• The Journal of Advanced Prosthodontics
• /
• v.6 no.6
• /
• pp.456-461
• /
• 2014

PURPOSE. Translucency and colour stability are two most important aspects for an aesthetic dental restoration. Glass ceramic restorations are popular amongst clinicians because of their superior aesthetic properties. In the last decade, zirconia has generated tremendous interest due to its favorable mechanical and biological properties. However, zirconia lacks the translucency that lithium disilicate materials possess and therefore has limitations in its use, especially in esthetically demanding situations. There has been a great thrust in research towards developing translucent zirconia materials for dental restorations. The objective of the study was to evaluate and compare the transmittance of a translucent variant of zirconia to lithium disilicate. MATERIALS AND METHODS. Two commercially available zirconia materials (conventional and high translucency) and 2 lithium disilicate materials (conventional and high translucency) with standardized dimensions were fabricated. Transmittance values were measured for all samples followed by a microstructural analysis using a finite element scanning electron microscope. One way analysis of variance combined with a Tukey-post hoc test was used to analyze the data obtained (P=.05). RESULTS. High translucency lithium disilicate showed highest transmittance of all materials studied, followed by conventional lithium disilicate, high translucency zirconia and conventional zirconia. The difference between all groups of materials was statistically significant. The transmittance of the different materials correlated to their microstructure analysis. CONCLUSION. Despite manufacturers' efforts to make zirconia significantly more translucent, the transmittance values of these materials still do not match conventional lithium disilicate. More research is required on zirconia towards making the material more translucent for its potential use as esthetic monolithic restoration.

• Journal of Digital Contents Society
• /
• v.8 no.1
• /
• pp.1-8
• /
• 2007

Recently, As the increase in interaction between the person and the person, the people plentifully use a messenger. Thus, we propose a new messenger program, we call Hellow Fellow Messenger. The hollow fellow messenger has functions of general messenger such as chatting, note exchange, friend addition. Also, hollow fellow messenger provide with special function, which find friends satisfied conditions in PDA and PC environment. So, Client can find not only friend who is register already but also friend who is the possibility of seeing a movie and can comfortably talk together and so on. For this, server sends information for users satisfied in condition from databases to client and client selects a user among received information for users. Client-server communication is implemented using MFC[1].

• Journal of Ocean Engineering and Technology
• /
• v.29 no.6
• /
• pp.418-426
• /
• 2015

Recently, shipping operators have been making efforts to reduce the fuel cost in various ways, such as trim optimization and bulb re-design. Furthermore, IMO restricts the hydro-dioxide emissions to the environment based on the EEDI (Energy Efficiency Design Index), EEOI (Energy Efficiency Operational Indicator), and SEEMP (Ship Energy Efficiency Management Plan). In particular, ship speed is one of the most important factors for calculating the EEDI, which is based on methods suggested by ITTC (International Towing Tank Conference) or ISO (International Standardization Organization). Many shipbuilding companies in Korea have carried out speed trials around the Korea Straits. However, the conditions for these speed trials have not been exactly the same as those for model tests. Therefore, a ship’s speed is corrected by measured environmental data such as the seawater temperature, density, wind, waves, swell, drift, and rudder angle to match the conditions of the model tests. In this study, fundamental research was performed to evaluate the ship resistance performance due to changes in the water temperature and salinity, comparing the ISO method and numerical simulation. A numerical simulation of a KCS (KRISO Container ship) with a free-surface was performed using the commercial software Star-CCM+ under three conditions that were assumed based on the water temperature and salinity data in the Korea Straits. In the simulation results, the resistance increased under low water temperature & high salinity conditions, and it decreased under high water temperature & low salinity conditions. In addition, the ISO method showed the same result as the simulation.

• Journal of Digital Convergence
• /
• v.14 no.7
• /
• pp.431-437
• /
• 2016

Since the game is industrialized in the 1970s, efforts to study attributions throughout the definition of the game has been continued. This study analyzed the importance of 7 attributions including rule, goal, conflict, activity, decision-making, voluntary, art that were collectively organized by Katie Salen & Eric Zimmerman using AHP. For this, we analyzed the data after subjected to pair-wise comparison survey through the gaming industry experts, and the result was confirmed that match the analysis model comparing with the survey of game players. In this analysis of the importance, Goal(24%) is the greatest important in the seven factors mentioned above. Art(16%),Voluntary(15%), Rule(13%) followed after it. So, We can find out which attributes are considered important in the game development process through this Research.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.58 no.5
• /
• pp.1025-1034
• /
• 2009

In steel making production line, steel slabs are given a unique identification number. This identification number, Slab management number(SMN), gives information about the use of the slab. Identification of SMN has been done by humans for several years, but this is expensive and not accurate and it has been a heavy burden on the workers. Consequently, to improve efficiency, automatic recognition system is desirable. Generally, a recognition system consists of text localization, text extraction, character segmentation, and character recognition. For exact SMN identification, all the stage of the recognition system must be successful. In particular, the text localization is great important stage and difficult to process. However, because of many text-like patterns in a complex background and high fuzziness between the slab and background, directly extracting text region is difficult to process. If the slab region including SMN can be detected precisely, text localization algorithm will be able to be developed on the more simple method and the processing time of the overall recognition system will be reduced. This paper describes about the slab region localization using SIFT(Scale Invariant Feature Transform) features in the image. First, SIFT algorithm is applied the captured background and slab image, then features of two images are matched by Nearest Neighbor(NN) algorithm. However, correct matching rate can be low when two images are matched. Thus, to remove incorrect match between the features of two images, geometric locations of the matched two feature points are used. Finally, search rectangle method is performed in correct matching features, and then the top boundary and side boundaries of the slab region are determined. For this processes, we can reduce search region for extraction of SMN from the slab image. Most cases, to extract text region, search region is heuristically fixed [1][2]. However, the proposed algorithm is more analytic than other algorithms, because the search region is not fixed and the slab region is searched in the whole image. Experimental results show that the proposed algorithm has a good performance.

• Journal of Electrical Engineering and Technology
• /
• v.13 no.5
• /
• pp.2045-2049
• /
• 2018

An antenna arrays for a satellite navigation systems require more antenna elements to mitigate multiple jamming signals. In order to maintain the small array size while increasing the number of antenna elements, miniaturization technique is essential for antenna design. In this work, an electrically small circular microstrip patch antenna with a 3 dB hybrid coupler is designed as an element antenna, where the 3 dB hybrid coupler can yield the circularly polarized radiation characteristic. The miniaturized element antenna typically has too large capacitance in GPS L1 and GLONASS G1 bands, making it difficult to match with a single stand-alone non-Foster matching circuit (NFMC) in a stable state. Therefore, we propose a new matching technique, referred to as the hybrid matching method, which consists of a NFMC and a passive circuit. This passive tuning circuit manages reactance of antenna elements at an appropriate capacitance without a pole in the operating frequency range. The antenna array is fabricated, and the measured results show a reflection coefficient of less than -10 dB and an isolation of greater than 50 dB. In addition, peak gain of the proposed antenna is increased by 22.3 dB compared to the antenna without the hybrid matching network.

• Journal of the Korean Society of Safety
• /
• v.26 no.1
• /
• pp.1-7
• /
• 2011

When the pumps stopped in the operation by the power failure, the hydraulic transients take place in the sudden change of a velocity of pipe line. Each and every water hammer problem shows the critical stage to be greatly affected the facts of safety and reliability in case of power failure. The field tests of the water hammer executed at Cheong-Yang booster pump station having an air chamber. The effects were studied by both the practical experiments and the CFD(Computational Fluid Dynamics : Surge 2008). The result states that the system with water hammering protection equipment was much safer when power failure happens. The following data by a computational fluid dynamic analysis are to be shown below, securing the system stability and integrity. (1) With water hammering protection equipment. (1) Change of pressure : Up to $15.5\;kg/cm^2$ in contrary to estimating $16.88\;kg/cm^2$. (2) Change rate of water level : 52~33% in contrary to estimating 55~27%. (3) Note that the operational pressure of pump runs approx. 145 m, lowering 155 m of the regularity head of pump. (4) Note that the cycle of water hammering delays from 80 second to 100 second, together with easing the function of air value at the pneumatic lines. (2) Change of pressure without water hammering protection equipment : Approximate $22.86\;kg/cm^2$. The comprehensive result says that the computational fluid dynamics analysis would match well with the practical field-test. It was able to predict Max. or Min. water hammering time in a piping system. This study aims effectively to alleviate water hammering in a pipe line to be installed with air chamber at the pumping station and results in making the stability of pump system in the end.

• Journal of Engineering Education Research
• /
• v.15 no.2
• /
• pp.20-29
• /
• 2012

The purpose of this study was to explore the academic achievements, learning attitudes, and career compromising processes for successful undergraduate students in the College of Engineering. To achieve this goal, research was conducted to analyze whether there was a strong major-career connection among Engineering students of Seoul National University. Afterwards, differences in levels of academic achievement, learning attitude, and academic aspiration were analyzed between students who had achieved a major-career match and students who had not. As a result, it was found that the level of major-career connection was highly correlated to the level of academic achievement; furthermore, learning attitudes were strongly related to the level of motivation towards a high academic achievement, and influenced future learning attitudes as well. These findings suggest that further academic support, career guidance, and major switching policies are needed for undergraduate students in Colleges of Engineering.

• Journal of Fashion Business
• /
• v.13 no.4
• /
• pp.60-76
• /
• 2009

Expression of woman characters in fusion traditional dramas plays a role of making the progress of dramas not bigoted and new. Especially, woman characters have a high weight as a heroine by an increase in their image in fusion traditional dramas. Expression of characters harmonizing modern with tradition has also given a help in reflecting a trend of the present times. Hair style and face makeup of woman characters in fusion traditional dramas are in the process of fusionization getting an effect from postmodernism. They are expressing the hair style of symbolization modern elements of hair style to traditional hair styles. They also expressed a neutral image with faded hair styles in the shaggy cut style and dye of neoplaticism. Neo-hippie style was changed into the style of naturalism and nationalism and the hair style braided in various branches as the one of Indians was changed into a primitive and national feature. It is producing a new style by permitting even a long-hair permanent wave hair style. Expression of straight hair style, a long-hair shaggy & bulging wave style and a hair style of neoplaticism, was distinguished. In the side of face makeup, they expressed its luxurious and splendid style by attaching great importance to its luster and are exposing images of characters by a smoky makeup emphasizing eye lines. Their face makeup was almost never separated from present dramas as using pearl shadow in a glossy lips makeup and color, which made it possible to express it more dramatically in fusion traditional dramas than in present dramas. In the event of the makeup element of fusion traditional dramas permitting diversity, the character makeup of fusion traditional dramas made a foundation to show people diverse elements of makeup by mix & match a present elements and past elements of historical research, which made it possible to express a unique makeup or a special makeup. Diverse makeup expressions were limited by reflection of illumination even in the existing videos. Therefore, 'Fusion' made it possible to express it more freely in fusion traditional dramas than in present dramas.

• Smart Structures and Systems
• /
• v.26 no.6
• /
• pp.681-692
• /
• 2020

Conventional Piezoelectric Energy Harvesters (CPEH) have been extensively studied for maximizing their electrical output through material selection, geometric and structural optimization, and adoption of efficient interface circuits. In this paper, the performance of Stepped Piezoelectric Energy Harvester (SPEH) under harmonic base excitation is studied analytically, numerically and experimentally. The motivation is to compare the energy harvesting performance of CPEH and SPEHs with the same characteristics (resonant frequency). The results of this study challenge the notion of achieving higher voltage and power output through incorporation of geometric discontinuities such as step sections in the harvester beams. A CPEH consists of substrate material with a patch of piezoelectric material bonded over it and a tip mass at the free end to tune the resonant frequency. A SPEH is designed by introducing a step section near the root of substrate beam to induce higher dynamic strain for maximizing the electrical output. The incorporation of step section reduces the stiffness and consequently, a lower tip mass is used with SPEH to match the resonant frequency to that of CPEH. Moreover, the electromechanical coupling coefficient, forcing function and damping are significantly influenced because of the inclusion of step section, which consequently affects harvester's output. Three different configurations of SPEHs characterized by the same resonant frequency as that of CPEH are designed and analyzed using linear electromechanical model and their performances are compared. The variation of strain on the harvester beams is obtained using finite element analysis. The prototypes of CPEH and SPEHs are fabricated and experimentally tested. It is shown that the power output from SPEHs is lower than the CPEH. When the prototypes with resonant frequencies in the range of 56-56.5 Hz are tested at 1 m/s2, three SPEHs generate power output of 482 μW, 424 μW and 228 μW when compared with 674 μW from CPEH. It is concluded that the advantage of increasing dynamic strain using step section is negated by increase in damping and decrease in forcing function. However, SPEHs show slightly better performance in terms of specific power and thus making them suitable for practical scenarios where the ratio of power to system mass is critical.