scholarly journals Rheological characteristics of aluminium oxide (AL2O3) based nanolubricant

2020 ◽  
Vol 39 (2) ◽  
pp. 424-432
Author(s):  
M. Ogbonnaya ◽  
O.O. Ajayi ◽  
M.A. Waheed
Keyword(s):  
Shear Rate ◽  
Exponential Function ◽  
Dynamic Viscosity ◽  
Mass Concentration ◽  
Aluminium Oxide ◽  
Al2o3 Nanoparticles ◽  
Step Method ◽  
Rheological Measurement ◽  
Linear Fit ◽  
The Relationship

This paper presents the rheological measurement of aluminium oxide (Al2O3) nanolubricant. The nanolubricant was prepared using the two-step method from dry Al2O3 nanoparticles and Capella D lubricant as base fluid. The dynamic viscosity of the Al2O3 nanolubricant at constant shear rate was measured at atmospheric pressure in the temperature range of 278 K to 323 K for pure based lubricant along with nanolubricant mass concentration of 1%, 2% and 4% with nanoparticle size of 10 nm, 20-30 nm and 80 nm. The measured data was analysed using the linear fit and exponential function fit. The result showed that at constant particle size and concentration, the dynamic viscosity reduces with increase in temperature while at constant temperature, the viscosity increased with nanoparticle concentration. The exponential function fit regression best describe the relationship between the viscosity and temperature when compared with the linear fit regression while the polynomial function fit best describe the relationship between the viscosity and mass concentration. Keywords: Dynamic viscosity, nanolubricant, shear rate, regression, concentration, temperature

Flow recirculation zone length and shear rate are differentially affected by stenosis severity in human coronary arteries

2013 ◽  
Vol 304 (4) ◽  
pp. H559-H566 ◽  
Author(s):  
Ashkan Javadzadegan ◽  
Andy S. C. Yong ◽  
Michael Chang ◽  
Austin C. C. Ng ◽  
John Yiannikas ◽  
...  
Keyword(s):  
Shear Rate ◽  
Coronary Arteries ◽  
Recirculation Zone ◽  
Fluid Dynamic ◽  
Zone Length ◽  
Flow Recirculation ◽  
Stenosis Severity ◽  
Recirculation Zones ◽  
The Relationship

Flow recirculation zones and shear rate are associated with distinct pathogenic biological pathways relevant to thrombosis and atherogenesis. The interaction between stenosis severity and lesion eccentricity in determining the length of flow recirculation zones and peak shear rate in human coronary arteries in vivo is unclear. Computational fluid dynamic simulations were performed under resting and hyperemic conditions on computer-generated models and three-dimensional (3-D) reconstructions of coronary arteriograms of 25 patients. Boundary conditions for 3-D reconstructions simulations were obtained by direct measurements using a pressure-temperature sensor guidewire. In the computer-generated models, stenosis severity and lesion eccentricity were strongly associated with recirculation zone length and maximum shear rate. In the 3-D reconstructions, eccentricity increased recirculation zone length and shear rate when lesions of the same stenosis severity were compared. However, across the whole population of coronary lesions, eccentricity did not correlate with recirculation zone length or shear rate ( P = not signficant for both), whereas stenosis severity correlated strongly with both parameters ( r = 0.97, P < 0.001, and r = 0.96, P < 0.001, respectively). Nonlinear regression analyses demonstrated that the relationship between stenosis severity and peak shear was exponential, whereas the relationship between stenosis severity and recirculation zone length was sigmoidal, with an apparent threshold effect, demonstrating a steep increase in recirculation zone length between 40% and 60% diameter stenosis. Increasing stenosis severity and lesion eccentricity can both increase flow recirculation and shear rate in human coronary arteries. Flow recirculation is much more sensitive to mild changes in the severity of intermediate stenoses than is peak shear.

scholarly journals Investigation of the Sedimentation Property of Backfill Material on the Basis of Rheological Test: A Case Study of Iron Tailings

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Yong Wang ◽  
Aixiang Wu ◽  
Lianfu Zhang ◽  
Hongjiang Wang ◽  
Fei Jin
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Mass Concentration ◽  
Filling Material ◽  
Quantitative Characterization ◽  
Filling Materials ◽  
Characterization Studies ◽  
Rheological Test ◽  
Sedimentation Property

Sedimentation of filling materials could cause pipe blocking accident in mines. However, few quantitative characterization studies have investigated the sedimentation characteristics of filling materials. In this study, the sedimentation property of iron tailings with a cement-sand ratio of 1 : 4 and mass concentration of 73%∼82% was investigated based on rheology measurements. Results showed that shear stress increased as shear rate rose from 0 s−1to 120 s−1. The shear stress increased as the filling material concentration increased as well. However, when the shear rate was reversed from 120 s−1to 0 s−1, the shear stress presented an increase-constant-decrease change pattern as the mass concentration increases in the rheological curve. Accordingly, the sedimentation performance of iron tailings filling material was divided into three types: intense sedimentation (the ascending rheological curve) in the mass concentration range of 73%∼76%, slight sedimentation (the constant rheological curve) in the mass concentration range of 77%∼79%, and almost no sedimentation (the descending rheological curve) in the mass concentration range of 80%∼82%. The associated mechanism involving slurry mass concentration-rheological curves-sedimentation performance was illustrated. A correlation between the pipeline rheology and filling material sedimentation performance was established, which provides a practical guide to avoid pipeline blocking while transporting the filling material.

Influence of Fillers on the Viscosity Properties of One-Pack Polyurethane Sealants

2021 ◽  
Vol 410 ◽  
pp. 605-610
Author(s):  
Kseniya A. Timakova ◽  
Yuriy T. Panov ◽  
Evgeniy A. Timakov
Keyword(s):  
Shear Rate ◽  
Dynamic Viscosity ◽  
Sharp Increase ◽  
Sharp Decrease ◽  
Shear Forces ◽  
Complex Orientation ◽  
Developed Surface ◽  
Mineral Fillers ◽  
Constant Shear Rate ◽  
Shape Of Particles

The paper investigates the effect of fillers on the viscosity properties of one-pack polyurethane sealants. It is noted that with the introduction of such mineral fillers as Mikarb, Midol, MTD2 chalk and aluminum hydroxide, the dynamic viscosity of the composition increases uniformly, while when filled with chemically precipitated Calofort SV chalk and MT-GShM talc, an abnormally sharp increase in viscosity is observed. Such an increase in viscosity for Calofort SV is explained by a highly developed surface, in contrast to other fillers. Talc is characterized by a plate-like shape of particles, which leads to a complex orientation of talc particles in the composition and shear difficulties.It was found that a sealant filled with chemically precipitated chalk has more than 100 pts. wt.(parts by weight), per 100 pts. wt. of the prepolymer under the influence of shear forces (at a constant shear rate) during the first 10 minutes of exposure, a sharp decrease in viscosity is observed, which is characteristic of thixotropic compositions, reaching a constant value after 5-10 minutes. After 10 minutes, the thixotropy of the sealant is restored. Talc does not impart thixotropic properties to the sealant composition.

scholarly journals Relationship between Psychological Empowerment and Spiritual Intelligence with Marital Satisfaction in Female and Male Teachers in Ahvaz

2016 ◽  
Vol 12 (6) ◽  
pp. 132 ◽  
Author(s):  
Zahra Kordzangeneh ◽  
Hamdollah Jayervand
Keyword(s):  
Marital Satisfaction ◽  
Sampling Method ◽  
Psychological Empowerment ◽  
Pearson Correlation ◽  
Spiritual Intelligence ◽  
Step Method ◽  
Male And Female ◽  
Female Teachers ◽  
The Relationship ◽  
Coefficient Method

<p>The present study was aimed to examine the relationship between psychological empowerment and spiritual intelligence with marital satisfaction in male and female teachers in Ahvaz from 2014 to 2015. Hence, 350 teachers were selected using random-stratified sampling method. Research tools were Spriters' psychological empowerment questionnaire (1995), Badie's et al. spiritual intelligence questionnaire (2010), Enrich's marital satisfaction questionnaire (1997); in order to do analysis, a Pearson Correlation Coefficient method and a regression method was used. Results showed that there is a relationship between psychological empowerment and spiritual intelligence with marital satisfaction in male and female teachers in Ahvaz. The results obtained from multi-fold regression analysis, using step-by-step method, showed that effectiveness, spiritual intelligence, and significance are able to predict marital satisfaction significantly. In addition, psychological empowerment has a closer relationship with spiritual intelligence, and spiritual intelligence has a closer relationship with marital satisfaction. </p>

Abstract 182: Time is Brain on the Collateral Clock! Collaterals and Reperfusion Determine Tissue Injury

Stroke ◽  
2015 ◽  
Vol 46 (suppl_1) ◽  
Author(s):  
David S Liebeskind ◽  
Dezhi Liu ◽  
Nerses Sanossian ◽  
Sunil A Sheth ◽  
Conrad Liang ◽  
...  
Keyword(s):  
Linear Models ◽  
Tissue Injury ◽  
Ischemic Injury ◽  
Realistic Model ◽  
Consecutive Series ◽  
Imaging Data ◽  
Advanced Imaging ◽  
Lesion Growth ◽  
Linear Fit ◽  
The Relationship

Background: The pace of ischemic injury due to stroke may vary due to collaterals and degree of reperfusion. Previous linear models that estimate time is brain have not incorporated individual patient data from advanced imaging such as diffusion-weighted imaging (DWI) and angiographic assessment of collateral grade or reperfusion. We developed a realistic model of ischemic injury using detailed imaging data in a homogenous cohort of isolated M1 middle cerebral artery occlusions. Methods: Retrospective analysis of a consecutive series of isolated M1 occlusions was conducted at an expert core lab. ASITN collateral grade was assessed at baseline and extent of reperfusion after endovascular therapy (EVT) was scored with 3 distinct versions of TICI. A separate imaging expert measured DWI lesion volumes on serial MRI acquired from admission to discharge. Graphical analyses illustrated curves demarcating extent of injury over time, based on both collateral grade and extent of reperfusion. Results: 126 patients (median age 73; 88 women; median NIHSS 17; median time to 1 st DWI, 4h08min) with acute stroke due to M1 occlusion (61 proximal, 65 distal) underwent EVT during a 6-year period. Median collateral grade was 2 (range 0-4) and median TICI, 2B (range 0-3). mTICI scores were 0 (n=18), 1 (6), 2A (25), 2B (73), and 3 (4) with 24 TICI 2C scores when evaluated in detail. Total number of DWI scans was 323, with mean 2.5 per patient. Collateral grade strongly influenced pace of development of initial tissue injury (ASITN 0, 0.445 cc/min; 1, 0.276 cc/min; 2, 0.178 cc/min; 3, 0.106 cc/min; 4, 0.031 cc/min). The relationship between time and DWI lesion growth was not linear, but best fit logarithmically (R 2 = 0.985, RMSE 2.1 for log fit; R 2 = 0.757, RMSE 8.1 for linear fit). Individual lesion growth varied markedly with both collateral grade (ANOVA p<0.001) and the degree (TICI 2B/3 vs. 0,1,2A) of reperfusion (ANOVA p=0.013). Conclusions: Collateral grade and the degree of reperfusion strongly dictate the timecourse of ischemic injury in the brain after stroke onset. Advanced imaging and angiographic assessment of collaterals and reperfusion confirm a logarithmic, not linear, model that can be used to differentiate stroke patients and streamline therapeutic strategies.

scholarly journals Gravimetrically prepared carbon dioxide standards in support of atmospheric research

2019 ◽  
Vol 12 (1) ◽  
pp. 517-524 ◽  
Author(s):  
Bradley D. Hall ◽  
Andrew M. Crotwell ◽  
Benjamin R. Miller ◽  
Michael Schibig ◽  
James W. Elkins
Keyword(s):  
Carbon Dioxide ◽  
Trace Gases ◽  
Step Method ◽  
Atmospheric Research ◽  
Excellent Internal Consistency ◽  
One Step ◽  
Linear Fit ◽  
Steel Surfaces ◽  
Adsorption Of Co2 ◽  
Low Uncertainty

Abstract. We have explored a one-step method for gravimetric preparation of CO2-in-air standards in aluminum cylinders. We consider both adsorption to stainless steel surfaces used in the transfer of highly pure CO2 and adsorption of CO2 to cylinder walls. We demonstrate that CO2-in-air standards can be prepared with relatively low uncertainty (∼ 0.04 %, ∼95 % confidence level) by introducing aliquots whose masses are known to high precision and by using well-characterized cylinders. Five gravimetric standards, prepared over the nominal range of 350 to 490 µmol mol−1 (parts per million, ppm), showed excellent internal consistency, with residuals from a linear fit equal to 0.05 ppm. This work compliments efforts to maintain the World Meteorological Organization, Global Atmosphere Watch, mole fraction scale for carbon dioxide in air, widely used for atmospheric monitoring. This gravimetric technique could be extended to other atmospheric trace gases, depending on the vapor pressure of the gas.

Relationship between MODIS based Aerosol Optical Depth and PM10 over Croatia

2014 ◽  
Vol 6 (1) ◽  
Author(s):  
Sanja Grgurić ◽  
Josip Križan ◽  
Goran Gašparac ◽  
Oleg Antonić ◽  
Zdravko Špirić ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Mass Concentration ◽  
Meteorological Data ◽  
Neural Network Approach ◽  
Data Set ◽  
Independent Variables ◽  
Data Variability ◽  
Modis Aod ◽  
The Relationship

AbstractThis study analyzes the relationship between Aerosol Optical Depth (AOD) obtained from Terra and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) and ground-based PM10 mass concentration distribution over a period of 5 years (2008–2012), and investigates the applicability of satellite AOD data for ground PM10 mapping for the Croatian territory. Many studies have shown that satellite AOD data are correlated to ground-based PM mass concentration. However, the relationship between AOD and PM is not explicit and there are unknowns that cause uncertainties in this relationship.The relationship between MODIS AOD and ground-based PM10 has been studied on the basis of a large data set where daily averaged PM10 data from the 12 air quality stations across Croatia over the 5 year period are correlated with AODs retrieved from MODIS Terra and Aqua. A database was developed to associate coincident MODIS AOD (independent) and PM10 data (dependent variable). Additional tested independent variables (predictors, estimators) included season, cloud fraction, and meteorological parameters — including temperature, air pressure, relative humidity, wind speed, wind direction, as well as planetary boundary layer height — using meteorological data from WRF (Weather Research and Forecast) model.It has been found that 1) a univariate linear regression model fails at explaining the data variability well which suggests nonlinearity of the AOD-PM10 relationship, and 2) explanation of data variability can be improved with multivariate linear modeling and a neural network approach, using additional independent variables.

scholarly journals The Black Hole Mass vs Bulge Mass Relationship in Spiral Galaxies

2001 ◽  
Vol 205 ◽  
pp. 58-61
Author(s):  
Alessandro Marconi ◽  
David Axon ◽  
John Atkinson ◽  
James Binney ◽  
Alessandro Capetti ◽  
...  
Keyword(s):  
Black Hole ◽  
Spatial Resolution ◽  
Mass Concentration ◽  
Rotation Curve ◽  
Spiral Galaxies ◽  
Surface Photometry ◽  
Black Hole Mass ◽  
Limited Sample ◽  
First Results ◽  
The Relationship

We describe an on-going HST program aimed at determining the relationship between the nuclear black hole mass and bulge mass in spiral galaxies. We have selected a volume limited sample of 54 nearby spiral galaxies for which we already have ground based emission line rotation curves, CCD surface photometry and radio maps. We are now obtaining HST/STIS longslit observations of each of the galaxies in the sample in order to determine the nuclear Hα rotation curve at high (∼ 0.1) spatial resolution. We will use these data to measure the unresolved dark mass concentration at the nucleus of each object. Here we show the first results from observations of objects in the sample.

scholarly journals Attribute Reduction in Soft Contexts Based on Soft Sets and Its Application to Formal Contexts

Mathematics ◽  
2020 ◽  
Vol 8 (5) ◽  
pp. 689
Author(s):  
Won Keun Min
Keyword(s):  
Attribute Reduction ◽  
Extraction Process ◽  
Formal Context ◽  
Soft Sets ◽  
Step Method ◽  
The Relationship

We introduce the notion of the reduct of soft contexts, which is a special notion of a consistent set for soft contexts. Then, we study its properties and show that this notion is well explained by the two classes, 1 0 and 2 0 , of independent attributes. In particular, we describe in detail how to extract a reduct from a given consistent set. Then, based on this extraction process, we propose a six-step method for constructing a reduct from a given consistent set. Additionally, to apply this method to formal contexts, we examine the relationship between the reducts of a given formal context and the reducts of the associated soft context. We finally illustrate the process of obtaining reducts in a formal context using this relationship and the six-step method using an example.

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