• 한국철도학회논문집
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• 제10권1호
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• pp.67-73
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• 2007

Experiments were carried out to investigate smoke movement in platform of a subway station which currently is in service in Pusan, the second largest city in Korea. The recently constructed underground station of the "bank type" (two platforms on both sides of track) which is the popular layout of platforms in Korea, is chosen in Pusan. The smoke generator and heater are used for simulating the smoke movement at the fire break in the platform located in the 2nd basement of the station. Video recordings were used to monitor smoke lowering. In this study, the movements of smoke in the underground station are investigated under various smoke-control operating modes. Three tests wire conducted according to its operating mode of the ventilation systems in the platform: no operation of any ventilation systems, smoke extraction mode in occurrence of fire (presently running mode) and full capacity of smoke extraction where all vents are activated in the platform. The results can be used for comparing with the numerical prediction results of fire subway stations.

• 대한기계학회논문집
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• 제13권4호
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• pp.799-806
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• 1989

본 논문에서는 일반적으로 축방향 변위에 대한 모우드만을 가지고 있는 경우의 합성을 위해 축방향 변위 모우드의 커브-피팅을 이용하여 기울기 정보를 얻고 모델링된 요소의 연결부에 부여함으로써, 변위 정보만을 사용하는 방법보다 좀 더 정확한 고유값을 얻을 수 있음을 보이고자 한다.

• 한국항해학회지
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• 제15권3호
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• pp.73-97
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• 1991

The analysis and investigation are described for White's[2] equations compared to the equations of Runeburg[3] and Milano[5] for continuous icebreaking mode, Tunik[8-1] and Ghoneim[8-2] for ramming icebreaking mode. Calculation results compare reasonably well with published model-scale and full-scale icebreaker data by Baker[1] and Dick[11]. During continuous and ramming mode operation, using characteristics of an incebreaker, down ward force on ice and standard ice thickness broken are predicted. Additionally draft, trim and extraction difficulty are also predicted. The bow part line of an icebreakin $g^{ply}$ vessel is designed aiming to maximize the ice breaking capabiltiy as following conditions-low bow angle[20 degrees] at designed waterline, small spread angle complement [6 degrees] at designed waterline, small spread angle complement [6 degrees] and high propeller thrust [220tons]. with plow, two reamers and wave type bumper.

• Journal of Power Electronics
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• 제14권4호
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• pp.641-648
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• 2014

This paper presents the design considerations and analysis for an interleaved boundary conduction mode power factor correction buck converter. A thorough analysis of the harmonic content of the AC line current is presented to examine the allowable voltage gain (K value) for meeting the EN61000-3-2, Class D standard while maximizing efficiency. The results of the harmonic analysis are used to derive the required value of K and therefore the output voltage necessary to meet the class D requirements for a given AC line voltage. The discussed design consideration and harmonic current analysis are verified on a 300W universal line experimental prototype converter with an 80V output. The measured efficiencies remain above 96% down to 20% of the full load. The input current harmonics also meet the IEC61000-3-2 (class D) standard.

• Journal of the Optical Society of Korea
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• 제12권4호
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• pp.314-318
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• 2008

We investigate the conditions of the complete tunneling of light across a composite barrier made of multiple layers involving metamaterials. It is shown that complete tunneling phenomena are related to the resonance transmission properties of local modes formed in barrier layers and that there are two distinctive kinds of local barrier modes involved in actual complete tunneling: the degenerate inner-barrier mode and the full barrier mode. Complete tunneling occurs via two successive mode couplings: from the incident plane wave to the plane wave in the transmission layer through the direct mediation of these two kinds of local barrier modes.

• Journal of Power Electronics
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• 제19권1호
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• pp.296-306
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• 2019

The flyback topology is being widely used in power adapters. The coupling capacitance between primary and secondary windings of a flyback transformer is the main path for common-mode (CM) noise conduction. A Y-cap is usually used to effectively suppress EMI noise. However, this results in problems in space, cost, and the danger of safety leakage current. In this paper, the CM noise behaviors due to the electric field coupling of the transformer windings in a flyback adapter with synchronous rectification are analyzed. Then a scheme with balance winding is proposed to reduce the CM noise with a transformer winding design that eliminates the Y-cap. The planar transformer has advantages in terms of its low profile, good heat dissipation and good stray parameter consistency. Based on the proposed scheme, with the help of a full-wave simulation tool, the key parameter influences of the transformer PCB winding design on CM noise are further analyzed. Finally, a PCB transformer for an 18W adapter is designed and tested to verify the effectiveness of the balance winding scheme.

• Advances in nano research
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• 제12권1호
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• pp.65-72
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• 2022

The dynamic properties (frequencies, mode shapes, damping ratios) of the scaled WPC warehouse are compared using the operational modal analysis approach to the dynamic parameters (frequencies, mode shapes, damping ratios) of the full outer surface of titanium dioxide, 70 micron in thickness. Micro tremor ambient vibration data on ground level was used to provide ambient excitation. For the output-only modal identification, Enhanced Frequency Domain Decomposition (EFDD) was used. This study discovered a strong correlation between mode shapes. Titanium dioxide applied to the entire outer surface of the scaled WPC warehouse results in an average 14.05 percent difference in frequency values and 7.61 percent difference in damping ratios, demonstrating that nanomaterials can be used to increase rigidity in structures, or for reinforcement. Another significant finding in the study was the highest level of adherence of titanium dioxide and similar nanomaterials mentioned in the introduction to WPC structure surfaces.

• Current Optics and Photonics
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• 제6권2호
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• pp.129-136
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• 2022

We propose a photonic crystal fiber (PCF) with a slotted porous core and elliptical-hole cladding, for high birefringence in the terahertz regime. Asymmetry in the guided mode is obtained mainly by using arrays of elliptical air holes in the TOPAS^® polymer cladding. We investigate the tradeoff between several structural parameters and find optimized values that can have a high birefringence while satisfying the single-mode condition. The optical properties in the terahertz regime are thoroughly analyzed in numerical simulations, using a full-vector finite-element method with the perfectly-matched-layer condition. In an optimal design, the proposed photonic crystal fiber shows a high birefringence of 8.80 × 10^-2 and an effective material loss of 0.07 cm^-1 at a frequency of 1 THz, satisfying the single-mode-guidance condition at the same time. The proposed PCF would be useful for various polarization-management applications in the terahertz range.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2020년도 전력전자학술대회
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• pp.261-262
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• 2020

본 논문은 DC/DC 위상천이 풀브릿지 컨버터의 과도상태 개선을 위한 듀얼모드 제어를 제안한다. 기존의 discontinuous conduction mode (DCM)과 continuous conduction mode (CCM)을 이용하여 운용하는 위상천이 풀브릿지 컨버터는 각 모드의 상이한 전압게인의 특성을 고려하지 않아 급격한 로드 변동시 출력 전압의 언더슈트 혹은 오버슈트가 크게 발생한다. 제안하는 듀얼모드 제어는 DCM과 CCM 각 모드 별개로 제어가 적용되고 출력 전류의 변화에 대응하는 적응형 feed-forward 제어가 적용되어 컨버터의 과도상태를 개선할 수 있다. 듀얼모드의 제어 방법의 성능과 타당성을 시뮬레이션을 통해 입증한다.

• 한국인터넷방송통신학회논문지
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• 제9권1호
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• pp.39-45
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• 2009

본 논문에서는 최근 무선 통신 시스템에서 빠른 데이터전송 방식으로서 사용되고 있는 OFDM 통신방식의 저소비전력화 방안을 제안한다. 일반적으로 OFDM에서 주요 신호처리 방식은 디지털을 이용한 프리에 변환이다. 이런 디지털 프리에 변환은 많은 소비전력이 필요하며 이것은 무선통신 시스템에 있어서 커다란 제약이 되고 있다. 전류모드를 이용한 아날로그 프리에 변환(FFT) LSI는 이러한 소비전력의 문제를 해결할 수 있는 주요 대안으로 떠오르고 있다. 그러나 이러한 신호처리 방식을 사용하기 위해서는 전류모드를 이용한 직병렬/병직렬 변환기(Serial-to-Parallel/Parallel-to-Serial Converter)가 필수적으로 필요하다. 본 논문에서는 전류모드로 구성한 아날로그 프리에 변환(FFT) LSI를 이용해 수신단의 저소비전력을 실현하기 위해 필수적인 새로운 전류모드 직병렬/병직렬 변환기를 제시하였으며 설계된 칩의 측정결과가 시뮬레이션 결과와 일치하는 것을 확인하였다. 제안된 전류모드 직병렬/병직렬 변환기의 개발로 저소비전력에 큰 장점을 지니고 있는 아날로그 FFT LSI의 활용이 가능해졌으며 송수신단 시스템에서 큰 소비전력의 감소효과를 가져올 것으로 기대된다.