Integral-Balance Solution to the Stokes' First Problem of a Viscoelastic Generalized Second Grade Fluid

Integral balance solution employing entire domain approximation and the penetration dept concept to the Stokes' first problem of a viscoelastic generalized second grade fluid has been developed. The solution has been performed by a parabolic profile with an unspecified exponent allowing optimization through minimization of the norm over the domain of the penetration depth. The closed form solution explicitly defines two dimensionless similarity variables and, responsible for the viscous and the elastic responses of the fluid to the step jump at the boundary. The solution was developed with three forms of the governing equation through its two dimensional forms (the main solution and example 1) and the dimensionless version showing various sides of the flow field and how the dimensionless groups control it: mainly the effect of the Deborah number. Numerical simulations demonstrating the effect of the various operating parameter and fluid properties on the developed flow filed have been performed.Comment: 19 pages, 6 figures; in press Thermal Science, volume 16, 2012, issue

The High Sensitivity of Employment to Agency Costs: The Relevance of Wage Rigidity

This paper studies the interaction of financing constraints and labor market imperfections on the labor market and economic activity. My analysis builds on the agency cost framework of Carlstrom and Fuerst [1998. Agency costs and business cycles. Economic Theory, 12(3):583-597]. The aim of this article is to show that financing constraints can substantially amplify and propagate total factor productivity shocks in cyclical labor market dynamics. I find that under the Nash bargaining solution financing constraints increase substantially the volatility of wages, and in turn, amplification for the labor variables falls short of the observed volatilities in the data. Atop of this, the comovement between output and labor share is counterfactual. However, there is substantial scope for any type of wage rigidity and financing constraints to reinforce each other, and to generate the observed volatilities in the labor market, moreover, to produce a wide range of comovements between output and labor share.Credit and search frictions, Labor market, Unemployment

Static supersymmetric black holes in AdS_4 with spherical symmetry

We elaborate further on the static supersymmetric AdS_4 black holes found in arXiv:0911.4926, investigating thoroughly the BPS constraints for spherical symmetry in N = 2 gauged supergravity in the presence of Fayet-Iliopoulos terms. We find Killing spinors that preserve two of the original eight supercharges and investigate the conditions for genuine black holes free of naked singularities. The existence of a horizon is intimately related with the requirement that the scalars are not constant, but given in terms of harmonic functions in analogy to the attractor flow in ungauged supergravity. The black hole charges depend on the choice of the electromagnetic gauging, with only magnetic charges for purely electric gaugings. Finally we show how these black holes can be embedded in N = 8 supergravity and thus in M-theory.Comment: 28 pages; v2 minor change

6d-5d-4d reduction of BPS attractors in flat gauged supergravities

Via a series of Kaluza-Klein (KK) and Scherk-Schwarz (SS) compactifications we relate BPS attractors and their complete (in general non-BPS) flows to a Minkowski vacuum in gauged supergravities with vanishing scalar potential in 4, 5, and 6 dimensions. This way we can look at a class of extremal non-BPS black holes and strings from IIB string theory viewpoint, keeping 4 supercharges on the horizon. Our results imply the existence of a dual 2d N = (0,2) superconformal field theory (SCFT) that originates from a parent N=(4,4) theory living on a D1-D5 system. This is achieved starting from the BPS black string in 6d with an AdS_3xS^3 attractor and taking two different routes to arrive at a 1/2 BPS AdS_2xS^2 attractor of a non-BPS black hole in 4d N=2 flat gauged supergravity. The two inequivalent routes interchange the order of KK reduction on AdS_3 and SS reduction on S^3. We also find the commutator between the two operations after performing a duality transformation: on the level of the theory the result is the exchange of electric with magnetic gaugings; on the level of the solution we find a flip of the quartic invariant I_4 to -I_4.Comment: 20 pages, 2 flow charts; v2 improved discussion and added referenc

Analysis, Design and Fabrication of centimeter-wave Dielectric Fresnel Zone Plate Lens and reflector

Fresnel lens has a long history in optics. This concept at non-optical wavelengths is also applicable. In this paper we report design and fabrication of a half and quarter wave dielectric Fresnel lens made of Plexiglas, and a Fresnel reflector at 11.1 GHz frequency. We made two lenses and one reflector at same frequency and compare their gain and radiation pattern to simulated results. Some methods for better focusing action will be introduced

Practical Data Correlation of Flashpoints of Binary Mixtures by a Reciprocal Function: The Concept and Numerical Examples

Simple data correlation of flashpoint data of binary mixture has been developed on a basic of rational reciprocal function. The new approximation requires has only two coefficients and needs the flashpoint temperature of the pure flammable component to be known. The approximation has been tested by literature data concerning aqueous-alcohol solution and compared to calculations performed by several thermodynamic models predicting flashpoint temperatures. The suggested approximation provides accuracy comparable and to some extent better than that of the thermodynamic methods.Comment: 6 pages and 5 tables IN PRESS; Thermal Science vol. 15, issue 3, 201

Nonlocal Operational Calculi for Dunkl Operators

The one-dimensional Dunkl operator $D_k$ with a non-negative parameter $k$, is considered under an arbitrary nonlocal boundary value condition. The right inverse operator of $D_k$, satisfying this condition is studied. An operational calculus of Mikusinski type is developed. In the frames of this operational calculi an extension of the Heaviside algorithm for solution of nonlocal Cauchy boundary value problems for Dunkl functional-differential equations $P(D_k)u=f$ with a given polynomial $P$ is proposed. The solution of these equations in mean-periodic functions reduces to such problems. Necessary and sufficient condition for existence of unique solution in mean-periodic functions is found