Atmospheric NLTE-Models for the Spectroscopic Analysis of Blue Stars with Winds. III. X-ray emission from wind-embedded shocks

X-rays/EUV radiation emitted from wind-embedded shocks in hot, massive stars can affect the ionization balance in their outer atmospheres, and can be the mechanism responsible for the production of highly ionized species. To allow for these processes in the context of spectral analysis, we have implemented such emission into our unified, NLTE model atmosphere/spectrum synthesis code FASTWIND. The shock structure and corresponding emission is calculated as a function of user-supplied parameters. We account for a temperature and density stratification inside the post-shock cooling zones, calculated for radiative and adiabatic cooling in the inner and outer wind, respectively. The high-energy absorption of the cool wind is considered by adding important K-shell opacities, and corresponding Auger ionization rates have been included into the NLTE network. We tested and verified our implementation carefully against corresponding results from various alternative model atmosphere codes, and studied the effects from shock emission for important ions from He, C, N, O, Si, and P. Surprisingly, dielectronic recombination turned out to play an essential role for the ionization balance of OIV/OV around Teff = 45,000 K. Finally, we investigated the behavior of the mass absorption coefficient, kappa_nu(r), important in the context of X-ray line formation in massive star winds. In almost all considered cases, direct ionization is of major influence, and Auger ionization significantly affects only NVI and OVI. The approximation of a radially constant kappa_nu is justified for r > 1.2 Rstar and lambda < 18 A, and also for many models at longer wavelengths. To estimate the actual value of this quantity, however, the HeII opacities need to be calculated from detailed NLTE modeling, at least for wavelengths longer than 18 to 20 A, and information on the individual CNO abundances has to be present.Comment: accepted by A&

Pseudo-dynamic method for structural analysis of automobile seats

This work describes the application of a pseudo-dynamic (PsD) method to the dynamic analysis of passenger seats for the automotive industry. The project of such components involves a structural test considering the action of dynamic forces arising from a crash scenario. The laboratory certification of these automotive components consists essentially on the inspection of the propagation and extension of plastic deformations zones in metallic members of the seat structure as consequence of the mutual action between the seat and the passenger fastened to the seat via seat belt anchorages. This work presents a relatively simple experiment using PsD techniques as a novel method to performa test equivalent to the dynamic model of a dummy-seat pair subjected to impulsive loads from a car crash. Essentially, the PsD test method is a hybrid and hierarchic computer-driven testing procedure where a numerical algorithm and experimental step are used and combined on-line in order to solve a problem in the scope of structural dynamics. The implementation of the method is not expensive and has the leading advantage of offering the operator a total control of any intermediate structure state during the test still keeping the realism of a real dynamic testing.Project: NDT-AUTO Ref 13-02-2003-FDR-01281 (Agencia de Inovação

The advantages of SMRT sequencing

Of the current next-generation sequencing technologies, SMRT sequencing is sometimes overlooked. However, attributes such as long reads, modified base detection and high accuracy make SMRT a useful technology and an ideal approach to the complete sequencing of small genomes

Numerical modelling code based on the finite volume method in unstructured grids

In this work, the implementation employed in the new modeling code is described. It is based on the FVM with on a SIMPLE type scheme suitable for unstructured meshes.Fundação para a Ciência e a Tecnologia (FCT

On the performance of profile extrusion dies

This work presents a study performed with an in-house 3D numerical modelling code, used to evaluate the sensitivity of extrusion dies, optimized with alternative strategies, to process parameters, such as machining inaccuracies, melt rheology and processing conditions.FC

Design of complex profile extrusion dies through numerical modeling

The achievement of a balanced flow is one of the major tasks encompassed in the design of profile extrusion dies [1]. For this purpose numerical modeling codes may be a very useful aid. The research team involved in this work has been working during the last decade on the development of numerical tools to aid the conception of extrusion dies [1,2]. The design code developed so far carries out the automatic search of a final geometry via an optimization routine coupled with geometry and mesh generators and a 3D computational fluid dynamics (CFD) code based on the finite volume method (FVM). This CFD code is able to model the flow of polymer melts in confined channels, but is inadequate to deal with complex geometries, since it is limited to structured meshes. This work describes the recent efforts made to enlarge the scope of the design procedures, that are currently focused on the development of a modeling code able to deal with unstructured meshes. This code solves the continuity and linear momentum conservation equations, with generalized Newtonian fluids, using a SIMPLE based approach. This paper describes the developed numerical modelling code and its employment in a case study that involves the design of a medical catheter extrusion die, focused on the search of a balanced flow distribution. The results obtained show that the developed numerical code is able to deal with complex geometrical problems, being thus a valuable tool to aid the design of extrusion dies to produce complex profiles.The authors gratefully acknowledge funding from Fundacao para a Ciencia e Tecnologia through the PhD Grant SFRH/BD43632/2008 and FCT (COMPETE Program) under the Projects FCOMP-01-0124 - FEDER-010190 (Ref. PTDC/EME - MFE/102729/2008) and FCOMP-01-0124-FEDER-015126 (Refa. FCT PTDC/EME-MFE/113988/2009), and FEDER, via FCT, under the PEst-C/CTM/LA0025/2011 (Strategic Project - LA 25 - 2011-2012)

Development of numerical tools to aid the design of complex geometry profile extrusion dies

The research team of this work is involved since the mid-nineties on the development of computational tools to aid the design of profile extrusion dies. Initially, the numerical code employed was based on structured meshes that limited its application to simple geometries. The work planned in this PhD programme comprises the development of a numerical modelling code able to deal with unstructured meshes and its application on the design of profile extrusion dies comprising complex cross sections. In its current state the numerical code under development is able to model de flow of generalized Newtonian fluids inside flow channels using unstructured meshes. This paper describes briefly the current state of the developed code and illustrates its application in a case study involving the design of a profile extrusion die comprising a complex cross section

Using computational modelling to study extensional rheometry tests for inelastic fluids

The present work focuses on the extensional rheometry test, performed with the Sentmanat extensional rheometer (SER) device, and its main objectives are: (i) to establish the modelling requirements, such as the geometry of the computational domain, initial and boundary conditions, appropriate case setup, and (ii) to investigate the effect of self-induced errors, namely on the sample dimensions and test temperature, on the extensional viscosity obtained through the extensional rheometry tests. The definition of the modelling setup also comprised the selection of the appropriate mesh refinement level to model the process and the conclusion that gravity can be neglected without affecting the numerical predictions. The subsequent study allowed us to conclude that the errors on the sample dimensions have similar effects, originating differences on the extensional viscosity proportional to the induced variations. On the other hand, errors of a similar order of magnitude on the test temperature promote a significant difference in the predicted extensional viscosity.This work was funded by FEDER funds through the COMPETE 2020 Program and National Funds through FCT-Portuguese Foundation for Science and Technology under the projects UIDB/05256/2020/, UIDP/05256/2020, CPCA/A2/6202/2020, CPCA_A2_6231_2020, NORTE-08-5369- FSE-000034, under program IMPULSE-Polímeros e Compósitos: Drivers da Inovação Tecnológica e da Competitividade Industrial