• Journal of the Korean Society for Precision Engineering
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• v.25 no.10
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• pp.33-40
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• 2008

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.11a
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• pp.63-68
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• 2004

본 연구는 우리나라 유리건축에서 적용되고 있는 유리투과체를 조사하여 투과율이 다른 4종류 즉, 투명유리, 색유리, 파스텔유리, 로이유리를 선정하여 복층유리로 제작하였다. 투과체에 따른 실내공간의 채광성능평가를 위하여 축소모형을 1/10으로 제작하였으며, 투과체의 구성을 일반형과 이중분할형으로 구성하여 기준실과 실험실에 설치하였다. 또한, 채광성능평가시 IEA모니터링 프로토콜을 적용하여 작업면, 벽면, 천정면에 대하여 조도를 외부조도와 동시에 측정하였고, 본 논문에서는 작업면에 대한 채광성능평가를 중심으로 분석하였다. 평가지표로서 주광조도비를 사용하였으며, 일반형과 이중분할형에 대한 가변 유리투과체를 변화시켰을 경우 투과율에 따른 실내공간의 채광성능을 평가하였다. 가변 유리투과체로 구성된 실내공간의 채광성능평가는 다음과 같이 분석되었다. 첫째, 실내공간에 일반형을 적용하여 서로 다른 투광성능을 가진 유리투과체가 적용된 경우 외부조도에 대한 내부조도 비율은 투과율이 증가할수록 일정하게 증가하는 것으로 나타났다. 이는 투과체가 갖는 투과성능의 영향으로 판단된다. 둘째, 일반형에 비해 이중분할형은 채광창으로 유입되는 채광학적 기여가 증가하여 실 전체의 조도를 증가시키며 특히, 실 중간부와 후면부의 경우 채광적 잠재력이 증대되어 실의 쾌적함과 시 환경적 질이 증대될 것으로 사료된다. 현재 유리건축물에 많이 적용되고 있는 저 투과체에 이중분할형을 적용할 경우 채광학적으로 많은 효과가 있을 것으로 기대된다.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.3
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• pp.252-259
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• 2008

The deep-sea mining system is generally composed of surface vessel, lifting system, buffer, flexible pipe and miner. The mining system can be regarded as a large-scale system in which each subsystem is interconnected to other ones. In order to control a large-scale system, decentralized control approaches have been proposed recently. In this paper, as a basic study on application of decentralized control, firstly, the mining system was modeled in a simplified way. Lifting system and buffer were regarded as a spherical pendulum and the flexible pipe was taken as a two-dimensional linear spring connection. Based on the simplified model dynamics, the mining system can be decentralized two subsystems, the one consisting of surface vessel, lifting system and buffer, and the other, the miner. Next, this paper proposed the design of controller for each decentralized subsystem by regarding the interacting terms as disturbances. The controllers kept the constant distance between two subsystems during the miner was moving on the specified track. Finally, the efficiency of proposed controller was proven through the numerical simulation of the derived model.

• Journal of the Korean Solar Energy Society
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• v.27 no.4
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• pp.129-136
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• 2007

자연광의 이용은 큰 어려움 없이 지속 가능한 에너지 기술을 구현할 수 있는 방안으로 고려되고 있다. 여러 개의 작은 반사경을 적용한 태양 추적식 자연채광 시스템은 비교적 단순한 메카니즘을 적용하여 그 성능과 효용성의 극대화를 꾀할 수 있으며, 또한 그 제작, 설치 작동 그리고 활용성에서 상당한 이점이 있다. 본 연구에서는 작은 mini-dish형 반사경(직경<30cm 이하)을 이용한 화이버 광학 집광기의 설계, 제작 및 작동 특성에 대하여 소개하고, 아울러 광추적 프로그램인 Photopia를 이용하여 그 성능에 대한 시뮬레이션을 수행하였다. 주요 구성 요소에서의 광추적에 의한 시뮬레이션 결과치는 실제 시스템의 설계 및 성능 예측에 중요한 기술적 데이터를 제공하며, 특히 실측이 곤란한 측정 면에서의 빛의 경로 해석에 유용하게 적용될 수 있다.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.3
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• pp.168-177
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• 2008

Trafficablility of a miner and potential environmental impacts due to mining activities should be considered in the selection of a commercial manganese nodule mining site. These two factors can be evaluated comparatively with physical properties and shear strength of sea-bed sediments. For the qualitative comparison of potential minig sites in terms of these two factors, physical properties such as water contents, void ratios, porosities, and grain densities, and shear strengths of surface sediments were determined for the three potential manganese nodule mining sites(KR1, KR2, and KR5) in the Korean manganese nodule contract area, northeast Pacific. For the study, sediment samples were collected from 107 stations from 2004 to 2006. The physical properties of surface sediments showed more significant differences between northern(KR1, KR2) and southern(KR5) blocks than between northern blocks(KR1 vs. KR2). Water content, void ratio, and porosity of sediments from KR5 were relatively higher than those from KR1 and KR2. Grain density of sediments from KR5 was relatively lower than those from KR1 and KR2. Shear strengths of the top 10cm sediments were higher in KR1 and KR2, whereas those of the deeper part were highest in KR5 block. Generally, sediments of high water contents are less suspendible than those of the low water contents by benthic disturbances, thus less disturbance is expected in the sediments of high water content by mining activities. In terms of trafficability, the shear strength of sediment below 10 cm deep is more important than shallower part because miner will disturb at least top 10 cm interval of the surface sediments. Base on these results, we conclude that KR5 area will be the best site for commercial mining among three investigated sites in this study.

• Journal of Energy Engineering
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• v.25 no.4
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• pp.62-73
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• 2016

Daylighting systems offer substantial advantages over conventional ones in illuminating the building interior. Especially, considering that lighting accounts for about 28% of total energy consumption in buildings, the use of daylighting systems deem very important in lessening the dependency on artificial lighting. This work has carried out a survey and analysis to explore the characteristics and current status of various daylighting systems with solar tracking features recently introduced in Korea.

• Journal of Navigation and Port Research
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• v.34 no.3
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• pp.195-203
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• 2010

This paper concerns about total dynamic analysis of integrated mining system. This system consists of vertical steel pipe, intermediate buffer station, flexible pipe and self-propelled miner. The self-propelled miner and buffer are assumed as rigid-body of 6-dof. Discrete models of vertical steel pipe and flexible pipe are adopted, which are obtained by means of lumped-parameter method. The motion of mining vessel is not considered. Instead, the motion of mining vessel is taken into account in form of various boundary conditions (e.g. forced excitation in slow motion and/or fast oscillation and so on). A terramechanics model of extremely cohesive soft soil is applied to the self-propelled miner. Hinged and ball constraints are used to define the connections between sub-systems (vertical steel pipe, buffer, flexible pipe, self-propelled miner). Equations of motion of the coupled model are derived with respect to the each local coordinates system. Four Euler parameters are used to express the orientations of the sub-systems. To solve the equations of motion of the total dynamic model, an incremental-iterative formulation is employed. Newmark-${\beta}$ method is used for time-domain integration. The total dynamic responses of integrated mining system are investigated.

• Journal of the Korean Society of Radiology
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• v.14 no.5
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• pp.635-642
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• 2020

The purpose of this study was to analysis the effects of shielding area of field configuration with changing of sensitivity and density on tube current (milliampere-seconds, mAs) and image quality in automatic exposure control (AEC) system. The equipment used a digital radiography device (Digital Diagnost, Philips, Netherlands), which has a integral type with an X-ray tube and an indirect digital detector. The AEC system conditions were consisted of 9 setting environments, that mode changing of the sensitivity (S200, S400, S800) and the density (+2.5, 0, -2.5). The tube current evaluated automatically exposed mAs under 81 combination conditions crossed by AEC conditions in fixed at 40 kVp. The image quality evaluated the radiographic images that selected valid images by visual assessment the radiographic images of the self-produced conical pyramid phantom and then measured their signal to noise ratio (SNR). As a result, the maximum tube current was 60.0 mAs that automatically exposed conditions were the 100% of shielding area and the sensitivity of S200 and the density of +2.5. The minimum tube current was 0.9 mAs with non-shielding area and the sensitivity of S800 and the density of -2.5. When the shielded area 0% with the sensitivity of S200 and the density of +2.5, the maximum SNR was the highest as 25.2. But when the shielded area 25% with the sensitivity of S800 and the density of -2.5, the minimum SNR was the lowest as 4.7.

• Journal of Energy Engineering
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• v.21 no.2
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• pp.124-132
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• 2012

This study presents the simulation results of Photopia when a lecture room with north-facing windows were illuminated by two different types of daylighting systems to improve the imbalance in its lighting conditions. Especially, the candela power distribution curves (CDCs) on a clear sunny day at the summer solstice, reaching $80^{\circ}$ in solar altitude, were analyzed with respect to the illuminance available at task areas (work planes). The difference between its illuminance on the north and south areas exceeded 1,000 lux without any daylighting system. This, however, decreased drastically with the application of a daylighting system. When a light tube system was introduced, it reduced from 906lx to 603lx and, even further to 308lx with the application of a dish concentrator system. Generally, the performance of a light tube system was greatly influenced by solar altitude while its effect on the dish concentrator system was rather negligible.

• Tunnel and Underground Space
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• v.24 no.4
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• pp.282-288
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• 2014

Stoping method has been acknowledged as one of the typical metalliferous underground mining methods. Notwithstanding with the popularity of the method, the majority of stoping mines are suffering from excessive unplanned dilution which often becomes as the main cause of mine closure. Thus a reliable unplanned dilution management system is imperatively needed. In this study, reliable unplanned dilution prediction system is introduced by adopting artificial neural network (ANN) based on data investigated from one underground stoping mine in Western Australia. In addition, contributions of input parameters were analysed by connection weight algorithm (CWA). To validate the reliability of the proposed ANN, correlation coefficient (R) was calculated in the training and test stage which shown relatively high correlation of 0.9641 in training and 0.7933 in test stage. As results of CWA application, BHL (Length of blast hole) and SFJ (Safety factor of Joint orientation) show comparatively high contribution of 18.78% and 19.77% which imply that these are somewhat critical influential parameter of unplanned dilution.