• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.9B
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• pp.1518-1526
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• 2000

This paper proposes an optical transmission link design method based on an optimum compensation scheme using dispersion compensating fiber (DCF), so that high-speed long-distance optical transmission would be possible over the conventional standard single mode fiber (SMF) link. The proposed design method provides the maximized transmission distances according to the signal speeds, where the amplifier spacing and repeater spacing are optimized wit respect to self-phase modulation(SPM) due to fiber nonlinearity and amplified spontaneous emission (ASE) noises caused by optical amplifies. It is also shown that there exists an optimum input signal power range balancing the effects of ASE noise and SPM for the given amplifier spacing and repeater spacing.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.7
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• pp.748-751
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• 2013

We perform a wideband radiated pulse coupling analysis of simple building structures using the finite-deference time-domain(FDTD) method. Toward this purpose, the building structures composed of concrete and window materials are assumed and we numerically model the electrical properties of each material. In this work, we apply a dispersive FDTD algorithm for the electromagnetic analysis of building structures and investigate their shielding effectiveness in the frequency range of 50 MHz to 1 GHz.

• Journal of the Korean Society for Library and Information Science
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• v.35 no.3
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• pp.35-54
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• 2001

The Libraries are face to difficult of academic journal subscription for the increasing price of journal and the increasing number of journal. Bibliographic citation analysis is one of method of evaluating the use of a journal collection. This study is used bibliographic use and scatting of foreign academic journal in Library and Information Science found in doctorial dissertation of graduate students in Seoul city, for serve to complement another method of journal evaluation. Journal selection and cancellation may be done on the basis to dispersion of journal citation to usefulness of journal subscription in the library budget. But the library should not rely on one single evaluation technique, it should take advantage of combination technique.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.8
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• pp.1159-1163
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• 2012

In this paper, a new method is suggested to reduce the size of a wide-band array antenna. The power-divider for the feeding structure is made compact as ${\lambda}/8$ with the help of a novel Metamaterial UWB bandpass filter. This power divider is clearly different from others in that the proposed design uses microstrip structured Composite Right and Left-Handed (CRLH) filters, while others use two dielectric layers or long tapered transmission lines. In order to validate the proposed design method, the circuit and full-wave simulated results of the power divider with the Metamaterial UWB filters are compared to each other, and the Metamaterial properties of the structure are shown with the electric field at the ZOR and dispersion diagram. Furthermore, the antenna performance of the fabricated antenna with the power divider is measured and compared with the prediction. Also, the size reduction effect by the proposed scheme is addressed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.341-345
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• 2001

In this study, nano-sized powders of SiO$_2$-0∼15mo1%B$_2$O$_3$ composition were prepared by sol-gel processing method using TEOS(Tetra ethyl ortho silicate) and H$_3$BO$_3$ solution. The powders were tape-cast on High silicate glass sheet(HSG) substrate and sintered to form a layer of undercladding for the planar light wave module. During the sol-gel processing, H$_2$O/Si mole ratio were varied to modify the size of the powders in a range from 600 to 75nm. The dispersion of the powder was modified by changing the pH of the slurry. Sintering temperature of the tape was observed to decrease with the size of the powder and the B$_2$O$_3$ content in the powder. When the silica powders of 75∼125nm in diameter containing 15mo1% B$_2$O$_3$ were used, 98 TD% was obtained at 1250$^{\circ}C$, which is approximately 300$^{\circ}C$ reduction in sintering temperature compared with micrometer-sized powders.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.8 no.1
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• pp.18-27
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• 1996

Efforts are concentrated onto effective simulation of surface discharged heat water in two-dimensional depth-averaged finite element model using Gaussian puff algorithm incorporating near-field characteristics as patches computed from CORMIX3 with ambient flow variations. Concise analyses of horizontal and vertical temperature distributions are made for real coastal power plant discharges through four field observations and the results from this proposed method are in good agreements with observations in far-field as well as near-field. Thus, this method can simulate the heat dispersion effectively for the whole region since the complex jet momentum characteristics and ambient flows are easily represented in 10 meters of finite element discretization around a discharging point.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.2
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• pp.239-245
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• 2013

In this paper, we propose a time-frequency domain reflectometry (TFDR) based measurement method for localizing concentric neutrals corrosion on live underground power cable. It consists of two inductive couplers which can transmit the reference signal into live underground power cable and measure the reflected signals from the impedance discontinuities of concentric neutrals corrosion. In order to compensate the dispersion of the measured reflected signal via inductive coupler, an equalizer based on Wiener filtering is designed. To improve the localizing performance of concentric neutrals corrosion in the vicinity of the measurement point, the reference signal is removed from the measured reflected signals. The localization performance of the proposed method is verified by the concentric neutrals corrosion localization experiment.

• The Journal of Information Technology
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• v.6 no.1
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• pp.65-70
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• 2003

In this papers, we proposed the new method in order to diagnosis partial discharge type of transformers. For wavelet transform, Daubechie's filter is used,, we can obtain wavelet coefficients which is used to extract featrue of statistical parameters(maximum value, average value, dispersion, skewness, kurtosis) about high frequency current signal per 3-electrode type(needle-plane electrode, IEC electrode and Void electrode). Also, these coefficients are used to identify signal of internal partial discharge in transformer. As a result, from compare of high frequency current signal amplitude and average value, we are obtained results of IEC electrode> Void electrode> Needle-Plane electrode. Otherwise, in case of skewness and kurtosis, we are obtained results of Void electrode> IEC electrode> Needle-Plane electrode. As improved method in order to diagnosis partial discharge type of transformers, we use neural network.

• Nuclear Engineering and Technology
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• v.42 no.1
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• pp.9-16
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• 2010

Experimental examinations for evaluating fracutres were conducted by using transparent replicas of a single fracture in order to obtain the fracture data to contribute to the methodlogy on how to improve the definitaion of representative parameter values used for a parallel plate fracture model. Quantitative aperture distribution and quantitative tracer concentration data at each point in time were obtained by measuring the attenuation of transmitted light through the fracture in high spatial resolution. the representative aperture values evaluated from the multiple different measurement methods, such as arithmetic mean of aperture distribution measured by the optical method, transport aperture evaluated from the tracer test, and average aperture evaluated from the fracture void volume measurement converged to a unique value that indicates the accuracy of this experimental study. The aperture data was employed for verifying the numerical simulation under the assuption of Local Cubic Law and showed that the calculated flow rate through the fracture is 10%-100% larger than hydraulic test results. The quantitative tracer concentration data is also very valuable for validating existing numerical code for advection dispersion transport in-plane heterogeneous fractures.

• Journal of the Korean Applied Science and Technology
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• v.14 no.3
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• pp.29-38
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• 1997

Low toxic concentrated oil dispersant using n-Paraffin and Di(ethylene glycol)mono butylether mixed solvent was prepared, and tested by oil dispersant performance test method, and oil dispersant efficiency was measured using vertical shaking method to 3 kinds of Crude oil, Bunker oil and W/O emulsions with different physical properties by appling the prepared dispersant. Although toxicity test was performed with Flat fish and Rock fish by appling the mixed oils emulsified using prepared oil dispersant, couldn't find the toxicity to them. Concentrated oil dispersant prepared has a good dispersion efficiency of 97.2% after 0.5min settling time and 28.3% after 10min settling time to Bunker B oil with 10% water solution. Especially, the concentrated oil dispersant showing the low toxicity to Oryzias Latipes(24hr, TLm) was 54,000 ppm and to Brine Shrimp Artemia(24hr, TLm) was 51,000ppm, and also, it was completely biodegradated to 99.1% after $7{\sim}8$days.