• Electrical & Electronic Materials
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• v.10 no.9
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• pp.960-967
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• 1997

• Journal of the Korean Society of Radiology
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• v.17 no.3
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• pp.449-457
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• 2023

Shielding for reducing exposure dose can make the diagnosis limited. The purpose of this study is to increase the efficiency of radiation protection and minimize the loss of image information by producing the shielding made of the water and the contrast medium which has different proportion and finding out the ideal proportion of them. Each shielding materials were made of water and water-soluble iodine contrast medium with the different proportion. The attenuation rate of absorbed dose was evaluated by the shielding materials in the plastic contents for measuring the efficiency of the radiation protection. As a result, the higher ratio of the contrast medium, the more efficient it is for radiation attenuation. The anatomical structure was observed most properly in case of the solution with 20 ml of the contrast medium and most difficultly in case of more than 60 ml of the contrast medium. In case of the signal intensity between skeleton and gas, the difference of average value had a significant as p < 0.001. Shielding with contrast medium attenuates less than the conventional shielding but in the examination for the sensitive part to radiation, it can be used to minimize the loss of the image information and reduce the exposure dose.

• Tunnel and Underground Space
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• v.27 no.3
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• pp.132-145
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• 2017

Shock loss was not applied for the tunnel ventilation of road tunnel in the past. However, pressure losses due to the shock loss can be significant in network double-deck road tunnel in which combining and separating road structures exist. For the optimum ventilation design of network double-deck road tunnel, this study conducted 3D CFD numerical analysis for the shock loss at the combining and separating flows. The CFD model was made with the real-scale model that was the standard section of double-deck road tunnel. The shock loss coefficient of various combining and separating angles and road width was obtained and compared to the existing design values. As a result of the comparison, the shock loss coefficient of the $30^{\circ}$ separating flow model was higher and that of the two-lane combining flow model was lower. Since the combining and separating angles and road width can be important for the design of shock loss estimation, it is considered that this study can provide the accurate design factors for the calculation of ventilation system capacity. In addition, this study conducted 3D CFD analysis in order to calculate the shock loss coefficient of both combining and separating flows at flared intersection, and the result was compared with the design values of ASHRAE. The model that was not widened at the intersection showed three times higher at the most, and the other model that was widened at the intersection resulted two times higher shock loss coefficients.

• The Journal of the Korea Contents Association
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• v.6 no.8
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• pp.20-29
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• 2006

This paper proposes a quality measurement model for video phone service over IP environment. Proposed model enhances conventional E-Model by using quality analysis and this model is suitable for ubiquitous environment. This research measures video phone quality by applying bust packet loss and recency effect. It uses delay and recency effect for compensating actual quality and recognized quality of user using NR and UR factor. Simulation results show that this model can provide more precise results than conventional model by considering recency effect of video phone service quality measurement model.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.8
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• pp.763-771
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• 2013

In this paper, the propagation characteristics for ISM(Industrial Scientific and Medical) and TVWS(TV White Space) in indoor building environment are analyzed in comparison with theoretical and experimental results, the excellent propagation characteristics of the TVWS is confirmed. To this end, signals which have center frequencies of 503 MHz and 2.4 GHz are generated in building propagation environment. Through that, received power strength is measured according to the location and measured path loss is analyzed. Theoretical path loss is calculated using Hata, Extended Hata, Extended Hata SRD, ITU-R P.1238 and reliability for channel model in indoor environment is analyzed.

• Proceedings of the KIEE Conference
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• 2008.05a
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• pp.193-195
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• 2008

에폭시-층상실리케이트 나노콤포지트의 여러 가지 특성인 전기적, 기계적, 구조적 특성에 대해서 많은 연구가 진행되었고, 그에 대한 특성 향상을 가져왔다. 그러나 절연성능에 대한 평가는 우수하지만 열적특성 중열전도에 대한 영향은 그히 부족한 상태였다. 열적특성은 열적열화의 원인이 되어 신뢰성에 크게 영향을 준다. 여러종류 Organoclay(10A, 15A, 20A, 30B, 93A)의 에폭기-층상실리케이트 나노콤포지트 Tg 분석결과 10A의 경우 우수한 열적특성을 나타내었다. DNA 점탄성 및 기계적 손실측정에서도 10A의 경우 고온부($140^{\circ}C$) 탄성계수 및 기계적손실 피르가 가장작고, 고온으로 이동되어 발생된 경우로 열적 특성이 우수함을 알 수 있었다. 열전도 측정결과 강력초음파를 적용한 경우와 미적용의 경우 열전도측정으로 볼 때 전반적으로 초음파 적용 경우 열전도향상이 크게 증가된 결과를 얻었다. 향후 몰드 및 함침절연의 전력기기 적용시 유용한 자료로 이용이 가능하여, 더욱더 많은 연구가 필요할 것으로 생각된다.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.10
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• pp.10-15
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• 1990

Theory and experimental results of measuring the microwave dielectric characteristics of low-loss materials by using dielectric rod resonator method are presented. The $TE_{011}$ mode resonance frequency was adapted to minimize the effect of the air gap between the rod and the conducting plates. The dielectric properties were computed from the resonance frequency, sample geometry and 3 dB bandwidth. The error of measurements was within ${\pm}3{\%}$ for dielectric constant and was within ${\pm}12{\%}$ for dielectric loss.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.5
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• pp.402-411
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• 2000

This study investigates the method to measure the viscoelastic properties of asphalt cement, one of the viscoelastic materials, using the ultrasound. The wave speed and attenuation were measured from $-20^{\circ}C$ to $60^{\circ}C$ at the frequency of 2.25MHz. Then, the storage and loss longitudinal moduli, loss tangent storage and loss longitudinal compliances were found depending on the temperatures based on the linear viscoelastic theory. Stress relaxation, creep, and viscosity were predicted using Maxwell and Voigt-Kelvin viscoelastic models. The validity of superposition principle and shift factor were verified by comparing the present results to the data reported in the literatures.

• Journal of the Korean Magnetics Society
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• v.22 no.1
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• pp.23-26
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• 2012

New digital feedback algorithm was developed to measure iron loss of soft magnetic materials under a condition of sinusoidal flux waveform. $V_{in}$(B) curve was used instead of H(B) curve to decide next input waveform in the feedback module so that adjusting phases of current waveform, flux waveform, and input waveform could be removed. The effectiveness of the developed algorithm was verified when iron loss of ferrite cores was measured under frequencies of 1 and 10 kHz.

• Solar Energy
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• v.15 no.3
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• pp.119-125
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• 1995

Since the using of heating energy associated with infiltration is significant in a building, the efforts to minimize the infiltration while ensuring minimum ventilation rates for various types of occupancy will be beneficial. In constrast to that many efforts have been made to reduce heat loss by improving thermal resistance of building envelope, little has been tried to reduce heat loss from infiltration. For achieving such an objective, measurement of air leakage rate will be pre-requisite as a diagnostic tool. A blower door system, a depressurization/pressurization method, was employed and it demonstrated a good potential for measuring airtightness performance of residential buildings. Based on the test results, annual energy savings for residential heating was estimated by reducing infiltration to a level of reasonably airtight or to a level of ASHRAE Standard 62-1989 for minimum ventilation.