6,500 research outputs found
A data envelopment analysis approach to multicriteria decision problems with incomplete information
AbstractAs a decision aid for discrete multicriteria decision problems, this paper proposes a multilevel graph of alternatives to represent the ranking, to the extent that this is possible when incomplete information on weights is available under the assumption of the additive value function. To construct it, the nested decomposition of the set of alternatives is established along the lines of data envelopment analysis (DEA). A numerical example is given to illustrate a multilevel graph based on the nested decomposition and compare it with the hierarchical dominance graph based on dominance relations proposed by Park and Kim
An Efficient Algorithm for Enumerating Chordless Cycles and Chordless Paths
A chordless cycle (induced cycle) of a graph is a cycle without any
chord, meaning that there is no edge outside the cycle connecting two vertices
of the cycle. A chordless path is defined similarly. In this paper, we consider
the problems of enumerating chordless cycles/paths of a given graph
and propose algorithms taking time for each chordless cycle/path. In
the existing studies, the problems had not been deeply studied in the
theoretical computer science area, and no output polynomial time algorithm has
been proposed. Our experiments showed that the computation time of our
algorithms is constant per chordless cycle/path for non-dense random graphs and
real-world graphs. They also show that the number of chordless cycles is much
smaller than the number of cycles. We applied the algorithm to prediction of
NMR (Nuclear Magnetic Resonance) spectra, and increased the accuracy of the
prediction
Anisotropic magnetic fluctuations in the ferromagnetic superconductor UCoGe studied by angle-resolved ^{59}Co NMR
We have carried out direction-dependent ^{59}Co NMR experiments on a single
crystal sample of the ferromagnetic superconductor UCoGe in order to study the
magnetic properties in the normal state. The Knight shift and nuclear
spin-lattice relaxation rate measurements provide microscopic evidence that
both static and dynamic susceptibilities are ferromagnetic with strong Ising
anisotropy. We discuss that superconductivity induced by these magnetic
fluctuations prefers spin-triplet pairing state.Comment: 4 pages, 4 figure
Slow-roll Inflation with the Gauss-Bonnet and Chern-Simons Corrections
We study slow-roll inflation with the Gauss-Bonnet and Chern-Simons
corrections. We obtain general formulas for the observables: spectral indices,
tensor-to-scalar ratio and circular polarization of gravitational waves. The
Gauss-Bonnet term violates the consistency relation r = -8n_T. Particularly,
blue spectrum n_T > 0 and scale invariant spectrum |8n_T|/r << 1 of tensor
modes are possible. These cases require the Gauss-Bonnet coupling function of
\xi _{,\phi } \sim 10^8/M_{Pl}. We use examples to show new-inflation-type
potential with 10M_{Pl} symmetry breaking scale and potential with flat region
in \phi \gtrsim 10M_{Pl} lead to observationally consistent blue and scale
invariant spectra, respectively. Hence, these interesting cases can actually be
realized. The Chern-Simons term produce circularly polarized tensor modes. We
show an observation of these signals supports existence of the Chern-Simons
coupling function of \omega _{,\phi } \sim 10^8/M_{Pl}. Thus, with future
observations, we can fix or constrain the value of these coupling functions, at
the CMB scale.Comment: 21 pages, 5 figure
Design of Sliding Mode Techniques for a CMG-based Testbed Attitude Control System
Precise pointing accuracy and rapid maneuvering are two key features for attitude control missions of small spacecraft. Control moment gyroscopes (CMGs) are applied as ideal actuator for large torque output capability but are usually limited due to the problem of inherent mechanical singularity. This paper proposes a robust attitude control methodology, based on Sliding Mode Control (SMC) techniques, in presence of CMG practical restrictions and disturbances. Two second-order SMC techniques are designed, to guarantee accuracy and limited convergence time. Moreover, attitude control torques are generated by means of four single gimbal CMGs in pyramidal configuration, considering the design of an experimental testbed. The effectiveness of the proposed methodologies are shown in simulations, for different mission scenarios, including singularity points
Environment related practices for emergency response to infectious disease outbreak on cruise ships
ISSUE/PROBLEM: COVID-19 pandemic halted cruise operations globally. This project explored strategies and measures that could be adopted internationally for mitigating a disease outbreak on-board of a cruise ship by bringing evidence-based recommendations for an emergency response against current COVID-19 outbreak and future infectious threats. DESCRIPTION OF THE PROBLEM: Research took place in October 2020-March 2021. Methods comprised of: a) consultation sessions with five international experts on public health, epidemiology, tourism and cruise management, b) both systematic and narrative literature reviews. Present guidance analysed why cruise ships promote an opportunistic environment for infectious outbreaks, along with a strategy for reducing the risks among passengers and crew. RESULTS: Results were organised under four main themes: a) advice on surface interactions and virus viability; b) prevention and control measures; c) suggestions on short and long term responses; d) advice on thermal and ventilation conditions and how they affect virus transmission. The guidance was very similar to other built environment contexts, ignoring the particularities of sociospatial interactions in cruise ships. Moreover, there was limited provision for the wellbeing and mental health during the outbreak. LESSONS: This project summarised recommendations for the preparedness of cruise ships during a pandemic from ports, off-board and on-board measures to repatriation. Demonstrated the importance of spatial characteristics in the preparedness of a ship. Pointed the effect pandemic can have upon crew and passengers. This needs to be taken into account when operations restart. Cruise experience would have to change due to covid-19, especially when social activity on board has to be restricted. The importance of future studies focusing on how this change will impact cruise industry arose, including crew hygiene, safety and supporting mental health during outbreaks. KEY MESSAGES: Multi-disciplinary approach on providing a set of recommendations for emergency response to infectious disease outbreak on cruise ships including environmental preparedness. Actions should include also the mental health of crew and passengers on copying with stress during infectious outbreaks
Decoupled and inhomogeneous gas flows in S0 galaxies
A recent analysis of the "Einstein" sample of early-type galaxies has
revealed that at any fixed optical luminosity Lb S0 galaxies have lower mean
X-ray luminosity Lx per unit Lb than ellipticals. Following a previous
analytical investigation of this problem (Ciotti & Pellegrini 1996), we have
performed 2D numerical simulations of the gas flows inside S0 galaxies in order
to ascertain the effectiveness of rotation and/or galaxy flattening in reducing
the Lx/Lb ratio. The flow in models without SNIa heating is considerably
ordered, and essentially all the gas lost by the stars is cooled and
accumulated in the galaxy center. If rotation is present, the cold material
settles in a disk on the galactic equatorial plane. Models with a time
decreasing SNIa heating host gas flows that can be much more complex. After an
initial wind phase, gas flows in energetically strongly bound galaxies tend to
reverse to inflows. This occurs in the polar regions, while the disk is still
in the outflow phase. In this phase of strong decoupling, cold filaments are
created at the interface between inflowing and outflowing gas. Models with more
realistic values of the dynamical quantities are preferentially found in the
wind phase with respect to their spherical counterparts of equal Lb. The
resulting Lx of this class of models is lower than in spherical models with the
same Lb and SNIa heating. At variance with cooling flow models, rotation is
shown to have only a marginal effect in this reduction, while the flattening is
one of the driving parameters for such underluminosity, in accordance with the
analytical investigation.Comment: 32 pages LaTex file, plus 5 .ps figures and macro aasms4.sty --
Accepted on Ap
Superconductivity induced by longitudinal ferromagnetic fluctuations in UCoGe
From detailed angle-resolved NMR and Meissner measurements on a ferromagnetic
(FM) superconductor UCoGe (T_Curie ~ 2.5 K and T_SC ~ 0.6 K), we show that
superconductivity in UCoGe is tightly coupled with longitudinal FM spin
fluctuations along the c axis. We found that magnetic fields along the c axis
(H || c) strongly suppress the FM fluctuations and that the superconductivity
is observed in the limited magnetic field region where the longitudinal FM spin
fluctuations are active. These results combined with model calculations
strongly suggest that the longitudinal FM spin fluctuations tuned by H || c
induce the unique spin-triplet superconductivity in UCoGe. This is the first
clear example that FM fluctuations are intimately related with
superconductivity.Comment: 4 pages, 5 figures, to appear in PR
Discovery of TUG-770: a highly potent free fatty acid receptor 1 (FFA1/GPR40) agonist for treatment of type 2 diabetes
Free fatty acid receptor 1 (FFA1 or GPR40) enhances glucose-stimulated insulin secretion from pancreatic β-cells and currently attracts high interest as a new target for the treatment of type 2 diabetes. We here report the discovery of a highly potent FFA1 agonist with favorable physicochemical and pharmacokinetic properties. The compound efficiently normalizes glucose tolerance in diet-induced obese mice, an effect that is fully sustained after 29 days of chronic dosing
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