Thermomechanical deformation behavior of a dynamic strain aging alloy, Hastelloy X

An experimental study was performed to identify the effects of dynamic strain aging (solute drag) and metallurgical instabilities under thermomechanical loading conditions. The study involved a series of closely controlled thermomechanical deformation tests on the solid-solution-strenghened nickel-base superalloy, Hastelloy X. This alloy exhibits a strong isothermal strain aging peak at approximately 600 C, promoted by the effects of solute drag and precipitation hardening. Macroscopic thermomechanical hardening trends are correlated with microstructural characteristics through the use of transmission electron microscopy. These observations are compared and contrasted with isothermal conditions. Thermomechanical behavior unique to the isothermal database is identified and discussed. The microstructural characteristics were shown to be dominated by effects associated with the highest temperature of the thermomechanical cycle. Results indicate that the deformation behavior of Hastelloy X is thermomechanically path dependent. In addition, guidance is given pertaining to deformation modeling in the context of macroscopic unified theory. An internal state variable is formulated to qualitatively reflect the isotropic hardening trends identified in the TMD experiments

The incidence of mid-infrared excesses in G and K giants

Using photometric data from the 2MASS and GLIMPSE catalogues, I investigate the incidence of mid-infrared excesses (~10 microns) of G and K stars of luminosity class III. In order to obtain a large sample size, stars are selected using a near-IR colour-magnitude diagram. Sources which are candidates for showing mid-IR excess are carefully examined and modelled to determined whether they are likely to be G/K giants. It is found that mid-IR excesses are present at a level of (1.8 +/- 0.4) x 10^-3. While the origin of these excesses remains uncertain, it is plausible that they arise from debris discs around these stars. I note that the measured incidence is consistent with a scenario in which dust lifetimes in debris discs are determined by Poynting-Robertson drag rather than by collisions.Comment: Accepted for publication in MNRAS. 13 pages, 5 figures, 2 tables (1 landscape table

Capacity sharing within Virtual Centre: How much delay can be reduced?

Airspace Architecture Study proposed the future Single European Airspace System, based on modern technologies that could divide the air traffic service provision from local infrastructure for data provision, enabling the decoupling of geographical location from the service provision. This decoupling would enable virtualisation where service providers could use data from the common data services, opening doors to different organisation of air traffic service provision, namely more advanced capacity sharing. Virtualisation concept is still under development and several recent studies evaluated some aspects of virtualisation in ATM, but did not yet address in detail the impacts of different Virtual Centre implementation scenarios. In this paper, we propose a linear optimisation model to evaluate the impact of virtualisation and capacity sharing in terms of delay reduction. We show that taking into account the current airspace design and air traffic management resources, even the air navigation service providers that accumulate the highest capacity-caused delays could decrease those in the range of 25-50% up to about 80% through internal collaboration. Furthermore, the decrease of over 50% of the total capacity caused delays could be obtained if FABEC1 were to form a Virtual Centre, and the decrease of about 90% of the total European delay if the Single European Sky (SES) area would form a Virtual Centre. The analysed capacity sharing collaborations indicate the possibility of significant delay reductions, but would not be sufficient, on their own, to eliminate capacity-caused issues in Europe

Projet de conversion et d'unification des titres des Series B. C. & D. de la Dette Ottomane

Taha Toros Arşivi, Dosya No: 71-Duyun-u Umumiyeİstanbul Kalkınma Ajansı (TR10/14/YEN/0033) İstanbul Development Agency (TR10/14/YEN/0033

Student-like models for risky asset with dependence

We present a new construction of the Student and Student-like fractal activity time model for risky asset. The construction uses the diffusion processes and their superpositions and allows for specified exact Student or Student-like marginal distributions of the returns and for exible and tractable dependence structure. The fractal activity time is asymptotically self-similar, which is a desired feature seen in practice

Theoretical fits of the \delta Cephei light, radius and radial velocity curves

We present a theoretical investigation of the light, radius and radial velocity variations of the prototype $\delta$ Cephei. We find that the best fit model accounts for luminosity and velocity amplitudes with an accuracy better than $0.8\sigma$, and for the radius amplitude with an accuracy of $1.7\sigma$. The chemical composition of this model suggests a decrease in both helium (0.26 vs 0.28) and metal (0.01 vs 0.02) content in the solar neighborhood. Moreover, distance determinations based on the fit of light curves agree at the $0.8\sigma$ level with the trigonometric parallax measured by the Hubble Space Telescope (HST). On the other hand, distance determinations based on angular diameter variations, that are independent of interstellar extinction and of the $p$-factor value, indicate an increase of the order of 5% in the HST parallax.Comment: accepted for publication on ApJ Letter

Improved flexibility and equity for airspace users during demand-capacity imbalance - an introduction to the user-driven prioritisation process

ATFM slot-swapping represents the first step towards the participation of airspace users (AUs) in air traffic management and airport collaborative processes. SESAR is advancing this through development of the user driven prioritisation process (UDPP) to achieve additional flexibility for AUs to adapt their operations in a more cost-efficient manner in the presence of unforeseen demand and capacity imbalances that require the application of delays to flights. The contribution of this paper is twofold: (i) to present the challenges achieved so far with respect to UDPP concepts, in particular regarding fleet delay apportionment and selective flight protection; (ii) to pave the way towards future UDPP concepts through the introduction of enhanced selective flight protection