• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.674-682
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• 2018

Large industrial motors require a large area because of the high risk of shutdown accidents and large industrial accidents due to the lowering of the dielectric strength of the armature windings and overheating problems. Therefore, there is a demand for a large-capacity motor that has small size, light weight, and excellent dielectric strength compared with conventional motors. Superconducting motors have advantages of high efficiency and output power, low size, low weight, and improved stability. This results from greatly increasing the magnetic field generation by using superconductive field coils in rotating machines such as generators and motors. It is very important to design and analyze the cooling system to lower the critical temperature of the wires to achieve superconducting performance. In this study, a field loss analysis and low-temperature heat transfer analysis of the cooling system were performed through the conceptual design of a 100-HP high-temperature superconducting synchronous motor. The field loss analysis shows that a uniform pore magnetic flux density appears when high-temperature superconducting wire is used. The low-temperature heat transfer analysis for gaseous neon and liquid neon showed that a flow rate of 1 kg/min of liquid neon is suitable for maintaining low-temperature stability of the high-temperature superconducting wire.

• Journal of the Korean Wood Science and Technology
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• v.38 no.4
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• pp.306-315
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• 2010

The stress laminated timber, which could be manufactured by small dimension lumber on construction site, has high possibilities for bridges in remote area, such as recreation forest or forest road, because those bridges may be short span and low frequency in use. The stress laminated timber has merits of easiness for preservative treatment and transportation because it is manufactured with small dimension lumber. This study was carried out to analyze performances of stress laminated timber manufactured with preservative treated domestic pitch pine for developing structural design data for stress laminated timber bridges for vehicular traffic. Perpendicular to grain compressive performance by preservative treatment and bending performance by bored holes of pitch pine lumber was analyzed. Then, the effects of bending performance by pre-stress pressure, distance of bolts, number of laminations and planning were analyzed. Conclusively, planning of lumber was not necessary for manufacturing stress laminated timber, and 80% of bending stiffness criteria was maintained as pre-stress pressure was higher than 3.0 kg/$cm^2$. However, further researches are needed to define the effects of bolt distances and number of laminations. The results of this research would be basic data for design stress laminated timber bridges for vehicular traffic in Korea.

• Explosives and Blasting
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• v.20 no.3
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• pp.15-23
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• 2002

철골구조물은 일반 철근 콘크리트 구조와는 달리 단순히 천공을 하고 폭약을 장약하여 기폭시키는 방법으로는 해체 또는 절단이 어렵다. 국내의 경우 최근 철골 구조로 건축되는 강교와 건축물 등이 증가하는 추세이며, 내구연한이 다하거나 구조적 결함으로 인하여 해체 대상으로 지목되는 철골구조물에 대해서는 특수한 형태의 해체 기술을 필요로 한다. 1997년 이후 국내에 철골구조물의 발파해체를 위하여 성형폭약에 의한 폭발절단기술에 관한 연구가 소개된 이후로 폭발절단력에 미치는 성형폭약의 라이너(Liner), 폭약의 종류, 형상 및 이격거리(Stand-off distance) 등에 대한 연구가 활발히 이루어졌으며, 또한 국산화를 위한 기초적인 설계변수에 관한 연구 등이 보고 된 바 있다. 현재 성형폭약의 사용범위가 철골구조물의 절단해체 뿐만 아니라 긴급구조를 필요로 하는 특수한 용도나 군사폭약의 해체, 항공산업 등 그 적용범위가 확대되고 있는 실정이다. 그러나, 성형폭약의 성능 향상 및 품질 보증을 위한 체계적인 설계 변수의 검토 설정에 관한 연구와 산업f'의 적용을 위한 구체적인 결과는 보고 된 바 없는 실정이다. 그래서, 보다 체계적인 현장 적용 시험 등에 대한 연구가 효율적으로 진행될 경우 국내 고유 기술에 의한 철구조물의 절단 및 해체공법에 획기적인 변화를 가져올 수 있을 것으로 기대된다. 따라서, 본 연구에서는 국산화되어 현장에 적용되고 있는 성형폭약 HAKO 제품을 기준으로 이미 국내에 알려진 성형폭약과 비교 분석하였다. 또한 보다 효율적인 산업계의 적용을 위한 각종 시험 결과 및 국산화 현황과 향후 활용 방안 등에 대하여 소개하고자 한다.

• Journal of Soil and Groundwater Environment
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• v.21 no.6
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• pp.114-127
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• 2016

An increase of groundwater flux in BHE system creates that ground temperature (locT) becomes lower in summer and higher in winter time. In other words, it improves significantly the performance of BHE system. The size of thermal plume made up by advection driven-flow under the balanced energy load is relatively small in contrast to the unbalanced energy load where groundwater flow causes considerable change in the size of thermal plume as well ground temperature. The ground temperatures of the up gradient and down gradient BHEs under conduction only heat transport are same due to no groundwater flow. But a significant difference of the ground temperature is observed between the down gradient and up gradient BHE as a result of groundwater flow-driven thermal interference took placed in BHE field. As many BHEs are designed under the obscure assumption of negligible groundwater flow, failure to account for advection can cause inefficiencies in system design and operation. Therefore including groundwater flow in the design procedure is considered to be essential for thermal and economic sustain ability of the BHE system.

• Journal of Soil and Groundwater Environment
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• v.21 no.3
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• pp.64-81
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• 2016

To analyze the influence of various groundwater flow rates (specific discharge) on BHE system with balanced and unbalanced energy loads under assuming same initial temperature (15℃) of ground and groundwater, numerical modeling using FEFLOW was used for this study. When groundwater flow is increased from 1 × 10⁻⁷ to 4 × 10⁻⁷m/s under balanced energy load, the performance of BHE system is improved about 26.7% in summer and 22.7% at winter time in a single BHE case as well as about 12.0~18.6% in summer and 7.6~8.7% in winter time depending on the number of boreholes in the grid, their array type, and bore hole separation in multiple BHE system case. In other words, the performance of BHE system is improved due to lower avT in summer and higher avT in winter time when groundwater flow becomes larger. On the contrary it is decreased owing to higher avT in summer and lower avT in winter time when the numbers of BHEs in an array are increased, Geothermal plume created at down-gradient area by groundwater flow is relatively small in balanced load condition while quite large in unbalanced load condition. Groundwater flow enhances in general the thermal efficiency by transferring heat away from the BHEs. Therefore it is highly required to obtain and to use adequate informations on hydrogeologic characterristics (K, S, hydraulic gradient, seasonal variation of groundwater temperature and water level) along with integrating groundwater flow and also hydrogeothermal properties (thermal conductivity, seasonal variation of ground temperatures etc.) of the relevant area for achieving the optimal design of BHE system.

• Journal of Bio-Environment Control
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• v.27 no.4
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• pp.294-301
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• 2018

In winter, thermal screens are widely used to reduce heat loss from greenhouse to save energy. Unfortunately, not much data are available to the farmer to compare thermal screens while selecting the one that meets their specific requirements. Thus, there is a need to investigate the thermal performance of thermal screens. To address this issue, the Building Energy Simulation (BES) model of a hot box was used to calculate the overall heat transfer coefficient (U-value) of the thermal screens. To validate the model, computed and experimental U-values of single-and double-layered polyethylene (PE) material were compared. This validated model was used to predict the U-values of the selected thermal screens under defined weather conditions. We quantified the U-values of each selected material and significant changes in their U-values were noted in response to different weather conditions. Notably, the thermal properties of the tested screens were taken from the previous literature to calculate U-values using the BES model. The U-values of the thermal screens can help researchers and farmers evaluate their screens and make pre-design decisions that suit their investment capabilities.

• Fire Science and Engineering
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• v.34 no.3
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• pp.8-17
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• 2020

In this study, the characteristics of HFIX insulated wire sheaths contaminated by pollutants were examined. KS C IEC 60811-1-3 standard was followed in performing the water-resistance wire tests. Pollutants were selected, and the specimens were exposed to the pollutants for a maximum duration of four weeks. The maximum tensile load and the elongation rate were measured each week. As the period of pollution exposure increased, the maximum tensile load of the specimens decreased by 6.22% and 6.52% at room temperature and high temperature, respectively, and 19.94% for specimens coated with a rust-proof lubricant. The elongation rate also decreased rapidly, such that the reductions in the properties of the sheath were significant. From the analysis of the surfaces using a scanning microscope, as the contamination period increased, structural changes such as perforation, split, and melting occurred, and the mechanical properties of the specimens decreased. Therefore, it is necessary to develop and follow an inspection cycle and periodically carry out repairs to prevent the deterioration of insulated wires.

• Journal of the Korean Solar Energy Society
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• v.31 no.4
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• pp.136-141
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• 2011

The lightshelf system reduces intense illumination levels of indoor from direct sun light and reflect to lead diffused light into indoor deeply. This study aims to design acurved-lightshelf by a ray tracing method and evaluate the daylighting performance of window integrated with the curved-lightshelf by computer simulations. For this purpose, evaluation test model was designed for the experiments to validate the simulation model, and the curved-lightshelf was designed by the ray tracing method using Ecotect. After the office model was designed using 3D simulation, the average indoor illuminance, luminance and distribution of illuminance were evaluated by simulation which has a algorithm of Radiosity and Ray-Tracing method under four different cases(case1;no lightshelf, case2; Flat board, case3; tilted at $30^{\circ}$ angle, case4; the curved-lightshelf). As results, it turns out that case1 showed higher average illuminance and case4 was more uniformly distributed than case2 and case3, In addition average luminance of case1 was also lower. indicating that the curved-lightshelf would reduce the possibility of the glare, while maintaining the sufficient daylight level.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.2
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• pp.8-15
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• 2006

To reduce costs and address other practical concern related to architectural lighting, we have been involved in various aspects of advanced daylighting design and control. If we look toward future building trends, we see that the advanced has already successfully deployed such complex lighting control systems. This paper takes a broad view of what advanced manufacturers have done to develop energy efficient lighting control technologies such as sensors, lumen maintenance, time of day scheduling, peak demand reduction and so forth. First of all strategies, daylighting controls would also need to be commissioned to respond to the specific daylighting signature of the zone. To translate the daylight in term of the amount of energy savings, an electric lighting system is designed and automatic on-off control system integrated with the contribution of daylighting has been applied to the operating of the artificial lighting. The lighting analysis program, Lumen-Micro predicts the optimal layout of conventional fluorescent and incandescent lighting fixtures to meet the designed lighting level and calculates unit power density, which translates the demanded amount of lighting energy.

• Journal of the Korea Concrete Institute
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• v.17 no.3 s.87
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• pp.393-400
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• 2005

Steel encased composite columns have been used for buildings and piers of bridges. Since the column section for the pier is relatively larger than that of building columns, economical steel ratio needs to be investigated for the required performance. Composite action between concrete and embedded steel sections can be obtained by bond and friction. However, the behavior of the column depends on the load introduction mechanism. Compression can be applied to concrete section, steel section and composite section. In this paper, experiments on shear strength of the steel encased composite column were performed to study the effect of confinement by transverse reinforcements, mechanical interlock by holes, and shear connectors. Bond strength obtained from the tests showed considerably higher value than the design value. Confinement, mechanical interlock and stud connectors Increased the shear strength and these values can be used effectively to obtain composite action of Steel Reinforced Concrete(SRC) columns.