• Journal of Digital Convergence
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• v.18 no.11
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• pp.247-257
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• 2020

The Purpose of this study is to present effective Anti-Drone systems to protect national important facilities against drones that are illegally used by crime groups and terrorists with malicious intents. In order to accomplish the purpose of the study, technical and policy reports regarding Anti-Drone systems, open documents from manufacturers and various research papers are reviewed, and in-depth interviews with experts were conducted. Studies have shown that it is effective to overlay and mix different detection systems so that they can improve detection rates by supplementing each other's advantages and disadvantages, and that the means of incapacitation need to acquire flexibility by using both soft-kill and hard-kill methods in accordance with operational environment for the effective usage. In other words, the establishment of an illegal drone pre-management system, mixed and overlapping detection assets, determining appropriate countermeasures, and multiple distribution of means of incapacitation. The establishment of a protection system for important national facilities through the operation of overlapping and complex anti-drone systems is the most urgent task.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.2
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• pp.139-148
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• 2013

In this study, an ejector was designed to recirculate the anodic off-gas of SOFC, and a parametric study of the system performance was conducted at various ejector entrainment ratios. Aspen Plus, a chemical engineering program, was used to calculate the operational conditions of the ejector. To minimize the calculation load of the CFD and to ensure the global optimum, a genetic algorithm and Kriging model were used for the optimization. The optimization results showed that the dominant design variables of the sonic ejector are the throat diameter and the first flow nozzle position. The designed ejector has enough flexibility for different operating conditions of a 1-kW SOFC system. When the ejector was applied to the SOFC, it reduced 56% of the steam and 8.4% of the fuel compared to the reference case.

• Journal of Advanced Navigation Technology
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• v.21 no.5
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• pp.443-449
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• 2017

Swarm of low-cost UAVs for search mission has benefit in the sense of rapid search compared to use of single high-end UAV. As the number of UAVs forming swarm increases, not only the time for the mission planning increases, but also the system to operate UAVs has excessive burden. This paper addresses a decentralized area search algorithm adequate for multiple UAVs which takes advantages of flexibility, robustness, and simplicity. To down the cost, it is assumed that each UAV has limited ability: close-communication, basic calculation, and limited memory. In close-communication, heath conditions and search information are shared. And collision avoidance and consensus of next search direction are then done. To increase weight on un-searched area and to provide overlapped search, the score function is introduced. Performance and operational characteristics of the proposed search algorithm and mission planning logic are verified via numerical simulations.

• Journal of the Korea Society for Simulation
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• v.17 no.4
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• pp.133-142
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• 2008

AGV systems are widely used to increase the flexibility and the efficiency of the material handling systems. AGV systems are one of critical factors which determine the overall performance of the manufacturing systems. To this end, the optimal design for AGV systems is essential. Commercial simulation software is often used as an analysis tool during the design of AGV systems, however a series of procedures are desirable to simplify the analysis processes. In this paper, we present and develop the architecture for unidirectional AGV systems simulator which is able to consider approximate optimal unidirectional flow path and various operational parameters. The designed AGV systems simulator is based on JAVA, and it is developed to support designing approximate optimal unidirectional network by using Tabu search method. In addition, it enables users to design and evaluate AGV systems and to analyze alternative solutions easily. Simulation engine is consists of layout designer, AGV operation plan designer, and integrated AGVS layout designer. Users enter their system design/operation information into input window, then the entered information is automatically utilized for modeling and simulating AGV systems in simulation engine. By this series of procedures, users can get the feed back quickly.

• Fire Science and Engineering
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• v.30 no.5
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• pp.130-136
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• 2016

In this study, the budget investment state of the technology classification structure in a fire-fighting and safety research development program and the capability of a fire-fighting safety research program were analyzed between 2007 and 2013 with support from the ministry of public safety. The Ministry of public safety and security's fire safety research funding has shown a gradual increasing tendency. More 80% of the budget was invested in fire safety and disaster response technologies and the fire safety and special disaster prevention response technology of R&D. From the results of analyzing the capacity of fire-fighting safety and rescue safety, it was found to have a moderate level of 3.5 on a 7 point scale basis. To develop the Ministry of Public Safety and Security's fire safety research in the future, the flexibility and reasonableness of the budget/legal/institutional framework and support should be ensured to improve the operational capability of resources. In addition, a proliferation program is necessary for the commercialization and industrialization of research results.

• ETRI Journal
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• v.37 no.5
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• pp.877-887
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• 2015

This paper is a first-hand summary on our comprehensive live trial of cellular-assisted device-to-device (D2D) communications currently being ratified by the standards community for next-generation mobile broadband networks. In our test implementation, we employ a full-featured 3GPP LTE network deployment and augment it with all necessary support to provide realtime D2D connectivity over emerging Wi-Fi-Direct (WFD) technology. As a result, our LTE-assisted WFD D2D system enjoys the required flexibility while meeting the existing standards in every feasible detail. Further, this paper provides an account on the extensive measurement campaign conducted with our implementation. The resulting real-world measurements from this campaign quantify the numerical effects of D2D functionality on the resultant system performance. Consequently, they shed light on the general applicability of LTE-assisted WFD solutions and associated operational ranges.

• Journal of the Korean Society of Hazard Mitigation
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• v.5 no.4 s.19
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• pp.59-69
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• 2005

Drought is difficult to detect and monitor, but it is easy to interpret through the drought index. The Palmer Drought Severity Index(PDSI), which is most commonly used as one of drought indices, have been widely used, however, the index have limitation as operational tools and triggers for policy responses. Recently, a new index, the Standardized Precipitation Index(SPI), was developed to improve drought detection and monitoring capabilities. The SPI has an improvement over previous indices md has several characteristics including its simplicity and temporal flexibility that allow its application for water resources on all timescales. Keetch-Byram Dought Index(KBDI) was defined as a number representing the net effect of evapotranspiration and precipitation in producing cumulative moisture deficiency in deep duff or upper soil layer. The purpose of this study is to analyze drought in Korea by using PDSI, SPI and KBDI. The result of this study suggests standard drought index by comparing of estimated drought indices. The data are obtained from Korea Meteorological Administration 56 stations over 30 years in each of the 8 sub-basins covering the whole nation. It is found that the PDSI had the advantage to detect the stage of drought resulting from cumulative shortage of rainfall, while SPI and KBDI had the advantage to detect the stage of drought resulting from short-term shortage of rainfall.

• Journal of Information Technology and Architecture
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• v.9 no.1
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• pp.33-42
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• 2012

Present many organizations are introduced to smartwork for reducing the operational cost and getting the labor's flexibility. The smartwork is the future-oriented worker's environment in which they can engage in their task, anytime and anywhere conveniently and efficiently. In spite of many smartwork advantages, the security problems are major issues and prevent to introducing and spreading of smartwork for organizations. Therefore, the success of the organization for smartwork environment is put in place appropriate security control model. This study is about security threats for smartwork security control model. We apply the exploratory method for this research, which are reviewing, analyzing of literature for extracting the security threats and clustering of the extracted security threats. Finally we define the 16's security threats according to the aspect of smartwork service layers.

• Korean Journal of Materials Research
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• v.27 no.12
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• pp.658-663
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• 2017

Urchin-structured zinc oxide(ZnO) nanorod(NR) gas sensors were successfully demonstrated on a polyimide(PI) substrate, using single wall carbon nanotubes(SWCNTs) as the electrode. The ZnO NRs were grown with ZnO shells arranged at regular intervals to form a network structure with maximized surface area. The high surface area and numerous junctions of the NR network structure was the key to excellent gas sensing performance. Moreover, the SWCNTs formed a junction barrier with the ZnO which further improved sensor characteristics. The fabricated urchin-structured ZnO NR gas sensors exhibited superior performance upon $NO_2$ exposure with a stable response of 110, fast rise and decay times of 38 and 24 sec, respectively. Comparative analyses revealed that the high performance of the sensors was due to a combination of high surface area, numerous active junction points, and the use of the SWCNTs electrode. Furthermore, the urchin-structured ZnO NR gas sensors showed sustainable mechanical stability. Although degradation of the devices progressed during repeated flexibility tests, the sensors were still operational even after 10000 cycles of a bending test with a radius of curvature of 5 mm.

• Smart Structures and Systems
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• v.6 no.5_6
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• pp.561-578
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• 2010

This study proposes a multi-level damage localization strategy to achieve an effective damage detection system for civil infrastructure systems based on wireless sensors. The proposed system is designed for use of distributed computation in a wireless sensor network (WSN). Modal identification is achieved using the frequency-domain decomposition (FDD) method and the peak-picking technique. The ASH (angle-between-string-and-horizon) and AS (axial strain) flexibility-based methods are employed for identifying and localizing damage. Fundamentally, the multi-level damage localization strategy does not activate all of the sensor nodes in the network at once. Instead, relatively few sensors are used to perform coarse-grained damage localization; if damage is detected, only those sensors in the potentially damaged regions are incrementally added to the network to perform finer-grained damage localization. In this way, many nodes are able to remain asleep for part or all of the multi-level interrogations, and thus the total energy cost is reduced considerably. In addition, a novel distributed computing strategy is also proposed to reduce the energy consumed in a sensor node, which distributes modal identification and damage detection tasks across a WSN and only allows small amount of useful intermediate results to be transmitted wirelessly. Computations are first performed on each leaf node independently, and the aggregated information is transmitted to one cluster head in each cluster. A second stage of computations are performed on each cluster head, and the identified operational deflection shapes and natural frequencies are transmitted to the base station of the WSN. The damage indicators are extracted at the base station. The proposed strategy yields a WSN-based SHM system which can effectively and automatically identify and localize damage, and is efficient in energy usage. The proposed strategy is validated using two illustrative numerical simulations and experimental validation is performed using a cantilevered beam.