arXiv subjects

V. Berejnov

Publications and source records attributed to V. Berejnov.

8 recordsLinked to original sources

arXiv2025

Continuous Recovery of Phase from Single Interferogram

A new method for phase recovery from a single two-beam interferogram is presented. Conventional approaches, relying on trigonometric inversion followed by phase unfolding and unwrapping, are hindered by discontinuities typically addressed through intricate algorithms. Our method bypasses the unfolding and unwrapping, instead formulating a first-order differential equation directly relating the phase to the interferogram. Integration of this equation enables continuous retrieval of phase along any straight path. Representing a new class of analytical tools for single-interferogram phase retrieval, this approach is derived from first principles and accommodates both Newton-type and Fizeau-type interferograms. Its performance is demonstrated on multiple idealized synthetic interferograms of increasing complexity, validating against the known seed phase.

physics.optics↗

arXiv2024

A new direct method of continuous unwrapping phase from a single interferogram

A new method recovers the phase difference of interfering wavefronts from a pattern of interference fringes, avoiding the phase discontinuity problem. The method relies on the numerical solution of one-dimensional first-order ordinary differential equations. The solution of each equation allows to compute a corresponding cross section of the two-dimensional phase, leading to the effective recovery of the phase surface. The unwrapping procedure can be performed in each orthogonal direction.

physics.optics↗

arXiv2024

A direct method of continuous unwrapping the phase from an interferogram image

A new method recovers phase difference of interfering wavefronts from a pattern of interference fringes, avoiding discontinuity problem. The continuous phase is a solution of the first order differential equation of the interferogram function computed from the fringe intensity profile selected along the pathway over the interferogram.

physics.data-an↗

arXiv2010

A simple method of measuring profiles of thin liquid films for microfluidics experiments by means of interference reflection microscopy

A simple method was developed to observe the interference patterns of the light reflected by the interfaces of thin liquid films. Employing a fluorescent microscope with epi-illumination, we collected the 2D patterns of interference fringes containing information of the liquid film topography at microscale. To demonstrate the utility of the proposed visualization method we developed a framework for reconstructing the profiles of liquid films by analysing the reflected interferograms numerically. Both the visualization and reconstruction methods should be useful for variety of microfluidic applications involving the flows with droplets and bubbles in which the knowledge of the topography of the interfacial liquid film is critical.

physics.optics↗

arXiv2008

A Microfluidic Pore Network Approach to Investigate Water Transport in Fuel Cell Porous Transport Layers

Pore network modelling has traditionally been used to study displacement processes in idealized porous media related to geological flows, with applications ranging from groundwater hydrology to enhanced oil recovery. Very recently, pore network modelling has been applied to model the gas diffusion layer (GDL) of a polymer electrolyte membrane (PEM) fuel cell. Discrete pore network models have the potential to elucidate transport phenomena in the GDL with high computational efficiency, in contrast to continuum or molecular dynamics modelling that require extensive computational resources. However, the challenge in studying the GDL with pore network modelling lies in defining the network parameters that accurately describe the porous media as well as the conditions of fluid invasion that represent realistic transport processes. In this work, we discuss the first stage of developing and validating a GDL-representative pore network model. We begin with a two-dimensional pore network model with a single mobile phase invading a hydrophobic media, whereby the slow capillary dominated flow process follows invasion percolation. Pore network geometries are designed, and transparent hydrophobic microfluidic networks are fabricated from silicon elastomer PDMS using a soft lithography technique. These microfluidic networks are designed to have channel size distributions and wettability properties of typical GDL materials. Comparisons between the numerical and experimental flow patterns show reasonable agreement. Furthermore, the fractal dimension and saturation are measured during invasion, revealing different operating regimes that can be applied to GDL operation. Future work for model development will also be discussed.

physics.flu-dyn↗

arXiv2007

Comment on "Self-Running Droplet: Emergence of Regular Motion from Nonequilibrium Noise"

In a recent Letter (Y. Sumino et al., PRL 94, 068301 (2005)) a spontaneous motion of an oil droplet in the surrounding aqueous media along a glass surface was reported. The authors suggested that the self-locomotion is driven by a difference in wettability between the front and the rear of a droplet sustained by its translational motion. We disagree with the author's explanations. We analyzed the supplementary materials provided by Sumino et al. and found that their data did not support their conclusions. We provide an interpretation of the experimental data of Sumino et al. and the underlying physical mechanism of the self-locomotion.

physics.flu-dyn↗

arXiv2003

Measurements of Protein-Protein Interactions by Size Exclusion Chromatography

A method is presented for determining second virial coefficients B_2 of protein solutions from retention time measurements in size exclusion chromatography (SEC). We determine B_2 by analyzing the concentration dependance of the chromatographic partition coefficient. We show the ability of this method to track the evolution of B_2 from positive to negative values in lysozyme and bovine serum albumin solutions. Our SEC results agree quantitatively with data obtained by light scattering.

cond-mat.soft↗

arXiv2001

Interaction of two deformable viscous drops under external temperature gradient

The axisymmetric deformation and motion of interacting droplets in an imposed temperature gradient is considered using boundary-integral techniques for slow viscous motion. Results showing temporal drop motion, deformations and separation are presented for equal-viscosity fluids. The focus is on cases when the drops are of equal radii or when the smaller drop trails behind the larger drop. For equal-size drops, our analysis shows that the motion of a leading drop is retarded while the motion of the trailing one is enchanced compared to the undeformable case. The distance between the centers of equal-sized deformable drops decreases with time. When a small drop follows a large one, two patterns of behavior may exist. For moderate or large initial separation the drops separate. However, if the initial separation is small there is a transient period in which the separation distance initially decreases and only afterwards the drops separate. This behavior stems from the multiple time scales that exist in the system.

physics.flu-dyn↗