• 소성∙가공
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• 제16권7호
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• pp.502-508
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• 2007

Effect of the process parameters of the cogging process on the void crushing has been studied in order to identify the most effective factor. The process parameters considered in this study are die width ratio, reduction ratio and pre-cooling time before cogging process. Void crushing analysis with the selected process parameters was carried out using FE analysis. The results of FE analysis were evaluated by Taguchi method. It was found that the efficiency of void crushing increases with an increase in the values of all selected process parameters and the principal factor controlling the void crushing was identified as the reduction ratio.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1503_1504
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• 2009

MEMS 구조물은 ${\mu}m$단위의 크기로 만들어지므로 각속도계와 같이 정밀한 센서를 만들 때에는 노이즈 문제를 해결하지 않으면 신호를 측정할 수가 없다. MEMS 구조물의 미세한 진동에 의해 발생되는 수 pico-coulomb의 전하를 측정해야하므로 구동 신호가 검출 전극에서 Feed-through되어 나타나는 경우 그 크기가 구동에 의한 신호보다 100배 이상 크기 때문에 원하는 신호를 검출할 수 없다. 본 논문에서는 이러한 Feed-through 현상에 의한 노이즈를 줄이기 위하여 Guard-ring을 이용한 blocking 방법과 dummy port를 이용한 canceling 방법을 고안하고 Feed-through reduction 회로를 설계, 제작, 실험하여 그 효과를 확인하였다. 그 결과 구동신호가 6Vpp, 30kHz일 때, -53.186dBm이었던 Feed-through 신호가 -77.107dBm으로 줄어드는 것을 확인하였다. 또한 노이즈를 제거하지 않은 경우 측정할 수 없었던 Q-factor를 Feed-through reduction 회로를 사용하여 측정한 결과 진공 패키징된 Si 기반 자이로스코프가 공진주파수 약 7.018kHz에서 Q-factor가 약 2500임을 확인하였다.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 1998년도 추계학술대회 논문집
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• pp.122-125
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• 1998

In this article, a reduction method for nominal variables is presented and its use illustrated. Factor analysis model (FAM) generally enables us to reduce variables having interval or ratio scale based on their correlation coefficients. We developed an extensive method that makes FAM applicative to the case of nominal variables which does not give correlation coefficients, but only the degree of association. Cramer's V coefficient is a well-established measure that provides the strength of association for nominal variables with a range of [0,1]. When Cramer's V coefficient can logically substitute for correlation coefficient, FAM would be extensively used for reduction of nominal variables.

• ETRI Journal
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• 제28권4호
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• pp.529-532
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• 2006

This letter describes a compact printed helical resonator and its application to a microwave oscillator circuit implemented in coplanar waveguide (CPW) technology. The high quality (Q)-factor and spurious-free characteristic of the resonator contribute to the phase noise reduction and the harmonic suppression of the resulting oscillator circuit, respectively. The designed resonator showed a loaded Q-factor of 180 in a chip area of only 40% of the corresponding miniaturized hairpin resonator without any spurious resonances. The fully planar oscillator incorporated with this resonator showed an additional phase noise reduction of 10.5 dB at a 1 MHz offset and a second harmonic suppression enhancement of 6 dB when compared to those of a conventional CPW oscillator without the planar helical resonator structure.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.125-126
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• 2009

유효보폭 모델은 횡하중하의 포스트 텐션(PT) 플랫 플레이트 골조 해석에 사용된다. PT 플랫 플레이트의 정확한 해석을 위해서 슬래브의 강성감소는 정확하게 평가되어야 한다. 이 목적을 위하여 본 연구는 기존 연구자들의 PT 플랫 플레이트 실험체를 수집하였으며. 반복적인 작업으로 실험체 강성에 수렴하는 유효보폭모델의 강성을 찾기 위하여 슬래브 폭을 감소시켰다. 이러한 데이터를 수집하여 비선형 회귀분석을 통하여 PT 플랫 플레이트의 강성 감소 계수식을 제안하였다.

• 한국산학기술학회논문지
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• 제8권4호
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• pp.848-852
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• 2007

널말뚝의 관입속도 예측을 위한 해석수단 중 많은 경우에 얕은 근입깊이에 대해서 관입속도를 지나치게 크게 평가하기 때문에 해석법의 신뢰성을 떨어뜨리는 요인으로 작용한다. 본 연구에서는 이러한 해석상의 단점을 보완하고자 널말뚝의 휨진동모델을 정립하고 휨진동에 의해 발생하는 에너지 손실량을 평가하였다. 또한 휨진동에 의한 에너지손실에 따른 진동타입력의 감소를 하중감소계수를 써서 반영하고자 하였다.

• Membrane and Water Treatment
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• 제10권1호
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• pp.39-44
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• 2019

LID facilities do not consider environmental factors, and due to inappropriate vegetation planting causing degradation in efficiency due to plant damage and difficulty in maintenance. Therefore, in this study, assessment of impact environmental factor by seasonal variation of chlorophyll and growth of vegetation planted in LID technologies and change of pollutant reduction were conducted. In the case of B-SJ and B-RI, growth rate decreased after summer (August), and B-MG showed steady growth until autumn (September). Chlorophyll was found to increase during spring season while it decreased during autumn season. The chlorophyll concentration was found to affect the plant growth pattern. TN reduction efficiency was highest with greater than 80% efficiency in summer, and it was analyzed that plants were identified as the main factor affecting the seasonal reduction efficiency of TN. Also, temperature and relative humidity were analyzed to affect plant growth, activity and pollutant removal efficiency. Plant type and growth pattern are considered as factors to be considered in selection of appropriate plant types in LID technologies.

• ETRI Journal
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• 제44권3호
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• pp.379-388
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• 2022

This study proposes a novel low-complexity algorithm for computing inverse fast Fourier transform (IFFT)/fast Fourier transform (FFT) operations in binary phase shift keying-modulated orthogonal frequency division multiplexing (OFDM) communication systems without requiring any twiddle factor multiplications. The peak-to-average power ratio (PAPR) reduction capacity of an efficient PAPR reduction technique, that is, H-SLM method, is evaluated using the proposed IFFT algorithm without any complex multiplications, and the impact of oversampling factor for the accurate calculation of PAPR is analyzed. The power spectral density of an OFDM signal generated using the proposed multiplierless IFFT algorithm is also examined. Moreover, the bit-error-rate performance of the H-SLM technique with the proposed IFFT/FFT algorithm is compared with the classical methods. Simulation results show that the proposed IFFT/FFT algorithm used in the H-SLM method requires no complex multiplications, thereby minimizing power consumption as well as the area of IFFT/FFT processors used in OFDM communication systems.

• 조명전기설비학회논문지
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• 제24권12호
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• pp.100-108
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• 2010

A low voltage wire should be used considering that a load used in the end is a low voltage. In regard to these wires, there are needs for research about the wire thickness calculation in accordance with IEC standard because the standardization process for IEC (KS standard) was completed on June 30, 2005, and they stopped producing NEC-standard products by the order from Korean Agency for Technology and Standards under Ministry of Knowledge Economy (former Ministry of Commerce, Industry and Energy) since July 1, 2006. This study compared, in terms of the thickness calculation of low voltage wire, a reduction factor application by IEC standard about allowed current and an application for calculation of voltage drop. It also proposed the formula for IEC standard to decrease errors and resolve the difficulty of standardized calculation by analyzing the difference between simplified formula and standardized formula that are the most frequently used calculation method of voltage drop.

• Earthquakes and Structures
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• 제8권5호
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• pp.1091-1111
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• 2015

Base isolation is an effective method for protecting structures against earthquake hazard. It elongates the period of vibration and introduces supplemental damping to the structural system. The stiffness, damping and displacement are coupled forcing the code seismic design procedure to be unnecessarily complicated. In addition, the force reduction factor -a key parameter in the design procedurehas not been well addressed by seismic design codes at the high levels of damping due to the pronounced difference between pseudo and actual accelerations. In this study, a comparison has been conducted to evaluate eight different methods, in the literature, for calculating the force reduction factor due to damping. Accordingly, a simplified seismic analysis procedure has been proposed based on the well documented N2 method. Comprehensive analysis has been performed for base-isolated structure models for direct application and verification of the proposed procedure. The results have been compared with those of the European code EC8, the nonlinear time history analysis and investigations in the literature, where good agreement has been reported. In addition, a discussion has been elaborated for the resulted response of the base-isolated structure models with respect to the dynamic characteristics of the base isolation system.