Isomorph-free generation of 2-connected graphs with applications

Many interesting graph families contain only 2-connected graphs, which have ear decompositions. We develop a technique to generate families of unlabeled 2-connected graphs using ear augmentations and apply this technique to two problems. In the first application, we search for uniquely K_r-saturated graphs and find the list of uniquely K_4-saturated graphs on at most 12 vertices, supporting current conjectures for this problem. In the second application, we verifying the Edge Reconstruction Conjecture for all 2-connected graphs on at most 12 vertices. This technique can be easily extended to more problems concerning 2-connected graphs.Comment: 15 pages, 3 figures, 4 table

Neural Network based Electron Identification in the ZEUS Calorimeter

We present an electron identification algorithm based on a neural network approach applied to the ZEUS uranium calorimeter. The study is motivated by the need to select deep inelastic, neutral current, electron proton interactions characterized by the presence of a scattered electron in the final state. The performance of the algorithm is compared to an electron identification method based on a classical probabilistic approach. By means of a principle component analysis the improvement in the performance is traced back to the number of variables used in the neural network approach.Comment: 20 pages, latex, 16 figures appended as uuencoded fil

Improving Irrigation Scheduling and Water use Efficiency in Cotton

Cotton (Gossypium hirsutum L) is an important crop in the southern United States. The crop is grown in both irrigated and rainfed situations and is seldom free from periods of water shortages at some stage during the season. In recent years the need for consistency in yields and a stable cash flow has resulted in a rapid expansion in the number of irrigated acres of cotton in the Mississippi Delta. Irrigation research has, however, not kept pace with this expansion. This project represents a start at meeting this urgent need. The influence of weather patterns necessitates that these studies be conducted over several years, and the results given here are, therefore, only preliminary observations. The early termination of irrigation has not resulted in any significant decrease in yield or lint quality on the Sharkey clay, although there was a slight detrimental trend when irrigation was terminated too early in August. These studies have helped to clarify the relationship between soil-moisture deficit and plant stress, especially as relates to yield, for cotton cropped on a Sharkey clay soil. Evaluation of crop indicators of water deficit showed that leaf water potential and the air-canopy temperature differential are reliable indicators of the onset of water stress. Leaf extension growth is also a sensitive indicator, but of no practical value in irrigation management. With further research, leaf water potential and canopy-air temperature differentials could provide useful indicators for use in conjunction with traditional methods of scheduling irrigation for cotton in the humid mid-south. A better understanding of the irrigation requirements of the crop will improve management and will have a very significant dollar reduction in the cost of production of the crop

Prompt photon processes in photoproduction at HERA

We present results for the photoproduction of inclusive prompt photons and for prompt photons accompanied by jets, measured with the ZEUS detector at HERA. Cross sections as a function of pseudorapidity and transverse energy are presented for 5 5 GeV in the centre of mass energy range 120-270 GeV. Comparisons are made with predictions from leading logarithm parton shower Monte Carlos and next-to-leading order QCD calculations using currently available models of the photon structure. NLO QCD calculations describe the shape and magnitude of the measurements reasonably well.Comment: Talk given at Photon99 Conference, Freiburg, German

Data refinement for true concurrency

The majority of modern systems exhibit sophisticated concurrent behaviour, where several system components modify and observe the system state with fine-grained atomicity. Many systems (e.g., multi-core processors, real-time controllers) also exhibit truly concurrent behaviour, where multiple events can occur simultaneously. This paper presents data refinement defined in terms of an interval-based framework, which includes high-level operators that capture non-deterministic expression evaluation. By modifying the type of an interval, our theory may be specialised to cover data refinement of both discrete and continuous systems. We present an interval-based encoding of forward simulation, then prove that our forward simulation rule is sound with respect to our data refinement definition. A number of rules for decomposing forward simulation proofs over both sequential and parallel composition are developed