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Showing 1 to 20 of 58 for “"eigenmodes"”.
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Computing Eigenmodes of Elliptic Operators on Manifolds Using Radial Basis Functions
… based on meshless methods is proposed to obtain eigenmodes of Laplace-Beltrami operator on manifolds, and its performance is compared against existing alternative methods. Radial Basis Function (RBF)-based methods allow one to obtain interpolation and differentiation matrices easily by using …
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Investigation of Alfvén eigenmodes in Alcator C-Mod using active MHD spectroscopy
Alfvén eigenmodes that exist in the shear Alfvén continuum of toroidal magnetic fusion devices may be important for the confinement of energetic particles, particularly fusion-born alpha particles in burning plasma experiments. Interaction between these energetic particles and weakly damped …
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A study of reversed shear Alfvén eigenmodes in Alcator C-Mod with phase contrast imaging
… oscillation and may exist in tokamak plasmas as eigenmodes with a global structure and discrete frequencies. The inhomogeneity of the plasma profiles in conjunction with tokamak geometry tends to focus the Alfvén waves in regions of near uniformity defined by local extrema in the Alfvén …
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Measurement and interpretation of stable and unstable Alfvén eigenmodes in the presence of fast ions in Alcator C-Mod
… of two types of lightly damped resonant eigenmodes in the presence of energetic ions is studied in Alcator C-Mod. Global Alfven eigenmodes (GAEs) can exist at frequencies between the continua of adjacent poloidal mode numbers to avoid strong continuum damping. Toroidicity-induced Alfven …
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Solving an eigenvalue problem in laser simulation
… and powerful approach for modeling laser cavity eigenmodes is presented. This approach is based on an eigenvalue problem for singularly perturbed partial differential operators with complex coefficients; such operators have not been investigated in detail until now. The eigenvalue problem is …
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Novel decoupling networks for small antenna arrays
… a step-by-step decoupling of the characteristic eigenmodes of the array. An alternative approach to achieve port decoupling is also proposed. It involves a modal feeding network which makes use of the orthogonality of the eigenmodes of the array to achieve decoupling. The input ports to the …
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Solving Buckling Problems and Computing Critical Points Using the Multigrid Method
The algorithms make use of the eigenmodes of the tangent stiffness operator to create constraints which improve the conditioning of the tangent stiffness operator. The resultant systems are solved using the bordering algorithm and each equation solution is performed using the modified tangent …
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A Ray-Based Investigation of the Statistical Characteristics and Efficient Representation of Multi-Antenna Communication Channels
… transmit power into the most advantageous eigenmodes of the channel when fewer eigenmodes have power allocated to them by the waterfilling capacity solution. In higher signal to noise ratio cases, more eigenmodes of the channel receive power when waterfilling, and the capacity improvement …
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Statistical Modeling of Wave Chaotic Transport and Tunneling
… The impedance can be written as a summation over eigenmodes where the eigenmodes can typically be classified as either regular or chaotic. By appropriate characterizations of regular and chaotic contributions, we obtain statis- tical predictions for the impedance. We then test these predictions by …
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Stereoscopic PIV measurements and proper orthogonal decomposition of a supersonic axisymmetric base flow
… convergence and the structures found in the eigenmodes are used to gain insight into the organization of the flow that may not be apparent by observation of the mean flow statistics or the instantaneous images. The resulting eigenmodes of the POD analysis indicate that there is a dominant …
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A study of prompt fast ion losses from neutral beam injection in the DIII-D tokamak
… (MHD) activity, such as reverse shear Alfven eigenmodes (RSAEs) and toroidal Alfven eigenmodes (TAEs), which will be of great importance for predominately self-heated reactor scenarios.
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The Effects of Weak Collisions on Nonlinear Plasma Kinetics
… continuous spectrum, which are the underlying eigenmodes of the collisionless system, are completely eliminated and replaced by a discrete spectrum (hereafter referred to as the NBS spectrum). The NBS spectrum includes Landau-damped roots as exact eigenmodes, but is significantly broader, …
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Experimental measurements and numerical modeling of fast-ion distributions in the Alcator C-Mod Tokamak
… can drive unstable modes such as Toroidal Alfvén Eigenmodes (TAEs) and Reversed Shear Alfvén Eigenmodes (RSAEs). Furthermore, energetic ions may display plasma properties that differ from the bulk plasma. It is crucial to benchmark current simulation codes with measurements from highly energetic …
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Baroclinic instability of a meridionally varying basic state
… amplitude evolution of weakly unstable, linear eigenmodes in a meridionally varying version of Phillips' two-layer model. It is shown in chapter four that interactions between neutral modes and the unstable mode strongly influence the evolution of the latter and are capable of stabilising it …
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Random perturbations of delay differential equations at the verge of instability and periodically driven nonlinear oscillators
… studies analyze the amplitude of the critical eigenmodes using the averaging approach, and in the spirit of multiscale analysis. This thesis is an attempt to make the averaging approach rigorous. Errors in other articles using multiscale approach are pointed out. Markovian noises of the …
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Forced Capillary-Gravity Waves in a 2D Rectangular Basin
… for the complex valued amplitudes of the two eigenmodes. The system can be reduced to one real-valued differential equation. Its solutions yield the solutions of the original system and their properties. A condition for the existence of homoclinic orbits connecting the trivial equilibrium is …
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Oscillations and waves in anisotropic plasmas
… of a generalized eigenfunction expansion with eigenmodes corresponding to zeros of the appropriate plasma dispersion function. The expansion coefficients for eigenmodes corresponding to simple and second order real zeros of the plasma dispersion function are also presented, and constitute some …
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Beitrag zur kontinuierlichen interferometrischen Untersuchung der Eigenschwingungsformen rotierender Bauteile
… knowledge for continuous inspection of eigenmodes of rotating objects by means of an electronic speckle interferometer and an optical image derotator. The system suggested consists of a rotor, a derotator and an electronic speckle interferometer. Elimination of the rotation by the …
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Synthesis of electromagnetic modes in photonic band gap fibers
… the superposed images into low energy eigenmodes (m < 3), and compute each of the eigenmode's contribution in the superposition. We show that the contributions of the HE11 and TE01 behave sinusoidally in their superpostions. Finally we also explain the minor discrepancies between the …
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Influence of symmetry on the stability behaviour of plane and space frames
… that the order of emergence of symmetries for eigenmodes of higher eigenvalues was from the subgroups of Cnv with the highest order of elements to those with the lowest order of elements and this order of emergence repeats every 2n eigenvalue. The study also found that when eigenvalues are …
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