51,363 research outputs found
Enhanced thermoelectric figure of merit in vertical graphene junctions
In this work, we investigate thermoelectric properties of junctions
consisting of two partially overlapped graphene sheets coupled to each other in
the cross-plane direction. It is shown that because of the weak van-der Waals
interactions between graphene layers, the phonon conductance in these junctions
is strongly reduced, compared to that of single graphene layer structures,
while their electrical performance is weakly affected. By exploiting this
effect, we demonstrate that the thermoelectric figure of merit can reach values
higher than 1 at room temperature in junctions made of gapped graphene
materials, for instance, graphene nanoribbons and graphene nanomeshes. The
dependence of thermoelectric properties on the junction length is also
discussed. This theoretical study hence suggests an efficient way to enhance
thermoelectric efficiency of graphene devices.Comment: 6 pages, 4 figures, submitte
Isogeometric analysis for functionally graded microplates based on modified couple stress theory
Analysis of static bending, free vibration and buckling behaviours of
functionally graded microplates is investigated in this study. The main idea is
to use the isogeometric analysis in associated with novel four-variable refined
plate theory and quasi-3D theory. More importantly, the modified couple stress
theory with only one material length scale parameter is employed to effectively
capture the size-dependent effects within the microplates. Meanwhile, the
quasi-3D theory which is constructed from a novel seventh-order shear
deformation refined plate theory with four unknowns is able to consider both
shear deformations and thickness stretching effect without requiring shear
correction factors. The NURBS-based isogeometric analysis is integrated to
exactly describe the geometry and approximately calculate the unknown fields
with higher-order derivative and continuity requirements. The convergence and
verification show the validity and efficiency of this proposed computational
approach in comparison with those existing in the literature. It is further
applied to study the static bending, free vibration and buckling responses of
rectangular and circular functionally graded microplates with various types of
boundary conditions. A number of investigations are also conducted to
illustrate the effects of the material length scale, material index, and
length-to-thickness ratios on the responses of the microplates.Comment: 57 pages, 14 figures, 18 table
A new root-knot nematode, Meloidogyne moensi n. sp. (Nematoda : Meloidogynidae), parasitizing Robusta coffee from Western Highlands, Vietnam
A new root-knot nematode, parasitizing Robusta coffee in Dak Lak Province, Western Highlands of Vietnam, is described as Meloidogyne moensi n. sp. Morphological and molecular analyses demonstrated that this species differs clearly from other previously described root-knot nematodes. Morphologically, the new species is characterized by a swollen body of females with a small posterior protuberance that elongated from ovoid to saccate; perineal patterns with smooth striae, continuous and low dorsal arch; lateral lines marked as a faint space or linear depression at junction of the dorsal and ventral striate; distinct phasmids; perivulval region free of striae; visible and wide tail terminus surrounding by concentric circles of striae; medial lips of females in dumbbell-shaped and slightly raised above lateral lips; female stylet is normally straight with posteriorly sloping stylet knobs; lip region of second stage juvenile (J2) is not annulated; medial lips and labial disc of J2 formed dumbbell shape; lateral lips are large and triangular; tail of J2 is conoid with rounded unstriated tail tip; distinct phasmids and hyaline; dilated rectum. Meloidogyne moensi n. sp. is most similar to M. africana, M. ottersoni by prominent posterior protuberance. Results of molecular analysis of rDNA sequences including the D2-D3 expansion regions of 28S rDNA, COI, and partial COII/16S rRNA of mitochondrial DNA support for the new species status
Variety and the evolution of refinery processing
Evolutionary theories of economic development stress the role of variety as both a determinant and a result of growth. In this paper we develop a measure of variety, based on Weitzman's maximum likelihood procedure. This measure is based on the distance between products, and indicates the degree of differentiation of a product population. We propose a generic method, which permits to regroup the products with very similar characteristics values before choosing randomly the product models to be used to calculate Weitzman's measure. We apply the variety measure to process characteristics of oil refining. The results obtained for this technology show classic evolutionary specialization patterns that can be understood on the basis of niche theory. Here the changes in variety are related to changes in the range of the services the technology considered can deliver, range which plays a role similar to that of the size of the habitat of a biological species.TECHNOLOGICAL EVOLUTION; REFINERY PROCESSES; NICHE THEORY; WEITZMAN MEASURE
Comparison of single-phase matrix converter and H-bridge converter for radio frequency induction heating
This paper compares the newly developed single-phase matrix converter and the more conventional H- bridge converter for radio frequency induction heating. Both the converters exhibit unity power factor, very low total harmonic distortion at the utility supply interface, good controllability under soft switching condition for a wide range of power, and high efficiencies, whilst still having simple structures. A novel switching control pattern has been proposed for the matrix converter in order to maintain the comparable performance to the H-bridge converter. Simulation and experimental results for both converters are presented. Comparisons between two converters have confirmed the excellent performance of the proposed matrix converter
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