最新刊期
卷 45 ， 期 3 ， 2013
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Numerical Simulation for Air Cushion Isolation of High Arch Dams Considering the Nonlinearity Effect
摘要：Abstract:In order to study the influence of nonlinearity to air cushion isolation effects of high arch dams,the gas-liquid-solid tri-phase coupling numerical model of the air cushion isolation control of high arch dams was presented,in which the material nonlinearity of air cushion was considered.The isolation effect simulation of Jinping high arch dam under Wenchuan seismic wave was carried out,and the results were compared to the ones neglecting the air cushion nonlinearity.It was showed that air cushion reduces the hydrodynamic pressure significantly.In normal and dead water level,the maximum of hydrodynamic pressure is reduced 70.2% and 75.3%, respectively with 1 m air cushion.Air cushion also causes a general reduction of tension stress and an improvement of stress distribution.Thereby,the anti-seismic capacity of the arch dam is improved significantly.Compared with the results neglecting the air cushion nonlinearity,the error of hydrodynamic pressure is less than 10%.Therefore,when the proportion of hydrodynamic pressure in total pressure is smaller,the material nonlinearity of air cushion can be ignored in air cushion isolation simulation of high arch dams.关键词：high arch dam;dynamic control;air cushion isolation;hydrodynamic pressure;fluid-solid coupling- 2080
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发布时间：2023-11-14 - 摘要：Abstract:Based on an expression with a fractional calculus form,a new four-element nonlinear viscoelasto-plastic rheological model was proposed,by using the Riemann-Liouville fractional calculus theory and drawing ideas from the classic element combination modeling.The constitutive equation and creep equation of the model were given, in which the creep strain rate at the first,second and third stages can be effectively controlled by adjusting creep parameters β1 andβ2,respectively.The prediction of the model on existed data was examined,and the result showed that the nonlinear rheological model can effectively describe three steps of rock creep with comparable prediction accuracy to existed theoretical models. It was found that in a lower stress level,the model can reflect the primary creep and steady creep,while if the stress level exceeds the long-term rock strength, the model will reflect the accelerated creep. Meanwhile, the use of the soft elements plays a role to reduce the element number and parameters in the model.关键词：fractional calculus;soft element;nonlinear creep;viscoelasto-plastic
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发布时间：2023-11-14 - 摘要：Abstract:To solve the problem that the flow pattern was in contradiction with the demand of fish, the fish passage structure was studied.Taking the rare species Schizothorax Prenanti living in the Dadu River as an example,an velocity index system was established to describe the fish’s swimming ability by using a series of annular flume tests,and a feasible structure and layout of fishway for creating flow pattern were proposed by analyzing numerical simulation and physical model data.The results showed that the three-dimensionalk-εturbulence model coupling with the VOF model dealing with free surface problem is feasible to simulate the fishway flow field. The maximum velocity appears at the end of waterfall after the vertical slot,the biggest influences on flow field is the slope of fishway and the Schizothorax Prenanti is adapted to the slope of fishway less than 2.6%.关键词：Schizothorax prenanti;swimming ability;vertical slot fishway;creating flow pattern
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发布时间：2023-11-14 - 摘要：Abstract:A high steep hill with two-side slopes and a high steep hill with one-side slope near National Road 213 were used as a prototype.A full process from initial deformation to sliding of the slope during ground shaking was simulated by a new discrete element method(CDEM).The results showed that there are some commonalities and differences about the dynamic responses between the slopes with two-side and one-side.The stress concentration phenomenon appears at the top of the sliding mass firstly,and then some tension failure points and some shear failure points appear there, which expands toward the toe of the sliding mass from the top of that along the structural plane.The number of tension failure points gradually increases.At last,the toe of the sliding mass breaks,and then the sliding mass shears out from the toe,which results in the landslide.There are some differences in the accelerations on the slope and in the slope,as well as the Fourier spectrums of accelerations and the responses of the accelerations on the slope,which fully verifies that there are some remarkable effects of the slope angle and the slope structural kinds on those dynamic responses.关键词：high steep slope;earthquake;dynamic responses;CDEM;landslide
- 2038
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发布时间：2023-11-14 - 摘要：Abstract:The drag force of vegetation was introduced in the depth-averaged momentum equation and the analytical solutions of depth-averaged velocity and bed shear stress were presented. Based on the feature of cross-section of vegetated rectangular compound channels,the force balance equation was built at the interface between main channel and floodplain and then two boundary conditions were carried out.The predicted results of these two boundary conditions were compared and their results were almost the same at a high relative flow height while some differences were in the shear layer at a low one.The continuity condition which contained the wall shear stress in the main channel provided better predictions.Finally,eight groups of experimental data were applied to verify the predicted ability of the better boundary condition.The results showed that optimal secondary flow coefficients in each domain result in much better lateral distributions of depth-averaged velocity and bed shear stress,especially in main channels.Good predicted results can be obtained by choosing appropriate secondary flow coefficients in each case.
- 2488
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发布时间：2023-11-14 - 摘要：Abstract:In view of the worse geological structure in Xiaowan high arch dam abutment at EL.1 210 m,a geomechanical model was used to simulate its geological structure.Through overloading failure test,the failure mechanism of natural foundation and strengthening foundation was compared.The test results showed that after taken reinforcement measure,the dam abutment displacement becames less,damage area reduces, overload coefficient KP is improved from 2.2 to 3.0 ~ 4.0.According to the test results,it was proved that this reinforcement measures can change transfer direction of the thrust and enhance deformation ability.The proposed design method is not only helpful to ensure the stability of the dam abutment，but also provides valuable experiences for the reinforcement of the dam abutment in similar projects.关键词：stability of dam abutment;geological mechanical model test;transmission and shear resistance structure;failure mechanism;reinforcement measures evaluation
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发布时间：2023-11-14 - 摘要：Abstract:Based on pseudo-static experimental results of 16 steel box columns and numerical results of 85 calculated members,the hysteretic behaviors of eccentrically constant-compressed steel box columns under cyclic lateral loading were investigated.By regression analysis on experimental and numerical results,the formulas for key points in skeleton curve were obtained.According to the experimental results,the degeneration rules of strength and stiffness of eccentrically constant-compressed columns under cyclic lateral loading were suggested.The restoring force model of steel box columns in large span spatial structures was proposed.Finally,the comparisons between results from the restoring force model and experiments were conducted.It was found that the restoring force model shows high solution precision,especially in the degeneration property of strength and stiffness of eccentrically constant-compressed columns under cyclic lateral loading. The restoring force model could be applied to the elastic-plastic analysis of large span spatial structures.关键词：steel box column;pseudo-static experiment;finite element simulation;skeleton curve;hysteretic rules;restoring force model
- 2380
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发布时间：2023-11-14 - 摘要：Abstract:Through field survey, it was found that the great majority of the landslides in Xiangjiaba segment of Jinsha River develop from the dam site to the Xinshi town segment where outcrop Jurassic strata, and most of these landslides are bedding slopes. The bedding landslide is apt to revive and the bedding bank slop is prone to revive after the reservoir impounding. A landslide database was established through field survey and with the help of geotechnical investigation dates. The effect of different dip angles to the development of landslides was studied by the contribution rate method, which is also applied to the bank structure types and river bought types. A quantitative statistic on those three factors was also made to analyze the contribution rate to landslides.The results showed that the dip angles of bedding surface to the maximum contribution rate are between 10° and 19°, the minimal contribution rate is between 30° and 34°.Similar to the dip angles,and the maximum contribution rate is gently dipping outer forward layered bank slope ,the minimal contribution rate is medium dipping outer forward layered bank slope.The concave bank of the river has the maximum contribution rate while the convex bank of the river has the minimal one. These results were coincide with the actual situation, which offers a quantitative criteria for evaluating the risk of reservoir bank slop and provides basis for planning and constructing of the reservoir in the future.关键词：Xiangjiaba reservoir region;bank structure;dip angle of strata;contribution rate;landslide
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发布时间：2023-11-14 - 摘要：Abstract:In order to investigate the impact of sediment deposition at confluence reaches in reservoir areas on the normal operation of reservoir,based on the summaries of existing studies on changes of deposition and erosion at confluence reaches,Baishi Reservoir on Daling River in Liaoning was used as the research object,the influence of different coming sediment,confluence angles and flood feathers at main stream and branches on sedimentation characteristics at different confluence reaches in reservoir areas were explored.Research results showed that under the same condition of coming sediment,confluence angle and probability of flood at main stream and branches,sediment deposition in confluence reaches of perennial reservoirs is much bigger than that of fluctuating backwater area. Sediment deposition in confluence reaches of Mangniu River is relatively bigger in perennial reservoirs of Baishi River,sand bars are formed at longitudinal direction in main stream of confluence reaches. Sand bars development will bring adverse effect to reservoir normal use.关键词：reservoir area;confluence flow;deposit;BaiShi reservoir
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发布时间：2023-11-14 - 摘要：Abstract:In order to comprehensively study the flow field characteristics of pumped storage power station’s whole flow system in pump mode, a geometric model of the flow system including diversion tunnel,surge chamber,penstock,pump turbine unit and tailrace tunnel was established. The flow characteristic in pump mode was simulated by control equations which considered gravity influence and shear stress transmission SST k-ω mode. Hydraulic losses were calculated and analyzed based on the numerical results. Results showed that using the numerical simulation method considered gravity influence could get more realistic results with the efficiency error of 0.9% and lift error of 1.0% in the rated condition, which are less than 3.5% and 3.0% in other cases,respectively.Hydraulic loss of unit-block is significant,by contrast,it is small in the water conveyance system that takes up 10.4% of total hydraulic loss averagely.The main reason of unit-block’s hydraulic loss is different at different flow conditions with the same guide vane opening, flow pattern disordered at inlet of runner and asymmetric at outlet of runner intensified hydraulic loss at the low flow conditions,while the hydraulic loss at high flow conditions mainly because the opening of guide vanes is not big enough.关键词：pumped storage power station;hydraulic loss;whole flow system;gravity field;numerical simulation
- 1983
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发布时间：2023-11-14 - 摘要：Abstract:Considering the near-bank fluvial erosion,the soil composition and mechanical properties,the degrees of riverbank stability for composite bank in the Upper Jingjiang Reach (UJR) were analyzed during different water level periods using BSTEM,and the process of bank failure was simulated.The results indicated that the degrees of riverbank stability are high during the periods of low water level and water-level rising before the flood season,which leads to the stage of weak bank failure,and they are low during the periods of high water level and water-level recession with the continuous bank collapse occurring,which belongs to the stage of intensive bank failure.In addition,the effects of bank toe erosion and water table variation on the degree of bank stability were investigated.This analysis indicated that these two factors have an important influence on the process of bank failure,and they can cause respectively intensive bank failure during the high water and recession periods.Finally,with the bank toe erosion,water table variation and deposition form of the collapsed bank soil being considered in the calculation,the process of bank failure of the right riverbank at Jing34 section was simulated over the period from Nov.2008 to Oct.2010.The model-predicted results were in well agreement with the measured data of the total bank retreat width and the collapsed bank shape.Therefore,these influencing factors should be included when simulating the process of composite riverbank failure.关键词：modeling of bank failure;BSTEM;Upper Jingjiang Reach;toe erosion;water table
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发布时间：2023-11-14 - 摘要：Abstract:Traditional image rectification mainly aims to minimizing the least-squares distance between the matching points, however, the rectification process may cause great geometric distortion, which not only makes it impossible to offer information for 3-dimensional reconstruction, but also results in extra errors. An improved algorithm was proposed which minimizes the distortion by combining a newly developed projective transform with a properly chosen shearing transform. Firstly, projective transformation was developed to make the polar lines of two images align to the same direction. Secondly, shear transformation was introduced to ensure the image aspect ratio remain constant. Experimental result demonstrated that the proposed method is quite robust and well qualified to the rectification for 3D reconstruction.关键词：stereo vision;epipolar geometry;projective rectification;fundamental matrix;shearing transformation
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发布时间：2023-11-14 - 摘要：Abstract:In order to overcome drawbacks of manually segmenting the maternal artifacts from 3D fetal ultrasound image even by experienced sonographers, an interactive segmentation approach was proposed based on level set framework. This algorithm could detect the boundary of objects by controlling the propagation speed function based on gradient orientation and scalar. In order to apply level set framework into 3D ultrasound segmentation, the Narrow-band scheme was put forward, which increases the segmenting speed and accuracy dramatically by restricting propagation process between two equidistant curves instead of updating it at all the points on the grid. Experiments were performed on 3D fetal ultrasound datasets from two different ultrasound machines containing 30 fetal images of different position, orientation and weeks. The result showed that this approach achieves fast and accurate segmentation of 3D fetal ultrasound image with size of 255×255×128 in 5 seconds on a dualcore 2.0 GHz computer.关键词：3D fetal ultrasound image;Level set;image segmentation;narrow band scheme
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发布时间：2023-11-14 - 摘要：Abstract:To ensure the fair exchange of buyers and sellers，the fairness of mobile payment protocol was formally analyzed with the theorem of unsolicited test and the existence of sending edge. It was pointed out that the mobile payment protocol has security shortages on fairness. By adding timestamps to the original protocol and changing entity of some messages，an improved protocol was proposed to overcome the security shortages. The improved protocol was proved to satisfy with the fairness under the premise of not affecting performance by the extended strand space model. The research result indicated that the proposed approach can analyze the fairness of protocol efficiently.关键词：WAP;mobile payment protocol;fairness;extended strand space model
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发布时间：2023-11-14 - 摘要：Abstract:A new algorithm for the detection and parameters estimation of linear frequency modulation (LFM) signal was proposed．Firstly,the influence of LFM signal on the phase diagram of the Duffing chaotic oscillator was analyzed,and then the demodulation frequency processing was implemented to transform the LFM signal into periodic signal．At last,Duffing oscillators filter array was constructed to realize the detection and parameters estimation of LFM signal and Lyapunov exponent was exploited to judge the state of the system.The numerical simulation showed that this algorithm operated easily and could effectively detect the weak LFM signal.Moreover,better parameter estimation precision was obtained in the case of low signal-noise-ratio (SNR).关键词：signal detection;chaotic oscillator;parameter estimation
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发布时间：2023-11-14 - 摘要：Abstract:A packet-layer model for speech quality assessment was proposed to monitor the quality of networked speech.Without resorting to any media-related payload information,the proposed model predicted the speech quality only in terms of the information provided by packet headers.First，the analysis of content feature was performed to locate the voiced segments and silence segments by analyzing the information from packet headers,and the coding and packet loss parameters of voiced segments were obtained.Then the coding distortion was estimated according to the coding parameters of voiced segments,based on which the overall speech quality was further evaluated by taking account of the impact of packet loss.Experimental results showed that the proposed model could get an increment about 0.041 2 in Pearson correlation coefficient (PCC) and a decrement about 0.045 1 in root mean squared error (RMSE) compared with the E-model proposed in ITU T recommendation G.107.关键词：speech coding;speech transmission;quality of service;packet loss
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发布时间：2023-11-14 - 摘要：Abstract:By means of linear matrix inequality (LMI) based Lyapunov method,a nonlinear observer was proposed for a class of Lipschitz nonlinear system with output uncertainty.The observer gain matrix was selected according to LMI with the output uncertainty satisfying Lipschitz conditions.The sufficient condition on ensuring the asymptotic stability of the observer was presented by Lyapunov method.At the same time a calculation method of the maximum Lipschitz constant was obtained.The simulation results demonstrated the effectiveness of the proposed observer.关键词：uncertainty;Lipschitz conditions;nonlinear system;linear matrix inequality;Lyapunov
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发布时间：2023-11-14 - 摘要：Abstract:In order to accurately describe the impact of distance protection on voltage sag characteristic in meshed network，a novel voltage sag stochastic evaluation method was proposed with the consideration of meshed network topology characteristic and distance protection operation characteristic. Based on the operation principle of distance protection,the protection operation time was determined according to short-circuit calculation result.Comparing the operation time of distance protection at each end of the line,whether or not a fault will lead to a multistage voltage sag could be confirmed.The magnitude of multistage voltage sag was determined by modifying nodal impedance matrix,and multistage voltage sag was converted to rectangular voltage sag based on the concept of loss of voltage.The proposed method was applied to a 250-bus test system, and the simulation results showed that the proposed method could quantify the impact of distance protection operation time on voltage sag magnitude and duration,and over-estimation of multistage voltage sag could be avoid.Compared with the traditional method，the proposed method was more accordant to practical power system operating condition.关键词：voltage sag characteristic;meshed network;distance protection;time characteristic;multistage sag;stochastic evaluation
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发布时间：2023-11-14 - 摘要：Abstract:To evaluate the most possible failure state of sensitive equipment when they encounter voltage sags,a lattice order based method was studied.Starting with the physical nature of equipment multi-valued mapping outcome due to voltage sag,a multi-valued mapping based outcome state describing method was proposed.Interval numbers which possess the characteristics of lattice order with the upper and lower probabilities of each outcome state as two endpoints were used to describe equipment state,and then the outcome states of decision-making problem could be lattice ordered.The possibility degree concept was introduced,and the possibility degree matrices were used to compare outcome states which don’t satisfy connectedness axioms and the most possible outcome state could be obtained.Comparing the simulation result with actual testing result showed that the proposed method can objectively reflect equipment failure state and quantitatively determine the most possible state.The method is accurate,less-sample-dependent and be of great engineering application significance.关键词：voltage sag;equipment failure;multi-valued mapping;lattice ordered;possibility degree matrix;sample dependence
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发布时间：2023-11-14 - 摘要：Abstract:Mn-Ce/AC catalyst was prepared by impregnation method and tested for selective catalytic reduction (SCR) of NO with ammonia through temperature programmed reaction(TPR). Results indicted that both the n(NH3)/n(NO) ratio and space velocity have certain effect on the performance of Mn-Ce/AC catalyst. The NO conversion is up to 90% at 90 ℃ on Mn-Ce/AC when n(NH3)/n(NO) ratio is 1:1 and space velocity is 2 000 h-1, and a higher conversion of 99% is obtained during the reaction temperature of 120~250 ℃. Mn-Ce/AC catalyst shows good H2O resistance and SO2resistance,which can keep high activity when water vapor existed at higher temperature.With the increase of the SO2 concentration to 1 500 μL/L, the NO conversion decreases significantly to 70%.
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发布时间：2023-11-14 - 摘要：Abstract:In order to improve the flame retardant efficiency of APP-PETA，APP-PA6T and APP-PPTA system on acrylonitrile-butadiene-styrene (ABS) resin ,red phosphorus was introduced to play as the second acid source. The effect and FTIR spectrum of flame retardant residue of these systems were analyzed,and PETA and PPTA were chosen as char agent,APP and red phosphorus as acid source to form the flame retardant.When the mass fraction of two-stage flame retardant was 30%,the LOIof flame retardant ABS was 34 and UL-94 vertical burning test reached V-0,even when the loading decreased to 20%,the LOIvalues still has 27 and past the V-0 test.FTIR spectrum of two-stage flame retardant residue suggested that there was a distinct cooperation which prolong the working time. The macroscopical structure of char layer showed this flame retardant had two work processes,swollen and shrunk,the second process made char layer more compact,The ABS composites SEM photograph after completely combustion showed that two-stage flame retardant would form compact char layer when mass fraction was 30% or 20%,and this endow ABS good flame retardancy.关键词：ABS;two stages;intumescent-contractive flame retardant;char agent
- 1988
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发布时间：2023-11-14 - 摘要：Abstract:The WC-8Co cemented carbides were sintered at low temperature and pressure.The influences of sintering temperature and pressure on the microstructure and properties of the cemented carbides were investigated.Results showed that with the increase of sintering temperature, the quantity of pores decreases, the grain size and density of the cemented carbides increase simultaneously.The hardness and bending strength of the cemented carbides are improved with the increase of density.When the sintering temperature is above 1 280 ℃, the sintering method of the cemented carbides is liquid-phase sintering.The improvement of density is contributed to the sintering pressure .When the sintering temperature is 1 300 ℃ and the sintering pressure is 5 MPa, the density, hardness and bending strength of the cemented carbides are 14.61 g/cm3, 90.7 HRA and 1 830 MPa, respectively.关键词：cemented carbides;sintering;lower temperature and pressure
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发布时间：2023-11-14 - 摘要：Abstract:A kind of composite buffering material was made by filling the voids of honeycomb paperboard with polyurethane. Static compression tests were performed to evaluate the energy absorption capacity of the material. Based on the tests results,the mechanical behaviors of the material under different conditions were analyzed, the inherent influencing laws of some factors on the material’s static buffering performance were obtained. It was shown that the elasticity limit (increased from 0.224 0 MPa to 0.542 2 MPa) and yield stress (about 3~4 times the yield stress of the honeycomb paperboard) of composite material increased obviously.Compression strength and yield stress varied inversely with the void diameter,and directly with thickness of the honeycomb paperboard and composite material.The influence of void diameter on the mechanical properties of the composite material was very significant.The absorbed energy of the composite material was about 1.85 times the total absorbed energy of the honeycomb paperboard and polyurethane.The energy absorption efficiency and the ideal energy absorption efficiency of the composite material were better than those of honeycomb paperboard and polyurethane.关键词：honeycomb paperboard filled with polyurethane;static compression test;energy absorption capacity;composite material
- 1937
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发布时间：2023-11-14 - 摘要：Abstract:In order to improve the traditional throttling technology and promote intelligent downhole throttling technology, many advanced technologies were adopted to build up an intelligent downhole choke system which can realize remote control and monitoring, and a control algorithm for this system was designed. Various key techniques of the chock system were elaborated, such as electric control system design based on CAN bus technology, mechanical structure design based on CAD/CAE, downhole temperature and pressure data collection and processing based on digital information technology and software design based on modular layering method. The control software and operation process of the practical system were tested and analyzed. The result demonstrated that the intelligent downhole throttle system has two main advantages of real-time monitoring and real-time remote control and throttling, which can provide equipment supports for intelligent throttling technology. These methods have some reference for other researches in developments of intelligent downhole tools.关键词：gas well;downhole throttling;throttle system;intelligent control
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发布时间：2023-11-14 - 摘要：Abstract:In order to solve the problem of FROG-LEG vacuum manipulators’dynamic compensation,based on its structure,the dynamics in the level and upright direction was discussed, respectively, by using New-Euler method to give dynamics equations.Rotor flux oriented of PMSM was analyzed,which was the dynamic source of vacuum manipulators.Robot tool of MATLAB was utilized to simulate the kinematics and dynamics of vacuum manipulators,proving that dynamic current feed forward compensation is an effective way to realize vacuum manipulators’smooth control.关键词：vacuum manipulator;dynamics;Lagrange equation;rotor flux oriented;simulation of dynamics
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发布时间：2023-11-14 - 摘要：Abstract:It is difficult to establish a cutting model using traditional mathematical methods for the abrasive water jet because of the complex nonlinear relationship between the cutting performance and the influencing factors.A BP neural network cutting model of abrasive water jet,which contains six influencing factors as jet pressure,abrasive flow,cutting target distance,work piece thickness,abrasive nozzle diameter and cutting speed,was established based on BP artificial neural network theory and the results of the cutting experiment with typical material.A portable abrasive water jet cutting speed artificial neural network prediction unit was developed to realize the visualization of the network model based on Delphi,providing conditions for the integration of network model and NC system.The results showed that the network model integrated with NC system can predict the cutting speed rapidly,and accurately reliably and realize the effective control of the cutting quality.关键词：abrasive water jet;cutting model;BP neural network;visualization
- 1965
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发布时间：2023-11-14 - 摘要：Abstract:Spatial engaging theory was used to deduce mathematical equation of gear surface. Mathematical equation of arc tooth line of cylindrical gear surface shaped by origin face of rotary cutter,which could be used for both theoretical analysis and computer simulation,was built by dividing arc tooth line of cylindrical tooth surface into three main component surface,establishing dynamic and static coordinate system in machining process,constructing working surface mathematical equations based on theory of conjugate surface,deriving tooth bottom surface equation and tooth root surface equation from coordinate transformation and establishing equations of gear surface on this basis.Point cloud data of the tooth surface was calculated and output,tooth surface was tailored on the relationship between gear surfaces,and 3D model entities of arc tooth line of cylindrical gear was obtained.The arc tooth line cylindrical gear 3D model obtained by this method was consistent with the model generated by the method of simulating machining means.关键词：arc tooth line of cylindrical gear;3D modeling;rotary cutter;mathematical modeling
- 2307
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- 11
发布时间：2023-11-14 - 摘要：Abstract:Based on the assumption that the shape of wheel profile is unchanged and only the wheel out-of-roundness (OOR) changes,which is more accurate than the model of equivalent track excitations,the polygonal wheels were simulated by programming.Then,the coupled model incorporating the vehicle-track system dynamics was set up.The dynamic performance of ideal wheel and polygon wheel under high-speed running were simulated and the critical range of the wheel out of roundness was determined.The simulation results showed that the wheel OOR will increase the carbody responses and affect the passenger ride comfort,and result in large wheel-rail vertical forces,which is more strongly related to the OOR order than amplitude and vehicle running speed.The safety limits for 1, 2, 3 and 4 order polygon are 1.0,0.4,0.4 and 0.3 mm.关键词：wheel out-of-roundness;polygonal wheel;dynamics
- 2073
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发布时间：2023-11-14 - 摘要：Abstract:A method for identifying structural stiffness of aeroelastic wind tunnel model was proposed based on photogrammetry.With the known loads (bending moment or respectively torsional moment) acting on the static aeroelastic model,the changes of marking points’ 3D coordinates were measured by photogrammetry,and then the bending stiffness or torsional stiffness of model was solved.It was demonstrated by the numerical simulation and practical tests that compared with the traditional contact measurement method this model is useful and correct due to its better accuracy, shorter period and without additional stiffness.关键词：static aeroelastic model;stiffness test;stiffness identification;photogrammetry
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发布时间：2023-11-14 - 摘要：Abstract:As a part of coupled transmission with load sharing system based on wind turbine gearboxes,a multi-stage transmission system with two-stage planetary gear train and one-stage parallel-shaft gear train was considered.A dynamic mechanical model for three stage gear train was presented using lumped-parameter method.Many factors were taken into account,such as mesh stiffness and mesh damping of gear pairs of the transmission system,errors of gear pairs,torsional coupling stiffness of the connecting section, and the inertia of the system.The natural frequencies and vibration modes of the system were obtained through solution of the associated eigenvalue problem by using the related parameters. Based on the properties of the transmission system,the vibration modes of the system were classified into eight categories,which were coupling vibration mode between the first stage and the second stage,coupling vibration mode between the second stage and the third stage,overall rotational mode of the system,planet mode of the first stage,planet mode of the second stage, single-stage vibration mode of the first planetary gears,single-stage vibration mode of the second planetary gears and single-stage vibration mode of the parallel-shaft gears,respectively.Moreover,the influences of the coupling stiffness between the carrier of the first stage and the ring of the second stage on the natural characteristics were studied. The analysis showed that vibration modes of multi-stage planetary transmission system are more diverse and complex than that of single-stage system.关键词：load sharing;eigenvalue;mathematic model;vibration mode;natural characteristic
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发布时间：2023-11-14
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