• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.5
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• pp.1240-1255
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• 1996

This paper suggests power optimization technique in multi-level SCPC system as a method for efficient utilization of limited satellite power. The power optimization is realized by optimal assignment of satellite input carrier powers considering interference and noise generated in up-link and down-link. The Fletcher-Powell algorithm searching minimum(or maximum) point using gradient information is used to detemine the optimal input carrier powers. To apply Flectcher-Powell algorithm mathematical descriptions and their partial derivatives to interference and nose are presented. Because a target, which should be optimized, is satellite input carrier power, amplitude of each carrier group will be assumed to be an independent variable. The performance criterion for optimal power assignmentis classified into 4 categories with respect to CNR of destination receiver earth station to meet the requirement for various satellite link environment. Simulation results for two-level, four-level and six-level SCPC system are presented.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.511-516
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• 2000

In order to not only perform as a extreme model under the severe operating condition but also acquire more diverse and advanced control capability utilizing high compliance, active vibration control of a flexible 2-link robot manipulator are investigated. Multi variable-structured frequency shaped optimal sliding mode is proposed for the flexible robot manipulator like control system, whose control variables, an angular motion of joint and vibration of flexible link, have to be controlled simultaneously by one control torque at a driving joint. The control system is divided into two subsystems, a control input related subsystem and an added subsystem. The proposed sliding mode, composed of multi control variables, makes optimized relation between subsystems and a individual control input, thus, the sliding mode controller can compensate whole dynamics of each subsystems simultaneously. And the possibility and effectiveness are verified by vibration control of a manipulator having two flexible links. Simulation and experiment results show that the proposed control scheme achieves the purpose effectively.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.5
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• pp.422-428
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• 2013

Recently, we use a static synchronous compensator(STATCOM) with cascaded H-bride topologies, because it is easy to increase capacity and to reduce total harmonic distortion(THD). When we use equipment for reactive power compensation, dc-link voltage unbalances occur from several reasons although loads are balanced. In the past, switching pattern change of single phase inverter and reference voltage magnitude change of inverter equipped with power sensor have been used for dc-link voltage balance. But previous methods are more complicated and expensive because of additional component costs. Therefore, this paper explains reasons of dc-link voltage unbalance and proposes solution. This solution is complex method that is composed of reference voltage magnitude change of inverter without additional hardware and shifted phase angle of inverter reference voltages change. It proves possibility through 1000[KVA] system simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.8B
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• pp.674-682
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• 2003

This paper presents the studies on wireless channel modeling and reverse link synchronization of CATV. This paper analyzes multi-path fading channel to the cause of signal distortion in the wireless communication environment. We represent the microwave link characteristics according to the channel model. Multi-path channel can affect fading.

• Journal of information and communication convergence engineering
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• v.14 no.1
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• pp.21-25
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• 2016

N-screen is a promising technology to improve support for multimedia multicasting, content sharing, content mobility, media scalability, and seamless mobility. In this paper, the WiMedia distributed-MAC (D-MAC) protocol is adopted for development of a seamless N-screen wireless service. Furthermore, to provide a multi-hop, one source multi-use N-screen service through point to point streaming in a seamless D-MAC protocol, a dynamic multi-frame transmission technology is proposed. In this technology, a dynamic time slot allocation scheme and a multi-hop resource reservation scheme are combined. In the proposed dynamic time slot allocation scheme, two thresholds, a hard threshold and a soft threshold, are included to satisfy the power consumption and delay requirements. A multi-frame DRP reservation scheme is proposed to minimize end-to-end delay during the multi-hop transmissions between N-screen devices. The proposed dynamic multi-frame transmission scheme enhances N-screen performance in terms of the multi-hop link establishment success rate and link establishment time compared to the conventional WiMedia D-MAC system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.171-172
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• 2008

• Journal of IKEEE
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• v.14 no.4
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• pp.312-316
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• 2010

We describe in this paper how to facilitate ad hoc routing with a particle filter in a hostile radio environment for multi-hop wireless ad hoc networks that connect multi-robots. The proposed scheme increases a connection's throughput by exploiting alternative links without going through the procedure of route discovery when link failure happens among multi-robots' networking. The scheme is implemented by using a particle filter to find strongly connected nodes. The filter estimates the probability distribution function in a sample-based manner with N particles. The particles are associated with a weight which represents the probability of the corresponding node to be the node with the best link. At every step of the estimation, the weights of particles are calculated and particles are resampled based on the weights. Since a node with the strongest link status possesses the largest number of particles, we take this node to forward the packets.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.11
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• pp.955-965
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• 2013

The joint tactical information distribution system (JTIDS) is used as the communication terminal of Link-16 by the United States armed forces, north atlantic treaty organization (NATO), and other allied forces. A portion of Link-16 frequencies may be shortly remapped to other systems owing to the growing demand for frequencies, especially in civil aviation, which is witnessing a constant increase in air traffic. This will affect the performance of Link-16. Therefore, in this paper, we analyze the effect of frequency band reduction on the performance of Link-16 waveform under partial-band noise jamming with Nakagami fading, via simulation and numerical analysis. The multi-net and anti-jamming performance of Link-16 with frequency remapping is compared with that of conventional Link-16 systems. The results show that the performance of Link-16 waveform is degraded with the reduction in frequencies. Nonetheless, Link-16 retains its jam resistance, and it can support multiple users in the same time slots.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.4
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• pp.166-173
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• 2013

An aluminum suspension corner module is widely used in high class passenger cars to reduce vehicle weight and improve fuel economy. According to the change of material and suspension type, the evaluation of the static strength and failure mode of the corner module is important. In this study, static strength and failure mode analysis of aluminium multi-link suspension corner module is presented. Static strength test system is designed and static failure mode tests of the corner module are carried out in longitudinal, lateral, and vertical direction. From the resuls of the tests we found that the failure modes are different compare to those of the steel corner module. The static failure modes and load-displacement curves of this study will be used as a guidance in design of a passenger car aluminium multi-link suspension corner module.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.10
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• pp.2691-2695
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• 2009

Nowadays Fiber optical communication systems have limitless bandwidth and can be used for transmitting various multimedia data with in real time. It is necessary to construct integrated service systems that can be used in our society whole to communicate multimedia data such as text, image, audio and video data in fiber optic communication systems. In this paper, we have designed and constructed the fiber optical link application system for multi-video/audio data transmission using only one core optical cable upgrading previous fiber optical communication systems based on WDM (Wavelength Division Multiplexer). Using the proposed fiber optical link application system enables us to managing fiber optical communication systems with only one core optical cable using WDM (Wavelength Division Multiplexer) and DEWDM/Wavelength splitter.