• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.391-391
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• 2016

The carrier transport is a key factor that determines the device performances of semiconductor devices such as solar cells and transistors [1]. Particularly, devices composed of in amorphous semiconductors, the transport is often restricted by carrier trapping, associated with various defects. So far, the trapping has been studied for as-grown films at room temperature; however it has not been studied during growth under plasma processing. Here, we demonstrate the detection of trapped carriers in hydrogenated amorphous silicon (a-Si:H) films during plasma processing, and discuss the carrier trapping and defect kinetics. Using an optically pump-probe technique, we detected the trapped carriers (electrons) in an a-Si:H films during growth by a hydrogen diluted silane discharge [2]. A device-grade intrinsic a-Si:H film growing on a glass substrate was illuminated with pump and probe light. The pump induced the photocurrent, whereas the pulsed probe induced an increment in the photocurrent. The photocurrent and its increment were separately measured using a lock-in technique. Because the increment in the photocurrent originates from emission of trapped carriers, and therefore the trapped carrier density was determined from this increment under the assumption of carrier generation and recombination dynamics [2]. We found that the trapped carrier density in device grade intrinsic a-Si:H was the order of 1e17 to 1e18 cm-3. It was highly dependent on the growth conditions, particularly on the growth temperature. At 473K, the trapped carrier density was minimized. Interestingly, the detected trapped carriers were homogeneously distributed in the direction of film growth, and they were decreased once the film growth was terminated by turning off the discharge.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.915-918
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• 2016

Virtual testing devices are required due to rapid changes in the health care industry and the increase of the medical or nursing workforce. The importance of devices such as the simulator, blood vessels, and lab equipment for modeling blood flow to the heart is increasing too. In this study, we made heart pump by using a step motor and developed device which simulates arterial, venous blood pressure, and blood flow. We finally evaluated the function of proposed device. The proposed system is composed of the pump for simulating, the valve device to describe the resistance of the artery and vein, and a reducing device showing the characteristics of the venous system. We used BOXER pump for heart simulator and silicon tube for arterial and venous vessels, and designed a reducing device. We also used the pressure sensor to measure arterial blood pressure. For the evaluation of the proposed system, we selected a range of 50~100mmHg of the blood circuit 60 per minute and then compared the blood pressure of a person and the measured blood pressure.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.59-59
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• 2012

Vacuum pumping remains central to the performance and economy of many manufacturing processes, scientific instruments and scientific research. More vacuum is being used in many of the latest or leading edge manufacturing processes: Current examples include 3D semiconductor devices, EUV lithography, 450 mm silicon wafers, AMOLED displays, LEDs, Lithium-ion batteries and steel degassing. In other applications, vacuum pumping technology developments have led to much lower product costs which for example have enabled mass spectrometers to become a ubiquitous tool is life science research. Vacuum pumps have continuously evolved during the past 100 years of vacuum-based industrial processing but remain a key component which is often on the critical path of process and product improvements. This is especially so in the growing number of applications where the pumps are highly stressed. This presentation outlines significant developments in vacuum that have brought about this progress. The likely course of continued improvements is discussed in terms of increased performance and reliability, robust by-product handling, better cost efficiency and reduced environmental impact especially power consumption.

• Journal of the Korean Society of Visualization
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• v.1 no.1
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• pp.75-81
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• 2003

A custom micro-PIV optics assembly has been used to measure the flow fold inside a T-junction of a microchannel. The micro-PIV system consists of microscope objectives of various magnifications, a dichroic cube, and an 8-bit CCD camera. Fluorescent particles of diameters 620 nm have been used with a Nd:YAG laser and color filters. A programmable syringe pump with Teflon tubings were used to inject particle-seeded distilled water into the channel at flow rates of 2.0, 4.0, 6.0 mL/hr. The micro-channels are fabricated with PDMS with a silicon mold, then O$_{2}$ -ion bonded onto a slide glass. Results show differences in flow characteristics and resolution according to fluid injection rates, and magnifications, respectively. The results include PIV data with vector-to-vector distances of 2 $\mu$m with 32 pixel-square interrogation windows at 50$\%$ overlap.

• Proceedings of the KSMRM Conference
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• 2001.11a
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• pp.134-134
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• 2001

Purpose： To evaluate the physiologic background of poorly visualized aneurysms during DSA a contrast-enhanced MRA(CEMRA) due to hemodynamical isolation on clinical and experiment data. Method： Two cases of intracranial aneurysm which were poorly visualized on DSA a CEMRA and one case of intracranial aneurysm which had poor turnover of contrast mediu during DSA were selected for this clinical study. We evaluated the turnover of blood in t terminal aneurysm of handmade elastic silicon phantoms for comparative experiment. Flo experiments with DSA and contrast enhanced MRA were performed in elastic phantoms aneurysm with 3 different diameters (2, 5 and 10 mm) of neck mimicking basilar ti aneurysm, attached to pulsatile pump similar to that of human physiologic parameters. W compared the results with those of computational flow dynamics(CFD).

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.423-426
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• 2002

A custom micro-PIV optics assembly has been used to measure the flow field inside a T-shaped microchannel. The micro-PIV system consists of microscope objectives of various magnifications, a dichroic cube, and an 8-bit CCD camera. Fluorescent particles of diameters 620nm have been used with a Nd:YAG laser and color filters. A programmable syringe pump with Teflon tubings were used to inject particle-seeded distilled water into the channel at flow rates of $420,\;40,\;60{\mu}L/hr$. The microchannels are fabricated with PDMS with a silicon mold, then $O_2-ion$ bonded onto a slide glass. Results show differences in flow characteristics and resolution according to fluid injection rates, and magnifications, respectively. The results show PIV results with vector-to-vector distances of $2{\mu}m$ with 32 pixel-square interrogation windows at $50{\%}$ overlap.

• Journal of the Korean Society of Visualization
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• v.11 no.3
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• pp.12-16
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• 2013

The impact and spreading behaviors of silicon dioxide nanoparticle colloidal suspension droplets were quantitatively visualized using a high-speed imaging system. Millimeter-scale droplets were generated by a syringe pump and a needle. Droplets of different velocity were impacted on a non-porous solid surface. Images were consecutively recorded using a CMOS high-speed camera at 5000 fps (frames per second) for millimeter-scale droplets. Temporal variations of droplet diameter, velocity and maximum spreading diameters were evaluated from the sequential images captured for each experimental condition. Effects of Reynolds number, Weber number, and particle concentration were investigated experimentally.

• International Journal of Air-Conditioning and Refrigeration
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• v.6
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• pp.45-55
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• 1998

A theoretical and experimental study is performed to investigate the characteristics of ice slurry product. By diffusion-controlled evaporation model the possibility of ice slurry is theoretically anticipated. The water vapor evaporated from the surface of droplets is extracted continuously from the chamber by a vacuum pump. The droplet diameter is measured by silicon immersion method. The ice slurry is obtained by spraying droplets of ethylene glycol aqueous solution in the chamber where pressure is maintained under the triple point of water. The droplet with the diameter of 300 $\mu\textrm{m}$and the initial temperature of 2$0^{\circ}C$ was changed into ice particle within the chamber of 1.33m in height.

• Journal of radiological science and technology
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• v.25 no.1
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• pp.55-62
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• 2002

Aneurysm-mimicking findings were frequently visualized due to hemodynamical causes of dephasing effects around area of A-com artery during magnetic resonance angiography(MRA) and these kind of phenomena have not been clearly known yet. We investigated the hemodynamical patterns of dephasing effect around area of the A-com artery that might be a cause of false intracranial aneurysms on MRA. For experimental study, We used hand-made silicon phantoms of the asymmetric A-com artery as like a bifurcation configuration. In a closed circulatory system with UHDC computer driven cardiac pump system. MRA and fast digital subfraction angiography(DSA) involved the use of these phantoms. Flow patterns were evaluated with axial and coronal imaging of MRA(2D-TOF, 3D-TOF) and DSA of Phantoms constructed from an automated closed-type circulatory system filled with glycerol solution [circulation fluid(glycerol:water = 1:1.4)]. These findings were then compared with those obtained from computational fluid dynamic(CFD) for inter-experimental correlation study. Imaging findings of MRA, DSA and CFD on inflow zone according to the following: a) MRA demonstrated high signal intensity zone as inflow zone on silicon phantom; b) Patterns of DSA were well matched with MRA on trajectory of inflow zone; and c) CFD were well matched with MRA on the pattern of main flow. Imaging findings of MRA. DSA and CFD on turbulent flow zone according to the following: a) MRA demonstrated hyposignal intensity zone at shoulder and axillar zone of main inflow; b) DSA delineated prominent vortex flow at the same area. The hemodynamical causes of signal defect, which could Induce the false aneurysm on MRA, turned out to be dephasing effects at axilla area of bifurcation from turbulent flow as the results of MRA, DSA and CFD.

• Korean Journal of Materials Research
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• v.17 no.7
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• pp.366-370
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• 2007

Silicon nitride ($Si_3N_4$) ceramics have been considered for various components of nuclear power plants such as the mechanical seal of a reactor coolant pump (RCP), the guide roller for a control rod drive mechanism (CRDM), and a seal support, etc. Corrosion behavior of $Si_3N_4$ ceramics in a high-temperature and high-pressure water must be elucidated before they can be considered as components for nuclear power plants. In this study, the corrosion behaviors of $Si_3N_4$ ceramics containing MgO and $Al_2O_3$ as sintering aids were investigated at a hydrothermal condition ($300^{\circ}C$, 9.0 MPa) in pure water and 35 ppm LiOH solution. The corrosion reactions were controlled by a diffusion of the reactive species and/or products through the corroded layer. The grain-boundary phase was preferentially corroded in pure water whereas the $Si_3N_4$ grain seemed to be corroded at a similar rate to the grain-boundary phase in LiOH solution. Flexural strengths of the $Si_3N_4$ ceramics were significantly degraded due to the corrosion reaction. Results of this study imply that a variation of the sintering aids and/or a control (e.g., crystallization) of the grain-boundary phase are necessary to increase the corrosion resistance of $Si_3N_4$ ceramics in a high-temperature water.