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Kwag, S.,Lee, J.M.,Oh, J.,Ryu, J.S. North-Holland Pub. Co 2014 Nuclear engineering and design Vol.266 No.-
The reactor pool working platform (RPWP) has been newly designed for an open-tank-in-pool type research reactor, and its seismic response, structural integrity, serviceability, and seismic margin have been evaluated during and after seismic events in this paper. The main important concept of the RPWP is to minimize the pool top radiation level by physically covering the reactor pool of the open-tank-in-pool type research reactor and suppressing the rise of flow induced by the primary cooling system. It is also to provide easy handling of the irradiated objects under the pool water by providing guide tubes and refueling cover to make the radioisotopes irradiated and protect the reactor structure assembly. For this concept, the new three dimensional design model of the RPWP is established for manufacturing, installation and operation, and the analytical model is developed to analyze the seismic performance. Since it is submerged under and influenced by water, the hydrodynamic effect is taken into account by using the hydrodynamic added mass method. To investigate the dynamic characteristics of the RPWP, a modal analysis of the developed analytical model is performed. To evaluate the structural integrity and serviceability of the RPWP, the response spectrum analysis and response time history analysis have been performed under the static load and the seismic load of a safe shutdown earthquake (SSE). Their stresses are analyzed for the structural integrity. The possibility of an impact between the RPWP and the most adjacent structure is investigated for the serviceability. The analysis results show that the maximum stress values of the base frame, guide tubes and refueling cover of the RPWP under the seismic event are within the specified code limits. It is confirmed that an impact does not take place under a seismic event. Also, the seismic margin of the RPWP is studied, and the seismic limit to sustain the structural integrity and serviceability is attained based on the deterministic and probability methods. Lastly, the hydrodynamic effect on the seismic performance of the RPWP is quantitatively investigated and from the result, an objective basis of the consideration of the hydrodynamic influence is acquired. Therefore, it is concluded that the newly devised RPWP is safely designed in that no damage to the structural integrity and serviceability, and a sufficient seismic margin is expected.
Research on the Insulation Design of a 154 kV Class HTS Power Cable and Termination
Kwag, D.S.,Cheon, H.G.,Choi, J.H.,Kim, H.J.,Cho, J.W.,Kim, S.H. Institute of Electrical and Electronics Engineers 2007 IEEE transactions on applied superconductivity Vol.17 No.2
<P>A 154 kV class high-temperature superconducting (HTS) power cable system Is developing in Korea. For insulation design of this cable, the grading method of insulating paper is proposed. The electrical insulation material has been used two kind of laminated polypropylene paper (LPP) that has different thickness. The use of graded insulation gives improved mechanical bending properties of the cable. Also, within a HTS cable technology the terminations are important components. A HTS cable termination is energized with the line-to-ground voltage between the coaxial center and outer surrounding conductors, in the axial direction there is a temperature difference from ambient to about 77 K. For insulation design of this termination, the insulation material of the termination body used glass fiber reinforced plastic (GFRP) and the capacitance-graded method is proposed. Therefore, in order to insulating design of a 154 kV class HTS power cable and termination, this paper will report on the experimental investigations in impulse breakdown and surface flashover characteristics of the insulation materials. Based on these experimental data, the electrical insulation design of a 154 kV class HTS power cable and termination were calculated.</P>
Construction and commissioning of a position-sensitive ionization chamber
Kwag, M. S.,Chae, K. Y.,Cha, S. M.,Kim, A.,Kim, M. J.,Lee, E. J.,Lee, J. H. 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol. No.
<P>A position-sensitive ionization chamber has been constructed and commissioned at the Physics Department of Sungkyunkwan University to extract position information on incident charged particles for future nuclear reaction measurements. By utilizing the newly-designed position-sensitive anodes and the previously-commissioned portable gas-filled ionization chamber by Chae et al., position information on incident particles could be obtained. The device was tested with an Am-241 alpha-emitting source, and the standard deviation of the fitted Gaussian distribution was measured to be 1.76 mm when a collimator with a 2 mm hole was used.</P>
Electronic property of Group IV phthalocyanine dimers: SiPcMPc
Kwag, G.,Bae, C.,Kim, S.,Lee, J.J.,Kenney, M.E. Elsevier Sequoia [etc.] 2009 Inorganica chimica acta Vol.362 No.6
A series of Group IV phthalocyanine (Pc) dimers, (n-C<SUB>6</SUB>H<SUB>13</SUB>)<SUB>3</SUB>SiOSiPcOSiPcOSi(n-C<SUB>6</SUB>H<SUB>13</SUB>)<SUB>3</SUB> (SiPcSiPc), (n-C<SUB>6</SUB>H<SUB>13</SUB>)<SUB>3</SUB>SiOSiPcOGePcOSi(n-C<SUB>6</SUB>H<SUB>13</SUB>)<SUB>3</SUB> (SiPcGePc), and (n-C<SUB>6</SUB>H<SUB>13</SUB>)<SUB>3</SUB>SiOSiPcOSnPcOH (SiPcSnPc), was characterized by cyclic voltammetry and DFT calculation. Two oxidations and two reductions were observed for (n-C<SUB>6</SUB>H<SUB>13</SUB>)<SUB>3</SUB>SiOSiPcOSiPcOSi(n-C<SUB>6</SUB>H<SUB>13</SUB>)<SUB>3</SUB> and (n-C<SUB>6</SUB>H<SUB>13</SUB>)<SUB>3</SUB>SiOSiPcOGePcOSi(n-C<SUB>6</SUB>H<SUB>13</SUB>)<SUB>3</SUB>, while there were two oxidations and three reductions for (n-C<SUB>6</SUB>H<SUB>13</SUB>)<SUB>3</SUB>SiOSiPcOSnPcOH. The Pc with a bigger size of the central metal in one part of the dimeric compound is more difficult to be oxidized but it is easier to be reduced at the same time: i.e., both oxidation and reduction potentials showed a positive shift with the increase of the size of the central metal atom. Density functional theory was used to optimize the structures of the Pc dimers and to understand the electrochemical properties. The optimized structures of HOSiPcOSiPcOH, HOSiPcOGePcOH and HOSiPcOSnPcOH as model compounds for SiPcSnPc, SiPcGePc, SiPcSiPc, respectively, show that all the Pc dimers are staggered, the plane-to-plane distances are 3.394, 3.538 and 3.722A, respectively. Tin generates a saddle-type structure of phthalocyanine, but silicon or germanium does not greatly distort the ring structure, and yields a planar ring structure. A large plane-to-plane distance and a high degree of plane distortion yield a red-shift of Q-band, a low ring current, high oxidation and low reduction potentials and high ionization energies.
Kwag, D.-S.,Cheon, H.-G.,Choi, J.-H.,Kim, H.-J.,Cho, J.-W.,Kim, S.-H. IEEE 2008 IEEE transactions on applied superconductivity Vol.18 No.2
<P>A high temperature superconducting (HTS) DC cable is ideal for transmitting large amount of electrical power over a long distance. However, it must be designed to operate reliably within the constraints of the electrical systems. Therefore, a study of the electrical insulation is important to develop a HTS DC cable because it is operated in a cryogenic high voltage environment. This paper discusses the dielectric constructions of the cable and summarizes the experiment results on the DC and impulse dielectric characteristics of the insulation material, in sheet form and mini-model cable configuration. This shows how to design such insulation to be operated reliably. These studies are essential for the insulation design of a HTS DC cable operating in cryogenic environment.</P>
초저온 캐스케이드 냉동사이클의 LNG 열교환기 압력강하 특성
윤정인(J. I. Yoon),최광환(K. H. Choi),곽진우(J. W. Kwag),손창효(C. H. Son),백승문(S. M. Baek) 한국태양에너지학회 2012 한국태양에너지학회 학술대회논문집 Vol.2012 No.3
Natural gas is converted in to LNG by chilling and liquefying the gas to the temperature of -162℃, when liquefied, the volume of natural gas is reduced to 1/600th of its standard volume. This gives LNG the advantage in transportation. The pressure dorp of the cascade liquefaction cycle was investigated and simulated using HYSYS software. The simulation results showed that the pressure drop in the LNG heat exchanger is set to 50 kPa considering the increase in the compressor work; of cryogenic cascade liquefaction cycle.
2011년 KSTAR 캠페인 중 HRS 비상정지 복구 결과
주재준(J.J. Joo),문경모(K.M. Moon),박동성(D.S. Park),장용복(Y.B. Chang),곽상우(S.W. Kwag),송낙형(N.H. Song),이현정(H.J. Lee),박영민(Y.M. Park),김남원(N.W. Kim),우인식(I.S. Woo),양형렬(H.L. Yang) 대한설비공학회 2012 대한설비공학회 학술발표대회논문집 Vol.2012 No.6
The KSTAR cool-down operation is divided 3 steps. One is cool down from ambient temperature to 4.5 K and another is keeping cryogenic state during the plasma experiment and the other is warm up to room temperature. During the 4th campaign of KSTAR, the Helium Refrigeration System (HRS) had been operated for 4 months. In this period, four times of the emergency shutdown (ESD) were happened due to the various reasons. The recovery process from the ESD should be different depending on the temperature of KSTAR cold system and the HRS operating status. At each phase, recovery procedure and recovery period are different.
Effects of Individuals and Behaviors on Acoustic Features of Ultrasonic Vocalizations in Rats
Jeon, J.H.,Song, J.I.,Jeon, B.S.,Kwag, J.H.,Park, K.H.,Kang, H.S.,Kim, D.H. Asian Australasian Association of Animal Productio 2010 Animal Bioscience Vol.23 No.4
The goal of this study was to investigate how spectrographic features of ultrasonic vocalizations (USVs) in rats vary among individuals and behaviors. Eighteen pairs of rats were allocated to individual pair cages. Each pair's behaviors and vocalizations were recorded during the 900s a known cage-mate was returning to the cage. The effects of individuals, behaviors, and the interaction between individuals and behaviors ($individuals{\times}behaviors$) were tested on the duration and peak frequencies. There was difference in the duration and peak frequency: i) among individuals (p<0.0001 and p<0.0001, respectively); ii) among behaviors (p = 0.0667 and p<0.0001, respectively); iii) among individuals${\times}$behaviors (p<0.0001 and p<0.0001, respectively). The frequency of ultrasonic vocalizations changed with a frequency ranging from 40 to 71 kHz which were emitted by individuals, whereas the frequency of ultrasonic vocalizations changed with a frequency ranging from 60 to 70 kHz which were emitted by behaviors. The peak frequency of call on 'contact' behavior was lower than that of call on other behaviors, but call duration of call on 'contact' was longer than on other behaviors. Especially, 40 kHz calls were found on 'contact' and 'other' behaviors. We suggest that ultrasonic vocalizations need to be subdivided and the effects of individuals and behaviors must be considered to assess emotional state of rats because these may influence the features of ultrasonic vocalizations.
곽진우(J. W. Kwag),백승문(S. M. Baek),정영권(Y. K. Jung),이곤재(G. J. Lee),윤정인(J. I. Yoon) 한국마린엔지니어링학회 2010 한국마린엔지니어링학회 학술대회 논문집 Vol.2010 No.10
This paper presents the prevention of frying oil rancidity by using a refrigerator. Fries in a hot frying process is done automatically by the reaction of oxygen in the air and heat degradation occurs by oxidation, heating, combined heat and oxidative polymerization occurs, and Fries will cause the loss of nutrition. This development technique using freezer on the bottom of the fryer, a couple of layers of water oxidation, won who is the main byproduct of the removal and allows the removal of trans fat. And frying oil for a long time to clean the aim is to enable. Frying oil frequent replacement due to oil rancidity, reducing the effective cost savings generated during and after use frying oil pollution of the environment is intended to reduce the problem.