• 한국콘텐츠학회논문지
• /
• 제5권2호
• /
• pp.53-60
• /
• 2005

e-teaming은 시간적, 공간적 제약으로부터의 자유스러움으로 인해 전통적 교육의 보조 도구로써, 또는 전통적 교육을 대신해서 이미 많은 부분에서 e-learning이 이루어지고 있다. 본 논문은 e-learning의 중요성과 그것이 차지하는 비중이 상당히 커져 있는 시점에서 e-learning 교육 경험자들이 인터넷 기반 e-learning의 학습효과를 전통적 교육에 비해 어느 정도로 인식하고 있는지에 대한 조사를 수행하였다. 또한 인터넷 기반 e-learning의 학습효과에 대한 요인변수를 도출하고, 인터넷 기반e-loaming의 학습효과로 인식하는 정도가 어떠한 요인에 의해 얼마만큼의 영향을 받고 있는지를 파악하여 제시하였다.

• 한국정밀공학회지
• /
• 제24권5호
• /
• pp.68-76
• /
• 2007

It is strongly requested to reduce fuel consumption because of high oil price and exhaust gases of road vehicles for environmental preservation. To solve these problems, several types of hybrid vehicles have been developed. Among them, flywheel hybrid vehicle using variable displacement pump/motor was already proposed as one of the feasible hybrid systems in place of hybrid vehicle by the conventional storage battery. The proposed flywheel hybrid vehicle is to keep constant pressure of high pressure line by the control of swash plate angle of flywheel pump/motor as pressure compensator. The efficiency of the overall system depends severely on the efficiency of hydraulic pump/motor in the energy saving hydraulic control system by simulation. According to the control methods of swash plate angle of piston pump/motor, there remain several problems to be solved. In this paper, experimental setup for energy saving is fabricated and the efficiency of energy saving is investigated by experiments with respect to various experimental conditions.

• 한국소음진동공학회논문집
• /
• 제12권5호
• /
• pp.389-396
• /
• 2002

In this study, the dynamic absorbing system for gas operated gun has been investigated. For this purpose, firstly. mathematical model of gas-operated shoulder-fired gun has been constructed. Through a series of experimental works using the devised test setup, the characteristic behavior of mathematical model was compared to the test results. In order to design the dynamic absorbing system, parameter optimization process has been performed based on the simplified isolation system under constraints of moving displacement and transmitted force. In order to implement the more efficient dynamic absorbing system, the characteristic performance of stroke-dependent variable damping system has been analyzed with some opening area curves. Finally, the performance of the designed dynamic absorbing system has been evaluated by simulation and experiment using the previous test apparatus.

• 대한조선학회논문집
• /
• 제34권4호
• /
• pp.99-107
• /
• 1997

본 논문에서는 박판보 구조물의 전단변형 효과를 보다 정확히 해석할 수 있는 모델인 불균일전단 뒤틀림 보이론에 대하여 혼합형 유한요소 해석법을 적용하였다. 일반적으로 알려져 있는 바와 같이 혼합형 유한요소는 구조물의 변위 및 용력을 해석함에 있어서 변위형 유한요소에 비해서는 정도면에서 보다 균형 잡힌 해석 결과를 제공하는 특성이 있음을 밝힌다. 계산예로서, 단면의 형상이 불연속적으로 변화하는 변단면 박판보에 양단 비틀림 모멘트가 작용하는 전형적인 보의 굽힘-비틀림 연성 거동 문제에 대하여 개발된 유한요소 해석모델을 적용함으로써 그 유용성을 확인하였다.

• International Journal of Aeronautical and Space Sciences
• /
• 제14권4호
• /
• pp.310-323
• /
• 2013

In this paper, the aeroelastic static response of flexible wings with arbitrary cross-section geometry via a coupled CUF-XFLR5 approach is presented. Refined structural one-dimensional (1D) models, with a variable order of expansion for the displacement field, are developed on the basis of the Carrera Unified Formulation (CUF), taking into account cross-sectional deformability. A three-dimensional (3D) Panel Method is employed for the aerodynamic analysis, providing more accuracy with respect to the Vortex Lattice Method (VLM). A straight wing with an airfoil cross-section is modeled as a clamped beam, by means of the finite element method (FEM). Numerical results present the variation of wing aerodynamic parameters, and the equilibrium aeroelastic response is evaluated in terms of displacements and in-plane cross-section deformation. Aeroelastic coupled analyses are based on an iterative procedure, as well as a linear coupling approach for different free stream velocities. A convergent trend of displacements and aerodynamic coefficients is achieved as the structural model accuracy increases. Comparisons with 3D finite element solutions prove that an accurate description of the in-plane cross-section deformation is provided by the proposed 1D CUF model, through a significant reduction in computational cost.

• 치과방사선
• /
• 제14권1호
• /
• pp.89-98
• /
• 1984

The purpose of the present study is to offer the fundamental materials for the diagnosis of dentigerous cyst by analysis of the clinical and radiographic findings of these lesions. The subject for this study consisted 118 patients admitted to the Department of Oral Radiology, Kyung Hee University and Seoul National University from 1974 to 1983. Conclusions from this study were as follows: 1. There was a higher incidence in males (70.34%) than in females (29.66%), and the incidence was highest in the second and third decade (26.27%) with the same incidence. (Average age: 25 year) 2. There was a higher incidence in the maxillary teeth (66.10%) than in the mandibular teeth (33.90%) and the maxillary supernumerary tooth (45.76%) was the most frequently involved one. The mandibular third molar (16.10%) was next in order of frequency of involvement followed by maxillary canine (7.63%), mandibular second premolar (5.08%). 3. There was a greater incidence of the central type than the lateral type in the maxilla, while a higher incidence of the lateral type in the mandible. 4. There was a greater incidence of the smooth type (84.26%) than that of the scalloped type (15.74%) and a higher incidence of minor type (70.91%) than the major type (29.09%) in the displacement of associated tooth. 5. Root apices of teeth encompassed or approached by the cysts showed variable resorption in 68.47% of cases.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2003년도 춘계학술대회논문집
• /
• pp.82-87
• /
• 2003

Nuclear fuel with a big slenderness ratio is susceptible to flow-induced vibration under very severe conditions of high temperature, high flow and exposure to irradiation in nuclear reactor. The fuel assembly should, therefore, be designed to escape any resonance due to the vibration during the reactor operation, in particular, in case of the design changes. In addition, the amplitudes due to the grid vibration, the fuel rod vibration and the fuel assembly vibration should be minimized to reduce the grid-to-rod fretting wear. Fuel assembly vibration tests in air at room temperature and in water at high temperature have been performed to investigate fuel vibration behaviors. The frequency and damping during the test in air have been compared to those in water. Through the hydraulic test, the advanced assembly has been evaluated not to be susceptible to any resonance. In addition, the test data from the tests can be used to make fuel model and to evaluate grid-to-rod fretting wear.

• Structural Engineering and Mechanics
• /
• 제45권6호
• /
• pp.759-777
• /
• 2013

In this paper, a topology optimization method based on the element independent nodal density (EIND) is developed for continuum solids with multiple load cases and multiple constraints. The optimization problem is formulated ad minimizing the volume subject to displacement constraints. Nodal densities of the finite element mesh are used a the design variable. The nodal densities are interpolated into any point in the design domain by the Shepard interpolation scheme and the Heaviside function. Without using additional constraints (such ad the filtering technique), mesh-independent, checkerboard-free, distinct optimal topology can be obtained. Adopting the rational approximation for material properties (RAMP), the topology optimization procedure is implemented using a solid isotropic material with penalization (SIMP) method and a dual programming optimization algorithm. The computational efficiency is greatly improved by multithread parallel computing with OpenMP to run parallel programs for the shared-memory model of parallel computation. Finally, several examples are presented to demonstrate the effectiveness of the developed techniques.

• 대한기계학회논문집A
• /
• 제20권4호
• /
• pp.1320-1332
• /
• 1996

In the present study, we consider modified 5-node equivalent solid element which has smallest degree of freedom among 2-dimensional solid elements accounting bending deformation as well as extensional and shear deformations, We shall investigate static and dynamic characteristics of this element, which is very effective in thin beam, thick beam, large displacement problems, beam of variable thickness, and asymmetrically stepped beam, etc., as well as relatively simple problems of beam. The degree of freedom of this element is 10, which is smaller than 18 of 9-node element, 16 of 8-node elemtns, 12 of modified 6-node element and Q6 element. Therefore, this element is expected to broaden the effective range of application of the solid elements in the bending problems further.

• 한국생산제조학회지
• /
• 제20권3호
• /
• pp.357-360
• /
• 2011

Machine tools of Gantry type have been performing machine work as a moving machinery. In a large machine tools, the machinery is moving with bed and it is structurally unstable. When the objects are processed, machine tools gets loads in the direction of Z-axis. In other words, the machine tools which become bigger was performed by the trend of complexation. It made that the increased machine weight can't be passed over. In order to enhance manufacturing precision, it needs to compensate Z-axis deflection of weight for machine tools. In this paper, Machine tools of Gantry type were miniaturized and deflection was measured by LVDT sensors. When deflection was measured, block mass weighted 50kg is moving on particular distance. Then, the displacement of fixed point and moving point is measured by recording telemeter.