• Journal of Broadcast Engineering
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• v.25 no.4
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• pp.497-506
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• 2020

A chameleonic surface proposed in this study was a pin-art and 3D display device for generating arbitrary shapes. A smooth and continuous surface was formed using slim telescopic actuators and high-elasticity composite material. Realistic 3D shapes were continuously generated by projecting dynamic mapping images on the surface. A slim telescopic actuator was designed to show long strokes and minimize area for staking. A 3D shape was formed by thrusting and extruding the high-elasticity material using multiple telescopic actuators. This structure was advantageous for generating arbitrary continuous surface, projecting dynamic images and lightening weight. Because of real-time synchronization, a distributed controller based on EtherCAT was applied to operate hundreds of telescopic actuators smoothly. Integrated operating software consecutively generated realistic scenes by coordinating extruded shapes and projecting 3D image from multiple projectors. An opera content was optimized for the chameleon surface and showed to an audience in an actual concert.

• Smart Media Journal
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• v.4 no.4
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• pp.24-32
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• 2015

Recently, SDN is actively used as datacenter networks and gradually increase its applied areas. Along with this change of networking environment, research of deploying network security systems on SDN becomes highlighted. Especially, systems for detecting network flooding attacks by monitoring every packets through ports of OpenFlow switches have been proposed. However, because of the centralized management of a SDN controller which manage multiple switches, it may be substantial overhead that the attack detection system continuously monitors all the flows. In this paper, a sampling based network flooding attack detection and prevention system is proposed to reduce the overhead of monitoring packets and to achieve reasonable functionality of attack detection and prevention. The proposed system periodically takes sample packets of network flows with the given sampling conditions, analyzes the sampled packets to detect network flooding attacks, and block the attack flows actively by managing the flow entries in OpenFlow switches. As network traffic sampler, sFlow agent is used, and snort, an opensource IDS, is used to detect network flooding attack from the sampled packets. For active prevention of the detected attacks, an OpenDaylight application is developed and applied. The proposed system is evaluated on the local testbed composed with multiple OVSes (Open Virtual Switch), and the performance and overhead of the proposed system under various sampling condition is analyzed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.9
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• pp.7-13
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• 2019

Unlike a typical video wall system, video wall systems used for integrated monitoring in smart city environments should be able to display various videos, images, and texts simultaneously. In this paper, we propose an Internet Protocol (IP)-based video wall system that has no limit on the number of videos that can be monitored simultaneously, and that can arrange the monitor screen layout without restrictions. The proposed system is composed of multiple display servers, a wall controller, and video source providers, and they communicate with each other through an IP network. Since the display server receives and decodes the video stream directly from the video source devices, and displays it on the attached monitor screens, more videos can be simultaneously displayed on the entire video wall. When one video is displayed over several screens attached to multiple display servers, only one display server receives the video stream and transmits it to the other display servers by using IP multicast communications, thereby reducing the network load and synchronizing the video frames. Experiments show that as the number of videos increases, a system consisting of more display servers shows better decoding and rendering performance, and there is no performance degradation, even if the display server continues to be expanded.

• The Journal of the Acoustical Society of Korea
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• v.16 no.4
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• pp.11-20
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• 1997

The passive noise control techniques used until now cancel the noise in terms of the characteristics of materials, which increase the mass and the dimension and have a limit that is effective only to attenuate the high frequency components of the noise. But the active noise control techniques developed in recent years have merits that they decrease the mass and the dimension and are effective to attenuating the low frequency noises. In this paper, the real-time active noise control system attenuating the engine booming noise in a car using the digital signal processing(DSP) techniques in terms of the principle of active noise control. The multiple-error filtered-x LMS(Least-Mean Square) algorithm is used as the adaptive algorithm for active noise control and is implemented using the DSP processor Motorola DSP56001 as a controller. According to the result that the experiments are performed for the engine as the RPM changes in a car, the noise attenuating performances are achieved in an overall car interior and is verified to be 20 dB higher for pure-tone and globally, 15 dB.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.7B
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• pp.440-449
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• 2005

This paper proposes the measurement scheme for network overload and the control technique in case of breaking several control channels when we support the call services of DAMA through communication satellite(GEO, Geostationary Earth Orbit). And its performance is analyzed. The proposed schemes measure the overload of access control channel of a network controller to control the call connections, detect the level of network overload, notify the terminals of DAMA network of the state, and excute overload control. As a result, it improves the system performance and the network stability at overload state. Moreover hysteresis is applied to the change of overload state for the restriction of the frequent state shifts. The results show that the proposed algorithm prevents excessive increment of call-setup delay and too much lowering of call success rate, and improves the network stability.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.5
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• pp.85-91
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• 2003

TLCD is a good alternative to TMD for control of structures because of its cost efficiency, ease of installation, little maintenance requirement, potential for multiple usage, and ease of re-tuning. In this study, the control performances of TMD and TLCD are evaluated and compared for seismically excited structures. Results show that TLCD is more effective than TMD for interstory drift control while TLCD is as effective as TMD for acceleration control. In special. it is shown that interstory drifts are maximally controlled in lower floors and accelerations are reduced most in upper floors. This indicates that TLCD is an effective controller for earthquake-induced structures in terms of structural safety as well as serviceability.

• Smart Structures and Systems
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• v.25 no.2
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• pp.155-167
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• 2020

This paper demonstrates a real-time hybrid substructuring (RTHS) shake table test to evaluate the seismic performance of a base isolated building. Since RTHS involves a feedback loop in the test implementation, the frequency dependent magnitude and inherent time delay of the actuator dynamics can introduce inaccuracy and instability. The paper presents a robust stability and performance analysis method for the RTHS test. The robust stability method involves casting the actuator dynamics as a multiplicative uncertainty and applying the small gain theorem to derive the sufficient conditions for robust stability and performance. The attractive feature of this robust stability and performance analysis method is that it accommodates linearized modeled or measured frequency response functions for both the physical substructure and actuator dynamics. Significant experimental research has been conducted on base isolators and dampers toward developing high fidelity numerical models. Shake table testing, where the building superstructure is tested while the isolation layer is numerically modeled, can allow for a range of isolation strategies to be examined for a single shake table experiment. Further, recent concerns in base isolation for long period, long duration earthquakes necessitate adding damping at the isolation layer, which can allow higher frequency energy to be transmitted into the superstructure and can result in damage to structural and nonstructural components that can be difficult to numerically model and accurately predict. As such, physical testing of the superstructure while numerically modeling the isolation layer may be desired. The RTHS approach has been previously proposed for base isolated buildings, however, to date it has not been conducted on a base isolated structure isolated at the ground level and where the isolation layer itself is numerically simulated. This configuration provides multiple challenges in the RTHS stability associated with higher physical substructure frequencies and a low numerical to physical mass ratio. This paper demonstrates a base isolated RTHS test and the robust stability and performance analysis necessary to ensure the stability and accuracy. The tests consist of a scaled idealized 4-story superstructure building model placed directly onto a shake table and the isolation layer simulated in MATLAB/Simulink using a dSpace real-time controller.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.7
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• pp.943-949
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• 2013

Recently, an electric vehicle (EV) has been become a huge issue in the automotive industry. The EV has many electrical units: electric motors, batteries, converters, etc. The DC distribution power system (DPS) is essential for the EV. The DC DPS offers many advantages. However, multiple loads in the DC DPS may affect the severe instability on the DC bus voltage. Therefore, a voltage bus conditioner (VBC) may use the DC DPS. The VBC is used to mitigate the voltage transient on the bus. Thus, a suitable control technique should be selected for the VBC. In this research, Current controller with fixed switching frequency is designed and applied for the VBC. The DC DPS consist of both a resistor load and a boost converter load. The load variations cause the instability of the DC DPS. This instability is mitigated by the VBC. The simulation results by Matlab simulink and experimental results are presented for validating the proposed VBC and designed control technique.

• Journal of Korea Multimedia Society
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• v.20 no.3
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• pp.511-519
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• 2017

This Paper introduces the design and communication method between PLC (Programmable Logic Controller) and Arduino based on MODBUS Protocol. MODBUS connection can be established in a new or existing system very easily, therefore we used this protocol in our proposed system. In the field of automatic devices, multi-function serial port such as RS232, RS422, RS485, and so on creates a great convenience to the developer. This proposed system used RS485 as a key mediator for data exchanging on a connected network. We also believe that it will reduce the development cost in various automated industry because this system can be reused or can be implemented any such PLC installed machines. RS485 is used as a communication interface between PLC (as a slave) and Arduino (as a master), through which a reliable network is created for safe and fast communication. Furthermore, RS485 allows multiple devices(up to 32) to communicate at half duplex on a single pair of wires and provides a long connectivity area (up to 1200 meters) as compare to other device, which makes it a user-friendly for various devices in the automated industry. Moreover, Arduino can play as a mediator by connecting third party device and setup a communication network with PLC.

• Journal of Advanced Navigation Technology
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• v.18 no.2
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• pp.128-133
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• 2014

This paper is the study of BNWAS based on TLC. The functionality of BNWAS and its operations are investigated through its international standard. But the BNWAS to be used currently in the ship have difficulty in monitoring. Several kinds of data are generated from many equipments in BNWAS, such as NMEA-0183 data or NMEA-2000. Although these data are mainly used for the safe navigation of ship, their usability may be enhanced if they are managed to control the BNWAS equipment with sensors. The purpose of this system is prevent the marine accidents on sailing voyages due to drowsiness of watchers. On Night sailing, watcher is collected the navigation information from multiple devices and he determines the safe operation of the ship through continuous monitoring.