Orientation Distributions of Cellulose Nanofibrils and Nanocrystals in Confined Flow

2019 ◽  
Author(s):  
Tomas Rosen ◽  
Ruifu Wang ◽  
Chengbo Zhan ◽  
Hongrui He ◽  
Shirish Chodankar ◽  
...  
Keyword(s):  
Cellulose Nanofibrils ◽  
Low Flow ◽  
Particle Interactions ◽  
Flow Rates ◽  
X Ray Scattering ◽  
Strong Shear ◽  
Confined Flow ◽  
Orientational Distribution ◽  
Orientation Distributions ◽  
Elongated Nanoparticles

The pursuit of sustainable and environmentally friendly materials has been driving a tremendous interest in biobased alternatives in the last decade. Nanocellulose has been widely seen as a prime contender due to its impressive properties as well as being abundant and biodegradable. Recently, it has been demonstrated how nanocellulosic materials can be hydrodynamically aligned in flows and assembled continuously into materials with tunable macroscopic properties. However, the aligning mechanisms of the highly entangled system of elongated nanoparticles in different flow situations still remain largely unknown. Here, we investigate the orientation distributions of cellulose nanofibrils and nanocrystals (CNF and CNC) in a straight quadratic channel at various flow rates using small-angle X-ray scattering (SAXS), where CNF and CNC are aligned by strong shear flow close to the walls. In dilute systems, CNC behave as Brownian ellipsoids, while at semi-dilute concentrations there seems to be a limit to how high alignment of CNF and CNC can be achieved in a shear dominated flow even though particle interactions clearly aid in aligning the system at low flow rates. Furthermore, we show how some essential parameters in the orientational distribution can be obtained with polarized optical microscopy.

Orientation Distributions of Cellulose Nanofibrils and Nanocrystals in Confined Flow

2019 ◽  
Author(s):  
Tomas Rosen ◽  
Ruifu Wang ◽  
Chengbo Zhan ◽  
Hongrui He ◽  
Shirish Chodankar ◽  
...  
Keyword(s):  
Cellulose Nanofibrils ◽  
Low Flow ◽  
Particle Interactions ◽  
Flow Rates ◽  
X Ray Scattering ◽  
Strong Shear ◽  
Confined Flow ◽  
Orientational Distribution ◽  
Orientation Distributions ◽  
Elongated Nanoparticles

The pursuit of sustainable and environmentally friendly materials has been driving a tremendous interest in biobased alternatives in the last decade. Nanocellulose has been widely seen as a prime contender due to its impressive properties as well as being abundant and biodegradable. Recently, it has been demonstrated how nanocellulosic materials can be hydrodynamically aligned in flows and assembled continuously into materials with tunable macroscopic properties. However, the aligning mechanisms of the highly entangled system of elongated nanoparticles in different flow situations still remain largely unknown. Here, we investigate the orientation distributions of cellulose nanofibrils and nanocrystals (CNF and CNC) in a straight quadratic channel at various flow rates using small-angle X-ray scattering (SAXS), where CNF and CNC are aligned by strong shear flow close to the walls. In dilute systems, CNC behave as Brownian ellipsoids, while at semi-dilute concentrations there seems to be a limit to how high alignment of CNF and CNC can be achieved in a shear dominated flow even though particle interactions clearly aid in aligning the system at low flow rates. Furthermore, we show how some essential parameters in the orientational distribution can be obtained with polarized optical microscopy.

Quantifying Multiple Crystallite Orientations and Crystal Heterogeneities in Complex Thin Film Materials

2019 ◽  
Author(s):  
Jonathan Ogle ◽  
Daniel Powell ◽  
Eric Amerling ◽  
Detlef Matthias Smilgies ◽  
Luisa Whittaker-Brooks
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Structural Design ◽  
Grazing Incidence ◽  
Crystallite Orientation ◽  
Miller Index ◽  
X Ray ◽  
X Ray Scattering ◽  
Orientation Distributions ◽  
Orientation Information

<p>Thin film materials have become increasingly complex in morphological and structural design. When characterizing the structure of these films, a crucial field of study is the role that crystallite orientation plays in giving rise to unique electronic properties. It is therefore important to have a comparative tool for understanding differences in crystallite orientation within a thin film, and also the ability to compare the structural orientation between different thin films. Herein, we designed a new method dubbed the mosaicity factor (MF) to quantify crystallite orientation in thin films using grazing incidence wide-angle X-ray scattering (GIWAXS) patterns. This method for quantifying the orientation of thin films overcomes many limitations inherent in previous approaches such as noise sensitivity, the ability to compare orientation distributions along different axes, and the ability to quantify multiple crystallite orientations observed within the same Miller index. Following the presentation of MF, we proceed to discussing case studies to show the efficacy and range of application available for the use of MF. These studies show how using the MF approach yields quantitative orientation information for various materials assembled on a substrate.<b></b></p>

Assessment of the Use of Humidified Nasal Cannulas for Oxygen Therapy in Patients with Epistaxis

ORL ◽  
2021 ◽  
pp. 1-5
Author(s):  
Jingjing Liu ◽  
Tengfang Chen ◽  
Zhenggang Lv ◽  
Dezhong Wu
Keyword(s):  
Flow Rate ◽  
Oxygen Therapy ◽  
Preliminary Investigation ◽  
Nasal Cannula ◽  
Low Flow ◽  
Antiplatelet Drugs ◽  
Flow Rates ◽  
The Past ◽  
Oxygen Inhalation ◽  
Significant Difference

<b><i>Introduction:</i></b> In China, nasal cannula oxygen therapy is typically humidified. However, it is difficult to decide whether to suspend nasal cannula oxygen inhalation after the nosebleed has temporarily stopped. Therefore, we conducted a preliminary investigation on whether the use of humidified nasal cannulas in our hospital increases the incidence of epistaxis. <b><i>Methods:</i></b> We conducted a survey of 176,058 inpatients in our hospital and other city branches of our hospital over the past 3 years and obtained information concerning their use of humidified nasal cannulas for oxygen inhalation, nonhumidified nasal cannulas, anticoagulant and antiplatelet drugs, and oxygen inhalation flow rates. This information was compared with the data collected at consultation for epistaxis during these 3 years. <b><i>Results:</i></b> No significant difference was found between inpatients with humidified nasal cannulas and those without nasal cannula oxygen therapy in the incidence of consultations due to epistaxis (χ<sup>2</sup> = 1.007, <i>p</i> &#x3e; 0.05). The same trend was observed among hospitalized patients using anticoagulant and antiplatelet drugs (χ<sup>2</sup> = 2.082, <i>p</i> &#x3e; 0.05). Among the patients with an inhaled oxygen flow rate ≥5 L/min, the incidence of ear-nose-throat (ENT) consultations due to epistaxis was 0. No statistically significant difference was found between inpatients with a humidified oxygen inhalation flow rate &#x3c;5 L/min and those without nasal cannula oxygen therapy in the incidence of ENT consultations due to epistaxis (χ<sup>2</sup> = 0.838, <i>p</i> &#x3e; 0.05). A statistically significant difference was observed in the incidence of ENT consultations due to epistaxis between the low-flow nonhumidified nasal cannula and nonnasal cannula oxygen inhalation groups (χ<sup>2</sup> = 18.428, <i>p</i> &#x3c; 0.001). The same trend was observed between the 2 groups of low-flow humidified and low-flow nonhumidified nasal cannula oxygen inhalation (χ<sup>2</sup> = 26.194, <i>p</i> &#x3c; 0.001). <b><i>Discussion/Conclusion:</i></b> Neither high-flow humidified nasal cannula oxygen inhalation nor low-flow humidified nasal cannula oxygen inhalation will increase the incidence of recurrent or serious epistaxis complications; the same trend was observed for patients who use anticoagulant and antiplatelet drugs. Humidification during low-flow nasal cannula oxygen inhalation can prevent severe and repeated epistaxis to a certain extent.

scholarly journals TEMPO-oxidised cellulose nanofibrils; probing the mechanisms of gelation via small angle X-ray scattering

2018 ◽  
Vol 20 (23) ◽  
pp. 16012-16020 ◽  
Author(s):  
Julien Schmitt ◽  
Vincenzo Calabrese ◽  
Marcelo A. da Silva ◽  
Saskia Lindhoud ◽  
Viveka Alfredsson ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Small Angle ◽  
Cellulose Nanofibrils ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

The structure of dispersions of TEMPO-oxidised cellulose nanofibrils at various concentrations, in water and in NaCl aqueous solutions, was probed using small angle X-ray scattering and results were compared with rheology.

Structural Stability of CdSe Nanocrystallite Dispersions

1995 ◽  
Vol 400 ◽  
Author(s):  
H. Mattoussi ◽  
C.B. Murray ◽  
M.G. Bawendi ◽  
R. Ober
Keyword(s):  
Thermodynamic Properties ◽  
Structural Stability ◽  
Particle Interactions ◽  
X Ray ◽  
X Ray Scattering ◽  
Crystallite Surface ◽  
Ray Scattering

AbstractX-ray scattering at small angles (SAXS) is used to study the structure and the thermodynamic properties of dispersions of CdSe nanocrystallite particles. In particular, this study allowed us to probe the inter particle interactions, and their dependence on several relevant parameters, such as the nature and size of the capping units attached to the crystallite surface and solvent.

Effect of Tip Clearance on Suction Performance at Different Flow Rates in a Mixed Flow Pump

2014 ◽  
Author(s):  
Yo Han Jung ◽  
Young Uk Min ◽  
Jin Young Kim
Keyword(s):  
Performance Test ◽  
Stokes Equations ◽  
Flow Characteristics ◽  
Tip Clearance ◽  
Low Flow ◽  
Tip Leakage Flow ◽  
Mixed Flow ◽  
Flow Rates ◽  
Suction Performance ◽  
Flow Pump

This paper presents a numerical investigation of the effect of tip clearance on the suction performance and flow characteristics at different flow rates in a vertical mixed-flow pump. Numerical analyses were carried out by solving three-dimensional Reynolds-averaged Navier-Stokes equations. Steady computations were performed for three different tip clearances under noncavitating and cavitating conditions at design and off-design conditions. The pump performance test was performed for the mixed-flow pump and numerical results were validated by comparing the experimental data for a system characterized by the original tip clearance. It was shown that for large tip clearance, the head breakdown occurred earlier at the design and high flow rates. However, the head breakdown was quite delayed at low flow rate. This resulted from the cavitation structure caused by the tip leakage flow at different flow rates.

Experimental Investigation of Pressure Fluctuations on Inner Wall of a Centrifugal Pump

2019 ◽  
Vol 36 (4) ◽  
pp. 401-410 ◽  
Author(s):  
Xiao-Qi Jia ◽  
Bao-Ling Cui ◽  
Zu-Chao Zhu ◽  
Yu-Liang Zhang
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
High Flow ◽  
Low Flow ◽  
Centrifugal Pumps ◽  
Flow Rates ◽  
Pressure Distributions ◽  
Blade Passing Frequency

Abstract Affected by rotor–stator interaction and unstable inner flow, asymmetric pressure distributions and pressure fluctuations cannot be avoided in centrifugal pumps. To study the pressure distributions on volute and front casing walls, dynamic pressure tests are carried out on a centrifugal pump. Frequency spectrum analysis of pressure fluctuation is presented based on Fast Fourier transform and steady pressure distribution is obtained based on time-average method. The results show that amplitudes of pressure fluctuation and blade-passing frequency are sensitive to the flow rate. At low flow rates, high-pressure region and large pressure gradients near the volute tongue are observed, and the main factors contributing to the pressure fluctuation are fluctuations in blade-passing frequency and high-frequency fluctuations. By contrast, at high flow rates, fluctuations of rotating-frequency and low frequencies are the main contributors to pressure fluctuation. Moreover, at low flow rates, pressure near volute tongue increases rapidly at first and thereafter increases slowly, whereas at high flow rates, pressure decreases sharply. Asymmetries are observed in the pressure distributions on both volute and front casing walls. With increasing of flow rate, both asymmetries in the pressure distributions and magnitude of the pressure decrease.

EFFECT OF AXIAL CASING GROOVE GEOMETRY ON ROTOR-GROOVE INTERACTIONS IN THE TIP REGION OF A COMPRESSOR

2021 ◽  
pp. 1-54
Author(s):  
Subhra Shankha Koley ◽  
Huang Chen ◽  
Ayush Saraswat ◽  
Joseph Katz
Keyword(s):  
Rotor Blade ◽  
Leading Edge ◽  
Secondary Flows ◽  
Low Flow ◽  
Flow Angle ◽  
Flow Rates ◽  
Piv Measurements ◽  
Tip Leakage ◽  
Large Vortex ◽  
Blade Leading Edge

Abstract This experimental study characterizes the interactions of axial casing grooves with the flow in the tip region of an axial turbomachine. The tests involve grooves with the same inlet overlapping with the rotor blade leading edge, but with different exit directions located upstream. Among them, U grooves, whose circumferential outflow opposes the blade motion, achieve a 60% reduction in stall flowrate, but degrade the efficiency around the best efficiency point (BEP) by 2%. The S grooves, whose outlets are parallel to the blade rotation, improve the stall flowrate by only 36%, but do not degrade the BEP performance. To elucidate the mechanisms involved, stereo-PIV measurements covering the tip region and interior of grooves are performed in a refractive index matched facility. At low flow rates, the inflow into both grooves, which peaks when they are aligned with the blade pressure side, rolls up into a large vortex that lingers within the groove. By design, the outflow from S grooves is circumferentially positive. For the U grooves, fast circumferentially negative outflow peaks at the base of each groove, causing substantial periodic variations in the flow angle near the blade leading edge. At BEP, interactions with both grooves become milder, and most of the tip leakage vortex remains in the passage. Interactions with the S grooves are limited hence they do not degrade the efficiency. In contrast, the inflow into and outflow from the U grooves reverses direction, causing entrainment of secondary flows, which likely contribute to the reduced BEP efficiency.

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