Search results for "COMPUTATION"
showing 10 items of 7362 documents
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…
Viruses are ancient parasites that have influenced the evolution of contemporary and archaic forms of life
2010
Modeling friction between shearing brittle surfaces with a discrete element method
2018
Hauraiden materiaalien murtuminen on eräs materiaalifysiikan peruskysymyksistä. Sille ei ole vieläkään olemassa täydellistä teoreettista selitystä, joten ennusteiden tekeminen nojaa vahvasti kokeisiin ja niihin perustuviin numeerisiin malleihin. Tässä työssä suunnittelemme ja toteutamme diskreettielementtimenetelmän sellaisen fysikaalisen systeemin tutkimiseen, jossa kaksi haurasta pintaa leikkaavat toisiaan. Keskitymme erityisesti siihen kuinka erilaiset voimamallit sisäiselle kitkalle vaikuttavat materiaalin ulkoiseen kitkaan. Käyttämällä graniittia koemateriaalina huomaamme, että sen ulkoinen kitka riippuu voimakkaasti sen sisäisestä kitkasta, kun ulkoinen paine on lähellä materiaalin pu…
A coupled discontinuous Galerkin-Finite Volume framework for solving gas dynamics over embedded geometries
2021
Author(s): Gulizzi, Vincenzo; Almgren, Ann S; Bell, John B | Abstract: We present a computational framework for solving the equations of inviscid gas dynamics using structured grids with embedded geometries. The novelty of the proposed approach is the use of high-order discontinuous Galerkin (dG) schemes and a shock-capturing Finite Volume (FV) scheme coupled via an $hp$ adaptive mesh refinement ($hp$-AMR) strategy that offers high-order accurate resolution of the embedded geometries. The $hp$-AMR strategy is based on a multi-level block-structured domain partition in which each level is represented by block-structured Cartesian grids and the embedded geometry is represented implicitly by a…
Calculating the implied correlation matrix for a Path Analysis model
2014
To overcome the limitations of two existing methods for calculating a Path Analysis implied correlation matrix, this paper presents an alternative method for calculating this matrix. This new method is based on a recurrence principle which is easy and quick to implement. This method is also operational regardless of the number of variables. The consequences of this result with the estimation or testing stages will be illustrated on the basis of examples.
SPI/INTEGRAL in-flight performance
2003
The SPI instrument has been launched on-board the INTEGRAL observatory on October 17, 2002. SPI is a spectrometer devoted to the sky observation in the 20 keV-8 MeV energy range using 19 germanium detectors. The performance of the cryogenic system is nominal and allows to cool the 19 kg of germanium down to 85 K with a comfortable margin. The energy resolution of the whole camera is 2.5 keV at 1.1 MeV. This resolution degrades with time due to particle irradiation in space. We show that the annealing process allows the recovery of the initial performance. The anticoincidence shield works as expected, with a low threshold at 75 keV, reducing the GeD background by a factor of 20. The digital …
Human Sensorimotor Communication: A Theory of Signaling in Online Social Interactions
2013
Although the importance of communication is recognized in several disciplines, it is rarely studied in the context of online social interactions and joint actions. During online joint actions, language and gesture are often insufficient and humans typically use non-verbal, sensorimotor forms of communication to send coordination signals. For example, when playing volleyball, an athlete can exaggerate her movements to signal her intentions to her teammates (say, a pass to the right) or to feint an adversary. Similarly, a person who is transporting a table together with a co-actor can push the table in a certain direction to signal where and when he intends to place it. Other examples of ``si…
Where lol is: function and position of lol used as a discourse marker in YouTube comments
2020
Lol is probably one of the most popular words in computer-mediated communication. It is generally taken to be the acronym of “laughing out loud”, but it is not always used to indicate a humorous response; rather, it is multifunctional. Drawing on previous studies of the different functions of lol, this paper explores a possible correlation between the position and function of non-lexicalized lol in the specific context of YouTube comments. The hypothesis is that the function of lol largely depends on its position: clause-initial lol is not used with the same functions as clause-final lol. The data for the study come from the comment threads of three popular YouTube videos posted in 2017, 20…