Transactions of Nanjing University of Aeronautics & Astronautics
Volume 35,Issue 5,2018 Table of Contents
2018, 35(5):739-748.
DOI: 10.16356/j.1005-1120.2018.05.739
Abstract:
An air source heat pump (ASHP) with refrigerant injection is proposed for the air conditioning system of electric vehicles (EVs), especially for efficient heating in cold winter, when there is no wasted heat of engines. The simulation model is built with the framework of two-phase fluid network, where the compressor is separated as two compressors and the economizer is treated as two heat exchangers in the injection path and the main refrigerant path. With the validated simulation model, the heating performance is analyzed, and the results show that the coefficient of performance (COP) of ASHP with refrigerant injection is higher than 1.4 and the discharge temperature is less than 100℃ when the outdoor temperature is -20℃. The above performance ensures that the air conditioning system and EVs can operate normally with high efficiency even in the cold winter, which is much helpful for the practicability of EVs.
An air source heat pump (ASHP) with refrigerant injection is proposed for the air conditioning system of electric vehicles (EVs), especially for efficient heating in cold winter, when there is no wasted heat of engines. The simulation model is built with the framework of two-phase fluid network, where the compressor is separated as two compressors and the economizer is treated as two heat exchangers in the injection path and the main refrigerant path. With the validated simulation model, the heating performance is analyzed, and the results show that the coefficient of performance (COP) of ASHP with refrigerant injection is higher than 1.4 and the discharge temperature is less than 100℃ when the outdoor temperature is -20℃. The above performance ensures that the air conditioning system and EVs can operate normally with high efficiency even in the cold winter, which is much helpful for the practicability of EVs.
2018, 35(5):749-759.
DOI: 10.16356/j.1005-1120.2018.05.749
Abstract:
A non-resonant piezoelectric linear motor with a flexible driving end, which has an extensive working frequency range and good operation stability, is studied theoretically and experimentally. Based on the microscopic vibration characteristics of the motor stator, the longitudinal vibration model is established for the whole motor system. According to the Coulomb friction model and the motor vibration model, the friction mechanism of the non-resonant piezoelectric linear motor is investigated by dynamical analysis of the whole motor system. Furthermore, the vibration characteristics and mechanical output characteristics of the stator are simulated and experimentally studied on the basis of the friction drive mechanism model. Finally, both the simulation and experimental results show that this kind of motor remain stable in the frequency domain from 2.2 kHz to 3.5 kHz and that when the pre-stress is 4 N and the driving voltage is 90 V, the maximum velocity of the motor is above 4 mm/s and the maximum thrust is nearly 0.5 N.
A non-resonant piezoelectric linear motor with a flexible driving end, which has an extensive working frequency range and good operation stability, is studied theoretically and experimentally. Based on the microscopic vibration characteristics of the motor stator, the longitudinal vibration model is established for the whole motor system. According to the Coulomb friction model and the motor vibration model, the friction mechanism of the non-resonant piezoelectric linear motor is investigated by dynamical analysis of the whole motor system. Furthermore, the vibration characteristics and mechanical output characteristics of the stator are simulated and experimentally studied on the basis of the friction drive mechanism model. Finally, both the simulation and experimental results show that this kind of motor remain stable in the frequency domain from 2.2 kHz to 3.5 kHz and that when the pre-stress is 4 N and the driving voltage is 90 V, the maximum velocity of the motor is above 4 mm/s and the maximum thrust is nearly 0.5 N.
2018, 35(5):760-769.
DOI: 10.16356/j.1005-1120.2018.05.760
Abstract:
The dynamic response performance of a large, cylindrical, fluid-filled steel container under high-speed impact is evaluated through fluid-structure interaction analysis using arbitrary Lagrange-Eulerian (ALE) method. The ALE method is adopted to accurately calculate the structural behavior induced by the internal liquid impact of the container. The stress and strain results obtained from the finite element analysis are in line with the experimental shell impact data. The influences of drop angle, drop height, and flow impact frequency are discussed. Calculation results indicate that the impact stress and damage of the container increase with drop height. However, the amplitude of the oscillation and the impact stress increase when the container and flow impact resonance occur at a certain drop height. The impact stress shows a nonlinear relationship with drop angle.
The dynamic response performance of a large, cylindrical, fluid-filled steel container under high-speed impact is evaluated through fluid-structure interaction analysis using arbitrary Lagrange-Eulerian (ALE) method. The ALE method is adopted to accurately calculate the structural behavior induced by the internal liquid impact of the container. The stress and strain results obtained from the finite element analysis are in line with the experimental shell impact data. The influences of drop angle, drop height, and flow impact frequency are discussed. Calculation results indicate that the impact stress and damage of the container increase with drop height. However, the amplitude of the oscillation and the impact stress increase when the container and flow impact resonance occur at a certain drop height. The impact stress shows a nonlinear relationship with drop angle.
2018, 35(5):770-777.
DOI: 10.16356/j.1005-1120.2018.05.770
Abstract:
Under the condition of thermal anti-icing, the liquid water on the leading edge of the airfoil that would flow to the downstream non-protective zone will produce ridge ice, thus endangering flight safety. Based on the existing three-dimensional (3D) icing model which considers the water film flow on the ice layer, an icing model with thermal boundary condition is introduced. With the boundary conditions of none anti-icing and thermal anti-icing, glaze ice accretion and ridge ice accretion are simulated on a simplified airfoil of unmanned aerial vehicle(UAV), and then the lift coefficient and drag coefficient are calculated and compared with the smooth airfoil under the same conditions. The results show that the lift-drag ratio obviously decreases after glaze ice occurred on the leading edge under the condition of none anti-icing; and that after setting the condition of anti-icing heat flux in the impingement area, the glaze ice on the leading edge becomes thinner and the ridge ice occurs in the non-protective zone, so the airfoil with this icing characteristic gets a lower lift-drag ratio.
Under the condition of thermal anti-icing, the liquid water on the leading edge of the airfoil that would flow to the downstream non-protective zone will produce ridge ice, thus endangering flight safety. Based on the existing three-dimensional (3D) icing model which considers the water film flow on the ice layer, an icing model with thermal boundary condition is introduced. With the boundary conditions of none anti-icing and thermal anti-icing, glaze ice accretion and ridge ice accretion are simulated on a simplified airfoil of unmanned aerial vehicle(UAV), and then the lift coefficient and drag coefficient are calculated and compared with the smooth airfoil under the same conditions. The results show that the lift-drag ratio obviously decreases after glaze ice occurred on the leading edge under the condition of none anti-icing; and that after setting the condition of anti-icing heat flux in the impingement area, the glaze ice on the leading edge becomes thinner and the ridge ice occurs in the non-protective zone, so the airfoil with this icing characteristic gets a lower lift-drag ratio.
2018, 35(5):778-788.
DOI: 10.16356/j.1005-1120.2018.05.778
Abstract:
A dual-jet consisting of a wall jet and an offset jet has been numerically simulated using lattice Boltzmann method to examine the effects of jet spacing between two jet centerlines, defined as s. The Reynolds number based on jet-exit-width d is set to be Re=56 and the jet spacing is set to be less than or equal 10 times the jet-exit-width. Computational results reveal that the flow field displays periodic vortex shedding when the jet spacing is in the range of 9 ≤ s/d ≤ 10, while it remains steady with two counter-rotating vortices in the converging region when s/d ≤ 8. When s/d=9, the power spectral analyses indicate that the vortex shedding phenomenon has specific frequency. The significant oscillation stresses induced by the periodic components of velocities are found to mainly exist in the inner shear layer regions, implying stronger momentum transfer occuring in these regions.
A dual-jet consisting of a wall jet and an offset jet has been numerically simulated using lattice Boltzmann method to examine the effects of jet spacing between two jet centerlines, defined as s. The Reynolds number based on jet-exit-width d is set to be Re=56 and the jet spacing is set to be less than or equal 10 times the jet-exit-width. Computational results reveal that the flow field displays periodic vortex shedding when the jet spacing is in the range of 9 ≤ s/d ≤ 10, while it remains steady with two counter-rotating vortices in the converging region when s/d ≤ 8. When s/d=9, the power spectral analyses indicate that the vortex shedding phenomenon has specific frequency. The significant oscillation stresses induced by the periodic components of velocities are found to mainly exist in the inner shear layer regions, implying stronger momentum transfer occuring in these regions.
2018, 35(5):789-799.
DOI: 10.16356/j.1005-1120.2018.05.789
Abstract:
This study takes the novel approach of using a counterflowing jet positioned on the nose of a lifting-body vehicle to explore its drag reduction effect at a range of angles of attack. Numerical studies are conducted at a free-stream Mach number of 8 in standard atmospheric conditions corresponding to the altitude of 40 km. The effects of jet pressure ratio and flying angles of attack on drag reduction of the model are systematically investigated. Considering the reverse thrust generated from the counterflowing jet, the drag on the nose at hypersonic speeds could be reduced up to 66%. The maximum lift-to-drag ratio of the model is obtained at 6°; meanwhile, the counterflowing jet produces a drag reduction of 8.8% for the whole model. In addition to the nose, the counterflowing jet influences the drag by increasing the pressure drag of the model and reducing the skin friction drag of the first cone within 8°. The results show that the potential of the counterflowing jet as a means of active flow control for drag reduction is significant in the engineering application on hypersonic lifting-body vehicles.
This study takes the novel approach of using a counterflowing jet positioned on the nose of a lifting-body vehicle to explore its drag reduction effect at a range of angles of attack. Numerical studies are conducted at a free-stream Mach number of 8 in standard atmospheric conditions corresponding to the altitude of 40 km. The effects of jet pressure ratio and flying angles of attack on drag reduction of the model are systematically investigated. Considering the reverse thrust generated from the counterflowing jet, the drag on the nose at hypersonic speeds could be reduced up to 66%. The maximum lift-to-drag ratio of the model is obtained at 6°; meanwhile, the counterflowing jet produces a drag reduction of 8.8% for the whole model. In addition to the nose, the counterflowing jet influences the drag by increasing the pressure drag of the model and reducing the skin friction drag of the first cone within 8°. The results show that the potential of the counterflowing jet as a means of active flow control for drag reduction is significant in the engineering application on hypersonic lifting-body vehicles.
2018, 35(5):800-811.
DOI: 10.16356/j.1005-1120.2018.05.800
Abstract:
A coupled Navier-Stokes/free-wake method is developed to predict the rotor aerodynamics and wake. The widely-used Farassat 1A formulation is adopted to predict the rotor noise. In the coupled method, the Reynolds-averaged Navier-Stokes (RANS) solver is established to simulate complex aerodynamic phenomena around blade and the tip-wake is captured by a free-wake model without numerical dissipation in the off-body wake zone. To overcome the time-consuming of the coupling strategy in previous studies, a more efficient coupling strategy is presented, by which only the induced velocity on the outer boundary grid need to be calculated. In order to obtain blade control settings, a delta trimming procedure is developed, which is more efficient than traditional trim method in the calculation of Jacobian matrix. Several flight conditions are simulated to demonstrate the validity of the coupled method. Then the rotor noise of operational load survey (OLS) is studied by the developed method as an application and the computational results are shown to be in good agreements with the available experimental data.
A coupled Navier-Stokes/free-wake method is developed to predict the rotor aerodynamics and wake. The widely-used Farassat 1A formulation is adopted to predict the rotor noise. In the coupled method, the Reynolds-averaged Navier-Stokes (RANS) solver is established to simulate complex aerodynamic phenomena around blade and the tip-wake is captured by a free-wake model without numerical dissipation in the off-body wake zone. To overcome the time-consuming of the coupling strategy in previous studies, a more efficient coupling strategy is presented, by which only the induced velocity on the outer boundary grid need to be calculated. In order to obtain blade control settings, a delta trimming procedure is developed, which is more efficient than traditional trim method in the calculation of Jacobian matrix. Several flight conditions are simulated to demonstrate the validity of the coupled method. Then the rotor noise of operational load survey (OLS) is studied by the developed method as an application and the computational results are shown to be in good agreements with the available experimental data.
2018, 35(5):812-819.
DOI: 10.16356/j.1005-1120.2018.05.812
Abstract:
This paper studies airline partner selection. The international airline operation involves considerable cooperations with other airlines at home and abroad. How to choose the most suitable partners is a realistic issue for Chinese airlines. In this paper the quality of service index (QSI) model is improved by applying more necessary indexes based on the analysis of large scale of data. A partner selection model is established to help airlines identify the best partner(s) in a scientific and effective way among potential candidates. Finally, real data from an airline company in China is applied to test the model. The outcome verify the effectiveness of the partner selection model proposed in this paper. The model can be helpful for selecting more suitable partners and increasing coordination value through cooperation with the partners.
This paper studies airline partner selection. The international airline operation involves considerable cooperations with other airlines at home and abroad. How to choose the most suitable partners is a realistic issue for Chinese airlines. In this paper the quality of service index (QSI) model is improved by applying more necessary indexes based on the analysis of large scale of data. A partner selection model is established to help airlines identify the best partner(s) in a scientific and effective way among potential candidates. Finally, real data from an airline company in China is applied to test the model. The outcome verify the effectiveness of the partner selection model proposed in this paper. The model can be helpful for selecting more suitable partners and increasing coordination value through cooperation with the partners.
2018, 35(5):820-828.
DOI: 10.16356/j.1005-1120.2018.05.820
Abstract:
Image matching technology is theoretically significant and practically promising in the field of autonomous navigation. Addressing shortcomings of existing image matching navigation technologies, the concept of high-dimensional combined feature is presented based on sequence image matching navigation. To balance between the distribution of high-dimensional combined features and the shortcomings of the only use of geometric relations, we propose a method based on Delaunay triangulation to improve the feature, and add the regional characteristics of the features together with their geometric characteristics. Finally, k-nearest neighbor (KNN) algorithm is adopted to optimize searching process. Simulation results show that the matching can be realized at the rotation angle of -8° to 8° and the scale factor of 0.9 to 1.1, and when the image size is 160 pixel×160 pixel, the matching time is less than 0.5 s. Therefore, the proposed algorithm can substantially reduce computational complexity, improve the matching speed, and exhibit robustness to the rotation and scale changes.
Image matching technology is theoretically significant and practically promising in the field of autonomous navigation. Addressing shortcomings of existing image matching navigation technologies, the concept of high-dimensional combined feature is presented based on sequence image matching navigation. To balance between the distribution of high-dimensional combined features and the shortcomings of the only use of geometric relations, we propose a method based on Delaunay triangulation to improve the feature, and add the regional characteristics of the features together with their geometric characteristics. Finally, k-nearest neighbor (KNN) algorithm is adopted to optimize searching process. Simulation results show that the matching can be realized at the rotation angle of -8° to 8° and the scale factor of 0.9 to 1.1, and when the image size is 160 pixel×160 pixel, the matching time is less than 0.5 s. Therefore, the proposed algorithm can substantially reduce computational complexity, improve the matching speed, and exhibit robustness to the rotation and scale changes.
2018, 35(5):829-837.
DOI: 10.16356/j.1005-1120.2018.05.829
Abstract:
In order to improve the target location accuracy of unmanned aerial vehicle (UAV), a novel target location method using multiple observations is proposed. Firstly, the camera intrinsic parameters are calibrated. Then, the weighted least squares estimation is used to improve the localization precision because the traditional crossover method is vulnerable to noise and has low precision. By repeatedly measuring the same target point, a nonlinear observation equation is established and then covered to linear equations using Taylor expansion. The weighted matrix is obtained according to the height of the measurement point and the camera optic axis pointing angle, and then the weighted least squares estimation is used to calculate the target position iteratively. Finally, the effectiveness and robustness of this method is verified by numerical simulation and flight test. The results show that this method can effectively improve the precision of target location.
In order to improve the target location accuracy of unmanned aerial vehicle (UAV), a novel target location method using multiple observations is proposed. Firstly, the camera intrinsic parameters are calibrated. Then, the weighted least squares estimation is used to improve the localization precision because the traditional crossover method is vulnerable to noise and has low precision. By repeatedly measuring the same target point, a nonlinear observation equation is established and then covered to linear equations using Taylor expansion. The weighted matrix is obtained according to the height of the measurement point and the camera optic axis pointing angle, and then the weighted least squares estimation is used to calculate the target position iteratively. Finally, the effectiveness and robustness of this method is verified by numerical simulation and flight test. The results show that this method can effectively improve the precision of target location.
2018, 35(5):838-848.
DOI: 10.16356/j.1005-1120.2018.05.838
Abstract:
Aero-engine blade-off event could cause serious malfunction and endanger flight safety, which is an important issue widely concerned for a long period. This paper presents a comprehensive review on the regulation requirements, the major research methods and status at home and abroad. Firstly, the relevant certification regulations and standards about aero-engine structure safety due to blade-off event were overviewed and the research gaps between the abroad and the domestic were compared. Then, the simulation and experimental methodologies on aero-engine supporting structures undertake abnormal load due to blade-off event were discussed as major issue. Finally, the safety certification verification technology system for aero-engine support structures during blade-off event was proposed.
Aero-engine blade-off event could cause serious malfunction and endanger flight safety, which is an important issue widely concerned for a long period. This paper presents a comprehensive review on the regulation requirements, the major research methods and status at home and abroad. Firstly, the relevant certification regulations and standards about aero-engine structure safety due to blade-off event were overviewed and the research gaps between the abroad and the domestic were compared. Then, the simulation and experimental methodologies on aero-engine supporting structures undertake abnormal load due to blade-off event were discussed as major issue. Finally, the safety certification verification technology system for aero-engine support structures during blade-off event was proposed.
12 Nonlinear Control Method for Hypersonic Vehicle Based on Double Power Reaching Law of Sliding Mode
2018, 35(5):849-857.
DOI: 10.16356/j.1005-1120.2018.05.849
Abstract:
The intelligence nonlinear control scheme via double power reaching law based sliding mode control method is proposed to solve the problems of model uncertainties and unknown outside disturbances. Firstly, the aerodynamic parameters of the morphing vehicle are replaced with curve-fitted approximation to build the accurate model for control design in the hypersonic flight. Then the nonlinear vehicle model is transformed into the strict feedback multi-input/multi-output nonlinear system by using the input-output feedback linearization approach. At the same time, the disturbance observer is used to approximate the unknown disturbance, and the sliding mode method is used to solve the problem of non-matching and uncertainty. Finally, according to the buffeting problem in sliding mode control, the double power is improved. Simulation results show that the proposed method can ensure the global stability of the closed-loop system, and has good tracking and robust performance.
The intelligence nonlinear control scheme via double power reaching law based sliding mode control method is proposed to solve the problems of model uncertainties and unknown outside disturbances. Firstly, the aerodynamic parameters of the morphing vehicle are replaced with curve-fitted approximation to build the accurate model for control design in the hypersonic flight. Then the nonlinear vehicle model is transformed into the strict feedback multi-input/multi-output nonlinear system by using the input-output feedback linearization approach. At the same time, the disturbance observer is used to approximate the unknown disturbance, and the sliding mode method is used to solve the problem of non-matching and uncertainty. Finally, according to the buffeting problem in sliding mode control, the double power is improved. Simulation results show that the proposed method can ensure the global stability of the closed-loop system, and has good tracking and robust performance.
2018, 35(5):858-865.
DOI: 10.16356/j.1005-1120.2018.05.858
Abstract:
Based on the finite element method, the angled surface defects have been investigated by using the laser generated surface acoustic wave (SAW). The feature of laser generated SAW interaction with the angled defect is analyzed in time and frequency domains. An increase in the amplitude of SAW at the edge of the defect is observed, and the spectral feature is angle dependent. With the angle decreasing from 120° to 30°, the maximum amplitude of frequency spectrum of SAW increases gradually. The corresponding experimental results verify the feasibility of numerical analyses and reach a good agreement with simulation results.
Based on the finite element method, the angled surface defects have been investigated by using the laser generated surface acoustic wave (SAW). The feature of laser generated SAW interaction with the angled defect is analyzed in time and frequency domains. An increase in the amplitude of SAW at the edge of the defect is observed, and the spectral feature is angle dependent. With the angle decreasing from 120° to 30°, the maximum amplitude of frequency spectrum of SAW increases gradually. The corresponding experimental results verify the feasibility of numerical analyses and reach a good agreement with simulation results.
2018, 35(5):866-873.
DOI: 10.16356/j.1005-1120.2018.05.866
Abstract:
The constitution, structure, working principle and launching process of the wedge-shaped pneumatic launcher of an unmanned aerial vehicle(UAV) are described.By simplifying its physical model, two dynamic models of the UAV launch system are established based on Lagrange equation and MSC.ADAMS, respectively. The curves of the acceleration and the velocity of UAV changing with time are obtained. The simulation results are compared with the experimental results to verify the correctness of the model. Then, the influence of the parameters on the launch is explored. Finally, the system is optimized. The maximum overload and the acceleration fluctuation are reduced.
The constitution, structure, working principle and launching process of the wedge-shaped pneumatic launcher of an unmanned aerial vehicle(UAV) are described.By simplifying its physical model, two dynamic models of the UAV launch system are established based on Lagrange equation and MSC.ADAMS, respectively. The curves of the acceleration and the velocity of UAV changing with time are obtained. The simulation results are compared with the experimental results to verify the correctness of the model. Then, the influence of the parameters on the launch is explored. Finally, the system is optimized. The maximum overload and the acceleration fluctuation are reduced.
2018, 35(5):874-882.
DOI: 10.16356/j.1005-1120.2018.05.874
Abstract:
Based on the transfer matrix method and Forman equation, a new method is proposed to conduct the modal and fatigue life analysis of a beam with multiple transverse cracks. In the modal analysis, the damping loss factor is introduced by the complex elastic modulus, bending springs without mass are used to replace the transverse cracks, and the characteristic transfer matrix of the whole cracked beam can be derived. In the fatigue life analysis, considering the interaction of the beam vibration and fatigue cracks growth, the fatigue life of the cracked beam is predicted by the timing analysis method. Numerical calculation shows that cracks have a significant influence on the modal and fatigue life of the beam.
Based on the transfer matrix method and Forman equation, a new method is proposed to conduct the modal and fatigue life analysis of a beam with multiple transverse cracks. In the modal analysis, the damping loss factor is introduced by the complex elastic modulus, bending springs without mass are used to replace the transverse cracks, and the characteristic transfer matrix of the whole cracked beam can be derived. In the fatigue life analysis, considering the interaction of the beam vibration and fatigue cracks growth, the fatigue life of the cracked beam is predicted by the timing analysis method. Numerical calculation shows that cracks have a significant influence on the modal and fatigue life of the beam.
2018, 35(5):883-889.
DOI: 10.16356/j.1005-1120.2018.05.883
Abstract:
This paper presents a frequency domain approach for the calculation of the random response of fluid-conveying steel catenary risers under random wave force. The partial differential equations of motion of the steel catenary riser under a combination of internal flow and random wave excitation are established based on a series of earlier publications. The mass matrix, stiffness matrix, damping matrix and wave loading for steel catenary riser are derived in frequency domain by using Hamilton's principle. Analysis of free vibrations is then carried out to investigate the effect of flow velocity on natural frequency. By further introducing the pseudo-excitation method, the dynamic analysis of the steel catenary riser subject to wave excitation is performed in frequency domain to see how the flow velocity affects the bending moment response of the steel catenary riser. The parametric studies on the example steel catenary riser show that flow velocity may decrease the natural frequencies and increase the dynamic response of the steel catenary riser. Moreover, the dynamic stability of fluid-conveying steel catenary risers is investigated and the critical fluid velocity is identified.
This paper presents a frequency domain approach for the calculation of the random response of fluid-conveying steel catenary risers under random wave force. The partial differential equations of motion of the steel catenary riser under a combination of internal flow and random wave excitation are established based on a series of earlier publications. The mass matrix, stiffness matrix, damping matrix and wave loading for steel catenary riser are derived in frequency domain by using Hamilton's principle. Analysis of free vibrations is then carried out to investigate the effect of flow velocity on natural frequency. By further introducing the pseudo-excitation method, the dynamic analysis of the steel catenary riser subject to wave excitation is performed in frequency domain to see how the flow velocity affects the bending moment response of the steel catenary riser. The parametric studies on the example steel catenary riser show that flow velocity may decrease the natural frequencies and increase the dynamic response of the steel catenary riser. Moreover, the dynamic stability of fluid-conveying steel catenary risers is investigated and the critical fluid velocity is identified.
2018, 35(5):890-895.
DOI: 10.16356/j.1005-1120.2018.05.890
Abstract:
Various kinds of deflection characteristics on the steel cable-stayed bridge (Nanjing No.3 Yangtze River Bridge) are investigated by different mathematical statistical methods. Firstly, via Pearson correlation coefficient calculation, it shows good consistency between the adjacent measuring point of side span or middle span. Secondly, taking mid-span deflection as an example, the correlation analysis of deflection and temperature is conducted. They are synchronous via cross correlation coefficient calculation but not completely linear and a "hysteresis loop" phenomenon of three stages is formed. The fitting result on the monitoring data at day time is consistent with the numerical value through the application of unit temperature difference between the cable and girder and the positive temperature gradient of girder in the finite element model. And the temperature effect is considerable. Vehicle loads effect is obtained from wavelet analysis. The extracted curve can indirectly reflect the change of traffic loads. Finally, the structural damage is analyzed through the trend fusion on the deflection, cable force and visual inspection from 2006 to 2015. Relevant conclusions can provide a basis for management departments to carry out special detection.
Various kinds of deflection characteristics on the steel cable-stayed bridge (Nanjing No.3 Yangtze River Bridge) are investigated by different mathematical statistical methods. Firstly, via Pearson correlation coefficient calculation, it shows good consistency between the adjacent measuring point of side span or middle span. Secondly, taking mid-span deflection as an example, the correlation analysis of deflection and temperature is conducted. They are synchronous via cross correlation coefficient calculation but not completely linear and a "hysteresis loop" phenomenon of three stages is formed. The fitting result on the monitoring data at day time is consistent with the numerical value through the application of unit temperature difference between the cable and girder and the positive temperature gradient of girder in the finite element model. And the temperature effect is considerable. Vehicle loads effect is obtained from wavelet analysis. The extracted curve can indirectly reflect the change of traffic loads. Finally, the structural damage is analyzed through the trend fusion on the deflection, cable force and visual inspection from 2006 to 2015. Relevant conclusions can provide a basis for management departments to carry out special detection.
2018, 35(5):896-912.
DOI: 10.16356/j.1005-1120.2018.05.896
Abstract:
Let R=GR(4,m) be a Galois ring with Teichmuller set Tm and Trm be the trace function from R to Z4. In this paper, two classes of quaternary codes C1={c(a,b):a∈R,b∈Tm/2}, where c(a,b)=(Trm(ax)+Trm/2(2bx2m/2+1))x∈Tm, and C2={c(a,b):a∈R,b∈Tm}, where c(a,b)=(Trm(ax+2bx2k+1))x∈Tm, and (m)/(gcd(m,k)) is even, are investigated, respectively. The Lee weight distributions, Hamming weight distributions and complete weight distributions of the codes are completely given.
Let R=GR(4,m) be a Galois ring with Teichmuller set Tm and Trm be the trace function from R to Z4. In this paper, two classes of quaternary codes C1={c(a,b):a∈R,b∈Tm/2}, where c(a,b)=(Trm(ax)+Trm/2(2bx2m/2+1))x∈Tm, and C2={c(a,b):a∈R,b∈Tm}, where c(a,b)=(Trm(ax+2bx2k+1))x∈Tm, and (m)/(gcd(m,k)) is even, are investigated, respectively. The Lee weight distributions, Hamming weight distributions and complete weight distributions of the codes are completely given.
CHINA AERO-SCIENCES
Mobile website
Transactions of Nanjing University of Aeronautics & Astronautics ® 2024 All Rights Reserved