| 1. |
- Håkansson, Andreas, et al.
(författare)
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Experimental investigations of turbulent fragmenting stresses in a rotor stator mixer. Part 1. Estimation of turbulent stresses and comparison to breakup visualizations
- 2017
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Ingår i: Chemical Engineering Science. - : Elsevier BV. - 0009-2509. ; 171, s. 625-637
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Tidskriftsartikel (refereegranskat)abstract
- Despite large industrial relevance, the relation between rotor-stator geometry, hydrodynamics and drop breakup is poorly understood, partly since no methods for measuring the fragmenting stresses acting on drops have been established. This study attempts to bridge this gap by developing, applying and evaluating two approaches for estimating local turbulent stresses based on particle image velocimetry data: namely one traditional but indirect approach based on the dissipation rate of turbulent kinetic energy, and another more direct approach based on the spatial turbulent spectrum that has proven useful in other high-intensity emulsification processing. The approaches are evaluated in terms of validity of underlying assumptions, how they compare to breakup visualizations in the same geometry and with regard to the reliability of primary measurables. Results show three consistent regions of high stress in the rotor-stator region: in a plume extending into the stator-hole from the trailing edge, in the shear layers of the jet exiting the hole and in the macroscopic flow structure formed after the rotor blocks a stator hole. Following, a drop travelling along an average velocity flow field, the measurement predict disrupting stresses exceeding the stabilizing stress at the stator hole exit, at approximately the same position where drop breakup is observed in breakup visualizations. Both methods are therefore able to predict the most likely breakup positions. It is also concluded that both methods have limitations, and that average stress alone cannot describe all aspects of the fragmentation process in rotor-stator mixers.
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| 2. |
- Håkansson, Andreas, et al.
(författare)
-
Experimental investigations of turbulent fragmenting stresses in a rotor-stator mixer. Part 2. Probability distributions of instantaneous stresses
- 2017
-
Ingår i: Chemical Engineering Science. - : Elsevier BV. - 0009-2509. ; 171, s. 638-649
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Tidskriftsartikel (refereegranskat)abstract
- Drop fragmentation in high intensity turbulent emulsification processing equipment-such as rotor-stator mixers (RSMs)-has traditionally been described in terms of a stress balance; between the stabilizing stress of the drop and the time-averaged turbulent stress at the most intense position of the flow. As shown in part 1 of this series, this approach is often a fruitful first approximation. However, the instantaneous local stress experienced by drops differs from the time-averaged local stress due to hydrodynamics in general and the stochastic nature of a turbulent flow in particular.This study estimates the probability distribution of instantaneous turbulent stresses in an RSM from velocity fields obtained using particle image velocimetry. Results show that regions with low average stress still have a substantial probability of having instantaneously high stresses. This explains why low probability breakup is observed at these positions in visualization experiments.Results also show that the probability distribution of instantaneous stresses is approximately lognormal. The results are compared to two commonly used models for how to take the stochastic variations into account: the exponential decay model, and the multifractal emulsification model. It is concluded that both models predict reasonable distributions shapes but underestimate the width of the stress distribution.
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| 3. |
- Pajalic, Oleg, 1964, et al.
(författare)
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An evaluation by elderly people living at home of the prepared meals distributed by their municipality - a study with focus on the Swedish context.
- 2015
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Ingår i: Global journal of health science. - : Canadian Center of Science and Education. - 1916-9744 .- 1916-9736. ; 7:3, s. 59-68
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Tidskriftsartikel (refereegranskat)abstract
- Prepared meals distributed by municipalities is a service to elderly people, or persons with health related impairments, who live in their own home, have difficulties preparing their own food and cannot meet their food requirements in any other way. This study aimed to provide a brief picture of how elderly people living at home perceive the food they receive through their municipal food service and what is important to them. The data was collected using questionnaires. 274 out of 276 participants answered the questionnaire (n=173 women 62% and n=101 man 37%). The data was analyzed using Principal Component Analysis (PCA). The results showed that the elderly persons receiving meals through the service were often satisfied, especially with the size of the portions and the delivery time. Those who had been using the food delivery service for a longer time were not satisfied with the alternative dishes they were been offered. There was no significant difference between the views of either gender. Further, those who were receiving special food were, in general, unsatisfied with the meals delivered. Development of the food distribution service by systematic quality insurance and interactive knowledge exchange between the producers and consumers seems to be a way to promote a more holistic and individual adjusted service. Evaluation of the municipal FD service is a powerful tool that can contribute to the development of this service. The food service can be improved and consequently even the quality of life and health of its receivers. The present survey should be revisited and developed in order to detect differences between genders.
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| 4. |
- van der Mei, Rob, et al.
(författare)
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State of the Art and Research Challenges in the Area of Autonomous Control for a Reliable Internet of Services
- 2018
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Ingår i: Autonomous Control for a Reliable Internet of Services. - Cham : Springer Publishing Company. ; , s. 1-22
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Bokkapitel (refereegranskat)abstract
- The explosive growth of the Internet has fundamentally changed the global society. The emergence of concepts like service-oriented architecture (SOA), Software as a Service (SaaS), Platform as a Service (PaaS), Infrastructure as a Service (IaaS), Network as a Service (NaaS) and Cloud Computing in general has catalyzed the migration from the information-oriented Internet into an Internet of Services (IoS). This has opened up virtually unbounded possibilities for the creation of new and innovative services that facilitate business processes and improve the quality of life. However, this also calls for new approaches to ensuring quality and reliability of these services. The goal of this book chapter is to first analyze the state-of-the-art in the area of autonomous control for a reliable IoS and then to identify the main research challenges within it. A general background and high-level description of the current state of knowledge is presented. Then, for each of the three subareas, namely the autonomous management and real-time control, methods and tools for monitoring and service prediction, and smart pricing and competition in multi-domain systems, a brief general introduction and background are presented, and a list of key research challenges is formulated.
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