5,741 research outputs found
Learning optimization models in the presence of unknown relations
In a sequential auction with multiple bidding agents, it is highly
challenging to determine the ordering of the items to sell in order to maximize
the revenue due to the fact that the autonomy and private information of the
agents heavily influence the outcome of the auction.
The main contribution of this paper is two-fold. First, we demonstrate how to
apply machine learning techniques to solve the optimal ordering problem in
sequential auctions. We learn regression models from historical auctions, which
are subsequently used to predict the expected value of orderings for new
auctions. Given the learned models, we propose two types of optimization
methods: a black-box best-first search approach, and a novel white-box approach
that maps learned models to integer linear programs (ILP) which can then be
solved by any ILP-solver. Although the studied auction design problem is hard,
our proposed optimization methods obtain good orderings with high revenues.
Our second main contribution is the insight that the internal structure of
regression models can be efficiently evaluated inside an ILP solver for
optimization purposes. To this end, we provide efficient encodings of
regression trees and linear regression models as ILP constraints. This new way
of using learned models for optimization is promising. As the experimental
results show, it significantly outperforms the black-box best-first search in
nearly all settings.Comment: 37 pages. Working pape
Fair task allocation in transportation
Task allocation problems have traditionally focused on cost optimization.
However, more and more attention is being given to cases in which cost should
not always be the sole or major consideration. In this paper we study a fair
task allocation problem in transportation where an optimal allocation not only
has low cost but more importantly, it distributes tasks as even as possible
among heterogeneous participants who have different capacities and costs to
execute tasks. To tackle this fair minimum cost allocation problem we analyze
and solve it in two parts using two novel polynomial-time algorithms. We show
that despite the new fairness criterion, the proposed algorithms can solve the
fair minimum cost allocation problem optimally in polynomial time. In addition,
we conduct an extensive set of experiments to investigate the trade-off between
cost minimization and fairness. Our experimental results demonstrate the
benefit of factoring fairness into task allocation. Among the majority of test
instances, fairness comes with a very small price in terms of cost
Aesthetic Beauty in the 18th Century Chinese Novel Guwanyan (Preposterous Words)
This paper explores the tension between the radical sexual description and orthodox rhetoric in 18th century Chinese vernacular narrative. My research focuses on a xiaoshuo fiction, Guwangyan (Preposterous Words), authored by Cao Qujing and composed in 1730. This novel pictures the domestic lives of four families in Nanjing from the end of the 17th century to the early 18th century, including many explicit sexual descriptions. I argue that the author projects the ethic concern through the structure and characterization, while presents the anxiety towards desire in graphic sexual descriptions in the novel. The contrast and complementarity of the structural frame and content make Guwangyan as an important text to study in order to analyze and understand the changing meaning and uses of sexual explicit material in Chinese novels. My argument includes three parts: first, I will introduce the literati’s reading and response to erotic novels in the morally conservative Chinese society of the 18th century. Second, I will demonstrate how the novel is systematically structured by karmic retribution, sexual competition and yin-yang numerology. Third, I suggest that the author of Guwangyan adopts yin-yang fluidity idea to manipulate the characterization, balancing the portrayal of the lewd women, libertines, female heroes and chaste men in the whole narrative. I conclude that although this novel includes several graphic descriptions of sexuality, through yin-yang metaphysics the author always attempts to contain the representation of lust and desire without at the same time disrupting both the self and the social order
Assessment of a marine polysaccharide for use as excipient in pharmaceutical hot-melt extrusion
Pharmaceutical Hot Melt Extrusion (HME) is currently investigated by both industry and academia as a method for manufacturing solid oral dosages with improved bioavailability of poorly-water soluble active pharmaceutical ingredients (APIs) and control drug release of water-soluble APIs. Although HME is traditionally utilizing synthetic polymers to produce such dosages, biopolymers constantly gain ground by virtue of renewability, biocompatibility and in some cases biodegradability. In this work, the possibility of using Keltone, a marine polysaccharide derived from brown seaweed, as a polymeric excipient for pharmaceutical HME is explored. Keltone is insoluble in acidic pH and soluble in basic pH, therefore making it suitable for intestinal drug release. The processability of Keltone by extrusion using water and Eudragit EPO as plasticizers, and Diphenhydramine Hydrochloride and Clotrimazoleas as active pharmaceutical ingredients is assessed. The amount of residual water in the extrudates is determined by thermogravimetric analysis. The thermal transitions of the extrudates are determined by Differential Scanning Calorimetry
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