• The Mathematical Education
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• v.48 no.1
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• pp.33-45
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• 2009

The purpose of this article is to study characteristics of Soma Cube in combinatorial-geometric point of view, and to present basic substances and direction for efficient Soma cube activities in school mathematics upon systematical analysis of methods of finding solutions using Inclusion-Exclusion Method. We can apply Inclusion-Exclusion Method to find all possible solutions in Soma Cube activities not as trial-and-error method but as analytical method. Because Inclusion-Exclusion Method can reduce the number of problem-solving variables by making high conjunction in the choice of pieces. Soma cube pieces can be sorted as 'flat' ones and 'non-flat' ones, which would be another effective method in the manipulation of Soma Cube pieces.

• Journal of KIISE:Databases
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• v.33 no.2
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• pp.175-187
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• 2006

The data cube is an aggregation operator that computes group-bys for all possible combination of dimension attributes. %on the number of the dimension attributes is n, a data cube computes $2^n$ group-bys. Each group-by in a data cube is called a cuboid. Data cubes are often precomputed and stored as materialized views in data warehouses. These data cubes need to be updated when source relation change. The incremental maintenance of a data cube is to compute and propagate only its changes. To compute the change of a data cube of $2^n$ cuboids, previous works compute a delta cube that has the same number of cuboids as the original data cube. Thus, as the number of dimension attributes increases, the cost of computing a delta cube increases significantly. Each cuboid in a delta cube is called a delta cuboid. In this paper. we propose an incremental cube maintenance method that can maintain a data cube by using only $_nC_{{\lceil}n/2{\rceil}}$ delta cuboids. As a result, the cost of computing a delta cube is substantially reduced. Through various experiments, we show the performance advantages of our method over previous methods.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.7
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• pp.905-914
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• 1998

View factor determination is very important in thermal analysis problems with surface radiation but it is very difficult to determine view factors for complex geometries. Exact calculation of view factors for crystal growth furnace is essential due to not only its high surface temperature but the radiation shield, complicated heating system. In this study, view factor calculation algorithm is introduced and applied to cylindrical crystal growth furnace. This algorithm is based on the Hemi-Cube Algorithm and the results obtained with this algorithm show good agreements with those of analytical solution. As an application of this algorithm, temperature profiles and heating value distributions for various furnaces are calculated and the shape criteria for better furnace are suggested.

• Journal of Aerospace System Engineering
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• v.8 no.1
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• pp.42-47
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• 2014

The role of Electrical Power Subsystem (EPS) is to generate a power and distribute it to the electrical devices for the system operation. For on-orbit operation of cube satellite, it is also necessary to supply power to on-board mission devices as commercial satellite does. Recently, commercial EPS products dedicated for the cube satellite application has been developed and widely used for the power subsystem design. In this paper, a permanent magnet attitude stabilization method without external power has been introduced because it has advantage from power consumption point of view and the EPS design of cube satellite by applying the commercial EPS products has been introduced and investigated. This paper also deals with the specification of the commercial EPS products for the beginner of the cube satellite design.

• Communications of Mathematical Education
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• v.25 no.1
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• pp.207-219
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• 2011

The purpose of this article is to study characteristics of diabolical cube in geometric point of view, and to present educational materials and direction for efficient diabolical cube activities in gifted education upon systematical analysis of methods of finding solutions. We can apply inclusion-exclusion Method to find all possible combination of solutions in diabolical cube activities not as trial-and-error method but as analytical method. Through teacher's questions and problem posing in activities using diabolical cube, we systematically came up with most solution and case of all possible combinations be solution in classifying properties of pieces and combining selected pieces.

• Journal of KIISE:Databases
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• v.28 no.4
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• pp.587-595
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• 2001

Precomputation and materialization of parts. commonly called views of a data cube is a common technique in data warehouses The view is defined as the result of a query which is defined through aggregate functions In this paper we introduce the concept of fine granule view. The fine granule view is the result of a query defined through aggregate functions and the range on each dimension, where the subdivision of each dimension is based on queries access patterns. For the representation and selection of fine granule views to materialize, we define the ANO-OR cube graph and AND-OR minimum cost graph. With these structures, we propose a fine granule view materialization method. And through experiments, we evaluate the performance of the proposed method.

• 한국데이터정보과학회:학술대회논문집
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• 2003.10a
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• pp.239-247
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• 2003

Decision tree algorithms are used extensively for data mining in many domains such as retail target marketing, fraud dection, data reduction and variable screening, etc. CHAID(Chi-square Automatic Interaction Detector), is an exploratory method used to study the relationship between a dependent variable and a series of predictor variables. In this paper we propose and CHAID algorithm by cube-based sampling and explore CHAID algorithm in view of accuracy and speed by the number of variables.

• Korean Journal of Child Studies
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• v.22 no.2
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• pp.315-327
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• 2001

This study investigated young children's spatial representation of geometrical relations based on their drawings of cube buildings. One hundred seventy-six children from 3 to 6 years of ages were selected from private kindergartens and day care centers. Their drawings were classified into 6 developmental levels: level 1 - drawings show only scribbles or several circles; level 2 - drawings show plane squares from a front view; level 3 - positional relations are included in the drawings; level 4 - separate-joint relations or the general outline of a cube building are shown; level 5 - rotated drawing and an additional square for hidden faces are attempted to represent the lateral view; level 6 - parallel lines are drawn to represent 3-dimensional structures. Three-to four-year-olds were between levels 1 and 2; four-to six-year olds were between levels 3 and 4; and children over six years old were between levels 3 and 5.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.11
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• pp.1426-1433
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• 1999

Topological and kinematical studies of the singular points found in flows around a surface-mounted cube in a channel are presented. Numerical simulation was carried out using high-resolution grid systems. Singular points(saddles and nodes) were found around the cube, which satisfy the topological rules suggested by Hunt et al. As the Reynolds number increases, the structure of vortices around the cube becomes complex and the number of singular points increases. Nevertheless, the rule governing the numbers of singular points is still valid. This confirms that our simulation is correct from topological and kinematical point of view, and enables one to infer complex flow patterns in our simulation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.6
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• pp.522-528
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• 2014

A UHF/VHF full-duplex communication using monopole and dipole antenna has been widely used for cube satellite applications. This kind of communication system requires a dedicated structure panel for antenna integration, which is the one of the disadvantages of the conventional communication system from the accommodation point of view considering the extremely limited volume of the cube satellite. In this study, to maximize the accommodation efficiency of the cube satellite, the commercial UHF half-duplex antenna combined with buck converter for communication modes transition has been considered in the communication system design. Its effectiveness has been verified through link budget analysis based on the antenna specifications and satellite's operation conditions. In addition, the antenna deployment mechanism for the synchronous release of multi-antennas has also been introduced.