In the measurement of film thickness by extinction ellipsometry， the angle of incidence， as an important process parameter that changes the polarization states of incident and reflected light waves， significantly affects the accuracy of film thickness measurements. A He-Ne laser with a wavelength of 632.8 nm is used to establish a mathematical model between incident angle deviation and measured film thickness deviation under different incident angles. The model is verified by constructing an extinction ellipsometry setup and testing a silica-on-silicon sample. For the measured sample with a film thickness of 102.55 nm， theoretical calculations show that every 0.01° variation in the incident angle introduces a maximum error of 0.008 7 nm to the measured film thickness. Measurement results demonstrate that the actual error caused by incident angle deviation is consistent with model expectations， which further validates the reliability of the extinction ellipsometry setup. The analysis method for the uncertainty component introduced by incident angle deviation in extinction ellipsometry is optimized. The uncertainty component introduced by the incident angle of the setup is 0.004 nm.
To trace the six-degree-of-freedom （6-DOF） measurement results back to high-precision one-dimensional laser interferometry， a non-kinematic calibration-based dimensionality-reduced task-space interpolation compensation method is proposed. Specifically， linear and angular errors of each degree of freedom are measured using a high-precision one-dimensional laser interferometer， and the residual pose errors at multiple discrete points within the task space are obtained. A fuzzy inference system（FIS） is established to predict and compensate residual errors across arbitrary pose points in the task space. Experimental results show that the proposed method reduces the root mean square errors （e RMS）of 6-DOF position and orientation measurements to 1 μm and 10 μrad， corresponding to improvements of 77.98% and 86.34% in measurement accuracy， respectively.
A multilevel method for water supply pipeline leak localization is proposed， integrating leak detection and precise localization. To improve robustness under complex noise conditions， a two-stage adaptive denoising framework based on time-varying filter empirical mode decomposition （TVFEMD） is developed.In the detection stage， dynamic intrinsic principal component analysis is used to model normal-condition signals， from which compressed time- and frequency-domain features are extracted to construct dynamic and static fault indicators. In the localization stage， leak signals are decomposed into intrinsic mode functions （IMFs） using TVFEMD， and a two-stage IMF selection strategy combining cross-correlation analysis and peak prominence ratio criteria is applied to suppress stationary and random noise. Leak positions are determined using the time difference of arrival （TDOA） method.Experiments demonstrate high robustness and accuracy in noisy environments， achieving a precision rate of 98.5% for two-leak scenarios and reducing the average localization error by 20.3% compared with raw signals.
A precision rolling test module based on a ball-on-disk tribometer was developed to measure oil film thickness under boundary lubrication using the contact resistance method. The theoretical relationship between contact resistance and film thickness for point contact was derived from electrical contact and tribological theories， and its applicability under dynamic rolling conditions was experimentally validated. After calibrating the contact resistance under dry rolling to eliminate systematic errors， rolling lubrication tests were conducted under various loads and speeds to obtain dynamic contact resistance. The measured contact resistance was below 10 kΩ in boundary and mixed lubrication regimes， with a repeatability of 84 Ω. Oil film thickness was simultaneously measured using the optical interference method with a resolution of 0.8 nm. By correlating contact resistance with film thickness under identical operating conditions， a dynamic contact resistance-film thickness model for point-contact rolling under medium loads was established， achieving a goodness of fit of 0.96. The results demonstrate the feasibility of applying the contact resistance method to practical point-contact rolling lubrication conditions.
To ensure the accurate and consistent transfer of laser power scales， a direct comparison between the primary standard and the secondary standard for 0.1~100 mW laser power was conducted. The comparison was carried out under both broadband uniform irradiation condition and laser beam condition. Excellent agreement was achieved under uniform irradiation condition， with a relative deviation within -0.08% and an E n value of -0.08. Under the laser beam condition， the initial relative deviation of the power realizations was -1.64%. The response uniformity of the primary standard and the secondary standard was experimentally investigated， revealing that the secondary reference device exhibited a measurable non-uniformity under laser beam conditions. After correcting the responsivity of the secondary standard based on the response uniformity， the relative deviation decreased to -0.26%. and the E n value of -0.25， which achieved an excellent agreement for realization of the 0.1~100 mW laser power primary standard and the secondary standard.
To improve the calibration accuracy of a 3D laser projection system， a method for internal parameter calibration based on an improved dung beetle optimization algorithm （LT-CDBO） is proposed. This method is used to determine the mapping relationship between the projection coordinate system and the 2D galvanometer deflection angles in a 3D projection system. The original dung beetle algorithm is enhanced by introducing Logistic-Tent chaotic mapping to initialize the population， ensuring population diversity. Additionally， a Cauchy mutation strategy is employed to mutate the optimal solution of the dung beetle algorithm， thereby improving the algorithm's global search capability. Experimental results show that， compared to the particle swarm optimization and dung beetle optimizer， the root mean square error （E RMSE） of the internal parameter calibration results using the proposed improved dung beetle algorithm is reduced by 44.79% and 18.74%， respectively. It can provide a new optimization method for improving the calibration accuracy of internal parameters in 3D laser projection systems.
In the operation of many industrial equipment such as rotating equipment， reciprocating equipment and regulating valves， the generation of pulsating flow is often caused， and the unstable flow of fluid has a great influence on the accuracy of flow measurement. By building an experimental circuit for pulsating flow measurement， using Venturi and differential pressure sensor to measure flow and differential pressure under different working conditions， the measurement characteristics of Venturi under pulsating flow are studied， the effects of pulsating flow， lead pipe length and pulsation frequency on the accuracy of differential pressure measurement are explored， and the feasibility of high-frequency pressure sensor to measure the pulsating differential pressure is comparatively analyzed. The results show that the increase of pulsating flow will cause the amplitude of the pulsating differential pressure to increase， the length of the pilot tube and the pulsation frequency have a significant effect on the measurement results of the pulsating differential pressure， and the shorter pilot tube and lower pulsation frequency can help to improve the accuracy of the measurement of the pulsating differential pressure， the high-frequency pressure sensor has the reliability of the measurement under the conditions of pulsating flow， and it can effectively eliminate the error caused by the pilot tube. The results of the study provide a reference for the optimization of fluid measurements under pulsating flow conditions.
For the laser interferometric absolute gravity instrument， analyze the motion characteristics of the cart and the falling object accelerated separation stage， use the laser vibrometer to get the vertical motion parameters of the cart， determine the time point of separation of the trailer and the falling object， project the vertical motion model after the separation of the falling object， and at the same time， use the laser interferometer to measure the actual motion curve of the falling object to validate it. The experiment shows that the separation time between the FG5-X type absolute gravity meter carriage and the falling object is 9.77±0.02 ms. The falling object displacement curve measured by laser interferometer is validated against the falling object motion model， and the results show that the difference between the measured falling object displacement and the falling object motion model displacement is small， the difference is distributed between ±2×10-6 mm， and the standard deviation of the residual of the difference is 5.57×10-7 mm， which is in good consistency.
The measurement accuracy of the track inspection car body acceleration system is affected by multiple factors， including vehicle vibration， sensor sensitivity drift， and micro-variations in the mechanical structure at the installation position， leading to measurement errors. To evaluate the system status and correct test results during its operational state， a dynamic calibration method for the track inspection car body acceleration system is proposed. First， a mathematical model is established based on system identification and prediction methods， using measurement data from a miniaturized transfer device as the reference to predict and correct the data from the track inspection car body acceleration system. Then， an online verification method is applied to evaluate and analyze the data before and after correction， demonstrating the feasibility of the data correction process. Experimental results show that after system identification and correction， the correlation coefficient of the track inspection car body acceleration data is improved by up to 6.9%， the RMSE is reduced by up to 34.1%， the MAE is optimized by up to 27.3%， and the 95th percentile is improved by up to 45.2%. This method significantly enhances the accuracy and reliability of the measurement data from the track inspection car body acceleration system.
A calibration method is proposed for three-dimensional shape evaluation of Rockwell diamond conical indenters based on laser scanning confocal microscopy. High-resolution surface measurements were obtained from four sets of working indenters from different manufacturers and one standard indenter. By acquiring three-dimensional height data at the spherical tip and applying a least-squares fitting algorithm， the influence of sampling window size on the fitted radius was systematically analyzed. The results demonstrate that the proposed method enables comprehensive reconstruction of the indenter tip morphology and provides a quantitative assessment of local geometric deviations. Significant variations in local tip radius were observed under different simulated indentation depths， and distinct trends were identified among indenters from different manufacturers， reflecting the influence of processing techniques on consistency. Furthermore， a technical procedure for indenter morphology calibration was developed， including recommendations for scanning parameters， data fitting， and deviation evaluation. This approach offers a practical and accurate tool for assessing spherical tip of the Rockwell diamond conical indenters， providing essential data support for improving quality control in Rockwell hardness and scratch testing， as well as for enhancing traceability and standardization in hardness measurement.
Accurate measurement of hydrophone phase response is critical for underwater acoustic detection， communication， and metrology. However， in open water environments， multipath reflections and ambient noise often cause traditional methods to fail. To address this issue， a high-robustness phase detection method based on the time delay spectrometry （TDS） technique is proposed. By transmitting a broadband linear frequency modulated （LFM） signal， it leverages the linear time-frequency coupling characteristics of the chirp to establish a time delay-frequency domain correlation model. Combined with a controllable time window to effectively isolate the direct sound from boundary reflections， this approach significantly suppresses multipath interference. In laboratory tests within an anechoic tank， phase difference measurements across three different hydrophones showed errors <±1.3°. To validate field applicability， real-world testing was conducted in Qiandao Lake. Using TDS method successfully overcame challenges from surface waves， suspended particle scattering， and lakebed reflections， extracting phase deviations <±2° across the entire measured frequency band， confirming its anti-interference capability. Further analysis demonstrates that TDS effectively suppresses environmental noise through time-domain gating （10 ms window width） and achieves phase decoupling without relying on prior sound speed models.
The calibration for the resolution and discriminability of multi-beam echo sounding system （MBES） is not yet standardized by any technical publication. In light of this circumstance， to suggest the resolution and discriminability calibration methods approach for MBES. To perform the calibration experiment of central beam resolution and discriminability of MBES， the water depth data obtained by MBES is taken as the measured value， and the model data obtained from the theoretical model is taken as the standard value. Using the R2Sonic 2020 shallow water multi-beam depth sounder as an example， the results demonstrate that the expanded uncertainty of resolution and discriminability is better than 4.7 cm and 1.1 cm， respectively （k=2） under the experimental conditions of a water depth of 7.0 m and a sector opening angle of 30 °. This can serve as a reference for the calibration method of standardized multi-beam depth sounder system resolution and discriminability.
Power sensors ensure the accuracy of power values through power primary standard， a new calibration method for thermocouple type power sensors is introduced， which can determine the effective efficiency of the power sensor by measuring the output potential of the thermocouple. Compared with the previous low-frequency calibration method， it reduces the influence of heat generated by the internal electronic circuit of the power sensor on the calibration process. The experimental results of the coaxial 1.85 mm power primary standard show that the baseline drift level of the thermoelectric stack of this calibration method is reduced from 2.53 μV to 0.25 μV compared to the low-frequency correction method， and the experimental standard deviation of the effective efficiency is below 0.4%. The measurement curve of the thermoelectric stack voltage of the microcalorimeter， the thermocouple voltage measurement curve of the power sensor， and effective efficiency calculation results are provided. The new calibration method is applied to the coaxial 1.85 mm power primary standard， and the calibrated thermocouple type power sensor can be used as a standard to carry out value transfer work， improving China's coaxial power level transfer capability to 67 GHz.
In power systems， accurately measuring the dielectric loss angle is crucial for equipment performance evaluation and fault diagnosis. The Fast Fourier Transform is a common method for measuring the dielectric loss angle. However， it is prone to spectral leakage and picket fence effects under asynchronous sampling， leading to low measurement accuracy. To address this issue， a high-precision dielectric loss angle measurement method based on time-domain filtering and reconstruction calibration is proposed. First， the method applies time-domain filtering to the original signal to accurately estimate the fundamental frequency. Finally， the dielectric loss angle is accurately measured through reconstruction calibration. Simulation experiments show that the proposed method reduces the influence of fundamental frequency variations， harmonics， ADC quantization bits and noise on measurement results， effectively improving the accuracy of dielectric loss angle measurements. The maximum absolute error of the dielectric loss angle obtained from the actual hardware testing platform is rad， meeting the requirements of the DL/T 1154-2012 Standard， thus verifying the effectiveness and accuracy of the proposed method.
To improve the prediction accuracy of the state of health （SOH） of lithium-ion batteries and to address the challenges of empirical dependency and inefficiency in hyperparameter optimization， a prediction model based on an improved bi-directional long short-term memory network （IBiLSTM） optimized by the adaptive grey wolf optimizer （AGWO） is proposed. First， the degradation trend of the discharge capacity is extracted from the lithium battery aging data as the input to the model， and a Dropout mechanism is introduced at the input layer to suppress noise interference. Second， IBiLSTM architecture is constructed by integrating a convolutional neural network， bi-directional long short-term memory， and an attention mechanism， in order to enhance feature extraction and temporal dependency modeling. Finally， the AGWO is employed to adaptively optimize the key hyperparameters of the model， and the network is trained based on the optimal configuration to achieve the final SOH prediction. Experiments conducted on the NASA battery dataset demonstrate that the proposed method achieves a root mean square error E RMSE and mean absolute error E MAE both within 2.5%， with the coefficient of determination R² consistently exceeding 0.95， indicating superior prediction accuracy compared to other benchmark algorithms.
To complete the metrological traceability sysetm of low-frequency voltage transformers（LFVTs）， a 35 kV-class calibration system operating in the （15~30）Hz frequency range was developed. The system comprises a low-frequency voltage source， a low-frequency standard voltage transformer， and a low-frequency electronic transformer test set， enabling on-site verification of LFVTs. Experimental studies were conducted to evaluate the influence of frequency variations on the ratio error and phase displacement of voltage transformers. A prototype LFVT was calibrated using the system， followed by comprehensive uncertainty analysis. Results indicate that frequency fluctuations significantly affect both ratio error and phase displacement， highlighting the necessity of frequency-specific calibration. The proposed system is validated for calibrating LFVTs with accuracy classes of 0.5 and below.
The response characteristics of the ionization chamber under various ultra-high dose rates were investigated. Firstly， the saturation characteristics of six flat-plate and cylindrical ionization chambers were investigated under six conditions of ultra-high dose rate electron beam irradiation by adjusting the dose per pulse of the electron beam current. Secondly， the dose at the reference measurement point was determined using alanine dosimeters， and in conjunction with theoretical composite correction calculations， the applicability of the dual-voltage method for ion recombination correction at ultra-high dose rates was systematically studied. The results show that at ultra-high dose rates with a dose per pulse ≥0.65 Gy/Pulse， the measured values of the six ionization chambers increased with increasing bias voltage within the range of -50V to -600V， but none reached the saturation region. When the dose per pulse is 0.22 Gy/Pulse， the IBA PPC 05 entered the saturation region at a bias voltage of -200 V. When the dose per pulse exceeded 0.22 Gy/Pulse， the calculated recombination correction factors using the dual-voltage method for five ionization chambers， including the PTW 34001， deviated from the theoretical values， making it challenging to accurately correct the recombination effect in these chambers. At an ultra-high dose rate of 0.22 Gy/Pulse， the IBA PPC05 demonstrates a saturation region. The deviation between the composite correction factor calculated using the double-voltage method and the theoretical composite correction factor is only 1.8%， with a polarization correction factor of 1.004 1. This indicates the applicability of the IBA PPC 05 under an electron beam dose per pulse of 0.22 Gy/Pulse.
With the promulgation and implementation of the standards GB 2760—2024 and GB 5009.35—2023， the detection and limitation of synthetic colorants in food have attracted the attention of the entire food industry as well as the testing， inspection， and certification （TIC） industry. This article reviews the development of the traceability detection system for synthetic colorants in food in recent years. Starting with the classification and use of food colorants， the paper focuses on introducing the new National Standard for synthetic colorant detection methods， certified reference material （CRM） and national standard sample （GSB） of synthetic colorants. Then the revision changes between the old and new method standards are analyzed and compared， and the CRMs of synthetic food colorants are summarized and combed both domestically and internationally， Finally the paper points out that the combined detection of synthetic colorants （rapid screening by on-site immunoassay + quantitative analysis by HPLC-DAD or HPLC-MS/MS） is the trend of synthetic colorant detection and will surely be widely applied in food safety supervision.
In high intensity focused ultrasound（HIFU） tumor treatment， accurate prediction of thermal damage results is necessary.Focused ultrasound is used to heat the sample tissue， and ‘the finite amplitude insertion-substitution method’ was used to measure the sound velocity and thickness of porcine fat， muscle， and liver， and to measure the attenuation coefficient of isolated tissues during temperature change. The fitting formulas of attenuation coefficient dependent on the temperature of three tissues at a frequency of 1 MHz are proposed， respectively. A multi-physics coupling model of nonlinear acoustic propagation and biological tissue heat transfer is established by using COMSOL， and the influence of dynamic attenuation coefficient on the prediction results of thermal damage is analyzed. The experimental results show that the attenuation coefficient of the ex vivo tissues has a strong dependence on temperature， and presents different changing trends. The simulation results show that the dynamic attenuation coefficient will lead to higher temperature rise and larger thermal damage area during HIFU treatment. The research can be used to guide clinicians in optimizing HIFU treatment plans and achieving precise treatment.
Repetitive transcranial magnetic stimulation （rTMS） generates induced currents through a time-varying magnetic field， which can regulate the neural excitability of post stroke movement disorder （PSMD） patients. The study recruited 38 participants， including 20 healthy participants and 18 stroke patients. Using rTMS stimulation of the primary motor cortex （M1） combined with motor task intervention， the impact on brain function was explored through electroencephalography （EEG） technology combined with relative power spectrum and microstate analysis.The results showed that after intervention， the behavioral scores of PSMD patients significantly increased （P<0.05）， and the relative power of theta and gamma bands near the C3 electrode in the M1 region significantly decreased （P<0.05）， approaching a healthy level. The parameters of microstate C increased significantly （P<0.05）， while those of microstate E decreased significantly （P<0.05）. High frequency band relative power and microstate C can serve as biomarkers for rTMS intervention， providing a new perspective for understanding the neural mechanisms by which rTMS improves motor function in stroke patients.
