• Proceedings of the KIEE Conference
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• 2009.04a
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• pp.86-88
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• 2009

This article suggests an online-based remote fault current mode discrimination method in order to identify the causes of the power line faults with various causes. For that, it refers to existing cause identification methods and categorizes modes by fault causes based on statistical techniques beforehand and performs the pre-treatment process of fault currents by each cause acquired from the fault recorder into a phase space in order to extract the characteristics of fault currents by each cause. After that, for the fault mode categorization, it discriminates modes by each cause using data by each cause as leaning data through utilizing RBF network. And then it tests the validity of the suggested method as applying it to the data of the actual fault currents acquired from the fault recorder in the electric power transmission center.

• Journal of the Semiconductor & Display Technology
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• v.3 no.2
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• pp.5-9
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• 2004

Microcircuit fabrication requires precise control of impurities in tiny regions of the silicon. These regions must be interconnected to create components and VLSI circuits. The patterns to define such regions are created by lithographic processes. In order to image features smaller than 70 nm, it is necessary to employ non-optical technology (or next generation lithography: NGL). One such NGL is extreme ultra-violet lithography (EUVL). EUVL transmits the pattern on the wafer surface after reflecting ultra-violet through mask pattern. If particles exist on the blank mask, it can't transmit the accurate pattern on the wafer and decrease the reflectivity. It is important to care the blank mask. We removed the particles on the wafer using focused ion beam (FIB). During removal, FIB beam caused damage the multi layer mask and it decreased the reflectivity. The relationship between particle removal and reflectivity is examined: i) transmission electron microscope (TEM) observation after particle removal, ii) reflectivity simulation. It is found that the image mode of FIB is more effective for particle removal than spot and bar mode.

• Structural Engineering and Mechanics
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• v.8 no.3
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• pp.243-256
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• 1999

Using appropriate transformations, the differential equation for flexural free vibration of a cantilever bar with variably distributed mass and stiffness is reduced to a Bessel's equation or an ordinary differential equation with constant coefficients by selecting suitable expressions, such as power functions and exponential functions, for the distributions of stiffness and mass. The general solutions for flexural free vibration of one-step bar with variable cross-section are derived and used to obtain the frequency equation of multi-step cantilever bars. The new exact approach is presented which combines the transfer matrix method and closed form solutions of one step bars. Two numerical examples demonstrate that the calculated natural frequencies and mode shapes of a 27-storey building and a television transmission tower are in good agreement with the corresponding experimental data. It is also shown through the numerical examples that the selected expressions are suitable for describing the distributions of stiffness and mass of typical tall buildings and high-rise structures.

• Journal of information and communication convergence engineering
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• v.2 no.3
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• pp.182-186
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• 2004

When most of existing instant messengers log on server, they transmit to sever in encoding password to RC5. but RC5 don't be secured because it has been known many of password cracking tools. Also, messengers don't have any protection on the transmitted information with communicating two hosts since loging on, endangering the privacy of the user. As a counter measure, messengers need to provide security service including message encryption. In this paper, we designed a key exchange method of password representing fast, effective and high security degree, using ECC(Elliptic Curve Cryptography) that being known the very stronger than another public key cryptography with same key size. To effectively improve data transmission and its security using IPSec protocol between users, tunnel mode is introduced. Tunnel mode transmits Host-to-Host data through virtual pipelines on the Internet.

• Journal of KIISE:Information Networking
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• v.31 no.6
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• pp.595-607
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• 2004

Networks often evolve to provide a host with multiple access points to the Internet. In this paper, we propose a transport layer load distribution mechanism utilizing the multiple network interfaces simultaneously. We specifically propose an extension of Stream Control Transmission Protoco1 (SCTP) to have load sharing over multiple network interfaces. We named the particular service provided by the Proposed load sharing mechanism to be LS (Load Sharing) mode service. LS mode service is based on the following four key elements: (i) the separation of flow control and congestion control, (ii) congestion window based striping, (iii) redundant packet retransmission for fast packet loss recovery, (iv) a novel mechanism to keep track of the receiver window size with the SACKS even if they arrive out-of-order. Through simulations, it is shown that the proposed LS mode service can aggregate the bandwidth of multiple paths almost ideally despite of the disparity in their bandwidth. When a path with a delay of 100% greater is utilized as the second path, the throughput is enhanced about 20%.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.9A
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• pp.892-899
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• 2006

In this paper, we propose an automatic switching technology between the ad-hoc and the infrastructure modes without user intervention in the IEEE 802.11b wireless LAN. Also, we design our proposed technology and implemented on the Linux machine. For this operation, the area within an Access Point (AP) coverage is defined as a switching area, and a node without any transmission in this area is assumed to be able to relay frames between the AP and nodes in the shaded area that is outside the coverage and cannot reach the AP. By using the proposed technology, it is possible to provide the seamless Internet access service to nodes at the ad-hoc mode in the shaded area. In this paper, we explains the operation of the detection method of the switching area, presents the flowchart and implementation environment. To prove the operation of our technology, we obtain the results of captured packets transmitted between nodes and throughput results through ftp transmission experiment. Hence, we can see that our proposed scheme can be improve the wireless access service in wireless and mobile networks.

• The Journal of the Korea Contents Association
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• v.6 no.3
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• pp.38-45
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• 2006

A dual-level low voltage differential signalling (DLVDS) circuit is proposed aiming at reducing transmission lines for a LCD driver IC. We apply two data to the proposed DLVDS circuit as inputs. Then, the transmitter converts two inputs to two kinds of fully differential signals. In this circuit, two transmission lines are sufficient to transfer two inputs while keeping the LVDS feature. However, the circuit has a common mode bias fluctuation due to difference of the input bias and the reference bias. We compensate the common mode bias fluctuation using a feedback circuit of the current source bias. The receiver recovers the original input data through a level decoding circuit. We fabricated the proposed circuit using $0.25{\mu}m$ CMOS technology. The simulation results of proposed circuit shows 1-Gbps/2-line data rate and 35mW power consumption at 2.5V supply voltage, respectively.

• Journal of Advanced Navigation Technology
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• v.12 no.4
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• pp.311-316
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• 2008

A configuration scheme of optical link effectively compensating chromatic dispersion and nonlinear effects accumulated in optical link with single mode fibers (SMFs) is proposed. The proposed optical link configuration consist of optical phase conjugator (OPC) placed at middle of total transmission length and inline dispersion management (DM) as a role of compensating cumulated in each optical repeater of SMF by dispersion compensating fiber (DCF). Net residual dispersion (NRD) of this optical link is designed to be controlled through precompensation and postcompensating. The precompensation and postcompensation are designed to be determined by DCF after transmitter and before receiver, respectively. It is confirmed that optical link configuration with symmetric dispersion map with respect to OPC, which is implemented by controlling NRD through both precompensation and postcompensation, is better to be effective and adaptive than other configuration with NRD controlled by only precompensation or postcompensation.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.5
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• pp.19-26
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• 2021

This report proposes a waveguide spatial combiner with high power low loss. The proposed spatial combiner implements high power by combining from the center of each port through a waveguide. In particular, we implement low loss using TE01 mode, which has the lowest transmission track loss among modes of circular waveguide, and miniaturization is achieved by applying a new mode conversion method. IIn addition, it was confirmed that it was suitable for high output by calculating the insulation breakdown voltage of the new mode conversion structure through E-field analysis. The final 8-way waveguide spatial combiner was designed and manufactured, and the insertion loss was less than 0.4dB and the combining efficiency was 97% or more, confirming that the electrical performance was very good compared to the planar combining method.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.30 no.2
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• pp.11-19
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• 2016

By incorporating a polarization-diversity loop configuration, we have demonstrated the inline switching of transmission and reflection spectra of one of two short-period fiber gratings (SPFGs) with different resonance wavelengths without reconfiguring the filter structure. The proposed filtering apparatus consists of a fiber-pigtailed polarization beam splitter, two SPFGs, and three quarter-wave plates (QWPs). The proposed filter can independently choose the transmission or reflection spectrum of each SPFG through the appropriate adjustment of the orientation angles of the QWPs within the filter without additional optical switches and couplers. The average insertion loss, band rejection ratio, and side-mode suppression ratio of the fabricated filter were measured as ~4.59, ~17.88, and ~19.67dB, respectively.