Robustness of SDOF elastoplastic structure subjected to double-impulse input under simultaneous uncertainties of yield deformation and stiffness

A series of impulse-type inputs has been extensively used to evaluate the critical response of an elastoplastic structure subjected to diverse types of pulse-type inputs, including a near-fault ground motion. In this paper, we consider the critical double-impulse input for a single-degree-of-freedom elastic–perfectly plastic structure, and study effects of structural uncertainties. When the natural frequency (or, equivalently, the stiffness) is fixed, the critical response of the structure does not necessarily decrease as the yield deformation (or, equivalently, the yield force) increases. As the first contribution, we give through investigation of this non-monotonicity property. Moreover, we present a systematic method for finding the worst-case scenario when the yield deformation and the stiffness of a structure assumed to be uncertain simultaneously. Numerical examples are presented to illustrate that the robustness of a structure does not necessarily improve when the yield deformation and/or the yield force is increased.     

Side chain engineering of naphthalene diimide–bithiophene‐based polymer acceptors in all‐polymer solar cells

Two novel polymeric acceptors based on naphthalene diimide (NDI) and 2.2′‐bithiophene, named as P(NDI2THD‐T2) and P(NDI2TOD‐T2), were designed and synthesized for all polymer solar cells application. The structural and electronic properties of the two acceptors were modulated through side‐chain engineering of the NDI units. The optoelectronic properties of the polymers and the morphologies of the blend films composed of the polymer acceptors and a donor polymer PTB7‐Th were systemically investigated. With thiophene groups introduced into the side chains of the NDI units, both polymers showed wider absorption from 350 nm to 900 nm, compared with the reference polymer acceptor of N2200. No redshift of absorption spectra from solutions to films indicated reduced aggregation of the polymers due to the steric hindrance effect of thiophene rings in the side chains. The photovoltaic performance were characterized for devices in a configuration of ITO/PEDOT:PSS/PTB7‐Th:acceptors/2,9‐bis(3‐(dimethylamino)propyl)anthra[2,1,9‐def:6,5,10‐def]diisoquinoline‐1,3,8,10(2H,9H)‐tetraone (PDIN)/Al. With the addition of diphenyl ether as an additive, the power conversion efficiencies (PCEs) of 2.73% and 4.75% for P(NDI2THD‐T2) and P(NDI2TOD‐T2) based devices were achieved, respectively. The latter showed improved J_sc, Fill Factor (FF), and PCE compared with N2200 based devices. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3679–3689     

Beam emittance investigation in high brightness injector using different driver laser profiles

Beam emittance plays an important role in any accelerator, and it is a main parameter to judge the performance of an accelerator. Emittance optimization is an indispensable part in conditioning and operation of the facility. For a laser-driven high brightness injector, different time structure of the laser pulse has different effects on transverse emittance. In order to compare Gaussian and flat-top laser pulse, systematic simulations of 500 pC have been done. From the simulation results, one can see that flat-top pulse laser will yield smaller minimal transverse beam size and transverse beam emittance than Gaussian pulse laser.     

Transition from the hierarchical distribution to a homogeneous formation in injection molded isotactic polypropylene (iPP) with dynamic mold temperature control

There is an increasing demand to produce injection molded thermoplastic parts with high performance and more uniform microstructure. In this study, an injection mold with dynamic mold temperature control was developed to create a thermo-mechanical environment in which a high mold temperature and slow cooling rate were retained. Two-dimensional wide angle X-ray diffraction (2D-WAXD) and polarized optical microscopy (POM) studies were carried out to investigate the morphological distribution of isotactic polypropylene (iPP) through the depth. Due to the fast relaxation of polymer chains at a high temperature, the macroscopic orientated structure of iPP in conventional injection molding was eliminated, that is transited from the hierarchical morphology distribution to a more homogeneous formation. A homogeneous appearance without layer boundary was shown and many radial spherulites with loosely packed lamellae distributed uniformly throughout the sample.     

Crystal structure of an antiviral ankyrin targeting the HIV-1 capsid and molecular modeling of the ankyrin-capsid complex

Ankyrins are cellular repeat proteins, which can be genetically modified to randomize amino-acid residues located at defined positions in each repeat unit, and thus create a potential binding surface adaptable to macromolecular ligands. From a phage-display library of artificial ankyrins, we have isolated Ank^GAG1D4, a trimodular ankyrin which binds to the HIV-1 capsid protein N-terminal domain (NTD^CA) and has an antiviral effect at the late steps of the virus life cycle. In this study, the determinants of the Ank^GAG1D4-NTD^CA interaction were analyzed using peptide scanning in competition ELISA, capsid mutagenesis, ankyrin crystallography and molecular modeling. We determined the Ank^GAG1D4 structure at 2.2 Å resolution, and used the crystal structure in molecular docking with a homology model of HIV-1 capsid. Our results indicated that NTD^CA alpha-helices H1 and H7 could mediate the formation of the capsid-Ank^GAG1D4 binary complex, but the interaction involving H7 was predicted to be more stable than with H1. Arginine-18 (R18) in H1, and R132 and R143 in H7 were found to be the key players of the Ank^GAG1D4-NTD^CA interaction. This was confirmed by R-to-A mutagenesis of NTD^CA, and by sequence analysis of trimodular ankyrins negative for capsid binding. In Ank^GAG1D4, major interactors common to H1 and H7 were found to be S45, Y56, R89, K122 and K123. Collectively, our ankyrin-capsid binding analysis implied a significant degree of flexibility within the NTD^CA domain of the HIV-1 capsid protein, and provided some clues for the design of new antivirals targeting the capsid protein and viral assembly.     

First principle electronic structure calculations of ternary alloys Hg1−xMnxTe in zinc-blende structure

We have investigated the structural, electronic, magnetic and optical properties of Hg_1?xMn_xTe in the zinc-blende phase for 0≤x≤1. The calculations were performed by using the full potential linearized augmented plane wave plus local orbitals method within the framework of the density functional theory. The lattice constants of Hg_1?xMn_xTe at different Mn concentrations exhibit Vegard's law perfectly. For spin-up channel the Mn 3d bands are occupied and mixed with the Te 5p bands whereas for spin-down channel the Mn 3d bands are unoccupied. The values of the p–d exchange splitting energy, ?_x(pd) as produced by the Mn 3d states are given. The contribution of the valence band and the conduction band in the process of exchange and splitting is described by the exchange coupling constants N₀α and N₀β. Due to p–d hybridization the magnetic moment of the Mn atom reduces, which results in small local magnetic moments on the non-magnetic Hg and Te sites. The potential applications of Hg_1?xMn_xTe in infrared device have been discussed on the basis of its optical properties.     

EPR,ENDOR and optical spectroscopy of Yb3+ ion in KZnF3 single crystals

The paramagnetic center of tetragonal symmetry formed by the Yb³⁺ ion in the KZnF₃ crystal has been studied using methods of EPR, ENDOR and optical spectroscopy. The location of the impurity ion and the structural model of the complex differing from the model of the Yb³⁺ center in KMgF₃ have been established. The empirical scheme of the energy levels of the Yb³⁺ ion has been found. The parameters of its interaction with the crystal electrostatic field and the hyperfine interaction with ligands of the nearest environment have been determined. The parameters of the crystal field were used for the analysis of the distortions of the crystal lattice in the vicinity of Yb³⁺. The parameters of the transferred hyperfine interaction have been calculated for the distances between Yb³⁺ and F⁻ ions of the nearest environment obtained taking into account the found distortions. They are in good agreement with the experimental values.