• Title/Summary/Keyword: Change Factor

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A Study On the Property and Influence Factor in Measuring of the Dynamic Stiffness of Damping Materials (바닥충격음 완충재의 동탄성계수 특성 및 측정 영향인자)

  • Kim, Kyoung-Woo;Choi, Hyon-Jung;Kang, Jae-Sik;Yang, Kwan-Seop
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2006.05a
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    • pp.1256-1259
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    • 2006
  • The purpose of this study was to investigate the current status and influence factor in measuring the dynamic stiffness of damping materials. The property of the dynamic stiffness of damping materials was tested and analysed in condition such as the size of test samples and the change of relative humidity in heating chamber. Test results showed that the dynamic stiffness of after-heating was lower than that of before-heating in most samples and the change of relative humidity in heating chamber got little influence of the dynamic stiffness. The resonant frequency of test sample decreased $2{\sim}7Hz$ as the decrease of the size of sample. Because it was increased that total mass per unit area of sample, the change of dynamic stiffness had little influence.

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The Investigation of Six Grade Students' Preconceptions about the Cause of Seasonal Change (계절 변화의 원인에 대한 초등학교 6학년 학생들의 선개념 조사)

  • Chae, Dong-Hyun
    • Journal of Korean Elementary Science Education
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    • v.30 no.2
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    • pp.204-212
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    • 2011
  • This research is about the six graders' preconceptions in elementary school about a cause of the seasonal change before learning. The result of this research is that the patterns of six graders's preconceptions in elementary school are earth's rotation, earth's revolution, the distance between the earth and the sun and the location factor between the sun and our country, which are mixed up with two more things. Especially many patterns of students explain the seasonal change of our country using the change of location of our country by earth's rotation, the location factor between the earth and the sun and the distance between the earth and the sun by earth's revolution.

Experimental Research of Change in Magnetic Flux Density Due to Load for Measuring KI (응력확대계수측정을 위한 하중에 의한 자속밀도변화의 실험적 연구)

  • Lee, Jeong-Hee
    • Journal of the Korean Society of Industry Convergence
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    • v.7 no.1
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    • pp.129-132
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    • 2004
  • In order to determine the effective way of measuring the Mode I stress intensity factor, $K_I$, by means of the alternating current potential drop(ACPD) technique for a material containing a two-dimensional surface crack, the change in magnetic flux density above the cracked specimen surface was studied experimentally. The change in magnetic flux in the air above the cracked specimen made of aluminum alloy is measured by changing the load by four-point bending. The magnetic flux in the air is almost not changed by increasing the load in teh specimen. The change in potential drop due to load is not caused by the change in electro-motive force induced in the coiled measuring system. This experimental result agree to the result of theoretical analysis in reference 7).

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The Computation of Reinforcement Length of Afforestation Slope (사면녹화 보강토공법의 보강재길이 산정에 관한 연구)

  • Park, Sik-Choon;Nam, Kwang-On;Kim, Jong-Hwan;Lee, Soo-Yang
    • Proceedings of the Korean Geotechical Society Conference
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    • 2010.03a
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    • pp.1302-1308
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    • 2010
  • This study the change of the safety factor before and after the reinforcement were compared by performing the parameter research based on the limit equilibrium analysis regarding the same cross section after carrying out the safety factor before the reinforcement on the virtual section in order to observe the change of the safety factor of the slop reinforced with the slope planting reinforced earth, and the variation of the safety factor according to the increase of the length of the reinforcement materials and the change of the slope height was analyzed. As the result, the reinforcement effect was insignificant at no more than 0.6 of L/H, the reinforcement length ratio when the reinforcement length was increased, as the increase of the safety factor was slow comparing with the non-reinforced slope. At 3.0m of the slope height, reinforcement on the slope is not necessary, and at 3.0m to 5.0m of the slope height, the inclination was not influencing at no less than 0.6 of L/H. At 5.0m to 9.0m of the slope height, the safety factor was mostly secured on the slope at 0.8 of L/H and the over-reinforced slope appeared at no less than 1.0 of L/H. Also, the safety factor increased as the slope height increases and the slope gets steeper till 0.8 of L/H, but the slope steepness affects more on the increase of the safety factor than the reinforcement material, as the reinforcing force by the reinforcement material became steady.

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Exploring the effects of speed and scale on a ship's form factor using CFD

  • Terziev, Momchil;Tezdogan, Tahsin;Demirel, Yigit Kemal;Villa, Diego;Mizzi, Simon;Incecik, Atilla
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.13 no.1
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    • pp.147-162
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    • 2021
  • The problem of predicting a ship's form factor and associated scale effects has been subject to many investigations in recent years. In this study, an attempt is made to investigate whether the form factor is influenced by a change in the ship's speed by numerically modelling a geosim series of the KCS hull form by means of a RANS solver. The turbulence dependence of the problem is also studied by altering the closure model among three widely used approaches (the k-𝜔, k-𝜔 SST, and k-𝜀 models). The results show that at very low speeds (Froude numbers in the range of 0.02-0.06) the numerical model predicts changes in the form factor of a ship between 10% and 20%, depending on the turbulence model and scale factor choices. As the speed is increased further, the form factor exhibits little change, usually in the range of 1% or less. Simulations where the Reynolds number is changed by approximately two orders of magnitude, achieved by altering the value of viscosity, confirmed that the form factor can be considered Froude-dependent only for low speeds, predicting essentially identical values when high speed cases are considered.

The Verification of Mediating Effects of Childcare Teachers' Job Satisfaction on the Relationship between Their Intention to Change Jobs and the Directors' Emotional Leadership (어린이집 원장의 감성리더십과 보육교사의 이직의도와의 관계에서 직무만족도의 매개효과 검증)

  • Cho, Hye Suk;Cho, Songyon
    • Human Ecology Research
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    • v.51 no.5
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    • pp.527-535
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    • 2013
  • The objective of this study was to investigate whether childcare teachers' job satisfaction plays a mediating role between their intention to change jobs and directors' emotional leadership. The participants of this study were 282 childcare teachers in Seoul. The instruments for this study were Director's Emotional Leadership Scale (2 factors with 18 items), Childcare Teacher's Job Satisfaction Scale (K-CTJSS, 6 factors with 40 items), and Childcare Teacher's Intention to Change Jobs Scale (1 factor with 7 items). These instruments were verified by Cronbach's ${\alpha}$ as a reliability and factor analysis as a validity. The data were analysed by Pearson's productive correlation, stepwise multiple regression and path analysis by the SPSS ver. 20.0 and AMOS ver. 20.0. The results were as follows: First, there were significant negative correlations between directors' emotional leadership and childcare teachers' intention to change jobs, and between childcare teachers' job satisfaction and their intention to change jobs, whereas there were significant positive correlations between directors' emotional leadership and childcare teachers' job satisfaction. Second, the directors' emotional leadership was explained by 22% and the childcare teachers' job satisfaction was explained by 9% of their intention to change jobs. Last, the childcare teachers' job satisfaction mediated between the directors' emotional leadership and childcare teachers' intention to change jobs.

Analysis of Rainfall-Runoff Characteristics on Bias Correction Method of Climate Change Scenarios (기후변화 시나리오 편의보정 기법에 따른 강우-유출 특성 분석)

  • Kum, Donghyuk;Park, Younsik;Jung, Young Hun;Shin, Min Hwan;Ryu, Jichul;Park, Ji Hyung;Yang, Jae E;Lim, Kyoung Jae
    • Journal of Korean Society on Water Environment
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    • v.31 no.3
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    • pp.241-252
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    • 2015
  • Runoff behaviors by five bias correction methods were analyzed, which were Change Factor methods using past observed and estimated data by the estimation scenario with average annual calibration factor (CF_Y) or with average monthly calibration factor (CF_M), Quantile Mapping methods using past observed and estimated data considering cumulative distribution function for entire estimated data period (QM_E) or for dry and rainy season (QM_P), and Integrated method of CF_M+QM_E(CQ). The peak flow by CF_M and QM_P were twice as large as the measured peak flow, it was concluded that QM_P method has large uncertainty in monthly runoff estimation since the maximum precipitation by QM_P provided much difference to the other methods. The CQ method provided the precipitation amount, distribution, and frequency of the smallest differences to the observed data, compared to the other four methods. And the CQ method provided the rainfall-runoff behavior corresponding to the carbon dioxide emission scenario of SRES A1B. Climate change scenario with bias correction still contained uncertainty in accurate climate data generation. Therefore it is required to consider the trend of observed precipitation and the characteristics of bias correction methods so that the generated precipitation can be used properly in water resource management plan establishment.

Fugitive Emission Characteristics of HFC-134a from Reefer Container (냉동컨테이너에서의 HFC-134a 탈루배출 특성에 대한 연구)

  • Kim, Eui-Kun;Kim, Seungdo;Lee, Young Phyo;Byun, Seokho;Kim, Hyerim
    • Journal of Korean Society for Atmospheric Environment
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    • v.30 no.2
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    • pp.110-118
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    • 2014
  • This paper addresses the fugitive emission factors of Reefer Container at use-phase and disposal-phase. The residual quantities and operation time of thirty nine Container were weighed, using a commercial recover of refrigerants to determine the emission factors at the use-phase. The emission factor at the disposal-phase, refrigerant is accomplished has not recycled, the residual rate was assumed that the emission factor. The average residual rate of thirty nine Container is determined to be $70.8{\pm}4.0%$. The emission factor at the use-phase is estimated to be $4.9{\pm}0.9%/yr$ in the case of using average age of 8.1 years and the average residual rate determined here. We estimate 162.7 g/yr for the average emission quantity of refrigerant per operating Container, while 2038.1 g for that per waste Container. Since the chemical compositions of refrigerant of waste Container were the same as those of new refrigerant, it is expected that the refrigerant recovered from waste Container can be reused for refrigerant.

A Study on Flow Characteristics of Branch Type Sparger in Drain Tank for Depressurization (감압용 배수탱크내의 분기형 증기분사기의 유동특성에 관한 연구)

  • 김광추;박만흥;박경석
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.13 no.5
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    • pp.356-367
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    • 2001
  • A numerical analysis on branch type sparger in drain tank for depressurization is performed to investigate the flow characteristics due to the change of design factor. As the result of this study, sparger\\`s flow resistance coefficient(K) is 3.53 at the present design condition when engineering margin for surface roughness is considered as 20%, and flow ratio into branch pipe ($Q_s/Q_i$) is 0.41. The correlation for calculating flow resistance coefficients as design factor is presented. Flow resistance coefficient is increased as section area ratio of branch pipe for main pipe and outlet nozzle diameter of main pipe decreasing, but the effects of branch angle and inlet flow rate of main pipe are small. As the change rate of ($Q_s/Q_i$)becomes larger, the change rate of flow resistance coefficient increases. The rate of pressure loss has the largest change as section area ratio changing. The condition of maximum flow resistance in sparger is when the outlet nozzle diameter ratio of main pipe ($D_e/D_i$) is 0.167, the section area ratio ($A_s/A_i$) is 0.1 and the branch angle ($\alpha$) is 55^{\circ}$.

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Analysing Productivity Change in Vietnamese Garment Industry Using Global Malmquist Index

  • MAI, Thanh Khac;NGUYEN, Van;VU, Trang Huyen Thi
    • The Journal of Asian Finance, Economics and Business
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    • v.7 no.11
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    • pp.1033-1039
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    • 2020
  • Vietnam is conducting an export-led growth model and labour-intensive industries contributing majorly to the total export value. In the context of Industry 4.0, the labour-based industries are significantly affected; hence, enhancing productivity is the key measure to maintain these industries. The garment industry contributes significantly to the total export value of Vietnam. Based on meta-frontier framework, the approach of data envelopment analysis is used to measure technical efficiency of Vietnamese garment firms and the global Malmquist TFP index is utilised to identify productivity change and its components including efficiency, technology and technical gaps between different groups of firms. The data of Vietnamese garment firms from 2013 to 2018 collected from the Vietnam General Statistic Office is used in this study. The results show that: (i) The total factor productivity of Vietnamese garment firms growth, technical progress is the main contributor; (ii) The private garment sector is the leading group; (iii) There is a large technological gap among Vietnamese garment sectors. The private and FDI garment firms have experienced a growth in all components of total factor productivity change. Meanwhile, technological progress change is the main reason to constrain the productivity growth of state-owned garment firms.