Baroclinic eddy formation in a Rhine plume model

A three-dimensional finite difference tidal model, including advective and diffusive transport of salinity, is used in the two-layer model for simulation of Rhine water outflow. Layer depths are adjusted in a way that no advective transports between upper and lower layer take place in case of sufficiently stable stratification.Model results show frontal eddy development related to (limited) growing internal waves in case of weak northeasterly to southeasterly winds. It is shown that baroclinically unstable conditions occur, related to vertical velocity shear, resulting in frontal meanders with wave lengths between 18 and 30 km. Satellite images of sea surface temperature show a comparable behaviour of the temperature front, which is strongly correlated with the salinity front of the Rhine plume.     

Do the selected Trans European transport investments pass the cost benefit test?

This paper assesses the economic justification for the selection of priority projects defined under the auspices of the Trans-European transport network. Three different transport models are used to analyse the costs and benefits associated with the current list of 30 priority projects. Most of these projects fail the cost-benefit test and few of the economically justifiable projects would need European subsidies to ensure their viability. Two remedies are proposed to minimise the inefficiencies surrounding project selection. The first remedy would oblige each member state or group of states to perform a cost-benefit analysis, followed by peer review and ensure that the results were published publicly prior to the ranking of federally funded priority projects. The second remedy would require federal funding to be made available only for projects with important spillovers to other countries in order to avoid pork barrel political behaviour.     

Pruning and ranking the Pareto optimal set,application for the dynamic multi‐objective network design problem

Solving the multi‐objective network design problem (MONDP) resorts to a Pareto optimal set. This set can provide additional information like trade‐offs between objectives for the decision making process, which is not available if the compensation principle would be chosen in advance. However, the Pareto optimal set of solutions can become large, especially if the objectives are mainly opposed. As a consequence, the Pareto optimal set may become difficult to analyze and to comprehend. In this case, pruning and ranking becomes attractive to reduce the Pareto optimal set and to rank the solutions to assist the decision maker. Because the method used, may influence the eventual decisions taken, it is important to choose a method that corresponds best with the underlying decision process and is in accordance with the qualities of the data used. We provided a review of some methods to prune and rank the Pareto optimal set to illustrate the advantages and disadvantages of these methods. The methods are applied using the outcome of solving the dynamic MONDP in which minimizing externalities of traffic are the objectives, and dynamic traffic management measures are the decision variables. For this, we solved the dynamic MONDP for a realistic network of the city Almelo in the Netherlands using the non‐dominated sorting genetic algorithm II. For ranking, we propose to use a fuzzy outranking method that can take uncertainties regarding the data quality and the perception of decision makers into account; and for pruning, a method that explicitly reckons with significant trade‐offs has been identified as the more suitable method to assist the decision making process. Copyright © 2012 John Wiley & Sons, Ltd.     

在不同水质地区实地进行海洋生物膜对SS UNS S32760不锈钢腐蚀行为研究（英文）

In the presence of biofilms, stainless steels(SS) exhibits an increase in corrosion potential, called ennoblement. In the present study, the corrosion potential(Ecorr) behavior of the duplex SS UNS S32760 was recorded simultaneously with the in situ marine biofilm formation in two areas at Arraial do Cabo,Southeastern Brazil. The biofilm at Forno Harbor(an anthropogenically disturbed area) was characterized by higher relative abundances of Bacteria at day 2, followed by diatoms(especially Navicula sp.) on day 10 and dinoflagellates on day 18,whereas no clear trend was recorded at Cabo Frio Island(an undisturbed area). The ennoblement of Ecorr values was site-dependent. In a complementary laboratory assay, biofilms were removed and the Ecorr values registered in sterile conditions for the subsequent 10 days and corroborated in situ results. Understanding biofilms and SS interactions has important implications for materials science and engineering decisions as well as helping to fill in important gaps in this knowledge.     

Measuring hierarchical differentiation: connectivity and dominance in the European urban network

Abstract

This paper presents an examination of the empirical merits of a set of spatial interaction indices for measuring hierarchical differentiation (i.e. dominance and connectivity) in a spatial network. To allow for the comparison of the degree of hierarchical differentiation in networks with different numbers of nodes/links, we propose to normalize the ratio between the real measures and the corresponding values for a rank size distribution in order to obtain readily interpretable measures of hierarchical differentiation. When applied to data on air passenger flows within Europe, the normalized indices, interpreted together, appear to give a good idea of the tendency toward hierarchical differentiation. The potential usefulness of this analytical framework is discussed in the context of studies on (transnational) inter-city relations and empirical assessments of changes in the spatial configuration of airline networks.     

Operational route choice methodologies for practical applications

This paper focuses on the application of tractable route choice models and presents a set of methods for deriving relevant disaggregate and aggregate route choice indicators, namely link and route flows. Tractability is achieved at the disaggregate level by the recursive logit model and at the aggregate level by the mental representation item (\(\mathrm {MRI}\)) approach. These two approaches are analyzed here, and extensions of the \({\mathrm {MRI}}\) approach are presented. The analysis elaborates on the features of each model and allows to draw insights into the use of a specific model, depending on the needs of the application and the data availability. The performance of the two models is tested on real data. The results demonstrate the validity of the \({\mathrm {MRI}}\) model that is intended for aggregate analysis.

     

Governance for Sustainability: Insights from Marine Resource Use in a Tropical Setting in the Western Indian Ocean

The last decade has seen a shift in the Natural Resource Management discourse, a shift from management to governance. Governance is held forward as a prime solution to problems associated with the sustainability of natural resources, including fisheries and other marine resources. Several countries in the Western Indian Ocean are framing governance solutions as a response to coastal/marine resource depletion and environmental degradation, but the challenges are huge and success stories remain few. This study provides an analysis of the governance situation in Chwaka Bay, Zanzibar, Tanzania. It presents the governance actors and how governance is expressed in terms of hierarchy (state), heterarchy (self-organized networks of resource users), and anarchy (market). The analysis illustrates the extreme difficulties of using governance approaches to steer human behavior to solve environmental problems and achieve sustainability. The study also provides some insights when considering the use of governance as a tool for the “designing” and/or “steering” social–ecological systems in subsistence contexts with weak formal institutions. These include the consideration of governance as an intrinsic part of complex societal processes, the idealization of governance as a template for redressing management failure and broader issues such as the importance of meta-governance.     

Traffic accident risk perception among drivers: a latent variable approach

ABSTRACT

Governments require decision tools to deal with road traffic accidents, a pandemic resulting in millions of deaths around the world. Evidence shows that human factors are one of the major causes of road accidents, and there is much interest in identifying variables that may have an impact on drivers’ perception of risk. To this aim, we design a stated choice experiment with eight hypothetical driving scenarios considering attributes that have been strongly associated with increased accident risks: (i) driving speed, (ii) driving the wrong way in a one-way street, (iii) overtaking on a bend, and (iv) driving under the influence of alcohol or drugs. Data from a sample of survey respondents are used to estimate a hybrid discrete choice model incorporating two latent variables, Driver Concentration and Safe Driving. Our results may contribute to the design of public policies geared to prevent accidents by encouraging safer driving behaviour.     

Addressing endogeneity in strategic urban mode choice models

Transportation - Endogeneity is a potential anomaly in econometric models, which may cause inconsistent parameter estimates. Transport models are prone to this problem and applications that...     

Multi-fidelity optimization of a high-speed foil-assisted semi-planing catamaran for low wake

The wakes of high-speed passenger-only ferries that operated through Rich Passage, on the Seattle-Bremerton ferry route, caused beach erosion and damage to habitat. A task was initiated to design a low-wake high-speed vessel using multi-fidelity CFD based design optimization by using low-fidelity potential flow solvers for initial global design optimization and by using URANS solvers for high-fidelity tuning of the optimized design. This simulation based design process involved a close collaboration between ship designers, and hydrodynamics and CFD specialists, whose collective expertise guided the evolution of the design based on both hydrodynamic and structural aspects. The initial hull shape optimization using potential flow code was carried out by blending three different initial concepts provided by the designers. Subsequently, URANS was used to evaluate the potential flow optimized hull and to further optimize the hull configuration parameters, namely, the centre-of-gravity, demihull spacing, foil location, foil angle and slenderness ratio at different displacement conditions. The URANS based configuration optimization also took into account the far field wakes’ energy spectrum with an objective of reducing the energetic, low frequency far field wakes which are associated with beach flattening on the mixed sand and gravel beaches. Calculation of the far field wake using URANS would require an unfeasibly large domain size; therefore, a Havelock code with a source distribution matching the URANS calculated near field wave elevation was used to propagate the wakes into the far field. The end result of the optimization was a design with significantly reduced far field wake, which is currently being built for experimental testing.