Seaport research: A structured literature review on methodological issues since the 1980s

This study aims to investigate how seaport research has been conducted from the methodological perspective. To this end, this study reviews published port literature for the last three decades (1980-2000s). The investigation primarily categorises the literature according to various methodological issues such as research paradigm, research strategy, base-disciplines, research methods and analysis techniques in order to provide meaningful implications on methodological evolution in seaport research for the period. This study suggests methodological bias in port research to a positivistic paradigm, following a quantitative trajectory moving from conceptual to empirical studies. In addition, the increased use of mathematical modelling and advanced statistical analysis methods is clearly observed. The introduction of advanced analytical tools used in other academic disciplines facilitates discussions in particular research area and amplifies the literature in those areas. This paper also suggests research gaps from the methodological perspective and implications for future port research.     

Integration of a single cylinder engine model and a boost system model for efficient numerical mapping of engine performance and fuel consumption

A numerical engine mapping methodology is proposed for the engine performance and fuel consumption map generation. An integrated model is developed by coupling a single cylinder GT-Power® engine model with a MATLAB/ Simulink® based boost system model to simulate a turbocharged diesel engine over the entire engine operating speed and load ranges within reasonable computational constraints. A single cylinder engine model with the built-in multi-zone combustion modeling option in GT-Power® is configured as a predictive engine model. The cycle averaged simulation result from the engine model is used as the boundary conditions of the boost system including intake and exhaust manifolds and a turbocharger. The boost system model developed in MATLAB/Simulink® platform calculates the intake and exhaust conditions which are fed back to the engine model. The integrated system model predicts the performance and fuel consumption of a turbocharged diesel engine with better predictive capability than mean value engine models. Its computational time is fast enough to simulate the engine over the entire engine operation range compared to multi-cylinder engine models.     

Development of a new analytical model for a railway vehicle equipped with independently rotating wheels

The urban tram introduced recently has a low-floor structure for the convenience of passengers getting on and off. To adjust the low-floor level and improve performance on curves, most low-floor trams have IRWs (independently rotating wheels) with no central axle between the two wheels. Eliminating the central axle, however, creates several inherent problems, such as insufficient guiding force and excessive wear. To analyze these problems, a new analytical model is described in this paper to describe the dynamic characteristics of IRWs more precisely. This analytical model is developed to consider the effects of longitudinal creep in particular, which have been ignored in conventional analytical models of IRWs. In addition, a running stability analysis based on the newly developed analytical model is conducted to compare the critical speeds of IRW-axle vehicles and rigid-axle vehicles. The dynamic characteristics of an initial disturbance are compared to verify that the analytical model is effective in expressing the dynamic characteristics of IRWs.     

New metal fitting geometry and optimization of the swaging parameters for an automobile power steering hose

To solve the power steering (PS) hose oil leakage problem in automobile applications, a new geometry design of the metal fitting is required, and the swaging conditions applied to the PS hose should be optimized. In this study, a new metal fitting geometry for the PS hose was proposed. A CAE simulation for both the proposed and the conventional metal fittings was conducted, and both the stress and the strain in the PS hose were compared. An experimental verification was also performed with these two different metal fittings. Additionally, the swaging conditions were optimized by the durability cycle time, which was measured in an impulse test of the swaged PS hose. For a more economical production, practical working conditions were also recommended and experimentally verified.     

Thermo-oxidative degradation of a carbon black compounded EPDM rubber hose

A method to measure the crosslink density of carbon black was used to analyze the aging behavior of a radiator hose made of carbon black filled EPDM (ethylene-propylene diene monomer) rubber under thermo-oxidative stresses. The crosslink density and the strength of the skin of the rubber specimens initially decreased slightly but then increased over time. The elongation at the break considerably reduced and did not show any similarity to the behaviors of the crosslink density. A possible cause of this reaction might be from the formation of rigid sulphoxide crosslinks and the crosslinks produced by the reaction of unvalcunized sulfurs. Aging the rubber specimens at 180°C caused a slight increase in the crosslink density and a large decrease in tensile strength and elongation. The aging experiment also caused a rapid increase of microhardness in the surface skin region. The formation of carbonyl groups in EPDM molecule chains and the formation of rigid sulphoxide crosslink, rather than the crosslink density variation, may have had a large influence. The changing behaviours of the mechanical properties, molecule chains and crosslinks showed significantly different characteristics in the skin and the interior with aging temperature and time.     

Enhanced selective forwarding scheme for alert message propagation in vehicular <Emphasis Type="Italic">ad hoc</Emphasis> networks

Vehicle-based applications were recently introduced to improve traffic safety and efficiency. These applications are classified into either safety-oriented or non-safety-oriented applications. Safety-oriented applications are typically provided by means of vehicle-to-vehicle (V2V) communications to support reliable and fast alert message propagation to all surrounding vehicles when an emergency occurs on the road. In vehicular ad-hoc network (VANET) broadcast-based packet forwarding is typically preferred for the propagation of urgent traffic-related information to all reachable nodes within a specified dangerous region. However, this approach may cause broadcast storm problems, which can lead to serious contention between transmissions from adjacent nodes. In this paper, we propose an alert message propagation scheme that is based on selective forwarding and aims to i) minimize the number of rebroadcasting nodes and ii) guarantee reliable and fast alert message delivery to all reachable nodes. Our scheme was evaluated using two different highway scenarios. The simulation results demonstrated that the performance of the proposed scheme was better than that of existing broadcast schemes in terms of the message delivery latency, the message delivery ratio, and the message rebroadcasting ratio.     

Properties of roadway particles from interaction between the tire and road pavement

A large fraction of urban PM₁₀ concentrations is due to non-exhaust traffic emissions, including road dust, particles from tire/road interface, and brake lining particles. Although potential health and environmental impacts associated with tire wear debris have increased, few environmentally and biologically relevant studies of actual tire wear debris have been conducted. Tire wear particles (TWP) are released from the tire tread as a result of the interaction between the tire and the pavement. Roadway particles (RP), meanwhile, are particles on roads composed of a mixture of elements from tires, pavement, fuels, brakes, environmental dust, and the atmosphere. The main objective of the present study is to identify the contribution of tires to the generation of RP and to assess the potential environmental and health impacts of this contribution. First, a mobile measurement system was constructed and used to measure the RP on asphalt roads according to vehicle speed. The equipment of the mobile system provides PM₁₀ concentration by DustTrak DRX, and mass and number size distribution of fine and ultrafine particles by a fast mobility particle sizer (FMPS) and an aerosol particle sizer (APS). The dependence of RP mass and particle number concentration on vehicle speed was observed. It was also found that many particles were generated by rapid deceleration of the vehicle.     

A clustering based traffic flow prediction method with dynamic spatiotemporal correlation analysis

Transportation - There are significant spatiotemporal correlations among the traffic flows of neighboring road sections in the road network. Correctly identifying such correlations makes an...     

Evaluating the impacts of urban corridor traffic signal optimization on vehicle emissions and fuel consumption

This study investigates the impacts of traffic signal timing optimization on vehicular fuel consumption and emissions at an urban corridor. The traffic signal optimization approach proposed integrates a TRANSIMS microscopic traffic simulator, the VT-Micro model (a microscopic emission and fuel consumption estimation model), and a genetic algorithm (GA)-based optimizer. An urban corridor consisting of four signalized intersections in Charlottesville, VA, USA, is used for a case study. The result of the case study is then compared with the best traffic signal timing plan generated by Synchro using the TRANSIMS microscopic traffic simulator. The proposed approach achieves much better performance than that of the best Synchro solution in terms of air quality, energy and mobility measures: 20% less network-wide fuel consumption, 8–20% less vehicle emissions, and nearly 27% less vehicle-hours-traveled (VHT).     

Effect of minor elements on the creep resistance of Mg-Zn-Mn-(Ca) alloy

Along with alumium, titanium and composite alloys, magnesium alloys have been given much attention by industry for applications such as lightweight automobiles and electronics because of their high strength, low specific density and good damping characteristics. In this paper, creep tests were done with magnesium alloys (Mg-3% Zn-1% Mn, Mg-1.2% Zn-1% Mn, and Mg-3% Zn-1% Mn-0.3% Ca) containing different amounts of Zn to investigate the effect of Zn and Ca on the deformation behavior and the rupture time for Mg alloy creep under elevated temperatures. The alloys were obtained as follows: (1) pure magnesium (9.7 kg) was melted at 720°C in an SF6 atmosphere; (2) the temperature was increased up to 800–820°C after adding 0.3 kg of pure Mn to make the Mg-1% Mn master alloy; (3) the minor element (Zn, Ca) was added to the master alloy; and (4) the magnesium alloy melts were cast into a metallic mold preheated to 150°C. The creep tests were executed under a constant load and temperature to measure the steady-state rate and rupture time of creep. Based on the experimental results, the creep behavior of the alloys seemed to be controlled by dislocation climb at around 0.5∼0.55T_m (T_m; melting temperature). In addition, the results showed that the addition of Ca was effective for increasing the creep resistance of a Mg alloy: the more Zn present in the alloy, the stronger the creep strength of the alloy.