This study is concerned with transient natural convection in an isosceles triangular enclosure subject to non-uniformly cooling at the inclined surfaces and uniformly heating at the base. The ...numerical simulations of the unsteady flows over a range of Rayleigh numbers and aspect ratios are carried out using Finite Volume Method. Since the upper inclined surfaces are linearly cooled and the bottom surface is heated, the flow is potentially unstable. It is revealed from the numerical simulations that the transient flow development in the enclosure can be classified into three distinct stages; an early stage, a transitional stage, and a steady stage. The flow inside the enclosure depends significantly on the governing parameters, Rayleigh number and aspect ratio. The effect of Rayleigh number and aspect ratio on the flow development and heat transfer rate are discussed. The key finding for this study is to analyze the pitchfork bifurcation of the flow about the geometric center line. The heat transfer through the roof and the ceiling as a form of Nusselt number is reported in this study.
Using a total of 9.0 fb−1 of e+e− collision data with center-of-mass energies between 4.15 and 4.30 GeV collected by the BESIII detector, we search for the processes e+e−→γX(3872) with X(3872)→π0χcJ ...for J=0, 1, 2. We report the first observation of X(3872)→π0χc1, a new decay mode of the X(3872), with a statistical significance of more than 5σ for all systematic fit variations. Normalizing to the previously established process e+e−→γX(3872) with X(3872)→π+π−J/ψ, we find B(X(3872)→π0χc1)/B(X(3872)→π+π−J/ψ)=0.88−0.27+0.33±0.10, where the first error is statistical and the second is systematic. We set 90% confidence level upper limits on the corresponding ratios for the decays to π0χc0 and π0χc2 of 19 and 1.1, respectively.
Fundamental understanding on microscopic physical changes of plant materials is vital to optimize product quality and processing techniques, particularly in food engineering. Although grid-based ...numerical modelling can assist in this regard, it becomes quite challenging to overcome the inherited complexities of these biological materials especially when such materials undergo critical processing conditions such as drying, where the cellular structure undergoes extreme deformations. In this context, a meshfree particle based model was developed which is fundamentally capable of handling extreme deformations of plant tissues during drying. The model is built by coupling a particle based meshfree technique: Smoothed Particle Hydrodynamics (SPH) and a Discrete Element Method (DEM). Plant cells were initiated as hexagons and aggregated to form a tissue which also accounts for the characteristics of the middle lamella. In each cell, SPH was used to model cell protoplasm and DEM was used to model the cell wall. Drying was incorporated by varying the moisture content, the turgor pressure, and cell wall contraction effects. Compared to the state of the art grid-based microscale plant tissue drying models, the proposed model can be used to simulate tissues under excessive moisture content reductions incorporating cell wall wrinkling. Also, compared to the state of the art SPH-DEM tissue models, the proposed model better replicates real tissues and the cell-cell interactions used ensure efficient computations. Model predictions showed good agreement both qualitatively and quantitatively with experimental findings on dried plant tissues. The proposed modelling approach is fundamentally flexible to study different cellular structures for their microscale morphological changes at dehydration.
SPH-DEM based microscale drying model can predict shrinkage and cell wall wrinkling of plant cells in tissues at different moisture contents and turgor pressures during drying (top row: full tissue view, bottom row: enlarged view).
In this work, a numerical model that enables simulation of the deformation and flow behaviour of differently aged Red Blood Cells (RBCs) is developed. Such cells change shape and decrease in ...deformability as they age, thus impacting their ability to pass through the narrow capillaries in the body. While the body filters unviable cells from the blood naturally, cell aging poses key challenges for blood stored for transfusions. Therefore, understanding the influence RBC morphology and deformability have on their flow is vital. While several existing models represent young Discocyte RBC shapes well, a limited number of numerical models are developed to model aged RBC morphologies like Stomatocytes and Echinocytes. The existing models are also limited to shear and stretching simulations. Flow characteristics of these morphologies are yet to be investigated. This paper aims to develop a new membrane formulation for the numerical modelling of Stomatocyte, Discocytes and Echinocyte RBC morphologies to investigate their deformation and flow behaviour. The model used represents blood plasma using the Lattice Boltzmann Method (LBM) and the RBC membrane using the discrete element method (DEM). The membrane and the plasma are coupled by the Immersed Boundary Method (IBM). Previous LBM-IBM-DEM formulations represent RBC membrane response based on forces generated from changes in the local area, local length, local bending, and cell volume. In this new model, two new force terms are added: the local area difference force and the local curvature force, which are specially incorporated to model the flow and deformation behaviour of Stomatocytes and Echinocytes. To verify the developed model, the deformation behaviour of the three types of RBC morphologies are compared to well-characterised stretching and shear experiments. The flow modelling capabilities of the method are then demonstrated by modelling the flow of each cell through a narrow capillary. The developed model is found to be as accurate as benchmark Smoothed Particle Hydrodynamics (SPH) approaches while being significantly more computationally efficient.
Inhaled nanoparticles (NPs) are experienced by the first biological barrier inside the alveolus known as lung surfactant (LS), a surface tension reducing agent, consisting of phospholipids and ...proteins in the form of the monolayer at the air-water interface. The monolayer surface tension is continuously regulated by the alveolus compression and expansion and protects the alveoli from collapsing. Inhaled NPs can reach deep into the lungs and interfere with the biophysical properties of the lung components. The interaction mechanisms of bare gold nanoparticles (AuNPs) with the LS monolayer and the consequences of the interactions on lung function are not well understood. Coarse-grained molecular dynamics simulations were carried out to elucidate the interactions of AuNPs with simplified LS monolayers at the nanoscale. It was observed that the interactions of AuNPs and LS components deform the monolayer structure, change the biophysical properties of LS and create pores in the monolayer, which all interfere with the normal lungs function. The results also indicate that AuNP concentrations >0.1 mol% (of AuNPs/lipids) hinder the lowering of the LS surface tension, a prerequisite of the normal breathing process. Overall, these findings could help to identify the possible consequences of airborne NPs inhalation and their contribution to the potential development of various lung diseases.
Display omitted
•AuNPs pollutants affect the structural and dynamical properties of the lung surfactant monolayer in MD simulations.•AuNPs inhibit to lower the surface tension values of surfactant monolayer during the breathing process.•A high concentration of AuNPs in the surfactant monolayer induces pore formation.•Upon entering the LS monolayer lipids adsorb to the surface of the AuNPs, before the AuNPs aggregate into clusters.
The effect of deposition rate on the microstructure of Ti thin films prepared by magnetron sputtering was investigated. The microstructure of Ti thin films was characterized by X-ray diffraction ...(XRD), scanning electron microscopy, transmission electron microscopy and atomic force microscopy. The Ti thin films exhibit a composite structure of amorphous matrix embodied with nanocrystallines. The nanocrystallization is improved with the increase of deposition rate. XRD patterns show that the crystallographic orientation transits from random distribution to (002) preferred orientation, and this crystallographic growth texture is enhanced with increasing deposition rate. Three-dimensional hexagonal particles are formed at the deposition rate of 0.35nm/s, while flaky slices occur at the surface at larger deposition rate. Moreover, the growth process of Ti thin films controlled by the deposition rate is discussed.
•Deposition rate-controlled microstructure of Ti thin films was studied.•The microstructure is characterized by amorphous–nanocrystalline composite.•Crystallinity and texture are enhanced with increasing deposition rate.•A transition of growth mode from 3D islands to 2D flaky slices is observed.
Using a data sample corresponding to an integrated luminosity of 2.93 fb−1 recorded by the BESIII detector at a center-of-mass energy of 3.773 GeV, we present an analysis of the decays D0 → π−π0e+νe ...and D+ → π−π+e+νe. By performing a partial wave analysis, the π+π− S-wave contribution to D+ → π−π+e+νe is observed to be (25.7 ± 1.6 ± 1.1)% with a statistical significance greater than 10σ, besides the dominant P-wave contribution. This is the first observation of the S-wave contribution. We measure the branching fractions B(D0 → ρ−e+νe) = (1.445 ± 0.058 ± 0.039) × 10−3, B(D+ → ρ0e+νe) = (1.860 ± 0.070 ± 0.061) × 10−3, and B(D+ → f0(500)e+νe, f0(500) → π+π−) = (6.30 ± 0.43 ± 0.32) × 10−4. An upper limit of B(D+ → f0(980)e+νe, f0(980) → π+π−) < 2.8 × 10−5 is set at the 90% confidence level. We also obtain the hadronic form factor ratios of D → ρe+νe at q2 = 0 assuming the single-pole dominance parametrization: rV = {V(0)/A1(0)} = 1.695 ± 0.083 ± 0.051, r2 = {A2(0)/A1(0)} = 0.845 ± 0.056 ± 0.039.
We report the first observation of D+→τ+ντ with a significance of 5.1σ. We measure B(D+→τ+ντ)=(1.20±0.24stat±0.12syst)×10−3. Taking the world average B(D+→μ+νμ)=(3.74±0.17)×10−4, we obtain ...Rτ/μ=Γ(D+→τ+ντ)/Γ(D+→μ+νμ)=3.21±0.64stat±0.43syst., which is consistent with the standard model expectation of lepton flavor universality. Using external inputs, our results give values for the D+ decay constant fD+ and the Cabibbo-Kobayashi-Maskawa matrix element |Vcd| that are consistent with, but less precise than, other determinations.
Using e+e− annihilation data corresponding to an integrated luminosity of 3.19 fb−1 collected at a center-of-mass energy of 4.178 GeV with the BESIII detector, we measure the absolute branching ...fractions BDs+→ηe+νe = (2.323±0.063stat ± 0.063syst)% and BDs+→η′e+νe = (0.824±0.073stat ± 0.027syst)% via a tagged analysis technique, where one Ds is fully reconstructed in a hadronic mode. Combining these measurements with previous BESIII measurements of BD+→η(′)e+νe, the η−η′ mixing angle in the quark flavor basis is determined to be ϕP = (40.1±2.1stat ± 0.7syst)°. From the first measurements of the dynamics of Ds+ → η(′)e+νe decays, the products of the hadronic form factors f+η(′)(0) and the Cabibbo-Kobayashi-Maskawa matrix element |Vcs| are determined with different form factor parametrizations. For the two-parameter series expansion, the results are f+η(0)|Vcs| = 0.4455±0.0053stat±0.0044syst and f+η′(0)|Vcs|=0.477±0.049stat±0.011syst.
We measure the Born cross sections of the process e+e−→K+K−K+K− at center-of-mass (c.m.) energies, s, between 2.100 and 3.080 GeV. The data were collected using the BESIII detector at the BEPCII ...collider. An enhancement at s=2.232 GeV is observed, very close to the e+e−→ΛΛ¯ production threshold. A similar enhancement at the same c.m. energy is observed in the e+e−→ϕK+K− cross section. The energy dependence of the K+K−K+K− and ϕK+K− cross sections differs significantly from that of e+e−→ϕπ+π−.
PDF
