• Structural Engineering and Mechanics
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• 제57권2호
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• pp.239-263
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• 2016

The paper studies the natural oscillation of the three-layered solid sphere with a middle layer made of Functionally Graded Material (FGM). It is assumed that the materials of the core and outer layer of the sphere are homogeneous and isotropic elastic. The three-dimensional exact equations and relations of linear elastodynamics are employed for the investigations. The discrete-analytical method proposed by the first author in his earlier works is applied for solution of the corresponding eigenvalue problem. It is assumed that the modulus of elasticity, Poisson's ratio and density of the middle-layer material vary continuously through the inward radial direction according to power law distribution. Numerical results on the natural frequencies related to the torsional and spheroidal oscillation modes are presented and discussed. In particular, it is established that the increase of the modulus of elasticity (mass density) in the inward radial direction causes an increase (a decrease) in the values of the natural frequencies.

• 문화기술의 융합
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• 제10권4호
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• pp.23-31
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• 2024

이 연구의 목적은 최근 3년(2021년, 2022년, 2023년) 교육부 교원양성 연수과에서 발표하는 교원 연수 중점 추진 방향을 분석하여 미래 사회에 교원 연수의 방향을 제시하는 것이다. 연구 결과는 다음과 같다. 첫째, 최근 3년 교원 연수 추진 배경은 변화된 것이 없었다. 최근 3년의 교원 연수 추진 배경은 교원 전문성 신장, 미래 환경 대응, 교원 연수 질 제고, 교육정책 추진력 확보이다. 추진 배경 세부 내용도 최근 3년 변함이 없다. 둘째, 최근 3년 교원 연수 비전의 경우 교원 연수체제 혁신이다. 이를 위하여 2021년에는 미래 교육환경 변화 선도를, 2022년에는 미래 공교육 선도를, 2023년에는 개별 학생 맞춤형 교육지원을 비전으로 하고 있다. 연수 목표의 경우 2021년에는 교원 생애 단계에 맞는 지속적 전문성 신장과 미래 교육환경에 부합하는 교원 핵심역량 제고를, 2022년에는 미래 교육체제에 적합한 교원 역량 강화와 교원 연수 내실화를 통한 사회적 신뢰 확보를, 2023년에는 미래 교육체제에 적합한 교원 역량 강화와 교원 연수 내실화를 통한 교실 수업의 변화에 두고 있다. 최근 3년 교원 연수 중점 추진 방향은 3가지이다. 첫째, 맞춤형 연수지원, 둘째, 미래형 연수체제 강화, 셋째, 교원 연수 내실화이다. 이 세 가지는 최근 3년 모두 유사하다. 결론적으로 최근 3년 교원 연수 중점 추진 방향에는 큰 변화가 없었다.

• 한국세라믹학회지
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• 제49권4호
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• pp.347-351
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• 2012

Vermiculite-silica composites with a layered structure were fabricated by adding cellulose fibers as a pore former and by a simple uniaxial pressing and subsequent sintering process. Three different combinations of additives were used and their effects on the compressive strength and thermal conductivity of the composites were investigated. Both compressive strengths (42-128 MPa) and thermal conductivities (0.75-1.48 $W/m{\cdot}K$) in the direction perpendicular to the pressing direction (T) were higher than those (19-81 MPa and 0.32-1.04 $W/m{\cdot}K$) in the direction parallel to the pressing direction (S) in all samples. The anisotropy in both properties was attributed to the microstructural anisotropy, which was caused by the layered structure developed in the composites.

• 한국레이저가공학회지
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• 제5권3호
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• pp.1-8
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• 2002

Finite element analysis and experiment were peformed to estimate the fatigue strength for the lap joint of laser weld. To consider quantitatively residual stress which effects on the fatigue strength of the lap joint of laser weld, after three dimensional modeling for the longitudinal and transverse direction, residual stress fields in the weldment were calculated using thermo-elastic-plastic finite element analysis, then the equivalent fatigue stress considering the residual stress was obtained. To ensure reliability of calculated fatigue strength, fatigue tests were performed. The calculated and experimental results showed a good agreement. The fatigue strength considering a residual stress was lower than that of without considering a residual stress in the lap joint of laser welding. The fatigue strength in the transverse direction was higher than that of longitudinal direction.

• Carbon letters
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• 제1권2호
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• pp.76-81
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• 2000

Physical properties of artificial graphite electrodes were evaluated along three different directions; circumferential (X), radial (Y), and axial (Z) directions. Four kinds of commercial electrode products were used in this study for the evaluation; pole (AP) and nipple (AN) of manufacturer A, pole (BP) and nipple (BN) of manufacturer B. The mechanical, electrical, and thermal properties in X and Y directions were very similar to each other. In Z direction, however, the mechanical properties, including flexural strength and compressive strength, were higher, and electric resistance and thermal expansion were much lower than those in the other directions. The microstructures observed by optical microscope and scanning electron microscope revealed that the differences in properties by the measuring direction were caused by the preferential alignment of needle cokes along the Z direction. When comparing the properties of the electrode samples in the same direction, the mechanical properties mainly depended on the bulk density or porosity of the samples as well as preferential alignment of needle cokes.

• 한국멀티미디어학회논문지
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• 제25권4호
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• pp.568-574
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• 2022

In this paper, direction normalization and CNN deep learning are used to develop a more reliable license plate recognition system. The existing license plate recognition system consists of three main modules: license plate detection module, character segmentation module, and character recognition module. The proposed system minimizes recognition error by adding a direction normalization module when a detected license plate is inclined. Experimental results show the superiority of the proposed method in comparison to the previous system.

• 한국운동역학회지
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• 제17권2호
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• pp.167-176
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• 2007

The purpose of this study was to offer suitable model for performing Tippelt motion and data for training Tippelt motion through the quantitative kinematical analysis of Tippelt motion in parallel bars. The results of analysing kinematic variations through three-dimensional reflection analysis of three members of the national team as the objects of the study were shown as follows. 1. It seemed that the shoulder-joints which are stretched as much as possible affects the whole Tippelt motion while one is swinging downward. The time of process of the center of mass for the body reaching to the maximum flection point should be quick and body's moving from the vertical phase to the front direction should be controled as much as possible. 2. While one is swinging upward, the stability of flying motion could be made certain by the control of body's rapid moving to the front direction and stretching shoulder-joints and hip-joint to reverse direction. 3. While one is flying upward, the body should be erected quickly and lessening the angle of the hip-joint affects the elevation of flight. When the powerful counter turn motion is performed, the stable motion could be made. As a result of this study, It seems that sudden fall and the maximum stretch of shoulder-joints is important during performing Tippelt motion in parallel bars. Also, it concludes that the maximum bending of hip-joints at the starting point of upward swing, sudden stretch to the reverse direction of shoulder-joints and hip-joints when one is leaving bars, control of body's moving to the front direction, and lessening the angle of hip-joints at the flying phase is important.

• PNF and Movement
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• 제17권2호
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• pp.207-214
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• 2019

Purpose: Although multi-directional reaching exercises are commonly used clinically, the effects of specific movement directions on the muscle systems of the lower extremities have not been explored. We therefore investigated lower extremity muscle activity during reaching exercises with different sagittal and horizontal plane movements. Methods: The surface electromyography responses of the bilateral rectus femoris, tibialis anterior, peroneus longus, and gastrocnemius muscles were measured during reaching exercises in three directions in the horizontal plane (neutral, $45^{\circ}$ horizontal shoulder adduction, and $45^{\circ}$ abduction) and three directions in the sagittal plane (neutral, $120^{\circ}$ flexion, and $60^{\circ}$ flexion). A total of 20 healthy, physically active participants completed six sets of reaching exercises. Two-way repeated ANOVA was performed: body side (ipsilateral and contralateral) was set as the intra-subject factor and direction of reach as the inter-subject factor. Results: Reaching at $45^{\circ}$ horizontal shoulder adduction significantly increased the activity of the contralateral rectus femoris and gastrocnemius muscles, while $45^{\circ}$ horizontal shoulder abduction activated the ipsilateral rectus femoris and gastrocnemius muscles. The rectus femoris activity was significantly higher with reaching at a $120^{\circ}$ shoulder flexion compared to the other conditions. The gastrocnemius activity decreased significantly as the shoulder elevation angle increased from $60^{\circ}$ to $120^{\circ}$. Conclusion: Our results suggest that multi-directional reaching stimulates the lower extremity muscles depending on the movement direction. The muscles acting on two different joints responded to the changes in reaching direction, whereas the muscles acting on one joint were not activated with changes in reaching direction.

• 한국전산구조공학회논문집
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• 제35권3호
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• pp.191-196
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• 2022

본 연구에서는 3D 프린팅 FDM 방식의 적층 방향에 따라 기계적 물성이 달라지는 이방성 특성을 확인하고 이를 이용하여 위상 최적설계를 수행하였다. 벤치마크 문제인 자동차 현가장치 부품 중 하나인 로어 컨트롤 암에 대하여 밀도법 기반 위상 최적설계를 수행하였으며, 외부 하중과 이방성 특성에 따라 위상 최적결과가 다르게 나타나는 것을 확인하였다. 이를 이용하여 최적화된 모델에 대하여 3D 프린터로 적층 방향을 달리하여 2가지 시험품을 제작하였으며 인장시험을 수행하였다. 시험시 3D 비접촉 변형률 측정기를 이용하여 변형률을 구하였으며 이를 CAE 응답해석으로 얻은 변형률과 비교한 결과가 정량 및 정성적으로 일치하는 것을 확인하였다. 3D 프린팅 적층 방향을 고려한 위상 최적모델의 인장 실험 결과를 통해 해당 최적설계 방법론의 유효성을 검증하였다.

• 한국방재학회 논문집
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• 제10권6호
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• pp.109-117
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• 2010

본 연구에서는 하천유역에 대한 호우의 방향성을 von Mises 분포를 이용하여 정량화하고, 그 대표 이동방향을 결정하였다. 추가로 호우 발생특성(장마, 태풍, 대류성 강우)에 따른 호우의 방향적 특성을 도출하여 비교하였다. 대상유역인 내성천 유역에서 수집된 101개 호우사상을 이용한 결과, von Mises 분포는 대상 호우사상의 방향적 특성이 적절히 표현됨을 확인하였다. 또한 호우의 이동방향은 그 발생특성에 따라 차이를 보이며, 이들 특성은 한반도의 기후특성과도 일치함을 확인하였다. 본 연구의 결과는 호우 이동방향에 따른 유출응답의 차이를 보다 정량적으로 파악하는데 도움이 될 수 있을 것이다.