• 제목/요약/키워드: rotating beams

검색결과 99건 처리시간 0.021초

등방성 빔 단면과 비등방성 공간 부분 코히어런스 특성을 갖는 가우시안 셀 모델 빔의 구현에 대한 해석적 연구 (Analytic study on the realization of partially coherent Gaussian Schell-model beams with isotropic cross section and anisotropic degree of coherence function)

  • 김휘;김태수;최경식;이병호
    • 한국광학회지
    • /
    • 제15권3호
    • /
    • pp.200-213
    • /
    • 2004
  • 등방성 빔 단면과 비등방성 공간 부분 코히어런스 특성을 갖는 가우시안 셀 모델 빔의 구현에 대하여 연구하였다. He-Ne 레이저의 가우시안 빔이 회전하는 홀로그래픽 확산판을 통과하면서 생성된 확산광을 등방성 빔 단면과 비등방성 공간 코히어런스 특성을 갖는 가우시안 셀 모델 빔으로 만드는 광학계를 제안하였다. 광학계의 해석적 설계 방정식을 유도하였고 이를 사용한 설계 예를 제시하였다.

A SIW Fed Antipodal Linear Tapered Slot Planar Multi-Beam Antenna for Millimeter-Wave Application

  • Zhang, Yingsong;Hong, Wei;Kuai, Zhenqi
    • Journal of electromagnetic engineering and science
    • /
    • 제10권3호
    • /
    • pp.175-178
    • /
    • 2010
  • In this paper, a millimeter-wave multi-beam antenna is studied by rotating the antipodal linear tapered slot antenna(ALTSA) with respect to a center is successfully designed. In order to lowering the SLL and enhancing the isolation between the ALTSA elements, a row of metallic via is inserted between the ALTSAs. A 9 beams antenna is designed and experimented at Ka band. The measured and simulated results agree well with each other. The antenna can provide horizontal wide angle coverage up to ${\pm}62^{\circ}$. The gain of each beam can achieve about 12.5 dB. The mutual coupling between ports is all below 20 dB.

균열 및 부착슬립효과를 고려한 철근콘크리트 구조물의 비선형 유한요소해석 (Nonlinear Finite Element Analysis of Reinforced Concrete Structures Considering the Crack and Bond-Slip Effects)

  • 곽효경
    • 한국전산구조공학회:학술대회논문집
    • /
    • 한국전산구조공학회 1992년도 봄 학술발표회 논문집
    • /
    • pp.65-70
    • /
    • 1992
  • This study deals with the finite element analysis of the monotonic behavior of reinforced concrete beams and beam-column joint subassemblages. It is assumed that the behavior of these members can be discribed by a plane stress field. Concrete and reinforcing steel are represented by separate material models which are combined together with a model of the interaction between reinforcing bar and concrete through bond-slip to discribe the behavior of the composite reinforced concrete material. To discribe the concrete behavior, a nonlinear orthotropic model is adopted and the crack is discribed by a system of orthogonal cracks, which are rotating as the principal strain directions are changed. A smeared finite element model based on the fracture mechanics principles are used to overcome the numerical defect according to the finite element mesh size. Finally, correlation studies between analytical and experimental results and several parameter studies are conducted with the objective to estabilish the validity of the proposed model and identify the significance of various effects on the local and global response of reinforced concrete members.

  • PDF

회전하는 두꺼운 외팔보의 모델링 및 진동특성 해석 (Modeling and Vibration Analysis of Rotating Thick Beams)

  • 신상하;유홍희
    • 한국소음진동공학회:학술대회논문집
    • /
    • 한국소음진동공학회 1995년도 추계학술대회논문집; 한국종합전시장, 24 Nov. 1995
    • /
    • pp.179-184
    • /
    • 1995
  • 본 논문은 단면관성 효과와 전단효과를 고려한 회전하는 두껍고 짧은 외팔보의 진동해석모델링을 제시하였으며 수치해석을 통해 다음과 같은 결론을 얻었다. 세장비가 큰 경우(.alpha.는 70 이상) Timoshenko 해석모델과 Euler 해석모델에 의한 고유진동수 예측은 거의 차이가 없다. 그러나 세장비가 작은 경우 Euler 해석모델은 Timoshenko 해석모델에 비해 큰 무차원 고유진동수 값을 예측하며 특히 고차모드에서 두 모델은 큰 해석결과의 차이를 보여주었다. 따라서 보의 세장비가 작은 경우, 보가 회전할 때도 일반적 해석경우와 마찬가지로 Timoshenko 해석모델을 사용해야 된다는 자연스러운 결론을 얻을 수 있었다.

  • PDF

Plastification procedure of laterally-loaded steel bars under a rising temperature

  • Huang, Zhan-Fei;Tan, Kang-Hai;England, George L.
    • Structural Engineering and Mechanics
    • /
    • 제35권6호
    • /
    • pp.699-715
    • /
    • 2010
  • This paper investigates the structural responses of axially restrained steel beams under fire conditions by a nonlinear finite element method. The axial restraint is represented by a linear elastic spring. Different parameters which include beam slenderness ratio, external load level and axial restraint ratio are investigated. The process of forming a mid-span plastic hinge at the mid-span under a rising temperature is studied. In line with forming a fully plastic hinge at mid-span, the response of a restrained beam under rising temperature can be divided into three stages, viz. no plastic hinge, hinge forming and rotating, and catenary action stage. During catenary action stage, the axial restraint pulls the heated beam and prevents it from failing. This study introduces definitions of beam limiting temperature $T_{lim}$, catenary temperature $T_{ctn}$ and warning time $t_{wn}$. Influences of slenderness ratio, load level and axial restraint ratio on $T_{lim}$, $T_{ctn}$ and $t_{wn}$ are examined.

해양환경에서 선박 추적을 위한 라이다를 이용한 궤적 초기화 및 표적 추적 필터 (Track Initiation and Target Tracking Filter Using LiDAR for Ship Tracking in Marine Environment)

  • 황태현;한정욱;손남선;김선영
    • 제어로봇시스템학회논문지
    • /
    • 제22권2호
    • /
    • pp.133-138
    • /
    • 2016
  • This paper describes the track initiation and target-tracking filter for ship tracking in a marine environment by using Light Detection And Ranging (LiDAR). LiDAR with three-dimensional scanning capability is more useful for target tracking in the short to medium range compared to RADAR. LiDAR has rotating multi-beams that return point clouds reflected from targets. Through preprocessing the cluster of the point cloud, the center point can be obtained from the cloud. Target tracking is carried out by using the center points of targets. The track of the target is initiated by investigating the normalized distance between the center points and connecting the points. The regular track obtained from the track initiation can be maintained by the target-tracking filter, which is commonly used in radar target tracking. The target-tracking filter is constructed to track a maneuvering target in a cluttered environment. The target-tracking algorithm including track initiation is experimentally evaluated in a sea-trial test with several boats.

적외선 조명 및 단일카메라를 이용한 입체거리 센서의 개발 (3D Range Measurement using Infrared Light and a Camera)

  • 김인철;이수용
    • 제어로봇시스템학회논문지
    • /
    • 제14권10호
    • /
    • pp.1005-1013
    • /
    • 2008
  • This paper describes a new sensor system for 3D range measurement using the structured infrared light. Environment and obstacle sensing is the key issue for mobile robot localization and navigation. Laser scanners and infrared scanners cover $180^{\circ}$ and are accurate but too expensive. Those sensors use rotating light beams so that the range measurements are constrained on a plane. 3D measurements are much more useful in many ways for obstacle detection, map building and localization. Stereo vision is very common way of getting the depth information of 3D environment. However, it requires that the correspondence should be clearly identified and it also heavily depends on the light condition of the environment. Instead of using stereo camera, monocular camera and the projected infrared light are used in order to reduce the effects of the ambient light while getting 3D depth map. Modeling of the projected light pattern enabled precise estimation of the range. Identification of the cells from the pattern is the key issue in the proposed method. Several methods of correctly identifying the cells are discussed and verified with experiments.

라인 레이저의 산란에 강인한 심도 측정 방법 (Depth Measurement Method Robust against Scattering of Line Lasers)

  • 고광진;연승호;김재민
    • 한국멀티미디어학회논문지
    • /
    • 제21권2호
    • /
    • pp.181-187
    • /
    • 2018
  • Line-laser beams are used for depth measurement of welding beads along the circumference of a pipe. For this, first we project a line-laser beam on an rotating pipe and take a sequence of images of the beam projected on the pipe using a CCD camera. Second, the projected line laser beam in each image is detected, converted into a thin curve. Finally measure the distance between the thinned curve and an imaginary line. When a line-laser beam is projected to a rough metal surface such as arc welding beads, the beam is severely scattered. This severe scattering makes the thinned curve perturbed. In this paper, we propose a thinning method robust against scattering of line lasers. First, we extract a projected line laser beam region using an adaptive threshold. Second, we model a thinned curve with a spline curve with control points. Next, we adjust the control points to fit the curve to the projected line-laser beam. Finally, we take a weighted mean of thin curves on a sequence of image frames. Experiments shows that the proposed thinning method results in a thinning curve, which is smooth and fit to the projected line-laser beam with small error.

Nonlinear 3-D behavior of shear-wall dominant RC building structures

  • Balkaya, Can;Schnobrich, W.C.
    • Structural Engineering and Mechanics
    • /
    • 제1권1호
    • /
    • pp.1-16
    • /
    • 1993
  • The behavior of shear-wall dominant, low-rise, multistory reinforced concrete building structures is investigated. Because there are no beams or columns and the slab and wall thicknesses are approximately equal, available codes give little information relative to design for gravity and lateral loads. Items which effect the analysis of shear-wall dominant building structures, i.e., material nonlinearity including rotating crack capability, 3-D behavior, slab-wall interaction, floor flexibilities, stress concentrations around openings, the location and the amount of main discrete reinforcement are investigated. For this purpose 2 and 5 story building structures are modelled. To see the importance of 3-D modelling, the same structures are modelled by both 2-D and 3-D models. Loads are applied first the vertical then lateral loads which are static equivalent earthquake loads. The 3-D models of the structures are loaded in both in the longitudinal and transverse directions. A nonlinear isoparametric plate element with arbitrarily places edge nodes is adapted in order to consider the amount and location of the main reinforcement. Finally the importance of 3-D effects including the T-C coupling between walls are indicated.

광자결정 제작을 위한 홀로그라피 공정 연구 (A Study on the Holographic Process for Photonic Crystal Fabrication)

  • 여종빈;윤상돈;이현용
    • 한국전기전자재료학회논문지
    • /
    • 제20권8호
    • /
    • pp.726-730
    • /
    • 2007
  • Two dimensional photonic crystals (2D PCs) have been fabricated by a double exposure holographic method using a He-Cd laser with a wavelength of 442nm. The arrays of the 2D PCs exhibit variable lattice structures from square to triangle according to a change of rotating angle $({\gamma})$ for double exposure beams. In addition, the period and filling factor of PCs as well as the forms (dot or antidot) could be controlled by experimental conditions. $A l.18-{\mu}m-thick$ resist was spin-coated on Si substrate and the 1st holographic exposure was carried out at incident angle $({\theta})$ of $11^{\circ}$. Then the sample was rotated to ${\gamma}=45^{\circ}{\sim}90^{\circ}$ and the 2nd holographic process was performed at ${\theta}=11^{\circ}$. The variation of diffraction efficiency during the exposure process was observed using a He-Ne laser in real time. The images of 2D PCs prepared were analyzed by SEM and AFM. We believe that the double holographic method is a tool suitable to realize the 2D PCs with a periodic array of large area.