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(1 - 7 of 7)
- Title
- Classifying and Predicting Walking Speed From Electroencephalography Data.
- Creator
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Rahrooh, Allen, Huang, Helen, Huang, Hsin-Hsiung, Samsam, Mohtashem, University of Central Florida
- Abstract / Description
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Electroencephalography (EEG) non-invasively records electrocortical activity and can be used to understand how the brain functions to control movements and walking. Studies have shown that electrocortical dynamics are coupled with the gait cycle and change when walking at different speeds. Thus, EEG signals likely contain information regarding walking speed that could potentially be used to predict walking speed using just EEG signals recorded during walking. The purpose of this study was to...
Show moreElectroencephalography (EEG) non-invasively records electrocortical activity and can be used to understand how the brain functions to control movements and walking. Studies have shown that electrocortical dynamics are coupled with the gait cycle and change when walking at different speeds. Thus, EEG signals likely contain information regarding walking speed that could potentially be used to predict walking speed using just EEG signals recorded during walking. The purpose of this study was to determine whether walking speed could be predicted from EEG recorded as subjects walked on a treadmill with a range of speeds (0.5 m/s, 0.75 m/s, 1.0 m/s, 1.25 m/s, and self-paced). We first applied spatial Independent Component Analysis (sICA) to reduce temporal dimensionality and then used current popular classification methods: Bagging, Boosting, Random Forest, Na(&)#239;ve Bayes, Logistic Regression, and Support Vector Machines with a linear and radial basis function kernel. We evaluated the precision, sensitivity, and specificity of each classifier. Logistic regression had the highest overall performance (76.6 +/- 13.9%), and had the highest precision (86.3 +/- 11.7%) and sensitivity (88.7 +/- 8.7%). The Support Vector Machine with a radial basis function kernel had the highest specificity (60.7 +/- 39.1%). These overall performance values are relatively good since the EEG data had only been high-pass filtered with a 1 Hz cutoff frequency and no extensive cleaning methods were performed. All of the classifiers had an overall performance of at least 68% except for the Support Vector Machine with a linear kernel, which had an overall performance of 55.4%. These results suggest that applying spatial Independent Component Analysis to reduce temporal dimensionality of EEG signals does not significantly impair the classification of walking speed using EEG and that walking speeds can be predicted from EEG data.
Show less - Date Issued
- 2019
- Identifier
- CFE0007517, ucf:52642
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007517
- Title
- Fluctuations in Walking Speeds and Spatiotemporal Gait Parameters When Walking on a Self-Paced Treadmill at Level, Incline, and Decline Slopes.
- Creator
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Castano, Cesar, Huang, Helen, Viana, Felipe, Samsam, Mohtashem, University of Central Florida
- Abstract / Description
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On a daily basis, humans walk over a variety of terrains. Studies have shown that spatiotemporal gait parameters, such as stride length, stride frequency, stride variability, etc., change when humans walk down a decline and up an incline compared to level ground. However, these studies have been limited to using fixed speed treadmills or analyzing a small number of strides when conducted over ground. Thus, there is a need to investigate the fluctuations in spatiotemporal gait parameters of...
Show moreOn a daily basis, humans walk over a variety of terrains. Studies have shown that spatiotemporal gait parameters, such as stride length, stride frequency, stride variability, etc., change when humans walk down a decline and up an incline compared to level ground. However, these studies have been limited to using fixed speed treadmills or analyzing a small number of strides when conducted over ground. Thus, there is a need to investigate the fluctuations in spatiotemporal gait parameters of humans walking at their self-selected speed, which requires recording hundreds of strides. Here we hypothesized that subjects will walk with a slower speed and have greater stride variability on an incline or decline compared to level ground. We used a self-paced treadmill and had 7 young adults walk on three slopes (+9 degrees, incline; 0 degrees, level; -9 degrees, decline). A motion capture system was used to calculate spatiotemporal gait parameters. The results showed that subjects walked the fastest on level ground (1.15 +/- 0.17 m/s). Subjects walked more slowly during decline walking (1.06 +/- 0.14 m/s) and walked the slowest during incline walking (0.92 +/- 0.18 m/s). There was not a single steady-state speed that subjects used for all slopes. Instead, there were multiple periods when the subject was not at a steady state. Only ~60% of the strides could be classified as being at steady-state. When walking down a decline, subjects needed ~10 +/- 1 more strides to reach the first steady-state period. When walking on an incline and decline, stride length variability increased by ~1.6x (0.0014m^2 (&)#177; 0.0008m^2) and ~1.2x (0.0012m^2 (&)#177; 0.0008m^2 ) compared to level ground (0.0005 m^2 (&)#177; 0.0003 m^2). Stride width variability increased by ~20.6x (0.0108m^2 (&)#177; 0.0121m^2 ) and ~14.2x (0.0076m^2 (&)#177; 0.0044m^2 ) for incline and decline slopes compared to level ground (0.0005 m^2 (&)#177; 0.0003 m^2). These results provide greater insight on the fluctuations during self-selected walking speeds subjects use on different slopes. This could have implications on balance control and fall risk during walking.
Show less - Date Issued
- 2019
- Identifier
- CFE0007441, ucf:52709
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007441
- Title
- Characterization, Classification, and Genesis of Seismocardiographic Signals.
- Creator
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Taebi, Amirtaha, Mansy, Hansen, Kassab, Alain, Huang, Helen, Vosoughi, Azadeh, University of Central Florida
- Abstract / Description
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Seismocardiographic (SCG) signals are the acoustic and vibration induced by cardiac activity measured non-invasively at the chest surface. These signals may offer a method for diagnosing and monitoring heart function. Successful classification of SCG signals in health and disease depends on accurate signal characterization and feature extraction.In this study, SCG signal features were extracted in the time, frequency, and time-frequency domains. Different methods for estimating time-frequency...
Show moreSeismocardiographic (SCG) signals are the acoustic and vibration induced by cardiac activity measured non-invasively at the chest surface. These signals may offer a method for diagnosing and monitoring heart function. Successful classification of SCG signals in health and disease depends on accurate signal characterization and feature extraction.In this study, SCG signal features were extracted in the time, frequency, and time-frequency domains. Different methods for estimating time-frequency features of SCG were investigated. Results suggested that the polynomial chirplet transform outperformed wavelet and short time Fourier transforms.Many factors may contribute to increasing intrasubject SCG variability including subject posture and respiratory phase. In this study, the effect of respiration on SCG signal variability was investigated. Results suggested that SCG waveforms can vary with lung volume, respiratory flow direction, or a combination of these criteria. SCG events were classified into groups belonging to these different respiration phases using classifiers, including artificial neural networks, support vector machines, and random forest. Categorizing SCG events into different groups containing similar events allows more accurate estimation of SCG features.SCG feature points were also identified from simultaneous measurements of SCG and other well-known physiologic signals including electrocardiography, phonocardiography, and echocardiography. Future work may use this information to get more insights into the genesis of SCG.
Show less - Date Issued
- 2018
- Identifier
- CFE0007106, ucf:51944
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007106
- Title
- Probing the Effects of Substrate Stiffness on Astrocytes Mechanics.
- Creator
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Bizanti, Ariege, Steward, Robert, Samsam, Mohtashem, Huang, Helen, University of Central Florida
- Abstract / Description
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Astrocytes are among the most functionally diverse population of cells in the central nervous system (CNS) as they are essential to many important neurological functions including maintaining brain homeostasis, regulating the blood brain barrier, and preventing build-up of toxic substances within the brain, for example. Astrocyte importance to brain physiology and pathology has inspired a host of studies focused on understanding astrocyte behavior primarily from a biological and chemical...
Show moreAstrocytes are among the most functionally diverse population of cells in the central nervous system (CNS) as they are essential to many important neurological functions including maintaining brain homeostasis, regulating the blood brain barrier, and preventing build-up of toxic substances within the brain, for example. Astrocyte importance to brain physiology and pathology has inspired a host of studies focused on understanding astrocyte behavior primarily from a biological and chemical perspective. However, a clear understanding of astrocyte dysfunction and their link to disease has been hampered by a lack of knowledge of astrocyte behavior from a biomechanical perspective. Furthermore, astrocytes (and all cells) can sense and respond to their external biomechanical environment via the extracellular matrix and various other biomechanical cues.One such biomechanical cue, substrate stiffness changes within the brain under certain pathologies, which subsequently leads to changes in the biomechanical behavior of the cell. For example, increased tissue stiffness is a hallmark of brain tumors that subsequently alters astrocyte biomechanical behavior. Therefore, to gain a better understanding of this process we cultured astrocytes on stiffnesses that mimicked that of the normal brain, meningioma, and glioma and investigated astrocyte biomechanical behavior by measuring cell-substrate tractions and cell-cell intercellular stresses utilizing traction force microscopy and monolayer stress microscopy, respectively. Our findings showed an increase in traction forces, average normal intercellular stress, maximum shear intercellular stress, and strain energy proportional to increased substrate stiffness. A substrate stiffness of 4 kPa showed 2.1 fold increase in rms tractions, 1.8 fold increase in maximum shear stress, 2.6 fold increase in average normal stress, and 1.6 fold increase in strain energy. While 11 kPa showed a 4.6 fold increase in rms tractions, 6.6 fold increase in maximum shear stress, 5.2 fold increase in average normal stress, and 2.3 fold increase in strain energy. Cell velocity, on the other hand, showed a decreasing trend with increasing stiffness. This study demonstrates for the first time that astrocytes can bear intercellular stresses and that astrocyte intercellular stresses and traction can be modified using substrate stiffness. We believe this study will be of great importance to brain pathology, specifically as it relates to treatment methods for brain tumors.
Show less - Date Issued
- 2018
- Identifier
- CFE0007312, ucf:52126
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007312
- Title
- Energy Expenditure and Stability During Self-Paced Walking on Different Slopes.
- Creator
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Raffaelli, Alanna, Huang, Helen, Fu, Qiushi, Kassab, Alain, University of Central Florida
- Abstract / Description
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Metabolic power and cost of transport (COT) are common quantifiers for effort when performing tasks including walking and running. Most studies focus on using a range of normal walking speeds over level ground or varied slopes. However, these studies use fixed-speed conditions. Fatigue, stability, metabolic expenditure, heart rate, and many other factors contribute to normal walking speed varying over time. This study aimed to show that allowing a subject to walk with a self-paced speed...
Show moreMetabolic power and cost of transport (COT) are common quantifiers for effort when performing tasks including walking and running. Most studies focus on using a range of normal walking speeds over level ground or varied slopes. However, these studies use fixed-speed conditions. Fatigue, stability, metabolic expenditure, heart rate, and many other factors contribute to normal walking speed varying over time. This study aimed to show that allowing a subject to walk with a self-paced speed should correlate to a minimum COT at a given slope. This study also aimed to determine if a preferred slope exists based on minimizing metabolic expenditure or maximizing stability. In this study, subjects walked at four different speed conditions including three fixed speeds (0.75 m/s, 1.0 m/s, 1.25 m/s) and their self-paced speed at five different slopes (-6(&)deg;, -3(&)deg;, 0(&)deg;, 3(&)deg;, 6(&)deg;) while metabolic energy expenditure and motion were recorded. The minimum COT occurred at a 3(&)deg; decline. At this slope, some subjects preferred to walk at a faster speed compared to level ground, whereas other subjects walked with a slower speed compared to level ground. Thus, there was a greater range of self-paced speeds, from 0.745 m/s-2.045 m/s. In comparison, at a 6(&)deg; incline, the range of self-paced speeds was much smaller, from 0.767 m/s-1.434 m/s. The variance among self-paced speeds and slope conditions between subjects suggests that COT, alone, does not explain walking decisions; stability might play a greater role than initially believed. These results provide greater insight into why humans choose to walk at a certain speed over a range of slopes and terrains.
Show less - Date Issued
- 2019
- Identifier
- CFE0007515, ucf:52629
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007515
- Title
- Investigation of Flow Field Structures in a Rectangular Channel with a Pin Fin Array.
- Creator
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Tran, Patrick, Kapat, Jayanta, Bhattacharya, Samik, Huang, Helen, University of Central Florida
- Abstract / Description
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Pin fin arrays are commonly found in heat exchangers, turbine blades, and electronic heat sinks. Fin arrays are extended surfaces that are used as turbulence promoters by inducing horseshoe vortex (HSV) and von Karman vortex (KV) structures. The horseshoe vortex are primarily studied in the leading edge of the blunt body, whereas the KV are formed in the trailing side. This study presents an experimental investigation of flow field structures and pressure loss on staggered pin fin array in...
Show morePin fin arrays are commonly found in heat exchangers, turbine blades, and electronic heat sinks. Fin arrays are extended surfaces that are used as turbulence promoters by inducing horseshoe vortex (HSV) and von Karman vortex (KV) structures. The horseshoe vortex are primarily studied in the leading edge of the blunt body, whereas the KV are formed in the trailing side. This study presents an experimental investigation of flow field structures and pressure loss on staggered pin fin array in the wake region, where KV are dominate. These flow structures increase the local levels turbulence and generate eddies that promote flow mixing, which in turn allows for higher levels of heat transfer. Improvement in heat transfer can increase the efficiency of the heat exchanger by reducing the thermal load and stress on the components which can extended product life. A study of the vortex shedding using a Particle Image Velocimetry (PIV) technique is used to measure flow field using a closed loop vertical water tunnel. A Time Resolved Particle Image Velocimetry (TR-PIV) study for both steady and unsteady flow structures in the fully developed region of a pin fin array at multiple wall normal cross sections are performed. The pin fin array consists of circular pin fins with 8 rows of 7.5 pins in rectangular channel with Reynolds number varying from 10,000 to 20,000. The Pin array is in a staggered configuration with stream wise (Y/D) spacing of 2.5 and span wise (X/D) spacing of 2.5, and height to pin diameter (H/D) of 2. A supplemental computation fluid dynamic (CFD) study is also for comparison with the PIV flow field. The goal of the present study is to determine the major vortex structures that found the flow at different Z/D, quantify parameters that numerical methods are unable to solve, and provide a base line for other parameters that can be used to improve the accuracy of numerical models. The novelty of this work is to provide data and characterize the near the viscous sub layer of Z/D =0.
Show less - Date Issued
- 2019
- Identifier
- CFE0007736, ucf:52446
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007736
- Title
- Conceptualization and Fabrication of a Bioinspired Mobile Robot Actuated by Shape Memory Alloy Springs.
- Creator
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Richardson, Lietsel, Das, Tuhin, Pal, Sudeshna, Huang, Helen, University of Central Florida
- Abstract / Description
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This work is an experimental study and fabrication of design concepts to validate the feasibility of smart materials and their applications in bio-inspired robotics. Shape-Memory Alloy (SMA) springs are selected as the smart material actuators of interest to achieve locomotion in the proposed mobile robot. Based on a previous design of the robot, this work focuses on both implementing a new locomotion concept and reducing size and weight of the previous design, both using SMA based actuators....
Show moreThis work is an experimental study and fabrication of design concepts to validate the feasibility of smart materials and their applications in bio-inspired robotics. Shape-Memory Alloy (SMA) springs are selected as the smart material actuators of interest to achieve locomotion in the proposed mobile robot. Based on a previous design of the robot, this work focuses on both implementing a new locomotion concept and reducing size and weight of the previous design, both using SMA based actuators. Objectives are met in consideration of the conceptual mechanics of circular robot locomotion. The first prototype is a variation of the original design. It consists of a soft, rubber outer shell with three intrinsically attached diametric SMA springs that deform the outer shell during contraction and relaxation. The springs were provided with electrical current in patterns to produce deformation needed to generate momentum and allow the robot to tumble and roll. This design was further improved to provide more stability while rolling.The second design concept is a modification of our previous design leading to reduction in size and weight while maintaining essentially the same mechanism of locomotion. In this case, the SMA springs were externally configured between the end of equi-spaced spokes and the circular core. Upon actuation, the spokes function as diametrically translating legs to generate locomotion. These design concepts are fabricated and experimented on, to determine their feasibility, i.e. whether rolling/tumbling motion is achieved. The scope of the project was limited to demonstration of basic locomotion, which was successful. Future work on this project will address the design of automatic control to generate motion using closed-loop sensor-based actuation.
Show less - Date Issued
- 2019
- Identifier
- CFE0007524, ucf:52589
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007524
