Entropic thermodynamics of nonlinear photonic chain networks

AbstractThe convoluted nonlinear behaviors of heavily multimode photonic structures have been recently the focus of considerable attention. The sheer complexity associated with such multimode systems, allows them to display a host of phenomena that are otherwise impossible in few-mode settings. At the same time, however, it introduces a set of fundamental challenges in terms of comprehending and harnessing their response. Here, we develop an optical thermodynamic approach capable of describing the thermalization dynamics in large scale nonlinear photonic tight-binding networks. For this specific system, an optical Sackur-Tetrode equation is obtained that explicitly provides the optical temperature and chemical potential of the photon gas. Processes like isentropic expansion/compression, Joule expansion, as well as aspects associated with beam cleaning/cooling and thermal conduction effects in such chain networks are discussed. Our results can be used to describe in an effortless manner the exceedingly complex dynamics of highly multimoded nonlinear bosonic systems.

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Enabling Large-Scale Simulations of Quantum Transport with Manycore Computing

Electronics ◽

10.3390/electronics10030253 ◽

2021 ◽

Vol 10 (3) ◽

pp. 253

Author(s):

Yosang Jeong ◽

Hoon Ryu

Keyword(s):

Quantum Transport ◽

Large Scale ◽

Performance Enhancement ◽

Silicon Nanowire ◽

Matrix Multiplication ◽

Tight Binding ◽

Optimization Techniques ◽

Wide Energy Range ◽

Processing Unit ◽

Binding Model

The non-equilibrium Green’s function (NEGF) is being utilized in the field of nanoscience to predict transport behaviors of electronic devices. This work explores how much performance improvement can be driven for quantum transport simulations with the aid of manycore computing, where the core numerical operation involves a recursive process of matrix multiplication. Major techniques adopted for performance enhancement are data restructuring, matrix tiling, thread scheduling, and offload computing, and we present technical details on how they are applied to optimize the performance of simulations in computing hardware, including Intel Xeon Phi Knights Landing (KNL) systems and NVIDIA general purpose graphic processing unit (GPU) devices. With a target structure of a silicon nanowire that consists of 100,000 atoms and is described with an atomistic tight-binding model, the effects of optimization techniques on the performance of simulations are rigorously tested in a KNL node equipped with two Quadro GV100 GPU devices, and we observe that computation is accelerated by a factor of up to ∼20 against the unoptimized case. The feasibility of handling large-scale workloads in a huge computing environment is also examined with nanowire simulations in a wide energy range, where good scalability is procured up to 2048 KNL nodes.

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Feedforward and feedback frequency-dependent interactions in a large-scale laminar network of the primate cortex

Science Advances ◽

10.1126/sciadv.1601335 ◽

2016 ◽

Vol 2 (11) ◽

pp. e1601335 ◽

Cited By ~ 76

Author(s):

Jorge F. Mejias ◽

John D. Murray ◽

Henry Kennedy ◽

Xiao-Jing Wang

Keyword(s):

Large Scale ◽

Complex Dynamics ◽

Predictive Coding ◽

Causality Analysis ◽

Frequency Dependent ◽

Brain Functions ◽

Wide Range ◽

Cortical Laminar ◽

Feedback Frequency ◽

Visual Cortical

Interactions between top-down and bottom-up processes in the cerebral cortex hold the key to understanding attentional processes, predictive coding, executive control, and a gamut of other brain functions. However, the underlying circuit mechanism remains poorly understood and represents a major challenge in neuroscience. We approached this problem using a large-scale computational model of the primate cortex constrained by new directed and weighted connectivity data. In our model, the interplay between feedforward and feedback signaling depends on the cortical laminar structure and involves complex dynamics across multiple (intralaminar, interlaminar, interareal, and whole cortex) scales. The model was tested by reproducing, as well as providing insights into, a wide range of neurophysiological findings about frequency-dependent interactions between visual cortical areas, including the observation that feedforward pathways are associated with enhanced gamma (30 to 70 Hz) oscillations, whereas feedback projections selectively modulate alpha/low-beta (8 to 15 Hz) oscillations. Furthermore, the model reproduces a functional hierarchy based on frequency-dependent Granger causality analysis of interareal signaling, as reported in recent monkey and human experiments, and suggests a mechanism for the observed context-dependent hierarchy dynamics. Together, this work highlights the necessity of multiscale approaches and provides a modeling platform for studies of large-scale brain circuit dynamics and functions.

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Large-Scale Electronic Structure Calculation on Blue Phosphor BaMgAl10O17:Eu2+Using Tight-Binding Quantum Chemistry Method Implemented for Rare-Earth Elements

Japanese Journal of Applied Physics ◽

10.1143/jjap.46.2534 ◽

2007 ◽

Vol 46 (4B) ◽

pp. 2534-2541 ◽

Cited By ~ 11

Author(s):

Hiroaki Onuma ◽

Hideyuki Tsuboi ◽

Michihisa Koyama ◽

Akira Endou ◽

Hiromitsu Takaba ◽

...

Keyword(s):

Electronic Structure ◽

Rare Earth ◽

Quantum Chemistry ◽

Rare Earth Elements ◽

Large Scale ◽

Tight Binding ◽

Structure Calculation ◽

Chemistry Method ◽

Blue Phosphor ◽

Quantum Chemistry Method

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Reaction Diffusion and Chemotaxis for Decentralized Gathering on FPGAs

International Journal of Reconfigurable Computing ◽

10.1155/2009/639249 ◽

2009 ◽

Vol 2009 ◽

pp. 1-15 ◽

Cited By ~ 1

Author(s):

Bernard Girau ◽

César Torres-Huitzil ◽

Nikolaos Vlassopoulos ◽

José Hugo Barrón-Zambrano

Keyword(s):

Large Scale ◽

Complex Dynamics ◽

Diffusion Mechanism ◽

Reaction Diffusion ◽

Fpga Implementation ◽

Cellular Slime Mold ◽

Reaction Diffusion Model ◽

Cellular Slime ◽

Computational Resources ◽

Embedded Implementation

We consider here the feasibility of gathering multiple computational resources by means of decentralized and simple local rules. We study such decentralized gathering by means of a stochastic model inspired from biology: the aggregation of theDictyostelium discoideumcellular slime mold. The environment transmits information according to a reaction-diffusion mechanism and the agents move by following excitation fronts. Despite its simplicity this model exhibits interesting properties of self-organization and robustness to obstacles. We first describe the FPGA implementation of the environment alone, to perform large scale and rapid simulations of the complex dynamics of this reaction-diffusion model. Then we describe the FPGA implementation of the environment together with the agents, to study the major challenges that must be solved when designing a fast embedded implementation of the decentralized gathering model. We analyze the results according to the different goals of these hardware implementations.

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A Predictive Energy Landscape Model of Metamorphic Protein Conformational Specificity

10.1101/2021.11.16.468851 ◽

2021 ◽

Author(s):

James O. Wrabl ◽

Keila Voortman-Sheetz ◽

Vincent J. Hilser

Keyword(s):

Amino Acid ◽

Structure Prediction ◽

Large Scale ◽

Energy Landscape ◽

Thermodynamic Approach ◽

High Identity ◽

Denatured State ◽

Metamorphic Protein ◽

The Stability ◽

The Impact

'Metamorphic' proteins challenge state-of-the-art structure prediction methods reliant on amino acid similarity. Unfortunately, this obviates a more effective thermodynamic approach necessary to properly evaluate the impact of amino acid changes on the stability of two different folds. A vital capability of such a thermodynamic approach would be the quantification of the free energy differences between 1) the energy landscape minima of each native fold, and 2) each fold and the denatured state. Here we develop an energetic framework for conformational specificity, based on an ensemble description of protein thermodynamics. This energetic framework was able to successfully recapitulate the structures of high-identity engineered sequences experimentally shown to adopt either Streptococcus protein GA or GB folds, demonstrating that this approach indeed reflected the energetic determinants of fold. Residue-level decomposition of the conformational specificity suggested several testable hypotheses, notably among them that fold-switching could be affected by local de-stabilization of the populated fold at positions sensitive to equilibrium perturbation. Since this ensemble-based compatibility framework is applicable to any structure and any sequence, it may be practically useful for the future targeted design, or large-scale proteomic detection, of novel metamorphic proteins.

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Development of Problem Solving Environment for Large Scale Electronic Structure Calculations Based on Tight Binding Method

Journal of Convergence Information Technology ◽

10.4156/jcit.vol5.issue4.20 ◽

2010 ◽

Vol 5 (4) ◽

pp. 195-203

Author(s):

Kentaro Takai ◽

Chioko Kaneta ◽

Yuji Uehara ◽

Yoshimasa Kadooka

Keyword(s):

Electronic Structure ◽

Problem Solving ◽

Large Scale ◽

Tight Binding ◽

Electronic Structure Calculations ◽

Problem Solving Environment ◽

Tight Binding Method ◽

Structure Calculations

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Dodecagonal bilayer graphene quasicrystal and its approximants

npj Computational Materials ◽

10.1038/s41524-019-0258-0 ◽

2019 ◽

Vol 5 (1) ◽

Cited By ~ 14

Author(s):

Guodong Yu ◽

Zewen Wu ◽

Zhen Zhan ◽

Mikhail I. Katsnelson ◽

Shengjun Yuan

Keyword(s):

Large Scale ◽

Lattice Mismatch ◽

Tight Binding ◽

Bilayer Graphene ◽

Dominant Factor ◽

Honeycomb Lattice ◽

Fermi Velocity ◽

Band Theory ◽

Incommensurate Structures ◽

Unfolding Method

AbstractDodecagonal bilayer graphene quasicrystal has 12-fold rotational order but lacks translational symmetry which prevents the application of band theory. In this paper, we study the electronic and optical properties of graphene quasicrystal with large-scale tight-binding calculations involving more than ten million atoms. We propose a series of periodic approximants which reproduce accurately the properties of quasicrystal within a finite unit cell. By utilizing the band-unfolding method on the smallest approximant with only 2702 atoms, the effective band structure of graphene quasicrystal is derived. The features, such as the emergence of new Dirac points (especially the mirrored ones), the band gap at $$M$$M point and the Fermi velocity are all in agreement with recent experiments. The properties of quasicrystal states are identified in the Landau level spectrum and optical excitations. Importantly, our results show that the lattice mismatch is the dominant factor determining the accuracy of layered approximants. The proposed approximants can be used directly for other layered materials in honeycomb lattice, and the design principles can be applied for any quasi-periodic incommensurate structures.

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Influence of Local Deformation Mode of Cable-Stayed Bridge on Unballasted Tracks: Experimental Research

Advances in Civil Engineering ◽

10.1155/2020/2316524 ◽

2020 ◽

Vol 2020 ◽

pp. 1-10 ◽

Cited By ~ 1

Author(s):

Xingwang Sheng ◽

Weiqi Zheng ◽

Jianxian Wu ◽

Handong Zhang

Keyword(s):

Large Scale ◽

Deformation Mode ◽

Local Deformation ◽

Deformation Characteristics ◽

Isolation Layer ◽

Segment Model ◽

Cable Stayed Bridge ◽

Deformation Behaviors ◽

Nonlinear Behaviors ◽

Deformation Modes

The complex local deformation modes of the cable-stayed bridge influence the deformation characteristics of the unballasted tracks laid on it. In this work, a large-scale segment model of a cable-stayed bridge was fabricated, and the maximum upward bending deformation mode of the cable-stayed bridge was realized by multipoint loading on the segment model to study the deformation behaviors of the unballasted tracks. Experimental results indicated that the nonlinear behaviors of the rubber isolation layers are apparent with the loading increased, and the interlayer behaviors of the unballasted track can be improved by the rubber isolation layer. Besides, the relative tensile deformations at interlayers of the unballasted track are inevitable. It is noted that no void and silt form at interlayers of the unballasted tracks with rubber isolation layers due to the precompressions of the rubber material. However, it is entirely possible to produce some diseases such as voids and silts at interlayers of the unballasted track with the geotextile isolation layers paved on the cable-stayed bridge. Furthermore, it is feasible to use the elastic isolation layer to improve the interlayer deformation characteristics because a particular elastic buffer is provided at interlayers of the unballasted track.

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Ultrarelativistic Gas with Zero Chemical Potential

Symmetry ◽

10.3390/sym11020249 ◽

2019 ◽

Vol 11 (2) ◽

pp. 249

Author(s):

Daniel Mata-Pacheco ◽

Gonzalo Parga ◽

Fernando Angulo-Brown

Keyword(s):

Chemical Potential ◽

Ideal Gas ◽

Cavity Radiation ◽

Classical Gas ◽

Photon Gas ◽

Spin Degeneracy ◽

Classical Particles

In this work, we propose a set of conditions such that an ultrarelativistic classical gas can present a photon-like behavior. This is achieved by assigning a zero chemical potential to the ultrarelativistic ideal gas. The resulting behavior is similar to that of a Wien photon gas. It is found to be possible only for gases made of very lightweight particles such as neutrinos, as long as we treat them as classical particles, and it depends on the spin degeneracy factor. This procedure allows establishing an analogy between an evaporating gas and the cavity radiation.

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