Tech Briefs

Fuzzy System for Fault Diagnostics in Power Electronics-Based Brake-by-Wire System

Research in fuzzy diagnostics of brake-by-wire systems focuses on the power electronics switches, since they are often considered to be the weakest link in the system. The objective of fault diagnostics in the power electronics of the brake-by-wire system is to accurately locate any faults within the circuit as soon as they occur.

Posted in: Briefs, Electronics & Computers
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High-Voltage, High-Temperature Power Electronics Capacitor

A novel high- temperature, high- voltage power electronics capacitor incorporates materials of construction and electrical components that have been initially designed as a segment of an integral electronics component, package, or system to be subjected to harsh or high- temperature environments. The capacitor can withstand operating temperatures in excess of 300°C, while maintaining a capacitance between a fraction of 1 to several μFs.

Posted in: Briefs, Electronics & Computers
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Cluster-Assembled Soft Magnets for Power Electronics Applications

This technique uses nanocluster assembly to produce model soft magnetic materials with simpler chemical composition than existing materials and well-controlled nanostructure, and to use these materials to improve understanding of the fundamental mechanisms responsible for the soft magnetic properties. An inert-gas condensation deposition chamber was developed, and transition-metal, rare-earth, and alloy nanoparticles with mean grain size D from 5 - 50 rim were deposited.

Posted in: Briefs, Materials
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Evaluation of Performance of WL Fe-Based Spin-LEDs

A study was performed to evaluate the performance of a recently developed type of Fe-based spin-light-emitting diodes (spin-LEDs) that incorporate wetting layers (WLs). [The term "wetting layer" has two slightly different meanings as explained below.] Light beams emitted by the WL Febased spin-LEDs were found to exhibit the same high degree of circular polarization as do those of previously developed Fe-based spin-LEDs, but differ in one very important aspect: they are an order of magnitude brighter than those emitted by their previously developed counterparts. As a consequence, the WL Fe-based spin-LEDs function reliably at room temperature, whereas their previously developed counterparts do not.

Posted in: Briefs, Photonics
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Advances Toward Affordable High-Energy Laser Modules

A multidisciplinary research project entitled “Affordable High-Energy Lasers” has made numerous contributions to the development of several types of advanced laser modules, including not only lasers but also coupling optics and integral laser/ coupling-optic combinations. There are numerous potential applications for such modules, including weaponry, lidar, high-data-rate optical communications, interferometry, spectroscopy, remote sensing, and processing of materials. The devices developed in this project include novel fiber lasers, novel vertical-external-cavity surface emitting lasers (VECSELs), and a radially emitting photonic-bandgap (PBG) polymer fiber laser. Somewhat more specifically, the contributions are summarized as follows:

Posted in: Briefs, Photonics, Design processes, Lasers, Product development, Research and development
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Lasing Consequences of Silicon Nanostructures

While silicon electronics has been a success in modem technologies, silicon photonics is still in development and in need of a laser source. Many approaches have been explored, from anodized silicon luminescence, to generating direct emissions by quantum-confinement, and to indirect down-conversion of a shorter wavelength laser light via silicon's nonlinear dielectric responses. One approach that was developed has led to the demonstration of laser emission in silicon-on-insulator at cryogenic temperatures (<85K).

Posted in: Briefs, Photonics
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Software Optimizes Multi-Core Platforms

Perseus is a suite of tools that allows existing x86-based software (in binary form) to be optimized for commodity multi-core platforms. Optimizations are made with respect to both performance (e.g., by avoiding undesirable cache effects) and power consumption (e.g., by modulating frequency and voltage of cores according to necessary workloads). The Perseus solution works by using dynamic binary instrumentation to both insert probes and modify deployed code, and by using genetic-algorithm-based searches to determine optimal deployments within the potential design space.

Posted in: Briefs, Software
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Fluidic Flexible Matrix Composites for Autonomous Structural Tailoring

In previous research, a high-mechanical- advantage actuator system inspired by the fibrillar networks in plant cell walls was developed. One of the basic elements in the actuator system is a composite tube consisting of a flexible matrix and multiple layers of oriented, high-performance fibers such as carbon. By tailoring the properties of the fibers and matrix of the flexible matrix composite (FMC) tube, one can create a material that is flexible in certain directions, yet compliant in others. For example, the ratio of Young's moduli in the directions parallel and transverse to the fibers can range from 102 to 104. Strands of such FMC material can be wound into a tube at selected angles relative to the winding axis (a process called filament winding) such that the tube can contract or elongate axially via internal pressurization. It was previously shown that large strain and large force can be achieved with individual, pressurized FMC tubes, and that parallel arrays of tubular elements can be integrated to form 2D adaptive structures (e.g., skins and plates with multiple tubes).

Posted in: Briefs, Materials
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Macromolecular Carriers for Nanomedicine and Nano Devices

Tailoring the surface properties of biodegradable nanospheres and microspheres for in-vivo blood-contacting applications includes defining relationships among chemical composition, processing parameters, nanosphere sizes and size distributions, and surface structure. Developments include: 1) a facile method for achieving magnetite-polylactide nanospheres that can be dispersed in aqueous media; 2) methods for functionalizing the termini of the hydrophilic brushes on the nanospheres in order to conjugate targeting moieties; 3) development of a nanosphere processing approach that yields nanospheres in the desired size range with a narrow distribution of sizes; and 4) maintainence of all of these characteristics with up to approximately 60 weight percent of magnetite incorporated into the nanospheres.

Posted in: Briefs, Medical
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Genetic Studies of Responses of Bones to Mechanical Stresses

Progress has been reported in a continuing program of molecular genetic studies of the responses of bones to mechanical stresses. Prior studies in mice and humans had provided evidence that mechanical loading stimulates bone formation and that immobilization or loss of mechanical stimulation leads to decreasing bone formation and increasing bone loss. Other prior studies in humans and mice had demonstrated that bone anabolic response differs widely among individuals subjected to the same degree of mechanical loading. The initiation of the present studies was motivated by the conjecture that variations in bone anabolic response among individuals are attributable to differences in the transcription levels of genes; that is, they are genetically controlled.

Posted in: Briefs, Medical
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Characterization of a MEMS Directional Sound Sensor

There is a wide range of potential military applications in which ambiguity in bearing occurs with respect to sound. For example, autonomous unmanned aerial vehicles (UAVs) could employ a sensor to determine the bearing of an explosion and conduct battle damage assessment (BDA) on it. With existing sensors this is difficult to do because the explosion is too short in duration to use the Doppler effect to determine the bearing. Also, an autonomous underwater vehicle (AUV) acting as a quiet platform to tow a short, omni-directional hydrophone array must contend with bearing ambiguity.

Posted in: Briefs, Physical Sciences
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Two-Camera Imaging System for Kinematic Measurements

A high-speed imaging system has been devised as a noninvasive means of collecting data on the kinematics of working models of developmental underwater or aerial vehicles that would utilize flapping fins or flapping wings for propulsion. The system includes two high-speed digital electronic cameras aimed along orthogonal axes that acquire snapshots of a model simultaneously in rapid succession. The data from successive images are postprocessed to obtain three-dimensional coordinates of points of interest on the model as functions of time. In the case of a flapping appendage, the points of interest are tips on the appendage, and the temporal evolution of the tip coordinates through multiple flapping cycles is utilized, in conjunction with computational fluid dynamics and other analytical tools, in an iterative process of testing and design directed toward improving the swimming or flying performance of the model. The system can, of course, be used as a noninvasive means of kinematic testing of models other than those of vehicles utilizing flapping appendages.

Posted in: Briefs, Physical Sciences
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Synthesizing Pseudo-Finer-Resolution MODIS Data Products

A document discusses a methodology for synthesizing finerresolution data products from outputs of the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments aboard NASA's Terra and Aqua satellites. Typical MODIS ocean color data have 1-km resolution, but those in five wavelength bands have 500-m resolution and those in two wavelength bands have 250-m resolution. Finer-resolution bio-optical-property data products improve our capability for monitoring coastal ocean and estuarine processes.

Posted in: Briefs, Physical Sciences
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Infrastructure for Development of Secure, Reliable Software

The Verification and Automated Reasoning research group at Cornell University has been building an infrastructure, comprising human expertise and computational resources, for the development of secure, reliable software for critical military applications. Such software includes distributed real-time embedded software systems, which are inherently complex and difficult to understand and specify. The infrastructure includes both efficient means of constructing the software and mathematically rigorous means of ensuring that the software will be secure and correct by construction.

Posted in: Briefs, Information Technology
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A Formal Model of the Attack Surface of a Software System

A formal model has been devised to impart some mathematical rigor to the concept of the attack surface of a software system. Complementing the model is a definition of a quantitative measure of the attack surface as an indicator of the relative insecurity of the system (the larger the attack surface, the more insecure the system). The model and the quantitative measure are intended to serve as systematic means of assessing progress in the development of secure software; they are expected to be especially valuable for evaluating the relative degree of security of two successive versions of nominally the same computer program.

Posted in: Briefs, Information Technology
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Nanostructured Ferromagnetic-Wire/Insulator Composites

A research and development effort now in progress is focused on nano-structured ferromagnetic- wire/insulator composite materials to be used as the magnetic-core materials of sensors for measuring weak magnetic fields. Figure 1 schematically depicts an example of such a sensor — a flux-gate magnetometer that resembles a traditional orthogonal flux-gate magnetometer except that, instead of a single cylindrical ferromagnetic core, there are multiple parallel ferromagnetic wire cores packed together with insulating material between them. An overriding consideration in the design, fabrication, and operation of such a magnetometer is that high effective magnetic permeability of the core is necessary as one of the prerequisites for obtaining high sensitivity.

Posted in: Briefs, Physical Sciences
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Barium Ferrite Materials for Microwave Circulators

Barium ferrite thick disks have been fabricated for incorporation in self-biased microwave devices. The process uses barium ferrite nanopowder mixed with epoxy. The mix is placed on alumina substrates to fabricate 500 μm thick disks of BaM to achieve good magnetic properties such as magnetic saturations from 2,000 to 2,500 G and coercivities fom 3800 to 4000 Oe. In addition, the barium ferrite thick disks have been incorporated into microwave devices and successfully deposited into copper contact lines for testing and use.

Posted in: Briefs, Materials
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Lubrication Considerations for Military Equipment

Military equipment is subject to increasingly harsh environmental conditions and performance requirements. Simultaneously, engineers and equipment operators are demanding longer service life and less maintenance. The proper approach to lubrication is critical to minimizing equipment failures and meeting rigorous performance specifications. While a multitude of environmental and technical variables may affect lubricant selection and use, the following considerations are important to address whenever a new lubricant is selected:

Posted in: Briefs, Materials
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Thermal Characterization of Thin Films for MEMS Applications

Dielectric thin films play a very important role in the development of microelectromechanical systems (MEMS). These dielectric materials often are used as insulating layers in devices, major components in MEMS structures, or even as materials strictly used for fabrication processes in a clean-room environment. In these applications, heat is often a crucial factor. Whether it be heat transfer through a device to stimulate operation, a device being exposed to certain temperatures during fabrication, or any other manner of heat transfer, these thermal processes are critical to device operation in MEMS. As such, thermal properties of these thin film dielectrics, especially thermal conductivity, are very important parameters to insure proper device operation.

Posted in: Briefs, Materials, Microelectricmechanical device, Heat transfer, Insulation, Materials properties
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Optical Microwave-Signal-Channelization Technique Analyzed

In a recent study, a proposed technique for optical frequency-band channelization of a microwave signal or other wide-band radio signal in a receiver was analyzed and compared with prior electronic and acousto-optical techniques. In frequency-band channelization, which is commonly used in wide-band radio receivers, a received signal is divided into narrow frequency bands (channels) and the signal in each channel is detected by a relatively narrow-band sub-receiver. In principle, frequency-band channelization offers benefits of reduced noise bandwidth and processing gain in the narrowband sub-receivers, leading to increased sensitivity, such that the wide-receiver could have a sensitivity approaching that of a narrow-band receiver. The quality of the channelization ultimately determines the performance of the receiver.

Posted in: Briefs, Electronics & Computers
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High-Cycle Life Testing of RF MEMS Switches

The electromechanical, RF, and charging properties of an "air-gap" capacitive switch enable it to be utilized in high-cycle life testing. Monitoring both high-speed and low-speed switching characteristics provides insight into quantifying the lifetime properties of the switch, and enable estimation of switching lifetime under a variety of operating conditions.

Posted in: Briefs, Electronics & Computers
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Reduced Power Laser Designation Systems

This work contributes to the Micropulse Laser Designation (MPLD) project to develop a six-pound eye-safe micro-pulse laser system to locate, identify, range, mark, and designate stationary and moving targets. MPLD uses laser pulses of much lower energy and higher repetition rates than in existing laser designation systems. Because of this, MPLD presents a range of new circuit design and signal processing problems.

Posted in: Briefs, Photonics
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Continuous-Wave Laser Diodes Based on a Novel InGaAsNSb Material System

Laser sources operating in the spectral region from 2 to 3.5 μm are in demand for ultra-sensitive laser spectroscopy, medical diagnostics, home security, industrial process monitoring, infrared countermeasures, and optical wireless communications. Currently, solid-state lasers and optical parametric oscillators and amplifiers are used as coherent light sources in this spectral region.

Posted in: Briefs, Photonics
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Photon Counting Chirped Amplitude Modulation Ladar

This work is a follow-up to prior efforts to develop a method using Geiger-mode avalanche photodiode (GM-APD) photon counting detectors in chirped amplitude modulation (AM) ladar receivers to yield sensitivities approaching the shot noise limit. Such sensitivities represent about four orders of magnitude improvement over the sensitivities of the currently used unity-gain, opto- electronic mixing (OEM) metal-semiconductor-metal (MSM) detectors. These sensitivity improvements may enable compact, low-power, eye-safe, and/or long-range ladar with low-cost, low-bandwidth readout integrated circuits for foliage and camouflage penetration, target ID, manned and unmanned ground and air vehicle navigation, 3D face recognition, battle damage assessment, and change detection.

Posted in: Briefs, Photonics
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SparkJet Actuators for Controlling Flows

SparkJet actuators are under investigation as means of controlling flows — especially supersonic and hypersonic flows. In one important class of potential applications, SparkJet actuators would be used to effect rapid and flexible steering of advanced aerospace vehicles. Effective manipulation of flow fields in aerospace systems could afford significant benefits, including increases in performance, maneuverability, payload, and range, as well as reductions in overall costs. These macro-scale benefits would be achieved through the use of SparkJet actuators to alter such phenomena as laminar-to-turbulent transition, turbulence, and flow separation on a micro scale.

Posted in: Briefs, Mechanical Components
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Stability of Rotors Supported by Hydrodynamic Film Bearings

The document, "Hydrodynamic Fluid Film Bearings and Their Effect on the Stability of Rotating Machinery" represents a lecture in a series "Design and Analysis of High-Speed Pumps," held in 2006 under the auspices of the North Atlantic Treaty Organization. The document introduces the basic principles of hydrodynamic lubrication and the fundamental equation of classical lubrication theory, then proceeds through derivation of the static and dynamic performance characteristics of short cylindrical journal bearings, with application to the dynamic forced performance of a rigid rotor supported on plain bearings. The Sommerfeld number is introduced and shown to define the relation among load, speed, and equilibrium eccentricity of a journal within a radial bearing. Rotordynamic force coefficients (direct and cross-coupled stiffnesses) are introduced and the relationships between them and instabilities of the rotor-and-bearing system are thoroughly discussed. The relationship between the whirl frequency ratio (the ratio between the frequency of undesired orbital rotor motion about the nominal journal axis and the frequency of rotation) and the threshold rotational frequency for instability is discussed. The document concludes with a review of practical journal-bearing configurations, including summaries of their major advantages and disadvantages and brief descriptions of typical applications.

Posted in: Briefs, Mechanical Components
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Prototype Rocket Engine for a Nanosat Launch Vehicle

A paper discusses a prototype rocket engine for a suborbital Reusable Nanosat Launch Vehicle (RNLV). The engine must operate with thrust levels from 3,000 to 5,000 lbf. The engine is comprised of three major subassemblies: the injector, igniter, and the combustion chamber nozzle. Propellants are introduced and mixed in the combustion chamber utilizing a combination of triplet and unlike doublet injector elements. In addition, film cooling is provided in order to extend the life of the ablative chamber. Ignition is accomplished with solid propellant ports mounted on the side of the chamber.

Posted in: Briefs, Mechanical Components
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Improvements in Manufacturing BMI/Fiber Composites Using AFP

A program now in progress is dedicated to making improvements in automated fiber placement (AFP) for the manufacture of advanced composite-material (matrix/fiber) structural components — especially skin and shell components for aircraft. [In AFP, a composite-material part is formed by laying down fiber tow or tape pre-impregnated with a matrix resin (“prepreg”) onto a mandrel that defines the shape of the part.] Improvements are sought for the following reasons:

Posted in: Briefs, Manufacturing & Prototyping
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Patterning of Polycrystalline Bi2Te3 Thin Films on Silicon

Experiments in patterning of thin films of polycrystalline bismuth telluride (Bi2Te3) on silicon substrates have been performed. Bi2Te3 is representative of a family of thermoelectric materials that are well suited for use in extracting electric energy from thermal gradients associated with flows of waste heat at temperatures in the approximate range of 0 to 150°C. Techniques and processes for fabricating macroscopic thermoelectric devices from bulk thermoelectric materials are mature and well known, but the same cannot yet be said concerning the fabrication of microscopic thermoelectric devices. The experiments reported here were performed as part of a continuing effort to develop capabilities for fabrication (including mass production) of microscopic thermoelectric devices, with a view toward eventually enabling the incorporation of them as integral parts of micro-electromechanical systems (MEMS) that could also include heat exchangers, sensors, actuators, and/or flow channels. Thus, the development of microscopic thermoelectric devices could benefit from the established industrial infrastructure for manufacturing MEMS and other silicon-based microsystems.

Posted in: Briefs, Manufacturing & Prototyping
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Tactical Medical Coordination System

The term "tactical medical coordination system" (TacMedCS) denotes any of several prototype electronic systems for tracking patients in a scenario that may involve multiple instances of treatment by different medical personnel in different locations. The TacMedCS was conceived as a means of facilitating coordination of care of military personnel injured in combat and/or facilitating coordination of care of victims of large-scale disasters. The most advanced prototype has already been demonstrated to be effective in operations at a Navy fleet hospital.

Posted in: Briefs, Medical
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