Nematic Cells for Digital Light Deflection

Smectic A (SmA) prisms can be made in a variety of shapes and are useful for visible spectrum and infrared beam steerage.

Smectic A (SmA) materials can be used in non-mechanical, digital beam deflectors (DBDs) as fillers for passive birefringent prisms based on decoupled pairs of electrically controlled, liquid crystalline polarization rotators, like twisted nematic (TN) cells and passive deflectors. DBDs are used in free-space laser communications, optical fiber communications, optical switches, scanners, and in-situ wavefront correction.

Posted in: Briefs, TSP, Materials, Optics, Optics, Materials properties

Ultra-Stable Beacon Source for Laboratory Testing of Optical Tracking

A prototype laser beacon assembly provides reference for testing tracking and pointing systems.

The ultra-stable beacon source (USBS) provides a laser-beam output with a very low angular jitter and can be used as an absolute angular reference to simulate a beacon in the laboratory. The laser is mounted on the top of a very short (≈1 m) inverted pendulum (IP) with its optical axis parallel to the carbon fiber pendulum leg. The 85-cm, carbon fiber rods making up the leg are very lightweight and rigid, and are supported by a flex-joint at the bottom (see figure). The gimbal-mounted laser is a weight-adjustable load of about 1.5 kg with its center of rotation co-located with the center of percussion of the inverted pendulum. This reduces the coupling of transverse motion at the base of the pendulum to angular motion of the laser at the top.

Posted in: Briefs, TSP, Physical Sciences, Lasers, Lasers, Vibration, Vibration, Mountings, Test equipment and instrumentation

Delaying Trains of Short Light Pulses in WGM Resonators

Delays would not be limited by resonator ring-down times.

Suitably configured whispering-gallery-mode (WGM) optical resonators have been proposed as delay lines for trains of short light pulses. Until now, it has been common practice to implement an optical delay line as a coiled long optical fiber, which is bulky and tends to be noisy. An alternative has been to implement an optical delay line as a coupled-resonator optical waveguide (a chain of coupled optical resonators), which is compact but limits the width of the pulse spectrum to the width of an optical resonance and thereby places a lower limit on the duration of a pulse. In contrast, a delay line according to the proposal could be implemented as a single WGM resonator, and the pulses delayed by the resonator could be so short that their spectral widths could greatly exceed the spectral width of any single resonance.

Posted in: Briefs, Physical Sciences, Fiber optics, Optics, Waveguides, Fiber optics, Optics, Waveguides

Improving the Optical Quality Factor of the WGM Resonator

New iterative annealing and polishing increases the resonator’s finesse over the fundamental limit.

Resonators usually are characterized with two partially dependent values: finesse (ℱ) and quality factor (Q). The finesse of an empty Fabry-Perot (FP) resonator is defined solely by the quality of its mirrors and is calculated asℱ = πR1/2/(1 – R).

Posted in: Briefs, Physical Sciences, Mirrors, Optics, Optics

Multiphysics Modeling Simplifies Analysis of Electrical and Electromagnetic Effects

Effects of lightning strikes and electromagnetic fields are simulated and modeled easily.

The Saab Group has 17 business units, which are split into defense and security, systems and products, and aeronautics. Over the years, the company has taken advantage of the many paradigm shifts that have taken place in engineering analysis. One example is implementing comprehensive engineering methodologies that combine traditional experiments and testing with newer tools such as computer modeling and simulation. In the 1980s, Saab began applying largescale computer simulations, which were used to verify the lightning-protection components in the wings of the Gripen fighter aircraft.

Posted in: Briefs, Software, Analysis methodologies, Simulation and modeling

Geophysical Wave Propagation Calculation Using Multiphysics

Geologists can conduct in-field calculations without the need for large computing resources.

The propagation of shear (S) and compression (P) waves within the Earth represents a critically important phenomenon for geologists. For many years, geologists have developed specialized computational programs to calculate wave propagation within complex geophysical regions. These programs have been instrumental in determining the location and characteristics of natural phenomena (e.g., earthquakes) and manmade activity (e.g., nuclear-blast tests).

Posted in: Briefs, Software, Computer software / hardware, Computer software and hardware, Computer software / hardware, Computer software and hardware, Research and development

Simulating the Manufacturing Process of Ceramic Matrix Composites

Multiphysics simulation enables analysis of a range of physical phenomena occurring in the manufacturing process.

Increasing the temperature at which jet aircraft engines operate would significantly improve thrust and fuel efficiency with reduced emissions. However, current engines operate within 50 degrees of the inherent melting point of the conventional materials used in engine construction. Thus, new materials capable of operating at higher temperatures for prolonged times must be developed and manufactured.

Posted in: Briefs, Software, Computer simulation, Manufacturing processes, Ceramics, Composite materials

3D Program Aids Design of Custom Iron Work

Software allows architectural iron works manufacturer to simplify the design process.

Keuka Studios designs and manufactures custom architectural iron work and cable railings for commercial and home use. Keuka Studios first designs a product in CAD, CNC machines it to shape, and then takes the assembly to their forge, which adds the design elements. Dan White, founder and president of Keuka Studios, was frustrated by the limitations of existing design tools. Despite over 25 years of experience as a mechanical engineer with a deep working knowledge of 3D CAD, animation, rendering, and finite element analysis software, he could not be as creative with product design as he wanted.

Posted in: Briefs, Software, CAD / CAM / CAE, CAD, CAM, and CAE, Manufacturing processes, Iron

Displaying CFD Solution Parameters on Arbitrary Cut Planes

USMC6 is a Fortran 90 computer program for post-processing in support of visualization of flows simulated by computational fluid dynamics (CFD). The name “USMC6” is partly an abbreviation of “TetrUSS — USM3D Solution Cutter,” reflecting its origin as a post-processor for use with USM3D — a CFD program that is a component of the Tetrahedral Unstructured Software System and that solves the Navier-Stokes equations on tetrahedral unstructured grids. “Cutter” here refers to a capability to acquire and process solution data on (1) arbitrary planes that cut through grid volumes, or (2) user-selected spheroidal, conical, cylindrical, and/or prismatic domains cut from within grids. Cutting saves time by enabling concentration of post-processing and visualization efforts on smaller solution domains of interest.

Posted in: Briefs, TSP, Software, Computational fluid dynamics, Computer software / hardware, Computer software and hardware, Computer software / hardware, Computer software and hardware

Flow Solver for Incompressible 2-D Drive Cavity

This software solves the Navier- Stokes equations for the incompressible driven cavity flow problem. The code uses second-order finite differencing on a staggered grid using the Chorin projection method. The resulting intermediate Poisson equation is efficiently solved using the fast Fourier transform.

Posted in: Briefs, Software, Computational fluid dynamics, Computer software / hardware, Computer software and hardware, Computer software / hardware, Computer software and hardware

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