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1.
Serra Sónia R. Q. Calapez Ana Raquel Simões Nuno Eduardo Sá Marques José A. A. Laranjo Maria Feio Maria João 《Urban Ecosystems》2019,22(6):1173-1186
Urban Ecosystems - Urban streams provide important ecosystem services to cities’ population, from the maintenance of urban biodiversity, temperature, humidity and air quality to improving... 相似文献
2.
A graph is locally irregular if the neighbors of every vertex v have degrees distinct from the degree of v. A locally irregular edge-coloring of a graph G is an (improper) edge-coloring such that the graph induced on the edges of any color class is locally irregular. It is conjectured that three colors suffice for a locally irregular edge-coloring. In the paper, we develop a method using which we prove four colors are enough for a locally irregular edge-coloring of any subcubic graph admiting such a coloring. We believe that our method can be further extended to prove the tight bound of three colors for such graphs. Furthermore, using a combination of existing results, we present an improvement of the bounds for bipartite graphs and general graphs, setting the best upper bounds to 7 and 220, respectively. 相似文献
3.
4.
Point processes are the stochastic models most suitable for describing physical phenomena that appear at irregularly spaced
times, such as the earthquakes. These processes are uniquely characterized by their conditional intensity, that is, by the
probability that an event will occur in the infinitesimal interval (t, t+Δt), given the history of the process up tot. The seismic phenomenon displays different behaviours on different time and size scales; in particular, the occurrence of
destructive shocks over some centuries in a seismogenic region may be explained by the elastic rebound theory. This theory
has inspired the so-called stress release models: their conditional intensity translates the idea that an earthquake produces
a sudden decrease in the amount of strain accumulated gradually over time along a fault, and the subsequent event occurs when
the stress exceeds the strength of the medium. This study has a double objective: the formulation of these models in the Bayesian
framework, and the assignment to each event of a mark, that is its magnitude, modelled through a distribution that depends
at timet on the stress level accumulated up to that instant. The resulting parameter space is constrained and dependent on the data,
complicating Bayesian computation and analysis. We have resorted to Monte Carlo methods to solve these problems. 相似文献
5.
Dynamic reliability models with conditional proportional hazards 总被引:1,自引:0,他引:1
A dynamic approach to the stochastic modelling of reliability systems is further explored. This modelling approach is particularly appropriate for load-sharing, software reliability, and multivariate failure-time models, where component failure characteristics are affected by their degree of use, amount of load, or extent of stresses experienced. This approach incorporates the intuitive notion that when a set of components in a coherent system fail at a certain time, there is a jump from one structure function to another which governs the residual lifetimes of the remaining functioning components, and since the component lifetimes are intrinsically affected by the structure function which they constitute, then at such a failure time there should also be a jump in the stochastic structure of the lifetimes of the remaining components. For such dynamically-modelled systems, the stochastic characteristics of their jump times are studied. These properties of the jump times allow us to obtain the properties of the lifetime of the system. In particular, for a Markov dynamic model, specific expressions for the exact distribution functions of the jump times are obtained for a general coherent system, a parallel system, and a series-parallel system. We derive a new family of distribution functions which describes the distributions of the jump times for a dynamically-modelled system. 相似文献
6.
7.
Aline Canetti Patrícia Póvoa de Mattos Evaldo Muñoz Braz Sylvio Pellico Netto 《Urban Ecosystems》2017,20(5):1057-1068
Urban afforestation improves life quality in urban centers providing social and environmental benefits. Understanding growth of urban trees exposed to air pollution will support planning, managing and expanding urban areas. This approach intends to determine growth patterns of urban trees to support future urban planning. Non-destructive samples were collected from trees of Araucaria angustifolia (Bertol.) Kuntze in Araucaria city, Parana State, Brazil. Growth rings were related to pollutant concentrations and meteorological series. Growth reduction was observed except in the border areas of the city. Trees established during or after the period of industrialization incentives were most affected by air pollution, indicating that immature plants are more vulnerable. Sulphur dioxide and nitric oxide significantly affected growth of smaller trees. Those greater than 60 cm dbh did not demonstrate significant correlation with any identified pollutant. As the trees established before accentuated urbanization were less affected by air pollution, it is reinforced the importance of preserving remaining urban trees. We suggest that planning urban afforestation should precede industries placing. When urban planning is impossible, new planted trees should not be expected to grow as in free pollution areas, but they will still present satisfactory diameter increment, contributing to improve local urban environment. 相似文献
8.
Mycorrhizal fungi symbioses can be critical determining if established seedlings survive or not. Currently, in remnant forests, plants and their fungal symbionts are exposed to varied anthropomorphic effects related to urbanization, however, little is known about their impact on this association. We investigated the relationship between mycorrhizal fungi and tree seedling survival along an urbanization gradient. We planted three species of temperate tree seedlings (Acer rubrum, Carya ovata, and Quercus rubra) in three landscapes: urban, suburban, and rural. We measured the percent of root length colonized by mycorrhizal fungi and monitored survival during their first growing season. We analyzed mycorrhizal colonization as a function of landscape type (urban-rural) and additional variables known to contribute to mycorrhizal colonization (phosphorus, nitrogen, initial plant height). We then analyzed seedling survival as a function of the degree of mycorrhizal fungi colonization associated with the landscape gradient and of additional environmental factors (light and soil moisture). Within a species we found no changes in the levels of mycorrhizal fungi colonization across the urbanization gradient. Each species, however, had markedly different levels of colonization. Survival of A. rubrum was independent of mycorrhizal colonization, while C. ovata and Q. rubra had a significant positive response to increased mycorrhizal fungi. These findings highlight the resilience of mycorrhizal communities across the rural-urban gradient typical of this region, but they also underscore the potential sensitivity of some tree species to lower levels of mycorrhizal fungi colonization. 相似文献
9.
From a developmental perspective, workgroups adjust and modify the way they function over time. The present study aims to test, at the group level, the moderating role of the group’s life phase in the relationship between workgroup interdependence ties in terms of task, outcome and functions, assessed by social network density and group satisfaction. A sample of 84 teams from various companies participated in this research. The results showed that the group’s development phase determines the way that outcome interdependence density in teams is associated with satisfaction and reveal the existence of differences between the second and fourth development stages. Therefore, the group’s life cycle stage should be considered as a relevant variable in research and intervention with groups in the workplace. 相似文献
10.
Bruno Cardinale Lagomarsino Matías Gutman Lucía Freira María Laura Lanzalot Maximiliano Lauletta Leandro E. Malchik Felipe Montaño Campos Bianca Pacini Martín A. Rossi Christian Valencia 《Economic inquiry》2017,55(3):1579-1584
We provide experimental evidence on the effect of peer pressure on individual behavior. Specifically, we study the effect of being exposed to an observer in a public restroom on handwashing and urinal flushing behavior. Our estimates show that being exposed to an observer increases the probability of handwashing by 13 percentage points and the probability of urinal flushing by 15 percentage points. Given that handwashing and urinal flushing have social benefits that exceed individual benefits, our findings provide support for peer pressure as an additional way of addressing the social suboptimality arising from externalities. (JEL C91, C93) 相似文献