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Abstract:
Global warming has intensified and carbon emissions have become one of the key factors. Carbon dioxide is considered to be the main greenhouse gas(GHGs). The high-precision monitoring technology is assumed to be the basis for GHGs tracking. Carbon dioxide isotope components are monitored, which not only realized high-precision concentration monitoring, but also distinguished the contribution of different emission sources, and achieved the tracking and traceability of anthropogenic and natural emissions. High-precision carbon dioxide isotope monitoring technology is of great significance for improving the accuracy of carbon emission inventories and optimizing carbon emission reduction measures. However, in nature, carbon isotope gas concentrations are on the order of 10−6 of atmospheric concentrations and have been subject to measurement conditions, which has led to increased difficulty in carbon isotope measurements. The research progress of the infrared absorption technique for measuring carbon dioxide stable isotope concentration is reviewed, the principle and research progress of the high-sensitivity frequency-stabilized optical cavity decay spectroscopy technique are analyzed, and the future direction of the stable isotope spectroscopy research is envisioned. Cavity Ring-Down spectroscopy has become an emerging optical detection technology that has overcome the shortcomings of traditional methods such as insufficient measurement accuracy and low sensitivity, while a new generation of standardized methods for GHGs and isotope abundance measurement will has been established.
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To evaluate the uncertainty of determination of the gross alpha radioactivity and the gross beta radioactivity in drinking water by thick source method. According to GB/T 5750.13-2023 "Standard Examination Methods for Drinking Water Part 13 Radioactivity Index", the gross alpha radioactivity and beta radioactivity in drinking water are measured. The measurement repeatability was regarded as type A uncertainty, and the factors introduced by the residue mass, water sample volume, instrument detection efficiency, recovery rate, etc. were regarded as type B uncertainty. The measured gross alpha and beta radioactivity concentrations were 0.66 Bq/L and 0.48 Bq/L, the relative combined uncertainties were 6.0% and 5.7%, and the expanded uncertainties were 0.08 Bq/L and 0.06 Bq/L. Uncertainty introduced by the instrument count rate (n) is the main source of uncertainty and has the greatest influence. The measurement repeatability, the counting efficiency (ε) of standard powder source and radioactivity recovery rate (F) have greater influence. The influences of total mass of the water sample residue (W), mass of the water residue weighed to prepare the sample source (m) , and the volume (V) of the water sample are less and negligible.
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A method based on microscopic imaging flow cytometry was established to measure the concentration of milk somatic cells in the standard substance for milk somatic cell count. This method labels milk somatic cells using the fluorescent dye Ethium Bromide, and the single cell multi parameter microscopic images provided by flow cytometry can effectively assist in identifying target cells in flow cytometry analysis, thereby providing the correctness and repeatability of the gate strategy. Through multiple measurements and analysis of milk somatic cell standard substance samples with different concentrations of somatic cells, it has been proven that this method has good indoor and daytime repeatability. A mathematical model for measuring the concentration of milk somatic cells in a standard substance for milk somatic cell count based on microscopic imaging flow cytometry technology was established. The analysis determined that the uncertainty of this measurement method mainly comes from measurement repeatability, sample pretreatment, reagent addition, gate operation, and measurement volume. Comprehensive evaluation, targeting the candidate V-grade (~1.0×106/mL) of the standard substance for milk somatic cell count prepared in the study, the relative uncertainty of the measurement method for milk somatic cell concentration based on microscopic imaging flow cytometry is 4.84%.
Abstract:
As one of the key components of heavy-duty electric locomotives, the bogie is closely related to the operational and safety performance of heavy-duty electric locomotives. In the design and manufacturing process of bogies, there are problems such as ineffective traceability and insufficient detection methods in large-scale specialized testing devices such as bogie rolling vibration test benches. Moreover, during the testing process, the measurement results are inevitably affected by load effects, mechanical wave interference, locomotive vibration, wheel hub distortion, and other factors; The existing traceability methods for bogie values adopt offline calibration, ignoring the influence of factors such as actual installation position, electromagnetic interference, and environmental disturbance, making calibration data difficult to apply. The author analyzed the basic structure and working principle of the rolling vibration test bench for heavy-duty electric locomotive bogies, and summarized a series of technical indicators that can comprehensively and objectively reflect the measurement characteristics of the test bench. The calibration items and specific testing methods of the test bench were clarified, and the most critical performance indicator torque of the test bench was selected for measurement uncertainty analysis. Finally, three test benches developed by CRRC Zhuzhou Machinery Co., Ltd. were selected for experimental verification, proving that the calibration method of the discussed test benches is scientific and reasonable.
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To guarantee the accuracy of the measurement of the low-frequency shaker’s performance parameters and to reduce the cost and complexity, the Machine vision-based method used for determining the parameters of the low-frequency shaker is proposed. Firstly, the guide rail is equivalent to a large radius arc, the displacement change of the feature marker in the vertical direction is analyzed, and the bending condition is fitted by the least squares method to realize the measurement of the bending degree of the guide rail. Then, the subpixel-level edge extraction method in the region of interest of the motion sequence image is used to accurately measure the motion displacement of the shaking table. Finally, the sine approximation method is used to fit the motion displacement of the shaker to obtain its fitting amplitude, and then the key performance parameters of the shaker are solved. In addition, high-precision measurement of these parameters can be achieved with just a simple set of visual measuring devices. Experimental results show that the bending degree obtained by the machine vision method is highly similar to that of the traditional method when three different loads are added. For the measurement of other performance parameters, the machine vision method can also obtain reliable measurement accuracy and efficiency in the range of 0.01-10 Hz.
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This article studies the calibration method of ultrasonic chordal phantom, designed and developed a ultrasonic chord phantom calibration device based on intelligent technology. This device can collect the rotational speeds of the ultrasonic capstan and driven wheels of the chordal phantom through a dual channel laser velocimeter and input them into the analysis system for analysis and calculation, in order to calculate the chordal speed of the chordal phantom. And it can collect the line speeds of each point within the physiological waveform cycle and compare them with the standard physiological waveform line speeds in the database, in order to determine whether the physiological waveform curve at the setting speed meets the requirements. The experimental results indicate that compared to the existing detection methods for constant blood flow velocity, this method and device can not only conveniently and efficiently detect constant blood flow velocity, but also detect physiological waveforms intelligently, they solved the calibration and traceability problem of ultrasonic chordal phantom effectively.
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Drones are widely used in monitoring and forecasting of land and marine climate, monitoring and treatment of forest pests and fires, monitoring and control of agricultural pests, monitoring and warning of geological disasters, exploration and positioning of geological and mineral storage, search and rescue of personnel loss, monitoring and warning of national defense security, and intelligent cluster performances. The stability, reliability, and safety of drones are essential for providing prediction, early warning, treatment, exploration, and outcome assurance. With the booming development of the drone industry, the performance of drones varies, and it is necessary to implement testing of drone performance. This article combines current domestic and foreign drone related standards to sort out and analyze key factors that affect drone flight stability, reliable data transmission, precise navigation and positioning, and adaptability to climate and electrical environments. It studies detection methods and provides performance testing basis for drones to safely and reliably complete command targets under different environmental conditions.
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Specific Absorption Rate (SAR), as a mandatory parameter for the personal safety of electromagnetic radiation involving wireless communication products, has new requirements for the validation of the measurement system as its measurement method and measurement system need to be updated due to the change of the device under test. Based on the in-depth understanding of the validation methods in the current standard, the validation methods of the three traditional validation steps, namely, Extrapolation routine verification, Probe linearity verification and others, are measured and analyzed through electromagnetic simulation and experimental measurements, and the validation methods are extended by combining with the new requirements of the new test. The measured results show the feasibility and stability of the extended verification method. Since the reference values are obtained by the self-developed method, the validation method can be extended and the validation configurations, such as the validation points, can be customized according to the needs. This provides technical support for the study of the validation method for new and domestic SAR measurement systems.
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In order to explore the effectiveness of anti-Compton technology in γ spectrum measurement applications, an anti-Compton measurement study of uranium ore was conducted in the laboratory using the CSS-D-60 type anti-Compton γ spectrometer system. Specific measurements were taken for mixed uranium-thorium, uranium-radium equilibrium, and single thorium powder samples. The proportion distribution of Compton scattering photons in the actual spectrum in the energy range of 186 keV~1847 keV for these various samples was obtained. The experimental results show that the proportion of anti-Compton correction data increases exponentially with energy, and the correction percentage at the 1001 keV energy peak of interest in direct uranium measurement technology exceeds 60%. The research results of this paper can provide important data reference for the development of gamma spectrum uranium measurement technology equipment.
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When conducting drug experiments on cells cultured in vitro, drug treatment can cause cell death, and different methods for detecting cell survival rates can have impacts on the experimental results. This experiment takes Hela cells as the experimental object, and treats the cells with different concentrations of cisplatin. The cell survival rates detected with or without floating cells in the old culture medium are compared. The experimental results indicated that using the CCK8 method to detect the cell survival rates of 96 well plates and 24 well plates, the cell survival rates of the experimental group without removing the old culture medium was higher than that of the experimental group removing the old culture medium. At a cisplatin concentration of 0.625 μM, there is a significant difference in cell survival rates between the experimental group with and without removing the old medium. In 6-well plates and 100 mm dishes, a cell counter was used to detect the floating cells in the cell culture medium after application of drugs, and the presence of viable cells in the floating cells in the medium was found. Therefore, the floating living cells in the culture medium will affect the experimental results of cell drug experiment.
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In order to reduce the environmental pollution caused by the use of diesel fuel, and to promote the development of the automotive industry in the direction of more environmental protection and efficiency, China’s diesel quality has completed the upgrade from China Ⅳ to China Ⅵ, with increasingly stringent requirements on the physicochemical properties of diesel within the standards. The quality upgrade has a direct impact on the physicochemical properties of diesel fuel, which in turn is determined by its chemical composition. Therefore, investigating the relationship between the chemical composition and physicochemical properties of diesel fuel can help fuel producers to optimise diesel fuel formulations to meet higher quality requirements, and can also help users to choose diesel fuel products in accordance with their own needs in order to improve diesel fuel utilisation and reduce environmental pollution. This study reviews the intrinsic relationship between the chemical composition of diesel fuel and density, cetane number, lubricity, low temperature fluidity, sulfur-containing compounds, nitrogen-containing compounds and fatty acid methyl esters. This study provides a theoretical basis for diesel blending and quality upgrading, as well as a useful reference for sustainable energy development and environmental protection.
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There are many types and applications of resistance strain sensors, which are widely used in industries and fields such as bridges, tunnels, construction, aerospace, etc. They are often used to monitor their structures. Therefore, it is very important to evaluate the dynamic characteristics of resistance strain sensors reasonably. This article discusses and analyzes the characteristics of resistance strain sensors and the description of metrological characteristics in relevant domestic and foreign standards and specifications. In view of the current status of metrological calibration of resistance strain sensors, this paper discusses a method for calibrating the dynamic characteristics of resistance strain sensors using existing vibration measuring devices. This method is based on the existing vibration standard device, collecting vibration table signals and strain sensor signals through a dynamic signal analyzer, and analyzing the measurement signals to obtain dynamic sensitivity, completing the calibration of sensor dynamic characteristics. The feasibility and good repeatability of this method were verified through experiments. Finally, the data processing process was explained and the uncertainty of the dynamic sensitivity of the sensor was evaluated.
Abstract:
The traditional vibrating wire strain gauge calibration device generally uses manual or low-power motor drive as the driving force, which is difficult to meet the calibration requirements of vibrating wire strain gauges that require large measurement forces. Based on this, this article designs and develops a hydraulic driven vibrating wire strain gauge calibration device to solve the problem of difficult calibration of large force vibrating wire strain gauges. The calibration device can be adjusted within a range of (50-200) mm, and a universal fixture has been designed to achieve clamping and fastening of vibrating wire strain gauges of different sizes, models, and shapes. The device has a compact structure, convenient and labor-saving operation. It has been verified that the hydraulic drive greatly reduces the force required for calibration, while the calibration results are consistent with the traditional strain gauge measurement data. The experimental measurement uncertainty U=0.6% (k=2) is less than 0.7%, which meets the calibration specification requirements.
Abstract:
For identifying loudspeaker model parameters, the conventional fixed step gradient descent algorithm is time-consuming and often unstable when the initial parameter error is large. Therefore, a variable gradient descent algorithm with adaptive stepsize for identifying speaker system parameters in the frequency domain is proposed. This adaptive method monitors the trend of recognition parameter identification and adaptively adjusts the corresponding learning rate. This method eliminates the need to manually adjust the learning rate. In addition, since it is not easy to directly calculate the gradient of a complex model, a central difference method is used to approximate the gradient of the model. By establishing a dynamic loudspeaker model, setting different initial values and iteration error end criteria, the convergence and identification performance of fixed step method, least squares method, and adaptive step method were compared. And micro loudspeakers were used for testing and verification. Simulation and experiments show that this method has higher efficiency and better robustness to initial errors
Abstract:
During the production and transportation of GIL, internal defects may occur, leading to localized partial discharge faults during operation, accompanied by abnormal vibration and sound signals. When GIL malfunctions, it not only causes serious damage to the equipment itself, but also poses a threat to the stable operation of the power system. This paper studies a method for detecting partial discharge faults in GIL based on vibration signals, which can accurately identify specific units and locations of the faults. The paper analyzes the characteristics of vibration signals in GIL localized partial discharge fault states. By processing and identifying signals collected from simulated experiments and on-site tests, the identification method has been optimized, enabling accurate and effective determination of whether GIL has experienced localized partial discharge faults.
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For high sampling frequency narrowband active noise control system, with no secondary path information, a simplified narrowband frequency-domain ANC algorithm is proposed in this paper. This algorithm directly calculates the amplitude and phase information of the frequency bins, which are corresponding to the reference signal and error signal in the frequency domain by substituting the reference signal sampling point into the DFT definition. These frequency bins are evenly divided into lots of sub-frequency bin groups. For each sub-frequency bin group, the optimal update direction of the adaptive filter coefficient is chosen from the four directions of 0°, 180° and 90° to realize narrowband noise reduction. Compared with the FDFxLMS algorithm, all the full-band frequency bins are avoided to participate in the calculation, so as to improv the calculation efficiency. When the number of effective frequency bins meets certain conditions, the calculation amount can be reduced. The single frequency, multi-frequency, and narrowband noise are used as the primary noise in the simulation, respectively, and results show the proposed algorithm has the similar noise reduction performance as the FDFxLMS algorithm, and has good stability and tracking characteristics.
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Positional offset of the reference microphone (REF) and the microphone to be tested (DUT) are considered to be an important component causing measurement uncertainty in the free-field comparison method. In order to assess the effect of point offset on the sensitivity and frequency response calibration results, this paper quantitatively analyses the effect of position offset on the sensitivity level at each frequency by controlling the horizontal and axial offset of the positions of the REF and the DUT microphone during the calibration process, and by performing a least-squares fit of the calibration results of the sensitivity level to the displacement offset in the frequency range of 250 Hz to 20 kHz, with corresponding fit curves. The corresponding fitting curves are given. Statistical tests were also carried out on the fitting results. According to the slopes of the fitted curves and the significance levels of the tests, it is shown that: with the increase of frequency, the calibration results of the sensitivity level are significantly improved by the horizontal offset, and the maximum slope of 0.016 dB/mm is reached at 20 kHz; the effects of the sensitivity level on axial deviation are different at different frequency points, and part of the frequency is insensitive to the axial offset.
Abstract:
Scientific research instruments are the basic conditions and achievements of scientific and technological innovation. Under the situation of a new round of scientific and technological revolution and industrial reform, they have become the focus of scientific and technological innovation competition in the world, including China. Taking the scientific research output in the national major scientific research instrument development project (NMSRIDP) as the research object, this paper used bibliometric analysis to reveal the quantity, quality characteristics and internal laws of scientific papers from different dimensions, such as the output quantity, published journals, citation frequency, output institutions, etc. At the same time, combined with highly cited papers and hot papers, this paper analyzed the funding effectiveness of instrument development projects from 2011 to 2022 in terms of output, output influence, input-output ratio and other dimensions. It is expected to provide a basis for the performance evaluation of the achievements and outputs of science fund projects, and provide reference value for understanding the role of instrument fund in promoting the frontier breakthrough of basic research in China.
Abstract:
In order to solve the problem of excessive environment noise in the laboratory, a new type sound-absorbing composite board was developed. The board had a composite structure of perforated plate - melamine foam-asphalt damping layer- cellucotton - rigid backing (including skeleton), and its sound absorption coefficient was no less than 0.6 from 100 Hz to 5000 Hz. Firstly, the Biot’s theory was introduced to establish the sound transmission model of the composite plate, while a sound wave was randomly incident on it. And the simulation results were calculated by finite element methods. Then a sample was placed into a reverberation room to test its sound absorption coefficient. The results were highly consistent with the simulation results, which proved the feasibility of the model. Finally, the sound-absorbing composite board was used in the environmental noise control project of the GMIT thermal laboratory. The sound pressure level of the noise was successfully reduced from 79.8 dB(A) to 64.1 dB(A). The high performance of this new type of sound-absorbing composite board was confirmed again.
Abstract:
Point at present situation of measuring small pulling forcegauge inmetrological service,small pulling forcegauge calibration device was developed,so some matterswhensmallpulling forcegauge is measured usingWeight,for example ,heavy working intensity,unablezeroed and full scale range cannot be measured ,can be solved.
Abstract:
Digital PCR (dPCR) is an absolute quantitative technique of nucleic acid, which is widely used in transgenic and gene detection. In order to ensure the accuracy and reliability of digital PCR measurement results in China, 16 laboratories were tested using transgenic plasmid DNA samples. The comparison results showed that the difference between the ratio of foreign gene to internal copy number (<25%) to evaluate the measuring ability of the laboratories. The 16 laboratories were all within the acceptable range, and there was no significant difference among different digital PCR platforms. Due to the influence of plasmid conformation, the absolute copy number content of plasmid DNA measured in 7 laboratories was significantly lower than the reference value. It is suggested that when using digital PCR for quantitative measurement of plasmid DNA copy number, it should be confirmed whether the conformation of plasmid has an effect on amplification.
, Available online  , doi: 10.12338/j.issn.2096-9015.2020.0166
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Abstract:
In mmwave technology a low frequency is always multiplied to generate a much higher frequency. Phase noise will be also increased and phase noise test will be more important in mmwave band. It is limited with spectrum analyzer method because of some reasons. And phase noise analyzer can only cover up to 50 GHz in a single unit. After the basic introduction of phase noise test technology in mmwave band two external mixer method is provided. Result shows that with this method we can get a stable test result.