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Terms modified by Triangular Selected AbstractsSynthesis and Self-Assembly of Triangular and Hexagonal CdS Nanocrystals,ADVANCED MATERIALS, Issue 24 2005H. Warner CdS nanocrystals with cubic, triangular, and hexagonal geometries have been synthesized using simple wet-chemistry techniques. Analysis of the crystal structures revealed that the cubic nanocrystals have a zinc-blende crystal structure whilst the triangular and hexagonal CdS nanocrystals have a wurtzite crystal structure. When dried, these CdS nanocrystals self-assemble to form complex structures such as linear rods (see Figure), nanoarrows and dimers. [source] Non-centrosymmetric section forming shoulders in packaging machinesPACKAGING TECHNOLOGY AND SCIENCE, Issue 2 2006Yi-Jie Zhou Abstract The mathematical description of a non-centrosymmetric section, trapezoid shoulder is presented and the equations of the bending curve, the shoulder curved surface and the fringe curve are developed. Triangular, flat-round, rectangular and round shoulders are discussed as special cases of the non-centrosymmetric shoulder. To confirm the validity of the mathematical description, 3-D shoulders are modelled on computer, and actual shoulders are manufactured by rapid manufacturing machine. Copyright © 2005 John Wiley & Sons, Ltd. [source] Titelbild: Two-Dimensional Triangular and Square Heterometallic Clusters: Influence of the Closed-Shell d10 Electronic Configuration (Angew. Chem.ANGEWANDTE CHEMIE, Issue 51 200951/2009) Vergoldete "Flöße" können aus Heterometallclustern entstehen. In der Zuschrift auf S.,9843,ff. beschreiben P. Braunstein, M. Bénard et,al. die Synthese, Struktur und theoretische Analyse einer einzigartigen Reihe zweidimensionaler Heterometall-Raft-Cluster der Art {M[m]}n (M=Cu, n=3; M=Ag, Au, n=4; der verbrückende Metalloligand [m] ist {MoCp(CO)3}). Intramolekulare, metallophile d10 -d10 -Wechselwirkungen treten sowohl in der ,2 -dreieckigen (M=Cu) als auch in den ,2 -quadratischen (M=Ag, Au) Strukturen der Metallkerne auf. [source] Two-Dimensional Triangular and Square Heterometallic Clusters: Influence of the Closed-Shell d10 Electronic Configuration,ANGEWANDTE CHEMIE, Issue 51 2009Sabrina Sculfort Handwerk mit goldenem Boden: Die Cluster {M[m]}n mit zweidimensionalem Kern (M=Cu, n=3; M=Ag oder Au, n=4; siehe Bild) und demselben verbrückenden Metalloligand [m]={CpMo(CO)3} wurden strukturanalytisch charakterisiert. Die ,2 -Dreiecks- (M=Cu) oder ,2 -Quadratstrukturen (M=Ag, Au) ihrer Kerne ermöglichen einen Vergleich der d10,,,d10 -Metall-Metall-Wechselwirkungen. Rechnungen deuten auf das Vorliegen diagonaler Au,,,Au- oder Ag,,,Ag-Wechselwirkungen hin. [source] Shape, height, and location of the lingula for sagittal ramus osteotomy in ThaisCLINICAL ANATOMY, Issue 7 2009P. Jansisyanont Abstract This study aims to investigate the shape, height, and location of the lingula in relation to surrounding structures for sagittal ramus osteotomy. Dried Thai mandibles were studied and compared with other races. From both sides of 92 mandibles, the shape of the lingula was classified into triangular, truncated, nodular, or assimilated types. Of 92 mandibles, 146 sides with at least a premolar and a molar on the same side were selected for distance measurement. Height of the lingula was measured from the lingular tip to the mandibular foramen. The location was determined by five distances from the lingular tip to: the anterior and the posterior borders of the mandibular ramus, the mandibular notch, the distal surface of the mandibular second molar, and the occlusal plane. The results showed that truncated lingulae were most frequently found (46.2%) and most appeared to be bilateral (71.7%). Triangular, nodular, and assimilated shapes presented in 29.9%, 19.6%, and 4.3%, respectively. The mean lingular height was 8.2 ± 2.3 mm. The lingula was located at 20.6 ± 3.5 mm from the anterior border of the mandibular ramus and 16.6 ± 2.9 mm from the mandibular notch. In the majority of the mandibles studied, the lingula was located above the occlusal plane. In conclusion, the shape and metric characteristics of the lingula in relation to surrounding structures in Thais vary from other races. All parameters associated with the lingula should be considered for sagittal ramus osteotomy to avoid intraoperative complications. Clin. Anat. 22:787,793, 2009. © 2009 Wiley-Liss, Inc. [source] Naturally Occurring Female Hairline PatternsDERMATOLOGIC SURGERY, Issue 6 2009BERNARD P. NUSBAUM MD BACKGROUND Hair transplantation is gaining popularity in women. Although much has been written about hairline design in male patients, more information is needed about natural female hairlines. OBJECTIVE To determine the frequency, dimensions, and location of structures that compose the female hairline. METHODS Hairline characteristics were measured in 360 female volunteers at an informal hair salon setting. RESULTS A widow's peak was present in 81%. The mean distance from the mid-eyebrow to the frontal midpoint was 5.5 cm. Lateral mounds were observed in 98%. The mean distance from the frontal midpoint to the apex of the lateral mounds was 3.74 cm on the right and 3.97 cm on the left. The mean distance from the apex of the lateral mounds to the apex of the temporal points was 3.78 cm on the right and 3.51 cm on the left. The shape of the temporal recessions was concave triangular or concave oval in 87% of the subjects. CONCLUSION This study provides proposed guidelines for designing the hairline in women. [source] Plasticity-fibre model for steel triangular plate energy dissipating devicesEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 9 2002Chung-Che Chou Abstract Properly fabricated triangular-plate added damping and stiffness (TADAS) devices can sustain a large number of yield reversals without strength degradation, thereby dissipating a significant amount of earthquake-induced energy. A pronounced isotropic-hardening effect is recognized in the force-deformation relationships of the TADAS devices made from two grades of low yield strength steel. The proposed plasticity-fibre model employing two surfaces (a yield surface and a bounding surface) in plasticity theory accurately predicts the experimental responses of the TADAS devices. This model is also implemented into a computer program DRAIN2D+ to investigate a frame response with the TADAS devices. Substructure pseudo-dynamic tests and analytical studies of a two-storey steel frame constructed with the low yield strength steel, LYP-100 or LYP-235 grade, TADAS devices confirm that the dynamic structural response can only be predicted if the proposed plasticity-fibre model is used for LYP-100 steel TADAS device. Copyright © 2002 John Wiley & Sons, Ltd. [source] Syntheses, Structures and Magnetic Properties of Trinuclear CuIIMIICuII (M = Cu, Ni, Co and Fe) and Tetranuclear [2×1+1×2] CuIIMnII,2CuII Complexes Derived from a Compartmental Ligand: The Schiff Base 3-Methoxysalicylaldehyde Diamine Can also Stabilize a CocrystalEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2010Arpita Biswas Abstract The present investigation describes syntheses, characterization and studies of the mononuclear compound [CuIIL,(H2O)] (1), the triangular, trinuclear monophenoxido-bridged compounds [{CuIIL}2MII(H2O)2](ClO4)2·nH2O [2 (M = Cu, n = 0), 3 (M = Ni, n = 3), 4 (M = Co, n = 0), 5 (M = Fe, n = 0)] and the tetrametallic self-assembled complex [{CuIILMnII(H2O)3}{CuIIL}2](ClO4)2·H2O (6) derived from compartmental Schiff base ligand, H2L, which is the [2+1] condensation product of 3-methoxysalicylaldehyde and trans -1,2-diaminocyclohexane. Single-crystal X-ray structures of 2, 5 and 6 were determined. Two pairs of terminal···central metal ions in the trinuclear cores in 2 and 5 are monophenoxido-bridged. Interestingly, the CuO6 and FeO6 environments have tetragonally compressed octahedral geometries. On the other hand, the structure of 6 reveals that it is a [2×1+1×2] cocrystal of one diphenoxido-bridged dinuclear [CuIILMnII(H2O)3]2+ dication and two mononuclear [CuIIL] moieties. Cocrystallization in 6 takes place as a result of water encapsulation. The variable-temperature (2,300 K) magnetic susceptibilities of compounds 2,6 have been measured. The exchange integrals obtained are: the CuII3 compound 2, J = ,78.9 cm,1; the CuIINiIICuII compound 3, J = ,22.8 cm,1; the CuIICoIICuII compound 4, J = ,7.8 cm,1; the CuIIFeIICuII compound 5, J = ,3.0 cm,1; the CuII3MnII compound 6, J = ,15.1 cm,1. The monophenoxido-bridging core in 3 and 4 has been proposed after comparison of the structures and magnetic properties of these two compounds with those of 2, 5 and related other compounds. This paper presents rare examples of monophenoxido-bridged CuIIMIICuII (M = Cu, Ni, Co and Fe) compounds, provides an understanding of the structures from magnetic exchange integrals, and, most importantly, reports on the first example of a cocrystal derived from a 3-methoxysalicylaldehyde diamine compartmental ligand. [source] Globalization and the transformation of the national political space: Six European countries comparedEUROPEAN JOURNAL OF POLITICAL RESEARCH, Issue 6 2006HANSPETER KRIESI The structural opposition between globalization ,winners' and ,losers' is expected to constitute potentials for political mobilization within national political contexts, the mobilization of which is expected to give rise to two intimately related dynamics: the transformation of the basic structure of the national political space and the strategic repositioning of the political parties within the transforming space. The article presents several hypotheses with regard to these two dynamics and tests them empirically on the basis of new data concerning the supply side of electoral politics from six Western European countries (Austria, Britain, France, Germany, the Netherlands and Switzerland). The results indicate that in all the countries, the new cleavage has become embedded into existing two-dimensional national political spaces, that the meaning of the original dimensions has been transformed, and that the configuration of the main parties has become triangular even in a country like France. [source] Automatic generation control of multi-area power system using fuzzy logic controllerEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 3 2008P. Subbaraj Abstract This paper presents an application of Fuzzy Logic Controller (FLC) with triangular and gauss membership functions to study Automatic Generation Control (AGC) of a four-area interconnected power system. Out of the four areas three have steam turbines and one has hydro turbine. All steam turbines in the system contain the reheat effect of non-linearity and hydro turbine contains upper and lower constraints for generation rate. The result proves that the performance of FLC with Gaussian membership function is better than that of conventional controller. Copyright © 2007 John Wiley & Sons, Ltd. [source] Order Distance in Regular Point PatternsGEOGRAPHICAL ANALYSIS, Issue 3 2009Masashi Miyagawa This article examines the kth nearest neighbor distance for three regular point patterns: square, triangular, and hexagonal lattices. The probability density functions of the kth nearest distance and the average kth nearest distances are theoretically derived for k=1, 2, ,, 7. As an application of the kth nearest distance, we consider a facility location problem with closing of facilities. The problem is to find the optimal regular pattern that minimizes the average distance to the nearest open facility. Assuming that facilities are closed independently and at random, we show that the triangular lattice is optimal if at least 68% of facilities are open by comparing the upper and lower bounds of the average distances. El siguiente artículo examina la distancia de los k-vecinos más cercanos en látices cuadrados, triangulares y hexagonales. La funciones de densidad de probabilidad para las distancias k-más próximas y para las k-promedio más próximas son derivadas teóricamente para k=1,2,,7. Con el fin de demostrar una aplicación de la distancia k-más próxima los autores utilizan un ejemplo de localización y clausura de instalaciones. El objetivo es identificar el patrón regular óptimo que minimice la distancia promedio a la instalación abierta más cercana. Bajo el supuesto que las instalaciones cierran independientemente y aleatoriamente, y comparando los límites extremos superiores e inferiores de las distancias promedio, los autores demuestran que el patrón triangular es el óptimo si es que por lo menos 68 por ciento de las instalaciones permanecen abiertas. [source] Extension of Vedernikov's Graph for Seepage from CanalsGROUND WATER, Issue 2 2001Bhagu R. Chahar In this investigation, using previously derived equations by Vedernikov and Morel-Seytoux, closed-form solutions have been obtained to compute the seepage from a slit and a strip. Also, a graphical solution as an extension of Vedernikov's graph has been presented for computing quantity of seepage from triangular, rectangular, and trapezoidal canals. The solution replaces approximately the cumbersome evaluation of improper integrals with unknown implicit transformation variables. [source] A metric for spaceHIPPOCAMPUS, Issue 12 2008Edvard I. Moser Abstract Not all areas of neuronal systems investigation have matured to the stage where computation can be understood at the microcircuit level. In mammals, insights into cortical circuit functions have been obtained for the early stages of sensory systems, where signals can be followed through networks of increasing complexity from the receptors to the primary sensory cortices. These studies have suggested how neurons and neuronal networks extract features from the external world, but how the brain generates its own codes, in the higher-order nonsensory parts of the cortex, has remained deeply mysterious. In this terra incognita, a path was opened by the discovery of grid cells, place-modulated entorhinal neurons whose firing locations define a periodic triangular or hexagonal array covering the entirety of the animal's available environment. This array of firing is maintained in spite of ongoing changes in the animal's speed and direction, suggesting that grid cells are part of the brain's metric for representation of space. Because the crystal-like structure of the firing fields is created within the nervous system itself, grid cells may provide scientists with direct access to some of the most basic operational principles of cortical circuits. © 2008 Wiley-Liss, Inc. [source] Phase transformation behaviour and bending properties of hybrid nickel,titanium rotary endodontic instrumentsINTERNATIONAL ENDODONTIC JOURNAL, Issue 4 2007Y. Hayashi Abstract Aim, To investigate the bending properties of hybrid rotary nickel,titanium endodontic instruments in relation to their transformation behaviour. Methodology, Four types of nickel,titanium rotary endodontic instruments with different cross-sectional shapes (triangular-based and rectangular-based) and different heat treatment conditions (super-elastic type and hybrid type with shape memory effect) were selected to investigate bending properties and phase transformation behaviour. Bending load of the instruments was measured in a cantilever-bending test at 37 °C with the maximum deflection of 3.0 mm. A commercial rotary instrument, ProFile (PF; Dentsply Maillefer, Ballaigues, Switzerland) was used as a reference for the bending test. Phase transformation temperatures were calculated from the diagrams obtained from differential scanning calorimetry. Data were analysed by anova and Scheffe's test. Results, The bending load values of the hybrid type that had undergone additional heat treatment at the tip were significantly lower (P < 0.05) than those of the super-elastic type with no additional heat treatment. The bending load values of rectangular-based cross-sectional shaped instruments were significantly lower (P < 0.05) than those of triangular-based cross-sectional shaped instruments. Phase transformation temperatures (Ms and Af points) of the hybrid type were significantly higher (P < 0.05) than the super-elastic type. The Mf and As points of the tip part were significantly higher (P < 0.05) than those of the whole part of the hybrid instrument. Conclusions, Additional heat treatment of hybrid nickel,titanium instruments may be effective in increasing the flexibility of nickel,titanium rotary instruments. [source] Finite element analysis of land subsidence above depleted reservoirs with pore pressure gradient and total stress formulationsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 4 2001Giuseppe Gambolati Abstract The solution of the poroelastic equations for predicting land subsidence above productive gas/oil fields may be addressed by the principle of virtual works using either the effective intergranular stress, with the pore pressure gradient regarded as a distributed body force, or the total stress incorporating the pore pressure. In the finite element (FE) method both approaches prove equivalent at the global assembled level. However, at the element level apparently the equivalence does not hold, and the strength source related to the pore pressure seems to generate different local forces on the element nodes. The two formulations are briefly reviewed and discussed for triangular and tetrahedral finite elements. They are shown to yield different results at the global level as well in a three-dimensional axisymmetric porous medium if the FE integration is performed using the average element-wise radius. A modification to both formulations is suggested which allows to correctly solve the problem of a finite reservoir with an infinite pressure gradient, i.e. with a pore pressure discontinuity on its boundary. Copyright © 2001 John Wiley & Sons, Ltd. [source] Modeling and simulation of bioheat transfer in the human eye using the 3D alpha finite element method (,FEM)INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 8 2010Eric Li Abstract Computational modeling is an effective tool for the detection of eye abnormalities and a valuable assistant to hyperthermia treatments. In all these diagnoses and treatments, predicting the temperature distribution accurately is very important. However, the standard finite element method (FEM) currently used for such purposes has strong reliance on element meshes and the discretized system exhibits the so-called ,overly stiff' behavior. To overcome this shortcoming, this paper formulates an alpha finite element method (,FEM) to compute two-dimensional (2D) and three-dimensional (3D) bioheat transfer in the human eyes. The ,FEM can produce much more accurate results using triangular (2D) and tetrahedron (3D) elements that can be generated automatically for complicated domains and hence is particularly suited for modeling human eyes. In the ,FEM, a scaling factor ,,[0, 1] is introduced to combine the ,overly stiff' FEM model and ,overly soft' node-based finite element method (NS-FEM) model. With a properly chosen ,, the ,FEM can produce models with very ,close-to-exact' stiffness of the continuous system. Numerical results have shown that the present method gives much more accurate results compared with the standard FEM and the NS-FEM. Copyright © 2010 John Wiley & Sons, Ltd. [source] Study on the degeneration of quadrilateral element to triangular elementINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 9 2004L.-X. Li Abstract In this paper, the problems involved in the process of degeneration of quadrilateral element into triangular element are thoroughly analysed. The contents include the formulation of the geometry mapping induced by collapsing one side of the quadrilateral element and the construction of the shape functions. The study focuses first on a 4-node bilinear quadrilateral (Q4) element to 3-node constant strain triangular (CST) element, and then on a 8-node serendipity (Q8) element to 6-node triangular element (T6). In the analysis, the quadrilateral element and degenerate triangular element are assumed to be enclosed by straight edges. The theoretical results show that there is another better approach to realize the degeneration, and that even for conventional approach of degeneration we can give more reasonable explanation to the unclear problems like the CST property in degenerate CST element and the necessity of the additional terms in degenerate T6 element. Copyright © 2004 John Wiley & Sons, Ltd. [source] Numerically exact integration of a family of axisymmetric finite elementsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 4 2003T. E. Price Abstract Axisymmetric finite element stress analysis involves repeated integration of a rational polynomial integrand. For elements near the axis of symmetry, such integrals are quasi-singular, are difficult to integrate numerically, and can lead to significant computational errors. This paper describes a Gaussian quadrature procedure to integrate exactly, within computational limits, a class of rational polynomials over undistorted triangular and quadrilateral finite elements. The procedure's accuracy and efficiency are illustrated through a numerical example. Copyright © 2003 John Wiley & Sons, Ltd. [source] Vibrations of skewed cantilevered triangular, trapezoidal and parallelogram Mindlin plates with considering corner stress singularitiesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 13 2005C. S. Huang Abstract Based on the Mindlin shear deformation plate theory, a method is presented for determining natural frequencies of skewed cantilevered triangular, trapezoidal and parallelogram plates using the Ritz method, considering the effects of stress singularities at the clamped re-entrant corner. The admissible displacement functions include polynomials and corner functions. The admissible polynomials form a mathematically complete set and guarantee the solution convergent to the exact frequencies when sufficient terms are used. The corner functions properly account for the singularities of moments and shear forces at the re-entrant corner and accelerate the convergence of the solution. Detailed convergence studies are carried out for plates of various shapes to elucidate the positive effects of corner functions on the accuracy of the solution. The results obtained herein are compared with those obtained by other investigators to demonstrate the validity and accuracy of the solution. Copyright © 2005 John Wiley & Sons, Ltd. [source] A numerical integration scheme for special finite elements for the Helmholtz equationINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 4 2003Peter Bettess Abstract The theory for integrating the element matrices for rectangular, triangular and quadrilateral finite elements for the solution of the Helmholtz equation for very short waves is presented. A numerical integration scheme is developed. Samples of Maple and Fortran code for the evaluation of integration abscissæ and weights are made available. The results are compared with those obtained using large numbers of Gauss,Legendre integration points for a range of testing wave problems. The results demonstrate that the method gives correct results, which gives confidence in the procedures, and show that large savings in computation time can be achieved. Copyright © 2002 John Wiley & Sons, Ltd. [source] Some results on the accuracy of an edge-based finite volume formulation for the solution of elliptic problems in non-homogeneous and non-isotropic mediaINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 3 2009Darlan Karlo Elisiário de Carvalho Abstract The numerical simulation of elliptic type problems in strongly heterogeneous and anisotropic media represents a great challenge from mathematical and numerical point of views. The simulation of flows in non-homogeneous and non-isotropic porous media with full tensor diffusion coefficients, which is a common situation associated with the miscible displacement of contaminants in aquifers and the immiscible and incompressible two-phase flow of oil and water in petroleum reservoirs, involves the numerical solution of an elliptic type equation in which the diffusion coefficient can be discontinuous, varying orders of magnitude within short distances. In the present work, we present a vertex-centered edge-based finite volume method (EBFV) with median dual control volumes built over a primal mesh. This formulation is capable of handling the heterogeneous and anisotropic media using structured or unstructured, triangular or quadrilateral meshes. In the EBFV method, the discretization of the diffusion term is performed using a node-centered discretization implemented in two loops over the edges of the primary mesh. This formulation guarantees local conservation for problems with discontinuous coefficients, keeping second-order accuracy for smooth solutions on general triangular and orthogonal quadrilateral meshes. In order to show the convergence behavior of the proposed EBFV procedure, we solve three benchmark problems including full tensor, material heterogeneity and distributed source terms. For these three examples, numerical results compare favorably with others found in literature. A fourth problem, with highly non-smooth solution, has been included showing that the EBFV needs further improvement to formally guarantee monotonic solutions in such cases. Copyright © 2008 John Wiley & Sons, Ltd. [source] The natural volume method (NVM): Presentation and application to shallow water inviscid flowsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 1 2009R. Ata Abstract In this paper a fully Lagrangian formulation is used to simulate 2D shallow water inviscid flows. The natural element method (NEM), which has been used successfully with several solid and fluid mechanics applications, is used to approximate the fluxes over Voronoi cells. This particle-based method has shown huge potential in terms of handling problems involving large deformations. Its main advantage lies in the interpolant character of its shape function and consequently the ease it allows with respect to the imposition of Dirichlet boundary conditions. In this paper, we use the NEM collocationally, and in a Lagrangian kinematic description, in order to simulate shallow water flows that are boundary moving problems. This formulation is ultimately shown to constitute a finite-volume methodology requiring a flux computation on Voronoi cells rather than the standard elements, in a triangular or quadrilateral mesh. St Venant equations are used as the mathematical model. These equations have discontinuous solutions that physically represent the existence of shock waves, meaning that stabilization issues have thus been considered. An artificial viscosity deduced from an analogy with Riemann solvers is introduced to upwind the scheme and therefore stabilize the method. Some inviscid bidimensional flows were used as preliminary benchmark tests, which produced decent results, leading to well-founded hopes for the future of this method in real applications. Copyright © 2008 John Wiley & Sons, Ltd. [source] Progressive optimization on unstructured grids using multigrid-aided finite-difference sensitivitiesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 10-11 2005L. A. Catalano Abstract This paper proposes an efficient and robust progressive-optimization procedure, employing cheap, flexible and easy-to-program multigrid-aided finite-differences for the computation of the sensitivity derivatives. The entire approach is combined with an upwind finite-volume method for the Euler and the Navier,Stokes equations on cell-vertex unstructured (triangular) grids, and validated versus the inverse design of an airfoil, under inviscid (subsonic and transonic) and laminar flow conditions. The methodology turns out to be robust and highly efficient, the converged design optimization being obtained in a computational time equal to that required by 11,17 (depending on the application) multigrid flow analyses on the finest grid. Copyright © 2004 John Wiley & Sons, Ltd. [source] An approximate projection method for incompressible flowINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 10 2002David E. Stevens This paper presents an approximate projection method for incompressible flows. This method is derived from Galerkin orthogonality conditions using equal-order piecewise linear elements for both velocity and pressure, hereafter Q1Q1. By combining an approximate projection for the velocities with a variational discretization of the continuum pressure Poisson equation, one eliminates the need to filter either the velocity or pressure fields as is often needed with equal-order element formulations. This variational approach extends to multiple types of elements; examples and results for triangular and quadrilateral elements are provided. This method is related to the method of Almgren et al. (SIAM J. Sci. Comput. 2000; 22: 1139,1159) and the PISO method of Issa (J. Comput. Phys. 1985; 62: 40,65). These methods use a combination of two elliptic solves, one to reduce the divergence of the velocities and another to approximate the pressure Poisson equation. Both Q1Q1 and the method of Almgren et al. solve the second Poisson equation with a weak error tolerance to achieve more computational efficiency. A Fourier analysis of Q1Q1 shows that a consistent mass matrix has a positive effect on both accuracy and mass conservation. A numerical comparison with the widely used Q1Q0 (piecewise linear velocities, piecewise constant pressures) on a periodic test case with an analytic solution verifies this analysis. Q1Q1 is shown to have comparable accuracy as Q1Q0 and good agreement with experiment for flow over an isolated cubic obstacle and dispersion of a point source in its wake. Copyright © 2002 John Wiley & Sons, Ltd. [source] Dual high-gain-based adaptive output-feedback control for a class of nonlinear systems,INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 1 2008P. Krishnamurthy Abstract We propose an adaptive output-feedback controller for a general class of nonlinear triangular (strict-feedback-like) systems. The design is based on our recent results on a new high-gain control design approach utilizing a dual high-gain observer and controller architecture with a dynamic scaling. The technique provides strong robustness properties and allows the system class to contain unknown functions dependent on all states and involving unknown parameters (with no magnitude bounds required). Unlike our earlier result on this problem where a time-varying design of the high-gain scaling parameter was utilized, the technique proposed here achieves an autonomous dynamic controller by introducing a novel design of the observer, the scaling parameter, and the adaptation parameter. This provides a time-invariant dynamic output-feedback globally asymptotically stabilizing solution for the benchmark open problem proposed in our earlier work with no magnitude bounds or sign information on the unknown parameter being necessary. Copyright © 2007 John Wiley & Sons, Ltd. [source] Synthesis and Self-Assembly of Triangular and Hexagonal CdS Nanocrystals,ADVANCED MATERIALS, Issue 24 2005H. Warner CdS nanocrystals with cubic, triangular, and hexagonal geometries have been synthesized using simple wet-chemistry techniques. Analysis of the crystal structures revealed that the cubic nanocrystals have a zinc-blende crystal structure whilst the triangular and hexagonal CdS nanocrystals have a wurtzite crystal structure. When dried, these CdS nanocrystals self-assemble to form complex structures such as linear rods (see Figure), nanoarrows and dimers. [source] Predators, parasitoids and pathogens: species richness, trophic generality and body sizes in a natural food webJOURNAL OF ANIMAL ECOLOGY, Issue 1 2000J. Memmott Summary 1.,A food web is presented which describes trophic interactions among the herbivores, parasitoids, predators and pathogens associated with broom, Cytisus scoparius (L.) Link. The data come from published work on the community at a single site. The web comprises a total of 154 taxa: one plant, 19 herbivores, 66 parasitoids, 60 predators, five omnivores and three pathogens. There are 370 trophic links between these taxa in the web. The taxa form 82 functionally distinct groups, called trophic species. 2.,Predators consumed significantly more species than did parasitoids: a median of two prey species per species of predator (range = 1,9), compared to a median of one host species per species of parasitoid (range = 1,4). Significant differences in the number of species consumed were also found among the five predator groups: birds (median = 4), spiders (median = 5), Coleoptera (median = 1), Diptera (median = 2) and Hemiptera (median = 7). 3.,Vulnerability, measured by numbers of consumer species, was significantly affected by the herbivores' feeding styles: externally feeding herbivores were most vulnerable and the concealed herbivores were least vulnerable. Miners were vulnerable to the most parasitoid species and externally feeding herbivores were the most vulnerable to predators. 4.,Resource species had a median vulnerability of 13 consumer species, a figure far higher than that in most published food webs. No significant relationship was found between species' vulnerability to predators and vulnerability to parasitoids. However, there was a strong negative relationship between the percentage mortality due to predation and percentage mortality due to parasitism. 5.,The broom food web contains nine orders of insects, a figure higher than previously recorded. The web also contains vertebrates, arachnids, bacteria and fungi. Most of the interactions between the orders were weak. Connectance was calculated for the complete web, the parasitoid sub-web and the predator sub-web. The connectance of the predator sub-web, a value of 0·0364, was more than an order of magnitude larger than the connectance of the entire web (0·0156) or the parasitoid sub-web (0·018). 6.,The body lengths of 52 species in the food web were estimated from field guides or museum specimens. Larger predators consumed smaller prey in 93% of predator,prey interactions. Smaller parasitoids consumed larger hosts in 79% of parasitoid,host interactions. Parasitoids were significantly smaller than predators. 7.,The 52 species were arranged in order of increasing body length along the columns and down the rows of a food web matrix. The predator sub-web was predominantly upper triangular with 8% of non-zero elements falling below the leading diagonal. The parasitoid sub-web was predominantly lower triangular with 21% non-zero elements falling above the leading diagonal. The entire web contains entries both above and below the main diagonal and thus violates a central assumption of the cascade model. [source] Body size, biomic specialization and range size of African large mammalsJOURNAL OF BIOGEOGRAPHY, Issue 7 2005Manuel Hernández Fernández Abstract Aim, The goal of this paper is to examine the relationships between body size, biomic specialization and range size in the African large mammals, which are defined as all the African species corresponding to the orders Primates, Carnivora, Proboscidea, Perissodactyla, Hyracoidea, Tubulidentata, Artiodactyla and Pholidota. Location, The study used the large mammal assemblage from Africa. Methods, The degree of biomic specialization of African large mammals is investigated using the biomic specialization index (BSI) for each mammal species, based on the number of biomes it inhabits. Range size for each species is measured as the latitudinal extent of the geographical distribution of the species. We have analysed our data using both conventional cross-species analyses and phylogenetically independent contrasts. Results, There is a polygonal relationship between species biomic specialization and body size. While small and large species are biomic specialists, medium-sized species are distributed along the whole range of biomic specialization. The latitudinal extent,body size relationship is approximately triangular. Small-bodied species may have either large or small ranges, whereas large-bodied ones have only large ranges. A positive correlation between latitudinal extent and biomic specialization is evident, although their relationship is better described as triangular. Main conclusions, We found a polygonal relationship between species biomic specialization and body size, which agrees with previous arguments that small-bodied species have more limited dispersal and, therefore, they may come to occupy a lesser proportion of their potential inhabitable biomes. On the other hand, large-bodied species are constrained to inhabit biomes with a high productivity. A polygonal relationship between species latitudinal extent and body size in African large mammals agrees with previous studies of the relationship between range size and body size in other continents. The independent study of the macroecological pattern in biomic specialization highlights different factors that influence the body size,range size relationship. Although body size is usually implicated as a correlate of both specialization and geographical range size in large mammals, much of the variation in these variables cannot be attributed to size differences but to biome specific factors such as productivity, area, history, etc. [source] On the nature of Ti(IV)-pillared layered metal hydroxides prepared from green, water-soluble Ti-peroxideAICHE JOURNAL, Issue 5 2010Jing He Abstract Ti-peroxide pillared layered double hydroxides (LDHs) have been prepared for the first time using water-soluble Ti-peroxide as an intercalating precursor. It is novel and alluring that the whole preparation procedure does not involve any usage of organic or chlorine-containing hazards. Intercalated into the LDH interlayer region, Ti-peroxide is prevented partially from condensation in the solvent evaporation. The interlayer TiO2 unit exists in triangular (,2) structure with C2, symmetry in most cases, giving an interlayer gallery of 0.50,0.60 nm. But in the case of pH 4.0, monodentate (,1) structure is also observed, giving an interlayer gallery of 0.70 nm. All the Ti-peroxide pillared LDHs prepared in this work show catalytic activity in the selective oxidation of thioether. The Ti-peroxide introduced into the interlayer regions of Mg/Al LDH with a particle size of around 50,120 nm exhibits better recyclability than Ti-peroxide gel, either in bulk or adsorbed on the exterior surface of LDH particles. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Regional variations in the outer retina of atherinomorpha (Beloniformes, Atheriniformes, Cyprinodontiformes: Teleostei): Photoreceptors, cone patterns, and cone densitiesJOURNAL OF MORPHOLOGY, Issue 3 2003Frank Reckel Abstract The outer retinae of adults of 13 atherinomorph species, representing nine different families, were examined by both light and electron microscopy. The retinae were investigated with respect to photoreceptor types, cone densities, and cone patterns. All data were composed to eye maps. This procedure allows an interspecific comparison of the regional differences within the outer retina among these shallow-water fish. Furthermore, for a more detailed pattern analysis nitro-blue tetrazolium chloride- (NBT)-stainings in the retina of Melanotaenia maccullochi are presented. Apart from rods, eight morphologically different cone types could be identified: short, intermediate, and long single cones, double cones (equal and unequal), triple cones (triangular and linear), and in Ameca splendens one quadruple cone. Dimensions and occurrence of photoreceptors vary among the respective species and within the retinal regions. In the light-adapted state, the cones are arranged in highly ordered mosaics. Five different cone tessellation types were found: row patterns, twisted row patterns, square patterns, pentagonal patterns, and, exclusively in Belone belone, a hexagonal pattern. In Melanotaenia maccullochi the different spectral photoreceptor classes correspond well with the distribution of morphological photoreceptor classes within the mosaic. Double cone density maxima together with a highly ordered cone arrangement usually occur in the nasal and/or ventral to ventrotemporal retina. In most of the species that were examined these high-density regions are presumed to process visual stimuli from the assumed main directions of vision, which mainly depend on feeding behavior and predator pressure. Our findings are discussed with respect to the variable behavioral and visual ecology and phylogeny of the respective species. J. Morphol. 257:270,288, 2003. © 2003 Wiley-Liss, Inc. [source] | ||||||||||||||||||||||||||||