• Korean Journal of Materials Research
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• v.33 no.3
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• pp.101-105
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• 2023

A mixture of elemental Co₅₀Si₅₀ powders was subjected to mechanical alloying (MA) at room temperature to prepare a CoSi thermoelectric compound. Consolidation of the Co₅₀Si₅₀ mechanically alloyed powders was performed in a spark plasma sintering (SPS) machine using graphite dies up to 800 ℃ and 1,000 ℃ under 50 MPa. We have revealed that a nanocrystalline CoSi thermoelectric compound can be produced from a mixture of elemental Co₅₀Si₅₀ powders by mechanical alloying after 20 hours. The average grain size estimated from a Hall plot of the CoSi intermetallic compound prepared after 40 hours of MA was 65 nm. The degree of shrinkage of the consolidated samples during SPS became significant at about 450 ℃. All of the compact bodies had a high relative density of more than 94 % with a metallic glare on the surface. X-ray diffraction data showed that the SPS compact produced by sintering mechanically alloyed powders for 40-hours up to 800 ℃ consisted of only nanocrystalline CoSi with a grain size of 110 nm.

• Journal of the Korean Solar Energy Society
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• v.32 no.6
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• pp.100-105
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• 2012

In previous study, to investigate the impression of the compound lighting based on the AC-Model at the full-size room, the impressions of various compound lighting were completed as compared with that of the uniform lightings through the comparison method (a paired comparison) by Semantic Differential scaling. Also, we examined the effect of the supplementary lighting type increasing the lights at the side of the window and the blind-control lighting type, and they were compared with the existing compound lighting type. In results, pared comparison of the compound lighting and the uniform lighting, indicates that the impression of the compound lighting is generally similar to that of the uniform lighting when there are same ratios of the light from the window. Based on these results, we suggest that the AC-Model might be applied to various conditions. And we also introduce the method for daylighting that it is possible to reduce discomfort glare and to improve visual impressions as the supplementary type and blind-control type on the compound lighting. And it was found that electric power consumption of the compound lighting room was lower than that of the uniform lighting room when as same lighting ratio of the compound lighting and the uniform lighting from the window was provided or there was the lighting distribution simulated to same light ratio from the window. Since the method of the ACModel was described in the experimental condition, additional studies should be performed to determine if this model could be applied to different window configurations, lighting layout and types of a room.

• KIEAE Journal
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• v.15 no.6
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• pp.101-109
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• 2015

Purpose: Glazing and shading devices influence a lot on the thermal and visual environment in office buildings. Solar heat and daylight are contrary concept, therefore proper arrangement of thermal and optical performance is needed when designing a glazing and shading devices. The purpose of this study is to examine the conditions of the glazing and shading devices available for promoting the reduction of cooling loads + lighting loads and the improvement in thermal comfort and visual comfort for the summer season in an office building installed with venetian blind. Method: This study established 12 simulation cases which have different glazings and the positions of venetian blind for evaluating different thermal and optical performance. And by using EnergyPlus v8.1 and Window v7.2 program, we quantitatively analyzed cooling loads + lighting loads, thermal comfort and visual comfort in an office building installed with the glazing and shading devices. Result: Consequently, Case 9(Double Low-E+Exterior Blind) is the best arrangement of solar heat gain and daylight influx, thereby becomes the most excellent case of reducing cooling+lighting loads(46.8%) and simultaneously becomes the enhancement case in thermal comfort. Also, DGI(Daylight glare index) under clear sky conditions in summer was evaluated to be 19.6, and thereby satisfied the recommendation level of allowing visual comfort.

• Korean Journal of Digital Imaging in Medicine
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• v.9 no.1
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• pp.53-65
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• 2007

PACS has been run at the Kyung Hee University Medical Center(KHMC) since 2001, and the installation and operation of PACS have contributed to automation and quantification of KHMC's medical environment During these five years our greatest concern is how to make our own guiding principle of diagnostic monitor QA which is adapted to international standards. In accordance with the terms of 'KHMC QA Guideline', 'AAPM TG18', 'SMPTE RP133', 'DICOM Part14', 'DIN V 6868-57', 'JESRA X-0093', 'JIS Z4752-2-5' and 'KCARE', concern about quality assurance of medical images are on the increase. With the investigation of acceptance testing and quality control of international standards for medical display devices, and data collection and analysis for recommended guideline, it is reported that acceptance testing(quality control), including geometrical distortion, display reflection, luminance response, luminance uniformity, display resolution, display noise, veiling glare and color chromaticity being adequate and effective to domestic hospital environments for medical display devices and assessment methods according to each performance. Accordingly, KHMC classified the checkpoint items by period, at the time of monitor setting, monthly, quarterly, half-yearly and annually. Periodic classification of checkpoint items for monitor QA makes a good guideline for image QA/QC and useful guideline for persistent good quality of monitor.

• Proceedings of the KIEE Conference
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• 2008.09a
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• pp.140-143
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• 2008

In this study, it was studied about the improved road light design for drivers and pedestrians using ray- or reverse ray-tracing method. Many of conventional road lights are not suitable for drivers and pedestrians because it has some serious problems such as glare effect or randomicity of illuminated areas. It was oriented from customary design method which was pointed at simple target such as luminance or electrical power. But it was not truth any more that the high luminance or electrical power consumption mean more bright and good mad light. We studied ray-tracing method for road light reflector design to get the several goals. It means that good road light has easy for drivers and Pedestrians eyes and illuminating objects on the road clearly. So, we set the design targets such as uniformity on the road area per one road light, shading angles and continuous luminance uniformity on the long distance road. We designed ideal road light conditions using ray-tracing method. We set the height of drivers and pedestrians eyes and calculated design guideline to make above design targets. Then we designed road light reflector using reverse ray-tracing method. And we achieved same luminance on the road almost half power consumption because we reduced loss of light. We achieved ideal design guide as 75 degrees of shading angles and 0.5 of luminance uniformity on the road area. Finally, we suggested reflector design for 250 watts power consumption CDM light source.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.3
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• pp.347-350
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• 2009

In this study, it was studied about the improved road light design for drivers and pedestrians using forward or reverse ray-tracing method. Many of conventional road lights are not suitable for drivers and pedestrians because it has some serious problems such as glare effect or randomicity of illuminated areas. It was oriented from customary design method which was pointed at simple target such as luminance or electrical power. But it was not truth any more that the high luminance or electrical power consumption mean more bright and good road light. We studied ray-tracing method for road light reflector design to get the several goals. It means that good road light has easy for drivers and pedestrians eyes and illuminating objects on the road clearly. So, we set the design targets such as uniformity on the road area per one road light, shading angles and continuous luminance uniformity on the long distance road. We designed ideal road light conditions using ray-tracing method. We set the height of drivers and pedestrians eyes and calculated design guideline to make above design targets. Then we designed road light reflector using reverse ray-tracing method. And we achieved same luminance on the road almost half power consumption because we reduced loss of light. We achieved ideal design guide as 75 degrees of shading angles and 0.5 of luminance uniformity on the road area. It is superior than conventional road light ability such as 0.35 of luminance uniformity of 400 watts power consumption lamp. Finally, we suggested reflector design for 250 watts power consumption CDM Iight source.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.6
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• pp.39-44
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• 2005

Due to mismatch of thermal expansion coefficients between aluminum sheet and glass/epoxy sheet, thermal residual stresses generally appear in the FML. These stresses will affect the yield and fatigue strength of the FML. The numerically determined residual stresses in the Fiber-Metal-Laminates(FML) have been compared to the residual stresses measured from the curvature and tensile test methods. These two experimental methods have been developed for assessing the influence of residual stress in FML. Post-stretching process has been applied to remove the thermal residual stress and reverse the stress distribution. After post-stretching process, the residual stress has been measured from experiments. The results obtained show that analytical and experimental data are well agreed. The thermal residual stress can be removed by post-stretching process and it will increase the yield strength of FML.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.8
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• pp.1-7
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• 2009

This study is intended to propose the environment friendly lighting which can be excluded the element of obtrusive light(glare, spill light) and to make the sight environment of the external and internal road more comfortable as newly approaching the lower positioned lighting from the current high pole lighting. Taking account of the current situation of putting the stress on the road sight scene. It is proposed the study focused on the aesthetic design for playing a role of scenery. For this, it is searched used situation of the low light at interior of the country and abroad and tried to find the improvement. Also it is tried find out how to raise the effectiveness. And throughout the site inspection and the data searching about the road facility of a road to be installed the low height lighting, it is suggested the standard of the lighting installation and the direction for the future on the light design and development of the low height lighting which is suitable for the domestic situation.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.2
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• pp.26-34
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• 2008

The purpose of this study is to analyze daylight distribution and characteristics of light on the Korean traditional paper and to investigate a possibility as the shading systems. First of all, daylight distribution through the Korean traditional paper windows and doors of the Traditional House is analyzed at Genjaegotaek of the Asan Oeam Traditional Village. After making a model, the characteristics of light on the Korean traditional paper and Roller Shade fabric are analyzed Korean traditional paper has a good efficiency to diffuse the light and is less glare than Roller Shade fabric. In the present office buildings and apartmant houses, daylight characteristics of the Korean traditional paper windows and doors could be used as preliminary data to develop a window system which makes greatest performance of daylight.

• KIEAE Journal
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• v.13 no.5
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• pp.59-66
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• 2013

Current Architectural Facade Designs have been trending to increased glass areas resulting in increasing impact on interior lighting and daylighting. In regards to indoor environmental quality, the increase in window space has a large impact on the daylighting received which ultimately impacts the liveability of a space. Especially when considering seasons, in the summer, excessive daylighting can result in glare as well as put an increased load in conditioning the air space further reducing energy efficiency. As a result, in order to improve the sustainability performance of a building, it is important to limit the natural lighting exposure to properly meet the needs and conditions of the building occupants. One of the most representative features to limit excessive sunlight exposure, is to incorporate operable blind systems. To this end, this research has been based on simulations performance through the Radiance Program. Radiance is capable of analyzing performance of daylight and impact of sunlight. Through analysis of different slat angles and blind shapes, impact and minimization of energy usage was evaluated. Furthermore, seasonal analysis was performed in order to understand the effects of seasonal climate factors. Ultimately this research provides an analysis of operable blinds optimization and effects of blind shape, control factors and angle of shading.