• Journal of Advanced Marine Engineering and Technology
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• v.37 no.5
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• pp.493-499
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• 2013

This paper presents are experimental investigation to figure out impact pressure and flow characteristics of a wedge type structure in free fall. The flow field has been obtained by 2-frame grey level cross correlation PIV(Particle Image Velocimetry) method, the impact pressure of free fall structure by a pressure acquisition system apply to Dewetron system. The angles between a model and the free surface are adapted $15^{\circ}$, $25^{\circ}$, $35^{\circ}$ and $45^{\circ}$ respectively. Velocity field of water exit has higher better than water entry. The impact pressure under the bottom of the model has been appeared higher values at $15^{\circ}$ than $45^{\circ}$, and also at P1.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.4
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• pp.44-54
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• 2018

In a spray experiment using a venturi mounted on a lean premixed LPP injector, droplets appear to have non-uniform distributions. To solve this problem, the exit angle of the venturi was changed to form a dump surface on the nozzle neck. The dump surface improved the atomization performance and minimized droplet loss while forming recirculation zone in the venturi exit. In order to solve the non-uniform spray of the injector, the flow characteristics inside the venturi and SMD of the spray are compared. Finally, an optimum venturi shape is selected to minimize the spray loss and improve the spray performance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.83-89
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• 2021

To improve the performance of self-driving cars, the introduction of V2X, a communication technology that connects vehicles, infrastructure, and vehicles, is essential. Even if traffic information of the other vehicle is known, the structure of the intersection and a distance calculation algorithm are required for accurate calculations at roundabouts. This paper proposes a design algorithm for a rotating intersection and implemented in Matlab that complies with the national design rules and enables accurate calculations. Assuming the roundabout and the entrance/exit path to be a circle, a method for measuring the distance between vehicles at an arbitrary point was proposed using the horizontal shift of the entrance circle to the main circle. The algorithm could be used in fully autonomous vehicles by designing a roundabout suitable for the terrain by arbitrarily varying the angle between branches and the radius of curvature of the entrance and exit roads, and transmitting a warning signal when a collision between two driving vehicles is expected.

• Journal of Korean Ophthalmic Optics Society
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• v.5 no.1
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• pp.1-6
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• 2000

This study was to calculate spot size, focus shift and optical focus by use of OSLO when 3 wavelength, ${\omega}{\upsilon}_1=0.588{\mu}$, ${\omega}{\upsilon}_2=0.486{\mu}$ and ${\omega}{\upsilon}_3=0.656{\mu}$ in composite lens optics system & ocular optical system were respectively here, Entrance Beam Radius(mm) 1 mm, Field angle(deg) 5.7296e-0.5 mm, Image Aperture 0.053055 mm, Exit Aperture 0.903711 mm, Reflective focal length 25.181544 mm, Petzval radius -19.21839 mm, n = 1.523. It was found that a range of spot size was 0.002 mm~0.07 mm when a range of back curvature radius was 1 mm~30 mm, and 0.0005 mm~0.002 mm when of it more than 50 mm. Focus shift, 50 mm a range 3 kinds of lens was small, and it saw that of all tendency was high up to 1 mm~15 mm and up to 25 mm beyond that limits, it was going down and then going up again, optical focus 100 mm lens was best and the value when optimization with this lens was $60{\pm}1mm$.

• The KSFM Journal of Fluid Machinery
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• v.17 no.5
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• pp.43-53
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• 2014

This paper presents a the study on air curtain system of top and bottom bi-directional jet air discharge for blocking the spread of smoke in case of tunnel fire. The five kinds different air curtains of A, B, C, D, and E of models for various performance tested after manufactured. A results of the various performance test obtained the best efficiency from E model air curtain. And optimize the injection angle of the air curtain nozzle through the three-dimensional computational fluid dynamics (CFD) analysis and analyzed the effects of external pressure of tunnel. and also single factor design have been applied. At present, our attention is focused on the velocity distribution(flow width and flow position) of 1.5m on the ground in tunnel. Also, analyzed the influence of draft in the tunnel. Detailed effects of discharge angle of air curtain and velocity at nozzle exit are discussed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.5
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• pp.1172-1182
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• 1993

In orthogonal machining a quantitative model for burr formation process and fracture when tool exits workpiece is proposed. When no fracture during burr formation burr formation process is divided by three parts; Initiation, Development and Final burr formation. According to the properties of workpiece fracture will happen or not after initiation of burr formation. Considering the fact that fracture depends on the ductility of workpiece, the fracture strain obtained from ductile fracture criterion is used for prediction. It is verified that the fracture strain from tension test can be used as fracture criterion in burr formation without large error. For detailed observation of burr formation an experimental stage for micro orthogonal cutting inside SEM (Scanning Electron Microscope) is built. Through the comparison between model prediction and experimental result from orthogonal machining in milling machine the model is verified.

• Restorative Dentistry and Endodontics
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• v.13 no.1
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• pp.161-171
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• 1988

The purpose of this study was to examine the morphological changes of different simulated canals according to the preparation procedures. With the use of clear casting resin, simulated straight and curved canals were created so that canal preparation procedures could be directly visualized and compared. Thirty clear polyester casting resin blocks which contained four simulated canals divided into three groups; Group A($0^{\circ}$), Group B($15^{\circ}$), and Group C($30^{\circ}$). In each block, 3 canals were prepared different preparation techniques, which were conventional method, step-back method, and giromatic filing. But, one canal was not prepared as a control group. The results were as follows: 1. There was no difference on canal shape among three canal preparation methods in straight canals (Group A). 2. When conventional method and Giromatic filing were used in curved canals (Group B, C), elbow, zip and hour-glass shape were formed in apical third. 3. When conventional method and Giromatic filing were used in curved canals (Group B, C), tear-drop appearance developed at the site of the canal exit in curved canals. 4. In curved canals (Group B, C), file tend to straighten within the canal. 5. There was no difference on canal shape according to curved angle in step-back method (p > 0.1). But there was significant difference on canal shape according to curved angle in conventional method and Giromatic filing (p < 0.001). 6. Step-back method was significantly more effective than conventional method and Giromatic preparation in morphologic aspects of apical third of original canals.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.5
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• pp.645-652
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• 2010

The aim of this investigation was study on the non-evaporation diesel spray characteristics injected through a common-rail diesel injector under various ambient pressure. The diesel spray was investigated with observation of macroscopic characteristics such as spray tip penetration and spray cone angle by the shadowgraph and the image processing method. The numerical study was conducted using a computational fluid dynamics code, AVL-FIRE. The breakup models used were WAVE model and standard $k-{\varepsilon}$ turbulence model was applied. The numerical study used input data which spray cone angle and fuel injection rate was achieved by Zeuch's method. Comparison with experimental result such as spray tip penetration was good agreement. Distribution of droplet diameter were conducted on four planes where the axial distances were 5, 15, 39 and 49mm respectively downstream from the orifice exit.

• Journal of radiological science and technology
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• v.22 no.2
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• pp.27-32
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• 1999

Cochlear implant poses a contraindication to the magnetic resonance imaging(MRI) process, because MRI generates artifacts, inducing an electrical current and causing device magnetization. CT is relatively expensive and the metal electrodes scatter the image. Post-implantation radiological studies using anterior-posterior transorbital, submental-vertex and lateral views, the intracochlear electrodes are not well displayed. Therefore, the authors developed a special view, which we call the cochlear view. The patient is sitting in front of a vertical device. Then the midsagittal plane is adjusted to form an angle of $15^{\circ},\;30^{\circ}$, and $45^{\circ}$ with the film. The flexion of the neck is adjusted to make the infraorbitomeatal line(IOML) is parallel with the transverse axis of the film. The central ray is directed to exit from the skull at point which is 3.0 cm anterior and 2.0 cm superior to the EAM(external auditory meatus). Results have shown that single radiography of the cochlear view provides sufficient information to demonstrate the position of the electrodes array and the depth of insertion in cochlear. Radiography of the cochlear view in angle of $45^{\circ}$ is an excellent image. The cochlear view gives the greatest amount of medical information with the least radiation and lowest medical cost. It can be widely used in all cochlear implant clinics.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.530-533
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• 2010

This paper presents numerical analysis and design optimization of various turbine blade cooling techniques with three-dimensional Reynolds-averaged Navier-Stokes(RANS) analysis. The fluid flow and heat transfer have been performed using ANSYS-CFX 11.0. A fan-shaped hole for film-cooling has been carried out to improve film-cooling effectiveness with the radial basis neural network method. The injection angle of hole, lateral expansion angle of hole and ratio of length-to-diameter of the hole are chosen as design variables and spatially averaged film-cooling effectiveness is considered as an objective function which is to be maximized. The impingement jet cooling has been performed to investigate heat transfer characteristic with geometry variables. Distance between jet nozzle exit and impingement plate, inclination of nozzle and aspect ratio of nozzle hole are considered as geometry variables. The area averaged Nusselt number is evaluated each geometry variables. A rotating rectangular channel with staggered array pin-fins has been investigated to increase heat transfer performance ad to decrease friction loss using KRG modeling. Two non-dimensional variables, the ratio of the eight diameter of the pin-fins and ratio of the spacing between the pin-fins to diameter of the pin-fins selected as design variables. A rotating rectangular channel with staggered dimples on opposite walls are formulated numerically to enhance heat transfer performance. The ratio of the dimple depth and dimple diameter are selected as geometry variables.