计量科学与技术

Application of Infrared Thermography in Measuring the Focal Plane of a Focused Ultrasound Transducer

ZHAO Wei, CAO Huiyuan, WU Yanqi, TAO Jie, YU Yaping

, Available online , doi: 10.12338/j.issn.2096-9015.2023.0280

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To better study the acoustic field characteristics of focused ultrasound transducers, this paper proposes a method for measuring the focal region size using infrared thermal imaging technology. By placing a thin-film sound-absorbing material on the focal plane of the transducer and measuring the temperature distribution under ultrasonic power using an infrared thermal imager, the focal size is determined. Additionally, the hydrophone scanning method was used to measure the same focused transducer, and a theoretical analysis of the sound field distribution was conducted. The results showed that the discrepancy in the -6 dB beam width was within 5%, verifying the feasibility of using infrared thermal imaging to measure the sound field distribution of focused ultrasound transducers.

Investigation of the Diffraction Efficiency of LiF220 Crystals

WANG Zhen, GUO Siming, HUANG Shikui, LI Zhiwei, ZHOU Xing, SHU Ziyao, FAN Lipeng, WANG Zhongtao

, Available online , doi: 10.12338/j.issn.2096-9015.2023.0322

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Using K fluorescence X-rays, we conducted diffraction efficiency experiments on LiF220 crystals at energies of 23.3 keV and 31 keV. By adjusting the Bragg angle of the incident monochromatic X-rays, we measured the diffracted monochromatic X-rays. The experimental results showed that the crystals produced relatively complete diffraction peaks at both energies. Under irradiation at energies of 23.3 keV and 31 keV, maximum diffraction efficiencies of approximately 2.46% and 1.33% were obtained at incident angles of 10.8° and 8.1°, respectively, which are consistent with theoretical values. This study provides experimental data support and reference for research in materials science and other related fields. Measurements of diffraction efficiency can be used to verify the accuracy of experimental results, providing a tool to test experimental conditions and data interpretation, ensuring the reproducibility and reliability of the study.

Research on Automated Detection Methods and Device for Geometric Parameters of Quartz Pendulous Reeds

WANG Jing, CHEN Xiaolei, DONG Qingyu, ZHANG Guorui, CUI Can

, Available online , doi: 10.12338/j.issn.2096-9015.2024.0034

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The quartz flexible accelerometer is a fundamental measuring element in inertial navigation systems, used to measure the system's linear acceleration. Due to its advantages of high precision, high sensitivity, and high stability, quartz flexible accelerometers are widely used in the aerospace field. The quartz pendulous reed is the core component of the quartz flexible accelerometer. It senses physical information such as the speed and acceleration of the measured object. The processing accuracy of the quartz pendulous reed affects the performance of the quartz flexible accelerometer. Therefore, it is particularly important to measure the geometric parameters of the quartz pendulous reed. In this paper, an automated measuring instrument for the geometric parameters of the quartz pendulous reed is introduced. Using this system, methods for measuring the thickness, step height, and droop of the quartz pendulous reed based on a chromatic confocal sensor are proposed. The uncertainties of different measurement methods are analyzed. Experimental measurements of the geometric parameters of quartz pendulous reeds demonstrate that the device has the advantages of simple operation and high accuracy. The device achieves automatic detection of the geometric parameters of quartz pendulous reeds, greatly improving detection efficiency and having significant implications for their automated inspection.

Investigation of Seismometer Calibration and Consistency with Transfer Function

KONG Chuijie, ZUO Aibin, ZHOU Jinfeng

, Available online , doi: 10.12338/j.issn.2096-9015.2024.0055

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This study employs the national standard ultra-low frequency vibration apparatus to conduct sensitivity calibration of seismometers, using the 3T-120PH as a typical example. The vibration calibration data are compared and analyzed against the seismometer's transfer function results. At lower frequencies (below 10 Hz), the vibration calibration results show excellent agreement with the transfer function results. However, at higher frequencies (above 10 Hz), discrepancies begin to emerge between the two methods. The vibration calibration method realistically transmits vibration signals to the seismometer, closely mimicking actual usage conditions. Consequently, the shaker calibration method provides a more accurate representation of the seismometer's performance under real working conditions compared to the electrical calibration method. This study highlights the importance of using appropriate calibration techniques for ensuring the accuracy and reliability of seismometer measurements across different frequency ranges.

Research on Traceability Techniques for Helicobacter pylori ¹³C Breath Test

HAO Jingkun, LIU Yiling, HU Shuguo, MA Xing, XIE Conghui, YIN Dongmei, WANG Defa

, Available online , doi: 10.12338/j.issn.2096-9015.2024.0144

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Addressing the challenge of ineffective traceability in Helicobacter pylori ¹³C urea breath test (13C-UBT) in China, this study employed a dynamic continuous generation system to produce reference gases with delta over baseline (DOB) values ranging from 0 to 50‰. The metrological performance of ¹³C breath test equipment was evaluated using these reference gases. Experimental results demonstrated good agreement between the DOB reference gas values and the measurements of the ¹³C breath test equipment, with indication errors at each concentration point less than ±1.5‰ and repeatability within 0.3‰. To simulate human breath conditions (34°C, 90% RH), reference gases were humidified using a standard gas humidification device. The study compared the performance of ¹³C breath test equipment using reference gases under three conditions: simulated human breath (34°C, humidified), room temperature with humidity, and room temperature without humidification (dry gas). Results showed no significant differences or trends among these conditions, supported by theoretical derivations and principle analyses. This demonstrates that altering the temperature and humidity of reference gases does not affect the reported DOB values. Consequently, room temperature dry gas can be used as a reference gas for calibrating ¹³C-UBT analyzers and similar devices, simplifying the traceability process without compromising accuracy.

Research on Characterization Methods and Uncertainty Evaluation for Freezing Point Reference Materials

LIU Zhe, HONG Tao, ZHANG Yu, LI Qingwu, ZHANG Zhengdong

, Available online , doi: 10.12338/j.issn.2096-9015.2024.0168

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Jet fuel, commonly known as aviation kerosene in China, is primarily represented by No. 3 jet fuel. The freezing point is a crucial indicator of jet fuel's low-temperature fluidity. During flight, as jet fuel temperature decreases, solid hydrocarbon crystallization can occur, potentially blocking filters and compromising flight safety. According to GB 6537-2018, the freezing point of No. 3 jet fuel must not exceed −47°C. Two methods are specified for determining the freezing point: GB/T 2430-2008 "Standard Test Method for Freezing Point of Aviation Fuels" and SH/T 0770-2005 "Standard Test Method for Freezing Point of Aviation Fuels (Automatic Phase Transition Method)," with GB/T 2430-2008 designated as the arbitration method. This study investigates the effects of various factors, including sample volume, cooling bath temperature, and stirring rate, on freezing point measurement results. It also examines the consistency between the two methods and evaluates the uncertainties introduced by the characterization method. Results indicate that a 0.01 mL change in sample volume leads to a 0.07°C variation in test results. Stirring rates between 1 and 1.5 revolutions per second cause a 0.2°C change in measurements. Cooling bath temperatures ranging from −60°C to −80°C have minimal impact on freezing point results. Experimental validation shows a maximum deviation of 0.7°C between the two methods, surpassing the reproducibility requirements of the standard method. The uncertainty components introduced by sample volume, stirring rate, method selection, and data rounding are 0.040°C, 0.058°C, 0.20°C, and 0.14°C, respectively. The expanded uncertainty of the characterization method is 0.50°C (k=2).

Application of the Residual Period Method in Low-Frequency Hydrophone Sensitivity Calibration

QU Minglong, DUAN Chao, CAI Yue, ZHANG Kai, XIE Jianyu, ZHAO Peng, GUO Shixu

, Available online , doi: 10.12338/j.issn.2096-9015.2023.0279

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This study addresses the challenges in calibrating hydrophone sensitivity at low frequencies, which arise from limitations in water tank dimensions, unavoidable reflections in water pools, and superposition of reflections in the low-frequency range. Building upon the free-field comparison method, we propose a technique that fits the amplitude, frequency, and phase of residual periodic signals to lower the frequency limit for sensitivity calibration. Experimental results demonstrate that this method enables sensitivity calibration in the 2.5-20 kHz frequency range, with errors within 0.6 dB. It effectively eliminates calibration errors caused by reflected sound fields, validating its efficacy in low-frequency calibration. However, the residual period method has some practical limitations. Factors such as environmental noise, attenuation of reflected sound fields, and nonlinear effects can impact the method's accuracy. Despite these challenges, the proposed approach shows promise in expanding the frequency domain for hydrophone calibration, particularly in low-frequency ranges where traditional methods face significant obstacles.

Research Progress in Optical Quantum Pressure Standards

MA Kun, YANG Yuanchao, FENG Xiaojuan

, Available online , doi: 10.12338/j.issn.2096-9015.2024.0113

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Optical quantum pressure standards offer significant advantages in primary measurement, including extremely high resolution, inherent accuracy, and independence from physical artifacts. These characteristics make them the preferred direction for developing next-generation pressure measurement benchmarks. Numerous metrology research institutions and universities worldwide have conducted relevant studies in this field. This paper introduces the working principle of optical quantum pressure measurement based on Fabry-Pérot cavities. It provides a comprehensive review of the current research status in optical quantum pressure standards both domestically and internationally. The article also recounts the work conducted by the National Institute of Metrology of China to enhance the performance of optical quantum pressure standard devices. This includes research progress in suppressing vacuum outgassing effects, eliminating zero-point errors, and independently determining correction factors. Furthermore, the paper discusses future research priorities and development trends for optical quantum pressure standards.

Application of CNN-LSTM Model Integrating Prophet and PCA Technology in Water Quality Prediction

XIAO Ke, ZHANG Jianjun, TAN Wenwu, WANG Li, SONG Lingyu, LIN Haijun

, Available online , doi: 10.12338/j.issn.2096-9015.2024.0109

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To reduce the error rate that may occur when traditional CNN-LSTM models are used for water quality prediction, a CNN-LSTM water quality prediction method based on the Prophet model and Principal Component Analysis (PCA) is proposed. During the cleaning process of water quality monitoring data, the Prophet model is used for outlier handling, while PCA is employed to reduce the dimensionality of influencing variables and eliminate variable correlation. The processed results are then used as input for the CNN-LSTM model to predict the total nitrogen index of water quality. Experimental results validate the effectiveness of the proposed method. Compared to the standard CNN-LSTM model, the proposed method shows significant improvements in three evaluation metrics: Mean Absolute Error (MAE), Root Mean Square Error (RMSE), and Mean Squared Error (MSE). Specifically, MSE improved by 13%, RMSE by 6.7%, and MAE by 5.6%.

Detection and Standardization of Homovanillic Acid and Vanillylmandelic Acid

YU Lintao, CHENG Long, KANG Shiyue, ZHANG Qiaoxuan, HAN Liqiao, ZHAN Min, ZHANG Pengwei, YAN Jun

, Available online , doi: 10.12338/j.issn.2096-9015.2024.0136

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Homovanillic acid (HVA) and vanillylmandelic acid (VMA) are end metabolites of catecholamines. Measurement of HVA and VMA in urine not only serves as an indirect indicator of catecholamine secretion in the body but also holds significant importance in the early diagnosis and differential diagnosis of central nervous system diseases such as neuroblastoma and pheochromocytoma. Although various methods for detecting HVA and VMA are available, significant discrepancies exist in the results obtained from the same sample when tested within or across different institutions. Therefore, establishing reference methods and reference systems to ensure the accuracy and comparability of HVA and VMA measurement results, as well as traceability and standardization of testing, has become a new goal and challenge in the field of clinical detection. This article reviews the clinical significance, detection methods, and current status of standardization of HVA and VMA testing.

Development and Application of Automatic Ultraviolet Oil Measuring Instrument

GUO Bo, ZHOU Li, ZHANG Sen, LIU Chuanrong, SUI Feng, YANG Zhongyuan

, Available online , doi: 10.12338/j.issn.2096-9015.2024.0205

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Based on the testing requirements of the national environmental protection standard HJ 970-2018 “Water quality- Determination of petroleum-Ultraviolet spectrophotometric method”, the principle of UV oil spectrophotometer was analysed. Then, a new type of automatic ultraviolet oil measuring instrument was developed by means of automatic and integrated design of injection system, extraction system, adsorption system and detection system. The structure, principle, application and maintenance of the instrument were introduced emphatically. In addition, the instrument was calibrated according to JJF (Min) 1141-2023 “Calibration Specification for Oil Content Analyzers of Ultraviolet”. In the range of (0.0～16.0) mg/L, the linearity was 0.9999. When the measured value was not more than 2 mg/L, taking 1.0 mg/L as example, the indication error was −0.042 mg/L. When the measured value was more than 2 mg/L, taking 4.0 mg/L, 8.0 mg/L and 16.0 mg/L as examples, the indication error were −3.6% , −2.2% and −1.7%, respectively. In addition, the items of instrument repeatability, minimum detectable concentration, zero drift and indication drift were calibrated. Through the above calibration experiments verified that the performance of the instrument was excellent. By using the automatic ultraviolet oil measuring instrument, the environmental protection workers could reduce the working intensity, improve the working efficiency, reduce the organic hazards, and ensure the accuracy and efficiency of the environmental monitoring work.

Application of Osmotic Coefficient Theory of Electrolyte in Metrology of Physical Chemistry Quantities Including Water Activity

WANG Haifeng, LI Jia

, Available online , doi: 10.12338/j.issn.2096-9015.2024.0191

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Osmotic coefficient (ϕ) is a measure of the deviation of the solvent of electrolyte from the ideal solution. ϕ was usually determined by the manometric method and the electromotive force method. National bureau of standard of United States of America published the reference value of osmotic coefficient equal to the average of many scientific data and its standard deviation based on the statistics. This reference data was expressed as the Debye-Hückel equation. When the molality of the electrolyte was introduced in the equation, and thus the corresponding osmotic coefficient was deduced. ϕ can be used to calculate the water activity, freezing point depression and osmotic pressure concentration of the solution of electrolyte, and thus the reference solution of these quantities were determined and then used to calibrate the instrument of these quantities. Sodium chloride was the most commonly used electrolyte. The reference values specified by the related international or national standard were well consistent with the results calculated using the reference data of ϕ. The reference values of related physical chemistry quantities calculated using the reference data of ϕ were traceable to SI units of vapor pressure or potential of the electromotive force indirectly.

Effect of paddy varieties on the measurement accuracy of capacitive grain moisture tester

CUI Tiyun, SHEN Taotao, WU Xin, LIU Yuming, ZHANG Wendong

, Available online , doi: 10.12338/j.issn.2096-9015.2024.0106

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As an instrument to measure grain moisture rapidly, capacitive grain moisture tester is widely used in grain trade settlement, and it is one of the measuring instruments under compulsory management of the state. The measurement accuracy of paddy moisture content based on the principle of capacitive method is affected by many factors. In this paper, the influence factors of paddy varieties are studied and analyzed. The moisture content of 7 different varieties of paddy was measured by 3 capacitive grain moisture testers at two moisture points of about 11.5% and 16.5% respectively. The results show that the paddy varieties have significant influence on the measurement accuracy of the capacitive grain moisture tester, and it is not advisable to use the same moisture tester to measure the water content of different varieties of paddy.

Determination and Uncertainty Assessment of Lactic Acid in Serum

ZHU Tianyi, DING Min, DUAN Manlei, MENG Jiaoran

, Available online , doi: 10.12338/j.issn.2096-9015.2023.0353

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An isotope dilution-gas chromatography-mass spectrometry method for the determination of lactic acid concentration in serum was established, and the uncertainty of the measurement results was evaluated. Sodium lactate isotope label was added to the serum sample as internal standard. After pretreatment and silanization derivatization, samples were detected by gas chromatography-tandem mass spectrometry in selected ion monitoring mode. The established quantitative analysis method was used to analyze five different concentrations of lactic acid in serum. The results showed that the method had good linearity, and the correlation coefficient was r>0.999. The average spike recovery rate was 101.2%～102.6%, and the relative standard deviation was 0.16%～0.59 % (n = 6). The concentration of lactic acid in five different serum was 1.16 mmol/L, 2.01 mmol/L, 5.50 mmol/L, 10.02 mmol/L, and 15.63 mmol/L, and the related expanded uncertainty U_rel of the results was less than 3.0% (k = 2). The method had good repeatability, high accuracy, reliable results, which could be used for accurate detection of lactic acid concentration in clinical serum sample.

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