• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.05a
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• pp.633-635
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• 2018

The compensation characteristics of the distorted WDM channels compensated for by dispersion management (DM) and optical phase conjugation in the long-haul (50 fiber spans ${\times}$ 80 km) transmission link with the randomly distributed single mode fiber (SMF) length and residual dispersion per spans (RDPS) are investigated as a function of the arrangement of SMF and dispersion compensating fiber (DCF) and the control position of net residual dispersion (NRD).

• Journal of information and communication convergence engineering
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• v.13 no.3
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• pp.167-171
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• 2015

A radio over fiber (RoF) system is a kind of analog optical transmission system and considered as a strong candidate for the next-generation fronthaul link in the future mobile network. In RoF systems, nonlinearity compensation is essential to increase the link capacity. In this paper, we propose a nonlinearity detection and compensation scheme using a monitoring channel in RoF systems. A monitoring channel is added at the transmitter site and used for transmitting a reference signal in an RoF transmission. The nonlinearity in the RoF transmission is detected by comparing the received monitoring signal and the original reference signal at the receiver site. Finally, the nonlinearity is compensated at the receiver by giving the reverse function of the detected nonlinearity. Our results show that the proposed scheme can almost remove the error vector magnitude degradation induced by the nonlinearity in the RoF system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.563-565
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• 2011

In this paper, the implementation consideration of communication system is suggested in IEEE 802.15.4a based wireless sensor network, and the practical issues for UWB ranging system design are investigated. First, design of UWB signals for ranging applications is considered, and selection of various signal parameters is studied. Then, link analysis is performed in order to determine UWB signal quality as a function of distance.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.487-488
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• 2008

SiOC films containing alkyl groups have a low dielectric constant because of the interaction between the C-H hydrogen bonds and the oxygen of high electro-negative atom. The Si-$CH_3$ in a void is broken by the $O_2$, therefore the strength of CH bond in Si-O-O-$CH_3$ bond increases. The Si-O-O-$CH_3$ bond is broken by nucleophilic attack due to Si atom, again. The elongation of C-H bond causes the red shift, and the compression of C-H bond causes the blue shift. Among these chemical shifts, the blue shift from $1000\;cm^{-1}$ to $1250\;cm^{-1}$ was related with the formation of pores. If the oxygen is deficient condition, the methylradicals of the electron-rich substitution group terminate easily the Si-O-Si cross-link, and the pore is originated from the cross-link breakdown due to much methyl radicals of Si-$CH_3$. The dielectric constant of the films decreases due to pore generation.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.349-350
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• 2008

Average throughput estimation of EV-DO forward link is implemented on the basis of the serving coverage area per sector instead of time consuming and complicated Monte Carlo simulation. For the implementation of this analysis function in cell planning tool, $CellTREK^{(R)}$, developed by KT, both SNR vs. DRC mapping table and receiver sensitivity are suggested as the satisfying criteria to be satisfied above each threshold level simultaneously.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.77.6-77
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• 2002

This paper describes a motored wheelchair that is suitable for disabled persons. A distinguish feature of our wheelchair is that a closed link mechanism is introduced. This link module changes conventional motored wheelchairs to computer controlled ones. It means that using intelligent functions of the computer, conventional motored wheelchairs can be navigated like an intelligent robot. Three examples of intelligent navigation functions are demonstrated. The first one is a motored wheelchair controlled by the head movement of the operator. The second one is a motored wheelchair with the image processing. Last one is a motored wheelchair with the remote sensing function.

• Journal of Power System Engineering
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• v.5 no.2
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• pp.79-86
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• 2001

A method is presented for generating the path which significantly reduces residual vibration of the redundant, flexible robot manipulator in the presence of obstacles. The desired path is optimally designed so that the system completes the required move with minimum residual vibration, avoiding obstacles. The dynamic model and optimal path are effectively formulated and computed by using special moving coordinate, called VLCS, to represent the link flexibility. The path to be designed is developed by a combined Fourier series and polynomial function to satisfy both the convergence and boundary condition matching problems. The concept of correlation coefficients is used to select the minimum number of design variables. A planar three-link manipualtor is used to evaluate this method. Results show that residual vibration can be drastically reduced by selecting an appropriate path, in the presence of obstacles.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10b
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• pp.890-895
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• 1990

A theoretical and experimental study of a single link flexible arm a tip mass is presented for the translational end-point positioning. The problem of shifting the end-point from its initial position to the commanded position by the amount of W $_{d}$ is considered for the open loop control such that the base follows up the given path function. The theoretical results are obtained by applying the method of the Laplace transform to the governing equation, and the solution is calculated by the method of numerical inversion. Experimental results are obtained and compared with the theoretical ones.s.

• Journal of information and communication convergence engineering
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• v.7 no.3
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• pp.372-376
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• 2009

In this paper, new and simple optical transmission link with fixed dispersion management (DM) scheme, i.e., pre(post) compensation and residual dispersion per span (RDPS) are fixed to net residual dispersion (NRD) = 0 ps/nm, and optical phase conjugator (OPC) having optimal position depending on launch power in WDM transmission system is proposed. Also, effective launch power range of WDM channels resulting 1 dB eye opening penalty (EOP) is induced as a function of OPC position. First, it is confirmed that, for applying DM into WDM transmission link fixed pre(post)compensation and RDPS, which are independence on exact system parameters except launch power, sufficiently are used in WDM links, but OPC with optimal position is needed for effective compensating impairments of WDM channels. And, it is confirmed that effective launch power is broader in case of RDPS = 100 ps/nm than in RDPS = 50 ps/nm. But, it is shown that the best OPC position offset is -0.6 km from a point of view of power window, which is defined as difference between maximum and minimum effective launch power.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.511-515
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• 2003

This paper presents a novel prototype of the utility-interfaced sinusoidal pulse width modulated (SPWM) inverter using the high-frequency flyback transformer fur the small-scale solar photo-voltaic power conditioner (1kW - 4kW). The proposed SPWM power conditioner circuit with a high-frequency link has a function of electrical isolation, which is vital fur solar photovoltaic power conditioner systems with the viewpoint of safety and convenience. The discontinuous conduction mode (DCM) operation of the flyback transformer is also maintained to simplify the topology of the inverter circuit and control scheme. First, the operating principle of the proposed circuit is described far the understanding of the circuit parameters establishment. Then, the digitally constructed SPWM control scheme is presented. The proposed circuit is verified by the computer simulation and the prototype experiment.