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Effect of Laser Noise on an Analog RF/Photonic Link

Aset of equations has been formulated to enable quantification of several aspects of the performance of an analog photonic communication link as affected by laser noise. A procedure for measuring the laser noise has been devised to provide laser-noise data for use in the equations. The equations and procedure are generally applicable to diverse analog photonic links, in the design and operation of which laser noise is of great concern. Analog photonic links have been found to be useful as subsystems, radio-antenna-arraying systems, optoelectronic oscillators, and wide-band signal-processors.

Posted in: Briefs, Photonics, Finite element analysis, Lasers, Noise measurement
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C++ Architecture for Simulating UAVs

A conference paper describes the use of the CADAC++ software system for simulating operations of uninhabited aerial vehicles (UAVs) in conjunction with moving ground targets while interacting with other UAVs and with satellites that assist in targeting. CADAC++ was developed by rewriting the prior Fortran-language CADAC software to take advantage of features of C++ that enable multiple instantiation of UAVs, targets, and satellites, thereby enabling the study of such phenomena as fly-out trajectories, third-party targeting, and distributed information sharing. [CADAC (Com puter Aided Design of Aerospace Con cepts) is chiefly an engineering tool to aid in developing aerospace vehicles.] The architecture of CADAC++ is based on the hierarchical structure of inherited classes, wherein, among other things, every instantiated vehicle object is encapsulated with its methods and data. The paper discusses this architecture in more detail, outlining its class structure and a global data bus through which encapsulated vehicle-objects communicate. The paper then discusses a simulation involving a generic UAV model having five degrees of freedom in order to demonstrate the interactive features of the simulation and to support the conclusion that C++ is the programming environment of choice for networked simulations.

Posted in: Briefs, Information Technology, Computer simulation, Satellites, Unmanned aerial vehicles
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Overcoming Obstacles to DoD Software Technology Transition

The term "Software Wind Tunnel" (SWiT) denotes an institution proposed to be established as a means of overcoming obstacles that, heretofore, have impeded technology transition in connection with research on, and development and utilization of, software needed for software- intensive systems of the Department of Defense (DoD). The term "technology transition" should not be confused with the term "technology transfer," which denotes a process in which an item of technology developed by or for the government is transferred to industry (usually) or vice versa. Instead, "technology transition" denotes a process in which an item of technology is made to evolve from its developmental form into a mature form and in which that item is adopted by its intended end users.

Posted in: Briefs, Information Technology
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Magneto-Fluid Dynamics Calculations for Aerodynamics

Governing differential equations, and algorithms to solve the equations numerically, have been developed to enable computational simulation of weakly ionized aerodynamic flows in the presence of electromagnetic fields. The equations and algorithms are intended mainly for application to airflows about, and within the engines of, contemplated hypersonic vehicles. There, strong imposed magnetic fields and perhaps imposed electric fields might be used, variously, for reducing transfer of heat to solid surfaces, for extracting electric energy from flows, or for accelerating or decelerating flows to enhance combustion of fuel or otherwise increase energy efficiency.

Posted in: Briefs, Information Technology
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GOx/CNT/Silica Composites for Bioelectrodes

Composites of glucose oxidase (GOx), carbon nanotubes (CNTs), and biologically synthesized silica have been synthesized and tested. These composites are prototypes of biological/electrical interfacial materials and could enable the development of the next generation of devices for a variety of medical, scientific, industrial, and military applications. In particular, it is envisioned that materials based on these prototypes will be integrated into bioelectrodes for biosensors and biofuel cells.

Posted in: Briefs, Materials, Biomaterials, Composite materials, Materials properties, Nanotechnology
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Planning Observations by Unmanned Surface Vessels

Three algorithms, and software that implements the algorithms, have been conceived and analyzed as means of effecting automated planning of scientific observations by a fleet of unmanned surface vessels (USVs) equipped with sensors and operating over a large and possibly changing ocean area. Typical observations envisioned in the development of these algorithms include water-temperature measurements ahead of the path of a hurricane (see figure) and fluorometer readings to track harmful algal blooms.

Posted in: Briefs, Information Technology
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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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