Nano-meter Displacement Measurement by Phase Analysis of Fringe Patterns Obtained by Optical Methods

0Introduction Inordertomonitorthehealthofstructures,straingagesanddisplacementtransducersare usuallyused.Thereasonisthatmanyrulesorcodesforinspectionofstructuresrequiretousestrain gagesanddisplacementtransducers,anditiseasytousethem.However,thesemethodsarebasically one pointmeasurementmethods.Theyareexpensiveandtime consumingfordistributionanalysis.Opticalmethodssuchasgrating projection,geometricmoir啨,moir啨interferometry,holographic interferometryandspeckleinterferometryareusefultomeasuredi…     

Preparation of ultrafine chitosan particles by reverse microemulsion

Ultrafine chitosan particles were prepared by reverse microemulsion consisting of water, Triton X-100, octanol and cyclohexane. Two methods of preparing ultrafine chitosan particles were adopted and compared using TEM and IR, and possible mechanisms for the formation of ultrafine chitosan particles were proposed. Experimental results show that the method which combined ionic gelation and cross-linking gave uniformly sized chitosan nanoparticles with an average diameter of 92 nm, while the cross-linking without ionic gelation produced spindly chitosan particles with an average length of 943 nm and width of 188 nm.     

Effect of process conditions on the synthesis of carbon nanotubes by catalytic decomposition of methane

A new dual-composition catalyst based on Ni-Mo/MgO with high efficiency of producing carbon nanotubes （CNTs） from methane was reported recently. In the present article, with this type of catalyst, the impact of such experimental parameters as reaction temperature, reaction time, concentration of H2, flow rate ratio of CH4 to H2 on yield and graphitization were investigated, leading to the following optimal growth conditions： reaction time 60min, reaction temperature 900℃, CH4：H2 about 100：20mL/min, under which high-yield multi-walled CNTs bundles were synthesized. Raman measurement indicated that the as-synthesized product was well-graphitized, and the purity was estimated over 95% by TG-DSC analysis. In terms of the above results, an explanation of high-efficiency formation of CNTs bundles and the co-catalysis mechanism of Ni-Mo/MgO were suggested. 2007 Chinese Societv of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V.     

Magnetic filtration of an iron oxide aerosol by means of magnetizable grates

The cleaning of gases with low concentrations of small ferromagnetic or paramagnetic particles is a difficult task for conventional filtration. A new alternative procedure, magnetic filtration, is used in this work. Iron oxide aerosol was generated by elutriation of iron oxide particles from a fluidized bed consisting of a mixture of Geldart-C iron oxide powder and large spherical Geldart-B sand particles. The aerosol was filtered by means of a magnetic filter which consisted of one, two or three iron grates staggered to each other. The experimental installation contained also an isokinetic sampling system and a Microtrac SRA 150 Particle Analyser. A theoretical expression for filtration efficiency was deduced from a previous model taking into account the different forces acting on the iron oxide particles. Experimental filtration efficiency matches quite well calculated theoretical efficiency. It was found that an increase in particle size, in thee number of grates or in the applied magnetic field produced higher filtration efficiencies up to 100% in some cases. In all filtration experiments pressure drop through the magnetic filter was very small.     

Hausdorff dimension of set generated by exceptional oscillations of a class of N-parameter Ganssian processes

A class of N-parameter Gaussian processes are introduced,which are more general than the N-parameter Wiener process.The definition of the set generated by exceptional oscillations of a class of these processes is given,and then the Hansdorff di- mension of this set is defined.The Hausdorff dimensions of these processes are studied and an exact representative for them is given,which is similar to that for the two-parameter Wiener process by Zacharie(2001).Moreover,the time set considered is a hyperrectangle which is more general than a hyper-square used by Zacharie(2001).For this more gen- eral case,a Fernique-type inequality is established and then using this inequality and the Slepian lemma,a Lévy's continuity modulus theorem is shown.Independence of incre- ments is required for showing the representative of the Hausdorff dimension by Zacharie (2001).This property is absent for the processes introduced here,so we have to find a different way.     

Hausdorff dimension of set generated by exceptional oscillations of a class of N-parameter Gaussian processes

A class of N-parameter Gaussian processes are introduced, which are more general than the N-parameter Wiener process. The definition of the set generated by exceptional oscillations of a class of these processes is given, and then the Hausdorff dimension of this set is defined. The Hausdorff dimensions of these processes are studied and an exact representative for them is given, which is similar to that for the two-parameter Wiener process by Zacharie （2001）. Moreover, the time set considered is a hyperrectangle which is more general than a hyper-scluare used by Zacharie （2001）. For this more general case, a Fernique-type inequality is established and then using this inequality and the Slepian lemma, a Levy＇s continuity modulus theorem is shown. Independence of increments is required for showing the representative of the Hausdorff dimension by Zacharie （2001）. This property is absent for the processes introduced here, so we have to find a different way.     

Improved algorithm of light scattering by a coated sphere

An efficient numerical algorithm for computing the light scattering by a coated sphere is proposed. The calculation of relevant functions by different recurrence algorithms is discussed. The new algorithm avoids the numerical difficulties, which give rise to significant errors encountered in practice by prior methods. Exemplifying results such as extinction efficiency, scattering efficiency, light scattering intensity as well as calculation speed are provided. The results show that this algorithm is efficient, fast, numerically stable and accurate.     

Sedimentation acceleration of remanent iron oxide by magnetic flocculation

Sedimentation based processes are widely used in industry to separate particles from a liquid phase. Since the advent of the ＂Nanoworld＂ the demand for effective separation technologies has rapidly risen, calling for the development of new separation concepts, one of which lies in hybrid separation using the superposition of a magnetic field for magnetic particles. Possible product portfolio of such separation consists of pigment production, nanomagnetics production for electronics and bio separation, A promising step in that direction is magnetic field enhanced cake filtration, which has by now progressed from batch to continuous ooeration. In sedimentation processes in a mass force field the settling behaviour of particles strongly depends on physico-chemical properties, concentration and size distribution of the particles. By adjusting the pH, the interparticle forces, in particular the electrostatic repulsion, can be manipulated. For remanent magnetic particles such as magnetite, pre-treatment in a magnetic field could lead to a change of interparticle interactions. By magnetizing the particles apart from van der Waals attraction and electrostatic repulsion, an additional potential is induced, the magnetic attraction, which could easily dominate the other potentials and result in agglomeration in the primary minimum. By sedimentation analysis, a wide spectrum of parameters like pH, magnetic field strength and concentration have been investigated. The results show a strong increase of sedimentation velocity by magnetic flocculation of the raw suspension. This leads to a rise in throughput due to the acceleration of sedimentation kinetics by imparting a non-chemical interaction to the physico-chemical properties in the feed stream of the separation apparatus.     

Inverse determination of liquid viscosity by means of the Bleustein–Gulyaev wave

The Bleustein–Gulyaev (B–G) wave in piezoelectric materials of orthorhombic mm2 crystal class is reported to be a promising candidate for application to liquid sensing. In this work we present a rigorous quantitative investigation of the propagation of B–G wave in mm2 crystals in contact with a viscous liquid. An inversion algorithm is formulated to determine the liquid viscosity from the wave speed and attenuation data. Numerical results and discussions are given for potassium niobate (KNbO₃). The inversion results demonstrate that the liquid viscosity can be successfully determined from wave propagation characteristics.     

Non-linear flexural–torsional dynamic analysis of beams of arbitrary cross section by BEM

In this paper, a boundary element method is developed for the non-linear flexural–torsional dynamic analysis of beams of arbitrary, simply or multiply connected, constant cross section, undergoing moderately large deflections and twisting rotations under general boundary conditions, taking into account the effects of rotary and warping inertia. The beam is subjected to the combined action of arbitrarily distributed or concentrated transverse loading in both directions as well as to twisting and/or axial loading. Four boundary value problems are formulated with respect to the transverse displacements, to the axial displacement and to the angle of twist and solved using the Analog Equation Method, a BEM based method. Application of the boundary element technique leads to a system of non-linear coupled Differential–Algebraic Equations (DAE) of motion, which is solved iteratively using the Petzold–Gear Backward Differentiation Formula (BDF), a linear multistep method for differential equations coupled to algebraic equations. The geometric, inertia, torsion and warping constants are evaluated employing the Boundary Element Method. The proposed model takes into account, both the Wagner's coefficients and the shortening effect. Numerical examples are worked out to illustrate the efficiency, wherever possible the accuracy, the range of applications of the developed method as well as the influence of the non-linear effects to the response of the beam.     

Aerodynamic characteristics of solid particles�� acceleration by shock waves

In this study, the interaction of a planar shock wave with a group of particles has been investigated using high-speed photography and dynamic pressure measurements. Experiments were carried out in a horizontal circular shock tube. The influence of the particle loading ratio, particle diameter, driving gas and shock wave Mach number on the acceleration was studied. It was found that the higher the particle loading ratio, the greater was the particle velocity. This is due to the higher driving pressure. Helium and nitrogen gases play quite different roles in acceleration. Pressure multiplication during shock wave interaction with particles also appears. Based on the experimental results, the discussion regarding partial quantitative velocities and accelerations of particle groups, as well as the attenuation factors when shock waves pass through the particles, is given.     

Blockage of constrictions by particles in fluid–solid transport

Blockage is an important phenomenon in particulate flow. Work was undertaken to provide a better understanding of key hydrodynamic multiphase flow factors which cause, or contribute to, stalling and blockage in particulate feeding systems such as those used for feeding biomass into reactors. Rubber and plastic particles were hydraulically conveyed along a horizontal rectangular duct leading to constrictions of different geometries. Experimental results showed that large size, irregular shape, high volumetric concentrations of particles, small constriction dimensions and particle compressibility all increased the likelihood of blockage. Reynolds number also had a significant effect on particle behaviour and blockage propensity. The pressure drop needed to break a blockage is also considered, based on a simple horizontal packed bed model.     

Disruption of Shaped‐Charge Jets by a Pulsed Current

This paper gives results from experimental studies of the effect of electricpulse parameters on the development of current instability and disruption of shapedcharge jets. A simple physical model for the development of current instability and the decrease in the cavern depth in the target is proposed. Notations are introduced and analytical expressions are obtained for the critical current (critical linear current density) and the ideal shape of the current pulse required for the disruption of shapedcharge jets. It is shown that the estimate of the final cavern depths in steel target for the proposed model is in fairly good agreement with both experimental values of cavern depths in targets and with the results of numerical calculations using quasitwodimensional unsteady models of MHD instability and volume disruption.     

Experimental study of subsonic flows by liquid‐crystal thermogfraphy

The physical basis of liquidcrystal thermography, which allows visualization and measurement of temperature and heatflux fields, are expounded. An experimental technique and methods of obtaining quantitative results are described. Two approaches (monochromatic and chromatic) to interpretation of visualization data are considered. Results illustrating the possibilities of the method in an aerophysical experiment are given.     

Nonlinear analysis of a structure loaded by a stochastic excitation

For a non-linear system excited by a stochastic load which is expressed as a time series,a recursive method based on the Z-transform is presented.To identify the obtained response time series,a discrete wavelet transform (DWT) technique is proposed.     

Calculation of Layered Shells by the Pseudogeometrical–Nonlinearity Method

The problem of determining the stress—strain state of a multilayered shell is solved. It is assumed that the layer material is nonlinearly elastic and the strain—displacement relations are nonlinear. The displacements are expanded in terms of the functions of transverse coordinate that contain unknown parameters. The governing equations are derived with the use of the Lagrange variational principle. A technique for minimizing the energy functional is proposed. An example of a three–layered beam is considered, calculation results are compared with the exact solution, and the specific features of the approach proposed are analyzed.     

Cracking analysis of fracture mechanics by the finite element method of lines （FEMOL）

The Finite Element Method of Lines (FEMOL) is a semi-analytic approach and takes a position between FEM and analytic methods. First, FEMOL in Fracture Mechanics is presented in detail. Then, the method is applied to a set of examples such as edge-crack plate, the central-crack plate, the plate with cracks emanating from a hole under tensile or under combination loads of tensile and bending. Their dimensionless stress distribution, the stress intensify factor (SIF) and crack opening displacement (COD) are obtained, and comparison with known solutions by other methods are reported. It is found that a good accuracy is achieved by FEMOL. The method is successfully modified to remarkably increase the accuracy and reduce convergence difficulties. So it is a very useful and new tool in studying fracture mechanics problems. The English text was polished by Yunming Chen.     

Dynamic Diagnosis of Railway Tracks by Means of the Karhunen–Loève Transformation

Maintenance of the quality of the railway track is crucial forthe safety and comfort of passengers on high-speed trains. We believe itis possible to detect deterioration of the track by constant monitoringthe dynamic vehicle response to track features. Our project is workedout in close cooperation with Deutsche Bahn AG (German Rail).     

Fracture of films caused by uniaxial tensions: a numerical model

Surface cracks are commonly observed in coatings and films. When structures with coatings are subject to stretching, opening mode cracks are likely to form on the surface, which may further lead to other forms of damage, such as interfacial delamination and substrate damage. Possible crack forms include cracks extending towards the interface and channeling across the film. In this paper, a two-dimensional numerical model is proposed to obtain the structural strain energy at arbitrary crack lengt...     

Simulation of Initially Slackened and Stiffened Structures by Virtual Distortions∗

ABSTRACT

Variational principles and computational methods for analysis of initially slackened and stiffened structures are discussed. The simulation of clearances or internal dry fraction in structural elements by virtual (eigen) distortions is applied. Considerations presented are used in the problem of nonstandard design of structural settings, with clearances or friction in the structural joints, for load capacity maximization.