New complex dimensionless variable in cyclic staircase voltammetry on the rotating disk electrode

Cyclic staircase voltammograms of a simple, reversible oxidation on the rotating disk electrode is analysed by the digital simulation. It is demonstrated that the peak currents and potentials depend on the single dimensionless variable that considers nonlinear relationship between peak currents and the potential increment. The reverse, cathodic branch of voltammograms depends on this variable differently than the anodic one.

Unsteady Boundary Layer Flow Over a Permeable Stretching/Shrinking Cylinder Immersed in Nanofluid

In this study, the unsteady boundary layer flow over a stretching/shrinking cylinder immersed in nanofluid with the presence of suction effect is analyzed. The governing partial differential equations are converted to ordinary differential equations by introducing similarity transformation variables. The shooting method is applied to solve the system where the numerical solutions are obtained and presented graphically. The study's objective is to investigate the effect of nanoparticle volume fraction, the unsteadiness parameter, the stretching/shrinking parameter on the velocity and temperature gradients. It is found that the dual solutions are obtained in a specific range of these parameters for both stretching and shrinking cylinders. Besides, a high volume of the nanoparticle in the base fluid increases the velocity gradient and decreases the temperature gradient at the surface. Also, increasing nanoparticle volume fraction in the base fluid expands the solution's range, which denotes the boundary layer separation from the surface has been delayed. The existence of dual solutions allows stability analysis performance by introducing a new dimensionless variable and is solved using bvp4c function in Matlab software. This phase obtains the smallest eigenvalue, showing that the first solution is stable and physically realizable while the second solution is not stable.

Network Mapping of Time to Antithrombotic Therapy Among Patients With Ischemic Stroke and Transient Ischemic Attack (TIA)

Background: There is emphasis on timely administration of thrombolysis and clot retrieval but not antithrombotic therapy within 48 h for ischemic stroke (frequency of 64% in Australia and 97% in North America). We planned to assess the time metrics and variables associated with delaying antithrombotics (antiplatelet and anticoagulant therapy) administration.Methods: This was a retrospective study at Monash Health over 12 months in 2015. We plotted the cumulative event and mapped the key drivers (dimensionless variable Shapley value/SV) of antithrombotics.Results: There were 42 patients with transient ischemic attack/TIA and 483 with ischemic stroke [mean age was 71.8 ± 15.4; 56.0% male; nil by mouth (NBM) 74.5 and 49.3% of patients received “stat” (immediate and one off) dose antithrombotics]. The median time to imaging for the patients who did not have stroke code activated was 2.3 h (IQR 1.4–3.7), from imaging to dysphagia screen was 14.6 h (IQR 6.2–20.3), and from stopping NBM to antithrombotics was 1.7 h (IQR 0–16.5). TIA patients received antithrombotics earlier than those with ischemic stroke (90.5 vs. 86.5%, p = 0.01). Significant variables in regression analysis for time to antithrombotics were time to dysphagia screen (β 0.20 ± 0.03, SV = 3.2), nasogastric tube (β 19.8 ± 5.9, SV = −0.20), Alteplase (β 8.6 ± 3.6, SV = −1.9), stat dose antithrombotic (β −18.9 ± 2.9, SV = −10.8) and stroke code (β −5.9 ± 2.5, SV = 2.8). The partial correlation network showed that the time to antithrombotics increased with delay in dysphagia screen (coefficient = 0.33) and decreased if “stat” dose of antithrombotics was given (coefficient = −0.32).Conclusion: The proportion of patients receiving antithrombotics within 48 h was higher than previously reported in Australia but remained lower than the standard achieved in North American hospitals. Our process map and network analysis show avenues to shorten the time to antithrombotic.

Approximate Solution of the Varying Speed Impact of 3D Bodies on the Water Surface

The present paper proposes an approximate solution for the varying speed impact of 3D bodies on the water surface, with the assumptions that the fluid is considered to be incompressible, inviscid, weightless and with negligible surface tension effects and the flow ro be irrotational. The approximate solution provides a linear relationship between Cp and a dimensionless variable K, and the equation of body acceleration. These equations can be used to rapidly predict the pressure distribution on the body surface and the motions of the body. The predictions of the approximate solution match the CFD results very well for the varying speed impacts, including the normal and oblique impacts of a cone on the water surface and the normal impact of a pyramid on the water surface. The present approximate solution can be suitable for the 2D, axisymmetric and fully 3D impacts of bodies on the water surface with varying speed.

Probing the Private Quantum Life of s Electrons in Atoms of Nanomaterials -A New Quantum Theoretical Insight

The exotic properties exhibited by some of the nanomaterials could not be explained by the existing quantum theory. As a result one is forced to look back at the development of the quantum theory and some of the inelegancies. First, the quantized orbital angular momentum of s electron in an atom is taken as zero. This may be an acceptable fact for s electrons in an individual atom, but for the s electrons in a crystal or nanomaterial, this is far from the real situation. Secondly, in the wave function Ψ(r,θ), θ is considered as a dimensionless variable. These inelegancies lead to the impression that the present quantum theory is a steppingstone to a more complete description of nature. Here arises a necessity for probing the private quantum life of s electrons in crystal or nanomaterial. By assigning dimension to θ on par with r, we have quantum engineered the orbital angular momentum and hence the orbital degrees of freedom of s electrons and their signatures in a crystal. This restoration leads to new non-zero angular quantum numbers to s electrons of atoms in a crystal/nanomaterial. As a result the s electron occupation in nanomaterial is altered. Its new physics implications in material science, quantum chemistry and quantum technology are highlighted in this paper.

Numerical and Theoretical Study on the Varying Speed Impact of Wedge Bodies on a Water Surface

The varying speed impact of wedge bodies on a water surface is studied numerically and theoretically to provide a fast and accurate prediction of the pressure on the wedge surface and the motion of wedge bodies during the free impact, which can be a two-dimensional (2D) model for the strip theory or 2D + t strategy. The fluid is assumed to be incompressible, inviscid, with negligible gravity effect and surface tension effect. The computational fluid dynamics (CFD) method is based on the volume of fluid (VOF) method and global moving mesh (GMM) method. Various cases of a varying speed impact are shown for the CFD method, and a linear relationship between the pressure coefficient Cp and a dimensionless variable K is observed. To clearly explain the linear relationship between Cp and K, we follow the potential theory to derive the Cp expression based on several assumptions on the free surface drawn from the CFD results. The Cp expression and the motion of wedge bodies for a free impact derived from it are considered as an approximate solution for a varying speed impact. The approximate solution is compared with the existing analytical models and the published experimental data. The approximate solution can work well for different deadrise angles, while the existing analytical models can only be used for small deadrise angles. Good agreement is also obtained between the approximate solution and the experimental test results, including the time history of wedge acceleration and the pressure on the wedge surface.

Vortex dynamics under pulsatile flow in axisymmetric constricted tubes

Improved understanding of how vortices develop and propagate under pulsatile flow can shed important light on the mixing and transport processes occurring in such systems, including the transition to turbulent regime. For example, the characterization of pulsatile flows in obstructed artery models serves to encourage research into flow-induced phenomena associated with changes in morphology, blood viscosity, wall elasticity and flow rate. In this work, an axisymmetric rigid model was used to study the behaviour of the flow pattern with varying degrees constriction ($d_0$) and mean Reynolds ($\bar{Re}$) and Womersley numbers ($\alpha$). Velocity fields were obtained experimentally using Digital Particle Image Velocimetry and generated numerically. For the acquisition of data, $\bar{Re}$ was varied from 385 to 2044, $d_0$ was 1.0 cm and 1.6 cm, and $\alpha$ was varied from 17 to 33 in the experiments and from 24 to 50 in the numerical simulations. Results for the Reynolds number considered showed that the flow pattern consisted of two main structures: a central jet around the tube axis and a recirculation zone adjacent to the inner wall of the tube, where vortices shed. Using the vorticity fields, the trajectory of vortices was tracked and their displacement over their lifetime calculated. The analysis led to a scaling law equation for maximum vortex displacement as a function of a dimensionless variable dependent on the system parameters Re and $\alpha$.

A Non-Tuned Machine Learning Technique for Abutment Scour Depth in Clear Water Condition

Abutment scour is a complex three-dimensional phenomenon, which is one of the leading causes of marine structure damage. Structural integrity is potentially attainable through the precise estimation of local scour depth. Due to the high complexity of scouring hydrodynamics, existing regression-based relations cannot make accurate predictions. Therefore, this study presented a novel expansion of extreme learning machines (ELM) to predict abutment scour depth (ds) in clear water conditions. The model was built using the relative flow depth (h/L), excess abutment Froude number (Fe), abutment shape factor (Ks), and relative sediment size (d50/L). A wide range of experimental samples was collected from the literature, and data was utilized to develop the ELM model. The ELM model reliability was evaluated based on the estimation results and several statistical indices. According to the results, the sigmoid activation function (correlation coefficient, R = 0.97; root mean square error, RMSE = 0.162; mean absolute percentage error, MAPE = 7.69; and scatter index, SI = 0.088) performed the best compared with the hard limit, triangular bias, radial basis, and sine activation functions. Eleven input combinations were considered to investigate the impact of each dimensionless variable on the abutment scour depth. It was found that ds/L = f (Fe, h/L, d50/L, Ks) was the best ELM model, indicating that the dimensional analysis of the original data properly reflected the underlying physics of the problem. Also, the absence of one variable from this input combination resulted in a significant accuracy reduction. The results also demonstrated that the proposed ELM model significantly outperformed the regression-based equations derived from the literature. The ELM model presented a fundamental equation for abutment scours depth prediction. Based on the simulation results, it appeared the ELM model could be used effectively in practical engineering applications of predicting abutment scour depth. The estimated uncertainty of the developed ELM model was calculated and compared with the conventional and artificial intelligence-based models. The lowest uncertainty with a value of ±0.026 was found in the proposed model in comparison with ±0.50 as the best uncertainty of the other models.

Buoyancy Effects on MHD Unsteady Convection of a Radiating Chemically Reacting Fluid Past a Moving Porous Vertical Plate in a Binary Mixture

In this paper, the problem of unsteady magnetohydrodynamic free convective flow with thermal radiation and chemical reaction past a porous vertical plate moving through a binary mixture in an optically thin environment is investigated. The viscosity of the fluid is assumed to vary linearly with temperature. Due to the nature of corresponding dimensionless variable for temperature and its boundary condition as in the case of binary mixture, Boussinesq approximation and temperature dependent viscosity model were modified. The governing boundary layer equations are transformed using suitable similarity transformation and solved numerically. A parametric study of selected parameters is conducted and results for velocity, temperature, concentration, local skin friction coefficient, local Nusselt number and local Sherwood number are illustrated and physical aspects of the problem are discussed. Increasing the temperature dependent variable fluid viscosity leads to increase in the velocity of the fluid and heat transfer rate at the surface when Grashof related parameters are greater than one-tenth.