scholarly journals Dynamic RCS Estimation according to Drone Movement Using the MoM and Far-Field Approximation

2021 ◽  
Vol 21 (4) ◽  
pp. 322-328
Author(s):  
Dong-Yeob Lee ◽  
Jae-In Lee ◽  
Dong-Wook Seo
Keyword(s):  
Fourier Transform ◽  
Cross Section ◽  
Method Of Moments ◽  
Iterative Process ◽  
Rotation Angle ◽  
Field Approximation ◽  
Far Field ◽  
Impedance Matrix ◽  
The Matrix ◽  
The Fourier Transform

Micro-Doppler signatures from the rotating propellers of a drone can be utilized to distinguish the drone from clutter or airborne organisms with similar radar cross section (RCS) levels, such as birds and bats. To obtain the micro-Doppler signatures of a drone, calculation or measurement of the electric field scattered from the rotating propellers is essential. In this paper, using the relative angle concept and far-field approximation, we propose a way to rapidly estimate the dynamic RCS of a drone with several propellers according to its movement. In addition, based on the fact that the shape of the propeller does not change even if it rotates, we construct an impedance matrix only once and apply the matrix to the method of moments instead of the iterative process of calculating the impedance matrix and inverse matrix for each rotation angle of the propeller. Finally, by using the Fourier transform of the results from the proposed method, the rotation frequencies of the propellers according to the movement of the drone can be obtained.

scholarly journals Controlled Release of Agrochemicals Intercalated into Montmorillonite Interlayer Space

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Harrison Wanyika
Keyword(s):  
Fourier Transform ◽  
Controlled Release ◽  
Interlayer Space ◽  
Rotary Evaporation ◽  
Surface Areas ◽  
Space Reduction ◽  
Immersion Technique ◽  
The Matrix ◽  
The Fourier Transform ◽  
Mmt Clay

Periodic application of agrochemicals has led to high cost of production and serious environmental pollution. In this study, the ability of montmorillonite (MMT) clay to act as a controlled release carrier for model agrochemical molecules has been investigated. Urea was loaded into MMT by a simple immersion technique while loading of metalaxyl was achieved by a rotary evaporation method. The successful incorporation of the agrochemicals into the interlayer space of MMT was confirmed by several techniques, such as, significant expansion of the interlayer space, reduction of Barrett-Joyner-Halenda (BJH) pore volumes and Brunauer-Emmett-Teller (BET) surface areas, and appearance of urea and metalaxyl characteristic bands on the Fourier-transform infrared spectra of the urea loaded montmorillonite (UMMT) and metalaxyl loaded montmorillonite (RMMT) complexes. Controlled release of the trapped molecules from the matrix was done in water and in the soil. The results reveal slow and sustained release behaviour for UMMT for a period of 10 days in soil. For a period of 30 days, MMT delayed the release of metalaxyl in soil by more than 6 times. It is evident that MMT could be used to improve the efficiency of urea and metalaxyl delivery in the soil.

Directional Image Filtering Based on the Fourier Transform

2014 ◽  
Vol 19 (2-3) ◽  
pp. 7-13
Author(s):  
Przemysław Korohoda ◽  
Joanna Grabska-Chrząstowska ◽  
Jaromir Przybyło
Keyword(s):  
Fourier Transform ◽  
Rotation Angle ◽  
Image Filtering ◽  
Suggested Method ◽  
Fourier Domain ◽  
Fourier Space ◽  
Direct Rotation ◽  
The Fourier Transform ◽  
Directional Image

Abstract An algorithm to design the small size 2-D filter masks with arbitrarily selected rotation angle has been proposed. The classical filter mask of size 3 × 3 is obtained from the reference Fourier space characteristics, rotated in the Fourier domain. The efficiency of the suggested method was illustrated with examples based on the Sobel gradient mask and two test images. Comparative computations indicated that the accuracy of the filtering result with use of the small size filters is noticeably better when the filter has been designed with use of the Fourier characteristics rotation than after direct rotation of the mask in the pixel domain.

scholarly journals Analysis of Sound Waves with Semi Perforated Pipe

2019 ◽  
Vol 2 (3) ◽  
pp. 704-710
Author(s):  
Burhan Tiryakioglu
Keyword(s):  
Boundary Condition ◽  
Fourier Transform ◽  
Wave Equation ◽  
Pipe Wall ◽  
Far Field ◽  
Sound Waves ◽  
Hopf Equation ◽  
Hopf Method ◽  
The Fourier Transform ◽  
Perforated Pipe

The paper presents analytical results of radiation phenomena at the far field and solution of the wave equation with adequate boundary condition imposed by the pipe wall. An infinite pipe with perforated part is considered. The solution is obtained by using the Fourier transform technique in conjunction with the Wiener-Hopf Method. Applying the Fourier transform technique, the boundary value problem is described by Wiener Hopf equation and then solved analytically.

Zum kollektiven Anteil des Plasma-Mikrofeldes

1968 ◽  
Vol 23 (10) ◽  
pp. 1488-1498
Author(s):  
K. Hunger ◽  
R.W. Larenz
Keyword(s):  
Fourier Transform ◽  
Dipole Moment ◽  
Space Charge ◽  
Long Range ◽  
Field Distribution ◽  
Computer Experiments ◽  
Far Field ◽  
Nearest Neighbour ◽  
Charge Fluctuations ◽  
The Fourier Transform

The Holtsmark microfield evaluation is rediscussed. It is shown that in the usual computation of the Fourier transform a term is neglected which has the dimension of a dipole moment density. This term occurs only for long range forces (here Coulomb ones) and remains undetermined in the limit of an infinitely large system without interaction. Furthermore, it is sensitive to deviations from ergodicity. The true microfield distribution results as a Holtsmark distribution centered at the generally nonvanishing far field. As the distribution of the latter is Gaussian the complete distribution results as a convolution of the Holtsmark distribution with that of the far field. The parameter of the Gaussian far field distribution is computed for a non interacting plasma consisting of N charges, by taking into account explicitely the collective field of space charge fluctuations. The formulae arrived at with respect to the microfield as well as the micropotential suggest to perform numerical computer experiments (HUNGER, LARENZ and WILKE, to be published). For an interacting plasma, the far field is obtained qualitatively. It agrees with the microfield of HUNGER and LARENZ (1961). The far field dominates the Holtsmark nearest neighbour field at plasma conditions kT/e2n1/3 > 1.

scholarly journals Spectral Functions for the Vector-Valued Fourier Transform

2018 ◽  
Vol 2018 ◽  
pp. 1-17
Author(s):  
Vadim Mogilevskii
Keyword(s):  
Distribution Function ◽  
Fourier Transform ◽  
Spectral Function ◽  
Vector Function ◽  
Finite Interval ◽  
Spectral Functions ◽  
The Matrix ◽  
The Fourier Transform ◽  
Vector Valued

A scalar distribution function σ(s) is called a spectral function for the Fourier transform φ^(s)=∫Reitsφ(t)dt (with respect to an interval I⊂R) if for each function φ∈L2(R) with support in I the Parseval identity ∫Rφ^s2dσ(s)=∫Rφt2dt holds. We show that in the case I=R there exists a unique spectral function σ(s)=(1/2π)s, in which case the above Parseval identity turns into the classical one. On the contrary, in the case of a finite interval I=(0,b), there exist infinitely many spectral functions (with respect to I). We introduce also the concept of the matrix-valued spectral function σ(s) (with respect to a system of intervals {I1,I2,…,In}) for the vector-valued Fourier transform of a vector-function φ(t)={φ1(t),φ2(t),…,φn(t)}∈L2(I,Cn), such that support of φj lies in Ij. The main result is a parametrization of all matrix (in particular scalar) spectral functions σ(s) for various systems of intervals {I1,I2,…,In}.

scholarly journals Application of FTIR Method for the Assessment of Immobilization of Active Substances in the Matrix of Biomedical Materials

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 2972 ◽  
Author(s):  
Dorota Kowalczuk ◽  
Monika Pitucha
Keyword(s):  
Fourier Transform ◽  
Fourier Transform Infrared ◽  
Spectroscopic Technique ◽  
Modification Process ◽  
The Matrix ◽  
Ideal Tool ◽  
Reflectance Ftir ◽  
The Fourier Transform ◽  
Specific Reactions ◽  
Active Substances

Background: The purpose of the study was to demonstrate the usefulness of the Fourier transform infrared spectroscopy (FTIR) method for the evaluation of the modification process of biomaterials with the participation of active substances. Methods: Modified catheter samples were prepared by activating the matrix with an acid, iodine, or bromine, and then immobilizing the active molecules. To carry out the modification process, the Fourier transform infrared-attenuated total reflectance (FTIR-ATR) method was used. Results: FTIR analysis indicated the presence of the immobilized substances in the catheter matrix and site-specific reactions. Conclusion: We surmise that the infrared spectroscopic technique is an ideal tool for the assessment of the drug immobilization and the changes occurring in the course of the modification process.

The Study of the Morphology and Dielectric Properties of PVC + TiO2-Based Nanocomposites

2019 ◽  
Vol 201 (1) ◽  
pp. 178-182
Author(s):  
M. A. Ramazanov ◽  
A. M. Rahimli
Keyword(s):  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Dielectric Properties ◽  
Polymer Matrix ◽  
Chemical Structure ◽  
Sem Analysis ◽  
The Matrix ◽  
Agglomeration Of Nanoparticles ◽  
The Fourier Transform

In given work, PVC + TiO2-based nanocomposites were synthesized and their structure and dielectric properties were investigated. SEM analysis of samples was performed to determine the distribution of nanoparticles in the polymer matrix. It was pointed out that the nanoparticles play the role of structure nucleation centers when they are distributed in the polymer matrix in small quantities. As the concentration of particles increases, changes in the supramolecular structure of the polymer occurs, as well as the agglomeration of nanoparticles in the matrix, which leads to an increase in their size. The Fourier transform infrared spectroscopy (FTIR) measurements for pure polymer and nanocomposites were carried out. It has been determined that, as the concentration of TiO2 nanoparticles increases, there is no change in the chemical structure of the polymer and only decreases the intensity of the maxima of the spectra. It has been shown that polymer matrix is only physically interacted with the nanoparticles and does not form any chemical bond with nanoparticles. It has also been established that the increase in the percentage of TiO2 nanoparticles in the polymer has increased the dielectric permittivity of nanocomposites and it has started to decline at a certain concentration.

Measurement of Fractional Optical Vortex by a Ring-Type Multi-Pinhole Interferometer

2012 ◽  
Vol 433-440 ◽  
pp. 6339-6344 ◽  
Author(s):  
Gong Xiang Wei ◽  
Yun Yan Liu ◽  
Sheng Gui Fu ◽  
Ping Wang
Keyword(s):  
Fourier Transform ◽  
Topological Charge ◽  
Linear Part ◽  
Azimuthal Angle ◽  
Optical Vortex ◽  
Far Field ◽  
Diffraction Intensity ◽  
Intensity Pattern ◽  
Ring Type ◽  
The Fourier Transform

We presented a method for measuring the topological charge of a Fractional optical vortex (FOV) by a ring-type multi-pinhole interferometer (RMPI). We retrieved the sampled phase of the FOV passing through a ring-type multi-pinhole plate from the Fourier transform of a single far-field diffraction intensity pattern, and found the phase of FOV around the center approximately be linear with the azimuthal angle, the slope of the phase to the azimuthal angle at the linear part is equal to the topological charge of the FOV. Thus we proposed a method for measuring the l state and determining orbital angular momentum (OAM) of a FOV based on the property.

scholarly journals Some Comments on the Analysis of Excitation Functions Using Different Transforms

1969 ◽  
Vol 22 (4) ◽  
pp. 537 ◽  
Author(s):  
J Hellstrom
Keyword(s):  
Fourier Transform ◽  
Statistical Theory ◽  
Cross Section ◽  
Nuclear Reactions ◽  
Personal Communication ◽  
Middle Point ◽  
Excitation Functions ◽  
Level Width ◽  
The Mean ◽  
The Fourier Transform

The statistical theory of nuclear reactions (Brink and Stephen 1963; Ericson 1963) has been used successfully for some years. When it comes to determining properties like the mean level width r several authors (Bohning 1965; Ericson 1965, personal communication; Hellstrom and Dallimore 1969) have suggested and used a. Fourier analysis instead of the autocorrelation function C(E+?, E) because the former is associated with smaller errors, particularly when the average cross section has a slow variation with energy. The aim of this note is to elucidate some of the properties of the Fourier transform applied to analysis of excitation functions and also to point out that other transforms are possible. To fix notation, we take the Fourier transform F of the cross section a(E) over an energy interval I with middle point Eo as

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