Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 181 for “"fourth order"”.
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Tests for fourth order autoregressive processes.
… variables. This statistic is able to detect a fourth order autoregressive disturbance of the form: Ɛ(ʈ)=ƿ(1)Ɛ(ʈ-1)+ƿ(4)Ɛ(ʈ-4)+ƞ(ʈ) in the general model Y=Xβ+Ɛ. To correct for this disturbance and thus yield efficient regression estimates, a data transformation was derived using the inverse of …
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Active electromechanical control of fourth-order continua.
Massachusetts Institute of Technology. Dept. of Electrical Engineering. Thesis. 1966. M.S.
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A fourth order [Sigma] [Delta] bandpass modulator
A fourth order bandpass [Sigma] [Delta] modulator is proposed to digitize signals from a MEMS gyroscope. The modulator samples the amplitude-modulated signal at eight times the carrier frequency and achieves an SNR of 82dB with a sampling frequency of 640kHz and a bandwidtn o 1.oKnz. ms document …
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Fourth order spectral theory and diffusion-driven instability
… diffusion operator with a combination of the fourth order bi-Laplacian operator and the second order Laplacian. We find new phenomena when the fourth order and second order terms are competing, meaning one of them stabilizes the system whereas the other destabilizes it. We characterize Turing …
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On the Oscillation of a Fourth Order Nonhomogeneous Differential Equation.
… oscillation of solutions of (NH). Oscillation of fourth order homogeneous equations has been studied by M. S. Keener, and W. Leighton and Z. Nehari.
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Relativistic neutron stars in general relativity and fourth order gravity
… resulting coupled system of PDEs with a third order WENO scheme in space and an IMEX scheme in time. We obtained 18 frequencies from the Fast Fourier Transform (FFT) of the evolved perturbation equations, which were consistent with the frequencies of the neutron star's Sturm-Liouville problem. …
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Localized Method of Approximate Particular Solutions for Solving Fourth-Order PDEs
<p>In the past, dealing with fourth-order partial differential equations using the Local Method was not reliable due to difficulties in solving them directly. An approach such as splitting these equations into two Poisson differential equations was adopted to alleviate such challenges. However, …
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Nontrivial solutions for nonlinear discrete boundary value problems of the fourth order
… multiple nontrivial solutions for two nonlinear fourth order discrete boundary value problems. We first establish criteria for the existence of at least two nontrivial solutions of the problems and obtain conditions to guarantee that the two solutions are sign-changing. Under some appropriate …
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A study of solutions and perturbations of spherically symmetric spacetimes in fourth order gravity.
… one of the most widely studied classes of fourth order gravity. We begin by introducing f(R) theories of gravity and present the general equations for these theories. We investigate the problem of matching different regions of spacetime, shedding light on the problem of constructing …
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Numerical Boundary Conditions for the Fourth -Order Accurate Finite -Difference Time -Domain Solution of Maxwell's Equations
… is the key to the proper implementation of high-order finite-difference time-domain (FDTD) methods for Maxwell's equations. In this dissertation, a new set of numerical boundary conditions at perfectly conducting walls and dielectric interfaces is proposed for Fang's fourth-order FDTD schemes. …
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Comparison of smallest eigenvalues and extremal points for third and fourth order three point boundary value problems.
… These results are then extended to the nth order problem using two different methods. One method involves finding the Green's function for –u⁽ⁿ⁾ = 0 satisfying the higher order boundary conditions, and the other involves making a substitution that allows us to work with a variation of the …
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Critical analysis of a practical fourth order finite-difference time-domain algorithm for the solution of Maxwell's equations
… on a central differencing scheme which is second order accurate (second order). The high complexity of today's electromagnetic problems necessitate a FDTD formulation that can use less computational memory and complete simulations faster than current second order FDTD formulations. Many …
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Positive Solutions, Existence Of Smallest Eigenvalues, And Comparison Of Smallest Eigenvalues Of A Fourth Order Three Point Boundary Value Problem
… we will extend the problem to the fifth order via the Green's Function and again via Substitution. Applying the comparison theorems and the properties of $u_0$-positive operators to determine the existence of smallest eigenvalues. The existence of these smallest eigenvalues is then …
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High Order Energy - Conserved Splitting FDTD Methods for Maxwell's Equations
… thesis, we first develop and analyze the spatial fourth order energy-conserved splitting FDTD scheme for Maxwell's equations in two dimensions. For each time stage, while the spatial fourth-order difference operators are used to approximate the spatial derivatives on strict interior nodes, the …
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Hierarchical summer habitat selection by the North American porcupine in western Montana
… to gather basic natural history information in order to make informed management decisions. This study strives to quantify home range and hierarchical habitat selection at the second, third, and fourth order, while noting both mortality and reproductive rates. Second and third order habitat …
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Hierarchical summer habitat selection by the North American porcupine in western Montana
… to gather basic natural history information in order to make informed management decisions. This study strives to quantify home range and hierarchical habitat selection at the second, third, and fourth order, while noting both mortality and reproductive rates. Second and third order habitat …
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The phonon spectra of simple metals - higher order effects of the electron-ion interaction
… In the former, some terms of third and fourth order are retained, whereas in the latter, only terms of second order are retained, as has been customary in the past. An. expression for the bulk modulus is derived by studying the long-wavelength behavior of the phonon dynamical matrix in …
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A comparison of numerical algorithms for solution of the transient stability problem
… behavior. The five algorithms studied are: fourth-order Runge-Kutta; state transition; the trapezoidal rule; Adams-Moulton predictor-corrector; and Hamming predictor-corrector. The five algorithms, using various step sizes, are applied to three test systems, including the IEEE l4-bus system, …
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High resolution sequence stratigraphy of late Mississippian carbonates in the Appalachian Basin
… to Glen Dean interval consists of up to twelve fourth-order depositional sequences (300 to 400 k.y. average duration). The sequences (a few meters to over a hundred meters thick) consist of eolianites, lagoonal carbonate muds, ooid shoals, and skeletal banks, and open marine skeletal wackestone …
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