Forced waves for diffusive competition systems in shifting environments

In this paper, we derive the existence of forced waves for diffusive competition systems in shifting environments. First, we derive two different classes of forced waves for a 3-species competition system. Then we obtain forced waves for 2-species competition systems with at least one weak competitor. In all cases, the minimal environmental shifting speeds are determined under the equal diffusivities condition.     

Preparation of mesoporous hematite particles by a forced hydrolysis reaction accompanying a peptide production reaction

The influence of carbodimide (CI), well known as a condensing agent for producing peptides from l-phenylalanine (l-Phe), on the formation of hematite (-Fe₂O₃) particles through a forced hydrolysis reaction of acidic FeCl₃ solution was examined. The large ellipsoidal particles were produced together with needle-like -FeOOH and fine Fe₃O₄ ones in the systems both with l-Phe and CI, though the system only with CI was not essentially changed the particle shape. CI produced the characteristic large ellipsoidal particle accompanying the production of peptides by condensing l-Phe. This behavior was explained by the adsorption of peptides on β-FeOOH and polynuclear (PN) particles; the adsorption of peptides retarded the phase transformation from β-FeOOH to hematite along with the heterogeneous aggregation of PNs, resulting the large ellipsoidal hematite particles. CI reduced Fe³⁺ to Fe²⁺ ions during aging the solution. The decomposition of urea, by-products of peptide formation, produced two kinds of amines to raise the solution pH and provided -FeOOH and Fe₃O₄ particles. The large ellipsoidal hematite particles exhibited large specific surface area and high mesoporosity by adsorption of peptides onto PN particles within the hematite particles. The morphology and inner structure of hematite particles were exceedingly altered by using a reaction of peptide production and this procedure is expected for a new developing method of high-quality porous materials.     

Forced nonlinear oscillations of elastic membranes

An initial-boundary-value problem is considered for the spatially two-dimensional damped Boussinesq equation with a forcing term. The problem in question is argued to serve as a model for describing small nonlinear oscillations of a circular membrane under the influence of acoustic pressure. Eigenfunction expansion method is used for constructing the global-in-time solution of the problem in question. Existence and uniqueness follow from the construction. Long-time asymptotics is computed on the basis of the obtained series representation. Numerical simulations are conducted. The algorithm shows excellent convergence properties.     

Control on shape, porosity and surface hydrophilicity of hematite particles by using polymers

The shape, porosity, and surface hydrophilicity of hematite particles formed from a forced hydrolysis reaction of acidic FeCl₃ solution were controlled by using a trace of polymers (0.001 and 0.003 wt%). The spherical particles were produced on the systems with polyvinyl alcohol (PVA) and polyaspartic acid (PAS). In the case of polyacryl amide (PAAm), slightly small spherical particles were precipitated at 0.003 wt%. However, polyacrylic acid (PAAc) and poly-γ-glutamic acid (PGA) gave ellipsoidal particles. This morphological change on hematite particles depended on the order of functional groups of polymers as –OH<–CONH₂<–COOH<–COOH and ⟩C=O, corresponding to the order in extent of polymer molecules for complexation to Fe³⁺ ions and adsorption onto particle surface. Accompanying this order, the hematite particles produced were changed from less porous to microporous. On the other hand, only the system with 0.003 wt% of PAAm produced mesoporous hematite particles. Choosing the kinds of polymers also controlled the ultramicroporosity and surface hydrophilicity of the particles.     

Desorption kinetics of surfactants at fluid interfaces by novel coaxial capillary pendant drop experiments

Surfactants appear in multiphase fluid systems in which the interface and the adjacent bulk phase have been removed from equilibrium. Here, a new method is described for the measurement of rate constants of desorption of surface-active materials from fluid/fluid interfaces and the extent to which adsorption is reversible: the coaxial capillary pendant drop experimental technique.

Kinetic constants are determined by desorption experiments in pendant drops in which the interface adjacent to a surfactant solution is removed from equilibrium by replacing the subphase of the drop with pure water. Further, we demonstrate that although the rate of subphase exchange is comparatively slow with respect to the desorption timescale, it is possible to resolve desorption processes which occur under local equilibrium with the adjacent bulk phase from those that are determined in part by sorption kinetics. Experiments which measure the desorption kinetic coefficient, , using a homologous series of n-alkyl (C₈, C₁₀, C₁₂, C₁₄) dimethyl phosphine oxides are presented.     

Comments on Reply to Comments on “Non-Darcian Forced Convection Flow of Viscous Dissipating Fluid Over a Flat Plate Embedded in a Porous Medium”

This note is a comment on the reply by Aydin and Kaya (Transp Porous Media (to appear), 2008b) to comments by Rees and Magyari (Transp Porous Media (to appear), 2008) on an article by Aydin and Kaya (Transp Porous Media (to appear), 2008a) concerning the combined effects of viscous dissipation and surface mass flux on the forced convection boundary-layer flow in a saturated porous medium modeled by the Brinkman equation. It is argued that the statements by Rees and Magyari are in fact appropriate. The thermal boundary condition imposed at the edge of the boundary-layer by Aydin and Kaya is incompatible with the energy equation, and thus the results of their paper are inconsistent with the physics of the situation. The attempts of Aydin and Kaya to justify their paper are flawed by an inappropriate assumption and calculations with an insufficiently large parameter.     

Dynamic effects of the power-conversion module in a reciprocating engine

The forced response characteristics of piston, connecting rod and their assembly, henceforth called power-conversion module, is studied subjecting a forced response model of such a module to combustion characteristics in order to investigate clattering noise characteristics brought with compression ignition excitation. Existing research either focused on the piston or the connecting rod solely. As demonstrated by the modal analysis of the whole power-conversion module, it is revealed that the natural frequencies of the entire module dominate the noise-characteristics of clattering noise even when using a linear model. A subsequent parametric study applying different combustion characteristics with different pressure rise rates, but similar peak pressures on the modal-model of the power-conversion module delivered novel insights into the root cause of clattering noise characteristics. Moreover, the approach delivers an amended understanding of disturbing noises occurring in knock control systems of internal combustion engines. The reason for empirically elaborated limits of the maximum cylinder pressure rise rate to achieve smooth engine acoustics, published first in the late 1920s, was revealed.     

End-wall errors in temperature measurement of external convective heat transfer with Moiré deflectometry

Moiré deflectometry is a robust and simple optical method that allows obtaining the temperature field in flows with uniform pressure and two-dimensional and axisymmetric flows. Since in real configurations it is not possible to keep exactly the hypothesis of two-dimensional flow, it is necessary to asses this influence. Therefore this work studies a procedure to estimate the errors due to the end-wall and 3-D effects when Moiré deflectometry is used for measuring the temperature field of an external convective heat transfer flow with free edges.According to the value of the parameter Gr/Re², results show two tendencies. The error in temperature measurement is smaller than 1% for ratios of thermal boundary layer thickness to the test field width lower than 0.4, in turbulent forced convection flows for temperature differences of 40 K. Temperature effects are significative, multiplying the error by two for a temperature difference 50% greater. These results enable researchers to evaluate the errors of this measurement technique associated with the end-wall effect.     

A theoretical analysis of forced convection in a porous-saturated circular tube: Brinkman–Forchheimer model

Fully developed forced convection inside a circular tube filled with saturated porous medium and with uniform heat flux at the wall is investigated on the basis of a Brinkman–Forchheimer model. The matched asymptotic expansion method is applied at small Darcy numbers. For large Darcy numbers, the solution for the Brinkman–Forchheimer momentum equation is found in terms of an asymptotic expansion. Once the velocity distribution is determined, the energy equation is solved using the same asymptotic technique. The results for the two limiting cases of clear fluid and Darcy flow conditions show good agreement with those available in the literature.