• Membrane Journal
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• v.21 no.3
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• pp.236-246
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• 2011

In this study, we used prepared a cylindrical module consisting 100 hollow fibers of commercialized (hydrophobic) polyethylene membrane of $0.4{\mu}m$ pore size and systematically studied performance of direct contact membrane distillation (DCMD) and sweep gas membrane distillation (SGMD) in terms of variation of permeate flux and salt rejection with respect to temperature drop across the membrane, salt concentrations in feed, and flow rates of cooling water and sweep gas. SGMD was regarded as DCMD with a sweep gas layer between permeate-side membrane surface and cooling water. Sweep gas flow decreases the permeate flux from that of DCMD by providing an additional gas-layer resistance. We compared DCMD and SGMD performance by using mass balance with a fitting parameter (${\omega}$), indicating fraction of permeate flow rate.

• Bulletin of the Society of Naval Architects of Korea
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• v.11 no.1
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• pp.35-44
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• 1974

열박음(shrink fitting)으로 인(因)한 동심형(同心形) 구멍을 가진 복합(複合)실린더의 과도적(過渡的) 온도분포(溫度分布), 열응력(熱應力) 및 열변형도(熱變形度)를 이론해석(理論解析)하였다. 온도분포해석(溫度分布解析)에서 외부(外部) 실린더는 균일온도(均一溫度)로 가열(加熱)되어, 실온(室溫)의 내부(內部) 실린더와 접촉면(接觸面)에서 일어나는 열전도(熱傳導)에 의(依)하여 냉각(冷却)되고, 외부(外部) 표면(表面)은 대기중(大氣中)에 노출(露出)된 상태(狀態)로 취급(取扱)하였다. 열응력(熱應力)은 평면변형도조건(平面變形度條件)을 만족(滿足)하는 것으로 생각하였으며, 물성(物性)은 온도(溫度)에 무관(無關)한 상수(常數)로 취급(取扱)하였다. 온도분포(溫度分布)는 열전도문제(熱傳導問題)만을 고려(考慮)함으로서도 유효(有效)한 해(解)를 얻을 수 있으며 열응력(熱應力)은 접촉면(接觸面)에서부터 형성(形成)되며, 반경방향응력(半徑方向應力)은 시간(時間)이 경과(經過)함에 따라 압축응력(壓縮應力)이 증가(增加)하여 접촉면(接觸面)에서 최대치(最大値)를 갖고, 원주방향응력(圓周方向應力)은 접촉면(接觸面)에서 초기(初期)부터 거의 최종상태(最終狀態)와 같은 크기를 갖음을 알 수 있다. 균일온도분포(均一溫度分布)가 이루어지면 열응력(熱應力)의 형성(形成)은 완료(完了)되게 되며, 이때의 열응력(熱應力)의 크기와 분포경향(分布傾向)은 평면응력조건(平面應力條件)을 사용(使用)하였다는 사실(事實)을 고려(考慮)하면 $Lam\acute{e}$의 이론해(理論解)와 일치(一致)함을 알 수 있었다.

• Informatization Policy
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• v.22 no.4
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• pp.91-104
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• 2015

This study tests the effects of differential association, definitions, differential reinforcement and imitation from social learning theory in the explanation of university students' crimes in social network services. In addition, this study tests the interaction effects between social learning factors and other factors such as low self-control, subcultural environment, and crime opportunity for the integrated approach. Using data from 486 university students in Seoul, results show that both definition and imitation have significant influences on crimes, even though differential association and differential reinforcement factors have no significant influences on crimes in social network services. Results also reveal that there are significant interaction effects between definition and subcultural environment, which meana that definition has a strong effect on crimes in high subcultural environment. In addition, it is found that reinforcement has also a strong effect on crimes in high crime opportunity and that interaction effect between imitation and low self-control is significant, which means that imitation has a strong effect on crimes in low self-control students.

• Korean Journal of Materials Research
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• v.3 no.1
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• pp.58-64
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• 1993

The degree of work hardening in the subsurface zones varied with the experimental conditions under the rolling contact fatigue wear test of high carbon Cr-Ti alloy steel was evaluated by the distribution of residual stresses. Surface residual stresses before the test did not affect the wear property. Surface residual stresses after the test decreased by the increase of contact stress and running. velocity. but the maximum compressive residual stress and its depth of saturation in the subsurface zone increased. The relationship between these experimental results and the distribution of the theoritical shear stress was also discussed.

• Journal of Astronomy and Space Sciences
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• v.17 no.2
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• pp.163-172
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• 2000

The EB type contact binaries show large temperature difference $(\mid\bigtriangleup T\mid\geq1,000K)$ between two components. Thus we have modified the mode 3 of the WD program to adjust albedos, limb darkening coefficients and gravity darkening exponents for both components of such binaries, while the values for those parameters should be same for both components in the original WD program. Both of the modified and the original versions have been applied to the EB type contact binaries such as DO Cas, GO Cyg, and FS Lup. The computed light curves with modified version fit better to the observations.

• Journal of Energy Engineering
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• v.9 no.2
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• pp.138-145
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• 2000

고체재료의 열확산계수나 열전도계수와 같은 열물성을 비접촉식 방법으로 측정하기 위하여 광열변위법에 대한 이론적인 해석을 수행하였다. 가열빔의 파형을 코사인파, 삼각파 그리고 사각파로 가정하여 2차원 열전도 방정식과 열탄성 방정식의 엄밀해를 구하였고, 이를 가열빔으로부터 직접 구한 실제파의 결과와 비교하였다. 코사인파의 결과가 다른 파형에 비하여 실제파와 가장 유사한 것으로 보아 비교적 해석이 복잡한 실제파를 코사인파로 가정하여도 무방하다.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03a
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• pp.248-267
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• 2004

우리나라의 경우, 국토 면적은 제한되어 있고 특히 밀집한 도심지 인근 공사 시에 사면 경사를 결정하는 것은 쉬운 일이 아니다. 또한 주어진 조건 내(부지의 부족, 환경고려 등)에서 이미 결정되어진 사면경사를 어떻게 유지하느냐 하는 것이 사면에 종사하는 기술자들의 임무인 것이다. 지금까지의 사면분화에 대한 접근 이론들이 너무 고전적인 방법에 치우쳐 있는 경향이 없지 않았다. 또한 기술자들의 보수주의적 경향으로 새로운 이론의 접촉을 멀리한 것도 부인할 수 없다.(중략)

• Plant Journal
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• v.13 no.1
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• pp.30-36
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• 2017

During the start-up of 500 MW class coal-fired power plant, abnormal shaft vibration was occurred on bearings installed on both side of high and intermediate pressure steam turbine. Shaft vibration was analyzed to investigate the reason and find the resolution, based on well-known theory in this study. Typical vibration characteristics which occur when rotating parts contact with stationary parts were observed at the analysis of frequency, amplitude and phase angle. The reason of abnormal vibration was assumed to be rub and internal parts wear was observed during repair period. As a result of applying low speed turning and balancing for resolution of abnormal vibration, balancing was more effective for rub removal. So balancing could be excellent resolution in the case of abnormal vibration which is similar to this study.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.6
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• pp.591-598
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• 1984

The results of measurements showing normal vibrations and rubbing noise generated during unlubricated smooth sliding between metal surfaces are presented. The measurements were made on pin-on-disc type apparatus instrumented with piezoelectric acceleration transducers and microphones. Spectral analysis of the both signals up to frequency of 10kHz indicates that they are closely correlated. The major components of both signals in this frequency range are primarily associated with the normal contact vibrations which are excited by surface irregularities being swept through the contact region during sliding. As an approximation to the seismic input of surface irregularities, an effective surface wavenumber spectrum was assumed in the form of an inverse vibration and noise measurements for a number of surface finishes and mean loads. The predominant frequency component of which levels of the normal vibration and noise are close to overall levels of the both signals is induced by contact resonance between the two bodies and its frequency can be calculated from the Hertzian theory.

• Proceedings of the KIEE Conference
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• 2001.10a
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• pp.110-112
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• 2001

본 논문에서는 전력선 통신 시스템의 전송신호가 비수용가로 전송되는 현상을 차단하기 위한 비접촉식 Blocking Filter를 유한요소법을 이용하여 해석하였다. 새로운 통신망 시스템이 연구되면서 기존의 전력케이블 망을 이용한 전력선 통신방식에 대한 연구가 이루어 졌으나, 전력선 통신이 서비스 지역 이외에 다른 지역으로 통신신호들이 전송될 수 있는 문제점이 제기되었으며, 또한 지정된 지역 내에서 최적화된 통신환경의 구성이 요구되었다. 따라서 본 논문은 타 지역으로의 신호 간섭을 차단하기 위한 비접촉식 Blocking Filter의 기본 모델을 제시하였으며, 이러한 비접촉식 Blocking Filter를 유한요소법을 기초로 한 전자장 수치해석 기법과 전송선 이론을 도입하여 신호 전송 특성을 해석하였다.