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Characteristics of Elementary Students따 Conception of Temperature with their Heat Conception (초등학생의 열 개념에 따른 온도 개념의 특성)

  • 권성기;김익진
    • Journal of Korean Elementary Science Education
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    • v.22 no.1
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    • pp.15-28
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    • 2003
  • The purpose of this study was to explore the relationships between the concept of heat and that of temperature for elementary students. Eight multiple choice type questions with explanation of reasons for selection were developed based on previous researches and the analysis of science curriculum for elementary students. The students of 9, 10, 11 years(n=292) were selected from two elementary schools in Taegu City. The responses of students' multiple choice and their explanations were analysed in each items χ² test used for the relationships between types of heat and temperature conceptions Half of elementary student could discriminate the two terms of heat and temperature, majority of them thought that heat is likely to be hot and temperature is the quantity of heat, which is not based on scientific conception. Elementary students thinkings about heat could be classified with material type of heat and molecular kinematics type. Material type of heat were more popular than with molecular kinematics type, although the latter is increased. Majority of students answered correctly in qualitative questions of mixing of hot and cold water, but about only one third of them answers in quantitative questions. Subtraction of cold temperature from hot temperature was the most popular explanation, even though one-quarter of students summed up the two temperature in quantitative situation of mixing hot and cold waters. Those who thought heat as the molecular kinetic responded more correctly in most difficult questions than those who as the material. Therefore, we concluded that the types of heat conceptions affected the concept formation of temperature.

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Development of Material Switching System for Microstructure with Multiple Material in Projection Microstereolithography (전사방식 마이크로 광 조형에서 복합 재료의 미세구조물 제작을 위한 수지 교한 시스템 개발)

  • Jo, Kwang-Ho;Park, In-Baek;Ha, Young-Myoung;Kim, Min-Sub;Lee, Seok-Hee
    • Journal of the Korean Society for Precision Engineering
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    • v.28 no.8
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    • pp.1000-1007
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    • 2011
  • For enlarging the applications of microstereolithography, the use of diverse materials is required. In this study, the material switching system (MSS) for projection microstereolithography apparatus is proposed. The MSS consists of three part; resin level control, resin dispensing control, and vat level control. Curing characteristic of materials used in fabrication has been identified. Through repeated fabrication of test models, the critical fabrication error is investigated and a possible solution to this error is suggested. The developed system can be applied to improve the strength of microstructure and extended to fabricate an array of microstructures with multiple materials.

Numerical Analysis of Deformation Characteristics in the Double-Layer Liner According to Explosive Material Distribution (이중층 라이너에서 폭발 재료 분포에 따른 변형 특성 수치해석)

  • Mun, Sang Ho;Kim, See Jo;Lee, Chang Hee;Lee, Seong
    • Journal of the Korea Institute of Military Science and Technology
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    • v.19 no.5
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    • pp.618-628
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    • 2016
  • The development of new concepts of liners is required in order to effectively neutralize the enemy's attack power concealed in the armored vehicles. A multiple-layer liner is one of possibilities and has a mechanism for explosion after penetrating the target which is known as "Behind Armor Effect." The multiple-layer explosive liner should have sufficient kinetic energy to penetrate the protective structure and explosive material react after target penetration. With this in mind, double-layer liner materials were obtained by cold spray coating methods and these material properties were experimentally characterized and used in this simulation for double-layer liners. In this study, numerical simulations in the three different layer types, i.e., single, A/B, A/B/A in terms of the layer location were verified in terms of finite element mesh sizes and numerical results for the jet tip velocity, kinetic energy, and the corresponding jet deformation characteristics were analysed in detail depending on the structure of layer types.

Material Maintenance Information System for Electric Multiple Unit (도시철도 차량 유지보수를 위한 자재시스템 정보화에 대한 연구)

  • Ahn, Tae-Ki
    • Proceedings of the KIEE Conference
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    • pp.241-243
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    • 2006
  • To supply the materials the right time, and the right place, it is required some information maintenance system to manage this procedure effectively. In this paper, we represent the standard products classification for EMU and the materials maintenance information system to manage the parts used EMU maintenance efficiently. The standard material classification is matched to G2B code made by the Supply Administration. The implemented material information system can perform various functions such as the inquiry of the number of stocks, the demand of the materials, and etc.

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Controlling of detonation strength through inserted gaps in multi-material shock physics simulation (화약내 Gap을 통한 폭발력 제어 가능성에 대한 수치해석적 연구)

  • Lee, Jinwook;Yoh, Jai-ick
    • 한국연소학회:학술대회논문집
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    • pp.275-278
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    • 2012
  • We investigate the interaction between the propagation of detonation and inserted gaps in the high explosive. The Eulerian-based multi-material simulation code validated through comparison with experimental results was used. A series of gap materials is used to understand the detonation propagation characteristic in the presence of multiple gaps.

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Braking Characteristics of Wet-type Multiple Disc Brakes on Friction Materials (마찰재에 따른 휠굴삭기용 습식 다판 디스크 브레이크의 제동특성)

  • Bae, Myung-Ho;Cho, Yon-Sang
    • Tribology and Lubricants
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    • v.25 no.6
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    • pp.381-386
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    • 2009
  • In general, a brake system of axle for heavy duty machine as a wheel excavator makes use of wettype multiple disk brakes. These disk bakes are very important parts of heavy duty machine because they are dvanced in durability and braking power, and can be designed compactly. Thus, we adesigned and made wettype multiple disk brakes of axle for the wheel excavator to be localization of these imported all. In this study, wet multiple disk brakes were made a comparative test with the 3 types materials of friction disk by the SAE No.2 dynamometer. The friction characteristics were measured and analyzed to decide a suitable material as wear depth of friction disk and dynamic and static friction coefficient on temperature of oil and applied pressure.

Braking Characteristics of Friction Disk made of Carbon Paper for Wet-type Multiple Disk Brakes of Crane Turning Decelerator (크레인 선회감속기의 습식 다판 브레이크를 위한 카본 페이퍼 마찰 디스크의 제동 특성)

  • Cho, Yonsang;Bae, Myongho
    • Tribology and Lubricants
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    • v.28 no.3
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    • pp.112-116
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    • 2012
  • wet-type multiple disk brakes are very important parts of turning decelerator for deck crane, because they are advanced in durability and braking power, and can be designed compactly. Thus, we designed and made wet-type multiple disk brakes of turning decelerator for deck crane to be localization of these imported all. In this study, wet multiple disk brakes were made a comparative test with the 2 types materials of friction disk by the SAE No.2 dynamometer. The friction characteristics were measured and analyzed to decide a suitable material as wear depth of friction disk and dynamic and static friction coefficient.

Estimation of Flowability and Strength in Controlled Low Strength Material Using Multiple Regression Analysis (다중회귀분석을 이용한 CLSM의 유동성 및 강도 특성 예측)

  • Han, WooJin;Lee, Jong-Sub;Byun, Yong-Hoon
    • Journal of the Korean Geoenvironmental Society
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    • v.18 no.12
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    • pp.65-75
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    • 2017
  • Flowability and strength with curing time of controlled low-strength material (CLSM) are required differently according to the construction purpose. In this paper, the flowability and strength were estimated from the mixing ratio of CLSM using multiple regression analysis to design the CLSM. The flow values and strength at 12 hrs and 7days were measured in accordance with the mixing ratio of CLSM which consists of 7 different materials, such as CSA expansive agent, ordinary Portland cement, fly ash, sand, silt, water, and accelerator. The multiple regression was performed with the proportions of each material of CLSM as independent variables and the measured properties as dependent variables using SPSS Statistics 23 which is a statistical analysis program. The regression coefficients were estimated from the first to third order equation models for the materials. From the results, the third order model for the flow values and the first order models for 12hrs and 7days strength are the most appropriate models. This study suggests that the mixing ratio required for constructions may be effectively estimated from the regression models about the characteristics of CLSM, before performing experimental tests.

Effect of Strain Rate and Material Hardness on Residual Stress in Multiple Impact Shot Peening (다중충돌 쇼트피닝에서 변형률 속도와 소재 경도가 잔류응력에 미치는 영향에 관한 연구)

  • Kim, Tae-Woo;Yang, Zhao-Rui;Na, Doo-Hyun;Lee, Young-Seog
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.35 no.11
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    • pp.1369-1375
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    • 2011
  • Shot ball impacts to materials cause residual compressive stress on their surfaces. Improving the fatigue strength of a material that has this residual compress stress is the purpose of the shot peening process. A numerical study was performed to evaluate the effect of the strain rate sensitivity and hardness of the shot ball on the residual compressive stress. We calculated the residual compressive stress due to multiple impact shot peening using ABAQUS 6.9-1. AISI 4340 steel was the material used in this study. We compared the effects of high strain rate sensitivities and low strain rate sensitivities and found that when the material's sensitivity to the strain rate increased, the residual compressive stress decreased. In addition, the residual compressive stress of low-hardness material is higher than that of high-hardness material.

Optimization of Device Process Parameters for GaAs-AlGaAs Multiple Quantum Well Avalanche Photodiodes Using Genetic Algorithms (유전 알고리즘을 이용한 다중 양자 우물 구조의 갈륨비소 광수신소자 공정변수의 최적화)

  • 김의승;오창훈;이서구;이봉용;이상렬;명재민;윤일구
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.14 no.3
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    • pp.241-245
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    • 2001
  • In this paper, we present parameter optimization technique for GaAs/AlGaAs multiple quantum well avalanche photodiodes used for image capture mechanism in high-definition system. Even under flawless environment in semiconductor manufacturing process, random variation in process parameters can bring the fluctuation to device performance. The precise modeling for this variation is thus required for accurate prediction of device performance. The precise modeling for this variation is thus required for accurate prediction of device performance. This paper will first use experimental design and neural networks to model the nonlinear relationship between device process parameters and device performance parameters. The derived model was then put into genetic algorithms to acquire optimized device process parameters. From the optimized technique, we can predict device performance before high-volume manufacturign, and also increase production efficiency.

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