• Geomechanics and Engineering
• /
• 제20권6호
• /
• pp.547-556
• /
• 2020

An understanding of the influence of MR (Magmatic Rock) thickness on the surrounding rock behaviors is essential for the prevention and management of dynamic disasters in coal mining. In this study, we used FLC3D to study the breaking and instability laws of surrounding rock with different MR thicknesses in terms of strata movement, stress and energy. The mechanism of dynamic disasters was revealed. The results show that the thicker the MR is, (1) the smaller the subsidence of the overlying strata is, but the subsidence span of the overlying strata become wider, and the corresponding displacement deformation value of the basin edge become smaller. (2) the slower the growth rate of abutment pressure in front of the working face is, but the peak value is smaller, and the influence range is larger. The peak value decreases rapidly after the breaking, and the stress concentration coefficient is maintained at about 1.31. (3) the slower the peak energy in front of coal wall, but the range of energy concentration increases (isoline "O" type energy circle). Finally, a case study was conducted to verify the disaster-causing mechanism. We anticipate that the research findings presented herein can assist in the control of dynamic hazards.

• 조명전기설비학회논문지
• /
• 제23권9호
• /
• pp.55-61
• /
• 2009

본 논문에서는 구역전기사업자를 구성하는데 적용하기 위해, 기존의 최적화 기법인 Discrete Particle Swarm Optimization (DPSO) 알고리즘을 개량한 Phasor DPSO (PDPSO) 알고리즘을 새롭게 제시한다. 구역전기사업자는 전력구입 뿐만 아니라 전력판매도 가능하고, 미리 계약한 수용가의 전력부하에게 전력을 공급할 의무가 있다. 하나의 배전계통에 다수의 구역전기사업자가 존재할 경우, 해당 배전계통 내의 모든 수용가에게 최소의 운영비용으로 전력을 공급하기 위해서는 다수 구역전기사업자 간에 구성형태를 조정할 필요가 있다. 이에 적용할 최적화 기법으로 본 논문은 PDPSO 알고리즘을 제안하며, 제안된 알고리즘의 각 개체는 기존의 다변수 벡터 대신 크기와 위상각으로 이루어진 다변수 페이저 값을 갖는다.

• 물과 미래
• /
• 제7권2호
• /
• pp.83-91
• /
• 1974

Fill Type Dam에 있어서 일반적으로 축조재료는 경제성을 감안하여 Dam Site 부근에서 구해야하므로 Core 용재료로서는 차수성의 문제만 해결된다면 마시토도 사용가능할 것이라는 전제하에 본문에서는 마사토를 단독 또는 혼합재료로서 각종시험을 실시하여 사용가능성 여부를 검토하고 기사용범위를 정함으로써 앞으로의 사용자들에게 편의를 제공코저 한다.

• Nuclear Engineering and Technology
• /
• 제41권7호
• /
• pp.969-978
• /
• 2009

The ASSERT-PV subchannel code developed by AECL has been applied as a design-assist tool to the advanced $CANDU^{(R)1}$ reactor fuel bundle. Based primarily on the $CANFLEX^{(R)2}$ fuel bundle, several geometry changes (such as element sizes and pitch-circle diameters of various element rings) were examined to optimize the dryout power and pressure-drop performances of the new fuel bundle. An experiment was performed to obtain dryout power measurements for verification of the ASSERT-PV code predictions. It was carried out using an electrically heated, Refrigerant-134a cooled, fuel bundle string simulator. The axial power profile of the simulator was uniform, while the radial power profile of the element rings was varied simulating profiles in bundles with various fuel compositions and burn-ups. Dryout power measurements are predicted closely using the ASSERT-PV code, particularly at low flows and low pressures, but are overpredicted at high flows and high pressures. The majority of data shows that dryout powers are underpredicted at low inlet-fluid temperatures but overpredicted at high inlet-fluid temperatures.

• 에너지공학
• /
• 제8권2호
• /
• pp.224-232
• /
• 1999

캡슐형 잠열재를 이용한 열저장 시스템은 바닥 난방 및 건물 난방에서 매우 효과적인 시스템이다. 이러한 시스템 개발에 필수적인 요소가 열유동 매체가 순환하는 파이프 주변의 캡슐내 온도 분포와 열유동 매체의 유량 등이다. 그러므로 본 연구에서는 3차원 비정상 상태에서 Navier-Stokes 방정식, 난류모델을 비롯한 스칼라 보존 방정식을 적용하여 캡슐 블록의 온도 분포 및 파이프 내의 유동장 해석을 수행하였다. 또한 본 연구와 같이 계산 영역이 특별한 기하학적 현상을 형상(circle+square)인 문제 해결하는데 적용할 수 있는 새로운 격자 생성 기술(MBFGE/CCM)을 개발하였다. 격자계는 파이프에서 원형 격자를 이용하였고, 캡슐 블록에서 사각 격자를 이용하여 다중격자와 미세격자를 결합하여 사용하였다. 본 연구의 목적은 컴퓨터를 이용한 수치해석적 방법을 미세 캡슐을 이용한 축열보드에 적용하여 2종류의 열경계 상태에 대하여 속도와 온도분포를 계산하여 비교분석을 하는 것이다. 온도는 축열 보드의 한 쪽면은 대류면이고 다른 한쪽면은 단열면인 경우(Case 2)보다 양면 모두 단열인 경우(Case 1)일 때 더 높게 상승하였다. 온수 파이프 중심선인 Y=0 에 가까운 영역에서 Case 1과 Case 2사이에 축열 보드 내에서 온도 차이는 확연하게 나타났다. 향후 수치해석의 정확도를 높이고 축열 보드의 열전달 현상을 보다 정확히 계산하기 위해서는 위치 및 시간에 따른 정밀한 온도 측정값이 필요하고 특히 잠열재인 미세 캡슐이 상변화를 하므로 온도 변화에 따른 물질의 비열(C$_{p}$)과 열전달율(λ)을 고려한 방정식이 요구된다.

• Structural Engineering and Mechanics
• /
• 제86권5호
• /
• pp.647-661
• /
• 2023

It is recognized that the installation of energy dissipation devices, such as the tuned mass damper (TMD), decreases the dynamic response of structures, however, the best parameters of each device persist hard to determine. Unlike many works that perform only a deterministic optimization, this work proposes a complete methodology to minimize the dynamic response of footbridges by optimizing the parameters of multiple tuned mass dampers (MTMD) taking into account uncertainties present in the parameters of the structure and also of the human excitation. For application purposes, a steel footbridge, based on a real structure, is studied. Three different scenarios for the MTMD are simulated. The proposed robust optimization problem is solved via the Circle-Inspired Optimization Algorithm (CIOA), a novel and efficient metaheuristic algorithm recently developed by the authors. The objective function is to minimize the mean maximum vertical displacement of the footbridge, whereas the design variables are the stiffness and damping constants of the MTMD. The results showed the excellent capacity of the proposed methodology, reducing the mean maximum vertical displacement by more than 36% and in a computational time about 9% less than using a classical genetic algorithm. The results obtained by the proposed methodology are also compared with results obtained through traditional TMD design methods, showing again the best performance of the proposed optimization method. Finally, an analysis of the maximum vertical acceleration showed a reduction of more than 91% for the three scenarios, leading the footbridge to acceleration values below the recommended comfort limits. Hence, the proposed methodology could be employed to optimize MTMD, improving the design of footbridges.

• 한국태양에너지학회:학술대회논문집
• /
• 한국태양에너지학회 2011년도 추계학술발표대회 논문집
• /
• pp.87-92
• /
• 2011

The heat from PV modules should be removed for better electrical performance, and can be converted into useful thermal energy. A photovoltaic-thermal(PVT)module is a combination of PV module with a solar thermal collector which forms one device that converts solar radiation into electricity and heat simultaneously. The performance of the PV/Thermal combined collector module is directly influenced by solar radiation that also has an effect on PV module temperature. It is also has believe that the energy performance of PV/T collector is related to absorber design as well as PV module temperature. The existing study has been paid to the PV/Thermal combined collector module with circle tube absorbers. The aim of this study is to analyze the experimental performance of the PV/Thermal combined collector rectangular tube absorbers according to solar radiation. The experimental result show that the average thermal and electrical efficiencies of the PVT collector were 43% and14.81% respectively. Solar radiation is one of the most influential factors to determine the energy performance of PVT collector, but from a certain level of solar radiation the PVT collector receives on, its efficiencies began to decrease.

• 대한한의학원전학회지
• /
• 제23권1호
• /
• pp.101-114
• /
• 2010

In the perspective of the correspondence of heaven and man[天人相應], people live through Gi of heaven and earth[天地之氣], and the human body which is a small universe[小宇宙] itself receives influence while sympathizing with the Gi and heaven[天氣]. So with unexpected incident of the Eum and Yang, four season[陰陽四時], ups and downs of warmth of cold and chilliness of warm[寒熱溫涼] differs, and the position of Gi of human[人氣] changes, regimen and application of acupuncture, and images[象] of the pulse changes. In "Maekyojeongmiron(脈要精微論)", ups and downs of Eum and Yang changes by four season[四時], and correspondence of ups and downs of pulse law is explained with compass, carpenter's square, the beam of balance and the weight of balance[規矩權衡]. Compass[規] is a measure of instrument that can draw a circle, like regulating the measure and differing the center of the circle and diameter and drawing a circle, compass is a image of Gi of Yang[陽氣] that was staying deep inside the body in winter stretching out by big fault[太過不及] of year and energy[元氣] of human in spring. Carpenter's square[矩] is a instrument that draws direction, which is a image of Gi of Yang flourishing in summer and when it gets highly flourished, again the Gi of Eum[陰氣] comes alive and falls. The beam of balance[衡] is a scale, like a scale that tilts at once when one side is slightly heavy, the beam of balance is a image Gi of yang that is fully flourished in summer and about to descent again, which is just about to fall but not going down yet. The weight of balance [權] is a image of gi of yang which as descent to the bottom and staying in the deepest place. compass, carpenter's square, the beam of balance and the weight of balance is not a direct pulse image[脈象], but standard image of pulse of pulse corresponding to the Gi of human[人氣] that changes by four season, and the explanation includes the pulse image of four season like the taut, full, floating, deeply gather[弦鉤浮營] of "Okgijinjangron(玉機眞藏論)" or taut, full, skip, float, deep [弦鉤代毛石] of "Pyeong-ingisangron(平人氣象論)". So with compass, carpenter's square, the beam of balance and the weight of balance, can judge is human correspond in Eum and Yang, four seasons, this is importantly used in examination of pulse[診脈] with existence and nonexistence, and prognosis of illness.

• 한국지반신소재학회논문집
• /
• 제20권4호
• /
• pp.73-84
• /
• 2021

최근 지구온난화에 따른 이상 기후 현상으로 세계적으로 환경 문제에 관한 관심이 높아지고 있다. 기후변화에 적극적으로 대응하기 위해 전 지구적인 노력이 이어지고 있으나, 여전히 화석연료의 의존도는 매우 높다. 특히, 북극권은 막대한 양의 화석연료와 광물자원이 매장되어 있어 개발과 건설 사업이 활발히 추진되고 있다. 북극권 자원(석유·가스자원) 개발 사업의 참여 및 협력은 우리나라 에너지·자원 공급의 대안 중 하나라 할 수 있다. 북극권 자원 개발은 극한 기후에 따른 열악한 개발 환경과 기술적 한계, 자원 개발에 따른 환경 문제, 사회적 영향 등 일반적인 자원 개발과 비교해 사전에 면밀한 검토가 요구되고 있다. 본 논문에서는 북극권 자원 개발 및 건설 활동 추진을 위해 북극해 연안 국가들의 기후변화 대응 법규 및 지침을 고찰하였다. 또한, 북극권 자원 개발 사업을 위해 필요한 영구 동토층의 지반 안정화 기술, 극한의 기후 조건에 작동하고 자원 개발의 효율성을 높일 수 있는 기술 사례 등을 조사하고 분석하였다. 본 연구의 조사·분석 결과는 자원 개발 사업의 성공적 추진과 운영을 좌우하는 새로운 리스크 요인에 대응하는 전략수립 등에 활용될 것으로 기대한다.

• Journal of Electrical Engineering and Technology
• /
• 제12권5호
• /
• pp.1991-2000
• /
• 2017

This paper presents a compensative microstepping based position control with passive nonlinear adaptive observer for permanent magnet stepper motor. Due to the resistance uncertainties, a position error exists in the steady-state, and a ripple of position error appears during operation. The compensative microstepping is proposed to remedy this problem. The nonlinear controller guarantees the desired currents. The passive nonlinear adaptive observer is designed to estimate the phase resistances and the velocity. The closed-loop stability is proven using input to state stability. Simulation results show that the position error in the steady-state is removed by the proposed method if the persistent excitation conditions are satisfied. Furthermore, the position ripple is reduced, and the Lissajou curve of the phase currents is a circle.