Portable, Rapid-Test Fuel Tank Leak Detection System

In 1988, the EPA issued Underground Storage Tank (UST) regulations for fuel storage in order to implement monthly monitoring and annual tightness testing. Monthly monitoring requires that the leak detection system be certified for a leak rate of 0.2 gallons per hour (GPH), and annual tightness testing requires a certified leak rate of 0.1 GPH, both with a probability of detection of at least 95%, and a probability of false alarm of no more than 5%. The DoD owns and operates hundreds of underground storage tanks that are less than 100,000 gallons. These tanks, commonly operating at base fuel farms, must comply with EPA, state, and local regulations, and require that either an annual tightness test with monthly inventory reconciliation or monthly monitoring tests be conducted in accordance with published performance standards. Existing technologies either cannot meet performance standards for the large 50-K to 100-K gallon USTs or do not provide a cost-effective solution. The Portable Rapid Test (PRT) is designed and recommended for testing tanks containing lower-volatile, heavier-type fuels such as diesel, JP-5, JP-8, etc.

Posted in: Briefs, Physical Sciences, Defense industry, Fuel tanks, Certification, Inspections, Test procedures

Ballistic Filter for GPS and Accelerometer Measurements

Ballistic filtering describes the dynamic equations that can be used to form Extended Kalman Filters (EKF) for the estimation of a projectile’s trajectory. The steps associated with initialization and implementing an EKF are demonstrated through a specific task. The performance of an EKF processing Global Positioning System (GPS) observation is compared to the performance of an EKF processing both GPS and axial accelerometer observations. Hit point prediction error is used as the measure of effectiveness. Both filters use the same dynamics for state and covariance propagation.

Posted in: Briefs, Information Technology, Trajectory control, Mathematical models, Measurements, Global positioning systems, Global positioning systems (GPS), Military vehicles and equipment

Procedure to Determine and Correct for Transmission Line Resistances for Direct-Current, On-Wafer Measurements

Resistances of tenths of ohms to several ohms in transmission lines have been measured in laboratory systems from the power supply to the device under test (DUT). High-current semiconductor devices may draw currents of several amps. In cases such as these, the voltage drop in the transmission lines may rise up to several volts. In order to properly characterize the DUT, the losses in the transmission line and the voltage drop across the line must be measured and accounted for. A procedure for measuring the transmission line resistances is described. Once these values are known, it is necessary to apply a transform to the raw measured data in order to determine the actual voltages on the device of interest. A simple MATLAB code for determining the DUT current and voltage behavior is presented when the raw IV data and the transmission line resistances are known.

Posted in: Briefs, Electronics & Computers, CAD / CAM / CAE, Measurements, Wiring, Semiconductors

Channel Field Effect Transistors

Narrow bandgap semiconductors offer high carrier mobilities and low contact resistances, while wide bandgap semiconductors offer high breakdown voltages. A series of heterojunction transistors has been investigated and proved to be effective for improving both speed and power output. These devices include double heterostructure InP/InGaAs/InP bipolar transistors and composite-channel InAlAs/InGaAs/lnP/InAlAs high-electron-mobility transistors (HEMTs), which have taken full advantage of the matched lattice constant (or pseudomorphic growth).

Posted in: Briefs, Electronics & Computers, Architecture, Transistors, Semiconductors, Performance tests

Self-Aware Computing

This project performed an initial exploration of a new concept for computer system design called Self-Aware Computing. A self-aware computer leverages a variety of hardware and software techniques to automatically adapt and optimize its behavior according to a set of high-level goals and its current environment. The heart of a complete self-aware system is a new “organic” operating system (OOS). The OOS acts as the ringleader, monitoring applications and making adjustments to hardware and software to increase performance, efficiency, and reliability automatically.

Posted in: Briefs, Electronics & Computers, Artificial intelligence, Computer software / hardware, Product development, Research and development

Computational Photonics in Laser Communications Through Clouds

This work explored the concept of creating a partially coherent laser beam consisting of an array of spatially overlapping or separated Gaussian beams with possible individual control of each individual emitter’s wavelength. The idea was to test whether such a transmitter array could propagate more effectively through weak or strong atmospheric turbulence. It was proposed that a versatile, multi-wavelength, multi-emitter configuration could be realized via an array of optically pumped, vertical external-cavity surface emitting semiconductor lasers (VECSELs).

Posted in: Briefs, Photonics, Lasers, Semiconductors, Test procedures, Turbulence

Fire Resistance of Geopolymer Concretes

Geopolymer concrete has been proposed as an alternative to Portland cement concrete in applications requiring high degrees of fire resistance, because the intrinsic chemistry of the geopolymer binder does not require the retention of water or hydration within gel phases to maintain structural integrity of the binder. Portland cement concrete contains a high level of chemically bound water, which is essential to the gel binder structure, and which is lost upon heating to several hundred degrees Celsius, whereas the water present within a geopolymer concrete is overwhelmingly present in pores and is not an essential part of the strength-generating phases. However, predictions of geopolymer concrete fire performance have up to this time been based on small-scale laboratory testing (usually on paste or mortar specimens), rather than the study of large concrete sections, which provides significance to this work.

Posted in: Briefs, Materials, Composite materials, Heat resistant materials, Polymers, Fire

Tomographic Electrical Resistance-Based Damage Sensing in Nano-Engineered Composite Structures

Advanced composite materials are increasingly replacing metals in the aerospace industry as they offer weight-saving improvements such as high specific strength and stiffness, while providing resistance to fatigue and corrosion. Traditional advanced composites, however, exhibit significantly reduced electrical and thermal conductivity relative to metals, and matrix-rich regions at ply interfaces result in relatively poor interlaminar properties. Additionally, composites that have sustained damage often have non-visible or barely visible damage, complicating damage assessment. Recent efforts to address the limitations of advanced composites include the incorporation of carbon nanotubes (CNTs) to take advantage of intrinsic and scale-dependent properties of these nanostructures.

Posted in: Briefs, Materials, Aircraft structures, Composite materials, Conductivity, Nanomaterials

Uncooled Tunable LWIR Microbolometers

Uncooled infrared detectors have significant potential capabilities that have been little explored. Micro-machined uncooled detectors with tunable spectral characteristics across the long-wave infrared (LWIR, λ~8-12 μm) have been developed. In the middle wavelength infrared (MWIR) and LWIR regions, the fabrication of Fabry-Perot filters is more complex because the optical materials must be infrared-compatible and the layer thicknesses must be larger. It is very difficult to build filters for uncooled LWIR thermal detectors, which has limited previous researchers to demonstrations of discretely tunable 2- or 3-color thermal detectors rather than continuously tunable ones.

Posted in: Briefs, Physical Sciences, Architecture, Sensors and actuators, Thermal testing

Fluid Helmet Liner for Protection Against Blast-Induced Traumatic Brain Injury

An Advanced Combat Helmet liner design uses the novel idea of including filler materials inside channels in the liner. An energy-absorbing foam was selected for the main liner structure, and several filler material candidates of widely varying properties are being considered. To date, material has been evaluated both experimentally and numerically. Numerical studies will include coupled simulations with a detailed finite element head model, providing insight into the effect of the new liner on the brain’s response to a blast wave impact.

Posted in: Briefs, Physical Sciences, Finite element analysis, Foams, Head injuries, Protective equipment, Military vehicles and equipment