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Numrering	Referens	Omslagsbild	Hitta
1.	Benckert, Lars (författare) Wood drying studies using white light speckle photography 1992 Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 10:1, s. 24-30 Tidskriftsartikel (refereegranskat)abstract White light speckle photography is a powerful tool for measuring displacement fields in the sub-millimetre range. Here it has been utilised to study deformation and crack development in a block of wood during drying. The use of a series of single exposures made it possible to monitor the changes of the wood's surface with time. By combining two of the negatives the displacements over a given time interval were obtained for, at least in principle, all points on the surface.
2.	Holm, Martin, et al. (författare) Simulation of flow meter calibration factors for various installation effects 1995 Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 15:4, s. 235-244 Tidskriftsartikel (refereegranskat)abstract The determination of flow meter calibration factors has been made using a computer simulation approach. The proposed technique is based on computational fluid dynamics (CFD). The CFD tools were used to determine the flow field in a flow meter as developed by three different pipe configurations. These flow fields were used to determine the calibration factor for an ultrasonic flow meter. The results have been compared with calibration factors obtained by CFD using detailed LDV input boundary data, analytical calculations and experimental data. Tests were made for reference conditions of 100D straight-pipe and for single- and double-elbow pipe configurations using Reynolds numbers from 100 to 100,000. For reference conditions good agreement is shown. For disturbed flow conditions the simulations well resembled the experimental data. However we find differences for transitional and swirl flows.
3.	Alizadeh, Mahmoud, et al. (författare) A two-tone test for characterizing nonlinear dynamic effects of radio frequency amplifiers in different amplitude regions 2016 Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 89, s. 273-279 Tidskriftsartikel (refereegranskat)abstract A new two-tone test method for radio frequency power amplifiers is presented. The test signal is a two-tone probing-signal superimposed on large-signals of different amplitude. The amplifier is, thus, excited in different amplitude regions. The amplitude and phase of the 3rd order intermodulation (IM) products are measured vs. frequency spacing and probing-signal amplitude in each region. The IM magnitude is a measure of the nonlinearity, while the frequency dependence and asymmetry are measures of the memory effects in the different regions. A Doherty and a class-AB amplifier were tested. For both amplifiers the IM magnitude increased by ∼15 dB from the lowest to the highest amplitude region. For the Doherty amplifier the behavior of the IM products vs. frequency spacing was similar in all regions, indicating similar memory effects. For the class-AB amplifier the IM vs. frequency spacing was significantly different in the different regions, which indicates different memory effects.
4.	Andersson, Henrik, et al. (författare) Principle of FT Spectrometer based on a Lateral Effect Position Sensitive Detector and Multi Channel Fabry-Perot Interferometer 2009 Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 42:5, s. 668-671 Tidskriftsartikel (refereegranskat)abstract The principle of a new type of multi channel Fourier-Transform spectrometer based on a multi channel wedge Fabry-Perot interferometer using a one dimensional lateral effect Position Sensitive Detector and a scanning slit for interferogram readout have been shown. The design of this spectrometer is very compact and the readout electronics very simple. The drawback of using a scanning slit system is minimized by the use of a position sensitive detector where the position is inherently known for each measurement. Experiments show that the position can be resolved with high accuracy and the summation of the two photocurrents gives the interferogram after scanning the slit between the wedge interferometer and the position sensitive detector. The spectral resolution obtained with a 25mm wedge interferometer together with a 45mm position sensitive detector and a 25µm slit is about 5nm around 600nm wavelength range, which is close to the theoretically anticipated resolution. The evaluated spectrometer setup show promising results and could be used in applications where compact and low cost spectrometers are required.
5.	Arrhenius, Karine, et al. (författare) An inter-laboratory comparison between 13 international laboratories for eight components relevant for hydrogen fuel quality assessment 2024 Ingår i: Measurement. - : Elsevier B.V.. - 0263-2241 .- 1873-412X. ; 230 Tidskriftsartikel (refereegranskat)abstract The quality of the hydrogen delivered by refuelling stations is critical for end-users and society. The purity of the hydrogen dispensed at hydrogen refuelling points should comply with the technical specifications included in the ISO 14687:2019 and EN 17124:2022 standards. Once laboratories have set up methods, they need to verify their performances, for example through participation in interlaboratory comparisons. Due to the challenge associated with the production of stable reference materials and transport of these which are produced in hydrogen at high pressure (>10 bar), interlaboratory comparisons have been organized in different steps, with increasing extent. This study describes an inter-laboratory comparison exercise for hydrogen fuel involving a large number of participants (13 laboratories), completed in less than a year and included eight key contaminants of hydrogen fuel at level close to the ISO14687 threshold. These compounds were selected based on their high probability of occurrence or because they have been found in hydrogen fuel samples. For the results of the intercomparison, it appeared that fully complying with ISO 21087:2019 is still challenging for many participants and highlighted the importance of organising these types of exercises. Many laboratories performed corrective actions based on their results, which in turn significantly improved their performances. © 2024 The Author(s)
6.	Avoci Ugwiri, M., et al. (författare) Benefits of enhanced techniques combining negentropy, spectral correlation and kurtogram for bearing fault diagnosis 2021 Ingår i: Measurement. - : Elsevier B.V.. - 0263-2241 .- 1873-412X. ; 185 Tidskriftsartikel (refereegranskat)abstract In condition monitoring based on vibrations for rotating machines fault detection, one of the typical symptoms is the presence of repetitive transients, which are characterized by impulsive and cyclostationarity signature. The approach quite popular nowadays in the industry for their detection is time–frequency techniques. Those techniques are mainly analysis tools instead of processing tools, and in any case, they are unable to offer a versatile methodology that applies to all mechanical signals in all circumstances. On the one hand, the paper is motivated by ideas borrowed from thermodynamics, where transients are seen as departures from a state of equilibrium; it is proposed to measure the negentropy of the squared envelope (SE) and the squared envelope spectrum (SES) of the signal. On the other hand, the paper proposes an adequate approach to exploit methods such as spectral correlation and kurtogram. The work's main objective is to investigate connections in those approaches to capture the signature of this repetitive behavior. The methodology used in this paper proposes to display as images all three proposed techniques. The impulsive events are then detected and localized in frequency by high values of the squared envelope spectrum (SES) infogram in some frequency bands. In order to analyze the signal in the frequency domain, the Short-Time Fourier Transform (STFT) is then used. The STFT is suggested in this study due to its simplicity and high flexibility. For fault, such as bearings, Kurtogram was demonstrated to be efficient. However, kurtosis based on temporal signals is effective under some conditions; its performance is low in the presence of a low signal-to-noise ratio. The paper analyzed the case of Ball Pass Frequency Inner Race (BPFI), where bearings are housed in a casing allowing the shaft to rotate while driven by a variable speed electric motor. A radial load is applied using a hydraulic cylinder, and different sizes of defects are realized. For fault like BPFI, the negentropy gives more information even for a shallow size of fault and allows a prompt fault detection, and it can also be used for fault localization. The paper demonstrated that results obtained from negentropy through infograms combining with spectral correlation could significantly extend the domain of the applicability of the Kurtogram. © 2021 Elsevier Ltd
7.	Bernstone, Christian, et al. (författare) Image analysis for monitoring of crack growth in hydropower concrete structures 2009 Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 42:6, s. 878-893 Tidskriftsartikel (refereegranskat)abstract A digital image analysis technique for crack monitoring using a standard web-camera has been further developed to acquire continuous data sets on crack development in concrete dams. The method is based on an existing robust and straightforward non-contact method for experimental deformation analysis. It allows for the measurement of suspected serious cracks, identified from inspections, through a sequence of images captured at intervals. The crack opening displacements at the surface of investigated objects are obtained by an algorithm that makes it possible to automatically track the motions of discrete markers painted on the object surface markers and compute their centre of mass in a sequence of images. The data acquisition process is straightforward and is well suited for this type of environment. Results from laboratory experiments and a field-test on a commuter bridge in Sweden are presented. The study implies that the technique can be useful for hydropower concrete structure applications. (C) 2009 Elsevier Ltd. All rights reserved.
8.	Björsell, Niclas, 1964-, et al. (författare) A waveform digitizer-based automatic modulation classifier for a flexible spectrum management 2011 Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 44:6, s. 1007-1017 Tidskriftsartikel (refereegranskat)abstract The paper presents the development and validation of an automatic digital modulation classifier based on a waveform digitizer architecture. The proposed automatic digital modulation classifier can be used for signal recognition in the next generation telecommunication systems, characterized by a flexible and dynamic management of the radio spectrum. It has been implemented on a PC architecture, connected with two different types of waveform digitizers. The experimental validation has been carried out by means of actual telecommunication signals, even in presence of narrowband and wideband interference. (C) 2011 Elsevier Ltd. All rights reserved.
9.	Björsell, Niclas, et al. (författare) Truncated Gaussian Noise in ADC Histogram Tests 2007 Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 40:1, s. 36-42 Tidskriftsartikel (refereegranskat)abstract One method to characterize analogue to digital converters (ADCs) is to use a histogram, where Gaussian noise may be used as stimulus signal. However, a Gaussian noise signal that excites all transition levels also generates input values outside working range of the ADC. Modern signal generators can generate arbitrary signals. Hence, excluding undesired values outside the ADC full scale can minimize test sequences. Truncating the signal to the working range gives further advantages, which are explored in this paper. The Cramer-Rao lower bound and a minimum variance estimator for histogram tests with an arbitrary stimulus are derived. These are applied for truncated Gaussian noise and the result is theoretically evaluated and compared to untruncated noise. It is shown that accuracy increases for a fixed sample length and that variation over transition levels decrease.
10.	Brandt, Anders, et al. (författare) Integrating time signals in frequency domain : comparison with time domain integration 2014 Ingår i: Measurement. - : Elsevier. - 0263-2241 .- 1873-412X. ; 58, s. 511-519 Tidskriftsartikel (refereegranskat)abstract Integrating sampled time signals is a common task in signal processing. In this paper we investigate the performance of two straightforward integration methods: (i) integration in the frequency domain by a discrete Fourier transform (DFT), division by jω followed by inverse DFT (IDFT) back to the time domain, and (ii) a method using a weighted overlap-add (WOLA) technique which is developed in the paper. These two methods are compared with two time domain methods: (a) the trapezoidal rule, and (b) an optimized IIR filter. It is shown that the intuitive method of a straightforward DFT/IDFT is a very good method which is recommended for data lengths exceeding 16 K samples, provided data are short enough to allow a single DFT. The IIR filter integration is shown to have very similar accuracy and can also be recommended. The WOLA integration method is shown to perform well in most cases for steady-state conditions. For cases with short transients it should, however, be avoided. A signal integrated by the WOLA method is further shown to be incoherent with the signal before integration. This suggests that the WOLA method should be avoided in cases where coherence between the signals before and after integration is important. It is also demonstrated by a simulation example that integration by the trapezoidal rule should be avoided, as it gives biased results, particularly for higher frequencies.
11.	Böckler, H B, et al. (författare) Metrology infrastructure for high-pressure gas and liquified hydrogen flows. A brief outline of the MetHyInfra project, measurement challenges, and first results 2024 Ingår i: Measurement. - : Elsevier B.V.. - 0263-2241 .- 1873-412X. ; 232 Tidskriftsartikel (refereegranskat)abstract This paper gives an overview of the ongoing Joint Research Project (JRP) 20IND11 “Metrology infrastructure for high pressure gas and liquefied hydrogen flows” (MetHyInfra), which will ensure traceability in the hydrogen distribution chain. For this purpose, very precise nozzles with well-defined geometries have been produced. In this project, Critical Flow Venturi Nozzles (CFVNs) will be traceably calibrated for the first time with hydrogen and pressures up to 100 MPa using a Coriolis Flow Meter (CFM) as a secondary standard. A CFM has been successfully calibrated with hydrogen against a gravimetric primary standard. Equations of State (EoS) are important for the high-pressure calibration of the nozzles, but also for Computational Fluid Dynamics (CFD) simulations. With regard to CFD, a numerical model has been developed to simulate high pressure hydrogen flow in the CFVN. In a parameter study, non-ideal nozzle shapes are investigated using a shape variation parameter. New Speed of Sound (SoS) measurements were conducted at temperatures from 273 to 323 K and pressures from 1 to 100 MPa. These new data were then used to develop a new EoS for normal hydrogen, optimized for gas phase calculations. In addition to gaseous hydrogen, the project has a strong focus on liquefied hydrogen. Here a three-pronged approach allows traceable measurements. Each of the approaches presented is based on a unique flow calibration principle and relies on independent traceability schemes. The results of the project will ensure traceable measurements and thus a higher level of confidence among end users. © 2024 The Authors
12.	Capriglione, D., et al. (författare) Development of a test plan and a testbed for performance analysis of MEMS-based IMUs under vibration conditions 2020 Ingår i: Measurement. - : Elsevier B.V.. - 0263-2241 .- 1873-412X. ; 158 Tidskriftsartikel (refereegranskat)abstract Micro-Electro-Mechanical Systems (MEMS) are today widespread in many industrial and consumer applications. In the field of terrestrial transportation, cellular, wearable devices, robotics, drone, to cite a few, MEMS-based Inertial Measurement Units (IMUs) are widely employed for assuring several tasks as for the object tracking, self-driving vehicles, human motion and so on. Expected performance of such systems and also recent literature and technical standards miss considering both a context-awareness reliability analysis and metrological performance analyses of MEMS-based IMUs when operating in real scenarios characterized by the presence of significant temperature excursions, humidity, vibrations, mechanical shocks and so on. In particular, standard procedures to be applied for testing MEMS-based IMUs are not still available. Trying to fill these needs, this paper proposes both a suitable testbed and test plans for performance analysis of such kinds of devices under vibration conditions. The application to a real IMUs has confirmed that the proposed tests allow identifying the effects of mechanical stress on both the reliability and metrological performance of such devices. These results could be useful also for the international committees involved in the definition of technical standards to be adopted for testing these kinds of devices. © 2020 Elsevier Ltd
13.	Carratù, M., et al. (författare) A Sound Level Meter featured with automatic estimation of the measurement uncertainty 2022 Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 188 Tidskriftsartikel (refereegranskat)abstract In the area of measuring the environmental noise the equivalent sound pressure level LA,eq is adopted and compared with legal thresholds in order to characterize the site of interest. The paper describes an innovative Sound Level Meter (SLM) able to provide information about the measurand contribution to the measurement uncertainty estimation. This measurement technology is made possible thanks to an approach based on bootstrap method for selecting the suitable measurement episode for an estimation of LAeq. The firmware implementation of the developed SLM is disclosed with reference to a low-cost platform for real-time execution of the proposed methodology. Finally, a metrological characterization of the prototype performed in laboratory is reported as well as the performance comparison with a class 1 SLM in a real scenario. As a result, the smart features of the new SLM may be easily implemented by including commercial devices into the instrument schematics.
14.	Cervantes, Michel, et al. (författare) Reformulation of the pressure-time method for application without flow rate cut-off 2022 Ingår i: Measurement. - : Elsevier. - 0263-2241 .- 1873-412X. ; 188 Tidskriftsartikel (refereegranskat)abstract The paper presents a reformulation of the standard pressure-time method for flow rate measurement in closed conduits. According to the IEC 60041 standard, the method is used with turbines flow rate cut-off. Its current formulation requires complete closure of the turbine shut-off device, generally guide vanes for reaction turbines and valves for impulse turbines, which may cause wear and tear on the machine. Any leakage through the closed shut-off device also needs to be measured. In the present work, a new formulation of the pressure-time method is derived, extending the actual use. The newly formulated method allows the determination of the flow rate at any instant of time from a load variation and, thus, the initial, incremental, and final flow rate. The load variation may be positive or negative. Measurements of any leakage flow are eliminated. Numerical and experimental cases are used to assess the validity and applicability of the proposed formulation. The numerical results demonstrate the correctness of the derivation. The experimental results exemplify the applicability of the method. Limitations of the derived methodology are discussed.
15.	Chelgani, Saeed Chehreh, et al. (författare) Modeling of Free Swelling Index Based on Variable Importance Measurements of Parent Coal Properties by Random Forest Method 2016 Ingår i: Measurement. - : Elsevier. - 0263-2241 .- 1873-412X. ; 94, s. 416-422 Tidskriftsartikel (refereegranskat)abstract Coke quality has a critical role in the steelmaking industry. The aim of this study is to examine the complex relationships between various conventional coal analyses using coke making index “free swelling index (FSI)”. Random forest (RF) associated with variable importance measurements (VIMs), which is a new powerful statistical data mining approach, is utilized in this study to analyze a high-dimensional database (3961 samples) to rank variables, and to develop an accurate FSI predictive model based on the most important variables. VIMs was performed on various types of analyses which indicated that volatile matter, carbon, moisture (coal rank parameters) and organic sulfur are the most effective coal properties for the prediction of FSI. These variables have been used as an input set of RF model for the FSI modeling and prediction. Results of FSI model indicated that RF can provide a satisfactory prediction of FSI with the correlation of determination R2 = 0.96 and mean square error of 0.16 from laboratory FSIs (which is smaller than the interval unit of FSI; 0.5). Based on this result, RF can be used to rank and select effective variables by evaluating nonlinear relationships among parameters. Moreover, it can be further employed as a non-parametric reliable predictive method for modeling, controlling, and optimizing complex variables; which to our knowledge has never been utilized in the fuel and energy sectors.
16.	Chelgani, Saeed Chehreh, et al. (författare) Support vector regression modeling of coal flotation based on variable importance measurements by mutual information method 2018 Ingår i: Measurement. - : Elsevier. - 0263-2241 .- 1873-412X. ; 114, s. 102-108 Tidskriftsartikel (refereegranskat)abstract Support vector regression (SVR) modeling was used to predict the coal flotation responses (recovery (R∗) and flotation rate constant (k)) as a function of measured particle properties and hydrodynamic flotation variables. Coal flotation is a complicated multifaceted separation process and many measurable and unmeasurable variables can be considered for its modeling. Therefore, feature selection can be used to save time and cost of measuring irrelevant parameters. Mutual information (MI) as a powerful variable selection tool was used through laboratory measured variables to assess interactions and choose the most effective ones for predictions of R∗ and k. Feature selection by MI through variables indicated that the best arrangements for the R∗ and k predictions are the sets of particle Reynolds number-energy dissipation and particle size-bubble Reynolds number, respectively. Correlation of determination (R2) and difference between laboratory measured and SVR predicted values based on MI selected variables indicated that the SVR can model R∗ and k quite accurately with R2 = 0.93 and R2 = 0.72, respectively. These results demonstrated that the MI-SVR combination can quite satisfactorily measure the importance of variables, increase interpretability, reduce the risk of overfitting, decrease complexity and generate predictive models for high dimension of variables based on selected features for complicated processing systems.
17.	Chen, Dingfu, et al. (författare) Bayesian uncertainty evaluation of stitching interferometry for cylindrical surface 2020 Ingår i: Measurement. - : ELSEVIER SCI LTD. - 0263-2241 .- 1873-412X. ; 157 Tidskriftsartikel (refereegranskat)abstract Uncertainty evaluation is one of the most important concepts in metrological characterizations. This paper proposes a method for uncertainty evaluation of measurements of cylindrical surfaces by means of stitching interferometry. The proposed method is based on the Bayesian statistical analysis. The prior deviation for a tested surface is determined by both calculation of standard deviation through multiple measurements of a single sub-aperture and calibration of the optical system error. The probability distribution functions (PDF) of the prior and real misalignment error and measured data of the aperture are derived according to the stitching model. Simulated observations are approximated with the Gibbs Sampler using the Markov Chain Monte Carlo (MCMC) method. Our proposed method is a promising alternative to the ordinary least square technique (LST) with the maximum likelihood estimation (MLE) for obtaining the uncertainty of the misalignment and measurement error in the stitching results. Moreover, it can take the inevitable environment errors into account. The prediction of the uncertainty interval makes our method more attractive in industrial applications. (C) 2020 Elsevier Ltd. All rights reserved.
18.	Chi, Zhexiang, et al. (författare) Data-driven approach to study the polygonization of high-speed railway train wheel-sets using field data of China’s HSR train 2020 Ingår i: Measurement. - : Elsevier. - 0263-2241 .- 1873-412X. ; 149 Tidskriftsartikel (refereegranskat)abstract Environmental factors, like seasonality, have been proved to exert significant impact on reliability of China high-speed rail train wheels in this article. Most studies on polygonization of train wheels are based on physical models, mathematical models or simulation systems. Normally, characteristics and mechanisms of wheel polygonization are studied under ideal conditions without considering the impact of the environment. However, in practical use, there are many irregular wear wheels and irregular wear cannot be explained by theoretical models with assumptions of ideal conditions. We look at two possible factors in polygonization: seasonality and proximity to engines. Our analysis of field data shows the environmental factor has more impact on wheel polygonization than the mechanical factor. Based on the Bayesian models, the mean time to failure of the wheels under different operation conditions is conducted. A case study of China’s HSR train wheels is conducted to confirm the finding. The case study shows the degree of polygonal wear is much more severe in summer than other seasons. The finding may give a totally new research perspective on polygonization of train wheels. We use Bayesian analysis because this method is useful for small and incomplete data sets. We propose three Bayesian data-driven models.
19.	Costa, Marcelo Azevedo, et al. (författare) Failure detection in robotic arms using statistical modeling, machine learning and hybrid gradient boosting 2019 Ingår i: Measurement. - : ELSEVIER SCI LTD. - 0263-2241 .- 1873-412X. ; 146, s. 425-436 Tidskriftsartikel (refereegranskat)abstract Modeling and failure prediction are important tasks in many engineering systems. For these tasks, the machine learning literature presents a large variety of models such as classification trees, random forest, artificial neural networks, among others. Standard statistical models such as the logistic regression, linear discriminant analysis, k-nearest neighbors, among others, can be applied. This work evaluates advantages and limitations of statistical and machine learning methods to predict failures in industrial robots. The work is based on data from more than five thousand robots in industrial use. Furthermore, a new approach combining standard statistical and machine learning models, named hybrid gradient boosting, is proposed. Results show that the hybrid gradient boosting achieves significant improvement as compared to statistical and machine learning methods. Furthermore, local joint information has been identified as the main driver for failure detection, whereas failure classification can be improved using additional information from different joints and hybrid models. (C) 2019 Elsevier Ltd. All rights reserved.
20.	Dróżdż, Artur, et al. (författare) Hot-wire spatial resolution issues in adverse pressure gradient turbulent boundary layers 2024 Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 237 Tidskriftsartikel (refereegranskat)abstract The effect of a finite length of hot-wire probe sensor length on the measured streamwise velocity fluctuations is well understood in canonical wall-bounded flow, where the small-scale energy has been found to be universal and invariant with Reynolds number. A straightforward application of that assumption to non-canonical flows such as strong adverse pressure gradient (APG) flows has, however, been hampered since the effect of Re and APG could not conclusively be studied separately due to the lack of data with a clear scale separation. The present experimental investigation at Reτ≈4000 in weak, moderate and strong APGs with different wire length shows that spatial averaging effects are not only limited to the inner layer. A note of caution is hence warranted for measurements that seemingly try to take the bias effect of spatial attenuation into account by performing measurements with albeit long but fixed viscous-scaled wire length.
21.	Endrias, Dawit H., et al. (författare) A combinatorial optimization approach for evaluating minimum-zone spatial straightness errors 2012 Ingår i: Measurement. - : Elsevier. - 0263-2241 .- 1873-412X. ; 45:5, s. 1170-1179 Tidskriftsartikel (refereegranskat)abstract This paper presents a new and robust approach for the accurate evaluation of minimumzone spatial straightness error from a set of coordinate measurement data points. The algorithm iteratively searches for the specific data points that define the minimum bound of the spatial straightness zone using combinatorial optimization. It is based on the fact that the minimum circumscribed cylinder of a point set, which is equivalent to the minimum spatial straightness zone of the measurement data, will pass through three, four, or five of the data points that constitute the convex hull vertices of the entire data set. Computed results have shown that although the presented approach may lead to increased computational time, it is robust and able to construct the exact minimum circumscribed cylinder for a given point set. The minimum-zone spatial straightness error can thus be evaluated with the best possible accuracy. The advantage of the presented algorithm is demonstrated via comparison with published computed results of existing algorithms.
22.	Galar, Diego, et al. (författare) Context awareness for maintenance decision making : A diagnosis and prognosis approach 2015 Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 67, s. 137-150 Tidskriftsartikel (refereegranskat)abstract All assets necessarily suffer wear and tear during operation. Prognostics can assess the current health of a system and predict its remaining life based on features capturing the gradual degradation of its operational capabilities. Prognostics are critical to improve safety, plan successful work, schedule maintenance, and reduce maintenance costs and down time. Prognosis is a relatively new area but has become an important part of Condition-based Maintenance (CBM) of systems. Broadly stated, prognostic methods are either data-driven, rule based, or model-based. Each approach has advantages and disadvantages; consequently, they are often combined in hybrid applications. A hybrid model can combine some or all model types; thus, more complete information can be gathered, leading to more accurate recognition of the fault state. In this context, it is important to evaluate the consistency and reliability of the measurement data obtained during laboratory testing and the prognostic/diagnostic monitoring of the system under examination.This approach is especially relevant in systems where the maintainer and operator know some of the failure mechanisms with a sufficient amount of data, but the sheer complexity of the assets precludes the development of a complete model-based approach. This paper addresses the process of data aggregation into a contextual awareness hybrid model to get Residual Useful Life (RUL) values within logical confidence intervals so that the life cycle of assets can be managed and optimised.
23.	González-González, Asier, et al. (författare) Condition Monitoring of Wind Turbine Pitch Controller : A Maintenance Approach 2018 Ingår i: Measurement. - : Elsevier. - 0263-2241 .- 1873-412X. ; 123, s. 80-93 Tidskriftsartikel (refereegranskat)abstract With the increase of wind power capacity worldwide, researchers are focusing their attention on the operation and maintenance of wind turbines. A proper pitch controller must be designed to extend the life cycle of a wind turbine’s blades and tower. The pitch control system has two main, but conflicting, objectives: to maximize the wind energy captured and converted into electrical energy and to minimize fatigue and mechanical load. Four metrics have been proposed to balance these two objectives. Also, diverse pitch controller strategies are proposed in this paper to evaluate these objectives. This paper proposes a novel metrics approach to achieve the conflicting objectives with a maintenance focus. It uses a 100 kW wind turbine as a case study to simulate the proposed pitch control strategies and evaluate with the metrics proposed. The results are showed in two tables due to two different wind models are used.
24.	Hadavandi, E., et al. (författare) Estimation of coking indexes based on parental coal properties by variable importance measurement and boosted-support vector regression method 2019 Ingår i: Measurement. - : Elsevier. - 0263-2241 .- 1873-412X. ; 135, s. 306-311 Tidskriftsartikel (refereegranskat)abstract Coke as a fuel has a critical role for steel making industries. Since coke is a product of blended coals, it is essential to study relationships between parental coal components with quality of their coke products. Free swelling index (FSI) and maximum fluidity (MF) are standard coking indexes that widely used for blending coals and measuring quality of products. This study has been explored interdependencies between measured coal components by mutual information (MI) method and evaluated their importance in the prediction of coking indexes for a wide range of Illinois coal samples. MI results indicated that the set of moisture-organic sulfur and moisture-nitrogen-sulfate sulfur were the best variables for predictions of log(MF) and FSI, respectively. Adaptive Boosting method based on support vector regression (SVR), called Boosted-SVR, was used the selected variable sets for predictions of coking indexes. In testing stage of models, correlation of determination (R2) between actual and predicted values for the log(MF) and FSI were 0.89 and 0.90, respectively. These results indicated that Boosted-SVR model could quite satisfactory predict coking indexes. In general, outcomes of this investigation demonstrated an appropriate potential of coking quality prediction with limited numbers of input variables and suggested that a combination of MI with Boosted-SVR model as a new powerful tool which can be used for the computation of other complex fuel and processing problems based on measurement of conventional properties.
25.	Hagqvist, Petter, 1986-, et al. (författare) Emissivity estimation for high temperature radiation pyrometry on Ti–6Al–4V 2013 Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 46:2, s. 871-880 Tidskriftsartikel (refereegranskat)abstract The paper demonstrates a versatile procedure suitable for industrial implementation of temperature measurement on a hot titanium alloy. The driving force has been the need for an accurate temperature measurement during additive manufacturing using laser welding technology where Ti–6Al–4V-wire is melted. The challenges consider both industrial constraints and the varying emissivity of the surface. Measurements makes use of a narrow bandwidth spot radiation pyrometer and a calibration procedure for estimation of the surface temperature through spectral emissivity estimation. The theoretical results are validated through experiments. A number of difficulties in radiation temperature measurements for metals with varying surface properties are discussed; especially the case of surface oxidation. The uncertainty in temperature reading due to the uncertainty in the emissivity estimate is established along with a model that qualitatively describes surface oxidation. The procedure is expected to be useful for several manufacturing applications where it is important to control high temperatures.
26.	Hansson, Lars, et al. (författare) Microwave penetration in wood using imaging sensor 2005 Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 38, s. 15-20 Tidskriftsartikel (refereegranskat)abstract It is possible to determine properties of wood using microwave scanning techniques. The purpose of this study was to verify the measured values from a microwave imaging sensor. Attenuation and phase shift of an electromagnetic wave transmitted through birch wood were measured and compared with theoretical calculated values. A test piece with varying thickness was measured with a scanner based on a microwave sensor (Satimo 9.375GHz) at different temperatures and moisture contents. The density distribution of the test piece was determined by computer tomography scanning. The result showed good correspondence between measured and theoretical values. The proportion of noise was higher at low moisture content due to lower attenuation. There is more noise in attenuation measurement than in measurement of phase shift. A reason for this could be that wood is an inhomogeneous material in which reflections and scattering affect attenuation more than phase shift. The microwave scanner has to be calibrated to a known dielectric to quantify the error in the measurement
27.	He, Zhiyi, et al. (författare) Kernel flexible and displaceable convex hull based tensor machine for gearbox fault intelligent diagnosis with multi-source signals 2020 Ingår i: Measurement. - : Elsevier. - 0263-2241 .- 1873-412X. ; 163 Tidskriftsartikel (refereegranskat)abstract The methods based on traditional pattern recognition and deep learning have been successfully applied in gearbox intelligent diagnosis. However, traditional pattern recognition methods cannot directly classify feature tensors of multi-source signals, and deep learning networks hardly handle the classification of small samples. Therefore, for the gearbox intelligent diagnosis with multi-source signals, a novel tensor classifier called kernel flexible and displaceable convex hull based tensor machine (KFDCH-TM) is proposed. In KFDCH-TM, the kernel flexible and displaceable convex hull of tensor samples in tensor feature space is defined firstly. Then, an optimal separating hyper-plane between two kernel flexible and displaceable convex hulls is constructed. Meanwhile, feature tensors extracted from multi-source signals through wavelet packet transform (WPT) are used to diagnose gearbox fault by KFDCH-TM. The results of two cases demonstrate that KFDCH-TM can effectively identify gearbox fault with multi-source signals and has better robustness.
28.	Händel, Peter, 1962- (författare) Amplitude estimation using IEEE-STD-1057 three-parameter sine wave fit : Statistical distribution, bias and variance 2010 Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 43:6, s. 766-770 Tidskriftsartikel (refereegranskat)abstract There has been a recent interest on the performance of amplitude estimation employing a coherently sampled sinusoidal model to noisy measurements. In [F. Correa Alegria, Bias of amplitude estimation using three-parameter sine fitting in the presence of additive noise, Measurement 42 (2009) 748-756.], several issues regarding the bias of the amplitude estimate were studied. In this work, the results are generalized to include a description of the distribution of the amplitude estimate, with explicit results on bias and variance as by-products. Simple closed form expressions for bias and variance are derived. It is shown that the amplitude estimate in finite samples obeys a Rician distribution. The biased amplitude estimator is also shown to beat all unbiased estimators in terms of mean square error, in a wide spread of scenarios.
29.	Händel, Peter, 1962-, et al. (författare) Combating the effect of chassis squat in vehicle performance calculations by accelerometer measurements 2010 Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 43:4, s. 483-488 Tidskriftsartikel (refereegranskat)abstract The performance of a vehicle is measured as the time to complete an assigned task while accelerating. Non-intrusive performance measurements are often based on inertial navigation, i.e. measurements from an accelerometer are integrated once to obtain an estimate of the speed of the vehicle. A second integration results in a measure of the traveled distance. However, the suspension system of the vehicle introduces error in the measurements, owing to the tendency of the chassis to rise in the front and drop in the back during acceleration. An approach is derived based on the method of weighted least-squares for estimating the misalignment angle as a function of the horizontal acceleration. The proposed method includes a parametric model describing the effect of the tilt of the vehicle on the accelerometer measurements. Further. the method employs an external reference. It is shown that for a particular parametric model, the problem at hand has a closed-form solution. Certain practical applications are studied in some detail. A relative error of 0.5% in the elapsed time and 5% in the final speed is illustrated on 201-m straight track races.
30.	Händel, Peter, 1962-, et al. (författare) Estimation of velocity and size of particles from two channel laser anemometry measurements 1997 Ingår i: Measurement. - 0263-2241 .- 1873-412X. ; 21:3, s. 113-123 Tidskriftsartikel (refereegranskat)
31.	Ivanov, I. I., et al. (författare) Expanding catalytic sensor capabilities to combustible gas mixtures monitoring 2022 Ingår i: Measurement. - : Elsevier. - 0263-2241 .- 1873-412X. ; 194 Tidskriftsartikel (refereegranskat)abstract Preventing the explosion of mixtures of combustible gases and vapors is an important task in industry. This research presents an approach for rapid assessment of the explosiveness of combustible gas mixtures of unknown composition. The technique is based on registering the amount of heat released during the combustion of a portion of gases inside the catalytic sensor. The phenomenological theory of the approach for rapid assessment of the explosiveness was also presented. To carry out the measurements, a two-stage heating pulse and an approach to the calibration of the catalytic sensor were developed. The experiments were carried out for various mixtures of methane, propane, butane and hexane within the pre-explosive range (up to 50% Low Explosive Limit). In order to calculate the Lower Explosive Limit (LEL) of a mixture of flammable gases, Le Chatelier's rule was used. Industrial catalytic sensors with additional diaphragm that limits the gas leakage into the sensor were used for measurements. The advanced data processing which is based on integrating the area under the measured dependence of sensor response on time was used to calculate the heat released. The parameters affecting the measurement results were analyzed. The measurement values were in good agreement with the prescribed values. The measurement errors did not exceed 10%. Since in this approach there is no need to identify gases, or their quantity and concentration, it can be used in industry for quick determination of potentially explosive mixtures in the air.
32.	Jafari, M., et al. (författare) Measurement of collector concentrations to make an efficient mixture for flotation of a low grade apatite 2018 Ingår i: Measurement. - : Elsevier. - 0263-2241 .- 1873-412X. ; 121, s. 19-25 Tidskriftsartikel (refereegranskat)abstract It was well documented that a mixture of collectors could have synergistic advantages over the use of an individual collector for apatite flotation. Therefore, it would be an essential procedure to determine an optimum amount of each collector for development of an efficient mixture (collector). In this study, a mixture design (MD) model was used to find an optimum amount of different typical apatite anionic collectors (Atrac, Alke and Dirol) and make an efficient mixture for the direct flotation of a low grade apatite ore. Assessment of responses for apatite flotation tests which their collectors were designed by MD showed that Dirol has the highest selectivity whereas Alke has the highest collectivity for the direct flotation of apatite. According to the experiments, the MD model computed that a mixture collector with Dirol: 364 (g/t), Alke: 295.2 (g/t) and Atrac: 140.8 (g/t) concentrations can provide the most efficient responses through the apatite flotation. Results based on the purposed concentrations for the mixed collector demonstrated that higher apatite flotation responses (grade: 14%, recovery: 76%, and S.E.: 66%) in comparison with the performance of tests with a single collector. These results can be used to design flotation conditions for the apatite flotation-separation in the industrial scale and assessment of collector concentrations for other investigations.
33.	Jouybari, Arash, et al. (författare) Methods comparison for attitude determination of a lightweight buoy by raw data of IMU 2019 Ingår i: Measurement. - : Elsevier. - 0263-2241 .- 1873-412X. ; 135, s. 348-354 Tidskriftsartikel (refereegranskat)abstract Today, one of the most important issues is the determination of instantaneous sea level and distinguishing the Tsunami by floating buoy in the ocean. Usually, gyroscopes are used to measure the angular velocity of a buoy. On the other hand, considering the advancement of various technologies in the field of precise accelerometers, make it possible to use these kinds of sensors for navigation purpose. In this research, stable and optimal methods for determining the orientation of a moving buoy is presented using a combination of the gyroscope, accelerometers, and magnetic sensors data. In order to prove the effectiveness of the proposed methods, the raw data were collected from accelerometers, gyroscopes, and magnetometers of (Xsens MTI-G-700) mounted on a Buoy in coastal waters of Kish Island, Iran. Then, by using the proposed methods, the Euler angles of the buoy are determined, while the Euler angles are derived from the Xsens sensor we are considered as a reference. Based on the results, RMSD for Madgwick algorithm are 0.57° 0.37° and 0.50° for Mahony algorithm are 0.56° 0.37° and 0.50° and finally for Complementary algorithm is 0.63° 0.26° and 2.38° which these values are for roll, pitch, and yaw angles respectively. Thus Mahony algorithm for determining roll and yaw Euler angles is more accurate than other algorithms; however, this differences is negligible compared to the Madgwick algorithm. The Complementary algorithm is less accurate than the other two algorithms, especially for determining the yaw angle of the buoy.
34.	Jönsson, Gustav, et al. (författare) Gas flow measurement of evaporated liquid nanoflows 2023 Ingår i: Measurement. - 0263-2241 .- 1873-412X. ; 216 Tidskriftsartikel (refereegranskat)abstract Following the miniaturisation of fluidic components, the demand for traceable measurements of micro and nanoflows is increasing in various technological fields such as pharmaceuticals, biotechnology and automotive industry. Gravimetric flow measurement methods are accurate at microflows and above, but have a lower limit of about 5nLmin−1. Several alternative approaches have been developed to circumvent this limit. Here a measurement setup and proof of principle is presented for a method measuring the gas flows generated by complete evaporation of liquid ethanol nanoflows. The gas flow measurement is based on the well-established method of determining the pressure drop across a geometrically precisely defined circular opening in the molecular flow regime. Liquid flow rates from a syringe pump in the range of 5nLmin−1 to 200nLmin−1 are measured with an expanded uncertainty as low as 340pLmin−1 at instantaneous flow rates. Strategies to further improve accuracy are discussed.
35.	Kadam, Prachi, et al. (författare) FVEstimator : A novel food volume estimator Wellness model for calorie measurement and healthy living 2022 Ingår i: Measurement. - : Elsevier. - 0263-2241 .- 1873-412X. ; 198 Tidskriftsartikel (refereegranskat)abstract Identifying the calorific value of food requires a correct estimate of its volume and size dimensions. The food volumetric estimation can be done rationally and efficiently by measuring the food dimensions in terms of surface parameters. Food volume estimation can be effectively implemented with a computer vision-based application. The food image size can be estimated for its volumetric and calorific calibration with food area measures. However, studies in this area are limited to finding dimensions of a food item with geometrically regular, irregular, amorphous, and solid food shapes. There is a particular challenge with amorphous food items which do not have any shape and are usually calibrated with subjective container sizes by the dietitians and hence cause relative measures. Instance segmentation techniques are implemented at the pixel level and classify a pixel into a food type leading to higher accuracy in classification and segmentation of food over the background. In this work, mask-based RCNN is employed that helps accurate segmentation of food images with regular and irregular shapes in multi-food dish scenarios. The RCNN based food segmentation is applied as a volume estimator model. It is developed by fine-tuning the pre-trained ResNet model and trained over a dataset of 8 different classes of Indian breakfast food images in all shapes. The estimator model yields a precision of 90.9% for convex-shaped food images, 90.46% for amorphous food images in regular serving containers, and 98.5% to 98.9% for regular shaped (square and circle) food items. The accuracy of the presented volume estimator thus opens opportunities for further research with diverse food types and shapes.
36.	Khosravi, Mahdi, 1988-, et al. (författare) Modification of correlation optimized warping method for position alignment of condition measurements of linear assets 2022 Ingår i: Measurement. - : Elsevier. - 0263-2241 .- 1873-412X. ; 201 Tidskriftsartikel (refereegranskat)abstract This paper proposes a modification to a well-known alignment method, correlation optimized warping (COW), to improve the efficiency of the method and reduce the positional errors in the measurements of linear assets. The modified method relaxes the restrictions of COW in aligning the start and end of datasets and decreases the computational time. Furthermore, the method takes advantage of the interdependencies between simultaneously measured channels to overcome the missing data problem. A case study on railway track geometry measurements was conducted to implement the proposed method and assess its performance in reducing the positioning inaccuracy of the measurements. The findings revealed that the modified method could decrease the positional errors of defects to below 25 cm in 94% of the trials.
37.	Khosravi, Mahdi, 1988-, et al. (författare) Reducing the Positional Errors of Railway Track Geometry Measurements Using Alignment Methods : a Comparative Case Study 2021 Ingår i: Measurement. - : Elsevier. - 0263-2241 .- 1873-412X. ; 178 Tidskriftsartikel (refereegranskat)abstract To predict the occurrence of geometry defects and to achieve a reliable maintenance strategy, accurate positioning of track geometry measurements is of great importance. This paper aims to reduce the positional errors in track geometry measurements by finding an efficient alignment method. Therefore, five alignment methods, i.e. the cross-correlation function, recursive alignment by fast Fourier transform, dynamic time warping, correlation optimized warping, and a combined method, were evaluated and compared concerning their ability to align the measurements precisely, keep the original shape of the measurements, and minimise the use of time and memory. Furthermore, the influence of choosing a proper reference dataset was investigated. A case study based on track geometry data from the Main Western Line in Sweden was conducted to implement and assess the methods. Findings revealed that the combined method could decrease the positional errors of single defects to below 0.25 m in 90% of the trials.
38.	Kroner, Corinna, et al. (författare) Metrology for reliable fuel consumption measurements in the maritime sector 2024 Ingår i: Measurement. - : Elsevier B.V.. - 0263-2241 .- 1873-412X. ; 226 Tidskriftsartikel (refereegranskat)abstract Reliable fuel consumption measurements play an essential role in the maritime sector whether for emission determinations or the use of novel fuels. A verification of the performance of flow meters used for fuel consumption determination under realistic conditions is thus of interest. Apart from the influence of the pressure- and temperature-dependent transport properties of the fuels, a characterization of the measurement performance under dynamic fuel consumption is of relevance. Traceable metrological infrastructure and procedures, which will enable an evaluation of the measurement performance of flow meters in this regard, are being developed in the scope of the EMPIR project “Safest” (20IND13). A consumption profile of a ferry navigating in a harbour serves as basis. In addition to the measurement accuracy under dynamic conditions, first investigations of the performance of flow meters are carried out in terms of fluid temperature and fuel transport properties for the example of spindle screw meters.
39.	Kulkarni, Rohan, 1991-, et al. (författare) Unsupervised rail vehicle running instability detection algorithm for passenger trains (iVRIDA) 2023 Ingår i: Measurement. - : Elsevier. - 0263-2241 .- 1873-412X. ; 216, s. 112894-112894 Tidskriftsartikel (refereegranskat)abstract Intelligently identifying rail vehicle faults instigating running instability from carbody floor acceleration is essential to ensure operational safety and reduce maintenance costs. However, the vehicle-track interaction's nonlinearities and scarcity of running instability occurrences complicate the task. The running instability is an anomaly in the vehicle-track interaction. Thus, we propose unsupervised anomaly detection and clustering algorithms based iVRIDA framework to detect and identify running instability and corresponding root cause. We deploy and compare the performance of the PCA-AD (baseline), Sparse Autoencoder (SAE-AD), and LSTM-Encoder-Decoder (LSTMEncDec-AD) model to detect the running instability occurrences.Furthermore, we deploy a k-means algorithm on latent space to identify clusters associated with root causes instigating instability. We deployed the iVRIDA framework on simulated and measured accelerations of European high-speed rail vehicles where SAE-AD and LSTMEncDec-AD models showed 97% accuracy. The proposed method contributes to smart maintenance by intelligently identifying anomalous vehicle-track interaction events.
40.	Leturiondo, Urko, et al. (författare) Architecture for hybrid modelling and its application to diagnosis and prognosis with missing data 2017 Ingår i: Measurement. - : Elsevier. - 0263-2241 .- 1873-412X. ; 108, s. 152-162 Tidskriftsartikel (refereegranskat)abstract The advances in technology involving internet of things, cloud computing and big data mean a new perspective in the calculation of reliability, maintainability, availability and safety by combining physics-based modelling with data-driven modelling. This paper proposes an architecture to implement hybrid modelling based on the fusion of real data and synthetic data obtained in simulations using a physics-based model. This architecture has two levels of analysis: an online process carried out locally and virtual commissioning performed in the cloud. The former results in failure detection analysis to avoid upcoming failures whereas the latter leads to both diagnosis and prognosis. The proposed hybrid modelling architecture is validated in the field of rotating machinery using time-domain and frequency-domain analysis. A multi-body model and a semi-supervised learning algorithm are used to perform the hybrid modelling. The state of a rolling element bearing is analysed and accurate results for fault detection, localisation and quantification are obtained. The contextual information increases the accuracy of the results; the results obtained by the model can help improve maintenance decision making and production scheduling. Future work includes a prescriptive analysis approach.
41.	Li, Xuebing, et al. (författare) A data-driven approach for tool wear recognition and quantitative prediction based on radar map feature fusion 2021 Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 185 Tidskriftsartikel (refereegranskat)abstract Tool wear monitoring during the cutting process is crucial for ensuring part quality and productivity. A datadriven monitoring approach based on radar map feature fusion is proposed for tool wear recognition and quantitative prediction, aiming at tracking the evolution of tool wear comprehensively. Specifically, the sensitive features from multi-source signals are fused by a radar map, and health indicators capable of characterizing the tool wear evolution are obtained. For the recognition of tool wear state and the quantitative prediction of tool wear values, the Adaboost Decision Tree (Adaboost-DT) ensemble learning model and stacked bi-directional long short-term memory (SBiLSTM) deep learning network are established, respectively. Experimental results demonstrated that the proposed approach could recognize the current wear state quickly and accurately whilst predicting wear values based on limited historical data available. Combining tool wear recognition and prediction results contributes to making a more flexible tool replacement decision in intelligent manufacturing processes.
42.	Liguori, Consolatina, et al. (författare) Innovative bootstrap approach for the estimation of minimum measurement time interval in road traffic noise evaluation 2017 Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 98, s. 237-242 Tidskriftsartikel (refereegranskat)abstract It is observed that in order to characterize the environmental noise in a site, during diurnal reference time (6–22h) or nocturnal reference time (22–6h), relatively at preset time window, observation period, a single value of the equivalent continuous A-weighted sound pressure level LA,eq is used. This value is determined by integrating and averaging the squared A-weighted sound pressure of fluctuating noise during the measurement time interval, in which there are representative values of acoustic event pressure levels: so it is very important accurately to select the suitable integration time. Such matter are highly relevant to the area of measuring environmental noise and this paper aims to present a statistical method, for determining the minimum measurement time interval for an accurate estimation of LAeq. The proposed algorithm, based on CPER bootstrap method, has been experimentally verified with real data obtained from road traffic noise measurement and it showed a very good stability. The methodology is suitable for upgrading the level meter firmware in order to have the real time information on the measurand uncertainty estimation and on the minimum measurement time interval.
43.	Liguori, Consolatina, et al. (författare) Proposal for the automatic evaluation of workers' exposure to acoustic noise following task-based approach 2021 Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 173 Tidskriftsartikel (refereegranskat)abstract Accurate measurement of exposure to noise in the workplace is important for employee health prevention as well as cost implications for employers. Standard ISO 9612 employs an engineering methodology for estimating noise exposure levels including levels of uncertainty. In this procedure some aspects are left to the discretion of the operator. Beginning with preliminary studies on the determination of the measurement intervals for evaluating workers' exposure to noise, this paper proposes an innovative approach to estimating work conditions for bus drivers. Measurement results are analysed and compared to the estimations based on both the ISO 9612 and the continuous acquisition analysis showing the feasibility of the proposal for accurately measuring the exposure to acoustic noise in a typical work situation.
44.	Lin, Jiachun, et al. (författare) Compensation of mounting error in in-situ wear measurement during gear pitting test 2022 Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 191 Tidskriftsartikel (refereegranskat)abstract A profilometer can be used to monitor the tooth surface topography evolution during gear pitting tests. Due to the mounting relationship variation between the instrument and the gear, the tooth profile's measurement position deviation from its theoretical location will introduce a measurement error. In this study, the tooth profile measurement error introduced by mounting using a tactile profilometer was theoretically analysed and experimentally confirmed as a fish shape. A mounting error compensation method based on projection onto the perpendicular plane to the gear's datum axis was proposed. The results show that the fish-shaped tooth profile measurement error can be effectively compensated, benefitting the evaluation of the gear tooth surface wear during gear pitting tests.
45.	Lundberg, Oskar, 1980-, et al. (författare) A compact internal drum test rig for measurements of rolling contact forces between a single tread block and a substrate 2017 Ingår i: Measurement. - : Elsevier. - 0263-2241 .- 1873-412X. ; 103, s. 370-378 Tidskriftsartikel (refereegranskat)abstract A novel test rig design is presented which enables detailed studies of the three force components generated in the impact and release phase of rolling contact between a tyre tread block and a substrate. The design of the compact internal drum test rig provides realistic impact and release angles for the tread block-substrate contact and enables force measurements at high rolling speeds with a high signal-to-noise ratio. Measurements of the rolling contact forces are presented for different values of rolling velocity, static pre-load and acceleration. It is demonstrated that this test rig provides results which contribute to the understanding of tyre road interaction and can be used as input to modelling-based development of both tyres and roads aiming for improved handling, safety, energy efficiency and comfort.
46.	Lundin, Henrik, 1976-, et al. (författare) Bounds on the performance of analog-to-digital converter look-up table post-correction 2009 Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 42:8, s. 1164-1175 Tidskriftsartikel (refereegranskat)abstract Analog-to-digital converter additive post-correction using look-up tables is considered. The problem of successfully predicting the converter's performance after correction is treated in particular. An accurate expression is provided that predicts the ADC performance after correction. The expression depends on differential non-linearity, random noise variance, and the numerical precision of the correction terms. The theory shows good agreement when compared with simulations and experimental converter data. The results are useful when designing systems involving ADCs and post-correction, since the performance parameters can be obtained with knowledge of a few ADC intrinsic parameters and the correction system resolution.
47.	Lundström, Jens, 1981-, et al. (författare) Assessing, exploring, and monitoring quality of offset colour prints 2013 Ingår i: Measurement. - Amsterdam : Elsevier. - 0263-2241 .- 1873-412X. ; 46:4, s. 1427-1441 Tidskriftsartikel (refereegranskat)abstract Variations in offset print quality relate to numerous parameters of printing press and paper. To maintain a constant high print quality press operators need to assess, explore and monitor quality of prints. Today assessment is mainly done manually. This paper presents a novel system for assessing and predicting values of print quality attributes, where the adopted, random forests (RFs)-based, modeling approach also allows quantifying the influence of different paper and press parameters on print quality. In contrast to other print quality assessment systems the proposed system utilises common, simple print marks known as double grey-bars. Novel virtual sensors assessing print quality attributes using images of double grey-bars are presented. The inferred influence of paper and printing press parameters on quality of colour prints shows clear relation with known print quality conditions. Thorough analysis and categorisation of related work is also given in the paper. (C) 2012 Elsevier Ltd. All rights reserved.
48.	Manami, Mohammadreza, et al. (författare) Deep learning models for improved accuracy of a multiphase flowmeter 2023 Ingår i: Measurement: Journal of the International Measurement Confederation. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 206 Tidskriftsartikel (refereegranskat)abstract Measurement of oil and gas two-phase flow with variable flow regimes relies to a large extent on flow patterns and their transitions. Using multiphase flowmeters in flows with high gas volume fractions is therefore usually associated with large uncertainties. This work presents a dynamic neural network method to measure the flow rate using a nonlinear autoregressive network with exogenous inputs (NARX). Total temperature and total pressure are used as network inputs and the obtained results are compared with a multilayer perceptron (MLP). Comparison between modeling results and the experimental data shows that the NARX network can predict oil and gas flow with variable flow regimes with less error compared to the MLP model, e.g. an absolute average percentage deviation (AAPD) of 0.68% instead of 1.02%. The present work can hence be seen as a proof-of-concept study that should motivate further applications of deep learning models to facilitate enhanced accuracy in flow metering.
49.	Martinez-Osuna, Juan F., et al. (författare) Coastal buoy data acquisition and telemetry system for monitoring oceanographic and meteorological variables in the Gulf of Mexico 2021 Ingår i: Measurement. - : Elsevier. - 0263-2241 .- 1873-412X. ; 183 Tidskriftsartikel (refereegranskat)abstract This paper presents a data acquisition and telemetry system designed and built to monitor oceanographic and meteorological parameters. A voltage regulator and readout module was designed for the reading of data from a set of dedicated commercial sensors and to continuously monitor the voltage level of the power supply. In order to monitor the measured parameters and the status of the buoy remotely, a data string was transmitted every hour using an Iridium satellite transceiver. The described system was implemented and tested in four coastal oceanographic buoys that were deployed and operated in remote sites in the Gulf of Mexico (GoM) for several months in 2016. The data recorded by the buoys is used to describe the oceanographic and meteorological conditions at each site. The system proved to be reliable for long-term monitoring at offshore sites, requiring only minor corrective maintenance during their operation in the field.
50.	Mašláň, S, et al. (författare) Interlaboratory comparison of battery impedance analyzers calibration 2023 Ingår i: Measurement. - : Elsevier B.V.. - 0263-2241 .- 1873-412X. ; 218 Tidskriftsartikel (refereegranskat)abstract The paper reports a results of series of interlaboratory comparisons of low impedance measurements at frequencies relevant for electrochemical impedance spectroscopy (EIS) of commercial lithium-ion cells. Two comparisons are presented. The first, bilateral comparison has focused on low impedance standards calibration in a full complex plane using digital sampling setups. The second comparison has focused on calibration and use of commercial 4-terminal battery EIS meters. Both comparisons have covered the impedance range from 50μ℧ to 100m℧ across the full complex plane in a frequency range from 0.01Hz up to 5kHz. Finally, the paper summarizes practices identified as critical for achieving measurement compatibility among various labs. © 2023 The Authors

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