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UPCommons, the website that provides open access to the knowledge of UPC, is formed by the group of open institutional repositories of UPC and its aim is to guarantee the safeguarding of the material produced by lecturers and researchers at the University, to maximise that material’s visibility and, consequently, to increase its impact on education and research worldwide.Mon, 29 Aug 2016 03:51:10 GMT2016-08-29T03:51:10ZUPCommonshttp://upcommons.upc.edu/themes/UPCommons/images/logoUPC.png
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Vademecum-based approach to multi-scale topological material design
http://hdl.handle.net/2117/89387
Vademecum-based approach to multi-scale topological material design
Ferrer Ferré, Àlex; Oliver Olivella, Xavier; Cante Terán, Juan Carlos; Lloberas Valls, Oriol
The work deals on computational design of structural materials by resorting to computational homogenization and topological optimization techniques. The goal is then to minimize the structural (macro-scale) compliance by appropriately designing the material distribution (microstructure) at a lower scale (micro-scale), which, in turn, rules the mechanical properties of the material. The specific features of the proposed approach are: (1) The cost function to be optimized (structural stiffness) is defined at the macro-scale, whereas the design variables defining the micro-structural topology lie on the low scale. Therefore a coupled, two-scale (macro/micro), optimization
problem is solved unlike the classical, single-scale, topological optimization problems. (2) To overcome the exorbitant computational cost stemming from the multiplicative character of the aforementioned multiscale approach, a specific strategy, based on the consultation of a discrete material catalog of micro-scale optimized topologies (Computational Vademecum) is used. The Computational Vademecum is computed in an offline process, which is performed only once for every constitutive-material, and it can be subsequently consulted as many times as desired in the online design process. This results into a large diminution of the resulting computational costs, which make
affordable the proposed methodology for multiscale computational material design. Some representative examples assess the performance of the considered approach.
Fri, 26 Aug 2016 12:00:23 GMThttp://hdl.handle.net/2117/893872016-08-26T12:00:23ZFerrer Ferré, ÀlexOliver Olivella, XavierCante Terán, Juan CarlosLloberas Valls, OriolThe work deals on computational design of structural materials by resorting to computational homogenization and topological optimization techniques. The goal is then to minimize the structural (macro-scale) compliance by appropriately designing the material distribution (microstructure) at a lower scale (micro-scale), which, in turn, rules the mechanical properties of the material. The specific features of the proposed approach are: (1) The cost function to be optimized (structural stiffness) is defined at the macro-scale, whereas the design variables defining the micro-structural topology lie on the low scale. Therefore a coupled, two-scale (macro/micro), optimization
problem is solved unlike the classical, single-scale, topological optimization problems. (2) To overcome the exorbitant computational cost stemming from the multiplicative character of the aforementioned multiscale approach, a specific strategy, based on the consultation of a discrete material catalog of micro-scale optimized topologies (Computational Vademecum) is used. The Computational Vademecum is computed in an offline process, which is performed only once for every constitutive-material, and it can be subsequently consulted as many times as desired in the online design process. This results into a large diminution of the resulting computational costs, which make
affordable the proposed methodology for multiscale computational material design. Some representative examples assess the performance of the considered approach.HRA*: hybrid randomized path planning for complex 3D environments
http://hdl.handle.net/2117/89386
HRA*: hybrid randomized path planning for complex 3D environments
Teniente Avilés, Ernesto Homar; Andrade-Cetto, Juan
We propose HRA*, a new randomized path planner for complex 3D environments. The method is a modified A* algorithm that uses a hybrid node expansion technique that combines a random exploration of the action space meeting vehicle kinematic constraints with a cost to goal metric that considers only kinematically feasible paths to the goal. The method includes also a series of heuristics to accelerate the search time. These include a cost penalty near obstacles, and a filter to prevent revisiting configurations. The performance of the method is compared against A*, RRT and RRT* in a series of challenging 3D outdoor datasets. HRA* is shown to outperform all of them in computation time, and delivering shorter paths than A* and RR
Fri, 26 Aug 2016 10:14:58 GMThttp://hdl.handle.net/2117/893862016-08-26T10:14:58ZTeniente Avilés, Ernesto HomarAndrade-Cetto, JuanWe propose HRA*, a new randomized path planner for complex 3D environments. The method is a modified A* algorithm that uses a hybrid node expansion technique that combines a random exploration of the action space meeting vehicle kinematic constraints with a cost to goal metric that considers only kinematically feasible paths to the goal. The method includes also a series of heuristics to accelerate the search time. These include a cost penalty near obstacles, and a filter to prevent revisiting configurations. The performance of the method is compared against A*, RRT and RRT* in a series of challenging 3D outdoor datasets. HRA* is shown to outperform all of them in computation time, and delivering shorter paths than A* and RRNumerical implementation and computational results of nonlinear network optimization with linear side constraints
http://hdl.handle.net/2117/89385
Numerical implementation and computational results of nonlinear network optimization with linear side constraints
Heredia, F.-Javier (Francisco Javier); Nabona Francisco, Narcís
Thu, 25 Aug 2016 13:03:53 GMThttp://hdl.handle.net/2117/893852016-08-25T13:03:53ZHeredia, F.-Javier (Francisco Javier)Nabona Francisco, NarcísDynamic modeling and controllability analysis of an ethanol reformer for fuel cell application
http://hdl.handle.net/2117/89384
Dynamic modeling and controllability analysis of an ethanol reformer for fuel cell application
García, Vanesa Mariel; Lopez Null, Eduardo; Serra, Maria; Llorca Piqué, Jordi; Riera Colomer, Jordi
This work presents a controllability analysis of a low temperature ethanol reformer based on a cobalt catalyst for fuel cell application. The study is based on a nonlinear dynamic model of a reformer which operates in three separate stages: ethanol dehydrogenation to acetaldehyde and hydrogen, acetaldehyde steam reforming, and water gas shift reaction. The controllability anal
ysis is focused on the rapid dynamics due to mass balances and is based on a linear
ization of the complex non-linear model of the reformer. RGA, CN and MRI analysis tools are applied to the linear model suggesting that a good performance can be
obtained with decentralized control for frequencies up to 0.1 rad/s.
Wed, 24 Aug 2016 12:41:35 GMThttp://hdl.handle.net/2117/893842016-08-24T12:41:35ZGarcía, Vanesa MarielLopez Null, EduardoSerra, MariaLlorca Piqué, JordiRiera Colomer, JordiThis work presents a controllability analysis of a low temperature ethanol reformer based on a cobalt catalyst for fuel cell application. The study is based on a nonlinear dynamic model of a reformer which operates in three separate stages: ethanol dehydrogenation to acetaldehyde and hydrogen, acetaldehyde steam reforming, and water gas shift reaction. The controllability anal
ysis is focused on the rapid dynamics due to mass balances and is based on a linear
ization of the complex non-linear model of the reformer. RGA, CN and MRI analysis tools are applied to the linear model suggesting that a good performance can be
obtained with decentralized control for frequencies up to 0.1 rad/s.Exact interval propagation for the efficient solution of position analysis problems on planar linkages
http://hdl.handle.net/2117/89383
Exact interval propagation for the efficient solution of position analysis problems on planar linkages
Celaya Llover, Enric; Creemers, Tom Lambert; Ros Giralt, Lluís
This paper presents an interval propagation algorithm for variables in planar single-loop linkages. Given intervals of allowed values for all variables, the algorithm provides, for every variable, the whole set of values, with out over-estimation, for which the linkage can actually be assembled. We show further how this algorithm can be integrated in a branch-and-prune search scheme, in order to solve the position analysis of general planar multi-loop linkages. Experimental results are included, comparing the method’s perfor mance with that of previous techniques given for the same task.
Wed, 24 Aug 2016 10:56:12 GMThttp://hdl.handle.net/2117/893832016-08-24T10:56:12ZCelaya Llover, EnricCreemers, Tom LambertRos Giralt, LluísThis paper presents an interval propagation algorithm for variables in planar single-loop linkages. Given intervals of allowed values for all variables, the algorithm provides, for every variable, the whole set of values, with out over-estimation, for which the linkage can actually be assembled. We show further how this algorithm can be integrated in a branch-and-prune search scheme, in order to solve the position analysis of general planar multi-loop linkages. Experimental results are included, comparing the method’s perfor mance with that of previous techniques given for the same task.Stock management in hospital pharmacy using chance-constrained model predictive control
http://hdl.handle.net/2117/89382
Stock management in hospital pharmacy using chance-constrained model predictive control
Jurado, Isabel; Maestre Torreblanca, José María; Velarde, Pablo; Ocampo-Martínez, Carlos; Fernandez, Isabel; Isla Tejera, Beatriz; del Prado, José Ramón
One of the most important problems in the pharmacy department of a hospital is stock management. The clinical needs of drugs must be satisfied with limited work labor while minimizing the use of economical resources. The complexity of the problem resides in the random nature of the drug demand and the multiple constraints that must be taken into account in every decision. In this article, chance-constrained model predictive control is proposed to deal with this problem. The flexibility of model predictive control allows taking into account explicitly the different objectives and constraints involved in the problem while the use of chance constraints provides a trade-off between conservativeness and efficiency. The solution proposed is assessed to study its implementation in two Spanish hospitals
Wed, 24 Aug 2016 10:09:12 GMThttp://hdl.handle.net/2117/893822016-08-24T10:09:12ZJurado, IsabelMaestre Torreblanca, José MaríaVelarde, PabloOcampo-Martínez, CarlosFernandez, IsabelIsla Tejera, Beatrizdel Prado, José RamónOne of the most important problems in the pharmacy department of a hospital is stock management. The clinical needs of drugs must be satisfied with limited work labor while minimizing the use of economical resources. The complexity of the problem resides in the random nature of the drug demand and the multiple constraints that must be taken into account in every decision. In this article, chance-constrained model predictive control is proposed to deal with this problem. The flexibility of model predictive control allows taking into account explicitly the different objectives and constraints involved in the problem while the use of chance constraints provides a trade-off between conservativeness and efficiency. The solution proposed is assessed to study its implementation in two Spanish hospitalsOptimal location of fast charging stations in Barcelona: a flow-capturing approach
http://hdl.handle.net/2117/89381
Optimal location of fast charging stations in Barcelona: a flow-capturing approach
Cruz Zambrano, Miguel; Corchero García, Cristina; Igualada González, Lucía; Bernardo, Valeria
The aim of this paper is to find the optimal location of electric vehicle (EV) fast charging stations by means of two methodologies: a classical flow-capturing optimization model involving only mobility needs, and an advanced flow-capturing optimization model including distribution network and location costs. While the first model aims to maximize the public service provided by the fast charging stations, the second also considers the incurred cost for providing it. Results from both models are compared in order to analyse the effect of both planning approaches in total cost of installation. As a case study it has been chosen the city of Barcelona.
Wed, 24 Aug 2016 08:57:52 GMThttp://hdl.handle.net/2117/893812016-08-24T08:57:52ZCruz Zambrano, MiguelCorchero García, CristinaIgualada González, LucíaBernardo, ValeriaThe aim of this paper is to find the optimal location of electric vehicle (EV) fast charging stations by means of two methodologies: a classical flow-capturing optimization model involving only mobility needs, and an advanced flow-capturing optimization model including distribution network and location costs. While the first model aims to maximize the public service provided by the fast charging stations, the second also considers the incurred cost for providing it. Results from both models are compared in order to analyse the effect of both planning approaches in total cost of installation. As a case study it has been chosen the city of Barcelona.IOStack: Software-Defined Object Storage
http://hdl.handle.net/2117/89380
IOStack: Software-Defined Object Storage
Gracia-Tinedo, Raúl; García-López, Pedro; Sánchez-Artigas, Marc; Sampé, Josep; Moatti, Yosef; Rom, Eran; Naor, Dalit; Nou, Ramon; Cortés, Toni; Oppermann, William; Michiardi, Pietro
The complexity and scale of today’s cloud storage systems is growing fast. In response to these challenges, Software-
Defined Storage (SDS) has recently become a prime candidate to simplify storage management in the cloud.
This article presents IOStack: The first SDS architecture for object stores (OpenStack Swift). At the control plane,
the provisioning of SDS services to tenants is made according to a set of policies managed via a high-level DSL. Policies may target storage automation and/or specific SLA objectives. At the data plane, policies define the enforcement of SDS services, namely filters, on a tenant’s requests. Moreover, IOStack is a framework to build a variety of filters, ranging from general-purpose computations close to the data to specialized data management mechanisms.
Our experiments illustrate that IOStack enables easy and effective policy-based provisioning, which can significantly
improve the operation of a multi-tenant object store.
Tue, 23 Aug 2016 12:38:24 GMThttp://hdl.handle.net/2117/893802016-08-23T12:38:24ZGracia-Tinedo, RaúlGarcía-López, PedroSánchez-Artigas, MarcSampé, JosepMoatti, YosefRom, EranNaor, DalitNou, RamonCortés, ToniOppermann, WilliamMichiardi, PietroThe complexity and scale of today’s cloud storage systems is growing fast. In response to these challenges, Software-
Defined Storage (SDS) has recently become a prime candidate to simplify storage management in the cloud.
This article presents IOStack: The first SDS architecture for object stores (OpenStack Swift). At the control plane,
the provisioning of SDS services to tenants is made according to a set of policies managed via a high-level DSL. Policies may target storage automation and/or specific SLA objectives. At the data plane, policies define the enforcement of SDS services, namely filters, on a tenant’s requests. Moreover, IOStack is a framework to build a variety of filters, ranging from general-purpose computations close to the data to specialized data management mechanisms.
Our experiments illustrate that IOStack enables easy and effective policy-based provisioning, which can significantly
improve the operation of a multi-tenant object store.A bilevel programming formulation for modelling the location of information: points for traffic conditions
http://hdl.handle.net/2117/89379
A bilevel programming formulation for modelling the location of information: points for traffic conditions
Montero Mercadé, Lídia; Codina Sancho, Esteve; Marín, Angel
Tue, 23 Aug 2016 11:36:25 GMThttp://hdl.handle.net/2117/893792016-08-23T11:36:25ZMontero Mercadé, LídiaCodina Sancho, EsteveMarín, AngelExploring interconnect energy savings under East-West traffic pattern of MapReduce clusters
http://hdl.handle.net/2117/89378
Exploring interconnect energy savings under East-West traffic pattern of MapReduce clusters
Fischer e Silva, Renan; Carpenter, Paul M.
An important challenge of modern data centers is to reduce energy consumption, of which a substantial proportion is due to the network. Energy Efficient Ethernet (EEE) is a recent standard that aims to reduce network power consumption, but current practice is to disable it in production use, since it has a poorly understood impact on real world application performance. An important application framework commonly used in modern data centers is Apache Hadoop, which implements the MapReduce programming model. This paper is the first to analyse the impact of EEE on MapReduce workloads, in terms of performance overheads and energy savings. We find that optimum energy savings are possible if the links use
packet coalescing. Packet coalescing must, however, be carefully configured in order to avoid excessive performance degradation.
Fri, 19 Aug 2016 12:50:31 GMThttp://hdl.handle.net/2117/893782016-08-19T12:50:31ZFischer e Silva, RenanCarpenter, Paul M.An important challenge of modern data centers is to reduce energy consumption, of which a substantial proportion is due to the network. Energy Efficient Ethernet (EEE) is a recent standard that aims to reduce network power consumption, but current practice is to disable it in production use, since it has a poorly understood impact on real world application performance. An important application framework commonly used in modern data centers is Apache Hadoop, which implements the MapReduce programming model. This paper is the first to analyse the impact of EEE on MapReduce workloads, in terms of performance overheads and energy savings. We find that optimum energy savings are possible if the links use
packet coalescing. Packet coalescing must, however, be carefully configured in order to avoid excessive performance degradation.