小型帆船自适应自动舵

帆船由于其结构的特殊使其动态特性呈严重的非线性，航向很难控制。首先针对一种小型竞赛用的12m长美洲杯赛帆船，从其结构出发建立数学模型，并对该模型进行了开环仿真试验以验证其真实程度。然后利用MATLAB辨识工具在不同的外部条件下得到各具特色的不同模型，由此确认模型参数的巨大变化难以用一个近似于当前运行模式下的线性化模型设计控制器，因而设计了一个采用自适应LQR的自动舵以控制帆船尖不同外部条件下都能保持航向。最后在该模型上作了仿真，取得了较好的效果。     

Revisiting port pricing; a proposal for seven port pricing principles

A review of seven large landlord port authorities around the world reveals a notable diversity of pricing structures. While port authorities increasingly act as commercial undertakings, port pricing often seems to be not driven by commercial considerations. In this paper, we argue that ports can be regarded as “business ecosystems” with multiple users. This provides a valuable perspective on pricing and raises the question of whether ports can be regarded as two-sided markets. We argue this is not the case. The business ecosystem perspective provides a basis for deducing seven pricing principles for port authorities that are detailed in the paper and illustrated with cases these principles. These pricing principles are broadly follow a direct user pays approach; capture value from “non-core” tenants; price aggressively for activities with a high strategic value; differentiate pricing based on price elasticity and connectivity improvements; maximize revenue from long-term lease agreements, price port dues competitively; critically consider differentiation of charges based on environmental performance; and finally use incentives to align interests of terminal operators and shipping lines. We conclude that the ecosystem perspective is central to the understanding of pricing decisions of port authorities and that various pricing issues deserve more attention.     

Response of coastal zone management programs to sea level rise in the United States

Abstract

State coastal zone management programs are responding to the potential impacts of accelerated sea level rise through a wide range of activities and policies. This article provides a brief overview of the Coastal Zone Management Act and other federal laws that provide the basis for coastal state regulatory activities. It surveys the level of response to sea level rise by state coastal management programs in 24 marines coastal states, from formal recognition to implementation of policies addressing the issue. Individual state CZMP responses and policies that have been implemented or proposed are categorized. The adaptation of sea level rise to ongoing institutional objectives is discussed and policy constraints and trends are summarized.     

Mass and heat transports in the NE Barents Sea: Observations and models

The strait between Novaya Zemlya and Frans Josef Land, here called the Barents Sea Exit (BSX) is investigated using data obtained from a current-meter array deployed in 1991–1992, and two numerical models (ROMS and NAME). Combining the observations and models the net volume flux towards the Arctic Ocean was estimated to 2.0 ± 0.6 Sv (1 Sv = 10⁶ m³s^? 1). The observations indicate that about half of this transport consists of dense, Cold Bottom Water, which may penetrate to great depths and contribute to the thermohaline circulation. Both models give quite similar net transport, seasonal variations and spatial current structures, and the discrepancies from the observations were related to the coarse representation of the bottom topography in the models. Also the models indicate that actual deployment did not capture the main in- and outflows through the BSX. A snapshot of the hydrographic structure (CTD section) indicates that both models are good at reproducing the salinity. Nevertheless, they react differently to atmospheric cooling, although the same meteorological forcing was applied. This may be due to the different parameterisation of sea ice and that tides were included in only one of the models (ROMS). Proxies for the heat transport are found to be small at the BSX, and it can not be ruled out that the Barents Sea is a heat sink rather than a heat source for the Arctic Ocean.     

Large-scale network partitioning for decentralized traffic management and other transportation applications

For numerous large-scale engineering and science problems, domain decomposition (DD) has generally been accepted by research communities as among the most attractive methods to obtain solutions efficiently. As a prerequisite for the DD solution process, a large domain must be partitioned into several smaller subdomains, with the key to success (of any DD partitioning algorithm) being the number of system boundary nodes. The lower this number, the more efficiently the subdomains can be processed. Although various transportation researchers have hinted at the use of DD, for example, in intelligent transportation systems-enabled decentralized traffic management, it is assumed that the partition is given. This article presents a simple, efficient, and effective algorithm to decompose a transportation network into a predefined number of interconnected subdomains such that the number of system boundary nodes is small (first priority) and the number of nodes in each subdomain is of similar size (second priority). To assess the effectiveness (in terms of minimizing the number of system boundary nodes) of the proposed Shortest Distance Decomposition Algorithm, it is compared with METIS version 5.1.0, currently among the most widely used graph partitioning algorithms worldwide. Using large-scale, real-world transportation test networks, it was found that the Shortest Distance Decomposition Algorithm is better than METIS in 21 of the 27 examples tested; on average, it provided (approximately) 42.0% of the system boundary nodes (as compared to METIS results) in our large-scale examples.     

A review of port devolution and governance models with compound eyes approach

Port devolution and port governance are focal issues in port studies. This paper argues that the previous typology of port devolution and port governance, including port function matrix models, might have to be modified, in particular for Asian port cases, because they have not considered socio, economic, and political systems and historical aspects behind the port devolution continuum. This paper uses the “compound eyes” approach comprising of many similar, closely-packed facets called ommatidia, with a multiple angle view, to revisit and review previous port devolution and governance models. The paper aims to identify the limitations and rectify fallacies in previous port studies by conducting a critical review and taking a couple of Asian container port cases as examples. This paper contributes to the literature of port devolution and governance, illuminating crucial gaps that the previous studies have not addressed.     

Reducing CO<Subscript>2</Subscript> from cars in the European Union

The European Union (EU) recently adopted CO₂ emissions mandates for new passenger cars, requiring steady reductions to 95 gCO₂/km in 2021. We use a multi-sector computable general equilibrium (CGE) model, which includes a private transportation sector with an empirically-based parameterization of the relationship between income growth and demand for vehicle miles traveled. The model also includes representation of fleet turnover, and opportunities for fuel use and emissions abatement, including representation of electric vehicles. We analyze the impact of the mandates on oil demand, CO₂ emissions, and economic welfare, and compare the results to an emission trading scenario that achieves identical emissions reductions. We find that vehicle emission standards reduce CO₂ emissions from transportation by about 50 MtCO₂ and lower the oil expenditures by about €6 billion, but at a net added cost of €12 billion in 2020. Tightening CO₂ standards further after 2021 would cost the EU economy an additional €24–63 billion in 2025, compared with an emission trading system that achieves the same economy-wide CO₂ reduction. We offer a discussion of the design features for incorporating transport into the emission trading system.     

Highway alignment optimization through feasible gates

An efficient optimization approach, called feasible gate (FG), is developed to enhance the computation efficiency and solution quality of the previously developed highway alignment optimization (HAO) model. This approach seeks to realistically represent various user preferences and environmentally sensitive areas and consider them along with geometric design constraints in the optimization process. This is done by avoiding the generation of infeasible solutions that violate various constraints and thus focusing the search on the feasible solutions. The proposed method is simple, but improves significantly the model's computation time and solution quality. Such improvements are demonstrated with two test examples from a real road project.     

Evaluating the pedestrian realm: instrumental rationality,communicative rationality and phenomenology

Following the passage of ISTEA, increased attention to pedestrian planning has led to the development of pedestrian plans, particularly at the metropolitan and municipal levels. This has raised the issue of how cities and metropolitan areas evaluate the walkability of the pedestrian realm and identify improvement projects. Three approaches to evaluating the pedestrian realm are examined: instrumental rationality, communicative rationality, and phenomenology. Case studies demonstrating the application of these approaches to the development of pedestrian plans are examined in the Phoenix metropolitan area, Portland, Oregon, and Cambridge, Massachusetts.

Estimating bus run times for new limited-stop service using archived AVL and APC data

In recent years, several transit agencies have been trying to be more competitive with the automobile to attract choice riders. Transit agencies can only be competitive if they can provide services that are reliable, have a short access and egress time, and have run times that are comparable to automobiles. Several transit agencies try to be competitive through offering faster service, such as limited-stop (express) bus service. This study uses AVL and APC data, in addition to a disaggregate data obtained from a travel behavior survey, to select stops and estimate run times for a new limited-stop service that will run parallel to a heavily used bus route (67 Saint-Michel) in Montréal, Canada. Three different scenarios are developed based on theory and practice to select stops to be incorporated in the new limited service. The time savings for each scenario are then evaluated as a range and a fourth scenario is developed. A limited-stop service is recommended based on selecting stops serving both directions of the route, major activity points and stop spacing. This study shows that implementing a limited-stop service would yield substantial time savings for both, the new limited service and the existing regular service running in parallel.