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During the last years, several thrust control systems of aerospace rocket engines have been developed. The fluidic thrust vectoring is one of them; it is simple in design and offers a substantial gain in weight and in performance. Most of the studies related to this device were carried out with cold gas. It is quite legitimate to expect that the thermophysical properties of the gases may affect considerably the flow behavior. Besides, the effects of reacting gases at high temperatures, under their effects all flow parameters like to vary. This study aims to develop a new methodology that allows studying and analyzing the fluidic thrust vectoring for a perfect gas, by taking into account the effects chemical reactions on the flow parameters, such as separation point, reattachment point downstream and pressure distribution upstream the injection port. In this study, the thrust vectorization implying frozen reacting hot gases was carried out by considering a chemical reaction mechanism. The thermodynamic parameters of the flow are calculated within the combustion chamber and different sections of the supersonic part of the nozzle. The results show a good agreement for cold gas, and as expected a slight difference for hot reacting gases. In parallel, in order to give more credibility to our work a study was carried out by numerical simulation for supersonic reactive and perfect flows in order to analyze the results of the method developed. In this work, the CFD performance of the fluidic thrust vectoring has been qualitatively and quantitatively analyzed. The Schlieren visualization and the wall pressure results are compared to analytical and experimental findings. Performance analysis is conducted, and basic conclusions are drawn in terms of thermodynamic gas properties effect on the fluidic thrust vector system. The primary effect was related to the gas molecular weight and its specific heat ratio. It is observed that for fixed injection conditions, the vectoring angle is different when the injected gas molecular weight and specific heat ratio are different. For a given mission of the launcher, it can be concluded that the mass of the embedded gas, used for the fluidic vectorization system, can be significantly reduced, depending on its molecular weight and specific heat ratio. [ABSTRACT FROM AUTHOR]

The interest from both consumers and industry toward flexible and organic electronics has grown enormously due to the unique properties of the materials used (flexible, stretchable, reconfigurable, and not easily breakable). In radio frequency and electronic organic systems fabrication, one important feature is the substrate complex dielectric constant. Particularly, in the context of the development of printed organic electronics technology, one of the major challenges is the knowledge of the effect on substrates complex dielectric constant retrieval when using organic conductive materials instead of classical metals (gold, copper, etc). Indeed, the precision on the determination of this parameter depends also on the characteristics of the conductive material used for the characterization of the substrate. When looking to full polymer devices, it is important to evaluate the precision on the determination of the parameters of interest without using metallic structures for the tests. This paper presents the characterization of a substrate on which a conductive polymer, polyaniline (PANI) doped with multiwall carbon nanotubes (MWCNTs) is deposited. The characterization technique is based on the well‐known 2 microstrip lines method. The microstrip lines, fabricated from PANI/MWCNTs, are processed on a substrate made of Kapton, which is a good candidate for flexible electronics. The extraction of the complex dielectric constant is made on the frequency range (1‐8 GHz). [ABSTRACT FROM AUTHOR]

In this communication, a fully organic dual-band antenna is presented. It consists of a coplanar waveguide coupled to an elliptical monopole antenna designed on a kapton substrate. This antenna is fabricated from a process, based on the use of a conductive polymer (Polyaniline) doped with multiwall carbon nanotubes, that has been optimized for this application. The flexibility of both kapton substrate and doped conductive polymer gives the antenna the ability to be freely crumpled paving the way to body-worn high data rate communications at microwave frequencies. Applications in wireless networks can also be addressed by using this kind of antennas. In this study, a comparison between the performance of an antenna under bending conditions (using a three-dimensional support) and its uncrumpled version is presented. We evaluate the crumpling effect on the resonant frequency, the bandwidth and the radiation patterns. A good agreement is observed between measurements and simulations data, even when the antenna is crumpled. [ABSTRACT FROM PUBLISHER]

Nanocrystalline FeAl alloy samples were prepared by mechanical alloying process using planetary high-energy ball mill. The alloy formation and different physical properties were investigated as a function of milling time, t, (in the 0-24 h range) by means of X-ray diffraction technique, scanning electron microscopy (SEM), energy dispersive X-ray, and Mössbauer spectroscopy. The complete formation of bcc-FeAl solid solution was observed after 4 h of milling. The lattice parameter quickly increased to a maximum value of 0.291 nm within the first hours of 12 h of milling, then decreased to a value of 0.2885 nm after 24 h. The grain size decreased from 55 to 10 nm, while the strain increased from 0.18 to 0.88%. Grain morphologies at different formation stages were observed by SEM. The Mössbauer spectrum showed the presence of a singlet and sextet after 4 h of milling. The singlet indicated the presence of paramagnetic phase characteristic of A disordered structure and the sextet with a mean hyperfine field, 〈 H〉, of 21 T was indicative of ordered DO structure. After 8 h of milling, the paramagnetic phase disappeared allowing the appearance of a sextet. For the higher milling time, i.e., 24 h, the Mössbauer spectrum was analyzed with two components. The first with 〈 H〉 equal to 29.9 T and the second with a 〈 H〉 value of 10.25 T. [ABSTRACT FROM AUTHOR]

This study aims to corroborate experimental studies in mechanical alloying by theoretical studies, particularly the calculation of the contact temperature at the impact point of the balls, basing on the mathematical model of a compact powder between two colliding balls. Indeed, within this study, we show the influence of some geometrical, dynamic, and thermophysical parameters on the variation in the contact temperature of balls and Al and Ti powders inside a vial of planetary ball mill. [ABSTRACT FROM AUTHOR]

The Fe60Co40 alloys were prepared by mechanical alloying of the Fe and Co powders using a high-energy ball mill. They were studied with respect to phase formation and magnetic properties using x-ray diffraction, scanning electron microscopy, and measurements of coercivity and remanence (Br). The evaluation of Fe lattice parameters during milling showed that formation of a body-centered cubic solid solution occurred by mechanical alloying after 12 h of milling. Intensive milling of Fe-Co powders results in a nonequilibrium microstructure characterized by grain refinement to a minimum of 10-13 nm and the introduction of internal strain up to 0.5%. [ABSTRACT FROM AUTHOR]