High-Frequency Diffraction of a Point Source Field by a Strongly Elongated Elliptic Cylinder

2019 ◽  
Vol 105 (6) ◽  
pp. 912-917
Author(s):  
Ivan V. Andronov
Keyword(s):  
Point Source ◽  
Cross Section ◽  
Acoustic Field ◽  
High Frequency ◽  
Elliptic Cylinder ◽  
Linear Source ◽  
Source Field ◽  
Major Semiaxis

The problem of diffraction of a high-frequency point source acoustic field by an infinite elliptic cylinder with a strongly elongated cross-section is studied. At every direction of propagation, the solution is shown to be similar to those of a linear source field diffraction by a cylinder with correspondingly enlarged major semiaxis.

High-Frequency Diffraction by an Elliptic Cylinder With a Strongly Elongated Cross-Section

2015 ◽  
Vol 101 (5) ◽  
pp. 908-914
Author(s):  
I. V. Andronov ◽  
V. V. Monakhov
Keyword(s):  
Cross Section ◽  
High Frequency ◽  
Elliptic Cylinder

Uniform Horizontal Groundwater Flow against Dispersion in a Shallow Aquifer: Two Analytical Models

1992 ◽  
Vol 23 (1) ◽  
pp. 1-12
Author(s):  
Ram Raj Vinda ◽  
Raja Ram Yadava ◽  
Naveen Kumar
Keyword(s):  
Point Source ◽  
Groundwater Flow ◽  
Cross Section ◽  
Analytical Solutions ◽  
Concentration Distribution ◽  
Analytical Models ◽  
Shallow Aquifer ◽  
Horizontal Cross Section ◽  
Flow Components ◽  
Reactive Pollutant

Analytical solutions converging rapidly at large and small values of times have been obtained for two mathematical models which describe the concentration distribution of a non reactive pollutant from a point source against the flow in a horizontal cross-section of a finite saturated shallow aquifer possessing uniform horizontal groundwater flow. Zero concentration or the conditions in which the flux across the extreme boundaries are proportional to the respective flow components are applied. The effects of flow and dispersion on concentration distribution are also discussed.

Turbulent buoyant convection from a source in a confined region

1969 ◽  
Vol 37 (1) ◽  
pp. 51-80 ◽  
Author(s):  
W. D. Baines ◽  
J. S. Turner
Keyword(s):  
Point Source ◽  
Cross Section ◽  
Laboratory Experiments ◽  
Region Of Interest ◽  
Constant Cross Section ◽  
General Shape ◽  
Turbulent Environment ◽  
Starting Conditions ◽  
Upward Velocity ◽  
Local Mean

This paper considers the effect of continuous convection from small sources of buoyancy on the properties of the environment when the region of interest is bounded. The main assumptions are that the entrainment into the turbulent buoyant region is at a rate proportional to the local mean upward velocity, and that the buoyant elements spread out at the top of the region and become part of the non-turbulent environment at that level. Asymptotic solutions, valid at large times, are obtained for the cases of plumes from point and line sources and also periodically released thermals. These all have the properties that the environment is stably stratified, with the density profile fixed in shape, changing at a uniform rate in time at all levels, and everywhere descending (with ascending buoyant elements).The analysis is carried out in detail for the point source in an environment of constant cross-section. Laboratory experiments have been conducted for this case, and these verify the major predictions of the theory. It is then shown how the method can be extended to include more realistic starting conditions for the convection, and a general shape of bounded environment. Finally, the model is applied quantitatively to a variety of problems in engineering, the atmosphere and the ocean, and the limitations on its use are discussed.

The scaled RCS measurement method for lossy targets via dynamically matching the reflection coefficients in the THz band

2021 ◽  
Author(s):  
Shuang Pang ◽  
Yang Zeng ◽  
Qi Yang ◽  
Bin Deng ◽  
Hong-Qiang Wang
Keyword(s):  
Cross Section ◽  
High Frequency ◽  
Measurement Method ◽  
Dielectric Material ◽  
Frequency Estimation ◽  
Estimation Method ◽  
Physical Optics ◽  
Reflection Coefficients ◽  
Effective Solution ◽  
Terahertz Band

Abstract In the terahertz band, the dispersive characteristic of dielectric material is one of the major problems in the scaled radar cross section (RCS) measurement, which is inconsistent with the electrodynamics similitude deducted according to the Maxwell’s equations. Based on the high-frequency estimation method of physical optics (PO), a scaled RCS measurement method for lossy objects is proposed through dynamically matching the reflection coefficients according to the distribution of the object’s facets. Simulations on the model of SLICY were conducted, the inversed RCS of the lossy prototype was obtained using the proposed method. Via comparing the inversed RCS with the calculated results, the validity of the proposed method is demonstrated. The proposed method provides an effective solution to the scaled RCS measurement for lossy objects in the THz band.

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