Transactions of Nanjing University of Aeronautics & Astronautics
Issue S,2022 Table of Contents
2022(S):1-8.
DOI: 10.16356/j.1005-1120.2022.S.001
Abstract:
In order to study the crash resistance of the civil aircraft structure in different crash environments， two environmental models of soft soil and water are established to analyze the dynamic response of the fuselage section subjected to the vertical at the impact velocity of 7 m/s. Simulation results show that the soft crash environment can have a certain cushioning effect on the structure crash， but it will prolong the crash time and change the energy absorption mode. This work suggests that soft environment may not be suitable for forced landing.
In order to study the crash resistance of the civil aircraft structure in different crash environments， two environmental models of soft soil and water are established to analyze the dynamic response of the fuselage section subjected to the vertical at the impact velocity of 7 m/s. Simulation results show that the soft crash environment can have a certain cushioning effect on the structure crash， but it will prolong the crash time and change the energy absorption mode. This work suggests that soft environment may not be suitable for forced landing.
2022(S):9-15.
DOI: 10.16356/j.1005-1120.2022.S.002
Abstract:
The large eddy simulation （LES） method combined with the global dynamic grid strategy is used to numerically study the influence of pitch angles on cavitation and ventilation phenomena in the rear of fuselage during ditching. The volume of fluid （VOF） method is used to capture the interface. By analyzing the normal force， moment， pressure distribution and nephograms， we find that the pitch angle has a great influence on the total load， the cavitation occurrence time and its transition to ventilation， thus affects the longitudinal load distribution and the controlling of aircraft dynamics.
The large eddy simulation （LES） method combined with the global dynamic grid strategy is used to numerically study the influence of pitch angles on cavitation and ventilation phenomena in the rear of fuselage during ditching. The volume of fluid （VOF） method is used to capture the interface. By analyzing the normal force， moment， pressure distribution and nephograms， we find that the pitch angle has a great influence on the total load， the cavitation occurrence time and its transition to ventilation， thus affects the longitudinal load distribution and the controlling of aircraft dynamics.
3 Dynamic Load Identification for Structures with Variable Stiffness Based on Extended Kalman Filter
2022(S):16-22.
DOI: 10.16356/j.1005-1120.2022.S.003
Abstract:
We introduce the extended Kalman filter （EKF） method combined with the least square estimation to identify the unknown load acting on the time-varying structure and realize the tracking of the structural parameters of the time-varying system. Firstly， we propose the dynamic load identification method when the unknown parameters are stiffness coefficients. Then， a five-degree-of-freedom slowly-varying-stiffness structure is introduced to verify the effectiveness and the accuracy of the EKF method. The results show that the EKF method can accurately identify unknown loads and structural parameters simultaneously even considering noises in the input data.
We introduce the extended Kalman filter （EKF） method combined with the least square estimation to identify the unknown load acting on the time-varying structure and realize the tracking of the structural parameters of the time-varying system. Firstly， we propose the dynamic load identification method when the unknown parameters are stiffness coefficients. Then， a five-degree-of-freedom slowly-varying-stiffness structure is introduced to verify the effectiveness and the accuracy of the EKF method. The results show that the EKF method can accurately identify unknown loads and structural parameters simultaneously even considering noises in the input data.
2022(S):23-31.
DOI: 10.16356/j.1005-1120.2022.S.004
Abstract:
To address the control of low frequency noises， we propose an new perforated thin-plate acoustic metamaterials with the attachable Helmholtz resonator （AHR） which can be directly attached to the existing structure to suppress acoustic radiation. Sound transmission loss of the aluminium plate with AHR has been simulated using the finite element method under a normal incident plane sound wave. The results show that AHR works well in the 50—500 Hz frequency band， with two peaks of insulation occurring and the corresponding frequency of the first insulation peak dropping to around 120 Hz. The study of the effects of plate thickness， cavity depth， perforation radius and perforation length on the sound insulation performance of metamaterials demonstrates that the effective suppression of acoustic radiation at specific frequencies can be achieved by changing the acoustic radiation properties of the structure.
To address the control of low frequency noises， we propose an new perforated thin-plate acoustic metamaterials with the attachable Helmholtz resonator （AHR） which can be directly attached to the existing structure to suppress acoustic radiation. Sound transmission loss of the aluminium plate with AHR has been simulated using the finite element method under a normal incident plane sound wave. The results show that AHR works well in the 50—500 Hz frequency band， with two peaks of insulation occurring and the corresponding frequency of the first insulation peak dropping to around 120 Hz. The study of the effects of plate thickness， cavity depth， perforation radius and perforation length on the sound insulation performance of metamaterials demonstrates that the effective suppression of acoustic radiation at specific frequencies can be achieved by changing the acoustic radiation properties of the structure.
2022(S):32-41.
DOI: 10.16356/j.1005-1120.2022.S.005
Abstract:
Enhanced pool boiling heat transfer of the porous structure is critical to the thermal management technology. In this paper， pool boiling heat transfer experiments are performed on copper foam welded surfaces in de-ionized water to investigate the effects of basic parameters of copper foam on heat transfer enhancement. Boiling phenomenon is observed to facilitate the understanding of enhancement mechanism. The results show that copper foam welded surfaces can significantly enhance the pool boiling heat transfer performance， reduce the boiling incipience temperature by 7-9 ℃ ， and reach two times heat transfer coefficient compared with smooth plain surfaces due to numerous nucleation sites， extended surface areas， and enhanced turbulent effect. Pore density and thickness of foam have two side effects on heat transfer.
Enhanced pool boiling heat transfer of the porous structure is critical to the thermal management technology. In this paper， pool boiling heat transfer experiments are performed on copper foam welded surfaces in de-ionized water to investigate the effects of basic parameters of copper foam on heat transfer enhancement. Boiling phenomenon is observed to facilitate the understanding of enhancement mechanism. The results show that copper foam welded surfaces can significantly enhance the pool boiling heat transfer performance， reduce the boiling incipience temperature by 7-9 ℃ ， and reach two times heat transfer coefficient compared with smooth plain surfaces due to numerous nucleation sites， extended surface areas， and enhanced turbulent effect. Pore density and thickness of foam have two side effects on heat transfer.
2022(S):42-50.
DOI: 10.16356/j.1005-1120.2022.S.006
Abstract:
The response surface methodology is used to study the effect of stirring parameters on the mechanical properties of magnesium matrix composites （MMCs）. The composites are manufactured using different stirring speeds （500， 600， and 700 r/min）， stirring time （10， 20， and 30 min）， and weight fractions （0， 2.5%， 5%， and 10%） of silicon carbide particles. The experimental results show that 700 r/min and 20 min are the best conditions for obtaining the best mechanical properties. Based on the desirability function methodology， the optimum parameter values for the best mechanical characteristics of produced composites are reached at 696.102 r/min， 19.889 min， and 9.961%（in weight）.
The response surface methodology is used to study the effect of stirring parameters on the mechanical properties of magnesium matrix composites （MMCs）. The composites are manufactured using different stirring speeds （500， 600， and 700 r/min）， stirring time （10， 20， and 30 min）， and weight fractions （0， 2.5%， 5%， and 10%） of silicon carbide particles. The experimental results show that 700 r/min and 20 min are the best conditions for obtaining the best mechanical properties. Based on the desirability function methodology， the optimum parameter values for the best mechanical characteristics of produced composites are reached at 696.102 r/min， 19.889 min， and 9.961%（in weight）.
2022(S):51-58.
DOI: 10.16356/j.1005-1120.2022.S.007
Abstract:
Laser-MIG hybrid welding experiments of 7 mm thick Invar alloy are carried out. The macro appearance of joints is observed and the influence of arc energy on the cross-section morphology is analyzed. The distribution of temperature field is simulated to explain the relationship between heat effect and microstructure. Besides， the average grain size of weld under different arc energies is quantitatively studied. The results indicate that welded joints with uniformity and good formation are obtained. The weld width and the weld seam area increase and the depth to width ratio decreases with the increase of arc heat input. The transition of columnar crystals to equiaxed crystals is observed from the fusion line to the weld center. It is found that the higher the arc energy， the coarser the columnar crystal.
Laser-MIG hybrid welding experiments of 7 mm thick Invar alloy are carried out. The macro appearance of joints is observed and the influence of arc energy on the cross-section morphology is analyzed. The distribution of temperature field is simulated to explain the relationship between heat effect and microstructure. Besides， the average grain size of weld under different arc energies is quantitatively studied. The results indicate that welded joints with uniformity and good formation are obtained. The weld width and the weld seam area increase and the depth to width ratio decreases with the increase of arc heat input. The transition of columnar crystals to equiaxed crystals is observed from the fusion line to the weld center. It is found that the higher the arc energy， the coarser the columnar crystal.
2022(S):59-64.
DOI: 10.16356/j.1005-1120.2022.S.008
Abstract:
The purpose of this study is to reveal the microstructure and mechanical properties of friction stir welding （FSW） joints prepared in water/air. For comparable analysis， the submerged FSW （SFSW） and conventional FSW are both conducted on 6061-T6 aluminum alloy plates at the combination rotation speed of 800 r/min and the traverse rate of 50 mm/min. The results show that a greatest grain refinement is achieved by SFSW， which is remarkably smaller than that of the base material （BM） and air FSW （AFSW） samples， leading to a significant improvement of tensile strength from 202.5 MPa in the AFSW sample to 232 MPa in the SFSW sample.
The purpose of this study is to reveal the microstructure and mechanical properties of friction stir welding （FSW） joints prepared in water/air. For comparable analysis， the submerged FSW （SFSW） and conventional FSW are both conducted on 6061-T6 aluminum alloy plates at the combination rotation speed of 800 r/min and the traverse rate of 50 mm/min. The results show that a greatest grain refinement is achieved by SFSW， which is remarkably smaller than that of the base material （BM） and air FSW （AFSW） samples， leading to a significant improvement of tensile strength from 202.5 MPa in the AFSW sample to 232 MPa in the SFSW sample.
2022(S):65-72.
DOI: 10.16356/j.1005-1120.2022.S.009
Abstract:
To solve the multi-variable and multi-objective optimization problem in the thermal design process of the dual-input aeronautic static inverter， an optimization method based on the combination of the multi-objective evolutionary algorithm based on decomposition （MOEA/D） and the fuzzy set theory is proposed. The heat transfer path of the power device is analyzed and an equivalent heat circuit is conducted. We take junction temperature of the power device， mass， and cost of the heat sink as optimization goals， and take the heat sink structure parameters as design variables to conduct thermal optimization based on MOEA/D. This paper carries out a comparative study， and the results show that the proposed improved algorithm can meet the different requirements for multi-objective weights， and have good rapidity and robustness.
To solve the multi-variable and multi-objective optimization problem in the thermal design process of the dual-input aeronautic static inverter， an optimization method based on the combination of the multi-objective evolutionary algorithm based on decomposition （MOEA/D） and the fuzzy set theory is proposed. The heat transfer path of the power device is analyzed and an equivalent heat circuit is conducted. We take junction temperature of the power device， mass， and cost of the heat sink as optimization goals， and take the heat sink structure parameters as design variables to conduct thermal optimization based on MOEA/D. This paper carries out a comparative study， and the results show that the proposed improved algorithm can meet the different requirements for multi-objective weights， and have good rapidity and robustness.
2022(S):73-81.
DOI: 10.16356/j.1005-1120.2022.0S.010
Abstract:
In order to alleviate the flight congestion in terminal areas （TMAs）， it is of great significance to develop an effective method. An arrival sequencing model based on the serial point merge systems （PMSs） is constructed to improve the operational benefits of arrival flights. The approach of first come first service （FCFS） combined with the method of constraint position shift （CPS） is used as the sequencing strategy. Through the simulated annealing algorithm， the results show that the arrival flights sequencing through serial PMSs has significant advantages in reducing delays and increasing runway throughput especially in the case of high traffic loads. The proposed approach is conducive in promoting the implementation and application of serial PMS.
In order to alleviate the flight congestion in terminal areas （TMAs）， it is of great significance to develop an effective method. An arrival sequencing model based on the serial point merge systems （PMSs） is constructed to improve the operational benefits of arrival flights. The approach of first come first service （FCFS） combined with the method of constraint position shift （CPS） is used as the sequencing strategy. Through the simulated annealing algorithm， the results show that the arrival flights sequencing through serial PMSs has significant advantages in reducing delays and increasing runway throughput especially in the case of high traffic loads. The proposed approach is conducive in promoting the implementation and application of serial PMS.
2022(S):82-89.
DOI: 10.16356/j.1005-1120.2022.S.011
Abstract:
The South China Sea is rich in wind and wave energy resources， and the wind-wave combined power generation device is currently in the concept research and development stage. In recent years， extreme sea conditions such as super typhoons have frequently occurred， which poses a serious challenge to the safety of offshore floating platforms. In view of the lack of safety analysis of wind-wave combined power generation devices in extreme sea conditions at present， this paper takes the OC4-WEC combined with semi-submersible wind turbine （Semi-OC4） and the oscillating buoy wave energy converter as the research object， and establishes a mesoscale WRF-SWAN-FVCOM （W-S-F） real-time coupling platform based on the model coupling Toolkit （MCT） to analyze the spatial and temporal evolution of wind-wave-current in offshore wind farms during the whole process of super typhoon “Rammasun” transit. Combined with the medium/small scale nested method， the flow field characteristics of OC4-WEC platform are analyzed. The results show that the simulation accuracy of the established W-S-F platform for typhoon track is 42.51% higher than that of the single WRF model. Under the action of typhoon-wave-current， the heave motion amplitude of OC4-WEC platform is reduced by 38.1%， the surge motion amplitude is reduced by 26.7%， and the pitch motion amplitude is reduced by 23.4%.
The South China Sea is rich in wind and wave energy resources， and the wind-wave combined power generation device is currently in the concept research and development stage. In recent years， extreme sea conditions such as super typhoons have frequently occurred， which poses a serious challenge to the safety of offshore floating platforms. In view of the lack of safety analysis of wind-wave combined power generation devices in extreme sea conditions at present， this paper takes the OC4-WEC combined with semi-submersible wind turbine （Semi-OC4） and the oscillating buoy wave energy converter as the research object， and establishes a mesoscale WRF-SWAN-FVCOM （W-S-F） real-time coupling platform based on the model coupling Toolkit （MCT） to analyze the spatial and temporal evolution of wind-wave-current in offshore wind farms during the whole process of super typhoon “Rammasun” transit. Combined with the medium/small scale nested method， the flow field characteristics of OC4-WEC platform are analyzed. The results show that the simulation accuracy of the established W-S-F platform for typhoon track is 42.51% higher than that of the single WRF model. Under the action of typhoon-wave-current， the heave motion amplitude of OC4-WEC platform is reduced by 38.1%， the surge motion amplitude is reduced by 26.7%， and the pitch motion amplitude is reduced by 23.4%.
2022(S):90-97.
DOI: 10.16356/j.1005-1120.2022.S.012
Abstract:
The effect of silica fume on the early performance of precast concrete with an early strength agent was investigated. The ternary compounding technique of silica fume， fly ash and early strength agent were used to examine the compressive strength， heat of hydration， hydration products， and microstructures of the precast concrete. The experimental results showed that the optimum amount of silica fume in the precast concrete was 9%. Silica fume filled the fine pores between the cement particles. However， the cement hydration was mainly influenced by the water-to-cement ratio and cement particle size. As the hydration reaction continued， silica fume provided more nucleation sites， and the characteristic volcanic ash reaction increased both the hydration degree and hydration rate of the early strength agent doped cementitious materials.
The effect of silica fume on the early performance of precast concrete with an early strength agent was investigated. The ternary compounding technique of silica fume， fly ash and early strength agent were used to examine the compressive strength， heat of hydration， hydration products， and microstructures of the precast concrete. The experimental results showed that the optimum amount of silica fume in the precast concrete was 9%. Silica fume filled the fine pores between the cement particles. However， the cement hydration was mainly influenced by the water-to-cement ratio and cement particle size. As the hydration reaction continued， silica fume provided more nucleation sites， and the characteristic volcanic ash reaction increased both the hydration degree and hydration rate of the early strength agent doped cementitious materials.
2022(S):98-105.
DOI: 10.16356/j.1005-1120.2022.S.013
Abstract:
On the basis of the three-dimensional （3D） random aggregate & mortar two-phase mesoscale finite element model， C++ programming was used to identify the node position information of the interface between the aggregate and mortar elements. The nodes were discretized at this position and the zero-thickness cohesive elements were inserted. After that， the crack energy release rate fracture criterion based on the fracture mechanics theory was assigned to the failure criterion of the interface transition zone （ITZ） elements. Finally， the three-phase meso-mechanical model based on the combined finite discrete element method （FDEM） was constructed. Based on this model， the meso-crack extension and macro-mechanical behaviour of coral aggregate concrete （CAC） under uniaxial compression were successfully simulated. The results demonstrated that the meso-mechanical model based on FDEM has excellent applicability to simulate the compressive properties of CAC.
On the basis of the three-dimensional （3D） random aggregate & mortar two-phase mesoscale finite element model， C++ programming was used to identify the node position information of the interface between the aggregate and mortar elements. The nodes were discretized at this position and the zero-thickness cohesive elements were inserted. After that， the crack energy release rate fracture criterion based on the fracture mechanics theory was assigned to the failure criterion of the interface transition zone （ITZ） elements. Finally， the three-phase meso-mechanical model based on the combined finite discrete element method （FDEM） was constructed. Based on this model， the meso-crack extension and macro-mechanical behaviour of coral aggregate concrete （CAC） under uniaxial compression were successfully simulated. The results demonstrated that the meso-mechanical model based on FDEM has excellent applicability to simulate the compressive properties of CAC.
2022(S):106-112.
DOI: 10.16356/j.1005-1120.2022.S.014
Abstract:
The generalized Tikhonov regularization method is one of the most classical methods for the solution of linear systems of equations that arise from the discretization of linear ill-posed problems. However， the approximate solution obtained by the Tikhonov regularization method in general form may lack many details of the exact solution. Combining the fractional Tikhonov method with the preconditioned technique， and using the discrepancy principle for determining the regularization parameter， we present a preconditioned projected fractional Tikhonov regularization method for solving discrete ill-posed problems. Numerical experiments illustrate that the proposed algorithm has higher accuracy compared with the existing classical regularization methods.
The generalized Tikhonov regularization method is one of the most classical methods for the solution of linear systems of equations that arise from the discretization of linear ill-posed problems. However， the approximate solution obtained by the Tikhonov regularization method in general form may lack many details of the exact solution. Combining the fractional Tikhonov method with the preconditioned technique， and using the discrepancy principle for determining the regularization parameter， we present a preconditioned projected fractional Tikhonov regularization method for solving discrete ill-posed problems. Numerical experiments illustrate that the proposed algorithm has higher accuracy compared with the existing classical regularization methods.
2022(S):113-119.
DOI: 10.16356/j.1005-1120.2022.S.015
Abstract:
H2S is one of the most important characteristic decomposition components of SF6 insulated gas， and the detection of trace H2S is significant for early fault diagnosis of gas insulated electrical equipment. A 1 578 nm wavelength distributed feedback diode laser （DFB-DL） based cavity ring-down spectroscopy （CRDS） experimental platform is developed to monitor the concentrations of H2S in SF6 and SF6/N2 mixture carrier gas. The detection sensitivity is higher than 1×10-6. The absorption cross section parameter σ is vital for calculating the concentration. With repeated experiments using standard gas samples， parameter σ of H2S in pure SF6 and SF6/N2 mixture carrier with different mixing ratios is calibrated. Compared with the simulated σ values， the influence of carrier gas on the broadening of spectral profile is discussed. The variation of absorption cross section σ with different carrier gas mixing ratios is studied as well， so that the calculation of the concentration in the carrier gas of any mixing ratio is possible. Thus， the application of CRDS in trace component detection of gas insulated electrical equipment is promising.
H2S is one of the most important characteristic decomposition components of SF6 insulated gas， and the detection of trace H2S is significant for early fault diagnosis of gas insulated electrical equipment. A 1 578 nm wavelength distributed feedback diode laser （DFB-DL） based cavity ring-down spectroscopy （CRDS） experimental platform is developed to monitor the concentrations of H2S in SF6 and SF6/N2 mixture carrier gas. The detection sensitivity is higher than 1×10-6. The absorption cross section parameter σ is vital for calculating the concentration. With repeated experiments using standard gas samples， parameter σ of H2S in pure SF6 and SF6/N2 mixture carrier with different mixing ratios is calibrated. Compared with the simulated σ values， the influence of carrier gas on the broadening of spectral profile is discussed. The variation of absorption cross section σ with different carrier gas mixing ratios is studied as well， so that the calculation of the concentration in the carrier gas of any mixing ratio is possible. Thus， the application of CRDS in trace component detection of gas insulated electrical equipment is promising.
ZHANG Zijian
,
SHAO Ming
,
SHANG Kai
,
LI Xuekong
,
HUANG Chunliang
,
SHI Jinku
,
CUI Huaxian
,
DONG Yangyang
2022(S):120-126.
DOI: 10.16356/j.1005-1120.2022.S.016
Abstract:
Polygonal coil systems are designed for increasing and more kinds of sensors and electromagnetic systems. This paper presents a method for calculating mutual inductance between polygonal coils including irregular polygons. Based on the Biot-Savart law， the method calculates mutual inductance by dividing a polygonal coil into finite wires， and expresses the magnetic induction intensity generated by the excitation coil as a function of the spatial position of each vertex of the coil. The calculation method of the feasible region of the objective function is updated and the calculation process is simplified， so the calculation accuracy is improved. For octagon coils arbitrarily positioned in space， the accuracy of the algorithm is verified by the simulation and experiment.
Polygonal coil systems are designed for increasing and more kinds of sensors and electromagnetic systems. This paper presents a method for calculating mutual inductance between polygonal coils including irregular polygons. Based on the Biot-Savart law， the method calculates mutual inductance by dividing a polygonal coil into finite wires， and expresses the magnetic induction intensity generated by the excitation coil as a function of the spatial position of each vertex of the coil. The calculation method of the feasible region of the objective function is updated and the calculation process is simplified， so the calculation accuracy is improved. For octagon coils arbitrarily positioned in space， the accuracy of the algorithm is verified by the simulation and experiment.
2022(S):127-134.
DOI: 10.16356/j.1005-1120.2022.S.017
Abstract:
A shear wave electromagnetic acoustic transducer （EMAT） optimized structure is proposed by using circumferential annular Halbach magnet structure. Based on the orthogonal test， the effects of the coil conductor width， the spacing between adjacent conductors， the number of turns and the lifting distance on EMAT energy conversion effect are studied， and the optimal parameter combination is given. The structural design of the Halbach magnet is proposed. The cost coefficient S of the Halbach structure is defined， and the optimal thickness of auxiliary magnetic pole is obtained. The optimized EMAT coil diameter is reduced by 35% and the echo signal strength is significantly improved. Finally， C-scan imaging is carried out on the sample to verify the detection ability of EMAT.
A shear wave electromagnetic acoustic transducer （EMAT） optimized structure is proposed by using circumferential annular Halbach magnet structure. Based on the orthogonal test， the effects of the coil conductor width， the spacing between adjacent conductors， the number of turns and the lifting distance on EMAT energy conversion effect are studied， and the optimal parameter combination is given. The structural design of the Halbach magnet is proposed. The cost coefficient S of the Halbach structure is defined， and the optimal thickness of auxiliary magnetic pole is obtained. The optimized EMAT coil diameter is reduced by 35% and the echo signal strength is significantly improved. Finally， C-scan imaging is carried out on the sample to verify the detection ability of EMAT.
2022(S):135-142.
DOI: 10.16356/j.1005-1120.2022.S.018
Abstract:
This paper presents a method to reconstruct 3-D models of trees from terrestrial laser scan （TLS） point clouds. This method uses the weighted locally optimal projection （WLOP） and the AdTree method to reconstruct detailed 3-D tree models. To improve its representation accuracy， the WLOP algorithm is introduced to consolidate the point cloud. Its reconstruction accuracy is tested using a dataset of ten trees， and the one-sided Hausdorff distances between the input point clouds and the resulting 3-D models are measured. The experimental results show that the optimal projection modeling method has an average one-sided Hausdorff distance （mean） lower by 30.74% and 6.43% compared with AdTree and AdQSM methods， respectively. Furthermore， it has an average one-sided Hausdorff distance （RMS） lower by 29.95% and 12.28% compared with AdTree and AdQSM methods. Results show that the 3-D model generated fits closely to the input point cloud data and ensures a high geometrical accuracy.
This paper presents a method to reconstruct 3-D models of trees from terrestrial laser scan （TLS） point clouds. This method uses the weighted locally optimal projection （WLOP） and the AdTree method to reconstruct detailed 3-D tree models. To improve its representation accuracy， the WLOP algorithm is introduced to consolidate the point cloud. Its reconstruction accuracy is tested using a dataset of ten trees， and the one-sided Hausdorff distances between the input point clouds and the resulting 3-D models are measured. The experimental results show that the optimal projection modeling method has an average one-sided Hausdorff distance （mean） lower by 30.74% and 6.43% compared with AdTree and AdQSM methods， respectively. Furthermore， it has an average one-sided Hausdorff distance （RMS） lower by 29.95% and 12.28% compared with AdTree and AdQSM methods. Results show that the 3-D model generated fits closely to the input point cloud data and ensures a high geometrical accuracy.
2022(S):143-149.
DOI: 10.16356/j.1005-1120.2022.S.019
Abstract:
Combining two Bose-Einstein condensates （BECs） may result in a miscible or immiscible mixture. In this study， we investigate the miscibility-immiscibility transition of binary BEC mixture trapped in an isotropic harmonic potential， with both inter-species s-wave and p-wave scattering interaction included. The mean-field Gross-Pitaevskii equations with p-wave interaction term are numerically solved to obtain the ground-state phase diagram. Due to the p-wave interaction competing with isotropic s-wave interaction， the spatial density profile of binary BEC mixtures transforming from immiscible phase to miscible phase is observed. The p-wave interaction caused miscibility can be observed in current experiments of Bose-Bose mixture tuned near a p-wave Feshbach resonance.
Combining two Bose-Einstein condensates （BECs） may result in a miscible or immiscible mixture. In this study， we investigate the miscibility-immiscibility transition of binary BEC mixture trapped in an isotropic harmonic potential， with both inter-species s-wave and p-wave scattering interaction included. The mean-field Gross-Pitaevskii equations with p-wave interaction term are numerically solved to obtain the ground-state phase diagram. Due to the p-wave interaction competing with isotropic s-wave interaction， the spatial density profile of binary BEC mixtures transforming from immiscible phase to miscible phase is observed. The p-wave interaction caused miscibility can be observed in current experiments of Bose-Bose mixture tuned near a p-wave Feshbach resonance.
2022(S):150-157.
DOI: 10.16356/j.1005-1120.2022.S.020
Abstract:
A lightweight multi-layer residual temporal convolutional network model （RTCN） is proposed to target the highly complex kinematics and temporal correlation of human motion. RTCN uses 1-D convolution to efficiently obtain the spatial structure information of human motion and extract the correlation in the time series of human motion. The residual structure is applied to the proposed network model to alleviate the problem of gradient disappearance in the deep network. Experiments on the Human 3.6M dataset demonstrate that the proposed method effectively reduces the errors of motion prediction compared with previous methods， especially of long-term prediction.
A lightweight multi-layer residual temporal convolutional network model （RTCN） is proposed to target the highly complex kinematics and temporal correlation of human motion. RTCN uses 1-D convolution to efficiently obtain the spatial structure information of human motion and extract the correlation in the time series of human motion. The residual structure is applied to the proposed network model to alleviate the problem of gradient disappearance in the deep network. Experiments on the Human 3.6M dataset demonstrate that the proposed method effectively reduces the errors of motion prediction compared with previous methods， especially of long-term prediction.
21 A Hybrid Method of Extractive Text Summarization Based on Deep Learning and Graph Ranking Algorithms
2022(S):158-165.
DOI: 10.16356/j.1005-1120.2022.S.021
Abstract:
In the era of Big Data， we are faced with an inevitable and challenging problem of “overload information ”. To alleviate this problem， it is important to use effective automatic text summarization techniques to obtain the key information quickly and efficiently from the huge amount of text. In this paper， we propose a hybrid method of extractive text summarization based on deep learning and graph ranking algorithms （ETSDG）. In this method， a pre-trained deep learning model is designed to yield useful sentence embeddings. Given the association between sentences in raw documents， a traditional LexRank algorithm with fine-tuning is adopted fin ETSDG. In order to improve the performance of the extractive text summarization method， we further integrate the traditional LexRank algorithm with deep learning. Testing results on the data set DUC2004 show that ETSDG has better performance in ROUGE metrics compared with certain benchmark methods.
In the era of Big Data， we are faced with an inevitable and challenging problem of “overload information ”. To alleviate this problem， it is important to use effective automatic text summarization techniques to obtain the key information quickly and efficiently from the huge amount of text. In this paper， we propose a hybrid method of extractive text summarization based on deep learning and graph ranking algorithms （ETSDG）. In this method， a pre-trained deep learning model is designed to yield useful sentence embeddings. Given the association between sentences in raw documents， a traditional LexRank algorithm with fine-tuning is adopted fin ETSDG. In order to improve the performance of the extractive text summarization method， we further integrate the traditional LexRank algorithm with deep learning. Testing results on the data set DUC2004 show that ETSDG has better performance in ROUGE metrics compared with certain benchmark methods.
2022(S):166-174.
DOI: 10.16356/j.1005-1120.2022.S.022
Abstract:
Non-convex methods play a critical role in low-rank tensor completion for their approximation to tensor rank is tighter than that of convex methods. But they usually cost much more time for calculating singular values of large tensors. In this paper， we propose a double transformed tubal nuclear norm （DTTNN） to replace the rank norm penalty in low rank tensor completion （LRTC） tasks. DTTNN turns the original non-convex penalty of a large tensor into two convex penalties of much smaller tensors， and it is shown to be an equivalent transformation. Therefore， DTTNN could take advantage of non-convex envelopes while saving time. Experimental results on color image and video inpainting tasks verify the effectiveness of DTTNN compared with state-of-the-art methods.
Non-convex methods play a critical role in low-rank tensor completion for their approximation to tensor rank is tighter than that of convex methods. But they usually cost much more time for calculating singular values of large tensors. In this paper， we propose a double transformed tubal nuclear norm （DTTNN） to replace the rank norm penalty in low rank tensor completion （LRTC） tasks. DTTNN turns the original non-convex penalty of a large tensor into two convex penalties of much smaller tensors， and it is shown to be an equivalent transformation. Therefore， DTTNN could take advantage of non-convex envelopes while saving time. Experimental results on color image and video inpainting tasks verify the effectiveness of DTTNN compared with state-of-the-art methods.
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