The Experts below are selected from a list of 53784 Experts worldwide ranked by ideXlab platform
Yuan Hu - One of the best experts on this subject based on the ideXlab platform.
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functionalized lignin for halogen free flame retardant rigid polyurethane foam preparation thermal stability fire performance and mechanical properties
Journal of Polymer Research, 2013Co-Authors: Weiyi Xing, Haixia Yuan, Ping Zhang, Hongyu Yang, Lei Song, Yuan HuAbstract:Halogen-free flame retardant rigid polyurethane foams (RPUF) were synthesized by substituting a part of polyther polyol with polyol-modified lignin and filled with phenolic encapsulated ammonium polyphosphate (PFAPP). Lignin was chemically modified with flame retardant elements, phosphorous, via a three-step reaction. The foams maintained a Regular Cell structure and had even smaller average Cell size than pure foam. The effects of lignin polyol and PFAPP on the apparent density, compressive strength were discussed. The thermal stability, flame retardant properties and mechanical properties of the foams are improved. Compared with pure foam (0.2 % char residue at 700 °C), modified foam with lignin and PFAPP exhibits much higher char formation (42.7 % char residue at 700 °C). The FR properties of these modified foams were evaluated by cone calorimeter and limiting oxygen index (LOI). The modified lignin in foam system further reduces the heat release rate and shows the combustion process. The addition of 15 % PFAPP and 10 % modified lignin into RPUF led to a considerable increase of the compressive strength with respect to the neat RPUF.
Patricia Hersh - One of the best experts on this subject based on the ideXlab platform.
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Regular Cell complexes in total positivity
Inventiones mathematicae, 2014Co-Authors: Patricia HershAbstract:Fomin and Shapiro conjectured that the link of the identity in the Bruhat stratification of the totally nonnegative real part of the unipotent radical of a Borel subgroup in a semisimple, simply connected algebraic group defined and split over ${\mathbb{R}}$ is a Regular CW complex homeomorphic to a ball. The main result of this paper is a proof of this conjecture. This completes the solution of the question of Bernstein of identifying Regular CW complexes arising naturally from representation theory having the (lower) intervals of Bruhat order as their closure posets. A key ingredient is a new criterion for determining whether a finite CW complex is Regular with respect to a choice of characteristic maps; it most naturally applies to images of maps from Regular CW complexes and is based on an interplay of combinatorics of the closure poset with codimension one topology.
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Regular Cell complexes in total positivity
arXiv: Combinatorics, 2007Co-Authors: Patricia HershAbstract:This paper proves a conjecture of Fomin and Shapiro that their combinatorial model for any Bruhat interval is a Regular CW complex which is homeomorphic to a ball. The model consists of a stratified space which may be regarded as the link of an open Cell intersected with a larger closed Cell, all within the totally nonnegative part of the unipotent radical of an algebraic group. A parametrization due to Lusztig turns out to have all the requisite features to provide the attaching maps. A key ingredient is a new, readily verifiable criterion for which finite CW complexes are Regular involving an interplay of topology with combinatorics.
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On optimizing discrete Morse functions
arXiv: Combinatorics, 2003Co-Authors: Patricia HershAbstract:Forman introduced discrete Morse theory as a tool for studying CW complexes by essentially collapsing them onto smaller, simpler-to-understand complexes of critical Cells in [Fo]. Chari reformulated discrete Morse theory for Regular Cell complexes in terms of acyclic matchings on face posets in [Ch]. This paper addresses two questions: (1) under what conditions may several gradient paths in a discrete Morse function simultaneously be reversed to cancel several pairs of critical Cells, to further collapse the complex, and (2) how to use lexicographically first reduced expressions for permutations (in the sense of [Ed]) to make (1) practical for poset order complexes. Applications include Cohen-Macaulayness of a new partial order, recently introduced by Remmel, on the symmetric group (by refinement on the underlying partitions into cycles) as well as a simple new proof of the homotopy type for intervals in the weak order for the symmetric group. Additional applications appear in [HW].
M. Mouly - One of the best experts on this subject based on the ideXlab platform.
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Regular Cellular reuse patterns
[1991 Proceedings] 41st IEEE Vehicular Technology Conference, 1991Co-Authors: M. MoulyAbstract:The author attempts to define what Regular Cell reuse patterns are in the case of omnidirectional hexagonal Cells and shows that there are more such patterns than the ones usually presented; for instance, patterns of 5 or 11 Cells are possible. An exhaustive presentation of the reuse patterns satisfying the definition is given. Some rough performance evaluations are included, giving some ideas of the C/I (carrier to interference ratio) protection with a simple propagation model. Some related problems are addressed, such as the application to frequency hopping and the problem of how to allocate frequencies in order to limit adjacent frequency interferences.
Maher Sadiq A R Albaghdadi - One of the best experts on this subject based on the ideXlab platform.
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a cfd study of hygro thermal stresses distribution in pem fuel Cell during Regular Cell operation
Renewable Energy, 2009Co-Authors: Maher Sadiq A R AlbaghdadiAbstract:A three-dimensional, multi-phase, non-isothermal computational fluid dynamics model of a proton exchange membrane fuel Cell has been developed and used to investigate the displacement, deformation, and stresses inside the whole Cell, which developed during the Cell operation due to the changes of temperature and relative humidity. The behaviour of the fuel Cell during operation has been studied and investigated under real Cell operating conditions. A unique feature of the present model is to incorporate the effect of hygro and thermal stresses into actual three-dimensional fuel Cell model for a complete Cell with both the membrane-electrode-assembly and the gas distribution flow channels. The results show that the non-uniform distribution of stresses, caused by the temperature gradient in the Cell, induces localized bending stresses, which can contribute to delaminating between the membrane and the gas diffusion layers. The non-uniform distribution of stresses can also contribute to delaminating between the gas diffusion layers and the channels, especially in the cathode side. These stresses may explain the occurrence of cracks and pinholes in the fuel Cells components under steady-state loading during Regular Cell operation, especially in the high loading conditions.
Maher A.r. Sadiq Al-baghdadi - One of the best experts on this subject based on the ideXlab platform.
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A CFD study of hygro–thermal stresses distribution in PEM fuel Cell during Regular Cell operation
Renewable Energy, 2009Co-Authors: Maher A.r. Sadiq Al-baghdadiAbstract:A three-dimensional, multi-phase, non-isothermal computational fluid dynamics model of a proton exchange membrane fuel Cell has been developed and used to investigate the displacement, deformation, and stresses inside the whole Cell, which developed during the Cell operation due to the changes of temperature and relative humidity. The behaviour of the fuel Cell during operation has been studied and investigated under real Cell operating conditions. A unique feature of the present model is to incorporate the effect of hygro and thermal stresses into actual three-dimensional fuel Cell model for a complete Cell with both the membrane-electrode-assembly and the gas distribution flow channels. The results show that the non-uniform distribution of stresses, caused by the temperature gradient in the Cell, induces localized bending stresses, which can contribute to delaminating between the membrane and the gas diffusion layers. The non-uniform distribution of stresses can also contribute to delaminating between the gas diffusion layers and the channels, especially in the cathode side. These stresses may explain the occurrence of cracks and pinholes in the fuel Cells components under steady-state loading during Regular Cell operation, especially in the high loading conditions.
