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Abstract:The application effectiveness of traditional optical parametric amplification systems has long been limited by the performance of the driving source. To address this issue, a high-power mid-IR optical parametric amplifier is demonstrated using a 1.5 μm all-polarization-maintaining erbium-doped fiber master oscillator power amplifier (MOPA) system. The OPA is seeded by a 3.27 μm continuous-wave (CW) interband cascade laser, where the femtosecond pump pulses perform nonlinear slicing and efficient amplification of the CW seed within a periodically poled lithium niobate crystal. Experimental results demonstrate that at a pump power of 4.6 W, the system delivers mid-IR femtosecond pulses centered at 3.25 μm with a spectral bandwidth of 36.4 nm and a maximum average power of up to 440 mW. Notably, the 1.5 μm pumping scheme employed in this work fundamentally circumvents the bottlenecks of parasitic visible absorption and severe thermal lensing inherently suffered by traditional 1 μm pumped architectures. Benefiting from this exceptional immunity to thermal damage and a higher quantum efficiency limit, massive parametric gain is successfully extracted by utilizing a long nonlinear crystal. Furthermore, radio-frequency spectral analysis reveals a signal-to-noise ratio exceeding 50 dB at the fundamental frequency, confirming that the system maintains superior time-frequency stability alongside its high-power performance. This architecture offers a highly scalable and robust technical paradigm for the development of compact, high-power mid-infrared femtosecond sources.

Abstract:To address the low signal intensity and limited detection sensitivity of traditional femtosecond laser-induced plasma spectroscopy, the high-voltage discharge-enhanced femtosecond laser-induced plasma spectroscopy method has been proposed. Using discharge-assisted femtosecond laser-induced plasma spectroscopy, taking copper element as the research object, this study comparatively analyzed spectral responses under different discharge conditions and the time-resolved spectral characteristics of the entire process. Experimental results indicate that the discharge can enhance the spectral signal intensities significantly. At 7 kV, the intensities of the three spectral lines (Cu II 521 nm, Cu I 578 nm, and Cu I 793 nm) are enhanced by factors of 22, 31, and 36, respectively, compared to those without discharge. Different spectral lines exhibit distinct responses to the applied voltage. Time-resolved spectral analysis indicates that the discharge-enhanced signal primarily originates from the prolonged plasma fluorescence lifetime. This study provides a reference for the development of highly sensitive and stable plasma spectroscopic analysis techniques. This method plays a positive role in advancing the application of laser-induced plasma spectroscopy in related fields such as materials analysis and trace detection.

Abstract:In response to the difficulty of achieving high spatiotemporal resolution measurements of boundary layer flow velocity using existing techniques, the femtosecond laser-induced cyano chemiluminescence speed measurement technique (FLICC) has been proposed. This technique employs femtosecond laser pulses to generate filaments in a methane / nitrogen mixed flow field, inducing intense and long-lived cyano radical CN (B-X) fluorescence as a tracer marker, thereby enhancing signal quality and extending the temporal tracking window to enable high-precision velocity measurements within the boundary layer. Experimental results demonstrate that the FLICC technique can effectively adapt to complex flow environments and successfully achieve high spatiotemporal resolution measurements of low-velocity flow fields in the boundary layer region, with the lower limit of velocity measurement reaching as low as 5 m / s. This provides a new high-precision diagnostic tool for flow field velocity measurements in fluid dynamics and aerospace research.

Abstract:To address the problem of insufficient magnetic field uniformity in solenoid coils for rubidium optical clocks under limited size constraints, this paper conducts a parametric modeling study on a multi-segment C-field coil structure inside a magnetic shield cylinder using the COMSOL Multiphysics simulation software. The number of coil segments, turns density, and other structural parameters are optimized to enhance the magnetic field uniformity in the target region along the central axis. The research results show that after optimization, the magnetic field non-uniformity in the [80, 120] mm region of the five-segment coil is reduced to 0.078%, while that of the seven-segment coil is further reduced to 0.033%. This research provides important technical insights for achieving a high-uniformity C-field in rubidium optical clocks within confined spaces.

Abstract:This paper introduces the development trajectory of force measurement technology, as well as the working principles, technical characteristics and applications of traditional force measurement technologies, including mechanical, hydraulic, resistance strain gauge and piezoelectric methods, and emerging techniques such as fiber-optic, electromagnetic, and quantum force measurement. It expounds the development directions of the high-end force measuring instruments in terms of high precision, extreme force value, multi-dimension, high dynamic performance, intellectualization and engineering application against the background of rapid upgrading of strategic emerging industries such as aerospace and high-end equipment manufacturing. It analyzes the research progress of current high-end force measurement technology in various directions, and discusses the development status and construction ideas of the force value traceability system, as well as the technical status and core difficulties of static / dynamic force calibration, multi-component force calibration and uncertainty evaluation. It points out that traditional force measurement technologies still need to be improved in terms of accuracy, measurement range and environmental adaptability. The future development is outlined, proposing the need for innovation in new materials and processes, interdisciplinary collaboration, and deep integration with such emerging techniques as internet of things, big data, and artificial intelligence to drive the industrialization of high-end force measurement instruments and provide technology support for national high-quality manufacturing development.

Abstract:Aiming at the problems of high acceleration test cost and the lack of systematic modeling and uncertainty quantification in existing virtual methods for the life verification of high-reliability MEMS sensor complete machines, this paper proposes a virtual assessment framework based on Physics of Failure (PoF). This method obtains local stress through multi-scale digital prototyping and thermal-vibration coupling simulation, and constructs a modular PoF model library to predict the life of key failure modes of critical devices. To quantify the uncertainty in manufacturing processes and service environments, a physical source-driven hybrid probability distribution modeling strategy is introduced. On this basis, a two-level competitive failure model consisting of "intra-device multi-mode fusion" and "inter-device first-passage failure" is established to realize the prediction of the Time-to-Failure (TTF) of the complete machine. Taking the MPU9250 as an example for verification, the independently conducted thermal-vibration combined physical test shows that the digital prototype has satisfactory accuracy (case temperature deviation shall not exceed ± 0.2℃, modal error < 5%), the predicted TTF of the complete machine is 12 721 h, and the weak link is accurately identified. The results show that the proposed method can effectively reduce the dependence on physical tests and improve the efficiency and credibility of life assessment.

Abstract:Silicon-based piezoresistive pressure sensors suffer from insufficient reliability and reduced service life due to issues such as output drift and sensitivity degradation in harsh environments. This study aims to systematically elucidate the physical mechanisms of stability degradation and to develop a high-precision life prediction model. Utilizing the failure physics analysis theory, it adopted variable-amplitude cyclic loading and accelerated fatigue testing methods to conduct accelerated tests by applying alternating pressure with different amplitudes. It established a dataset of sensor failure degradation through microscopic examination and performance monitoring, and overcame the challenge of analyzing the coupled effects of multiple mechanisms, including diaphragm cracking, piezoresistor creep, and packaging stress failure, ultimately constructed a life prediction model under uniaxial pressure loading conditions. Accelerated life testing demonstrated that under a pressure load of 140% of the full-scale range, the sensor's linearity increased by over 50% after approximately 2.2 million cycles, which is defined as failure. The developed model achieved an error of less than 15% between the predicted and measured lifespan, enabling effective prediction of the sensor's failure cycle. This study holds significant theoretical and practical application value, providing crucial support for advancing the design optimization and lifetime prediction of highly reliable silicon-based pressure sensors.

Abstract:To address the severe inter-axis cross-coupling and positioning accuracy limitations in three-dimensional piezoelectric nano-positioning platforms during multi-axis motion that hinder nanometer-level measurement requirements, this study proposes a hybrid control algorithm integrating feed-forward decoupling control theory with sliding mode control. The method involves: first, establishing a coupled error model and employing least squares estimation for parameter identification to design feed-forward decoupling controllers that separate the coupled system into independent single-axis control units; then, developing a non-singular terminal sliding mode self-stabilizing controller to mitigate piezoelectric hysteresis nonlinearity, residual coupling effects, and external disturbances, while utilizing extended state observers for real-time disturbance estimation and compensation, and using exponential convergence laws to suppress sliding mode chattering. The effectiveness of the control algorithm was verified through MATLAB / Simulink simulation, and an experimental platform based on a laser interferometer was constructed for coupled testing of a three-dimensional piezoelectric nano-positioning system. Experimental results demonstrate that the proposed sliding-mode decoupling control algorithm reduces the error caused by inter-axis coupling to below 0.03 μm, with the grid scanning trajectory closely matching the planned path, thereby meeting the nanometer-level positioning accuracy requirements of the multi-axis piezoelectric platform.

Abstract:In the time delay estimation (TDE) of ultrasonic signals, the traditional fixed step size least mean square (LMS) algorithm struggles to balance convergence speed and steady-state accuracy. Moreover, existing variable step size algorithms often rely on instantaneous errors and fixed function models, leading to poor adaptability under non-stationary echo signals. To address these issues, a TDE method using a fuzzy variable step size LMS algorithm is proposed for ultrasonic thickness measurement in this paper. Based on the time-varying characteristics of ultrasonic echo signals, the conventional single-error feedback mechanism is discarded. Instead, the local correlation coefficient error between the output and desired signals, along with its variation, are extracted as the dual inputs for a fuzzy controller. A zero-order Sugeno fuzzy inference system is then designed to establish a nonlinear mapping rule between these input features and the step size, enabling adaptive dynamic adjustment of the step size. Numerical simulations are presented using simulated echo signals under different signal-to-noise ratios. The results demonstrate that the proposed method yields better overall performance compared to the fixed step size LMS, the hyperbolic tangent variable step size LMS, and the instantaneous error-based fuzzy variable step size LMS. It significantly reduces the steady-state misadjustment while ensuring fast convergence, thereby offering higher measurement accuracy and noise robustness. This is further verified using measurements made on standard gauge blocks with a laboratory ultrasonic thickness measurement platform. The experimental results show that the relative measurement errors of the proposed method for gauge blocks of varying thicknesses are consistently smaller than those of the other three LMS algorithms, with a maximum relative error of 0.710%. Ultimately, the fuzzy variable step size LMS method for TDE provides vital technical support for high-precision ultrasonic time-of-flight (TOF) calculations. It facilitates the development of ultrasonic non-destructive testing technologies and holds significant practical value in engineering applications.

Abstract:To address the issue of wind-speed distortion in the two-dimensional （2D） wind retrieval using traditional Velocity-Azimuth Processing （VAP） algorithm, the Relative Total Variation （RTV） model is incorporated to improve the algorithm. Based on the correlation between wind-speed distortion and radial wind speed, a threshold is established to identify distorted regions, enabling subsequent correction. Then the RTV model is employed to eliminate irregular textures generated during the correction process，and extract the 2D overall wind structure. Furthermore, the local texture features of 2D wind field are reconstructed by combining the texture information from the actual radial wind speed. Experimental results demonstrate that the improved algorithm can effectively mitigate the wind-speed distortion issue in VAP algorithm. Compared to the preliminary results retrieved by VAP algorithm, the improved algorithm reduces root mean square error by 0.42 m / s for wind speed and 4.85° for wind direction, significantly improving the accuracy of wind retrieval.

Abstract:The traditional multispectral algorithm used for temperature field measurement on the surface of aeroengine turbine blades has high computational complexity, requiring singular value decomposition of spectral data for temperature field data calculation. In addition, the accuracy of turbine blade positioning signals is affected by simulated speed signals, resulting in deviations in temperature data. If no speed offset correction is performed, the calculated temperature data cannot accurately reflect the uneven combustion temperature and design defects of the blade discs and blades. To address the above issues, this paper optimizes the data processing algorithm for temperature field measurement on the surface of turbine blades in complex thermal environments, analyzes and constructs a multispectral temperature measurement model, and performs monochromatic temperature auxiliary calculation. Compared with the existing traditional multispectral optimization algorithm, the "multispectral + monochromatic temperature auxiliary correction" method improves the calculation efficiency by more than 30% without loss of temperature measurement accuracy. In addition, this paper proposes an adaptive speed offset correction algorithm that dynamically and adaptively adjusts the filter parameters. Compared with the existing adaptive correction algorithm, this method reduces the offset correction error by 15%. The optimized data processing algorithm for temperature field measurement on the surface of turbine blades can adapt to complex working conditions with multiple speeds, making up for the shortcomings of existing temperature measurement algorithms in engineering applications.

Abstract:Aiming at the complex distribution characteristics of annular temperature fields, including radial gradient heterogeneity, circumferential periodic fluctuation, and local temperature inversion, as well as the deficiencies of traditional reconstruction methods in annular structure adaptability and physical consistency, this paper proposes an annular temperature field reconstruction method combining adaptive Radial Basis Function (RBF) interpolation, a Convolutional Neural Network (CNN)-Long Short-Term Memory (LSTM) hybrid network, and hierarchical physical constraints. Firstly, a hybrid-kernel RBF interpolation with radially adaptive kernel parameters is adopted to construct the initial temperature field through sparse measurement data. Then, the CNN-LSTM hybrid network is utilized to extract spatial local features and circumferential periodic features to correct the residual error of the initial temperature field. Finally, according to the heat conduction law, differentiated hierarchical physical constraints are applied to different regions of the temperature field to improve the physical rationality and credibility of the reconstruction results. Multi-condition experimental results show that the reconstruction errors of the proposed method under typical working conditions of 500 K, 1 000 K, and 1 750 K all meet the engineering error threshold of 5%. The spatial resolution reaches 0.5 mm, which is better than the engineering index of 2 mm. Ablation experiments verify that the LSTM module ensures the circumferential continuity of the temperature field, and the hierarchical physical constraints significantly enhance the physical credibility of the reconstruction results. The proposed method can provide a reliable technical support for high-precision annular temperature field reconstruction, condition monitoring, and performance optimization of aero-engines.

Abstract:Aiming at the problems of low efficiency, high cost, equipment disassembly requirement and potential equipment damage in traditional calibration methods for temperature scanning valves, this paper proposes a fully automatic in-situ calibration method based on a "four-layer architecture". A fully automatic in-situ calibration system for temperature scanning valves was constructed, adopting a four-layer architecture design consisting of standard signal layer, signal switching layer, data acquisition layer, and control and analysis layer. By using dedicated metering aviation plugs, on-site calibration was realized, eliminating the equipment disassembly and assembly steps required in traditional methods. Systematic parameter optimization experiments were performed, in which four key parameters including measurement time, data acquisition interval, two-point calibration standard value combination, and channel switching stabilization time were comparatively analyzed, and the optimal parameter configuration balancing accuracy and efficiency was determined. A fully automated calibration workflow was developed, enabling complete automatic execution from equipment connection, data acquisition to coefficient calculation and writing, which simplifies the operation process and reduces errors. The results show that under the optimal configuration (measurement time of 8 s, data acquisition interval of 250 ms, calibration standard values of (10 mV, 40 mV), and channel switching stabilization time of 3 750 ms), the measurement repeatability (standard deviation) of the system is 0.003 3 mV, corresponding to an equivalent temperature error of 0.083 ℃, which meets the requirement of an error not exceeding ± 0.5 ℃. The proposed calibration method provides a reliable metrology support for the engineering application of temperature scanning valves.

Abstract:To address the current lack of systematic methods for constructing virtual models of measurement equipment, a digital modeling method for measurement equipment based on a function-structure-motion composite model is proposed. By analyzing the measurement principle, function, and operational procedure, the measurement capability of the equipment is clarified and a functional model is constructed. The structural composition of the equipment is disassembled, and the components are assembled according to the hierarchical structural relationships to build a structural model. The degrees of freedom and kinematic constraints of the mechanism are analyzed, and the motion mechanisms associated with the functions are established to construct a motion model. A coordinate measuring machine is taken as an example for application verification. The results show that this method can effectively simulate the measurable and reachable workspace, motion trajectory, and interference conditions of the measurement equipment, support reachability analysis and measurement path planning, and lay a technical foundation for simulated measurement and future remote metrology applications.

Abstract:The chilled-mirror precision dew point meter is a device for measuring the dew point temperature of gas, and it plays an important role in the humidity measurement system. However, its photoelectric signal is insensitive to the change of the mirror temperature of the chilled-mirror precision dew point meter, which makes it difficult to determine the optimal voltage change value at different dew point temperatures, resulting in low accuracy of the finally measured dew point temperature. In response to this issue, a mirror image feature analysis test based on the growth law of mirror condensation was designed. With the test, the relationship between the voltage change value of the photoelectric signal and different dew point temperatures was studied, and the law under different dew point temperatures was analyzed. At the same time, an electron microscope was used to analyze the mirror image at different voltage change values. The image features were extracted by calculating the number and density of condensates. The growth law of mirror condensate at the same dew point temperature but different voltage change values was summarized, and the selection range of the optimal voltage change values for different dew point temperatures was clarified. This study solved the problem of insensitivity of the photoelectric signal of the chilled-mirror precision dew point meter to the mirror temperature change, and improved the accuracy of dew point measurement of the chilled-mirror precision dew point meter.

Abstract:To solve the technical difficulties in the collaborative design of wide range, high accuracy, and smooth ope-ration of domestic reciprocating piston flowmeters, this paper establishes a four piston linkage kinematic model based on crank slider mechanism, and analyzes the piston motion law and dynamic characteristics systematically. By utilizing gap optimization control technology, it studies the influence mechanism of motion pair clearance on piston resistance and lea-kage, breaking through the key technical difficulties of gap matching and dynamic sealing under high-precision working conditions, and ultimately achieves the structural optimization design of a four piston linkage piston flowmeter. Experimental results show that the flow measurement range of the developed prototype can reach 5 ～ 10 000 mL / min, and the error does not exceed ± 0.54% over a 200∶1 turndown ratio. This study can effectively meet the technical requirements of industrial sites for wide range and high-precision flow measurement, and has good engineering applicability.