| 51. |
- Abadikhah, Hossein, 1987
(författare)
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Dynamic higher order equations
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The subject of this thesis is to derive and evaluate governing equations and correspondingboundary conditions for solid cylinders and rectangular plates, where the materialconstituting the cylinder or plate are governed by classical elasticity, micropolar elasticityor a functionally graded case of the previously mentioned models. This is achieved by asystematic power series expansion approach, by either adopting a generalized Hamilton'sprinciple or a direct approach.For the solid cylinders a power series expansion in the radial coordinate for the sought fields are adopted. Equations of motion together with consistent sets of end boundaryconditions are derived in a systematic fashion up to arbitrary order using a generalizedHamilton's principle. Governing equations are obtained for longitudinal, torsional, andexural modes. In the case of the rectangular plate, a power series expansion of thesought fields are adopted in the thickness coordinate. Governing equations of motion, forextensional and exural case, together with consistent sets of edge boundary conditionsare derived in a systematic fashion up to arbitrary order with use of the direct approach.Both the governing equations for the solid cylinder and the rectangular plate areasymptotically correct to all studied orders. Numerical examples are presented fordifferent sorts of problems, using exact theory, the present series expansion theories ofdifferent order, various classical theories and other newly developed approximate theories.These results cover dispersion curves, eigenfrequencies, various curves of cross sectionalquantities such as displacements, stresses and micro-rotations, as well as fixed frequencymotion due to prescribed end displacement or lateral distributed forces. The resultsillustrate that the present approach may render benchmark solutions provided higher ordertruncations are used, and act as engineering equations when using low order truncations.
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| 52. |
- Abadikhah, Hossein, 1987
(författare)
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Dynamic higher order equations for structural elements
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The subject of this thesis is to derive and evaluate governing equations and corresponding boundary conditions for solid isotropic cylinders and isotropic micropolar rectangular plates. This is achieved by a systematic power series expansion approach, by either adopting a generalized Hamilton's principle or a direct approach.For the solid cylinders a power series expansion in the radial coordinate is adopted. Equations of motion together with consistent sets of end boundary conditions are derived in a systematic fashion up to arbitrary order using a generalized Hamilton's principle. Governing equations are obtained for longitudinal, torsional, and flexural modes. In the case of the isotropic micropolar plate a power series expansion of the displacements and micro-rotations are adopted in the thickness coordinate. Governing equations of motion, for extensional and flexural case, together with consistent sets of edge boundary conditions are derived in a systematic fashion up to arbitrary order with use of the direct approach.Both the governing equations for the solid cylinder and the micropolar plate are asymptotically correct to all studied orders. Numerical examples are presented for different sorts of problems, using exact theory, the present series expansion theories of different order, various classical theories and other newly developed approximate theories. These results cover dispersion curves, eigenfrequencies, various curves of cross sectional quantities such as displacements, stresses and micro-rotations, as well as fixed frequency motion due to prescribed end displacement or lateral distributed forces. The results illustrate that the present approach may render benchmark solutions provided higher order truncations are used, and act as engineering equations using low order truncation.
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| 53. |
- Abadikhah, Hossein, 1987, et al.
(författare)
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Dynamic Higher Order Functionally Graded Micropolar Plate Equations
- 2014
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Ingår i: Civil-Comp Proceedings. - Stirlingshire, UK : Civil-Comp Press. - 1759-3433. ; 106
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Tidskriftsartikel (refereegranskat)abstract
- The work, described in this paper, considers the analysis and derivation of dynamical equations on rectangular functionally graded plates governed by micropolar continuum theory. The proposed method is based on a power series expansion of the displacement field, micro-rotation field and material parameters in the thickness coordinates of the plate. This assumption results in sets of equations of motion together with consistent sets of boundary conditions. These derived equations are hyperbolic and can be constructed in a systematic fashion to any order desired. It is believed that these sets of equations are asymptotically correct. The construction of the equation is systematized by the introduction of recursion relations which relates higher order displacement and micro-rotation terms with the lower order terms. The fundamental eigenfrequency is obtained for the plate using different truncations orders of the present theory. Also various plots of mode shapes and stress distributions are compared for the fundamental eigenfrequency.
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| 54. |
- Abadikhah, Hossein, 1987, et al.
(författare)
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Dynamic higher order micropolar plate equations
- 2013
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Ingår i: Proceedings of the 11th International Conference on Vibration Problems (ICOVP-2013)”, Lisbon, Portugal, 9-12 September, 2013. - 9789899626447 ; , s. p.133-
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Konferensbidrag (refereegranskat)abstract
- This work considers the analysis and derivation of dynamical equations on rectangular plates governed by micropolar continuum theory. The proposed method is based on a power series expansion of the displacement field and micro-rotation field in the thickness coordinate of the plate. This assumption results in sets of equations of motion together with consistent sets of boundary conditions. These derived equations are hyperbolic and can be constructed in systematic fashion to any order desired. Hence it is believed that these sets of equations are asymptotically correct. The construction of the equation is systematized by the introduction of recursion relations which relates higher order displacement and micro-rotation terms with the lower order terms. Furthermore the equations can be divided into two categories of motions, namely extensional and flexural motion.Results are only obtained for the flexural motion of the plate using different truncations orders of the present theory, comparisons are performed with the plate theory developed by Eringen and the exact theory for micropolar continuum. Numerical examples are presented for dispersion curves on an infinite plate for the three lowest flexural modes. The three lowest eigenfrequencies for a simply supported plate are presented for different truncation orders, Eringen's plate theory and the exact theory. Also various plots on mode shapes stress distributions are compared for a infinite plate vibrating with a fix frequency.
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| 55. |
- Abadikhah, Hossein, 1987, et al.
(författare)
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Higher order beam equations
- 2012
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Ingår i: Civil-Comp Proceedings. - Stirlingshire, UK : Civil-Comp Press. - 1759-3433. ; 99
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Tidskriftsartikel (refereegranskat)abstract
- This paper considers the dynamic equations of circular cylindrical beams. The method is based on the three dimensional theory, adopting the generalized Hamilton's principle. By adopting a power series expansion method in the radial coordinate, together with a Fourier series expansion in the circumferential direction, this procedure results in sets of equations of motion together with consistent sets of end boundary conditions. These are derived in a systematic fashion up to arbitrary order, and are believed to be asymptotically correct. As such, the equations of motion are hyperbolic. Among the derived equation set are recursion relations, from which it is possible to express higher order displacement and stress fields in terms of lower order displacement fields. Results are obtained for all Fourier modes, among which axisymmetric, torsional and flexural modes are special cases. Special attention is paid towards the flexural mode. Using different truncation orders of the present theory, comparisons may be performed with classical theories such as the Euler-Bernoulli and the Timoshenko theories, besides the exact theory. Numerical examples are presented for dispersion curves of an infinite beam for the three lowest modes. Here various truncation orders are presented, as well as the exact theory. It is clear that higher accuracy is obtained as more terms are used. The lowest mode curve is accurately captured in the lower frequency range for all theories. Higher order truncations are indistinguishable from the exact curves in the presented range. Concerning eigenfrequencies, the three lowest frequencies for two different beams are presented for different truncation orders, classical theories as well as the exact theory for simply supported ends. As for the dispersion curves, the series expansion results converge to the exact results as the power series orders are increased. It is clear that more accurate results are obtained for lower frequencies and slender beams as expected. The Timoshenko theory is astonishingly accurate while the Euler-Bernoulli theory confirms the well known fact that this theory renders reasonably accurate results for slender beams in the low frequency spectra. Various plots on mode shapes and stress distributions are compared for the fundamental frequency for a simply supported beam. Here the curves using the lowest series expansion theory are very close to the exact results. There are more pronounced differences between theories for the mode shapes and the stress distributions, compared to the eigenfrequency calculations and the dispersion curves. The differences are most prominent for the stress distributions.
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| 56. |
- Abanades, J. C., et al.
(författare)
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Emerging CO2 capture systems
- 2015
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836. ; 40, s. 126-166
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Tidskriftsartikel (refereegranskat)abstract
- In 2005, the IPCC SRCCS recognized the large potential for developing and scaling up a wide range of emerging CO2 capture technologies that promised to deliver lower energy penalties and cost. These included new energy conversion technologies such as chemical looping and novel capture systems based on the use of solid sorbents or membrane-based separation systems. In the last 10 years, a substantial body of scientific and technical literature on these topics has been produced from a large number of R&D projects worldwide, trying to demonstrate these concepts at increasing pilot scales, test and model the performance of key components at bench scale, investigate and develop improved functional materials, optimize the full process schemes with a view to a wide range of industrial applications, and to carry out more rigorous cost studies etc. This paper presents a general and critical review of the state of the art of these emerging CO2 capture technologies paying special attention to specific process routes that have undergone a substantial increase in technical readiness level toward the large scales required by any CO2 capture system.
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| 57. |
- Abarenkov, Kessy, et al.
(författare)
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Annotating public fungal ITS sequences from the built environment according to the MIxS-Built Environment standard – a report from a May 23-24, 2016 workshop (Gothenburg, Sweden)
- 2016
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Ingår i: MycoKeys. - : Pensoft Publishers. - 1314-4057 .- 1314-4049. ; 16, s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- Recent molecular studies have identified substantial fungal diversity in indoor environments. Fungi and fungal particles have been linked to a range of potentially unwanted effects in the built environment, including asthma, decay of building materials, and food spoilage. The study of the built mycobiome is hampered by a number of constraints, one of which is the poor state of the metadata annotation of fungal DNA sequences from the built environment in public databases. In order to enable precise interrogation of such data – for example, “retrieve all fungal sequences recovered from bathrooms” – a workshop was organized at the University of Gothenburg (May 23-24, 2016) to annotate public fungal barcode (ITS) sequences according to the MIxS-Built Environment annotation standard (http://gensc.org/mixs/). The 36 participants assembled a total of 45,488 data points from the published literature, including the addition of 8,430 instances of countries of collection from a total of 83 countries, 5,801 instances of building types, and 3,876 instances of surface-air contaminants. The results were implemented in the UNITE database for molecular identification of fungi (http://unite.ut.ee) and were shared with other online resources. Data obtained from human/animal pathogenic fungi will furthermore be verified on culture based metadata for subsequent inclusion in the ISHAM-ITS database (http://its.mycologylab.org).
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| 58. |
- Abasian, Alireza, et al.
(författare)
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Vacuum-Packaged Piezoelectric Energy Harvester for Powering Smart Grid Monitoring Devices
- 2019
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Ingår i: IEEE Transactions on Industrial Electronics. - 0278-0046 .- 1557-9948. ; 66:6, s. 4447-4456
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents an analytical method for the design and power optimization of vacuum-packaged piezoelectric energy harvesters. It is shown that the maximum power point of a vacuum-packaged energy harvester is different from the conventional one which occurs when the electrical damping ratio equals to its mechanical counter-part. Also, it is shown that the captured power by a vacuum-packaged energy harvester is highly sensitive to the vibration frequency due to very low-mechanical damping ratio, e.g., up to 50% power drops corresponding to 2% deviations in the frequency. The analysis and design are performed in the context of an ac-line magnetic field energy harvester in which the line frequency is also fixed and this energy harvester is useful for developing the self-powered wireless monitoring devices. Furthermore, the vacuum-packaged devices are inherently robust against dust storm and icing phenomenon, which occur for overhead power lines. The proposed analytical method is established based on simplified assumptions and then an accurate method is developed for the analysis of vacuum-packaged devices. Obtained theoretical results are verified in the laboratory through a prototype of the vacuum-packaged piezoelectric device, which captures up to 90 mu W from a 10-A line current.
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| 59. |
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| 60. |
- Abay, Simon, 1980, et al.
(författare)
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Charge transport in InAs nanowire Josephson junctions
- 2014
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Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969 .- 1098-0121. ; 89:21, s. 214508-
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Tidskriftsartikel (refereegranskat)abstract
- We present an extensive experimental and theoretical study of the proximity effect in InAs nanowires connected to superconducting electrodes. We fabricate and investigate devices with suspended gate-controlled nanowires and nonsuspended nanowires, with a broad range of lengths and normal-state resistances. We analyze the main features of the current-voltage characteristics: the Josephson current, excess current, and subgap current as functions of length, temperature, magnetic field, and gate voltage, and compare them with theory. The Josephson critical current for a short-length device, L = 30 nm, exhibits a record high magnitude of 800 nA at low temperature that comes close to the theoretically expected value. The critical current in all other devices is typically reduced compared to the theoretical values. The excess current is consistent with the normal resistance data and agrees well with the theory. The subgap current shows a large number of structures; some of them are identified as subharmonic gap structures generated by multiple Andreev reflection. The other structures, detected in both suspended and nonsuspended devices, have the form of voltage steps at voltages that are independent of either the superconducting gap or length of the wire. By varying the gate voltage in suspended devices, we are able to observe a crossover from typical tunneling transport at large negative gate voltage, with suppressed subgap current and negative excess current, to pronounced proximity junction behavior at large positive gate voltage, with enhanced Josephson current and subgap conductance as well as a large positive excess current.
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