13,187 research outputs found
Vertex elimination orderings for hereditary graph classes
We provide a general method to prove the existence and compute efficiently
elimination orderings in graphs. Our method relies on several tools that were
known before, but that were not put together so far: the algorithm LexBFS due
to Rose, Tarjan and Lueker, one of its properties discovered by Berry and
Bordat, and a local decomposition property of graphs discovered by Maffray,
Trotignon and Vu\vskovi\'c. We use this method to prove the existence of
elimination orderings in several classes of graphs, and to compute them in
linear time. Some of the classes have already been studied, namely
even-hole-free graphs, square-theta-free Berge graphs, universally signable
graphs and wheel-free graphs. Some other classes are new. It turns out that all
the classes that we study in this paper can be defined by excluding some of the
so-called Truemper configurations. For several classes of graphs, we obtain
directly bounds on the chromatic number, or fast algorithms for the maximum
clique problem or the coloring problem
Low rank perturbations and the spectral statistics of pseudointegrable billiards
We present an efficient method to solve Schr\"odinger's equation for
perturbations of low rank. In particular, the method allows to calculate the
level counting function with very little numerical effort. To illustrate the
power of the method, we calculate the number variance for two pseudointegrable
quantum billiards: the barrier billiard and the right triangle billiard
(smallest angle ). In this way, we obtain precise estimates for the
level compressibility in the semiclassical (high energy) limit. In both cases,
our results confirm recent theoretical predictions, based on periodic orbit
summation.Comment: 4 page
Hall Conductance of a Two-Dimensional Electron Gas in Periodic Lattice with Triangular Antidots
The topic of this contribution is the investigation of quantum states and
quantum Hall effect in electron gas subjected to a periodic potential of the
lateral lattice. The potential is formed by triangular quantum antidos located
on the sites of the square lattice. In a such system the inversion center and
the four-fold rotation symmetry are absent. The topological invariants which
characterize different magnetic subbands and their Hall conductances are
calculated. It is shown that the details of the antidot geometry are crucial
for the Hall conductance quantization rule. The critical values of lattice
parameters defining the shape of triangular antidots at which the Hall
conductance is changed drastically are determined. We demonstrate that the
quantum states and Hall conductance quantization law for the triangular antidot
lattice differ from the case of the square lattice with cylindrical antidots.
As an example, the Hall conductances of magnetic subbands for different antidot
geometries are calculated for the case when the number of magnetic flux quanta
per unit cell is equal to three.Comment: 6 pages, 5 figure
Geometric Phase, Curvature, and Extrapotentials in Constrained Quantum Systems
We derive an effective Hamiltonian for a quantum system constrained to a
submanifold (the constraint manifold) of configuration space (the ambient
space) by an infinite restoring force. We pay special attention to how this
Hamiltonian depends on quantities which are external to the constraint
manifold, such as the external curvature of the constraint manifold, the
(Riemannian) curvature of the ambient space, and the constraining potential. In
particular, we find the remarkable fact that the twisting of the constraining
potential appears as a gauge potential in the constrained Hamiltonian. This
gauge potential is an example of geometric phase, closely related to that
originally discussed by Berry. The constrained Hamiltonian also contains an
effective potential depending on the external curvature of the constraint
manifold, the curvature of the ambient space, and the twisting of the
constraining potential. The general nature of our analysis allows applications
to a wide variety of problems, such as rigid molecules, the evolution of
molecular systems along reaction paths, and quantum strip waveguides.Comment: 27 pages with 1 figure, submitted to Phys. Rev.
Identifying and prioritising services in European terrestrial and freshwater ecosystems
Ecosystems are multifunctional and provide humanity with a broad array of vital services. Effective management of services requires an improved evidence base, identifying the role of ecosystems in delivering multiple services, which can assist policy-makers in maintaining them. Here, information from the literature and scientific experts was used to systematically document the importance of services and identify trends in their use and status over time for the main terrestrial and freshwater ecosystems in Europe. The results from this review show that intensively managed ecosystems contribute mostly to vital provisioning services (e.g. agro-ecosystems provide food via crops and livestock, and forests provide wood), while semi-natural ecosystems (e.g. grasslands and mountains) are key contributors of genetic resources and cultural services (e.g. aesthetic values and sense of place). The most recent European trends in human use of services show increases in demand for crops from agro-ecosystems, timber from forests, water flow regulation from rivers, wetlands and mountains, and recreation and ecotourism in most ecosystems, but decreases in livestock production, freshwater capture fisheries, wild foods and virtually all services associated with ecosystems which have considerably decreased in area (e.g. semi-natural grasslands). The condition of the majority of services show either a degraded or mixed status across Europe with the exception of recent enhancements in timber production in forests and mountains, freshwater provision, water/erosion/natural hazard regulation and recreation/ecotourism in mountains, and climate regulation in forests. Key gaps in knowledge were evident for certain services across all ecosystems, including the provision of biochemicals and natural medicines, genetic resources and the regulating services of seed dispersal, pest/disease regulation and invasion resistance
Commentary on 'What is the point: will screening mammography save my life?' by Keen and Keen
Commentary on Keen and Keen 'What is the point: will screening mammography save my life?' BMC Medical Informatics and Decision Making, 200
PENGARUH KUALITAS PELAYANAN TERHADAP KEPUASAN KONSUMEN DI PT. RAMAYANA MOTOR SUKOHARJO
This final project writing aims to find out the satisfaction level the
consumers feel on the service given by PT Ramayana Motor Sukoharjo through
the dimensions of service quality including Tangible, Reliability, Responsiveness,
Assurance and empathy.
The problem statement developed in this research is to find out the
consumer satisfaction level on the performance given by PT. Ramayana Motor
Sukoharjo.
Technique of collecting data employed was observation, interview, and
questionnaire method. The sampling technique used was simple random sampling
with 100 respondents.
In this research, technique of discussing used was descriptive analysis one,
namely, the one to make a systematic, factual and accurate description about an
object studied, while the consumer satisfaction was measured using importance
performance analysis.
From the research on 100 respondents about the service quality given by
PT. Ramayana Motor Sukoharjo, it can be found that the results of consumer
assessment on the performance given by the company include: viewed from the
importance performance analysis, the highest consumer satisfaction level is in
service procedure attribute or factor that will be done quickly, it can be seen from
the percentage goodness of fit level of 113.28%, while the smallest attribute is that
the employees have knowledge to answer the consumers’ question of 71.15%.
The conclusion that can be drawn is that the result of Cartesian diagram of
factors becomes the primary priority of PT. Ramayana Motor Sukoharjo and
should be done because this factor is considered as important by the company and
consumers, including: non strategic and not affordable dealer location,
unattractive and untidy physical facility appearance.
The recommendation given is that from the location side, the dealer should
post the banner in front of its building so that the consumers can find the dealer
location easily. From physical facility side, the product arrangement should be
adjusted with the types of each product.
Keywords: Tangible, Reliability, Responsiveness, Assurance and empathy
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