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2023 Vol. 42, No. 14 Published: 2023-07-28 1 Inversion study of soft foundation sluice bottom plate emptying based on a GPR surrogate model and a GA-APSO hybrid optimization algorithm LI Huokun1，KE Xianyong1,2，HUANG Wei1，LIU Shuangping1,2，TANG Yiyuan1，FANG Jing1 The floor void of sluice on soft foundation is a very harmful and undetectable disease caused by environmental factors such as water erosion during long-term service of sluice gates. Since the damage area is underwater, it is difficult to be detected by traditional methods. In this paper, a dynamic inversion method based on Gaussian Process Regression(GPR) surrogate model and Genetic Algorithm-Adaptive Particle Swarm Optimization(GA-APSO) hybrid optimization algorithm is proposed to detect the voiding of soft foundation sluice floor.. Firstly, a GPR surrogate model is constructed to characterize the nonlinear relationship between the emptying parameters and the modal parameters of the sluice structure; secondly, an optimization mathematical model for emptying parameter inversion is established based on the GPR surrogate model and the measured modal parameters of the sluice, and the inversion problem is transformed into an objective function optimization solution problem; Finally, in order to improve the accuracy of the algorithm, a GA-APSO hybrid optimization algorithm is proposed to perform the inversion calculation of the objective function for the emptying, and a more reasonable index to judge the relative error between the inversion voiding area and the actual voiding area—area non-coincidence is proposed. In order to verify the performance of the proposed method, the physical model of an indoor soft foundation sluice is used as an example, and two different emptying conditions are set for analysis. The results show that the relative errors of the inverse emptying area and the actual set emptying area of the model are 8.47% and 10.77%, respectively, with smaller relative error values. and the proposed method can effectively inverse perform the emptying of the sluice bottom plate, which can be a new method for inversion detection of soft foundation sluice floor. 2023 Vol. 42 (14): 1-10 [Abstract] ( 304 ) HTML (1 KB)  PDF (2050 KB)  ( 121 ) 11 Calculation method of the wave force on a single cylinder pile induced by solitary waves LU Shenglong，ZHU Jin，JIANG Shangjun，KANG Rui，LI Yongle In order to study the wave load on the bridge pier of a sea-crossing bridge under the action of solitary waves and obtain the simplified calculation method of solitary wave force, the computational fluid dynamics software OpenFOAM was used to simulate the solitary waves in the ocean. Two groups of simulation experiments were carried out under different incoming wave heights and initial water depths. The three-dimensional numerical simulation was performed to directly calculate the wave force on the cylinder, while the two-dimensional numerical simulation was conducted to obtain the velocity field to derive the Morison equation. By comparing with the results of the existing literatures, this paper discusses the applicability of the original Morison equation to the calculation of solitary wave force and the variation law of solitary wave nonlinearity, and verifies the applicability of the modified Morison equation with nonlinear term to predict solitary wave load. The results obtained are as follows. When calculating the solitary wave load, the nonlinear influence can not be ignored, and with the increase of the ratio of wave height to water depth H/d, the nonlinearity of solitary waves becomes stronger and stronger. Compared with the original Morison equation, the modified Morison equation considering nonlinear effects can predict the interaction between solitary waves and cylindrical piles more accurately. When applying the modified Morison equation to predict solitary wave load, the values of wave force parameters CD and CM are uniquely determined by H/d, and have nothing to do with the absolute values of wave height H, water depth d and cylindrical pile diameter D; Based on the results of several simulation experiments, the values of CD and CM in the range of 0.15≤H/d≤0.65 are given, which can provide reference for the rapid calculation of solitary wave load. 2023 Vol. 42 (14): 11-19 [Abstract] ( 200 ) HTML (1 KB)  PDF (1499 KB)  ( 84 ) 20 Adaptive direct fast iterative filtering based rolling bearing fault diagnosis DING Wenhai1,2，ZHENG Jinde1,2，PAN Haiyang1,2，MENG Rui1,2，NIU Limin1,2 Direct fast iterative filtering (DFIF) is a recently proposed nonlinear and non-stationary signal analysis method. Aiming at the problems that the DFIF method needs to preset the adjustment parameter of filtering interval, which lacks adaptability in the process of iterative calculation. In this paper, adaptive direct fast iterative filtering method is proposed based on the instantaneous frequency fluctuation energy difference criterion, which can adaptively determine the optimal filter interval adjustment parameters in the iterative screening process of each layer in the outer loop of DFIF algorithm. The ADFIF method can adaptively decompose a given nonlinear and non-stationary signal into the sum of several approximately narrow band signals whose instantaneous frequency has physical significance and a trend term. Through the simulated and measured signal analysis of rolling bearings, the proposed ADFIF method is compared with original DFIF, the adaptive local iterative filtering, variational mode decomposition, and empirical mode decomposition and the results show that the proposed ADFF method has certain advantages in suppressing mode mixing and noise resistance, and can extract more fault characteristic information of rolling bearing. 2023 Vol. 42 (14): 20-29 [Abstract] ( 304 ) HTML (1 KB)  PDF (2915 KB)  ( 94 ) 30 Motion control of a multi-layer multi-modal platform structure with a tuned liquid damper DOU Peng1，WANG Zhidong1，LING Hongjie2，XU Xiaosen2 Based on the two-way fluid structure coupling theory, the numerical model of tuned liquid damper (TLD) and multi-layer multi-modal platform structure was established in this paper. The effects of TLD damping frequency and installation height on the first two resonant modes of multi-layer structure were systematically studied. The damping force has been quantified by numerical method. Combined with the phase delay relationship of sloshing wave and platform motion, the damping characteristics of TLD on multi-layer multi-modal platform structure were analyzed. The results show that the control effect of different installation positions of TLD is related to the maximum vibration mode of the corresponding mode of the structure. The damping frequency band of TLD can be widened by the frequency doubling excitation generated in the sloshing process. In addition, keeping the mass ratio of 2% unchanged, the multi-TLD system has a more stable vibration reduction effect on the multi-layer structure without local negative excitation. The average vibration reduction ratio at the two resonance points is better than that of other schemes. 2023 Vol. 42 (14): 30-39 [Abstract] ( 145 ) HTML (1 KB)  PDF (3815 KB)  ( 153 ) 40 Failure effect and structure optimization of a fuselage panel under impact load LI Yongpeng1，XU Yuxin1,2,3，YANG Xiang4，LI Xudong5 Under the constraint of non-containment explosion-proof structure, the damage effect of shock wave and plug on the fuselage panel is studied. Taking the fuselage panel at the impact position of directional non-containment explosion-proof structure as the research object, through finite element numerical simulation, the failure mode and degree of shock wave and plug acting on the body panel at different positions under the constraint of non-containment explosion-proof structure are analyzed. Then, in order to limit the damage range of the fuselage panel, we optimize the structure of the fuselage panel at the impact position. The results show that the main failure modes of the fuselage panel under shock wave impact are skin shear plug, rib tearing along and perpendicular to the tendons, and rib fracture, while under plug impact, the skin is torn along and perpendicular to the tendons and the ribs are broken. The influence of impact position on the damage degree of fuselage panel under plug impact is more obvious than that of shock wave impact. The position of the plug impact bar has less damage to the fuselage panel as a whole, so it is a better impact scheme. Vertical reinforcement has obvious restraint effect on the crack expansion of fuselage panel under two impact modes, but the restraint effect is better under the action of end. When the plug hits the position of two bars or single bar, the damage area of vertical reinforcement panel is reduced by 56.0% and 39.0% respectively. The research results can provide guidance for the structural design of non-contained explosion-proof vessels for civil aircraft and the structural design of fuselage panels at the impact position. 2023 Vol. 42 (14): 40-47 [Abstract] ( 177 ) HTML (1 KB)  PDF (2315 KB)  ( 80 ) 48 Influence of guide plates on the side of the edge girder on the VIV performance of the π-shaped composite deck section and its vibration suppression mechanism LEI Wei1,2，WANG Qi1,2，LIAO Haili1,2，LI Zhiguo1,2 The -shaped section with open form is a kind of bluff body section which is prone to vortex-induced vibrations (VIVs). In order to elaborate the VIV performance of a cable-stayed bridge with -shaped composite deck and a main span of 520m, 1:25 large-scale section model wind tunnel tests were carried out to compare the effects of different guide plates arranged on the side of the edge girder on VIV performance of the deck. The experimental results show that significant vertical VIVs exist at -3° and -5° wind attack angles as for the original section. The guide plates on the side of the edge girder with a width of 1.5m and 35° tilt angle can suppress VIVs at all the wind attack angles. Finally, the causes of vertical VIVs and the vibration suppression mechanism of the guide plates are analyzed preliminarily through the numerical simulation of the flow field around the deck. The results show that the guide plates help reduce the size of vortices under the deck, thus mitigating the aerodynamic force and the periodic pressure difference between the upper and lower surfaces of the deck. It is achieved that the factors inducing VIVs are controlled, and VIVs of the deck are suppressed. The results can provide a reference for the design of the aerodynamic countermeasures for -shaped composite deck section. 2023 Vol. 42 (14): 48-55 [Abstract] ( 83 ) HTML (1 KB)  PDF (2403 KB)  ( 64 ) 56 Effect of baffles on the shell side heat transfer performance of a conical spiral tube bundle JI Jiadong1，LU Yu1，ZHANG Jingwei1，LI Feiyang2，DENG Ruyi1 Based on the conical spiral elastic tube bundle (CSETB) heat exchanger, an elastic bundle heat transfer equipment with higher heat transfer performance can be obtained by installing pulsating/drainage baffle plate in the heat exchanger. The vibration enhancement performances of CSETB heat exchanger under different shell inlet velocities and different structural schemes were studied by using two-way fluid-structure coupling calculation method. The results show that the amplitude of CSETB increases with the increase of inlet velocity, and only installing pulsating baffle plate can make CSETB show relatively large high-frequency vibration, while both installing pulsating baffle plate and drainage baffle plate can make CSETB show relatively large low frequency vibration. The installation of baffle plate can enhance the regularity of fluid flow and the stratified distribution of temperature field, and can greatly improve the heat transfer ability of shell side of heat exchanger. Vibration can enhance heat transfer, and the degree of heat transfer enhancement is more obvious at high inlet velocity, and the installation of baffle plate can significantly improve the vibration enhanced heat transfer performance of CSETB. In addition, the existence of drainage baffle reduces the comprehensive heat transfer performance of heat exchanger. 2023 Vol. 42 (14): 56-63 [Abstract] ( 85 ) HTML (1 KB)  PDF (1865 KB)  ( 63 ) 64 Failure mode of a steel-concrete shaft structure in soil under the action of lateral explosion SUN Shanzheng，LU Hao In order to study the failure mode of steel plate-reinforced concrete shaft structure subjected to lateral explosion in soil, the model test and finite element numerical simulation method were used to analyze the failure characteristics of shaft structure under different proportion of detonation distances and the influence of shaft structure end on failure mode and failure degree. According to the failure characteristics of the structure, the failure grade was divided, and the criterion index of failure grade and the corresponding threshold of each failure grade were determined. The effects of concrete strength, thickness-diameter ratio of concrete and thickness-diameter ratio of steel plate on the failure characteristics and degree of shaft structure are analyzed by parametric analysis. The following conclusions were obtained: ①With the decrease of proportional explosion distance, there are four typical failure modes of shaft structure in soil : elastic-plastic dynamic response; plastic hinge line formation; local penetration of shaft wall concrete; punching failure of shaft wall concrete and deformation of steel plate under impact of concrete block; ②According to the deformation characteristics of the shaft structure, the dimensionless circumferential relative displacement , which measures the deformation degree of the circular cross section of the structure, and the dimensionless axial relative displacement , which measures the beam deformation of the structure, were determined as the criterion indexes of the damage degree of the shaft structure, and the threshold range of each damage grade   and   were given quantitatively; ③The blast resistance of shaft structure increases and the damage degree decreases with the increase of concrete strength, the thickness-diameter ratio of steel plate and concrete. 2023 Vol. 42 (14): 64-75 [Abstract] ( 95 ) HTML (1 KB)  PDF (3586 KB)  ( 52 ) 76 Experimental study on the gas-liquid two-phase flow-induced vibration in a U-tube MA Xiaoxu1,2，LIU Shuai1，ZHANG Zheng2，TIAN Maocheng2 The dynamic response characteristic of gas-liquid two-phase flow-induced vibration in a transverse U-shaped tube was studied experimentally. The effects of flow pattern, superficial gas velocity Ug, superficial gas velocity Ul, volume void fraction β on vibration response arms were studied. The results show that the vibration response in the transverse U-tube mainly presents the flapping phenomenon in plane direction at low frequency. The amplitude of the frequency spectrum presents the approximate parabola distribution along the axial measured points of the U-shaped elbow and reaches the maximum at the 90-degree position of the elbow. The order of the arms is slug-wavy flow, annular-wavy flow, annular dispersed flow, plug-bubble flow and plug-stratified flow. For a given Ug, the arms presents a trend of approximately flat growth and then a sharp increase with the increase of Ug. The boundary of the sharp increase is about Ug = 1m/s. For a given Ug, the arms increases with the rise of Ul. For a given β, arms presents a very slow growth trend with the increasing of β. However, when β increase to a certain value, arms increases greatly with the rise of β. The certain value decreases with the increasing of superficial liquid velocity. 2023 Vol. 42 (14): 76-83 [Abstract] ( 101 ) HTML (1 KB)  PDF (1994 KB)  ( 41 ) 84 Experimental validation and numerical analyses of a novel type of vibro-impact tri-mass damper ZHENG Yuqiang1，WANG Jingjing2 A novel type of control device, vibro-impact tri-mass damper (VITM), is proposed. VITM is developed based on three types of mass dampers, including a tuned mass damper, a nonlinear energy sink, and a free mass between them. The middle mass can collide with the two side masses. First, the working principle of VITM is introduced and the equation of motion and impact model are derived. Then, experiment is conducted to validate the theoretical model of VITM. Finally, numerical simulations are performed to examine the energy dissipation feature, parameter influences, frequency and energy robustness, and seismic performance of VITM. The results show that VITM mainly relies on vibro impacts rather than device damping to mitigate structural response. The impacts are within the device thus do not increase the structural acceleration. VITM has stronger frequency and energy robustness than its counterparts and shows excellent control capacity under both impulsive and seismic excitation, providing a new method for seismic protection of engineering structure. 2023 Vol. 42 (14): 84-91 [Abstract] ( 93 ) HTML (1 KB)  PDF (2770 KB)  ( 122 ) 92 Seismic energy response analysis of a concrete-filled steel tube diagrid structure CAI Wenzhe1,2，WANG Bin2,3，SHI Qingxuan2,3，GE Minglan1 Combined with the established axial restoring force model of the concrete-filled steel tube (CFST) column, the elastoplastic time-history analysis of the diagrid tube structure was carried out, and the distribution law of each energy item in the structure was studied. The distribution of hysteretic energy dissipation was analyzed in turn from the three levels of structure-member-floor, and the influence of structural dynamic characteristics and ground motion parameters on the distribution of hysteretic energy dissipation was discussed. The research shows that the structure mainly balances the earthquake input energy through damping energy dissipation and hysteretic energy dissipation. The main energy dissipation components of diagrid tube structure are inclined column and coupling beam. The hysteretic energy dissipation of the inclined column decreases with the increase of the floor and there is an obvious sudden change at the junction of the modules, so the large sudden stiffness change should be avoided in the design. The study reveals the damage mode and energy dissipation mechanism of diagrid tube structure from the perspective of energy, which provides a reference for establishing the seismic damage assessment method of the diagrid structure. 2023 Vol. 42 (14): 92-106 [Abstract] ( 79 ) HTML (1 KB)  PDF (6535 KB)  ( 54 ) 107 Band gaps characteristics and vibration reduction mechanism of power exponential prismatic local resonance phononic crystal plates JIN Xing，ZHANG Zhenhua The hull plate with a new form of phononic crystals was constructed. It is found that the low frequency bandgap and high frequency bandgap can lead to the vibration reduction of the thin-slab structure. The low frequency bandgap of phononic crystals was produced by the locally resonant mechanism, and there is a bandgap in a frequency range of 78-115Hz. The U-shaped dispersion curve hidden in the flat band was found in the dispersion curves of phononic crystals. The frequency band between the U-shaped dispersion curves can effectively reduce the vertical vibration of the plate. The mechanism of high-frequency band gap generation is a local resonance formed by the energy aggregation effect of a power exponential prismatic slope. Height of scatterer is the most important factor in low frequency bandgap. Shape of basal body has no effect on the low frequency bandgap, but has great effect to high frequency bandgap. With the increase of scatterer height, the center frequency of the low frequency band gap decreased. Increasing the power will decrease the start frequency and stop frequency of high frequency bandgap. Increasing the edge thickness will gradually decrease the bandwidth of high frequency bandgap. Compared with the traditional acoustic black hole, the new form of phononic crystals can effectively improve the structural strength of the hull plate, which possesses a certain guiding value in ship structure engineering. The results obtained could provide a reference for the structural vibration control of warship. 2023 Vol. 42 (14): 107-114 [Abstract] ( 93 ) HTML (1 KB)  PDF (2458 KB)  ( 174 ) 115 Dynamic load fast localization and reconstruction based on the Wilson-θ explicit algorithm ZHANG Jing1，YUAN Bo1，ZHANG Fang2 By transforming the Wilson-θ numerical algorithm into an equivalent explicit expression, a dynamic load identification method based on the Wilson-θ explicit algorithm is established. The algorithm is unconditionally stable when the appropriate parameter θ is selected, and avoids the problem that the identified results diverge seriously due to the error accumulation caused by recursive calculation in previous implicit identification algorithms. By introducing response coefficient matrix, the explicit algorithm can flexibly select response types for load identification calculation. At the same time, combined with the variable separation method, the load location information is extracted from the established model matrix, so as to reduce the times of matrix inversion and improve the efficiency of load localization. The load identification method is verified by simulation examples and experimental tests of a simply supported beam. The results show that the  dynamic load fast localization and reconstruction method based on Wilson-θ explicit algorithm can effectively identify the load position and the corresponding time history. Compared with the traditional load identification method, this method has higher accuracy and faster operation efficiency. 2023 Vol. 42 (14): 115-123 [Abstract] ( 70 ) HTML (1 KB)  PDF (1376 KB)  ( 115 ) 124 Fault diagnosis of rolling bearings based on locally joint sparse marginal embedding ZHOU Hongdi，ZHANG Hang，ZHONG Fei Rolling bearing is one of the important parts of machinery and equipment, and it is great significance to the safe operation of machinery and equipment through timely and effective monitoring and diagnosis. In order to address the high dimensionality and information redundancy caused by information fusion in existing bearing fault diagnosis methods, a novel bearing defection diagnosis method based on Locally Joint Sparse Marginal Embedding (LJSME) was proposed. LJSME uses L_2,1 -norm to reconstruct within-class and between-class matrices and introduces local graphs to preserve the neighborhood relations among high-dimensional features, and uses L_2,1 -norm as the regular term of the objective function to obtain the joint sparsity of feature extraction, thus ensuring the effectiveness of feature extraction. The method first extracts a high-dimensional feature dataset consisting of time-domain and frequency-domain information from the bearing vibration signal; then extracts sensitive low-dimensional features in the high-dimensional feature space dataset using LJSME; and finally achieves the fault pattern recognition of rolling bearings using a K-nearest neighbor classifier. The proposed method is validated by two sets of rolling bearing fault datasets, and the proposed algorithm can effectively extract sensitive features of rolling bearing vibration signals compared with other three dimensionality reduction algorithms. 2023 Vol. 42 (14): 124-130 [Abstract] ( 88 ) HTML (1 KB)  PDF (1624 KB)  ( 41 ) 131 Vertical dynamics optimization of a light bus suspension system ZHOU Tingrong1，WANG Liangmo1，WANG Tao1，YUAN Liukai2 In order to improve the ride comfort of a light bus, the matching research of air spring performance and suspension system was carried out. The multi-body dynamics model of the whole vehicle is established, and the accuracy of the suspension simulation model is verified through the K&C bench test of the front suspension and the theoretical calculation of the rear suspension. is too big. A co-simulation platform is built, and the parameters of torsion bar spring and air spring are used as design variables, and radial basis neural network and neural network are used to establish the vertical acceleration surrogate model of driver position and passenger position, and the surrogate model is multi-objective combined with genetic algorithm Optimization, the suspension parameter optimization scheme is obtained. The results show that: when the optimized vehicle passes the impulse road at 20km/h and 30km/h, the maximum vertical acceleration of the passenger position is reduced by 26.46% and 24.88% respectively; The rms value of the vertical acceleration of the position is reduced by 23.72%. At the same time, the smoothness of the driver's position remains basically unchanged, which significantly improves the smoothness of the entire vehicle. 2023 Vol. 42 (14): 131-137 [Abstract] ( 106 ) HTML (1 KB)  PDF (2097 KB)  ( 47 ) 138 Structural damage identification based on the wavelet scattering convolution neural network MA Yafei1，LI Cheng1，HE Yu1，WANG Lei1，TU Ronghui1,2 Damage identification is one of the key issues in the field of structural condition assessment, which is of great importance to ensure structural safety. Deep learning algorithm has led to many breakthroughs in vibration-based structural damage identification, but it is still an urgent technical challenge to obtain the key information on structural damage from massive amounts of data. This paper proposes a multi-type structural damage identification model based on one-dimensional convolutional network (1DCNN) deep learning. The wavelet scattering transform is used to replace the convolutional filter in the first layer of the 1DCNN architecture. The scattering coefficients are used to achieve dimensionality reduction and feature extraction of the original data in the input layer, and the CNN convolutional layer, activation layer and pooling layer are combined to achieve feature enhancement processing of monitoring data. The 1DCNN fully-connected layer and Softmax function are combined to classify the feature data, thus realizing the location and quantitative identification of multi type structural damage. The above frame is verified by two numerical models of steel truss structure and cable-stayed bridge. The results show that compared with the normal convolutional neural network model, the accuracy of structural damage identification based on the wavelet scattering based convolutional neural network is significantly improved, and the accuracy of damage classification is more than 95%. In addition, with the increase of the proportion of environmental noise of sensor data, the accuracy of the wavelet scattering convolutional neural network damage classification slightly decreases but still has high accuracy, indicating that this method has strong robustness and anti noise ability. 2023 Vol. 42 (14): 138-146 [Abstract] ( 156 ) HTML (1 KB)  PDF (3396 KB)  ( 49 ) 147 Swing triggered non-sinusoidal oscillation system and technological parameters for continuous casting mold ZHOU Chao1,2，LI Fengli1，ZHANG Xingzhong2,3，WANG Fang4 By controlling the angular speed of the servomotor to realize all the parameters of non-sinusoidal oscillation adjusted online, an oscillator synchronously driven by two symmetry laid servomotors turning in the opposite direction was proposed. Firstly，the working principle of the oscillator was explained. And the three-dimensional model of the system was established. Secondly, the global function of non-sinusoidal oscillation waveform was analyzed. Meanwhile, the angular speed of servomotor to realize non-sinusoidal oscillation waveform of global function was presented. The calculation methods of technological parameters were given and the multi technological parameter curve was obtained. Based on the technological parameters of a caster for a plant, the synchronous control model of among the casting speed, oscillation frequency and amplitude was determined. The results show that technological parameters of non-sinusoidal oscillation can meet the requirement of value limit in theory, which provide an important reference for shallowing oscillation remark, improving the lubrication condition between mold and slab, enhancing casting speed and slab surface quality further. 2023 Vol. 42 (14): 147-153 [Abstract] ( 82 ) HTML (1 KB)  PDF (1598 KB)  ( 59 ) 154 Energy evolution and failure mechanism of diabase under different stress paths MIAO Shengjun，DUAN Yixuan，YIN Ziwei，LIU Zejing The single & tri axial cyclic loading-unloading pressure test and the constant axial unloading confining pressure test were carried out on the diabase in Lingbao mining area as the research object. The stress-strain curves and damage patterns were analyzed, and the energy evolution process and damage mechanism of diabase under different stress paths were studied. The study shows that in the process of deformation and damage by triaxial cyclic loading-unloading, the area of the hysteresis loop gradually increases with the increase of the number of cycles, and the dissipation energy and elastic energy of the rock sample both increase, and the growth rate of dissipation energy gradually becomes larger, and the growth rate of elastic energy gradually becomes smaller, and the larger the enclosing pressure is, the larger the energy dissipation ratio is, and the fracture expansion and confluence phenomenon inside the rock sample increase significantly; in the process of deformation and damage by constant axial  unloading confining pressure, the influence of the confining pressure on the compressive strength and lateral deformation of diabase increases significantly. In the process of constant axial  unloading confining pressure, the influence of confining pressure on the compressive strength and lateral deformation of diabase is greater; under the same initial confining pressure, the elastic energy density of specimen destruction is greater under the unloading stress path compared with the cyclic loading-unloading stress path. 2023 Vol. 42 (14): 154-161 [Abstract] ( 63 ) HTML (1 KB)  PDF (2010 KB)  ( 44 ) 162 Parameter optimization of a dual mass flywheel considering clutch engagement stability during the starting of a DCT vehicle GUO Zheng1,QIN Datong1,LI Shengwei2,LIU Yonggang1 In the starting process, the fluctuation of engine output torque leads to unstable clutch engagement and affects the ride comfort of the vehicle powertrain. Dual mass flywheel (DMF) can reduce the influence of engine torque fluctuation on clutch and vehicle powertrain. Aiming at the problem that clutch engagement instability affects vehicle ride comfort during the starting process, the influence of DMF stiffness, damping and inertia ratio of primary and secondary flywheel of DMF on clutch engagement stability of DCT vehicle during the starting process was studied by taking Dual clutch automatic transmission (DCT) vehicle as the research object. A multi-objective optimization model with clutch stick slip ratio and vehicle jerk as the objective function was established. The model was optimized by genetic algorithm. The optimal parameter combination of DMF which improves the clutch engagement stability and significantly reduces the vehicle impact was obtained. 2023 Vol. 42 (14): 162-169 [Abstract] ( 99 ) HTML (1 KB)  PDF (1594 KB)  ( 36 ) 170 Modification design and load tooth contact analysis of a cylindrical gear with variable hyperbolic circular arc tooth trace MA Dengqiu1,2,LIU Yongping1,YE Zhenhuan2,LI Dawei1,WEI Yongqiao1 To improve the load-bearing capacity and dynamic characteristics of the variable hyperbolic circular arc tooth trace cylindrical gear (VHCATT cylindrical gear), the modification design method of the VHCATT cylindrical gear’s surface was put forward, that is, the cutter inclination method in the direction of tooth line and the parabola modification blade method in the direction of tooth profile. Firstly, according to the gear meshing principle and the modified tooth surface shaping principle of the VHCATT cylindrical gear, the modified tooth surface equation was derived, and the tooth surface reconstruction was realized by using MATLAB and UG. Secondly, the tooth contact analysis was to calculate the tooth surface clearance. At the same time, the contact point flexibility matrix was calculated by using the finite element method, and the load-bearing contact nonlinear mathematical programming model was established to obtain the load-bearing meshing characteristics further. Then, the influences of cutter inclination angle, parabolic coefficient and parabolic vertex position on load distribution and load transmission error of modified tooth surface were analyzed. The results show that: the reasonable cutter inclination angle and parabolic vertex position can effectively reduce the load of the tooth surface and improve the system load transmission error characteristics. The reasonable parabolic coefficient can improve the sudden change of load in the intermeshing of single tooth and double tooth. The further design and industrial applications of the VHCATT cylindrical gear can be accomplished based on the result. 2023 Vol. 42 (14): 170-179 [Abstract] ( 117 ) HTML (1 KB)  PDF (2518 KB)  ( 40 ) 180 Stability and sensitivity of a 4-1 type cable-driven parallel robot LIU Peng1,2,CAO Xiangang1,ZHANG Xuhui1,QIAO Xinzhou1 A 4-1 cable-driven parallel robot (CDPR) has excellent performance and good application potential, but it is crucial to evaluate and ensure the stability of the robot. Therefore, in this paper, the stability measure method of the robot is investigated, and furthermore, a stability measurement method with the position influencing factors and the cable tension influencing factors is proposed. The stability sensitivity analysis model for the robot is established, and the influence degree of the positions of the end-effector and cable tensions on the stability is explored and analyzed. The correlation degree is proposed to investigate and measure the influence degree of the factors on the stability for the robot. The presented stability evaluation model and sensitivity analysis model are simulated on a cable-driven gangue sorting robot, and the position set of the end-effector where the end-effector meets the predetermined stability requirements is obtained. The results show that the stability of the cable-driven gangue sorting robot is sensitive to the cable tensions, and in more detail, the correlation degrees of the cable tensions are 0.9387-0.9647; and while, the correlation degrees of the positons of the end-effector are 0.5439-0.7743. 2023 Vol. 42 (14): 180-188 [Abstract] ( 92 ) HTML (1 KB)  PDF (1295 KB)  ( 34 ) 189 Experimental research on monitoring the alternating stress of the prestressed steel strand based on the method of magnetic resonance LIU Huiling1,2,ZHANG Hong1,2,ZHANG Senhua1,2,XIA Junfeng1,2,ZHOU Jianting1,2 The alternating stress of the prestressed steel strand is difficult to measure. In order to clarify the applicability of magnetic resonance method for monitoring the alternating stress of prestressed steel strand, based on the magnetoelastic effect and hysteresis effect, the inductance variation of induction coil induced by tensile strain effect during stress alternation is analyzed, and the steel stranded wire stress monitoring test under the action of the alternation load was carried out. Changes of corresponding sensor induced voltages under different alternating load is researched, the corresponding relationship between the sensor induced voltages and the alternation load is clarified, and the influence mechanism of the alternation load on the sensor induced voltages is revealed. The results show that there is a linear relationship between induced voltage and load, and the stress monitoring error is less than 5%. The magnetic resonance method can monitor the alternating stress of prestressed steel strands. 2023 Vol. 42 (14): 189-197 [Abstract] ( 64 ) HTML (1 KB)  PDF (2874 KB)  ( 20 ) 198 Adaptive time-stepping increment-dimensional precise integration method for solving structural dynamic equations HUANG Yuxi1,CUI Ying2,YANG Guogang1 The increment-dimensional precise integration method is a high-precision step-by-step integration algorithm for solving structural dynamic equations. The step size will have a great influence on the calculation accuracy of the algorithm, and it is difficult to determine the appropriate step size in practical applications. To meet the requirements of accuracy and efficiency in the calculation, an estimation method of calculation error was proposed, and an adaptive time-stepping increment-dimensional precise integration method was established based on the estimation error and iterative convergence speed. The numerical results of three structural dynamic equations show that when considering all kinds of linear and nonlinear vibration problems, the proposed method can quickly and effectively control the calculation step size under the premise of ensuring the calculation accuracy, and only requires less additional calculation consumption, which significantly improves the efficiency of the increment-dimensional precise integration method， making the method more computationally advantageous and practical in solving structural dynamic equations. 2023 Vol. 42 (14): 198-203 [Abstract] ( 95 ) HTML (1 KB)  PDF (1428 KB)  ( 96 ) 204 Water immersion nonlinear ultrasonic wave mixing method for fatigue crack inspection L Hongtao1,JIAO Jingpin2,WANG Juntao1,LIU Zhiyi1,LI Feng1,ZHANG Xiangchun1,SHI Liang1 The water-immersion non collinear shear wave mixing method was researched for fatigue crack detection in this paper. Using the developed water-immersion non-collinear shear wave mixing detection system and signal processing method of polarity reversal, the experiments of fatigue crack inspection were carried out, and the influence of the two exciting waves’ interaction angle and frequency ratio on wave mixing effect were studied. Then, the two-dimensional automatic scanning inspection was conducted on the sample blocks with fatigue crack. It is shown that the polarity reversal method can be used for wave mixing effect extraction. The optimal interaction angle and frequency ratio in the case of fatigue crack deviate from the resonance conditions. The fatigue cracks in the steel structure can be detected, located and quantified by using the two-dimensional scanning of shear wave mixing. The work makes a beneficial exploration for the engineering application of nonlinear ultrasonic wave mixing. 2023 Vol. 42 (14): 204-210 [Abstract] ( 71 ) HTML (1 KB)  PDF (2736 KB)  ( 67 ) 211 Damping characteristics of filling layer self-compacting concrete applied in a slab track system CHEN Junhao1,XIE Youjun1,ZENG Xiaohui1,LIU Jinhui2,GUO Taoming2,GUAN Jibo3,LONG Guangcheng1 Damping properties have an important influence on the dynamic behavior of civil engineering structures. However, there has been no research on the damping performance of filling layer self-compacting concrete (SCC) of subway slab track. In this paper, the MTS test system was used to study the influence law and variation mechanism of different stress amplitude, rubber content and size on the hysteretic energy and loss factor of SCC, and the hysteretic energy of SCC was numerically simulated. The results showed that the hysteretic energy of SCC increased first slowly and then rapidly with the increase of stress amplitude, which was closely related to its damage evolution and dynamic elastic modulus degradation, and the energy dissipation of internal defects was the main damping mechanism of SCC; The hysteretic energy was a power function relationship with the stress amplitude, among them, the power exponent value of SCC was the smallest, indicating that the nonlinear degree of SCC was the lowest; Rubber significantly increased the damping performance of SCC. Under the same stress amplitude, the hysteresis energy of SCC increased with the increase of rubber content and the decrease of size. The Kelvin model can be used to simulate the hysteretic energy of SCC under cyclic loading, and the theoretical value was in good agreement with the experimental value. 2023 Vol. 42 (14): 211-219 [Abstract] ( 64 ) HTML (1 KB)  PDF (2536 KB)  ( 24 ) 220 Impact resistance of seawater sea-sand concrete beams reinforced with BFRP bars ZHU Deju,ZHONG Weilin,XU Zhenqin,LIU Zhijian,GUO Shuaicheng,LI Anling In order to study the impact resistance of Seawater Sea-sand Concrete (SSC) beams reinforced with Basalt Fiber Reinforced Polymer (BFRP) bars, the impact responses of BRP-SSC beams with different reinforcement ratios (0.23%, 0.48%) and concretes strengths (30MPa, 50MPa) were tested by using a drop-hammer impact equipment under different impact energies (1818J, 2727J, 3636J, 4848J), and the residual load-carrying capacity of the beams was also tested after impact. The experimental results indicate that the failure mode of BFRP-SSC beam changes from bending failure to shear failure with the increase of impact energy, and the residual load-carrying capacity factor decreases gradually. Increasing reinforcement ratio or seawater sea-sand concrete strength can effectively decrease the maximum midspan deflection of the beams, and increase the initial peak impact force and impact resistance. This study can serve as important reference for the impact resistance design of the BFRP-SSC beam. 2023 Vol. 42 (14): 220-228 [Abstract] ( 87 ) HTML (1 KB)  PDF (3272 KB)  ( 61 ) 229 Online detection method for bearing incipient faults based on contrastive learning WANG Yanhong1,WEN Xiaohuan1,JIE Yongqin1,WANG Shaowei2 Incipient fault detection is not only an important role in prognostics and health management, but also has an increasing practical value in industry. This paper proposes a novel online detection method for bearing incipient fault based on contrastive learning from the perspective of industrial big data. Firstly, a novel deep encoder is proposed based on depth-wise separable convolution and residual connections, which is able to extract features from signal effectively. Then, contrastive learning method is utilized to train the proposed encoder by setting up a specific proxy task. The trained encoder is able to learn differences between signal samples. Finally, a novel online detection algorithm is proposed. The algorithm is able to detect abnormal condition and incipient fault effectively. Experiments are carried out on the XJTU-SY dataset. The results demonstrate our method outperforms existing ones and contributes to enriching bearing health management method under different working conditions. 2023 Vol. 42 (14): 229-236 [Abstract] ( 134 ) HTML (1 KB)  PDF (1699 KB)  ( 67 ) 237 Paving density recognition based on the vibration characteristics of a screed device LUO Qingyun1, LIU Honghai1, WU Ping2, SHI Yanni1 To detect the paving mixture density, the contact mode between tamper and mixture was analyzed. According to contact mode between tamper and mixture, screed device vibration was divided into four states. Two-degree-of-freedom vibration model was established. The model was solved by Newmark-β method. Screed device displacement and acceleration during paving operation were obtained. The relations between screed displacement amplitude、acceleration amplitude and screed vibrator frequency、tamper frequency、mixture characteristics were analyzed. Screed device acceleration frequency spectrum was obtained. Experimental research was carried out. The results show that the screed device acceleration spectrum contains the screed vibrator frequency、the tamper frequency and its harmonic components. The amplitude ratio of tamper main frequency to screed vibrator main frequency in acceleration spectrum increases with paving mixture density, which can be used to detect paving mixture density. The research results can provide references for detecting paving density and improving pavement quality. 2023 Vol. 42 (14): 237-244 [Abstract] ( 70 ) HTML (1 KB)  PDF (2095 KB)  ( 27 ) 245 Bearing fault diagnosis based on deep dynamic domain adaptation WANG Junhui, LEI Wenping, LIU Huajie， WEI Lijun， HAN Dongyang Aiming at the problem that the data distribution of source domain and target domain in transfer learning is very different, and it is difficult to adapt to the dynamic changes of marginal distribution and conditional distribution in traditional learning, a bearing fault diagnosis method based on deep dynamic domain adaptation is proposed. In the domain adaptation layer, a dynamic distribution adaptation method is introduced, and edge distribution alignment and conditional distribution alignment are performed by domain classifiers, and dynamic domain adaptation is performed by dynamically measuring the contribution of conditional distribution and edge distribution to the domain according to the balance factor. Through the migration diagnosis test and comparative analysis of bearing data sets of Case Western Reserve University and Jiangnan University under variable working conditions, the accuracy of cross-domain diagnosis is effectively improved, and the effectiveness and excellence of the proposed method are verified. 2023 Vol. 42 (14): 245-250 [Abstract] ( 92 ) HTML (1 KB)  PDF (1574 KB)  ( 50 ) 251 Analysis of TLP dynamic responses under tendon breakage LIU Weixing1，LIU Lei1， WU Haitao2， CUI Lin3， WANG Xin1， ZHANG Zhiyang1 The dynamic behavior of a tension leg platform (TLP) under different damaged mooring conditions is studied. A fully-coupled numerical tool ANSYS/AQWA is used to develop a nonlinear hull-tendon model, and an effective method for simulating tendon failure is proposed. The transient effects of tendon breakage, the transient responses of the platform for simultaneous and progressive tendon failure, and the performance changes of the platform after tendon failure are studied. The results show that, first, tendon breakage can lead to transient overshoots of the platform; Second, the transient responses caused by simultaneous tendon failure are more significant than those for progressive tendon failure; Third, the performance of the platform has a significant change after tendon failure. Therefore, the effects of tendon breakage on the dynamic response of the platform should be examined in advance to prevent the safety of the platform from being threatened. 2023 Vol. 42 (14): 251-259 [Abstract] ( 95 ) HTML (1 KB)  PDF (2505 KB)  ( 25 ) 260 Parameter prediction model of Clough-Penzien power spectrums considering random effects and ground motion synthesis DING Jiawei1,2, L Dagang1,2, CAO Zhenggang1,2 There have existed many investigations on the prediction equations of typical ground motion parameters, such as PGA, PGV, SAS, IA, DS, among other. However, there has been little research on prediction equations of power spectrum model parameters, which represent ground motion frequency-spectrum characteristics. In view of the close relationships between the spectral characteristics of ground motions and source characteristics, propagation path and site conditions, a prediction model of Clough-Penzien power spectrum model parameters is established in this paper based on the physical mechanism of ground motion propagation. In order to better describe the correlation between different records of different seismic events, considering the random effect of the model, the prediction random effect model of spectral parameters is established. The improved one-time iterative regression algorithm of random effects is used to conduct regression analysis on the prediction random effect models of various parameters of Clough-Penzien power spectrum model of various sites, and the model coefficients are determined. Finally, combing with the physical propagation model of phase spectrum and the prediction model of Clough-Penzien power spectrum parameters proposed in this paper, a random function model of "source propagation-site" physical propagation mechanism is constructed. It is shown by a practical example that the prediction equation model of spectral parameters proposed in this paper fits well with the actual power spectrum, and the time-frequency characteristics of the simulated seismic records are very close to those of the original seismic records, so it is helpful to seismic hazard, fragility, and risk analysis as well as seismic design and evaluation of engineering structures. 2023 Vol. 42 (14): 260-269 [Abstract] ( 108 ) HTML (1 KB)  PDF (2107 KB)  ( 30 ) 270 Influence of accumulator parameters on the hydraulic impact of a chopping and cutting load sensing system CHEN Yuanling, CHEN Chengzong,PENG Zhuo,CHEN Haonan,WANG Mengqiao,SHI Hao In the process of sugarcane mechanization harvesting, the load with large amplitude fluctuation and the frequent operation of multi-way directional valve produce large hydraulic impact. In this paper, the sugarcane chopping and cutting load sensitive system of sugarcane combine harvester is studied, and an accumulator is added at the outlet of pump to suppress hydraulic shock. Based on the measured load data of sugarcane, the simulation model of chopping and cutting load sensing system is established based on AMESim. The influence rule of accumulator parameters on hydraulic shock of sugarcane chopping and cutting load sensing system and the optimization matching method are studied, and the simulation results are verified by experiments. The results show that the closer the pre-charging pressure of the accumulator is to the working pressure, the better the pressure shock suppression effect is, and the faster the pressure response speed is. The optimal range of the pre-charging pressure of the accumulator is 50% to 83% of the normal working pressure of the system. 2023 Vol. 42 (14): 270-277 [Abstract] ( 64 ) HTML (1 KB)  PDF (2128 KB)  ( 16 ) 278 Experimental study on the flow-induced vibration of two tandem stepped cylinders in uniform flow JI Chunning1, ZHANG Yan1, YIN Tong1, ZHAO Yawei1, YUAN Dekui2, XU Dong1 Flow-induced vibration of two tandem stepped cylinders in uniform flow is investigated experimentally in the range of Reynolds number from 570 to 5000, with the coverage ratio of the stepped cylinders being R=50% and the spacing ratio being D/d =1.5. In the experiments, the upstream cylinder is fixed and the downstream cylinder vibrates freely in the cross-flow direction. Four spacing ratios of s/D* = 2, 4, 8 and 16 are investigated with the in-phase and out-of-phase arrangements of the upstream and downstream cylinders being considered. The results show that the spacing ratio has a significant effect on the interaction between the tandem stepped cylinders, and a change in spacing ratio alters the gap flow pattern between the cylinder which leads to the different vibration characteristics of the downstream cylinder. For the out-of-phase arrangement of the tandem cylinders, the downstream cylinder undergoes wake-induced vibration when the spacing ratio is small and the reduced velocity is high. That is, the amplitude increases significantly with the increasing reduced velocity. However, when the spacing ratio s/D* ≥ 8, the influence of the geometry shape phase is negligible. 2023 Vol. 42 (14): 278-286 [Abstract] ( 96 ) HTML (1 KB)  PDF (1692 KB)  ( 17 ) 287 Long-term characteristics of damping ratio of the Z24 bridge influenced by different factors SHANG Zhiqiang1,2, XIA Ye3, SUN Limin3,4,5, XIN Gongfeng1,2 To investigate long-term characteristics of damping ratio of Z24 bridge influenced by different factors, a time series semantic segmentation method was introduced to extract free attenuation data segments from monitored acceleration of Z24 bridge. Then, about 10-month damping ratio of 1st vibration mode was calculated using exponential attenuation method. Based on the calculated damping ratio, influences of three factors including temperature, vibration intensity, and structural damage were analyzed. The results show that there exists a strong correlation between the damping ratio of Z24 bridge and temperature variation. Specifically, the damping ratio exhibits an increasing trend followed by a decreasing trend after the temperature drops below 0℃, while the damping ratio exhibits a linearly decreasing trend after the temperature goes beyond 0℃, in which time the correlation coefficient even reaches 0.98. The vibration intensity presents little impact on the damping ratio under both of the excitation of vehicles passing below the bridge and the excitation of drop weight on the bridge. The structural damage also exhibits very limited influences on the damping ratio, thus further investigation is still required in the future to obtain effective damage features based on the identified damping ratio. The influences of the above factors should be considered in damping ratio-related applications including structural control and damage detection to achieve reasonable and reliable results. 2023 Vol. 42 (14): 287-295 [Abstract] ( 91 ) HTML (1 KB)  PDF (2204 KB)  ( 40 ) 296 Disturbance observer based trajectory tracking control for a riveting robot LI Zonggang1,2， LI Longxiong1,2, DU Yajiang1,2, CHEN Yinjuan1,2 In order to solve the problem of higher chatter and lower trajectory tracking accuracy caused by external disturbances during the operation of the riveting robot, an adaptive control method combining a disturbance observer and a fractional-order sliding mode controller is designed. Firstly, the local dynamics model of the riveting robot is established by introducing the time delay estimation strategy, and the visible disturbances to the system model are observed in real time by using the disturbance observer, and secondly, the fractional-order sliding mode surface is designed to replace the traditional sliding mode control for the chatter, and the new convergence law is used to make the system move continuously and smoothly on the switching surface, and the adaptive strategy is designed to fully compensate for the external disturbances. Finally, the effectiveness of the designed controller is demonstrated by the Lyapunov function. The results show that the peak tracking errors of each joint of the robot are reduced by 50%, 59% and 63% respectively, compared with the fractional-order sliding mode control, the controller can not only effectively eliminate the chattering problem caused by the large interference of the system, but also improve the robustness and trajectory tracking accuracy of the riveting robot. 2023 Vol. 42 (14): 296-305 [Abstract] ( 94 ) HTML (1 KB)  PDF (1936 KB)  ( 144 ) 306 Uncertainty quantification for the aerodynamic noise of high-speed aircrafts in dynamic atmospheric environment ZHENG Linghua1,2, CHEN Qiang1,2, LI Yanbin1,2,FANG Fang3, FEI Qingguo1,2 Due to the dynamic variation of atmospheric parameters in near space, the aerodynamic noise of high-speed aircrafts presents significant uncertain characteristics, which is useful for structural design. In this paper, a typical wing of high-speed aircraft is taken as research model. First, the reduced order model for aerodynamic noise prediction is established, by using proper orthogonal decomposition and surrogate model, to improve the aerodynamic noise analysis efficiency. Then, based on the reduced order model and random distribution characteristics of the atmospheric parameters, the aerodynamic noise uncertainty characteristics are efficiently quantified. Finally, the influence of atmospheric parameters on aerodynamic noise is studied by sensitivity analysis. Results show that the uncertainty characteristics of aerodynamic noise could be accurately and efficiently quantified using the reduced order model. A nonlinear relationship between the atmospheric parameters and the aerodynamic noise can be observed. Shock wave and boundary layer separation behind shock wave are the important reasons for the aerodynamic noise violent fluctuation. The density variation contributes greatly to the uncertainty of aerodynamic noise. 2023 Vol. 42 (14): 306-313 [Abstract] ( 124 ) HTML (1 KB)  PDF (1637 KB)  ( 73 ) 314 Performances of a reaction wheel vibration isolator with a spring made ofmanganese-copper high damping alloy WANG Yixin， XU Yang， SHENG Xiaowei， YIN Xianbo In order to solve the problem of satellite imaging quality degradation caused by micro-vibration of reaction wheel, a six-dof passive vibration isolation system was designed according to the micro-vibration characteristics of reaction wheel. The vibration isolation system reduces the overall modal frequency of the system through spring stiffness design, and the high damping manganese-copper alloy is used as vibration isolation element material to improve vibration energy attenuation. Firstly, the dynamic model of vibration isolation system was established by Lagrange equation. Considering the influence of stiffness on vibration isolation performance, different structural parameters of spring were designed for comparison. The relationship between the stiffness ratio of diameter-axis and the fundamental frequency of the system was analyzed, and the optimal structural parameters of vibration isolation were determined. Secondly, the finite element method is used to analyze the modal and vibration transfer characteristics of the vibration isolation system, and the vibration suppression performance under various degrees of freedom is discussed. Finally, a Kistler micro-vibration test platform was built to measure the micro-vibration of the reaction wheel before and after vibration isolation, and the vibration reduction effect of the isolator was analyzed and verified. The results show that the vibration isolation effect of the vibration isolation system is significant in six disturbance directions and in the range of middle and high frequency, and the vibration isolation effect is more than 40dB at 1000Hz main frequency vibration. The vibration reduction percentage of the maximum vibration amplitude in the Fz direction from 0 to 2500rpm is 92.42%. 2023 Vol. 42 (14): 314-320 [Abstract] ( 86 ) HTML (1 KB)  PDF (2043 KB)  ( 54 ) 321 Energy flow model for a high-frequency vibrating plate with free-layer damping treatment JIANG Xudong1, HAN Yuedong2, TENG Xiaoyan2 To predict the high-frequency vibrational response for a plate with free layer damping (FLD) treatment, the energy density equation considering high damping effect was derived using energy flow analysis (EFA) method combined with complex stiffness method. Wave transmission analysis was performed for power transfer relation at discontinuous interface of FLD. Then the energy density equation for a plate with partial FLD treatment is also achieved by EFA of coupled plate. The energy finite element method (EFEM) was employed to solve the derived energy density equations for the plate with full or partial FLD treatment. Simulated results obtained by EFEM were compared with those obtained by modal superposition method, which were used as a reference. It demonstrates that the proposed EFA model can predict the energy density of the high-frequency vibrating plate with FLD treatment with reasonable accuracy. 2023 Vol. 42 (14): 321-330 [Abstract] ( 94 ) HTML (1 KB)  PDF (2273 KB)  ( 124 )

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