scholarly journals Dynamic disorder phonon scattering mediated by Cu atomic hopping and diffusion in Cu3SbSe3

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Chen Wang ◽  
Yixuan Wu ◽  
Yanzhong Pei ◽  
Yue Chen
Keyword(s):  
Nearest Neighbor ◽  
Elevated Temperatures ◽  
Phonon Scattering ◽  
Low Cost ◽  
Phonon Transport ◽  
Ab Initio Molecular Dynamics ◽  
Phonon Modes ◽  
Tetrahedral Framework ◽  
Superionic Transition ◽  
The Relationship

Abstract Cu3SbSe3 that exhibits distinct liquid-like sublattice due to the heterogeneous bonding environment has emerged as a promising low cost superionic semiconductor with intrinsic ultralow thermal conductivity. However, the relationship between atomic dynamics resulting in liquid-like diffusion and anomalous phonon transport properties remains poorly understood. Herein, combing ab initio molecular dynamics with temperature-dependent Raman measurements, we have performed a thorough investigation on the lattice dynamics of Cu3SbSe3. Superionic transition is unveiled for both structurally inequivalent Cu atoms at elevated temperatures, while the Se-formed tetrahedral framework can simultaneously maintain. An intermediate state of Cu3SbSe3 through the mixture of quasi-1D/2D Cu nearest-neighbor vacancy hopping is discovered below the superionic transition temperature. Our results also manifest that phonons predominately involved with Cu contributions along diffusion channels have been strongly scattered during the superionic transition, whereas the liquid-like diffusion of Cu is too slow to completely breakdown the propagation of all transverse phonon modes. The insight provided by this work into the atomic dynamics and phonon scattering relationship may pave the way for further phonon engineering of Cu3SbSe3 and related superionic materials.

Study on Phonon Drag Effect and Phonon Transport in Thin Si-on-Insulator Layers

2015 ◽  
Vol 1117 ◽  
pp. 86-89 ◽  
Author(s):  
Hiroya Ikeda ◽  
Takuro Oda ◽  
Yuhei Suzuki ◽  
Yoshinari Kamakura ◽  
Faiz Salleh
Keyword(s):  
Seebeck Coefficient ◽  
Carrier Concentration ◽  
Phonon Scattering ◽  
Phonon Transport ◽  
Infrared Photodetector ◽  
Phonon Drag ◽  
Drag Effect ◽  
Phonon Modes ◽  
Highly Sensitive ◽  
Insulator Layers

The Seebeck coefficient of P-doped ultrathin Si-on-insulator (SOI) layers is investigated for the application to a highly-sensitive thermopile infrared photodetector. It is found that the Seebeck coefficient originating from the phonon drag is significant in the lightly doped region and depends on the carrier concentration with increasing carrier concentration above ~5×1018 cm-3. On the basis of Seebeck coefficient calculations considering both electron and phonon distribution, the phonon-drag part of SOI Seebeck coefficient is mainly governed by the phonon transport, in which the phonon-phonon scattering process is dominant rather than the crystal boundary scattering even in the SOI layer with a thickness of 10 nm. This fact suggests that the phonon-drag Seebeck coefficient is influenced by the phonon modes different from the thermal conductivity.

Atomistic Simulations of G-Type Phonons in Silicon Devices

Volume 4 ◽  
2004 ◽  
Author(s):  
Sanjiv Sinha ◽  
P. K. Schelling ◽  
S. R. Phillpot ◽  
K. E. Goodson
Keyword(s):  
Energy Density ◽  
Phonon Scattering ◽  
Initial Energy ◽  
Phonon Transport ◽  
Phonon Modes ◽  
Decay Channels ◽  
Silicon Devices ◽  
Atomic Displacements ◽  
Initial Energy Density ◽  
Novel Method

Heat conduction in highly compact silicon transistors is impeded due to localization of the electronically generated heat in the device drain. This work studies phonon transport from such heat sources using parallel molecular dynamics. Device Monte Carlo calculations provide an estimate of the size and energy density of the phonon source which is embedded in a one-dimensional crystal. We calculate the scattering times and decay channels for the excited phonons in the absence of thermal phonons. The hotspot is evolved in time and resulting atomic displacements are Fourier analyzed for various phonon modes. Simulations show that decay channels differ depending on the initial energy density of the hotspot. This approach provides a novel method of extracting anharmonic phonon scattering rates for non-equilibrium conditions in a transistor, where first order perturbation theory based calculations may be inaccurate.

A Split-Flux Model for Phonon Transport Near Hotspots

2004 ◽  
Author(s):  
S. Sinha ◽  
E. Pop ◽  
K. E. Goodson
Keyword(s):  
Electric Fields ◽  
Phonon Scattering ◽  
Semiconductor Device ◽  
Longitudinal Optical ◽  
Phonon Transport ◽  
Boltzmann Transport ◽  
Phonon Modes ◽  
Relaxation Time Approximation ◽  
Occupation Numbers ◽  
The Impact

Intense electron-phonon scattering near the peak electric field in a semiconductor device results in nanometer-scale phonon hotspots with power densities on the order of 1 W/μm3. To study the impact of the hotspot on phonon transport, we solve the phonon Boltzmann transport equation under the relaxation time approximation to yield the departure from equilibrium amongst phonon modes. The departure function is split into two contributions: one arising from the far-from-equilibrium emitted phonons and the other from the near-equilibrium thermal phonons. The model predictions are compared with existing data on ballistic phonon transport in silicon. Computations of transient and steady state phonon occupation numbers for a device geometry show the predominance of longitudinal optical phonons for electric fields on the order of 1 MV/m. Due to the low group velocity of these modes, there is an energy stagnation at the hotspot which results in an excess temperature rise of about 13% for a 90 nm bulk silicon device. During device switching, emitted phonons have sufficient time to relax completely when the duty cycle is 30% on a period of 100 ps.

scholarly journals Anharmonic lattice dynamics of superionic lithium nitride

2021 ◽  
Author(s):  
Gabriel Krenzer ◽  
Chang-Eun Kim ◽  
Kasper Tolborg ◽  
Benjamin Morgan ◽  
Aron Walsh
Keyword(s):  
Lattice Dynamics ◽  
Diffusion Processes ◽  
Ab Initio Molecular Dynamics ◽  
Superionic Conductors ◽  
Vibrational Properties ◽  
Phonon Modes ◽  
Lithium Nitride ◽  
Physical Mechanisms ◽  
Anharmonic Lattice ◽  
Superionic Transition

Superionic crystals reach an ionic conductivity comparable to liquid electrolytes following a superionic transition at high temperature. The physical mechanisms that lead to this behaviour remain poorly understood. It has been proposed that superionic transitions are accompanied by the breakdown of specific phonon modes linked to characteristic diffusion processes. Any changes in vibrational properties across the superionic transition may therefore provide insights into the underlying physics of this phenomenon. Here, we apply a combination of lattice dynamics and ab initio molecular dynamics to probe the vibrational properties of the archetypal superionic conductor Li3N. We assess harmonic, quasi-harmonic, and anharmonic descriptions of the phonons. The harmonic and quasi-harmonic models show no change in features across the superionic transition. The fully anharmonic model, however, exhibits a phonon breakdown for all modes above the superionic transition temperature. The implications for developing lattice-dynamics based descriptors for superionic conductors are discussed.

scholarly journals COVIMOS: A Coastal Video Monitoring System

2017 ◽  
Vol 1 (1) ◽  
pp. 1
Author(s):  
I Made Oka Widyantara ◽  
I Made Dwi Asana Putra ◽  
Ida Bagus Putu Adnyana
Keyword(s):  
Monitoring System ◽  
Nearest Neighbor ◽  
Low Cost ◽  
Video Image ◽  
Video Monitoring ◽  
Reference Object ◽  
Self Organizing Map ◽  
K Nearest Neighbor ◽  
Ip Camera ◽  
Class Labels

This paper intends to explain the development of Coastal Video Monitoring System (CoViMoS) with the main characteristics including low-cost and easy implementation. CoViMoS characteristics have been realized using the device IP camera for video image acquisition, and development of software applications with the main features including detection of shoreline and it changes are automatically. This capability was based on segmentation and classification techniques based on data mining. Detection of shoreline is done by segmenting a video image of the beach, to get a cluster of objects, namely land, sea and sky, using Self Organizing Map (SOM) algorithms. The mechanism of classification is done using K-Nearest Neighbor (K-NN) algorithms to provide the class labels to objects that have been generated on the segmentation process. Furthermore, the classification of land used as a reference object in the detection of costline. Implementation CoViMoS system for monitoring systems in Cucukan Beach, Gianyar regency, have shown that the developed system is able to detect the shoreline and its changes automatically.

Effects of Elevated Temperatures on the Compressive Strength of HFCC

2011 ◽  
Vol 261-263 ◽  
pp. 416-420 ◽  
Author(s):  
Fu Ping Jia ◽  
Heng Lin Lv ◽  
Yi Bing Sun ◽  
Bu Yu Cao ◽  
Shi Ning Ding
Keyword(s):  
Compressive Strength ◽  
Elevated Temperature ◽  
Fly Ash ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Relative Strength ◽  
Ordinary Concrete ◽  
Residual Compressive Strength ◽  
Fly Ash Concrete ◽  
The Relationship

This paper presents the results of elevated temperatures on the compressive of high fly ash content concrete (HFCC). The specimens were prepared with three different replacements of cement by fly ash 30%, 40% and 50% by mass and the residual compressive strength was tested after exposure to elevated temperature 250, 450, 550 and 650°C and room temperature respectively. The results showed that the compressive strength apparently decreased with the elevated temperature increased. The presence of fly ash was effective for improvement of the relative strength, which was the ratio of residual compressive strength after exposure to elevated temperature and ordinary concrete. The relative compressive strength of fly ash concrete was higher than those of ordinary concrete. Based on the experiments results, the alternating simulation formula to determine the relationship among relative strength, elevated temperature and fly ash replacement is developed by using regression of results, which provides the theoretical basis for the evaluation and repair of HFCC after elevated temperature.

Kinetostatic backflip strategy for self-recovery of quadruped robots with the selected rotation axis

Robotica ◽  
2021 ◽  
pp. 1-19
Author(s):  
Shengjie Wang ◽  
Kun Wang ◽  
Chunsong Zhang ◽  
Jian S Dai
Keyword(s):  
Optimal Design ◽  
Energy Analysis ◽  
Rotation Axis ◽  
Low Cost ◽  
Minimum Energy ◽  
Design Parameters ◽  
Quadruped Robots ◽  
Design Idea ◽  
The Relationship

Abstract A kinetostatic approach applied to the design of a backflip strategy for quadruped robots is proposed in this paper. Inspired by legged animals and taking the advantage of the leg workspace, this strategy provides an optimal design idea for the low-cost quadruped robots to achieve self-recovery after overturning. Through kinetostatic and energy analysis, a four-stepped backflip strategy based on the selected rotation axis with minimum energy is proposed, with a process of selection, lifting, rotating, and protection. The kinematic factors that affect the backflip are investigated, along with the relationship between the design parameters of the leg and trunk being analyzed. At the end of this paper, the strategy is validated by a simulation and experiments with a prototype called DRbot, demonstrating that the strategy endows the robot a strong self-recovery ability in various terrains.

AN EXPLORATION OF THE RELATIONSHIP BETWEEN THE QUALITY OF PUBLIC GOVERNANCE AND INCOME INEQUALITY: A CASE STUDY OF VIETNAM

2021 ◽  
pp. 1-15
Author(s):  
PHUC VAN PHAN
Keyword(s):  
Income Inequality ◽  
Local Governance ◽  
Low Cost ◽  
Generalized Method Of Moments ◽  
Dynamic Panel Data ◽  
Living Standard ◽  
Public Governance ◽  
The Relationship

Public governance and income inequality relationship is complex and debatable. This paper examines the extent to which the quality of local governance affects inequality in Vietnam spanning the 2006–2016 period. I apply a generalized method of moments (GMM) estimators to a dynamic panel data extracted from the Vietnam’s provincial competitiveness index and the Vietnam household living standard surveys. The findings are that there is a positive inequality — corruption link but no statistically significant correlation coefficient between the overall level of governance and income disparity. The study, therefore, suggests that the Vietnamese Government at all levels should consider both more effective legal practices and economic low-cost solutions to mitigate corruption.

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