18,189 research outputs found
Electrical gas heater with large flow range capability
Auxiliary heat transfer device in form to tightly-wound helical tube was incorporated into conventional heater design to provide hydrogen heater with turn-down ratio greater than 100. Device greatly increases low flow rate capacity of heater by providing maximum heat-transfer area for low mass flows
The resistance of selected high strength alloys to embrittlement by a hydrogen environment
Selected high strength iron base and cobalt base alloys were resistant to degradation of mechanical properties in a one atmosphere hydrogen environment at ambient temperature. These alloys were strengthened initially by cold working which produced strain induced martensite and fcc mechanical twins in an fcc matrix. Heat treatment of the cobalt base alloy after cold working produced carbide precipitates with retention of an hcp epsilon phase which increased the yield strength level. High strength alloys can be produced which have some resistance to degradation of mechanical properties by a hydrogen environment under certain conditions
Localising subcategories for cochains on the classifying space of a finite group
The localising subcategories of the derived category of the cochains on the
classifying space of a finite group are classified. They are in one to one
correspondence with the subsets of the set of homogeneous prime ideals of the
cohomology ring .Comment: 5 pages, minor changes, accepted for publication in C. R. Math. Acad.
Sci. Pari
Local cohomology and support for triangulated categories
We propose a new method for defining a notion of support for objects in any
compactly generated triangulated category admitting small coproducts. This
approach is based on a construction of local cohomology functors on
triangulated categories, with respect to a central ring of operators. Suitably
specialized one recovers, for example, the theory for commutative noetherian
rings due to Foxby and Neeman, the theory of Avramov and Buchweitz for complete
intersection local rings, and varieties for representations of finite groups
according to Benson, Carlson, and Rickard. We give explicit examples of objects
whose triangulated support and cohomological support differ. In the case of
group representations, this allows us to correct and establish a conjecture of
Benson.Comment: 40 pages. Relatively minor changes (clarifications, corrections, new
references, etc). This article will appear in the Ann. Sci. Ecole Norm. Su
Stratifying modular representations of finite groups
We classify localising subcategories of the stable module category of a
finite group that are closed under tensor product with simple (or, equivalently
all) modules. One application is a proof of the telescope conjecture in this
context. Others include new proofs of the tensor product theorem and of the
classification of thick subcategories of the finitely generated modules which
avoid the use of cyclic shifted subgroups. Along the way we establish similar
classifications for differential graded modules over graded polynomial rings,
and over graded exterior algebras.Comment: 37 pages; minor changes from the first version. This is slated to
appear in the January 2012 issue of Annals of Math., volume 175, no.
Colocalizing subcategories and cosupport
The Hom closed colocalizing subcategories of the stable module category of a
finite group are classified. Along the way, the colocalizing subcategories of
the homotopy category of injectives over an exterior algebra, and the derived
category of a formal commutative differential graded algebra, are classified.
To this end, and with an eye towards future applications, a notion of local
homology and cosupport for triangulated categories is developed, building on
earlier work of the authors on local cohomology and support.Comment: 38 pages; minor changes; to appear in J. Reine. Angew. Mat
Numerical solution to the glancing sidewall oblique shock wave/turbulent boundary layer interaction in three dimension
A supersonic three-dimensional viscous forward-marching computer design code called PEPSIS is used to obtain a numerical solution of the three-dimensional problem of the interaction of a glancing sidewall oblique shock wave and a turbulent boundary layer. Very good results are obtained for a test case that was run to investigate the use of the wall-function boundary-condition approximation for a highly complex three-dimensional shock-boundary layer interaction. Two additional test cases (coarse mesh and medium mesh) are run to examine the question of near-wall resolution when no-slip boundary conditions are applied. A comparison with experimental data shows that the PEPSIS code gives excellent results in general and is practical for three-dimensional supersonic inlet calculations
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