A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

Graphynes (GYs) are carbon allotropes with single-atom thickness that feature layered 2D structure assembled by carbon atoms with sp- and sp2- hybridization form. Various functional theories have predicted GYs to have natural band gap with Dirac cones structure, presumably originating from inhomogeneous π-bonding between those carbon atoms with different hybridization and overlap of the carbon 2pz orbitals. Among all the GYs, graphdiyne (GDY) was the first reported to be prepared practically and, hence, attracted the attention of many researchers toward this new planar, layered material, as well as other GYs. Several approaches have been reported to be able to modify the band gap of GDY, containing invoking strain, boron/nitrogen doping, nanoribbon architectures, hydrogenation, and so on. GDY has been well-prepared in many different morphologies, like nanowires, nanotube arrays, nanowalls, nanosheets, ordered stripe arrays, and 3D framwork. The fascinating structure and electronic properties of GDY make i...

Progress in Research into 2D Graphdiyne-Based Materials

The quantum phase problem: a critical review

A method of and device for generating an amplified optical signal directly in an optical fiber by way of phase-sensitive amplification based on one or more four-wave mixing (FWM) processes. In one embodiment, an input signal and two pump waves are applied to a highly nonlinear fiber (HNLF). The input signal is amplified in the HNLF due to energy transfer from the pump waves to the input signal via a degenerate phase-conjugation (PC) process. In another embodiment, an input signal and first and second pump waves are applied to a first HNLF to generate, via a Bragg scattering (BS) process, an idler signal corresponding to the input signal. The second pump wave is then filtered out and the first pump wave, a third pump wave, and the input and idler signals are applied to a second HNLF, where they interact via a non-degenerate PC process to produce an amplified output signal.

Phase-sensitive amplification in a fiber

An instrument is provided for migration through a lumen of a tubular part. The instrument comprises a distal section including a distal bladder adapted to be inflated and deflated; a proximal section including a proximal bladder adapted to be inflated and deflated; and, an intermediate section including an intermediate bladder adapted to be inflated and deflated. A device is associated with the distal section. A coupler is interposed between the distal and intermediate sections for movably coupling the distal section to the intermediate section. A drive mechanism is coupled between the distal and intermediate sections for effecting movement of the distal section about the coupler. A controller is provided for selectively inflating and deflating the distal, proximal and intermediate bladders to effect migration of the distal, intermediate and proximal sections through the lumen.

Lumen traversing device

The work described in this paper represents an effort to demonstrate the validity of the hybrid approach to the analysis of structural deformation. Mathematical modelling was incorporated into the process of reducing data from a digital correlation analysis of a speckled surface. The experimental data was collected both by directly imaging the surface onto a digitizing vidicon system and by transmitting the image through a coherent optical fiber bundle. Considerable savings of time and resources can be realized through the hybrid approach and the strengths of the theoretical and experimental procedures complement each other beautifully. The final results agreed within a few percent of each other and with values obtained by another independent method (high frequency moire), demonstrating the accuracy of the procedure. Hybrid approach The idea of a hybrid approach to structural analysis is not new(1,2,3,4). Although a long history of development can be traced for engineering studies based on mathematical models (finite-difference equations, boundary value integrals, finite element models) and on experimentally obtained data (gaging, optical or acoustical metrology), each method has well known limitations. Mathematical studies depend on the correspondence between some abstract model undergoing specified affects and a real structure subjected to a complex of interacting forces. A detailed model quickly becomes very large and mathematically complex, placing large burdens on the computational and financial resources of the designer. Also, the validity of the results depends on how well boundary conditions have been incorporated into the model. On the other hand, direct experimental methods of analysis often depend on only a few data values, measured at isolated points on the structure. The obtaining of this data for certain critical regions may be difficult or dangerous (complex structures, inaccessible locations, hazardous environments). In such cases, the surface can be illuminated by an incoherent fiber optic bundle and the image transmitted back through a coherent fiber optic bundle to a remote analyzing system. The hybrid method is an attempt to take advantage of the strengths of these two approaches, while minimizing their weaknesses. Basically, the idea is to drastically reduce the finite element mesh required and to incorporate real measured values instead of generalized boundary conditions. Speckle metrology

finite element modelling

Radial metrology combines standard optical measurement techniques with a unique panoramic annular lens (PAL) system to study material properties and deformations on the inner surfaces of the cavities found, for example, inside pipes, tubes, and boreholes. A PAL profilometer using speckle metrology is analyzed and the equations obtained from the analysis are used to calibrate the PAL profilometer when it is used to profile the inner surface of a cylindrical pipe and to measure the deformation of the pipe when it is subjected to diametral compression.

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Endoscopic measurement using radial metrology with digital correlation

The application of Armstrong’s super-regenerative principle to a laser amplifier shows that it is possible to control the phase of even a low-gain He-Ne laser amplifier by injecting as few as four or five photons just after the laser is turned on and while it goes through threshold. Estimation of the uncertainties in determining the level of the injected signal and the phase of the laser output indicates that measurements approaching the limit ΔnΔϕ≅1/2 may be possible.

Phase-sensitive optical amplifier

A windowing technique for the automated analysis of holo-interferograms

The panoramic annular lens (PAL) consists of a single piece of glass, with spherical surfaces, that produces a flat annular image of the entire 360-deg surround of the optical axis of the lens. This paper describes the attributes of the PAL and shows that the lens maps elements from object to image space via a constant aspect ratio polar mapping. A panoramic video system (PVS) is described to illustrate how the characterization can be applied in experimental mechanics for cavity inspection and measurement.

Donald R. Matthys

Papers

finite element modelling

Endoscopic measurement using radial metrology with digital correlation

Phase-sensitive optical amplifier

A windowing technique for the automated analysis of holo-interferograms

Characterization of the Panoramic Annular Lens