Transient Stage Research Articles

Transient dynamics in mode-locked all-PM Er-doped fiber laser with NALM

In this study, we utilized the Time-Stretch Dispersive Fourier Transform (TS-DFT) method to explore rapid transient states in both time and frequency domains of an all-polarization-maintaining dispersion-managed figure-eight mode-locked laser with Nonlinear Amplifying Loop Mirror (NALM). We detail the different stages of build-up dynamics at varying pump powers, encompassing the Q-switching (QS) stage, transient single pulse formation, pulsation beating patterns, bound states, and the final transition to a single pulse state. Our findings reveal that the mode-locked bound state regime emerges from a single pulse stage following QS, different from previously reported directly resulting from QS pulses or relaxation oscillations. In a novel contribution to the field, we have experimentally demonstrated the transient single pulse stage of build-up dynamics and compared it with the fundamental mode-locked single pulse.

Unconventional gasoline spray injection events: Compared evolution of experimental data and numerical simulations

The current homologation standards in the automotive field impose the manufacturers to develop very efficient and clean engines. Low-Temperature Combustion engines have the potential to simultaneously reduce all the pollutants released while maintaining high efficiency. Among them, in Gasoline Compression Ignition (GCI) combustion technology, multiple injections allow to generate a tailored stratified charge which can auto ignite limiting the rough Pressure Rise Rate (PRR) and heat release rate typical of GCI. Therefore, the three-dimensional local distribution of the mixture becomes the key-point which the engine performance depends on. Due to emphasis on the multi-dimensional and local nature of the mixture formation phenomenon, three-dimensional CFD simulations are a promising and attractive method aiming at the design of the injection event features (timing, pattern, etc.). This paper deals with both experimental and CFD campaign on the evolution of a gasoline spray at ultra high-pressure multiple injection as well as high backpressure, typical of Gasoline Compression Ignition engines. The experimental tests have been conducted on a reference Diesel Common-Rail injector which shots in a constant-volume chamber. The hydraulic behaviour of the injector was characterized by means of the Bosch Tube principle whilst the Mie-scattering technique was used to capture the spray images. The numerical methodology is required to predict the Liquid Length Penetration and the jet morphology features (shape, area). Both experiments and simulations were conducted at different values of injection pressure (350, 500, 700 bar), back pressure (1–8 bar), energizing time (350, 600 µs), according to the operations of a real reference GCI test engine. Furthermore, a dedicated sub-model which takes into consideration the effect of the spray dynamics during the injection transient opening stage has been validated. The importance of this approach when dealing with short energizing time (e.g. 350 μs) is shown.Comparing both the experimental and numerical results, the model has proven to efficiently reproduce the spray penetration and morphology features, also under the hypothesis of injector ballistic phase operations, whose determination is crucial in the early development and sustainability of such combustion concept.

The effect of pipeline length on the transient process of an electric pump during start-up of a hybrid rocket motor

The electric pump in the propellant supply system, with a wide range of fast thrust adjustment capabilities, can significantly enhance rocket motor performance. Previous research has focused on the performance and feasibility of hydrogen peroxide electric pumps for hybrid rocket motors; however, their dynamic characteristics remain unclear. This study numerically and experimentally investigated the transition stages in the flow field and head for an electric pump during the start-up of a hybrid rocket motor, as well as analyzed the effect of pipeline length between the pneumatic valve and the adjustable Venturi on the flow field and head. The simulation and experimental results indicate that during the start-up of the hybrid rocket motor, six transient stages are recorded when the pipeline length between the pneumatic valve and adjustable Venturi is 3 m. The head and internal flow field of the electric pump during the transient process were determined by the throttling position as well as by the filling status of the pipeline. The simulation results suggest that the shorter the pipeline length, the steadier and safer is the supply system. Our investigation provides a practical optimization strategy for electric pump supply systems in rocket motors.

Transient dynamics of dissipative solitons formation in a net-normal dispersion mode-locked fiber laser based on nonlinear polarization evolution.

In mode-locked fiber lasers, the formation of ultrashort pulses from noisy or unstable states is a crucial area of research. Investigating these complex nonlinear dynamics can lead to valuable insights and new practical engineering techniques, particularly for the design and optimization of optical systems. Time-stretch dispersive Fourier transform, utilized in our study to investigate dissipative solitons formation in a net-normal dispersion nonlinear polarization evolution mode-locked fiber laser, provides a window into the intricate dynamics of such systems. In our experiments, the identification of five distinct transient stages in the formation process sheds light on the underlying mechanisms of dissipative soliton (DS) formation. The five distinct transient stages involved in the formation process include relaxation oscillation, modulation instability, spectral broadening, soliton explosions (SEs), and stable mode-locking. Notably, we also observed the generation of dissipative rogue waves during the SE stage. Our findings shed light on the intricate dynamics of DS formation and offer valuable insights for the design and optimization of mode-locked fiber lasers.

Effect of Si solution in α-Mo on oxidation behavior of Mo-Si-B alloy and oxidation kinetics model

In the present work, two Mo-12Si-8.5B alloys were prepared with α-Mo phase of a higher (2.72 at.%) and a lower (about 0 at.%) Si solid solubility. The oxidation behavior at 1100 °C indicated that a higher (2.72 at.%) Si solution in α-Mo phase improved the oxidation resistance of the Mo-Si-B alloy by enhancing the oxidation resistance of α-Mo itself and promoting the rapid coverage of protective borosilicate scale. As a result, the oxidation rate was decreased appreciably and the degeneration of the alloy was reduced by at least 77% during 30 h of the oxidation compared with that of the alloy with lower Si solution in α-Mo. An oxidation kinetics model for Mo-Si-B alloys was developed on the transient oxidation stage and it further confirmed the enhanced oxidation resistance by showing an increase decay time constant for the α-Mo phase with higher Si solution.

Natural killer cell subsets in endometrial fluid: a pilot study of their association with the endometrial cycle and reproductive parameters.

To investigate if there are natural killer (NK) cells in endometrial fluid (EF) and their relationship with the endometrial cycle and reproductive parameters. The population under study consisted of 43 women aged 18-40 undergoing infertility workup at our University Hospital in 2021-2022. The EF samples were obtained at the first visit to our unit, on occasion of the mock embryo transfer. The day of the cycle was considered only in cycles of 27-29 days. An immunophenotype study of NK in EF was performed by flow cytometry analysis. In a subgroup of women, on the same day, NK was studied in EF and peripheral blood. Our study is the first to evidence NK cells in EF. None of the NK cells observed corresponded to a mature peripheral blood NK cell population (stages 4-5), and neither endometrial nor decidual uNK cells were detected. Nevertheless, we found 2 patient groups with an NK cell subset with a higher expression of CD16+, which could belong to an intermediate or transient stage between the uNK and pbNK NK cell population in the EF. We found that CD16 was significantly increased in the mid-late luteal phase and its correlation with the day of the cycle. The NK immunophenotype was different in EF and peripheral blood. We described a new component of the EF, the NK cells, whose CD16 activity is closely correlated with the day of the cycle. These cells could play a role in implantation/implantation failure.

A methodology for post-processing the four-point beam bending data and computing stiffness modulus using harmonic analysis

The computation of modulus of bituminous mixes from a beam bending test conforming to an undamaged yet steady state is not straightforward. The most widely used practice of choosing the 50th or 100th cycle, for modulus computation, does not ensure that the material response has reached a steady state, crossing the initial transient stage of drastic modulus reduction. In the current study, it is analytically shown that the material retardation time governs the attainment of a steady state response. The study proposes a methodology for post-processing the four-point beam bending test data so as to identify the cycles that could result in a sensible computation of material modulus. The experimental investigations involve four-point beam bending (4-PB) tests carried out on four bituminous mixes, prepared using an unmodified and three modified binders. The 4-PB tests are carried out at 20 oC, 10 Hz frequency at strain levels of 200, 400, 600 and 800 micro-strains. The harmonics of the input/output waveform has been used to identify the cycles that can be used for the computation of a material modulus, and the modulus is computed from the Lissajous plots (stress–strain plots) of the cycles prior to damage initiation. Based on harmonic analysis, the current study specifies a range of modulus for each mix at various strain levels, and the values are further compared with the modulus computed using the conventional post-processing procedure. It is observed that the conventional procedure of using the stiffness modulus at 100th cycle results in higher values of modulus than the ones computed using the proposed post-processing method, as a consequence of the transient response of the material before attaining a steady state.

The influence of Cr on the oxidation behavior of a sputtered Pt+γ’ phase-equilibrium coating at 1150 ℃

Two sputtered phase-equilibrium coating (Pt+γ’ and Pt-Cr+γ’ coating) were manufactured in this work. No TCPs appeared around the interface of coating/superalloy after being oxidized at 1150 ℃ for 1000 h. The addition of chromium changes the oxidation kinetics of Pt-Cr+ γ’ coating both in transient and steady oxidation stage. In transient-oxidation stage, chromium accelerates the transition of aluminum oxide from θ-Al2O3 to α-Al2O3, which lowers the compressive stress in oxide scale. The presence of Cr in coating also refines the grain size of α-Al2O3 scale, which leads to a higher growth rate in the later steady oxidation-stage.

Generalized Multiphase-Shift Transient Modulation for Dual-Active-Bridge Series-Resonant Converter

Given the wide-range applications of bidirectional dual-active-bridge series-resonant converter (DABSRC), its complex nonlinear dynamic behavior is an interesting phenomenon that deserves attention of power electronics engineers. It is observed that if the control variables (i.e., phase-shift angles) are directly updated through conventional transient modulation, large-amplitude transient oscillations and dc offsets will be induced in the high-frequency-link voltages and currents during transient stage, which can ultimately degrade the converter's waveform quality significantly. The relatively few prior works in studying the transient oscillatory behavior of DABSRC have only focused on single-phase-shift modulation. In this article, a new transient modulation method referred to as generalized trajectory-switching modulation (GTSM) is first proposed for enhancing the transient performance of multi-phase-shift modulated DABSRC. GTSM can simultaneously mitigate the problems of transient oscillations and dc offsets regardless of operation modes and power-flow directions, thus always ensuring safe transient operation. It also enables the resonant voltages and currents as well as magnetizing current to seamlessly reach the desired new steady-state values swiftly. Finally, the said theoretical claims are verified experimentally under both open loop and closed loop with model predictive control, and the influence of deviations from nominal resonant tank's parameters on GTSM is also considered.

Analysis of the response of damped and parametrically driven, strongly anharmonic Klein-Gordon chain - Part 2: Beat-waves

This paper continues a series of publications devoted to the analysis of strongly nonlinear wave phenomena, emerging in genuinely anharmonic, Klein-Gordon cyclic chains, subjected to a traveling-wave parametric excitation. In this study, we analyze a special type of nonlinear waves, which will be further referred to as beat-waves. These are spatially extended, and strongly modulated waves manifested by the extreme amplitude modulation, which can be of stationary or nonstationary type. Stationary beat-waves of Klein-Gordon chains propagate with constant group velocity, that depends on the beat-wave amplitude. In the vicinity of 2:1 parametric resonance, we derive the parametrically driven, discrete p-Schrödinger (PD-DpS) model, which depicts the slow modulation of the response of a parametric oscillator chain. Special coordinates' transformation applied on the PD-DpS model allows the exact reduction of extremely modulated beat-waves to an invariant manifold of this slow-flow system. The system dynamics reduced to the beat-wave invariant manifold is depicted by three collective coordinates. In the undamped case, the analysis of the slow-flow system dynamics on the invariant manifold reveals a special family of nonlinear beat-waves characterized by an extreme amplitude modulation. Among these beat-wave solutions lying on the manifold, our analysis identifies some special solutions manifested by the solitary-pulse like, temporal evolution of the beat-wave amplitude which can either decay to zero or to a constant nonzero value. We derive the exact analytical solutions for these special types of waves as well as obtain an explicit analytical approximation for the beat-waves of other types. In the damped case, analysis of the slow-flow system dynamics on the invariant manifold fully recovers the mechanism of system synchronization on the special, stationary beat-wave solutions characterized by the harmonically modulated envelope. Importantly, the derived reduced order model accurately captures the transient evolution stage as well as the steady-state stage of the collective beat-wave response of PD-DpS model, initialized on the beat-wave invariant manifold. A detailed bifurcation analysis of the stationary undamped as well as the stationary damped beat-waves recovers their entire bifurcation structure and enables to fully characterize the zones of system parameters guaranteeing the existence of this special type of non-linear wave solutions. The results of analytical study of various types of beat wave solutions are in excellent agreement with the results of numerical simulation of both PD-DpS as well as the original, parametrically driven, genuinely an-harmonic, discrete Klein-Gordon model.

Solute drag-controlled grain growth in magnesium investigated by quasi in-situ orientation mapping and level-set simulations

Critical properties of metallic materials, such as the yield stress, corrosion resistance and ductility depend on the microstructure and its grain size and size distribution. Solute atoms that favorably segregate to grain boundaries produce a pinning atmosphere that exerts a drag pressure on the boundary motion, which strongly affects the grain growth behavior during annealing. In the current work, the characteristics of grain growth in an annealed Mg-1 wt.%Mn-1 wt.%Nd magnesium alloy were investigated by advanced experimental and modeling techniques. Systematic quasi in-situ orientation mappings with a scanning electron microscope were performed to track the evolution of local and global microstructural characteristics as a function of annealing time. Solute segregation at targeted grain boundaries was measured using three-dimensional atom probe tomography. Level-set computer simulations were carried with different setups of driving forces to explore their contribution to the microstructure development with and without solute drag. The results showed that the favorable growth advantage for some grains leading to a transient stage of abnormal grain growth is controlled by several drivers with varying importance at different stages of annealing. For longer annealing times, residual dislocation density gradients between large and smaller grains are no longer important, which leads to microstructure stability due to predominant solute drag. Local fluctuations in residual dislocation energy and solute concentration near grain boundaries cause different boundary segments to migrate at different rates, which affects the average growth rate of large grains and their evolved shape.

Methodology for determining the reactive parameters of aviation electrical energy consumers based on voltage and current data in transients

Modern trends in the aircraft development are associated with a significant increase in the level of its electrification. The emergence of new types of electricity consumers entails an increase in the power and number of consumers in the aircraft power supply system. At this stage of operation, direct control of the internal parameters (in particular, the parameters of reactive elements) of electricity consumers in the aircraft power supply system is not carried out. The aviation equipment control system is built taking into account the built-in system for monitoring the technical condition of the object. However, for greater efficiency, the built-in control can be supplemented with control capabilities through digital intelligent power distribution systems (local load control center). During the operation of aviation electrical equipment, the values of its parameters change relative to the nominal values. Deviations of equipment parameters from the nominal values should not exceed the specified values, which are determined by the operational technical documentation. Input impedances of secondary power supply sources can be investigated in a mode characterized by transient processes in the investigated component of aircraft equipment. Based on the experimental data of voltage and input current at the stage of transients in equivalent circuits of secondary power supplies, it is proposed to determine the values of the parameters of reactive elements. Changing the values of reactive elements gives information about the technical condition of the input stages of electrical energy receivers. This makes it possible to monitor the process of degradation of their properties or to diagnose a failure in the event of an abrupt change in reactive parameters. This method is proposed to be used for diagnosing electrical equipment during its operation on board the aircraft. This work is devoted to the development of methods for determining the parameters of secondary power sources of aircraft electrical equipment, characterizing its reactive properties.

The Recovery of Mediterranean Soils After Post-Fire Management: The Role of Biocrusts and Soil Microbial Communities

Although Mediterranean ecosystems are adapted to fire disturbances, soils are prone to degradation. Therefore, post-fire forest management is a critical step for ecosystem recovery: it can either reduce soil degradation or add a new disturbance. Post-fire management in Mediterranean burnt forests includes interventions with contrasting approaches, including the management of burnt trees, soil protection, or practices devoted to ecosystem restoration via the improvement of components or processes in the affected ecosystem. The consequences of forest management on soils are complex, thereby, in the context of the intensification of fire events and climate change, understanding the response of key soil components in managed ecosystems is critical for prioritizing soil conservation. One interesting component in the early post-fire stages is moss biocrust. The rapid colonization of biocrust-forming mosses in early successional stages post-disturbance stabilizes soils in their most vulnerable period. However, it is completely unknown further implications as active agents in the recovery and resilience of soils, in the transient stage before vascular vegetation regrowth. In combination with the biocrust, the response of soil microbial communities to forest management is crucial for evaluating the soil recovery progress, given their active role in fundamental ecosystem functions. The additive consequences of fires and forest management on biocrust emergence or microbial composition and functionality are usually neglected in the investigation of post-fire systems, although of major relevance to support strategies to preserve soils against functionality loss.

Some properties of a gas flow submitted to a temperature gradient

The flow of gases through channels generated by a temperature gradient along the channel surfaces is analyzed. This flow is characterized by the Thermomolecular Pressure Difference (TPD) at steady state and by the relaxation time, a characteristic of the transient stage, which indicates the rate at which the flow reaches the steady state. From a simple analytical description an expression to estimate the TPD is proposed. Experimental data obtained in channels with rectangular and circular cross-sections are analyzed, showing good agreement with the estimated TPD. Two normalizations of TPD are suggested that eliminate the gas and cross-section dependences, allowing application of this normalization to a channel with an unknown cross-section. Then, a quasi-analytical expression of the relaxation time is proposed. This expression makes it possible to explicitly calculate the relaxation time for the thermal creep flow in a channel of the rectangular and circular cross-sections using the numerical results obtained from the kinetic theory of gases. The proposed expressions are compared to the experimental data and the good agreement is found. In the case of channels of unknown cross-section, the relaxation time can be related to the channel conductance and the relaxation time can also be calculated using the proposed expression.

A non-isothermal reactive transport model of the long-term geochemical evolution at the disposal cell scale in a HLW repository in granite

The assessment of the long-term performance of the engineered barrier systems of high-level radioactive waste (HLW) repositories requires the use of reactive transport models. Here a non-isothermal reactive transport model of the long-term geochemical evolution of a HLW disposal cell in a granitic host rock is presented. The model includes the vitrified waste (40 cm in diameter), the carbon-steel canister (5 cm thick), the saturated FEBEX bentonite buffer (75 cm thick) and the reference granitic rock. The model accounts for the thermal transient stage and assumes generalized steel corrosion under anaerobic conditions with a corrosion rate equal to 1.41 m/y. Canister failure is assumed to occur when the remaining canister thickness is equal to 3.5 cm at t = 25,000 years. Canister corrosion caused an increase in pH. The computed pH in the canister just before canister failure (t = 25,000 years) was equal to 9.25 and ranged from 7.82 to 9.25 in the bentonite. Magnetite, the main corrosion product, precipitated in the bentonite and especially in the canister. The thickness of magnetite precipitation band in the bentonite was ≈ 1 cm. Siderite precipitated at both sides of the canister/bentonite interface. The precipitation front penetrated >1 cm into the bentonite. Nuclear glass started dissolving after canister failure (t > 25,000 years). The concentration of dissolved silica increased in the inner part of the glass until t = 30,000 years and decreased in the outer part of the glass due to the out diffusion of dissolved silica into the canister and the bentonite. This diffusive flux caused the precipitation of greenalite at the glass/canister and canister/bentonite interfaces. The pH at the end of the simulation (t = 50,000 years) ranged from 7.93 to 7.89 in the glass, from 7.89 to 8.66 in the canister and from 7.87 to 8.6 in the bentonite. Magnetite precipitated in the canister while there was carbon steel to corrode. Once the canister was fully corroded, magnetite redissolved near the glass/canister interface. Greenalite precipitated in the canister and the bentonite, especially at the glass/canister interface and siderite precipitated at the canister/bentonite interface. The simulation results should be useful for the performance assessment of engineered barriers of radioactive waste repositories in granitic host rocks.

Experimental study of thermomechanical behaviour of Gum Metal during cyclic tensile loadings: the quantitative contribution of IRT and DIC

ABSTRACT Thermomechanical behaviour of Gum Metal (Ti–23Nb–0.7Ta–2.0Zr–1.2O, at.%) under cyclic tension was experimentally investigated using infrared thermography and digital image correlation. The thermomechanical characteristics of particular stages of the subsequent loading-unloading cycles of Gum Metal were identified, i.e. (I) the linear, elastic loading accompanied by the temperature drop, (II) the nonlinear super-elastic loading related to the temperature growth, (III) the transient stage (at which both the superelastic-like behaviour and the plastic one are present simultaneously) and the temperature starts growing fast, (IV) the plastic deformation with a significant growth of temperature, (V) the superelastic-like unloading accompanied by a fast drop in temperature, (VI) the transient unloading with a slower decrease in temperature and (VII) the elastic unloading, with a slight increase in temperature. Thermoelastic effect in Gum Metal during both loading and unloading was analysed in each tensile cycle. Finally, the evolution of strain and temperature fields just before unloading in each cycle was discussed and a comparison of the fields at selected stages of cycles 12 and 24 was presented. The results of this work enabled us to identify the non-dissipative processes of elastic and superelastic-like deformations as well as the dissipative process of plastic deformation.

Experimental and modelling results of the QUENCH-20 experiment with BWR test bundle

The experiment QUENCH-20 with BWR simulation bundle was conducted at KIT on 9th October 2019. This test was performed in the framework of EU SAFEST project and its international access to European SA research infrastructure of the users from Swedish Radiation Safety Authority (SSM) in collaboration with Westinghouse Sweden, GRS and KTH. The test objective was the investigation of the BWR fuel assembly degradation including a control blade with B4C neutron absorbers. The test bundle represented one quarter of a BWR fuel assembly. 24 electrically heated fuel rod simulators were filled with krypton (pressure of about 0.6 MPa), whereas the holes of absorber pins were filled with helium (overpressure 0.02 MPa). According to the pre-test calculations performed with ATHLET-CD, the bundle was heated to a temperature of 1230 K at the cladding of the central rod at the hottest elevation of 950 mm. This pre-oxidation phase in steam lasted 4 h. During the following transient stage, the bundle was heated to a maximal temperature of 2000 K. The cladding failures were observed at temperatures about 1700 K and lasted about 200 s. Massive absorber melt relocation was observed 50 s before the end of the transient stage. The test was terminated by the injection of quench water with a flow rate of 50 g/s into the bundle bottom. Fast temperature escalation from 2000 to 2300 K during 20 s was observed. The mass spectrometer measured release of COx and little CH4 during the reflood as products of absorber oxidation; corresponding mass of reacted B4C was 4.3% of the total mass of B4C pins. Hydrogen production during the reflood amounted to 32 g (57.4 g during the whole test) including 10 g from B4C oxidation. The results of the post-test simulations with the AC2/ATHLET-CD code show a good agreement with the experimental observations concerning the thermal behavior. However, melting and relocation of BWR components was not calculated and the B4C oxidation was underestimated.

Creep damage in 9-12% Cr steel notched components: Microstructural evolution and stress state dependence

To understand the stress state dependent creep damage, following creep tests in 9–12% Cr steel notched components with different root radii, a study of associated time dependent microstructural evolution is presented in this work. Particular attention is paid to the dependence of creep damage evolution on the stress state. The average creep strain of notched component exhibits a typical three-stage characteristic (transient, steady and tertiary stages). During the transient stage, remarkable re-distribution in stress state (equivalent stress and stress triaxiality) is found. The rapid relaxation of equivalent stress near the notch root, associated with the initial coarsening of substructure would delay the nucleation or growth of cavity. By contrast, the time-dependent increase of equivalent stress combined with the relatively high stress triaxiality seems to be responsible for the higher cavity density at the center of notched component. The precipitate coarsening is heterogeneous and promoted by the high level of equivalent stress or stress triaxiality. During the steady stage, the creep damage behavior is related to the magnitude of stress state. Higher cavity density and greater reduction in hardness are mainly found in the region where both the equivalent stress and stress triaxiality are high. As a whole, both the redistribution process of stress states and their levels exhibit significant influence on microstructural evolution and creep damage behavior of notched components at elevated temperatures.

“I just ended up in nursing”: Inequalities in health professions education and migration aspirations among medical and nursing students in Ghana

This paper investigates educational experiences and the factors that shape the intention to migrate among current students enrolled in nursing and medical schools within migrant sending nations. The focus on nursing and medical students reflects the existence of a global labor market in which there is a demand for the international recruitment of health professionals. Empirically, this research is situated in Ghana, West Africa, a country that has faced large scale emigration of its professional and skilled labor force. Based on individual and focus group interviews with students in Ghana, this paper argues that stratification within secondary and tertiary educational institutions; lack of access to selective institutions and programs of first choice; and inadequate resources within the institutions where they receive training, fuel the desire to migrate. Findings reveal how stratification in educational prestige in medicine inheres within an immigrant sending country, and how it in turn shapes the desire for prospective health professionals to migrate [with the United States as their most desired destination]. Conceptually, this research contributes to studies going beyond the “brain drain” frame in discussions of the migration of health professionals. It reveals migration desires that are imagined as part of a transient stage in the life course, to escape under resourced educational environments, build human capital, broaden life goals, and to return to contribute to the homeland.

Global asymptotic dynamics of the cubic galileon interacting with dark matter

In this paper we perform a thorough dynamical systems analysis of the cubic galileon model non-minimally coupled to the dark matter. Three well-known classes of interacting models are considered where the energy exchange between the dark components is a function of the dark matter density and of the dark energy density: $Q_1=3\alpha H\rho_m$, $Q_2=3\beta\rho_m\dot{\phi}$ and $Q_3=3 \epsilon H \rho_\phi$, respectively. We are able to show the global asymptotic dynamics of the model for the exponential potential in a homogeneous and isotropic background. The cosmological implications of the proposed scenarios are explored and it is found that, in addition to the appearance of new equilibrium configurations that do not appear neither in the non-interacting cubic galileon model nor in the interacting quintessence model, there is a significant impact of the non-minimal coupling through modification of the stability properties of the critical points. The resulting cosmological scenario provides a bigbang origin of the cosmic expansion, an early transient stage of inflationary expansion, as well as matter-scaling late time stable state of the universe, among other solutions of lesser cosmological interest. This work extends previous studies of coupled dark energy to a broader class of gravitational theories.