• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11b
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• pp.430-437
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• 2000

Fertilizer impaction mechanism was simulated using a commercial program RecurDyn$^{(R)}$ a dynamic program that could handle contact problems. Even if there had been numerous papers on modeling of fertilizer applicator, the performance predictions were not satisfactory due to simplification in modeling. The most significant simplification was assumption of fertilizer particles as a solid particle. The assumption would eliminate rotation of fertilizer particles during the impaction mechanism. However, impaction of rotating body would be different from that of a solid particle. This paper introduced how the impaction was modeled using RecurDyn$^{(R)}$. In order to simulate, restitution coefficient and contact time was measured. A stiffness coefficient and a damping coefficient of a fertilizer was theoretically estimated using the measured data. Validity of the simulation result was not proved yet, but judged to be promising.ged to be promising.ing.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.81-82
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• 2006

Conveyor-type transporters have been widely used as a typical delivery system of semi-conductor, FPD and other IT-related products. However, as the IT-product is getting larger in size and higher in resolution, several problems are caused by mechanical contacts between the transporter and target object. In this context, recently, lots of efforts are being devoted for development of various contact-free handling systems to get rid of deffets and oil contaminations. The objectives of this paper are to characterize suspension mechanisms and to investigate air flow effects on air levitation transport system. For this purpose, a series of CFD analyses were carried out and the simulation data showed a good agreement with the corresponding experimental ones. It is anticipated that the promising result can be used as a basis for concept design of the transport system.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.34 no.2
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• pp.133-142
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• 2016

KOMPSAT-3A (KOrea Multi-Purpose SATellite-3A) was launched in March 25 2015 with specification of 0.5 meters resolution panchromatic and four 2.2 meters resolution multi spectral sensors in 12km swath width at nadir. To better understand KOMPSAT-3A positional accuracy, this paper reports a test result on the accuracy of recently released KOMPSAT-3A beta test images. A number of ground points were acquired from 1:1,000 digital topographic maps over the target area for the accuracy validation. First, the original RPCs (Rational Polynomial Coefficients) were validated without any GCPs (Ground Control Points). Then we continued the test by modeling the errors in the image space using shift-only, shift and drift, and the affine model. Ground restitution accuracy was also analyzed even though the across track image pairs do not have optimal convergence angle. The experimental results showed that the shift and drift-based RPCs correction was optimal showing comparable accuracy of less than 1.5 pixels with less GCPs compared to the affine model.

• Journal of Biosystems Engineering
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• v.14 no.4
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• pp.242-250
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• 1989

The performance of a vertical type centrifugal distributor of granular materials was studied by means of mathematical models and experimental investigations. To develop the mathematical description of particle motion, some assumptions were made. The distribution process consisted of three stages: the entrance of a particle to the blade, the motion of the particle on the blade, and the motion of the particle in the air. The physical properties of fertilizer, which affected the particle motion, were investigated: bluk density, coefficient of friction, coefficient of restitution, and particle size distribution. The particle motion were simulated by using a computer. A prototype distributor was designed and constructed for experimental tests. The following conclusions were drawn from the computer simulation and experiment results. 1. The fertilizer may slide or roll at the point of contact when they impact on the blade and move along the blade. 2. The interaction among fertilizers may prevent them from bouncing. 3. When fertilizers roll on the blade, rolling resistance is one of the factors affecting the particle's motion. 4. The trajectory angle and position of fertilizers from a disc depend on the blade position and particle shape, but the rotating speed of the disc affected them only slightly.

• Structural Engineering and Mechanics
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• v.55 no.1
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• pp.191-204
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• 2015

Control of the mechanical behavior of composite materials and structures under monotonic and dynamic loads for cracks and damage is a vast and complex area of research. The modeling of the different physical phenomena and behavior characteristics of a composite material during deformation play an important role in the structural design. Our study aims to analyze numerically the energy release rate parameter G of a composite laminated plate (glass or boron / epoxy) cross-ply [$+{\alpha}$, $-{\alpha}$] in the presence of a crack between two circular notches under the effect of several parameters such as fiber orientation ${\alpha}$, the crack orientation ${\beta}$, the orientation ${\gamma}$ of the two considered circular notches and the effect of mechanical properties. Our results show clearly that both notches orientation has more effect on G than the cracks and fibers orientations.

• Journal of Mechanical Science and Technology
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• v.20 no.8
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• pp.1266-1274
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• 2006

A numerical study is performed to investigate the effect of inner surface roughness and micro-particles on adiabatic single phase frictional pressure drop in a perfect square micro channel. With the variation of particles sizes (0.1 to $1{\mu}m$) and occupied volume ratio (0.01 to 10%) by particles, the Eulerian multi-phase model is applied to a $100{\mu}m$ hydraulic diameter perfect square micro channel in laminar flow region. Frictional pressure loss is affected significantly by particle size than occupied volume ratio by particles. The particle properties like density and coefficient of restitution are investigated with various particle materials and the density of particle is found as an influential factor. Roughness effect on pressure drop in the micro channel is investigated with the consideration of roughness height, pitch, and distribution. Additionally, the combination effect by particles and surface roughness are simulated. The pressure loss in microchannel with 2.5% relative roughness surface can be increased more than 20% by the addition of $0.5{\mu}m$ diameter particles.

• Proceedings of the Korean Institute of Landscape Architecture Conference
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• 2007.10b
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• pp.107-112
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• 2007

This study had the purpose to restore imaginary environment involved to symbolic thinking system of Eastern culture discontinued by scientific and reasonable rationalism of Western. To restore imaginary environment, this study selected example places such as Seoul, Beijing, Kyoto which were ancient cities of Korea, China, Japan each and used hermeneutics and phenomenological access method to draw out the element of imaginary environment by analyzing historical and cultural view of example cities. Through comparison and re-interpretation of historical and cultural view of three countries[Korea, China, Japan] in Northeast Asia, as the result of drawing imaginary environment involved within it, it was structured that the spirit and the factor of natural environment of places involved to each cities were reflected as the factor of civilized environment, organized that each element was united, and more sanctified the spirit of place step by step. This study has the meaning as first trial which comparatively analyzed city spaces of existent place of human life by new concept called imaginary environment. It may has the meaning that verifying the universality of imaginary environment involved to historical and cultural view of three Northeast Asian countries, however, there was limitation to examine specificity up to detailed elements of each city.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.14 no.4
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• pp.67-80
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• 2011

This study is focused upon developing repairing and restoration methodologies of the Paleolithic sites. The Paleolithic era is not only the remote past, which ended ten thounds years ago, but the period of much different ecological condition compared with that of these days. There have been two kinds of conservation method adopted to restoration of Paleolithic sites which are historic park and ecological park. But there left not much historic remains than ecological sources in most Paleolithic sites, restoring them into ecological park is thought to be more reasonable for the purpose of conserving sites and remains. The first step of restoring Paleolithic sites is reconstructing environmental background in which they earned a living with their own life style at that time. There are three ways of ecological restoration for prehistoric sites, which are the reclamation, the rehabilitation, and the restoration. The reclamation requires physical modification, and the rehabilitation does biological modification, but only the restoration requires improved management. Among them, the most desirable way applicable upon the Paleolithic sites restitution is the reclamation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.6
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• pp.1421-1429
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• 2015

During the six years from 2006 to 2011, based on a study of projects with an area equivalent to or less than $2,700m^2$ located in Jeju self-governing province, it was shown, through comparison with the pre-existing calculation methods, that there were many problems with the application of the standard cost. Accounting for the uniqueness of Jeju province, the study suggested an alternative method for applying the standard cost, basing it on property usage of either urban area or non-urban area pursuant to the National Land Planning and Utilization Act rather than land type of either mountain area or non-mountain area, with the utilization of T-test and ANOVA raising the reliability of this study.

• Journal of the Korean housing association
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• v.21 no.2
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• pp.101-109
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• 2010

Various environmental problems due to rapid industrialization and urbanization have worsened to such an extent that they threaten the environmental restitution of the globe and become a critical international issue. Korean government has presented the concept of green growth as a new state vision for the next 60 years and is making efforts to solve these environmental problems. Daegu Metropolitan City has faced various environmental problems including overpopulation of the city, traffic pollution, household waste accumulation and the green zone problem because of the increase of urbanization over the last few decades. As such urbanization continues, the quality of residential environments is rapidly deteriorating and the intensive use of the land leads to an increase of building area, raising the temperatures of cities. There have therefore been demands for healthy, pleasant and satisfying residential environments and for the improvement of existing residential environments, and this demand has been fully recognized by society. Nevertheless, current residential complex developments concentrate only on raising the efficiency of land use. In related laws of the past (Daegu Metropolitan City, Urban Planning Municipal Ordinance as of October 10, 2003) an attempt was made to impose a standard to segmentalize the building-to-land ratio, floor area ratio and regulations of number of floors vertically. However, these laws have now been abolished and the regulations are being eased. The purpose of this study was to analyze the characteristics of the floating wind before and after the vertical segmentation of residential areas (Daegu Metropolitan City, Urban Planning Municipal Ordinance as of October 10, 2003) by using KLAM_21, a model that enables analysis and prediction of the flow and generation of cold wind. The purpose is also to present a plan to improve the quality of residential areas when developing a building lot and redeveloping housing areas.