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‘인식된 짐스러움’과 ‘좌절된 소속감’이 청소년 자살생각에 미치는 영향
하정미(Ha Jung-Mi),설연욱(Seol Yeon-Uk),좌문경(Jwa Mun-Gyeong) 경성대학교 사회과학연구소 2010 社會科學硏究 Vol.26 No.4
본 연구에서는 조이너의 대인관계 이론에서 설명하고 있는 ‘인식된 짐스러움’과 ‘좌절된 소속감’이라는 두 가지 변수가 청소년의 자살생각에 어떤 영향을 미치는지를 살펴보고자 경상남도 지역의 중학교 3학년 그리고 고등학교 1, 2학년 990명을 대상으로 설문 조사를 실시하였다. 연구결과, 조사대상자의 성별, 가정의 경제적 수준에 따라 자살생각에 유의미한 차이가 있었으며, 두 독립변수인 ‘인식된 짐스러움’과 ‘좌절된 소속감’은 자살생각에 대해 주효과와 상호작용효과 모두 가지는 것으로 파악되었다. 이상과 같은 결과를 바탕으로 청소년 대상의 자살예방교육 및 사회적 관계망과 지지체계의 구축, 소속감 증진활동의 활성화 필요성을 제언하였다. This study is to understand the effect of 'perceived burdensomeness' and 'failed belongingness', which Joiner explains on his Interpersonal Theory of Suicide, to youth's suicidal ideation. 990 students, who were attending at middle and high schools in Gyeong-Nam province, were surveyed. The result revealed that participants' gender and families' economic status affect significantly on their suicidal ideation and both perceived burdensomeness and failed belongingness have both statistically significant major effects and interaction effects on youth's suicidal ideation. On the base of the result of this study suicide prevention education, systematic approaches, and group activities for social networking, and social support building have been suggested.
Gyeong Uk Jang,김창완,Dae-Sung Bae,Younghoon Cho,이정종,조승현 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.3
This study performed reliability-based robust design optimization (RBRDO) of stator and rotor shape of the IPM type electric motor to reduce the torque ripple considering uncertainties. A metamodel based on the design of experiments results, which was calculated by using 2-D electromagnetic finite element analysis, was used to calculate manufacturing uncertainties and material property distribution. As a result, the mean torque ripple of the optimum electric motor design was reduced by 56.4 % and the robustness was increased by 61.8 % compared with the initial design. The RBRDO design was compared with the designs of deterministic design optimization and reliability-based design optimization, and it was shown that, by using the RBRDO method, the optimum IPMSM can be designed to satisfying not only the minimum torque ripple but also the robustness and the reliability of output torque and torque ripple.
높은 Pr 수의 유체를 사용한 수직 원형관 외부의 자연대류 실험
강경욱(Gyeong-Uk Kang),정범진(Bum-lin Chung) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.5
수직 원형관 외부의 자연대류는 많은 실용적인 관심의 대상이 되고 있으며 곡률효과에 대한 이론과 열전달상관식은 교과서에도 잘 정리되어 있다. 본 연구에서는 유사성 원리를 이용하여 매우 높은 Pr 수의 유체를 사용하여 수직 원형관 외부의 자연대류 열전달 현상을 실험적으로 연구하였다. 황산-황산구리 수용액의 전기도금계를 물질전달계로 채택하였으며, 실험은 직경 0.005m~0.035m의 음극을 사용하여 Pr 수 2,094~4,173 그리고 Gr<SUB>H</SUB> 수 5.2×10?~1.0×10¹?에서 열전달계수를 측정하였다. 실험을 통하여 도출한 충류 상관식은 NU<SUB>H</SUB> = 0.55Ra<SUB>H</SUB><SUP>0.25</SUP>, 난류 상관식은 Nu<SUB>H</SUB> = 0.12Ra<SUB>H</SUB><SUP>0.28</SUP>Pr<SUP>0.1</SUP>였다. 충류에서 실험한 결과는 King, Jakob와 Linke, McAdams, Bottemanne의 수직 원형관 자연대류의 열전달 상관식에 일치하였다. 그러나 난류에서는 McAdams의 상관식과 일치하지 않았고 수직평판 난류 자연대류 상관식인 Fouad의 상관식과 일치하였고 Pr 수에 대한 의존성이 나타났다. 그 원인은 높은 Pr 수에 따라서 열경계층 두께가 관의 직경보다 매우 얇았기 때문인 것으로 판단된다. Natural convection on the outer surface of a vertical pipe has drawn research interests for many practical purposes and well established theories on the curvature effect and heat transfer correlations are available in textbooks. This study investigated the phenomena using mass transfer experiments with high Pr number using the analogy concept. A cupric acid-copper sulfate electroplating system was adopted as the mass transfer system. Tests were performed for Gr<SUB>H</SUB> numbers from 5.2×10? to 1.0×10¹?, Pr numbers from 2,094 to 4,173, and the diameters from 0.005m to 0.035m. The obtained correlations were NU<SUB>H</SUB> = 0.55Ra<SUB>H</SUB><SUP>0.25</SUP> for laminar and Nu<SUB>H</SUB> = 0.12Ra<SUB>H</SUB><SUP>0.28</SUP>Pr<SUP>0.1</SUP> for turbulent. The test results for laminar flow conditions agreed well with the correlations of King, Jakob & Linke, McAdam, and Bottemanne. However, for turbulent conditions, the test results show discrepancy with the correlation of McAdams developed for vertical pipe geometry but instead they showed agreement with the heat transfer correlations of Fouad developed for a vertical plate and also show the dependence on Pr numbers. The very thin thermal boundary layer compared to the diameter of the pipe due to the high value of Pr number seems to make the curvature effect negligible.
높은 Pr 수의 유체를 사용한 수직 원형관 외부의 자연대류 실험
강경욱(Gyeong-Uk Kang),정범진(Bum-Jin Chung) 대한기계학회 2011 大韓機械學會論文集B Vol.35 No.1
유사성 원리를 이용하여 매우 높은 Pr 수의 유체를 사용하여 수직 원형관 외부의 자연대류 열전달 현상을 실험적으로 연구하였다. 황산-황산구리 수용액의 전기도금계를 물질전달계로 채택하였으며, 실험은 직경 0.005m~0.035m의 음극을 사용하여 Pr 수 그리고 2,094~4,173 RaH 수 1.4×10?~4×10₁₃에서 열전달계수를 측정하였다. 층류에서 실험한 결과는 King, Jakob와 Linke, McAdams, Bottemanne의 수직원형관 자연대류의 열전달 상관식에 일치하였고 난류에서는 수직평판 난류 자연대류 상관식인 Fouad의 상관식과 일치하였고 Pr 수에 대한 의존성이 나타났다. 실험을 통하여 도출한 층류 상관식은 NuH=0.55Ra<SUP>0.25</SUP>H, 난류 상관식은 NuH=0.12Ra<SUP>0.28</SUP>HPr<SUP>0.1</SUP>였다. 층류와 난류사이의 천이는 . RaH 수 약 10¹²에서 발생하였다. In this study, we investigated the natural convection on the outer surface of a vertical pipe by performing mass transfer experiments using fluids with high Pr number using the concept of analogy between heat and mass transfer. A cupric acid-copper sulfate electroplating system was adopted as the mass transfer system. Tests were performed for RaH numbers from 1.4×10? to 4×10¹³, Pr numbers from 2,094 to 4,173, and diameters from 0.005 m to 0.035 m. The test results for laminar flow conditions were in good agreement with the correlations reported by King, Jakob and Linke, McAdam, and Bottemanne, and those for turbulent conditions with the correlations presented by Fouad for a vertical plate and also proved the dependence on Pr numbers. The obtained correlations were NuH=0.55Ra<SUP>0.25</SUP>H for laminar and NuH = 0.12Ra<SUP>0.28</SUP>HPr<SUP>0.1</SUP> for turbulent. The transition between laminar and turbulent occurs at RaH of about 10¹².
Kang, Gyeong-Uk,Chung, Bum-Jin,Kim, Hyoung-Jin Elsevier 2014 INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER - Vol.79 No.-
<P><B>Abstract</B></P> <P>Natural convection experiments on both vertical thin- and thick-cylinders were performed for Rayleigh numbers from 1.4×10<SUP>9</SUP> to 3.2×10<SUP>13</SUP>, the <I>H</I>/<I>D<SUB>O</SUB> </I> from 0.6 to 140 at high Prandtl numbers. A sulfuric acid–copper sulfate electroplating system based on analogy concepts were employed for the measurements of heat transfer rates. For vertical thin-cylinders, Nusselt numbers were in satisfactory agreements with the existing correlation on vertical plates. Especially, those measured at the high <I>H</I>/<I>D<SUB>O</SUB> </I> were higher even though the thermal boundary layer is much thinner than the cylinder diameter. This was due to the flow interactions, which promoted the development of momentum boundary layer and velocity fluctuations, leading to the enhancement of the Nusselt number. For vertical thick-cylinders, Nusselt numbers in laminar flows were in satisfactory with the existing correlations. However, those in turbulent flows decreased as Prandtl number increased in this study. Its phenomena are caused by the formation of very thin thermal boundary layer within viscous sublayer by very high Prandtl number. In this case, the velocity within thermal boundary layer becomes very low by no-slip condition near the heated wall and the heat is transferred by conduction rather than advection. Based upon the results, empirical correlations on vertical thick-cylinders were derived for laminar and turbulent flows.</P>
Kang, Gyeong-Uk,Chung, Bum-Jin Elsevier 2015 INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER - Vol.87 No.-
<P><B>Abstract</B></P> <P>Natural convection heat transfer was investigated in vertical cavities where either all surfaces were active, or only the vertical surface was active for four different geometries, which were varied by placing a disk at the top and/or bottom of the cavity. A cupric acid–copper sulfate electroplating system was employed for mass transfer experiments exploiting the analogy with heat transfer. The Rayleigh number was varied in the range 4.55×10<SUP>9</SUP> ⩽ <I>Ra<SUB>Lw</SUB> </I> ⩽3.79×10<SUP>13</SUP>. Preliminary tests for a vertical pipe, upward- and downward-facing horizontal disks showed good agreement with existing correlations. The measured Nusselt numbers in the vertical cavities with all surfaces active were always greater than those with only the vertical surface active, which is attributed to greater hydrodynamic interaction of the flows generated by different surfaces. When all surfaces were active, the bottom-closed cavity exhibited the largest heat transfer rates, followed by both-closed, top-closed, and both ends open cavities; this trend was observed with laminar and turbulent flows. With only the vertical surface active, similar trends were observed except that the heat transfer rates were almost identical for both-open and top-closed cavities, which is attributed to the weak influence of the top disk on the heat transfer characteristics. Using these results, empirical correlations were derived for both laminar and turbulent flow conditions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Natural convection inside a vertical pipe with/without top and bottom lids. </LI> <LI> A comprehensive review of the literature was made. </LI> <LI> It covers laminar and turbulent flows and either active or inactive top and bottom lids. </LI> <LI> Phenomenological explanation including the secondary flows was discussed. </LI> <LI> Heat transfer correlations were derived and proposed. </LI> </UL> </P>