• Journal of Communications and Networks
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• v.18 no.3
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• pp.476-483
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• 2016

Super Wi-Fi is a Wi-Fi-like service exploiting TV white space (WS) which is expected to achieve larger coverage than today's Wi-Fi thanks to its superior propagation characteristics. Super Wi-Fi has been materialized as an international standard, IEEE 802.11af, targeting indoor and outdoor applications, and is undergoing worldwide field tests. This paper demonstrates the true potential of indoor Super Wi-Fi, by experimentally comparing the signal propagation characteristics of Super Wi-Fi and Wi-Fi in the same indoor environment. Specifically, we measured the wall and floor attenuation factors and the path-loss distribution at 770MHz, 2.401 GHz, and 5.540 GHz, and predicted the downlink capacity of Wi-Fi and Super Wi-Fi. The experimental results have revealed that TVWS signals can penetrate up to two floors above and below, whereas Wi-Fi signals experience significant path loss even through a single floor. It has been also shown that Super Wi-Fi mitigates shaded regions of Wi-Fi by providing almost-homogeneous data rates within its coverage, performs comparable to Wi-Fi utilizing less bandwidth, and always achieves better spectral efficiency than Wi-Fi. The observed phenomena imply that Super Wi-Fi is suitable for indoor applications and has the potential of extending horizontal and vertical coverage of today's Wi-Fi.

• Journal of the Korean Institute of Landscape Architecture
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• v.29 no.1
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• pp.124-130
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• 2001

We have increasing number of new ponds planned and designed in traditional styles. However, many of the stoneworks at the edges of those new ponds are not the characteristics of our traditional ponds. This study is aiming at surveying and analysing the building techniques of Korean traditional water edges built with stones, by investigating selected ponds in royal palace gardens. This study was conducted through field investigation and literature reviews. Nine ponds from Gyongbok Palace, Changdeok Palace, and Changgyong Palace, which have many well-preserved ponds of various styles, were surveyed. First of all, the building materials (stones), or the kinds and sizes of stones used for the edges of ponds were surveyed. Secondly, construction methods, or the height and techniques of buildings stone walls were surveyed. Major findings were, first, the edges of most ponds constructed with granite Jangdaeseok, usually 120cm-140cm long, and 30cm-40cm thick. The only exceptions were those ponds which seemed to have been influenced by Japanese style. Second, typical pond ages were up-right vertical walls. Granite jangdaeseoks were piled-up 2 stories or up to six stories. Exceptions were Bandoji Pond and Chundangji Pond which had been constructed during latest period(King 'Ghojong' period). Third, heith of stone walls were between 60cm and 220cm. The depth of ponds were about 150cm or less, and the rest of the edge wall height was freeboard. Though the results of this study was not made by precise investigation and actual measurement, they could be fundamental information and data for the traditional styles of the Chosun dynasty Palace. It is believed that continuous researches on this matter will result in important and fundamental data of the establishment of traditional water edges.

• Journal of the Korea Furniture Society
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• v.27 no.1
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• pp.8-14
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• 2016

Increasing concerns of environment need to make change furniture field to more environmentally friendly approach, such as reuse of by-products from wooden products. As it is, the methods of recycling wood for industrial purposes have the advantage of productivity and adaptability. However, the industrial way is required a certain production facility of processing wooden by-products and has possible hygienic problems due to contaminated sources. Many designers have developed their own methods for reuse of wood in unique and artistic ways. Even so, because of confined sources, it could be not enough supply. Therefore, I developed the design methodology utilizing wooden by-products from S Design Company to relieve former ways' problems. The design suggestion took materials from a safe and abundant source. The wooden leftover pieces were connected together with epoxy clay, so previous process traces of furniture are remained as a decorative factor. Moreover, the synthesized material was able to be processed by ordinary woodworking facilities without additional installations. In doing so, console table focused on a commercial purpose and dining table for an artistic objective were successfully fabricated as final suggestions. In consideration of the proposal using wooden furniture leftovers, diverse recycling designs should be investigated for future reference.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.6
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• pp.443-451
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• 2015

Design formula for estimating the wave loading on the perforated caisson having two wave chambers is yet available. In this study, the analysis results are presented with the experimental data for the wave force acting on such a breakwater model. Based on the experimental results, it was able to clarify the variation of wave action according to five different wave phases that are associated with peak wave loading at the three vertical walls. Then the force adjustment factor for double-chamber caisson was estimated, similarly as Takahashi and Shimosako (1994), which needs to be further validated with subsequent experiments and practical application in the field.

• Korean Institute of Interior Design Journal
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• v.21 no.5
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• pp.34-45
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• 2012

In these days, restaurants are not simply used as a physical space but used as a cultural space in which people can enjoy and experience different cultures and traditional images. Moreover, from the restaurants design elements which help to form the atmosphere of the restaurants which serve food of specific country, we can see the history and traditions of that country. The additional value of the traditional decorative components which are the main factors forming the atmosphere of the restaurant will be different according to the various expressions used in the restaurant space. For this article, 12 restaurants, Norangjugory korean restaurant, Yongsusan korean restaurant, Best well-bing food restaurant, Awoolim, Mugunhwa, Ondal in Korea, and Songhelou, South Beauty, Xuxian restaurant & lounge, Beijing dadong roast duck restaurant, The horizon chinese restaurant, Dynasty jade garden in China, were selected for the field study. This study focused on a comparative analysis of the traditional decorative elements, especially, the application rate of the traditional decorative elements. The analyzed elements are nature, religious beliefs, history and culture for the intangible elements and facade, courtyard, trademark, ground, wall, ceiling, door, window, furniture and adornment for the tangible elements. After that, we analyzed the rates of the use of traditional decorative elements and modern decorative elements. Through the survey result and ratio analysis, we concluded as below. In Korean restaurant, traditionality is expressed in furnitures while, in Chinese restaurant, traditionality is expressed in decorative pattern. When it comes to the intangible elements among the traditional decorative components of the Korean and Chinese restaurants, Chinese and Korean restaurants have similarities in emphasizing the natural elements. Korean restaurants focus much on the environmentally friendly parts, while Chinese restaurants focus much on the fantastic natural atmospheres like those shown and expressed in the poems. As for religion characteristics, Chinese restaurants emphasize "geomancy" more than Korean restaurant. When it comes to the visible elements among the traditional decorative components of the Korean and Chinese restaurants, in Korean restaurants, the interior part has more traditionality than exterior part, while in Chinese restaurants, the exterior part has more traditionality than the interior part.

• The Plant Pathology Journal
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• v.18 no.6
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• pp.328-332
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• 2002

Wheat samples showing typical spot blotch symptoms on stems and sheaths were collected from the field after physiological maturity, and were sealed in paper bags and stored in the laboratory at room temperature to study the survival of Bipolaris sorokiniana conidia on wheat straw. The materials were observed at monthly intervals to assess the conidia viability during storage. After 4 months, the frequency of individual conidia already present on wheat straw at the time of sampling was reduced and appeared to be progressively replaced by the formation of round structures consist-ing of conidia aggregates. After 5 months, distinct, individual conidia were no longer detected, and only 'clumps of conidia' were observed. These dark black aggregates or 'clumps of conidia’measured 157-170$\mu\textrm{m}$ in diameter and were grouped into boat-shaped olivacious conidia showing thick wall and measuring 50-82$\times$20-30$\mu\textrm{m}$. The germination was unipolar and below 0.5%, suggesting the occurrence of dormancy, In contrast, individual conidium produced on wheat during the growing season were 96-130$\times$16-20$\mu\textrm{m}$, slightly curved, hyaline to light pale, and euseptate with a bipolar germination reaching 98-100%. Bipolaris sorokiniana conidia produced on PDA were 55-82$\times$20-27$\mu\textrm{m}$, tapered at both ends, dark brown to olivacious, distoseptate, showed up to 1% germination, and were predominantly unipolar. Results of the present study suggest that B. sorokiniana conidia belonged to two different physiological categories corresponding to the pathogen's infection phase and its survival, respectively. The infection phase is characterized by a high germination percentage as opposed to the survival phase harboring apparent dormancy.

• Tribology and Lubricants
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• v.32 no.3
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• pp.101-105
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• 2016

Trap effect of groove is evaluated in a lubricating system using computational fluid dynamics (CFD) analysis. The simulation is based on the standard k-ε turbulence model and the discrete phase model (DPM) using a commercial CFD code FLUENT. The simulation results are also capable of showing the particle trajectories in flow field. Computational domain is meshed using the GAMBIT pre-processor. The various grooves are applied in order to improve lubrication characteristics such as reduction of friction loss, increase in load carrying capacity, and trapping of the wear particles. Trap effect of groove is investigated with variations in cross-sectional shape and Reynolds number in this research. Various cross-sectional shapes of groove (rectangular, triangle, U shaped, trapezoid, elliptical shapes) are considered to evaluate the trap effect in simplified two-dimensional sliding bearing. The particles are assumed to steel, and defined a single particle injection condition in various positions. The “reflect” boundary condition for discrete phase is applied to the wall boundary, and the “escape” boundary condition to “pressure inlet” and “pressure outlet” conditions. The streamlines are compared with particles trajectories in the groove. From the results of numerical analysis in the study, it is found that the cross-sectional shapes favorable to the creation of vortex and small eddy current are effective in terms of particle trapping effect. Moreover, it is found that the Reynolds number has a strong influence on the pattern of vortex or small eddy current in the groove, and that the pattern of the vortex or small eddy current affects the trap effect of the groove.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.174-174
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• 2010

Gallium Nitride(GaN) attracts great attention due to their wide band gap energy (3.4eV), high thermal stability to the solid state lighting devices like LED, Laser diode, UV photo detector, spintronic devices, solar cells, sensors etc. Recently, researchers are interested in synthesis of polycrystalline and amorphous GaN which has also attracted towards optoelectronic device applications significantly. One of the alternatives to deposit GaN at low temperature is to use Single Source Molecular Percursor (SSP) which provides preformed Ga-N bonding. Moreover, our group succeeds in hybridization of SSP synthesized GaN with Single wall carbon nanotube which could be applicable in field emitting devices, hybrid LEDs and sensors. In this work, the GaN thin films were deposited on c-axis oriented sapphire substrate by MBE (Molecular Beam Epitaxy) using novel single source precursor of dimethyl gallium azido-tert-butylamine($Me_2Ga(N_3)NH_2C(CH_3)_3$) with additional source of ammonia. The surface morphology, structural and optical properties of GaN thin films were analyzed for the deposition in the temperature range of $600^{\circ}C$ to $750^{\circ}C$. Electrical properties of deposited thin films were carried out by four point probe technique and home made Hall effect measurement. The effect of ammonia on the crystallinity, microstructure and optical properties of as-deposited thin films are discussed briefly. The crystalline quality of GaN thin film was improved with substrate temperature as indicated by XRD rocking curve measurement. Photoluminescence measurement shows broad emission around 350nm-650nm which could be related to impurities or defects.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.2587-2593
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• 2014

Ceramic Injection Molding (CIM) is one of wide used processes in industry field and the applications are gradually being expanded to parts of medical and electric devices. In this study, the CIM process were analyzed with FEM and process parameters were studied and analyzed the effect on product quality. The shape of simple flat plate was compared to the shapes with the hole, with the round corner portion or with the side wall portion. If there are holes then the hole around the uneven density distribution and the defects such as weld lines could be occurred. The Large radius of the corners of the product give good formability and fluidity. Not only the shape parameters of product but also the process parameters during CIM are studied. The simulation results showed that the process parameters of temperature, initial fractions and velocity are important design parameters to improve the quality of products.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.2
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• pp.78-88
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• 2005

The combustion characteristics of End-Burning hybrid combustor using different types of injector system are numerically investigated to visualize the temperature fields in the combustion chamber The basic characteristics of combustion with different O/F ratio is also analyzed in order to capture the main behavior of diffusion flame inside the swirl induced hybrid combustion chamber It was found that the arrangement of oxidizer injectors give strong effect on the temperature field dominating mixing between fuel and oxidizer. The results show that among five different oxidizer injectors arrangement, the counter flow injector has the highest mixing efficiency. However, the observed high wall temperature presence near the oxidizer injectors remains to be solved.