• 대한전자공학회논문지SD
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• 제41권2호
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• pp.27-32
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• 2004

Absolute optical angle 센서는 디지털 광학 장치의 핵심적인 부분이라고 말할 수 있으며, 이 장치의 목적은 Pseudorandom-code와 Geometry-code를 이 용하여 코드화된 원판(coded disk)의 상대적/절대적 변위 (Relative/Absolute angle position)를 해결하기 위함이다. 이 기술에서 디스크의 각 위치(Angular position)는 먼저 Pseudorandom-code에 의해 "Coarse" angle이 검출되어 결정되어지며, 그런 다음 Geometry-code의 Pixel 계산에 의해서 얻어지는 "Fine" angular position 데이터는, 7㎛의 Line image 센서를 사용 시, 시스템의 0.006°분해능 결과를 구할 수 있다. 제안된 기술은 비접촉 반사 특성, 시스템의 높은 분해능, 상대적으로 간단한 코트 패턴 그리고 센서의 고유한 디지털 성질을 갖는 등 많은 면에서 새로운 방식이다 더 나아가서 시스템은 두 개의 코드화된 원판에 적용하여 얻어진 절대 자의 변형(Absolute angular displacement)을 관찰하는 방식으로 쉽게 토크 센서로 변경할 수 있다. 제안된 센서의 디지털 광전 특성은 토크와 각을 동시에 측정함으로써 자동 차량 시스템에 사용 시 이상적인 시스템을 만든다. 본문에서는 코드화된 원판의 정확한 각 위치(Angular position)를 결정하기 위하여 Pseudo random-code와 Geometry-code를 활용한 기술을 제안하며, 아이디어의 실행 가능성을 구현하는 실험 결과를 제시하였다.

• 대한기계학회논문집A
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• 제26권7호
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• pp.1426-1437
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• 2002

Using the Lagrangian explicit time-integration finite element code NET3D which can treat three-dimensional high-velocity impact problems, oblique penetration processes of long rod projectile with yaw against thin plate are simulated. Through the comparison of simulation result with experimental result and other code's computational result, the adaptability and accuracy of NET3D is evaluated under the complex situation in which yaw angle and oblique angle exist simultaneously. Main research contents to be handled in this paper include the followings. First, the accuracy and efficiency estimation of NET3D code result obtained from the oblique penetration simulations of long rod projectile with yaw against thin plate. Second, the effect of increasing impact velocity. Third, the effect of initial yaw for the spaced-plate target. Residual velocities, residual lengths, angular velocities, and final deformed configurations obtained from the NET3D computations are compared with the experimental results and other code's computational results such as Eulerian code MESA and Lagrangian code EPIC. As a result of comparisons, it has been found that NET3D code is superior to EPIC code and MESA code in the prediction capability of residual velocity and residual length of penetrator. The key features obtained from the experiment can be successfully reproduced through NET3D simulations. Throughout the study, the applicability and accuracy of NET3D as a metallic armor system design tool is verified.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.189-192
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• 2002

In this paper, the submarine model, called DARPA SUBOFF model, has been numerically analyzed to investigate the aerodynamic forces variation in terms of angle of attacks and yaw angles. The SUBOFF model is consisted of the three parts : axisymmetric body, fairwater, and four symmetric stern appendages. Three dimensional unsteady incompressible Wavier-Stokes equation was used on curvilinear multi-block grid system. To validate the present code, the SUBOFF tare hull and an ellipsoid at angle of attacks of $10^{\circ}\;and\;30^{\circ}$ were simulated and a good agreement with experiments was obtained. After the code validation, the flows over SUBOFF model were simulated at three different angle of attacks and yaw angles. The variation of aerodynamic forces in terms of angle of attack and yaw angle were calculated. Also, to understand the flow features around a submarine with variation of yaw and attack angle, the pressure contours and streamlines were plotted.

• 한국진공학회지
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• 제15권4호
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• pp.387-394
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• 2006

본 연구에서는 반응성 이온빔을 low-angle forward reflection으로 생성시킨 중성빔을 이용하여 Aspect Ratio Dependent Etching (ARDE) 현상이 제거되는 효과에 대하여 연구하였다. SF6 가스를 사용하여 Inductively Coupled Plasma system과 이온빔으로 각각 poly-Si 을 식각한 결과 ARDE 현상을 관찰할 수 있었으며, Si 기판위에 증착된 Poly-Si을 식각하는 것보다 $SiO_2$ 기판 위에 증착된 Poly-Si을 식각하는 것이 ARDE 현상이 더 많이 나타난다는 것을 관찰할 수 있었다. 반면에 같은 공정 조건에서 중성빔으로 poly-Si을 식각한 결과 이러한 ARDE 현상이 효과적으로 제거되었음을 관찰할 수 있었다. 중성빔을 이용하여 ARDE 현상이 제거되는 원리는 2 차원의 XOOPIC code 와 TRIM code를 사용하여 여러가지 나노스케일의 형상을 컴퓨터 시뮬레이션하여 증명하였다.

• 한국군사과학기술학회지
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• 제8권4호
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• pp.5-13
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• 2005

The impact of a long-rod penetrator into oblique plates with combined obliquity and yaw is investigated. The study was done using a newly developed three dimensional dynamic and impact analysis code, which uses the explicit finite element method. Through the comparison of simulation result with experimental result and other code's result, the adaptability and accuracy of the developed code is evaluated under the complex situation in which yaw angle and oblique angle exist simultaneously. As a result of comparison, it has found that deformed shape, residual length and velocity, rotational velocity of long-rod show good agreement with experimental data. Through this study, the applicability and accuracy of the code as a metallic armour system design tool is verified.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.1103-1108
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• 2001

ACI 318-99 predicts the torsional moment of reinforced concrete members by assuming that the angle of diagonal compressive concrete is equal to 45 degree. However, this angle depends on the difference of longitudinal and transverse steel ratios. This paper compares the torsional moments calculated by ACI 318-99 code and a truss model considering compatibility of strains. The comparison indicated that the torsion equation in ACI code underestimated the real torsional moment of reinforced concrete beam in which the ratio of longitudinal reinforcement was larger than that of transverse reinforcement.

• 대한조선학회논문집
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• 제43권4호
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• pp.460-466
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• 2006

The three-dimensional RANS equations were applied to analyze the flow field of a submarine. To validate the code, the DARPA SUBOFF bare hull and an eliipsoid at angles of attack of $10^{\circ}\;and\;30^{\circ}$ were simulated and good agreement with experiments was obtained. After the code validation, the flows over the full configuration of DARPA SUBOFF model having a fairwater and four stern appendages were simulated at four angles of attack $(0^{\circ},\;10^{\circ},\;20^{\circ},\;30^{\circ})$ and three yaw angles $(10^{\circ},\;20^{\circ},\;30^{\circ})$ Specifically, the pressure contours and streamlines of fairwater and stern appendage were compared as the angle of attack and yaw angle changed. The variations of hydrodynamic forces were also calculated.

• KCI Concrete Journal
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• 제11권3호
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• pp.5-17
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• 1999

In recent years. the concept of the modified compression field theory (MCFT) was develped and applied to the analysis of reinforced concrete beams subjected to shear, moment, and axial load. Although too complex for regular use in the shear design or beams. the procedure has value in its ability to provide a rational method of anlysis and design for reinforced concrete members. The objective of this paper is to review the MCFT and apply it for the prediction of the response and shear strength of reinforced concrete beams A Parametric analysis was Performed on a reinforced T-section concrete beam to evaluate and compare the effects of concrete strength. longitudinal reinforcement ratio shear reinforcement ratio, and shear span to depth ratio in two different approaches the MCFT and the ACI code. The analytical study showed that the concrete contribution to shear strength by the MCFT was higher than the one by the ACI code in beams without stirrups, while it was lower with stirrups. On the other hand. shear reinforcement contribution predicted by the MCFT was much higher than the one by the ACI code. This is because the inclination angle of shear crack is much smaller than 45$^{\circ}$assumed in the ACI code.

• Structural Engineering and Mechanics
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• 제68권5호
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• pp.537-547
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• 2018

This research presents the effect of anisotropy of the hollow disc mode under Brazilian test using PFC3D. The Brazilian tensile strength test was performed on the hollow disc specimens containing the bedding layers and then these specimens were numerically modeled by using the two dimensional discrete element code (PFC3D) to calibrate this computer code for the simulation of the cracks propagation and cracks coalescence in the anisotropic bedded rocks. The thickness of each layer within the specimens varied as 5 mm, 10 mm and 20 mm and the layers angles were changed as $0^{\circ}$, $25^{\circ}$, $50^{\circ}$, $75^{\circ}$ and $90^{\circ}$. The diameter of internal hole was taken as 15 mm and the loading rate during the testing process kept as 0.016 mm/s. It has been shown that for layers angles below $25^{\circ}$ the tensile cracks produce in between the layers and extend toward the model boundary till interact and break the specimen. The failure process of the specimen may enhance as the layer angle increases so that the Brazilian tensile strength reaches to its minimum value when the bedding layers is between $50^{\circ}$ and $75^{\circ}$ but its value reaches to maximum at a layer angle of $90^{\circ}$. The number of tensile cracks decreases as the layers thickness increases and with increasing the layers angle, less layer mobilize in the failure process.

• Nuclear Engineering and Technology
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• 제51권1호
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• pp.13-30
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• 2019

This paper presents the recent improvements in the DeCART code for HTGR analysis. A new 190-group DeCART cross-section library based on ENDF/B-VII.0 was generated using the KAERI library processing system for HTGR. Two methods for the eigen-mode adjoint flux calculation were implemented. An azimuthal angle discretization method based on the Gaussian quadrature was implemented to reduce the error from the azimuthal angle discretization. A two-level parallelization using MPI and OpenMP was adopted for massive parallel computations. A quadratic depletion solver was implemented to reduce the error involved in the Gd depletion. A module to generate equivalent group constants was implemented for the nodal codes. The capabilities of the DeCART code were improved for geometry handling including an approximate treatment of a cylindrical outer boundary, an explicit border model, the R-G-B checker-board model, and a super-cell model for a hexagonal geometry. The newly improved and implemented functionalities were verified against various numerical benchmarks such as OECD/MHTGR-350 benchmark phase III problems, two-dimensional high temperature gas cooled reactor benchmark problems derived from the MHTGR-350 reference design, and numerical benchmark problems based on the compact nuclear power source experiment by comparing the DeCART solutions with the Monte-Carlo reference solutions obtained using the McCARD code.