Free piston engine generator: Technology review and an experimental evaluation with hydrogen fuel

Free piston engine generators which utilize a free piston engine and a linear generator are under investigation by a number of research groups around the world. Free piston engines give power output in a more efficient way when compared to conventional crankshaft engines, because the former do not have a crank mechanism which brings about additional mechanical loss. However, for the reliable and stable operation of the free piston engine generators, it is required to have a viable control system to address the uncertainty of piston motion. In this paper, most of the successful free piston engine generator developments were reviewed and a recent experimental result on a prototype free piston system was also presented with regard to engine performance with different mixture preparation strategies.     

Examination of nanoparticles from gasoline direct-injection (GDI) engines using transmission electron microscopy (TEM)

Gasoline direct-injection (GDI) engines have been reported to produce significantly more particulate matter (PM) mass and particulate number (PN) emissions than do port-fuel-injection (PFI) spark ignition engines. Because smallsized particles are of great concern in terms of their regulation, transmission electron microscopy (TEM) was used to evaluate the sizes of primary and aggregate particles that were thermophoretically collected from three different GDI engines under various engine operating conditions. A low load and retarded fuel injection generally reduced the particle size. Consequently, when the fuel injection timing was delayed at low loads, primary and aggregate particles became extremely small. In particular, a number of nanoparticles were sub-23-nm particles. Careful high-resolution TEM (HRTEM) analyses provided the first evidence that these nanoparticles are solid carbon particles with clear fringe patterns and young soot (and/or highly condensed semi-volatiles) with amorphous carbon patterns. Therefore, this result suggests that the current cut-off size at 23 nm for PN regulation in Euro 6 must be further reduced to include sub-23-nm carbon nanoparticles.     

Network performance analysis and manuever model for overtaking assistant service using wave

We present network requirements for an overtaking assistant service using wireless access in vehicular environment (WAVE). Currently, DNPW has been proposed as a representative overtaking assistant service with vehicle-tovehicle (V2V) communication. In order to analyze its network performance, we construct a maneuver model for an overtaking system. According to this model, we configured a scenario for network simulation based on the 802.11p WAVE standard. The results confirm that a radio range for overtaking needs only a single hop without routing methods. Moreover, we propose an additional safe distance for the communication delay generated by an increase in the numbers of neighboring vehicles. And for high priority activity of safety services, we present a proper access category (AC) of enhanced distributed channel access (EDCA). These analysis results should be tested considered in real safety service systems that use V2V communication.     

Learning daily activity patterns with probabilistic grammars

Daily activity pattern is the reflection and abstraction of actual individual activity participation on daily basis. It carries information on activity type, frequency and sequence. Preference of daily activity patterns varies among population, and thus can be interpreted as personal life styles. This paper advances studies on human daily activity patterns by providing new perspective and methodology in the modeling and learning of daily activity patterns using probabilistic context-free grammars. In this paper, similarities between daily activity pattern—which is defined as activity sequence—and language are explored. We developed context-free grammars to parse and generate daily activity patterns. To replicate people’s heterogeneity in selecting daily activity patterns, we introduced probabilistic context-free grammars and proposed several formulations to estimate the probability of a context-free grammar with daily activity patterns observed in household travel survey. We conducted experiments on the proposed formulations, finding that under proper context-free grammar and problem formulation, the estimated probabilistic context-free grammar is able to reproduce the observed pattern distribution in household travel survey with satisfactory precision. Practically, the proposed methodology sheds light on the issue of generating stochastic and accessibility-dependent choice sets for daily activity pattern models in certain activity-based modeling frameworks.     

Burnout in seafarers: its antecedents and effects on incidents at sea

Seafarer health and well-being has long been a concern in the shipping industry because of the unique characteristics of working at sea. This paper aims to identify the role of burnout in seafarer health and well-being and its effect on safety. In particular, we differentiated seafarer burnout into personal and work-related burnout to reflect the ambiguous distinction between rest and work in seafarers’ job environment. We also investigate the effectiveness of emotion regulation for seafarers to reduce burnout. This study proposes a conceptual framework to identify the causal relationship between occupational stress, sleepiness, emotion regulation, burnout, and incidents at sea. To verify the proposed framework, scales were adapted from established scales in the literature; a cross-sectional survey was also conducted to collect empirical data for analysis with path and simultaneous equation models. The analysis results revealed that personal and work-related burnout in seafarers are mutually affected; however, only work-related burnout exerts a direct effect on incidents. Reappraisal is an effective emotion regulation strategy in seafarers to reduce personal burnout, but not work-related burnout. Occupational stress and sleepiness exert positive effects on both personal and work-related burnout; yet, their effect on incidents is mediated by work-related burnout.     

Decision to lease outer continental Shelf Lands

Abstract

The process by which a decision is made in many instances limits and shapes the form of that decision. The institutions involved, the timing of their involvement, and the ultimate goal of the process itself are integral factors in determining the substance of a decision. It is the thesis of this paper that the decision to lease areas of our Outer Continental Shelf is determined more by the process of making that decision than by any other factor. This thesis is explored from an historical and an analytical perspective and the conclusion drawn is that the present leasing process limits the scope of alternative decisions. For although the Department of the Interior has demonstrated an increased sensitivity to a broad spectrum of environmental and economic issues in the micro‐decision process, such as specific tract nominations and oil spill prevention, they have remained reluctant to apply this sensitivity to the macro‐decision process, that process which determines the optimal utilization of our ocean and land resources.     

A system dynamics approach to land use / transportation system performance modeling Part II: Application

This paper presents a system dynamics approach to simultaneous land use/transportation system performance modeling. A model is designed based on the causality functions and feedback loop structure between a large number of physical, socioeconomic, and policy variables. The model system consists of 7 sub‐models: population, migration of population, household, job growth‐employment‐land availability, housing development, travel demand, and traffic congestion level. The model is formulated in DYNAMO simulation language, and tested on a data set from Montgomery County, MD. In Part I: Methodology, the overall approach and the structure of the model system is discussed and the causal‐loop diagrams and major equations are presented. In Part II: Application, the model is calibrated and tested with data from Montgomery County, MD. Least square method and overall system behavior are used to estimate the model parameters. The model is fitted with the 1970–80 data and validated with the 1980–1990 data. Robustness and sensitivities with respect to input parameters such as birth rate or regional economy growth are analyzed. The model performance as a policy analysis tool is also examined by predicting the year by year impacts of highway capacity expansion on land use and transportation system performance. While this is a first attempt in using dynamic system simulation modeling in simultaneous treatment of land use and transportation system interactions, and model development and application are limited to some extent due to data availability, the results clearly indicate that the proposed method is a promising approach in dealing with complex urban land use/transportation modeling     

Comparative measurements on the flow structure of a marine propeller wake between an open free surface and closed surface flows

In order to investigate the effects of a free surface on the wake behind a rotating propeller, experiments were carried out in a circulating water channel for two cases: one with an open free surface and one with a closed free surface covered by a rigid plate. Four hundred instantaneous velocity fields were measured using a two-frame particle image velocimetry (PIV) technique at four different blade phases. These were ensemble-averaged to investigate the time-averaged flow structure in the near-wake region. For a surface ship, the flow behind the propeller is influenced by the hull wake and the free surface. The phase-averaged mean velocity fields show the potential wake and the viscous wake formed by the boundary layers developed on the blade surfaces. The interaction between the bilge vortices and the incoming flow along the ship’s hull deforms the wake structure. Tip vortices are generated periodically, and the slipstream contraction occurs in the near-wake region. The free surface was found to affect the axial velocity component and vortex structure behind the propeller. As the flow goes downstream, the tip and trailing vortices dissipate due to turbulent diffusion and active mixing with adjacent vortices.     

Competition for transhipment containers by major ports in Southeast Asia: slot capacity analysis

Container ports in Southeast Asia accounted for an estimated 30.0% of the world's transhipment traffic in 2004. The share of the region's transhipment trade was forecasted to increase to 32.5% in 2015. The potential offered by this large and expanding market encouraged major container terminal operators located in Port Klang, Singapore and Tanjung Pelepas to compete intensively for this business by attracting major container shipping lines that operated along key east-west sailing routes to hub at their terminals.

This paper analyses the annual slot capacity connected to the three selected ports that was deployed by all the container shipping lines in 1999-2004. The data are computed and categorized based on shipping trade routes. The study aims to shed light on port competition in Southeast Asia for transhipment containers by an in-depth and quantitative analysis.

The analysis finds that competition from Port Klang and Tanjung Pelepas had a negative impact on Singapore's transhipment performance. Although Singapore continued to enjoy a dominant position as the premier transhipment hub in the region in terms of market share by both transhipment throughput and annualized slot capacity, the evidence suggested that its hold on the market appeared to be slipping, albeit gradually. Overall, Tanjung Pelepas is expected to pose the strongest challenge to Singapore's transhipment hub ambitions. Managerial implications for the ports are drawn.