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921.
Daniel Scheid Moritz von der Lühe Markus Gallei 《Macromolecular rapid communications》2016,37(19):1573-1580
A convenient synthetic approach for the preparation of uniform metallopolymer‐containing hollow spheres based on 2‐(methacryloyloxy)ethyl ferrocenecarboxylate (FcMA) as monomer by sequential starved feed emulsion polymerization is described. Core/shell particles consisting of a noncrosslinked poly(methyl methacrylate) core and a slightly crosslinked ferrocene‐containing shell allows for the simple dissolution of core material and, thus, monodisperse metallopolymer hollow spheres are obtained. Since PFcMA is incorporated in the particle shell, herein investigated hollow spheres can be addressed by external triggers, i.e., solvent variation and redox chemistry in order to change the particle swelling capability. PFcMA‐containing core/shell particles and hollow spheres are characterized by transmission electron microscope (TEM), scanning electron microscopy, cryogenic TEM, thermogravimetric analysis, and dynamic light scattering in terms of size, size distribution, hollow sphere character, redox‐responsiveness, and composition. Moreover, the general suitability of prepared stimulus‐responsive nanocapsules for the use in catch‐release systems is demonstrated by loading the nanocapsules with malachite green as model payload followed by release studies.
922.
923.
An Euler tour of a hypergraph (also called a rank‐2 universal cycle or 1‐overlap cycle in the context of designs) is a closed walk that traverses every edge exactly once. In this paper, using a graph‐theoretic approach, we prove that every triple system with at least two triples is eulerian, that is, it admits an Euler tour. Horan and Hurlbert have previously shown that for every admissible order >3, there exists a Steiner triple system with an Euler tour, while Dewar and Stevens have proved that every cyclic Steiner triple system of order >3 and every cyclic twofold triple system admits an Euler tour. 相似文献
924.
D. P. Igoe A. V. Parisi S. Wagner 《International Journal of Mathematical Education in Science & Technology》2017,48(4):641-645
Smartphones used as tools provide opportunities for the teaching of the concepts of accuracy and precision and the mathematical concept of arctan. The accuracy and precision of a trigonometric experiment using entirely mechanical tools is compared to one using electronic tools, such as a smartphone clinometer application and a laser pointer. This research has demonstrated how two classroom activities based on tool-making can enhance student measurement and application of accuracy and precision considerations through a trigonometric activity investigating arctan. 相似文献
925.
In [1], Bannai presents a fusion condition and uses this to consider central Schur rings (S-rings) over the simple groups PSL(2,q) where q is a prime power. In this paper, we concretely describe all such S-rings in terms of symmetric S-rings over cyclic groups. The final section discusses counting these. 相似文献
926.
927.
Dr. rer. nat. D. W. Schmidt Ing. W. Schmidt Dipl.-Phys. W. J. Wagner 《Heat and Mass Transfer》1973,6(4):221-227
Measurements of the temperature fluctuations in flows are restricted to low fluctuation frequencies, if the temperature probes which have been available and which have a relative high thermal inertia are used. A newly constructed metalfilm probe, which works in principle as a resistance thermometer, overcomes this restriction to a large degree so that temperature fluctuations in the order of 0.01 °C can be measured up to fluctuation frequencies of about 5 kHz. The construction, the procedure of manufacture, and a method of calibration are presented for the newly developed probe, and its applicability for the measurement of temperature fluctuations in flows is demonstrated by some examples (measurements of the natural temperature fluctuations in the wake of a circular rod in air flow at a Reynolds number of about 5 · 104). Some further applications of the probe are mentioned, in which its high sensitivity and its low thermal inertia is especially advantageous (measurement of flow velocities and measurement of fast temperature variations by infra-red detectors). 相似文献
928.
Addition of a viscoelastic material based on silanols cured by boron oxide was used to delay sharkskin and stick–slip instabilities
in extrusion of linear low-density polyethylene (LLDPE). Delay of flow instabilities to rates of extrusion 25–35 times higher
than without additive and about 40% less extrusion pressure at the same throughput are achieved by the use of this material
as an additive (∼0.1%) to LLDPE or as a coating of the extrusion die. Mechanical properties of the lubricant were changed
by small variations of composition to investigate the impact of elasticity on lubrication and sharkskin delay. Both lubrication
and sharkskin delay were considerably improved when more elastic lubricants were used while the chemical composition of the
lubricants was nearly the same. Filling the lubricants with powders of metal oxides or especially particulates having plate-like
particles (kaolin, mica, BN) helped to delay the flow instabilities further to even higher throughputs. Together with experimental
results, we present a tentative explanation for the importance of elasticity of polymer processing aids in the delay of sharkskin
and the stabilization of slip.
This paper was presented at Annual European Rheology Conference (AERC) held in Hersonisos, Crete, Greece, April 27–29, 2006. 相似文献
929.
The structure of the flow behind wings with finite span (3D) is significantly more complex than the flow behind infinite span (2D) wings. It has been shown that the presence of wingtip vortices behind finite span wings significantly modifies the geometry of the wake flow. It is felt that this modification alters the dynamics of interaction between leading and trailing edge vorticity in a manner that affects the ability of 2D flapping wings to produce thrust. A model of the mean flow skeleton has been proposed from qualitative flow visualization experiments. An unambiguous quantitative representation of the actual flow is required for comparison to the proposed model. To accomplish this the full 3D 3C velocity is required in the volume behind the 3D flapping wing. It is proposed to use stereoscopic multigrid digital particle image velocimetry (SMDPIV) measurements to investigate this unsteady oscillatory flow. This paper reports preliminary SMDPIV measurements along the plane of a symmetrical NACA-profile wing at a Strouhal number of 0.35. Phase averaged measurements are used to investigate the complex flow topology and the influence of the forcing flow on the evolution of the large scale structure of a jet-flow. This paper focuses on optimizing the SMDPIV experimental methodology applied to liquid flows. By refining the 2D 3C technique, the 3D topology of the flow can be investigated with a high degree of accuracy and repeatability. Preliminary results show that the flow is characterized by two pairs of coherent structures of positive and negative vorticity. The arrangement of these structures in the flow is controlled by the motion of the wing. Vorticity of opposite rotation is shed at the extreme heave and pitch positions of the aerofoil to set up a thrust indicative vortex street in support of the suggested topological model. 相似文献