| 1. |
- Tavassoli, Sam, et al.
(author)
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The role of regional context on innovation persistency of firms
- 2018
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In: Papers in regional science (Print). - : Wiley. - 1056-8190 .- 1435-5957. ; 97:4, s. 931-956
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Journal article (peer-reviewed)abstract
- This paper analyses the role of regional context on innovation persistency of firms. Using the Community Innovation Survey in Sweden, we have traced firms' innovative behaviour from 2002 to 2012, in terms of four Schumpeterian types of innovation: product, process, organizational, and marketing. Controlling for an extensive set of firm-level characteristics, we find that certain regional characteristics matter for innovation persistency of firms. In particular, those firms located in regions with: (i) thicker labour market or (ii) higher extent of knowledge spillover exhibit higher probability of being persistent innovators up to 14 percentage points. Such higher persistency is mostly pronounced for product innovators.
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| 2. |
- Tavassoli, Z, et al.
(author)
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Analysis of counter-current imbibition with gravity in weakly water-wet systems
- 2005
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In: Journal of Petroleum Science and Engineering. - : Elsevier BV. - 0920-4105 .- 1873-4715. ; 48:1-2, s. 94-104
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Journal article (peer-reviewed)abstract
- Counter-current imbibition in one dimension is analyzed, in which a wetting phase (water) displaces a non-wetting phase against gravity. An approximate analytical approach is used to derive an expression for the saturation profile in the case where the mobility of the displaced phase at the inlet is finite. This approach is applicable to waterflooding in hydrocarbon reservoirs, flow in geothermal systems, or the displacement of non-aqueous phase liquid (NAPL) or air by water. Solutions are developed for both gravity-dominated and capillary-dominated cases. In the capillary-dominated limit the predicted recoveries compare very well with experimental data from the literature, over all time scales. The use of this expression for field-scale dual-porosity modeling of flow in fractured systems is briefly discussed.
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| 3. |
- Tavassoli, Z., et al.
(author)
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Analytic analysis for oil recovery during counter-current imbibition in strongly water-wet systems
- 2005
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In: Transport in Porous Media. - : Springer Science and Business Media LLC. - 0169-3913 .- 1573-1634. ; 58:1-2, s. 173-189
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Journal article (peer-reviewed)abstract
- We study counter-current imbibition, where a strongly wetting phase ( water) displaces non-wetting phase spontaneously under the influence of capillary forces such that the non-wetting phase moves in the opposite direction to the water. We use an approximate analytical approach to derive an expression for saturation profile when the viscosity of the non-wetting phase is non-negligible. This makes the approach applicable to water flooding in hydrocarbon reservoirs, or the displacement of non-aqueous phase liquid (NAPL) by water. We find the recovery of non-wetting phase as a function of time for one-dimensional flow. We compare our predictions with experimental results in the literature. Our formulation reproduces experimental data accurately and is superior to previously proposed empirical models.
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| 4. |
- Tavasszy, L., et al.
(author)
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Comprehensive Versus Simplified Models
- 2013
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In: Modelling Freight Transport. - : Elsevier. - 9780124104006 ; , s. 245-256
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Book chapter (peer-reviewed)abstract
- Many factors play a role in the decision how complex a model should become. The essence of modelling is to produce a replication of a system that is as rich as needed, with a model specification that is as lean as possible. Usually, a desire for a model that is both broad in scope and deep in detail, is detrimental for the modelling process (and result, eventually). In many cases, there are strict limits to model complexity due to constraints in data availability or computer power. This chapter intends to provide a simple guide for practical modelling applications, especially for those situations where there is a pressure for developing simple models, that follow the basic 4-step transport model architecture. We discuss the idea of model complexity including its relation to transport policy, and present strategies to implement the 4-step architecture, depending on the desired level of complexity. These strategies include the modelling of partial systems, integration of submodels and aggregation of agents.
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| 5. |
- Tavasszy, L., et al.
(author)
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Introduction
- 2013
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In: Modelling Freight Transport. - : Elsevier Inc.. - 9780124104006 ; , s. 1-12
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Book chapter (other academic/artistic)abstract
- In this introductory chapter we provide a concise overview of the state of the art of mathematical models of the freight transport system, focussing mainly on areas where it deviates from passenger transport models. We introduce a conceptual model of the freight transport system that includes production, consumption and trade, as well as inventory and transport logistics. A brief explanation is given of the disciplinary background and the state of the art of freight modelling in these areas, and the different theoretical perspectives behind freight transport models are highlighted. Finally we provide an introduction to the different chapters of the book. The chapters largely follow the conceptual model introduced here and include overarching topics on data issues, simplified models and application for policy.
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| 6. |
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| 7. |
- Tavast, Daniel, 1978-
(author)
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Improved Usage of Wood Raw Material through Modification of the Kraft Process
- 2015
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Licentiate thesis (other academic/artistic)abstract
- The kraft process is a complex system with many variables, and though the process is fairly well understood, there is still much we do not know. This thesis examines some aspects of the kraft process that could prove to be of interest for the pulp and paper industry, specifically, the impact of wood chip impregnation and of the chemical structure of xylan on spruce kraft pulp. The intent is to suggest modifications to the kraft process as it is used today. The effect of wood chip impregnation varies with the prevalent conditions, and increases the effect of the subsequent kraft cook. Longer impregnation at a lower temperature was found to increase screened pulp yield, reduce shives content, make it possible to reach a certain kappa number at a lower H-factor, and make it possible to reach a certain kappa number at a lower total alkali consumption. Xylan has previously been found to have a strength-enhancing effect on pulp, and the chemical structure of the xylan in question was found to be the main strength-enhancing factor. For spruce xylan, the structure that provides the largest increase in strength is not the same as the structure that increases the yield the most. Removing xylan was determined to have a negative impact on pulp strength. Xylan extracted from agro waste can be used as an additive to increase pulp strength. This could be viable, especially when combined with the production of green plastics from hemicelluloses extracted from the agro waste. A suggested configuration of a future pulp mill is presented, incorporating the following modifications to the now standard kraft cooking system:impregnation at a lower temperature for a longer time;extracting xylan-enriched black liquor at an early stage of the impregnation or cook, and adding this liquor at a late stage of the cook;terminating the cook at a higher kappa number;increasing oxygen delignification to compensate for the increased kappa number at the end of the cook, keeping the kappa number constant going into the bleaching plant; andadding agro-waste xylan during oxygen delignification.
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| 8. |
- Tavast, Daniel, et al.
(author)
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Influence of spruce xylan characteristics on tensile strength of spruce kraft pulp
- 2015
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In: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 69:1, s. 1-7
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Journal article (peer-reviewed)abstract
- The aim of the study was to investigate the possibility to use spruce xylan more efficiently by possible relocation of dissolved xylan with certain characteristics from the first part of the kraft cooking to the later part, when precipitation occur. The characteristics of re-located xylan was controlled by replacing half the black liquor (BL) at a late stage of a kraft cook, with the same amount of black liquor containing spruce xylan with known molecular weight and content of uronic acid (UA). Pulp with addition of xylan with high amount of UA groups responded strongly on beating, resulting in improved tensile strength. It is proposed that the best effect of xylan on tensile strength occurs when the xylan penetrates some distance into the subsurface of the fiber wall. Both low molecular weight (M-w) and a high degree of substitution decreases the tendency of xylan to aggregate, which enables the dissolved xylan to penetrate some distance into the exposed fiber surface. Upon beating, this xylan will be exposed thus facilitating improved fiber-fiber joint formation, which leads to increased tensile strength.
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| 9. |
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| 10. |
- Tavazzi, L., et al.
(author)
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Efficacy and safety of ivabradine in chronic heart failure across the age spectrum: insights from the SHIFT study
- 2013
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In: European Journal of Heart Failure. - : Wiley. - 1388-9842 .- 1879-0844. ; 15:11, s. 1296-1303
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Journal article (peer-reviewed)abstract
- AIMS: To test whether the efficacy and safety of the selective heart rate-reducing agent ivabradine changes according to age in chronic heart failure (HF) patients. METHODS AND RESULTS: The ivabradine and placebo arms of SHIFT, which enrolled 6505 chronic HF patients, were combined and age distribution was divided by quartiles to give four groups (<53 years, n = 1522; 53 to <60 years, n = 1521; 60 to <69 years, n = 1750; and >/=69 years, n = 1712). The effects of ivabradine on cardiovascular outcomes, changes in heart rate, and adverse events, particularly bradycardia, were evaluated according to age group. A subgroup (602 patients) underwent 24 h ambulatory ECG Holter monitoring. The relative risk of the primary endpoint (cardiovascular death or hospitalization for worsening HF) was reduced by ivabradine in all age groups, ranging from 38% [hazard ratio (HR) 0.62, 95% confidence interval (CI) 0.50-0.78, P < 0.001] in the youngest patients <53 years to 16% (HR 0.84, 95% CI 0.71-0.99, P = 0.035) in the oldest patients >/=69 years. Ivabradine up-titration reduced heart rate similarly in all age groups, by 11 b.p.m. As anticipated, bradycardia and phosphenes occurred more frequently with ivabradine, at a similar rate whatever the age. In the Holter substudy, there were no episodes of severe bradycardia and no clinically relevant pauses with ivabradine in any age group. CONCLUSIONS: Age does not limit the appropriate use of ivabradine in patients with chronic HF and systolic dysfunction. The safety and efficacy of ivabradine are comparable across all age groups.
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