• 한국멀티미디어학회논문지
• /
• 제21권6호
• /
• pp.667-677
• /
• 2018

Since sensor networks consist of sensor nodes with limited energy resources, so efficient energy use of sensor nodes is very important in the design of sensor networks. Sensor nodes consume a lot of energy for data transmission. Clustering technique is used to efficiently use energy in data transmission. Recently, mobile sink techniques have been proposed to reduce the energy load concentrated on the cluster header near a sink node. The CMS(Cluster-based Mobile sink) technique minimizes the generation of control messages by creating a data transmission path while creating clusters, and supports the inter-cluster one-hop transmission. But, there is a case where there is no connectivity between neighbor clusters, it causes a problem of having a long hop data transmission path regardless of local distance. In this paper, we propose a SCBC(Strong connection balancing cluster) to support the path of the minimum number of hops. The proposed scheme minimizes the number of hops in the data transmission path and supports efficient use of energy in the cluster header. This also minimizes a number of hops in data transmission paths even when the sink moves and establishes a new path, and it supports the effect of extending the life cycle of the entire sensor network.

• 대한수학회논문집
• /
• 제12권1호
• /
• pp.193-201
• /
• 1997

The paper presens results on the perturbation problem of invariant manifolds of differential equations. It is well-known that if there is a pseudohyperbollic structure on an invariant manifold then one is strongly indestructible. The set of strongly inderstructible invariant manifolds is wider than the set of persistent (normally hyperbolic) manifolds. The following theorem is main result of the paper: if the condition of transversality holds on an invariant manifold, except, possibly, for the non-degenerate strong sources and non-degenerate strong sinks, then there is the pseudohyperbolic structure on the invariant manifold. From this it follows the conditions for the indestructibility of locally non-unique invariant manifolds. An example is considered.

• 한국정보과학회논문지:시스템및이론
• /
• 제32권8호
• /
• pp.426-431
• /
• 2005

그래프 G의 다대다 k-서로소인 경로 커버(k-DPC)는 k개의 서로 다른 소스 정점과 싱크 정점 쌍을 연결하며 그래프에 있는 모든 정점을 지나는 k개의 서로소인 경로 집합을 말한다. 이 논문에서는 이중 루프 네트워크 G(mn;1,m)에서 다대다 2-DPC를 고찰하여, 이분 그래프가 아닌 모든 G(mn;l,m), $m{\geq}3$은 임의의 두 소스-싱크 쌍을 연결하는 다대다 2-DPC가 존재하고 이분 그래프인 G(mn;1,m)은 두 흰색-검정 소스-싱크 쌍이거나 혹은 검정-검정, 흰색-흰색 쌍을 연결하는 2-DPC가 존재함을 보인다. G(mn;1,m)은 m이 홀수이고 n이 짝수일 경우에만 이분 그래프이다.

• 한국대기환경학회지
• /
• 제13권2호
• /
• pp.161-170
• /
• 1997

The concentrations of dimethylsulfide (DMS) were determined using samples collected from a station located at Kosan, Cheju Island during two field campaigns held in December 1996 and January 1997. The atmospheric DMS concentrations measured at 6-hr intervals during the entire campaign periods, after excluding a few extreme values, spanned in the range of 14 to 410 pptv with mean and 1 SD value of 127 $\pm$ 94 pptv (N=42). Between two month periods during which the field campaigns were conducted, a notable reduction in DMS levels was observed which was comparable to the dramatic shift in air temperature. A considerable difference was also noted in DMS levels, when data were grouped by day/night basis. The cause of unexpected, high day-to-night DMS ratios is best explained in terms of high efficiency of daytime source processes relative to low efficiency of nighttime sink processes due to the characteristics of the study location. The surface water DMS of the study site, although scarcely measured, also behaved similarly to its atmospheric counterpart with its range from 0.3 to 19 nM (N=11). When correlation analysis was conducted between the atmospheric DMS concentration and other concurrently determined parameters, significant correlations were observed from most basic meteorological parameters such as windspeed, relative humidy, and air temperature. However, the existence of "not-so-strong" correlations between air temperature and DMS concentrations relative to other ones indicated that the effect of temperature on DMS behavior must be reflected in more complicated manners at the study site. The sea-to-air flux of DMS was approximated through an application of the mass-balance flux calculation method of Wylie and de Mora (1996) under the assumption that sink mechanism within the marine boundary layer is in steady-state condition with its counterpart, source mechanism. Based on this estimation method, we reached a conclusion that oceanic DMS emitted from the southwest sea of the Korean Peninsula can amount to approximately 9 $\sim$ 36 Gg S $yr^{-1}$.$yr^{-1}$.

• 한국대기환경학회지
• /
• 제7권3호
• /
• pp.197-202
• /
• 1991

It is observed that the outbreak of dust storms (yellow sand) from Northern China and Mongolia occurs a few times in April 1988 and 1990. It is found that a dust storm initiated with strong gusty winds after the passage of a cold front, particularly after defrost of the ground surface of a source region in the early spring. According to meteorological chart, satellite images and trajectory analyses, dust clouds invaded Korea in April 1988 and 1990 were landing in the sink area after 2 $\sim$ 4 days travelling for 2,000 $\sim$ 3,000 km from a source region. It was also observed that in the west coast total suspended particulated (TSP) were 100 $\sim$ 200 $\mug m^{-3}$ and sulphates $(SO_4=)$ were 3 $\sim$ 10 $\mug m^{-3}$. These values clearly exceed the concentrations of a background level measured in the Arctic and Atlantic Ocean. Trajectory analyses and meteorological analyses suggest that the high values occurred with prevailing westerly flows coming from anthropogenic sources in China. High concentrations of air pollutants occurred in the backside of an anticyclone and in the area "col".col".uot;.

• 한국에너지공학회:학술대회논문집
• /
• 한국에너지공학회 2000년도 추계 학술발표회 논문집
• /
• pp.127-137
• /
• 2000

Accelerator Driven System (ADS) named HYPER(Hybrid Power Extraction Reactor) is being developed for the transmutation of nuclear waste in Korea Atomic Energy Research Institute(KAERI). The concept of the HYPER is using 1GeV proton to drive a subcritical core. HYPER system is believed to have much more stable dynamics than the critical system in terms of neutronics. However, the HYPER system is supposed to have some drawbacks for the cooling system accidents. Loss of Flow(LOF) and Loss of Heat Sink (LOHS) cause a strong damage. As results, those accidents would stop the power production in the critical system. On the other hand, the negative reactivity feedback could not stop the HYPER system because the HYPER is driven by an accelerator rather than reactivity.(omitted)

• Fisheries and Aquatic Sciences
• /
• 제5권1호
• /
• pp.5-20
• /
• 2002

To investigate the effect of mechanical parameters on the circulation and its fluctuation in Sagami Bay, baroclinic model experiments were carried out by use of a two-layer source-sink flow in a rotating tank. In the experiment, a simple coastal topography with flat bottom was reproduced. The results show that the path of the Through Flow, which corresponds to the branch current of the Kuroshio, depends on external Rossby number (Ro) and internal Rossby number $(Ro^*)$, and divided into two regimes. For $Ro^*\leq1.0$ in which Rossby internal radius of deformation of the Through Flow is smaller than the width of the approaching channel, the current flows along the Oshima Island as a coastal boundary density current separated from the western boundary of the channel. For $Ro^*>1.0$ it changes to a jet flow along the western boundary of the channel, separated from the coast of Oshima Island. The current is independent on both Ro and Ro* in the regime of $Ro^*>1.0,\;Ro\geq0.06$ and $Ro^*\leq1.0,\;Ro\geq0.06$. The pattern of the cyclonic circulation in the inner part of the bay is also determined by Ro and Ro*. In case of $Ro^*\leq1.0$, frontal eddies are formed in the northern boundary of the Through Flow. These frontal eddies intrude into the inner part along the eastern boundary of the bay providing vorticity to form and maintain the inner cyclonic circulation. For $Ro^*>1.0$, the wakes from the Izu peninsula are superposed intensifying the cyclonic circulation. The pattern of the cyclonic circulation is divided into three types; 1) weak cyclonic circulation and the inner anticyclonic circulation $(Ro<0.12)$. 2) cyclonic circulation in the bay $(0.12\leq Ro<0.25)$. 3) cyclonic circulation with strong boundary current $(RO\geq0.25)$.

• 원예과학기술지
• /
• 제19권4호
• /
• pp.555-559
• /
• 2001

본 연구는 유도일장과 강광도 조건에서 화아발달 시기에 간이 엽록소 측정기(SPAD-502 chlorophyll meter)를 이용한 국화잎의 위치별 엽록소 함량변화를 조사하기 위하여 실시하였다. SPAD 값은 수확기에 줄기의 최상부에서부터 매 3엽씩 하부로 내려가면서 서로 다른 일장과 광도조건에서 측정하였다. 10시간의 단일에서 SPAD 값이 가장 높았고, 뒤를 이어 13시간과 16기간 일장 순이었다. 특히 단일조건에서는 화아의 아래로부터 첫 번째인 가장 어린잎에서 가장 높았으며, 줄기의 하부로 내려갈수록 감소하였다. 장일조건에서는 줄기의 상부에서 15-27번째의 잎이 가장 높은 SPAD 값을 나타내었고, 줄기 최상단의 어린잎에서는 최소값을 기록하였다. 이러한 결과는 단일 조건에서는 상부의 잎들이 발달하는 꽃들을 지지하기 위한 중요한 소스(source)가 되는 반면, 영양생장기의 국화는 상부에서 분화 또는 발달하는 어린잎이 여전히 중요한 싱크(sink)의 하나로서 역할하고 있는 것으로 판단된다. SPAD 값은 강광도 조건에서 증가하였고, 광도가 낮아짐에 따라 감소하였다.

• 지구물리
• /
• 제9권4호
• /
• pp.397-408
• /
• 2006

남극 반도와 그 주변에서의 온난화는 시간적, 공간적 변동이 크기 때문에 이 지역에서의 국지 기후를 이해하는 것이 필요하다. 이 연구의 목적은 남극 세종 기지 주변에서의 지표 복사, 기온 그리고 풍향의 특징을 밝혀내고, 그 변수들간의 상관 관계를 조사하는 것이다. 연구지는 연간 15-20 Wm-2의 복사 에너지를 흡수하지만, 여름 (12월-1월)에는 평균적으로 85 Wm-2의 복사 에너지를 흡수하였다. 이 흡수량은 남극의 다른 지역에 비해 상당히 큰 값이다. 월 평균 기온은 -7.7-2.8oC 이었으며, 매년 다른 변동을 보였다. 북서, 서 및 동풍이 주풍이었으며, 풍향의 변동이 기온 변동을 설명할 수 있었다. 찬 동풍과 따뜻한 북서 및 북풍 빈도의 변동이 특히 여름철 지표 복사 수지에도 크게 영향을 주었으며, 이 시기의 대기와 지면 간의 에너지 교환에 풍향이 중요한 역할을 하는 것으로 보인다.

• 분석과학
• /
• 제16권2호
• /
• pp.143-151
• /
• 2003

서울시에 소재한 7개 측정점으로부터 입자상물질에 결합된 금속성분의 농도를 약 1년여 기간동안 관측하였다 (2001년 3월~2002년 5월). 본 관측자료를 토대로 공간적 요인이 금속성분의 분포특성에 어떠한 방식으로 영향을 미치는 가를 조사하였다. 이러한 분석을 위해, 변이계수, 시간적 변이성, 상관성 발생의 빈도 등과 같은 기준을 활용하였다. 본 연구 결과에 의하면, 금속성분의 농도분포가 상당히 다양한 요인들의 영향에 종속된다는 사실이 확인되었다. 특히 Fe, Mn, Pb 등의 성분들은 이질적인 지역들간에도 대단히 강한 유사성을 보이는데 반해, Cu와 같은 성분은 이러한 경향을 전혀 찾기가 어려웠다. 이러한 공간적 요인의 특성을 상세하기 설명하기 위해서는 개별 성분의 지화학적 요인을 발생/소멸현상과 연계하여 설명하는 것이 중요하다.