An experimental testbed for mobile offshore base control concepts

 The concept of a mobile offshore base (MOB) reflects the need to stage and support military and humanitarian operations anywhere in the world. A MOB is a self-propelled, modular, floating platform that can be assembled into lengths of up to 2 km, as required, to provide logistic support to US military operations where fixed bases are not available or adequate. It accommodates the take-off and landing of C17 aircraft, and can be used for storage, as well as to send resources quickly to shore. In most concepts, the structure is made of three to five modules, which have to perform long-term station-keeping in the presence of winds, waves, and currents. This is usually referred to as dynamic positioning (DP). In the MOB, the alignment is maintained through the use of thrusters, connectors, or a combination of both. In this paper, we consider the real-time control of scaled models of a MOB. The modules are built at the 1 : 150 scale, and are kept aligned by rotating thrusters under a hierarchical hybrid control scheme. This paper describes a physical testbed developed at the University of California, Berkeley, under a grant from the US Office of Naval Research, for the purpose of evaluating competing MOB control concepts. Received: June 4, 2002 / Accepted: October 30, 2002 Acknowledgments. This material is based on work supported by the MOB Program of the US Office of Naval Research under grant N00014-98-1-0744. The authors would like to thank the Link Foundation for its support. Many thanks go to Stephen Spry for his experimental work. The photographs are courtesy of Bill Stone, Gerald Stone, and Jay Sullivan of the PATH Publications staff. Address correspondence to: A.R. Girard (e-mail: anouck@eecs.berkeley.edu)     

Explaining the “immigrant effect” on auto use: the influences of neighborhoods and preferences

Since immigrants will account for most urban growth in the United States for the foreseeable future, better understanding their travel patterns is a critical task for transportation and land use planners. Immigrants initially travel in personal vehicles far less than the US-born, even when controlling for demographics, but their reliance on autos increases the longer they live in the US. Cultural or habitual differences, followed by assimilation to auto use, could partly explain this pattern; and it may also be partly due to changes in locations and characteristics of home and work neighborhoods. Previous studies have rarely investigated non-work travel, and have not tested workplace land use measures, compared the relative influences of enclave and home neighborhood measures, or looked at the role of culturally-bound residential preferences or motivations for migration. This study relies on a unique and rich dataset consisting of a survey of US residents born in South Asia, Latin America, and the US, joined to spatial information in a GIS. I find that the home built environment is the most consistently influential factor in explaining the lower auto use of both recent and settled Latin American immigrants. Indian immigrants use autos less than would be expected given their home and work neighborhoods. There is little evidence that either ethnic enclaves, or cultural differences, play a role in lower auto use by immigrants. These results suggest there may be a role for neighborhood built environment policies in delaying immigrant assimilation to auto use in the US.     

The impact of port operations on efficient ship operation from both economic and environmental perspectives

Recently, shipping lines have focused on efficient ship operation, which relates to energy efficiency issues in shipping and, particularly, to operational issues such that the minimisation of fuel consumption and resulting greenhouse gas emissions. Efficient ship operation in container lines is closely related to the ship’s time at sea and ship’s time in port. Reduction in port time, thanks to high-quality port operations, allows improvement in the operational efficiency of a liner service by reducing the fuel consumption of a ship at sea and its resulting CO₂ emissions. The main goal of this article is to investigate how time in port affects efficient ship operation in terms of operating costs, CO₂ emissions and externalities. For this, as a methodology, a simulation based upon system dynamics is introduced. Major finding is that less time in port resulting from the improvement of port operations contributes to efficient ship operation in terms of operating costs, amount of CO₂ emissions and external effects in the liner shipping industry. In particular, a sensitivity analysis on efficient ship operation vis-à-vis the quality of port operation shows that bigger ships need to select highly productive calling ports that provide less time in port.     

Bridging the gap between complex data and decision-makers: an example of an innovative interactive tool

Abstract

The increasing capacity of technological tools, as well as the advent of geographic information systems, has multiplied the ability to process large sets of microdata. At the same time, modeling concerns and the quest for a more in-depth understanding of individual behaviors is requiring more, and better, data. The gap between scientific modeling and informational tools for decision-making seems to be widening.

In the Greater Montreal area, large sets of microdata have been available for more than 30 years. Along with the development of modeling and planning tools, particular attention has been given to the continuous enlightening of planners and decision-makers with respect to the outcomes of the various surveys. This has led to the development of particular interactive tools, specifically addressed at local planners, which present the most significant information regarding travel and demography, for geopolitically relevant areas.

This paper presents the most recent interactive tool that has been developed for local planners in the Montreal area. It integrates information from both the most recent travel survey held in the region and the Canadian census. It offers both ease of use and relevant analytical means to assist in exploring the complex relations between spatial locations, demographic features, and activity-travel indicators.     

Winter intensification and water mass evolution from yearlong current meters in the Northeast Water Polynya

In the summer of 1992, four current meter moorings were deployed in and later retrieved from the Northeast Water (NEW) polynya on the East Greenland Shelf by the USCGC Polar Sea. The moorings provided hourly temperature, salinity and current data for approximately one year. In the NEW, the circulation intensified and steadiness increased during winter. This intensification was most readily observed at 150 m on the southern side of Westwind trough. The surface layer freshened from summer through December due to ice-melt and freshwater runoff mixing down to at least 75 m. From December through early spring, salinity increased probably due to brine rejected during ice formation. Wintertime events showed water at 75 m with temperatures at the freezing point. Knee Water (KW) was not observed in the current meter data. However, a warmer and fresher than KW watermass was observed at 150 m over the shelf and may result from mixing outside the NEW among KW and the major water masses influencing the region. Polar Water and Atlantic Intermediate Water. Several short-lived events of 3 to 7 days duration perturbed the T-S character at each of the current meters. We believe that these T-S shifts were anticyclonic eddies advecting through the NEW polynya. During such perturbations, T-S values found generally at 75 m were observed at 150 m and T-S values generally at 150 m were observed at 250 m. On the northern side of the Westwind trough, the current meter data provided direct evidence for westward flow into the western extent of the trough at a depth of 250 m. This southwesterly current along the northwest slope of the trough at 250 m is in agreement with the summertime ADCP measurements made in 1992 aboard Polar Sea, and is consistent with the flow inferred from summer hydrography measured from Polarstern in 1993.     

KERFIX, a time-series station in the Southern Ocean: a presentation

Between January 1990 and March 1995, the research project KERFIX undertook the first regular noncoastal multiyear acquisition of parameters related to the carbon cycle in the Southern Ocean at a time series station located at 50°40′ S–68°25′ E, 60 miles southwest of the Kerguelen Islands. The objectives of KERFIX are (1) to monitor the ocean/atmosphere CO₂ and O₂ exchanges and to understand which processes govern these exchanges (2) to observe and interpret the seasonal and interannual variability of the production, flux, decomposition and dissolution of carbon and associated elements at this location. In addition, micropaleontological studies describe the present and past flux dynamics in this oceanic area, to improve the knowledge of the transfer functions of some oceanographic proxies. This paper presents a survey of the KERFIX program: scientific objectives, organization of the field operations and some main results obtained since the beginning of KERFIX program, as well as the results of the temporal evolution of hydrological, chemical and biological parameters.     

Inter-firm relationships and shipping services: the case of car carriers and automobile importers to the United States

This paper is an initial exploration of inter-industry relationships and linkages in the context of automobile imports to the United States. It is our contention that the nature and structure of the engagement between automobile importers and shipping lines is central to understanding the evolution of the car carrier trade. Building on the literature on transactions costs, and supply and value chains, we show that the regimes currently governing car carriage services range from markets to vertical integration via network forms of engagement. We illustrate this through a detailed discussion of Japanese inter-firm networks and an examination of automobile import data to the US from 1980 to 2000. The findings raise important questions for future research on the impact of inter-industry relationships in various strategic decisions of steamship lines, shippers and port authorities including port entry, port choice and routeing, technological and investment choices, and trajectories of supply chain development.     

Approaches to the future in U.S. urban transportation planning

In appreciation of the fact that longer-run considerations are particularly important in the development of urban transportation, during the past three decades American transportation planning has been employing increasingly sophisticated approaches to the future. This article discusses four phases in this evolution, with a given focus dominant in each period.During the first period, following on the initial provision of federal government funds for the construction of highways in and around cities, major reliance was based on simple projections of travel demand in metropolitan regions, based mainly on current patterns.This was followed by an approach which focused on an analysis of impacts on transportation systems of projected land uses, based on forecasts of population and economic growth for a target year, on the assumption that facilities were to be provided to move all vehicles that wanted to move from here to there at least possible cost.The third period was characterized by an increasing consciousness of the value of articulating national and local goals in making transportation decisions, going beyond narrow economic and mobility objectives, and including the notion of trade-offs among goals.The most recent period discussed is one characterized by rising interest in futures studies, using methods such as Delphi and cross-impact analysis and approaches such as alternative futures, as well as a search for achieving flexibility in transportation development and for means of limiting resource commitment in the face of the uncertainties of the future (keeping options open).It is pointed out that we still have a long way to go in learning how to evolve feasible images of the future, with associated explicit urban life-style goals, that come to grips with societal variety and conflicting interests.     

Land requirements for public transport facilities in urban areas—A statistical approach

The major aim of this work is to develop a primary tool for the quantitative determination of land areas needed to fulfil the diverse functions of public transport. The need for such a tool is obvious; worldwide there is a lack of criteria for determining the types of areas needed, their size, and relative location in the urban system. Moreover, there is a lack of awareness regarding land allocation during the various planning stages, both by urban planners and decision makers. This work attempts to identify various types of facilities to be allocated within the urban framework, and to determine quantitative guidelines for the land needed for them. A statistical analysis is performed in order (i) to identify major transit facilities and operational data functions for which land must be allocated, and (ii) to forecast areas for types of facilities not dealt with by the statistical analysis. The statistical forecast is based on fitting a regression model to the input data. The outcome of this work is presented in terms of three statistical relationships and an indirect relationship: between socio-economic and demographic variables (independent) to the dependent variables, either operating variables or land area variables, and between operating variables (independent) and land area variables (dependent), where for the latter there is also an indirect relationship while using standards.