• Journal of Broadcast Engineering
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• v.4 no.2
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• pp.134-143
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• 1999

In this paper, in order to implement the IDWT(inverse discrete wavelet transform) with relatively low complexity, we propose a VLSI architecture for odd-tap linear-phase IDWT filters. By considering the symmetric property of the linear phase filter, the input is added to the one located at symmetrical position of the filter before filtering. Then. we rearrange the delay line of the filter in a U-shaped fashion. requiring no global interconnection between the components. The proposed architecture for the IDWT filter consists of delay units. operator units, adder units. and postprocessor unit. Since each units are configured regularly and interconnected locally. the proposed architecture can accommodate arbitrary linear phase IDWTs by simply adding/removing the corresponding units. The M -level IDWT can be implemented by interconnecting the proposed architecture in a cascaded or semi-recursive form. It is expected that the proposed architecture for the IDWT can be effectively employed in the related area including MPEG-4, since the proposed architecture is less complex than the conventional architectures.

• Korean Journal of Optics and Photonics
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• v.30 no.6
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• pp.226-229
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• 2019

We investigated an interrogation system for fiber Bragg gratings by using a 50-GHz 96-channel array waveguide grating. Linearity of the sensitivity (the wavelength shift in response to the change in strain or temperature) is achieved for a Bragg grating of sufficiently wide bandwidth. The present wavelength-monitoring system could measure the change in Bragg wavelength with a resolution of 0.01 nm, at intervals of 10 seconds. When this interrogation system was used for a linear array of 12 acrylaterecoated fiber gratings, the wavelength sensitivity changed from 0.018 nm/℃ to 0.01 nm/℃ when the operating temperature changed from -25℃ to 85℃.

• Korean Journal of Optics and Photonics
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• v.5 no.4
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• pp.473-480
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• 1994

We have applied nonlinear interferometry of coherent anti-Stokes Raman spectroscopy (CARS) to measure the nonresonant third order susceptibilities of various gases. For the experiment, we placed two gas cells serially and filled the first cell with argon as a calibration standard and the second cell with gases under test. The interference fringes of the CARS signals generated in the two gas cells were obtained by changing the thickness of the phase shifting unit which was made of BK-7 glass. The total effective nonresonant susceptibilities were determined from the measured amplitudes of the interference fringes of the CARS signals of the gases. The nonresonant susceptibilities were obtained by subtracting off resonant vibrational contributions from the total effective susceptibilities. The results of this work are compared with the published data and the overall uncertainty is estimated to be less than 5%. an 5%.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.251-253
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• 2019

본 논문은 1.8kW (4.5kV, 450mA)출력의 마그네트론을 구동하기 위한 2.5kW (5kV, 0.5A) 고전압 DC 전원장치 설계에 대해 기술한다. 무선 전력 전송을 위한 위상배열 시스템에 이용되는 마그네트론의 경우 인가되는 전압의 리플 최소화는 필수적이다. 본 논문에서는 소프트 스위칭을 기반으로한 400kHz 이상의 스위칭 주파수로 컨버터를 설계함으로써 출력리플을 저감하고 필터성분을 최소화 하여 전력밀도를 높일 수 있도록 한다. 변압기의 누설인덕턴스 만을 이용하여 공진 인덕터를 구현하고 변압기의 기생 커패시터 성분과 직렬로 스택킹 된 출력 정류 다이오드의 전압 밸런싱을 위한 커패시터를 병렬 공진 커패시터로 활용한 LCC 공진형 컨버터 고밀도 설계에 대하여 기술한다. 또한, 공진전류의 Trapezoidal 해석 및 설계를 통해 도전 손실을 줄일 수 있는 LCC공진형 컨버터 기반의 마그네트론 구동전원 설계에 대하여 상세 기술하고 PSpice를 이용한 Simulation 및 실험 결과를 통하여 개발된 전원의 우수성을 검증한다.

• Korean Journal of Optics and Photonics
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• v.17 no.1
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• pp.7-17
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• 2006

In this paper, we proposed an optical true time-delay (TTD) for planar phased array antennas (PAAs), which is composed of a wavelength-dependent optical true time delay (WDOTTD) followed by a wavelength-independent optical true time delay (WIOTTD). The WDOTTD is a fiber Bragg gratings (FBGs) Prism and the WDOTTD is a fiber delay-lines matrix of which each component consists of a certain length of fiber connected to cross-ports of a 2${\times}$2 MEMS switch. A 10-GHz 2-bit${\times}$4-bit two-dimensional optical TTD has been fabricated by cascading a WDOTTD with a maximum time delay of 810 ps to a WIOTTD of $\pm$50 ps. Time delay and insertion loss for each radiation angle have been measured. Time delay error for the WIOTTD has been measured to be less than $\pm$1 ps. We have also designed a two-dimensional 10-GHz PAA composed of 8${\times}$8 microstrip patch antenna elements driven by the proposed TTD. The radiation patterns of this PAA have been obtained by simulation and analyzed.

• Applied Chemistry for Engineering
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• v.26 no.4
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• pp.495-504
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• 2015

This work investigated the characteristics of a packed-bed plasma reactor system and the performances of the plasma reactors connected in series or in parallel for the decomposition of ethylene. Before the discharge ignition, the effective capacitance of the ${\gamma}$-alumina packed-bed plasma reactor was larger than that of the reactor without any packing, but after the ignition the effective capacitance was similar to each other, regardless of the packing. The energy of electrons created by plasma depends mainly on the electric field intensity, and was not significantly affected by the gas composition in the range of 0~20% (v/v) oxygen (nitrogen : 80~100% (v/v)). Among the various reactive species generated by plasma, ground-state atomic oxygen and ozone are understood to be primarily involved in oxidation reactions, and as the electric field intensity increases, the amount of ground-state atomic oxygen relatively decreases while that of nitrogen atom increases. Even though there are many parameters affecting the performance of the plasma reactor such as a voltage, discharge power, gas flow rate and residence time, all parameters can be integrated into a single parameter, namely, specific input energy (SIE). It was experimentally confirmed that the performances of the plasma reactors connected in series or in parallel could be treated as a function of SIE alone, which simplifies the scale-up design procedure. Besides, the ethylene decomposition results can be predicted by the calculation using the rate constant expressed as a function of SIE.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.7
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• pp.435-443
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• 2017

The Characteristics of the flowfields of a square prism having a small square prism were investigated by measuring of lift and drag on the square prism and visualizing the flowfield using PIV. The experimental parameters were the width ratios(H/B=0.2~0.6) of small square prisms to the prism width and the gap ratios (G/B=0~3) between the prism and the small square prism. The drag reduction rate of the square prism initially increased and then decreased with the G/B ratio for the same H/B ratio, and increased with the H/B ratio for the same G/B ratio. The maximum drag reduction rate of 98.0% was observed at H/B=0.6 and G/B=1.0. The lift reduction rate of the square prism was not affected by the width and gap ratios; the total average value was approximately 66.5%. In case of a square prism having a small square prism, the stagnation regions were represented in the upstream and downstream sides of the square prism.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.8
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• pp.35-45
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• 1999

In this paper, the addition and the multiplicative algorithm of two polynomials over finite field $GF(p^m)$ are presented. The 4-valued arithmetic processor of the serial input-parallel output modular structure on $GF(4^3)$ to be performed the presented algorithm is implemented by current mode CMOS. This 4-valued arithmetic processor using current mode CMOS is implemented one addition/multiplication selection circuit and three operation circuits; mod(4) multiplicative operation circuit, MOD operation circuit made by two mod(4) addition operation circuits, and primitive irreducible polynomial operation circuit to be performing same operation as mod(4) multiplicative operation circuit. These operation circuits are simulated under $2{\mu}m$ CMOS standard technology, $15{\mu}A$ unit current, and 3.3V VDD voltage using PSpice. The simulation results have shown the satisfying current characteristics. The presented 4-valued arithmetic processor using current mode CMOS is simple and regular for wire routing and possesses the property of modularity. Also, it is expansible for the addition and the multiplication of two polynomials on finite field increasing the degree m and suitable for VLSI implementation.

• Journal of the Korean Geotechnical Society
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• v.32 no.1
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• pp.5-18
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• 2016

In this study, we grasped the resistance state of the back ground which had a notable influence on computing the lateral resistance of the laterally loaded pile group in the homogeneous ground by the model test. Resistance state was grasped as the depth of rotation-point, wedge failure angle, and wedge wing angle. The model experiment is performed by varying the width, spacing and number of piles and the relative density of sand in this study. According to the observation of the rear ground surface deformation of the piles in lateral load, rotation point ratio, wedge failure angle, and wedge wing angle of the front row were similar to those of the middle row; however, those of the back row were relatively smaller. The rotation point ratio, wedge failure angle and wedge wing angle of the piles in parallel were the same as those of a single pile. Based on the model test results, equations for estimation of the rotation-point, wedge failure angle, and wedge wing angle are proposed.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.5
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• pp.350-355
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• 2005

The probes of fiber optic OTDR (Optical Time Domain Reflectometry) sensor was developed to measure displacements of social infrastructures. This probe was simply constructed with two conventional optical fiber connectors, and a fiber bending part, which transforms displacement to optical loss. When the displacement was affected on the bending loss part, the reflected light intensity of one optical connector was changed. The displacement was determined from this reflected light intensity change of the connector. fiber optic OTDR displacement sensor was developed as the multiplexed type of one fiber line with 5 sensor probes. Multiplexing operation was tested by these 5 sensor probes.