Percolation Model of Graphite-modified Asphalt Concrete

The addition of graphite powder in conventional asphalt mixture can prodaced asphalt concrete with excellent electrical performance. Percolation theory was employed to discuss the relation between the conductivity and graphite content of graphite-rnodified asphalt concrete. It was found that the results of percolation model are consistent with experimental values. The percolation threshold of graphite-modified asphalt concrete is 10.94% graphite content account for the total volume of the binder phase consisting of asphalt and graphite. The critical exponent is 3.16, beyond the range of 1.6-2.1 for the standard lattice continuous percolation problem. Its reason is that the tunnel conduction mechanism originates near the critical percent content , which causes this system to be not universal. Tunnel mechanism is demonstrated by the nonlinear voltage-current characteristic near percolation threshald. The percolation model is able to well predict the formation and development of conductive network in graphite-modified asphalt concrete.     

Stress Field of Straight Edge Dislocation in Magnetic Field

To study the changes in mechanical properties of materials within magnetic fields and the motion of dislocations, stress fields of dislocation in magnetic field need to be calculated. The straight edge dislocation is of basic importance in various defects . The stress field of straight edge dislocation in an external static magnetic field is determined by the theory of elasticity and electrodynamics according to the Volterra dislocation model for continuous media. This reduces to the known stress field when the magnet field is zero. The results can be used for further study on the strain energy of dislocations and the interactions between dislocations in magnetic fields.     

Novel grey forecast model and its application

The advancement of grey system theory provides an effective analytic tool for power system load forecast. All kinds of presently available grey forecast models can be well used to deal with the short-term load forecast. However, they make big errors for medium or long-term load forecasts, and the load that does not satisfy the approximate exponential increasing law in particular. A novel grey forecast model that is capable of distinguishing the increasing law of load is adopted to forecast electric power consumption (EPC) of Shanghai. The results show that this model can be used to greatly improve the forecast precision of EPC for a secondary industry or the whole society.     

Generalization of Hill’s yield criterion to tension-compression asymmetry materials

This paper is devoted to developing a yield criterion that can model the asymmetry and anisotropy in yielding of pressure insensitive metals,in terms of accuracy and simplicity of formulation.First,a new isotropic yield criterion,which can model the asymmetry in yielding of pressure insensitive metals,is proposed.Further,using Cazacu’s generalizations to anisotropic conditions of the invariants of the deviatoric stress,the proposed isotropic yield criterion is extended to orthotropy.The proposed anisotropic criterion has a quite simple form,and the number of material constants involved is only half of that of Cazacu’s(2004) yield criterion.Compared to Hill’s(1948) yield criterion,the proposed anisotropic yield criterion has three additional constants,which are used to model the tension-compression asymmetry of materials.All the material constants involved in the criterion can be determined by simple tests.The proposed criterion reduces to Hill’s(1948) yield criterion if the tensile and compressive yield stresses are equal.In other words,the proposed anisotropic yield criterion can be considered as an extension of Hill’s(1948) criterion to tension-compression asymmetry materials.The anisotropic yield criterion is used to describe the plastic response of Cu-Al-Be shape memory alloy(data after Laydi and Lexcellent) and Ni3Al based intermetallic alloy IC10 sheets.It is shown that the proposed yield criterion can describe very well the asymmetry and anisotropy observed in those materials.     

Research of Velocity Compensation Method Based on Range Profile Feature

In this paper, based on the feature of high resolution one-dimensional range profile, two effective motion compensation methods are presented. Firstly, the processing method of stepped-frequency and the response of target moving to range profile are analyzed. Secondly, the function of range profile entropy and range profile contrast are presented for velocity compensation, and then the theory analysis, math model, and solution method are analyzed in detail. Finally, several simulation experiments are designed to prove the accuracy and effectiveness of these two methods. From the final theory analysis and simulation experiments, the conclusion can be drawn that these two methods are effective, which can get much higher velocity estimation accuracy, well real-time and easy to be used in project application. After motion compens-ation, the high resolution one-dimensional range profile will be much better than that used to be, and is used for the detection, recognition and ranging of moving targets.     

RANDOM MICROSTRUCTURE FINITE ELEMENT METHOD AND ITS VERIFICATION FOR EFFECTIVE PROPERTIES OF COMPOSITE MATERIALS

The present study aims at developing a new method--Random Microstructure Finite Element Method (RMFEM) for the effective properties of com posite materials.In this method, a random microstructure model is used to simulate the microstructure of the real composite materials.The physical fields in such a random microstructure model under specified boundary and initial conditions are analyzed by finite element method.The effective properties of composite materials can be obtained from the analysis results.As verification, some effective properties of composite materials, such as elastic module.thermal expansion coefficient, thermal conductivity and elastoplastic properties,are investigated by random microstructure finite element method.The numerical results are given together with the experimental data.It is revealed that the random microstructure finite element method is a very valid method for the determination of the effective properties of composite materials.     

Rheological properties of tailing paste slurry

The initial shear stress (τ) and plastic cohesion (η) are the most important parameters reflecting the rheological properties of the paste slurry. The rheological parameters as well as the quantitative relationship among the consumption of different fill materials were obtained through the experiment and research on these parameters.They can be used to predict the scope of the values of r and ηin production for a given ratio, which can reduce the conveying resistance of fill slurry along the pipelines and avoid the blockage of the pipelines. It is found that the rheological model of the total tailing slurry belongs to the Bingham type, which has a feature of strong internal structure and large initial shear stress. The calculation formula for the resistance loss of pipelines conforms nicely to the field test and the actual production in Jinehuan Nickel Mine.     

Research on Percolation Network and Physical Properties of Graphite/Antimony Composites

The microstructure, friction and wear behaviour of graphite preform and graphite/antimony composites are analysed based on the percolation theory of hydrodynamics to investigate the relationship between the percolation network and physical properties of graphite/antimony composites. The result shows that there are two important factors to enhance friction and wear behaviour of graphite/antimony composites at high temperature： 1） the formation of the pore network in the preform, which is called the first percolation and 2） the optimization of infiltration method in the process of infiltrating antimony, which is called the second percolation. By adding some pyrolysate and controlling the roasting process, perfect net pores and sub-micron percolation microstructure may be formed in the graphite preform. By con- trolling the infiltration process, the saturation of molten antimony infiltrating into perfect pores can be optimized.     

Simulation of people＇s evacuation in tunnel fire

The simulation model Tunev（tunnel evacuation） was developed for people＇s evacuation in tunnel fire. It contains simple database of the people＇s behavioral reaction and structure characteristic parameters of tunnel fireproofing. The model can be used to calculate the total evacuation time in various scenes when fire occurs in the different locations of the tunnel. Combined with fire simulation soft ware CFD- POENICS3.5, Tunev model can be used to calculate the fire danger coming time; by comparing with these two kinds of time, it can be used to assess the safety of the evacuation, and the evacuation process also have a dynamic demo. The simulation results show that the Tunev model can be used to predict the reliability of safe evacuation for people in tunnel fire and provide references for people＇s safe escape scheme. Some relevant concepts of the model were described and an evacuation simulation of a typical tunnel case, i.e. Xuefeng Mountain Tunnel was performed by using this model. And the model＇s validation and actual aoolication were also described.     

A new model of foraging behavior in ant system

Foraging behavior in ant colonies has come to be viewed as a prototypical example to describe how complex group behavior can arise from simple individuals. In order to research the feature of self-organization in swarm intelligence (SI), a mean field model is given and analyzed in foraging process with three sources in this paper. The distance of trails and the richness of each source are considered. Both of the theoretical numerical analysis and Monte Carlo simulation show the power law relationship between the completion time and the flux of foragers. The work presented here guides a better understanding on self-organization and swarm intelligence. It can be used to design more efficient, adaptive, and reliable intelligent systems.     

The grain grading model and prediction of deleterious porosity of cement-based materials

The calculating model for the packing degree of spherical particles system was modified. The grain grading model of cement-based materials was established and could be applied in the global grading system as well as in the nano-fiber reinforced system. According to the grain grading model, two kinds of mortar were de- signed by using the global grain materials and nano-fiber materials such as fly ash, silica fume and NR powder. In this paper, the densities of two above systems cured for 90d were tested and the relationship of deleterious porosity and the total porosity of hardened mortar was discussed. Research results show that nano-fiber material such as NR powder can increase the density of cement-based materials. The.relationship of deleterious porosity and the total porosity of hardened mortar accords with logarithmic curve. The deleterious porosity and the rationality of the grading can be roughly predicted through calculating the packing degree by the grain grading model of cement-based materials.     

A simplified adsorption model for water vapor adsorption on activated carbon

A simplified model was developed to describe the water vapor adsorption on activated carbon. The development of the simplified model was started from the original model proposed by DO and his co-workers. Two different kinds of carbon materials were prepared for water vapor adsorption, and the adsorption experiments were conducted at different temperatures（20-50 °C） and relative humidities（5%-99%） to test the model. It is shown that the amount of adsorbed water vapor in micropore decreases with the temperature increasing, and the water molecules form larger water clusters around the functional group as the temperature is up to a higher value. The simplified model describes reasonably well for all the experimental data. According to the fitted values, the parameters of simplified model were represented by the temperature and then the model was used to calculate the water vapor adsorption amount at 25 °C and 35 °C. The results show that the model can get relatively accurate values to calculate the water vapor adsorption on activated carbon.     

Cellular automata modelling of phase-change memories

A novel approach to modelling phase-transition processes in phase change materials used for optical and electrical data storage applications is presented. The model is based on a cellular automaton (CA) approach to predict crystallization behaviour that is linked to thermal and electrical simulations to enable the study of the data writing and erasing processes. The CA approach is shown to be able to predict the evolution of the microstructure during the rapid heating and cooling cycles pertinent to data storage technology, and maps crystallization behaviour on the nanoscale. A simple example based on possible future nonvolatile phase-change random access solid-state memory is presented.     

Lighting Model of the Real World in Augmented Reality

Construction of a lighting model of the real world is one of the critical aims in an augmented reality (AR) system. The theory of lighting modeling used in computer graphics(CG) is applied in this study. The position of the real light-source is first conjectured from light and shade of the registration image element by element using a ray tracking algorithm. Then the virtual light-source and virtual fiducial are constructed in the CG environment, in which, the Phong model is used to draw the light effect. By comparing the CG scene with the real image, one can modify the parameters of the lighting model over and over again, until the lighting effect of the CG scene is close enough to that of the real image. It is proved that this method works well in the indoor AR system. The method can be used feasibly in most applications with some improvements.     

Angular velocity dynamics identification of small unmanned helicopter using fuzzy model

Attitude identification method for unmanned helicopter based on fuzzy model at hovering is presented.The dynamical attitude model is considered as basis for attitude control and it is very complex.To reduce the complexity of model,nonlinear model of unmanned helicopter with unknown parameters are to be determined by fuzzy system first and then derivative based gradient method is used to identify unknown parameters of model.Gradient method is used due to ability that fuzzy system is not necessarily to be linear in parameters,therefore all fuzzy sets for input and output can be adjusted.The validity of the proposed model was verified using experimental data obtained by the commercially available flight simulator X-Plane.The simulation results showed high accuracy of the modeling method and attitude dynamics data matched well with experimental data.     

Multi-scale modeling of the effective chloride ion diffusion coefficient in cement-based composite materials

N-layered spherical inclusions model was used to calculate the effective diffusion coefficient of chloride ion in cement-based materials by using multi-scale method and then to investigate the relationship between the diffusivity and the microstructure of cement-basted materials where the microstructure included the interfacial transition zone（ITZ）between the aggregates and the bulk cement pastes as well as the microstructure of the bulk cement paste itself.For the convenience of applications,the mortar and concrete were considered as a four-phase spherical model,consisting of cement continuous phase,dispersed aggregates phase,interface transition zone and their homogenized effective medium phase.A general effective medium equation was established to calculate the diffusion coefficient of the hardened cement paste by considering the microstructure.During calculation,the tortuosity（n）and constrictivity factors（D_s/D₀）of pore in the hardened pastes are n≈3.2,D_s/D₀=1.0×10^-4respectively from the test data.The calculated results using the n-layered spherical inclusions model are in good agreement with the experimental results;The effective diffusion coefficient of ITZ is 12 times that of the bulk cement for mortar and 17 times for concrete due to the difference between particle size distribution and the volume fraction of aggregates in mortar and concrete.     

Kinetics model of aerobic phase in hybrid anoxic-oxic process

Kinetics models of COD degradation,biomass growth of the anoxic-oxic ( A/O) system as well as NH3-N degradation in aerobic phase were presented according to the mass balance theory,reaction-diffusion theory and Fick law. Then these models were testified by comparson with experimental results. It is demonstrated that the variation trends of theoretical and experimental values for COD degradation and biomass growth are similar. The deviation rate between theoretical and experimental values is always under 20% even it increases along with the fluctuation of influent organic loading. In terms of NH3-N degradation,nitrification can also be well simulated by the model as the substrates of influent are sufficient. It indicates that the model can accurately reflect the reaction in hybrid A/O process. Models presented herein provide a theoretical basis for the design, operation and control of hybrid A/O process.     

On the Elastic Vibration Model for High Length-Diameter Ratio Rocket with Attitude Control System

An elastic vibration model for high length-diameter ratio spinning rocket with attitude control sys-tem which can be used for trajectory simulation is established. The basic theory of elastic dynamics and vibra-tion dynamics were both used to set up the elastic vibration model of rocket body. In order to study the prob-lena more conveniently, the rocket‘s body was simplified to be an even beam with two free ends. The model was validated by simulation results and the test data.     

ELASTOPLASTIC ANALYSIS OF THICK-WALL CYLINDER CONSIDERING THE MATERIAL＇S DILATANCY CHARACTER

Impermeable bentonite or its mixtures have been proposed as candidate materials to be used in the geotechnical disposal of radioactive nuclear waste. These materials are filled in the space between a canister containing radioactive nuclear waste and an underground chamber to absorb the radionuclide emitting from the canister and simultaneously retard its migration accompanying the permeation of underground water to prevent the surrounding environment from pollution. On the basis of the established elastoplastic strain-hardening mechanical model considering the material‘s dilatancy character, the authors carry out the stress-strain analysis of a thick-wall cylinder in a plane strain state subjected to a pressure difference between internal and external pressures. The analysis may be expected to be a theoretical basis for developing a coupled shear and permeability test apparatus for conducting a permeability test along a sheared plane in a specimen. The apparatus will be used to study the effects of shear strain on the variation of geotechnical materials′ permeability coefficient in order to evaluate the influence of shear strain caused by nonuniform deformation and/or earthquake on the long-term safety of the disposal system of radioactive nuclear waste. The theoretical analysis methods in this paper can be directly spread to the analysis of the deformation and stability of tunnels or roadways driven in soft soils or high moisture-bearing soft rocks.