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Soft-x-ray Bragg reflection from two Ru/[B.sub.4]C multilayers with 10 and 63 periods was used for independent determination of both real and imaginary parts of the refractive index n = 1 - [delta] + i[delta] close to the boron K edge (~188 eV). Prior to soft x-ray measurements, the structural parameters of the multilayers were determined by x-ray reflectometry using hard x rays. For the 63-period sample, the optical properties based on the predictions made for elemental boron major deviations were found close to the K edge of boron for the 10-period sample explained by chemical bonding of boron to [B.sub.4]C and various boron oxides. OCIS codes: 120.4530, 310.6860, 340.7470.

A representation theorem is proved for the solution of the problem of two perfectly bonded isotropic semi-infinite plates under the influence of an arbitrary vertical load located in the midplane of the interior of one of them. Its function is to show that if the deflection of an unbounded isotropic plate under the influence of an arbitrary vertical load is known, then the corresponding deflections for two perfectly bonded isotropic semi-infinite plates are explicitly determinable, solely, and compactly in terms of the known deflection. Indeed, whatever the nature of the mechanism of loading is, the induced bending moments and shears in the two bonded plates are determinable by the process of differentiation only. A systematic repeated application of the theorem then yields a well-structured series solution when the arbitrary vertical load is arbitrarily located in a compound plate comprising two semi-infinite dissimilar isotropic plates separated by another dissimilar isotropic plate strip of finite breadth. As an application, we determine the effective elastic constants of a compound plate comprising a homogeneous isotropic plate in which a finite number of isotropic parallel plate strips of small breadths are embedded at such distances apart that their interaction effects may be taken as independent of one another. [DOI: 10.1115/1.3130813] Keywords: isotropic materials, compound plates, bending, effective elastic constants, repeated reflection

Resonant features in the response of finite arrays of rectangular grooves ruled on a metallic plate have been reported in connection with the excitation of phase resonances. These anomalies are generated by a particular arrangement of the magnetic field phases inside the subwavelength grooves when the structure is illuminated by a p-polarized electromagnetic wave. We show that this kind of resonance is also present for grooves of circular cross section and appear as sharp peaks in the specular response, the number of which increases with the number of grooves in the structure. A significant intensification of the field within the grooves is also found for these particular phase configurations. The dependence of the response on the geometrical parameters of the structure is analyzed in detail, in order to consider these structures for potential applications such as frequency selectors and polarizers. OCIS codes: 050.1950, 240.3695.

This study employs an existing finite-difference model based on the hyperbolic form of the modified mild slope equation (MMSE) to investigate wave reflection near bathymetric depressions such as dredged borrow pits and nearshore canyons. First, the model is tested for numerical limitations on the higher order bottom slope and curvature terms using idealized cases of a simple depth transition and a symmetric trapezoidal trench, with comparisons of the MMSE to both the traditional mild slope equation (MSE) solution and a shallow water analytic solution. It is demonstrated that the model gives accurate solutions on slopes as steep as 1 : 1, and that the solutions from all three models agree in the shallow water region. However, for waves in intermediate depths, predicted wave reflection from nearshore depressions is shown to differ significantly between the MMSE and MSE models. Next, geometrical data from a wide range of existing and proposed borrow pits and a submarine canyon are gathered and analyzed for whether wave reflection is an important process near realistic nearshore depressions. The geometric data show that realistic nearshore depressions lie within the tested range of the MMSE model and that borrow pits are generally not in shallow water, which means it is important to use a MMSE-type model to calculate reflection from these features. In addition, storm conditions on average lead to a 50% increase in reflection coefficient in comparison to the mean wave conditions, due to the increase in wave period. Finally, the results also indicate borrow pit design criteria that can be used to ensure minimal reflection. DOI: 10.1061/(ASCE)0733-950X(2008)134:1(1) CE Database subject headings: Wave reflection; Nearshore; Dredging; Numerical models.

Solitary wave interaction with porous breakwaters is studied by using a two-dimensional numerical model. In this model, flows outside of porous media are described by Reynolds-averaged Navier-Stokes equations. For porous flows, the spatially averaged Navier-Stokes equations, in which the effect of porous media is considered by including additional inertia and drag forces, are derived and implemented. The drag force is modeled according to Morison's equation assuming uniform spherical particles within porous media. The corresponding drag force coefficient is expressed as the function of Reynolds number and hence the proposed porous flow model is valid in a wide range of porous flow regimes, i.e., laminar (linear friction), transitional, and turbulent (nonlinear friction) flows. The numerical model is validated against available theories and experimental data for both long wave and solitary wave interaction with porous breakwaters. The model is then employed to study solitary wave interaction with fully emerged rectangular porous breakwaters with different length and particle size. Based on the results, the characteristics of wave reflection, transmission and energy dissipation are discussed. Additional numerical tests are conducted to study the effects of depth of submergence and porosity of breakwaters on wave transformation. The scale effects in small scale and large scale model tests are also discussed by performing numerical experiments in the reduced and enlarged numerical wave flumes. DOI: 10.1061/(ASCE)0733-950X(2007)133:5(352) CE Database subject headings: Solitary waves; Porous flow; Breakwaters; Wave reflection; Energy dissipation; Scale effect; Numerical analysis.

To characterize the linear birefringence of a multiple-order wave plate (MWP), an oblique incidence is one of the methods available. Multiple reflections in the MWP are produced, and oscillations in the phase retardation measurement versus the oblique incident angle are then measured. Therefore, an antireflection coated MWP is required to avoid oscillation of the phase retardation measurement. In this study, we set up a phase-sensitive heterodyne ellipsometer to measure the phase retardations of an uncoated MWP versus the oblique incident angle, which was scanned in the x-z plane and y-z plane independently. Thus, the effect on multiple reflections by the MWP is reduced by means of subtracting the two measured phase retardations from each other. As a result, a highly sensitive and accurate measurement of retardation parameters (RPs), which includes the refractive indices of the extraordinary ray [n.sub.e] and ordinary ray no, is obtained by this method. On measurement, a sensitivity ([n.sub.e], [n.sub.o]) of [10.sup.-6] was achieved by this experiment setup. At the same time, the spatial shifting of the P and S waves emerging from the MWP introduced a deviation between experimental results and the theoretical calculation. OCIS codes: 120.3180, 040.2840, 120.5050, 120.5410.

The inverse gamma distributed texture is important for modeling compound-Gaussian clutter (e.g. for sea reflections), due to the simplicity of estimating its parameters. We develop maximum-likelihood (ML) and method of fractional moments (MoFM) estimates to find the parameters of this distribution. We compute the Cramer-Rao bounds (CRBs) on the estimate variances and present numerical examples. We also show examples demonstrating the applicability of our methods to real lake-clutter data. Our results illustrate that, as expected, the ML estimates are asymptotically efficient, and also that the real lake-clutter data can be very well modeled by the inverse gamma distributed texture compound-Gaussian model.

Holographic recording media with a reflection layer are useful because they make it possible to maintain backward compatibility with CDs and DVDs, and a conventional servo system is easily attachable. The incident beam is fed back to the recording layer by the reflection layer, so there are four beam pairs to record the transmission and reflection holograms. We analyze the basic property of the transmission and reflection holograms and evaluate the problem when the transmission and reflection holograms are recorded at the same time. It is shown that the shrinkage in the photopolymer medium has a different effect on each hologram, so the readout image from the two holograms is misaligned. Those diffraction beams make the interference pattern, and the signal-to-noise ratio (SNR) of the output image decreased. Taking into account the difference in wavelength selectivity between the transmission and the reflection holograms, we propose a way to select one hologram to get the diffraction beam and eliminate the interference pattern using the tuning readout wavelength. By using this method, we can eliminate the diffraction beam from the reflection hologram and keep a high SNR. OCIS codes: 090.7330, 160.5470.

A super-structure-grating distributed Bragg reflector (SSG-DBR) laser allows stable single-mode operation for broad quasicontinuous wavelength tuning by optimizing SSG reflectors and cavity structure. Optimization of SSG achieves broad band tuning range and high mode selectivity. Optimization of the cavity structure is possible by computer-aided simulation of wavelength tuning which incorporates the effects of inhomogeneity in the gain spectrum and an increase in the waveguide loss. A 1.55 micrometers InGaAsP-InP SSG-DBR laser demonstrates 34 nanometers quasicontinuous tuning.

Some dew-covered plants are strongly retroreflective. The bright glow seen when the antisolar point falls on grass is known as the heiligenschein. Its widely accepted explanation requires that the grass be covered with hair. The discovery of the sylvanshine, a closely related phenomenon best seen at night, revealed that strong retroreflection can occur on hairless dew-covered plants. A simple model shows that below a contact angle of 90 [degrees], the enhancement in the backscatter direction is virtually identical to that given by a diffusely reflecting surface, but as the contact angle climbs to 140 [degrees], enhancement increases by 2 orders of magnitude. Plants that exhibit such large contact angles are not the norm, but can be found chiefly among coniferous trees, a few of which display the sylvanshine with great brilliance.

Changes in the angle of reflection of the moon's image on stationary water is investigated mathematically for different positions of the moon in the sky. The image of the moon reflected on water surface is elongated when the moon is close to the horizon. The length is almost infinite, limited only by the horizon and boundaries of the lake. The reflected image of the moon becomes shorter as the moon rises higher. The image is the smallest when the moon is at the zenith. The reflection of stars on the surface of rippled lake water is also investigated mathematically.

Anti-stokes fluorescence cooling (optical refrigeration) is measured in ytterbium-doped yttrium aluminum garnet (YAG). Pumping the 2.3 percent Yb(super 3+): YAG crystal with 1.8 W of 1030 nm laser light produced a temperature drop of 8.9 degrees C from room temperature.

The effect of wave reflection on the single-mode operation of a gyrotron is investigated with the help of Rieke diagrams. For this purpose, a set of self-consistent equations describing the beam-field interaction is solved, taking into account the effect of the electron beam and the reflection coefficient on the frequency and RF field profile. Index Terms--Gyrotron, reflection.