• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.6
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• pp.1547-1555
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• 1993

An experimental study on convection heat transfer characteristics from a heated tube to an oscillating flow has been carried out, . This problem is of particular interest in the design of heat exchangers in Stirling cycle machines. Experimental system has been developed to measure temporal variations of temperature inside a heater tube during oscillating modes in a Stirling cycle machine. The dependence of temperature distributions and heat transfer rates on the oscillating frequency as well as the swept volume ratio and the mean pressure of a Stirling cycle machine is investigated in detail. The experimental results indicate that the measured temporal variations of temperature become nearly sinusoidal. The amplitude of temperature variation in the core of the tube is much more substantial than that near the tube wall, whereas the reverse is true for pulsating flows. It is also found that the heat transfer rate is increased significantly as the oscillating frequency or oscillating amplitude or the mean pressure in a tube is increased.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2004.10a
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• pp.281-284
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• 2004

수년 내 서비스가 개시될 휴대인터넷 서비스는 현재 모든 통신사업자에게 큰 이슈로 떠오르고 있다. 관련산업 포함 연 16조원에 달하는 서비스로서 고속의 이동 무선인터넷 서비스를 제공한다. 그러나 아직 휴대인터넷의 시장에서의 위상이나 기존 서비스와의 대체 보완 관계가 정확히 연구되고 있지 않다. 본 논문에서는 휴대인터넷 서비스의 포지셔닝과 함께 휴대인터넷과 기존의 이동통신, 초고속인터넷, 및 DMB서비스와의 관계를 동시에 살펴본다.

• Korean Chemical Engineering Research
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• v.44 no.5
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• pp.505-512
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• 2006

Characteristics of particle holdup and heat transfer were investigated in a liquid-particle swirling fluidized bed whose diameter was 0.102 m and 2.5 m in height. Effects of liquid velocity, particle size and swirling liquid ratio($R_s$) on the particle holdup and immersed heater-to-bed overall heat transfer coefficient were examined. The particle holdup increased with increasing particle size and swirling liquid ratio but decreased with increasing liquid velocity.The local particle holdup was relatively high in the region near the heater when the $R_s$ value was 0.1~0.3, but the radial particle holdup was almost uniform when the $R_s$ value was 0.5, whereas, when the $R_s$ value was 0.7, the local particle holdup was relatively low in the region near the heater. The heat transfer characteristics between the immersed heater and the bed was well analyzed by means of phase space portraits and Kolmogorov entropy(K) of the time series of temperature difference fluctuations. The phase space portraits of temperature difference fluctuations became stable and periodic and the value of Kolmogorov entropy tended to decrease with increasing the value of $R_s$ from 0.1 to 0.5. The Kolmogorov entropy exhibited its maximum value with increasing liquid velocity. The value of overall heat transfer coefficient(h) showed its maximum value with the variation of liquid velocity, bed porosity or swirling liquid ratio, but it increased with increasing particle size. The value of K exhibited its maximum at the liquid velocity at which the h value attained its maximum. The particle holdup and overall heat transfer coefficient were well correlated in terms of dimensionless groups of operating variables.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.3
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• pp.381-388
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• 2001

Presented are heat data which describe the effect of interaction between bulk flow pulsations and a vortex embedded in a turbulent boundary layer. The pulsation frequencies are 3 Hz, 15 Hz and 30 Hz. A half delta wing with the same height as the boundary layer thickness is used to generate the vortex flow. The convection heat transfer coefficients on a constant heat-flux surface are measured by embedded 77 T-type thermocouples. Spanwise profiles of convection heat transfer coefficients show that upwash region of vortex flow is influenced by bulk flow pulsations. The local heat transfer coefficient increases approximately by 7 percent. The increase in the local change of convection heat transfer coefficient is attributed to the spanwise oscillatory motion of vortex flow especially at the low Strouhal number and to the periodic change of vortex size.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.3
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• pp.218-227
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• 2016

Korean government plans to launch a lunar orbiter and a lander to the Moon by 2020. Before launch these two proves, an experimental lunar orbiter will be launched by 2018 to obtain key space technologies for the lunar exploration. Several payloads equipped in experimental lunar orbiter will monitor the surface of the Moon and will gather science data. Lunar orbiter sends telemetry and receives tele-command from ground using S-band while science data is sent to ground stations using X-band when the visibility is available. Korean deep space network will be mainly used for S and X-band communication with lunar orbiter. Deep Space Network or Universal Space Network can also be used for the S-band during trans-lunar phase when korean deep space network is not available and will be used for the S-band in normal mission orbit as a backup. This paper analyzes a visibility condition based on the combination of various ground antennas and its mask angles according to mission scenario to predict the number of contacts per day and to build an operational scenario for the lunar orbiter.

• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.1
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• pp.51-57
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• 2009

In this study, a new topology optimization method is developed to design heat-dissipating structure with forced convection. To cool down electrical devices or mechanical machines, two types of convection models have been widely used: the natural convection model with a large Archimedes number and the forced convection with a small Archimedes number. In these days, lots of engineering application areas such as electrochemical conversion devices (Fuel cell) or rocket propulsion engines adopt the forced convection to dissipate the generated heat. Therefore, to our knowledge, it becomes an important issue to design flow channels inside which the generated heat dissipate. Thus, this paper studies optimal topological designs considering fluid-heat interactions. To consider the effect of the advection in the heat transfer problem, the incompressible Navier-stokes equation is solved. This paper numerically studies the coupling phenomena and presents optimal channel design considering forced convection.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.1
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• pp.20-26
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• 2005

Ultrasonic guided waves have been widely employed for long range inspection of structures such as plates, rods and pipes. There are numerous modes with different wave velocities, and the appropriate mode selection is one of key techniques in the application of guided waves. In the present work, phase tuning by an array transducer was applied to generate ultrasonic guided waves. For this purpose, 8-channel ultrasonic pulser/receiver and their controller which enables sequential activation of each channels with given time delay were developed. Eight transducers were fabricated in order to generate guided waves by using an array transducer. The selective tuning of wave mode can be achieved by changing the interval between elements of an array transducer.

• The monthly packaging world
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• s.176
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• pp.97-117
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• 2007

(사)한국물류협회(회장 서병륜)와 건설교통부, 매일경제신문이 공동으로 주최하는 2007년도 한국물류대상 시상식이 지난 달 15일 서울 중구 대한상공회의소에서 개최됐다. 이번 행사에서는 건설교통부 장관과 서병륜 (사)한국물류협회장, 물류산업계 및 학계 인사 등 5백여명이 참석한 가운데 거행됐다. 한국물류대상을 한국물류협회, 건설교통부, 매일경제신문이 공동으로 주최하는 행사로 1993년부터 매년 시행하는 물류부문 정부 포상이다. 효율적이고 체계적인 물류혁신에 노력한 기업과 개인을 발굴하여 포상하고 있으며 매년 그 위상이 격상되어 오고있다. 이번 한국물류대상에는 대통령포창상에 (주)포스코 등 4개 업체, 국무총리표창상에 (주)LG CNS Entrue 컨설팅 등 2개 업체, 건교부장관표창상에 대화물류(주) 등 8개업체, 매일경제신문회장상에 한국후지쯔(주) 등 2개 업체, 한국물류협회장상 코레일로지스(주) 등 3개 업체, 근정포상에 전일수 교수가 수상, 20개 단체 및 개인이 수상의 영예를 안았다. 본 고에서는 제15회 한국물류대상 수상자들의 활약상을 살펴본다.

• Journal of The Korean Association For Science Education
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• v.13 no.1
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• pp.1-11
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• 1993

1980년 이래로 자연현상에 관한 유년적 사고에 관한 연구가 국내,외에 활발히 보고되어 왔지만, 그 근원에 관한 연구는 다소 소홀히 다루어져 왔다. 연구는 천문학에 관한 학생들의 유년적 사고와 그 사고의 근원을 조사한 것이다. 이의 대상은 국민학교 6학년 5명, 중학교 2학년 5명, 고등학교 1학년 5명으로 하였다. 연구방법으로는 질문지법(Open-ended Written Questions)과 면접법(Interview)을 이용하였다. 이 연구에서는 계절 변화, 달 위상 변화의 원인에 관하여, 국민학생에서 고등학생에 이르기까지 대다수의 학생들이 유년적 사고를 지니고 있는 것으로 밝혀졌고, 이들 유년적 사고의 근원으로는 '학교 교사'와 '교과서' 라고 대답하는 학생이 대부분으로 나타났다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.3
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• pp.809-823
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• 1991

본 연구에서는 Wiener 필터링 이론에 의하여 소음원의 입력신호에 대한 최적 한 예측을 할 수 있는 최적예측기(optimal predictor)로써 부가적인 음을 발생시키고 입력신호 및 출력신호 간의 차인 오차를 최소화시키도록 하는 적응신호처리방법에 대 해 설명하고 이러한 적응 신호처리 방법을 이용한 능동 소음 제어 방법을 제시하였다. 이와 아울러 제어계의 환경 변화에 따른 파라메타의 변화에 적응적으로 응답이 가능해 야 하는 적응 소음 제어계에서, 음향궤환과 함께 필히 고려해야하는 부가적인 전달함 수-모델과 스피커를 포함하는 보조경로 및 오차미이크로폰을 포함하는 오차경로의 전 달함수의 영향을 고려한 능동소음제어에 대해 연구하였다.