摘要:The aim of this paper is to seek the numerical solution of a class of variable order fractional integral-differential equation in terms of Bernstein polynomials.The fractional derivative is described in the Caputo sense.Four kinds of operational matrixes of Bernstein polynomials are introduced and are utilized to reduce the initial equation to the solution of algebraic equations after dispersing the variable.By solving the algebraic equations,the numerical solutions are acquired.The method in general is easy to implement and yields good results.Numerical examples are provided to demonstrate the validity and applicability of the method.
摘要:A multi-layered model for heat conduction analysis of a thermoelectric material strip(TEMs)with a Griffith crack under the electric flux and energy flux load has been developed.The materials parameters of the TEMs vary continuously in an arbitrary manner.To derive the solution,the TEMs is divided into several sub-layers with different material properties.The mixed boundary problem is reduced to a system of singular integral equations,which are solved numerically.The effect of strip width on the electric flux intensity factor and thermal flux intensity factor are studied.
摘要:In this paper we propose a novel two-stage method to solve the threedimensional Poisson equation in an arbitrary bounded domain enclosed by a smooth boundary.The solution is decomposed into a particular solution and a homogeneous solution.In the first stage a multiple-scale polynomial method(MSPM)is used to approximate the forcing term and then the formula of Tsai et al.[Tsai,Cheng,and Chen(2009)]is used to obtain the corresponding closed-form solution for each polynomial term.Then in the second stage we use a multiple/scale/direction Trefftz method(MSDTM)to find the solution of Laplace equation,of which the directions are uniformly distributed on a unit circle 1,and the scales are determined a priori by the collocation points on boundary.Two examples of 3D data interpolation,and several numerical examples of direct and inverse Cauchy problems in complex domain confirm the efficiency of the MSPM and the MSDTM.
摘要:Monte Carlo Simulations(MCS),commonly used for reliability analysis,require a large amount of data points to obtain acceptable accuracy,even if the Subset Simulation with Importance Sampling(SS/IS)methods are used.The Second Order Reliability Method(SORM)has proved to be an excellent rapid tool in the stochastic analysis of laminated composite structures,when compared to the slower MCS techniques.However,SORM requires differentiating the performance function with respect to each of the random variables involved in the simulation.The most suitable approach to do this is to use a symbolic solver,which renders the simulations very slow,although still faster than MCS.Moreover,the inability to obtain the derivative of the performance function with respect to some parameters,such as ply thickness,limits the capabilities of the classical SORM.In this work,a Neural Network-Based Second Order Reliability Method(NNBSORM)is developed to replace the finite element algorithm in the stochastic analysis of laminated composite plates in free vibration.Because of the ability to obtain expressions for the first and second derivatives of the NN system outputs with respect to any of its inputs,such as material properties,ply thicknesses and orientation angles,the need for using a symbolic solver to calculate the derivatives of the performance function no longer exists.The proposed approach is accordingly much faster,and easily allows for the consideration of ply thickness uncertainty.The present analysis showed that dealing with ply thicknesses as random variables results in 37%increase in the laminate’s probability of failure.
摘要:This paper is devoted to the homogenization and statistical multiscale analysis of a transient heat conduction problem in random porous materials with a nonlinear radiation boundary condition.A novel statistical multiscale analysis method based on the two-scale asymptotic expansion is proposed.In the statistical multiscale formulations,a unified linear homogenization procedure is established and the second-order correctors are introduced for modeling the nonlinear radiative heat transfer in random perforations,which are our main contributions.Besides,a numerical algorithm based on the statistical multiscale method is given in details.Numerical results prove the accuracy and efficiency of our method for multiscale simulation of transient nonlinear conduction and radiation heat transfer problem in random porous materials.
摘要:A new and efficient Grey Wolf Optimization(GWO)algorithm is implemented to solve real power economic dispatch(RPED)problems in this paper.The nonlinear RPED problem is one the most important and fundamental optimization problem which reduces the total cost in generating real power without violating the constraints.Conventional methods can solve the ELD problem with good solution quality with assumptions assigned to fuel cost curves without which these methods lead to suboptimal or infeasible solutions.The behavior of grey wolves which is mimicked in the GWO algorithm are leadership hierarchy and hunting mechanism.The leadership hierarchy is simulated using four types of grey wolves.In addition,searching,encircling and attacking of prey are the social behaviors implemented in the hunting mechanism.The GWO algorithm has been applied to solve convex RPED problems considering the all possible constraints.The results obtained from GWO algorithm are compared with other state-ofthe-art algorithms available in the recent literatures.It is found that the GWO algorithm is able to provide better solution quality in terms of cost,convergence and robustness for the considered ELD problems.
摘要:The action of drifting ice floes may induce strong vibrations of offshore structures,and further reduce the structural safety and serviceability.The aim of this paper is to develop a method by considering ice crushing as a stochastic process.On the basis of ice force spectrum which considers the time and spatial correlation between the local ice forces,a simulation methodology to generate the stochastic ice forces process of vertical offshore structure is proposed.The crucial segment in the simulation is to accurately calculate the effective ice pressure,and it is accomplished by an empirical formula which can provide a high calculation accuracy.Considering the effect of incidence angle and tangential ice force,global ice force spectrum is established,and the synthesis of the local ice force is realized.The presented simulation methodology is conducted on the Norstr?msground lighthouse to verify its efficacy.The results show that the simulated maximum global ice forces are close to those measured data,and the frequency contents of the generations coincide well with the target.They directly proves the validity of the proposed simulation method.Compared with the traditional methods,such as field measurement and ice force identification,the present simulation method has advantages in the application range.It can be used to simulate the stochastic global ice force for an arbitrary width offshore structure.In addition,it can also be used for extreme ice force analysis and dynamic response analysis of offshore structures.
摘要:In this paper,the three-variable shifted Jacobi operational matrix of fractional derivatives is used together with the collocation method for numerical solution of threedimensional multi-term fractional-order PDEs with variable coefficients.The main characteristic behind this approach is that it reduces such problems to those of solving a system of algebraic equations which greatly simplifying the problem.The approximate solutions of nonlinear fractional PDEs with variable coefficients thus obtained by threevariable shifted Jacobi polynomials are compared with the exact solutions.Furthermore some theorems and lemmas are introduced to verify the convergence results of our algorithm.Lastly,several numerical examples are presented to test the superiority and efficiency of the proposed method.
摘要:In fully mechanized solid backfilling mining(FMSBM),the loose gangues backfill body(LGBB)that filled into the goaf becomes the main body of bearing the overburden load.The deformation resistance of LGBB is critical for controlling overburden movement and surface subsidence.During the process of load bearing,LGBB will experience grain crushing,which has a significant effect on its deformation resistance.Gangues block will be accompanied with obvious acoustic emissions(AE)features in process of slipping,flipping and damaging.Under confined compression test,monitoring the AE parameters of LGBB can reveal the impact mechanism of grain crushing on LGBB deformation.The study is of great significance for obtaining an in-depth understanding of the mechanical properties of LGBB,and providing guidance to the engineering practice of FMSBM.In order to study the rules of acoustic emissions(AE)of graded Loose gangues backfill body(LGBB)in confined compression test,this article introduces the AE systems to conventional confined compression test to monitor AE signals resulted from the friction and fragmentation among LGBB.The test results show that in the process of LGBB compaction,AE parameters are highly correlated with the strain-stress curve.AE events of balanced-sized graded gangues are more inactive than other two graded samples in different compression stages,AE events of large-particle-dominated graded gangues are most active.In the spatial distribution,AE events are the most active on the edges and the middle part of test samples and the phenomenon of grain crushing is the most obvious in these positions.
摘要:A spike response model(SRM)based on the spikes generator circuit(SGC)of adaptive fuzzy spiking neurons(AFSNs)is developed.The SRM is simulated in MatlabTM environment.The proposed model is applied to a configuration of a fuzzy exclusive or(fuzzy XOR)operator,as an illustrative example.A description of the comparison of AFSNs with other similar methods is given.The novel method of the AFSNs is used to determine the value of the weights or parameters of the fuzzy XOR,first with dynamic weights or self-tuning parameters that adapt continuously,then with fixed weights obtained after training,finally with fixed weights and a dynamic gain or self-tuning gain for a fine adjustment of amplitude.
摘要:In this paper,the classical composite middle rectangle rule for the computation of Cauchy principal value integral(the singular kernel 1=(x-s))is discussed.With the density function approximated only while the singular kernel is calculated analysis,then the error functional of asymptotic expansion is obtained.We construct a series to approach the singular point.An extrapolation algorithm is presented and the convergence rate of extrapolation algorithm is proved.At last,some numerical results are presented to confirm the theoretical results and show the efficiency of the algorithms.
摘要:It is very important to determine the daily horizontal global,diffuse and beam irradiations correctly in planning energy systems,in cost analysis,in the atmosphere,and in the productivity evaluations.Besides,the knowledge of accurate solar irradiation is the most important component of the essential climate variables according to the Global Climate Observing System(GCOS)in August 2010.It is known that the changes of these irradiation parameters directly affect our atmosphere and cloud formation processes.Turkey is one of the countries,which has high solar energy potential by reason of its climatic and regional factors.Especially,Konya and Karaman regions(in Central Anatolia Region)are seen as the most efficient area in where the solar energy systems will be processed.Because of this reason that region has been designated as an Energy Specialized Industrial Zone(ESIZ)in Turkey.Solar energy inputs must carefully be determined in this region where the systems will be installed with respect to the climate and energy efficiency.In this work aims to understand the components of daily solar irradiation on a horizontal surface in selected region are analyzed by using the HELIOSAT method by setting satellite images.Results have been determined by comparing with ground measured data and method were analyzed by using statistical errors.According to the seven-year data,the accuracy of the daily global and diffuse solar irradiations estimation was found acceptable levels.Nevertheless,the estimated results reveal that this method can easily be adapted to any point in the world resembles with the Central Anatolia Region climate type.Especially,the obtained results are significant for the simulation studies such as solar PV power plants performance,payback time,and cost of energy analysis.Also,these results can be used to increase the performance of the solar energy system and to determine long-term a road map for climate change studies.
摘要:Adsorption deformation significantly affects the seepage characteristics of coal.However,effect of sorption time on coal permeability and gas pressure has not been investigated systematically.In this study,the sorption experiment of coal samples is conducted to elaborate the importance of sorption equilibration time.Then a coupled coal deformation and gas flow model is established considering the sorption characteristic and permeability evolution.This coupled model is implemented through finite element method to analyze the effect of sorption time on coal permeability and gas pressure.The simulation results reveal that the gas pressure of the coal will change with the adsorption time.The fracture pressure maintains a high level while the matrix pressure is relatively low during the adsorption process.The sorption time has a great influence on the distribution of gas pressure.The smaller the adsorption time is,the lower the gas pressure becomes.
摘要:This research paper proposes a single phase fifteen level inverter for a grid connected PV system.The proposed inverter is also called cascaded asymmetric multilevel inverter.By adopting appropriate hybrid modulation technique improved output voltage is obtained with minimum number of power electronic switches.By reducing the number of gate triggering circuits of the switches,the size and power consumption of the driving circuits can be reduced.The total harmonic distortion of the output of the inverter is improved by this inverter.The proposed inverter developed by cascading a full bridge inverter with modified H bridge multilevel inverter.The validity of the proposed system is verified through MATLAB simulations.
摘要:In this paper,by introducing a chemical field,the J-integral formulation is presented for the chemo-mechanical coupled medium based on the laws of thermodynamics.A finite element implementation of the J-integral was performed to study the mode I chemo-mechanical coupled fracture problem.For derivation of the coupled J-integral,the equivalent domain integral(EDI)method was applied to obtain the mode I J-integral,with expression of the area integrals based on constitutive relationships of a linear elastic small deformation for chemo-mechanical coupling,instead of the finite deformation problem.A finite element procedure is developed to compute the mode I J-integral,and numerical simulation of the y-direction stress field is studied by a subroutine UEL(User defined element)developed in ABAQUS software.Accuracy of the numerical results obtained using the mode I J-integral was verified by comparing them to a well-established model based on linear elastic fracture mechanics(LEFM).Furthermore,a numerical example was presented to illustrate path-independence of the formulated J-integral for a chemo-mechanical coupled specimen under different boundary conditions,showing a high accuracy and reliability of the present method.The variation laws of J-integral and the y-direction stress field with external chemical,mechanical loading and time are revealed.The J-integral value increases with larger external concentration loading in the same integral domain.The extent of diffusion is much greater with larger concentration,which leads to a stronger coupling effect due to the chemical field.This work provides new insights into the fracture mechanics for the chemo-mechanical coupled medium.
摘要:A semi-analytical form of complex modal analysis is proposed for the time-variant dynamical problem of rotating pipe conveying fluid system.The complex mode superposition method is introduced for the dynamic analysis in the time and frequency domains,in which appropriate orthogonality conditions are constructed to decouple the time-variant equation of motion.Consequently,complex frequencies and modes of vibration are analytically formulated and the variations of frequencies and damping of the system are evaluated.Numerical time-variant example of rotating pipe conveying fluid illustrates the effectiveness and accuracy of this method.Furthermore,the proposed solution scheme is also applicable to other similar time-variant dynamical problems.
摘要:This article presents an improved method of despeckling the ultrasound medical images.In this paper a modified local statistics mean variance filter method has been proposed.In the proposed method,more consideration is given to local statistics since local statistical features are more important rather than global features.Various parameters like mean square error,peak signal to noise ratio,quality index,and structural similarity index measure are calculated to analyze the quality of the despeckled image.
摘要:In this article,the post-peak softening stage of the constitutive relation and the elastic stiffness degradation of concrete are investigated,and a highly reasonable constitutive relation curve is proposed.At the material level,the energy change in the concrete failure process is studied based on the different stress-strain curves of concrete under uniaxial tension and compression.The concrete failure criterion based on elastic strain energy density is deemed suitable and consistent with the experimental phenomena.The hysteresis phenomenon(lags behind the peak strength)is also discussed.At the structure level,the strength reduction method is employed for the stability analysis,the energy change in the failure process of the Long Xi-Kou Dam is examined,and the results show that the dam failure criterion based on elastic strain energy shows a greater significance in practical applications compared with other conventional structural failure criteria in engineering.This criterion is objective and can avoid subjective arbitrariness.
摘要:In this paper,a three dimension model is built according to real surface cleaner in airport runway rubber mark cleaning vehicle and numerical simulation of this model is carried out using Ansys Fluent software.After comparison and analysis of the flow fields between high speed rotating waterjet and static waterjet formerly studied by other researchers,the influences of different standoff distances from nozzle outlet to runway surface and rotation speeds on rubber mark cleaning effect are simulated and analyzed.Results show the optimal operation parameters for the simulated model and quantitative advices are given for design,manufacture and operation of the airport runway rubber mark cleaning vehicle.
摘要:The failure behavior of the precast prestressed concrete T girder was investigated by destructive test and finite-element analysis,and the mid-span deflection,girder stiffness and the variation of the cross section strain in the loading process were obtained,and the mechanical properties,mechanical behavior,elastic and plastic behavior and ultimate bearing capacity of T girder with large span were revealed.Furthermore,the relationship between the beam stiffness degradation,the neutral axis in cross-section,steel yielding and concrete cracking are investigated and analyzed.A method was proposed to predict the residual bearing capacity of a bridge based on the variation of the position of the cross section strain distribution and the section neutral axis,which provided a theoretical basis for predicting the stiffness detection and carrying capacity assessment of prestressed concrete beam.
摘要:In this paper,an interacting multiple-model(IMM)method based on datadriven identification model is proposed for the prediction of nonlinear dynamic systems.Firstly,two basic models are selected as combination components due to their proved effectiveness.One is Gaussian process(GP)model,which can provide the predictive variance of the predicted output and only has several optimizing parameters.The other is regularized extreme learning machine(RELM)model,which can improve the overfitting problem resulted by empirical risk minimization principle and enhances the overall generalization performance.Then both of the models are updated continually using meaningful new data selected by data selection methods.Furthermore,recursive methods are employed in the two models to reduce the computational burden caused by continuous renewal.Finally,the two models are combined in IMM algorithm to realize the hybrid prediction,which can avoid the error accumulation in the single-model prediction.In order to verify the performance,the proposed method is applied to the prediction of moisture content of alkali-surfactant-polymer(ASP)flooding.The simulation results show that the proposed model can match the process very well.And IMM algorithm can outperform its components and provide a nice improvement in accuracy and robustness.
摘要:Cryptography and steganography are two important and related fields of information security.But,steganography is slightly different in the sense that it hides the existence of secret information from unauthorized users.It is one of the most appealing research domains,have applications like copyright protection,data integrity protection and manipulation detection.Several steganography techniques have been proposed in literature.But,in this work a new information hiding algorithm is presented.The proposed technique de-correlates frequency components of cover image using discrete cosine transform and uses the least significant bits of frequency components for hiding secret information.The tech-nique hides variable number of bits of secret message in different frequency components.Therefore,it hides different amount of secret information in different regions of cover im-age and results in enhancement of security.The algorithm has the flexibility to change the hiding capacity and quality of final stego image.It has been observed from experimental results that a hiding a capacity from 3%to 43%can be achieved with significantly good quality of 41 dB to 37 dB in term of peak signal to noise ratio.The successful recovery of the hidden information need the pattern,called stego key,in which is used in hiding process.The algorithm provides twofold security;hiding keeps the existence of hidden information secret and the large key size makes the retrieval of hidden information difficult for intruders.
摘要:Biodegradable zinc alloy stents are a prospective solution for complications caused by the incompatibility between artery and permanent stents.However,insufficient scaffolding has limited the clinical application of biodegradable zinc alloy stents.Therefore,in this study,a new stent concept was designed to improve the scaffolding.The mechanical performances of the new and a traditional design stent were investigated and compared using finite element analysis(FEA).The new and traditional design stent were expanded to the intended radial displacement of 0.24 mm under the expansion pressure of 0.58 MPa and 0.45 MPa,respectively.Then,a pressure load of 0.35 MPa was exerted on the outer surfaces of the two stents to compress them.The results showed that the radial recoiling ratio were 45.3%and 83.3%for the new and the traditional stent,respectively.The simulations demonstrate that the biodegradable zinc alloy stent offers enhanced support because of the new structural design.This study implies that biodegradable zinc alloy stent can be a new competitive intervention device for the future clinical cardiovascular application.
摘要:An improved teaching-learning-based optimization(I-TLBO)algorithm is proposed to adjust the parameters of extreme learning machine with parallel layer perception(PELM),and a well-generalized I-TLBO-PELM model is obtained to build the model of NOX emissions of a boiler.In the I-TLBO algorithm,there are four major highlights.Firstly,a quantum initialized population by using the qubits on Bloch sphere replaces a randomly initialized population.Secondly,two kinds of angles in Bloch sphere are generated by using cube chaos mapping.Thirdly,an adaptive control parameter is added into the teacher phase to speed up the convergent speed.And then,according to actual teaching-learning phenomenon of a classroom,students learn some knowledge not only by their teacher and classmates,but also by themselves.Therefore,a self-study strategy by using Gauss mutation is introduced after the learning phase to improve the exploration ability.Finally,we test the performance of the I-TLBO-PELM model.The experiment results show that the proposed model has better regression precision and generalization ability than eight other models.
摘要:This paper describes a study of the effects of graphite nodule characteristics on a subsurface crack in austempered ductile iron(ADI).A representative specimen of ADI,subjected to sliding contact load,is modeled using finite elements aiming to obtain the shear stress intensity factor(KII).The parameters varied were(i)the nodule diameter(two different values were considered),(ii)the distance between the nodule and the tip of the crack and(iii)the position of the load relative to the tip of the crack.The results of the numerical simulations show that the smaller diameter nodule has a larger influence on KII,suggesting a higher contact fatigue crack propagation rate in the material with the smaller nodule.These results are the opposite of those observed in experimental studies and would appear to indicate that other factors should be also considered to ensure realistic estimates of the contact fatigue strength of ADI.
摘要:This paper presents form finding and collapse analysis of cable net structure under strong wind using the finite particle method(FPM).As a kind of particle method,the theoretical fundamentals of the FPM are given.Methods to handle geometric and material nonlinearities of cable element are proposed.The fracture criterion and model for cable element are built to simulate the failure of cable nets.The form-finding and load analysis of two cable nets are then performed in order to initialize the successive of nonlinear analysis.The failure progress of cable nets under dynamic loads is simulated,and the dynamic responses of the typical fracture element are given in details.Analyses of the energy variations during the collapse process also show the failure mechanisms of cable nets,which is useful for the structure collapse resistance design.The numerical applications highlight the capability of the proposed procedure to solve complicate collapse problems with the FPM.
摘要:When the simulation takes account of dissipative mechanisms,e.g.heat conduction and viscosity,the shocks become smeared out to produce thin layers of rapidly and continuously varying energy,density,pressure and velocity rather than discrete surfaces of mathematical discontinuity.In the mid twentieth century,Von Neumann and Richtmyer suggested the use of a viscous pressure term(bulk viscosity)in the equilibrium equations for ideal gases in order to examine the shock while avoiding numerical oscillations at the shock front.When the bulk viscosity is included in the conservation equations,the comprehensive physics present a continuous solution satisfying the Rankine-Hugoniot conditions.Nevertheless,the published literature includes few engineering and research studies presenting the novel equilibrium equations in which the incorporation of bulk viscosity generates a continuous solution in keeping with conservation laws.The present work is aimed at demonstrating that the artificial bulk viscosity defined by Von Neumann and Richtmyer is also applicable to fluids described by a density-linear equation of state,that the novel equations present a continuous solution,and that a shock layer of the same order as the computational grid is generated.Although the method has been employed and mathematically proven for onedimensional flow,it would seem to be just as relevant to the analysis of more complex flow dynamics and fluid structure interactions via an application of the Arbitrary Lagrangian Eulerian(ALE)formulation.
摘要:This study developed a new technology for preparing high-chromium cast iron(HCCI)/low-carbon steel(LCS)wear-resistant composite plates by hot rolling at a 1050°C and a rolling speed of 0.2 m/s.The effects of different rolling reductions(30%,45%,and 60%)on the microstructure(interface and HCCI layer)and mechanical properties(bonding strength,hardness,and wear resistance)of the composite plate were studied.SEM images showed that when the reduction was increased,no impurities and interlayers were found between the microscopic interfaces after hot rolling,and the bonding interface exhibited a wave-like shape.EDS analysis showed that the Cr element diffusion between two metals after hot rolling was promoted when the reduction was increased,thereby improving the bonding quality under the same rolling temperature and rolling speed.Experiments showed that due to the stress release effect of the LCS of the cladded layer,the macro-slab shape after hot rolling performed well,and the brittle HCCI layer underwent thermoplastic deformation without cracking.Moreover,the increase of rolling reduction improved the bonding quality.As the rolling reduction was increased,the volume fraction of Cr-carbides in the HCCI layer also increased,resulting in an increase of hardness and wear-resistance.
摘要:An identification technique for sharp interface and penetrated isolated particles is developed for simulating two-dimensional,incompressible and immiscible two-phase flows using meshless particle methods in this paper.This technique is based on the numerically computed density gradient of fluid particles and is suitable for capturing large interface deformation and even topological changes such as merging and breaking up of phases.A number of assumed particle configurations will be examined using the technique,including these with different level of randomness of particle distribution.The tests will show that the new technique can correctly identify almost all the interface and isolated particles,and also show that it is better than other existing popular methods tested.
摘要:Exact solutions of the cubic Duffing equation with the initial conditions are presented.These exact solutions are expressed in terms of leaf functions and trigonometric functions.The leaf function r=sleafn(t)or r=cleafn(t)satisfies the ordinary differential equation dx2/dt2=-nr2n-1.The second-order differential of the leaf function is equal to-n times the function raised to the(2n-1)power of the leaf function.By using the leaf functions,the exact solutions of the cubic Duffing equation can be derived under several conditions.These solutions are constructed using the integral functions of leaf functions sleaf2(t)and cleaf2(t)for the phase of a trigonometric function.Since the leaf function and the trigonometric function are used in combination,a highly accurate solution of the Duffing equation can be easily obtained based on the data of leaf functions.In this study,seven types of the exact solutions are derived from leaf functions;the derivation of the seven exact solutions is detailed in the paper.Finally,waves obtained by the exact solutions are graphically visualized with the numerical results.