18,634 research outputs found
Perceived Risk, Product Returns, and Optimal Resource Allocation: Evidence from a Field Experiment
Relatively few retailers include metrics such as product returns in their customer selection and optimal resource allocation algorithms when measuring and maximizing customer value. Even when they do include this metric, increases in product return behavior are usually considered merely an economic cost that must be managed by decreasing the marketing resource allocations toward the customers making the returns. However, recent research has suggested that satisfactory product return experiences can actually benefit firms by lowering the customer’s perceived risk of current and future purchases. To better understand the role of this perceived risk in the firm–customer exchange process, the authors conduct a large-scale customer selection and optimal resource allocation field experiment with 26,000 customers from an online retailer over six months. They find that the firm is able to increase both its short and long-term profits when accounting for the perceived risk related to product returns in addition to managing product return costs. Furthermore, the authors find that by including this risk, rather than simply implementing traditional customer lifetime value–based models generically, the firm can target more profitable customers
On the distribution of career longevity and the evolution of home run prowess in professional baseball
Statistical analysis is a major aspect of baseball, from player averages to
historical benchmarks and records. Much of baseball fanfare is based around
players exceeding the norm, some in a single game and others over a long
career. Career statistics serve as a metric for classifying players and
establishing their historical legacy. However, the concept of records and
benchmarks assumes that the level of competition in baseball is stationary in
time. Here we show that power-law probability density functions, a hallmark of
many complex systems that are driven by competition, govern career longevity in
baseball. We also find similar power laws in the density functions of all major
performance metrics for pitchers and batters. The use of performance-enhancing
drugs has a dark history, emerging as a problem for both amateur and
professional sports. We find statistical evidence consistent with
performance-enhancing drugs in the analysis of home runs hit by players in the
last 25 years. This is corroborated by the findings of the Mitchell Report [1],
a two-year investigation into the use of illegal steroids in major league
baseball, which recently revealed that over 5 percent of major league baseball
players tested positive for performance-enhancing drugs in an anonymous 2003
survey.Comment: 5 pages, 5 figures, 2-column revtex4 format. Revision has change of
title, a figure added, and minor changes in response to referee comment
Isoperimetric Inequalities for Minimal Submanifolds in Riemannian Manifolds: A Counterexample in Higher Codimension
For compact Riemannian manifolds with convex boundary, B.White proved the
following alternative: Either there is an isoperimetric inequality for minimal
hypersurfaces or there exists a closed minimal hypersurface, possibly with a
small singular set. There is the natural question if a similar result is true
for submanifolds of higher codimension. Specifically, B.White asked if the
non-existence of an isoperimetric inequality for k-varifolds implies the
existence of a nonzero, stationary, integral k-varifold. We present examples
showing that this is not true in codimension greater than two. The key step is
the construction of a Riemannian metric on the closed four-dimensional ball B
with the following properties: (1) B has strictly convex boundary. (2) There
exists a complete nonconstant geodesic. (3) There does not exist a closed
geodesic in B.Comment: 11 pages, We changed the title and added a section that exhibits the
relation between our example and the question posed by Brian White concerning
isoperimetric inequalities for minimal submanifold
Risk-based Surveillance of Antimicrobial Residues – Identification of Potential Risk Factors
Today in Denmark, residue surveillance is conducted at random. However, if the surveillance is targeted to high-risk finisher pig herds, then the number of samples can be reduced whereby resources can be saved without jeopardizing public health. An analysis of Danish data covering 2.5 years has shown that finisher pig herds with a very high prevalence of chronic pleuritis have a higher risk of residue findings in the surveillance programme. If this is incorporated into the own control, then cost savings of 25% can be obtained. However, as shown in the Danish data there are other reasons for the presence of residues such as miscommunication and insufficient marking of treated animals. Such cases should be prevented through information campaigns addressed to the farmers and their advisors
Particle production and equilibrium properties within a new hadron transport approach for heavy-ion collisions
The microscopic description of heavy-ion reactions at low beam energies is
achieved within hadronic transport approaches. In this article a new approach
SMASH (Simulating Many Accelerated Strongly-interacting Hadrons) is introduced
and applied to study the production of non-strange particles in heavy-ion
reactions at GeV. First, the model is described including
details about the collision criterion, the initial conditions and the resonance
formation and decays. To validate the approach, equilibrium properties such as
detailed balance are presented and the results are compared to experimental
data for elementary cross sections. Finally results for pion and proton
production in C+C and Au+Au collisions is confronted with HADES and FOPI data.
Predictions for particle production in collisions are made.Comment: 30 pages, 30 figures, replaced with published version; only minor
change
An Ultra-Stable Referenced Interrogation System in the Deep Ultraviolet for a Mercury Optical Lattice Clock
We have developed an ultra-stable source in the deep ultraviolet, suitable to
fulfill the interrogation requirements of a future fully-operational lattice
clock based on neutral mercury. At the core of the system is a Fabry-P\'erot
cavity which is highly impervious to temperature and vibrational perturbations.
The mirror substrate is made of fused silica in order to exploit the
comparatively low thermal noise limits associated with this material. By
stabilizing the frequency of a 1062.6 nm Yb-doped fiber laser to the cavity,
and including an additional link to LNE-SYRTE's fountain primary frequency
standards via an optical frequency comb, we produce a signal which is both
stable at the 1E-15 level in fractional terms and referenced to primary
frequency standards. The signal is subsequently amplified and frequency-doubled
twice to produce several milliwatts of interrogation signal at 265.6 nm in the
deep ultraviolet.Comment: 7 pages, 6 figure
Sliding mode control of quantum systems
This paper proposes a new robust control method for quantum systems with
uncertainties involving sliding mode control (SMC). Sliding mode control is a
widely used approach in classical control theory and industrial applications.
We show that SMC is also a useful method for robust control of quantum systems.
In this paper, we define two specific classes of sliding modes (i.e.,
eigenstates and state subspaces) and propose two novel methods combining
unitary control and periodic projective measurements for the design of quantum
sliding mode control systems. Two examples including a two-level system and a
three-level system are presented to demonstrate the proposed SMC method. One of
main features of the proposed method is that the designed control laws can
guarantee desired control performance in the presence of uncertainties in the
system Hamiltonian. This sliding mode control approach provides a useful
control theoretic tool for robust quantum information processing with
uncertainties.Comment: 18 pages, 4 figure
Variable Stars in the Unusual, Metal-Rich Globular Cluster NGC 6388
We have undertaken a search for variable stars in the metal-rich globular
cluster NGC 6388 using time-series BV photometry. Twenty-eight new variables
were found in this survey, increasing the total number of variables found near
NGC 6388 to ~57. A significant number of the variables are RR Lyrae (~14), most
of which are probable cluster members. The periods of the fundamental mode RR
Lyrae are shown to be unusually long compared to metal-rich field stars. The
existence of these long period RRab stars suggests that the horizontal branch
of NGC 6388 is unusually bright. This implies that the metallicity-luminosity
relationship for RR Lyrae stars is not universal if the RR Lyrae in NGC 6388
are indeed metal-rich. We consider the alternative possibility that the stars
in NGC 6388 may span a range in [Fe/H]. Four candidate Population II Cepheids
were also found. If they are members of the cluster, NGC 6388 would be the most
metal-rich globular cluster to contain Population II Cepheids. The mean V
magnitude of the RR Lyrae is found to be 16.85+/-0.05 resulting in a distance
of 9.0 to 10.3 kpc, for a range of assumed values of for RR Lyrae. We
determine the reddening of the cluster to be E(B-V)=0.40+/-0.03 mag, with
differential reddening across the face of the cluster. We discuss the
difficulty in determining the Oosterhoff classification of NGC 6388 and NGC
6441 due to the unusual nature of their RR Lyrae, and address evolutionary
constraints on a recent suggestion that they are of Oosterhoff type II.Comment: 35 pages, 16 figures, emulateapj5/apjfonts style. Astronomical
Journal, in press. We recommend the interested reader to download instead the
preprint with full-resolution figures, which can be found at
http://www.noao.edu/noao/staff/pritzl/clusters.htm
Strong spin-orbit splitting on Bi surfaces
Using first-principles calculations and angle-resolved photoemission, we show
that the spin-orbit interaction leads to a strong splitting of the surface
state bands on low-index surfaces of Bi. The dispersion of the states and the
corresponding Fermi surfaces are profoundly modified in the whole surface
Brillouin zone. We discuss the implications of these findings with respect to a
proposed surface charge density wave on Bi(111) as well as to the surface
screening, surface spin-density waves, electron (hole) dynamics in surface
states, and to possible applications to the spintronics.Comment: 4 pages 2 figure
Specific probes efficiently distinguish root-knot nematode species using signature sequences in the ribosomal intergenic spacer
Ont été établies des sondes moléculaires - destinées à identifier les espèces de #Meloidogyne - grâce à des différences spécifiques dans l'espaceur intergénique (IGS) de l'ADN ribosomal. Les séquences de nucléotides de l'IGS ont été obtenues en séquençant l'ADN amplifiée par PCR. L'alignement des séquences de l'IGS de #M. chitwoodi et #M. fallax a révélé plusieurs régions contenant des différences localisées. Des amorces PCR ont été synthétisées qui ont donné des produits d'amplification spécifiques lorsqu'utilisées avec des produits d'amorce non spécifiques, ont pu être séparés par leur taille dans un gel d'agarose, procurant ainsi un test fiable et précis ne nécessitant pas de restriction enzymatique. L'amplification de l'ADN d'un nématode juvénile ou d'un oeuf par PCR multiplex a permis d'identifier #M. chitwoodi et #M. fallax et de les séparer de #M. hapla, #M. javanica, #M. arenaria et #M. mayaguensis$. (Résumé d'auteur
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