What are the costs of procurement and who bears them?

The costs of procurement are transaction costs which are separate from the direct costs of a project. In this paper discussion is concentrated on costs of tendering. Types of cost, including money costs and opportunity costs, short-term and long-term costs, private and social costs are defined and examined in relation to various types of product and methods of procurement. The costs of the contractor and of the client are considered and tentative conclusions drawn as to who bears these costs in the short-run and in the long run. They may fall on the parties to the process for the particular project, on other contractors and clients or on society as a whole

A Common Explosion Mechanism for Type Ia Supernovae

Type Ia supernovae, the thermonuclear explosions of white dwarf stars composed of carbon and oxygen, were instrumental as distance indicators in establishing the acceleration of the universe's expansion. However, the physics of the explosion are debated. Here we report a systematic spectral analysis of a large sample of well observed type Ia supernovae. Mapping the velocity distribution of the main products of nuclear burning, we constrain theoretical scenarios. We find that all supernovae have low-velocity cores of stable iron-group elements. Outside this core, nickel-56 dominates the supernova ejecta. The outer extent of the iron-group material depends on the amount of nickel-56 and coincides with the inner extent of silicon, the principal product of incomplete burning. The outer extent of the bulk of silicon is similar in all SNe, having an expansion velocity of ~11000 km/s and corresponding to a mass of slightly over one solar mass. This indicates that all the supernovae considered here burned similar masses, and suggests that their progenitors had the same mass. Synthetic light curve parameters and three-dimensional explosion simulations support this interpretation. A single explosion scenario, possibly a delayed detonation, may thus explain most type Ia supernovae.Comment: 8 pages, 2 figure

R-Process in Collapsing O/Ne/Mg Cores

Several circumstantial arguments point to the formation of the third r-process peak at A about 190, near platinum, in stars of mass of about 8-10 solar masses: 1) The delayed production of europium with respect to iron imposes a time scale that restricts the progenitor stars to less than about 10 solar masses; 2) the r-process demands a dominant robust mechanism at least for barium and above, since the relative abundance pattern of those r-process elements in low-metallicity stars is consistent with the solar pattern; 3) stars of about 8-10 solar masses produce nearly identical degenerate O/Ne/Mg cores that collapse due to electron capture; and 4) the resulting low-mass cores may produce both an r-process in a prompt explosion and a subsequent r-process in a neutrino driven wind. The prompt explosion of an O/Ne/Mg core yields low entropy and low electron fraction, and hence may produce a reasonable r-process peak at A about 190 as well as all of the r-process elements with Z greater than 56. The possible differences in the neutrino-driven wind and associated r-process due to the low-mass neutron stars expected in this mass range are also discussed.Comment: 16 pages, LaTeX aasms4; to be published in ApJ Letter

The impact of procurement method on costs of procurement

Collaborative working methods offer the hope of reduced waste, lower tendering costs and improved outputs. The costs of tendering may be influenced by the introduction of different working methods. Transaction cost economics appears to offer an analytical framework for studying the costs of tendering, but it is more to do with providing explanations at the institutional/industry level, not at the level of individual projects. Surveys and interviews were carried out with small samples in UK. The data show that that while tendering costs are not necessarily higher in collaborative working arrangements, there is no correlation between costs of tendering and the way the work is organized. Practitioners perceive that the benefits of working in collaborative procurement routes far outweigh the costs. Tendering practices can be improved to avoid waste, and the suggested improvements include restricting selective tendering lists to 23 bidders, letting bidders know who they are competing with, reimbursing tendering costs for aborted projects and ensuring that timely and comprehensive information is provided to bidders

UK construction companies’ strategies in the face of business cycles

Firms in the construction industry have always had to deal with the challenges of the economic cycle and develop strategies to deal with the resulting fluctuations in their business environment. In the context of the 2008–2011 double-dip recession in the UK, the results of a survey targeting the top one hundred construction companies in the UK are reported here. This research is particularly intended to assess whether the strategies of large companies in the construction sector, when faced with the issues associated with the variation in the economic cycle, have changed since the previous business cycle (i.e. the 1986–1990 boom followed by the 1990–1991 recession). The survey reveals the challenges that companies have faced, reports on company behaviour and on the policies adopted. While there are many similarities between policies adopted during the recessionary periods of the two cycles, the research found notable changes in attitudes towards diversification, human resource management and price bidding

Early light curves for Type Ia supernova explosion models

Upcoming high-cadence transient survey programmes will produce a wealth of observational data for Type Ia supernovae. These data sets will contain numerous events detected very early in their evolution, shortly after explosion. Here, we present synthetic light curves, calculated with the radiation hydrodynamical approach Stella for a number of different explosion models, specifically focusing on these first few days after explosion. We show that overall the early light curve evolution is similar for most of the investigated models. Characteristic imprints are induced by radioactive material located close to the surface. However, these are very similar to the signatures expected from ejecta-CSM or ejecta-companion interaction. Apart from the pure deflagration explosion models, none of our synthetic light curves exhibit the commonly assumed power-law rise. We demonstrate that this can lead to substantial errors in the determination of the time of explosion. In summary, we illustrate with our calculations that even with very early data an identification of specific explosion scenarios is challenging, if only photometric observations are available.Comment: 15 pages, 14 figures, 3 tables, accepted for publication in MNRA

Breaking the color-reddening degeneracy in type Ia supernovae

A new method to study the intrinsic color and luminosity of type Ia supernovae (SNe Ia) is presented. A metric space built using principal component analysis (PCA) on spectral series SNe Ia between -12.5 and +17.5 days from B maximum is used as a set of predictors. This metric space is built to be insensitive to reddening. Hence, it does not predict the part of color excess due to dust-extinction. At the same time, the rich variability of SN Ia spectra is a good predictor of a large fraction of the intrinsic color variability. Such metric space is a good predictor of the epoch when the maximum in the B-V color curve is reached. Multivariate Partial Least Square (PLS) regression predicts the intrinsic B band light-curve and the intrinsic B-V color curve up to a month after maximum. This allows to study the relation between the light curves of SNe Ia and their spectra. The total-to-selective extinction ratio RV in the host-galaxy of SNe Ia is found, on average, to be consistent with typical Milky-Way values. This analysis shows the importance of collecting spectra to study SNe Ia, even with large sample publicly available. Future automated surveys as LSST will provide a large number of light curves. The analysis shows that observing accompaning spectra for a significative number of SNe will be important even in the case of "normal" SNe Ia.Comment: 11 pages, 11 figure

Properties of Deflagration Fronts and Models for Type Ia Supernovae

Detailed models of the explosion of a white dwarf, which include self-consistent calculations of the light curve and spectra, provide a link between observational quantities and the underlying explosion.These calculations assume spherical geometry and are based on parameterized descriptions of the burning front during the deflagration phase. Recently, first multi-dimensional calculations for nuclear burning fronts have been performed. Although a fully consistent treatment of the burning fronts is beyond the current state of the art, these calculations provided a new and better understanding of the physics, and new descriptions for the flame propagation have been proposed. Here, we have studied the influence on the results of previous analyses of Type Ia Supernovae, namely, the nucleosynthesis and structure of the expanding envelope. Our calculations are based on a set of delayed detonation models with parameters that give a good account of the optical and infrared light curves, and of the spectral evolution. In this scenario, the burning front propagates first in a deflagration mode and, subsequently, turns into a detonation. The explosions and light curves are calculated using a one-dimensional Lagrangian radiation-hydro code, including a detailed nuclear network.Comment: 9 pages, 4 figures, macros 'crckapb.sty'. The Astrophysical Journal (accepted

Simple Model of Propagating Flame Pulsations

A simple model which exhibits dynamical flame properties in 1D is presented. It is investigated analytically and numerically. The results are applicable to problems of flame propagation in supernovae Ia.Comment: 10 pages, 8 figures, revised version accepted by MNRA