As the polarization direction is unknown in free-space three-dimensional (3D) electromagnetic pulse (EMP) measurement, the components in three directions are usually measured first, and then the total vector is calculated. The waveform (magnitude) and polarization direction define the 3D process. Because of the uncertainty produced in the component measurement, there is also uncertainty in the calculated 3D process. This paper investigates the propagation of uncertainty during the total vector calculation process. The magnitude and polarization angle uncertainty propagation formulas are derived through analysis. The results show that the uncertainty of the calculated magnitude is less than the maximal measurement uncertainty of the three components, and the uncertainty of the polarization angle is less than sqrt(2) times the maximal uncertainty of the three components divided by the magnitude of the measured field. Finally, a Monte-Carlo (MC) simulation is run to validate the results of the analysis. The simulation results agree well with the analysis results.

In this paper, an efficient method for the denoising of electrocardiogram (ECG) signals is presented. As it is well-known, the efficient translation-invariant (TI) denoising technique, first introduced by Coifman and Donoho, uses K pre-processing shift-rotation operations, K denoising operations similar to the standard Donoho’s thresholding algorithm, K post-processing inverse shift-rotation operations, and finally, the K new less noisy copies generated by the preceding steps are averaged to produce a final denoised signal. Thus and conversely to the previously mentioned TI algorithm, the suggested technique consists of the design of a low computational translation-invariant-like strategy that eliminates the K pre-processing shift-rotation and the K post-processing inverse shift-rotation operations and only keeps the K wavelet-based denoising operations where for each one we use a different mother wave among a set of K mother waves ψ₁; ψ₂;...; ψ_K. Consequently, each mother wave generates a new less noisy copy from the original noisy signal. Finally, the produced less noisy multiple copies are averaged to reach the final denoised signal. Through this strategy, we can avoid the use of multiple hardware sensors to generate multiple noisy copies to be averaged to restore the clean version of the signal. Consequently, the proposed approach can considerably reduce the cost of the acquisition system. Additionally, the several results produced from extensive simulations show that the proposed algorithm outperforms many translation-invariant-like methods and can be considered as one of the top-ranking recent algorithms to tackle the denoising problem.

Micro-acceleration generation during ultra-low-frequency micro-vibration calibration is a sensitive issue. There are issues of traditional pendulum tables being unable to change the pendulum radius and direction to produce micro-accelerations of different magnitudes, and the line shakers having a low signal-to-noise ratio when the vibration amplitude is the same as that of the pendulum tables. Therefore, a novel ultra-low-frequency micro-vibration calibration method is proposed to solve the above issues based on virtual pendulum motion trajectories of the Stewart platform. The micro-accelerations of 10^–5 to 10^–3 m/s² can be generated by the trajectories with the radius of up to 12 m, the displacement amplitudes of up to 11.636 mm and the frequencies between 0.01 and 0.1 Hz. In the virtual pendulum motion, the maximum acceleration can be 2481 times greater than the acceleration of linear motion at the same frequency and displacement amplitude. In a comparison experiment with the current rotating platform, the maximum relative deviation of sensitivity amplitude calibration for pendulum motion around the x- and y-axis based on the Stewart platform are 0.411% and 0.295% respectively. The above results demonstrate the validity and reliability of this kind of method.

In process analytical chemistry, mass spectrometry analysis using a soft electron ionization (EI) source has qualitative advantages. However, the relatively small ionization cross-section of soft EI leads to lower sensitivity. To address this issue, a novel method has been developed to enhance the sensitivity of soft EI by utilizing a dual electron repeller and an ionization chamber to form a U-shaped electric field, causing electrons to oscillate within the field and effectively increasing the electron collision cross-sectional area. By combining with an electron lens, the virtual cathode effect at low electron energy can be reduced or even eliminated, thereby improving ionization efficiency. This method has resulted in a significant increase in signal intensity for m/z 18(H₂O), with a factor of 4.2 at an electron energy of 25 eV and a factor of 3.75 at 20 eV, compared to the electron receiving mode. Additionally, it reduces the required emission current, which is beneficial for prolonging the life of the filament. The proposed technique is expected to expand the application of soft EI, particularly for rapid online analysis in process analytical chemistry such as catalyst research and chemical reaction process monitoring.

This paper describes an efficient method of designing and implementing in FPGA devices complex tapped delay lines (CTDL) with pico and sub-picosecond resolution. Achieving a higher resolution and better linearity is possible by appropriate selection of single time coding tapped delay lines (TDL) involved in creation of CDTL. The proposed TDL selection algorithm significantly optimizes the size of the device’s logical resources required to implement CDTL with assumed parameters and provides a proper selection scenario. Ultimately, the presented solution allows to create CTDLs with different user-defined configurations based on a fixed set of available logical resources. Therefore, it is particularly recommended for prototyping in smaller FPGA devices. In this work, we investigate how the order of line selection influences the increase of the multiple time coding lines resolution. Furthermore, we determine the relation between the equivalent resolution value and the number of TDLs involved. Obtained results allow to estimate the upper limit of resolution that can be achieved using a given technology. In addition, the ranges of resolutions achievable with a fixed number of lines is also examined. The presented research results have been performed on a Kintex UltraScale FPGA chip, manufactured by Xilinx in the 20-nm CMOS process.

The paper presents a method of measuring the angle of light polarisation plane rotation. Measurement is done with a tilted fibre Bragg grating (TFBG), with a tilt angle of 7°, and an optical spectrum analyser. Data obtained with the analyser are processed with a Fast Fourier Transform (FFT) to obtain frequency representation (FFT coefficients). The rotation angle is calculated by comparing these coefficients obtained from the measurement with the ones collected during measurement set calibration. It has been shown that FFT coefficients change in the function of polarisation plane rotation and, in the case of some of them, these changes have a regular character and can be used to determine rotation. The method shown works in the range of 0 – 180° of rotation with an average error of 0.076° and a median error of 0.033°. The highest values of errors appear at about 0, 45, 90, 135 and 180°, which is caused by flat characteristics of many frequencies for these angles of rotation. The method discussed could find applications in many fields of structure monitoring and maintenance, where rotation or twist could be used as a quality parameter.

This paper describes the development and evaluation of a force-pressure balance system utilizing a highprecision force transducer. This setup aims to calibrate hydraulic pressure gauges commonly used in industrial applications, with a measurement range of up to 50 MPa. Detailed investigations were conducted to determine the metrological characteristics and calibration coefficients of the new force-pressure balance setup. Comparisons were made between the results obtained from the new setup and those obtained from another reference pressure standard. The findings highlighted a decrease in the accuracy of the pressure balance within the lower pressure range. This decrease in accuracy can be attributed to the hysteresis effect caused by the force transducer utilized in the setup. Additionally, an error was observed in the pressure characteristic of the piston’s performance, particularly in the lower pressure range. These findings indicate the need for further improvements in the force-pressure balance system to enhance accuracy across the entire pressure range.

In this article a complete procedure to investigate thin semiconductor plates (epitaxial layers), including high-resolution X-ray diffraction measurements, mathematical modelling of both crystalline structure and crystalline microstructure and computations to approximate solving inverse problems, is proposed and described in detail. The method is successfully applied to estimate crystalline homogeneity of a square indium-arsenide plate epitaxially-grown on gallium-arsenide substrate. To this end, the specimen is tested in nine areas around points forming a square grid. It is demonstrated that whole specimen may be regarded as a single large crystalline grain consisting of crystallites separated by small-angle boundaries. The crystallites occur as rode-like cuboids elongated in the direction perpendicular to the plate surface, with different areas of the sample and with base sizes not much differing. The mean-absolute second-order strain is very small and almost constant in the whole sample. The first-order strain also appears and, effectively, the structure of the crystalline layer is tetragonal with unit-cell parameters being smaller parallelly and larger perpendicularly to the layer surface and varying slightly in the layer. The results are presented in tables and figures and commented.

The occurrence of asymmetric probability distributions is quite common. Phenomena such as salary, number of failures, sound level values, etc. have skewed distributions. In such cases, estimating the mean using the interval method can be inaccurate as it ignores the distribution’s asymmetry. Another method of constructing confidence intervals, which does not require symmetry of distributions, is the method based on Chebyshev’s theorem. However, the intervals thus obtained are symmetrical. The approach proposed in this article uses the concept of Chebyshev’s theorem and semivariances to construct new confidence and uncertainty intervals. The article examines the properties of semivariance-based confidence intervals for long-term noise indicators from acoustic monitoring of the city of Gdansk and compares them with classical confidence intervals. The new uncertainty assessment tool proposed in this article in the form of a semivariance-based uncertainty interval can therefore be the basis for new uncertainty assessment methodology and more effective uncertainty.

The paper describes the results of investigations illustrating the influence of the method of determining the excess of junction temperature and the selection of a function approximating the thermometric characteristic used in the procedure of measuring thermal resistance of a power MOS transistor on the measurement results. The investigations involved the measurements made using an indirect electrical method. Three methods of determining the excess of junction temperature of the transistor are presented, using a linear function and nonlinear function approximating thermometric characteristics. The thermal resistance measurement results obtained using each of the considered methods were compared. The measurement error caused by the selection of the considered methods was also analyzed.

The Lithuanian national standard of voltage is maintained as the basis for calibration and measurement capabilities of Lithuania published in the Key Comparison Database of the International Bureau of Weights and Measures (BIPM). The stability and uncertainty of the voltage value measurements, performed since 2004 using the calibrated values of the Zener solid-state voltage standards (zeners) to predict their future behavior, are discussed. Conclusions regarding short- and long-term predictability of their behavior, which can be used for choosing an appropriate calibration period, are presented. An estimate of merit for approximations is proposed; based upon the estimate, it is concluded that the hyperbolic approximation is the best one in the most of the cases. Also discussed is the behavior of voltage dividers used in the zeners as well as the recovery of the zeners after a failure of their power supply. It is concluded that the voltage standards operated by the Lithuanian National Electrical Standards Laboratory feature stable drift of the voltage reproduced, which is well predictable by means of linear or non-linear regression.

Image intensifier tubes (IITs) are the most important modules of night vision devices used in huge numbers by military forces worldwide. Resolution is the most important parameter of IITs that presents information about ability of these devices to produce output images preserving information about details of the observed scenery. Despite its importance, it is still a common practice to measure resolution subjectively, by an observer looking at image of a resolution target created by a tested IIT. A series of attempts have been carried out to develop objective methods for accurate resolution measurement of IITs but with limited success. Accuracy of these methods varies depending on the tested IIT. This paper presents detailed analysis of proposed methods for objective resolution measurement. This analysis has shown that significant variability of accuracy of these methods is caused by one main drawback: the methods do not take into account influence of the spatial noise effect on human perception of image of the resolution target. Thus, an improved method taking into account spatial noise and its impact on target detection has been proposed. The method has been validated through experimental verification that shows accuracy improvements compared to other objective methods. This new approach improves accuracy of measurement of resolution of IITs to a level that can be accepted at professional test stations. In this way, this new method has potential to replace the standard subjective method to measure resolution of IITs and fix the biggest flaw of the standard test stations: measurement subjectivity.

Accurate information about the vehicle state such as sideslip angle is critical for both advanced assisted driving systems and driverless driving. These vehicle states are used for active safety control and motion planning of the vehicle. Since these state parameters cannot be directly measured by onboard sensors, this paper proposes an adaptive estimation scheme in case of unknown measurement noise. Firstly, an estimation method based on the bicycle model is established using a square-root cubature Kalman filter (SQCKF), and secondly, the expectation maximization (EM) approach is used to dynamically update the statistic parameters of measurement noise and integrate it into SQCKF to form a new expectation maximization square-root cubature Kalman filter (EMSQCKF) algorithm. Simulations and experiments show that EMSQCKF has higher estimation accuracy under different driving conditions compared to the unscented Kalman filter.

In this paper a comparison of different types of maximum power point search methods for the photovoltaic panels is presented. The methods that represent each group of maximum power point techniques will be implemented in the software that allows to test the behaviour of photovoltaic panels in different environment conditions including partial shading. In this paper each implemented method was compared including time of convergence with the maximum power point, tracking error and differences in the energy obtained from photovoltaics during the simulation time. The algorithms were compared under both uniform lighting and partial shade conditions.

Many gas companies build and operate gas distribution system in the city country and around the world. The traditional open-cut excavation requires the ground to be broken up by heavy equipment, the soil and asphalt need to be removed. Traditionally, a technician requires a minimum of 60 cm by 180 cm excavation to perform routine procedures. Often the trench must be temporarily supported using some type of shoring before a utility worker can enter the hole to perform the repairs to the utility pipe. This process is costly, time consuming, dangerous and is inconvenient to traffic patterns. We propose a new solution called keyhole technology which minimizes labor and restoration costs compared with conventional practices. In our design, the same construction and maintenance procedures can be accomplished through a 45 cm diameter circular holes above the utility pipe to be repaired. However, specially designed, long handled tools that operate remotely are necessary. This process is more cost-efficient, less dangerous and less disruptive to traffic patterns because there is no additional milling and overlaying of the road. The small hole requires little replacement materials to fill the hole. Because the concept is relatively new to the public utility sector, there is a lack of equipment/tools available that could perform the required services. The finite element analyses using commercial package Abaqus will be employed to obtain the force needed to close the pipe. As a final example, we will show the topology optimization of squeeze–off tool as the act of an iterative process. The correctness of the numerical calculations was verified by a pipe compression experiment on Instron 8850 testing machine.