Method For Measurement Of Distribution Research Articles

Visualization of Aerial Droplet Distribution for Unmanned Aerial Spray Systems Based on Laser Imaging

Unmanned aerial spray systems (UASSs) are a commonly used spraying method for plant protection operations. However, their spraying parameters have complex effects on droplet distribution. The large-scale 3D droplet density distribution measurement method is insufficient, especially since the downwash wind is easily affected by the environment. Therefore, there is a need to develop a technique that can quickly visualize 3D droplet distribution. In this study, a laser imaging method was proposed to quickly scan moving droplets in the air, and a test method that can visualize 3D droplet distribution was constructed by using the traveling mode of the machine perpendicular to the scanning plane. The 3D droplet distribution of targeted and conventional UAVs was tested, and the methods for signal processing, noise reduction, and point cloud rebuilding for laser imaging were developed. Compared with the simulation results, laser imaging showed the pattern of droplet distribution from the two UAV structures well. The results showed that the laser imaging based method for detecting 3D droplet distribution is feasible, fast, and environmentally friendly.

Comparison of size distribution and electrical particle sensor measurement methods for particle lung deposited surface area (LDSAal) in ambient measurements with varying conditions

Abstract. It has become evident that additional metrics along the particle mass concentration, together with dense air quality monitoring networks within cities, are needed to understand the most efficient ways to tackle the health burden of particulate pollution. Particle lung-deposited surface area (LDSAal) is a metric to estimate particle exposure in the lung alveoli, and it has gained interest as a parameter for air quality monitoring as it is relatively easy and cost-efficient to measure with electrical particle sensors. Also, various studies have indicated its potential as a health-relevant metric. In addition to the electrical particle sensors, the LDSAal can be measured with various size distribution methods. However, different LDSAal measurement methods have fundamental differences in their operation principles, e.g., related to the measurement size ranges, size classification or conversion from the originally measured quantity into the LDSAal. It is not well understood how these differences affect the accuracy of the measurement in ambient conditions, where especially the particle effective density and hygroscopicity can considerably change the particle lung deposition efficiencies. In this study, the electrical particle sensor measurement (Partector) and two size distribution approaches (ELPI+ and DMPS/SMPS) were compared in road traffic environments with different environmental conditions in Helsinki and Prague. The results were compared by utilising the general assumptions of the LDSAal measurement (spherical hydrophobic particles with the standard density) and by evaluating the effects of the particle effective density and hygroscopicity. Additionally, the Partector and ELPI+ approaches were compared in various urban environments near road traffic, airports, river traffic and residential wood combustion. The results show that the comparison of different LDSAal measurement methods can be complicated in ambient measurements. The challenges were especially related to the accumulation mode particles roughly larger than 200–400 nm for which the dominant deposition mechanism in the lung changes from diffusion to impaction and the particle effective density and hygroscopicity tend to increase. On the other hand, the results suggest that the differences between the methods are reasonably low when considering only ultrafine and soot particles, which have an effective density closer to the standard (1.0 g cm−3) and are more hydrophobic, highlighting the suitability of the LDSAal as a monitored metric when estimating the spatial differences in the particulate pollution within cities.

WATERHYPERNET: a prototype network of automated in situ measurements of hyperspectral water reflectance for satellite validation and water quality monitoring

This paper describes a prototype network of automated in situ measurements of hyperspectral water reflectance suitable for satellite validation and water quality monitoring. Radiometric validation of satellite-derived water reflectance is essential to ensure that only reliable data, e.g., for estimating water quality parameters such as chlorophyll a concentration, reach end-users. Analysis of the differences between satellite and in situ water reflectance measurements, particularly unmasked outliers, can provide recommendations on where satellite data processing algorithms need to be improved. In a massively multi-mission context, including Newspace constellations, hyperspectral missions and missions with broad spectral bands not designed for “water colour”, the advantage of hyperspectral over multispectral in situ measurements is clear. Two hyperspectral measurement systems, PANTHYR (based on the mature TRIOS/RAMSES radiometer) and HYPSTAR® (a newly designed radiometer), have been integrated here in the WATERHYPERNET network with SI-traceable calibration and characterisation. The systems have common data acquisition protocol, data processing and quality control. The choice of validation site and viewing geometry and installation considerations are described in detail. Three demonstration cases are described: 1. PANTHYR data from two sites are used to validate Sentinel-2/MSI (A&B); 2. HYPSTAR® data at six sites are used to validate Sentinel-3/OLCI (A&B); 3. PANTHYR and HYPSTAR® data in Belgian North Sea waters are used to monitor phytoplankton parameters, including Phaeocystis globosa, over two 5 month periods. Conclusion are drawn regarding the quality of Sentinel-2/MSI and Sentinel-3/OLCI data, including indications where improvements could be made. For example, a positive bias (mean difference) is found for ACOLITE_DSF processing of Sentinel-2 in clear waters (Acqua Alta) and clues are provided on how to improve this processing. The utility of these in situ measurements, even without accompanying hyperspectral satellite data, is demonstrated for phytoplankton monitoring. The future evolution of the WATERHYPERNET network is outlined, including geographical expansion, improvements to hardware reliability and to the measurement method (including uncertainty estimation) and plans for daily distribution of near real-time data.

Damage evolution of coal with a strong bursting liability and 3D measurement method for elastic deformation energy distribution

When coal with a strong bursting liability is disturbed by a load, catastrophic instability disasters and rockbursts can easily occur. Loaded coal with a strong bursting liability undergoes complex damage evolution and failure behavior due to the intricate interplay among loads, gangue, fractures, and the coal matrix. Intuitively quantifying and characterizing the complex discontinuous structural features, deformation fields, and energy fields within coal is the foundation for the scientific analysis and prevention of disaster mechanisms caused by rockbursts. Therefore, studying the distribution and evolutionary processes of deformation fields and energy fields caused by the evolution of discontinuous structures within coal is highly important for the prevention and control of coal mine rockburst disasters and the protection of coal mine safety during mining operations. In this study, a series of X-ray computed tomography (X-CT) tests were conducted on coal specimens with varying gangue contents under uniaxial compressive loading. The X-CT images clearly illustrated the internal damage evolution of coal with a strong bursting liability, revealing fracture propagation, shear bands, and localized failure under varying loading conditions. Image segmentation was employed to quantitatively analyze the development of damage in coal with a strong bursting liability, revealing the influence patterns of gangue content on the prepeak deformation localization and strength of coal. Additionally, using digital volume correlation, the 3D volumetric displacement and strain of loaded impact-prone coal were determined based on the changes in natural speckle images. The nonuniform distribution of strain was mainly caused by the nonuniform distribution of gangue and pore fractures at the microscopic scale, which explains the localized deformation in coal materials. Importantly, this study provides new full-field strain tensor data and a novel method for measuring the elastic deformation energy of the 3D deformation and cracking processes of loaded coal.

Non-contact three-dimensional emissivity distribution measurement method of M8 LiDAR echo

Non-contact three-dimensional emissivity distribution measurement method of M8 LiDAR echo

Nondestructive dielectric measurement method for orientation distribution of liquid crystal polymers film

Liquid crystal polymers (LCP) are widely used materials in 5G applications. The LCP films easily tend to form an uneven orientation distribution that degrades their service properties. However, tailoring its orientation distribution remains a challenge, primarily because traditional measurement methods are unable to non-destructively measure the orientation distribution of large-area LCP films attributed to penetration depth constraints or sample preparation requirements. Capitalizing on its inherent orientation-induced dielectric anisotropy, we propose a nondestructive dielectric measurement method for the orientation distribution of LCP film using an interdigital electrodes array. Compared to polarized FTIR and WAXS/SAXS, the dielectric method provides a universally applicable solution, even in intricate scenarios like regions with wrinkles in LCP films, films with substantial thickness, and those lacking large-scale structures. Moreover, the accurate measurement of orientation distribution confirms that the large surface roughness and significant variations in thickness distribution are attributed to the uneven orientation distribution. The findings provide a “visual window” for precisely tailoring the orientation structure of LCP films for 5G applications and beyond.

A DIC-based Taylor impact test by measuring inertia force from acceleration distribution to obtain uniaxial stress–strain behavior of pure aluminum

The digital image correlation (DIC) technique is widely used to capture several kinematical quantities fields including displacement, velocity, strain, strain rate and acceleration in various kinds of the mechanical tests with the deformation of specimen. Considering the nature of nonuniform deformation in Taylor impact test, except the mentioned fields, the axial stress distribution is also required to evaluate the deformation behavior of materials. Recently, a measurement method for axial stress distribution is proposed based on an assumption of bilinear internal force distribution in specimen. However, the measured result only gives an approximate result. Besides, because the satisfaction of the assumption limits to several conditions, only the result obtained at a particular moment and position region is reliable. On the other hand, it is possible to calculate the axial stress distribution from the momentum balance law to avoid the mentioned assumption if the axial acceleration distribution is captured by the DIC technique. Unfortunately, the feasibility and accuracy for the method has not been discussed yet, even though some challenges on introducing DIC technique to Taylor impact test has already been done. Here, a method based on momentum balance law and axial acceleration distribution is newly proposed to obtain the axial stress distribution. The stress–strain curve in Taylor impact test is obtained by a simultaneously spatial combination between the stress and strain distributions. Then, the feasibility of the proposed method is discussed computationally and experimentally.

Dynamic Change of Forest Ecological Benefit of the Natural Forest Protection Project in the Upper Reaches of Yangtze River

The Natural Forest Protection Project (NFPP) is an ecological restoration project aimed at safeguarding natural forests, and is one of China’s six main forestry initiatives. The upper reaches of the Yangtze River represent the main distribution area of natural forests in China, and are an important area for the implementation of the NFPP. A systematic assessment of forest ecosystem changes in the upper Yangtze River region before and after implementation of the NFPP is of great scientific significance for the improvement of the project implementation effect, regional ecological protection, and further protection and restoration of natural forest resources. This study uses the NFPP area in the Yangtze River’s upper reaches as the study area; the data are primarily derived from the 1998 and 2020 forest resources category II survey data, long-term monitoring data from forest ecological stations, and public social data published by authoritative Chinese organizations. Based on the above data, we used the full index system of forest ecosystem services, continuous observation, and inventory system with the distributed measurement method to analyze the dynamic changes in forest ecosystem services in the study area in terms of three aspects: physical quality, value quality, and dominant function. The results of the study show that: (1) over the studied time scale, compared to the 1998 baseline, the physical quantities (soil erosion control, water regulation, and PM10 retention) and value of each service function of the forest ecosystem in the upper reaches of the Yangtze River project area in 2020 showed a significant increasing trend; (2) at the spatial scale, changes in forest ecosystem service functions in the upper reaches of Yangtze River under the NFPP showed significant spatial heterogeneity from 1998 to 2020; (3) in 2020, the total value of forest ecosystem services in the study area was 3,261,161,000,000 yuan/a, of which the functional value of biodiversity conservation was 1,294,426,000,000 yuan/a and the functional value of water conservation was 841,069,000,000 yuan/a, indicating that the forest ecosystem of the study area plays an important role as a “green gene pool” and “green water reservoir”; (4) the forest ecosystem service functions of the NFPP in the upper reaches of Yangtze River are intricately tied to forest resource features such as forest area, forest volume, age-group structure of arbor forest, etc., which influence the physical quantity and value of each forest ecosystem service function to varying degrees. In addition to illustrating the amazing efficiency of the natural forest preservation initiative, this study provides a scientific foundation for future natural forest resource conservation and restoration. It can serve as a reference for the project’s subsequent development as well to provide scientific foundations and guidance for the development of the natural forest protection and restoration program and to promote the protection and restoration of more natural forest resources.

Research on a measurement method for spatio-temporal distribution of fragments based on a high-speed camera network

To reliably measure multiple spatio-temporal distribution parameters of fragments in the blast field, a measurement method for spatio-temporal distribution of fragments based on a high-speed camera network is proposed. The method is based on the principle of binocular stereo vision measurement and consists of four steps: fragment image acquisition, target detection of multi-view images, fitting of motion trajectory, and calculation of the spatio-temporal distribution parameters. The test results demonstrate that the method can simultaneously measure multiple parameters in the intersecting field of view. Compared with the measurement results of the array target, the absolute value of the measurement relative error of velocity was less than 1.5%, and the measurement results of scatter angle and distribution density were consistent. It indicates that the measurement results of the proposed method are reliable, and the method is a feasible and effective measurement method for spatio-temporal distribution parameters of fragments in the explosion filed.

Visualization of Lidar-Based 3D Droplet Distribution Detection for Air-Assisted Spraying

Air-assisted spraying is a commonly used spraying method for orchard plant protection operations. However, its spraying parameters have complex effects on droplet distribution. The lack of large-scale 3D droplet density distribution measurement methods of equipment has limited the optimization of spraying parameters. Therefore, there is a need to develop a method that can quickly obtain 3D droplet distribution. In this study, a 2D LiDAR was used to quickly scan moving droplets in the air, and a test method that can obtain the visualization of 3D droplet distribution was constructed by using the traveling mode of the machine perpendicular to the scanning plane. The 3D droplet distribution at different positions of the nozzle installed in the air-assisted system was tested at different fan rotation speeds, and the methods for signal processing, point cloud noise reduction, and point cloud division for 2D LiDAR were developed. The results showed that the LiDAR-based method for detecting 3D droplet distribution is feasible, fast, and environmentally friendly.

Microscale mapping of thermal contact resistance using lock-in thermography

This paper proposes a new thermal contact resistance distribution measurement method using lock-in thermography. This method was used to evaluate a two-dimensional local thermal contact resistance distribution. To be able to measure the distribution, a uniform intensity laser heating system was developed. The developed system has a top-hat intensity distribution with a diameter of 30 mm. By combining this heat source and the lock-in thermography, a new measurement instrument was developed, which can evaluate local temperature behavior in the frequency domain, including the information of the contact interface in high spatial resolution of about 70 μm. Additionally, a new thermal contact resistance measurement principle was constructed based on a one-dimensional heat transfer equation that considers the reflected and transmitted temperature waves at the boundary and contact interface. The thermal contact resistance was acquired as a solution to the inverse problem of the temperature response done by fitting analyses. The validation of this method was performed quantitatively with two samples made of two bonded isotropic graphite plates. The one sample has an intentional defect area that has a slightly higher thermal resistance. The other sample has the known thermal contact resistance value measured with a validated method. Based on the results, the measurement value agreed with the referenced value. Also, the defect area was quantitatively detected clearly as a high thermal resistance region. Furthermore, as a practical example, the measurement method was applied for two different contact interface roughness samples consisting of aluminum alloys and thermal grease. Consequently, it was revealed and visualized that the contact interface with a rough surface has a high thermal resistance spot.

The Size Distribution Measurement and Shape Quality Evaluation Method of Manufactured Aggregate Material Based on Deep Learning

Abstract Manufactured aggregate is a substitute for natural aggregate particles that is formed by mechanically crushing parent rock. Its particle shape has a great impact on the working performance, mechanical performance, and durability for preparing high-performance concrete. Therefore, a particle shape quality evaluation method combining deep learning and distance transformation topology is proposed. In this method, the YOLO v4 network is used to locate the particle region, and the centroid point is recognized as the feature point of this region; then, the feature points are used for distance transformation topology to approximately divide the particles area. Based on the divided results, the pixel-level segmentation result is obtained using a local threshold algorithm. The 2–8-mm limestone manufactured aggregate in a 2 million ton (1,000 kg)/year manufactured aggregate production line is carried out to demonstrate the effectiveness of the proposed method, achieving above 90 % precision in the real manufactured aggregate quality evaluation.

Implementation of an Accurate Measurement Method for the Spatial Distribution of the Electromagnetic Field in a WPT System

In an inductive wireless power transfer (WPT) system, the transferred power depends on the coupling between the transmitter coil and the receiver coil and, consequently, on their spatial positioning with respect to each other. Since this positioning needs to be as flexible as possible, one can design various construction shapes for the coils, in terms of both winding geometry and core geometry. The system efficiency for different positionings and configurations can be assessed if the structure and distribution of the electromagnetic field (EMF) in the space close to the system are determined. In this context, this paper proposes an investigation method based on measuring the intensity of the electromagnetic field generated by the emitting coil in the WPT space in terms of both modulus and direction. The measurements needed to be performed at a sufficient number of points, so that the entire field was determined. The EMF value was estimated by linear spatial interpolation between the measured points. Moreover, this paper presents the method and the results of investigations carried out only in the presence of the emitting coil. Calibration or correction solutions were also proposed to obtain sufficient accuracy, and the viability of the method was therefore demonstrated.

Small scale magnetic field source detection using recessed atomic vapor cell

With the development of high spatial resolution spin image and magnetic field distribution measurement in atomic vapor cell, one can localize the position and calculate the magnetic moment of the field source around the cell. However, traditional cubic or spherical vapor cell can only measure the magnetic field distribution on one side of the field source, which limits the precision of the field inversion results. Here, we use a recessed atomic vapor cell to obtain field distribution around the source, which is positioned at the center of the cell. The magnetic field distributions around five sides of the field source are measured using movable stages and digital micro-mirror device. We combine the Levenberg–Marquardt algorithm with a genetic algorithm as the magnetic source localization algorithm to realize a quick global search as well as a precise local extreme point search. We obtain a spatial resolution of 219.2 × 387.0 × 451.5 μ m 3 and a magnetic field sensitivity of 0.06 nT / Hz 1 / 2 in a volume pixel of 0.0383 mm 3. The error in the localization of the magnetic source is 1.295 mm in the x direction, 185 μ m in the y direction, and 40 μ m in the z direction. The field distribution measurement method using recessed atomic vapor cell and related inversion algorithm demonstrated here have great potential applications in small scale field source detection of biology and materials science.

A Novel Measurement Method for Spin Polarization Three Axis Spatial Distribution in Spin-Exchange Relaxation Free Atomic Magnetometer

The measurement of atomic spin polarization distribution in spin-exchange relaxation free (SERF) magnetometer is an important topic for improving the sensitivity and consistency of multi-channel magnetic field measurement applications. A novel spin polarization spatial distribution measurement method is presented based on the transient response of the magnetometer after modulating the pumped light with a chopper. Polarization is obtained by a slow-down factor based on the fast spin-exchange interaction effects. Longitudinal and transverse polarization distributions are measured simultaneously without interrupting the operation of the SERF status. Under different oscillating magnetic fields, the spin polarization is measured at the cell centroid. Residual magnetic field inside the magnetometer is obtained from the linear relationship between the precession frequency and the oscillating magnetic field. The one-dimensional polarization distributions in the x, y, and z axes are measured using a digital micromirror device with a resolution of 0.25 cm. The measurement results conform to the Lambert-Bier absorption law and the Gaussian distribution law. Furthermore, 7 × 7 two-dimensional spatial distribution measurements of polarization on the xy and yz planes are performed. Nonuniformity of 1.04 in the xy plane and 1.82 in the yz plane in the built magnetometer. Compared with other measurement methods, the distribution measurement method proposed is independent of optical depth and suitable for low polarization and high polarization applications. Based on the results of the proposed measurement method of spin polarization spatial distribution, further compensation can improve the application consistency of multi-channel magnetic field measurements and improve the sensitivity of single-channel differential measurements.

Characterization of thermal neutron distribution of an Am–Be neutron source setup by CdZnTe detector

Owing to the developments in prompt gamma neutron activation analysis (PGNAA) and prompt gamma ray activation imaging (PGAI), it is necessary to develop an online thermal neutron distribution measurement method. The CdZnTe detector is considered as an alternative thermal neutron detector because of its high thermal neutron capture cross section. In this study, the thermal neutron field of an 241Am–Be neutron source was determined by CdZnTe detector. The intrinsic neutron detection efficiency of CdZnTe detector was calculated by using indium foil activation, and the value was 3.65%. Then the characteristics of neutron source were conducted with the calibrated CdZnTe detector. The thermal neutron fluxes in front of beam port were measured at several distances ranging from 0 cm up to 28 cm. Thermal neutron field at distances of 1 cm and 5 cm were also measured. The experimental data were then compared with Monte Carlo simulation. The results demonstrated that the simulated data agree well with experimental measurements.

Measurement of current distribution using infrared thermography.

Current distribution measurement methods are widely used in medical examinations, predicting faults in semiconductor devices and assessing structural integrity. Several methods for measuring current distribution are available, such as electrode arrays, coils, and magnetic sensors. However, these measurement methods are unable to obtain images of current distribution with high spatial resolution. Therefore, there is a need to develop a non-contact method to measure current distribution that is capable of capturing images with high spatial resolution. In this study, a non-contact current distribution measurement method based on infrared thermography is proposed. The method uses thermal variations to quantify the current amplitude and reconstructs the current direction based on the passivity of the electric field. For quantification of low frequency current amplitude, the experimental results show that the method can provide accurate current measurement results, for example, at the power frequency (50Hz), in the range of 1.05-3.45A, its relative error can be improved to ±3.66% when the calibration fitting method is used. For the high-frequency current, an effective estimate of the current amplitude is obtained using the first-order derivative of temperature variation. When applied to the eddy current detection (256 KHz), it achieves a high-resolution image of the current distribution, and the effectiveness of the method is verified through simulation experiments. The experimental results show that the proposed method not only measures the current amplitude accurately but also improves the spatial resolution in acquiring two-dimensional current distribution images.

Multiphase holdup measurement of oil-gas-water flow using new dual receiver fiber-optical probe array multiphase logging tool.

To solve the problem of multiphase holdup measurement, a new dual-receiver fiber-optical probe array multiphase logging tool (NDRFOPA_MLT) is designed and developed. This paper first constructed the mechanism model of an NDRFOP for phase holdup measurement by using the ray tracing method and theoretically analyzed the feasibility of NDRFOP to measure phase holdup; considering the shortcomings of NDRFOP local measurement, a NDRFOPA sensor for oil production three-phase flow is designed and developed. At the same time, the volume of fluid model was used to simulate the distribution characteristics of the medium in the NDRFOPA_MLT measurement pipeline under the working conditions of oil-gas-water flow with a total flow rate range of 0.42-1.25m3/h, water holdup range of 50%-80%, oil holdup range of 10%-30%, and gas holdup range of 10%-40%. In addition, the NDRFOPA_MLT measurement models for different multiphase flow conditions were established by the ZEMAX ray tracing method, and the sensitivity distribution, response characteristics, and phase holdup measurement methods were studied to obtain the phase holdup measurement results under multiphase flow conditions. Finally, a multiphase flow experimental platform with a measurement pipe diameter of 20mm and a measurement pipe length of 300mm was established, and experiments were conducted under multiphase flow conditions, such as a gas flow rate range of 0.04-0.16m3/h, oil flow rate range of 0.64-1.70m3/h, and water flow rate range of 0.53-2.58m3/h. The experimental results showed that phase holdup measurement error was mainly kept within 10%.

Analysis of uncertainties in the measurement of the space charge distribution in dielectrics

The results obtained from the commonly used space charge distribution measurement methods are frequently apparent and one-dimensional results of a localized area; moreover, random errors can be caused by various factors. In this work, three factors—sample thickness uniformity, pressure wave intensity uniformity, and space charge distribution uniformity—that may cause measurement uncertainties are examined. The analysis and evaluation of the experimental data are affected by the measurement uncertainties, which are particularly noticeable in experiments on semiconductive electrode-flat polyethylene samples that use the laser-induced pressure propagation method. These factors are investigated separately using several auxiliary experiments, including laser beam spot energy distribution measurements and space charge distribution measurements, at different measurement positions on the same uniform sample. A clear and intelligible model is developed to discuss the influence of these factors on the uncertainties in the space charge distribution measurement in dielectrics.

PEA–Kerr Combined Measurement Method for Space Charge and Electric Field Distribution of Oil–Paper Composite Insulation

The distribution of space charge and electric field of oil–paper composite insulation is of great importance to the operation and design of converter transformers. However, the widely used pulsed electric-acoustic (PEA) method and Kerr method are difficult to measure the structure of thick pressboard + oil independently. In this article, a PEA–Kerr combined measurement method is proposed. It can not only compensate for each other’s shortcomings but also correct the effects of ultrasonic attenuation on space charge measurement by combining the two measurement signals. By integrating and optimizing the system structure and signal processing methods of PEA and Kerr measurement, the PEA–Kerr combined measurement system is built. The test results show that the system has good linearity, the spatial resolution of the electroacoustic measurement part is 8.8%, and the maximum error of the electrooptic measurement part is 2.5%. Finally, the system is used to measure the structure of 2-mm pressboard + 3-mm oil gap. The relationship between the distribution of space charge and the interface charge density under different voltage amplitudes and polarities is analyzed, and the influence of electric field distortion caused by space charge on the interface charge measurement of oil–paper composite insulation is revealed. This article can provide a basis for measuring and analyzing the distribution of space charge and electric field on thick and complex structures.