20,293 research outputs found
Progressive managerial bonuses in a spatial Bertrand duopoly
The relationship of managerial bonuses and profit maximization is interesting both from an economic and a managerial viewpoint. Our contribution to this literature is showing that progressive managerial bonuses can increase profits in a spatial Bertrand competition, and furthermore they can help collusion
Tunnel Spin Polarization Versus Energy for Clean and Doped Al2O3 Barriers
The variation of the tunnel spin-polarization (TSP) with energy is determined using a magnetic tunnel transistor, allowing quantification of the energy dependent TSP separately for both ferromagnet/insulator interfaces and direct correlation with the tunnel magnetoresistance (TMR) measured in the same device. The intrinsic TSP is reduced below the Fermi level, and more strongly so for tunneling into empty states above the Fermi level. For artificially doped barriers, the low bias TMR decreases due to defect-assisted tunneling. Yet, this mechanism becomes ineffective at large bias, where instead inelastic spin scattering causes a strong TMR decay
Omphale: Streamlining the Communication for Jobs in a Multi Processor System on Chip
Our Multi Processor System on Chip (MPSoC) template provides processing tiles that are connected via a network on chip. A processing tile contains a processing unit and a Scratch Pad Memory (SPM). This paper presents the Omphale tool that performs the first step in mapping a job, represented by a task graph, to such an MPSoC, given the SPM sizes as constraints. Furthermore a memory tile is introduced. The result of Omphale is a Cyclo Static DataFlow (CSDF) model and a task graph where tasks communicate via sliding windows that are located in circular buffers. The CSDF model is used to determine the size of the buffers and the communication pattern of the data. A buffer must fit in the SPM of the processing unit that is reading from it, such that low latency access is realized with a minimized number of stall cycles. If a task and its buffer exceed the size of the SPM, the task is examined for additional parallelism or the circular buffer is partly located in a memory tile. This results in an extended task graph that satisfies the SPM size constraints
The Right Mutation Strength for Multi-Valued Decision Variables
The most common representation in evolutionary computation are bit strings.
This is ideal to model binary decision variables, but less useful for variables
taking more values. With very little theoretical work existing on how to use
evolutionary algorithms for such optimization problems, we study the run time
of simple evolutionary algorithms on some OneMax-like functions defined over
. More precisely, we regard a variety of
problem classes requesting the component-wise minimization of the distance to
an unknown target vector . For such problems we see a crucial
difference in how we extend the standard-bit mutation operator to these
multi-valued domains. While it is natural to select each position of the
solution vector to be changed independently with probability , there are
various ways to then change such a position. If we change each selected
position to a random value different from the original one, we obtain an
expected run time of . If we change each selected position
by either or (random choice), the optimization time reduces to
. If we use a random mutation strength with probability inversely proportional to and change
the selected position by either or (random choice), then the
optimization time becomes , bringing down
the dependence on from linear to polylogarithmic. One of our results
depends on a new variant of the lower bounding multiplicative drift theorem.Comment: an extended abstract of this work is to appear at GECCO 201
Fast and Simple Relational Processing of Uncertain Data
This paper introduces U-relations, a succinct and purely relational
representation system for uncertain databases. U-relations support
attribute-level uncertainty using vertical partitioning. If we consider
positive relational algebra extended by an operation for computing possible
answers, a query on the logical level can be translated into, and evaluated as,
a single relational algebra query on the U-relation representation. The
translation scheme essentially preserves the size of the query in terms of
number of operations and, in particular, number of joins. Standard techniques
employed in off-the-shelf relational database management systems are effective
for optimizing and processing queries on U-relations. In our experiments we
show that query evaluation on U-relations scales to large amounts of data with
high degrees of uncertainty.Comment: 12 pages, 14 figure
Spin injection and perpendicular spin transport in graphite nanostructures
Organic and carbon-based materials are attractive for spintronics because
their small spin-orbit coupling and low hyperfine interaction is expected to
give rise to large spin-relaxation times. However, the corresponding
spin-relaxation length is not necessarily large when transport is via weakly
interacting molecular orbitals. Here we use graphite as a model system and
study spin transport in the direction perpendicular to the weakly bonded
graphene sheets. We achieve injection of highly (75%) spin-polarized electrons
into graphite nanostructures of 300-500 nm across and up to 17 nm thick, and
observe transport without any measurable loss of spin information. Direct
visualization of local spin transport in graphite-based spin-valve sandwiches
also shows spatially uniform and near-unity transmission for electrons at 1.8
eV above the Fermi level
Spin-1/2 Triangular Lattice with Orbital Degeneracy in a Metallic Oxide Ag2NiO2
A novel metallic and magnetic transition metal oxide Ag2NiO2 is studied by
means of resistivity, magnetic susceptibility, specific heat and X-ray
diffraction. The crystal structure is characterized by alternating stacking of
a Ni3+O2 layer and a (Ag2)+ layer, the former realizing a spin-1/2 triangular
lattice with eg orbital degeneracy and the latter providing itinerant
electrons. It is found that the NiO2 layer exhibits orbital ordering at Ts =
260 K and antiferromagnetic spin ordering at TN = 56 K. Moreover, a moderately
large mass enhancement is found for the itinerant electrons, suggesting a
significant contribution from the nearly localized Ni 3d state to the Ag 5s
state that forms a broad band.Comment: 9 pages, 5 figures, to be published in Rapid Communications, Phys.
Rev.
- …