1,179 research outputs found

    Quantitying the Effects of Traffic Calming on Emissions Using on-road Measurement

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    The objective of this work was to determine the effect of one form of traffic calming on emissions. Traffic calming is aimed at reducing average vehicle speeds, especially in residential neighborhoods, often using physical road obstructions such as speed bumps, but it also results in a higher number of acceleration/deceleration events which in turn yield higher emissions. Testing was undertaken by driving a warmed-up Euro-1 spark ignition passenger car over a set of speed bumps on a level road, and then comparing the emissions output to a noncalmed level road negotiated smoothly at a similar average speed. For the emissions measurements, a novel method was utilized, whereby the vehicle was fitted with a portable Fourier Transform Infrared (FTIR) spectrometer, capable of measuring up to 51 different components in real-time on the road. The results showed that increases in emissions were much greater than was previously reported by other researchers using different techniques. When traffic-calmed results were compared to a smooth non-calmed road, there were substantial increases in CO2 (90%), CO (117%), NOx (195%) and THC (148%). These results form the basis for a good argument against traffic calming using speed bumps, especially for aggressive drivers. Slowing traffic down with speed restrictions enforced by speed cameras is a more environmentally friendly option

    Evaluation of a FTIR Emission Measurement System for Legislated Emissions Using a SI Car

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    A series of chassis dynamometer test trials were conducted to assess the performance of a Fourier Transform Infra Red (FTIR) system developed for on-road vehicle exhaust emissions measurements. Trials used a EURO 1 emission compliant SI passenger car which, alongside the FTIR, was instrumented to allow the routine logging of engine speed, road speed, throttle position, air-fuel ratio, air flow and fuel flow in addition to engine, exhaust and catalyst temperatures. The chassis dynamometer facility incorporated an ‘industry standard’ measurement system comprising MEXA7400 gas analyzer and CVS bag sampling which was the ‘benchmark’ for the evaluation of FTIR legislated gas-phase emissions (CO, NOx, THC and CO2) measurements. Initial steady state measurements demonstrated strong correlations for CO, NOx and THC (R2 of 0.99, 0.97 0.99, respectively) and a good correlation for CO2 (R2 = 0.92). Subsequent transient and total mass emissions measurements from replicate samplings of four different driving cycles (two standard cycles, FTP75 and NEDC, and two novel cycles based on real-world data collected in Leeds) also show good response of FTIR and satisfied agreement between the FTIR and CVS bag sampling measurements. In general, the trial results demonstrate that the on-board FTIR emission measurement system provides reliable in-journey emissions data

    Study of PDMS characterization and its applications in biomedicine: a review

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    Polydimethylsiloxane, also known as PDMS, has been widely used in the biomedical industry because of its biocompatible material and its biomechanical behavior is similar to biological tissues, with applications in the study of aneurysmal behavior and devices such as: Micro pumps, optical systems, microfluidic circuits. Many advances in research have been reached, but further tests are still necessary to understand the mechanical behavior and applicability of the material. For the study of PDMS behavior, two different techniques are employed: numerical and experimental. In experimental studies, it is extremely popular to use a field technique, in which the most appropriate technique to measure the field displacement of PDMS, without decorrelation, is the Digital Image Correlation (DIC) method. In this paper, we revised the most important experimental works with PDMS material and, simultaneously, we present its mechanical properties and its biomedical applications.info:eu-repo/semantics/publishedVersio

    Numerical characterization of a hyperelastic material to shear stress

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    In last years, some studies have been proved that there is an association between the wall shear stress with intracranial aneurysm rupture, however, is very difficult to understand the mechanical tissue behaviour when subjected to shear stresses. In this work, it is implemented numerical simulations to characterise the polydimethylsiloxane (PDMS) material when it is subjected to a shear solicitation. For this, it was initially necessary to perform some experimental tests to characterize the mechanical behaviour of the material. Based on these results, several numerical simulations were performed with the most common constitutive models in the simulation of hyperelastic materials by varying numerical factors and parameters of the numerical models.info:eu-repo/semantics/publishedVersio

    Characterization of shear strain on PDMS: numerical and experimental approaches

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    Polydimethylsiloxane (PDMS) is one of the most popular elastomers and has been used in di erent fields, especially in biomechanics research. Among the many interesting features of this material, its hyperelastic behavior stands out, which allows the use of PDMS in various applications, like the ones that mimic soft tissues. However, the hyperelastic behavior is not linear and needs detailed analysis, especially the characterization of shear strain. In this work, two approaches, numerical and experimental, were proposed to characterize the e ect of shear strain on PDMS. The experimental method was implemented as a simple shear testing associated with 3D digital image correlation and was made using two specimens with two thicknesses of PDMS (2 and 4 mm). A finite element software was used to implement the numerical simulations, in which four di erent simulations using the Mooney–Rivlin, Yeoh, Gent, and polynomial hyperelastic constitutive models were performed. These approaches showed that the maximum value of shear strain occurred in the central region of the PDMS, and higher values emerged for the 2 mm PDMS thickness. Qualitatively, in the central area of the specimen, the numerical and experimental results have similar behaviors and the values of shear strain are close. For higher values of displacement and thicknesses, the numerical simulation results move further away from experimental values.This work has been supported by FCT – Fundação para a Ciência e Tecnologia within the R&D Units Project Scope: CIMO UIDB/00690/2020info:eu-repo/semantics/publishedVersio

    Applications of the ACGT Master Ontology on Cancer

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    In this paper we present applications of the ACGT Master Ontology (MO) which is a new terminology resource for a transnational network providing data exchange in oncology, emphasizing the integration of both clinical and molecular data. The development of a new ontology was necessary due to problems with existing biomedical ontologies in oncology. The ACGT MO is a test case for the application of best practices in ontology development. This paper provides an overview of the application of the ontology within the ACGT project thus far

    Abundance and evolution of galaxy clusters in cosmological models with massive neutrino

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    The time evolution of the number density of galaxy clusters and their mass and temperature functions are used to constrain cosmological parameters in the spatially flat dark matter models containing a fraction of hot particles (massive neutrino) additional to cold and baryonic matter. We test the modified MDM models with cosmic gravitational waves and show that they neither pass the cluster evolution test nor reproduce the observed height of the first acoustic peak in ΔT/T\Delta T/T spectrum, and therefore should be ruled out. The models with a non-zero cosmological constant are in better agreement with observations. We estimate the free cosmological parameters in Λ\LambdaMDM with a negligible abundance of gravitational waves, and find that within the parameter ranges h∈(0.6,0.7)h\in (0.6, 0.7), n∈(0.9,1.1)n\in (0.9, 1.1), (i) the value of ΩΛ\Omega_\Lambda is strongly affected by a small fraction of hot dark matter, fν≡Ων/Ωm∈(0,0.2)f_\nu\equiv\Omega_\nu /\Omega_m\in (0, 0.2): 0.45<ΩΛ<0.70.45 <\Omega_\Lambda <0.7 (1σ1\sigma CL), and (ii) the redshift evolution of galaxy clusters alone reveals the following explicit correlation between ΩΛ\Omega_\Lambda and fνf_\nu: ΩΛ+0.5fν=0.65±0.1\Omega_\Lambda +0.5f_\nu =0.65\pm 0.1. The present accuracy of observational data allows only to bound the fraction of hot matter, fν∈(0,0.2)f_\nu\in (0, 0.2) (the number of massive neutrino species remains undelimited, Nν=1,2,3N_\nu =1, 2, 3).Comment: 9 pages, 7 figures, submitted in A&

    Stress Concentration on PDMS: An evaluation of three numerical constitutive models using digital image correlation

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    The examination of hyperelastic materials’ behavior, such as polydimethylsiloxane (PDMS), is crucial for applications in areas as biomedicine and electronics. However, the limitations of hyperelastic models for specific stress scenarios, with stress concentration, are not well explored on the literature. To address this, firstly, three constitutive models were evaluated (Neo-Hookean, Mooney-Rivlin, and Ogden) using numerical simulations and Digital Image Correlation (DIC) analysis during a uniaxial tensile test. The samples were made of PDMS with stress concentration geometries (center holes, shoulder fillets, and edge notches). Results of ANOVA analysis showed that any of the three models can be chosen for numerical analysis of PDMS since no significant differences in suitability were found. Finally, the Ogen model was chosen to obtain the stress concentration factors for these geometries, a property which characterize how discontinuities change the maximum stress supported by an element. Our study provides new values for variables needed to analyze and design hyperelastic elements and produce a foundation for understanding PDMS stress-strain behavior.The authors acknowledge the projects EXPL/EME-EME/0732/2021 and 2022.06207.PTDC for the financial support, through national funds (OE), within the scope of the Scientific Research and Technological Development Projects (IC&DT) program in all scientific domains (PTDC), PORTUGAL 2020 Partnership Agreement, European Regional Development Fund (FEDER), via the Foundation for Science and Technology, I.P. (FCT, I.P) and the R&D Units projects (UIDB/00690/2020 and UIDP/00690/2020) (CIMO), SusTEC (LA/P/0007/2020), UIDB/ 04077/2020, UIDP/04077/2020, UIDB/04436/2020 and UIDB/00532/ 2020. Andrews Souza acknowledges FCT for the Ph.D. scholarship 2021.07961.BD.info:eu-repo/semantics/publishedVersio
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