Papers by Matthew Fiedler
Fused particle fabrication (FPF) (or fused granular fabrication (FGF)) has potential for increasi... more Fused particle fabrication (FPF) (or fused granular fabrication (FGF)) has potential for increasing recycled polymers in 3-D printing. Here, the open source Gigabot X is used to develop a new method to optimize FPF/FGF for recycled materials. Virgin polylactic acid (PLA) pellets and prints were analyzed and were then compared to four recycled polymers including the two most popular printing materials (PLA) and acrylonitrile butadiene styrene (ABS)) as well as the two most common waste plastics (polyethylene terephthalate (PET) and polypropylene (PP)). The size characteristics of the various materials were quantified using digital image processing. Then, power and nozzle velocity matrices were used to optimize the print speed, and a print test was used to maximize the output for a two-temperature stage extruder for a given polymer feedstock. ASTM type 4 tensile tests were used to determine the mechanical properties of each plastic when they were printed with a particle drive extruder system and were compared with filament printing. The results showed that the Gigabot X can print materials 6.5× to 13× faster than conventional printers depending on the material, with no significant reduction in the mechanical properties. It was concluded that the Gigabot X and similar FPF/FGF printers can utilize a wide range of recycled polymer materials with minimal post processing.
Studies in health technology and informatics, 2007
Virtual reality (VR) simulation has been used to improve training for manual laparoscopy and to g... more Virtual reality (VR) simulation has been used to improve training for manual laparoscopy and to give surgeons superior performance in the operating room. However, VR has not been used to train surgeons in robotic laparoscopy. Five students of the University of Nebraska Medical Center (UNMC) and the University of Nebraska at Omaha gave consent according to UNMC ethical guidelines. Subjects performed with the Da Vinci robotic surgical system 5 trials for each of two tasks (Bimanual Carrying, BC; Needle Passing, NP). Each task was performed first in the actual robotic operating environment and then in VR. The data analysis included time to task completion, instrument tips distance traveled and the corresponding speed, and range of motion of the elbow flexion and extension of each subject. The BC and NP tasks were not significantly different between the two environments with respect to robot tip speed and the elbow range of motion for both arms. Time to task completion and distance trav...
1. Dynamic visual acuity (DVA) is reduced in the vertical plane at frequencies of 2 Hz and in the... more 1. Dynamic visual acuity (DVA) is reduced in the vertical plane at frequencies of 2 Hz and in the horizontal plane at frequencies of 0.8 Hz. DVA varies with target location, with acuity optimized for targets in the plane of motion. Perturbations at low frequency motions (0.1-2 Hz) may exacerbate sensorimotor deficits after space flight. 2. Low imperceptible levels of white noise based electrical stimulation of the vestibular system improves balance performance consistent with the stochastic resonance phenomenon in normal healthy control subjects. The amplitude of optimal stimulus for improving balance performance was predominantly in the range of 100-400 μA. 3. An SRVS based device may be fielded, either as a training modality to enhance adaptability or skill acquisition, or as a miniature patch type stimulator that may be worn by astronauts to enhance adaptation following gravitational transitions including people with disabilities due to aging or disease, improving posture and loc...
Experimental Brain Research, 2011
Stochastic resonance (SR) is a phenomenon whereby the response of a non-linear system to a weak p... more Stochastic resonance (SR) is a phenomenon whereby the response of a non-linear system to a weak periodic input signal is optimized by the presence of a particular non-zero level of noise. Stochastic resonance using imperceptible stochastic vestibular electrical stimulation, when applied to normal young and elderly subjects, has been shown to significantly improve ocular stabilization reflexes in response to whole-body tilt; improved balance performance during postural disturbances and optimize covariance between the weak input periodic signals introduced via venous blood pressure receptors and the heart rate responses. In our study, 15 subjects stood on a compliant surface with their eyes closed. They were given low-amplitude binaural bipolar stochastic electrical stimulation of the vestibular organs in two frequency ranges of 1-2 and 0-30 Hz over the amplitude range of 0 to ±700 lA. Subjects were instructed to maintain an upright stance during 43-s trials, which consisted of baseline (zero amplitude) and stimulation (non-zero amplitude) periods. Measures of stability of the head and trunk using inertial motion unit sensors attached to these segments and the whole body using a force plate were measured and quantified in the mediolateral plane. Using a multivariate optimization criterion, our results show that the low levels of vestibular stimulation given to the vestibular organs improved balance performance in normal healthy subjects in the range of 5-26% consistent with the stochastic resonance phenomenon. In our study, 8 of 15 and 10 of 15 subjects were responsive for the 1-2-and 0-30-Hz stimulus signals, respectively. The improvement in balance performance did not differ significantly between the stimulations in the two frequency ranges. The amplitude of optimal stimulus for improving balance performance was predominantly in the range of ±100 to ±400 lA. A device based on SR stimulation of the vestibular system might be useful as either a training modality to enhance adaptability or skill acquisition, or as a miniature patch-type stimulator that may be worn by people with disabilities due to aging or disease to improve posture and locomotion function.
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Papers by Matthew Fiedler