• 한국농림기상학회지
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• 제9권2호
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• pp.75-87
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• 2007

광릉 슈퍼사이트 내 원두부 소유역에서 지하수위변동법, 이온수지법, 수문곡선분리법 등 세가지 방법을 적용하여 지하수 함양률을 평가하고, 방법별 결과들을 비교하였다. 이를 위한 자료는 우기에 해당하는 2005년 6월부터 9월까지 취득하였다. 두 가지 다른 지하수위변동법으로는 각각 25.9%, 23.6%의 지하수 함양률이 산출되었고, 염소를 이용한 이온수지법은 평균 13.4%의 함양률이, 그리고 6개의 수문곡선과 염소 이온자료를 이용한 기저유출 분리법은 평균 14.0%의 순기저유출률이 산출되었다. 장기적으로 지하수 저장량의 변화가 없는 정류상태를 가정하는 이온수지법과 수문곡선 분리법에서 산출된 지하수 함양률이 지하수 함양으로 인해 지하수위의 상승과 저장량의 변화를 고려하는 지하수위변동법에서 산출된 지하수 함양률보다 작게 산정되었다. 따라서 수문순환의 동력학적 특성을 이해하는 측면에서는, 지하수위변동법에 의한 지하수 함양률 평가가 다른 방법들보다 우월함을 보인다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2005년도 제31회 KOSCO SYMPOSIUM 논문집
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• pp.231-237
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• 2005

Interruption of good fluidization in a fluidized bed ash cooler(FBAC) for discharging bed materials such as sand or coal ash particles from the CFB combustor is frequently happened because of agglomeration of the particles in the bed. This unstable operation may, in the worst case, result in an unscheduled boiler shut down. In this study, we examined the operation problems of the FBAC of Tonghae CFB boiler and studied and introduced the simple detection and solution techniques with analyzing the mixing property and the occurrence of defluidization in a simulated fluidized bed ash cooler system (0.5m-H x 0.5m-W x 1.0m-L). The bridge of the large particles at the bed surface could be observed, and this caused to form the defluidization area at the entrance of the FBAC. The defluidization was affected not only by airflow rates but also by the particles discharging rates as well as particle size distribution in the FBAC. The local defluidization could be detected by analysis of the accumulated standard deviation error at a given period of time. Also, the regulation of the overall or local airflow rate made clearing up the local defluidization possible.

• 대한기계학회논문집
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• 제19권5호
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• pp.1340-1350
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• 1995

The effects of thermal stratification on the flow past a heated circular cylinder with various heating rates were examined in a wind tunnel. Turbulent intensities, r.m.s.values of temperature and turbulent convective heat flux distributions in the cylinder wakes with and without thermal stratification were measured by using a hot-wire and cold-wire combination probe. The phase averaging method was also used to estimate coherent contributions to the turbulent flow field in the near wake. The results show that the scalar mixing process is very different according to the mean temperature fields especially in the upper part of the wake. The coherent structure of the temperature field makes a large contribution to the time mean value like velocity components. However, the coherency of the temperature fluctuation is very different with the change of mean temperature fields, though the velocity coherent motions are quite similar in all experimental conditions.

• 한국통신학회논문지
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• 제35권6B호
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• pp.895-900
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• 2010

다양한 통신 서비스가 개발되면서, 네트워크 설계자들은 시간상관성, 폭주성, 예측 불가능한 트래픽의 통계적 변동성 때문에 발생하는 혼잡을 제어하기 위한 방안을 모색하여 왔다. 본 논문에서는 패킷 도착률과 토큰 생성률을 통합하여 관리하는 리키버킷 방식을 이용하여 네트워크의 혼잡을 예방하는 모형에 대하여 분석한다. 본 논문에서 다루는 모형에서는 패킷 도착률과 토큰 생성 시간간격을 대기중인 패킷수에 따라 제어함으로써 네트워크 혼잡을 예방하게 된다. 모형의 분석을 위하여 임베디드 마코프체인과 부가변수 기법을 사용하며, 대기중인 패킷수 확률분포, 패킷손실확률, 평균대기시간 등의 특성치를 구한다.

• 약학회지
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• 제37권1호
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• pp.84-88
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• 1993

Brovincamine is a selective cerebral vasodilator that was apparently produced via a slow calcium blockade. Brovincamine has been shown to increase ATP production and glucose and oxygen consumption in brain, improving energy metabolism. Also brovincamine inhibited platelet aggregation induced by ADP and collagen in vivo and in vitro via an increase of cAMP concentration, promoting therapeutic effects on cerebral circulatory disorders. So we investigated and represented the clinical effects and safety of brovincamine in patients with cerebral stroke. Thirty patients of cerebral stroke that was older than 2 months, who were 22 cases of cerebral infarction, 6 of cerebral embolism that originated from carebral infarction, 6 of cerebral embolism that originated from cardiac diseases, and 2 of cerebral embolism that originated from cardiac diseases, and 2 of cerebral hemorrhage, were administered of 20 mg of oral brovincamine three times daily for 8 weeks. Improvement rates of each symptom after 8 week administration were 30.8% for subjective symptoms, 76% for psychiatric symptoms and 65.6% for neurologic symptoms. In final global improvement rates, much improvement was 10%, improvement was 23.3% slight improvement is 36.7%, and no change was 30%. So global improvement rate including slight improvement was 70%. As for side effects, there were 3 cases of mild gastrointestinal symptoms, but there were no other subjective side effects and significant fluctuation in laboratory examination. Conclusively throughout the present study, brovincamine is judged to be well tolerated and effective in patients with cerebral stroke.

• 한국통신학회논문지
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• 제34권1A호
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• pp.1-11
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• 2009

OFDMA 및 SC-FDMA 시스템에서, 수신기에서 특별한 시공간 처리를 하지 않으면서 다이버시티를 얻기 위해서, 다수 안테나를 이용하여 시간축의 변화를 일으키거나 주파수 선택적 채널을 만들 수 있다. 분산할당 SC-FDMA 시스템에서 시간 변화를 발생하기 위해 위상 회전 기술을 사용하기 위해서는 낮은 채널부호화율을 적용하는 것이 필요하지만, 시간 변화가 적은 채널을 가정할 때 주파수 선택적 특성을 증가시키기 위하여 순환지연 다이버시티를 적용할 때에는 상대적으로 높은 채널부호화율을 적용하여도 무방하다. 이에 반해서 블록호핑 SC-FDMA 시스템에서는 두 개의 다이버시티 기술이 최적의 채널부호화율 측면에서 큰 차이를 가지지 않는다.

• 한국자기공명학회논문지
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• 제10권2호
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• pp.197-202
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• 2006

[ $^{11}B$ ] nuclear magnetic resonance (NMR) measurements were performed on the single crystals of $TbB_4$ to investigate local electronic structure and 4f spin dynamics. $^{11}B$ NMR spectrum, Knight shift, spin-lattice and spin-spin relaxation rates were measured down to 4K at 8T. $^{11}B$ NMR shift and linewidth are huge and strongly temperature dependent due to the 4f moments. In addition, both are proportional to magnetic susceptibility, indicating that the hyperfine field at the boron site originates from the 4f spins of Tb. Below $T_N$, the single broad resonance peak of $^{11}B$ NMR splits into several peaks reflecting the local magnetic fields due to antiferromagnetic spin arrangements. The longitudinal and the transverse relaxation rates, $1/T_1\;and\;1/T_2$, independent of temperature above $T_N$, decreases tremendously confirming huge suppression of spin fluctuation below $T_N$.

• Nuclear Engineering and Technology
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• 제56권4호
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• pp.1398-1406
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• 2024

The control rod worth is a key safety parameter required to be measured in commercial pressurized water reactors (PWRs). Conventionally, the control rod worth is measured after reaching the critical state, which occupies the considerable time in the zero-power physics test. In this study, an efficient control-rod worth measurement technique has been proposed based on the improved neutron-source multiplication method, which can be implemented with the source-range detector count rates in the subcritical states. Moreover, the noise reduction technique has been adopted to smooth the large fluctuation existing in the original signals. In order to verify the engineering performance of the proposed measurement technique, the measured source-range detector count rates during the rod withdrawal process before reaching critical state in a CNP1000 reactor have been employed. It demonstrated that almost all estimated results of control rod worth satisfy the engineering acceptance criteria, except one control rod with the relative difference over 10 %, which indicates the capability of the proposed method in estimating control rod worth.

• 말소리와 음성과학
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• 제5권1호
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• pp.11-16
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• 2013

This paper proposes robust feature extraction for accurate voice activity detection (VAD). VAD is one of the principal modules for speech signal processing such as speech codec, speech enhancement, and speech recognition. Noisy environments contain nonstationary noises causing the accuracy of the VAD to drastically decline because the fluctuation of features in the noise intervals results in increased false alarm rates. In this paper, in order to improve the VAD performance, harmonic-weighted energy is proposed. This feature extraction method focuses on voiced speech intervals and weighted harmonic-to-noise ratios to determine the amount of the harmonicity to frame energy. For performance evaluation, the receiver operating characteristic curves and equal error rate are measured.

• 한국환경과학회지
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• 제5권3호
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• pp.361-367
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• 1996

An inverse fluidized-bed biofilm reactor (IFBBR) was used for the treatment of highly-emulsified oily wastewater. When the concentration of biomass which was cultivated in the synthetic wastewater reached to 6000 mg/1, the oily wastewater was employed to the reactor with a input COD concentration range of 50 mg/1 to 1900 mg/l. Virtually the IFBBR showed a high stability during the long operation period although soma fluctuation was observed. The COD removal efficiency was maintained over 9% under the condition that organic loading rate should be controlled under the value of 1.5 kgCOD/$m^3$/day, and F/M ratio is 1.0 kgCOD/kgVSS/day at $22{\circ}C$ and HRT of 12 hrs. As increasing organic loading rates, the biomass concentration was decreased steadily with decreasing of biofilm dry density rather than biofilm thickness. Based on the experimental jesuits, it was suggested that the decrease in biofilm dry density was caused by a loss of biomass inside the biofilm.