计量科学与技术

Rapid Identification of Alcohol-Based Gasoline Types Using Modelling of Effective Chemical Information from Near-Infrared Spectroscopy

ZHANG Zhengdong, LI Ke, DING Chaomin, XIAO Zhe, LIU Fan, GUO Xiaoyan, LI Qi

2023, 67(12): 3-12. doi: 10.12338/j.issn.2096-9015.2023.0331

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Abstract:
Methanol gasoline and ethanol gasoline, as two distinct types of clean energy sources, possess unique properties and characteristics. Accurate identification of these alcohol-based gasoline types is crucial for ensuring fuel quality and vehicle safety. Near-Infrared Spectroscopy (NIR) is a pivotal method for identifying alcohol-based gasoline types, and modelling based on NIR's effective characteristic wavelengths can overcome the effects of interfering and noisy spectral segments on model accuracy. This study employed the characteristic spectral bands of methanol and ethanol molecules in NIR spectra to develop a Partial Least Squares Discriminant Analysis (PLS-DA) model for distinguishing between methanol and ethanol gasoline. The success rates of full-wavelength spectral, Variable Importance in Projection (VIP) spectral, and feature spectral band models were compared under identical modelling conditions. Results indicated that the full-wavelength and VIP spectral models showed lower accuracy in identifying low-content alcohol-based gasoline samples, with success rates of 90% and 96.7% respectively. In contrast, the optimal feature spectral band model, constructed using the complete differential spectral information of methanol and ethanol molecules (4500～5200+5600～7200+7900～8800 cm⁻¹), achieved a 100% success rate in identifying alcohol-based gasoline samples with volume fractions of 0.5% to 80%. The study demonstrates that selecting feature spectral bands based on chemical structure is an effective wavelength selection method, enhancing model accuracy significantly. In summary, this research successfully establishes a highly accurate model for the qualitative identification of alcohol-based gasoline types using selected NIR spectral bands based on chemical information, showing potential for application in other fuel type identifications.

Case Analysis and Discussion on Nucleic Acid Extractor Calibration Techniques

WANG Zhidong, SHEN Haiying, WU Xiao, GAO Yunhua

2023, 67(12): 13-19, 58. doi: 10.12338/j.issn.2096-9015.2023.0316

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Addressing the challenges in the calibration process of nucleic acid extractors, this study explores the key metrological characteristics and measurement traceability system based on the JJF 1874-2020 standard, "Calibration Specification for (Automatic) Nucleic Acid Extractors." Using common nucleic acid extractors as examples, this paper analyzes the calibration methods and uncertainty assessments for four metrological characteristics: temperature, vibration frequency, and nucleic acid extraction efficiency. The results include temperature indication errors of 0.5 ℃ at 55 ℃ and 0.7 ℃ at 70 ℃, temperature uniformity of 0.3 ℃ at 55 ℃ and 0.5 ℃ at 70 ℃, temperature stability of ±0.1 ℃, vibration frequency stability of ±0.1 Hz, nucleic acid extraction efficiency of 82.9%, efficiency homogeneity of 6.3%, and repeatability of 4.5%. The study evaluates the uncertainty of temperature indication errors and nucleic acid extraction efficiency. Compared to the JJF 1874-2020 standard, additional uncertainty components from the micro spectrophotometer, pipettor, and electronic balance are included. The study summarizes the types and pros and cons of temperature and vibration frequency measuring devices, analyzes factors affecting nucleic acid recovery rate, and highlights the importance of using consistent extraction methods and reagents. It proposes solutions and optimization methods for calibration challenges and discusses the concept and detection methods of cross-contamination rates in nucleic acid extractors, with an experimental finding of 0.0% cross-contamination rate.

Determination of Tin in Infant Supplementary Food Rice Powder Using Inductively Coupled Plasma Mass Spectrometry with Standard Addition Method

ZHANG Shilong, CAI Wei, ZHAO Bo, CHEN Huanhuan, LU Hai, LI Xiao

2023, 67(12): 20-26. doi: 10.12338/j.issn.2096-9015.2023.0269

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Quantitative analysis of tin content in infant supplementary food rice powder was conducted using external standard and standard addition methods. The study investigated the effects of different acids added during pre-digestion and complex matrices on the tin content results. An accurate method for determining tin content in infant supplementary food rice powder was established using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The study analyzed the sources of uncertainty in the determination process of infant supplementary food rice powder, evaluated each component of uncertainty, and calculated the method's expanded uncertainty. The analysis showed that pre-digestion with nitric acid followed by the addition of hydrochloric acid before microwave digestion, and the standard addition method for tin analysis resulted in a correlation coefficient (r²) above 0.9998. The method detection limit was 0.02 mg/kg, and the measurement deviation for certified reference material was +1.2%. When tin content was measured at 1.31 mg/kg, the expanded uncertainty was 0.04 mg/kg with a coverage factor of k=2. The standard addition method was suitable for determining tin content in infant supplementary food rice powder, proving to be more accurate and reliable.

Long Range Localization Method for Underwater Sound Sources Based on Beamforming Technique

TONG Haoyang, LIU Yucai, YI Wensheng, LI Shui

2023, 67(12): 27-33, 66. doi: 10.12338/j.issn.2096-9015.2023.0301

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For calibrating the emission sound source level of mobile sound sources in open waters, the location of the sound source is usually determined using GPS, ultra-short baseline, or inertial navigation instruments. After calibration experiments, it's essential to calibrate the time axis of both sound source level data and positional measurement data. As sound pressure data and sound source location are often collected on different vessels, a time axis calibration of both sets of data is needed before processing. To simplify this calibration process, a method based on beamforming for precise long-distance measurement of underwater sound sources is proposed. This method uses the geometric relationship between the virtual source created by water surface reflections and the actual sound source position for long-distance precise measurement and derives a formula for distance calculation. The feasibility of the theory was verified through numerical simulations, and the impact of linear array design on this method was discussed. Further validation was conducted during lake tests, analyzing the influence of the experimental sound field on the positioning algorithm. Within 200 meters, the positioning difference between this method and GPS results was less than 1%, demonstrating its feasibility.

Investigating Measurement Techniques for Assessing Noise Reduction in Active Noise-Cancelling Earphones

WANG Xueyan, CHEN Weisong, NIU Feng

2023, 67(12): 34-39, 58. doi: 10.12338/j.issn.2096-9015.2023.0268

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Investigating the appropriate experimental conditions and parameter settings for evaluating active noise-cancelling earphones’ performance is crucial for developing industry standards and conducting enterprise product tests. This study utilizes three types of active noise-cancelling earphones to explore the effects of sound source layout and quantity on noise reduction measurements. In an anechoic chamber, various numbers of sound sources are positioned at different azimuthal angles to measure earphones’ noise reduction capabilities. The study analyzes the earphones’ active noise reduction performance under varying sound source conditions. Results indicate that in the earphones’ primary operational frequency band, using a single sound source placed at different angles and averaging these measurements can substitute for testing with eight simultaneous sources. The mean of two measurements with four sources at corresponding angles closely aligns with the European Telecommunications Standards Institute’s current eight-source testing standard. Thus, for active noise reduction assessment, using a single sound source at multiple angles for separate noise reduction measurements, and averaging these results, can effectively replace the need for eight simultaneous sources. A more precise approach involves two measurements with four sources at designated angles, with the results averaged. These methodologies simplify the testing apparatus while ensuring measurement reliability.

A Review of Dynamic Force Decoupling and Calibration Techniques

SONG Panfeng

2023, 67(12): 40-46, 66. doi: 10.12338/j.issn.2096-9015.2023.0326

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Dynamic force, a key measurement parameter in fields such as aerospace, material science, automobile manufacturing, and weapon efficacy, refers to force that varies over time. Ideally, dynamic force measurements should be unaffected by other sensor outputs, focusing solely on the test channel's directional output. Nevertheless, limitations in processing and installation technologies often result in inadvertent coupling of signals from other directions, leading to dynamic coupling. Accurate dynamic force measurements hinge on identifying the interdimensional coupling relationships among forces. Additionally, sensor calibration prior to testing is essential for enhancing measurement accuracy. Currently, the prevalent practice of using static calibration for dynamic force measurement often results in significant errors. Hence, the study and application of dynamic force decoupling and calibration methods are of paramount importance. This paper synthesizes various literature, summarizing common methods of dynamic force decoupling and calibration, comparing their strengths and weaknesses, and providing future perspectives.

Investigation into the Factors Affecting Windproof Performance Testing of Microphone Windscreens

QIN Zhaoqi, NIU Feng

2023, 67(12): 47-50, 12. doi: 10.12338/j.issn.2096-9015.2023.0309

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Microphone windscreens, pivotal in acoustic detection systems, serve to mitigate wind noise interference in outdoor testing, ensuring accurate and reliable data. The windproof efficacy of these windscreens is critical to test outcomes. This study focuses on the methodologies for assessing windscreen windproof performance and the factors influencing these results. The windscreen's windproof capability is quantified using the 1/3 octave frequency difference pre- and post-windscreen application at a constant wind speed. The impacts of measuring point position and background noise on windproof performance are explored. Results reveal that the turbulence increase at the flow field edge leads to test results at the wind tunnel inlet's edge being 2.0 to 32.8 dB higher than those in the central region. Thus, it is advisable to avoid the tunnel inlet's edge for test positioning. Additionally, altering the wind tunnel's background noise with sound sources demonstrated that test outcomes remain unaffected by background noise if the 1/3 octave band sound pressure level is at least 7 dB lower than the measurement band's sound pressure level. Consequently, to determine if background noise meets testing standards, the 1/3 octave band sound pressure level should be used, ensuring it is at least 7 dB lower than the measured band's level.

Analyzing Influential Factors on the Measurement Accuracy of Laser Meters

LIU Shaochun, JIANG Yuanlin, MIAO Dongjing, WANG Mingyu, WANG Deli, LI Jianshuang

2023, 67(12): 51-58. doi: 10.12338/j.issn.2096-9015.2023.0241

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This study analyzes factors affecting the measurement accuracy of laser meters, identifying three key factors: the movement speed, the angle of incidence between the measurement line and the measurement surface's normal, and the spacing distance between the laser transmitter and the measurement surface. Employing a controlled variable method, one factor is varied while the others remain constant, and the impact of each factor on measurement accuracy is determined by comparing and analyzing the laser meter's distance measurement indication error. Experimental analysis reveals that the angle of incidence between the measurement line and the normal of the measurement surface is the primary influential factor, followed by the distance between the laser transmitter and the measurement surface, both requiring strict control to maintain error within the instrument's nominal accuracy. The effect of movement speed and state on accuracy is minimal, thus not a primary factor. Consequently, special attention should be given to the placement angle and distance from the measurement surface when using and calibrating the laser meter to achieve high measurement accuracy.

Assessment and Analysis of Uncertainty in ICP-MS Measurement of Lead in Metronidazole Pharmaceuticals

ZHANG Jing, LIU Shanshan, ZHANG Yinbao, YU Zhirui, LI Xueyang

2023, 67(12): 59-66. doi: 10.12338/j.issn.2096-9015.2023.0285

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This study investigates the sources of uncertainty in determining the lead content in metronidazole pharmaceuticals using inductively coupled plasma mass spectrometry (ICP-MS). Following the 2321 method of the Pharmacopoeia of the People’s Republic of China (2020 edition), lead content was measured using ICP-MS post-microwave digestion. The study analyzed the uncertainty contributed by sample weighing, microwave digestion, preparation of standard working solutions, regression fitting of the standard curve, and repeatability of measurements to establish combined and expanded uncertainties. The findings indicate that the preparation of standard working solutions is the primary contributor to uncertainty, with a relative uncertainty of 1.44%. Other factors such as sample weighing, microwave digestion, and repeatability have a lesser impact on the overall uncertainty. For a sample weight of 0.10 g, the lead content in metronidazole tablets was found to be 0.5063 μg/g, with an expanded uncertainty of 0.01793 μg/g (k = 2).

Architectural and Acoustic Design in a Sports Center

ZHANG Xiaogai, JIN Pian, XU Dengfeng, HU Wengdan, CHEN Jian, XIAO Jian

2023, 67(12): 67-74. doi: 10.12338/j.issn.2096-9015.2023.0271

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The indoor architecture and design of sports venues require careful consideration of both the acoustic environment and spatial aesthetics. Given that most venues have large volumes and unique shapes, they are prone to prolonged reverberation, leading to challenges like low speech intelligibility, echoes, and acoustic focusing. Consequently, specific architectural acoustic designs tailored to the venue's needs are essential. This paper outlines the architectural acoustic design process for an indoor gymnasium and swimming pool within a sports center. It begins by establishing a target range for the reverberation time, followed by utilizing sound-absorbing materials and strategic interior layout to reduce reverberation. The design's efficacy was affirmed through theoretical calculations and onsite measurements. Results indicate that the achieved acoustic environment fulfills the design objectives, adequately supporting the sports center's daily operational needs and serving as a valuable reference for future large-scale sports center projects.

2023 Vol. 67, No. 12

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