• The Journal of Engineering Geology
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• v.7 no.1
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• pp.37-52
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• 1997

This paper discribes the practical application of stability analysis on the revetment structures, and four different sections of revetment structures are considered in this study. As a result of stability analysis, the the section of inclined revetment with T.T.P. block shows the highest safety factor against to the sliding failure of cap concrete block, while the section of inclined revetment with rubble stone shows the highest safety factor against to the straight and circular sliding failure. And the safety factors are increased by increasing of the rigidity of covered materials and by decreasing of the slope angle. For the safety factor of overturnning and bearing capacity, the section of inclined revetment structures shows higher safety factors than the section of vertical structures, and the safety factors are increased by decreasing of the slope angle and by increasing of the bottom width of the structures.

• Wind and Structures
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• v.24 no.5
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• pp.447-464
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• 2017

The flutter instability is one of the most important themes need to be carefully investigated in the design of long-span bridges. This study takes the central-slotted ideal thin flat plate as an object, and examines the characteristics of unsteady surface pressures of stationary and vibrating cross sections based on computational fluid dynamics (CFD) simulations. The flutter derivatives are extracted from the surface pressure distribution and the critical flutter wind speed of a long span suspension bridge is then calculated. The influences of angle of attack and the slot ratio on the flutter performance of central-slotted plate are investigated. The results show that the critical flutter wind speed reduces with increase in angle of attack. At lower angles of attack where the plate shows the characteristics of a streamlined cross-section, the existence of central slot can improve the critical flutter wind speed. On the other hand, at larger angles of attack, where the plate becomes a bluff body, the existence of central slot further reduces the flutter performance.

• Transactions of the KSME C: Technology and Education
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• v.2 no.1
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• pp.39-46
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• 2014

This study presents computational analysis of aerodynamic characteristics of two-dimensional airfoil sections with elastic flap attached at the trailing edge. EDISON_CFD was utilized to simulate the incompressible turbulent flow around the foil and MIDAS_IT was employed to estimate the deflection of the flap under the pressure loading. Using iterative procedure, the terminal deflection was estimated and the resulting lift-drag ratio indicates that the favorable effect of the flap is expected within certain amount of angle of attack.

• Steel and Composite Structures
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• v.25 no.4
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• pp.443-456
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• 2017

Many authors have established the usefulness of concrete filled steel tubular (CFST) sections as compression members while few have proved their utility as flexural members. To explore their prospective as part of CFST frame structures, two types of connections using extended end plate and seat angle are proposed for exterior joints of CFST beams and CFST columns. To investigate the performance and failure modes of the proposed bolted connections subjected to static loads, an experimental program has been executed involving ten specimens of exterior beam-to-column joints subjected to monotonically increasing load applied at the tip of beam, the performance is appraised in terms of load deformation behaviour of joints. The test parameters varied are the beam section type, type and diameter of bolts. To validate the experimental behaviour of the proposed connections in CFST beam-column joints, finite element analysis for the applied load has been performed using software ATENA-3D and the results of the proposed models are compared with experimental results. The experimental results obtained agree that the proposed CFST beam-column connections perform in a semi-rigid and partial strength mode as per specification of EC3.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.6
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• pp.15-23
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• 2000

In the present study, flow characteristics of turbulent pulsating flow in the square-sectional $180^{\circ}$curved duct are investigated experimentally. In order to measure axial direction velocity and secondary flow distributions, experimental studies for air flow are conducted in the square-sectional $180^{\circ}$curved duct by using the LDV system with the data acquisition and the processing system of the Rotating Machinery Resolver (RMR) and the PHASE software. The experiment is conducted on seven sections form the inlet($\phi=0^{\circ}$) to the outlet($\phi=180^{\circ}$) at $30^{\circ}$intervals of the duct. The results obtained from the experimentation are summarized as follows : In the axial direction velocity distributions of turbulent pulsating flow, when the ratio of velocity amplitude (A1) is less than one, there is hardly any velocity change in the section except near the wall and in axial velocity distribution along the phase. The secondary flow of turbulent pulsating flow has a positive value at the bend angle of $150^{\circ}$regardless of the ratio of velocity amplitude. The dimensionless value of secondary flow becomes gradually weak and approaches zero in the region of bend angle $180^{\circ}$without regard to the ratio of velocity amplitude.

• Transactions of Materials Processing
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• v.29 no.5
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• pp.282-289
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• 2020

Flexible roll forming is an advanced sheet-metal-forming process that allows the production of parts with various cross-sections. During the flexible process, material is subjected to three-dimensional deformation such as transverse bending, inhomogeneous elongations, or contraction. Because of the effects of process variables on the quality of the roll-formed products, the approaches used to investigate the roll-forming process have been largely dependent on experience and trial- and-error methods. Web-warping is one of the major shape defects encountered in flexible roll forming. In this study, an SVR model was developed to predict the web-warping during the flexible roll forming process. In the development of the SVR model, three process parameters, namely the forming-roll speed condition, leveling-roll height, and bend angle were considered as the model inputs, and the web-warping height was used as the response variable for three blank shapes; rectangular, concave, and convex shape. MATLAB software was used to train the SVR model and optimize three hyperparameters (λ, ε, and γ). To evaluate the SVR model performance, the statistical analysis was carried out based on the three indicators: the root-mean-square error, mean absolute error, and relative root-mean-square error.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.3
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• pp.14-25
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• 1998

This paper describes the numerical modelling for the steady and unsteady forces of 3-D wings flying near the free surface based on a potential based panel method. For the steady problem where a wing flies over the fixed float surface, steady lift and drag forces are calculated for wings with and without end-plates having different sections, angle of attacks, aspect patios and flying heights. These numerical results are compared with the wind tunnel test results. The unsteady problem is treated as a boundary value one where a wing flies over the described wavy surface. The unsteady lift force variations of a wing due to different wave lengths and heights are calculated at different flying heights.

• Restorative Dentistry and Endodontics
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• v.7 no.1
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• pp.131-138
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• 1981

The purpose of this study was to evaluate the marginal leakage of composite resin. Preparing 144 class V cavities on freshly extracted noncarious teeth, composite resins were prepared and inserted by one dentist according to the manufacturer's instructions. The experiments were performed in two different groups; In group I; Class V cavities with $90^{\circ}$ cavosurface angle, In group II; Class V cavities with $135^{\circ}$ cavosurface angle. And each group was divided 2 subgroups; In control group; composite resin restoraions without acid etch technique. In experimental group; composite resin restorations with acid etch technique. All specimens were immersed in 0.05% crystal violet solution. Before examination, the restored teeth were subjected to thermal stress. The specimens were sectioned occlusogingivally through the center of the restorations with a diamond disk. The sections were examined under a reflected light microscope at 1 day, 7 days and 30 days after immersing the specimens in dye solution. The results were as follows; 1. Control group of group I and group II showed marginal leakage. 2. The degree of marginal leakage in experimental group was greater reduced than control group. 3. In control group, the degree of marginal leakage in group I was greater than group II. 4. In experimental group, there is not statistical differences of the degree of marginal leakage between group I & group II.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.7
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• pp.669-674
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• 2013

To design the optimized low noise planetary gear sets, a program called pRMC(planetary run many cases) is developed. The pRMC is especially using a combination analysis method for all gear specifications and also able to analyze any type of planetary gear sets. The pRMC is composed of the 5 sections those are generate, setting, evaluate, combine and analysis. After calculating all candidate gear sets, the pRMC could show many results that represent the character of each gear set including the transmission error which is the main gear noise factor, the contact ratios, the bending stress and so on. By comparing the results objectively, user could predict and select the optimized gear set which has quiet noise level and desired durability. The planetary gear designed by pRMC could have reduced noise and vibration level from 5 to 10 dB than previous-designed one.

• Wind and Structures
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• v.34 no.1
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• pp.29-42
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• 2022

Following the BARC initiative, wind tunnel measurements have been performed on a 5:1 rectangular cylinder. Pressure distribution has been measured in several sections, checking the two-dimensionality of the flow around the model. Mean values compare well with previous data. These measurements have been processed using the standard Proper Orthogonal Decomposition (POD) and the snapshot POD to obtain phase-resolved cycles. This decomposition has been used to analyze the characteristics of the flow around the cylinder, in particular, the behavior of the recirculation bubble in the upper/lower surfaces. The effect of the angle of attack, the turbulence intensity and the Reynolds number has been studied. First and second modes extracted from POD have been found to be related to the reattachment of the flow in the upper surface. Increasing the angle of attack is related to a delay in the reattachment position, while an increase in turbulence intensity makes the reattachment point to move towards the windward face.