974 research outputs found

    The optimisation of a strategic business process

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    The optimisation of a Tendering Process for Warship Refit Contracts is presented. The Pre Contract Award process (PCA) involves all the activities needed to successfully win a Refit Contract, e.g. estimating, planning, tendering and negotiation. Process activities and information flows have been modelled using Integrated computer aided manufacturing DEFinition methodology (IDEF0) and a Design Structure Matrix (DSM) with optimisation performed via a Genetic Algorithm (DSM-GA) search technique [1]. The aim of the DSM-GA is to provide the user with an enhanced sequence of performing process activities. A new process was extracted from the optimised solution, showing an improved sequence with reduced iteration and planned activity concurrency based on carefully considered information requirements. This is of practical benefit to enhance understanding and to provide a guide to implementation. The approach suggests an enhanced sequence of process activities, based on information requirements, and can lead to improved business practice. This Paper discusses the potential benefits and limitations of this approach in a practical setting

    The optimisation of the estimating and tendering process in warship refit - a case study

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    The optimisation of a tendering process for warship refit contracts is presented. The tendering process, also known as the pre-contract award process (PCA), involves all the activities needed to be successfully awarded a refit contract. Process activities and information flows have been modelled using Integrated Definition Language IDEF0 and a Dependency Structure Matrix (DSM) with optimisation performed via a Genetic Algorithm (DSM-GA) search technique. By utilising this approach the process activities were re-sequenced in such an order that the number and size of rework cycles were reduced. The result being a 57% reduction in a criterion indicating 're-work' cycles

    A comparison of SNPs and microsatellites as linkage mapping markers: lessons from the zebra finch (Taeniopygia guttata)

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    Background: Genetic linkage maps are essential tools when searching for quantitative trait loci (QTL). To maximize genome coverage and provide an evenly spaced marker distribution a combination of different types of genetic marker are sometimes used. In this study we created linkage maps of four zebra finch (Taeniopygia guttata) chromosomes (1, 1A, 2 and 9) using two types of marker, Single Nucleotide Polymorphisms (SNPs) and microsatellites. To assess the effectiveness and accuracy of each kind of marker we compared maps built with each marker type separately and with both types of marker combined. Linkage map marker order was validated by making comparisons to the assembled zebra finch genome sequence. Results: We showed that marker order was less reliable and linkage map lengths were inflated for microsatellite maps relative to SNP maps, apparently due to differing error rates between the two types of marker. Guidelines on how to minimise the effects of error are provided. In particular, we show that when combining both types of marker the conventional process of building linkage maps, whereby the most informative markers are added to the map first, has to be modified in order to improve map accuracy. Conclusions: When using multiple types and large numbers of markers to create dense linkage maps, the least error prone loci (SNPs) rather than the most informative should be used to create framework maps before the addition of other potentially more error prone markers (microsatellites). This raises questions about the accuracy of marker order and predicted recombination rates in previous microsatellite linkage maps which were created using the conventional building process, however, provided suitable error detection strategies are followed microsatellite-based maps can continue to be regarded as reasonably reliable

    The Quark Propagator from the Dyson-Schwinger Equations: I. the Chiral Solution

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    Within the framework of the Dyson-Schwinger equations in the axial gauge, we study the effect that non-perturbative glue has on the quark propagator. We show that Ward-Takahashi identities, combined with the requirement of matching perturbative QCD at high momentum transfer, guarantee the multiplicative renormalisability of the answer. Technically, the matching with perturbation theory is accomplished by the introduction of a transverse part to the quark-gluon vertex. We show that this transverse vertex is crucial for chiral symmetry breaking, and that massless solutions exist below a critical value of the strong coupling constant. Using the gluon propagator that we previously calculated, we obtain small corrections to the quark propagator, which keeps a pole at the origin in the chiral phase.Comment: 21 pages, 6 figures; McGill/94-24, SHEP 93/94-26 We generalise our results by showing that they are not sensitive to the specific choice that we make for the transverse vertex. We illustrate that fact in two new figure

    OSETI with STACEE: A Search for Nanosecond Optical Transients from Nearby Stars

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    We have used the STACEE high-energy gamma-ray detector to look for fast blue-green laser pulses from the vicinity of 187 stars. The STACEE detector offers unprecedented light-collecting capability for the detection of nanosecond pulses from such lasers. We estimate STACEE's sensitivity to be approximately 10 photons per square meter at a wavelength of 420 nm. The stars have been chosen because their characteristics are such that they may harbor habitable planets and they are relatively close to Earth. Each star was observed for 10 minutes and we found no evidence for laser pulses in any of the data sets.Comment: 38 pages, 12 figures. Accepted for publication in Astrobiolog

    Levels of extra-pair paternity are associated with parental care in penduline tits (Remizidae)

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    In most passerine birds, individuals attempt to maximise their fitness by providing parental care while also mating outside their pair bond. A sex-specific trade-off between these two behaviours is predicted to occur since the fitness benefits of extra-pair mating differs between the sexes. We use nest observations and parentage analysis to reveal a negative association between male care and the incidence of extra-pair paternity across three species of penduline tit (Remizidae)

    Very high energy observations of the BL Lac objects 3C 66A and OJ 287

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    Using the Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE), we have observed the BL Lac objects 3C 66A and OJ 287. These are members of the class of low-frequency-peaked BL Lac objects (LBLs) and are two of the three LBLs predicted by Costamante and Ghisellini to be potential sources of very high energy (>100 GeV) gamma-ray emission. The third candidate, BL Lacertae, has recently been detected by the MAGIC collaboration. Our observations have not produced detections; we calculate a 99% CL upper limit of flux from 3C 66A of 0.15 Crab flux units and from OJ 287 our limit is 0.52 Crab. These limits assume a Crab-like energy spectrum with an effective energy threshold of 185 GeV.Comment: 24 pages, 15 figures, Accepted for publication in Astroparticle Physic

    Pion Content of the Nucleon as seen in the NA51 Drell-Yan experiment

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    In a recent CERN Drell-Yan experiment the NA51 group found a strong asymmetry of uˉ\bar u and dˉ\bar d densities in the proton at x0.18x\simeq0.18. We interpret this result as a decisive confirmation of the pion-induced sea in the nucleon.Comment: 10 pages + 3 figures, Preprint KFA-IKP(TH)-1994-14 .tex file. After \enddocument a uu-encodeded Postscript file comprising the figures is appende

    A posteriori inclusion of parton density functions in NLO QCD final-state calculations at hadron colliders: The APPLGRID Project

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    A method to facilitate the consistent inclusion of cross-section measurements based on complex final-states from HERA, TEVATRON and the LHC in proton parton density function (PDF) fits has been developed. This can be used to increase the sensitivity of LHC data to deviations from Standard Model predictions. The method stores perturbative coefficients of NLO QCD calculations of final-state observables measured in hadron colliders in look-up tables. This allows the posteriori inclusion of parton density functions (PDFs), and of the strong coupling, as well as the a posteriori variation of the renormalisation and factorisation scales in cross-section calculations. The main novelties in comparison to original work on the subject are the use of higher-order interpolation, which substantially improves the trade-off between accuracy and memory use, and a CPU and computer memory optimised way to construct and store the look-up table using modern software tools. It is demonstrated that a sufficient accuracy on the cross-section calculation can be achieved with reasonably small look-up table size by using the examples of jet production and electro-weak boson (Z, W) production in proton-proton collisions at a center-of-mass energy of 14 TeV at the LHC. The use of this technique in PDF fitting is demonstrated in a PDF-fit to HERA data and simulated LHC jet cross-sections as well as in a study of the jet cross-section uncertainties at various centre-of-mass energies

    Form Factors in the radiative pion decay

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    We perform an analysis of the form factors that rule the structure-dependent amplitude in the radiative pion decay. The resonance contributions to pion -> e nu_e gamma decays are computed through the proper construction of the vector and axial-vector form factors by setting the QCD driven asymptotic properties of the three-point Green functions VVP and VAP, and by demanding the smoothing of the form factors at high transfer of momentum. A comparison between theoretical and experimental determinations of the form factors is also carried out. We also consider and evaluate the role played by a non-standard tensor form factor. We conclude that, at present and due to the hadronic incertitudes, the search for New Physics in this process is not feasible.Comment: 14 pages, no figures. Typos corrected. Accepted for publication in The European Physical Journal
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