Modeling the combined effect of surface roughness and shear rate on slip flow of simple fluids

Molecular dynamics (MD) and continuum simulations are carried out to investigate the influence of shear rate and surface roughness on slip flow of a Newtonian fluid. For weak wall-fluid interaction energy, the nonlinear shear-rate dependence of the intrinsic slip length in the flow over an atomically flat surface is computed by MD simulations. We describe laminar flow away from a curved boundary by means of the effective slip length defined with respect to the mean height of the surface roughness. Both the magnitude of the effective slip length and the slope of its rate-dependence are significantly reduced in the presence of periodic surface roughness. We then numerically solve the Navier-Stokes equation for the flow over the rough surface using the rate-dependent intrinsic slip length as a local boundary condition. Continuum simulations reproduce the behavior of the effective slip length obtained from MD simulations at low shear rates. The slight discrepancy between MD and continuum results at high shear rates is explained by examination of the local velocity profiles and the pressure distribution along the wavy surface. We found that in the region where the curved boundary faces the mainstream flow, the local slip is suppressed due to the increase in pressure. The results of the comparative analysis can potentially lead to the development of an efficient algorithm for modeling rate-dependent slip flows over rough surfaces.Comment: 32 pages, 14 figure

The effective slip length and vortex formation in laminar flow over a rough surface

The flow of viscous incompressible fluid over a periodically corrugated surface is investigated numerically by solving the Navier-Stokes equation with the local slip and no-slip boundary conditions. We consider the effective slip length which is defined with respect to the level of the mean height of the surface roughness. With increasing corrugation amplitude the effective no-slip boundary plane is shifted towards the bulk of the fluid, which implies a negative effective slip length. The analysis of the wall shear stress indicates that a flow circulation is developed in the grooves of the rough surface provided that the local boundary condition is no-slip. By applying a local slip boundary condition, the center of the vortex is displaced towards the bottom the grooves and the effective slip length increases. When the intrinsic slip length is larger than the corrugation amplitude, the flow streamlines near the surface are deformed to follow the boundary curvature, the vortex vanishes, and the effective slip length saturates to a constant value. Inertial effects promote vortex flow formation in the grooves and reduce the effective slip length.Comment: 32 pages, 14 figure

Slip boundary conditions for shear flow of polymer melts past atomically flat surfaces

Molecular dynamics simulations are carried out to investigate the dynamic behavior of the slip length in thin polymer films confined between atomically smooth thermal surfaces. For weak wall-fluid interactions, the shear rate dependence of the slip length acquires a distinct local minimum followed by a rapid growth at higher shear rates. With increasing fluid density, the position of the local minimum is shifted to lower shear rates. We found that the ratio of the shear viscosity to the slip length, which defines the friction coefficient at the liquid/solid interface, undergoes a transition from a nearly constant value to the power law decay as a function of the slip velocity. In a wide range of shear rates and fluid densities, the friction coefficient is determined by the product of the value of surface induced peak in the structure factor and the contact density of the first fluid layer near the solid wall.Comment: 27 pages, 11 figure

Developing a neural network model to monitor and predict waiting times in the emergency department

In parallel with manufacturing context, quality control toward provided services in service organisations have been growing as well including healthcare industry, but often models of healthcare service quality face challenges in measuring quality. The developed meta-algorithm and ANN models in this thesis can facilitate measuring service quality in Healthcare industry

Molecular dynamics simulations of oscillatory Couette flows with slip boundary conditions

The effect of interfacial slip on steady-state and time-periodic flows of monatomic liquids is investigated using non-equilibrium molecular dynamics simulations. The fluid phase is confined between atomically smooth rigid walls, and the fluid flows are induced by moving one of the walls. In steady shear flows, the slip length increases almost linearly with shear rate. We found that the velocity profiles in oscillatory flows are well described by the Stokes flow solution with the slip length that depends on the local shear rate. Interestingly, the rate dependence of the slip length obtained in steady shear flows is recovered when the slip length in oscillatory flows is plotted as a function of the local shear rate magnitude. For both types of flows, the friction coefficient at the liquid-solid interface correlates well with the structure of the first fluid layer near the solid wall.Comment: 31 pages, 11 figure

Developments of the Interim Order of the International Court of Justice: From Precaution to Protection, The case of the Gambia v. Myanmar 2020

The International Court of Justice (ICJ), the institution for resolving disputes between states, issues an interim injunction in accordance with its mandate in specific circumstances at the request of each party. It owes its mandate, in accordance with the Charter of the United Nations, to the application of international law and the attainment of the purposes of the Charter, where necessary. The issuance of orders and the determination of interim measures are based on the criteria of urgency, necessity, irreparable damage and insane competence. The main question of the present case is how the Court of Justice issued its interim injunction in the case of the application of the Convention on the Prevention and Punishment of the Crime of Genocide (Gambia v. Myanmar) on 23 January 2020 and what changes in the type of obligations arising from the interim injunctions Created on human rights? By expanding its jurisdiction, the Court has paid more attention to human rights issues and has contributed to the human-centered development of international law. Examining the interim order of the Court in this case, it can be seen that the approach of the Court in issuing an interim order in the field of human rights has changed from a precautionary aspect to a protective aspect

The Suitability of Artificial Neural Networks in Service Quality Control and Forecasting for Healthcare Contexts

Over the last decade there has been considerable research into the area of service quality. Service, however, as an intangible, perishable, and heterogenic transaction, is very difficult to quantify and measure, and little success has been reported on a systematic approach in modeling of quality of service transactions (with SERVQUAL and its derivatives as the notable exception). In this paper, we propose an Artificial Neural Network (ANN) to monitor quality of service transaction as a dynamic and real-time monitoring and forecasting system. ANNs are widely used in many engineering fields to model and simulate complex systems. The resulting near-perfect models are particularly suited for applications where real-world complexities make it difficult or even impossible to mathematically model the system. Given the complex nature of healthcare decisions, the following reports on a research in progress study that focuses on applying ANN to a specific healthcare context of the emergency room

A 4-gene expression score associated with high levels of Wilms Tumor-1 (WT1) expression is an adverse prognostic factor in acute myeloid leukaemia

Wilms Tumor-1 (WT1) expression level is implicated in the prognosis of acute myeloid leukaemia (AML). We hypothesized that a gene expression profile associated with WT1 expression levels might be a good surrogate marker. We identified high WT1 gene sets by comparing the gene expression profiles in the highest and lowest quartiles of WT1 expression in two large AML studies. Two high WT1 gene sets were found to be highly correlated in terms of the altered genes and expression profiles. We identified a 17-probe set signature of the high WT1 set as the optimal prognostic predictor in the first AML set, and showed that it was able to predict prognosis in the second AML series after adjustment for Europe

Removal of endocrine disrupting chemicals from water through urethane functionalization of microfiltration membranes via electron beam irradiation

Polyethersulphone (PES) membranes modified with urethane functional groups were prepared through an interfacial reaction using electron beam irradiation. The removal of eight endocrine disrupting chemicals (EDCs) was studied using both pristine and functionalized PES membranes. The prepared membranes underwent characterization using several techniques, including attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, scanning electron microscopy, contact angle analysis, and measurements of pure water flux. Furthermore, dynamic adsorption experiments were conducted to evaluate the adsorption mechanism of the prepared membrane toward the eight EDCs. The urethane functionalized membranes were hydrophilic (52° contact angle) and maintained a high permeate flux (26000 L/h m2 bar) throughout the filtration process. Dynamic adsorption results demonstrated that the introduction of urethane functional groups on the membranes significantly enhanced the removal efficiency of 17β-estradiol, estriol, bisphenol A, estrone, ethinylestradiol, and equilin. The adsorption loading of 17β-estradiol on the functionalized PES membrane was 6.7 ± 0.7 mg/m2, exhibiting a 5-fold increase compared to the unmodified PES membrane. The membranes were successfully regenerated and reused for three adsorption cycles without experiencing any loss of adsorption capacity.Projekt DEA

Surface Nano-structured Coating for Improved Performance of Axial Piston Pumps

The work starts from the consideration that most of the power losses in a hydraulic pump is due to frictional losses made by the relative motion between moving parts. This fact is particularly true at low operating velocities, when the hydraulic lift effect must be able to maintain a minimum clearance in meatus to limit the volumetric losses. The potential of structured coatings at nanoscale, with super-hydrophobic and oleophobic characteristics, has never been exploited before in an industrial application. The work studies the potential application of nano-coating on piston slippers surface in a real industrial case. The aim is to develop a new industrial solution to increase the energetic efficiency of hydraulic pump used in earthmoving machines. The proposed solution is investigated using a dedicated test bench, designed to reproduce real working conditions of the pump. The results showa reduction of friction coefficient while changing working pressure and rotation velocity