Plane Surface (plane + surface)

Distribution by Scientific Domains

Selected Abstracts

Surface waves in a general anisotropic poroelastic solid half-space

M. D. Sharma
SUMMARY A method is introduced for studying surface waves in a general anisotropic poroelastic medium. The method is analogous to the one used for isotropic media and derives a complex secular equation to represent the propagation of surface waves at the stress-free plane surface of a non-dissipative porous medium. The point of importance is that the derived equation is, analytically, separable into real and imaginary parts and hence can be solved by iterative numerical methods. A root of this secular equation represents the existence of surface waves and calculates the apparent phase velocity along a given direction on the surface. Numerical work is carried out for the model of a crustal rock. The propagation of surface waves is studied numerically for the top three anisotropies (i.e. triclinic, monoclinic, orthorhombic). [source]

Diffusion Characteristics of VOCs Indoors

Shin-ichi Shibata Student Member
Abstract Diffusion characteristics of volatile organic compounds (VOCs) were investigated indoors using tin oxide gas sensors. The chemicals cause various kinds of symptoms in humans, for example, the sick house syndrome. In this study, eight sensors were installed in a vertical direction and on a plane surface. These sensors were of the same type. The VOC is placed in a generation source, and the sensor output increases as the chemical diffuses. The sensor output becomes higher as the concentration increases. The following chemicals were tried as air pollutants: formaldehyde, toluene, and xylene. The sensor output changes in short, quick steps by slight fluctuations of the wind velocity. Therefore, the differential characteristic of the sensor output was adopted and the noise component was removed as far as possible. A threshold time tth to the characteristic was set up. It is assumed that the examining chemical reaches the installed sensor point in a time greater than this time. The new speed of arrival is proposed using the threshold time. The speed s [cm/min] is indicated using the distance d and the reaching time tth, namely, s = d/tth. Here, d means the distance between the sensor position and the polluting source. As a result, the speed for the sensor that is installed near the ceiling (at a height of 260 cm from the floor) is the highest. And, it became obvious that s was larger for the chemical with a smaller molecule. The speed of formaldehyde for the sensor installed near the ceiling was 700 cm/min and that for the sensor installed at the height of 100 cm from the floor was 370 cm/min. There is almost a two times difference in the speed. Copyright 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source]

Study on the action of the active earth pressure by variational limit equilibrium method

Li Xinggao
Abstract Within the framework of limiting equilibrium approach, the problem of active earth pressure on rigid retaining wall is formulated in terms of the calculus of variations by means of Lagrange multipliers. It is transcribed as the functional of extreme-value problem by two undetermined function arguments, and is further transformed into determining the minimax solution of restrained functions incorporating the geometrical relations of the problem. The function of (fmincon) in the optimization toolbox of MATLAB 6.1 can be used to find the minimax solution. Computation results show there exist two kinds of modes of failure sliding along plane surface and rotating around log-spiral cylinder surface when the soil behind the walls reaches the critical active state. The magnitude of active earth pressure in the case of translational mode is less than that in the case of rotational mode. The location of action point of earth pressure in the case of translational mode is at or below height of the wall, and in the case of rotational mode, is above height of the wall. Preliminary study indicates a pair of numbers by two theoretical modes can be regarded as an interval estimation of active pressure. Copyright 2009 John Wiley & Sons, Ltd. [source]

Stochastic modeling of particle motion along a sliding conveyor

AICHE JOURNAL, Issue 1 2010
Kevin Cronin
Abstract The sliding conveyor consists of a plane surface, known as the track, along which particles are induced to move by vibrating the bed sinusoidal with respect to time. The forces on the particle include gravity, bed reaction force and friction. Because friction coefficients are inherently variable, particle motion along the bed is erratic and unpredictable. A deterministic model of particle motion (where friction is considered to be known and invariant) is selected and its output validated by experiment. Two probabilistic solution techniques are developed and applied to the deterministic model, in order to account for the randomness that is present. The two methods consider particle displacement to be represented by discrete time and continuous time random processes, respectively, and permits analytical solutions for mean and variance in displacement versus time to be found. These are compared with experimental measurements of particle motion. Ultimately this analysis can be employed to calculate residence-time distributions for such items of process equipment. 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]

Experimental investigation of transient and thermal effects on lubricated non-conformal contacts

R. Bassani
Abstract In this work, thermal and transient effects on non-conformal lubricated contacts are investigated through experimental analyses. Experiments between a ball and a plane surface of a disc are described. Friction coefficients and film thicknesses are measured (the film thickness only for the glass-on-steel contact). A paraffin base mineral oil is used as a lubricant. First experiments are carried out under steady-state conditions. To include effects due to different thermal properties of contacting materials, a steel-on-steel and a glass-on-steel contact with different slide-to-roll ratios are tested. If the contacting materials have different thermal properties, as in the case of a glass-on-steel contact, thermal effects like the temperature,viscosity wedge action could clearly be shown. It is found that the friction coefficients are influenced by the slide-to-roll ratio and the thermal properties of the contacting materials. Under transient conditions, the entraining velocity is varied with a sinusoidal law. Squeeze effects explain ,loops' of friction and film thickness found also in previous works. The formation of friction loops is related to the measured film thickness differences. However, also under non-steady-state conditions, thermal effects, like the temperature,viscosity wedge action, influence the friction coefficients. Copyright 2007 John Wiley & Sons, Ltd. [source]

Scattering and absorption of electromagnetic waves on a plane with hemispherical bosses

Xiaoxiong Gu
Abstract We apply multiple scattering equations to study the scattering of electromagnetic waves on a perfectly conducting plane surface with a random dense distribution of hemispherical bosses. We derive a multipole solution up to third order to analyze close range interactions between nearby bosses. Results show significant improvement of accuracy compared with the traditional dipole approximation solution. Absorption on a lossy embossed surface is obtained from the field solution for the perfectly conducting surface. The surface current and absorption enhancement factor are further computed numerically. 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2681,2686, 2007; Published online in Wiley InterScience ( DOI 10.1002/mop.22855 [source]

Stretching a plane surface in a viscoelastic fluid with prescribed skin friction

M. Sajid
Abstract A model of forced convection flow due to stretching surface is derived to represent the physical system with prescribed skin friction. To achieve the similar solutions, the partial differential equations are reduced into ordinary differential equations. The analytic solutions of the resulting problems have been obtained by a homotopy analysis method. The convergence of the developed series solution is seen. Finally, the results of velocity, temperature, the stretching velocity, and Nusselt number are analyzed. 2008 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2009 [source]

Optical characterization of bulk GaN substrates with c -, a -, and m -plane surfaces

P. P. Paskov
Abstract Thick free-standing GaN grown by hydride vapour phase epitaxy and epi-ready substrates with c -, a -, m -plane surfaces are examined by variable-temperature photoluminescence (PL), polarized PL and spatially resolved micro-PL. Both as-grown samples and polished substrates exhibit linewidth of the donor-bound exciton emission below 0.7 meV at 2 K indicative of a high structural quality of the material. For as-grown samples the relative intensity of green (2.4 eV) and red (1.8 eV) deep-level-defect emissions are found to decrease with increasing sample thickness. Based on plentiful two-electron-transition spectra measured in the samples the electronic fine structure of the donors and their bound-exciton complexes was examined and discussed. ( 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

M -plane InGaN/GaN light emitting diodes fabricated by MOCVD regrowth on c -plane patterned templates

Christopher A. Schaake
Abstract In this work we demonstrate a light emitting diode (LED) with m -plane quantum wells fabricated on a (000) template. N-polar, n-type GaN was grown by MOCVD on vicinal sapphire substrates. Stripes, measuring 500 nm wide, 500 nm tall and spaced 2 ,m apart, were etched parallel to the ,110, direction leading to sidewalls that are approximately {100}. Sputtered AlN was used as a regrowth mask on the c -plane surfaces. An active region consisting of 5 InGaN quantum wells and GaN barriers followed by p-type was grown. The regrowth occurred mostly on the exposed m -plane sidewalls, leading to lateral growth in the ,100, direction. The LED was processed using conventional methods. A thick metal contact was used to connect the p-regions together. Current vs. voltage measurements showed good rectifying behavior with a turn on of about 6 volts. On-wafer electroluminescence measurements revealed a peak wavelength of 422 nm. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]