Abstract:Solid?state femtosecond lasers are widely favored by the market due to their small size, low cost, long service life, high stability, and relatively mature technology. Repetition frequency is an important parameter of femtosecond lasers. In practical applica?tions, high repetition frequency can bring many important advantages such as high efficiency and high precision. This paper introduces the commonly used mode?locking technologies and development of GHz solid?state femtosecond lasers such as SESAM mode?locking, KLM mode?locking and high?order harmonic mode?locking, and expounds the performance advantages of GHz femtosecond light sources in application scenarios such as laser processing, distance measurement and spectrum measurement. It also predicts the deve?lopment direction of GHz repetition rate solid?state femtosecond laser technology, and provides reference for promoting the improvement of GHz repetition rate solid?state laser technology.

Abstract:In the engine test, the fluctuating pressure data of the thrust chamber is an important basis for studying the performance of the engine and judging the unstable combustion. In view of the characteristics of engine test fluctuating pressure data and the shortcomings of traditional fourier transform in the field of time?frequency analysis, the engine test fluctuating pressure data are analyzed according to the advantages of empirical mode decomposition (EMD) method, such as good adaptive characteristics, accurate positioning of instantaneous frequency, local instantaneous expression ability and extraction of signal components. The method and steps of analyzing fluctuating pressure data by EMD method are introduced. FFT method, EMD decomposition and wavelet analysis method based on different wavelet basis functions are used to analyze fluctuating pressure data respectively. The shortcomings of FFT and wavelet analysis methods in analyzing nonlinear and non-stationary data are summarized. The results show that the EMD method can well analyze the nonlinear and non-stationary data of fluctuating pressure. This method has important application and popularization value for studying and analyzing the frequency spectrum characteristics of engine test fluctuating pressure data and unstable combustion.

Abstract:Aiming at the problem of compound calibration of inertial instruments, a self?learning switching control method based on a centrifugal?temperature compound device is designed to realize the temperature control with high precision and high uniformity. According to the different structure of the temperature box control system under different working conditions of the centrifuge, a switching control scheme is designed to satisfy the accuracy requirements at both high and low temperature conditions. A self?learning PID control algorithm is designed to solve the temperature fluctuation problem in the control process. The experimental verification is carried out under the rotating state and static state of the centrifuge respectively. The results show that the control system has good performance, and the temperature control accuracy is better than 0.1 ℃ in the temperature range from -55～80 ℃.

Abstract:In order to solve the problem that the interference absorption peak affects the accuracy of temperature measurement in the current TDLAS wavelength scanning direct absorption method temperature measurement, an integral absorbance calculation method based on the symmetry of absorption spectral line was proposed. By using the absorbance in the frequency range from the center frequency to the side of the noninterference absorption peak, the integral absorbance in the whole frequency domain is obtained according to the symmetry, so as to eliminate the influence of the interference absorption peak and improve the temperature measurement accuracy. Two H₂O absorption lines at 7185.6 cm^-1 and 7444.4 cm^-1 were selected, and 8 temperature points were selected for temperature simulation calculation in the range of 400 ~ 2600 K using the absorption spectrum simulation data. At the same time, a TDLAS measurement system was set up in the laboratory environment to measure the tube furnace temperature in the temperature range of 573 ~ 1173 K, and the measurement results of the symmetrical integral absorbance calculation method of absorption spectral lines were compared with those of the single?peak method that ignored the influence of interference peaks. The results showed that the average temperature relative errors calculated by simulation are 1.11% and 5.66% respectively, while the average temperature relative errors measured by experiment are 1.02% and 9% respectively, which verifies the feasibility and accuracy of temperature measurement based on the integrated absorbance obtained by the symmetry of absorption spectral line in the presence of interference absorption peak. It provides an important reference for promoting the development of TDLAS temperature measurement technology.

Abstract:In the field of airborne test technology, the data amount of airborne data bus is increasing rapidly, the data processing method becomes more and more complex, and the requirement for software reusability is getting higher and higher. To meet these requirements, we introduce abstract factory design pattern to the field of aviation bus data processing. Based on the characteristics and application scenarios of this design pattern, we instantiate data bus by types to form a unified interface to users. Then we perform data processing on different bus interfaces. For the interface is only related to the protocol standards and technical characteristics of the bus, and independent of specific signals, it realizes the generalization of data processing method, and avoids processing each interface signal separately. So, it meets the requirements of software reusability and improves the efficiency and reliability of data processing for airborne bus.

Abstract:Aiming at the problems that the resonance characteristics of aero?engine turbine blades may lead to fatigue fracture and vibration failure of the blades, this paper takes a certain type of aero?engine turbine blade as the research object to carry out resonance margin analysis research. Firstly, the vibration characteristics of the blade are analyzed simultaneously based on the test self?hammering method and the finite element physical simulation calculation method, and the correctness and practicability of the model are verified by extracting the modal analysis results of the first six orders of the blade under the two working states. Secondly, on the basis of the existing model, by drawing the Campbell resonance curves at different working speeds and combining with the actual working parameters of this type of engine, the check and analysis of the speed resonance margin is carried out. The rotational speeds at which resonance may occur on the blades are analyzed and the optimization and improvement plan is proposed. This method mainly provides sufficient scientific basis and methods for the preliminary design and manufacture of the blade and the resonance safety inspection.

Abstract:The preparation of chip scale atom vapor cells with high performance is one of the key technologies that urgently need to be solved in the development of chip scale quantum sensing instruments at present. In order to solve the problems of difficult quantitative filling of alkali metals and poor hermeticity in the preparation of chip scale atom vapor cells, the fabrication of the chip scale alkali atom vapor cells with high hermeticity was studied. The microelectromechanical system (MEMS) technology was used to realize the batch fabrication of chip scale atom vapor cells. The silicon cavity was prepared by deep silicon etching technology. The preparation and quantitative filling of alkali atoms were realized by photolysis of RbN₃. The atom vapor cell was sealed by silicon wafer/glass bonding twice using the anodic bonding technology. Rb alkali metal atom vapor cells with N₂ as buffer gas were successfully obtained . The bonding strength, hermeticity and absorption spectrum of the prepared atom vapor cell were tested. The results showed that the glass/silicon wafer/glass bonding strength of the atom vapor cell was high. The average leakage rate of the atom vapor cells in group B was 2.2×10^-9 Pa?m³?s^-1, which is the leading level in the industry currently. Finally, the reasons for the performance difference between the two groups of atom vapor cells were analyzed from the preparation processes, which lays an important foundation for promoting the development of chip scale integration technology of quantum sensing instruments.

Abstract:Tritium is a key nuclide for radiation protection monitoring in tritium related sites. It is of great significance to effectively monitor the concentration of gaseous tritium. According to the requirements in Part 5 of GB/T7165.5-2008, the reference tritium gas consistent in composition with the object to be tested should be used in the tritium activity monitoring and calibration. To solve this problem, we need to study and establish the preparation method and certification method of reference tritium gas to ensure the effectiveness of the source of tritium gas activity measurement. Tritium reference gas is prepared based on dilution method, the tritium activity concentration is measured based on length compensation method, and the measurement uncertainty is analyzed. The development of tritium gas standard source fills the gap in this field in China and provides an important support for the traceability of tritium monitoring instrument.

Abstract:In order to meet the needs of precision temperature measurement and solve the problem that the temperature measurement results of standard photoelectric pyrometers are easily affected by the ambient temperature, a multi?point temperature control system is designed. The system realizes the overall temperature control of the inner shell through multi?point control. The thin?film heating sheet is used as the temperature control element, and the self?designed temperature control circuit is adopted. Tests were carried out to verify the temperature control stability and repeatability of the system and the temperature measurement stability of the standard photoelectric pyrometer. The results showed that the multi?point temperature control system fluctuated 0.09 ℃ in 2.5 hours after it was stable, and the temperature control repeatability for three days was 0.1 ℃. At room temperature, a standard photoelectric pyrometer is used to test the silver fixed?point blackbody radiation source. The temperature fluctuations when using the multi?point temperature control system and not using the multi?point temperature control system are 0.1 ℃ and 0.7 ℃ respectively. The multi?point temperature control system of the standard photoelectric pyrometer introduced in this paper has the advantages of good stability, small volume, light weight, easy control and so on. It can effectively meet the precision temperature measurement needs of the standard photoelectric pyrometer and promote the performance improvement of domestic precision temperature measurement instruments.

Abstract:In order to meet the requirement of output pulse amplitude and width of high?voltage pulse source in power semiconductor device parameter measurement, a pulse high?voltage source with continuously adjustable pulse amplitude and width is designed based on the principle of Marx generator, which can be used for fast measurement of power semiconductor device parameters. The pulse high?voltage source reduces the charging time of the pulse generator by improving the basic structure of the Marx generator and using the dual power charging mode. The synchronous discharge circuit is adopted to improve the output precision of the pulse voltage. On this basis, fast recovery diode is used to isolate each stage of the Marx circuit to reduce the charging loss. By controlling the charging voltage of the dual power supply and the conduction time of the solid?state switch in the discharge circuit, the amplitude and width of the output pulse voltage can be continuously adjusted. The experimental results show that the pulse high?voltage source can be continuously adjusted between the pulse amplitude of 0~8000 V and the pulse width of 200~1000 μs, and the rise time is 35 ns, which can meet the needs of fast measurement of power semiconductor device parameters.

Abstract:In order to solve the measurement problem caused by the two?dimensional angle deflection of the pull wire sensor in the static strength deformation measurement test, the turntable provided the standard deflection angle, and the method of orthogonal installation test broke through the calibration technology of the pull wire sensor under the variable angle working condition, and the sensitivity coefficient calibration method based on the orthogonal installation proposed. The calibration device constructed, and through the synthesis of the sensitivity coefficients in two orthogonal directions, The establishment method of the orthogonal error model of the pull wire sensor proposed, which finally provided a scheme for the field error measurement under the variable angle working condition, realized the rapid evaluation of the deformation measurement in the static strength test, and the exploration of the calibration method of the pull wire sensor, promotes its application in other testing fields.

Abstract:Wavelength measurement of frequency?stabilized lasers using optical frequency combs (OFC) is a necessary procedure to establish OFC?based wavelength standards. In order to establish the wavelength standard based on OFC and provide technical preparations for laser wavelength calibration, the wavelength of an acetylene?stabilized laser at 1542 nm was measured using a self?developed fiber OFC. By means of frequency beating between the reference laser generated by the OFC and the laser to be measured, the absolute frequency and vacuum wavelength of the acetylene?stabilized laser were obtained through simple algebraic relationship and were compared with the corresponding internationally recommended values. The measured vacuum wavelength of the acetylene?stabilized laser was 1542.38371235742 nm, within the uncertainty range given by CIPM. The stability was measured to be 4.13×10^-13 in 1 s. The wavelength measurement results of the acetylene?stabilized laser by two different OFCs were highly consistent, which further proved the accuracy of OFC?based wavelength measurement. This research is of great significance for conforming to the international development trend of length standards, and will accelerate the application of OFCs in the field of laser wavelength measurement.

Abstract:Based on the demands of accuracy and reliability integrated logistics support for materiel, the meanings of the materiel metrology support and integrated logistics support are deeply analyzed. With the testability demand as the link, the methods to integrate the two concepts in the standard specification system are discussed. The idea for constructing a new standard specification system giving consideration to both accuracy and reliability is put forward，which will help to establish the armament support standard system including the accuracy as well as the reliability requirements.