Dr. Mary Ann Vinton, Associate Professor and Director of Environmental Science, Creighton University
An Interdisciplinary Study of Place in the Nebraska Sandhills: Using Remote Sensing to Analyze Resilience of Natural and Social Systems in a Working Landscape
This project uses NASA-supported resources to study natural and human processes in the Nebraska Sandhills, one of the most unique biophysical ecosystems in North America. The Sandhills region is the largest area of stabilized sand dunes in the western hemisphere, with intact grassland habitat and unparalleled ground water resources. The dominant land use is cattle grazing with seasonal hay harvest in lowland meadows, a regime that has supported a human community based on ranching for the last century. One of the key questions about the unique ecoregion of the Nebraska Sandhills is: what is its long term stability in the face of increased stressors to the natural and social systems, such as drought, population decline and public service scarcity and consolidation? We will use remote sensing and drone photography, as well as ethonographic analyses and interviews with residents to understand the past, current status and future projections of sustainability in this place.
Dr. Vivien Marmelat, Assistant Professor, Center for Research in Human Movement and Variability, University of Nebraska at Omaha
Relationship between gait variability and obstacle avoidance
Astronauts experience undesirable neuromuscular and sensorimotor alterations as a result of spending time in a micro-gravity environment. These degradations may affect crewmembers’ locomotor adaptability to gravitational environments, in particular their ability to safely avoid obstacles immediately after landing on a planetary surface. Consequently, the focus of this project is to identify predictors of gait adaptability for astronauts, and to understand how crewmembers’ gait adaptability is impacted by long-duration spaceflights. These predictors could be used to determine each astronauts’ propensity for adaptation and would also serve to individualize countermeasures for each specific astronaut.
The proposed research will address fundamental questions about the relationship between locomotor control during steady-state walking and gait kinematics during obstacle avoidance tasks. As a first step towards addressing these questions, this project will focus on subjects with Parkinson’s disease (PD), a cohort considered as a ‘model’ of high-risk fallers. We will apply sophisticated non-linear analysis to gait kinematics to test our main hypothesis that steady-state walking variability (i.e., the step-to-step variations occurring over time) reflects gait adaptability observed during more challenging conditions, in particular obstacle avoidance at preferred and fast walking speed. Our findings could facilitate the detection of gait impairments pre and post space mission, and provide new tools to evaluate the efficacy of preventive or rehabilitative programs for gait adaptability.
Dr. Lim Nguyen, Professor, College of Electrical and Computer Engineering, University of Nebraska-Lincoln
Conductive Concrete for Anechoic Chamber Facility Applications
This project performs the R & D to determine the RF characteristics of electrically conductive concrete that would benefit the construction and performance of anechoic chamber facility (ACF) for testing spacecraft antennas and structures.
Our work have demonstrated that conductive concrete could be used to construct shielded facility for shielding electromagnetic (EM) waves. The results from this project would enable conductive concrete to be used in the construction of the ACF where both EM shielding and absorption properties are required. This would mitigate the need for the traditional RF and microwave absorbers that are bulky and expensive, and required in addition to the metal panel shielded enclosure. Conductive concrete provide both structured shielding and EM absorption, thereby eliminating the metal panel enclosure and absorbers.
Traditional ACF construction require a structured building that house a metal panel enclosure for EM shielding. The inside of the shielded volume then must be covered with radio frequency (RF) and microwave absorbers to prevent reflection from the metal walls that would interfere with the antenna measurements. The photo illustrates the full-scale Orion model that was developed for antenna performance testing within the Anechoic Chamber at Johnson Space Center. The chamber absorbs EM energy to simulate an open space environment. However, both the metal panel enclosure and the EM absorbers would add to the cost of the structure. Moreover, EM absorbers are typically expensive and bulky, requiring a larger and costly shielded volume.
The results from this project thus would enable conductive concrete to be used in cost effective construction of the ACF where both EM shielding and absorption properties are provided by the structured EM concrete. This would mitigate the need for the traditional RF and microwave absorbers that are bulky and expensive, and in addition to eliminating the metal panel shielded enclosure.
Using the Keysight E5071C network analyzer with the Time-Domain Analysis software, we measured the reflection of conductive concrete test samples. The signal from the E5071C was transmitted through the TX horn antenna to the test samples. The RX horn antenna received the reflection and detected by the E5071C. From the frequency sweep measurement of the network analyzer, the Time Domain Analysis software performed the inverse Fourier analysis to compute the pulse response that determined the reflection of the concrete samples.
The photos and graphs below show the preliminary experimental set up and results. The concrete sample was a conductive concrete test cube with the dimension 4.5ft x 4.5ft x 3.5ft. The test data were obtained with the network analyzer in 1-port (S11) and 2-port (S21) configuration from 2 GHz to 8.4 GHz. It can be seen that the network analyzer successfully resolves the transmitted and reflected pulses in the time-domain mode. The S11 and S21 results indicate that the return loss from the conductive concrete surface would average about 6 dB to 10 dB better compared to a metal surface. The return loss is expected to improve for a more random and rough concrete surface.
Dr. Raj Dasgupta, University of Nebraska at Omaha
Multi-agent Game Theoretic Techniques for Externally Influencing and Controlling UAV Swarm Behaviors
In this project, we plan to investigate novel techniques that will address the problem of counter-swarming by a team of unmanned aerial vehicles (UAVs). Counter-swarming deals with methods to thwart or break up a team of mobile entities, such as a team of UAVs that are performing their operations using swarming techniques. Swarming-based techniques observed in nature have been adapted by humans with great success in numerous areas of technology, most importantly in warfare and defense-related activities. However, to the best of our knowledge, there has not been any systematic study of counter-swarming methods or technology in literature. In this project, we plan to address this gap in existing research by investigating novel methods that can quickly and effectively stop an ongoing swarming activity. We will pursue two specific research aims in the project: (1) Investigate methods to build a mathematical model of the behavior of a swarm derived from observations of its features such as the type of interaction strategy between the swarm units, the most influential units or leaders in the swarm, and the most vulnerable points and units in the swarm. (2) Using the constructed model, we will investigate a mathematical framework from game theory called graphical games that will enable to inject strategically-determined behavior patterns into the swarm by implanting “spy swarm units” into it and thwart the swarm’s activities and ultimately take it down. The proposed techniques will be evaluated in simulation, and potentially on UAV and ground robot platforms.
Dr. Jack Gabel, Creighton University
Testing Dynamic Models of Quasar Outflow Systems with Correlation Studies of UV Spectral Properties
Our research project supports the Creighton astrophysics research group’s studies of energetic quasar outflows. Quasars are the energetic cores of galaxies that emit tremendous amounts of radiation, powered by accretion of matter into supermassive blackholes lying in the centers of distant galaxies. High velocity winds are observed to be driven from a significant fraction of these objects. This research project involves a novel approach to study the source and driving mechanism of these mass outflow systems through an analysis of thousands of quasars in the Sloan Digital Sky Survey database and modeling these data in terms of theoretical accretion disk wind models.