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Jansson, Ida
Publications (10 of 12) Show all publications
Jansson, I. & Åkerstedt, H. (2015). The dynamics of cylinder in a confined swirling flow with constant vorticity (ed.). Paper presented at . European journal of mechanics. B, Fluids, 54, 98-104
Open this publication in new window or tab >>The dynamics of cylinder in a confined swirling flow with constant vorticity
2015 (English)In: European journal of mechanics. B, Fluids, ISSN 0997-7546, E-ISSN 1873-7390, Vol. 54, p. 98-104Article in journal (Refereed) Published
Abstract [en]

In this work, we present a rigid body dynamics model that accounts for phenomena earlier studied both within hydrodynamic stability theory and the area of fluid-induced vibrations. The model captures the transverse dynamics of a rigid cylinder in a confined swirling flow. We show that a linear inviscid stability analysis of the whole system with respect to two-dimensional disturbances could be decomposed intoa solution governing rotational disturbances with homogeneous boundary conditions and a solution governing irrotational disturbances with inhomogeneous boundary conditions. This implies that the continuous stable spectrum of rotational disturbances is unchanged by the supposition of a free boundary. Moreover, the time-dependence of irrotational disturbances is governed by the disturbance of the rigid cylinder. Consequently, a rigid body dynamics model suffices to determine the time evolutionof irrotational disturbances. The model is based on the definition of a merged homogeneous state in which the solid mass of the rigid cylinder equals the displaced fluid mass and the flow is in solid body rotation. A departure from this merged homogeneous state yields an imbalance of the fictitious Coriolis and centrifugal force of the rigid cylinder and the counterbalancing motion-induced fluid forces. Thisimbalance makes the fluid flow support propagation of waves and may render a concentric position of the body unstable. A non-uniform distribution of the angular velocity delays the onset of instability so that the rigid cylinder can maintain a concentric position even though it is denser than the fluid.

National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-14148 (URN)10.1016/j.euromechflu.2015.06.015 (DOI)000362614600010 ()2-s2.0-84938891501 (Scopus ID)d7bbab73-13dc-4ea6-b6ed-d546a2530091 (Local ID)d7bbab73-13dc-4ea6-b6ed-d546a2530091 (Archive number)d7bbab73-13dc-4ea6-b6ed-d546a2530091 (OAI)
Note
Validerad; 2015; Nivå 2; 20150812 (idajoh)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Åkerstedt, H. & Jansson, I. (2015). The stability of a flexibly mounted rotating cylinder in turbulent annular flow (ed.). Paper presented at . Journal of Fluids and Structures, 58, 152-172
Open this publication in new window or tab >>The stability of a flexibly mounted rotating cylinder in turbulent annular flow
2015 (English)In: Journal of Fluids and Structures, ISSN 0889-9746, E-ISSN 1095-8622, Vol. 58, p. 152-172Article in journal (Refereed) Published
Abstract [en]

In this paper, we determine the inviscid linear stability with respect to two-dimensional disturbances of a fluid flow between two concentric cylinders. The inner rigid cylinder rotates with the angular velocity Ω0 and is fixed on elastic hinges at each end in the transverse direction. The outer cylinder does not rotate and is rigidly fixed. We assume that the fluid flow has an inner core that rotates as a solid body with angular velocity Ω0/2 and outside the core there are turbulent boundary layers. The velocity profile of the turbulent boundary layers satisfies the viscous Camassa−Holm equations. The perturbed fluid flow is derived from Rayleigh’s equation. The analysis yields an equation of motion of the cylinder equivalent to previous work without boundary layers and a basic flow of constant angular vorticity. The analysis is not restricted to a small gap between the cylinders. The results are compared with the results by Antunes et al. (1996), who consider a similar problem with uniform velocity profile and the limit of small gap. For ρc/ρf<1ρc/ρf<1 the results disagree in that the present analysis shows stability whereas Antunes et al. find instability. For ρc/ρf>1ρc/ρf>1 both theories predict stability and for larger values of ρc/ρfρc/ρf the agreement is good especially for small gap.

National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-12906 (URN)10.1016/j.jfluidstructs.2015.08.004 (DOI)000364248200010 ()2-s2.0-84943149440 (Scopus ID)c0d7cb7d-8780-4b17-a884-fc51ca8e51be (Local ID)c0d7cb7d-8780-4b17-a884-fc51ca8e51be (Archive number)c0d7cb7d-8780-4b17-a884-fc51ca8e51be (OAI)
Note
Validerad; 2015; Nivå 2; 20150812 (hake)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Jansson, I. (2014). On the notion of a rotating fluid force induced by swirling flow (ed.). Paper presented at . Journal of Sound and Vibration, 333(25), 7076-7083
Open this publication in new window or tab >>On the notion of a rotating fluid force induced by swirling flow
2014 (English)In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 333, no 25, p. 7076-7083Article in journal (Refereed) Published
Abstract [en]

The Bently/Muszynska (B/M) model shows that oil whirl and oil whip are both self-sustained vibrations associated with two unstable modes of a rotor–fluid system. The model includes a rotating fluid damping and inertia force. In certain configurations, the rotating damping force overcomes the frictional internal damping of the rotor and pushes the rotor into a stable limit cycle of circular orbiting. Such a notion of a rotating fluid force is based on bulk-flow models of fluid-filled clearances that could be approximated as narrow since the tangential velocity of the fluid then translates to one angular velocity at a certain radial distance defined by an average radius. This paper scrutinizes the assumption of a rotating fluid inertia force and pinpoints the additional inertial effects of the swirling flow as the gap width increases. These effects are clarified by deriving the equation of motion of a body with a mass subjected to motion-induced fluid forces of a confined swirling flow. We show that the inertial effects of the swirling flow counteract the destabilizing effect of the rotating damping force. However, if the body mass is larger than the displaced fluid mass, instability follows. The frequency of the unstable mode is unchanged by the additional inertial effects and is always equal to the frequency of the damping that induces the instability.

National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-4543 (URN)10.1016/j.jsv.2014.07.017 (DOI)000343337900018 ()2-s2.0-84908118117 (Scopus ID)27fb56aa-661b-4e92-b380-9fae0a9ddd70 (Local ID)27fb56aa-661b-4e92-b380-9fae0a9ddd70 (Archive number)27fb56aa-661b-4e92-b380-9fae0a9ddd70 (OAI)
Note
Validerad; 2014; 20140908 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Jansson, I. (2013). Vibrant bodies of swirling flow: On the limits of mechanical power transformation (ed.). (Doctoral dissertation). Paper presented at . Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Vibrant bodies of swirling flow: On the limits of mechanical power transformation
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Vibrerande kroppar av virvlande vatten : Energiomvandlingens gränser hos mekaniska system
Abstract [en]

This thesis pinpoints the intertwined nature of inertia. A vibrant body of a swirling flow is neither just a flow nor a body. It is both. The overall aim is to foresee and visualize vibrant motion and unsteady flow phenomena that follow with the release of power, addressed in the following two research problems: i) How are unsteady flow phenomena during the start-up sequence of a Kaplan turbine manifested as a vibratory twisting and heaving motion of its rotating system? ii) How does inertia come into play in the vibrant motion of a cylindrical interface adjacent to a solid core and a swirling flow confined by a concentric fixed cylinder? Dynamic measurements of axial and torsional strain on the middle shaft of a Kaplan-unit are represented by their energy intensity as a function of the orthogonal coordinates time and frequency. High energy intensities during adverse flow conditions are identified associated with coherent structures and their decay of turbulent flow in the draft tube and the swirl chamber above the runner. Previously non-identified self-sustained vibrations are detected during the loading of the generator, proposed to be induced by interaction of a resonator in the electrical system with an eigenmode of the hydraulic circuit. A strategy is developed to identify the dynamic behaviour of the rigid body mode of a swirling flow in a fixed cylindrical container with a solid core. The rigid body mode defines the fluid motion that follows by a motion of the rigid interface of the solid core to the swirling fluid. Interplay between fictitious forces yields rotating waves in the swirling flow and a vibrant motion of the solid core. The equation of motion of the rigid interface is analogous to a point mass subjected to external motion-induced forces. The vibratory motion of the rigid interface follows by a departure from a merged homogenous state, in which the solid core and fluid are of equal density and the fluid rotates as a solid body. As the rigid interface moves with a constant velocity, the constant vorticity of the fluid induces a fictitious force that opposes the fictitious Coriolis force induced by the solid body. If the angular velocity of the fluid is not constant, these forces do not cancel out each other, which implies that a swirling flow can withhold a solid core denser than the fluid in a concentric position.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2013
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-25835 (URN)b5c86814-2259-4434-b5c9-ece601183d8a (Local ID)978-91-7439-714-7 (ISBN)978-91-7439-715-4 (ISBN)b5c86814-2259-4434-b5c9-ece601183d8a (Archive number)b5c86814-2259-4434-b5c9-ece601183d8a (OAI)
Note
Godkänd; 2013; 20130823 (idajoh); Tillkännagivande disputation 2013-09-06 Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Ida Jansson Ämne: Strömningslära/Fluid Mechanics Avhandling: Vibrant Bodies of Swirling Flow: On the Limits of Mechanical Power Transformation Opponent: Professor Don-Hyun Kim, Dept of Aerospace and System Engineering, Gyeongsang National University, Jinju, Sydkorea Ordförande: Professor Staffan Lundström, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Tid: Fredag den 27 september 2013, kl 09.00 Plats: E246, Luleå tekniska universitetAvailable from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-24Bibliographically approved
Jansson, I., Åkerstedt, H. O., Aidanpää, J.-O. & Lundström, T. S. (2012). The effect of inertia and angular momentum of a fluid annulus on lateral transversal rotor vibrations (ed.). Paper presented at . Journal of Fluids and Structures, 28, 328-342
Open this publication in new window or tab >>The effect of inertia and angular momentum of a fluid annulus on lateral transversal rotor vibrations
2012 (English)In: Journal of Fluids and Structures, ISSN 0889-9746, E-ISSN 1095-8622, Vol. 28, p. 328-342Article in journal (Refereed) Published
Abstract [en]

An extensive amount of work exists on experimental and theoretical analysis of unsteady flow phenomena in hydraulic turbines. Still, resonance phenomena and self-excited vibrations of the rotor of hydropower machines are not considered as a major problem during normal operation conditions. Nevertheless, in development and research it is not sufficient to rely on earlier experience. An accurate predictive rotor model is crucial in risk assessment of rotor vibrations of hydraulic generator units. This paper discusses the effects of inertia and the rotational energy of the fluid in the turbine on lateral transversal shaft vibrations of hydraulic generator units. There is a lack of agreement among engineers upon how fluid inertia of the turbine should be included in rotor models. The rotational energy of the fluid has a potential risk of feeding self-excited vibrations. A fluid-rotor model is presented that captures the effect of inertia and angular momentum of a fluid annulus on vibrations of an inner rigid cylinder. The purpose of the model is to gain physical understanding of the phenomena at work and it is not applicable to specific turbines. The linearized equation of motion of the cylinder surrounded by a fluid annulus is solved for by one single complex equation. The constrained cylinder has two degrees of freedom in the plane perpendicular to its axis. By the assumption of irrotational cyclic flow, the fluid motion is described by a complex potential function. The motion of the cylinder is described by three parameters. Two surfaces are defined that splits the parameter space into regions with different qualitative behaviour. One surface defines the limit of stability whereas the other defines a limit when the eigenvalues have opposite signs or are both positive. The response to an external periodic rotating force is visualized by the magnitude of the inverse of the complex dynamic stiffness.

National Category
Fluid Mechanics and Acoustics Applied Mechanics
Research subject
Fluid Mechanics; Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-9972 (URN)10.1016/j.jfluidstructs.2011.10.008 (DOI)000301161800021 ()2-s2.0-84856212293 (Scopus ID)8b4de7e3-b973-42f6-a6b1-c2f60e348a63 (Local ID)8b4de7e3-b973-42f6-a6b1-c2f60e348a63 (Archive number)8b4de7e3-b973-42f6-a6b1-c2f60e348a63 (OAI)
Note
Validerad; 2012; 20111209 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Jansson, I. & Åkerstedt, H. O. (2011). Hur en cylinders egensvängningar beror av en omgivande fluids rörelse (ed.). Paper presented at Svenska mekanikdagar 2011 : 13/06/2011 - 15/09/2011. Paper presented at Svenska mekanikdagar 2011 : 13/06/2011 - 15/09/2011.
Open this publication in new window or tab >>Hur en cylinders egensvängningar beror av en omgivande fluids rörelse
2011 (Swedish)Conference paper, Oral presentation only (Refereed)
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-32039 (URN)6669fe48-fe98-4630-ace5-51f0affc9aa4 (Local ID)6669fe48-fe98-4630-ace5-51f0affc9aa4 (Archive number)6669fe48-fe98-4630-ace5-51f0affc9aa4 (OAI)
Conference
Svenska mekanikdagar 2011 : 13/06/2011 - 15/09/2011
Note
Godkänd; 2011; 20111010 (ysko)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-28Bibliographically approved
Jansson, I. (2010). The effect of flowing water on turbine rotor vibrations (ed.). (Licentiate dissertation). Paper presented at . Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>The effect of flowing water on turbine rotor vibrations
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Alternative title[sv]
Hur strömmande vatten påverkar turbinaxelvibrationer
Abstract [en]

There is a lack of standardized rules on how the fluid in the turbine should be included in rotor models of hydraulic machinery. This thesis is an attempt to shed some light on this issue. We approach the problem from two viewpoints, situated at place at a hydropower plant and by mathematical analysis.One goal of the thesis is to develop a measurement system that monitors the instantaneous pressure at several locations of a runner blade on a 10 MW Kaplan prototype in Porjus along Lule river. Paper A outlines the development of the measurement system and the instrumentation of the runner blade. Miniature piezo-resisitive pressure transducers were mounted flush to the surface. If instrumentation is successful, the pressure field of the runner blade could be measured simultaneously as the loads and displacements of the guide bearings and the generator.The second objective is concerned with how the motion-induced fluid force affects the dynamic behaviour of the rotor. Inertia and angular momentum of the fluid and shrouding are expected to influence the dynamic behaviour of the turbine. Paper B scrutinizes this assumption by presenting a simple fluid-rotor model that captures the effects of inertia and angular momentum of the fluid on the motion of a confined cylinder. The simplicity of the model allows for powerful analytical solution methods. The results show that fluid inertia, angular momentum and shrouding of hydraulic turbines could have substantial effects on lateral rotor vibrations. This calls for further investigation with a more complex fluid-rotor model that accounts for flexural bending modes.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2010. p. 37
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-17485 (URN)3985b740-c052-11df-a707-000ea68e967b (Local ID)978-91-7439-137-4 (ISBN)3985b740-c052-11df-a707-000ea68e967b (Archive number)3985b740-c052-11df-a707-000ea68e967b (OAI)
Note
Godkänd; 2010; 20100915 (idajoh); LICENTIATSEMINARIUM Ämnesområde: Strömningslära/Fluid Mechanics Examinator: Professor Staffan Lundström, Luleå tekniska universitet Diskutant: Filosofie doktor Jörgen Burman, ITT Water & Wastewater Sverige, Sundbyberg Tid: Fredag den 15 oktober 2010 kl 10.00 Plats: E243, Luleå tekniska universitetAvailable from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Jansson, I., Åkerstedt, H. O., Lundström, S. & Aidanpää, J.-O. (2009). Fluidinducerade reaktionskrafter för vertikalaxlade vattenkraftturbiner och dess betydelse för axelns laterala egensvängningar (ed.). In: (Ed.), (Ed.), Svenska mekanikdagarna: Södertälje 2009. Paper presented at Svenska mekanikdagar 2009 : 15/06/2009 - 17/06/2009 (pp. 97). Stockholm: Svenska nationalkommittén för mekanik
Open this publication in new window or tab >>Fluidinducerade reaktionskrafter för vertikalaxlade vattenkraftturbiner och dess betydelse för axelns laterala egensvängningar
2009 (Swedish)In: Svenska mekanikdagarna: Södertälje 2009, Stockholm: Svenska nationalkommittén för mekanik , 2009, p. 97-Conference paper, Meeting abstract (Other academic)
Place, publisher, year, edition, pages
Stockholm: Svenska nationalkommittén för mekanik, 2009
Keywords
Engineering mechanics - Fluid mechanics, Teknisk mekanik - Strömningsmekanik
National Category
Fluid Mechanics and Acoustics Applied Mechanics
Research subject
Fluid Mechanics; Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-37382 (URN)b62eada0-9dfe-11de-a77c-000ea68e967b (Local ID)b62eada0-9dfe-11de-a77c-000ea68e967b (Archive number)b62eada0-9dfe-11de-a77c-000ea68e967b (OAI)
Conference
Svenska mekanikdagar 2009 : 15/06/2009 - 17/06/2009
Note
Godkänd; 2009; 20090910 (ysko)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2017-11-28Bibliographically approved
Jansson, I., Cervantes, M. & Aidanpää, J.-O. (2008). A monitoring system to estimate the pressure field of a Kaplan runner blade prototype (ed.). In: (Ed.), Hydro technology and the evironment for the new century: 24th IAHR Symposium on Hydraulic Machinery and Systems, October 27 - 31, 2008, Foz do Iguassu, Brazil. Paper presented at IAHR Symposium on Hydraulic Machinery and Systems : 27/10/2008 - 31/10/2008. Foz do Iguassu
Open this publication in new window or tab >>A monitoring system to estimate the pressure field of a Kaplan runner blade prototype
2008 (English)In: Hydro technology and the evironment for the new century: 24th IAHR Symposium on Hydraulic Machinery and Systems, October 27 - 31, 2008, Foz do Iguassu, Brazil, Foz do Iguassu, 2008Conference paper, Published paper (Refereed)
Abstract [en]

The technical development of hydraulic machinery has gone towards lighter components and higher power concentration levels. A deregulation of the power market world-wide means that the machines experience more transient loads and are sometimes operated at off-design points. Those facts demand a more precise dynamic analysis at the design level of hydraulic machinery than what was formerly customary. Mechanical engineering needs enhanced tools for this purpose. Prediction models need to be validated against experimental data. There are limited possibilities to perform experimental investigations of hydropower prototypes. Fundamental in an experimental dynamic analysis is to determine the forces acting on the machine. This paper is concerned with a monitoring system to estimate the angular resolved pressure field on the suction- and pressure side of a prototype Kaplan runner blade. By measuring the pressure at different positions on the runner blade, we have a tool to determine the hydraulic load acting on the runner. This is part of an experimental dynamic analysis of the behavior of 10 MW prototype of a low-head Kaplan prototype lodged in an old machine hall inaugurated 1914 situated above the polar circle in Porjus, Sweden.

Place, publisher, year, edition, pages
Foz do Iguassu: , 2008
National Category
Fluid Mechanics and Acoustics Applied Mechanics
Research subject
Fluid Mechanics; Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-31579 (URN)5ccf20b0-b0aa-11dd-9c9d-000ea68e967b (Local ID)5ccf20b0-b0aa-11dd-9c9d-000ea68e967b (Archive number)5ccf20b0-b0aa-11dd-9c9d-000ea68e967b (OAI)
Conference
IAHR Symposium on Hydraulic Machinery and Systems : 27/10/2008 - 31/10/2008
Note

Godkänd; 2008; Bibliografisk uppgift: CD-ROM; 20081112 (ysko)

Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Cervantes, M., Jansson, I., Jourak, A., Glavatskih, S. & Aidanpää, J.-O. (2008). Porjus U9A full-scale hydropower research facility (ed.). In: (Ed.), Hydro technology and the evironment for the new century: 24th IAHR Symposium on Hydraulic Machinery and Systems, October 27 - 31, 2008, Foz do Iguassu, Brazil. Paper presented at IAHR Symposium on Hydraulic Machinery and Systems : 27/10/2008 - 31/10/2008. Foz do Iguassu
Open this publication in new window or tab >>Porjus U9A full-scale hydropower research facility
Show others...
2008 (English)In: Hydro technology and the evironment for the new century: 24th IAHR Symposium on Hydraulic Machinery and Systems, October 27 - 31, 2008, Foz do Iguassu, Brazil, Foz do Iguassu, 2008Conference paper, Published paper (Refereed)
Abstract [en]

Hydropower still faces complex scientific and technical challenges in order to secure the availability and reliability of the power plants despite more than a century of development. The main challenge is due to new market constrains such as electrical market deregulation and introduction of renewable sources of energy. The major problem is related to the dynamic of the rotor involving several fields: hydraulics, power engineering and mechanics. On the other side, the large and growing hydropower world market represents an opportunity for technically advanced companies offering better efficiency. The difficulty to scale rigorously any technical advance makes full-scale experiment a necessity. World unique facilities are available at Porjus, Sweden, for this purpose. The Porjus Hydropower Centre is composed of a Francis (U8) and a Kaplan (U9) turbine of 10 MW, each exclusively dedicated to education, research and development. In order to further investigate specific issues related to availability and reliability, a project was initiated in 2006. The main objective is to make U9 a full-scale hydropower laboratory able firstly to furnish the necessary data for the development of rotor-dynamic models but also turbines and bearings. To this purposes more than 200 sensors have been installed to measure displacements, forces, pressure, film thickness, strains... The work presents an overview of the newly upgrade facility as well as some of the problems faced during the instrumentation of the machine.

Place, publisher, year, edition, pages
Foz do Iguassu: , 2008
National Category
Fluid Mechanics and Acoustics Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Applied Mechanics
Research subject
Fluid Mechanics; Machine Elements; Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-35842 (URN)a871a6b0-a9dd-11dd-b578-000ea68e967b (Local ID)a871a6b0-a9dd-11dd-b578-000ea68e967b (Archive number)a871a6b0-a9dd-11dd-b578-000ea68e967b (OAI)
Conference
IAHR Symposium on Hydraulic Machinery and Systems : 27/10/2008 - 31/10/2008
Note

Godkänd; 2008; Bibliografisk uppgift: CD-ROM; 20081103 (cervante)

Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-01-14Bibliographically approved
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