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181.
182.
Panayotis Dimopoulos Eggenschwiler Dimitrios N. Tsinoglou Jacqueline Seyfert Christian Bach Ulrich Vogt Michal Gorbar 《Experiments in fluids》2009,47(2):209-222
Several properties of ceramic foams render them promising substrates for various industrial processes. For automotive applications,
the foam properties that need to be further studied include the substrate impact on the exhaust gas flow, in terms of pressure
drop and flow uniformity. In this paper, pressure drop measurements are performed with different honeycomb and ceramic foam
substrates, and pressure drop correlations are discussed. The flow uniformity upstream and downstream of the substrates is
evaluated using particle image velocimetry. The results show that ceramic foam substrates induce higher pressure drop, while
increasing the uniformity of the flow. In contrast to honeycomb monoliths, the flow uniformity downstream of ceramic foams
does not decrease with increasing flow velocity. The higher flow uniformity of ceramic foams is not only caused by their higher
pressure drop, but also by flow homogenization that occurs inside the ceramic foam structure, as a result of the momentum
exchange perpendicular to the main flow direction. 相似文献
183.
Anastasios Dondos Dimitrios Papanagopoulos 《Journal of Polymer Science.Polymer Physics》2003,41(7):707-710
A new universal calibration for gel permeation chromatography is proposed in which the hydrodynamic volume of the macromolecular chains is expressed by the quantity [η]M/Φ instead of the commonly used quantity [η]M (where [η] is the intrinsic viscosity, M is the molecular mass, and Φ is Flory's parameter). Introducing Φ into the hydrodynamic volume is necessary because its value changes from one polymer to another when the polymers present a certain draining effect. The proposed procedure also allows the determination of Φ of any wormlike polymer. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 707–710, 2003 相似文献
184.
Gavril D Loukopoulos V Georgaka A Gabriel A Karaiskakis G 《Journal of chromatography. A》2005,1087(1-2):158-168
Selective CO oxidation (SCO) has attracted scientific and technological interest due to its application to the operation of proton electrolyte membrane fuel cells (PEM-FCs). CO adsorption, being an elementary step of SCO, is studied over silica supported monometallic Rh and Rh0.50 + Pt0.50 alloy catalysts, under various hydrogen atmospheres, namely: 25% H2 + 75% He, 50% H2 + 50% He and 75% H2 + 25% He carrier gas mixture compositions. The investigation of CO adsorption is done by utilizing reversed-flow gas chromatography (RF-GC). As a result rate constants for the adsorption (k1), desorption (k(-1)) and irreversible CO binding (k2) over the studied catalysts as well as the respective activation energies are determined. The variation of the rate constants and the activation energies against the nature of the used catalyst (monometalic or alloy) and the amount of hydrogen in the carrier gas gives useful information for the selectivity as well as the activity of CO oxidation over group VIII noble metals. At low temperatures and under H2-rich conditions compatible with the operation of PEM fuel cells the activity of the monometallic and the alloy catalysts is expected to be similar, however the selectivity of Rh0.50 + Pt0.50 alloy catalyst is expected to be higher, making Pt-Rh alloy catalyst as a better candidate for CO preferential oxidation (PROX). The low energy barrier values found in the present work, most likely are referred to high surface amounts of CO. The desorption barriers determined are in any case much lower than the respective activation energies found for CO desorption in the absence of hydrogen indicating a H2-induced desorption, which can explain the observed in the literature rate enhancement of SCO oxidation. 相似文献
185.
We have studied the effect of small amounts of added liquid on the dynamic behavior of a granular system consisting of a mixture of glass beads of two different sizes. Segregation of the large beads to the top of the sample is found to depend in a nontrivial way on the liquid content. A transition to viscoplastic behavior occurs at a critical liquid content, which depends upon the bead size. We show that this transition can be interpreted as a condensation due to the hysteretic liquid bridge forces connecting the beads, and we provide the corresponding phase diagram. 相似文献
186.
In contrast to gravity in the weak-field regime, which has been subject to numerous experimental tests, gravity in the strong-field regime is largely unconstrained by observations. We show that gravity theories that pass solar system tests, but that diverge from general relativity in the strong-field regime, predict neutron stars with significantly different properties than their general relativistic counterparts. The range of redshfits of surface atomic lines predicted by such theories is significantly wider than the uncertainty introduced by our lack of knowledge of the equation of state of ultradense matter. Measurements of such lines with x-ray observatories can thus put new constraints on strong-field gravity. 相似文献
187.
The treatment of 16α-bromo-17-ketosteroids and 2-bromo-3-ketosteroids with thiourea in dimethylformamide give the corresponding 2′-formamidothiazolosteroids. The resulting 2′-formamidothiazoles were identical with those obtained in a similar reaction from 17β-bromo-16α,17α-oxidoandrostane with thiourea. Hydrolysis of the 2′-formamido-thiazolosteroids led to the corresponding 2′-aminothiazoles, which also resulted from the interaction of bromoketones and thiourea in isopropanol. The title compounds prepared were substantiated by examination of infrared, ultraviolet, mass and nuclear magnetic resonance spectra. 相似文献
188.
Dimitrios G. Liakos Emmanuel D. Simandiras Nikolaos Psaroudakis Konstantinos Mertis 《ChemInform》2007,38(22):no-no
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. 相似文献
189.
Iordanis Tzanidis Feidias Bairamis Dr. Lamprini Sygellou Dr. Konstantinos S. Andrikopoulos Prof. Apostolos Avgeropoulos Prof. Ioannis Konstantinou Prof. Dimitrios Tasis 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(29):6643-6651
Nanoscale two-dimensional nanostructures have shown great potential as functional components in photocatalysis. Here, investigations on the synthesis of heterostructured hybrids, comprised of 0D CdS nanoparticles as semiconductor and 2D/2D graphene/MoSx as co-catalyst, are reported. The approach involves a rapid microwave-assisted reaction in autoclave conditions, by adopting either a one-step or a two-step protocol. The chemical speciation of the nanocomposites was found to depend strongly on the compounding conditions of the precursor substances. The photocatalytic activity was assessed by monitoring the photodegradation rate of 4-nitrophenol in solution using simulated solar light irradiation. The photocatalytic activity of the hybrids may be attributed to a combination of beneficial characteristics, strongly related to the chemical speciation of the composite components. Moreover, intimate contacts of the latter result in efficient heterojunctions. Overall, the present study provides valuable insight into the development of functional heterostructured photocatalysts comprised of two-dimensional nanomaterials. 相似文献
190.
Synthesis,characterization and self‐assembly of well‐defined linear heptablock quaterpolymers
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Christos Ntaras George Polymeropoulos George Zapsas Konstantinos Ntetsikas George Liontos Apostolos Karanastasis Dimitrios Moschovas Sofia Rangou Charlotte Stewart‐Sloan Nikos Hadjichristidis Edwin L. Thomas Apostolos Avgeropoulos 《Journal of Polymer Science.Polymer Physics》2016,54(15):1443-1449
Two well‐defined heptablock quaterpolymers of the ABCDCBA type [Α: polystyrene (PS), B: poly(butadiene) with ~90% 1,4‐microstructure (PB1,4), C: poly(isoprene) with ~55% 3,4‐microstructure (PI3,4) and D: poly(dimethylsiloxane) (PDMS)] were synthesized by combining anionic polymerization high vacuum techniques and hydrosilylation/chlorosilane chemistry. All intermediates and final products were characterized by size exclusion chromatography, membrane osmometry, and proton nuclear magnetic resonance spectroscopy. Fourier transform infrared spectroscopy was used to further verify the chemical modification reaction of the difunctional PDMS. The self‐assembly in bulk of these novel heptablock quarterpolymers, studied by transmission electron microscopy and small angle X‐ray scattering, revealed 3‐phase 4‐layer alternating lamellae morphology of PS, PB1,4, and mixed PI3,4/PDMS domains. Differential scanning calorimetry was used to further confirm the miscibility of PI3,4 and PDMS blocks. It is the first time that PDMS is the central segment in such multiblock polymers (≥3 chemically different blocks). © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1443–1449 相似文献