• Journal of the Korean Society of Safety
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• v.11 no.4
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• pp.10-15
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• 1996

In studying the fatigue strength of fillet welded the section of pressure vessel pad, this study was to evaluate the effect of weld toe notch and to compare the results of numerical analysis with the results of fatigue experiments of fillet welded A5l6 grade 60 steel specimens. The fatigue life for the Bead welded specimen was about 1.4 times as much it as the 1Pad welded specimen. Also, The fatigue life for the 2Pad welded specimen was about 1.5 times as much it as the 1Pad welded specimen. In $da/dN-{\Delta}K$ curve, the fatigue crack growth rate for the 1Pad welded specimen appeared higher than that of the 2Pad welded specimen in the same initial region of ${\Delta}K$, had a similar Inclination In the stabled region.

• Korean Institute of Interior Design Journal
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• no.5
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• pp.30-36
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• 1995

Light plays an important role in making a continuity of space and in determining the distinctive expression and char-acter of a space. Particularly, the introduction of natural light derives from our esthetic needs, as well as from the fundamental biologi-cal necessities of human beings. And also, adaptation to time and space is the vital factor of human survival and prosperity. Our visual recognition of light is usually formed not only by practical illumination but by analogy, expection and expe-rienced of lighting itself. As the forecase of natural light is (almost) impossible be-cause of variables such as changing weather, reflection rate of light and the patterns of shade, in designing the introduc-tion of daylight, there should be follow-ed careful considera-tion of the adaptation to such variety and the impet-us of light. The research was conducted to mane a contribution to cre-ate more rich and beautiful interior spaces by studying the characteristic of light which is one of the important factors of interior space design, and by inquiring the way to intro-duce light and its effect through the practical examples of Alvar Aalto, Le Corbusier and Louis I. Kahn.

• Korean Journal of Optics and Photonics
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• v.11 no.2
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• pp.130-134
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• 2000

In this paper, the configuration of a reflectIve bistable tWIsted nematic (BTN) liquid crystal cell is optmnzed for high contrast and high brightness operation. We searched for the optimum opncal parameters of a reflective BTN cell by calculating its optical performances at 3 wavelengths; red, green, and blue. By studying the effect of each optical parameter on the optical performances, we found that the angle of !he polmlzer IS more important than any other opnea! parmlleters iu the deSIgn of a reflective BTN cell. We fablicated a reflective BTN cell with a wide-band retardation Him, whose measmed contrast ratio is 10.6: 1. .6: 1.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.8
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• pp.120-125
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• 2000

This paper proposes a tilt sensor made by MEMS technology. The sensor consists of an electrode glass a small mercury drop a circular channel and a cover glass. The mercury drop is used as medium of a current flow and in contact with two circular chromel electrodes used as an angular-motion resistance When this sensor inclines the mercury drop inside the circular channel moves into the bottom under the influence of gravity. A tilt angle can be measured by changed resistance as tilting this sensor, This sensor has a linear section between +50.$^{\circ}$ and -50.$^{\circ}$ with the accuracy of 2.$^{\circ}$. We are also studying about the enlargement of the linear section and the effect of the size of the mercury drop.

• Proceedings of the Korea Multimedia Society Conference
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• 2003.05b
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• pp.840-843
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• 2003

본 논문은 '컴퓨터를 이용한 교육방안의 홍수 속에서, 그 효과성은 어느 정도 인지되고 있는가？' '컴퓨터에 대한 일반적 기대치만큼이나 그 효율성은 신뢰도가 있는가？'라는 멀티미디어 교육자재들의 효과성에 대한 근본적인 의문점을 제기하고 학습자들이 쉽게 접할 수 있는 게임형 도형 맞추기를 수업에 접목함으로써 CAI의 효과성을 검증하였다. 실험 후 CAI로 수업을 실시한 집단에게 학습효과가 높고, 멀티미디어 CAI를 도입하여 진행된 수업은 학습자의 학습효과를 높여준다는 결과를 얻을 수 있었다. 멀티미디어의 효과성검증은 컴퓨터가 기존의 학습방법을 완전히 배제하는 혁신적 기제임을 주장하지는 않는다. 컴퓨터의 교육적 활용은 전통학습방법을 보완하여 학습자의 능동적, 창의적 능력을 개발, 육성하고 변화의 흐름을 주도하는 바람직한 인간형 실현에 목표를 두고 있다. 급격한 정보 변혁의 시대에 학교교육의 효율성을 최대화하기 위한 다양한 컴퓨터 보조 수업물이 연구, 제작되고 있는 실정에서, 그 기제들의 효과성을 검증하는 것은 멀티미디어의 잠재적 가능성을 지속적으로 개발, 발전시키는데 우선적인 조건이라 할 수 있을 것이다.

• Coupled systems mechanics
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• v.6 no.1
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• pp.1-15
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• 2017

Despite the exceptional mechanical properties of individual carbon nanotubes (CNTs), the effective properties of CNT-reinforced composites remain below expectations. The composite's microstructure has been identified as a key factor in explaining this discrepancy. In this contribution, a method for generating representative volume elements of aligned CNT sheets is presented. The model captures material characteristics such as random waviness and entanglement of individual nanotubes. Thus it allows studying microstructural effects on the composite's effective properties. Simulations investigating the strengthening effect of the application of a pre-stretch on the CNTs are carried out and found to be in very good agreement with experimental values. They highlight the importance of the nanotube's waviness and entanglement for the mechanical behavior of the composite. The presented representative volume elements are the first to accurately capture the waviness and entanglement of CNT sheets for realistically high volume fractions.

• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.24-32
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• 2018

Nanocellulose was surface-functionalized toward the applications in enhanced oil recovery (EOR) as a green alternative. The focus of this paper is on the effect of this material based nanofluid (NF) on foam lamella stabilization through studying its bubble breakup dynamics and flow behaviors in constricted mircofluidic devices. The NF stabilized foam produced an improved flow resistance across the capillary largely due to the capillary trapped bubbles at the contraction. The "snap-off" caused the NF stabilized foam to produce finer textured bubbles, which can migrate readily forward to the deep porous media, as revealed by the pressure profiles.

• Korean Journal of Remote Sensing
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• v.21 no.1
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• pp.15-29
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• 2005

Superconducting Gravimeters (SG) are the most sensitive instruments for measuring temporal gravity variations. The gravimeter is an integrating sensor therefore the gravity variations caused by different sources must be separated for studying a special effect by applying different models and data analysis methods. The present reduction methods for gravity variations induced by atmosphere and hydrosphere including the ocean and the detection and determination of the most surface gravity effects are shown. Some examples demonstrate the combination of ground (SG) and space techniques especially the combination of SG with GRACE satellite derived temporal gravity variations. Resulting from the performance of the SG and the applied data analysis methods some proposals are made for future SG applications.

• Nuclear Engineering and Technology
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• v.49 no.5
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• pp.1095-1099
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• 2017

A fission source can act as a stabilization element in coupled Monte Carlo simulations. We have observed this while studying numerical instabilities in nonlinear steady-state simulations performed by a Monte Carlo criticality solver that is coupled to a xenon feedback solver via fixed-point iteration. While fixed-point iteration is known to be numerically unstable for some problems, resulting in large spatial oscillations of the neutron flux distribution, we show that it is possible to stabilize it by reducing the number of Monte Carlo criticality cycles simulated within each iteration step. While global convergence is ensured, development of any possible numerical instability is prevented by not allowing the fission source to converge fully within a single iteration step, which is achieved by setting a small number of criticality cycles per iteration step. Moreover, under these conditions, the fission source may converge even faster than in criticality calculations with no feedback, as we demonstrate in our numerical test simulations.

• Ocean Systems Engineering
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• v.9 no.1
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• pp.97-109
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• 2019

Accurate calculation of the mean drift forces and moments is necessary when studying the higher order excitations on the floater in waves. When taking the time average of the second order forces and moments, the second order potential and motion diminish with only the first order terms remained. However, in the results of the first order forces or motions, the irregular frequency effects are often observed in higher frequencies, which will affect the accuracy of the calculation of the second order forces and moments. Therefore, we need to pay close attention to the irregular frequency effects in the mean drift forces. This paper will discuss about the irregular frequency effects in the calculations of the mean drift forces and validate our in-house program MDL Multi DYN using some examples which are known to have irregular frequency effects. Finally, we prove that it is necessary to remove the effects and demonstrate that the effectiveness of the formula and methods adopted in the development of our program.