• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.157-159
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• 2007

The conventional hard disk has been the dominant database storage system for over 25 years. Recently, hybrid systems which incorporate the advantages of flash memory into the conventional hard disks are considered to be the next dominant storage systems to support databases for desktops and server computers. Their features are satisfying the requirements like enhanced data I/O, energy consumption and reduced boot time, and they are sufficient to hybrid storage systems as major database storages. However, we need to improve traditional index node management schemes based on B-Tree due to the relatively slow characteristics of hard disk operations, as compared to flash memory. In order to achieve this goal, we propose a new index node management scheme called FNC-Tree. FNC-Tree-based index node management enhanced search and update performance by caching data objects in unused free area of flash leaf nodes to reduce slow hard disk I/Os in index access processes.

• 한국지능시스템학회논문지
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• 제15권3호
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• pp.343-348
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• 2005

This paper describes an automatic finite element (FE) mesh generation for three-dimensional structures consisting of free-form surfaces. This mesh generation process consists of three subprocesses: (a) definition of geometric model, i.e. analysis model, (b) generation of nodes, and (c) generation of elements. One of commercial solid modelers is employed for three-dimensional solid structures. Node is generated if its distance from existing node points is similar to the node spacing function at the point. The node spacing function is well controlled by the fuzzy knowledge processing. The Delaunay method is introduced as a basic tool for element generation. Automatic generation of FE meshes for three-dimensional solid structures holds great benefits for analyses. Practical performances of the present system are demonstrated through several mesh generations for three-dimensional complex geometry.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2005년도 춘계학술대회 학술발표 논문집 제15권 제1호
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• pp.139-142
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• 2005

This paper describes an automatic finite element (FE) mesh generation for three-dimensional structures consisting of free-form surfaces. This mesh generation process consists of three subprocesses: (a) definition of geometric model, i.e. analysis model, (b) generation of nodes, and (c) generation of elements. One of commercial sol id modelers is employed for three-dimensional sol id structures. Node is generated if its distance from existing node points is similar to the node spacing function at the point. The node spacing function is well control led by the fuzzy knowledge processing. The Delaunay method is introduced as a basic tool for element generation. Automatic generation of FE meshes for three-dimensional sol id structures holds great benefits for analyses. Practical performances of the present system are demonstrated through several mesh generations for three-dimensional complex geometry.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.740-745
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• 2003

The so-called boundary node method (or NDIF method) that was developed by the authors has been extended for free vibration analysis of arbitrarily shaped plates with free edges. Since the proposed method is based on the collocation method, no integration procedure is needed on boundary edges of the plates and only a small amount of numerical calculation is required. A special coordinate transformation has been devised to consider the complicated free boundary conditions at boundary nodes. By the use of the special coordinate transformation, the radius of curvature involved in the free boundary conditions can be successfully dealt with. Finally, verification examples show that natural frequencies obtained by the present method agree well with those given by exact method and other analytical methods.

• Journal of Communications and Networks
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• 제18권5호
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• pp.796-805
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• 2016

In many wireless sensor network (WSN) applications, the information transmitted by an individual entity or node is of limited use without the knowledge of its location. Research in node localization is mostly geared towards multi-hop range-free localization algorithms to achieve accuracy by minimizing localization errors between the node's actual and estimated position. The existing localization algorithms are focused on improving localization accuracy without considering efficiency in terms of energy costs and algorithm convergence time. In this work, we show that our proposed localization scheme, called DV-maxHop, can achieve good accuracy and efficiency. We formulate the multi-objective optimization functions to minimize localization errors as well as the number of transmission during localization phase. We evaluate the performance of our scheme using extensive simulation on several anisotropic and isotropic topologies. Our scheme can achieve dual objective of accuracy and efficiency for various scenarios. Furthermore, the recently proposed algorithms require random uniform distribution of anchors. We also utilized our proposed scheme to compare and study some practical anchor distribution schemes.

• Radiation Oncology Journal
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• 제2권1호
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• pp.41-47
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• 1984

From March of 1979 through December of 1982, 84 Patients with supraglottic carcinoma were seen and evaluated in the Department of Therapeutic Radiology, Seoul National University Hospital. Of these, 68 patients were treated with a curative intent by employing either radiotherapy alone or a combined approach of radiotherapy Plus surgery. Sixteen patients refused to complete the treatment program. Seventy-three per cent of patients had $T_3\;and\;T_4$ lesions and $63\%$ of patients had lymph node metastasis at the time of diagnosis. Actuarial recurrence-free survival at 3 year was: Stage $I\~II\;62\;%,\;Stage\;III \;54\%,\;Stage\;IV\;18\%$, For $T_{1-2},\;T_3\;and\;T_4$ lesions, the actuarial recurrence free survival at 3 years were 50\%,\;34\;%\;and \;9\%$ respectively. Of 39 Patients with treatment failure, 29 Patients $(78\%)$ had uncontrol or ultimate recurrence at the primary site while 9 patients having lymph node recurrence, 14 patients$(21\%)$ had lymph node recurrence, and S patients had distant metastasis. It is suggested that planned combined radiotherapy is indicated for advanced but rescetable supraglottic carcinoma.

• 전산구조공학
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• 제11권1호
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• pp.251-259
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• 1998

개구부를 갖는 콘크리트 전단벽을 두께가 얇은 직사각형 평판으로 모델화하였다. 판의 두가지 경계조건에 대한 안정해석 결과를 판좌굴계수 k로 표시하였다. 경계조건이 다른 변수로는 휨으로 인한 힘/연직하중비 .alpha., 수평 전단력/연직하중비 .betha. 및 개구부의 위치 및 크기 변화이다. 유한요소법에 의한 결과를 얻기 위하여 예제의 판을 27*9의 정사각형 요소로 분할하였으며 node에서 3가지 자유도를 갖는 c.deg. 유한요소를 택하였다. 일반적으로 개구부의 크기가 증가함에 따라 판 개구부가 판 중앙에서 자유연(free edge)으로 접근할수록 좌굴계수는 감소하는 현상을 보이고 있다.

• 한국강구조학회 논문집
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• 제24권1호
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• pp.59-71
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• 2012

프리폼 구조의 노드는 용접 및 볼트 접합 특성을 반영하는 것이 어려워 구조 성능을 해석적으로 평가하는 것에는 한계가 있다. 본 연구에서는 축하중을 받는 프리폼 구조 노드의 구조 거동을 알아보고 성능을 평가하기 위해 실험을 수행하였다. 실험은 노드 중심부의 성능을 알아보기 위한 노드 볼 실험과 노드부 전체의 내력 평가를 위한 노드부 실험으로 구분된다. 노드 볼 구조 성능 평가에서는 축력에 대한 단조가력과 반복가력 실험을 하였고 노드부 구조 성능 평가에서는 단조가력 실험을 수행하였다. 실험 결과 노드 접합부 설계가 적합하므로 실제 구조물에 인장 발생 시 노드 볼이 충분한 내력을 가지며 안전할 것으로 판단되나 압축 발생 시 노드 볼 형상의 비대칭에 따른 모멘트 발생으로 내력이 저하된 현상을 보였다.

• 한국공간정보시스템학회 논문지
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• 제11권2호
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• pp.1-6
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• 2009

Localization of nodes is a key technology for application of wireless sensor network. Having a GPS receiver on every sensor node is costly. In the past, several approaches, including range-based and range-free, have been proposed to calculate positions for randomly deployed sensor nodes. Most of them use some special nodes, called anchor nodes, which are assumed to know their own locations. Other sensors compute their locations based on the information provided by these anchor nodes. This paper uses a single mobile anchor node to move in the sensing field and broadcast its current position periodically. We provide a weighted centroid localization algorithm that uses coefficients, which are decided by the influence of mobile anchor node to unknown nodes, to prompt localization accuracy. We also suggest a criterion which is used to select mobile anchor node which involve in computing the position of nodes for improving localization accuracy. Weighted centroid localization algorithm is simple, and no communication is needed while locating. The localization accuracy of weighted centroid localization algorithm is better than maximum likelihood estimation which is used very often. It can be applied to many applications.

• Journal of Communications and Networks
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• 제5권3호
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• pp.249-257
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• 2003

Ring networks are very commonly exploited among local area and metropolitan area networks (LAN/MAN), whereas cells or small fixed-size packets are widely used in synchronized ring networks. In this paper, we present an analytical method for evaluating the delay-throughput performance of a MAC protocol with multiple self-tokens in a slotted ring network under uniform traffic. In our analysis, we introduce the stationary probability, which indicates the number of packets in a node. Also, it is assumed that each node has a sufficiently large amount of self-tokens, and a slotted ring has the symmetry. The analytical results with respect to delay-throughput performance have similar values to computer simulated ones. Furthermore, in order to achieve fair access under non-uniform traffic, we propose an adaptive MAC protocol, where the number of self-tokens in a node dynamically varies, based on the number of packets transmitted within a specified period. In the proposed protocol, when the number of packets transmitted by a node within a specified period is larger than a specified threshold, the node decreases the number of self-tokens in a per-node distributed method. That results in creating free slots in the ring, thus all nodes can obtain an equal opportunity to transmit into the ring. Performance results obtained by computer simulation show that our proposed protocol can maintain throughput fairness under non-uniform traffic.