• The KIPS Transactions:PartC
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• v.16C no.1
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• pp.133-142
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• 2009

This paper proposes an analytical performance model of IEEE 802.15.4 in the presence of hidden nodes. Conventional 802.15.4 mathematical models assume ideal situations where every node can detect the transmission signal of every other nodes different from the realistic environments. Since nodes can be randomly located in real environments so that some nodes' presence is hidden from other ones, this assumption leads to wrong performance evaluation of 802.15.4. For solving this problem, we develop an extended performance model which combines the traditional 802.15.4 performance model with one for accounting the presence of hidden nodes. The extended model predicts the rapid performance degradation of 802.15.4 due to the small number of hidden nodes. The performance, for example, degrades by 62% at maximum when 5% of the total nodes are hidden. These predictions are confirmed to be equal to those of ns-2 simulations by less than 6% difference.

• Corrosion Science and Technology
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• v.9 no.1
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• pp.48-55
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• 2010

The many vessels are built with FRP(Fiber-Reinforced Plastic) material for small boats and medium vessels. However, FRP is impossible to be used for recyclable material owing to environmental problems and causes large proportion of collision accidents because radar reflection wave is so weak that large vessels could not detect FRP ships during the sailing. Hence, Al alloy comes into the spotlight to solve these kinds of problems as a new-material for next generation instead of FRP. Al alloy ships are getting widely introduced for fish and leisure boats to save fuel consumption due to lightweight. In this study, it was selected 6061-T6 Al alloy which are mainly used for Al-ships and carried out various electrochemical experiment such as potential, anodic/cathodic polarization, Tafel analysis, potentiostatic experiment and surface morphologies observation after potentiostatic experiment for 1200 sec by using the SEM equipment to evaluate optimum corrosion protection potential in sea water. It is concluded that the optimum corrosion protection potential range is -1.4 V ~ -0.7 V(Ag/AgCl) for 6061-T6 Al alloy, in the case of application of ICCP(Impressed current cathodic protection), which was shown the lowest current density at the electrochemical experiment and good specimen surface morphologies after potentiostatic experiment for Al-Mg-Si(6061-T6) Al alloy in seawater environment.

• Journal of the Korea Society for Simulation
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• v.16 no.1
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• pp.31-37
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• 2007

The importance of NPC's role in computer games is increasing. An NPC must perform its tasks by perceiving obstacles and other characters and by moving through them. It has been proposed to plan a natural-looking path against fixed obstacles by using a generalized visibility graph. In this paper we develop the execution module for an NPC to move efficiently along the path planned on the generalized visibility graph. The planned path consists of line segments and arc segments, so we define steering behaviors such as linear behaviors, circular behaviors, and an arriving behavior for NPC's movements to be realistic and utilize them during execution. The execution module also includes the collision detection capability to be able to detect dynamic obstacles and uses a decision tree to react differently according to the detected obstacles. The execution module is tested through the simulation based on the example scenario in which an NPC interferes the other moving NPC.

• Journal of Communications and Networks
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• v.18 no.2
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• pp.218-226
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• 2016

Coordination among users is an inevitable but time-consuming operation in wireless networks. It severely limit the system performance when the data rate is high. We present FC-MAC, a novel MAC protocol that can complete a contention within one contention slot over a joint frequency-code domain. When a node takes part in the contention, it generates randomly a contention vector (CV), which is a binary sequence of length equal to the number of available orthogonal frequency division multiplexing (OFDM) subcarriers. In FC-MAC, different user is assigned with a distinct signature (i.e., PN sequence). A node sends the signature at specific subcarriers and uses the sequence of the ON/OFF states of all subcarriers to indicate the chosen CV. Meanwhile, every node uses the redundant antennas to detect the CVs of other nodes. The node with the minimum CV becomes the winner. The experimental results show that, the collision probability of FC-MAC is as low as 0.05% when the network has 100 nodes. In comparison with IEEE 802.11, contention time is reduced by 50-80% and the throughput gain is up to 200%.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.3
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• pp.139-147
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• 2007

In military transportation, the use of wide trailer for transporting the large and heavy weight equipments such as tank, armoured vehicle, and mobile gunnery is quite common. So, the vulnerability of causing traffic accidents for these wide military trailer to bump or collide with another car in adjacent lane is very high due to its broad width in excess of its own lane's width. Also, the possibility of these strayed accidents can be increased especially by the careless driver. In this paper, the recognition system of lane and vehicle headway direction is developed to detect the possible collision and warn the driver to prevent the fatal accident. In the system development, Kalman filtering is used first to extract the border of driving lane from the video images supplied by the CCD camera attached to the vehicle and the driving lane detection is completed with regression analysis. Next, the vehicle headway direction is recognized by using neural network scheme with the extracted parameters of the detected driving lane feature. The practical experiments for the developed system are also carried out in the real traffic road of Seoul city area and the results show us the more than 90% accuracy in recognizing the driving lane and vehicle headway direction.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.05a
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• pp.313-316
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• 2009

A novel approach for electrocardiogram (ECG) analysis within a functional sensor node has been developed and evaluated. The main aim is to reduce data collision, traffic over loads and power consumption in healthcare applications of wireless sensor networks (WSN). The sensor node attached on the patient's bodysurface around the heart can perform ECG analysis based on a QRS detection algorithm to detect abnormal condition of the patient. Data transfer is activated only after detected abnormality in the ECG. This system can reduce packet loss during transmission by reducing traffic overload. In addition, it saves power supply energy leading to more reliable, cheap and user-friendly operation in the WSN based ubiquitous health monitoring.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.6
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• pp.1365-1372
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• 2018

Recently, the aging of agricultural society has caused a rapid increase in safety accidents in -agricultural machinery. Sometimes, the wounded may be left unattended resulting serious situation. In order to solve these problems, ICT technology is used to detect and inform the accident quickly when a safety accident such as overturning, collision or other accidents occurs during the operation or moving the agricultural machinery, such as cultivator, rearing machine, and tractor. A system capable of minimizing the amount of data is required. In this paper, an ICT - based automatic accident detection & propagation system is proposed for the agricultural machinery accident such as colliding crashes or overturning of agricultural machinery. The proposed system enables quick rescue by sending a text message automatically to family, acquaintances, hospitals and 119 in the event of an agricultural accident.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.6
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• pp.807-812
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• 2021

In order to be able to interact with the user to experience it as if it were real in virtual reality contents, input/output devices that make them feel the five senses of humans are required . In virtual reality (VR), devices that stimulate sight and hearing are the most representative. For a more realistic experience, suits and gloves that stimulate the sense of touch have recently been released, but there are not many cases applied to actual contents due to the limitation of device . In this paper, we analyze a virtual reality glove that can detect hand movement and touch in a virtual world. Based on the analysis, we propose an algorithm that can sense the intensity of collision with a VR object by tactile sense by improving the UI/UX using the vibration of the feedback method used in the existing virtual reality glove. In addition, the system implemented by the algorithm is applied to an actual case.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.2
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• pp.692-712
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• 2022

Buoys used for Aid to Navigation systems are widely used to guide the sea paths and are powered by batteries, requiring continuous battery replacement. However, since human labor is required to replace the batteries, humans can be exposed to dangerous situation, including even collision with shipping vessels. In addition, Maritime sensors are installed on the route signs, so that these are often damaged by collisions with small and medium-sized ships, resulting in significant financial loss. In order to prevent these accidents, maritime object detection technology is essential to alert ships approaching buoys. Existing studies apply a number of filters to eliminate noise and to detect objects within the sea image. For this process, most studies directly access the pixels and process the images. However, this approach typically takes a long time to process because of its complexity and the requirements of significant amounts of computational power. In an emergent situation, it is important to alarm the vessel's rapid approach to buoys in real time to avoid collisions between vessels and route signs, therefore minimizing computation and speeding up processes are critical operations. Therefore, we propose Fast Connected Component Labeling (FCCL) which can reduce computation to minimize the processing time of filter applications, while maintaining the detection performance of existing methods. The results show that the detection performance of the FCCL is close to 30 FPS - approximately 2-5 times faster, when compared to the existing methods - while the average throughput is the same as existing methods.

• Journal of the Society of Disaster Information
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• v.20 no.2
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• pp.315-328
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• 2024

Purpose: The purpose of this paper is to present a service construction plan using multiple complex sensor information to detect abnormal situations in urban life safety that are difficult to identify on CCTV. Method: This study selected service scenarios based on actual testbed data and analyzed service importance for local government control center operators, which are main users. Result: Service scenarios were selected as detection of day and night dynamic object, Detection of sudden temperature changes, and Detection of time-series temperature changes. As a result of AHP analysis, walking and mobility collision risk situation services and fire foreshadowing detection services leading to immediate major disasters were highly evaluated. Conclusion: This study is significant in proposing a plan to build an anomaly detection service that can be used in local governments based on real data. This study is significant in proposing a plan to build an anomaly detection service that can be used by local governments based on testbed data.