Tech Briefs

Ultraviolet Polymerization of Hydrodynamically Shaped Fibers

Materials composed of stacked plates are stronger than the same materials in bulk. However, such stacked plate materials are generally composed of hard, inorganic materials cemented together by a more flexible substance, and do not occur in long fiber shapes. Very few natural or manmade materials are composed of stacks of plate-like fibers. Manmade polymer fibers are nearly always round because they are fabricated using two-phase systems; for example, a solubilized polymer precursor or a monomer–initiator solution is introduced into air by electrospinning, extrusion, or pulling.

Posted in: Briefs, Materials, Fabrication, Fibers, Materials properties, Polymers

Fabrication of Transparent Carbon Nanotube Films for OLED Applications

The process to prepare single-wall carbon nanotube (SWCNT) solutions with a good degree of dispersion of individually isolated SWCNTs and very thin SWCNT bundles was optimized. The SWCNT-dispersion solutions are so stable that they can be stored and used repeatedly for some period of time.

Posted in: Briefs, Manufacturing & Prototyping, Fabrication, Nanomaterials, Durability

Testbed for Reconfigurable Network Security Research and Experimentation

A novel, reconfigurable network testbed has been developed, suitable for the implementation, testing, and analysis of new and existing network-based defenses against various information attacks. The system is based on a cluster of reconfigurable networking nodes that can be configured to emulate an arbitrary network infrastructure.

Posted in: Briefs, Electronics & Computers, Analysis methodologies, Cyber security, Test procedures

Architectures for Cognitive Systems

A need exists for small, autonomic systems in the battlefield. Autonomy allows the creation of unmanned systems to perform complex, high-risk, and/or covert operations in the battlefield without the need for constant human operation. Current computing systems are not optimized to perform intelligent operations such as environmental awareness, learning, and autonomic decisions in a size, weight, and power form factor that matches platforms envisioned for future use.

Posted in: Briefs, Electronics & Computers, Architecture, Autonomous vehicles, Military vehicles and equipment

Circuit-Switched Memory Access in Photonic Interconnection Networks for High-Performance Embedded Computing

High-performance embedded systems, such as those found in aerial surveillance platforms and handheld devices used by the military, are of key importance. These systems are characterized by stringent power budgets and the need for extremely fast, streaming access to memory. While general-purpose processors offer a customizable solution, they typically do not meet the power and performance requirements for the systems in question. For this reason, specialized chip multiprocessors (CMPs) are used.

Posted in: Briefs, Electronics & Computers, Embedded software, Surveillance, Military vehicles and equipment

Analysis of Voltage and Current Signal Processing in a Li-ion Battery Management System

A Battery Management System (BMS) manages Li-ion batteries in a storage system for pulsed power weapons aboard Naval vessels. The system charges the batteries with a buck converter according to the Constant Current Constant Voltage method. The BMS uses analog equipment to measure signals and then digitally converts signals for transmittal to a Field Programmable Gate Array (FPGA).

Posted in: Briefs, Electronics & Computers, Analysis methodologies, Lithium-ion batteries, Marine vehicles and equipment, Military vehicles and equipment

Development of Soldier Conformable Antennas Using Conducting Polymers

Soldiers performing dismounted operations in the field use radios that have antennas with a distinct visible signature and can become easy targets. These antennas also tend to snag on other equipment or vegetation, creating a hazard and a distraction to any ongoing operation. Therefore, it has become necessary to develop an antenna that can conform to soldiers and be virtually indistinguishable from a soldier’s body armor.

Posted in: Briefs, Manufacturing & Prototyping, Antennas, Radio equipment, Protective clothing, Military vehicles and equipment

Variable-Thrust, Multiple-Start Hybrid Motor Solutions

Interceptor boost propulsion has traditionally been dominated by solid rocket systems due to their responsiveness and high mass fraction capabilities. However, increased costs of handling these flammable motors, the need to evolve more and more insensitive munitions, the static thrust profile created at propellant casting, and the inherent performance limitations of solid propellants have motivated the interest in exploring alternate technologies.

Posted in: Briefs, Mechanical Components, Solid propellants, Product development, Hybrid engines

Wheel Force Transducer

Aconcept wheel force transducer has been developed that can measure the forces and moments between a tire and a road on a High Mobility Multi-purpose Wheeled Vehicle (HMMWV or Humvee) driven under off-road conditions. The proposed wheel force transducer is an important step in correcting the gap in current tire testing and modeling knowledge to ensure that future off-road vehicle models and simulation efforts are conducted with confidence. In order to obtain tire characteristics over off-road terrain, cost-effective field test equipment was required.

Posted in: Briefs, Mechanical Components, Tires and traction, Wheels, Test equipment and instrumentation, Off-highway vehicles and equipment

Airbrush-Fabricated Carbon Nanotube Supercapacitor Electrodes

In order for the batteries used by soldiers to provide peak power, an increase in battery size and weight is necessary, which is becoming a burden. A light, compact alternative to large batteries for supplying peak power is electrochemical double-layer capacitors. These supercapacitors have a much higher energy density than conventional capacitors. Supercapacitors also have a higher cycle life, higher efficiencies, and a higher specific power than conventional batteries. Such supercapacitors will complement batteries and fuel cells to produce hybrid systems with extended capabilities.

Posted in: Briefs, Electronics & Computers, Ultracapacitors and supercapacitors, Lightweight materials, Nanomaterials

Compact Superconducting Power Systems for Airborne Applications

In the development of future airborne megawatt-class power generation, it is important to minimize both the size and the weight of the system. The primary means of increasing the power density within the generator, as for all rotating machinery such as motors and alternators, is to maximize the magnetic flux density. This can be achieved by using a higher current-carrying capacity wire to increase the ampere-turns in the windings without adding more turns via a longer length of wire. This has already been accomplished through the incorporation of superconducting wire in magnetic resonance imaging (MRI) magnets used in the medical field.

Posted in: Briefs, Electronics & Computers, Avionics, Electric cables, High voltage systems, Magnetic resonance imaging (MRI), Semiconductors

Development and Test of a Medium-Voltage Converter for Ocean Observatories

A critical component in regional-scale undersea power systems is the medium-voltage converter (MVC). The MVC is a DC-DC converter in the primary network infrastructure that receives a medium-voltage power input from the shore-based power feed equipment (PFE) via the telecom cable, typically at 1-10 KVDC, and provides down-conversion to one or more lower-voltage outputs, typically 300-600 VDC, to feed power to science nodes and instrumentation in the secondary network infrastructure.

Posted in: Briefs, Electronics & Computers, Architecture, Voltage regulators, Electric power, Marine vehicles and equipment

Two-Phase Electronics Cooling for Vehicle Applications

Replacing many of the traditional mechanical power and control systems with electronic equivalents will enable significant improvements by reducing weight, lowering fuel usage, increasing design flexibility, and enhancing overall functionality. This trend is apparent in “drive-by-wire” and “fly-by-wire” system designs. The past few iterations of Army vehicle programs have focused on increasing the use of electrical systems throughout the vehicle for many of the same reasons. Some of these programs have focused on new fully hybrid vehicles, while others have looked at improvements that can be made to legacy systems.

Posted in: Briefs, Electronics & Computers, Electrical systems, Electronic equipment, Cooling, Hybrid electric vehicles, Military vehicles and equipment

Surface Plasmon-Enhanced Si:Er Infrared Light-Emitting Diodes

Plasmons are collective oscillations of the free electrons in a metal or an ionized gas. Plasmons dominate the optical properties of noble-metal nanoparticles, which enables a variety of applications including electromagnetic energy transport at nanoscale dimensions, single-molecule Raman spectroscopy, and photothermal cancer therapy. Plasmons also affect the spontaneous emission dynamics of optical emitters positioned in the vicinity of metal nanoparticles. The luminescence intensity can either be enhanced or quenched, depending on the geometry. Since the associated enhancements can potentially be several orders of magnitude, plasmon-enhanced luminescence is the subject of intense research. This project focused on plasmon-enhanced luminescence of silicon quantum dots (Si QDs) and optically active erbium ions. Both these emitters are compatible with silicon processing technology, and are therefore of great technological interest.

Posted in: Briefs, Photonics, Light emitting diodes (LEDs), Gases, Materials properties, Nanomaterials

Fundamental Interaction Between Gold Nanoparticles and DNA

Quantum dots (QDs) and nanoparticles (NPs) are made of metal and/or semiconductor materials with diameters ranging from 5 to 100 nm. The properties of these nanomaterials, which depend on their size and the material they are made from, are usually completely different than the properties of their corresponding bulk materials. There may be anywhere from 1 to 1,000 electrons in a single QD, providing numerous possibilities for their opti-

cal and electrical properties.

Posted in: Briefs, Materials, Composite materials, Materials properties, Metals, Nanomaterials, Semiconductors

High Critical Current in Metal Organic Derived YBCO Films

High-temperature superconducting (HTS) YBCO wire is a versatile technology for a number of military and commercial applications. However, anticipated military applications such as energy-dense electric propulsion systems (including motor and adjustable speed motor drives), directed-energy weapons (including the gyrotron magnet and power supply), and commercial applications such as motors, generators, transformers, and power transmission lines require improvement in the performance of such wires before these applications are broadly realized.

Posted in: Briefs, Materials, Electric cables, Materials properties, Industrial vehicles and equipment, Military vehicles and equipment

Dense Transducer Array

A dense transducer array is an acoustic transducer with relatively high operational bandwidth. It includes a cable harness component that provides and organizes various conductors within piezocomposite substrates to form transducer arrays with minimum impact on electroacoustic performance. Several underwater sonar applications exist for high-frequency wideband transducer arrays having individual elements. In order to form and steer acoustic beams with an array of individual elements, the array elements must be spaced not more than one-half the acoustic wavelength at the highest frequency of interest. This implies, for square-shaped elements at least, that the elements' lateral dimensions are inversely proportional to frequency. Therefore, for fully populated radiating apertures, the number of elements increases exponentially as the spacing decreases.

Posted in: Briefs, Electronics & Computers, Electronic equipment, Acoustics, Marine vehicles and equipment

Temperature Effect on Drop-Weight Impact of Hybrid Woven Composites

The main idea of composite material is to combine different materials to produce a new material with performance unattainable by the individual constituents. It gives flexibility to the designer to tailor the new material with properties to obtain peak performance for a particular application.

Posted in: Briefs, Materials, Design processes, Composite materials, Materials properties

Synthesis of Long-Chain-Branched (LCB) Polysulfones for Multifunctional Transport Membranes

Increasing numbers of technologies are based on the idea of harnessing charge transport for useful processes such as energy harvesting, actuation, and sensing. Although much progress exists based on perfluorosulfonated platforms, new and more complicated parameters arise as applications require multifunctionality in engineering materials. For instance, in addition to using lightweight, durable, stable, high-conductivity proton-exchange membranes in a fuel cell, it may be desirable to have the energy source bear load and operate as a structural installment. The most prevalent class of materials potentially capable of such a tradeoff is rubbery “salt-in-polymer” electrolytes that employ polymer segmental motion for transport of free ions from co-dissolved salts.

Posted in: Briefs, Materials, Fabrication, Conductivity, Elastomers, Electrolytes

Biodegradable MEMS Based on Cellulose Paper

Electro-Active Paper(EAPap) has been recognized as a new smart material that can be used for sensors, actuators, biomimetic robots, and smart wallpapers. EAPap is made with cellulose paper by coating thin electrodes on both sides of it. This paper can produce a bending or longitudinal strain in the presence of an electric field. Also, it can produce an induced charge under the external stress. This EAPap material has many advantages in terms of large displacement output, low actuation voltage, low power consumption, dryness, flexibility, sensing capability, and biodegradable characteristics.

Posted in: Briefs, Materials, Microelectricmechanical device, Sensors and actuators, Fabrication, Lightweight materials, Materials properties, Smart materials

Functionalized Silk Materials

T he goal of this work was to exploit the novel structural, physical, and biological features of silk proteins towards functionalization of materials systems generated from this family of protein. A new generation of functional silk systems is sought to provide novel materials with precise control of material features. Three main directions were planned: (a) protein chimeras to form organic (silk) – inorganic nanocomposites; (b) formation of electronic materials using a similar design strategy, but based on enzymatic coupling reactions to form conducting polymers; and (c) continuing to understand and exploit novel processing approaches with these proteins towards new functional materials systems.

Posted in: Briefs, Materials, Research and development, Fabrication, Biomaterials, Materials properties

Dynamic Response and Failure Mechanisms of Layered Ceramic-Elastomer-Polymer/Metal Composites

A thorough study through a combination of ballistic and impact experiments, microscopic failure characterization, and numerical simulations has been carried out in order to decipher the underlying mechanisms involved in the interaction between a blast and/or a blast-induced high-velocity projectile and advanced ceramic-polymer and metal-polymer composites, resulting in an improved ballistic efficiency and impact- and blast-resistant structural system.

Posted in: Briefs, Materials, Ceramics, Composite materials, Elastomers, Metals, Protective equipment, Military vehicles and equipment

Ultra-Low-Power Radios for Ad-Hoc Sensing Networks

Anew method has been developed for the design of a miniature, low-power, low-cost radio node capable of self-organization and communication within an ad-hoc network. The integrated radio transceiver, combined with a backend processor in a single networkable node, offers unique network scalability and low power levels that will enable applications that are not possible with any existing sensor node platform. One unique feature of this radio is that the proposed integrated microchip can be mass produced in a CMOS process without a costly external crystal so that the network formed by a set of homogeneous nodes is robust to network changes or node failure. These characteristics enable formation of reliable, inexpensive ad-hoc networks with group intelligence and long lifetimes.

Posted in: Briefs, Electronics & Computers, Communication protocols, Integrated circuits, Radio equipment, Durability

MEMS Resettable Circuit Breaker and Switch for DC-DC Voltage Converters

Resettable circuit breaker cantilevers use silicon dioxide (SiO2) for temper ature compensation. The compressive stress in the SiO2 causes the cantilever to bow upwards 400 μm after release. In the DC-DC voltage converter, the gap between the electrodes is 1.4 μm. After release, the cantilevers are stuck down. A short-loop experiment was conducted to better understand the cantilever behavior by omitting the contact metal and SiO2 layers from test cantilevers.

Posted in: Briefs, Electronics & Computers, Microelectricmechanical device, Switches, Test procedures

Finite-Element Simulations of Field and Current Distributions in Multifilament Superconducting Films

The separation of high-temperature superconducting (HTS) tapes in filaments is a viable approach to reduce AC losses in HTS high-power applications, where AC currents and/or fields may be applied in addition to any DC field present. Methods such as mechanical, laser scribing, photolithography, or direct printing on buffered substrates using inkjet deposition have been used to create the filaments in the second-generation HTS coated conductors in order to reduce hysteretic losses. However, losses of the finely striated tapes can still be noticeably larger than predicted by analytical expressions, due to the addition of coupling currents or lack of field penetration, and such deviation tends to grow with increasing filament density. In order to reduce the magnetic coupling between filaments and the associated AC losses, an in-depth understanding of flux and current dynamics in the multifilamentary HTS, in realistic conditions, is required.

Posted in: Briefs, Electronics & Computers, Finite element analysis, Electromagnetic compatibility, Voltage regulators, Conductivity

Nozzles for Focusing Aerosol Particles

Several nozzles have been designed to aerodynamically focus aerosol particles into a small-diameter jet, so that individual particles can be illuminated by a laser beam and their light scattering and/or laser-induced fluorescence (LIF) spectra can be measured. An additional nozzle can aerodynamically puff selected particles out of the airstream so that they can be sorted and collected.

Posted in: Briefs, Mechanical Components, Nozzles, Test procedures, Aerodynamics

Parallel Hybrid Vehicles Using Fuzzy Logic Control

A fuzzy logic controller for hybrid vehicles with parallel configuration was proposed. Using the state-of-charge (SOC) of the energy storage, the driver command, and the motor/generator speed, a set of rules was developed. The fuzzy logic controller can determine the split between the electric motor and the internal combustion engine to achieve better fuel economy and low emission performance without losing vehicle performance.

Posted in: Briefs, Mechanical Components, Fuzzy logic, Architecture, Hybrid electric vehicles, Vehicle performance

Development of an Electrochemical Biosensor for Organophosphate Chemicals

Detection of organophosphate (OP) compounds has attracted much attention in terms of safeguarding human health, owing to their frequent use as pesticides in agriculture and their potential use as chemical warfare agents. Among a variety of biological methods based on the biocatalytic activity of organophosphorus hydrolase (OPH), amperometric, potentiometric, and optical biosensing devices have been developed for detecting OPs. Electrochemical biosensors in particular have been widely investigated to monitor various pesticides including OP compounds such as paraoxon, parathion, sarin, and soman via an enzyme-catalyzed hydrolysis reaction by OPH due to their fast speed, high efficiency, low cost, and small sample size.

Posted in: Briefs, Physical Sciences, Sensors and actuators, Volatile organic compounds, Medical, health, and wellness

Novel Active Transient Cooling Systems

Energy-efficient cooling technology is extremely important in today’s society, considering the need for energy conservation and the urgent need to mitigate global warming. Near-room-temperature magnetic refrigeration is an emerging cooling technology that has several advantages compared to conventional gas-compression technology. It utilizes the magnetocaloric effect (MCE) in which heating and cooling of a magnetocaloric material (MCM) is induced by a varying external magnetic field. The magnetocaloric effect (the temperature change of a magnetic material due to the application of an external magnetic field) is the cornerstone of magnetic cooling.

Posted in: Briefs, Physical Sciences, Energy conservation, Cooling, Magnetic materials

Diode Laser Sensor for Scramjet Inlets

The supersonic combustion ramjet (scramjet) engine is one of the more promising high-speed flight propulsion technologies. One of the reasons for this is the simplicity of the engine design, having no moving parts and requiring no external ignition source, and the fact that scramjets do not need to provide their own oxidizer. Despite this simplicity, several obstacles to the use of scramjet propulsion systems have become apparent, including the ability to produce sufficient fuel-air mixing at high speed, large total pressure losses, reduction in specific impulse with increasing flight Mach number, and the sensitivity of combustion to inlet temperature. This last problem can be very significant.

Posted in: Briefs, Physical Sciences, Lasers, Sensors and actuators, Combustion and combustion processes, Scramjet engines