Analysis of Step-Velocity-Dependent Concentration of Magnesium in GaN Based on Burton−Cabrera−Frank Theory and Step-Edge Segregation Model

Based on Burton−Cabrera−Frank theory and the step-edge segregation model, we analyzed the reported difference in the sheet concentration of doped magnesium under naturally formed surface stripes on homo-epitaxially grown layers on a freestanding GaN substrate misoriented from a c-plane by 0.3°. By assuming the step height being equal to the peak-to-valley height of the surface stripes, we considered the growth steps on gently and sharply sloped surfaces to be supplied, respectively, from mixed dislocations and the misorientation from the c-plane. The step-velocity dependence of the magnesium concentration was reproduced with the reported magnesium diffusivity of 3×10−14 cm2s−1.

Polaritonic crystal formed of a tunnel-coupled microcavity array and an ensemble of quantum dots

Propagation of polariton excitations in a defect-containing one-dimensional lattice of microcavities with embedded ultracold atomic nanoclusters (quantum dots) is being considered. The virtual crystal approximation is used to study the properties of electromagnetic excitation spectrum resulting from random variations of the atomic subsystem composition and positions of micropores, as well as from a homogeneous elastic deformation of the considered one-dimensional structure. The group velocity dependence of polariton excitations on structural defect concentration and on deformation parameter is being numerically modeled.

Unshielded precipitation gauge collection efficiency with wind speed and hydrometeor fall velocity

Collection efficiency transfer functions that compensate for wind-induced collection loss are presented and evaluated for unshielded precipitation gauges. Three novel transfer functions with wind speed and precipitation fall velocity dependence are developed, including a function from computational fluid dynamics modelling (CFD), an experimental fall velocity threshold function (HE1), and an experimental linear fall velocity dependence function (HE2). These functions are evaluated alongside universal (KUniversal) and climate-specific (KCARE) transfer functions with wind speed and temperature dependence. Transfer function performance is assessed using 30 min precipitation event accumulations reported by unshielded and shielded Geonor T-200B3 precipitation gauges over two winter seasons. The latter gauge was installed in a Double Fence Automated Reference (DFAR) configuration. Estimates of fall velocity were provided by the Precipitation Occurrence Sensor System (POSS). The CFD function reduced the RMSE (0.08 mm) relative to KUniversal (0.20 mm), KCARE (0.13 mm), and the unadjusted measurements (0.24 mm), with a bias error of 0.011 mm. The HE1 function provided a RMSE of 0.09 mm and bias error of 0.006 mm, capturing the collection efficiency trends for rain and snow well. The HE2 function better captured the overall collection efficiency, including mixed precipitation, resulting in a RMSE of 0.07 mm and bias error of 0.006 mm. These functions are assessed across solid and liquid hydrometeor types and for temperatures between −22 and 19 ∘C. The results demonstrate that transfer functions incorporating hydrometeor fall velocity can dramatically reduce the uncertainty of adjusted precipitation measurements relative to functions based on temperature.

Disentangling acceleration-, velocity-, and duration-dependency of the short- and medium-latency stretch reflexes in the ankle plantarflexors

Previous research and definitions of the stretch reflex and spasticity have focused on velocity dependence. We showed that perturbation acceleration, velocity, and duration all shape the M1 and M2 response, often via nonlinear or interacting dependencies. Consequently, systematic execution and reporting of stretch reflex and spasticity studies, avoiding uncontrolled parameter interdependence, is essential for proper understanding of the reflex neurophysiology.

Velocity Dependence and Tracer Dispersion in Newtonian Fluids Undergoing Creeping Flow

The dynamics of tracer particles in a viscous Newtonian fluid is studied analytically and numerically through channels of varying thickness for fluids undergoing creeping flow. Exact analytical solutions of mass conservation equations of tracer particles including consideration for pressure forces are obtained. Results of the analysis indicates that Stokes velocity is an indispensable parameter and is dependent on parameters such as channel thickness (height), viscosity of the fluid, pressure gradient driven the fluid and Reynolds number corresponding to the channel thickness. The accuracy of the solution obtained is verified by comparing its velocity profiles with those obtained from finite-element-based numerical simulation studies.

Micro-patterned deposition of MoS2 ultrathin-films by a controlled droplet dragging approach

Micropatterning of transition metal dichalcogenide (TMDC) ultrathin-films and monolayers has been demonstrated by various multi-step approaches. However, directly achieving a patterned growth of TMDC films is still considered to be challenging. Here, we report a solution-based approach for the synthesis of patterned MoS2 layers by dragging a precursor solution droplet with variable velocities across a substrate. Utilizing the pronounced shearing velocity dependence in a Landau-Levich deposition regime, MoS2 films with a spatially modulated thickness with alternating mono/bi- and few-layer regions are obtained after precursor annealing. Generally, the presented facile methodology allows for the direct preparation of micro-structured functional materials, extendable to other TMDC materials and even van der Waals heterostructures.