Analytical Investigation of Water Transport

Sukkee Um,Kwan-Soo Lee,Hye-Mi Jung 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5

Comprehensive analytical models focusing on the anode water loss, the cathode flooding, water equilibrium, and water management strategy are developed for polymer electrolyte fuel cells. Analytical solutions presented in this study are compared with two-dimensional computational results and shows a good agreement in predicting those critical characteristics of water. General features of water concentration profile as a function of membrane thickness and current density are presented to illustrate the net effect of the back-diffusion of water from the cathode to anode and the water production by the cathode catalytic reaction on water transport over a fuel cell domain. As one of practical applications, the required humidity level of feed streams for full saturation at the channel outlets are investigated as a function of the physical operating condition. These analytical models can provide good understanding on the characteristic water.

현대비극 담론과 셰익스피어 비극의 전복성

고석기(Koh Sukkee) 한국셰익스피어학회 2006 셰익스피어 비평 Vol.42 No.4

Until the 1960s, criticism of King Lear was dominated by overtly or implicitly Christian accounts. Despite the play's pagan setting and deliberate reduction of the Christian allusions overpopulating its chief dramatic source, a host of critics had laboured to turn the tragedy back into the kind of drama whose doctrinal clutch it was plainly anxious to escape. Still more had followed the less blatant trail blazed by A. C. Bradley and G. Wilson Knight, who devised readings in which Christian patterns and concepts survived in figurative disguise with their moralizing spirituality intact. The idea of King Lear as a dramatized parable of sin, sacrifice and redemption took a nosedive, however, after Barbara Everett's sceptical attack in 1960, and never regained height after the publication of W. R. Elton's King Lear and the Gods. Such refutations helped foster the environment in which two new critical dynasties emerged to contest the throne from which the Christian interpretation of King Lear was being toppled. Conservative humanist critics redefined Lear's heroism as his capacity to absorb endless agonies and endure death itself without prospect of salvation, finding his life's purpose in this world rather than beyond the grave. Pitted against this view was a far bleaker reading of the playas refusing altogether the consolation of significance, whether Christian or secular, and abandoning us at the close without any support from systems of moral or artistic belief at all. But the framework of assumptions and objectives within which these and other kinds of reading are now pursued has altered so dramatically over the last ten years as to justify our speaking of a new era in the study of King Lear. The reasons for the shift in direction can be summed up in one word: politics. Hitherto, critical quarrels about the vision of King Lear has largely been conducted in blithe indifference to the play's social implications for the present or its past political function reconsidered from a modern point of view. But the 1980s spawned a whole series of theoretically informed, polemical studies of Shakespeare, which exposed the conservative consequences of established approaches to his drama and promoted instead a range of perspectives committed to re-reading the plays in the light of innovative work on gender, race, power, language and the function of criticism itself.

교통사고 현장구경(Rubbernecking) 임시 차폐시설 설치 효과분석: 영동고속도로를 중심으로

홍석기(HONG, Sukkee),이지연(LEE, Ji Yeon),정희정(JUNG, Hee Jeong) 대한교통학회 2022 교통 기술과 정책 Vol.19 No.2

Romeo and juliet에 나타난 여성의 주체성과 낭만적 사랑

고석기 현대영미어문학회 2002 현대영미어문학 Vol.20 No.3

Critical approaches to Romeo and Juliet which depend upon prescriptive theories of tragedy have largely exhausted themselves; concern with whether the play is a "tragedy of character" or a "tragedy of fate" has ebbed. Those who would point the moral lesson of Friar Lawrence instructing the lovers in moderation sound overly didactic, yet those who would vindicate the protagonists by placing responsibility for the tragic action on an inevitable fate offer an overly deterministic viewpoint. For even in his earliest attempts at tragedy, Shakespeare is capable of managing the delicate balance between choice and chance: Juliet and Romeo are neither condemned by their decisions, as the "tragedy of character" critics would have us believe, nor damned by a mechanical fate, as the "tragedy of fate" critics would have believe. Incorporating these polarized interpretations allows a consideration of the protagonists' strengths with their weaknesses and a recognition of the feud's power that does not skew it into an inevitable fate. Romeo and Juliet is a play concerned with language, forms, and conventions-a phenomenon not overlooked by critical commentary. Virtuosic poetic passages and set pieces-oxymora, rhymed couplets, sestets, sonnets, an epithalamium, and an aubade- stud the play like jewels. While they may obtrude during a private reading upon our absorption with character in action, they enhance our enjoyment of the play in performance.

Effect of Baffle Pattern Applied to Cathode Parallel Channel on PEMFC Performance

Jonghyun Son,Sukkee Um,Young Beom Kim 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.11 No.1

Many efforts have been made to improve the performance of polymer electrolyte membrane fuel cells (PEMFCs). One approach has been the enhancement of the mass transport property by applying various channel designs and modifying them. Of those channels, the parallel channel as applied in PEMFCs has a low pressure drop and poor mass transfer property. To improve the mass transfer, a baffle that forces the reactant flow into the gas diffusion layer (GDL) from the channel can be installed in the parallel channel. In this study, various parallel channels designed with different baffle patterns and the effect was assessed by the PEMFC performance. All the baffle patterns analyzed in this study improved the performance of the PEMFC. However, depending on the baffle pattern, the reactant transfer and the current density of the PEMFC were affected differently. The staggered baffle pattern showed the best PEMFC performance among the analyzed models; when the staggered pattern was located near the outlet and the gap between the staggered baffles was wide, the PEMFC performance was further improved and the pressure drop of the cathode flow field was also lower than with the other baffle patterns.

Numerical Study on Interfacial Contact Characteristics between Composite Transport Media for Fuel Cell Applications

Junyu Chen,Jiawen Liu,Sukkee Um 한국신재생에너지학회 2021 AFORE Vol.2021 No.10

Electrochemical modeling for the prediction of potential distributions in Liion batteries for HEVs at subzero temperatures

Yongsam Kim,Donghee Kim,Sukkee Um 한국자동차공학회 2011 한국자동차공학회 학술대회 및 전시회 Vol.2011 No.11

Thermo-electrical properties of composite semiconductor thin films composed of nanocrystalline graphene-vanadium oxides.

Jung, Hye-Mi,Um, Sukkee American Scientific Publishers 2014 Journal of nanoscience and nanotechnology Vol.14 No.12

<P>This paper presents an experimental comparative study involving the characterization of the thermo-electrical and structural properties of graphene-based vanadium oxide (graphene-VOx) composite thin films on insulating and conducting surfaces (i.e., fused quartz and acrylic resin-impregnated graphite) produced by a sol-gel process via dipping-pyrolysis. A combination of FE-SEM and XPS analyses revealed that the graphene-VOx composite thin films (coated onto fused quartz) exhibiting the microstructure of 2-graded nanowire arrays with a diameter of 40-80 nm were composed of graphene, a few residual oxygen-containing functional groups (i.e., C-O and C=O), and the VO2 Magn?li phase. The temperature-dependent electrical resistance measured on the as-deposited thin films clearly demonstrated that the graphene-VOx composite nanowire arrays thermally grown on fused quartz act as a semiconductor switch, with a transition temperature of 64.7 degrees C in the temperature range of -20 degrees C to 140 degrees C, resulting from the contributions of graphene and graphene oxides. In contrast, the graphene-VOx composite thin films deposited onto acrylic resin-impregnated graphite exhibit a superlinear semiconducting property of extremely low electrical resistance with negative temperature coefficients (i.e., approximately four orders of magnitude lower than that of the fused quartz), despite the similar microstructural and morphological characteristics. This difference is attributed to the synergistic effects of the paramagnetic metal feature of the tightly stacked nanowire arrays consisting of hexagonal V2O3 on the intrinsic electrical properties of the acrylic resin-impregnated graphite substrate, as revealed by FE-SEM, EDX, AFM, and XRD measurements. Although the thermo-sensitive electrical properties of the graphene-VOx composite thin films are very substrate specific, the applicability of graphene sheets can be considerably effective in the formation of highly planar arrays of VOx nanowires to enhance carrier transport.</P>

Thermofluidic analysis of interior permanent magnet synchronous motors with internal air circulation by protrusion-shaped flow inducers for effective thermal management

Jonghyo Lee,Namkwon Lee,Sukkee Um 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.8

A three-dimensional thermofluidic model was developed for simulating fluid flow and heat transfer in interior permanent magnet synchronous motors (IPMSMs) with internal air circulation for effective thermal management. Protrusion-shaped flow inducers were introduced to facilitate the internal air circulation through rotor ventilation holes, increasing convection and preventing temperature rises in primary motor components. The numerical model agreed well with the experimental data. Subsequently, various geometrical design variables of the protrusion were selected to determine the thermofluidic characteristics of the electric motor associated with local temperature distributions for critical motor components. The protrusion increased the mass flow into the ventilation holes; accordingly, the maximal rotor temperature was inversely proportional to the protrusion design. Additionally, a thin airgap between the stator and rotor affected the radial heat transfer rate by forming additional thermal resistance layers. This flow was modeled using the Taylor-Couette paradigm, with the relative error under 1 %.

열 사상법을 이용한 유도 기동형 동기 전동기의 비정상 3차원 열해석

김치원(Chiwon Kim),엄석기(Sukkee Um) 한국자동차공학회 2012 한국자동차공학회 학술대회 및 전시회 Vol.2012 No.11

This paper describes thermal modeling of a line start permanent magnet (LSPM) motor using a computational flow dynamics method. First, 2-dimensional electromagnetic design is carried out in order to comprehend heat losses at winding, stator, rotor and cage. New coupling method called Heat mapping method (HMM) will be introduced which converts 2-D information of electromagnetic domain to 3-D information of thermal domain. Transient thermal analysis under rated operating conditions is performed to identify the load saturation time and temperatures in the LSPM motor. Experimental results are collected under the same operating conditions and computational results are verified against the experimental data. Finally, thermal path analysis at a steady-state is conducted to figure out the direction and magnitude of heat flux in the LSPM motor. These results can be useful to design effective cooling systems of electrical motors.