Browsing by Subject "Laplace transforms"

Now showing 1 - 6 of 6

Open Access
Fast multipole methods in service of various scientific disciplines
(IEEE, 2014) Gürel, Levent
For more than two decades, several forms of fast multipole methods have been extremely successful in various scientific disciplines. Reduced complexity solutions are obtained for solving different forms of equations that are derived from Maxwell's equations, such as Helmholtz's equation for electrodynamics and Laplace's equation for electrostatics. Fast multipole solvers are developed for and applied to the integral equations derived from Helmholtz's and Laplace's equations. Fast multipole solvers are kernel-dependent techniques, i.e., they rely on certain analytical properties of the integral-equation kernels, such as diagonalizability. Electromagnetics is not the only discipline benefiting from the fast multipole methods; a plethora of computations in various disciplines, such as the solution of Schroedinger's equation in quantum mechanics and the calculation of gravitational force in astrophysics, to name a few, exploit the reduced-complexity nature of the fast multipole methods. Acoustics, molecular dynamics, structural mechanics, and fluid dynamics can be mentioned as other disciplines served by the fast multipole methods. © 2014 IEEE.
Open Access
Improving AWE accuracy using multipoint Pade approximation
(IEEE, 1994-05-06) Çelik, Mustafa; Ocali, Ogan; Tan, Mehmet Ali; Atalar, Abdullah
A new method is proposed for dominant pole-zero analysis of large linear circuits containing both lumped and distributed elements. This method is based on a multipoint Pade approximation. It finds a reduced order s-domain transfer function using a data set obtained by solving the circuit at only a few frequency points. The proposed method yields more accurate computation of transient and frequency responses with respect to the AWE-type techniques.
Open Access
A note on "continuous review perishable inventory systems: models and heuristics"
(2003) Gürler, Ü.; Özkaya, B. Y.
In a recent paper, Lian and Liu (2001) consider a continuous review perishable inventory model with renewal arrivals, batch demands and zero lead times. However, the main analytical result they provide holds only for some special cases such as Poisson arrivals with exponential interarrival times. In this note we generalize Theorem 1 of Lian and Liu (2001) for the case where the arrivals follow an arbitrary renewal process.
Open Access
On the boundary control of a flexible robot arm
(IEEE, 2001) Morgül, Ömer
We consider a flexible robot arm modeled as a single flexible link clamped to a rigid body. We assume that the system performs only planar motion. For this system, we pose two control problems; namely, the orientation and stabilization of the system. We propose a class of controllers to solve these problems.
Open Access
PID controller design for fractional-order systems with time delays
(Elsevier, 2011-11-22) Özbay, Hitay; Bonnet, C.; Fioravanti, A.R.
Classical proper PID controllers are designed for linear time invariant plants whose transfer functions are rational functions of sα, where 0<α<1, and s is the Laplace transform variable. Effect of inputoutput time delay on the range of allowable controller parameters is investigated. The allowable PID controller parameters are determined from a small gain type of argument used earlier for finite dimensional plants.
Open Access
Purkinje images: conveying different content for different luminance adaptations in a single image
(Blackwell Publishing Ltd, 2015) Arpa, S.; Ritschel, T.; Myszkowski, K.; Çapin, T.; Seidel, Hans-Peter
Providing multiple meanings in a single piece of art has always been intriguing to both artists and observers. We present Purkinje images, which have different interpretations depending on the luminance adaptation of the observer. Finding such images is an optimization that minimizes the sum of the distance to one reference image in photopic conditions and the distance to another reference image in scotopic conditions. To model the shift of image perception between day and night vision, we decompose the input images into a Laplacian pyramid. Distances under different observation conditions in this representation are independent between pyramid levels and pixel positions and become matrix multiplications. The optimal pixel colour can be found by inverting a small, per-pixel linear system in real time on a GPU. Finally, two user studies analyze our results in terms of the recognition performance and fidelity with respect to the reference images. Providing multiple meanings in a single piece of art has always been intriguing to both artists and observers. We present Purkinje images, which have different interpretations depending on the luminance adaptation of the observer. Finding such images is an optimization that minimizes the sum of the distance to one reference image in photopic conditions and the distance to another reference image in scotopic conditions. To model the shift of image perception between day and night vision, we decompose the input images into a Laplacian pyramid. © 2014 The Eurographics Association and John Wiley & Sons Ltd.