scholarly journals Analysis of Current Distributions and Radar Cross Sections of Line Source Scattering from Impedance Strip by Fractional Derivative Method

2019 ◽  
Vol 8 (2) ◽  
pp. 108-113 ◽  
Author(s):  
K. Karacuha ◽  
E. I. Veliyev ◽  
V. Tabatadze ◽  
E. Karaçuha
Keyword(s):  
Analytical Solution ◽  
Fractional Derivative ◽  
Cross Section ◽  
Cross Sections ◽  
Current Distribution ◽  
Line Source ◽  
Near Field ◽  
Radar Cross Sections ◽  
Derivative Method ◽  
Impedance Strip

In this paper, we have studied the analysis of current distributions and radar cross sections of line source scattering from impedance strip. The problem was solved with fractional derivative method previously. Here, the specific case of fractional derivative method is investigated. The problem under consideration on the basis of various methods is studied well, however, they are mainly done by numerical methods. The fractional derivative method, allows an analytical solution in a specific situation. This method allows to obtain analytical solution of impedance strip for a special case which is fractional order  is equal to 0.5. When fractional order is 0.5, there is an analytical solution which is explained and current distribution, radar cross section and near field patterns are given in this paper. Here, as a first time, current distribution, bi-static radar cross section and near field for the upper and lower part of the strip are studied.

scholarly journals Non-lithographic nanofluidic channels with precisely controlled circular cross sections

RSC Advances ◽  
2018 ◽  
Vol 8 (35) ◽  
pp. 19651-19658 ◽  
Author(s):  
Yang-Seok Park ◽  
Jung Min Oh ◽  
Yoon-Kyoung Cho
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Near Field ◽  
Size And Shape ◽  
Nanofluidic Channels ◽  
Section Size ◽  
Nanochannel Arrays

Printing nanochannel arrays with controlled cross section size and shape using near-field electrospinning.

Line source diffraction by double strips with different fractional boundary conditions

2021 ◽  
pp. 1-17
Author(s):  
Kamil Karaçuha ◽  
Vasil Tabatadze ◽  
Eldar Ismailovich Veliyev
Keyword(s):  
Boundary Conditions ◽  
Cross Sections ◽  
Line Source ◽  
Integral Boundary Conditions ◽  
Neumann Boundary ◽  
Cylindrical Wave ◽  
Integral Boundary ◽  
Radar Cross Sections ◽  
Fractional Boundary Conditions ◽  
Scattered Fields

In this study, the cylindrical wave diffraction by double strips with different lengths and boundary conditions are investigated. The scattered fields are found by the Numerical-Analytical Approach. The double-strip structure satisfies integral boundary conditions which are the generalization of Dirichlet and Neumann boundary conditions. The electric field, current distribution, and Total Radar Cross Sections are investigated. The results are compared with other methods and previous findings such as the Method of Moments and Physical Optics. The theoretical and numerical analyses indicate that the fractional order, the position of the line source have tremendous effects on the total-field distributions.

The dynamics of the near field of strong jets in crossflows

1989 ◽  
Vol 200 ◽  
pp. 95-120 ◽  
Author(s):  
Sergio L. V. Coelho ◽  
J. C. R. Hunt
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Near Field ◽  
Three Dimensional ◽  
Vortex Sheet ◽  
Transverse Component ◽  
Viscous Effects ◽  
Mean Velocity ◽  
Pressure Drag ◽  
The Cross

An inviscid three-dimensional vortex-sheet model for the near field of a strong jet issuing from a pipe into a crossflow is derived. The solution for this model shows that the essential mechanisms governing this idealized flow are the distortion of the main transverse vorticity by the generation of additional axial and transverse vorticity within the pipe owing to the pressure gradients induced by the external flow, and the convection of both components of vorticity from the upwind side of the jet to its downwind side.The deformation of the cross-section of the jet which is predicted by this model is compared with the deformation predicted by the commonly used time-dependent two-dimensional vortex-sheet model. Differences arise because the latter model does not take into account the effects of the transport of the transverse component of vorticity. The complete three-dimensional vortex-sheet model leads to a symmetrical deformation of the jet cross-section and no overall deflection of the jet in the direction of the stream.To account for viscous effects, the initial region of a strong jet issuing into a uniform crossflow is modelled as an entraining three-dimensional vortex sheet, which acts like a sheet of vortices and sinks, redistributing the vorticity in the bounding shear layer and inducing non-symmetrical deformations of the cross-section of the jet. This leads to a deflection of the jet in the direction of the stream, and the loci of the centroids of the cross-sections of the jet describe a quadratic curve.Deformations predicted by each of the three models are compared with measurements obtained from photographs of the cross-sections of a jet of air emerging into a uniform crossflow in a wind tunnel. Mean velocity measurements around the jet made with a hot-wire anemometer agree with the theory; they clearly invalidate models of jets based on ‘pressure drag’.

scholarly journals Bistatic High Frequency Radar Ocean Surface Cross Section for an FMCW Source with an Antenna on a Floating Platform

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Yue Ma ◽  
Weimin Huang ◽  
Eric W. Gill
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
High Frequency ◽  
Continuous Wave ◽  
Ocean Surface ◽  
Radar Cross Section ◽  
Second Order ◽  
Floating Platform ◽  
High Frequency Radar ◽  
Radar Cross Sections

The first- and second-order bistatic high frequency radar cross sections of the ocean surface with an antenna on a floating platform are derived for a frequency-modulated continuous wave (FMCW) source. Based on previous work, the derivation begins with the general bistatic electric field in the frequency domain for the case of a floating antenna. Demodulation and range transformation are used to obtain the range information, distinguishing the process from that used for a pulsed radar. After Fourier-transforming the autocorrelation and comparing the result with the radar range equation, the radar cross sections are derived. The new first- and second-order antenna-motion-incorporated bistatic radar cross section models for an FMCW source are simulated and compared with those for a pulsed source. Results show that, for the same radar operating parameters, the first-order radar cross section for the FMCW waveform is a little lower than that for a pulsed source. The second-order radar cross section for the FMCW waveform reduces to that for the pulsed waveform when the scattering patch limit approaches infinity. The effect of platform motion on the radar cross sections for an FMCW waveform is investigated for a variety of sea states and operating frequencies and, in general, is found to be similar to that for a pulsed waveform.

scholarly journals Absolute Calibration of Jason-1 and Envisat Altimeter Ku-Band Radar Cross Sections from Cross Comparison with TRMM Precipitation Radar Measurements

2005 ◽  
Vol 22 (9) ◽  
pp. 1389-1402 ◽  
Author(s):  
N. Tran ◽  
O-Z. Zanife ◽  
B. Chapron ◽  
D. Vandemark ◽  
P. Vincent
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Absolute Calibration ◽  
Precipitation Radar ◽  
Radar Cross Sections ◽  
Trmm Precipitation ◽  
Radar Calibration ◽  
One Year ◽  
Rain Radar ◽  
Ku Band

Abstract One year of collocated, rain-free nadir Ku-band backscatter cross-section measurements from the Tropical Rainfall Mapping Mission (TRMM) precipitation radar (PR) and both Jason-1 and Envisat RA-2 altimeter measurements have been compiled to compare these three sources of Ku-band radar cross section. With the exception of a +1.46 dB relative offset between Jason-1 and PR measurements and a −1.40 dB offset between Envisat and PR ones, all three Ku-band measurements compare very well in terms of dependencies upon model wind speed estimates and significant wave height measurements. The altimeter radars and the rain radar thus provide consistent measurements, and observed biases can be rationalized as differences in the radar calibration. The precipitation radar, which also covers off-nadir measurements, has been absolutely calibrated using an active radar calibrator. Consequently, the observed relative offsets can be used to indirectly calibrate both Jason-1 and Envisat altimeter Ku-band radar cross sections in an absolute sense.

Electron Irradiation Effects in Polyoxymethylene Crystals Grown Inside Trioxane Crystals

1971 ◽  
Vol 29 ◽  
pp. 78-79
Author(s):  
J. P. Colson ◽  
D. H. Reneker
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Detailed Examination ◽  
The Other ◽  
Electron Micrograph ◽  
Irradiation Effects ◽  
Threefold Axis ◽  
Typical Sample ◽  
Polymer Crystals ◽  
Chain Axis

Polyoxymethylene (POM) crystals grow inside trioxane crystals which have been irradiated and heated to a temperature slightly below their melting point. Figure 1 shows a low magnification electron micrograph of a group of such POM crystals. Detailed examination at higher magnification showed that three distinct types of POM crystals grew in a typical sample. The three types of POM crystals were distinguished by the direction that the polymer chain axis in each crystal made with respect to the threefold axis of the trioxane crystal. These polyoxymethylene crystals were described previously.At low magnifications the three types of polymer crystals appeared as slender rods. One type had a hexagonal cross section and the other two types had rectangular cross sections, that is, they were ribbonlike.

A quantitative approach to inner shell losses

1978 ◽  
Vol 36 (1) ◽  
pp. 526-527 ◽  
Author(s):  
R.D. Leapman ◽  
P. Rez ◽  
D.F. Mayers
Keyword(s):  
Energy Transfer ◽  
Cross Section ◽  
Cross Sections ◽  
Accurate Determination ◽  
Background Intensity ◽  
Core Excitation ◽  
Quantitative Basis ◽  
Cross Section Differential ◽  
Bound Electrons

Microanalysis by EELS has been developing rapidly and though the general form of the spectrum is now understood there is a need to put the technique on a more quantitative basis (1,2). Certain aspects important for microanalysis include: (i) accurate determination of the partial cross sections, σx(α,ΔE) for core excitation when scattering lies inside collection angle a and energy range ΔE above the edge, (ii) behavior of the background intensity due to excitation of less strongly bound electrons, necessary for extrapolation beneath the signal of interest, (iii) departures from the simple hydrogenic K-edge seen in L and M losses, effecting σx and complicating microanalysis. Such problems might be approached empirically but here we describe how computation can elucidate the spectrum shape.The inelastic cross section differential with respect to energy transfer E and momentum transfer q for electrons of energy E0 and velocity v can be written as

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