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61.
Hai Hong Le Katrin Reincke Amit Das Klaus‐Werner Stöckelhuber Swen Wiessner Tung Pham Quang Khang Do Xuan Tung Hoang Wolfgang Grellmann Gert Heinrich Hans‐Joachim Radusch 《大分子材料与工程》2016,301(4):414-422
The selective wetting behavior of silica in emulsion styrene butadiene rubber (ESBR)/solution styrene butadiene rubber (SSBR) blends is characterized by the wetting concept, which is further developed for filled blends based on miscible rubbers. It is found that not only the chemical rubber–filler affinity but also the topology of the filler surface significantly influences the selective filler wetting in rubber blends. The nanopore structure of the silica surface has been recognized as the main reason for the difference in the wetting behavior of the branched ESBR molecules and linear SSBR molecules. However, the effect of nanopore structure becomes more significant in the presence of silane. It is discussed that the adsorption of silane on silica surface constricts the nanopore to some extent that hinders effectively the space filling of the nanopores by the branched ESBR molecules but not by the linear SSBR molecules. As a result, in silanized ESBR/SSBR blends the dominant wetting of silica surface by the tightly bonded layer of SSBR molecules causes a low‐energy dissipation in the rubber–filler interphase. That imparts the low rolling resistance to the blends similar to that of a silica‐filled SSBR compound, while the ESBR‐rich matrix warrants the good tensile behavior, i.e., good abrasion and wear resistance of the blends.
62.
C. Oelgardt J. Anderson J.G. Heinrich G.L. Messing 《Journal of the European Ceramic Society》2010,30(3):649-656
We report on how the mechanical properties of sintered ceramics (i.e., a random mixture of equiaxed grains) with the Al2O3–Y2O3–ZrO2 eutectic composition compare with those of rapidly or directionally solidified Al2O3–Y2O3–ZrO2 eutectic melts. Ceramic microcomposites with the Al2O3–Y2O3–ZrO2 eutectic composition were fabricated by sintering in air at 1400–1500 °C, or hot pressing at 1300–1400 °C. Fully dense, three phase composites of Al2O3, Y2O3-stabilized ZrO2 and YAG with grain sizes ranging from 0.4 to 0.8 μm were obtained. The grain size of the three phases was controlled by the size of the initial powders. Annealing at 1500 °C for 96 h resulted in grain sizes of 0.5–1.8 μm. The finest scale microcomposite had a maximum hardness of 19 GPa and a four-point bend strength of 282 MPa. The fracture toughness, as determined by Vickers indentation and indented four-point bending methods, ranged from 2.3 to 4.7 MPa m1/2. Although strengths and fracture toughnesses are lower than some directionally or rapidly solidified eutectic composites, the intergranular fracture patterns in the sintered ceramic suggest that ceramic microcomposites have the potential to be tailored to yield stronger, tougher composites that may be comparable with melt solidified eutectic composites. 相似文献
63.
Dr. Tjibbe Bosma Dr. Rick Rink Dr. Markus A. Moosmeier Prof. Dr. Gert N. Moll 《Chembiochem : a European journal of chemical biology》2019,20(14):1754-1758
Many therapeutic peptides can still be improved with respect to target specificity, target affinity, resistance to peptidases/proteases, physical stability, and capacity to pass through membranes required for oral delivery. Several modifications can improve the peptides’ properties, in particular those that impose (a) conformational constraint(s). Screening of constrained peptides and the identification of hits is greatly facilitated by the generation of genetically encoded libraries. Recent breakthrough bacterial, phage, and yeast display screening systems of ribosomally synthesized post-translationally constrained peptides, particularly those of lanthipeptides, are earning special attention. Here we provide an overview of display systems for constrained, genetically encoded peptides and indicate prospects of constrained peptide-displaying phage and bacterial systems as such in vivo. 相似文献
64.
Polymer crystallization under flow was investigated because final properties of polymers strongly depend on the crystalline structure and morphology formed during processing. In-situ synchrotron WAXS and SAXS were used to investigate the structure formation and morphological developments during quiescent and shear-induced crystallization of iPP with 3 different concentrations (0.01, 0.03 and 0.1 wt%) of β-nucleating agent. Under quiescent conditions, a high β-content was obtained at all those concentrations indicating the high β-nucleating efficiency of the nucleating agent. After application of shear, the β-nucleating ability at small concentration was retained, while at larger concentrations it was strongly retarded. Furthermore, the addition of β-nucleating agent was beneficial for the molecular alignment during processing, the anisotropic particles of β-nucleating agent were much more effective to align the molecular chains in the flow direction compared to isotropic ones. A crystallization scheme for the iPP β-nucleating agent under shear was proposed. 相似文献
65.
Cornelus F. van Nostrum Theo F.J. Veldhuis Gert W. Bos Wim E. Hennink 《Polymer》2004,45(20):6779-6787
This study shows that the degradation mechanism and kinetics of monodisperse oligo(lactic acid)s esterified with N-(2-hydroxypropyl)methacrylamide (HPMAm) are strongly influenced by the nature of the chain end. Oligomers with free hydroxyl chain ends degraded predominantly by chain end scission via a backbiting mechanism with a pseudo first-order rate constant kbb=2.7 h−1 in aqueous buffer (37 °C, pH 7.2). Once the hydroxyl groups were protected by acetylation, random chain scission became the rate limiting step with kr=0.022 h−1 under the same conditions. Using these rate constants, the theoretical time-resolved degradation profile was calculated for every (intermediate) degradation product and corresponded very well with the experimental results. The rate of formation of HPMAm was independent of the chain length for the acetylated oligomers, while the hydroxyl terminated oligomers with an even number of lactic acid units formed HPMAm more rapidly than oligomers with an odd number of units. The possibility to fine-tune the degradation rate is relevant when applied as e.g. hydrogels for controlled release or tissue engineering materials. 相似文献
66.
Operational transfer path analysis 总被引:2,自引:0,他引:2
Gert De Sitter Christof Devriendt Patrick Guillaume Erik Pruyt 《Mechanical Systems and Signal Processing》2010,24(2):416-431
One of the tools used to study the NVH behaviour of a system is the transfer path analysis. It aims to identify the operational forces and the propagation paths of the vibrations and is especially interesting in the case when the system is composed of different subsystems. The classical techniques identify the transfer paths when the system is disassembled. This way one eliminates flanking transfer paths. Yet it is very time-consuming and the boundary conditions are not correct anymore. The presented method makes it possible to identify the transfer paths without disassembling the system. The advantages are that the overall testing time is reduced and that the real boundary conditions are present. In this article the theory will be reviewed and it will be validated using data generated by finite element simulations. 相似文献
67.
The paper presents an alternative constraint-handling technique that converts a nonlinear constrained programming problem
into an unconstrained multi-objective optimisation problem. The technique is derived from the behavioural memory constraint-handling
method, which was originally implemented for single-objective optimisation with genetic algorithms. We compare our presented
technique with two other popular constraint-handling concepts and demonstrate its superiority over them when applied to a
propeller optimisation problem. We conclude that the multi-objective behavioural memory constraint-handling technique conjugated
with the non-dominated sorting genetic algorithm (NSGA-II) is a prudent method to apply to problems with an infeasible initial
design and where constraints have a natural order of satisfaction, which, if not conformed to, would lead to unrealistic designs
that impair the search by GA. 相似文献
68.
Martijn Kuik Gert‐Jan A. H. Wetzelaer Jurre G. Laddé Herman T. Nicolai Jurjen Wildeman Jörgen Sweelssen Paul W. M. Blom 《Advanced functional materials》2011,21(23):4502-4509
The effect of on‐chain ketone defects on the charge transport of the polyfluorene derivative poly(9,9‐dioctylfluorene) (PFO) is investigated. Using MoO3 as ohmic hole contact, the hole transport in a pristine PFO diode is observed to be limited by space‐charge, whereas fluorenone contaminated PFO (PFO‐F) is shown to be trap limited by the occurrence of an exponential trap distribution with a trap depth of 0.18 eV. The electron transport in PFO is also observed to be trap limited, but in order to describe the electron transport of PFO‐F, an additional trap level with a depth of 0.46 eV must be introduced. The obtained energy levels of the fluorenone trapping sites are in close agreement with cyclic voltammetry (CV) measurements reported in literature. As a result, the fluorenone defects are shown to simultaneously act as hole‐ and electron trap. Moreover, through ideality factor measurements, the green emission associated with these defects is observed to originate from trap‐assisted recombination. 相似文献
69.
70.
The enthusiasm for the use of so-called native plants and the rejection of so-called exotic plants in 20th-century garden and landscape design is explored. The underlying ideas and ideology are discussed using examples in Germany, particularly from the time of National Socialism, and the United States. 相似文献