Search results for "mallit"

Adding ‘Sense’ to Conceptual Modeling : An Interdisciplinary Approach

2019

In this paper, our aim is to widen the prevailing foundations of conceptual modeling theories and practices, particularly in the context of information systems development. The approach shifts the focus from the link between a model and the modelled reality to the link between human cognition and the model. Our approach combines theoretical issues of different disciplines relevant to conceptual modeling. We shall make an explicit distinction between individual conceptions and interpersonal concepts and show how this distinction could be utilized to have conceptual models of a better consistency. We wish that this article could also serve as a starting point for a profound scientific discuss…

Lyapunov quantities and limit cycles in two-dimensional dynamical systems : analytical methods, symbolic computation and visualization

2011

On computation in statistical models with a psychophysical application

2004

FM Janne Kujalan tieteellisen laskennan väitöskirjan ”On computation in statistical models with a psychophysical application” (Laskennasta tilastollisissa malleissa psykofysiikkaan soveltaen) tarkastustilaisuus. Vastaväittäjänä FT Keijo Ruotsalainen (Oulun yliopisto) ja kustoksena professori Pekka Neittaanmäki.Kujala tehosti väitöskirjatutkimuksessaan tilastollisten ja fysikaalisten mallien laskentaa. Vaikka erinäisiin ongelmiin voidaan varsin helposti keksiä laskennallisia malleja, niiden käyttäminen ja vertailu on usein käytännössä mahdotonta tietokoneiden rajallisen tehon takia. Kujala etsi työssään vähemmän tehoa vaativia oikoteitä laskennallisten mallien käyttöön. Esimerkiksi kahden no…

Numerical methods for acoustics and noise control

2010

Artikkeliväitöskirja. Sisältää yhteenveto-osan ja viisi artikkelia. Article dissertation. Contains an introduction part and five articles. This dissertation considers numerical methods for wave propagation modelling and noise control. The first part of the dissertation discusses an efficient method for solving time-harmonic wave equations in acoustic (the Helmholtz equation) and elastic domains (the Navier equation). The solver is based on preconditioning a Krylov subspace method, such as GMRES, with approximations of damped variants of the corresponding wave equations. An algebraic multigrid method is used in approximating the inverse of damped operators. The method can be used in complex …

Multi-objective actuator placement optimization for local sound control evaluated in a stochastic domain

2011

A method to find optimal locations and properties of anti-noise actuators in local noise control system is considered. The local noise control performance is approximated by a finite element method based approach, that attempts to estimate the average performance of optimal active noise control (ANC) system. The local noise control uses a fixed number of circular actuators that are located on the boundary of a three-dimensional enclosed acoustic space. Actuator signals are used to minimize the known harmonic noise at specified locations. The average noise reduction is maximized at two frequency ranges by adjusting the anti-noise actuator configuration, which is a non-linear multi-objective …

Multi-objective actuator placement optimization for local sound control evaluated in a stochastic domain

2013

A method to find optimal locations and properties of anti-noise actuators in a local noise control system is considered. The local noise control performance is approximated by an approach based on a finite element method, attempting to estimate the average performance of an optimal active noise control (ANC) system. Local noise control uses a fixed number of circular actuators that are located on the boundary of a three-dimensional enclosed acoustic space. Actuator signals are used to minimize the known harmonic noise at specified locations. The average noise reduction is maximized at two frequency ranges by adjusting the anti-noise actuator configuration, which is a non-linear multi-object…

Modelling phytoplankton in boreal lakes

2014

The “Seili-index” For The Prediction of Chlorophyll-α Levels In The Archipelago Sea of The Northern Baltic Sea, Southwest Finland

2021

AbstractTo build a forecasting tool for the state of eutrophication in the Archipelago Sea, we fitted a Generalized Additive Mixed Model (GAMM) to marine environmental monitoring data, which were collected over the years 2011–2019 by an automated profiling buoy at the Seili ODAS-station. The resulting “Seili-index” can be used to predict the chlorophyll-α (chl-a) concentration in the seawater a number of days ahead by using the temperature forecast as a covariate. An array of test predictions with two separate models on the 2019 data set showed that the index is adept at predicting the amount of chl-a especially in the upper water layer. The visualization with 10 days of chl-a level predict…

Se pyörii sittenkin : kolmiulotteisen konkreettisen mallin hyödyt planetaaristen ilmiöiden opetuksessa, havainnollisen mallin kehittäminen ja testaus

2007

Species distributions models may predict accurately future distributions but poorly how distributions change: A critical perspective on model validat…

2023

Aim: Species distribution models (SDMs) are widely used to make predictions on how species distributions may change as a response to climatic change. To assess the reliability of those predictions, they need to be critically validated with respect to what they are used for. While ecologists are typically interested in how and where distributions will change, we argue that SDMs have seldom been evaluated in terms of their capacity to predict such change. Instead, typical retrospective validation methods estimate model's ability to predict to only one static time in future. Here, we apply two validation methods, one that predicts and evaluates a static pattern, while the other measures change…