Second-order Phenomenon Research Articles

An Analytical Solution for Unsteady Aerodynamic Forces on Streamlined Box Girders with Coupled Vibration

This paper is a contribution to analyzing the aerodynamic forces on a streamlined box girder (SBG) with coupled vibration in a potential flow. The key enabling step was to assume that the normal velocity of the airflow at an arbitrary point on the surface of the SBG was equal to the normal velocity of the surface motion. The aerodynamic drag force, lift force, and pitching moment were expressed as functions of the motion state of the SBG and the SBG’s shape-related parameters. To investigate the applicability of this force model, the analytical solution at various angles of attack was compared with a numerical simulation in a viscous flow. The results imply that the amplitude of the analytical lift force and pitching moment agree well with the numerical results under the angles of attack of 0° and ±3°. Furthermore, the analytical drag force effectively predicts the second-order phenomenon resulting from the multiplication of the vertical and torsional vibration velocities. As a consequence, the present analytical solution provides an effective method for analyzing the aerodynamic forces acting on SBGs with coupled vibration.

Grounding Functionalism and Explanatory Unificationism

AbstractIn this essay, I propose a functionalist theory of grounding (functionalist-grounding). Specifically, I argue that grounding is a second-order phenomenon that is realized by relations that play the noncausal explanatoriness role. I also show that functionalist-grounding can deal with a powerful challenge. Appeals to explanatory unificationism have been made to argue that the success of noncausal explanations does not depend on the existence of grounding relations. Against this, I argue that a systematization involving functionalist-grounding is superior to its anti-relational counterpart.

Fruitful femtofluidics using fast (acousto)fluidics

Acoustic streaming relies upon viscous attenuation of a propagating acoustic wave in a fluid to generate momentum flux and fluid flow. It is a nonlinear second-order phenomenon that generally produces rapid (∼10 cm/s) fluid flow but only against weak (∼10 kPa) pressure gradients. Here we describe a new form of acoustic streaming—acoustogeometric streaming—that is still nonlinear but relies on the interaction between the acoustic wave and the bounds of the fluid passage. If the boundaries oscillate with an amplitude that is significant in comparison to the width of the fluid passage, similarly rapid fluid flows may be generated even against very large (>1MPa) pressure gradients. This is used to propel fluids at 6 mm/s in 20–150 μm wide, 100 nm tall nanoslit geometries and to transport, split, combine, and mix ∼100 fl droplets of fluid. In this presentation, we will also show what happens when the nanoslit height is reduced below 10 nm, and demonstrate specific examples with some simple analysis that explains the various phenomena, closed by some explanation of the broader potential benefit of this approach.

Quantum physics applied to modern optical metal oxide semiconductor transistor

In recent years, traditional complementary metal–oxide–semiconductor (CMOS) scaling techniques have begun to reach the technological limits of available materials. A revolution in block-to-block communication is necessary to meet the ever-growing demand for microprocessor computational power. On-chip optical communication has been designated as a promising solution to circumvent the CMOS scaling bottlenecks: second-order phenomenon, which causes significant interconnect delays, and the nonscalability of the thermal voltage, which becomes significant in submicron CMOS technology. The metal oxide semiconductor quantum well transistor, a silicon-on-insulator metal–oxide–semiconductor field-effect transistor device, with a channel thickness reduced to the single nanometer scale is examined. The nanometric gate oxide, silicon, and buried oxide heterostructure in the channel forms a quantum potential well, creating discrete sub-bands within the silicon layer. Inter-sub-band-transitions within the quantum well may allow for radiative recombination in indirect band gap materials.

Time-averaged second-order pressure and velocity measurements in a pressurized oscillating flow prime mover

Nonlinear phenomena in oscillating flow devices cause the appearance of a relatively minor secondary flow known as acoustic streaming, which is superimposed on the primary oscillating flow. Knowledge of control parameters, such as the time-averaged second-order velocity and pressure, would elucidate the non-linear phenomena responsible for this part of the decrease in the system’s energetic efficiency. This paper focuses on the characterization of a travelling wave oscillating flow engine by measuring the time-averaged secondorder pressure and velocity. Laser Doppler velocimetry technique was used to measure the time-averaged second-order velocity. As streaming is a second-order phenomenon, its measurement requires specific settings especially in a pressurized device. Difficulties in obtaining the proper settings are highlighted in this study. The experiments were performed for mean pressures varying from 10 bars to 22 bars. Non-linear effect does not constantly increase with pressure.

Geometry-induced phase transition in fluids: Capillary prewetting

We report a new first-order phase transition preceding capillary condensation and corresponding to the discontinuous formation of a curved liquid meniscus. Using a mean-field microscopic approach based on the density functional theory we compute the complete phase diagram of a prototypical two-dimensional system exhibiting capillary condensation, namely that of a fluid with long-ranged dispersion intermolecular forces which is spatially confined by a substrate forming a semi-infinite rectangular pore exerting long-ranged dispersion forces on the fluid. In the T-μ plane the phase line of the new transition is tangential to the capillary condensation line at the capillary wetting temperature T(cw). The surface phase behavior of the system maps to planar wetting with the phase line of the new transition, termed capillary prewetting, mapping to the planar prewetting line. If capillary condensation is approached isothermally with T>T(cw), the meniscus forms at the capping wall and unbinds continuously, making capillary condensation a second-order phenomenon. We compute the corresponding critical exponent for the divergence of adsorption.

Unsteady Contribution of Water Vapor Condensation to Heat Losses at Flame-Wall Interaction

This study addresses experimentally the influence of a second-order phenomenon concerning wall heat losses in combustion chambers, namely water vapour phase change, that is likely to occur subsequently to flame-wall interaction. For this purpose, flame quenching experiments are carried out on methane-air mixtures in a constant volume combustion chamber, using heat gauges based on surface thermometry. The transient effect of condensation on wall heat flux, that was already predicted using numerical simulation, is evidenced in our experiments. Its evolution and magnitude are quantified and compared to the relevant literature. Although the time evolution of condensation heat flux was poorly predicted by numerical simulation, its magnitude is well estimated thanks to mass diffusion across the quenched layer at the wall. In the conditions investigated, the contribution of condensation to wall heat flux reaches about 0.1 MW/m2, which represents around 6% of conductive wall heat flux at quenching and up to 23% during the cooling phase after combustion.

3-D Formal Resolution of Maxwell Equations for the Computation of the No-Load Flux in an Axial Flux Permanent-Magnet Synchronous Machine

This paper presents a 3-D analytical model of an axial flux permanent-magnet synchronous machine, based on formal resolution of Maxwell equations. This method requires much less computation time than conventional 3-D finite elements, and is therefore suitable for optimization purposes. In a first part, the mathematical procedure used to compute the machine no-load flux is described in detail. This method is 3-D, and then takes into account the radial edge effects of the machine, as well as the curvature effects by a resolution in cylindrical coordinates. Moreover, the originality of this method lies in the fact that it is totally analytical. The obtained results are verified using 3-D finite elements, and compared with simpler analytical models of axial flux machines, taken from the literature. This work puts in evidence the advantages of the proposed model. In particular, it is shown that the radial edge effects are important for a correct estimation of the no-load flux. On the contrary, the curvature effects are a second-order phenomenon.

Quantification of the gas mass emitted during single explosions on Stromboli with the SO 2 imaging camera

We performed measurements using an SO 2 imaging camera of the SO 2 gas mass emitted during five discrete explosive events on Stromboli volcano on 3 October 2006. The SO 2 gas mass released during discrete explosions was 15–40 kg per explosion, producing 3–8% of the total daily SO 2 gas emission, demonstrating that in terms of gas flux Strombolian explosions are a second-order phenomenon compared with quiescent degassing. Using the typical gas composition measured with OP-FTIR allows us to determine the total gas mass released during an explosion as 360–960 kg with a volume of 1500–4100 m 3 at 1 bar. At the probable source pressure of gas slug formation of 75 MPa this gas amount would occupy a volume equivalent to a sphere with a radius of 0.8–1 m, comparable with estimates of Stromboli's conduit geometry.

Causal models in epidemiology: past inheritance and genetic future

The eruption of genetic research presents a tremendous opportunity to epidemiologists to improve our ability to identify causes of ill health. Epidemiologists have enthusiastically embraced the new tools of genomics and proteomics to investigate gene-environment interactions. We argue that neither the full import nor limitations of such studies can be appreciated without clarifying underlying theoretical models of interaction, etiologic fraction, and the fundamental concept of causality. We therefore explore different models of causality in the epidemiology of disease arising out of genes, environments, and the interplay between environments and genes. We begin from Rothman's "pie" model of necessary and sufficient causes, and then discuss newer approaches, which provide additional insights into multifactorial causal processes. These include directed acyclic graphs and structural equation models. Caution is urged in the application of two essential and closely related concepts found in many studies: interaction (effect modification) and the etiologic or attributable fraction. We review these concepts and present four important limitations.1. Interaction is a fundamental characteristic of any causal process involving a series of probabilistic steps, and not a second-order phenomenon identified after first accounting for "main effects".2. Standard methods of assessing interaction do not adequately consider the life course, and the temporal dynamics through which an individual's sufficient cause is completed. Different individuals may be at different stages of development along the path to disease, but this is not usually measurable. Thus, for example, acquired susceptibility in children can be an important source of variation.3. A distinction must be made between individual-based and population-level models. Most epidemiologic discussions of causality fail to make this distinction.4. At the population level, there is additional uncertainty in quantifying interaction and assigning etiologic fractions to different necessary causes because of ignorance about the components of the sufficient cause.

On marginally resolved objects in optical interferometry

With the present and soon-to-be breakthrough of optical interferometry, countless objects shall be within reach of interferometers; yet, most of them are expected to remain only marginally resolved with hectometric baselines. In this paper, we tackle the problem of deriving the properties of a marginally resolved object from its optical visibilities. We show that they depend on the moments of flux distribution of the object: centre, mean angular size, asymmetry, and curtosis. We also point out that the visibility amplitude is a second-order phenomenon, whereas the phase is a combination of a first-order term, giving the location of the photocentre, and a third-order term, more difficult to detect than the visibility amplitude, giving an asymmetry coefficient of the object. We then demonstrate that optical visibilities are not a good model constraint while the object stays marginally resolved, unless observations are carried out at different wavelengths. Finally, we show an application of this formalism to circumstellar discs.

Stokes and anti-Stokes photoluminescence of Rhodamine B in porous silicon

Rhodamine B (RhB) solution has been used to impregnate oxidised porous silicon (PS) in order to form RhB/PS nanocomposites. The photoluminescence (PL) mechanism of RhB/PS nanocomposites has been investigated through the effect of RhB concentration in solution and energy excitation. It was found that the energy transfer from PS nanocrystallites to RhB molecules is possible but it is not the principal route for radiative recombination. We note that chemical species on PS surface can play a key role on PL emission. An anti-Stokes photoluminescence (APL) has been observed when the excitation energy is in the range of PS photoluminescence band. The sublinear variation of the APL intensity with the laser power ( I APL∝P 0.59) excludes the processes of two-step two-photon absorption as origin of this PL. We show that its origin is related to a second-order phenomenon where phonon absorption plays an important role.

Gravitational oscillations of a liquid column in a pipe

We report gravity oscillations of a liquid column partially immersed in a bath of liquid. We stress some peculiarities of this system, namely (i) the fact that the mass of this oscillator constantly changes with time; (ii) the singular character of the beginning of the rise, for which the mass of the oscillator is zero; (iii) the sources of dissipation in this system, which is found to be dominated at low viscosity by the entrance (or exit) effects, leading to a long-range damping of the oscillations. We conclude with some qualitative descriptions of a second-order phenomenon, which is the eruption of a jet at the beginning of the rise.

Exact analysis of cascaded second-order nonlinearity in rotated Ti:LiNbO3 Couplers

The effects of anisotropic coupling on the nonlinear behavior of different LiNbO3 waveguides and couplers employing cascaded second-order nonlinearity are analyzed and the importance of leaky mode effect is shown. A set of practical coupling structures made of both symmetric and asymmetric waveguides is investigated and their performance is compared. The home-made computer-code, based on coupled wave theory and anisotropic mode propagation in the complex domain, allows an exact electromagnetic investigation of devices, taking into account both guided and leaky propagation in structures which exhibit losses, the generated second harmonic wave having leaky nature. As an example, for the well-investigated slab three layer waveguide, by taking into account the leaky nature of the generated second harmonic, the modal mismatch Δβ = 333 m−1 is obtained at the azimuthal angle θm ≅ 61.9∘ (between the crystal optical c-axis and the propagation direction) while the angle found via the conventional approach is θm ≅ 63.5∘. Moreover, the calculated second harmonic wave exhibits an attenuation equal to 7.44 × 10−1dB/cm that strongly influences the whole cascaded second-order phenomenon. The simulation results, for those structures in which it is possible to neglect the hybrid and leaky nature of the propagation modes, are compared with the literature data and an excellent agreement is found.

Gene Ties Arthropods Together

Boston—Scientists have argued that insects, which have unbranched limbs, and crustaceans—with branched ones—are two very distinct groups. New developmental evidence, however, points to a much closer relationship. Limb branching in both groups is a second-order phenomenon, scientists report, affected by a single gene, called Distal-less ( Dll ). It shouldn't be used to separate the groups, but to bring them together (see Report on p. 1363 ).

Generation of higher-order squeezing of quantum electromagnetic fields.

The concept of Nth-order squeezing and intrinsic Nth-order squeezing is introduced and applied to several physical situations that are known to exhibit second-order squeezing. It is shown that the field produced in degenerate parametric down-conversion is squeezed to all orders, as well as being intrinsically squeezed to orders 2,6,10,. . . . The same is true for the fundamental mode in second-harmonic generation within the short-time approximation, but in this case there is only intrinsic second-order squeezing. In resonance fluorescence from a two-level atom squeezing is again found to be intrinsically a second-order phenomenon, although an intrinsic second-order effect can give rise to a weak form of higher-order squeezing.

Les phénomènes du second ordre rayonnants dans les ondes de gravité

Les phénomènes du second ordre rayonnants dans les ondes de gravité

Scattering in an Infinitely Extended Inhomogeneous Medium

Scattering in a medium containing patches of inhomogeneities consists of a splitting up of the incident sound into incoherent waves as well as of a focusing and defocusing action of the inhomogeneities. The first phenomenon causes rapidly varying interferences leading to an amplitude distribution between Gaussian and Rayleigh; the second causes a slow spreading of this amplitude distribution toward lower and higher values of sound pressure. The interference component can be derived from a simple model consisting of infinite slabs having properties similar to those of the patches of inhomogeneity along the line connecting source and receiver; the focusing component follows from a consideration of the divergence of a beam caused by refraction. The pressure scattered in the forward direction is out of phase by 90 degrees with respect to the unscattered sound and causes only a change of phase when the patches are large; but when the patches are small, the scattered pressure is found to be Rayleigh distributed and to affect the amplitude as well as the phase of the transmitted sound. With the aid of results derived by Potter and Murphy (Applied Physics Laboratory, University of Washington, APL/UW/TE/55-12), the total pressure and its fluctuation can be computed for any frequency and any size of the scattering patches. The maximum radius “a” of a patch sensibly contributing to the intensity at a distance r is found to be given by a + (r/k)12, where k is the wave number. With increasing frequency, scattering turns from a first-order to a second-order phenomenon, so that finally we are left with focusing effects as given by ray theory. The usual practice connecting the correlation function with the intensity proves to be applicable only when the frequency is low or the patches are small and leads to completely wrong results for higher frequencies or for larger patches.