| 1. |
- Ge, Yaxin, 1992, et al.
(författare)
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Impacts of fresh bed materials on alkali release and fuel conversion rate during wood pyrolysis and char gasification
- 2023
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 353
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Tidskriftsartikel (refereegranskat)abstract
- Bed materials provide efficient heat transfer and catalytic function in the thermochemical conversion of biomass, but their interactions with the fuel remain incompletely understood. In this study, the effects of bed materials on alkali release and fuel conversion during wood pyrolysis and CO2 gasification are investigated by online alkali detection combined with thermogravimetric analysis. The investigated bed materials include silica, sea sand, alumina and the natural ores olivine, ilmenite and dolomite. Only dolomite has a significant effect on fuel mass loss and alkali release during wood pyrolysis, while all bed materials influence char reactivity and alkali release during gasification. Sea sand, alumina and dolomite enhance the char gasification during the whole or most of the gasification process, which is related to alkali migration from the bed materials. All bed materials affect char reactivity and alkali release when the conversion approaches completion, and small amounts of some bed materials reduce the alkali release by an order of magnitude. The findings can be understood based on the chemical composition of the different materials. Silicon-rich materials reduce the levels of catalytically active alkali by formation of stable alkali silicates, and a similar explanation applies for ilmenite that captures alkali efficiently. Magnesium and calcium in contrast promote alkali release through their influence on alkali silicate chemistry. Analysis of char surfaces using scanning electron microscopy with energy dispersive spectroscopy indicates that low amounts of several elements are transferred from the bed material to the char where they may be directly involved in the char conversion process. The transferred elements are specific for each bed material and relates to their chemical composition. Mechanisms for material exchange between bed material and char are discussed.
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| 2. |
- Ge, Yaxin, 1992, et al.
(författare)
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Effect of fresh bed materials on alkali release and thermogravimetric behavior during straw gasification
- 2023
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 336
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Tidskriftsartikel (refereegranskat)abstract
- Alkali-associated problems are key issues for the efficient use of straw that is available as a major renewable energy resource worldwide. The effects of six bed materials commonly used in fluidized bed reactors on straw pyrolysis and char gasification were evaluated using online monitoring of alkali release and thermogravimetric analysis. Scanning electron microscopy with energy dispersive spectroscopy was used to determine the elemental composition of the char surface. In the straw pyrolysis stage, alkali release is reduced by the addition of dolomite and silica due to alkali adsorption on the bed materials, and enhanced by the addition of alumina because of its high sodium content. In the char gasification stage, silica, sea sand, olivine, and ilmenite reduce the char reactivity and alkali release, which is attributed to transfer of Si and Ti from the bed materials to the char and reaction with alkali to form stable and catalytically inactive compounds. Alumina also reduces the char conversion rate by transfer of Al to the char and formation of K-Al-Si and Ca-Al-Si compounds, while alkali release from the straw and alumina blend remains high due to the high Na content in alumina. Dolomite initially appears to increase the char gasification reactivity, but the results are affected by conversion of volatile matter that deposited on the dolomite in the straw pyrolysis stage. Dolomite also significantly increases the alkali release, which is attributed to Ca reactions with aluminosilicate compounds that allow potassium to remain in volatile form. Fresh bed materials are concluded to have significant effects on straw conversion depending on their chemical composition, and the results can contribute to the understanding required for efficient use of straw in commercial applications of biomass thermochemical conversion.
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| 3. |
- Andric, Jelena, 1979, et al.
(författare)
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A study of a flexible fiber model and its behavior in DNS of turbulent channel flow
- 2013
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Ingår i: Acta Mechanica. - : Springer Science and Business Media LLC. - 0001-5970 .- 1619-6937. ; 224:10, s. 2359-2374
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Tidskriftsartikel (refereegranskat)abstract
- The dynamics of individual flexible fibers in a turbulent flow field have been analyzed, varying their initial position, density and length. A particlelevel fiber model has been integrated into a general-purpose, open source Computational Fluid Dynamics (CFD) code. The fibers are modeled as chains of cylindrical segments connected by ball and socket joints. The equations of motion of the fibers contain the inertia of the segments, the contributions from hydrodynamic forces and torques, and the connectivity forces at the joints. Direct Numerical Simulation (DNS) of the incompressible Navier–Stokes equations is used to describe the fluid flow in a plane channel and a one-way coupling is considered between the fibers and the fluid phase. We investigate the translational motion of fibers by considering the mean square displacement of their trajectories. We find that the fiber motion is primarily governed by velocity correlations of the flow fluctuations. In addition, we show that there is a clear tendency of the thread-like fibers to evolve into complex geometrical configurations in a turbulent flow field, in fashion similar to random conformations of polymer strands subjected to thermal fluctuations in a suspension. Finally, we show that fiber inertia has a significant impact on reorientation time-scales of fibers suspended in a turbulent flow field.
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| 4. |
- Ahlström, Richard, 1952-, et al.
(författare)
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Affluence and Unsustainable Consumption Levels: The Role of Consumer Credit
- 2020
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Ingår i: Cleaner and Responsible Consumption. - : Elsevier BV. - 2666-7843. ; 1
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Tidskriftsartikel (refereegranskat)abstract
- Several pressures on planetary boundaries are directly linked to the production of goods and services driven by people’s ever-increasing spending of money to improve their material living standard beyond a comfortable life. The over-spending on material consumption by people in industrialized countries, and in the growing middle and upper classes of developing countries, constitutes a serious threat to the planet, does not boost individual happiness, and exposes citizens in a society to inequalities known to negatively affect their well-being. Owing to economic means and psychological factors spurring consumption, affluence increases spending on consumption of expensive luxury goods and services that aggregated have detrimental effects on the planet. We conjecture that these effects are increased by consumer credit enabling moderately affluent people to match their peers’ and the very affluent people’s spending on expensive luxury consumption, and making less affluent people over-spend money on purchases of inexpensive short-lived fast-fashion consumer products. In addition to other means to curtail current unsustainable consumption levels, our analysis highlights that consumer credit may need to be restricted.
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| 5. |
- Ainegren, Mats, 1963-, et al.
(författare)
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Effects of Aerodynamic Drag and Drafting on Propulsive Force and Oxygen Consumption in Double Poling Cross-Country Skiing
- 2022
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Ingår i: Medicine & Science in Sports & Exercise. - 0195-9131 .- 1530-0315. ; 54:7, s. 1058-1065
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Tidskriftsartikel (refereegranskat)abstract
- Purpose This study aimed to investigate the effects of aerodynamic drag and drafting on propulsive force (FPROP), drag area (CDA), oxygen cost (V˙O2), metabolic rate (Ė), and heart rate (HR) during roller skiing on a treadmill in a wind tunnel using the double poling technique. A secondary aim was to investigate the effects of wind versus no-wind test conditions on the same physiological parameters. Methods Ten subjects of each gender participated in the experiments. One pair of skiers of the same gender roller skied simultaneously in line with the air flow; the distance between the skiers was 2.05 m. Each pair was tested as follows: I) with wind, leading; II) with wind, drafting; and III) without wind. The treadmill inclination was 0° throughout the tests. For the wind conditions, the air velocity was similar to the treadmill belt speed: 3 to 7 m·s-1 for men and 3 to 6 m·s-1 for women. Results Drafting resulted in significantly (P < 0.05) lower FPROP,CDA, V˙O2, and Ė, compared with leading, for both genders at racing speed but not at lower speeds, whereas HR was only affected for the male skiers at racing speed. The test without wind resulted in significantly lower FPROP, V˙O2, and Ė at all tested speeds compared with the tests with wind present, whereas HR was lower only at higher speeds. Conclusions At racing speed, but not at lower speeds, the positive effects of drafting behind a skier during double poling were obvious and resulted in a lower FPROP, CDA, V˙O2, Ė, and HR. Tests without wind present put even lower demands on the skiers' physiology, which was also evident at lower speeds.
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| 6. |
- Cvitic, Petya Hristova, et al.
(författare)
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Investigating Software Testing and Maintenance of Open-Source Distributed Ledger
- 2023
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Ingår i: Proceedings - 2023 IEEE International Conference on Software Analysis, Evolution and Reengineering, SANER 2023. - : IEEE. - 2833-9061. - 9781665452786
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Konferensbidrag (refereegranskat)abstract
- A distributed ledger is the backbone of all blockchain solutions. It provides a shared database spreading across a network of nodes. The number of DL solutions and their implementations has grown in recent years. Besides the architectural and performance promises of thesesolutions, organizations seekingto implement DL also need to consider the overall quality of the software available and its ecosystem. Particularly, previous research has identified the need to better understand the testing and maintenance practices behind these types of technologies. This paper investigates the testing and maintenance of 18 different open-source projects that implement distributed ledgers. We perform a manual inspection of test artefacts and mine the history of commits, issues and contributors of the chosen projects to understand the landscape of testing and maintenance in these projects. Our findings suggest that unit and integration tests are present in most projects, they do not follow a holistic system testing approach. Moreover, projects rely on a small team of core contributors (5 on average). While the projects are continuously maintained, larger changes are uncommon. Our results can be used for benchmarking and pinpointing areas of improvement for the development of distributed ledgers.
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| 7. |
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| 8. |
- Hirsch, J. M., et al.
(författare)
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Additive manufacturing and 3D printing
- 2020
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Ingår i: Lasers in Oral and Maxillofacial Surgery. - Cham : Springer International Publishing. - 9783030296049 - 9783030296032 ; , s. 227-237
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This chapter discusses recent applications and findings in additive manufacturing (AM), or 3D printing, applied in oral and maxillofacial surgery. The reader will get an introduction to the basics of AM technology followed by oral and maxillofacial applications like printing of anatomical models and the design and manufacturing of customised implants. Recent research on the biological response of some AM metal alloys is also discussed at the end of the chapter. © Springer Nature Switzerland AG 2020. All rights reserved.
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| 9. |
- Mamontov, Eugen, 1955, et al.
(författare)
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Nonsearch paradigm for large-scale parameter-identification problems in dynamical systems related to oncogenic hyperplasia
- 2006
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Ingår i: Systems, Control, Modeling and Optimization. IFIP International Federation for Information Processing. - : Springer US. - 1571-5736. - 9780387338811 - 0387338810 ; 202, s. 269-278
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Konferensbidrag (refereegranskat)abstract
- In many engineering and biomedical problems there is a need to identify parameters of the systems from experimental data. A typical example is the biochemical-kinetics systems describing oncogenic hyperplasia where the dynamical model is nonlinear and the number of the parameters to be identified can reach a few hundreds. Solving these large-scale identification problems by the local- or global-search methods can not be practical because of the complexity and prohibitive computing time. These difficulties can be overcome by application of the non-search techniques which are much less computation- demanding. The present work proposes key components of the corresponding mathematical formulation of the nonsearch paradigm. This new framework for the nonlinear large-scale parameter identification specifies and further develops the ideas of the well-known approach of A. Krasovskii. The issues are illustrated with a concise analytical example. The new results and a few directions for future research are summarized in a dedicated section.
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| 10. |
- Mamontov, Eugen, 1955, et al.
(författare)
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Stochastic mechanics in the context of the properties of living systems
- 2006
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Ingår i: Mathl Comput. Modelling. - : Elsevier BV. - 0895-7177 .- 1872-9479. ; 44:7-8, s. 595-607
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Tidskriftsartikel (refereegranskat)abstract
- Many features of living systems prevent the application of fundamental statistical mechanics (FSM) to study such systems. The present work focuses on some of these features. After discussing all the basic approaches of FSM, the work formulates an extension of the kinetic theory paradigm (based on the reduced one-particle distribution function) that exhibits all of the living-system properties considered. This extension appears to be a model within the generalized kinetic theory developed by N. Bellomo and his co-authors. In connection with this model, the work also stresses some other features necessary for making the model relevant to living systems. A mathematical formulation of homeorhesis is also derived. An example discussed in the work is a generalized kinetic equation coupled with a probability-density equation representing the varying component content of a living system. The work also suggests a few directions for future research. [All rights reserved Elsevier]
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