The paper proposes an automated system for measuring the thermal conductivity of solids in the range from 5 to 400 W/(m·K) with increased accuracy and reduced duration of thermal conductivity measurement. The main element of this system is a thermal conductivity measuring transducer built on a bridge diagram balanced by heat flows. Using the theory of thermal circuits, the authors built a mathematical model of the measuring transducer. To implement the automated system for measuring thermal conductivity, materials of heat-conducting elements, reference specimens, and comparative elements were selected, and their design parameters were calculated. The setting parameters of the control system for balancing the bridge measuring diagram were determined. The authors also carried out the calibration of the developed thermal conductivity measuring system using reference specimens and obtained its calibration characteristic with a correlation coefficient R-square of 0.9987.

In recent years, due to the proliferation of inertial measurement units (IMUs) in mobile devices such as smartphones, attitude estimation using inertial and magnetic sensors has been the subject of considerable research. Traditional methods involve probabilistic and iterative state estimation; however, these approaches do not generalize well over continuously changing motion dynamics and environmental conditions. Therefore, this paper proposes a deep learning-based approach for attitude estimation. This approach segments data from sensors into different windows and estimates attitude by separately extracting local features and global features from sensor data using a residual network (ResNet18) and a long short-term memory network (LSTM). To improve the accuracy of attitude estimation, a multi-scale attention mechanism is designed within ResNet18 to capture finer temporal information in the sensor data. The experimental results indicate that the accuracy of attitude estimation using this method surpasses that of other methods proposed in recent years.

The background oriented schlieren (BOS) imaging relies on measuring the light deflection angle in proportion to the refractive index gradient due to the change in the density of a medium. BOS imaging is sensitive to light deflection, and the quantitative measurement requires a reliable calibration method. It is convenient to calibrate the BOS based on the measurement of light deflection. All current BOS calibrations use the random dot as the background and digital image correlation (DIC) as the processing algorithm. Such calibrations can induce an inaccurate measurement. This paper proposes a new method to calibrate the BOS based on measuring a known light deflection angle of a wedge prism. The proposed method uses a fringe pattern instead of the random-dot and works based on phase demodulation. The fringe patterns are phase modulated by the wedge prism (the schlieren object). The demodulation utilizes the Hilbert transform (HT) on the BOS images, giving the phase difference of the images. The BOS converts the phase difference into the deflection angle. The calibration relies on the deviation of the angle measured by the BOS with the known angle of a wedge prism. The results show that the measurement accuracy of the BOS can achieve more than 95%. This result shows high accuracy in measuring the light deflection angle. Also, the proposed method is more accurate than other methods, and fringe patterns outperform random dot patterns in BOS imaging. Soon, this proposed calibration method can be adopted to validate the instruments for measuring the physical properties of a transparent medium in two-dimensional (2-D) visualization, in a contactless and non-intrusive manner.

The accurate measurement of time-of-flight (TOF) is essential in ultrasonic testing. Further, noise interference is the key factor affecting the measurement accuracy. Therefore, to develop a reliable computational method of TOF for test pieces working in noisy environments, an integration method of a hybrid genetic algorithm and the Levenberg–Marquardt algorithm (GA–LM) for ultrasonic thickness measurement is proposed in the present research. A Gaussian model is first established for an echo signal. Further, the model-based parameter estimation is converted into a nonlinear optimization problem by applying the least square method. As the parameter estimation methods are easily affected by the initial value, an integrating innovation of the GA–LM algorithm is proposed. The initial values of the model parameters are selected by GA to obtain an approximate global optimal solution. Subsequently, this approximate solution is used as the initial value for the LM algorithm to perform iterations. The accurate global optimal solution of the Gaussian model is obtained through these iterations. Finally, the measuring accuracy and robustness of the GA–LM algorithm for TOF computation are verified by both numerical simulation and experiment data

For some industries such as automotive, defence, aerospace, pharmaceutical manufacturing, dynamic pressure measurement is an important requirement. In a primary level dynamic pressure measurement system with a drop weight method, the dynamic pressure value is calculated using parameters such as the effective area value depending on the piston cylinder unit, the maximum acceleration value measured by a laser interferometer. On the other hand, the type of liquid used in the measuring head is another important factor affecting repeatability and providing ease of measurement. In this study, a new measurement head, piston and cylinders were designed, manufactured and the Taguchi method was used to accurately determine some parameters affecting the measurements in a dynamic primary pressure measurement system operating with the drop weight method. In the studies carried out, four pistons, four cylinders, four sampling frequency values and two liquid types were considered. By using the Taguchi method, the optimum parameters of the dynamic pressure measurement system with drop weight method were determined with only sixteen experiments instead of one hundred and twenty-eight.

In order to ensure the safe operation of electromagnetic suspension (EMS) maglev trains, it is necessary to pay attention to the control loop performance of the suspension system. The suspension system with closed-loop control is tuned to achieve excellent performance at its early stage of operation. After running for a period of time, the control loop may encounter problems e.g., degraded operation, and paralysis may occur in severe cases. In order to quantify the control performance of the suspension system in an explicable manner, this paper proposed a data-driven control loop performance evaluation method based on fractal analysis, which does not require any external sensors and can be applied without data source restrictions such as dimension, volume and resolution. The control loop performances of such suspension systems were monitored, analysed, and evaluated by cross-sectional study, based on the field data of a commercial operation line in the commissioning stage. Furthermore, the track condition was revealed by capturing performance changes of the suspension system running on different guideway girders. The results demonstrate that the proposed method enables early warning of the degeneration of the suspension systems and the track.

Transparent Yb³⁺/Er³⁺glass-ceramic was successfully obtained by the extrusion method. The extrusion of oxyfluoride tellurite-germanate glass co-doped with Yb³⁺and Er³⁺ions at 520°C resulted in the formation of Ba_0:75Er_0:25F_2:25 nanocrystals, leading to an increase in the upconversion (UC) emission intensity of 35 times in glass-ceramic with respect to the glass. The glass to glass-ceramic transition was confirmed by X-ray diffraction (XRD) and Transmission electron microscope (TEM). Also, the structural changes that occurred during crystallization were assessed using Fourier-transform infrared (FTIR) spectroscopy. Furthermore, the pump power and temperature UC emission dependence of glass and glass-ceramic under 976 nm laser excitation were investigated in detail. The assessments showed that i) two-phonons are involved in the UC process and ii) the temperature has a significant influence over it. The Yb³⁺/Er³⁺ codoped glass-ceramic shows relatively high S_a and S_r values in a wide temperature range from 300 to 573 K, presenting the maximal S_a value of 3:50 x 10^–3 at 573 K and the maximal S_r value of 6:30 x 10^–3at 364 K. These results suggest that the glass-ceramic is a good candidate for optical applications such as luminescent thermometry.

Over the past decade, studies published on the evaluation of intraoral scanners (IOSs) have mainly considered two parameters, precision and trueness, to determine accuracy. The third parameter, resolution, not much studied, seems essential for an application in dentistry. Objective: The objective of this preliminary study is to create an original method – a Resolution-Trueness- Precision (RTP) protocol to evaluate these three main parameters – resolution trueness and precision – at the same time. Material and Method: A ceramic tip with particular and calibrated dimensions is determined as the reference object and its mesh recorded with a scanning microtomograph, and compared with the one extracted to the IOS. It is the particular geometric shape of the object that will make it possible to simultaneously assess: resolution, trueness and precision. Results: The results have shown a mean resolution of 79.2 μm, a mean for trueness of 17.5 and a mean for precision of 12.3 μm. These values are close to previous results published for this camera. So, the RTP protocol is the first including the three parameters at the same time. Simple, fast and precise, its application can be useful for comparisons between IOSs within research laboratories or test organizations. Finally, this study could be a first step to create a reference kit for practitioners allowing them to control the quality of their IOS over time.

This paper presents the results of a study of three methods for estimating the respiratory wave (RW) and respiratory rate (RR) using the electrocardiogram (ECG). There were applied methods from different groups: amplitude modulation ECG-Derived Respiration (EDR), frequency modulation Respiratory Sinus Arrhythmia (RSA) and Baseline Wander (BW) processing with the Savitzky–Golay filter (S–G). The theoretical aspects of the methods were presented in the Part 1 of the publication which was entitled: “Three Methods for the Determination of the Respiratory Waves from ECG Part I”. RR parameter estimation was performed for all the three methods for 12 subjects. The research concerning the influence of the parameters: Body Mass Index (BMI), Tidal Volume (TV) -, Forced Expiratory Volume in 1 second (FEV1) and – Forced Vital Capacity (FVC) on the errors of the estimated parameter RR. Moreover, all 12 signals, which were acquired with the help of a 12-lead Holter ECG were taken into consideration. The results indicate a preliminary dependence of respiratory parameters and BMI on the Respiratory Wave and, further, on the RR estimation errors. Consequently, the type of method and ECG Holter leads depend on the BMI and respiratory parameters. Studies with larger numbers of objects to definitively confirm these relationships are planned. In addition, an optimal selection of S–G filter parameters was carried out. Finally, a proprietary reference embedded system for recording RW and calculating RR was demonstrated.

The paper presents the results of research on commercial photovoltaic cells made of crystalline silicon. In particular, the focus was on the description of the elaborated by the authors measuring system with measurements methodology used for assessment of the influence of temperature on spectral characteristics of the tested cells, describing the dependence of the current sensitivity (spectral response, responsivity) and the external quantum efficiency on the wavelength of optical radiation. The investigations carried out in the proposed test system made it possible to evaluate the properties of the cells in the conditions similar to the operating conditions.

A comparison of measurements of voltage transformer (VT) voltage ratio and phase displacement was performed between the National Center for High Voltage Measurement (NCHVM), China and the National Measurement Institute (NMI), Australia, with two voltage transformers provided by the NCHVM being used as the travelling standards. Voltage ratios of the 10 kV/100 V transformer measured by the two institutes differed by less than 5 μV/V and the phase displacement by less than 6 μrad, while voltage ratios of the (110/p3 kV)/100 V transformer differed by less than 16 μV/V and 13 μrad. These results confirmed that measurement results of the two institutes agreed within detailed measurement uncertainties evaluation. The comparison further enhances the confidence in both methods, which are widely used for calibration of voltage transformers in the electricity industry.

Gear transmission errors are influenced by temperature especially in the aerospace field. A model is proposed to investigate the influence of temperature on cylindrical gear transmission errors based on the thermal network (TETN). The gear temperature field distribution model is established based on the thermal network method, and gear thermal deformation can be calculated along the gear meshing line. Regarding the gear single-flank rolling process, the variation of gear transmission errors under temperature is determined. In numerical calculations in MATLAB, the variation of gear transmission errors at 100°C compared to 20°C is –4.20 μm, which decreases almost linearly while the thermal expansion coefficient of the gear material increases. The simulation of the gear transmission errors variation of temperatures using the finite element method (FEM) were carried out in Workbench software under Ansys and the average difference of the TETN model results between calculations and FEM for different temperatures was 0.24 μm. Experiments were carried out on the gear tester in temperatures ranging from 0°C to 100°C, the TETN model results in calculations were compared with the results of the tester, and the average difference was –1.15 μm. The results show that the proposed TETN can be used as an algorithm to determine the variation of gear transmission errors under the influence of temperature.