758 research outputs found
Structural Factorization of Plants to Compute their Functional and Architectural Growth
Numerical simulation of plant growth has been facing a bottleneck due to the cumbersome computation implied by the complex plant topological structure. In this article, the authors present a new mathematical model for plant growth, GreenLab, overcoming these difficulties. GreenLab is based on a powerful factorization of the plant structure. Fast simulation algorithms are derived for deterministic and stochastic trees. The computation time no longer depends on the number of organs and grows at most quadratically with the age of the plant. This factorization finds applications to build trees very efficiently, in the context of geometric models, and to compute biomass production and distribution, in the context of functional structural models
Les analysis on cylinder cascade flow based on energy ratio coefficient
The flow field around the cylinder cascade is widely used to
analyze the interaction of vortex shedding and the information
on heat transfer. Large eddy simulation (LES) can be used to
get the turbulent flow information in detail. The resolved largescale
structures are determined by the size of the grid, and the
turbulent vortex dissipation is modeled with a subgrid scale
model. Whereas there is no accurate criterion to provide the
subgrid scale with the physical meaning. Based on turbulent
energy ratio coefficient and numerical simulation results with
turbulent model, the subgrid was generated for the
incompressible fluid flowing around a column of cylinder
cascade with a gap-to-diameter ratio of 2. Smagorinsky-Lily
(SM) model was applied to LES analysis. The turbulent flow
information was compared with the experimental data by PIV.
Two cases with different Reynolds numbers were studied.
When the turbulent energy ratio coefficient reached to 30%-
40%, the turbulent dissipation could be captured by LES
method with less grid number. The large scale vortex
interaction behind the cylinder cascade was analyzed further. It
is verified that LES method can be used for engineering based
on the turbulent energy ratio coefficient with acceptable
computational cost.papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016
GreenLab: A New Methodology Towards Plant Functional-Structural Model -- Structural Part
GreenLab model is an on-going research program conducted jointly by researchers from France and China since 1998. It is oriented to be a functional-structural model for agronomy/forestry applications. Therefore, while keeping a property of being faithful to botanical knowledge, a new methodology is developed within GreenLab by stressing on simplicity of the model. This paper presents briefly our understanding towards plant functional-structural model, but only a model related to plant structures is given to show some progresses of the GreenLab. For a single stand of plant, GreenLab applies its newly developed "dual-scale automaton" approach to generate stochastic structures of plants. Using graph-based interface, this approach provides users with straightforward means of integrating botanical knowledge, i.e., metamers and growth unit, in construction of topological and morphological structures of plants. On the other hand, for a complex tree or a plantation application, a strategy of substructures is employ d in GreenLab model for fast construction of plants and calculation of yields in terms of organs. Simulation results indicate promising benefits in using the new methodology to develop a generic plant model in regard to the structural part. (Résumé d'auteur
Fine-Tuning Solution for Hybrid Inflation in Dissipative Chaotic Dynamics
We study the presence of chaotic behavior in phase space in the
pre-inflationary stage of hybrid inflation models. This is closely related to
the problem of initial conditions associated to these inflationary type of
models. We then show how an expected dissipative dynamics of fields just before
the onset of inflation can solve or ease considerably the problem of initial
conditions, driving naturally the system towards inflation. The chaotic
behavior of the corresponding dynamical system is studied by the computation of
the fractal dimension of the boundary, in phase space, separating inflationary
from non-inflationary trajectories. The fractal dimension for this boundary is
determined as a function of the dissipation coefficients appearing in the
effective equations of motion for the fields.Comment: 10 pages, 4 eps figures (uses epsf), Revtex. Replaced with version to
match one in press Physical Review
Particle production and classical condensates in de Sitter space
The cosmological particle production in a expanding de Sitter universe
with a Hubble parameter is considered for various values of mass or
conformal coupling of a free, scalar field. One finds that, for a minimally
coupled field with mass (except for ),
the one-mode occupation number grows to unity soon after the physical
wavelength of the mode becomes larger than the Hubble radius, and afterwards
diverges as , where . However, for a field with ,
the occupation number of a mode outside the Hubble radius is rapidly
oscillating and bounded and does not exceed unity. These results, readily
generalized for cases of a nonminimal coupling, provide a clear argument that
the long-wavelength vacuum fluctuations of low-mass fields in an inflationary
universe do show classical behavior, while those of heavy fields do not. The
interaction or self-interaction does not appear necessary for the emergence of
classical features, which are entirely due to the rapid expansion of the de
Sitter background and the upside-down nature of quantum oscillators for modes
outside the Hubble radius.Comment: Revtex + 5 postscript figures. Accepted for Phys Rev D15. Revision of
Aug 1996 preprint limited to the inclusion and discussion of references
suggested by the referee
Superfluidity of flexible chains of polar molecules
We study properties of quantum chains in a gas of polar bosonic molecules
confined in a stack of N identical one- and two- dimensional optical lattice
layers, with molecular dipole moments aligned perpendicularly to the layers.
Quantum Monte Carlo simulations of a single chain (formed by a single molecule
on each layer) reveal its quantum roughening transition. The case of finite
in-layer density of molecules is studied within the framework of the J-current
model approximation, and it is found that N-independent molecular superfluid
phase can undergo a quantum phase transition to a rough chain superfluid. A
theorem is proven that no superfluidity of chains with length shorter than N is
possible. The scheme for detecting chain formation is proposed.Comment: Submitted to Proceedings of the QFS2010 satellite conference "Cold
Gases meet Many-Body Theory", Grenoble, August 7, 2010. This is the expanded
version of V.
Exact Master Equation and Non-Markovian Decoherence for Quantum Dot Quantum Computing
In this article, we report the recent progress on decoherence dynamics of
electrons in quantum dot quantum computing systems using the exact master
equation we derived recently based on the Feynman-Vernon influence functional
approach. The exact master equation is valid for general nanostructure systems
coupled to multi-reservoirs with arbitrary spectral densities, temperatures and
biases. We take the double quantum dot charge qubit system as a specific
example, and discuss in details the decoherence dynamics of the charge qubit
under coherence controls. The decoherence dynamics risen from the entanglement
between the system and the environment is mainly non-Markovian. We further
discuss the decoherence of the double-dot charge qubit induced by quantum point
contact (QPC) measurement where the master equation is re-derived using the
Keldysh non-equilibrium Green function technique due to the non-linear coupling
between the charge qubit and the QPC. The non-Markovian decoherence dynamics in
the measurement processes is extensively discussed as well.Comment: 15 pages, Invited article for the special issue "Quantum Decoherence
and Entanglement" in Quantum Inf. Proces
A novel function of TLR2 and MyD88 in the regulation of leukocyte cell migration behavior during wounding in zebrafish larvae
Analysis and StochasticsComputer Systems, Imagery and Medi
Basic principles of stable isotope analysis in humanitarian forensic science.
While the identity of a victim of a localized disaster – such as a train or bus crash – may be established quickly through personal effects, fingerprints, dental records, and a comparison of decedent DNA to family reference specimen DNA, a different scenario presents itself in mass disasters, such as the Asian Tsunami of 2004. In the aftermath of the tsunami, visual appearance was initially used to assign “foreign” or “indigenous” classifications to the remains of thousands of victims. However, this visual identification approach was undermined by the speed with which bodies deteriorated under the hot and humid conditions. Time was spent populating ante-mortem DNA databases for different nationalities, which led to problems when creating a post-mortem DNA database because recovery of viable DNA was compromised due to rapid decomposition. As a consequence, only 1.3% of victims were identified by DNA; in contrast, 61% were identified based on dental examination, although this process took several months and a significant number of deceased from the 2004 Asian Tsunami still remain to be identified
From QFT to DCC
A quantum field theoretical model for the dynamics of the disoriented chiral
condensate is presented. A unified approach to relate the quantum field theory
directly to the formation, decay and signals of the DCC and its evolution is
taken. We use a background field analysis of the O(4) sigma model keeping
one-loop quantum corrections (quadratic order in the fluctuations). An
evolution of the quantum fluctuations in an external, expanding metric which
simulates the expansion of the plasma, is carried out. We examine, in detail,
the amplification of the low momentum pion modes with two competing effects,
the expansion rate of the plasma and the transition rate of the vacuum
configuration from a metastable state into a stable state.We show the effect of
DCC formation on the multiplicity distributions and the Bose-Einstein
correlations.Comment: 34 pages, 10 figure
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