• Journal of the Korean Wood Science and Technology
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• 제46권2호
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• pp.149-154
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• 2018

The changes in sound absorption capability and air permeability of Malas wood after high temperature heat treatment were investigated. The average air permeability of Malas in longitudinal direction after heated under the temperature of $190^{\circ}C$ during 3 hours was about 23.48 darcys and that of control was about 3.11 darcys. The noise reduction coefficients of Malas specimens were 17% for treatment and 10% for control. The means of sound absorption coefficient of specimens in the frequency range of 50~6,400 Hz were 42% for treatment and 17% for control, respectively.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.699-702
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• 2005

This study evaluates the properties of porous concrete for pavement according to content of silica fume and steel fiber. The results of the test indicate that in every condition, the void ratio and the coefficient of water permeability of porous concrete for pavement satisfy both the domestic standards and proposition values. Among the properties of strength, the compressive strength satisfies the standards in the specification of KNHC as for every factor of mixture but in the case of the flexural strength, more than $0.6vol.\%$ of steel fiber satisfied the JCI proposition values. The case when silica fume and steel fiber are used simultaneously presents the strongest durability and Noise Reduction Coefficient is 0.48 to prove that it possesses almost $50\%$ sound absorption.

• Journal of Mechanical Science and Technology
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• 제14권5호
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• pp.518-529
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• 2000

A detailed and thorough parametric study of digital image correlation method is presented. A theoretical background and development of the method were introduced and the effects of various parameters on the determination of displacement outputs from the raw original and deformed image information were examined. Use of the normalized correlation coefficient, the use of 20 to 40 pixels for a searching window side, 6 variables searching, bi-cubic spline sub pixel interpolations and the use of coarse-fine search are some of the key choices among the results of parametric studies. The displacement outputs can be further processed with two dimensional curve fitting for the data noise reduction as well as displacement gradient calculation.

• Journal of the Korean Wood Science and Technology
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• 제50권5호
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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.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 추계학술대회논문집
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• pp.152-157
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• 2008

Enclosure is widely used for the sound insulation in a ship. But it is very difficult to estimate the sound insertion loss for the enclosure because the sound field between the enclosure and the machine is so complex. Therefore, it is usually estimated experimentally. In this research, sound insertion loss of the enclosure is estimated by theory assuming that the sound field in the enclosure is reverberation field. And the results from the theory are compared to those from the experiment.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.234-237
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• 2007

To protect a satellite and electronic equipment from the acoustic load generated by rocket propulsion system, many launch vehicle use acoustic blanket. Acoustic load is main source of random vibration working on the payload. Most high frequency region of the acoustic loads is reduced by payload fairing skins and acoustic blanket, but low frequency region is not. In order to reduce acoustic load of low frequency region, we designed array resonator panel which was made of composite materials. Insertion loss capacity of the payload fairing with acoustic blanket was verified from PLF acoustic test in the acoustic chamber.

• 한국소음진동공학회논문집
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• 제21권6호
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• pp.491-498
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• 2011

The structural vibration due to earthquake or outside impact causes serious problem for building safety. A dynamic model of a friction damper which can be constructed and installed easily is needed to reduce the vibration of the building. In this paper, the experimental equation of a circular friction damper is derived and designed for reduction of a earthquake vibration of a building. The developed experimental equation is defined to simply design the capacity on design of the circular friction damper based on the results of the performance test. Finally this experimental equation can be used for the design of a circular friction damper.

• 대한전자공학회논문지TC
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• 제41권8호
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• pp.99-103
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• 2004

본 논문에서는 Hairpin 발진기의 위상잡음을 개선시키기 위하여 접지 면에 Aperture를 구현하였다 Aperture를 마이크로스 트립 Hairpin 공진기에 적용함으로써 결합계수의 증가로 인해 마이크로스트립라인이 가지고 있는 Q값을 증가시켰다. 기존의 마이크로스트립 Hairpin 발진기와 비교하였을 때 Aperture를 적용한 발진기가 위상잡음을 100KHz offset에서 약 19dBc 개선시켰다. 제작된 발진기는 5.83GHz 대역이고, 출력전력은 -4.33dBm을 획득하였다.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.28-32
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• 2003

Aperture has been employed on the ground plane in the Hair Pin resonator. Aperture made by etching the part of the ground effected coupling coefficient and then quality factor of Hair Pin resonator has been increased. When the hair pin oscillator using aperture has been compared with the conventional hair pin oscillator using microstrip, it has been improved the phase noise about 19dBc @100KHz. Oscillation frequency of the hair pin oscillator using aperture has been 5.83GHz band and output power is -4.33dBm.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.979-984
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• 2003

A Dynamic vibration absorber(DVA) is developed to reduce the excessive vibration of an optical disk drive(ODD) originated from the deriving range of an wobble disk and unbalanced disk. We design the material properties and shapes of the DVA by simulating Frequency response function(FRF) such as target frequency, mass of the DVA, stiffness of damper, damping coefficient, shape and dimension, analyze dynamic characteristics and provide its design guide line for suppressing the vibration of an optical disk derive. To examine the performance of the DVA, the vibration of the feeding system with DVA and without DAA are measured by using a three-axis accelerometer, PCB derive and Pulse analyzer. The result show that the proposed DVA reduces the vibration of wide range in ODD.