• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.9 s.252
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• pp.873-881
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• 2006

The present study investigates the pressure drop characteristics in rotating two-pass ducts. The duct has an aspect ratio (W/H) of 0.5 and a hydraulic diameter $(D_h)$ of 26.67mm. Rib turbulators are attached crossly in the four different arrangements on the leading and trailing surfaces of the test ducts. The ribs have a rectangular cross section of $2mm(e){\times}3mm(w)$ and an attack angle of $70^{\circ}C$. The pitch-to-rib height ratio (pie) is 7.5, and the rib height-to-hydraulic diameter ratio $(e/D_h)$ is 0.075. The results show that the highest pressure drop among each region appears in the turning region for the stationary case, but appears in the upstream region of the second pass for the rotating case. Effects of cross rib arrangements are almost the same in the first pass for the stationary and rotating cases. In the second pass, however, heat transfer and pressure drop are high for the cases with cross NN or PP type ribs in the stationary ducts. In the rotating ducts, they are high for the cases with cross NP or PP type ribs.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.9 s.252
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• pp.882-890
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• 2006

The present study investigates the pressure drop characteristics in rotating two-pass ducts. The duct has an aspect ratio (W/H) of 0.5 and a hydraulic diameter $(D_h)$ of 26.67mm. Rib turbulators are attached parallel in the four different arrangements on the leading and trailing surfaces of the test ducts. The ribs have a rectangular cross section of $2m(e){\times}3mm(w)$ and an attack angle of $70^{\circ}C$. The pitch-to-rib height ratio (p/e) is 7.5, and the rib height-to-hydraulic diameter ratio $(e/D_h)$ is 0.075. The results show that the highest pressure drop among each region appears in the turning region for the stationary case, but appears in the upstream region of the second pass for the rotating case. Effects of parallel rib arrangements are almost the same in the first pass for the stationary and rotating cases. In the second pass, however, heat transfer and pressure drop are high for the cases with parallel NN or PP type ribs in the stationary ducts. In the rotating ducts, they are high for the cases with parallel NN or PN type ribs.

• Applied Chemistry for Engineering
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• v.20 no.5
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• pp.547-552
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• 2009

When fiber reinforced plastics (FRP) products are manufactured, dust and odor materials are inevitably generated in a workplace. To improve the bad condition of the workshop, we developed the Hybrid Bag Filter attached activated carbon fiber (ACF) and installed the system at two companies producing FRP goods. In order to raise the efficiency of dust collection, we set the ducts both on the ceiling and at the bottom of the wall and according to the circumstances of the workshop's space, moving dust collector also adopted as a different type of flexible duct. Pulse Jet Type Bag Filter is also equipped to operate the system more effectively, for the improved fine environment because of high dust removal efficiency. Finally, we investigated the removal tendency of the dust and odor when operating the System of Hybrid Bag Filter.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.38.2-38.2
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• 2011

A large number of offshore wind turbines with fixed foundations have been installed in water depths up to 30 meters supporting 3-5MW wind turbines. Some floating platform concepts of offshore wind turbines were designed to be suitable for deployment in water depths greater than 60 meters. However the optimal design of this system in water depth 50 meters remains unknown. In this paper, a 5-MW wind turbine located on a TLP type platform was suggested for installation in this water depth. It is moored by a taut mooring line. For controlling the wind turbine always be operated at the upwind direction, one yaw controlling was attached at the tower. To study motion characteristics of this platform, a model was built with a 1/128 scale ratio. The model test was carried out in various conditions, including waves, winds and rotating rotor effect in the Ocean Engineering Wide Tank of the University Of Ulsan (UOU). The characteristic motions of the TLP platform were captured and the effective RAOs were obtained.

• Journal of Biosystems Engineering
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• v.27 no.4
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• pp.311-316
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• 2002

This study was carried out to investigate the optimum operating conditions of the air injection type onion peeling device which could be attached to a prototype onion peeler. An onion, stem and root was cut and some vertical line was dug in 1 mm depth on the skin, was put on the two parallel rollers. The diameters of the rollers were 105 mm and the ratio of peripheral velocity was 3:2, and moved by a geared motor. Air from the nozzle with high pressure and velocity was jetted to the rotating onion on the revolving rollers, and then the skin of the onion was stripped. On the test, the rolling characteristics of the experimental materials were measured. The effective peeling conditions were, the number of digging line on the skin of the onion was 4, and the air jet pressure was above 392.3 kPa(4.0 kg/$\textrm{cm}^2$) when the peripheral velocity was at 2.4 m/s. On these conditions, time requirement to peel an onion was less than 2 sec.

• Laser Solutions
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• v.12 no.1
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• pp.19-24
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• 2009

Because of its fast and precise welding performance, laser welding is becoming a new excellent welding method. However, the precise focusing and robust seam tracking are required to apply laser welding to the practical fields. In order to laser weld a type of T joint like a circular pipe on a square pipe, which could be met in the three dimensional structure such as an aluminum space frame, a visual sensor system was developed for automation of focusing and seam tracking. The developed sensor system consists of a digital CCD camera, a structured laser, and a vision processor. It is moved and positioned by a 2-axis motorized stage, which is attached to a 6 axis robot manipulator with a laser welding head. After stripe-type structured laser illuminates a target surface, images are captured through the digital CCD camera. From the image, seam error and defocusing error are calculated using image processing algorithms which includes efficient techniques handling continuously changed image patterns. These errors are corrected by the stage off-line during welding or teaching. Laser welding of a circular pipe on a square pipe was successful with the vision tracking system by reducing the path positioning and de focusing errors due to the robot teaching or a geometrical variation of specimens and jig holding.

• International Journal of Naval Architecture and Ocean Engineering
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• v.2 no.2
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• pp.104-111
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• 2010

The complete avoidance of cavitation, as a result of gap flow between the fixed and movable portion of a horn type rudder system, is difficult. To reduce gap flow, it is a common practice to attach a half round prismatic bar that protrudes beyond the concave surface of the horn facing the gap and laid along the centerplane of the rudder. However the employment of such a device does not always yield satisfactory results. Previously, the authors have shown that a pair of blocking bars, attached on the convex surface of the movable portion, better enhance the blocking ability of gap flow to that of a single centre bar installed on the concave surface. This also circumvents difficulties that might occur in practical applications. In the present study, a series of numerical computations show that flow injected into the gap of a rudder may also block the flow within, without employment of any physical devices, such as a half circular bar. This study also shows that the combination of flow injection and blocking bars may result in the synergic augmentation of blocking efficiency of gap flow, as demonstrated in computations for a three dimensional rudder system.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.40 no.4
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• pp.220-225
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• 2007

The succession of marine benthic algae and the restoration of an artificial seaweed forest on a porous type (shaped half saw teeth) artificial reef at Jeju island, Korea was studied. Young thalli of Sargassum horneri and Ecklonia cava were attached to different artificial substrates. In general, the succession on the artificial reefs led from filamentous algae to perennial algae and involved more than 25 species that are useful fishery resources, including E. cava. Coralline algae were dominant on the artificial reefs at the Kangjung site. The maximum algal biomass on the artificial reef in October 2005 was $1,990g/m^2$ at Biyang. In conclusion, a climax community and seaweed forest can be attained one year after the substrate is constructed.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.6
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• pp.608-614
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• 2008

This paper describes a location tracking system to guide landing process of an Unmanned Helicopter(UMH) exploiting MIT Cricket nodes. For automatic landing of a UMH, a precise positioning system is indispensable. However, GPS(Global Positioning System) is inadequate for tracking the three dimensional position of a UMH because of large positioning errors. The Cricket systems use Time-Difference-of-Arrival(TDoA) method with ultrasonic and RF(Radio Frequency) signals to measure distances. They operate in passive mode in that a listener attached to a moving device receives distance signals from several beacons located at fixed points on ground. Inevitably, this passive type of implementation causes large disturbances in measuring distances between beacons and the listener due to wind blow from propeller and turbulence of UMH body. To cope with this problem, we proposed active type of implementation for positioning a UMH. In this implementation, a beacon is set up at UMH body and four listeners are located at ground area at least where the UMH will land. A pair of Ultrasonic and RF signals from the beacon arrives at several listeners to calculate the position of the UMH. The distance signals among listeners are synchronized with a counter value appended to each distance signals from the beacon.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.343-343
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• 2008

Newly designed structure of a thin ultrasonic rotary motor was proposed. Thin brass plate was used as a cross shaped vibrator and eight ceramic plates were attached on the upper and bottom sides of the brass plate as in Figure 1. The thin type ultrasonic motor has the structure adherent piezoelectric ceramic on the top and bottom surface of the thin elastic body. The direction of polarization is decided so as to occur the elliptical displacement in regular sequence at touch point A, B, C and D of stator contacted with rotor. By applying two electric fields which have 90 degree phase difference on the ceramics, each contact points make rotational displacements as in figure 2. Finite element analysis program ATILA was used to find the optimal size of the stator. As a result of the simulation, elliptical displacements of the tips were obtained at off-resonance frequencies. The maximum displacements of the contact tips were obtained at the length of 16[mm], width of 6[mm] and thickness of 0.4[mm]. Changes of the resonance frequencies were inversely proportional to the length of ceramic and proportional to the width of ceramic. Elliptical motions of the contact tips. of the stator were consistently obtained at off resonance frequencies. From a prototype motor, speed of 600[rpm] was obtained at 20[Vrms].