• The Journal of Advanced Prosthodontics
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• v.10 no.4
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• pp.328-334
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• 2018

PURPOSE. To evaluate the reproducibility of scan-based abutments using a blue light model scanner. MATERIALS AND METHODS. A wax cast abutment die was fabricated, and a silicone impression was prepared using a silicone material. Nine study dies were constructed using the prepared duplicable silicone, and the first was used as a reference. These dies were classified into three groups and scanned using a blue light model scanner. The first three-dimensional (3D) data set was obtained by scanning eight dies separately in the first group. The second 3D data set was acquired when four dies were placed together in the scanner and scanned twice in the second group. Finally, the third 3D data set was obtained when eight dies were placed together in the scanner and scanned once. These data were then used to define the data value using third-dimension software. All the data were then analyzed using the non-parametric Kruskal-Wallis H test (${\alpha}=.05$) and the post-hoc Mann-Whitney U-test with Bonferroni's correction (${\alpha}=.017$). RESULTS. The means and standard deviations of the eight dies together were larger than those of the four dies together and of the individual die. Moreover, significant differences were observed among the three groups (P<.05). CONCLUSION. With larger numbers of abutments scanned together, the scan becomes more inaccurate and loses reproducibility. Therefore, scans of smaller numbers of abutments are recommended to ensure better results.

• Journal of the Korean Society of Marine Environment & Safety
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• v.15 no.2
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• pp.119-125
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• 2009

Recently the construction of bridges crossing navigable waterways is being promoted aiming at expanding social infrastructure and optimizing the overland routes through private investment. The construction, however, tends to focus on more the commercial requirements than the marine safety and efficient port management that it has a big risk not only to fail in ensuring the safety of ship traffic, but also to muse some severe conflicts between the parties concerned. These problems result from the lacking of standards about the design guidelines and discussing process considering the marine traffic safety when designing bridges. This research attempts to show the problems mused by bridge construction and suggest the standard discussing process through the survey and process analysis on Kwangyang Bridge and Incheon Bridge.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.10
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• pp.1002-1010
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• 2015

Natural gas hydrates are newly emerging as an environment-friendly source of energy to substitute for fossil fuels in the 21stcentury.NGHs are reported to holds much amounts of natural gas (up to 182 standard volumes of gas per volume of hydrate); they are easy to store and safe to carry at about minus 20 degree Celsius under atmospheric pressure because of the self-preservation phenomenon of gas hydrates. The transporting method by gas-ice-hydrate ship carriers has been introduced and developed by a variety of industry and research institutions. Our team has been conducted to develop NGH total systems, including a breakthrough NGH carrier for sea transportation, since 2011. The NGH pellet carrier does not require a separate cooling system for cargo, and the initial temperature is maintained through insulation of the cargo tanks throughout the transport to the final destination. The heat conducted from the exterior and passing through the insulation material of the hull should be cut off as much as possible, but heat inflow inside the cargo tank from an external source is inevitable during transport. In this study, the heat transfer in a cargo tank of a 115K NGH carrier was analyzed through simulation with a commercial CFD code to estimate the boil-off gas/boil-off rate on the developed carrier and understand major hazards that could significantly impact the safety of the vessel.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2005.04a
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• pp.35-38
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• 2005

In our country, the skin image and MR Microscopy research has been processed but there were not their outstanding results. So this study start to improve the techniques can get high resolution skin images and to make RF surface coils. Volume coils are sometimes unavailable, or do not provide adequate RF power or SNR for some applications. In high resolution skin and tissue structure images current coils have a technical limitation. It is well known that standard single-loop surface coils, although offering high SNR characteristics, have poor B1 homogeneity. As the RF surface coil need change its geometry we get improved images. So, The magnetic field simulation that is first step to make and design RF surface coil will support reference data.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.5
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• pp.345-356
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• 2009

Tetrapod has been used as the armor blocks of most rubble mound breakwaters constructed in Korea. The Hudson formula has been widely used in the design of breakwater armor blocks in Korea. In the present study, we calculate the load and resistance partial safety factors of the Hudson formula for Tetrapod armors. The partial safety factors were calculated for the typical breakwater cross-sections of 12 trade harbors and 8 coastal harbors in Korea. The mean and standard deviation of them were also calculated. The mean values were compared with the partial safety factors of US Army (2006). The load and resistance factors are slightly smaller and larger, respectively, than the US Army values. However, the overall safety factors obtained by multiplying the load and resistance factors are close to the US Army values. The result of the present study could be used as the basic data to propose authorized partial safety factors in the future.

• Journal of the Korean Society for Railway
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• v.20 no.2
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• pp.173-181
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• 2017

The obstacle deflector sweeps obstacles off the track or absorbs crash energy with an energy absorber to prevent derailment of a train and to minimize damage and casualties after an accident. In this study, an obstacle deflector and its operational mechanism were designed with a tension-type energy absorber and a 4-bar linkage system. Also, a test method was suggested and verified with FEA (Finite Element Analysis) and UTM (Universal Test Machine) for testing of the static load and energy absorbing ability according to EN 15227 regulations. Through this study, an obstacle deflector that meets the EN 15227 standard was designed and a test method was suggested to adjust the collapse load easily and to verify it experimentally according to the design and verification procedure of the obstacle deflector.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.5
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• pp.297-302
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• 2020

Korea has many mountainous regions, and slope collapse that can lead to damage in road facilities and loss of lives often occurs. Rockfall-protection facilities are necessary to reduce such damages. Among these facilities, the standard Korean rockfall-protection fence is designed to resist 50 kJ of rockfall impact energy. However, the range of rockfall energy significantly varies depending on the condition of the slope, and it sometimes reaches up to 100 kJ. Thus, providing several types of standardized rockfall-protection fence is necessary to address the different rockfall impact energy for efficient response to rockfalls. This paper presents a study on standardized rockfall-protection fence for various rockfall impact energy using finite-element analysis. According to the results, standardized rockfall-protection fences against rockfall impact energy of 30 and 100 kJ were proposed and have been verified.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.3
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• pp.392-399
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• 1998

A full-scope replica type simulator whose MCR(main control room) has the same features and operation functions as MCR of the reference power plant has been developed for a fossil power plant. This simulator was developed with the model of Poryung Fossil Power Plant #3,4 which is the standard model of the Korean fossil power plant. It is the first localized simulator for the supercritical, variable boiler pressure type fossil power plant. The simulator provides various kinds of accidents which are in normal plant operation and thus enables operators to recover or reduce possible damages. To design and develop this kind of simulator, we need to integrate high technologies such as system analysis, plant operation and system integration of mechanics, physics, computer science. CASE(Computer Aided Software Engineering) tools were used to develop the dynamic model. This simulator will greatly contribute to the improvement of the safety and efficiency of the fossil power plant by implementing operator training. In this paper, the outline of software and hardware configuration and characteristics of the simulator are described, and the results of 30%, 50%, 75%, 100% load operation test will be discussed.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.2
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• pp.60-67
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• 2010

We designed Average Current Control PFC IC which has make the average value of boost inductor current became the shape of sine wave. Designed IC has fixed frequency of 75kHz to meet EMI standard requirement. And also RC compensation loop has been designed into the error amp and the current amp, in order that it has wide bandwidth for high speed control. And we use the oscillator which generates by square wave and triangle wave, and add to UVLO, OVP, OCP, TSD which is in order to operate stability. We simulated by using Spectre of Cadence to verify the unity power factor function and various protection circuits and fabricated in a $1{\mu}m$ High Voltage(20V) CMOS process.

• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.4
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• pp.1-8
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• 2012

Domestic steel moment resisting frames were designed in accordance with the former KBC2005 and the current KBC2009, and then their seismic performance was evaluated in accordance with FEMA355F by utilizing nonlinear dynamic analysis. The results from the procedure in FEMA355F were different with those from the capacity spectrum method utilizing nonlinear static push-over analysis. In particular, the domestic steel moment resisting frames have a weak panel zone, so their behavior can be estimated more precisely by nonlinear dynamic analysis. The domestic steel moment resisting frames satisfied the performance goal if located at a site class $S_B$ or $S_C$, regardless of the story number and the response modification factor. However, if they are located at a site class $S_D$ or $S_E$, performance goal satisfaction cannot be guaranteed. No matter what standard is used for the design, KBC2005 or KBC2009, the domestic steel moment resisting frames may possess satisfactory seismic performance if the site condition is relatively good.