5,982 research outputs found
LINEAR FEATURES IN PHOTOGRAMMETRY
Traditional photogrammetric activities such as orientation, triangulation, and object
space reconstruction have been relying on distinct points in their underlying
operations. With the evolution of digital photogrammetry, there has been a
tremendous interest in utilizing linear features in various photogrammetric
activities. This interest has been motivated by the fact that the extraction of linear
features from the image space is easier to automate than distinct points. On the other
hand, object space linear features can be directly derived form terrestrial Mobile
Mapping Systems (MMS), GIS databases, and/or existing maps. Moreover,
automatic matching of linear features, either within overlapping images or between
image and object space, is easier than that of distinct points. Finally, linear features
possess more semantic information than distinct points since they most probably
correspond to object boundaries. Such semantics can be automatically identified in
imagery to facilitate higher-level tasks (e.g., surface reconstruction and object
recognition). This paper summarizes the use of linear features, which might be
represented by analytical functions (e.g., straight-line segments) or irregular (freeform)
shapes, in photogrammetric activities such as automatic space resection,
photogrammetric triangulation, camera calibration, image matching, surface
reconstruction, image-to-image registration, and absolute orientation. Current
progress, future expectations, and possible research directions are discussed as well
Conceptual model of effect and form of architecture and structures
In addition to having the most stability, the first task that every building has to do is having the economic factor, which is one of the concerns of the builders. One of the tools for the advent of architectural form is the structure. This is despite the fact that the limitless artistic thinking has very little unity with numerical and enclosed numerical thinking in the framework of structural engineering math. The date of the interaction between the architecture and the structure implies that the industrial revolution and the consequences are considered as a major event contributed to the further disruption of the relationship between architecture and structural engineering. In many studies, the form of architecture, structure, and nature have been distinctly examined, but in the present study, it was tried to link these two relatives, structures and architectures from the form in nature using technology. First, the evolution of structural and architectural harmony in different historical periods was studied. Then, we focused on natural patterns such as human, plant, and animal structures and finally, works by the Spanish architect, Gullart, was analyzed as an external case study. Regarding the above, this study has achieved a model and a strategy to enhance the quality of construction and interaction of structure and architecture using the structural structure in the existing forms in nature.Keywords: Architecture, Structures, Nature, Architectural and Structural Interactio
Exchange energy and generalized polarization in the presence of spin-orbit coupling in two dimensions
We discuss a general form of the exchange energy for a homogeneous system of
interacting electrons in two spatial dimensions which is particularly suited in
the presence of a generic spin-orbit interaction. The theory is best formulated
in terms of a generalized fractional electronic polarization. Remarkably we
find that a net generalized polarization does not necessarily translate into an
increase in the magnitude of the exchange energy, a fact that in turn favors
unpolarized states. Our results account qualitatively for the findings of
recent experimental investigations
Young stellar populations in early-type dwarf galaxies; occurrence, radial extent and scaling relations
To understand the stellar population content of dwarf early-type galaxies
(dEs) and its environmental dependence, we compare the slopes and intrinsic
scatter of color-magnitude relations (CMRs) for three nearby clusters, Fornax,
Virgo and Coma. Additionally we present and compare internal color profiles of
these galaxies to identify central blue regions with younger stars.
We use the imaging of the HST/ACS Fornax cluster in the magnitude range of
-18.7 <= M_g' <= -16.0, to derive magnitudes, colors and color profiles, which
we compare with literature measurements.
Based on analysis of the color profiles, we report a large number of dEs with
young stellar populations in their center in all three clusters. While for
Virgo and Coma the number of blue-cored dEs is found to be 85 +/- 2% and 53 +/-
3% respectively, for Fornax, we find that all galaxies have a blue core. We
show that bluer cores reside in fainter dEs, similar to the trend seen in
nucleated dEs. We find no correlation between the luminosity of the galaxy and
the size of its blue core. Moreover, a comparison of the CMRs of the three
clusters shows that the scatter in Virgo's CMR is considerably larger than in
the Fornax and Coma clusters. Presenting adaptive smoothing we show that the
galaxies on the blue side of the CMR often show evidence for dust extinction,
which strengthens the interpretation that the bluer colors are due to young
stellar populations. We also find that outliers on the red side of the CMR are
more compact than expected for their luminosity. We find several of these red
outliers in Virgo, often close to more massive galaxies. No red outlying
compact early-types are found in Fornax and Coma in this magnitude range while
we find three in the Virgo cluster. We suggest that the large number of
outliers and larger scatter found for the Virgo cluster CMR is a result of
Virgo's different assembly history.Comment: 24 pages, accepted for publication in Astronomy and Astrophysic
Chaos in Time Dependent Variational Approximations to Quantum Dynamics
Dynamical chaos has recently been shown to exist in the Gaussian
approximation in quantum mechanics and in the self-consistent mean field
approach to studying the dynamics of quantum fields. In this study, we first
show that any variational approximation to the dynamics of a quantum system
based on the Dirac action principle leads to a classical Hamiltonian dynamics
for the variational parameters. Since this Hamiltonian is generically nonlinear
and nonintegrable, the dynamics thus generated can be chaotic, in distinction
to the exact quantum evolution. We then restrict attention to a system of two
biquadratically coupled quantum oscillators and study two variational schemes,
the leading order large N (four canonical variables) and Hartree (six canonical
variables) approximations. The chaos seen in the approximate dynamics is an
artifact of the approximations: this is demonstrated by the fact that its onset
occurs on the same characteristic time scale as the breakdown of the
approximations when compared to numerical solutions of the time-dependent
Schrodinger equation.Comment: 10 pages (12 figures), RevTeX (plus macro), uses epsf, minor typos
correcte
Effect of salt intake on beatâtoâbeat blood pressure nonlinear dynamics and entropy in saltâsensitive versus saltâprotected rats
Blood pressure exhibits substantial shortâ and longâterm variability (BPV). We assessed the hypothesis that the complexity of beatâtoâbeat BPV will be differentially altered in saltâsensitive hypertensive Dahl rats (SS) versus rats protected from saltâinduced hypertension (SSBN13) maintained on highâsalt versus lowâsalt diet. Beatâtoâbeat systolic and diastolic BP series from nine SS and six SSBN13 rats (http://www.physionet.org) were analyzed following 9 weeks on low salt and repeated after 2 weeks on high salt. BP complexity was quantified by detrended fluctuation analysis (DFA), shortâ and longârange scaling exponents (αS and αL), sample entropy (SampEn), and traditional standard deviation (SD) and coefficient of variation (CV(%)). Mean systolic and diastolic BP increased on highâsalt diet (P < 0.01) particularly for SS rats. SD and CV(%) were similar across groups irrespective of diet. Saltâsensitive and âprotected rats exhibited similar complexity indices on lowâsalt diet. On high salt, (1) SS rats showed increased scaling exponents or smoother, systolic (P = 0.007 [αL]) and diastolic (P = 0.008 [αL]) BP series; (2) saltâprotected rats showed lower SampEn (less complex) systolic and diastolic BP (P = 0.046); and (3) compared to protected SSBN13 rats, SS showed higher αL for systolic (P = 0.01) and diastolic (P = 0.005) BP. Hypertensive SS rats are more susceptible to high salt with a greater rise in mean BP and reduced complexity. Comparable mean pressures in sensitive and protective rats when on lowâsalt diet coupled with similar BPV dynamics suggest a protective role of lowâsalt intake in hypertensive rats. This effect likely reflects better coupling of biologic oscillators.We investigated the nonâlinear dynamical properties of blood pressure variability, specifically complexity analysis and detrended fluctuation analysis (DFA), of the systolic and diastolic blood pressure time series in 9 salt sensitive and 6 protected rats. We showed that salt sensitive rats exhibit varying non linear BP dynamics compared to protected rats (smoother time series), irrespective of diet; we also showed the differential impat of salt intake on complexity and DFA metrics in both strains of rats.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/122419/1/phy212823_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/122419/2/phy212823.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/122419/3/phy212823-sup-0001-SupInfo.pd
Stochastic Inflation:The Quantum Phase Space Approach
In this paper a quantum mechanical phase space picture is constructed for
coarse-grained free quantum fields in an inflationary Universe. The appropriate
stochastic quantum Liouville equation is derived. Explicit solutions for the
phase space quantum distribution function are found for the cases of power law
and exponential expansions. The expectation values of dynamical variables with
respect to these solutions are compared to the corresponding cutoff regularized
field theoretic results (we do not restrict ourselves only to \VEV{\F^2}).
Fair agreement is found provided the coarse-graining scale is kept within
certain limits. By focusing on the full phase space distribution function
rather than a reduced distribution it is shown that the thermodynamic
interpretation of the stochastic formalism faces several difficulties (e.g.,
there is no fluctuation-dissipation theorem). The coarse-graining does not
guarantee an automatic classical limit as quantum correlations turn out to be
crucial in order to get results consistent with standard quantum field theory.
Therefore, the method does {\em not} by itself constitute an explanation of the
quantum to classical transition in the early Universe. In particular, we argue
that the stochastic equations do not lead to decoherence.Comment: 43 page
Stochastic approach to inflation II: classicality, coarse-graining and noises
In this work we generalize a previously developed semiclassical approach to
inflation, devoted to the analysis of the effective dynamics of coarse-grained
fields, which are essential to the stochastic approach to inflation. We
consider general non-trivial momentum distributions when defining these fields.
The use of smooth cutoffs in momentum space avoids highly singular quantum
noise correlations and allows us to consider the whole quantum noise sector
when analyzing the conditions for the validity of an effective classical
dynamical description of the coarse-grained field. We show that the weighting
of modes has physical consequences, and thus cannot be considered as a mere
mathematical artifact. In particular we discuss the exponential inflationary
scenario and show that colored noises appear with cutoff dependent amplitudes.Comment: 18 pages, revtex, no figure
Optimal power routing scheme between and within interlinking converters in unbalanced hybrid ACâDC microgrids
An optimal power routing (OPR) scheme between and within interlinking converters (ICs) in unbalanced hybrid ACâDC microgrids to minimise the power imbalance factor at the point of common coupling, active power losses, and voltage deviation indices for microgrids in grid-connected operating mode is proposed in this study. These goals are achieved through a multi-objective optimisation model by optimal distributing of mobile loads between available charging stations and at the same time, OPR within three phases of three-phase four-lag AC/DC converters. Numerical results obtained from implementing the proposed method on the modified IEEE 13-bus system, as an unbalanced hybrid microgrid, and IEEE 34-bus test system, as an unbalanced distribution system, demonstrate that proposed OPR algorithm is successful to satisfy the optimisation goals. For this purpose, four case studies are defined and studied to demonstrate the unique features of the proposed OPR comparing with other power routing schemes. In addition to simulation results, the OPR scheme between ICs is realistically implemented at Florida International University smart grid testbed to show the effect of the power routing on energy losses reduction
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