Browsing by Author "Freeborn, Todd J."
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Item An analysis of parasitic capacitances in ioimpedance spectroscopy and their impact on impedance measurements(University of Alabama Libraries, 2019) Mathews, Robert Joseph; Freeborn, Todd J.; University of Alabama TuscaloosaElectrical Impedance Spectroscopy techniques have long been used to investigate the frequency dependent electrical properties of biological tissues. Typically termed BioImpedance Spectroscopy, or BIS, these measurements are used in many medical and fitness-related applications. However, many of these measurements suffer from a "hook-artifact", or erroneous increase in reactance at high ($f >$ 500 kHz) frequencies. Existing work models this hook with a stray capacitance in parallel with an existing tissue circuit model. While this model certainly produces a hook artifact, it does not account for the presence of electrodes in the circuit model. This thesis expands on this model to include the impedance of the electrode/tissue interface expected in bioimpedance measurements and include an additional stray capacitance that may exist as a result. This thesis develops the circuit theory to describe the impacts of the electrode/tissue impedance and parasitics in this expanded model. This circuit theory is validated through both simulation and experimental results of the proposed circuit model. From the proposed model, a correction technique to reduce the hook artifact based on measuring both the applied and return currents in a bioimpedance test setup is proposed and explored in simulations.Item Association among aerobic performance, resting heart rate and heart rate variability in physically active college-aged adults(University of Alabama Libraries, 2018) Martin, Darrell; Esco, Michael R.; University of Alabama TuscaloosaThe purpose of this study was to determine the relationship between smartphone-derived heart rate measures (resting heart rate [RHR] and heart rate variability [HRV]) and performance on an aerobic performance test. Seventeen male college students performed 55-second HR measures in the seated position every morning for 5 days. The root mean square of successive normal-to-normal interval differences (RMSSD) was used as the HRV metric. The weekly mean and coefficient of variation of RHR (RHRM and RHRCV, respectively) and RMSSD (RMSSDM and RMSSDCV, respectively) were determined. Participants completed the 2 mile run (2MR) on the last day of the week. Intra-class correlations (ICC) were used to determine the stability in the heart rate measures across the 5-day period. Pearson correlations were performed to determine the relationship between 2MR and RHRCV, HRM, RMSSDM and RMSSDCV. RHR (ICC = 0.87 [0.74 to 0.95], p < 0.05) displayed better stability over the 5-day period relative to the RMSSD (ICC = 0.66 [0.32 to 0.86], p < 0.05). RHRM was very strongly correlated with 2MR (r = 0.63), as was RMSSDCV (r = 0.55). Conversely, neither RHRCV nor RMSSDM correlated significantly to the 2MR. Therefore, both RHRM and RMSSDCV may be useful objective heart rate indicators to reflect aerobic performance.Item Bioimpedance Applied on Skeletal Muscle Assessing to Resistance Training Effects(University of Alabama Libraries, 2020) Fu, Bo; Freeborn, Todd J.; University of Alabama TuscaloosaElectrical impedance measurements of biological tissues, termed as bioimpedance, quantify the passive electrical properties of biological tissues including skeletal muscles. Resistance training is important to skeletal muscle in terms of strength gaining, but could introduce fatigue and damage with improper training protocols. For this dissertation, the effect of bicep curl exercise is studied using bioimpedance measurement on localized bicep tissue. Several research tasks are set for this dissertation. Firstly, the accuracy and limitations of impedance measurements with Keysight E4990A impedance analyzer under high residual impedance were studied, with OSL compensation, tetrapolar configuration and 10 kHz to 100 kHz recommended for bioimpedance measurement for maximum accuracy. Secondly, localized bioimpedance was used to assess the changes of bicep tissue of healthy young adults participating in isotonic exercise designed to induce skeletal muscle fatigue with significant changes of pre- and post-exercise impedances observed, caused by the change of muscle property. Next, bioimpedance experiment was further performed on bicep tissue of healthy young adults participating and recovering from eccentric bicep curls exercise with significant change of impedance observed 72 and 96 hours post-exercise, different from isotonic experiment result in terms of recovery time potentially due to the delayed-onset feature of eccentric exercise. Lastly, the use of an equivalent electrical circuit, the Cole-impedance model, to represent bicep tissue bioimpedance was evaluated by fitting the data collected from isotonic and eccentric exercises. Significant changes in Cole impedance parameters, Rinf, R1 and C were observed in isotonic eccentric exercise, proposed to be related to muscle swelling and architecture alteration, respectively. Conclusions and contributions of the current study were shown at the end, as well as limitations and future improvements.Item Body fat percentage via dual energy X-ray absorptiometry following multiple different approaches compared to a laboratory-based 3-compartment model(University of Alabama Libraries, 2019) Welborn, Bailey Arthur; Esco, Michael R.; University of Alabama TuscaloosaThe purpose of this study was to examine the accuracy of using dual energy X-ray absorptiometry (DXA) derived body volume (BV) equations in a multi-compartment model for estimates of body fat percentage (BF%) in comparison to traditional under water weighing (UWW) measures of BV. BF% was estimated using three-compartment (3C), two-compartment (2C) models, and the DXA. The 3C-Siri equation with UWW for BV and deuterium oxide (D2O) for total body water (TBW) was used as the criterion. One hundred twenty-nine adults (55 men and 74 women) volunteered to participate (age = 30 ± 13 years). DXA-derived BV was determined with the recent equations from Smith-Ryan et al. and Wilson et al. and then incorporated into multi-compartment models (i.e., 3CSiri-SR and 3CSiri-W). The 3CSiri-SR and 3CSiri-W DXA-derived BV values were highly correlated with UWW measured BV (74.24L, 74.30L, and 71.97L, respectively, and r=.999 for both). However, the mean BF% was overestimated in all multi-compartment models regardless of which DXA-derived BV equation was used. These results were consistent for the total sample and when stratified by sex, with the observed error ranging from 4.92% to 17.75% (effect size [ES] = .61 to 1.96, all p<.001). The correlation between the DXA-derived BV and 3C-criterion BF% was strongest for both Smith-Ryan et al. and Wilson et al. when utilized in the Siri model (i.e., 3CSiri-SR and 3CSiri-W) in the total sample, (r= .979 and .964, respectively) for men, (r= .974 and .971, respectively) and for women (r= .981 and .973, respectively). The 3CSiri-SR yielded the best accuracy in the total sample, as well as when stratified by men, and women as indicated by the smallest SEE of all methods (1.91%, 1.83%, and 1.76% respectively), although it overestimated BF% by 6% in both sex-specific subgroups. These data indicate that both DXA-derived BV equations are strongly correlated with UWW, however do not provide an accurate measure when incorporated in a 3-compartment model for estimation of BF%. This is likely due to the higher BV values produced by the DXA-derived equations (roughly 2 liters), which overestimated BF% by roughly 5%.Item Cole-Impedance Model Representations of Right-Side Segmental Arm, Leg, and Full-Body Bioimpedances of Healthy Adults: Comparison of Fractional-Order(MDPI, 2021) Freeborn, Todd J.; Critcher, Shelby; University of Alabama TuscaloosaThe passive electrical properties of a biological tissue, referred to as the tissue bioimpedance, are related to the underlying tissue physiology. These measurements are often well-represented by a fractional-order equivalent circuit model, referred to as the Cole-impedance model. Objective: Identify if there are differences in the fractional-order (alpha) of the Cole-impedance parameters that represent the segmental right-body, right-arm, and right-leg of adult participants. Hypothesis: Cole-impedance model parameters often associated with tissue geometry and fluid (R-infinity, R-1, C) will be different between body segments, but parameters often associated with tissue type (alpha) will not show any statistical differences. Approach: A secondary analysis was applied to a dataset collected for an agreement study between bioimpedance spectroscopy devices and dual-energy X-ray absoptiometry, identifying the Cole-model parameters of the right-side body segments of N = 174 participants using a particle swarm optimization approach. Statistical testing was applied to the different groups of Cole-model parameters to evaluate group differences and correlations of parameters with tissue features. Results: All Cole-impedance model parameters showed statistically significant differences between body segments. Significance: The physiological or geometric features of biological tissues that are linked with the fractional-order (alpha) of data represented by the Cole-impedance model requires further study to elucidate.Item Cole-impedance parameters representing biceps tissue bioimpedance in healthy adults and their alterations following eccentric exercise(Elsevier, 2020) Fu, Bo; Freeborn, Todd J.; University of Alabama TuscaloosaThe purpose of this study is to identify if participation in an eccentric exercise protocol altered the Cole-impedance model parameters that represent localized bicep tissue bioimpedance. This supports continued efforts to identify which features of tissue bioimpedance may be effective markers to non-invasively identify skeletal muscle damage. Here, the Cole-impedance model parameters that best fit the localized electrical impedance of exercised (using an eccentric stimulus) and unexercised biceps of 6 participants (collected before, immediately after and at 24 h, 48 h, 72 h and 96 h) are determined using a numerical optimization technique. Statistical tests comparing the pre-exercise and post-exercise model parameters report significant decreases in R-infinity and R-1 with significant increases in Cat 72 h and 96 h post-exercise for exercised biceps (aligning with noted periods of peak swelling). These changes in R-infinity, R-1, and C were not observed in the unexercised biceps. These results support that the C parameter of the Cole-impedance model fit to bioimpedance data may be a suitable marker for identifying skeletal muscle damage. (C) 2020 The Authors. Published by Elsevier B.V. on behalf of Cairo University.Item A Comparative Study of Two Fractional-Order Equivalent Electrical Circuits for Modeling the Electrical Impedance of Dental Tissues(MDPI, 2020) Herencsar, Norbert; Freeborn, Todd J.; Kartci, Aslihan; Cicekoglu, Oguzhan; Brno University of Technology; University of Alabama Tuscaloosa; Bogazici UniversityBackground: Electrical impedance spectroscopy (EIS) is a fast, non-invasive, and safe approach for electrical impedance measurement of biomedical tissues. Applied to dental research, EIS has been used to detect tooth cracks and caries with higher accuracy than visual or radiographic methods. Recent studies have reported age-related differences in human dental tissue impedance and utilized fractional-order equivalent circuit model parameters to represent these measurements. Objective: We aimed to highlight that fractional-order equivalent circuit models with different topologies (but same number of components) can equally well model the electrical impedance of dental tissues. Additionally, this work presents an equivalent circuit network that can be realized using Electronic Industries Alliance (EIA) standard compliant RC component values to emulate the electrical impedance characteristics of dental tissues. Results: To validate the results, the goodness of fits of electrical impedance models were evaluated visually and statistically in terms of relative error, mean absolute error (MAE), root mean squared error (RMSE), coefficient of determination (R2), Nash-Sutcliffe's efficiency (NSE), Willmott's index of agreement (WIA), or Legates's coefficient of efficiency (LCE). The fit accuracy of proposed recurrent electrical impedance models for data representative of different age groups teeth dentin supports that both models can represent the same impedance data near perfectly. Significance: With the continued exploration of fractional-order equivalent circuit models to represent biological tissue data, it is important to investigate which models and model parameters are most closely associated with clinically relevant markers and physiological structures of the tissues/materials being measured and not just "fit" with experimental data. This exploration highlights that two different fractional-order models can fit experimental dental tissue data equally well, which should be considered during studies aimed at investigating different topologies to represent biological tissue impedance and their interpretation.Item Comparison of methods for modeling OCXO frequency aging behavior(University of Alabama Libraries, 2019) Griffin, Samuel James; Lemmon, Andrew N.; University of Alabama TuscaloosaFrequency aging is an important factor in frequency standards. Aging is the portion of frequency drift that is intrinsic to the frequency standard. Improving the knowledge surrounding the mechanisms of aging provides means to minimize their impact. To study frequency aging further, several known models used to describe frequency aging were investigated. A set of oven-controlled oscillator datasets were obtained in order to evaluate two frequency aging models. The first model is a logarithmic model, which was selected due to its ubiquity. The second model is a linear Kalman Filter model, which was chosen for its dynamic capabilities. The results of each modeling procedure were analyzed using linear frequency aging baseline comparison, coefficients of determination, and residual analysis. It was determined that the linear Kalman Filter model provides better model fidelity than the logarithmic model. Additionally, the analysis found that the linear frequency aging baseline comparison and residual analysis provide a sufficient comparison suite, with the coefficient of determination adding little in terms of further insight.Item Comparison of weekly HRV measures collected from two different recording times and their relation to performance in collegiate female rowers(University of Alabama Libraries, 2018) Sherman, Sara Rae; Esco, Michael R.; Fedewa, Michael V.; University of Alabama TuscaloosaINTRODUCTION: Root-mean-square difference of successive RR intervals (RMSSD) is a common heart rate variability (HRV) metric used in the realm of athletic monitoring. Time constraints in a collegiate sport environment and irregular practice hours are challenges that make obtaining the mean value (RMSSDM) and coefficient of variation (RMSSDCV) of daily RMSSD assessment difficult. It is unclear whether the time of day (i.e., measured immediately upon waking versus immediately prior to morning practice) influences these metrics and their relationships to performance. PURPOSE: To compare HRV values when recorded immediately upon waking to values recorded later in the morning prior to practice, and to determine the associations of HRV measures with performance outcomes in competitive female rowers. METHODS: Thirty-one NCAA Division I rowers were monitored for six consecutive days. Two seated RMSSD measurements were obtained on at least three mornings using a photoplethysmography application. Each 1-minute RMSSD measure was recorded following a 1-minute stabilization period. The first (T1) measurement occurred at the athlete’s home following waking, the second (T2) upon arrival at the team’s boathouse immediately before practice. From the daily measures, RMSSD mean and CV were calculated. Rank was determined by the coaches based on performance for that week. Two objective performance assessments were conducted on an indoor rowing ergometer on separate days: timed 2000m and distance covered in 30 minutes. Paired samples t-test was used to assess the potential differences between T1 and T2. Bivariate correlations were assessed using an intraclass correlation coefficient (ICC). Statistical significance assessed using α-level, p<0.05. RESULTS: No differences in RMSSDM and RMSSDCV were observed between T1 and T2 (p=0.73, p=0.66, respectively). RMSSDM at T1 and T2 were strongly correlated (ICC=0.82, 95% CI=0.63 to 0.92), as well as RMSSDCV at both times (ICC=0.75, 95% CI=0.48 to 0.88) (both p<0.01). RMSSDM at T1 and T2 was moderately associated with athlete rank (r=-0.55, r=-0.46, respectively), 30-min distance (r=0.40, r=0.41, respectively), and 2,000m at T1 (r=-0.37). No significant correlations were observed for RMSSDCV. CONCLUSIONS: Ultra-short RMSSD can be measured immediately upon waking or prior to practice, however assessing HRV immediately upon waking yielded stronger correlations with performance.Item Computationally efficient design and implementation of sic mosfet models in spice(University of Alabama Libraries, 2020-12) Nelson, Blake Whitmore; Lemmon, Andrew N.; University of Alabama TuscaloosaTransient simulation of complex converter topologies is a challenging problem, especially in detailed analysis tools like SPICE. Much of the recent literature on SPICE transistor modeling ignores the requirements of application designers and instead emphasizes detail, physical accuracy, and complexity. While these advancements greatly improve model fidelity, they also serve to increase computational complexity, making the resulting models less attractive to application designers. This is in part because transistor models presented for SPICE are generally evaluated by accuracy alone, without consideration for the computational cost of model elements. Models designers tend to optimize toward the metrics by which their work is judged; with little precedent for disclosing computation time in addition to accuracy, the natural outcome is a plethora of highly accurate, detailed models which are less than ideal for complex application simulations. In order to optimize models for such simulations, this dissertation quantifies the relative computational performance of modeling approaches and contextualizes the results with regard to accuracy. This required the development of a new methodology for quantifying model computational performance. An extensive review of the relevant literature is undertaken to select candidate SiC MOSFET models likely to fare well in complex application simulations. By analyzing the accuracy and computational performance tradeoffs of these candidates, new insights into transistor model design and optimization are identified. These insights inform a new SiC MOSFET model synthesized and optimized from the best-of-breed model elements identified. By focusing on retaining high accuracy while making critical performance optimizations, the new model is ideally suited for complex converter simulations.Item Electrical impedance myography: A critical review and outlook(Elsevier, 2021) Sanchez, Benjamin; Martinsen, Orjan G.; Freeborn, Todd J.; Furse, Cynthia M.; University of Utah; University of Oslo; University of Alabama TuscaloosaElectrical impedance myography (EIM) technology is finding application in neuromuscular disease research as a tool to assess muscle health. Correlations between EIM outcomes, functional, imaging and histological data have been established in a variety of neuromuscular disorders; however, an analytical discussion of EIM is lacking. This review presents an explanation for clinicians and others who are applying EIM and interpreting impedance outcomes. The background of EIM is presented, including the relation between EIM, volume conduction properties, tissue structure, electrode configuration and conductor volume. Also discussed are technical considerations to guide the reader to critically evaluate EIM and understand its limitations and strengths. (c) 2020 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.Item Electro-thermal circuit modeling in atomic clock mechanical structures(University of Alabama Libraries, 2017) Miskell, Kyle; Lemmon, Andrew N.; University of Alabama TuscaloosaAs electrical and electronics engineers have striven to create more energy-dense and efficient designs, thermal non-idealities have risen to the forefront of such design endeavors as impediments to miniaturizing and densifying electrical products. In order to overcome these thermal design barriers, engineers require detailed prediction of their circuits' thermal characteristics. Modern electrical engineers must often understand the thermal dynamics of their systems equally as well as the electrical characteristics. In this thesis, an overview of electrical design areas affected by thermal concerns is given, and a literature review of thermal modeling techniques commonly utilized in electrical designs is provided. Furthermore, the thermal modeling of atomic clock mechanical structures is identified as the primary focus of this thesis, and the well-known Cauer electro-thermal circuit framework for thermal modeling is identified as an optimal modeling solution for atomic clock geometries. Subsequently, a full description of the Cauer model and its associated conductive, convective, and radiant physics is given with specific emphasis on atomic clock thermal modeling. Additionally, experimental and numerical techniques utilized in the extraction of Cauer network parameters are discussed, and background on the practical implementation and physical behavior of thermal sensors is given. Last, experimental validation of the Cauer model and its applicability to atomic clock geometries is shown through the application of the techniques and theories discussed in this thesis.Item Fatigue-Induced Cole Electrical Impedance Model Changes of Biceps Tissue Bioimpedance(MDPI, 2018) Freeborn, Todd J.; Fu, Bo; University of Alabama TuscaloosaBioimpedance, or the electrical impedance of biological tissues, describes the passive electrical properties of these materials. To simplify bioimpedance datasets, fractional-order equivalent circuit presentations are often used, with the Cole-impedance model being one of the most widely used fractional-order circuits for this purpose. In this work, bioimpedance measurements from 10 kHz to 100 kHz were collected from participants biceps tissues immediately prior and immediately post completion of a fatiguing exercise protocol. The Cole-impedance parameters that best fit these datasets were determined using numerical optimization procedures, with relative errors of within approximately +/- 0.5% and +/- 2% for the simulated resistance and reactance compared to the experimental data. Comparison between the pre and post fatigue Cole-impedance parameters shows that the R-infinity, R-1, and f(p) components exhibited statistically significant mean differences as a result of the fatigue induced changes in the study participants.Item Flexible PCB Failures From Dynamic Activity and Their Impacts on Bioimpedance Measurements: A Wearable Case Study(IEEE, 2021) Critcher, Shelby; Freeborn, Todd J.; University of Alabama TuscaloosaWearable health monitoring systems that collect data in free-living environments are becoming increasingly popular. Flexible printed circuits provide a commercially available option that can conform to the shape of a wearable system and support electronic sensing and flexible interconnect. However, repetitive dynamic activity can stress and damage the interconnect of flexible PCBs which degrades data quality. This case study evaluated the performance of flexible PCBs providing interconnect between electrodes and sensing electronics for tissue bioimpedance measurements in a wearable system. Resistance data (1 kHz to 128 kHz) was collected from localized knee tissues of 3 participants using the wearable design with flexible PCBs over 7 days of free-living. From electrical and optical inspection after use trace cracking of the flexible PCBs occurred, degrading tissue resistances reported by the wearable system. Exploration of these results advances understanding of how flexible PCBs perform in free-living conditions for wearable bioimpedance applications.Item Heart rate variability over three days relates to body mass index but not aerobic fitness in adult women(University of Alabama Libraries, 2018) Liu, Yuan; Esco, Michael R.; University of Alabama TuscaloosaBACKGROUND: Heart rate variability (HRV) is an efficient non-invasive method to represent the autonomic nervous system (ANS) activity. In clinical settings, HRV has been demonstrated to be a prognostic indicator related to cardiovascular diseases (CVD). A common approach for measuring HRV is to record within an isolated condition. However, HRV varies from day to day, hence an isolated measurement is often not suitable for reflecting a true change in ANS status. According to previous research utilizing isolated HRV recordings, both aerobic fitness and body mass index (BMI) are correlated with HRV. Yet, the extent to which aerobic fitness and BMI independently relate to HRV is less clear, especially when HRV is expressed as an average over time or as the coefficient of variation (CV) of multiple measures. Furthermore, our understanding of these relationships among young adult women subjects is limited as the majority of HRV research has involved men. PURPOSE: To determine if HRV collected over a period of days is associated with aerobic fitness and BMI in young adult women. METHODS: Healthy, untrained young adult women (n=30; 20.6±1.2 yr) who were overweight (26.9 ±7.1 kg/m2) participated in this study. HRV was measured for three consecutive days at the same time in the early morning and averaged (3dayM). A maximal graded exercise test on the treadmill was performed to evaluate the peak oxygen consumption (VO2peak) after 3-day HRV data collection. BMI was calculated using subjects’ height and weight. Independent associations between HRV (i.e., 3dayM and corresponding CV [3dayCV]) and aerobic fitness and BMI were evaluated using correlations. RESULTS: Aerobic fitness (VO2peak) was not correlated with any of the HRV parameters for the 3dayM and 3dayCV values (all P>0.05). BMI was not correlated with any of the HRV parameters for the 3dayM values (all P>0.05), however, BMI was correlated with all but one HRV parameter (HFCV, p>0.05) for 3dayCV: SDNNCV (r=0.471, p=0.009), RMSSDCV (r=0.396, p=0.030), LFCV (r=0.499, p=0.005), SD1CV (r=0.394, p=0.031), and SD2CV (r=0.426, p=0.019). CONCLUSION: The results of this study showed that HRVCV values were significantly correlated to BMI among 30 healthy, untrained women subjects over 3-day measurement.Item Intelligent wireless multi-beam directional routing with software-defined network implementation(University of Alabama Libraries, 2017) Bao, Ke; Hu, Fei; University of Alabama TuscaloosaWireless mesh networks (WMNs) have drawn lots of attention in the past decades due to its scalability, robustness, and flexibility. However, the performance of WMNs is still limited by the wireless bandwidth, radio frequency interference, etc. To deal with the limitation, our research first focuses on a particular radio frequency technology, called Multi-beam directional antennas (MBDAs). The MBDA allows a node to simultaneously send out packets in multiple directions without interference among the beams. Thus it significantly improves the throughput and elongates the transmission distance compared with omni-directional or single-beam directional antennas. Our goal in this study is to come up with a series of Artificial Intelligent (AI) strategies to explore MBDAs during routing implementation. Then, the AI method is expanded to a more general WMNs with heterogeneous wireless devices, in which we use centralized network management structure for the purpose of traffic engineering optimization. First, we present a novel routing scheme for WMNs with MBDAs. It has the following 3 features: (1) Ripple-Diamond-Chain (RDC) shaped routing: to explore the multi-direction transmission capability of the MBDAs, we propose to use rateless codes to obtain loss-resilient symbols for original packets. Those symbols can go through each beam in the same time. Then we propose to use ripples to differentiate each hop of nodes in the tree topology of the WMN, which consists of mesh routers (tree roots) and a large number of mesh clients (tree nodes). The main path consists of the nodes with the best link quality and reliability. The symbols are divergent into multiple paths but converge into the main path node in the next hop. The entire routing topology looks like a diamond chain. By using such RDC style routing, we can fully explore the MBDA benefits. (2) Systematic link quality modeling: Our research targets the highly dynamic radio conditions in the WMN. The directional antennas can cause node capture issue. The link could have deep fading in each hop. The rateless codes need to adjust the transmission pause time. We propose to integrate all these factors together to determine the link quality in dynamical network conditions. (3) AI-Augmented path link selection: Our routing scheme is augmented via Artificial Intelligence (AI) algorithms. Especially, we use two AI techniques to enhance the routing performance: Fuzzy Logic (FL): To adapt different QoS requirements, we propose to use Fuzzy Logic to define the weighted link quality. Thus we know which link should be selected for different QoS flows. Reinforcement Learning (RL): Since the dynamic radio conditions need a long-term consideration of the throughput performance within multiple phases of routing path control, we propose to use RL to select the main path based on the cumulative throughput rewards in all links. In the simulations, we use real-time video as well as other types of traffic types to validate the high-throughput, QoS-differentiated, multi-beam routing efficiency, as well as its intelligent path determination in dynamic WMN environment. Second, we expand the routing/TE problem from conventional WMNs to Software-Defined Networking based WMNs (SD-WMNs) and propose a novel TE structure on SD-WMN called "Prediction-based Link Uncertainty Solution in SD-WMNs" (PLUS-SW). The SDN aims to realize a centralized monitor and control upon a network by detaching the control module from data plane, in which an independent control plane is employed for the network management and all the routers on data plane are simplified to the dummy packet forwarding devices. Although the centralized control achieved by SDN is promising on the significant improvement of traffic engineering via network-wide management, it is naturally inadequate when responding to the uncertainty of WMNs in terms of latency reduction and coarse control panel management. We thus propose PLUS-SW to overcome these shortages. The PLUS-SW possesses a centralized traffic engineering and wireless channel scheduling on WMNs according to the paradigm of SDN in order to efficiently arrange the network traffic and omit wireless interference in a global manner. Moreover, PLUS-SW employs double-layer supervised learning model to predict unexpected wireless link failure in the sense that the central controller can notice the potential link failure threat and send back the backup solution to affected routers ahead the link failure. The rerouting calculation of PLUS-SW on congested traffic is based on the network-wide observation while keeping the overhead of centralized control at a low level. Finally, a wireless network platform is also introduced. This platform is built with Software Defined Radio hardware, called USRP. In this platform, we achieved some preliminary functions of WMNs, such as real-time video transmission, cross-layer design and etc. The platform can work as a test bed to estimate the performance of proposed design of traffic engineering.Item Localized Bioimpedance Measurements with the MAX3000x Integrated Circuit: Characterization and Demonstration(MDPI, 2021) Critcher, Shelby; Freeborn, Todd J.; University of Alabama TuscaloosaThe commercial availability of integrated circuits with bioimpedance sensing functionality is advancing the opportunity for practical wearable systems that monitor the electrical impedance properties of tissues to identify physiological features in support of health-focused applications. This technical note characterizes the performance of the MAX3000x (resistance/reactance accuracy, power modes, filtering, gains) and is available for on-board processing (electrode detection) for localized bioimpedance measurements. Measurements of discrete impedances that are representative of localized tissue bioimpedance support that this IC has a relative error of <10% for the resistance component of complex impedance measurements, but can also measure relative alterations in the 250 m Omega range. The application of the MAX3000x for monitoring localized bicep tissues during activity is presented to highlight its functionality, as well as its limitations, for multi-frequency measurements. This device is a very-small-form-factor single-chip solution for measuring multi-frequency bioimpedance with significant on-board processing with potential for wearable applications.Item Localized Multi-Site Knee Bioimpedance as a Predictor for Knee Osteoarthritis Associated Pain Within Older Adults During Free-Living(IEEE, 2023) Critcher, Shelby; Parmelee, Patricia; Freeborn, Todd J.; University of Alabama TuscaloosaThe drastic increase in the aging population has increased the prevalence of osteoarthritis in the United States. The ability to monitor symptoms of osteoarthritis (such as pain) within a free-living environment could improve understanding of each person's experiences with this disease and provide opportunities to personalize treatments specific to each person and their experience. In this work, localized knee tissue bioimpedance and self-reports of knee pain were collected from older adults ($N=20$) with and without knee osteoarthritis over 7 days of free-living to evaluate if knee tissue bioimpedance is associated with persons' knee pain experience. Within the group of persons' with knee osteoarthritis increases in 128 kHz per-length resistance and decreases in 40 kHz per-length reactance were associated with increased probability of persons having active knee pain ($p=0.038$ and $p=0.044$).Item Modeling and simulation of radiated emissions and susceptibility(University of Alabama Libraries, 2021) Wallner, Tripp Christian; Lemmon, Andrew; University of Alabama TuscaloosaThe ongoing development of finite element analysis (FEA) software has made it possible for high validity evaluations to be conducted in simulated environments. In the realm of emissions and susceptibility analysis, rigorous field and lab testing of shielding effectiveness is an expensive and resource-intensive necessity to ensure accordance with electrical standards. The use of FEA software can reduce the cost of achieving compliance by enabling system optimization prior to the investment of significant resources incompliance testing. However, this simulated compliance approach must be carefully calibrated to ensure relevance to real-world results. The development of a consistent methodology for achieving this relevance can satiate a demand for confidence in meeting electrical standards prior to field and lab testing. This thesis aims to establish a procedure for simulating radiated susceptibility in simulated environments analogous to those used in field and lab tests. Frequency domain simulation provides a means for the exploration of frequency-dependent effects as a result of shielding choices. Furthermore, time domain simulation provides predictions that can be readily compared to physical measurements. Finally, FEA software permits evaluation of ideal conditions, such as perfect conduction and lossless mediums, in order to expose designs to conditions more severe than actuality. Using these ideal simulation conditions in conjunction with the aforementioned domains of study can provide results for a worst-case scenario, in turn instilling confidence in shielding effectiveness prior to real-world field testing.Item A novel method for in-situ extracting bio-impedance model parameters optimized for embedded hardware(Nature Portfolio, 2023) Simic, Mitar; Freeborn, Todd J.; Sekara, Tomislav B.; Stavrakis, Adrian K.; Jeoti, Varun; Stojanovic, Goran M.; University of Novi Sad; University of Alabama Tuscaloosa; University of BelgradeA novel method for embedded hardware-based parameter estimation of the Cole model of bioimpedance is developed and presented. The model parameters R-infinity, R-1 and C are estimated using the derived set of equations based on measured values of real (R) and imaginary part (X) of bioimpedance, as well as the numerical approximation of the first derivative of quotient R/X with respect to angular frequency. The optimal value for parameter alpha is estimated using a brute force method. The estimation accuracy of the proposed method is very similar with the relevant work from the existing literature. Moreover, performance evaluation was performed using the MATLAB software installed on a laptop, as well as on the three embedded-hardware platforms (Arduino Mega2560, Raspberry Pi Pico and XIAO SAMD21). Obtained results showed that the used platforms can perform reliable bioimpedance processing with the same accuracy, while Raspberry Pi Pico is the fastest solution with the smallest energy consumption.