• Explosives and Blasting
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• v.22 no.3
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• pp.79-84
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• 2004

It is well accepted that modem emulsion explosives are intrinsically much less sensitive than traditional products such as dynamites or black powder. However, they have still been involved in a significant number of accidental explosions. In October 1975, Canadian Research, Limited's, Energetic Research Laboratory in Quebec exploded. Although explanations for the incident varied, one logical explanation was that the pump used in transporting the emulsion dead headed, thereby turning mechanical work in to frictional heating under a zero flow rate. There is a minimum pressure required for combustion(MBP) to propagate in emulsion explosives. A stable deflagration may lead to a deflagration-to-detonation transition(DDT) in emulsion explosives. Tests were also performed on sensitized sampled consisting of 6 to 21% waters as well as 1 to 11% aluminium powder. It was founded the emulsion explosives consisting of 6% waters had the lowest minimum homing pressure(MBP) of 3 bar, and the 21% waters were unable to achieve sustained homing at pressures as high as 100 bar. The aluminium contained explosives tested here displayed a MBP higher than that of without emulsion. It appears that this test may offer a firm ground for the classification of emulsion explosives in view of the regulating the hazards associated with the various process used for their manufacturing and transport.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.9
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• pp.763-771
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• 2014

As a preliminary study on the spray behavior characteristics of emulsified fuel, the fuel properties (viscosity, surface tension, and density) and evaporation characteristics of a fuel droplet were investigated. The emulsified fuel was made by mixing diesel and $H_2O_2$. In addition, the macroscopic spray behavior characteristics such as the spray penetrations and spray angles of the emulsified and diesel fuels were compared. The stirring condition of the emulsified fuel was a 9:1 mixture of the diesel fuel and the surfactant span 80. The mixing ratios for the hydrogen peroxide were set at EF2, EF12, EF22, EF32, EF42, EF52, EF62, EF72, EF82, and EF92. The injection pressures were set at 400, 600, 800, and 1000 bar. We found that as the mixing ratio of the hydrogen peroxide was increased from EF2 to EF52, the viscosity of the emulsified fuel increased. However, afterward, the viscosity of the emulsified fuel gradually decreased and approached the viscosity value of the diesel fuel. Therefore, generally oil-in-water emulsions were used for the hydrogen peroxide mixing ratios up to 52 (EF52), and water-in-oil emulsions were used for the hydrogen peroxide mixing ratios above 52. Finally, the spray behavior characteristics (spray penetration and spray angle) of the emulsified fuel were found to be almost independent of the mixing ratio.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.12
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• pp.346-353
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• 2020

The purpose of this study was to explore types of longitudinal changes in interactions between mothers and 4-year-old children in primary school as well as the effects on media device addiction. To explore interaction types between mothers and children, latent class growth modeling (LCGM) and BCH were used in a three-step approach. Data from the 6-10th wave of the Panel Study of Korea Children were used. First, the trajectory of the mother-child interactions was linear and decreased across time. This linear decrease was classified into the following three trajectories: high-decreasing, average-deceasing, and low-decreasing. Second, BCH was performed to examine media device addiction in each trajectory, and the findings show that children who had low initial mother-child interactions over time were more likely to experience daily disturbances in adaptive functions such as withdraw or tolerance than other groups of children. The results indicate that maximizing the quality of mother-child interactions in childhood through primary school can lower media device addiction in children.

• The Mathematical Education
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• v.63 no.1
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• pp.19-33
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• 2024

This study investigates longitudinal patterns in middle school students' mathematics interest and achievement using panel data from the 4th to 6th year of the Gyeonggi Education Panel Study. Results from the multivariate growth mixture model confirmed the existence of heterogeneous characteristics in the longitudinal trajectory of students' mathematics interest and achievement. Students were classified into four latent classes: a low-level class with weak interest and achievement, a high-level class with strong interest and achievement, a middlelevel-increasing class where interest and achievement rise with grade, and a middle-level-decreasing class where interest and achievement decline with grade. Each class exhibited distinct patterns in the change of interest and achievement. Moreover, an examination of the correlation between intercepts and slopes in the multivariate growth mixture model reveals a positive association between interest and achievement with respect to their initial values and growth rates. We further explore predictive variables influencing latent class assignment. The results indicated that students' educational ambition and time spent on private education positively affect mathematics interest and achievement, and the influence of prior learning varies based on its intensity. The perceived instruction method significantly impacts latent class assignment: teacher-centered instruction increases the likelihood of belonging to higher-level classes, while learner-centered instruction increases the likelihood of belonging to lower-level classes. This study has significant implications as it presents a new method for analyzing the longitudinal patterns of students' characteristics in mathematics education through the application of the multivariate growth mixture model.

• Journal of the Korea Convergence Society
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• v.6 no.1
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• pp.1-5
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• 2015

In this paper, we describe the design of a fusion labeling system which is controlled by the Wi-Fi signals. The Current labeling system which is used in the industry is designed to work independently on the production line not connected with internet network services. For such reasons, it is very inconvenient for the labeling system to transfer such labeling data of the production line to the server computer. We propose a labeling system connected to the Wi-Fi service being able to send real-time transmission of labeling data. This system can supply the labeling data of production line to the server computer in realtime and improve the production quality than the existing system.

• Journal of the Korea Convergence Society
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• v.7 no.1
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• pp.9-15
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• 2016

In this paper, we describe the design of a high speed data acquisition system(DAS) with STM32 processor based on Cortex-M4. The system is used for the sensor devices to collect raw data on production lines at factory and send them to the servo computer in real time. The system is designed for multi functions with universal asynchronous receiver and transmitter(UART), analog to digital converter(ADC), digital to analog converter(DAC), and general purpose input output(GPIO). those are well tested for various data acquisition and high speed motor control in real time.

• Annual Conference on Human and Language Technology
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• 2003.10d
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• pp.113-118
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• 2003

기존 문서 검색 시스템의 경우 단순히 문서 내에서 텍스트를 추출한 후 그 텍스트를 색인, 검색하는 형태를 가지고 있었다. 본 논문에서는 MS Word, Excel, HWP 등 다양한 형태의 문서에서 텍스트, 표, 이미지, 차트, 동영상 등의 문서 개체를 분석, 색인하고 이를 검색하는 시스템의 개발 방법을 제외하였다. 제안된 시스템은 문서의 내부 자료 구조를 CDML(Composite Document Markup Language)로 변환하고, 이를 색인, 저장함으로 기존의 전문 검색 시스템의 한계를 효과적으로 극복했으며, 문서 내의 검색 대상 개체로 자동 이동하고 하일라이팅 시키는 기술을 구현함으로 사용자 편익성을 높였다. 개발된 시스템의 성능을 평가한 결과, 다양한 문서 형식에 대해 평균 97% 이상의 CDML변환 성공률과 개체 검색 성공률을 보였으며, 이진 파일에서 직접 개체를 추출함으로 매우 높은 분석 및 색인 속도가 달성되었음을 확인할 수 있었다. 본 논문에서 소개된 새로운 패러다임의 문서 검색 솔루션을 통해 다양한 기술적 상업적 파급 효과가 기대되고 있다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.2
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• pp.491-496
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• 2010

This paper describes an analysis of the effectiveness for an anti-ARM technique to protect a radar system. We investigate the optimum deployment of decoy antennas which are widely using for anti-ARM and the electromagnetic field at the ARM receiver. To verify the effect of decoy antennas, we analyze the field intensity and phase at the receiver and develop a numerical simulation program using Matlab. We conduct an analysis of ARM attack in case of using multiple decoy antennas and these results can be used to decide the optimum positions of the decoys for anti-ARM.

• Journal of Satellite, Information and Communications
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• v.7 no.3
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• pp.105-109
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• 2012

In this paper, we developed an adoptable deployment method to the transmitting antennas of a ground based GPS system for aircraft. Aircraft generally uses satellite providing GPS signals for accurate position information, but transfers to ground based GPS signals time to time due to jamming signals or bad weather. The position accuracy of the ground based GPS system is highly dependent on the number and position of the GPS transmitting antennas. In this research, we found an algorism to predict the DOP due to the location of the GPS transmitting antennas and had an accurate DOP 2.5 area into 3-dimension from 0 to 10 km by 12 transmitting antennas.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.2
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• pp.235-243
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• 2010

Three-dimensional structural analysis system for nuclear containment building is presented in this paper. This system includes high-performance plate/shell elements as finite element library. It also adopts numerical modeling technique for unbonded tendon as well as bonded tendon in prestressed concrete structures. This system is constructed by connecting several in-house program to a commercial program DIANA, and then is capable of performing nonlinear analysis for ultimate pressure capacity of nuclear containment building. Finally, three-dimensional structural analysis of CANDU-type containment building is carried out in order to test the reliability of this system. These numerical results are compared with reference values, which obtained from axisymmetric structural analysis.