1,072 research outputs found
ASPIRE Flight Mechanics Modeling and Post Flight Analysis
The Advanced Supersonic Parachute Inflation Research and Experiment (ASPIRE) is a series of sounding rocket flights aimed at understanding the dynamics of supersonic parachutes that are used for Mars robotic applications. SR01 was the first sounding rocket flight of ASPIRE that occurred off the coast of Wallops Island, VA on Oct. 4, 2017 and showed the successful deployment and inflation of a Mars Science Laboratory built-to- print parachute in flight conditions similar to the 2012 Mars Science Laboratory (MSL) mission. SR02 was the second sounding rocket flight that also occurred off the coast of Wallops Island on March 31, 2018 and showcased the successful deployment and inflation of a new strengthened parachute being considered for the Mars 2020 mission at fifty percent higher dynamic pressure than observed on MSL. Prior to both flights, a multi-body flight dynamics simulation was developed to predict the parachute dynamics and was used, in conjunction with other tools, to target Mars-relevant flight conditions. After each flight, the reconstructed trajectory was used to validate the pre-flight dynamics simulation and recommend changes to improve predictions for future flights planned for the ASPIRE pro- gram. This paper describes the flight mechanics simulation and the post flight reconciliation process used to validate the flight models
Variational Trajectory Optimization Tool Set: Technical description and user's manual
The algorithms that comprise the Variational Trajectory Optimization Tool Set (VTOTS) package are briefly described. The VTOTS is a software package for solving nonlinear constrained optimal control problems from a wide range of engineering and scientific disciplines. The VTOTS package was specifically designed to minimize the amount of user programming; in fact, for problems that may be expressed in terms of analytical functions, the user needs only to define the problem in terms of symbolic variables. This version of the VTOTS does not support tabular data; thus, problems must be expressed in terms of analytical functions. The VTOTS package consists of two methods for solving nonlinear optimal control problems: a time-domain finite-element algorithm and a multiple shooting algorithm. These two algorithms, under the VTOTS package, may be run independently or jointly. The finite-element algorithm generates approximate solutions, whereas the shooting algorithm provides a more accurate solution to the optimization problem. A user's manual, some examples with results, and a brief description of the individual subroutines are included
Toward a unified description of hadro- and photoproduction: S-wave pi- and eta-photoproduction amplitudes
The Chew-Mandelstam parameterization, which has been used extensively in the
two-body hadronic sector, is generalized in this exploratory study to the
electromagnetic sector by simultaneous fits to the pion- and
eta-photoproduction S-wave multipole amplitudes for center-of-mass energies
from the pion threshold through 1.61 GeV. We review the Chew-Mandelstam
parameterization in detail to clarify the theoretical content of the SAID
hadronic amplitude analysis and to place the proposed, generalized SAID
electromagnetic amplitudes in the context of earlier employed parameterized
forms. The parameterization is unitary at the two-body level, employing four
hadronic channels and the gamma-N electromagnetic channel. We compare the
resulting fit to the MAID parameterization and find qualitative agreement
though, numerically, the solution is somewhat different. Applications of the
extended parameterization to global fits of the photoproduction data and to
global fits of the combined hadronic and photoproduction data are discussed.Comment: 9 pages, 9 figures; added figures and tex
Two-dimensional tetramer-cuprate Na5RbCu4(AsO4)4Cl2: phase transitions and AFMorder as seen by 87Rb NMR
We report the Rb nuclear magnetic resonance (NMR) results in a recently
synthesized Na5RbCu4(AsO4)Cl2. This complex novel two-dimensional (2D) cuprate
is an unique magnetic material, which contains layers of coupled Cu4O4
tetramers. In zero applied magnetic field, it orders antiferromagnetically via
a second-order low-entropy phase transition at TN = 15(1) K. We characterise
the ordered state by 87Rb NMR, and suggest for it a noncollinear rather than
collinear arrangement of spins. We discuss the properties of Rb nuclear site
and point out the new structural phase transition(s) around 74 K and 110 K.Comment: 2 pages, 2 figures, Proceedings of SCES'05, Vienna 200
Factors affecting treatment practices of patent medicine vendors for malaria in under-five children: implications for malaria control in Nigeria
Background: Patent medicine vendors (PMVs) are the most common source of antimalarial drugs and treatment for majority of Nigerians. The quality of their practice could have implications for malaria control. This study sought to explore the factors influencing the malaria treatment practices of PMVs for under-five children in Akwa Ibom State.Methods: A cross-sectional survey using an interviewer-administered questionnaire was conducted among 176 PMVs selected by simple random sampling from two local government areas (LGAs). In addition, four focus group discussions (FGD) were conducted to generate qualitative data. Quantitative data was analysed using SPSS version 20 while content analysis was done on the qualitative data.Results: Artemisinin Combination Therapy (ACT) was the most frequently recommended antimalarial treatment by PMVs (75.6%) for children as against chloroquine (17%) and Sulphadoxine/Pyrimethamine (2.8%). However, only 39.2% of PMVs recommended the appropriate antimalarial treatment (ACTs at the right dose for age), while 71% recommended referral for severe malaria. Factors found to be associated with appropriate management of malaria from quantitative analysis included Educational qualification, attending malaria training and their knowledge of malaria. The FGDs showed that severity ofchild’s illness, parents/caregivers drug request and perceived ability of the parents/caregiver to afford the drugs influenced PMVs malaria treatment practices.Conclusion: Knowledge of malaria, severity of child’s illness and parents’ drug request influenced the treatment practices of PMVs. Training PMVs on appropriate malaria management and community health education/sensitization to leverage on the influence of client-demand on ACT use is recommended to improve PMVs treatment practice.Keywords: Malaria, under-five children, patent medicine vendors, ACT, NigeriaFunding: This study was conducted using mainly personal funds of the lead author with some support from the Universityof Uyo Teaching Hospital
Supersonic Flight Dynamics Test 1 - Post-Flight Assessment of Simulation Performance
NASA's Low Density Supersonic Decelerator (LDSD) project conducted its first Supersonic Flight Dynamics Test (SFDT-1) on June 28, 2014. Program to Optimize Simulated Trajectories II (POST2) was one of the flight dynamics codes used to simulate and predict the flight performance and Monte Carlo analysis was used to characterize the potential flight conditions experienced by the test vehicle. This paper compares the simulation predictions with the reconstructed trajectory of SFDT-1. Additionally, off-nominal conditions seen during flight are modeled in post-flight simulations to find the primary contributors that reconcile the simulation with flight data. The results of these analyses are beneficial for the pre-flight simulation and targeting of the follow-on SFDT flights currently scheduled for summer 2015
Gas emissions, minerals, and tars associated with three coal fires, Powder River Basin, USA.
Ground-based surveys of three coal fires and airborne surveys of two of the fires were conducted near Sheridan, Wyoming. The fires occur in natural outcrops and in abandoned mines, all containing Paleocene-age subbituminous coals. Diffuse (carbon dioxide (CO(2)) only) and vent (CO(2), carbon monoxide (CO), methane, hydrogen sulfide (H(2)S), and elemental mercury) emission estimates were made for each of the fires. Additionally, gas samples were collected for volatile organic compound (VOC) analysis and showed a large range in variation between vents. The fires produce locally dangerous levels of CO, CO(2), H(2)S, and benzene, among other gases. At one fire in an abandoned coal mine, trends in gas and tar composition followed a change in topography. Total CO(2) fluxes for the fires from airborne, ground-based, and rate of fire advancement estimates ranged from 0.9 to 780mg/s/m(2) and are comparable to other coal fires worldwide. Samples of tar and coal-fire minerals collected from the mouth of vents provided insight into the behavior and formation of the coal fires
Post-Flight Assessment of Low Density Supersonic Decelerator Flight Dynamics Test 2 Simulation
NASA's Low Density Supersonic Decelerator (LDSD) project conducted its second Supersonic Flight Dynamics Test (SFDT-2) on June 8, 2015. The Program to Optimize Simulated Trajectories II (POST2) was one of the flight dynamics tools used to simulate and predict the flight performance and was a major tool used in the post-flight assessment of the flight trajectory. This paper compares the simulation predictions with the reconstructed trajectory. Additionally, off-nominal conditions seen during flight are modeled in the simulation to reconcile the predictions with flight data. These analyses are beneficial to characterize the results of the flight test and to improve the simulation and targeting of the subsequent LDSD flights
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