scholarly journals Decentralized Bioinspired Non-Discrete Model for Autonomous Swarm Aggregation Dynamics

2020 ◽  
Vol 10 (3) ◽  
pp. 1067
Author(s):  
Panagiotis Oikonomou ◽  
Stylianos Pappas
Keyword(s):  
Learning Strategy ◽  
Polynomial Regression ◽  
Initial Conditions ◽  
Cost Minimization ◽  
Center Of Mass ◽  
Scalar Fields ◽  
Discrete State ◽  
Robotic Swarms ◽  
Discrete Mathematical Model ◽  
Basin Hopping

In this paper a microscopic, non-discrete, mathematical model based on stigmergy for predicting the nodal aggregation dynamics of decentralized, autonomous robotic swarms is proposed. The model departs from conventional applications of stigmergy in bioinspired path-finding optimization, serving as a dynamic aggregation algorithm for nodes with limited or no ability to perform discrete logical operations, aiding in agent miniaturization. Time-continuous simulations were developed and carried out where nodal aggregation efficiency was evaluated using the following metrics: time to aggregation equilibrium, agent spatial distribution within aggregate (including average inter-nodal distance, center of mass of aggregate deviation from target), and deviation from target agent number. The system was optimized using cost minimization of the above factors through generating a random set of cost datapoints with varying initial conditions (number of aggregates, agents, field dimensions, and other specific agent parameters) where the best-fit scalar field was obtained using a random forest ensemble learning strategy and polynomial regression. The scalar cost field global minimum was obtained through basin-hopping with L-BFGS-B local minimization on the scalar fields obtained through both methods. The proposed optimized model describes the physical properties that non-digital agents must possess so that the proposed aggregation behavior emerges, in order to avoid discrete state algorithms aiming towards developing agents independent of digital components aiding to their miniaturization.

scholarly journals On Lagrangian and vortex-surface fields for flows with Taylor–Green and Kida–Pelz initial conditions

2010 ◽  
Vol 661 ◽  
pp. 446-481 ◽  
Author(s):  
YUE YANG ◽  
D. I. PULLIN
Keyword(s):  
Incompressible Flows ◽  
Initial Conditions ◽  
Scalar Fields ◽  
Local Geometry ◽  
Optimization Approach ◽  
Vortex Reconnection ◽  
Barotropic Flow ◽  
Lagrangian Surfaces ◽  
Definition Of ◽  
Surface Fields

For a strictly inviscid barotropic flow with conservative body forces, the Helmholtz vorticity theorem shows that material or Lagrangian surfaces which are vortex surfaces at time t = 0 remain so for t > 0. In this study, a systematic methodology is developed for constructing smooth scalar fields φ(x, y, z, t = 0) for Taylor–Green and Kida–Pelz velocity fields, which, at t = 0, satisfy ω·∇φ = 0. We refer to such fields as vortex-surface fields. Then, for some constant C, iso-surfaces φ = C define vortex surfaces. It is shown that, given the vorticity, our definition of a vortex-surface field admits non-uniqueness, and this is presently resolved numerically using an optimization approach. Additionally, relations between vortex-surface fields and the classical Clebsch representation are discussed for flows with zero helicity. Equations describing the evolution of vortex-surface fields are then obtained for both inviscid and viscous incompressible flows. Both uniqueness and the distinction separating the evolution of vortex-surface fields and Lagrangian fields are discussed. By tracking φ as a Lagrangian field in slightly viscous flows, we show that the well-defined evolution of Lagrangian surfaces that are initially vortex surfaces can be a good approximation to vortex surfaces at later times prior to vortex reconnection. In the evolution of such Lagrangian fields, we observe that initially blob-like vortex surfaces are progressively stretched to sheet-like shapes so that neighbouring portions approach each other, with subsequent rolling up of structures near the interface, which reveals more information on dynamics than the iso-surfaces of vorticity magnitude. The non-local geometry in the evolution is quantified by two differential geometry properties. Rolled-up local shapes are found in the Lagrangian structures that were initially vortex surfaces close to the time of vortex reconnection. It is hypothesized that this is related to the formation of the very high vorticity regions.

scholarly journals Dynamics of Space Particles and Spacecrafts Passing by the Atmosphere of the Earth

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Vivian Martins Gomes ◽  
Antonio Fernando Bertachini de Almeida Prado ◽  
Justyna Golebiewska
Keyword(s):  
Initial Conditions ◽  
Equations Of Motion ◽  
Center Of Mass ◽  
The Sun ◽  
Three Body Problem ◽  
The Earth ◽  
Before And After ◽  
Three Body ◽  
Body Energy ◽  
Spacecraft Position

The present research studies the motion of a particle or a spacecraft that comes from an orbit around the Sun, which can be elliptic or hyperbolic, and that makes a passage close enough to the Earth such that it crosses its atmosphere. The idea is to measure the Sun-particle two-body energy before and after this passage in order to verify its variation as a function of the periapsis distance, angle of approach, and velocity at the periapsis of the particle. The full system is formed by the Sun, the Earth, and the particle or the spacecraft. The Sun and the Earth are in circular orbits around their center of mass and the motion is planar for all the bodies involved. The equations of motion consider the restricted circular planar three-body problem with the addition of the atmospheric drag. The initial conditions of the particle or spacecraft (position and velocity) are given at the periapsis of its trajectory around the Earth.

CHAOS IN THE REORIENTATION PROCESS OF A DUAL-SPIN SPACECRAFT WITH TIME-DEPENDENT MOMENTS OF INERTIA

2000 ◽  
Vol 10 (05) ◽  
pp. 997-1018 ◽  
Author(s):  
M. IÑARREA ◽  
V. LANCHARES
Keyword(s):  
Chaotic Behavior ◽  
Initial Conditions ◽  
Center Of Mass ◽  
Melnikov Method ◽  
Moments Of Inertia ◽  
Suitable Parameter ◽  
Nutation Angle ◽  
Principal Axes ◽  
Reorientation Process ◽  
Subharmonic Resonances

We study the spin-up dynamics of a dual-spin spacecraft containing one axisymmetric rotor which is parallel to one of the principal axes of the spacecraft. It will be supposed that one of the moments of inertia of the platform is a periodic function of time and that the center of mass of the spacecraft is not modified. Under these assumptions, it is shown that in the absence of external torques and spinning rotors the system possesses chaotic behavior in the sense that it exhibits Smale's horseshoes. We prove this statement by means of the Melnikov method. The presence of chaotic behavior results in a random spin-up operation. This randomness is visualized by means of maps of the initial conditions with final nutation angle close to zero. This phenomenon is well described by a suitable parameter that measures the amount of randomness of the process. Finally, we relate this parameter with the Melnikov function in the absence of the spinning rotor and with the presence of subharmonic resonances.

A Genetic Algorithm for Cost Estimating Turned Parts in an Interactive DFM Environment

2003 ◽  
Author(s):  
R. Sebastian Schrader ◽  
Michael L. Philpott ◽  
Gautam Subbarao ◽  
Dale E. Holmes
Keyword(s):  
Genetic Algorithms ◽  
Initial Conditions ◽  
Cost Minimization ◽  
Optimization Technique ◽  
Minimum Cost ◽  
Cutting Parameters ◽  
Replacement Policy ◽  
Total Production ◽  
Machining Parameters ◽  
Tool Replacement

This paper presents a method for the optimization of machining parameters, essential for the determination of an economical operating point for multi-pass turning operations. Optimal selection of cutting parameters such as the number of passes, depth of cuts, cutting speeds and feed rates are critical to process planning and cost optimization. This in turn creates a crossing point between product design and manufacturing. Generally, machining models are complex since they are highly non-linear. This research utilizes genetic algorithms as an optimization technique in order to maximize the accuracy of results, the computational achievement, and to minimize the influence of initial conditions and part geometry. A new approach that uses conventional turning process modeling along with genetic algorithms to rapidly search and optimize the feasible workspace is considered. The total production cost minimization is achieved by adding together the minimum cost of each roughing pass and the final finishing pass. In addition, the preventive tool replacement policy used in practice is incorporated. Finally, the results obtained for test cases are evaluated and compared.

scholarly journals Anisotropic flow of identified particles in Pb–Pb collisions at √SNN = 5.02 TeV

2018 ◽  
Vol 171 ◽  
pp. 17002
Author(s):  
Redmer Alexander Bertens
Keyword(s):  
Initial Conditions ◽  
Center Of Mass ◽  
Heavy Ion ◽  
Gluon Plasma ◽  
Mass Energy ◽  
Initial State ◽  
Anisotropic Flow ◽  
Center Of Mass Energy ◽  
Ion Collisions ◽  
Hydrodynamic Calculations

Anisotropic flow is sensitive to the shear (η/s) and bulk (ζ/s) viscosity of the quark-gluon plasma created in heavy-ion collisions, as well as the initial state of such collisions and hadronization mechanisms. In these proceedings, elliptic (υ2) and higher harmonic (υ3, υ4) flow coefficients of π±, K±, p(p) and the ϕ-meson, are presented for Pb—Pb collisions at the highest-ever center-of-mass energy of [see formula in PDF] = 5.02 TeV. Comparisons to hydrodynamic calculations (IP-Glasma, MUSIC, UrQMD) are shown to constrain the initial conditions and viscosity of the medium.

Controlling Flow Structures by Wing Motion in a Flapping-Flight Model

2012 ◽  
Vol 84 ◽  
pp. 59-65 ◽  
Author(s):  
Makoto Iima ◽  
Naoto Yokoyama ◽  
Norio Hirai ◽  
Kei Senda
Keyword(s):  
Hydrodynamic Force ◽  
Initial Conditions ◽  
Center Of Mass ◽  
Flapping Flight ◽  
Flow Structures ◽  
Mass Motion ◽  
Final State ◽  
Wing Motion ◽  
Short Time ◽  
Flight Model

We have studied flow control in a two-dimensional flapping flight model for insects. The insect's center-of-mass motion can move in both horizontal and vertical directions according to the hydrodynamic force generated by flapping. Under steady flapping motion, the model converges to steady flight states depending on initial conditions. Further, we show that a short-time wing stop can control the final steady flight states. The model's flight finally converges to a final state by way of another quasi-steady state, which is not observed as a (stable) steady flight.

scholarly journals Dynamical attractors in contracting spacetimes dominated by kinetically coupled scalar fields

2021 ◽  
Vol 2021 (12) ◽  
pp. 030
Author(s):  
Anna Ijjas ◽  
Frans Pretorius ◽  
Paul J. Steinhardt ◽  
David Garfinkle
Keyword(s):  
Scalar Field ◽  
Initial Conditions ◽  
Scalar Fields ◽  
Density Fluctuations ◽  
Microwave Background ◽  
Scale Invariant ◽  
Linear Evolution ◽  
Kinetic Coupling ◽  
Wide Range ◽  
Non Linear

Abstract We present non-perturbative numerical relativity simulations of slowly contracting spacetimes in which the scalar field driving slow contraction is coupled to a second scalar field through an exponential non-linear σ model-type kinetic interaction. These models are important because they can generate a nearly scale-invariant spectrum of super-Hubble density fluctuations fully consistent with cosmic microwave background observations. We show that the non-linear evolution rapidly approaches a homogeneous, isotropic and flat Friedmann-Robertson-Walker (FRW) geometry for a wide range of inhomogeneous and anisotropic initial conditions. Ultimately, we find, the kinetic coupling causes the evolution to deflect away from flat FRW and towards a novel Kasner-like stationary point, but in general this occurs on time scales that are too long to be observationally relevant.

Capillary network formation and structure in a modified discrete mathematical model of angiogenesis

2021 ◽  
Author(s):  
Madjid Soltani
Keyword(s):  
Mathematical Model ◽  
Network Formation ◽  
Initial Conditions ◽  
Capillary Network ◽  
Cancer Development ◽  
Border Effect ◽  
Capillary Networks ◽  
The Matrix ◽  
Discrete Mathematical Model ◽  
Mathematical Foundations

Abstract Angiogenesis, as part of cancer development, involves hierarchical complicated events and processes. Multiple studies have revealed the significance of the formation and structure of tumor-induced capillary networks. In this study, a discrete mathematical model of angiogenesis is studied and modified to capture the realistic physics of capillary network formation. Modifications are performed on the mathematical foundations of an existing discrete model of angiogenesis. The main modifications are the imposition of the matrix density effect, implementation of realistic boundary and initial conditions, and improvement of the method of governing equations based on physical observation. Results show that endothelial cells accelerate angiogenesis and capillary formation as they migrate toward the tumor and clearly exhibit the physical concept of haptotactic movement. On the other hand, consideration of blood flow-induced stress leads to a dynamic adaptive vascular network of capillaries which intelligibly reflects the brush border effect . The present modified model of capillary network formation is based on the physical rationale that defines a clear mathematical and physical interpretation of angiogenesis, which is likely to be used in cancer development modeling and anti-angiogenic therapies.

scholarly journals Mass hierarchy and energy scaling of the Tsallis – Pareto parameters in hadron productions at RHIC and LHC energies

2018 ◽  
Vol 171 ◽  
pp. 14008 ◽  
Author(s):  
Gábor Bíró ◽  
Gergely Gábor Barnaföldi ◽  
Tamás Sándor Biró ◽  
Keming Shen
Keyword(s):  
Initial Conditions ◽  
Center Of Mass ◽  
System Size ◽  
Collective Effects ◽  
Mass Hierarchy ◽  
Proton Proton ◽  
Center Of Mass Energy ◽  
Nuclear Collisions ◽  
Hadron Spectra ◽  
Parameter Values

The latest, high-accuracy identified hadron spectra measurements in highenergy nuclear collisions led us to the investigation of the strongly interacting particles and collective effects in small systems. Since microscopical processes result in a statistical Tsallis – Pareto distribution, the fit parameters q and T are well suited for identifying system size scalings and initial conditions. Moreover, parameter values provide information on the deviation from the extensive, Boltzmann – Gibbs statistics in finite-volumes. We apply here the fit procedure developed in our earlier study for proton-proton collisions [1, 2]. The observed mass and center-of-mass energy trends in the hadron production are compared to RHIC dAu and LHC pPb data in different centrality/multiplicity classes. Here we present new results on mass hierarchy in pp and pA from light to heavy hadrons.

scholarly journals INFLATIONARY COSMOLOGY AND OSCILLATING UNIVERSES IN LOOP QUANTUM COSMOLOGY

2005 ◽  
Vol 20 (11) ◽  
pp. 2347-2357 ◽  
Author(s):  
DAVID J. MULRYNE ◽  
N. J. NUNES ◽  
REZA TAVAKOL ◽  
JAMES E. LIDSEY
Keyword(s):  
Comparative Study ◽  
Quantum Cosmology ◽  
Initial Conditions ◽  
Scalar Fields ◽  
Inflationary Cosmology ◽  
Loop Quantum Cosmology ◽  
Oscillatory Dynamics ◽  
Slow Roll ◽  
Positively Curved ◽  
Slow Roll Inflation

We study oscillatory universes within the context of Loop Quantum Cosmology. We make a comparative study of flat and positively curved universes sourced by scalar fields with either positive or negative potentials. We investigate how oscillating universes can set the initial conditions for successful slow-roll inflation, while ensuring that the semi-classical bounds are satisfied. We observe rich oscillatory dynamics with negative potentials, although it is difficult to respect the semi-classical bounds in models of this type.

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