4,333 research outputs found
A tight lower bound for an online hypercube packing problem and bounds for prices of anarchy of a related game
We prove a tight lower bound on the asymptotic performance ratio of
the bounded space online -hypercube bin packing problem, solving an open
question raised in 2005. In the classic -hypercube bin packing problem, we
are given a sequence of -dimensional hypercubes and we have an unlimited
number of bins, each of which is a -dimensional unit hypercube. The goal is
to pack (orthogonally) the given hypercubes into the minimum possible number of
bins, in such a way that no two hypercubes in the same bin overlap. The bounded
space online -hypercube bin packing problem is a variant of the
-hypercube bin packing problem, in which the hypercubes arrive online and
each one must be packed in an open bin without the knowledge of the next
hypercubes. Moreover, at each moment, only a constant number of open bins are
allowed (whenever a new bin is used, it is considered open, and it remains so
until it is considered closed, in which case, it is not allowed to accept new
hypercubes). Epstein and van Stee [SIAM J. Comput. 35 (2005), no. 2, 431-448]
showed that is and , and conjectured that
it is . We show that is in fact . To
obtain this result, we elaborate on some ideas presented by those authors, and
go one step further showing how to obtain better (offline) packings of certain
special instances for which one knows how many bins any bounded space algorithm
has to use. Our main contribution establishes the existence of such packings,
for large enough , using probabilistic arguments. Such packings also lead to
lower bounds for the prices of anarchy of the selfish -hypercube bin packing
game. We present a lower bound of for the pure price of
anarchy of this game, and we also give a lower bound of for
its strong price of anarchy
Is the Eldest Son Different? The Residential Choice of Siblings in Japan
In this paper, we analyze the determinants of the living arrangements (coresidence behavior) of elderly parents and their children (whether elderly parents live with their children, and if so, with which child) in Japan using micro data from a household survey. Our results provide support for all four explanations of coresidence behavior but especially for the life cycle and dynasty models (both of which assume selfishly motivated parents) and social norms and traditions: The fact that parents who were self-employed before retirement are more likely to live with their children, the fact that parents are less likely to live with sons who adopt their wife’s surname, and the fact that parents are more likely to live with daughters whose husbands adopt their surname constitute evidence in favor of the dynasty model. The fact that parents who were (relatively wealthy) executives before retirement and parents who are homeowners are more likely to live with their children and the fact that parents are more likely to live with less educated children constitute evidence in favor of the selfish life cycle model (or the altruism model). And the fact that parental attitudes toward their children affect their coresidence behavior, the fact that parents are more likely to live with their eldest child if their eldest child is a son, and the fact that parents are most likely to live with their eldest son even if he is not the eldest child constitute evidence in favor of social norms and traditions.
Evaluation of scanning earth sensor mechanism on engineering test satellite 4
The results of the analysis and the evaluation of flight data obtained from the horizon sensor test project are described. The rotary mechanism of the scanning earth sensor composed of direct drive motor and bearings using solid lubricant is operated satisfactorily. The transmitted flight data from Engineering Test Satellite IV was evaluated in comparison with the design value
On k-leaf-connected graphs
AbstractA graph G is Hamilton-connected if given any two vertices u and v of G, there is a Hamilton path in G with ends u and v. In this note we consider a generalization of this property. For k ≥ 2 we say that a graph G = (VG, EG) is k-leaf-connected if |VG| > k and given any subset S of VG with |S| = k, G has a spanning tree T such that the set S is the set of endvertices of T. Thus a graph is 2-leaf-connected if and only if it is Hamilton-connected. This generalization is due to U. S. R. Murty. We prove that the k-leaf-connectedness property is (|VG| + k − 1)-stable, give sufficient conditions for a graph to be k-leaf-connected, present some necessary conditions and other related results. We show that for all naturals n, k, 2 ≤ k < n − 2, there is a sparse k-leaf-connected graph of order n
Ground state of graphite ribbons with zigzag edges
We study the interaction effects on the ground state of nanographite ribbons
with zigzag edges. Within the mean-field approximation, we found that there are
two possible phases: the superconducting (SC) phase and the excitonic insulator
(EI). The two phases are separated by a first-order transition point. After
taking into account the low-lying fluctuations around the mean-field solutions,
the SC phase becomes a spin liquid phase with one gapless charge mode.
On the other hand, all excitations in the EI phase, especially the spin
excitations, are gapped.Comment: 6 pages, 3 figure
Nonuniversal Shot Noise in Disordered Quantum Wires with Channel-Number Imbalance
The number of conducting channels for one propagating direction is equal to
that for the other direction in ordinary quantum wires. However, they can be
imbalanced in graphene nanoribbons with zigzag edges. Employing the model
system in which a degree of channel-number imbalance can be controlled, we
calculate the shot-noise power at zero frequency by using the
Boltzmann-Langevin approach. The shot-noise power in an ordinary diffusive
conductor is one-third of the Poisson value. We show that with increasing the
degree of channel-number imbalance, the universal one-third suppression breaks
down and a highly nonuniversal behavior of shot noise appears.Comment: 10 pages, 3 figure
Novel Orbital Ordering induced by Anisotropic Stress in a Manganite Thin Film
We performed resonant and nonresonant x-ray diffraction studies of a
Nd0.5Sr0.5MnO3 thin film that exhibits a clear first-order transition. Lattice
parameters vary drastically at the metal-insulator transition at 170K (=T_MI),
and superlattice reflections appear below 140K (=T_CO). The electronic
structure between T_MI and T_CO is identified as A-type antiferromagnetic with
the d_{x2-y2} ferroorbital ordering. Below T_CO, a new type of antiferroorbital
ordering emerges. The accommodation of the large lattice distortion at the
first-order phase transition and the appearance of the novel orbital ordering
are brought about by the anisotropy in the substrate, a new parameter for the
phase control.Comment: 4pages, 4figure
Anomalous Enhancement of the Boltzmann Conductivity in Disordered Zigzag Graphene Nanoribbons
We study the conductivity of disordered zigzag graphene nanoribbons in the
incoherent regime by using the Boltzmann equation approach. The band structure
of zigzag nanoribbons contains two energy valleys, and each valley has an
excess one-way channel. The crucial point is that the numbers of conducting
channels for two propagating directions are imbalanced in each valley due to
the presence of an excess one-way channel. It was pointed out that as a
consequence of this imbalance, a perfectly conducting channel is stabilized in
the coherent regime if intervalley scattering is absent. We show that even in
the incoherent regime, the conductivity is anomalously enhanced if intervalley
scattering is very weak. Particularly, in the limit of no intervalley
scattering, the dimensionless conductance approaches to unity with increasing
ribbon length as if there exists a perfectly conducting channel. We also show
that anomalous valley polarization of electron density appears in the presence
of an electric field.Comment: 10 pages, 3 figure
Epitaxial-strain effect on charge/orbital order in Pr0.5Ca0.5MnO3 films
Effect of growth orientation on charge- and orbital-ordering (CO-OO)
phenomena has been studied for Pr0.5Ca0.5MnO3 epitaxial thin films fabricated
on (LaAlO3)0.3-(SrAl0.5Ta0.5O3)0.7 (LSAT) substrates by means of resistivity,
synchrotron x-ray diffraction, and polarized optical microscopy measurements.
CO-OO transition is observed around 220 K for a film grown on an LSAT (011)
substrate ((011)-film), similarly to a bulk sample, while a film grown on a
(001) plane of LSAT ((001)-film) shows much higher transition temperature
around 300 K. The domain size of OO is approximately 3 times as large in the
(011)-film as in the (001)-film. These results demonstrate that various
properties of CO-OO phenomena can be controlled with the growth orientation via
the epitaxial strain from the substrate.Comment: 4 pages, 4 figure
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