47,748 research outputs found
Exchange Monte Carlo Method and Application to Spin Glass Simulations
We propose an efficient Monte Carlo algorithm for simulating a
``hardly-relaxing" system, in which many replicas with different temperatures
are simultaneously simulated and a virtual process exchanging configurations of
these replica is introduced. This exchange process is expected to let the
system at low temperatures escape from a local minimum. By using this algorithm
the three-dimensional Ising spin glass model is studied. The ergodicity
time in this method is found much smaller than that of the multi-canonical
method. In particular the time correlation function almost follows an
exponential decay whose relaxation time is comparable to the ergodicity time at
low temperatures. It suggests that the system relaxes very rapidly through the
exchange process even in the low temperature phase.Comment: 10 pages + uuencoded 5 Postscript figures, REVTe
Computer aided manual tracking
A scheme was developed to assist the human operator by augmenting an optic sight manual tracking loop with target rate estimates from a computer control algorithm which can either be a Kalman Filter or an alpha, beta, gamma filter. The idea is for the computer to provide rate tracking while the human operator is responsible for nullifying the tracking error. A simple schematic is shown to illustrate the implementation of this concept. A hybrid real-time man-in-loop simulation was used to compare the tracking performance of the same flight trajectory with or without this form of computer-aided track. Preliminary results show the advantage of computer-aided track against high speed aircraft at close range. However, good tracking before target state estimator maturity becomes more critical for aided track than without. Results are presented for a constant velocity flight trajectory
In the eye of the storm: T cell behavior in the inflammatory microenvironment.
Coordinated unfolding of innate and adaptive immunity is key to the development of protective immune responses. This functional integration occurs within the inflamed tissue, a microenvironment enriched with factors released by innate and subsequently adaptive immune cells and the injured tissue itself. T lymphocytes are key players in the ensuing adaptive immunity and their proper function is instrumental to a successful outcome of immune protection. The site of inflammation is a "harsh" environment in which T cells are exposed to numerous factors that might influence their behavior. Low pH and oxygen concentration, high lactate and organic acid content as well as free fatty acids and reactive oxygen species are found in the inflammatory microenvironment. All these components affect T cells as well as other immune cells during the immune response and impact on the development of chronic inflammation. We here overview the effects of a number of factors present in the inflammatory microenvironment on T cell function and migration and discuss the potential relevance of these components as targets for therapeutic intervention in autoimmune and chronic inflammatory diseases
The Failure of Local and Federal Prosecutors to Curb Police Brutality
Although police departments across the country have attempted to ameliorate the hostility between police officers and the cumminity, through careful screening of applicants, minority recruitment, and community policing, police brutality remains a problem within our urban cities. This Essay will first argue that police brutality is largely ignored. Second, it will examine the obstacles facing local and federal prosecutors in obtaining convictions. Then it will compare the advantages and disadvantages of delegating primary responsibility for these cases to the state versus the federal level. Finally, it will argue that, although there are obstacles and advantages for both local and federal prosecutors, ultimately justice is best seved when police brutality is primarily pursued by local prosecutors
Continuity for self-destructive percolation in the plane
A few years ago two of us introduced, motivated by the study of certain
forest-fireprocesses, the self-destructive percolation model (abbreviated as
sdp model). A typical configuration for the sdp model with parameters p and
delta is generated in three steps: First we generate a typical configuration
for the ordinary percolation model with parameter p. Next, we make all sites in
the infinite occupied cluster vacant. Finally, each site that was already
vacant in the beginning or made vacant by the above action, becomes occupied
with probability delta (independent of the other sites).
Let theta(p, delta) be the probability that some specified vertex belongs, in
the final configuration, to an infinite occupied cluster. In our earlier paper
we stated the conjecture that, for the square lattice and other planar
lattices, the function theta has a discontinuity at points of the form (p_c,
delta), with delta sufficiently small. We also showed remarkable consequences
for the forest-fire models.
The conjecture naturally raises the question whether the function theta is
continuous outside some region of the above mentioned form. We prove that this
is indeed the case. An important ingredient in our proof is a (somewhat
stronger form of a) recent ingenious RSW-like percolation result of
Bollob\'{a}s and Riordan
Morse theory on spaces of braids and Lagrangian dynamics
In the first half of the paper we construct a Morse-type theory on certain
spaces of braid diagrams. We define a topological invariant of closed positive
braids which is correlated with the existence of invariant sets of parabolic
flows defined on discretized braid spaces. Parabolic flows, a type of
one-dimensional lattice dynamics, evolve singular braid diagrams in such a way
as to decrease their topological complexity; algebraic lengths decrease
monotonically. This topological invariant is derived from a Morse-Conley
homotopy index and provides a gloablization of `lap number' techniques used in
scalar parabolic PDEs.
In the second half of the paper we apply this technology to second order
Lagrangians via a discrete formulation of the variational problem. This
culminates in a very general forcing theorem for the existence of infinitely
many braid classes of closed orbits.Comment: Revised version: numerous changes in exposition. Slight modification
of two proofs and one definition; 55 pages, 20 figure
AOSD Ontology 1.0 - Public Ontology of Aspect-Orientation
This report presents a Common Foundation for Aspect-Oriented Software Development. A Common Foundation is required to enable effective communication and to enable integration of activities within the Network of Excellence. This Common Foundation is realized by developing an ontology, i.e. the shared meaning of terms and concepts in the domain of AOSD. In the first part of this report, we describe the definitions of an initial set of common AOSD terms. There is general agreement on these definitions. In the second part, we describe the Common Foundation task in detail
- …