A user‐resource planning framework for offshore recreational artificial reefs

Abstract

Artificial reefs have been used extensively in coastal waters to attract and enhance recreational fishery resources. In the United States, they have been traditionally built from “materials of opportunity”; using limited budgets. This paper explores some past planning philosophies and presents a recent artificial reef deployment case that demonstrates a lack of sensitivity to local and regional recreational demand. A systems framework is developed to guide future planning efforts in artificial reef development. The framework is intended to integrate previously fragmented knowledge and to demonstrate the interdisciplinary nature of artificial reef planning. Emphasis is given to advance planning, user dimensions, and the integral issue of reef access.     

Flow-field guided steering control for rigid autonomous ground vehicles in low-speed manoeuvring

ABSTRACT

This paper studies the low-speed manoeuvring problem for autono-mous ground vehicles operating in complex static environments. Making use of the intrinsic property of a fluid to naturally find its way to an outflow destination, a novel guidance method is proposed. In this approach, a reference flow field is calculated numerically through Computational Fluid Dynamics, based on which both the reference path topology and the steering reference to achieve the path are derived in a single process. Steering control considers three constraints: obstacle and boundary avoidance, rigidity of the vehicle, plus the non-holonomic velocity constraints due to the steering system. The influences of the parameters used during the flow field simulation and the control algorithm are discussed through numerical cases. A divergency field is defined to evaluate the quality of the flow field in guiding the vehicle. This is used to identify any problematic branching features of the flow, and control is adapted in the neighbourhood of such branching features to resolve possible ambiguities in the control reference. Results demonstrate the effectiveness of the method in finding smooth and feasible motion paths, even in complex environments.     

列车内饰设计趋势之一——旅客信息系统备受全球欢迎

让旅客享受娱乐已经不再被运营商认为是会对成本造成进一步损失而成为一种奢望。因为，通过为旅客提供一些他们想要的休闲娱乐项目和设施。已经成为提高运营收入的有效来源。     

单壳油轮何去何从

按照规定,单壳油轮已经被逐步淘汰,而我们却还在2009年年未考虑淘汰所带来的影响,这看起来也许有点奇怪。有些人甚至会觉得,自己回到了五年前。那时候,这是一个重要的争论焦点,而围绕2010年这个期限尚有不少疑问。在2004年，这是任何重大海运会议都必定涉及的首要问题。事实上，我记得一位业界观察家好像评论说，     

单壳油轮何去何从

按照规定,单壳油轮已经被逐步淘汰,而我们却还在2009年年未考虑淘汰所带来的影响,这看起来也许有点奇怪。有些人甚至会觉得,自己回到了五年前。那时候,这是一个重要的争论焦点,而围绕2010年这个期限尚有不少疑问。在2004年，这是任何重大海运会议都必定涉及的首要问题。事实上，我记得一位业界观察家好像评论说，     

Managing passenger behavioral intention: an integrated framework for service quality,satisfaction, perceived value,and switching barriers

This paper seeks to improve our understanding of passengers’ behavioral intention by proposing an integrated framework from the attitudinal perspective. According to the literature in marketing research, we establish a causal relationship model that considers “service quality-satisfaction-behavioral intentions” paradigm, perceived value theory, and switching barrier theory. Exploring passengers’ behavioral intention from satisfaction and perceived value help to understand how passengers are attracted by the company, while switching barriers assist in realizing how passengers are “locked” into a relationship with the current company. Furthermore, in order to capture the nature of service quality, we adopt a hierarchical factor structure which serves service quality as the higher-order factor. In this study, coach industry is selected as our research subject. The empirical results, as hypothesized, show that all causal relationships are statistically significant, and perceived value us the most important predictor of satisfaction and passengers’ behavioral intention. In conclusion, the managerial implications and suggestions for future research are discussed.     

Building legitimacy for risky policies: The cost of avoiding conflict in Stockholm

The controversial nature of urban congestion charging policies makes them politically risky. Urban planners, policy makers and politicians are forced to consider how they can legitimately introduce a policy that the public may not want. Implementation in London, and failure in Edinburgh, raise questions about whether they should seek full citizen support, or work strategically towards implementation in the face of public opposition.This paper reports on an investigation of the Stockholm congestion charging trial (SCCT). It analyses the strategy developed by the city authorities to create legitimacy for the implementation of the SCCT. The SCCT is examined in two steps, firstly how the ‘trial + referendum’ approach was successful in securing public acceptance, and secondly how key aspects of the design of the trial and the subsequent referendum were adjusted in response to emerging risks, demonstrating the pragmatic approach of the city leaders managing the policy process. The study suggests that the city leaders chose a clearly pragmatic approach, grounded in compromise, yet subtly designed to avoid openly confronting the status quo. The strategy was continuously adapted and adjusted, in the face of emerging risks, and clearly served to create consensus while avoiding difficult questions of urban mobility.     

Nutrient cycling and primary production in the marine systems of the Arctic and Antarctic

Primary production events in both the Arctic and the Antarctic are highly localized. Carbon-14 incubations that did not account for this caused antarctic primary production estimates to be revised too far downwards from the historic view of high productivity. The primary production regime in the Arctic is even more heterogeneous than in the Antarctic. Arctic primary production rates are in the process of being revised upwards because of a better spatial and temporal distribution of incubation experiments and a re-awakening of interest in estimating new production from the distribution of chemical variables. Similarly, recent examination of temporal changes in nitrate concentrations and recognition of the importance of ice-edge blooms has caused antarctic primary productivity to be revised upwards. In both the Arctic and the Antarctic, the ratio of “new” to total primary production is high, and neglect of this fact can lead to an underestimation of the potential that these regions have for influencing global cycles of bioactive chemicals. Some recent data on temporal changes in nitrate from Fram Strait emphasize the poor state of our knowledge by suggesting an unexpectedly high “new” production rate of 1 g C m⁻² d⁻¹ for a 35 day experiment that encountered an early Phaeocystis bloom. Chemical distributions suggest that new production over the shelf seas that border the Polar Basin is about 50 g Cm⁻² yr⁻¹.The shelves in the Arctic Ocean's marginal and adjacent seas comprise 25% of the total global continental shelf. These extensive shallow regions have much higher rates of primary production than the Polar Basin and may be globally significant sites of denitrification. Globally significant silica deposition could occur on these shelves or on the adjacent slopes.Because of the differences in geomorphology and stratification, global warming is likely to increase primary production in the Arctic and will probably decrease antarctic primary production.In addition to sharing high ratios of “new” to total primary production, high ammonium concentrations occur in the Arctic and Antarctic. It is possible that these accumulations arise from a strong repression of nitrification at low temperatures.