• KIPS Transactions on Software and Data Engineering
• /
• v.3 no.11
• /
• pp.479-486
• /
• 2014

MapReduce is a programing model used for parallelly processing a large amount of data. To analyze a large amount data, the data cube is widely used, which is an operator that computes group-bys for all possible combinations of given dimension attributes. When the number of dimension attributes is n, the data cube computes $2^n$ group-bys. In this paper, we propose an efficient method for computing data cubes using MapReduce. The proposed method partitions $2^n$ group-bys into $_nC_{{\lceil}n/2{\rceil}}$ batches, and computes those batches in stages using ${\lceil}n/2{\rceil}$ MapReduce jobs. Compared to the existing methods, the proposed method significantly reduces the amount of intermediate data generated by mappers, so that the cost of sorting and transferring those intermediate data is reduced significantly. Consequently, the total processing time for computing a data cube is reduced. Through experiments, we show the efficiency of the proposed method over the existing methods.

• International Journal of Concrete Structures and Materials
• /
• v.10 no.2
• /
• pp.163-175
• /
• 2016

This paper presents a revised procedure for computation of double-K fracture parameters of concrete split-tension cube specimen using weight function of the centrally cracked plate of finite strip with a finite width. This is an improvement over the previous work of the authors in which the determination of double-K fracture parameters of concrete for split-tension cube test using weight function of the centrally cracked plate of infinite strip with a finite width was presented. In a recent research, it was pointed out that there are great differences between a finite strip and an infinite strip regarding their weight function and the solution of infinite strip can be utilized in the split-tension specimens when the notch size is very small. In the present work, improved version of LEFM formulas for stress intensity factor, crack mouth opening displacement and crack opening displacement profile presented in the recent research work are incorporated. The results of the double-K fracture parameters obtained using revised procedure and the previous work of the authors is compared. The double-K fracture parameters of split-tension cube specimen are also compared with those obtained for standard three point bend test specimen. The input data required for determining double-K fracture parameters for both the specimen geometries for laboratory size specimens are obtained using well known version of the Fictitious Crack Model.

• Journal of Astronomy and Space Sciences
• /
• v.30 no.4
• /
• pp.335-344
• /
• 2013

TRiplet Ionospheric Observatory-CubeSat for Ion, Neutron, Electron & MAgnetic fields (TRIO-CINEMA) is a CubeSat with 3.14 kg in weight and 3-U ($10{\times}10{\times}30$ cm) in size, jointly developed by Kyung Hee University and UC Berkeley to measure magnetic fields of near Earth space and detect plasma particles. When a satellite is launched into orbit, it encounters ultra-high vacuum and extreme temperature. To verify the operation and survivability of the satellite in such an extreme space environment, experimental tests are conducted on the ground using thermal vacuum chamber. This paper describes the temperature control device and monitoring system suitable for CubeSat test environment using the thermal vacuum chamber of the School of Space Research, Kyung Hee University. To build the chamber, we use a general purpose thermal analysis program and NX 6.0 TMG program. We carry out thermal vacuum tests on the two flight models developed by Kyung Hee University based on the thermal model of the TRIO-CINEMA satellite. It is expected from this experiment that proper operation of the satellite in the space environment will be achieved.

• Journal of the Korean Society for Precision Engineering
• /
• v.24 no.9
• /
• pp.148-157
• /
• 2007

A new method which uses distance fields scheme and marching cube algorithm is proposed in order to get an accurate offset model of arbitrary shapes composed of triangular net. In the method, the space bounding the triangular net is divided into smaller cells. For the efficient calculation of distance fields, valid cells which will generate a portion of offset model are selected previously by the suggested detection algorithm. These valid cells are divided again into much smaller voxels which assure required accuracy. At each voxel distance fields are created by calculating the minimum distances between corner points of voxels and triangular net. After generating the whole distance fields, the offset surface were constructed by using the conventional marching cube algorithm together with mesh smoothing scheme. The effectiveness and validity of this new offset method was demonstrated by performing numerical experiments for the various types of triangular net.

• Wind and Structures
• /
• v.8 no.1
• /
• pp.49-60
• /
• 2005

A tornado changes its wind speed and direction rapidly; therefore, it is difficult to study the effects of a tornado on buildings in a wind tunnel. The status of the tornado-structure interaction and various models of the tornado wind field found in literature are surveyed. Three dimensional computer modeling work using the turbulence model based on large eddy simulation is presented. The effect of a tornado on a cubic building is considered for this study. The Navier-Stokes (NS) equations are approximated by finite difference method, and solved by an semi-implicit procedure. The force coefficients are plotted in time to study the effect of the Rankine combined vortex model. The tornado is made to translate at a $0^{\circ}$ and $45^{\circ}$ angle, and the grid resolution is refined. Some flow visualizations are also reported to understand the flow behavior around the cube.

• Korean Journal of Computational Design and Engineering
• /
• v.19 no.2
• /
• pp.103-110
• /
• 2014

Engineering changes are indispensable engineering and management activities for manufactures to develop competitive products and to maintain consistency of its product data. Analysis of engineering changes provides a core functionality to support decision makings for engineering change management. This study aims to develop a method for analysis of engineering changes based on On-Line Analytical Processing (OLAP), a proven database analysis technology that has been applied to various business areas. This approach automates data processing for engineering change analysis from product databases that follow an international standard for product data management (PDM), and enables analysts to analyze various aspects of engineering changes with its OLAP operations. The study consists of modeling a standard PDM database and a multidimensional data model for engineering change analysis, implementing the standard and multidimensional models with PDM and data cube systems and applying the implemented data cube to core functions of engineering change management, the evaluation and propagation of engineering changes.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.35 no.12
• /
• pp.1135-1142
• /
• 2007

STSAT-2 has an on-board satellite retroreflector array for precise orbit determination. Satellite retroreflector array reflects photon emitted from laser and uses to determine precisely the distance from ground station to satellite by the round-trip travel time of photon. The retroreflector array of protoflight model has been developed and verified through environmental tests. This paper describes the protoflight model of retroreflector array and reports environmental test results. The environmental tests of protoflight model retroreflector array were performed successfully without damage of corner cube prism occurred in engineering model development.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.42 no.4
• /
• pp.106-115
• /
• 2019

A sharing economy has emerged through today's trust-building mechanisms, and a sharing economy is called a future economic model through a positive future market prospect. In this context, while the overseas sharing economic business is becoming a global trend, the domestic sharing economic business is busy following the global trend. The purpose of this study is to investigate the development direction of sharing economic business in Korea. First, the sharing economic cases of 50 oversea and domestic businesses were analyzed by time series analysis. Next, a cross-country analysis to analyze the business distribution and KCERN's sharing economic model through sharing economic cube model was conducted. Finally, profit model analysis through business case study and the relationship between the derived factors were investigated. As a result of the analysis, this study found comparative trends between overseas and domestic including differences in cultural and institutional environments and profit models. This study suggested directions for domestic sharing economy business.

• Proceedings of the KIEE Conference
• /
• 1986.07a
• /
• pp.385-388
• /
• 1986

• The Journal of the Acoustical Society of Korea
• /
• v.15 no.5
• /
• pp.73-81
• /
• 1996

In multiprocessor systems with multiple processors and memories, efficient communication between processors and memories is critical for high performance. Various types of multistage networks have been proposed. The economic feasibility and the improvements in both computing throughput and fault tolerance/diagnosis have been some of the most important factors in the development of these computer systems. In this paper, we present an efficient algorithm for the diagnosis of generalized cube interconnection networks with a fan-in/fan-out of 2. Also, using the assumed fault model present total fault diagnosis by generating suitable fault-detection and fault-location test sets for link stuck fault, switching element fault in direct/cross states, including broadcast diagnosis methods based on some basic properties or generalized cube interconnection networks. Finally, we illustrate some example.