• 대한수학회보
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• 제52권1호
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• pp.125-135
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• 2015

Let R be a commutative ring and U an R-module. The aim of this paper is to study the duality between U-reflexive (pre)envelopes and U-reflexive (pre)covers of R-modules.

• 대한수학회보
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• 제50권2호
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• pp.459-467
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• 2013

In this paper, Matlis injective modules are introduced and studied. It is shown that every R-module has a (special) Matlis injective preenvelope over any ring R and every right R-module has a Matlis injective envelope when R is a right Noetherian ring. Moreover, it is shown that every right R-module has an ${\mathcal{F}}^{{\perp}1}$-envelope when R is a right Noetherian ring and $\mathcal{F}$ is a class of injective right R-modules.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1996년도 영남지부 학술발표회 논문집 Acoustic Society of Korean Youngnam Chapter Symposium Proceedings
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• pp.70-75
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• 1996

In this paper, the pre-precessing method for the recognition of single vowels by use of spectrum envelope is presented , we use new method of an extrating spectrum envelope using the diffusion filter bank. We reduced the total processing time, and got higher enhancement of discrimination . By getting 88.3% of average recognition rate for single vowels of real voice through computer simulation, we confirmed it to be useful for speech recongition which use spectrum analysis for voice signal to have many frequency components.

• Wind and Structures
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• 제16권1호
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• pp.1-23
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• 2013

The wind-induced transient response of internal pressure following the creation of a sudden dominant opening during the occurrence of high external pressure, in low-rise residential and industrial buildings was numerically investigated. The values of the ill-defined parameters namely the flow contraction coefficient, loss coefficient and the effective slug length were calibrated by matching the analytical response with the computational fluid dynamics predictions. The effect of a sudden i.e., "instantaneously created" windward opening in the Texas Technical University (TTU) test building envelope was studied for two different envelope flexibility-leakage combinations namely: (1) a quasi-statically flexible and non-porous envelope and (2) a quasi-statically flexible and porous envelope. The responses forced by creating the openings at different time leads/lags with respect to the occurrence of the peak external pressure showed that for cases where the openings are created in close temporal proximity to the peak pressure, the transient overshoot values of internal pressure could be higher than the peak values of internal pressure in the pre-sequent or subsequent resonant response. In addition, the influence of time taken for opening creation on the level of overshoot was also investigated for the TTU building for the two different envelope characteristics. Non-dimensional overshoot factors are presented for a variety of cavity volume-opening area combinations for (1) buildings with rigid/quasi-statically flexible non-porous envelope, and (2) buildings with rigid/quasi-statically flexible and porous envelope (representing most low rise residential and industrial buildings). While the factors appear slightly on the high side due to conservative assumptions made in the analysis, a careful consideration regarding the implication of the timing and magnitude of such overshoots during strong gusts, in relation to the steady state internal pressure response in cyclonic regions, is warranted.

• ETRI Journal
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• 제25권1호
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• pp.52-54
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• 2003

We propose an improved algorithm for detecting audio watermarks based on a spread spectrum in the spectral domain. Since the energy of a watermark is much smaller than that of the cover audio data, pre-processing to reduce the effect of the cover data is needed to reliably extract watermarks. We introduce a spectral envelope filter as a pre-process that enhances detecting performance by filtering out the intrinsic spectral character of cover data. The proposed watermarking structure can be easily included in the compression system and can extract watermarks from partially decompressed spectral data. Our experimental results demonstrate that with a bit error rate of around 10 dB against general attacks, the proposed detecting scheme works better than detectors without the spectral filter.

• JSTS:Journal of Semiconductor Technology and Science
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• 제14권3호
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• pp.313-321
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• 2014

A low-power low-cost polar transmitter for EDGE is designed in $0.18{\mu}m$ CMOS. A differential delta-sigma modulator (DSM) tunes a three-terminal voltage-controlled oscillator (VCO) to perform RF phase modulation, where the VCO tuning curve is digitally pre-compensated for high linearity and the carrier frequency is calibrated by a dual-mode low-power frequency-locked loop (FLL). A digital intermediate-frequency (IF) pulse-width5 modulator (PWM) drives a complementary power-switch followed by an LC filter to achieve envelope modulation with high efficiency. The proposed transmitter with 9mW power dissipation relaxes the time alignment between the phase and envelope modulations, and achieves an error vector magnitude (EVM) of 4% and phase noise of -123dBc/Hz at 400kHz offset frequency.

• 항공우주기술
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• 제4권2호
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• pp.27-35
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• 2005

본 연구에서는 에어터보램제트(ATR) 엔진의 탈설계점 성능해석을 위한 코드를 개발하고 이를 이용하여 기 설계된 ATR 엔진에 대한 탈설계점 성능해석을 수행하였다. 미리 정의한 작동 영역 중 중요 작동점을 정의하여 성능해석을 수행하였으며, 작동 영역이 넓음을 고려하여 가변 흡입구 및 가변 노즐을 사용하는 것으로 가정하였다. 각 요소 부품은 탈설계점 성능을 계산할 수 있도록 수학적 모델을 개발하였으며, 이 과정에서 일부 설계 개념을 도입하여 각 요소 부품의 설계 인자에 따른 성능 변화도 계산하였다. 성능해석 결과 기 설계된 엔진은 ATR 비행체의 임무 영역(마하 6.0, 고도 30km)을 모두 달성하기 어렵고, 낮은 마하 수에서 예냉각기의 역할이 크지 않음을 알 수 있었다.

• 한국정보통신학회논문지
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• 제18권8호
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• pp.1847-1853
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• 2014

이동통신 시스템의 OFDMA 방식은 신호에 대한 PAPR(Peak to Average Power Ratio) 값의 증가를 가져왔다. 이동통신 시스템 전력 소모의 대부분을 차지하는 전력 증폭기에 대한 효율 개선은 매우 중요한 핵심 기술이다. 전력 증폭기의 선형 특성 개선을 위해 디지털전치왜곡 기술을 사용하였으며, 전력 증폭기의 효율 개선을 위해 비대칭 도허티(Asymmetric Doherty) 방식을 사용하였다. 본 논문에서는 기존 비대칭 도허티 구조와 다른 새로운 구조의 비대칭 도허티 구조를 제안하였다. 제안하는 새로운 구조의 비대칭 도허티 방식에서는 전력 증폭기 구동단을 주경로와 첨두경로로 분리하였으며, 위상 변환기를 이용하여 도허티 증폭기의 전력 결합 특성을 개선하였다. 또한 구동단 첨두 증폭기 gate bais에 대한 포락선 추적 기술을 적용하여 효율을 개선하였다.

• 대한수학회논문집
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• 제20권2호
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• pp.209-219
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• 2005

Tor-torsion theory was defined by Jan Trlifaj in 2000. In this paper we introduce the notion of Co envelopes, CoCovers and Tor-generators as dual of envelopes, covers and generators in cotorsion(Ext-torsion) theory and deduce that each R-module has a projective and a cotorsion coprecover.

• 미생물학회지
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• 제28권1호
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• pp.6-12
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• 1990

adr 아형 B형 간염바이러스의 preS2염기서열을 베타갈락토시다세 유전자에 연결시켜 클론닝한 후, 융합단백질의 형태로 대장균에서 발현시켰다. 한국인 간염환자로부터 분리된 표면항원으로 유도한 단일 클론항체 H8는 preS2에 특이성을 지니고 있으며, 상기의 융합단백질과 특이적으로결합하였다. 이 단일 클론항체는 adw2아형 preS2 융합단백질과는 단지 낮은 수준의 결합성을 보여주었는데, 이와 같은 단일클론항체 H8의 adr 아형과 adw2아형에 대한 결합성의 차이는 preS2부위의 아미노산 차이에 기인한다고볼 수 있다.