• Composites Research
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• v.17 no.2
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• pp.34-39
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• 2004

In this paper, a modified and representative unit cell model was employed to study the tensile behaviour of closed-cell metallic foams with varying spatial density distribution as well as material imperfections. The density variation was assumed to follow a statistical probability distribution of the Gaussian type. A multiple cell finite element model, utilising the modified unit cell, was developed. The model exhibits deformation patterns similar to those observed in tensile testing. The nominal stress-strain curve obtained from quasistatic tensile of the foam was compared with experimental findings and was found to be in good agreement in the scheme of maximum strength only if the appropriate density distribution and volume fraction of internal imperfections are taken into account. Moreover, maximum tensile strength of the aluminium foam was found to be more sensitive to the volume fraction of imperfection than standard deviation of the density.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.1
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• pp.80-87
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• 2009

The purpose of this study is to analyze the MAUP's effect in visibility analysis using GIS. MAUP normally occurs in the process in terrain spatial analysis including visibility analysis. There are two different types of grid data(based on digital map and Digital Terrain Elevation Data) and 10 different types of areal units are made for modeling, such as $5m{\times}5m,\;10m{\times}10m,\;15m{\times}15m,\;20m{\times}20m,\;25m{\times}25m,\;30m{\times}30m,\;35m{\times}35m,\;40m{\times}40m,\;45m{\times}45m,\;50m{\times}50$. By analyzing the result, it was possible to observe varying viewshed areas according to different grid cell sizes and the viewshed area did not varied linearly as expected. From a general point of view, smaller unit data map out the real world in more detail, but the results of modeling do not always reach a good conclusion when data are used in modeling for terrain analysis because of the MAUP' effect. The grid cell sizes of 30m or less seems to be adequate for visibility analysis, including terrain analysis considering vegetation heights.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.8
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• pp.783-789
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• 2002

In this paper, V-band MMIC coupled oscillator arrays are presented. In the proposed array, two push-pull patch antennas are synchronized by using strong electromagnetic coupling between two antennas. As a result, total size of the array is reduced and the array can be integrated in a single chip. To verify proposed array concept, two 1$\times$2 arrays are designed and fabricated using standard 0.15 um gate length pHEMT MMIC process. The circuits are mounted in an oversized waveguide and measured. The first array shows 0.5 dBm at 56.372 GHz and the second one has an output of 5.85 dBm at 60.147 GHz.

• Journal of the Institute of Convergence Signal Processing
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• v.10 no.2
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• pp.127-131
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• 2009

In the digital waveguide theory, traveling waves are represented by general solution to the wave equation that is second-order linear partial differential equation. The movement of these waves can be implemented using only delay lines. An unit delay in the general digital waveguide describes a sampling time interval. However, in the space-based digital waveguide the unit delay implies the spatial sampling distance. In consideration of these differences between two models, it is known that the space-based digital waveguide model is adequate to synthesize pitch-shifted sounds such as vibrato because the propagation distance can be directly control. In this paper, the time-based digital waveguide model which also synthesizes pitch-shifted sounds is proposed and compared with space-based digital waveguide.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.297-302
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• 2002

The subsystems of two channel correlation radiometer such as RF front-end, IF and LF unit, LO unit, software based I/Q demodulator and complex correlator are characterized and their performance is analyzed in this paper. The limited hardware calibration method and receiver design consideration are discussed. The receiver architecture of 37GHz correlation radiometer is integrated. The designed radiometer employs a single-sideband superheterodyne receiver. The center frequency of the radiometer is 37 GHz and IF center frequency is 1.95 GHz with the equivalent noise bandwidth of 79.6 MHz. The receiver has less than 4.2 dB noise figure which is calculated by the Y-factor method and its gain can be adjusted from 60 dB to 80 dB.

• Journal of the Korean Institute of Rural Architecture
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• v.23 no.3
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• pp.9-18
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• 2021

This paper conducted a survey of residents and public officials for the projects to make smart-city plans of Geumsan-gun. In introduction, several domestic and foreign cases related to smart-city projects were Investigated. To initiate the smart-city project of Geumsan-gun, the local status of Geumsan-gun was investigated regarding various aspects of natural, social, urban environment and smart-city facilities. The results of this survey are as follows: Overall, more than half of survey respondents said they had satisfaction of their housing quality. Several problems in their residence areas, such as insufficient welfare systems, shortage of parking spaces, industrial infrastructure, were reported. Meanwhile, the survey result indicated that tourism and leisure facilities, health care support systems, industries promote the economy and job market of the area. An interview with public official is also important to select the relevant meaningful projects and regional issues. Three models for each spatial unit were proposed in Geumsan-gun based on the natural, agricultural, and geographical environment. In result, the three smart-city models are categorized as urban type(large area), complex city type(medium area), and smart village type(small area)

• Journal of the Korean Institute of Educational Facilities
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• v.26 no.5
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• pp.17-23
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• 2019

The classroom is a learning space where students live mainly in school, and it is the most important space within the entire educational space of the school. Although our educational system has been trying to revise and change the curriculum many times, it still does not provide space for the educational concept of modern society. The impact of the abolished 'school facility standard design' in 1992 is still evident in the design of school facilities at present. Specifically, the uniformity of the educational space, the rigid boundary of the classroom unit, the blockage between the school facility and the outside, and the separation due to the break of the inner and outer spaces. In the future, we need a flexible space that can contain the contents of the future education, and it is necessary to study the composition and type of educational space that can escape uniformity and spatial breakdown. In this paper, we analyze the successful cases of Irvine school facilities and examine the type and composition of classroom space, and it will be a task to find the direction and change of thinking about our educational space.

• Journal of the Korean Society of Safety
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• v.39 no.1
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• pp.96-103
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• 2024

The demand for mass calculation of offsite consequence analysis to conduct exhaustive single-unit or multi-unit Level 3 PSA is increasing. In order to perform efficient offsite consequence analyses, the Korea Atomic Energy Research Institute is conducting model optimization studies to minimize the analysis time while maintaining the accuracy of the results. A previous study developed a model optimization method using efficient plume segmentation and verified its effectiveness. In this study, we investigated the possibility of optimizing the model through particle size distribution setting by checking the reduction in analysis time and deviation of the results. Our findings indicate that particle size distribution setting affects the results, but its effect on analysis time is insignificant. Therefore, it is advantageous to set the particle size distribution as fine as possible. Furthermore, we evaluated the effect of multithreading and confirmed its efficiency. Future optimization studies should be conducted on various input factors of offsite consequence analysis, such as spatial grid settings.

• Journal of Broadcast Engineering
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• v.14 no.6
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• pp.796-806
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• 2009

SVC (Scalable Video Coding) is a new video coding standard to provide convergence media service in heterogeneous environments with different networks and diverse terminals through spatial-temporal-quality combined flexible scalabilities. This paper presents the performance analysis on packet loss in the delivery of SVC over IP networks and an efficient adaptation method to packet loss caused by buffer overflow. In particular, SVC with MGS (Medium Grained Scalability) as well as spatial and temporal scalabilities is addressed in the consideration of packet-based adaptation since finer adaptation is possible with a sufficient numbers of quality layers in MGS. The effect on spatio-temporal quality due to the packet loss of SVC with MGS is evaluated. In order to minimize quality degradation resulted by packet loss, the proposed adaptation of MGS based SVC first sets adaptation unit of AU (Access Unit) or GOP corresponding to allowed delay and then selectively discards packets in order of importance in terms of layer dependency. In the experiment, the effects of packet loss on quantitative qualities are analyzed and the effectiveness of the proposed adaptation to packet loss is shown.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.2503-2510
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• 2014

This study chiefly aims to find out the efficient ways of designing community facility convertible to refuge in case of emergency. In order to reach this goal, this study analyzed (1) definition of terminologies regarding disaster and refuge space, (2)present situation of regarding acts and standards, (3)function and spatial specialties of existing community facilities. Besides, in order to clarify the efficient design methods of 'function-convertible-type' community facility, this study executes archival research on (1)spatial requirements, (2)methods of designing futuristic community facility. When making design directives of community facilities, it is important to consider (1)vertical integration of rescue related function, (2)spatial division and architectural installation concerning privacy, (3)proper layout of locker room, shower room, toilet, etc. (4)appropriate size of unit space. It is desirable to execute the refuge function with minimum psychological anxiety in case of disaster through design guideline for 'function-convertible-type' community facility.