• Composites Research
• /
• v.23 no.3
• /
• pp.19-30
• /
• 2010

The present study describes a method for analytical solution to elastic field in structural elements of general symmetric laminated composite materials. The two dimensional plane stress elasticity problems under mixed boundary conditions are reduced to the solution of a single fourth order partial differential equation, expressed in terms of a single unknown function, called displacement potential function. In addition, all the components of stress and displacement are expressed in terms of the same displacement potential function, which makes the method suitable for any boundary conditions. The method is applied to obtain analytical solutions to two particular problems of structural elements consisting of an angle-ply laminate and a cross-ply laminate, respectively. Some numerical results are presented for both the problems with reference to the glass/epoxy composite. The results are highly accurate and reliable as all the boundary conditions including those in the critical regions of supports and loads are satisfied exactly. This verifies the method as a simple and reliable one as well as capable to obtain exact analytical solution to elastic field in structural elements of composite materials under mixed and any other boundary conditions.

• The Journal of the Korea Contents Association
• /
• v.12 no.4
• /
• pp.510-519
• /
• 2012

The purpose of this study is to investigate how interactions and affective factors are influencing on-line English Grammar courses of higher education. This study addressed the following questions: (1) How are the interactions going in on-line English Grammar courses? (2) Are affective factors influencing effective learning in on-line English Grammar courses? The questionnaire was conducted on 170 college students who have taken on-line English course of K University. The data analysis of 300 college students' responses on their courses showed that e-learning has both positive and negative effects compared to face to face classroom instructions. Analysis showed that the percentage of students who have got negative opinions on e-learning was 17%, while that of students who have got positive opinions was 49.3%. The percentage of those in the middle was 33.3%. However, results demonstrated that immediate feedback and affective factors could be facilitated through Q&A bulletin and feedback program for completing on-line learning. Negative effects of on-line learning can be solved by a planned and well-supported on-line approach that includes a theory-based instructional model rather than the new method replaced by 'blended learning' that combines face-to-face classroom instruction with on-line learning.

• Korean Journal of Optics and Photonics
• /
• v.9 no.2
• /
• pp.96-99
• /
• 1998

In this study, a novel long term stabilization method of optical feedback for the resonant cavity coupled semiconductor lasers is proposed, and its utility was shown experimentally. The proposed method is realized by using the pahse discriminator of optical feedback with high gain. The phase discriminating signal was obtained by the polarization spectroscopic technique using reflection light from the external reflector, which is a confocal Fabry-Perot cavity. Experimental result shows that stable control state can be maintained up to 20 hours. The period can be increased by reducing size of the system and/or fixing position stably of optical parts used, which were arranged on an optical table by using magnetic bases in this experiment. The proposed long-term stabilization method of optical feedack of a resonant external cavity coupled semiconductor laser is very useful for the field of high sensitivity measurement, and for the use in the laboratory level in particular.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.13 no.4
• /
• pp.643-652
• /
• 1989

The purpose of this research is to analyze the impact behavior of beam-like laminates due to the transverse impact of a steel ball according to the changes of stacking sequence and aspect ratio. For this purpose, it is carried out the dynamic finite element analyses using the modified beam theory for laminates and the first order shear deformation plate theory. The results of these analyses are compared with those of experimental impact tests. The composite materials are composed of [0.deg./45.deg./0.deg./-45.deg./0.deg.]$_{2S}$ and [90.deg./45.deg./90.deg./-45.deg./90.deg.]$_{2S}$ stacking sequences and have 4.5 t * 5(10, 20 & 30)w * 200(300)l(mm)dimensions. In all analyses, the specimens are clamped at both ends.cimens are clamped at both ends.

• Proceedings of the KOSOMBE Conference
• /
• v.1991 no.05
• /
• pp.74-78
• /
• 1991

Conventional compression bone fracture plates sometimes cause osteoporosis under the plate due to their high rigidity which in turn transfer physiological load mostly through the plates and screws. In order to prevent the osteopenia we have designed a system which have a viscoelastic washer between plate and screw head. The washer is made of a biocompatible ploymer (untra high molecular weight polyethylene, UHMWPE). Three-dimensional finite element meshes of the human femur with the conventional and new concept bone plate ere generated and the comparative stress analyses are performed with static half-stance loading condition. The results of analyses showed that could reduce the stress shielding effect compared with the conventional plate.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2001.10a
• /
• pp.129-133
• /
• 2001

A finite element-based, integrated process model is presented for a three dimensional, coupled analysis of the thermo-mechanical behavior of the strip and work roll in the continuous hot strip rolling. The validity of the proposed model is examined through comparison with measurements. The effect of Edge-Heater on the finishing delivery temperatures is examined by using the present model. The models capability of revealing the effect of diverse process parameters is demonstrated through a series of process simulation.

• Proceedings of the KIEE Conference
• /
• 2008.04c
• /
• pp.71-73
• /
• 2008

본 논문에서는 편측식 선형 유도전동기의 2차측 도체의 구조에 따른 동특성 해석을 유한요소법을 사용하여 수행하였고 결과를 비교 분석하였다. 2차측 구조를 주로 사용되는 판 형태와 농형 그리고 이중농형의 구조로 나누어 해석을 수행하였으며 추력, 수직력, 추력리플, 수직력 리플, 주파수 및 슬립에 따른 특성 등을 비교 분석 하였다.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.4 no.2
• /
• pp.76-80
• /
• 2003

In this study, it is presented analysis results of bending problems in the orthotropic thick plates and the orthotropic thin plates. Finite element method in this analysis was used. Both Kirchoffs assumptions and Mindlin assumptions are used as the basic governing equations of bending problems in the orthotropic plates. The analysis results are compared between the orthotropic thick plates and the orthotropic thin plates for the variations of thickness-width ratios.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.11a
• /
• pp.718-721
• /
• 2007

The ionic-polymer-metal-composite actuators have the best merit for bio-mimetic locomotion because of their large bending performance. Especially, they have the advantage for mimicking a fish-like motion because IPMCs are useful to be actuated in water. So we have developed IPMC actuators with multiple electrodes for realization of biomimetic motion. This actuator is fabricated by combining electroless plating and electroplating techniques capable of patterning precisely and controlling a thickness of Pt electrode layer. The FRF analysis was conducted by a mechanical shaker and direct electrical excitation which is based on sweep sine wave function. From this result, the proper young‘s modulus of Platinum was investigated and applied on expecting the vibration characteristics of patterned IPMC actuator. The calculated maximum displacement of the patterned IPMC was 2.32mm under an applied 4mN/mm. The natural frequency was increased however displacement was decreased in according to increase a thickness of Pt.

• Journal of the Korean Society for Precision Engineering
• /
• v.19 no.6
• /
• pp.104-108
• /
• 2002

Sandwich plate structure is widely used in various fields of industry due to its excellent strength and stiffness compared with weight. In this paper, the mechanical behavior of sandwich plate structure with honeycomb core considering buckling is investigated in detail. The focus of the analysis is to evaluate strength and stiffness of the plate structure with critical stress, natural frequency, and mode shapes. The results of this investigation are obtained from detailed finite element analysis for various parameters, such as length, height ratio, and thickness ratio of honeycomb core.