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Cylindrical Surface (cylindrical + surface)
Selected AbstractsUniform Head in Horizontal and Vertical WellsGROUND WATER, Issue 1 2006David R. Steward The steady-state head within a fully penetrating well may be estimated by evaluating the Thiem equation at the radius of the well. A method is presented here to extend results from the Thiem equation to horizontal wells and to partially penetrating wells. The particular model used in this investigation is based upon the analytic element method; it accurately reproduces a boundary condition of uniform head along the cylindrical surface at the perforated face of the well. This model is exercised over a representative range of parameters including the well's length, radius, and pumping rate, and the aquifer's hydraulic conductivity and thickness. Results are presented in a set of figures and tables that compare the well's drawdown to the drawdown that would have been obtained using the Thiem solution with the same pumping rate and radius. A methodology is presented to estimate the head within a horizontal or partially penetrating well by adding a correction term to results that can be readily obtained from computer models of vertical fully penetrating wells. This approach may also be used to contrast the differences in head between horizontal and vertical wells of various lengths, radii, and placement elevations. [source] Performance enhancement of a chemical reactor utilizing flow instability,JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2-3 2003Mohammad F Kabir Abstract A detailed analysis has been performed for a heterogeneous photocatalytic Taylor vortex reactor that uses flow instability to recirculate fluid continually from the vicinity of the rotating inner cylindrical surface to the stationary outer cylindrical surface of an annulus. A comprehensive time accurate computation shows the different stages of flow evolution and the effects of finite length of the reactor in creating eddies, the overall effects of which shows very high efficiency of photocatalytic conversion. The physical arrangement considered is such that pollutant degradation is maximized by a combination of the Controlled Periodic Illumination (CPI) effect and the motion of fluid particles in a specific regime of centrifugal instability. © 2003 Society of Chemical Industry [source] Packed bed structure: Evaluation of radial particle distributionTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2002Néstor J. Mariani Abstract A model describing the radial distribution of monosized spheres in randomly packed beds up to distances of about two particle diameters from the vessel wall is presented here. The model is based on the existence of a highly ordered layer of particles adjacent to the wall followed by a more diffuse, but still identifiable, second layer. Expressions generated from simple geometrical concepts (intersection between a cylindrical surface and a sphere) straightforwardly allow calculating the radial voidage profile given the radial distribution of particle centers and vice versa. These expressions are employed to fit the model to measures of voidage profiles within a wide range of aspect ratios, a = (RT/RP). The model can be used to accurately predict radial voidage profiles, but it is stressed that the identification of particle distribution constitutes more valuable information than an empirical expression for describing voidage variations. On présente ici un modèle décrivant la distribution radiale de sphères monodisperses dans des lits garnis aléatoires jusqu'à des distances d'environ deux diamètres de particules de la paroi du réservoir. Le modèle s'appuie sur l'existence d'une couche très ordonnée de particules adjacentes à la paroi, suivie d'une seconde couche, plus diffuse mais cependant identifiable. Les expressions provenant de concepts géométriques simples (intersection entre une surface cylindrique et une sphère) permettent de calculer directement le profil de vide radial lorsque la distribution radiale des centres de particules est donnée et vice versa. Ces expressions servent à caler le modèle de mesures de profils de vide dans une vaste gamme de paramètres d'élancement, a = (RT/RP. Le modèle peut être utile pour prédire de manière précise les profils de vide radiaux, mais il faut dire que la détermination de la distribution des particules constitue une information plus valable qu'une expression empirique pour décrire les variations de vide. [source] Evaluation of radial voidage profiles in packed beds of low-aspect ratiosTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2000Nestor J. Mariani Abstract The relationship between the radial voidage profile, ,(r), and the radial distribution of centres of mono-sized spherical particles, f(r), is revised. A close expression is given for the section S(r1, rc), the area of the segment of a cylindrical surface of radius r intersected by a particle centred at rC. From this expression, ,(r) can be evaluated straightforwardly from the knowledge of f(r). The range 1, a , 2 of aspect ratios (a = dT/dp is then analysed specifically. For this range, the distribution of spherical particles has been characterized theoretically (Govindarao et al., 1992) and a simple expression allows the evaluation of ,(r). The use of this expression for actual catalyst particles, imperfect spheres showing a distribution of sizes, in finally analyzed. La relation entre le profil de vide radial,,(r), et la distribution radiale des centres de particules sphériques de taille unique, f(r), est examinée. Une expression analytique est donnée pour la section S(r,rc), la région du segment d'une surface cylindrique de rayon r intersectée par une particule centrée en rc. À partir de cette expression, il est possible d'évaluer ,(r) directement à partir de f(r). La gamme des élance-ments 1 , a , 2 (a =d, / dp est ensuite évaluée spéci-fiquement. Pour cette gamme, la distribution des particules sphériques a été caractérisée de manière thérique (Govindarao et al., 1992) et une expression simple permet l'évaluation de ,(r). Enfin, on analyse l'emploi de cette expression pour des particules de catalyseurs réelles, des sphères imparfaites présentant une distribution des tailles. [source] Fabrication of Flexible Binary Amplitude Masks for Patterning on Highly Curved SurfacesADVANCED FUNCTIONAL MATERIALS, Issue 20 2009Audrey M. Bowen Abstract This paper describes soft lithography methods that expand current fabrication capabilities by enabling high-throughput patterning on nonplanar substrates. These techniques exploit optically dense elastomeric mask elements embedded in a transparent poly(dimethylsiloxane) (PDMS) matrix by vacuum-assisted microfluidic patterning, UV,ozone-mediated irreversible sealing, and chemical etching. These protocols provide highly flexible photomasks exhibiting either positive- or negative-image contrasts, which serve as amplitude masks for large-area photolithographic patterning on a variety of curved (and planar) surfaces. When patterning on cylindrical surfaces, the developed masks do not experience significant pattern distortions. For substrates with 3D curvatures/geometries, however, the PDMS mask must undergo relatively large strains in order to make conformal contact. The new methods described in this report provide planar masks that can be patterned to compliantly compensate for both the displacements and distortions of features that result from stretching the mask to span the 3D geometry. To demonstrate this, a distortion-corrected grid pattern mask was fabricated and used in conjunction with a homemade inflation device to pattern an electrode mesh on a glass hemisphere with predictable registration and distortion compensation. The showcased mask fabrication processes are compatible with a broad range of substrates, illustrating the potential for development of complex lithographic patterns for a variety of applications in the realm of curved electronics (i.e., synthetic retinal implants and curved LED arrays) and wide field-of-view optics. [source] Variations in the Earth's gravity field caused by torsional oscillations in the coreGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2004Mathieu Dumberry SUMMARY We investigate whether a component of the flow in the Earth's fluid core, namely torsional oscillations, could be detected in gravity field data at the surface and whether it could explain some of the observed time variations in the elliptical part of the gravity field (J2). Torsional oscillations are azimuthal oscillations of rigid coaxial cylindrical surfaces and have typical periods of decades. This type of fluid motion supports geostrophic pressure gradients, which produce deformations of the core,mantle boundary. Because of the density discontinuity between the core and the mantle, such deformations produce changes in the gravity field that, because of the flow geometry, are both axisymmetric and symmetric about the equator. Torsional oscillations are thus expected to produce time variations in the zonal harmonics of even degree in the gravity field. Similarly, the changes in the rotation rates of the mantle and inner core that occur to balance the change in angular momentum carried by the torsional oscillations also produce zonal variations in gravity. We have built a model to calculate the changes in the gravity field and in the rotation rates of the mantle and inner core produced by torsional oscillations. We show that the changes in the rotation rate of the inner core produce changes in J2 that are a few orders of magnitude too small to be observed. The amplitudes of the changes in J2 from torsional oscillations are 10 times smaller than the temporal changes that are observed to occur about a linear secular trend. However, provided the mechanism responsible for these changes in J2 is identified and that this contribution is removed from the data, it may be possible in the future to detect the lowest harmonic degrees of the torsional oscillations in the gravity field data. We also show that torsional oscillations have contributed to the linear secular change in J2 by about ,0.75 × 10,12 per year in the last 20 years. Finally, the associated change in the vertical ground motion at the surface of the Earth that is predicted by our mechanism is of the order of 0.2 mm, which is too small to be detected with the current precision in measurements. [source] Method of moments modelling of cylindrical microwave integrated circuits interconnectionsINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 2 2004M. S. Al Salameh Abstract In this paper, a numerical technique suitable for characterizing a wide variety of interconnection configurations printed on cylindrical surfaces, is presented. The interconnection lines may have either finite or infinitesimal cross-sections. To model cylindrical interfaces, suitable space-domain integral equations are formulated to represent the potential on conductors and electric field at dielectric interfaces. The solution of the integral equations is then obtained numerically by applying the method of moments (MOM). The objective of this approach is to determine the capacitance matrix of cylindrical interconnection systems with different configurations. From the capacitance matrix, other quantities such as characteristic impedance, coupling coefficient and effective permittivity can be determined. The numerical technique described in this paper is implemented as a general computer program. Various circular cylindrical as well as elliptical cylindrical structures have been solved including microstrip lines and coplanar waveguide lines. The results obtained compare very well with other published data. Copyright © 2004 John Wiley & Sons, Ltd. [source] | |||||||||||||