• Transactions of the Korean Society of Mechanical Engineers
• /
• v.14 no.2
• /
• pp.470-483
• /
• 1990

Turbulent jet in a crossflow, issuing from a row of holes on a convex surface of 90 .deg. bend duct, is predicted by a 3-dimensional numerical method. The Cartesian coordinate system in adopted in upstream and downstream tangents and the cylindrical polar coordinate system in curved region. The Reynolds stresses and heat fluxes are obtained from a standard k-e model in the core region and van Driest model in the vicinity of the wall. The governing equations are discretized by a finite volume method and solutions are obtained by a locally elliptic calculation procedure. Pressure and convective terms are treated by SIMPLE algorithm and hybrid scheme respectively. A vortex initially induced by the injected jet has been built up due to the interaction with the secondary flow caused by pressure gradient and centrifugal force. The vortex structure has a strong influence on the wall cooling effectiveness. Another vortex like horseshoe is formed in the vicinity of the injection hole and its strength is getting weak as it moves downward.

• Journal of Korean Society of Rural Planning
• /
• v.10 no.3 s.24
• /
• pp.27-32
• /
• 2004

The purpose of this study is on identifying the restoration guidelines of supplementary village grove and villageside forest in case of Neunggil village in Jinan county of Korea. These forests were managed very well before industrialization by village residents in order to obtain fuels and organic fertilizers traditionally. But recently, these forests were abandoned by using natural gas, oil and chemical fertilizer. Therefore, species diversity of these forests was downward and traditional rural landscape was lost. Accordingly, this study suggested the restoration guidelines of these forests through restoring the relationship between man and nature. For this, vegetation map was made by quadrat method. And management guidelines of these forests were suggested by the analysis of vegetation map. Also, for the restoration of supplementary village grove, Miyawiki professor's method of Yokohama university through introducing potential natural vegetation was suggested.

• Archives of Plastic Surgery
• /
• v.36 no.2
• /
• pp.194-199
• /
• 2009

Purpose: The orbital fat buldging may cause irregular contour of lower eyelid, which is not youthful appearance. The conventional method of fat excision may cause the eyeball to move backward and downward, making enopthalmia is inevitable. The transcutaneous approach to reach the orbital septum can increase the risks of scleral show resulting from scarification at the level of the septum orbicularis junction and damaging the vertical motor branches of the preseptal orbicularis oculi muscle of the lower eyelid. Method: From July 2007 to March 2008, total of 21 patients underwent transconjunctival capsulopapebral fascia fixation procedure. In 8 patients, the herniated fat pad of the lower eyelid was relocated back into the orbit without external skin excision using capsulopalpebral fascia fixation. But in 13 patients, excision of redundant skin of the lower eyelid was performed using pinching technique, not involving orbicularis oculi muslce. In 5 patients, lateral canthotomy was done bilaterally for good visual field. In 6 patients, lateral canthopexy was also combined to correct loosening of lower eyelid. Results: Most of the patients were satisfied after at least 5 months of follow up. No patient showed scleral show. But 2 patients complained of undercorrection slightly, without secondary operation in 1 patient and re - capsulopalpebral fascia fixtation through transconjunctival approach in another patient. Conclusion: Orbital fat repositioning using transconjunctival capsulopalpebral fascia fixation is a good procedure to show youthful appearance without increasing the risk of scleral show and also showed fast recovery compared to the conventional transcutaneous approach.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.12 no.2
• /
• pp.150-160
• /
• 2000

Turbulent natural convective flow and heat transfer in a square enclosure with horizontal partition are investigated numerically. The enclosure is composed of a lower hot and a upper cold horizontal walls and adiabatic vertical walls. Partitions carried with the upward, downward, and both control plates are attached perpendicularly to the one of the vertical insulated walls, respectively. The low Reynolds number $k-\varepsilon$ model is adopted to calculate the turbulent thermal convection. The governing equations are solved by using the finite element method with Galerkin method. The computations have been carried out by varying the length of partition, the position of control plates, and the Rayleigh number based on the temperature difference between two horizontal walls and the enclosure height for water(Pr=4.95). When the control plates are attached at the edge of partition, the stability of oscillating flow grows wrose with the increase of Rayleigh number and the partition length. The heat transfer rate has been reducer than that of no control plate due to the restraint of control plates with the increase of Rayleigh number.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2018.10a
• /
• pp.430-433
• /
• 2018

This paper proposes the Kalman filter (KF) with optical flow method to estimate the position and the velocity of unmanned aerial vehicles (UAVs) in the absence of global positioning system (GPS). A downward-looking camera, a gyroscope and an ultrasonic sensor are fused to compensate the measurement from optical-flow method. To overcome the problem of dealing with noise in onboard sensors, the KF is incorporated to efficiently predict the velocity and estimate the position. Basic mechanisms of optical flow and the KF are introduced and experiments are conducted to show how the techniques involved improve the estimations.

• Journal of Ocean Engineering and Technology
• /
• v.27 no.5
• /
• pp.16-21
• /
• 2013

The flow around a circular cylinder advancing beneath the free surface is numerically investigated using a VOF method. The simulations cover Froude numbers in the range of 0.2~0.6 and gap ratios (h/d) in the range of 0.1~2.0, where h is the distance from the free surface to a cylinder, and d is the diameter of a cylinder at Reynolds number 180. It is observed that the vortex suppression effect and surface deformation increase as the gap ratio decreases or the Froude number increases. The most important results of the present study are as follows. The proximity of the free surface causes an initial increase in the Strouhal number and drag coefficient, and the maximum Strouhal number and drag coefficient occur in the range of 0.5~0.7. However, this trend reverses as the gap ratio becomes small, and the lift coefficient increases downward as the gap ratio decreases.

• Geomechanics and Engineering
• /
• v.34 no.4
• /
• pp.381-396
• /
• 2023

The present paper evaluates seismic bearing capacity of rock masses subjected to loads of strip footings using the upper bound method. A general formula was proposed to evaluate the seismic bearing capacity considering both the horizontal and vertical accelerations of the earthquake and the effects of footing embedment depth simultaneously. Modified Hoek-Brown failure criterion was employed for the rock mass. Some comparisons were made with the available solutions and the finite element numerical models to show the accuracy of the developed upper bound formulations. The obtained results show significant improvement compared to the other available solutions. By increasing the horizontal earthquake acceleration from 0.1 to 0.3, the bearing capacity was reduced by up to 39%, while the effect of the vertical earthquake acceleration depends on its direction. An upward acceleration in the range of zero to 0.2 results in an increase in the bearing capacity by up to 24%, while the downward earthquake acceleration has an adverse effect. Also, by increasing the embedment depth of the footing from zero to 5 times the footing width, the value of seismic bearing capacity was raised about 86%. The obtained results were presented as design tables for use in practical applications.

• Journal of Fisheries and Marine Sciences Education
• /
• v.29 no.2
• /
• pp.570-580
• /
• 2017

In this study, we designed a fishing system to reproduce the underwater movement of the living Sword tip squid (Loligo edulis) used as bait in the red seabream long line fishery, and conducted the experiment of the fishing operation in 2 ways, i.e., a pole and line fishing method (fishermen) and a bait control fishing system used at fishing sites. Based on the catches in fishing operation, the experiment was conducted over a six times (2014 & 2015), and then 107 fishes were caught by the line fishing method while 57 fishes were caught by the bait control fishing system. The fishermen method actively controlled the speed of gear movement upward and downward while checking the reaction of red seabreams to the bite in the process which a jerk was transmitted to single line hook fishing gear manually. The bait control fishing system is a passive method which fishermen visually check only the movements at the end of fishing pole, enabled differentiation of bite reactions of red seabream during fishing operation. Thus, the difference between fishermen method and the bait control fishing system was found to about 53.3% in the catches. We confirmed the possibility of a site fishing operation based on the bait control fishing system designed newly as a result of this study. Improvement is in several areas for commercialization at the site. This fishing system is expected to be able to find wide-ranging applications as a new labor-saving method for the fishing red seabreams if it is applied to the fishing sites after aforesaid process.

• Journal of the Korean Geotechnical Society
• /
• v.22 no.11
• /
• pp.151-158
• /
• 2006

Centrifuge tests have shown that a uniformly placed sand layer will first initiate liquefaction near the surface and that liquefaction will progress downward during shaking. This appears to be in conflict with the overburden stress effect on soil liquefaction (i.e., $K_0$ effect) observed in laboratory testing. This discrepancy can be explained by stress-induced densification at depth which overcomes the effect of confining stress on liquefaction resistance. Stress densification occurs in centrifuge model tests but its effect has generally not been considered when preparing or evaluating centrifuge models. A new centrifuge model preparation method is proposed by considering stress-induced densification upon spin-up. The proposed method can be used to explore $K_0$ effects. The method is supported in this study by numerical predictions.

• The korean journal of orthodontics
• /
• v.36 no.6
• /
• pp.412-421
• /
• 2006

Objective: The result of finite element analysis depends on material properties, structural expression, density of element, and boundar or loading conditions. To represent proper elastic behavior, a finite element model was made using Hounsfield unit (HU) values in CT images. Methods: A 13 year 6 month old male was used as the subject. A 3 dimensional visualizing program, Mimics, was used to build a 3D object from the DICOM file which was acquired from the CT images. Model 1 was established by giving 24 material properties according to HU. Model 2 was constructed by the conventional method which provides 2 material properties. Protraction force of 500g was applied at a 45 degree downward angle from Frankfort horizontal (FH) plane. Results: Model 1 showed a more flexible response on the first premolar region which had more forward and downward movement of the maxillary anterior segment. Maxilla was bent on the sagittal plane and frontal plane. Model 2 revealed less movement in all directions. It moved downward on the anterior part and upward on the posterior part, which is clockwise rotation of the maxilla. Conclusion: These results signify that different outcomes of finite element analysis can occur according to the given material properties and it is recommended to use HU values for more accurate results.