• ETRI Journal
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• 제42권6호
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• pp.827-836
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• 2020

Measuring the diffraction loss for high frequencies, long distances, and large diffraction angles is difficult because of the high path loss. Securing a well-controlled environment to avoid reflected waves also makes long-range diffraction measurements challenging. Thus, the prediction of diffraction loss at millimeter-wave frequency bands relies on theoretical models, such as the knife-edge diffraction (KED) and geometrical theory of diffraction (GTD) models; however, these models produce different diffraction losses even under the same environment. Our observations revealed that the KED model underestimated the diffraction loss in a large Fresnel-Kirchhoff diffraction parameter environment. We collected power-delay profiles when millimeter waves propagated over a building rooftop at millimeter-wave frequency bands and calculated the diffraction losses from the measurements while eliminating the multipath effects. Comparisons between the measurements and the KED and GTD diffraction-loss models are shown. Based on the measurements, an approximation model is also proposed that provides a simple method for calculating the diffraction loss using geometrical parameters.

• 한국통신학회논문지
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• 제38C권9호
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• pp.757-763
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• 2013

본 논문에서는 수도권 서북부 지역의 3차원 지리정보를 바탕으로 다중예봉모형을 (multiple knife-edge model) 적용해 전파교란기와 수신기의 지리적 위치에 따른 회절손실을 (diffraction loss) 계산하고, 이를 바탕으로 광대역 잡음재밍 (wideband Gaussian null-to-null noise jamming), 스펙트럼일치형재밍 (matched spectrum jamming), 연속파재밍에 (continuous wave jamming) 의한 GPS (global positioning system) L1 C/A (coarse/acquisition) 신호의 여유재밍전력을 (marginal jamming power) 보인다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.718-723
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• 2004

The insertion loss of a noise barrier comes from the effects of diffraction, transmission loss, absorption coefficient and attenuation by direct propagation. The noise level after the noise barrier, differs reatly from the diffraction on the upper part of the barrier. Maekawa, furze and Anderson presented a empirical formula for calculating the diffraction of a semi infinte screen shaped noise barrier. In this syudy, Noise reduction performance software was developed for the proper design and assessment of new plastic barrier . Predicted sound pressure level from using the software is compared with the site-measurement results to verify the noise reduction performance and feasibility of prediction software for insertion loss of noise barrier.

• KIEE International Transactions on Electrophysics and Applications
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• 제5C권5호
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• pp.204-210
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• 2005

Alternating current (AC) losses of two Bi-2223 ([Bi, Pb]: Sr: Ca: Cu: O = 2:2:2:3) tapes [(Tape I, un-twist-pitch) and the other with a twist-pitch of 10 mm (Tape II)] were measured and compared. These samples, produced by the powder-in-(Ag) tube (PIT) method, are multi-filamentary. Also, it's produced by non-twist and different twist pitch (8, 10, 13, 30, 50 and 70 mm). The critical current measurement was carried out under the environment in liquid Nitrogen and in zero-field by 4-probe method. Susceptibility measurements were conducted while cooling in a magnetic field. Flux loss measurements were conducted as a function of ramping rate, frequency and field direction. The AC flux loss increases as the twist-pitch of the tapes decreased, in agreement with the Norris Equation. Neutron-diffraction measurements have been carried out investigate the crystal structure, magnetic structures, and magnetic phase transitions in Bi-2223([Bi, Pb]:Sr:Ca:Cu:O)

• 해양환경안전학회지
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• 제19권3호
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• pp.264-269
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• 2013

This paper is to investigate propagation path characteristics of GPS potential jamming signal. To do this, the spherical ground diffraction model is applied to the potential jamming scenario referred to the GPS jamming events occurred in recent years. The fundamental theory on the propagation path loss is discussed and a specific model is applied to several vehicles types which have own heights of antennas in order to compare their propagation path loss values at same 2-D location. The transmitting powers are appropriately given as the ordinary GPS jamming events. And then the received powers in dBW are obtained with given transmitting powers and the estimated total loss. The result of received jamming power at various locations due to the given scenario was distinct. For example, propagation loss values were estimated as -147 ~ -142dBW and -167 ~ -162dBW in $10^6W$ and $10^4W$, respectively. This computation result of the loss can be seriously considered with the tolerable jammer power against L1- C/A GPS receiver under any real jamming situations.

• 한국환경보건학회지
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• 제24권2호
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• pp.145-150
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• 1998

This study was carried out to investigate the loss amount of collection at the different of precipitatation time, high voltage and gas speed. This work has focused on the dependence of the collection efficiency in the collector zone with gas speed and high voltage. This advanced Model is developed by research of the different parameter as the conventionnal modem of study. In order to investigate collection efficiency of electrostatic precipitator, the loss amount of knocking was measured with Monitek-Treubung and the particle size was analyzed by He-Ne laser diffraction spectroscopy.

• 한국광학회지
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• 제13권1호
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• pp.21-26
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• 2002

기존의 성형결합기는 광파가 자유전파영역에서 회절에 의해 전파되는 사실이 잘 알려져 있다. 본 논문에서는 손실을 줄이기 위하여 회절에 의한 광파의 전파가 아닌 W-테이퍼 도파로에 의한 광파의 전파를 하는 새로운 개념의 성형결합기를 제안하였고, 이를 광도파로열 격자 파장 필터에 적용시켜 여러 가지 특성을 조사하였다. 새로운 개념의 저 손실 성형결합기 및 이를 이용한 광도파로열 격자 파장 필터는 기존의 성혈결합기 및 광토파로열 격자 파장 필터와 같은 성능을 나타내면서도 손실이 작음을 확인하였다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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• pp.373-376
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• 2004

The measurement of diffraction of LCOS microdisplay with various pixel size, interpixel gap, pixel height and coatings demonstrates that pixel size is the leading factor for diffraction loss, while the role of varying pixel gap is less significant comparatively. One-dimensional diffraction simulation is found to be in good agreement with the measurement. Noticeable deviation occurs when pixel size is as small as 8um.

• 소음진동
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• 제10권1호
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• pp.49-56
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• 2000

In this paper performance of the noise barrier which is 53 m long and 6m high, and is located between the high rise apartment and road, is studied by using experimental and analytic method. The insertion loss is measured by using the direct method in accordance with the ISO code, while theoretical prediction is based on Muradali and Fyfe's method (Applied Acoustics, Vol. 53, 49~75, 1998). In addition to the diffraction at the top of the barrier, the waves are reflected infinite times between the building and the barrier, which is equivalent to replacing the building by the infinite series of the image receiver points. In two-dimensional study, the prediction of the insertion loss results in significantly overestimated values compared with the measurement. However three-dimensional analysis shows reasonable agreements, where traffic noise is assumed as incoherent line source and the length of the source is larger than that of the barrier.

• 한국전자파학회논문지
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• 제8권3호
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• pp.289-296
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• 1997

본 논문에서는 대표적인 희절공식들을 살펴보고, 쐐기 형태의 구조물에 대한 희절손실 예측치를 비교해 모았다. 또한 시뮬레이션 결과를 측정치와 비교, 분석하였다. 은 산란체가 의절체 부근에 존재하는 실제 환경에서 수직편파에 대한 의절손실은 단순한 knife-edge 공식이 측정치와 잘 일치하였다. 일치하였다.