| 1. |
- Abbasiasl, Taher, et al.
(författare)
-
Effect of intensified cavitation using poly (vinyl alcohol) microbubbles on spray atomization characteristics in microscale
- 2020
-
Ingår i: AIP Advances. - : American Institute of Physics (AIP). - 2158-3226. ; 10:2
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, cavitating flows inside a transparent cylindrical nozzle with an inner diameter of 0.9 mm were visualized, and the effect of cavitation on atomization characteristics of emerging sprays was investigated. Different patterns of cavitating flows inside the nozzle were visualized using a high-speed camera. In-house codes were developed to process the captured images to study the droplet size distribution and droplet velocity in different flow regimes. The results show that cavitating flows at the microscale have significant effects on atomization characteristics of the spray. Two working fluids, namely, water and poly(vinyl alcohol) microbubble (PVA MB) suspension, were employed. Accordingly, the injection pressures were detected as 690 kPa, 1035 kPa, and 1725 kPa for cavitation inception, supercavitation, and hydraulic flip flow regimes in the case of water, respectively. The corresponding pressures for the aforementioned patterns for PVA MB suspension were 590 kPa, 760 kPa, and 1070 kPa, respectively. At the microscale, as a result of a higher volume fraction of cavitation bubbles inside the nozzle, there is no large difference between the cavitation numbers corresponding to cavitating and hydraulic flip flows. Although the percentage of droplets with diameters smaller than 200 μm was roughly the same for both cases of water and PVA MB suspension, the Sauter mean diameter was considerably lower in the case of PVA MBs. Moreover, higher droplet velocities were achieved in the case of PVA MBs at lower injection pressures.
|
|
| 2. |
- Adebiyi, Abdulafeez, et al.
(författare)
-
Effect of surface friction on ultrafast flame acceleration in obstructed cylindrical pipes
- 2019
-
Ingår i: AIP Advances. - : American Institute of Physics (AIP). - 2158-3226. ; 9:3
-
Tidskriftsartikel (refereegranskat)abstract
- The Bychkov model of ultrafast flame acceleration in obstructed tubes [Valiev et al., "Flame Acceleration in Channels with Obstacles in the Deflagration-to-Detonation Transition," Combust. Flame 157, 1012 (2010)] employed a number of simplifying assumptions, including those of free-slip and adiabatic surfaces of the obstacles and of the tube wall. In the present work, the influence of free-slip/non-slip surface conditions on the flame dynamics in a cylindrical tube of radius R, involving an array of parallel, tightly-spaced obstacles of size αR, is scrutinized by means of the computational simulations of the axisymmetric fully-compressible gasdynamics and combustion equations with an Arrhenius chemical kinetics. Specifically, non-slip and free-slip surfaces are compared for the blockage ratio, α, and the spacing between the obstacles, ΔZ, in the ranges 1/3 ≤ α ≤ 2/3 and 0.25 ≤ ΔZ/R ≤ 2.0, respectively. For these parameters, an impact of surface friction on flameacceleration is shown to be minor, only 1-4%, slightly facilitating acceleration in a tube with ΔZ/R = 0.5 and moderating acceleration in thecase of ΔZ/R = 0.25. Given the fact that the physical boundary conditions are non-slip as far as the continuum assumption is valid, the presentwork thereby justifies the Bychkov model, employing the free-slip conditions, and makes its wider applicable to the practical reality. Whilethis result can be anticipated and explained by a fact that flame propagation is mainly driven by its spreading in the unobstructed portion ofan obstructed tube (i.e. far from the tube wall), the situation is, however, qualitatively different from that in the unobstructed tubes, wheresurface friction modifies the flame dynamics conceptually.
|
|
| 3. |
- Ahlberg Helgee, Edit, 1986, et al.
(författare)
-
Adsorption of metal atoms at a buckled graphene grain boundary using model potentials
- 2016
-
Ingår i: AIP Advances. - : AIP Publishing. - 2158-3226 .- 2158-3226. ; 6:1
-
Tidskriftsartikel (refereegranskat)abstract
- Two model potentials have been evaluated with regard to their ability to model adsorption of single metal atoms on a buckled graphene grain boundary. One of the potentials is a Lennard-Jones potential parametrized for gold and carbon, while the other is a bond-order potential parametrized for the interaction between carbon and platinum. Metals are expected to adsorb more strongly to grain boundaries than to pristine graphene due to their enhanced adsorption at point defects resembling those that constitute the grain boundary. Of the two potentials considered here, only the bond-order potential reproduces this behavior and predicts the energy of the adsorbate to be about 0.8 eV lower at the grain boundary than on pristine graphene. The Lennard-Jones potential predicts no significant difference in energy between adsorbates at the boundary and on pristine graphene. These results indicate that the Lennard-Jones potential is not suitable for studies of metal adsorption on defects in graphene, and that bond-order potentials are preferable.
|
|
| 4. |
- Alnoor, Hatim, et al.
(författare)
-
Effect of precursor solutions stirring on deep level defects concentration and spatial distribution in low temperature aqueous chemical synthesis of zinc oxide nanorods
- 2015
-
Ingår i: AIP Advances. - : AMER INST PHYSICS. - 2158-3226. ; 5:8
-
Tidskriftsartikel (refereegranskat)abstract
- Hexagonal c-axis oriented zinc oxide (ZnO) nanorods (NRs) with 120-300 nm diameters are synthesized via the low temperature aqueous chemical route at 80 degrees C on silver-coated glass substrates. The influence of varying the precursor solutions stirring durations on the concentration and spatial distributions of deep level defects in ZnO NRs is investigated. Room temperature micro-photoluminesnce (mu-PL) spectra were collected for all samples. Cathodoluminescence (CL) spectra of the as-synthesized NRs reveal a significant change in the intensity ratio of the near band edge emission (NBE) to the deep-level emission (DLE) peaks with increasing stirring durations. This is attributed to the variation in the concentration of the oxygen-deficiency with increasing stirring durations as suggested from the X-ray photoelectron spectroscopy analysis. Spatially resolved CL spectra taken along individual NRs revealed that stirring the precursor solutions for relatively short duration (1-3 h), which likely induced high super saturation under thermodynamic equilibrium during the synthesis process, is observed to favor the formation of point defects moving towards the tip of the NRs. In contrary, stirring for longer duration (5-15 h) will induce low super saturation favoring the formation of point defects located at the bottom of the NRs. These findings demonstrate that it is possible to control the concentration and spatial distribution of deep level defects in ZnO NRs by varying the stirring durations of the precursor solutions.
|
|
| 5. |
- Amiri, A., et al.
(författare)
-
A replacement model to simulate the nonlinear dynamics of electro-responsive liquid crystal coatings
- 2023
-
Ingår i: AIP Advances. - : AIP Publishing. - 2158-3226. ; 13:3
-
Tidskriftsartikel (refereegranskat)abstract
- An electric circuit replacement model is proposed to simulate the key nonlinear dynamics of electro-responsive liquid crystal polymer networks (LCNs). LCNs are known for having great potential to be integrated into smart functional surfaces due to their ability to generate various surface patterns. However, due to their complex molecular dynamics, low-order dynamic models that can accurately describe and predict their dynamic behavior are still lacking. In light of this research gap, we develop a lumped-parameter replacement model based on the observed dynamics in the experimental data and the physics of LCN dielectric properties. The unique assembly of lumped parameters in its simplest form describes the transformation of a high-frequency input voltage to a relatively slow increase in the local height of the LCN coating in between the electrodes, serving as an excitation mechanism to induce height change. The nonlinear dynamics of this height increase, as a function of both excitation frequency and voltage, is described by the proposed model. Furthermore, the comparison of the simulation results with the experimental data from LCN shows that key LCN response characteristics are captured well by the model. This model makes it possible to accurately predict and control the response of the electro-responsive LCN surfaces to obtain a predefined desired deformation pattern, which is a vital requirement for integrating them in haptic and smart surface devices.
|
|
| 6. |
- Azina, Clio, et al.
(författare)
-
Effect of titanium and zirconium carbide interphases on the thermal conductivity and interfacial heat transfers in copper/diamond composite materials
- 2019
-
Ingår i: AIP Advances. - : AMER INST PHYSICS. - 2158-3226. ; 9:5
-
Tidskriftsartikel (refereegranskat)abstract
- Thermal properties of metal matrix composite materials are becoming ever more relevant with the increasing demand for thermally efficient materials. In this work, the thermal conductivity and heat transfers at the interfaces of copper matrix composite materials reinforced with diamond particles (Cu/D) are discussed. The composite materials contain either ZrC or TiC interphases and exhibit, respectively, higher and lower thermal conductivities with respect to their pure Cu/D counterparts. These thermal conductivities are accounted to the presence of strong covalent bonds and increased relative densities. The role of these interphases is also discussed regarding the phonon transmission at the interfaces. (c) 2019 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
|
|
| 7. |
- Azzouz, Hatim, et al.
(författare)
-
Efficient single particle detection with a superconducting nanowire
- 2012
-
Ingår i: AIP Advances. - : AIP Publishing. - 2158-3226. ; 2:3
-
Tidskriftsartikel (refereegranskat)abstract
- Detection of alpha- and beta-particles is of paramount importance in a wide range of applications. Current particle detectors are all macroscopic and have limited time resolution. We demonstrate a nanoscale particle detector with a small detection volume, high detection efficiency, short dead times and low dark count levels. We measure alpha- and beta-particle detection efficiencies close to unity using different sources and also demonstrate blindness towards gamma-rays. Our nanoscale detector offers particle detection measurements with unprecendented spatial resolution.
|
|
| 8. |
- Bejhed Stjernberg, Rebecca, et al.
(författare)
-
Magnetic nanobeads present during enzymatic amplification and labeling for a simplified DNA detection protocol based on AC susceptometry
- 2015
-
Ingår i: AIP Advances. - : AIP Publishing. - 2158-3226. ; 5:12
-
Tidskriftsartikel (refereegranskat)abstract
- Magnetic biosensors are promising candidates for low-cost point-of-care biodiagnostic devices. For optimal efficiency it is crucial to minimize the time and complexity of the assay protocol including target recognition, amplification, labeling and read-out. In this work, possibilities for protocol simplifications for a DNA biodetection principle relying on hybridization of magnetic nanobeads to rolling circle amplification (RCA) products are investigated. The target DNA is recognized through a padlock ligation assay resulting in DNA circles serving as templates for the RCA process. It is found that beads can be present during amplification without noticeably interfering with the enzyme used for RCA (phi29 polymerase). As a result, the bead-coil hybridization can be performed immediately after amplification in a one-step manner at elevated temperature within a few minutes prior to read-out in an AC susceptometer setup, i.e. a combined protocol approach. Moreover, by recording the phase angle xi = arctan(chi ''/chi'), where chi and chi '' are the in-phase and out-of-phase components of the AC susceptibility, respectively, at one single frequency the total assay time for the optimized combined protocol would be no more than 1.5 hours, often a relevant time frame for diagnosis of cancer and infectious disease. Also, applying the phase angle method normalization of AC susceptibility data is not needed. These findings are useful for the development of point-of-care biodiagnostic devices relying on bead-coil binding and magnetic AC susceptometry.
|
|
| 9. |
- Bergström, Magnus
(författare)
-
A theoretical investigation of the influence of the second critical micelle concentration on the solubilization capacity of surfactant micelles
- 2018
-
Ingår i: AIP Advances. - : AMER INST PHYSICS. - 2158-3226. ; 8:5
-
Tidskriftsartikel (refereegranskat)abstract
- The solubilization of hydrophobic components by surfactants that form microemulsion droplets has been investigated from a theoretical point of view. By means of combining thermodynamics of self-assembly to form small systems with bending elasticity theory, we have been able to demonstrate a strong correlation between the second critical micelle concentration (CMC2) of surfactant micelles and their solubilization capacity (sigma). The correlation may be rationalized as a consequence of all three bending elasticity constants spontaneous curvature (H-0), bending rigidity (k(c)) and saddle-splay constant ((k) over bar (c)) showing similar trends with respect to the two quantities, i.e. sigma increases and CMC2 decreases with decreasing values of k(c)H(0) and increasing values of k(c) and (k) over bar (c), respectively. As a result, we demonstrate that the solubilization capacity is predicted to always be higher for a gemini surfactant with CMC2 = 11 mM as compared with a gemini surfactant with CMC2 = 18 mM. The predicted correlation between solubilization capacity and CMC2 agrees with experimental observations showing that surfactants forming larger micelles in general have better solubilization capacity than surfactants forming smaller micelles. The theory also demonstrates, in agreement with experiments, that sigma is raised in the entire range of surfactant concentrations, below as well as aboveCMC(2), regardless of micelle size. Consequently, our theory predicts that small micelles formed below CMC2 increase in size, whereas large rodlike or wormlike micelles formed above CMC2 decrease in size, as a hydrophobic solubilizate is added to a micellar solution.
|
|
| 10. |
- Bondarenko, Artem, 1992-, et al.
(författare)
-
Stochastic dynamics of strongly-bound magnetic vortex pairs
- 2017
-
Ingår i: AIP Advances. - : American Institute of Physics (AIP). - 2158-3226. ; 7:5
-
Tidskriftsartikel (refereegranskat)abstract
- We demonstrate that strongly-bound spin-vortex pairs exhibit pronounced stochastic behaviour. Such dynamics is due to collective magnetization states originating from purely dipolar interactions between the vortices. The resulting thermal noise exhibits telegraph-like behaviour, with random switching between different oscillation regimes observable at room temperature. The noise in the system is further studied by varying the external field and observing the related changes in the frequency of switching and the probability for different magnetic states and regimes. Monte Carlo simulations are used to replicate and explain the experimental observations.
|
|
