Management of corals and coral ecosystems in the United States

Abstract

Corals and coral communities provide substantial societal benefits by virtue of their recreational and esthetic appeal, the habitat provided for commercially harvested fish and shellfish, the structural foundation provided for productive coastal ecosystems, and the market value of harvested coral specimens. Coral resources are subject to adverse effects from pollution, dredging, specimen collecting, anchor damage, commercial fishing, overharvesting, and activities related to offshore petroleum development. Management programs which protect coral resources in the United States comprise a patchwork of separate federal and state programs. They attempt to adapt broad regulatory authorities for parks, fisheries, offshore mineral resources, and other subjects for the purpose of coral conservation. These programs embody species‐specific, area‐specific, and generic approaches to coral management. This paper traces the evolution of U.S. coral management programs and comments on their respective strengths and weaknesses. Alternative approaches for strengthening management systems could include new coordinating committees, legislation, memoranda of agreement between involved agencies, and others.     

On the degradation of performance for traffic networks with oblivious users

We consider the problem of characterizing user equilibria and optimal solutions for routing in a given network. We extend the known models by considering users oblivious to congestion in the following sense: While in the typical user equilibrium setting the users follow a strategy that minimizes their individual cost by taking into account the (dynamic) congestion due to the current routing pattern, an oblivious user ignores congestion altogether; instead, he or she decides his routing on the basis of cheapest routes on a network without any flow whatsoever. These cheapest routes can be, for example, the shortest paths in the network without any flow. This model tries to capture the fact that a certain percentage of travelers base their route simply on the distances they observe on a map, without thinking (or knowing, or caring) about the delays experienced on this route due to their fellow travelers. In this work we study the effect of such users using as the measure of network performance its price of anarchy, i.e., the ratio of the total latency experienced by the users (oblivious or not) at equilibrium over the social optimum.     

A multiobjective model for maximizing fleet availability under the presence of flight and maintenance requirements

Every aircraft, military or civilian, must be grounded for maintenance after it has completed a certain number of flight hours since its last maintenance check. In this paper, we address the problem of deciding which available aircraft should fly and for how long, and which grounded aircraft should perform maintenance operations, in a group of aircraft that comprise a combat unit. The objective is to achieve maximum availability of the unit over the planning horizon. We develop a multiobjective optimization model for this problem, and we illustrate its application and solution on a real life instance drawn from the Hellenic Air Force. We also propose two heuristic approaches for solving large scale instances of the problem. We conclude with a discussion that gives insight into the behavior of the model and of the heuristics, based on the analysis of the results obtained.     

Sensitivity analysis of the probabilistic damage stability regulations for RoPax vessels

In the light of the newly developed harmonised probabilistic damage stability regulations, set to come into force in 2009, this article presents a systematic and thorough analysis of the sensitivity of the Attained Subdivision Index with reference to a wide range of related design parameters. The sensitivity of the probabilistic regulations was investigated for a typical large RoPax vessel, with variation of parameters, such as the number, positioning and local optimisation of transverse bulkheads; the presence and position of longitudinal bulkheads below the main vehicle deck; the presence of side casings; and the height of the main deck and double bottom. The effects of water on deck and of operational parameters (draught, centre of gravity and trim) were also investigated. The results of the study, presented in graphical form, can provide valuable assistance to the designer when determining subdivision characteristics at the very early stage of the design process, resulting in optimal, efficient and safe ships.     

The assessment of market efficiency in the shipping sector: a new approach

The aim of this paper is to use an alternative measure of the efficiency of the different shipping industries, i.e. VLCC/ULCC (250000dwt), Suezmax (140000dwt), Aframax (80000dwt), which are the main carriers of crude oil, and Handymax (40000dwt), which carries the vast majority of clean (oil) products. The results of the theoretical analysis confirm that, under pure expectations theory, the larger vessels demonstrate higher volatility, as measured by the standard deviation, than the smaller vessels, thereby supporting the proposition that period freight rates do indeed appear to be perfect foresights of the future spot rates.     

Recent aspects of the EU maritime transport policy

Since the 1980s the EU merchant fleet has suffered a dramatic decline mainly due to sharp competition from the Far East and developing countries and the operation of foreign registers ('flags of convenience'). At present the EU aims to complete the single market in shipping and improve the competitive ability of a viable European-flag fleet. It has therefore developed a policy for a European register (EUROS) to run parallel to national registers. This paper argues that the EU policy would prove to be ineffective unless it can differentiate between kinds of shipping.     

Finding time‐robust fuel‐efficient paths for a call‐taxi in a stochastic city road network

Intra‐city commuting is being revolutionized by call‐taxi services in many developing countries such as India. A customer requests a taxi via phone, and it arrives at the right time and at the right location for the pick‐up. This mode of intra‐city travel has become one of the most reliable and convenient modes of transportation for customers traveling for business and non‐business purposes. The increased number of vehicles on city roads and raising fuel costs has prompted a new type of transportation logistics problem of finding a fuel‐efficient and quickest path for a call‐taxi through a city road network, where the travel times are stochastic. The stochastic travel time of the road network is induced by obstacles such as the traffic signals and intersections. The delay and additional fuel consumption at each of these obstacles are calculated that are later imputed to the total travel time and fuel consumption of a path. A Monte‐Carlo simulation‐based approach is proposed to identify unique fuel‐efficient paths between two locations in a city road network where each obstacle has a delay distribution. A multi‐criteria score is then assigned to each unique path based on the probability that the path is fuel efficient, the average travel time of the path and the coefficient of variation of the travel times of the path. Copyright © 2016 John Wiley & Sons, Ltd.     

Modelling the investment decision of the entrepreneur in the tanker sector: choosing between a second-hand vessel and a newly built one

It is often the case that the investor in the shipping sector faces the dilemma of investing in a second-hand vessel or building a new one. This happens because an active second-hand market for almost all kinds of vessels exists. We argue that one of the prime considerations for the investment decision should not be the price of the vessel per se, second-hand (SH) or newly built (NP) but

• ?(a)?the relative price ratio (SH/NP) second-hand price over the new building price and

• ?(b)?the movement of this ratio.

We investigate the determinants of this ratio across different vessel sizes in the tanker sector and show that it can be used as an effective tool in investment decision as well as in asset appraisal.

We employ monthly data between 1995 and 2006 for four different ship sizes–VLCC, Suezmax, Aframax and Handysize–and implement an error correction model.

The investment decision depends on a number of risk and return variables as well as the perceived speed of adjustment of the price ratio to its equilibrium level.

Overall we claim that the cyclicality of the shipping sector together with expectations formed by the agents operating in it (the entrepreneur, the ship-owner and the broker), determine the movement of the ratio and hence the decision of the entrepreneur.