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DTSTART;TZID=Europe/Berlin:20211108T160000
DTEND;TZID=Europe/Berlin:20211108T170000
DTSTAMP:20210811T093446Z
CREATED:20210519T085020Z
LAST-MODIFIED:20210811T093446Z
UID:5606-1636387200-1636390800@alop.uni-trier.de
SUMMARY:ALOP-Colloquium with Daniel Aloise\, Polytechnique Montréal
DESCRIPTION:On Monday\, November 8\, 2021 at 16:00 c.t.  Dr. Daniel Aloise\, Polytechnique Montréal will present his recent work at our colloquium.  \nTitle: Convex fuzzy k-medoids clustering \nAbstract: \nK-medoids clustering is among the most popular methods for cluster analysis\, but it carries several assumptions about the nature of the latent clusters. In this work\, we introduce the Convex Fuzzy k -Medoids (CFKM) model\, whose underlying formulation not only relaxes the assumption that objects must be assigned entirely to one and only one medoid\, but also that medoids must be assigned entirely to one and only one cluster. Moreover\, due to its convexity\, CFKM resolution is completely robust to initialization. We compare our model with two fuzzy k-medoids clustering models found in the literature: the Fuzzy k -Medoids (FKM) and the Fuzzy Clustering with Multi-Medoids (FMMdd)\, both solved approximately by heuristics because of their hard computational complexity. Our experiments in synthesized and real-world data sets reveal that our model can uniquely discover important aspects of clustered data which are inherently fuzzy in nature\, besides being more robust regarding the hyperparameters of the fuzzy clustering task. \nThis presentation will take place via ZOOM. A link will be e-mailed prior to the event.
URL:https://alop.uni-trier.de/event/alop-colloquium-with-daniel-alois-polytechnique-montreal/
CATEGORIES:Colloquium
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
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DTSTART;TZID=Europe/Berlin:20211115T160000
DTEND;TZID=Europe/Berlin:20211115T170000
DTSTAMP:20210521T050924Z
CREATED:20210519T085624Z
LAST-MODIFIED:20210521T050924Z
UID:5608-1636992000-1636995600@alop.uni-trier.de
SUMMARY:ALOP-Colloquium with Sungho Shin\, University of Wisconsin-Madison
DESCRIPTION:On Monday\, November 15\, 2021\, at 16:00 c.t.\, Ph.D. candidate Sungho Shin\, University of Madison-Wisonsin will speak about his recent work: \n  \nTitle: Graph-Structured Nonlinear Programming: Properties and Algorithms \n  \nA graph-structured nonlinear program (NLP) is a nonlinear optimization problem whose algebraic structure is induced by a graph. These problems arise in diverse applications such as dynamic optimization (model predictive control and moving horizon estimation)\, network optimization (energy systems and supply chain)\, optimization with embedded discretized partial differential equations\, and multi-stage stochastic programming. Building upon the existing NLP sensitivity theory\, we show that the nodal solution sensitivity against parametric perturbation decays exponentially with respect to the distance from the perturbation point. Remarkably\, this result (which we call exponential decay of sensitivity; EDS) holds under fairly standard regularity assumptions used in classical NLP sensitivity theory: second-order sufficiency conditions and the linear independence constraint qualification. EDS allows the creation of novel computing strategies\, the overlapping Schwarz decomposition method (also known as domain decomposition). This method decomposes a graph-structured NLP into multiple smaller subproblems over overlapping subdomains and solves the subproblems in parallel and iteratively with the exchange of information at boundries. Based on the EDS result\, we prove that for a certain class of problems satisfying the regularity assumptions\, the convergence rate of the overlapping Schwarz method improves exponentially with the size of overlap; thus\, overlap accelerates the convergence. With real-world case studies on gas and electric networks\, we demonstrate the effectiveness of the overlapping Schwarz method. \n  \nThis presentation will take place via ZOOM. A link will be e-mailed prior to the event
URL:https://alop.uni-trier.de/event/alop-colloquium-with-sungho-shin-university-of-wisconsin-madison/
CATEGORIES:Colloquium
ORGANIZER;CN="RTG ALOP at Trier University":MAILTO:ALOP@uni-trier.de
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