Simulation optimization of the berth allocation in a container terminal with flexible vessel priority management

ABSTRACT

Solving the berth allocation problem (BAP) in ports is not trivial where the berth resources are limited and various sizes of vessels arrive with dramatically dissimilar loads. Especially in real scenarios, arriving vessels are accepted for a berth with the first come first served (FCFS) priority rule. This study proposes a decision support system coupled with a simulation optimization module based on the swarm-based Artificial Bee Colony optimization algorithm for solving the BAP. The proposed methodology was implemented for the Izmir port in Turkey. To investigate the influences of the vessel priorities on the BAP, four different experimental scenarios based on the single (SQM) and multiple queue models (MQM) were coupled with FCFS and proposed hybrid queue priority (HQP) rule. The results indicated that SQM scenarios were superior to MQM scenarios in a manner of minimizing the average vessel waiting times and the implementation of a dynamic berth allocation strategy for the MQM significantly decreases the vessel waiting times. Results of the SQM also imply that utilization of the HQP approach further minimizes the average vessel waiting times and increases the berth utilization and port throughput without yielding excessive waiting times for the larger vessels compared with the FCFS priority rule.     

Aircraft Landing Gear Dynamics: Simulation and Control

The landing gear is an inevitable system for the aircraft. It absorbs the energy of the landing impact and carries the aircraft weight at all ground operations, including take off, taxiing, and towing. Numerical simulation has become an invaluable tool for the assessment of landing gear dynamics as well as of aircraft/landing gear interaction. This paper gives an overview of the landing gear requirements and illustrates landing gear operational conditions, i.e., the shimmy problem, the dynamics at touch down and at ground roll. Furthermore, three software packages used in the simulation of aircraft ground dynamics are presented. A look at flight simulators and landing gear test facilities follows. Finally, the possible application of controlled landing gears is discussed.     

Ability of a “minimum” microbial food web model to reproduce response patterns observed in mesocosms manipulated with N and P, glucose, and Si

We compared an idealised mathematical model of the lower part of the pelagic food web to experimental data from a mesocosm experiment in which the supplies of mineral nutrients (nitrogen and phosphorous), bioavailable dissolved organic carbon (BDOC, as glucose), and silicate were manipulated. The central hypothesis of the experiment was that bacterial consumption of BDOC depends on whether the growth rate of heterotrophic bacteria is limited by organic-C or by mineral nutrients. In previous work, this hypothesis was examined qualitatively using a conceptual food web model. Here we explore the extent to which a “simplest possible” mathematical version of this conceptual model can reproduce the observed dynamics. The model combines algal–bacterial competition for mineral nutrients (phosphorous) and accounts for alternative limitation of bacterial and diatom growth rates by organic carbon and by silicate, respectively. Due to a slower succession in the diatom–copepod, compared to the flagellate–ciliate link, silicate availability increases the magnitude and extends the duration of phytoplankton blooms induced by mineral nutrient addition. As a result, Si interferes negatively with bacterial consumption of BDOC consumption by increasing and prolonging algal–bacterial competition for mineral nutrients. In order to reproduce the difference in primary production between Si and non-Si amended treatments, we had to assume a carbon overflow mechanism in diatom C-fixation. This model satisfactorily reproduced central features observed in the mesocosm experiment, including the dynamics of glucose consumption, algal, bacterial, and mesozooplankton biomass. While the parameter set chosen allows the model to reproduce the pattern seen in bacterial production, we were not able to find a single set of parameters that simultaneously reproduces both the level and the pattern observed for bacterial production. Profound changes in bacterial morphology and stoichiometry were reported in glucose-amended mesocosms. Our “simplest possible” model with one bacterial population with fixed stoichiometry cannot reproduce this, and we suggest that a more elaborate representation of the bacterial community is required for more accurate reproduction of bacterial production.     

Optimal toll locations and toll levels in congestion pricing schemes: a case study of Stockholm

As congestion pricing has moved from theoretical ideas in the literature to real-world implementation, the need for decision support when designing pricing schemes has become evident. This paper deals with the problem of finding optimal toll levels and locations in a road traffic network and presents a case study of Stockholm. The optimisation problem of finding optimal toll levels, given a predetermined cordon, and the problem of finding both optimal toll locations and levels are presented, and previously developed heuristics are used for solving these problems. For the Stockholm case study, the possible welfare gains of optimising toll levels in the current cordon and optimising both toll locations and their corresponding toll levels are evaluated. It is shown that by tuning the toll levels in the current congestion pricing cordon used in Stockholm, the welfare gain can be increased significantly, and furthermore improved by allowing a toll on a major bypass highway. It is also shown that, by optimising both toll locations and levels, a congestion pricing scheme with welfare gain close to what can be achieved by marginal social cost pricing can be designed with tolls being located on only a quarter of the tollable links.     

Improving operational safety during icebreaker operations

The study presented in this paper aims at investigating what safety measures that can be taken to improve the operational safety during icebreaker operations in the Baltic Sea. During icebreaker operations, the icebreaker and the assisted vessel operate in close proximity to each other, a distance which can be even smaller if weather and ice conditions are severe. This poses a severe threat to the operation, since the extremely short distance between the vessels leaves no room for error. The results, which are based on data collected through individual interviews and questionnaires, indicate several possible improvements. Firstly, on a regulatory level, the introduction of an ice navigation certificate for deck officers would set a minimal level of formal competency. Secondly, on a knowledge level, more ice navigation training and better language skills work in favour for the safety. Thirdly, on a technical level, having an electronic chart with target tracking capability increases the efficiency and safety of the passage through ice. In addition to these results, this study shows a need to further research the communication and language situation during icebreaker operations.     

Energy use in passenger transport in OECD countries: Changes since 1970

This paper analyzes some of the changes that took place in the structure of energy use for passenger travel in industrialized countries. Data is presented on energy use and travel activity for the four major modes of travel — automobile, bus, rail and air — for eight OECD countries: the United States, Japan, the United Kingdom, West Germany, France, Italy, Sweden, and Norway. We use the Laspeyres and Divisia indices to analyze the causes of the change in energy use between 1970 and 1987. The total change in energy use for travel is explained by changes in domestic passenger transport volumes, the mix of modes of travel, and the energy intensities of each mode. We have found two important effects that have a fundamental impact on energy use for travel since 1970. First, shifts among modes of transport towards more energy-intensive ones and large increases in volumes of travel (measured in passenger-kilometers) increased energy use for travel in many OECD countries, often more rapidly than the overall growth in GDP. Second, energy intensities, measured in mJ/passenger-kilometer, of passenger transport fell only in a few countries between 1970 and 1987. Even though individual automobiles have become more energy-efficient, greater size, power, and weight, worsening traffic conditions in Japan and Europe, and fewer people in cars restrained or even offset efficiency improvements. Particularly notable are the increases in intensities in Japan and Germany. The most important exception to this trend was the United States, but the intensities of land-based travel remain higher there than in most other countries. These findings lead to a pessimistic outlook for future energy use for travel. After all, if little or no energy was saved during the decades of high fuel prices, what can be expected in the 1990s?     

锰粉加工工人心血管功能的调查研究

对 ５５ 名锰粉加工工人和 ５６ 名对照工人的调查结果显示，工人工作地点 Ｍｎ Ｏ２ 浓度几何均值为 １９６ ｍ ｇ／ｍ ３ （锰尘 ０１７～２２．２４ ｍ ｇ／ｍ ３ ），样品超标率 ８８７％ 。接触组头晕头痛、睡眠障碍、容易疲劳和记忆不良的主诉率明显高于对照组（ Ｐ＜００５～００１）。接触组和对照组的心电图异常、高血压和低舒张压检出率未见显著性差异，其心率、 Ｐ Ｒ间期、 Ｑ Ｒ Ｓ波、收缩压和舒张压的均值比较也没有显著性差异。接触组心电图异常和低舒张压的 Ｏ Ｒ分别是 １．５６（９５％ 可信区间为 ０７０～３．５０）和 ２．０８（９５％ 可信区间为 ０１８～２３．５７）。     

The development of public attitudes towards the Stockholm congestion trial

A full-scale congestion charging trial was carried out in Stockholm the first months of 2006. Almost half of respondents in a county-wide survey stated that they changed their attitudes towards congestion charges during the trial. Most of them became more positive.An analysis of media shows that the attitudinal change in media towards the trial coincides with the attitudinal change of the public. There was no dramatic change in the proportion of articles expressing a negative view. Instead, the result indicates that the increase in positive views was driven by a shift from neutral to positive articles during the trial.In order to ascertain why the public attitudes swung, we have analysed the anticipated and perceived effects of the trial. Generally, the analysis seems to indicate that improved understanding of the type and magnitude of concrete effects was not a main driving force behind the attitudinal change. Instead, it seems that the public attitude changed because personal experience gave a new understanding of the implications of the charges for the personal well-being. This would imply that trials, generally, may be a more useful tool than information in the process of implementing ‘difficult’ policy measures, such as congestion charges.     

Self- and peer-assessments of ambulance drivers' driving performance

The aim of the present study was to develop and examine the quality of the Ambulance Driver Self-assessment Questionnaire (ADSQ) and the Ambulance Driver Peer-assessment Questionnaire (ADPQ) measuring aspects of, driving performance, driving style and driving competence. In addition the ADSQ measures self-reflection and safety-attitudes. The aim of the study was also to examine ambulance drivers' self- and peer-assessments as well as to examine the accuracy of self-assessments by comparing self-assessed and peer-assessed driving performance, driving style and competence. 76 ambulance drivers employed at two ambulance stations in northern Sweden completed ADSQ and ADPQ. Item analyses were conducted to examine the psychometric properties of the items, and based on the results some revisions were made to improve the questionnaires. The revised questionnaires were functioning rather well, although some subscale demonstrated low internal consistency. Subscale inter-correlations provided support for construct validity. Self- and peer-assessments indicated safe driving performance and good driver competence, which is positive from a traffic safety perspective. A comparison of mean self- and peer-assessment ratings, controlling for age, gender and driving experience showed no significant differences, except for the subscale overtaking. This indicates that ambulance drivers' self-assessments are realistic in most areas.     

Weather variability and travel behaviour – what we know and what we do not know

Given that severe weather conditions are becoming more frequent, it is important to understand the influence of weather on an individual’s daily activity-travel pattern. While some previously rare events are becoming more common, such as heavy rain, unpredicted snow, higher temperatures, it is still largely unknown how individuals will change and adapt their travel patterns in future climate conditions. Because of this concern, the number of research studies on weather and travel behaviour has increased in recent decades. Most of these empirical studies, however, have not used a cost–benefit analysis (CBA) framework, which serves as the the main tool for policy evaluation and project selection by stakeholders. This study summarises the existing findings regarding relationships between weather variability and travel behaviour, and critically assesses the methodological issues in these studies. Several further research directions are suggested to bridge the gap between empirical evidence and current practices in CBA.