• 산업기술연구
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• 제27권A호
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• pp.169-175
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• 2007

In High-Speed DSP systems, crosstalk between transmission lines of multi-channel can degrade the performance of equipment operations. This paper presents a microwave board to measure multi-channel coaxial cable assembly. The designed board has good performances from DC to 3 GHz, which have improved characteristic impedance, reduced crosstalk by using via fence, and low transmission loss. Using the designed board, we can measure characteristics of DUT(Device Under Test) such as return loss, insertion loss, crosstalk phase delay, and characteristic impedance. The measured results are used to improve performances of a produced coaxial cable assembly.

• International Journal of Concrete Structures and Materials
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• 제11권1호
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• pp.151-159
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• 2017

The action of rainwater on reinforced concrete walls has led to an erosion phenomenon. The erosion is very apparent when the walls are inclined. This phenomenon is studied on a real site characterized by different architectural forms. The site dates back to the seventies; it was designed by the architect, modeler of concrete, Oscar Nie Meyer. On this site, the erosion has damaged the cover of the reinforcements and reduced its depth. In this research work, a method of quantification of the erosion is developed. Using this method, the amount of mass loss by erosion was measured on imprints taken from the site. The results are expressed by the rate of mass loss by erosion; they are associated to the height and the inclination of the walls. Moreover, laboratory analysis was carried out on samples taken from the site. From this study, it is recommended to consider the erosion, in any building code, to determine the cover thickness.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(5)
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• pp.103-106
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• 2001

In this paper, a soft switching half-bridge converter using secondary switches for output control and conduction loss reduction is proposed. The conventional half-bridge converter must be fixed on duty cycle for soft switching. The proposed converter was consisted of two added switches in series of the secondary rectifier diodes. The main switches with constant duty cycle are operated ZVS. The secondary switches are operated ZV-ZCS. Especially, the primary switches were fixed duty cycle for maximum voltage conversion ratio. Output of converter is controlled by duty cycle or phase-shifted time of secondary switches. The conduction loss of the proposed converter can be reduced by the secondary switches. The operation characteristic, analysis, simulation and experimental results of the proposed converter are presented.

• 전력전자학회논문지
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• 제1권1호
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• pp.27-37
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• 1996

This paper proposes the control algorithm for maximum efficiency drive of PWM inverter - induction motor system with high dynamic performance. If the induction motor is driven under light load with rated magnetizing current, the Iron loss is excessively large compared with the codder loss which results in doer motor efficiency. Maximum efficiency drive of an induction motor can be achieved by controlling the magnetizing current to satisfy the optimal ratio that leads the total motor loss to be a minimum value at a given speed. The proposed control algorithm essentially uses vector control technique and adopts voltage decoupling control strategy to prevent the degradation of dynamic performance due to reduced magnetizing current. To verify the proposed method, digital simulations and experiments are carried out for a squirrel-cage induction motor with the rating of 2.2[kW].

• 한국광학회지
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• 제1권2호
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• pp.162-168
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• 1990

내경이 2.1mm인 Pyrex 모세관을 사용하여 길이가 150mm인 도파형 이산화탄소 레이저를 제작하였으며, 공진기내에 임의의 손실을 가할 수 있는 ZnSe 손실판을 설치하여 공진기의 내부손실에 따른 출력변화를 여러 방전조건에 대해 측정하였다. 본 실험에 Rigrod 이론을 적용하여 내부손실에 따른 출력변화를 예측했으며 실험치로부터 포화출력 및 불포화 이득계수를 구할 수 있었다. 방전전류와 혼합기체의 유입률이 증가함에 따라 포화출력은 증가하며, 불포화 이득계수는 감소하는 경향을 볼 수 있었다.

• 한국소음진동공학회논문집
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• 제20권3호
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• pp.257-262
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• 2010

Lower tunnels and concrete based tracks are introduced to newly constructed metro lines to reduce the construction and track maintenance fees. But such a lower tunnel together with concrete based track causes higher interior noise of metro trains. It is required that the trains should not only be a transportation media but also be comfortable. So, to lower the metro train's interior noise level, design was made to increase the transmission loss per sectional part. Through such a design, it is expected that about 7 dB(A) of noise level will be reduced compared to that of the conventional train.

• 태양에너지
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• 제11권1호
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• pp.87-91
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• 1991

Pool cover를 이용한 수영장에서의 열손실에 관하여 실험적 연구를 수행하였다. 그 결과 본 연구의 실험조건에서 pool cover 를 이용할 경우, 전체열손실이 50% 이상 줄어 듬을 알 수 있었다.

• 한국토양비료학회지
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• 제42권4호
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• pp.231-238
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• 2009

본 연구는 고랭지 경사밭에서 발생하는 유거수량, 토양유실, 영양물질 유출량을 감소시키는 완충식생대의 효과를 연구하기 위하여 수행하였다. 시험에 사용된 포장의 토양은 운교통이고, 가로 2.5m, 세로 20m인 무저 lysimeter에서 시험하였다. 연구포장은 경사율 17%를 가진 경사밭이며, 배추를 재배하였다. 완충식생대로 이용된 초종은 Rye(Secale cereale L.), Tallfescue(Festuca arundinacea Schreb) Orchardgrass(Dactylis glomerata L.)이다. 이들은 경사밭 아래 부분에 조성되었다. 호밀 식생대의 폭은 1m, 2m, 4m를 두었고, Orchard grass와 Tall fescue는 2m로 설정하였다. 완충식생대를 조성하기 위해 각 초종을 2005년 9월에 파종하였고, 배추는 2006년 6월에 정식하였다. 토양유실량, 유거수량, 영양물질 유출량의 측정은 2006년 6월부터 8월까지 수행하였다. 유거수량, 토양유실량 및 영양물질 유실량은 강우가 집중된 7월에 가장 높았다. 유거수를 감소시키는 완충식생대의 효과를 대조구와 비교해 볼 때, 2m로 폭이 같은 완충식생대에서 호밀은 3%, Orchard grass는 1%, Tall fescue는 2% 저감 효과가 있었다. 폭이 다른 호밀 완충식생대간의 비교에서, 1m는 1%, Rye 2m는 3%, Rye 4m는 13%의 저감효과가 나타나 Rye 4m의 효과가 가장 좋았다. 토양유실저감측면에서 대조구와 비교할 때, 2m 완충식생대 중 호밀식생대는 59%, Orchard grass 46%, Tall fescue 28% 토양유실을 줄이는 것으로 나타나 같은 폭에서 호밀식생대의 효과가 가장 좋았다. 폭이 다른 호밀 식생대의 비교에서 1m는 62%, 2m는 60%, 4m는 88%의 토양유실 저감 효과가 나타나, 4m의 효과가 토양유실을 저감하는데 가장 좋은 효과를 보였다. 한편, 유거수와 토양에서 발생한 N, P, K 유출 저감에서는 호밀 2m완충식생대에서 각각 54%, 16%, 11%, Orchard grass는 각각 22%, 24%, 22%를, Tall fescue는 10%, 7%, 12% 영양물질유출을 줄였다. 호밀완충식생 중에서 폭이 큰 4m에서 영양물질 유출저감효과가 가장 좋았다. 이 연구의 결과, 유거수량, 토양유실 저감효과는 호밀완충식생대가 다른 초종의 식생대보다 좋아서 유거수, 토양유실 그리고 영양물질 유출 저감을 위해 폭이 큰 호밀완충식생대의 설치가 효과적이라 생각된다.

• Tribology and Lubricants
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• 제34권5호
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• pp.183-190
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• 2018

Tilting pad journal bearing is widely used for steam turbines because of its excellent dynamic stability. As the turbine capacity increases, power loss in the bearings becomes a matter of concern. Power loss in tilting pad journal bearings can be reduced by increasing the bearing clearance and reducing the pad arc length. In this study, the tilting pad journal bearing is tested by changing the seal tooth clearance to verify the static characteristics of the bearing. Bearing power loss and bearing metal temperature are evaluated to compare the bearing's performance and reliability for several test cases. The test bearing is a tilting pad journal bearing with 300.62mm inner diameter and 120.00mm active length. The bearing power loss, its metal temperature, and oil film thickness are measured and evaluated based on the rotor's rotational speed, oil flow rate, and bearing load. Test results show that a tilting pad journal bearing with large seal tooth clearance has 40% lower power loss compared with a bearing with a small seal tooth clearance. As the seal tooth clearance is increased, the power loss of the tilting pad journal bearing decreases. However, with respect to the bearing metal temperatures, a detuning point is observed that makes the minimum bearing metal temperature. Moreover, as the seal tooth clearance is increased, the oil film thickness increases due to high viscosity.

• 분석과학
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• 제14권5호
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• pp.384-391
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• 2001

본 연구에서는 ESI-MS/MS를 이용해 혈액내에서 아실카르니틴과 아미노산을 신속하게 정량분석하는 방법을 개발하였다. 아실카르니틴과 아미노산은 3N butanolic hydrogen chloride를 사용하여 유도체화 과정을 거친 뒤 이중질량분석기로 분석하였다. 아실카르니틴은 precursor 85 ion scan을 사용하여 분석하였고, 아미노산들중 알라닌, 발린, 루신/이소루신, 메티오닌, 페닐알라닌, 타이로신, 아스파르트산, 글루탐산 등은 neutral loss 102 scan, 오르니틴과 시트롤린은 neutral loss 119 scan, 글리신은 neutral loss 56 scan, 아르기닌은 neutral loss 161 scan 그리고 아르기니노석시닉산은 product ion 459 scan을 사용하여 분석하였다. 이 방법은 일반적인 액체 크로마토그래피나 아미노산 분석기에 비해서 시료의 전처리가 비교적 간단하며, 높은 감도와 좋은 재현성을 보여주었다.