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| 85. |
- Fakhrai, Reza, et al.
(författare)
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Multi-disciplinary problem based learning in computational fluid dynamics
- 2014
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Ingår i: STAR Global Conference 2014, Vienna Austria.
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Konferensbidrag (refereegranskat)abstract
- KTH Royal Institute of Technology (KTH) is one of European’s key centers of innovation and intellectual talent for almost two centuries. Recognized as Sweden’s most prestigious technical university, KTH is also the country’s oldest and largest. Computerized simulation technique was recognized as a fundamental component of the higher-education sector at KTH as early as the fifties. Although the utilization of these tools in research is now considered to be standard, the educational aspects are not. In this field, the method of instruction followed by practice is considered to be a superior pedagogic method compared to lecture to many. The current method emphasizes on demonstrative activities of the learners known as phenomeno-graphic learning. However, phenomeno-graphic learning is viable if there are breadth and depth in the physic, mathematic, computer science and graphic, operational strategy and methodology, etc. illuminating weakness of learning by doing method. This work aims to report the success and progress of the course, numerical methods in energy technology, which utilizes Computational Fluid Dynamics cods such as STAR-CCM+ as the tool. Learning methodology is based on instructional design and andragogically approach that offers an elaboration on the mechanism of learning process and its premeditated in context of a prescribed framework. The results indicated the prominence of student sensitive and constructive learning process and the advantages of using a preferred framework in guiding the students in a pertinent context (area). The method particularly incorporates the constructivist principles that lead to enhance the learning process. In addition, the conclusions of this study similarly illuminate the vast potentials of computational fluid dynamic for research, evaluation and educational purposes.
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| 86. |
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| 87. |
- Fakhrai, Reza, et al.
(författare)
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Utilization Of Numerical Methods In Context Of Learning Process Enhancement For Mutli-Disciplinary Field Of Science
- 2012
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Ingår i: INTED2012 Proceedings. - : Iated. - 9788461555635 ; , s. 6138-6143
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Konferensbidrag (refereegranskat)abstract
- Computerized simulation technique is a fundamental component of the higher education and is a vital mechanism, utilized in phenomena-graphic studies in science. The system offers recreation of an alternative reality in front of scientist's eyes, giving an insight into the biggest and smallest scales (astronomy to nanotechnology) yet cannot be comprehended otherwise. Currently the tool is utilized in research and taught one on one. The progress in computational technology and the advent of commercial codes equipped with user-friendly interface have facilities the introduction of computational fluid dynamic in undergraduate education promoting critique of various learning opportunities through visualization technique. Nevertheless the outcomes of each study is highly influenced by the ideas, approaches, knowledge in phenomena, mathematical rules and measures, computer science, cads, post processing and interpretation of the results. The user of such system acts as the facilitator and liaison between the real and virtual phenomena. The user should own the proper education, experience, emphasizing the relevance of the teaching strategy; understanding the key mechanisms in learning process. Unlocking the full power of computational fluid dynamic, some critical topics in educational area need to be addressed. One is to identify the learning process, approaches and methodology. One task with three different definitions was given to groups and the data regarding the learning process, strategies for solving the problem adapted by students for, engagements of the participants in work was monitored. The data were gathered through a net based learning tool. The progress of the groups were scrutinized weekly, aiming at directing the group in pre-define learning scope. This work is based on instructional design and andragogically approach. It offers an elaboration on the mechanism of learning process and is premeditated in context of prescribed framework. The results indicated the prominence of student sensitive and constructive learning process and the advantages of using a preferred framework in guiding the students in pertinent context (area) particularly incorporation of constructivist principles that may lead to enhance learner's learning experience. In addition, the conclusions of this study similarly illuminate the vast potentials of computational fluid dynamic for research, evaluation and educational purposes.
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| 88. |
- Fan, Liangdong, 1985-
(författare)
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Development and characterization of functional composite materials for advanced energy conversion technologies
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The solid oxide fuel cell (SOFC) is a potential high efficient electrochemical device for vehicles, auxiliary power units and large-scale stationary power plants combined heat and power application. The main challenges of this technology for market acceptance are associated with cost and lifetime due to the high temperature (700-1000 oC) operation and complex cell structure, i.e. the conventional membrane electrode assemblies. Therefore, it has become a top R&D goal to develop SOFCs for lower temperatures, preferably below 600 oC. To address those above problems, within the framework of this thesis, two kinds of innovative approaches are adopted. One is developing functional composite materials with desirable electrical properties at the reduced temperature, which results of the research on ceria-based composite based low temperature ceramic fuel cell (LTCFC). The other one is discovering novel energy conversion technology - Single-component/ electrolyte-free fuel cell (EFFC), in which the electrolyte layer of conventional SOFC is physically removed while this device still exhibits the fuel cell function. Thus, the focus of this thesis is then put on the characterization of materials physical and electrochemical properties for those advanced energy conversion applications. The major scientific content and contribution to this challenging field are divided into four aspects except the Introduction, Experiments and Conclusions parts. They are:Continuous developments and optimizations of advanced electrolyte materials, ceria-carbonate composite, for LTCFC. An electrolysis study has been carried out on ceria-carbonate composite based LTCFC with cheap Ni-based electrodes. Both oxygen ion and proton conductance in electrolysis mode are observed. High current outputs have been achieved at the given electrolysis voltage below 600 oC. This study also provides alternative manner for high efficient hydrogen production. Compatible and high active electrode development for ceria-carbonate composite electrolyte based LTCFC. A symmetrical fuel cell configuration is intentionally employed. The electro-catalytic activities of novel symmetrical transition metal oxide composite electrode toward hydrogen oxidation reaction and oxygen reduction reaction have been experimentally investigated. In addition, the origin of high activity of transition metal oxide composite electrode is studied, which is believed to relate to the hydration effect of the composite oxide.A novel all-nanocomposite fuel cell (ANFC) concept proposal and feasibility demonstration. The ANFC is successfully constructed by Ni/Fe-SDC anode, SDC-carbonate electrolyte and lithiated NiO/ZnO cathode at an extremely low in-situ sintering temperature, 600 oC. The ANFC manifests excellent fuel cell performance (over 550 mWcm-2 at 600 oC) and a good short-term operation as well as thermo-cycling stability. All results demonstrated its feasibility and potential for energy conversion.Fundamental study results on breakthrough research Single-Component/Electrolyte-Free Fuel Cell (EFFC) based on above nanocomposite materials (ion and semi-conductive composite) research activities. This is also the key innovation point of this thesis. Compared with classic three-layer fuel cells, EFFC with an electrolyte layer shows a much simpler but more efficient way for energy conversion. The physical-electrical properties of composite, the effects of cell configuration and parameters on cell performance, materials composition and cell fabrication process optimization, micro electrochemical reaction process and possible working principle were systematically investigated and discussed. Besides, the EFFC, joining solar cell and fuel cell working principle, is suggested to provide a research platform for integrating multi-energy-related device and technology application, such as fuel cell, electrolysis, solar cell and micro-reactor etc.This thesis provides a new methodology for materials and system innovation for the fuel cell community, which is expected to accelerate the wide implementation of this high efficient and green fuel cell technology and open new horizons for other related research fields.
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| 89. |
- Fedulov, Vitali
(författare)
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Educational evaluation of an interactive multimedia learning platform : computerized educational platform in heat and power technology
- 2005
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Learning materials have multiple forms, such as books, overhead slides, computer files, blackboard notes by teachers, narration to the notes, video/audio tapes etc. Since the forms are highly inhomogeneous, it becomes difficult to collect and practically use them by a particular learner for individual study at home. Such multiple media are also expensive in management, since human resources are needed to keep the material repositories in order. One solution of the problem lies in centralized active digital repositories. Such repositories aim to simplify the learner’s work and boost learning efficiency. With introduction of interactivity and live communication tools such repositories become learning platforms exceeding the functionality of “passive” digital libraries. Such learning platforms could be easily used both for on-campus and distance education. This dissertation presents an evaluation of a digital repository of interactive multimedia content in the field of Heat and Power Technology: Computerized Educational Platform (CompEdu HPT). The platform evaluation consisted of integration of the tool into the university curriculum and then collection of feedback from students and teachers. The evaluation concerned usefulness of the platform for learning, aspects of instruction improvement, collecting observations about how the platform is used by students, as well as their opinions about the IT application direction chosen. The methods included: online feedback forms, questionnaires, interviews, discussions and observations. The evaluation demonstrated that the main strength of the platform is the integration of learning materials in one portable package. The students appreciated structured and logically arranged information that was available for easy access. Coverage of a broad area of knowledge related to heat and power technology was also pointed out as an advantage with reflection on the very low price of acquisition of the materials. The most popular elements of the content in use included: simulations, lecture notes, the print function, the glossary, and calculation exercises. A major part of the students declared the high value of CompEdu in facilitating home study. Nevertheless, not all the students had a positive impression: around one-fifth of them did not find the platform useful and expressed preference for more traditional learning media. The majority of the negative opinions concerned content quality, which directly related to weaknesses of the content production and review process. The evaluation emphasized the importance of material quality and amount as the key issue for a good learning platform with relatively smaller importance of presentation forms. The evaluation also considered aspects of functionality from the user point of view. Differentiation between popularity of simulations showed that simulations used by teachers during lectures have higher educational value than those for individual use only. The popularity of the printing option indicated a need for adaptation of digital materials for paper publishing. The general conclusion for practical use of multimedia tools in education was that high usability and simplicity of information access should be the focus point of any chosen approach in the direction. The CompEdu evaluation suggested that after thorough content review and addition of an efficient search mechanism the platform can successfully deliver rich learning content. The platform gave an extensive real-case illustration of how multimedia can be used in educational practice. Due to the evaluation, the CompEdu e-learning group has collected rich experience and know-how in the field of active knowledge repositories. The experience will be used for development of a more sophisticated learning platform working in the global Internet environment with major focus on information accessibility by easy search.
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| 90. |
- Ferria, Hakim
(författare)
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Contribution to Numerical and Experimental Studies of Flutter in Space Turbines. Aerodynamic Analysis of Subsonic or Supersonic Flows in Response to a Prescribed Vibratory Mode of the Structure.
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Modern turbomachines are designed towards thinner, lighter and highly loaded blades. This gives rise to increased sensitivity to flow induced vibrations such as flutter, which leads to structure failure in a short period of time if not sufficiently damped. Although numerical tools are more and more reliable, flutter prediction still depends on a large degree on simplified models. In addition, the critical nature of flutter, resulting in poor well-documented real cases in the open literature, and the lack of experimental database typical of engine flows make its apprehension even more challenging. In that context, the present thesis is dedicated to study flutter in recent turbines through aerodynamic analysis of subsonic or supersonic flows in response to a prescribed vibratory mode of the structure. The objective is to highlight some mechanisms potentially responsible for flutter in order to be in better position when designing blades. The strategy consists in leading both experimental and numerical investigations. The experimental part is based on a worldwide unique annular turbine sector cascade employed for measuring the aeroelastic response by means of the aerodynamic influence coefficient technique. The cascade comprises seven low pressure gas turbine blades one of which can oscillate in a controlled way as a rigid body. Aeroelastic responses are measured at various mechanical and aerodynamic parameters: pure and combined modeshapes, reduced frequency, Mach number, incidence angle. In addition to turbulence level measurements, the database aims at assessing the influence of these parameters on the aerodynamic damping, at validating the linear combination principle and at providing input for numerical tools.The numerical part is based on unsteady computations linearized in the frequency domain and performed in the traveling wave mode. The focus is put on two industrial space turbines:2D computations are performed on an integrally bladed disk, also called blisk; its very low viscous material damping results in complex motions with combined modes and extremely high reduced frequency. The blisk operates at low subsonic conditions without strong non-linearities. Although the blades have been predicted aeroelastically stable, an original methodology based on elementary decompositions of the blade motion is presented to identify the destabilizing movements. The results suggest that the so-called classical flutter is surprisingly prone to occur. Moreover, the aerodynamic damping has been found extremely sensitive to the interblade phase angle and cut-on/cut-off conditions.3D computations are then performed on a supersonic turbine, which features shock waves and boundary layer separation. In contrast, the blade motion is of elementary nature, i.e. purely axial. The blades have been predicted aeroelastically unstable for backward traveling waves and stable for forward traveling waves. The low reduced frequencies allow quasi-steady analysis, which still account for flutter mechanisms: the shock wave motion establishes the boundary between stable and unstable configurations.
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