79 research outputs found
Carbon dioxide concentrator
Passed exhaled air through electrochemical cell containing alkali metal carbonate aqueous solution, and utilizes platinized electrodes causing reaction of oxygen at cathode with water in electrolyte, producing hydroxyl ions which react with carbon dioxide to form carbonate ions
Aircrew oxygen system development carbon dioxide concentrator subsystem report
Carbon dioxide concentrator subsystem for closed loop aircrew oxygen syste
Electrolysis cell for orbital test
Water electrolysis subsystems for orbital test - application to spacecraft environmental control system
BPS black holes in N=2 D=4 gauged supergravities
We construct and analyze BPS black hole solutions in gauged N=2, D=4
supergravity with charged hypermultiplets. A class of solutions can be found
through spontaneous symmetry breaking in vacua that preserve maximal
supersymmetry. The resulting black holes do not carry any hair for the scalars.
We demonstrate this with explicit examples of both asymptotically flat and
anti-de Sitter black holes. Next, we analyze the BPS conditions for
asymptotically flat black holes with scalar hair and spherical or axial
symmetry. We find solutions only in cases when the metric contains ripples and
the vector multiplet scalars become ghost-like. We give explicit examples that
can be analyzed numerically. Finally, we comment on a way to circumvent the
ghost-problem by introducing also fermionic hair.Comment: 40 pages, 2 figures; v2 references added; v3 minor changes, published
versio
An iterative decision-making scheme for Markov decision processes and its application to self-adaptive systems
Software is often governed by and thus adapts to phenomena that occur at runtime. Unlike traditional decision problems, where a decision-making model is determined for reasoning, the adaptation logic of such software is concerned with empirical data and is subject to practical constraints. We present an Iterative Decision-Making Scheme (IDMS) that infers both point and interval estimates for the undetermined transition probabilities in a Markov Decision Process (MDP) based on sampled data, and iteratively computes a confidently optimal scheduler from a given finite subset of schedulers. The most important feature of IDMS is the flexibility for adjusting the criterion of confident optimality and the sample size within the iteration, leading to a tradeoff between accuracy, data usage and computational overhead. We apply IDMS to an existing self-adaptation framework Rainbow and conduct a case study using a Rainbow system to demonstrate the flexibility of IDMS
Supersymmetric AdS_4 black holes and attractors
Using the general recipe given in arXiv:0804.0009, where all timelike
supersymmetric solutions of N=2, D=4 gauged supergravity coupled to abelian
vector multiplets were classified, we construct the first examples of genuine
supersymmetric black holes in AdS_4 with nonconstant scalar fields. This is
done for various choices of the prepotential, amongst others for the STU model.
These solutions permit to study the BPS attractor flow in AdS. We also
determine the most general supersymmetric static near-horizon geometry and
obtain the attractor equations in gauged supergravity. As a general feature we
find the presence of flat directions in the black hole potential, i.e.,
generically the values of the moduli on the horizon are not completely
specified by the charges. For one of the considered prepotentials, the
resulting moduli space is determined explicitely. Still, in all cases, we find
that the black hole entropy depends only on the charges, in agreement with the
attractor mechanism.Comment: 25 pages, uses JHEP3.cl
The supersymmetric solutions and extensions of ungauged matter-coupled N=1,d=4 supergravity
We find the most general supersymmetric solutions of ungauged N=1,d=4
supergravity coupled to an arbitrary number of vector and chiral
supermultiplets, which turn out to be essentially pp-waves and strings. We also
introduce magnetic 1-forms and their supersymmetry transformations and 2-forms
associated to the isometries of the scalar manifold and their supersymmetry
transformations. Only the latter can couple to BPS objects (strings), in
agreement with our results.Comment: Some misprints and citations correcte
Supersymmetric solutions of gauged five-dimensional supergravity with general matter couplings
We perform the characterization program for the supersymmetric configurations
and solutions of the , Supergravity Theory coupled to an
arbitrary number of vectors, tensors and hypermultiplets and with general
non-Abelian gaugins. By using the conditions yielded by the characterization
program, new exact supersymmetric solutions are found in the
model for the hyperscalars and with as the gauge group. The
solutions also content non-trivial vector and massive tensor fields, the latter
being charged under the U(1) sector of the gauge group and with selfdual
spatial components. These solutions are black holes with
near horizon geometry in the gauged version of the theory and for the ungauged
case we found naked singularities. We also analyze supersymmetric solutions
with only the scalars of the vector/tensor multiplets and the metric
as the non-trivial fields. We find that only in the null class the scalars
can be non-constant and for the case of constant we refine
the classification in terms of the contributions to the scalar potential.Comment: Minor changes in wording and some typos corrected. Version to appear
in Class. Quantum Grav. 38 page
Supersymmetric Vacua in N=2 Supergravity
We use the embedding tensor formalism to analyse maximally symmetric
backgrounds of N=2 gauged supergravities which have the full N=2 supersymmetry.
We state the condition for N=2 vacua and discuss some of their general
properties. We show that if the gauged isometries leave the SU(2) R-symmetry
invariant, then the N=2 vacuum must be Minkowski. This implies that there are
no AdS backgrounds with eight unbroken supercharges in the effective N=2
supergravity of six-dimensional SU(3) x SU(3) structure compactifications of
type II string theory and M-theory. Combined with previous results on N=1
vacua, we show that there exist N=2 supergravities with a given set of gauged
Abelian isometries that have both N=2 and N=1 vacua. We also argue that an
analogue of our analysis holds in five and six spacetime dimensions.Comment: 14 pages, v2: references added, statement on SU(3) x SU(3) structure
compactifications clarified; v3: published version with statement on moduli
space of N=2 AdS vacua correcte
All timelike supersymmetric solutions of N=2, D=4 gauged supergravity coupled to abelian vector multiplets
The timelike supersymmetric solutions of N=2, D=4 gauged supergravity coupled
to an arbitrary number of abelian vector multiplets are classified using
spinorial geometry techniques. We show that the generalized holonomy group for
vacua preserving N supersymmetries is GL((8-N)/2,C) N/2 C^((8-N)/2)
GL(8,R), where N=0,2,4,6,8. The spacetime turns out to be a
fibration over a three-dimensional base manifold with U(1) holonomy and
nontrivial torsion. Our results can be used to construct new supersymmetric AdS
black holes with nontrivial scalar fields turned on.Comment: 35 pages, uses JHEP3.cl
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