25,867 research outputs found
Strain induced band gap deformation of H/F passivated graphene and h-BN sheet
Strain induced band gap deformations of hydrogenated/fluorinated graphene and
hexagonal BN sheet have been investigated using first principles density
functional calculations. Within harmonic approximation, the deformation is
found to be higher for hydrogenated systems than for the fluorinated systems.
Interestingly, our calculated band gap deformation for hydrogenated/fluorinated
graphene and BN sheets are positive, while those for pristine graphene and BN
sheet are found to be negative. This is due to the strong overlap between
nearest neighbor {\pi} orbitals in the pristine sheets, that is absent in the
passivated systems. We also estimate the intrinsic strength of these materials
under harmonic uniaxial strain, and find that the in-plane stiffness of
fluorinated and hydrogenated graphene are close, but larger in magnitude as
compared to those of fluorinated and hydrogenated BN sheet.Comment: Submitted to PR
A Conversation with George G. Roussas
George G. Roussas was born in the city of Marmara in central Greece, on June
29, 1933. He received a B.A. with high honors in Mathematics from the
University of Athens in 1956, and a Ph.D. in Statistics from the University of
California, Berkeley, in 1964. In 1964--1966, he served as Assistant Professor
of Mathematics at the California State University, San Jose, and he was a
faculty member of the Department of Statistics at the University of Wisconsin,
Madison, in 1966--1976, starting as an Assistant Professor in 1966, becoming a
Professor in 1972. He was a Professor of Applied Mathematics and Director of
the Laboratory of Applied Mathematics at the University of Patras, Greece, in
1972--1984. He was elected Dean of the School of Physical and Mathematical
Sciences at the University of Patras in 1978, and Chancellor of the university
in 1981. He served for about three years as Vice President-Academic Affairs of
the then new University of Crete, Greece, in 1981--1985. In 1984, he was a
Visiting Professor in the Intercollege Division of Statistics at the University
of California, Davis, and he was appointed Professor, Associate Dean and Chair
of the Graduate Group in Statistics in the same university in 1985; he served
in the two administrative capacities in 1985--1999. He is an elected member of
the International Statistical Institute since 1974, a Fellow of the Royal
Statistical Society since 1975, a Fellow of the Institute of Mathematical
Statistics since 1983, and a Fellow of the American Statistical Association
since 1986. He served as a member of the Council of the Hellenic Mathematical
Society, and as President of the Balkan Union of Mathematicians.Comment: Published in at http://dx.doi.org/10.1214/09-STS299A the Statistical
Science (http://www.imstat.org/sts/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Characterization of soft stripe-domain deformations in Sm-C and Sm-C* liquid-crystal elastomers
The neoclassical model of Sm-C (and Sm-C*) elastomers developed by Warner and Adams predicts a class of “soft” (zero energy) deformations. We find and describe the full set of stripe domains—laminate structures in which the laminates alternate between two different deformations—that can form between pairs of these soft deformations. All the stripe domains fall into two classes, one in which the smectic layers are not bent at the interfaces, but for which—in the Sm-C* case—the interfaces are charged, and one in which the smectic layers are bent but the interfaces are never charged. Striped deformations significantly enhance the softness of the macroscopic elastic response
What do Information Frictions Do?
Numerous researchers have incorporated labor or credit market frictions within simple neoclassical models to (i) facilitate quick departures from the Arrow-Debreu world, thereby opening up the role for institutions, (ii) inject some realism into their models, and (iii) explain cross country di.erences in output and employment.We present an overlapping generations model with production in which a labor market friction (moral hazard) coexists along with a credit market friction (costly state verification).The simultaneous presence and interaction of these two frictions is studied.We show that credit frictions have a multiplier effect on economic activity, by directly a.ecting investment and indirectly through the unemployment rate.The labor market friction, on the other hand, a.ects unemployment in the short- and long-run but has only a short-run effect on capital accumulation.information;labour market;employment;moral hazard;credit markets;unemployment
Chaotic Planning Solutions in the Textbook Model of Labor Market Search and Matching
This paper demonstrates that cyclical and chaotic planning solutions are possible in the standard textbook model of search and matching in labor markets. More specifically, it takes a discretetime adaptation of the continuous-time matching economy described in Pissarides (1990, 2001), and computes the solution to the dynamic planning problem.The solution is shown to be completely characterized by a first-order, non-linear map with a unique stationary solution.Additionally, the existence of a large number of periodic and even aperiodic non-stationary solutions is shown.Even when the well-known Li-Yorke and three-period cycle conditions for chaos are violated, we are able to verify the new Mitra (2001) su.cient condition for topological chaos.The implication is that even in a simple economy characterized by search and matching frictions, an omniscient social planner may have to contend with a fairly robust and bewildering variety of possible dynamic paths.labour market;planning;matching;chaos;job search
Hydrodynamic interactions of spherical particles in suspensions confined between two planar walls
Hydrodynamic interactions in a suspension of spherical particles confined
between two parallel planar walls are studied under creeping-flow conditions.
The many-particle friction matrix in this system is evaluated using our novel
numerical algorithm based on transformations between Cartesian and spherical
representations of Stokes flow. The Cartesian representation is used to
describe the interaction of the fluid with the walls and the spherical
representation is used to describe the interaction with the particles. The
transformations between these two representations are given in a closed form,
which allows us to evaluate the coefficients in linear equations for the
induced-force multipoles on particle surfaces. The friction matrix is obtained
from these equations, supplemented with the superposition lubrication
corrections. We have used our algorithm to evaluate the friction matrix for a
single sphere, a pair of spheres, and for linear chains of spheres. The
friction matrix exhibits a crossover from a quasi-two-dimensional behavior (for
systems with small wall separation H) to the three-dimensional behavior (when
the distance H is much larger than the interparticle distance L). The crossover
is especially pronounced for a long chain moving in the direction normal to its
orientation and parallel to the walls. In this configuration, a large pressure
buildup occurs in front of the chain for small values of the gapwidth H, which
results in a large hydrodynamic friction force. A standard wall superposition
approximation does not capture this behavior
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