• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
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• pp.93-94
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• 2006

The sheath of a single-conductor cable for ac service acts as a secondary of a transformer, the current in the conductor induces a voltage in the sheath. When the sheaths of single-conductor cables are bonded to each other, as is common practice for multi-conductor cables, the induced voltage causes current to flow in the completed circuit. This current causes losses in the sheath. Various methods of bonding may be used for the purpose of minimizing sheath losses. In korea, sheath cross bonding system was employed for the prevention of sheath losses, the sheaths wire subjected to at voltages, and the bonding was designed to keep the magnitude of the induced voltages within small limits so as to prevent the possibility of sheath corrosion. But, sheath cross bonding system without transposition of cable can not achieve an exact balance of induced sheath voltages unless the cables are lain in trefoil. This paper describes a transposition system with sheath cross bonding using EMTP(Electromagnetic Transient Program). The transposition system with cross bonding can be extended to longer cable circuits for laid in flat as wall as trefoil by the methods described in this paper.

• 한국군사과학기술학회지
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• 제22권6호
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• pp.763-772
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• 2019

There is a need to use sheath flow nozzle to detect bioaerosol such as virus and bacteria due to their characteristics. In order to enhance the detection performance depending on nozzle parameters, numerical analysis was carried out using a commercial code, ANSYS CFX. Eulerian-lagrangian approach method is used in this simulation. Multiphase flow characteristics between primary fluid and solid were considered. The detection performance was evaluated based on the results of flow field in nozzle chamber such as focusing efficiency and swirl strength. In addition, Latin hypercube sampling(LHS) of design of experiment(DOE) was used for generating a near-random sampling. Then, the acceleration section is optimized using response surface method(RSM). Results show that the optimized model achieved a 6.13 % in a focusing efficiency and 11.47 % increase in swirl strength over the reference model.

• 한국대기환경학회지
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• 제20권3호
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• pp.411-419
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• 2004

Titania particles are widely used as a photocatalyst to treat various contaminants in air and water. Titania particles were formed by vapor-phase oxidation of titanium tetraisopropoxide (TTIP) in a tube furnace between 773 and 1,273 K. The effect of process variables such as furnace temperature, flow rate of carrier air, and flow rate of sheath air on powder size and phase characteristics was investigated using a scanning mobility particle sizer (SMPS), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The size distribution of synthesized titania particles was characterized with mode diameter and peak concentration. The mode diameter ranging from 20 to 80 nm decreased with increasing flow rates of sheath air and carrier air, and increased with increasing furnace temperature. The peak concentration increased with increasing flow rates of sheath air and carrier air The best synthetic condition for high production rate can be derived from the experimental data set represented by mode diameter and peak concentration. The crystal structure of synthesized titania particles was found to be anatase phase, ensuring high photocatalytic potential.

• 한국전기전자재료학회논문지
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• 제17권6호
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• pp.678-682
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• 2004

Generally Bi-2223/Ag tapes have a broad S/N transition region and their sheath is a good electric conductor. In this study, the current distribution between superconductor and metal sheath in HTS tapes were investigated. AC with its peak value above 10 times $I_{c}$ was applied to HTS tapes for around 6 cycles and V-I characteristics were measured. Using the resistance of the sheath and V-I curves, the current distribution between superconductor and metal sheath was calculated. When 150 $A_{p}$ was applied, more than 2/3 of the current flows through superconductor. However, in the case of 304 $A_{p}$, most of the applied current came to flow through the metal sheath at the 6th cycle.e.e.e.

• Korean Chemical Engineering Research
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• 제48권4호
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• pp.470-474
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• 2010

본 연구는 간편한 마이크로플루이딕 칩을 이용하여 매우 균일한 PEG 마이크로섬유 제작방법을 소개한다. 두 섞이지 않는 상의 주입을 통하여, 연속상의 덮개유동(sheath flow)이 분산상의 안정된 늘어지는 유동(Elongated flow)을 형성하고 채널 내부에 자외선 조사를 통해 고분자 마이크로섬유가 형성되도록 한다. 안정된 마이크로 유동형성의 최적화를 위해 각 사용되는 분산상 유체의 부피유속과 케필러리 수의 상관관계를 이용하여 조사하고 이를 이용하여 최적조건을 확립하였다. 안정된 유동영역에서 형성된 마이크로섬유는 매우 균일하며 재현성이 우수하다. 중요하게는 부피제어를 통해 마이크로섬유의 두께 제어가 가능하며 이를 이용하여 원하는 두께를 손쉽게 얻을 수 있다. 또한, 이와 같은 시스템을 통해 얻어진 마이크로섬유에 물리적으로 생체물질을 고정화하여 바이오센서 및 조직공학에서 적용 가능한 도구로 사용될 수 있음을 보여준다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.581-584
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• 2008

A generation of a particle beam is the key technique in a flow cytometry that measures the fluorescence and light scattering of individual cell and other particulate or molecular analytes in biomedical research. Recent methods performing this function require a laborious and time-consuming assembly. In the present work, we propose a novel device for the generation of an axisymmetrical focusing beam of microparticles (3-D focusing) in a single capillary without sheath flows. This work uses the concept that the particles migrate toward the centerline of the channel when they lag behind the parabolic velocity profile. Particle focusing of spherical particles was successfully made with a beam diameter of about 10 ${\mu}$m. Proposed device provides crucial solutions for simple and innovative 3-D particle focusing method for the applications to the MEMS-based micro-flow cytometry. We believe that this device can be utilized in a wide variety of applications, such as biomedical/ biochemical engineering.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2692-2695
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• 2008

Polydiacetylene (PDA) is chemosensor materials that exhibit non-fluorescent-to-fluorescent transition as well as blue-to-red visible color change upon chemical or thermal stress. They have been studied in forms of film or microarray chip, so far. In this paper, we provide a novel technique to fabricate continuous micro-fiber PDA sensor using in-situ laser-polymerization technique and 3-D hydrodynamic focusing on a microfluidic chip. The flow of a monomer solution with diacetylene (DA) monomer is focused by a sheath flow on a 3-D microfluidic chip. The focused flow is exposed to 365 nm UV laser beam for in-situ polymerization which generates a continuous fiber containing DA monomers. Then, the fiber is exposed to 254 nm UV light to polymerize DA monomers to PDA. Preliminary results indicate that the fiber size can be controlled by the flow rates of the monomer solution and sheath flows and that a PDA sensor fiber successively responds to chemical and thermal stress.

• 대한기계학회논문집B
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• 제27권12호
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• pp.1766-1771
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• 2003

House made differential mobility analyzer(DMA) is calibrated with NIST SRM 1691(300 nm PSL). Then the particle size and uncertainty for differential mobility analyzer(DMA) using the NIST SRM 1963(100 nm PSL). In result, calibration of prototype DMA is measured using 300 nm NIST SRM 1691, then sheath air flow was corrected 126.67 ㎤/s. Corrected sheath air flow is used in uncertainty measurement of prototype DMA. Uncertainty analysis is performed using NIST SRM 1963(100 nm PSL). The experimental result shows that NIST SRM 1963 is measured as 102.17 nm with a type A uncertainty of 0.33 nm.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1998년도 춘계학술발표회논문집(2)
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• pp.216-221
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• 1998

A study on induction plasma deposition with ceramic materials, yttria-stabilized-zirconia ZrO$_2$-Y$_2$O$_3$ (m.p 264O $^{\circ}C$), was conducted with a view developing a new method for nuclear fuel fabrication Before making dense pellets more than 96％TD., the spraying condition was optimized through the process parameters, such as chamber pressure, plasma plate power powder spraying distance, sheath gas composition, probe position, particle size and powders different morphology. The results with a 5mm thick deposit on rectangular planar graphite substrates showed a 97.11％ theoretical density when the sheath gas flow rate was Ar/H$_2$120/20 l/min, probe position 8cm, particle size -75 ${\mu}{\textrm}{m}$ and spraying distance 22cm by AMDRY146 powder. The degree of influence of the main effects on density were powder morphology. particle size, sheath gas composition, plate power and spraying distance, in that order. Among the two parameter interactions, the sheath gas composition and chamber pressure affects density greatly. By using the multi-pellets mold wheel type, the pellet density did not exceed 94%T.D., owing to the spraying angle.

• 한국수정란이식학회지
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• 제26권3호
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• pp.181-186
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• 2011

Spermatozoa sorted by flow cytometry have been successfully used to produce offspring in domestic animals and are commercially available for cattle. Also sheath fluid is the important environment for viability of sex-sorted sperm in flow cytometry. The aim of this study was to investigate whether or not HEPES (N-2-hydroxyethylpiperazine-N'-2-Ethanesulfonic acid) has any effect on the viability in sex-sorted Hanwoo (Korean native cattle) sperm. In this study, the semen was collected from Hanwoo of Hoengseong Livestock Cooperation by artificial vagina method then pooled and subjected to cryopreservation in straws. Sperm were cultured for 0, 30, 60 and 120 min with 0, 2.5, 5, 7.5 and 10 mM of HEPES added to the sheath fluid and incubated at 4, 20 and 38$^{\circ}C$, respectively. For the cytometric analysis the frozen-thawed semen was extended with 5 mM HEPES extender to final concentration ($2{\times}10^7$ spermatozoa) at 4, 20 and 37$^{\circ}C$. Sperm viability was assessed with SYBR-14 and propidium iodide (PI) staining. This study shows that the viability of sperm was decreased with prolongation of incubation time in all of test. But the viability of sperm which were treated with 38$^{\circ}C$ was gently decreased than that of treated with other temperature. The viability of the control was sharply decreased (p<0.05) than all of the HEPES treatment group at 60 to 120 min in 38$^{\circ}C$. X-sexed sperm was more sensitive than Y-sexed sperm to temperature during f10w cytometry (p<0.05). In conclusion, the results of this study suggest that the sheath fluid with 5 mM HEPES has effect on maintenance of viability after sperm sexing at 37$^{\circ}C$ in Hanwoo.