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  • Imitation Learning based on Generative Adversarial Networks for Robot Path Planning

    Yi, Xianyong (2020-11-24) [Thesis]
    Advisor: Michels, Dominik L.
    Committee members: Wonka, Peter; Moshkov, Mikhail
    Robot path planning and dynamic obstacle avoidance are defined as a problem that robots plan a feasible path from a given starting point to a destination point in a nonlinear dynamic environment, and safely bypass dynamic obstacles to the destination with minimal deviation from the trajectory. Path planning is a typical sequential decision-making problem. Dynamic local observable environment requires real-time and adaptive decision-making systems. It is an innovation for the robot to learn the policy directly from demonstration trajectories to adapt to similar state spaces that may appear in the future. We aim to develop a method for directly learning navigation behavior from demonstration trajectories without defining the environment and attention models, by using the concepts of Generative Adversarial Imitation Learning (GAIL) and Sequence Generative Adversarial Network (SeqGAN). The proposed SeqGAIL model in this thesis allows the robot to reproduce the desired behavior in different situations. In which, an adversarial net is established, and the Feature Counts Errors reduction is utilized as the forcing objective for the Generator. The refinement measure is taken to solve the instability problem. In addition, we proposed to use the Rapidly-exploring Random Tree* (RRT*) with pre-trained weights to generate adequate demonstration trajectories in dynamic environment as the training data, and this idea can effectively overcome the difficulty of acquiring huge training data.
  • Eddy-induced transport and kinetic energy budget in the Arabian Sea

    Zhan, Peng; Guo, Daquan; Hoteit, Ibrahim (Geophysical Research Letters, American Geophysical Union (AGU), 2020-11-23) [Article]
    This study investigates the vertical eddy structure, eddy-induced transport, and eddy kinetic energy (EKE) budget in the Arabian Sea (AS) using an eddy-resolving reanalysis product. The EKE intensifies during summer in the western AS. Anticyclonic eddies (AEs) and cyclonic eddies (CEs) present warm-fresh and cold-salty cores, respectively, with interleaved salinity structures. The eddy-induced swirl transport is larger in the western AS and tends to compensate for heat transport by the mean flow. Zonal drift transport by AEs and CEs offset each other, and meridional transport is generally weaker. Eddies also produce notable upward heat flux during summer in the western AS, where ageostrophic circulations are induced to maintain a turbulent thermal wind balance. Plausible mechanisms for EKE production are governed by baroclinic and barotropic instabilities, which are enhanced in summer in the western basin, where signals are quantitatively one order larger than the turbulent wind inputs.
  • Compositional Fluctuations Locked by Athermal Transformation Yielding High Thermoelectric Performance in GeTe.

    Tsai, Yi-Fen; Wei, Pai-Chun; Chang, Liuwen; Wang, Kuang-Kuo; Yang, Chun-Chuen; Lai, Yen-Chung; Hsing, Cheng-Rong; Wei, Ching-Ming; He, Jian; Snyder, G Jeffrey; Wu, Hsin Jay (Advanced materials (Deerfield Beach, Fla.), Wiley, 2020-11-20) [Article]
    Phase transition in thermoelectric (TE) material is a double-edged sword-it is undesired for device operation in applications, but the fluctuations near an electronic instability are favorable. Here, Sb doping is used to elicit a spontaneous composition fluctuation showing uphill diffusion in GeTe that is otherwise suspended by diffusionless athermal cubic-to-rhombohedral phase transition at around 700 K. The interplay between these two phase transitions yields exquisite composition fluctuations and a coexistence of cubic and rhombohedral phases in favor of exceptional figures-of-merit zT. Specifically, alloying GeTe by Sb2 Te3 significantly suppresses the thermal conductivity while retaining eligible carrier concentration over a wide composition range, resulting in high zT values of >2.6. These results not only attest to the efficacy of using phase transition in manipulating the microstructures of GeTe-based materials but also open up a new thermodynamic route to develop higher performance TE materials in general.
  • Advances in the Design of Heterogeneous Catalysts and Thermocatalytic Processes for CO2 Utilization

    De, Sudipta; Dokania, Abhay; Galilea, Adrian; Gascon, Jorge (ACS Catalysis, American Chemical Society (ACS), 2020-11-20) [Article]
    Utilization of CO2 as feedstock to produce fine chemicals and renewable fuels is a highly promising field, which presents unique challenges in its implementation at scale. Heterogeneous catalysis with its simple operation and industrial compatibility can be an effective means of achieving this challenging task. This review summarizes the current developments in heterogeneous thermal catalysis for the production of carbon monoxide, alcohols, and hydrocarbons from CO2. A detailed discussion is provided regarding structure−activity correlations between the catalyst surface and intermediate species which can aid in the rational design of future generation catalysts. Effects of active metal components, catalyst supports, and promoters are discussed in each section, which will guide researchers to synthesize new catalysts with improved selectivity and stability. Additionally, a brief overview regarding process design considerations has been provided. Future research directions are proposed with special emphasis on the application scope of new catalytic materials and possible approaches to increase catalyst performance.
  • MXenes for Rechargeable Batteries Beyond the Lithium-Ion

    Ming, Fangwang; Liang, Hanfeng; Huang, Gang; Bayhan, Zahra; Alshareef, Husam N. (Advanced Materials, Wiley, 2020-11-20) [Article]
    Research on next-generation battery technologies (beyond Li-ion batteries, or LIBs) has been accelerating over the past few years. A key challenge for these emerging batteries has been the lack of suitable electrode materials, which severely limits their further developments. MXenes, a new class of 2D transition metal carbides, carbonitrides, and nitrides, are proposed as electrode materials for these emerging batteries due to several desirable attributes. These attributes include large and tunable interlayer spaces, excellent hydrophilicity, extraordinary conductivity, compositional diversity, and abundant surface chemistries, making MXenes promising not only as electrode materials but also as other components in the cells of emerging batteries. Herein, an overview and assessment of the utilization of MXenes in rechargeable batteries beyond LIBs, including alkali-ion (e.g., Na+ , K+ ) storage, multivalent-ion (e.g., Mg2+ , Zn2+ , and Al3+ ) storage, and metal batteries are presented. In particular, the synthetic strategies and properties of MXenes that enable MXenes to play various roles as electrodes, metal anode protective layers, sulfur hosts, separator modification layers, and conductive additives in these emerging batteries are discussed. Moreover, a perspective on promising future research directions on MXenes and MXene-based materials, ranging from material design and processing, fundamental understanding of the reaction mechanisms, to device performance optimization strategies is provided.
  • High-speed filtered Rayleigh scattering thermometry in premixed flames through narrow channels

    Krishna, Yedhu; Mahuthannan, Ariff Magdoom; Luo, Xinguang; Lacoste, Deanna; Magnotti, Gaetano (Combustion and Flame, Elsevier BV, 2020-11-20) [Article]
    High-speed filtered Rayleigh scattering at 10 kHz repetition rate for time-resolved temperature measurements in premixed flames propagating in mm-high channels is demonstrated for the first time. The instrument relies on a pulse burst laser with a 200 ns temporal width, and a CCD camera operated in subframe burst gate mode to achieve high signal to noise ratio despite the limited optical access. A 10-inch-long iodine cell acts as a molecular filter and the laser, which is seeded using an external cavity diode laser and operated in a temporally stretched mode, is wavelength-tuned to the peak of a strong iodine absorption line. A CCD camera, operated in the sub-frame burst gating mode with the help of an external slit configuration, is used as the detector to achieve improved camera noise performance. Filtered Rayleigh scattering temperature measurements in premixed flat flames stabilized over a McKenna burner indicate an instrument precision of 3%. Temperature measurements in the products region are within 3% of measurements obtained with conventional Rayleigh scattering. The system's capabilities are demonstrated through time-resolved temperature measurements in a premixed methane-air flame propagating in a 1.5 mm-high rectangular channel designed to study flame quenching in flame arrestors. Surface scattering from the optical windows and the channel surfaces is successfully suppressed and time-resolved temperature profiles are obtained for both quenching and no-quenching events.
  • Richtmyer-Meshkov instability of an imploding flow with a two-fluid plasma model

    Li, Y.; Samtaney, Ravi; Bond, D.; Wheatley, V. (Physical Review Fluids, American Physical Society (APS), 2020-11-20) [Article]
    The two-fluid (ions and electrons) plasma Richtmyer-Meshkov instability of a cylindrical light-heavy density interface is numerically investigated without an initial magnetic field. Varying the Debye length scale, we examine the effects of the coupling between the electron and ion fluids. When the coupling becomes strong, the electrons are restricted to co-move with the ions and the resulting evolution is similar to the hydrodynamic neutral fluid case. The charge separation that occurs between the electrons and ions is responsible for the self-generated electromagnetic fields. We show that the Biermann battery effect dominates the generation of magnetic field when the coupling between the electrons and ions is weak. In addition to the Rayleigh-Taylor stabilization effect during flow deceleration, the interfaces are accelerated by the induced spatiotemporally varying Lorentz force. As a consequence, the perturbations develop into the Rayleigh-Taylor instability, leading to an enhancement of the perturbation amplitude compared with the hydrodynamic case.
  • Diels-Alder Polymer Networks with Temperature-Reversible Cross-Linking-Induced Emission Yu Jiang*, and Nikos Hadjichristidis*

    Hadjichristidis, Nikos; Jiang, Yu (Angewandte Chemie, Wiley, 2020-11-19) [Article]
    A novel synthetic strategy toward reversible cross-linked polymeric materials with tunable fluorescence properties is presented. Dimaleimide-substituted tetraphenylethene (TPE-2MI), which is nonemissive due to the photo-induced electron transfer (PET) between maleimide (MI) and tetraphenylethene (TPE) groups, was used to cross-link random copolymers of methyl (MM), decyl (DM) or lauryl (LM) with furfuryl methacrylate (FM). The mixture of copolymer and TPE-2MI in DMF showed reversible fluorescence with “on/off” behavior depending on the Diels-Alder (DA)/retro-DA process, which is easily adjusted by temperature. At high temperatures, the retro-DA reaction of polymer networks is dominant, and the fluorescence is quenched by the PET mechanism. In contrast, at low temperatures, the emission recovers as the DA reaction takes over. Based on these results, a transparent PMFM/TPE-2MI film was prepared, and the emission behavior was investigated. It was found that the polymer film shows an accurate response to the external temperature and exhibited tunable fluorescent “turn on/off” behavior. These excitingresults suggest the possible application of this type of reversible cross-linked materials in many areas, including information security and transmission. An example of invisible/visible writing is given.
  • Application of phase-field method in rechargeable batteries

    Wang, Qiao; Zhang, Geng; Li, Yajie; Hong, Zijian; Wang, Da; Shi, Siqi (npj Computational Materials, Springer Science and Business Media LLC, 2020-11-19) [Article]
    AbstractRechargeable batteries have a profound impact on our daily life so that it is urgent to capture the physical and chemical fundamentals affecting the operation and lifetime. The phase-field method is a powerful computational approach to describe and predict the evolution of mesoscale microstructures, which can help to understand the dynamic behavior of the material systems. In this review, we briefly introduce the theoretical framework of the phase-field model and its application in electrochemical systems, summarize the existing phase-field simulations in rechargeable batteries, and provide improvement, development, and problems to be considered of the future phase-field simulation in rechargeable batteries.
  • Developing the Raster Big Data Benchmark: A Comparison of Raster Analysis on Big Data Platforms

    Haynes, David; Mitchell, Philip M.; Shook, Eric (ISPRS International Journal of Geo-Information, MDPI AG, 2020-11-19) [Article]
    Technologies around the world produce and interact with geospatial data instantaneously, from mobile web applications to satellite imagery that is collected and processed across the globe daily. Big raster data allow researchers to integrate and uncover new knowledge about geospatial patterns and processes. However, we are at a critical moment, as we have an ever-growing number of big data platforms that are being co-opted to support spatial analysis. A gap in the literature is the lack of a robust assessment comparing the efficiency of raster data analysis on big data platforms. This research begins to address this issue by establishing a raster data benchmark that employs freely accessible datasets to provide a comprehensive performance evaluation and comparison of raster operations on big data platforms. The benchmark is critical for evaluating the performance of spatial operations on big data platforms. The benchmarking datasets and operations are applied to three big data platforms. We report computing times and performance bottlenecks so that GIScientists can make informed choices regarding the performance of each platform. Each platform is evaluated for five raster operations: pixel count, reclassification, raster add, focal averaging, and zonal statistics using three raster different datasets.
  • Gas-Phase Thermochemistry of MX3 and M2X6 (M = Sc, Y; X = F, Cl, Br, I) from a Composite Reaction-Based Approach: Homolytic versus Heterolytic Cleavage

    Minenkova, Irina; Osina, Evgeniya L.; Cavallo, Luigi; Minenkov, Yury (Inorganic Chemistry, American Chemical Society (ACS), 2020-11-19) [Article]
    A domain-based local-pair natural-orbital coupled-cluster approach with single, double, and improved linear-scaling perturbative triple correction via an iterative algorithm, DLPNO-CCSD(T1), was applied within the framework of the Feller-Peterson-Dixon approach to derive gas-phase heats of formation of scandium and yttrium trihalides and their dimers via a set of homolytic and heterolytic dissociation reactions. All predicted heats of formation moderately depend on the reaction type with the most and least negative values obtained for homolytic and heterolytic dissociation, respectively. The basis set size dependence, as well as the influence of static correlation effects not covered by the standard (DLPNO-)CCSD(T) approach, suggests that exploitation of the heterolytic dissociation reactions with the formation of M3+ and X- ions leads to the most robust heats of formation. The gas-phase formation enthalpies ΔHf°(0 K)/ΔHf°(298.15 K) and absolute entropies S°(298.15 K) were obtained for the first time for the Sc2F6, Sc2Br6, and Sc2I6 species. For ScBr3, ScI3, Sc2Cl6, and Y2Cl6, we suggest a reexamination of the experimental heats of formation available in the literature. For other compounds, the predicted values were found to be in good agreement with the experimental estimates. Extracted MX3 (M = Sc, Y; X = F, Cl, Br, and I) 0 K atomization enthalpies indicate weaker bonding when moving from fluorine to iodine and from yttrium to scandium. Likewise, the stability of yttrium trihalide dimers degrades when going from fluorine to iodine. Respective scandium trihalide dimers are less stable, with 0 K dimer dissociation energy decreasing in the row fluorine - chlorine - bromine ≈ iodine. Correlation of the (n - 1)s2p6 electrons on bromine and iodine, inclusion of zero-point energy, relativistic effects, and the effective-core-potential correction as well as amelioration of the DLPNO localization inaccuracy are shown to be of similar magnitude, which is critical if accurate heats of formation are a goal.
  • Introducing a Cantellation Strategy for the Design of Mesoporous Zeolite-like Metal–Organic Frameworks: Zr-sod-ZMOFs as a Case Study

    Alsadun, Norah Sadun; Mouchaham, Georges; Guillerm, Vincent; Czaban-Jozwiak, Justyna; Shkurenko, Aleksander; Jiang, Hao; Bhatt, Prashant; Parvatkar, Prakash Tukaram; Eddaoudi, Mohamed (Journal of the American Chemical Society, American Chemical Society (ACS), 2020-11-19) [Article]
    Herein we report novel mesoporous zirconium-based metal-organic frameworks (MOFs) with zeolitic sodalite (sod) topology. Zr-sod-ZMOF-1 and -2 are constructed based on a novel cantellation design strategy. Distinctly, organic linkers are judiciously designed in order to promote the deployment of the 12-coordinated Zr hexanuclear molecular building block (MBB) as a tetrahedral secondary building unit, a prerequisite for zeolite-like nets. The resultant Zr-sod-ZMOFs exhibit mesopores with a diameter up to ≈43 Å, while the pore volume of 1.98 cm3·g-1 measured for Zr-sod-ZMOF-1 is the highest reported experimental value for zeolite-like MOFs based on MBBs as tetrahedral nodes.
  • Elucidating the Promotional Effect of Cerium in the Dry Reforming of Methane

    Rodriguez Gomez, Alberto; Lopez-Martin, Angeles; Ramirez, Adrian; Gascon, Jorge; Caballero, Alfonso (ChemCatChem, Wiley, 2020-11-19) [Article]
    A series of Ni-Ce catalysts supported on SBA-15 has been prepared by co-impregnation, extensively characterized and evaluated in the carbon dioxide reforming of methane (DRM). The characterization by TEM, XRD and TPR has allowed us to determine the effect of metal loading on metal dispersion. Cerium was found to improve nickel location inside the mesopores of SBA-15 and to suppress coke formation during the DRM reaction. The analysis by XPS allowed us to associate the high cerium dispersion with the presence of low-coordinated Ce 3+ sites, being main responsible for its promotional effect. A combination of XAS and XPS has permitted us to determine the physicochemical properties of metals under reduction conditions. The low nickel coordination number determined by XAS in Ni-Ce doped systems after reduction suggests the generation of very small nickel particles which showed greater catalytic activity and stability in the reaction, and a remarkable resistance to coke formation.
  • Molecularly-porous ultrathin membranes for highly selective organic solvent nanofiltration

    Huang, Tiefan; Moosa, Basem; HOANG, PHUONG; Liu, Jiangtao; Chisca, Stefan; Zhang, Gengwu; Alyami, Mram Z.; Khashab, Niveen M.; Nunes, Suzana Pereira (Nature Communications, Springer Science and Business Media LLC, 2020-11-18) [Article]
    AbstractEngineering membranes for molecular separation in organic solvents is still a big challenge. When the selectivity increases, the permeability tends to drastically decrease, increasing the energy demands for the separation process. Ideally, organic solvent nanofiltration membranes should be thin to enhance the permeant transport, have a well-tailored nanoporosity and high stability in harsh solvents. Here, we introduce a trianglamine macrocycle as a molecular building block for cross-linked membranes, prepared by facile interfacial polymerization, for high-performance selective separations. The membranes were prepared via a two-in-one strategy, enabled by the amine macrocycle, by simultaneously reducing the thickness of the thin-film layers (<10 nm) and introducing permanent intrinsic porosity within the membrane (6.3 Å). This translates into a superior separation performance for nanofiltration operation, both in polar and apolar solvents. The hyper-cross-linked network significantly improved the stability in various organic solvents, while the amine host macrocycle provided specific size and charge molecular recognition for selective guest molecules separation. By employing easily customized molecular hosts in ultrathin membranes, we can significantly tailor the selectivity on-demand without compromising the overall permeability of the system.
  • MXene-Modulated Electrode/SnO2 Interface Boosting Charge Transport in Perovskite Solar Cells

    Wang, Yunfan; Xiang, Pan; Ren, Aobo; Lai, Huagui; Zhang, Zhuoqiong; Xuan, Zhipeng; Wan, Zhenxi; Zhang, Jingquan; Hao, Xia; Wu, Lili; Sugiyama, Masakazu; Schwingenschlögl, Udo; Liu, Cai; Tang, Zeguo; Wu, Jiang; Wang, Zhiming; Zhao, Dewei (ACS Applied Materials & Interfaces, American Chemical Society (ACS), 2020-11-17) [Article]
    Interface engineering is imperative to boost the extraction capability in perovskite solar cells (PSCs). We propose a promising approach to enhance the electron mobility and charge transfer ability of tin oxide (SnO2) electron transport layer (ETL) by introducing a two-dimensional carbide (MXene) with strong interface interaction. The MXene-modified SnO2 ETL also offers a preferable growth platform for perovskite films with reduced trap density. Through a spatially resolved imaging technique, profoundly reduced non-radiative recombination and charge transport losses in PSCs based on MXene-modified SnO2 are also observed. As a result, the PSC achieves an enhanced efficiency of 20.65% with ultralow saturated current density and negligible hysteresis. We provide an in-depth mechanistic understanding of MXene interface engineering, offering an alternative approach to obtain efficient PSCs.
  • Investigating Water Injection in Single-Cylinder Gasoline Spark-Ignited Engines at Fixed Speed

    Singh, Eshan; Hlaing, Ponnya; Dibble, Robert W. (Energy & Fuels, American Chemical Society (ACS), 2020-11-17) [Article]
    Increasingly stringent emission norms have always brought forth innovative measures to improve engine efficiency. Spark-ignited engines have been limited in efficiency, traditionally by knock, and more recently by preignition too. Water injection has recently regained interest as a knock suppressant. The current work explored water injection via port and direct injection at a fixed engine speed of 2000 rpm and varying engine loads. The data presented in this work emphasize that the gains from using water injection are best realized at a specific injection timing (neither too early nor too late), and the effectiveness of water in suppressing knock decreases rapidly with increasing water mass injected. In general, direct water injection offers a more significant knock reduction because of better utilization of the charge cooling effect than port water injection. Engine-out emission confirms a reduction in NOx and CO, while the HC emissions increased when using water injection. No preignition events were observed at the engine load up to 27 bar. Chemical kinetics simulations confirm the role of water in suppressing reactivity under the operating conditions considered in the current study.
  • Single-Crystalline All-Oxide α–γ–β Heterostructures for Deep-Ultraviolet Photodetection

    Li, Kuang-Hui; Kang, Chun Hong; Min, Jung-Hong; Alfaraj, Nasir; Liang, Jian-Wei; Braic, Laurentiu; Guo, Zaibing; Hedhili, Mohamed N.; Ng, Tien Khee; Ooi, Boon S. (ACS Applied Materials & Interfaces, American Chemical Society (ACS), 2020-11-17) [Article]
    Recent advancements in gallium oxide (Ga2O3)-based heterostructures have allowed optoelectronic devices to be used extensively in the fields of power electronics and deep-ultraviolet photodetection. While most previous research has involved realizing single-crystalline Ga2O3 layers on native substrates for high conductivity and visible-light transparency, presented and investigated herein is a single-crystalline β-Ga2O3 layer grown on an α-Al2O3 substrate through an interfacial γ-In2O3 layer. The single-crystalline transparent conductive oxide layer made of wafer-scalable γ-In2O3 provides high carrier transport, visible-light transparency, and antioxidation properties that are critical for realizing vertically oriented heterostructures for transparent oxide photonic platforms. Physical characterization based on X-ray diffraction and high-resolution transmission electron microscopy imaging confirms the single-crystalline nature of the grown films and the crystallographic orientation relationships among the monoclinic β-Ga2O3, cubic γ-In2O3, and trigonal α-Al2O3, while the elemental composition and sharp interfaces across the heterostructure are confirmed by Rutherford backscattering spectrometry. Furthermore, the energy-band offsets are determined by X-ray photoelectron spectroscopy at the β-Ga2O3/γ-In2O3 interface, elucidating a type-II heterojunction with conduction- and valence-band offsets of 0.16 and 1.38 eV, respectively. Based on the single-crystalline β-Ga2O3/γ-In2O3/α-Al2O3 all-oxide heterostructure, a vertically oriented DUV photodetector is fabricated that exhibits a high photoresponsivity of 94.3 A/W, an external quantum efficiency of 4.6 × 104%, and a specific detectivity of 3.09 × 1012 Jones at 250 nm. The present demonstration lays a strong foundation for and paves the way to future all-oxide-based transparent photonic platforms.
  • Ultra-compact terahertz plasmonic wavelength diplexer

    Yuan, Mingrui; Wang, Qingwei; Li, Yanfeng; Zhang, Xixiang; Han, Jiaguang; Zhang, Weili (Applied Optics, The Optical Society, 2020-11-17) [Article]
    Terahertz (THz) spoof surface plasmon polariton (SPP) waveguides can provide subwavelength confinement, which makes it possible for the THz waves to transmit at low loss over long distances along a metallic surface. In this work, an ultra-compact wavelength diplexer formed by THz spoof SPP waveguiding structures is reported on the design and actualization. By adding a certain number of periodic pillars in the coupling part of the directional coupler, the refractive index of the anti-symmetrically distributed odd modes can be engineered, thereby adjusting the coupling length. By adjusting the periodic pillar parameters properly, the SPP modes at two target frequencies will be coupled in the device for an odd or even number of times, so that SPP modes at these two frequencies can be coupled out from different ports. The length of the wavelength diplexer is 1.6 mm, which is about 12.8% of its traditional counterpart. Minimum simulated transmittances of -24.34 dB and -26.27 dB can be obtained at 0.637 THz and 0.667 THz, respectively. The insertion losses at the two operating frequencies are less than 0.46 dB, and the extinction ratios are both better than 19 dB. By cascading the proposed diplexers, a compact wavelength demultiplexer with more channels can be obtained, which has important applications for future THz integrated communication systems.
  • Polyurethanes from Direct Organocatalytic Copolymerization of p-Tosyl Isocyanate with Epoxides.

    Gnanou, Yves; Jia, Mingchen; Hadjichristidis, Nikos; Feng, Xiaoshuang (Angewandte Chemie (International ed. in English), Wiley, 2020-11-17) [Article]
    The direct copolymerization of p -tosyl isocyanate (TSI) with epoxides, initiated by onium salts in the presence of trialkylborane, to produce polyurethanes is reported. The rate of copolymerization and the (regio)selectivity were investigated in relation to the trialkylborane and initiator used. Under optimized conditions such copolymerizations have been successfully performed for a wide range of epoxides, including ethylene oxide, propylene oxide, 1-octene oxide, cyclohexene oxide, and allyl glycidyl ether. These copolymerizations afford a new category of polyurethanes, clear of side products such as cyclic oxazolidinone, isocyanurate, and poly(isocyanate) linkages. The experimental conditions used in this work are compatible with those for the organocatalytic (co)polymerization of other oxygenated monomers and CO 2 , holding the potential for their terpolymerization with p -tosyl isocyanate and the development of new materials with unprecedented properties.
  • DFT-based investigation of different properties for transition metal-doped germanium TMGen (TM = Ru, Rh; n = 1-20) clusters.

    Benaida, Meriem; Aiadi, Kamal Eddine; Mahtout, Sofiane; Bentouila, Omar; Djaadi, Soumaia; Harb, Moussab (Journal of molecular modeling, Springer Science and Business Media LLC, 2020-11-17) [Article]
    The geometries and energetic, electronic, and magnetic features of transition metal-doped germanium (TMGen with TM = Ru, Rh; n = 1-20) clusters are systematically studied by means of first principle computations on the basis of the density functional theory (DFT) approach. The doping TM atom largely participates to strengthen the Gen cluster stability by increasing the binding energies. A good stability is obtained for RuGe12, RhGe12, and RhGe14 clusters. The various explored isomers of TMGen clusters possess a total spin magnetic moment going from 0 to 2μB, except for RhGe2 with 3μB. These results open nice perspectives of these good candidate clusters for applications in nanoelectronics and nanotechnologies.

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