Kyle Mitchell

Embeddable modular hardware for multi-functional sensor networks

A multi-layer node is described for multi-functional sensor networks. The generation-4 smart sensor node (G4SSN) is light weight, has a small footprint, and is low power to support dedicated, embedded applications. It has core layers for data sensing, data processing and wireless networking. The modular physical layout is built around a flexible, multi-channel bus architecture and routing protocols are easily tailored. Additional stackable layers and devices can be easily configured and programmed to meet specific application requirements, especially for prototyping and research investigations. The feasibility for high-resolution sensor data acquisition and wireless transmission is demonstrated using the dynamic strain behavior of an instrumented cantilever beam. The G4SSN is adaptable with different hardware components such as different sensor types and radio layer capabilities.

In Vitro Comparison of Two Different Mechanical Circulatory Support Devices Installed in Series and in Parallel

This study investigates the novel approach of placing a ventricular assist pump in the descending aorta in series configuration with the heart and compares it with the two traditional approaches of left-ventricle-to-ascending-aorta (LV-AA) and left-ventricle-to-descending-aorta (LV-DA) placement in parallel with the heart. Experiments were conducted by using the in-house simulator of the cardiovascular blood-flow loop (SCVL). The results indicate that the use of the LV-AA in-parallel configuration leads to a significant improvement in the systemic and pulmonic flow as the level of continuous flow is increased; however, this approach is considered highly invasive. The use of the LV-DA in-parallel configuration leads to an improvement in the systemic and pulmonic flow at lower levels of continuous flow but at higher levels of pump support leads to retrograde flow. In both in-parallel configurations, increasing the level of pump continuous flow leads to a decrease in pulsatility to a certain extent. The results of placing the pump in the descending aorta in series configuration show that the pressure drop upstream of the pump facilitates cardiac output as a result of afterload reduction. In addition, the pressure rise downstream of the pump may assist with renal perfusion. However, at the same time, the pressure drop generated at the proximal part of the descending aorta induces a slight drop in carotid perfusion, which would be autoregulated by the brain in a native cardiovascular system. The pulse wave analysis shows that placing the pump in the descending aorta leads to improved pulsatility in comparison with the traditional in-parallel configurations.

General Aviation Aircraft Flight Operations Quality Assurance: Overcoming the Obstacles

This describes the initiative to introduce a capable yet affordable Flight Operations Quality Assurance (FOQA) program into the general aviation industry. A brief overview of the FOQA concept is given along with a historical perspective to the evolution of such programs. Initial development of a FOQA program for general aviation by the Center for Sensors and Sensor Systems at Saint Louis University is introduced herein. A brief discussion of the obstacles in developing such a system is presented, as well as strategies for overcoming these obstacles. The system consists mainly of a quick access recorder (QAR) that is conceived to be a stand-alone, non-intrusive system that collects parametric flight data, a preprocessor system to analyze initial data sets and validate their use, and post-processor software used in the analysis of available flight parameters. The program concepts are presented for initial determination of the needs and possibilities, and examples are presented along with flight data collected in the Universitys fleet of aircraft.

Low-power hardware implementation of artificial neural network strain detection for extrinsic Fabry-Pérot interferometric sensors under sinusoidal excitation

Artificial neural networks are studied for use in estimating strain in extrinsic Fabry-Perot interferometric sensors. These networks can require large memory spaces and a large number of calculations for implementation. We describe a modified neural network solution that is suitable for implementation on relatively low cost, low-power hardware. Moreover, we give strain estimates resulting from an implementation of the artificial neural network algorithm on an 8-bit 8051 processor with 64 kbytes of memory. For example, one of our results shows that for 2048 samples of the transmittance signal, the presented neural network algorithm requires around 24,622 floating point multiplies and 35,835 adds, and where the data and algorithm fit within the 64-kbyte memory.

Simultaneous analysis of vascular norepinephrine and ATP release using an integrated microfluidic system

BACKGROUND Sympathetic nerves are known to release three neurotransmitters: norepinephrine, ATP, and neuropeptide Y that play a role in controlling vascular tone. This paper focuses on the co-release of norepinephrine and ATP from the mesenteric arterial sympathetic nerves of the rat. NEW METHOD In this paper, a quantification technique is described that allows simultaneous detection of norepinephrine and ATP in a near-real-time fashion from the isolated perfused mesenteric arterial bed of the rat. Simultaneous detection is enabled with 3-D printing technology, which is shown to help integrate the perfusate with different detection methods (norepinephrine by microchip-based amperometery and ATP by on-line chemiluminescence). RESULTS Stimulated levels relative to basal levels of norepinephrine and ATP were found to be 363nM and 125nM, respectively (n=6). The limit of detection for norepinephrine is 80nM using microchip-based amperometric detection. The LOD for on-line ATP detection using chemiluminescence is 35nM. COMPARISON WITH EXISTING METHOD In previous studies, the co-transmitters have been separated and detected with HPLC techniques. With HPLC, the samples from biological preparations have to be derivatized for ATP detection and require collection time before analysis. Thus real-time measurements are not made and the delay in analysis by HPLC can cause degradation. CONCLUSIONS In conclusion, the method described in the paper can be used to successfully detect norepinephrine and ATP simultaneously and in a near-real-time fashion.

Hardware complexity for extrinsic Fabry-Perot interferometer sensor processing

A number of Extrinsic Fabry-Perot Interferometer processing techniques have been demonstrated for use to extract gaugelength measurements from optical detector output signals. These include: (1) an artificial Neural Network method, (2) a direct phase synthesid method, and (3) an iterative search method. For applications where the processing is to be performed with low-power hardware, co-located with the sensor, the hardware implementation architecture and complexity become critical for a practical solution. In this paper, implementation complexity tradeoffs and comparisons are given for various implementation architectures for each method with respect to each gauge-length estimate. Our research considers complexity as measured in terms of the number of hardware-resident arithmetic operators, the total number of arithmetic operations performed, and the data memory size. It is shown that accurate gauge-length estimates are achievable with implementation architectures suitable for applications including low-power implementations and scalable implementations.

An iterative search method for strain measurement in EFPI sensors

In this paper, a new method is given for estimating strain in extrinsic, Fabry-Perot, interferometric (EFPI) fiber-optic sensors under sinusoidal excitation at the sensor. The algorithm has a low complexity and is appropriate for low-cost applications. It is an iterative search algorithm based upon a known, sinusoidal excitation and a mean-square-error objective function. The algorithm provides an estimate of the maximum time-varying strain due to the excitation. It is shown that, for a broad range of parameters, the algorithm converges to the global minima with a high degree of probability. Empirical test results for two fiber-optic sensors with different gauge lengths along with corresponding measurements from a resistive strain gauge are given and shown to compare very well.

Peak strain detection in EFPI sensors via direct phase difference synthesis

This paper presents a method for estimating peak strain using EFPI fiber-optic sensors. The method involves directly synthesizing the optical phase difference from the measured interference signal. Empirical results are presented which demonstrate that this method can measure peak strain to within about ±5 % of the strain measured with respect to a resistive strain gauge sensor.