161,445 research outputs found
Network support for integrated design
A framework of network support for utilization of integrated design over the Internet has been developed. The techniques presented also applicable for Intranet/Extranet. The integrated design system was initially developed for local application in a single site. With the network support, geographically dispersed designers can collaborate a design task through out the total design process, quickly respond to clients’ requests and enhance the design argilty. In this paper, after a brief introduction of the integrated design system, the network support framework is presented, followed by description of two key techniques involved: Java Saverlet approach for remotely executing a large program and online CAD collaboration
Nonparametric IV estimation of shape-invariant Engel curves
This paper concerns the identification and estimation of a shape-invariant Engel
curve system with endogenous total expenditure. The shape-invariant specification
involves a common shift parameter for each demographic group in a pooled
system of Engel curves. Our focus is on the identification and estimation of both
the nonparametric shape of the Engel curve and the parametric specification of the
demographic scaling parameters. We present a new identification condition, closely
related to the concept of bounded completeness in statistics. The estimation procedure
applies the sieve minimum distance estimation of conditional moment restrictions
allowing for endogeneity. We establish a new root mean squared convergence
rate for the nonparametric IV regression when the endogenous regressor has unbounded
support. Root-n asymptotic normality and semiparametric efficiency of
the parametric components are also given under a set of ‘low-level’ sufficient conditions.
Monte Carlo simulations shed lights on the choice of smoothing parameters
and demonstrate that the sieve IV estimator performs well. An application is made
to the estimation of Engel curves using the UK Family Expenditure Survey and
shows the importance of adjusting for endogeneity in terms of both the curvature
and demographic parameters of systems of Engel curves
Semi-nonparametric IV estimation of shape-invariant Engel curves
This paper studies a shape-invariant Engel curve system with endogenous total expenditure, in which the shape-invariant specification involves a common shift parameter for each demographic group in a pooled system of nonparametric Engel curves. We focus on the identification and estimation of both the nonparametric shapes of the Engel curves and the parametric specification of the demographic scaling parameters. The identification condition relates to the bounded completeness and the estimation procedure applies the sieve minimum distance estimation of conditional moment restrictions, allowing for endogeneity. We establish a new root mean squared convergence rate for the nonparametric instrumental variable regression when the endogenous regressor could have unbounded support. Root-n asymptotic normality and semiparametric efficiency of the parametric components are also given under a set of "low-level" sufficient conditions. Our empirical application using the U.K. Family Expenditure Survey shows the importance of adjusting for endogeneity in terms of both the nonparametric curvatures and the demographic parameters of systems of Engel curves
A Lattice Boltzmann method for simulations of liquid-vapor thermal flows
We present a novel lattice Boltzmann method that has a capability of
simulating thermodynamic multiphase flows. This approach is fully
thermodynamically consistent at the macroscopic level. Using this new method, a
liquid-vapor boiling process, including liquid-vapor formation and coalescence
together with a full coupling of temperature, is simulated for the first time.Comment: one gzipped tar file, 19 pages, 4 figure
Meissner state in finite superconducting cylinders with uniform applied magnetic field
We study the magnetic response of superconductors in the presence of low
values of a uniform applied magnetic field. We report measurements of DC
magnetization and AC magnetic susceptibility performed on niobium cylinders of
different length-to-radius ratios, which show a dramatic enhance of the initial
magnetization for thin samples, due to the demagnetizing effects. The
experimental results are analyzed by applying a model that calculates the
magnetic response of the superconductor, taking into account the effects of the
demagnetizing fields. We use the results of magnetization and current and field
distributions of perfectly diamagnetic cylinders to discuss the physics of the
demagnetizing effects in the Meissner state of type-II superconductors.Comment: Accepted to be published in Phys. Rev. B; 15 pages, 7 ps figure
Selecting between two transition states by which water oxidation intermediates on an oxide surface decay
While catalytic mechanisms on electrode surfaces have been proposed for
decades, the pathways by which the product's chemical bonds evolve from the
initial charge-trapping intermediates have not been resolved in time. Here, we
discover a reactive population of charge-trapping intermediates with states in
the middle of a semiconductor's band-gap to reveal the dynamics of two parallel
transition state pathways for their decay. Upon photo-triggering the water
oxidation reaction from the n-SrTiO3 surface with band-gap, pulsed excitation,
the intermediates' microsecond decay reflects transition state theory (TST)
through: (1) two distinct and reaction dependent (pH, T, Ionic Strength, and
H/D exchange) time constants, (2) a primary kinetic salt effect on each
activation barrier and an H/D kinetic isotope effect on one, and (3) realistic
activation barrier heights (0.4 - 0.5 eV) and TST pre-factors (10^11 - 10^12
Hz). A photoluminescence from midgap states in n-SrTiO3 reveals the reaction
dependent decay; the same spectrum was previously assigned by us to
hole-trapping at parallel Ti-O(dot)-Ti (bridge) and perpendicular Ti-O(dot)
(oxyl) O-sites using in situ ultrafast vibrational and optical spectroscopy.
Therefore, the two transition states are naturally associated with the decay of
these respective intermediates. Furthermore, we show that reaction conditions
select between the two pathways, one of which reflects a labile intermediate
facing the electrolyte (the oxyl) and the other a lattice oxygen (the bridge).
Altogether, we experimentally isolate an important activation barrier for water
oxidation, which is necessary for designing water oxidation catalysts with high
O2 turn over. Moreover, in isolating it, we identify competing mechanisms for
O2 evolution at surfaces and show how to use reaction conditions to select
between them
Nonmonotonic External Field Dependence of the Magnetization in a Finite Ising Model: Theory and MC Simulation
Using field theory and Monte Carlo (MC) simulation we investigate
the finite-size effects of the magnetization for the three-dimensional
Ising model in a finite cubic geometry with periodic boundary conditions. The
field theory with infinite cutoff gives a scaling form of the equation of state
where
is the reduced temperature, is the external field and
is the size of system. Below and at the theory predicts a
nonmonotonic dependence of with respect to at fixed and a crossover
from nonmonotonic to monotonic behaviour when is further increased. These
results are confirmed by MC simulation. The scaling function obtained
from the field theory is in good quantitative agreement with the finite-size MC
data. Good agreement is also found for the bulk value at .Comment: LaTex, 12 page
Non-universal size dependence of the free energy of confined systems near criticality
The singular part of the finite-size free energy density of the O(n)
symmetric field theory in the large-n limit is calculated at finite
cutoff for confined geometries of linear size L with periodic boundary
conditions in 2 < d < 4 dimensions. We find that a sharp cutoff
causes a non-universal leading size dependence
near which dominates the universal scaling term . This
implies a non-universal critical Casimir effect at and a leading
non-scaling term of the finite-size specific heat above .Comment: RevTex, 4 page
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