Now showing 1 - 10 of 67
  • Publication
    Comparative Study of Polyethylene Films Embedded with Oxide Nanoparticles of Granulated and Free-Standing Nature
    ( 2022) ;
    Le Guyon, Valerie
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    ; ; ;
    El-Rifai, Joumana
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    Dmitrenko, Mariia
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    Penkova, Anastasia
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    Zou, Lusi
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    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.
      2
  • Publication
    Recent Progress in Ionic Liquids for Stability Engineering of Perovskite Solar Cells
    ( 2022) ;
    Wang, Fei
    ;
    Ge, Chuang-ye
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    Duan, Dawei
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    Lin, Haoran
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    Naumov, Panče
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    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.
      6
  • Publication
    Ionic Liquid Engineering in Perovskite Photovoltaics
    ( 2022) ;
    Wang, Fei
    ;
    Duan, Dawei
    ;
    Singh, Mriganka
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    Sutter‐Fella, Carolin M
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    Lin, Haoran
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    Naumov, Panče
    ;
    Hu, Hanlin
    Over the past decade, perovskite photovoltaics have approached other currently available technologies and proven to be the most prospective type of solar cells. Although the many-sided research in this very active field has generated consistent results with regards to their undisputed consistently increasing power conversion efficiency, it also produced several rather contradictory opinions. Among other important details, debate surrounding their proneness to surface degradation and poor mechanical robustness, as well as the environmental footprint of this materials class remains a moot point. The application of ionic liquids appears as one of the potential remedies to some of these challenges due to their high conductivity, the opportunities for chemical ‘tuning’ of the structure, and relatively lower environmental footprint. This article provides an overview, classification, and applications of ionic liquids in perovskite solar cells. We summarize the use and role of ionic liquids as versatile additives, solvents, and modifiers in perovskite precursor solution, charge transport layer, as well as for interfacial and stability engineering. Finally, challenges and the future prospects for the design and/or selection of ionic liquids with a specific profile that meets the requirements for next generation highly efficient and stable perovskite solar cells are proposed.
      5
  • Publication
    Light and Secure Encryption Technique Based on Artificially Induced Chaos and Nature-Inspired Triggering Method
    ( 2022) ;
    Muhammed J. Al-Muhammed
    Encryption is the de facto method for protecting information, whether this information is locally stored or on transit. Although we have many encryption techniques, they have problems inherited from the computational models that they use. For instance, the standard encryption technique suffers from the substitution box syndrome—the substitution box does not provide enough confusion. This paper proffers a novel encryption method that is both highly secure and lightweight. The proposed technique performs an initial preprocessing on its input plaintext, using fuzzy substitutions and noising techniques to eliminate relationships to the input plaintext. The initially encrypted plaintext is next concealed in enormously complicated codes that are generated using a chaotic system, whose behavior is controlled by a set of operations and a nature-inspired triggering technique. The effectiveness of the security of the proposed technique is analyzed using rigorous randomness tests and entropy.
      33  4
  • Publication
    Ultrafast, Light, Soft Martensitic Materials
    ( 2022) ;
    Ejaz Ahmed
    ;
    Durga Prasad Karothu
    ;
    Jad Mahmoud Halabi
    ;
    Ibrahim Tahir
    ;
    Kevin Quirós Canales
    ;
    Panče Naumov
    Martensitic transformations are well documented in metals and alloys where the atoms connected via metallic bonds rearrange concertedly and rapidly; however, due to the metal atoms, these materials are inherently very dense and add significant weight and bulkiness to actuating devices. Here, remarkably rapid lattice switching of molecular martensitic materials is reported where the rate of structural transformation exceeds other phase transitions several orders of magnitude. With a determined speed in the range of 0.3–0.6 m s−1, the new phase advances throughout the crystal about ten thousand times faster relative to spin-crossover transitions, and about hundred to hundred thousand times faster than other common structural phase transitions. Macroscopic crystals of these materials respond by rapid expansion or contraction of about 0.02 m s−1 for unrestrained crystals and 0.02–0.03 m s−1 for clamped crystals. Monte–Carlo simulation of the spatiotemporal profile of the transition and of the local distribution of elastic and kinetic energies induced by domain growth reveals the critical role of the dynamic phase boundary and the lattice edges in the structure switching. Within a broader context, this study indicates that the martensitic organic crystals are prospective lightweight substitutes of metals for ultrafast and clean energy transduction.
      15  2
  • Publication
    Variation in sooting characteristics and cetane number of diesel with the addition of a monoterpene biofuel, α-pinene
    ( 2022) ;
    Alanood Al Zaabi
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    Abhijeet Raj
    ;
    Mirella Elkadi
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    Dalaver Anjum
    ;
    Azhagapillai Prabhu
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    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.
      31  1Scopus© Citations 1
  • Publication
    Encryption technique based on chaotic neural network space shift and color‑theory‑induced distortion
    ( 2022) ;
    Al-Muhammed, Muhammed J.
    Protecting information privacy is likely to promote trust in the digital world and increase its use. This trust may go a long way toward motivating a wider use of networks and the internet, making the vision of the semantic web and Internet of Things a reality. Many encryption techniques that purport to protect information against known attacks are available. However, since the security challenges are ever-growing, devising effective techniques that counter the emerging challenges seems a rational response to these challenges. This paper proffers an encryption technique with a unique computational model that inspires ideas from color theory and chaotic systems. This mix offers a novel computation model with effective operations that (1) highly confuse plaintext and (2) generate key-based enormously complicated codes to hide the resulting ciphertext. Experiments with the prototype implementation showed that the proposed technique is effective (passed rigorous NIST/ENT security tests) and fast.
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  • Publication
    Organic Single‐Crystal Actuators and Waveguides that Operate at Low Temperatures
    ( 2022) ;
    Linfeng Lan
    ;
    Qi Di
    ;
    Xuesong Yang
    ;
    Xiaokong Liu
    ;
    Panče Naumov
    ;
    Hongyu Zhang
    Applications in extreme conditions, such as those encountered in space exploration, require lightweight materials that can retain their elasticity in extremely cold environments. However, cryogenic treatment of most soft polymeric and elastomeric materials results in complete loss of their ability for elastic flow, whereby such materials that are normally ductile become stiff, brittle, and prone to cracking. Here, a facile method for preparation of hybrid organic crystalline materials that are not only cryogenically robust but are also capable of large, recoverable, and reversible deformation at low temperatures is reported. To that end, flexible organic crystals are first mechanically reinforced by a polymer coating and combined with a thermally responsive polymer. The resulting hybrid materials respond linearly and reversibly to temperatures from −15 to −120 °C without fatigue in air as well as in cold vacuum. The approach proposed here not only circumvents one of the main drawbacks that are inherent to the amorphous nature and has thus far limited the applications of polymeric materials at low temperatures, but it also provides a cost-effective access to a myriad of lightweight sensing, electronic, optical or actuating devices that can operate in low-temperature environmental settings.
      20  1
  • Publication
    Shrinkage, hydration, and strength development of limestone calcined clay cement (LC3) with different sulfation levels
    ( 2022) ;
    Rotana Hay
    ;
    Kemal Celik
    This study investigated autogenous shrinkage of limestone calcined clay cement (LC3)-based mixes with various sulfation levels of hemihydrate. Physicochemical evolution and strength development were also monitored. Superior mechanical performance of the mixes was achieved at an optimal sulfation level, although the shrinkage was reduced with the sulfate content. Calorimetry data showed the hemihydrate delayed and broadened the second aluminate peak. Both gypsum and ettringite formed early during hydration, and carboaluminates were observed after 3 days of curing. Ettringite in the LC3 mixes was of smaller sizes in comparison to that in the ordinary Portland cement (OPC) mixes, attributable to the pore refinement in the LC3 matrices. The content of portlandite (Ca(OH)2) was reduced with the curing time due to pozzolanic reactions. The findings demonstrated a coupling effect of both the chemical and microstructural change on the observed autogenous shrinkage and the consequent performance of LC3-based concrete composites.
      38  4Scopus© Citations 1
  • Publication
    Recent Advances in Harris Hawks Optimization: A Comparative Study and Applications
    ( 2022) ;
    Hussie, Abdelazim
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    Abualig, Laith
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    Hashim, Fatma
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    Amin, Mohamed
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    Saber, Abeer
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    Almotair, Khaled
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    Gandomi, Am
    The Harris hawk optimizer is a recent population-based metaheuristics algorithm that simulates the hunting behavior of hawks. This swarm-based optimizer performs the optimization procedure using a novel way of exploration and exploitation and the multiphases of search. In this review research, we focused on the applications and developments of the recent well-established robust optimizer Harris hawk optimizer (HHO) as one of the most popular swarm-based techniques of 2020. Moreover, several experiments were carried out to prove the powerfulness and effectivness of HHO compared with nine other state-of-art algorithms using Congress on Evolutionary Computation (CEC2005) and CEC2017. The literature review paper includes deep insight about possible future directions and possible ideas worth investigations regarding the new variants of the HHO algorithm and its widespread applications.
      10