Strategic maritime container transport design in oligopolistic markets

AbstractThis paper considers the maritime container assignment problem in a market setting with two competing firms. Given a series of known, exogenous demands for service between pairs of ports, each company is free to design a liner service network serving a subset of the ports and demand, subject to the size of their fleets and the potential for profit. The model is designed as a three-stage complete information game: in the first stage, the firms simultaneously invest in their fleet; in the second stage, they individually design their networks and solve the route assignment problem with respect to the transport demand they expect to serve, given the fleet determined in the first stage; in the final stage, the firms compete in terms of freight rates on each origin-destination movement. The game is solved by backward induction. Numerical solutions are provided to characterize the equilibria of the game

A cost-based maritime container assignment model and port choice

A recently proposed frequency-based maritime container assignment model (Bell et al, 2011) seeks an assignment of full and empty containers to paths that minimises expected container travel time, whereas containers are in practice more likely to be assigned to minimise expected cost. There are significant economies of scale in the maritime transport of containers; the cost per container per unit time falls with increasing ship occupancy and larger ships when full cost less per container per unit time than smaller ships. A cost-based container assignment model is proposed here. The objective is to assign containers to maritime routes to minimize sailing costs plus expected dwell costs at the ports of origin and transhipment. The constraints in the model are extended to include route as well as port capacity constraints. Although the cost per container per unit time depends on ship occupancy, it is shown that the problem remains a linear program. A small numerical example is presented to illustrate the properties of the model. The paper concludes by considering the many applications of the proposed maritime container assignment model

Taxation

This article reviews significant recent developments in the laws affecting Virginia state and local taxation. Its sections cover legislative activity, judicial decisions, and selected opinions or pronouncements from the Virginia Department of Taxation and the Attorney General of Virginia over the past year

Frequency‐based transit assignment revisited

This working paper reformulates the Spiess and Florian frequency-based transit assignment method in matrix algebra revealing a new solution method. It is shown that the number of destination-specific passenger wait times at stops is equal to the number of flow conservation constraints (Proposition 1). The frequency-based transit assignment is found by matrix manipulation and when there are line capacity constraints the equilibrium effective frequencies are obtained iteratively. The existence of equilibrium effective frequencies is proven (Proposition 2). It is shown that a wider range of fare schemes, for example flat fares, can be modeled by the use of legs in the network representation. Numerical examples are presented and solved by R code

Modelling the impact of liner shipping network perturbations on container cargo routing: Southeast Asia to Europe application

Understanding how container routing stands to be impacted by different scenarios of liner shipping network perturbations such as natural disasters or new major infrastructure developments is of key importance for decision-making in the liner shipping industry. The variety of actors and processes within modern supply chains and the complexity of their relationships have previously led to the development of simulation-based models, whose application has been largely compromised by their dependency on extensive and often confidential sets of data. This study proposes the application of optimisation techniques less dependent on complex data sets in order to develop a quantitative framework to assess the impacts of disruptive events on liner shipping networks. We provide a categorization of liner network perturbations, differentiating between systemic and external and formulate a container assignment model that minimises routing costs extending previous implementations to allow feasible solutions when routing capacity is reduced below transport demand. We develop a base case network for the Southeast Asia to Europe liner shipping trade and review of accidents related to port disruptions for two scenarios of seismic and political conflict hazards. Numerical results identify alternative routing paths and costs in the aftermath of port disruptions scenarios and suggest higher vulnerability of intra-regional connectivity

Collective excitation spectrum of a disordered Hubbard model

We study the collective excitation spectrum of a d=3 site-disordered Anderson-Hubbard model at half-filling, via a random-phase approximation (RPA) about broken-symmetry, inhomogeneous unrestricted Hartree-Fock (UHF) ground states. We focus in particular on the density and character of low-frequency collective excitations in the transverse spin channel. In the absence of disorder, these are found to be spin-wave-like for all but very weak interaction strengths, extending down to zero frequency and separated from a Stoner-like band, to which there is a gap. With disorder present, a prominent spin-wave-like band is found to persist over a wide region of the disorder-interaction phase plane in which the mean-field ground state is a disordered antiferromagnet, despite the closure of the UHF single-particle gap. Site resolution of the RPA excitations leads to a microscopic rationalization of the evolution of the spectrum with disorder and interaction strength, and enables the observed localization properties to be interpreted in terms of the fraction of strong local moments and their site-differential distribution.Comment: 25 pages (revtex), 9 postscript figure

Topological Structure of Manufacturing Industry Supply Chain Networks

Empirical analyses of supply chain networks (SCNs) in extant literature have been rare due to scarcity of data. As a result, theoretical research have relied on arbitrary growth models to generate network topologies supposedly representative of real-world SCNs. Our study is aimed at filling the above gap by systematically analysing a set of manufacturing sector SCNs to establish their topological characteristics. In particular, we compare the differences in topologies of undirected contractual relationships (UCR) and directed material flow (DMF) SCNs. The DMF SCNs are different from the typical UCR SCNs since they are characterised by a strictly tiered and an acyclic structure which does not permit clustering. Additionally, we investigate the SCNs for any self-organized topological features. We find that most SCNs indicate disassortative mixing and power law distribution in terms of interfirm connections. Furthermore, compared to randomised ensembles, self-organized topological features were evident in some SCNs in the form of either overrepresented regimes of moderate betweenness firms or underrepresented regimes of low betweenness firms. Finally, we introduce a simple and intuitive method for estimating the robustness of DMF SCNs, considering the loss of demand due to firm disruptions. Our work could be used as a benchmark for any future analyses of SCNs

SOLVING TRAFFIC CONGESTION FROM THE DEMAND SIDE

It is nowadays widely accepted that solving traffic congestion from the demand side is more important and more feasible than offering more capacity or facilities for transportation. Following a brief overview of evolution of the concept of Travel Demand Management (TDM), there is a discussion on the TDM foundations that include demand-side strategies, traveler choice and application settings and the new dimensions that ATDM (Active forms of Transportation and Demand Management) bring to TDM, i.e. active management and integrative management. Subsequently, the authors provide a short review of the state-of-the-art TDM focusing on relevant literature published since 2000. Next, we highlight five TDM topics that are currently hot: traffic congestion pricing, public transit and bicycles, travel behavior, travel plans and methodology. The paper closes with some concluding remarks

Exploring Halo Substructure with Giant Stars IV: The Extended Structure of the Ursa Minor Dwarf Spheroidal

We present a large area photometric survey of the Ursa Minor dSph. We identify UMi giant star candidates extending to ~3 deg from the center of the dSph. Comparison to previous catalogues of stars within the tidal radius of UMi suggests that our photometric luminosity classification is 100% accurate. Over a large fraction of the survey area, blue horizontal branch stars associated with UMi can also be identified. The spatial distribution of both the UMi giant stars and the BHB stars are remarkably similar, and a large fraction of both samples of stars are found outside the tidal radius of UMi. An isodensity contour map of the stars within the tidal radius of UMi reveals two morphological peculiarities: (1) The highest density of dSph stars is offset from the center of symmetry of the outer isodensity contours. (2) The overall shape of the outer contours appear S-shaped. We find that previously determined King profiles with ~50' tidal radii do not fit well the distribution of our UMi stars. A King profile with a larger tidal radius produces a reasonable fit, however a power law with index -3 provides a better fit for radii > 20'. The existence of UMi stars at large distances from the core of the galaxy, the peculiar morphology of the dSph within its tidal radius, and the shape of its surface density profile all suggest that UMi is evolving significantly due to the tidal influence of the Milky Way. However, the photometric data on UMi stars alone does not allow us to determine if the candidate extratidal stars are now unbound or if they remain bound to the dSph within an extended dark matter halo. (Abridged)Comment: accepted by AJ, 32 pages, 15 figures, emulateapj5 styl

DDO Photometry of M71: Carbon and Nitrogen Patterns Among Evolving Giants

We present V, B-V, and DDO C(41-42) and C(42-45) photometry for a sample of 75 red giants down to M_V = +2 in the relatively metal-rich Galactic globular cluster M71. The C(41-42) colors reveal a bimodal distribution of CN band strengths generally anticorrelated with CH band strength as measured by the C(42-45) color. Both DDO colors agree well with those found in 47 Tucanae -- a nearby globular cluster of similar metallicity -- and suggest nearly identical C and N abundance patterns among the giants of both clusters. A comparison with synthetic DDO colors demonstrates that little change in surface C or N abundance is required to match the colors of the M71 giants over the entire luminosity range observed. Apparently like 47 Tuc (a cluster of much greater mass and central concentration), M71 exhibits an abundance pattern which cannot be solely the result of internal mixing.Comment: To appear in the Astronomical Journal, November 2001. 17 Pages, 5 Figure