• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.104-108
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• 2004

Micro turbine is an electric power generating system using a gas turbine whose rated power is under 300kW, and it is featured as a small, efficient. maintenance free and environment-friendly system. Air foil bearing has several advantages over conventional bearings for micro turbine because it is oilless and non-contact. Recently, air foil bearings for high temperature over $500^{\circ}C$ has been developed for the application of 65kW micro turbine system. In this paper, the development and current status are summarized in detail.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.1
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• pp.150-156
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• 2006

A Flapping foil Produces an effective angle of attack, resulting in a normal force vector with thrust and lift components, and it can be expected to be a new highly effective propulsion system. A heaving foil model was made and it was operated within a circulating water channel at low Reynolds numbers. The unsteady thrust and lift acting on the heaving foil were measured simultaneously using a 6-axis force sensor based on force and moment detectors. We have been examined various conditions such as heaving frequency and amplitude in NACA 0010 Profile. The results showed that thrust coefficient and efficiency increased with reduced frequency and amplitude. We also Presented the experimental results on the unsteady fluid forces of a heaving foil at various Parameters.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.222-227
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• 2005

A Flapping foil produces an effective angle of attack, resulting in a normal force vector with thrust and lift components, and it can be expected to be a new highly effective propulsion system. A heaving foil model was made and it was operated within a circulating water channel at low Reynolds numbers. The unsteady thrust and lift acting on the heaving foil were measured simultaneously using a 6-axis force sensor based on force and moment detectors. We have been examined various conditions such as heaving frequency and amplitude in NACA 0010 profile. The results showed that thrust coefficient and efficiency increased with reduced frequency and amplitude. We also presented the experimental results on the unsteady fluid forces of a heaving foil at various parameters.

• The KSFM Journal of Fluid Machinery
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• v.8 no.6 s.33
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• pp.47-54
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• 2005

An oscillating foil can produce a driving force through the generation of a reversed $K\'{a}rm\'{a}n$ vortex street, and it can be expected to be a new highly effective propulsion system. A simple pitching foil model was made and it was operated within a water channel. The wake formation behind a pitching foil was visualized and unsteady fluid forces were measured using a 6-axis force sensor based on force and moment detectors. We have been examined various conditions such as reduced frequency, amplitude and pivot point in NACA 0010. The results showed that thrust coefficients increased with a reduced frequency. We also presented the experimental results on the characteristics of a pitching foil at various parameters.

• Journal of radiological science and technology
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• v.40 no.4
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• pp.533-542
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• 2017

In diagnostic radiology, the imaging system has been changed from film/screen to digital system. However, the method for removing scatter radiation such as anti-scatter grid has not kept pace with this change. Therefore, authors have devised the indirect flat panel detector (FPD) system with net-like lead in substrate layer which can remove the scattered radiation. In clinical context, there are many radiographic examinations with angulated incident X-ray. However, our proposed FPD has net-like lead foil so the vertical lead foil to the angulate incident X-ray would have bad effect on its performance. In this study, we identified the effect of vertical/horizontal lead foil component on the novel system's performance and improved the structure of novel system for clinical usage with angulated incident X-ray. Grid exposure factor and image contrast were calculated to investigate various structure of novel system using Monte Carlo simulation software when the incident X-ray was tilted ($0^{\circ}$, $15^{\circ}$, and $30^{\circ}$ from the detector plane). More photons were needed to obtain same image quality in the novel system with vertical lead foil only then the system with horizontal lead foil only. An optimal structure of novel system having different heights of its vertical and horizontal lead foil component showed improved performance compared with the novel system in a previous study. Therefore, the novel system will be useful in a clinical context with the angulated incident X-ray if the height and direction of lead foil in the substrate layer are optimized as the condition of conventional radiography.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.8
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• pp.89-96
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• 2004

Micro-tensile testing system, consisting of a micro tensile loading system and micro-ESPI(Electronic Speckle Pattern Interferometry) system, has been developed for measurement of micro-tensile properties of thin micro-materials. Micro-tensile loading system had a load cell with the maximum capacity of 50N and micro actuator with resolution of 4.5nm in stroke. The system was used to apply a tensile load to the micro-sized specimen. During tensile loading, the micro-ESPI system acquired interferornetric speckle patterns in the deformed specimen and measured the in-plane tensile strain. The ESPI system consisted of a CCD-camera with a lens and the window-based program developed for this experiment. Using this system, stress-strain curves for 4 kinds of electrolytic copper foil 18$\square$m thick were obtained. From these curves, tensile properties, including the elastic modulus. yielding strength and tensile strength, were determined and also values of the plastic exponent and coefficient based on Ramberg-Osgood relationship were evaluated.

• Tribology and Lubricants
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• v.24 no.6
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• pp.378-385
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• 2008

In foil bearings, the friction between bumps and their mating surfaces is the major factor which exerts great influence on the bearing performance. From this point of view, many efforts have been made to improve the understanding of the influence of the friction on the foil bearing performance by developing a number of analytical models. However, most of them did not consider the hysteretic behavior of the foil structure resulting from the friction. The present work developed the static structural model in which hysteretic behavior of the friction was considered. The foil structure was modeled using finite element method and the algorithm which determines the conditions of the contact nodes and the directions of the friction forces was used to take into account the friction. The developed model was integrated into the foil bearing prediction code to investigate the effects of the friction on the static performance of the bearing. The results of analysis show that multiple static equilibrium positions are presented for the one static load under the influence of the friction, inferring its great effects on the dynamic performance. However, the effect of friction on the minimum film thickness which determines load capacity of the bearing is negligible.

• Journal of Powder Materials
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• v.18 no.6
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• pp.526-531
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• 2011

Fecralloy is the promising materials for high temperature exhaust filtering system due to the excellent its oxidation resistance property. In this research, Fecralloy nanoparticles coated Fecralloy thin foil was prepared by a single nozzle electrospray system in order to increase surface area of Fecralloy foil. Fecralloy nanoparticles were fabricated by electrical wire explosion method in ethanol using Fecralloy wires as a source material. Electrospray modes with applied D.C voltages to Fecralloy colloidal solution were investigated to make a stable cone-jet mode. Coated layers with and without additional heat treatment were observed by FE-SEM (field emission-scanning electron microscope) and tape test for evaluating their adhesion to substrate were performed as well.

• Tribology and Lubricants
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• v.14 no.4
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• pp.64-71
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• 1998

In this study deals with measurement of the vibration amplitudes of rotor-bearing system supported by foil bearing were performed experimentally, and the stability of the system were analyzed by using those results. Considering initial operating friction, compare bearing lubricated with only air and bearing surface lubricated with oil. Analyzing the transient data, the understanding of the characteristics fur startup and shutdown of rotor-bearing system are available and the dynamic characteristics of the system also can be analyzed exactly.

• 제어로봇시스템학회:학술대회논문집
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• 1995.10a
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• pp.150-153
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• 1995

In this paper the attitude control system is developed for longitudinal motion of Foil-Catamaran in regular waves with all-movable foils which attached to fore and after part of the ship and verified the system by theoretical calculation and model-tests. The linearized equations of motion of the ship is employed to apply the linear control theories, the PID control and the LQR. The strip method was used to calculate hydrodynamic coefficients and wave exciting forces of the demi hull, and unsteady hydrodynamic forces of foils are considered by using the result of Wu(1972). About 40-60% of motions is reduced in experiments. The control system described in this paper is able to extended to 6-DOF motions or control in irregular wave with trivial modification. And it is applicable to hull shape development for better seakeeping performance and to determine the size and the position of hydrofoils for the attitude control.