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  • Degirmenci, Niyazi Cem, et al. (författare)
  • A Unified Numerical Simulation of Vowel Production That Comprises Phonation and the Emitted Sound
  • 2017
  • Ingår i: Proceedings of the Annual Conference of the International Speech Communication Association, INTERSPEECH 2017. - : The International Speech Communication Association (ISCA). ; , s. 3492-3496
  • Konferensbidrag (refereegranskat)abstract
    • A unified approach for the numerical simulation of vowels is presented, which accounts for the self-oscillations of the vocal folds including contact, the generation of acoustic waves and their propagation through the vocal tract, and the sound emission outwards the mouth. A monolithic incompressible fluid-structure interaction model is used to simulate the interaction between the glottal jet and the vocal folds, whereas the contact model is addressed by means of a level set application of the Eikonal equation. The coupling with acoustics is done through an acoustic analogy stemming from a simplification of the acoustic perturbation equations. This coupling is one-way in the sense that there is no feedback from the acoustics to the flow and mechanical fields. All the involved equations are solved together at each time step and in a single computational run, using the finite element method (FEM). As an application, the production of vowel [i] has been addressed. Despite the complexity of all physical phenomena to be simulated simultaneously, which requires resorting to massively parallel computing, the formant locations of vowel [i] have been well recovered.
  • Degirmenci, Niyazi Cem, 1982- (författare)
  • Adaptive Finite Element Methods for Fluid Structure Interaction Problems with Applications to Human Phonation
  • 2018
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • This work presents a unified framework for numerical solution of Fluid Structure Interaction (FSI) and acoustics problems with focus on human phonation. The Finite Element Method is employed for numerical investigation of partial differential equations that model conservation of momentum and mass. Since the resulting system of equations is very large, an efficient open source high performance implementation is constructed and provided. In order to gain accuracy for the numerical solutions, an adaptive mesh refinement strategy is employed which reduces the computational cost in comparison to a uniform refinement. Adaptive refinement of the mesh relies on computable error indicators which appear as a combination of a computable residual and the solution of a so-called dual problem acting as weights on computed residuals. The first main achievement of this thesis is to apply this strategy to numerical simulations of a benchmark problem for FSI. This FSI model is further extended for contact handling and applied to a realistic vocal folds geometry where the glottic wave formation was captured in the numerical simulations. This is the second achievement in the presented work. The FSI model is further coupled to an acoustics model through an acoustic analogy, for vocal folds with flow induced oscillations for a domain constructed to create the vowel /i/. The comparisons of the obtained pressure signal at specified points with respect to results from literature for the same vowel is reported, which is the final main result presented.
  • Ekström, Mats, 1961, et al. (författare)
  • Three tasks for mediatization research: contributions to an open agenda
  • 2016
  • Ingår i: Media Culture and Society. - : Sage Publications. - 0163-4437 .- 1460-3675. ; 38:7, s. 1090-1108
  • Tidskriftsartikel (refereegranskat)abstract
    • Based on the interdisciplinary experience of a Swedish research committee, this article discusses critical conceptual issues raised by the current debate on mediatization – a concept that holds great potential to constitute a space for synthesized understandings of media-related social transformations. In contrast to other, more metaphorical constructions, mediatization can be studied empirically in systematic ways through various sub-processes that together provide a complex picture of how culture and everyday life evolve in times of media saturation. The first part of this article argues that mediatization researchers have sometimes formulated too grand claims as to mediatization’s status as a unitary approach, a meta-theory or a paradigm. Such claims have led to problematic confusions around the concept and should be abandoned in favour of a more open agenda. In line with such a call for openness, the second part of the article introduces historicity, specificity and measurability as three transdisciplinary and transparadigmatic tasks for the contemporary mediatization research agenda.
  • Fagman, Johan Bourghardt, 1980, et al. (författare)
  • The androgen receptor confers protection against diet-induced atherosclerosis, obesity, and dyslipidemia in female mice.
  • 2015
  • Ingår i: FASEB journal : official publication of the Federation of American Societies for Experimental Biology. - : Federation of American Societies for Experimental Biology. - 1530-6860 .- 0892-6638. ; 29:4, s. 1540-1550
  • Tidskriftsartikel (refereegranskat)abstract
    • Androgens have important cardiometabolic actions in males, but their metabolic role in females is unclear. To determine the physiologic androgen receptor (AR)-dependent actions of androgens on atherogenesis in female mice, we generated female AR-knockout (ARKO) mice on an atherosclerosis-prone apolipoprotein E (apoE)-deficient background. After 8 weeks on a high-fat diet, but not on a normal chow diet, atherosclerosis in aorta was increased in ARKO females (+59% vs. control apoE-deficient mice with intact AR gene). They also displayed increased body weight (+18%), body fat percentage (+62%), and hepatic triglyceride levels, reduced insulin sensitivity, and a marked atherogenic dyslipidemia (serum cholesterol, +52%). Differences in atherosclerosis, body weight, and lipid levels between ARKO and control mice were abolished in mice that were ovariectomized before puberty, consistent with a protective action of ovarian androgens mediated via the AR. Furthermore, the AR agonist dihydrotestosterone reduced atherosclerosis (-41%; thoracic aorta), subcutaneous fat mass (-44%), and cholesterol levels (-35%) in ovariectomized mice, reduced hepatocyte lipid accumulation in hepatoma cells in vitro, and regulated mRNA expression of hepatic genes pivotal for lipid homeostasis. In conclusion, we demonstrate that the AR protects against diet-induced atherosclerosis in female mice and propose that this is mediated by modulation of body composition and lipid metabolism.-Fagman, J. B., Wilhelmson, A. S., Motta, B. M., Pirazzi, C., Alexanderson, C., De Gendt, K., Verhoeven, G., Holmäng, A., Anesten, F., Jansson, J. -O., Levin, M., Borén, J., Ohlsson, C., Krettek, A., Romeo, S., Tivesten, A. The androgen receptor confers protection against diet-induced atherosclerosis, obesity, and dyslipidemia in female mice.
  • Hakansson, B., et al. (författare)
  • The bone conduction implant - a review and 1-year follow-up
  • 2019
  • Ingår i: International Journal of Audiology. - 1499-2027 .- 1708-8186. ; 58:12, s. 945-955
  • Tidskriftsartikel (refereegranskat)abstract
    • Objective: The objective of this study is to evaluate its safety and effectiveness of the bone conduction implant (BCI) having an implanted transducer and to review similar bone conduction devices. Design: This is a consecutive prospective case series study where the patients were evaluated after 1, 3, 6 and 12 months. Outcome measures were focussed on intraoperative and postoperative safety, the effectiveness of the device in terms of audiological performance and patient's experience. Study sample: Sixteen patients with average age of 40.2 (range 18-74) years have been included. Thirteen patients were operated in Gothenburg and three in Stockholm. Results: It was found that the procedure for installing the BCI is safe and the transmission condition was stable over the follow-up time. No serious adverse events or severe adverse device effects occurred. The hearing sensitivity, speech in noise and the self-assessment as compared with the unaided condition improved significantly with the BCI. These patients also performed similar or better than with a conventional bone conduction reference device on a softband. Conclusions: In summary, it was found that the BCI can provide a safe and effective hearing rehabilitation alternative for patients with mild-to-moderate conductive or mixed hearing impairments.
  • Hakansson, B., et al. (författare)
  • VEMP using a new low-frequency bone conduction transducer
  • 2018
  • Ingår i: Medical Devices-Evidence and Research. - 1179-1470. ; 11, s. 301-312
  • Tidskriftsartikel (refereegranskat)abstract
    • Objective: A new prototype bone conduction (BC) transducer B250, with an emphasized low-frequency response, is evaluated in vestibular evoked myogenic potential (VEMP) investigations. The aim was to compare cervical (cVEMP) and ocular (oVEMP) responses using tone bursts at 250 and 500 Hz with BC stimulation using the B250 and the conventional B81 transducer and by using air conduction (AC) stimulation. Methods: Three normal subjects were investigated in a pilot study. BC stimulation was applied to the mastoids in cVEMP, and both mastoid and forehead in oVEMP investigations. Results: BC stimulation was found to reach VEMP thresholds at considerably lower hearing levels than in AC stimulation (30-40 dB lower oVEMP threshold at 250 Hz). Three or more cVEMP and oVEMP responses at consecutive 5 dB increasing mastoid stimulation levels were only obtained in all subjects using the B250 transducer at 250 Hz. Similar BC thresholds were obtained for both ipsilateral and contralateral mastoid stimulation. Forehead stimulation, if needed, may require a more powerful vibration output. Conclusion: Viable VEMP responses can be obtained at a considerably lower hearing level with BC stimulation than by AC stimulation. The cVEMP and oVEMP responses were similar when measured on one side and with the B250 attached to both ipsilateral and contralateral mastoids.
  • Hergens, Maria-Pia, et al. (författare)
  • Use of Scandinavian Moist Smokeless Tobacco (Snus) and the Risk of Atrial Fibrillation
  • 2014
  • Ingår i: Epidemiology. - : Wolters Kluwer Health/LWW. - 1044-3983 .- 1531-5487. ; 25:6, s. 872-876
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Snus is a smokeless tobacco product, widely used among Swedish men and increasingly so elsewhere. There is debate as to whether snus is an acceptable "harm-reduction" tobacco product. Since snus use delivers a dose of nicotine equivalent to cigarettes, and has been implicated in cardiac arrhythmia because of associations with sudden cardiovascular death, a relation with atrial fibrillation is plausible and important to investigate.METHODS:: To assess the relation between use of snus and risk of atrial fibrillation, we carried out a pooled analysis of 7 prospective Swedish cohort studies. In total, 274,882 men, recruited between 1978 and 2004, were followed via the National Patient Register for atrial fibrillation. Primary analyses were restricted to 127,907 never-smokers. Relative risks were estimated using Cox proportional hazard regression.RESULTS:: The prevalence of snus use was 25% among never-smokers. During follow-up, 3,069 cases of atrial fibrillation were identified. The pooled relative risk of atrial fibrillation was 1.07 (95% confidence interval = 0.97-1.19) in current snus users, compared with nonusers.CONCLUSION:: Findings from this large national pooling project indicate that snus use is unlikely to confer any important increase in risk of atrial fibrillation.
  • Hoffman, Johan, et al. (författare)
  • A General Galerkin Finite Element Method for the Compressible Euler Equations
  • 2008
  • Ingår i: SIAM Journal on Scientific Computing. - 1064-8275 .- 1095-7197.
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper we present a General Galerkin (G2) method for the compressible Euler equations, including turbulent ow. The G2 method presented in this paper is a nite element method with linear approximation in space and time, with componentwise stabilization in the form  of streamline diusion and shock-capturing modi cations. The method conserves mass, momentum  and energy, and we prove an a posteriori version of the 2nd Law of thermodynamics for the method.  We illustrate the method for a laminar shock tube problem for which there exists an exact analytical  solution, and also for a turbulent flow problem
  • Hoffman, Johan, et al. (författare)
  • Adaptive modeling of turbulent flow with residual based turbulent kinetic energy dissipation
  • 2011
  • Ingår i: Computer Methods in Applied Mechanics and Engineering. - 0045-7825 .- 1879-2138. ; 200:37-40, s. 2758-2767
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper we first review our recent work on a new framework for adaptive turbulence simulation: we model turbulence by weak solutions to the Navier-Stokes equations that are wellposed with respect to mean value output in the form of functionals, and we use an adaptive finite element method to compute approximations with a posteriori error control based on the error in the functional output. We then derive a local energy estimate for a particular finite element method, which we connect to related work on dissipative weak Euler solutions with kinetic energy dissipation due to lack of local smoothness of the weak solutions. The ideas are illustrated by numerical results, where we observe a law of finite dissipation with respect to a decreasing mesh size.
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