• Title/Summary/Keyword: absorbers

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EM Wave Absorbers with Au Coated Conductive Sheets

  • Song Jae-Man;O Kyeung-Jin;Kim Dong-Il
    • Journal of electromagnetic engineering and science
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    • v.6 no.1
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    • pp.71-75
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    • 2006
  • In this study, EM wave absorbers based on Au coated conductive sheets were prepared, and their reflection and transmission coefficients were investigated. An Au coated conductive sheet showed the transmission loss higher than 40 dB in $1{\sim}18$ GHz. Ba ferrite EM wave absorbers with an Au coated conductive sheet showed enhanced EM wave absorption and shield to compare with Ba ferrite EM wave absorbers without conductive sheets. Proposed EM wave absorbers with conductive sheets are useful to protect EM machines from EM interference by strayfields.

Investigation of expanding-folding absorbers with functionally graded thickness under axial loading and optimization of crushing parameters

  • Chunwei, Zhang;Limeng, Zhu;Farayi, Musharavati;Afrasyab, Khan;Tamer A., Sebaey
    • Steel and Composite Structures
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    • v.45 no.6
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    • pp.775-796
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    • 2022
  • In this study, a new type of energy absorbers with a functionally graded thickness is investigated, these type of absorbers absorb energy through expanding-folding processes. The expanding-folding absorbers are composed of two sections: a thin-walled aluminum matrix and a thin-walled steel mandrel. Previous studies have shown higher efficiency of the mentioned absorbers compared to the conventional ones. In this study, the effect of thickness which has been functionally-graded on the aluminum matrix (in which expansion occurs) was investigated. To this end, initial functions were considered for the matrix thickness, which was ascending/descending along the axis. The study was done experimentally and numerically. Comparing the experimental data with the numerical results showed high consistency between the numerical and experimental results. In the final section of this study, the best energy absorber functionally graded thickness was introduced by optimization using a third-order genetic algorithm. The optimization results showed that by choosing a minimum thickness of 1.6 mm and the exponential coefficient of 3.25, the most optimal condition can be obtained for descending thickness absorbers.

Development of Electromagnetic Wave Absorbers far Mobile Phone Using Sendust (Sendust를 이용한 휴대전화용 전파 흡수체의 개발)

  • Choi Jung-Hyun;Kim Dong-Il;Song Jae-Man;Jung Jae-Hyun
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.16 no.8 s.99
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    • pp.842-847
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    • 2005
  • In this paper, we fabricated sheet-type EM wave absorbers for mobile phones by using sendusts and tested EM wave absorption of it. The band-width of EM wave absorbers coated with $Al_2O_3$ were larger than non-coated EM wave absorbers. Particle size decreased with increasing milling time, which made the result of increasing of EM wave absorption. The fabricated EM wave absorbers show a reflection coefficient 17.4 dB at 946 MHz for a 4 mm sample and 5 dB at 1.8 GHz for a 1 mm sample.

The Comparative Analysis on Mechanical Property Test of Carbon Nanotube-based Shock Absorbers (탄소나노튜브를 기반으로 하는 충격흡수제의 물리적 특성 비교분석)

  • Kim, Jong-Woo;Chae, Woen-Sik
    • Korean Journal of Applied Biomechanics
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    • v.22 no.2
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    • pp.237-242
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    • 2012
  • The purpose of this study was (a) to develop carbon nanotube-based shock absorbers for reducing potentially harmful impact forces and excessive foot pronation, and (b) to briefly determine how the effects of carbon nanotube-based shock absorbers on biomechanical variance during drop landing. A university student(age: 24.0 yrs, height: 176.2 cm, weight: 679.5 N) who has no musculoskeletal disorder was recruited as the subject. Hardness, specific gravity, tensile strength, elongation, 100% modulus, tear strength, split tear strength, compression set, resilience, vertical GRF, and loading rate were determined for each material. For each dependent variable, a descriptive statistics was used for different conditions. The property test results showed that tensile strength, tear strength, split tear strength, compression set, and resilience in carbon nanotube-based shock absorbers were greater than general Ethylene Vinyl Acetate(EVA). These indicated that resistance against variable strength in developed carbon nanotube-based shock absorbers were greater than general EVA. In vertical GRF of CNTC was less than those of EVA during drop landing and loading rate of CNTC was greater than EVA. It seems that the use of CNT can be a effective way of reducing and controlling shock from impact.

Enhancement of Sound Clarity of Classrooms Using Sound Diffusers and Panel Absorbers

  • Shin, Sang-Bong;Haan, Chan-Hoon
    • The Journal of the Acoustical Society of Korea
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    • v.28 no.2E
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    • pp.60-65
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    • 2009
  • The present study aims to investigate the effects of sound diffusers and absorbers on the sound clarity in classrooms. In order to do this, computer simulations were carried out to find the effective area of treatment which could enhance the sound clarity in the room. Acoustic measurements were undertaken in a lecture room with several conditions changing the surface of walls and ceilings with diffusers and absorbers. Diffusion and absorption treatments were applied to the side walls, rear wall and the ceiling of the classroom. SPL, RT, D50, RASTI were measured at 9 measurement points with one sound source and MLS was used as the sound source signal. The results show that higher sound clarity was obtained when diffusers were applied to rear walls and ceiling rather than side walls. Also, it was confirmed that absorption increased sound clarity more effectively with smaller amount in comparison with diffusers. It was also concluded that the effects of sound diffusers and absorbers on the sound clarity could be obtained distinctly at the rear area of the classroom.

A Study on the Measurement of Absorbption Characteristics for Ferrite Electromagnetic Wave Absorbers Using Parallel Stripline. (평형스트립라인을 이용한 페라이트계 전파흡수체의 특성측정에 관한 연구)

  • 김동일
    • Journal of the Korean Institute of Navigation
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    • v.17 no.3
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    • pp.77-83
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    • 1993
  • The goal of this research is to get a measuring system for absorption characteristics over the frequency band with 30MHz to 1, 000MHz concerning the ferrite electromagnetic wave absorbers, for example, grid-type and sintered flat type, etc. It is, however, very difficult to measure the absorption characteristics as in low frequency as in 30 MHz. In this research, therefore, we propose a standing wave method using parallel striplines, fabricate the measuring system, and measure the characteristic of ferrite microwave absorbers using the proposed mea-suring system.

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Characteristics of Carbon-Ferrite Microwave Absorbers (카아본-페라이트 전파흡수체의 특성)

  • ;;;Yoshiyuki Naito
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.26 no.11
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    • pp.1721-1727
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    • 1989
  • Carbon-ferrite microwave absorbers were designed experimentally and fabricated trialy, as a result of which the relative frequency bandwith of 7.3 to 8.2% were obtained under the tolerance limits of the reflection coefficients lower than -20 dB, and the matching thickness becomes 1.4 to 1.6mm, which is significantly thinner than that of the conventional ones. Furthermore, attenuation has been founded by measuring the material constants of the microwave absorbers for microwave oven and the results are compared and discussed.

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The Partnership between PM and Manufacturers of Shock Absorbers, a Success History

  • Romero, Antonio
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09a
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    • pp.592-593
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    • 2006
  • Manufacturers of shock absorbers are continuously innovating for improving safety and enhance comfort in cars. The PM industry, as important supplier of components for shock absorbers, has gone along with this evolution by developing the required technology. This paper presents examples of components and technology to meet demanding market requirements. They have been selected by their representative character but there are many other interesting components that we cannot show because of the limited extension of a paper.

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Design of Broad Band Electromagnetic Wave Absorbers with Cross-Shaped Ferrite. (십자형 광대역 페라이트 전자파흡수체의 설계)

  • 김동일;전상엽;정세모
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 1996.09a
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    • pp.125-134
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    • 1996
  • A design method of double layered electromagnetic wave absorbers with cross-shaped ferrite prominence in the second layer which has broad band frequency characteristics was proposed. The broad band electromagnetic wave absorber can be designed under some approximations by the theoretical model using the equivalent material constants method for the second layer. Based on the developed model broad band electromagnetic wave absorbers with excellent reflectivity frequency characteristics in the frequency range of 30MHz to 3,990MHz were designed.

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Research on the Influence of Absorbing Sheet for Electrical Performance of NFC Antenna (NFC 안테나의 흡수체에 따른 전기적 특성 연구)

  • Jung, Young-Bae;Lee, Seung-Ho;Oh, Hyeok-Jun;Jeon, Tae-Joon
    • Journal of IKEEE
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    • v.16 no.3
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    • pp.167-172
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    • 2012
  • In this paper, we analyze the antenna performance variation by the ferrite absorbers which are widely used to optimize the antenna performance in near-field communications(NFC). Using various commercial absorbers, it was confirmed that the absorbers affect the electric performance of NFC antenna, and how to experimentally analyze the electrical influence of the absorbers in NFC antennas is proposed.