scholarly journals Broadband Radar Absorbing Structures with a Practical Approach from Design to Fabrication

2020 ◽  
Vol 20 (4) ◽  
pp. 254-261
Author(s):  
Won-Ho Choi ◽  
Woon-Hyung Song ◽  
Won-Jun Lee
Keyword(s):  
Multiple Scattering ◽  
Electromagnetic Waves ◽  
Point Of View ◽  
Design Concept ◽  
Field Analysis ◽  
Design Values ◽  
Absorption Performance ◽  
Incident Waves ◽  
Lossy Materials ◽  
Space Measurement

In this study, a novel broadband radar absorbing volume structure (RAVS) is proposed and demonstrated with a practical point of view from design to fabrication. The proposed RAVS uses a design concept of repeatedly stacked carbon nanotube (CNT) composites and foam cores of the same thickness to improve the applicability to real structures while maintaining absorption performance. The repeatedly stacked CNT composites, which act as electrically lossy materials, result in the multiple scattering of incident electromagnetic waves trapped inside the structure. The trapped incident waves then lose their energy by multiple scattering. Based on this design concept, the RAVS designed through field analysis and parametric study achieved a −10 dB absorption performance from 4 GHz to 16 GHz. With reference to the design values, RAVS was fabricated for verification, and the absorption performance was measured using a free space measurement system. The measurement result showed excellent absorption performance that satisfied −10 dB from 5.8 GHz or less to 14 GHz.

Multiple scattering of ultra-high frequency electromagnetic waves by two plasma cylinders

2012 ◽  
Vol 111 (7) ◽  
pp. 073303 ◽  
Author(s):  
Wu Xiao-po ◽  
Shi Jia-ming ◽  
Wang Jia-chun ◽  
Yuan Zhong-cai ◽  
Xu Bo ◽  
...  
Keyword(s):  
Multiple Scattering ◽  
High Frequency ◽  
Electromagnetic Waves ◽  
Ultra High Frequency

scholarly journals Complexes for continuous monitoring of drilling fluid parameters during drilling

2021 ◽  
Vol 6 (3) ◽  
pp. 144-151
Author(s):  
Sergey V. Lakhtionov ◽  
Ivan S. Chumakov ◽  
Sergey G. Filinkov ◽  
Dmitry M. Chukin ◽  
Evgeny N. Ishmetyev
Keyword(s):  
Continuous Monitoring ◽  
Drilling Fluid ◽  
Point Of View ◽  
Complete Analysis ◽  
Drilling Fluids ◽  
Automatic Mode ◽  
Design Values ◽  
Drilling Rigs ◽  
Almost All ◽  
Fluid Parameters

Background. The article provides an overview of existing complexes (units) for continuous monitoring of drilling fluid parameters in automatic mode. Aim. To justify the need to develop a complex (module) that will allow combining existing technologies and making a step forward in the field of process automation in terms of monitoring the parameters of drilling fluids. Materials and methods. In the current realities of well construction, the control of drilling fluid parameters on almost all drilling rigs operating on the territory of Russia (possibly with the exception of a few off shore projects) is carried out by the work of a solution engineer, usually a representative of a service company. The analysis of the parameters, depending on the number of personnel, the speed of penetration, the complexity or importance of the well, can be carried out from 2 to 6 times a day [1, 2]. This means a complete analysis, rather than monitoring the density and conditional viscosity, which can be measured by a representative of the drilling crew, for rapid response, and with greater frequency. Due to such a low measurement discreteness, there is a high probability of a significant deviation of the drilling fluid parameters from the design values. As a result, the probability of various complications, both geological and technological, increase significantly. Results. During the analysis of information from open sources, the most promising complexes (modules) from the point of view of application in the current conditions were identified, their positive and negative sides were evaluated. As a result of the conducted review of open sources, the most promising complexes (modules) in terms of application in the current conditions are identified, the positive and negative sides of the systems under consideration are displayed, and the need to develop a complex (module) that will combine all the best that is available today and make a qualitative step forward in the field of “peopleless” technologies used during drilling wells in terms of monitoring the parameters of drilling fluids is justified. Conclusions. The necessity of developing a complex (module) for automating processes in terms of monitoring the parameters of drilling fluids is justified.

scholarly journals The Electromagnetic Wave Absorption Performance and Mechanical Properties of Cement-Based Composite Material Mixed with Functional Aggregates with High Fe2O3 and SiC

2021 ◽  
Vol 31 (4) ◽  
pp. 249-255
Author(s):  
Zuoqun Zhang ◽  
Chaoshan Yang ◽  
Hua Cheng ◽  
Xiaohan Huang ◽  
Yuhao Zhu
Keyword(s):  
Composite Material ◽  
Electromagnetic Wave ◽  
Electromagnetic Waves ◽  
Building Materials ◽  
Magnetic Loss ◽  
Frequency Range ◽  
Electromagnetic Wave Absorption ◽  
Wave Absorption ◽  
Test Board ◽  
Absorption Performance

Now there’re many researches on the electromagnetic radiation protection function of the cement-based electromagnetic wave absorbing materials, such materials have been widely used in various types of buildings. This paper proposed an idea for preparing a cement-based composite material by mixing functional aggregates with high content of Fe2O3 and SiC, that is, adding Fe3O4 powder and nano-SiC of different contents in the clay, and then sintering at 1190℃; the prepared aggregates showed obvious magnetic loss and dielectric loss to electromagnetic waves, and the numerical tube pressure could reach 16.83MPa. The double-layer reflectivity test board made of functional aggregates showed excellent electromagnetic wave absorption performance, its reflection loss was less than -10dB in the frequency range of 8~18GHz (corresponding to energy absorption greater than 90% EM), and its maximum RL reached -12.13dB. In addition, the compressive strength of the cement-based composite material at the age of 28 days reached 50.1 MPa, which can meet the strength requirements of building materials.

Finite element sound field analysis on measurement of absorption coefficient in a reverberation room -Relationships between inclination of walls and measurement results-

2021 ◽  
Vol 263 (1) ◽  
pp. 5571-5577
Author(s):  
Reiji Tomiku ◽  
Noriko Okamoto ◽  
Toru Otsuru ◽  
Shun Iwamoto ◽  
Shoma Suzuki
Keyword(s):  
Finite Element ◽  
Absorption Coefficient ◽  
Sound Field ◽  
Field Analysis ◽  
Reverberation Time ◽  
Absorption Coefficients ◽  
Sound Fields ◽  
Measurement Results ◽  
Coefficient Measurement ◽  
Absorption Performance

The absorption coefficients in a reverberation room are most representative measure for evaluating absorption performance of architectural materials. However, it is well known that measurement results of the coefficient vary according to a room shape of the measurement and area of the specimen. Numerical analyses based on wave acoustics are effective tools to investigate these factors on absorption coefficient measurement in reverberation room. In this study, sound fields for the measurement of absorption coefficient in reverberation room are analyzed by time domain finite element method (TDFEM). This study shows effectiveness of the analysis for investigation on causes of variation in the measurement results and improvement methods of the measurement. First, some measurement sound fields for absorption coefficient in reverberation rooms the walls of which are incline or decline are analyzed by the TDFEM. Next, reverberation times in each sound fields are calculated from the results obtained by TDFEM and the absorption coefficients are evaluated from the reverberation time of the room with and without specimen. Finally, the relationships among room shape, degree of inclination of the wall, the sound absorption coefficient of the specimen, frequencies and the measurement absorption coefficient are investigated.

Rayleigh–Bloch surface waves along periodic gratings and their connection with trapped modes in waveguides

1999 ◽  
Vol 386 ◽  
pp. 233-258 ◽  
Author(s):  
R. PORTER ◽  
D. V. EVANS
Keyword(s):  
Finite Number ◽  
Surface Waves ◽  
Cross Section ◽  
Electromagnetic Waves ◽  
Mode Shapes ◽  
Special Choice ◽  
Trapped Mode ◽  
Uniform Cross Section ◽  
New Type ◽  
Incident Waves

Rayleigh–Bloch surface waves are acoustic or electromagnetic waves which propagate parallel to a two-dimensional diffraction grating and which are exponentially damped with distance from the grating. In the water-wave context they describe a localized wave having dominant wavenumber β travelling along an infinite periodic array of identical bottom-mounted cylinders having uniform cross-section throughout the water depth. A numerical method is described which enables the frequencies of the Rayleigh–Bloch waves to be determined as a function of β for an arbitrary cylinder cross-section. For particular symmetric cylinders, it is shown how a special choice of β produces results for the trapped mode frequencies and mode shapes in the vicinity of any (finite) number of cylinders spanning a rectangular waveguide or channel. It is also shown how one particular choice of β gives rise to a new type of trapped mode near an unsymmetric cylinder contained within a parallel-sided waveguide with locally-distorted walls. The implications for large forces due to incident waves on a large but finite number of such cylinders in the ocean is discussed.

Microwave Absorbing Properties of Radar Absorbing Structure Composites Filling with Carbon Nanotubes

2011 ◽  
Vol 328-330 ◽  
pp. 1109-1112 ◽  
Author(s):  
Zheng Quan Zhang ◽  
Li Ge Wang ◽  
En Ze Wang
Keyword(s):  
Carbon Nanotubes ◽  
Electromagnetic Wave ◽  
Carbon Fibers ◽  
Electromagnetic Waves ◽  
Glass Fibers ◽  
Network Analyzer ◽  
Microwave Absorbing Properties ◽  
Radar Absorbing Structure ◽  
Lossy Materials ◽  
Wave Properties

Radar absorbing structures (RAS) can’t only load bearing but also absorb electromagnetic wave energy by inducing dielectric loss and minimizing reflected electromagnetic waves. Therefore, the development of the RAS haves become important to reduce RCS of the object. These composites possess excellent specific stiffness and strength. The electromagnetic wave properties of RAS can be effectively tailored by controlling the content of the lossy materials. Radar absorbing structures composed of glass fibers, carbon fibers and epoxy resin filling with carbon nanotubes (CNTs), was designed and prepared. Permittivity of the composite was measured by using a network analyzer, HP8510B. The contents of composites were observed to be different from each composite. Reflection of electromagnetic waves energy of RAS was calculated by using the genetic algorithm, it was discovered that the composites can be applied to design an optional RAS composites filling with CNTs.

XXVI.—On a Polarised Light Quantum

1927 ◽  
Vol 46 ◽  
pp. 306-313
Author(s):  
J. M. Whittaker
Keyword(s):  
Electromagnetic Waves ◽  
Maxwell’S Equations ◽  
Maxwell's Equations ◽  
Point Of View ◽  
Light Quantum ◽  
Electric Force ◽  
Polarised Light

In the theory of radiation recently advanced by Sir J. J. Thomson it is supposed that electromagnetic waves and quanta are both present in a beam of light. The quanta, which are responsible for the photoelectric effects, are closed rings of electric force propagated in the direction normal to the plane of the ring. Professor Whittaker has discussed this conception from the point of view of Maxwell's equations, and has shown that it is consistent with them ; or rather with an extension of them in which a magnetic density μ analogous to the electric density ρ is introduced.

Sign in / Sign up

Export Citation Format

Share Document