On the estimation algorithm used in adaptive performance optimization of turbofan engines

The performance seeking control algorithm is designed to continuously optimize the performance of propulsion systems. The performance seeking control algorithm uses a nominal model of the propulsion system and estimates, in flight, the engine deviation parameters characterizing the engine deviations with respect to nominal conditions. In practice, because of measurement biases and/or model uncertainties, the estimated engine deviation parameters may not reflect the engine's actual off-nominal condition. This factor has a necessary impact on the overall performance seeking control scheme exacerbated by the open-loop character of the algorithm. The effects produced by unknown measurement biases over the estimation algorithm are evaluated. This evaluation allows for identification of the most critical measurements for application of the performance seeking control algorithm to an F100 engine. An equivalence relation between the biases and engine deviation parameters stems from an observability study; therefore, it is undecided whether the estimated engine deviation parameters represent the actual engine deviation or whether they simply reflect the measurement biases. A new algorithm, based on the engine's (steady-state) optimization model, is proposed and tested with flight data. When compared with previous Kalman filter schemes, based on local engine dynamic models, the new algorithm is easier to design and tune and it reduces the computational burden of the onboard computer

Holography and Variable Cosmological Constant

An effective local quantum field theory with UV and IR cutoffs correlated in accordance with holographic entropy bounds is capable of rendering the cosmological constant (CC) stable against quantum corrections. By setting an IR cutoff to length scales relevant to cosmology, one easily obtains the currently observed rho_Lambda ~ 10^{-47} GeV^4, thus alleviating the CC problem. It is argued that scaling behavior of the CC in these scenarios implies an interaction of the CC with matter sector or a time-dependent gravitational constant, to accommodate the observational data.Comment: 7 pages, final version accepted by PR

Thermodynamics of viscous dark energy in an RSII braneworld

We show that for an RSII braneworld filled with interacting viscous dark energy and dark matter, one can always rewrite the Friedmann equation in the form of the first law of thermodynamics, $dE=T_hdS_h+WdV$, at apparent horizon. In addition, the generalized second law of thermodynamics can fulfilled in a region enclosed by the apparent horizon on the brane for both constant and time variable 5-dynamical Newton's constant $G_5$. These results hold regardless of the specific form of the dark energy. Our study further support that in an accelerating universe with spatial curvature, the apparent horizon is a physical boundary from the thermodynamical point of view.Comment: 11 page

Resummed Quantum Gravity

We present the current status of the a new approach to quantum general relativity based on the exact resummation of its perturbative series as that series was formulated by Feynman. We show that the resummed theory is UV finite and we present some phenomenological applications as well.Comment: 4 pages, 1 figure; presented at ICHEP0

M31's Heavy Element Distribution and Outer Disk

Hubble Space Telescope imaging of 11 fields in M31 were reduced to color-magnitude diagrams. The fields were chosen to sample all galactocentric radii to 50 kpc. Assuming that the bulk of the sampled stellar populations are older than a few Gyr, the colors of the red giants map to an abundance distribution with errors of order 0.1 dex in abundance. The radially sampled abundance distributions are all about the same width, but show a mild abundance gradient that flattens outside ~20 kpc. The various distributions were weighted and summed with the aid of new surface brightness profile fits to obtain an abundance distribution representative of the entirety of M31. M31 is a system near chemical maturity. This ``observed closed box'' is compared to analytical closed box models. M31 suffers from a lack of metal-poor stars and metal-rich stars relative to the simplest closed-box model in the same way as the solar neighborhood.Comparing to several simple chemical evolution models, neither complete mixing of gas at all times nor zero mixing, inhomogeneous models give the most convincing match to the data. As noted elsewhere, the outer disk of M31 is a factor of ten more metal-rich than the Milky Way halo, ten times more metal-rich than the dwarf spheroidals cospatial with it, and more metal-rich than most of the globular clusters at the same galactocentric radius. Difficulties of interpretation are greatly eased if we posit that the M31 disk dominates over the halo at all radii out to 50 kpc. In fact, scaling from current density models of the Milky Way, one should not expect to see halo stars dominating over disk stars until beyond our 50 kpc limit. A corollary conclusion is that most published studies of the M31 "halo" are actually studies of its disk.Comment: 28 pages, 11 black-and-white figures, in press, Astrophysical Journa

Selectividad y eficacia de algunos herbicidas en viveros de planta aromática ornamental

Se han realizado unos ensayos preliminares de selectividad a los herbicidas diuron, isoxaben, metazacioro y propizamida, en las aromáticas tomillo común, tomillo aurea, lavanda, cantueso, lavandín híbrido, romero, orégano, salvia, hierbabuena y santolina. Los tratamientos se efectuaron a esquejes ya enraizados recien transplantados

Selectividad y eficacia de algunos herbicidas en vivero de planta forestal

Se ha realizado un ensayo, con el fin de evaluar la selectividad y eficacia de los herbicidas simazina, isoxaben y tiazopir a cuatro especies forestales en condiciones de vivero. Los tratamientos se efectuaron en preemergencia de las adventicias y pre-nascencia del cultivo sobre Quercus ilex L., Pinus halepensis Mill., Pinus pinea L. y Pistacia terebinthus L. A las dosis empleadas, simazina, isoxaben y la mezcla de ambos, han resultado selectivos para todas las especies, mientras que tiazopir provocó diferentes grados de fitotoxicidad según especies y su control sobre malas hierbas no fue adecuad

Mass-Varying Neutrinos from a Variable Cosmological Constant

We consider, in a completely model-independent way, the transfer of energy between the components of the dark energy sector consisting of the cosmological constant (CC) and that of relic neutrinos. We show that such a cosmological setup may promote neutrinos to mass-varying particles, thus resembling a recently proposed scenario of Fardon, Nelson, and Weiner (FNW), but now without introducing any acceleronlike scalar fields. Although a formal similarity of the FNW scenario with the variable CC one can be easily established, one nevertheless finds different laws for neutrino mass variation in each scenario. We show that as long as the neutrino number density dilutes canonically, only a very slow variation of the neutrino mass is possible. For neutrino masses to vary significantly (as in the FNW scenario), a considerable deviation from the canonical dilution of the neutrino number density is also needed. We note that the present `coincidence' between the dark energy density and the neutrino energy density can be obtained in our scenario even for static neutrino masses.Comment: 8 pages, minor corrections, two references added, to apear in JCA

Selectividad y eficacia de algunos herbicidas en vivero de palmáceas

Con el fin de reducir la competencia herbácea en viveros de Phoenix canariensis Chabaud y Washingtonia filifera Linden se han realizado unos tratamientos de preemergencia con los herbicidas simazina, diuron y metabenzotiazuron, en los que también se ha evaluado la tolerancia, en distintas condiciones, de estas palmáceas. Según los resultados obtenidos, ambas especies se muestran intolerantes a todas las dosis ensayadas de diuron. Simazina fué selectiva a 1 y 3 kg/ha para P.canariensis y para W. filifera solo en tratamiento dirigido, aunque buenos resultados contra malas hierbas se obtuvieron con las dosis altas. Metabenzotiazuron fue selectivo a 1 y 3 kg/ha para P.canariensis, mientras VW. filifera sólo toleró 1 kg/ha en tratamiento dirigido; con ambas dosis se obtuvo un buen control de la vegetación espontánea. En tratamiento no dirigido Y. filifera sólo toleró dosis de 0,5 kg/ha de estos herbicidas

Dynamical dark energy with a constant vacuum energy density

We present a holographic dark-energy model in which the Newton constant $G_{N}$ scales in such a way as to render the vacuum energy density a true constant. Nevertheless, the model acts as a dynamical dark-energy model since the scaling of $G_{N}$ goes at the expense of deviation of concentration of dark-matter particles from its canonical form and/or of promotion of their mass to a time-dependent quantity, thereby making the effective equation of state (EOS) variable and different from -1 at the present epoch. Thus the model has a potential to naturally underpin Dirac's suggestion for explaining the large-number hypothesis, which demands a dynamical $G_{N}$ along with the creation of matter in the universe. We show that with the aid of observational bounds on the variation of the gravitational coupling, the effective-field theory IR cutoff can be strongly restricted, being always closer to the future event horizon than to the Hubble distance. As for the observational side, the effective EOS restricted by observation can be made arbitrary close to -1, and therefore the present model can be considered as a ``minimal'' dynamical dark-energy scenario. In addition, for nonzero but small curvature (|\Omega_{k0}| \lsim 0.003), the model easily accommodates a transition across the phantom line for redshifts z \lsim 0.2 , as mildly favored by the data. A thermodynamic aspect of the scenario is also discussed.Comment: 14 pages, 2 figures, revised, title modified, references added, to appear in Phys. Lett.