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Full-Text Articles in Engineering Science and Materials

The Causes And Consequences Of Particle Size Change In Fluvial Systems, Kimberly Louise Litwin Miller Jan 2014

The Causes And Consequences Of Particle Size Change In Fluvial Systems, Kimberly Louise Litwin Miller

Publicly Accessible Penn Dissertations

One of the most common features in fluvial environments is the systematic downstream decline in grain size, which is usually attributed to either abrasion - the reduction in sediment size due to attrition of mass - or selective sorting - the size segregation of grains due to their relative transport mobility. Despite the ubiquity of this grain pattern and the extensive research on both of these processes, there remains questions regarding the underlying principles driving abrasion and sorting, as well as the relative contribution of these processes to grain fining. Therefore, a mechanistic understanding of these processes is necessary to observe their direct ...


A Pde-Based Method For Optimizing Solar Cell Performance, Xiaoxian Liu Jan 2014

A Pde-Based Method For Optimizing Solar Cell Performance, Xiaoxian Liu

Publicly Accessible Penn Dissertations

In this paper, we address the optimal design problem for organic solar cells (OSC).

In particular, our focus is to enhance short-curcuit photocurrent by optimizing the

donor-acceptor interface. To that end, we propose two drift-diffusion models for

organic solar cells, both of which account for the physics of OSC's that charge

carriers are mostly generated in the region near the donor-acceptor interface. For

the first drift-diffusion model, the generation of charge carriers is translated into

a boundary condition across the donor-acceptor interface. We apply the theory of

shape optimization to compute the shape gradient functional of the photocurrent. In ...


On Controlled Linear Diffusions With Delay In A Model Of Optimal Advertising Under Uncertainty With Memory Effects, Fausto Gozzi, Carlo Marinelli, Sergei Savin Aug 2009

On Controlled Linear Diffusions With Delay In A Model Of Optimal Advertising Under Uncertainty With Memory Effects, Fausto Gozzi, Carlo Marinelli, Sergei Savin

Operations, Information and Decisions Papers

We consider a class of dynamic advertising problems under uncertainty in the presence of carryover and distributed forgetting effects, generalizing the classical model of Nerlove and Arrow (Economica 29:129–142, 1962). In particular, we allow the dynamics of the product goodwill to depend on its past values, as well as previous advertising levels. Building on previous work (Gozzi and Marinelli in Lect. Notes Pure Appl. Math., vol. 245, pp. 133–148, 2006), the optimal advertising model is formulated as an infinite-dimensional stochastic control problem. We obtain (partial) regularity as well as approximation results for the corresponding value function. Under ...