• 전기학회논문지
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• 제60권6호
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• pp.1128-1133
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• 2011

In a wind farm, a large number of small wind turbine generators (WTGs) operate whilst a small number of a large generator do in a conventional power plant. To maintain high quality and reliability of electrical energy, a wind farm should have equal performance to a thermal power plant in the transient state as well as in the steady state. The wind farm shows similar performance to the conventional power plant in the steady state due to the advanced control technologies. However, it shows quite different characteristics during fault conditions in a grid, which gives significant effects on the operation of a wind farm and the power system stability. This paper presents an analysis of response of a wind farm during grid fault conditions. During fault conditions, each WTG might produce different frequency components in the voltage. The different frequency components result in the non-fundamental frequencies in the voltage and the current of a wind farm, which is called by "beats". This phenomenon requires considerable changes of control technologies of a WTG to improve the characteristics in the transient state such as a fault ride-through requirement of a wind farm. Moreover, it may cause difficulties in protection relays of a wind farm. This paper analyzes the response of a wind farm for various fault conditions using a PSCAD/EMTDC simulator.

• 한국소음진동공학회논문집
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• 제20권11호
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• pp.1025-1032
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• 2010

Gas turbine compressor blades used in a combined cycle power plant are possibly damaged and fractured during their operation. There are two possible causes of the failure of compressor blades; one is a defect of material quality which can be detected through some microscopic inspections for the fracture section, the other is high cycle fatigue problem caused by vibration and can be diagnosed by carrying out dynamic characteristics analysis for the blades. In this paper, in order to determine the cause of the failure of compressor blades in a combined cycle power plant, examination of the fracture section and the propagation mechanism of the crack via stress analysis are performed. Dynamic characteristics analysis via FRF estimation is also performed to identify the cause of failure.

• 신재생에너지
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• 제10권2호
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• pp.5-11
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• 2014

Squirrel cage induction motor is the main driving system of industrial field and familiar with its use in a large variety of applications. The structure and operating characteristics of induction generator is almost identical to induction motor, but the induction generator part is used restrictively from hydropower power and wind power development etc. Recently induction generator is commonly used for micro & small hydro power applications due to its simplicity, reliability, low cost and robustness. Input and output of induction motor has turned against at the induction generator operation. Rotation speed of induction generator is small faster than synchronous speed of induction motor. As output of induction machines increases with the increasement of speed, so loss is same. Actually, generator efficiency is lower than motor at this condition. If induction generator is connected with mechanical load such as increaser, total efficiency is decreased. Consequently the quality in compliance with an induction motor parameter applying like that in the generator is a possibility of having the error of some. In this paper, we analyzed that input, output, torque and efficiency of induction machine is different from each other above and below synchronous speed.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.477-478
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• 2006

Characteristics of InAs/GaAs quantum dot (QD) ridge laser diodes (LDs) are investigated for high-power $1.3\;{\mu}m$ applications. For QD ridge LDs with a $5-{\mu}m$-wide stripe and a 1-mm-long cavity, the emission wavelength of 1284.1 nm, the single-uncoated-facet CW output power as high as 90 mW, the external efficiency of 0.31 W/A and the threshold current density of $800\;mA/cm^2$ are obtained. The linewidth enhancement factor ($\alpha$-factor) is successfully measured to be between 0.4 and 0.6, which are about four times as small values with respect to conventional quantum well structure. It is possible that this result significantly reduce the filamentation of far-field profiles resulting in better beam quality for high power operation.

• Journal of Power Electronics
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• 제7권2호
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• pp.109-117
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• 2007

In this paper, a novel proposal for a utility-interactive three-phase soft commutation sinewave PWM power conditioner with an auxiliary active resonant DC-link snubber is developed for fuel cell and solar power generation systems. The prototype of this power conditioner consists of a PWM boost chopper cascaded three-phase power conditioner, a single two-switch auxiliary resonant DC-link snubber with two electrolytic capacitors incorporated into one leg of a three-phase V-connection inverter and a three-phase AC power source. The proposed cost-effective utility-interactive power conditioner implements a unique design and control system with a high-frequency soft switching sinewave PWM scheme for all system switches. The operating performance of the 10 kW experimental setup including waveform quality, EMI/RFI noises and actual efficiency characteristics of the proposed power conditioner are demonstrated on the basis of the measured data.

• 동아시아식생활학회지
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• 제23권6호
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• pp.760-767
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• 2013

This study investigated the quality of noodles containing different amounts of collagen powder. Noodles were prepared at ratios of 1, 3, 5 and 7% collagen power based on flour weight. The water binding capacity of the collagen powder was higher than that of flour. The rate of weight increase and volume increase of the noodles as well as the pH and turbidity of the soups were significantly increased with increasing amounts of collagen powder. The noodles showed decreased L and a values, and increased b values with increasing collagen powder in the flour composite. Hardness, springiness and chewiness of cooked noodles increased significantly with the increase in collagen powder content. cohesiveness and brittleness decreased with increasing amounts of added collagen powder. DPPH radical scavenging activity was improved significantly the addition of the collagen powder. Finally sensory evaluation results indicated that the noodles containing 1, 3% collagen powder had higher quality as compared to the other samples. Overall the results suggest that collagen powder is effective for improving the appearance and texture of noodles.

• 대한인간공학회지
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• 제31권6호
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• pp.793-800
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• 2012

Objective: This study investigated the problems that could be faced with when engineers try to improve the affective quality using the DMAIC model. Background: Affective quality is considered one of the most influential factors for the competitive power of consumer products and many engineers make effort to improve the affective quality. Since the Six Sigma process is effective and wide-used method for quality improvement, it can also be used to improve the affective quality. However six sigma tools cannot be directly used for affective quality because of the subjective and qualitative characteristics of the human affection. Method: Investigate the goals, processes and key factors of DMAIC model and find the difficulties to use six sigma tools for the affective quality. Results: Most of the problems arise from measuring and quantifying the human affective response level and understanding the relationship between the human affective factors. Conclusion: Both the protocol for measuring human affection and the monitoring system to find the affective response change for the product or service are required. Application: The results of this study could be helpful for the engineers not specialized in ergonomics to improve the affective quality in systematic approach.

• 조명전기설비학회논문지
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• 제21권7호
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• pp.68-74
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• 2007

본 논문은 카네이션의 생산성 향상을 위하여, 펄스 전원을 활용한 소형 저비용 방전관형 오존발생기를 설계 제작하였다. 펄스 전원의 출력전압, 원료 가스인 모의공기의 유량과 오존발생기의 작동 개수에 따른 방전관형 오존발생기의 방전 및 오존생성특성을 연구 검토하였다. 방전관형 오존발생기의 방전전압 및 전류는 펄스 전원의 출력전압에 비례하였다. 방전관형 오존발생기의 오존생성농도 및 오존발생량은 펄스 전원의 출력전압 및 오존발생기의 작동 개수에 비례하였다. 방전관형 오존발생기의 최대 오존생성농도 및 오존발생량으로 각각890[ppm] 및 59.7[mg/h]를 얻을 수 있었다. 방전관형 오존발생기를 카네이션 재배 하우스에 사용하였을 때, 카네이션 꽃대 길이와 굵기가 균일하여 품질 향상과 대기 토질 개선을 통한 카네이션 생산성 향상의 효과를 얻을 수 있었다.

• 한국정밀공학회지
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• 제19권7호
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• pp.106-115
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• 2002

Growth characteristics of micro carbon structures fabricated by laser-assisted chemical vapor deposition are studied. Argon ion laser and ethylene were used as the energy source and reaction gas, respectively, to grow micro carbon rod through pyrolytic decomposition of the reaction gas. Experiments were performed at various conditions to investigate the influence of process parameters on growth characteristics such as the diameter or growth rate of the micro carbon rod with respect to reaction gas pressure and incident laser power. Reaction gas pressure in experiments ranges from 200 to 600Torr and the incident laser power from 0.3 to 3.8W. For these conditions, the diameter of the rod increases linearly with respect to the laser power but is almost independent of the reaction gas pressure. Growth rate of the rod changes little with gas pressure when the laser power remains below IW. For a constant reaction gas pressure, the growth rate increase with Increasing laser power, but the rate of increase decreases gradually, implying that the chemical vapor deposition condition changes from a kinetically-limited regime to a mass-transport-limited regime. When the carbon rod was grown at near threshold laser power, a very smooth surface is obtained on the rod. By continuously moving the focusing lens in the direction of growth, a micro carbon rod with a diameter of 287${\mu}{\textrm}{m}$ and aspect ratio of 100 was fabricated..

• 조명전기설비학회논문지
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• 제30권2호
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• pp.85-92
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• 2016

The paper presents a method to assess system voltage sag performance considering sag durations as well as magnitudes. In general, voltage sag assessment for large power systems is performed only considering sag magnitudes at sensitive load points. However some equipment can be affected by certain sag durations. The duration of the voltage sag is depend on the time of fault current flow in the system. Therefore, the duration can be determined by analyzing the operating characteristic of the protection system. In this paper, an effective method to evaluate sag durations regarding the characteristics and failure rates of the protection system is described. The proposed method can be used to assess the long-term performance of the voltage sags in large power system.