• Title/Summary/Keyword: 열분석적 특성

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Selecting a mother wavelet for univariate wavelet analysis of time series data (시계열 자료의 단변량 웨이블릿 분석을 위한 모 웨이블릿의 선정)

  • Lee, Hyunwook;Lee, Jinwook;Yoo, Chulsang
    • Journal of Korea Water Resources Association
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    • v.52 no.8
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    • pp.575-587
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    • 2019
  • This study evaluated the effect of a mother wavelet in the wavelet analysis of various times series made by combining white noise and/or sine function. The result derived is also applied to short-memory arctic oscillation index (AOI) and long-memory southern oscillation index (SOI). This study, different from previous studies evaluating one or two mother wavelets, considers a total of four generally-used mother wavelets, Bump, Morlet, Paul, and Mexican Hat. Summarizing the results is as follows. First, the Bump mother wavelet is found to have some limitations to represent the unstationary behavior of the periodic components. Its application results are more or less the same as the spectrum analysis. On the other hand, the Morlet and Paul mother wavelets are found to represent the non-stationary behavior of the periodic components. Finally, the Mexican Hat mother wavelet is found to be too complicated to interpret. Additionally, it is also found that the application result of Paul mother wavelet can be inconsistent for some specific time series. As a result, the Morlet mother wavelet seems to be the most stable one for general applications, which is also assured by the recent trend that the Morlet mother wavelet is most frequently used in the wavelet analysis research.

A Study on GNSS Data Pre-processing for Analyzing Geodetic Effects on Crustal Deformation due to the Earthquake (지진에 의한 측지학적 지각변동 분석을 위한 GNSS 자료 전처리 연구)

  • Sohn, Dong Hyo;Kim, Du Sik;Park, Kwan Dong
    • Journal of Korean Society for Geospatial Information Science
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    • v.23 no.1
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    • pp.47-54
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    • 2015
  • In this study, we developed strategies for pre-processing GNSS data for the purpose of separating geodetic factors from crustal deformation due to the earthquakes. Before interpreting GNSS data analysis results, we removed false signals from GNSS coordinate time series. Because permanent GNSS stations are located on a large tectonic plate, GNSS position estimates should be affected by the tectonic velocity of the plate. Also, stations with surrounding trees have seasonal signals in their three-dimensional coordinate estimates. Thus, we have estimated the location of an Euler pole and angular velocities to deduce the plate tectonic velocity and verified with geological models. Also, annual amplitudes and initial phases were estimated to get rid of those false annual signals showing up in the time series. By considering the two effects, truly geodetic analysis was possible and the result was used as preliminary data for analyzing post-seismic deformation of the Korean peninsula due to the Tohoku-oki earthquake.

Influence of Job Stressors on Flourishing and Job Engagement: Comparison Between Head Office Personnel and Foreign Subsidiary Personnel (직무스트레스 요인이 번영과 직무열의에 미치는 영향: 해외진출 기업의 국내 인력과 해외 현지법인 현지 인력 간의 비교 연구)

  • Jung, Sung Cheol
    • Asia-Pacific Journal of Business Venturing and Entrepreneurship
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    • v.12 no.2
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    • pp.137-149
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    • 2017
  • This study aims to verify culture-universal invariances and culture-particular differences in the relationship of job stress, flourishing, and job engagement. For this purpose, we selected a global korean company having a local corporation in China in order to minimize the influence of organizational factor and a self-report questionnaire survey was conducted by 141 personnels of head office and 107 personnels of chinese branch. At first, the mediating effect of flourishing on the relationship between job stress and job engagement was significant for both korean and chinese personnel. Second, regression analyses were conducted in order to demonstrate influence of detailed job stress on flourishing and job engagement. As for flourishing, decision making and responsibility factor was significant for korean personnel, and lack of social support factor and job characteristic factor were significant for chinese personnel. Regarding job engagement, lack of social support factor and job characteristic factor were significant for both two samples and decision making and responsibility factor was significant for korean personnel whereas non-significant for chinese personnel. The results could give a meaningful perspectives to companies interested in extending their business abroad. Finally, implications and limitations of the study and suggestions for future research were discussed.

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A Fundamental Study on the Correlationship between Hydration Heat and Autogenous Shrinkage of High Strength Concrete at an Early Age (초기재령 고강도콘크트의 수화발열과 자기수축 특성의 상관관계에 관한 기초적 연구)

  • Kim, Gyu-Yong;Lee, Eui-Bae;Koo, Kyung-Mo;Choi, Hyeong-Gil
    • Journal of the Korea Concrete Institute
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    • v.20 no.5
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    • pp.593-600
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    • 2008
  • In this study, to analyze the correlation between hydration heat and autogenous shrinkage of high strength concrete at an early age, hydration heating velocity and autogenous shrinking velocity as quantitative coefficients which represent the main properties of hydration heat and autogenous shrinkage were proposed. Two coefficients were calculated by statistical analysis and were equal with the regression coefficient. The complemented semi-adiabatic temperature rise test as test method to evaluate the hydration heat and autogenous shrinkage of concrete were proposed. In results of proposed test and analysis method, it was possible that early age properties of hydration heat and autogenous shrinkage of concrete were expressed numerically, and autogenous shrinkage was represented by equation with coefficients of hydration heat.

Prediction of Steady-State Stresses within Heat Affected Zone Due to Creep Mismatch in Welded Straight Pipes (직관 용접부의 크리프 특성 불균일에 따른 열영향부 정상상태 응력 예측)

  • Han, Jae-Jun;Kim, Sang-Hyun;Chung, Jin-Taek;Kim, Yun-Jae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.37 no.3
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    • pp.405-412
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    • 2013
  • This paper reports the steady-state stresses within the heat affected zone (HAZ) of a welded straight pipe subject to creep. The creep constants and exponent are varied systematically to see the effect of various mismatches in creep properties on the steady-state creep stresses, via detailed two-dimensional finite element (FE) creep analyses. The weldments consist of the base metal and weld metal with the HAZ, which are characterized using the idealized power creep laws with the same creep exponent. The internal pressure and axial loading are considered to see the effect of the loading mode. To quantify the creep stresses, a creep mismatch factor is introduced as a function of the creep constants and exponent. It is concluded that the ratio of the section-averaged stresses for a mismatched case to those for an evenmatched case are linearly dependent on the mismatch factor. The results are compared with the FE results, including the Type IV region, as well as the R5 procedure.

A Numerical Analysis on the Thermal Protection System Applied Phase Change Material (상변화물질을 이용한 열방어체계의 수치해석 연구)

  • Oh, Chang-Mook;Yoo, Yung-Joon;Min, Seong-Ki
    • Journal of the Korean Society of Propulsion Engineers
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    • v.16 no.4
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    • pp.80-86
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    • 2012
  • This study is for figuring out a possibility of realization of the thermal protection system(TPS) for temporary use under high temperature condition and improving a design of the future TPS. On this purpose, environmental condition of the system has been simplified: the boundary conditions consist of a internally heating surface and a externally heated surface which is simulating the external high temperature condition. Configuration of the system is simplified as a hexahedon. Melting characteristics of the phase change material(PCM) and air temperature variation of TPS with or without connector have been numerically analyzed and compared. As a result of numerical analysis, the heat from the internally heated surface could not be effectively transferred. Therefore, temperature of inner space has been increased.

A Study on Extinguishing Concentration of K2CO3-Zeolite Composites (K2CO3가 흡착된 합성제올라이트 구조체의 소화농도에 관한 연구)

  • Kim, Seung-Il;Shin, Chang-Sub
    • Fire Science and Engineering
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    • v.26 no.4
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    • pp.42-47
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    • 2012
  • In the study, fire extinguishing concentration of $K_2CO_3$-Zeolite composite was measured. Zeolite composite is a porous adsorbent which has small particle size, low density and anti-catalytic effect. Scanning Electron Microscopy, X-Ray diffraction and thermal analysis were also conducted to investigate the structural properties of composite. The result showed that despite of weight ratio, the extinguishing concentration of the composite was lower than pure $K_2CO_3$. The extinguishing concentration of $K_2CO_3$-Zeolite composite which has weight ratio of 7 : 3 was 5.72 times lower than that of pure $K_2CO_3$ and 1.1 times lower than that of ABC powder. The SEM and XRD patterns showed that $K_2CO_3$ was adsorbed on the Zeolite properly, and through the thermal analysis, it was founded that the composite is more effective extinguishing agent than pure $K_2CO_3$.

Research on the Torque and Starting Characteristics of a Turbopump Turbine (터보펌프 터빈의 토크 및 시동특성 연구)

  • Jeong, Eunhwan;Lee, Hang-Gi;Park, Pyun-Goo;Hong, Moongeun;Kim, Jinhan
    • Journal of the Korean Society of Propulsion Engineers
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    • v.17 no.1
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    • pp.35-41
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    • 2013
  • Torque characteristics of a turbopump turbine was analyzed using the turbine performance test result. Specific torque of the subject turbine could be expressed as a linear function of corrected rotor speed at a fixed pressure ratio and it has been confirmed by the test result. It also found that corrected rotor speed-specific torque characteristics does not change anymore if the turbine pressure ratio is set bigger than a certain value. Using the turbine torque characteristics and pyro-starter performance test results, rotational speed development behavior of the turbopump was predicted. Prediction revealed that the lap time reaching 50% of turbopump design speed is less than 0.7 second. Effect of the thermal loss between pyro-starter and turbopump was negligible.

진공상태에서의 9,10-di(2-naphthyl)anthracene (ADN) 재료의 상평형 특성 연구

  • Sim, Seop;Yun, Ju-Yeong;Kim, Jin-Tae;An, Jong-Gi;Sin, Jae-Su;Lee, Chang-Hui;Gwon, O-Hyeon
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.02a
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    • pp.150-150
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    • 2013
  • Organic Light Emitting Diode (OLED)에 사용되는 유기발광재료 9,10-di(2-naphthyl)anthracene (ADN)의 상평형 특성을 저진공에서 고진공 조건에 따라 연구하였다. ADN재료의 지속적인 가열과 압력제어가 가능한 진공시스템에서 진공도를 변화시키면서 ADN재료의 온도변화에 따른 상전이 현상을 확인하였다. 본 연구장비의 신뢰성평가를 위하여 상압에서 기존의 Differential Scanning Calorimetry (DSC) 열분석으로 측정한 ADN의 melting point와 비교하였고 각각의 진공조건에서 3회 반복 측정하여 장비신뢰성을 검증하였다. 연구결과, 0.1 Torr에서부터는 상압의 경우와 달리 ADN이 승화하는 것을 확인하였고, 예상대로 진공도가 높아질수록 상전이가 시작되는 온도가 낮아지는 것을 알 수 있었다. 이러한 결과는 기존의 DSC열분석으로는 확인할 수 없었던 고진공에서의 유기재료의 상전이 현상을 관측하였다는데 큰 의미가 있다. 향후, 이러한 방법을 활용한 고진공에서의 유기재료의 상전이 특성 관측은 유기재료를 이용한 진공 증착공정방법의 최적화와, 다양한 유기재료의 열안정성 특성 파악에 도움이 될 것으로 기대가 된다.

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Research on the Torque and Starting Characteristics of a Turbopump Turbine (터보펌프 터빈의 토크 및 시동특성 연구)

  • Jeong, Eun-Hwan;Lee, Hang-Gi;Park, Pyun-Goo;Hong, Moon-Geun;Kim, Jin-Han
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2012.05a
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    • pp.4-10
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    • 2012
  • Torque characteristics of a 75-tonf turbopump turbine was analyzed using the turbine performance test result. Specific torque of the subject turbine could be expressed as a linear function of corrected rotor speed at a fixed pressure ratio and it has been confirmed by the test result. It also found that corrected rotor speed-specific torque characteristics does not change anymore if the turbine pressure ratio is set bigger than a certain value. Using the turbine torque characteristics and pyro-starter performance test results, rotational speed development behavior of the turbopump was predicted. Prediction revealed that the lap time reaching 50% of turbopump design speed is less than 0.7 second. Effect of the thermal loss between pyro-starter and turbopump was negligible.

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