Search results for "Ull"
showing 10 items of 3152 documents
Plant functional and taxonomic diversity in European grasslands along climatic gradients
2021
Aim European grassland communities are highly diverse, but patterns and drivers of their continental-scale diversity remain elusive. This study analyses taxonomic and functional richness in European grasslands along continental-scale temperature and precipitation gradients. Location Europe. Methods We quantified functional and taxonomic richness of 55,748 vegetation plots. Six plant traits, related to resource acquisition and conservation, were analysed to describe plant community functional composition. Using a null-model approach we derived functional richness effect sizes that indicate higher or lower diversity than expected given the taxonomic richness. We assessed the variation in abso…
Environmental Characteristics and Anthropogenic Impact Jointly Modify Aquatic Macrophyte Species Diversity
2018
Species richness and spatial variation in community composition (i.e. beta diversity) are key measures of biodiversity. They are largely determined by natural factors, but also increasingly affected by anthropogenic factors. Thus, there is a need for a clear understanding of the human impact on species richness and beta diversity, the underlying mechanisms, and whether human-induced changes can override natural patterns. Here, we dissect the patterns of species richness, community composition and beta diversity in relation to different environmental factors as well as human impact in one framework: aquatic macrophytes in 66 boreal lakes in Eastern Finland. The lakes had been classified as h…
Assessing spillover from Marine Protected Areas and its drivers: a meta-analytical approach
2020
International audience; Overfishing may seriously impact fish populations and ecosystems. Marine protected areas (MPAs) are key tools for biodiversity conservation and fisheries management, yet the fisheries benefits remain debateable. Many MPAs include a fully protected area (FPA), restricting all activities, within a partially protected area (PPA) where potentially sustainable activities are permitted. An effective tool for biodiversity conservation, FPAs, can sustain local fisheries via spillover, that is the outward export of individuals from FPAs. Spillover refers to both: “ecological spillover”: outward net emigration of juveniles, subadults and/or adults from the FPA; and “fishery sp…
Geographic mosaic of selection by avian predators on hindwing warning colour in a polymorphic aposematic moth
2020
AbstractWarning signals are predicted to develop signal monomorphism via positive frequency-dependent selection (+FDS) albeit many aposematic systems exhibit signal polymorphism. To understand this mismatch, we conducted a large-scale predation experiment in four locations, among which the frequencies of hindwing warning coloration of aposematic Arctia plantaginis differ. Here we show that selection by avian predators on warning colour is predicted by local morph frequency and predator community composition. We found +FDS to be strongest in monomorphic Scotland, and in contrast, lowest in polymorphic Finland, where different predators favour different male morphs. +FDS was also found in Geo…
Why aren't warning signals everywhere? : On the prevalence of aposematism and mimicry in communities
2021
Warning signals are a striking example of natural selection present in almost every ecological community - from Nordic meadows to tropical rainforests, defended prey species and their mimics ward off potential predators before they attack. Yet despite the wide distribution of warning signals, they are relatively scarce as a proportion of the total prey available, and more so in some biomes than others. Classically, warning signals are thought to be governed by positive density-dependent selection, i.e. they succeed better when they are more common. Therefore, after surmounting this initial barrier to their evolution, it is puzzling that they remain uncommon on the scale of the community. He…
Using Recorded Audio Feedback in Cross-Cultural e-Education Environments to Enhance Assessment Practices in a Higher Education
2018
Providing feedback to learners on their writing assignments is perhaps one of the most important and time-consuming tasks that a supervisor performs. In e-Education environments, giving feedback becomes more challenging because there are often no possibilities for face-to-face discussions with learners. Typically, a supervisor provides comments to learners in written form via email; however, the use of recorded audio feedback (RAF) in e-Education environments has become a viable alternative. The purpose of this case study was to examine learners’ perceptions of RAF and written feedback for their assignments at the University of Jyväskylä (Finland) and at Keio University SFC (Japan). Formati…
Decoupled nonlinear adaptive control of position and stiffness for pneumatic soft robots
2020
This article addresses the problem of simultaneous and robust closed-loop control of joint stiffness and position, for a class of antagonistically actuated pneumatic soft robots with rigid links and compliant joints. By introducing a first-order dynamic equation for the stiffness variable and using the additional control degree of freedom, embedded in the null space of the pneumatic actuator matrix, an innovative control approach is introduced comprising an adaptive compensator and a dynamic decoupler. The proposed solution builds upon existing adaptive control theory and provides a technique for closing the loop on joint stiffness in pneumatic variable stiffness actuators. Under a very mi…
Disturbance observer-based disturbance attenuation control for a class of stochastic systems
2016
This paper studies a class of stochastic systems with multiple disturbances which include the disturbance with partially-known information and the white noise. A disturbance observer is constructed to estimate the disturbance with partially-known information, based on which, a disturbance observer-based disturbance attenuation control (DOBDAC) scheme is proposed by combining pole placement and linear matrix inequality (LMI) methods.
Parametric Hull Design with Rational Bézier Curves
2021
AbstractIn this paper, a tool able to support the sailing yacht designer during the early stage of the design process has been developed. Quadratic and cubic Rational Bézier curves have been selected to describe the main curves defining the hull of a sailing yacht. The adopted approach is based upon the definition of a set of parameters, say the length of water line, the beam of the waterline, canoe body draft and some dimensionless coefficients according to the traditional way of the yacht designer. Some geometrical constraints imposed on the curves (e.g. continuity, endpoint angles) have been conceived aimed to avoid unreasonable shapes. These curves can be imported in any commercial CAD …
Physical Load Among Construction Workers and Analysis with Objective Ergonomics Research Method
2016
There is growing number of work related musculoskeletal disorders among workers in construction industry. Employees in construction professions admit physical load and discomfort in various body parts after the work. Accordingly to Eurostat statistical data 60 % of total work related diseases are attributed to musculoskeletal disorders in Latvia. The aim of this study was to determine physical load of construction auxiliary workers and bricklayers using objective ergonomics research method HR monitoring and subjective ergonomic risk assessment methods. The research involved full time 8 auxiliary construction workers and 7 bricklayers. Analysis of the heart rate monitoring data proved that o…