Short Measurement Time Research Articles

Seismic spectrum decomposition based on sparse time-frequency analysis

Time-frequency analysis is widely used in many engineering fields. However, the traditional time-frequency analysis methods suffer from issues such as low resolution or the interference of cross terms. To solve the above issues, this paper proposes a sparse time-frequency analysis by using an L1-norm constraint, fitting the sparse prior of a signal's spectrum. This process begins with the relationship between the sparse spectrum and the short-time measurement in order to propose the short-time sparse spectrum inversion model. Then, the first-order primal-dual method is employed to solve the proposed model. In this way, the reconstructed spectrum is constrained to be sparse. On the one hand, the concentration of the proposed algorithm is high due to the adoption of the L1-norm constraint. On the other hand, cross terms are avoided because the proposed method is based on the short-time Fourier transform and convex optimization technology. To show the performance of the proposed method, experiments based on both the theoretical signal and the real seismic signal are then conducted and compared with state-of-the-art time-frequency methods. The results show that the proposed method can obtain more accurate time-frequency distributions than other algorithms. Finally, we apply the proposed method in the decomposition of a seismic signal spectrum. The experiments show that the proposed method is capable of obtaining high-resolution frequency slices and more precisely exploring the spatial distribution of a reservoir than traditional time-frequency methods.

Correction of spherical surface measurements by confocal microscopy

Refractive microlenses are nowadays widely used in optical systems. Characterizing their surface is essential to ensure their quality and to optimize their fabrication process. This is realized by optical surface profilers thanks to their vertical resolution, short measurement time and areal information. However, when measuring non-flat surfaces, errors appear caused by aberrations of the microscope objective used in such systems, which significantly limit the achievable quality of the manufactured spherical surfaces. Approaches have been proposed to tackle these errors, but none of them demonstrated its validity for measurements of high quality microlenses. In this work, we demonstrate that the surface error depends on the surface position within the field of view of the microscope objective and on the surface slope. We then explain how to record the value of this error experimentally: this can be done by measuring a reference ball placed at different positions in the field of view. We finally use a machine learning algorithm to fit the experimental data in order to correct subsequent measurements. We apply this approach to measurements performed by a 20× numerical aperture 0.6 microscope objective of a confocal microscope. The effectiveness of the proposed method is demonstrated by showing that the surface error corresponds to a RMS wavefront error of λ/7 before correction and of λ/50 after correction for glass microlenses used in the visible range. This method thus allows the use of high numerical aperture microscope objectives for an accurate characterization of microlenses. Likewise, the fabrication capability of microlenses in terms of slope and quality is greatly extended, which is especially important for aspheres or freeforms.

Knowledge-based approach in the field of non-destructive inspection of CFRP metal hybrid components via optical lock-in thermography

The present development trend in lightweight construction is characterised by an increased application of material-hybrid transition areas which are frequently involved with an intensified and considerably challenging quality concern.This research explores a complete referencing process in order to acquire statistically secured datasets in the field of non-destructive inspection of CFRP metal hybrid components via optical lock-in thermography by introducing a novel defect abstraction method. Thereby, the knowledge-based management of the generated datasets constitutes the ultimate scope. The experimentally determined datasets comprise both an examiner-specific probability of detection and an adequate defect visibility in a preferably short measurement time.

Simultaneous multi-point measurement of strain and temperature utilizing Fabry-Perot interferometric sensors composed of low reflective fiber Bragg gratings in a polarization-maintaining fiber

A fiber Bragg grating (FBG)-based multi-point sensing system for the simultaneous measurement of strain and temperature is proposed, with a Fabry-Perot interferometer (FPI) consisting of low reflective FBGs inscribed inside a polarization-maintaining (PM) fiber is introduced as a sensor head. A multi-point sensing method with high dynamic range and short measurement time can be realized by analyzing the reflection spectrum of low reflective FBG-FPIs, and a simultaneous measurement of strain and temperature using two orthogonal polarization modes is enabled by the high birefringence of a PM fiber. An experimental demonstration of multi-point measurement utilizing the proposed system is reported.

Burnup measurement error analysis of HTR fuel spheres using ab-initio Monte-Carlo simulations

Multi-pass pebble-bed HTRs need a fast and efficient burnup measurement system (BUMS) for irradiated spherical fuel elements. Typically, for every single pass through the system, we are restricted to 55 h cooling time and 10 s measurement time. These restrictions make a high precision gamma spectrum collection and analysis difficult in general. Using the ab-initio Monte-Carlo simulation approach, we determine the one-sigma relative statistical uncertainty to be ±6.5% at the final 200 MWth MODUL burnup of 9.2% FIMA when the traditional gamma measurement systems are used. This FIMA uncertainty range is originated from the limiting statistics of a very short measurement time and the simultaneous interference of neighboring peaks at so short cooling times. It is the first time that the analysis contains the consideration of a 140La caused Compton shoulder which influenced the background near the Cs-137 peak. Longer cooling times would reduce peak interference and longer measurement times would allow better statistics, as would higher count rates in more advanced gamma counting systems and a narrower width of the four photopeaks in the near 137Cs spectrum. Thereby, the relative statistical error could be brought down to 2–3%, which would be better for engineers. The always existing relative statistical error which can be accepted and recommended in the real measurement should be evaluated in many aspects comprehensively.

Adolescent Learning of Academic Vocabulary in Iceland

AbstractThe fields of vocabulary instruction, literacy professional development, and global language issues framed this research. Situated in Iceland, the intervention consisted of professional development for 10th‐grade teachers focused on academic words in various subject materials, increasing the learners’ proficiency in using explicit strategies to detect word meanings, and offering learners multimodal ways of working with the vocabulary. There were no significant differences between the participants in the experimental schools (n = 157) and in the control schools (n = 88). There were gains from pretest to posttest in vocabulary and in comprehension, and there were some promising trends that distinguished the experimental group from the control group on the reading comprehension test. The nature, intensity, and length of the professional development offered to the high school teachers and the relatively short time of measurement of student outcomes are suggested explanations of the results.

Design of Reconfigurable Time-to-Digital Converter Based on Cascaded Time Interpolators for Electrical Impedance Spectroscopy.

This paper presents a reconfigurable time-to-digital converter (TDC) used to quantize the phase of the impedance in electrical impedance spectroscopy (EIS). The TDC in the EIS system must handle a wide input-time range for analysis in the low-frequency range and have a high resolution for analysis in the high-frequency range. The proposed TDC adopts a coarse counter to support a wide input-time range and cascaded time interpolators to improve the time resolution in the high-frequency analysis without increasing the counting clock speed. When the same large interpolation factor is adopted, the cascaded time interpolators have shorter measurement time and smaller chip area than a single-stage time interpolator. A reconfigurable time interpolation factor is adopted to maintain the phase resolution with reasonable measurement time. The fabricated TDC has a peak-to-peak phase error of less than 0.72° over the input frequency range from 1 kHz to 512 kHz and the phase error of less than 2.70° when the range is extended to 2.048 MHz, which demonstrates a competitive performance when compared with previously reported designs.

Determination of the ash content of coal samples by nuclear techniques with bismuth germanate detectors

ABSTRACT A new promising nuclear technique to determine the coal-ash content was investigated using a bismuth germinate (BGO) detector instead of a sodium iodide-thallium [NaI(Tl)] detector for the dual-energy gamma-ray transmission (DEGT) measurements at 59.6 and 661.7 keV. The peak detection efficiency of the high-energy gamma-ray radiation was about two- to three-fold higher when using a BGO than a NaI(Tl) detector. This would increase the potential operation safety by allowing the use of a lower radioactivity level or a shorter measurement time. To analyze the coal-ash content using DEGT, the relationship between the transmittance ratios and the coal-ash content was successfully achieved as a linear equation, while the coal-ash contents determined by DEGT were in a very good agreement with those determined by X-ray fluorescence spectroscopy and standard chemical ASTM3174 methods, showing a highly linear relationship. In brief, the DEGT at 59.6 and 661.7 keV using a BGO detector could be developed to be a new promising approach to determine the coal-ash content as a real-time and on-belt analysis or a portable device in further investigation.

A high visibility Talbot-Lau neutron grating interferometer to investigate stress-induced magnetic degradation in electrical steel

Neutron grating interferometry (nGI) is a unique technique allowing to probe magnetic and nuclear properties of materials not accessible in standard neutron imaging. The signal-to-noise ratio of an nGI setup is strongly dependent on the achievable visibility. Hence, for analysis of weak signals or short measurement times a high visibility is desired. We developed a new Talbot-Lau interferometer using the third Talbot order with an unprecedented visibility (0.74) over a large field of view. Using the third Talbot order and the resulting decreased asymmetry allows to access a wide correlation length range. Moreover, we have used a novel technique for the production of the absorption gratings which provides nearly binary gratings even for thermal neutrons. The performance of the new interferometer is demonstrated by visualizing the local magnetic domain wall density in electrical steel sheets when influenced by residual stress induced by embossing. We demonstrate that it is possible to affect the density of the magnetic domain walls by embossing and therefore to engineer the guiding of magnetic fields in electrical steel sheets. The excellent performance of our new setup will also facilitate future studies of dynamic effects in electric steels and other systems.

Deblurring Sinograms Using a Covolutional Neural Network to Achieve Fast X-ray Computed Tomography Scanning

X-ray computed tomography (CT) allows for visualization of the interior of solid objects in a non-destructive and non-invasive manner. However, producing high-precision measurements takes a long time because thousands of sharp transmission images are required to reconstruct CT volumes. To address this problem, we propose a CT measurement method based on Convolutional Neural Networks (CNNs) that yields sharp transmission images by deblurring blurry ones. In this method, first, blurry images are obtained in a short measurement time, then they are deblurred by CNNs with fine-tuning and integrated by linear interpolation. This method shortens the measurement time indirectly because the process related to the CNNs is fast with GPUs and the blurry images with low levels of noise intensity do not require a long time. Besides, the fine-tuning may improve the output images’ sharpness. According to our experimental results, the proposed method is fast and can maintain the quality of data to a certain extent.

Mass spectrometric detection of enantioselectivity in three-component complexation, copper(ii)-chiral tetradentate ligand-free amino acid in solution.

By using electrospray ionization mass spectrometry coupled with the use of deuterium-labelled quasienantiomers, enantioselective coordination of a free amino acid as the second ligand of a copper(ii) complex with a novel chiral tetradentate ligand was evaluated quantitatively in a short measurement time.

Listening difficulty estimation model using short-time objective intelligibility measure for outdoor public address systems

Listening difficulty estimation model using short-time objective intelligibility measure for outdoor public address systems

Single-Channel Speech Enhancement Based on Adaptive Low-Rank Matrix Decomposition

The low-rank matrix decomposition (LMD) algorithm based on the maximum correntropy criterion (MCC) has recently shown its superiority to other algorithms in classification (e.g., face recognition), and we develop it into single-channel speech enhancement for the low-rank structure of speech signals in the time domain. However, a new issue has arisen: some residual noise exists in the enhanced speech due to its sensitivity to the exact rank value. To address this issue, we propose a novel adaptive LMD (ALMD) algorithm in which the energy threshold technique is adopted to adaptively update the effective rank value of each frame of the speech matrix. Our proposed ALMD algorithm can achieve an acceptable performance for low signal-to-noise ratio (SNR) levels without approximating the speech phase with the noisy phase. We compare ALMD algorithm with common conventional algorithms in Gaussian white noise and non-Gaussian noise conditions. The simulation results demonstrate that ALMD algorithm can achieve its superiority in terms of the segmental SNR (segSNR), perceptual evaluation of speech Quality (PESQ), and short-time objective intelligibility measure (STOI), when compared with tested baseline algorithms.

System for Measuring Emittance Characteristics of Ion Sources

The article presents the results of the development of a system for measuring emittance characteristics of ion sources studied at the IAP NAS of Ukraine with the aim of obtaining the ion beams with a high brightness. The emittance measurement system is based on the scheme of an electrostatic scanner and consists of two main parts: the scanner, which moves in the direction perpendicular to the beam axis using a stepper motor, and the electronic system of control, processing and data acquisition. The electronic system contains a Raspberry pi 3B microcomputer, precision DAC/ADCs, the high-voltage amplifier of a scanning voltage up to ±500 V on deflection plates of the scanner and a wide range current integrator. The determination of the emittance consists in measuring the ion beam intensity distribution when the scanner moves along the x-coordinate and the electrostatic scanning along the x´ angle. The obtained two-dimensional data array allows determining the main characteristics of ion beam: geometric 90% emittance, the root mean square (rms) emittance, the Twiss parameters and phase ellipse of rms emittance, the beam current profile and the angle current density distribution. To test the performance and functionality of the system, the emittance characteristics of the penning type ion source were measured. The working gas was helium, and the beam energy varied within 7–15 keV. At 13 keV of beam energy the following emittances of the He+ ions beam was obtained: 90% emittance is 30 π∙mm∙mrad, rms emittance is 8.4 mm∙mrad, and the normalized rms emittance is equal to 0.022 mm∙mrad. The developed system for measuring the emittance of the ion beams is characterized by a short measurement time of 10-15 minutes.

Minimum measurement time of masseteric electromyogram required for assessment of awake bruxism during the daytime

ABSTRACT Objective: Assessments of diurnal awake bruxism (d-AB) using masseteric electromyogram (EMG) during various lengths of measurement time within a day were examined as the first step of research to clarify the minimum measurement time required for assessment of d-AB by subject. Methods: Subjects were 33 outpatients. Assessment of d-AB by EMG during partial measurement time (PMT) with durations ranging from 30 minutes to 6 hours was compared with that during total measurement time (TMT) used as the reference standard. Results: No significant difference was found between TMT data and PMT data. There were significant correlations in all combinations between TMT data and PMT data. Accuracy was 0.909 or more for 2.5 hours or longer. Discussion: The results suggest that the tendency of daytime muscle activity in 1 day can be assessed even by using masseteric EMG data obtained during a relatively short measurement time.

Large-area thickness measurement of transparent multi-layer films based on laser confocal reflection sensor

It is critical to maintain uniform coating thicknesses over large area in order to manufacture high-quality coated transparent films. Optical thickness measurement technique gives relatively short measurement time and non-destructive measurement. Among the available optical techniques, a laser confocal method that detects reflected light at the interfaces between layers provides highly reliable and accurate height information. Because confocal sensors utilize focusing optics, both the numerical aperture of the focusing lens and refractive index of the film material must be considered when calibrating the actual thickness from the recorded displacement of the focusing lens. In this paper, we proposed a measurement method calibrated for the actual thickness of single- and double-layer transparent films. Also, we developed a large-area thickness measurement system for transparent substrates and the uniformity of hard-coated samples is evaluated using the laser confocal reflection sensor. Experimental results are compared with the thickness measured using a mechanical thickness gauge.

Probability distributions of continuous measurement results for two noncommuting variables and postselected quantum evolution

We address the statistics of a simultaneous continuous weak linear measurement of two noncommuting variables on a few-state quantum system subject to a postselected evolution. The results of both postselected quantum measurement and simultaneous monitoring of two noncommuting variables differ drastically from the results of either classical or quantum projective measurement. We explore the peculiarities arising from the combination of the two. We concentrate on the distribution function of two measurement outcomes integrated over a time interval. We formulate a proper formalism for the evaluation of such distribution, and further compute and discuss the resulting statistics for idealized and experimentally relevant setups. We demonstrate the visibility and manifestations of the interference between initial and final states in the statistics of measurement outcomes for both variables in various regimes. We analytically predict the peculiarities at the circle ${\mathcal{O}}_{1}^{2}+{\mathcal{O}}_{2}^{2}=1$ in the distribution of measurement outcomes ${\mathcal{O}}_{1,2}$ in the limit of short measurement times and confirm this by numerical calculation at longer measurement times. We demonstrate analytically the anomalously large values of the time-integrated output cumulants in the limit of short measurement times and zero overlap between initial and final states, and give the detailed distributions for this case. We term this situation sudden jump. We present the numerical evaluation of the probability distributions for experimentally relevant parameters in several regimes and demonstrate that interference effects in the postselected measurement can be accurately predicted even if they are small.

Advanced Nuclear Physical Analytical Techniques

Among the modern analytical methods, the nuclear analytical techniques, and especially neutron activation analysis, pay an important role in accurate and sensitive analysis. The capabilities of this technique and its application range have broadened lately with the development and employment of a combination of special more or less novel sub-techniques. These techniques are (a) bss-free counting gamma-ray spectrometry, (b) radioactive decay compensation and (c) repeated activation and measurement. The first technique permits short-time measurements at high count rates in multielement activation analysis with a wide nuclide concentration and half-life range, while by the other two techniques the counting statistics can be improved considerably especially in short-lived nuclide analysis. Thus, because of the high throughput rate, more customers can be served even far from the reactor site by mailing the samples and getting the analytical results back.

Identifying defect size in organic coatings by electrochemical noise, galvanostatic step and potentiostatic step techniques

Organic coating effectively protects metal from corrosion in atmospheric environment. As the coating undergoes degradation in harsh environment enriched with Cl− and at high temperature, there is a need to develop in-situ electrochemical methods to in-field detect the defect size in organic coatings that exposed to atmospheric conditions. This work aims to develop several electrochemical methods including open circuit potential (OCP), electrochemical current noise (ECN), electrochemical impedance spectroscopy (EIS), galvanostatic step and potentiostatic step, and the parameters obtained from each method are compared. Experimental results indicate that, apart from corrosion potential, the other four techniques can effectively detect the defect size in organic coatings by using polarization resistance or charge transfer resistance. Galvanostatic step and potentiostatic step can be used in field corrosion detection due to its concise instrumentation and short measurement time.

Terahertz High Resolution Gas Spectroscopy for the Analysis of the Composition of Products of Thermal Decomposition of Cereal Grains (Oat, Barley)

The basic principles of high-resolution terahertz spectroscopy based on the effect of free damping polarization and a spectrometer in which this effect is realized in the mode of phase shift keying of radiation acting on a gas are considered. The presented approach is characterized by high selectivity and sensitivity, short measurement time, and safety. The possibility of using high-resolution terahertz spectroscopy in agricultural applications, such as component analysis of grain composition during its thermal decomposition based on the analysis of grain odor composition, is considered. Measurements of the subterahertz spectra of samples of oats and barley at their thermal decomposition were carried out, and the absorption lines of various organic substances were identified.