• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년 학술대회 논문집 정보 및 제어부문
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• pp.416-418
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• 2006

In this paper, a new acoustic echo cancellation approach based on the DUET algorithm and scaling factor estimation is proposed to solve the scaling ambiguity in case of blind separation based acoustic echo cancellation in a noisy environment. In hands-free full-duplex communication system. acoustic noises picked up by the microphone are mixed with echo signal. For this reason, the echo cancellation system may provide poor performance. For that purpose, a degenerate unmixing estimation technique, adjusted in the time-frequency domain, is employed to separate undesired echo signals and noises. Also, since scaling and permutation ambiguities have not been solved in the blind source separation algorithm, kurtosis for the desired signal selection and a scaling factor estimation algorithm are utilized in this rarer for the separation of an echo signal. Simulation results demonstrate that the proposed approach yields better echo cancellation and noise reduction performances, compared with conventional methods.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
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• pp.282-283
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• 2006

A frequency relaying algorithm which is used system separation and load shedding to improve transient stability is proposed. The algorithm can trip the generator and shed load in the abnormal frequency condition. The computer simulations of load flow analysis is used to determine the amount of load to be shed in an under frequency condition. Furthermore dynamic brake energization in the simulation is performed for the control of overfrequency.

• 한국군사과학기술학회지
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• 제9권4호
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• pp.128-136
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• 2006

The purpose of this paper is to examine the dynamic stall characteristics of an elliptic airfoil when subject to constant pitch motions. In this study, which was motivated by the pressing need for a greater understanding of the reduced frequency$({\kappa})$ effects on flow patterns of elliptic airfoil, the various reduced frequencies were considered. The result confirms that the reduced frequency has a profound effects on the flow patterns. The increase of ${\kappa}$ accelerate the separation bubble bursting process up to ${\kappa}=0.10$, then diminish with further increase in ${\kappa}$. Compared with static condition, the dynamic pitching airfoil delays stall angle approximate $4{\circ}{\sim}5{\circ}$ during pitch-up stroke for ${\kappa}=0.10$. Results from this qualitative analysis provided valuable insight Into the control of dynamics stall.

• 천문학회보
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• 제37권2호
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• pp.108.2-108.2
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• 2012

Recent results from microlensing surveys show that a free-floating planet or a wide-separation planet is more numerous than a main-sequence star in the Galaxy. Moreover, the detection efficiency of the planets will be improved in next-generation experiments with a high survey monitoring frequency. However, microlensing events produced by both planets appear similar light curves with a short duration timescale, thus it is difficult to distinguish them. In this paper, we investigated the detectable separation range of a wide-separation planet as the planet bound to its host star. We construct the fractional deviation maps using the magnifications of the planetary lensing and the single-lensing by planet itself for various parameters such as a mass ratio, separation, and source radius. As a result, we found that the pattern of the fractional deviation is related to the ratio of source radius to caustic size, and the ratio satisfying the detection criterion (i.e., ${\geq}5%$ in the fractional deviation) varies with a separation. Hence, we derived a fitting formula as the function of a mass ratio and a source radius to reflect the variation in the calculations of the detectable separation range of a wide-separation planet as the planet bound to its host star. In addition, we estimated the condition that a wide-separation planet can be detected as a single-lensing event under the finite source effect. We found that such a case is possible provided that the source radius is smaller than ~2.5 times of Einstein ring radius of a planet, regardless of a separation or a mass ratio.

• 한국산림과학회지
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• 제45권1호
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• pp.51-61
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• 1979

교배(交配) 모수(母樹)인 P. alba화분(花粉) 모수(母樹)인 P. glandulosa 및 그의 잡종(雜種)인 ${\times}$P. albaglandulosa에 관(關)한 화분모세포(花粉母細胞)의 감수분열(減數分裂)에 있어 염색체행동(染色体行動)과 대합(對合) 현상(現象)에 관(關)해 조사(調査)하였다. 1. Metaphase II에서 Earyl separation chromosome을 갖는 핵판(核板)이 가장 적은 개체(個体)는 P. glandulosa로 11.0%며 ${\times}$P. albaglandulosa는 13.0%로 가장 높았다. 2. Metaph se II에서 ${\times}$P. albaglandulosa는 11.0%의 Early separation chromosome이 출현(出現)했으나 양친양친수(兩親兩親樹)와 차이(差異)는 없었다. 3. Anahase I에서 Lagging chromosome의 출현율(出現律)은 ${\times}$P. albaglandulosa가 다소(多少) 높아 11.6%로 나타났으며 chromosome bridge에서는 양친수(兩親樹)와 거의 차(差)가 없었다. 4. Anaphase II때 Lagging chromososome은 ${\times}$P. albaglandulosa에서 다소(多少) 높은 빈도(頻度)로 10.2%였으며 chromosome bridge P. glandulosa에서 가장 높은 빈도(頻度)로 출현(出現)하였다. 5. Abnormal pollen sporad는 ${\times}$P. albaglandulosa에서 가장 많이 출현(出現)하여 8.2%를 나타냈다. 이상(以上)의 결과(結果) P. alba, P. glandulosa 및 ${\times}$P. albaglandulosa는 화분모세포분열(花粉母細胞分裂)에 있어서 염색체분열접합(染色体分裂接合)이 정상적(正常的) 행동(行動)을 하고 있어 결국(結局) 정상(正常) 화분형식(花粉形式)을 행(行)하는 수종(樹種)이라 결론(結論)할 수 있다.

• 자원리싸이클링
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• 제29권3호
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• pp.36-42
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• 2020

이 연구에서는 1 mm의 지르코니아볼(5.6 g/㎤)층을 진동시켜 스파이스(6.74 g/㎤)와 석회석 (2.7 g/㎤) 입자가 지르코니아볼층을 매체로 비중선별이 가능한지 조사하였다. 진동세기를 18 Hz부터 26 Hz까지 변화시켜 스파이스와 석회석의 입자개수 증가에 따른 부유율과 분리효율을 분석하였다. 진동 중 지르코니아볼은 용기내부를 순환하며, 스파이스는 지르코니아볼과 함께 가라앉지만 석회석 입자는 지르코니아볼 표면에 잔존하였다. 스파이스와 석회석의 입자 개수가 증가할수록 입자가 가라앉는 경로에 정체현상이 발생하여 입자가 가라앉는 속도가 감소하며, 스파이스 입자와 겹쳐진 석회석 입자가 같이 가라앉는 현상도 발생하였다. 따라서 입자개수가 증가할수록 스파이스와 석회석의 분리효율은 감소하나, 진동세기가 증가하면 정체현상이 해소되어 분리효율이 증가하는 현상이 관찰되었다. 특히 각 3개의 입자를 투입한 경우 22 Hz에서 100 %의 분리효율이 관찰되어 건조공정이 요구되지 않는 건식 비중선별 공정이 가능한 것이 확인되었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.366.1-366
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• 2002

It is addressed that the turbulent broadband sound power from a sirocco fan can be modeled by the trailing edge noise. The trailing edge noise is usually influenced by inflow turbulence, separation, and boundary layer on the blade. The design parameters such as solidity(c/s) and stagger angle are specified to predict performance and noise level because the separation and slip velocity are strong1y affected by them along with the flow coefficient. (omitted)

• 대한기계학회논문집
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• 제19권4호
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• pp.1134-1147
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• 1995

POD (proper orthogonal decomposition) is applied to turbulent leading-edge separation bubble to extract coherent structures. A two-dimensional leading-edge separation bubble is simulated by discrete-vortex method, where a time-dependent source forcing is incorporated. Based on the wealth of numerical data, POD is applied in a range of the forcing amplitude ( $A_{o}$ = 0, 0.5, 1.0 and 1.5) and forcing frequency (0 .leq. $f_{F}$H/ $U_{\infty}$.leq. 0.3). It is demonstrated that the structures of POD have noticeable changes with local forcings. In an effort to investigate the mechanism of decreasing reattachment length, dynamic behaviors of the expansion coefficients and contributions of the eigenfunctions of POD are scrutinized. As the forcing amplitude increases, the large-scale vortex structures are formed near the forcing amplitude increases, the large-scale vortex structures are formed near the separation point and the flow structures become more organized and more regular, accompanying with the reduction of reattachment length. By further inverstigation of POD global entropy, it is seen that the reattachment length is closely linked to the degree of organization of the flow structures.es.s.

• 아동학회지
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• 제27권2호
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• pp.101-126
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• 2006

In this comparison of the relative effects of children's separation from their parents, socio-emotional adjustment was assessed by emotional and behavioral problems and emotional intelligence. Subjects were 502 elementary school children separated from their parents(162 in Yanbian and 340 in Korea) and their caregivers. Data analysis was by frequency, t-test, and multiple regression controlled by gender and grade in school. Caregivers living with children and their parenting efficacy were significant variables for the development of socio-emotional adjustment in Korean-Chinese children in Yanbian, but reasons for parent-child separation, caregivers' psychological and behavioral characteristics, and SES were significant variables for children in Korea. Implications are that regional differences should be considered in understanding and supporting the development of children's socio-emotional adjustment.

• ETRI Journal
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• 제38권1호
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• pp.112-122
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• 2016

This paper presents a set of candidate regulatory requirements for TV band devices (TVBDs) in the Rep. of Korea. To guarantee the protection of incumbent services, especially digital TV (DTV) and wireless microphones, in TV frequency bands, we suggest minimum separation distances of TVBDs from the noise-limited contour according to incumbent users and TVBD types. This paper also deals with multiple sets of separation distances of a co-channel TVBD network from a DTV protected contour on the basis of the radio propagation characteristics of different geographic areas to make good use of TV white space (TVWS) and safely protect the DTV service. We present a low-power transmission mode of TVBDs and the relevant separation distances for small-cell deployment. The service coverage reduction ratio of a TVBD network is investigated in the presence of DTV interference in four geographic areas. The TVWS field verification results, conducted on the island of Jeju (Rep. of Korea), show that incumbent services operate well without harmful interference from neighboring TVBDs with the proposed separation distances.