281 research outputs found
Reducing liver lesion incidence in the Dutch pork supply chain
Livers with lesions are an cmportant quality aspect among slaughter pig producers and slaughterhouses. Total losses of non-marketable livers with lesions, lower growth and higher feed intake of pigs in the Netherlands in 2003 were estimated at €3.5 million. The major cause of liver lesions is the roundworm Ascaris suum. Worm treatment on the farm can be effective in reducing liver lesions. Before July 2004 an insurance with a fixed premium for each slaughtered pig was in place in the Netherlands to compensate slaughterhouses for pathological lesions. Individual pig producers had low incentcves to take control measures. In July 2004 a new incentive mechanism was introduced: a reduction in the payment of €1 for each pig with a liver lesion. Thcs placed the financcal burden of levers with lesions on the producer, thereby increasing incentives to treat roundworm infections. We analysed the data of 1,104 farms wcth 55,802 deliveries from 2003 to 2006. The mean liver lesion incidence decreased from 8% in 2003 when a collectcve insurance was in place to 5% in 2006, after the change to the price reduction. Of the producers, 68% reduced liver lesion mcidence. Of the producers with an increased incidence, 83% showed a low increase (less than 5%). We conclude that the price reduction was effective in reducing the mean incidence of liver lesions, although large differences between individual producers exist. Further research is needed to determme what causes these large differences
Application of stochastic programming to reduce uncertainties in quality-based supply planning of slaughterhouses
To match products of different quality with end market preferences under supply uncertainty, it is crucial to integrate product quality information in logistics decision making. We present a case of this integration in a meat processing company that faces uncertainty in delivered livestock quality. We develop a stochastic programming model that exploits historical product quality delivery data to produce slaughterhouse allocation plans with reduced levels of uncertainty in received livestock quality. The allocation plans generated by this model fulfil demand for multiple quality features at separate slaughterhouses under prescribed service levels while minimizing transportation costs. We test the model on real world problem instances generated from a data set provided by an industrial partner. Results show that historical farmer delivery data can be used to reduce uncertainty in quality of animals to be delivered to slaughterhouses
On Convergence of the Inexact Rayleigh Quotient Iteration with the Lanczos Method Used for Solving Linear Systems
For the Hermitian inexact Rayleigh quotient iteration (RQI), the author has
established new local general convergence results, independent of iterative
solvers for inner linear systems. The theory shows that the method locally
converges quadratically under a new condition, called the uniform positiveness
condition. In this paper we first consider the local convergence of the inexact
RQI with the unpreconditioned Lanczos method for the linear systems. Some
attractive properties are derived for the residuals, whose norms are
's, of the linear systems obtained by the Lanczos method. Based on
them and the new general convergence results, we make a refined analysis and
establish new local convergence results. It is proved that the inexact RQI with
Lanczos converges quadratically provided that with a
constant . The method is guaranteed to converge linearly provided
that is bounded by a small multiple of the reciprocal of the
residual norm of the current approximate eigenpair. The results are
fundamentally different from the existing convergence results that always
require , and they have a strong impact on effective
implementations of the method. We extend the new theory to the inexact RQI with
a tuned preconditioned Lanczos for the linear systems. Based on the new theory,
we can design practical criteria to control to achieve quadratic
convergence and implement the method more effectively than ever before.
Numerical experiments confirm our theory.Comment: 20 pages, 8 figures. arXiv admin note: text overlap with
arXiv:0906.223
Asymptotic behaviour of a semilinear elliptic system with a large exponent
Consider the problem \begin{eqnarray*} -\Delta u &=& v^{\frac 2{N-2}},\quad
v>0\quad {in}\quad \Omega, -\Delta v &=& u^{p},\:\:\:\quad u>0\quad {in}\quad
\Omega, u&=&v\:\:=\:\:0 \quad {on}\quad \partial \Omega, \end{eqnarray*} where
is a bounded convex domain in with smooth boundary
We study the asymptotic behaviour of the least energy
solutions of this system as We show that the solution remain
bounded for large and have one or two peaks away form the boundary. When
one peak occurs we characterize its location.Comment: 16 pages, submmited for publicatio
Light hadron spectroscopy in two-flavor QCD with small sea quark masses
We extend the study of the light hadron spectrum and the quark mass in
two-flavor QCD to smaller sea quark mass, corresponding to
--0.35. Numerical simulations are carried out using the
RG-improved gauge action and the meanfield-improved clover quark action at
( fm from meson mass). We observe that the light
hadron spectrum for small sea quark mass does not follow the expectation from
chiral extrapolations with quadratic functions made from the region of
--0.55. Whereas fits with either polynomial or continuum
chiral perturbation theory (ChPT) fails, the Wilson ChPT (WChPT) that includes
effects associated with explicit chiral symmetry breaking successfully
fits the whole data: In particular, WChPT correctly predicts the light quark
mass spectrum from simulations for medium heavy quark mass, such as m_{PS}/m_V
\simgt 0.5. Reanalyzing the previous data %at --0.55 with
the use of WChPT, we find the mean up and down quark mass being smaller than
the previous result from quadratic chiral extrapolation by approximately 10%,
[MeV] in the continuum limit.Comment: 33 page
Finite element simulation of three-dimensional free-surface flow problems
An adaptive finite element algorithm is described for the stable solution of three-dimensional free-surface-flow problems based primarily on the use of node movement. The algorithm also includes a discrete remeshing procedure which enhances its accuracy and robustness. The spatial discretisation allows an isoparametric piecewise-quadratic approximation of the domain geometry for accurate resolution of the curved free surface.
The technique is illustrated through an implementation for surface-tension-dominated viscous flows modelled in terms of the Stokes equations with suitable boundary conditions on the deforming free surface. Two three-dimensional test problems are used to demonstrate the performance of the method: a liquid bridge problem and the formation of a fluid droplet
Prospective Volumetric Assessment of the Liver on a Personal Computer by Nonradiologists Prior to Partial Hepatectomy
Ó The Author(s) 2010. This article is published with open access at Springerlink.com Background A small remnant liver volume is an important risk factor for posthepatectomy liver failure. ImageJ and OsiriX Ò are both free, open-source image processing software packages. The aim of the present study was to compare ImageJ and OsiriX Ò in performing prospective computed tomography (CT) volumetric analysis of the liver on a personal computer (PC) in patients undergoing major liver resection. Methods Patients scheduled for a right hemihepatectomy were eligible for inclusion. Two surgeons and one surgical trainee measured volumes of total liver, tumor, and future resection specimen prospectively with ImageJ and OsiriX Ò. A radiologist also measured these volumes with CT scanner-linked Aquarius iNtuition Ò software. Resection volumes were compared with the actual weights of the live
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