scholarly journals The Conversion of Excitation Energy into Generated Energy at the Resonant Frequencies of a Transparent Nonlinear Layer

2019 ◽  
Vol 8 (1) ◽  
pp. 66-74 ◽  
Author(s):  
L. Angermann ◽  
V. V. Yatsyk ◽  
M. V. Yatsyk
Keyword(s):  
Electromagnetic Waves ◽  
Eigenvalue Problems ◽  
Excitation Frequency ◽  
Resonant Frequencies ◽  
Radiation Properties ◽  
Nonlinear Object ◽  
Consistent Solution ◽  
Rigorous Treatment ◽  
Eigen Frequencies ◽  
Resonant Radiation

An iterative algorithm is presented for analyzing the optimal resonant radiation properties of electromagnetic waves by cubically polarized nonlinear layers. The analysis is based on mathematical models for the rigorous treatment of the following problems: Self-consistent solution of both the system of boundary value problems of electrodynamics at resonant frequencies of excitation and generation, as well as the corresponding linearized eigenvalue problems with induced dielectric coefficients. The choice of the resonant excitation frequency of a nonlinear object in dependence on the real parts of the eigen frequencies of the spectral problems is discussed.

scholarly journals Structural Improvement of the ω-Type High-Speed Rail Clip Based on a Study of Its Failure Mechanism

2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Xiaogang Gao ◽  
Anbin Wang ◽  
Yu He ◽  
Xiaohan Gu
Keyword(s):  
Failure Mechanism ◽  
Fatigue Test ◽  
High Frequency ◽  
High Speed ◽  
Excitation Frequency ◽  
Test System ◽  
Vibration Measurement ◽  
High Speed Rail ◽  
Resonant Frequencies ◽  
Rail Wear

In the circumstances of high-speed railways, the wheel-rail vibration is significantly aggravated by polygonal wheel wear and rail corrugation, which subsequently leads to the wheel-rail interaction at higher frequencies and potential failure of the rail fastening. In this paper, a ω-type clip of the fastening in the CRH high-speed rail was used to investigate the failure mechanism. First, a dynamic wheel-rail coupling model and a finite element analysis of the rail clip were developed, from which the rail vibration frequency and modal frequencies of the clip with different installation torques were obtained. The experimental tests and modal simulation results were mutually verified. In addition, the real-time vibration measurement and the wheel-rail wear monitoring were carried out at a CRH high-speed railway site. It was found that the resonant frequencies of the ω-type clip in the installation condition coincided with the excitation frequencies of the wheel-rail interaction induced by wheel-rail wear. The high-frequency dynamic failure mechanism of a typical ω-type clip, W300-1, is put forward for the first time. Moreover, a high-frequency rail clip fatigue test system was designed and developed specifically for this study. The loading excitation frequency of the clip test used was set as 590 Hz, and the loading amplitude was 0.05 mm. After 125-minute operation of the test system, the clip was broken at the expected location predicted by the FEA model. The high-frequency fatigue test result further verified that the failure mechanism of the ω-type clip was due to the resonance of the clip with its excitation force from the wheel-rail interaction. Finally, the clip was then structurally improved taking into account the stiffness and mass, which led to its resonant frequencies shifting away from the high-frequency excitation range, hence avoiding resonance failure of the subject clip.

Experimental Study of the Incidence of Changing a Synthetic Jet Orifice in Heat Transfer Using a Taguchi Method Approach

2019 ◽  
Vol 11 (3) ◽  
Author(s):  
Juan Sebastian Cano ◽  
Gustavo David Cordova ◽  
Christian Narvaez ◽  
Luis Segura ◽  
Luis Carrion
Keyword(s):  
Heat Transfer ◽  
Steel Plate ◽  
Excitation Frequency ◽  
Acoustic Resonance ◽  
Synthetic Jet ◽  
Cooling Time ◽  
Coefficient Of Performance ◽  
Resonant Frequencies ◽  
Jet Velocity ◽  
Method Approach

The current study allows the recognition of the most optimal combination of excitation frequency, kind of orifice, and synthetic jet-to-surface spacing in order to obtain the fastest cooling time using a Taguchi experimental design. To this end, the heat transfer and synthetic jet velocity behavior using different kinds of orifices are obtained experimentally. A piezoelectric diaphragm has been selected as a vibrating actuator. Four kinds of orifices have been studied: circular, rectangular, triangular, and square. First, the study consists of recognizing the excitation frequency in which each orifice produces the highest flow velocity. A hotwire anemometer has been used in order to measure the synthetic jet velocity. Additionally, a steel plate has been heated and then cooled using the synthetic jet set at the excitation frequency in which the jet velocity was the largest for each orifice. For the statistical analysis, the input study variables are the type of orifice and jet-to-surface spacing. The output variable has been the cooling time. The results show that using a combination of a rectangle orifice, 20 mm of jet-to-surface spacing and an excitation frequency of 2000 Hz, it is obtained the fastest cooling time. In addition, using these parameters, a mean heat transfer coefficient of 11.05 (W/m2K) with a coefficient of performance (COP) of 49.21 has been obtained. Finally, for each kind of orifice, there is the presence of two resonant frequencies, the Helmholtz (acoustic resonance) frequency and piezoelectric diaphragm natural frequency.

scholarly journals Carbon-Based Composite Microwave Antennas

Electronics ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 590 ◽  
Author(s):  
Nikolai A. Dugin ◽  
Tatiana M. Zaboronkova ◽  
Catherine Krafft ◽  
Grigorii R. Belyaev
Keyword(s):  
Composite Materials ◽  
Electromagnetic Waves ◽  
Carbon Composite ◽  
Microwave Antennas ◽  
Horn Antennas ◽  
Radiation Properties ◽  
Wide Range ◽  
Carbon Composite Materials ◽  
5 Ghz ◽  
Carbon Based

Applications of metamaterials to microwave antennas are reviewed over the past decade. The manufacturing of microwave antennas using graphene-containing carbon composite materials was developed and prototypes of dipole and horn antennas made from such materials were created. The radiation properties of the designed antennas and their metal analogs were measured and compared. The standing wave ratios, the radiation patterns and the amplitude-frequency characteristics were analyzed for horn antennas at frequencies 1.6 GHz and 5 GHz and for dipole antennas in the frequency range 0.2–0.6 GHz. The polarization characteristics of the horn antennas were studied. The effects of different carbon composite materials’ structures (fiber or fabric) on the antennas’ parameters were estimated. It is shown that antennas made from graphene-containing composite materials are able to operate efficiently and exhibit almost the same radiation properties as conventional metal antennas of the same geometry and size. However, the carbon-based antennas have much smaller weights and enhanced stability in a wide range of temperatures. In the future, such antennas should replace the conventional ones for many applications, especially for the excitation and reception of electromagnetic waves in space plasmas.

scholarly journals Coupled Acoustic-Structure Analysis of an Annular DLE Combustor

1998 ◽  
Author(s):  
Peter J. M. Cronemyr ◽  
Chris J. Hulme ◽  
Christian Troger
Keyword(s):  
Gas Turbines ◽  
Pressure Wave ◽  
Thermal Loading ◽  
Excitation Frequency ◽  
Rocket Engines ◽  
Pressure Pulsations ◽  
Acoustic Structure ◽  
Low Emission ◽  
Industrial Gas Turbines ◽  
Eigen Frequencies

With the advent of today’s dry low emission (DLE) combustors for industrial gas turbines (GT), an additional type of load case other than thermal loading on the combustor structure, has put itself heavily into focus, namely pulsation loading. Although recognised for decades in rocket engines and ram-jets, it was not until the incorporation of diluted flames and completely closed combustors, used to reduce NOx emissions, that thermo-acoustically excited pressure pulsations became an issue in the design of industrial GT combustors. This paper presents the computational methods that are available for the analysis of this phenomenon, and their application in the development of ABB’s latest annular DLE combustor. Among these are calculations of burner excitation frequency, pressure wave propagation within the combustor, acoustic and structural eigen frequencies, and coupled acoustic structural analysis. Guidelines for the combustor design to prevent instabilities and coupling of air and structure pulsations are suggested.

Propagation of nonlinear waves in a plasma in a magnetic field

1968 ◽  
Vol 2 (2) ◽  
pp. 105-118 ◽  
Author(s):  
Jeffrey P. Freidberg
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Waves ◽  
Local Density ◽  
Travelling Wave ◽  
Travelling Wave Solutions ◽  
Resonant Frequencies ◽  
Wave Solutions ◽  
Nonlinear Dispersion Relation ◽  
The Waves ◽  
The Magnetic Field

The propagation of nonlinear electromagnetic waves in a plasma is investigated by seeking travelling wave solutions to the macroscopic plasma equations. The model considered is that of a warm, anisotropic electron plasma in a magnetic field, in which the waves are allowed to propagate at any angle with respect to the magnetic field. A nonlinear dispersion relation is obtained which is valid for frequencies sufficiently close to the resonant frequencies. Travelling wave solutions are found for all amplitudes for which the local density remains positive. Also in sufficiently anisotropic plasmas the nature (i.e. propagating or cut-off) of one of the resonant waves can depend upon the amplitude.

scholarly journals Novel antenna concepts via coordinate transformation

2013 ◽  
Vol 2 (1) ◽  
pp. 25 ◽  
Author(s):  
P.-H. Tichit ◽  
S. N. Burokur ◽  
X. Wu ◽  
D. Germain ◽  
A. De Lustrac
Keyword(s):  
Coordinate Transformation ◽  
Electromagnetic Waves ◽  
Near Field ◽  
Antenna Design ◽  
Electromagnetic Properties ◽  
Field Pattern ◽  
Radiation Properties ◽  
Space Coordinate ◽  
And Control ◽  
Far Field Pattern

Coordinate transformation is an emerging field which offers a powerful and unprecedented ability to manipulate and control electromagnetic waves. Using this tool, we demonstrate the design of novel antenna concepts by tailoring their radiation properties. The wave manipulation is enabled through the use of engineered dispersive composite metamaterials that realize the space coordinate transformation. Three types of antennas are considered for design: a directive, a beam steerable and a quasi-isotropic one. Numerical simulations together with experimental measurements are performed in order to validate the coordinate transformation concept. Near-field cartography and far-field pattern measurements performed on a fabricated prototype agree qualitatively with Finite Element Method (FEM) simulations. It is shown that a particular radiation pattern can be tailored at ease into a desired one by modifying the electromagnetic properties of the space around radiator. This idea opens the way to novel antenna design techniques for various application domains such as the aeronautical and transport fields.

scholarly journals The velocity of propagation of electromagnetic waves derived from the resonant frequencies of a cylindrical cavity resonator

1948 ◽  
Vol 194 (1038) ◽  
pp. 348-361 ◽  
Keyword(s):  
Electromagnetic Waves ◽  
Cavity Resonator ◽  
Space Velocity ◽  
Maximum Error ◽  
Internal Diameter ◽  
Experimental Conditions ◽  
Resonant Frequencies ◽  
Half Wave ◽  
Velocity Of Propagation ◽  
Cylindrical Cavity Resonator

The frequency of resonance of an evacuated cavity resonator in the form of a right circular cylinder is given by the formula f = v 0 √[( r/πD ) 2 + ( n /2 L ) 2 ][1-1/2 Q ], in which v 0 is the free-space velocity of electromagnetic waves, D and L are the internal diameter and length respectively of the cylinder, r is a constant for a particular mode of resonance, n is the number of half-wave-lengths in the resonator and Q is the quality factor. Assuming the validity of this equation the value of v 0 can be obtained from measured values of f , D , L and Q . A copper cylinder of diameter approximately 7.4 cm. and length 8.5 cm. was constructed with the greatest uniformity of diameter and squareness of end-faces and its dimensions were measured. The resonant frequencies for a number of different modes were measured and experiments were made to show that the effects on frequency of the coupling probes to the oscillator and detector were negligibly small. It was concluded from these measurements that the most favourable experimental conditions can be obtained for the E 010 and E 011 modes. Final measurements on these gave v 0 = 299,792 km. /sec. The estimated maximum error of the result is 9 km. /sec. (3 parts in 10 5 ). This is the error of a single measurement and, since most of the errors are not necessarily random, little is gained by making a large number of measurements. The value is 16 km. /sec. greater than the recently determined values of the velocity of light, although the results are not in disagreement when the combined limits of accuracy are taken into account.

scholarly journals Improving the GPR Detectability Using a Novel Loop Bowtie Antenna

2017 ◽  
pp. 9-16 ◽  
Author(s):  
K.K. Ajith ◽  
Amitabha Bhattacharya
Keyword(s):  
Electromagnetic Waves ◽  
Experimental Results ◽  
Reinforced Concrete Structure ◽  
Destructive Testing ◽  
Antenna Performance ◽  
Radiation Properties ◽  
Bowtie Antenna ◽  
Operating Bandwidth ◽  
Ground Penetrating ◽  
Non Destructive

The Ground Penetrating Radar (GPR) technique finds immense applications in civil engineering today, as the most suitable approach for non-destructive testing of pavements, highways, concrete structures, and more. The major challenge in carrying out a GPR evaluation is that the properties of the probed medium are usually unknown. The permittivity and conductivity of the medium may vary from those of air to water. The electromagnetic waves also have a frequency dependent attenuation. The ability of GPR to detect signals reflected and scattered by the targets largely depends upon the antenna performance. This paper studies a novel 11:1 wideband loop bowtie antenna with very good radiation properties in the entire operating bandwidth. Synthetic and experimental results are presented for the return loss and gain of the antenna. Furthermore, experimental results are presented for the radiation patterns in the E- and H-plane. We also used the antenna to measure B-scans over two different pipes, a bamboo, and a reinforced concrete structure. All results obtained with the proposed antenna have been compared with results obtained by using a RC loaded antenna. It has been found that the loop bowtie antenna has excellent detection capability and produces less clutter. The loop loading technique can be applied to existing antennas for improved GPR imaging. This will improve the detectability of GPR by improving the target return signal.

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