Optimizing the transportation of international container cargoes in Korea

This paper considers a multimodal transportation problem, which is the problem of determining the transportation flow, i.e. volume of container cargoes, and the transportation mode in each trade route, for the objective of minimizing the sum of shipping and inland transportation costs. The problem takes account of two restrictions: maximum cargo volumes capacitated at each seaport and maximum number of vehicles available at each transportation mode. To solve optimally the problem, this paper employs a mixed integer programming, which is an operations research technique. A case study is performed on the container cargo data in Korea and we draw several implications to improve efficiency in the transportation of international trade cargoes in Korea.     

Disruption risks and mitigation strategies: an analysis of Asian ports

The critical nature of a seaport is a connection point. In addition to the effect on port operations, a port disruption will be a strain on trade flows and the various parties concerned. Climate change, oil spill, security, social and political instability are increasing concerns over the years which would lead to higher risks. With significant growing trade volume in Asia, there is a pressing need for comprehensive studies to prepare ports for disruptions. This paper aims to analyse and categorise the disruptions that have occurred in Asian ports and estimate the likelihood of recurrence based on the data since the year 1900. Results reveal a rising trend of disruptive events. Natural disasters and labour strikes are the two main causes of port disruptions, while natural disasters lead to the highest severity in terms of cargo tons affected. Mitigation strategies proposed in terms of both preventive and reactive measures are specifically designed to reduce the likelihood and severity of the various types of port disruptions. The paper provides recommendations on risk mitigation for relevant parties.     

Relationships Between US Consumer Expenditures on Communications and Transportation Using Almost Ideal Demand System Modeling: 1984–2002

Abstract

This study analyzes aggregate consumer expenditure data from the US between 1984 and 2002, to determine relationships between expenditures on transportation and communications. We first identified 15 categories of goods – nine for transportation, five for communications, and one for all others – and obtained prices for each category across time. Then, we applied the linear approximate almost ideal demand system (AIDS) method for estimating consumer demand functions, aggregating the categories to six (non-personal vehicle (PV), PV capital, PV operation, electronic communications media, print communications media, and all others) due to the small sample size. The results indicate that transportation and communications categories have both substitution and complementarity relationships. The existence of effects in both directions (substitution and complementarity) is testimony to the complexity of the relationships involved, with both generation and replacement possible and happening simultaneously. In addition, expenditures in the transportation categories are generally more income-elastic and price-elastic than those in communications, indicating that communications expenditures are more essential than those for travel. The transportation categories have both substitution and complementarity relationships with each other, while the two communications categories have a substitution relationship.     

Opportunistic preventive maintenance optimization for multi-unit series systems with combing multi-preventive maintenance techniques

This paper proposes a dynamic opportunistic preventive maintenance (PM) optimization policy for multi-unit series systems by integrating multi PM techniques. Two PM techniques, periodic PM and sequential PM, are considered. Whenever one of the units reaches its reliability threshold, a PM action has to be performed on that unit. At that time the whole system has to be stopped and PM opportunities arise for the other units of the system. An optimal PM practice is determined by maximizing the short-term cumulative opportunistic maintenance (OM) cost savings for the whole system. Numerical examples are given to show how this approach works. Finally, a comparison between the proposed PM policy and the other policies is given.     

我在澳洲的八辆车

在十几岁时,我随着家人移民到澳大利亚——一个主要靠汽车代步的国家。那时的我对汽车并没多少兴趣,更喜欢在国内一直开的摩托。但澳洲这边路况好车速快,最安全还是开汽车,所以到达后,我就开始读考驾照的书籍,很快就拿到了驾照。     

Age and cross-cultural comparison of drivers’ cognitive workload and performance in simulated urban driving

Driving demands significant psychomotor attention and requires even more when drivers are engaged in secondary tasks that increase cognitive workload and divert attention. It is well established that age influences driving risk. Less is known about how culture impacts changes in attention. We conducted parallel driving simulations in the US and Korea to measure the extent to which age and culture influence dual-task performance. There were 135 participants divided into two groups: a younger group aged 20∼29, and an older group aged 60∼69. Whereas some differences by culture appeared in absolute control measures, the younger participants showed similar mean velocity and compensatory patterns associated with increased cognitive load in the urban setting; however, the results from the older samples were less similar.     

Optimizing the shape of a bumper beam section considering pedestrian protection

This paper presents a design technique to optimize the shape of a vehicle bumper beam that satisfies both the safety requirements for a front rigid-wall impact and the regulations protecting pedestrians from lower leg injuries caused by bumper impacts. An intermediate response surface modeling (IRSM) technique was introduced to approximate the non-linear force-displacement curves obtained from the front impact analysis of a vehicle bumper. The accuracy of the IRSM model was tested by comparing its results with those of the non-linear finite element analysis. The maximum displacement error between the two models did not exceed 3%. Using pedestrian impact analyses based on the experimental arrangement of the Plackett-Burman design, the approximate functions describing the response values acting on the lower legs were calculated. The shape of the bumper beam was optimized by integrating the IRSM with the force-displacement model and the approximate functions on lower leg impact. The optimization results satisfied safety regulations on the maximum allowable displacement of the vehicle bumper, and also the regulations protecting pedestrians from lower leg injuries caused by bumper impacts.     

Effect of cetane enhancer on spray and combustion characteristics of compressed ignition type LPG fuel

This research investigated the spray and combustion characteristics of compressed ignition type LPG fuel when a cetane number enhancing additive was applied to a constant volume chamber. Because LPG has a lower cetane number, DTBP and alpha olefin were added to the LPG (100% butane) to enhance the cetane number and viscosity. By adding the cetane enhancer, stable combustion over the wide range of the ambient conditions was possible as well. According to the blending rates of DTBP and alpha olefin, various proportions of LPG blended fuels were obtained. In a constant volume chamber, a high speed digital camera was also employed to visualize the combustion characteristics of LPG fuel. The combustion pressures and heat-release rates of the LPG blends were also compared at various ambient pressures. As the results of measurements of exhaust emissions, CO and HC were reduced considerably, but CO₂ was increased by blending LPG with DTBP and alpha olefin.     

Effect of various LPG supply systems on exhaust particle emission in spark-ignited combustion engine

The particle size distribution and particle number (PN) concentration emitted by internal combustion engine are a subject of significant environmental concern because of their adverse health effects and environmental impact. This subject has recently attracted the attention of the Particle Measurement Programme (PMP). In 2007, the UN-ECE GRPE PMP proposed a new method to measure particle emissions in the diluted exhaust of automotive engines and a regulation limit (<6.0×10¹¹ #/km, number of particles). The specific PN regulation of spark-ignited combustion engine will be regulated starting on September 1, 2014 (EURO 6). In this study, three types of LPG supply systems (a mixer system and a multi-point injection system with gas-phase or liquid-phase LPG fuel) were used for a comparison of the particulate emission characteristics, including the nano-sized particle number density. Each of the three LPG vehicles with various LPG injection systems contained a multi-cylinder engine with same displacement volumes of 2,000 cm³ and a three-way catalytic converter. The test fuel that was used in this study for the spark-ignited combustion engine was n-butane basis LPG fuel, which is primarily used for taxi vehicles in Korea. The characteristics of nano-particle size distribution and number concentration of particle sizes ranging from 20 to 1,000 nm (aerodynamic diameter) that were emitted from the three LPG vehicles with various LPG supply systems were investigated by using a condensation particle counter (CPC), which is recommended by the PMP under both the NEDC and FTP-75 test modes on a chassis dynamometer. The experimental results indicate that the PN emission characteristics that were obtained by the CPC system using the PMP procedure are sufficiently reliable compared to other regulated emissions. Additionally, the sources of PN emissions in ascending order of magnitude are as follows: mixer type, gas-phase LPG injection (LPGi) and liquid-phase LPG injection (LPLi) passenger vehicles. The liquid-phase LPG injection system produced relatively large particle sizes and number concentrations compared to the gaseous system, regardless of the vehicle driving cycle. This phenomenon can be explained by unburned micro-fuel droplets that were generated due to a relatively short homogeneous fuel-air mixture duration in the engine intake manifold. Also the particle number emissions from the LPG vehicle were influenced by the vehicle driving cycle.     

Analytical study to estimate the performance of the Power Shift Drive (PSD) Axle for a forklift

In this study, a new concept for a power delivery system is developed. Power Shift Drive (PSD) Axle vehicle modeling and dynamic movement analysis are performed via simulation. The dynamic vehicle model is constructed from data obtained from the derived equation, considering the specific characteristics of each part. The model is composed of a torque converter, a gear box, a differential, hub reduction and an engine, which is the power source of the 1st forward and reverse PSD-Axle. By unifying the mathematical equations for each component, a mathematical model of the 1st forward gear is derived. The system dynamic model is created using MATLAB/Simulink based on the mathematical model. Simulation is carried out using Simulink to estimate the dynamic behavior of the PSD-Axle. In addition, the dynamo test result is used to verify the model. Finally, a successful model is created. This study will be used to establish the basic conceptual design for the PSD-Axle multi-gear system.