715 research outputs found
Cyclic cycle systems of the complete multipartite graph
In this paper, we study the existence problem for cyclic -cycle
decompositions of the graph , the complete multipartite graph with
parts of size , and give necessary and sufficient conditions for their
existence in the case that
On the equivalence of strong formulations for capacitated multi-level lot sizing problems with setup times
Several mixed integer programming formulations have been proposed for modeling capacitated multi-level lot sizing problems with setup times. These formulations include the so-called facility location formulation, the shortest route formulation, and the inventory and lot sizing formulation with (l,S) inequalities. In this paper, we demonstrate the equivalence of these formulations when the integrality requirement is relaxed for any subset of binary setup decision variables. This equivalence has significant implications for decomposition-based methods since same optimal solution values are obtained no matter which formulation is used. In particular, we discuss the relax-and-fix method, a decomposition-based heuristic used for the efficient solution of hard lot sizing problems. Computational tests allow us to compare the effectiveness of different formulations using benchmark problems. The choice of formulation directly affects the required computational effort, and our results therefore provide guidelines on choosing an effective formulation during the development of heuristic-based solution procedures
Defining interactions: a conceptual framework for understanding interactive behaviour in human and automated road traffic
Rapid advances in technology for highly automated vehicles (HAVs) have raised concerns about coexistence of HAVs and human road users. Although there is a long tradition of research into human road user interactions, there is a lack of shared models and terminology to support cross-disciplinary research and development towards safe and acceptable interaction-capable HAVs. Here, we review the main themes and findings in previous theoretical and empirical interaction research, and find large variability in perspectives and terminologies. We unify these perspectives in a structured, cross-theoretical conceptual framework, describing what road traffic interactions are, how they arise, and how they get resolved. Two key contributions are: (1) a stringent definition of âinteractionâ, as âa situation where the behaviour of at least two road users can be interpreted as being influenced by the possibility that they are both intending to occupy the same region of space at the same time in the near futureâ, and (2) a taxonomy of the types of behaviours that road users exhibit in interactions. We hope that this conceptual framework will be useful in the development of improved empirical methodology, theoretical models, and technical requirements on vehicle automation
A Novel Method of Determining Portal Systemic Shunting using Biodegradable 99TCm Labelled Albumin Microspheres
Portal systemic shunting (PSS) and portal pressure were measured in control rats and in animals
with portal hypertension induced by partial portal vein ligation (PPVL). The portal pressure in
rats with partial portal vein ligation (13.4 ± 0.5 mm.Hg.) was significantly higher (p < 0.005) than
in the control group (9.6 ± 0.6 mm.Hg.). Portal systemic shunting measured by consecutive
injections of radiolabelled methylene diphosphonate (MDP), a non-diffusable marker and
albumin microspheres directly into the splenic pulp was significantly increased (P < 0.005) in the
portal hypertensive animals (30.8 ± 2.5%) compared to sham operated rats (2.6 ± 1.5%). Similarly,
in portal hypertensive rats portal systemic shunting measured by intrasplenic injections of
radiolabelled cobalt microspheres (37.1 ± 3.9%) was significantly greater (p < 0.005) than in
control animals. There was a good correlation and agreement (r = 00.97) between the two
methods of measuring portal systemic shunting. However because the 99Tcm-albumin microspheres
are biodegradable the method allows portal systemic shunting to be measured in man.
Furthermore since the computer adjusts the baseline to zero after each determination of portal
systemic shunting the methodology allows repeated measurements to be made
Impact of electron correlations on the k -resolved electronic structure of PdCrO 2 revealed by Compton scattering
Delafossite PdCrO2 is an intriguing material which displays nearly-free electron and Mott insulating behaviour in different layers. Both angle-resolved photoemission spectroscopy (ARPES) and Compton scattering measurements have established a hexagonal Fermi surface in the materialâs paramagnetic phase. However, the Compton experiment detected an additional structure in the projected occupancy which was originally interpreted as an additional Fermi surface feature not seen by ARPES. Here, we revisit this interpretation of the Compton data. State-of-the-art density functional theory (DFT) with dynamical mean field theory (DMFT), the so-called DFT+DMFT method, predicts the Mott insulating state along with a single hexagonal Fermi surface in excellent agreement with ARPES and Compton. However, DFT+DMFT fails to predict the intensity of the additional spectral weight feature observed in the Compton data. We infer that this discrepancy may arise from the DFT+DMFT not being able to correctly predict certain features in the shape and dispersion of the unoccupied quasiparticle band near the Fermi level. Therefore, a theoretical description beyond our DFT+DMFT model is needed to incorporate vital electron interactions, such as inter-layer electron coupling interactions which for PdCrO2 gives rise to the Kondo-like so-called intertwined excitation
Hydrodynamics of the stream-disk impact in interacting binaries
We use hydrodynamic simulations to provide quantitative estimates of the
effects of the impact of the accretion stream on disks in interacting binaries.
For low accretion rates, efficient radiative cooling of the hotspot region can
occur, and the primary consequence of the stream impact is stream overflow
toward smaller disk radii. The stream is well described by a ballistic
trajectory, but larger masses of gas are swept up and overflow at smaller, but
still highly supersonic, velocities. If cooling is inefficient, overflow still
occurs, but there is no coherent stream inward of the disk rim. Qualitatively,
the resulting structure appears as a bulge extending downstream along the disk
rim. We calculate the mass fraction and velocity of the overflowing component
as a function of the important system parameters, and discuss the implications
of the results for X-ray observations and doppler tomography of cataclysmic
variables, low-mass X-ray binaries and supersoft X-ray sources.Comment: 16 pages, including 8 figures. 1 color figure as a jpeg. ApJ, in
pres
Changing legal systems: Abrogation and annulment. Part I: Revision of defeasible theories
In this paper we investigate how to model legal abrogation and annulment in Defeasible Logic. We examine some options that embed in this setting, and similar rule-based systems, ideas from belief and base revision. In both cases, our conclusion is negative, which suggests to adopt a different logical model
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Moving and handling and managing physiological deterioration of deceased children in hospice cool rooms: practice guidelines for care after death
YesChildrenâs hospices provide a range of services for babies, children and young people who have life-shortening conditions, including care after death in specialist âcool bedroomsâ. Caring for children after death is a challenging area of hospice care, with variation seen within, and between organisations. The study aims to identify current practices and to produce guidelines that promote safe practice in moving and handling and managing physiological deterioration of children after death.
An electronic questionnaire was sent to all 54 British childrenâs hospices; 33 responded (=62% of hospices). Variation in the way in which childrenâs hospices delivered care after death was identified, in terms of the length of stay, care provision and equipment used, owing to demands of individual families and the experience and confidence of practitioners. Internal
variation in practice can lead to practitioner anxiety, and risk-taking when providing care, particularly in the presence of family members. Practice recommendations have been made that reflect the practical demands of caring for a childâs body after death; these have been split into two parts: moving and handling considerations and managing physiological deterioration.
These recommendations should be used to support the development of policy and practice, allowing organisations to standardise staff expectations and to support practitioners when caring for children after death
Bulk and element specific magnetism of the medium and high entropy Cantor-Wu alloys
Magnetic Compton scattering, x-ray magnetic circular dichroism spectroscopy
and bulk magnetometry measurements are performed on a set of medium (NiFeCo and
NiFeCoCr) and high (NiFeCoCrPd and NiFeCoCrMn) entropy Cantor-Wu alloys. The
bulk spin momentum densities determined by magnetic Compton scattering are
remarkably isotropic, and this is a consequence of the smearing of the
electronic structure by disorder scattering of the electron quasiparticles.
Non-zero x-ray magnetic circular dichroism signals are observed for every
element in every alloy indicating differences in the populations of the
majority and minority spin states implying finite magnetic moments. When Cr is
included in the solid solution, the Cr spin moment is unambiguously
antiparallel to the total magnetic moment, while a vanishingly small magnetic
moment is observed for Mn, despite calculations indicating a large moment. Some
significant discrepancies are observed between the experimental bulk and
surface magnetic moments. Despite the lack of quantitative agreement, the
element specific surface magnetic moments seem to be qualitatively reasonable
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