• Journal of Broadcast Engineering
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• v.27 no.5
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• pp.762-772
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• 2022

Current disaster alert broadcasting based on mobile communication systems targets personal mobile terminals such as smartphones. However, smart cities require IoT-based services such as smart homes and offices. Therefore, when severe disasters such as earthquakes occur, smart cities must quickly perform appropriate control and respond to buildings and factories. For this, a disaster warning broadcasting technique for IoT terminals for smart cities is required. In this paper, we propose a disaster alert transmission method based on 4G/5G mobile communication for IoT terminals for smart cities. The proposed method effectively utilizes the image display method for CBS, a cell-based broadcasting service, and shows the superiority of the proposed approach through simulation.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.10
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• pp.239-244
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• 2013

This paper presents a design of the CMOS LDO regulator with a UVLO protection function for a high speed PMIC. Proposed LDO regulator circuit consists of a BGR reference circuit, an error amplifier and a power transistor and so on. UVLO block between the power transistor and the power supply is added for a low input protection function. Also, UVLO block showed normal operation with turn-off voltage of 2.7V and turn-on voltage of 4 V in condition of 5 V power supply. Proposed circuit generated fixed 3.3 V from a supply of 5V. From SPICE simulation results using a $1{\mu}m$ high voltage CMOS technology, simulation results were 5.88 mV/V line regulation and 27.5 uV/mA load regulation with load current 0 mA to 200 mA.

• Ecology and Resilient Infrastructure
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• v.8 no.4
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• pp.165-178
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• 2021

We studied driftwood behaviors including generation and deposition in a tsunami using a numerical simulation. We used an integrated two-dimensional numerical model, which included a driftwood dynamics model. The study area was Sendai, Japan. Observation data collected by Inagaki et al. (2012) were used to verify the simulation results by comparing them with driftwood deposition patterns. A simplified model was developed to consider the threshold of driftwood generation by the drag force of water flows. To consider the volume of driftwood generated, we estimated the total wood number in the study area using Google Earth. Therefore, we simulated more than 13,000 pieces of driftwood that were generated and transported inland from approximately 300,000 trees that were growing in the forest. The final distribution of the driftwood was similar to the observation data. The reproducibility of the generation and deposition patterns of driftwood showed good agreement in terms of longitudinal deposition pattern. In the future, a sensitivity analysis on driftwood parameters, such as the size of the wood, boundary conditions, and grid size, will be implemented to predict the travel patterns of driftwood. Such modeling will be a useful methodology for disaster prediction based on water flow and driftwood.

• Journal of KIISE:Information Networking
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• v.36 no.6
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• pp.514-527
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• 2009

Wireless sensor networks (WSNs) can be used in various applications for military or environmental purpose. Recently, there are lots of on-going researches for detecting and tracking the spread of continuous objects or phenomena such as poisonous gas, wildfires, earthquakes, and so on. Some previous work has proposed techniques to detect edge nodes of such a continuous object based on the information of all the 1-hop neighbor nodes. In those techniques, however, a number of nodes are redundantly selected as edge nodes, and thus, the boundary of the continuous object cannot be presented accurately. In this paper, we propose a new edge detection method in which edge nodes of the continuous object are detected based on the information of the neighbor nodes obtained via the Localized Delaunay Triangulation so that a minimum number of nodes are selected as edge nodes. We also define the sensor behavior rule for tracking continuous objects energy-efficiently. Our simulation results show that the proposed edge detection method provides enhanced performance compared with previous 1-hop neighbor node based methods. On the average, the accuracy is improved by 29.95% while the number of edge nodes, the amount of communication messages and energy consumption are reduced by 54.43%, 79.36% and 72.34%, respectively. Moreover, the number of edge nodes decreases by 48.38% on the average in our field test with MICAz motes.