• 전기학회논문지
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• 제60권4호
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• pp.753-758
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• 2011

Magnetic field and Electric field of High Temperature Superconducting magnet are very important to analysis of superconducting magnet. The maximum perpendicular magnetic field was applied to the outermost pancake windings. The critical current of all the magnet windings is limited by the critical current of the outermost pancake windings. The E-J relation was used to determine the critical current, and an evolution s trategy was adopted for the optimization of gap length between each pancake windins. The results of calculations show that the critical current and the central magnetic field and uniformity increased by 82.6% and 31.6% and 50.8%, respectively, for a magnet consisting of ten pancake windings. This paper did an analysis the cause of increase the critical current and central magnetic field and uniformity in no gap and optimal gap model.

• 한국환경과학회지
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• 제17권7호
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• pp.817-826
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• 2008

Using high voltage electric fields induced by high voltage AC (10-12 kV/cm, 20 kHz) and pulsed (20-30 kV/cm, 40 Hz) electric field generator as a semipermanent and environment-friendly disinfecting apparatus, the disinfection effect of coliform group in the effluent of sewage plant was investigated. The effects of electric field strength, treatment time, discharge area of a discharge tube, water quality factors (electric conductivity, pH and SS) on its death rate were examined. The death rate of coliform group was increased with increasing electric field strength and treatment time. For AC and pulsed electric field generator, the critical electric field strength was 6 kV/cm and 2 kV/cm, respectively, and the critical treatment time was 5 min and 2 min, respectively, regardless of electric field strength. Comparing the death rate of coliform group by AC and pulsed electric fields used in this study, its death rate was higher for the latter than the former, but did not increase linearly with increasing electric field strength. The results obtained for the effects of discharge area, electric conductivity, pH and SS on the death rate of coliform group using AC electric field (12 kV/cm, 20 kHz) were as follows: its death rate showed the trend to increase linearly with increasing discharge area; for the effect of electric conductivity, its death rate was increased with increasing electric conductivity, regardless of ionic species, increased with increasing cationic valency, but was similar between the same cationic valency; the pH $5{\sim}9$ used in this study did not affect its death rate; its death rate was decreased with increasing SS concentration.

• 전기학회논문지
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• 제66권4호
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• pp.659-665
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• 2017

Power semiconductor devices required the low on-resistance and high breakdown voltage. Wide band-gap materials opened a new technology of the power devices which promised a thin drift layer at an identical breakdown voltage. The diamond had the wide band-gap of 5.5 eV which induced the low power loss, high breakdown capability, low intrinsic carrier generation, and high operation temperature. We investigated the p-type pseudo-vertical diamond Schottky barrier diodes using a numerical simulation. The impact ionization rate was material to calculating the breakdown voltage. We revised the impact ionization rate of the diamond for adjusting the parallel-plane breakdown field at 10 MV/cm. Effects of the field plate on the breakdown voltage was also analyzed. A conventional diamond Schottky barrier diode without field plate exhibited the high forward current of 0.52 A/mm and low on-resistance of $1.71{\Omega}-mm$ at the forward voltage of 2 V. The simulated breakdown field of the conventional device was 13.3 MV/cm. The breakdown voltage of the conventional device and proposed devices with the $SiO_2$ passivation layer, anode field plate (AFP), and cathode field plate (CFP) was 680, 810, 810, and 1020 V, respectively. The AFP cannot alleviate the concentration of the electric field at the cathode edge. The CFP increased the breakdown voltage with evidences of the electric field and potential. However, we should consider the dielectric breakdown because the ideal breakdown field of the diamond is higher than that of the $SiO_2$, which is widely used as the passivation layer. The real breakdown voltage of the device with CFP decreased from 1020 to 565 V due to the dielectric breakdown.

• Current Applied Physics
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• 제18권11호
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• pp.1426-1430
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• 2018

High magnetic field effects on the microstructure and magnetic properties of $BaFe_{12}O_{19}$ hexaferrites synthesized hydrothermal method have been investigated. The obtained results indicate that the lattice constant decreases gradually as the magnetic field strength increases, which may be attributed to the lattice distortion resulted from the high magnetic field. Polycrystalline $BaFe_{12}O_{19}$ samples prepared under magnetic field strength at zero and 5 T are single phase. It is found that application of external magnetic field during synthesis can induce orientated growth of the hexaferrite crystals along the easy magnetic axis. The magnetic properties can be effectively regulated by an application of high magnetic fields. It is observed that the $BaFe_{12}O_{19}$ prepared under a 5 T magnetic field exhibits a higher room-temperature saturation magnetization (66.3 emu/g) than that of the sample (43.6 emu/g) obtained without magnetic field. The results can be explained as the enhanced crystalline, improvement of $Fe^{3+}$ ions occupancy and the oriented growth induced by the external magnetic field. The growing orientation of particles gives rise to increased coercivity due to the enhancement in shape anisotropy. It is expected that an application of magnetic field during the formation of magnetic nanoparticles could be a promising technique to modify magnetic properties with excellent performance.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1999년도 제17회 학술발표회 논문개요집
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• pp.62-62
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• 1999

Carbon based materials have many attractive properties such as a wide band gap, a low electron affinity, and a high chemical and mechanical stability. Therefore, researches on the carbon-based materials as field emitters have been drawn extensively to enhance the field emission properties. Especially, diamond gives high current density, high current stability high thermal conductivity durable for high temperature operation, and low field emission behaviors, Among these properties understanding the origin of low field emission is a key factor for the application of diamond to a filed emitter and the verification of the emission site and its distribution of diamond is helpful to clarify the origin of low field emission from diamond There have been many investigations on the origin of low field emission behavior of diamond crystal or chemical vapor deposition (CVD) diamond films that is intentionally doped or not. However, the origin of the low field emission behavior and the consequent field emission mechanism is still not converged and those may be different between diamond crystal and CVD diamond films as well as the diamond that is doped or not. In addition, there have been no systematic studies on the dependence of nondiamond carbon on the spatial distribution of emission sites and its uniformity. Thus, clarifying a possible mechanism for the low field emission covering the diamond with various properties might be indeed a difficult work. On the other hand, it is believed that electron emission mechanisms of diamond are closely related to the emission sites and its distributions. In this context, it will be helpful to compare the spatial distribution of emission sites and field emission properties of the diamond films prepared by systematic variations of structural property. In this study, we have focused on an understanding of the field emission variations of structural property. In this study, we have focused on an understanding of the field emission mechanism for the CVD grown undoped polycrystalline diamond films with significantly different structural properties. The structural properties of the films were systematically modified by varying the CH4/H2 ratio and/or applying positive substrate bias examined. It was confirmed from the present study that the field emission characteristics are strongly dependent on the nondiamond carbon contents of the undoped polycrystalline diamond films, and a possible field emission mechanism for the undoped polycrystalline diamond films is suggested.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.384-384
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• 2011

Carbon nanotubes (CNTs) have been studied as an ideal material for field emitters due to the high aspect ratio, excellent electrical property and good mechanical strength. There were many reports on CNT emitters fabricated on rigid substrates, but rare reports about CNT flexible field emitters. Recently, we considered that CNTs can be a good candidate for a flexible field emitter material because of their excellent Young's modulus and elasticity, which could not be achieved with metal tips or semiconducting nanowire tips. In this work, we demonstrated the CNT flexible field emitters fabricated by a simple method and studied the field emission properties of the CNT flexible field emitters under various bending conditions. The flexible field emitters showed stable and uniform emission characteristics. Especially, there is no remarkable change of the field emission properties at the CNT flexible field emitters according to the bending conditions. The CNT flexible field emitters also exhibited a good field emission performance like the low turn-on field and high emission current. Therefore, we suggest that the CNT flexible emitters can be used in many practical applications under different bending conditions.

• Journal of Ginseng Research
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• 제4권2호
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• pp.175-185
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• 1980

A study was made to clarify the topographical. and Physical characteristics of ginseng field in terms of soil science and to find the relationship between soil characteristics and ginseng growth, as well as yield of ginseng roots Forty nine farmer's red ginseng field of ginseng growing area were chosen for this study and investigated for two years. The results obtained were as follow. 1. Ginseng fie1ds with high yield which represent the more than 1.8kg of ginseng root per 3.2m2 were found in soil series of Bancheon, Yeongog, Weongog, etc. whose texture were the clay loam to clay soil. On the other hand, ginseng field with low yield were observed in soil series of seogto whose texture was loamy soil with high content of gravels. 2 Soil of ginseng field with high yield had higher content of clay. silt soil moisture and soil pore as compared with soils of low yields. These soil characteristics were positively correlated with stem length stem diameter and root weight of ginseng plsnt and negatively correlated with rate of missing plant 3. The adequate ranges of soil 3 phase from high yield ginseng field were 40 to 50% of solid Phase, 22 to 35% of liquid phase, 25 to 35% of gaseous phase in top soil and 45 to 55% of solid phase. 28 to 30% of liquid phase. 15 to 20% of gaseous phase in subsoil respectively.

• 전기학회논문지
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• 제61권11호
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• pp.1641-1645
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• 2012

In this study, the ZnO nanorod is grown on the seed layered glass substrate by applying an external electric field to fabricate the ZnO nanorod with the high quality and to increase the yield of the ZnO nanorod. It is possible to grow the definite and clear hexagonal ZnO nanorod as the cathode of the high voltage is connected to the side of the seed layered glass substrate and the anode is connected to the opposite side because more $Zn^{2+}$ ions are located around the ZnO seed layer and are accumulated easily due to the external electric field. As a result, it is succeeded to fabricate the definite hexagonal ZnO nanorod having better structural characteristics by applying the external electric field during the growth process. Therefore, it is demonstrated that the external electric field is effective to fabricate the high quality ZnO nanorod without changing any composition of the ZnO nanorod.

• 폴리머
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• 제30권6호
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• pp.563-567
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• 2006

생체 적합성이 우수한 gelatin(GEL)과 기계적 물성이 뛰어난 poly(vinyl alcohol)(PVA)로 이루어진 블렌드막을 $3{\sim}10kV$의 고전장하에서 용액 캐스팅 법에 의해 제조하였고, 막중에 형성되는 미세한 domain 구조의 배향에 미치는 전장의 효과를 조사하였다. 5 kV이상의 높은 전장하에서 제조된 막의 경우 SEM 사진으로부터 막중의 GEL domain이 전장인가 방향으로 배향되어 있음을 관찰하였다. 이는 제막 중 상분리된 두 상의 계면장력 감소에 기인한 Maxwell의 정전 분산 효과에 의한 것으로 해석될 수 있다. 또한, 고전장 인가시 전극 판에서 발생하는 열과 GEL domain의 연신 배향 효과에 의해 PVA/GEL 블렌드막의 결정화도가 증가하는 것을 WAXD와 팽윤거동 관찰을 통해 확인 할 수 있었다.

• The Journal of Korean Physical Therapy
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• 제34권4호
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• pp.135-139
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• 2022

Purpose: We investigated the satisfaction of physical therapy course according to teaching ways after COVID-19. Methods: 336 students in major of physical therapy were recruited in this study. Based on the classification of subjects in the national examination, the questionnaire was divided into 6 subjects in the basic field of physical therapy, 2 subjects in the field of physical therapy diagnostic evaluation, 8 subjects in the field of physical therapy intervention, and 3 subjects in other fields. The Likert scale was used. Results: In the basic field of physical therapy, all subjects were shown the high score of the satisfactory in face-to-face classes except for the public health and medical law compared to the non-face-to-face classes and mixed classes. Regarding the field of physical therapy diagnostic evaluation, the principle of diagnostic evaluation was shown the high score of the satisfactory in face-to-face classes compared to the non-face-to-face classes and mixed classes. In the field of physical therapy intervention, all subjects were shown the high score of the satisfactory in face-to-face classes compared to the non-face-to-face classes and mixed classes. Conclusion: We found that the face-to-face classes in most of subjects was shown the high score of satisfactory. We believed that our results can be used as basic data for physical therapy major learning methods.