Presentation of KI-COF, a phenomenological model of variable friction in fretting contact

International audienceIn this paper, a new phenomenological model, called KI-COF is developed to account for variable coefficient of friction (COF) in space and time. The COF is no longer considered as a global value valid for the whole contact area. A local value is introduced instead, the evolution of which is governed by the local history of the contact and the amount of slip

A Novel Architectural Framework on IoT Ecosystem, Security Aspects and Mechanisms: A Comprehensive Survey

For the past few years, the Internet of Things (IoT) technology continues to not only gain popularity and importance, but also witnesses the true realization of everything being smart. With the advent of the concept of smart everything, IoT has emerged as an area of great potential and incredible growth. An IoT ecosystem centers around innovation perspective which is considered as its fundamental core. Accordingly, IoT enabling technologies such as hardware and software platforms as well as standards become the core of the IoT ecosystem. However, any large-scale technological integration such as the IoT development poses the challenge to ensure secure data transmission. Perhaps, the ubiquitous and the resource-constrained nature of IoT devices and the sensitive and private data being generated by IoT systems make them highly vulnerable to physical and cyber threats. In this paper, we re-define an IoT ecosystem from the core technologies view point. We propose a modified three layer IoT architecture by dividing the perception layer into elementary blocks based on their attributed functions. Enabling technologies, attacks and security countermeasures are classified under each layer of the proposed architecture. Additionally, to give the readers a broader perspective of the research area, we discuss the role of various state-of-the-art emerging technologies in the IoT security. We present the security aspects of the most prominent standards and other recently developed technologies for IoT which might have the potential to form the yet undefined IoT architecture. Among the technologies presented in this article, we give a special interest to one recent technology in IoT domain. This technology is named IQRF that stands for Intelligent Connectivity using Radio Frequency. It is an emerging technology for wireless packet-oriented communication that operates in sub-GHz ISM band (868 MHz) and which is intended for general use where wireless connectivity is needed, either in a mesh network or point-to-point (P2P) configuration. We also highlighted the security aspects implemented in this technology and we compare it with the other already known technologies. Moreover, a detailed discussion on the possible attacks is presented. These attacks are projected on the IoT technologies presented in this article including IQRF. In addition, lightweight security solutions, implemented in these technologies, to counter these threats in the proposed IoT ecosystem architecture are also presented. Lastly, we summarize the survey by listing out some common challenges and the future research directions in this field.publishedVersio

Vitesse de circulation monétaire et son implication sur la demande de monnaie au Maroc

The objective of this paper is to propose a theoretical model for estimating the speed of money circulation in Morocco. This concept is closely related to the implications of the estimation and stability of the demand for money. Theoretically, this relationship is identified in a monetarist framework and consists of an equation linking the amount of real cash held by the public to a scale variable and the opportunity cost of holding it. This investigation is applied to quarterly data covering the period from the first quarter of 2007 to the last quarter of 2020. The estimates were based on several equations (assumptions), including the one that measures the demand for money in the long term, its dynamics in the short term, and the one that captures an empirical estimate of the speed of money circulation. The results confirm that there is indeed a cointegrating relationship in the money demand equation and that the parity of the long-term coefficients is not rejected, which makes the estimation of the speed of money circulation possible. In this case, the results state that the spreads of short and long rates can approximate the opportunity cost of holding money, which makes the speed of money circulation high.Ce travail a pour objectif de proposer un modèle théorique permettant d’estimer la vitesse de circulation monétaire au Maroc. Ce concept est étroitement lié aux implications de l’estimation et la stabilité de la demande de monnaie. Théoriquement, cette relation est cernée dans un cadre monétariste et elle est constituée d’une équation reliant le montant des encaisses réelles détenues par le public à une variable d’échelle et au coût d’opportunité que fait supporter cette détention. Cette investigation est appliquée sur des données trimestrielles couvrant la période du premier trimestre de l’année 2007 jusqu’au dernier trimestre de l’année 2020. Les estimations ont été basées sur plusieurs équations (hypothèses), notamment celle qui mesure la demande de monnaie dans le long terme, et sa dynamique dans le court terme et celle qui capte une estimation empirique de la vitesse de circulation de monnaie. Les résultats confirment qu’il existe certes une relation de cointégration dans l’équation de la demande de monnaie et que la parité des coefficients de long terme n’est pas rejetée ce qui rend l’estimation de la vitesse de monnaie possible. Dans ce cas, les résultats affirment que les écarts des taux courts et longs peuvent approximer le coût d’opportunité de la détention de monnaie ce qui rend la vitesse de réaction élevée

POETS - Process-Oriented Enterprise Transaction Systems

Dieser Endbericht der Projektgruppe 509 mit dem Titel Process-Oriented Enterprise Transaction Systems (POETS) des Lehrstuhls 14 des Fachbereichs Informatik der Universität Dortmund dient dazu, den bisherigen Verlauf und die Ergebnisse der Lehrveranstaltung aus dem Wintersemester 2006/2007 und dem Sommersemester 2007 vorzustellen. Im ersten Semester wurden nach der Einarbeitung in das Thema, Konzepte und Methoden erarbeitet, um die Projektgruppenziele zu erreichen. Die Möglichkeiten der beteiligten Softwareplattformen wurden ergründet und die notwendigen Erweiterungen konzipiert und teilweise bereits implementiert. Im zweiten Semester wurde die Implemetierung des Systems fortgeführt und beendet. Es wurden wichtige Erkenntnisse gesammelt über die Fähigkeiten des Systmes im Bereich Business Process Reengineering (BPR)und Continuous Process Improvement (CPI). Die Fähigkeiten des Systems im Bereich Logging und Monitoring wurden erweitert. Es wurde eine Softwareschnittstelle erstellt, die den Anschluss von Sensoren aus dem SmarterWohnen Umfeld an das System zulässt. Das Projekt SmarterWohnen, das Grundlage unserer Arbeit ist, ist ein breites und interessantes Themenfeld. Die technischen Vorgaben und Möglichkeiten wurden mit den Methoden, welche die Informatik bietet, untersucht und strukturiert. Das System wurde bewertet und mit ähnlichen Systemen verglichen. Au erdem wurde eine Bewertung der Projektorganisation erstellt

Detection of each DENV serotype by RT-LAMP

Background 4 one-step, real-time, reverse transcription loop-mediated isothermal amplification (RT-LAMP) assays were developed for the detection of dengue virus (DENV) serotypes by considering 2,056 full genome DENV sequences. DENV1 and DENV2 RT-LAMP assays were validated with 31 blood and 11 serum samples from Tanzania, Senegal, Sudan and Mauritania. DENV3 and DENV4 RT-LAMP assays were validated with 25 serum samples from Cambodia Methodology/Principal findings 4 final reaction primer mixes were obtained by using a combination of Principal Component Analysis of the full DENV genome sequences, and LAMP primer design based on sequence alignments using the LAVA software. These mixes contained 14 (DENV1), 12 (DENV2), 8 (DENV3) and 3 (DENV4) LAMP primer sets. The assays were evaluated with an External Quality Assessment panel from Quality Control for Molecular Diagnostics. The assays were serotype-specific and did not cross-detect with other flaviviruses. The limits of detection, with 95% probability, were 22 (DENV1), 542 (DENV2), 197 (DENV3) and 641 (DENV4) RNA molecules, and 100% reproducibility in the assays was obtained with up to 102 (DENV1) and 103 RNA molecules (DENV2, DENV3 and DENV4). Validation of the DENV2 assay with blood samples from Tanzania resulted in 23 samples detected by RT-LAMP, demonstrating that the assay is 100% specific and 95.8% sensitive (positive predictive value of 100% and a negative predictive value of 85.7%). All serum samples from Senegal, Sudan and Mauritania were detected and 3 untyped as DENV1. The sensitivity of RT-LAMP for DENV4 samples from Cambodia did not quite match qRT-PCR. Conclusions/Significance We have shown a novel approach to design LAMP primers that makes use of fast growing sequence databases. The DENV1 and DENV2 assays were validated with viral RNA extracted clinical samples, showing very good performance parameters

Impact Of Covid-19 Lockdown On Smoking (Waterpipe And Cigarette) And Participants\u27 Bmi Across Various Sociodemographic Groups In Arab Countries In The Mediterranean Region

INTRODUCTION Tobacco smokers are at high risk of developing severe COVID-19. Lockdown was a chosen strategy to deal with the spread of infectious diseases; nonetheless, it influenced people\u27s eating and smoking behaviors. The main objective of this study is to determine the impact of the COVID-19 lockdown on smoking (waterpipe and cigarette) behavior and its associations with sociodemographic characteristics and body mass index. METHODS The data were derived from a large-scale retrospective cross-sectional study using a validated online international survey from 38 countries (n=37207) conducted between 17 April and 25 June 2020. The Eastern Mediterranean Region (WHO-EMR countries) data related to 10 Arabic countries that participated in this survey have been selected for analysis in this study. A total of 12433 participants were included in the analysis of this study, reporting their smoking behavior and their BMI before and during the COVID-19 lockdown. Descriptive and regression analyses were conducted to examine the association between smoking practices and the participant\u27s country of origin, sociodemographic characteristics, and BMI (kg/m2). RESULTS Overall, the prevalence rate of smoking decreased significantly during the lockdown from 29.8% to 23.5% (p\u3c0.05). The percentage of females who smoke was higher than males among the studied population. The highest smoking prevalence was found in Lebanon (33.2%), and the lowest was in Oman (7.9%). In Egypt, Kuwait, Lebanon, and Saudi Arabia, the data showed a significant difference in the education level of smokers before and during the lockdown (p\u3c0.05). Smokers in Lebanon had lower education levels than those in other countries, where the majority of smokers had a Bachelor\u27s degree. The findings show that the BMI rates in Jordan, Lebanon, Oman, and Saudi Arabia significantly increased during the lockdown (p\u3c0.05). The highest percentages of obesity among smokers before the lockdown were in Oman (33.3%), followed by Bahrain (28.4%) and Qatar (26.4%), whereas, during the lockdown, the percentage of obese smokers was highest in Bahrain (32.1%) followed by Qatar (31.3%) and Oman (25%). According to the logistic regression model, the odds ratio of smoking increased during the pandemic, whereas the odds ratio of TV watching decreased. This finding was statistically significant by age, gender, education level, country of residence, and work status. CONCLUSIONS Although the overall rates of smoking among the studied countries decreased during the lockdown period, we cannot attribute this change in smoking behavior to the lockdown. Smoking cessation services need to anticipate that unexpected disruptions, such as pandemic lockdowns, may be associated with changes in daily tobacco consumption. Public health authorities should promote the adoption of healthy lifestyles to reduce the long-term negative effects of the lockdown

Assessment of Eating Habits and Lifestyle during Coronavirus Pandemic in the MENA region: A Cross-Sectional Study

© The Authors 2020. The coronavirus disease (COVID-19) has rapidly spread globally, forcing countries to apply lockdowns and strict social distancing measures. The aim of this study was to assess eating habits and lifestyle behaviors among residents of the Middle East and North Africa (MENA) region during the lockdown. A cross-sectional study among adult residents of the MENA region was conducted using an online questionnaire designed on Google Forms during April 2020. A total of 2970 participants from 18 countries participated in the current study. During the pandemic, over 30% reported weight gain, 6.2% consumed five or more meals per day compared to 2.2% before the pandemic (p\u3c0.001), and 48.8% did not consume fruits on daily basis. Moreover, 39.1% did not engage in physical activity, over 35% spent more than five hours per day on screens. A significant association between the frequency of training during the pandemic and the reported change in weight was found (p \u3c 0.001). A significantly higher percentage of participants reported physical and emotional exhaustion, irritability, and tension either all the time or a large part of the time during the pandemic (p \u3c 0.001). Although a high percentage of participants reported sleeping more hours per night during the pandemic, 63% had sleep disturbances. The study highlights that the lockdown due to the COVID-19 pandemic caused a variety of lifestyle changes, physical inactivity, and psychological problems among adults in the MENA region

A facultative mutualistic feedback enhances the stability of tropical intertidal seagrass beds

Marine foundation species such as corals, seagrasses, salt marsh plants, and mangrove trees are increasingly found to engage in mutualistic interactions. Because mutualisms by their very nature generate a positive feedback between the species, subtle environmental impacts on one of the species involved may trigger mutualism breakdown, potentially leading to ecosystem regime shifts. Using an empirically parameterized model, we investigate a facultative mutualism between seagrass and lucinid bivalves with endosymbiotic sulfide-oxidizing gill bacteria in a tropical intertidal ecosystem. Model predictions for our system show that, by alleviating the build-up of toxic sulfide, this mutualism maintains an otherwise intrinsically unstable seagrass ecosystem. However, an increase in seagrass mortality above natural levels, due to e.g. desiccation stress, triggers mutualism breakdown. This pushes the system in collapse-and-recovery dynamics ('slow-fast cycles') characterized by long-term persistent states of bare and seagrass-dominated, with rapid transitions in between. Model results were consistent with remote sensing analyses that suggest feedback-mediated state shifts induced by desiccation. Overall, our combined theoretical and empirical results illustrate the potential of mutualistic feedbacks to stabilize ecosystems, but also reveal an important drawback as small environmental changes may trigger shifts. We therefore suggest that mutualisms should be considered for marine conservation and restoration of seagrass beds

Perceptions and sociocultural factors underlying adoption of conservation agriculture in the Mediterranean

The Mediterranean region is facing major challenges for soil conservation and sustainable agriculture. Conservation agriculture (CA), including reduced soil disturbance, can help conserve soils and improve soil fertility, but its adoption in the Mediterranean region is limited. Examining farmers’ perceptions of soil and underlying sociocultural factors can help shed light on adoption of soil management practices. In this paper, we conducted a survey with 590 farmers across Morocco, Spain and Tunisia to explore concepts that are cognitively associated with soil and perceptions of tillage. We also evaluated differences in perceptions of innovation, community, adaptive capacity, and responsibility for soil. We found that farmers’ cognitive associations with soil show awareness of soil as a living resource, go beyond agriculture and livelihoods to reveal cultural ties, and link to multiple levels of human needs. Beliefs about the benefits of tillage for water availability and yield persist among the surveyed farmers. We found that openness towards innovation, perceived adaptive capacity and responsibility for soil were associated with minimum tillage, whereas community integration was not. Education, age and farm lifestyle were also associated with differences in these perceptions. CA promotion in the Mediterranean should emphasize the multiple values of soil, should demonstrate how sufficient yields may be achieved alongside resilience to drought, and be tailored to differing levels of environmental awareness and economic needs across north and south