Search results for "linear"
showing 10 items of 7165 documents
Recent climate change in Japan ? spatial and temporal characteristics of trends of temperature
2008
Abstract. In this paper temperature series of Japan were statistically analysed in order to answer the question whether recent climate change can be proved for Japan; the results were compared and discussed with the global trends. The observations in Japan started for some stations in the 1870s, 59 stations are available since 1901, 136 stations since 1959. Modern statistical methods were applied, such as: Gaussian binominal low-pass filter (30 yr), trend analysis (linear regression model) including the trend-to-noise-ratio as measure of significance and the non-parametric, non-linear trend test according to MANN (MANN's Q). According to the results of the analyses, climate change in Japan …
Comparative Analysis of Spatial Interpolation Methods in the Mediterranean Area: Application to Temperature in Sicily
2015
An exhaustive comparison among different spatial interpolation algorithms was carried out in order to derive annual and monthly air temperature maps for Sicily (Italy). Deterministic, data-driven and geostatistics algorithms were used, in some cases adding the elevation information and other physiographic variables to improve the performance of interpolation techniques and the reconstruction of the air temperature field. The dataset is given by air temperature data coming from 84 stations spread around the island of Sicily. The interpolation algorithms were optimized by using a subset of the available dataset, while the remaining subset was used to validate the results in terms of the accur…
More is not always better—non-linear effects in crowdfunding
2019
Abstract This research focuses on crowdfunding project features and its relation with the success of this project. The main purpose is to improve probability of success of crowdfunding projects. One can argue that “more is always better” resulting in attempts of daily updates. Contrarily, backers may be weary of numerous updates to work through, indicating a possible wear-out effect, implying the existence of an optimal level of updates. Our preliminary results show that previous research, built upon linear modeling, widely ignores important aspects of the relationship between key variables. We therefore picked six key variables that were previously marked as success drivers in crowdfunding…
Multiplicity results for asymmetric boundary value problems with indefinite weights
2004
We prove existence and multiplicity of solutions, with prescribed nodal properties, to a boundary value problem of the formu″+f(t,u)=0,u(0)=u(T)=0. The nonlinearity is supposed to satisfy asymmetric, asymptotically linear assumptions involving indefinite weights. We first study some auxiliary half-linear, two-weighted problems for which an eigenvalue theory holds. Multiplicity is ensured by assumptions expressed in terms of weighted eigenvalues. The proof is developed in the framework of topological methods and is based on some relations between rotation numbers and weighted eigenvalues.
Impact of the terrestrial reference frame on the determination of the celestial reference frame.
2022
Currently three up-to-date Terrestrial Reference Frames (TRF) are available, the ITRF2014 from IGN, the DTRF2014 from DGFI-TUM, and JTRF2014 from JPL. All use the identical input data of space-geodetic station positions and Earth orientation parameters, but the concept of combining these data is fundamentally different. The IGN approach is based on the combination of technique solutions, while the DGFI is combining the normal equation systems. Both yield in reference epoch coordinates and velocities for a global set of stations. JPL uses a Kalman filter approach, realizing a TRF through weekly time series of geocentric coordinates. As the determination of the CRF is not independent of the T…
Comparing Different approaches - Data mining, Geostatistic, and Deterministic pedology - to assess the Frequency of WRB reference soil groups in the …
2014
Estimating frequency of soil classes in map unit is always affected by some degree of uncertainty, especially at small scales, with a larger generalization. The aim of this study was to compare different possible approaches - data mining, geostatistic, deterministic pedology - to assess the frequency of WRB Reference Soil Groups (RSG) in the major Italian soil regions. In the soil map of Italy (Costantini et al., 2012), a list of the first five RSG was reported in each major 10 soil regions. The soil map was produced using the national soil geodatabase, which stored 22,015 analyzed and classified pedons, 1,413 soil typological unit (STU) and a set of auxiliary variables (lithology, land-use…
System identification via optimised wavelet-based neural networks
2003
Nonlinear system identification by means of wavelet-based neural networks (WBNNs) is presented. An iterative method is proposed, based on a way of combining genetic algorithms (GAs) and least-square techniques with the aim of avoiding redundancy in the representation of the function. GAs are used for optimal selection of the structure of the WBNN and the parameters of the transfer function of its neurones. Least-square techniques are used to update the weights of the net. The basic criterion of the method is the addition of a new neurone, at a generic step, to the already constructed WBNN so that no modification to the parameters of its neurones is required. Simulation experiments and compa…
Linguistic diversity and assessment in multilingual schools
2018
En un entorno en el que la diversidad lingüística es natural, la metodología de evaluación afronta nuevos retos. La equidad en el proceso evaluativo aconseja la consideración de aspectos relacionados con las características psicométricas de las pruebas, el desarrollo de la competencia lingüística, o el contexto sociolingüístico, a través de modelos explicativos sobre las variables contextuales de naturaleza lingüística que inciden en el rendimiento. Utilizando datos poblacionales de centros educativos de segundo curso de enseñanza secundaria obligatoria que ofertan más de un modelo lingüístico en la Comunidad Autónoma del País Vasco (N=45), este trabajo analiza las respuestas de 2783 estudi…
Refugees’ perception of their new life in Germany
2021
Since 2015, Germany has been hosting noticeable incoming flows of refugees and asylum seekers and despite the quality of life of refugees is expected to be improved in the aftermath of their arrival to Germany, refugees are still facing several problems of integration and economic deprivation. Using a sample of individuals from the first wave of the German IAB-BAMF-SOEP Survey of Refugees, we present some preliminary analyses on their life satisfaction (LS). A gamma glm was estimated to focus on the association among levels of LS and main socio-demographic characteristics as well as post-migration factors. Greater stability (both in the legal and personal sphere) in refugees’ lives is posit…
Complex dynamics, hidden attractors and continuous approximation of a fractional-order hyperchaotic PWC system
2018
In this paper, a continuous approximation to studying a class of PWC systems of fractionalorder is presented. Some known results of set-valued analysis and differential inclusions are utilized. The example of a hyperchaotic PWC system of fractional order is analyzed. It is found that without equilibria, the system has hidden attractors.