• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.5
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• pp.577-582
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• 2015

This paper is the fundamental study for the application of cold storage system to the transportation equipment by sea and land. This numerical study presents the solid-liquid phase change phenomenon of calcium chloride solution of 30wt %. The governing equations are 1-dimensional unsteady state heat transfer equations of $1^{st}$ order partial differential equations. This type of latent heat storage material is often usable in fishery vessel for controlling the temperature of container with constant condition. The governing equation was discretized with finite difference method and the program was composed with Mathcad program. The main parameters of this solution were the initial temperature of heat storage material, ambient temperature of cold air and the velocity of cold air. The data of boundary layer thickness becomes thin with the increasing of cold air flowing velocity and also the heat storage completion time become shorten.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.3
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• pp.299-305
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• 2010

In general, the flexible forming die that has been used in the flexible forming process has the identical punch size; hence, its flexibility is relatively low because the range of allowable curvature radii is limited due to the uniform punch tip radius. Hence, a conceptual design of a sectional flexible die is presented for enhancing the flexibility of the forming process. Two punches of different sizes are used to configure the arbitrary forming surface. For a forming region with a relatively large curvature radius, a large punch array block is used; on the other hand, for the forming regions with small curvature radii, a small punch block is used. The cross-sectional profiles are compared with the target shape for evaluating the effectiveness of the process. Consequently, it is confirmed that the sectional flexible die can be used along with a combination of punch blocks of different sizes for manufacturing objective surfaces of complex shapes.

• Korean Journal of Optics and Photonics
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• v.26 no.1
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• pp.9-16
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• 2015

We have developed ellipsometry lidar and measured aerosol and ice-cloud characteristics. To measure a full normalized backscattering phase matrix (NBSPM) composed of nine elements, we have designed an optical system with three kinds of transmission and three kinds of reception, composed of ${\lambda}/2$ waveplate, ${\lambda}/4$ waveplate and empty optic. To find systematic optical errors, we used clean day middle-altitude (4-6km) lidar signals for which the aerosol's concentration was small and its orientation chaotic. After calibrating our lidar system, we have calculated NBSPM elements scattered from an aerosol and from an ice cloud. In the case of an aerosol, we found that the off-diagonal values $m_{12},{\ldots},m_{34}$ of the NBSPM are smaller than those for a cirrus cloud. Also, the off-diagonal values of the NBSPM from a cirrus cloud depend on atmospheric conditions.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.12
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• pp.1380-1387
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• 2012

The transmit/receive(T/R) module is a key component in the active phased array system. The brick-type T/R module has been widely used and the miniaturization has been an important factor to get the flexibility of the system configuration. For the miniaturization, multi-function chips(MFC) having a common leg configuration are suitable to reduce the number of required MMICs and a high isolation between transmit and receive paths is necessary for the high gain T/R modules. In this work, we propose a bias timing scheme for the compact T/R module and show the optimum timing based on measurements, in order to improve the feed-back path loop problem and the consequent isolation problem of the common leg configuration. We have implemented high power(7 W/channel) and high T/R gain(35 dB transmit and 30 dB receive gains) within the half size($140{\times}80{\times}16mm^3$) of the conventional T/R modules.

• Journal of KIISE:Databases
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• v.31 no.3
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• pp.331-339
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• 2004

XML has got to be a new standard for data representation and exchanging by its many good points, and the core part of many new researches and emerging technologies. However, the self-describing characteristic, which is one of XML's good points, caused the spreading of XML documents with different structures, and so the need of the research for the effective XML-document search has been proposed. This paper is for the analysis of the problem in BitCube, which is a bitmap indexing that shows high performance grounded on its fast retrieval. In addition, to resolve the problem of BitCube, we did design and implement xPlaneb(XML Plane Web) which it a new 3-dimensional bitmap indexing made of linked lists. We propose an effective information retrieval technique by replacing BitCube operations with new ones and reconstructing 3-dimensional array index of BitCube with effective nodes. Performance evaluation shows that the proposed technique is better than BitCube, as the amount of document increases, in terms of memory consumptions and operation speed.

• Journal of the Korean Wood Science and Technology
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• v.36 no.3
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• pp.24-29
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• 2008

Numerical analysis model was used to analyse the behaviors of multiple bolted connections. Axial-bending element was supposed as basic model, and the effects of frame members and steel fasteners were classified for the behavior analysis. In the condition only two bolts were used, the traditional analytical methods, which show somewhat accuracy, have some advantages more than numerical analysis that need many time consuming, However, more many bolts were used in practical field condition. Also, it is impossible to analyse the behaviors of various bolts layouts and arrangements conditions by traditional analytical methods. Therefore, there is only numerical analysis method for the accurate behavioranalysis on the practical bolted connection condition. Therefore, numerical analysis method was applied on the various multiple bolted connections. On the result exactness and the reflection of connection condition, numerical analysis method showed the superiority more than widely used traditional empirical analysis methods as yield model.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.26 no.1
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• pp.85-91
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• 2008

When a large sparse matrix is calculated for a horizontal geodetic network adjustment, it needs to go through the process of matrix reordering for the efficiency of time and space. In this study, several reordering methods for sparse matrix were tested, using Sparse Matrix Manipulation System(SMMS) program, total processing time and Fill-in number produced in factorization process were measured and compared. As a result, Minimum Degree(MD) and Mutiple Minimum Degree(MMD), which are based on Minimum Degree are better than Gibbs-Poole-Stockmeyer(GPS) and Reverse Cuthill-Mckee(RCM), which are based on Minimum Bandwidth. However, the method of the best efficiency can be changed dependent on distribution of non-zero elements in a matrix. This finding could be applied to heighten the efficiency of time and storage space for national datum readjustment and other large geodetic network adjustment.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.10
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• pp.687-694
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• 2019

A circular composite spar in the wing of ultra-light aircraft is subjected to both bending moment and transverse shear loads. However, the beam being used in the aircraft may be inefficient because the design would not take into account the characteristics of the circular tube that supports the bending moment in top and bottom arc parts and the transverse load in left and right ones. Therefore, it is necessary to efficiently fabricate the circular tube beam by properly selecting the stacking sequences or the laminated composite structure. In order to increase both bending and transverse shear strengths of the beams, in this study, a cross-section of circular tube is divided into four arcs: top, bottom, left and right ones. The commercial program, MSC/NASTRAN is used to calculate vertical displacement and the normal and shear strains with variation of parameters such as division angle of arc and fiber orientation. Based on the results, the effective parameters for the new circular composite beam are presented to increase its bending and shear strengths.

• Journal of Convergence for Information Technology
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• v.7 no.2
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• pp.53-58
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• 2017

This paper describes the design of a simulator for analyzing the accuracy of a correlative interferometer(CI) direction finder. CI direction finder is robust to noise, so it is often used in aircraft or ships where complex antenna installation is required, and the direction finding accuracy is very high. When the radio wave is incident at a specific azimuth angle, the phase difference calculated in a noiseless environment and the phase difference measured in a real environment with noise are fused to estimate the largest correlation coefficient as the azimuth angle of the radio wave. The simulator receives RF frequency, the number of antennas, the antenna coordinates, the transmission signal intensity, the bandwidth of the receiver, the gain and the payload effect, and calculates the direction finding accuracy of 0-360 degrees azimuth and 0-60 degree elevation with 0.5 degree. accuracy.

• Korean Journal of Plant Taxonomy
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• v.34 no.4
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• pp.297-319
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• 2004

Morphological characters of 14 taxa in 6 sections Ischnostachya(one taxon), Anomalae(one taxon), Capitellatae (five taxa), Debiles (one taxon), Capillares (one taxon) and Molliculae (five taxa) of genus Carex (Cyperaceae) were reexamined. The epidermal patterns of perigynium, achene and leaf were investigated using by using a scanning eletron microscope (SEM) and a light microscope (LM). Morphological characters such as rhizome, spike, width of leaf, leaf sheath, involucre, involucre sheath, beak of perigynium, perigynium shape, and leaf epidermal patterns were useful for the identification of observed fourteen taxa. The number of spike, arrangement of psitillate or staminate spike and presence of bract were very useful characters to divide the treated 14 taxa into two groups. A key based on data was presented here.