Maritime transportation research: topics and methodologies

The purpose of this paper is to review and analyze maritime transportation academic research. For articles published in Maritime Policy & Management (MPM) in the period 2001 to 2012, the most frequent topics addressed include shipping performance/management and shipping finance. For articles published in Maritime Economics & Logistics (MEL) in the period 2002 to 2012, the most frequent topics addressed include port performance and shipping performance/management. MPM articles are more likely than MEL articles to utilize the institutional (IS) methodology and MEL articles are more likely than MPM articles to utilize the optimization (OP) methodology. Maritime transportation proposition theoretical research may be particularly useful in undertaking research in maritime transportation areas for which data are unavailable, insufficient, difficult to obtain, or of poor quality. Future maritime transportation research needs to include focus on: (i) maritime shippers, (ii) maritime transport chains, (iii) maritime transportation as a service, (iv) the quality of maritime transportation, and (v) maritime theoretical proposition research.     

有限水深中垂直下潜弹性薄板的水波散射(英文)

The problem of water wave scattering by a thin vertical elastic plate submerged in uniform finite depth water is investigated here.The boundary condition on the elastic plate is derived from the Bernoulli-Euler equation of motion satisfied by the plate.Using the Green’s function technique,from this boundary condition,the normal velocity of the plate is expressed in terms of the difference between the velocity potentials(unknown)across the plate.The two ends of the plate are either clamped or free.The reflection and transmission coefficients are obtained in terms of the integrals’involving combinations of the unknown velocity potential on the two sides of the plate,which satisfy three simultaneous integral equations and are solved numerically.These coefficients are computed numerically for various values of different parameters and depicted graphically against the wave number in a number of figures.     

Numerical simulation of 2D and 3D sloshing waves in a regularly and randomly excited container

In this paper,various aspects of the 2D and 3D nonlinear liquid sloshing problems in vertically excited containers have been studied numerically along with the help of a modified-transformation.Based on this new numerical algorithm,a numerical study on a regularly and randomly excited container in vertical direction was conducted utilizing four different cases： The first case was performed utilizing a 2D container with regular excitations.The next case examined a regularly excited 3D container with two different initial conditions for the liquid free surface,and finally,3D container with random excitation in the vertical direction.A grid independence study was performed along with a series of validation tests.An iteration error estimation method was used to stop the iterative solver（used for solving the discretized governing equations in the computational domain） upon reaching steady state of results at each time step.In the present case,this method was found to produce quite accurate results and to be more time efficient as compared to other conventional stopping procedures for iterative solvers.The results were validated with benchmark results.The wave elevation time history,phase plane diagram and surface plots represent the wave nonlinearity during its motion.     

Numerical analysis of homogeneous mixture formation for a direct injection liquid LPG engine

A method to form a homogeneous mixture using low pressure direct injection of liquid phase LPG, pent-roof combustion chamber, flat-top piston and center-located injector layout is presented. To validate the method, the mixture formation processes in the cylinder were investigated using the CFD code. The effect of different injection timing and engine loads on the mixture formation processes were researched. The simulated results showed that, the intake tumble for high load conditions or the inclined intake swirl for part load conditions would break into small-scale vortex (turbulence) near the end of compression stroke, which enhanced the homogeneous mixture formation. The results also showed that if the liquid phase LPG was injected at 60–80°CA ATDC in intake stroke even at different loads, the homogeneous mixture would be formed under any engine load conditions.     

Improved optimal controller for start-up of amt trucks in consideration of driver’s intention

A linear-quadratic optimal controller is proposed for vehicle start-up, which is designed as a linear feedback form of the states and the measured (estimated) disturbances. The requirements of less friction loss and less driveline shock are represented by the weighting matrices of the cost function. The driver’s intension is also considered and the controller gains are adjusted on-line accordingly. The designed control strategy is tested on a complete powertrain simulation model. Through large amount of simulations, it is verified that the system is robust to the variations of driving conditions, such as variation of vehicle mass and road grade. It is also shown that the control performance is influenced greatly by the estimation error of engine torque and clutch torque, and the acceptable level of mean estimation error is about ±10%.     

Optimal fuel-cut driving method for better fuel economy

Eco-drive methods are being applied in modern passenger cars in the form of LCD displays showing real-time fuel consumption rates. The eco-drive is one of the most promising methods to enhance the fuel economy of vehicles. The ecodrive method can be made more effective by using the fuel-cut function. The fuel is not injected when the driver does not depress the gas pedal of a vehicle with engine speeds higher than approximately 1,500 rpm above the mid-vehicle speed range. This function is known as the fuel-cut function, and almost every modern vehicle is equipped with this function. The fuel-cut is most frequently activated on downhill sections of highway. Therefore, the CO₂ exhausted from the vehicle can be zero in this downhill section. In this study, the fuel-cut function is simulated with CRUISE of AVL to find the most effective driving pattern in downhill sections. Simulations with the CRUISE software showed that the lower limit of the vehicle speed for fuelcut should be raised to improve fuel economy on steeper downhill sections. The fuel economy can be optimized when the fuelcut coasting and reacceleration is completed in the downhill part of the road. The simulation result was also compared to previous test results. Fuel consumption was reduced by approximately 4% in both the experimental and simulated results for the West Coast Highway in South Korea.     

Comparison of driving characteristics between drivers in Korea and in the united states of America based on driver-vehicle interaction field database

Research and development involving intelligent vehicles of today is geared to safe, driver-friendly and sensitive vehicles that provide a driver with a pleasant and convenient driving environment while preventing him or her from possible risks of accident. In developing convenient and safe vehicles, research on drivers’ driving patterns, reactions and state characteristics depending on road conditions in actual field is essential in order to devise more driver-friendly intelligent vehicles. This paper describes how a driver-vehicle interaction (DVI) field database is built in order to obtain a driver’s input in normal road driving condition on highways, country roads, and city roads, and his or her state information, as well as data on the vehicle and traffic conditions. And the newly built database is compared with the RDCW FOT database established by UMTRI of the US for analysis to suggest that the driving tendencies of drivers in Korea and the road driving conditions are not the same as those in the US, reconfirming the need to establish a DVI field database, which will be used for the development of intelligent vehicles suitable for the Korean environment. The DVI data collected from actual driving in field are anticipated to be widely utilized as basic data for research on various intelligent driving safety systems, advanced driver assistance systems (ADAS) and human-vehicle interface (HVI) that are suitable for the driving environment in Korea.     

Reduction of emissions with propane addition to a diesel engine

Recent studies on dual-fuel combustion in compression-ignition (CI) engines, also known as diesel engines, fall into two categories. In the first category are studies focused on the addition of small amounts of gaseous fuel to CI engines. In these studies, gaseous fuel is regarded as a secondary fuel and diesel fuel is regarded as the main fuel for combustion. The objectives of these studies typically involve reducing particulate matter (PM) emissions by using gaseous fuel as a partial substitution for diesel fuel. However, the addition of gaseous fuel raises the combustion temperature, which increases emissions of nitrogen oxides (NO_x). In the second category are studies focused on reactivity-controlled compression-ignition (RCCI) combustion. RCCI combustion can be implemented by early diesel injection with a large amount of low-reactivity fuel such as gasoline or gaseous fuel. Although RCCI combustion promises lower NO_x and PM emissions and higher thermal efficiency than conventional diesel combustion, it requires a higher intake pressure (usually more than 1.7 bars) to maintain a lean fuel mixture. Therefore, in this study, practical applications of dual-fuel combustion with a low air-fuel ratio (AFR), which implies a low intake pressure, were systemically evaluated using propane in a diesel engine. The characteristics of dualfuel combustion for high and low AFRs were first evaluated. The proportion of propane used for four different operating conditions was then increased to decrease emissions and to identify the optimal condition for dual-fuel combustion. Although the four operating conditions differ, the AFR was maintained at 20 (? approximately equal to 0.72) and the 50% mass fraction burned (MFB 50) was also fixed. The results show that dual-fuel combustion can reduce NO_x and PM emissions in comparison to conventional diesel combustion.