Due to the excellent self-centering and load-carrying capability,curvic couplings have been widely used in advanced aero-engine rotors.However,curvic tooth surface errors lead to poor assembly precision.Traditional ph...Due to the excellent self-centering and load-carrying capability,curvic couplings have been widely used in advanced aero-engine rotors.However,curvic tooth surface errors lead to poor assembly precision.Traditional physical-master-gauge-based indirect tooth surface error measurement and circumferential assembly angle optimization methods have the disadvantages of high cost and weak generality.The unknown tooth surface fitting mechanism is a big barrier to assembly precision prediction and improvement.Therefore,this work puts forward a data-driven assembly simulation and optimization approach for aero-engine rotors connected by curvic couplings.The origin of curvic tooth surface error is deeply investigated.Using 5-axis sweep scan method,a large amount of high-precision curvic tooth surface data are acquired efficiently.Based on geometric models of parts,the fitting mechanism of curvic couplings is uncovered for assembly precision simulation and prediction.A circumferential assembly angle optimization model is developed to decrease axial and radial assembly runouts.Experimental results show that the assembly precision can be predicted accurately and improved dramatically.By uncovering the essential principle of the assembly precision formation and proposing circumferential assembly angle optimization model,this work is meaningful for assembly quality,efficiency and economy improvement of multistage aero-engine rotors connected by curvic couplings.展开更多
Tip clearances of multistage rotors and stators greatly affect aero-engines’ aerodynamic efficiency, stability and safety. The inevitable machining and assembly errors, as well as the complicated error propagation me...Tip clearances of multistage rotors and stators greatly affect aero-engines’ aerodynamic efficiency, stability and safety. The inevitable machining and assembly errors, as well as the complicated error propagation mechanism, cause overproof or non-uniform tip clearances. However, it is generally accepted that tip clearances are difficult to predict, even under assembly state. In this paper, a tip clearance prediction model is proposed based on measured error data. Some 3 D error propagation sub-models, regarding rotors, supports and casings, are built and combined. The complex error coupling relationship is uncovered using mathematical methods. Rotor and stator tip clearances are predicted and analyzed in different phase angles. The maximum, minimum and average tip clearances can be calculated. The proposed model is implemented by a computer program,and a case study illustrates its performance and verifies its feasibility. The results can be referred by engineers in assembly quality judgement and decision-making.展开更多
Several elastic scattering angular distributions of ^(12)C from target nuclei of A ≥39 are analyzed to extract the Woods-Saxon potential parameters with the fixed imaginary potential and Coulomb radius parameters.Usi...Several elastic scattering angular distributions of ^(12)C from target nuclei of A ≥39 are analyzed to extract the Woods-Saxon potential parameters with the fixed imaginary potential and Coulomb radius parameters.Using the best fitted diffuseness parameters,the correlations of the real part parameters with A_1^(1/3)+ A_2^(1/3) and incident energy are revealed, and the systematic Woods-Saxon potential parameters are presented for nucleus-nucleus interaction.The proposed potential parameters can reproduce not only the elastic scattering angular distributions induced by ^(12)C,but also many elastic scattering angular distributions induced by the projectiles other than ^(12)C,thus providing important inputs for the study of nuclear reactions of heavy-ion systems.展开更多
Phase transformation is one of the essential topics in the studies on high entropy alloys(HEAs).However,characterization of the nucleation behavior in the phase transformation for HEAs is still challenging through exp...Phase transformation is one of the essential topics in the studies on high entropy alloys(HEAs).However,characterization of the nucleation behavior in the phase transformation for HEAs is still challenging through experimental methods.In the present work,HfNbTaTiZr HEA was chosen as the representative material,and molecular dynamics/Monte Carlo(MD/MC)simulations were performed to investigate the nucleation behavior in temperature-induced BCC-to-HCP transformation for this HEA system.The results indicate that Nb–Ta,Ti–Zr,Hf–Zr and Hf–Ti atom pairs are preferred in the BCC solid solution of HfNbTaTiZr HEA and Hf–Ti–Zr-rich atom cluster with chemical short range order acts as the nucleation site for HCP phase.The nucleation process follows the non-classical two-step nucleation model:BCC-like structure with severe lattice distortion forms first and then HCP structure nucleates from the BCC-like structure.Moreover,at low temperature,the BCC-to-HCP nucleation hardly occurs,and the BCC solid solution is stabilized.The present work provides more atomic details of the nucleation behavior in temperature-induced BCC-to-HCP phase transformation for HEA,and can help in deep understanding of the phase stability for HEAs.展开更多
Two new fluorescent organogelators based on cholesterol containing benzothiadiazole group have been de- signed and synthesized. Three methods for gels preparation have been presented, such as heating-cooling process, ...Two new fluorescent organogelators based on cholesterol containing benzothiadiazole group have been de- signed and synthesized. Three methods for gels preparation have been presented, such as heating-cooling process, ultrasonic treatment and mixed solvents under room temperature. For both of the gels, their states and emission col- ors exhibit striking changes upon addition of Hg^2+. The gelation properties, structural characteristics and fluores- cence of the gels were studied by FT-IR, UV-Vis absorption and PL spectra. The underlying mechanism of gelation property was studied by X-ray diffraction combined with theoretical calculation, and the important role of π-π in- teractions in forming the gels has been proved.展开更多
A set of semiconductor laser pulse seed sources based on an embedded chip is proposed.The greatest feature is that the optical pulse frequency and width can be independently adjusted in real time.The pulse seed source...A set of semiconductor laser pulse seed sources based on an embedded chip is proposed.The greatest feature is that the optical pulse frequency and width can be independently adjusted in real time.The pulse seed sources can be switched independently and online from the gain-switched mode to the quasi-continuous wave mode to obtain optimal optical parameters for specific applications.To explore the physical mechanism of the semiconductor laser source,the rate equation that describes the carrier-photon transient change in a semiconductor laser cavity is numerically derived and solved.Subsequently,problems that need to be considered while designing the drive circuit are identified.The system evaluation indicates that the optical pulse frequency adjustment range is 250 Hz to 42 MHz,and the narrowest optical pulse output width is 80 ps.The pulse seed source can drive semiconductor lasers with different central wavelengths(1064,1550,and 1970 nm),and can also simultaneously drive two semiconductor lasers and output dual-band optical pulses.It can be used as a seed source for general high-power optical systems,and exhibits good application value and extensive market prospects.展开更多
基金co-supported by the National Basic Research Project(Nos.J2022-VII-0001-0043 and 2017-VII-0010-0104)the Fundamental Research Funds for the Central Universities,and the National Natural Science Foundation of China(No.72231008)。
文摘Due to the excellent self-centering and load-carrying capability,curvic couplings have been widely used in advanced aero-engine rotors.However,curvic tooth surface errors lead to poor assembly precision.Traditional physical-master-gauge-based indirect tooth surface error measurement and circumferential assembly angle optimization methods have the disadvantages of high cost and weak generality.The unknown tooth surface fitting mechanism is a big barrier to assembly precision prediction and improvement.Therefore,this work puts forward a data-driven assembly simulation and optimization approach for aero-engine rotors connected by curvic couplings.The origin of curvic tooth surface error is deeply investigated.Using 5-axis sweep scan method,a large amount of high-precision curvic tooth surface data are acquired efficiently.Based on geometric models of parts,the fitting mechanism of curvic couplings is uncovered for assembly precision simulation and prediction.A circumferential assembly angle optimization model is developed to decrease axial and radial assembly runouts.Experimental results show that the assembly precision can be predicted accurately and improved dramatically.By uncovering the essential principle of the assembly precision formation and proposing circumferential assembly angle optimization model,this work is meaningful for assembly quality,efficiency and economy improvement of multistage aero-engine rotors connected by curvic couplings.
基金co-supported by the Equipment Pre-Research Foundation (No. 61409230204)the National Basic Research Project (No. 2017-VII-0010-0104)+2 种基金the Defense Industrial Technology Development Program (No. XXXX2018213A001)the National Natural Science Foundation of China(No. 51875475)the Key Development Program of Shaanxi Province (Nos. 2018ZDXM-GY-068 and 2016KTZDGY4-02)。
文摘Tip clearances of multistage rotors and stators greatly affect aero-engines’ aerodynamic efficiency, stability and safety. The inevitable machining and assembly errors, as well as the complicated error propagation mechanism, cause overproof or non-uniform tip clearances. However, it is generally accepted that tip clearances are difficult to predict, even under assembly state. In this paper, a tip clearance prediction model is proposed based on measured error data. Some 3 D error propagation sub-models, regarding rotors, supports and casings, are built and combined. The complex error coupling relationship is uncovered using mathematical methods. Rotor and stator tip clearances are predicted and analyzed in different phase angles. The maximum, minimum and average tip clearances can be calculated. The proposed model is implemented by a computer program,and a case study illustrates its performance and verifies its feasibility. The results can be referred by engineers in assembly quality judgement and decision-making.
基金supported by the National Natural Science Foundation of China(Grant Nos.11375269,and 11490560)the National Basic Research Program of China(Grant No.2013CB834406)the National Key Research and Development Program of China(Grant No.2016YFA0400502)
文摘Several elastic scattering angular distributions of ^(12)C from target nuclei of A ≥39 are analyzed to extract the Woods-Saxon potential parameters with the fixed imaginary potential and Coulomb radius parameters.Using the best fitted diffuseness parameters,the correlations of the real part parameters with A_1^(1/3)+ A_2^(1/3) and incident energy are revealed, and the systematic Woods-Saxon potential parameters are presented for nucleus-nucleus interaction.The proposed potential parameters can reproduce not only the elastic scattering angular distributions induced by ^(12)C,but also many elastic scattering angular distributions induced by the projectiles other than ^(12)C,thus providing important inputs for the study of nuclear reactions of heavy-ion systems.
基金funded by the China Postdoctoral Science Foundation(No.2020M672787)the National Natural Science Foundation of China(Nos.51701125,51801128,52001123)the Guangdong Basic and Applied Basic Research Foundation(No.2021A1515012278)。
文摘Phase transformation is one of the essential topics in the studies on high entropy alloys(HEAs).However,characterization of the nucleation behavior in the phase transformation for HEAs is still challenging through experimental methods.In the present work,HfNbTaTiZr HEA was chosen as the representative material,and molecular dynamics/Monte Carlo(MD/MC)simulations were performed to investigate the nucleation behavior in temperature-induced BCC-to-HCP transformation for this HEA system.The results indicate that Nb–Ta,Ti–Zr,Hf–Zr and Hf–Ti atom pairs are preferred in the BCC solid solution of HfNbTaTiZr HEA and Hf–Ti–Zr-rich atom cluster with chemical short range order acts as the nucleation site for HCP phase.The nucleation process follows the non-classical two-step nucleation model:BCC-like structure with severe lattice distortion forms first and then HCP structure nucleates from the BCC-like structure.Moreover,at low temperature,the BCC-to-HCP nucleation hardly occurs,and the BCC solid solution is stabilized.The present work provides more atomic details of the nucleation behavior in temperature-induced BCC-to-HCP phase transformation for HEA,and can help in deep understanding of the phase stability for HEAs.
文摘Two new fluorescent organogelators based on cholesterol containing benzothiadiazole group have been de- signed and synthesized. Three methods for gels preparation have been presented, such as heating-cooling process, ultrasonic treatment and mixed solvents under room temperature. For both of the gels, their states and emission col- ors exhibit striking changes upon addition of Hg^2+. The gelation properties, structural characteristics and fluores- cence of the gels were studied by FT-IR, UV-Vis absorption and PL spectra. The underlying mechanism of gelation property was studied by X-ray diffraction combined with theoretical calculation, and the important role of π-π in- teractions in forming the gels has been proved.
基金Project supported by the Basic Research Foundation of Knowledge Innovation Program of Shenzhen City,China(No.JCYJ20180301-171044707)the University-Enterprise Cooperation Research and Development Project of Shenzhen Technology University,China(Nos.2018010802002,2018010802005,and 2019310103001)。
文摘A set of semiconductor laser pulse seed sources based on an embedded chip is proposed.The greatest feature is that the optical pulse frequency and width can be independently adjusted in real time.The pulse seed sources can be switched independently and online from the gain-switched mode to the quasi-continuous wave mode to obtain optimal optical parameters for specific applications.To explore the physical mechanism of the semiconductor laser source,the rate equation that describes the carrier-photon transient change in a semiconductor laser cavity is numerically derived and solved.Subsequently,problems that need to be considered while designing the drive circuit are identified.The system evaluation indicates that the optical pulse frequency adjustment range is 250 Hz to 42 MHz,and the narrowest optical pulse output width is 80 ps.The pulse seed source can drive semiconductor lasers with different central wavelengths(1064,1550,and 1970 nm),and can also simultaneously drive two semiconductor lasers and output dual-band optical pulses.It can be used as a seed source for general high-power optical systems,and exhibits good application value and extensive market prospects.