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Artykuły w czasopismach na temat "Excitation of even modes"
1
Denisov, Artem, Anton Bubis, Stanislau Piatrusha, Nadezhda Titova, Albert Nasibulin, Jonathan Becker, Julian Treu i in. "Heat-Mode Excitation in a Proximity Superconductor". Nanomaterials 12, nr 9 (25.04.2022): 1461. http://dx.doi.org/10.3390/nano12091461.
Pełny tekst źródłaStreszczenie:
Mesoscopic superconductivity deals with various quasiparticle excitation modes, only one of them—the charge-mode—being directly accessible for conductance measurements due to the imbalance in populations of quasi-electron and quasihole excitation branches. Other modes carrying heat or even spin, valley etc. currents populate the branches equally and are charge-neutral, which makes them much harder to control. This noticeable gap in the experimental studies of mesoscopic non-equilibrium superconductivity can be filled by going beyond the conventional DC transport measurements and exploiting spontaneous current fluctuations. Here, we perform such an experiment and investigate the transport of heat in an open hybrid device based on a superconductor proximitized InAs nanowire. Using shot noise measurements, we investigate sub-gap Andreev heat guiding along the superconducting interface and fully characterize it in terms of the thermal conductance on the order of Gth∼e2/h, tunable by a back gate voltage. Understanding of the heat-mode also uncovers its implicit signatures in the non-local charge transport. Our experiments open a direct pathway to probe generic charge-neutral excitations in superconducting hybrids.
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Denisov, Artem, Anton Bubis, Stanislau Piatrusha, Nadezhda Titova, Albert Nasibulin, Jonathan Becker, Julian Treu i in. "Heat-Mode Excitation in a Proximity Superconductor". Nanomaterials 12, nr 9 (25.04.2022): 1461. http://dx.doi.org/10.3390/nano12091461.
Pełny tekst źródłaStreszczenie:
Mesoscopic superconductivity deals with various quasiparticle excitation modes, only one of them—the charge-mode—being directly accessible for conductance measurements due to the imbalance in populations of quasi-electron and quasihole excitation branches. Other modes carrying heat or even spin, valley etc. currents populate the branches equally and are charge-neutral, which makes them much harder to control. This noticeable gap in the experimental studies of mesoscopic non-equilibrium superconductivity can be filled by going beyond the conventional DC transport measurements and exploiting spontaneous current fluctuations. Here, we perform such an experiment and investigate the transport of heat in an open hybrid device based on a superconductor proximitized InAs nanowire. Using shot noise measurements, we investigate sub-gap Andreev heat guiding along the superconducting interface and fully characterize it in terms of the thermal conductance on the order of Gth∼e2/h, tunable by a back gate voltage. Understanding of the heat-mode also uncovers its implicit signatures in the non-local charge transport. Our experiments open a direct pathway to probe generic charge-neutral excitations in superconducting hybrids.
3
Denisov, Artem, Anton Bubis, Stanislau Piatrusha, Nadezhda Titova, Albert Nasibulin, Jonathan Becker, Julian Treu i in. "Heat-Mode Excitation in a Proximity Superconductor". Nanomaterials 12, nr 9 (25.04.2022): 1461. http://dx.doi.org/10.3390/nano12091461.
Pełny tekst źródłaStreszczenie:
Mesoscopic superconductivity deals with various quasiparticle excitation modes, only one of them—the charge-mode—being directly accessible for conductance measurements due to the imbalance in populations of quasi-electron and quasihole excitation branches. Other modes carrying heat or even spin, valley etc. currents populate the branches equally and are charge-neutral, which makes them much harder to control. This noticeable gap in the experimental studies of mesoscopic non-equilibrium superconductivity can be filled by going beyond the conventional DC transport measurements and exploiting spontaneous current fluctuations. Here, we perform such an experiment and investigate the transport of heat in an open hybrid device based on a superconductor proximitized InAs nanowire. Using shot noise measurements, we investigate sub-gap Andreev heat guiding along the superconducting interface and fully characterize it in terms of the thermal conductance on the order of Gth∼e2/h, tunable by a back gate voltage. Understanding of the heat-mode also uncovers its implicit signatures in the non-local charge transport. Our experiments open a direct pathway to probe generic charge-neutral excitations in superconducting hybrids.
4
CAO, LI-GANG, i ZHONG-YU MA. "SOFT DIPOLE MODES IN NEUTRON-RICH Ni-ISOTOPES IN QRRPA". Modern Physics Letters A 19, nr 38 (14.12.2004): 2845–56. http://dx.doi.org/10.1142/s0217732304015233.
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The soft dipole modes in neutron-rich even–even Ni-isotopes are investigated in the quasiparticle relativistic random phase approximation. We study the evolution of strengths distribution, centroid energies of dipole excitation in low-lying and normal GDR regions with the increase of the neutron excess. It is found in the present study that the centroid energies of the soft dipole strengths strongly depend on the thickness of neutron skin along with the neutron-rich even–even Ni-isotopes.
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Tang, Deman, i Earl H. Dowell. "Reduced Order Model Analysis for Two-Dimensional Molecular Dynamic Chain Structure Attached to an Atomic Force Microscope". Journal of Dynamic Systems, Measurement, and Control 126, nr 3 (1.09.2004): 531–46. http://dx.doi.org/10.1115/1.1789969.
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Dynamic analysis and numerical simulation of a protein-ligand chain structure connected to a moving atomic force microscope (AFM) has been conducted. The elements of the chain are free to extend and rotate relative to each other in a two-dimensional plane. Sinusoidal base excitation of the cantilevered beam of the AFM is considered in some detail. Reduced order (dynamic) models are constructed using global modes for both linear and nonlinear dynamic systems with and without the “nearest neighbor assumption.” The agreement between the original and reduced order models (ROM) is very good even when only one global mode is included in the ROM for either the linear case or for the nonlinear case, provided the excitation frequency is lower than the fundamental natural frequency of the linear system. For higher excitation frequencies, more global modes are required. The computational advantage of the reduced order model is clear from the results presented.
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Liu, Kaicheng, i Cheng Yan. "Investigation of the Influence of Splitter Blades on the Resonance Conditions of Impellers". Applied Sciences 9, nr 10 (18.05.2019): 2051. http://dx.doi.org/10.3390/app9102051.
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The conventional resonance conditions are derived based on the conventionally designed impellers without splitter blades. This paper proposes the resonance conditions for impellers under the excitation from the impeller–diffuser interaction with attention paid on the influence of splitter blades. A lumped parameter model is established and the modal analysis is carried out. The blade-based representative modal vector (RMV) is defined. The influence of splitter blades on the impeller’s traits of modes is investigated by analyzing the spatial harmonic contents of the RMV. Then, given the specific form of the diffuser-induced engine order excitation acting on the main and splitter blades, the resonance conditions are derived. Tuned and mistuned cases are provided for a practical impeller. The resonance conditions are verified by harmonic response calculations. The applications of the proposed resonance conditions in resonance identification and hazard evaluation of different excitations are given. The differences between the proposed resonance conditions and the conventional ones are discussed. The research indicates that even the RMV of the tuned impeller contains two harmonic components due to the existence of splitter blades. When the excitation frequency equals the natural frequency of the impeller and the excitation order matches with either harmonic index of the two harmonics, the resonance occurs. The results of case studies show that the harmfulness of various engine orders of excitation can be exactly evaluated by the joint use of the spatial harmonic contents analysis result and the proposed resonance conditions; however, analyzing based on the conventional resonance conditions may lead to the misjudgment of the harmfulness of the excitations.
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Al-Khudair, Falih H. "Investigation of isospin excited and mixed-symmetry states in even–even N = Z nuclei". International Journal of Modern Physics E 27, nr 08 (sierpień 2018): 1850065. http://dx.doi.org/10.1142/s0218301318500659.
Pełny tekst źródłaStreszczenie:
Mixed-symmetry and isospin excited states are typical of the interacting boson model with isospin (IBM-3). With a view to look for such states, levels scheme of the IBM-3 dynamical symmetry is discussed. A systematic investigation in the proton and neutron degrees of freedom of the energy levels has been carried out. A sequence of isospin excitation bands has been identified. We have analyzed the wave functions and given the symmetrical labeling of the states. The transition probabilities between the isospin excitation states of model limits are analyzed in terms of isoscalar and isovector decompositions. The present calculations suggest that a combination of isospin excitation and mixed-symmetry states can provide substantial information on the structure of nuclear states. Calculations for [Formula: see text] and [Formula: see text] nuclei are presented and compared with the results of the shell model and available experimental data.
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Han, Jian Ping, i Pei Juan Zheng. "Modal Parameter Identification of a Rigid Frame-Continuous Girders Bridge under Ambient Excitation by Fast Bayesian FFT Method". Advanced Materials Research 639-640 (styczeń 2013): 985–91. http://dx.doi.org/10.4028/www.scientific.net/amr.639-640.985.
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Bayesian theory is adopted in modal parameter identification, finite element model updating and residual capacity evaluation of the structures recently. Fast Bayesian FFT modal identification approach provides a rigorous way to obtain modal parameters and well-separated modes using the fast Fourier transform under ambient excitation. Moreover, it avoids choosing the modal order or removing false modes based on the stable diagram and has its obvious advantages. In this paper, modal parameters of a rigid frame-continuous girders bridge under ambient excitation are identified by this approach. Comparison with stochastic subspace identification (SSI) method indicates that Fast Bayesian FFT is a good approach to identify the modal parameters even for a large number of measurement channels.
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Waluk, Jacek. "Non-classical effects in proton or hydrogen transfer". Pure and Applied Chemistry 88, nr 10-11 (1.11.2016): 1063–71. http://dx.doi.org/10.1515/pac-2016-0706.
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AbstractResults of thorough investigations of tautomerism in the ground and excited electronic states performed for various organic molecules under different regimes: condensed phases, isolated and single molecules, with a special emphasis on porphycene, a porphyrin isomer, demonstrate that, in order to precisely describe the proton/hydrogen transfer path, one has to explicitly consider tunneling. Tautomerization is a multidimensional process, controlled by excitation of specific vibrational modes. Vibrational excitation can both enhance or hinder the reaction. The role of specific vibrational modes can now be assessed, even at the level of single molecules.
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Wang, Zuo-Cai, Chun-Yang Huang, Zhi-Chao He i Yong-Ping Wang. "Strain modes identification using cross-correlation function of measured dynamic strain". Advances in Structural Engineering 20, nr 1 (28.07.2016): 96–104. http://dx.doi.org/10.1177/1369433216646008.
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Strain modes of structures reflect the distribution rule of dynamic strain and can be of service to structural health monitoring. This article presents a new method to estimate the strain modes of beam structures based on the measured dynamic strain. Since the cross-correlation matrix of the modal coordinates is a diagonal matrix, thus, the cross-correlation matrix of the measured dynamic strain is also a diagonal matrix, and the strain modes can be obtained to find the eigenvectors of the strain cross-correlation matrix. The strain modes of a simply support beam and a continuous beam subjected to various impulsive excitations are identified from the numerical simulations using the proposed method. The noise effect is also investigated in this article. The numerical results show that the proposed method can effectively identify the strain modes even with noise effect. Finally, the method is verified through the experiment of a simply supported beam under hammering excitation. The test results also show that the proposed method can estimate the strain modes of beam structures with a high accuracy.
Rozprawy doktorskie na temat "Excitation of even modes"
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Kumar, Pawan Goldreich Peter Martin. "Excitation and damping of solar p-modes /". Diss., Pasadena, Calif. : California Institute of Technology, 1988. http://resolver.caltech.edu/CaltechETD:etd-09092008-090628.
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Bryan-Brown, Guy Peter. "Optical excitation of electromagnetic modes using grating coupling". Thesis, University of Exeter, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280664.
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Strojny, Brandan Thomas. "EXCITATION AND ANALYSIS OF CHARACTERISTIC MODES ON COMPLEX ANTENNA STRUCTURES". The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1301006813.
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Wang, Feng. "Modes, Excitation and Applications of Plasmonic Nano-apertures and Nano-cavities". Kent State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=kent1348588159.
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Chen, Yi. "Propagation and Excitation of Electromagnetic Modes for Travelling-wave MRI Applications". The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1449158025.
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Lamriben, Cyril. "Transferts anisotropes d'énergie en turbulence en rotation et excitation de modes d'inertie". Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00734192.
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Nous présentons une étude expérimentale de l'influence d'une rotation d'ensemble sur le déclin d'un écoulement turbulent dans une géométrie confinée. L'écoulement est généré en translatant rapidement une grille dans un récipient parallélépipédique, et nous mesurons les champs de vitesse dans un plan vertical (parallèle à l'axe de rotation) grâce à un dispositif de PIV embarqué. Nous montrons dans un premier temps qu'une partie significative de l'énergie est contenue dans un écoulement moyen reproductible, qui s'identifie à une superposition de modes d'inertie résonnants de la cuve. Le couplage possible entre cet écoulement et la turbulence suggère que la turbulence ainsi créée n'est pas en déclin libre. Nous montrons cependant qu'il est possible d'inhiber l'apparition de ces modes d'inertie en modifiant les caractéristiques géométriques de la grille. Cette nouvelle configuration permet alors de caractériser dans l'espace physique les transferts d'énergie pour une turbulence en déclin libre. L'énergie associée aux incréments de vitesse et la densité de flux d'énergie sont calculées à partir d'un grand nombre de réalisations indépendantes. Nous montrons que la rotation provoque une forte bidimensionalisation de la distribution d'énergie, et que celle-ci est contrôlée par une densité de flux d'énergie qui reste quasi-radiale, mais qui fait apparaître une dépendance angulaire marquée. Enfin, nous étudions également l'écoulement dans un cube, que nous soumettons à une libration longitudinale afin d'exciter les modes observés initialement avec le dispositif de turbulence de grille. En comparant les champs de vitesse expérimentaux aux prédictions numériques des modes inviscides, nous montrons que seul un certain nombre de modes, compatibles avec les symétries du forçage, peuvent être excités par libration. Nous caractérisons en particulier la résonance du mode de plus bas ordre compatible avec les symétries du forçage, et discutons du rôle de la viscosité.
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Elston, Stephen John. "Characterisation of ferroelectric liquid crystal layers by the excitation of optic modes". Thesis, University of Exeter, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277166.
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Al-Anbaki, Atheer Faisal Hameed. "Footfall excitation of higher modes of vibration in low-frequency building floors". Thesis, University of Exeter, 2018. http://hdl.handle.net/10871/34081.
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This thesis investigates the footfall excitation of higher modes of vibration in low-frequency floor structures. This is motivated by the increased number of floors reportedly failing to meet the required occupants comfort level although being designed in accordance with the current state-of-the-art design guidelines. In particular modern, lightweight, and slender floor structures. The contribution to knowledge of this thesis can be summarised as: quantifying the signal energy of measured walking forces within and above the natural frequency cut-off proposed by the current state-of-the-art design guidelines; quantifying the contribution of higher modes of vibration to the overall response of low-frequency floors to human walking; propose measures to judge the response nature of low-frequency floors, these are the relevant change of the point stiffness and the shape of frequency response functions; proposing a frequency-domain approach that enables designers to include higher modes of vibration in the design against human-induced vibration. It was found that the signal energy of walking forces is distributed well beyond the natural frequency cut-off proposed by the current state-of-the-art design guidelines. Also, the contribution of localised, higher, modes of vibration to the overall response of ultra-lightweight floors was significant. Moreover, it was found that higher modes affect the response of floors of various construction types in one way or another. Hence, it was recommended to consider their contribution in the design of floors against human-induced vibration. Also, it was found that the higher the relative change of the point stiffness the more higher modes contribute to the overall response of floors. Finally, the frequency-domain analysis was found less expensive than time-domain analysis and could result in similarly useful information.
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Novikau, Ivan [Verfasser]. "Excitation and damping mechanisms of geodesic acoustic modes in tokamaks / Ivan Novikau". Ulm : Universität Ulm, 2020. http://d-nb.info/121694928X/34.
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Zarzuela, Fernández Ricardo. "Novel quantum phenomena and excitation modes in type-I superconductors and magnetic vortices". Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/285263.
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The aim of this thesis was to study quantum phenomena and excitation modes in type-I superconductors and magnetic vortices.
The intermediate state in type-I superconductors is characterized by the gradual penetration of magnetic flux and the coexistence of normal and superconducting domains. This thermodynamic phase shows a magnetic irreversibility of topological origin, even in the case of defect-free samples. This irreversibility has been explored in disk-shaped samples made of lead (the prototype of a type-I superconductor) using a magnetic field applied perpendicularly to the disk plane, by means of the measurement
of hysteresis cycles at different temperatures, zero-field-cooled and field-cooled magnetization curves at different magnetic fields and magnetic relaxations along the descending branch of the hysteresis cycles. Non-thermal magnetic relaxations have been observed in these samples at low temperatures, which have been attributed to the tunnel effect of normal-superconductor interfaces through pinning energy barriers. A quantum model based on the Caldeira-Leggett theory for dissipative systems have been developed to explain these experimental observations. The interface is described as a 2D elastic manifold that is pinned by a planar defect. The pinning barrier can be controlled by a supercurrent that exerts a force on the interface.
The vortex state turns out to be the ground state of magnetic disks for a wide variety of thicknesses and radii. It is characterized by the curling of the magnetization in the plane of the disk, leaving virtually no magnetic ‘charges’. The very weak uncompensated magnetic moment of the disk sticks out of a small area confined to the vortex core. The low-frequency dynamics of the vortex state is characterized by the spiral-like precessional motion of the vortex core as a whole (gyrotropic mode), which can be induced by the application of an in-plane magnetic field. The presence of structural defects in these magnetic disks affects the dynamics of the vortex state, which is indicative of the elastic nature of the vortex core along the axial direction of the disk. It has been studied whether the gyrotropic mode allows spatial dispersion similar to spin waves of a finite wavelength in ferromagnets. The excitation spectrum splits into two branches, one related to the gyrotropic mode with a gap given by the gyrofrequency of the disk and the other related to the existence of an effective mass associated to the vortex core. The magnetic irreversibility of the vortex state has been also explored by means of an experimental protocol analogous to that used in the case of type-I superconductors. Non-thermal magnetic relaxations have been observed again at low temperatures, which is attributed to the tunnel effect of a segment of the vortex core line through pinning barriers. A quantum model based on the Caldeira-Leggett theory for dissipative systems have been developed to explain these experimental observations. The interface is described as a 1D elastic manifold that is pinned by a linear defect.
To conclude, the effect of the vortex state on the supercurrent of a Josephson junction has been studied in the case where the non-superconducting layer consists of a magnetic disk with the vortex as the ground state. It has been concluded that the variation of the Josephson current with tiny displacements of the vortex core can be detected experimentally.El objetivo de esta tesis ha sido estudiar fenómenos cuánticos y modos de excitación en superconductores tipo-I y vórtices magnéticos. La irreversibilidad magnética en muestras de plomo con forma de disco en el estado intermedio ha sido explorada mediante medidas de ciclos de histéresis a diferentes temperaturas, medidas de las curvas de magnetización zero-field-cooled y field-cooled a diferentes campos y relajaciones magnéticas a lo largo de la rama descendiente de los ciclos de histéresis. Se han observado relajaciones magnéticas independientes de la temperatura en estas muestras, las cuales se atribuyen al efecto túnel de las interficies normal-superconductor a través de barreras de anclaje. Un modelo de efecto túnel basado en la teoría de Caldeira-Leggett para sistemas disipativos se ha construido para explicar estas observaciones experimentales, donde la interfície se trata como una variedad 2D elástica que se ancla a defectos planares. La barrera de anclaje se puede controlar mediante la inyección de supercorriente en el sistema. El núcleo del estado vórtice muestra una naturaleza elástica a lo largo de la dirección axial de los discos magnéticos que lo presentan como estado fundamental. Se ha estudiado bajo qué condiciones el modo girótropo es compatible con una dispersión espacial semejante a las ondas de espín de longitud de onda finita presentes en un ferromagneto. El espectro de excitaciones axiales presenta dos ramas bien definidas, una asociada al modo girótropo y la otra originada por la existencia de una masa efectiva asociada al núcleo. También se ha explorado la irreversibilidad magnética del estado vórtice mediante un protocolo análogo al de los superconductores tipo-I. De nuevo se ha observado un comportamiento no térmico a bajas temperaturas en las relajaciones magnéticas, el cual es atribuido al efecto túnel de un segmento del núcleo vorticial a través de las barreras de anclaje. Un modelo de efecto túnel basado en la teoría de Caldeira-Leggett para sistemas disipativos se ha construido para explicar estas observaciones experimentales, donde el núcleo vorticial se trata como una variedad 1D elástica anclada a un defecto lineal. Por último, se ha estudiado cuál sería el efecto del estado vórtice sobre la supercorriente de una unión Josephson si como capa no superconductora se escogiera un disco magnético con este estado fundamental. Se ha concluido que la variación de la corriente Josephson con desplazamientos pequeños del núcleo vorticial es detectable experimentalmente.
Książki na temat "Excitation of even modes"
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Papadopoulos, Pantelis. Excitation of single modes in graded index optical fibres. Salford: University of Salford, 1985.
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Eli, Reshotko, i Lewis Research Center, red. Excitation of continuous and discrete modes in incompressible boundary layers. [Cleveland, Ohio]: National Aeronautics and Space Administration, Lewis Research Center, 1998.
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Kavka, Alexander Edgar. Coulomb excitation: Analytical methods and experimental results on even selenium nuclei. Uppsala: Academia Ubsaliensis, 1989.
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Salvestrini, Francesco, Gian Maria Varanini i Anna Zangarini, red. La morte e i suoi riti in Italia tra Medioevo e prima Età moderna. Florence: Firenze University Press, 2008. http://dx.doi.org/10.36253/978-88-8453-648-8.
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Consciously repressed by the current dominating culture, in Italy and Europe in the late mediaeval and early modern age death was addressed with greater confidence and awareness, and sometimes even with serenity. The modes of dying and of conceiving death – and the varied and rich religious and civil rituals that accompanied it – reflected the values and the choices of rich and poor, of kings and peasants, merchants and soldiers, nobles and churchmen, men and women. Several decades after the major studies that opened the road to these strands of research in Italy too (Ariès, Tenenti), this book offers a series of penetrating and suggestive explorations of a fascinating and complex theme which no reader can consider extraneous.
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Delogu, Cristina, red. Tecnologia per il web learning. Florence: Firenze University Press, 2008. http://dx.doi.org/10.36253/978-88-8453-571-9.
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This book maps out a course through the methodological and technological innovations of internet-based training, setting the emphasis on the collaborative character of experiences of learning and on the interactivity of the virtual workshops. On the one hand, this underscores the possibilities offered by the net to make available educational modes centred on the social process that enables learning in an active manner, rather than on the centrality of contents to be passively transferred to the students. On the other hand, it also shows how in the virtual workshops it is possible to develop one's understanding of the phenomena that are the subject of learning as a result of the interaction with the phenomena themselves, reproduced in the computer, acting upon them and observing the consequences of one's own actions. The effect is to underline how this type of model of learning can help to overcome the technology gap between different countries and social groups (the digital divide) and also to make learning more accessible even to disabled students.
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Lee, Yong-Inn. Collective electronic excitation modes in a superlattice. 1985.
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Zeitlin, Vladimir. Resonant Wave Interactions and Resonant Excitation of Wave-guide Modes. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198804338.003.0012.
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The idea of resonant nonlinear interactions of waves, and of resonant wave triads, is first explained using the example of Rossby waves, and then used to highlight a mechanism of excitation of wave-guide modes, by impinging free waves at the oceanic shelf, and at the equator. Physics and mathematics of the mechanism, which is related to the phenomena of parametric resonance and wave modulation, are explained in detail in both cases. The resulting modulation equations, of Ginzburg–Landau or nonlinear Schrodinger type, are obtained by multi-scale asymptotic expansions and elimination of resonances, after the explanation of this technique. The chapter thus makes a link between geophysical fluid dynamics and other branches of nonlinear physics. A variety of nonlinear phenomena including coherent structure formation is displayed. The resonant excitation of wave-guide modes provides an efficient mechanism of energy transfer to the wave guides from the large to the small.
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National Aeronautics and Space Administration (NASA) Staff. Excitation of Continuous and Discrete Modes in Incompressible Boundary Layers. Independently Published, 2018.
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Giant Resonances: Fundamental High-Frequency Modes of Nuclear Excitation (Oxford Studies in Nuclear Physics). Oxford University Press, USA, 2001.
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Kyritsis, Dimitrios. Two Modes of Judicial Deference. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780199672257.003.0007.
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In order to preserve the courts’ subsidiarity, even when they monitor the legislature, we must develop a suitable concept of judicial deference. This is the aim of this chapter. It distinguishes two modes of deference, the epistemic and the robust. On the epistemic model, deference affects the deliberative process of judges but does not change the standard by which we evaluate legislative decisions. On the robust model, deference does not affect judicial deliberation but changes what is the right thing to do; it may require giving effect to the authority’s decision, although it is sub-optimal as far as its content is concerned on the strength of countervailing considerations of institutional design. These two modes of deference can also be combined (composite deference). Deference, thus understood, is not erratic and ad hoc but sensitive to reasons of political morality and amenable to rational application.
Części książek na temat "Excitation of even modes"
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Hoyng, P. "Excitation of Dynamo Modes". W Solar Photosphere: Structure, Convection, and Magnetic Fields, 359–74. Dordrecht: Springer Netherlands, 1990. http://dx.doi.org/10.1007/978-94-009-1061-4_41.
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Sage, Martin L. "Multiphoton Excitation of Bond Modes". W Atomic and Molecular Processes with Short Intense Laser Pulses, 447–51. Boston, MA: Springer US, 1988. http://dx.doi.org/10.1007/978-1-4613-0967-3_53.
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Yaduvanshi, Rajveer S., i Gaurav Varshney. "Hybrid Modes Excitation into DRA". W Nano Dielectric Resonator Antennas for 5G Applications, 125–41. First edition. | Boca Raton, FL : CRC Press, 2020.: CRC Press, 2020. http://dx.doi.org/10.1201/9781003029342-7.
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Nordlund, Åke, i Robert F. Stein. "Excitation and Damping of P-Modes". W New Eyes to See Inside the Sun and Stars, 199–212. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-4982-2_46.
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Diestmann, Thomas, Nils Broedling, Benedict Götz i Tobias Melz. "Surrogate Model-Based Uncertainty Quantification for a Helical Gear Pair". W Lecture Notes in Mechanical Engineering, 191–207. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-77256-7_16.
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AbstractCompetitive industrial transmission systems must perform most efficiently with reference to complex requirements and conflicting key performance indicators. This design challenge translates into a high-dimensional multi-objective optimization problem that requires complex algorithms and evaluation of computationally expensive simulations to predict physical system behavior and design robustness. Crucial for the design decision-making process is the characterization, ranking, and quantification of relevant sources of uncertainties. However, due to the strict time limits of product development loops, the overall computational burden of uncertainty quantification (UQ) may even drive state-of-the-art parallel computing resources to their limits. Efficient machine learning (ML) tools and techniques emphasizing high-fidelity simulation data-driven training will play a fundamental role in enabling UQ in the early-stage development phase.This investigation surveys UQ methods with a focus on noise, vibration, and harshness (NVH) characteristics of transmission systems. Quasi-static 3D contact dynamic simulations are performed to evaluate the static transmission error (TE) of meshing gear pairs under different loading and boundary conditions. TE indicates NVH excitation and is typically used as an objective function in the early-stage design process. The limited system size allows large-scale design of experiments (DoE) and enables numerical studies of various UQ sampling and modeling techniques where the design parameters are treated as random variables associated with tolerances from manufacturing and assembly processes. The model accuracy of generalized polynomial chaos expansion (gPC) and Gaussian process regression (GPR) is evaluated and compared. The results of the methods are discussed to conclude efficient and scalable solution procedures for robust design optimization.
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Samadi, R. "Stochastic Excitation of Acoustic Modes in Stars". W The Pulsations of the Sun and the Stars, 305–40. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-19928-8_11.
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Crossley, David J. "The Excitation of Core Modes by Earthquakes". W Geophysical Monograph Series, 41–50. Washington, D. C.: American Geophysical Union, 2013. http://dx.doi.org/10.1029/gm046p0041.
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Petersen, R. A., M. M. Samet i T. A. Long. "Excitation of Azimuthal Modes in an Axisymmetric Jet". W Turbulence Management and Relaminarisation, 435–43. Berlin, Heidelberg: Springer Berlin Heidelberg, 1988. http://dx.doi.org/10.1007/978-3-642-83281-9_29.
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Yaduvanshi, Rajveer S., i Harish Parthasarathy. "RDRA Angular Excitation Mathematical Model and Resonant Modes". W Rectangular Dielectric Resonator Antennas, 181–98. New Delhi: Springer India, 2015. http://dx.doi.org/10.1007/978-81-322-2500-3_8.
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Lin, Chia-Hsien, i Werner Däppen. "Investigating the Excitation of Acoustic Modes Using Homomorphic Deconvolution". W Helioseismic Diagnostics of Solar Convection and Activity, 553–60. Dordrecht: Springer Netherlands, 2000. http://dx.doi.org/10.1007/978-94-011-4377-6_39.
Pełny tekst źródłaStreszczenia konferencji na temat "Excitation of even modes"
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Tamir, T., J. J. Burke i George I. Stegeman. "Excitation of surface-plasmon modes along thin metal films". W OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1985. http://dx.doi.org/10.1364/oam.1985.wp7.
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A thin metal film can support two (Fano) plasmon modes, of which one exhibits a symmetric and the other an antisymmetric field with respect to the plane bisecting the film. It has recently been shown1 that, when the metal film is placed on a dielectric substrate, each of the two Fano modes evolves into two other distinct modes. However, the possible excitation of all four modes by realistic sources has not yet been explored. We therefore examine the field produced by an elementary (point or line) source placed in the film substrate geometry; any other arbitrary source can be described by a suitable superposition of such elementary sources. We then find that each of the two Fano modes along an isolated metal film accounts for a single viable mode when the film is placed on a substrate. Even though they are also solutions of the secular equation, the other two modes do not provide a distinct contribution to the total field due to an actual source. We therefore conclude that only two of the four plasmon modes may be experimentally observed in a film substrate geometry.
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Tang, Deman, i Earl H. Dowell. "Reduced Order Model Analysis for Two Dimensional Molecular Dynamic Chain Structure Attached to an Atomic Force Microscope". W ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-42496.
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Dynamic analysis and numerical simulation of a protein-ligand chain structure connected to a moving atomic force microscope (AFM) has been conducted. The elements of the chain are free to extend and rotate relative to each other in a two-dimensional plane. Sinusoidal base excitation of the cantilevered beam of the AFM is considered in some detail. Reduced order (dynamic) models are constructed using global modes for both linear and nonlinear dynamic systems with and without the “nearest neighbor assumption”. The agreement between the original and reduced order models (ROM) is very good even when only one global mode is included in the ROM for either the linear case or for the nonlinear case, provided the excitation frequency is lower than the fundamental natural frequency of the linear system. For higher excitation frequencies, more global modes are required. The computational advantage of the reduced order model is clear from the results presented.
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Allison, Timothy C., J. Jeffrey Moore, Andrew H. Lerche i Harold R. Simmons. "Revisiting the SAFE Diagram for Analysis of Mistuned Bladed Disks". W ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-69014.
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The SAFE diagram is a design tool that is often used for analyzing modes of concern in bladed disks. The diagram implements the concept of phase cancellation in order to show what bladed disk modes can and cannot be excited by upstream flow obstructions. In many cases, phase cancellation theory dictates that even if a modal frequency corresponds with an excitation order, the mode may not be excited if the total work calculated by integrating the excitation profile around the mode shape is equal to zero. This paper reviews the theory behind the SAFE diagram and explores the effects of blade mistuning on SAFE diagram analysis from both theoretical and experiential viewpoints. Modal test data, mistuned finite element analysis, and two case studies all indicate that mistuned modes may not exhibit the pure nodal diameter patterns that are predicted by a symmetric analysis and are required for phase cancellation. These mistuned asymmetric modes may result in high blade stresses and blade failure even if a SAFE diagram analysis indicates that the mode will not be excited.
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Kavarana, Farokh H., i R. Gordon Kirk. "Cracked Shaft Detection Using the Unbalance Excitation Technique". W ASME 1995 Design Engineering Technical Conferences collocated with the ASME 1995 15th International Computers in Engineering Conference and the ASME 1995 9th Annual Engineering Database Symposium. American Society of Mechanical Engineers, 1995. http://dx.doi.org/10.1115/detc1995-0494.
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Abstract The ever-growing interest of the modern rotordynamicist in the early detection of rotor cracks in turbomachinery has been the direct result of multiple catastrophic experiences that industry has faced in recent times due to cracked rotors. The complete failure of the rotor due to crack propagation is easily recognized as one of the most serious modes of plant failure. Even though the past decade has witnessed some laudable attempts that have been moderately successful in detecting cracked rotors, this aspect has not received the attention it warrants. A complete test rig has been designed and constructed for experimental research on the response characteristics of cracked rotors, the results of which will permit increased confidence in detecting the presence of rotor cracks in turbomachinery. The rig is capable of testing cracked shafts under the effect of lateral and coupled lateral/torsional vibrations. Conventional vibration signature analysis has been employed for the purpose of crack detection. This paper presents the details of the rig capabilities and results from the unbalance excitation technique applied for crack detection. The response of a cracked shaft differs markedly from that of an uncracked shaft when subjected to a known unbalance. This paper shows that unbalance excitation is a promising tool for cracked shaft detection.
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Förster, Alwin, i Lars Panning-von Scheidt. "Calculation of Nonlinear Systems Under Narrow Band Excitation Using Equivalent Linearization and Path Continuation". W ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/gt2021-58437.
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Abstract Turbomachines experience a wide range of different types of excitation during operation. On the structural mechanics side, periodic or even harmonic excitations are usually assumed. For this type of excitation there are a variety of methods, both for linear and nonlinear systems. Stochastic excitation, whether in the form of Gaussian white noise or narrow band excitation, is rarely considered. As in the deterministic case, the calculations of the vibrational behavior due to stochastic excitations are even more complicated by nonlinearities, which can either be unintentionally present in the system or can be used intentionally for vibration mitigation. Regardless the origin of the nonlinearity, there are some methods in the literature, which are suitable for the calculation of the vibration response of nonlinear systems under random excitation. In this paper, the method of equivalent linearization is used to determine a linear equivalent system, whose response can be calculated instead of the one of the nonlinear system. The method is applied to different multi-degree of freedom nonlinear systems that experience narrow band random excitation, including an academic turbine blade model. In order to identify multiple and possibly ambiguous solutions, an efficient procedure is shown to integrate the mentioned method into a path continuation scheme. With this approach, it is possible to track jump phenomena or the influence of parameter variations even in case of narrow band excitation. The results of the performed calculations are the stochastic moments, i.e. mean value and variance.
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Walmsley, Ian. "A model of the quantum noise in the Stokes pulse energy spectrum from a transient-stimulated Raman generator". W OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/oam.1990.wu2.
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Recently Swanson et al.1 have shown that, even in the transient regime of a Raman generator, when the Stokes pulses are nominally transform-limited, the mean frequency of the pulses fluctuates from pulse to pulse. The coherent modes model2 provides a simple, intuitive and computationally efficient method for determining the statistics of the Stokes light from a Raman generator. We use this model to calculate the probability density of the mean frequency of the Stokes pulse energy spectrum and show that it gives reasonable agreement with Swanson et al.'s experimental results. The spectral fluctuations in the transient regime arise because the excitation of high-order temporally coherent modes produces a time-dependent phase structure in the Stokes pulse. The phase of the Stokes field is more sensitive to the excitation of these high-order modes than is its amplitude, so that the pulse energy spectrum exhibits measurable fluctuations in the transient regime, even though the pulse temporal shape does not.3
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Dasgupta, Abhijit, Ed Habtour, Raman Sridharan i Elaine Lin. "Durability of Large Electronic Components Undergoing Multi-Axial Vibratory Excitation". W ASME 2015 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems collocated with the ASME 2015 13th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/ipack2015-48709.
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Shaker table vibration testing is nothing new for electronic components. Such environmental tests are most often conducted in a sequential uniaxial setup, where the test article is sequentially rotated and excited along three different orthogonal orientations. While sequential axis testing does excite modes in all three directions sequentially, it does not quantify or qualify how modes along different axes interact with one another when excited simultaneously. Traditional linear dynamics does not predict any cross-axis interactions between different spectral modes in vibrating structures, but this has long been suspected to be an oversimplification for many cases. The authors demonstrated this in a previous experiment, in which printed wiring assemblies (PWAs) of the same design were subjected to sequential uniaxial and simultaneous biaxial excitations. Boards undergoing bi-axial excitation suffered fatigue damage accumulation rates much higher than the superposition of damage rates from sequential uniaxial tests. Even as far back as 2010, the military added multi degree of freedom (MDoF) vibration tests to their 810G standard — so MDoF testing is rapidly gaining traction in the accelerated stress testing community. The cost of performing MDoF vibration durability testing can be significant, so an important technical issue turns into identifying when MDoF testing is necessary, and when single degree of freedom (SDoF) testing is sufficient. This study addresses this issue using a combination of mathematical models and FEA simulations. It is intuitively obvious that larger and more massive circuit components are more susceptible to these nonlinear cross-axis interactions, especially as the excitation levels become significant; however our long term goal is to quantify the effects of such parameters on the nonlinear interactions. The focus of the study is a simple beam with a tip mass — representing a circuit component with leads for mounting to the printed wiring board (PWB). The study also considers the effect of the PWB dynamics on the mechanical response of the circuit element, as it undergoes worst case excitation. The effects of several parameters are investigated, including component properties (e.g. mass, and height) as well as bi-axial excitation conditions (eg. frequency, relative phase and amplitude).
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Kim, W., i J. Rastegar. "Robot Manipulator Trajectory Synthesis for Minimal Vibrational Excitation". W ASME 1997 Design Engineering Technical Conferences. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/detc97/dac-3862.
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Abstract As a robot manipulator is forced to track a given trajectory, the required actuating torques (forces) may excite the natural modes of vibration of the system. Due to their nonlinear dynamics, internally and externally induced high harmonic excitation torques are generally generated even though such harmonics have been eliminated from the synthesized trajectories and filtered from the drive inputs. It is therefore desirable to synthesize trajectories such that the actuating torques required to realize them do not contain higher harmonic components with significant amplitudes. In this paper, a systematic method is presented for synthesizing such trajectories. With such trajectories, a robot manipulator can operate at higher speeds and achieve higher tracking accuracy with suppressed residual vibration. It is shown that in general and for a given starting point, such trajectories can only be synthesized to a portion of the operating space of the manipulator. The method is developed based on the Trajectory Pattern Method (TPM). The application of the method to optimal trajectory synthesis for a plane 2R manipulator is presented.
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Ng, Leslie, i Richard Rand. "Nonlinear Effects on Coexistence Phenomenon in Parametric Excitation". W ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-32406.
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We investigate the effect of nonlinearites on a parametrically excited ordinary differential equation whose linearization exhibits the phenomena of coexistence. The differential equation studied governs the stability mode of vibration in an unforced conservative two degree of freedom system used to model the free vibrations of a thin elastica. Using perturbation methods, we show that at parameter values corresponding to coexistence, nonlinear terms can cause the origin to become nonlinearly unstable, even though linear stability analysis predicts the origin to be stable. We also investigate the bifurcations associated with this instability.
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Li, Aiqin, i Earl H. Dowell. "Modal Reduction of Mathematical Models of Biological Molecules". W ASME 2005 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/detc2005-84056.
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This paper reports a detailed study of modal reduction based on either linear normal mode(LNM) analysis or proper orthogonal decomposition(POD) for modeling a single α-D glucopyranose monomer as well as a chain of monomers. Also a modal reduction method combining POD and component modal synthesis(CMS) is developed. The accuracy and efficiency of these methods are reported. The focus of this study is to determine to what extent these methods can reduce the time and cost of molecular modeling and simultaneously provide the required accuracy. It has been demonstrated that a linear reduced order model(ROM) is valid for small amplitude excitation and low frequency excitation. It is found that a nonlinear ROM based on POD modes provides a good approximation even for large excitation while the nonlinear ROM using linear eigenmodes as the basis vectors is less effective for modeling molecules with a strong nonlinearity. The ROM based on CMS using POD modes for each component also gives a good approximation. With the reduction in the dimension of the system using these methods the computational time and cost can be reduced significantly.
Raporty organizacyjne na temat "Excitation of even modes"
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Gorelenkov, N. N., L. E. Zakharov i M. V. Gorelenkova. A threshold for excitation of neoclassical tearing modes. Office of Scientific and Technical Information (OSTI), styczeń 1996. http://dx.doi.org/10.2172/206579.
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Bernabei, S., Z. Chang i D. Darrow. Correlation between excitation of Alfven modes and degradation of ICRF heating efficiency in TFTR. Office of Scientific and Technical Information (OSTI), maj 1997. http://dx.doi.org/10.2172/304148.
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Biglari, H., i L. Chen. A unified theory of resonant excitation of kinetic ballooning modes by energetic ions/alpha particles in tokamaks. Office of Scientific and Technical Information (OSTI), październik 1991. http://dx.doi.org/10.2172/5125641.
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Sesnic, S., R. Kaita, S. Kaye, M. Okabayashi, H. Takahashi, R. E. Bell, S. Bernabei i in. Excitation of high frequency pressure driven modes by non-axisymmetric equilibrium at high {beta}{sub pol} in PBX-M. Office of Scientific and Technical Information (OSTI), czerwiec 1993. http://dx.doi.org/10.2172/10169579.
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Rahmani, Mehran, Xintong Ji i Sovann Reach Kiet. Damage Detection and Damage Localization in Bridges with Low-Density Instrumentations Using the Wave-Method: Application to a Shake-Table Tested Bridge. Mineta Transportation Institute, wrzesień 2022. http://dx.doi.org/10.31979/mti.2022.2033.
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This study presents a major development to the wave method, a methodology used for structural identification and monitoring. The research team tested the method for use in structural damage detection and damage localization in bridges, the latter being a challenging task. The main goal was to assess capability of the improved method by applying it to a shake-table-tested prototype bridge with sparse instrumentation. The bridge was a 4-span reinforced concrete structure comprising two columns at each bent (6 columns total) and a flat slab. It was tested to failure using seven biaxial excitations at its base. Availability of a robust and verified method, which can work with sparse recording stations, can be valuable for detecting damage in bridges soon after an earthquake. The proposed method in this study includes estimating the shear (cS) and the longitudinal (cL) wave velocities by fitting an equivalent uniform Timoshenko beam model in impulse response functions of the recorded acceleration response. The identification algorithm is enhanced by adding the model’s damping ratio to the unknown parameters, as well as performing the identification for a range of initial values to avoid early convergence to a local minimum. Finally, the research team detect damage in the bridge columns by monitoring trends in the identified shear wave velocities from one damaging event to another. A comprehensive comparison between the reductions in shear wave velocities and the actual observed damages in the bridge columns is presented. The results revealed that the reduction of cS is generally consistent with the observed distribution and severity of damage during each biaxial motion. At bents 1 and 3, cS is consistently reduced with the progression of damage. The trends correctly detected the onset of damage at bent 1 during biaxial 3, and damage in bent 3 during biaxial 4. The most significant reduction was caused by the last two biaxial motions in bents 1 and 3, also consistent with the surveyed damage. In bent 2 (middle bent), the reduction trend in cS was relatively minor, correctly showing minor damage at this bent. Based on these findings, the team concluded that the enhanced wave method presented in this study was capable of detecting damage in the bridge and identifying the location of the most severe damage. The proposed methodology is a fast and inexpensive tool for real-time or near real-time damage detection and localization in similar bridges, especially those with sparsely deployed accelerometers.
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Alders, George. L51630A In-Line Detection and Sizing of Stress Corrosion Cracks Using EMAT Ultrasonics - Phase II. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), listopad 1991. http://dx.doi.org/10.55274/r0011370.
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This report covers that part of a Phase II effort that was completed by Magnasonics, Inc. prior to its liquidation by an adverse court ruling. The Phase I program investigated several configurations of Electromagnetic Acoustic Transducers (EMAT5) to arrive at an optimum approach to the problem of detecting and sizing stress corrosion cracks (SCC) in operating pipelines. Phase II was designed to optimize the most promising configuration by applying it to as many pipe samples as possible. Three pipe samples that contained several colonies of 5CC were made available to Magnasonics and a computerized data collection apparatus was assembled to collect ultrasonic data on the cracked areas. In agreement with the Phase I findings, high order Lamb wave modes were found to reflect strongly from the stress corrosion cracks and thus provide a sensitive detection method. In order to develop sizing capacitates, the crack depths in the colonies of SCC were measured with an eddy current technique and by a new surface acoustic wave method. Good qualitative correlation between the severity of cracking and the amplitude of the reflected ultrasonic energy was observed but real quantitative comparisons must wait on destructive measurement of the actual crack depths. Since only 30% of the funding has been used to date, it is hoped that additional measurements can be made on even more samples in the future.
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Rosenfeld, Michael, i John Kiefner. PR-218-063505-R03 Safe Inspection Procedures for Dent and Gouge Damage. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), listopad 2018. http://dx.doi.org/10.55274/r0011532.
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Recommendations are often made that the operating pressure of a pipeline be reduced prior to investigating suspected mechanical damage in the field, due to the unknown severity of the dam-age. The ensuing question is: knowing only what can be inferred from in-line inspection and the characteristics of the pipeline, what is the appropriate amount of pressure reduction? A common recommendation is to lower the operating pressure to 80% of a recent high pressure level. Oper-ators may question whether the same pressure reduction is necessary or adequate for all pipelines, e.g. different Location Classes, and all modes of damage, e.g. rock-induced damage as opposed to encroachment damage. With some operations, pressure reduction by an arbitrary proportion is impractical or very costly. Two levels of assessment are provided: a conservative "Level 1" assessment relying mainly on qualitative information and requiring no calculation, and a "Level 2" assessment that is consider-ably more involved but which could justify a smaller pressure reduction (or even no pressure re-duction). The choice of assessment level will depend on the information available to the operator, as well as on the degree of conservatism the operator desires to invoke. This report presents procedures for determining whether or not a pressure reduction is needed to assure safety of maintenance personnel before excavating and examining plain dents or dent-with-gouge defects on pipelines based on information obtained from in-line inspection (ILI) data. The procedures also allow for calculating the amount of pressure reduction that is needed.
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Wu, Yingjie, Selim Gunay i Khalid Mosalam. Hybrid Simulations for the Seismic Evaluation of Resilient Highway Bridge Systems. Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, listopad 2020. http://dx.doi.org/10.55461/ytgv8834.
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Bridges often serve as key links in local and national transportation networks. Bridge closures can result in severe costs, not only in the form of repair or replacement, but also in the form of economic losses related to medium- and long-term interruption of businesses and disruption to surrounding communities. In addition, continuous functionality of bridges is very important after any seismic event for emergency response and recovery purposes. Considering the importance of these structures, the associated structural design philosophy is shifting from collapse prevention to maintaining functionality in the aftermath of moderate to strong earthquakes, referred to as “resiliency” in earthquake engineering research. Moreover, the associated construction philosophy is being modernized with the utilization of accelerated bridge construction (ABC) techniques, which strive to reduce the impact of construction on traffic, society, economy and on-site safety. This report presents two bridge systems that target the aforementioned issues. A study that combined numerical and experimental research was undertaken to characterize the seismic performance of these bridge systems. The first part of the study focuses on the structural system-level response of highway bridges that incorporate a class of innovative connecting devices called the “V-connector,”, which can be used to connect two components in a structural system, e.g., the column and the bridge deck, or the column and its foundation. This device, designed by ACII, Inc., results in an isolation surface at the connection plane via a connector rod placed in a V-shaped tube that is embedded into the concrete. Energy dissipation is provided by friction between a special washer located around the V-shaped tube and a top plate. Because of the period elongation due to the isolation layer and the limited amount of force transferred by the relatively flexible connector rod, bridge columns are protected from experiencing damage, thus leading to improved seismic behavior. The V-connector system also facilitates the ABC by allowing on-site assembly of prefabricated structural parts including those of the V-connector. A single-column, two-span highway bridge located in Northern California was used for the proof-of-concept of the proposed V-connector protective system. The V-connector was designed to result in an elastic bridge response based on nonlinear dynamic analyses of the bridge model with the V-connector. Accordingly, a one-third scale V-connector was fabricated based on a set of selected design parameters. A quasi-static cyclic test was first conducted to characterize the force-displacement relationship of the V-connector, followed by a hybrid simulation (HS) test in the longitudinal direction of the bridge to verify the intended linear elastic response of the bridge system. In the HS test, all bridge components were analytically modeled except for the V-connector, which was simulated as the experimental substructure in a specially designed and constructed test setup. Linear elastic bridge response was confirmed according to the HS results. The response of the bridge with the V-connector was compared against that of the as-built bridge without the V-connector, which experienced significant column damage. These results justified the effectiveness of this innovative device. The second part of the study presents the HS test conducted on a one-third scale two-column bridge bent with self-centering columns (broadly defined as “resilient columns” in this study) to reduce (or ultimately eliminate) any residual drifts. The comparison of the HS test with a previously conducted shaking table test on an identical bridge bent is one of the highlights of this study. The concept of resiliency was incorporated in the design of the bridge bent columns characterized by a well-balanced combination of self-centering, rocking, and energy-dissipating mechanisms. This combination is expected to lead to minimum damage and low levels of residual drifts. The ABC is achieved by utilizing precast columns and end members (cap beam and foundation) through an innovative socket connection. In order to conduct the HS test, a new hybrid simulation system (HSS) was developed, utilizing commonly available software and hardware components in most structural laboratories including: a computational platform using Matlab/Simulink [MathWorks 2015], an interface hardware/software platform dSPACE [2017], and MTS controllers and data acquisition (DAQ) system for the utilized actuators and sensors. Proper operation of the HSS was verified using a trial run without the test specimen before the actual HS test. In the conducted HS test, the two-column bridge bent was simulated as the experimental substructure while modeling the horizontal and vertical inertia masses and corresponding mass proportional damping in the computer. The same ground motions from the shaking table test, consisting of one horizontal component and the vertical component, were applied as input excitations to the equations of motion in the HS. Good matching was obtained between the shaking table and the HS test results, demonstrating the appropriateness of the defined governing equations of motion and the employed damping model, in addition to the reliability of the developed HSS with minimum simulation errors. The small residual drifts and the minimum level of structural damage at large peak drift levels demonstrated the superior seismic response of the innovative design of the bridge bent with self-centering columns. The reliability of the developed HS approach motivated performing a follow-up HS study focusing on the transverse direction of the bridge, where the entire two-span bridge deck and its abutments represented the computational substructure, while the two-column bridge bent was the physical substructure. This investigation was effective in shedding light on the system-level performance of the entire bridge system that incorporated innovative bridge bent design beyond what can be achieved via shaking table tests, which are usually limited by large-scale bridge system testing capacities.
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Taucher, Jan, i Markus Schartau. Report on parameterizing seasonal response patterns in primary- and net community production to ocean alkalinization. OceanNETs, listopad 2021. http://dx.doi.org/10.3289/oceannets_d5.2.
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We applied a 1-D plankton ecosystem-biogeochemical model to assess the impacts of ocean alkalinity enhancement (OAE) on seasonal changes in biogeochemistry and plankton dynamics. Depending on deployment scenarios, OAE should theoretically have variable effects on pH and seawater pCO2, which might in turn affect (a) plankton growth conditions and (b) the efficiency of carbon dioxide removal (CDR) via OAE. Thus, a major focus of our work is how different magnitudes and temporal frequencies of OAE might affect seasonal response patterns of net primary productivity (NPP), ecosystem functioning and biogeochemical cycling. With our study we aimed at identifying a parameterization of how magnitude and frequency of OAE affect net growth rates, so that these effects could be employed for Earth System Modell applications. So far we learned that a meaningful response parameterization has to resolve positive and negative anomalies that covary with temporal shifts. As to the intricacy of the response patterns, the derivation of such parameterization is work in progress. However, our study readily provides valuable insights to how OAE can alter plankton dynamics and biogeochemistry. Our modelling study first focuses at a local site where time series data are available (European Station for Time series in the Ocean Canary Islands ESTOC), including measurements of pH, concentrations of total alkalinity, dissolved inorganic carbon (DIC), chlorophyll-a and dissolved inorganic nitrogen (DIN). These observational data were made available by Andres Cianca (personal communication, PLOCAN, Spain), Melchor Gonzalez and Magdalena Santana Casiano (personal communication, Universidad de Las Palmas de Gran Canaria). The choice of this location was underpinned by the fact that the first OAE mesocosm experiment was conducted on the Canary Island Gran Canaria, which will facilitate synthesizing our modelling approach with experimental findings. For our simulations at the ESTOC site in the Subtropical North Atlantic we found distinct, non-linear responses of NPP to different temporal modes of alkalinity deployment. In particular, phytoplankton bloom patterns displayed pronounced temporal phase shifts and changes in their amplitude. Notably, our simulations suggest that OAE can have a slightly stimulating effect on NPP, which is however variable, depending on the magnitude of OAE and the temporal mode of alkalinity addition. Furthermore, we find that increasing alkalinity perturbations can lead to a shift in phytoplankton community composition (towards coccolithophores), which even persists after OAE has stopped. In terms of CDR, we found that a decrease in efficiency with increasing magnitude of alkalinity addition, as well as substantial differences related to the timing of addition. Altogether, our results suggest that annual OAE during the right season (i.e. physical and biological conditions), could be a reasonable compromise in terms of logistical feasibility, efficiency of CDR and side-effects on marine biota. With respect to transferability to global models, the complex, non-linear responses of biological processes to OAE identified in our simulations do not allow for simple parameterizations that can easily adapted. Dedicated future work is required to transfer the observed responses at small spatiotemporal scales to the coarser resolution of global models.
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ENERGY DISSIPATING MODES AND DESIGN RECOMMENDATION OF H-SHAPED STEEL BAFFLES SUBJECTED TO BOULDER IMPACT. The Hong Kong Institute of Steel Construction, grudzień 2021. http://dx.doi.org/10.18057/ijasc.2021.17.4.3.
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Flexible barriers are one of the most effective protective structures, which have been widely used for the mitigation of rockfalls. As the only compression members in a flexible barrier system, steel posts maintain the integrity of the interception structure to keep the function of the system. Due to the random trajectories of rockfalls, steel posts may be impacted by boulders directly. The impact scenario may result in the failure of the post and even the collapse of the system. In this paper, firstly, steel baffles were proposed to be an additional structural countermeasure to avoid the direct impact of posts. Secondly, numerical method was adopted to study the structural behaviour of steel baffles under direct boulder impact. Then, an available published experimental test of H-shaped steel beams under drop weight impact loading by others was back analyzed to calibrate the finite element model. Finally, numerical simulations were carried out to investigate the energy dissipating modes and energy dissipating efficiency of the H-shaped steel baffles. The simulation results show that there are three typical energy dissipating modes of H-shaped baffles subjected to boulder impact, namely flexural, local compression buckling and shear buckling. Local compression buckling is the most efficient energy dissipating mode. The thickness of the web of an H-shaped baffle is suggested to be 4 mm and 6 mm for the rated dissipating energy of 50 kJ and 100 kJ, respectively.