• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.6
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• pp.1205-1212
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• 2021

Robots that can actually help people a lot by dealing with dangerous tasks that are difficult for people to do, such as disaster situations, lifesaving, handling dangerous goods, and reconnaissance of dangerous areas, continue to become an issue. Therefore, in this paper, we intend to implement a mobile robot arm that can implement a human motion will on the robot arm to enable active response according to the situation and control the vehicle according to hand movements to give mobility. A controller is manufactured using a flex sensor and agyro sensor, and the roll and pitch values of the two gyro sensors are adjusted to control the angle of the robot arm and specify the vehicle direction. In addition, by designating the levels of the three flex sensors, the motor is operated according to hand movements, and a robot arm is implemented so that objects can be picked up and moved.

• Journal of The Korean Society of Agricultural Engineers
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• v.63 no.3
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• pp.13-26
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• 2021

Recent drought events in the South Korea and the magnitude of drought losses indicate the continuing vulnerability of the agricultural drought. Various studies have been performed on drought hazard assessment at the regional scales, but until recently, drought management has been response oriented with little attention to mitigation and preparedness. A vulnerability assessment is introduced in order to preemptively respond to agricultural drought and to predict the occurrence of drought. This paper presents a method for spatial, Geographic Information Systems-based assessment of agricultural drought vulnerability in South Korea. It was hypothesized that the key 14 items that define agricultural drought vulnerability were meteorological, agricultural reservoir, social, and adaptability factors. Also, this study is to analyze agricultural drought vulnerability by comparing vulnerability assessment according to weighting method. The weight of the evaluation elements is expressed through the Analytic Hierarchy Process (AHP), which includes subjective elements such as surveys, and the Entropy method using attribute information of the evaluation items. The agricultural drought vulnerability map was created through development of a numerical weighting scheme to evaluate the drought potential of the classes within each factor. This vulnerability assessment is calculated the vulnerability index based on the weight, and analyze the vulnerable map from 2015 to 2019. The identification of agricultural drought vulnerability is an essential step in addressing the issue of drought vulnerability in the South Korea and can lead to mitigation-oriented drought management and supports government policymaking.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.5
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• pp.131-138
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• 2023

In this paper, a free space optical communication device that can be used in a mobile base station of several km or less was fabricated and its characteristics were investigated. To overcome the loss due to atmospheric transmission, an optical fiber amplifier (EDFA) with an output of 23 dBm or more was used. In order to increase the focusing speed and miniaturization of the laser beam, an optical lens was manufactured, and a transmission lens was designed to have beam divergence within the range of 1.5 to 1.8 [mrad]. A PT module that controls PAN/TILT was fabricated in order to reduce pointing errors and effective automatic alignment between transceiver devices. In this study, Reed-Solomon (RS) code was used to maintain the transmission quality above a certain level. It was manufactured to be able to communicate at a wireless distance of 300m in a weather situation with visibility of 300m. For performance measurement, it was measured using BERT and eye pattern analyzer, and it was confirmed that BER can be maintained at 2.5Gbps.

• Smart Structures and Systems
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• v.33 no.2
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• pp.119-131
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• 2024

Drift angle is a significant index for diagnosing post-event structures. A common way to estimate this drift response is by using modal parameters identified under natural excitations. Although the modal parameters of shear structures cannot be identified accurately in the real environment, the identification error has little impact on the estimation when measurements from several floors are used. However, the estimation accuracy falls dramatically when there is only one accelerometer. This paper describes the susceptibility of single sensor identification to modelling error and simulations that preliminarily verified this characteristic. To make a robust evaluation from measurements of one floor of shear structures based on imprecisely identified parameters, a novel scheme is devised to approximately correct the mode shapes with respect to fictitious frequencies generated with a genetic algorithm; in particular, the scheme uses constrained minimization to take both the mathematical aspect and the realistic aspect of the mode shapes into account. The algorithm was validated by using a full-scale shear building. The differences between single-sensor and multiple-sensor estimations were analyzed. It was found that, as the number of accelerometers decreases, the error rises due to insufficient data and becomes very high when there is only one sensor. Moreover, when measurements for only one floor are available, the proposed method yields more precise and appropriate mode shapes, leading to a better estimation on the drift angle of the lower floors compared with a method designed for multiple sensors. As well, it is shown that the reduction in space complexity is offset by increasing the computation complexity.

• Korean Journal of Agricultural and Forest Meteorology
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• v.19 no.3
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• pp.195-202
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• 2017

This study aims to suggest the basics for the implementation of the farmstead-specific early warning system (FEWS) for weather risk management nationwide. A survey by questionnaire was conducted to examine farmer's response, and a cost-benefit analysis was made to examine the effect of the FEWS on the economy. The farmers who volunteered to participate in this survey responded that they were generally satisfied with the FEWS, and that they used it well for farming. Willingness to pay (WTP) for the early warning service was estimated to be 8,833 KRW per month by survey respondents. If the early warning service is extended to nationwide and 50% of farmers use it for six months, then the ratio of benefit to cost will be 2.2, indicating that nationwide expansion of the FEWS is very feasible.

• Journal of the Korean Institute of Gas
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• v.22 no.5
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• pp.79-88
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• 2018

This study presents an evaluation method to estimate the damage scale of chemical storage tank of petrochemical plant due to the earthquake that is likely to occur among NaTech damage types. Based on this, the risk for damage reduction of chemical storage tanks was evaluated. As a result of the study, the risk of the storage tank increased greatly considering the earthquake, and the risk was greatly reduced as a result of evaluating the proposed measures to mitigate the damage impact on the earthquake. This study is expected to contribute to the research on the reduction of NaTech damages such as typhoons and thunderstorms as well as earthquakes, and to establish an emergency response plan. In the future, it is necessary to systematically study and institutionalize the risk reduction measures considering earthquakes.

• Smart Structures and Systems
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• v.23 no.6
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• pp.653-667
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• 2019

Using cross-ties to connect cables together when forming a cable network is regarded as an efficient method of mitigating cable vibrations. Cross-ties have been extended and fixed on bridge decks or towers in some engineering applications. However, the dynamics of this kind of system need to be further studied, and the effects of extending cross-links to bridge decks/towers on the modal response of the system should be assessed in detail. In this paper, a system of two cables connected by an inter-supported cross-link with another lower cross-link extended to the ground is proposed and analyzed. The characteristic equation of the system is derived, and some limiting solutions in closed form of the system are derived. Roots of cable system with special configurations are also discussed, attention being given to the case when the two cables are identical. A predictable mode behavior was found when the stiffness of inter-connection cross-link and the cross-link extended to the ground were the same. The vector of mode energy distribution and the degree of mode localization index are proposed so as to distinguish global and local modes. The change of mode behaviors is further discussed in the case when the two cables are not identical. Effects of cross-link stiffness, cross-link location, mass-tension ratio, cable length ratio and frequency ratio on $1^{st}$ mode frequency and mode shape are addressed.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.117-129
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• 2009

This paper studied the safety management network system of infrastructure which constructed smart sensors, closed-circuit television(CCTV) and monitoring system. This safety management of infrastructure applied to bridge, cut slop and tunnel, embankment etc. The system applied to technologies of standardization guidelines, data acquirement technologies, data analysis and judgment technologies, system integration setup technology, and IT technologies. It was constructed safety management network system of various infrastructure to improve efficient management and operation for many infrastructure. Integrated safety management network system of infrastructure consisted of the real-time structural health monitoring system of each infrastructure, integrated control center, measured data transmission using i of tet web-based, collecting data using sf ver, early alarm system which the dangerous event of infrastructure occurred. Integrated control center consisted of conference room, control room to manage and analysis the data, server room to present the measured data and to collect the raw data. Early alarm system proposed realization of warning and response within 5 minute or less through development of sensor-based progress report and propagation automation system using the media such as MMS, VMS, EMS, FMS, SMS and web services of report and propagation. Based on this, the most effective u-Infrastructure Safety Management System is expected to be stably established at a less cost, thus making people's life more comfortable. Information obtained from such systems could be useful for maintenance or structural safety evaluation of existing structures, rapid evaluation of conditions of damaged structures after an earthquake, estimation of residual life of structures, repair and retrofitting of structures, maintenance, management or rehabilitation of historical structures.

• Journal of The Geomorphological Association of Korea
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• v.20 no.4
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• pp.117-131
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• 2013

2010 eruption of Eyjafjallajokull volcano in Iceland and 2011 Shinmoedake's eruption in Japan evoked concerns from researchers for the possibility of explosion of Baekdusan volcano after long dormancy (repose period). National Emergency Management Administration has tried to evaluate the vulnerability of volcanic disaster and to prepare response to the potential risk and to mitigate the damages from the volcanic eruption, but a few studies have focused on the activities of Baekdusan. This study aims to clarify what the criteria between dormant volcano and active volcano based on geomorphologists' and geologists' researches. Volcanic experts have made a criterion of activeness such as the evidence of volcanic eruption within 10,000 year before present. More rigorous criterion which was made in 1991 by Japanese Meteorological Administration was 2000 years B.P. Both Baekdusan and Hallasan satisfy two criteria, so it is necessary for us to monitor the activity of both volcanoes and to reflect the facts into the curriculum.

• Geomechanics and Engineering
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• v.28 no.4
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• pp.335-346
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• 2022

Buckling failure is a typical slope instability mode that should be paid more attention to. It is difficult to provide systematic guidance for the monitoring and management of such slopes due to unclear mechanism. Here we examine buckling failure as the potential instability mode for a slope above a railway tunnel in southwest China. A comprehensive model test system was developed that can be used to conduct buckling failure experiments. The displacement, stress, and strain of the slope were monitored to document the evolution of buckling failure during the experiment. Monitoring data reveal the deformation and stress characteristics of the slope with different slipping mass thicknesses and under different top loads. The test results show that the slipping mass is the main subject of the top load and is the key object of monitoring. Displacement and stress precede buckling failure, so maybe useful predictors of impending failure. However, the response of the stress variation is earlier than displacement variation during the failure process. It is also necessary to monitor the bedrock near the slip face because its stress evolution plays an important role in the early prediction of instability. The position near the slope foot is most prone to buckling failure, so it should be closely monitored.