• Smart Structures and Systems
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• 제20권4호
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• pp.441-450
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• 2017

The objective of this work is to present a conceptual design and the modelling of a distributed sensor system based on fiber optic devices (Fiber Bragg Grating, FBG), aimed at measuring span-wise and chord-wise variations of an adaptive (morphing) trailing edge. The network is made of two different integrated solutions for revealing deformations of the reference morphing structure. Strains are confined to typical values along the span (length) but they are expected to overcome standard ranges along the chord (width), up to almost 10%. In this case, suitable architectures may introduce proper modulations to keep the measured deformation low while preserving the information content. In the current paper, the designed monitoring system combines the use of a span-wise fiber reinforced patch with a chord-wise sliding beam. The two elements make up a closed grid, allowing the reconstruction of the complete deformed shape under the acceptable assumption that the transformation refers to regular geometry variations. Herein, the design logic and some integration issues are reported. Preliminary experimental test results are finally presented.

• Korea-Australia Rheology Journal
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• 제20권2호
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• pp.89-94
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• 2008

To satisfy good mechanical and optical properties of polymer-coated film products, it will be indispensable to elucidate the molecular orientation of polymer chains within coating liquids in coating flows. Using hybridized numerical method between computational fluid dynamics (CFD) and Brownian dynamics (BD) simulations can provide the useful information for the better quality control of coated films. Flexible polymer chains, e.g., ${\lambda}$-DNA molecules here, change their conformation according to the flow strength and the flow type. The molecular conformation within the coated film on the web or substrate is quite different, because the polymer chains experience the complicated flow strength and flow types in flow field. Especially in the slot coating flow, these chains are more extended by the extension-like flow field generated in the free surface curvature just beyond the downstream die region. Also, the polymer chain extension beneath the free surface can be affected by the die geometry, e.g., the coating gap, changing flow field.

• 한국해양공학회지
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• 제22권5호
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• pp.25-30
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• 2008

A B-spline based high order panel method was developed for the motion of bodies in an ideal fluid, either of infinite extent or with a free boundarysurface. In this method, both the geometry and the potential are represented by the B-spline, which guarantees more accurate results than most potential based low order methods. In the present work, we applied this B-spline based high order method to the radiation problem of floating bodies. The boundary condition on the free surface was satisfied by adopting a Kelvin-type Green function and irregular frequencies were removed by placing additional control points on the free surface surrounding the body. The numerical results were validated by comparison with existing numerical and experimental results.

• Journal of Welding and Joining
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• 제13권2호
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• pp.68-81
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• 1995

This paper presents an analytical solution to predict the transient temperature distribution in fillet arc welding. The analytical solution is obtained by solving a transient three -dimensional heat conduction equation with convection boundary conditions on the surfaces of an infinite plate with finite thicknesses, and mapping an infinite plate onto the fillet weld geometry with energy equation. The electric arc heat input on fillet weld and on infinite plate is assumed to have a traveling bivariate Gaussian distribution. To check the validity of the solution, GTA and FCA welding experiments were performed under various welding conditions. The actual isotherms of the weldment cross - sections at various distances from the arc start point are compared with those of simulation result. As the result shows a satisfactory accuracy, this analytical solution can be used to predict the transient temperature distribution in the fiIIet weld of finite thickness under a moving bivariate Gaussian distributed heat source. The simplicity and short calculation time of the analytical solution provides rationales to use the analytical solution for modeling the welding control systems or for an optimization tool of welding process parameters.

• 콘크리트학회지
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• 제7권6호
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• pp.167-175
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• 1995

본 연구에서는 매스콘크리트 양생시 수화열에 의한 온도 상승을 예측할 수 있는 온도해석 프로그램 $\boxDr$TAMCON$\boxUl$을 개발하였다. 수치해석 방법으로는 복잡한 형태를 지니고 다양한 경계조건을 만족시켜야 하는 구조물에 대한 온도해석을 용이하게 하기 위하여 유한요소법이 채택되었다. $\boxDr$TAMCON$\boxUl$의 타당성을 검증하기 위하여 벽상구조물과 기초매트에 대하여 이미 문헌에 보고된 수치해석 및 실험치를 본 연구의 해석 결과와 비교한 바 이들이 서로 잘 일치하고 있음을 확인하였다. $\boxDr$TAMCON$\boxUl$은 콘크리트 구조물의 온도균열 방지를 위한 온도제어 및 필요한 양생방법의 도입을 위한 시공관리에 효과적으로 활용될 수 있다.

• 전자공학회논문지SC
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• 제45권6호
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• pp.55-59
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• 2008

야외 환경에서 무인차량의 자율주행에 있어서 효과적인 기동제어를 위해서는 장애물 탐지나 지형의 기하학적인 형상 정보외에 탐지된 장애물 및 지형 표면에 대한 재질 유형의 인식 및 분류 또한 중요한 요소이다. 영상 기반의 지표면 분류 알고리듬은 입력 영상에 대한 전처리, 특징추출, 분류 및 후처리의 절차로 수행된다. 본 논문에서는 컬러 CCD 카메라로부터 획득된 야외 지형영상에 대해 색상 및 질감 정보를 이용한 지형분류 기법을 제시한다. 전처리 단계에서 색공간 변환을 수행하고, 색상과 질감 정보를 이용하기 위해 웨이블릿 변환 특징을 사용하였으며, 분류기로서는 SVM(support vector machine)을 적용하였다. 야외 환경에서 획득된 실영상에 대한 실험을 통하여 제시된 알고리듬의 분류 성능을 평가하였으며, 제시된 알고리듬에 의한 효과적인 야지 지형분류의 가능성을 확인하였다.

• 대한기계학회논문집
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• 제18권8호
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• pp.2158-2166
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• 1994

In order to understand the package crack emanating from the edge of leadframe after the delamination between leadframe and epoxy molding compound in an electronic packaging of surface mounting type, the M-integral and J-integral in fracture mechanics are obtained. The effects of geometry, material properties and molding process temperature on the package crack are investigated taking into account the temperature dependence of the material properties, which simulates a more realistic condition. If the temperature dependence of the material properties is considered the result of analysis conforms with observations that the crack is kinked at between 50 and 65 degree. However, in case of constant material properties at the room temperature it is found that the J-integral is underestimated and the kink crack angle is different form the observation. The effects of the material properties and molding process temperature on J-integral and crack angle are less significant that the chip size for the cases considered here. It is suggested that the geometric factors such as ship size, leadframe size are to be well designed in order to prevent(or control) the occurrence and propagation of the package crack.

• 한국기계가공학회지
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• 제15권1호
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• pp.14-19
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• 2016

Transmission error (TE) is the most important cause of gear noise and vibration because TEs affect the changes of the force and the speed of gears. TE is usually expressed as an angular deviation, or a linear deviation measured at the pitch point and calculated at successive positions of the pinion as it goes through the meshing cycle. Accurate measurement of TE for gear transmission will provide a reasonable basis for gear design, manufacturing processes and quality control. Therefore, in order to study the accuracy of the gear transmission, stability, TE, vibration and noise after gear micro-geometry modification, a gear transmission test rig is proposed in this paper, which is based on the existing technical conditions, by using reasonable testing methods, hardware and a signal processing method. All of the details and the experience can be taken into consideration in the next upgraded test rig.

• 한국생산제조학회지
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• 제8권2호
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• pp.116-116
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• 1999

In this study we propose a novel approach with which design engineers can define and design free-from surface more easily. Free-from surface is defined as a parameterics shape which consists of a set of contr ol points. Parametric shape which not only has the advantage of allowing users to perform design changes efficiently, but also provides designers with a natural design environment in which they can do their work more naturally and creatively. The objective of this study is to develop a PC level freeform surface modelling system which explicitly represents information of part geometry. In this study, freeform surface modeling system consist of three modules : freeform surface modeler, input/output modules and interface with Database. In recent year there are increasing demands for the 5-axis machining of a complicated shape. This study is the development of a CAM software system (or NC module) for the 5-axis machining of a general shape with a flat-end mill, a round-end mill, a ball-end mill.

• 한국수학교육학회지시리즈A:수학교육
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• 제52권4호
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• pp.531-547
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• 2013

The purpose of the study is to examine how effects of activities using Google SketchUp on students' spatial ability and 3D geometric thinking in measuring the volume of solid figures. By comparing the results from pre- and post-tests between the experimental group and control group, we found that activities using Google SketchUp help students improve their spatial ability in the spatial orientation and visualization. In addition, more than half students in the experimental group moved from level 4 up to level 7 in thinking process of measuring the volume in terms of Battista(2004)'s levels. This study suggests that the instruction with Google SketchUp can help to improve students' spatial ability and 3D geometric thinking in the regular class in middle school. In addition, SketchUp can be an advanced technological tool to support students' self-directed learning, which create an efficient educational environment and a great opportunity to learn geometry in an effective manner.