Reflected Intensity Distribution Research Articles

An echolocation model for the restoration of an acoustic image from a single-emission echo

Bats can form a fine acoustic image of an object using frequency-modulated echolocation sound. The acoustic image is an impulse response, known as a reflected-intensity distribution, which is composed of amplitude and phase spectra over a range of frequencies. However, bats detect only the amplitude spectrum due to the low-time resolution of their peripheral auditory system, and the frequency range of emission is restricted. It is therefore necessary to restore the acoustic image from limited information. The amplitude spectrum varies with the changes in the configuration of the reflected-intensity distribution, while the phase spectrum varies with the changes in its configuration and location. Here, by introducing some reasonable constraints, a method is proposed for restoring an acoustic image from the echo. The configuration is extrapolated from the amplitude spectrum of the restricted frequency range by using the continuity condition of the amplitude spectrum at the minimum frequency of the emission and the minimum phase condition. The determination of the location requires extracting the amplitude spectra, which vary with its location. For this purpose, the Gaussian chirplets with a carrier frequency compatible with bat emission sweep rates were used. The location is estimated from the temporal changes of the amplitude spectra.

A computational model of echolocation: Transformation of spectrogram into the reflected intensity distribution for range discrimination of multiple closely spaced objects

Using frequency-modulated echolocation, bats can discriminate the range of objects with an accuracy of less than a millimeter. However, the echolocation mechanism is not well understood. The delay separation of three or more closely spaced objects can be determined through analysis of the echo spectrum. However, delay times cannot be properly correlated with objects using only the echo spectrum because the sequence of delay separations cannot be determined without information on temporal changes in the interference pattern of the echoes. To illustrate this, Gaussian chirplets with a carrier frequency compatible with bat emission sweep rates were used. The delay time for object 1, T1, can be estimated from the echo spectrum around the onset time. The delay time for object 2 is obtained by adding T1 to the delay separation between objects 1 and 2 (extracted from the first appearance of interference effects). Further objects can be located in sequence by this same procedure. This model can determine delay times for multiple closely spaced objects with an accuracy of about 1 microsecond, when all the objects are located within 30 microseconds of delay separation. This accuracy is possible even with objects having different reflected intensities and in a noisy environment.

An echolocation model for range discrimination of multiple closely spaced objects: transformation of spectrogram into the reflected intensity distribution.

Using frequency-modulated echolocation, bats can discriminate the range of objects with an accuracy of less than a millimeter. However, bats' echolocation mechanism is not well understood. The delay separation of three or more closely spaced objects can be determined through analysis of the echo spectrum. However, delay times cannot be properly correlated with objects using only the echo spectrum because the sequence of delay separations cannot be determined without information on temporal changes in the interference pattern of the echoes. To illustrate this, Gaussian chirplets with a carrier frequency compatible with bat emission sweep rates were used. The delay time for object 1, T1, can be estimated from the echo spectrum around the onset time. The delay time for object 2 is obtained by adding T1 to the delay separation between objects 1 and 2 (extracted from the first appearance of interference effects). Further objects can be located in sequence by this same procedure. This model can determine delay times for three or more closely spaced objects with an accuracy of about 1 micros, when all the objects are located within 30 micros of delay separation. This model is applicable for the range discrimination of objects having different reflected intensities and in a noisy environment (0-dB signal-to-noise ratio) while the cross-correlation method is hard to apply to these problems.

AE—Automation and Emerging Technologies: Novel Imaging Spectroscopy for Grass Sward Characterization

Attempts to improve grassland management may benefit from the use of new sensing techniques, such as imaging spectroscopy. In order to explore the potential of hyperspectral imaging spectroscopy for rapid and objective characterization of grass swards an experimental prototype has been developed. From a height of 1 m, the system detects reflections at high spatial (0·16–1·45 mm 2) and high spectral resolutions (5–17 nm) at wavelengths between 405 and 1659 nm. Detailed information is provided on design, characteristics and test results. Results show that reflection intensity is related to height position in the sward and leaf angle. Grass leaves were recognized accurately. Images of a sports field and a production sward with similar ground cover fractions could be easily distinguished. With the described system, canopy structure can be characterized by ground cover, the distribution of reflection intensity and image texture. Spectral characteristics can be obtained at leaf level.

X-ray diffraction analysis of stacking and twin faults in f.c.c. metals: a revision and allowance for texture and non-uniform fault probabilities

A revision is presented of the original description by Warren [X-ray Diffraction, (1969), pp. 275–298. Massachusetts: Addison-Wesley] of the intensity distribution of powder-pattern reflections from f.c.c. metal samples containing stacking and twin faults. The assumptions (in many cases unrealistic) that fault probabilities need to be very small and equal for all fault planes and that the crystallites in the sample have to be randomly oriented have been removed. To elucidate the theory, a number of examples are given, showing how stacking and twin faults change the shape and position of diffraction peaks. It is seen that significant errors may arise from Warren's assumptions, especially in the peak maximum shift. Furthermore, it is explained how to describe powder-pattern reflections from textured specimens and specimens with non-uniform fault probabilities. Finally, it is discussed how stacking- and twin-fault probabilities (and crystallite sizes) can be determined from diffraction line-profile measurements.

X-ray scattering by crystals with local lattice rotation fields

X-ray (or neutron) scattering by crystals with local rotation fields arising from dislocations is treated on the basis of the formalism of the kinematical diffraction theory. Such fields mostly change the intensity distribution of reflections in the azimuthal plane. Scattering intensity in the azimuthal plane for crystals with one or two sets of different-type dislocation walls, causing local rotations in the lattice, is analysed. In this case the intensity distribution is close to Lorentzian in the radial direction and to Gaussian in the azimuthal direction. The expressions for the scattering intensity are valid when averaging over a large statistical ensemble of defects. If this condition is not fulfilled, the intensity distribution in the azimuthal plane will split into several spikes. The mean distance between these spikes in the reciprocal-lattice space is connected with the disorientation between the walls. The conditions necessary for such splitting of the reflection into spikes are considered. The values of the limiting disorientation angle for some common scattering volumes and distances between dislocation walls are evaluated.

X-ray structural study of 4kF Wigner crystal and 4kF Peierls state in DCNQI complex with 1/4 filled quasi one-dimensional band

Using newly developed X-ray low temperature camera, 4k F periodic modulation was observed in organic quasi one-dimensional(Q1D) compounds (DMe-DCNQI) 2 Ag (abbreviated as DMe) and (DI-DCNQI) 2 Ag (abbreviated as DI). From 4kF satellite reflection intensity distribution in q-space, periodic molecular displacement in DMe and periodic molecular deformation possibly related with molecular valence ordering in DI were found. These modulation pattems suggest occurrence of 4k F bond CDW in DM and 4k F site CDW in DI. The 4k F site CDW possibly caused by a market intersite correlation V, can be intepreted as a Wigner crystal.

Coating techniques in optical interferometric metrology

In optical interferometry diffuse reflectivity of the surface under study should be high and homogeneous. Application of a white reflective coating can strongly improve measurement results. The optical properties of bronze powder, TiO(2) powder, white Chinese ink, and MgO coatings are discussed. Measurements of reflected intensity distribution show that white Chinese ink and MgO have superior optical characteristics, and electron microscopy shows that these coatings cause thickness artifacts of less than 7.5 and 17 mum, respectively. The effect on deformation measurements is demonstrated by moiré topography on a thin membrane that is deformed under small static pressures. The membrane center displacement varies from 15 to 100 mum, and within a measuring precision of 2.5 mum no artifacts on this deformation are found.

Long-period modulated structures of Bi2Sr2(Ca1−xPrx)Cu2O8+δceramics studied by electron diffraction and high-resolution electron microscopy

Seven specimens of Bi2Sr2(Ca1− xPrx)Cu2O8 + δ ceramics in the concentration range 0 < x < 0.64 have been prepared by solid-state reaction. The sample with x = 0.16 was examined in detail by means of electron diffraction and an intensity distribution of lattice reflections in reciprocal space was constructed on the basis of the experimental results. The intensity distribution is consistent with a calculation using a long-period modulated-structure (LPMS) model. This model with b = 37b0 takes the (3,1)5 mode of lattice modulation having the modulation period 2.31b0 (1.25 nm). The period is defined as the reciprocal of the wave number of a satellite reflection. The specimens with other concentrations also showed an intensity distribution of lattice reflections similar to that of x = 0.16. On the basis of the above results, lattice modulation periods have been examined for all the prepared specimens. The period decreases roughly from ~ 1.28 to ~ 1.15 nm with increasing concentration x. Seven modulation modes of the lattice have been determined by high-resolution observation; the modulation period of the LPMS model with each modulation mode is also nearly equal to the measured period.

Optical Surface Roughness Measurement Using a Two-Dimensional Gaussian Function.

A new noncontact optical technique for rapidly measuring the surface roughness was proposed. The surfaces of ground specimens were illuminated with a LED light. The reflected light intensity distribution was measured with a CCD optical sensor, and it was approximated by a two-dimensional (2-D) Gaussian function. The standard deviations of the 2-D Gaussian function, σx and σy, with respect to the x and y axes were calculated for evaluating the broadness of the reflected intensity distribution curve in the two directions. The standard deviation σx with respect to the axis perpendicular to the ground direction increased with increasing the center line-averaged surface roughness Ra, giving the experimental relationship Ra = 21.9σ2x-6.8σx+0.6. On the other hand, the standard deviation σy with respect to the ground direction remained unchanged, independent of the surface roughness Ra. This technique allows optical measurement of the surface roughness in two perpendicularly intersecting directions simultaneously.

Optical monitoring for plasma-etching depth process

A novel technique for monitoring the opaque thin-film etching depth during the plasma-etching process is presented. The feature of this technique is that a small laminar grating is overlaid on the empty region of the wafer along with the etching pattern. By coherent illumination, a reflected intensity distribution from the laminar grating for different orders of diffraction can be obtained. Since the etching depth and the diffraction distribution are related, by analyzing the intensity profiles due to laminar depth grating, the etching depth of the specimen can be measured. The accuracy of this measurement can be as high as 100 AA.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A Technique for Rapidly Measuring Surface Roughness Using a Laser

An optical technique for rapidly measuring surface roughness using a laser is proposed. The reflected intensity distribution of a laser beam irradiated on a surface of an aluminum specimen was measured with a plasma-coupled device (PCD). The reflected intensity curve can be approximated by a Gaussian function. The broadness of the intensity curve was evaluated with the standard deviation, called a Gaussian curve parameter (GCP), of a Gaussian function approximating the intensity distribution curve. The GCP can be determined in 2s. The smoothing of the reflected intensity data is not necessary in calculating GCP because GCP's with and without data smoothing almost agreed. The center line averaged roughness Ra increases with increasing GCP.

The application of omega scans for the characterization of graphite intercalation compounds

The broad two-dimensional intensity distribution of 00ℓ reflections of graphite intercalation compounds (GICs), caused mainly by the mosaic spread, was measured for stage 2 CdCl 2-graphite and stage 2 PdCl 2-graphite by use of the ω-scan technique. For CdCl 2-GICs, the profiles of the measured rocking curves were smooth, similar to the curve profiles of other well-known GICs. For the rocking curves of the PdCl 2-GICs a rough shape was found, characterized by several local intensity maxima. This profile type was observed for the first time with GICs; this will require a multitude of measurements for the determination of the entire two-dimensional intensity distribution. The exposure to air of first stage FeCl 3-GICs results in a phase separation that is recognizable in the reappearance of the graphite 002 reflection. The profile of the rocking curve of this reflection shows a “smoothed” Gaussian shape, in contrast with the “rough” profile of pristine graphite.

A technique for rapidly measuring surface roughness using a laser.

An optical technique for rapidly measuring surface roughness using a laser is proposed. The reflected intensity distribution of a laser beam irradiated on a surface of an aluminum specimen was measured with a plasma-coupled device (PCD). The reflected intensity curve can be approximated by a Gaussian function. The broadness of the intensity curve was evaluated with the standard deviation, called a Gaussian curve parameter (GCP), of a Gaussian function approximating the intensity distribution curve. The GCP can be determined in 2s. The smoothing of the reflected intensity data is not necessary in calculating GCP because GCP's with and without data smoothing almost agreed. The center line averaged roughness Ra increases with increasing GCP.

Distribution of Reflected Power From the Bed by Radio Echo-Sounding in the Shirase Glacier Drainage Area, East Dronning Maud Land, Antarctica

A large part of the area of the Shirase Glacier drainage basin has been surveyed by airborne (operating frequency: 179 MHz) and ground-based (60 MHz) radio echo-sounding to define the bedrock topography and to investigate the condition of bed/ice interface since 1982.It is shown that the reflection intensity from the bed, which is corrected for attenuation in the ice sheet, has a higher value for reflection intensity in the down-stream area of Shirase Glacier than in the up-stream area. The area of strongest intensity of reflection from the bed coincides with the area for which the calculated temperature at the bed is above −1°C. The boundary area between the highest and lowest values of corrected reflected intensity corresponds to the area of decreasing basal shear stress. It is found that the distribution of high corrected reflection intensity corresponds to the area of thinning of the ice sheet, which has been measured by ice-flow observation in the Shirase Glacier drainage basin.

Distribution of Reflected Power From the Bed by Radio Echo-Sounding in the Shirase Glacier Drainage Area, East Dronning Maud Land, Antarctica

A large part of the area of the Shirase Glacier drainage basin has been surveyed by airborne (operating frequency: 179 MHz) and ground-based (60 MHz) radio echo-sounding to define the bedrock topography and to investigate the condition of bed/ice interface since 1982. It is shown that the reflection intensity from the bed, which is corrected for attenuation in the ice sheet, has a higher value for reflection intensity in the down-stream area of Shirase Glacier than in the up-stream area. The area of strongest intensity of reflection from the bed coincides with the area for which the calculated temperature at the bed is above −1°C. The boundary area between the highest and lowest values of corrected reflected intensity corresponds to the area of decreasing basal shear stress. It is found that the distribution of high corrected reflection intensity corresponds to the area of thinning of the ice sheet, which has been measured by ice-flow observation in the Shirase Glacier drainage basin.

Interpretation of the shape of electron diffraction spots from small polyhedral crystals by means of the crystal shape amplitude

The influence of the crystal shape on the fine structure of transmission electron diffraction (TED) patterns described by the crystal shape amplitude is discussed. A general algebraic expression for the crystal shape amplitude of any crystal polyhedron is used for computing the intensity distribution of TED reflections. The computer simulation method is applied to the analysis of the fine structure of TED patterns of small gold and palladium crystals having octahedral and tetrahedral habits.

Detection of surface electromagnetic waves by reflected intensity distribution measurements

The complex dielectric constant of silver films at optical frequencies has been measured by detecting the reflected intensity distribution (RID) of the light leaked by free surface electromagnetic waves (SEW). This new detection technique offers in the optical range a number of advantages with respect to more traditional methods as attenuated total reflection or scattered light measurements.

Visualizing reflections in rooms with computer graphics

A computational technique has been developed to calculate and display, in two dimensions, wave fronts from a point source reflected in rooms of variable shape. The reflections are generated in a series of time frames, generally at 10‐ms intervals, for both a plan and section of the room. The technique calculates reflections from re‐entrant surfaces such as balconies and suspended ceiling panels, and it includes variation in sound intensity and surface absorption. Rapid changes may be made in room shape and source location. Visual estimates can be quickly made of intensity distribution and arrival time of early reflections. The method has been used to examine some acoustical qualities of existing auditoriums, to evaluate the effects of remodeling room shapes, and to demonstrate acoustic defects.

Successive Jahn-Teller Phase Transitions in K2PbCu(NO2)6

The successive phase transitions in K 2 PbCu(NO 2 ) 6 have been studied by precise X-ray and neutron measurements. In phase II, we have observed the satellite reflections at ( H ±0.416, K ±0.430, 0) around each fundamental Bragg reflection. In phase III, we have observed the superlattice reflections, instead of the satellite reflections of phase II, at (\(H\pm\frac{1}{2}\), \(K\pm\frac{1}{2}\), \(L\pm\frac{1}{2}\)). This fact indicates that the crystal undergoes the successive phase transitions as normal→incommensurate→commensurate phase. The mode analysis of the Jahn-Teller active phonon mode was carried out and the experimental intensity distribution of satellite and super lattice reflections were analysed from the standpoint of the condensation of the phonon mode. The displacements in phase II is explained as the condensation of the transverse acoustic mode as well as the optical mode compatible with local Jahn-Teller active mode with the wave vector k 0 =(0.42,0.43,0), while these in phase III is explained as the condensation of the same modes with k 0 =(1/2,1/2,1/2).