three tests were used for testing. The experimental results show that the proposed approach can provide reasonably good estimates of the crack size using the indirectly excited acoustic signal.

In this paper, we report the first demonstration of multiplexed fibre Bragg grating strain sensors in a multicore fibre for shape measurement and their application to structural monitoring. Sets of gratings, acting as strain gauges, are co-located in the multicore fibre such that they enable the curvature to be determined via differential strain measurement. Multiple sets of these gratings allow the curvature to be measured at several points along the fibre. In this paper, the multicore fibre is configured to measure the deflection of a simple mechanical beam arising from the displacement of concrete tunnel sections. Laboratory tests are presented in which the system was demonstrated capable of displacement measurement with a resolution of ±0.1 mm over a range of several millimetres. © 2006 IOP Publishing Ltd.