• Title/Summary/Keyword: absorption coefficient

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Investigation on Femtosecond Laser Processing of Polymeric Thin Films (펨토초 레이저를 이용한 폴리머 박막 재료 초미세 공정에 관한 연구)

  • Jeoung S.C.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2006.05a
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    • pp.669-670
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    • 2006
  • Two-photon absorption coefficient of a series of dyes in polymer thin films was determined by measuring the femtosecond laser ablation threshold. The threshold value of polymeric thin films decreased gradually when the dopant increased. The two-photon absorption coefficient of the dye molecules dispersed in the polymer film was estimated by using the theoretical relationship between the ablation threshold of the blended polymeric thin films and the dye concentration. The relative values of two-photon absorption cross-section are in good agreement with those measured in solution. On the other hand, the absolute values are smaller than the latter.

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Korea Industrial Standardization Draft for ISO 354 (ISO 354 (잔향실법 흡음률 측정방법)의 KS 규격화)

  • Jung, Sung-Soo;Kook, Chan;Kim, Sun-Woo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.11a
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    • pp.857-860
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    • 2003
  • We introduced the basic direction of revision for KS F 2805 (method for measurement of sound absorption coefficient in a reverberation room). It is fundamentally equal to ISO 354 (measurement of sound absorption in a reverberation room) which was state of ISO/FDIS 354. Two main points were strongly reviewed. First, the sound absorption coefficient values for Type J test specimen mounting was investigated. Next, the reverberation time difference between the conventional method and new additional one, impulse response method were compared.

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Performance Characteristics on the Mixed Flow Type Absorption Chiller-Heater (혼합흐름 사이클용 흡수식 냉온수기의 성능특성)

  • Yoon, J.I.;Shin, G.B.;Park, S.H.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.8 no.3
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    • pp.351-360
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    • 1996
  • This study focuses on the development and evaluation of the high efficiency absorption chiller-heater, which can be applied to a direct gas fired, double effect system with 40RT (508,000kJ) cooling capacity. The performance of the absorption chiller-heater is investigated through cycle simulation and experiment to obtain the system characteristics with the inlet tenperature of cooling, chilled water, and gas input flow rate. The efficiency of the different cycles has been studied and the simulation and experiment results show that higher coefficient of performance could be obtained for mixed flow cycle. The five percent difference was obtained from the comparison between experimental and cycle simulation results. As a result of this study, the optimum designs were determined based on the operating conditions and the coefficient of performance.

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A Study on Characteristic of Photoelectric Absorption with Diagnostic X-ray Contrast Media (X-선 진단용 조영제의 광전흡수 특성에 관한 연구)

  • Kim, Young-Keun;Han, Jae-Jin;Lee, Kyung-Sup
    • Journal of radiological science and technology
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    • v.21 no.1
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    • pp.46-51
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    • 1998
  • The absorption coefficient of contrast media was measured in region of diagnostic radiology. Relative values of absorption coefficient was found the largest peak in the range of $60{\sim}70\;kVp$ for barium sulfate and 60 kVp for iodine. Increasing the thickness of contrast media and patient, the values of absorption coefficient was rising. In the Radiograph, desired $70{\sim}80\;kVp$ in the gastrointestinal digestion tract with barium sulfate and the vascular tract is before and behind 65 kVp of exposure.

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Properties of Inclined Silicon Carbide Thin Films Deposited by Vacuum Thermal Evaporation

  • Hamadi Oday A.;Yahia Khaled Z.;Jassim Oday N.S.
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.5 no.3
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    • pp.182-186
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    • 2005
  • In this work, thermal evaporation system was employed to deposit thin films of SiC on glass substrates in order to determine the parameters of them. Measurements included transmission, absorption, Seebak effect, resistivity and conductivity, absorption coefficient, type of energy band-gap, extinction coefficient as functions of photon energy and the effect of increasing film thickness on transmittance. Results explained that SiC thin film is an n-type semiconductor of indirect energy band-gap of ${\sim}3eV$, cut-off wavelength of 448nm, absorption coefficient of $3.4395{\times}10^{4}cm^{-1}$ and extinction coefficient of 0.154. The experimental measured values are in good agreement with the typical values of SiC thin films prepared by other advanced deposition techniques.

Absorption Characteristics of Building Interior Decoration Materials (건축내장재의 흡음 특성)

  • Kang, Dae-Joon;Lee, J.W.;Lee, W.S.;Hong, J.K.;Jo, Y.H.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2006.05a
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    • pp.1190-1193
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    • 2006
  • It is important to consider absorption characteristics of building interior decoration materials when we design a building and simulate acoustics in a room. The purpose of this study is to accumulate acoustic data on building interior decoration materials and give a basic data for improving absorption performance by testing absorption coefficient of 9 types of ceiling materials, 14 types of wall paper and 20 types of floor papers.

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Analysis on the Acoustical Characteristics for Arrounding of Bridge by Absortion Panel Attatchment (흡음 외장재 부착에 따른 교량 주변 음향 특성 해석)

  • Lee, You Yub
    • Journal of the Korea Safety Management & Science
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    • v.16 no.4
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    • pp.391-396
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    • 2014
  • For the purpose of finding out the acoustical characteristics of exterior materials in bridge, analytical studies are performed with boundary elements method by using the commercial program SYSNOISE. Before analysis, to figure out material property, it was conducted experiments of absorption coefficient for absorptive material. And prediction of pressure were conducted I GIRDER type (before & after installation of absorption panel ) and BOX GIRDER type (before & after installation of absorption panel) The results show that when the absorption panel is installed, environment around bridge can help reduce traffic noise. It was proved to be the effective noise reduction counter-plan for a traffic noise in the bridges.

Investigation of Sound Absorption Ability of Hinoki Cypress (Chamaecyparis obtusa) Cubes

  • JANG, Eun-Suk
    • Journal of the Korean Wood Science and Technology
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    • v.50 no.5
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    • pp.365-374
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    • 2022
  • Today, commercialized Hinoki cypress cubes are used for fragrance, humidification, and pillows in Korea. In this study, the sound absorption ability of Hinoki cypress (Chamaecyparis obtusa) cubes was examined. The three groups of Hinoki cypress cubes were prepared depending on their dimension (L: 9 × 9 × 9, M: 7 × 7 × 7, S: 4 × 4 × 4 mm). Their sound absorption coefficient was examined after filling 6, 8, 10, and 12 cm height in impedance tubes, respectively. Overall, the sound absorption ability depending on dimension was superior in the M group compared to the L and S groups. Also, as the filling height increased, the sound absorption capacity increased. In sum, noise reduction coefficients (NRC) of all Hinoki cypress cubes were 0.41-0.59. Thus, this research found that Hinoki cypress cubes have a sound-absorbing function.

Experimental Investigation of the Sound Absorption Capability of Wood Pellets as an Eco-Friendly Material

  • JANG, Eun-Suk
    • Journal of the Korean Wood Science and Technology
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    • v.50 no.2
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    • pp.126-133
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    • 2022
  • In this study, I used wood pellets as an eco-friendly sound-absorbing material. The aim of the research was to analyze the effect of the filling height of wood pellets on sound absorption. This was done using two types of wood pellets of different lengths (A group: 1.5-3 cm, B group: less than 1.5 cm). With increasing filling height of the wood pellets, the optimum sound absorption shifted towards a lower frequency. The group B wood pellets had better sound absorption capacity than the group A ones. The optimum sound absorption coefficient of group A filled to a height of 7 cm was 0.722 at 864 Hz. On the other hand, that of group B filled to a height of 7 cm was 0.764 at 862 Hz, 5.82% higher than that of group A. While wood pellets are used as an eco-friendly fuel, the results of this study suggest the possibility of using wood pellets as an eco-friendly sound-absorbing material.

Modeling of absorption coefficient and transition energy for intersubband transitions in quantum wells (양자우물에서의 전자의 에너지 부준위간 천이에 의한 광자의 흡수계수와 천이 에너지의 모델링)

  • 김경염;이병호;이찬호
    • Journal of the Korean Institute of Telematics and Electronics D
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    • v.35D no.8
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    • pp.44-52
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    • 1998
  • The theoretical modeling of transition energy and absorption coefficient for intersubband transitions in quantum wells in presented. We include, as well as hartree and exchange-correlation potentials, boht depolarization effect and exciton-like effect which play great roles in heavily doped cases where practically reasonable absorption coefficients are available. Also, the calculated results are compared with the existing experimental values for .delta.-doped Si quantum wells to check the validity of our theoretical calculation.

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