• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 춘계학술대회논문집
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• pp.97-103
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• 2009

A numerical study of the flow characteristics inside a U-type circular tube is carried out in this paper. The numerical simulations carried out by using a Navier-Stokes code which is commercially available. Before detailed numerical simulations, validation of present numerical approach is made by comparing numerical solutions with experimental data. Numerical simulations are performed to study the effect of curvature on the flow characteristics inside a U-type tube. Numerical solutions show that a significant effect on the secondary flow structure in the cross section of the tube, especially in the curved section is shown when the curvature ratio, ratio of curvature to tube diameter, is smaller than about 3.5. As the curvature ratio decreases below 3.5, a counter rotating vortex is found below the primary vortex in the cross section of the tube. Another dramatic change of the flow structure is the formation of streamwise separation zone when the curvature ratio is decreased below 1.25.

• 대한기계학회논문집A
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• 제32권8호
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• pp.617-623
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• 2008

The membrane filter adhered with nanostructured porous layer was made by heat treatment after deposition of nanoparticle-agglomerates sintered in aerosol phase onto a conventional micron-fibrous metal filter as a substrate filter. The Sintered-Nanoparticle-Agglomerates-coated NanoStructured porous layer Membrane Filter (SNA-NSMF), whose the filtration performance was improved compared with the conventional metal membrane filters, was developed by adhesion of nanoparticle-agglomerates of dendrite structure sintered onto the micron-fibrous metal filter. The size of nanoparticle-agglomerates of dendrite structure decreased with increasing the sintering temperature because nanoparticle-agglomerates shrank. When shrinking nanoparticle-agglomerates were deposited and treated with heat onto the conventional micron-fibrous metal filter, pore size of nanostructured porous layer decreased. Therefore, pressure drops of SNA-NSMFs increased from 0.3 to 0.516 kPa and filtration efficiencies remarkably increased from 95.612 to 99.9993%.

• Journal of electromagnetic engineering and science
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• 제18권1호
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• pp.7-12
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• 2018

This article proposes an ultrahigh frequency band radio frequency identification (RFID) tag antenna for drug runout management that can be used in hospitals. The RFID tag antenna is designed to function as a sensor that alerts drug runout when a drug inside a drip chamber is completely consumed but does not work when a drug remains inside a drop chamber. A previously proposed 915 MHz dipole antenna, is too large to be attached to the drip chamber of a feeding bag. Moreover, the length of the dipole (L) should be increased for conjugate matching with an RFID chip. Therefore, the dipole antenna is downsized so that it can be attached to the drip chamber through a fine meander line structure coupling with a corrugate meander line. A transparent cover is added to enhance the grip force between the designed antenna and the drip chamber and to enable detachment. The dimensions of the completed antenna structure attachable to a drip chamber are 32.59 mm (height) and 13.5 mm (width). The gain reduction due to the decreased antenna length is enhanced. The fabricated antenna shows an average omni-directional read range of 10.65 m on a horizontal plane and has the function of sensing the presence of a drug.

• Journal of Plant Biology
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• 제17권4호
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• pp.163-170
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• 1974

Leaf tissue of Glycine max Merr. was fixed in para-formaldehyde-glutarldehyde and postfixed in osmium tetroxide or postassium permanganate for electron microscopy. The origin of cytolysome-like organelles of mesophyll cell was studied and changes of fine structure of the organelles according to treating solutions such as gibberellin (GA), kinethin (KI), 2,4-dichlorophenoxy acetic acid(2, 4-D) or 2, 4-D＋GA(1mg/l, respectively) were observed. The cylolysome-like organelles differentiate in endoplasmic reticulum and plasmalemma, and they drop into vacuoles being isolated from the formers. They seem to change into myelin-like structure and to be degenerated by autodigestion. Cytolysome-like organelles involved in cell walls and vacuoles showed activity of acid phosphatase. In the group of GA and KI treatment, cytolysome-like organelles were similar to that of the control group. But in the treatmental groups of 2,4-D and 2,4-D＋GA, myelin-like structures increased in size and autodigestion of this organelles were similar to that of the control group. But in the treatmental groups of 2,4-D and 2,4-D＋GA, myelin-like structures increased in size and autodigestion of this organelle seemed to be accelerated. In the treatmental group of 2,4-D＋GA, myelin-like structures shown high electron density were observed in cytoplasm and vacuoles together.

• Korean Chemical Engineering Research
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• 제46권2호
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• pp.397-401
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• 2008

레이저 애블레이션에 의해서 가지상 구조체 형상인 나노입자 응집체를 합성하였다. 기존 마이크론 금속섬유 필터의 표면상에 나노입자 응집체를 고착하여 여과성능을 향상시켰다. 에어로졸 상에서 소결 처리된 나노입자 응집체를 증착한 후 열처리를 하여 나노구조체가 표면상에 형성된 소결 처리된 나노입자 응집체 고착 필터를 제작하였다. 소결 온도가 증가할수록 마이크론 금속섬유 필터 표면상에 고착된 나노입자 응집체의 표면적 증가로 인하여 차압은 조금 증가하지만 여과효율은 현저하게 증가하였다.

• 한국전산유체공학회지
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• 제14권3호
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• pp.105-114
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• 2009

A numerical study of the flow characteristics inside a U-type circular tube is carried out in this paper. The numerical simulations carried out by using a Navier-Stokes code which is commercially available. Before detailed numerical simulations, validation of present numerical approach is made by comparing numerical solutions with experimental data. Numerical simulations are performed to study the effect of curvature on the flow characteristics inside a U-type tube. Numerical solutions show that a significant effect on the secondary flow structure in the cross section of the tube, especially in the curved section is shown when the curvature ratio, ratio of curvature to tube diameter, is smaller than about 3.5. As the curvature ratio decreases below 3.5, a counter rotating vortex is found below the primary vortex in the cross section of the tube. Another dramatic change of the flow structure is the formation of streamwise separation zone when the curvature ratio is decreased below 1.25.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 C
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• pp.932-934
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• 1999

In this paper, the new IGBT structures with trap injection are proposed to improve switching characteristics of the conventional SOI LIGBT. The simulations are used in order to investigate the effects of the position, width and concentration of trap injection region using 2D device simulator MEDICI. And, their electrical characteristics are analyze and the optimum design parameters are extracted. As a result of simulation, the turn off time for the proposed LIGBT model A by the trap injection is $0.78{\mu}s$. And, the latch up voltage is 3.4V and forward blocking voltage is 168V which are superior to that of conventional structure. In addition, the proposed model is achieved more efficient in switching time and process effort. Therefore, It is shown that the trap injection is very effective to reduce the turn off time with a little increasing of on-state voltage drop if its design and process parameters are optimized.

• 한국주조공학회지
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• 제27권4호
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• pp.167-172
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• 2007

In the present study, the microstructural evolution and mechanical properties of $Al_{71.6}Ge_{28.4}$ eutectic alloy have been investigated. Stable (fcc ${\alpha}$-Al and diamond cubic ${\beta}$-Ge) and various metastable crystalline (monoclinic, rhombohedral) phases were produced by competitive phase selection during non-equilibrium processing methods i.e. melt spinning and injection casting. The as-injection casted samples containing metastable-equilibrium eutectic (${\alpha}$-Al + monoclinic) structure showed much higher strength than samples with equilibrium eutectic (${\alpha}-Al+{\beta}-Ge$) structure but plasticity disappointingly diminished. In order to endow the enhanced ductility without significant strength drop, the alloys was heat-treated at transition temperature from metastable phase to stable phase. The annealed specimen displayed the phase transformed microstructural evolution and enhanced macroscopic plasticity.

• 한국분말재료학회지
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• 제22권6호
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• pp.391-395
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• 2015

We report on the successful fabrication of ZnO nanorod (NR)/polystyrene (PS) nanosphere hybrid nanostructure by combining drop coating and hydrothermal methods. Especially, by adopting an atomic layer deposition method for seed layer formation, very uniform ZnO NR structure is grown on the complicated PS surfaces. By using zinc nitrate hexahydrate $[Zn(NO_3)_2{\cdot}6H_2O]$ and hexamine $[(CH_2)_6N_4]$ as sources for Zn and O in hydrothermal process, hexagonal shaped single crystal ZnO NRs are synthesized without dissolution of PS in hydrothermal solution. X-ray diffraction results show that the ZnO NRs are grown along c-axis with single crystalline structure and there is no trace of impurities or unintentionally formed intermetallic compounds. Photoluminescence spectrum measured at room temperature for the ZnO NRs on flat Si and PS show typical two emission bands, which are corresponding to the band-edge and deep level emissions in ZnO crystal. Based on these structural and optical investigations, we confirm that the ZnO NRs can be grown well even on the complicated PS surface morphology to form the chestnut-shaped hybrid nanostructures for the energy generation and storage applications.

• 한국공간구조학회논문집
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• 제3권2호
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• pp.69-75
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• 2003

In case of rectangular lattice dome which shearing rigidity is very small, it has a concern to drop Buckling strength considerably by external force. So, by means of system to increase buckling-strength, there is a method of construction that lattice of dome is one with roof material. In a case like this, shearing rigidity of roof material increases buckling-strength of the whole of structure and can be designed economically from the viewpoint of practice. In case of analysis is achieved considering roof material that adheres to lattice of dame, there is method that considers the rigidity that use effective width frame as method to evaluate rigidity of roof material. therefore, this study is aimed at deciding effective width of roof material united with rectangular lattice dome to evaluate rigidity of roof material by effective width of frame and investigating how much does rigidity of roof material united with lattice of dome increase buckling-strength of the whole of structure according to rise-ratio. Conditions of loading are vertical-type-uniform loading. Analysis method is based on FEM dealing with the geometrically nonlinear deflection problems.