• Journal of Electrical Engineering and Technology
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• 제10권3호
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• pp.1304-1310
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• 2015

In remote islands, due to expense of existing generation systems, installation of photovoltaic cells (PVs) and wind turbines has a chance of reducing generation costs. However, in island power systems, even short-term power fluctuations change the frequency of grids because of their small inertia constant. In order to compensate power fluctuations, the authors proposed the power consumption control of pumps which send water to tanks. The power control doesn’t affect water users’ convenience as long as tanks hold water. Based on experimental characteristics of a pump system, this paper shows methods to determine reference power consumption of the system with compensation for short-term PV fluctuations while satisfying water demand. One method uses a PI controller and the other method calculates reference power consumption from water flow reference. Simulations with a PV and a pump system are carried out to find optimum parameters and to compare the methods. Results show that both PI control method and water flow calculation method are useful for satisfying the water demand constraint. The water demand constraint has a little impact to suppression of the short-term power fluctuation in this condition.

• 대한토목학회논문집
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• 제3권2호
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• pp.97-107
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• 1983

비선형(非線型) 2차원조석(次元潮汐)모델의 경기만남부해역(京畿灣南部海域)에의 적용(適用)이 서술(敍述)되었다. 모델을 이용(利用)하여 만체계(灣體系)의 조류유동현상(潮流流動現像), 해저마찰력(海底摩擦力) 및 에너지소산(消散)에 대(對)한 초기평가(初期評價)를 할 수 있었다. 또한 모델에 의(依)한 수치실험(數値實驗)을 통(通)해 아산만접근수로(牙山灣接近水路)를 준설(浚渫)할 경우(境遇) 주태음반일주조(主太陰半日週潮)($M_2$)의 영향(影響) 및 해면(海面)에 작용(作用)하는 $10dyne/cm^2$의 균일정상풍(均一定常風)에 의(依)한 유동현상(流動現像)의 변화(變化)를 평가(評價)하였다. 초기결과(初期結果)들이 제시(提示)되었으며 토의(討議)되었다.

• Journal of Power Electronics
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• 제16권5호
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• pp.1743-1751
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• 2016

The increasing demand for high voltage DC grids resulting from the continuous installation of offshore wind farms in the North Sea has led to the concept of multi-terminal direct current (MTDC) grids, which face some challenges. Power (current) flow control is a challenge that must be addressed to realize a reliable operation of MTDC grids. This paper presents a reduced switch count topology of a current flow controller (CFC) for power flow and current limiting applications in MTDC grids. A simple control system based on hysteresis band current control is proposed for the CFC. The theory of operation and control of the CFC are demonstrated. The key features of the proposed controller, including cable current balancing, cable current limiting, and current nulling, are illustrated. An MTDC grid is simulated using MATLAB/SIMULINK software to evaluate the steady state and dynamic performance of the proposed CFC topology. Furthermore, a low power prototype is built for a CFC to experimentally validate its performance using rapid control prototyping. Simulation and experimental studies indicate the fast dynamic response and precise results of the proposed topology. Furthermore, the proposed controller offers a real solution for power flow challenges in MTDC grids.

• 한국항공우주학회지
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• 제30권5호
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• pp.56-61
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• 2002

평판 날개의 플러터에 대한 실험적 연구가 수행되었으며, 여러 가지 플러터 해석 방법들을 실험결과와 비교함으로써 검증하였다. 플러터 실험을 위한 날개 모델과 장치들이 아음속 풍동에 설치되었다. 시스템 식렬법을 이용하여 풍동 실험 데이터로부터 플러터 속도를 예측하였다. 날개 모델의 플러터 해석을 위해 MSC/NASTRAN, V-g방법, 근궤적법이 사용되었다. 해석으로 구한 플러터 속도와 실험으로부터 추정된 플러터 속도를 비교하였으며, 그 결과 잘 일치하였다. 본 연구의 날개 모델이 플러터 해석의 벤치마크 모델로 사용될 수 있을 것이다.

• Steel and Composite Structures
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• 제2권6호
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• pp.441-460
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• 2002

In the design of bridges, it is important to consider the thermal stresses induced by the non-linear temperature distribution as well as the variation of effective temperature in the bridge deck. To cope with this, design temperature profiles are provided by design codes, which are normally based on extensive research work. This paper presents the results of a comprehensive investigation on the thermal behaviour of bridges in Hong Kong with special emphasis on composite bridges. The temperature distribution in bridges depends primarily on the solar radiation, ambient air temperature and wind speed in the vicinity. Apart from data of the meteorological factors, good estimates of the thermal properties of material and the film coefficients are necessary for the prediction of temperature distribution. The design temperature profiles for various types of composite bridge deck with bituminous surfacing and concrete slab of different thicknesses are proposed. The factors affecting the design effective temperature are also reviewed and suitable values for Hong Kong are proposed. Results are compared with recommendations of the current local code. The method facilitates the development of site-specific temperature profiles for code documents, and it can also be applied to create zoning maps for temperature loading for large countries where there are great climatic differences.

• 설비공학논문집
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• 제29권3호
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• pp.134-141
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• 2017

The purpose of this study was to analyze physiological changes via a cold air reaction experiment to generate basic data that are useful for the development of an automobile active air conditioning system to prevent drowsiness. The $CO_2$ concentration causing drowsiness in vehicle operation was kept below a certain level. Air was blown to the driver's face by using an indoor air cooling apparatus. Sleepiness and the arousal state of the driver in cold wind were measured by physiological signals. It was evident in the EEG that alpha waves decreased and beta waves increased, caused by cold air stimulation. The ${\alpha}/{\beta}$ ratio was reduced by about 52.9% and an alert state confirmed. In the electrocardiogram analysis, the efficiency of cold air stimulation was confirmed by the mean heart rate interval change. The R-R interval had a delay time of about one minute compared to the EEG response. The findings confirmed an arousal effect from sleepiness due to cold air stimulation.

• 국제초고층학회논문집
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• 제1권4호
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• pp.271-281
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• 2012

Tianjin Goldin Finance 117 tower has an architectural height of 597 m, total of 117 stories, and the coronation of having the highest structural roof of all the buildings under construction in China. Structural height-width ratio is approximately 9.5, exceeding the existing regulation code significantly. In order to satisfy earthquake and wind-resisting requirements, a structure consisting of a perimeter frame composed of mega composite columns, mega braces and transfer trusses and reinforced concrete core containing composite steel plate wall is adopted. Complemented by some of the new requirements from the latest Chinese building seismic design codes, design of the super high-rise building in high-intensity seismic area exhibits a number of new features and solutions to professional requirements in response spectrum selection, overall stiffness control, material and component type selection, seismic performance based design, mega-column design, anti-collapse and stability analysis as well as elastic-plastic time-history analysis. Furthermore, under the prerequisite of economic viability and a series of technical requirements prescribed by the expert review panel for high-rise buildings exceeding code limits, the design manages to overcome various structural challenges and realizes the intentions of the architect and the client.

• 한국지진공학회논문집
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• 제20권2호
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• pp.125-134
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• 2016

In order to improve seismic safety of nuclear power plant (NPP) structures in high seismicity area, seismic isolation system can be adapted. In this study, friction pendulum system (FPS) is used as the seismic isolation system. According to Coulomb's friction theory, friction coefficient is constant regardless of bearing pressure and sliding velocity. However, friction coefficient under actual situation can be changed according to bearing pressure, sliding velocity and temperature. Seismic responses of friction pendulum system with constant friction and various velocity-dependent friction are compared. The velocity-dependent friction coefficients of FPS are varied between low-and fast-velocity friction coefficients according to sliding velocity. From the results of seismic analysis of FPS with various cases of friction coefficient, it can be observed that the yield force of FPS becomes larger as the fast-velocity friction coefficient becomes larger. Also, the displacement response of FPS becomes smaller as the fast-velocity coefficient becomes larger.

• Geomechanics and Engineering
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• 제7권4호
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• pp.459-475
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• 2014

In this study, a CPT-based p-y analysis method was proposed for the displacement analysis of laterally loaded piles. Key consideration was the continuous soil profiling capability of CPT and cone resistance profiles that do not require artificial assumption or simplification for input parameter selection. The focus is on the application into offshore mono-piles embedded in clays. The correlations of p-y function components to the effective cone resistance were proposed, which can fully utilize CPT measurements. A case example was selected from the literature and used to validate the proposed method. Various parametric studies were performed to examine the effectiveness of the proposed method and investigate the effect of property profile and its depth resolution on the p-y analysis. It was found that the calculation could be largely misleading if wrongly interpreted sub-layer condition or inappropriate resolution of input soil profile was involved in the analyses. It was also found that there is a significant influence depth that dominates overall load response of pile. The soil profile and properties within this depth range affect most significantly calculated load responses, confirming that the soil profile within this depth range should be identified in more detail.

• 동국한의학연구소논문집
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• 제5권
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• pp.15-31
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• 1996

The purpose of this study was to generalize the conception of chronic pelvic pain(CPP)through the literature of oriental medicine and occidental medicine. The results are obtained as follows. First, chronic pelvic pain(pain of more than 6 months duration) may include pain of gynecologic, gastroenterologic, urologic, neurologic, and musculoskeletal origin. In this study, the etiology of chronic pelvic pain may remain obscure and the relationship between certain types of pathology, such as endometriosis or adhesions, and the pain response may be inconsistent and often inexplicable. Second, the causes of CPP through the literature of oriental medicine were reviewed as pains due to a wind-pathogen, a cold, disorder of Qi, disorder of blood stasis, a improper diet, disorder of fluid, and deficiency type etc... And the charateristic pains were concerned with a aching pain, a heavy pain, a distending pain. a pain due to mass in the abdoman, a pain likes pulling etc... The degree and classification of charateristic pains in current of time were dependent on subjective factors. Third. in oriental medicine, it wasn't to be suggested concretely recognition of etiological factor in pain. But they recognised that facters were influenced by pain. For example, diretic peripheral demages were concerned with a blood stasis, a phlegm, a damp phlegm, heart, and the pains that were occurrenced by sevn emotions were concerned with a stagnancy of Qi or a stagnancy of liver-Qi.