High Measurement Accuracy Research Articles

Online continuous measurement of arterial pulse pressure and pressure waveform using ultrasound

Noninvasive measurement of local pulse pressure (PP) and blood pressure waveforms, especially in central arteries, is crucial for diagnosing and preventing cardiovascular diseases (CVDs). This work presents an ultrasound system that uses a low-computational method to evaluate local pulse wave velocity (PWV) and diameter waveforms online, enabling continuous and noninvasive measurement of PP and blood pressure waveforms without calibration. The system was validated both in vitro and in vivo, demonstrating high accuracy in PP and blood pressure waveform measurements in cardiovascular phantom experiments. In human carotid experiments, the system was compared to an arterial tonometer, showing excellent accuracy in PP and pressure waveform similarity. Comparative experiments with the volume clamp device further demonstrated the system's ability to accurately trace blood pressure changes induced by deep breathing. Thus, the developed system holds promise for noninvasively measuring arterial PP and blood pressure waveforms continuously, facilitating the diagnosis and prevention of CVDs.

Are camera, projector, and camera-projector calibrations different?

Structured light projection systems have become a referent in three-dimensional optical metrology. Calibration of the cameras and projectors of these systems is one of the most critical procedures to achieve high-accuracy measurements. However, the calibration process requires some clarifications for adequate experimental implementation. For instance, it is typically assumed that the calibration of a camera-projector pair differs from calibrating a camera, and the calibration of a projector is possible only with an attached auxiliary camera. This paper presents a unified methodology for camera, projector, and camera-projector calibrations. Experimental results are discussed, providing practical insights into how structured light systems are calibrated. The MATLAB code and data employed in this study are available.

Broadband microwave photonic channelizer with high optical spectrum efficiency based on odd- and even-order local optical frequency combs

Microwave photonic channelizers assisted by coherent dual optical frequency combs (OFCs) have been widely considered for wideband radio frequency (RF) spectrum analysis. However, it requires dual OFCs with a large free spectral range (FSR) and multiple comb lines to support a wide RF coverage, leading to a complicated system structure and low optical spectrum efficiency. To this end, we propose a simplified, high optical spectrum-efficiency microwave photonic channelizer, wherein the odd-order and even-order OFCs with a double frequency spacing are generated and isolated to directly slice two frequency-shifted modulated optical spectra into a series of subbands. N comb lines can support 4 × N channels but take up a significantly reduced optical spectrum range. Partial experiments and simulations are presented to demonstrate the scheme. By exploiting a four-lines odd-order OFC and three-lines even OFC, a wideband RF spectrum range of 0–56 GHz is divided into 28 channels with a channel bandwidth of 2 GHz, and various wideband signals are spectrally analyzed with a high measurement accuracy and large image rejection suppression higher than 30 dB. Moreover, a 16-quadrature amplitude modulation (16QAM) vector signal with a center frequency of 7 GHz and a bit rate of 1 Gbps is channelized and successfully recovered with a good constellation diagram.

Characterisation of a Coriolis flow meter for fuel consumption measurements in realistic drive cycle tests

When testing light-duty and heavy-duty vehicles on chassis dynamometers, as in the WLTP, or engines on engine test benches, as in the WHDC, it is required to measure the fuel consumption. In the preferable case, the measurement of the fuel consumption is carried out with suitable flow meters. These require high measurement accuracy in a wide flow range, independent of the fuel type, as the flow rate range is often very large and depends on the power range of the vehicle engines. Moreover, the fuel flow rate in the test cycles is very dynamically related to the loads. In the scope of the ongoing EMPIR Joint Research Project 20IND13 SAFEST the dynamic flow behaviour as well as the measurement accuracy of flow meters for different types of fuels are investigated. This paper presents first results from the realisation of dynamic flow profiles, and flow measurements with a Coriolis Flow Meter with different representative fuels in a wide density and viscosity range and a wide flow rate range at different fuel temperatures.

High-performance phase measuring profilometry architecture based on Zynq SoC.

This paper presents a novel high-performance heterogeneous computation architecture, to the best of our knowledge, for stereo structure light using the phase measuring profilometry (PMP) algorithm based on a Zynq UltraScale+ system on chip (SoC). The proposed architecture aims to achieve real-time and high-accuracy 3D shape measurement. The experiment results indicate that the calculation time of a standard four-step PMP algorithm with a resolution of 1280×1024 is 14.11ms. It is nearly 51 times faster than the well-optimized software implementation running on a Raspberry Pi and nearly three times faster than a high-end PC, with 15 times less power consumption. Consequently, the proposed architecture is deemed suitable for real-time 3D measurements in embedded applications.

Measurement of transparent liquid concentration based on ultrasonic grating method

In this experiment, ultrasonic grating method is used to measure the concentration of transparent liquid. The principle is that the liquid forms standing waves, namely ultrasonic grating, by using a signal generator. The monochromatic parallel light diffracted after entering the ultrasonic grating, and the sound velocity could be obtained by the spacing of diffraction fringes. The experimental equipment includes three parts: light source system, ultrasonic generation system and digital observation system. The experimental test shows that the experimental device can be used to measure the concentration of sugar water, salt water and other transparent liquid, with simple operation and high measurement accuracy.

Tackling range uncertainty in proton therapy: Development and evaluation of a new multi-slit prompt-gamma camera (MSPGC) system

In theory, the sharp dose falloff at the distal end of a proton beam allows for high conformal dose to the target. However, conformity has not been fully achieved in practice, primarily due to beam range uncertainty, which is approximately 4% and varies slightly across institutions. To address this issue, we developed a new range verification system prototype: a multi-slit prompt-gamma camera (MSPGC). This system features high prompt-gamma detection sensitivity, an advanced range estimation algorithm, and a precise camera positioning system. We evaluated the range measurement precision of the prototype for single spot beams with varying energies, proton quantities, and positions, as well as for spot-scanning proton beams in a simulated SSPT treatment using a phantom. Our results demonstrated high accuracy (<0.4 mm) in range measurement for the tested beam energies and positions. Measurement precision increased significantly with the number of protons, achieving 1% precision with 5 × 108 protons. For spot-scanning proton beams, the prototype ensured more than 5 × 108 protons per spot with a 7 mm or larger spot aggregation, achieving 1% range measurement precision. Based on these findings, we anticipate that the clinical application of the new prototype will reduce range uncertainty (currently approximately 4%) to 1% or less.

Theoretical and experimental investigation of the molecular depolarization ratio for broadband polarization lidar techniques.

The molecular depolarization ratio (MDR) is of great significance for polarization lidar techniques in terms of validating the measurement accuracy, etc. However, previous studies mainly focused on cases with narrowband laser linewidths, and the transmittance of the Cabannes line in the receiver has been assumed constant. In this work, the narrowband theoretical model of MDR has been re-examined by taking the transmittance of the Cabannes line into account. A large relative deviation of beyond 200% has been found if the wavelength-shift reaches up to 0.5 nm for a receiving bandwidth of 0.5 nm at 532 nm, which is much larger than the case without considering the transmittance of the Cabannes line, i.e., only 15%, reported in previous studies. Besides, a broadband theoretical model has been proposed to evaluate the MDR for polarization lidar using high-power multimode laser diodes as light sources. Simulation studies have revealed that the MDR is highly related to the laser linewidth, the receiving bandwidth, as well as the wavelength-shift between the laser wavelength and the center wavelength of the receiver. The MDR at 520 nm calculated by the broadband theoretical model is about 21% larger than the value evaluated without considering the laser linewidth, when the receiving bandwidth is equivalent to the laser linewidth (e.g., 2 nm). Validation measurements, employing a 520-nm imaging-based polarization lidar with a 3.4-nm laser linewidth and a 10-nm receiving bandwidth, illustrated that the volume depolarization ratio in a clean atmospheric region (0.129±0.0025) was highly consistent with the theoretical MDR (0.132). The good agreement between theoretical and experimental results demonstrated a high measurement accuracy of the imaging-based polarization lidar and excellent feasibility of the broadband theoretical model.

Surface structured light sensor with simultaneous color mapping

To obtain geometric information and color texture simultaneously, a surface structured light sensor consisting of a monochrome camera, a color camera, and a projector is proposed. The sensor uses a color camera to acquire surface color information while using it as a geometric measurement unit and matching with the monochrome camera to obtain geometric information. Due to the Bayer array and demosaicing algorithm of the color camera, pixel RGB components are always coupled with interference from other channels. However, existing color de-crosstalk in reconstruction is merely applied to the decoupling of color composite patterns, ignoring the intensity errors present in color fringe patterns under monochrome illumination. In our sensor, de-crosstalk of monochromatic patterns is considered to guarantee the reconstruction accuracy. The high-accuracy measurement of the sensor is validated by reconstructing standard steps, yielding a mean absolute error of 0.008 mm for distance measurements. In addition, the reconstruction experiment of a terracotta warrior verifies that the proposed sensor has potential application in the digital preservation of cultural relics.

A method to produce low lead blank silicon dioxide gel as an emitter for isotopic analysis of sub-nanogram lead sample

Lead (Pb) isotopes have been widely used in isotopic dating and geochemical tracing. The rapid development in Earth sciences requires high precision and accuracy of isotopic measurements of low Pb contents or small amounts of samples. However, low ionization efficiency can significantly affect the sensitivity and precision of the measurement. Emitters, such as silicon dioxide (SiO2) gel used in the thermal ionization mass spectrometer (TIMS) measurement of Pb isotopes, can reduce Pb loss at the low-temperature stage and improve Pb ionization efficiency at the high-temperature stage, but they inevitably introduce Pb blank and affect the quality of the results. Therefore, the emitters should possess the features of both high ionization efficiency and low Pb blank. In the present study, a SiO2 gel solution was produced via a double-bottle method and then purified by the Sr-spec® resin. We further measured Pb blank value of this emitter using the isotopic dilution method and examined its ionization efficiency via measuring isotopic composition of standard reference materials of Pb solution and rock powders using different amounts of Pb. Analytical data show that Pb blank values of the twice-purified SiO2 gel solution are lower than 1 pg/μL (lowest value of ∼0.3 pg/μL). Moreover, it can effectively improve Pb ionization, and maintain high and stable ion signal intensity during the measurement runs. Analytical results of Pb isotopic compositions, obtained from nano- to subnano-gram Pb amounts of reference materials, all fall in the ranges of their reference values, meeting the requirements in precision and accuracy for the measurements on micro-samples. This emitter is useful for Pb isotopic measurement of micro-samples and predictable to promote the application of Pb isotopic geochemistry.

High-velocity measurement method in dual-frequency laser interference tracker based on beam expander and acousto-optic modulator.

The laser tracker, as a new large-scale measuring instrument of combining conventional measurement technology and modern control technology, has the advantages of intelligence, portability, large measurement space, high measurement accuracy and short detection period. However, the laser tracker has strict requirements on the moving speed of the spherically mounted retroreflector. This deficiency not only limits the application of the measuring instrument in the field of high-velocity measurement, but also greatly reduces the measurement efficiency. In this work, we analyze the factors that affect the tracking velocity of the laser tracker, and propose for the first time to use the beam expander device to improve the transverse tracking measurement velocity of the instrument. The experimental results show that the laser tracker miss distance can reach 2.25 mm. The transverse tracking velocity and acceleration can reach 4.34 m/s and 2.4 g, respectively. Additionally, the acousto-optic modulator is used to increase the frequency difference between the reference beam and the measuring beam, so that the value is greater than 19 MHz. The radial tracking measurement velocity can reach 6.2 m/s. The high-velocity laser interference tracker developed by this new method can be used in the field of large-scale space precision measurement such as nuclear power, medical treatment and rail transit.

A Similarity Model of Specific Heat Loss Determined by Dimensional Analysis

This article describes an innovative method for the determination of heat flow (specific heat loss; linear heat flow density) from a one-metre length of a twin pipe directly-buried heat network. Such heat losses are currently described by applying analytical procedures based on the heat transfer theory. It is rather complicated to accurately express the heat loss using such procedures, due to the necessity to determine the individual values of thermal resistance. A simpler method to express heat loss is the balance method, as it requires measuring a temperature gradient Δt between the starting point of the heat network and the end point of the heat collection. A suitable measuring device must provide high-accuracy measurements of the temperature. In the case of very well-insulated distribution pipelines and short pipes, the temperature measurements must be accurate to the hundredths of a degree Celsius. It is impossible to install such devices as fixed equipment on every heat distribution network, due to such networks measuring many kilometres and the cost of the appropriate measuring technology. For the aforesaid reasons, the authors created a mathematical model for specific heat losses based on dimensional analysis. This method facilitates the identification of dimensionless criteria based on the relevant dimensional quantities. Functional correlations between the identified criteria may be identified on the basis of the results of physical or numerical experiments. In this study, a database of the results obtained from physical experiments conducted on two heat networks was used. The output of the similarity model was a function describing the heat flow from a one-meter pipe length that was applicable to various alternatives in relation to the geometrical, physical and boundary conditions. The standard deviation of a difference in the heat losses identified by applying the balance method and using the proposed criterial equation for a twin pipe directly-buried pre-insulated heat network was 0.515 W·m−1.

Three-component strain gauge for precise measurement of load fluctuations

The aim was to assess the loading of large-size elements of machine structures using versatile strain gauges. A strain gauge was developed using a system analysis of failures and deficiencies in the manufacture and operation of large-scale structures, strain gauging, strength of materials methods, as well as the theory of elasticity of ring elastic elements. The ANSIS software package was used to calculate rational sensor parameters. The conducted study of ring elastic deformation (determination of stiffness and stress-strain state) allowed the authors to propose that the ring shape should be replaced by an octahedral polygon. This form is suitable for mounting strain gauges for simultaneous measurement of tension and compression, as well as bending and torsion, i.e., forces arising in a machine structural element or in the manufacture of large-size surfaces. The obtained results were used to derive dependences to determine the measurement error of the gauge under study. A comparative analysis of ring and octahedral gauges identified unique features of the latter, consisting in the possibility of assessing the measured values along the three coordinate axes with a high degree of accuracy. The conducted research shows that the proposed strain gauges are capable of registering the magnitude and fluctuations of loads with a high measurement accuracy. The proposed scheme of gauge placement makes it possible to determine the vertical and horizontal components of the forces arising in a structural element and to assess deviations in the process of measurement. In addition, the proposed measuring scheme minimizes the error of mutual influence of sensors. The developed force meter is a versatile device that can be used for registering static and dynamic impacts, as well as for digital control of force parameters in the range of up to 5 mm.

DRFM Repeater Jamming Suppression Method Based on Joint Range-Angle Sparse Recovery and Beamforming for Distributed Array Radar

Distributed array radar achieves high angular resolution and measurement accuracy, which could provide a solution to suppress digital radio frequency memory (DRFM) repeater jamming. However, owing to the large aperture of a distributed radar, the far-field plane wave assumption is no longer satisfied. Consequently, traditional adaptive beamforming methods cannot work effectively due to mismatched steering vectors. To address this issue, a DRFM repeater jamming suppression method based on joint range-angle sparse recovery and beamforming for distributed array radar is proposed in this paper. First, the steering vectors of the distributed array are reconstructed according to the spherical wave model under near-field conditions. Then, a joint range-angle sparse dictionary is generated using reconstructed steering vectors, and the range-angle position of jamming is estimated using the weighted L1-norm singular value decomposition (W-L1-SVD) algorithm. Finally, beamforming with joint range-angle nulling is implemented based on the linear constrained minimum variance (LCMV) algorithm for jamming suppression. The performance and effectiveness of proposed method is validated by simulations and experiments on an actual ground-based distributed array radar system.

Extensive evaluation of DNA methylation of functional elements in the murine Fkbp5 locus using high-accuracy DNA methylation measurement via targeted bisulfite sequencing.

FKBP5 is an important stress-regulatory gene implicated in stress-related psychiatric diseases. Single nucleotide polymorphisms of the FKBP5 gene were shown to interact with early life stress to alter the glucocorticoid-related stress response and moderate disease risk. Demethylation of cytosine-phosphate-guanine-dinucleotides (CpGs) in regulatory glucocorticoid-responsive elements was suggested to be the mediating epigenetic mechanism for long-term stress effects, but studies on Fkbp5 DNA methylation (DNAm) in rodents are so far limited. We evaluated the applicability of high-accuracy DNA methylation measurement via targeted bisulfite sequencing (HAM-TBS), a next-generation sequencing-based technology, to allow a more in-depth characterisation of the DNA methylation of the murine Fkbp5 locus in three different tissues (blood, frontal cortex and hippocampus). In this study, we not only increased the number of evaluated sites in previously described regulatory regions (in introns 1 and 5), but also extended the evaluation to novel, possibly relevant regulatory regions of the gene (in intron 8, the transcriptional start site, the proximal enhancer and CTCF-binding sites within the 5'UTR). We here describe the assessment of HAM-TBS assays for a panel of 157 CpGs with possible functional relevance in the murine Fkbp5 gene. DNAm profiles were tissue-specific, with lesser differences between the two brain regions than between the brain and blood. Moreover, we identified DNAm changes in the Fkbp5 locus after early life stress exposure in the frontal cortex and blood. Our findings indicate that HAM-TBS is a valuable tool for broader exploration of the DNAm of the murine Fkbp5 locus and its involvement in the stress response.

Accurate Nonlinearity and Temperature Compensation Method for Piezoresistive Pressure Sensors Based on Data Generation.

Piezoresistive pressure sensors exhibit inherent nonlinearity and sensitivity to ambient temperature, requiring multidimensional compensation to achieve accurate measurements. However, recent studies on software compensation mainly focused on developing advanced and intricate algorithms while neglecting the importance of calibration data and the limitation of computing resources. This paper aims to present a novel compensation method which generates more data by learning the calibration process of pressure sensors and uses a larger dataset instead of more complex models to improve the compensation effect. This method is performed by the proposed aquila optimizer optimized mixed polynomial kernel extreme learning machine (AO-MPKELM) algorithm. We conducted a detailed calibration experiment to assess the quality of the generated data and evaluate the performance of the proposed method through ablation analysis. The results demonstrate a high level of consistency between the generated and real data, with a maximum voltage deviation of only 0.71 millivolts. When using a bilinear interpolation algorithm for compensation, extra generated data can help reduce measurement errors by 78.95%, ultimately achieving 0.03% full-scale (FS) accuracy. These findings prove the proposed method is valid for high-accuracy measurements and has superior engineering applicability.

High-speed 360° 3D shape measurement based on virtual stereo phase unwrapping method

360° three-dimensional (3D) shape measurement is of great significance in the fields of defect detection and reverse modeling. Fringe projection profilometry (FPP) is widely used due to the advantages of high-accuracy and full-field measurement, but the movement of object corrupts the phase measurement. Stereo phase unwrapping (SPU) technique is adopted to improve imaging efficiency, but requires multi-cameras which resulting in high system complexity and cost. In this work, we proposed virtual stereo phase unwrapping (VSPU) method for high-speed 360° 3D shape measurement. This method uses the virtual camera-projector systems formed by the rotation of object for phase unwrapping which only requires single camera-projector to achieve 360° 3D shape measurement. The phase consistency checking in SPU method is modified. Experiments demonstrate that proposed method has strong robustness and can achieve 360° 3D shape measurement in 47 s with an accuracy of 100 μm during continuous rotation of the object.

A DIC method for thermal micro-deformation measurement of satellite high stability composite structure in simulated space environment

In order to ensure the stability and reliability of the entire satellite and onboard equipment indicators, the satellite highly stable structure can only produce small deformation or “near zero deformation” under the space on-orbit (thermal/vacuum) environment. The effective measurement and verification of its dimensional stability indicators directly determine the success or failure of the development of highly stable satellites. This work proposes a method for measuring the thermal deformation of highly stable satellite structures based on digital image correlation, (DIC), which designs a combined methodology of the digital image correlation measurement scheme, a measurement instrument protection method, a highly uniform temperature measurement and control system in the simulated space on-orbit thermal/vacuum environment. The methodology proposed in the work makes the digital image correlation measurement system suitable for space on-orbit measurement, and verifies that the measurement system can maintain high measurement accuracy. The research results indicate that this method can effectively solve the problems of measurement field interference, high uniform temperature control, speckle measurement camera, and measurement baseline protection. The thermal stability measurement experiment of a highly stable structure of a certain satellite has been successfully completed, and it has been verified that this method can meet the effectiveness and measurement accuracy of simulating thermal deformation measurement of structures in the simulated space on-orbit thermal environment.

An MLS-based high-accuracy measurement and automatic analysis method for roadway deformation

The 3D laser scanning has increasingly been applied in the field of monitoring roadway deformation. Different from a terrestrial laser scanner (TLS), a mobile laser scanner (MLS) is more flexible in on-site operations, but its scanning range accuracy is only precise to the centimeter level. still remains in centimeters. In addition, extracting deformation information from point cloud data of roadway is a complex process. In order to improve the accuracy of deformation monitoring and the efficiency of point cloud processing, with the aid of the identification plate for measurement (IPM) and the statistical analysis methods, an MLS-based high-accuracy measurement and automatic analysis method of roadway deformation is proposed. In this approach, the center point of the identification plate for measurement (IPM-CP) is taken as the control point for deformation monitoring (CPDM). The IPMs in the point cloud are positioned based on the locations of the seed points. The K-radius search algorithm and the density-based spatial clustering of applications with noise (DBSCAN) algorithm are introduced to extract and segment the point cloud of the target area (PCTA). The calculation methods for the key parameters of the algorithms are developed. The judgement index for identifying the IPM point cloud and the methods for target point extraction are presented. The convergence features of the surrounding rocks is analyzed by comparing the lengths of measuring lines of monitoring sections at different stages. The method was applied and validated in the Sanshandao Gold Mine for roadway deformation monitoring. The results show that this method is able to automatically obtain a highly precise data on roadway deformation.

Comparison of the Number of Particle History for Monte Carlo Codes in Gamma-Ray Spectroscopy

Monte Carlo is a numerical computation algorithm that is widely used in many fields of science and is used to obtain numerical results with a large number of repeated random samplings. Radiation transport with Monte Carlo simulation continues to increase its popularity in the fields of radiation measurement. The high accuracy and precision measurement of radionuclide activity amounts in gamma-ray spectrometry depends on the efficiency calibration of the detector. Efficiency calibration is carried out in two ways, using certified reference materials, by experimental method or Monte Carlo simulation method. The experimental method is expensive, procedurally complex and time-consuming due to the supply of reference material. The use of the Monte Carlo technique in a reliable way without the need for a standard radioactive source in determining the detector efficiency is becoming common. The most critical step for accurate and precise results in getting the response of a detector with the Monte Carlo method is modeling the detector with its realistic dimensions. Another parameter as important as detector modeling is the number of histories in the simulation code examined in this study. The effect of the number of histories on efficiency was examined in detail using PHITS, GESPECOR and DETEFF Monte Carlo simulation codes. Since there is no definite number about this effect, which is important for obtaining meaningful and realistic results, the change in the efficiency value was examined by increasing the number of stories from 105 to 108. The results obtained in this work showed that at least 107 particle numbers should be used in all three programs where the uncertainty is below 1%. If the existing facilities are sufficient, it can be increased to 108s in case of having a more equipped and fast computer. However, going higher than this value does not make any sense as seen from the study.