• Title/Summary/Keyword: Inception Layer

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Electrical Insulation Design of a 154kV-Class HTS Power Cable

  • Choi, Jin-Wook;Kwag, Dong-Soon;Choi, Jae-Hyeong;Kim, Hae-Jong;Cho, Jeon-Wook;Kim, Sang-Hyun
    • Progress in Superconductivity and Cryogenics
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    • v.11 no.2
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    • pp.25-28
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    • 2009
  • A 154kV class high-temperature superconducting (HTS) power cable system is developing in Korea. For insulation design of this cable, it is important that study on cryogenic electrical insulation design to develop the cold dielectric type HTS cable because the cable is operated under the high voltage environment in cryogenic temperature. Therefore, this paper describes a design method for the electrical insulation layer of the cold dielectric type HTS cable adopting the partial discharge-free design under ac stress, based on the experimental results such a ac breakdown strength, partial discharge inception stress, $V_{ac}$-t characteristics, $V_{imp}$-n characteristics, and impulse breakdown strength of liquid nitrogen/laminated polypropylene paper (LPP) composite insulation system in which the mini-model cable is immersed into pressurized liquid nitrogen.

Electrical Insulation Characteristics of HTS Cables according to Bending Strain (고온초전도 케이블의 굴곡 변화에 따른 전기절연 특성)

  • Kwang, Dong-Soon;Kim, Sang-Hyun
    • Progress in Superconductivity and Cryogenics
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    • v.11 no.1
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    • pp.45-48
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    • 2009
  • Research on the mechanical properties of the dielectric paper and mini-model cable are important for optimum electrical insulation design of HTS cable, because the HTS cable experience of mechanical stress, such as tensile and bending stress. Also, it is operated at cryogenic temperature. Therefore, this paper discusses the experiment results on the AC and lighting impulse breakdown characteristics, partial discharge inception and extinction characteristics, and external shape change of the insulation layer according to bending strain of the mini-model cable.

The evolution characteristics of incipient soot particles in ethylene/air inverse diffusion flame (에틸렌/공기 역확산 화염에서의 초기 매연 입자의 성장 특성)

  • Oh, Kwang-Chul;Lee, Uen-Do;Shin, Hyun-Dong;Lee, Eui-Ju
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.1172-1177
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    • 2004
  • The evolution of incipient soot particles has been examined by high resolution electron microscopy (HRTEM) and elemental analyzer in ethylene-air inverse diffusion flames. Laser Induced Incandescence(LII) and laser scattering methods were introduced for examining the change of soot volume fraction and morphological properties in combustion generated soot qualitatively. Soot particles, collected by thermophoretic sampling were analyzed by using HRTEM to examine the nano structure of precursor particles. HRTEM micrographs apparently reveal a transformation of condensed phase of semitransparent tar-like material into precursor particles with relatively distinct boundary and crystalline which looks like regular layer structures. During this evolution histories C/H analysis was also performed to estimate the chemical evolution of precursor particles. The changes of C/H ratio of soot particles with respect to residence time can be divided into two parts: one is a very slowly increasing regime where tar-like materials are transformed into precursor particles (inception process) the other is an increasing region with constant rate where surface growth affects the increase of C/H ratio dominantly (surface growth region). These results provide a clear picture of a transition to mature soot from precursor materials.

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A study on the hydrofoil section shapes in consideration of viscous effects for marine propeller blades (점성의 영향을 고려한 선박 추진기용 익형의 단면 형상에 관한 연구)

  • 김시영
    • Journal of Advanced Marine Engineering and Technology
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    • v.12 no.2
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    • pp.46-56
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    • 1988
  • The author has presented a new approach to design hydrofoil section shapes in consideration of viscous for marine propeller blades. In suction sides of propeller blades, the pressure distribution on hydrofoil sections in non-cavitating flow should be examined before the study of cavitation characteristics. Generally, the calculation results for hydrofoil conformal mapping method by which neglect viscous effects do not agree with experimental ones. Moreover, another papers reported that laminar separation bubble and transition played an important role on the cavitation inception. From these considerations, it is very important to study the viscous effects of the hydrofoil sections, especially the mechanism separation bubble and the apparent thickness of hydrofoil section. Therefore, the new design method of hydrofoil sections in consideration of viscous effects in comparison to the airfoil section should be studied. In designing the new hydrofoil section shapes, based on Eppler theory, the author tried to give the peak negative pressure in leading edge region for NACA airfoil in consideration of viscous effects without turbulent boundary layer separation as much as possible. The design method was verified from the fact that the boundary characteristics was improved and the lifts of new hydrofoils were slightly in creased in comparison to these of NACA 16-012 symmetrical, NACA 4412 non-symmetrical airfoils.

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The evolution characteristics of incipient soot particles in ethylene/air inverse diffusion flame (에틸렌/공기 역확산 화염에서의 초기 매연 입자의 성장 특성)

  • Oh, Kwang-Chul;Lee, Uen-Do;Shin, Hyun-Dong;Lee, Eui-Ju
    • Journal of the Korean Society of Combustion
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    • v.9 no.2
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    • pp.38-44
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    • 2004
  • The evolution of incipient soot particles has been examined by high resolution electron microscopy (HRTEM) and elemental analyzer in ethylene-air inverse diffusion flames. Laser Induced Incandescence(LII) and laser scattering methods were introduced for examining the soot volume fraction and morphological properties in combustion generated soot qualitatively. Soot particles, collected by thermophoretic sampling, were analyzed by using HRTEM to examine the nano structure of precursor particles. HRTEM micrographs apparently reveal a transformation of condensed phase of semitransparent tar-like material into precursor particles with relatively distinct boundary and crystalline which looks like regular layer structures. During this evolution histories, C/H analysis was also performed to estimate the chemical evolution of precursor particles. The changes of C/H ratio of soot particles with respect to residence time can be divided into two parts: one is a very slowly increasing regime where tar-like materials are transformed into precursor particles (inception process) the other is an increasing region with constant rate where surface growth affects the increase of C/H ratio dominantly (surface growth process). These results provide a clear picture of a transition to mature soot from precursor materials.

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A Study on the MgO Protective Layer Deposited by Oxygen-Neutral-Beam-Assisted Deposition in AC PDP (산소 중성빔으로 보조증착된 MgO 보호막을 갖는 AC PDP의 특성에 관한 연구)

  • Li, Zhao-Hui;Kwon, Sang-Jik
    • Journal of the Korean Vacuum Society
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    • v.17 no.2
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    • pp.96-101
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    • 2008
  • The magnesium oxide (MgO) protective layer plays an important role in plasma display panels (PDPs). Our previous work demonstrated that the properties of MgO thin film could be improved, which were deposited by Ion-Beam-Assisted Deposition (IBAD). However arc discharge always occurs during the IBAD process. To avoid this problem, Oxygen-Neutral-Beam-Assisted Deposition (NBAD) is used to deposit MgO thin films in this paper. The energy of the oxygen neutral beam was used as the parameter to control the deposition. The experimental results showed that the oxygen neutral beam energy was effective in determining in structural and discharge characteristics. The lowest firing inception voltage, the highest brightness and the highest luminous efficiency were obtained when the MgO thin film was deposited with an oxygen neutral beam energy of 300eV. The surface morphology of MgO thin film was also analyzed using AFM (Atomic Force Microscopy) and SEM (Scanning Electron Microscopy).

Structural and Discharge Characteristics of MgO Deposited by Oxygen-Ion-Beam-Assisted Deposition in AC PDP (산소 이온 빔 보조 증착된 AC PDP용 MgO 보호막의 특성 연구)

  • Li, Zhao-Hui;Kim, Kwang-Ho;Ahn, Min-Hung;Hong, Seng-Jae;Im, Seung-Kyeok;Kwon, Sang-Jik
    • Journal of the Korean Vacuum Society
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    • v.16 no.5
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    • pp.338-342
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    • 2007
  • The magnesium oxide (MgO) protective layer plays an important role in plasma display panels (PDPs). In this paper, we describe the structural and discharge properties of MgO thin films, which were prepared by the ion-beam-assisted deposition (IBAD) of oxygen as the protective layer of PDPs. The energy of the oxygen ion beam was used as the parameter to control the deposition. We found that the oxygen ion beam energy was effective in determining in structural and discharge characteristics. The lowest firing inception voltage, the highest brightness and the highest luminous efficiency were obtained when the MgO thin film was deposited with an oxygen ion beam energy of 300 eV. The crystallization of the MgO thin film was also measured by X-ray diffraction analysis, and the surface quality was measured by atomic force microscopy.

Defect Diagnosis of Cable Insulating Materials by Partial Discharge Statistical Analysis

  • Shin, Jong-Yeol;Park, Hee-Doo;Lee, Jong-Yong;Hong, Jin-Woong
    • Transactions on Electrical and Electronic Materials
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    • v.11 no.1
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    • pp.42-47
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    • 2010
  • Polymer insulating materials such as cross linked polyethylene (XLPE) are employed in electric cables used for extra high voltage. These materials can degrade due to chemical, mechanical and electric stress, possibly caused by voids, the presence of extrinsic materials and protrusions. Therefore, this study measured discharge patterns, discharge phase angle, quantity and occurrence frequency as well as changes in XLPE under different temperatures and applied voltages. To quantitatively analyze the irregular partial discharge patterns measured, the discharge patterns were examined using a statistical program. A three layer sample was fabricated, wherein the upper and lower layers were composed of non-void XLPE, while the middle layer was composed of an air void and copper particles. After heating to room temperature and $50^{\circ}C$ and $80^{\circ}C$ in silicone oil, partial discharge characteristics were studied by increasing the voltage from the inception voltage to the breakdown voltage. Partial discharge statistical analysis showed that when the K-means clustering was carried out at 9 kV to determine the void discharge characteristics, the amount discharged at low temperatures was small but when the temperature was increased to $80^{\circ}C$, the discharge amount increased to be 5.7 times more than that at room temperature because electric charge injection became easier. An analysis of the kurtosis and the skewness confirmed that positive and negative polarity had counterclockwise and clockwise clustering distribution, respectively. When 5 kV was applied to copper particles, the K-means was conducted as the temperature changed from $50^{\circ}C$ to $80^{\circ}C$. The amount of charge at a positive polarity increased 20.3% and the amount of charge at a negative polarity increased 54.9%. The clustering distribution of a positive polarity and negative polarity showed a straight line in the kurtosis and skewness analyses.

A Study on the Use of Contrast Agent and the Improvement of Body Part Classification Performance through Deep Learning-Based CT Scan Reconstruction (딥러닝 기반 CT 스캔 재구성을 통한 조영제 사용 및 신체 부위 분류 성능 향상 연구)

  • Seongwon Na;Yousun Ko;Kyung Won Kim
    • Journal of Broadcast Engineering
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    • v.28 no.3
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    • pp.293-301
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    • 2023
  • Unstandardized medical data collection and management are still being conducted manually, and studies are being conducted to classify CT data using deep learning to solve this problem. However, most studies are developing models based only on the axial plane, which is a basic CT slice. Because CT images depict only human structures unlike general images, reconstructing CT scans alone can provide richer physical features. This study seeks to find ways to achieve higher performance through various methods of converting CT scan to 2D as well as axial planes. The training used 1042 CT scans from five body parts and collected 179 test sets and 448 with external datasets for model evaluation. To develop a deep learning model, we used InceptionResNetV2 pre-trained with ImageNet as a backbone and re-trained the entire layer of the model. As a result of the experiment, the reconstruction data model achieved 99.33% in body part classification, 1.12% higher than the axial model, and the axial model was higher only in brain and neck in contrast classification. In conclusion, it was possible to achieve more accurate performance when learning with data that shows better anatomical features than when trained with axial slice alone.

Incipient motion criteria of uniform gravel bed under falling spheres in open channel flow

  • Khe, Sok An;Park, Sang Deog;Jeon, Woo Sung
    • Proceedings of the Korea Water Resources Association Conference
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    • 2018.05a
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    • pp.149-149
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    • 2018
  • Prediction on initial motion of sediment is crucial to evaluate sediment transport and channel stability. The condition of incipient movement of sediment is characterized by bed shear stress, which is generated from force of moving water against the bed of the channel, and by critical shear stress, which depends on force resisting motion of sediment due to the submerged weight of the grains. When the bed shear stress exceeds the critical shear stress, sediment particles begin rolling and sliding at isolated and random locations. In Mountain River, debris flow frequently occurs due to heavy rainfall and can lead some natural stones from mountain slope into the bed river. This phenomenon could add additional forces to sediment transport system in the bed of river and also affect or change direction and magnitude of sediment movement. In this paper, evaluations on incipient motion of uniform coarse gravel under falling spheres impacts using small scale flume channel were conducted. The drag force of falling spheres due to water flow and length movement of falling spheres were investigated. The experiments were carried out in flume channel made by glass wall and steel floor with 12 m long, 0.6 m wide, and 0.6 m deep. The bed slopes were selected with the range from 0.7% to 1.5%. The thickness of granular layer was at least 3 times of diameter of granular particle to meet grain placement condition. The sphere diameters were chosen to be 4cm, 6 cm, 8 cm, 10 cm. The spheres were fallen in to the bed channel for critical condition and under critical condition of motion particle. Based on the experimental results, the Shields curve of particles Reynold number and dimensionless critical shear stress were plotted. The relationship between with drag force and the length movement of spheres were plotted. The pathways of the bed material Under the impact of spheres falling were analyzed.

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