• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.345-345
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• 2007

ZnS/$Na_3AlF_6$/ZnS/Cu multi-layered thin film were simulated by EMP. EMP is a comprehensive software package for the design and analysis of optical thin film. ZnS and $Na_3AlF_6$ was selected as a high refractive index material and low refractive index material And Cu was selected as mid reflective material. Optical properties including color effect were systematically studied in terms of different low refractive index materials thickness. $Na_3AlF_6$ were changed 0.25, 0.5, 0.75, $1.0{\lambda}$. The thin film showed $0.25{\lambda}$ : blue, purple / $0.5{\lambda}$ : yellow $0.75{\lambda}$ : blue, purple, red / $1.0{\lambda}$ : yellow, green, blue, purple. It was becaused by different optical thickness of $Na_3AlF_6$. The maximum of optical interference by refractive layer.

• Korean Journal of Materials Research
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• v.23 no.12
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• pp.672-679
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• 2013

$Fe_4[Fe(CN)_6]_3$ coated on a mica or $TiO_2$/mica surface as infrared reflective blue pigment was prepared by a hydrothermal method. $Fe_4[Fe(CN)_6]_3$, used as coloring agent, was uniformly coated on mica or $TiO_2$/mica under the optimized condition of a 1.2 : 1 weight ratio between iron(III) chloride hexahydrate and potassium ferrocyanidetrihydrate at the initial pH level of 4.5 at $70^{\circ}C$. The infrared (IR)-reflective pigments were characterized by SEM, Zeta-potenial, FT-IR, and UV-VIS NIR spectrophotometry. Especially the CIE color coordinate and total solar reflectance(TSR) properties of the pigments were investigated in relation to variation of the coating and coated substrate thicknesses. Isolation-heat paint was prepared with 20 wt% blue pigments fully dispersed in acryl-urethane resin and several additives to coat the film uniformly. The films were also measured with CIE color coordinate, TSR, and the surface temperature was recorded by an isolation-heat measuring system. The pigments and films of $Fe_4[Fe(CN)_6]_3$ coated on mica and $TiO_2$/mica showed high TSR values compared with the TSR value of $Fe_4[Fe(CN)_6]_3$ itself. According to the increase of TSR value, the property of isolation-heat is effective. To realize the optimal blue color, we applied the the pigment to $TiO_2$ coated mica(TM(b)) which has blueish interference color. The pigment of $Fe_4[Fe(CN)_6]_3$ coated on TM(b) shows a strong blue color compared with that of $Fe_4[Fe(CN)_6]_3$ coated on $TiO_2$/Mmca(TM(w)), which has a whitish interference color.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.251-254
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• 2001

This paper describes an efficiency improvement of buried contact solar cell (BSCS) with a structure of MgF$_2$/CeO$_2$/Ag/Cu/Ni grid/n$^{+}$ emitter/p-type Si base/p$^{+}$/Al. Theoretical and experimental investigations were performed on a double layer antireflection (DLAR) coating of MgF$_2$/CeO$_2$. We investigated CeO$_2$ films as an AR layer because they have a proper refractive index of 2.46 and demonstrate the same lattice constant as Si substrate. An optimized DLAR coating shewed a reflectance as low as 2.04 % in the wavelengths ranged from 0.4 ${\mu}{\textrm}{m}$ to 1.1 ${\mu}{\textrm}{m}$. BCSC cell efficiency was improved from 16.2 % without any AR coating to 19.9 % by employing DLAR coatings. Further details on MgF$_2$/CeO$_2$ DLAR coatings on the BCSC cells are presented in this paper.per.

• Fire Science and Engineering
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• v.32 no.4
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• pp.42-49
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• 2018

In this study, in order to investigate whether or not the emergency broadcasting sound generated from an emergency broadcasting speaker is clearly transmitted to the occupant through architectural sound simulation, when the loudspeaker for emergency broadcasting is installed at intervals of 25 m according to NFSC 202 for a rectangular hallway. The sound pressure level and speech intelligibility index were analyzed according to changes in building finishing materials. With a reflective material finishing, sound pressure level satisfied the standard while speech intelligibility index was low. As a result of applying the sound absorbing material finishing, clarity and speech transmission index was improved to a level that could be understood by the occupant, whereas the sound pressure level delivered to the occupant decreased in the same space.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.7
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• pp.665-668
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• 2008

Multi-layered thin films of $Fe_2O_3/Na_3AlF_6/Fe_2O_3/Cu$, Cr, Al were deposited on glass substrate by evaporation process. As high and low refractive index material, $Fe_2O_3$ and $Na_3AlF_6$ were selected and additionally Cu, Al and Cr were chosen as mid reflective layer respectively. Optical properties including reflectance were systematically studied depending on optical thickness of $Na_3AlF_6$ especially $0.25{\lambda}$ and $0.5{\lambda}$. In order to expect the experimental result, the simulation program, the Essential Macleod Program(EMP) was adopted and compared with the experimental data. Based on the results taken by spectrophotometer at viewing angle $45^{\circ}C$, the $Fe_2O_3/Na_3AlF_6/Fe_2O_3/Cu$ show the colour rage between red and orange in $0.25{\lambda}$ and green and pupple in $0.5{\lambda}$ respectively. When the Al was used as mid reflective layers in $Fe_2O_3/Na_3AlF_6/Fe_2O_3$ system, typical yellow colour and mixed colour between green and pupple were appeared in $0.25{\lambda}$ and $0.5{\lambda}$ of $Na_3AlF_6$ respectively. As compared the experimental result to simulation data, it was found out that the experimental data is relatively well matched with the EMP simulation data.

• Korean Journal of Applied Biomechanics
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• v.27 no.2
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• pp.133-140
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• 2017

Objective: The purpose of this study was to determine the relationship between center of pressure (CoP) and local stability of the lower joints, which was calculated based on approximate entropy (ApEn) during walking in elderly women. Method: Eighteen elderly women were recruited (age: $66.4{\pm}1.2yrs$; mass: $55.4{\pm}8.3kg$; height: $1.56{\pm}0.04m$) for this study. Before collecting data, reflective marker triads composed of 3 non-collinear spheres were attached to the lateral surface of the thigh and shank near the mid-segment to measure motion of the thigh and shank segments. To measure foot motion, reflective markers were placed on the shoe at the heel, head of the fifth metatarsal, and lateral malleolus, and were also placed on the right anterior-superior iliac spine, left anterior-superior iliac spine, and sacrum to observe pelvic motion. During treadmill walking, kinematic data were recorded using 6 infrared cameras (Oqus 300, Qualisys, Sweden) with a 100 Hz sampling frequency and kinetic data were collected from a treadmill (Instrumented Treadmill, Bertec, USA) for 20 strides. From kinematic data, 3D angles of the lower extremity's joint were calculated using Cardan technique and then ApEn were computed for their angles to evaluate local stability. Range of CoP was determined from the kinetic data. Pearson product-moment and Spearman rank correlation coefficient were applied to find relationship between CoP and ApEn. The level of significance was determined at p<.05. Results: There was a negative linear correlation between CoP and ApEn of hip joint adduction-abduction motion (p<.05), but ApEn of other joint motion did not affect the CoP. Conclusion: It was conjectured that ApEn, local stability index, for adduction/abduction of the hip joint during walking could be useful as a fall predictor.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.8
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• pp.395-401
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• 2015

Recently, many research studies have been carried out on the efficiency of light-shelf daylighting systems, especially comparing performance improvements and the limitations of reflective surfaces and their lighting performance. In this study, a crystal face reflective surface is proposed. The objective of the study is to evaluate the lighting performance of a crystal face light-shelf through a performance study. The performance study was carried out in a full scale test-bed in order to calculate the light distribution and energy consumption utilizing the standard indoor illumination as an index. The conclusions of the performance study are as follows. 1) The optimal angle of incidence for daylighting for both the operable flat type light-shelf and the crystal face light-shelf are taken in the natural environment on the dates of the winter and summer solstices, as well as the autumn and spring equinoxes. 2) The application and installation of the crystal face light-shelf can produce a 29.9%~34.3% increase of light distribution within the indoor space. However, the increase of light distribution can also lead to a decrease in the uniformity ratio, a design challenge that should be considered when applying a crystal face light-shelf. 3) It is possible to achieve a 7.98%~13.3% greater reduction in energy consumption when applying a crystal face light-shelf than when applying a flat type light-shelf. The increase in the number of crystal faces should concur with the analysis of the energy reduction. A limitation of the study is that only one predetermined pattern was performance tested for a crystal face light-shelf. In order to carry out further research on crystal face light-shelves, additional performance studies are needed based on alternative patterns and designs.

• Safety and Health at Work
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• v.14 no.3
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• pp.325-331
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• 2023

Background: Heat stress is a harmful physical hazard in many occupational settings. However, consequences of occupational heat exposure among workers in a sugarcane factory in Ethiopia are not well characterized. This study aimed to assess the level of occupational heat exposure-related symptoms and contributing factors. Methods: In this cross-sectional study, five workstations were selected for temperature measurement. Heat stress levels were measured using a wet-bulb globe temperature index meter. A stratified random sampling technique was used to select 1,524 participants. Heat-related symptoms were assessed using validated questionnaires. Results: The level of occupational heat exposure was 72.4% (95% CI: 70.2%-74.8%), while 71.6% (95% CI: 69.3%-74.9%) of participants experienced at least one symptom related to heat stress. The most common heat-related symptoms were swelling of hands and feet (78%), severe thirst (77.8%) and dry mouth (77.4%). The identified risk factors were a lack of reflective shields (AOR: 2.20, 95% CI: 1.53, 3.17), not-enclosed extreme heat sources (AOR: 1.76, 95% CI: 1.23, 2.51), a lack of access to shade (AOR: 9.62, 95% CI: 6.20, 14.92), and inappropriate protective clothing provision (AOR: 1.58, 95% CI: 1.27, 2.71). Conclusions: The burden of occupational heat exposure and heat-induced symptoms was high. Lack of reflective shields, the absence of enclosed extreme heat sources, a lack of access to shade, and inappropriate protective clothing provision were considerable attributes of heat stress. Therefore, the use of mechanical solutions to stop heat emissions at their sources and the key factors identified were areas for future intervention.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.90.2-90.2
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• 2010

The crystalline silicon solar cells have been optical losses. but it can be reduced using light trapping by texture structure and anti-reflection coating. The high reflective index of crystalline silicon at solar wavelengths(400nm~1000nm) creates large reflection losses that must be compensated for by applying anti-reflection coating. In this study, the use of porous silicon(PSi) as an active material in a solar cell to take advantage of light trapping and blue-harvesting photoluminescence effect. Porous silicon is form by anodization and can be obtained in an electrolyte with hydrofluoric. We expect our research can results approaching to lower than 10% of several reflectance by porous silicon solar cells.

• Textile Coloration and Finishing
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• v.8 no.2
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• pp.56-63
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• 1996

Low-temperature plasma treatment or sputter etching is of interest as one of the techniques to modify polymer surface. In this study, poly(ethylene terephthalate)(PET), nylon 6 and cotton fabrics dyed three black dyes were subjected to low-temperature argon plasma and also sputter etching. In relation to bathochromic effect, the surface characteristics of the treated fabrics and films were investigated by means of critical surface tension, SEM and ESCA measurement. The depth of shade of fabrics more increased by the sputter etching technique than argon plasma treatment. Many microcraters on the fiber surface formed by the sputter etching resulted in increase of surface area of the fiber and wettability, but the hydrophobic group was increased by the results of ESCA analysis. In particular the change in reflective index of the fibers was much more effective than the chemical composition of the fiber surface on increasing of the depth of shade.