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Development of Air Foil Bearing for High Speed Generator (고속 발전기용 Air Foil Bearing 개발)

  • 염병용;박희용;백기영;이영섭;김명섭
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2001.11a
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    • pp.349-353
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    • 2001
  • An air foil bearing is developed for the high speed generator. The bearing is type of multi-leaf and is stable on 60,000RPM. The vibration level is 12um(p-p) and the highest temperature level is below 100C. The dynamic parameter of air foil bearing is acquired by experimental method using exciter. The air foil bearing is also good condition at test of real generator and load condition. The condition of foil is very good after 3,000cycle start-stop test. Therefore the air foil bearing is ideal for high speed, light weight and modem turbo-machinery.

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Optimal Guidance of Guided Projectile for Range Maximization with Boundary Condition on Fin Deployment Timing (조종날개 전개시점 경계조건을 포함한 지능화 탄약의 사거리 최대화 유도 기법)

  • Kim, Yongjae
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.68 no.1
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    • pp.129-139
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    • 2019
  • In order for a gun-launched guided projectile to glide to the maximum range, when to deploy the fin and start flight with guidance and control should be considered in range optimization process. This study suggests a solution to the optimal guidance problem for flight range maximization of the flight model of a guided projectile in vertical plane considering the aerodynamic properties. After converting the nonlinear Multi-Phase Optimal Control Problem to Two-Point Boundary Value Problem, the optimized guidance command and the best fin deployment timing are calculated by the proposed numerical method. The optimization results of the multiple flight rounds with various initial velocity and launch angle indicate that determining specific launch condition incorporated with the guidance scheme is of importance in terms of mechanical energy consumption.

Explanatory Study on Online Shopping Mall Startup by Young Entrepreneurs (청년자영업자의 온라인쇼핑몰 창업에 관한 탐색적 연구)

  • Kim, Jong Sung;Kim, Do Hyeon;Shin, Jee Mahn
    • Asia-Pacific Journal of Business Venturing and Entrepreneurship
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    • v.16 no.2
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    • pp.35-49
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    • 2021
  • The purpose of this study is by using the Grounded Theory method to examine the process of starting a business in an online shopping mall for young self-employed people with experience in using Company N's Partner Square (Gwangju), a startup infrastructure institution. In this study, in-depth interview survey data were used, and theoretical sampling method was used in the selection of study participants. After proceeding in the order of open coding, axis coding, and selective coding suggested by Strauss & Corbin, it was analyzed with a paradigm model. The main research results are as follows. First, even when parents were unaware about online shopping malls or had a negative mindset about it, but they had a positive mindset about their children's start-ups, it was found that their children tended to start online shopping mall businesses. However, if parents had a negative mindset about online shopping malls and about their children's start-up, then the child could not start an online shopping mall business. Second, it was found that the ability to use online shopping malls is important as a condition for entrepreneurship and achievement in online shopping malls for young people. In particular, Partner Square (Gwangju) was found to increase the ability to use online shopping malls and positively influence startups in online shopping malls. Third, it was found that young people have increased their self-esteem, discovering opportunities, and reinforcing their creativity, in addition to simply increasing their sales after starting the online shopping mall.

Evaluation of Long-Term Seasonal Predictability of Heatwave over South Korea Using PNU CGCM-WRF Chain (PNU CGCM-WRF Chain을 이용한 남한 지역 폭염 장기 계절 예측성 평가)

  • Kim, Young-Hyun;Kim, Eung-Sup;Choi, Myeong-Ju;Shim, Kyo-Moon;Ahn, Joong-Bae
    • Atmosphere
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    • v.29 no.5
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    • pp.671-687
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    • 2019
  • This study evaluates the long-term seasonal predictability of summer (June, July and August) heatwaves over South Korea using 30-year (1989~2018) Hindcast data of the Pusan National University Coupled General Circulation Model (PNU CGCM)-Weather Research and Forecasting (WRF) chain. Heatwave indices such as Number of Heatwave days (HWD), Heatwave Intensity (HWI) and Heatwave Warning (HWW) are used to explore the long-term seasonal predictability of heatwaves. The prediction skills for HWD, HWI, and HWW are evaluated in terms of the Temporal Correlation Coefficient (TCC), Root Mean Square Error (RMSE) and Skill Scores such as Heidke Skill Score (HSS) and Hit Rate (HR). The spatial distributions of daily maximum temperature simulated by WRF are similar overall to those simulated by NCEP-R2 and PNU CGCM. The WRF tends to underestimate the daily maximum temperature than observation because the lateral boundary condition of WRF is PNU CGCM. According to TCC, RMSE and Skill Score, the predictability of daily maximum temperature is higher in the predictions that start from the February and April initial condition. However, the PNU CGCM-WRF chain tends to overestimate HWD, HWI and HWW compared to observations. The TCCs for heatwave indices range from 0.02 to 0.31. The RMSE, HR and HSS values are in the range of 7.73 to 8.73, 0.01 to 0.09 and 0.34 to 0.39, respectively. In general, the prediction skill of the PNU CGCM-WRF chain for heatwave indices is highest in the predictions that start from the February and April initial condition and is lower in the predictions that start from January and March. According to TCC, RMSE and Skill Score, the predictability is more influenced by lead time than by the effects of topography and/or terrain feature because both HSS and HR varies in different leads over the whole region of South Korea.

Biohydrogen production using photosynthesis (광합성을 이용한 바이오수소 생산)

  • Sim, Sang-Jun;Kim, Jun-Pyo
    • 한국신재생에너지학회:학술대회논문집
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    • 2006.06a
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    • pp.478-481
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    • 2006
  • Energy is vital to global prosperity, yet dependence on fossil fuels as our primary energy source contributes to global climate change environmental degradation, and health problems. Hydrogen (H2) offers tremendous potential as a clean renewable energy currency. Hydrogen has the highest gravimetric energy density of any known fuel and is compatible with electrochemical and combustion processes for energy conversion without producing carbon-based emission that contribute to environmental pollution and climate change. Numerous methodologies have been developed for effective hydrogen production. Among them, the biological hydrogen production has gained attention, because hydrogen can be produced by cellular metabolismunder the presence of water and sunlight. The green alga Chlamydomonas reinhardtii is capable of sustained H2 photoproduction when grown under sulfur deprived condition. Under sulfur deprived conditions, PSII and photosynthetic O2 evolution are inactivated, resulting in shift from aerobic to anaerobic condition in the culture. After anaerobiosis, sulfur deprived algal cells induce a reversible hydrogenase and start to evolve H2 gas in the light. According to above principle, we investigated the effect of induction parameters such as cell age, cell density. light intensity, and sulfate concentration under sulfur deprived condition We also developed continuous hydrogen production system by sulfate re-addition under sulfur deprived condition.

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The Nature of start Businessman and Service Strategy (소래대교 건설공사 감리 사례)

  • 전성환
    • Journal of the Korean Professional Engineers Association
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    • v.34 no.2
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    • pp.42-45
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    • 2001
  • This Grand Sorae Bridge was built in order to lead to balanced reigoonal development by linking the 2nd Seoul - Inchon Highway to WestCiast Highway and it will contribute to develop the economy of the region and traffic of its vicinities by helping ease traffic in and around Inchon. It extends 470 meter across Sorae port by using 10 continuous steel box griders under benoto(all casing) system considering ultra soft ground condition of the site.

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Sensorless Vector Control of Induction Motor Using the Flux Estimator (자속추정기를 이용한 유도전동기 센서리스 벡터제어)

  • 김경서;조병국
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.52 no.2
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    • pp.87-92
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    • 2003
  • This paper presents a flux estimator for the sensorless vector control of induction motors. The proposed method utilize the combination of the voltage model based on stator equivalent model and the current model based on rotor equivalent model, which enables stable estimation of rotor flux in high speed region and in low speed region. The dynamic performance of proposed method is verified through the experiment. The experimental results show that motors ran easily start even under 150[%] load condition and operate continuously below 0.5[Hz].

Electric-optical Characteristics of LED Flat Light Source in Low Temperature Condition (저온환경에서의 LED 평판 조명의 전기광학적 특성에 대한 연구)

  • Choi, Dae Seub
    • Proceedings of the KIEE Conference
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    • 2015.07a
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    • pp.940-941
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    • 2015
  • LCD (liquid crystal display) industry is needed to goods of high reliability and is interested in products without harmful material. In this experiment, we made the LED backlight unit for Automotive-navigation. And for making this backlight unit we used to eight side emitting type white LEDs with 1W high power of the lumileds company. We could know that this backlight unit releases to 6500 nit in 14W power consumption and start up voltage time is under the15ms in the ambient temperature 20C.

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A Study on Thermal Cycle Characteristics of Solid Oxide Fuel Cell (고체 산화물 연료전지의 열사이클 따른 성능 열화 특성 연구)

  • Kim, Eung-Yong;Song, Rak-Hyun;Jeon, Kwang-Sun;Shin, Dong-Ryul;Kang, Thae-Khapp
    • Proceedings of the KIEE Conference
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    • 1998.07d
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    • pp.1312-1314
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    • 1998
  • SOFC system is often subject to thermal cycle condition during normal start/stop, shutdown, and emergence state. Under the thermal cycle condition of heating and cooling, the SOFC components expand or shrink, which produces thermal stress and thermal shock. The SOFC performance is degraded by the thermal factors. To protect SOFC system from the thermal degradation, the optimum thermal condition must be clarified. In this study, to examine the thermal cycle characteristics, we fabricated single cells of planar SOFC with an area of 5×5cm. The electrolyte and PEN were tested under thermal cycle conditions in the range of28C/min. After thermal cycle test. crack creation of the components were examined using ultraviolet apparatus. No crack in the electrolyte and PEN were observed. The single cell system with alumina frame were also tested under thermal cycle conditions of 2, 3, 4C/min. The single cell was fractured at the thermal cycle of 3 and 4C/min and the optimum condition of the thermal cycle to be found below 2C/min.

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The correlation between noise of outdoor unit and thermodynamic properties of cycle at transient condition of room air-conditioner (가정용 에어컨 실외기의 기동 소음 분석)

  • Son, Young-boo;Lee, Seung-mock;Ha, Jong-hun;Lee, Byeoung-chul
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2012.10a
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    • pp.577-582
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    • 2012
  • Recently, noise reduction of air-conditioner is one of the important design factors for high quality product. Especially, customer complaints arise due to noise problem of the outdoor unit. After the operation of air-conditioner start, noise level of outdoor unit is increased gradually and sometimes abnormal noise occurs until it reaches steady state condition. The aim of this paper is to investigate the relation between noise of outdoor unit and thermodynamic properties of cycle at transient condition of room air-conditioner. In order to find out the noise characteristics of outdoor unit, noise and vibration measurements are carried out. Also, the thermodynamic properties of compressor and heat exchanger are measured by using temperature and pressure sensors and experimental results are discussed. Finally, we find out the relation between noise and cycle properties at starting of room air-conditioner and the improvement method to reduce noise level is proposed.

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