165 research outputs found
Impact of pupillary dilation on the efficacy of laser peripheral iridotomy
No full textPurpose: To assess outcomes of laser peripheral iridotomy (LPI) procedures following dilation by evaluating the pressure difference across the iris posterior-anterior chamber resulting from varying hole sizes and locations. Methods: Using an anterior segment optical coherence tomography (AS-OCT) image, we created a 3-D finite element model of the iris. We then manually identified a dilator region where the dilator stress was applied to simulate pupillary dilation. To mimic LPI, we made a hole of 200 microns in diameter near the pupillary margin, at the mid-periphery, and at the periphery of the iris. Using computational fluid dynamics methods, we computed the pressure difference developed by the hole before and after pupil dilation at each location. This process was then repeated with a hole of 400 microns in diameter. Results: The pressure difference developed across a 200-micron hole when the hole was placed near the pupil, at the iris mid-periphery, and near the iris periphery was 0.85 Pa, 0.80 Pa, and 0.92 Pa, respectively. Following pupil dilation, the pressure difference increased in all cases. For the compressible iris model, the pressure increased by 4.70%, 63.75%, and 52.17% near the pupil, at the iris mid-periphery, and near the iris periphery, respectively. For the nearly incompressible model, the pressure increased by 7.06%, 51.25%, and 55.43% near the pupil, at the iris mid-periphery, and near the iris periphery, respectively. Across a 400-micron diameter hole, the pressure difference developed was extremely small (< 0.1 Pa) across all cases, both before and following dilation. Conclusion: While LPI offers a solution for narrow or closed anterior chamber angles, in some patient populations the angles remain occludable following LPI. One possible reason could be attributed to the additional pressure difference across the anterior and posterior chamber due to the change in LPI hole size following dilationinduced iris deformation. Our study shows that the LPI hole size/location affects the pressure difference in both compressible and nearly incompressible irides
Solving rank one revised linear systems by the scaled ABS method
No full textIn mathematical programming, an important tool is the use of active set strategies to update the current solution of a linear system after a rank one change in the constraint matrix. We show how to update the general solution of a linear system obtained by use of the scaled ABS method when the matrix coefficient is subjected to a rank one change
Enhancement of microgrid reliable operation using an adaptive protection strategy
Get PDFThe objective of this project is to apply adaptive protection technique as a noticeable solution, to eradicate microgrid protection problems caused by connecting distributed generation plants. From technical point of view, Distributed Generators (DGs) create more stable and maneuverable power system by compensating voltage sag during the pick hours. Although presence of DG in Distribution Network (DN), causes some problems in existing power system. Concerns are different from a DN to another one and they depend on the DN structure and topology. However, the main problem is always protection coordination issues. In this research, a Distribution Network (DN), is created in DigSILENT Powerfactory software and an adaptive protection system is developed. Different scenarios for microgrid operation are determined in software and protection scheme is able to distinguish these distinctive modes of operation. Based on microgrid’s operation mode, protection system changes the relays settings to guarantee proper coordination among protecting devices in all modes. This report includes a comprehensive study for different types of protective relays and their performance along with an instruction of the Over-Current (OC) relays coordination. DN protection problems in presence of DG are clarified later. This includes IEEE standards for microgrid operation and protection. Furthermore, adaptive protection fundamentals are developed. Modeling and simulation results are performed using DigSILENT Powerfactory software including an introduction about DigSILENT software programming language respectively. Finally, there is a conclusion for all results and findings.California State University, Northridge. Department of Electrical and Computer Engineering.Includes bibliographical references (pages 59-60
A new nonmonotone adaptive trust region algorithm
Get PDFsummary:We propose a new and efficient nonmonotone adaptive trust region algorithm to solve unconstrained optimization problems. This algorithm incorporates two novelties: it benefits from a radius dependent shrinkage parameter for adjusting the trust region radius that avoids undesirable directions and exploits a new strategy to prevent sudden increments of objective function values in nonmonotone trust region techniques. Global convergence of this algorithm is investigated under some mild conditions. Numerical experiments demonstrate the efficiency and robustness of the proposed algorithm in solving a collection of unconstrained optimization problems from the CUTEst package
A new structured quasi-Newton algorithm using partial information on Hessian
No full textAbstractThis paper presents a modified quasi-Newton method for structured unconstrained optimization. The usual SQN equation employs only the gradients, but ignores the available function value information. Several researchers paid attention to other secant conditions to get a better approximation of the Hessian matrix of the objective function. Recently Yabe et al. (2007) [6] proposed the modified secant condition which uses both gradient and function value information in order to get a higher-order accuracy in approximating the second curvature of the objective function. In this paper, we derive a new progressive modified SQN equation, with a vector parameter which use both available gradient and function value information, that maintains most properties of the usual and modified structured quasi-Newton methods. Furthermore, local and superlinear convergence of the algorithm is obtained under some reasonable conditions
Fielding Peter Carey: economy, archive, celebrity
No full text© 2018 Dr. Keyvan AllahyariThis thesis accounts for a method of reading Carey’s fiction as works of national literature in the minor register (colonial, peripheral, small) which refract a sense of the possibility of circulation in transnational literary markets. The publication of Carey’s debut work, The Fat Man in History, by the University of Queensland Press in 1974 coincided with the termination of The Traditional Markets Agreement, which resulted in assisting American publishers to roam more freely in the Australian literary market. Drawing on Pierre Bourdieu’s concepts of the literary field, capital, and habitus, my thesis starts by examining the publication of The Fat Man as a microevent to better understand the macroevent of Carey’s position-taking in the transnational marketplace. The mid-1970s shifted Carey’s position in the field and established a trajectory through which he accumulated significant cultural and economic capital in the following decades. This method interrogates Carey’s rising visibility in relation to the construction of a new status for the postcolonial authors and the possibilities of the global publishing industry since the 1960s throughout to the present moment, including the politics of literary prizes and literary festivals, the rise of literary agents, the commodification of literary archives, and the merging of conglomerate publishing houses.
Carey’s fiction exhibits the anxieties of an Australian author ensnared in neoliberal systems of literary production and distribution, a free market economy biased against national territories (such as Australia) on the periphery of a world republic of letters. Drawing on the sociological paradigm of Pierre Bourdieu, this thesis asks how, and to what extent, can we think of Carey’s fiction and his writerly persona as cultural objects circulating within the global literary marketplace? How does his fiction refract the global forces that produce and distribute his books and celebrity? And what is the relationship between Carey’s stories and the literary marketplace, between the making of his books and the reading of them? Thus, my study offers a lateral examination of two interrelated aspects of Carey’s fiction. On the one hand, it captures a continuum of Australian and transnational practices of literary distinction and advancement that governed the critical and financial success of Carey’s fiction; on the other, it produces insights into the structural homologies between the literary spaces that Carey inhabits and those of his Australian characters confined to minor systems of cultural production and consumption
COMBINATION ADAPTIVE TRUST REGION METHOD BY NON-MONOTONE STRATEGY FOR UNCONSTRAINED NONLINEAR PROGRAMMING
No full text In this paper, we present a new trust region method for unconstrained nonlinear programming in which we blend adaptive trust region algorithm by non-monotone strategy to propose a new non-monotone trust region algorithm with automatically adjusted radius. Both non-monotone strategy and adaptive technique can help us introduce a new algorithm that reduces the number of iterations and function evaluations. The new algorithm preserves the global convergence and has local superlinear and quadratic convergence under suitable conditions. Numerical experiments exhibit that the new trust region algorithm is very efficient and robust for unconstrained optimization problems. </jats:p
A new diagonal quasi-Newton algorithm for unconstrained optimization problems
No full textsummary:We present a new diagonal quasi-Newton method for solving unconstrained optimization problems based on the weak secant equation. To control the diagonal elements, the new method uses new criteria to generate the Hessian approximation. We establish the global convergence of the proposed method with the Armijo line search. Numerical results on a collection of standard test problems demonstrate the superiority of the proposed method over several existing diagonal methods
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