Analytical and numerical treatment of oscillatory mixed differential equations with differentiable delays and advances

NOTICE: this is the author’s version of a work that was accepted for publication in Journal of computational and applied mathematics. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of computational and applied mathematics, 235(2011), doi: 10.1016/j.cam.2011.04.041This article discusses the oscillatory behaviour of the differential equation of mixed type

Reviewing traffic conflict techniques for potential application to developing countries

The economic and social costs due to road crashes are disproportionately higher in developing countries. In addition, underreporting, coupled with an incomplete and inconsistent recording of reported crashes is a major issue in such settings. A brief outline of the dimension of road safety problems in developing countries and the most common limitations of existing crash databases is given in the paper. The challenges in applying traditional approaches for traffic safety evaluation and initiatives are also discussed. Diagnosis of road safety problems using traffic conflict techniques has received considerable research interest and has gained acceptance as a proactive surrogate measure in developed countries. Significant studies have been accomplished to develop, validate and apply different surrogate indicators for the estimation of traffic conflicts, as well as an assessment of the safety problem in different road geometric and operating conditions. This has provided a substitute for the historical crash records in traffic safety research. The main objective of this paper is to assess the application potentiality of this surrogate safety measures to address safety issues in developing countries. To do that, this paper critically reviews and synthesizes the different indicators of surrogate safety measures. The main principles, as well as advantages and disadvantages of the major indicators and prospects of application, are presented here. Finally, future research directions for road traffic safety assessment are outlined in the perspective of understanding the most concerning human issue due to traffic crashes in developing countries

The Urban Toolkit: A Grammar-based Framework for Urban Visual Analytics

While cities around the world are looking for smart ways to use new advances in data collection, management, and analysis to address their problems, the complex nature of urban issues and the overwhelming amount of available data have posed significant challenges in translating these efforts into actionable insights. In the past few years, urban visual analytics tools have significantly helped tackle these challenges. When analyzing a feature of interest, an urban expert must transform, integrate, and visualize different thematic (e.g., sunlight access, demographic) and physical (e.g., buildings, street networks) data layers, oftentimes across multiple spatial and temporal scales. However, integrating and analyzing these layers require expertise in different fields, increasing development time and effort. This makes the entire visual data exploration and system implementation difficult for programmers and also sets a high entry barrier for urban experts outside of computer science. With this in mind, in this paper, we present the Urban Toolkit (UTK), a flexible and extensible visualization framework that enables the easy authoring of web-based visualizations through a new high-level grammar specifically built with common urban use cases in mind. In order to facilitate the integration and visualization of different urban data, we also propose the concept of knots to merge thematic and physical urban layers. We evaluate our approach through use cases and a series of interviews with experts and practitioners from different domains, including urban accessibility, urban planning, architecture, and climate science. UTK is available at urbantk.org.Comment: Accepted at IEEE VIS 2023. UTK is available at http://urbantk.or

Sun-dried pears: Phenolic compounds and antioxidant activity.

Two different regional varieties of pears, S. Bartolomeu and Amêndoa, were analyzed fresh and after sun-drying. The total phenolic composition and antioxidant capacity of these pears were determined. The total antioxidant capacity was compared using two different methods: DMPD (N,N-dimethyl-p-phenylenediamine) and the method of ABTS (2,2’-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)) radical scavenging. The ABTS method, when compared with the DMPD method, showed a better correlation between the content of phenolic compounds of the pears and their antioxidant activity. The fresh pear possessed higher amounts of phenolic compounds and higher antioxidant capacity when compared to sun-dried pear. The antioxidant efficiency was expressed as Trolox equivalent and as ascorbic acid equivalent. For both methods, the Trolox equivalent was higher than the ascorbic acid equivalent

Numerical treatment of oscillary functional differential equations

NOTICE: this is the author’s version of a work that was accepted for publication in Journal of computational and applied mathematics. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of computational and applied mathematics, 234(2010), doi: 10.1016/j.cam.2010.01.035This preprint is concerned with oscillatory functional differential equations (that is, those equations where all the solutions oscillate) under a numerical approximation. Our interest is in the preservation of qualitative properties of solutions under a numerical discretisation. We give conditions under which an equation is oscillatory, and consider whether the discrete schemes derived using linear v-methods will also be oscillatory. We conclude with some general theor

μlED-Based Single-Wavelength Bi-directional POF Link with 10 Gb/s Aggregate Data Rate

We report record 10 Gb/s bi-directional data transmission over a single 10 m SI-POF, by employing blue micro-light-emitting diodes (μLEDs) at a single wavelength, APD receivers and a PAM-32 modulation scheme. The implementation of 10 Gb/s LED-POF links takes advantage of the bi-directional configuration, which doubles the overall channel capacity, and APDs which provide an enhanced link power budget owing to their improved sensitivity compared with conventional PIN photodiodes. Moreover, the high spectral efficiency of the PAM-32 modulation scheme employed, together with equalization techniques, enable the full utilization of the link bandwidth and the transmission of data rates higher than those obtained with conventional on-off-keying (OOK). Simulation and experimental results demonstrate the feasibility of such a bi-directional link and simultaneous 5 Gb/s data transmission is realized in each direction, achieving an aggregate data rate of 10 Gb/s with a BER<10-3. The crosstalk penalty between the two directions of the link is measured to be less than 0.5 dB.This is the final version of the article. It first appeared from IEEE via http://dx.doi.org/10.1109/JLT.2015.244398

2 Gb/s μlED-APD based visible light communications using feed-forward pre-equalization and PAM-4 modulation

Feed-forward pre-equalization is investigated to extend the transmission capability of μLED-based links, providing better receiver sensitivities up to 5dB compared with post-equalization. Error-free 2Gb/s free-space VLC over 0.6m is demonstrated using a PAM-4 modulated blue μLED and an APD receiver.This work is supported by the UK EPSRC via the UPVLC Project.This is the author accepted manuscript. The final version is available from IEEE via http://dx.doi.org/10.1109/ECOC.2015.734188

PACKING LINE EVALUATION FOR DROP IMPACTS ON PERSIMMON QUALITY "RAMA FORTE"

Excessive and inadequate handling of fruits and vegetables provides high incidences of physical damage, consequently, post harvest losses. The main goal of this work was to evaluate the impact magnitude in persimmon packing lines, "Rama Forte", and to determine, at the laboratory, its impact limits. For evaluating the critical points it was used an instrumented sphere of 76 mm of diameter (Technmark, Inc, Lansing, USA), which registered the impact magnitude in seven distinctive impact lines located in four packing houses. For determining physical damages, tests were carried out at the laboratory, where fruit drop was related to impact magnitude, physical damage incidence and fruit post harvest losses. At the packing lines, the values found varied from 21 to 87 G on the transfer points and the majority of registered impacts (over 94%) were down 50G. Drops from 20 cm caused an increase in weight losses after six days of storage at room temperature. Drops from 20 and 30 cm caused skin darkness (low L values), associated to a decrease in color intensity (chroma). Impact drop did not affect pulp fruit chemical features.29464265

6.25 Gb/s POF link using GaN μLED arrays and optically generated pulse amplitude modulation

Optically-generated PAM schemes using μLED arrays are implemented for high-speed POF links for the first time. 6.25Gb/s PAM-16 transmission is demonstrated using 4 μLEDs, exhibiting 3.8dB greater power-margin than a link with a single μLED.This work is supported by the UK Engineering and Physical Sciences Research Council (EPSRC) via the Ultra Parallel Visible Light Communication (UP-VLC) Project.This is the accepted manuscript of a paper published in CLEO: 2015 (X. Li, N. Bamiedakis, J. Wei, J. Mckendry, E. Xie, R. Ferreira, E. Gu, M. Dawson, R. V. Penty, and I. H. White, "6.25 Gb/s POF Link Using GaN μLED Arrays and Optically Generated Pulse Amplitude Modulation," in CLEO: 2015, OSA Technical Digest (online) (Optical Society of America, 2015), paper STu4F.7.). The final version is available at http://dx.doi.org/10.1364/CLEO_SI.2015.STu4F.7 © 2015 Optical Society of America. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited

Intercentre reproducibility of cardiac apparent diffusion coefficient and fractional anisotropy in healthy volunteers

BACKGROUND: Diffusion tensor cardiac magnetic resonance (DT-CMR) enables probing of the microarchitecture of the myocardium, but the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) reported in healthy volunteers have been inconsistent. The aim of this study was to validate a stimulated-echo diffusion sequence using phantoms, and to assess the intercentre reproducibility of in-vivo diffusion measures using the sequence. METHODS AND RESULTS: A stimulated-echo, cardiac-gated DT-CMR sequence with a reduced-field-of-view, single-shot EPI readout was used at two centres with 3 T MRI scanners. Four alkane phantoms with known diffusivities were scanned at a single centre using a stimulated echo sequence and a spin-echo Stejskal-Tanner diffusion sequence. The median (maximum, minimum) difference between the DT-CMR sequence and Stejskal-Tanner sequence was 0.01 (0.04, 0.0006) × 10(-3) mm(2)/s (2%), and between the DT-CMR sequence and literature diffusivities was 0.02 (0.05, 0.006) × 10(-3) mm(2)/s (4%). The same ten healthy volunteers were scanned using the DT-CMR sequence at the two centres less than seven days apart. Average ADC and FA were calculated in a single mid-ventricular, short axis slice. Intercentre differences were tested for statistical significance at the p < 0.05 level using paired t-tests. The mean ADC ± standard deviation for all subjects averaged over both centres was 1.10 ± 0.06 × 10(-3) mm(2)/s in systole and 1.20 ± 0.09 × 10(-3) mm(2)/s in diastole; FA was 0.41 ± 0.04 in systole and 0.54 ± 0.03 in diastole. With similarly-drawn regions-of-interest, systolic ADC (difference 0.05 × 10(-3) mm(2)/s), systolic FA (difference 0.003) and diastolic FA (difference 0.01) were not statistically significantly different between centres (p > 0.05), and only the diastolic ADC showed a statistically significant, but numerically small, difference of 0.07 × 10(-3) mm(2)/s (p = 0.047). The intercentre, intrasubject coefficients of variance were: systolic ADC 7%, FA 6%; diastolic ADC 7%, FA 3%. CONCLUSIONS: This is the first study to demonstrate the accuracy of a stimulated-echo DT-CMR sequence in phantoms, and demonstrates the feasibility of obtaining reproducible ADC and FA in healthy volunteers at separate centres with well-matched sequences and processing