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Abstract:
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:
Continuous advancements in optical component processing technology have significantly expanded the applications of freeform surface optical elements across aviation, aerospace, and extreme ultraviolet lithography. These elements bring about revolutionary changes in contemporary optical design, posing not only a formidable challenge to processing technology due to its exacting precision requirements but also introducing new demands for inspecting profiles and establishing standards in the metrology of these freeform optical surfaces. This paper provides a comprehensive review of the progress and applications of high-precision surface measurement methods for freeform surfaces. These methods are systematically classified into two primary technologies: coordinate scanning measurement and surface imaging measurement. Due to the broader applicability of coordinate measurement methods, rendering them more suitable as standard surface measurement devices, we provide a detailed exposition on the historical development and research progress of swing-arm coordinate measurement, Cartesian coordinate measurement, and cylindrical coordinate measurement. Detailed information is provided for the measurement accuracy, application scenarios, as well as a summary of the advantages and disadvantages for each measurement method. Drawing insights from advanced measurement techniques, the paper proposes an innovative standard aspherical surface measurement device featuring a miniature interference probe. Proposed measurement method can effectively avoid the accumulation of measurement errors during the scanning motion, thus preserving measurement accuracy.offering a practical solution to the challenges of consistency and traceability in high-precision surface measuring instruments. Finally, we succinctly summarize key research directions and potential development trends in the field.
Abstract:
Multi-sensor coordinate machines are increasingly used in the measurement of complex feature parameters by combining different types of sensors which can obtain more comprehensive and accurate measurement data more quickly. The calibration of multi-sensor CMM needs to consider the metrological characteristics and combination characteristics of sensors, and the relevant standard methods are introduced.The Chinese Institute of Metrology has carried out applied research on photogrammetry targets and hardness indenter parameters based on multi-sensor coordinate technology, developed an optical-mechanical dual-purpose standard, and realized the accuracy evaluation of the combined measurement system of image sensor and contact sensor. Finally, some problems to be studied in multi-sensor coordinate measurement technology are given.
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.
Abstract:
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:
Large-scale metrology technology is a key technique for accurately measuring or calibrating the length, positional attitude, and shape parameters of large-sized objects. It finds wide applications in industrial manufacturing, large-scale construction, and industrial measurement fields. With the progressive development of advanced optical technology, precision measurement technology, data fusion technology, and engineering application technology, large-scale metrology technology has been undergoing continuous innovation and giving birth to a series of advanced measurement techniques. These breakthroughs have overcome the limitations of traditional large-scale metrology, such as single-value measurements and offline traceability, and are gradually transitioning towards composite parameters and in-situ traceability. This transition aims to achieve a digitalized, streamlined, and intelligent high-precision large-scale metrology transformation. This article provides an overview and analysis of advanced measurement techniques in indoor industrial measurement and outdoor geodetic measurement within the domain of large-scale metrology. It also offers insights into the future development trends of large-scale metrology and presents new ideas for further advancements in advanced large-scale metrology technology.
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:
End standards measurement is a fundamental work in dimensional metrology. A lot of research has been carried out on the high precision measurement of gauge block, gauge block pairs, and step height gauge. The measurement methods of the gauge block are divided into the comparison method and the absolute interference method. For the comparison method, a high-precision gauge block comparator based on a high positioning repeatability probe and interference comparison technology was introduced, and its measurement uncertainty was 0.04 μm+0.4×10−6L. For the absolute interferometry method, the measurement principle of absolute interferometry of gauge block and its development history in China were introduced. The absolute interferometry method mainly includes single ended and double ended gauge block interferometry measurement methods. Correspondingly, the single ended phase shifting gauge block interferometer that require wrung onto a platen and the double ended phase shifting gauge block interferometer that do not require wrung onto a platen have been developed, with a measurement uncertainty of 15 nm+0.15×10−6L. Based on the phase shifting gauge block interferometers, the research was conducted on the measurement methods of gauge block pairs and step height gauges. In order to achieve high precision measurement of gauge block pairs, the limited measurement conditions for measuring gauge block pairs using a single ended phase shifting gauge block interferometer were obtained through uncertainty analysis and experimental verification. The measurement uncertainty of the length difference between gauge block pairs by phase shifting interferometer does not exceed 10 nm. The high precision measurement of step height gauge can be achieved by using a single ended phase shifting gauge block interferometer. Through the analysis and calculation of interference fringes, the measurement uncertainty of the height of the step height gauge on centre point reaches (0.01~0.1) µm. To meet the needs for ultra-high precision length measurement, the research on ultra-high precision interferometry is the development trend of end standards measurement. The existing single ended and double ended phase shifting interferometry technologies have laid the foundation for the development of ultra-high precision interferometer based on a completely new design, thereby achieving end standard measurement with nanoscale measurement uncertainty.
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.