• Journal of the Society of Naval Architects of Korea
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• v.48 no.2
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• pp.113-120
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• 2011

Fins are widely used for roll stabilization of passenger ferries and high performance naval ships, among others. The Coanda effect is noticeable when a jet stream is applied tangentially to a curved wing surface since the jet can augment the lift by increasing the circulation. The Coanda effect has been found useful in various fields of aerodynamics and speculated to have practical applicability in marine hydrodynamics where various control surfaces are used to control motions of ships and the other offshore structures. In the present study, numerical computations have been performed to find proper jet momentum coefficients $C_j$ and trailing edge shapes suitable for the application of the Coanda effect to a stabilizer fin. The results show that the lift coefficient of the modified Coanda fin at the zero angle of attack ${\alpha}$ identically coincides with that of the original fin at ${\alpha}\;=\;25^{\circ}$ when Coanda jet is supplied at the rate of $C_j$ = 0.1. It is also shown that a fixed type fin stabilizer utilizing the Coanda effect can be implemented without changing the fin angle to actively control the motions of ships and the other offshore structures.

• Journal of Korean Port Research
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• v.13 no.2
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• pp.409-418
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• 1999

Gamcheon Bay has complicated and unique flow pattern which is affected by topography characteristics of a semi-closed bay and warm water discharge from the power plant located at the bay. It is very important to consider warm water discharge with tidal period and wind effects, which are mainly acting on the surface flow patterns in Gamcheon Bay. The results of observation show as follows; i) Because Gamcheon bay has much elongated shape to the north-south direction and narrow entrance with two separated breakwaters, the flow is very weak inside the bay. ii) The main flow path is at the west side of the bay. The direction of flood current is northward along the west side of the bay and the direction of ebb current is southward along the west side of the bay. The southward direction of warm water discharge has curved to the west side of the bay. iii)At the period of flood current for neap tide, the flow direction is southward in the bay, which is thought by the effects of warm water discharge. But at the bottom layer, the effects of tidal current reached to the middle of the bay, and showed features like eddy. iv) The wind effect is very strong, especially, prominent in the west and east side of the bay.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.215-220
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• 2008

A microchannel PCHE is manufactured by the two technologies of micro photo-etching and diffusion bonding. In this paper, heat transfer and pressure drop characteristics by applying various configuration for the flow channel in the microchannel PCHE is experimentally investigated. The flow channel configurations are designed three types such as straight, wavy and offset strip channels. The performance experiment of each configuration is performed for Reynolds numbers in ranges of $100{\sim}700$ under various flow conditions for the hot side and the Reynolds number of cold side is fixed at 350. The inlet temperatures of the hot side and cold side are conducted as $40^{\circ}C$ and $20^{\circ}C$, respectively. The heat transfer performance of wavy channel, which was similar to that of offset strip channel, was much higher than that of straight channel. The effectiveness of wavy channel and offset strip channel was evaluated as about $0.5{\sim}0.9$. The pressure drop of wavy channel was highest among configurations and that of offset strip channel was lower than that of straight channel because the round curved surface of each strip edge was reduced the pressure loss.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.6
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• pp.569-578
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• 2008

The Coanda effects demonstrate that a jet stream applied tangential to a curved surface can generate lift force by increasing the circulation. Many experimental and numerical studies have been performed on the Coanda effect and it is found to be useful in various fields of aerodynamics. The Coanda effect may have practical application to marine hydrodynamics since various control surfaces are being used to control behaviors of ships and offshore structures. In the present study, numerical computations are performed to find the applicability of the Coanda effect to the marine control surfaces. For the purpose, changes in flow characteristics around a flapped foil due to the Coanda effect have been simulated by RANS equations discretized with a cell-centered finite volume method (FVM). In the process, special attention has been given to the influence of jet nozzle arrangement on the lift characteristics of the Coanda foil. It is found that the shape as well as the location of the jet intake and jet exit affects the lift performance of the foil significantly.

• Korean Journal of Agricultural Science
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• v.27 no.1
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• pp.20-24
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• 2000

External morphological characteristics of male and female of Degeeria separata, which was endoparasited in adult of the Asian ladybird, were studied by using the scanning electron microscopy (SEM). The antenna of Degeeria separata was consisted of three segment and arista. Aristae were about $750{\mu}m$ length and $30{\mu}m$ in diameter. The surface of antennae was covered with many sensilla. They were long or short, slender or thick, and straight or curved. Each three morphological types of sensilla were observed on the second and third segment of antennae. The mouthpart was sponging type. It was consisted with clypeus, labellum, labium, labrum, and maxillary palp. The labellum is $400{\mu}m$ width and double folded vertically. The leg consist of tarsus, tarsus claw, pulvilli, and empodium.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.2
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• pp.120-125
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• 2011

As an effort to secure economically viable heat recovery units, innovative fin shapes for industrial boilers are studied for better performance. In the present study a numerical modeling for the analysis of heat exchanger performance is conducted using a commercial software, ANSYS CFX and the results are compared with the experimental data. Out of several candidate fin shapes curved wavy fin is selected for the present study. Both numerical and experimental data are directly compared for heat transfer rate and pressure drop with the assumed constant surface temperature of $60^{\circ}C$. Exhaust gas is obtained from a test apparatus which supplies variable flow rates. The numerical results show reasonable agreements with the experimental data within 10% in terms of both total heat transfer and pressure loss.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.400-405
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• 2018

This paper presents a compact ultra-wideband (UWB) flexible monopole antenna design on a paper substrate. The proposed antenna is made of iterations of a circular slot inside an octagonal metallic patch. This fractal-based geometry has been deployed to achieve compactness along with improved bandwidth, measured reflection coefficient -10 dB bandwidth ranging from 2.7 to 15.8 GHz. The overall size of the antenna is $26mm{\times}19mm{\times}0.5mm$, which makes it a compact one. The substrate used is paper and the main features like environment friendly, flexibility, green electronics applications and low cost of fabrication are the key factors for the proposed antenna. The aforementioned UWB prototype is suitable for many wireless communication systems such as WiMAX, WiFi, RFID and WSN applications. Antenna has been tested for the effect of bending by placing it over a curved surface of a very small radius of 10 mm.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.3
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• pp.163-168
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• 2020

We studied the change of photovoltaic properties of a flexible CuIn_xGa(_1-x)Se₂ (CIGS) solar cell fabricated on polyimide by mechanical bending with curvature radii of 75 mm (75R) and 20 mm (20R). The flexible CIGS cells were flattened on a PET film, then placed and forced against the surface of a curved block fabricated with pre-designed curvatures. Both up (compressive) and down (tensile) bending were applied to a specimen of CIGS on PET with curvatures of 75R and 20R for 10,000 times and 2,000 times, respectively. From J-V measurements, we found that the conversion efficiency (Eff.) was reduced by 3% and 4% for up-and down-bending, respectively, at curvature 75R; it was greatly reduced by 15% for curvature 20R in the up-bending. However, the open circuit voltage (V_oc) and short-circuit current density (J_sc) seemed to change little, within 3%, for the applied mechanical stresses. The degradation in Eff. resulted from the deterioration of the series (R_s) and shunt (R_sh) resistances of the solar cell.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.569-571
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• 2010

In this paper, we develop a vision inspection system for inspecting flaws on plastic products such as insufficient moldings, spots, scratches. The inspection algorithm for this system consist of image binarization for curved structure of plastic products, image noise removal using morphology operation, labeling methods for candidate regions and image filtering and calibration method for flaw inspection. In order to improve its performance, we also develop fast image processing algorithm based on GUI. To verify the effectiveness of this system, we conducted evaluation for the system accuracy and the inspection algorithm processing time.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1524-1525
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• 2007

A flexible tactile sensor module based on polyimide matrix integrated with sensing elements and pluggable terminals connector was fabricated by polymer micromachining technology for robotic applications. The tactile sensor arrays are composed of $4{\times}4$, $8{\times}8$ and $16{\times}16$ sensing elements connected with pluggable terminals connector, respectively. Especially, both the tactile sensor array and the pluggable terminals are formed in the sensor module during the fabrication process. The fabricated tactile sensor module is measured continuously in the normal force range of $0{\sim}1N$ with tactile sensor auto-evaluation system. The value of resistance is relatively increased linearly with normal force in the overall range. The variation rate of resistance is about 2.0%/N in the range of $0{\sim}0.6N$ and 1.5%/N in the range of $0.6{\sim}1N$. Also, the flexibility of the sensing module is adequate to be placed on any curved surface as cylinder because the matrix consists of polymer and metal thin film.