最新刊期
卷 48 ， 期 1 ， 2016
- 摘要：Abstract:There are significant differences between the classical theory of sediment movement mechanics and natural mountain river system bed load movement.Considering this status,based on the analysis of mountainous watered sediment supply conditions,the responses of mountain river channel adjustment and mutation mechanism were studied.The influence of the recharge conditions of sediment on non uniform gravel starting and the transport characteristics,and the relationship among the sand pebbles recharge, mountain river formation and hindering navigation was revealed.At the same time,the variation of water and sediment movement characteristics in the singular and width and floodplain compound navigation channels in response to the bed mutations phenomenon was provided.The study showed that using the water and sediment load shifting,separation of water and sediment build degree reduction technology means to control the peak period of the disaster pebble river sediment supply conditions is the core of flash floods and sediment disaster hazard prevention and control of risk reduced order.关键词：river sediment;pebble bed;river bed adjustment;flash floods and sediment disasters;disaster prevention and control;sediment supply
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发布时间：2023-11-14 - 摘要：Abstract:The generalized finite difference method (GFDM) is a newly developed domain type meshless method,which could truly get rid of time consuming meshing generation and numerical quadrature at every time step and be adopted to simulate the non linear moving boundary physical problems.According to the Lagrangian approach,the GFDM and the leap frog approach were adopted for spatial and temporal discretizations of the sloshing problem in a two dimensional numerical tank,respectively.Results and comparisons via the numerical examples of free sloshing and forced sloshing verified the accuracy,efficiency and stability of the proposed meshless numerical scheme.关键词：sloshing;generalizedfinitedifferencemethod;meshlessmethod;Lagrangianapproach;leap frogapproach
- 1993
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- 950
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发布时间：2023-11-14 - 摘要：Abstract:In the top of the rock shed,a certain thickness of sand cushion could play a significant energy dissipation function.The effect of different thickness of sand cushion is greatly diverse.Hence,how to determine the thickness of sand cushion became one of the key issues in the shed design.Based on the actual shed tunnel structures as prototypes,the dynamic finite element numerical simulation was used to analyze the dynamic response of sand cushions with multi thickness under different impact energies and the mechanism of energy absorption.The results showed that under low impact energy,the changes of sand cushion thickness had little influence on the rock fall impact force,whereas there were extremely differences in the energy absorption of different thickness sand cushions under high impact energy.Increasing the thickness of sand cushions could effectively weaken the slabs’deformation caused by rock fall impact,however enlarged the weight of structures.With the consideration of both economic rationality and structural reliability,the optimal cushion thickness was obtained by calculation.关键词：rock fall impact;rock shed;sandy soil cushion;cushion thickness;energy dissipation
- 1977
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发布时间：2023-11-14 -
Preliminary Study on Change Law of AC Impedance Characteristics of Concrete During Splitting Tensile
摘要：Abstract:A method based on AC impedance characteristics of concrete was put forward for crack detection and damage assessment.Using the steel bars as electrodes,three groups of concrete specimens with different strengths were designed for splitting tensile testing,and both the impedance amplitude (z) and phase angle (φ) were measured by MT4090 LCR measuring instrument during testing.The results showed that there are significant differences in crack evolutionary among the three phases of splitting tensile process,meanwhile,the change law of value of z and φ is closely related to the crack evolution characteristics in the different phases.With the increase of the damage degree,the values of z and φ increase consistently in same rate.There is certain linear relationship between the initial value of z，φ and the strength.The method of crack detection and damage assessment by the electrochemical parameters may come true.关键词：concrete;AC impedance spectroscopy;impedance amplitude;crack;detection- 1698
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发布时间：2023-11-14 - 摘要：Abstract:The fluid structure interaction (FSI) of free rigid bodies is a hot issue in computational fluid dynamics,and also a common problem in engineering applications. In order to use the iterative force based immersed boundary lattice Boltzmann (IB LB) coupling scheme to simulate FSI problems in which free rigid bodies are involved,the equations of motion were firstly added to the governing equations,then the mathematical model was discretized and solved by the IB LB coupling scheme.Using the sedimentation of two particles as an example,the numerical results of present method and other FSI algorithms were compared.Finally,a challenging problem concerning the fluttering of a rectangular plate in a water tank was addressed in the IB LB framework.The trajectories of the rigid bodies and the flow patterns were in good agreement with the existing experimental results.The comparison of the execution time per time step and the measured averaged velocities with that of existing FSI algorithms showed that this method is computational efficient and accurate in simulating complex FSI problems.关键词：fluidstructureinteraction;immersedboundarymethod;latticeBoltzmannmethod;rigidbody;freelysedimentation
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发布时间：2023-11-14 - 摘要：Abstract:Aimed at the impact force of the debris flow occurred on July 10,2013,which buried the facilities including Duwen highway at the deposition fan of Taoguan gully,the formation condition and development characteristic of the debris flow through field investigation were identified,and relevant kinematics parameters were determined by using the rain flood method.Applying large scale fluid dynamics software CFX,the process of 10th July debris flow in Duwen highway segment and its motion feature were simulated.The motional dynamics and hazardous zone of the debris flow were obtained.The distribution of the velocity field and the influence on facilities localized along the debris flow gully were analyzed.Meanwhile,the impact force of the debris flow and the corresponding risk on the bridge pier of Duwen highway were intensively studied.The simulated results agreed well with the calculated ones by empirical formula with an error of only 5.8%.关键词：earthquake disaster region;debris flow;dynamic characteristics;hazardous region
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发布时间：2023-11-14 - 摘要：Abstract:A cushion layer can efficiently protect the structures in mountainous areas from impact damages of rockfall hazard.The aluminium foam,as a kind of energy dissipation cushion material,was introduced into rockfall disaster mitigation areas.This type of cushion was composed of aluminium foam with embedded steel plate that was made to be a sandwich board structure.Dynamic response of rockfall impacting the aluminum foam sandwich panels was analyzed by static experiment and dynamic finite element method,revealing the energy dissipation buffer mechanism of aluminium foam sandwich board.The results showed the existence of a wide energy buffer platform in the stress yield stage,which could absorb lots of energy so as to achieve the purposes of energy dissipating.The sandwich board structure could effectively reduce the deflection deformation of the structures.When the embedded steel plate thickness increases,the cushion impact pit depth decreases and the deformation of protected structure center also decreases remarkably.However,too thick steel plate will increase the overall rigidity of the sandwich panel,and reduce the energy dissipation of the panel.Therefore,the double indexes of deformation and impact force under rockfall impact structure should be comprehensively considered when the structure of aluminum foam sandwich board is designed.关键词：rockfall;aluminumfoam;sandwichslab;energydissipation
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发布时间：2023-11-14 - 摘要：Abstract:The conceptual model for effect of pumping well on two streams was developed.The three dimensional ground water model (interactive ground water model,IGW) was applied for simulating the conceptual model.All of the numerical solution was compared with Wilson’s analytical solution.Several examples were presented for illustrating the effect of pumping well on streams,which demonstrated stream depletion affected by the river shapes,the anisotropy and the clay lens in aquifer individually.The results showed the priority and the limitation of Wilson’s analytical solution.关键词：groundwater;aquifer;streamflow depletion;water withdrawal
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发布时间：2023-11-14 - 摘要：Abstract:〗In order to study the mitigation function of the Herringbone Water Sediment Separation Structure to debris flows with driftwood,a series of laboratory experiments were carried out.Influences of the structure parameters to the water wood separation were analyzed,and the optimization of main structure parameters were discussed based on the experimental results and previous research.The results showed that the herringbone grid can stop the driftwood effectively if the structure parameters are reasonably set.The spillway width of the draining dyke should be at least 0.5~1.0 times of the length of the driftwood.Velocity of the driftwood is commonly greater than the mean velocity of debris flow,so the length of the herringbone water sediment separation structure should be enlarged.The distance between ribbed beams should be less than 3.85 times of the width of the driftwood.The ribbed beam should be set perpendicular to the flow direction.关键词：debrisflow;driftwood;herringbonewater sedimentseparationstructure;parametersoptimization
- 1905
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发布时间：2023-11-14 - 摘要：Abstract:In order to study the real strength characteristics of expansive soil,the low stress shear strength of remolded expansive soils under the constant amplitude dry wet cycle cyclic conditions was tested by using the conventional direct shear test.The change relationship between the low stress shear strength parameters of the remolded expansive soils,the number of cycles and the amplitude of the cycle were studied.The nonlinear function of the cohesion with the variables that contains the initial moisture content,cycle amplitude and number of cycles was established.The test results showed that under the same cycle amplitude and initial control water rate condition,the cohesion of expansive soil decayed with the increase of the number of cycles.Under the same cycle number and the initial control water rate,the cohesion of expansive soil decayed with the increase of the amplitude of the cycle.The relationship between the internal friction angle,the amplitude of cycles and the cycle times could not be expressed by a function.The nonlinear cohesive strength attenuation function was obtained by simple laboratory test,which can be used to calculate the cohesion of expansive soil under the condition of amplitude dry wet circulation.关键词：expansivesoil;constantamplitudedrywetcycle;lowstressshearstrength;cyclicamplitude
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发布时间：2023-11-14 -
Developmentand ExperimentalResearchofSamplePreparationDevice forNewUniaxialTensileSpecimen
摘要：Abstract:For uniaxial tension test result can be largely affected by sample forms and tensile length,both of which are quite different in the current experimental research.A set of dumbbell uniaxial tensile sample preparation mould was developed for preparing samples with different tensile lengths.Sample preparation mould consisted of two horizontal loading section moulds,two vertical stretching section moulds and one sample preparation base plate,in which loading section moulds were connected with stretching section moulds by dovetail slot. Based on this,the uniaxial tensile test of clay specimen was carried out to analyze the tensile properties of clay and discuss the influence of sample forms and tensile length on the failure mode,tensile strength and peak displacement.The results showed that end relaxation and stress concentration issues can be avoided in the tensile process for applying dumbbell specimens and the tensile fracture plane occurs in the range of effective tensile length;failure mode of clay is not pure brittle failure,but there is a softening phrase after tensile strength.With the increase of tensile length, uniaxial tensile strength decreases but peak displacement raises,and both show a logarithmic relation with tensile length.关键词：uniaxialtensile;failure mode;tensilelength;samplepreparationmould;tensile strength- 1947
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发布时间：2023-11-14 - 摘要：Abstract:In order to solve the problem that the roaming authentication protocol of current mobile sensing nodes has some defects in light weight property,switching speed,and security,a roaming authentication protocol based on non linear pair was put forward.Theoretical analysis showed that this protocol not only satisfies the general security requirements,but also the untraceability of current roaming authentication protocol.Computation and comparison showed that the protocol has a lower computation load.Finally,through simulation,the robustness of the protocol under complex network environment was analyzed.The comparison to the roaming authentication protocols of several typical mobile nodes showed that the present protocol processes good robustness under moderate severe conditions.关键词：InternetofThings(IOT);mobilesensornodes;roamingauthentication;non linearpair
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发布时间：2023-11-14 - 摘要：Abstract:In order to efficiently eliminate the security shortcomings of the dynamic ID based remote user authentication scheme using smart cards (short for XJWM scheme) proposed by Xu et al.,a new multi server and multi factor anonymous remote authenticated key agreement protocol was presented,based on Diffie Hellman key agreement algorithm and biometrical authentication technology.The new protocol can not only overcome the security flaws of XJWM scheme,but also add smart card’s password and bio information authentication for the cardholder to avoid the smart card stolen attack.The security of the new protocol was proved by the improved BAN logic and the result showed that the new scheme can ensure the correctness of key agreement,key confidentiality,key freshness and mutual authentication.The security and performance analysis demonstrated that the proposed protocol provides better security without increasing too much computation overhead.关键词：smartcard;Diffie Hellmankeyagreement;anonymousauthentication;BANlogic
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发布时间：2023-11-14 - 摘要：Abstract:Based on Brakerski et.al’s scheme and by applying the idea of key private proxy re encryption,combining with the Switchkey process,the first key private fully homomorphic proxy re encryption scheme was presented.This scheme allows a proxy with the re encryption key to change a ciphertext under delegator’s (Alice’s) public key into one that can be decrypted using delegatee’s (Bob’s) private key,and the identity of Alice and Bob will not revealed.According to the homomorphic property,the proxy can operate on the changed ciphertexts,thus evaluate on ciphertexts encrypted under different keys,which means that the proposed scheme is a FHE and a proxy re encryption scheme.Moreover,if users don't use the function of proxy re encryption,the scheme will turn into an efficient fully homomorphic scheme.At last,CPA security and key private property of the above proxy re encryption scheme in the standard model were proved.关键词：publickeysystem;fullyhomomorphicencryption;proxyre encryption;LWEproblem
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发布时间：2023-11-14 - 摘要：Abstract:〗In order to solve the problem that network security incidents occurred frequently and anomaly detection methods are mostly focused on the modeling of the system call data,an intrusion detection method based on hidden Markov model was proposed.Joint information of system calls and function return address chain was used to establish the host process of hidden Markov model.In addition,a fast algorithm was designed to train the parameters of the model.The experimental results showed that the introduction of joint information of system calls and function return address chain could effectively distinguish between normal behavior and abnormal behavior of the process,and significantly reduce the operation time.关键词：intrusiondetection;hiddenMarkovmodel;systemcallsequence
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发布时间：2023-11-14 - 摘要：Abstract:In order to solve the problem that all attribute node beliefs are influenced dynamically by the observed attack events in attack graph model,based on Bayesian attack graph,a dynamic risk assessment model was presented.The probability attack graph,which describes the cause consequence relationships among the steps in one attack progress,was built by using Bayesian belief networks.The probability of vulnerabilities, which is successfully executed by an attacker,was computed by using index of common vulnerability scoring system,and the static security risk of the property node was assessed by introducing local conditional probability tables.Then,by combining real time attack events being observed by intrusion detection system,the posterior probability was calculated dynamically when the attack occurred by applying Bayesian inference.Finally,the security risk of the target networks was evaluated.Experimental results showed that the model can assess dynamical security risk and deduce attack path, and provide effective guidance for taking security hardening strategy.关键词：riskassessment;attackgraph;Bayesiannetwork;attackbehavior
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发布时间：2023-11-14 - 摘要：Abstract:In order to defend against smart jamming and eavesdropping attacks simultaneously in wireless multi channel networks,based on game theory and power control,an anti jamming transmission Stackelberg game was proposed.In the proposed game,the source node plays as the leader,chooses its transmit power and defends against the attacks.The jammer chooses its own transmit power based on the behaviors of source node.Then a distributed learning algorithm for the jammer inspired by stochastic learning automata was proposed to achieve the Stackelberg equilibrium of proposed game.The result showed that the intercept probability can be decreased through increasing the gain of wiretap channel,and the proposed model performs better in defending against the physical layer attacks by compared with the other models.关键词：wirelessmulti channelnetworks;smartjamming;eavesdropping;Stackelberggame;distributedlearningalgorithm
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发布时间：2023-11-14 - 摘要：Abstract:In order to enhance the information security of three dimensional(3D) new media,a 3D optical image cryptosystem in Fresnel domain was proposed.The 3D optical images were encrypted and decrypted by discrete Fresnel diffraction and computational integral imaging system that was implemented with smart pseudoscopic to orthoscopic conversion model.The results showed that these parameters of the cryptosystem can be used as the secret keys,such as the parameters of integral imaging system,the wavelength of incident light and the distance of diffraction.The dimensions of secret key are increased.The space of secret key is also expanded.The security and anti attack of the new cryptosystem are enhanced.This research can be applied in the aspects of information hiding and digital watermarking which are needed for information security of 3D new media.关键词：integralimaging;3Dopticalimagecryptosystem;Fresneldomain
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发布时间：2023-11-14 - 摘要：Abstract:In order to protect multi type sensitive information (SI) in internet of thing,some characteristic attributes were defined in global data life time,relative rules were designed to mark dynamic security level, and the relationship between attributes and leakage points was measured.Moreover identity based encryption (IBE) was applied in middle layer,finally patch distribution was performed to prevent expiration in above layers.Experiments were accomplished for SI in three heterogeneous networks and the result showed that the security of encryption algorithm can be ensured with low overhead.关键词：IOT;sensitiveinformation;characteristicattribute;IBE;patchdistribution
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发布时间：2023-11-14 - 摘要：Abstract:Jiang’s lattice-based proxy signature scheme couldn’t provide public verifiability of delegation,and depends on the existence of secure channel to transmit delegation information.To solve this problem,an improved scheme was presented by introducing the warrant to realize the delegation’s public verifiability and getting rid of the dependence on secure channel.Furthermore,in the new proxy signature algorithm,authorization method was changed,and the basic signature operation downed from two times to one time,so that the scheme’s efficiency was further improved.In addition,a revocation list was introduced,and the delegation revocation was achieved during the period of validity.The proposed scheme has with better security and efficiency compared to Jiang’s scheme.关键词：lattice-basedcryptography;proxysignature;delegationrevocation;signaturewithouttrapdoor;postquantumcryptography
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发布时间：2023-11-14 - 摘要：Abstract:In order to take the advantage of prior knowledge to improve clustering performance,based on distance metric learning (ML SMC),a semi supervised multi view spectral clustering algorithm was proposed.The prior knowledge was incorporated into clustering process by distance metric learning, which mapped data into a new space which subjects to prior knowledge.Each graph of views was constructed according to similarity metric, and then the problem of multi view clustering was formulated as an optimization problem of minmum normalized cut.Experiments showed that the quality of clustering results of ML SMC is superior to three classical multiview clustering algorithms and four semi supervised single view clustering algorithms,and the precision of ML SMC could be significantly improved by incorporating some prior knowledge.关键词：distancelearning;multiviewclustering;spectralclustering;semi supervisedclustering;datamining
- 2011
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发布时间：2023-11-14 - 摘要：Abstract:〗In order to learn the higher-order semantic relatedness among multiple instance of target word,a hypergraph_model was proposed for word sense induction.First,a lexical chain based method was used for discovering the higher order semantic relatedness.Then a hypergraph was constructed,in which nodes represent the instances of contexts where a target word occurs,and hyperedges were formed by lexical chains.Finally,a maximum density based hypergraph clustering method was used for finding word senses. Experiments based on Semeval-2013 WSI task showed that this model gives an improvement of 5.6% and 6.4% in sense detection and sense ranking respectively, compared to the traditional graph model.关键词：wordsenseinduction;hypergraph;higher-ordersemanticrelatedness
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发布时间：2023-11-14 - 摘要：Abstract:In order to improve the throughput of opportunistic networks during congestion phase caused by multiple copies packet forwarding method,based on cellular learning automataa novel congestion control strategy was proposed.Different from conventional congestion control strategies,in which only particular information of nodes or packets are considered,this novel strategy takes into account the packets retain information from neighbor nodes.Each node is described as a cellular equipped with multiple learning automata in the network.According to the packets information stored in neighbor nodes,each node updates drop probability of packets under the rule of learning automata automatically.Furthermore,the buffer entropy of each neighbor node is taken into account when a packet is replicated,and a novel policy of dropping and replicating packets is also employed to increase nodes’ entropy.The simulation results showed that the present approach effectively reduces the network overhead,packets delivery latency and improves packets delivery ratio.关键词：opportunisticnetworks;congestioncontrol;cellularlearningautomata;bufferentropy
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发布时间：2023-11-14 - 摘要：Abstract:In order to improve the targets for training acoustic model which cannot reflect the nature of speech exactly,a new kind of target obtained by forward backward algorithm was proposed.In the proposed target,a speech frame was aligned to several adjacent states with different probabilities.The new target improved the robustness of the model,as could describe the transition boundary and reflect the nature of speech much more exactly.Meanwhile,for a trade off between the model robustness and the distinction among modeling units,the targets obtained by forward backward algorithm were windowed.The experiments were carried out on Mandarin conversational speech recognition in the customer service domain. In the experiments,a small set of training data were used to verify the importance of the targets in the training and determine the parameter of the window length.Finally,the durations of training data were increased to 60,80 and 100 hours.The results showed that the proposed system achieved consistent improvements,and the relative character error rate reduction ranged from 1.10% to 3.65%.All of the experiments verified the effectiveness of the proposed target.关键词：speechrecognition;deepneuralnetwork;forward-backwardalgorithm;targetoptimization
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发布时间：2023-11-14 - 摘要：Abstract:Because of the nonlinearity of the elastic sensitive element and the signal noise ratio,the precision of the traditional force sensor can hardly be higher than 0.02%.A force sensor with electromagnetic force balance lever structure was introduced.The sensor utilized a controllable electromagnet which can generate the controllable electromagnetic force to offset the load while the value of the load can be obtained by the coil voltage,which solved the problem of signal noise ratio.By analyzing the electromagnetic force curves under different temperature by the method of piecewise linearization，the electromagnetic force with high linearity was acquired,which solved the problem of nonlinearity.Test results indicated that the linearity of the sensor was 0.001%,and its precision was 0.003%.关键词：forcesensor;linearity;signal noiseratio;electromagneticforce
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发布时间：2023-11-14 - 摘要：Abstract:The design method of the teleoperation control system using industrial robot KUKA for was introduced the hazard environment and the control algorithm with heterogeneous master/slave structure.Using the Eth.KRLXML software package,a communication based on TCP/IP was connected between the robot controller and the remote computer.The joint angles and positions of the endpoint of the KUKA robot were sent periodically to the remote computer and commands from the remote computer were received and executed by the KUKA robot.Teleoperation control algorithm with relative scale transformation was adopted in the teleoperation system.Motions of the master manipulator was transformed to the slave manipulator’s coordinate.By implementing the scaled relative position and pose transformation,the proposed control algorithm not only could be used in the designed heterogeneous master/slave structure,but also could satisfied different operation space requirements with high accuracy.Physical experiments verified the proposed teleoperation system and the proposed master/slave control algorithm.关键词：KUKAindustrialrobot;heterogeneousteleoperation;master/slavecontrol;scaletransformation;homeomorphictransformation
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发布时间：2023-11-14 - 摘要：Abstract:Dual conjugated meshing zone plays an important role in improving the torsional stiffness and transmission accuracy of the harmonic drives with double-circular-arc tooth profiles (DCTP).A novel method was proposed to amplify the dual conjugated meshing zones effectively.Segmented functions and matrix of meshing invariant were introduced to establish arc length parameterization function and theoretical meshing equation for a single flexspline tooth of a harmonic drive,respectively.In this way,the computation of theoretical conjugate tooth profiles of harmonic drives could be significantly simplified.Employing the conjugated tooth profiles difference as the objective function,single-parameter and multiple-parameter optimizations were conducted with concave tooth profile radius,common tangent longitudinal length and the angle of inclination with common tangent as the independent variables.The results demonstrated that the optimization design method is helpful for reasonable selection of the tooth profile parameters of flexspline teeth,which would ensure the motion accuracy of dual-conjugated meshing zones.关键词：harmonicdrive;double-circular-arctoothprofile;toothprofileparameters;conjugatedtoothprofile;optimizationdesign
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发布时间：2023-11-14 - 摘要：Abstract:Fortheproblemofgasrarefiedeffectinsidetheaerostaticbearinginconditionofmicroclearance,theReynoldsequationsuitableforcompressiblegasintherarefiedeffectwasdeducedthroughintroducingflowfactoroftherarefiedeffecttotheReynoldsequation.TheReynoldsequationwasdissociatedbyusingthefiniteelementmethod,pressuredistributioninthebearingundertherarefiedeffectwereanalyzedbythesoftwareMATLAB,theinfluenceruleofrarefiedeffecttothebearingperformancecapacityandstiffnesswasstudied,whichwasverifiedbyexperimentindirectly.Theresultsshowedthatthestiffnessofbearinginconditionofconsideringtheflowfactorwasclosetothestiffnesstestedbyexperimentwhenthegasclearancewas8~10μm.Thevalueofanalysiswas20%lessthantheexperiment,whichprovidedatheoreticalbasistotheresearchoftheperformanceofbearingsinmicro-scale.关键词：aerostaticbearing;rarefiedeffect;flowfactor;finitedifferencemethod
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发布时间：2023-11-14 - 摘要：Abstract:Experiments found that the influence of gas pressure on the melt extrusion was very significant in gas assisted extrusion (GAE).In order to ascertain the influence mechanism of the gas pressure on the melt extrusion,a gas/melt two phase fluid model was established,the non isothermal viscoelastic numerical simulation of the GAE was performed using finite element method,the change discipline of melt extrudate profile,flow velocities,pressure drop and first normal stress difference etc were obtained under different gas pressures.Simulation results demonstrated that gas pressure has a significant effect on the flow distributions and extrudate profile of melt.When the gas pressure is little and stable gas layer can be formed,the flow velocities is uniform, pressure drop and first normal stress difference is little,and no extrudate deformation appears.But with the increase of gas pressure,the flow velocities,pressure drop,first normal stress difference,and the extrudate shrinkage degree of melt all evidently increase.It was demonstrated that the first normal stress difference at the entrance of the gas/melt interface is the main reason for triggering the extrudate deformation and flow distributions changes due to the influence of gas.关键词：polymer;extrusionforming;gasassisted;gaspressure;numericalsimulation
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发布时间：2023-11-14 - 摘要：Abstract:ByusingGAMBITsoftware,thecomputationaldomainofthethrottleclearancewasmeshedinthemixedgridunittypeofhexahedronandwedge.Basedonlaminarflowmodel,threedimensionalnumericalsimulationoftheworkingstateoffloatingring’sthrottleclearanceunderdifferentaxisdiametersandworkingconditionswascarriedoutinFLUENTthroughSIMPLEalgorithm.Twonewequations,oneofwhichcanbeusedtocalculatethecriticalcircumferentialReynoldsnumberforeccentricannularspaceandtheothercanbeusedtocalculateleakagerate,wereobtainedfromthesimulationdata.Theresultsindicatedthattheleakageincreasedwiththeincreaseofeccentricityratio,heightofgapandpressuredrop,whiletheinfluenceoftheaxis’rotationspeedwasnegligible.Theresultslaidafoundationforfurtherinvestigationanddesignofafloatingringseal.关键词：floatingringseal;CFD;circumferentialcriticalReynoldsnumber;simulation;leakage
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发布时间：2023-11-14 - 摘要：Abstract:Al(Ⅲ) complexes with flavonoids luteolin and baicalein in ethanol were synthesized and characterized using ultraviolet visible spectrometry，infrared spectrometry and mass spectrometry.The molar ratio method and mass spectrometry were applied to ascertain the stoichiometry ratio of the flavonoid metal complexes.Both of the methods indicated a 1〖DK〗∶2 (metal/ligand) composition for the two complexes.Spectroscopic data suggested that coordination reaction occurred in the 4-carbonyl-5-hydroxyl groups and the 3’,4’-dihydroxyl groups for luteolin Al(Ⅲ) complex，and 4-carbonyl-5-hydroxyl groups and 6,7-dihydroxy groups for baicalein-Al(Ⅲ) complex，respectively.Specifically, as the center, Al(Ⅲ) coordinated two molecules of flavonoid to form one five membered ring and one six membered ring using tetra coordinate complex. Antioxidant abilities of the free ligands and complexes were also investigated under an electrochemical point of view. Both the ligands and complexes has scavenging effects on DPPH，hydroxyl and superoxide radicals.Overall，the avonoid metal complexes are more effective antioxidants than the free avonoids.关键词：luteolin;baicalein;complexes;spectroscopy;antioxidant activity
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发布时间：2023-11-14
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