152 research outputs found
Modeling water flow on Façade
No full textThis study aims to develop a novel method by which visually to simulate water flow paths on building facades. Rainwater runoff affects the designs of facades in terms of safety and aesthetics because runoff leaves dirt and stains on an aesthetic facade. The first step is to review flow simulation algorithms and identify its limitations in fluid visualization research on flow path simulations. The second step is to review an existing CFD program to identify its limitations, and then establish the goals of the newly proposed method. The third step is to identify the properties and behaviors of water on a surface, including basic fluid mechanics to establish the mechanical relationship between the water and the facade material. The fourth step involves an experiment with water flows to reveal their characteristics based on the literature. The fifth step is to develop an algorithm which visually simulates water flows on a building facade. As a result, "Rainflow01" and "Rainflow02" are developed based on the open-source Grasshopper component "Drainage Polysurface" and Rhino. Rainflow01 and Rainflow02, which work based on the angle variation and critical sliding angle of the water path, present an innovative approach for predictions of water paths over a facade.
Shape effect of ceria in Cu/ceria catalysts for preferential CO oxidation
No full textCopper was deposited on different shapes of ceria supports (i.e., rods, cubes, and octahedra) and used as catalysts for preferential CO oxidation in excess amounts of hydrogen. When the same amount of copper was deposited, the copper content on the surface measured by X-ray photoelectron spectroscopy differed significantly, with more copper on the ceria octahedra. Copper seemed to migrate into the bulk ceria to a greater degree on the rods. The Cu/ceria-octahedra showed the highest activity of 95% at 140 degrees C among the three shapes, whereas the Cu/ceria-rods showed higher CO conversion than the Cuiceria-octahedra at higher temperatures. The Cu/ceria-octahedra showed no activity degradation for CO conversion at 140 C over 100 h, whereas the activity decreased by 13% for Cu/ceria-rod and 32% for Cu/ceria-cube at the same temperature. The metals Au and Pt were also deposited on the different shapes of ceria, and their activity and selectivity were evaluated. (C) 2010 Elsevier B.V. All rights reserved
Investigating Structural Effects of Quaternizing Additives on Shape Transitions of Block Copolymer Particles
No full textCo-assembly of block copolymers (BCPs) and organic/inorganic additives affords the design of various hierarchical nanostructures. In this work, we investigate the shape-changing capabilities of poly(styrene-block-2-vinylpyridine) (PS-b-P2VP) BCP particles upon quaternization with a series of bromoalkyl benzene additives with different alkyl spacer lengths. The bromoalkyl benzene additives exhibit different hydrolyzing and quaternizing behaviors depending on their chemical structures. When benzyl bromide (BB) is used, the PS-b-P2VP BCP particles exhibit dramatic shape transitions from ellipsoids to ellipsoids with swelled discs, swelled buds, and vesicles. These morphological transitions are attributed to the synergistic quaternization and protonation of the P2VP chains via the hydrolysis of BB in aqueous media. Upon increasing the molar ratio of BB to 2VP units, the pH of the surrounding aqueous solutions significantly decreases, and the protonated P2VP domains are swelled by the surrounding water, which eventually results in interfacial instability of the emulsion interface. When the additives contain longer alkyl spacers (e.g., ethyl, butyl, and hexyl), the additives lead to a narrower range of quaternization-dependent particle morphologies due to the absence of the hydrolysis of the additives. However, a broader spectrum of particle shapes is observed for additives with longer alkyl chains, due to their stronger quaternizing capabilities. We carefully investigate the structural effect of the quaternizing additives on the change of pH, degree of quaternization, and interfacial tension to elucidate the mechanism of the additive-driven particle morphology transitions
Investigating Structural Effect of Quaternizing Additives on Shape Transition of Block Copolymer Particles
No full textImportance of Polymer Ligand Conformation to Entropy-Driven Assembly of Nanoparticles within Block Copolymer Particles
No full textChemical doping-assisted shape transformation of block copolymer particles
No full textShape-tunable block copolymer (BCP) particles have attracted significant attention due to their applications as smart materials. Herein, we report iodine (I2)-mediated doping of polystyrene-block-polybutadiene (PS-b-PB) particles as a facile strategy to transform spherical BCP particles into nonspherical shaped particles. Upon introducing the I2 molecules to internally phase-separated spherical PS-b-PB particles, I2 selectively reacts with the double bonds in PB blocks while leaving the PS block unaffected. Monitoring the shape-transformation process reveals a gradual structural transition from spheres to oblates and ellipsoids as a function of reaction time, consistent with the increasing conversion of the double bonds into I2-doped cation radicals. Consequently, the interfacial tension of I2-doped PB blocks decreases, neutralizing the interfacial interaction of BCP and its surroundings, thereby restructuring the spherical particles into shape-anisotropic forms. Furthermore, the versatility of I2-mediated shape transition is demonstrated by applying the same chemistry to polystyrene-block-poly(4-vinylpyridine) BCP particles. Finally, spheroidal particles doped with I2 exhibit photothermal heating behavior, highlighting their potential application as photothermal agents.,Iodine-mediated chemical modification approach was developed for the facile shape transformation of block copolymer colloidal particles.,
Self-Assembly of Molecular Weight-Controlled Bottlebrush Block Copolymer within Evaporative Emulsion
No full textOn quasirecurrent manifolds
No full textsummary:We introduce a type of Riemannian manifolds (namely, quasirecurrent manifold) and study its several geometric properties. Among others, we prove that the scalar curvature of such a manifold is constant, and that the manifold is Einstein under certain condition. In addition, we deal with a quasirecurrent product manifold. Finally, we ensure the existence of quasirecurrent manifold by a proper example
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