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X-WR-CALDESC:Events for Namur Institute For Complex Systems
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DTSTART;TZID=Europe/Paris:20181206T130000
DTEND;TZID=Europe/Paris:20181206T140000
DTSTAMP:20260429T132213
CREATED:20181016T113010Z
LAST-MODIFIED:20181207T091454Z
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SUMMARY:Thomas Parmentier (UGhent)
DESCRIPTION:Title: Ants and their associates as a model system to test host-symbiont network dynamics \nAbstract: An extremely large number of organisms engage in symbiotic relationships with ants. Interestingly\, these relationships are highly variable in terms of host-specificity and span the entire mutualism-antagonism continuum. In this talk\, we present different types of network analyses focusing on ant-symbiont interactions. We argue that ant-symbiont communities are highly suitable to test a wide range of network hypotheses in terrestrial ecosystems.  \n 
URL:https://www.naxys.be/event/thomas-parmentier-kuleuven-unamur/
LOCATION:E25
CATEGORIES:NAXYS Seminar
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BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20181213T130000
DTEND;TZID=Europe/Paris:20181213T140000
DTSTAMP:20260429T132213
CREATED:20181019T202631Z
LAST-MODIFIED:20181122T092014Z
UID:501-1544706000-1544709600@www.naxys.be
SUMMARY:Fabian Bastin (Université de Montréal)
DESCRIPTION:Title: Staffing optimization in call centers \nAbstract: Call centers are prominent in modern life\, and labor intensive. We aim to determine the minimum number of agents in a multi-skill call center\, while ensuring the desired level of quality of service to customers. We consider the case where the arrival rates cannot be forecast perfectly\, leading to a two-stage stochastic optimization problem. The arrival rates are modeled as random variables with large variance (uncertainty) in the first stage of the staffing decision process. The number of agents can however be adjusted in a second stage\, under some penalty costs\, when the information on the arrival rates is more accurate. The quality of service is measured by the service level\, defined as the proportion of calls answered within a given time\, called the acceptable wait threshold. Since the number of calls coming into the call center is unknown\, we only require that the service level constraints are satisfied with given (high) probabilities. These constraints cannot be evaluated analytically and are approximated using sample averages computed using simulation. We use a decomposition approach\, based on the L-shaped method\, to efficiently address the resulting optimization problem. We provide numerical studies to illustrate the performance of the decomposition algorithm\, along with a validation study of the approach. \nJoint work with Anh Thuy Ta\, Wyean Chan\, and Pierre L’Ecuyer.
URL:https://www.naxys.be/event/fabian-bastin-universite-de-montreal/
LOCATION:E25
CATEGORIES:NAXYS Seminar
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DTSTART;TZID=Europe/Paris:20181220T130000
DTEND;TZID=Europe/Paris:20181220T140000
DTSTAMP:20260429T132213
CREATED:20181120T102045Z
LAST-MODIFIED:20181122T115758Z
UID:513-1545310800-1545314400@www.naxys.be
SUMMARY:Justin Delloye (Luxembourg Institute of Socio-Economic Research LISER)
DESCRIPTION:Title: A New Approach to Complexity in Economic Geography \nAbstract: The design of efficient regional policies calls for a reliable understanding of complex regional dynamics. Dedicated scientific efforts have historically been split up in two distinct research strands that are Location Theory and Complex Systems. In this presentation\, I propose a conciliating modelling approach and I use it to address multiple equilibria issues in a model of New Economic Geography. In this field\, the question of equilibrium selection traditionally reduces to a dependence on initial conditions. In more recent core-periphery models\, the introduction of heterogeneous preferences generates exogenous shocks and therefore complex path-dependent dynamics. However\, these recent models use averaging procedures which prevent them from discussing path-dependent dynamics. Starting from the footloose entrepreneur model\, this method proposes a novel approach to adjustment dynamics\, based on stochastic migration models\, by which the dynamics of the population distribution is a continuous-time Markov chain. Using a diffusion approximation\, it computes the evolution of the transition probability function in the state space of the regional system\, which enables to discuss in particular the appearance of multiple peaks\, denoting substantial divergences of sample paths. It enables further to identify\, in explicit time units and at both short- and long-term horizons\, periods when heterogeneous preferences may substantially affect the regional dynamic. Thus\, this method raises new opportunities to improve the operational potential of New Economic Geography models.
URL:https://www.naxys.be/event/justin-delloye-luxembourg-institute-of-socio-economic-research-liser/
LOCATION:E25
CATEGORIES:NAXYS Seminar
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