Physics, Mathematics, Computer science
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Valerie Le Guyon
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Sorbonne University Abu Dhabi Library
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AE
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Abu Dhabi

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Now showing 1 - 10 of 68
  • Publication
    Comparative Study of Polyethylene Films Embedded with Oxide Nanoparticles of Granulated and Free-Standing Nature
    ( 2022)
    Christopoulos, Stavros
    ;
    Slimani, Ahmed
    ;
    Li, Liang
    ;
    Le Guyon, Valerie
    ;
    Bsaibess, Eliane
    ;
    El-Rifai, Joumana
    ;
    Angastiniotis, Nicos
    ;
    Koutsokeras, Loukas
    ;
    Duponchel, Benoît
    Nanocomposite polymer films are a very diverse research field due to their many applications. The search for low-cost, versatile methods, producing regulated properties of the final products, has thus become extremely relevant. We have previously reported a bulk-scale process, dispersing granulated metal oxide nanoparticles, of both unary and multi-component nature, in a low-density polyethylene (LDPE) polymer matrix, establishing a reference in the produced films’ optical properties, due to the high degree of homogeneity and preservation of the primary particle size allowed by this method. In this work, unmodified, free-standing particles, namely zinc oxide (ZnO) , titanium dioxide (TiO2), aluminum oxide (Al2O3), and silicon dioxide (SiO2) are blended directly with LDPE, and the optical properties of the fabricated films are compared to those of films made using the granulation process. The direct blending process evidently allows for control of the secondary particle size and ensures a homogeneous dispersion of the particles, albeit to a lesser extent than the granulation process. Despite the secondary particle size being comparatively larger than its granulated counterpart, the process still provides a regulated degree of deagglomeration of the free-standing oxide particles, so it can be used as a low-cost alternative. The regulation of the secondary particle size tunes the transmission and reflection spectra, in both unary and mixed oxide compositions. Finally, the direct blending process exhibits a clear ability to tune the energy band gap in mixed oxides.
      20  6
  • Publication
    Organic Crystalline Optical Waveguides That Remain Elastic from -196 to ≈ 200°C
    ( 2022)
    Li, Liang
    ;
    Tang, Shiyue
    ;
    Ye, Kaiqi
    ;
    Commins, Patrick
    ;
    Naumov, Panče
    ;
    Zhang, Hongyu
    Organic crystals that are capable to deform (reversibly or irreversibly) similar to polymer materials have been widely reported over the past ten years. However, most of the reported organic crystals can only be elastically bent within a narrow temperature range, and reports on their thermal behavior that would encourage applications of these energy-transducing elements in extreme conditions are not readily available. This work designs a linear and flat π-conjugated molecule with double intramolecular hydrogen bonds that prevent thermally induced conformational distortions. The molecule assembles as a rigid building block into centimeter-sized wide organic crystals that can be elastically bent over a temperature range spanning close to 400 °C, from −196 to ≈200 °C. The emission wavelength of the crystals is also temperature dependent, and can be continually tuned from 547 to 577 nm upon heating from 20 to ≈200 °C. This inspires the design of a lightweight, organic, elastic optical waveguide where the output energy is controlled by the operating temperature. The wide range of crystal flexibility expands the range of conditions for application of organic crystals as optical waveguides.
      8
  • Publication
    Effect of sintering temperature of NBT–6BT lead-free ceramics on the structural, ferroelectric and piezoelectric properties
    ( 2022)
    Slimani, Ahmed
    ;
    O. Turki
    ;
    Z. Sassi
    ;
    H. Khemakhem
    ;
    N. Abdelmoula
    ;
    L. Lebrun
    The lead-free Na 0.5 Bi 0.5 0.94 Ba 0.06 TiO 3 (NBT-6BT) ceramics was fabricated at various sintering temperatures using a conventional solid-state reaction method. The effect of calcination temperature was systematically investigated on the structural properties. The XRD results show that the 850 °C is the best calcination temperature, where the NBT-6BT ceramic had the largest crystallite size with a dense sample, 96% of the theoretical value. However, the density decreased significantly with increasing the calcination temperature above 850 °C due to the secondary phase formation. On the other hand, the effect of sintering temperature was studied on the piezoelectric and ferroelectric properties evolutions. It is found that the optimal ferroelectric and piezoelectric values were obtained at 1150 °C (P r = 27 µC/cm 2 , E c = 3.89 kV/mm and d 33 = 110 pC/N). According to these results, we suggest that 850 °C and 1150 °C can be considered as optimal calcination and sintering temperature in NBT-6BT ceramic, respectively.
      15  6
  • Publication
    A Low-Temperature-Resistant Flexible Organic Crystal with Circularly Polarized Luminescence
    ( 2022)
    Li, Liang
    ;
    Pan, Xiuhong
    ;
    Zheng, Anyi
    ;
    Di, Qi
    ;
    Duan, Pengfei
    ;
    Ye, Kaiqi
    ;
    Naumov, Panče
    ;
    Zhang, Hongyu
    ;
    Yu, Xu
    Flexible organic crystals with unique mechanical properties and excellent optical properties are of paramount significance for their wide applications in various research fields such as adaptive optics and soft robotics. However, low-temperature-resistant flexible organic crystal with circularly polarized luminescence (CPL) ability has never been reported. Herein, chiral organic crystals with CPL activity and low-temperature flexibility (77 K) are fabricated by the solvent diffusion method from chiral Schiff bases, S(R)-4- b romo-2-(((1- p henyl e thyl)imino) m ethyl) p henol (S(R)-BPEMP). The corresponding chiroptical properties for the two enantiomeric crystals were thoroughly investigated, including the measurements of circular dichroism (CD) and CPL. To the best of our knowledge, this is the first report on low-molecular-weight flexible organic crystals with CPL activity, and we believe that the results will give a new impetus to the research of organic crystals.
      4  14
  • Publication
    Recent Progress in Ionic Liquids for Stability Engineering of Perovskite Solar Cells
    ( 2022)
    Li, Liang
    ;
    Wang, Fei
    ;
    Ge, Chuang-ye
    ;
    Duan, Dawei
    ;
    Lin, Haoran
    ;
    Naumov, Panče
    ;
    Hu, Hanlin
    Perovskite solar cells attract widespread attention due to their impressive power conversion efficiencies, high absorption coefficients, tunable bandgap, and straightforward manufacturing protocols. However, in the process of further development and optimization toward mass production, the long-term stability stands as one of the most urgent challenges that need to be overcome. Given the excellent thermal stability and high structural designability, ionic liquids (ILs) are relatively green room-temperature molten salts that have been widely applied to perovskite photovoltaic devices with promising results in view of improved stability and enhanced device performance. In this review, the reasons and mechanisms of instability of such devices under external and internal factors are analyzed. The current strategies of ILs engineering for improved stability of the devices are classified and summarized, including the IL-assisted perovskite film evolution and IL-modified photophysical properties of the perovskite photoactive layer and the related stability and photovoltaic performance of the devices. The challenges that stand as obstacles toward further development of perovskite solar cells based on IL engineering and their prospects are also discussed.
      7
  • Publication
    Development of Lévy flight-based reptile search algorithm with local search ability for power systems engineering design problems
    ( 2022)
    Zitar, Raed
    ;
    Ekinci, Serdar
    ;
    Izci, Davut
    ;
    Alsoud, Anas Ratib
    ;
    Abualigah, Laith
    The need for better-performing algorithms to solve real-world power systems engineering problems has always been a challenging topic. Due to their stochastic nature, metaheuristic algorithms can provide better results. Thus, they have a rising trend in terms of investigation. This paper is a further attempt to offer a better optimizing structure, therefore, aims to provide a better-performing algorithm both for designing an appropriate proportional-integral-derivative (PID) controller to effectively operate an automatic voltage regulator (AVR) system and extracting the optimum parameters of a power system stabilizer (PSS) employed in a single-machine infinite-bus (SMIB) power system. Therefore, the paper discusses the development of the Lévy flight-based reptile search algorithm with local search capability and evaluates its potential against challenging power systems engineering optimization problems. The Lévy flight concept is used for better exploration capability in the proposed algorithm, whereas the Nelder-Mead simplex search algorithm is integrated for further exploitation. The latter case is confirmed through 23 benchmark functions with different features using statistical and nonparametric tests. The superiority of the proposed Lévy flight-based reptile search and Nelder-Mead (L-RSANM) algorithm-based PID controller for the AVR system is demonstrated comparatively using convergence, statistical and nonparametric tests along with transient and frequency responses. Besides, it is also assessed against previously reported and different methods, showing further superiority for AVR system control. Furthermore, the extraordinary ability of the L-RSANM algorithm to design an efficient PSS employed in the SMIB power system is demonstrated, as well. In conclusion, the proposed L-RSANM algorithm is shown to be more capable to solve the challenging power systems engineering design problems.
      10
  • Publication
    An intelligent cybersecurity system for detecting fake news in social media websites
    ( 2022)
    Zitar, Raed
    ;
    Mughaid, Ala
    ;
    Al-Zu'bi, Shadi
    ;
    Arjan, A
    ;
    Al-Amrat, Rula
    ;
    Alajmi, Rathaa
    ;
    Abualigah, Laith
    ;
    Maalej, Ahmed
    People worldwide suffer from fake news in many life aspects, healthcare, transportation, education, economics, and many others. Therefore, many researchers have considered seeking techniques for automatically detecting fake news in the last decade. The most popular news agencies use e-publishing on their websites; even websites can publish any news they want. However, thus before quotation any news from a website, there should be a close look at news resource ranking by using a trusted websites classifier, such as the website world rank, which reflects the repute of these websites. This paper uses the world rank of news websites as the main factor of news accuracy by using two widespread and trusted websites ranking. Moreover, a secondary factor is proposed to compute the news accuracy similarity by comparing the current news with fakes news and getting the possible news accuracy. Experiments results are conducted on several benchmark datasets. The results showed that the proposed method got promising results compared to other comparative methods in defining the news accuracy.
      17  8Scopus© Citations 1
  • Publication
    An enhanced binary Rat Swarm Optimizer based on local-best concepts of PSO and collaborative crossover operators for feature selection
    ( 2022)
    Zitar, Raed
    ;
    Awadallah, Mohammed A.
    ;
    Al-Betar, Mohammed Azmi
    ;
    Braik, Malik Shehadeh
    ;
    Hammouri, Abdelaziz I.
    ;
    Abu Doush, Iyad
    In this paper, an enhanced binary version of the Rat Swarm Optimizer (RSO) is proposed to deal with Feature Selection (FS) problems. FS is an important data reduction step in data mining which finds the most representative features from the entire data. Many FS-based swarm intelligence algorithms have been used to tackle FS. However, the door is still open for further investigations since no FS method gives cutting-edge results for all cases. In this paper, a recent swarm intelligence metaheuristic method called RSO which is inspired by the social and hunting behavior of a group of rats is enhanced and explored for FS problems. The binary enhanced RSO is built based on three successive modifications: i) an S-shape transfer function is used to develop binary RSO algorithms; ii) the local search paradigm of particle swarm optimization is used with the iterative loop of RSO to boost its local exploitation; iii) three crossover mechanisms are used and controlled by a switch probability to improve the diversity. Based on these enhancements, three versions of RSO are produced, referred to as Binary RSO (BRSO), Binary Enhanced RSO (BERSO), and Binary Enhanced RSO with Crossover operators (BERSOC). To assess the performance of these versions, a benchmark of 24 datasets from various domains is used. The proposed methods are assessed concerning the fitness value, number of selected features, classification accuracy, specificity, sensitivity, and computational time. The best performance is achieved by BERSOC followed by BERSO and then BRSO. These proposed versions are comparatively assessed against 25 well-regarded metaheuristic methods and five filter-based approaches. The obtained results underline their superiority by producing new best results for some datasets.
      12
  • Publication
    Variation in sooting characteristics and cetane number of diesel with the addition of a monoterpene biofuel, α-pinene
    ( 2022)
    Li, Liang
    ;
    Alanood Al Zaabi
    ;
    Abhijeet Raj
    ;
    Mirella Elkadi
    ;
    Dalaver Anjum
    ;
    Azhagapillai Prabhu
    ;
    Gerardo D.J. Pena
    ;
    Abraham George
    ;
    Mariam Nasser Al Shebli
    Diesel fuel combustion generates soot particles, which are harmful for human health and the environment. To reduce soot emission, various solutions are proposed in the literature such as the use of metal-additives in fuels, fuel blending with biofuels, and the use of diesel particulate filters. This study analyses the effect of the addition of a bicyclic monoterpene hydrocarbon biofuel, α-pinene to diesel in different proportions on the fuel cetane number, sooting propensity, and the physicochemical properties of soot nanoparticles. The addition of 10% α-pinene to diesel exhibited a synergistic effect on sooting tendency and reduced the threshold sooting index of diesel by 21%, even though α-pinene is an unsaturated hydrocarbon, and had a minimal impact on cetane number, which reduced from 63.5 for diesel to 61.5 for the blended fuel. The influence of α-pinene addition to diesel on soot nanostructural characteristics and reactivity is determined through different characterization approaches including HRTEM, TGA, XRD, SEM-EDX, and EELS. The results indicate that α-pinene addition to diesel imposes curvatures in soot nanostructure, creates relatively smaller fringes (PAHs) in soot, and reduces soot aromatic content to improve soot oxidation rate.
      32  1Scopus© Citations 2
  • Publication
    Stochastic forecasting of COVID-19 daily new cases across countries with a novel hybrid time series model
    ( 2022)
    Chakraborty, Tanujit
    ;
    Shesh N. Rai
    ;
    Arinjita Bhattacharyya
    An unprecedented outbreak of the novel coronavirus (COVID-19) in the form of peculiar pneumonia has spread globally since its first case in Wuhan province, China, in December 2019. Soon after, the infected cases and mortality increased rapidly. The future of the pandemic’s progress was uncertain, and thus, predicting it became crucial for public health researchers. These predictions help the effective allocation of health-care resources, stockpiling, and help in strategic planning for clinicians, government authorities, and public health policymakers after understanding the extent of the effect. The main objective of this paper is to develop a hybrid forecasting model that can generate real-time out-of-sample forecasts of COVID-19 outbreaks for five profoundly affected countries, namely the USA, Brazil, India, the UK, and Canada. A novel hybrid approach based on the Theta method and autoregressive neural network (ARNN) model, named Theta-ARNN (TARNN) model, is developed. Daily new cases of COVID-19 are nonlinear, non-stationary, and volatile; thus, a single specific model cannot be ideal for future prediction of the pandemic. However, the newly introduced hybrid forecasting model with an acceptable prediction error rate can help healthcare and government for effective planning and resource allocation. The proposed method outperforms traditional univariate and hybrid forecasting models for the test datasets on an average.
      78  2Scopus© Citations 1