• Journal of Advanced Marine Engineering and Technology
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• v.20 no.2
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• pp.48-56
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• 1996

This paper is concerned with a method for calibrating five-hole probes of both angle-tube and prismatic geometries to measure local total and static pressures and the magnitude and direction of the mean velocity vector. Descriptions of the calibration technique, the typical calibration data, and an accompanying discussion of the interpolation procedure are included. The flow properties are determined explicitly from measured probe pressures using calibration data. Flow angles are obtained within the deviation angle of 1.0 degree and dynamic pressures within 0.03 with 95% certainty. The variations in the calibration data due to Reynolds number are also discussed. For the range of Reynolds number employed, no effect was detected on the pitch, yaw abd total pressure coefficients. However, the static pressure coefficient showed change to cause minor variations in the magnitude of the calculated velocity vector. To account for these variations, average correction factors need to be incorporated into the static pressure coefficient.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.556-561
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• 2000

This paper deals with the control of an active bending actuator fur a catheter. The bending actuator with 40mm in length utilizes three zigzag SMA (shape memory alloy) springs which are equally located in the circumference between inner $({\phi}2.5 mm)$ and outer $({\phi}3.0mm)$ tube. It is purposed on realization of desired bending angle $(90^{\circ})$ and direction $(360^{\circ})$. It is also installed in front of the catheter and used to guide a path at extremely bent or branched blood vessel. The performance-analysis of the bending actuator are investigated fur the purpose of optimizing the control of the bending actuator. The analog joy stick is used to command a bending angle and direction for the fast and accurate response. According to the commands of the joy stick, tensile force of each SMA spring is computed and obtained by controlling the temperature of each SMA spring using PWM (pulse width modulation) of supplied electric power.

• Journal of ILASS-Korea
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• v.9 no.1
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• pp.1-7
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• 2004

This paper describes the characteristics of injection rate and macroscopic behavior of fuel spray injected from common-rail type diesel injectors with different nozzle geometries. The injection rates according to the nozzle geometries were measured at different energizing duration of the injector solenoid and injection pressure by using the Bosch's injection rate meter based on the pressure variation in the tube. The spray behaviors injected from the different nozzles were visualized using the spray visualization system composed of an Ar-ion laser, an ICCD camera, and a synchronization system at various injection and ambient pressures. It is revealed that VCO nozzle has higher spray tip velocity at the early stage of injection duration and wider spray cone angle than the mini-sac nozzles. Also the spray cone angle is increased with the increase of nozzle diameter.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.21-27
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• 2003

This paper proposes a new model of the pressure drop for more accurate description of oscillating flow through regenerator under pulsating pressure conditions in contrast to an existing model based on steady flow. For the universal uses of the oscillating flow model, non-dimensional parameters, which consist of Reynolds number, Valensi number gas domain length ratio, oscillating flow friction factor and phase angle of pressure drop, are derived from the capillary tube model of the regenerator. Two correlation equations of the model are obtained from the experiments for the twill square screen regenerators under various operating frequencies and inlet mass flow rates. The oscillating friction factor is a function of only the Reynolds number and the phase angle of pressure drop is a function of the Valensi number and the gas domain length ratio. Experiment is also performed to examine the effects of the shape of screens.

• Journal of the Semiconductor & Display Technology
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• v.10 no.2
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• pp.109-113
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• 2011

Hot air flow simulations of the wet station dryer module for the solar cell cleaning were conducted. Air incident angles such as to the substrates ($45^{\circ}$), to the bottom ($90^{\circ}$), and to the wall ($135^{\circ}$) were considered. Based on the simulated velocity and temperature profiles, appropriate incident angle was proposed, and it was well matched to experimental results. Additionally, uniform and non-uniform air hole sizes of the tube were compared for the uniform air flow distribution through the batch.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.488-491
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• 2000

Bi-2223/Ag superconducting wires have been mainly prepared by a powder-in-tube method. The drawing and the rolling are main processes to increase the core density and wire length. In the fabrication of long wire, especially, the drawing should be precisely controlled to assure the filament homogeneity. In this paper, the influences of drawing die angle, bearing length and reduction ratio on the sausaging and the critical current density of the wire are investigated. Single cored and multi-filamentary wires are fabricated by PIT method with different conditions. The core densities and sausaging in the wires are investigated and are discussed regarding their relationship to the I$_{c}$. It was made clear that the geometry of drawing die is sensitively dependent on the sausaging. The improvement of I$_{c}$ was achieved by reducing the die angle and high core density.ity.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.56-57
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• 2006

Porosity in spray-formed materials is an important issue, but the formation of porosity is not completely understood. The paper gives some examples picked from literature, which show some general correlations between process parameters and porosity. To improve the understanding of porosity formation it is necessary to know more about the conditions of the droplets and the deposit at the point of impingement. Determining the impact conditions is a challenge because usually they are not constant with time and some values are difficult to measure. Our experiments show a strong correlation between the deposit surface temperature and the porosity. The average impact angle weighted by the local particle mass flux is also an important parameter.

• Electronics and Telecommunications Trends
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• v.34 no.2
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• pp.10-18
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• 2019

Since the introduction of CRT(Cathode Ray Tube) in the 1950s, display technologies have been developed continuously. Flat panel displays such as PDP(Plasma Display Panel) and LCD(Liquid Crystal Display) were commercialized in the late 1990s, and OLED(Organic Light Emitting Diodes) and Micro-LED(Micro-Light Emitting Diodes) are now being developed and are becoming widespread. In the future, we expect to develop ultra-realistic, flexible, embedded sensor displays. Ultra-realistic display can be applied to AR/VR(Augmented Reality/Virtual Reality) devices and spatial light modulators for holography. The sensor-embedded display can be applied to robots; electronic skin; and security devices, including iris recognition sensors, fingerprint recognition sensors, and tactile sensors. AR/VR technology must be developed to meet technical requirements such as viewing angle, resolution, and refresh rate. Holography requires optical modulation technology that can significantly improve resolution, viewing angle, and modulation method to enable wide-view and high-quality hologram stereoscopic images. For electronic skin, stable mass production technology, large-area arrays, and system integration technologies should be developed.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.6
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• pp.803-809
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• 2018

Generally, the gap-and-sag method is used in the shipbuilding stage before coupling the shafts to check whether they are installed at the same position as designed and derived from shaft alignment calculation. The primary installed propeller shaft becomes a reference point, the position of the remaining shafts are sequentially determined through the gap-and-sag value derived from the deflection and deflection angle at each shaft flange by own weight. If the reference point varies against the design value, it would have a series of effects on the installation of the remaining shafts. Moreover, after coupling the shafts, even if the bearing reaction forces derived from measurement are satisfied by the allowable limit range, consequently it might have an adverse effect on the stability of the shafting system by not being able to estimate the relative slope angle between the propeller shaft and the after-stern tube bearing. In this paper, to deal with above-mentioned phenomenon, the theoretical calculations related to designing an effective support point of the aft stern tube bearing and analysis by measurement is conducted through a case of open-up inspections. Based on this, a shaft installation guideline is proposed to minimize the misalignment related to preventing wiping damage of the after-stern tube bearing.

• The KSFM Journal of Fluid Machinery
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• v.6 no.1 s.18
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• pp.6-13
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• 2003

Variations of performance and NPSH of a turbo pump inducer were measured. The flows at the inlet and the outlet of the inducer were also experimentally investigated by measuring flow velocity and angle using a 3-hole Pilot tube. Performance and velocity profiles show a similarity for tested speeds, however not for efficiencies. Strong recirculating flows appears at the inlet of inducer even at the design condition. Cavitating flows were also visualized at several NPSH's.