상호영향을 고려한 조류발전용 터빈의 배치에 따른 수치해석적 성능 연구

이정기 한국해양대학교 대학원 2016 국내박사

There are plenty of renewable energies in the ocean. Among the renewable energies, tidal energy is the reliable and unlimited resource since the tides are caused by gravitational force exerted by the moon and the sun. In order to utilize tidal energy, many companies have been developed various turbine systems which generally consisted of horizontal-axis turbine(HAT) and vertical-axis turbine(VAT) and developed systems have been performed field test for evaluation of turbine efficiency and grid connection. Tidal farm have multi-arrayed turbine systems for utilizing tidal stream energy. It is also required that each unit has to be deployed in order to avoid hydrodynamic interference between turbines and environmental effects. For horizontal-axis turbine(HAT) farm, the European Marine Energy Centre(EMEC) proposed guidelines that turbines must be spaced far apart, but there are no regulation and suggestion for vertical-axis turbine(VAT). Moreover performances of adjacent VATs are able to be increased or decreased, so that it is important to find suitable VATs arrangement. The present paper deals with the numerical study on performance vertical-axis turbine system as arrangement considering interaction using CFD. All numerical study was performed using FLUENT which was based on Reynolds averaged Navier-Stokes(RANS) equations and contents of this study were consist of four parts. For the study of first, hydrodynamic aspects on three-dimensional effects were investigated for VAT. Performance of VAT can be evaluated to convenient 2-D calculation for simple geometry but there are some discrepancy between experiment and 2-D results. In this respect, it is important to investigate the differences of flow characteristics between 2-D and 3-D. Numerical approach was made to reveal the differences of flow physics between 2-D estimation and rigorous 3-D simulation. It was shown that the 3-D effects were dominant mainly due to the variation of tip vortices around the tip region of rotor blade, causing the loss of lift for steadily translating hydrofoil and the reduction of torque for rotating turbine blade. Due to the 3-D effect, efficiency of 3-D turbine had discrepancy about 16% than 2-D efficiency on TSR=3. For the study of second, numerical calculations were performed to investigate interactions between adjacent two turbines in terms of rotational direction, distance between turbines, diameter. For VATs, it has advantage that each turbine rotates counter-clockwise and clockwise direction, its power coefficient was higher about 9.2% than two times of single turbines' and such improvement caused by increasing velocity between turbines. Performance change were almost disappear that each turbine were spaced 15times of turbine diameter apart. On the other hand, for adjacent HATs, it doesn't have advantage and efficiency was decreased just about 4% than two times of single HAT on high TSR. For the study of third, non-uniform inflow characteristics and turbine performance on the flow condition were investigated. Thermal and nuclear power plants on shore commonly use the sea water for cooling facility. Discharged cooling water has the high kinematic energy potential due to amount of water flux. Discharged channel can be assumed to a kind of confined water and flow characteristics around its inlet was similar with jet flow due to flux about 50ton per second. In this respect, numerical analyses were made to investigate for turbine performance on the non-uniform inflow condition in terms of turbine diameter to inlet size, axial distance, single and dual inlet. Basically, Performance of VAT operated on the non-uniform condition was decreased 15% compared with uniform condition. For the single inlet with HAT and VAT, the mean power coefficient appeared to be gradually decreased with increasing distance, and maximum power was obtained when the turbine diameter was same with the inlet diameter. For the dual inlet with VATs, better performance was obtained, compared with single inlet, due to turbine interaction when the turbine rotated clockwise-counterclockwise. For the study of the last, performance of hextuple VATs according to various arrangements was investigated. It is reasonable that plenty of turbine systems are able to deploy in the ocean, but numerical calculations were performed to investigate turbine performance for only six VATs, the arrangement was included single-type and canard-types. Canard-types were consisted of Dual, Triple, Hextuple. Numerical calculations were performed to compare with efficiency and power for single and Canard-types. For the single-type, performance was almost same with single turbines'. For the Dual, Triple, Hextuple, performances were increased about 13, 16, 18 percent each compared with single turbines'. Velocity deficits of far wake were compared for each types, velocity recovery of canard-types was slower than single-type. It means that longitudinal distance of canard-types for maximum power was required more than single-type. To find out the best arrangement in terms of total power and power per unit, two-rows non-staggered and staggered arrangements were considered with respect to various scenarios for three sites. Among the canard-types, Hextuple was generally the best arrangement in aspect of total power and power per unit for scenarios, but dual and triple were mostly useful for flexible arrangements. Finally, hexagonal staggered dual and triple arrangements utilizing VATs were proposed.

NATM 터널 일방향 역굴착에 따른 터널거동 및 안정성에 관한 연구

노수동 부경대학교 산업대학원 2008 국내석사

In a tunnel excavation work, the inside of tunnel is excavated by a bidirectional excavation using a ground stability and longitudinal arching effect of a tunnel but recently an unidirectional excavation is tried to reduce a public grievance and promote effective excavation. But construction cases and study products about the unidirectional excavation is insufficient. Therefore this research investigated theoretically a stability of the unidirectional inverse excavation. As a result of the three dimensional numerical analysis in the unidirectional inverse excavation and bidirectional excavation, a crown settlement is similar in the two conditions that is caused by a ground reinforcement effect using an umbrella arch method. A bending compressive stress of the shotcrete and an axial force of the rock bolt was shown secure a tunnel stability because a stress of the shotcrete and rock bolt is within allowable value in all two methods. An infinitesimal ahead displacement of portal slopes that is in the limits of stability in general is generated by a tunnel excavation in all two methods . In this research, a noise reduction effect of about 15dB in the unidirectional inverse excavation process shows less than those of bidirectional method.

원심모형실험과 현장계측에 의한 원형수직구의 3차원 주동토압 분석

김경열 연세대학교 대학원 2013 국내박사

현재 국내의 토사지반에 설치하는 원형수직구 설계에 있어서 벽체에 작용하는 토압은 Rankine 토압이 주로 적용되고 있다. 그러나, 원형단면의 수직구에 작용하는 토압은 응력이완에 따른 벽체의 변위발생과 3차원 아칭효과로 인하여 평면변형률 조건의 2차원 Rankine 토압 보다는 작은 토압이 작용하게 된다. 따라서, 본 연구에서는 3차원 아칭효과를 고려한 원형수직구의 주동토압을 분석하고자 토사지반에 설치된 원형수직구를 대상으로 원심모형실험과 현장실증실험을 수행하였으며, 그 결과를 기존 이론식과 비교분석하였다.

편측성구순구개열 환자를 대상으로 한 술전비치조정형장치 치료의 효과 : 2차원적 분석과 3차원적 분석 비교

박은우 서울대학교 치의학대학원 2011 국내석사

Numerical investigation of the insulation structure and pressure effect on the liquid hydrogen storage tank insulation performance

주현우 중앙대학교 대학원 2024 국내석사

Hydrogen energy is an efficient, environmentally friendly, and potentially excellent clean energy source. However, it is limited by technical limitations in storage, which prevents hydrogen energy from being widely applied. This study establishes a three-dimensional model of the liquid hydrogen tank insulation layer. It investigates the effect of vapor-cooled shield (VCS) structure and insulation pressure on insulation performance to find a solution for improving hydrogen energy storage. We established five models with four VCS tubes, ranging in diameter from 4 mm to 12 mm, as well as five models with a diameter of 12 mm and tube numbers ranging from two to eight. We also analyzed the insulation performance at the insulation pressure of 10-5 Pa, 10-3 Pa, 0.1 Pa, 1 Pa, and 10 Pa. By comparing these cases, it is possible to derive a trend for the optimal design of VCS structures and the best range of insulation pressures for maintenance. The practical implications of the research are clear. Under the low insulation pressure condition (10-5 Pa), increasing the VCS diameter from 4 mm to 12 mm expands the heat transfer area between the VCS and multi-layer insulation (MLI), improving the insulation performance by 32.04%. Similarly, increasing the number of VCS tubes from 2 to 8 enhances the insulation performance by 49.14%. However, as the insulation pressure increases, the insulation performance weakens. Particularly, when the insulation pressure exceeds 10-3 Pa, the effect of VCS decreases, and the heat flux through the insulation increases sharply. Therefore, it is advisable to maintain the insulation pressure below 10-3 Pa to ensure the insulation performance. These findings provide valuable insights for the optimal design and maintenance of VCS structures, contributing to improving hydrogen energy storage. 수소에너지는 효율적이고 친환경적이며 잠재력이 뛰어난 청정 에너지원이다. 하지만 저장 기술의 한계로 인해 수소 에너지가 널리 사용되지 못하고 있다. 그러므로 본 연구에서는 액화 수소 저장 탱크 단열층의 3차원 모델을 구축하여 VCS 구조와 단열층 압력이 단열 성능에 미치는 영향을 조사하여 수소 에너지 저장 개선 방안을 연구했다. VCS tube 개수가 4개일 때 직경이 4 mm에서 12 mm까지인 5개 모델과 tube 직경이 12 mm일 때 개수가 2개에서 8개까지인 5개 모델을 구축했으며, 단열층 압력이 각각 10-5 Pa, 10-3 Pa, 0.1 Pa, 1 Pa, 10 Pa의 경우 단열층의 단열 성능을 분석했다. 이러한 case를 비교함으로써 VCS 구조의 최적 설계 추세와 단열층 압력의 최적 유지 범위를 도출할 수 있다. 낮은 단열층 압력 조건(10-5 Pa)에서 VCS tube 직경을 4 mm에서 12 mm로 늘리면 VCS와 MLI 사이의 열전달 면적이 넓어져 단열 성능이 32.04% 향상된다. 또한 VCS tube 개수를 2개에서 8개로 늘리면 단열 성능이 49.14% 향상된다. 하지만 단열층 압력이 증가할 경우 단열층의 단열 성능은 오히려 약화한다. 특히 단열층 압력이 10-3 Pa를 초과하면 VCS의 효과가 감소하고 침입 heat flux가 급격히 증가한다. 따라서 단열 성능을 보장하기 위해 단열층 압력을 10-3 Pa 이하로 유지하는 것이 좋다. 이러한 연구 결과는 VCS 구조의 최적 설계 및 단열층 최적 유지 압력을 파악하기 위한 중요한 참고가 될 수 있으며 수소 에너지 저장 기술의 개선에 도움이 된다.

Efficient Three-Dimensional Inversion of Magnetotelluric Data Using Approximate Sensitivities and Its Application to Field Data

한누리 서울대학교 대학원 2009 국내박사

보강형 자립식 흙막이벽체의 수평변위 감소효과에 관한 연구

최웅희 연세대학교 공학대학원 2013 국내석사

입체표현을 중심으로 한 아동미술교육 프로그램 연구 : 6〜9세 아동을 대상으로

이해윤 수원대학교 2017 국내석사

The reality of art education for children is that there are not enough educational program and environment capable of fostering the divergent thinking that helps children to think and express freely. The ability to seek and discover answers by themselves instead of passively waiting for the answer to or the direction of a problem is one of the most basic and important skills that the school must teach. This is also emphasized in art activities in order to shape up this skill. It is also important to develop this skill into a comprehensive formative activity based on formative elements and principles and diversify various formative characteristics and the characteristics of themes to let children explore many different subjects instead of setting up a framework limiting the boundaries of a certain area. Especially, the three-dimensional modeling, unlike two-dimensional modeling, induces children to immerse themselves into the modeling through the diversity of materials and by arousing great interest and strong curiosity to achieve educational effect. This study suggests a teaching plan for children’s art education centering on three-dimensional expression based on the results obtained from children at 6-9 years of age who have continuously been participating in an art course for children for at least 36 months. Prior to this, for the understanding of the art education for children, this study examined the concept of art education for children, the concept of three-dimensional expression, the characteristics of three-dimensional expression in the art education for children, scholars’ views on children’s understanding of the development of three-dimensional expression by their age, and the materials for three-dimensional expression and also described the educational effect of the three-dimensional expression activities. Finally, the teaching plan for three-dimensional expression activity program by the three-dimensional expression materials used specifically in the order of introduction, development, finish, and evaluation. In the process of activities, it was found that the children who are easily distracted and had short attention span must have motivation in the introduction phase and it was possible to draw their attention and curiosity toward the search of materials by showing the materials that they prefer or a variety of eccentric or new materials, which directly led to work and children immersed themselves into work while paying great attention. As explained, the three-dimensional expression activities help children to bring out their own thoughts and express them specifically at ease, enhance confidence through the understanding of the subject to guide them to impressive expression, and expand the breadth of thought to enable creative expression. Also, since the interest arising from three-dimensional expression activities mostly means autonomous participation, it is deemed that children participate in the program actively, which leads to excellent learning effect. Most of all, children would be accustomed to the attitude of concentrating their attention, endurance, and perseverance through the three-dimensional expression materials and would also develop the sense of responsibility while finishing their work autonomously. Especially, the process of using the entire body in an activity promotes forebrain development, coordination of eyes and hands, and physical development of gross and fine motor skills and also enhances the ability to think visually represented by imagery, a drawing in mind, and the development of time and space perception. Once the external environmental condition is set, it can enhance the imagination and conceptualization which becomes the basis for creativity with important three-dimensional activities that can stimulate imagination, the potential ability, for they have the potential capacity to imagine by themselves and it would also provide a passage through which the children without verbal expression skills can vent the emotions that had built up inside them through the sense of tension, conflict, and frustration alongside their thoughts and feelings. As discussed, children feel happy from the joy of expressing their own thoughts and feelings through the three-dimensional expression activities in art education for children and thereby inducing them to appreciate and experience beauty through finished work, stabilizing and refining emotion to develop emotional and artistic sensitivities for fostering the feeling and attitude that aims at more beautiful things, developing positive self-concept and sense of achievement, knowing that themselves are unique and distinguished from others when their works are respected and accepted, and developing the ‘Image of Healthy Person’ while developing the sociality of recognizing the existence and value of others, all of which are the purpose of the three-dimensional expression activities. Furthermore, I hope the professionals in the field of art education for children have interest in the multilateral effect of the three-dimensional expression activities to promote the activities and conduct many in-depth studies to initiate great development in three-dimensional expression activities in the art education for children.

Simulation of Three-Dimensional Stacked Capacitorless DRAM Architecture Using Partially Etched Nanosheets : 부분 에칭 나노시트를 이용한 3D 적층 Capacitorless DRAM 설계 시뮬레이션

김민석 경북대학교 대학원 2025 국내석사

DRAM (Dynamic Random Access Memory) 은 높은 집적도와 빠른 읽기/쓰기 속도에 기반하여 컴퓨팅 시스템의 주요 메모리로서 사용되고 있습니다. 하지만 인공지능과 클라우드 컴퓨팅의 발전으로 보다 높은 집적도의 메모리 수요가 급증하면서, 전통적인 DRAM의 구조는 여러 한계에 직면하였습니다. 1개의 커패시터와 1개의 트랜지스터로 구성된 1T-1C DRAM은 높은 종횡비의 커패시터 공정의 어려움과 트랜지스터의 누설 전류 제어 문제로 인해 스케일링 한계에 도달했습니다. 이러한 문제를 해결하기 위해 3D 적층 구조를 통한 집적도 향상이 연구되어 왔지만, 1T-1C DRAM을 기반으로 하기에 여전히 측면에 배치된 커패시터를 필요로 하여 전체적인 집적도를 저하시키고 공정난이도가 증가되는 문제가 있었습니다. 이에 본 연구에서는 커패시터 없이 메모리 동작을 수행할 수 있는 새로운 3D 적층 Capacitorless DRAM(1T-DRAM) 설계를 제안합니다. 제안된 설계는 플로팅 바디 효과를 활용하여 메모리 동작을 수행하며, 3D 어레이의 수직 설계된 워드라인 (WL) 과 수직 적층된 나노시트의 구조적 유사성에서 착안되었습니다. 특히 본 설계는 부분 에칭 공정을 통하여 저장 영역과 소자 동작 영역을 구분함으로써 메모리 성능을 크게 향상시켰습니다. 제안된 구조의 타당성을 검증하기 위해 기존의 나노시트 1T-DRAM과 부분 에칭 나노시트 1T-DRAM을 비교 분석하였으며, Sentaurus TCAD 시뮬레이션을 통해 신뢰성 있는 분석을 수행하였습니다. 시뮬레이션 결과, 제안된 부분 식각 나노시트 1T-DRAM 설계는 우수한 유지 시간 (RT)과 센싱 마진 (SM)을 보여주었습니다. 부분 에칭 나노시트 1T-DRAM 소자는 기존 나노시트 1T-DRAM 소자뿐만 아니라 다른 비평면 소자들보다도 우수한 성능을 보여주었습니다. 또한 홀드 상태에서 WL이나 비트라인 (BL)에 교란 (Disturb-ance) 이 발생했을 때 SM과 RT의 감소를 조사하였으며, 제안된 설계가 교란에 대해 강건성을 가짐을 확인하였습니다. 본 연구는 3D 적층 가능한 1T-DRAM 구조를 구현할 뿐 아니라, 우수한 SM과 RT 성능을 보여주며 교란에 대한 강한 저항성을 가지는 소자를 제안합니다. 이는 향후 고집적 메모리 기술 발전에 중요한 기여를 할 것으로 기대됩니다.

Study of improved visual characteristics of volumetric three-dimensional display

김현호 경희대학교 대학원 2021 국내석사

In this dissertation, propose a method for realizing a multi-layered three-dimensional display in the form of projections by devising a method for recognizing the depth of human eyes. The purpose of this study is to implement a three-dimensional display of a large screen with better characteristics in existing multi-layer display systems. The conventional 2D display lacks much information about the depth that can be provided in the image. To provide this information, multilayer three-dimensional display system among Volumetric three-dimensional display systems is needed. Advantage of this system is that it requires relatively little data in expressing depth compared to other three- dimensional displays. This means that 3D images can be implemented quickly and data obtained in real time can be directly reflected in the 3D display. In addition to a conducted experiment, in order to correct the image by changing the structure of the software image and the hardware, depth fusion theory was used to solve the problems. Discontinuity of the image and the angle of view constraints caused by the display implementation, not just the simple implementation of the three-dimensional display would be an example. In this dissertation, we have studied the visual characteristics of the images formed by implementing the multi-layer display and discussed in depth what can be done through this experiment. 본 논문은 사람 눈의 깊이를 인식하는 방법을 고안하여 프로젝션 형태의 다층 3차원 디스플레이를 구현하는 방법을 제안한다. 본 연구의 목적은 기존의 다층 3차원 디스플레이 시스템에서 영상의 시각적 특성을 향상 한 가진 대형 화면의 3차원 디스플레이를 구현하는 것이다. 기존의 2D 디스플레이에 존재하지 않는 깊이에 대한 정보를 볼류메트릭 3차원 디스플레이 시스템 중 하나인 프로젝션 형태의 다층 3차원 디스플레이 시스템을 사용하였고, 구현되는 영상의 특성을 개선하는 연구를 진행하였다. 본 시스템의 장점은 다른 3차원 디스플레이와 비교하여 깊이의 표현에 상대적으로 적은 데이터가 필요하다는 것으로, 3D 영상을 신속하게 구현가능 하다는 이점이 있다. 영상의 시각적 특성을 향상하는 실험은 소프트웨어 보정와 하드웨어의 구조를 변경하여 진행되었다. 소프트웨어를 통한 영상 보정은 Depth-fusing 이론을 적용하였다. 또한 하드웨어 보정은 스페이서의 간격과 디스플레이의 구조 변경을 통해 수행하였다. 이를 통해 단순한 3차원 디스플레이 구현 만이 아니라 이미지의 불연속성 및 시야각의 제약을 해결하였음을 확인하였다. 본 논문은 다층 디스플레이를 구현하여 형성된 영상의 시각적 특성을 연구하였으며, 그에 대한 실험 방법 및 결과를 작성하였다.