13,251 research outputs found
Reactivation of Limestone-Derived Sorbents using Hydration: Preliminary Results From a Fluidised Bed
A simple method of CO~2~ capture is by using the calcium looping cycle. The calcium looping cycle uses CaCO~3~ as a CO~2~ carrier, via the reversible reaction CaO(s) + CO~2~(g) = CaCO~3~(s), to extract CO2 from the exhaust stream and provide a pure stream of CO~2~ suitable for sequestration. 
A problem associated with the technology is that the capacity of the sorbent to absorb CO~2~ reduces significantly with the number of cycles of carbonation and calcination. The energy penalty of the cycle is considerably increased by cycling unreacted sorbent: hydration of unreactive sorbent has emerged as a promising strategy of reducing this penalty by regenerating the reactivity of exhausted sorbent.
A small atmospheric pressure fluidised bed reactor has been built and tested, that allows repeated cycling between two temperatures up to 1000 °C. 
Work presented here focuses on the effects of variation of the calcination temperature before hydration. Hydration has been found to more than double the reactivity of a spent sorbent cycled under the mildest conditions studied (calcination temperature of 840 °C). However, as calcination temperature is increased the observed reactivation decreases until little reactivation is observed for the sorbent cycled at 950 °C. The primary reason for this appears to be a substantial increase in friability of particles, with reactivity normalised for mass losses appearing similar independent of cycling temperature
On a generalization of Valiron's inequality for k-hypermonogenic functions on upper half-space
We present some results on the asymptotic growth behavior of periodic k-hypermonogenic functions on upper half-space. A generalization of the classical Valiron inequality for this class of functions and some basic properties are discussed
On Optimal Binary One-Error-Correcting Codes of Lengths and
Best and Brouwer [Discrete Math. 17 (1977), 235-245] proved that
triply-shortened and doubly-shortened binary Hamming codes (which have length
and , respectively) are optimal. Properties of such codes are
here studied, determining among other things parameters of certain subcodes. A
utilization of these properties makes a computer-aided classification of the
optimal binary one-error-correcting codes of lengths 12 and 13 possible; there
are 237610 and 117823 such codes, respectively (with 27375 and 17513
inequivalent extensions). This completes the classification of optimal binary
one-error-correcting codes for all lengths up to 15. Some properties of the
classified codes are further investigated. Finally, it is proved that for any
, there are optimal binary one-error-correcting codes of length
and that cannot be lengthened to perfect codes of length
.Comment: Accepted for publication in IEEE Transactions on Information Theory.
Data available at http://www.iki.fi/opottone/code
A Way to Dynamically Overcome the Cosmological Constant Problem
The Cosmological Constant problem can be solved once we require that the full
standard Einstein Hilbert lagrangian, gravity plus matter, is multiplied by a
total derivative. We analyze such a picture writing the total derivative as the
covariant gradient of a new vector field (b_mu). The dynamics of this b_mu
field can play a key role in the explanation of the present cosmological
acceleration of the Universe.Comment: 5 page
Fuzzy Logic based Modelling and Simulation Approach for the estimation of Tire Forces
AbstractTire modeling is an important aspect of vehicle dynamics as the forces and moments required to control the vehicle's motion are eventually transmitted through the tire and the tire road interface is also an important source for the dynamic excitation of the vehicle. This paper presents a fuzzy logic based approach for estimating tire forces, aligning moment of tire for the different slip ratio and slip angles. Proposed fuzzy logic approach requires slip angle and slip ratio, as the input variables, and estimates the longitudinal force, lateral force, aligning moment as the output variables. Membership functions of input, output variables and fuzzy rules are formulated based on the values obtained using the widely adopted Magic formula for tire model. Simulation values for longitudinal, lateral forces and aligning moment of the tire using the proposed fuzzy model is found to provide good correlation with the magic model. Proposed fuzzy logic frame work does not require the estimation of model parameters used in the Magic formula and it will be useful in developing vehicle control system
A shrinking core model for steam hydration of CaO-based sorbents cycled for CO2 capture
Calcium looping is a developing CO2 capture technology. It is based on the reversible carbonation of CaO
sorbent, which becomes less reactive upon cycling. One method of increasing the reactivity of unreactive
sorbent is by hydration in the calcined (CaO) form. Here, sorbent has been subjected to repeated cycles of
carbonation and calcination within a small fluidised bed reactor. Cycle numbers of 0 (i.e., one calcination),
2, 6 and 13 have been studied to generate sorbents that have been deactivated to different extents.
Subsequently, the sorbent generated was subjected to steam hydration tests within a thermogravimetric
analyser, using hydration temperatures of 473, 573 and 673 K. Sorbents that had been cycled less prior to
hydration hydrated rapidly. However, the more cycled sorbents exhibited behaviour where the hydration
conversion tended towards an asymptotic value, which is likely to be associated with pore blockage. This
asymptotic value tended to be lower at higher hydration temperatures; however, the maximum rate of
hydration was found to increase with increasing hydration temperature. A shrinking core model has been
developed and applied to the data. It fits data from experiments that did not exhibit extensive pore blockage
well, but fits data from experiments that exhibited pore blockage less well
On the distribution of estimators of diffusion constants for Brownian motion
We discuss the distribution of various estimators for extracting the
diffusion constant of single Brownian trajectories obtained by fitting the
squared displacement of the trajectory. The analysis of the problem can be
framed in terms of quadratic functionals of Brownian motion that correspond to
the Euclidean path integral for simple Harmonic oscillators with time dependent
frequencies. Explicit analytical results are given for the distribution of the
diffusion constant estimator in a number of cases and our results are confirmed
by numerical simulations.Comment: 14 pages, 5 figure
Structurally dynamic spin market networks
The agent-based model of stock price dynamics on a directed evolving complex
network is suggested and studied by direct simulation. The stationary regime is
maintained as a result of the balance between the extremal dynamics, adaptivity
of strategic variables and reconnection rules. The inherent structure of node
agent "brain" is modeled by a recursive neural network with local and global
inputs and feedback connections. For specific parametric combination the
complex network displays small-world phenomenon combined with scale-free
behavior. The identification of a local leader (network hub, agent whose
strategies are frequently adapted by its neighbors) is carried out by repeated
random walk process through network. The simulations show empirically relevant
dynamics of price returns and volatility clustering. The additional emerging
aspects of stylized market statistics are Zipfian distributions of fitness.Comment: 13 pages, 5 figures, accepted in IJMPC, references added, minor
changes in model, new results and modified figure
Chiral Extensions of the MSSM
We present a class of extensions of the MSSM characterized by a fully chiral
field content (no mu-terms) and no baryon or lepton number violating term in
the superpotential due to an extra U'(1) gauge symmetry. The minimal model
consist of the usual matter sector with family dependent U'(1) charges, six
Higgs weak doublets, and three singlets required to give masses to the
Higgsinos and cancel anomalies. We discuss its main features such as the tree
level mass spectrum and the constraints on flavor changing processes.Comment: 13 pages. V2: Superpotential and U'(1) charges changed. Analysis of
the spectrum for the new model added. References update
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