101,084 research outputs found
On cost-effective communication network designing
How to efficiently design a communication network is a paramount task for
network designing and engineering. It is, however, not a single objective
optimization process as perceived by most previous researches, i.e., to
maximize its transmission capacity, but a multi-objective optimization process,
with lowering its cost to be another important objective. These two objectives
are often contradictive in that optimizing one objective may deteriorate the
other. After a deep investigation of the impact that network topology, node
capability scheme and routing algorithm as well as their interplays have on the
two objectives, this letter presents a systematic approach to achieve a
cost-effective design by carefully choosing the three designing aspects. Only
when routing algorithm and node capability scheme are elegantly chosen can
BA-like scale-free networks have the potential of achieving good tradeoff
between the two objectives. Random networks, on the other hand, have the
built-in character for a cost-effective design, especially when other aspects
cannot be determined beforehand.Comment: 6 pages, 4 figure
QCD Evolutions of Twist-3 Chirality-Odd Operators
We study the scale dependence of twist-3 distributions defined with
chirality-odd quark-gluon operators. To derive the scale dependence we
explicitly calculate these distributions of multi-parton states instead of a
hadron. Taking one-loop corrections into account we obtain the leading
evolution kernel in the most general case. In some special cases the evolutions
are simplified. We observe that the obtained kernel in general does not get
simplified in the large- limit in contrast to the case of those twist-3
distributions defined only with chirality-odd quark operators. In the later,
the simplification is significant.Comment: 9 pages, 2 figure
Octupole degree of freedom for the critical-point candidate nucleus Sm in a reflection-asymmetric relativistic mean-field approach
The potential energy surfaces of even-even Sm are investigated in
the constrained reflection-asymmetric relativistic mean-field approach with
parameter set PK1. It is shown that the critical-point candidate nucleus
Sm marks the shape/phase transition not only from U(5) to SU(3)
symmetry, but also from the octupole-deformed ground state in Sm to the
quadrupole-deformed ground state in Sm. By including the octupole
degree of freedom, an energy gap near the Fermi surface for single-particle
levels in Sm with is found, and the
important role of the octupole deformation driving pair and is demonstrated.Comment: 11 pages, 3 figure
Impact of pairing correlations on the orientation of the nuclear
For the first time, the tilted axis cranking covariant density functional
theory with pairing correlations has been formulated and implemented in a fully
self-consistent and microscopic way to investigate the evolution of the spin
axis and the pairing effects in rotating triaxial nuclei. The measured energy
spectrum and transition probabilities for the Nd-135 yrast band are reproduced
well without any ad hoc renormalization factors when pairing effects are taken
into account. A transition from collective to chiral rotation has been
demonstrated. It is found that pairing correlations introduce additional
admixtures in the single-particle orbitals, and, thus, influence the structure
of tilted axis rotating nuclei by reducing the magnitude of the proton and
neutron angular momenta while merging their direction.Comment: 13 pages, 5 figure
Revenue maximizing envy-free fixed-price auctions with budgets
Traditional incentive-compatible auctions [6,16] for selling multiple goods to unconstrained and budgeted bidders can discriminate between bidders by selling identical goods at different prices. For this reason, Feldman et al. [7] dropped incentive compatibility and turned the attention to revenue maximizing envy-free item-pricing allocations for budgeted bidders. Envy-free allocations were suggested by classical papers [9,15]. The key property of such allocations is that no one envies the allocation and the price charged to anyone else. In this paper we consider this classical notion of envy-freeness and study fixed-price mechanisms which use nondiscriminatory uniform prices for all goods. Feldman et al. [7] gave an item-pricing mechanism that obtains 1/2 of the revenue obtained from any envy-free fixed-price mechanism for identical goods. We improve over this result by presenting an FPTAS for the problem that returns an (1 − ε)-approximation of the revenue obtained by any envy-free fixed-price mechanism for any ε > 0 and runs in polynomial time in the number of bidders n and 1/ ε even for exponential supply of goods m. Next, we consider the case of budgeted bidders with matching-type preferences on the set of goods, i.e., the valuation of each bidder for each item is either v i or 0. In this more general case, we prove that it is impossible to approximate the optimum revenue within O( min (n,m)1/2 − ε ) for any ε > 0 unless P = NP. On the positive side, we are able to extend the FPTAS for identical goods to budgeted bidders in the case of constant number of different types of goods. Our FPTAS gives also a constant approximation with respect to the general envy-free auction
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