602 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
Assessing the Aeroacoustic Response of a Vehicle to Transient Flow Conditions from the Perspective of a Vehicle Occupant
No full textOn-road, a vehicle experiences unsteady flow conditions due to turbulence in the natural wind, moving through the unsteady wakes of other road vehicles and travelling through the stationary wakes generated by roadside obstacles. Separated flow structures in the sideglass region of a vehicle are particularly sensitive to unsteadiness in the onset flow. These regions are also areas where strong aeroacoustic effects can exist, in a region close to the passengers of a vehicle. The resulting aeroacoustic response to unsteadiness can lead to fluctuations and modulation at frequencies that a passenger is particularly sensitive towards. Results presented by this paper combine on-road measurement campaigns using instrumented vehicles in a range of different wind environments and aeroacoustic wind tunnel tests.
A new cabin noise simulation technique was developed to predict the time-varying wind noise in a vehicle using the cabin noise measured in the steady environment of the wind tunnel, and a record of the unsteady onset conditions on the road, considering each third-octave band individually. The simulated cabin noise predicted using this quasi-steady technique was compared against direct on-road cabin noise measurements recorded under the same flow conditions to assess the response of the vehicle to oncoming flow unsteadiness.
The technique predicted the modulation of the wind noise under unsteady on-road conditions with good fidelity. This is because the cabin noise response to oncoming flow unsteadiness remained generally quasi-steady up to fluctuation frequencies of approximately 2 to 5 Hz, with fluctuations at higher scales having a progressively smaller impact, and because most of the onset flow fluctuation energy on the road occurs at frequencies below this threshold.
The relative impact of the baseline level of cabin noise and the sensitivity of the cabin noise to changes in yaw angle were assessed in terms of occupant perception and this highlighted the importance of modulation. This can provide guidance when assessing the on-road wind noise performance of vehicle geometry modifications and of different vehicles
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
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
The mitochondrial T1095C mutation increases gentamicin-mediated apoptosis
No full textAbstract not availableHakan Muyderman, Neil R. Sims, Masashi Tanaka, Noriyuki Fuku, Ravinarayan Raghupathi, Dominic Thyagaraja
Vector Autoregressions, Policy Analysis, and Directed Acyclic Graphs: An Application to the U.S. Economy
No full textThe paper considers the use of directed acyclic graphs (DAGs), and their construction from observational data with PC-algorithm TETRAD II, in providing over-identifying restrictions on the innovations from a vector autoregression. Results from Sims’ 1986 model of the US economy are replicated and compared using these data-driven techniques. The directed graph results show Sims’ six-variable VAR is not rich enough to provide an unambiguous ordering at usual levels of statistical significance. A significance level in the neighborhood of 30 % is required to find a clear structural ordering. Although the DAG results are in agreement with Sims’ theory-based model for unemployment, differences are noted for the other five variables: income, money supply, price level, interest rates, and investment. Overall the DAG results are broadly consistent with a monetarist view with adaptive expectations and no hyperinflation.vector autoregression; directed graphs; policy analysis
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
Aproximaciones a la Econometría
No full textEn la concepción de la Econometría pueden adoptarse básicamente dos tipos de enfoques, que corresponden a dos formas distintas de concebir esta disciplina. Esta nota se hace eco de los comentarios críticos que la orientación econométrica basada en el supuesto de que las relaciones económicas son exactas ha recibido en la literatura, y se alinea en la corriente econométrica que se ha venido desarrollando a partir del trabajo pionero de Haavelmo (1944). Sobre esta publicación se puede decir, utilizando palabras de Hendry et al. (1989) que "merecidamente es considerada como el trabajo que constituyó a la Econometría moderna coma una disciplina separada". La nota concluye sobre una serie de consideraciones sobre la enseiianza de la Econometría
Designing a Turbine Blade Cooling System Using a Generalised Regression Genetic Algorithm
No full textThe design of a turbine blade cooling system is a multi-objective optimisation problem involving constraints and complex interaction among its design variables. The aim of this paper is to develop a methodology to optimise this design using Evolutionary Computing techniques. This paper presents Generalised Regression Genetic Algorithm (GRGA) and the mathematical model of a real-life turbine blade cooling system. Even in the presence of variable interaction, the methodology identifies a number of good feasible designs from which one could be finally chosen based on designer's preferences. The research also demonstrates that GRGA is capable of optimising a real-life design
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
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