Integrating congestion pricing,transit subsidies and mode choice

We model and analyze optimal (welfare maximizing) prices and design of transport services in a bimodal context. Car congestion and transit design are simultaneously introduced and consumers choose based on the full price they perceive. The optimization variables are the congestion toll, the transit fare (and hence the level of subsidies) and transit frequency. We obtain six main results: (i) the optimal car-transit split is generally different from the total cost minimizing one; (ii) optimal congestion and transit price are interdependent and have an optimal frequency attached; (iii) the optimal money price difference together with the optimal frequency yield the optimal modal split; (iv) if this modal split is used in traditional stand-alone formulations – where each mode is priced independently–resulting congestion tolls and transit subsidies and fares are consistent with the optimal money price difference; (v) self-financing of the transport sector is feasible; and (vi) investment in car infrastructure induces an increase in generalized cost for all public transport users.     

Integrating GIS concepts into transportation network data structures

Transportation network data structures must be designed to meet the requirements of the analyses being conducted and must be compatible with the selected graphical user interface. Increasing interest in geographic information systems (GIS) and intelligent transportation systems (ITS) have further burdened the network data structure. It is possible to implement object oriented programming (OOP) technology to satisfy these needs, without making the data structure excessively complicated.

This paper shows how a well‐developed network data structure can incorporate major capabilities normally associated with stand‐alone GIS's. The design of a network data structure derives from both theoretical and practical considerations. A design of a network data structure, composed entirely of objects, is presented. Examples of its implementation, limitations, advantages, and possible extensions are drawn from experience with the General Network Editor (GNE).     

The existence of an equilibrium solution to the traffic assignment problem when there are junction interactions

We consider a network with interactions and capacity constraints at each junction. We give conditions on the interactions and constraints which, if satisfied at each separate junction, ensure that any feasible assignment problem has an equilibrium solution. Two illustrative examples are provided; the first arises naturally and does not satisfy our conditions, while the second does satisfy our conditions but is somewhat unnatural.     

The most likely trip matrix estimated from traffic counts

For a large number of applications conventional methods for estimating an origin destination matrix become too expensive to use. Two models, based on information minimisation and entropy maximisation principles, have been developed by the authors to estimate an O-D matrix from traffic counts. The models assume knowledge of the paths followed by the vehicles over the network. The models then use the traffic counts to estimate the most likely O-D matrix consistent with the link volumes available and any prior information about the trip matrix. Both models can be used to update and improve a previous O-D matrix. An algorithm to find a solution to the model is then described. The models have been tested with artificial data and performed reasonably well. Further research is being carried out to validate the models with real data.     

The adaptation of the Polish shipping companies to market conditions

At the end of the eighties, fundamental changes took place in Polish shipping. Implementation of the market economy system was at first demonstrated in the introduction of the principles of self-dependence, self-government and self-financing of the shipping companies. Privatization performed a key role in the program of transformation of the centrally planned system into market oriented financially independent shipping organizations. The previous principle of the necessary participation of the home fleet in transporting domestic sea-borne trade has been mostly replaced by cross-trade. Many shipping services have left its basic ports in the country for a West European basis, securing alimentation of home and transit cargoes by feeder–service systems. Joint stock companies in shipping with substantial shares of foreign capital are welcomed, and the previously obligatory system of administrative methods of the state monopoly has been abolished. The principles of shipping policy represented in the past by Poland and also by UNCTAD in the 1960s have lost their impact and must be change and adapted to the new demands of the shipping markets.     

Aquaculture Parks in the Coastal Zone: A Review of Legal and Policy Issues in the Gulf of Mexico State Waters

The goal of this study is to apply industrial park concepts to the development of aquaculture parks in public waters. The objectives are to identify the permitting process, relevant agencies, and legislation needed to facilitate development. Gulf of Mexico states are surveyed: private parks exist in Florida, but no public parks have developed yet; plans for parks exist in Mississippi, but lack of funding prevents development; no regulations prohibit parks in Alabama, although none currently exist; Texas regulations hinder development of parks; and an experimental park has been proposed in Louisiana, but regulatory gaps have delayed permit issuance.     

Air pollution impact of maritime shipping operations in the port of Houston

Abstract

Major air pollutants from maritime shipping operations are sulfur oxides, nitrogen oxides, and particulate matter emissions from combustion of fuel oil during cruise, berth, and start‐up modes. Sulfur oxides emissions are substantial from steamships burning high‐sulfur residual fuel oil, where shipping contributes 66 percent of the total sulfur dioxide emissions from transportation sources, and almost 3 percent of the total for Harris county, Texas. Nitrogen oxides emissions are significant during cruise conditions for both steamships and motor ships, while particulate emissions are substantial during start‐up and tube cleaning.

Significant marine air pollutant emission sources are found in busy harbor areas such as the Houston Ship Channel. Offshore terminals for unloading large tankers may result in emissions of 10 to 20 tons of sulfur oxides daily per ship, and 3 to 5 tons of nitrogen oxides daily per ship during pumping operations. Trace‐metal constituents present in the oil may catalyze sulfur dioxide and nitrogen dioxide oxidation to their respective sulfate and nitrate aerosols in the humid Texas Gulf Coast atmospheres to aggravate photochemical air pollution problems once the air masses reach industrial and populated urban areas on land. Onshore sulfur dioxide and particulate‐matter emission controls may be necessary for some large ships in port to minimize potential impact on coastal zone air quality.     

On appropriate microstate descriptions in entropy modelling

Using an information-theoretic approach to entropy modelling, expressions for the possible number of microstates are derived from the sets of choices available to households and firms in given location/transport planning situations. In planning applications, the urban space is usually subdivided into discrete zones, and various classes of householders and firms are grouped into separate activities. Nevertheless, the location sites within zones may vary considerably in accessibility, price and quality, and amenity v. cost trade-offs between location and travel many differ markedly between individuals within the same activity group. The inclusion of such variations within a random utility framework is demonstrated to be equivalent to maximizing entropy with the microstates disaggregated to the level where these variations occur. Using constraints based on spatial conditions, observed behaviour and planning policy, entropy maximization is used to determine the most probable macrostate according to each choice set specification. The resulting distributions are compared and their revelance discussed.     

Competitive strategies and organizational performance in ship management

Ship management has been characterized by strong competition that resulted in structural changes in the industry, with the bigger companies merging or acquiring smaller ones in an effort to remain competitive. Competitiveness, however, may also be attained through the formulation and implementation of competitive business strategies that will improve performance. The aim of this paper has been to empirically examine the competitive strategy-performance relationship in the context of ship management companies. The findings suggest that there is a positive relationship between pursuing competitive strategies and company performance in ship management. Companies that apply competitive strategies are more likely to be high performers. The strongest influences on performance seem to be achieving economies of scale, differentiation (in particular through a wider range of services offered) and market-focus and competitor-analysis. It is suggested that high performers are more likely to pursue a combination of the generic strategies rather than pursuing one of the generic strategies in isolation.     

12毫米厚铝合金板的搅拌摩擦焊研究(英文)

Most of the investigations regarding friction stir welding(FSW)of aluminum alloy plates have been limited to about 5 to 6mm thick plates.In prior work conducted the various aspects concerning the process parameters and the FSW tool geometry were studied utilizing friction stir welding of 12 mm thick commercial grade aluminum alloy.Two different simple-tomanufacture tool geometries were used.The effect of varying welding parameters and dwell time of FSW tool on mechanical properties and weld quality was examined.It was observed that in order to achieve a defect free welding on such thick aluminum alloy plates,tool having trapezoidal pin geometry was suitable.Adequate tensile strength and ductility can be achieved utilizing a combination of high tool rotational speed of about 2000 r/min and low speed of welding around 28 mm/min.At very low and high dwell time the ductility of welded joints are reduced significantly.