A theoretical and experimental study of propellant combustion phenomena during rapid depressurization Final report

Modified solid propellant combustion model for steady state analyses of burning rate and flame temperatur

Power minimization of a 433-MHz LC VCO for an implantable neural recording system

Journal ArticleThis paper presents a new random-search based integrated inductor optimization algorithm. The algorithm provides the designer with valuable information about design tradeoffs. it is used to design an inductor to minimize power dissopation in an LC VCO. The measured results show that a 53:1 power savings can be achieved over VCOs using inductors optimized only for maximum Q. Six 433-MHz VCOs were fabricated and measured. The VCO using the optimal inductor design has a measured minimum power dissipation of 1.2 mW in a 0.5-μm three-meatal CMOS process

MDAC synapse for analog neural networks

Journal ArticleEfficient weight storage and multiplication are important design challenges which must be addressed in analog neural network implementations. Many schemes which treat storage and multiplication separately have been previously reported for implementation of synapses. We present a novel synapse circuit that integrates the weight storage and multiplication into a single, compact multiplying digital-to-analog converter (MDAC) circuit. The circuit has a small layout area (5400 μm2 in a 1.5-μm process) and exhibits good linearity over its entire input range. We have fabricated several synapses and characterized their presponses. Average maximum INL and DNL values of 0.2 LSB and 0.4 LSB, respectively, have been measured. We also report on the performance of an analog recurrent neural network which uses these new synapses

Design and implementation of multipattern generators in analog VLSI

Journal ArticleIn recent years, computational biologists have shown through simulation that small neural networks with fixed connectivity are capable of producing multiple output rhythms in response to transient inputs. It is believed that such networks may play a key role in certain biological behaviors such as dynamic gait control. In this paper, we present a novel method for designing continuous-time recurrent neural networks (CTRNNs) that contain multiple embedded limit cycles, and we show that it is possible to switch the networks between these embedded limit cycles with simple transient inputs. We also describe the design and testing of a fully integrated four-neuron CTRNN chip that is used to implement the neural network pattern generators. We provide two example multipattern generators and show that the measured waveforms from the chip agree well with numerical simulations

Wireless neural recording with single low-power integrated circuit

Journal ArticleWe present benchtop and in vivo experimental results from an integrated circuit designed for wireless implantable neural recording applications. The chip, which was fabricated in a commercially available 0.6- m 2P3M BiCMOS process, contains 100 amplifiers, a 10-bit analog-to-digital converter (ADC), 100 threshold-based spike detectors, and a 902-928 MHz frequency-shift-keying (FSK) transmitter. Neural signals from a selected amplifier are sampled by the ADC at 15.7 kSps and telemetered over the FSK wireless data link. Power, clock, and command signals are sent to the chip wirelessly over a 2.765-MHz inductive (coil-to-coil) link. The chip is capable of operating with only two off-chip components: a power/command receiving coil and a 100-nF capacitor

Wireless neural interface for chronic recording

Journal ArticleA primary goal of the Integrated Neural Interface Project (INIP) is to develop a wireless, implantable device capable of recording neural activity from 100 micromachined electrodes. The heart of this recording system is a low-power integrated circuit that amplifies 100 weak neural signals, detects spikes with programmable threshold-crossing circuits, and returns these data via digital radio telemetry. The chip receives power, clock, and command signals through a coil-to-coil inductive link. Here we report that the isolated integrated circuit successfully recorded and wirelessly transmitted digitized electrical activity from peripheral nerve and cortex at 15.7 kS/s. The chip also simultaneously performed accurate on-chip spike detection and wirelessly transmitted the spike threshold-crossing data. We also present preliminary successful results from full system integration and packaging

Evaluation of Nitrate Contamination in Major Porous Media Aquifers in Texas

This study aimed to evaluate the factors influencing nitrate contamination in major porous media aquifers across Texas by analyzing groundwater nitrate concentration data alongside nitrogen loading and aquifer susceptibility parameters. Attributes related to nitrogen loading included atmospheric deposition, fertilizers, land use, sewage and septic input proxies, population density, precipitation, and irrigation. Aquifer susceptibility attributes included land surface slope, soil drainage, clay content, and organic matter content. Multivariate logistic regression was employed to assess the probability of nitrate concentrations exceeding 4 mg/L nitrate-N in shallow wells (≤ 30 m) based on these variables. The final regression model incorporated precipitation, percentage of agricultural land, low-density residential land, and soil organic matter. Observed and predicted probabilities of elevated nitrate concentrations showed strong correlation in both calibration and validation datasets. The inverse relationship between precipitation and nitrate concentration may indicate dilution in high precipitation areas and possible evapoconcentration in low precipitation areas. While nitrate loading was not explicitly included in the model, agricultural land percentage served as a proxy for nitrogen loading from agricultural sources, and low-density residential land use served as a proxy for septic tank effluent. The percentage of organic matter may reflect denitrification in certain regions. This GIS and logistic regression analysis offers valuable insights into the factors influencing nitrate concentrations in groundwater. Future studies should complement this analysis with field sampling to validate the GIS and logistic regression findings and assess the impact of processes like dilution and denitrification on nitrate concentrations.Bureau of Economic Geolog

A non-intrusive nonlinear aeroelastic extension of loads packages with application to long range transport aircraft configuration

A new method for constructing geometrically-nonlinear aeroelastic systems from standard linear models is applied to an industry-level aircraft configuration. The new approach seamlessly integrates with current aeroelastic load packages performing linear analysis based on generic finite-element models (FEMs) and aerodynamic influence coefficient matrices (AICs). We generalize the methodology to incorporate control inputs, find the trimmed aircraft state, or generate gusts disturbances, which can be employed separately or combined to obtain a simplified flight dynamics model for load analysis. An initial study of the aeroelastic response of a long range aircraft is presented. Linear and nonlinear results are introduced in static and dynamic computations of manoeuvres, trim, and gust disturbances. These are compared to commercial software calculations, showing the need for geometrically nonlinear analysis in the production environment of airplanes with ultra high aspect ratio wings

Evaluation of ozone difluoride as a liquid propellant additive Final report

Ozone difluoride evaluated as liquid propellant additiv