Home About us Contact
|
Home About us Contact | ||
|
|
||
Infinite
Terms modified by Infinite Selected AbstractsON THE EVOLUTION OF HARMING AND RECOGNITION IN FINITE PANMICTIC AND INFINITE STRUCTURED POPULATIONSEVOLUTION, Issue 11 2009Laurent Lehmann Natural selection may favor two very different types of social behaviors that have costs in vital rates (fecundity and/or survival) to the actor: helping behaviors, which increase the vital rates of recipients, and harming behaviors, which reduce the vital rates of recipients. Although social evolutionary theory has mainly dealt with helping behaviors, competition for limited resources creates ecological conditions in which an actor may benefit from expressing behaviors that reduce the vital rates of neighbors. This may occur if the reduction in vital rates decreases the intensity of competition experienced by the actor or that experienced by its offspring. Here, we explore the joint evolution of neutral recognition markers and marker-based costly conditional harming whereby actors express harming, conditional on actor and recipient bearing different conspicuous markers. We do so for two complementary demographic scenarios: finite panmictic and infinite structured populations. We find that marker-based conditional harming can evolve under a large range of recombination rates and group sizes under both finite panmictic and infinite structured populations. A direct comparison with results for the evolution of marker-based conditional helping reveals that, if everything else is equal, marker-based conditional harming is often more likely to evolve than marker-based conditional helping. [source] Debt Neutrality and the Infinite,Lived Representative ConsumerJOURNAL OF PUBLIC ECONOMIC THEORY, Issue 4 2002Bertrand Crettez In this paper, we study the intertemporal equilibria of an infinite,lived representative agent model with public debt. We show that for a given path of government expenditures, there generally exists a continuum of equilibria depending on various debt policies. These equilibria are characterized by different paths of consumption and leisure. Two examples illustrate the results: in the first one consumption and leisure may converge to zero, in the second one consumption goes to infinity while leisure goes to its maximum value. In a third example with externalities à la Romer, the standard intertemporal equilibrium with zero public debt may be dominated by other intertemporal equilibria. [source] Ontological Priority, Fundamentality and MonismDIALECTICA, Issue 3 2009Winner of the 2008 dialectica essay prize In recent work, the interrelated questions of whether there is a fundamental level to reality, whether ontological dependence must have an ultimate ground, and whether the monist thesis should be endorsed that the whole universe is ontologically prior to its parts have been explored with renewed interest. Jonathan Schaffer has provided arguments in favour of ,priority monism' in a series of articles (2003, 2004, 2007a, 2007b, forthcoming). In this paper, these arguments are analysed, and it is claimed that they are not compelling: in particular, the possibility that there is no ultimate level of basic entities that compose everything else is on a par with the possibility of infinite ,upward' complexity. The idea that we must, at any rate, postulate an ontologically fundamental level for methodological reasons (Cameron 2008) is also discussed and found unconvincing: all things considered, there may be good reasons for endorsing ,metaphysical infinitism'. In any event, a higher degree of caution in formulating metaphysical claims than found in the extant literature appears advisable. [source] Characterization of Revenue EquivalenceECONOMETRICA, Issue 1 2009Birgit Heydenreich The property of an allocation rule to be implementable in dominant strategies by a unique payment scheme is called revenue equivalence. We give a characterization of revenue equivalence based on a graph theoretic interpretation of the incentive compatibility constraints. The characterization holds for any (possibly infinite) outcome space and many of the known results are immediate consequences. Moreover, revenue equivalence can be identified in cases where existing theorems are silent. [source] ON THE EVOLUTION OF HARMING AND RECOGNITION IN FINITE PANMICTIC AND INFINITE STRUCTURED POPULATIONSEVOLUTION, Issue 11 2009Laurent Lehmann Natural selection may favor two very different types of social behaviors that have costs in vital rates (fecundity and/or survival) to the actor: helping behaviors, which increase the vital rates of recipients, and harming behaviors, which reduce the vital rates of recipients. Although social evolutionary theory has mainly dealt with helping behaviors, competition for limited resources creates ecological conditions in which an actor may benefit from expressing behaviors that reduce the vital rates of neighbors. This may occur if the reduction in vital rates decreases the intensity of competition experienced by the actor or that experienced by its offspring. Here, we explore the joint evolution of neutral recognition markers and marker-based costly conditional harming whereby actors express harming, conditional on actor and recipient bearing different conspicuous markers. We do so for two complementary demographic scenarios: finite panmictic and infinite structured populations. We find that marker-based conditional harming can evolve under a large range of recombination rates and group sizes under both finite panmictic and infinite structured populations. A direct comparison with results for the evolution of marker-based conditional helping reveals that, if everything else is equal, marker-based conditional harming is often more likely to evolve than marker-based conditional helping. [source] Electrical Percolation Behavior in Silver Nanowire,Polystyrene Composites: Simulation and ExperimentADVANCED FUNCTIONAL MATERIALS, Issue 16 2010Sadie I. White Abstract The design and preparation of isotropic silver nanowire-polystyrene composites is described, in which the nanowires have finite L/D (< 35) and narrow L/D distribution. These model composites allow the L/D dependence of the electrical percolation threshold, ,c, to be isolated for finite- L/D particles. Experimental ,c values decrease with increasing L/D, as predicted qualitatively by analytical percolation models. However, quantitative agreement between experimental data and both soft-core and core,shell analytical models is not achieved, because both models are strictly accurate only in the infinite- L/D limit. To address this analytical limitation, a soft-core simulation method to calculate ,c and network conductivity for cylinders with finite L/D are developed. Our simulated ,c results agree strongly with our experimental data, suggesting i) that the infinite-aspect-ratio assumption cannot safely be made for experimental networks of particles with L/D < 35 and ii) in predicting ,c, the soft-core model makes a less significant assumption than the infinite- L/D models do. The demonstrated capability of the simulations to predict ,c in the finite- L/D regime will allow researchers to optimize the electrical properties of polymer nanocomposites of finite- L/D particles. [source] Methods to Determine Storativity of Infinite Confined Aquifers from a Recovery TestGROUND WATER, Issue 4 2002Djaouida Chenaf Starting from the equations of Theis and Cooper-Jacob, two new mathematical methods are proposed for interpreting the residual drawdown data for an infinite confined aquifer. Under Theis' assumptions and using the Cooper-Jacob approximation, the principal aquifer characteristics of transmissivity, pumping storativity, and recovery storativity are expressed without any correction or additional assumption. An actual case is used for illustration and confirms the validity of proposed equations and methods. [source] Wave-induced progressive liquefaction in a poro-elastoplastic seabed: A two-layered modelINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 5 2009Z. Liu Abstract In this study, the prediction model proposed by Sassa et al. (Geotechnique 2001; 51(10):847,857) for the wave-induced progressive liquefaction in marine sediment, based on two-layered inviscid fluid system, is re-examined. An alternative approach with a similar framework of Sassa et al. (Geotechnique 2001; 51(10):847,857) is developed to correct the inappropriate mechanism of wave components used. Then, a two-layered wave model which includes viscous effects is established and applied to describe the progressive nature of wave-induced liquefaction. A comprehensive comparison shows that Sassa's model overestimates the maximum liquefaction depth. It is found that the viscosity of liquefied soil cannot be ignored and the solution for an infinite seabed is not suitable for liquefaction analysis of shallow seabed. A parametric study demonstrates the significant influence of numerous wave and soil characteristics on the liquefaction depth. Copyright © 2008 John Wiley & Sons, Ltd. [source] A new stereo-analytical method for determination of removal blocks in discontinuous rock massesINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 10 2003Zixin Zhang Abstract The paper provides a new stereo-analytical method, which is a combination of the stereographic method and analytical methods, to separate finite removable blocks from the infinite and tapered blocks in discontinuous rock masses. The methodology has applicability to both convex and concave blocks. Application of the methodology is illustrated through examples. Addition of this method to the existing block theory procedures available in the literature improves the capability of block theory in solving practical problems in rock engineering. Copyright © 2003 John Wiley & Sons, Ltd. [source] A hypersingular time-domain BEM for 2D dynamic crack analysis in anisotropic solidsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 2 2009M. Wünsche Abstract A hypersingular time-domain boundary element method (BEM) for transient elastodynamic crack analysis in two-dimensional (2D), homogeneous, anisotropic, and linear elastic solids is presented in this paper. Stationary cracks in both infinite and finite anisotropic solids under impact loading are investigated. On the external boundary of the cracked solid the classical displacement boundary integral equations (BIEs) are used, while the hypersingular traction BIEs are applied to the crack-faces. The temporal discretization is performed by a collocation method, while a Galerkin method is implemented for the spatial discretization. Both temporal and spatial integrations are carried out analytically. Special analytical techniques are developed to directly compute strongly singular and hypersingular integrals. Only the line integrals over an unit circle arising in the elastodynamic fundamental solutions need to be computed numerically by standard Gaussian quadrature. An explicit time-stepping scheme is obtained to compute the unknown boundary data including the crack-opening-displacements (CODs). Special crack-tip elements are adopted to ensure a direct and an accurate computation of the elastodynamic stress intensity factors from the CODs. Several numerical examples are given to show the accuracy and the efficiency of the present hypersingular time-domain BEM. Copyright © 2008 John Wiley & Sons, Ltd. [source] Mapped infinite elements for three-dimensional multi-region boundary element analysisINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 3 2004W. Moser Abstract A formulation for an infinite boundary element (BE) is presented, which allows the modelling of infinite surfaces. The concept is that the finite surface is mapped to an infinite surface using special mapping functions. Using such mapping functions together with linear and quadratic interpolation for the displacements and the tractions, respectively, the desired decay behaviour can be modelled. The implementation of the proposed infinite elements becomes straightforward, since the Cauchy principal value, as well as the free term, are evaluated for the finite and infinite BEs with exactly the same techniques. The element developed can be used in a multi-region BE analysis of piecewise homogeneous domains, or for domains with joints and faults. The accuracy of the element is tested on some benchmark problems. Finally, a practical application in tunnelling is shown. Copyright © 2004 John Wiley & Sons, Ltd. [source] Non-reflecting artificial boundaries for transient scalar wave propagation in a two-dimensional infinite homogeneous layerINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 10 2003Chongbin Zhao Abstract This paper presents an exact non-reflecting boundary condition for dealing with transient scalar wave propagation problems in a two-dimensional infinite homogeneous layer. In order to model the complicated geometry and material properties in the near field, two vertical artificial boundaries are considered in the infinite layer so as to truncate the infinite domain into a finite domain. This treatment requires the appropriate boundary conditions, which are often referred to as the artificial boundary conditions, to be applied on the truncated boundaries. Since the infinite extension direction is different for these two truncated vertical boundaries, namely one extends toward x ,, and another extends toward x,- ,, the non-reflecting boundary condition needs to be derived on these two boundaries. Applying the variable separation method to the wave equation results in a reduction in spatial variables by one. The reduced wave equation, which is a time-dependent partial differential equation with only one spatial variable, can be further changed into a linear first-order ordinary differential equation by using both the operator splitting method and the modal radiation function concept simultaneously. As a result, the non-reflecting artificial boundary condition can be obtained by solving the ordinary differential equation whose stability is ensured. Some numerical examples have demonstrated that the non-reflecting boundary condition is of high accuracy in dealing with scalar wave propagation problems in infinite and semi-infinite media. Copyright © 2003 John Wiley & Sons, Ltd. [source] On the use of Somigliana's formula and Fourier series for elasticity problems with circular boundariesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 4 2003S. L. Crouch Abstract This paper considers the problem of an infinite, isotropic elastic plane containing an arbitrary number of non-overlapping circular holes and isotropic elastic inclusions. The holes and inclusions are of arbitrary size and the elastic properties of all of the inclusions can, if desired, be different. The analysis is based on the two-dimensional version of Somigliana's formula, which gives the displacements at a point inside a region V in terms of integrals of the tractions and displacements over the boundary S of this region. We take V to be the infinite plane, and S to be an arbitrary number of circular holes within this plane. Any (or all) of the holes can contain an elastic inclusion, and we assume for simplicity that all inclusions are perfectly bonded to the material matrix. The displacements and tractions on each circular boundary are represented as truncated Fourier series, and all of the integrals involved in Somigliana's formula are evaluated analytically. An iterative solution algorithm is used to solve the resulting system of linear algebraic equations. Several examples are given to demonstrate the accuracy and efficiency of the numerical method. Copyright © 2003 John Wiley & Sons, Ltd. [source] A Galerkin boundary integral method for multiple circular elastic inclusionsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 10 2001S. G. Mogilevskaya Abstract The problem of an infinite, isotropic elastic plane containing an arbitrary number of circular elastic inclusions is considered. The analysis procedure is based on the use of a complex singular integral equation. The unknown tractions at each circular boundary are approximated by a truncated complex Fourier series. A system of linear algebraic equations is obtained by using the classical Galerkin method and the Gauss,Seidel algorithm is used to solve the system. Several numerical examples are considered to demonstrate the effectiveness of the approach. Copyright © 2001 John Wiley & Sons, Ltd. [source] On the spectrum of the electric field integral equation and the convergence of the moment methodINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2001Karl F. Warnick Abstract Existing convergence estimates for numerical scattering methods based on boundary integral equations are asymptotic in the limit of vanishing discretization length, and break down as the electrical size of the problem grows. In order to analyse the efficiency and accuracy of numerical methods for the large scattering problems of interest in computational electromagnetics, we study the spectrum of the electric field integral equation (EFIE) for an infinite, conducting strip for both the TM (weakly singular kernel) and TE polarizations (hypersingular kernel). Due to the self-coupling of surface wave modes, the condition number of the discretized integral equation increases as the square root of the electrical size of the strip for both polarizations. From the spectrum of the EFIE, the solution error introduced by discretization of the integral equation can also be estimated. Away from the edge singularities of the solution, the error is second order in the discretization length for low-order bases with exact integration of matrix elements, and is first order if an approximate quadrature rule is employed. Comparison with numerical results demonstrates the validity of these condition number and solution error estimates. The spectral theory offers insights into the behaviour of numerical methods commonly observed in computational electromagnetics. Copyright © 2001 John Wiley & Sons, Ltd. [source] The Phelps,Koopmans theorem and potential optimalityINTERNATIONAL JOURNAL OF ECONOMIC THEORY, Issue 1 2010Debraj Ray D90; O41 The Phelps,Koopmans theorem states that if every limit point of a path of capital stocks exceeds the "golden rule," then that path is inefficient: there is another feasible path from the same initial stock that provides at least as much consumption at every date and strictly more consumption at some date. I show that in a model with nonconvex technologies and preferences, the theorem is false in a strong sense. Not only can there be efficient paths with capital stocks forever above and bounded away from a unique golden rule, such paths can also be optimal under the infinite discounted sum of a one-period utility function. The paper makes clear, moreover, that this latter criterion is strictly more demanding than the efficiency of a path. [source] On robust stability of uncertain systems with multiple time-delaysINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 15 2010Tong ZhouArticle first published online: 27 NOV 200 Abstract On the basis of an infinite to one mapping and the structure of the null space of a multivariate matrix polynomial (MMP), a novel sufficient condition is derived in this paper for the robust stability of a linear time-invariant system with multiple uncertain time-delays, parametric modelling errors and unmodelled dynamics. This condition depends on time-delay bounds and is less conservative than the existing ones. An attractive property is that this condition becomes also necessary in some physically meaningful situations, such as the case that there is only one uncertain time-delay and neither parametric perturbations nor unmodelling errors exist. Moreover, using ideas of representing a positive-definite MMP through matrix sum of squares, an asymptotic necessary and sufficient condition is derived for the robust stability of this system. All the conditions can be converted to linear matrix inequalities. Copyright © 2009 John Wiley & Sons, Ltd. [source] Semi-global stabilization of discrete-time systems subject to non-right invertible constraintsINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 11 2010Xu Wang Abstract This paper investigates time-invariant linear systems subject to input and state constraints. We study discrete-time systems with full or partial constraints on both input and state. It has been shown earlier that the solvability conditions of stabilization problems are closely related to important concepts such as the right invertibility or non-right invertibility of the constraints, the location of constraint invariant zeros, and the order of constraint infinite zeros. In this paper, for general time-invariant linear systems with non-right invertible constraints, necessary and sufficient conditions are developed under which semi-global stabilization in the admissible set can be achieved by state feedback. Sufficient conditions are also developed for such a stabilization in the case where measurement feedback is used. Such sufficient conditions are almost necessary. Controllers for both state feedback and measurement feedback are constructed as well. Copyright © 2009 John Wiley & Sons, Ltd. [source] A new absolute stability test for systems with state-dependent perturbationsINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 14 2002M. C. de Oliveira Abstract In this paper, a new test for the absolute stability of nonlinear systems with state-dependent nonlinearities is developed. Scalar nonlinearities are assumed to lie in sectors. Using a Lur'e function as a Lyapunov function, a linear matrix inequalities (LMI) stability condition is derived. The new condition lets one go from a pure integral (Persidskii) to a pure quadratic Lyapunov function in an unified framework. Several results available in the literature are generated as particular cases of the new test. An example shows that the proposed condition can be much less conservative than available diagonal stability and passivity based methods, as the circle and Popov criteria. Tests for infinite as well as finite nonlinearity sectors can be easily generated, since the parameters of the nonlinearity sectors appear in the LMI condition in a very convenient way. This feature can also provide optimization of the absolute stability sector through convex programming techniques. Copyright © 2002 John Wiley & Sons, Ltd. [source] Plant zero structure and further order reduction of a singular H, controllerINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 7 2002Takao Watanabe Abstract A new class of reduced-order controllers is obtained for the H, problem. The reduced-order controller does not compromise the performance attained by the full-order controller. Algorithms for deriving reduced-order H, controllers are presented in both continuous and discrete time. The reduction in order is related to unstable transmission zeros of the subsystem from disturbance inputs to measurement outputs. In the case where the subsystem has no infinite zeros, the resulting order of the H, controller is lower than that of the existing reduced-order H, controller designs which are based on reduced-order observer design. Furthermore, the mechanism of the controller order reduction is analysed on the basis of the two-Riccati equation approach. The structure of the reduced-order H, controller is investigated. Copyright © 2002 John Wiley & Sons, Ltd. [source] On the sample-complexity of ,, identificationINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 7 2001S. R. Venkatesh Abstract In this paper we derive the sample complexity for discrete time linear time-invariant stable systems described in the ,, topology. The problem set-up is as follows: the ,, norm distance between the unknown real system and a known finitely parameterized family of systems is bounded by a known real number. We can associate, for every feasible real system, a model in the finitely parameterized family that minimizes the ,, distance. The question now arises as to how long a data record is required to identify such a model from noisy input,output data. This question has been addressed in the context of l1, ,2 and several other topologies, and it has been shown that the sample-complexity is polynomial. Nevertheless, it turns out that for the ,, topology the sample-complexity in the worst case can be infinite. Copyright © 2001 John Wiley & Sons, Ltd. [source] Silicone oil: An effective absorbent for the removal of hydrophobic volatile organic compoundsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2010Guillaume Darracq Abstract BACKGROUND: Hydrophobic volatile organic compounds (VOCs), such as toluene, dimethyl sulfide (DMS) and dimethyl disulfide (DMDS), are poorly soluble in water and classical air treatment processes like chemical scrubbers are not efficient. An alternative technique involving an absorption step in an organic solvent followed by a biodegradation phase was proposed. The solvent must fulfil several characteristics, which are key factors of process efficiency, and a previous study allowed polydimethylsiloxane (or PDMS, i.e. silicone oil) to be selected for this purpose. The aim of this paper was to determine some of its characteristics like absorption capacity and velocity performances (Henry's constant, diffusivity and mass transfer coefficient), and to verify its non-biodegradability. RESULTS: For the three targeted VOCs, Henry's constants in silicone oil were very low compared to those in water, and solubility was infinite. Diffusivity values were found to be in the range 10,10 to 10,11 m2 s,1 and mass transfer coefficients did not show significant differences between the values in pure water and pure silicone oil, in the range 1.0 × 10,3 to 4.0 × 10,3 s,1 for all the VOCs considered. Silicone oil was also found to be non-biodegradable, since its biological oxygen demand (BOD5) value was zero. CONCLUSION: Absorption performances of silicone oil towards toluene, DMS and DMDS were determined and showed that this solvent could be used during the first step of the process. Moreover, its low biodegradability and its absence of toxicity justify its use as an absorbent phase for the integrated process being considered. Copyright © 2010 Society of Chemical Industry [source] Bootstrap prediction intervals for autoregressive models of unknown or infinite lag orderJOURNAL OF FORECASTING, Issue 4 2002Jae H. Kim Abstract Recent studies on bootstrap prediction intervals for autoregressive (AR) model provide simulation findings when the lag order is known. In practical applications, however, the AR lag order is unknown or can even be infinite. This paper is concerned with prediction intervals for AR models of unknown or infinite lag order. Akaike's information criterion is used to estimate (approximate) the unknown (infinite) AR lag order. Small-sample properties of bootstrap and asymptotic prediction intervals are compared under both normal and non-normal innovations. Bootstrap prediction intervals are constructed based on the percentile and percentile- t methods, using the standard bootstrap as well as the bootstrap-after-bootstrap. It is found that bootstrap-after-bootstrap prediction intervals show small-sample properties substantially better than other alternatives, especially when the sample size is small and the model has a unit root or near-unit root. Copyright © 2002 John Wiley & Sons, Ltd. [source] Proof of a conjecture on fractional Ramsey numbersJOURNAL OF GRAPH THEORY, Issue 2 2010Jason Brown Abstract Jacobson, Levin, and Scheinerman introduced the fractional Ramsey function rf (a1, a2, ,, ak) as an extension of the classical definition for Ramsey numbers. They determined an exact formula for the fractional Ramsey function for the case k=2. In this article, we answer an open problem by determining an explicit formula for the general case k>2 by constructing an infinite family of circulant graphs for which the independence numbers can be computed explicitly. This construction gives us two further results: a new (infinite) family of star extremal graphs which are a superset of many of the families currently known in the literature, and a broad generalization of known results on the chromatic number of integer distance graphs. © 2009 Wiley Periodicals, Inc. J Graph Theory 63: 164,178, 2010 [source] Between ends and fibersJOURNAL OF GRAPH THEORY, Issue 2 2007C. Paul Bonnington Abstract Let , be an infinite, locally finite, connected graph with distance function ,. Given a ray P in , and a constant C , 1, a vertex-sequence is said to be regulated by C if, for all n,,, never precedes xn on P, each vertex of P appears at most C times in the sequence, and . R. Halin (Math. Ann., 157, 1964, 125,137) defined two rays to be end-equivalent if they are joined by infinitely many pairwise-disjoint paths; the resulting equivalence classes are called ends. More recently H. A. Jung (Graph Structure Theory, Contemporary Mathematics, 147, 1993, 477,484) defined rays P and Q to be b-equivalent if there exist sequences and VQ regulated by some constant C , 1 such that for all n,,; he named the resulting equivalence classes b-fibers. Let denote the set of nondecreasing functions from into the set of positive real numbers. The relation (called f-equivalence) generalizes Jung's condition to . As f runs through , uncountably many equivalence relations are produced on the set of rays that are no finer than b -equivalence while, under specified conditions, are no coarser than end-equivalence. Indeed, for every , there exists an "end-defining function" that is unbounded and sublinear and such that implies that P and Q are end-equivalent. Say if there exists a sublinear function such that . The equivalence classes with respect to are called bundles. We pursue the notion of "initially metric" rays in relation to bundles, and show that in any bundle either all or none of its rays are initially metric. Furthermore, initially metric rays in the same bundle are end-equivalent. In the case that , contains translatable rays we give some sufficient conditions for every f -equivalence class to contain uncountably many g -equivalence classes (where ). We conclude with a variety of applications to infinite planar graphs. Among these, it is shown that two rays whose union is the boundary of an infinite face of an almost-transitive planar map are never bundle- equivalent. © 2006 Wiley Periodicals, Inc. J Graph Theory 54: 125,153, 2007 [source] Snap-off of a liquid drop immersed in another liquid flowing through a constricted capillaryAICHE JOURNAL, Issue 8 2009T. J. Peña Abstract Emulsions are encountered at different stages of oil production processes, often impacting many aspects of oilfield operations. Emulsions may form as oil and water come in contact inside the reservoir rock, valves, pumps, and other equipments. Snap-off is a possible mechanism to explain emulsion formation in two-phase flow in porous media. Quartz capillary tubes with a constriction (pore neck) served to analyze snap-off of long ("infinite") oil droplets as a function of capillary number and oil-water viscosity ratio. The flow of large oil drops through the constriction and the drop break-up process were visualized using an optical microscope. Snap-off occurrence was mapped as a function of flow parameters. High oil viscosity suppresses the breakup process, whereas snap-up was always observed at low dispersed-phase viscosity. At moderate viscosity oil/water ratio, snap-off was observed only at low capillary number. Mechanistic explanations based on competing forces in the liquid phases were proposed. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] A dual extremum principle in thermodynamics ,AICHE JOURNAL, Issue 8 2007Alexander Mitsos Abstract Phase equilibria of multicomponent mixtures are considered and a reinterpretation of the Gibbs tangent plane stability criterion is proposed via Lagrangian duality. The starting point is the natural primal problem of minimizing the Gibbs free energy subject to material balance. The stable phase split is the solution of the corresponding dual problem, providing a necessary and sufficient dual extremum principle. Only in the absence of duality gap is the physical phase split also the solution of the primal problem. The only requirements are continuity of the Gibbs free energy and the trivial requirement that each species is present in the overall composition. The number of phases is permitted to be infinite, and does not need to be known a priori. No assumption is made on the presence of all species in all phases. Case studies are presented based on the NRTL and UNIQUAC activity coefficient model. © 2007 American Institute of Chemical Engineers AIChE J, 2007 [source] Distillation in hollow fibersAICHE JOURNAL, Issue 9 2003Guoliang Zhang Distillation in hollow fibers can give better, more productive separations than distillation in random or structured packing. Since the hollow fibers used have little resistance to mass transfer, the selectivity of the separation depends on the relative volatility, just as in conventional distillation. Because the fibers are nonporous, the distillation can operate at high flows which normally cause flooding, and at low flows which normally compromise loading. As a result, the turndown ratio is nearly infinite and the height of a transfer unit can be as small as desired. Experiments do give values consistent with correlations developed for other membrane modules, although the practical value of hollow fiber distillation is uncertain because of the materials limitations. [source] Debt Neutrality and the Infinite,Lived Representative ConsumerJOURNAL OF PUBLIC ECONOMIC THEORY, Issue 4 2002Bertrand Crettez In this paper, we study the intertemporal equilibria of an infinite,lived representative agent model with public debt. We show that for a given path of government expenditures, there generally exists a continuum of equilibria depending on various debt policies. These equilibria are characterized by different paths of consumption and leisure. Two examples illustrate the results: in the first one consumption and leisure may converge to zero, in the second one consumption goes to infinity while leisure goes to its maximum value. In a third example with externalities à la Romer, the standard intertemporal equilibrium with zero public debt may be dominated by other intertemporal equilibria. [source] THE UNIVERSALITY OF JEWISH ETHICS: A Rejoinder to Secularist CriticsJOURNAL OF RELIGIOUS ETHICS, Issue 2 2008David Novak ABSTRACT Jewish ethics like Judaism itself has often been charged with being "particularistic," and in modernity it has been unfavorably compared with the universality of secular ethics. This charge has become acute philosophically when the comparison is made with the ethics of Kant. However, at this level, much of the ethical rejection of Jewish particularism, especially its being beholden to a God who is above the universe to whom this God prescribes moral norms and judges according to them, is also a rejection of Christian (or any other monotheistic) ethics, no matter how otherwise universal. Yet this essay argues that Jewish ethics that prescribes norms for all humans, and that is knowable by all humans, actually constitutes a wider moral universe than does Kantian ethics, because it can include non-rational human objects and even non-human objects altogether. This essay also argues that a totally egalitarian moral universe, encompassing all human relations, becomes an infinite, totalizing universe, which can easily become the ideological justification (ratio essendi) of a totalitarian regime. [source] | |||||||||||||||||||||||||||||||||||||||||||