Search results for "MVAR"
showing 10 items of 12 documents
Testing Frequency-Domain Causality in Multivariate Time Series
2010
We introduce a new hypothesis-testing framework, based on surrogate data generation, to assess in the frequency domain, the concept of causality among multivariate (MV) time series. The approach extends the traditional Fourier transform (FT) method for generating surrogate data in a MV process and adapts it to the specific issue of causality. It generates causal FT (CFT) surrogates with FT modulus taken from the original series, and FT phase taken from a set of series with causal interactions set to zero over the direction of interest and preserved over all other directions. Two different zero-setting procedures, acting on the parameters of a MV autoregressive (MVAR) model fitted on the ori…
Socio-technical Congruence Sabotaged by a Hidden Onshore Outsourcing Relationship: Lessons Learned from an Empirical Study
2012
Despite the popularity of outsourcing arrangements, distributed software development is still regarded as a complex endeavor. Complexity primarily comes from the challenges in communication and coordination among participating organizations. In this paper we discuss lessons learned from participatory research carried out in a highly distributed onshore outsourcing project. Previous research established that socio-technical congruence principles alleviate distributed work. In practice we have found that alignment between the systems structure and organizational structure can be studied from different abstraction levels and also during different phases of project lifecycle. We have found that…
New Forms of Work in the Light of Globalization in Software Development
2009
Globalization in software development introduced significant changes in the way organizations operate today. Software is nowadays produced by team members from geographically, temporally and culturally remote sites. Organizations seek for benefits that global market offers and face new challenges. Naturally resistant to change, these organizations often do not realize necessity for tailoring existing methods for distributed collaboration. Our empirical investigation shows a great variety in the ways organizations distribute responsibilities across remote sites and conclude that these can be divided into two main categories: joint collaboration that requires investments in team building and …
Critical comments on EEG sensor space dynamical connectivity analysis
2019
Many different analysis techniques have been developed and applied to EEG recordings that allow one to investigate how different brain areas interact. One particular class of methods, based on the linear parametric representation of multiple interacting time series, is widely used to study causal connectivity in the brain. However, the results obtained by these methods should be interpreted with great care. The goal of this paper is to show, both theoretically and using simulations, that results obtained by applying causal connectivity measures on the sensor (scalp) time series do not allow interpretation in terms of interacting brain sources. This is because (1) the channel locations canno…
Abnormal synchrony and effective connectivity in patients with schizophrenia and auditory hallucinations
2014
Auditory hallucinations (AH) are the most frequent positive symptoms in patients with schizophrenia. Hallucinations have been related to emotional processing disturbances, altered functional connectivity and effective connectivity deficits. Previously, we observed that, compared to healthy controls, the limbic network responses of patients with auditory hallucinations differed when the subjects were listening to emotionally charged words. We aimed to compare the synchrony patterns and effective connectivity of task-related networks between schizophrenia patients with and without AH and healthy controls. Schizophrenia patients with AH (n = 27) and without AH (n = 14) were compared with healt…
Structural Relationships between Floating and Deposited Monolayers of Docosanoic Acid
1991
Floating docosanoic acid (behenic acid) monolayers in the SmI and SmH phase were deposited with the Langmuir-Blodgett technique onto thin polymethylmethacrylate (PMMA) and Formvar substrates and investigated by electron diffraction. The molecular packing of the monolayers on the substrates vary from those on the water surface and are different for different substrates. On PMMA four phases (H, SmB, SmI, SmL) have been identified, depending on the deposition conditions. While SmB and SmI are known for docosanoic acid on the water surface, H and SmL have only been unequivocally observed in other substances or on other subphases. The monolayer structure on Formvar was identical under all deposi…
Analysis of measurements of stopping powers of formvar, polyimide, polysulfone, and vyns for 3.6 to 10.5 MeV7Li ions
2002
The stopping powers of formvar, polysulfone, polyimide, and vyns for 7Li projectiles have been measured with the transmission technique and thin foil targets. The experimental data have been analyzed in terms of modified Bethe–Bloch theory to extract characteristic values of the mean excitation energy and Barkas effect parameter, as well as to study the effects of including a single effective charge parameter. Results of this investigation are in general supportive of the outcomes of earlier similar studies with protons and α-particles traversing the same target materials in the sense that previously reported trends in projectile-dependent behavior of values of mean excitation energy and Ba…
En studie av de faktorer som bidrar til effekter ved PDAbruk i norsk hjemmesykepleie
2006
Masteroppgave i informasjonssystemer 2006 - Høgskolen i Agder, Kristiansand Helsesektoren i Norge er en belastet sektor som skal betjene et økende antall hjemmeboende klienter og bistå dem med helsetjenester og hjelp til daglige gjøremål. Etaten sliter med lav bemanning og begrensede midler. Dette har bidratt til at man har fått fremvekst av moderniseringstiltak i sektoren. Moderniseringen kan ta flere former og denne oppgaven ser i hovedsak på bruk av PDAer i norsk hjemmesykepleie. PDAer er små håndholdte PC-er som kan gi mobil tilgang til informasjon som tidligere var papirbasert og utilgjengelig for pleiepersonell ute på mobile oppdrag. Det er en rekke potensielle effekter ved slike PDA-…
The quality factor of a superconducting rf resonator in a magnetic field.
2010
The quality factor of a superconducting NbTi resonator at 1.6 MHz in a magnetic field up to 1.2 T as well as its temperature dependence is investigated. A hysteresis effect in the superconducting surface resistance as a function of the magnetic field is observed. An unloaded Q-value of the resonator of 40,500 is achieved at 3.9 K. It is shown that this Q-value is limited by dielectric losses in the FORMVAR insulation of the coils wire. The details of the Q-value optimization are discussed. In the temperature dependence of the Q-value a steep decrease is observed above T approximately = 7.5 K. Finally, the implications of these measurements for real trap experiments are discussed in detail.
On solving separable block tridiagonal linear systems using a GPU implementation of radix-4 PSCR method
2018
Partial solution variant of the cyclic reduction (PSCR) method is a direct solver that can be applied to certain types of separable block tridiagonal linear systems. Such linear systems arise, e.g., from the Poisson and the Helmholtz equations discretized with bilinear finite-elements. Furthermore, the separability of the linear system entails that the discretization domain has to be rectangular and the discretization mesh orthogonal. A generalized graphics processing unit (GPU) implementation of the PSCR method is presented. The numerical results indicate up to 24-fold speedups when compared to an equivalent CPU implementation that utilizes a single CPU core. Attained floating point perfor…