Graph edit distance from spectral seriation

This paper is concerned with computing graph edit distance. One of the criticisms that can be leveled at existing methods for computing graph edit distance is that they lack some of the formality and rigor of the computation of string edit distance. Hence, our aim is to convert graphs to string sequences so that string matching techniques can be used. To do this, we use a graph spectral seriation method to convert the adjacency matrix into a string or sequence order. We show how the serial ordering can be established using the leading eigenvector of the graph adjacency matrix. We pose the problem of graph-matching as a maximum a posteriori probability (MAP) alignment of the seriation sequences for pairs of graphs. This treatment leads to an expression in which the edit cost is the negative logarithm of the a posteriori sequence alignment probability. We compute the edit distance by finding the sequence of string edit operations which minimizes the cost of the path traversing the edit lattice. The edit costs are determined by the components of the leading eigenvectors of the adjacency matrix and by the edge densities of the graphs being matched. We demonstrate the utility of the edit distance on a number of graph clustering problems

A graph-spectral approach to shape-from-shading

In this paper, we explore how graph-spectral methods can be used to develop a new shape-from-shading algorithm. We characterize the field of surface normals using a weight matrix whose elements are computed from the sectional curvature between different image locations and penalize large changes in surface normal direction. Modeling the blocks of the weight matrix as distinct surface patches, we use a graph seriation method to find a surface integration path that maximizes the sum of curvature-dependent weights and that can be used for the purposes of height reconstruction. To smooth the reconstructed surface, we fit quadrics to the height data for each patch. The smoothed surface normal directions are updated ensuring compliance with Lambert's law. The processes of height recovery and surface normal adjustment are interleaved and iterated until a stable surface is obtained. We provide results on synthetic and real-world imagery

Selective vs. Broad-Spectrum Pesticides: When Do Private Decisions Differ from Socially Optimal Decisions?

This paper examines the spatial externalities of conventional and organic pest control methods to determine if, and how, the two types affect each other. These interactions make the problem more complicated than the usual analysis of a single externality. The numerical simulation model includes one organically managed and one conventionally managed field. One pest and one predator of the pest move between the two fields over five seasons. In each season, the conventional grower has the option of applying a broad-spectrum pesticide that kills the predator a selective pesticide that has no adverse effects on the predator but is either more expensive or less effective than the broad-spectrum pesticide. The organic grower can apply an organic pesticide, augment the predator population, or both. The simulation model identifies the socially optimal pest control decisions and the Nash equilibrium decisions of both growers over the five growing seasons. The relative price and efficacy of the selective pesticide, the type of predator, and the type of pest introduction all influence whether or not either or both growers make inefficient decisions. Under certain conditions, regional pest management, equivalent to coordination of pest control across growers, could increase total regional profits.spatial-dynamic games, spatial externalities, non-cooperative games, organic agriculture, biological control, agricultural policy, Agricultural and Food Policy, Crop Production/Industries, Resource /Energy Economics and Policy, C61, C72, Q18, Q52, Q57,

Induced p-wave superfluidity in strongly interacting imbalanced Fermi gases

The induced interaction among the majority spin species, due to the presence of the minority species, is computed for the case of a population-imbalanced resonantly-interacting Fermi gas. It is shown that this interaction leads to an instability, at low temperatures, of the recently observed polaron Fermi liquid phase of strongly imbalanced Fermi gases to a p-wave superfluid state. We find that the associated transition temperature, while quite small in the weakly interacting BCS regime, is experimentally accessible in the strongly interacting unitary regime.Comment: Published versio

Packet equalisation in PONs using adjustable gain-clamped semiconductor optical amplifiers (AGC-SOA)

The past ten years have witnessed a dramatic growth in the delivery of high bandwidth services through Passive Optical Networks (PONs), directly to the home or to the kerb. The bursty nature of upstream traffic in a PON (from the user to Optical Network Unit, ONU) combined with a wide dynamic range of signal strength (-15dB to -28dB the difference between a very close Optical Network Terminal (ONT) with a small split ratio and a distant ONT with a high split ratio), places severe demands on the burst mode receiver at the ONU. We report here on an adjustable gain-clamped semiconductor optical amplifier (AGC-SOA) designed to maximize the output saturated power while adjusting gain to regulate the power differences between packets without loss of linearity. This device is shown to be able to modulate gain at rates that are compatible with packet to packet equalisation. Through theoretical analysis coupled with experimental verification, this paper demonstrates for the first time that this is entirely feasible

Injury in Ireland

Injury mortality is the fourth commonest cause of death in Ireland. The treatment of injuries has a major impact on our hospitals and on our budget for health. Long term disability following accidents is a serious problem. The aim of this report is to examine the impact of accidents and injuries on the Irish population by analysing routine mortality and morbidity data, and to identify in turn those areas where preventive measures could have an impact. In Section One the literature review details the advantages and disadvantages of each type of routine data source used in this report. The interpretation of data should take account of the constraints of the available data collected. The usefulness of routine data collection is highlighted, while identifying areas for improvement. In Section Two the methodology employed in the study is detailed. In Section Three data on hospital admissions over a five-year period 1993-1997 are presented. An overview of injury admissions is presented, followed by further analysis of injury data by both cause and by age group. In Section Four data on all accident-related deaths over a 17-year period, 1980-1996, are presented, with overall mortality data and mortality data by age group and by major causes of injury death detailed. In Section Five comparisons are made between the eight health board regions for rates of admissions and deaths due to injury. In presenting the data we use a matrix format devised and recommended by the International Collaborative Effort on Injury Statistics to display injury simultaneously by cause and intent. The use of a common format will also facilitate regional and international comparisons. In Section Six the priority recommendations for injury prevention are outlined. The key findings are then discussed and further recommendations are presented with the aim of injury prevention, reduction of disability and improvement in injury surveillance

First Record of \u3ci\u3eOchlerotatus Japonicus\u3c/i\u3e (Diptera: Culicidae) in St. Joseph County, Indiana

A single female specimen of Ochlerotatus japonicus (Theobald)(formerly Aedes japonicus), the Asian bush mosquito, was captured in St. Joseph County, IN on 29 July 2004. This is the first report of that species in northern Indiana. Additional specimens were subsequently collected, indicating probable establishment throughout the county

Current driven instabilities of an electromagnetically accelerated plasma

A plasma instability that strongly influences the efficiency and lifetime of electromagnetic plasma accelerators was quantitatively measured. Experimental measurements of dispersion relations (wave phase velocities), spatial growth rates, and stability boundaries are reported. The measured critical wave parameters are in excellent agreement with theoretical instability boundary predictions. The instability is current driven and affects a wide spectrum of longitudinal (electrostatic) oscillations. Current driven instabilities, which are intrinsic to the high-current-carrying magnetized plasma of the magnetoplasmadynmic (MPD) accelerator, were investigated with a kinetic theoretical model based on first principles. Analytical limits of the appropriate dispersion relation yield unstable ion acoustic waves for T(i)/T(e) much less than 1 and electron acoustic waves for T(i)/T(e) much greater than 1. The resulting set of nonlinear equations for the case of T(i)/T(e) = 1, of most interest to the MPD thruster Plasma Wave Experiment, was numerically solved to yield a multiparameter set of stability boundaries. Under certain conditions, marginally stable waves traveling almost perpendicular to the magnetic field would travel at a velocity equal to that of the electron current. Such waves were termed current waves. Unstable current waves near the upper stability boundary were observed experimentally and are in accordance with theoretical predictions. This provides unambiguous proof of the existence of such instabilites in electromagnetic plasma accelerators

Operations planning simulation model extension study. Volume 5: Mariner Jupiter orbiter PL-12-A automated payload (upper stage used)

For abstract, see N75-20432