8,338 research outputs found
A stable range description of the space of link maps
We study the space of link maps, which are smooth maps from the disjoint
union of manifolds P and Q to a manifold N such that the images of P and Q are
disjoint. We give a range of dimensions, interpreted as the connectivity of a
certain map, in which the cobordism class of the "linking manifold" is enough
to distinguish the homotopy class of one link map from another.Comment: 10 page
Solidification macroprocesses - Thermal-mechanical Modeling of Stress, Distortion and Hot Tearing)
http://www.crcpress.com/product/isbn/9780849332166International audienceThe application of numerical methods to the mechanical modeling in solidification analysis has received a continuously growing interest over the last twenty years. After having concentrated their efforts on the thermal and microstructural predictions, research teams have been more and more interested in the coupled thermomechanical analysis. These developments have been motivated by the efforts done by the casting industry to increase the quality of final products while lowering the costs. Manufacturers are then interested in the development of new numerical tools able to model the thermomechanical response of castings during the processes. Accurate calculation of stress and distortions during casting is just the first step, however, as engineers are more interested in their practical consequences. These include residual stress and distortion, and defects such as segregation and the formation of cracks such as hot tears. As computing power and software tools advance, it is becoming increasingly possible to perform useful mechanical analysis of castings and these important related behaviors
Learning Markov Decision Processes for Model Checking
Constructing an accurate system model for formal model verification can be
both resource demanding and time-consuming. To alleviate this shortcoming,
algorithms have been proposed for automatically learning system models based on
observed system behaviors. In this paper we extend the algorithm on learning
probabilistic automata to reactive systems, where the observed system behavior
is in the form of alternating sequences of inputs and outputs. We propose an
algorithm for automatically learning a deterministic labeled Markov decision
process model from the observed behavior of a reactive system. The proposed
learning algorithm is adapted from algorithms for learning deterministic
probabilistic finite automata, and extended to include both probabilistic and
nondeterministic transitions. The algorithm is empirically analyzed and
evaluated by learning system models of slot machines. The evaluation is
performed by analyzing the probabilistic linear temporal logic properties of
the system as well as by analyzing the schedulers, in particular the optimal
schedulers, induced by the learned models.Comment: In Proceedings QFM 2012, arXiv:1212.345
Diversity and Distribution of the Terrestrial Mammals of the Yukon Territory: A Review
The diversity and distribution of the terrestrial mammals of the Yukon has not been systematically reviewed since 1975, a time when the occurrences of many species were not well known. Since then, single species and community studies, biological collections and expert observations have increased our knowledge of the land mammals of the Yukon. Taxonomic studies have resulted in some additional species. We provide an update on the diversity and distribution of recent land mammals of the Yukon, including previously unreported range extensions, and include a revised checklist. Research in adjoining jurisdictions has contributed more hypothetical species for the Yukon. The mammalian fauna of the Yukon is in a relatively dynamic state, and human-induced changes, particularly climate warming, will undoubtedly influence mammalian diversity and distributions in the coming decades
Mortality of Little Brown Bats, Myotis lucifugus, in a Rodent Trap in the Boreal Forest
Accidental mortality of bats is not often observed or reported in the literature. It may, however, have an impact on population size and structure. We report an observation of 53 Little Brown Bats (Myotis lucifugus) being trapped and drowned in a homemade rodent trap at an abandoned cabin in southern Yukon. Traps of this design may be commonly used in the boreal forest. We recommend not using such traps in cabins that are used by colonies of bats
Effects of Ponderosa Pine Ecological Restoration on Forest Soils and Understory Vegetation in Northern Arizona
The human exclusion of wildfire and overgrazing by livestock since settlement have caused dramatic changes in ponderosa pine (Pinus ponderosa Dougl ex Laws) forest ecosystems. These changes include increased numbers of tree stems, reduced understory cover and diversity, and the introduction of invasive, non-native understory species. This study evaluated the coverage and species composition of understory vegetation present in the “cool-season” (late spring and early summer) in a ponderosa pine forest on grazed and ungrazed plots that had undergone restoration treatments on three different soil/geologic parent material types near Flagstaff, Arizona, twelve years after tree thinning and grazing exclosure treatments were applied. Several measured soil properties, such as soil respiration and temperature, were also evaluated in this study. Species richness of “cool-season” vegetation was influenced more by grazing practices than restoration treatments. Differences could be less or greater when vegetation that is active later in the season is measured. Vegetative cover was significantly influenced by restoration treatments (9.3% cover under open canopies and 6.5% under dense canopies), probably due to differences in competition for light and other resources (i.e. soil moisture and nutrients). Unlike finding by Abella et al. (2015), who studied “warm-season” vegetation, “cool-season” understory cover was not influenced by soil parent material type in this study, which might suggest that differences in understory cover due to soil properties are only seen shortly after restoration treatments are applied, or the time of year vegetation is evaluated may play a role in the differences seen. Soil respiration was highest on limestone soil parent material type (3.3 g C-CO2 m-2 day-1), and soil temperature was lowest under closed canopy treatments (15°C)
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