• Transactions of the Korean Society of Automotive Engineers
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• 제11권4호
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• pp.68-78
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• 2003

Recently, low speed vehicle (LSV) is beginning to appear for various usages. The body of the LSV is usually made of the aluminum space frame (ASF) type rather than the monocoque or unitary construction type. A pa.1 of the reason is that it is easier to reduce mass efficiently while the required stiffness and strength are maintained. A design flow for LSV is proposed. Design specifications for structural performances of LSV do not exist yet. Therefore, they are defined through a comparative study with general passenger automobiles. An optimization problem is formulated by the defined specifications. At first, one pillar which has an important role in structural performances is selected and the reinforcements of the pillar are determined from topology optimization to maximize the stiffness. At second, the thicknesses of cross sections are determined to minimize the mass of the body while design specifications are satisfied. The optimum solution is compared with an existing design. The optimization process has been performed using a commercial optimization software system, GENESIS 7.0.

• Transactions of the Korean Society of Automotive Engineers
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• 제22권7호
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• pp.90-97
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• 2014

The effects of high pressure and low pressure exhaust gas recirculation (HP/LP EGR) portion on diesel engine combustion and emissions characteristics were investigated in a 2.2 L passenger-car diesel engine. The po3rtion of HP/LP EGR was varied from 0 to 1 while fixing the mass flow rate of fresh air. The intake manifold temperature was lowered with the increasing of the portion of LP EGR, which led to the retardation of heat release by pilot injection. The lowered intake manifold temperature also resulted in low nitrogen oxide (NOx) emissions due to decreased in-cylinder temperature and prolonged ignition delay, however, the carbon monoxide (CO) emission showed opposite trend to NOx emissions. The brake specific fuel consumption (BSFC) was decreased as the portion of LP EGR increased due to lowered exhaust manifold pressure by wider open of turbocharger vane. Consequently, the trade-off relationship between NOx and BSFC could be improved by increasing the LP EGR portion.

• Transactions of Materials Processing
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• 제13권7호
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• pp.635-641
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• 2004

Today the specific outputs of modern supercharger DI diesel engine for passenger cars reach values exceeding 50kw/1. By development of the articulated piston, specific output of up to 70kw/1 are sought. In doing so, peak cylinder pressure increases from the current 14-16MPa to 18-20MPa. The Articulated piston was composed Al cast skirt part and steel forged crown part. We have the target fer the design of forging process and die of the steel forged crown part. The design parameters of the forging process of the piston were obtained by the forging industry experiences and our experimental data and analysis result of finite element simulation. Especially, the design parameter of preform in blocker die was decided by finite element simulation using numerical package DEFROM3D. And also we can verify the design parameter by conducting visio-plasticity test using plasticine material. When we compared the results of analysis and experiment, a metal flow and load curve showed good agreement. Through this research, we could design optimal preform shape of articulated piston for this supercharged DI diesel engine.

• Journal of the Korean Society for Railway
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• 제10권3호
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• pp.271-277
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• 2007

The Korean Tilting Train eXpress (TTX) development program is in progress for the purpose of running speed or passenger's comfort improvement at the curved track. However, the speed up and light weight of train make poor the dynamic safety of the TTX in strong cross wind. In this paper, 3-dimensional numerical analysis on the flow field around the TTX under strong cross wind is performed for each operating condition, such as the train speed, cross wind speed, tilting/nontilting condition, and so on. Due to the strong cross wind, the pressure distribution around the train becomes asymmetric, especially at the leading car. Asymmetrical pressure distribution causes the side force and strong unstability. The side force on the train is proportional to the train speed and cross wind speed. Based on the numerical results, the overturning coefficients are predicted for investigation of the train stability, and all of them are less than the critical value, 0.9. The results in this study would be a good data for providing importance to judgement of cross wind safety of TTX.

• Asian Journal of Innovation and Policy
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• 제11권1호
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• pp.110-147
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• 2022

Many megacities are exposed to natural hazards such as earthquakes, and when located in coastal regions, are also vulnerable to hurricanes and tsunamis. The physical infrastructures of transportation systems in megacities have become so complicated that very few organizations can understand their response to extreme events such as earthquakes and can effectively mitigate subsequent economic downfalls. The technological advances made in recent years to support these complex systems have not grown as fast as the rapid demand on these systems burdened by population shift toward megacities. The objective of this paper is to examine the risks imposed on and recoveries of transportation systems in megacities as the result of extreme events such as an earthquake. First, the physical damage to transportation infrastructure, loss of the transportation system performance, and the corresponding economic loss from disruptions to passenger and freight traffic is evaluated. Then, traffic flows are re-routed to reduce vehicles' delay due to earthquakes using a microscopic traffic flow simulator with an optimization model and macroscopic terminal simulator. Finally, the economic impact of the earthquake is estimated nationwide. Southern California is regarded as the region of study. The results demonstrate the effectiveness of the integrated model and provide what and how to prepare innovative resilience policies of urban infrastructure for a natural disaster occurrence.

• KSCE Journal of Civil and Environmental Engineering Research
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• 제29권4D호
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• pp.499-507
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• 2009

A median barrier in the road is to separate driver and passenger the traffic flow in the 4-line over highway. In order to keep thee safety of and minimize the traffic jam in the traffic accidents, the ubiquitous intelligent median barrier system is proposed in this paper. This system is required to develop the sensor node fields in the median barrier, which detects the traffic accident using vibration sensors and wireless communication network. Free space test to sensing & receiving radio frequency, verification of middleware to report and countermeasure the accident intelligently to police and hospital are carried out.

• BMB Reports
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• 제57권8호
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• pp.369-374
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• 2024

Antigen 43 (Ag43) proteins, found on the outer membrane of Escherichia coli, are β-sheets that fold into a unique cylindrical structure known as a β-barrel. There are several known structural similarities between bacterial Ag43 autotransporters and physical components; however, the factors that stabilize the barrel and the mechanism for Ag43 passenger domain-mediated translocation across the pore of the β-barrel remain unclear. In this study, we analyzed Ag43β-enhanced green fluorescent protein chimeric variants to provide new insights into the autotransporter Ag43β-barrel assembly, focusing on the impact of the α-helical linker domain. Among the chimeric variants, Ag43β700 showed the highest surface display, which was confirmed through extracellular protease digestion, flow cytometry, and an evaluation of outer membrane vesicles (OMVs). The Ag43β700 module offered reliable information on stable barrel folding and chimera expression at the exterior of the OMVs.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제21권11호
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• pp.765-770
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• 2020

The turbochargers used widely in diesel and gasoline engines are effective devices to reduce fuel consumption and emissions. In this study, the isentropic turbine efficiency of the steady flow in a twin-scroll turbocharger for the passenger vehicle gasoline engine was analyzed. The cold gas test bench was designed and made. The pressure and temperature of the inlet and exit of the turbine were measured at 60,000, 70,000, 90,000, and 100,000rpm under the steady-state flow. The isentropic turbine efficiency was calculated. The efficiency was the range of 0.53 to 0.57. The BSR and expansion ratio were changed from 0.71 to 0.84 and from 1.24 to 1.72, respectively. The isentropic turbine efficiency decreased with increasing BSR and expansion ratio. The operation of only scroll A or B was compared with that of the twin-scroll turbine. The isentropic efficiency of using only scroll B was higher than those of only scroll A at 60,000rpm. The isentropic efficiency of using only scroll A was higher than those of only scroll B at 100,000rpm. Therefore, the twin-scroll turbine used in this study is operating effectively in the wide speed range.

• Journal of the Korean Society of Marine Environment & Safety
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• 제19권4호
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• pp.359-365
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• 2013

There are more than 10 ships and jetfoil passenger ships with speeds of 30~40 kts navigating between Japan and Busan ports per hour. Busan port has the highest density of traffic among the Korean ports and waterways. Jetfoil ships are the most frequently encountered amongst other vessels and about 18 % of passing jetfoil vessels violated port regulations. Based on the analysis of traffic survey carried out for 10 days, jetfoil vessels often overtook other vessels in route and deviated with high speed. This paper verified a proper speed and how to navigate in or out route of jetfoil ships by marine traffic flow simulation. A acceptable navigation speed for jetfoil vessel's mariner was calculated at less than about 32kts in Busan Port. It is a little different that shiphandling difficulty of jetfoil was almost the same whether passing in and out route in Busan Port. This paper proposes that the passing time of jetfoil ships should avoid the peak time to improve the traffic safety in Busan Port.

• Journal of Korean Society of Transportation
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• 제19권2호
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• pp.89-98
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• 2001

The objective of this Paper is to derive an adjustment factor for the presence of heavy vehicles when estimating capacity at unsignalized intersections (and/or at modern roundabouts). According to the 1997 and 2000 Highway Capacity Manual (HCM), potential capacity in such cases is estimated by simply adjusting base critical gap and base follow-up time. However, the procedure suggested in the HCM may lead to some errors in the adjustment, hence resulting in poor evaluation and design for the intersections, because it determines the value of adjusting factors by only the number of lanes on main streets regardless of the types of heavy vehicles. This paper shows a simple formula for making the adjustment. This formula is much like the HCM formula used for heavy vehicles in estimating highway capacity by the adoption of passenger car units (PCU). In contrast to the traditional approaches seen in the HCM, the PCU value of this case is explicitly expressed by the flow rate in the major streams and the gap difference in critical gaps chosen by passenger cars and particular heavy vehicles. Computational results of the adjustment factor are graphically illustrated.