Dissipative particle dynamics: the equilibrium for finite time steps

Dissipative particle dynamics (DPD) is a relatively new technique which has proved successful in the simulation of complex fluids. We caution that for the equilibrium achieved by the DPD simulation of a simple fluid the temperature depends strongly on the time step. An analytic expression for the dependence is obtained and shown to agree well with simulation results.Comment: 5 pages, LaTeX, 1 Postscript figure, submitted to Europhys.Letts., Algebraic corrections made to final resul

The Effect of Injection-Valve Opening Pressure on Spray-Tip Penetration

The effect of various injection-valve opening pressures on the spray-tip penetration was determined for several injection pressure. A common-rail fuel injection system was used. For a given injection pressure a maximum rate of penetration was obtained with an injection-valve opening pressure equal to the injection pressure. As the excess of the injection pressure over the injection-valve opening pressure was increased for a given injection pressure, the effect of the injection-valve opening pressure on the spray-tip penetration was increased

Optimization guide for programs compiled under IBM FORTRAN H (OPT=2)

Guidelines are given to provide the programmer with various techniques for optimizing programs when the FORTRAN IV H compiler is used with OPT=2. Subroutines and programs are described in the appendices along with a timing summary of all the examples given in the manual

Close Binary White Dwarf Systems: Numerous New Detections and Their Interpretation

We describe radial velocity observations of a large sample of apparently single white dwarfs (WDs), obtained in a long-term effort to discover close, double-degenerate (DD) pairs which might comprise viable Type Ia Supernova (SN Ia) progenitors. We augment the WD sample with a previously observed sample of apparently single subdwarf B (sdB) stars, which are believed to evolve directly to the WD cooling sequence after the cessation of core helium burning. We have identified 18 new radial velocity variables, including five confirmed sdB+WD short-period pairs. Our observations are in general agreement with the predictions of the theory of binary star evolution. We describe a numerical method to evaluate the detection efficiency of the survey and estimate the number of binary systems not detected due to the effects of varying orbital inclination, orbital phase at the epoch of the first observation, and the actual temporal sampling of each object in the sample. Follow-up observations are in progress to solve for the orbital parameters of the candidate velocity variables.Comment: 30 pages (LaTeX) + 6 figures (Postscript), aaspp4 styl

Distributional Impacts of Country-of-Origin Labeling in the U.S. Meat Industry

Concerns about the negative effects of U.S. meat and livestock imports on domestic livestock prices have increased interest in country-of origin labeling (COOL) legislation. An equilibrium displacement model is used to estimate short-run and long-run changes in equilibrium prices and quantities of meat and livestock in the beef, pork, and poultry sectors resulting from the implementation of COOL. Retail beef and pork demand would have to experience a one-time, permanent increase of 4.05% and 4.45%, respectively, so that feeder cattle and hog producers do not lose producer surplus over a 10-year period.country-of-origin labeling, equilibrium displacement model, producer surplus, Agribusiness,

Input inefficiency in commercial banks: a normalized quadratic input distance approach

A normalized quadratic input distance function is proposed with which to estimate technical efficiency on commercial banks regulated by the Federal Reserve System. The study period covers 1990 to 2000 using individual bank information from the Call and Banking Holding Company Database. A stochastic frontier model is specified to estimate the input normalized distance function and obtain measures of technical efficiency.Banks and banking

PREDICTING HOUSEHOLD WATER CONSUMPTION UNDER A BLOCK PRICE STRUCTURE

This study focuses on estimating the variations in per-capita water consumption and predicting the shares of consumption by pricing blocks in eight Kansas regions. Previous studies have considered household or micro-level consumption, but few have focused on aggregate level consumption across different regions. A probit model was used to estimate the consumption shares in individual blocks for each region. Per-capita water consumption varies significantly across the regions and as we move from Western to Eastern Kansas, shares of lower consumption block decrease and higher consumption block likely to increase.Resource /Energy Economics and Policy,

The Future is Now: the Formation of Single Low Mass White Dwarfs in the Solar Neighborhood

Low mass helium-core white dwarfs (M < 0.45 Msun) can be produced from interacting binary systems, and traditionally all of them have been attributed to this channel. However, a low mass white dwarf could also result from a single star that experiences severe mass loss on the first ascent giant branch. A large population of low mass He-core white dwarfs has been discovered in the old metal-rich cluster NGC 6791. There is therefore a mechanism in clusters to produce low mass white dwarfs without requiring binary star interactions, and we search for evidence of a similar population in field white dwarfs. We argue that there is a significant field population (of order half of the detected systems) that arises from old metal rich stars which truncate their evolution prior to the helium flash from severe mass loss. There is a consistent absence of evidence for nearby companions in a large fraction of low mass white dwarfs. The number of old metal-rich field dwarfs is also comparable with the apparently single low mass white dwarf population, and our revised estimate for the space density of low mass white dwarfs produced from binary interactions is also compatible with theoretical expectations. This indicates that this channel of stellar evolution, hitherto thought hypothetical only, has been in operation in our own Galaxy for many billions of years. One strong implication of our model is that single low mass white dwarfs should be good targets for planet searches because they are likely to arise from metal-rich progenitors. We also discuss other observational tests and implications, including the potential impact on SN Ia rates and the frequency of planetary nebulae.Comment: ApJ published versio

Time-resolved spectroscopy of the pulsating CV GW Lib

We present time-resolved optical spectroscopy of the dwarf nova GW Librae during its rare 2007 April superoutburst and compare these with quiescent epochs. The data provide the first opportunity to track the evolution of the principal spectral features. In the early stages of the outburst, the optically thick disc dominates the optical and the line components show clear orbital radial velocity excursions. In the course of several weeks, optically thin regions become more prominent as strong emission lines replace the broad disc absorption. Post-outburst spectroscopy covering the I band illustrates the advantages of Ca II relative to the commonly used Balmer lines when attempting to constrain binary parameters. Due to the lower ionization energy combined with smaller thermal and shear broadening of these lines, a sharp emission component is seen to be moving in between the accretion disc peaks in the Ca II line. No such component is visible in the Balmer lines. We interpret this as an emission component originating on the hitherto unseen mass donor star. This emission component has a mean velocity of similar to -15 +/- 5 km s(-1) which is associated with the systemic velocity., and a velocity semi-amplitude of K-em = 82.2 +/- 4.9 km s(-1). Doppler tomography reveals an asymmetric accretion disc, with the S-wave mapping to a sharp spot in the tomogram with a velocity consistent to what is obtained with line profile fitting. A centre of symmetry analysis of the disc component suggests a very small value for the WD orbital velocity K-1 as is also inferred from double Gaussian fits to the spectral lines. While our conservative dynamical limits place a hard upper limit on the binary mass ratio of q < 0.23, we favour a significantly lower value near q similar to 0.06. Pulsation modelling suggests a white dwarf mass similar to 1 M-circle dot. This, paired with a low-mass donor, near the empirical sequence of an evolved cataclysmic variable close to the period bounce, appears to be consistent with all the observational constraints to date