Modeling of impulsive propellant reorientation

The impulsive propellant reorientation process is modeled using the (Energy Calculations for Liquid Propellants in a Space Environment (ECLIPSE) code. A brief description of the process and the computational model is presented. Code validation is documented via comparison to experimentally derived data for small scale tanks. Predictions of reorientation performance are presented for two tanks designed for use in flight experiments and for a proposed full scale OTV tank. A new dimensionless parameter is developed to correlate reorientation performance in geometrically similar tanks. Its success is demonstrated

Modeling of pulsed propellant reorientation

Optimization of the propellant reorientation process can provide increased payload capability and extend the service life of spacecraft. The use of pulsed propellant reorientation to optimize the reorientation process is proposed. The ECLIPSE code was validated for modeling the reorientation process and is used to study pulsed reorientation in small-scale and full-scale propellant tanks. A dimensional analysis of the process is performed and the resulting dimensionless groups are used to present and correlate the computational predictions for reorientation performance

The effect of sterilization on biological, organic geochemical and morphological information in natural samples

The loss of biological, organic geochemical, and morphological science information that may occur should a Mars surface sample be sterilized prior to return to earth is examined. Results of experimental studies are summarized

Nitrite reduction in paracoccus halodenitrificans: Evidence for the role of a cd-type cytochrome in ammonia formation

Cell-free extracts prepared from Paracoccus halodenitrificans catalyzed the reduction of nitrate to ammonia in the presence of dithionite and methyl viologen. Enzyme activity was located in the soluble fraction and was associated with a cytochrome whose spectral properties resembled those of a cd-type cytochrome. Unlike the sissimilatory cd-cytochrome nitrate reductase associated with the membrane fraction of P. halodenitrificans, this soluble cd-cytochrome did not reduce nitrite to nitrous oxide

Inhibition of free radical-induced DNA damage by uric acid

AbstractSingle-strand DNA breaks were produced in isolated rat liver nuclei incubated with 3 separate oxygen free radical generating systems: xanthine oxidase-acetaldehyde plus Fe(II); hematin-R(H)OOH; Fe(II)-H2O2. Uric acid inhibited the induction of damage in the first two systems only. At concentrations below those found in human plasma, it was particularly effective against strand breaks produced by hematin-cumene hydroperoxide. These results offer additional evidence that uric acid may function as a cellular protective agent against Superoxide and hydroperoxyl free radical-induced cytotoxicity toxicity

Technology Resources for Earthquake Monitoring and Response (TREMOR)

Earthquakes represent a major hazard for populations around the world, causing frequent loss of life, human suffering, and enormous damage to homes, other buildings, and infrastructure. The Technology Resources for Earthquake Monitoring and Response (TREMOR) proposal is designed to address this problem. This proposal recommends two prototype systems integrating space-based and ground technology. The suggested pilot implementation is over a 10-year period in three focus countries – China, Japan, and Peru – that are among the areas in the world most afflicted by earthquakes. The first proposed system is an Earthquake Early Warning Prototype System that addresses the potential of earthquake precursors, the science of which is incomplete and considered controversial within the scientific community. We recommend the development and launch of two small satellites to study ionospheric and electromagnetic precursors. In combination with ground-based precursor research, the data gathered will improve existing knowledge of earthquake-related phenomena. The second proposed system is an Earthquake Simulation and Response Prototype. An earthquake simulator will combine any available precursor data with detailed knowledge of the affected areas using a Geographic Information System (GIS) to identify those areas that are most likely to experience the greatest level of damage. Mobile satellite communication hubs will provide telephone and data links between response teams, while satellite navigation systems will locate and track emergency vehicles. We recommend a virtual response satellite constellation composed of existing and future high resolution satellites. We also recommend education and training for response teams on the use of these technologies. The two prototypes will be developed and implemented by a proposed non-profit nongovernmental organization (NGO) called the TREMOR Foundation, which will obtain funding from government disaster management agencies and NGOs. A for-profit subsidiary will market any spin-off technologies and provide an additional source of funding. Assuming positive results from the prototype systems, Team TREMOR recommends their eventual and permanent implementation in all countries affected by earthquakes.Postprint (published version

Parallel, Adaptive Grid Computing of Multiphase Flows in Spacecraft Fuel Tanks

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97138/1/AIAA2012-761.pd

A Pediatric Knee Exoskeleton With Real-Time Adaptive Control for Overground Walking in Ambulatory Individuals With Cerebral Palsy

Gait training via a wearable device in children with cerebral palsy (CP) offers the potential to increase therapy dosage and intensity compared to current approaches. Here, we report the design and characterization of a pediatric knee exoskeleton (P.REX) with a microcontroller based multi-layered closed loop control system to provide individualized control capability. Exoskeleton performance was evaluated through benchtop and human subject testing. Step response tests show the averaged 90% rise was 26 ± 0.2 ms for 5 Nm, 22 ± 0.2 ms for 10 Nm, 32 ± 0.4 ms for 15 Nm. Torque bandwidth of P.REX was 12 Hz and output impedance was less than 1.8 Nm with control on (Zero mode). Three different control strategies can be deployed to apply assistance to knee extension: state-based assistance, impedance-based trajectory tracking, and real-time adaptive control. One participant with typical development (TD) and one participant with crouch gait from CP were recruited to evaluate P.REX in overground walking tests. Data from the participant with TD were used to validate control system performance. Kinematic and kinetic data were collected by motion capture and compared to exoskeleton on-board sensors to evaluate control system performance with results demonstrating that the control system functioned as intended. The data from the participant with CP are part of a larger ongoing study. Results for this participant compare walking with P.REX in two control modes: a state-based approach that provided constant knee extension assistance during early stance, mid-stance and late swing (Est+Mst+Lsw mode) and an Adaptive mode providing knee extension assistance proportional to estimated knee moment during stance. Both were well tolerated and significantly improved knee extension compared to walking without extension assistance (Zero mode). There was less reduction in gait speed during use of the adaptive controller, suggesting that it may be more intuitive than state-based constant assistance for this individual. Future work will investigate the effects of exoskeleton assistance during overground gait training in children with neurological disorders and will aim to identify the optimal individualized control strategy for exoskeleton prescription

Refinement type contracts for verification of scientific investigative software

Our scientific knowledge is increasingly built on software output. User code which defines data analysis pipelines and computational models is essential for research in the natural and social sciences, but little is known about how to ensure its correctness. The structure of this code and the development process used to build it limit the utility of traditional testing methodology. Formal methods for software verification have seen great success in ensuring code correctness but generally require more specialized training, development time, and funding than is available in the natural and social sciences. Here, we present a Python library which uses lightweight formal methods to provide correctness guarantees without the need for specialized knowledge or substantial time investment. Our package provides runtime verification of function entry and exit condition contracts using refinement types. It allows checking hyperproperties within contracts and offers automated test case generation to supplement online checking. We co-developed our tool with a medium-sized ($\approx$3000 LOC) software package which simulates decision-making in cognitive neuroscience. In addition to helping us locate trivial bugs earlier on in the development cycle, our tool was able to locate four bugs which may have been difficult to find using traditional testing methods. It was also able to find bugs in user code which did not contain contracts or refinement type annotations. This demonstrates how formal methods can be used to verify the correctness of scientific software which is difficult to test with mainstream approaches