• Transactions on Electrical and Electronic Materials
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• v.13 no.1
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• pp.16-18
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• 2012

LED lighting systems that combine lighting capability, emotional and physiological characteristics are required for lighting source and multifunctional applications. In this work, Simulation studies using optical analysis software packages, Light Tools, are presented. This is done to estimate the uniformity ratio of illuminance and photosynthetic photon flux density (PPFD) of the periodic 2D lattice arrangements, such as square, diamond, two-way bias quadrangular, hexagonal, and Kagome lattices, under the same transmissivity, absorptance and reflectivity. It has been found out that the two-dimensional Kagome lattice arrangement exhibited high uniformity ratio of illuminance and PPFD compared to other lattices. Accordingly, these results can be used to guide a design and improve the lighting environment which in turn would maximize the uniform distributions of illuminance.

• Structural Engineering and Mechanics
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• v.35 no.3
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• pp.335-348
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• 2010

Cutouts are often provided in structural and aircraft components for ventilation, for access, inspection, electric lines and fuel lines or sometimes to lighten the structure. This paper addresses the effects of cutout shape (i.e., circular, square, diamond, elliptical-vertical and elliptical-horizontal) and size on buckling and postbuckling response of quasi-isotropic (i.e., $(+45/-45/0/90)_{2s}$) composite laminate under uni-axial compression. The finite element method is used to carry out the investigation. The formulation is based on first order shear deformation theory and von Karman's assumptions are used to incorporate geometric nonlinearity. The 3-D Tsai-Hill criterion is used to predict the failure of a lamina while the onset of delamination is predicted by the interlaminar failure criterion. It is observed that for the smaller size cutout area there is no significant effect of cutout shape on load-deflection response of the laminate. It is also concluded that the cutout size has substantial influence on the buckling and postbuckling response of the laminate with elliptical-horizontal cutout, while this effect is observed to be the least in case of laminate with elliptical-vertical cutout.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.4
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• pp.304-311
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• 2006

Experiments on evaporative spray cooling on the square plate heaters with plain or micro-porous coated surfaces were performed in this study. Micro-porous coated surfaces were made by using DOM [Diamond particle, Omegabond 101, Methyl-Ethyl-Keton] method. In case of purely air-jet cooling, the micro-porous coating doesn't affect the cooling capacity. In spray cooling three different flow patterns (complete wetting, evaporative wetting, dryout) are observed on both plain and micro-porous coated surfaces. The effects of various operating conditions, such as water flow rate, particle size, and coating thickness were investigated on the micro-porous coated surfaces. It is found that the level of surface wetting is an important factor to determine the performance of spray cooling. It depends on the balance between absorbed liquid amount by capillary force over porosity and the evaporative amount. The micro-porous coated surface has largest cooling capacity, especially in the evaporative wetting zone. It is found that the effects of liquid flow rate and coating thickness are significant in evaporative wetting zone, but are not in complete wetting and dryout zones.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.6_2
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• pp.935-941
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• 2020

In this study, the effect of different shapes on the heat dissipation characteristics of other porous frames on LED lighting frames was studied using finite element analysis. In addition, the heat transfer characteristics of LED frames were tested using a thermal imaging camera and the results of finite element analysis were compared to derive the optimal hole shape. According to the study, the heat dissipation effect was better for frames with hole compared to existing ones without holes. In particular, the heat dissipation characteristics test showed that for frames with holes, the rise time to the maximum temperature is fast and the maximum temperature is significantly lower. Also, we could see that the square and diamond shapes were smaller than the circular pores, but had a greater heat dissipation effect. Through this study, we have concluded that there is a limit to increasing the heat dissipation effect of the frame with a perforated shape, and it is necessary to conduct further research on the change in the shape of the frame in order to achieve a better heat dissipation effect in the future.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.67.2-67.2
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• 2020

Not only the magnitude of the mirror surface error, the pattern matters as it produces certain aberrations. In particular, the surface error of the freeform mirrors, which are optimized to eliminate specific aberrations, might show much higher sensitivity in optical performance. Therefore, we analyze the mirror surface error with Zernike polynomials with the goal of generating a realistic error surface. We investigate the surface error of the freeform mirror fabricated by diamond turning machine to analyze the realistic tendency of the error. The surface error with 0.22 ㎛ root-mean-square value is fitted to the Zernike terms using the incremental fitting method, which increases the number of the fitting coefficients through steps. Furthermore, optical performance via surface error pattern based on Zernike terms is studied to see the influences of each term. With this study, realistic error surface generation may allow higher accuracy not only for the feasibility test but also for all tests and predictions using optical simulations.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.12
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• pp.8760-8766
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• 2015

In this paper a technology which gives directions to people and also localization of the robotic vacuum cleaners inside some spacious buildings is developed. For this purpose, it is confirmed that which pattern has a small error in dealing with the indoor localization with various RFID tag arrangements attached on the ground. This experiment was conducted by using MT92(900MHz range Antenna) and ALR 9900+(Reader). As a result, the square arrangement has the least error, 21.19cm, among other patterns which are diamond, rectangle and regular hexagon. However, it is necessary to consider the number of tags in the unit area, from this point of view the regular hexagon arrangement is the most efficient arrangement among other patterns because it needs only 6 tags in the unit area.

• Journal of the Korean Society of Clothing and Textiles
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• v.31 no.5 s.164
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• pp.742-752
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• 2007

The purpose of this study is the image of clothing according to the change of the dots' size was analyzed and its influence on the formation of the image of polka dots clothing was investigated. White waterdrop patterns were designed on the 12 kinds of black texture using Photoshop and CAD program in regular arrangement of diamond figure, composed of white waterdrop(0.5cm, 1.0cm, 1.5cm and 2cm in diameter) and interval(diameter : interval-1 : 1, 1 : 2, 1 : 4). Applying above specification, the photograph stimulus of 12 kinds of X-line one-piece dress with wide square neckline and without sleeve or detailed ornament was presented on a screen in the same size as when putting it on. The image of polka dots clothes was investigated by questionnaire survey. The object of the study was 320 females aged between 16 and 29. Factor analysis, one-way ANOVA, $Scheff\acute{e}$ verification and two-way ANOVA using SPSS 10.0 were carried out for data analysis. Followings are the results: 1) The image of polka dots clothing consists of 4 factors as aesthetics, brevity, dynamism and lightweight. 2) The size of the dot has a great influence on the formation of the image of polka dots clothing. 3) The evaluations of the image of polka dots clothing were different depending on the age and physical image, the personal characteristics of the object of investigation.

• Journal of the Korean Ceramic Society
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• v.48 no.4
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• pp.312-315
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• 2011

The effect of slurry composition and wafer flatness on a material removal rate (MRR) and resulting surface roughness which are evaluation parameters to determine the CMP characteristics of the on-axis 6H-SiC substrate were systematically investigated. 2-inch SiC wafers were fabricated from the ingot grown by a conventional physical vapor transport (PVT) method were used for this study. The SiC substrate after the CMP process using slurry added oxidizers into slurry consisted of KOH-based colloidal silica and nano-size diamond particle exhibited the significant MRR value and a fine surface without any surface damages. SiC wafers with high bow value after the CMP process exhibited large variation in surface roughness value compared to wafer with low bow value. The CMPprocessed SiC wafer having a low bow value of 1im was observed to result in the Root-mean-square height (RMS) value of 2.747 A and the mean height (Ra) value of 2.147 A.

• The Journal of Advanced Prosthodontics
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• v.6 no.4
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• pp.317-324
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• 2014

PURPOSE. This study was to evaluate the effect of grinding of the inner metal surface during the porcelain try-in stage on metal-porcelain bonding considering the maximum temperature and the vibration of samples. MATERIALS AND METHODS. Ninety-one square prism-shaped ($1{\times}1{\times}1.5mm$) nickel-chrome cast frameworks 0.3 mm thick were prepared. Porcelain was applied on two opposite outer axial surfaces of the frameworks. The grinding was performed from the opposite axial sides of the inner metal surfaces with a low-speed handpiece with two types of burs (diamond, tungsten-carbide) under three grinding forces (3.5 N, 7 N, 14 N) and at two durations (5 seconds, 10 seconds). The shear bond strength (SBS) test was performed with universal testing machine. Statistical analyzes were performed at 5% significance level. RESULTS. The samples subjected to grinding under 3.5 N showed higher SBS values than those exposed to grinding under 7 N and 14 N (P<.05). SBS values of none of the groups differed from those of the control group (P>.05). The types of bur (P=.965) and the duration (P=.679) did not affect the SBS values. On the other hand, type of bur, force applied, and duration of the grinding affected the maximum temperatures of the samples, whereas the maximum vibration was affected only by the type of bur (P<.05). CONCLUSION. Grinding the inner metal surface did not affect the metal-porcelain bond strength. Although the grinding affected the maximum temperature and the vibration values of the samples, these did not influence the bonding strength.

• Journal of Fashion Business
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• v.15 no.4
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• pp.122-134
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• 2011

The peanut-shaped cloth diaper has cut uncomfortable crotch region off the square-shaped cloth diaper into a peanut-shape, and finished the edge by bias with multi-layers of fabric. This study has the purpose on providing the basic data for designing the peanut-shaped cloth diaper. For this purpose, the peanut-shaped cloth diapers on market were collected and analyzed by their shape and size, and also the patterns and differences in making were compared. 26 products from 17 brands were collected as samples. The analysis factors are the shape and size of the peanut-shaped cloth diaper, and characteristics and patterns in making. Among the samples, only 3 diapers were straight-shaped; the rest of them were peanut-shaped. The size difference between the big and small peanut-shaped cloth diapers was very large; the total length of the small one was 36.5cm-39cm which was very common, and the total length of the big one was more than 44cm. All diapers had longer width in the back than the front. The width of the front and back was different for each sample, therefore, it seemed to have some difficulties to set the standard. The peanut-shaped cloth diaper had different make-up depending on its characteristics including. absorbance, washing and drying. It was usually made by cotton woven of diamond jacquard or knit, and finished the edge by woven bias or knit bias. The peanut-shaped cloth diapers were various including a sheet of diaper, two sheets of diapers fixed with velcro, three sheets of diapers, and etc. For the patterns of the diapers, only two samples out of all had three dimensional shape, and the rest were produced using flat shape. There were no distinction between the diapers of girls and boys. Therefore, it is necessary to make the product based on scientific data about the peanut-shaped cloth diaper.