• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.34 no.3
• /
• pp.137-149
• /
• 2021

Cable-stayed bridges are infrastructure facilities of a highly public nature; therefore, it is essential to ensure operational safety and prompt response in the event of a collapse or damage caused by natural and social disasters. Among social disasters, impact accidents can occur in bridges when a vehicle collides with a pier or when crashes occur due to aircraft defects. In the case of offshore bridges, ship collisions will occur at the bottom of the pylon. In this research, a procedure to evaluate the structural behavior of a cable-stayed bridge for aircraft impact is suggested based on a numerical analysis approach, and the feasibility of the procedure is demonstrated by performing an example assessment. The suggested procedure includes 1) setting up suitable aircraft impact hazard scenarios, 2) structural modeling considering the complex behavior mechanisms of cable-stayed bridges, and 3) structural behavior evaluation of cable-stayed bridges using numerical impact simulation. It was observed that the scenario set in this study did not significantly affect the target bridge. However, if impact analysis is performed through various scenarios in the future, the load position and critical load level to cause serious damage to the bridge could be identified. The scenario-based assessment process employed in this study is expected to facilitate the evaluation of bridge structures under aircraft impact in both existing bridges and future designs.

• Korean Journal of Applied Biomechanics
• /
• v.19 no.2
• /
• pp.311-322
• /
• 2009

Using the 3-D analysis, this study winpared and analyzed the 'fade-shot swing' which is one of the golf technique. The subjects of this study were 3 male pro golfers they experimented with only a 7 iron. The purpose was to enhance their performance by producing the important kinematical parameters, finding out the features in them and providing the data to a coach and players. As a result, the position of the club head showed from the outside orbit to the inside orbit. When position of the center of mass moved backwards, the probability of the failure of the fade-shot increased. Cocking angle had an effect on easing the wrist for a smooth follow-through after the impact. It showed that the changes in the shoulder movement was made first and followed by the waist. The hip joint angular velocity achieved a smooth fade-shot motion due to the hitting delay also the velocity of the club-head was faster when uncocking was released at the time of impact.

• Resources Recycling
• /
• v.16 no.5
• /
• pp.57-64
• /
• 2007

Triboelectrostatic separation of mixed three kinds of plastics, PVC, PET and PMMA, in the range of similar gravity has been performed through a two-stage separation process. Polypropylene (PP) and high-impact polystyrene (HIPS) were found to be the most effective materials for a tribo-charger in the separation of PVC, PET and PMMA. In the 1st stage using the PP cyclone charger, PVC grade and recovery depended considerably on the air velocity (10 m/s), the relative humidity (<30%), the electric field (>200 kV/m) and the splitter position (+2 cm from the center) in the triboelelctrostatic separator unit. At an optimum condition a PVC grade of 99.6% and a recovery of 97.5% was achieved. In the 2nd stage using the HIPS cyclone charger, a PMMA grade of 98.3% and a recovery of 97.0% was obtained under the conditions of 10m/s air velocity, over 250 kV/m electric field, central splitter position and less than 40% relative humidity.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.22 no.1
• /
• pp.424-430
• /
• 2021

Determining the cause of a traffic signal violation is difficult if the drivers' claims are contradictory. In this study, the process of identifying signal violations using a simulation was presented based on cases. First, statements from the driver or witness whose cause of the signal violation is unclear were excluded. Second, the final position, final location, damaged area, steering status, braking status, and road surface traces of the vehicle were collected. The impact point was investigated from the stop line. Third, simulation data were modified and entered until the collision situation of the accident vehicle and the final stop position were met. Fourth, if the simulation results were consistent with the crash situation, the facts were verified by cross-validation to conform to the driver's statement. The results of the simulation showed that the Lexus entered the left turn signal in the intersection at approximately 55 km/h. In comparison, the Sonata driver saw the vehicle straight ahead at the intersection, entered the 72 km/h intersection, and collided with the Lexus. Therefore, the Sonata was identified as a signal violation, and the claims of the Sonata driver, witnesses, and police were contradictory.

• Ocean Systems Engineering
• /
• v.12 no.2
• /
• pp.225-245
• /
• 2022

More and more shipping containers are falling into the sea due to bad weather. Containers lost at sea negatively affect the shipping line, the trader and the consumer, and the environment. The question of locating and recovering dropped containers is a challenging engineering problem. Model-testing of small-scaled container models is proposed as an efficient way to investigate their falling trajectories to salvage them. In this study, we first build a standard 20-ft container model in SOLIDWORKS. Then, a three-dimensional (3D) geometric model in the STL (Standard Tessellation Language) format is exported to a Stratasys F170 Fused Deposition Modeling (FDM) printer. In total, six models were made of acrylonitrile styrene acrylate (ASA) and printed for the purpose of testing. They represent three different loading conditions with different densities and center of gravity (COG). Two samples for each condition were tested. The physical models were dropped into the towing tank of University of New Orleans (UNO). From the experimental tests, it is found that the impact of the initial position after sinking can cause a certain initial rolling velocity, which may have a great impact on the lateral displacement, and subsequently affect the final landing position. This series of model tests not only provide experimental data for the study of the trajectory of box-shape objects but also provide a valuable reference for maritime salvage operations and for the pipeline layout design.

• Wind and Structures
• /
• v.39 no.2
• /
• pp.141-161
• /
• 2024

Engineering structures often suffer significant damage in the horizontal outflow region of downburst. The wall jet model, which simplifies the simulation device by only modeling the horizontal outflow region of downburst, has been widely employed to study downburst flow characteristics. However, research on downburst wind fields over hilly terrain using the wall jet model is limited, and the relationship between the downburst wind fields generated by wall jet and impinging jet remains unclear. This study investigates the flow characteristics of downburst-like wind over a 3D ideal hill model using wind tunnel tests with the wall jet and impinging jet models. The effects of hill height, slope, shape, and radial position on the speed-up ratio are examined using the wall jet flow. The results indicate that slope and radial position significantly affect the speed-up ratio, while hill height have a slight impact and shape have a minimal impact. Additionally, this study investigates the wind field characteristics over flat terrain using the impinging jet, and investigated the connection between the impinging jet model and the wall jet. Based on this connection, a comparison of the downburst-like flow characteristics over the same 3D ideal hill using the wall jet and impinging jet models is conducted, which further validates the reliability of the wall jet model for studying downburst flow characteristics over hilly terrain.

• Journal of Digital Convergence
• /
• v.11 no.2
• /
• pp.385-390
• /
• 2013

The meaning of things appeared in the frame vary according to how they look in a shot. Especially, position of frame shows how a form becomes a content in quality. This has a large impact on communication with audiences, reminds them a special feeling or atmosphere toward an object and plays a suggestive role for things that shows up. Thus, this study aimed to investigate how symbolisms appeared in the frame position are shown in the relation among characters' narrative, personality and conflict and understand correlation between frame position and characters accordingly. As an object to be analyzed, this study selected which was played with narratives of couples with different personalities. The results of analysis shows that it is deeply associated with couples' narrative, which means that trauma or the severance of relations between a couple is shown on left side, whereas a positive and future-oriented couple was mainly shown on right side and the rate of being situated in the center turned out to be high according to the power relations of love. Based on the comparison between symbolism appeared according to the frame position and narratives and traumas that various characters have, this study found that frame position is playing an important role in composing characters' personality.

• International Journal of Automotive Technology
• /
• v.5 no.4
• /
• pp.221-238
• /
• 2004

Wall interactions of direct injection spray were investigated using laser-sheet imaging, shadowgraphy, wetted footprint and phase Doppler interferometry techniques. A narrow-cone high-pressure swirl injector is used to inject iso-octane fuel onto a plate, which has three different impact angles inside a pressurized chamber. Heated air and plate conditions were compared with unheated cases. Injection interval was also varied in the heated case to compare dry- and wet- wall impingement behaviors. High-speed macroscopic Mie-scattering images showed that presence of wall and air temperature has only minor effect on the bulk spray structure and penetration speed for the narrow-cone injector tested. The overall bulk motions of the spray plume and its spatial position at a given time are basically unaffected until a few millimeters before impacting the wall. The surface properties of the impact surface, such as the temperature, the presence of a preexisting liquid film also have a small effect on the amount of wetting or the wetted footprint; however, they have strong influence on what occurs just after impact or after a film is formed. The shadowgraph in particular shows that the plate temperature has a significant effect on vapor phase propagation. Generally, 10-20% faster horizontal vapor phase propagation is observed along the wall at elevated temperature condition. For impingement onto a preexisting film, more splash and evaporation were also observed. Contrary to some preconceptions, there is no significant splashing and droplet rebounding from surfaces that are interposed in the path of the DI gasoline spray, especially for the oblique impact angle cases. There also appears to be a dense spray front consists of large sac spray droplets in the oblique impact angle cases. The bulk of the spray is not impacted on the surface, but rather is deflected by it The microscopic details as depicted by phase Doppler measurements show that the outcome of the droplet impaction events can be significantly influenced. Only droplets at the spray front have high enough Weber numbers for wall impact to wet, splash or rebound. Using the sign of vertical velocity, the time-resolved downward droplets and upward droplets are compared. The Weber number of upward moving droplets, which seldom exceeds unity, also decreases as the impact angle decreases, as the droplets tend to impact less and move along the wall in the deflected spray plume.

• Tunnel and Underground Space
• /
• v.31 no.1
• /
• pp.52-65
• /
• 2021

In this study, authors analyzed the vapor cloud explosion induced by propane leak at the PEMIX Terminal, which is the propane storage facility outside of Mexico City. TNT equivalence mass for the leaked 4750 kg propane was estimated to be 9398 kg. Blast parameters such as peak overpressure, positive phase duration, and impact at 40-400 (m) away from the center of the explosion were calculated by applying TNT Equivalency Method and Multi-Energy Method. The probability of damage due to lung damage, eardrum rupture, head impact, and whole-body displacement impact by applying the probit function obtained using blast parameters was evaluated. The peak overpressure obtained using Multi-Energy Method was found to be greater than the peak overpressure obtained by applying the TNT Equivalency Method at all distances considered, but it was evaluated that there was no significant difference from the points above 200 m. The peak overpressure obtained by Multi-Energy Method was computed to assess the extent of damage to the structure, and it was shown that structures within 100 m of the explosion center would collapse completely, and that the glasses of the structures 400 m away would be almost broken. The probability of death due to lung damage was shown to vary depending on a human body's position located in the propagating direction of shock wave, and if there is a reflecting surface in the immediate surroundings of a human body, the probability of death was estimated to be the greatest. The impact of shock wave on lung damage, eardrum rupture, head impact, and whole-body displacement impact was evaluated and found to affect whole-body impact < lung damage < eardrum rupture

• Journal of Advanced Navigation Technology
• /
• v.12 no.4
• /
• pp.295-303
• /
• 2008

Malfunction of satellite launch vehicles with high speed and long range can be a major concern for operations. Flight safety system that monitor the trajectory and identify any failure of the launch vehicles. Tracking filters for the flight safety systems are different from common tracking filters since filter reliability is more emphasized than accuracy. Reliable estimation of instantaneous impact points requires reliable velocity estimates as well as reliable position estimates. A fusion filter for a flight safety system was developed with the tracking sensor models for the Korea Satellite Launch Vehicle I. The fusion filter performances were evaluated by analyzing the trajectory and instantaneous impact point estimates.