• The Korean Journal of Ecology
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• 제19권1호
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• pp.36-46
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• 1996

Variation of Al tolerance in Pinus densiflora, P. rigida and P. thunbergii was investigated in a solution culture. Root length decreased as Al concentration increased, and decreased more in dilute culture media than in dense one. Aluminum tolerance based on relative root length was in the order of P. rigida ＞ P. densiflora ＞ P. thunbergii. Al content in tissue increased as Al concentration of the media increased, but the reverse was true for content of Ca and Mg. Al tolerance for root length showed intraspecific variation, even under the same Al concentration in the media.

• Journal of information and communication convergence engineering
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• 제6권1호
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• pp.19-23
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• 2008

The AQM (Active Queue Management) starts dropping packets earlier to notify traffic sources about the incipient stage of congestion. The AQM improves fairness between response flow (like TCP) and non-response flow (like UDP), and it can provide high throughput and link efficiency. In this paper, we suggest the QVARED (Queue Variation Adaptive RED) algorithm to respond to bursty traffic more actively. It is possible to provide more smoothness of average queue length and the maximum packet drop probability compared to RED and ARED (Adaptive RED). Therefore, it is highly adaptable to new congestion condition. Our simulation results show that the drop rate of QVARED is decreased by 80% and 40% compare to those of RED and ARED, respectively. This results in shorter end-to-end delay by decreasing the number of retransmitted packets. Also, the QVARED reduces a bias effect over 18% than that of drop-tail method; therefore packets are transmitted stably in the bursty traffic condition.

• Wind and Structures
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• 제34권1호
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• pp.137-149
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• 2022

In this paper, the fluctuating lift and drag forces on 5:1 rectangular cylinders with two different geometric scales in three turbulent flow-fields are investigated. The study is particularly focused on understanding the influence of the ratio of turbulence integral length scale to structure characteristic dimension (the length scale ratio). The results show that both fluctuating lift and drag forces are influenced by the length scale ratio. For the model with the larger length scale ratio, the corresponding fluctuating force coefficient is larger, while the spanwise correlation is weaker. However, the degree of influence of the length scale ratio on the two fluctuating forces are different. Compared to the fluctuating drag, the fluctuating lift is more sensitive to the variation of the length scale ratio. It is also found through spectral analysis that for the fluctuating lift, the change of length scale ratio mainly leads to the variation in the low frequency part of the loading, while the fluctuating drag generally follows the quasi-steady theory in the low frequency, and the slope of the drag spectrum at high frequencies changes with the length scale ratio. Then based on the experimental data, two empirical formulas considering the influence of length scale ratio are proposed for determining the lift and drag aerodynamic admittances of a 5:1 rectangular cylinder. Furthermore, a simple relationship is established to correlate the turbulence parameter with the fluctuating force coefficient, which could be used to predict the fluctuating force on a 5:1 rectangular cylinder under different parameter conditions.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1655-1660
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• 2004

Theoretical study has been conducted to clarify pressure characteristics of KTX(Korea Train eXpress) in tunnel. The external and internal pressure of rolling stock have been measured by using the atmospheric pressure sensors and portable data acquisition system on Seoul-Busan high speed railroad line. These pressure change may give rise to the ear-discomfort for passenger and fatigue for car body. In this study, the tunnels from 200m to 4000m in length have been chosen for the investigation of tunnel length effects. From the results of experiment, the pattern of pressure change generally agrees to RTRI's experimental result for Shinkansen. We found that there are similar patterns of external pressure variation for each critical tunnel length. The critical tunnel lengths are governed by train speed, train length and sonic velocity.

• 한국작물학회지
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• 제24권3호
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• pp.81-84
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• 1979

인삼변이계통의 선발에 필요한 기초자료를 얻고저 자경종, 황숙종, 미국종의 일년생에 대하여 여러 가지 농경형질의 변이를 조사하였던 바 그 결과를 요약하면 다음과 같다. 1. Panax quinquefolium이 Panax ginseng에 비하여 모든 형질의 변이가 큰 경향이었다. 2. Panax ginseng에 있어서는 자경종이 황숙종보다 형질변이가 크게 나타났다. 3. Panax ginseng, Panax quinquefolium 공히 경장, 엽장, 근장 등의 형질은 변이가 큰 반면에 경직경, 근직경 등의 형질은 비교적 적게 변화하였다.

• 한국소음진동공학회논문집
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• 제18권11호
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• pp.1185-1191
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• 2008

This paper presents an approach to define an optimal piezoactuator length to actively control structural vibration. The optimal ratio of the piezoactuator length against the beam length when a pair of piezoceramic actuator and accelerometer is used to suppress unwanted vibration with direct velocity feedback(DVFB) control strategy is not clearly defined so far. It is well known that DVFB control can be very useful when a pair of sensor and actuator is collocated on structures with a high gain and excellent stability. It is considered that three different collocated Pairs of piezoelectric actuators (20, 50 and 100 mm long) and accelerometers installed on three identical clamped-clamped beams($30{\times}20{\times}1mm$). The response of each sensor-actuator pair requires strictly positive real(SPR) property to apply a high feedback gain. However the length of the piezoactuator affects the SPR property of the sensor-actuator response. Intensive simulation and experiment show the effect of the actuator length variation is strongly related with the frequency range of the SPR property. Thus an optimal length ratio was suggested to obtain relevant performance with a good stability under the DVFB strategy.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제25회 추계학술대회논문집
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• pp.335-340
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• 2005

액체 로켓엔진 연소기에 적용되는 분사기 형상에 따른 연소특성 변화를 알아보기 위해 연소시험을 수행하였다. 사용된 분사기는 동축와류형으로서 챔버 와류실의 유무와 노즐 길이에 의한 특성변화에 초점을 맞추었다. 챔버 와류실의 유무에 따라 닫힘형과 열림형으로 구분이 된다. 노즐 길이에 따른 변화는 산화제와 연료가 분사되는 노즐을 증가시킨 분사기를 통해 이루어졌다. 연소기는 분사기가 한 개만 장착된 단일분사기 헤드, 내열재 형식의 연소실, 냉각 유로를 가진 동 재질의 노즐로 구성되어 있으며 연소실과 노즐의 외부는 스테인레스 스틸로 이루어졌다.

• Animal Systematics, Evolution and Diversity
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• 제29권1호
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• pp.18-22
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• 2013

A recent study on the mitochondrial genetic variation of the Carassius auratus population in South Korea suggested that there are 3 distinct mitochondrial lineages in the country, and that they are geographically separated between westward rivers and southward rivers, respectively. In this study, the population genetic structure of amplified fragment length polymorphism (AFLP) of Carassius auratus was investigated. The results of analysis of molecular variance (AMOVA) supported the geographic distinction between westward and southward river populations, but only 3.66% of total genetic variance lies among these populations. The panmicticity of the AFLP genetic variation is backed up by the results of the neighbor-joining dendrogram drawn from a linearized pairwise $F_{ST}$ matrix and Bayesian clustering analysis. The discordance of genetic structure between mitochondrial and AFLP genetic variation may come from difference in effective population size between these markers and/or gene flow between westward and southward river populations through river capture events.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1998년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.28-35
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• 1998

The seismic overstrength factor $\Omega$ is evaluated for 4-story reinforced concrete buildings in Korea(of which seismic intensity is low). The study model is designed according to aseismic guideline research - phase II in Korea. The effect of variation of span length and bay number, dead load is considered, especially including the variation of hardening ration after yielding. And push-over analysis is performed, in which the external and internal frame is connected by rigid-link and the $\Omega$ is calculated using the roof drift ratio at 2%. For Zone I, the mean value of $\Omega$ is ranged form 2.3 to 2.5, For Zone II, from 3.1 to 3.4. For low hardening ratio(3%) after yielding, $\Omega$ has little relations with the number of bay, like as the results of other research. But for 5% hardening ratio, $\Omega$ is increased as the number of bay is increased. Within general gravity-load bound, the variation of D.L. has variation of D. L. has no effect on $\Omega$. And, $\Omega$ is increased as the span length is increased.

• 한국산학기술학회논문지
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• 제12권3호
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• pp.1234-1243
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• 2011

본 연구의 목적은 지역사회획득 폐렴 입원 환자의 재원일수의 변이를 분석하기 위해 중증도 모형을 개발하였다. 2004~2006년 퇴원손상환자 조사자료 중 지역사회획득 폐렴환자 5,353건을 연구대상으로 하였으며, 재원일수의 차이분석은 t검정, 분산분석을 실시하였고, 중증도 보정 재원일수 예측 모형은 데이터마이닝 기법을 이용하였다. 여자에 비해 남자, 연령이 많을수록, 의료급여, 응급실 경유 환자의 재원일수가 긴 반면, 병원사망 여부에 따라서는 유의한 차이가 없었다. 개발된 의사결정나무 모형을 이용하여 예측 재원일수를 산출하고 표준화한 값을 비교한 결과 타지역 진료여부에 따라서 재원일수의 차이는 없는 반면, 보험유형과 지역별로 재원일수의 변이가 존재하는 것으로 나타났다. 환자 특성과 중증도를 통제하고 나타난 재원일수의 변이는 공급자 요인으로 설명될 수 있는데, 진료행태나 의료자원에 대한 후속 연구가 필요한 것으로 보인다. 본 연구는 행정 데이터를 이용하여 중증도 모형을 개발하고 변이를 확인하였다는 점에서 활용의 효용성을 높이는 데 기여할 것으로 사료된다.