investigation of particle dynamics and classification mechanism in a spiral jet mill through computational fluid dynamics and discrete element methods

Abstract Predicting the outcome of jet-milling based on the knowledge of process parameters and starting material properties is a task still far from being accomplished. Given the technical difficulties in measuring thermodynamics, flow properties and particle statistics directly in the mills, modelling and simulations constitute alternative tools to gain insight in the process physics and many papers have been recently published on the subject. An ideal predictive simulation tool should combine the correct description of non-isothermal, compressible, high Mach number fluid flow, the correct particle-fluid and particle-particle interactions and the correct fracture mechanics of particle upon collisions but it is not currently available. In this paper we present our coupled CFD-DEM simulation results; while comparing them with the recent modelling and experimental works we will review the current understating of the jet-mill physics and particle classification. Subsequently we analyze the missing elements and the bottlenecks currently limiting the simulation technique as well as the possible ways to circumvent them towards a quantitative, predictive simulation of jet-milling

Medial temporal lobe atrophy and posterior atrophy scales normative values

OBJECTIVES: The medial temporal lobe atrophy (MTA) and the posterior atrophy (PA) scales allow to assess the degree hippocampal and parietal atrophy from magnetic resonance imaging (MRI) scans. Despite reliable, easy and widespread employment, appropriate normative values are still missing. We aim to provide norms for the Italian population. // METHODS: Two independent raters assigned the highest MTA and PA score between hemispheres, based on 3D T1-weighted MRI of 936 Italian Brain Normative Archive subjects (age: mean ± SD: 50.2 ± 14.7, range: 20-84; MMSE>26 or CDR = 0). The inter-rater agreement was assessed with the absolute intraclass correlation coefficient (aICC). We assessed the association between MTA and PA scores and sociodemographic features and APOE status, and normative data were established by age decade based on percentile distributions. // RESULTS: Raters agreed in 90% of cases for MTA (aICC = 0.86; 95% CI = 0.69-0.98) and in 86% for PA (aICC = 0.82; 95% CI = 0.58-0.98). For both rating scales, score distribution was skewed, with MTA = 0 in 38% of the population and PA = 0 in 52%, while a score ≥ 2 was only observed in 12% for MTA and in 10% for PA. Median denoted overall hippocampal (MTA: median = 1, IQR = 0-1) and parietal (PA: median = 0, IQR = 0-1) integrity. The 90th percentile of the age-specific distributions increased from 1 (at age 20-59) for both scales, to 2 for PA over age 60, and up to 4 for MTA over age 80. Gender, education and APOE status did not significantly affect the percentile distributions in the whole sample, nor in the subset over age 60. // CONCLUSIONS: Our normative data for the MTA and PA scales are consistent with previous studies and overcome their main limitations (in particular uneven representation of ages and missing percentile distributions), defining the age-specific norms to be considered for proper brain atrophy assessment

Effects of Buoyancy on Mixed Turbulent Heat Transfer to Heavy liquid Metals in Vertical Annuli

Turbulent mixed convection in low Prandtl number fluids, such as heavy liquid metals, is studied because of the interest in such materials as possible coolants for nuclear power plants. Liquid metals show a behavior similar to that of ordinary fluids, such as water or air, when buoyancy effects are negligible in turbulent flows

Thermo-Hydraulic Analysis of a LFR Generation IV Reactor with a Porous Medium Approach

This paper analyzes the stationary behaviour of the LFR European reactor design ELSY with a porous medium approach by computing the three-dimensional average distribution of temperature, pressure and velocity fields. Knowledge of these physical quantities is of particular importance for the computation of reactor reactivity and heat stresses on the fuel structural elements. The numerical simulations of the flow in the lower and upper plena of the reactor are performed with a FEM code that solves the full three-dimensional set of the incompressible Navier-Stokes equations with energy and turbulence model. Due to the reactor huge size the code uses a simple LES (Large Eddy Simulation) turbulence model for the viscosity which takes into account the turbulence vorticity effects at scales greater than the typical grid spacing. In the core region the reactor complexity requires the adoption of a spatial scale greater than the assembly transverse dimension. This approximation implies the reduction of the core to a sort of {it porous medium} through which the lead coolant flows at the subchannel level. This approach leads to a two-scale model where the phenomena that occur at the high-resolution level may have impact on the lower resolution

Índice de enfisema pulmonar em coorte de pacientes sem doença pulmonar conhecida: influência da idade Emphysema index in a cohort of patients with no recognizable lung disease: influence of age

OBJETIVO: Investigar os efeitos da idade no enfisema pulmonar, com base nos valores do índice de enfisema (IE) em uma coorte de pacientes que nunca fumou e que não possuía doença pulmonar conhecida. MÉTODOS: Foram revisados exames de TC, considerados normais, de 315 pacientes. Tabagismo, doenças cardiorrespiratórias e exposição a drogas que poderiam causar doença pulmonar foram critérios de exclusão. Dessa coorte, selecionamos 32 pacientes (16 homens e 16 mulheres), igualmente divididos em dois grupos (idade < 50 anos e idade > 50 anos), que foram pareados por gênero e índice de massa corpórea. Realizou-se a quantificação do enfisema utilizando um programa específico. O IE foi calculado com um limiar de -950 UH. O volume pulmonar total (VPT) e a densidade pulmonar média (DPM) também foram avaliados. RESULTADOS: As médias gerais de VPT, DPM e IE foram 5.027 mL, -827 UH e 2,54%, respectivamente. A comparação entre os mais velhos e os mais novos mostrou as seguintes médias: VPT, 5.229 mL vs. 4.824 mL (p > 0,05); DPM, -846 UH vs. -813 UH (p < 0,04) e IE, 3,30% vs. 1,28% (p < 0,001). Houve correlações significativas entre IE e idade (r = 0,66; p = 0,001), IE e VPT (r = 0,58; p = 0,001) e IE e DPM (r = -0,67; p < 0,001). O IE previsto por idade foi definido através da equação de regressão (r² = 0,43): p50(IE) = 0,049 × idade - 0,5353. CONCLUSÕES: É importante considerar a influência da idade na quantificação de enfisema em pacientes com mais de 50 anos. Baseado na análise de regressão, valores de IE de 2,6%, 3,5% e 4,5% podem ser considerados normais para pacientes com 30, 50 e 70 anos, respectivamente.<br>OBJECTIVE: To investigate the effects of age on pulmonary emphysema, based on the values of the emphysema index (EI) in a cohort of patients who had never smoked and who had no recognizable lung disease. METHODS: We reviewed the CT scans, reported as normal, of 315 patients. Exclusion criteria were a history of smoking, cardiorespiratory disease, and exposure to drugs that could cause lung disease. From this cohort, we selected 32 patients (16 men and 16 women), matched for gender and body mass index, who were divided equally into two groups by age (< 50 years and > 50 years). We quantified emphysema using a computer program specific to that task. The EI was calculated with a threshold of -950 HU. We also evaluated total lung volume (TLV) and mean lung density (MLD). RESULTS: The overall means for TLV, MLD, and EI were 5,027 mL, -827 HU, and 2.54%, respectively. Mean values in the older and younger groups, respectively, were as follows: for TLV, 5,229 mL vs. 4,824 mL (p > 0.05); for MLD, -846 HU vs. -813 HU (p < 0.04); and for EI, 3.30% vs. 1.28% (p < 0.001). Significant correlations were found between EI and age (r = 0.66; p = 0.001), EI and TLV (r = 0.58; p = 0.001), and EI and MLD (r = -0.67; p < 0.001). The predicted EI per age was defined by the regression equation (r² = 0.43): p50(EI) = 0.049 × age - 0.5353. CONCLUSIONS: It is important to consider the influence of age when quantifying emphysema in patients over 50 years of age. Based on the regression analysis, EI values of 2.6%, 3.5%, and 4.5% can be considered normal for patients 30, 50, and 70 years of age, respectively

Machine Learning to Predict In-Hospital Mortality in COVID-19 Patients Using Computed Tomography-Derived Pulmonary and Vascular Features

Pulmonary parenchymal and vascular damage are frequently reported in COVID-19 patients and can be assessed with unenhanced chest computed tomography (CT), widely used as a triaging exam. Integrating clinical data, chest CT features, and CT-derived vascular metrics, we aimed to build a predictive model of in-hospital mortality using univariate analysis (Mann–Whitney U test) and machine learning models (support vectors machines (SVM) and multilayer perceptrons (MLP)). Patients with RT-PCR-confirmed SARS-CoV-2 infection and unenhanced chest CT performed on emergency department admission were included after retrieving their outcome (discharge or death), with an 85/15% training/test dataset split. Out of 897 patients, the 229 (26%) patients who died during hospitalization had higher median pulmonary artery diameter (29.0 mm) than patients who survived (27.0 mm, p &lt; 0.001) and higher median ascending aortic diameter (36.6 mm versus 34.0 mm, p &lt; 0.001). SVM and MLP best models considered the same ten input features, yielding a 0.747 (precision 0.522, recall 0.800) and 0.844 (precision 0.680, recall 0.567) area under the curve, respectively. In this model integrating clinical and radiological data, pulmonary artery diameter was the third most important predictor after age and parenchymal involvement extent, contributing to reliable in-hospital mortality prediction, highlighting the value of vascular metrics in improving patient stratification