Approach Tolerance in the Assemblies of Evolutionary Hybrid Prototypes

A new answer is proposed to replace the traditional “one shot” prototype (manufactured in one piece with one process): the hybrid rapid prototype. It is used to highly reduce time, cost and increase reactivity during the development times of new products. The part is decomposed in several components which can quickly be changed and can be manufactured with a process the most adapted. The main objective of the presented method is to propose an available technological assembly between the different components of the part in the respect of technological and topological function, and initial tolerance. Using a graph of representation, fuzzy logic and a tolerance point of view, some entities are associated with a CIA (Assembly Identity Card) in accordance with evolutionary and manufacturing analysis. This work will be illustrated by an industrial tooling for plastic injection.Mechanical Engineerin

Pair-dominated GeV-optical flash in GRB 130427A

We show that the light curve of the double GeV+optical flash in GRB 130427A is consistent with radiation from the blast wave in a wind-type medium with density parameter $A=\rho r^2\sim 5\times 10^{10}$ g cm$^{-1}$. The peak of the flash is emitted by copious $e^\pm$ pairs created and heated in the blast wave; our first-principle calculation determines the pair-loading factor and temperature of the shocked plasma. Using detailed radiative transfer simulations we reconstruct the observed double flash. The optical flash is dominated by synchrotron emission from the thermal plasma behind the forward shock, and the GeV flash is produced via inverse Compton (IC) scattering by the same plasma. The seed photons for IC scattering are dominated by the prompt MeV radiation during the first tens of seconds, and by the optical to X-ray afterglow thereafter. IC cooling of the thermal plasma behind the forward shock reproduces all GeV data from a few seconds to $\sim 1$ day. We find that the blast wave Lorentz factor at the peak of the flash is $\Gamma\approx 200$, and the forward shock magnetization is $\epsilon_B\sim 2\times 10^{-4}$. An additional source is required by the data in the optical and X-ray bands at times $>10^2$ s; we speculate that this additional source may be a long-lived reverse shock in the explosion ejecta.Comment: 5 pages, 3 figures, accepted to ApJ

Estimates for Lorentz factors of gamma-ray bursts from early optical afterglow observations

The peak time of optical afterglow may be used as a proxy to constrain the Lorentz factor Gamma of the gamma-ray burst (GRB) ejecta. We revisit this method by including bursts with optical observations that started when the afterglow flux was already decaying; these bursts can provide useful lower limits on Gamma. Combining all analyzed bursts in our sample, we find that the previously reported correlation between Gamma and the burst luminosity L_gamma does not hold. However, the data clearly shows a lower bound Gamma_min which increases with L_gamma. We suggest an explanation for this feature: explosions with large jet luminosities and Gamma < Gamma_min suffer strong adiabatic cooling before their radiation is released at the photosphere; they produce weak bursts, barely detectable with present instruments. To test this explanation we examine the effect of adiabatic cooling on the GRB location in the L_gamma - Gamma plane using a Monte Carlo simulation of the GRB population. Our results predict detectable on-axis "orphan" afterglows. We also derive upper limits on the density of the ambient medium that decelerates the explosion ejecta. We find that the density in many cases is smaller than expected for stellar winds from normal Wolf-Rayet progenitors. The burst progenitors may be peculiar massive stars with weaker winds or there might exist a mechanism that reduces the stellar wind a few years before the explosion.Comment: 24 pages, 7 figures, 2 tables, accepted for publication in Ap