• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.3
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• pp.339-346
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• 2018

A geological repository system consists of a disposal canister with packed spent fuel, buffer material, backfill material, and intact rock. The buffer is indispensable to assure the disposal safety of high-level radioactive waste. Since the heat generated from spent nuclear fuel in a disposal canister is released to the surrounding buffer materials, the thermal properties of the buffer material are very important in determining the entire disposal safety. Especially, since thermal expansion can cause thermal stress to the intact rock mass in the near-field, it is very important to evaluate thermal expansion characteristics of bentonite buffer materials. Therefore, this paper presents a thermal expansion coefficient prediction model of the Gyeongju bentonite buffer materials which is a Ca-bentonite produced in South Korea. The linear thermal expansion coefficient was measured considering heating rate, dry density and temperature variation using dilatometer equipment. Thermal expansion coefficient values of the Gyeongju bentonite buffer materials were $4.0{\sim}6.0{\times}10^{-6}/^{\circ}C$. Based on the experimental results, a non-linear regression model to predict the thermal expansion coefficient was suggested and fitted according to the dry density.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.7
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• pp.17-25
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• 2017

To resolve the problem of the temperature rise in LED or OLED lighting, until now a thick metal film has been used as a heat-sink. Conventionally, this thick metal film is made by the electroplating method and used as the heat-dissipating plate of the electronic devices. However, nowadays there is increasing need for a Cu metal film with a thickness of several hundred micrometers that can be formed by the dry deposition method. In this work, we designed and fabricated a Cu film deposition system where the heating element is separated from the ceramic crucible, which makes ultra-rapid deposition possible by preventing heat loss. In addition, the resulting induction heating also contributes to the high deposition rate. By tuning the various parameters, we obtained a $100-{\mu}m$ thick Cu film whose heat conductivity is high and whose thickness uniformity is better than 2%, while the deposition rate is as high as $1000{\AA}/s$.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.1
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• pp.42-51
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• 2007

An AC electrical railroad system has rapidly changing dynamic single-phase load, and at a feeding substation, three-phase electric power is transformed to the paired directional single-phase electric power. There is a great difference in electrical phenomenon between the load of AC electrical railroad system and that of general power system. Electric characteristics of AC electrical railroad's trainload are changed continuously according to the traction, operating characteristic, operating schedule, track slope, etc. Because of the long feeding distance of the dynamic trainload, power quality problems such as voltage drop, voltage imbalance and harmonic distortion my also occur to AC electrical railroad system. These problems affect not only power system stability, but also power quality deterioration in AC electrical railroad system. The dynamic simulation model of AC electrical railroad system presented by PSCAD/EMTDC is modeled in this paper, andthen, it is analyzed voltage drop for AC electrical railroad system both with single-phase distributed STATCOM(Static Synchronous Compensator) installed at SP(Sectioning Post) and without.

• Korean Chemical Engineering Research
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• v.47 no.6
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• pp.715-719
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• 2009

The phase change electrode board for the bio-information detection through electrical property response of phase change material was developed in this study. We manufactured the electrode board using Aluminum first that is widely used in conventional semiconductor device process. Without further treatment, these aluminum electrodes tend to contain voids in PETEOS(plasma enhanced tetraethyoxysilane) material that are easily detected by cross-sectional SEM(Scanning Electron Microscope). The voids can be easily attacked and transformed into holes in between PETEOS and electrodes after etch back and washing process. In order to resolve this issue of Al electrode board, we developed a electrode board manufacturing method using low resistivity TiN, which has advantages in terms of the step-coverage of phase change($Ge_2Sb_2Te_5$, GST) thin film as well as thermodynamic stability, without etch back and washing process. This TiN material serves as the top and bottom electrode in PRAM(Phase-change Random Access Memory). The good connection between the TiN electrode and GST thin film was confirmed by observing the cross-section of TiN electrode board using SEM. The resistances of amorphous and crystalline GST thin film on TiN electrodes were also measured, and 1000 times difference between the amorphous and crystalline resistance of GST thin film was obtained, which is well enough for the signal detection.

• Journal of Convergence for Information Technology
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• v.8 no.1
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• pp.131-138
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• 2018

The purpose of the study was to explore whether the Cyber Motion sickness used VR causes a change in the dynamic balance and fall. For 39 people who voluntarily participated in this study, this study measured the motion sickness questionnaires, the heart rate and stability of limit test in BioRescue. The study used Samsung Gear VR and applied the games to the To the homeland. The game proceeded 20minutes. Although the value of the stability after a VR application is slightly reduced, it did not reach statistical significance. The motion sickness questionnaires increased, and it had a statistical significant impact. Also Heart rate increased and it had a statistically significant impact. A virtual reality game affect for getting motion sickness but it did not affect the dynamic balance. So, cyber motion sickness caused by virtual reality wear does not result in decreased balance and falls.

• Journal of Korea Port Economic Association
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• v.26 no.3
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• pp.114-129
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• 2010

Busan port's main function is handling container cargo compared to world major ports and the percentage of handling general cargo such as dirty bulk cargo is very low. In other words, although total cargo weight of Busan port that recorded the handling result of 13.29million TEU in 2008 reached 113.05million ton, total cargo weight of general cargo was 15.31million ton, so container cargo accounted for 88.1% of whole cargo weight. However, it is the time to create high added value by the increase of handling and marketing dirty bulk cargo. Originally, the dirty bulk cargo was not the avoided object from the first. Somehow, it is a very high added value cargo, and is surely essential strategic material to basic industries of nation. However, it becomes dirty bulk cargo as the companies are reluctant to handle it because of environmental problem, distinct characteristic in handling, uncertain break even point due to imbalance between supply and demand compared to container cargo. However, items that are classified as dirty bulk cargo now are certainly necessary strategic materials to national basic industries or national life. Besides it seems to be a high added value cargo here and now. Therefore, it is time that increasing of handling dirty bulk cargo by marketing it and the system for efficient handling such as constructing the exclusive use wharf in Busan port, modernizing of facilities and equipments, stable secure of place for holding and handling through development of distribution complex by item, efficient data processing and closer cooperation by setting up a SCM of related authorities are needful.

• Journal of the Korean Geotechnical Society
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• v.29 no.6
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• pp.53-62
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• 2013

A 5-20 cm thick shocrete has been routinely constructed for NATM tunneling method to stabilize and confine the excavated rock of tunnel construction site. A $40kg/m^3$ of steel fibers are usually mixed into such shotcrete but these steel fibers may not be evenly distributed depending on shotcrete machines, mixing ratios and excavated rock conditions. In this study, square column shotcrete-mimicked concrete specimens of $15cm{\times}15cm{\times}55cm$ were prepared with 5 equal layers and 5 or 20% cement ratio. The specimens were prepared with different reinforced-patterns: non-reinforced, middle layer-reinforced, 1, 3, and 5 layers-reinforced, or all layers reinforced. The specimens were air-cured for 7 days and tested for flexural strength. The influence of steel-fiber distribution on flexural strength and toughness of shotcrete-mimicked concrete specimens was investigated. In the case of a specimen with cement ratio of 20%, a flexural strength increased as a number of fiber-reinforced layer increased. The flexural strength of one-layer reinforced specimen showed 20% less than that of evenly fiber-distributed specimen. On the other hand, a specimen with cement ratio of 5% decreased as the number of fiber-reinforced layers increased. A toughness index increased as the number of fiber-reinforced layers increased, regardless of cement ratios. The toughness index of evenly fiber-distributed specimen showed 2-3 times as large as that of one-layer reinforced specimen.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.29 no.1
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• pp.263-271
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• 2005

The most important point when we engage on waterway dredging work is supplying safe navigational passage to the vessels underway by narrowing dredge work area and removing submerged dangers. In order to meet this end it is neccessary to use auxiliary equipment for shifting actively and mooring and adopt automation of dredging work by integrating information on real time position, dredging depth, and work information. The danger with a spud control system in this study, by the way, is able to employed on continuous dredging work with the narrowest working area allowing wide and safe passages to vessels underway, by moving the dredger to the working zone with the spud controlled automatically. Furthermore, it has been improved definitely compared with the existing dredging proccess management system such that it shows the track of spud and working depth on the electronic navigation chart of window, together with the final outcome of dredging work. The test dredging work at the entrance of Busan North Port for system evaluation showed that actual working time available was twice of the one by the existing anchor system, and that it reduced 38% of time for preparation work and one man power.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.10
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• pp.34-40
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• 2014

With the economical data service delivery, the packet transport network (PTN) technologies have emerged as an important player in the next-generation transport networks. As the PTN continues to make such considerable progress, it is being challenged by network providers who need rapid and reliable recovery capabilities to guarantee the availability of their services. This paper introduces several fault detection mechanisms for a client signal failure in packet transport networks and proposes a reliable transmission method of IP flows from routers using the combination of Ethernet services. Based on the first fault detection methods, client signal fault is detected within tens or hundreds of milliseconds. It enables the client network devices to perform their own recovery processes within one second. The second mechanism enables failed Ethernet services to be bypassed via other Ethernet services over disjoint paths, so as to contribute on reducing packet loss of IP traffic.

• Progress in Medical Physics
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• v.22 no.3
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• pp.155-162
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• 2011

The analog image based system consisted of a simulator and medical linear accelerator (LINAC) for radiotherapy was upgraded to digital medical image based system by exchanging the X-ray film with Computed Radiography (CR). With minimum equipments shift and similar treatment process, it was possible that the new digital image system was adapted by the users in short time. The film cassette and the film developer device were substituted with a CR cassette and a CR Reader, where the ViewBox was replaced with a small size PC and a monitor. The viewer software suitable for radiotherapy was developed to maximize the benefit of digital image, and as the result the convenience and the effectiveness was improved. It has two windows to display two different images in the same time and equipped various search capability, contouring, window leveling, image resizing, translation, rotation and registration functions. In order to avoid any discontinuance of the treatment while the transition to digital image, the film and the CR was used together for 1 week, and then the film developer was removed. Since then the CR System has been operated stably for 2 months, and the various requests from users have been reflected to improve the system.