Time integration for diffuse interface models for two-phase flow

We propose a variant of the $\theta$-scheme for diffuse interface models for two-phase flow, together with three new linearization techniques for the surface tension. These involve either additional stabilizing force terms, or a fully implicit coupling of the Navier-Stokes and Cahn-Hilliard equation. In the common case that the equations for interface and flow are coupled explicitly, we find a time step restriction which is very different to other two-phase flow models and in particular is independent of the grid size. We also show that the proposed stabilization techniques can lift this time step restriction. Even more pronounced is the performance of the proposed fully implicit scheme which is stable for arbitrarily large time steps. We demonstrate in a Taylor flow application that this superior coupling between flow and interface equation can render diffuse interface models even computationally cheaper and faster than sharp interface models

Diffuse interface models of locally inextensible vesicles in a viscous fluid

We present a new diffuse interface model for the dynamics of inextensible vesicles in a viscous fluid. A new feature of this work is the implementation of the local inextensibility condition in the diffuse interface context. Local inextensibility is enforced by using a local Lagrange multiplier, which provides the necessary tension force at the interface. To solve for the local Lagrange multiplier, we introduce a new equation whose solution essentially provides a harmonic extension of the local Lagrange multiplier off the interface while maintaining the local inextensibility constraint near the interface. To make the method more robust, we develop a local relaxation scheme that dynamically corrects local stretching/compression errors thereby preventing their accumulation. Asymptotic analysis is presented that shows that our new system converges to a relaxed version of the inextensible sharp interface model. This is also verified numerically. Although the model does not depend on dimension, we present numerical simulations only in 2D. To solve the 2D equations numerically, we develop an efficient algorithm combining an operator splitting approach with adaptive finite elements where the Navier-Stokes equations are implicitly coupled to the diffuse interface inextensibility equation. Numerical simulations of a single vesicle in a shear flow at different Reynolds numbers demonstrate that errors in enforcing local inextensibility may accumulate and lead to large differences in the dynamics in the tumbling regime and differences in the inclination angle of vesicles in the tank-treading regime. The local relaxation algorithm is shown to effectively prevent this accumulation by driving the system back to its equilibrium state when errors in local inextensibility arise.Comment: 25 page

Inhibitory control and attentional bias toward stimuli specific to eating disorders in individuals with psychiatric disorder

Käesoleva töö eesmärgiks oli uurida emotsionaalse Go/No-Go katse abil pidurduslikku kontrolli ja tähelepanu kallutatust, mis väljendus reaktsiooniaegades ja distraktorstiimuli vigades (DSV). Go/No-Go katses kasutati toidu ja kehaga seotud emotsionaalset stiimulmaterjali. Valim koosnes 61 uuritavast vanuses 16-44 aastat: 27 psüühikahäirega , 25 tervet ning 9 mineviku psüühikahäirega, kuid hetkel tervet uuritavat. Go/No-Go katse abil ei leitud erinevusi katsegruppide reaktsiooniaegades, kuid distraktorstiimulile tehtud vigades esines oluline erinevus tervete uuritavate ja minevikupsüühikahäirega uuritavate vahel. Saadud tulemus väljendab pidurdusliku kontrolli defitsiiti mineviku psüühikahäirega uuritavate puhul. Depressiooni ning funktsionaalse impulsiivsuse enesekohaste küsimustike tulemused avaldasid vahendavat mõju reaktsiooniaegadele. Katsegrupid erinesid oluliselt enesekohaste hinnangute poolest, kuid reaktsiooniajad grupiti ei erinenud. Kuna kasutati söömishäiretele spetsiifilisi emotsionaalseid stiimuleid, ei pruugi need tekitada teiste psüühikahäirete puhul söömishäiretele sarnast tähelepanu kallutatust

Modelling of two-phase flow with surface active particles

Kolloidpartikel die von zwei nicht mischbaren Fluiden benetzt werden, tendieren dazu sich an der fluiden Grenzfläche aufzuhalten um die Oberflächenspannung zu minimieren. Bei genügender Anzahl solcher Kolloide werden diese zusammengedrückt und lassen die fluide Grenzfläche erstarren. Das gesamte System aus Fluiden und Kolloiden bildet dann eine spezielle Emulsion mit interessanten Eigenschaften. In dieser Arbeit wird ein kontinuum Model für solche Systeme entwickelt, basierend auf den Prinzipien der Massenerhaltung und der themodynamischen Konsistenz. Dabei wird die makroskopische Zwei-Phasen-Strömung durch eine Navier-Stokes Cahn-Hilliard Gleichung modelliert und die mikroskopischen Partikel an der fluiden Grenzfläche durch einen Phase-Field-Crystal Ansatz beschrieben. Zur Evaluation des verwendeten Strömungsmodells wird ein Test verschiedener Navier-Stokes Cahn-Hilliard Modelle anhand eines bekannten Benchmark Szenarios durchgeführt. Die Ergebnisse werden mit denen von anderen Methoden zur Simulation von Zwei-Phasen-Strömungen verglichen. Desweiteren wird eine neue Methode zur Simulation von Zwei-Phasen-Strömungen in komplexen Gebieten vorgestellt. Dabei wird die komplexe Geometrie implizit durch eine Phasenfeldvariable beschrieben, welche die charakteristische Funktion des Gebietes approximiert. Die Strömungsgleichungen werden dementsprechend so umformuliert, dass sie in einem größeren und einfacheren Gebiet gelten, wobei die Randbedingungen implizit durch zusätzliche Quellterme eingebracht werden. Zur Einarbeitung der Oberflächenkolloide in das Strömungsmodell wird schließlich die Variation der freien Energie des Gesamtsystems betrachtet. Dabei wird die Energie der Partikel durch die Phase-Field-Crystal Energie approximiert und die Energie der Oberfläche durch die Ginzburg-Landau Energie. Eine Variation der Gesamtenergie liefert dann die Phase-Field-Crystal Gleichung und die Navier-Stokes Cahn-Hilliard Gleichungen mit zusätzlichen elastischen Spannunngen. Zur Validierung des Ansatzes wird auch eine sharp interface Version der Gleichungen hergeleitet und mit der zuvor hergeleiteten diffuse interface Version abgeglichen. Die Diskretisierung der erhaltenen Gleichungen erfolgt durch Finiten Elemente in Kombination mit einem semi-impliziten Euler Verfahren. Durch numerische Simulationen wird die Anwendbarkeit des Modells gezeigt und bestätigt, dass die oberflächenaktiven Kolloide die fluide Grenzfläche hinreichend steif machen können um externen Kräften entgegenzuwirken und das gesamte System zu stabilisieren.Colloid particles that are partially wetted by two immiscible fluids can become confined to fluidfluid interfaces. At sufficiently high volume fractions, the colloids may jam and the interface may crystallize. The fluids together with the interfacial colloids compose an emulsion with interesting new properties and offer an important route to new soft materials. Based on the principles of mass conservation and thermodynamic consistency, we develop a continuum model for such systems which combines a Cahn-Hilliard-Navier-Stokes model for the macroscopic two-phase fluid system with a surface Phase-Field-Crystal model for the microscopic colloidal particles along the interface. We begin with validating the used flow model by testing different diffuse interface models on a benchmark configuration for a two-dimensional rising bubble and compare the results with reference solutions obtained by other two-phase flow models. Furthermore, we present a new method for simulating two-phase flows in complex geometries, taking into account contact lines separating immiscible incompressible components. In this approach, the complex geometry is described implicitly by introducing a new phase-field variable, which is a smooth approximation of the characteristic function of the complex domain. The fluid and component concentration equations are reformulated and solved in larger regular domain with the boundary conditions being implicitly modeled using source terms. Finally, we derive the thermodynamically consistent diffuse interface model for two-phase flow with interfacial particles by taking into account the surface energy and the energy associated with surface colloids from the surface PFC model. The resulting governing equations are the phase field crystal equations and Navier-Stokes Cahn-Hilliard equations with an additional elastic stress. To validate our approach, we derive a sharp interface model and show agreement with the diffuse interface model. We demonstrate the feasibility of the model and present numerical simulations that confirm the ability of the colloids to make the interface sufficiently rigid to resist external forces and to stabilize interfaces for long times

Simulating Organogenesis in COMSOL: Comparison Of Methods For Simulating Branching Morphogenesis

During organogenesis tissue grows and deforms. The growth processes are controlled by diffusible proteins, so-called morphogens. Many different patterning mechanisms have been proposed. The stereotypic branching program during lung development can be recapitulated by a receptor-ligand based Turing model. Our group has previously used the Arbitrary Lagrangian-Eulerian (ALE) framework for solving the receptor-ligand Turing model on growing lung domains. However, complex mesh deformations which occur during lung growth severely limit the number of branch generations that can be simulated. A new Phase-Field implementation avoids mesh deformations by considering the surface of the modelling domains as interfaces between phases, and by coupling the reaction-diffusion framework to these surfaces. In this paper, we present a rigorous comparison between the Phase-Field approach and the ALE-based simulation

ANALISA PERANCANGAN TATA LETAK FASILITAS PABRIK PADA RUMAH POTONG HEWAN DENGAN MENGGUNAKAN METODE KUALITATIF (ACTIVITY RELATIONSHIP CHART) (STUDI KASUS DI PT. ABATTOIR SURYA JAYA, BENOWO, SURABAYA)

Layout of production facility and work area planning is a problem which often be found in industrialized worlds. Production facility layout played an important role in the efficiency of the production process and the inter-departmental of work in the industrial building. PT. Abattoir Surya Jaya is standart operasional produksi blast freezer. The production process should be in accordance with the rrdinance is line flow system. ARC (Activity Relationship Chart) is a simple technique in planning the layout of the facility or Department based on the degree of activity relationship which is often expressed in qualitative assessment and tend to be based on considerations of the subjective judgement of each Department. Using ARC (Activity Relationship Chart) method, production units in PT. Abattoir Surya Jaya, can save distance 31 m from the initial conditions, can save broad work area for 26 m2 from initial condition. Production lasting optimal because production room have been arranged according to production operational standard ( Line Flow)

A phase-field model for active contractile surfaces

The morphogenesis of cells and tissues involves an interplay between chemical signals and active forces on their surrounding surface layers. The complex interaction of hydrodynamics and material flows on such active surfaces leads to pattern formation and shape dynamics which can involve topological transitions, for example during cell division. To better understand such processes requires novel numerical tools. Here, we present a phase-field model for an active deformable surface interacting with the surrounding fluids. The model couples hydrodynamics in the bulk to viscous flow along the diffuse surface, driven by active contraction of a surface species. As a new feature in phase-field modeling, we include the viscosity of a diffuse interface and stabilize the interface profile in the Stokes-Cahn-Hilliard equation by an auxiliary advection velocity, which is constant normal to the interface. The method is numerically validated with previous results based on linear stability analysis. Further, we highlight some distinct features of the new method, like the avoidance of re-meshing and the inclusion of contact mechanics, as we simulate the self-organized polarization and migration of a cell through a narrow channel. Finally, we study the formation of a contractile ring on the surface and illustrate the capability of the method to resolve topological transitions by a first simulation of a full cell division

MOLECULAR DOCKING STUDY ON 1H-(3,4d) PYRAZOLO-PYRIMIDINES AS CYCLIN DEPENDANT KINASE (CDK2) INHIBITORS

Objective: CDK2 inhibitors are implicated in several carcinomas viz. Carcinoma of lung, bladder, sarcomas and retinoblastoma. Pyrazolopyrimidines, being purine bioisosters inhibit more than one type of kinase. In this study, we are studying some novel derivatives of 1H-pyrazolo [3,4d] pyrimidines not reported earlier. The objective of the present study is an attempt towards design and development of 1H-[3,4-] pyrazolo-pyrimidines as CDK2 inhibitors through rational drug design.Methods: The present study has been done on CDK2 structure, PDB ID, 3WBL, co-crystallized with ligand PDY from RCSB protein data bank. A series of seventeen 1H-Pyrazolo [3,4-d] pyrimidines feasible for synthesis was docked on the said CDK2 receptor using Auto Dock 4 version, 1.5.6. Outputs were exported to discovery studio 3.5 client for visual inspection of the binding modes and interactions of the compounds with amino acid residues in the active sites.Results: The results of docking studies revealed that the present series of 1H-Pyrazolo[3,4-d] pyrimidines is showing significant binding through hydrogen bonding, hydrophobic, pi and Van der waals interactions, similar to the ligand PDY. Some conserved H-bond interactions comparable to bioisosters and compounds presently under human trials were noted. Ki values predicted in silico also suggest that the series will show promising CDK2 inhibitory activity.Conclusion: The series designed and docked can be further developed by synthesis and in vitro and in vivo activity. The receptor inhibitory activity can also be checked by specific receptor assays