• Title/Summary/Keyword: Wave Absorbing Characteristics

Search Result 75, Processing Time 0.04 seconds

A Study on Design of an Electromagnetic and Optical Characteristics in Transparent Conductor Coated Structures (투명 전도성 코팅체의 전자기적, 광학적 성능 설계 및 분석에 관한 연구)

  • Sung Sil Cho;Young Joon Yoon;Min Je Hwang;Kwang Sik Choi;Ic Pyo Hong
    • Journal of the Korea Institute of Military Science and Technology
    • /
    • v.27 no.1
    • /
    • pp.15-23
    • /
    • 2024
  • In order to avoid the high observability due to the cavity resonance or electromagnetic wave leakages from the bridge of a battleship or the cockpit of an aircraft, this paper presents a transparent conductive oxide coated structure to prevent the incoming/outgoing electromagnetic waves. Currently, most of the RCS reduction technologies were focused on radar absorbing material such as paints based on conductive or magnetic materials in the fuselage, and there is not much research on countermeasures for achieving the low observability of materials that required optical transparency in actual weapon systems. In this study, the transmission/reflection and absorption performance of the ITO coated structure according to the change of the surface resistance of the transparent conductor were analyzed. Finally, the relationship between the electromagnetic and optical characteristics was established through fabrication and measurement.

A Study on the Absorption Characteristics of Absorbents in Duct System with the Air Cavity (공기층을 갖는 공조덕트 구조물에서 흡음재의 흡음특성에 관한 연구)

  • 김찬묵;김도연;방극호
    • Journal of KSNVE
    • /
    • v.10 no.5
    • /
    • pp.892-897
    • /
    • 2000
  • In this paper, experimental methods to find acoustic characteristics of acoustically treated air-conditioning duct system are proposed. Existing methods to analyze acoustic properties of duct with absorbent material have dilemma which has to assume the wave in duct to be a plane wave. Under this assumption. applicable frequency limitation makes accurate analysis of practical air-conditioning system impossible. In order to analyze the properties of in-lined treated absorbent with high degree of accuracy, in this experiments the range of exciting frequency of sound source is broadband, which means that source speaker excited higher mode of in-duct sound field. Also, to define the relations of air cavity to the acoustic characteristics, acoustic experiments on ducts with air cavity of different depth are operated. In conclusion, air-cavity makes the absorbing ability of duct improved in low frequency range. Due to the interactions between the air cavity depth and the depth of absorbents, according to depth of cavity, the magnitude of absorption coefficients vs frequencies in specific range is changed. In lower frequency range, the absorption of sound energy by air cavity is more dominant than by absorbent itself, in higher range, the inversion is true.

  • PDF

Effects of geometric shape of LWSCR (lazy-wave steel catenary riser) on its global performance and structural behavior

  • Kim, Seungjun;Kim, Moo-Hyun
    • Ocean Systems Engineering
    • /
    • v.8 no.3
    • /
    • pp.247-279
    • /
    • 2018
  • This study aims to investigate the behavioral characteristics of the LWSCR (lazy-wave steel catenary riser) for a turret-moored FPSO (Floating Production Storage Offloading) by using fully-coupled hull-mooring-riser dynamic simulation program in time domain. In particular, the effects of initial geometric profile on the global performance and structural behavior are investigated in depth to have an insight for optimal design. In this regard, a systematic parametric study with varying the initial curvature of sag and arch bend and initial position of touch down point (TDP) is conducted for 100-yr wind-wave-current (WWC) hurricane condition. The FPSO motions, riser dynamics, constituent structural stress results, accumulated fatigue damage of the LWSCR are presented and analyzed to draw a general trend of the relationship between the LWSCR geometric parameters and the resulting dynamic/structural performance. According to this study, the initial curvature of the sag and arch bend plays an important role in absorbing transferred platform motions, while the position of TDP mainly affects the change of static-stress level.

Consideration on the Electromagnetic Wave Absorption Properties of the Plasma for the Stealth Technology (은신기술을 위한 플라즈마의 전자기파 흡수 특성에 대한 고찰)

  • In, S.R.
    • Journal of the Korean Vacuum Society
    • /
    • v.17 no.6
    • /
    • pp.501-510
    • /
    • 2008
  • The stealth technology to conceal an aircraft from the vision of a radar have been accomplished by coating the surface with special paints absorbing the electromagnetic wave. Nowadays, researches to utilize characteristics of the plasma-wave interaction for realizing the stealth technology are actively progressed. In this paper, to investigate the physical feasibility of the plasma stealth, calculation results for the required conditions of the plasma cloaking on the aircraft flying in the air for showing the stealth function, using a flat non-magnetized non-uniform plasma model, are reported and discussed.

Effects of Sintering Schedule of Ni-Zn Ferrites on Properties of Electromagnetic Wave Absorber between 30 MHz and 1000 MHz (30 MHz~1000 MHz 고주파 대역에서 Ni-Zn 계 페라이트의 소결조건에 따른 전파흡수 특성)

  • 김경용;김왕섭;주윤돈
    • Journal of the Korean Ceramic Society
    • /
    • v.28 no.8
    • /
    • pp.640-646
    • /
    • 1991
  • Recently intensive studies have been focussed on ferrites which have high magnetic loss because of the increasing need for the prevention of EMI (Electromagnetic Interference). We investigated effects of microstructures of Ni-Zn ferrites on magnetic losses, magnetic properties, and behaviors of electromagnetic wave absorbers. The characteristics of the absorber were influenced by the sintering conditions. A Ni-Zn ferrite with the thickness of 7$^{\circ}C$/min and the cooling rate of 7$^{\circ}C$/min. It satisfied the absorbing properties in the wide frequency ranges including VHF (90∼220 MHz), UHF (470∼770 MHz)

  • PDF

A STUDY ON IMPACT CHARACTERISTICS OF THE STACKING SEQUENCES IN CFRP COMPOSITES SUBJECTED TO FALLING-WEIGHT IMPACT LOADING

  • Im, K.H.;Park, N.S.;Kim, Y.N.;Yang, I.Y.
    • International Journal of Automotive Technology
    • /
    • v.4 no.4
    • /
    • pp.203-211
    • /
    • 2003
  • This paper describes a method for a falling weight impact test to estimate the impact energy absorbing characteristics and impact strength of CFRP (Carbon-fiber reinforced plastics) laminate plates based on considerations of stress wave propagation theory, which were converted to measurements of load and displacement verses time. The delamination area of impacted specimens for the different ply orientations was measured with an ultrasonic C-scanner to determine the correlation between impact energy and delamination area. The energy absorbed by a quasi-isotropic specimen having four interfaces was higher than that of orthotropic laminates with two interfaces. The more interfaces, the greater the energy absorbed. The absorbed energy of a hybrid specimen embedding GFRP (Glass-fiber reinforced plastics) layer was higher than that of normal specimens. Also, a falling weight impact tester was built to evaluate the characteristics and impact strength of CFRPs.

Effects of Frequency Characteristics of High Frequency-Hydraulic System for the Changes of Accumulators (축압기의 변화가 고주파 유압시스템의 주파수 특성에 미치는 영향)

  • Roh, Hyung-Woon;Kim, Jae-Soo;Park, Nam-Eun;Kim, Yang-Soo;Jeon, Seung-Bae;Na, Hong-Chul
    • Proceedings of the KSME Conference
    • /
    • 2003.04a
    • /
    • pp.1936-1941
    • /
    • 2003
  • Characteristics of the high frequency and pulsatile flow investigated experimentally to understand the flow phenomena in the hydraulic system. In the study, I axis fatigue tester which are widely used for automobile filed are selected. 4 Pressure transducer, amplifier, A/D convertor are used to analyse and to obtain the pulsatle pressure waveform with high frequencies in hydraulic system. Matlab are used. to analyse the characteristics of frequency. Variation of pump input pressure and actuator acceleration frequency, pressure wave are measured with or without accumulators. For with accumulator, frequency amplitude of pressure are very lower than those of without accumulator due to absorbing function of accumulator. As the actuator acceleration frequency increased, effect of accumulator are very important to decrease the pulsatile pressure waveform with high frequencies.

  • PDF

The Magnetic and Microwave Absorbing Characteristics of Ni-Zn Ferrite Composites (니켈-아연 페라이트복합재의 자기적특성과 전파흡수특성)

  • 조성백;오재희
    • Journal of the Korean Magnetics Society
    • /
    • v.3 no.2
    • /
    • pp.115-120
    • /
    • 1993
  • The relationship between magnetic parameter and microwave absorbing performance evaluation factor of electomagnetic wave absorber such as matching frequency, matching thickness were investigated for Ni-Zn ferrite composites. It was identified that the maximum value of ${\mu}_{r}$" is shift to low frequency with decrese Ni/Zn ratio and the value of ${\mu}_{r}$" is maximum in the case of Ni/Zn=1. All Ni-Zn ferrite composites in this study have two matching frequencies in 1-12 GHz frequency. It can be suggested that $f_{m1}$ is proportional to resonance frequency and $f_{m2}$ is proportional to the saturation magnetization.

  • PDF

Effect of Carbon Addition and Influence of Heat-treatment Temperature on Electromagnetic Wave Absorbing Properties of $Ni_{0.5}Cu_{0.1}Zn_{0.4}Fe_2O_4$-Rubber Composite ($Ni_{0.5}Cu_{0.1}Zn_{0.4}Fe_2O_4$ Ferrite-Rubber Composite의 전파흡수특성에 미치는 열처리 온도의 영향 및 Carbon 첨가효과)

  • 윤국태;이찬규;박연준
    • Journal of the Korean Magnetics Society
    • /
    • v.11 no.1
    • /
    • pp.14-20
    • /
    • 2001
  • The structure, shape, size, and magnetic properties of Ni$_{0.5}$Cu$_{0.1}$Zn$_{0.4}$Fe$_2$O$_4$ have been investigated as a function of annealing temperatures. In order to control the microwave absorbing properties of ferrite-rubber composite and the complex losses (magnetic loss and conduction loss), the effect of carbon addition was also studied. It was found that the coercive force decreased with increasing heat-treatment temperatures. Relative complex permeability and reflection loss were measured by the network analyzer. As a result, the natural resonance occurred in the low frequency tinge, and the matching frequency of the ferrite-rubber composite prepared at 130$0^{\circ}C$ was found to be lower. As heat-treatment temperatures were increased, the magnetic loss ($\mu$$_{r}$", $\mu$$_{r}$′) and the dielectric loss ($\varepsilon$$_{r}$"/$\varepsilon$$_{r}$′) were increased. It was caused that the absorption characteristics of the absorber were improved. The conduction loss and magnetic loss were expected to be occurred together because two matching frequencies were shown with carbon addition. It was confirmed that the matching frequency of the microwave absorber could be controlled by controlling heat-treatment temperatures and carbon additions.ons.tions.

  • PDF

A study on the noise reduction of practical duct system with the air cavity (공기층을 갖는 실제덕트 구조물에서의 소음저감에 관한 연구)

  • Kim, Chan-Mook;Lee, Doo-Ho;Bahng, Keuk-Ho
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2000.06a
    • /
    • pp.1687-1692
    • /
    • 2000
  • In this paper, experimental methods to find acoustic characteristics of acoustically treated air-conditioning duct system are proposed. Existing methods to analyze acoustic properties of duct with absorbent material have a dilemma which has to assume the wave in duct to be a plane wave. Under this assumption, applicable frequency limitation makes accurate analysis of practical air-conditioning system impossible. In order to analyze the properties of in-lined treated absorbent with high degree of accuracy, in this experiments the range of exciting frequency of sound source is broadband, which means that source speaker excites higher mode of in-duct sound field. Also, to define the relations of air cavity to the acoustic characteristics, acoustic experiments on ducts with air cavity of different depth are operated. In conclusion, air-cavity makes the absorbing ability of duct improved in low frequency range. Due to the interactions between the air cavity depth and the depth of absorbents, according to depth of cavity, the magnitude of absorption coefficients vs frequencies in specific range is changed. In lower frequency range, the absorption of sound energy by air cavity is more dominant than by absorbent itself, in higher range, the inversion is true.

  • PDF