Tech Briefs

Progress in Design and Synthesis of Nanostructured Materials

A five-and-a-half-year integrated multidisciplinary research project has been characterized by three themes pertinent to the development of advanced materials having tailorable microstructures and/or nanostructures. These themes are (1) biocompatible nanolithographic methods of patterning and templating of materials to have two- and three-dimensional nanostructures; (2) nucleic-acid-based approaches to preparing (both in solution and from predesigned, nanostructured surface templates) supramolecular structures tailored to perform specific functions; and (3) protein-based or inspired molecular and supramolecular architectures. The contributions of this and other related research projects can be expected to lead to the development of diverse nanostructured organic and inorganic materials and structures, including catalytic peptide tubes, hostguest materials for molecular separations, quantum-dot and magnetic-particle arrays, bio-nanoelectronic circuitry, photonicbandgap and three-dimensional electronic power structures, and novel biowarfare- detection materials.

Posted in: Briefs, Materials, Research and development, Fabrication, Nanomaterials, Nanotechnology
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Mixing and Combustion in Turbulent, High-Speed Flows

A collection of reports presents a detailed description of a research program that focused on fundamental investigations of mixing and combustion in turbulent subsonic and supersonic flows like those encountered in high-speed air-breathing aircraft engines. The research included close coordination of effort between experiments and numerical simulations. Recent advances in instrumentation, including some made as part of this program, were utilized in the experiments. The research has been responsible for significant progress in the understanding of molecular mixing in high-speed flows in complicated geometries relevant to scramjet combustors and to high-speed aircraft engines in general. The research included a study oriented toward improving predictions of hydrocarbon flames in such flows and understanding the requirements for combustion of hydrocarbons and holding flames. The study involved comparisons of detailed experiments and detailed predictions of phenomena in stagnation-flame environments that replicate the fundamental effects that influence the stability and extinction of flames. An investigation of the three-dimensional structure of scalar dispersion, with a focus on grid turbulence, has been started and already has yielded new information with relevance to applications of turbulent mixing, including non-premixed combustion and dispersion of pollutants.

Posted in: Briefs, Physical Sciences
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Microcompression Tests of a BMG and a Tungsten/BMG Composite

Uniaxial-compression tests of micron-scale specimens (microcompression tests) of a bulk metallic glass (BMG) and of a tungsten/BMG composite have been performed to contribute to understanding of size-dependent mechanical properties of these and other, similar materials. There is increasing interest in fabricating micro- electromechanical systems from BMGs, and in fabricating kinetic-energy (ballistic) penetrators from BMGs and tungsten/ BMG composites. While the mechanical properties and deformation mechanisms of macroscopic, monolithic BMGs in bulk form are generally well understood, these properties are not necessarily equivalent for the BMG alloys cast in composite form or for micron-scale specimens. In a tungsten/BMG composite, dissolution of tungsten in the BMG matrix frequently manifests itself in the formation of complex crystalline phases and the concomitant decrease in the overall amorphous content of the matrix. Hence, it becomes important to compare the properties and deformation mechanisms of the monolithic BMG with those of the BMG as found in the composite accompanied by other phases and heterogeneities.

Posted in: Briefs, Physical Sciences
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Kinetic Modeling of Laser-Induced D-T Fusion

A computational- simulation study was performed to assess the feasibility of laser-induced fusion of deuterium nuclei with tritium nuclei as a means of generating neutrons for use in neutron radiography. [D-T fusion reactions produce α particles (He nuclei) plus the desired neutrons.] As in prior studies of laser-induced D-T fusion, the basic idea is to irradiate a small deuterium-and- tritium-containing target with a brief, intense laser pulse that causes a shock wave to propagate into the target. The shock wave ionizes and accelerates a substantial portion of the D and/or T molecules, resulting in, among other phenomena, collisions between D and T nuclei. The question of feasibility is essentially the question of whether, by use of a realistic target and a realistic laser pulse, a sufficient number of ions could be accelerated to sufficient kinetic energy such that the number of resulting D-T fusion reactions would suffice to produce a radiographically usefully large number of neutrons.

Posted in: Briefs, Materials, Computer simulation, Lasers, Forming, Radiation
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FPGA-Based Communication Channel for Digital Signal Processor Chips

A method for networking, and a network of, digital signal processors (DSP) via at least one field-programmable gate array (FPGA) enables the simultaneous broadcast of data from a DSP to a number of DSPs. The apparatus comprises a host DSP, at least one FPGA in communication with the host DSP for receiving a digital signal from the host DSP, and at least one non-host DSP in communication with at least one FPGA for receiving the digital signal.

Posted in: Briefs, Electronics & Computers, Communication protocols, Integrated circuits, Wireless communication systems
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Applying Reconfigurable Computing to Acoustic Sensors Using FPGAs

A novel microsensor processing architecture allows a field-programmable gate array (FPGA) to act as a reprogrammable preprocessor or coprocessor to a general-purpose processor (GPP). The FPGA does most of the computationally complex pieces of the algorithm, while the GPP is lightly loaded, performing control, communications, and housekeeping tasks (Figure 1). The flexible architecture supports a wide range of low-power applications, while still being able to leverage emerging commercial technology.

Posted in: Briefs, Electronics & Computers
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Delta-Sigma UHF Digital Waveform Generator

A prototype Digital Waveform Generator (DWG) in the ultra-high-frequency (UHF) range uses Delta-Sigma (Δ−Σ) modulation techniques, which permit arbitrary and accurate waveform generation. The DWG meets the demanding and diverse waveform requirements of future radar applications, including linear-FM (LFM) and continuous wave (CW) signals. This DWG also allows for the generation of waveforms at other frequencies by up-conversion or down-conversion.

Posted in: Briefs, Electronics & Computers
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