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Fleet Size Control in First-Mile Ride-Sharing Problems

Ye, Jinwen Pantuso, Giovanni David Pisinger

The first-mile problem, which refers to the design of transport services that connect passengers to their nearby transit station, has attracted growing attention in recent years. In this paper we consider first-mile ride-sharing services and study the problem of optimally determining the fleet size and assigning vehicles to transport requests. We formulate the problem as a mixed-integer program and present a number of numerical experiments based on a small-scale system to analyse different configurations of the service, namely with and without fleet control (FC). Result shows that a configuration with FC is superior in terms of profits while service rates can be higher in a configuration without FC, depending on the revenue-sharing mechanism.

Springer / 2022
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Numerical Simulation of Combustion under Marine Engine Like Conditions

Arash Nemati

This thesis presents the numerical study of combustion under marine engine like condi- tions. The thesis is divided into two main parts. In the first part, combustion is studied in a large two-stroke marine engine with conventional diesel fuel. In the second part, two different dual-fuel combustion modes of diesel-methane i.e. non-premixed combus- tion and premixed combustion are studied. All numerical models are validated with the experimental data.
First, in a simplified geometry of the marine engine, conjugate heat transfer (CHT) calculations are applied to simultaneously solve the in-cylinder gas phase dynamics and the temperature field within the liner of the engine. The effects of different initial tem- peratures across the liner and the effects of the amount of water vapor in the air on the sulfuric acid formation and condensation in a large two-stroke marine engine are studied. An initial temperature is calculated based on heat transfer modeling and it is observed that the sulfuric acid vapor formation is more sensitive to the variation of the water vapor amount than the sulfuric acid condensation. In the next step, the effects of the turbulence modelling on the simulation of the full cycle of the engine including scavenging process, combustion, and emission formation is studied in a real geometry of a large two-stroke marine research engine. The Unsteady Reynolds Averaged Navier- Stokes (URANS) and Large Eddy Simulation (LES) turbulence models are utilized for modeling of in-cylinder turbulent flow. The accuracy of the tangential velocity and swirl flow in the top of the cylinder where the fuel is injected is crucial to predict the air-fuel mixing correctly. It is found that URANS predicts a solid body rotation for the tangential velocity in this region. However, LES predicts a tangential velocity that is uniformly distributed in the radial direction that is consistent with experimental results. Furthermore, during the scavenging process, LES is able to predict the Burgers vortex upstream of the cylinder near the scavenging ports. Also, LES predicts a higher angu- lar momentum inside the cylinder in comparison with URANS. During the combustion process, the LES model shows a moderately better performance in capturing the experi- mental pressure and heat release rate profiles than URANS. However, the predicted gas temperature at the liner wall is approximately 45 % higher for URANS than LES during the expansion stroke, which is attributed to a higher predicted turbulent viscosity in the URANS case. A higher temperature of gas beside the liner wall may decrease the sulfuric acid formation and increase the heat transfer. The higher predicted swirl by LES than that in URANS leads to an earlier and stronger interaction between the flame and the spray, decreasing the oxidation of the emissions. The second cycle LES simula- tion shows that the solutions after the scavenging process are in-sensitive to the initial conditions and the main governing parameters are boundary conditions and injection characteristics.
Next, two different dual-fuel combustion modes of non-premixed combustion and premixed combustion are studied. The non-premixed combustion is simulated and val- idated with the experimental data of a large two-stroke marine research engine under low and high engine loads. Based on the results, further methane jets penetration in the low load case leads to better air-fuel mixing and a higher combustion intensity than that in the high load. Effects of the pilot diesel fuel injection timing on combustion and emission formation and the governing mechanisms are also investigated in detail. Results indicate that the intense combustion of the accumulated methane expands the methane flame towards the piston when the pilot injection timing is retarded. The NO formation is lower in the high load case due to the lower combustion intensity. Also, retarding the pilot injection timing decreases the NO formation. Furthermore, the effect of the direction of pilot diesel injection is investigated which shows a significant effect on the methane start of combustion and intensity as well as flame propagation direction which leads to different heat transfer trends from the combustion chamber walls.
Premixed combustion is analysed in a constant volume combustion chamber (CVCC) and validated with experimental data. Results show that by simulation of methane-air mixing, the numerical model is able to capture the ignition delay time (IDT) within a maximum relative difference of 7 % to the measurements. A higher relative difference of 38% is obtained when methane gas injection is omitted and the methane-air and temperature are assumed homogeneous. Therefore, it is concluded that the simulation of methane-air mixing process is crucial in this type of combustion due to the presence of inhomogeneities in both methane fuel and temperature distribution after mixing. Creating the idealized inhomogeneities for separately investigation of methane and tem- perature inhomogeneities shows that the inhomogeneity in the temperature has a more profound influence on the IDT than the inhomogeneity in the methane distribution. Furthermore, the effects of the number of pilot fuel nozzle holes on the auto-ignition are studied. The auto-ignition process in two cases with 4 nozzle holes is investigated and compared with the base case with 8 nozzle holes. Considering the same amount of pilot fuel, the injection rate is assumed to be double in one of the cases, while in the other case, the injection duration is doubled. Results show that a reduction of the nozzle hole numbers can improve the pilot diesel ignition in the case with 4 nozzle holes and double injection duration compared to the base case with 8 nozzle holes. However, combustion in the case with 4 nozzle holes and a double injection rate is incomplete due to flame impingement on the walls.

Technical University of Denmark / 2022
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Designing for Emergent Safety in Engineering Systems

John Robert Taylor, Igor Kozin*

This chapter is about emergent safety hazards in engineering systems. These
hazards are those that emerge from a system without arising from any part of the
system alone, but because of interactions between parts. We distinguish two
approaches to analysing engineering systems: one is to view them as sociotechnical, and the other is to consider them as cyber-physical systems. We
illustrate a great deal of emergent hazardous behaviours and phenomena due to
unknown accident physics, malign actions, chemistry, and biology and due to
deficiencies in managements and organisations. The method that follows the
socio-technical view consists in the representation of a system by sequential
functionally unrelated processes that can in reality influence the performance of each other via sneak paths. The method that follows the cyber-physical systems
view focuses on the analysis of control loops (feedback, feedforward, positive,
and negative) and, especially, interrelated loops. The chapter explores also the
realm of security threats due to malign actions that can trigger safety-threatening events. And finally it gives general guidance for avoiding and eliminating safety hazards when designing engineering systems.

Handbook of Engineering Systems Design / 2022
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Competences related to ship design

George Panagakos

The safety of people and cargo onboard is a key functionality of a commercial ship.

The health and well-being of seafarers and passengers is protected through an extensive set of technical specifications, standards and norms that govern the design and commissioning of all vessels.

They differ by ship type and size, while the specific services to be provided and the specific geographic regions to be served also play an important role in this respect.

The requirements are of national and international character and vary also with the classification society that will commission the ship. Thus in a broader sense, all competences related to ship design are related one way or another to maritime health.

Much of the design of ships is overseen by a naval architect or marine engineer. It is rare to have the involvement of a medical professional except in the cruise industry.

Purpose and tasks
To ensure that the design of a ship includes the requirements to protect the health and well being of seafarers. More specifically, to identify areas of intervention that go beyond the usual engineering curricula where, nonetheless, the safety dimension is embedded through international standardization.

Textbook of Maritime Health / 2022
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Capitalism and the Sea: The Maritime Factor in the Making of the Modern World

Federico Jensen

What is the role of the sea in globalized capitalism? In their new book Capitalism and the Sea: The Maritime Factor in the Making of the Modern World, Liam Campling and Alejandro Colás explore this question through a historical and geographical lens. In this book, the authors track the larger history of maritime commerce and pursue new understandings of the role of the sea in the global economy. In doing so, they illuminate the understudied maritime spaces, systems, and flows that underpin the global economy and create the foundations of global material circulation.

The AAG Review of Books / 2022
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Societal impact of climate change and new Arctic shipping routes on shipping in Greenland

Jakobsen, Uffe

According to the narratives transmitted through media and political discourse, climate change reduces the ice coverage in the Arctic and enhances shipping and other forms of maritime activities. Especially, expectations of an increasing level of transit shipping between Asian, especially Chinese, ports and ports in Europe and North America is dominant. Evidence, however, tells that the numbers of transit shipping through the Arctic Ocean are very limited, and dominated by European shipping companies. For Greenland, political expectations have also been high, since Greenland has been seen as "strategically" situated in relation to new shipping routes in the Arctic, But, again, the actual development has been moderate and not related to international transits but conditions in Greenland itself.

Institut d'Études de Géopolitique Appliquée / 2021
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Shuo Ma: Economics of Maritime Business (1st Edition)

Liping Jiang

The year 2020 was largely defined by the unprecedented disruption caused by Covid-19 pandemic, which could have lasting adverse effects on every corners of human life. In the meanwhile, the pandemic has fundamentally changed the way of how industrial enterprises operate, empowering businesses to accelerate their digital transformation and reshaping their business models. Throughout the pandemic, shipping has been essential in terms of guaranteeing the global supply chain linkage and economic interdependency. As the world moves toward recovery, the maritime industry is also stepping up to the challenge and responds to these extraordinary disruptions. Against this background, a thorough, broader, and new review of maritime businesses will be particularly important.

WMU Journal of Maritime Affairs / 2021
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Numerical Study of Ship Performance in Calm Water and in Waves

Henrik Mikkelsen

Traditionally, most ship hulls are optimized for ideal conditions, where the ships are sailing in calm water with full speed in full load. In the last decade, some ships have been designed for a range of draughts and speeds in calm water. However, there is still a large gap between the ideal conditions the ships are designed for and conditions (waves, wind, currents, hull roughness ets.) the ships will operate in. The target for the thesis is to develop accurate numerical models that can help ship designers narrow a part of this gap.
The main body of this thesis is three papers. The first papers compares the speed/power performance of full-scale CFD simulations, towing tank predictions, and high quality speed trial measurements from six sister vessels. Much research have been conducted comparing model- scale CFD with towing tank results. However, very few studies have compared full-scale CFD with speed trial measurements. The study includes both a ro-ro vessel and a general cargo vessel. The present study finds that including the hull and propeller roughness directly into the CFD simulations by modifying the wall-functions provides more accurate results than the traditional approach of estimating the effect of roughness using an empirical formula.
Today, most ships are designed for sailing in calm water. However, very few ships sail entirely in calm water. Before numerical simulations can be used to predict added resistance in waves and seakeeping responses, a systematic verification and validation is required to ensure the accuracy. The second paper presents such a systematic verification and validation for the KCS container ship in oblique waves. Five wave headings and six wavelengths are studied. The estimated spatial and temporal discretization errors are found by an extensive verification study to be less than 5 %. Results from the verified CFD model are compared with existing potential flow and CFD results from the literature, as well as up to three experimental data sets. The comparison shows that the present CFD results in general show significantly better agreement with the experiments than previously published CFD results.
This CFD set-up is used in the third paper to study how sailing in oblique regular waves influences the nominal wake field of the KCS ship. Five different headings are studied and the waves have a steepness of 1/60 and a wave length equal to the ship length. The present study finds that the studied incident waves make the nominal wake field highly transient. Especially the transient bilge vortex and shadow from the skeg have a significant influence on the nominal wake field. The results show that the nominal wake fraction fluctuates up to 39 % of the mean nominal wake fraction for the studied waves. The mean nominal wake fraction is higher than in calm water for all headings besides head sea waves. It is found that the stern quartering sea waves has the maximum mean nominal wake fraction, with a 16 % higher mean nominal wake fraction than in calm water. Finally the study finds that the modified advance angle on the r/R = 0.7 circle in the propeller plane varies 3.5 degrees more in stern quartering than in calm water. This increases the risk of cavitation leading to potential vibrations and loss of propulsive efficiency.
The three papers show that CFD simulations can deliver highly accuracy results, when the CFD simulations are set-up very carefully and systematic verification and validation are conducted. The results from the three papers shows that numerical simulations have a massive potential as useful tools when designing ships for the conditions, the ship will operate in.

Technical University of Denmark / 2021
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Maritime Transport and the Environment: Energy Transport by Sea

Stanescu, Catalin Gabriel; Martinez Romera, Beatriz
Book chapter in in MM Roggenkamp, KJ de Graaf & RC Fleming (eds), Energy Law, Climate Change and the Environment / 2021
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Pragmatic Spaces and the Maritime Security Agenda

Bueger, Christian

The oceans are increasingly understood as a security space. Does the new maritime security agenda lead to new spatial configurations? This chapter introduces the concept of ‘pragmatic spaces’ to explore spatial configurations produced in responses to maritime security. Four exemplary spaces are discussed: how counter-piracy led to the development of high risk areas, how maritime security capacity building produced new regions constructed through codes of conduct, how the identification of smuggling routes established new forms of international partnerships, and how maritime domain awareness systems advance new transnational spaces of surveillance. These new spatial configurations were introduced to manage maritime security issues and enable transnational forms of governance.

Book chapter in in J Anderson, A Davies, K Peters & P Steinberg (eds), The Handbook of Ocean Space. Routledge. / 2021
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