• Journal of the Optical Society of Korea
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• 제8권4호
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• pp.156-162
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• 2004

The spectroscopic model is proposed to analyze the gain bandwidth of a fiber Raman amplifier (FRA) with a multiple wavelength pumping scheme based on Raman gain theory. The oscillatory lineshape, which is the analytic function to analyze Raman gain spectra, allows us to estimate the gain bandwidth of the FRA. Based on the proposed theoretical modeling, we design and analyze the characteristics of the FRA using the combined multiwavelength pumping sources. We achieved the extended gain bandwidth of the FRA over 80 nm with the small gain ripple less than 0.5 dB. Threshold pumping power and effective noise figure for the FRA can be also analyzed by using the proposed model, which is also applicable for versatile fibers with other doping materials. The proposed analysis method can be useful for the design of FRA with the multiwavelength pumping scheme.

• Current Optics and Photonics
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• 제5권2호
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• pp.180-185
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• 2021

A femtosecond-laser inscribed Yb:YAG surface channel waveguide (WG) laser with single-walled carbon nanotubes deposited on the top surface of the WG was passively Q-switched by evanescent field interaction. Q-switched operation of the 14-mm-long compact Yb:YAG WG laser was achieved near 1031 nm with two different pumping schemes (single- and double-pass pumping) with an output coupling transmission of 91%. The Q-switched pulse characteristics depending on the absorbed pump power were investigated for both pumping geometries and analyzed in detail based on theoretical modeling. The best performances (energy/pulse duration) for each configuration were 204.4 nJ/75 ns at a repetition rate of 1.87 MHz, and 201.1 nJ/81 ns at 1.75 MHz for single- and double-pass pumping, respectively.

• 한국광학회지
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• 제16권4호
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• pp.297-303
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• 2005

우리는 $^{87}Rb$ 원자의 $5S_{1/2}-5P_{3/2}-4D_{3/2,\;5/2}$ 전이선을 이용하여 레이저의 세기, 편광조합, 그리고 정렬상태에 따른 이중공명광펌핑(double resonance optical pumping; DROP) 스펙트럼을 조사하였다. $5P_{3/2}-4D_{5/2}$ 전이선에서 레이저의 세기에 따른 초미세 구조간의 DROP 신호의 변화가 크게 나타났고, 그 원인은 순환전이선의 낮은 광펌핑 효율 때문이었다. 두 레이저의 편광조합을 달리 했을 때 이중공명의 전이율이 변하고, 이러한 효과가DROP스펙트럼의 변화로 나타났다. 또한 두 레이저가 같은 방향으로 진행하는 경우와 반대 방향으로 진행하는 경우를 비교했을 때, 스펙트럼의 선폭은 각각 12.2 MHz 와 6.9 MHz로 측정되었다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제50권4호
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• pp.164-169
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• 2001

This paper deals with comparison of characteristics of continuous-sheet type low-Tc superconducting (LTS) power supply and discrete-sheet type LTS power supply. These characteristics have been analyzed through experiments. These power supplies consist of two exciters, a rotor, a stator, and a LTS load. A continuous-sheet type has a single continuous niobium (Nb) sheet attached to the inner surface of on the stator. In the case of discrete-sheet type, four separated Nb sheets are used. this experiment is using 1.81 mH LTS magnet load and maximum 30 A dc exciter current. A discrete-sheet type is expected to produce much better pumping rate than a continuous-sheet type. The experimental observations have been compared with the theoretical predictions. In this experiment, the maximum pumping-current has reached about 926 A.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 A
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• pp.337-339
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• 1998

This paper deals with the design and fabrication of a novel superconducting power supply system, and characteristics have been analyzed through experiments. Superconducting power supply consists of rotating and static parts, and superconducting magnet. In this experiment, the current-pumping characteristics have been analyzed with superconducting sheets placed in parallel within the static part of the machine. In addition, in order to observe the 3-dimensional flux distribution in the superconducting sheet, several hall-sensors were placed in it. With the flux distribution acquired, the effect of the flux on the superconducting sheet during the process of current pumping have been analyzed. Also, general operational characteristics of the superconducting power supply system have been investigated on the basis of the current and voltage data and magnetic field values acquired through the experiments. In this experiment, maximum pumping current has been achieved to about 1280 amps.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.567_568
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• 2009

In the past, pumping-storage generator pumped the water from the lower part storage to the upper part storage during the base load periods. And, it generated during the peak load or when other generator was outage. However, pumping-storage generator will operate different ways in the competitive power markets. It will pump during lower price periods and generate at higher price periods. This paper presents economic analysis of pumping-storage generator using price (or SMP) duration curve.

• 유공압시스템학회논문집
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• 제6권2호
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• pp.7-13
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• 2009

This study specifies the flow control characteristics of a flow control valve(FCV) in a submerged cargo pumping system through experiments and simulations. In the experiments, the functions of the major components of the FCV in relation to the FCV's flow characteristics are presented clearly. Through the simulations, it is shown that the simulation program suggested in this study can be utilized for the design of the FCV.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1697-1702
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• 2004

The waterhammer has recently become more important because the pumping stations were big and the systems conveying the fluid through the large and long transmission pipelines were complex. When the pumps are started or stopped for the operation or tripped due to the power failure. the hydraulic transients occur as a result of the sudden change in velocity. In this paper, the field tests on the waterhammer by the startup, stoppage, and power failure of a centrifugal pump were carried out for Yongma transmission pumping station in Seoul. The experimental results were compared with that of the numerical calculations. in which results the procedure of controlled pump normal shut-down and the two-step closing mode of controlling the ball valve for pump emergency stop are proposed to reduce the pressure surge.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 1999년도 추계 학술발표회 논문집
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• pp.149-154
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• 1999

This paper describes a passive safety injection system with free piston Stirling pump working withabundant decay heat in the nuclear reactor during the hypothetical accident. The water column in the tube assembly connected from the hot chamber to the cold chamber in the pump oscillates periodically due to thermal volume changes of non-condensable gas in each chamber. The oscillating pressure in the water column is converted into the pumping power with a suction-and-bleed type valve assembly. In this paper a dynamic model describing the frequency of oscillation and pumping pressure is developed. It was found that the pumping pressure is a function of the temperature difference between the chambers. Also, the frequency oscillation depends on the length of the tube with water column.

• 한국자동차공학회논문집
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• 제14권3호
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• pp.119-124
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• 2006

This paper deals with energy-saving effort in the hydraulic power steering system. Commonly, the hydraulic power steering systems are used for passenger cars and the reduction of pumping loss under non-steering condition is important to improve fuel economy. Experiments and simulations are performed simultaneously to examine the main factors to reduce the pumping loss-pressure loss and flow rate of the power steering systems. Fuel economy effect of the optimal design of power steering system is verified by vehicle test - more than 1% fuel consuming reduction is attained.