Novetats

Analysis of Crowdsourcing Logistics in B2C e-commerce: Costs and Environmental perspective

UPCommons - Vie, 12/22/2017 - 17:39
Analysis of Crowdsourcing Logistics in B2C e-commerce: Costs and Environmental perspective Bardasco San José, David Currently, the logistics in e-commerce is one of the big problems, especially in the deliveries between the company and the consumer, as result it generates additional costs that make the online service is not all efficient that it could be. Therefore, the present work focuses on the study of a new practice in the B2C e-commerce logistics, Logistic Crowdsourcing, as well as the creation of a model of costs and emissions about this innovative practice. To carry out the study about this practice has been made a literature review and the study of some projects of companies that nowadays are offering this service. Later, also it is created a model to calculate the costs and the emissions of the Crowdsourcing Logistics. Regarding the results, in the analysed articles there are nothing about Crowdsourcing Logistics, that is, there is a gap, even if there are real projects around this practice currently being carried out. This way, it has been possible to define this concept, how this practice is made and the most important players. About the creation of the model and the related simulations, it can say that the results have allow to extract some interesting conclusions, which allow to understand still better this innovative practice. So, this paper aims to offer an alternative to current problems in the B2C e-commerce logistics with the Crowdsourcing Logistics and study the costs and the emissions of some hypothetic scenarios with the model created for this practice. And this way understand better the concept and really if it is a good and optimal solution, alternative or not.
Categorías: Novetats

Implementation and comparison of linearization-based and backstepping controllers for quadcopters

UPCommons - Vie, 12/22/2017 - 17:16
Implementation and comparison of linearization-based and backstepping controllers for quadcopters Valle Rodríguez, Jesús In this work, two approaches to the control of a quadcopter are followed. The rst approach resorts to linear quadratic control (LQR) techniques and is based on the linearization of the quadcopter dynamics. Motivated by the fact that this linearization results in decoupled dynamics for the longitudinal, lateral, height and yaw axis, the LQR controllers can be designed separately. Moreover, the controllers for the longitudinal and lateral dynamics exploit the cascaded structure of the model. The second approach resorts to non-linear control and exploits the fact that the full non-linear model of the quadcopter also has a cascaded structure: the torque inputs control the angles which in turn determine the forces which drive the position states. The approach is based on a widely used non-linear control design technique for cascaded systems known as back-stepping. Simulations of the two approaches are carried out and conclusions are drawn on the pros and cons of each approach.
Categorías: Novetats

Phase - II Lepage - type CUSUM charts for joint monitoring of location and scale

UPCommons - Vie, 12/22/2017 - 17:15
Phase - II Lepage - type CUSUM charts for joint monitoring of location and scale Aguilar Lleyda, Victor Most control charts in nonparametric statistics tend to focus on detecting changes in the location or scale parameters. Since it is ideal to monitor both, researchers have proposed to combine them into a single statistic. From there, the Lepage-type family of tests was born, and it’s been updated with many versions. Chowdhury, Mukherjee, and Chrakaborti proposed merging the Ansari-Bradley and Wilcoxon Rank Sum tests into a single plotting statistic able to track persistent changes in the location and scale parameters in Phase II in the form of a CUSUM chart, using a reference sample from Phase I. The work from Guerrero (2016) based on several tests proposed by Conover et al. (1981) shows that there may be many statistics able to perform better than the Ansari-Bradley for monitoring the scale parameter. In the present work, we propose three Control charts based on the mentioned recommendations. These are the LP-M, LP-FK, and LP-SR CUSUM charts, in which the Ansari-Bradley statistic is replaced for the Mood, the Fligner and Killeen, and the Squared ranks tests respectively. Via Monte Carlo simulations, Control limits are tabulated for practitioners, plus the In-control and Out-of-control performance of the charts are calculated and compared with the CUSUM-Lepage Chart proposed by Chowdhury. This will help to choose the most useful CUSUM chart for each scenario. An example using real data illustrates how the proposed Control Charts must be implemented.
Categorías: Novetats

Thin film transistors obtained by hot wire CVD

UPCommons - Vie, 12/22/2017 - 16:58
Thin film transistors obtained by hot wire CVD Puigdollers i González, Joaquim; Orpella García, Alberto; Dosev, D; Voz Sánchez, Cristóbal; Peiró, D; Pallarés, J; Marsal, L F; Bertomeu Balaguero, Joan; Andreu Batallé, Jordi; Alcubilla González, Ramón Hydrogenated microcrystalline silicon films obtained at low temperature (150–280°C) by hot wire chemical vapour deposition at two different process pressures were measured by Raman spectroscopy, X-ray diffraction (XRD) spectroscopy and photothermal deflection spectroscopy (PDS). A crystalline fraction >90% with a subgap optical absortion 10 cm-1 at 0.8 eV were obtained in films deposited at growth rates >0.8 nm/s. These films were incorporated in n-channel thin film transistors and their electrical properties were measured. The saturation mobility was 0.72 ± 0.05 cm2/V s and the threshold voltage around 0.2 eV. The dependence of their conductance activation energies on gate voltages were related to the properties of the material.
Categorías: Novetats

A compact charge ratio expression for the emitter delay of polysilicon emitter bipolar transistors

UPCommons - Vie, 12/22/2017 - 16:43
A compact charge ratio expression for the emitter delay of polysilicon emitter bipolar transistors Castañer Muñoz, Luis María; Sureda, S; Bardés Llorensí, Daniel; Alcubilla González, Ramón A compact solution for the ratio of the excess minority carrier charge stored into the polysilicon to the charge stored in the single crystal part of the emitter of a polysilicon emitter bipolar transistor is derived. The solution is based on an existing comprehensive model which takes into account the interfacial oxide and an arbitrary number of grains in the polysilicon layer. The emitter charge partition in polysilicon and single crystal emitter components is summarized in contour plots for constant values of the ratio.
Categorías: Novetats

BCN en memoria circular

UPCommons - Vie, 12/22/2017 - 16:36
BCN en memoria circular Serralunga, Juan Manuel Esta Barcelona en Memoria Circular se propone ante todo redescubrir una ciudad tras la ciudad, y por lo tanto, poner evidencia un paisaje urbano circular, oculto y perdido en el extenso entramado de una metrópolis rectilínea. La dimensión circular de Barcelona puede interpretarse aquí, como una constelación de edificios, enlaces viales infraestructurales, espacios a cielo abierto y pequeños detalles arquitectónicos, que guardan directa relación con la geometría circular y que hacen -en parte- a la fisonomía de la ciudad. Estas presencias circulares de múltiples escalas y proporciones, se ven condensadas como un estrato o capa de información que nos revela un verdadero microcosmos cóncavo-convexo. Es en este sentido que el soporte argumental de esta tesina se despliega, en primer lugar, como una exploración que adquiere cuerpo de memoria gráfica, mapa y registro con la intencionada voluntad de interpelar a la ciudad y ampliar el panorama hacia nuevas lecturas y múltiples asociaciones. A partir de esta labor documental que explora la circularidad de Barcelona en su escala metropolitana, se ha profundizado en el estudio de tres edificios que por sus emplazamientos y relación con el entorno natural o construido, dan cuenta de distintos momentos históricos de la ciudad y su proceso de transformación. Estas arquitecturas congregadas por el patrón de la geometría circular, pueden verse categorizadas -en interrelación dimensional- como edificios de pequeña, de mediana y gran escala y este es el criterio con que se las ha ordenado en capítulos sucesivos. En cada una de las lecturas se verán enfatizadas, distintas dimensiones que hacen a la conceptualización circular del espacio arquitectónico; dimensiones que determinan la consistencia formal, material y estructural de los edificios, su condición simbólica, el carácter tipológico que determina un modo particular de habitar el espacio, como así también las atmósferas que en estos espacios se recrea. Màster universitari en Estudis Avançats en Arquitectura: Projecte. Procés i Programació
Categorías: Novetats

Modelado electrotérmico de baterías de litio para determinar su envejecimiento mediante la entropía irreversible

UPCommons - Vie, 12/22/2017 - 16:30
Modelado electrotérmico de baterías de litio para determinar su envejecimiento mediante la entropía irreversible Zolis, Anderson Kevin La llegada de baterías de ion-litio ha traído un cambio significativo al área de sistemas de batería de gran formato, dado que a anteriormente las baterías eran limitadas, pesados y voluminosas acumuladoras de ácido y plomo. En el presente proyecto, se busca modelizar electroquímicamente una batería de litio con el principal objetivo de investigar la entropía irreversible en esta. Como resultado, se destaca entre diferentes factores que la principal contribución al envejecimiento de la batería es la pérdida de capacidad de los electrodos de la misma. Simultáneamente se presenta un modelo termo-eléctrico de una batería genérica de ion-litio mediante uso de técnicas numéricas de elementos finitos implementadas en Matlab partiendo de un modelo ya desarrollado para la batería de Nickel Hidruro (Ni-MH). Así pues de manera semejante se presentará un modelo con la adaptación correspondiente a la batería de litio. Del mismo modo, este proyecto busca seguir conjuntamente el modelo implementado por (Gu, W B y Wang 2000): “Thermal-electrochemical coupled modellling of a lithium cell”. Debido a que este modelo ha sido similar a la simulación térmica y electroquímica como se afirmó anteriormente sobre la batería de Ni-MH. Dicho lo anterior y partiendo de estos modelos, este proyecto pretende adaptarse a la batería de litio.
Categorías: Novetats

On the optimal NFVI-PoP placement for SDN-enabled 5G networks

UPCommons - Mié, 12/20/2017 - 23:54
On the optimal NFVI-PoP placement for SDN-enabled 5G networks Santoyo González, Alejandro; Cervelló Pastor, Cristina 5G stringent requirements entail numerous challenges to overcome. Optimizing Network Function Virtualization Infrastructure Point of Presence (NFVI-PoP) placement in a Fog Computing/5G environment is one of these challenges. To solve this problem, this paper proposes an approach for the NFVI-PoP placement problem solution considering 5G mobile network requirements in a Fog Computing (FC) and Software De¿ned Networks (SDN) ecosystem.
Categorías: Novetats

DYMO self-forwarding: a simple way for reducing the routing overhead in MANETS

UPCommons - Mié, 12/20/2017 - 23:29
DYMO self-forwarding: a simple way for reducing the routing overhead in MANETS Zola, Enrica Valeria; Barceló Arroyo, Francisco; Martín Escalona, Israel Current routing protocols in Mobile Ad hoc Networks tend to use information on the position of the nodes in order to improve their features. In fact, without this information, protocols are hardly scalable since they tend to overflow the radio media with control packets, most of them being useless at the end. This paper presents the assessment of a modification of the DYMO protocol in order to include and use positioning information. The evaluation is carried out through simulations in realistic environments and connectivity condition. The possible error in the position is seldom considered in this kind of studies but here taken into account to catch the impact of realistic GPS devices or other sources of location techniques.
Categorías: Novetats

One-armed spiral instability in double-degenerate post-merger accretion disks

UPCommons - Mié, 12/20/2017 - 23:09
One-armed spiral instability in double-degenerate post-merger accretion disks kashyap, Rahul; Fisher, Robert T.; García-Berro Montilla, Enrique; Aznar-Siguán, Gabriela; Ji, Suoqing; Loren Aguilar, Pablo Increasing observational and theoretical evidence points to binary white dwarf (WD) mergers as the origin of some, if not most, normal Type Ia supernovae (SNe Ia). In this paper, we discuss the post-merger evolution of binary WD mergers and their relevance to the double-degenerate channel of SNe Ia. We present 3D simulations of carbon–oxygen (C/O) WD binary systems undergoing unstable mass transfer, where we vary both the total mass and the mass ratio. We demonstrate that these systems generally give rise to a one-armed gravitational spiral instability. The spiral density modes transport mass and angular momentum in the disk even in the absence of a magnetic field and are most pronounced in systems with secondary-to-primary mass ratios larger than 0.6. We further analyze carbon burning in these systems to assess the possibility of detonation. Unlike the case of a $1.1+1.0\,{M}_{\odot }$ C/O WD binary, we find that WD binary systems with lower mass and smaller mass ratios do not detonate as SNe Ia up to ~8–22 outer dynamical times. Two additional models do, however, undergo net heating, and their secular increase in temperature could possibly result in a detonation on timescales longer than those considered here.
Categorías: Novetats

Joint user association and backhaul routing for green 5G mesh millimeter wave backhaul networks

UPCommons - Mié, 12/20/2017 - 22:54
Joint user association and backhaul routing for green 5G mesh millimeter wave backhaul networks Mesodiakaki, Agapi; Zola, Enrica Valeria; Kassler, Andreas With the advance of fifth generation (5G) networks, network density needs to grow significantly in order to meet the required capacity demands. A massive deployment of small cells may lead to a high cost for providing fiber connectivity to each node. Consequently, many small cells are expected to be connected through wireless links to the umbrella eNodeB, leading to a mesh backhaul topology. This backhaul solution will most probably be composed of high capacity point-to-point links, typically operating in the millimeter wave (mmWave) frequency band due to its massive bandwidth availability. In this paper, we propose a mathematical model that jointly solves the user association and backhaul routing problem in the aforementioned context, aiming at the energy efficiency maximization of the network. Our study considers the energy consumption of both the access and backhaul links, while taking into account the capacity constraints of all the nodes as well as the fulfillment of the service-level agreements (SLAs). Due to the high complexity of the optimal solution, we also propose an energy efficient heuristic algorithm (Joint), which solves the discussed joint problem, while inducing low complexity in the system. We numerically evaluate the algorithm performance by comparing it not only with the optimal solution but also with reference approaches under different traffic load scenarios and backhaul parameters. Our results demonstrate that Joint outperforms the state-of-the-art, while being able to find good solutions, close to optimal, in short time.
Categorías: Novetats

Design and construction of a demonstrator for the autonomous picking system Komrob

UPCommons - Mié, 12/20/2017 - 20:23
Design and construction of a demonstrator for the autonomous picking system Komrob Menchón Campoy, Georgina
Categorías: Novetats

Alternative marketing channels: the case of the Door-to-Door Channels in a Food Company

UPCommons - Mié, 12/20/2017 - 20:23
Alternative marketing channels: the case of the Door-to-Door Channels in a Food Company Zorzano Walker, Ester Consumers seek products of excellence and value propositions that satisfy their needs and wishes. Companies, while meeting those needs, are facing challenges of how to design, select and manage distribution channels that will ensure maximum savings in distribution costs, enhance product availability and effective co-ordination of channel activities. At the same time, manufacturers are bedevilled with problems of how to provide fast deliveries to customers, maintain optimum inventory volume and ideal market coverage, minimize us of warehouses at the least carrying cost of stock, reduce total distribution costs and maximize customer satisfaction. Consequently, competence is increasing exponentially and things are getting more difficult for companies to reach de market. Thus, this study is focused on the task of carrying out a research about alternative marketing channels that complement the conventional ones in order to increase the market share and finally satisfy the current needs of the customers. All through the study, some topics can be highlighted: the theoretical research of the main concepts related with the marketing channels, a deeper inquiry in the alternative marketing channels and the door-to-door channel (theory, origins and current examples) and finally the study of a practical case including information about the company, the situation’s context or the social and business impact. Furthermore, along the evolution of the research, some interesting topics have been discovered and included in the thesis such as women’s empowerment in the direct selling channels and the fusion of the Corporate Social Responsibility and the Business’ Strategy.
Categorías: Novetats

On the implementation of strategic sourcing at World Vision Cambodia

UPCommons - Mié, 12/20/2017 - 20:23
On the implementation of strategic sourcing at World Vision Cambodia Batlle Ginette, Sergi
Categorías: Novetats

PRL i diòxid de titani nanoparticulat en una fàbrica de pintures

UPCommons - Mié, 12/20/2017 - 20:23
PRL i diòxid de titani nanoparticulat en una fàbrica de pintures Macias Guerrero, Carlos Dins de la indústria química, el sector de les pintures i recobriments és un dels destins on va a parar el TiO2 en forma de nanopartícules a escala global. Aquest compost, un dels més utilitzats a les fàbriques de pintura és utilitzat com a matèria primera en la fabricació d‟aquestes aportant diferents propietats al producte. Són moltes les treballadores i treballadors exposades diàriament al TiO2, tant en la seva forma nanomètrica com estàndard i és degut, tant a l‟estat incipient de la regulació com a la poca informació toxicològica disponible entorn de les formes nano, que no existeix, avui dia, un bon coneixement, registre o control que garanteixi la seguretat del personal exposat. Davant de l‟escenari existent sorgeix la necessitat d‟identificar i conèixer quin tipus de TiO2 s‟utilitza a les fàbriques, així com quantificar l‟exposició dels treballadors davant d‟aquest, establir més tard un ordre de preferències respecte a quines activitats impliquen més riscos i, tot plegat, dibuixar una metodologia que faciliti la realització de la mateixa feina a altres fàbriques. El desenvolupament del procediment es basa, primer, en la realització d‟un treball de camp en una fàbrica de pintures on s‟identifiquen matèries primeres, activitats, productes finals i treballadors en contacte amb el TiO2. Aquest és seguit d‟un anàlisis quantitatiu de les dades productives i un anàlisis qualitatiu de les dades coyunturals que acompanyen a les primeres. Aquest segon, recolzat per l‟eina Stoffenmanager nano com a mètode d‟avaluació qualitativa per realitzar la jerarquització del risc. Finalment, després de realitzar la discussió adient, es proposen les mesures preventives apropiades fent ús de l‟eina CBnanotool com a mètode no sols d‟avauació qualitativa sino també d‟obtenció de mesures a aplicar.
Categorías: Novetats

In-operation learning of optimal wind farm operation strategy

UPCommons - Mié, 12/20/2017 - 20:23
In-operation learning of optimal wind farm operation strategy Oliva Gratacós, Joan In a wind farm, power losses due to wind turbine wake effects can be up to 30-40% under certain conditions. As the global installed wind power capacity increases, the mitigation of wake effects in wind farms is gaining more importance. Following a conventional control strategy, each individual turbine maximizes its own power production without taking into consideration its effects on the performance of downstream turbines. Therefore, this control scheme results in operation conditions that yield suboptimal power production. In order to increase the overall wind farm power production, a cooperative control strategy can be used, which coordinates the control actions among the wind turbines in the wind farm. This work further investigates the model-free Bayesian Ascent optimization algorithm using SimWindFarm and a standalone Dynamic Wake Meandering model-based simulation tool An advantage of such optimization approach is that the control strategy adapts to operational conditions in the wind farm and is not model-dependent. An approximation of the wind farm power function is constructed using GP regression to fit the control action inputs and the noisy measured power outputs, which is then maximized to determine the optimal control inputs. This estimation is updated in every iteration, allowing the control system to learn from the target system while performing the optimization. The usage of all historical data, along with a trust region constraint in the sampling of new inputs, contribute to a fast convergence rate with gradual changes of the control actions. The developed learning technique is implemented in a wind farm controller and tested in both SimWindFarm and standalone Dynamic Wake Meandering model-based simulation tools. With the conducted tests, performance of the algorithm is assessed considering the different dynamics in the wind farm, thus obtaining an accurate representation of real farm operation. The developed controller reliably improves farm efficiency, even with uncertainty present in measurements. Compared to traditional control strategies, an increase in total wind farm power production is obtained when using a cooperative control strategy. Such enhancement in wind farm performance would result in an improvement of wind farm economics and hence in further growth of wind-energy based power generation.
Categorías: Novetats

Frequency control in power systems without must-run units

UPCommons - Mié, 12/20/2017 - 20:23
Frequency control in power systems without must-run units Dominguez López, Guillermo Nowadays, most of the ancillary services such as reserve capacity, inertia and frequency control relies on large conventional power plants. Approaching future power systems with high penetration of renewable energy sources (RES) has resulted in imperative need for the evaluation of ancillary services. This research focuses on the frequency stability which must be ensured in order to maintain the grid stability against imbalances between generation and load. This large conventional power plants that provide ancillary services are called “must-run” units. These facilities are generation power plants necessary during certain operating conditions and they are responsible for providing enough ancillary services to ensure a reliable operation of power systems. Given a high RES penetration in the future, must-run units are expected to be reduced or totally decommissioned reducing the power system inertia. This may result in insecure operation threatening the reliability of the power supply. This project investigates the frequency stability support from renewable energy generation such as wind power plants (WPPs) and solar photovoltaic systems (SPVSs) in future power systems with high penetration of RES and without must-run units. Sensitivity studies for frequency stability are performed on a simulated 2030 scenario for western Denmark (DK1) power system. The objective of this master thesis is to study the DK1 power system to analyse the ability of modern controllable WPPs to provide frequency stability without must-run units in a future scenario dominated by RES generation. This project examines the primary frequency control in DK1 simulating an overfrequency event islanding DK1 from the CE power system with high wind forecast. The main results of this project reveal that the fast deploy of active power by the RES generation counterbalances the reduced inertia in the power system, which can operate without a lack of stability of the power supply for overfrequency events without must-run units. However, there are technical capabilities and limitations that curtail the RES penetration. Recommendations on the parameters of the WPPs frequency control are made according to the droop, the ramp rate and the RES penetration. The virtual inertia is recommended for frequency control of WPPs and increases its importance when the RES penetration is high. The support of HVDC interconnections is an interesting facility to increase the RES penetration allowing the power system to operate with even less inertia online maintaining a stable supply. Although, the measurement and communication delay by the frequency controllers increases its importance when increasing the RES penetration as faster power deploy is needed.
Categorías: Novetats

Exceptional zeros and L-invariants of Bianchi modular forms

UPCommons - Mar, 12/19/2017 - 19:21
Exceptional zeros and L-invariants of Bianchi modular forms Barrera Salazar, Daniel Roberto; Williams, Chris
Categorías: Novetats

Concurs d’idees “Eix-Bruc” per a l’ordenació de l’àmbit de Sant Pasqual a Santa Coloma de Gramenet – UE1

UPCommons - Mar, 12/19/2017 - 16:53
Concurs d’idees “Eix-Bruc” per a l’ordenació de l’àmbit de Sant Pasqual a Santa Coloma de Gramenet – UE1 Toral Fernández, José Manuel
Categorías: Novetats

Field theory for a reaction-diffusion model of quasispecies dynamics

UPCommons - Mar, 12/19/2017 - 16:48
Field theory for a reaction-diffusion model of quasispecies dynamics Pastor Satorras, Romualdo; Solé, Ricard Vicenç RNA viruses are known to replicate with extremely high mutation rates. These rates are actually close to the so-called error threshold. This threshold is in fact a critical point beyond which genetic information is lost through a second-order phase transition, which has been dubbed as the “error catastrophe.” Here we explore this phenomenon using a field theory approximation to the spatially extended Swetina-Schuster quasispecies model [J. Swetina and P. Schuster, Biophys. Chem. 16, 329 (1982)], a single-sharp-peak landscape. In analogy with standard absorbing-state phase transitions, we develop a reaction-diffusion model whose discrete rules mimic the Swetina-Schuster model. The field theory representation of the reaction-diffusion system is constructed. The proposed field theory belongs to the same universality class as a conserved reaction-diffusion model previously proposed [F. van Wijland et al., Physica A 251, 179 (1998)]. From the field theory, we obtain the full set of exponents that characterize the critical behavior at the error threshold. Our results present the error catastrophe from a different point of view and suggest that spatial degrees of freedom can modify several mean-field predictions previously considered, leading to the definition of characteristic exponents that could be experimentally measurable.
Categorías: Novetats

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