1,013 research outputs found
Performance of a micro-engineered ultrasonic particle manipulator
No full textAn ultrasonic microfluidic particle manipulator has been modeled and its experimentally measured separation performance has been compared with the modeled results for 1 µm latex particles, and yeast particles in water
Dynamics of inertial disk particles in turbulent channel flow
No full textA suspension of oblate spheroidal (disk-like) particles in turbulent channel flow has been investigated with focus on the translational and rotational particle statistics. The effects of particle aspect ratio and inertia have been explored. The disk-like particles exhibited a significant preferential orientation in the plane of the mean shear. The influence of the particle shape on the orientation and rotation diminished as translational inertia increased from Stokes number 1 to 30. Isotropization of both orientation and rotation could be observed in the core region of the channel. Keywords: oblate spheroids, preferential orientation, shape effects, inertia effects
The characterization and enhancement of light scattering for thin solar cells
No full textPhotovoltaic (PV) power is one of the most promising technologies for worldwide clean and sustainable energy production and as the technology begins to enter the mainstream the requirement for efficient use of materials becomes increasingly important. However, reducing material thickness typically lowers optical absorption, leading to lower cell efficiency. One proven method for enhancing absorption in a thin device is by texturing interfaces, typically achieved in the top transparent conducting oxide (TCO) of a thin-film design. This works by scattering transmitted light and therefore increasing its effective optical path length within the absorber layer. However, introducing rough surfaces to a PV device can lead to fabrication issues and also increases surface recombination which is detrimental to the electrical characteristics of the end device. In recent years, possible alternatives to reliance on random texturing have been found through the use of optimized diffraction gratings and the plasmonic effects of metal nanoparticles. In this work, comprehensive optical characterization has been carried out on a range of samples using traditional and novel techniques. In particular, a custom built wavelength and angle resolved scattering (WARS) measurement system has been developed and used to determine key characteristics that would remain undetected by conventional measurements. The investigation of several commercial and experimental TCO films has been carried out and clear links between topography and optical characteristics have been determined. These textured surfaces have also been modelled using finite difference time domain (FDTD) simulations which have shown good agreement with measurement results. This has allowed for further investigation of the effects of TCO topography through simulation which has revealed that scattering is best enhanced by increasing the aspect ratio of the texture rather than the overall scale. Periodic arrays of silver nanoparticles incorporated into a thin-film solar cell back-reflector design have also been extensively characterized and modelled and shown to provide scattering through both diffraction and plasmonic mechanisms, leading to an increase in useful absorption by up to 140% in comparison to a planar device
Inertial effects on non-spherical particle rotation on turbulent channel flow
No full textWe investigated the rotation of non-spherical particles (rod-like and disk-like) in turbulent channel flow with focus on inertial effects. A direct numerical simulation (DNS) with an Eulerian-Lagrangian approach was performed. A wide range of particle aspect ratios, λ, ranging from 0.01 to 50 were considered for Stokes numbers St equal to 1 and 30. In the particle reference frame, statistical results reveal the importance of shape effect on the particle rotation. The rods (λ > 1) are spinning (rotation about their symmetry axis) more than tumbling (rotation about other axes) whereas disks (λ < 1) behave oppositely. With increasing particle inertia, i.e. higher St, the preferential tumbling of the disks and the spinning of the rods are reduced. We ascribe these observations to the varying degree of alignment of the particle symmetry axis with the fluid vorticity vector
A comparison of rosseland-mean opacities from op and opal
No full textMonochromatic opacities from the Opacity Project (OP) have been augmented by hitherto missing inner-shell contributions. OP Rosseland-mean opacities, κR, are compared with results from OPAL for the six elements H, He, C, O, S and Fe. The OPAL data are obtained from the project's website. Agreement for H is close everywhere except for the region of log(T) 6 and log(R) −1 (R=ρ/T36 where ρ is mass density in g cm3 and T6= 106×T with T in K). In that region κR(OPAL) is larger than κR(OP) by up to 13 per cent. The differences are caused by different equations of state (EOS). In the region concerned, OP has the H ground state undergoing dissolution, leading to a small H-neutral ionization fraction, while OPAL has larger values for that fraction. A similar difference occurs for He at log(R) −1 and log(T) 6.4, where OP has the He+ ground state undergoing dissolution. The OPAL website does not provide single-element Rosseland means for elements other than H and He. Comparisons between OP and OPAL are made for mixtures with X= 0.9, Z= 0.1 and Z containing pure C, O or S. There are some differences: at the lower temperatures, say log(T) ≤ 5.5, owing to differences in atomic data, with the OP R-matrix data probably being the more accurate; and at higher temperatures mainly owing to differences in level populations resulting from the use of different EOS theories. In the original OP work, R-matrix data for iron were supplemented by data obtained using the configuration-interaction (CI) code superstructure. The experiment is made of replacing much of the original iron data with new data from the CI code autostructure. Inclusion of intercombination lines gives an increase in κR of up to 18 per cent. The OPAL website does not allow for Z containing pure iron. Comparisons are made for an iron-rich mixture, X= 0.9, Z= 0.1 and Z containing C and Fe with C:Fe = 2:1 by number fraction. There are some differences between OP and OPAL for that case: the OP 'Z-bump' in κR is shifted to slightly higher temperatures, compared with OPAL. Overall, there is good agreement between OP and OPAL Rosseland-mean opacities for the six elements, but there are some differences. Recent work has shown that helioseismology measurements give a very accurate value for the depth of the solar convective zone, RCZ, and that, taking account of recent revisions in abundances, solar models give agreement with that value only if opacities at RCZ are about 20 per cent larger than OPAL values. For the six-element mix at RCZ we obtain κR(OP) to be larger than κR(OPAL) by 5 per cent
Iran's Islamic Revolution: the Ulama, the West, nationalism, and the growth of political consciousness
No full textThis dissertation seeks to offer an explanation for the Islamic Revolution, taking into account not only the social, political, and economic conditions of the time, but also religious and cultural elements. It seeks to determine the origins of the trends it identifies as important to an understanding of the causes of the Islamic Revolution.
These include the rise of nationalism, Iran’s exploitation by foreign powers, and the assertive posture of the Shi’a ulama
The Capture the Fracture® Partnership: an overview of a global initiative to increase the secondary fracture prevention care for patient benefit
No full textSummary: The Capture the Fracture® Partnership (CTF-P) is a unique collaboration between the International Osteoporosis Foundation, academic units and industry partners to enhance the implementation of effective, efficient fracture liaison services (FLSs) with a good patient experience. CTF-P has generated valuable resources for the specific countries as well as the broader FLS community to improve the initiation, effectiveness and sustainability of FLS in a wide range of healthcare settings.</p
Author Correction: Rapid increase in the risk of heat-related mortality.
No full textCorrection to: Nature Communicationshttps://doi.org/10.1038/s41467-023-40599-x, published online 24 August 2023 The original version of this Article omitted from the author list the 17th author, “Multi-Country Multi-City (MCC) collaborative research network”, which is the consortium providing the mortality data. A list of consortium authors and their affiliations are provided in the HTML version of this Correction. Part of the Author Contributions statement was incorrectly given and should have read ‘A.M.V.C., E.M.F., B.A., M.D.S.Z.S.C., Y.L.G., Y.G., Y.H., V.H., J.K., E.L., D.R., N.R., N.S., S.S., A.U., A.G. and the MCC were involved in resources and data curation.’ In addition, the primary affiliation ‘Climate Research Foundation (FIC), Madrid, Spain’ for Dominic Roye was missing
Modelling and simulation of fluidized-bed boilers and gasifiers for carbonaceous solids.
No full textSUMMARY
A comprehensive computer simulation program that
can deal with a wide range of different operating
conditions in fluidized bed combustion and gasification has
been developed.
It includes the possibility of simulating
operations with various types of coal, charcoal or wood and
can predict the behaviour of a real unit by giving several
important performance parameters, such as:
(a) Emulsion and bubble gas composition profiles throughout
the bed height. The components included are: CO2 , CO, 02,
N 2 , H2 0, H2 , CH4 , SO2 , NO, C2 H 6 , H2 S, NH3 and Tar.
(b) Gas phase composition throughout the freeboard height.
(c) Solid compositions of the coal (or any other
carbonaceous material), limestone and inert in the bed and
throughout the freeboard. The considered components are: C,
H, 0, N, S, ash, volatiles, moisture in the coal, CaCO3,
CaO, CaSO4 , moisture in the limestone, Si0 2 , and moisture
in the inert.
(d) Temperature profiles of all phases throughout the bed
and the freeboard.
(e) Solid particle size distributions in the bed and in the
freeboard sections. The considered effects are:
elutriation, entrainment, attrition and recycling in all
the three possible types of solid phases present;
(f) Heat transfered to water/steam inside the tubes, steam
production and tube surface temperatures in the case of
boiler simulation
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