221 research outputs found
Nonlinear cellular instabilities of planar premixed flames: numerical simulations of the Reactive Navier-Stokes equations
Two-dimensional compressible Reactive Navier-Stokes numerical simulations of intrinsic planar, premixed flame instabilities are performed. The initial growth of a sinusoidally perturbed planar flame is first compared with the predictions of a recent exact linear stability analysis, and it is shown the analysis provides a necessary but not sufficient test problem for validating numerical schemes intended for flame simulations. The long-time nonlinear evolution up to the final nonlinear stationary cellular flame is then examined for numerical domains of increasing width. It is shown that for routinely computationally affordable domain widths, the evolution and final state is, in general, entirely dependent on the width of the domain and choice of numerical boundary conditions. It is also shown that the linear analysis has no relevance to the final nonlinear cell size. When both hydrodynamic and thermal-diffusive effects are important, the evolution consists of a number of symmetry breaking cell splitting and re-merging processes which results in a stationary state of a single very asymmetric cell in the domain, a flame shape which is not predicted by weakly nonlinear evolution equations. Resolution studies are performed and it is found that lower numerical resolutions, typical of those used in previous works, do not give even the qualitatively correct solution in wide domains. We also show that the long-time evolution, including whether or not a stationary state is ever achieved, depends on the choice of the numerical boundary conditions at the inflow and outflow boundaries, and on the numerical domain length and flame Mach number for the types of boundary conditions used in some previous works
Linear stability of planar premixed flames: reactive Navier-Stokes equations with finite activation energy and arbitrary Lewis number
A numerical shooting method for performing linear stability analyses of travelling waves is described and applied to the problem of freely propagating planar premixed flames. Previous linear stability analyses of premixed flames either employ high activation temperature asymptotics or have been performed numerically with finite activation temperature, but either for unit Lewis numbers (which ignores thermal-diffusive effects) or in the limit of small heat release (which ignores hydrodynamic effects). In this paper the full reactive Navier-Stokes equations are used with arbitrary values of the parameters (activation temperature, Lewis number, heat of reaction, Prandtl number), for which both thermal-diffusive and hydrodynamic effects on the instability, and their interactions, are taken into account. Comparisons are made with previous asymptotic and numerical results. For Lewis numbers very close to or above unity, for which hydrodynamic effects caused by thermal expansion are the dominant destablizing mechanism, it is shown that slowly varying flame analyses give qualitatively good but quantitatively poor predictions, and also that the stability is insensitive to the activation temperature. However, for Lewis numbers sufficiently below unity for which thermal-diffusive effects play a major role, the stability of the flame becomes very sensitive to the activation temperature. Indeed, unphysically high activation temperatures are required for the high activation temperature analysis to give quantitatively good predictions at such low Lewis numbers. It is also shown that state-insensitive viscosity has a small destabilizing effect on the cellular instability at low Lewis numbers
Π€ΠΎΡΠΌΠΈΡΠΎΠ²Π°Π½ΠΈΠ΅ ΠΏΡΠ΅Π΄ΠΏΡΠΈΠ½ΠΈΠΌΠ°ΡΠ΅Π»ΡΡΠΊΠΈΡ ΡΠΌΠ΅Π½ΠΈΠΉ ΡΡΡΠ΄Π΅Π½ΡΠΎΠ² ΠΈΠ½ΠΆΠ΅Π½Π΅ΡΠ½ΠΎΠ³ΠΎ Π²ΡΠ·Π°
ΠΡΠ΅Π΄ΡΡΠ°Π²Π»Π΅Π½Π° ΠΌΠ΅ΡΠΎΠ΄ΠΈΠΊΠ° ΡΠΎΡΠΌΠΈΡΠΎΠ²Π°Π½ΠΈΡ ΠΏΡΠ΅Π΄ΠΏΡΠΈΠ½ΠΈΠΌΠ°ΡΠ΅Π»ΡΡΠΊΠΈΡ
ΡΠΌΠ΅Π½ΠΈΠΉ ΡΡΡΠ΄Π΅Π½ΡΠΎΠ² ΠΈΠ½ΠΆΠ΅Π½Π΅ΡΠ½ΠΎΠ³ΠΎ Π²ΡΠ·Π° Π½Π° ΠΎΡΠ½ΠΎΠ²Π΅ ΠΏΡΠ°ΠΊΡΠΈΠΊΠΎ-ΠΎΡΠΈΠ΅Π½ΡΠΈΡΠΎΠ²Π°Π½Π½ΠΎΠΉ ΠΏΠΎΠ΄Π³ΠΎΡΠΎΠ²ΠΊΠΈ, ΡΠΏΠΎΡΠΎΠ±ΡΡΠ²ΡΡΡΠ΅ΠΉ Π²Π½Π΅Π΄ΡΠ΅Π½ΡΠ΅ΡΠΊΠΎΠΉ Π΄Π΅ΡΡΠ΅Π»ΡΠ½ΠΎΡΡΠΈ ΠΈΠ½ΠΆΠ΅Π½Π΅ΡΠ° Π² ΡΠΎΠ²ΡΠ΅ΠΌΠ΅Π½Π½ΡΡ
ΡΡΠ»ΠΎΠ²ΠΈΡΡ
. ΠΡΠΎΠ²Π΅Π΄Π΅Π½ Π°Π½Π°Π»ΠΈΠ· ΡΠΎΡΡΠΎΡΠ½ΠΈΡ ΠΏΡΠΎΠ±Π»Π΅ΠΌΡ ΡΠΎΡΠΌΠΈΡΠΎΠ²Π°Π½ΠΈΡ ΠΏΡΠ΅Π΄ΠΏΡΠΈΠ½ΠΈΠΌΠ°ΡΠ΅Π»ΡΡΠΊΠΈΡ
ΡΠΌΠ΅Π½ΠΈΠΉ Π² Π ΠΎΡΡΠΈΠΈ. ΠΠΏΡΠ΅Π΄Π΅Π»Π΅Π½Ρ ΠΏΠ΅Π΄Π°Π³ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΈΠ΅ ΡΡΠ»ΠΎΠ²ΠΈΡ, ΡΠΏΠΎΡΠΎΠ±ΡΡΠ²ΡΡΡΠΈΠ΅ ΡΠΎΡΠΌΠΈΡΠΎΠ²Π°Π½ΠΈΡ Π³ΠΎΡΠΎΠ²Π½ΠΎΡΡΠΈ ΡΡΡΠ΄Π΅Π½ΡΠΎΠ² ΡΠ΅Ρ
Π½ΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΡΠ½ΠΈΠ²Π΅ΡΡΠΈΡΠ΅ΡΠ° ΠΊ ΠΊΠΎΠΌΠΏΠ»Π΅ΠΊΡΠ½ΠΎΠΉ ΠΈΠ½ΠΆΠ΅Π½Π΅ΡΠ½ΠΎΠΉ Π΄Π΅ΡΡΠ΅Π»ΡΠ½ΠΎΡΡΠΈ. Π‘ΡΠΎΡΠΌΡΠ»ΠΈΡΠΎΠ²Π°Π½ΠΎ ΠΏΠΎΠ½ΡΡΠΈΠ΅ ΠΏΡΠ΅Π΄ΠΏΡΠΈΠ½ΠΈΠΌΠ°ΡΠ΅Π»ΡΡΠΊΠΎΠΉ ΠΊΠΎΠΌΠΏΠ΅ΡΠ΅Π½ΡΠΈΠΈ ΠΈΠ½ΠΆΠ΅Π½Π΅ΡΠ°. ΠΠ±ΠΎΡΠ½ΠΎΠ²Π°Π½ΠΎ ΡΡΡΠ΅ΠΊΡΠΈΠ²Π½ΠΎΠ΅ ΠΏΡΠΈΠΌΠ΅Π½Π΅Π½ΠΈΠ΅ ΠΌΠ΅ΡΠΎΠ΄Π° ΠΏΡΠΎΠ΅ΠΊΡΠΎΠ² Π΄Π»Ρ ΡΠΎΡΠΌΠΈΡΠΎΠ²Π°Π½ΠΈΡ ΠΏΡΠ΅Π΄ΠΏΡΠΈΠ½ΠΈΠΌΠ°ΡΠ΅Π»ΡΡΠΊΠΈΡ
ΡΠΌΠ΅Π½ΠΈΠΉ ΡΡΡΠ΄Π΅Π½ΡΠΎΠ² ΠΈΠ½ΠΆΠ΅Π½Π΅ΡΠ½ΠΎΠ³ΠΎ Π²ΡΠ·Π°. ΠΡΠ΅Π΄ΡΡΠ°Π²Π»Π΅Π½Π° ΠΌΠΎΠ΄Π΅Π»Ρ ΡΠΎΡΠΌΠΈΡΠΎΠ²Π°Π½ΠΈΡ ΠΏΡΠ΅Π΄ΠΏΡΠΈΠ½ΠΈΠΌΠ°ΡΠ΅Π»ΡΡΠΊΠΈΡ
ΡΠΌΠ΅Π½ΠΈΠΉ ΡΡΡΠ΄Π΅Π½ΡΠΎΠ² ΠΈΠ½ΠΆΠ΅Π½Π΅ΡΠ½ΠΎΠ³ΠΎ Π²ΡΠ·Π° Ρ ΡΡΠ΅ΡΠΎΠΌ ΠΏΡΠΎΠ΅ΠΊΡΠ½ΠΎΠΉ Π΄Π΅ΡΡΠ΅Π»ΡΠ½ΠΎΡΡΠΈ ΠΈΠ½ΠΆΠ΅Π½Π΅ΡΠ°.The developing methods of entrepreneurial competences of engineering students, based on the practice-oriented training to encourage an implemental activity of an engineer in the modern context has been presented in the report. The analysis of the problem of entrepreneurial competencies development in Russia has been carried out. The pedagogical conditions encouraging the commitment of the technical university students for an integrated engineering activity has been defined. The concept of entrepreneurial competencies of an engineer has been stated. An effective appliance of project methods to develop entrepreneurial competences of the engineering university students has been proved. There has been presented the development model of entrepreneurial competences of engineering students
Stability of Relativistic Matter with Magnetic Fields for Nuclear Charges up to the Critical Value
We give a proof of stability of relativistic matter with magnetic fields all
the way up to the critical value of the nuclear charge .Comment: LaTeX2e, 12 page
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Delimitation and Possible Eradication or Control of the Apple Maggot (Rhagoletis Pomonella) in the Umatilla County, Oregon, 2008
ΠΠΊΠ»Π°Π΄ ΠΎΡΠ΅ΡΠ΅ΡΡΠ²Π΅Π½Π½ΡΡ Π»Π΅Π΄ΠΎΠΊΠΎΠ»ΠΎΠ² Π² ΠΎΡΠ²ΠΎΠ΅Π½ΠΈΠ΅ ΠΡΠΊΡΠΈΠΊΠΈ
The longitudinal carrier density distribution of an InGaAlAs high-power broad-area semiconductor laser has been measured using spontaneous emission from the side of the device. The laser shows continuously increasing carrier densities on the facet with the high reflectivity coating (reverse facet). This has a major impact on the efficiency and the lifetime of the laser. This behavior is in good agreement with one-dimensional calculations for the longitudinal carrier distribution
Localization and activity of the calcineurin catalytic and regulatory subunit complex at the septum is essential for hyphal elongation and proper septation in Aspergillus fumigatus: Analysis of the calcineurin complex in Aspergillus fumigatus
Calcineurin, a heterodimer composed of the catalytic (CnaA) and regulatory (CnaB) subunits, plays key roles in growth, virulence, and stress responses of fungi. To investigate the contribution of CnaA and CnaB to hyphal growth and septation, ΞcnaB and ΞcnaA ΞcnaB strains of A. fumigatus were constructed. CnaA co-localizes to the contractile actin ring early during septation and remains at the center of the mature septum. While CnaB's septal localization is CnaA-dependent, CnaA's septal localization is CnaB-independent but CnaB is required for CnaA's function at the septum. Catalytic null mutations in CnaA caused stunted growth despite septal localization of the calcineurin complex, indicating the requirement of calcineurin activity at the septum. Compared to the ΞcnaA and ΞcnaB strains, the ΞcnaA ΞcnaB strain displayed more defective growth and aberrant septation. While three Ca2+-binding motifs in CnaB were sufficient for its association with CnaA at the septum, the amino-terminal arginine-rich domains (16-RRRR-19 and 44-RLRKR-48) are dispensable for septal localization, yet required for complete functionality. Mutation of the 51-KLDK-54 motif in CnaB causes its mislocalization from the septum to the nucleus, suggesting it is a nuclear export signal sequence. These findings confirm a cooperative role for calcineurin complex in regulating hyphal growth and septation
Plasma Membrane Localization Is Required for RasA-Mediated Polarized Morphogenesis and Virulence of Aspergillus fumigatus
ABSTRACT Ras is a highly conserved GTPase protein that is essential for proper polarized morphogenesis of filamentous fungi. Localization of Ras proteins to the plasma membrane and endomembranes through posttranslational addition of farnesyl and palmitoyl residues is an important mechanism through which cells provide specificity to Ras signal output. Although the Aspergillus fumigatus RasA protein is known to be a major regulator of growth and development, the membrane distribution of RasA during polarized morphogenesis and the role of properly localized Ras signaling in virulence of a pathogenic mold remain unknown. Here we demonstrate that Aspergillus fumigatus RasA localizes primarily to the plasma membrane of actively growing hyphae. We show that treatment with the palmitoylation inhibitor 2-bromopalmitate disrupts normal RasA plasma membrane association and decreases hyphal growth. Targeted mutations of the highly conserved RasA palmitoylation motif also mislocalized RasA from the plasma membrane and led to severe hyphal abnormalities, cell wall structural changes, and reduced virulence in murine invasive aspergillosis. Finally, we provide evidence that proper RasA localization is independent of the Ras palmitoyltransferase homolog, encoded by erfB , but requires the palmitoyltransferase complex subunit, encoded by erfD . Our results demonstrate that plasma membrane-associated RasA is critical for polarized morphogenesis, cell wall stability, and virulence in A. fumigatus
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