A free-energy stable nodal discontinuous Galerkin approximation with summation-by-parts property for the Cahn-Hilliard equation

We present a nodal Discontinuous Galerkin (DG) scheme for the Cahn-Hilliard equation that satisfies the summation-by-parts simultaneous-approximation-term (SBP-SAT) property. The latter permits us to show that the discrete free-energy is bounded, and as a result, the scheme is provably stable. The scheme and the stability proof are presented for general curvilinear three-dimensional hexahedral meshes. We use the Bassi-Rebay 1 (BR1) scheme to compute interface fluxes, and an IMplicit-EXplicit (IMEX) scheme to integrate in time. Lastly, we test the theoretical findings numerically and present examples for two and three-dimensional problems

Anaerobic Digestion of Microalga Chlorella protothecoides and Metagenomic Analysis of Reddish-Colored Digestate

ABSTRACT: Microalga Chlorella protothecoides materials were assessed as substrates for anaerobic digestion (AD) aiming at the simultaneous production of biogas/methane and pigments: whole autotrophic (AA) and heterotrophic algae (H); extracted heterotrophic microalgae from lipid production (HExt); and pretreated heterotrophic microalgae through enzymatic (HPEnz), autoclave (HPA), and ultrasound (HPU) processes. AA was more suitable for AD than H, as it was more efficiently converted into methane (279 vs. 180 L CH4/kg VSin). In comparison, the pretreatment of heterotrophic microalgae had a positive effect on AD, with registered methane yield increases from 263 to 290 L CH4/kg VSin (HPU, HPA, HExt). Reddish pigmentation developed in H and HPU units due to the presence of purple non-sulfur bacteria (PNSB). This phenomenon and the changes in microbiota structure during AD were confirmed by metagenomic analysis. At the end of the process, the relative abundance of Clostridiales and Bacillales increased, enhancing the hydrolysis of compounds in acetate. Consistently, Methanosaeta became the comparatively dominant methanogen, meaning that methane was produced through the acetoclastic methanogenesis pathway. The obtained results indicate for AD biorefinery feasibility-regarding the simultaneous production of biogas/methane-a digestate flow and pigments (bacteriochlorophyll a and carotenoids).info:eu-repo/semantics/publishedVersio

Entropy-stable discontinuous Galerkin approximation with summation-by-parts property for the incompressible Navier-Stokes equations with variable density and artificial compressibility

We present a provably stable discontinuous Galerkin spectral element method for the incompressible Navier-Stokes equations with artificial compressibility and variable density. Stability proofs, which include boundary conditions, that follow a continuous entropy analysis are provided. We define a mathematical entropy function that combines the traditional kinetic energy and an additional energy term for the artificial compressiblity, and derive its associated entropy conservation law. The latter allows us to construct a provably stable split-form nodal Discontinuous Galerkin (DG) approximation that satisfies the summation-by-parts simultaneous-approximation-term (SBP-SAT) property. The scheme and the stability proof are presented for general curvilinear three-dimensional hexahedral meshes. We use the exact Riemann solver and the Bassi-Rebay 1 (BR1) scheme at the inter-element boundaries for inviscid and viscous fluxes respectively, and an explicit low storage Runge-Kutta RK3 scheme to integrate in time. We assess the accuracy and robustness of the method by solving the Kovasznay flow, the inviscid Taylor-Green vortex, and the Rayleigh-Taylor instability

Pretreatments applied to microalgae residues to enhance anaerobic digestion

ABSTRACT: Biomass of microalga Chlorella protothecoides, grown under autotrophic and heterotrophic conditions and subjected to pretreatments, were energetically valorized through anaerobic digestion process according to the substrates: autotrophic algae (A), heterotrophic algae (H), heterotrophic algae extracted (HE), autoclave pretreated heterotrophic algae (HPA), enzyme pretreated heterotrophic algae (HPE), ultrasound pretreated heterotrophic algae (HPU), and inoculum (I). Despite the application of pretreatments, the highest methane production was obtained in the algae extracted digestion with 172 mL CH4, against 153, 126 and 142 mL obtained in HPA, HPE and HPU, respectively. The COD removal capacity was higher in the HPA sample while the TS and VS removal reached higher values in the autotrophic alga.N/

Formaciones de "Antirrhinum majus" en los territorios hispalenses

Stands of Antirrhinum majus in the Hispalense sectorPalabras clave. Asociación, sintaxonomia, corología, sur Península Ibérica, Echio boissieri-Antirrhinetum majii.Key words. Association, syntaxonomy, chorology, south of the Iberian Peninsula, Echio boissieri-Antirrhinetum majii

Photometric study of three ultrashort-period contact binaries

We carried out high-precision photometric observations of three eclipsing ultrashort-period contact binaries (USPCBs). Theoretical models were fitted to the light curves by means of the Wilson-Devinney code. The solutions suggest that the three targets have evolved to a contact phase. The photometric results are as follows: (a) 1SWASP J030749.87−365201.7, q= 0.439 ± 0.003 , f= 0.0 ± 3.6 % ; (b) 1SWASP J213252.93−441822.6, q= 0.560 ± 0.003 , f= 14.2 ± 1.9 % ; (c) 1SWASP J200059.78+054408.9, q= 0.436 ± 0.008 , f= 58.4 ± 1.8 %. The light curves show O’Connell effects, which can be modeled by the assumed cool spots. The cool spots models are strongly supported by the night-to-night variations in the I-band light curves of 1SWASP J030749.87−365201.7. For a comparative study, we collected the whole set of 28 well-studied USPCBs with P 50 %). Generally, contact binaries with deep fill-out factors are going to merge, but it is believed that USPCBs have just evolved to a contact phase. Hence, the deep USPCB 1SWASP J200059.78+054408.9 seems to be a contradiction, making it very interesting. Particularly, 1SWASP J030749.87−365201.7 is a zero contact binary in thermal equilibrium, implying that it should be a turn-off sample as predicted by the thermal relaxation oscillation (TRO) theory.Fil: Liu, L.. Chinese Academy of Sciences; República de ChinaFil: Qian, S. B.. Chinese Academy of Sciences; República de ChinaFil: Fernandez Lajus, Eduardo Eusebio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Essam, A.. National Research Institute of Astronomy and Geophysics; EgiptoFil: El Sadek, M. A.. National Research Institute of Astronomy and Geophysics; EgiptoFil: Xiong, X.. Chinese Academy of Sciences; República de Chin

Photometric study of three ultrashort-period contact binaries

We carried out high-precision photometric observations of three eclipsing ultrashort-period contact binaries (USPCBs). Theoretical models were fitted to the light curves by means of the Wilson-Devinney code. The solutions suggest that the three targets have evolved to a contact phase. The photometric results are as follows: (a) 1SWASP J030749.87−365201.7, q= 0.439 ± 0.003 , f= 0.0 ± 3.6 % ; (b) 1SWASP J213252.93−441822.6, q= 0.560 ± 0.003 , f= 14.2 ± 1.9 % ; (c) 1SWASP J200059.78+054408.9, q= 0.436 ± 0.008 , f= 58.4 ± 1.8 %. The light curves show O’Connell effects, which can be modeled by the assumed cool spots. The cool spots models are strongly supported by the night-to-night variations in the I-band light curves of 1SWASP J030749.87−365201.7. For a comparative study, we collected the whole set of 28 well-studied USPCBs with P 50 %). Generally, contact binaries with deep fill-out factors are going to merge, but it is believed that USPCBs have just evolved to a contact phase. Hence, the deep USPCB 1SWASP J200059.78+054408.9 seems to be a contradiction, making it very interesting. Particularly, 1SWASP J030749.87−365201.7 is a zero contact binary in thermal equilibrium, implying that it should be a turn-off sample as predicted by the thermal relaxation oscillation (TRO) theory.Instituto de Astrofísica de La Plat

Photometric study of three ultrashort-period contact binaries

We carried out high-precision photometric observations of three eclipsing ultrashort-period contact binaries (USPCBs). Theoretical models were fitted to the light curves by means of the Wilson-Devinney code. The solutions suggest that the three targets have evolved to a contact phase. The photometric results are as follows: (a) 1SWASP J030749.87−365201.7, q= 0.439 ± 0.003 , f= 0.0 ± 3.6 % ; (b) 1SWASP J213252.93−441822.6, q= 0.560 ± 0.003 , f= 14.2 ± 1.9 % ; (c) 1SWASP J200059.78+054408.9, q= 0.436 ± 0.008 , f= 58.4 ± 1.8 %. The light curves show O’Connell effects, which can be modeled by the assumed cool spots. The cool spots models are strongly supported by the night-to-night variations in the I-band light curves of 1SWASP J030749.87−365201.7. For a comparative study, we collected the whole set of 28 well-studied USPCBs with P 50 %). Generally, contact binaries with deep fill-out factors are going to merge, but it is believed that USPCBs have just evolved to a contact phase. Hence, the deep USPCB 1SWASP J200059.78+054408.9 seems to be a contradiction, making it very interesting. Particularly, 1SWASP J030749.87−365201.7 is a zero contact binary in thermal equilibrium, implying that it should be a turn-off sample as predicted by the thermal relaxation oscillation (TRO) theory.Instituto de Astrofísica de La Plat