Frequency Characteristics of Diffracted Waves Considering Transition Region of GTD Shadow Boundary

2011 ◽  
Author(s):  
Jiro Iwashige ◽  
Leonard Barolli ◽  
Katsuki Hayashi ◽  
Ryo Nagao ◽  
Yuki Isayama
Keyword(s):  
Transition Region ◽  
Frequency Characteristics ◽  
Shadow Boundary ◽  
Diffracted Waves

scholarly journals Determination of exciting forces and amplitude-frequency characteristics during coupled motions of two ships in shallow water parallel to the vertical wall

2021 ◽  
pp. 37-47
Author(s):  
В.Ю. Семенова ◽  
К.И. Баканов
Keyword(s):  
Shallow Water ◽  
Vertical Wall ◽  
Three Dimensional ◽  
Joint Effect ◽  
Frequency Characteristics ◽  
Diffracted Waves ◽  
Exciting Forces ◽  
Domestic Practice ◽  
Simultaneous Influence

В статье рассматривается определение возмущающих сил и моментов и амплитудно-частотных характеристик возникающих при совместной качке двух судов в условиях мелководья параллельно вертикальной стенке на основании решения трехмерной потенциальной задачи. Определение потенциалов дифрагированного волнения, необходимых для расчетов возмущающих сил, осуществляется на основании методов интегральных уравнений и зеркальных отображений. Представленное решение в отечественной практике является новым. В статье приводятся результаты расчетов возмущающих сил и амплитудно-частотных характеристик поперечно-горизонтальных, вертикальных и бортовых колебаний, возникающих при качке двух одинаковых судов, расположенных лагом к волнению и параллельно вертикальной стенке в зависимости от изменения расстояний как между судами, так и между судами и вертикальной стенкой. Проводится исследование влияния различных фарватеров на величины возмущающих сил и амплитудно-частотных характеристик, а именно: мелководного фарватера, мелководного фарватера с вертикальной стенкой, мелководного фарватера со вторым параллельно качающимся судном и мелководного фарватера с вертикальной стенкой и вторым судном. Таким образом, в работе учитывается одновременное влияния мелководья, вертикальной стенки и второго судна. Показано увеличение значений возмущающих сил при уменьшении расстояний между судами и между судами и вертикальной стенкой. Также показано значительное совместное влияние вертикальной стенки и второго судна на амплитудно-частотные характеристики по сравнению со случаем качки судна на мелководье. The article discusses the determination of the exciting forces and moments and amplitude-frequency characteristics arising from the coupled motions of two ships in shallow water conditions parallel to the vertical wall based on the solution of a three-dimensional potential problem. The determination of the potentials of diffracted waves, necessary for calculating the exciting forces, is carried out on the basis of the methods of integral equations and mirror images. The presented solution is new in domestic practice. The article presents the results of calculations of exciting forces and amplitude-frequency characteristics of swaying, heaving and rolling arising from the motions of two identical ships located in the beam waves and parallel to the vertical wall, depending on the change in the distances both between ships and between ships and vertical wall. A study of the influence of various waterways on the magnitude of exciting forces and amplitude-frequency characteristics is being carried out, namely: a shallow waterway, a shallow waterway with a vertical wall, a shallow waterway with a second parallel oscillating ship and a shallow waterway with a vertical wall and a second ship. Thus, the work takes into account the simultaneous influence of shallow water, vertical wall and the second ship. An increase in the values ​​of the exciting forces is shown with a decrease in the distances between ships and between ships and the vertical wall. A significant joint effect of the vertical wall and the second ship on the amplitude-frequency characteristics is also shown in comparison with the case of the ship oscillating in shallow water.

scholarly journals Ray Optical Scattering from Uniform Reflective Cylindrical Metasurfaces using Surface Susceptibility Tensors

2022 ◽  
Author(s):  
Shulabh Gupta ◽  
Tom J. Smy ◽  
Scott Stewart
Keyword(s):  
Transition Region ◽  
Integral Equation Method ◽  
Optical Scattering ◽  
Normal Surface ◽  
Shadow Boundary ◽  
Uniform Theory Of Diffraction ◽  
Full Wave ◽  
Source Models ◽  
Scattered Fields ◽  
Surface Diffraction

A ray optical methodology based on the uniform theory of diffraction is proposed to model electromagnetic field scattering from curved metasurfaces. The problem addressed is the illumination of a purely reflective uniform cylindrical metasurface by a line source, models the surface with susceptibilities and employs a methodology previously used for cylinders coated in thin dielectric layers [1]. The approach is fundamentally based on a representation of the metasurface using the General Sheet Transition Conditions (GSTCs) which characterizes the surface in terms of susceptibility dyadics. An eigenfunction description of the metasurface problem is derived considering both tangential and normal surface susceptibilities, and used to develop a ray optics (RO) description of the scattered fields; including the specular geometrical optical field, surface diffraction described by creeping waves and a transition region over the shadow boundary. The specification of the fields in the transition region is dependent on the evaluation of the Pekeris caret function integral and the method follows [1]. The proposed RO-GSTC model is then successfully demonstrated for a variety of cases and is independently verified using a rigorous eigenfunction solution (EF-GSTC) and full-wave Integral Equation method (IE-GSTC), over the entire domain from the deep lit to deep shadow.

scholarly journals Ray Optical Scattering from Uniform Reflective Cylindrical Metasurfaces using Surface Susceptibility Tensors

2022 ◽  
Author(s):  
Shulabh Gupta ◽  
Tom J. Smy ◽  
Scott Stewart
Keyword(s):  
Transition Region ◽  
Integral Equation Method ◽  
Optical Scattering ◽  
Normal Surface ◽  
Shadow Boundary ◽  
Uniform Theory Of Diffraction ◽  
Full Wave ◽  
Source Models ◽  
Scattered Fields ◽  
Surface Diffraction

A ray optical methodology based on the uniform theory of diffraction is proposed to model electromagnetic field scattering from curved metasurfaces. The problem addressed is the illumination of a purely reflective uniform cylindrical metasurface by a line source, models the surface with susceptibilities and employs a methodology previously used for cylinders coated in thin dielectric layers [1]. The approach is fundamentally based on a representation of the metasurface using the General Sheet Transition Conditions (GSTCs) which characterizes the surface in terms of susceptibility dyadics. An eigenfunction description of the metasurface problem is derived considering both tangential and normal surface susceptibilities, and used to develop a ray optics (RO) description of the scattered fields; including the specular geometrical optical field, surface diffraction described by creeping waves and a transition region over the shadow boundary. The specification of the fields in the transition region is dependent on the evaluation of the Pekeris caret function integral and the method follows [1]. The proposed RO-GSTC model is then successfully demonstrated for a variety of cases and is independently verified using a rigorous eigenfunction solution (EF-GSTC) and full-wave Integral Equation method (IE-GSTC), over the entire domain from the deep lit to deep shadow.

Diffracted waves in the shadow boundary region

1977 ◽  
Vol 67 (4) ◽  
pp. 551 ◽  
Author(s):  
G. Otis ◽  
J.-L. Lachambre ◽  
J. W. Y. Lit ◽  
P. Lavigne
Keyword(s):  
Boundary Region ◽  
Shadow Boundary ◽  
Diffracted Waves

Effects of Ambipolar Diffusion on Prominence Thread Models

1994 ◽  
Vol 144 ◽  
pp. 315-321 ◽  
Author(s):  
M. G. Rovira ◽  
J. M. Fontenla ◽  
J.-C. Vial ◽  
P. Gouttebroze
Keyword(s):  
Energy Balance ◽  
Transition Region ◽  
Ambipolar Diffusion ◽  
Line Profiles ◽  
Balance Equations ◽  
Model Calculations ◽  
Partial Frequency ◽  
Frequency Redistribution ◽  
Partial Frequency Redistribution ◽  
Theoretical Structure

AbstractWe have improved previous model calculations of the prominence-corona transition region including the effect of the ambipolar diffusion in the statistical equilibrium and energy balance equations. We show its influence on the different parameters that characterize the resulting prominence theoretical structure. We take into account the effect of the partial frequency redistribution (PRD) in the line profiles and total intensities calculations.

New form of Transmission Cross Coefficient for High-Resolution Imaging

1990 ◽  
Vol 48 (1) ◽  
pp. 60-61
Author(s):  
Kazuo Ishizuka
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Transmission Function ◽  
Incident Beam ◽  
Optical Microscope ◽  
Strong Interactions ◽  
Small Range ◽  
Specimen Thickness ◽  
Beam Direction ◽  
Diffracted Waves

It is well known that taking into account spacial and temporal coherency of illumination as well as the wave aberration is important to interpret an image of a high-resolution electron microscope (HREM). This occues, because coherency of incident electrons restricts transmission of image information. Due to its large spherical and chromatic aberrations, the electron microscope requires higher coherency than the optical microscope. On an application of HREM for a strong scattering object, we have to estimate the contribution of the interference between the diffracted waves on an image formation. The contribution of each pair of diffracted waves may be properly represented by the transmission cross coefficients (TCC) between these waves. In this report, we will show an improved form of the TCC including second order derivatives, and compare it with the first order TCC.In the electron microscope the specimen is illuminated by quasi monochromatic electrons having a small range of illumination directions. Thus, the image intensity for each energy and each incident direction should be summed to give an intensity to be observed. However, this is a time consuming process, if the ranges of incident energy and/or illumination direction are large. To avoid this difficulty, we can use the TCC by assuming that a transmission function of the specimen does not depend on the incident beam direction. This is not always true, because dynamical scattering is important owing to strong interactions of electrons with the specimen. However, in the case of HREM, both the specimen thickness and the illumination angle should be small. Therefore we may neglect the dependency of the transmission function on the incident beam direction.

Electron Optical Study of Surface Morphologies of Crystals

1980 ◽  
Vol 38 ◽  
pp. 376-377
Author(s):  
Sumio Iijima ◽  
Tung Hsu
Keyword(s):  
Thin Film ◽  
Optical Study ◽  
Regular Array ◽  
Surface Steps ◽  
Diffracted Waves ◽  
Image Position ◽  
Surface Morphologies

Suppose the thickness of a thin film of a crystal varies periodically like a regular array of surface steps, kinematical intensities of diffracted waves from this crystal are modulated by a shape transform,

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