Gayane Piliposyan | University of Liverpool (original) (raw)
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Papers by Gayane Piliposyan
Journal of Sound and Vibration, 2010
The problem of bending waves localized near the free edge of a transversely isotropic plate is in... more The problem of bending waves localized near the free edge of a transversely isotropic plate is investigated using the Ambartsumian higher-order plate theory which takes account of the transverse shears generated by flexural deformation. Unlike the first-order Reissner–Mindlin theory, which also takes account of transverse shears, Ambartsumian's analysis does not demand that plane normal cross-sections remain plane during bending. Within
Journal of Physics D: Applied Physics, 2015
Propagation of electro-magneto-acoustic waves in a magneto-electro-elastic (MEE) periodic structu... more Propagation of electro-magneto-acoustic waves in a magneto-electro-elastic (MEE) periodic structure has been investigated with a three phase coupling between mechanical, electric and magnetic fields in each constituent layer. Due to this coupling electromagnetic waves couple with lattice vibrations resulting in both dielectric and magnetic phonon–polaritons which couple via the magneto-electric effect. Propagation properties of acoustic longitudinal and transverse vibrations in this superlattice have been investigated. For longitudinal acoustic vibrations perpendicular to the poling direction, the coupling of piezoelectric and piezomagnetic polaritons results in a propagating mode. For transverse lattice vibrations with the coupled MEE wave propagating parallel to the poling direction, there is a coupled piezoelectric–piezomagnetic phonon polariton gap. The MEE superlattice produces either negative permittivity or negative permeability functions but not double negativity to result in negative refraction crystal.
International Journal of Fracture, 2005
This paper considers the stress-strain state of a body consisting of two bonded uniform ferromagn... more This paper considers the stress-strain state of a body consisting of two bonded uniform ferromagnetic half-spaces, with an interfacial penny-shaped crack. The body is assumed to be acted on by a uniform magnetic field in a direction normal to the crack and interface. The problem is reduced to the solution of singular integral equations with respect to two unknown functions on a finite interval. These functions are defined analytically, allowing us to obtain formulae for the magnetoelastic stresses and coefficient of stress intensity. From these formulae, the influence of various physico-mechanical parameters and the magnetic field on the stress strain state of the body in the vicinity of crack is studied.
Concern is growing that climate change may amplify global flood risk but short hydrological data ... more Concern is growing that climate change may amplify global flood risk but short hydrological data series hamper hazard assessment. Lake sediment reconstructions are capturing a fuller picture of rare, high-magnitude events but the UK has produced few lake palaeoflood records. We report the longest lake-derived flood reconstruction for the UK to date, a 1500-year record from Brotherswater, northwest England. Its catchment is well-suited physiographically to palaeoflood research, but its homogeneous, dark brown sediment matrix precludes visual identification of flood layers. Instead, an outlier detection routine applied to high-resolution particle size measurements showed a >90% match, in stratigraphic sequence, to measured high river flows. Our late-Holocene palaeoflood reconstruction reveals nine multi-decadal periods of more frequent flooding (CE 510-630, 890-960, 990-1080, 1470-1560, 1590-1620, 1650-1710, 1740-1770, 1830-1890 and 1920-2012), and these show a significant associat...
Journal of Physics D: Applied Physics
Smart Structures and Materials 1997: Mathematics and Control in Smart Structures, 1997
Smart Structures and Materials 1995: Mathematics and Control in Smart Structures, 1995
Freshwater Biology, 2012
ABSTRACT 1. How climate warming may interact with other pressures on aquatic ecosystems is an imp... more ABSTRACT 1. How climate warming may interact with other pressures on aquatic ecosystems is an important issue for research and management. We combined lake monitoring data with a palaeolimnological study to explore the combined effects of eutrophication and subsequent oligotrophication with a long-term temperature increase in epilimnetic waters. Our goals were (i) to evaluate how well sediment-based reconstructions reflect the instrumental observations, (ii) to use the palaeo-record to characterise a reference state for the lake and (iii) to explore whether data from the sediment record can aid in separating the effects of nutrient load and temperature in a large and deep lake. 2. Lake Mjøsa is a large and deep lake in south-eastern Norway. Eutrophication symptoms peaked in the 1970s, which led to extensive measures to reduce the phosphorus load. A monitoring programme has run continuously from 1972. Monitoring has documented a marked decrease in phosphorus load and algal biomass and also revealed an increase in epilimnetic temperature and extended summer stratification. 3. Records of algal pigments and diatoms were extracted from sediment cores taken from 236 m depth. The pigment record documented dramatic changes in lake production consistent with the monitoring record. The diatom record reflected well the eutrophication history of the lake and also demonstrated that the assemblage of the recent recovery stage differs from that of the pre-eutrophication period. 4. Ordination of diatom assemblages over time constrained by proxies for nutrient load and temperature indicated that the diatom assemblage correlated with both factors, which together accounted for 60% of the variation in diatom composition. No interaction was detected between these factors. The results suggest that the diatom assemblage has responded to varying nutrient loads as well as to changes in temperature and/or factors that correlate with temperature. 5. Reconstructions of algal biomass and total phosphorus content mirrored known changes through the monitoring period, although the absolute phosphorus estimates were too high relative to the instrumental record. The sediment record from Lake Mjøsa provides a baseline for lake production in terms of algal pigments and organic contents, and for the diatom assemblage composition in a pristine stage.
Biologia, 2006
Sediment cores from nine different lakes in the Tatra Mountains, collected as part of the EU fund... more Sediment cores from nine different lakes in the Tatra Mountains, collected as part of the EU funded AL:PE, MOLAR and EMERGE projects investigating natural environmental records stored in remote mountain lake sediment sequences, were dated radiometrically by 210Pb and 137Cs. At five sites, Długi Staw Gąsienicowy and Zielony Staw Gąsienicowy on the Polish side of the Tatra Mountains and Starolesnianske pleso, Nižné Terianske pleso, and L’adové pleso on the Slovak side of the Tatra Mountains, the cores were sectioned at close intervals and analysed in detail to produce a high resolution chronology. For the remaining four sites, Zmarzly Staw Gąsienicowy (Poland), and Vel’ké Hincovo pleso, Vyšné Temnosmrečinské pleso, Vyšné Wahlenbergovo pleso (Slovakia), it was sufficient to establish a low resolution sketch chronology and only a few samples were analysed from each core. At L’adové pleso, multiple cores were collected in order to establish spatial distribution of sediments over the bed ...
International Journal of Solids and Structures, 2008
... In the case (5.5) the surface electro-elastic SH wave velocity V(k) monotonically increases f... more ... In the case (5.5) the surface electro-elastic SH wave velocity V(k) monotonically increases from V(0)=V GB to V qui =S 1 , when k changes from k = 0 to k=k qui , where the critical value k=k qui is defined from the following equation: (5.9)tanh(k qui ?? 2 (S 1 ))=?? qui =?? cons . ...
International Journal of Solids and Structures
Propagation of electro-elastic surface Love waves in a structure consisting of a piezoelectric ha... more Propagation of electro-elastic surface Love waves in a structure consisting of a piezoelectric half-space substrate of crystal class 6, 4, 6mm or 4mm and two layers, one of which (adjacent to the substrate) is a conducting material and the second is either a conducting or a dielectric material, is considered. The mathematical model obtained includes all the above crystal classes i.e. the surface wave problems related to all these classes are presented in a single mathematical model. The dispersion equation for the existence of Love surface waves with respect to phase velocity is obtained. Numerical calculations are carried out for three different layered structures. The effect of the second layer on the propagation behaviour of the surface Love wave in the structure is revealed.
International Journal of Solids and Structures
Propagation of electro-elastic surface Love waves in a structure consisting of a piezoelectric ha... more Propagation of electro-elastic surface Love waves in a structure consisting of a piezoelectric half-space substrate of crystal class 6, 4, 6mm or 4mm and two layers, one of which (adjacent to the substrate) is a conducting material and the second is either a conducting or a dielectric material, is considered. The mathematical model obtained includes all the above crystal classes i.e. the surface wave problems related to all these classes are presented in a single mathematical model. The dispersion equation for the existence of Love surface waves with respect to phase velocity is obtained. Numerical calculations are carried out for three different layered structures. The effect of the second layer on the propagation behaviour of the surface Love wave in the structure is revealed.
The differential equations and boundary conditions describing the vibrations and stability of sup... more The differential equations and boundary conditions describing the vibrations and stability of superconducting elastic plates in the external magnetic field were obtained. The effective numerical method is proposed for the solution of Neumann external problem The concrete problems of vibration and stability of superconducting rectangular plates were solved. The possibility of loss of static and dynamic stability under the influence of external longitudinal magnetic field was proved.
Basic equations and boundary conditions describing the behavior of two layered magnetostrictive, ... more Basic equations and boundary conditions describing the behavior of two layered magnetostrictive, ferromagnetic plates in a non-stationary magnetic field are obtained. On the basis of the formulated heterogeneous boundary problems it is shown that in the general case due to the heterogeneous structure of the plate and the magnetostrictive properties of its materials it is possible to excite bending resonance vibrations with the help of magnetic field periodic in time. The peculiarities of the account of magnetostrictive effect in the problems of static stability of ferromagnetic one-layer plate are revealed. The problem of forced lateral vibrations of two-layered magnetostrictive plate is considered.
Journal of Sound and Vibration, 2010
The problem of bending waves localized near the free edge of a transversely isotropic plate is in... more The problem of bending waves localized near the free edge of a transversely isotropic plate is investigated using the Ambartsumian higher-order plate theory which takes account of the transverse shears generated by flexural deformation. Unlike the first-order Reissner–Mindlin theory, which also takes account of transverse shears, Ambartsumian's analysis does not demand that plane normal cross-sections remain plane during bending. Within
Journal of Physics D: Applied Physics, 2015
Propagation of electro-magneto-acoustic waves in a magneto-electro-elastic (MEE) periodic structu... more Propagation of electro-magneto-acoustic waves in a magneto-electro-elastic (MEE) periodic structure has been investigated with a three phase coupling between mechanical, electric and magnetic fields in each constituent layer. Due to this coupling electromagnetic waves couple with lattice vibrations resulting in both dielectric and magnetic phonon–polaritons which couple via the magneto-electric effect. Propagation properties of acoustic longitudinal and transverse vibrations in this superlattice have been investigated. For longitudinal acoustic vibrations perpendicular to the poling direction, the coupling of piezoelectric and piezomagnetic polaritons results in a propagating mode. For transverse lattice vibrations with the coupled MEE wave propagating parallel to the poling direction, there is a coupled piezoelectric–piezomagnetic phonon polariton gap. The MEE superlattice produces either negative permittivity or negative permeability functions but not double negativity to result in negative refraction crystal.
International Journal of Fracture, 2005
This paper considers the stress-strain state of a body consisting of two bonded uniform ferromagn... more This paper considers the stress-strain state of a body consisting of two bonded uniform ferromagnetic half-spaces, with an interfacial penny-shaped crack. The body is assumed to be acted on by a uniform magnetic field in a direction normal to the crack and interface. The problem is reduced to the solution of singular integral equations with respect to two unknown functions on a finite interval. These functions are defined analytically, allowing us to obtain formulae for the magnetoelastic stresses and coefficient of stress intensity. From these formulae, the influence of various physico-mechanical parameters and the magnetic field on the stress strain state of the body in the vicinity of crack is studied.
Concern is growing that climate change may amplify global flood risk but short hydrological data ... more Concern is growing that climate change may amplify global flood risk but short hydrological data series hamper hazard assessment. Lake sediment reconstructions are capturing a fuller picture of rare, high-magnitude events but the UK has produced few lake palaeoflood records. We report the longest lake-derived flood reconstruction for the UK to date, a 1500-year record from Brotherswater, northwest England. Its catchment is well-suited physiographically to palaeoflood research, but its homogeneous, dark brown sediment matrix precludes visual identification of flood layers. Instead, an outlier detection routine applied to high-resolution particle size measurements showed a >90% match, in stratigraphic sequence, to measured high river flows. Our late-Holocene palaeoflood reconstruction reveals nine multi-decadal periods of more frequent flooding (CE 510-630, 890-960, 990-1080, 1470-1560, 1590-1620, 1650-1710, 1740-1770, 1830-1890 and 1920-2012), and these show a significant associat...
Journal of Physics D: Applied Physics
Smart Structures and Materials 1997: Mathematics and Control in Smart Structures, 1997
Smart Structures and Materials 1995: Mathematics and Control in Smart Structures, 1995
Freshwater Biology, 2012
ABSTRACT 1. How climate warming may interact with other pressures on aquatic ecosystems is an imp... more ABSTRACT 1. How climate warming may interact with other pressures on aquatic ecosystems is an important issue for research and management. We combined lake monitoring data with a palaeolimnological study to explore the combined effects of eutrophication and subsequent oligotrophication with a long-term temperature increase in epilimnetic waters. Our goals were (i) to evaluate how well sediment-based reconstructions reflect the instrumental observations, (ii) to use the palaeo-record to characterise a reference state for the lake and (iii) to explore whether data from the sediment record can aid in separating the effects of nutrient load and temperature in a large and deep lake. 2. Lake Mjøsa is a large and deep lake in south-eastern Norway. Eutrophication symptoms peaked in the 1970s, which led to extensive measures to reduce the phosphorus load. A monitoring programme has run continuously from 1972. Monitoring has documented a marked decrease in phosphorus load and algal biomass and also revealed an increase in epilimnetic temperature and extended summer stratification. 3. Records of algal pigments and diatoms were extracted from sediment cores taken from 236 m depth. The pigment record documented dramatic changes in lake production consistent with the monitoring record. The diatom record reflected well the eutrophication history of the lake and also demonstrated that the assemblage of the recent recovery stage differs from that of the pre-eutrophication period. 4. Ordination of diatom assemblages over time constrained by proxies for nutrient load and temperature indicated that the diatom assemblage correlated with both factors, which together accounted for 60% of the variation in diatom composition. No interaction was detected between these factors. The results suggest that the diatom assemblage has responded to varying nutrient loads as well as to changes in temperature and/or factors that correlate with temperature. 5. Reconstructions of algal biomass and total phosphorus content mirrored known changes through the monitoring period, although the absolute phosphorus estimates were too high relative to the instrumental record. The sediment record from Lake Mjøsa provides a baseline for lake production in terms of algal pigments and organic contents, and for the diatom assemblage composition in a pristine stage.
Biologia, 2006
Sediment cores from nine different lakes in the Tatra Mountains, collected as part of the EU fund... more Sediment cores from nine different lakes in the Tatra Mountains, collected as part of the EU funded AL:PE, MOLAR and EMERGE projects investigating natural environmental records stored in remote mountain lake sediment sequences, were dated radiometrically by 210Pb and 137Cs. At five sites, Długi Staw Gąsienicowy and Zielony Staw Gąsienicowy on the Polish side of the Tatra Mountains and Starolesnianske pleso, Nižné Terianske pleso, and L’adové pleso on the Slovak side of the Tatra Mountains, the cores were sectioned at close intervals and analysed in detail to produce a high resolution chronology. For the remaining four sites, Zmarzly Staw Gąsienicowy (Poland), and Vel’ké Hincovo pleso, Vyšné Temnosmrečinské pleso, Vyšné Wahlenbergovo pleso (Slovakia), it was sufficient to establish a low resolution sketch chronology and only a few samples were analysed from each core. At L’adové pleso, multiple cores were collected in order to establish spatial distribution of sediments over the bed ...
International Journal of Solids and Structures, 2008
... In the case (5.5) the surface electro-elastic SH wave velocity V(k) monotonically increases f... more ... In the case (5.5) the surface electro-elastic SH wave velocity V(k) monotonically increases from V(0)=V GB to V qui =S 1 , when k changes from k = 0 to k=k qui , where the critical value k=k qui is defined from the following equation: (5.9)tanh(k qui ?? 2 (S 1 ))=?? qui =?? cons . ...
International Journal of Solids and Structures
Propagation of electro-elastic surface Love waves in a structure consisting of a piezoelectric ha... more Propagation of electro-elastic surface Love waves in a structure consisting of a piezoelectric half-space substrate of crystal class 6, 4, 6mm or 4mm and two layers, one of which (adjacent to the substrate) is a conducting material and the second is either a conducting or a dielectric material, is considered. The mathematical model obtained includes all the above crystal classes i.e. the surface wave problems related to all these classes are presented in a single mathematical model. The dispersion equation for the existence of Love surface waves with respect to phase velocity is obtained. Numerical calculations are carried out for three different layered structures. The effect of the second layer on the propagation behaviour of the surface Love wave in the structure is revealed.
International Journal of Solids and Structures
Propagation of electro-elastic surface Love waves in a structure consisting of a piezoelectric ha... more Propagation of electro-elastic surface Love waves in a structure consisting of a piezoelectric half-space substrate of crystal class 6, 4, 6mm or 4mm and two layers, one of which (adjacent to the substrate) is a conducting material and the second is either a conducting or a dielectric material, is considered. The mathematical model obtained includes all the above crystal classes i.e. the surface wave problems related to all these classes are presented in a single mathematical model. The dispersion equation for the existence of Love surface waves with respect to phase velocity is obtained. Numerical calculations are carried out for three different layered structures. The effect of the second layer on the propagation behaviour of the surface Love wave in the structure is revealed.
The differential equations and boundary conditions describing the vibrations and stability of sup... more The differential equations and boundary conditions describing the vibrations and stability of superconducting elastic plates in the external magnetic field were obtained. The effective numerical method is proposed for the solution of Neumann external problem The concrete problems of vibration and stability of superconducting rectangular plates were solved. The possibility of loss of static and dynamic stability under the influence of external longitudinal magnetic field was proved.
Basic equations and boundary conditions describing the behavior of two layered magnetostrictive, ... more Basic equations and boundary conditions describing the behavior of two layered magnetostrictive, ferromagnetic plates in a non-stationary magnetic field are obtained. On the basis of the formulated heterogeneous boundary problems it is shown that in the general case due to the heterogeneous structure of the plate and the magnetostrictive properties of its materials it is possible to excite bending resonance vibrations with the help of magnetic field periodic in time. The peculiarities of the account of magnetostrictive effect in the problems of static stability of ferromagnetic one-layer plate are revealed. The problem of forced lateral vibrations of two-layered magnetostrictive plate is considered.