Dynamic character analysis for the arc welding power source based on fuzzy logic

A lot of experimental methods have been brought forth to assess the dynamic character of the arc welding power source, but up to now, this issue has not been solved very well. In this paper, based on the fuzzy logic reasoning method, a dynamic character assessing model for the arc welding power source was established and used to analyze the dynamic character of the welding power source. Three different types of welding machine have been tested, and the characteristic information of the electrical signals such as re-striking arc voltage, low welding current and so on of the welding process were extracted accurately by using a self-developed welding dynamic arc wavelet analyzer. The experimental results indicate that this model can be used as a new assessing method for the dynamic character of the arc welding power source.

Dynamic characteristics of multi-arc thermal plasma in four types of electrode configurations

The enhanced volume of thermal plasma is produced by a multi-arc thermal plasma generator with three pairs of discharge electrodes driven by three directed current power suppliers.Combined with a high-speed camera and an oscilloscope,which acquire optical and electric signals synchronously,the dynamic behavior of different kinds of multi-arc discharge adjusted by the electrode arrangement is investigated.Also,the spatial distributions and instability of the arc discharge are analyzed in four electrode configurations using the gray value statistical method.It is found that the cathodic arcs mainly show a contracting state,while the anodic arcs have a trend of transition from shrinkage to a diffusion-like state with the increase of the discharge current.As a result of the adjustment of the electrode configuration,a high temperature region formed in the center of the discharge region in configurations of adjacent electrodes with opposite flow distribution and opposite electrodes with swirl flow distribution due to severe fluctuation of arcs.The discharge voltage rises with increased discharge current in this novel multi-arc plasma generator.It is also found that anode ablation mainly occurs on the conical surface at the copper electrode tip,while cathode erosion mainly occurs on the surface of the inserted tungsten and the nearby copper.

Dynamic Mechanical Characterizations and Road Performances of Flame Retardant Asphalt Mortars and Concretes

To research the dynamic mechanical properties and road performances of flame retardant asphalt mortars and mixtures, four different asphalt mortars/mixtures were prepared: a reference group and three asphalt mortars/mixtures containing composite flame retardant materials(M-FRs) of different proportions. Temperature sweep, frequency sweep, repeated creep test, force ductility test and bending beam rheological test were carried out to research the dynamic mechanical properties of asphalt mortars containing M-FRs; wheeltracking test, low-temperature bending test and freeze-thaw split test were used to study the road performances of asphalt mixtures containing M-FRs. The results show that high-temperature performances of the three flame retardant asphalt mortars improve greatly, while low-temperature cracking resistances decline. Both hightemperature performances and water stabilities of asphalt mixtures containing M-FRs are quite good and exceed the specification requirements. However, their low-temperature performances decline in different degrees. In summary, besides their good flame retardancy, the flame retardant asphalt mortars and mixtures also exhibit acceptable road performance.

DYNAMICAL CHARACTER FOR A PERTURBED COUPLED NONLINEAR SCHRDINGER SYSTEM

The dynamical character for a perturbed coupled nonlinear Schrodinger system with periodic boundary condition was studied. First, the dynamical character of perturbed and unperturbed systems on the invariant plane was analyzed by the spectrum of the linear operator. Then the existence of the locally invariant manifolds was proved by the singular perturbation theory and the fixed-point argument.

Vibrations induced by tunnel boring machine in urban areas: In situ measurements and methodology of analysis

Excavation with tunnel boring machine(TBM)can generate vibrations,causing damages to neighbouring buildings and disturbing the residents or the equipment.This problem is particularly challenging in urban areas,where TBMs are increasingly large in diameter and shallow in depth.In response to this problem,four experimental campaigns were carried out in different geotechnical contexts in France.The vibration measurements were acquired on the surface and inside the TBMs.These measurements are also complemented by few data in the literature.An original methodology of signal processing is pro-posed to characterize the amplitude of the particle velocities,as well as the frequency content of the signals to highlight the most energetic bands.The levels of vibrations are also compared with the thresholds existing in various European regulations concerning the impact on neighbouring structures and the disturbance to local residents.

Design of a New Chaos Circuit and Its Encryption to Digital Information

A new hyperchaos circuit system with simple structure is designed in this paper. It can be implemented with changeable dimensions 3, 5, 7, 9, etc, therefore it can afford different security grades for applications. The dynamic characters of the 7th order circuit have been analyzed as an example. Using the hyperchaos time sequence produced by this circuit as key sequence, the encryption and decryption to digital signals of text and image files have been realized, and the real-time ability has been increased with encrypting digital signals per byte.

Characterization of the flowability dynamics of granular material flowing down a narrow channel

The flowability of granular material is commonly determined from shear cell tests,but in the real world,the granular flow is quite different in many cases.For this paper,the flowabilities in a narrow channel of five different granular materials were investigated.The flow parameters of the granular flows were determined to classify the flowabil让ies.Granular flow surface velocities and flow heights and thicknesses were measured,and it was found that the mean shear rates in the linear portions of the velocity profiles in crease with both flow rates and incli nation.A universal parameter,the ratio of the sine of the inclin ation to the shear rate in the linear part of the velocity profile,is proposed as a constant.This constant is independent of particle properties.In addition,a flowability parameter,the ratio of the mean shear rate to the cosine of the inclination,is proposed to characterize the friction between the particles in the flowing granular material.

Observation of Blobs and Holes in the Boundary Plasma of EAST Tokamak

Intermittent convective transport at the edge and in the scrape-off layer （SOL） of EAST was investigated by using fast reciprocating Langmuir probe. Holes, as part of plasma structures, were detected for the first time inside the shear layer. The amplitude probability distribution function of the turbulence is strongly skewed, with positive skewed events （＂blobs＂） prevailing in the SOL region and negative skewed events （＂holes＂） dominant inside the shear layer. The statistical properties coincide with previous observations from JET. The generation mechanism of blobs and holes is also discussed. In addition burst structure and dynamics character of them are also presented.

Regional Man-land System:Its Dynamics Characters,Structure and Evolutionary Models

From the point of view of dynamics, the author studies some important issues concerning the dynamics of the regional man land system. As a complex composition of man land interaction, the regional man land system is a semi open, nonlinear and partly controllable system which possesses a multi hierarchy interface structure and has its own evolutionary law. The dynamics characters, the dynamic structure and the evolutionary models of the regional man land system are all deeply discussed in this paper.

Binary Level Set Methods for Dynamic Reservoir Characterization by Operator Splitting Scheme

In this paper,operator splitting scheme for dynamic reservoir characterization by binary level set method is employed.For this problem,the absolute permeability of the two-phase porous medium flow can be simulated by the constrained augmented Lagrangian optimization method with well data and seismic time-lapse data.By transforming the constrained optimization problem in an unconstrained one,the saddle point problem can be solved by Uzawas algorithms with operator splitting scheme,which is based on the essence of binary level set method.Both the simple and complicated numerical examples demonstrate that the given algorithms are stable and efficient and the absolute permeability can be satisfactorily recovered.

Precisely monitoring and tailoring the surface structures of nanomaterials by in-situ electron microscopy

The transmission electron microscope(TEM)is now one of the most powerful tools for structural characterization due to its high spatial resolution,especially with the advent of the spherical aberration corrector.The interaction between electrons and specimens allows tailoring surface structures by electron irradiation.Furthermore,along with the development of special holders and specimen preparation techniques,the structural evolution of surfaces/interfaces can be dynamically monitored under external fields or reaction environments at the nanoscale,which promotes not only the establishment of the relationship between atomic structures and novel properties,but also potential applications in nanodevices.In this report,we review some of our recent results obtained by TEM,including dynamical observation of surface-mediated novel phenomena,controllable fabrication of nanostructures,and some potential applications in nanodevices.