Theoretical study of characteristics of laser-drilling with a Gaussian beam and a top-flat beam in time domain

Theoretical research on the phenomenon of negative refractive index materialwas cunducted. The material is a known metamaterial that can manipulate electromagneticwaves through it. By changing the permeability and permittivity of a medium that is worthimaginary, then the value is included in the equation will produce a refractive index that isnegative. This value can be achieved through material forms are designed so that themagnetic field and electric field manipulation. The equation used on electromagnetic wavesthat Maxwell's equations, is revealed to be some similarities propagation magnetic field andelectric field. The Methods Finite Difference Time Domain (FDT D) as a modifier equationwas then equations analysis, simulated using MatlabR2014 program. Based on simulationresults, visible when the electromagnetic waves through a material metamaterial, the wavesare deflected, do not pass part of the material covered.

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Time-domain anisotropic Gaussian beam prestack depth migration using optimized ray tracing system

10.1190/segam2021-3579780.1 ◽

2021 ◽

Author(s):

Qiang Liu ◽

Zhenchun Li ◽

Jian-en Xiao ◽

Kai Zhang ◽

Xuecheng Xu

Keyword(s):

Gaussian Beam ◽

Ray Tracing ◽

Time Domain ◽

Prestack Depth Migration ◽

Depth Migration

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Theoretical study on 252 terahertz Gaussian beam shaping based on an off-axis transmissive all-dielectric metasurface

OSA Continuum ◽

10.1364/osac.2.000201 ◽

2019 ◽

Vol 2 (1) ◽

pp. 201 ◽

Cited By ~ 2

Author(s):

Zewen Wang ◽

Qi Li

Keyword(s):

Gaussian Beam ◽

Theoretical Study ◽

Beam Shaping ◽

Dielectric Metasurface

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Theoretical and Experimental Study of Heading Stability and Heading Control of a Turret-Moored FPSO

Volume 1: Offshore Technology ◽

10.1115/omae2017-61390 ◽

2017 ◽

Cited By ~ 1

Author(s):

Karl E. Kaasen ◽

Halgeir Ludvigsen ◽

Ivar Nygaard ◽

Kristian Aas

Keyword(s):

Time Domain ◽

Theoretical Study ◽

Stability Study ◽

Time Domain Simulation ◽

Wave Excitation ◽

Hypothetical Case ◽

Simple Criterion ◽

Heading Control ◽

Basic Parameters ◽

The Stability

The behaviour and characteristics of a turret-moored FPSO subjected to loading from waves, wind and current are investigated. Of particular importance is to find out if fishtailing instabilities may occur, and if such instability can be disclosed by simple criteria involving basic parameters of the system’s mathematical model. Eight cases from model tests are chosen for theoretical study and time domain simulation. Four of the cases involve heading control with thrusters. For the stability study, a simplified linear model in sway and yaw is formulated. It is shown that the inherent characteristics of the model depend on the strengths and relative directions of the metocean processes. The eigenvalues of the sway-yaw model are computed for the eight selected cases to check the stability. A simple approximate criterion for heading stability is derived from the sway-yaw model. It is assumed, but not proven, that the criterion is a sufficiency criterion for stability. Both the experiments and the simulations show that the eight cases are stable. This is also confirmed by the eigenvalues of the sway-yaw model, while the simple criterion wrongly deems several cases unstable. The simple stability criterion is therefore probably conservative, at least when there is significant damping in the system. In one additional hypothetical case with only wave excitation and weak or lacking stability, the simplified criterion agrees well with the model test and simulation. Heading control is necessary when a heading different from the natural weathervaning heading is wanted. The controller used in the experiments and simulations is of simple SISO PID type. With control, the heading variations are reduced significantly.

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