• Proceedings of the KSR Conference
• /
• 2007.11a
• /
• pp.1337-1345
• /
• 2007

The present study is a basic investigation for systematically proceeding disaster prevention studying the effect of platform screen door in case of fire at the subway station. In the paper, the characteristics of screen door were surveyed and described. The fully closed platform screen door and the island type of subway station were employed for simulation-study. Numerical simulations of fire driven flow at the subway station with platform screen door were performed with commercial fire CFD code. For analyzing of the effect of platform screen door, the fire simulations with and without the platform screen door were compared. For the fire location, the one is located on the platform and the other case on the railway. The Ultrafast model was taken as fire growth scenario. The maximum heat release rate was 10MW. The propagated time of the heat and smoke to stairs was within 4 minute when the fire is located on the platform. However the heat and smoke propagation was block off by screen door when the fire is located on the railway.

• Journal of Korean Society on Water Environment
• /
• v.30 no.6
• /
• pp.673-682
• /
• 2014

A watershed model was constructed using Hydrological Simulation Program Fortran to predict the water temperature at major tributaries of Nakdong River basin, Korea. Water temperature is one of the most fundamental indices used to determine the nature of an aquatic environment. Most processes of an aquatic environment such as saturation level of dissolved oxygen, the decay rate of organic matter, the growth rate of phytoplankton and zooplankton are affected by temperature. The heat flux to major reservoirs and tributaries was analyzed to simulate water temperature accurately using HSPF model. The annual mean heat flux of solar radiation was estimated to $150{\sim}165W/m^2$, longwave radiation to $-48{\sim}-113W/m^2$, evaporative heat loss to $-39{\sim}-115W/m^2$, sensible heat flux to $-13{\sim}-22W/m^2$, precipitation heat flux to $2{\sim}4W/m^2$, bed heat flux to $-24{\sim}22W/m^2$ respectively. The model was calibrated at major reservoir and tributaries for a three-year period (2008 to 2010). The deviation values (Dv) of water temperature ranged from -6.0 to 3.7%, Nash-Sutcliffe efficiency(NSE) of 0.88 to 0.95, root mean square error(RMSE) of $1.7{\sim}2.8^{\circ}C$. The operational water temperature forecasting results presented in this study were in good agreement with measured data and had a similar accuracy with model calibration results.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.62 no.12
• /
• pp.1712-1718
• /
• 2013

This paper proposes a compact dual-band 3-way power divider that helps lowering the weight of a transceiver for the L-band or multi-purpose satellite communication. Instead of the multi stages or tapering which ends up with loss accumulation and size-growth, the non-linear dispersive phases from the metamaterial CRLH(composite right and left-handed) properties are obtained by the accurate formulation and implemented by the short transmission line segments. Firstly, the CRLH dual-band two-way unequal power divider and equal power divider are separately designed. And then, the input of the two-way equal power divider is plugged in the output port of the unequal one, and the entire geometry is slightly adjusted for the desirable performance. The circuit analysis and full-wave simulation are used to predict the frequency responses and validated by the measurement of the prototype. Besides, the size-reduction effect is addressed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.18 no.3
• /
• pp.142-148
• /
• 2004

Recently, with the growth of software for electromagnetic-thermal analysis, it has been studied that the precise analysis and investigation for cause of the electrical fire using computer simulation is on the basis of theroy for electromagnetic-thermal analysis. But it is very lacking for the precise analysis and investigation of cause for the electrical fire. In this paper, we have simulated the temperature distribution of wire to current and the force between the two conductors according to the current and the distance of the vinyl flat-type electrical wire(600 V, VFF, $2C{\times}$1.25mm^2) using the finite element method(Flux2D) in a overcurrent. And we will present the cause analysis method of electrical fire by experiment for distance between the two conductors according to current and time using large current supply device(Model: EHT_EFAD, Korea) in a overcurrent.

• Journal of Korea Multimedia Society
• /
• v.9 no.1
• /
• pp.59-72
• /
• 2006

The rapid growth of technology for network and terminal devices is able to service multimedia contents in mobile environments. But as the environment of networks and the performance of devices is varied, the same quality service is very difficult to be provided for user in internet and mobile environment. Therefore, multimedia streaming system must provide an adaptive service in considering network and device environment. Video transcoding techniques are the good solution that can provide video streaming service in various network environments adaptively. This paper proposes a dynamic frame-skipping transcoding scheme to provide adaptive streaming service in various network environments. This scheme uses the prediction period for transcoding. A proposed transcoding scheme can reduce time complexity through combination of prediction period and skipping period to control frame-skipping rate in encoder. In simulation results, the performance of proposed scheme is similar to the performance of a traditional dynamic frame-skipping scheme in PSNR value. But the performance of proposed scheme outperforms the performance of traditional scheme in time complexity.

• Journal of Advanced Marine Engineering and Technology
• /
• v.40 no.7
• /
• pp.622-628
• /
• 2016

The prosperity of IT technologies and the removal of restrictions regarding Unmanned Aerial Vehicles (UAVs), also known as drones, have driven growth in their popularity. However, without a proper solution to the problem of accident avoidance for UAVs, this popularity increases the potential for collisions between UAVs and between UAV and terrain features. These collisions can occur because UAVs to date have flown using radio control or image recognition based autonomous navigation. Therefore, we propose efficient UAV routing schemes to tackle the collision problem using vehicular communication systems. Performance evaluation by computer simulation shows that the proposed methods effectively reduce the collision probability and improve the routing efficiency of the UAV. Furthermore, the proposed algorithms are compatible and can be directly applied with small overhead to the commercial vehicular communication system implementation.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.3
• /
• pp.1299-1304
• /
• 2014

This paper is a study for developing an agriculture automatic hose reel of mobile robot. One of the important works in farming is pesticide spraying because it is related to the growth of crops. Therefore, we develop an automatic reel hose and mobile robot. Conducting kinematic analysis of steering performance, the mobile robot is designed to move smoothly even in a small space, and that is verified by simulation. To increase supplying accuracy of the automatic hose reel, the mobile robot use detecting tension mechanism on a hose and a device for the hose deployment. We conduct performance and on-farm evaluation. This system has been maximum speed of 2.5m/s, driving accuracy of ${\pm}0.18^{\circ}$ and driving safety speed of 2m/s. The system would solve an aging population and shortage of workforce in agriculture.

• Journal of Information Processing Systems
• /
• v.5 no.1
• /
• pp.33-40
• /
• 2009

Ever since the network-based malicious code commonly known as a 'worm' surfaced in the early part of the 1980's, its prevalence has grown more and more. The RCS (Random Constant Spreading) worm has become a dominant, malicious virus in recent computer networking circles. The worm retards the availability of an overall network by exhausting resources such as CPU capacity, network peripherals and transfer bandwidth, causing damage to an uninfected system as well as an infected system. The generation and spreading cycle of these worms progress rapidly. The existing studies to counter malicious code have studied the Microscopic Model for detecting worm generation based on some specific pattern or sign of attack, thus preventing its spread by countering the worm directly on detection. However, due to zero-day threat actualization, rapid spreading of the RCS worm and reduction of survival time, securing a security model to ensure the survivability of the network became an urgent problem that the existing solution-oriented security measures did not address. This paper analyzes the recently studied efficient dynamic network. Essentially, this paper suggests a model that dynamically controls the RCS worm using the characteristics of Power-Law and depth distribution of the delivery node, which is commonly seen in preferential growth networks. Moreover, we suggest a model that dynamically controls the spread of the worm using information about the depth distribution of delivery. We also verified via simulation that the load for each node was minimized at an optimal depth to effectively restrain the spread of the worm.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.4C
• /
• pp.403-413
• /
• 2009

We compare three predistortion methods to prevent signal distortion and spectral re-growth due to the high PAPR (peak-to-average ratio) of OFDM signal and the non-linearity of high-power amplifiers. The three predistortion methods are pth order inverse, indirect learning architecture and look up table. The pth order inverse and indirect learning architecture methods requires less memory and has a fast convergence because these methods use a polynomial model that has a small number of coefficients. Nevertheless the convergence is fast due to the small number of coefficients and the simple computation that excludes manipulation of complex numbers by separate compensation for the magnitude and phase. The look up table method is easy to implement due to simple computation but has the disadvantage that large memory is required. Computer simulation result reveals that indirect learning architecture shows the best performance though the gain is less than 1 dB at $BER\;=\;10^{-4}$ for 64-QAM. The three predistorters are adaptive to the amplifier aging and environmental changes, and can be selected to the requirements for implementation.

• Journal of the Institute of Convergence Signal Processing
• /
• v.11 no.1
• /
• pp.80-87
• /
• 2010

The method of function synthesis is essential when we control the systems not known their characteristic, by predicting the function to satisfy a relation between input and output from the given pairs of input-output data. In general the most systems operate non-linearly, it is easy to come about problem is composed with combinations of parameter, constant, condition, and so on. Genetic programming is proposed by one of function synthesis methods. This is a search method of function tree to satisfy a relation between input and output, with appling genetic operation to function tree to convert function into tree structure. In this paper, we indicate problems of a function synthesis method by an existing genetic programming propose four type of new improved method. In other words, there are control of function tree growth, selection of local search method for early convergence, effective elimination of redundancy in function tree, and utilization of problem characteristic of object, for preventing function from complicating when the function tree is searched. In case of this improved method, we confirmed to obtain superior structure to function synthesis method by an existing genetic programming in a short period of time by means of computer simulation for the two-spirals problem.