• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.763-768
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• 2002

This paper presents a mathematical model predicting the temperature distribution in rotating GMA welding. The bead width increases with rotation frequency at the same rotation diameter because the molten droplets are deflected by centrifugal force. The numerical solution is obtained by solving the transient three-dimensional heat conduction equation considering the heat input from the welding arc, cathode heating and molten droplets. Generally in GMA welding the heat input may be assumed as a normally distributed source, but the droplet deflection causes some changes in the heat input distribution. To estimate the heat flux distribution due to the molten droplet, the contact point where the droplet is transferred on the weld pool surface is calculated from the flight trajectory of the droplets under the arc plasma velocity field obtained from the arc plasma analysis. The numerical analysis shows a tendency of broadened bead width and shallow penetration depth with the increase of rotating frequency. The simulation results are in good agreement with those obtained by the experiments under various welding conditions.

• 산업기술연구
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• 제21권B호
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• pp.149-153
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• 2001

A study on the particle growth in $TEOS/O_2$ plasma was performed, and particle size and its distribution was measured by the electrical aerosol analyzer (EAA), light scattering particle size analyzer and the particle size was also determined by SEM. The effects of process variables such as total gas flow rate, reactor pressure, supplied power and initial reactant concentration on the particle growth were investigated. From the EAA results, the particle size distribution is divided into three groups of the cluster size and the small and large size particles. The particle size distribution measured by the light scattering particle size analyzer becomes bimodal, because the cluster size particles smaller than 20 nm in diameter cannot be detected by the light scattering particle size analyzer. The size of particles measured by the light scattering particle size analyzer is in good agreements with those by the SEM. Also we could understand that the particle formation is very sensitive to the changes of reactor pressure and reactant concentration. As the total gas flow rate increases, the particle size decreases because of the shorter residence time. As the reactor pressure, or the reactant concentration increases, the particle concentration increases and the particles grow more quickly by the faster coagulation between particles.

• 공업화학
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• 제21권6호
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• pp.676-679
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• 2010

이송식 직류 열플라즈마를 이용하여 ZrVFe 합금모재로부터 복합 나노 입자를 제조하여 플라즈마 가스 유량이 제조된 입자의 특성에 미치는 영향을 분석하였다. 입자의 특성은 전계방출 주사전자 현미경(FE-SEM), 입도 분석기(PSA), X선 분광기(EDS), X선 회절계(XRD), Brunauer-Emmett-Teller (BET) 비표면적 측정기를 사용하여 분석하였다. 플라즈마 가스 유량을 20 L/min에서 40 L/min으로 증가시키면 평균입자크기가 91 nm에서 55 nm로 감소하며 입도분포의 기하학적 편차가 줄어들었고 비표면적은 $200m^2/g$에서 $255m^2/g$으로 증가하였으며 제조된 입자의 조성에는 큰 영향을 미치지 못했지만 결정성이 향상되었다.

• Journal of Astronomy and Space Sciences
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• 제37권2호
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• pp.95-104
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• 2020

Properties of plasmas that constitute the plasma sheet in the near-Earth magnetotail vary according to the solar wind conditions and location in the tail. In this case study, we present multi-spacecraft observations by Cluster that show a transition of plasma sheet from cold, dense to hot, tenuous state. The transition was associated with the passage of a spatial boundary that separates the plasma sheet into two regions with cold, dense and hot, tenuous plasmas. Ion phase space distributions show that the cold, dense ions have a Kappa distribution while the hot, tenuous ions have a Maxwellian distribution, implying that they have different origins or are produced by different thermalization processes. The transition boundary separated the plasma sheet in the dawn-dusk direction, and slowly moved toward the dawn flank. The hot, tenuous plasmas filled the central region while the cold, dense plasmas filled the outer region. The hot, tenuous plasmas were moving toward the Earth, pushing the cold, dense plasmas toward the flank. Different types of dynamical processes can be generated in each region, which can affect the development of geomagnetic activities.

• 전기학회논문지
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• 제60권3호
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• pp.669-673
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• 2011

This study explores the numerical analysis method of fluid dynamics in the reaction section to improve the gas processing efficiency in the hazardous gas removal by atmospheric thermal plasma. This study also intends to contribute in technology advance to improve the processing efficiency and make the process more stable. Numerical analysis of temperature distribution in the reaction section dependent on the change in flow velocity of Ar and plasma temperature change, which are major control variables in the cracking process of HFC-23 using arc plasma, was done. The characteristic of incoming oxygen by temperature suggested that when temperature increased to 1600K, 1700K, 1800K respectively, the range of cracking temperature 1500K increased to 75.0%, 83.3%, 90.2% respectively. The temperature change of Ar by velocity change was widest in the area higher than 1500K when the velocity was 2.5m/s; however, since there was no big difference when the velocity was 2m/s, it is believed that 2 m/s would be most proper.

• 한국식품과학회지
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• 제10권3호
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• pp.313-319
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• 1978

무지방사료(無脂肪飼料) 및 여기에 17:0, 18:0 혹은 18:2을 첨가(添加)한 사료(飼料)를 병아리에 급여(給與)해서 간장(肝臟) 및 혈장(血漿)의 각지질분획(各脂質分劃)의 지방산조성(脂肪酸組成)에 미치는 급여지방산(給與脂肪酸)의 영향(影響)을 조사(調査)하였다. 그 결과(結果) 간장중(肝臟中)의 총지질함량(總脂質含量) 및 각지질분획(各脂質分劃)의 함량(含量)은 급여지방산(給與脂肪酸)에 의해서 영향(影響)받지 않았다. 그러나 17:0을 급여(給與)하면 간장(肝臟) 및 혈장(血漿)의 각지질분획(各脂質分劃)에 17:0 및 17:1 출현(出現)하고, 혈장(血漿)트리그리세라이드에서는 17:0이 또한 혈장(血漿)콜레스테롤에스텔에서는 17:1이 다른 분획(分劃)보다도 유의(有意)하게 높았다. 더욱이 간장(肝臟)에서는 각분획(各分劃)사이에 양지방산(兩脂肪酸)의 분포치(分布値)에 큰 차이(差異)가 없었다. 18:2의 급여(給與)도 17:0을 급여(給與)한때와 같이 간장(肝臟) 및 혈장(血漿)의 각지질분획(各脂質分劃)에 18:2이 출현(出現)하고, 특(特)히 간장인지질분획(肝臟燐脂質分劃)에서 18:2의 분포치(分布値)는 다른분획(分劃)보다도 유의(有意)하게 높았다. 그러나 18:0을 급여(給與)해도 이것이 간장(肝臟) 및 혈장중(血漿中)에 특별적(特別的)으로 증가(增加)하지는 않았다. 또한 17:0 및 18:2과 같은 외인성지방산(外因性脂肪酸)의 급여(給與)에 의하여 내인적(內因的)으로 합성(合成)되는 16:1 및 18:1의 분포치(分布値)는 간장(肝臟)에서 감소(減少)하는 경향(傾向)을 나타내었다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2006년도 전력전자학술대회 논문집
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• pp.470-474
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• 2006

This dissertation discuses about a ferrite core plasma source using low operating frequency without sputtering problem by the stored electric field. Compared with the conventional RF power system with 13.56MHz switching frequency, the proposed plasma power system is only separated at 400kHz, so that it makes possible to use of low cost switching elements, PWM control and soft switching. Moreover, it could improve the coupling efficiency for plasma and antenna by using the ferrite core in order to transfer the energy of the load This dissertation tried to analyze new plasma generation method for the plasma generation system by modeling the plasma load and grafting the concept of impedance matching in order to interpret it with the formula This dissertation verified the ferrite core inductive coupling plasma source authorized for 400kHz of low frequency power by applying to the semi-conductor ash process thru the measurement of ash capacity and uniformed plasma distribution on the actual wafer.

• 천문학회보
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• 제40권1호
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• pp.66.3-67
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• 2015

Without scrutinizing reflection, the plasma comprising a coronal loop is usually regarded to reside within a flux rope. This picture seems to have been adopted from laboratory plasma pinches, in which a plasma of high density and pressure is confined in the vicinity of the flux rope axis by magnetic tension and magnetic pressure of the concave inward magnetic field. Such a configuration, in which the plasma pressure gradient and the field line curvature vector are almost parallel, however, is known to be vulnerable to ballooning instabilities (to which belong interchange instabilities as a subset). In coronal loops, however, ideal MHD (magnetohydrodynamic) ballooning instabilities are impeded by a very small field line curvature and the line-tying condition. We, therefore, focus on non-ideal (resistive) effects in this study. The footpoints of coronal loops are constantly under random motions of convective scales, which twist individual loop strands quite randomly. The loop strands with the axial current of the same direction tend to coalesce by magnetic reconnection. In this reconnection process, the plasma in the loop system is redistributed in such a way that a smaller potential energy of the system is attained. We have performed numerical MHD simulations to investigate the plasma redistribution in coalescence of many small flux ropes. Our results clearly show that the redistributed plasma is more accumulated between flux ropes rather than near the magnetic axes of flux ropes. The Joule heating, however, creates a different temperature distribution than the density distribution. Our study may give a hint of which part of magnetic field we are looking to in an observation.

• Journal of Nutrition and Health
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• 제35권4호
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• pp.421-430
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• 2002

사철쑥 (Artemisia capitlaris Thunberg)으로 성인병의 예방목적으로 흰쥐 (Sprague-Dawley rats)의 혈액 및 간지질 대사에 미치는 영향에 대한 효과를 알아보았다. 1) 사료이용효율은 L, LM, LP군에서 높았다 (p < 0.01). 혈청의 콜레스테롤 농도, 동 맥 경화지수 (p <0.01), 중성지질 (p < 0.01)은 L, LM, LP군에서 높았지만, 사철쑥 분말 첨가에 의해 HDL-콜레스테롤과 HTR를 증가시켰다 (p < 0.01). 2) 혈청 및 간 조직의 과산화지질은 C군에 비하여 L군이 유의적으로 많았으며, 사철쑥 첨가시 감소하였다 (p < 0.05). 3) 간 조직의 지방침착은 L군에서 지방양성구의 크기와 분포가 두드러지게 높았고. LM군, LP길군에서는 감소하였다. 이상의 결과는 사철쑥은 혈액 및 간의 지질조성 및 지질 대사에 바람직한 효과를 갖는 것으로 보인다. 이는 사철쑥이 성인병예방에 유용한 기능성 식품으로서 가치가 있을 것으로 사료된다.

• Journal of Nutrition and Health
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• 제19권5호
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• pp.296-303
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• 1986

흰쥐의 lipoprotein을 제거한 혈장내의 지질전이 활성도와 지진전이를 저해하는 활성도를 측정하였다. 지질전이 활성도의 측정은 방사성 동위원소가 함유된 cholesteryl ester (CE)와 triglyceride (TG) 로 표지된 인체의 혈장 low density lipoprotein 으로부터 high high density lipoprotein(HDL) 으로 전이되는 방사성 동위원소의 양을 측정하여 계산하였다. 지질전이 저해 활성도는 정제한 인체 혈장 지질전이 단백질에 의한 지질전이를 저해하는 정도로서 측정하였다. 흰쥐의 혈장에는 지질전이 활성도가 거의 없으나, 지질전이를 저해하는 활성도는 존재하였다. 지질전이 저해정도는 측정용액내의 lipoprotein 양이 증가할수록 감소하였다. 일반적으로 흰쥐의 HDL은 인체의 HDL에 비하여 CE 의 함량은 높으며 TG의 함량은 낮다. 흰쥐의 혈장에 인체의 혈장으로부터 정제한 지질전이 단백질을 가하여 37$^{\circ}C$에 24시간 두었을 때, HDL 로부터 very low density lipoprotein (VLDL)으로 CE가 이동하여 VLDL 의 CE 함량이 4배나 증가하였다. 반면에 VLDL로부터 HDL$_2$로TG가 이동하여 $HDL_2$의 함량은 TG함량은 9배나 증가하였다. 이와같은 현상은 흰쥐의 혈장 Lipoportein이 지질전이의 기질로서의 결함은 없음을 보여준다. 따라서 지질대사에 관한 실험에서의 흰쥐에 의한 실험결과의 해석에는 인체 혈장에 비하여 혈장에는 lipoprotein사이의 중성지질의 전이나 교환이 거의 없다는 특성이 고려되어야한다.