• Journal of radiological science and technology
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• v.42 no.6
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• pp.477-482
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• 2019

Recently, due to the increased use of medical radiation, the radiation exposure of radiation workers should be considered as well as medical exposure of patients. And it is recommended to close the door during radiography. however, In this study, when the door was inevitably opened for radiography, the proposed method was to install the shield as a method of reducing the exposure dose. And its efficiency was analyzed. In simple chest radiography, the measurement point was changed according to the measurement location. Dose rate were measured 10 times for each condition using a dosimeter. And the average value was derived. Using this, the change of dose according to the opening and closing of the door and the installation of the shield was analyzed. Using this, we compared and analyzed the dose change according to the door opening and closing and the installation of the shield, and significance was verified through the SPSS ver. 24. Depending on whether the door was opened or closed, 11,215.35%, 159.0%, 101.9% increased in front of the door in the consol room, behind the wall and behind the lead glass. Depending on the installing of the shield, the 49.2%, 29.6%, 19.9%, 30.6% decrease in front of the door in the examination and consol room, behind the wall and lead glass. In addition, statistical analysis was showed that there were significant differences in both the results according to whether the door was opened or closed and shielding(p<.05). Close the door during radiography. However, when the door should be opened, it was confirmed that the dose rate were reduced by installing the shield. Therefore, to optimize radiation protection, it is recommended to install shields when opening the door.

• Fire Science and Engineering
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• v.30 no.5
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• pp.36-45
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• 2016

Integral fire shutters are installed indiscriminately, regardless of evacuation. There is always the risk of an accident because integral shutters are applied mainly to corridors, passages, and stairs of schools This study evaluated the problem of integral shutter's entrance, evacuation, construction management, and maintenance control through a fire shutter accident case, including present condition of fire shutter installed at school of Okgil, Bucheon and Dongtan, Hwaseong. The results suggest that emergency lighting or signs for passage be set up to check location of entrance easily and install obstruction sensors at fire shutter to reduce life damage. In addition, the number of efficiency tests of fire shutters should be increased by running a trial test monthly or weekly to maintain the performance of fire shutter. Schools need to install a fire shutter- applied sprinkler at the entire floor.

• Journal of the Korean Society for Railway
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• v.15 no.2
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• pp.122-128
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• 2012

Considering structure of depot, it is impossible to install the track circuit systems due to iron-beam. Because rails and earth are connected by the iron-beam, there is much leakage current. So, it is hard to apply the track circuit systems. Thus, when trains go to the depot, sign which indicates existence of trains is used manually. In case of wrong sign, accidents occur such as train crash, derailment etc. Currently, location of trains has been found by using optical sensor in the depot to prevent the accidents. However, it costs a great deal to install and maintain the optical sensor. Therefore, this method is hardly used in train operation institutes. In this paper, virtual track circuit systems are introduced by using software program in the depot. Also, algorithm of the virtual track circuit systems is proposed. In case that signal is handled to the depot which is occupied by the train, safety is ensured by indicating sign which means existence of trains and stop signal. Also, proper fault tolerance techniques are proposed to the software by analyzing reliability and availability.

• Journal of Navigation and Port Research
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• v.29 no.5 s.101
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• pp.383-388
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• 2005

To install a radar reflector on small ships, such as a small fishing vessel, a fishery buoy, and a barge ship for fishery, it is very important to develop the optimal system which may determine a proper installation location. For this, the response characteristics how waves have an effect on the small ships should be accurately analyzed. In this paper, we analyze the dynamic behaviors of small ships, which may be caused by irregular waves. To do this, we investigate how a barge ship responses to wavelength, water depth, and directions of incoming waves. The analyzed results shall be utilized to evaluate an effect on a radar cross section when we install an radar reflector on a barge ship for fishery and a small ship.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.12B
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• pp.719-727
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• 2007

The Wireless Mesh Network technology is able to provide an infrastructure for isolated islands, in which it is difficult to install cables or wide area such as battlefield of armed forces. Therefore, Wireless Mesh Network is frequently used to satisfy needs for internet connection and active studies and research on them are in progress However, as a result of increase in number of hops under hop-by-hop communication environment has caused a significant decrease in throughput and an increase in delay. Considering the heavy traffic of real-time data, such as voice or moving pictures to adaptive WMN, in a military environment, it is restricted for remote units to have their Mesh Node to get real-time services. Such phenomenon might cause an issue in fairness. In order to resolve this issue, the Location-based Packet Scheduling Scheme, which can provide an fair QoS to each mesh node that is connected to each echelon's AP and operates based on WRR method that gives a priority to emergency message and control packet. The performance of this scheme is validated.

• Journal of the Korean Society of Safety
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• v.33 no.1
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• pp.128-134
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• 2018

With the increase in frequency of typhoons and heavy rains following the climate change, the scale of damage from the calamities in the mountainous areas has been growing larger and larger, which is different from the past. For the case of Korea where 64% of land is consisted of the mountainous areas, establishment of the check dams has been drastically increased after 2000 in order to reduce the damages from the debris flow. However, due to the lack of data on scale, location and kind of check dams established for reducing the damages in debris flow, the measures to prevent damages based on experience and subjective basis have to be relied on. Under this study, the high-precision DEM data was structured by using the terrestrial LiDAR in the Jecheon area where the debris flow damage occurred in July 2009. And, from the numerical models of the debris flow, Kanako-2D that is available to reflect the erosion and deposition action was applied to install the erosion control facilities (water channel, check dam) and analyzed the effect of reducing the debris flow shown in the downstream.After installing the erosion control facilities, most of debris flow moves along the water channel to reduce the area to expand the debris flow, and after installing the check dam, the flow depth and flux of the debris flow were reduced along with the erosion. However, as a result of analyzing the diffusion area, flow depth, erosion and deposition volume of the debris flow generated from the deposition part after modifying the location of the check dams with the damages occurring on private residences and agricultural land located on the upstream area, the highest reduction effect was shown when the check dam is installed in the maximal discharge points.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.2
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• pp.211-217
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• 2009

This paper proposes a way of expanding the use area of localization technique by using a beacon. In other words, we have developed the auto-calibration algorithm that recognizes the location of this beacon by attaching the beacon on an arbitrary position and by using the information of existing beacon under this situation. By doing so, the moving robot can overcome the limitation that the localization of moving robot is only possible within the area that has installed the existing beacon since the beacon cannot be installed on the accurate location when passing through a danger zone or an unknown zone. Accordingly, the moving robot can slowly move to the unknown zone according to this auto-calibration algorithm and can recognize its own location at a later time in a safe zone. The localization technique is essentially needed in using a moving robot and it is necessary to guarantee certain degree of reliability. Generally, moving robots are designed in a way to work well under the situation that the surroundings is well arranged and the localization techniques of using camera, laser and beacon are well developed. However due to the characteristics of sensor, there may be the cases that the place is dark, interfering radio waves, and/or difficult to install a beacon. The effectiveness of the method proposed in this paper has been proved through an experiment in this paper.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.1
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• pp.145-150
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• 2009

Because it is difficult to install new large hydraulic structure, washland is considered as alternatives of hydraulic facility. As flood reduction effect of washland is dependent on flood, hydrograph, capacity of washland and spillway height, applying adequate spillway height is very important to maximize flood reduction effect of washland. In this study, effect of variation of spillway height on flood reduction effect of washlands is analyzed. The existing model developed to make decision for optimal location of washland using flood reduction effect as evaluation function and location of washland as decision variable was revised for this purpose. The spillway height of washland is added as decision variable and revised model finally give optimal location and spillway height of washland as result. The developed model has been applied to the Ansung River basin and application result was compared with that of existing model. The application result shows that developed model can give more efficient result than existing model.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.158-161
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• 2010

In the paper, the researcher has proposed to install a relay between Base Station (BS) and Mobile Station (MS) to improve receiving performance of the downlink transmission method of Long Term Evolution (LTE) system whose standards now being established by 3GPP. By setting the distance between the location of BS and the relay installed as by 500m, 1000m, and selecting OFDMA and SC-FDMA as transmission method, the researcher conducted a study to improve the receiving performance of LTE. The results from study revealed that when the location of Relay Station (RS) was closer to BS, it was better to use OFDMA at BS, and SC-FDMA at RS. On the contrary, when the distance between BS and RS was farther, it was better to use SC-FDMA at BS, and OFDMA at RS. In addition, around the center zone between the location of BS and of MS, the researcher was able to improve the receiving performance of the system by utilizing the transmission method suitable for the situation in that area.

• Journal of Korean Association for Spatial Structures
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• v.19 no.1
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• pp.75-82
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• 2019

In the precedent study, the retractable-roof spatial structure was selected as the analytical model and a tuned mass damper (TMD) was installed to control the dynamic response for the earthquake loads. Also, it is analyzed that the installation location of TMD in the analytical model and the optimal number of installations. A single TMD mass installed in the analytical model was set up 1% of the mass of the whole structure, and the optimum installation location was derived according to the number of change. As a result, it was verified that most effective to install eight TMDs regardless of opening or closing. Thus, in this study, eight TMDs were installed in the retractable-roof spatial structure and the optimum mass ratio was inquired while reducing a single TMD. In addition, the optimum mass distribution ratio was identified by redistributing the TMD masses differently depending on the installation position, using the mass ratio of vibration control being the most effective for seismic load. From the analysis results, as it is possible to confirm the optimum mass distribution ratio according to the optimum mass ratio and installation location of the TMD in the the retractable-roof spatial structure, it can be used as a reference in the TMD design for large space structure.