• 한국수학교육학회지시리즈B:순수및응용수학
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• 제9권1호
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• pp.57-61
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• 2002

Let G be a connected graph. A pebbling move on a graph G is the movement of taking two pebbles off from a vertex and placing one of them onto an adjacent vertex. The pebbling number f(G) of a connected graph G is the least n such that any distribution of n pebbles on the vertices of G allows one pebble to be moved to any specified, but arbitrary vertex by a sequence of pebbling moves. In this paper, the pebbling numbers of the compositions of two graphs are computed.

• 한국농공학회:학술대회논문집
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• 한국농공학회 1998년도 학술발표회 발표논문집
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• pp.419-424
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• 1998

The deduction methods for forced displacement depths caused by sea dike construction often assumed the shape of forced displacements and heaving. To investigate the shape of forced displacements and heaving, a model tests was performed. Results of the tests are as follows; 1) The shape of forced displacements can be assumed ellipse. 2) The shape of heaving can not be assumed uniform shape like a circle and Extents of heaving was varied with the loading height and width. 3) The shape of forced displacements caused by step construction, pebble embankments and soil embankments, also investigated.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2005년도 춘계학술발표회
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• pp.141-142
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• 2005

• 충청수학회지
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• 제14권1호
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• pp.7-14
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• 2001

Let G be a connected graph. A pebbling move on a graph G is taking two pebbles off one vertex and placing one of them on an adjacent vertex. The pebbling number of a connected graph G, f(G), is the least n such that any distribution of n pebbles on the vertices of G allows one pebble to be moved to any specified, but arbitrary vertex by a sequence of pebbling moves. In this paper, the pebbling numbers of the lexicographic products of some graphs are computed.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2005년도 추계학술발표회
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• pp.121-122
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• 2005

• 한국HCI학회:학술대회논문집
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• 한국HCI학회 2008년도 학술대회 1부
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• pp.13-18
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• 2008

최근 건강 관리에 대한 관심이 증가하면서 착용형 생체 신호 센서, 재택형 무구속계측 센서에 관한 연구가 활발하게 진행되고 있다. 그러나, 측정 기술의 발전과 달리 측정결과를 제공하는 단계에서는 심장 박동수, 체온 등의 값을 단일된 임계치 기반으로 판단하며, 분석된 결과가 사용자에게 어떤 의미를 주는지에 대한 해석은 제공하지 않고 있다. 따라서 본 논문에서는 사용하기 편한 돌 형태의 휴대형 생체신호 측정센서를 기반으로 사용자 별로 적합한 생체신호 해석 방법을 제안한다. 개인화된 생체 신호 해석을 위해 1 주일간 사용자의 시간대별 데이터를 획득하고 사용자 별 특성에 따라 모델링을 한 후, 모델에 기반하여 사용자에게 맞는 생체 신호 범위를 정하고 이를 판단하는 근거로 활용한다, 센서는 기존의 착용형 생체 신호 센서 및 이를 이용한 응용에 폭넓게 사용될 수 있다.

• Geomechanics and Engineering
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• 제4권4호
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• pp.281-294
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• 2012

Filtration using granular media such as quarried sand, anthracite and granular activated carbon is a well-known technique used in both water and wastewater treatment. A relatively new pre-filtration method called pebble matrix filtration (PMF) technology has been proved effective in treating high turbidity water during heavy rain periods that occur in many parts of the world. Sand and pebbles are the principal filter media used in PMF laboratory and pilot field trials conducted in the UK, Papua New Guinea and Serbia. However during first full-scale trials at a water treatment plant in Sri Lanka in 2008, problems were encountered in sourcing the required uniform size and shape of pebbles due to cost, scarcity and Government regulations on pebble dredging. As an alternative to pebbles, hand-made clay pebbles (balls) were fired in a kiln and their performance evaluated for the sustainability of the PMF system. These clay balls within a filter bed are subjected to stresses due to self-weight and overburden, therefore, it is important that clay balls should be able to withstand these stresses in water saturated conditions. In this paper, experimentally determined physical properties including compression failure load (Uniaxial Compressive Strength) and tensile strength at failure (theoretical) of hand-made clay balls are described. Hand-made clay balls fired between the kiln temperatures of $875^{\circ}C$ to $960^{\circ}C$ gave failure loads of between 3.0 kN and 7.1 kN. In another test when clay balls were fired to $1250^{\circ}C$ the failure load was 35.0 kN compared to natural Scottish cobbles with an average failure load of 29.5 kN. The uniaxial compressive strength of clay balls obtained by experiment has been presented in terms of the tensile yield stress of clay balls. Based on the effective stress principle in soil mechanics, a method for the estimation of maximum theoretical load on clay balls used as filter media is proposed and compared with experimental failure loads.

• Nuclear Engineering and Technology
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• 제55권8호
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• pp.2966-2976
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• 2023

A tritium breeder is a lithium-based material capable of producing tritium. Many researchers designing nuclear-fusion energy are studying tritium production using pebbles, which are solid-type breeders. The sphericity and size of the pebbles are critical in obtaining pebbles with good tritium-breeding efficiency. Furthermore, tritium-release efficiency can be increased by using pebbles with appropriate porosities. Promising raw materials for tritium-breeding materials include Li₄SiO₄ and Li₂TiO₃. Li₄SiO₄ has a higher lithium density than Li₂TiO₃ and exhibits excellent tritium-breeding efficiency. However, it has the disadvantage of being easily decomposed during the Li₄SiO₄-green-pebble sintering process because of its low structural stability at high temperatures and high lithium density. In this study, we attempted to determine the optimal conditions for manufacturing Li₄SiO₄ pebbles using the droplet-freeze-drying method. The optimal Li₄SiO₄ slurry conditions and sintering temperatures were determined. The optimal Li₄SiO₄ slurry-fabrication conditions were 3 wt% polyvinyl alcohol and 75 wt% Li₄SiO₄ based on the deionized-water weight content. The sintering temperature at which Li₄SiO₄ did not decompose and exhibited the optimum porosity of 10.8% was 900 ℃.

• 통합자연과학논문집
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• 제16권1호
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• pp.1-12
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• 2023

Leucosia anatum, also known as the pebble crab, is a species of crab that belongs to the family Leucosiidae. Crabs are the most conspicuous and abundant components of the epibenthic macrofauna of the mangrove ecosystems. The present investigation was carried out with the objective of enlightening the reproductive system of L.anatum through histological and histochemical studies. Histological analysis of the epithelial cells of vas deferens, the luminal size and shape of the vas deferens was carried out, since the spermatophore material is secreted and molded by the vas deferens. Histochemical analysis of the blood plasma, testis, proximal vas deferens, middle vas deferens, distal vas deferens, seminal plasma and spermatophore was done to reveal the possible transformation of their secretory materials into the spermatophoric components. Biochemical components present in the blood plasma, testis, proximal vas deferens (PVD), median vas deferens (MVD) and distal vas deferens (DVD) regions seminal plasma and spermatophore of pebble crab were analyzed to find out the quantity of free sugars, proteins, and fats. Thus the current study focuses on the histological and histochemical analysis of Testis and Vas Deferens and their secretions in L.anatum.

• 생태와환경
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• 제55권1호
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• pp.19-34
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• 2022

본 연구는 환경부에서 수행 중인 하구 수생태계 현황 조사 및 건강성 평가 연구용역의 일부이며, 2016년~2018년까지 수행된 조사 결과를 분석하였다. 조사 결과 총 325개의 하구 중 식생분포가 확인되지 않은 25개 지점을 제외한 300개 하구에서 총 187개의 식물군락 유형이 조사되었으며 이 중 염생식물 군락은 53개로 28.3%였다. 하구순환 유형에 따라서는 열린하구에서 41개, 닫힌하구에서 26개 염생식물 군락이 확인되었다. 분포하는 식생과 환경요인 간의 정준상관분석(CCA) 결과 수질요인에서는 염도(전기전도도) 및 T-N, T-P 농도가 상관성이 강했으며 하상재료 요인 중에서는 Silt, Sand, Pebble 구성비율이 가장 강한 상관성을 나타내었다. 본 연구의 결과를 종합할 때 한반도 해안 하구에 분포하는 염생식물 군락의 분포 특성은 해역, 하구순환 유형, 염도에 대한 내성, 하상재료 분포 비율 등에 따라 각 우점종의 입지가 차별화되는 결과를 나타내었다.