• 대한기계학회논문집A
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• 제38권8호
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• pp.899-904
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• 2014

자유벌징에 있어서 성형 높이를 최대화하기 위하여 블랭크의 두께 분포를 최적화 하였으며, 등가정하중을 이용한 구조최적화법을 사용하였다. 두께형상은 부드러운 곡선으로 나타내기 위하여 베지어곡선을 사용하였고 제어점의 위치가 설계변수이며, 최대 변형률을 일정 값으로 제한하였다. 사용된 소재는 인코넬 718 이며 최적화된 두께분포로 가공된 블랭크를 이용한 자유벌징 시험을 수행하여 평판형 블랭크를 사용한 결과보다 22% 더 높은 성형 높이를 얻었다. 최적화결과에서 예측된 변형형상, 정점에서의 변형 경향, 두께분포가 실험에서 얻은 결과와 유사하여 최적화 과정의 유효성을 입증하였고, 최적화 결과가 실제 구현될 수 있음을 검증하였다.

• 전력전자학회논문지
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• 제7권5호
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• pp.472-481
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• 2002

본 논문은 SRG(Switched Reluctance Generator)의 제어를 위하여 순시자속을 이용하여 위치를 추정하고, 추정한 위치에 근거하여 출력전압을 제어하는 방법이 제안되었다. SRG를 제어하기 위해서는 정확한 회전자의 위치정보가 필수적이다. 이러한 위치정보는 일반적으로 엔코더나 레졸버와 같은 정밀한 위치센서로부터 얻어진다. 그러나, 전자기적 간섭(Electromagnetic Interference), 진동, 열, 습도 등의 열악한 환경으로 인하여 정확한 위치를 검출하는데 많은 문제점을 가지고 있다. 따라서 이러한 문제점을 극복하기 위하여 위치·속도센서 없는 SRG의 제어기가 요구되어 진다. 본 논문에서는 SRG를 위한 새로운 위치·속도의 실시간 추정방법이 제안되었다. 순시자속은 측정한 전압과 전류에 의해 계산한 것과 위치와 자속 프로파일로부터 회전자의 위치를 추정하였다. 출력전압은 PID 제어 알고리즘에 의해 일정 제어되었다. 제안된 방법은 시뮬레이션을 통하여 확인하였고, DSP를 적용하여 구현하였다. 실험을 통하여 제안된 방법은 부하가 변동하더라도 일정하게 출력전압을 유지하고, SRG 제어가 안정됨을 확인하였다.

• 한국산림과학회지
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• 제95권1호
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• pp.5-11
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• 2006

이 연구는 김해시 상동면 매리 산사태지의 발생특성을 밝히기 위한 일련의 연구로 본보에서는 구조물의 안정해석을 실시하였다. 옹벽 및 석축의 외적 안정성 검토 결과, II-D단면을 제외하고는 모두 불안정한 것으로 산정되어 구조물에 대한 안정 대책이 필요한 것으로 판단되었다. 또한, 불안정한 옹벽은 보강하고 여기에 배수공을 추가로 설치하여 안정을 도모할 필요가 있을 것으로 사료된다. 아울러 이 지역의 석축 구조물은 사면활동에 저항하기 위하여 석축 상부의 사면을 완화하여 상부로부터의 하중을 감소시키는 방법이 유용할 것으로 생각된다.

• Journal of Welding and Joining
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• 제28권2호
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• pp.84-90
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• 2010

Fillet welding accounts for about 80% of all constructing process of ship and ocean structure. T-joint is one of the typical shapes which are frequently reported to experience the fatigue damage when the marine structure meets the storm loads. The fatigue damage is affected by the magnitude of residual stresses on the weld. Recently, many shipping registers and design guidances have required that the fatigue strength assessment method should be compensated by the effect of the residual stress in case that the random loading or storm loading is applied to the marine vessels. This study suggests the computational procedure to analyze the residual stresses of T-joint specimen that is frequently reported to get damaged by the storm loading. Experiment by XRD as well as the 3-D computational welding model is presented in order to get the profile of residual stress. Throughout the comparison of experimental result with the computational result, the computational model was validated. Thereafter, characteristics of he residual stresses in the joint are discussed.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.110-110
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• 2011

The nanomechanical properties of fully lithiated and unlithiated silicon nanowire deposited on silicon substrate have been studied with atomic force microscopy. Silicon nanowires were synthesized using the vapor-liquid-solid process on stainless steel substrates using Au catalyst. Fully lithiated silicon nanowires were obtained by using the electrochemical method, followed by drop-casting on the silicon substrate. The roughness, derived from a line profile of the surface measured in contact mode atomic force microscopy, has a smaller value for lithiated silicon nanowire and a higher value for unlithiated silicon nanowire. Force spectroscopy was utilitzed to study the influence of lithiation on the tip-surface adhesion force. Lithiated silicon nanowire revealed a smaller value than that of the Si nanowire substrate by a factor of two, while the adhesion force of the silicon nanowire is similar to that of the silicon substrate. The Young's modulus obtained from the force-distance curve, also shows that the unlithiated silicon nanowire has a relatively higher value than lithiated silicon nanowire due to the elastically soft amorphous structures. The frictional forces acting on the tip sliding on the surface of lithiated and unlithiated silicon nanowire were obtained within the range of 0.5-4.0 Hz and 0.01-200 nN for velocity and load dependency, respectively. We explain the trend of adhesion and modulus in light of the materials properties of silicon and lithiated silicon. The results suggest a useful method for chemical identification of the lithiated region during the charging and discharging process.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2011년도 춘계학술발표대회 논문집
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• pp.127-132
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• 2011

Worldwide, the building energy simulation becomes inevitable step for predicting the energy consumption in building. In simulation process, the expertise is required for the accurate analysis results. In Korea, however, most of user use the inconsistent data with Korea circumstance. In this step, we need to construct the standard input data matched building in Korea. In this study, electricity consumption of apartments in Daejeon is analyzed. The yearly data of a apartment complexes of 2009 are analyzed as monthly, daily(week and weekend), timely, and completion year. With this result, we are able to predict the demand pattern of electricity in a house and make the schedule by demand pattern. The results of this study are followed. The averaged amount of electricity consumption in winter is higher than summer because of the high capacity of heating equipment. All of the house has electric base load from 0.26kWh to 0.5kWh. The average of the electricity consumption of month is shown as 326.7kWh. A week is seperated as 4 part such as week, weekend, Saturday and Sunday. During week, the average of timely electricity consumption is shown as 0.442kWh. The Saturday consumption is 0.453kWh. The Sunday is 0.461kWh.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.157-171
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• 2009

A 151 storey super high-rise building located in an area of reclaimed land constructed over soft marine clay in Songdo, Korea is currently under design. This paper describes the design process of the foundation system of the supertall tower, which is required to support the large building vertical and lateral loads and to restrain the horizontal displacement due to wind and seismic forces. The behaviour of the foundation system due to these loads and foundation stiffness influence the design of the building super structure, displacement of the tower, as well as the raft foundation design. Therefore, the design takes in account the interactions between soil, foundation and super structure, so as to achieve a safe and efficient building performance. The site lies entirely within an area of reclamation underlain by up to 20m of soft to firm marine silty clay, which overlies residual soil and a profile of weathered rock. The nature of the foundation rock materials are highly complex and are interpreted as possible roof pendant metamorphic rocks, which within about 50m from the surface have been affected by weathering which has reduced their strength. The presence of closely spaced joints, sheared and crushed zones within the rock has resulted in deeper areas of weathering of over 80m present within the building footprint. The foundation design process described includes the initial stages of geotechnical site characterization using the results of investigation boreholes and geotechnical parameter selection, and a series of detailed two- and three-dimensional numerical analysis for the Tower foundation comprising over 172 bored piles of varying length. The effect of the overall foundation stiffness and rotation under wind and seismic load is also discussed since the foundation rotation has a direct impact on the overall displacement of the tower.

• 한국추진공학회지
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• 제21권3호
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• pp.18-24
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• 2017

가스터빈엔진의 시동점화 조건 달성 및 시동가속을 위해서는 엔진에 적합한 시동기를 선정하여야 한다. 이를 위해서는 시동 크랭킹 과정의 공력저항을 예측하여 시동성능을 파악하여야한다. 본 논문에서는 기 개발엔진의 Coast down 시험을 통하여 획득된 엔진속도 프로파일 데이터를 바탕으로 엔진 주축에 인간되는 공력저항을 도출하고, 압축기 부하를 기준으로 한 스케일링을 통해 대상엔진의 공력저항을 모델링하였다. 이후, 공력저항 모델과 공기시동기(ATS)의 토크 성능선도를 엔진 시동모델에 적용함으로써, 엔진시동에 적합한 시동기를 선정하는 방법을 제시한다.

• 한국산학기술학회논문지
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• 제11권11호
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• pp.4529-4536
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• 2010

본 논문에서는 배전계통 모의장치와 태양광전원 모의장치, LabVIEW를 이용한 감시제어장치로 구성된 태양광전원 계통연계 시험장치를 제작하여, 태양광전원의 연계용량과 계통의 선로 구성특성, 역율(역율1, 지상/진상역율)의 3가지 Parameter에 대한 태양광전원의 정상상태 운용특성을 모의하였다. 즉, 태양광전원의 연계 운용이 배전계통(수용가)에 미치는 영향과 배전계통이 태양광전원에 미치는 영향을 분석하여, 태양광전원의 계통연계 운용 시에 발생 가능한 기술적인 사항을 검토하였다. 그리고 계통연계 시험장치의 실험 결과치를 분석하기 위하여, 태양광전원 대응형 전압강하 계산 알고리즘을 제안하여, 이론적인 값과 시험치를 비교하여 태양광전원의 정상상태 특성에 대한 시험결과의 유용성을 확인하였다.

• Wind and Structures
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• 제19권4호
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• pp.421-441
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• 2014

With the assistance of typhoon field data at aerial elevation level observed by meteorological satellites and wind velocity and direction records nearby the ground gathered in Guangzhou Weather Station between 1985 and 2001, some key wind field parameters under typhoon climate in Guangzhou region were calibrated based on Monte-Carlo stochastic algorithm and Meng's typhoon numerical model. By using Peak Over Threshold method (POT) and Generalized Pareto Distribution (GPD), Wind field characteristics during typhoons for various return periods in several typical engineering fields were predicted, showing that some distribution rules in relation to gradient height of atmosphere boundary layer, power-law component of wind profile, gust factor and extreme wind velocity at 1-3s time interval are obviously different from corresponding items in Chinese wind load Codes. In order to evaluate the influence of typhoon field parameters on long-span flexible bridges, 1:100 reduced-scale wind field of type B terrain was reillustrated under typhoon and normal conditions utilizing passive turbulence generators in TJ-3 wind tunnel, and wind-induced performance tests of aero-elastic model of long-span Guangzhou Xinguang arch bridge were carried out as well. Furthermore, aerodynamic admittance function about lattice cross section in mid-span arch lib under the condition of higher turbulence intensity of typhoon field was identified via using high-frequency force-measured balance. Based on identified aerodynamic admittance expressions, Wind-induced stochastic vibration of Xinguang arch bridge under typhoon and normal climates was calculated and compared, considering structural geometrical non-linearity, stochastic wind attack angle effects, etc. Thus, the aerodynamic response characteristics under typhoon and normal conditions can be illustrated and checked, which are of satisfactory response results for different oncoming wind velocities with resemblance to those wind tunnel testing data under the two types of climate modes.