• Electronics and Telecommunications Trends
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• v.30 no.1
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• pp.65-76
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• 2015

스마트폰의 보급에 따른 대용량 멀디미디어 서비스의 폭발적인 수요 증가에 따라데이터센터의 100Gb/s 광트랜시버에 대한 수요는 2017년을 기점으로 10Gb/s를 추월하여 2018년 데이터콤 전체 시장의 50% 이상을 차지할 전망이다. 한편, 데이터센터의 소비전력 및 시스템 집적도 증가를 위해 광트랜시버의 Form-factor는 CFP(40G/100G Form-factor Pluggable)에서 QSFP28($4{\times}28G$ Quad Small Form-factor Pluggable)로 약 1/14배 소형화될 전망이며, 이에 따른 광트랜시버 구성 부품의 집적도는 높아지고 소비전력은 현재 대비 1/9로 낮아져야 한다. 본고에서는 소형화 및 저전력화를 위한 광트랜시버의 표준화 및 기술동향과 국내외 시장동향에 대해 기술한다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.991-992
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• 2013

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.15 no.1
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• pp.1-8
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• 2019

In this study, the effect of operating conditions of fan-coil unit with an oval tube type heat exchanger on its non-dimensional performance coefficient has been investigated. Pressure drops and heat transfer rates were measured under heating condition for various water flow rates, inlet temperatures and wind speeds. As a non-dimensional performance coefficient, Colburn j-factor was evaluated. The results show that the most sensitive parameter on heat flux is the inlet temperature, which affects the heat flux 4.7 and 7.2 times more than the wind speed and water flow rate, respectively. On the other hand, the Colburn j-factor as a non-dimensionalized index decreases with the wind speed, and has an maximum when the wind speed is about 1 m/s. the Colburn j-factor increases slowly with the water flow rate and inlet temperature but at a certain range of inlet temperature, the opposite phenomenon is found.

• Journal of the Korean Mathematical Society
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• v.53 no.2
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• pp.415-431
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• 2016

This note is concerned with examining nilradicals and Jacobson radicals of polynomial rings when related factor rings are Armendariz. Especially we elaborate upon a well-known structural property of Armendariz rings, bringing into focus the Armendariz property of factor rings by Jacobson radicals. We show that J(R[x]) = J(R)[x] if and only if J(R) is nil when a given ring R is Armendariz, where J(A) means the Jacobson radical of a ring A. A ring will be called feckly Armendariz if the factor ring by the Jacobson radical is an Armendariz ring. It is shown that the polynomial ring over an Armendariz ring is feckly Armendariz, in spite of Armendariz rings being not feckly Armendariz in general. It is also shown that the feckly Armendariz property does not go up to polynomial rings.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.7
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• pp.134-142
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• 2001

The integrals $J_k$(k=1,2) in the rectilinear anisotropis body in 2-D were determined using Lekhnitskii formalism. The relationship between $J_k$ and stress intensity factors are implified by the important equation between elastic compliance. The numerical evaluation of stress intensity factor for the single edge crack in mixed mode is determined by superposing known exact solutions.

• Journal of Mechanical Science and Technology
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• v.17 no.2
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• pp.254-268
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• 2003

The explicit formulation of the J-integral and the M-integral is constructed in terms of the stress intensity factor and the higher order stress coefficients for Mode II cracks under small or large scale yielding. Furthermore, the stress intensity factor and the higher order stress coefficients as well are computed with the aid of the two-state J- and the M-integral, which is found to be accurate and efficient. It is found that the contribution from the higher order singularities to the J-integral is closely related to the configuration of the plastic zone.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.121-125
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• 2008

In this study, the characteristics of internal flow and the heat transfer performance of dimpled plate heat exchanger were numerically investigated. For the numerical analysis, conjugate heat transfer method between cold fluid - plate - hot fluid was studied with appropriate boundary conditions. Velocity magnitude, temperature and pressure distribution were obtained from the simulation. Correlations for fanning f-factor and Colburn j-factor were obtained from numerical results and compared to the experimented data.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05c
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• pp.19-24
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• 2001

In this study, Pb(La Ce)$TiO_3$ composition ceramics were manufactured for 20 MHz resonator application. Electromechanical coupling factor, mechanical quality factor and dynamic range of thickness vibration mode were measured as the variations of L/T(length/thickness) ratio of ceramic substrats. Mechanical quality factor and dynamic range of third overtone thickness vibration mode showed the highest value of 2,773 and 52.22 dB at specimen S4(l/t=12), respectively. The excellent temperature stability of resonant frequency suitable for resonator application was shown, regardless of thermal shock.

• Structural Engineering and Mechanics
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• v.22 no.4
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• pp.469-481
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• 2006

A new method called fuzzy factor method for the stationary stochastic response analysis of fuzzy truss with global fuzzy structural parameters is presented in this paper. Considering the fuzziness of the structural physical parameters and geometric dimensions simultaneously, the fuzzy correlation function matrix of structural displacement response in time domain is derived by using the fuzzy factor method and the optimization method, the fuzzy mean square values of the structural displacement and stress response in the frequency domain are then developed with the fuzzy factor method. The influences of the fuzziness of structural parameters on the fuzziness of mean square values of the displacement and stress response are inspected via an example and some important conclusions are obtained. Finally, the example is simulated by Monte-Carlo method and the results of the two methods are close, which verified the feasibility of the method given in this paper.

• 대한예방의학회:학술대회논문집
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• 1999.10a
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• pp.136-137
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• 1999