Agent-based micro simulation to assess the performance of roundabouts considering different variables and performance indicators

Traffic congestion problems in intersections are usually solved by building infrastructures such as roundabouts. Several variables influence its performance, e.g. geometry, size and driving behaviour. Thus, it becomes necessary to compare these variables. This paper proposes a simulation model, developed to compare the performance of roundabouts, employing the object and agent modelling paradigms of Simio, to model the individual behaviour of vehicles. The results indicate the optimum size of roundabouts is around 40 meters of diameter and that the driving style has a greater influence on the performance of the roundabout than its unbalancing. In addition, it was found that roundabouts considering unbalancing and human behaviour decreased: The flow of vehicles in 8%, the waiting time per vehicle in 3 minutes, the queue size in 90%, the number of stops per vehicle in 88% and vehicles spent three times more fuel, than the roundabouts that did not consider these variables.(undefined)info:eu-repo/semantics/publishedVersio

Cerebral Sinovenous Thrombosis in Children: Clinical Presentation and Extension, Localization and Recanalization of Thrombosis

Many important questions regarding pathophysiology and treatment of cerebral sinovenous thrombosis need clarification and may depend on further knowledge on the etiology, site, extension and recanalization of the thrombosis. We studied these variables in a cohort of children and adolescents from seven Portuguese Centers. We conclude from our results that the deep venous system and the superior longitudinal sinus are less frequently affected with thrombosis but have a greater potential for serious neurologic disease and for major sequelae. Non-recanalization, at least in the long term, is not an adverse prognostic factor. Extensive propagation of the thrombus from the initial site of origin seems to be common. The early identification of risk factors and their treatment coupled with an aggressive attitude towards diagnosis and treatment for thrombosis involving the deep venous system would be warranted

Discrete simulation software ranking -A top list of the worldwide most popular and used tools

This paper documents a work on all-purpose discrete event simulation tools evaluation. Selected tools must be suitable for process design (e.g. manufacturing or services industries). Rather than making specific judgments of the tools, authors tried to measure the intensity of usage or presence in different sources, which they called "popularity". It was performed in several different ways, including occurrences in the WWW and scientific publications with tool name and vendor name. This work is an upgrade to the same study issued 5 years ago (2011), which in its turn was also an upgrade of 10 years ago (in 2006). It is obvious that more popularity does not assure more quality, or being better to the purpose of a simulation tool; however, a positive correlation may exist between them. The result of this work is a short list, of 19 commercial simulation tools, with probably the nowadays' most relevant ones.This work has been co-supported by SI I&DT project in joint-promotion nº 36265/2013 (HMIEXCEL) and by FCT Fundação para a Ciência e Tecnologia - project: PEst-OE/EEI/UI0319/2014. REFERENCESinfo:eu-repo/semantics/publishedVersio

Elimination of the numerical Cerenkov instability for spectral EM-PIC codes

When using an electromagnetic particle-in-cell (EM-PIC) code to simulate a relativistically drifting plasma, a violent numerical instability known as the numerical Cerenkov instability (NCI) occurs. The NCI is due to the unphysical coupling of electromagnetic waves on a grid to wave-particle resonances, including aliased resonances, i.e., $\omega + 2\pi\mu/\Delta t=(k_1+ 2\pi\nu_1/\Delta x_1)v_0$, where $\mu$ and $\nu_1$ refer to the time and space aliases and the plasma is drifting relativistically at velocity $v_0$ in the $\hat{1}$-direction. Recent studies have shown that an EM-PIC code which uses a spectral field solver and a low pass filter can eliminate the fastest growing modes of the NCI. Based on these studies a new spectral PIC code for studying laser wakefield acceleration (LWFA) in the Lorentz boosted frame was developed. However, we show that for parameters of relevance for LWFA simulations in the boosted frame, a relativistically drifting plasma is susceptible to a host of additional unstable modes with lower growth rates, and that these modes appear when the fastest growing unstable modes are filtered out. We show that these modes are most easily identified as the coupling between modes which are purely transverse (EM) and purely longitudinal (Langmuir) in the rest frame of the plasma for specific time and space aliases. We rewrite the dispersion relation of the drifting plasma for a general field solver and obtain analytic expressions for the location and growth rate for each unstable mode, i.e, for each time and space aliased resonances. We show for the spectral solver that when the fastest growing mode is eliminated a new mode at the fundamental resonance ($\mu=\nu_1=0$) can be seen. (Please check the whole abstract in the paper).Comment: 36 pages, 12 figure

Assessing the performance of a restaurant through discrete simulation in Simio

For the purpose of evaluating the level of service of a Portuguese self-service restaurant, a simulation model was developed in Simio. The purpose of such model was to quantify specific performance indicators. In this sense, data was gathered by conducting observations of the field, which allowed the authors to find relevant problems in the system. The simulation model was validated and, afterwards, simulation experiments were conducted, which suggested some changes that could be implemented, without reducing the performance of the restaurant and reduce the utilization of workers, who become available for other tasks with more added-value, such as supplying critical items (e.g., main dishes and soap). Moreover, the potential impact of the introduction of an information device used to warn workers responsible to supply items was assessed through simulation, indicating that it would lead to benefits both for customers and workers.This work has been supported by COMPETE: POCI-01-0145-FEDER-007043 and FCT –Fundação para a Ciência e Tecnologia within the Project Scope: UID/CEC/00319/2013 and by the Doctoral scholarship PDE/BDE/114566/2016 funded by FCT, the Portuguese Ministry of Science, Technology and Higher Education, through national funds, and co-financed by the European Social Fund (ESF) through the Operacional Programme for Human Capital (POCH)

A novel application of pre-signals to improve the performance of signalized intersections: Evaluation through simulation

To ponder less costlier solutions to solve traffic congestion problems at signalized intersections, this paper proposes a novel application consisting of using pre-signals. Hence, an agent-based traffic simulation model was developed, where it is possible to model different types of intersections - including roundabouts of different sizes - and quantify and compare their performance. By analyzing the simulation results, it was found that: on the intersection with pre-signals, an increase in the flow of 10% and 3% was registered, the vehicles spent 1 and 2 less minutes to cross the intersection and the fuel consumption was decreased in 22% and 44%, in comparison to regular intersections and roundabouts, respectively. Concerning the size of queues, it was noted that the queues of the regular intersection were 60 meters longer than the queues on the intersection with pre-signals and on the roundabout. Based on these findings, and by making cost assumptions, a small cost analysis was made, which indicates that at least 1 million € could be yearly saved.This work has been supported by FCT –Fundação para a Ciência e Tecnologia within the Project Scope: UID/CEC/00319/2019

A systematic literature review on the conversion of plastic wastes into valuable 2D graphene-based materials

Increasing the economic attractiveness of plastic waste reusing/recycling is expected to contribute towards reducing their input in the environment. The use of plastic wastes as feedstock for the synthesis of added-value carbon materials has been studied in this context. However, there is a lack of a systematic review of the published works on this topic. Bearing this in mind, a systematic review was carried out in this study, covering the available literature on the conversion of plastic wastes into carbon materials. Clearly defined methodologies/criteria were accordingly established. 142 studies were selected for qualitative/overall analysis, including type/condition of plastic (pristine or waste), and type of carbon materials obtained. It was found that most of the studies report the utilization of plastic wastes (75%); and that the most representative materials obtained are carbon nanotubes (CNTs; 47.1% of the studies under evaluation), activated carbons (ACs; 22.2%) and 2D graphene-based materials (9.2%). Nevertheless, despite already being the third most significant group of carbon materials produced from plastic wastes, none of the 12 review articles available in the literature is fully devoted to the conversion of plastic wastes into 2D graphene-based materials. Therefore, the literature available on this topic was thoroughly reviewed for the first time. These studies report the synthesis of monolayer, few-layer and multi-layer graphene (including flash graphene) obtained through 4 main synthesis methodologies: (i) thermal decomposition of the plastics directly over a metal substrate; (ii) prior thermal decomposition of the plastics, with the resulting hydrocarbon gases released being fed to a chemical vapour deposition (CVD) system containing the metal substrate; (iii) thermal decomposition followed by ball milling and microwave sintering; and (iv) flash Joule heating (FJH).This work was financially supported by project POCI-01-0145- FEDER-031439 (PLASTIC_TO_FUEL&MAT) funded by FEDER funds through COMPETE2020 – Programa Operacional Competitividade e Internacionalizaç˜ao (POCI), and by national funds (PIDDAC) through FCT/MCTES. We would also like to thank the scientific collaboration under Base Fundings - UIDP/50020/2020 of the Associate Laboratory LSRE-LCM and UIDB/00690/2020 of the Centro de Investigação de Montanha (CIMO) - funded by national funds through FCT/MCTES (PIDDAC).info:eu-repo/semantics/publishedVersio

Mitigation of numerical Cerenkov radiation and instability using a hybrid finite difference-FFT Maxwell solver and a local charge conserving current deposit

A hybrid Maxwell solver for fully relativistic and electromagnetic (EM) particle-in-cell (PIC) codes is described. In this solver, the EM fields are solved in $k$ space by performing an FFT in one direction, while using finite difference operators in the other direction(s). This solver eliminates the numerical Cerenkov radiation for particles moving in the preferred direction. Moreover, the numerical Cerenkov instability (NCI) induced by the relativistically drifting plasma and beam can be eliminated using this hybrid solver by applying strategies that are similar to those recently developed for pure FFT solvers. A current correction is applied for the charge conserving current deposit to correctly account for the EM calculation in hybrid Yee-FFT solver. A theoretical analysis of the dispersion properties in vacuum and in a drifting plasma for the hybrid solver is presented, and compared with PIC simulations with good agreement obtained. This hybrid solver is applied to both 2D and 3D Cartesian and quasi-3D (in which the fields and current are decomposed into azimuthal harmonics) geometries. Illustrative results for laser wakefield accelerator simulation in a Lorentz boosted frame using the hybrid solver in the 2D Cartesian geometry are presented, and compared against results from 2D UPIC-EMMA simulation which uses a pure spectral Maxwell solver, and from OSIRIS 2D lab frame simulation using the standard Yee solver. Very good agreement is obtained which demonstrates the feasibility of using the hybrid solver for high fidelity simulation of relativistically drifting plasma with no evidence of the numerical Cerenkov instability