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Sample records for accelerated steepest descent

  1. Steepest Descent

    SciTech Connect

    Meza, Juan

    2010-02-12

    The steepest descent method has a rich history and is one of the simplest and best known methods for minimizing a function. While the method is not commonly used in practice due to its slow convergence rate, understanding the convergence properties of this method can lead to a better understanding of many of the more sophisticated optimization methods. Here, we give a short introduction and discuss some of the advantages and disadvantages of this method. Some recent results on modified versions of the steepest descent method are also discussed.

  2. A new steepest descent method

    NASA Astrophysics Data System (ADS)

    Abidin, Zubai'ah Zainal; Mamat, Mustafa; Rivaie, Mohd; Mohd, Ismail

    2014-06-01

    The classical steepest descent (SD) method is known as one of the earliest and the best method to minimize a function. Even though the convergence rate is quite slow, but its simplicity has made it one of the easiest methods to be used and applied especially in the form of computer codes. In this paper, a new modification of SD method is proposed using a new search direction (dk) in the form of two parameters. Numerical results shows that this new SD has far superior convergence rate and more efficient than the classical SD method.

  3. Distributed Control by Lagrangian Steepest Descent

    NASA Technical Reports Server (NTRS)

    Wolpert, David H.; Bieniawski, Stefan

    2004-01-01

    Often adaptive, distributed control can be viewed as an iterated game between independent players. The coupling between the players mixed strategies, arising as the system evolves from one instant to the next, is determined by the system designer. Information theory tells us that the most likely joint strategy of the players, given a value of the expectation of the overall control objective function, is the minimizer of a function o the joint strategy. So the goal of the system designer is to speed evolution of the joint strategy to that Lagrangian mhimbhgpoint,lowerthe expectated value of the control objective function, and repeat Here we elaborate the theory of algorithms that do this using local descent procedures, and that thereby achieve efficient, adaptive, distributed control.

  4. A new steepest descent method with global convergence properties

    NASA Astrophysics Data System (ADS)

    Abidin, Zubai'ah Zainal; Mamat, Mustafa; Rivaie, Mohd.

    2016-06-01

    One of the earliest and the best method to minimize a function is the classical steepest descent (SD) method. In this paper, a new modification of SD method is suggested using a new search direction, d k. The numerical results are presented based on number of iterations and CPU time. It shows that the new d k are efficient when compared to the classical SD.

  5. Efficient Love wave modelling via Sobolev gradient steepest descent

    NASA Astrophysics Data System (ADS)

    Browning, Matt; Ferguson, John; McMechan, George

    2016-05-01

    A new method for finding solutions to ordinary differential equation boundary value problems is introduced, in which Sobolev gradient steepest descent is used to determine eigenfunctions and eigenvalues simultaneously in an iterative scheme. The technique is then applied to the 1-D Love wave problem. The algorithm has several advantages when computing dispersion curves. It avoids the problem of mode skipping, and can handle arbitrary Earth structure profiles in depth. For a given frequency range, computation times scale approximately as the square root of the number of frequencies, and the computation of dispersion curves can be implemented in a fully parallel manner over the modes involved. The steepest descent solutions are within a fraction of a per cent of the analytic solutions for the first 25 modes for a two-layer model. Since all corresponding eigenfunctions are computed along with the dispersion curves, the impact on group and phase velocity of the displacement behaviour with depth is thoroughly examined. The dispersion curves are used to compute synthetic Love wave seismograms that include many higher order modes. An example includes addition of attenuation to a model with a low-velocity zone, with values as low as Q = 20. Finally, a confirming comparison is made with a layer matrix method on the upper 700 km of a whole Earth model.

  6. Steepest descent ballistic deposition of complex shaped particles

    NASA Astrophysics Data System (ADS)

    Topic, Nikola; Pöschel, Thorsten

    2016-03-01

    We present an efficient event-driven algorithm for sequential ballistic deposition of complex-shaped rigid particles. Each of the particles is constructed from hard spheres (typically 5 … 1000) of variable radii. The sizes and relative positions of the spheres may mutually overlap and can be chosen such that the surface of the resulting particle appears relatively smooth. In the sequential deposition process, by performing steps of rolling and linear motion, the particles move along the steepest descent in a landscape formed by the boundaries and previously deposited particles. The computer time for the simulation of a deposition process depends on the total number of spheres but only weakly on the sizes and shapes of the particles. The proposed algorithm generalizes the Visscher-Bolsterli algorithm [1] which is frequently used for packing of spheres, to non-spherical particles. The proposed event-driven algorithm allows simulations of multi-million particle systems using desktop computers.

  7. Comparison of minimum-action and steepest-descent paths in gradient systems.

    PubMed

    Díaz Leines, Grisell; Rogal, Jutta

    2016-02-01

    On high-dimensional and complex potential energy surfaces, the identification of the most likely mechanism for the transition between local minima is a challenging task. Usually the steepest-descent path is used interchangeably with the minimum-energy path and is associated with the most likely path. Here we compare the meaning of the steepest-descent path in complex energy landscapes to the path integral formulation of a trajectory that minimizes the action functional for Brownian dynamics. In particular, for energy landscapes with bifurcation points and multiple minima and saddle points, there can be several steepest-descent paths associated with specific saddles that connect two predetermined states but largely differ from the path of maximum likelihood. The minimum-action path, however, additionally takes into account the scalar work along the trajectory. Minimizing the scalar work can be less ambiguous in the identification of the most likely path in different gradient systems. It can also be used to distinguish between multiple steepest-descent paths that connect reactant and product states. We illustrate that in systems with complex energy landscapes a careful assessment of the steepest-descent path is thus advisable. Here the evaluation of the action can provide valuable information on the analysis and description of the most likely path.

  8. Use of steepest descent and various approximations for efficient computation of minimum noise aircraft landing trajectories

    NASA Technical Reports Server (NTRS)

    Cook, G.; Witt, R. M.

    1976-01-01

    The following areas related to landing trajectory optimization research were discussed: (1) programming and modifying the steepest descent optimization procedure, (2) successfully iterating toward the optimum for a four-mile trajectory, (3) beginning optimization runs for a twenty-mile trajectory, and (4) adapt wind tunnel data for computer usage. Other related areas were discussed in detail in the two previous annual reports.

  9. Nonlinear Performance Seeking Control using Fuzzy Model Reference Learning Control and the Method of Steepest Descent

    NASA Technical Reports Server (NTRS)

    Kopasakis, George

    1997-01-01

    Performance Seeking Control (PSC) attempts to find and control the process at the operating condition that will generate maximum performance. In this paper a nonlinear multivariable PSC methodology will be developed, utilizing the Fuzzy Model Reference Learning Control (FMRLC) and the method of Steepest Descent or Gradient (SDG). This PSC control methodology employs the SDG method to find the operating condition that will generate maximum performance. This operating condition is in turn passed to the FMRLC controller as a set point for the control of the process. The conventional SDG algorithm is modified in this paper in order for convergence to occur monotonically. For the FMRLC control, the conventional fuzzy model reference learning control methodology is utilized, with guidelines generated here for effective tuning of the FMRLC controller.

  10. A topological study of gravity free-surface waves generated by bluff bodies using the method of steepest descents

    NASA Astrophysics Data System (ADS)

    Trinh, Philippe H.

    2016-07-01

    The standard analytical approach for studying steady gravity free-surface waves generated by a moving body often relies upon a linearization of the physical geometry, where the body is considered asymptotically small in one or several of its dimensions. In this paper, a methodology that avoids any such geometrical simplification is presented for the case of steady-state flows at low speeds. The approach is made possible through a reduction of the water-wave equations to a complex-valued integral equation that can be studied using the method of steepest descents. The main result is a theory that establishes a correspondence between different bluff-bodied free-surface flow configurations, with the topology of the Riemann surface formed by the steepest descent paths. Then, when a geometrical feature of the body is modified, a corresponding change to the Riemann surface is observed, and the resultant effects to the water waves can be derived. This visual procedure is demonstrated for the case of two-dimensional free-surface flow past a surface-piercing ship and over an angled step in a channel.

  11. Feature Clustering for Accelerating Parallel Coordinate Descent

    SciTech Connect

    Scherrer, Chad; Tewari, Ambuj; Halappanavar, Mahantesh; Haglin, David J.

    2012-12-06

    We demonstrate an approach for accelerating calculation of the regularization path for L1 sparse logistic regression problems. We show the benefit of feature clustering as a preconditioning step for parallel block-greedy coordinate descent algorithms.

  12. An extension of the steepest descent method for Riemann-Hilbert problems: the small dispersion limit of the Korteweg-de Vries (KdV) equation.

    PubMed

    Deift, P; Venakides, S; Zhou, X

    1998-01-20

    This paper extends the steepest descent method for Riemann-Hilbert problems introduced by Deift and Zhou in a critical new way. We present, in particular, an algorithm, to obtain the support of the Riemann-Hilbert problem for leading asymptotics. Applying this extended method to small dispersion KdV (Korteweg-de Vries) equation, we (i) recover the variational formulation of P. D. Lax and C. D. Levermore [(1979) Proc. Natl. Acad. Sci. USA76, 3602-3606] for the weak limit of the solution, (ii) derive, without using an ansatz, the hyperelliptic asymptotic solution of S. Venakides that describes the oscillations; and (iii) are now able to compute the phase shifts, integrating the modulation equations exactly. The procedure of this paper is a version of fully nonlinear geometrical optics for integrable systems. With some additional analysis the theory can provide rigorous error estimates between the solution and its computed asymptotic expression. PMID:11038618

  13. Comparing three stochastic search algorithms for computational protein design: Monte Carlo, replica exchange Monte Carlo, and a multistart, steepest-descent heuristic.

    PubMed

    Mignon, David; Simonson, Thomas

    2016-07-15

    Computational protein design depends on an energy function and an algorithm to search the sequence/conformation space. We compare three stochastic search algorithms: a heuristic, Monte Carlo (MC), and a Replica Exchange Monte Carlo method (REMC). The heuristic performs a steepest-descent minimization starting from thousands of random starting points. The methods are applied to nine test proteins from three structural families, with a fixed backbone structure, a molecular mechanics energy function, and with 1, 5, 10, 20, 30, or all amino acids allowed to mutate. Results are compared to an exact, "Cost Function Network" method that identifies the global minimum energy conformation (GMEC) in favorable cases. The designed sequences accurately reproduce experimental sequences in the hydrophobic core. The heuristic and REMC agree closely and reproduce the GMEC when it is known, with a few exceptions. Plain MC performs well for most cases, occasionally departing from the GMEC by 3-4 kcal/mol. With REMC, the diversity of the sequences sampled agrees with exact enumeration where the latter is possible: up to 2 kcal/mol above the GMEC. Beyond, room temperature replicas sample sequences up to 10 kcal/mol above the GMEC, providing thermal averages and a solution to the inverse protein folding problem. © 2016 Wiley Periodicals, Inc. PMID:27197555

  14. Comparing three stochastic search algorithms for computational protein design: Monte Carlo, replica exchange Monte Carlo, and a multistart, steepest-descent heuristic.

    PubMed

    Mignon, David; Simonson, Thomas

    2016-07-15

    Computational protein design depends on an energy function and an algorithm to search the sequence/conformation space. We compare three stochastic search algorithms: a heuristic, Monte Carlo (MC), and a Replica Exchange Monte Carlo method (REMC). The heuristic performs a steepest-descent minimization starting from thousands of random starting points. The methods are applied to nine test proteins from three structural families, with a fixed backbone structure, a molecular mechanics energy function, and with 1, 5, 10, 20, 30, or all amino acids allowed to mutate. Results are compared to an exact, "Cost Function Network" method that identifies the global minimum energy conformation (GMEC) in favorable cases. The designed sequences accurately reproduce experimental sequences in the hydrophobic core. The heuristic and REMC agree closely and reproduce the GMEC when it is known, with a few exceptions. Plain MC performs well for most cases, occasionally departing from the GMEC by 3-4 kcal/mol. With REMC, the diversity of the sequences sampled agrees with exact enumeration where the latter is possible: up to 2 kcal/mol above the GMEC. Beyond, room temperature replicas sample sequences up to 10 kcal/mol above the GMEC, providing thermal averages and a solution to the inverse protein folding problem. © 2016 Wiley Periodicals, Inc.

  15. Descent vehicles

    NASA Technical Reports Server (NTRS)

    Popov, Y. I.

    1985-01-01

    The creation of descent vehicles marked a new stage in the development of cosmonautics, involving the beginning of manned space flight and substantial progress in space research on the distant bodies of the Solar System. This booklet describes these vehicles and their structures, systems, and purposes. It is intended for the general public interested in modern problems of space technology.

  16. Comparison of a discrete steepest ascent method with the continuous steepest ascent method for optimal programing

    NASA Technical Reports Server (NTRS)

    Childs, A. G.

    1971-01-01

    A discrete steepest ascent method which allows controls which are not piecewise constant (for example, it allows all continuous piecewise linear controls) was derived for the solution of optimal programming problems. This method is based on the continuous steepest ascent method of Bryson and Denham and new concepts introduced by Kelley and Denham in their development of compatible adjoints for taking into account the effects of numerical integration. The method is a generalization of the algorithm suggested by Canon, Cullum, and Polak with the details of the gradient computation given. The discrete method was compared with the continuous method for an aerodynamics problem for which an analytic solution is given by Pontryagin's maximum principle, and numerical results are presented. The discrete method converges more rapidly than the continuous method at first, but then for some undetermined reason, loses its exponential convergence rate. A comparsion was also made for the algorithm of Canon, Cullum, and Polak using piecewise constant controls. This algorithm is very competitive with the continuous algorithm.

  17. Ascent/Descent Software

    NASA Technical Reports Server (NTRS)

    Brown, Charles; Andrew, Robert; Roe, Scott; Frye, Ronald; Harvey, Michael; Vu, Tuan; Balachandran, Krishnaiyer; Bly, Ben

    2012-01-01

    The Ascent/Descent Software Suite has been used to support a variety of NASA Shuttle Program mission planning and analysis activities, such as range safety, on the Integrated Planning System (IPS) platform. The Ascent/Descent Software Suite, containing Ascent Flight Design (ASC)/Descent Flight Design (DESC) Configuration items (Cis), lifecycle documents, and data files used for shuttle ascent and entry modeling analysis and mission design, resides on IPS/Linux workstations. A list of tools in Navigation (NAV)/Prop Software Suite represents tool versions established during or after the IPS Equipment Rehost-3 project.

  18. Random versus Deterministic Descent in RNA Energy Landscape Analysis

    PubMed Central

    Day, Luke; Abdelhadi Ep Souki, Ouala; Albrecht, Andreas A.; Steinhöfel, Kathleen

    2016-01-01

    Identifying sets of metastable conformations is a major research topic in RNA energy landscape analysis, and recently several methods have been proposed for finding local minima in landscapes spawned by RNA secondary structures. An important and time-critical component of such methods is steepest, or gradient, descent in attraction basins of local minima. We analyse the speed-up achievable by randomised descent in attraction basins in the context of large sample sets where the size has an order of magnitude in the region of ~106. While the gain for each individual sample might be marginal, the overall run-time improvement can be significant. Moreover, for the two nongradient methods we analysed for partial energy landscapes induced by ten different RNA sequences, we obtained that the number of observed local minima is on average larger by 7.3% and 3.5%, respectively. The run-time improvement is approximately 16.6% and 6.8% on average over the ten partial energy landscapes. For the large sample size we selected for descent procedures, the coverage of local minima is very high up to energy values of the region where the samples were randomly selected from the partial energy landscapes; that is, the difference to the total set of local minima is mainly due to the upper area of the energy landscapes. PMID:27110241

  19. Random versus Deterministic Descent in RNA Energy Landscape Analysis.

    PubMed

    Day, Luke; Abdelhadi Ep Souki, Ouala; Albrecht, Andreas A; Steinhöfel, Kathleen

    2016-01-01

    Identifying sets of metastable conformations is a major research topic in RNA energy landscape analysis, and recently several methods have been proposed for finding local minima in landscapes spawned by RNA secondary structures. An important and time-critical component of such methods is steepest, or gradient, descent in attraction basins of local minima. We analyse the speed-up achievable by randomised descent in attraction basins in the context of large sample sets where the size has an order of magnitude in the region of ~10(6). While the gain for each individual sample might be marginal, the overall run-time improvement can be significant. Moreover, for the two nongradient methods we analysed for partial energy landscapes induced by ten different RNA sequences, we obtained that the number of observed local minima is on average larger by 7.3% and 3.5%, respectively. The run-time improvement is approximately 16.6% and 6.8% on average over the ten partial energy landscapes. For the large sample size we selected for descent procedures, the coverage of local minima is very high up to energy values of the region where the samples were randomly selected from the partial energy landscapes; that is, the difference to the total set of local minima is mainly due to the upper area of the energy landscapes.

  20. Regulation of testicular descent.

    PubMed

    Hutson, John M; Li, Ruili; Southwell, Bridget R; Newgreen, Don; Cousinery, Mary

    2015-04-01

    Testicular descent occurs in two morphologically distinct phases, each under different hormonal control from the testis itself. The first phase occurs between 8 and 15 weeks when insulin-like hormone 3 (Insl3) from the Leydig cells stimulates the gubernaculum to swell, thereby anchoring the testis near the future inguinal canal as the foetus grows. Testosterone causes regression of the cranial suspensory ligament to augment the transabdominal phase. The second, or inguinoscrotal phase, occurs between 25 and 35 weeks, when the gubernaculum bulges out of the external ring and migrates to the scrotum, all under control of testosterone. However, androgen acts mostly indirectly via the genitofemoral nerve (GFN), which produces calcitonin gene-related peptide (CGRP) to control the direction of migration. In animal models the androgen receptors are in the inguinoscrotal fat pad, which probably produces a neurotrophin to masculinise the GFN sensory fibres that regulate gubernacular migration. There is little direct evidence that this same process occurs in humans, but CGRP can regulate closure of the processus vaginalis in inguinal hernia, confirming that the GFN probably mediates human testicular descent by a similar mechanism as seen in rodent models. Despite increased understanding about normal testicular descent, the common causes of cryptorchidism remain elusive.

  1. Entry, Descent, Landing Animation (Animation)

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Click on the image for Entry, Descent, Landing animation

    This animation illustrates the path the Stardust return capsule will follow once it enters Earth's atmosphere.

  2. Innovative Applications of Genetic Algorithms to Problems in Accelerator Physics

    SciTech Connect

    Hofler, Alicia; Terzic, Balsa; Kramer, Matthew; Zvezdin, Anton; Morozov, Vasiliy; Roblin, Yves; Lin, Fanglei; Jarvis, Colin

    2013-01-01

    The genetic algorithm (GA) is a relatively new technique that implements the principles nature uses in biological evolution in order to optimize a multidimensional nonlinear problem. The GA works especially well for problems with a large number of local extrema, where traditional methods (such as conjugate gradient, steepest descent, and others) fail or, at best, underperform. The field of accelerator physics, among others, abounds with problems which lend themselves to optimization via GAs. In this paper, we report on the successful application of GAs in several problems related to the existing CEBAF facility, the proposed MEIC at Jefferson Lab, and a radio frequency (RF) gun based injector. These encouraging results are a step forward in optimizing accelerator design and provide an impetus for application of GAs to other problems in the field. To that end, we discuss the details of the GAs used, including a newly devised enhancement, which leads to improved convergence to the optimum and make recommendations for future GA developments and accelerator applications.

  3. Simulation Test Of Descent Advisor

    NASA Technical Reports Server (NTRS)

    Davis, Thomas J.; Green, Steven M.

    1991-01-01

    Report describes piloted-simulation test of Descent Advisor (DA), subsystem of larger automation system being developed to assist human air-traffic controllers and pilots. Focuses on results of piloted simulation, in which airline crews executed controller-issued descent advisories along standard curved-path arrival routes. Crews able to achieve arrival-time precision of plus or minus 20 seconds at metering fix. Analysis of errors generated in turns resulted in further enhancements of algorithm to increase accuracies of its predicted trajectories. Evaluations by pilots indicate general support for DA concept and provide specific recommendations for improvement.

  4. EXOMARS Descent Module GNC Performance

    NASA Astrophysics Data System (ADS)

    Portigliotti, S.; Capuano, M.; Montagna, M.; Martella, P.; Venditto, P.

    2007-08-01

    The ExoMars mission is the first ESA led robotic mission of the Aurora Programme and combines technology development with investigations of major scientific interest. Italy is by far the major contributor to the mission through the strong support of the Italian Space Agency (ASI). ExoMars will search for traces of past and present life, characterize the Mars geochemistry and water distribution, improve the knowledge of the Mars environment and geophysics, and identify possible surface hazards to future human exploration missions. ExoMars will also validate the technology for safe Entry, Descent and Landing (EDL) of a large size Descent Module (DM) carrying a Rover with medium range surface mobility and the access to subsurface. The ExoMars project is presently undergoing its Phase B1 with Thales Alenia Space-Italia as Industrial Prime Contractor. Additionally, as Descent Module responsible, a dedicated simulation tool is under development in Thales Alenia Space-Italia, Turin site, for the end-to-end design and validation / verification of the DM Entry Descent and Landing.

  5. Ant colony optimization and stochastic gradient descent.

    PubMed

    Meuleau, Nicolas; Dorigo, Marco

    2002-01-01

    In this article, we study the relationship between the two techniques known as ant colony optimization (ACO) and stochastic gradient descent. More precisely, we show that some empirical ACO algorithms approximate stochastic gradient descent in the space of pheromones, and we propose an implementation of stochastic gradient descent that belongs to the family of ACO algorithms. We then use this insight to explore the mutual contributions of the two techniques. PMID:12171633

  6. Numerical analysis of the orthogonal descent method

    SciTech Connect

    Shokov, V.A.; Shchepakin, M.B.

    1994-11-01

    The author of the orthogonal descent method has been testing it since 1977. The results of these tests have only strengthened the need for further analysis and development of orthogonal descent algorithms for various classes of convex programming problems. Systematic testing of orthogonal descent algorithms and comparison of test results with other nondifferentiable optimization methods was conducted at TsEMI RAN in 1991-1992 using the results.

  7. The Steepest Slopes on the Moon: Gradual Degradation and Instant Removal by Basin-Forming Impacts

    NASA Astrophysics Data System (ADS)

    Kreslavsky, M. A.; Head, J. W., III

    2015-12-01

    We calculated topographic gradients over the surface of the Moon at a 25 m baseline using data obtained by the Lunar Orbiter Laser Altimeter (LOLA) instrument onboard the Lunar Reconnaissance Orbiter (LRO) spacecraft. The derived slope-frequency distribution revealed a steep roll-over for slopes close to the angle of repose. Slopes significantly steeper than the angle of repose are almost absent on the Moon due to (1) the general absence of cohesion/strength of the fractured and fragmented megaregolith of the lunar highlands, and (2) the absence of steep-slope producing geological processes in the recent geological past. The majority of slopes steeper than 32 - 35 degrees are associated with relatively young large impact craters. Very rare extremely steep (> 45 degrees) slopes are exclusively associated with large Copernican-age craters. Craters of Early Imbrian age and older are devoid of slopes steeper than ~35 degrees. We interpret these observations in the following way. Every basin-forming impact removes steep slopes by global seismic shaking causing slope collapse. The latest such impact formed Orientale basin and instantly removed all preexisting slopes steeper than ~35 degrees. This makes steep slopes a good global stratigraphic marker at Early/Late Imbrian boundary. After the Orientale impact, craters lose their steepest slopes progressively with time. This makes crater wall steepness an independent proxy for crater age. The global spatial distribution of the proportion of the steepest slopes correlates moderately well with the predicted spatial distribution of impact rate: low latitudes and the leading hemisphere have a higher steep slope proportion than high latitudes and the trailing hemisphere. However, the southern farside has a significant paucity of steep slopes, which remains unexplained. Acknowledgement: Data processing was performed at MIIGAiK by MK and supported by Russian Science Foundation, project 14-22-00197.

  8. Space Shuttle Orbiter descent navigation

    NASA Technical Reports Server (NTRS)

    Montez, M. N.; Madden, M. F.

    1982-01-01

    The entry operational sequence (OPS 3) begins approximately 2 hours prior to the deorbit maneuver and continues through atmospheric entry, terminal area energy management (TAEM), approach and landing, and rollout. During this flight phase, the navigation state vector is estimated by the Space Shuttle Orbiter onboard navigation system. This estimate is computed using a six-element sequential Kalman filter, which blends inertial measurement unit (IMU) delta-velocity data with external navaid data. The external navaids available to the filter are tactical air navigation (TACAN), barometric altimeter, and microwave scan beam landing system (MSBLS). Attention is given to the functional design of the Orbiter navigation system, the descent navigation sensors and measurement processing, predicted Kalman gains, correlation coefficients, and current flights navigation performance.

  9. Correlation as Probability of Common Descent.

    ERIC Educational Resources Information Center

    Falk, Ruma; Well, Arnold D.

    1996-01-01

    One interpretation of the Pearson product-moment correlation ("r"), correlation as the probability of originating from common descent, important to the genetic measurement of inbreeding, is examined. The conditions under which "r" can be interpreted as the probability of "identity by descent" are specified, and the possibility of generalizing this…

  10. Predictability of Top of Descent Location for Operational Idle-Thrust Descents

    NASA Technical Reports Server (NTRS)

    Stell, Laurel L.

    2010-01-01

    To enable arriving aircraft to fly optimized descents computed by the flight management system (FMS) in congested airspace, ground automation must accurately predict descent trajectories. To support development of the trajectory predictor and its uncertainty models, commercial flights executed idle-thrust descents at a specified descent speed, and the recorded data included the specified descent speed profile, aircraft weight, and the winds entered into the FMS as well as the radar data. The FMS computed the intended descent path assuming idle thrust after top of descent (TOD), and the controllers and pilots then endeavored to allow the FMS to fly the descent to the meter fix with minimal human intervention. The horizontal flight path, cruise and meter fix altitudes, and actual TOD location were extracted from the radar data. Using approximately 70 descents each in Boeing 757 and Airbus 319/320 aircraft, multiple regression estimated TOD location as a linear function of the available predictive factors. The cruise and meter fix altitudes, descent speed, and wind clearly improve goodness of fit. The aircraft weight improves fit for the Airbus descents but not for the B757. Except for a few statistical outliers, the residuals have absolute value less than 5 nmi. Thus, these predictive factors adequately explain the TOD location, which indicates the data do not include excessive noise.

  11. Descent Advisor Preliminary Field Test

    NASA Technical Reports Server (NTRS)

    Green, Steven M.; Vivona, Robert A.; Sanford, Beverly

    1995-01-01

    A field test of the Descent Advisor (DA) automation tool was conducted at the Denver Air Route Traffic Control Center in September 1994. DA is being developed to assist Center controllers in the efficient management and control of arrival traffic. DA generates advisories, based on trajectory predictions, to achieve accurate meter-fix arrival times in a fuel efficient manner while assisting the controller with the prediction and resolution of potential conflicts. The test objectives were: (1) to evaluate the accuracy of DA trajectory predictions for conventional and flight-management system equipped jet transports, (2) to identify significant sources of trajectory prediction error, and (3) to investigate procedural and training issues (both air and ground) associated with DA operations. Various commercial aircraft (97 flights total) and a Boeing 737-100 research aircraft participated in the test. Preliminary results from the primary test set of 24 commercial flights indicate a mean DA arrival time prediction error of 2.4 seconds late with a standard deviation of 13.1 seconds. This paper describes the field test and presents preliminary results for the commercial flights.

  12. Descent advisor preliminary field test

    NASA Technical Reports Server (NTRS)

    Green, Steven M.; Vivona, Robert A.; Sanford, Beverly

    1995-01-01

    A field test of the Descent Advisor (DA) automation tool was conducted at the Denver Air Route Traffic Control Center in September 1994. DA is being developed to assist Center controllers in the efficient management and control of arrival traffic. DA generates advisories, based on trajectory predictions, to achieve accurate meter-fix arrival times in a fuel efficient manner while assisting the controller with the prediction and resolution of potential conflicts. The test objectives were to evaluate the accuracy of DA trajectory predictions for conventional- and flight-management-system-equipped jet transports, to identify significant sources of trajectory prediction error, and to investigate procedural and training issues (both air and ground) associated with DA operations. Various commercial aircraft (97 flights total) and a Boeing 737-100 research aircraft participated in the test. Preliminary results from the primary test set of 24 commercial flights indicate a mean DA arrival time prediction error of 2.4 sec late with a standard deviation of 13.1 sec. This paper describes the field test and presents preliminary results for the commercial flights.

  13. Anteroposterior Knee Stability During Stair Descent.

    PubMed

    Borque, Kyle A; Gold, Jonathan E; Incavo, Stephen J; Patel, Rupal M; Ismaily, Sabir E; Noble, Philip C

    2015-06-01

    This study examined the influence of tibio-femoral conformity on anteroposterior (AP) knee stability during stair descent, particularly with a dished cruciate sacrificing (CS) design. A joint simulator simulated stair descent of cadaveric knees. Tibio-femoral displacement was measured. Knees were tested in intact, ACL-deficient, and TKA with cruciate-retaining (CR), CS and posterior-stabilizing (PS) inserts. Loading during stair descent simulation caused femur displacement anteriorly prior to quadriceps contraction. Quadriceps contraction reestablished the initial femoral AP position. During simulated stair descent, AP stability was restored using PS, CR or CS inserts with an intact PCL. The CS design without the PCL did not provide AP stability. Increasing quadriceps force to restore AP stability may explain the clinical findings of pain and fatigue experienced by some patients after TKA.

  14. Reference energy-altitude descent guidance: Simulator evaluation. [aircraft descent and fuel conservation

    NASA Technical Reports Server (NTRS)

    Abbot, K. H.; Knox, C. E.

    1985-01-01

    Descent guidance was developed to provide a pilot with information to ake a fuel-conservative descent and cross a designated geographical waypoint at a preselected altitude and airspeed. The guidance was designed to reduce fuel usage during the descent and reduce the mental work load associated with planning a fuel-conservative descent. A piloted simulation was conducted to evaluate the operational use of this guidance concept. The results of the simulation tests show that the use of the guidance reduced fuel consumption and mental work load during the descent. Use of the guidance also decreased the airspeed error, but had no effect on the altitude error when the designated waypoint was crossed. Physical work load increased with the use of the guidance, but remained well within acceptable levels. The pilots found the guidance easy to use as presented and reported that it would be useful in an operational environment.

  15. Assessment of GPS radiosonde descent data

    NASA Astrophysics Data System (ADS)

    Venkat Ratnam, M.; Pravallika, N.; Babu, S. Ravindra; Basha, G.; Pramitha, M.; Krishna Murthy, B. V.

    2014-04-01

    Radiosondes are widely used to obtain basic meteorological parameters such as pressure (P), temperature (T), relative humidity (RH) and horizontal winds during the balloon ascent up to the altitude of balloon burst, usually ~ 32-35 km. Data from the radiosondes released from Gadanki (13.5° N, 79.2° E), a tropical station in India, have been collected during the ascent and during the descent as well without attaching any parachute or its equivalent since the year 2008. In the present study an attempt has been made to characterize the radiosonde descent data with the main objective of exploring its usefulness and reliability for scientific purposes. We compared the data obtained during ascent and descent phases of the same sounding. The mean differences in T, RH and horizontal winds between ascent and descent data are found to be small and are sometimes even within the uncertainty of the measurements and/or expected diurnal variation itself. The very good consistency observed between the ascent and the descent data shows that one more profile of the meteorological parameters can be constructed within 3 h of time of balloon launch practically at no additional cost. Further checks are done by utilizing the 3-hourly radiosonde observations collected during the Tropical Tropopause Dynamics campaigns conducted at Gadanki. In the process of checking the consistency between the radiosonde ascent and descent data, several new findings are arrived at and are reported in this study. In general, it has taken more than half an hour for the balloon to reach the ground from the burst altitude. It is also observed that the fall velocity is close to 10 m s-1 near the surface. Finally, it is suggested to record the observations also when the balloon is descending as this information is useful for scientific purposes.

  16. Assessment of GPS radiosonde descent data

    NASA Astrophysics Data System (ADS)

    Venkat Ratnam, M.; Pravallika, N.; babu, S. Ravindra; Basha, G.; Pramitha, M.; Krishna Murthy, B. V.

    2013-12-01

    Radiosondes are widely used to obtain basic meteorological parameters such as pressure (P), temperature (T), relative humidity (RH), and horizontal winds during the balloon ascent up to the altitude of balloon burst, usually ∼32-35 km. Data from the radiosondes released from Gadanki (13.5° N, 79.2° E), a tropical station in India, has been collected during the ascent and during the descent as well without attaching any parachute or its equivalent since the year 2008. In the present study an attempt has been made to characterize the radiosonde descent data with the main objective of exploring its usefulness and reliability for scientific purposes. We compared the data obtained during ascent and descent phases of the same sounding. The mean differences in T, RH and horizontal winds between ascent and descent data are found to be small and are sometimes even within the uncertainty of the measurements and/or expected diurnal variation itself. The very good consistency observed between the ascent and the descent data shows that one more profile of the meteorological parameters can be constructed within 3 h of time of balloon launch practically at no additional cost. Further checks are done by utilizing the 3 hourly radiosonde observations collected during the Tropical Tropopause Dynamics campaign conducted at Gadanki. In the process of checking the consistency between the radiosonde ascent and descent data, several new findings are arrived at and are reported in this study. In general, it has taken more than half-an-hour for the balloon to reach the ground from the burst altitude. It is also observed that the fall velocity is close to 10 m s-1 near the surface. Finally, it is suggested to record also the observations when the balloon is descending as this information is also useful for scientific purposes.

  17. Entry, Descent, and Landing With Propulsive Deceleration

    NASA Technical Reports Server (NTRS)

    Palaszewski, Bryan

    2012-01-01

    The future exploration of the Solar System will require innovations in transportation and the use of entry, descent, and landing (EDL) systems at many planetary landing sites. The cost of space missions has always been prohibitive, and using the natural planetary and planet s moons atmospheres for entry, descent, and landing can reduce the cost, mass, and complexity of these missions. This paper will describe some of the EDL ideas for planetary entry and survey the overall technologies for EDL that may be attractive for future Solar System missions.

  18. The hormonal control of testicular descent.

    PubMed

    Levy, J B; Husmann, D A

    1995-01-01

    Descent of the testes is a complex event mediated by hormonal and mechanical factors. At present we hypothesize that testicular descent occurs as the result of the secretion of descendin from a normal testicle. Descendin secretion results in selective growth of the gubernacular cells. Gubernacular outgrowth results in masculinization of the inguinal canal. At the beginning of testicular descent, the patent processus migrates into the inguinal canal, transmitting intraabdominal pressure to the gubernaculum. The gubernaculum in turn applies traction to the testicle to introduce the testicle into the inguinal canal. Descent of the testes into and through the inguinal canal is an interplay between intraabdominal pressure transmitted by a patent processus vaginalis and androgen-induced gubernacular regression. Specifically, we hypothesize that androgens under control of an intact fetal hypothalamic-pituitary axis alter the viscoelastic properties of the gubernaculum. Reductions in the turgidity of the gubernaculum allow intraabdominal pressure to push the testicle into the scrotum. Functional abnormalities in any of the above factors will result in cryptorchidism. PMID:8867594

  19. Research study: STS-1 Orbiter Descent

    NASA Technical Reports Server (NTRS)

    Hickey, J. S.

    1981-01-01

    The conversion of STS-1 orbiter descent data from AVE-SESAME contact programs to the REEDA system and the reduction of raw radiosonde data is summarized. A first difference program, contact data program, plot data program, and 30 second data program were developed. Six radiosonde soundings were taken. An example of the outputs of each of the programs is presented.

  20. The hormonal control of testicular descent.

    PubMed

    Levy, J B; Husmann, D A

    1995-01-01

    Descent of the testes is a complex event mediated by hormonal and mechanical factors. At present we hypothesize that testicular descent occurs as the result of the secretion of descendin from a normal testicle. Descendin secretion results in selective growth of the gubernacular cells. Gubernacular outgrowth results in masculinization of the inguinal canal. At the beginning of testicular descent, the patent processus migrates into the inguinal canal, transmitting intraabdominal pressure to the gubernaculum. The gubernaculum in turn applies traction to the testicle to introduce the testicle into the inguinal canal. Descent of the testes into and through the inguinal canal is an interplay between intraabdominal pressure transmitted by a patent processus vaginalis and androgen-induced gubernacular regression. Specifically, we hypothesize that androgens under control of an intact fetal hypothalamic-pituitary axis alter the viscoelastic properties of the gubernaculum. Reductions in the turgidity of the gubernaculum allow intraabdominal pressure to push the testicle into the scrotum. Functional abnormalities in any of the above factors will result in cryptorchidism.

  1. America's Descent into Madness

    ERIC Educational Resources Information Center

    Giroux, Henry A.

    2014-01-01

    This article describes America's descent into madness under the regime of neoliberalism that has emerged in the United States since the late 1970s. In part, this is due to the emergence of a public pedagogy produced by the corporate-owned media that now saturates Americans with a market-driven value system that undermines those formative…

  2. Ka-Band Radar Terminal Descent Sensor

    NASA Technical Reports Server (NTRS)

    Pollard, Brian; Berkun, Andrew; Tope, Michael; Andricos, Constantine; Okonek, Joseph; Lou, Yunling

    2007-01-01

    The terminal descent sensor (TDS) is a radar altimeter/velocimeter that improves the accuracy of velocity sensing by more than an order of magnitude when compared to existing sensors. The TDS is designed for the safe planetary landing of payloads, and may be used in helicopters and fixed-wing aircraft requiring high-accuracy velocity sensing

  3. Descent Assisted Split Habitat Lunar Lander Concept

    NASA Technical Reports Server (NTRS)

    Mazanek, Daniel D.; Goodliff, Kandyce; Cornelius, David M.

    2008-01-01

    The Descent Assisted Split Habitat (DASH) lunar lander concept utilizes a disposable braking stage for descent and a minimally sized pressurized volume for crew transport to and from the lunar surface. The lander can also be configured to perform autonomous cargo missions. Although a braking-stage approach represents a significantly different operational concept compared with a traditional two-stage lander, the DASH lander offers many important benefits. These benefits include improved crew egress/ingress and large-cargo unloading; excellent surface visibility during landing; elimination of the need for deep-throttling descent engines; potentially reduced plume-surface interactions and lower vertical touchdown velocity; and reduced lander gross mass through efficient mass staging and volume segmentation. This paper documents the conceptual study on various aspects of the design, including development of sortie and outpost lander configurations and a mission concept of operations; the initial descent trajectory design; the initial spacecraft sizing estimates and subsystem design; and the identification of technology needs

  4. Coping with Discrimination among Mexican Descent Adolescents

    ERIC Educational Resources Information Center

    Edwards, Lisa M.; Romero, Andrea J.

    2008-01-01

    The current research is designed to explore the relationship among discrimination stress, coping strategies, and self-esteem among Mexican descent youth (N = 73, age 11-15 years). Results suggest that primary control engagement and disengagement coping strategies are positively associated with discrimination stress. Furthermore, self-esteem is…

  5. Method of descent for integrable lattices

    NASA Astrophysics Data System (ADS)

    Bogoyavlensky, Oleg

    2009-05-01

    A method of descent for constructing integrable Hamiltonian systems is introduced. The derived periodic and nonperiodic lattices possess Lax representations with spectral parameter and have plenty of first integrals. Examples of Liouville-integrable four-dimensional Hamiltonian Lotka-Volterra systems are presented.

  6. Optimum Strategies for Selecting Descent Flight-Path Angles

    NASA Technical Reports Server (NTRS)

    Wu, Minghong G. (Inventor); Green, Steven M. (Inventor)

    2016-01-01

    An information processing system and method for adaptively selecting an aircraft descent flight path for an aircraft, are provided. The system receives flight adaptation parameters, including aircraft flight descent time period, aircraft flight descent airspace region, and aircraft flight descent flyability constraints. The system queries a plurality of flight data sources and retrieves flight information including any of winds and temperatures aloft data, airspace/navigation constraints, airspace traffic demand, and airspace arrival delay model. The system calculates a set of candidate descent profiles, each defined by at least one of a flight path angle and a descent rate, and each including an aggregated total fuel consumption value for the aircraft following a calculated trajectory, and a flyability constraints metric for the calculated trajectory. The system selects a best candidate descent profile having the least fuel consumption value while the fly ability constraints metric remains within aircraft flight descent flyability constraints.

  7. A Descent Rate Control Approach to Developing an Autonomous Descent Vehicle

    NASA Astrophysics Data System (ADS)

    Fields, Travis D.

    Circular parachutes have been used for aerial payload/personnel deliveries for over 100 years. In the past two decades, significant work has been done to improve the landing accuracies of cargo deliveries for humanitarian and military applications. This dissertation discusses the approach developed in which a circular parachute is used in conjunction with an electro-mechanical reefing system to manipulate the landing location. Rather than attempt to steer the autonomous descent vehicle directly, control of the landing location is accomplished by modifying the amount of time spent in a particular wind layer. Descent rate control is performed by reversibly reefing the parachute canopy. The first stage of the research investigated the use of a single actuation during descent (with periodic updates), in conjunction with a curvilinear target. Simulation results using real-world wind data are presented, illustrating the utility of the methodology developed. Additionally, hardware development and flight-testing of the single actuation autonomous descent vehicle are presented. The next phase of the research focuses on expanding the single actuation descent rate control methodology to incorporate a multi-actuation path-planning system. By modifying the parachute size throughout the descent, the controllability of the system greatly increases. The trajectory planning methodology developed provides a robust approach to accurately manipulate the landing location of the vehicle. The primary benefits of this system are the inherent robustness to release location errors and the ability to overcome vehicle uncertainties (mass, parachute size, etc.). A separate application of the path-planning methodology is also presented. An in-flight path-prediction system was developed for use in high-altitude ballooning by utilizing the path-planning methodology developed for descent vehicles. The developed onboard system improves landing location predictions in-flight using collected flight

  8. 14 CFR 23.69 - Enroute climb/descent.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Enroute climb/descent. 23.69 Section 23.69... climb/descent. (a) All engines operating. The steady gradient and rate of climb must be determined at.... The steady gradient and rate of climb/descent must be determined at each weight, altitude, and...

  9. The steepest slopes on the Moon from Lunar Orbiter Laser Altimeter (LOLA) Data: Spatial Distribution and Correlation with Geologic Features

    NASA Astrophysics Data System (ADS)

    Kreslavsky, Mikhail A.; Head, James W.

    2016-07-01

    We calculated topographic gradients over the surface of the Moon at a 25 m baseline using data obtained by the Lunar Orbiter Laser Altimeter (LOLA) instrument onboard the Lunar Reconnaissance Orbiter (LRO) spacecraft. The relative spatial distribution of steep slopes can be reliably obtained, although some technical characteristics of the LOLA dataset preclude statistical studies of slope orientation. The derived slope-frequency distribution revealed a steep rollover for slopes close to the angle of repose. Slopes significantly steeper than the angle of repose are almost absent on the Moon due to (1) the general absence of cohesion/strength of the fractured and fragmented megaregolith of the lunar highlands, and (2) the absence of geological processes producing steep-slopes in the recent geological past. The majority of slopes steeper than 32°-35° are associated with relatively young large impact craters. We demonstrate that these impact craters progressively lose their steepest slopes. We also found that features of Early Imbrian and older ages have almost no slopes steeper than 35°. We interpret this to be due to removal of all steep slopes by the latest basin-forming impact (Orientale), probably by global seismic shaking. The global spatial distribution of the steepest slopes correlates moderately well with the predicted spatial distribution of impact rate; however, a significant paucity of steep slopes in the southern farside remains unexplained.

  10. Estimating genotypes with independently sampled descent graphs.

    PubMed

    Henshall, J M; Tier, B; Kerr, R J

    2001-12-01

    A method for estimating genotypic and identity-by-descent probabilities in complex pedigrees is described. The method consists of an algorithm for drawing independent genotype samples which are consistent with the pedigree and observed genotype. The probability distribution function for samples obtained using the algorithm can be evaluated up to a normalizing constant, and combined with the likelihood to produce a weight for each sample. Importance sampling is then used to estimate genotypic and identity-by-descent probabilities. On small but complex pedigrees, the genotypic probability estimates are demonstrated to be empirically unbiased. On large complex pedigrees, while the algorithm for obtaining genotype samples is feasible, importance sampling may require an infeasible number of samples to estimate genotypic probabilities with accuracy.

  11. Mars Exploration Entry, Descent and Landing Challenges

    NASA Technical Reports Server (NTRS)

    Braun, Robert D.; Manning, Robert M.

    2006-01-01

    The United States has successfully landed five robotic systems on the surface of Mars. These systems all had landed mass below 0.6 metric tons (t), had landed footprints on the order of hundreds of km and landed at sites below -1.4 km MOLA elevation due the need to perform entry, descent and landing operations in an environment with sufficient atmospheric density. At present, robotic exploration systems engineers are struggling with the challenges of increasing landed mass capability to 0.8 t while improving landed accuracy to tens of km and landing at a site as high as +2 km MOLA elevation for the Mars Science Laboratory project. Meanwhile, current plans for human exploration of Mars call for the landing of 40-80 t surface elements at scientifically interesting locations within close proximity (tens of m) of pre-positioned robotic assets. This paper summarizes past successful entry, descent and landing systems and approaches being developed by the robotic Mars exploration program to increased landed performance (mass, accuracy and surface elevation). In addition, the entry, descent and landing sequence for a human exploration system will be reviewed, highlighting the technology and systems advances required.

  12. Assessment on EXPERT Descent and Landing System Aerodynamics

    NASA Astrophysics Data System (ADS)

    Wong, H.; Muylaert, J.; Northey, D.; Riley, D.

    2009-01-01

    EXPERT is a re-entry vehicle designed for validation of aero-thermodynamic models, numerical schemes in Computational Fluid Dynamics codes and test facilities for measuring flight data under an Earth re-entry environment. This paper addresses the design for the descent and landing sequence for EXPERT. It includes the descent sequence, the choice of drogue and main parachutes, and the parachute deployment condition, which can be supersonic or subsonic. The analysis is based mainly on an engineering tool, PASDA, together with some hand calculations for parachute sizing and design. The tool consists of a detailed 6-DoF simulation performed with the aerodynamics database of the vehicle, an empirical wakes model and the International Standard Atmosphere database. The aerodynamics database for the vehicle is generated by DNW experimental data and CFD codes within the framework of an ESA contract to CIRA. The analysis will be presented in terms of altitude, velocity, accelerations, angle-of- attack, pitch angle and angle of rigging line. Discussion on the advantages and disadvantages of each parachute deployment condition is included in addition to some comparison with the available data based on a Monte-Carlo method from a Russian company, FSUE NIIPS. Sensitivity on wind speed to the performance of EXPERT is shown to be strong. Supersonic deployment of drogue shows a better performance in stability at the expense of a larger G-load than those from the subsonic deployment of drogue. Further optimization on the parachute design is necessary in order to fulfill all the EXPERT specifications.

  13. Kinetic analysis of stair descent: Part 1. Forwards step-over-step descent.

    PubMed

    Cluff, Tyler; Robertson, D Gordon E

    2011-03-01

    This study examined lower extremity biomechanics during the initiation of stair descent from an upright, static posture. Seventeen healthy subjects (aged 23±2.4 years) descended a five-step, steel-reinforced, wooden laboratory staircase (34° decline). Ten trials of stair descent were separated into two blocks of five trials. Beginning from an upright posture, subjects descended the staircase at their preferred velocity (0.53±0.082 m/s) and continued the length of the laboratory walkway (∼4 m). Joint mechanics were contrasted between gait cycles. Relative to the initiation cycle at the top of the staircase, the dissipative knee extensor (K3) and hip flexor (H2) moments and powers were independent of progression velocity and approximated steady-state (i.e., constant) values after the first cycle of the trail limb (Step 5 to Step 3). In contrast, a salient relationship was observed between progression velocity and ankle joint mechanics at initial-contact. The plantiflexor moment, power and work at initial-contact (A1) increased with centre of mass velocity. Our results demonstrate that while the knee extensor moment is the primary dissipater of mechanical energy in stair descent, the ankle plantiflexors are the primary dissipaters associated with increased progression velocity. In addition, the results show that steady-state stair descent may not be attained during the first gait cycle of the trail limb. These data shed light on locomotive strategies used in stair descent and can be applied in biomechanical models of human stair gait. Researchers and practitioners should take into consideration the influence of gait cycle and progression velocity when evaluating lower extremity function in stair descent. PMID:21292489

  14. APOLLO 11: Lunar Module Separates for descent

    NASA Technical Reports Server (NTRS)

    1974-01-01

    Separation of the Lunar module for descent to the Lunar surface From the film documentary 'APOLLO 11:'The eagle Has Landed'', part of a documentary series on the APOLLO missions made in the early '70's and narrated by Burgess Meredith. APOLLO 11: First manned lunar landing and return to Earth with Neil A. Armstrong, Michael Collins, and Edwin E. Aldrin. Landed in the Sea of Tranquilityon July 20, 1969; deployed TV camera and EASEP experiments, performed lunar surface EVA, returned lunar soil samples. Mission Duration 195 hrs 18 min 35sec

  15. System for Estimating Horizontal Velocity During Descent

    NASA Technical Reports Server (NTRS)

    Johnson, Andrew; Cheng, Yang; Wilson, Reg; Goguen, Jay; Martin, Alejandro San; Leger, Chris; Matthies, Larry

    2007-01-01

    The descent image motion estimation system (DIMES) is a system of hardware and software, designed for original use in estimating the horizontal velocity of a spacecraft descending toward a landing on Mars. The estimated horizontal velocity is used in generating rocket-firing commands to reduce the horizontal velocity as part of an overall control scheme to minimize the landing impact. DIMES can also be used for estimating the horizontal velocity of a remotely controlled or autonomous aircraft for purposes of navigation and control.

  16. Testicular descent: a hypothesis and review of current controversies.

    PubMed

    Husmann, Douglas A

    2009-06-01

    Descent of the testis into the scrotum occurs by a complex multifactorial process involving the normal development of the testis, the hormonal actions of insulin like growth factor 3, testosterone, a intact hypothalamic pituitary testicular axis, the patent processus vaginalis, gubernacular outgrowth and regression and intraabdominal pressure. The paper reviews the key components of testicular descent, the current hypothesis on how testicular descent occurs and the controversies surrounding this hypothesis.

  17. Regression Analysis of Top of Descent Location for Idle-thrust Descents

    NASA Technical Reports Server (NTRS)

    Stell, Laurel; Bronsvoort, Jesper; McDonald, Greg

    2013-01-01

    In this paper, multiple regression analysis is used to model the top of descent (TOD) location of user-preferred descent trajectories computed by the flight management system (FMS) on over 1000 commercial flights into Melbourne, Australia. The independent variables cruise altitude, final altitude, cruise Mach, descent speed, wind, and engine type were also recorded or computed post-operations. Both first-order and second-order models are considered, where cross-validation, hypothesis testing, and additional analysis are used to compare models. This identifies the models that should give the smallest errors if used to predict TOD location for new data in the future. A model that is linear in TOD altitude, final altitude, descent speed, and wind gives an estimated standard deviation of 3.9 nmi for TOD location given the trajec- tory parameters, which means about 80% of predictions would have error less than 5 nmi in absolute value. This accuracy is better than demonstrated by other ground automation predictions using kinetic models. Furthermore, this approach would enable online learning of the model. Additional data or further knowl- edge of algorithms is necessary to conclude definitively that no second-order terms are appropriate. Possible applications of the linear model are described, including enabling arriving aircraft to fly optimized descents computed by the FMS even in congested airspace. In particular, a model for TOD location that is linear in the independent variables would enable decision support tool human-machine interfaces for which a kinetic approach would be computationally too slow.

  18. A fast and scalable recurrent neural network based on stochastic meta descent.

    PubMed

    Liu, Zhenzhen; Elhanany, Itamar

    2008-09-01

    This brief presents an efficient and scalable online learning algorithm for recurrent neural networks (RNNs). The approach is based on the real-time recurrent learning (RTRL) algorithm, whereby the sensitivity set of each neuron is reduced to weights associated with either its input or output links. This yields a reduced storage and computational complexity of O(N(2)). Stochastic meta descent (SMD), an adaptive step size scheme for stochastic gradient-descent problems, is employed as means of incorporating curvature information in order to substantially accelerate the learning process. We also introduce a clustered version of our algorithm to further improve its scalability attributes. Despite the dramatic reduction in resource requirements, it is shown through simulation results that the approach outperforms regular RTRL by almost an order of magnitude. Moreover, the scheme lends itself to parallel hardware realization by virtue of the localized property that is inherent to the learning framework. PMID:18779096

  19. Evaluation of Residual Static Corrections by Hybrid Genetic Algorithm Steepest Ascent Autostatics Inversion.Application southern Algerian fields

    NASA Astrophysics Data System (ADS)

    Eladj, Said; bansir, fateh; ouadfeul, sid Ali

    2016-04-01

    The application of genetic algorithm starts with an initial population of chromosomes representing a "model space". Chromosome chains are preferentially Reproduced based on Their fitness Compared to the total population. However, a good chromosome has a Greater opportunity to Produce offspring Compared To other chromosomes in the population. The advantage of the combination HGA / SAA is the use of a global search approach on a large population of local maxima to Improve Significantly the performance of the method. To define the parameters of the Hybrid Genetic Algorithm Steepest Ascent Auto Statics (HGA / SAA) job, we Evaluated by testing in the first stage of "Steepest Ascent," the optimal parameters related to the data used. 1- The number of iterations "Number of hill climbing iteration" is equal to 40 iterations. This parameter defines the participation of the algorithm "SA", in this hybrid approach. 2- The minimum eigenvalue for SA '= 0.8. This is linked to the quality of data and S / N ratio. To find an implementation performance of hybrid genetic algorithms in the inversion for estimating of the residual static corrections, tests Were Performed to determine the number of generation of HGA / SAA. Using the values of residual static corrections already calculated by the Approaches "SAA and CSAA" learning has Proved very effective in the building of the cross-correlation table. To determine the optimal number of generation, we Conducted a series of tests ranging from [10 to 200] generations. The application on real seismic data in southern Algeria allowed us to judge the performance and capacity of the inversion with this hybrid method "HGA / SAA". This experience Clarified the influence of the corrections quality estimated from "SAA / CSAA" and the optimum number of generation hybrid genetic algorithm "HGA" required to have a satisfactory performance. Twenty (20) generations Were enough to Improve continuity and resolution of seismic horizons. This Will allow

  20. 14 CFR 23.69 - Enroute climb/descent.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Enroute climb/descent. 23.69 Section 23.69... climb/descent. (a) All engines operating. The steady gradient and rate of climb must be determined at...; (3) The wing flaps retracted; and (4) A climb speed not less than 1.3 VS1. (b) One engine...

  1. 14 CFR 23.69 - Enroute climb/descent.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Enroute climb/descent. 23.69 Section 23.69... climb/descent. (a) All engines operating. The steady gradient and rate of climb must be determined at...; (3) The wing flaps retracted; and (4) A climb speed not less than 1.3 VS1. (b) One engine...

  2. 25 CFR 11.711 - Descent and distribution.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 25 Indians 1 2010-04-01 2010-04-01 false Descent and distribution. 11.711 Section 11.711 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR LAW AND ORDER COURTS OF INDIAN OFFENSES AND LAW AND ORDER CODE Probate Proceedings § 11.711 Descent and distribution. (a) The court shall distribute...

  3. Hair Breakage in Patients of African Descent: Role of Dermoscopy.

    PubMed

    Quaresma, Maria Victória; Martinez Velasco, María Abril; Tosti, Antonella

    2015-09-01

    Dermoscopy represents a useful technique for the diagnosis and follow-up of hair and scalp disorders. To date, little has been published regarding dermoscopy findings of hair disorders in patients of African descent. This article illustrates how dermoscopy allows fast diagnosis of hair breakage due to intrinsic factors and chemical damage in African descent patients.

  4. Mars Science Laboratory Entry, Descent and Landing System Overview

    NASA Technical Reports Server (NTRS)

    Steltzner, Adam D.; San Martin, A. Miguel; Rivellini, Tomasso P.; Chen, Allen

    2013-01-01

    The Mars Science Laboratory project recently places the Curiosity rove on the surface of Mars. With the success of the landing system, the performance envelope of entry, descent and landing capabilities has been extended over the previous state of the art. This paper will present an overview to the MSL entry, descent and landing system design and preliminary flight performance results.

  5. Hair Breakage in Patients of African Descent: Role of Dermoscopy

    PubMed Central

    Quaresma, Maria Victória; Martinez Velasco, María Abril; Tosti, Antonella

    2015-01-01

    Dermoscopy represents a useful technique for the diagnosis and follow-up of hair and scalp disorders. To date, little has been published regarding dermoscopy findings of hair disorders in patients of African descent. This article illustrates how dermoscopy allows fast diagnosis of hair breakage due to intrinsic factors and chemical damage in African descent patients. PMID:27170942

  6. Planetary entry, descent, and landing technologies

    NASA Astrophysics Data System (ADS)

    Pichkhadze, K.; Vorontsov, V.; Polyakov, A.; Ivankov, A.; Taalas, P.; Pellinen, R.; Harri, A.-M.; Linkin, V.

    2003-04-01

    Martian meteorological lander (MML) is intended for landing on the Martian surface in order to monitor the atmosphere at landing point for one Martian year. MMLs shall become the basic elements of a global network of meteorological mini-landers, observing the dynamics of changes of the atmospheric parameters on the Red Planet. The MML main scientific tasks are as follows: (1) Study of vertical structure of the Martian atmosphere throughout the MML descent; (2) On-surface meteorological observations for one Martian year. One of the essential factors influencing the lander's design is its entry, descent, and landing (EDL) sequence. During Phase A of the MML development, five different options for the lander's design were carefully analyzed. All of these options ensure the accomplishment of the above-mentioned scientific tasks with high effectiveness. CONCEPT A (conventional approach): Two lander options (with a parachute system + airbag and an inflatable airbrake + airbag) were analyzed. They are similar in terms of fulfilling braking phases and completely analogous in landing by means of airbags. CONCEPT B (innovative approach): Three lander options were analyzed. The distinguishing feature is the presence of inflatable braking units (IBU) in their configurations. SELECTED OPTION (innovative approach): Incorporating a unique design approach and modern technologies, the selected option of the lander represents a combination of the options analyzed in the framework of Concept B study. Currently, the selected lander option undergoes systems testing (Phase D1). Several MMLs can be delivered to Mars in frameworks of various missions as primary or piggybacking payload: (1) USA-led "Mars Scout" (2007); (2) France-led "NetLander" (2007/2009); (3) Russia-led "Mars-Deimos-Phobos sample return" (2007); (4) Independent mission (currently under preliminary study); etc.

  7. Atomistic-level non-equilibrium model for chemically reactive systems based on steepest-entropy-ascent quantum thermodynamics

    NASA Astrophysics Data System (ADS)

    Li, Guanchen; Al-Abbasi, Omar; von Spakovsky, Michael R.

    2014-10-01

    This paper outlines an atomistic-level framework for modeling the non-equilibrium behavior of chemically reactive systems. The framework called steepest- entropy-ascent quantum thermodynamics (SEA-QT) is based on the paradigm of intrinsic quantum thermodynamic (IQT), which is a theory that unifies quantum mechanics and thermodynamics into a single discipline with wide applications to the study of non-equilibrium phenomena at the atomistic level. SEA-QT is a novel approach for describing the state of chemically reactive systems as well as the kinetic and dynamic features of the reaction process without any assumptions of near-equilibrium states or weak-interactions with a reservoir or bath. Entropy generation is the basis of the dissipation which takes place internal to the system and is, thus, the driving force of the chemical reaction(s). The SEA-QT non-equilibrium model is able to provide detailed information during the reaction process, providing a picture of the changes occurring in key thermodynamic properties (e.g., the instantaneous species concentrations, entropy and entropy generation, reaction coordinate, chemical affinities, reaction rate, etc). As an illustration, the SEA-QT framework is applied to an atomistic-level chemically reactive system governed by the reaction mechanism F + H2 leftrightarrow FH + H.

  8. Bridle Device in Mars Science Laboratory Descent Stage

    NASA Technical Reports Server (NTRS)

    2008-01-01

    This view of a portion of the descent stage of NASA's Mars Science Laboratory shows two of the stage's three spherical fuel tanks flanking the bridle device assembly. The photograph was taken in early October 2008 from the center of the descent stage looking outward. The top of the descent stage is toward the top of the image.

    The bridle device assembly is about two-thirds of a meter, or 2 feet, from top to bottom, and has two main parts. The cylinder on the top is the descent brake. The conical-shaped mechanism below that is the bridle assembly, including a spool of nylon and Vectran cords that will be attached to the rover.

    When pyrotechnic bolts fire to sever the rigid connection between the rover and the descent stage, gravity will pull the tethered rover away from the descent stage. The bridle or tether, attached to three points on the rover, will unspool from the bridle assembly, beginning from the larger-diameter portion. The rotation rate of the assembly, hence the descent rate of the rover, will be governed by the descent brake. Inside the housing of that brake are gear boxes and banks of mechanical resistors engineered to prevent the bridle from spooling out too quickly or too slowly. The length of the bridle will allow the rover to be lowered about 7.5 meters (25 feet) while still tethered to the descent stage.

    The Starsys division of SpaceDev Inc., Poway, Calif., provided the descent brake. NASA's Jet Propulsion Laboratory, Pasadena, Calif., built the bridle assembly. Vectran is a product of Kuraray Co. Ltd., Tokyo. JPL, a division of the California Institute of Technology, manages the Mars Science Laboratory Project for the NASA Science Mission Directorate, Washington.

  9. Simulator Evaluation of a New Cockpit Descent Procedure

    NASA Technical Reports Server (NTRS)

    Crane, Barry; Palmer, Everett; Smith, Nancy; Rosekind, Mark (Technical Monitor)

    1996-01-01

    An experiment was conducted to evaluate flight crew performance of the "Precision Descent," a new cockpit procedure designed to support the Descent Advisor (DA), one of the components in a new air traffic control advisory system called the "Center-TRACON Automation System" (CTAS). The DA predicts when aircraft will reach a specific waypoint on the arrival route, and presents controllers with clearance advisories designed to improve the sequencing of arriving aircraft. The effectiveness of the DA depends on the aircraft's descent trajectory: where it begins descent, what speed it maintains, how fast and at what altitude it crosses the bottom-of-descent waypoint. The Precision Descent allows controllers to assign these descent parameters to the flight crew. A Field Evaluation of the DA was conducted in Denver in 1995. Three separate clearances using standard ATC phraseology were used to support the cockpit descent procedure during this evaluation. The number and length of these clearances caused problems for both controllers and flight crews, causing readback errors, repeat requests and procedure misunderstandings. These observations led to a focus group meeting in which controller and pilot participants in the 1995 FE assisted in the redesign of the procedure. The Precision Descent eliminates one clearance used in the earlier study, and greatly reduces the length of the remaining clearances. This was accomplished by using non-standard clearance phraseology that relies on a published procedure chart for correct interpretation. Eight type-rated flight crews flew eight Precision Descents in a Boeing 747-400 simulator. No training was provided: crews received either a procedure chart or a procedure chart with a flight manual bulletin describing procedure techniques. Video and digital data were recorded for each descent. Preliminary results indicate that moving information from the verbal clearance to the chart was successful: the shorter clearances and the procedure

  10. Mars Science Laboratory Entry, Descent, and Landing Trajectory and Atmosphere Reconstruction

    NASA Technical Reports Server (NTRS)

    Karlgaard, Christopher D.; Kutty, Prasad; Schoenenberer, Mark; Shidner, Jeremy D.

    2013-01-01

    On August 5th 2012, The Mars Science Laboratory entry vehicle successfully entered Mars atmosphere and landed the Curiosity rover on its surface. A Kalman filter approach has been implemented to reconstruct the entry, descent, and landing trajectory based on all available data. The data sources considered in the Kalman filtering approach include the inertial measurement unit accelerations and angular rates, the terrain descent sensor, the measured landing site, orbit determination solutions for the initial conditions, and a new set of instrumentation for planetary entry reconstruction consisting of forebody pressure sensors, known as the Mars Entry Atmospheric Data System. These pressure measurements are unique for planetary entry, descent, and landing reconstruction as they enable a reconstruction of the freestream atmospheric conditions without any prior assumptions being made on the vehicle aerodynamics. Moreover, the processing of these pressure measurements in the Kalman filter approach enables the identification of atmospheric winds, which has not been accomplished in past planetary entry reconstructions. This separation of atmosphere and aerodynamics allows for aerodynamic model reconciliation and uncertainty quantification, which directly impacts future missions. This paper describes the mathematical formulation of the Kalman filtering approach, a summary of data sources and preprocessing activities, and results of the reconstruction.

  11. Fast curvature matrix-vector products for second-order gradient descent.

    PubMed

    Schraudolph, Nicol N

    2002-07-01

    We propose a generic method for iteratively approximating various second-order gradient steps - Newton, Gauss-Newton, Levenberg-Marquardt, and natural gradient - in linear time per iteration, using special curvature matrix-vector products that can be computed in O(n). Two recent acceleration techniques for on-line learning, matrix momentum and stochastic meta-descent (SMD), implement this approach. Since both were originally derived by very different routes, this offers fresh insight into their operation, resulting in further improvements to SMD.

  12. Surface erosion caused on Mars from Viking descent engine plume

    USGS Publications Warehouse

    Hutton, R.E.; Moore, H.J.; Scott, R.F.; Shorthill, R.W.; Spitzer, C.R.

    1980-01-01

    During the Martian landings the descent engine plumes on Viking Lander 1 (VL-1) and Viking Lander 2 (VL-2) eroded the Martian surface materials. This had been anticipated and investigated both analytically and experimentally during the design phase of the Viking spacecraft. This paper presents data on erosion obtained during the tests of the Viking descent engine and the evidence for erosion by the descent engines of VL-1 and VL-2 on Mars. From these and other results, it is concluded that there are four distinct surface materials on Mars: (1) drift material, (2) crusty to cloddy material, (3) blocky material, and (4) rock. ?? 1980 D. Reidel Publishing Co.

  13. Orion Entry, Descent, and Landing Simulation

    NASA Technical Reports Server (NTRS)

    Hoelscher, Brian R.

    2007-01-01

    The Orion Entry, Descent, and Landing simulation was created over the past two years to serve as the primary Crew Exploration Vehicle guidance, navigation, and control (GN&C) design and analysis tool at the National Aeronautics and Space Administration (NASA). The Advanced NASA Technology Architecture for Exploration Studies (ANTARES) simulation is a six degree-of-freedom tool with a unique design architecture which has a high level of flexibility. This paper describes the decision history and motivations that guided the creation of this simulation tool. The capabilities of the models within ANTARES are presented in detail. Special attention is given to features of the highly flexible GN&C architecture and the details of the implemented GN&C algorithms. ANTARES provides a foundation simulation for the Orion Project that has already been successfully used for requirements analysis, system definition analysis, and preliminary GN&C design analysis. ANTARES will find useful application in engineering analysis, mission operations, crew training, avionics-in-the-loop testing, etc. This paper focuses on the entry simulation aspect of ANTARES, which is part of a bigger simulation package supporting the entire mission profile of the Orion vehicle. The unique aspects of entry GN&C design are covered, including how the simulation is being used for Monte Carlo dispersion analysis and for support of linear stability analysis. Sample simulation output from ANTARES is presented in an appendix.

  14. Gradient Descent Learning for Rotor Associative Memory

    NASA Astrophysics Data System (ADS)

    Kitahara, Michimasa; Kobayashi, Masaki

    Complex-valued Associative Memory (CAM) is an extended model of Hopfield Associative Memory (HAM). The fundamental elements, such as input-output signals and connection weights of the CAM are extended to complex numbers. The CAM can deal with multi-states information. Rotor Associative Memory (RAM) is an extended model of the CAM. Rotor neurons are essentially equivalent to complex-valued neurons. Connection weights of the RAM are expressed by two by two matrices. Only hebb rule has been proposed for the learning of the RAM. Its storage capacity is small, so advanced learning methods are necessary. In this paper, we propose gradient descent learning rule for the RAM (GDR RAM). It is based on that for the CAM (GDR CAM) proposed by Lee. We solved the learning rule and performed computer simulations to compare the GDR CAM and the GDR RAM. At last, it turned out that the storage capacity of the GDR RAM is approximately twice as much as that of the GDR CAM and the noise robustness of the GDR RAM is much better than that of the GDR CAM.

  15. Auroral precipitation and descent of thermospheric NO

    NASA Astrophysics Data System (ADS)

    Kühl, Sven; Espy, Patrick; Hibbins, Robert; Paxton, Larry; Funke, Bernd

    2016-07-01

    Energetic particle precipitation in Auroras (E <20 keV) produces nitric oxide (NO) in the upper meso- and lower thermosphere region (UMLT). The subsequent descent of the NO produced in the UMLT to the lower meso- and upper stratosphere is referred to as the energetic particle precipitation indirect effect (EPP IE). The downwelling of NO produced in Auroras alters the chemistry of the mesosphere and upper stratosphere (e.g. by the NOx cycle) and possibly has important effects also on its dynamics. By observations of auroral precipitation from SSUSI(DMSP) and measurements of NO from MIPAS(ENVISAT) and SMR(ODIN) we investigate the quantitative relation of the electron fluxes and characteristic energies of auroral precipitation to the NO produced in the lower thermosphere and the subsequent downwelling of NO. Using additional ground-based (e.g. Meteor Radar, Microwave Radiometer) and satellite observations (SOFIE) we attempt to quantify the EPP IE and its impact on atmospheric chemistry and dynamics.

  16. Prediction of multilocus identity-by-descent.

    PubMed

    Hill, William G; Hernández-Sánchez, Jules

    2007-08-01

    Previous studies have enabled exact prediction of probabilities of identity-by-descent (IBD) in random-mating populations for a few loci (up to four or so), with extension to more using approximate regression methods. Here we present a precise predictor of multiple-locus IBD using simple formulas based on exact results for two loci. In particular, the probability of non-IBD X(ABC) at each of ordered loci A, B, and C can be well approximated by X(ABC) = X(AB)X(BC)/X(B) and generalizes to X(123...k) = X(12)X(23...)X(k)(-1,k)/X(k-2), where X is the probability of non-IBD at each locus. Predictions from this chain rule are very precise with population bottlenecks and migration, but are rather poorer in the presence of mutation. From these coefficients, the probabilities of multilocus IBD and non-IBD can also be computed for genomic regions as functions of population size, time, and map distances. An approximate but simple recurrence formula is also developed, which generally is less accurate than the chain rule but is more robust with mutation. Used together with the chain rule it leads to explicit equations for non-IBD in a region. The results can be applied to detection of quantitative trait loci (QTL) by computing the probability of IBD at candidate loci in terms of identity-by-state at neighboring markers.

  17. Ascent/descent ancillary data production user's guide

    NASA Technical Reports Server (NTRS)

    Brans, H. R.; Seacord, A. W., II; Ulmer, J. W.

    1986-01-01

    The Ascent/Descent Ancillary Data Product, also called the A/D BET because it contains a Best Estimate of the Trajectory (BET), is a collection of trajectory, attitude, and atmospheric related parameters computed for the ascent and descent phases of each Shuttle Mission. These computations are executed shortly after the event in a post-flight environment. A collection of several routines including some stand-alone routines constitute what is called the Ascent/Descent Ancillary Data Production Program. A User's Guide for that program is given. It is intended to provide the reader with all the information necessary to generate an Ascent or a Descent Ancillary Data Product. It includes descriptions of the input data and output data for each routine, and contains explicit instructions on how to run each routine. A description of the final output product is given.

  18. Men of African Descent and Carcinoma of the Prostate Consortium

    Cancer.gov

    The Men of African Descent and Carcinoma of the Prostate Consortium collaborates on epidemiologic studies to address the high burden of prostate cancer and to understand the causes of etiology and outcomes among men of African ancestry.

  19. Automation for Accommodating Fuel-Efficient Descents in Constrained Airspace

    NASA Technical Reports Server (NTRS)

    Coopenbarger, Richard A.

    2010-01-01

    Continuous descents at low engine power are desired to reduce fuel consumption, emissions and noise during arrival operations. The challenge is to allow airplanes to fly these types of efficient descents without interruption during busy traffic conditions. During busy conditions today, airplanes are commonly forced to fly inefficient, step-down descents as airtraffic controllers work to ensure separation and maximize throughput. NASA in collaboration with government and industry partners is developing new automation to help controllers accommodate continuous descents in the presence of complex traffic and airspace constraints. This automation relies on accurate trajectory predictions to compute strategic maneuver advisories. The talk will describe the concept behind this new automation and provide an overview of the simulations and flight testing used to develop and refine its underlying technology.

  20. Design and Development of the MSL Descent Stage Propulsion System

    NASA Technical Reports Server (NTRS)

    Weiss, Jeffrey M.; Guernsey, Carl S.

    2013-01-01

    On August 5, 2012, The Mars Science Laboratory mission successfully landed the largest interplanetary rover ever built, Curiosity, on the surface of Mars. The Entry, Descent, and Landing (EDL) phase of this mission was by far the most complex landing ever attempted on a planetary body. The Descent Stage Propulsion System played an integral and critical role during Curiosity's EDL. The Descent Stage Propulsion System was a one of a kind hydrazine propulsion system designed specifically for the EDL phase of the MSL mission. It was designed, built, and tested at the Jet Propulsion Laboratory (JPL). The purpose of this paper is to present an overview of the design and development of the MSL Descent Stage Propulsion System. Driving requirements, system design, component selection, operational sequence of the system at Mars, new developments, and key challenges will be discussed.

  1. Optimal sliding guidance algorithm for Mars powered descent phase

    NASA Astrophysics Data System (ADS)

    Wibben, Daniel R.; Furfaro, Roberto

    2016-02-01

    Landing on large planetary bodies (e.g. Mars) with pinpoint accuracy presents a set of new challenges that must be addressed. One such challenge is the development of new guidance algorithms that exhibit a higher degree of robustness and flexibility. In this paper, the Zero-Effort-Miss/Zero-Effort-Velocity (ZEM/ZEV) optimal sliding guidance (OSG) scheme is applied to the Mars powered descent phase. This guidance algorithm has been specifically designed to combine techniques from both optimal and sliding control theories to generate an acceleration command based purely on the current estimated spacecraft state and desired final target state. Consequently, OSG yields closed-loop trajectories that do not need a reference trajectory. The guidance algorithm has its roots in the generalized ZEM/ZEV feedback guidance and its mathematical equations are naturally derived by defining a non-linear sliding surface as a function of the terms Zero-Effort-Miss and Zero-Effort-Velocity. With the addition of the sliding mode and using Lyapunov theory for non-autonomous systems, one can formally prove that the developed OSG law is globally finite-time stable to unknown but bounded perturbations. Here, the focus is on comparing the generalized ZEM/ZEV feedback guidance with the OSG law to explicitly demonstrate the benefits of the sliding mode augmentation. Results show that the sliding guidance provides a more robust solution in off-nominal scenarios while providing similar fuel consumption when compared to the non-sliding guidance command. Further, a Monte Carlo analysis is performed to examine the performance of the OSG law under perturbed conditions.

  2. Descent from the Summit of 'Husband Hill'

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Click on the image for Descent from the Summit of 'Husband Hill' (QTVR)

    In late November 2005 while descending 'Husband Hill,' NASA's Mars Exploration Rover Spirit took the most detailed panorama so far of the 'Inner Basin,' the rover's next target destination. Spirit acquired the 405 individual images that make up this 360-degree view of the surrounding terrain using five different filters on the panoramic camera. The rover took the images on Martian days, or sols, 672 to 677 (Nov. 23 to 28, 2005 -- the Thanksgiving holiday weekend).

    This image is an approximately true-color rendering using camera's 750-, 530-, and 430-nanometer filters. Seams between individual frames have been eliminated from the sky portion of the mosaic to better simulate the vista a person standing on Mars would see.

    'Home Plate,' a bright, semi-circular feature scientists hope to investigate, is harder to discern in this image than in earlier views taken from higher up the hill. Spirit acquired this more oblique view, known as the 'Seminole panorama,' from about halfway down the south flank of Husband Hill, 50 meters (164 feet) or so below the summit. Near the center of the panorama, on the horizon, are 'McCool Hill' and 'Ramon Hill,' named, like Husband Hill, in honor of the fallen astronauts of the space shuttle Columbia. Husband Hill is visible behind the rover, on the right and left sides of the panorama. An arc of rover tracks made while avoiding obstacles and getting into position to examine rock outcrops can be traced over a long distance by zooming in to explore the panorama in greater detail.

    Spirit is now significantly farther downhill toward the center of this panorama, en route to Home Plate and other enigmatic soils and outcrop rocks in the quest to uncover the history of Gusev Crater and the 'Columbia Hills.'

  3. Steepest entropy ascent model for far-nonequilibrium thermodynamics: unified implementation of the maximum entropy production principle.

    PubMed

    Beretta, Gian Paolo

    2014-10-01

    By suitable reformulations, we cast the mathematical frameworks of several well-known different approaches to the description of nonequilibrium dynamics into a unified formulation valid in all these contexts, which extends to such frameworks the concept of steepest entropy ascent (SEA) dynamics introduced by the present author in previous works on quantum thermodynamics. Actually, the present formulation constitutes a generalization also for the quantum thermodynamics framework. The analysis emphasizes that in the SEA modeling principle a key role is played by the geometrical metric with respect to which to measure the length of a trajectory in state space. In the near-thermodynamic-equilibrium limit, the metric tensor is directly related to the Onsager's generalized resistivity tensor. Therefore, through the identification of a suitable metric field which generalizes the Onsager generalized resistance to the arbitrarily far-nonequilibrium domain, most of the existing theories of nonequilibrium thermodynamics can be cast in such a way that the state exhibits the spontaneous tendency to evolve in state space along the path of SEA compatible with the conservation constraints and the boundary conditions. The resulting unified family of SEA dynamical models is intrinsically and strongly consistent with the second law of thermodynamics. The non-negativity of the entropy production is a general and readily proved feature of SEA dynamics. In several of the different approaches to nonequilibrium description we consider here, the SEA concept has not been investigated before. We believe it defines the precise meaning and the domain of general validity of the so-called maximum entropy production principle. Therefore, it is hoped that the present unifying approach may prove useful in providing a fresh basis for effective, thermodynamically consistent, numerical models and theoretical treatments of irreversible conservative relaxation towards equilibrium from far nonequilibrium

  4. Atmospheric properties reconstruction from the Mars Science Laboratory Entry, Descent and Landing

    NASA Astrophysics Data System (ADS)

    Holstein-Rathlou, Christina; Withers, Paul

    2014-11-01

    The Mars Science Laboratory (MSL) landed on August 5, 2012 in Gale Crater on Mars (4.5 S, 137.4 E) [1]. The MSL entry vehicle measured accelerations and angular velocity during its descent through the Martian atmosphere using accelerometers and gyroscopes in an inertial measurement unit. We have applied smoothing techniques previously developed for the NASA Phoenix Mars mission [2] to these acceleration data. Smoothed accelerations were used in conjunction with the vehicle’s aerodynamic database to reconstruct atmospheric density, pressure and temperature profiles to above 120 km altitude. The density profile was estimated using axial accelerations in the drag force equation. Corresponding pressure and temperature profiles were calculated using the hydrostatic equilibrium and ideal gas law, respectively. In contrast to previous missions, MSL used a guided entry that resulted in periods of near-horizontal flight at approximately 20 km altitude [3], during which pressure could not be determined from hydrostatic equilibrium. Instead, atmospheric pressures at low altitudes were determined independently by the Mars Entry Atmospheric Data System (MEADS) [4]. These were used in conjunction with accelerometer-derived densities to extend the atmospheric temperature profile through the period of near-horizontal flight. Although the results present only a snapshot of the regional atmospheric conditions at the time of entry, descent and landing of MSL, they have excellent vertical resolution and vertical extent, thereby complementing orbital observations. We will present an overview of our atmospheric reconstruction process, the derived atmospheric profiles, and preliminary scientific interpretation of the atmospheric results. References: [1] Vasavada, A.R. et al (2014), JGR-Planets, 119, 6, 1134-1161 [2] Withers, P. (2013) Planet. & Space Sci., 79-80, 52-55, [3] Dutta, S. et al. (2013) 23rd AAS/AIAA Space Flight Mechanics Meeting, AAS 13-309, [4] Schoenenberger, M. et al

  5. Mars Descent Imager (MARDI) on the Mars Polar Lander

    USGS Publications Warehouse

    Malin, M.C.; Caplinger, M.A.; Carr, M.H.; Squyres, S.; Thomas, P.; Veverka, J.

    2001-01-01

    The Mars Descent Imager, or MARDI, experiment on the Mars Polar Lander (MPL) consists of a camera characterized by small physical size and mass (???6 ?? 6 ?? 12 cm, including baffle; <500 gm), low power requirements (<2.5 W, including power supply losses), and high science performance (1000 x 1000 pixel, low noise). The intent of the investigation is to acquire nested images over a range of resolutions, from 8 m/pixel to better than 1 cm/pixel, during the roughly 2 min it takes the MPL to descend from 8 km to the surface under parachute and rocket-powered deceleration. Observational goals will include studies of (1) surface morphology (e.g., nature and distribution of landforms indicating past and present environmental processes); (2) local and regional geography (e.g., context for other lander instruments: precise location, detailed local relief); and (3) relationships to features seen in orbiter data. To accomplish these goals, MARDI will collect three types of images. Four small images (256 x 256 pixels) will be acquired on 0.5 s centers beginning 0.3 s before MPL's heatshield is jettisoned. Sixteen full-frame images (1024 X 1024, circularly edited) will be acquired on 5.3 s centers thereafter. Just after backshell jettison but prior to the start of powered descent, a "best final nonpowered descent image" will be acquired. Five seconds after the start of powered descent, the camera will begin acquiring images on 4 s centers. Storage for as many as ten 800 x 800 pixel images is available during terminal descent. A number of spacecraft factors are likely to impact the quality of MARDI images, including substantial motion blur resulting from large rates of attitude variation during parachute descent and substantial rocket-engine-induced vibration during powered descent. In addition, the mounting location of the camera places the exhaust plume of the hydrazine engines prominently in the field of view. Copyright 2001 by the American Geophysical Union.

  6. Design of automation tools for management of descent traffic

    NASA Technical Reports Server (NTRS)

    Erzberger, Heinz; Nedell, William

    1988-01-01

    The design of an automated air traffic control system based on a hierarchy of advisory tools for controllers is described. Compatibility of the tools with the human controller, a key objective of the design, is achieved by a judicious selection of tasks to be automated and careful attention to the design of the controller system interface. The design comprises three interconnected subsystems referred to as the Traffic Management Advisor, the Descent Advisor, and the Final Approach Spacing Tool. Each of these subsystems provides a collection of tools for specific controller positions and tasks. This paper focuses primarily on the Descent Advisor which provides automation tools for managing descent traffic. The algorithms, automation modes, and graphical interfaces incorporated in the design are described. Information generated by the Descent Advisor tools is integrated into a plan view traffic display consisting of a high-resolution color monitor. Estimated arrival times of aircraft are presented graphically on a time line, which is also used interactively in combination with a mouse input device to select and schedule arrival times. Other graphical markers indicate the location of the fuel-optimum top-of-descent point and the predicted separation distances of aircraft at a designated time-control point. Computer generated advisories provide speed and descent clearances which the controller can issue to aircraft to help them arrive at the feeder gate at the scheduled times or with specified separation distances. Two types of horizontal guidance modes, selectable by the controller, provide markers for managing the horizontal flightpaths of aircraft under various conditions. The entire system consisting of descent advisor algorithm, a library of aircraft performance models, national airspace system data bases, and interactive display software has been implemented on a workstation made by Sun Microsystems, Inc. It is planned to use this configuration in operational

  7. Data assimilation using a gradient descent method for estimation of intraoperative brain deformation.

    PubMed

    Ji, Songbai; Hartov, Alex; Roberts, David; Paulsen, Keith

    2009-10-01

    Biomechanical models that simulate brain deformation are gaining attention as alternatives for brain shift compensation. One approach, known as the "forced-displacement method", constrains the model to exactly match the measured data through boundary condition (BC) assignment. Although it improves model estimates and is computationally attractive, the method generates fictitious forces and may be ill-advised due to measurement uncertainty. Previously, we have shown that by assimilating intraoperatively acquired brain displacements in an inversion scheme, the Representer algorithm (REP) is able to maintain stress-free BCs and improve model estimates by 33% over those without data guidance in a controlled environment. However, REP is computationally efficient only when a few data points are used for model guidance because its costs scale linearly in the number of data points assimilated, thereby limiting its utility (and accuracy) in clinical settings. In this paper, we present a steepest gradient descent algorithm (SGD) whose computational complexity scales nearly invariantly with the number of measurements assimilated by iteratively adjusting the forcing conditions to minimize the difference between measured and model-estimated displacements (model-data misfit). Solutions of full linear systems of equations are achieved with a parallelized direct solver on a shared-memory, eight-processor Linux cluster. We summarize the error contributions from the entire process of model-updated image registration compensation and we show that SGD is able to attain model estimates comparable to or better than those obtained with REP, capturing about 74-82% of tumor displacement, but with a computational effort that is significantly less (a factor of 4-fold or more reduction relative to REP) and nearly invariant to the amount of sparse data involved when the number of points assimilated is large. Based on five patient cases, an average computational cost of approximately 2 min for

  8. Crew Procedures for Continuous Descent Arrivals Using Conventional Guidance

    NASA Technical Reports Server (NTRS)

    Oseguera-Lohr, Rosa M.; Williams, David H.; Lewis, Elliot T,

    2007-01-01

    This paper presents results from a simulation study which investigated the use of Continuous Descent Arrival (CDA) procedures for conducting a descent through a busy terminal area, using conventional transport-category automation. This research was part of the Low Noise Flight Procedures (LNFP) element within the Quiet Aircraft Technology (QAT) Project, that addressed development of flight guidance, and supporting pilot and Air Traffic Control (ATC) procedures for low noise operations. The procedures and chart were designed to be easy to understand, and to make it easy for the crew to make changes via the Flight Management Computer Control-Display Unit (FMC-CDU) to accommodate changes from ATC. The test runs were intended to represent situations typical of what exists in many of today's terminal areas, including interruptions to the descent in the form of clearances issued by ATC.

  9. MSL Entry, Descent and Landing Performance and Environments

    NASA Technical Reports Server (NTRS)

    Lockwood, Mary Kae; Dwyer-Cianciola, Alicia; Dyakonov, Artem; Edquist, Karl; Powell, Dick; Striepe, Scott; Way, David; Graves, Claude; Carman, Gil; Sostaric, Ron

    2005-01-01

    A viewgraph presentation on the MARS Science Laboratory (MSL) Entry, Descent and Landing (EDL) performance and environments is shown. The topics include: 1) High Altitude and Precision Landing; 2) Guided, Lifting, Ballistic Trade; 3) Supersonic Chute Deploy Altitude; 4) Guided, Lifting, Ballistic Landing Footprint Video; 5) Transition Indicator at Peak Heating Point on Trajectory; 6) Aeroheating at Peak Heating Point on Trajectory Nominal, No Uncertainty Included; 7) Comparison to Previous Missions; 8) Pork Chop Plots - EDL Performance for Mission Design; 9) Max Heat Rate Est (CBE+Uncert) W/cm2; 10) Nominal Super Chute Deploy Alt Above MOLA (km); 11) Monte Carlo; 12) MSL Option M2 Entry, Descent and Landing; 13) Entry Performance; 14) Entry Aeroheating and Entry g's; 15) Terminal Descent; and 16) How An Ideal Chute Deployment Altitude Varies with Time of Year and Latitude (JSC Chart).

  10. Mars Smart Lander Simulations for Entry, Descent, and Landing

    NASA Technical Reports Server (NTRS)

    Striepe, S. A.; Way, D. W.; Balaram, J.

    2002-01-01

    Two primary simulations have been developed and are being updated for the Mars Smart Lander Entry, Descent, and Landing (EDL). The high fidelity engineering end-to-end EDL simulation that is based on NASA Langley's Program to Optimize Simulated Trajectories (POST) and the end-to-end real-time, hardware-in-the-loop simulation testbed, which is based on NASA JPL's (Jet Propulsion Laboratory) Dynamics Simulator for Entry, Descent and Surface landing (DSENDS). This paper presents the status of these Mars Smart Lander EDL end-to-end simulations at this time. Various models, capabilities, as well as validation and verification for these simulations are discussed.

  11. Flight Data Entry, Descent, and Landing (EDL) Repository

    NASA Technical Reports Server (NTRS)

    Martinez, Elmain M.; Winterhalter, Daniel

    2012-01-01

    Dr. Daniel Winterhalter, NASA Engineering and Safety Center Chief Engineer at the Jet Propulsion Laboratory, requested the NASA Engineering and Safety Center sponsor a 3-year effort to collect entry, descent, and landing material and to establish a NASA-wide archive to serve the material. The principle focus of this task was to identify entry, descent, and landing repository material that was at risk of being permanently lost due to damage, decay, and undocumented storage. To provide NASA-wide access to this material, a web-based digital archive was created. This document contains the outcome of the effort.

  12. Entry, Descent and Landing Systems Analysis Study: Phase 1 Report

    NASA Technical Reports Server (NTRS)

    DwyerCianciolo, Alicia M.; Davis, Jody L.; Komar, David R.; Munk, Michelle M.; Samareh, Jamshid A.; Powell, Richard W.; Shidner, Jeremy D.; Stanley, Douglas O.; Wilhite, Alan W.; Kinney, David J.; McGuire, M. Kathleen; Arnold, James O.; Howard, Austin R.; Sostaric, Ronald R.; Studak, Joseph W.; Zumwalt, Carlie H.; Llama, Eduardo G.; Casoliva, Jordi; Ivanov, Mark C.; Clark, Ian; Sengupta, Anita

    2010-01-01

    NASA senior management commissioned the Entry, Descent and Landing Systems Analysis (EDL-SA) Study in 2008 to identify and roadmap the Entry, Descent and Landing (EDL) technology investments that the agency needed to make in order to successfully land large payloads at Mars for both robotic and human-scale missions. This paper summarizes the motivation, approach and top-level results from Year 1 of the study, which focused on landing 10-50 mt on Mars, but also included a trade study of the best advanced parachute design for increasing the landed payloads within the EDL architecture of the Mars Science Laboratory (MSL) mission

  13. Space shuttle descent design: From development to operations

    NASA Technical Reports Server (NTRS)

    Crull, T. J.; Hite, R. E., III

    1985-01-01

    The descent guidance system, the descent trajectories design, and generating of the associated flight products are discussed. The programs which allow the successful transitions from development to STS operations, resulting in reduced manpower requirements and compressed schedules for flight design cycles are addressed. The topics include: (1) continually upgraded tools for the job, i.e., consolidating tools via electronic data transfers, tailoring general purpose software for needs, easy access to tools through an interactive approach, and appropriate flexibility to allow design changes and provide growth capability; (2) stabilizing the flight profile designs (I-loads) in an uncertain environment; and (3) standardizing external interfaces within performance and subsystems constraints of the Orbiter.

  14. Descents and nodal load in scale-free networks

    NASA Astrophysics Data System (ADS)

    Bareinboim, Elias; Barbosa, Valmir C.

    2008-04-01

    The load of a node in a network is the total traffic going through it when every node pair sustains a uniform bidirectional traffic between them on shortest paths. We express nodal load in terms of the more elementary notion of a node’s descents in breadth-first-search [(BFS) or shortest-path] trees and study both the descent and nodal-load distributions in the case of scale-free networks. Our treatment is both semianalytical (combining a generating-function formalism with simulation-derived BFS branching probabilities) and computational for the descent distribution; it is exclusively computational in the case of the load distribution. Our main result is that the load distribution, even though it can be disguised as a power law through subtle (but inappropriate) binning of the raw data, is in fact a succession of sharply delineated probability peaks, each of which can be clearly interpreted as a function of the underlying BFS descents. This find is in stark contrast with previously held belief, based on which a power law of exponent -2.2 was conjectured to be valid regardless of the exponent of the power-law distribution of node degrees.

  15. APOLLO 16 TECHNICIAN ATTACHES PLAQUE TO LUNAR MODULE'S DESCENT STAGE

    NASA Technical Reports Server (NTRS)

    1972-01-01

    Working inside the Apollo 16 Saturn V space vehicle at the launch pad, technician Ken Crow attaches a stainless steel plaque bearing the names of Apollo 16 astronauts John W. Young, Thomas K. Mattingly II and Charles M. Duke, Jr., to the Lunar Module's descent stage, which will remain on the Moon's surface.

  16. A Portfolio of Outstanding Americans of Mexican Descent.

    ERIC Educational Resources Information Center

    Lelevier, Benjamin, Jr.

    A cross section of Mexican American achievement is presented in a portfolio of 37 portraits of outstanding Americans of Mexican descent. Drawn in black and white on heavy paper stock by Mr. David L. Rodriguez, the sketches are suitable for display purposes. With the likenesses are biographical sketches in both English and Spanish which were…

  17. "Rosetta" Mission's "7 Hours of Terror" and "Philae's" Descent

    ERIC Educational Resources Information Center

    Blanco, Philip

    2015-01-01

    In November 2014 the "Rosetta" mission to Comet 67P/Churyumov-Gerasimenko made the headlines when its "Philae" lander completed a successful unpowered descent onto the surface of the comet nucleus after "7 hours of terror" for the mission scientists. 67P's irregular shape and rotation made this task even more…

  18. 14 CFR 23.69 - Enroute climb/descent.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... each weight, altitude, and ambient temperature within the operational limits established by the...; (3) The wing flaps retracted; and (4) A climb speed not less than 1.3 VS1. (b) One engine inoperative. The steady gradient and rate of climb/descent must be determined at each weight, altitude, and...

  19. 14 CFR 23.69 - Enroute climb/descent.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... each weight, altitude, and ambient temperature within the operational limits established by the...; (3) The wing flaps retracted; and (4) A climb speed not less than 1.3 VS1. (b) One engine inoperative. The steady gradient and rate of climb/descent must be determined at each weight, altitude, and...

  20. Whole-body angular momentum during stair ascent and descent.

    PubMed

    Silverman, Anne K; Neptune, Richard R; Sinitski, Emily H; Wilken, Jason M

    2014-04-01

    The generation of whole-body angular momentum is essential in many locomotor tasks and must be regulated in order to maintain dynamic balance. However, angular momentum has not been investigated during stair walking, which is an activity that presents a biomechanical challenge for balance-impaired populations. We investigated three-dimensional whole-body angular momentum during stair ascent and descent and compared it to level walking. Three-dimensional body-segment kinematic and ground reaction force (GRF) data were collected from 30 healthy subjects. Angular momentum was calculated using a 13-segment whole-body model. GRFs, external moment arms and net joint moments were used to interpret the angular momentum results. The range of frontal plane angular momentum was greater for stair ascent relative to level walking. In the transverse and sagittal planes, the range of angular momentum was smaller in stair ascent and descent relative to level walking. Significant differences were also found in the ground reaction forces, external moment arms and net joint moments. The sagittal plane angular momentum results suggest that individuals alter angular momentum to effectively counteract potential trips during stair ascent, and reduce the range of angular momentum to avoid falling forward during stair descent. Further, significant differences in joint moments suggest potential neuromuscular mechanisms that account for the differences in angular momentum between walking conditions. These results provide a baseline for comparison to impaired populations that have difficulty maintaining dynamic balance, particularly during stair ascent and descent.

  1. Abuse against Women with Disabilities of Mexican Descent: Cultural Considerations

    ERIC Educational Resources Information Center

    Graf, Noreen M.; Reed, Bruce J.; Sanchez, Rubi

    2008-01-01

    Although considerable attention has been focused on violence against women with disabilities, environmental and cultural factors that contribute to this violence have received limited attention. This paper examines violence against women of Mexican descent with disabilities. Recommendations are offered to researchers, educators, and service…

  2. Stress within a Bicultural Context for Adolescents of Mexican Descent.

    ERIC Educational Resources Information Center

    Romero, Andrea J.; Roberts, Robert E.

    2003-01-01

    Folkman and Lazarus's theory of stress and coping was used to develop a measure assessing the perceived stress within a bicultural context. Middle school students of Mexican descent (N=881) reported their perceived stress from intergenerational acculturation gaps, within-group discrimination, out-group discrimination, and monolingual stress.…

  3. Simulation Results for Airborne Precision Spacing along Continuous Descent Arrivals

    NASA Technical Reports Server (NTRS)

    Barmore, Bryan E.; Abbott, Terence S.; Capron, William R.; Baxley, Brian T.

    2008-01-01

    This paper describes the results of a fast-time simulation experiment and a high-fidelity simulator validation with merging streams of aircraft flying Continuous Descent Arrivals through generic airspace to a runway at Dallas-Ft Worth. Aircraft made small speed adjustments based on an airborne-based spacing algorithm, so as to arrive at the threshold exactly at the assigned time interval behind their Traffic-To-Follow. The 40 aircraft were initialized at different altitudes and speeds on one of four different routes, and then merged at different points and altitudes while flying Continuous Descent Arrivals. This merging and spacing using flight deck equipment and procedures to augment or implement Air Traffic Management directives is called Flight Deck-based Merging and Spacing, an important subset of a larger Airborne Precision Spacing functionality. This research indicates that Flight Deck-based Merging and Spacing initiated while at cruise altitude and well prior to the Terminal Radar Approach Control entry can significantly contribute to the delivery of aircraft at a specified interval to the runway threshold with a high degree of accuracy and at a reduced pilot workload. Furthermore, previously documented work has shown that using a Continuous Descent Arrival instead of a traditional step-down descent can save fuel, reduce noise, and reduce emissions. Research into Flight Deck-based Merging and Spacing is a cooperative effort between government and industry partners.

  4. A Comparison of Inexact Newton and Coordinate Descent Meshoptimization Technqiues

    SciTech Connect

    Diachin, L F; Knupp, P; Munson, T; Shontz, S

    2004-07-08

    We compare inexact Newton and coordinate descent methods for optimizing the quality of a mesh by repositioning the vertices, where quality is measured by the harmonic mean of the mean-ratio metric. The effects of problem size, element size heterogeneity, and various vertex displacement schemes on the performance of these algorithms are assessed for a series of tetrahedral meshes.

  5. The Challenge of Mars EDL (Entry, Descent, and Landing)

    NASA Technical Reports Server (NTRS)

    Sostaric, Ronald

    2010-01-01

    This slide presentation reviews the some of the challenges of Martian atmospheric entry, descent and landing (EDL) on the surface of Mars. It reviews some of the technological difficulties, and some solutions that are being developed for future unmanned missions with larger payloads than previous landers, and ultimately human spacecraft landing.

  6. The Huygens Descent Trajectory Working Group and the Reconstruction of the Huygens Probe Entry and Descent Trajectory at Titan

    NASA Astrophysics Data System (ADS)

    Atkinson, David H.; Kazeminejad, Bobby; Lebreton*, Jean-Pierre

    2015-04-01

    Cassini/Huygens, a flagship mission to explore the rings, atmosphere, magnetic field, and moons that make up the Saturn system, is a joint endeavor of NASA, the European Space Agency, and Agenzia Spaziale Italiana. Comprising two spacecraft - a Saturn orbiter built by NASA and a Titan entry/descent probe built by the European Space Agency - Cassini/Huygens was launched in October 1997 and arrived at Saturn in 2004. The Huygens probe parachuted to the surface of Titan in January 2005. During the descent, six science instruments provided measurements of Titan's atmosphere, clouds, and winds, and photographed Titan's surface. It was recognized early in the Huygens program that to correctly interpret and correlate results from the probe science experiments and to provide a reference set of data for ground truth calibration of the Cassini orbiter remote sensing observations, an accurate reconstruction of the probe entry and descent trajectory and surface landing location would be necessary. The Huygens Descent Trajectory Working Group (DTWG) was chartered in 1996 as a subgroup of the Huygens Science Working Team. With membership comprising representatives from all the probe engineering and instrument teams as well as representatives of industry and the Cassini and Huygens Project Scientists, the DTWG presented an organizational framework within which instrument data was shared, the entry and descent trajectory reconstruction implemented, and the trajectory reconstruction efficiently disseminated. The primary goal of the Descent Trajectory Working Group was to develop retrieval methodologies for the probe descent trajectory reconstruction from the entry interface altitude of 1270 km to the surface using navigation data, and engineering and science data acquired by the instruments on the Huygens Probe, and to provide a reconstruction of the Huygens probe trajectory from entry to the surface of Titan that is maximally consistent with all available engineering and science

  7. Measurement of CPAS Main Parachute Rate of Descent

    NASA Technical Reports Server (NTRS)

    Ray, Eric S.

    2011-01-01

    The Crew Exploration Vehicle Parachute Assembly System (CPAS) is being designed to land the Orion Crew Module (CM) at a safe rate of descent at splashdown. Flight test performance must be measured to a high degree of accuracy to ensure this requirement is met with the most efficient design possible. Although the design includes three CPAS Main parachutes, the requirement is that the system must not exceed 33 ft/s under two Main parachutes, should one of the Main parachutes fail. Therefore, several tests were conducted with clusters of two Mains. All of the steady-state rate of descent data are normalized to standard sea level conditions and checked against the limit. As the Orion design gains weight, the system is approaching this limit to within measurement precision. Parachute "breathing," cluster interactions, and atmospheric anomalies can cause the rate of descent to vary widely and lead to challenges in characterizing parachute terminal performance. An early test had contradictory rate of descent results from optical trajectory and Differential Global Positioning Systems (DGPS). A thorough analysis of the data sources and error propagation was conducted to determine the uncertainty in the trajectory. It was discovered that the Time Space Position Information (TSPI) from the optical tracking provided accurate position data. However, the velocity from TPSI must be computed via numerical differentiation, which is prone to large error. DGPS obtains position through pseudo-range calculations from multiple satellites and velocity through Doppler shift of the carrier frequency. Because the velocity from DGPS is a direct measurement, it is more accurate than TSPI velocity. To remedy the situation, a commercial off-the-shelf product that combines GPS and an Inertial Measurement Unit (IMU) was purchased to significantly improve rate of descent measurements. This had the added benefit of solving GPS dropouts during aircraft extraction. Statistical probability

  8. RITD - Adapting Mars Entry, Descent and Landing System for Earth

    NASA Astrophysics Data System (ADS)

    Heilimo, Jyri; Harri, Ari-Matti; Aleksashkin, Sergei; Koryanov, Valeri; Arruego, Ignacio; Schmidt, Walter; Haukka, Harri; Finchenko, Valeri; Martynov, Maxim; Ponomarenko, Andrey; Kazakovtsev, Victor; Martin, Susana

    2015-04-01

    We have developed an atmospheric re-entry and descent system concept based on inflatable hypersonic decelerator techniques that were originally developed for Mars. The ultimate goal of this EU-funded RITD-project (Re-entry: Inflatable Technology Development) was to assess the benefits of this technology when deploying small payloads from low Earth orbits to the surface of the Earth with modest costs. The principal goal was to assess and develop a preliminary EDLS design for the entire relevant range of aerodynamic regimes expected to be encountered in Earth's atmosphere during entry, descent and landing. Low Earth Orbit (LEO) and even Lunar applications envisaged include the use of the EDLS approach in returning payloads of 4-8 kg down to the surface. Our development and assessments show clearly that this kind of inflatable technology originally developed for the Martian atmosphere, is feasible for use by Earth entry and descent applications. The preliminary results are highly promising indicating that the current Mars probe design could be used as it is for the Earth. According tp our analyses, the higher atmospheric pressure at an altitude of 12 km and less requires an additional pressurizing device for the in atable system increasing the entry mass by approximately 2 kg. These analyses involved the calculation of 120 different atmospheric entry and descent trajectories. The analysis of the existing technologies and current trends have indicated that the kind of inflatable technology pursued by RITD has high potential to enhance the European space technology expertise. This kind of technology is clearly feasible for utilization by Earth entry and descent applications.

  9. Two-dimensional descent through a compressible atmosphere: Sequential deceleration of an unpowered load

    NASA Astrophysics Data System (ADS)

    Silverman, M. P.

    2010-02-01

    Equations, based on Rayleigh's drag law valid for high Reynolds number, are derived for two-dimensional motion through a compressible atmosphere in isentropic equilibrium, such as characterizes the Earth's troposphere. Solutions yield horizontal and vertical displacement, velocity, and acceleration as a function of altitude and ground-level temperature. An exact analytical solution to the equations linearized in the aero-thermodynamic parameter is given; in general the equations must be solved numerically. The theory, applied to the unpowered fall of a large aircraft stabilized to flat descent by symmetrical, sequential deployment of horizontal and vertical decelerators, shows that such an aircraft can be brought down with mean peak deployment and impact decelerations below 10g.

  10. Analysis of various descent trajectories for a hypersonic-cruise, cold-wall research airplane

    NASA Technical Reports Server (NTRS)

    Lawing, P. L.

    1975-01-01

    The probable descent operating conditions for a hypersonic air-breathing research airplane were examined. Descents selected were cruise angle of attack, high dynamic pressure, high lift coefficient, turns, and descents with drag brakes. The descents were parametrically exercised and compared from the standpoint of cold-wall (367 K) aircraft heat load. The descent parameters compared were total heat load, peak heating rate, time to landing, time to end of heat pulse, and range. Trends in total heat load as a function of cruise Mach number, cruise dynamic pressure, angle-of-attack limitation, pull-up g-load, heading angle, and drag-brake size are presented.

  11. Apollo LM guidance computer software for the final lunar descent.

    NASA Technical Reports Server (NTRS)

    Eyles, D.

    1973-01-01

    In all manned lunar landings to date, the lunar module Commander has taken partial manual control of the spacecraft during the final stage of the descent, below roughly 500 ft altitude. This report describes programs developed at the Charles Stark Draper Laboratory, MIT, for use in the LM's guidance computer during the final descent. At this time computational demands on the on-board computer are at a maximum, and particularly close interaction with the crew is necessary. The emphasis is on the design of the computer software rather than on justification of the particular guidance algorithms employed. After the computer and the mission have been introduced, the current configuration of the final landing programs and an advanced version developed experimentally by the author are described.

  12. A Symmetric Time-Varying Cluster Rate of Descent Model

    NASA Technical Reports Server (NTRS)

    Ray, Eric S.

    2015-01-01

    A model of the time-varying rate of descent of the Orion vehicle was developed based on the observed correlation between canopy projected area and drag coefficient. This initial version of the model assumes cluster symmetry and only varies the vertical component of velocity. The cluster fly-out angle is modeled as a series of sine waves based on flight test data. The projected area of each canopy is synchronized with the primary fly-out angle mode. The sudden loss of projected area during canopy collisions is modeled at minimum fly-out angles, leading to brief increases in rate of descent. The cluster geometry is converted to drag coefficient using empirically derived constants. A more complete model is under development, which computes the aerodynamic response of each canopy to its local incidence angle.

  13. Efficient Sensor Placement Optimization Using Gradient Descent and Probabilistic Coverage

    PubMed Central

    Akbarzadeh, Vahab; Lévesque, Julien-Charles; Gagné, Christian; Parizeau, Marc

    2014-01-01

    We are proposing an adaptation of the gradient descent method to optimize the position and orientation of sensors for the sensor placement problem. The novelty of the proposed method lies in the combination of gradient descent optimization with a realistic model, which considers both the topography of the environment and a set of sensors with directional probabilistic sensing. The performance of this approach is compared with two other black box optimization methods over area coverage and processing time. Results show that our proposed method produces competitive results on smaller maps and superior results on larger maps, while requiring much less computation than the other optimization methods to which it has been compared. PMID:25196164

  14. Helicopter optimal descent and landing after power loss

    NASA Technical Reports Server (NTRS)

    Johnson, W.

    1977-01-01

    An optimal control solution is obtained for the descent and landing of a helicopter after the loss of power in level flight. The model considers the helicopter vertical velocity, horizontal velocity, and rotor speed; and it includes representations of ground effect, rotor inflow time lag, pilot reaction time, rotor stall, and the induced velocity curve in the vortex ring state. The control (rotor thrust magnitude and direction) required to minimize the vertical and horizontal velocity at contact with the ground is obtained using nonlinear optimal control theory. It is found that the optimal descent after power loss in hover is a purely vertical flight path. Good correlation, even quantitatively, is found between the calculations and (non-optimal) flight test results.

  15. RITD - Adapting Mars Entry, Descent and Landing System for Earth

    NASA Astrophysics Data System (ADS)

    Haukka, H.; Heilimo, J.; Harri, A.-M.; Aleksashkin, S.; Koryanov, V.; Arruego, I.; Schmidt, W.; Finchenko, V.; Martynov, M.; Ponomarenko, A.; Kazakovtsev, V.; Martin, S.

    2015-10-01

    We have developed an atmospheric re-entry and descent system concept based on inflatable hypersonic decelerator techniques that were originally developed for Mars. The ultimate goal of this EU-funded RITD-project (Re-entry: Inflatable Technology Development) was to assess the benefits of this technology when deploying small payloads from low Earth orbits to the surface of the Earth with modest costs. The principal goal was to assess and develop a preliminary EDLS design for the entire relevant range of aerodynamic regimes expected to be encountered in Earth's atmosphere during entry, descent and landing. Low Earth Orbit (LEO) and even Lunar applications envisaged include the use of the EDLS approach in returning payloads of 4-8 kg down to the surface.

  16. Flight Management System Execution of Idle-Thrust Descents in Operations

    NASA Technical Reports Server (NTRS)

    Stell, Laurel L.

    2011-01-01

    To enable arriving aircraft to fly optimized descents computed by the flight management system (FMS) in congested airspace, ground automation must accurately predict descent trajectories. To support development of the trajectory predictor and its error models, commercial flights executed idle-thrust descents, and the recorded data includes the target speed profile and FMS intent trajectories. The FMS computes the intended descent path assuming idle thrust after top of descent (TOD), and any intervention by the controllers that alters the FMS execution of the descent is recorded so that such flights are discarded from the analysis. The horizontal flight path, cruise and meter fix altitudes, and actual TOD location are extracted from the radar data. Using more than 60 descents in Boeing 777 aircraft, the actual speeds are compared to the intended descent speed profile. In addition, three aspects of the accuracy of the FMS intent trajectory are analyzed: the meter fix crossing time, the TOD location, and the altitude at the meter fix. The actual TOD location is within 5 nmi of the intent location for over 95% of the descents. Roughly 90% of the time, the airspeed is within 0.01 of the target Mach number and within 10 KCAS of the target descent CAS, but the meter fix crossing time is only within 50 sec of the time computed by the FMS. Overall, the aircraft seem to be executing the descents as intended by the designers of the onboard automation.

  17. The African Descent and Glaucoma Evaluation Study (ADAGES): Design and Baseline Data

    PubMed Central

    Sample, Pamela A.; Girkin, Christopher A.; Zangwill, Linda M.; Jain, Sonia; Racette, Lyne; Becerra, Lida M.; Weinreb, Robert N.; Medeiros, Felipe A.; Wilson, M. Roy; De León-Ortega, Julio; Tello, Celso; Bowd, Christopher; Liebmann, Jeffrey M.

    2009-01-01

    Objective To identify factors accounting for differences in glaucoma onset and rate of progression between individuals of African descent and European descent. Design A prospective, multicenter observational cohort study of 1221 participants of African descent and European descent with no glaucoma (normal), suspected glaucoma, and glaucoma. Six hundred eighty-six patient participants in the African Descent and Glaucoma Evaluation Study will be followed up longitudinally. Four hundred thirty-six participants of European descent from the Diagnostic Innovations in Glaucoma Study (DIGS) were also included. Baseline demographics, visual function (standard automated perimetry, short-wavelength automated perimetry, frequency doubling technology perimetry), optic nerve structure (retina tomography, optical coherence tomography), clinical status, and risk factors were measured. Results Individuals of African descent had (1) thinner corneas (P<.001) across all diagnostic groups, (2) a higher percentage of reported diabetes mellitus (P<.001) and high blood pressure (P<.001) and a lower percentage of reported heart disease (P=.001), and (3) worse pattern standard deviation for standard automated perimetry fields overall (P=.001) and within normal limits (P=.01) than individuals of European descent. No differences were present for mean intraocular pressure (P=.79). Conclusions Significant baseline differences were found in a number of clinical findings between persons of African descent compared with European descent. Longitudinal data from the African Descent and Glaucoma Evaluation Study will be important for determining which baseline features are important and predictive for accurate diagnosis and follow-up in this high-risk group. PMID:19752422

  18. Biomechanical Analysis of Stair Descent in Patients with Knee Osteoarthritis

    PubMed Central

    Igawa, Tatsuya; Katsuhira, Junji

    2014-01-01

    [Purpose] The purposes of this study were to investigate the lower extremity joint kinematics and kinetics of patients with the knee osteoarthritis (knee OA) during stair descent and clarify the biomechanical factors related to their difficulty in stair descent. [Subjects and Methods] Eight healthy elderly persons and four knee OA patients participated in this study. A 3-D motion analysis system and force plates were employed to measure lower extremity joint angles, ranges of motion, joint moments, joint powers, and ratios of contribution for the joint powers while descending stairs. [Results] Knee joint flexion angle, extension moment, and negative power during the early stance phase in the knee OA group were smaller than those in the healthy subjects group. However, no significant changes in these parameters in the ankle joint were observed between the two subject groups. [Conclusion] Knee OA patients could not use the knee joint to absorb impact during the early stance phase of stair descent. Hence, they might compensate for the roles played by the intact knee joint by mainly using ipsilateral ankle kinematics and kinetics. PMID:24926119

  19. Biomechanical analysis of stair descent in patients with knee osteoarthritis.

    PubMed

    Igawa, Tatsuya; Katsuhira, Junji

    2014-05-01

    [Purpose] The purposes of this study were to investigate the lower extremity joint kinematics and kinetics of patients with the knee osteoarthritis (knee OA) during stair descent and clarify the biomechanical factors related to their difficulty in stair descent. [Subjects and Methods] Eight healthy elderly persons and four knee OA patients participated in this study. A 3-D motion analysis system and force plates were employed to measure lower extremity joint angles, ranges of motion, joint moments, joint powers, and ratios of contribution for the joint powers while descending stairs. [Results] Knee joint flexion angle, extension moment, and negative power during the early stance phase in the knee OA group were smaller than those in the healthy subjects group. However, no significant changes in these parameters in the ankle joint were observed between the two subject groups. [Conclusion] Knee OA patients could not use the knee joint to absorb impact during the early stance phase of stair descent. Hence, they might compensate for the roles played by the intact knee joint by mainly using ipsilateral ankle kinematics and kinetics.

  20. Titan Explorer Entry, Descent and Landing Trajectory Design

    NASA Technical Reports Server (NTRS)

    Fisher, Jody L.; Lindberg, Robert E.; Lockwood, Mary Kae

    2006-01-01

    The Titan Explorer mission concept includes an orbiter, entry probe and inflatable airship designed to take remote and in-situ measurements of Titan's atmosphere. A modified entry, descent and landing trajectory at Titan that incorporates mid-air airship inflation (under a parachute) and separation is developed and examined for Titan Explorer. The feasibility of mid-air inflation and deployment of an airship under a parachute is determined by implementing and validating an airship buoyancy and inflation model in the trajectory simulation program, Program to Optimize Simulated Trajectories II (POST2). A nominal POST2 trajectory simulation case study is generated which examines different descent scenarios by varying airship inflation duration, orientation, and separation. The buoyancy model incorporation into POST2 is new to the software and may be used in future trajectory simulations. Each case from the nominal POST2 trajectory case study simulates a successful separation between the parachute and airship systems with sufficient velocity change as to alter their paths to avoid collision throughout their descent. The airship and heatshield also separate acceptably with a minimum distance of separation from the parachute system of 1.5 km. This analysis shows the feasibility of airship inflation on a parachute for different orientations, airship separation at various inflation times, and preparation for level-flight at Titan.

  1. A new method for forecasting the solar cycle descent time

    NASA Astrophysics Data System (ADS)

    Kakad, Bharati; Kakad, Amar; Sai Ramesh, Durbha

    2015-08-01

    The prediction of an extended solar minimum is extremely important because of the severity of its impact on the near-earth space. Here, we present a new method for predicting the descent time of the forthcoming solar cycle (SC); the method is based on the estimation of the Shannon entropy. We use the daily and monthly smoothed international sunspot number. For each nth SC, we compute the parameter [Tpre]n by using information on the descent and ascent times of the n - 3th and nth SCs, respectively. We find that [Tpre] of nth SC and entropy can be effectively used to predict the descent time of the n + 2th SC. The correlation coefficient between [Td]n+2 - [Tpre]n and [E]n is found to be 0.95. Using these parameters the prediction model is developed. Solar magnetic field and F10.7 flux data are available for SCs 21-22 and 19-23, respectively, and they are also utilized to get estimates of the Shannon entropy. It is found that the Shannon entropy, a measure of randomness inherent in the SC, is reflected well in the various proxies of the solar activity (viz sunspot, magnetic field, F10.7 flux). The applicability and accuracy of the prediction model equation is verified by way of association of least entropy values with the Dalton minimum. The prediction model equation also provides possible criteria for the occurrence of unusually longer solar minima.

  2. Factors Associated with Sleep Disturbance in Women of Mexican Descent

    PubMed Central

    Heilemann, MarySue V.; Choudhury, Shonali M.; Kury, Felix Salvador; Lee, Kathryn A.

    2014-01-01

    Aims The aims were to identify the most useful parameters of acculturation in relation to self reported sleep disturbance and describe risk factors for sleep disturbance in women of Mexican descent. Background Little is known about acculturation as a factor for poor sleep in the context of other personal factors such as income or sense of resilience or mastery for Latinas in the United States. Methods These personal factors were incorporated into a modification of the Conceptual Framework of Impaired Sleep to guide our secondary analysis of self-reported sleep disturbance. Cross sectional data from a convenience sample of 312 women of Mexican descent of childbearing age (21-40 years) located in an urban California community were collected and previously analyzed in relation to depressive symptoms and post traumatic stress disorder. The General Sleep Disturbance Scale (in English and Spanish) was used to assess sleep disturbance. Results Early socialization to the United States during childhood was the most useful acculturation parameter for understanding self reported sleep disturbance in this sample. In a multivariate regression analysis, three factors (higher acculturation, lower income, and higher depressive symptoms) were significant in accounting for 40% of the variance in sleep disturbance. Conclusion When low income Latinas of Mexican descent report sleep problems, clinicians should probe for environmental sleep factors associated with low income, such as noise, over-crowding, and exposure to trauma and violence, and refer the woman to psychotherapy and counselling rather than merely prescribe a sleep medication. PMID:22221152

  3. Entry, Descent, and Landing Performance of the Mars Phoenix Lander

    NASA Technical Reports Server (NTRS)

    Desai, Prasun N.; Prince, Jill L.; Wueen, Eric M.; Cruz, Juan R.; Grover, Myron R.

    2008-01-01

    On May 25, 2008, the Mars Phoenix Lander successfully landed on the northern arctic plains of Mars. An overview of a preliminary reconstruction analysis performed on each entry, descent, and landing phase to assess the performance of Phoenix as it descended is presented and a comparison to pre-entry predictions is provided. The landing occurred 21 km further downrange than the predicted landing location. Analysis of the flight data revealed that the primary cause of Phoenix s downrange landing was a higher trim total angle of attack during the hypersonic phase of the entry, which resulted in Phoenix flying a slightly lifting trajectory. The cause of this higher trim attitude is not known at this time. Parachute deployment was 6.4 s later than prediction. This later deployment time was within the variations expected and is consistent with a lifting trajectory. The parachute deployment and inflation process occurred as expected with no anomalies identified. The subsequent parachute descent and powered terminal landing also behaved as expected. A preliminary reconstruction of the landing day atmospheric density profile was found to be lower than the best apriori prediction, ranging from a few percent less to a maximum of 8%. A comparison of the flight reconstructed trajectory parameters shows that the actual Phoenix entry, descent, and landing was close to pre-entry predictions. This reconstruction investigation is currently ongoing and the results to date are in the process of being refined.

  4. Free-falls and parachute descents in the standard atmosphere

    NASA Technical Reports Server (NTRS)

    Webster, A P

    1947-01-01

    A detailed table of the standard equilibrium velocity and standard equilibrium time is presented for bodies falling in the standard atmosphere. This table gives the velocity at various altitudes and the time of fall from sea level to -4000 feet and from 80,000 feet to sea level. In addition to this standard table, there are given short tables and charts of an open-parachute descent and free-falls; the terminal velocity at sea level, and the variation of the weight-to-drag ratio (2w/cds)1/2 for various weight jumpers from 90 to 30 feet in open-parachute descent; and estimations of drag coefficients of silk and nylon parachutes. The table of standard equilibrium velocities and standard equilibrium times may be used directly for open-parachute descents, given the weight of the jumper, the diameter of the parachute, and the drag coefficient. For free-falls starting from horizontal flight, approximately 14 seconds must be added to the equilibrium time given in the table to obtain the total time to sea level. (author)

  5. Airborne Management of Traffic Conflicts in Descent With Arrival Constraints

    NASA Technical Reports Server (NTRS)

    Doble, Nathan A.; Barhydt, Richard; Krishnamurthy, Karthik

    2005-01-01

    NASA is studying far-term air traffic management concepts that may increase operational efficiency through a redistribution of decisionmaking authority among airborne and ground-based elements of the air transportation system. One component of this research, En Route Free Maneuvering, allows trained pilots of equipped autonomous aircraft to assume responsibility for traffic separation. Ground-based air traffic controllers would continue to separate traffic unequipped for autonomous operations and would issue flow management constraints to all aircraft. To evaluate En Route Free Maneuvering operations, a human-in-the-loop experiment was jointly conducted by the NASA Ames and Langley Research Centers. In this experiment, test subject pilots used desktop flight simulators to resolve conflicts in cruise and descent, and to adhere to air traffic flow constraints issued by test subject controllers. Simulators at NASA Langley were equipped with a prototype Autonomous Operations Planner (AOP) flight deck toolset to assist pilots with conflict management and constraint compliance tasks. Results from the experiment are presented, focusing specifically on operations during the initial descent into the terminal area. Airborne conflict resolution performance in descent, conformance to traffic flow management constraints, and the effects of conflicting traffic on constraint conformance are all presented. Subjective data from subject pilots are also presented, showing perceived levels of workload, safety, and acceptability of autonomous arrival operations. Finally, potential AOP functionality enhancements are discussed along with suggestions to improve arrival procedures.

  6. Mars Science Laboratory: Entry, Descent, and Landing System Performance

    NASA Technical Reports Server (NTRS)

    Way, David W.; Powell, Richard W.; Chen, Allen; Steltzner, Adam D.; San Martin, Alejandro M.; Burkhart, Paul D.; mendeck, Gavin F.

    2006-01-01

    In 2010, the Mars Science Laboratory (MSL) mission will pioneer the next generation of robotic Entry, Descent, and Landing (EDL) systems, by delivering the largest and most capable rover to date to the surface of Mars. To do so, MSL will fly a guided lifting entry at a lift-to-drag ratio in excess of that ever flown at Mars, deploy the largest parachute ever at Mars, and perform a novel Sky Crane maneuver. Through improved altitude capability, increased latitude coverage, and more accurate payload delivery, MSL is allowing the science community to consider the exploration of previously inaccessible regions of the planet. The MSL EDL system is a new EDL architecture based on Viking heritage technologies and designed to meet the challenges of landing increasing massive payloads on Mars. In accordance with level-1 requirements, the MSL EDL system is being designed to land an 850 kg rover to altitudes as high as 1 km above the Mars Orbiter Laser Altimeter defined areoid within 10 km of the desired landing site. Accordingly, MSL will enter the largest entry mass, fly the largest 70 degree sphere-cone aeroshell, generate the largest hypersonic lift-to-drag ratio, and deploy the largest Disk-Gap-Band supersonic parachute of any previous mission to Mars. Major EDL events include a hypersonic guided entry, supersonic parachute deploy and inflation, subsonic heatshield jettison, terminal descent sensor acquisition, powered descent initiation, sky crane terminal descent, rover touchdown detection, and descent stage flyaway. Key performance metrics, derived from level-1 requirements and tracked by the EDL design team to indicate performance capability and timeline margins, include altitude and range at parachute deploy, time on radar, and propellant use. The MSL EDL system, which will continue to develop over the next three years, will enable a notable extension in the advancement of Mars surface science by delivering more science capability than ever before to the surface of

  7. Mars Science Laboratory: Entry, Descent, and Landing System Performance

    NASA Technical Reports Server (NTRS)

    Way, David W.; Powell, Richard W.; Chen, Allen; SanMartin, A. Miguel; Burkhart, P. Daniel; Mendeck, Gavin F.

    2007-01-01

    In 2010, the Mars Science Laboratory (MSL) mission will pioneer the next generation of robotic Entry, Descent, and Landing (EDL) systems, by delivering the largest and most capable rover to date to the surface of Mars. To do so, MSL will fly a guided lifting entry at a lift-to-drag ratio in excess of that ever flown at Mars, deploy the largest parachute ever at Mars, and perform a novel Sky Crane maneuver. Through improved altitude capability, increased latitude coverage, and more accurate payload delivery, MSL is allowing the science community to consider the exploration of previously inaccessible regions of the planet. The MSL EDL system is a new EDL architecture based on Viking heritage technologies and designed to meet the challenges of landing increasing massive payloads on Mars. In accordance with level-1 requirements, the MSL EDL system is being designed to land an 850 kg rover to altitudes as high as 1 km above the Mars Orbiter Laser Altimeter defined areoid within 10 km of the desired landing site. Accordingly, MSL will enter the largest entry mass, fly the largest 70 degree sphere-cone aeroshell, generate the largest hypersonic lift-to-drag ratio, and deploy the largest Disk-Gap-Band supersonic parachute of any previous mission to Mars. Major EDL events include a hypersonic guided entry, supersonic parachute deploy and inflation, subsonic heatshield jettison, terminal descent sensor acquisition, powered descent initiation, sky crane terminal descent, rover touchdown detection, and descent stage flyaway. Key performance metrics, derived from level-1 requirements and tracked by the EDL design team to indicate performance capability and timeline margins, include altitude and range at parachute deploy, time on radar, and propellant use. The MSL EDL system, which will continue to develop over the next three years, will enable a notable extension in the advancement of Mars surface science by delivering more science capability than ever before to the surface of

  8. Descent of the hyoid in chimpanzees: evolution of face flattening and speech.

    PubMed

    Nishimura, Takeshi; Mikami, Akichika; Suzuki, Juri; Matsuzawa, Tetsuro

    2006-09-01

    The human supralaryngeal vocal tract develops to form a unique two-tube configuration with equally long horizontal and vertical cavities. This anatomy contributes greatly to the morphological foundations of human speech. It is believed to depend on the reduced growth of the palate and on the developmental descent of the larynx relative to the palate. Anatomically, the descent of the larynx is accomplished through both the descent of the laryngeal skeleton relative to the hyoid and the descent of the hyoid relative to the palate. We have studied the development of three living chimpanzees using magnetic resonance imaging. Our previous study showed that, as in humans, chimpanzees show rapid laryngeal descent, with changes in the relative proportion of the vocal tract during early infancy. However, this is not accompanied by the descent of the hyoid relative to the palate, although it is achieved with the descent of the laryngeal skeleton relative to the hyoid. Here, we show that subsequently the chimpanzee hyoid also descends to maintain the rapid descent of the larynx, similarly to humans. We argue that the descent of the larynx probably evolved in a common ancestor of extant hominoids, originally to confer an advantage via a function unrelated to speech. Thus, the descent of the larynx per se is not unique to humans, and facial flattening was probably the major factor that paved the way for speech in the human lineage.

  9. Steepest-entropy-ascent quantum thermodynamic modeling of the relaxation process of isolated chemically reactive systems using density of states and the concept of hypoequilibrium state

    NASA Astrophysics Data System (ADS)

    Li, Guanchen; von Spakovsky, Michael R.

    2016-01-01

    This paper presents a study of the nonequilibrium relaxation process of chemically reactive systems using steepest-entropy-ascent quantum thermodynamics (SEAQT). The trajectory of the chemical reaction, i.e., the accessible intermediate states, is predicted and discussed. The prediction is made using a thermodynamic-ensemble approach, which does not require detailed information about the particle mechanics involved (e.g., the collision of particles). Instead, modeling the kinetics and dynamics of the relaxation process is based on the principle of steepest-entropy ascent (SEA) or maximum-entropy production, which suggests a constrained gradient dynamics in state space. The SEAQT framework is based on general definitions for energy and entropy and at least theoretically enables the prediction of the nonequilibrium relaxation of system state at all temporal and spatial scales. However, to make this not just theoretically but computationally possible, the concept of density of states is introduced to simplify the application of the relaxation model, which in effect extends the application of the SEAQT framework even to infinite energy eigenlevel systems. The energy eigenstructure of the reactive system considered here consists of an extremely large number of such levels (on the order of 10130) and yields to the quasicontinuous assumption. The principle of SEA results in a unique trajectory of system thermodynamic state evolution in Hilbert space in the nonequilibrium realm, even far from equilibrium. To describe this trajectory, the concepts of subsystem hypoequilibrium state and temperature are introduced and used to characterize each system-level, nonequilibrium state. This definition of temperature is fundamental rather than phenomenological and is a generalization of the temperature defined at stable equilibrium. In addition, to deal with the large number of energy eigenlevels, the equation of motion is formulated on the basis of the density of states and a set of

  10. Evaluation of the orientation of the steepest meridian of regular astigmatism among highly myopic Egyptian patients seeking non-ablative surgical correction of the refractive error

    PubMed Central

    Refai, Tamer Adel

    2015-01-01

    Introduction: LASIK surgery is currently the preferred procedure to correct low to moderate myopia. The aim of this study was to determine the orientation of the steepest meridian of regular astigmatism in order to determine the relative incidence of vertical, horizontal, and oblique regular astigmatism among highly myopic Egyptian patients seeking non-ablative surgical correction of the refractive error. Methods: One hundred and one eyes of 68 highly myopic patients who were seeking refractive surgery were included in this consecutive case series study. The refractive errors were measured using an autorefractometer and confirmed by trial. We measured the uncorrected and best corrected visual acuity in Snellen lines. Keratometry, central corneal thickness, and anterior chamber depth also were measured. The cylinder power in diopters and the axis in degrees were reported. Astigmatism was graded as with the rule (i.e., vertical meridian steeper), against the rule (i.e., horizontal meridian steeper), and oblique astigmatism. The number and the percentage of eyes with the rule, against the rule, and oblique astigmatism were calculated, and the chi-squared test was performed to analyze the data. Results: The spherical refractive error ranged from −6.5 to −24.5 diopters (−13.45 ± 4.60). The cylinder power (Cyl) ranged from −0.25 to −7.5 diopters (−2.23 ± 1.28). The uncorrected visual acuity (UCVA) in Snellen lines ranged from 0.01 – 0.1 (0.03 ± 0.02). The mean for best corrected visual acuity (BCVA) in Snellen lines was 0.40 (± 0.23). The steepest meridian was vertical (i.e., with-the-rule astigmatism) in 44 eyes (43.56%), horizontal (i.e., against-the-rule astigmatism) in 27 eyes (26.73%), and oblique (i.e., oblique astigmatism) in 30 eyes (29.70%). Conclusions: The incidence of with-the-rule astigmatism in patients with high myopia was found to be much lower than in previous studies for non-myopic patients, with a higher incidence for against

  11. Linear Accelerators

    SciTech Connect

    Sidorin, Anatoly

    2010-01-05

    In linear accelerators the particles are accelerated by either electrostatic fields or oscillating Radio Frequency (RF) fields. Accordingly the linear accelerators are divided in three large groups: electrostatic, induction and RF accelerators. Overview of the different types of accelerators is given. Stability of longitudinal and transverse motion in the RF linear accelerators is briefly discussed. The methods of beam focusing in linacs are described.

  12. Entry, Descent, and Landing for Human Mars Missions

    NASA Technical Reports Server (NTRS)

    Munk, Michelle M.; DwyerCianciolo, Alicia M.

    2012-01-01

    One of the most challenging aspects of a human mission to Mars is landing safely on the Martian surface. Mars has such low atmospheric density that decelerating large masses (tens of metric tons) requires methods that have not yet been demonstrated, and are not yet planned in future Mars missions. To identify the most promising options for Mars entry, descent, and landing, and to plan development of the needed technologies, NASA's Human Architecture Team (HAT) has refined candidate methods for emplacing needed elements of the human Mars exploration architecture (such as ascent vehicles and habitats) on the Mars surface. This paper explains the detailed, optimized simulations that have been developed to define the mass needed at Mars arrival to accomplish the entry, descent, and landing functions. Based on previous work, technology options for hypersonic deceleration include rigid, mid-L/D (lift-to-drag ratio) aeroshells, and inflatable aerodynamic decelerators (IADs). The hypersonic IADs, or HIADs, are about 20% less massive than the rigid vehicles, but both have their technology development challenges. For the supersonic regime, supersonic retropropulsion (SRP) is an attractive option, since a propulsive stage must be carried for terminal descent and can be ignited at higher speeds. The use of SRP eliminates the need for an additional deceleration system, but SRP is at a low Technology Readiness Level (TRL) in that the interacting plumes are not well-characterized, and their effect on vehicle stability has not been studied, to date. These architecture-level assessments have been used to define the key performance parameters and a technology development strategy for achieving the challenging mission of landing large payloads on Mars.

  13. INSL3/RXFP2 signaling in testicular descent.

    PubMed

    Feng, Shu; Ferlin, Alberto; Truong, Anne; Bathgate, Ross; Wade, John D; Corbett, Sean; Han, Shuo; Tannour-Louet, Mounia; Lamb, Dolores J; Foresta, Carlo; Agoulnik, Alexander I

    2009-04-01

    Mutations of the insulin-like peptide 3 (INSL3) hormone or its receptor, RXFP2, cause intraabdominal cryptorchidism in male mice. Specific RXFP2 expression in mouse gubernacula was detected at embryonic day 14.5 and markedly increased after birth in the developing cremaster muscle, as well as in the epididymis and testicular Leydig and germ cells. INSL3 treatment stimulated cell proliferation of embryonic gubernacular and Leydig cells, implicating active INSL3-mediated signaling. The transcription factor SOX9, a known male sex determination factor, upregulated the activity of the RXFP2 promoter. INSL3 is sufficient to direct the first transabdominal phase of testicular descent in the absence of hypothalamic-pituitary-gonadal axis signaling or Hoxa10, although these factors are important for inguinoscrotal testicular descent. Similarly, conditional ablation of the androgen receptor gene in gubernacular cells resulted in disruption of inguinoscrotal descent. We performed mutation screening of INSL3 and RXFP2 in human patients with cryptorchidism and control subjects from different populations in Europe and the USA. Several missense mutations were described in both the INSL3 and RXFP2 genes. A novel V39G INSL3 mutation in a patient with cryptorchidism was identified; however, the functional analysis of the mutant peptide did not reveal compromised function. In more than 2000 patients and controls analyzed to date, the T222P RXFP2 mutation is the only one strongly associated with the mutant phenotype. The T222P mutant receptor, when transfected into 293T cells, had severely decreased cell membrane expression, providing the basis for the functional deficiency of this mutation.

  14. Powered Descent Guidance with General Thrust-Pointing Constraints

    NASA Technical Reports Server (NTRS)

    Carson, John M., III; Acikmese, Behcet; Blackmore, Lars

    2013-01-01

    The Powered Descent Guidance (PDG) algorithm and software for generating Mars pinpoint or precision landing guidance profiles has been enhanced to incorporate thrust-pointing constraints. Pointing constraints would typically be needed for onboard sensor and navigation systems that have specific field-of-view requirements to generate valid ground proximity and terrain-relative state measurements. The original PDG algorithm was designed to enforce both control and state constraints, including maximum and minimum thrust bounds, avoidance of the ground or descent within a glide slope cone, and maximum speed limits. The thrust-bound and thrust-pointing constraints within PDG are non-convex, which in general requires nonlinear optimization methods to generate solutions. The short duration of Mars powered descent requires guaranteed PDG convergence to a solution within a finite time; however, nonlinear optimization methods have no guarantees of convergence to the global optimal or convergence within finite computation time. A lossless convexification developed for the original PDG algorithm relaxed the non-convex thrust bound constraints. This relaxation was theoretically proven to provide valid and optimal solutions for the original, non-convex problem within a convex framework. As with the thrust bound constraint, a relaxation of the thrust-pointing constraint also provides a lossless convexification that ensures the enhanced relaxed PDG algorithm remains convex and retains validity for the original nonconvex problem. The enhanced PDG algorithm provides guidance profiles for pinpoint and precision landing that minimize fuel usage, minimize landing error to the target, and ensure satisfaction of all position and control constraints, including thrust bounds and now thrust-pointing constraints.

  15. Guidance and Control During Direct-Descent Parabolic Reentry

    NASA Technical Reports Server (NTRS)

    Foudriat, Edwin C.; Wingrove, Rodney C.

    1961-01-01

    The results of studies of four reentry guidance and control techniques for the energy management of vehicles returning to the earth at escape speeds are compared in this paper. The reentry trajectories are constrained to those of direct descent, that is, where the vehicle does not leave that portion of the atmosphere where useful aerodynamic forces are available after its initial entry. The guidance techniques compared are: (1) a piloted simulator study reference trajectory techniques; 2) An automatic controller using reference trajectory techniques; 3) A predictor system employing linear prediction (perturbation) techniques; and 4) A repetitive prediction system employing rapid-time computer techniques.

  16. Shuttle program: OFT ascent/descent ancillary data requirements document

    NASA Technical Reports Server (NTRS)

    Bond, A. C., Jr.; Knoedler, J.

    1980-01-01

    Requirements are presented for the ascent/descent (A/D) navigation and attitude-dependent ancillary data products to be generated for the space shuttle orbiter in support of the orbital flight test (OFT) flight test requirements, MPAD guidance and navigation performance assessment, and the mission evaluation team. The A/D ancillary data support for OFT mission evaluation activities is confined to providing postflight position, velocity, attitude, and associated navigation and attitude derived parameters for the Orbiter over particular flight phases and time intervals.

  17. Revalidation of the Huygens Descent Control Sub-System

    NASA Technical Reports Server (NTRS)

    2005-01-01

    The Huygens probe, part of the Cassini mission to Saturn, is designed to investigate the atmosphere of Titan, Saturn's largest moon. The passage of the probe through the atmosphere is controlled by the Descent Control Sub-System (DCSS), which consists of three parachutes and associated mechanisms. The Cassini / Huygens mission was launched in October 1997 and was designed during the early 1990's. During the time since the design and launch, analysis capabilities have improved significantly, knowledge of the Titan environment has improved and the baseline mission has been modified. Consequently, a study was performed to revalidate the DCSS design against the current predictions.

  18. OFT ascent/descent ancillary data requirements document

    NASA Technical Reports Server (NTRS)

    Bond, A. C., Jr.; Abramson, B.

    1978-01-01

    Requirements are presented for the ascent/descent (A/D) navigation and attitude-dependent ancillary data products to be generated for the space shuttle orbiter in support of orbital flight test requirements, MPAD guidance and navigation performance assessment, and the mission evaluation team. It was intended that this document serve as the sole requirements control instrument between MPB/MPAD and the A/D ancillary data users. The requirements are primarily functional in nature, but some detail level requirements are also included.

  19. STS-1 operational flight profile. Volume 5: Descent, cycle 3. Appendix C: Monte Carlo dispersion analysis

    NASA Technical Reports Server (NTRS)

    1980-01-01

    The results of three nonlinear the Monte Carlo dispersion analyses for the Space Transportation System 1 Flight (STS-1) Orbiter Descent Operational Flight Profile, Cycle 3 are presented. Fifty randomly selected simulation for the end of mission (EOM) descent, the abort once around (AOA) descent targeted line are steep target line, and the AOA descent targeted to the shallow target line are analyzed. These analyses compare the flight environment with system and operational constraints on the flight environment and in some cases use simplified system models as an aid in assessing the STS-1 descent flight profile. In addition, descent flight envelops are provided as a data base for use by system specialists to determine the flight readiness for STS-1. The results of these dispersion analyses supersede results of the dispersion analysis previously documented.

  20. Essential equivalence of the general equation for the nonequilibrium reversible-irreversible coupling (GENERIC) and steepest-entropy-ascent models of dissipation for nonequilibrium thermodynamics.

    PubMed

    Montefusco, Alberto; Consonni, Francesco; Beretta, Gian Paolo

    2015-04-01

    By reformulating the steepest-entropy-ascent (SEA) dynamical model for nonequilibrium thermodynamics in the mathematical language of differential geometry, we compare it with the primitive formulation of the general equation for the nonequilibrium reversible-irreversible coupling (GENERIC) model and discuss the main technical differences of the two approaches. In both dynamical models the description of dissipation is of the "entropy-gradient" type. SEA focuses only on the dissipative, i.e., entropy generating, component of the time evolution, chooses a sub-Riemannian metric tensor as dissipative structure, and uses the local entropy density field as potential. GENERIC emphasizes the coupling between the dissipative and nondissipative components of the time evolution, chooses two compatible degenerate structures (Poisson and degenerate co-Riemannian), and uses the global energy and entropy functionals as potentials. As an illustration, we rewrite the known GENERIC formulation of the Boltzmann equation in terms of the square root of the distribution function adopted by the SEA formulation. We then provide a formal proof that in more general frameworks, whenever all degeneracies in the GENERIC framework are related to conservation laws, the SEA and GENERIC models of the dissipative component of the dynamics are essentially interchangeable, provided of course they assume the same kinematics. As part of the discussion, we note that equipping the dissipative structure of GENERIC with the Leibniz identity makes it automatically SEA on metric leaves.

  1. Scintillation-producing Fresnel-scale irregularities associated with the regions of steepest TEC gradients adjacent to the equatorial ionization anomaly

    NASA Astrophysics Data System (ADS)

    Muella, M. T. A. H.; Kherani, E. A.; de Paula, E. R.; Cerruti, A. P.; Kintner, P. M.; Kantor, I. J.; Mitchell, C. N.; Batista, I. S.; Abdu, M. A.

    2010-03-01

    Using ground-based GPS and digital ionosonde instruments, we have built up at latitudes of the equatorial ionization anomaly (EIA), in the Brazilian sector, a time-evolving picture of total electron content (TEC), L-band amplitude scintillations, and F region heights, and we have investigated likely reasons for the occurrence or suppression of equatorial scintillations during the disturbed period of 18-23 November 2003. During the prestorm quiet nights, scintillations are occurring postsunset, as expected; however, during the storm time period, their spatial-temporal characteristics and intensity modify significantly owing to the dramatic changes in the ionospheric plasma density distribution and in the temporal evolution of TEC. The two-dimensional maps showing both TEC and amplitude scintillations revealed strong evidence of turbulences at the Fresnel length (causing scintillations) concurrent with those regions of steepest TEC gradients adjacent to the crests of the EIA. The largest density gradients have been found to occur in an environment of increased background electron density, and their spatial distribution and location during the disturbed period may differ significantly from the magnetic quiet night pattern. However, in terms of magnitude the gradients at equatorial and low latitudes appear to not change during both magnetic quiet and disturbed conditions. The scenarios for the formation or suppression of scintillation-producing Fresnel-scale irregularities during the prestorm quiet nights and disturbed nights are discussed in view of different competing effects computed from numerical simulation techniques.

  2. Essential equivalence of the general equation for the nonequilibrium reversible-irreversible coupling (GENERIC) and steepest-entropy-ascent models of dissipation for nonequilibrium thermodynamics.

    PubMed

    Montefusco, Alberto; Consonni, Francesco; Beretta, Gian Paolo

    2015-04-01

    By reformulating the steepest-entropy-ascent (SEA) dynamical model for nonequilibrium thermodynamics in the mathematical language of differential geometry, we compare it with the primitive formulation of the general equation for the nonequilibrium reversible-irreversible coupling (GENERIC) model and discuss the main technical differences of the two approaches. In both dynamical models the description of dissipation is of the "entropy-gradient" type. SEA focuses only on the dissipative, i.e., entropy generating, component of the time evolution, chooses a sub-Riemannian metric tensor as dissipative structure, and uses the local entropy density field as potential. GENERIC emphasizes the coupling between the dissipative and nondissipative components of the time evolution, chooses two compatible degenerate structures (Poisson and degenerate co-Riemannian), and uses the global energy and entropy functionals as potentials. As an illustration, we rewrite the known GENERIC formulation of the Boltzmann equation in terms of the square root of the distribution function adopted by the SEA formulation. We then provide a formal proof that in more general frameworks, whenever all degeneracies in the GENERIC framework are related to conservation laws, the SEA and GENERIC models of the dissipative component of the dynamics are essentially interchangeable, provided of course they assume the same kinematics. As part of the discussion, we note that equipping the dissipative structure of GENERIC with the Leibniz identity makes it automatically SEA on metric leaves. PMID:25974469

  3. Essential equivalence of the general equation for the nonequilibrium reversible-irreversible coupling (GENERIC) and steepest-entropy-ascent models of dissipation for nonequilibrium thermodynamics

    NASA Astrophysics Data System (ADS)

    Montefusco, Alberto; Consonni, Francesco; Beretta, Gian Paolo

    2015-04-01

    By reformulating the steepest-entropy-ascent (SEA) dynamical model for nonequilibrium thermodynamics in the mathematical language of differential geometry, we compare it with the primitive formulation of the general equation for the nonequilibrium reversible-irreversible coupling (GENERIC) model and discuss the main technical differences of the two approaches. In both dynamical models the description of dissipation is of the "entropy-gradient" type. SEA focuses only on the dissipative, i.e., entropy generating, component of the time evolution, chooses a sub-Riemannian metric tensor as dissipative structure, and uses the local entropy density field as potential. GENERIC emphasizes the coupling between the dissipative and nondissipative components of the time evolution, chooses two compatible degenerate structures (Poisson and degenerate co-Riemannian), and uses the global energy and entropy functionals as potentials. As an illustration, we rewrite the known GENERIC formulation of the Boltzmann equation in terms of the square root of the distribution function adopted by the SEA formulation. We then provide a formal proof that in more general frameworks, whenever all degeneracies in the GENERIC framework are related to conservation laws, the SEA and GENERIC models of the dissipative component of the dynamics are essentially interchangeable, provided of course they assume the same kinematics. As part of the discussion, we note that equipping the dissipative structure of GENERIC with the Leibniz identity makes it automatically SEA on metric leaves.

  4. Conceptual design of "Exomars-2018" Descent Module developed by federal enterprise "Lavochkin Association"

    NASA Astrophysics Data System (ADS)

    Khartov, V. V.; Martynov, M. B.; Lukiyanchikov, A. V.; Alexashkin, S. N.

    2015-12-01

    Goals and tasks for "ExoMars-2018" mission and share of responsibilities between European partners and p]Russia are presented. The main design requirements for a Descent Module (DM) that define its design concept as well as design specific features are given. The structure of the descent module, thermal control, means for securing systems interaction onboard the spacecraft "ExoMars-2018", and radio communication with the descent module are examined.

  5. An evaluation of descent strategies for TNAV-equipped aircraft in an advanced metering environment

    NASA Technical Reports Server (NTRS)

    Izumi, K. H.; Schwab, R. W.; Groce, J. L.; Coote, M. A.

    1986-01-01

    Investigated were the effects on system throughput and fleet fuel usage of arrival aircraft utilizing three 4D RNAV descent strategies (cost optimal, clean-idle Mach/CAS and constant descent angle Mach/CAS), both individually and in combination, in an advanced air traffic control metering environment. Results are presented for all mixtures of arrival traffic consisting of three Boeing commercial jet types and for all combinations of the three descent strategies for a typical en route metering airport arrival distribution.

  6. Arachnid aloft: directed aerial descent in neotropical canopy spiders.

    PubMed

    Yanoviak, Stephen P; Munk, Yonatan; Dudley, Robert

    2015-09-01

    The behaviour of directed aerial descent has been described for numerous taxa of wingless hexapods as they fall from the tropical rainforest canopy, but is not known in other terrestrial arthropods. Here, we describe similar controlled aerial behaviours for large arboreal spiders in the genus Selenops (Selenopidae). We dropped 59 such spiders from either canopy platforms or tree crowns in Panama and Peru; the majority (93%) directed their aerial trajectories towards and then landed upon nearby tree trunks. Following initial dorsoventral righting when necessary, falling spiders oriented themselves and then translated head-first towards targets; directional changes were correlated with bilaterally asymmetric motions of the anterolaterally extended forelegs. Aerial performance (i.e. the glide index) decreased with increasing body mass and wing loading, but not with projected surface area of the spider. Along with the occurrence of directed aerial descent in ants, jumping bristletails, and other wingless hexapods, this discovery of targeted gliding in selenopid spiders further indicates strong selective pressures against uncontrolled falls into the understory for arboreal taxa.

  7. Mars 2020 Entry, Descent and Landing Instrumentation 2 (MEDLI2)

    NASA Technical Reports Server (NTRS)

    Hwang, Helen H.; Bose, Deepak; White, Todd R.; Wright, Henry S.; Schoenenberger, Mark; Kuhl, Christopher A.; Trombetta, Dominic; Santos, Jose A.; Oishi, Tomomi; Karlgaard, Christopher D.; Mahzari, Milad; Pennington, Steven P.

    2016-01-01

    The Mars Entry Descent and Landing Instrumentation 2 (MEDLI2) sensor suite will measure aerodynamic, aerothermodynamic, and TPS performance during the atmospheric entry, descent, and landing phases of the Mars 2020 mission. The key objectives are to reduce design margin and prediction uncertainties for the aerothermal environments and aerodynamic database. For MEDLI2, the sensors are installed on both the heatshield and backshell, and include 7 pressure transducers, 17 thermal plugs, and 3 heat flux sensors (including a radiometer). These sensors will expand the set of measurements collected by the highly successful MEDLI suite, collecting supersonic pressure measurements on the forebody, a pressure measurement on the aftbody, direct heat flux measurements on the aftbody, a radiative heating measurement on the aftbody, and multiple near-surface thermal measurements on the thermal protection system (TPS) materials on both the forebody and aftbody. To meet the science objectives, supersonic pressure transducers and heat flux sensors are currently being developed and their qualification and calibration plans are presented. Finally, the reconstruction targets for data accuracy are presented, along with the planned methodologies for achieving the targets.

  8. Arachnid aloft: directed aerial descent in neotropical canopy spiders.

    PubMed

    Yanoviak, Stephen P; Munk, Yonatan; Dudley, Robert

    2015-09-01

    The behaviour of directed aerial descent has been described for numerous taxa of wingless hexapods as they fall from the tropical rainforest canopy, but is not known in other terrestrial arthropods. Here, we describe similar controlled aerial behaviours for large arboreal spiders in the genus Selenops (Selenopidae). We dropped 59 such spiders from either canopy platforms or tree crowns in Panama and Peru; the majority (93%) directed their aerial trajectories towards and then landed upon nearby tree trunks. Following initial dorsoventral righting when necessary, falling spiders oriented themselves and then translated head-first towards targets; directional changes were correlated with bilaterally asymmetric motions of the anterolaterally extended forelegs. Aerial performance (i.e. the glide index) decreased with increasing body mass and wing loading, but not with projected surface area of the spider. Along with the occurrence of directed aerial descent in ants, jumping bristletails, and other wingless hexapods, this discovery of targeted gliding in selenopid spiders further indicates strong selective pressures against uncontrolled falls into the understory for arboreal taxa. PMID:26289654

  9. Mars Science Laboratory Entry Descent and Landing Simulation Using DSENDS

    NASA Technical Reports Server (NTRS)

    Burkhart, P. Daniel; Casoliva, Jordi; Balaram, Bob

    2013-01-01

    The most recent planetary science mission to Mars was Mars Science Laboratory (MSL) with the Curiosity rover, launched November 26, 2011 and landed at Gale Crater on August 6, 2012. This spacecraft was the first use at Mars of a complete closed-loop Guidance Navigation and Control (GN&C) system, including guided entry with a lifting body that greatly reduces dispersions during the Entry, Descent and Landing (EDL) phase to achieve a 25 km X 20 km landing error relative to the selected Gale Crater landing target. In order to confirm meeting the above landing criteria, high-fidelity simulation of the EDL phase is required. The tool used for 6DOF EDL trajectory verification analysis is Dynamics Simulator for Entry, Descent and Surface landing (DSENDS), which is a high-fidelity simulation tool from JPLs Dynamics and Real-Time Simulation Laboratory for the development, test and operations of aero-flight vehicles. DSENDS inherent capability is augmented for MSL with project-specific models of atmosphere, aerodynamics, sensors and thrusters along with GN&C flight software to enable high-fidelity trajectory simulation. This paper will present the model integration and independent verification experience of the JPL EDL trajectory analysis team.

  10. Mars Science Laboratory Entry Descent and Landing Simulation Using DSENDS

    NASA Technical Reports Server (NTRS)

    Burkhart, P. Daniel; Casoliva, Jordi; Balaram, Bob

    2013-01-01

    The most recent planetary science mission to Mars is Mars Science Laboratory (MSL) with the Curiosity rover, launched November 26, 2011 and landed at Gale Crater on August 6, 2012. This spacecraft was the first use at Mars of a complete closed-loop Guidance Navigation and Control (GN&C) system, including guided entry with a lifting body that greatly reduces dispersions during the Entry, Descent and Landing (EDL) phase to achieve a 25 km x 20 km landing error relative to the selected Gale Crater landing target. In order to confirm meeting the above landing criteria, high-fidelity simulation of the EDL phase is required. The tool used for 6DOF EDL trajectory verification analysis is Dynamics Simulator for Entry, Descent and Surface landing (DSENDS), which is a high-fidelity simulation tool from JPLs Dynamics and Real-Time Simulation Laboratory for the development, test and operations of aero-flight vehicles. DSENDS inherent capability is augmented for MSL with project-specific models of atmosphere, aerodynamics, sensors and thrusters along with GN&C flight software to enable high-fidelity trajectory simulation. This paper will present the model integration and independent verification experience of the JPL EDL trajectory analysis team.

  11. Arachnid aloft: directed aerial descent in neotropical canopy spiders

    PubMed Central

    Yanoviak, Stephen P.; Munk, Yonatan; Dudley, Robert

    2015-01-01

    The behaviour of directed aerial descent has been described for numerous taxa of wingless hexapods as they fall from the tropical rainforest canopy, but is not known in other terrestrial arthropods. Here, we describe similar controlled aerial behaviours for large arboreal spiders in the genus Selenops (Selenopidae). We dropped 59 such spiders from either canopy platforms or tree crowns in Panama and Peru; the majority (93%) directed their aerial trajectories towards and then landed upon nearby tree trunks. Following initial dorsoventral righting when necessary, falling spiders oriented themselves and then translated head-first towards targets; directional changes were correlated with bilaterally asymmetric motions of the anterolaterally extended forelegs. Aerial performance (i.e. the glide index) decreased with increasing body mass and wing loading, but not with projected surface area of the spider. Along with the occurrence of directed aerial descent in ants, jumping bristletails, and other wingless hexapods, this discovery of targeted gliding in selenopid spiders further indicates strong selective pressures against uncontrolled falls into the understory for arboreal taxa. PMID:26289654

  12. Mars Exploration Rover Terminal Descent Mission Modeling and Simulation

    NASA Technical Reports Server (NTRS)

    Raiszadeh, Behzad; Queen, Eric M.

    2004-01-01

    Because of NASA's added reliance on simulation for successful interplanetary missions, the MER mission has developed a detailed EDL trajectory modeling and simulation. This paper summarizes how the MER EDL sequence of events are modeled, verification of the methods used, and the inputs. This simulation is built upon a multibody parachute trajectory simulation tool that has been developed in POST I1 that accurately simulates the trajectory of multiple vehicles in flight with interacting forces. In this model the parachute and the suspended bodies are treated as 6 Degree-of-Freedom (6 DOF) bodies. The terminal descent phase of the mission consists of several Entry, Descent, Landing (EDL) events, such as parachute deployment, heatshield separation, deployment of the lander from the backshell, deployment of the airbags, RAD firings, TIRS firings, etc. For an accurate, reliable simulation these events need to be modeled seamlessly and robustly so that the simulations will remain numerically stable during Monte-Carlo simulations. This paper also summarizes how the events have been modeled, the numerical issues, and modeling challenges.

  13. High mammographic density in women of Ashkenazi Jewish descent

    PubMed Central

    2013-01-01

    Introduction Percent mammographic density (PMD) adjusted for age and body mass index is one of the strongest risk factors for breast cancer and is known to be approximately 60% heritable. Here we report a finding of an association between genetic ancestry and adjusted PMD. Methods We selected self-identified Caucasian women in the California Pacific Medical Center Research Institute Cohort whose screening mammograms placed them in the top or bottom quintiles of age-adjusted and body mass index-adjusted PMD. Our final dataset included 474 women with the highest adjusted PMD and 469 with the lowest genotyped on the Illumina 1 M platform. Principal component analysis (PCA) and identity-by-descent analyses allowed us to infer the women's genetic ancestry and correlate it with adjusted PMD. Results Women of Ashkenazi Jewish ancestry, as defined by the first principal component of PCA and identity-by-descent analyses, represented approximately 15% of the sample. Ashkenazi Jewish ancestry, defined by the first principal component of PCA, was associated with higher adjusted PMD (P = 0.004). Using multivariate regression to adjust for epidemiologic factors associated with PMD, including age at parity and use of postmenopausal hormone therapy, did not attenuate the association. Conclusions Women of Ashkenazi Jewish ancestry, based on genetic analysis, are more likely to have high age-adjusted and body mass index-adjusted PMD. Ashkenazi Jews may have a unique set of genetic variants or environmental risk factors that increase mammographic density. PMID:23668689

  14. Gradient descent algorithm applied to wavefront retrieval from through-focus images by an extreme ultraviolet microscope with partially coherent source

    DOE PAGES

    Yamazoe, Kenji; Mochi, Iacopo; Goldberg, Kenneth A.

    2014-12-01

    The wavefront retrieval by gradient descent algorithm that is typically applied to coherent or incoherent imaging is extended to retrieve a wavefront from a series of through-focus images by partially coherent illumination. For accurate retrieval, we modeled partial coherence as well as object transmittance into the gradient descent algorithm. However, this modeling increases the computation time due to the complexity of partially coherent imaging simulation that is repeatedly used in the optimization loop. To accelerate the computation, we incorporate not only the Fourier transform but also an eigenfunction decomposition of the image. As a demonstration, the extended algorithm is appliedmore » to retrieve a field-dependent wavefront of a microscope operated at extreme ultraviolet wavelength (13.4 nm). The retrieved wavefront qualitatively matches the expected characteristics of the lens design.« less

  15. Gradient descent algorithm applied to wavefront retrieval from through-focus images by an extreme ultraviolet microscope with partially coherent source

    SciTech Connect

    Yamazoe, Kenji; Mochi, Iacopo; Goldberg, Kenneth A.

    2014-12-01

    The wavefront retrieval by gradient descent algorithm that is typically applied to coherent or incoherent imaging is extended to retrieve a wavefront from a series of through-focus images by partially coherent illumination. For accurate retrieval, we modeled partial coherence as well as object transmittance into the gradient descent algorithm. However, this modeling increases the computation time due to the complexity of partially coherent imaging simulation that is repeatedly used in the optimization loop. To accelerate the computation, we incorporate not only the Fourier transform but also an eigenfunction decomposition of the image. As a demonstration, the extended algorithm is applied to retrieve a field-dependent wavefront of a microscope operated at extreme ultraviolet wavelength (13.4 nm). The retrieved wavefront qualitatively matches the expected characteristics of the lens design.

  16. Can Accelerators Accelerate Learning?

    NASA Astrophysics Data System (ADS)

    Santos, A. C. F.; Fonseca, P.; Coelho, L. F. S.

    2009-03-01

    The 'Young Talented' education program developed by the Brazilian State Funding Agency (FAPERJ) [1] makes it possible for high-schools students from public high schools to perform activities in scientific laboratories. In the Atomic and Molecular Physics Laboratory at Federal University of Rio de Janeiro (UFRJ), the students are confronted with modern research tools like the 1.7 MV ion accelerator. Being a user-friendly machine, the accelerator is easily manageable by the students, who can perform simple hands-on activities, stimulating interest in physics, and getting the students close to modern laboratory techniques.

  17. Can Accelerators Accelerate Learning?

    SciTech Connect

    Santos, A. C. F.; Fonseca, P.; Coelho, L. F. S.

    2009-03-10

    The 'Young Talented' education program developed by the Brazilian State Funding Agency (FAPERJ)[1] makes it possible for high-schools students from public high schools to perform activities in scientific laboratories. In the Atomic and Molecular Physics Laboratory at Federal University of Rio de Janeiro (UFRJ), the students are confronted with modern research tools like the 1.7 MV ion accelerator. Being a user-friendly machine, the accelerator is easily manageable by the students, who can perform simple hands-on activities, stimulating interest in physics, and getting the students close to modern laboratory techniques.

  18. Can a single lower trunk body-fixed sensor differentiate between level-walking and stair descent and ascent in older adults? Preliminary findings.

    PubMed

    Weiss, Aner; Brozgol, Marina; Giladi, Nir; Hausdorff, Jeffrey M

    2016-10-01

    Stair ascent and descent are common forms of ambulation that may be challenging to detect. Here, we propose the first step towards differentiating between stair negotiation and level-walking using a single body-fixed sensor. Seventeen healthy older adults (age: 79.3±4.2 years, 47% women) wore a body-fixed sensor on the lower-back while performing level-walking and stair negotiation. Measures derived from the 3D acceleration and angular-velocity signals included medians, ranges, step duration, step and stride regularity, filtered vertical to horizontal acceleration ratio (VAF/HAF), and wavelet-based features. Friedman's and Wilcoxon tests compared between conditions. Stepwise-binary logistic-regression evaluated classification accuracy. During level-walking, yaw range was lowest and anterior-posterior and vertical step and stride regularity were highest (p≤0.007). Anterior-posterior step regularity (p=0.003), VAF/HAF (p=0.094), and yaw range (p=0.105) identified level-walking (92.2% accuracy). During stair ascent, roll range, median anterior-posterior acceleration and anterior-posterior wavelet-coefficient were lowest (p≤0.006), while VAF/HAF was highest (p=0.0029). Anterior posterior wavelet coefficient (p=0.038) and VAF/HAF (p=0.018) identified stair ascent (94.3% accuracy). During stair descent, vertical and medio-lateral ranges were highest and medio-lateral stride regularity and VAF/HAF were lowest (p≤0.006). VAF/HAF (p=0.01), medio-lateral acceleration range (p=0.069), and medio-lateral stride regularity (p=0.072) identified stair descent (90.2% accuracy). These findings suggest that a single worn body-fixed sensor can be used to differentiate between level-walking and stair negotiation.

  19. Evaluation of vertical profiles to design continuous descent approach procedure

    NASA Astrophysics Data System (ADS)

    Pradeep, Priyank

    The current research focuses on predictability, variability and operational feasibility aspect of Continuous Descent Approach (CDA), which is among the key concepts of the Next Generation Air Transportation System (NextGen). The idle-thrust CDA is a fuel economical, noise and emission abatement procedure, but requires increased separation to accommodate for variability and uncertainties in vertical and speed profiles of arriving aircraft. Although a considerable amount of researches have been devoted to the estimation of potential benefits of the CDA, only few have attempted to explain the predictability, variability and operational feasibility aspect of CDA. The analytical equations derived using flight dynamics and Base of Aircraft and Data (BADA) Total Energy Model (TEM) in this research gives insight into dependency of vertical profile of CDA on various factors like wind speed and gradient, weight, aircraft type and configuration, thrust settings, atmospheric factors (deviation from ISA (DISA), pressure and density of the air) and descent speed profile. Application of the derived equations to idle-thrust CDA gives an insight into sensitivity of its vertical profile to multiple factors. This suggests fixed geometric flight path angle (FPA) CDA has higher degree of predictability and lesser variability at the cost of non-idle and low thrust engine settings. However, with optimized design this impact can be overall minimized. The CDA simulations were performed using Future ATM Concept Evaluation Tool (FACET) based on radar-track and aircraft type data (BADA) of the real air-traffic to some of the busiest airports in the USA (ATL, SFO and New York Metroplex (JFK, EWR and LGA)). The statistical analysis of the vertical profiles of CDA shows 1) mean geometric FPAs derived from various simulated vertical profiles are consistently shallower than 3° glideslope angle and 2) high level of variability in vertical profiles of idle-thrust CDA even in absence of

  20. DISR imaging and the geometry of the descent of the Huygens probe within Titan's atmosphere

    NASA Astrophysics Data System (ADS)

    Karkoschka, Erich; Tomasko, Martin G.; Doose, Lyn R.; See, Chuck; McFarlane, Elisabeth A.; Schröder, Stefan E.; Rizk, Bashar

    2007-11-01

    The Descent Imager/Spectral Radiometer (DISR) provided 376 images during the descent to Titan and 224 images after landing. Images of the surface had scales between 150 m/pixel and 0.4 mm/pixel, all of which we assembled into a mosaic. The analysis of the surface and haze features in these images and of other data gave tight constraints on the geometry of the descent, particularly the trajectory, the tip and tilt, and the rotation of the Huygens probe. Huygens moved on average in the direction of 2∘ north of east from 145 to 50 km altitude, turning to 5∘ south of east between 30 and 20 km altitude, before turning back to east. At 6.5 km altitude, it reversed to WNW, before reversing back to SE at 0.7 km altitude. At first, Huygens was tilting slowly by up to 15∘ as expected for a descent through layers of changing wind speeds. As the winds calmed, tilts decreased. Tilts were approximately retrieved throughout the main-parachute phase, but only for 160 specific times afterwards. Average swing rates were 5∘/s at high and low altitudes, but 13∘/s between 110 and 30 km altitude. Maximum swing rates were often above 40∘/s, far above the design limit of 6∘/s, but they caused problems only for a single component of DISR, the Sun Sensor. The excitation of such high swing rates on the stabilizer parachute is not fully understood. Before the parachute exchange, the rotational rate of Huygens smoothly approached the expected equilibrium value of 3 rotations per vertical kilometer, although clockwise instead of counterclockwise. Starting at 40 s after the parachute exchange until landing, Huygens rotated erratically. Long-term averages of the rotational rate varied between 2.0 and 4.5 rotations/km. On time scales shorter than a minute, some 100 strong rotational accelerations or decelerations created azimuthal irregularities of up to 180∘, which caused DISR to take most exposures at random azimuths instead of pre-selected azimuths. Nevertheless, we

  1. Human Mars Entry, Descent, and Landing Architecture Study Overview

    NASA Technical Reports Server (NTRS)

    Cianciolo, Alicia D.; Polsgrove, Tara T.

    2016-01-01

    The Entry, Descent, and Landing (EDL) Architecture Study is a multi-NASA center activity to analyze candidate EDL systems as they apply to human Mars landing in the context of the Evolvable Mars Campaign. The study, led by the Space Technology Mission Directorate (STMD), is performed in conjunction with the NASA's Science Mission Directorate and the Human Architecture Team, sponsored by NASA's Human Exploration and Operations Mission Directorate. The primary objective is to prioritize future STMD EDL technology investments by (1) generating Phase A-level designs for selected concepts to deliver 20 t human class payloads, (2) developing a parameterized mass model for each concept capable of examining payloads between 5 and 40 t, and (3) evaluating integrated system performance using trajectory simulations. This paper summarizes the initial study results.

  2. On Belonging: The American Adolescent of Arab Descent.

    PubMed

    Khouri, Lama Z

    2016-08-01

    Although American families of Arab origin come from 22 countries and from varied backgrounds and cultures, reports suggest that they suffer equally from acculturation stress, stereotyping, discrimination, and the reverberations of the aftermath of September 11 as well as global affairs. However, because children and adolescents from these families, particularly those who are newly arrived immigrants, tend to do well in school, they are rarely targeted by research or policy. This article uses the narratives of 5 middle school age male students from Arab descent who were in a support group that met for 3 years (2004-2007), beginning shortly after President George W. Bush's declaration of the war on the "axis of evil." I used vignettes from this group to illustrate the stressors this population faces. The final section suggests an option for supporting this population. PMID:27472891

  3. The stabilization interval system of a tethered descent underwater vehicle

    NASA Astrophysics Data System (ADS)

    Gayvoronskiy, S. A.; Ezangina, T.; Khozhaev, I.; Efimov, S. V.

    2016-04-01

    To damp the vertical oscillations of a descent submersible caused by dusting the control system utilizing a shock-absorbing hoist located on the submersible was developed. A robust proportional-plus-integral action controller was included in the control loop to ensure acceptable dynamic properties of the system by interval variations of the module mass, the rope length, the equivalent value of stiffness of a spring linkage and the equivalent value of damping factor of the spring linkage. A parametric synthesis of the controller was carried out on the basis of the robust expansion of the coefficient method of the quality rating estimation. The system operability was confirmed by the results of the digital simulation parameters

  4. Mars Exploration Rovers Entry, Descent, and Landing Trajectory Analysis

    NASA Technical Reports Server (NTRS)

    Desai, Prasun N.; Knocke, Philip C.

    2004-01-01

    The Mars Exploration Rover mission successfully landed two rovers "Spirit" and "Opportunity" on Mars on January 4th and 25th of 2004, respectively. The trajectory analysis performed to define the entry, descent, and landing (EDL) scenario is described. The entry requirements and constraints are presented, as well as uncertainties used in a Monte Carlo dispersion analysis to statistically assess the robustness of the entry design to off-nominal conditions. In the analysis, six-degree-of-freedom and three-degree-of-freedom trajectory results are compared to assess the entry characteristics of the capsule. Comparison of the preentry results to preliminary post-landing reconstruction data shows that all EDL parameters were within the requirements. In addition, the final landing position for both "Spirit" and "Opportunity" were within 15 km of the predicted landing location.

  5. RITD - Adapting Mars Entry, Descent and Landing System for Earth

    NASA Astrophysics Data System (ADS)

    Heilimo, Jyri; Harri, Ari-Matti; Aleksashkin, Sergey; Koryanov, Vsevolod; Arruego, Ignacio; Schmidt, Walter; Haukka, Harri; Finchenko, Valery; Martynov, Maxim; Ostresko, Boris; Ponomarenko, Andrey; Kazakovtsev, Viktor; Martin, Susanna; Siili, Tero

    2014-05-01

    A new generation of inflatable Entry, Descent and Landing System (EDLS) for Mars has been developed. It is used in both the initial atmospheric entry and atmospheric descent before the semi-hard impact of the penetrator into Martian surface. The EDLS applicability to Earth's atmosphere is studied by the EU/RITD [1] project. Project focuses to the analysis and tests of the transonic behaviour of this compact and light weight payload entry system at the Earth re-entry. 1. EDLS for Earth The dynamical stability of the craft is analysed, concentrating on the most critical part of the atmospheric re-entry, the transonic phase. In Martian atmosphere the MetNet vehicle stability during the transonic phase is understood. However, in the more dense Earth's atmosphere, the transonic phase is shorter and turbulence more violent. Therefore, the EDLS has to be sufficiently dynamically stable to overcome the forces tending to deflect the craft from its nominal trajectory and attitude. The preliminary design of the inflatable EDLS for Earth will be commenced once the scaling of the re-entry system and the dynamical stability analysis have been performed. The RITD-project concentrates on mission and applications achievable with the current MetNet-type (i.e. 'Mini-1' category) of lander, and on requirements posed by other type Earth re-entry concepts. 2. Entry Angle Determination for Mini-1 - lander For successful Earth landing, the suitable re-entry angle and velocity with specific descent vehicle (DV) mass and heat flux parameters need to be determined. These key parameters in determining the Earth re-entry for DV are: qmax (kW/m2): maximal specific heat flux, Q (MJ/m2): specific integral heat flux to DV front shield, m (kg): descent vehicle (DV) mass, V (m/s): re-entry velocity and Θ (deg.): flight-path angle at Earth re-entry For Earth re-entry, the calculation results in the optimal value of entry velocity for MetNet ('Mini-1' category) -type lander, with mass of 22kg, being

  6. RITD - Adapting Mars Entry, Descent and Landing System for Earth

    NASA Astrophysics Data System (ADS)

    Heilimo, Jyri; Aleksashkin, Sergey; Martynov, Maxim; Schmidt, Walter; Harri, Ari-Matti; Vsevolod Koryanov, D.; Kazakovtcev, Victor; Haukka, Harri; Arruego, Ignacio; Finchenko, Valery; Ostresko, Boris; Ponomarenko, Andrei; Martin, Susanna; Siili, Tero

    Abstract A new generation of inflatable Entry, Descent and Landing System (EDLS) or Mars has been developed. It is used in both the initial atmospheric entry and atmospheric descent before the semi-hard impact of the penetrator into Martian surface. The EDLS applicability to Earth’s atmosphere is studied by the EU/RITD [1] project. Project focuses to the analysis and tests of the transonic behaviour of this compact and light weight payload entry system at the Earth re-entry 1. EDLS for Earth The dynamical stability of the craft is analysed, concentrating on the most critical part of the atmospheric re-entry, the transonic phase. In Martian atmosphere the MetNet vehicle stability during the transonic phase is understood. However, in the more dense Earth’s atmosphere, the transonic phase is shorter and turbulence more violent. Therefore, the EDLS has to be sufficiently dynamically stable to overcome the forces tending to deflect the craft from its nominal trajectory and attitude. The preliminary design of the inflatable EDLS for Earth will be commenced once the scaling of the re-entry system and the dynamical stability analysis have been performed. The RITD-project concentrates on mission and applications achievable with the current MetNet-type (i.e. “Mini-1” category) of lander, and on requirements posed by other type Earth re-entry concepts. 2. Entry Angle Determination for Mini-1 - lander For successful Earth landing, the suitable re-entry angle and velocity with specific descent vehicle (DV) mass and heat flux parameters need to be determined. These key parameters in determining the Earth re-entry for DV are: - qmax (kW/m2): maximal specific heat flux, - Q (MJ/m2): specific integral heat flux to DV front shield, - m (kg): descent vehicle (DV) mass, - V (m/s): re-entry velocity and - theta(deg.): flight-path angle at Earth re-entry For Earth re-entry, the calculation results in the optimal value of entry velocity for MetNet (“Mini-1” category) -type

  7. Stress within a bicultural context for adolescents of Mexican descent.

    PubMed

    Romero, Andrea J; Roberts, Robert E

    2003-05-01

    Folkman and Lazarus's theory of stress and coping was used to develop a measure assessing the perceived stress within a bicultural context. Middle school students of Mexican descent (N = 881) reported their perceived stress from intergenerational acculturation gaps, within-group discrimination, out-group discrimination, and monolingual stress. Although immigrant youths reported more total number of stressors, U.S.-born youths reported more stress from needing better Spanish and impact of parents' culture. Immigrant youths reported more stress from needing better English in school. Higher stress was associated with more depressive symptoms for both U.S.-born and immigrant youths. Although this study has identified some elements of stress, it has not identified positive coping mechanisms of the bicultural context for Latino youths.

  8. On Belonging: The American Adolescent of Arab Descent.

    PubMed

    Khouri, Lama Z

    2016-08-01

    Although American families of Arab origin come from 22 countries and from varied backgrounds and cultures, reports suggest that they suffer equally from acculturation stress, stereotyping, discrimination, and the reverberations of the aftermath of September 11 as well as global affairs. However, because children and adolescents from these families, particularly those who are newly arrived immigrants, tend to do well in school, they are rarely targeted by research or policy. This article uses the narratives of 5 middle school age male students from Arab descent who were in a support group that met for 3 years (2004-2007), beginning shortly after President George W. Bush's declaration of the war on the "axis of evil." I used vignettes from this group to illustrate the stressors this population faces. The final section suggests an option for supporting this population.

  9. Adapting Mars Entry, Descent and Landing System for Earth

    NASA Astrophysics Data System (ADS)

    Heilimo, J.; Harri, A.-M.; Aleksashkin, S.; Koryanov, V.; Guerrero, H.; Schmidt, W.; Haukka, H.; Finchenko, V.; Martynov, M.; Ostresko, B.; Ponomarenko, A.; Kazakovtsev, V.; Arruego, I.; Martin, S.; Siili, T.

    2013-09-01

    In 2001 - 2011 an inflatable Entry, Descent and Landing System (EDLS) for Martian atmosphere was developed by FMI and the MetNet team. This MetNet Mars Lander EDLS is used in both the initial deceleration during atmospheric entry and in the final deceleration before the semi-hard impact of the penetrator to Martian surface. The EDLS design is ingenious and its applicability to Earth's atmosphere is studied in the on-going project. In particular, the behavior of the system in the critical transonic aerodynamic (from hypersonic to subsonic) regime will be investigated. This project targets to analyze and test the transonic behavior of this compact and light weight payload entry system to Earth's atmosphere [1]. Scaling and adaptation for terrestrial atmospheric conditions, instead of a completely new design, is a favorable approach for providing a new re-entry vehicle for terrestrial space applications.

  10. CryoScout: A Descent Through the Mars Polar Cap

    NASA Technical Reports Server (NTRS)

    Hecht, M. H.; Saunders, R. S.

    2003-01-01

    CryoScout was proposed as a subsurface investigation of the stratigraphic climate record embedded in Mars North Polar cap. After landing on a gentle landscape in the midst of the mild summer season, CryoScout was to use the continuous polar sunlight to power the descent of a cryobot, a thermal probe, into the ice at a rate of about 1 m per day. CryoScout would probe deep enough into this time capsule to see the effects of planetary obliquity variations and discrete events such as dust storms or volcanic eruptions. By penetrating tens of meters of ice, the mission would explore at least one of the dominant "MOC layers" observed in exposed layered terrain.

  11. The descent of words: evolutionary thinking 1780-1880.

    PubMed

    van Wyhe, John

    2005-09-01

    Histories of evolutionary thought are dominated by organic evolution. The colossus in our midst that is evolutionary biology casts its shadow over history, making it appear that what is so widespread and important today was always the primary subject of evolutionary speculation. Thus many histories assume that the core meaning of evolution is the change of organic life and that other forms of evolutionary thinking, such as linguistic, social or cultural evolution, are only analogies or offshoots of the main biological evolutionary trunk. Ironically this is an ahistorical understanding. Long before the work of Charles Darwin, scholars were independently developing evolutionary concepts such as descent with modification and divergence from a common stock in order to understand cultural change.

  12. The Yearly Variation in Fall-Winter Arctic Winter Vortex Descent

    NASA Technical Reports Server (NTRS)

    Schoeberl, Mark R.; Newman, Paul A.

    1999-01-01

    Using the change in HALOE methane profiles from early September to late March, we have estimated the minimum amount of diabatic descent within the polar which takes place during Arctic winter. The year to year variations are a result in the year to year variations in stratospheric wave activity which (1) modify the temperature of the vortex and thus the cooling rate; (2) reduce the apparent descent by mixing high amounts of methane into the vortex. The peak descent amounts from HALOE methane vary from l0km -14km near the arrival altitude of 25 km. Using a diabatic trajectory calculation, we compare forward and backward trajectories over the course of the winter using UKMO assimilated stratospheric data. The forward calculation agrees fairly well with the observed descent. The backward calculation appears to be unable to produce the observed amount of descent, but this is only an apparent effect due to the density decrease in parcels with altitude. Finally we show the results for unmixed descent experiments - where the parcels are fixed in latitude and longitude and allowed to descend based on the local cooling rate. Unmixed descent is found to always exceed mixed descent, because when normal parcel motion is included, the path average cooling is always less than the cooling at a fixed polar point.

  13. The Role of la Familia for Women of Mexican Descent Who Are Leaders in Higher Education

    ERIC Educational Resources Information Center

    Elizondo, Sandra Gray

    2012-01-01

    The purpose of this qualitative case study was to describe the role of "la familia" for women of Mexican descent as it relates to their development as leaders and their leadership in academia. Purposeful sampling was utilized to reach the goal of 18 participants who were female academic leaders of Mexican descent teaching full time in…

  14. Ethnic Identity and Acculturative Stress as Mediators of Depression in Students of Asian Descent

    ERIC Educational Resources Information Center

    Lantrip, Crystal; Mazzetti, Francesco; Grasso, Joseph; Gill, Sara; Miller, Janna; Haner, Morgynn; Rude, Stephanie; Awad, Germine

    2015-01-01

    This study underscored the importance of addressing the well-being of college students of Asian descent, because these students had higher rates of depression and lower positive feelings about their ethnic group compared with students of European descent, as measured by the Affirmation subscale of the Ethnic Identity Scale. Affirmation mediated…

  15. The Power of Mexican Descent Families in the Successful Education of Their Children

    ERIC Educational Resources Information Center

    Hughes, Craig A.

    2006-01-01

    Mexican descent students leave school before completions at a much higher rate than other ethnic groups. Marginalization is one contributing factor. Thirty-two Mexican descent students were interviewed with two main objectives: What marginalization factors did they experience in their secondary schools? What factors allowed them to overcome…

  16. Atmospheric studies from the Mars Science Laboratory Entry, Descent and Landing atmospheric structure reconstruction

    NASA Astrophysics Data System (ADS)

    Holstein-Rathlou, C.; Maue, A.; Withers, P.

    2016-01-01

    The Mars Science Laboratory (MSL) entered the martian atmosphere on Aug. 6, 2012 landing in Gale crater (4.6°S, 137.4°E) in the local mid-afternoon. Aerodynamic accelerations were measured during descent and atmospheric density, pressure and temperature profiles have been calculated from this data. Using an averaging technique developed for the NASA Phoenix Mars mission, the profiles are extended to 134.1 km, twice that of the engineering reconstruction. Large-scale temperature oscillations in the MSL temperature profile are suggestive of thermal tides. Comparing the MSL temperature profile with measured Mars Climate Sounder temperature profiles and Mars Climate Database model output highlights the presence of diurnal tides. Derived vertical wavelengths for the diurnal migrating tide are larger than predicted from idealized tidal theory, indicating an added presence of nonmigrating diurnal tides. Sub-CO2 condensation mesospheric temperatures, very similar to the Pathfinder temperature profile, allude to the possibility of CO2 clouds. This is however not supported by recent observations and models.

  17. Direct-to-Earth Communications with Mars Science Laboratory During Entry, Descent, and Landing

    NASA Technical Reports Server (NTRS)

    Soriano, Melissa; Finley, Susan; Fort, David; Schratz, Brian; Ilott, Peter; Mukai, Ryan; Estabrook, Polly; Oudrhiri, Kamal; Kahan, Daniel; Satorius, Edgar

    2013-01-01

    Mars Science Laboratory (MSL) undergoes extreme heating and acceleration during Entry, Descent, and Landing (EDL) on Mars. Unknown dynamics lead to large Doppler shifts, making communication challenging. During EDL, a special form of Multiple Frequency Shift Keying (MFSK) communication is used for Direct-To-Earth (DTE) communication. The X-band signal is received by the Deep Space Network (DSN) at the Canberra Deep Space Communication complex, then down-converted, digitized, and recorded by open-loop Radio Science Receivers (RSR), and decoded in real-time by the EDL Data Analysis (EDA) System. The EDA uses lock states with configurable Fast Fourier Transforms to acquire and track the signal. RSR configuration and channel allocation is shown. Testing prior to EDL is discussed including software simulations, test bed runs with MSL flight hardware, and the in-flight end-to-end test. EDA configuration parameters and signal dynamics during pre-entry, entry, and parachute deployment are analyzed. RSR and EDA performance during MSL EDL is evaluated, including performance using a single 70-meter DSN antenna and an array of two 34-meter DSN antennas as a back up to the 70-meter antenna.

  18. Direct-to-Earth Communications and Signal Processing for Mars Exploration Rover Entry, Descent, and Landing

    NASA Astrophysics Data System (ADS)

    Satorius, E.; Estabrook, P.; Wilson, J.; Fort, D.

    2003-01-01

    For planetary lander missions, the most challenging phase of the spacecraft-to-ground communications is during the entry, descent, and landing (EDL). As each 2003 Mars Exploration Rover (MER) enters the Martian atmosphere, it slows dramatically. The extreme acceleration and jerk cause extreme Doppler dynamics on the 8.4-GHz (X-band) signal received on Earth. When the vehicle slows sufficiently, the parachute is deployed, causing almost a step in deceleration. After parachute deployment, the lander is lowered beneath the parachute on a bridle. The swinging motion of the lander imparts high Doppler dynamics on the signal and causes the received signal strength to vary widely due to changing antenna pointing angles. All this time, the vehicle transmits important health and status information that is especially critical if the landing is not successful. Even using the largest Deep Space Network antennas, the weak signal and high dynamics render it impossible to conduct reliable phase-coherent communications. Therefore, a specialized form of frequency-shift keying will be used. This article describes the EDL scenario, the signal conditions, the methods used to detect and frequency track the carrier and to detect the data modulation, and the resulting performance estimates.

  19. Y Chromosome Lineages in Men of West African Descent

    PubMed Central

    Keita, Shomarka O. Y.; Kittles, Rick A.

    2012-01-01

    The early African experience in the Americas is marked by the transatlantic slave trade from ∼1619 to 1850 and the rise of the plantation system. The origins of enslaved Africans were largely dependent on European preferences as well as the availability of potential laborers within Africa. Rice production was a key industry of many colonial South Carolina low country plantations. Accordingly, rice plantations owners within South Carolina often requested enslaved Africans from the so-called “Grain Coast” of western Africa (Senegal to Sierra Leone). Studies on the African origins of the enslaved within other regions of the Americas have been limited. To address the issue of origins of people of African descent within the Americas and understand more about the genetic heterogeneity present within Africa and the African Diaspora, we typed Y chromosome specific markers in 1,319 men consisting of 508 west and central Africans (from 12 populations), 188 Caribbeans (from 2 islands), 532 African Americans (AAs from Washington, DC and Columbia, SC), and 91 European Americans. Principal component and admixture analyses provide support for significant Grain Coast ancestry among African American men in South Carolina. AA men from DC and the Caribbean showed a closer affinity to populations from the Bight of Biafra. Furthermore, 30–40% of the paternal lineages in African descent populations in the Americas are of European ancestry. Diverse west African ancestries and sex-biased gene flow from EAs has contributed greatly to the genetic heterogeneity of African populations throughout the Americas and has significant implications for gene mapping efforts in these populations. PMID:22295064

  20. Hybridisations Of Simulated Annealing And Modified Simplex Algorithms On A Path Of Steepest Ascent With Multi-Response For Optimal Parameter Settings Of ACO

    NASA Astrophysics Data System (ADS)

    Luangpaiboon, P.

    2009-10-01

    Many entrepreneurs face to extreme conditions for instances; costs, quality, sales and services. Moreover, technology has always been intertwined with our demands. Then almost manufacturers or assembling lines adopt it and come out with more complicated process inevitably. At this stage, products and service improvement need to be shifted from competitors with sustainability. So, a simulated process optimisation is an alternative way for solving huge and complex problems. Metaheuristics are sequential processes that perform exploration and exploitation in the solution space aiming to efficiently find near optimal solutions with natural intelligence as a source of inspiration. One of the most well-known metaheuristics is called Ant Colony Optimisation, ACO. This paper is conducted to give an aid in complicatedness of using ACO in terms of its parameters: number of iterations, ants and moves. Proper levels of these parameters are analysed on eight noisy continuous non-linear continuous response surfaces. Considering the solution space in a specified region, some surfaces contain global optimum and multiple local optimums and some are with a curved ridge. ACO parameters are determined through hybridisations of Modified Simplex and Simulated Annealing methods on the path of Steepest Ascent, SAM. SAM was introduced to recommend preferable levels of ACO parameters via statistically significant regression analysis and Taguchi's signal to noise ratio. Other performance achievements include minimax and mean squared error measures. A series of computational experiments using each algorithm were conducted. Experimental results were analysed in terms of mean, design points and best so far solutions. It was found that results obtained from a hybridisation with stochastic procedures of Simulated Annealing method were better than that using Modified Simplex algorithm. However, the average execution time of experimental runs and number of design points using hybridisations were

  1. Descent strategy comparisons for TNAV-equipped aircraft under airplane-preferred operating conditions

    NASA Technical Reports Server (NTRS)

    Izumi, K. H.

    1989-01-01

    Three 4-D descent strategies were evaluated which were employed by TNAV-equipped aircraft in an advanced metering air traffic control environment. The Flow Management Evaluation Model (FMEM) was used to assess performance using three criteria when traffic enters the simulation under preferred cruise operating conditions (altitude and speed): throughput, fuel usage, and conflict probability. In comparison to an evaluation previously performed under NASA contract, the current analysis indicates that the optimal descent strategy is preferred over the clean-idle and constant descent angle (CFPA) strategies when all three criteria are considered.

  2. Rapid Generation of Optimal Asteroid Powered Descent Trajectories Via Convex Optimization

    NASA Technical Reports Server (NTRS)

    Pinson, Robin; Lu, Ping

    2015-01-01

    This paper investigates a convex optimization based method that can rapidly generate the fuel optimal asteroid powered descent trajectory. The ultimate goal is to autonomously design the optimal powered descent trajectory on-board the spacecraft immediately prior to the descent burn. Compared to a planetary powered landing problem, the major difficulty is the complex gravity field near the surface of an asteroid that cannot be approximated by a constant gravity field. This paper uses relaxation techniques and a successive solution process that seeks the solution to the original nonlinear, nonconvex problem through the solutions to a sequence of convex optimal control problems.

  3. Study of Some Planetary Atmospheres Features by Probe Entry and Descent Simulations

    NASA Technical Reports Server (NTRS)

    Gil, P. J. S.; Rosa, P. M. B.

    2005-01-01

    Characterization of planetary atmospheres is analyzed by its effects in the entry and descent trajectories of probes. Emphasis is on the most important variables that characterize atmospheres e.g. density profile with altitude. Probe trajectories are numerically determined with ENTRAP, a developing multi-purpose computational tool for entry and descent trajectory simulations capable of taking into account many features and perturbations. Real data from Mars Pathfinder mission is used. The goal is to be able to determine more accurately the atmosphere structure by observing real trajectories and what changes are to expect in probe descent trajectories if atmospheres have different properties than the ones assumed initially.

  4. Development of a Mars Airplane Entry, Descent, and Flight Trajectory

    NASA Technical Reports Server (NTRS)

    Murray, James E.; Tartabini, Paul V.

    2001-01-01

    An entry, descent, and flight (EDF) trajectory profile for a Mars airplane mission is defined as consisting of the following elements: ballistic entry of an aeroshell; supersonic deployment of a decelerator parachute; subsonic release of a heat shield; release, unfolding, and orientation of an airplane to flight attitude; and execution of a pull up maneuver to achieve trimmed, horizontal flight. Using the Program to Optimize Simulated Trajectories (POST) a trajectory optimization problem was formulated. Model data representative of a specific Mars airplane configuration, current models of the Mars surface topography and atmosphere, and current estimates of the interplanetary trajectory, were incorporated into the analysis. The goal is to develop an EDF trajectory to maximize the surface-relative altitude of the airplane at the end of a pull up maneuver, while subject to the mission design constraints. The trajectory performance was evaluated for three potential mission sites and was found to be site-sensitive. The trajectory performance, examined for sensitivity to a number of design and constraint variables, was found to be most sensitive to airplane mass, aerodynamic performance characteristics, and the pull up Mach constraint. Based on the results of this sensitivity study, an airplane-drag optimized trajectory was developed that showed a significant performance improvement.

  5. HLA Type Inference via Haplotypes Identical by Descent

    NASA Astrophysics Data System (ADS)

    Setty, Manu N.; Gusev, Alexander; Pe'Er, Itsik

    The Human Leukocyte Antigen (HLA) genes play a major role in adaptive immune response and are used to differentiate self antigens from non self ones. HLA genes are hyper variable with nearly every locus harboring over a dozen alleles. This variation plays an important role in susceptibility to multiple autoimmune diseases and needs to be matched on for organ transplantation. Unfortunately, HLA typing by serological methods is time consuming and expensive compared to high throughput Single Nucleotide Polymorphism (SNP) data. We present a new computational method to infer per-locus HLA types using shared segments Identical By Descent (IBD), inferred from SNP genotype data. IBD information is modeled as graph where shared haplotypes are explored among clusters of individuals with known and unknown HLA types to identify the latter. We analyze performance of the method in a previously typed subset of the HapMap population, achieving accuracy of 96% in HLA-A, 94% in HLA-B, 95% in HLA-C, 77% in HLA-DR1, 93% in HLA-DQA1 and 90% in HLA-DQB1 genes. We compare our method to a tag SNP based approach and demonstrate higher sensitivity and specificity. Our method demonstrates the power of using shared haplotype segments for large-scale imputation at the HLA locus.

  6. Human Mars Entry, Descent and Landing Architectures Study Overview

    NASA Technical Reports Server (NTRS)

    Polsgrove, Tara T.; Dwyer Cianciolo, Alicia

    2016-01-01

    Landing humans on Mars will require entry, descent and landing (EDL) capability beyond the current state of the art. Nearly twenty times more delivered payload and an order of magnitude improvement in precision landing capability will be necessary. Several EDL technologies capable of meeting the human class payload delivery requirements are being considered. The EDL technologies considered include low lift-to-drag vehicles like Hypersonic Inflatable Aerodynamic Decelerators (HIAD), Adaptable Deployable Entry and Placement Technology (ADEPT), and mid range lift-to-drag vehicles like rigid aeroshell configurations. To better assess EDL technology options and sensitivities to future human mission design variations, a series of design studies has been conducted. The design studies incorporate EDL technologies with conceptual payload arrangements defined by the Evolvable Mars Campaign to evaluate the integrated system with higher fidelity than have been performed to date. This paper describes the results of the design studies for a lander design using the HIAD, ADEPT and rigid shell entry technologies and includes system and subsystem design details including mass and power estimates. This paper will review the point design for three entry configurations capable of delivering a 20 t human class payload to the surface of Mars.

  7. Engineering description of the ascent/descent bet product

    NASA Technical Reports Server (NTRS)

    Seacord, A. W., II

    1986-01-01

    The Ascent/Descent output product is produced in the OPIP routine from three files which constitute its input. One of these, OPIP.IN, contains mission specific parameters. Meteorological data, such as atmospheric wind velocities, temperatures, and density, are obtained from the second file, the Corrected Meteorological Data File (METDATA). The third file is the TRJATTDATA file which contains the time-tagged state vectors that combine trajectory information from the Best Estimate of Trajectory (BET) filter, LBRET5, and Best Estimate of Attitude (BEA) derived from IMU telemetry. Each term in the two output data files (BETDATA and the Navigation Block, or NAVBLK) are defined. The description of the BETDATA file includes an outline of the algorithm used to calculate each term. To facilitate describing the algorithms, a nomenclature is defined. The description of the nomenclature includes a definition of the coordinate systems used. The NAVBLK file contains navigation input parameters. Each term in NAVBLK is defined and its source is listed. The production of NAVBLK requires only two computational algorithms. These two algorithms, which compute the terms DELTA and RSUBO, are described. Finally, the distribution of data in the NAVBLK records is listed.

  8. STS-40 descent BET products: Development and results

    NASA Technical Reports Server (NTRS)

    Oakes, Kevin F.; Wood, James S.; Findlay, John T.

    1991-01-01

    Descent Best Estimate Trajectory (BET) Data were generated for the final Orbiter Experiments Flight, STS-40. This report discusses the actual development of these post-flight products: the inertial BET, the Extended BET, and the Aerodynamic BET. Summary results are also included. The inertial BET was determined based on processing Tracking and Data Relay Satellite (TDRSS) coherent Doppler data in conjunction with observations from eleven C-band stations, to include data from the Kwajalein Atoll and the usual California coastal radars, as well as data from five cinetheodolite cameras in the vicinity of the runways at EAFB. The anchor epoch utilized for the trajectory reconstruction was 53,904 Greenwich Mean Time (GMT) seconds which corresponds to an altitude at epoch of approximately 708 kft. Atmospheric data to enable development of an Extended BET for this mission were upsurped from the JSC operational post-flight BET. These data were evaluated based on Space Shuttle-derived considerations as well as model comparisons. The Aerodynamic BET includes configuration information, final mass properties, and both flight-determined and predicted aerodynamic performance estimates. The predicted data were based on the final pre-operational databook, updated to include flight determined incrementals based on an earlier ensemble of flights. Aerodynamic performance comparisons are presented and correlated versus statistical results based on twenty-two previous missions.

  9. Physics-based Entry, Descent and Landing Risk Model

    NASA Technical Reports Server (NTRS)

    Gee, Ken; Huynh, Loc C.; Manning, Ted

    2014-01-01

    A physics-based risk model was developed to assess the risk associated with thermal protection system failures during the entry, descent and landing phase of a manned spacecraft mission. In the model, entry trajectories were computed using a three-degree-of-freedom trajectory tool, the aerothermodynamic heating environment was computed using an engineering-level computational tool and the thermal response of the TPS material was modeled using a one-dimensional thermal response tool. The model was capable of modeling the effect of micrometeoroid and orbital debris impact damage on the TPS thermal response. A Monte Carlo analysis was used to determine the effects of uncertainties in the vehicle state at Entry Interface, aerothermodynamic heating and material properties on the performance of the TPS design. The failure criterion was set as a temperature limit at the bondline between the TPS and the underlying structure. Both direct computation and response surface approaches were used to compute the risk. The model was applied to a generic manned space capsule design. The effect of material property uncertainty and MMOD damage on risk of failure were analyzed. A comparison of the direct computation and response surface approach was undertaken.

  10. Race, language, and mental evolution in Darwin's descent of man.

    PubMed

    Alter, Stephen G

    2007-01-01

    Charles Darwin was notoriously ambiguous in his remarks about the relationship between human evolution and biological race. He stressed the original unity of the races, yet he also helped to popularize the notion of a racial hierarchy filling the gaps between the highest anthropoids and civilized Europeans. A focus on Darwin's explanation of how humans initially evolved, however, shows that he mainly stressed not hierarchy but a version of humanity's original mental unity. In his book The Descent of Man, Darwin emphasized a substantial degree of mental development (including the incipient use of language) in the early, monogenetic phase of human evolution. This development, he argued, necessarily came before primeval man's numerical increase, geographic dispersion, and racial diversification, because only thus could one explain how that group was able to spread at the expense of rival ape-like populations. This scenario stood opposed to a new evolutionary polygenism formulated in the wake of Darwin's Origin of Species by his ostensible supporters Alfred Russel Wallace and Ernst Haeckel. Darwin judged this outlook inadequate to the task of explaining humanity's emergence. PMID:17623873

  11. Preliminary Study of a Model Rotor in Descent

    NASA Technical Reports Server (NTRS)

    McAlister, K. W.; Tung, C.; Sharpe, D. L.; Huang, S.; Hendley, E. M.

    2000-01-01

    Within a program designed to develop experimental techniques for measuring the trajectory and structure of vortices trailing from the tips of rotor blades, the present preliminary study focuses on a method for quantifying the trajectory of the trailing vortex during descent flight conditions. This study also presents rotor loads and blade surface pressures for a range of tip-path plane angles and Mach numbers. Blade pressures near the leading edge and along the outer radius are compared with data obtained on the same model rotor, but in open jet facilities. A triangulation procedure based on two directable laser-light sheets, each containing an embedded reference, proved effective in defining the spatial coordinates of the trailing vortex. When interrogating a cross section of the flow that contains several trailing vortices, the greatest clarity was found to result when the flow is uniformly seeded. Surface pressure responses during blade-vortex interactions appeared equally sensitive near the leading edge and along the outer portion of the blade, but diminished rapidly as the distance along the blade chord increased. The pressure response was virtually independent of whether the tip-path plane angle was obtained through shaft tilt or cyclic pitch. Although the shape and frequency of the pressure perturbations on the advancing blade during blade-vortex interaction are similar to those obtained in open-jet facilities, the angle of the tip-path plane may need to be lower than the range covered in this study.

  12. PASDA - a tool to design atmospheric descent bodies with parachutes

    NASA Astrophysics Data System (ADS)

    Adler, D.; Trogus, W.; Bachor, E.; Eiden, M.

    1995-03-01

    PASDA (Parachute System Design and Analysis Tool) is an unique integrated software package, funded by ESA, to design and analyse parachute based systems for space related applications and to provide the environment for collecting and storing parachute related information. PASDA supports future space science mission studies, where parachute systems are an essential part of the mission concept. Based on a sophisticated database of parachute related information for projects requiring descent in a planetary atmosphere, it assists the user in the selection, performance evaluation and specification of a parachute system for a specific mission. PASDA combines very different functions: trajectory simulation, parachute design and analysis, database tasks, graphical output, a sophisticated user interface, user guidance and software code to combine all functions. The parachute design package allows sizing of all parachute components e.g. canopy, lines, mortar, stowage volume, materials to be used, weight, etc. according to the loads derived in deployment and inflation analyses. Specific (parachute) knowledge is required to work efficiently with PASDA. However the integration of the different modules allows to let the computer perform the painstaking work of transforming outputs of one module into inputs for the next one and archiving results as numbers with description and graphics. Thus it provides an efficient integrated design and analysis approach to parachute system decelerators for studies of future space missions.

  13. Estimating Controller Intervention Probabilities for Optimized Profile Descent Arrivals

    NASA Technical Reports Server (NTRS)

    Meyn, Larry A.; Erzberger, Heinz; Huynh, Phu V.

    2011-01-01

    Simulations of arrival traffic at Dallas/Fort-Worth and Denver airports were conducted to evaluate incorporating scheduling and separation constraints into advisories that define continuous descent approaches. The goal was to reduce the number of controller interventions required to ensure flights maintain minimum separation distances of 5 nmi horizontally and 1000 ft vertically. It was shown that simply incorporating arrival meter fix crossing-time constraints into the advisory generation could eliminate over half of the all predicted separation violations and more than 80% of the predicted violations between two arrival flights. Predicted separation violations between arrivals and non-arrivals were 32% of all predicted separation violations at Denver and 41% at Dallas/Fort-Worth. A probabilistic analysis of meter fix crossing-time errors is included which shows that some controller interventions will still be required even when the predicted crossing-times of the advisories are set to add a 1 or 2 nmi buffer above the minimum in-trail separation of 5 nmi. The 2 nmi buffer was shown to increase average flight delays by up to 30 sec when compared to the 1 nmi buffer, but it only resulted in a maximum decrease in average arrival throughput of one flight per hour.

  14. Rapidly Registering Identity-by-Descent Across Ancestral Recombination Graphs.

    PubMed

    Yang, Shuo; Carmi, Shai; Pe'er, Itsik

    2016-06-01

    The genomes of remotely related individuals occasionally contain long segments that are identical by descent (IBD). Sharing of IBD segments has many applications in population and medical genetics, and it is thus desirable to study their properties in simulations. However, no current method provides a direct, efficient means to extract IBD segments from simulated genealogies. Here, we introduce computationally efficient approaches to extract ground-truth IBD segments from a sequence of genealogies, or equivalently, an ancestral recombination graph. Specifically, we use a two-step scheme, where we first identify putative shared segments by comparing the common ancestors of all pairs of individuals at some distance apart. This reduces the search space considerably, and we then proceed by determining the true IBD status of the candidate segments. Under some assumptions and when allowing a limited resolution of segment lengths, our run-time complexity is reduced from O(n(3) log n) for the naïve algorithm to O(n log n), where n is the number of individuals in the sample.

  15. ExoMars Entry, Descent, and Landing Science

    NASA Astrophysics Data System (ADS)

    Karatekin, Özgür; Forget, Francois; Withers, Paul; Colombatti, Giacomo; Aboudan, Alessio; Lewis, Stephen; Ferri, Francesca; Van Hove, Bart; Gerbal, Nicolas

    2016-07-01

    Schiaparelli, the Entry Demonstrator Module (EDM) of the ESA ExoMars Program will to land on Mars on 19th October 2016. The ExoMars Atmospheric Mars Entry and Landing Investigations and Analysis (AMELIA) team seeks to exploit the Entry Descent and Landing (EDL) engineering measurements of Schiaparelli for scientific investigations of Mars' atmosphere and surface. ExoMars offers a rare opportunity to perform an in situ investigation of the martian environment over a wide altitude range. There has been only 7 successfully landing on the surface of Mars, from the Viking probes in the 1970's to the Mars Science Laboratory (MSL) in 2012. ExoMars EDM is equipped with an instrumented heat shield like MSL. These novel flight sensors complement conventional accelerometer and gyroscope instrumentation, and provide additional information to reconstruct atmospheric conditions with. This abstract outlines general atmospheric reconstruction methodology using complementary set of sensors and in particular the use of surface pressure and radio data. In addition, we discuss the lessons learned from previous EDL and the plans for ExoMars AMELIA data analysis.

  16. Mars Science Laboratory Entry, Descent, and Landing System Overview

    NASA Technical Reports Server (NTRS)

    Steltzner, Adam D.; Burkhart, P. Dan; Chen, Allen; Comeaux, Keith A.; Guernsey, Carl S.; Kipp, Devin M.; Lorenzoni, Leila V.; Mendeck, Gavin F.; Powell, Richard W.; Rivellini, Tommaso P.; San Martin, A. Miguel; Sell, Steven W.; Prakash, Ravi; Way, David W.

    2010-01-01

    In 2012, the Mars Science Laboratory (MSL) mission will pioneer the next generation of robotic Entry, Descent, and Landing (EDL) systems by delivering the largest and most capable rover to date to the surface of Mars. In addition to landing more mass than prior missions to Mars, MSL will offer access to regions of Mars that have been previously unreachable. The MSL EDL sequence is a result of a more stringent requirement set than any of its predecessors. Notable among these requirements is landing a 900 kg rover in a landing ellipse much smaller than that of any previous Mars lander. In meeting these requirements, MSL is extending the limits of the EDL technologies qualified by the Mars Viking, Mars Pathfinder, and Mars Exploration Rover missions. Thus, there are many design challenges that must be solved for the mission to be successful. Several pieces of the EDL design are technological firsts, such as guided entry and precision landing on another planet, as well as the entire Sky Crane maneuver. This paper discusses the MSL EDL architecture and discusses some of the challenges faced in delivering an unprecedented rover payload to the surface of Mars.

  17. Beaconless stochastic parallel gradient descent laser beam control: numerical experiments.

    PubMed

    Piatrou, Piotr; Roggemann, Michael

    2007-09-20

    We apply a target-in-the-loop strategy to the case of adaptive optics beam control in the presence of strong atmospheric turbulence for air-to-ground directed energy laser applications. Using numerical simulations we show that in the absence of a cooperative beacon to probe the atmosphere it is possible to extract information suitable for effective beam control from images of the speckled and strongly turbulence degraded intensity distribution of the laser energy at the target. We use a closed-loop, single-deformable-mirror adaptive optics system driven by a target-in-the-loop stochastic parallel gradient descent optimization algorithm minimizing a mean-radius performance metric defined on the image of the laser beam intensity distribution formed at the receiver. We show that a relatively low order 25-channel zonal adaptive optical beam control system controlled in this way is capable of achieving a high degree of turbulence compensation with respect to energy concentration if the tilt can be corrected separately.

  18. Race, language, and mental evolution in Darwin's descent of man.

    PubMed

    Alter, Stephen G

    2007-01-01

    Charles Darwin was notoriously ambiguous in his remarks about the relationship between human evolution and biological race. He stressed the original unity of the races, yet he also helped to popularize the notion of a racial hierarchy filling the gaps between the highest anthropoids and civilized Europeans. A focus on Darwin's explanation of how humans initially evolved, however, shows that he mainly stressed not hierarchy but a version of humanity's original mental unity. In his book The Descent of Man, Darwin emphasized a substantial degree of mental development (including the incipient use of language) in the early, monogenetic phase of human evolution. This development, he argued, necessarily came before primeval man's numerical increase, geographic dispersion, and racial diversification, because only thus could one explain how that group was able to spread at the expense of rival ape-like populations. This scenario stood opposed to a new evolutionary polygenism formulated in the wake of Darwin's Origin of Species by his ostensible supporters Alfred Russel Wallace and Ernst Haeckel. Darwin judged this outlook inadequate to the task of explaining humanity's emergence.

  19. Minimum Landing Error Powered-Descent Guidance for Planetary Missions

    NASA Technical Reports Server (NTRS)

    Blackmore, Lars; Acikmese, Behcet

    2011-01-01

    An algorithm improves the accuracy with which a lander can be delivered to the surface of Mars. The main idea behind this innovation is the use of a lossless convexification, which converts an otherwise non-convex constraint related to thruster throttling to a convex constraint, enabling convex optimization to be used. The convexification leads directly to an algorithm that guarantees finding the global optimum of the original nonconvex optimization problem with a deterministic upper bound on the number of iterations required for convergence. In this innovation, previous work in powered-descent guidance using convex optimization is extended to handle the case where the lander must get as close as possible to the target given the available fuel, but is not required to arrive exactly at the target. The new algorithm calculates the minimum-fuel trajectory to the target, if one exists, and calculates the trajectory that minimizes the distance to the target if no solution to the target exists. This approach poses the problem as two Second-Order Cone Programs, which can be solved to global optimality with deterministic bounds on the number of iterations required.

  20. Estimating the degree of identity by descent in consanguineous couples.

    PubMed

    Carr, Ian M; Markham, Sir Alexander F; Pena, Sérgio D J

    2011-12-01

    In some clinical and research settings, it is often necessary to identify the true level of "identity by descent" (IBD) between two individuals. However, as the individuals become more distantly related, it is increasingly difficult to accurately calculate this value. Consequently, we have developed a computer program that uses genome-wide SNP genotype data from related individuals to estimate the size and extent of IBD in their genomes. In addition, the software can compare a couple's IBD regions with either the autozygous regions of a relative affected by an autosomal recessive disease of unknown cause, or the IBD regions in the parents of the affected relative. It is then possible to calculate the probability of one of the couple's children suffering from the same disease. The software works by finding SNPs that exclude any possible IBD and then identifies regions that lack these SNPs, while exceeding a minimum size and number of SNPs. The accuracy of the algorithm was established by estimating the pairwise IBD between different members of a large pedigree with varying known coefficients of genetic relationship (CGR).

  1. Prediction of identity by descent probabilities from marker-haplotypes.

    PubMed

    Meuwissen, T H; Goddard, M E

    2001-01-01

    The prediction of identity by descent (IBD) probabilities is essential for all methods that map quantitative trait loci (QTL). The IBD probabilities may be predicted from marker genotypes and/or pedigree information. Here, a method is presented that predicts IBD probabilities at a given chromosomal location given data on a haplotype of markers spanning that position. The method is based on a simplification of the coalescence process, and assumes that the number of generations since the base population and effective population size is known, although effective size may be estimated from the data. The probability that two gametes are IBD at a particular locus increases as the number of markers surrounding the locus with identical alleles increases. This effect is more pronounced when effective population size is high. Hence as effective population size increases, the IBD probabilities become more sensitive to the marker data which should favour finer scale mapping of the QTL. The IBD probability prediction method was developed for the situation where the pedigree of the animals was unknown (i.e. all information came from the marker genotypes), and the situation where, say T, generations of unknown pedigree are followed by some generations where pedigree and marker genotypes are known.

  2. The identity by descent process along the chromosome.

    PubMed

    Cannings, Chris

    2003-01-01

    The probabilities of the various possible identity by descent (IBD) states at a locus captures all the genealogical information for that locus for the set of individuals under consideration. Here we study the stochastic process of the IBD state as one moves across the genome of a set of individuals. In general it is no longer sufficient to specify the IBD state, one needs to increase the state space if one is to maintain the Markov property, as has been discussed by for instance McPeak and Sun [Am J Hum Genet 2000;66:1076-1094] and Browning and Browning [Theor Popul Biol 2002;62:1-8]. This paper discusses a general method of deriving the transition matrix for that Markov chain iteratively from one time point to a subsequent one. This method allows a considerable reduction in the size of the state space needed. The basic recursion is set out here and the application is illustrated by two specific examples.

  3. Future accelerators (?)

    SciTech Connect

    John Womersley

    2003-08-21

    I describe the future accelerator facilities that are currently foreseen for electroweak scale physics, neutrino physics, and nuclear structure. I will explore the physics justification for these machines, and suggest how the case for future accelerators can be made.

  4. Finite Element approach for Density Functional Theory calculations on locally refined meshes

    SciTech Connect

    Fattebert, J; Hornung, R D; Wissink, A M

    2007-02-23

    We present a quadratic Finite Element approach to discretize the Kohn-Sham equations on structured non-uniform meshes. A multigrid FAC preconditioner is proposed to iteratively solve the equations by an accelerated steepest descent scheme. The method was implemented using SAMRAI, a parallel software infrastructure for general AMR applications. Examples of applications to small nanoclusters calculations are presented.

  5. Finite Elements approach for Density Functional Theory calculations on locally refined meshes

    SciTech Connect

    Fattebert, J; Hornung, R D; Wissink, A M

    2006-03-27

    We present a quadratic Finite Elements approach to discretize the Kohn-Sham equations on structured non-uniform meshes. A multigrid FAC preconditioner is proposed to iteratively solve the equations by an accelerated steepest descent scheme. The method was implemented using SAMRAI, a parallel software infrastructure for general AMR applications. Examples of applications to small nanoclusters calculations are presented.

  6. Healing internalized racism: the role of a within-group sanctuary among people of African descent.

    PubMed

    Watts-Jones, Dee

    2002-01-01

    This article addresses the role of a "within-group" sanctuary for healing internalized racism among people of African descent. Internalized racism is distinguished from racism, juxtaposing the different experience of those who are oppressed and those who are privileged by racism. It is suggested that a context consisting exclusively of persons of African descent can provide an optimally safe space for initial stages of healing from internalized racism. The anxiety that a collective of African descendants can generate among whites, and subsequently among those of African descent, is examined by raising questions as to its possible meanings. Whites are encouraged to use their privilege to support such self-determined sanctuaries, rather than to obstruct them. People of African descent are encouraged to tolerate the anxiety that can be generated without "changing back," and to examine whether internalized racism is also implicated.

  7. A conflict analysis of 4D descent strategies in a metered, multiple-arrival route environment

    NASA Technical Reports Server (NTRS)

    Izumi, K. H.; Harris, C. S.

    1990-01-01

    A conflict analysis was performed on multiple arrival traffic at a typical metered airport. The Flow Management Evaluation Model (FMEM) was used to simulate arrival operations using Denver Stapleton's arrival route structure. Sensitivities of conflict performance to three different 4-D descent strategies (clear-idle Mach/Constant AirSpeed (CAS), constant descent angle Mach/CAS and energy optimal) were examined for three traffic mixes represented by those found at Denver Stapleton, John F. Kennedy and typical en route metering (ERM) airports. The Monte Carlo technique was used to generate simulation entry point times. Analysis results indicate that the clean-idle descent strategy offers the best compromise in overall performance. Performance measures primarily include susceptibility to conflict and conflict severity. Fuel usage performance is extrapolated from previous descent strategy studies.

  8. User's manual for a fuel-conservative descent planning algorithm implemented on a small programmable calculator

    NASA Technical Reports Server (NTRS)

    Vicroy, D. D.

    1984-01-01

    A simplified flight management descent algorithm was developed and programmed on a small programmable calculator. It was designed to aid the pilot in planning and executing a fuel conservative descent to arrive at a metering fix at a time designated by the air traffic control system. The algorithm may also be used for planning fuel conservative descents when time is not a consideration. The descent path was calculated for a constant Mach/airspeed schedule from linear approximations of airplane performance with considerations given for gross weight, wind, and nonstandard temperature effects. An explanation and examples of how the algorithm is used, as well as a detailed flow chart and listing of the algorithm are contained.

  9. Entry, Descent and Landing (EDL) Technology Investments Within NASA's Space Technology Mission Directorate (STMD)

    NASA Astrophysics Data System (ADS)

    Munk, M. M.

    2014-06-01

    NASA’s Space Technology Mission Directorate has several investments in entry, descent and landing technologies, across its nine programs. This presentation will give a top-level view of the various investments.

  10. Fabrication Assembly and Test of the Mars Science Laboratory Descent Stage Propulsion System

    NASA Technical Reports Server (NTRS)

    Parker, Morgan; Baker, Ray; Casillas, Art; Strommen, Dellon; Tanimoto, Rebekah

    2013-01-01

    The Descent Stage Propulsion System (DSPS) is the most challenging and complex propulsion system ever built at JPL. Performance requirements, such as the entry Reaction Control System (RCS) requirements, and the terminal descent requirements (3300 N maximum thrust and approximately 835,000 N-s total impulse in less than a minute), required a large amount of propellant and a large number of components for a spacecraft that had to fit in a 4.5 meter aeroshell. The size and shape of the aeroshell, along with the envelope of the stowed rover, limited the configuration options for the Descent Stage structure. The configuration and mass constraints of the Descent Stage structure, along with performance requirements, drove the configuration of the DSPS. This paper will examine some of the challenges encountered and solutions developed during the fabrication, assembly, and test of the DSPS.

  11. Antarctic Polar Descent and Planetary Wave Activity Observed in ISAMS CO from April to July 1992

    NASA Technical Reports Server (NTRS)

    Allen, D. R.; Stanford, J. L.; Nakamura, N.; Lopez-Valverde, M. A.; Lopez-Puertas, M.; Taylor, F. W.; Remedios, J. J.

    2000-01-01

    Antarctic polar descent and planetary wave activity in the upper stratosphere and lower mesosphere are observed in ISAMS CO data from April to July 1992. CO-derived mean April-to-May upper stratosphere descent rates of 15 K/day (0.25 km/day) at 60 S and 20 K/day (0.33 km/day) at 80 S are compared with descent rates from diabatic trajectory analyses. At 60 S there is excellent agreement, while at 80 S the trajectory-derived descent is significantly larger in early April. Zonal wavenumber 1 enhancement of CO is observed on 9 and 28 May, coincident with enhanced wave 1 in UKMO geopotential height. The 9 May event extends from 40 to 70 km and shows westward phase tilt with height, while the 28 May event extends from 40 to 50 km and shows virtually no phase tilt with height.

  12. Analysis of Flight Management System Predictions of Idle-Thrust Descents

    NASA Technical Reports Server (NTRS)

    Stell, Laurel

    2010-01-01

    To enable arriving aircraft to fly optimized descents computed by the flight management system (FMS) in congested airspace, ground automation must accurately predict descent trajectories. To support development of the predictor and its uncertainty models, descents from cruise to the meter fix were executed using vertical navigation in a B737-700 simulator and a B777-200 simulator, both with commercial FMSs. For both aircraft types, the FMS computed the intended descent path for a specified speed profile assuming idle thrust after top of descent (TOD), and then it controlled the avionics without human intervention. The test matrix varied aircraft weight, descent speed, and wind conditions. The first analysis in this paper determined the effect of the test matrix parameters on the FMS computation of TOD location, and it compared the results to those for the current ground predictor in the Efficient Descent Advisor (EDA). The second analysis was similar but considered the time to fly a specified distance to the meter fix. The effects of the test matrix variables together with the accuracy requirements for the predictor will determine the allowable error for the predictor inputs. For the B737, the EDA prediction of meter fix crossing time agreed well with the FMS; but its prediction of TOD location probably was not sufficiently accurate to enable idle-thrust descents in congested airspace, even though the FMS and EDA gave similar shapes for TOD location as a function of the test matrix variables. For the B777, the FMS and EDA gave different shapes for the TOD location function, and the EDA prediction of the TOD location is not accurate enough to fully enable the concept. Furthermore, the differences between the FMS and EDA predictions of meter fix crossing time for the B777 indicated that at least one of them was not sufficiently accurate.

  13. Mars Science Laboratory Entry, Descent and Landing System Development Challenges and Preliminary Flight Performance

    NASA Technical Reports Server (NTRS)

    Steltzner, Adam D.; San Martin, A. Miguel; Rivellini, Tommaso P.

    2013-01-01

    The Mars Science Laboratory project recently landed the Curiosity rover on the surface of Mars. With the success of the landing system, the performance envelope of entry, descent, and landing capabilities has been extended over the previous state of the art. This paper will present an overview of the MSL entry, descent, and landing system, a discussion of a subset of its development challenges, and include a discussion of preliminary results of the flight reconstruction effort.

  14. Reconstruction of the Mars Science Laboratory Parachute Performance and Comparison to the Descent Simulation

    NASA Technical Reports Server (NTRS)

    Cruz, Juan R.; Way, David W.; Shidner, Jeremy D.; Davis, Jody L.; Adams, Douglas S.; Kipp, Devin M.

    2013-01-01

    The Mars Science Laboratory used a single mortar-deployed disk-gap-band parachute of 21.35 m nominal diameter to assist in the landing of the Curiosity rover on the surface of Mars. The parachute system s performance on Mars has been reconstructed using data from the on-board inertial measurement unit, atmospheric models, and terrestrial measurements of the parachute system. In addition, the parachute performance results were compared against the end-to-end entry, descent, and landing (EDL) simulation created to design, develop, and operate the EDL system. Mortar performance was nominal. The time from mortar fire to suspension lines stretch (deployment) was 1.135 s, and the time from suspension lines stretch to first peak force (inflation) was 0.635 s. These times were slightly shorter than those used in the simulation. The reconstructed aerodynamic portion of the first peak force was 153.8 kN; the median value for this parameter from an 8,000-trial Monte Carlo simulation yielded a value of 175.4 kN - 14% higher than the reconstructed value. Aeroshell dynamics during the parachute phase of EDL were evaluated by examining the aeroshell rotation rate and rotational acceleration. The peak values of these parameters were 69.4 deg/s and 625 deg/sq s, respectively, which were well within the acceptable range. The EDL simulation was successful in predicting the aeroshell dynamics within reasonable bounds. The average total parachute force coefficient for Mach numbers below 0.6 was 0.624, which is close to the pre-flight model nominal drag coefficient of 0.615.

  15. Analysis of atmospheric mesoscale models for entry, descent, and landing

    NASA Astrophysics Data System (ADS)

    Kass, D. M.; Schofield, J. T.; Michaels, T. I.; Rafkin, S. C. R.; Richardson, M. I.; Toigo, A. D.

    2003-11-01

    Each Mars Exploration Rover (MER) is sensitive to the Martian winds encountered near the surface during the entry, descent, and landing (EDL) process. These winds are strongly influenced by local (mesoscale) conditions. In the absence of suitable wind observations, wind fields predicted by Martian mesoscale atmospheric models have been analyzed to guide landing site selection. In order to encompass the available models and render them useful to the EDL engineering team, a series of statistical techniques was applied to the model results. These analyses cover the high-priority landing sites during the expected landing times (1200-1500 LT). The number of sites studied is limited by the computational and analysis cost of the mesoscale models. The statistical measures concentrate on the effective mean wind (the wind as seen by the landing system) and on the vertical structure of the horizontal winds. Both aspects are potentially hazardous to the MER landing system. In addition, a number of individual wind profiles from the mesoscale model were processed into a form that can be used directly by the EDL Monte Carlo simulations. The statistical analysis indicates that the Meridiani Planum and Elysium landing sites are probably safe. The Gusev Crater and Isidis Basin sites may be safe, but further analysis by the EDL engineers will be necessary to quantify the actual risk. Finally, the winds at the Melas Chasma landing site (and presumably other Valles Marineris landing sites) are dangerous. While the statistical parameters selected for these studies were primarily of engineering and safety interest, the techniques are potentially useful for more general scientific analyses. One interesting result of the current analysis is that the depth of the convective boundary layer (and thus the resulting energy density) appears to be primarily driven by the existence of a well-organized mesoscale (or regional) circulation, primarily driven by large-scale topographic features at Mars.

  16. Application of inflatable aeroshell structures for Entry Descent and Landing

    NASA Astrophysics Data System (ADS)

    Jurewicz, David; Lichodziejewski, Leo; Tutt, Ben; Gilles, Brian; Brown, Glen

    Future space missions will require improvements in the Entry, Descent, and Landing (EDL) phases of the mission architecture. The focus of this paper is to discuss recent advances in analysis, fabrication techniques, ground testing, and flight testing of a stacked torus Hypersonic Inflatable Aerodynamic Decelerator (HIAD) and its application to the future of EDL. The primary structure of a stacked torus HIAD consists of nested inflatable tori of increasing major diameter bonded and strapped to form a rigid structure after inflation. The underlying structure of the decelerator is covered with a flexible Thermal Protection System (TPS) capable of high heat flux. The inflatable aeroshell and TPS are packed around a centerbody within the launch fairing and deployed prior to atmospheric reentry. Recent fabrication of multiple HIADs between 3 and 6 meters has led to significant advances in process control and validation of the scalability of the technology. Progress has been made in generating and validating LS-DYNA FEA models to replicate flight loading in addition to analytical models of substructures. Coupon and component testing has improved the validation of modeling techniques and assumptions at the subsystem level. A ground testing campaign at the National Full-Scale Aerodynamics Center (NFAC) wind tunnel at NASA Ames Research center generated substantial aerodynamic and loading data to validate full system modeling with comparable dynamic pressures to a hypersonic reentry. The Inflatable Reentry Vehicle - 3 (IRVE-3) sounding rocket flight test was conducted with NASA Langley Research Center in July 2012. The IRVE-3 mission verified the structural and thermal performance of the stacked torus configuration. Further development of the stacked torus configuration is currently being conducted to increase the thermal capability, deceleration loads, and understanding of the interactions and effects of constituent components. The results of this research have expanded the

  17. Physiological consequences of social descent: studies in Astatotilapia burtoni.

    PubMed

    Parikh, Victoria N; Clement, Tricia; Fernald, Russell D

    2006-07-01

    In many species, social interactions regulate reproductive capacity, although the exact mechanisms of such regulation are unclear. Since social stress is often related to reproductive regulation, we measured the physiological signatures of change in reproductive state as they relate to short-term stress and the stress hormone cortisol. We used an African cichlid fish, Astatotilapia burtoni, with two distinct, reversible male phenotypes: dominant (territorial, T) males that are larger, more brightly colored, more aggressive, and reproductively competent and non-dominant males (non-territorial, NT) that are smaller, camouflage colored, and have regressed gonads. Male status, and hence reproductive competence, depends on social experience in this system. Specifically, if a T male is placed among larger male fish, it quickly becomes NT in behavior and coloration, but complete regression of its reproductive axis takes ca. 3 weeks (White et al. 2002). Reproduction in all vertebrates is controlled by the hypothalamic-pituitary-gonadal axis in which the key signaling molecule from the brain to the pituitary is GnRH1. Here, we subjected T males to territory loss, a social manipulation which results in status descent. We measured the effects of this status change in levels of circulating cortisol and testosterone as well as mRNA levels of GnRH1 and GnRH receptor-1 (GnRH-R1) in the brain and pituitary, respectively. Following short-term social suppression (4 h), no change was observed in plasma cortisol level, GnRH1 mRNA expression, GnRH-R1 mRNA expression, or plasma testosterone level. However, following a somewhat longer social suppression (24 h), cortisol and GnRH1 mRNA levels were significantly increased, and testosterone levels were significantly decreased. These results suggest that in the short run, deposed T males essentially mount a neural 'defense' against loss of status.

  18. Mars 2020 Entry, Descent and Landing Instrumentation (MEDLI2)

    NASA Technical Reports Server (NTRS)

    Bose, Deepak; Wright, Henry; White, Todd; Schoenenberger, Mark; Santos, Jose; Karlgaard, Chris; Kuhl, Chris; Oishi, TOmo; Trombetta, Dominic

    2016-01-01

    This paper will introduce Mars Entry Descent and Landing Instrumentation (MEDLI2) on NASA's Mars2020 mission. Mars2020 is a flagship NASA mission with science and technology objectives to help answer questions about possibility of life on Mars as well as to demonstrate technologies for future human expedition. Mars2020 is scheduled for launch in 2020. MEDLI2 is a suite of instruments embedded in the heatshield and backshell thermal protection systems of Mars2020 entry vehicle. The objectives of MEDLI2 are to gather critical aerodynamics, aerothermodynamics and TPS performance data during EDL phase of the mission. MEDLI2 builds up the success of MEDLI flight instrumentation on Mars Science Laboratory mission in 2012. MEDLI instrumentation suite measured surface pressure and TPS temperature on the heatshield during MSL entry into Mars. MEDLI data has since been used for unprecedented reconstruction of aerodynamic drag, vehicle attitude, in-situ atmospheric density, aerothermal heating, transition to turbulence, in-depth TPS performance and TPS ablation. [1,2] In addition to validating predictive models, MEDLI data has highlighted extra margin available in the MSL forebody TPS, which can potentially be used to reduce vehicle parasitic mass. MEDLI2 expands the scope of instrumentation by focusing on quantities of interest not addressed in MEDLI suite. The type the sensors are expanded and their layout on the TPS modified to meet these new objectives. The paper will provide key motivation and governing requirements that drive the choice and the implementation of the new sensor suite. The implementation considerations of sensor selection, qualification, and demonstration of minimal risk to the host mission will be described. The additional challenges associated with mechanical accommodation, electrical impact, data storage and retrieval for MEDLI2 system, which extends sensors to backshell will also be described.

  19. Atmospheric Environments for Entry, Descent and Landing (EDL)

    NASA Technical Reports Server (NTRS)

    Justus, Carl G.; Braun, Robert D.

    2007-01-01

    Scientific measurements of atmospheric properties have been made by a wide variety of planetary flyby missions, orbiters, and landers. Although landers can make in-situ observations of near-surface atmospheric conditions (and can collect atmospheric data during their entry phase), the vast majority of data on planetary atmospheres has been collected by remote sensing techniques from flyby and orbiter spacecraft (and to some extent by Earth-based remote sensing). Many of these remote sensing observations (made over a variety of spectral ranges), consist of vertical profiles of atmospheric temperature as a function of atmospheric pressure level. While these measurements are of great interest to atmospheric scientists and modelers of planetary atmospheres, the primary interest for engineers designing entry descent and landing (EDL) systems is information about atmospheric density as a function of geometric altitude. Fortunately, as described in in this paper, it is possible to use a combination of the gas-law relation and the hydrostatic balance relation to convert temperature-versus-pressure, scientific observations into density-versus-altitude data for use in engineering applications. The following section provides a brief introduction to atmospheric thermodynamics, as well as constituents, and winds for EDL. It also gives methodology for using atmospheric information to do "back-of-the-envelope" calculations of various EDL aeroheating parameters, including peak deceleration rate ("g-load"), peak convective heat rate. and total heat load on EDL spacecraft thermal protection systems. Brief information is also provided about atmospheric variations and perturbations for EDL guidance and control issues, and atmospheric issues for EDL parachute systems. Subsequent sections give details of the atmospheric environments for five destinations for possible EDL missions: Venus. Earth. Mars, Saturn, and Titan. Specific atmospheric information is provided for these destinations

  20. Aerodynamics of Reentry Vehicle Clipper at Descent Phase

    NASA Astrophysics Data System (ADS)

    Semenov, Yu. P.; Reshetin, A. G.; Dyadkin, A. A.; Petrov, N. K.; Simakova, T. V.; Tokarev, V. A.

    2005-02-01

    From Gagarin spacecraft to reusable orbiter Buran, RSC Energia has traveled a long way in the search for the most optimal and, which is no less important, the most reliable spacecraft for manned space flight. During the forty years of space exploration, in cooperation with a broad base of subcontractors, a number of problems have been solved which assure a safe long stay in space. Vostok and Voskhod spacecraft were replaced with Soyuz supporting a crew of three. During missions to a space station, it provides crew rescue capability in case of a space station emergency at all times (the spacecraft life is 200 days).The latest modification of Soyuz spacecraft -Soyuz TMA -in contrast to its predecessors, allows to become a space flight participant to a person of virtually any anthropometric parameters with a mass of 50 to 95 kg capable of withstanding up to 6 g load during descent. At present, Soyuz TMA spacecraft are the state-of-the-art, reliable and only means of the ISS crew delivery, in-flight support and return. Introduced on the basis of many years of experience in operation of manned spacecraft were not only the principles of deep redundancy of on-board systems and equipment, but, to assure the main task of the spacecraft -the crew return to Earth -the principles of functional redundancy. That is, vital operations can be performed by different systems based on different physical principles. The emergency escape system that was developed is the only one in the world that provides crew rescue in case of LV failure at any phase in its flight. Several generations of space stations that have been developed have broadened, virtually beyond all limits, capabilities of man in space. The docking system developed at RSC Energia allowed not only to dock spacecraft in space, but also to construct in orbit various complex space systems. These include large space stations, and may include in the future the in-orbit construction of systems for the exploration of the Moon and

  1. Planning fuel-conservative descents in an airline environmental using a small programmable calculator: Algorithm development and flight test results

    NASA Technical Reports Server (NTRS)

    Knox, C. E.; Vicroy, D. D.; Simmon, D. A.

    1985-01-01

    A simple, airborne, flight-management descent algorithm was developed and programmed into a small programmable calculator. The algorithm may be operated in either a time mode or speed mode. The time mode was designed to aid the pilot in planning and executing a fuel-conservative descent to arrive at a metering fix at a time designated by the air traffic control system. The speed model was designed for planning fuel-conservative descents when time is not a consideration. The descent path for both modes was calculated for a constant with considerations given for the descent Mach/airspeed schedule, gross weight, wind, wind gradient, and nonstandard temperature effects. Flight tests, using the algorithm on the programmable calculator, showed that the open-loop guidance could be useful to airline flight crews for planning and executing fuel-conservative descents.

  2. Planning fuel-conservative descents in an airline environmental using a small programmable calculator: algorithm development and flight test results

    SciTech Connect

    Knox, C.E.; Vicroy, D.D.; Simmon, D.A.

    1985-05-01

    A simple, airborne, flight-management descent algorithm was developed and programmed into a small programmable calculator. The algorithm may be operated in either a time mode or speed mode. The time mode was designed to aid the pilot in planning and executing a fuel-conservative descent to arrive at a metering fix at a time designated by the air traffic control system. The speed model was designed for planning fuel-conservative descents when time is not a consideration. The descent path for both modes was calculated for a constant with considerations given for the descent Mach/airspeed schedule, gross weight, wind, wind gradient, and nonstandard temperature effects. Flight tests, using the algorithm on the programmable calculator, showed that the open-loop guidance could be useful to airline flight crews for planning and executing fuel-conservative descents.

  3. Tracer-Based Determination of Vortex Descent in the 1999-2000 Arctic Winter

    NASA Technical Reports Server (NTRS)

    Greenblatt, Jeffery B.; Jost, Hans-Juerg; Loewenstein, Max; Podolske, James R.; Hurst, Dale F.; Elkins, James W.; Schauffler, Sue M.; Atlas, Elliot L.; Herman, Robert L.; Webster, Christopher R.

    2001-01-01

    A detailed analysis of available in situ and remotely sensed N2O and CH4 data measured in the 1999-2000 winter Arctic vortex has been performed in order to quantify the temporal evolution of vortex descent. Differences in potential temperature (theta) among balloon and aircraft vertical profiles (an average of 19-23 K on a given N2O or CH4 isopleth) indicated significant vortex inhomogeneity in late fall as compared with late winter profiles. A composite fall vortex profile was constructed for November 26, 1999, whose error bars encompassed the observed variability. High-latitude, extravortex profiles measured in different years and seasons revealed substantial variability in N2O and CH4 on theta surfaces, but all were clearly distinguishable from the first vortex profiles measured in late fall 1999. From these extravortex-vortex differences, we inferred descent prior to November 26: 397+/-15 K (1sigma) at 30 ppbv N2O and 640 ppbv CH4, and 28+/-13 K above 200 ppbv N2O and 1280 ppbv CH4. Changes in theta were determined on five N2O and CH4 isopleths from November 26 through March 12, and descent rates were calculated on each N2O isopleth for several time intervals. The maximum descent rates were seen between November 26 and January 27: 0.82+/-0.20 K/day averaged over 50-250 ppbv N2O. By late winter (February 26-March 12), the average rate had decreased to 0.10+/-0.25 K/day. Descent rates also decreased with increasing N2O; the winter average (November 26-March 5) descent rate varied from 0.75+/-0.10 K/day at 50 ppbv to 0.40+/-0.11 K/day at 250 ppbv. Comparison of these results with observations and models of descent in prior years showed very good overall agreement. Two models of the 1999-2000 vortex descent, SLIMCAT and REPROBUS, despite theta offsets with respect to observed profiles of up to 20 K on most tracer isopleths, produced descent rates that agreed very favorably with the inferred rates from observation.

  4. Attitude and angular rates of planetary probes during atmospheric descent: Implications for imaging

    NASA Astrophysics Data System (ADS)

    Lorenz, Ralph D.

    2010-04-01

    Attitude dynamics data from planetary missions are reviewed to obtain a zeroth-order expectation on the tilts and angular rates to be expected on atmospheric probes during descent: these rates are a strong driver on descent imager design. While recent Mars missions have been equipped with capable inertial measurements, attitude measurements for missions to other planetary bodies are rather limited but some angular motion estimates can be derived from accelerometer, Doppler or other data. It is found that robust camera designs should tolerate motions of the order of 20-40°/s, encountered by Mars Pathfinder, Pioneer Venus, Venera and the high speed part of the Huygens descent on Titan. Under good conditions, parachute-stabilized probes can experience rates of 1-5°/s, seen by the Mars Exploration Rovers and Viking, Galileo at Jupiter, and the slow speed parts of the Huygens descent. In the lowest 20 km of the descent on Titan, the Huygens probe was within 2° of vertical over 95% of the time. Some factors influencing these motions are discussed.

  5. Diagnostic Clues to Frontal Fibrosing Alopecia in Patients of African Descent

    PubMed Central

    Reid, Sophia D.; Obayan, Olubusayo; Mcclellan, Liza; Sperling, Leonard

    2016-01-01

    Importance: Frontal fibrosing alopecia has previously been reported as rare among patients of African descent. The authors present 18 cases of frontal fibrosing alopecia affecting African American patients and review all published cases of frontal fibrosing alopecia involving patients of African descent. Observations: Since 2010, there have been 66 published cases of frontal fibrosing alopecia among patients of African descent; 59 women, five men, and two cases of unknown gender. Frontal fibrosing alopecia is not uncommon among patients of African descent. In this study, the authors find that female African American patients may have fewer symptoms and unique clinical presentations. Conclusion and relevance: Frontal fibrosing alopecia is an entity that can be seen in patients with many different ethnic backgrounds, often with varying presentations. The diagnosis of frontal fibrosing alopecia must be considered in any patient of African descent who presents with frontotemporal alopecia. In the authors’ patient population, there was a younger age of presentation. The presence of perifollicular hyperpigmentation along the hairline and concomitant facial hyperpigmentation may aid in making the diagnosis and distinguishing this entity from traction alopecia. PMID:27721910

  6. Analysis of foot clearance in firefighters during ascent and descent of stairs.

    PubMed

    Kesler, Richard M; Horn, Gavin P; Rosengren, Karl S; Hsiao-Wecksler, Elizabeth T

    2016-01-01

    Slips, trips, and falls are a leading cause of injury to firefighters with many injuries occurring while traversing stairs, possibly exaggerated by acute fatigue from firefighting activities and/or asymmetric load carriage. This study examined the effects that fatigue, induced by simulated firefighting activities, and hose load carriage have on foot clearance while traversing stairs. Landing and passing foot clearances for each stair during ascent and descent of a short staircase were investigated. Clearances decreased significantly (p < 0.05) post-exercise for nine of 12 ascent parameters and increased for two of eight descent parameters. Load carriage resulted in significantly decreased (p < 0.05) clearance over three ascent parameters, and one increase during descent. Decreased clearances during ascent caused by fatigue or load carriage may result in an increased trip risk. Increased clearances during descent may suggest use of a compensation strategy to ensure stair clearance or an increased risk of over-stepping during descent.

  7. TRW - Lunar Descent Engine. Chapter 6, Appendix H

    NASA Technical Reports Server (NTRS)

    Elverum, Gerard W.

    2009-01-01

    it came to Apollo 13, we went back into the record, and said, "Hey, we have pushed this system around up there on Apollo 5, and we have also restarted this tandem configuration." The requirements on Apollo 13 were to put it back into play. The spacecraft was out of free return to the earth at the time of the accident. It would not have come back. NASA said, "Okay, we ll use the descent engine to put the spacecraft in a free trajectory; it will go around the moon and be on free trajectory back to Earth." Then, as it came around the far side of the moon, the guys found out that they had an oxygen problem. As you remember, things were getting pretty bad in there. They said, "We ve got to get it back as fast as we can. Is it okay if we re-fire the engine? Now, we re in a free trajectory, so we want to put as much delta-v (or change in velocity) in as we can. Can we re-fire right now?" We said, "Yes, the data says it has been this period of time." We could re-fire the engine, run the rest of the duty cycle up as far as we needed while preserving enough fluids to make the final correction as the spacecraft got near Earth, and restart the engine. It was pretty fortuitous that we could give them those answers.

  8. Wakefield accelerators

    SciTech Connect

    Simpson, J.D.

    1990-01-01

    The search for new methods to accelerate particle beams to high energy using high gradients has resulted in a number of candidate schemes. One of these, wakefield acceleration, has been the subject of considerable R D in recent years. This effort has resulted in successful proof of principle experiments and in increased understanding of many of the practical aspects of the technique. Some wakefield basics plus the status of existing and proposed experimental work is discussed, along with speculations on the future of wake field acceleration. 10 refs., 6 figs.

  9. LINEAR ACCELERATOR

    DOEpatents

    Colgate, S.A.

    1958-05-27

    An improvement is presented in linear accelerators for charged particles with respect to the stable focusing of the particle beam. The improvement consists of providing a radial electric field transverse to the accelerating electric fields and angularly introducing the beam of particles in the field. The results of the foregoing is to achieve a beam which spirals about the axis of the acceleration path. The combination of the electric fields and angular motion of the particles cooperate to provide a stable and focused particle beam.

  10. Dissipative descent: rocking and rolling down an incline

    NASA Astrophysics Data System (ADS)

    Balmforth, N. J.; Bush, J. W. M.; Vener, D.; Young, W. R.

    We consider the dynamics of a hollow cylindrical shell that is filled with viscous fluid and another, nested solid cylinder, and allowed to roll down an inclined plane. A mathematical model is compared to simple experiments. Two types of behaviour are observed experimentally: on steeper slopes, the device accelerates; on shallower inclines, the cylinders rock and roll unsteadily downhill, with a speed that is constant on average. The theory also predicts runaway and unsteady rolling motions. For the rolling solutions, however, the inner cylinder cannot be suspended in the fluid by the motion of the outer cylinder, and instead falls inexorably toward the outer cylinder. Whilst only occurs after an infinite time, the system slows progressively as the gap between the cylinders narrows, owing to heightened viscous dissipation. Such a deceleration is not observed in the experiments, suggesting that some mechanism limits the approach to contact. Coating the surface of the inner cylinder with sandpaper of different grades changes the rolling speed, consistent with the notion that surface roughness is responsible for limiting the acceleration.

  11. Descent and Landing Triggers for the Orion Multi-Purpose Crew Vehicle Exploration Flight Test-1

    NASA Technical Reports Server (NTRS)

    Bihari, Brian D.; Semrau, Jeffrey D.; Duke, Charity J.

    2013-01-01

    The Orion Multi-Purpose Crew Vehicle (MPCV) will perform a flight test known as Exploration Flight Test-1 (EFT-1) currently scheduled for 2014. One of the primary functions of this test is to exercise all of the important Guidance, Navigation, Control (GN&C), and Propulsion systems, along with the flight software for future flights. The Descent and Landing segment of the flight is governed by the requirements levied on the GN&C system by the Landing and Recovery System (LRS). The LRS is a complex system of parachutes and flight control modes that ensure that the Orion MPCV safely lands at its designated target in the Pacific Ocean. The Descent and Landing segment begins with the jettisoning of the Forward Bay Cover and concludes with sensing touchdown. This paper discusses the requirements, design, testing, analysis and performance of the current EFT-1 Descent and Landing Triggers flight software.

  12. Advances in POST2 End-to-End Descent and Landing Simulation for the ALHAT Project

    NASA Technical Reports Server (NTRS)

    Davis, Jody L.; Striepe, Scott A.; Maddock, Robert W.; Hines, Glenn D.; Paschall, Stephen, II; Cohanim, Babak E.; Fill, Thomas; Johnson, Michael C.; Bishop, Robert H.; DeMars, Kyle J.; Sostaric, Ronald r.; Johnson, Andrew E.

    2008-01-01

    Program to Optimize Simulated Trajectories II (POST2) is used as a basis for an end-to-end descent and landing trajectory simulation that is essential in determining design and integration capability and system performance of the lunar descent and landing system and environment models for the Autonomous Landing and Hazard Avoidance Technology (ALHAT) project. The POST2 simulation provides a six degree-of-freedom capability necessary to test, design and operate a descent and landing system for successful lunar landing. This paper presents advances in the development and model-implementation of the POST2 simulation, as well as preliminary system performance analysis, used for the testing and evaluation of ALHAT project system models.

  13. Control of stair ascent and descent with a powered transfemoral prosthesis.

    PubMed

    Lawson, Brian Edward; Varol, Huseyin Atakan; Huff, Amanda; Erdemir, Erdem; Goldfarb, Michael

    2013-05-01

    This paper presents a finite state-based control system for a powered transfemoral prosthesis that provides stair ascent and descent capability. The control system was implemented on a powered prosthesis and evaluated by a unilateral, transfemoral amputee subject. The ability of the powered prosthesis to provide stair ascent and descent capability was assessed by comparing the gait kinematics, as recorded by a motion capture system, with the kinematics provided by a passive prosthesis, in addition to those recorded from a set of healthy subjects. The results indicate that the powered prosthesis provides gait kinematics that are considerably more representative of healthy gait, relative to the passive prosthesis, for both stair ascent and descent.

  14. ION ACCELERATOR

    DOEpatents

    Bell, J.S.

    1959-09-15

    An arrangement for the drift tubes in a linear accelerator is described whereby each drift tube acts to shield the particles from the influence of the accelerating field and focuses the particles passing through the tube. In one embodiment the drift tube is splii longitudinally into quadrants supported along the axis of the accelerator by webs from a yoke, the quadrants. webs, and yoke being of magnetic material. A magnetic focusing action is produced by energizing a winding on each web to set up a magnetic field between adjacent quadrants. In the other embodiment the quadrants are electrically insulated from each other and have opposite polarity voltages on adjacent quadrants to provide an electric focusing fleld for the particles, with the quadrants spaced sufficienily close enough to shield the particles within the tube from the accelerating electric field.

  15. Acceleration switch

    DOEpatents

    Abbin, J.P. Jr.; Devaney, H.F.; Hake, L.W.

    1979-08-29

    The disclosure relates to an improved integrating acceleration switch of the type having a mass suspended within a fluid filled chamber, with the motion of the mass initially opposed by a spring and subsequently not so opposed.

  16. Acceleration switch

    DOEpatents

    Abbin, Jr., Joseph P.; Devaney, Howard F.; Hake, Lewis W.

    1982-08-17

    The disclosure relates to an improved integrating acceleration switch of the type having a mass suspended within a fluid filled chamber, with the motion of the mass initially opposed by a spring and subsequently not so opposed.

  17. Eye Movement Patterns of the Elderly during Stair Descent:Effect of Illumination

    NASA Astrophysics Data System (ADS)

    Kasahara, Satoko; Okabe, Sonoko; Nakazato, Naoko; Ohno, Yuko

    The relationship between the eye movement pattern during stair descent and illumination was studied in 4 elderly people in comparison with that in 5 young people. The illumination condition was light (85.0±30.9 lx) or dark (0.7±0.3 lx), and data of eye movements were obtained using an eye mark recorder. A flight of 15 steps was used for the experiment, and data on 3 steps in the middle, on which the descent movements were stabilized, were analyzed. The elderly subjects pointed their eyes mostly directly in front in the facial direction regardless of the illumination condition, but the young subjects tended to look down under the light condition. The young subjects are considered to have confirmed the safety of the front by peripheral vision, checked the stepping surface by central vision, and still maintained the upright position without leaning forward during stair descent. The elderly subjects, in contrast, always looked at the visual target by central vision even under the light condition and leaned forward. The range of eye movements was larger vertically than horizontally in both groups, and a characteristic eye movement pattern of repeating a vertical shuttle movement synchronous with descent of each step was observed. Under the dark condition, the young subjects widened the range of vertical eye movements and reduced duration of fixation. The elderly subjects showed no change in the range of eye movements but increased duration of fixation during stair descent. These differences in the eye movements are considered to be compensatory reactions to narrowing of the vertical visual field, reduced dark adaptation, and reduced dynamic visual acuity due to aging. These characteristics of eye movements of the elderly lead to an anteriorly leaned posture and lack of attention to the front during stair descent.

  18. Evolutionary analyses of non-genealogical bonds produced by introgressive descent.

    PubMed

    Bapteste, Eric; Lopez, Philippe; Bouchard, Frédéric; Baquero, Fernando; McInerney, James O; Burian, Richard M

    2012-11-01

    All evolutionary biologists are familiar with evolutionary units that evolve by vertical descent in a tree-like fashion in single lineages. However, many other kinds of processes contribute to evolutionary diversity. In vertical descent, the genetic material of a particular evolutionary unit is propagated by replication inside its own lineage. In what we call introgressive descent, the genetic material of a particular evolutionary unit propagates into different host structures and is replicated within these host structures. Thus, introgressive descent generates a variety of evolutionary units and leaves recognizable patterns in resemblance networks. We characterize six kinds of evolutionary units, of which five involve mosaic lineages generated by introgressive descent. To facilitate detection of these units in resemblance networks, we introduce terminology based on two notions, P3s (subgraphs of three nodes: A, B, and C) and mosaic P3s, and suggest an apparatus for systematic detection of introgressive descent. Mosaic P3s correspond to a distinct type of evolutionary bond that is orthogonal to the bonds of kinship and genealogy usually examined by evolutionary biologists. We argue that recognition of these evolutionary bonds stimulates radical rethinking of key questions in evolutionary biology (e.g., the relations among evolutionary players in very early phases of evolutionary history, the origin and emergence of novelties, and the production of new lineages). This line of research will expand the study of biological complexity beyond the usual genealogical bonds, revealing additional sources of biodiversity. It provides an important step to a more realistic pluralist treatment of evolutionary complexity.

  19. LINEAR ACCELERATOR

    DOEpatents

    Christofilos, N.C.; Polk, I.J.

    1959-02-17

    Improvements in linear particle accelerators are described. A drift tube system for a linear ion accelerator reduces gap capacity between adjacent drift tube ends. This is accomplished by reducing the ratio of the diameter of the drift tube to the diameter of the resonant cavity. Concentration of magnetic field intensity at the longitudinal midpoint of the external sunface of each drift tube is reduced by increasing the external drift tube diameter at the longitudinal center region.

  20. Minimum-Cost Aircraft Descent Trajectories with a Constrained Altitude Profile

    NASA Technical Reports Server (NTRS)

    Wu, Minghong G.; Sadovsky, Alexander V.

    2015-01-01

    An analytical formula for solving the speed profile that accrues minimum cost during an aircraft descent with a constrained altitude profile is derived. The optimal speed profile first reaches a certain speed, called the minimum-cost speed, as quickly as possible using an appropriate extreme value of thrust. The speed profile then stays on the minimum-cost speed as long as possible, before switching to an extreme value of thrust for the rest of the descent. The formula is applied to an actual arrival route and its sensitivity to winds and airlines' business objectives is analyzed.

  1. Initial Field Evaluation of Pilot Procedures for Flying CTAS Descent Clearances

    NASA Technical Reports Server (NTRS)

    Palmer, Everett; Goka, Tsuyoshi; Cashion, Patricia; Feary, Michael; Graham, Holly; Smith, Nancy; Shafto, Michael (Technical Monitor)

    1994-01-01

    The Center TRACON Automation System (CTAS) is a new support system that is designed to assist air traffic controllers in the management of arrival traffic. CTAS will provide controllers with more information about current air traffic, enabling them to provide clearances for efficient, conflict-free descents that help achieve an orderly stream of aircraft at the final approach fix. CTAS is a computer-based system that functions as a "ground-based FMS" that can predict flight trajectories and arrival times for all incoming aircraft. CTAS uses an aircraft's cruise airspeed; current air traffic, winds and temperature; performance characteristics of the aircraft type; and individual airline preferences to create a flight profile from cruise altitude to the final approach fix. Controllers can use this flight profile to provide a descent clearance that will allow an aircraft to fly an efficient descent and merge more smoothly with other arriving aircraft. A field test of the CTAS Descent Advisor software was conducted at the Denver Center for aircraft arriving at the Stapleton International Airport from September 12-29. CTAS Descent clearances were given to a NASA flight test aircraft and to 77 airline flights that arrived during low traffic periods. For the airline portion of the field test, cockpit procedures and pilot briefing packages for both FMS equipped and unequipped aircraft were developed in cooperation with an airline. The procedures developed for the FMS equipped aircraft were to fly a VNAV descent at a controller specified speed to cross a metering fix at a specified altitude and speed. For nonFMS aircraft, the clearance also specified a CTAS calculated top-of-descent point. Some CTAS related flight deck issues included how much time was available to the pilots' for compliance, the amount of information that needed to be interpreted in the clearance and possible repercussions of misunderstandings. Data collected during the study ranged from subjective data

  2. Apollo 12 mission report: Descent, propulsion system final flight evaluation (supplement 5)

    NASA Technical Reports Server (NTRS)

    Seto, R. K. M.; Barrows, R. L.

    1972-01-01

    The results are presented of the postflight analysis of the Descent propulsion system (DPS) performance during the Apollo 12 Mission. The primary objective of the analysis was to determine the steady-state performance of the DPS during the descent phase of the manned lunar landing. This is a supplement ot the Apollo 12 Mission Report. In addition to further analysis of the DPS, this report brings together information from other reports and memorandums analyzing specific anomalies and performance in order to present a comprehensive description of the DPS operation during the Apollo 12 Mission.

  3. Cultural Beliefs Underlying Medication Adherence in People of Chinese Descent in the United States.

    PubMed

    Jin, Lan; Acharya, Lalatendu

    2016-01-01

    This article examines the meanings, practices, and cultural beliefs underlying medication adherence in people of Chinese descent living in the United States. The narratives were analyzed using interpretive phenomenology, resulting in the following themes that influenced the communication and behaviors around medication adherence of the participants: (a) cultural concepts of yin yang balance and "qi," (b) understandings of Western and Chinese medicine's efficacy profiles, (c) importance of family and social support, and (d) level of acculturation. This article discusses the influence of these themes on medication adherence and proposes that health communication campaigns, interventions, and doctor-patient communication about increasing medication adherence with people of Chinese descent should engage these understandings.

  4. Entry, Descent and Landing Systems Analysis: Exploration Class Simulation Overview and Results

    NASA Technical Reports Server (NTRS)

    DwyerCianciolo, Alicia M.; Davis, Jody L.; Shidner, Jeremy D.; Powell, Richard W.

    2010-01-01

    NASA senior management commissioned the Entry, Descent and Landing Systems Analysis (EDL-SA) Study in 2008 to identify and roadmap the Entry, Descent and Landing (EDL) technology investments that the agency needed to make in order to successfully land large payloads at Mars for both robotic and exploration or human-scale missions. The year one exploration class mission activity considered technologies capable of delivering a 40-mt payload. This paper provides an overview of the exploration class mission study, including technologies considered, models developed and initial simulation results from the EDL-SA year one effort.

  5. Overview of the NASA Entry, Descent and Landing Systems Analysis Study

    NASA Technical Reports Server (NTRS)

    Zang, Thomas A.; Dwyer-Cianciolo, Alicia M.; Kinney, David J.; Howard, Austin R.; Chen, George T.; Ivanov, Mark C.; Sostaric, Ronald R.; Westhelle, Carlos H.

    2010-01-01

    NASA senior management commissioned the Entry, Descent and Landing Systems Analysis (EDL-SA) Study in 2008 to identify and roadmap the Entry, Descent and Landing (EDL) technology investments that the agency needed to make in order to successfully land large payloads at Mars for both robotic and human-scale missions. This paper summarizes the approach and top-level results from Year 1 of the Study, which focused on landing 10-50 mt on Mars, but also included a trade study of the best advanced parachute design for increasing the landed payloads within the EDL architecture of the Mars Science Laboratory (MSL) mission.

  6. Analytical Dimensional Reduction of a Fuel Optimal Powered Descent Subproblem

    NASA Technical Reports Server (NTRS)

    Rea, Jeremy R.; Bishop, Robert H.

    2010-01-01

    Current renewed interest in exploration of the moon, Mars, and other planetary objects is driving technology development in many fields of space system design. In particular, there is a desire to land both robotic and human missions on the moon and elsewhere. The landing guidance system must be able to deliver the vehicle to a desired soft landing while meeting several constraints necessary for the safety of the vehicle. Due to performance limitations of current launch vehicles, it is desired to minimize the amount of fuel used. In addition, the landing site may change in real-time in order to avoid previously undetected hazards which become apparent during the landing maneuver. This complicated maneuver can be broken into simpler subproblems that bound the full problem. One such subproblem is to find a minimum-fuel landing solution that meets constraints on the initial state, final state, and bounded thrust acceleration magnitude. With the assumptions of constant gravity and negligible atmosphere, the form of the optimal steering law is known, and the equations of motion can be integrated analytically, resulting in a system of five equations in five unknowns. It is shown that this system of equations can be reduced analytically to two equations in two unknowns. With an additional assumption of constant thrust acceleration magnitude, this system can be reduced further to one equation in one unknown. It is shown that these unknowns can be bounded analytically. An algorithm is developed to quickly and reliably solve the resulting one-dimensional bounded search, and it is used as a real-time guidance applied to a lunar landing test case.

  7. 25 CFR 18.104 - May a tribe include provisions in its tribal probate code regarding the distribution and descent...

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 25 Indians 1 2010-04-01 2010-04-01 false May a tribe include provisions in its tribal probate code regarding the distribution and descent of trust personalty? 18.104 Section 18.104 Indians BUREAU OF INDIAN... May a tribe include provisions in its tribal probate code regarding the distribution and descent...

  8. Space shuttle descent flight control design requirements and experiments Learned, Pt. 1 p 617-628

    NASA Technical Reports Server (NTRS)

    Kafer, G.; Wilson, D.

    1983-01-01

    Some of the lessons learned during the development of the Space Shuttle descent flight control system (FCS) are reviewed. Examples confirm the importance for requirements definition, systems level analyses, and testing. In sounding these experiences may have implication for future designs or suggest the discipline required in this engineering art.

  9. Cinco De Mayo, Normative Whiteness, and the Marginalization of Mexican-Descent Students

    ERIC Educational Resources Information Center

    Hurd, Clayton A.

    2008-01-01

    This case study is concerned with how institutional practices of normative whiteness can impede the school involvement of Mexican-descent students. It examines how damaging forms of white normativity can operate in school settings where one might least expect to find them: in commemorations of Mexican cultural holidays. The author shows how such…

  10. Showing up, Remaining Engaged, and Partaking as Students: Resilience among Students of Mexican Descent

    ERIC Educational Resources Information Center

    Sosa, Teresa

    2012-01-01

    This paper examines the ways in which 12 high school students of Mexican descent remain resilient amid difficult and stressful realities. Through an examination of students' interview responses, a case is made that students' ability to engage in school and figure out everyday ways to partake as students are signs of resilience. This work suggests…

  11. Rotary-Wing Decelerators for Probe Descent Through the Atmosphere of Venus

    NASA Technical Reports Server (NTRS)

    Young, Larry A.; Briggs, Geoffrey; Aiken, Edwin; Pisanich, Greg

    2005-01-01

    An innovative concept is proposed for atmospheric entry probe deceleration, wherein one or more deployed rotors (in autorotation or wind-turbine flow states) on the aft end of the probe effect controlled descent. This concept is particularly oriented toward probes intended to land safely on the surface of Venus. Initial work on design trade studies is discussed.

  12. Feeling Frugal: Socioeconomic Status, Acculturation, and Cultural Health Beliefs among Women of Mexican Descent.

    ERIC Educational Resources Information Center

    Borrayo, Evelinn A.; Jenkins, Sharon Rae

    2003-01-01

    Investigates influences of acculturation, socioeconomic status (SES), and cultural health beliefs on Mexican-descent women's preventive health behaviors. In 5 focus group interviews sampling across levels of acculturation and SES, women expressing more traditional Mexican health beliefs about breast cancer screening were of lower SES and were less…

  13. Sexual Health Discussions between African-American Mothers and Mothers of Latino Descent and Their Children

    ERIC Educational Resources Information Center

    Murray, Ashley; Ellis, Monica U.; Castellanos, Ted; Gaul, Zaneta; Sutton, Madeline Y.; Sneed, Carl D.

    2014-01-01

    We examined approaches used by African-American mothers and mothers of Latino descent for informal sex-related discussions with their children to inform sexually transmitted infection (STI)/HIV intervention development efforts. We recruited mothers (of children aged 12-15) from youth service agencies and a university in southern California.…

  14. Access to Health Care Among Latinos of Mexican Descent in "Colonias" in Two Texas Counties

    ERIC Educational Resources Information Center

    Ortiz, Larry; Arizmendi, Lydia; Cornelius, Llewellyn J.

    2004-01-01

    Critical to resolving the problem of health disparities among Latinos is examining the needs within ethnic subpopulations. This paper focused on the unique challenges encountered by one ethnic subpopulation -- Latinos of Mexican descent living in colonias. Findings reaffirm the importance of looking within ethnic subpopulations to understand the…

  15. Education by Any Means Necessary: Peoples of African Descent and Community-Based Pedagogical Spaces

    ERIC Educational Resources Information Center

    Douglas, Ty-Ron Michael; Peck, Craig

    2013-01-01

    This study examines how and why peoples of African descent access and utilize community-based pedagogical spaces that exist outside schools. Employing a theoretical framework that fuses historical methodology and border-crossing theory, the researchers review existing scholarship and primary documents to present an historical examination of how…

  16. A Critical Analysis of Western Perspectives on Families of Arab Descent

    ERIC Educational Resources Information Center

    Beitin, Ben K.; Allen, Katherine R.; Bekheet, Maureen

    2010-01-01

    Western research on families of Arab descent has increased in the current decade, compared to the previous 30 years. In this review of 256 empirical articles, through a critical postcolonial lens, domestic violence and family planning were the two most established areas of study. Generally, samples have come from a small group of countries such as…

  17. Predictors of energy cost during stair ascent and descent in individuals with chronic stroke.

    PubMed

    Polese, Janaine Cunha; Scianni, Aline Alvim; Teixeira-Salmela, Luci Fuscaldi

    2015-12-01

    [Purpose] This study aimed to determine which clinical measures of walking performance and lower limb muscle strength would predict energy cost during stair ascent and descent in community-dwelling individuals with stroke. [Subjects and Methods] Regression analysis of cross-sectional data from 55 individuals between one and five years post-stroke was used to investigate the measures of walking (speed and distance covered during the 6-minute walk test [6MWT]), and strength of the paretic knee extensor and ankle plantar flexor muscles would predict energy cost during stair ascent and descent. [Results] Three predictors (habitual walking speed, distance covered during the 6MWT, and strength of the paretic knee extensor muscles) were kept in the model. Habitual walking speed alone explained 47% of the variance in energy cost during stair ascent and descent. When the strength of the paretic knee extensor muscles was included in the model, the explained variance increased to 53%. By adding the distance covered during the 6MWT, the variance increased to 58%. [Conclusion] Habitual walking speed, distance covered during the 6MWT, and strength of the paretic knee extensor muscles were significant predictors of energy cost during stair ascent and descent in individuals with mild walking limitations.

  18. Forward stair descent with hybrid neuroprosthesis after paralysis: Single case study demonstrating feasibility.

    PubMed

    Bulea, Thomas C; Kobetic, Rudi; Audu, Musa L; Schnellenberger, John R; Pinault, Gilles; Triolo, Ronald J

    2014-01-01

    The ability to negotiate stairs is important for community access and independent mobility but requires more effort and strength than level walking. For this reason, previous attempts to utilize functional neuromuscular stimulation (FNS) to restore stair navigation after spinal cord injury (SCI) have had limited success and are not readily generalizable. Stair descent is particularly challenging because it requires energy absorption via eccentric muscle contractions, a task not easily accomplished with FNS. This article presents the design and initial testing of a hybrid neuroprosthesis with a variable impedance knee mechanism (VIKM-HNP) for stair descent. Using a 16-channel percutaneous FNS system, a muscle activation pattern was synthesized to descend stairs with the VIKM-HNP in a step-by-step fashion. A finite state control system was implemented to deactivate knee extensor stimulation and utilize the VIKM-HNP to absorb energy and regulate descent speed. Feasibility testing was performed on one individual with complete thoracic-level SCI. Stair descent was achieved with maximum upper-limb forces of less than 45% body weight compared with previously reported value of 70% with FNS only. The experiments also provided insight into design requirements for future hybrid systems for stair navigation, the implications of which are discussed.

  19. Smart-Divert Powered Descent Guidance to Avoid the Backshell Landing Dispersion Ellipse

    NASA Technical Reports Server (NTRS)

    Carson, John M.; Acikmese, Behcet

    2013-01-01

    A smart-divert capability has been added into the Powered Descent Guidance (PDG) software originally developed for Mars pinpoint and precision landing. The smart-divert algorithm accounts for the landing dispersions of the entry backshell, which separates from the lander vehicle at the end of the parachute descent phase and prior to powered descent. The smart-divert PDG algorithm utilizes the onboard fuel and vehicle thrust vectoring to mitigate landing error in an intelligent way: ensuring that the lander touches down with minimum- fuel usage at the minimum distance from the desired landing location that also avoids impact by the descending backshell. The smart-divert PDG software implements a computationally efficient, convex formulation of the powered-descent guidance problem to provide pinpoint or precision-landing guidance solutions that are fuel-optimal and satisfy physical thrust bound and pointing constraints, as well as position and speed constraints. The initial smart-divert implementation enforced a lateral-divert corridor parallel to the ground velocity vector; this was based on guidance requirements for MSL (Mars Science Laboratory) landings. This initial method was overly conservative since the divert corridor was infinite in the down-range direction despite the backshell landing inside a calculable dispersion ellipse. Basing the divert constraint instead on a local tangent to the backshell dispersion ellipse in the direction of the desired landing site provides a far less conservative constraint. The resulting enhanced smart-divert PDG algorithm avoids impact with the descending backshell and has reduced conservatism.

  20. Forward stair descent with hybrid neuroprosthesis after paralysis: Single case study demonstrating feasibility

    PubMed Central

    Bulea, Thomas C.; Kobetic, Rudi; Audu, Musa L.; Schnellenberger, John R.; Pinault, Gilles; Triolo, Ronald J.

    2015-01-01

    The ability to negotiate stairs is important for community access and independent mobility but requires more effort and strength than level walking. For this reason, previous attempts to utilize functional neuromuscular stimulation (FNS) to restore stair navigation after spinal cord injury (SCI) have had limited success and are not readily generalizable. Stair descent is particularly challenging because it requires energy absorption via eccentric muscle contractions, a task not easily accomplished with FNS. This article presents the design and initial testing of a hybrid neuroprosthesis with a variable impedance knee mechanism (VIKM-HNP) for stair descent. Using a 16-channel percutaneous FNS system, a muscle activation pattern was synthesized to descend stairs with the VIKM-HNP in a step-by-step fashion. A finite state control system was implemented to deactivate knee extensor stimulation and utilize the VIKM-HNP to absorb energy and regulate descent speed. Feasibility testing was performed on one individual with complete thoracic-level SCI. Stair descent was achieved with maximum upper-limb forces of less than 45% body weight compared with previously reported value of 70% with FNS only. The experiments also provided insight into design requirements for future hybrid systems for stair navigation, the implications of which are discussed. PMID:25437932

  1. A Wind Tunnel Study on the Mars Pathfinder (MPF) Lander Descent Pressure Sensor

    NASA Technical Reports Server (NTRS)

    Soriano, J. Francisco; Coquilla, Rachael V.; Wilson, Gregory R.; Seiff, Alvin; Rivell, Tomas

    2001-01-01

    The primary focus of this study was to determine the accuracy of the Mars Pathfinder lander local pressure readings in accordance with the actual ambient atmospheric pressures of Mars during parachute descent. In order to obtain good measurements, the plane of the lander pressure sensor opening should ideally be situated so that it is parallel to the freestream. However, due to two unfavorable conditions, the sensor was positioned in locations where correction factors are required. One of these disadvantages is due to the fact that the parachute attachment point rotated the lander's center of gravity forcing the location of the pressure sensor opening to be off tangent to the freestream. The second and most troublesome factor was that the lander descends with slight oscillations that could vary the amplitude of the sensor readings. In order to accurately map the correction factors required at each sensor position, an experiment simulating the lander descent was conducted in the Martian Surface Wind Tunnel at NASA Ames Research Center. Using a 115 scale model at Earth ambient pressures, the test settings provided the necessary Reynolds number conditions in which the actual lander was possibly subjected to during the descent. In the analysis and results of this experiment, the readings from the lander sensor were converted to the form of pressure coefficients. With a contour map of pressure coefficients at each lander oscillatory position, this report will provide a guideline to determine the correction factors required for the Mars Pathfinder lander descent pressure sensor readings.

  2. A Terminal Descent Sensor Trade Study Overview for the Orion Landing and Recovery System

    NASA Technical Reports Server (NTRS)

    Dunn, Catherine; Prakash, Ravi

    2008-01-01

    This trade study was conducted as a part of the Orion Landing System Advanced Development Project to determine possible Terminal Descent Sensor (TDS) architectures that could be used for a rocket assisted landing system. Several technologies were considered for the Orion TDS including radar, lidar, GPS applications, mechanical sensors, and gamma ray altimetry.

  3. Mapping of Surface and Shallow Subsurface Signatures in the CONSERT Data during the Descent of Philae

    NASA Astrophysics Data System (ADS)

    Plettemeier, Dirk; Statz, Christoph; Hahnel, Ronny; Hegler, Sebastian; Kofman, Wlodek; Herique, Alain; Rogez, Yves; Pasquero, Pierre; Zine, Sonia; Ciarletti, Valerie

    2016-04-01

    The primary scientific objective of the Comet Nucleus Sounding Experiment by Radiowave Transmission (CONSERT) aboard Rosetta is the characterization of comet 67P/Chuyurmov-Gerasimenko's deep interior dielectric properties. This was done during the first science sequence (FSS) by means of bi-static radio propagation measurements between the the CONSERT instrument aboard lander Philae launched onto the comet's surface and its counterpart aboard the Rosetta orbiter. In addition to the FSS measurements, CONSERT was operated during the separation and descent of Philae onto the 67P/C-G's surface. The received CONSERT signal during the SDL consists of the direct propagation between Rosetta and Philae and indirect reflections of 67P/C-G's surface. Using the peak power measurements in the dominant direct path between Rosetta and Philae during the descent we were able to reconstruct the lander's attitude and estimate the spin rate of the lander along its descent trajectory. The deployment of the lander legs and CONSERT antennas as well as the orbiter change of attitude in order to orient the science towards the assumed lander position are visible in the measured CONSERT data as well. The information gained on Philae's attitude is used in the estimation of 67P/C-G's surface and near subsurface dielectric properties. Information on the surface of 67P/C-G are contained in the data during roughly the last third of the descent of Philae onto the comet's surface. The surface signatures in the measured data are mapped to the location of origin on 67P/C-G's surface. The results from the mapping process show good spatial diversity along the descent track of Philae necessary for the estimation of the dielectric properties of prominent features in the CONSERT SDL data.

  4. Particle acceleration

    NASA Technical Reports Server (NTRS)

    Vlahos, L.; Machado, M. E.; Ramaty, R.; Murphy, R. J.; Alissandrakis, C.; Bai, T.; Batchelor, D.; Benz, A. O.; Chupp, E.; Ellison, D.

    1986-01-01

    Data is compiled from Solar Maximum Mission and Hinothori satellites, particle detectors in several satellites, ground based instruments, and balloon flights in order to answer fundamental questions relating to: (1) the requirements for the coronal magnetic field structure in the vicinity of the energization source; (2) the height (above the photosphere) of the energization source; (3) the time of energization; (4) transistion between coronal heating and flares; (5) evidence for purely thermal, purely nonthermal and hybrid type flares; (6) the time characteristics of the energization source; (7) whether every flare accelerates protons; (8) the location of the interaction site of the ions and relativistic electrons; (9) the energy spectra for ions and relativistic electrons; (10) the relationship between particles at the Sun and interplanetary space; (11) evidence for more than one acceleration mechanism; (12) whether there is single mechanism that will accelerate particles to all energies and also heat the plasma; and (13) how fast the existing mechanisms accelerate electrons up to several MeV and ions to 1 GeV.

  5. Accelerated Achievement

    ERIC Educational Resources Information Center

    Ford, William J.

    2010-01-01

    This article focuses on the accelerated associate degree program at Ivy Tech Community College (Indiana) in which low-income students will receive an associate degree in one year. The three-year pilot program is funded by a $2.3 million grant from the Lumina Foundation for Education in Indianapolis and a $270,000 grant from the Indiana Commission…

  6. ACCELERATION INTEGRATOR

    DOEpatents

    Pope, K.E.

    1958-01-01

    This patent relates to an improved acceleration integrator and more particularly to apparatus of this nature which is gyrostabilized. The device may be used to sense the attainment by an airborne vehicle of a predetermined velocitv or distance along a given vector path. In its broad aspects, the acceleration integrator utilizes a magnetized element rotatable driven by a synchronous motor and having a cylin drical flux gap and a restrained eddy- current drag cap deposed to move into the gap. The angular velocity imparted to the rotatable cap shaft is transmitted in a positive manner to the magnetized element through a servo feedback loop. The resultant angular velocity of tae cap is proportional to the acceleration of the housing in this manner and means may be used to measure the velocity and operate switches at a pre-set magnitude. To make the above-described dcvice sensitive to acceleration in only one direction the magnetized element forms the spinning inertia element of a free gyroscope, and the outer housing functions as a gimbal of a gyroscope.

  7. Plasma accelerator

    DOEpatents

    Wang, Zhehui; Barnes, Cris W.

    2002-01-01

    There has been invented an apparatus for acceleration of a plasma having coaxially positioned, constant diameter, cylindrical electrodes which are modified to converge (for a positive polarity inner electrode and a negatively charged outer electrode) at the plasma output end of the annulus between the electrodes to achieve improved particle flux per unit of power.

  8. Flight Investigation of Effects of Transition, Landing Approaches, Partial-Power Vertical Descents, and Droop-Stop Pounding on the Bending and Torsional Moments Encountered by a Helicopter Rotor Blade

    NASA Technical Reports Server (NTRS)

    Ludi, LeRoy H.

    1959-01-01

    Flight tests have been conducted with a single-rotor helicopter, one blade of which was equipped at 14 percent and 40 percent of the blade radius with strain gages calibrated to measure moments rather than stresses, to determine the effects of transition, landing approaches, and partial-power vertical descents on the rotor-blade bending and torsional moments. In addition, ground tests were conducted to determine the effects of static droop-stop pounding on the rotor-blade moments. The results indicate that partial-power vertical descents and landing approaches produce rotor-blade moments that are higher than the moments encountered in any other flight condition investigated to date with this equipment. Decelerating through the transition region in level flight was found to result in higher vibratory moments than accelerating through this region. Deliberately induced static droop-stop pounding produced flapwise bending moments at the 14-percent-radius station which were as high as the moments experienced in landing approaches and partial-power vertical descents.

  9. Compact accelerator

    DOEpatents

    Caporaso, George J.; Sampayan, Stephen E.; Kirbie, Hugh C.

    2007-02-06

    A compact linear accelerator having at least one strip-shaped Blumlein module which guides a propagating wavefront between first and second ends and controls the output pulse at the second end. Each Blumlein module has first, second, and third planar conductor strips, with a first dielectric strip between the first and second conductor strips, and a second dielectric strip between the second and third conductor strips. Additionally, the compact linear accelerator includes a high voltage power supply connected to charge the second conductor strip to a high potential, and a switch for switching the high potential in the second conductor strip to at least one of the first and third conductor strips so as to initiate a propagating reverse polarity wavefront(s) in the corresponding dielectric strip(s).

  10. BICEP's acceleration

    SciTech Connect

    Contaldi, Carlo R.

    2014-10-01

    The recent Bicep2 [1] detection of, what is claimed to be primordial B-modes, opens up the possibility of constraining not only the energy scale of inflation but also the detailed acceleration history that occurred during inflation. In turn this can be used to determine the shape of the inflaton potential V(φ) for the first time — if a single, scalar inflaton is assumed to be driving the acceleration. We carry out a Monte Carlo exploration of inflationary trajectories given the current data. Using this method we obtain a posterior distribution of possible acceleration profiles ε(N) as a function of e-fold N and derived posterior distributions of the primordial power spectrum P(k) and potential V(φ). We find that the Bicep2 result, in combination with Planck measurements of total intensity Cosmic Microwave Background (CMB) anisotropies, induces a significant feature in the scalar primordial spectrum at scales k∼ 10{sup -3} Mpc {sup -1}. This is in agreement with a previous detection of a suppression in the scalar power [2].

  11. Local flow management/profile descent algorithm. Fuel-efficient, time-controlled profiles for the NASA TSRV airplane

    NASA Technical Reports Server (NTRS)

    Groce, J. L.; Izumi, K. H.; Markham, C. H.; Schwab, R. W.; Thompson, J. L.

    1986-01-01

    The Local Flow Management/Profile Descent (LFM/PD) algorithm designed for the NASA Transport System Research Vehicle program is described. The algorithm provides fuel-efficient altitude and airspeed profiles consistent with ATC restrictions in a time-based metering environment over a fixed ground track. The model design constraints include accommodation of both published profile descent procedures and unpublished profile descents, incorporation of fuel efficiency as a flight profile criterion, operation within the performance capabilities of the Boeing 737-100 airplane with JT8D-7 engines, and conformity to standard air traffic navigation and control procedures. Holding and path stretching capabilities are included for long delay situations.

  12. On the efficiency of a randomized mirror descent algorithm in online optimization problems

    NASA Astrophysics Data System (ADS)

    Gasnikov, A. V.; Nesterov, Yu. E.; Spokoiny, V. G.

    2015-04-01

    A randomized online version of the mirror descent method is proposed. It differs from the existing versions by the randomization method. Randomization is performed at the stage of the projection of a subgradient of the function being optimized onto the unit simplex rather than at the stage of the computation of a subgradient, which is common practice. As a result, a componentwise subgradient descent with a randomly chosen component is obtained, which admits an online interpretation. This observation, for example, has made it possible to uniformly interpret results on weighting expert decisions and propose the most efficient method for searching for an equilibrium in a zero-sum two-person matrix game with sparse matrix.

  13. Impact of mismodeled idle engine performance on calculation and tracking of optimal 4-D descent trajectories

    NASA Technical Reports Server (NTRS)

    Williams, D. H.

    1986-01-01

    Advanced flight management systems are being developed which are capable of calculating optimal 3-D and 4-D flight trajectories for arbitrary fuel and time costs. These systems require mathematical models of airplane performance in order to compute the optimal profiles. Mismodeled idle engine characteristics can result in descent trajectories requiring excessive throttle and/or speedbrake activity in order to achieve the desired end conditions. This paper evaluates the cost and fuel penalties, trajectory variations, and flight control requirements associated with typical idle engine modeling errors for a twin-jet transport airplane. Variations in idle power setting, thrust, fuel flow, and surge bleed operation were evaluated for a cruise/descent flight segment. The results of this analysis provide insight into the penalties associated with uncertainties in idle engine performance and suggest methods of modeling which minimize these penalties.

  14. The descent of ant: field-measured performance of gliding ants.

    PubMed

    Munk, Yonatan; Yanoviak, Stephen P; Koehl, M A R; Dudley, Robert

    2015-05-01

    Gliding ants avoid predatory attacks and potentially mortal consequences of dislodgement from rainforest canopy substrates by directing their aerial descent towards nearby tree trunks. The ecologically relevant measure of performance for gliding ants is the ratio of net horizontal to vertical distance traveled over the course of a gliding trajectory, or glide index. To study variation in glide index, we measured three-dimensional trajectories of Cephalotes atratus ants gliding in natural rainforest habitats. We determined that righting phase duration, glide angle, and path directness all significantly influence variation in glide index. Unsuccessful landing attempts result in the ant bouncing off its target and being forced to make a second landing attempt. Our results indicate that ants are not passive gliders and that they exert active control over the aerodynamic forces they experience during their descent, despite their apparent lack of specialized control surfaces. PMID:25788722

  15. Entry, Descent and Landing Systems Analysis Study: Phase 2 Report on Exploration Feed-Forward Systems

    NASA Technical Reports Server (NTRS)

    Dwyer Ciancolo, Alicia M.; Davis, Jody L.; Engelund, Walter C.; Komar, D. R.; Queen, Eric M.; Samareh, Jamshid A.; Way, David W.; Zang, Thomas A.; Murch, Jeff G.; Krizan, Shawn A.; Olds, Aaron D.; Powell, Richard W.; Shidner, Jeremy D.; Kinney, Daivd J.; McGuire, M. Kathleen; Arnold, James O.; Covington, M. Alan; Sostaric, Ronald R.; Zumwalt, Carlie H.; Llama, Eduardo G.

    2011-01-01

    NASA senior management commissioned the Entry, Descent and Landing Systems Analysis (EDL-SA) Study in 2008 to identify and roadmap the Entry, Descent and Landing (EDL) technology investments that the agency needed to successfully land large payloads at Mars for both robotic and human-scale missions. Year 1 of the study focused on technologies required for Exploration-class missions to land payloads of 10 to 50 t. Inflatable decelerators, rigid aeroshell and supersonic retro-propulsion emerged as the top candidate technologies. In Year 2 of the study, low TRL technologies identified in Year 1, inflatables aeroshells and supersonic retropropulsion, were combined to create a demonstration precursor robotic mission. This part of the EDL-SA Year 2 effort, called Exploration Feed Forward (EFF), took much of the systems analysis simulation and component model development from Year 1 to the next level of detail.

  16. Entry, Descent and Landing Systems Analysis: Exploration Feed Forward Internal Peer Review Slide Package

    NASA Technical Reports Server (NTRS)

    Dwyer Cianciolo, Alicia M. (Editor)

    2011-01-01

    NASA senior management commissioned the Entry, Descent and Landing Systems Analysis (EDL-SA) Study in 2008 to identify and roadmap the Entry, Descent and Landing (EDL) technology investments that the agency needed to successfully land large payloads at Mars for both robotic and human-scale missions. Year 1 of the study focused on technologies required for Exploration-class missions to land payloads of 10 to 50 mt. Inflatable decelerators, rigid aeroshell and supersonic retro-propulsion emerged as the top candidate technologies. In Year 2 of the study, low TRL technologies identified in Year 1, inflatables aeroshells and supersonic retropropulsion, were combined to create a demonstration precursor robotic mission. This part of the EDL-SA Year 2 effort, called Exploration Feed Forward (EFF), took much of the systems analysis simulation and component model development from Year 1 to the next level of detail.

  17. Multibody Modeling and Simulation for the Mars Phoenix Lander Entry, Descent and Landing

    NASA Technical Reports Server (NTRS)

    Queen, Eric M.; Prince, Jill L.; Desai, Prasun N.

    2008-01-01

    A multi-body flight simulation for the Phoenix Mars Lander has been developed that includes high fidelity six degree-of-freedom rigid-body models for the parachute and lander system. The simulation provides attitude and rate history predictions of all bodies throughout the flight, as well as loads on each of the connecting lines. In so doing, a realistic behavior of the descending parachute/lander system dynamics can be simulated that allows assessment of the Phoenix descent performance and identification of potential sensitivities for landing. This simulation provides a complete end-to-end capability of modeling the entire entry, descent, and landing sequence for the mission. Time histories of the parachute and lander aerodynamic angles are presented. The response of the lander system to various wind models and wind shears is shown to be acceptable. Monte Carlo simulation results are also presented.

  18. A Bayesian Framework for Landing Site Selection During Autonomous Spacecraft Descent

    NASA Technical Reports Server (NTRS)

    Serrano, Navid

    2006-01-01

    The success of a landed space exploration mission depends largely on the final landing site. Factors influencing site selection include safety, fuel-consumption, and scientific return. This paper addresses the problem of selecting the best available landing site based on these factors in real-time during autonomous spacecraft descent onto a planetary surface. The problem is modeled probabilistically using Bayesian Networks (BNs). BNs provide a means of representing the causal relationships between variables that impact the quality of a landing site. The final landing site is determined via probabilistic reasoning based on terrain safety derived from on-board sensors, available fuel based on spacecraft descent dynamics, and regions of interest defined by mission scientists.

  19. Caste-, work-, and descent-based discrimination as a determinant of health in social epidemiology.

    PubMed

    Patil, Rajan R

    2014-01-01

    Social epidemiology explores health in the context of broad social determinants of health, where the boundary lines between health and politics appear increasingly blurred. Social determinants of health such as caste, discrimination, and social exclusion are inherently political in nature, hence it becomes imperative to look at health through a broader perspective of political philosophy, ideology, and caste that imposes enormous obstacles to a person's full attainment of civil, political, economic, social, and cultural rights. Caste is descent based and hereditary in nature. It is a characteristic determined by one's birth into a particular caste, irrespective of the faith practiced by the individual. Caste denotes a system of rigid social stratification into ranked groups defined by descent and occupation. Under various caste systems throughout the world, caste divisions also dominate in housing, marriage, and general social interaction divisions that are reinforced through the practice and threat of social ostracism, economic boycotts, and even physical violence-all of which undermine health equality.

  20. The descent of ant: field-measured performance of gliding ants.

    PubMed

    Munk, Yonatan; Yanoviak, Stephen P; Koehl, M A R; Dudley, Robert

    2015-05-01

    Gliding ants avoid predatory attacks and potentially mortal consequences of dislodgement from rainforest canopy substrates by directing their aerial descent towards nearby tree trunks. The ecologically relevant measure of performance for gliding ants is the ratio of net horizontal to vertical distance traveled over the course of a gliding trajectory, or glide index. To study variation in glide index, we measured three-dimensional trajectories of Cephalotes atratus ants gliding in natural rainforest habitats. We determined that righting phase duration, glide angle, and path directness all significantly influence variation in glide index. Unsuccessful landing attempts result in the ant bouncing off its target and being forced to make a second landing attempt. Our results indicate that ants are not passive gliders and that they exert active control over the aerodynamic forces they experience during their descent, despite their apparent lack of specialized control surfaces.

  1. Performance evaluation of a lower limb exoskeleton for stair ascent and descent with paraplegia.

    PubMed

    Farris, Ryan J; Quintero, Hugo A; Goldfarb, Michael

    2012-01-01

    This paper describes the application of a powered lower limb exoskeleton to aid paraplegic individuals in stair ascent and descent. A brief description of the exoskeleton hardware is provided along with an explanation of the control methodology implemented to allow stair ascent and descent. Tests were performed with a paraplegic individual (T10 complete injury level) and data is presented from multiple trials, including the hip and knee joint torque and power required to perform this functionality. Joint torque and power requirements are summarized, including peak hip and knee joint torque requirements of 0.75 Nm/kg and 0.87 Nm/kg, respectively, and peak hip and knee joint power requirements of approximately 0.65 W/kg and 0.85 W/kg, respectively. PMID:23366287

  2. Preliminary Assessment of the Mars Science Laboratory Entry, Descent, and Landing Simulation

    NASA Technical Reports Server (NTRS)

    Way, David W.

    2013-01-01

    On August 5, 2012, the Mars Science Laboratory rover, Curiosity, successfully landed inside Gale Crater. This landing was only the seventh successful landing and fourth rover to be delivered to Mars. Weighing nearly one metric ton, Curiosity is the largest and most complex rover ever sent to investigate another planet. Safely landing such a large payload required an innovative Entry, Descent, and Landing system, which included the first guided entry at Mars, the largest supersonic parachute ever flown at Mars, and a novel and untested Sky Crane landing system. A complete, end-to-end, six degree-of-freedom, multibody computer simulation of the Mars Science Laboratory Entry, Descent, and Landing sequence was developed at the NASA Langley Research Center. In-flight data gathered during the successful landing is compared to pre-flight statistical distributions, predicted by the simulation. These comparisons provide insight into both the accuracy of the simulation and the overall performance of the vehicle.

  3. Assessment of the Mars Science Laboratory Entry, Descent, and Landing Simulation

    NASA Technical Reports Server (NTRS)

    Way, David W.; Davis, J. L.; Shidner, Jeremy D.

    2013-01-01

    On August 5, 2012, the Mars Science Laboratory rover, Curiosity, successfully landed inside Gale Crater. This landing was only the seventh successful landing and fourth rover to be delivered to Mars. Weighing nearly one metric ton, Curiosity is the largest and most complex rover ever sent to investigate another planet. Safely landing such a large payload required an innovative Entry, Descent, and Landing system, which included the first guided entry at Mars, the largest supersonic parachute ever flown at Mars, and a novel and untested Sky Crane landing system. A complete, end-to-end, six degree-of-freedom, multi-body computer simulation of the Mars Science Laboratory Entry, Descent, and Landing sequence was developed at the NASA Langley Research Center. In-flight data gathered during the successful landing is compared to pre-flight statistical distributions, predicted by the simulation. These comparisons provide insight into both the accuracy of the simulation and the overall performance of the vehicle.

  4. Capture Conditions for Merging Trajectory Segments to Model Realistic Aircraft Descents

    NASA Technical Reports Server (NTRS)

    Zhao, Yiyuan; Slattery, Rhonda A.

    1996-01-01

    A typical commercial aircraft trajectory consists of a series of flight segments. An aircraft switches from one segment to another when certain specified variables reach their desired values. Trajectory synthesis for air traffic control automation must be consistent with practical pilot procedures. We examine capture conditions for merging trajectory segments to model commercial aircraft descent in trajectory synthesis. These conditions translate into bounds on measurements of atmospheric wind, pressure, and temperature. They also define ranges of thrust and drag feasible for a descent trajectory. Capture conditions are derived for the Center-TRACON Automation System developed at NASA Ames Research Center for automated air traffic control. Various uses of capture conditions are discussed. A Boeing 727-200 aircraft is used to provide numerical examples of capture conditions.

  5. Advanced concepts for acceleration

    SciTech Connect

    Keefe, D.

    1986-07-01

    Selected examples of advanced accelerator concepts are reviewed. Such plasma accelerators as plasma beat wave accelerator, plasma wake field accelerator, and plasma grating accelerator are discussed particularly as examples of concepts for accelerating relativistic electrons or positrons. Also covered are the pulsed electron-beam, pulsed laser accelerator, inverse Cherenkov accelerator, inverse free-electron laser, switched radial-line accelerators, and two-beam accelerator. Advanced concepts for ion acceleration discussed include the electron ring accelerator, excitation of waves on intense electron beams, and two-wave combinations. (LEW)

  6. Accelerators and the Accelerator Community

    SciTech Connect

    Malamud, Ernest; Sessler, Andrew

    2008-06-01

    In this paper, standing back--looking from afar--and adopting a historical perspective, the field of accelerator science is examined. How it grew, what are the forces that made it what it is, where it is now, and what it is likely to be in the future are the subjects explored. Clearly, a great deal of personal opinion is invoked in this process.

  7. Scaling Up Coordinate Descent Algorithms for Large ℓ1 Regularization Problems

    SciTech Connect

    Scherrer, Chad; Halappanavar, Mahantesh; Tewari, Ambuj; Haglin, David J.

    2012-07-03

    We present a generic framework for parallel coordinate descent (CD) algorithms that has as special cases the original sequential algorithms of Cyclic CD and Stochastic CD, as well as the recent parallel Shotgun algorithm of Bradley et al. We introduce two novel parallel algorithms that are also special cases---Thread-Greedy CD and Coloring-Based CD---and give performance measurements for an OpenMP implementation of these.

  8. Entry, Descent, and Landing Aerothermodynamics: NASA Langley Experimental Capabilities and Contributions

    NASA Technical Reports Server (NTRS)

    Hollis, Brian R.; Berger, Karen T.; Berry, Scott A.; Bruckmann, Gregory J.; Buck, Gregory M.; DiFulvio, Michael; Horvath, Thomas J.; Liechty, Derek S.; Merski, N. Ronald; Murphy, Kelly J.; Rufer, Shann J.; Schoenenberger, Mark

    2014-01-01

    A review is presented of recent research, development, testing and evaluation activities related to entry, descent and landing that have been conducted at the NASA Langley Research Center. An overview of the test facilities, model development and fabrication capabilities, and instrumentation and measurement techniques employed in this work is provided. Contributions to hypersonic/supersonic flight and planetary exploration programs are detailed, as are fundamental research and development activities.

  9. Biological effects of fuel and exhaust components from spacecraft descent engines employing hydrazine

    NASA Technical Reports Server (NTRS)

    Lehwalt, M. E.; Woeller, F. H.; Oyama, V. I.

    1973-01-01

    The effect of the products of the Viking terminal descent engine fuel upon possible extraterrestrial life at the Martian landing site is examined. The effects of the engine exhaust, the hydrazine fuel, and the breakdown products of the latter on terrestrial microorganisms have been studied. The results indicate that the gaseous exhaust products would probably not be hazardous to microorganisms, but that liquid hydrazine would be lethal.

  10. Apollo experience report: Mission planning for lunar module descent and ascent

    NASA Technical Reports Server (NTRS)

    Bennett, F. V.

    1972-01-01

    The premission planning, the real-time situation, and the postflight analysis for the Apollo 11 lunar descent and ascent are described. A comparison between premission planning and actual results is included. A navigation correction capability, developed from Apollo 11 postflight analysis was used successfully on Apollo 12 to provide the first pinpoint landing. An experience summary, which illustrates typical problems encountered by the mission planners, is also included.

  11. Lessons Learned from the Development of the MSL Descent Stage Propulsion System

    NASA Technical Reports Server (NTRS)

    Guernsey, Carl S.; Weiss, Jeffrey M.

    2013-01-01

    Development of the MSL descent stage propulsion system required a number of new propulsion hardware developments incorporating technologies not normally found in spacecraft propulsion subsystems. These developments were driven by the relatively high (25,000 N) maximum thrust level and the requirement for precise throttling of the main engines. This paper presents lessons learned in the course of these developments, including surprises and anomalies discovered at both the component and subsystem levels.

  12. On the boundary conditions on a shock wave for hypersonic flow around a descent vehicle

    NASA Astrophysics Data System (ADS)

    Golomazov, M. M.; Ivankov, A. A.

    2013-12-01

    Stationary hypersonic flow around a descent vehicle is examined by considering equilibrium and nonequilibrium reactions. We study how physical-chemical processes and shock wave conditions for gas species influence the shock-layer structure. It is shown that conservation conditions of species on the shock wave cause high-temperature and concentration gradients in the shock layer when we calculate spacecraft deceleration trajectory in the atmosphere at 75 km altitude.

  13. Flying Schedule-Matching Descents to Explore Flight Crews' Perceptions of Their Load and Task Feasibility

    NASA Technical Reports Server (NTRS)

    Martin, Lynne Hazel; Sharma, Shivanjli; Lozito, Sharon; Kaneshige, John; Hayashi, Miwa; Dulchinos, Victoria

    2012-01-01

    Multiple studies have investigated the development and use of ground-based (controller) tools to manage and schedule traffic in future terminal airspace. No studies have investigated the impacts that such tools (and concepts) could have on the flight-deck. To begin to redress the balance, an exploratory study investigated the procedures and actions of ten Boeing-747-400 crews as they flew eight continuous descent approaches in the Los Angeles terminal airspace, with the descents being controlled using speed alone. Although the study was exploratory in nature, four variables were manipulated: speed changes, route constraints, clearance phraseology, and winds. Despite flying the same scenarios with the same events and timing, there was at least a 50 second difference in the time it took crews to fly the approaches. This variation is the product of a number of factors but highlights potential difficulties for scheduling tools that would have to accommodate this amount of natural variation in descent times. The primary focus of this paper is the potential impact of ground scheduling tools on the flight crews performance and procedures. Crews reported "moderate to low" workload, on average; however, short periods of intense and high workload were observed. The non-flying pilot often reported a higher level of workload than the flying-pilot, which may be due to their increased interaction with the Flight Management Computer, when using the aircraft automation to assist with managing the descent clearances. It is concluded that ground-side tools and automation may have a larger impact on the current-day flight-deck than was assumed and that studies investigating this impact should continue in parallel with controller support tool development.

  14. Strong refraction near the Venus surface - Effects observed by descent probes

    NASA Technical Reports Server (NTRS)

    Croft, T. A.

    1982-01-01

    The telemetry signals from Pioneer Venus probes indicated the strong downward refraction of radio waves. As the probes descended, the strength of the direct signal decreased because of absorption and refractive defocusing. During the last 30 km of descent there was a second measured component in addition to the direct signal. Strong atmospheric reaction is important in strengthening echoes that are scattered toward the earth. Such surface-reflected signals are good indicators of horizontal winds.

  15. A High-Heritage Blunt-Body Entry, Descent, and Landing Concept for Human Mars Exploration

    NASA Technical Reports Server (NTRS)

    Price, Humphrey; Manning, Robert; Sklyanskiy, Evgeniy; Braun, Robert

    2016-01-01

    Human-scale landers require the delivery of much heavier payloads to the surface of Mars than is possible with entry, descent, and landing (EDL) approaches used to date. A conceptual design was developed for a 10 m diameter crewed Mars lander with an entry mass of approx.75 t that could deliver approx.28 t of useful landed mass (ULM) to a zero Mars areoid, or lower, elevation. The EDL design centers upon use of a high ballistic coefficient blunt-body entry vehicle and throttled supersonic retro-propulsion (SRP). The design concept includes a 26 t Mars Ascent Vehicle (MAV) that could support a crew of 2 for approx.24 days, a crew of 3 for approx.16 days, or a crew of 4 for approx.12 days. The MAV concept is for a fully-fueled single-stage vehicle that utilizes a single pump-fed 250 kN engine using Mono-Methyl Hydrazine (MMH) and Mixed Oxides of Nitrogen (MON-25) propellants that would deliver the crew to a low Mars orbit (LMO) at the end of the surface mission. The MAV concept could potentially provide abort-to-orbit capability during much of the EDL profile in response to fault conditions and could accommodate return to orbit for cases where the MAV had no access to other Mars surface infrastructure. The design concept for the descent stage utilizes six 250 kN MMH/MON-25 engines that would have very high commonality with the MAV engine. Analysis indicates that the MAV would require approx.20 t of propellant (including residuals) and the descent stage would require approx.21 t of propellant. The addition of a 12 m diameter supersonic inflatable aerodynamic decelerator (SIAD), based on a proven flight design, was studied as an optional method to improve the ULM fraction, reducing the required descent propellant by approx.4 t.

  16. The relief formed by the descent phenomenon in the north-east part of Kosova.

    PubMed

    Bulliqi, Shpejtim; Isufi, Florim; Ramadani, Ibrahim; Gashi, Gani

    2012-04-01

    In the diverse relief of north-east part of Kosova a relatively wide range occupies the relief modelled by the descent phenomenon, which is conditioned by morph-structural and climatic factors quite suitable for their development. The morphogenesis activity of descent phenomenon is conditioned by the types of rocks, tectonic process of this region and climatic conditions. These factors condition horizontal and vertical relief fragmentation, slope, especially in Gollaku mountains and in SE part of Kopaonik mountain. Along the tectonic descents, the steepness is detaching and the detaching lines consisting of magmatic rocks show overthrows, demolitions and stony torrents, but the Teri gene composition formations are modelled by sliding and muddy torrents, depending upon the presence of clayey and alevrolite belts on these Teri gene ones. The impact of factors and conditions on the relief of this part, the phenomena like demolitions, overthrows, sliding, muddy torrents, stony torrents, etc, operate here, which play an important morphological role in the modelling of relief. PMID:23424844

  17. Flight-Deck Strategies and Outcomes When Flying Schedule-Matching Descents

    NASA Technical Reports Server (NTRS)

    Kaneshige, John T.; Sharma, Shivanjli; Martin Lynne; Lozito, Sandra; Dulchinos, Victoria

    2013-01-01

    Recent studies at NASA Ames Research Center have investigated the development and use of ground-based (air traffic controller) tools to manage and schedule air traffic in future terminal airspace. An exploratory study was undertaken to investigate the impacts that such tools (and concepts) could have on the flight-deck. Ten Boeing 747-400 crews flew eight optimized profile descents in the Los Angeles terminal airspace, while receiving scripted current day and futuristic speed clearances, to ascertain their ability to fly schedulematching descents without prior training. Although the study was exploratory in nature, four variables were manipulated: route constraints, winds, speed changes, and clearance phraseology. Despite flying the same scenarios with the same events and timing, there were significant differences in the time it took crews to fly the approaches. This variation is the product of a number of factors but highlights potential difficulties for scheduling tools that would have to accommodate this amount of natural variation in descent times. The focus of this paper is the examination of the crews' aircraft management strategies and outcomes. This includes potentially problematic human-automation interaction issues that may negatively impact arrival times, speed and altitude constraint compliance, and energy management efficiency.

  18. International Space Station (ISS) Soyuz Vehicle Descent Module Evaluation of Thermal Protection System (TPS) Penetration Characteristics

    NASA Technical Reports Server (NTRS)

    Davis, Bruce A.; Christiansen, Eric L.; Lear, Dana M.; Prior, Tom

    2013-01-01

    The descent module (DM) of the ISS Soyuz vehicle is covered by thermal protection system (TPS) materials that provide protection from heating conditions experienced during reentry. Damage and penetration of these materials by micrometeoroid and orbital debris (MMOD) impacts could result in loss of vehicle during return phases of the mission. The descent module heat shield has relatively thick TPS and is protected by the instrument-service module. The TPS materials on the conical sides of the descent module (referred to as backshell in this test plan) are exposed to more MMOD impacts and are relatively thin compared to the heat shield. This test program provides hypervelocity impact (HVI) data on materials similar in composition and density to the Soyuz TPS on the backshell of the vehicle. Data from this test program was used to update ballistic limit equations used in Soyuz TPS penetration risk assessments. The impact testing was coordinated by the NASA Johnson Space Center (JSC) Hypervelocity Impact Technology (HVIT) Group [1] in Houston, Texas. The HVI testing was conducted at the NASA-JSC White Sands Hypervelocity Impact Test Facility (WSTF) at Las Cruces, New Mexico. Figure

  19. MR Imaging in Diagnosis of Pelvic Floor Descent: Supine versus Sitting Position

    PubMed Central

    Renzi, Adolfo; Monaco, Luigi; Serra, Nicola; Feragalli, Beatrice; Iacomino, Aniello; Brunese, Luca; Cappabianca, Salvatore

    2016-01-01

    Introduction. Functional disorders of the pelvic floor represent have a significant impact on the quality of life. The advent of open-configuration systems allowed for the evaluation of defecation with MR imaging in sitting position. The purpose of the present study is to compare the results of static and dynamic pelvic MR performed in supine position versus sitting position, using a new MR prototype machine, in the diagnosis of pelvic floor descent. Materials and Methods. Thirty-one patients with pelvic floor disorders were enrolled, and underwent MR Defecography in supine position with 1.5 T closed magnet (MAGNETOM Symphony, Siemens, Germany) and in sitting position with a 0.25-Tesla open magnet system (G-Scan ESAOTE, Italy). Results. In rest and squeezing phases, positions of bladder, vagina, and ARJ were significantly different when the patient was imaged in supine versus sitting position. In the defecation phase, a significant difference for the bladder and vagina position was detected between the two exams whereas a significant difference for the ARJ was not found. A statistically significant difference exists when the pelvic floor descent is evaluated in sitting versus supine position. Conclusion. Our results show that MR Defecography in sitting position may represent a useful tool to correctly diagnose and grade the pelvic organ descent. PMID:26880893

  20. Rapid Generation of Optimal Asteroid Powered Descent Trajectories Via Convex Optimization

    NASA Technical Reports Server (NTRS)

    Pinson, Robin; Lu, Ping

    2015-01-01

    Mission proposals that land on asteroids are becoming popular. However, in order to have a successful mission the spacecraft must reliably and softly land at the intended landing site. The problem under investigation is how to design a fuel-optimal powered descent trajectory that can be quickly computed on-board the spacecraft, without interaction from ground control. An optimal trajectory designed immediately prior to the descent burn has many advantages. These advantages include the ability to use the actual vehicle starting state as the initial condition in the trajectory design and the ease of updating the landing target site if the original landing site is no longer viable. For long trajectories, the trajectory can be updated periodically by a redesign of the optimal trajectory based on current vehicle conditions to improve the guidance performance. One of the key drivers for being completely autonomous is the infrequent and delayed communication between ground control and the vehicle. Challenges that arise from designing an asteroid powered descent trajectory include complicated nonlinear gravity fields, small rotating bodies and low thrust vehicles.

  1. Simulation Results of the Huygens Probe Entry and Descent Trajectory Reconstruction Algorithm

    NASA Technical Reports Server (NTRS)

    Kazeminejad, B.; Atkinson, D. H.; Perez-Ayucar, M.

    2005-01-01

    Cassini/Huygens is a joint NASA/ESA mission to explore the Saturnian system. The ESA Huygens probe is scheduled to be released from the Cassini spacecraft on December 25, 2004, enter the atmosphere of Titan in January, 2005, and descend to Titan s surface using a sequence of different parachutes. To correctly interpret and correlate results from the probe science experiments and to provide a reference set of data for "ground-truthing" Orbiter remote sensing measurements, it is essential that the probe entry and descent trajectory reconstruction be performed as early as possible in the postflight data analysis phase. The Huygens Descent Trajectory Working Group (DTWG), a subgroup of the Huygens Science Working Team (HSWT), is responsible for developing a methodology and performing the entry and descent trajectory reconstruction. This paper provides an outline of the trajectory reconstruction methodology, preliminary probe trajectory retrieval test results using a simulated synthetic Huygens dataset developed by the Huygens Project Scientist Team at ESA/ESTEC, and a discussion of strategies for recovery from possible instrument failure.

  2. Involvement of Fibroblast Growth Factors and Their Receptors in Epididymo-Testicular Descent and Maldescent

    PubMed Central

    Hadziselimovic, Faruk

    2016-01-01

    Maldescent of the epididymo-testicular unit can occur as an isolated event or as a component of various syndromes. When part of a syndrome, crypto-epididymis is usually accompanied by other genital and/or extragenital features. Epididymis development is primarily regulated by androgens, and successful epididymo-testicular unit development and descent requires an intact hypothalamic-pituitary-gonadal axis. The developing gonadotropin-releasing hormone system is essential for epididymo-testicular descent and is highly sensitive to reduced fibroblast growth factor (FGF) signaling. Our understanding of the impact of FGFR1 in the process of epididymo-testicular descent has recently improved. At later stages of embryonic development, the undifferentiated epididymal mesenchyme is a specific domain for FGFR1 expression. The majority of individuals with syndromic crypto-epididymis, as well as individuals with isolated maldescent of the epididymo-testicular unit, exhibit some disturbance of FGF, FGFR1 and/or genes involved in hypothalamic-pituitary-gonadal axis regulation. However, the mechanisms underlying FGF dysregulation may differ between various syndromes. PMID:27022326

  3. Machado-Joseph disease in pedigrees of Azorean descent is linked to chromosome 14

    SciTech Connect

    George-Hyslop, P. St.; McLachlan, D.R.C.; Lang, A.E.; Wherrett, J.R.; Rogaeva, E.; Tsuda, T.; Rogaev, E.I.; Liang, Y.; Huterer, J.; Kennedy, J. )

    1994-07-01

    A locus for Machado-Joseph disease (MJD) has recently been mapped to a 30-cM region of chromosome 14q in five pedigrees of Japanese descent. MJD is a clinically pleomorphic neurodegenerative disease that was originally described in subjects of Azorean descent. In light of the nonallelic heterogeneity in other inherited spinocerebellar ataxias, the authors were interested to determine if the MJD phenotype in Japanese and Azorean pedigrees arose from mutations at the same locus. They provide evidence that MJD in five pedigrees of Azorean descent is also linked to chromosome 14q in an 18-cM region between the markers D14S67 and AACT (multipoint lod score +7.00 near D14S81). They also report molecular evidence for homozygosity at the MJD locus in an MJD-affected subject with severe, early-onset symptoms. These observations confirm the initial report of linkage of MJD to chromosome 14; suggest that MJD in Japanese and Azorean subjects may represent allelic or identical mutations at the same locus; and provide one possible explanation (MJD gene dosage) for the observed phenotypic heterogeneity in this disease. 22 refs., 3 figs., 1 tab.

  4. Kinetic comparison of older men and women during walk-to-stair descent transition.

    PubMed

    Singhal, Kunal; Kim, Jemin; Casebolt, Jeffrey; Lee, Sangwoo; Han, Ki Hoon; Kwon, Young-Hoo

    2014-09-01

    Stair walking is one of the most challenging tasks for older adults, with women reporting higher incidence of falls. The purpose of this study was to investigate the gender differences in kinetics during stair descent transition. Twenty-eight participants (12 male and 16 female; 68.5 and 69.0 years of mean age, respectively) performed stair descent from level walking in a step-over-step manner at a self-selected speed over a custom-made three-step staircase with embedded force plates. Kinematic and force data were combined using inverse dynamics to generate kinetic data for gender comparison. The top and the first step on the staircase were chosen for analysis. Women showed a higher trail leg peak hip abductor moment (-1.0 Nm/kg), lower trail leg peak knee extensor moment and eccentric power (0.74 Nm/kg and 3.15 W/kg), and lower peak concentric power at trail leg ankle joint (1.29 W/kg) as compared to men (p<0.05; -0.82 Nm/kg, 0.89 Nm/kg, 3.83 W/kg, and 1.78 W/kg, respectively). The lead leg knee eccentric power was also lower in women (p<0.05). This decreased ability to exert knee control during stair descent transition may predispose women to a higher risk of fall.

  5. MR Imaging in Diagnosis of Pelvic Floor Descent: Supine versus Sitting Position.

    PubMed

    Iacobellis, Francesca; Brillantino, Antonio; Renzi, Adolfo; Monaco, Luigi; Serra, Nicola; Feragalli, Beatrice; Iacomino, Aniello; Brunese, Luca; Cappabianca, Salvatore

    2016-01-01

    Introduction. Functional disorders of the pelvic floor represent have a significant impact on the quality of life. The advent of open-configuration systems allowed for the evaluation of defecation with MR imaging in sitting position. The purpose of the present study is to compare the results of static and dynamic pelvic MR performed in supine position versus sitting position, using a new MR prototype machine, in the diagnosis of pelvic floor descent. Materials and Methods. Thirty-one patients with pelvic floor disorders were enrolled, and underwent MR Defecography in supine position with 1.5 T closed magnet (MAGNETOM Symphony, Siemens, Germany) and in sitting position with a 0.25-Tesla open magnet system (G-Scan ESAOTE, Italy). Results. In rest and squeezing phases, positions of bladder, vagina, and ARJ were significantly different when the patient was imaged in supine versus sitting position. In the defecation phase, a significant difference for the bladder and vagina position was detected between the two exams whereas a significant difference for the ARJ was not found. A statistically significant difference exists when the pelvic floor descent is evaluated in sitting versus supine position. Conclusion. Our results show that MR Defecography in sitting position may represent a useful tool to correctly diagnose and grade the pelvic organ descent.

  6. Involvement of Fibroblast Growth Factors and Their Receptors in Epididymo-Testicular Descent and Maldescent.

    PubMed

    Hadziselimovic, Faruk

    2016-02-01

    Maldescent of the epididymo-testicular unit can occur as an isolated event or as a component of various syndromes. When part of a syndrome, crypto-epididymis is usually accompanied by other genital and/or extragenital features. Epididymis development is primarily regulated by androgens, and successful epididymo-testicular unit development and descent requires an intact hypothalamic-pituitary-gonadal axis. The developing gonadotropin-releasing hormone system is essential for epididymo-testicular descent and is highly sensitive to reduced fibroblast growth factor (FGF) signaling. Our understanding of the impact of FGFR1 in the process of epididymo-testicular descent has recently improved. At later stages of embryonic development, the undifferentiated epididymal mesenchyme is a specific domain for FGFR1 expression. The majority of individuals with syndromic crypto-epididymis, as well as individuals with isolated maldescent of the epididymo-testicular unit, exhibit some disturbance of FGF, FGFR1 and/or genes involved in hypothalamic-pituitary-gonadal axis regulation. However, the mechanisms underlying FGF dysregulation may differ between various syndromes.

  7. Controlled weather balloon ascents and descents for atmospheric research and climate monitoring

    NASA Astrophysics Data System (ADS)

    Kräuchi, Andreas; Philipona, Rolf; Romanens, Gonzague; Hurst, Dale F.; Hall, Emrys G.; Jordan, Allen F.

    2016-03-01

    In situ upper-air measurements are often made with instruments attached to weather balloons launched at the surface and lifted into the stratosphere. Present-day balloon-borne sensors allow near-continuous measurements from the Earth's surface to about 35 km (3-5 hPa), where the balloons burst and their instrument payloads descend with parachutes. It has been demonstrated that ascending weather balloons can perturb the air measured by very sensitive humidity and temperature sensors trailing behind them, particularly in the upper troposphere and lower stratosphere (UTLS). The use of controlled balloon descent for such measurements has therefore been investigated and is described here. We distinguish between the single balloon technique that uses a simple automatic valve system to release helium from the balloon at a preset ambient pressure, and the double balloon technique that uses a carrier balloon to lift the payload and a parachute balloon to control the descent of instruments after the carrier balloon is released at preset altitude. The automatic valve technique has been used for several decades for water vapor soundings with frost point hygrometers, whereas the double balloon technique has recently been re-established and deployed to measure radiation and temperature profiles through the atmosphere. Double balloon soundings also strongly reduce pendulum motion of the payload, stabilizing radiation instruments during ascent. We present the flight characteristics of these two ballooning techniques and compare the quality of temperature and humidity measurements made during ascent and descent.

  8. Controlled weather balloon ascents and descents for atmospheric research and climate monitoring

    NASA Astrophysics Data System (ADS)

    Kräuchi, A.; Philipona, R.; Romanens, G.; Hurst, D. F.; Hall, E. G.; Jordan, A. F.

    2015-12-01

    In situ upper-air measurements are often made with instruments attached to weather balloons launched at the surface and lifted into the stratosphere. Present day balloon-borne sensors allow near-continuous measurements from the Earth's surface to about 35 km (3-5 hPa), where the balloons burst and their instrument payloads descend with parachutes. It has been demonstrated that ascending weather balloons can perturb the air measured by very sensitive humidity and temperature sensors trailing behind them, particularly in the upper troposphere and lower stratosphere (UTLS). The use of controlled balloon descent for such measurements has therefore been investigated and is described here. We distinguish between the one balloon technique that uses a simple automatic valve system to release helium from the balloon at a pre-set ambient pressure, and the double balloon technique that uses a carrier balloon to lift the payload and a parachute balloon to control the descent of instruments after the carrier balloon is released at pre-set altitude. The automatic valve technique has been used for several decades for water vapor soundings with frost point hygrometers, whereas the double balloon technique has recently been re-established and deployed to measure radiation and temperature profiles through the atmosphere. Double balloon soundings also strongly reduce pendulum motion of the payload, stabilizing radiation instruments during ascent. We present the flight characteristics of these two ballooning techniques and compare the quality of temperature and humidity measurements made during ascent and descent.

  9. Content validation of a clinical assessment instrument for stair ascent and descent in individuals with hemiparesis

    PubMed Central

    Natalio, Mavie A.; Faria, Christina D. C. M.; Teixeira-Salmela, Luci F.; Michaelsen, Stella M.

    2014-01-01

    Background: Among the current instruments used to assess stair ambulation, none were observed that specifically evaluated the quality of movement or biomechanical strategies adopted by stroke patients. Objective: To evaluate the content validity of a clinical instrument designed to identify the qualitative and kinematic characteristics and strategies adopted by stroke patients during stair ascent and descent. Method: The first developed version, which comprised 80 items, had its content evaluated by an expert panel, which was composed of 9 well-known national and international professionals who are involved in stroke rehabilitation. The content validity index (CVI) and modified Kappa coefficients were employed for the statistical analyses. The items that demonstrated a CVI≥0.80 and Kappa≥0.75 were considered valid. Results: The content validation was performed in three stages. The final version of the instrument consisted of 38 items, which were divided into descriptive (8 items), a General Characteristics Domain (16 items) and adopted strategies (14 items) during stair ascent and descent. The total scores ranged from zero to 70 and zero to 74 for ascent and descent, respectively. Lower scores corresponded with better performance. Conclusion: Despite the satisfactory results obtained during the process of content validation, other psychometric properties of the instrument are necessary and must be evaluated. PMID:25054384

  10. The Uncertain Significance of Low Vitamin D levels in African Descent Populations: A Review of the Bone and Cardiometabolic Literature

    PubMed Central

    O'Connor, Michelle Y; Thoreson, Caroline K; Ramsey, Natalie L M; Ricks, Madia; Sumner, Anne E

    2014-01-01

    Vitamin D levels in people of African descent are often described as inadequate or deficient. Whether low vitamin D levels in people of African descent lead to compromised bone or cardiometabolic health is unknown. Clarity on this issue is essential because if clinically significant vitamin D deficiency is present, vitamin D supplementation is necessary. However, if vitamin D is metabolically sufficient, vitamin D supplementation could be wasteful of scarce resources and even harmful. In this review vitamin D physiology is described with a focus on issues specific to populations of African descent such as the influence of melanin on endogenous vitamin D production and lactose intolerance on the willingness of people to ingest vitamin D fortified foods. Then data on the relationship of vitamin D to bone and cardiometabolic health in people of African descent are evaluated. PMID:24267433

  11. System engineering challenges of real-time simulation for Mars SmartLander entry, descent, and landing

    NASA Technical Reports Server (NTRS)

    Martin, B. J.; Henriquez, D. A.; Balaram, B.; Sohl, G. A.; Pomerantz, M. I.

    2002-01-01

    The Jet Propulsion Laboratory (JPL) is developing a high-fidelity, real-time spacecraft simulator for Entry, Descent and Landing (EDL) on planetary and small bodies. This simulator, DSENDS (Dynamics Simulator for Entry, Descent and Surface landing), is an EDL-specific extension of the JPL Darts/Dshell multi-mission spacecraft dynamics and devices simulation toolkit which is in use by missions such as Cassini, Galileo, SIM, and Starlight.

  12. Accelerator system and method of accelerating particles

    NASA Technical Reports Server (NTRS)

    Wirz, Richard E. (Inventor)

    2010-01-01

    An accelerator system and method that utilize dust as the primary mass flux for generating thrust are provided. The accelerator system can include an accelerator capable of operating in a self-neutralizing mode and having a discharge chamber and at least one ionizer capable of charging dust particles. The system can also include a dust particle feeder that is capable of introducing the dust particles into the accelerator. By applying a pulsed positive and negative charge voltage to the accelerator, the charged dust particles can be accelerated thereby generating thrust and neutralizing the accelerator system.

  13. Biomechanical demands of the 2-step transitional gait cycles linking level gait and stair descent gait in older women.

    PubMed

    Alcock, Lisa; O'Brien, Thomas D; Vanicek, Natalie

    2015-12-16

    Stair descent is an inherently complex form of locomotion posing a high falls risk for older adults, specifically when negotiating the transitional gait cycles linking level gait and descent. The aim of this study was to enhance our understanding of the biomechanical demands by comparing the demands of these transitions. Lower limb kinematics and kinetics of the 2-step transitions linking level and descent gait at the top (level-to-descent) and the bottom (descent-to-level) of the staircase were quantified in 36 older women with no falls history. Despite undergoing the same vertical displacement (2-steps), the following significant (p<.05) differences were observed during the top transition compared to the bottom transition: reduced step velocity; reduced hip extension and increased ankle dorsiflexion (late stance/pre-swing); reduced ground reaction forces, larger knee extensor moments and powers (absorption; late stance); reduced ankle plantarflexor moments (early and late stance) and increased ankle powers (mid-stance). Top transition biomechanics were similar to those reported previously for continuous descent. Kinetic differences at the knee and ankle signify the contrasting and prominent functions of controlled lowering during the top transition and forward continuance during the bottom transition. The varying musculoskeletal demands encountered during each functional sub-task should be addressed in falls prevention programmes with elderly populations where the greatest clinical impact may be achieved. Knee extensor eccentric power through flexion exercises would facilitate a smooth transition at the top and improving ankle plantarflexion strength during single and double limb stance activities would ease the transition into level gait following continuous descent. PMID:26592439

  14. Biomechanical demands of the 2-step transitional gait cycles linking level gait and stair descent gait in older women.

    PubMed

    Alcock, Lisa; O'Brien, Thomas D; Vanicek, Natalie

    2015-12-16

    Stair descent is an inherently complex form of locomotion posing a high falls risk for older adults, specifically when negotiating the transitional gait cycles linking level gait and descent. The aim of this study was to enhance our understanding of the biomechanical demands by comparing the demands of these transitions. Lower limb kinematics and kinetics of the 2-step transitions linking level and descent gait at the top (level-to-descent) and the bottom (descent-to-level) of the staircase were quantified in 36 older women with no falls history. Despite undergoing the same vertical displacement (2-steps), the following significant (p<.05) differences were observed during the top transition compared to the bottom transition: reduced step velocity; reduced hip extension and increased ankle dorsiflexion (late stance/pre-swing); reduced ground reaction forces, larger knee extensor moments and powers (absorption; late stance); reduced ankle plantarflexor moments (early and late stance) and increased ankle powers (mid-stance). Top transition biomechanics were similar to those reported previously for continuous descent. Kinetic differences at the knee and ankle signify the contrasting and prominent functions of controlled lowering during the top transition and forward continuance during the bottom transition. The varying musculoskeletal demands encountered during each functional sub-task should be addressed in falls prevention programmes with elderly populations where the greatest clinical impact may be achieved. Knee extensor eccentric power through flexion exercises would facilitate a smooth transition at the top and improving ankle plantarflexion strength during single and double limb stance activities would ease the transition into level gait following continuous descent.

  15. Large Eddy Simulation of Aircraft Wake Vortices in a Homogeneous Atmospheric Turbulence: Vortex Decay and Descent

    NASA Technical Reports Server (NTRS)

    Han, Jongil; Lin, Yuh-Lang; Arya, S. Pal; Proctor, Fred H.

    1999-01-01

    The effects of ambient turbulence on decay and descent of aircraft wake vortices are studied using a validated, three-dimensional: large-eddy simulation model. Numerical simulations are performed in order to isolate the effect of ambient turbulence on the wake vortex decay rate within a neutrally-stratified atmosphere. Simulations are conducted for a range of turbulence intensities, by injecting wake vortex pairs into an approximately homogeneous and isotropic turbulence field. The decay rate of the vortex circulation increases clearly with increasing ambient turbulence level, which is consistent with field observations. Based on the results from the numerical simulations, simple decay models are proposed as functions of dimensionless ambient turbulence intensity (eta) and dimensionless time (T) for the circulation averaged over a range of radial distances. With good agreement with the numerical results, a Gaussian type of vortex decay model is proposed for weak turbulence: while an exponential type of Tortex decay model can be applied for strong turbulence. A relationship for the vortex descent based on above vortex decay model is also proposed. Although the proposed models are based on simulations assuming neutral stratification, the model predictions are compared to Lidar vortex measurements observed during stable, neutral, and unstable atmospheric conditions. In the neutral and unstable atmosphere, the model predictions appear to be in reasonable agreement with the observational data, while in the stably-stratified atmosphere, they largely underestimate the observed circulation decay with consistent overestimation of the observed vortex descent. The underestimation of vortex decay during stably-stratified conditions suggests that stratification has an important influence on vortex decay when ambient levels of turbulence are weak.

  16. Influence of seasonal cycles in Martian atmosphere on entry, descent and landing sequence

    NASA Astrophysics Data System (ADS)

    Marčeta, Dušan; Šegan, Stevo; Rašuo, Boško

    2014-05-01

    The phenomena like high eccentricity of Martian orbit, obliquity of the orbital plane and close alignment of the winter solstice and the orbital perihelion, separately or together can significantly alter not only the level of some Martian atmospheric parameters but also the characteristics of its diurnal and seasonal cycle. Considering that entry, descent and landing (EDL) sequence is mainly driven by the density profile of the atmosphere and aerodynamic characteristic of the entry vehicle. We have performed the analysis of the influence of the seasonal cycles of the atmospheric parameters on EDL profiles by using Mars Global Reference Atmospheric Model (Mars-GRAM). Since the height of the deployment of the parachute and the time passed from the deployment to propulsion firing (descent time) are of crucial importance for safe landing and the achievable landing site elevation we paid special attention to the influence of the areocentric longitude of the Sun (Ls) on these variables. We have found that these variables have periodic variability with respect to Ls and can be very well approximated with a sine wave function whose mean value depends only on the landing site elevation while the amplitudes and phases depend only on the landing site latitude. The amplitudes exhibit behavior which is symmetric with respect to the latitude but the symmetry is shifted from the equator to the northern mid-tropics. We have also noticed that the strong temperature inversions which are usual for middle and higher northern latitudes while Mars is around its orbital perihelion significantly alter the descent time without influencing the height of the parachute deployment. At last, we applied our model to determine the dependence of the accessible landing region on Ls and found that this region reaches maximum when Mars is around the orbital perihelion and can vary 50° in latitude throughout the Martian year.

  17. Altair Descent and Ascent Reference Trajectory Design and Initial Dispersion Analyses

    NASA Technical Reports Server (NTRS)

    Kos, Larry D.; Polsgrove, Tara T.; Sostaric, Ronald r.; Braden, Ellen M.; Sullivan, Jacob J.; Lee, Thanh T.

    2010-01-01

    The Altair Lunar Lander is the linchpin in the Constellation Program (CxP) for human return to the Moon. Altair is delivered to low Earth orbit (LEO) by the Ares V heavy lift launch vehicle, and after subsequent docking with Orion in LEO, the Altair/Orion stack is delivered through translunar injection (TLI). The Altair/Orion stack separating from the Earth departure stage (EDS) shortly after TLI and continues the flight to the Moon as a single stack. Altair performs the lunar orbit insertion (LOI) maneuver, targeting a 100-km circular orbit. This orbit will be a polar orbit for missions landing near the lunar South Pole. After spending nearly 24 hours in low lunar orbit (LLO), the lander undocks from Orion and performs a series of small maneuvers to set up for descending to the lunar surface. This descent begins with a small deorbit insertion (DOI) maneuver, putting the lander on an orbit that has a perilune of 15.24 km (50,000 ft), the altitude where the actual powered descent initiation (PDI) commences. At liftoff from Earth, Altair has a mass of 45 metric tons (mt). However after LOI (without Orion attached), the lander mass is slightly less than 33 mt at PDI. The lander currently has a single descent module main engine, with TBD lb(sub f) thrust (TBD N), providing a thrust-to-weight ratio of approximately TBD Earth g's at PDI. LDAC-3 (Lander design and analysis cycle #3) is the most recently closed design sizing and mass properties iteration. Upgrades for loss of crew (LDAC-2) and loss of mission (LDAC-3) have been incorporated into the lander baseline design (and its Master Equipment List). Also, recently, Altair has been working requirements analyses (LRAC-1). All nominal data here are from the LDAC-3 analysis cycle. All dispersions results here are from LRAC-1 analyses.

  18. Changes in labial capillary density on ascent to and descent from high altitude

    PubMed Central

    Gilbert-Kawai, Edward; Coppel, Jonny; Phillip, Hennis; Grocott, Michael; Ince, Can; Martin, Daniel

    2016-01-01

    Present knowledge of how the microcirculation is altered by prolonged exposure to hypoxia at high altitude is incomplete and modification of existing analytical techniques may improve our knowledge considerably. We set out to use a novel simplified method of measuring in vivo capillary density during an expedition to high altitude using a CytoCam incident dark field imaging video-microscope. The simplified method of data capture involved recording one-second images of the mucosal surface of the inner lip to reveal data about microvasculature density in ten individuals. This was done on ascent to, and descent from, high altitude. Analysis was conducted offline by two independent investigators blinded to the participant identity, testing conditions and the imaging site.  Additionally we monitored haemoglobin concentration and haematocrit data to see if we could support or refute mechanisms of altered density relating to vessel recruitment. Repeated sets of paired values were compared using Kruskall Wallis Analysis of Variance tests, whilst comparisons of values between sites was by related samples Wilcoxon Signed Rank Test. Correlation between different variables was performed using Spearman’s rank correlation coefficient, and concordance between analysing investigators using intra-class correlation coefficient. There was a significant increase in capillary density from London on ascent to high altitude; median capillaries per field of view area increased from 22.8 to 25.3 (p=0.021). There was a further increase in vessel density during the six weeks spent at altitude (25.3 to 32.5, p=0.017). Moreover, vessel density remained high on descent to Kathmandu (31.0 capillaries per field of view area), despite a significant decrease in haemoglobin concentration and haematocrit. Using a simplified technique, we have demonstrated an increase in capillary density on early and sustained exposure to hypobaric hypoxia at thigh altitude, and that this remains elevated on

  19. Entry, Descent, and Landing Communications for the 2011 Mars Science Laboratory

    NASA Technical Reports Server (NTRS)

    Abilleira, Fernando; Shidner, Jeremy D.

    2012-01-01

    The Mars Science Laboratory (MSL), established as the most advanced rover to land on the surface of Mars to date, launched on November 26th, 2011 and arrived to the Martian Gale Crater during the night of August 5th, 2012 (PDT). MSL will investigate whether the landing region was ever suitable to support carbon-based life, and examine rocks, soil, and the atmosphere with a sophisticated suite of tools. This paper addresses the flight system requirement by which the vehicle transmitted indications of the following events using both X-band tones and UHF telemetry to allow identification of probable root causes should a mission anomaly have occurred: Heat-Rejection System (HRS) venting, completion of the cruise stage separation, turn to entry attitude, atmospheric deceleration, bank angle reversal commanded, parachute deployment, heatshield separation, radar ground acquisition, powered descent initiation, rover separation from the descent stage, and rover release. During Entry, Descent, and Landing (EDL), the flight system transmitted a UHF telemetry stream adequate to determine the state of the spacecraft (including the presence of faults) at 8 kbps initiating from cruise stage separation through at least one minute after positive indication of rover release on the surface of Mars. The flight system also transmitted X-band semaphore tones from Entry to Landing plus one minute although since MSL was occulted, as predicted, by Mars as seen from the Earth, Direct-To-Earth (DTE) communications were interrupted at approximately is approx. 5 min after Entry ( approximately 130 prior to Landing). The primary data return paths were through the Deep Space Network (DSN) for DTE and the existing Mars network of orbiting assets for UHF, which included the Mars Reconnaissance Orbiter (MRO), Mars Odyssey (ODY), and Mars Express (MEX) elements. These orbiters recorded the telemetry data stream and returned it back to Earth via the DSN. The paper also discusses the total power

  20. Dietary Associations of Household Food Insecurity Among Children of Mexican Descent: Results of a Binational Study

    PubMed Central

    Rosas, Lisa G; Harley, Kim; Fernald, Lia CH; Guendelman, Sylvia; Mejia, Fabiola; Neufeld, Lynnette M

    2015-01-01

    Background/objective Children of Mexican descent frequently experience household food insecurity both in the United States (US) and Mexico, however, little is known about the associations of food insecurity with dietary intake. This study aimed to understand the level of perceived food insecurity and its association with dietary intake among children of Mexican descent residing in the US and Mexico. Design This cross-sectional study utilized data from a 2006 binational study of five-year-old children of Mexican descent living in migrant communities in California (CA) and Mexico (MX). Methods In CA, children were 301 participants from the CHAMACOS study, a longitudinal birth cohort in a Mexican immigrant community. MX children (n=301) were participants in the Proyecto Mariposa study, which was designed to capture a sample of women and their children living in Mexico who closely resembled the CA sample, yet who never migrated to the US. Household food insecurity was measured using the US Department of Agriculture Food Security Scale and dietary intake was assessed with food frequency questionnaires. Analysis of variance was used to examine unadjusted and adjusted differences in total energy, nutrient intake, and consumption of food groups by household food security status. Results Approximately 39% of the CA mothers and 75% of the MX mothers reported low or very low food security in the last 12 months (p<0.01). Children in the US, experiencing food insecurity consumed more fat, saturated fat, sweets and fried snacks than children not experiencing food insecurity. In contrast, in Mexico food insecurity was associated with lower intake of total carbohydrates, dairy and vitamin B6. Conclusions Programs and policies addressing food insecurity in the US and Mexico may need to take steps to address dietary intake among children in households experiencing food insecurity, possibly through education and programs to increase resources to obtain healthy foods. PMID:19942017

  1. Fast Automatic Step Size Estimation for Gradient Descent Optimization of Image Registration.

    PubMed

    Qiao, Yuchuan; van Lew, Baldur; Lelieveldt, Boudewijn P F; Staring, Marius

    2016-02-01

    Fast automatic image registration is an important prerequisite for image-guided clinical procedures. However, due to the large number of voxels in an image and the complexity of registration algorithms, this process is often very slow. Stochastic gradient descent is a powerful method to iteratively solve the registration problem, but relies for convergence on a proper selection of the optimization step size. This selection is difficult to perform manually, since it depends on the input data, similarity measure and transformation model. The Adaptive Stochastic Gradient Descent (ASGD) method is an automatic approach, but it comes at a high computational cost. In this paper, we propose a new computationally efficient method (fast ASGD) to automatically determine the step size for gradient descent methods, by considering the observed distribution of the voxel displacements between iterations. A relation between the step size and the expectation and variance of the observed distribution is derived. While ASGD has quadratic complexity with respect to the transformation parameters, fast ASGD only has linear complexity. Extensive validation has been performed on different datasets with different modalities, inter/intra subjects, different similarity measures and transformation models. For all experiments, we obtained similar accuracy as ASGD. Moreover, the estimation time of fast ASGD is reduced to a very small value, from 40 s to less than 1 s when the number of parameters is 105, almost 40 times faster. Depending on the registration settings, the total registration time is reduced by a factor of 2.5-7 × for the experiments in this paper.

  2. Acquired undescended testes and fertility potential: is orchiopexy at diagnosis better than awaiting spontaneous descent?

    PubMed

    van der Plas, E M; van Brakel, J; Meij-de Vries, A; de Muinck Keizer-Schrama, S M P F; Hazebroek, F W J; Hack, W W M; Dohle, G R

    2015-07-01

    The aim of this study was to evaluate testicular function in men with previous acquired undescended testis (UDT) in whom orchiopexy was performed at diagnosis compared with a similar group of men in whom spontaneous descent was awaited until puberty. Secondly, we examined the influence of age at orchiopexy on fertility parameters in adult life. A total of 169 men of the 'orchiopexy at diagnosis' group and 207 men of the 'wait and see' protocol group were invited for participation. All participants underwent an andrological evaluation, including medical history, physical examination, scrotal ultrasound, determination of reproductive hormones, and semen analysis. Results were compared for men in whom orchiopexy was performed at diagnoses with men in whom spontaneous descent was awaited until puberty followed by orchiopexy in case of non-descent. In the 'orchiopexy at diagnosis' group, 63 men of whom 14 with bilateral UDT, and in the 'wait and see' protocol group, 65 men of whom 15 with bilateral UDT were included. For unilateral UDT Inhibin B was found to be significantly lower and median progressive motility was higher in men with orchiopexy at diagnosis. For bilateral UDT, semen concentration and progressive motility showed a trend toward a favorable outcome for orchiopexy at diagnosis. Age at orchiopexy being under or above 10 years of age had no significant influence on the fertility potential. The outcome of physical examination, scrotal ultrasound, endocrine function, and semen analysis indicates a compromised fertility potential in men with previous acquired UDT. None of the protocols proved to be superior. For bilateral UDT, a trend toward favorable outcome of orchiopexy at diagnosis was seen. Furthermore, age at orchiopexy did not have an influence on fertility parameters. Therefore, in our opinion a 'conservative policy' is warranted for unilateral UDT, especially because over 50% of acquired UDT descend spontaneously.

  3. Three-dimensional object recognition using gradient descent and the universal 3-D array grammar

    NASA Astrophysics Data System (ADS)

    Baird, Leemon C., III; Wang, Patrick S. P.

    1992-02-01

    A new algorithm is presented for applying Marill's minimum standard deviation of angles (MSDA) principle for interpreting line drawings without models. Even though no explicit models or additional heuristics are included, the algorithm tends to reach the same 3-D interpretations of 2-D line drawings that humans do. Marill's original algorithm repeatedly generated a set of interpretations and chose the one with the lowest standard deviation of angles (SDA). The algorithm presented here explicitly calculates the partial derivatives of SDA with respect to all adjustable parameters, and follows this gradient to minimize SDA. For a picture with lines meeting at m points forming n angles, the gradient descent algorithm requires O(n) time to adjust all the points, while the original algorithm required O(mn) time to do so. For the pictures described by Marill, this gradient descent algorithm running on a Macintosh II was found to be one to two orders of magnitude faster than the original algorithm running on a Symbolics, while still giving comparable results. Once the 3-D interpretation of the line drawing has been found, the 3-D object can be reduced to a description string using the Universal 3-D Array Grammar. This is a general grammar which allows any connected object represented as a 3-D array of pixels to be reduced to a description string. The algorithm based on this grammar is well suited to parallel computation, and could run efficiently on parallel hardware. This paper describes both the MSDA gradient descent algorithm and the Universal 3-D Array Grammar algorithm. Together, they transform a 2-D line drawing represented as a list of line segments into a string describing the 3-D object pictured. The strings could then be used for object recognition, learning, or storage for later manipulation.

  4. Acquired undescended testes and fertility potential: is orchiopexy at diagnosis better than awaiting spontaneous descent?

    PubMed

    van der Plas, E M; van Brakel, J; Meij-de Vries, A; de Muinck Keizer-Schrama, S M P F; Hazebroek, F W J; Hack, W W M; Dohle, G R

    2015-07-01

    The aim of this study was to evaluate testicular function in men with previous acquired undescended testis (UDT) in whom orchiopexy was performed at diagnosis compared with a similar group of men in whom spontaneous descent was awaited until puberty. Secondly, we examined the influence of age at orchiopexy on fertility parameters in adult life. A total of 169 men of the 'orchiopexy at diagnosis' group and 207 men of the 'wait and see' protocol group were invited for participation. All participants underwent an andrological evaluation, including medical history, physical examination, scrotal ultrasound, determination of reproductive hormones, and semen analysis. Results were compared for men in whom orchiopexy was performed at diagnoses with men in whom spontaneous descent was awaited until puberty followed by orchiopexy in case of non-descent. In the 'orchiopexy at diagnosis' group, 63 men of whom 14 with bilateral UDT, and in the 'wait and see' protocol group, 65 men of whom 15 with bilateral UDT were included. For unilateral UDT Inhibin B was found to be significantly lower and median progressive motility was higher in men with orchiopexy at diagnosis. For bilateral UDT, semen concentration and progressive motility showed a trend toward a favorable outcome for orchiopexy at diagnosis. Age at orchiopexy being under or above 10 years of age had no significant influence on the fertility potential. The outcome of physical examination, scrotal ultrasound, endocrine function, and semen analysis indicates a compromised fertility potential in men with previous acquired UDT. None of the protocols proved to be superior. For bilateral UDT, a trend toward favorable outcome of orchiopexy at diagnosis was seen. Furthermore, age at orchiopexy did not have an influence on fertility parameters. Therefore, in our opinion a 'conservative policy' is warranted for unilateral UDT, especially because over 50% of acquired UDT descend spontaneously. PMID:26084887

  5. Trunk and Lower Extremity Kinematics During Stair Descent in Women With or Without Patellofemoral Pain

    PubMed Central

    Schwane, Brandi G.; Goerger, Benjamin M.; Goto, Shiho; Blackburn, J. Troy; Aguilar, Alain J.; Padua, Darin A.

    2015-01-01

    Context There is limited evidence indicating the contribution of trunk kinematics to patellofemoral pain (PFP). A better understanding of the interaction between trunk and lower extremity kinematics in this population may provide new avenues for interventions to treat PFP. Objective To compare trunk and lower extremity kinematics between participants with PFP and healthy controls during a stair-descent task. Design Cross-sectional study. Setting Research laboratory. Patients or Other Participants Twenty women with PFP (age = 22.2 ± 3.1 years, height = 164.5 ± 9.2 cm, mass = 63.5 ± 13.6 kg) and 20 healthy women (age = 21.0 ± 2.6 years, height = 164.5 ± 7.1 cm, mass = 63.8 ± 12.7 kg). Intervention(s) Kinematics were recorded as participants performed stair descent at a controlled velocity. Main Outcome Measure(s) Three-dimensional joint displacement of the trunk, hip, and knee during the stance phase of stair descent for the affected leg was measured using a 7-camera infrared optical motion-capture system. Pretest and posttest pain were assessed using a visual analogue scale. Kinematic differences between groups were determined using independent-samples t tests. A 2 × 2 mixed-model analysis of variance (group = PFP, control; time = pretest, posttest) was used to compare knee pain. Results We observed greater knee internal-rotation displacement for the PFP group (12.8° ± 7.2°) as compared with the control group (8.9° ± 4.4°). No other between-groups differences were observed for the trunk, hip, or other knee variables. Conclusions We observed no difference in trunk kinematics between groups but did note differences in knee internal-rotation displacement. These findings contribute to the current knowledge of altered movement in those with PFP and provide direction for exercise interventions. PMID:25898109

  6. Implementing the Mars Science Laboratory Terminal Descent Sensor Field Test Campaign

    NASA Technical Reports Server (NTRS)

    Montgomery, James F.; Bodie, James H.; Brown, Joseph D.; Chen, Allen; Chen, Curtis W.; Essmiller, John C.; Fisher, Charles D.; Goldberg, Hannah R.; Lee, Steven W.; Shaffer, Scott J.

    2012-01-01

    The Mars Science Laboratory (MSL) will deliver a 900 kg rover to the surface of Mars in August 2012. MSL will utilize a new pulse-Doppler landing radar, the Terminal Descent Sensor (TDS). The TDS employs six narrow-beam antennas to provide unprecedented slant range and velocity performance at Mars to enable soft touchdown of the MSL rover using a unique sky crane Entry, De-scent, and Landing (EDL) technique. Prior to use on MSL, the TDS was put through a rigorous verification and validation (V&V) process. A key element of this V&V was operating the TDS over a series of field tests, using flight-like profiles expected during the descent and landing of MSL over Mars-like terrain on Earth. Limits of TDS performance were characterized with additional testing meant to stress operational modes outside of the expected EDL flight profiles. The flight envelope over which the TDS must operate on Mars encompasses such a large range of altitudes and velocities that a variety of venues were neces-sary to cover the test space. These venues included an F/A-18 high performance aircraft, a Eurocopter AS350 AStar helicopter and 100-meter tall Echo Towers at the China Lake Naval Air Warfare Center. Testing was carried out over a five year period from July 2006 to June 2011. TDS performance was shown, in gen-eral, to be excellent over all venues. This paper describes the planning, design, and implementation of the field test campaign plus results and lessons learned.

  7. Puberty stage and spontaneous descent of acquired undescended testis: implications for therapy?

    PubMed

    Sijstermans, K; Hack, W W M; van der Voort-Doedens, L M; Meijer, R W; Haasnoot, K

    2006-12-01

    We assessed spontaneous descent of acquired undescended testis (UDT) at puberty. 299 Boys (aged 1.2-16.5 years, mean 9.4) with 350 acquired-UDT were examined annually during a 12.6-year period (mean 3.1). An acquired-UDT was defined as a previously intrascrotal testis which can no longer be manipulated into a stable scrotal position. Each year, position of the testis and pubertal development according to Tanner's stages were assessed. Early puberty was defined as puberty stage G2 (testicular volume 4-9 mL), mid-puberty as puberty stages G3 (testicular volume 10 mL) and G4 (testicular volume 11-15 mL), and late puberty as puberty stage G5 (testicular volume >15 mL). Follow-up was completed if spontaneous descent had occurred, if mid-pubertal orchidopexy (ORP) had to be performed, if the boy was lost for follow-up, or if pre-pubertal ORP was performed in another hospital. In 139 boys with 164 acquired-UDT follow-up was meanwhile completed. Twelve boys with 14 UDT were lost for follow-up. In an additional 16 boys with 21 UDT, ORP was performed in another hospital. In 98 of the remaining 129 (76.0%) acquired-UDT spontaneous descent at puberty occurred. Mean follow-up was 2.5 years (range 0.2-8.5). In 70 of 98 testes (71.4%) descent occurred in early puberty, in 26 of 98 testes (26.5%) in mid-puberty, and in two testes in late puberty. In 31 of 129 testes (24.0%) ORP had to be performed at mid (30 cases) or late (one case) puberty. In this series, 98 of 129 acquired-UDT (76.0%) descended spontaneously at puberty, whereas in 31 of 129 (24.0%) pubertal ORP was performed. If ORP is postponed until puberty stage G3 (testicular volume of 10 mL) three of four acquired-UDT will descend spontaneously.

  8. Multimode fiber laser beam cleanup based on stochastic parallel gradient descent algorithm

    NASA Astrophysics Data System (ADS)

    Zhao, Hai-Chuan; Ma, Hao-Tong; Zhou, Pu; Wang, Xiao-Lin; Ma, Yan-Xing; Li, Xiao; Xu, Xiao-Jun; Zhao, Yi-Jun

    2011-01-01

    We present experimental research on multimode fiber laser beam cleanup based on a stochastic parallel gradient descent (SPGD) algorithm. The multimode laser is obtained by injecting a 1064 nm central wavelength single mode fiber laser into a multimode fiber and the system is setup by using phase only liquid crystal spatial light modulators (LC-SLM). The quality evaluation function is increased by a factor of 10.5 and 65% of the laser energy is encircled in the central lobe when the system evolves from open-loop into close-loop state. Experimental results indicate the feasibility of the multimode fiber laser beam cleanup by adaptive optics (AO).

  9. Apollo 14 mission report. Supplement 5: Descent propulsion system final flight evaluation

    NASA Technical Reports Server (NTRS)

    Avvenire, A. T.; Wood, S. C.

    1972-01-01

    The performance of the LM-8 descent propulsion system during the Apollo 14 mission was evaluated and found to be satisfactory. The average engine effective specific impulse was 0.1 second higher than predicted, but well within the predicted l sigma uncertainty. The engine performance corrected to standard inlet conditions for the FTP portion of the burn at 43 seconds after ignition was as follows: thrust, 9802, lbf; specific impulse, 304.1 sec; and propellant mixture ratio, 1603. These values are + or - 0.8, -0.06, and + or - 0.3 percent different respectively, from the values reported from engine acceptance tests and were within specification limits.

  10. Design requirements and development of an airborne descent path definition algorithm for time navigation

    NASA Technical Reports Server (NTRS)

    Izumi, K. H.; Thompson, J. L.; Groce, J. L.; Schwab, R. W.

    1986-01-01

    The design requirements for a 4D path definition algorithm are described. These requirements were developed for the NASA ATOPS as an extension of the Local Flow Management/Profile Descent algorithm. They specify the processing flow, functional and data architectures, and system input requirements, and recommended the addition of a broad path revision (reinitialization) function capability. The document also summarizes algorithm design enhancements and the implementation status of the algorithm on an in-house PDP-11/70 computer. Finally, the requirements for the pilot-computer interfaces, the lateral path processor, and guidance and steering function are described.

  11. Mars Reconnaissance Orbiter Navigation Strategy for Mars Science Laboratory Entry, Descent and Landing Telecommunication Relay Support

    NASA Technical Reports Server (NTRS)

    Williams, Jessica L.; Menon, Premkumar R.; Demcak, Stuart W.

    2012-01-01

    The Mars Reconnaissance Orbiter (MRO) is an orbiting asset that performs remote sensing observations in order to characterize the surface, subsurface and atmosphere of Mars. To support upcoming NASA Mars Exploration Program Office objectives, MRO will be used as a relay communication link for the Mars Science Laboratory (MSL) mission during the MSL Entry, Descent and Landing sequence. To do so, MRO Navigation must synchronize the MRO Primary Science Orbit (PSO) with a set of target conditions requested by the MSL Navigation Team; this may be accomplished via propulsive maneuvers. This paper describes the MRO Navigation strategy for and operational performance of MSL EDL relay telecommunication support.

  12. Functional Equivalence Acceptance Testing of FUN3D for Entry Descent and Landing Applications

    NASA Technical Reports Server (NTRS)

    Gnoffo, Peter A.; Wood, William A.; Kleb, William L.; Alter, Stephen J.; Glass, Christopher E.; Padilla, Jose F.; Hammond, Dana P.; White, Jeffery A.

    2013-01-01

    The functional equivalence of the unstructured grid code FUN3D to the the structured grid code LAURA (Langley Aerothermodynamic Upwind Relaxation Algorithm) is documented for applications of interest to the Entry, Descent, and Landing (EDL) community. Examples from an existing suite of regression tests are used to demonstrate the functional equivalence, encompassing various thermochemical models and vehicle configurations. Algorithm modifications required for the node-based unstructured grid code (FUN3D) to reproduce functionality of the cell-centered structured code (LAURA) are also documented. Challenges associated with computation on tetrahedral grids versus computation on structured-grid derived hexahedral systems are discussed.

  13. Maraia Capsule Flight Testing and Results for Entry, Descent, and Landing

    NASA Technical Reports Server (NTRS)

    Sostaric, Ronald R.; Strahan, Alan L.

    2016-01-01

    The Maraia concept is a modest size (150 lb., 30" diameter) capsule that has been proposed as an ISS based, mostly autonomous earth return capability to function either as an Entry, Descent, and Landing (EDL) technology test platform or as a small on-demand sample return vehicle. A flight test program has been completed including high altitude balloon testing of the proposed capsule shape, with the purpose of investigating aerodynamics and stability during the latter portion of the entry flight regime, along with demonstrating a potential recovery system. This paper includes description, objectives, and results from the test program.

  14. Fuel-Efficient Descent and Landing Guidance Logic for a Safe Lunar Touchdown

    NASA Technical Reports Server (NTRS)

    Lee, Allan Y.

    2011-01-01

    The landing of a crewed lunar lander on the surface of the Moon will be the climax of any Moon mission. At touchdown, the landing mechanism must absorb the load imparted on the lander due to the vertical component of the lander's touchdown velocity. Also, a large horizontal velocity must be avoided because it could cause the lander to tip over, risking the life of the crew. To be conservative, the worst-case lander's touchdown velocity is always assumed in designing the landing mechanism, making it very heavy. Fuel-optimal guidance algorithms for soft planetary landing have been studied extensively. In most of these studies, the lander is constrained to touchdown with zero velocity. With bounds imposed on the magnitude of the engine thrust, the optimal control solutions typically have a "bang-bang" thrust profile: the thrust magnitude "bangs" instantaneously between its maximum and minimum magnitudes. But the descent engine might not be able to throttle between its extremes instantaneously. There is also a concern about the acceptability of "bang-bang" control to the crew. In our study, the optimal control of a lander is formulated with a cost function that penalizes both the touchdown velocity and the fuel cost of the descent engine. In this formulation, there is not a requirement to achieve a zero touchdown velocity. Only a touchdown velocity that is consistent with the capability of the landing gear design is required. Also, since the nominal throttle level for the terminal descent sub-phase is well below the peak engine thrust, no bound on the engine thrust is used in our formulated problem. Instead of bangbang type solution, the optimal thrust generated is a continuous function of time. With this formulation, we can easily derive analytical expressions for the optimal thrust vector, touchdown velocity components, and other system variables. These expressions provide insights into the "physics" of the optimal landing and terminal descent maneuver. These

  15. The Mars Exploration Rovers Entry Descent and Landing and the Use of Aerodynamic Decelerators

    NASA Technical Reports Server (NTRS)

    Steltzner, Adam; Desai, Prasun; Lee, Wayne; Bruno, Robin

    2003-01-01

    The Mars Exploration Rovers (MER) project, the next United States mission to the surface of Mars, uses aerodynamic decelerators in during its entry, descent and landing (EDL) phase. These two identical missions (MER-A and MER-B), which deliver NASA s largest mobile science suite to date to the surface of Mars, employ hypersonic entry with an ablative energy dissipating aeroshell, a supersonic/subsonic disk-gap-band parachute and an airbag landing system within EDL. This paper gives an overview of the MER EDL system and speaks to some of the challenges faced by the various aerodynamic decelerators.

  16. Perceived reasons for depression among low income women of Mexican descent.

    PubMed

    Heilemann, MarySue V; Coffey-Love, Melody; Frutos, Lisa

    2004-10-01

    From a larger cross-sectional study of 315 women of Mexican descent, this secondary analysis focused on short answers to open-ended questions related to reasons given by 107 women at risk for depression (>16 on CES-D) for feelings of sadness, hopelessness, or depression within the last month. Data were analyzed using grounded theory techniques. Six categories of reasons were derived from data including: (1) partner issues, (2) family issues, (3) feelings of being alone, (4) inability to provide for material needs, (5) bodily symptoms and experiences, and (6) vague nonspecific reasons. Results are useful for designing future treatment programs. PMID:15529284

  17. Calculation of identity-by-descent probabilities of short chromosome segments.

    PubMed

    Tuchscherer, A; Teuscher, F; Reinsch, N

    2012-12-01

    For some purposes, identity-by-descent (IBD) probabilities for entire chromosome segments are required. Making use of pedigree information, length of the segment and the assumption of no crossing-over, a generalization of a previously published graph theory oriented algorithm accounting for nonzero IBD of common ancestors is given, which can be viewed as method of path coefficients for entire chromosome segments. Furthermore, rules for setting up a gametic version of a segmental IBD matrix are presented. Results from the generalized graph theory oriented method, the gametic segmental IBD matrix and the segmental IBD matrix for individuals are identical.

  18. [Algorithm for calculating the probabilities of the identity of genes by descent in arbitrary pedigrees].

    PubMed

    Ageev, S V

    1983-04-01

    For an arbitrary locus (autosomal or X-linked), comprehensive enumeration of different variants of genes' identity by descent for two individuals is given. The algorithm for computation of probability of every variant is described for any two individuals in arbitrary pedigree. On the basis of the algorithm proposed, the problem of computation of Malecot's "coefficient de parente" and inbreeding coefficient is solved under sex-linked transmission. It has been also shown that the approach described is the most common method for solution of a problem of partitioning of covariances among relatives on genotypic components of the variance.

  19. Adventures in Parallel Processing: Entry, Descent and Landing Simulation for the Genesis and Stardust Missions

    NASA Technical Reports Server (NTRS)

    Lyons, Daniel T.; Desai, Prasun N.

    2005-01-01

    This paper will describe the Entry, Descent and Landing simulation tradeoffs and techniques that were used to provide the Monte Carlo data required to approve entry during a critical period just before entry of the Genesis Sample Return Capsule. The same techniques will be used again when Stardust returns on January 15, 2006. Only one hour was available for the simulation which propagated 2000 dispersed entry states to the ground. Creative simulation tradeoffs combined with parallel processing were needed to provide the landing footprint statistics that were an essential part of the Go/NoGo decision that authorized release of the Sample Return Capsule a few hours before entry.

  20. Studying the Effect of Adaptive Momentum in Improving the Accuracy of Gradient Descent Back Propagation Algorithm on Classification Problems

    NASA Astrophysics Data System (ADS)

    Rehman, Muhammad Zubair; Nawi, Nazri Mohd.

    Despite being widely used in the practical problems around the world, Gradient Descent Back-propagation algorithm comes with problems like slow convergence and convergence to local minima. Previous researchers have suggested certain modifications to improve the convergence in gradient Descent Back-propagation algorithm such as careful selection of input weights and biases, learning rate, momentum, network topology, activation function and value for 'gain' in the activation function. This research proposed an algorithm for improving the working performance of back-propagation algorithm which is 'Gradient Descent with Adaptive Momentum (GDAM)' by keeping the gain value fixed during all network trials. The performance of GDAM is compared with 'Gradient Descent with fixed Momentum (GDM)' and 'Gradient Descent Method with Adaptive Gain (GDM-AG)'. The learning rate is fixed to 0.4 and maximum epochs are set to 3000 while sigmoid activation function is used for the experimentation. The results show that GDAM is a better approach than previous methods with an accuracy ratio of 1.0 for classification problems like Wine Quality, Mushroom and Thyroid disease.

  1. Using survival analysis to determine association between maternal pelvis height and antenatal fetal head descent in Ugandan mothers

    PubMed Central

    Munabi, Ian Guyton; Luboga, Samuel Abilemech; Mirembe, Florence

    2015-01-01

    Introduction Fetal head descent is used to demonstrate the maternal pelvis capacity to accommodate the fetal head. This is especially important in low resource settings that have high rates of childbirth related maternal deaths and morbidity. This study looked at maternal height and an additional measure, maternal pelvis height, from automotive engineering. The objective of the study was to determine the associations between maternal: height and pelvis height with the rate of fetal head descent in expectant Ugandan mothers. Methods This was a cross sectional study on 1265 singleton mothers attending antenatal clinics at five hospitals in various parts of Uganda. In addition to the routine antenatal examination, each mother had their pelvis height recorded following informed consent. Survival analysis was done using STATA 12. Results It was found that 27% of mothers had fetal head descent with an incident rate of 0.028 per week after the 25th week of pregnancy. Significant associations were observed between the rate of fetal head descent with: maternal height (Adj Haz ratio 0.93 P < 0.01) and maternal pelvis height (Adj Haz ratio 1.15 P < 0.01). Conclusion The significant associations observed between maternal: height and pelvis height with rate of fetal head descent, demonstrate a need for further study of maternal pelvis height as an additional decision support tool for screening mothers in low resource settings. PMID:26918071

  2. [People of African descent in the region of the Americas and health equity].

    PubMed

    Torres, Cristina

    2002-01-01

    The Region of the Americas and the Caribbean has a complex demographic profile from an ethnic and racial perspective. One of the largest groups is composed of persons of African descent, who in some countries, such as Brazil and the Dominican Republic, comprise 46 and 84% of the total population, respectively. Recent analyses of the statistics available in some countries of the Region show wide gaps in terms of living conditions and health in these communities, as well as gaps in access to health services. PAHO, through its Public Policy and Health Program, under the Division of Health and Human Development, supports sectorial efforts and those of civil organizations that aim to improve health conditions in this segment of the population, while taking into account their sociodemographic and cultural characteristics. This article briefly summarizes health conditions and access to health services in selected countries, as well as some aspects of the recent changes to the legislation in those countries. Finally, collaborative activities on the part of United Nations agencies and international financial institutions for the benefit of people of African descent and other ethnic minorities are described.

  3. Mars Phoenix Entry, Descent, and Landing Simulation Design and Modelling Analysis

    NASA Technical Reports Server (NTRS)

    Prince, Jill L.; Desai, Prasun N.; Queen, Eric M.; Grover, Myron R.

    2008-01-01

    The 2007 Mars Phoenix Lander was launched in August of 2007 on a ten month cruise to reach the northern plains of Mars in May 2008. Its mission continues NASA s pursuit to find evidence of water on Mars. Phoenix carries upon it a slew of science instruments to study soil and ice samples from the northern region of the planet, an area previously undiscovered by robotic landers. In order for these science instruments to be useful, it was necessary for Phoenix to perform a safe entry, descent, and landing (EDL) onto the surface of Mars. The EDL design was defined through simulation and analysis of the various phases of the descent. An overview of the simulation and various models developed to characterize the EDL performance is provided. Monte Carlo statistical analysis was performed to assess the performance and robustness of the Phoenix EDL system and are presented in this paper. Using these simulation and modelling tools throughout the design and into the operations phase, the Mars Phoenix EDL was a success on May 25, 2008.

  4. Dynamic gradient descent learning algorithms for enhanced empirical modeling of power plants

    SciTech Connect

    Parlos, A.G.; Atiya, Amir; Chong, K.T. )

    1991-11-01

    A newly developed dynamic gradient descent-based learning algorithm is used to train a recurrent multilayer perceptron network for use in empirical modeling of power plants. The two main advantages of the proposed learning algorithm are its ability to consider past error gradient information for future use and the two forward passes associated with its implementation, instead of one forward and one backward pass of the backpropagation algorithm. The latter advantage results in computational time saving because both passes can be performed simultaneously. The dynamic learning algorithm is used to train a hybrid feedforward/feedback neural network, a recurrent multilayer perceptron, which was previously found to exhibit good interpolation and extrapolation capabilities in modeling nonlinear dynamic systems. One of the drawbacks, however, of the previously reported work has been the long training times associated with accurate empirical models. The enhanced learning capabilities provided by the dynamic gradient descent-based learning algorithm are demonstrated by a case study of a steam power plant. The number of iterations required for accurate empirical modeling has been reduced from tens of thousands to hundreds, thus significantly expediting the learning process.

  5. Flight Mechanics of the Entry, Descent and Landing of the ExoMars Mission

    NASA Technical Reports Server (NTRS)

    HayaRamos, Rodrigo; Boneti, Davide

    2007-01-01

    ExoMars is ESA's current mission to planet Mars. A high mobility rover and a fixed station will be deployed on the surface of Mars. This paper regards the flight mechanics of the Entry, Descent and Landing (EDL) phases used for the mission analysis and design of the Baseline and back-up scenarios of the mission. The EDL concept is based on a ballistic entry, followed by a descent under parachutes and inflatable devices (airbags) for landing. The mission analysis and design is driven by the flexibility in terms of landing site, arrival dates and the very stringent requirement in terms of landing accuracy. The challenging requirements currently imposed to the mission need innovative analysis and design techniques to support system design trade-offs to cope with the variability in entry conditions. The concept of the Global Entry Corridor has been conceived, designed, implemented and successfully validated as a key tool to provide a global picture of the mission capabilities in terms of landing site reachability.

  6. Trajectory Guidance for Mars Robotic Precursors: Aerocapture, Entry, Descent, and Landing

    NASA Technical Reports Server (NTRS)

    Sostaric, Ronald R.; Zumwalt, Carlie; Garcia-Llama, Eduardo; Powell, Richard; Shidner, Jeremy

    2011-01-01

    Future crewed missions to Mars require improvements in landed mass capability beyond that which is possible using state-of-the-art Mars Entry, Descent, and Landing (EDL) systems. Current systems are capable of an estimated maximum landed mass of 1-1.5 metric tons (MT), while human Mars studies require 20-40 MT. A set of technologies were investigated by the EDL Systems Analysis (SA) project to assess the performance of candidate EDL architectures. A single architecture was selected for the design of a robotic precursor mission, entitled Exploration Feed Forward (EFF), whose objective is to demonstrate these technologies. In particular, inflatable aerodynamic decelerators (IADs) and supersonic retro-propulsion (SRP) have been shown to have the greatest mass benefit and extensibility to future exploration missions. In order to evaluate these technologies and develop the mission, candidate guidance algorithms have been coded into the simulation for the purposes of studying system performance. These guidance algorithms include aerocapture, entry, and powered descent. The performance of the algorithms for each of these phases in the presence of dispersions has been assessed using a Monte Carlo technique.

  7. Caste-, work-, and descent-based discrimination as a determinant of health in social epidemiology.

    PubMed

    Patil, Rajan R

    2014-01-01

    Social epidemiology explores health in the context of broad social determinants of health, where the boundary lines between health and politics appear increasingly blurred. Social determinants of health such as caste, discrimination, and social exclusion are inherently political in nature, hence it becomes imperative to look at health through a broader perspective of political philosophy, ideology, and caste that imposes enormous obstacles to a person's full attainment of civil, political, economic, social, and cultural rights. Caste is descent based and hereditary in nature. It is a characteristic determined by one's birth into a particular caste, irrespective of the faith practiced by the individual. Caste denotes a system of rigid social stratification into ranked groups defined by descent and occupation. Under various caste systems throughout the world, caste divisions also dominate in housing, marriage, and general social interaction divisions that are reinforced through the practice and threat of social ostracism, economic boycotts, and even physical violence-all of which undermine health equality. PMID:24871772

  8. Enhancements on the Convex Programming Based Powered Descent Guidance Algorithm for Mars Landing

    NASA Technical Reports Server (NTRS)

    Acikmese, Behcet; Blackmore, Lars; Scharf, Daniel P.; Wolf, Aron

    2008-01-01

    In this paper, we present enhancements on the powered descent guidance algorithm developed for Mars pinpoint landing. The guidance algorithm solves the powered descent minimum fuel trajectory optimization problem via a direct numerical method. Our main contribution is to formulate the trajectory optimization problem, which has nonconvex control constraints, as a finite dimensional convex optimization problem, specifically as a finite dimensional second order cone programming (SOCP) problem. SOCP is a subclass of convex programming, and there are efficient SOCP solvers with deterministic convergence properties. Hence, the resulting guidance algorithm can potentially be implemented onboard a spacecraft for real-time applications. Particularly, this paper discusses the algorithmic improvements obtained by: (i) Using an efficient approach to choose the optimal time-of-flight; (ii) Using a computationally inexpensive way to detect the feasibility/ infeasibility of the problem due to the thrust-to-weight constraint; (iii) Incorporating the rotation rate of the planet into the problem formulation; (iv) Developing additional constraints on the position and velocity to guarantee no-subsurface flight between the time samples of the temporal discretization; (v) Developing a fuel-limited targeting algorithm; (vi) Initial result on developing an onboard table lookup method to obtain almost fuel optimal solutions in real-time.

  9. Equivalence by descent: pedigree analysis with inbreeding and gametic phase disequilibrium.

    PubMed

    Denniston, C

    2000-01-01

    In the presence of gametic phase disequilibrium and inbreeding, multiple locus genotype frequencies cannot be written solely in terms of identity by descent (IBD) probabilities. Following Cockerham & Weir (1973) we introduce the concept of 'equivalence by descent' (EBD), an extension of the concept of IBD to include non-allelic genes. Two genes are said to be EBD if they derive ultimately from the same founding gamete of a pedigree. Allelic genes that are EBD are also IBD. For two loci 11 EBD probabilities, the 'J-coefficients,' are required and for three loci 117 J-coefficients are required to write genotype probabilities. It is shown how the 117 J-coefficients for three loci can be reduced to a basic set of 37. Computer programs, written in the algebraic programming language, MAPLE, are described which are capable of calculating the two- and three-locus J-coefficients for any pedigree, subject only to size limitations. The MAPLE packages are available from the author upon request.

  10. Observations and Interpretation of Descent and Mixing in the Northern Hemisphere Brewer Dobson Circulation

    NASA Astrophysics Data System (ADS)

    Gille, J. C.; Karol, S.; Kinnison, D. E.; Yudin, V.; Nardi, B.

    2012-12-01

    In 1929 Brewer proposed that the motions now known as the Brewer-Dobson (BD) circulation were responsible for the observed high values of ozone at high latitudes, far from their low-latitude region of formation. Here data from the High Resolution Dynamics Limb Sounder (HIRDLS) instrument, with 1 km vertical resolution and 100 km along track spacing, are used examine how this circulation creates that distribution and its seasonal variation through the interactions between the overturning motions of the BD circulation and isentropic mixing in the lower and lowermost stratosphere (350-450K). Isopleths of ozone in equivalent latitude-potential temperature coordinates illustrate the high-latitude descent, controlled by diabatic cooling, from September to the lowest altitudes in January and February. This descent creates large gradients along isentropic surfaces, where mixing above ~ 360K is weak at this time. The strength of mixing is taken to be the effective diffusivity Deff as formulated by Nakamura [1996]. By late winter into spring the BD circulation weakens, as does the transport barrier near 35° associated with the sub-tropical jet. These processes allow strong equator-ward mixing, leading to progressively smaller latitudinal ozone gradients on the isentropes, and the rising and flattening of the ozone isopleths. By the end of the summer the isopleths show only small slopes, preparatory for the next cycle. These results for the ozone dynamics are similar, but not identical, to those obtained with NCAR's Whole Atmosphere Community Climate Model (WACCM) Version 4.

  11. POST2 End-To-End Descent and Landing Simulation for the Autonomous Landing and Hazard Avoidance Technology Project

    NASA Technical Reports Server (NTRS)

    Fisher, Jody l.; Striepe, Scott A.

    2007-01-01

    The Program to Optimize Simulated Trajectories II (POST2) is used as a basis for an end-to-end descent and landing trajectory simulation that is essential in determining the design and performance capability of lunar descent and landing system models and lunar environment models for the Autonomous Landing and Hazard Avoidance Technology (ALHAT) project. This POST2-based ALHAT simulation provides descent and landing simulation capability by integrating lunar environment and lander system models (including terrain, sensor, guidance, navigation, and control models), along with the data necessary to design and operate a landing system for robotic, human, and cargo lunar-landing success. This paper presents the current and planned development and model validation of the POST2-based end-to-end trajectory simulation used for the testing, performance and evaluation of ALHAT project system and models.

  12. Preliminary assessment of variable geometry stair ascent and descent with a powered lower limb orthosis for individuals with paraplegia.

    PubMed

    Ekelem, Andrew; Murray, Spencer; Goldfarb, Michael

    2015-08-01

    This paper describes a controller for a lower-limb exoskeleton that enables variable-geometry stair ascent and descent for persons with lower limb paralysis. The controller was evaluated on a subject with T10 complete spinal cord injury (SCI) on two staircases, one with a riser height and tread depth of 18.4 × 27.9 cm (7.25 × 11 in) and the other 17.8 × 29.8 cm (7 × 11.75 in). The controller enabled ascent and descent of both staircases without explicit tuning for each, and with an average step rate of 12.9 step/min during ascent and 14.6 step/min during descent. PMID:26737336

  13. Cardiovascular disease, diabetes and established risk factors among populations of sub-Saharan African descent in Europe: a literature review

    PubMed Central

    Agyemang, Charles; Addo, Juliet; Bhopal, Raj; de Graft Aikins, Ama; Stronks, Karien

    2009-01-01

    Background Most European countries are ethnically and culturally diverse. Globally, cardiovascular disease (CVD) is the leading cause of death. The major risk factors for CVD have been well established. This picture holds true for all regions of the world and in different ethnic groups. However, the prevalence of CVD and related risk factors vary among ethnic groups. Methods This article provides a review of current understanding of the epidemiology of vascular disease, principally coronary heart disease (CHD), stroke and related risk factors among populations of Sub-Sahara African descent (henceforth, African descent) in comparison with the European populations in Europe. Results Compared with European populations, populations of African descent have an increased risk of stroke, whereas CHD is less common. They also have higher rates of hypertension and diabetes than European populations. Obesity is highly prevalent, but smoking rate is lower among African descent women. Older people of African descent have more favourable lipid profile and dietary habits than their European counterparts. Alcohol consumption is less common among populations of African descent. The rate of physical activity differs between European countries. Dutch African-Suriname men and women are less physically active than the White-Dutch whereas British African women are more physically active than women in the general population. Literature on psychosocial stress shows inconsistent results. Conclusion Hypertension and diabetes are highly prevalent among African populations, which may explain their high rate of stroke in Europe. The relatively low rate of CHD may be explained by the low rates of other risk factors including a more favourable lipid profile and the low prevalence of smoking. The risk factors are changing, and on the whole, getting worse especially among African women. Cohort studies and clinical trials are therefore needed among these groups to determine the relative

  14. Prevalence of Hb S (HHB: c.20A > T) in a Honduran population of African descent.

    PubMed

    Erazo, Brian M; Ramírez, Gilberto A; Cerrato, Linda E; Pinto, Luis J; Castro, Edder J; Yanez, Néstor J; Montoya, Brayan; Fontecha, Gustavo A

    2015-01-01

    Sickle cell disease is the most common hemoglobinopathy worldwide, particularly in Africa and among people of African descent. Serious clinical consequences characterize the homozygous condition. To determine the prevalence of Hb S (HBB: c.20A > T) and anemia in a community of people of African descent from Honduras, 202 individuals were analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The high prevalence found indicates that it is necessary to implement a program to prevent the consequences of this disease in vulnerable populations of Honduras.

  15. Relationship of beliefs, epistemology, and alternate conceptions to college student understanding of evolution and common descent

    NASA Astrophysics Data System (ADS)

    Miller, Joyce Catherine

    Quantitative and qualitative methodologies were combined to explore the relationships between an understanding of evolution and 4 epistemology factors: (a) control of learning, (b) speed of learning , (c) stability of knowledge, and (d) belief in evolution/creationism. A 17-item instrument was developed that reliably measured a belief in creationism and subtle differences between this belief and an acceptance of evolution. The subjects were 45 students enrolled in a biology course at a 2-year community college. Evolution was taught in a traditional format, and common descent was taught in an inquiry-based laboratory session consisting of: (a) a comparison of hemoglobin DNA sequences of the human, chimpanzee, and gorilla; and (b) a comparison of 8 primate skull casts, including the modern human, chimpanzee, gorilla, and five prehistoric fossils. Prior to instruction the students completed an epistemology questionnaire and a knowledge test about evolution. Five weeks after instruction, the students completed a posttest. A t-test revealed no differences between the pretest and the posttest. However, the group of students that scored higher on the posttest than on the pretest was found to have a stronger belief in the uncertainty of knowledge. Pearson r was computed to check for relationships between the 4 epistemological factors and the understanding of evolution. There was a significant relationship between a belief in creationism and a lessor understanding of evolution as measured on both the pretest and the posttest (ps < .05). The relationship between gender and test scores was also examined with men demonstrating statistically significantly higher scores on the common descent component than women did. Narrative data included interviews and branching/grouping activities. Four alternate conceptions about common descent were identified. Even after instruction, 16 out of 39 students thought humans evolved from the chimpanzee. Additionally, students grouped the 8

  16. Transitioning from Free-Flight to TRACON Airspace: The Ground Perspective of User-Preferred Descents

    NASA Technical Reports Server (NTRS)

    Prevot, Thomas; Smith, Nancy; Palmer, Everett; Null, Cynthia (Technical Monitor)

    1999-01-01

    Free-flight is considered to play a major role in the future air traffic environment. Studies are underway addressing different concepts for free-flight and self separation in enroute airspace. One common opinion throughout the different concepts is that the airspace surrounding major airports, the Terminal Radar Approach CONtrol (TRACON) will not be a free flight area. This means that aircraft in this area are completely controlled by air traffic controllers, who may be supported by decision support system like the Center TRACON Automation System (CTAS). How the transition from the free-flight area (enroute airspace) to the terminal area will take place is currently unclear, This paper describes a study at NASA Ames Research Center addressing the perspective of air traffic controllers handling user-preferred (FMS-optimized) descent trajectories during this transition phase. Two major issues in enabling user preferred descents from the controllers' point of view are predictability and controllability. In an environment in which the air traffic services are highly responsive to user preferences controllers need to know, where and when aircraft will change their trajectory and they need to have appropriate means and procedures at hand to control the aircraft according to the overall traffic situation. Predictability shall be enhanced by: 1) Indicating airspace corridors for descending aircraft; 2) Modify the controller interface; 3) Using a ground based conflict probe; 4) Making use of downlinked intent information from the aircraft FMS; and 5) Requiring to fly pilots on user preferred trajectories coupled to the FMS in the lateral and vertical axis. Additional controllability shall be achieved by supporting the controllers with CTAS center tools: 1) Traffic Management Advisor (TMA); 2) Conflict Probing and Trial Planning (CP/TP); and 3) Enroute Descent Advisor (E/DA). The paper describes the general concept and the modifications to current systems required to enable

  17. The unusual phase curve of Titan's surface observed by Huygens’ Descent Imager/Spectral Radiometer

    NASA Astrophysics Data System (ADS)

    Schröder, S. E.; Keller, H. U.

    2009-12-01

    The Descent Imager/Spectral Radiometer onboard Huygens observed Titan's surface through the atmospheric methane windows [Tomasko, M.G., Doose, L., Engel, S., Dafoe, L.E., West, R., Lemmon, M., Karkoschka, E., See, C., 2008. A model of Titan's aerosols based on measurements made inside the atmosphere. Planet. Space Sci. 56, 669-707]. Infrared spectra obtained during the last stage of the descent, for which the atmospheric contribution is negligible, show that the reflectance of the surface around the sit increases with decreasing solar phase angle. Combining these with a spectrum reconstructed from reflected lamp light [Schröder, S.E., Keller, H.U., 2008. The reflectance spectrum of Titan's surface at the Huygens landing site determined by the Descent Imager/Spectral Radiometer. Planet. Space Sci. 56, 753-769] reveals a strong increase in reflectance towards zero phase angle: the opposition surge. Both shadow hiding and coherent backscatter are required to fit the phase curve with the Hapke [2002. Bidirectional Reflectance Spectroscopy 5. The Coherent Backscatter Opposition Effect and Anisotropic Scattering. Icarus 157, 523-534] model. We find the particle phase function below 60∘ phase angle to be close to isotropic, which is highly unusual for the surfaces of planetary bodies. A terrain with similar scattering properties has been identified on Triton [Lee, P., Helfenstein, P., Veverka, J., McCarthy, D., 1992. Anomalous-scattering region on Triton. Icarus 99, 82-97], and a connection with the tholins thought to be present on both worlds seems plausible. Indeed, tholin laboratory analogs are found to scatter in similar fashion [Lüthi, 2008. Remote sensing of the surface of Titan: Photometric properties, comparison with analogues, and future microscopic observations. Ph.D. Thesis, Philosophisch-naturwissenschaftlichen Fakultät, Universität Bern]. We conclude that Titan's unusual phase curve is consistent with the presence of tholins on the surface. Our result

  18. Laser driven ion accelerator

    DOEpatents

    Tajima, Toshiki

    2006-04-18

    A system and method of accelerating ions in an accelerator to optimize the energy produced by a light source. Several parameters may be controlled in constructing a target used in the accelerator system to adjust performance of the accelerator system. These parameters include the material, thickness, geometry and surface of the target.

  19. Iterative CT reconstruction using coordinate descent with ordered subsets of data

    NASA Astrophysics Data System (ADS)

    Noo, F.; Hahn, K.; Schöndube, H.; Stierstorfer, K.

    2016-04-01

    Image reconstruction based on iterative minimization of a penalized weighted least-square criteria has become an important topic of research in X-ray computed tomography. This topic is motivated by increasing evidence that such a formalism may enable a significant reduction in dose imparted to the patient while maintaining or improving image quality. One important issue associated with this iterative image reconstruction concept is slow convergence and the associated computational effort. For this reason, there is interest in finding methods that produce approximate versions of the targeted image with a small number of iterations and an acceptable level of discrepancy. We introduce here a novel method to produce such approximations: ordered subsets in combination with iterative coordinate descent. Preliminary results demonstrate that this method can produce, within 10 iterations and using only a constant image as initial condition, satisfactory reconstructions that retain the noise properties of the targeted image.

  20. Three cases of Troyer syndrome in two families of Filipino descent.

    PubMed

    Butler, Shauna; Helbig, Katherine L; Alcaraz, Wendy; Seaver, Laurie H; Hsieh, David T; Rohena, Luis

    2016-07-01

    Troyer syndrome is a complex hereditary spastic paraplegia (HSP) due to a mutation in SPG20 first reported in the Old Amish population. A genetic mutation in SPG20 is responsible for a loss of function of the protein spartin in this disease. Since its initial report, this syndrome has also been reported in Turkish and Omani families. Here we report the case of three patients of Filipino descent with Troyer syndrome. Whole exome sequencing (WES) identified a homozygous mutation c.364_365delAT which predicts p.Met122Valfs*2 in SPG20. This is the same mutation identified in affected patients from the Omani and Turkish families, and is the first report of this syndrome in the Filipino population. Although Troyer syndrome has characteristic phenotypic manifestations it is likely underdiagnosed due to its rarity and we expect that WES will lead to identifying this disease in other individuals. © 2016 Wiley Periodicals, Inc.

  1. Genetic drift. Descent, lineage, and pedigree of the Trojans in Homer's Iliad.

    PubMed

    Bazopoulou-Kyrkanidou, Euterpe

    2007-12-15

    Homer's Iliad, is an epic poem that describes the last 70 days of the Trojan War, which was waged against the city of Troy by the Achaeans. Here, the descent, lineage, and the pedigree of the Trojans are presented. In the Illiad, they are said to have originated from Zeus. Beginning with him, the Trojan pedigree comprised 17 men in 8 generations with Dardanus, founder of Dardania in the second generation; Tros, King of the Trojans in the fourth generation; and the two heroes Hector and Aeneas in the eighth generation. In the seventh generation, Priam, as King of the Trojans, had a huge family, including 50 sons: 19 children with his wife Hecabe, other sons with many different wives, and some daughters as well. Hector, the first born, became leader of the Trojans. Hector's brother, Paris, in abducting Helen of Sparta, the wife of King Menelaus, caused the Trojan War to break out. PMID:17985360

  2. Mars Science Laboratory (MSL) Entry, Descent, and Landing Instrumentation (MEDLI): Complete Flight Data Set

    NASA Technical Reports Server (NTRS)

    Cheatwood, F. McNeil; Bose, Deepak; Karlgaard, Christopher D.; Kuhl, Christopher A.; Santos, Jose A.; Wright, Michael J.

    2014-01-01

    The Mars Science Laboratory (MSL) entry vehicle (EV) successfully entered the Mars atmosphere and landed the Curiosity rover safely on the surface of the planet in Gale crater on August 6, 2012. MSL carried the MSL Entry, Descent, and Landing (EDL) Instrumentation (MEDLI). MEDLI delivered the first in-depth understanding of the Mars entry environments and the response of the entry vehicle to those environments. MEDLI was comprised of three major subsystems: the Mars Entry Atmospheric Data System (MEADS), the MEDLI Integrated Sensor Plugs (MISP), and the Sensor Support Electronics (SSE). Ultimately, the entire MEDLI sensor suite consisting of both MEADS and MISP provided measurements that were used for trajectory reconstruction and engineering validation of aerodynamic, atmospheric, and thermal protection system (TPS) models in addition to Earth-based systems testing procedures. This report contains in-depth hardware descriptions, performance evaluation, and data information of the three MEDLI subsystems.

  3. Cassini/Huygens Probe Entry, Descent, and Landing (EDL) at Titan Independent Technical Assessment

    NASA Technical Reports Server (NTRS)

    Powell, Richard W.; Lockwood, Mary Kae; Cruz, Juan R.; Striepe, Scott A.; Sutton, Kenneth; Fisher, Jody; Takashima, Naruhisa T.; Justus, Jere; Keller, Vernon W.; Bose, Deepak; Prabhu, Dinesh; Chen, Y. K.; Olejniczak, Joe; Cruz, Juan R; Duvall, Aleta

    2009-01-01

    Starting in January 2004, the NESC has received several communications from knowledgeable technical experts at NASA expressing shared concerns (mainly at the Langley Research Center (LaRC) and Ames Research Center (ARC)) about Huygens mission success. It was suggested that NASA become more technically involved directly in the analysis of Huygens' entry, descent and landing (EDL) focusing on the parachute deployment trigger performance and the resultant effects on the operation of the parachute system, and the determination of the radiative heating environment at Titan by ESA and the corresponding thermal protection system (TPS) response. A NESC Team was formed and tasked to provide an independent assessment of these concerns. The results of that assessment are documented in this report.

  4. Mars atmospheric winds indicated by motion of the Viking landers during parachute descent

    NASA Astrophysics Data System (ADS)

    Seiff, A.

    1993-04-01

    The parachute descent trajectories of the two Viking landers are used to determine winds in the Martian atmosphere at altitudes from 1.5 to 3.5 km. Viking 1 descended within a vigorously convective boundary layer, while Viking 2 at 1.5 km was above the boundary layer. Turbulent velocities in the Viking 1 boundary layer were approximately 3 m/sec, and mean upflow velocity was approximately 1 m/sec. The Viking 2 atmosphere was relatively quiescent, with orderly wind directional variation possibly suggesting the presence of waves. Comparison of the measured winds with a recent global circulation model showed little or no correspondence, probably an indication that the winds were locally controlled. The high sensitivity of winds at altitudes up to several kilometers to terrain slopes as small as a few meters per kilometer would suggest that slope winds may be widely found in the lowest few kilometers of the Martian atmosphere.

  5. Inflatable re-Entry and Descent Technology - Results of the IRDT-2 Mission and Future Applications

    NASA Astrophysics Data System (ADS)

    Walther, S.

    2002-01-01

    This paper will present the results of the second IRDT flight, a mission which is planned for May 2002. The first testflight successfully demonstrated its performance in 2000. The Inflatable Re-entry and Descent Technology (IRDT), an innovative lightweight return technology, is designed to provide significant mass and cost savings compared to conventionally fixed heat shield and parachute systems for returning elements from space. This technology is highly attractive for a broad range of applications, e.g. return of small capsules, larger objects like ATV or launcher elements from an Earth orbit and may also be used for planetary missions. IRDT can be adapted to existing vehicles or be used as baseline for new vehicles. Potential future application scenarios, e.g. a Download System to return payload from the ISS, will also be described.

  6. Parametric Mass Modeling for Mars Entry, Descent and Landing System Analysis Study

    NASA Technical Reports Server (NTRS)

    Samareh, Jamshid A.; Komar, D. R.

    2011-01-01

    This paper provides an overview of the parametric mass models used for the Entry, Descent, and Landing Systems Analysis study conducted by NASA in FY2009-2010. The study examined eight unique exploration class architectures that included elements such as a rigid mid-L/D aeroshell, a lifting hypersonic inflatable decelerator, a drag supersonic inflatable decelerator, a lifting supersonic inflatable decelerator implemented with a skirt, and subsonic/supersonic retro-propulsion. Parametric models used in this study relate the component mass to vehicle dimensions and mission key environmental parameters such as maximum deceleration and total heat load. The use of a parametric mass model allows the simultaneous optimization of trajectory and mass sizing parameters.

  7. Estimating the atmospheric correlation length with stochastic parallel gradient descent algorithm.

    PubMed

    Yazdani, R; Hajimahmoodzadeh, M; Fallah, H R

    2014-03-01

    The atmospheric turbulence measurement has received much attention in various fields due to its effects on wave propagation. One of the interesting parameters for characterization of the atmospheric turbulence is the Fried parameter or the atmospheric correlation length. We numerically investigate the feasibility of estimating the Fried parameter using a simple and low-cost system based on the stochastic parallel gradient descent (SPGD) algorithm without the need for wavefront sensing. We simulate the atmospheric turbulence using Zernike polynomials and employ a wavefront sensor-less adaptive optics system based on the SPGD algorithm and report the estimated Fried parameter after compensating for atmospheric-turbulence-induced phase distortions. Several simulations for different atmospheric turbulence strengths are presented to validate the proposed method.

  8. A Multidisciplinary Tool for Systems Analysis of Planetary Entry, Descent, and Landing (SAPE)

    NASA Technical Reports Server (NTRS)

    Samareh, Jamshid A.

    2009-01-01

    SAPE is a Python-based multidisciplinary analysis tool for systems analysis of planetary entry, descent, and landing (EDL) for Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Titan. The purpose of SAPE is to provide a variable-fidelity capability for conceptual and preliminary analysis within the same framework. SAPE includes the following analysis modules: geometry, trajectory, aerodynamics, aerothermal, thermal protection system, and structural sizing. SAPE uses the Python language-a platform-independent open-source software for integration and for the user interface. The development has relied heavily on the object-oriented programming capabilities that are available in Python. Modules are provided to interface with commercial and government off-the-shelf software components (e.g., thermal protection systems and finite-element analysis). SAPE runs on Microsoft Windows and Apple Mac OS X and has been partially tested on Linux.

  9. Construction and validation of the Measurement of Acculturation Strategies for People of African Descent (MASPAD).

    PubMed

    Obasi, Ezemenari M; Leong, Frederick T L

    2010-10-01

    This paper describes the development of the Measurement of Acculturation Strategies for People of African Descent (MASPAD), a bidimensional instrument designed to assess acculturation strategies (i.e., Traditionalist, Integrationist, Assimilationist, and Marginalist). Two studies were conducted to describe the development of the MASPAD and to assess its psychometric properties. Data were collected from 367 African American participants in Atlanta, GA; Columbus, OH; Los Angeles; and New York City, NY. The MASPAD consistently produced scores with adequate reliability and independent raters provided initial evidence for face and content validity. Pearson correlation coefficients supported the purported orthogonality of the MASPAD subscales. The MASPAD was found to be a significant predictor of cultural worldview and values. The bidimensional model of acculturation theorized to exist in the MASPAD was supported with a confirmatory factor analysis on data collected from 831 participants. Future directions for this body of research are discussed. PMID:21058816

  10. On the Use of a Range Trigger for the Mars Science Laboratory Entry Descent and Landing

    NASA Technical Reports Server (NTRS)

    Way, David W.

    2011-01-01

    In 2012, during the Entry, Descent, and Landing (EDL) of the Mars Science Laboratory (MSL) entry vehicle, a 21.5 m Viking-heritage, Disk-Gap-Band, supersonic parachute will be deployed at approximately Mach 2. The baseline algorithm for commanding this parachute deployment is a navigated planet-relative velocity trigger. This paper compares the performance of an alternative range-to-go trigger (sometimes referred to as Smart Chute ), which can significantly reduce the landing footprint size. Numerical Monte Carlo results, predicted by the POST2 MSL POST End-to-End EDL simulation, are corroborated and explained by applying propagation of uncertainty methods to develop an analytic estimate for the standard deviation of Mach number. A negative correlation is shown to exist between the standard deviations of wind velocity and the planet-relative velocity at parachute deploy, which mitigates the Mach number rise in the case of the range trigger.

  11. Development of advanced entry, descent, and landing technologies for future Mars Missions

    NASA Technical Reports Server (NTRS)

    Chu, Cheng-Chih (Chester)

    2006-01-01

    Future Mars missions may need the capability to land much closer to a desired target and/or advanced methods of detecting, avoiding, or tolerating landing hazards. Therefore, technologies that enable 'pinpoint landing' (within tens of meters to 1 km of a target site) will be crucial to meet future mission requirements. As part of NASA Research Announcement, NRA 03-OSS-01, NASA solicited proposals for technology development needs of missions to be launched to Mars during or after the 2009 launch opportunity. Six technology areas were identified as of high priority including advanced entry, descent, and landing (EDL) technologies. In May 2004, 11 proposals with PIs from universities, industries, and NASA centers, were awarded in the area of advanced EDL by NASA for further study and development. This paper presents an overview of these developing technologies.

  12. Quantification of Plume-Soil Interaction and Excavation Due to the Sky Crane Descent Stage

    NASA Technical Reports Server (NTRS)

    Vizcaino, Jeffrey; Mehta, Manish

    2015-01-01

    The quantification of the particulate erosion that occurs as a result of a rocket exhaust plume impinging on soil during extraterrestrial landings is critical for future robotic and human lander mission design. The aerodynamic environment that results from the reflected plumes results in dust lifting, site alteration and saltation, all of which create a potentially erosive and contaminant heavy environment for the lander vehicle and any surrounding structures. The Mars Science Lab (MSL), weighing nearly one metric ton, required higher levels of thrust from its retro propulsive systems and an entirely new descent system to minimize these effects. In this work we seek to quantify plume soil interaction and its resultant soil erosion caused by the MSL's Sky Crane descent stage engines by performing three dimensional digital terrain and elevation mapping of the Curiosity rover's landing site. Analysis of plume soil interaction altitude and time was performed by detailed examination of the Mars Descent Imager (MARDI) still frames and reconstructed inertial measurement unit (IMU) sensor data. Results show initial plume soil interaction from the Sky Crane's eight engines began at ground elevations greater than 60 meters and more than 25 seconds before the rovers' touchdown event. During this time, viscous shear erosion (VSE) was dominant typically resulting in dusting of the surface with flow propagating nearly parallel to the surface. As the vehicle descended and decreased to four powered engines plume-plume and plume soil interaction increased the overall erosion rate at the surface. Visibility was greatly reduced at a height of roughly 20 meters above the surface and fell to zero ground visibility shortly after. The deployment phase of the Sky Crane descent stage hovering at nearly six meters above the surface showed the greatest amount of erosion with several large particles of soil being kicked up, recirculated, and impacting the bottom of the rover chassis. Image

  13. Why the Viking descent probes found only one ionospheric layer at Mars

    NASA Astrophysics Data System (ADS)

    Mayyasi, Majd; Mendillo, Michael

    2015-09-01

    Radio wave transmissions from satellites revealed that Mars had two relatively distinct layers of ionization: a maximum electron density near 130 km, and a secondary layer near 110 km. When the Viking descent probes—with their in situ observing capabilities—passed through the ionosphere, the peak electron density was found, with no indication of a secondary layer below. Here we use an ionospheric model to show that profiles of electron density versus height have shapes that favor the detection of two layers at local times near dawn and dusk (where many thousands of radio occultation observations have been made), but that the two layers essentially merge into one during midday hours (when Viking measurements were made). The profile shapes are attributed to ionizing geometry of solar photons and to chemical processes that affect the profile shapes in a way that favors secondary peak formation near sunrise and sunset.

  14. Focal epithelial hyperplasia (Heck's disease): report of a case in a girl of Brazilian Indian descent.

    PubMed

    Martins, W D; de Lima, A A S; Vieira, S

    2006-01-01

    Summary. Background. This report describes the case of a patient with focal epithelial hyperplasia (FEH), a rare but distinctive entity of viral aetiology with characteristic clinical and histopathological features. Case report. The condition is usually seen in children and adolescents of American Indian and Eskimo background. Surgical removal of papillomatous lesions is the treatment of choice, either for aesthetic reasons, or when the lesions interfere with function or are readily traumatized. Recurrence and the site of new lesions are unpredictable, and continued review of the patient is often necessary. The patient described here has been followed for 24 months without recurrences or changes in the aspect of the remaining lesions. Conclusion. This case highlights a possible genetic predilection for FEH, since the patient is a descent of a Brazilian Xavante Indian.

  15. Simulation Framework for Rapid Entry, Descent, and Landing (EDL) Analysis. Volume 1

    NASA Technical Reports Server (NTRS)

    Murri, Daniel G.

    2010-01-01

    The NASA Engineering and Safety Center (NESC) was requested to establish the Simulation Framework for Rapid Entry, Descent, and Landing (EDL) Analysis assessment, which involved development of an enhanced simulation architecture using the Program to Optimize Simulated Trajectories II (POST2) simulation tool. The assessment was requested to enhance the capability of the Agency to provide rapid evaluation of EDL characteristics in systems analysis studies, preliminary design, mission development and execution, and time-critical assessments. Many of the new simulation framework capabilities were developed to support the Agency EDL Systems Analysis (EDL-SA) team, that is conducting studies of the technologies and architectures that are required to enable higher mass robotic and human mission to Mars. The findings of the assessment are contained in this report.

  16. Entry, Descent, and Landing Operations Analysis for the Mars Phoenix Lander

    NASA Technical Reports Server (NTRS)

    Prince, Jill L.; Desai, Prasun N.; Queen, Eric M.; Grover, Myron R.

    2008-01-01

    The Mars Phoenix lander was launched August 4, 2007 and remained in cruise for ten months before landing in the northern plains of Mars in May 2008. The one-month Entry, Descent, and Landing (EDL) operations phase prior to entry consisted of daily analyses, meetings, and decisions necessary to determine if trajectory correction maneuvers and environmental parameter updates to the spacecraft were required. An overview of the Phoenix EDL trajectory simulation and analysis that was performed during the EDL approach and operations phase is described in detail. The evolution of the Monte Carlo statistics and footprint ellipse during the final approach phase is also provided. The EDL operations effort accurately delivered the Phoenix lander to the desired landing region on May 25, 2008.

  17. Feedback control for fuel-optimal descents using singular perturbation techniques

    NASA Technical Reports Server (NTRS)

    Price, D. B.

    1984-01-01

    In response to rising fuel costs and reduced profit margins for the airline companies, the optimization of the paths flown by transport aircraft has been considered. It was found that application of optimal control theory to the considered problem can result in savings in fuel, time, and direct operating costs. The best solution to the aircraft trajectory problem is an onboard real-time feedback control law. The present paper presents a technique which shows promise of becoming a part of a complete solution. The application of singular perturbation techniques to the problem is discussed, taking into account the benefits and some problems associated with them. A different technique for handling the descent part of a trajectory is also discussed.

  18. The Unparalleled Systems Engineering of MSL's Backup Entry, Descent, and Landing System: Second Chance

    NASA Technical Reports Server (NTRS)

    Roumeliotis, Chris; Grinblat, Jonathan; Reeves, Glenn

    2013-01-01

    Second Chance (SECC) was a bare bones version of Mars Science Laboratory's (MSL) Entry Descent & Landing (EDL) flight software that ran on Curiosity's backup computer, which could have taken over swiftly in the event of a reset of Curiosity's prime computer, in order to land her safely on Mars. Without SECC, a reset of Curiosity's prime computer would have lead to catastrophic mission failure. Even though a reset of the prime computer never occurred, SECC had the important responsibility as EDL's guardian angel, and this responsibility would not have seen such success without unparalleled systems engineering. This paper will focus on the systems engineering behind SECC: Covering a brief overview of SECC's design, the intense schedule to use SECC as a backup system, the verification and validation of the system's "Do No Harm" mandate, the system's overall functional performance, and finally, its use on the fateful day of August 5th, 2012.

  19. Regolith-Derived Heat Shield for Planetary Body Entry and Descent System with In Situ Fabrication

    NASA Technical Reports Server (NTRS)

    Hogue, Michael D.; Mueller, Robert P.; Rasky, Daniel; Hintze, Paul; Sibille, Laurent

    2012-01-01

    In this paper we will discuss a new mass-efficient and innovative way of protecting high-mass spacecraft during planetary Entry, Descent & Landing (EDL). Heat shields fabricated in situ can provide a thermal-protection system (TPS) for spacecraft that routinely enter a planetary atmosphere. By fabricating the heat shield with space resources from regolith materials available on moons and asteroids, it is possible to avoid launching the heat-shield mass from Earth. Two regolith processing and manufacturing methods will be discussed: 1) Compression and sintering of the regolith to yield low density materials; 2) Formulations of a High-temperature silicone RTV (Room Temperature Vulcanizing) compound are used to bind regolith particles together. The overall positive results of torch flame impingement tests and plasma arc jet testing on the resulting samples will also be discussed.

  20. Approach and Entry, Descent, and Landing Operations for the Mars Science Laboratory Mission

    NASA Technical Reports Server (NTRS)

    Chen, Allen; Greco, Martin; Martin-Mur, Tomas; Portock, Brian; Steltzner, Adam

    2013-01-01

    On August 5th, 2012, at 10:31 PM PDT, the Mars Science Laboratory (MSL) rover Curiosity landed safely within Gale Crater. Her successful landing de-pended not only upon the flawless execution of the numerous critical activities during the seven minute entry, descent, and landing (EDL), but also upon the operational preparations and decisions made by the flight team during approach, the final weeks, days, and hours prior to landing. During this period, decisions made by the flight team balanced operational risk to the spacecraft in flight with any resulting risks incurred during EDL as a result of those decisions. This pa-per summarizes the operations plans made in preparation for Approach and EDL and the as flown decisions and actions executed that balanced the operational and EDL risks and prepared the vehicle for a successful landing.

  1. Overview of the NASA Entry, Descent and Landing Systems Analysis Exploration Feed-Forward Study

    NASA Technical Reports Server (NTRS)

    DwyerCianciolo, Alicia M.; Zang, Thomas A.; Sostaric, Ronald R.; McGuire, M. Kathy

    2011-01-01

    Technology required to land large payloads (20 to 50 mt) on Mars remains elusive. In an effort to identify the most viable investment path, NASA and others have been studying various concepts. One such study, the Entry, Descent and Landing Systems Analysis (EDLSA) Study [1] identified three potential options: the rigid aeroshell, the inflatable aeroshell and supersonic retropropulsion (SRP). In an effort to drive out additional levels of design detail, a smaller demonstrator, or exploration feed-forward (EFF), robotic mission was devised that utilized two of the three (inflatable aeroshell and SRP) high potential technologies in a configuration to demonstrate landing a two to four metric ton payload on Mars. This paper presents and overview of the maximum landed mass, inflatable aeroshell controllability and sensor suite capability assessments of the selected technologies and recommends specific technology areas for additional work.

  2. Electronic Nature of Step-edge Barriers Against Adatom Descent on Transition-metal Surfaces

    SciTech Connect

    Mo, Yina; Zhu, Wenguang; Kaxiras, Efthimios; Zhang, Zhenyu

    2008-01-01

    The activation barriers against adatom migration on terraces and across steps play an essential role in determining the growth morphology of surfaces, interfaces, and thin lms. By studying a series of adatoms on representative transition metal surfaces through extensive rst-principles calculations, we establish a clear correlation between the preferred mechanism and activation energy for adatom descent at a step and the relative degree of electronic shell lling between the adatom and the substrate. We also nd an approximate linear relation between the adatom hopping barriers at step edges and the adatom-surface bonding strength. These results may serve as simple guiding rules for predicting the precise atomic nature of surface morphologies in heteroepitaxial growth such as nanowires.

  3. Simulation Framework for Rapid Entry, Descent, and Landing (EDL) Analysis, Phase 2 Results

    NASA Technical Reports Server (NTRS)

    Murri, Daniel G.

    2011-01-01

    The NASA Engineering and Safety Center (NESC) was requested to establish the Simulation Framework for Rapid Entry, Descent, and Landing (EDL) Analysis assessment, which involved development of an enhanced simulation architecture using the Program to Optimize Simulated Trajectories II simulation tool. The assessment was requested to enhance the capability of the Agency to provide rapid evaluation of EDL characteristics in systems analysis studies, preliminary design, mission development and execution, and time-critical assessments. Many of the new simulation framework capabilities were developed to support the Agency EDL-Systems Analysis (SA) team that is conducting studies of the technologies and architectures that are required to enable human and higher mass robotic missions to Mars. The findings, observations, and recommendations from the NESC are provided in this report.

  4. Simulation Framework for Rapid Entry, Descent, and Landing (EDL) Analysis. Volume 2; Appendices

    NASA Technical Reports Server (NTRS)

    Murri, Daniel G.

    2010-01-01

    The NASA Engineering and Safety Center (NESC) was requested to establish the Simulation Framework for Rapid Entry, Descent, and Landing (EDL) Analysis assessment, which involved development of an enhanced simulation architecture using the Program to Optimize Simulated Trajectories II (POST2) simulation tool. The assessment was requested to enhance the capability of the Agency to provide rapid evaluation of EDL characteristics in systems analysis studies, preliminary design, mission development and execution, and time-critical assessments. Many of the new simulation framework capabilities were developed to support the Agency EDL Systems Analysis (EDL-SA) team, that is conducting studies of the technologies and architectures that are required to enable higher mass robotic and human mission to Mars. The appendices to the original report are contained in this document.

  5. Regolith-Derived Heat Shield for Planetary Body Entry and Descent System with In Situ Fabrication

    NASA Technical Reports Server (NTRS)

    Hogue, Michael D.; Mueller, Robert P.; Rasky, Daniel J.; Hintze, Paul E.; Sibille, Laurent

    2011-01-01

    In this paper we will discuss a new mass-efficient and innovative way of protecting high-mass spacecraft during planetary Entry, Descent & Landing (EDL). Heat shields fabricated in situ can provide a thermal-protection system (TPS) for spacecraft that routinely enter a planetary atmosphere. By fabricating the heat shield with space resources from regolith materials available on moons and asteroids, it is possible to avoid launching the heat-shield mass from Earth. Three regolith processing and manufacturing methods will be discussed: 1) oxygen & metal extraction ISRU processes produce glassy melts enriched in alumina and titania, processed to obtain variable density, high melting point and heat-resistance; 2) compression and sintering of the regolith yield low density materials; 3) in-situ derived high-temperature polymers are created to bind regolith particles together, with a lower energy budget.

  6. Supersonic Retropropulsion Technology Development in NASA's Entry, Descent, and Landing Project

    NASA Technical Reports Server (NTRS)

    Edquist, Karl T.; Berry, Scott A.; Rhode, Matthew N.; Kelb, Bil; Korzun, Ashley; Dyakonov, Artem A.; Zarchi, Kerry A.; Schauerhamer, Daniel G.; Post, Ethan A.

    2012-01-01

    NASA's Entry, Descent, and Landing (EDL) space technology roadmap calls for new technologies to achieve human exploration of Mars in the coming decades [1]. One of those technologies, termed Supersonic Retropropulsion (SRP), involves initiation of propulsive deceleration at supersonic Mach numbers. The potential benefits afforded by SRP to improve payload mass and landing precision make the technology attractive for future EDL missions. NASA's EDL project spent two years advancing the technological maturity of SRP for Mars exploration [2-15]. This paper summarizes the technical accomplishments from the project and highlights challenges and recommendations for future SRP technology development programs. These challenges include: developing sufficiently large SRP engines for use on human-scale entry systems; testing and computationally modelling complex and unsteady SRP fluid dynamics; understanding the effects of SRP on entry vehicle stability and controllability; and demonstrating sub-scale SRP entry systems in Earth's atmosphere.

  7. Entry, Descent, and Landing Operations Analysis for the Genesis Re-Entry Capsule

    NASA Technical Reports Server (NTRS)

    Desai, Prasun N.; Lyons, Dan T.

    2005-01-01

    On September 8, 2004, the Genesis spacecraft returned to Earth after spending 29 months about the sun-Earth libration point collecting solar wind particles. Four hours prior to Earth arrival, the entry capsule containing the samples was released for entry and subsequent landing at the Utah Test and Training Range. This paper provides an overview of the entry, descent, and landing trajectory analysis that was performed during the Mission Operations Phase leading up to final approach to Earth. The operations effort accurately delivered the entry capsule to the desired landing site. The final landing location was 8.3 km from the target, and was well within the allowable landing area. Preliminary reconstruction analyses indicate that the actual entry trajectory was very close to the pre-entry prediction.

  8. The Mast Cameras and Mars Descent Imager (MARDI) for the 2009 Mars Science Laboratory

    NASA Technical Reports Server (NTRS)

    Malin, M. C.; Bell, J. F.; Cameron, J.; Dietrich, W. E.; Edgett, K. S.; Hallet, B.; Herkenhoff, K. E.; Lemmon, M. T.; Parker, T. J.; Sullivan, R. J.

    2005-01-01

    Based on operational experience gained during the Mars Exploration Rover (MER) mission, we proposed and were selected to conduct two related imaging experiments: (1) an investigation of the geology and short-term atmospheric vertical wind profile local to the Mars Science Laboratory (MSL) landing site using descent imaging, and (2) a broadly-based scientific investigation of the MSL locale employing visible and very near infra-red imaging techniques from a pair of mast-mounted, high resolution cameras. Both instruments share a common electronics design, a design also employed for the MSL Mars Hand Lens Imager (MAHLI) [1]. The primary differences between the cameras are in the nature and number of mechanisms and specific optics tailored to each camera s requirements.

  9. A Study of Six South Texas Mexican Descent Former Students: Elementary School Experiences and Their Influence on the Students' Decision on High School Completion

    ERIC Educational Resources Information Center

    Ramirez, Lazaro

    2011-01-01

    The purpose of this study was to explore the interactions between elementary school students and school personnel, family members, and community members to identify factors that contributed to South Texas Mexican descent students dropping out of school. A second purpose is to gain a deeper understanding of Mexican descent former high school…

  10. The Lavoisier mission : A system of descent probe and balloon flotilla for geochemical investigation of the deep atmosphere and surface of Venus

    NASA Astrophysics Data System (ADS)

    Chassefière, E.; Berthelier, J. J.; Bertaux, J.-L.; Quèmerais, E.; Pommereau, J.-P.; Rannou, P.; Raulin, F.; Coll, P.; Coscia, D.; Jambon, A.; Sarda, P.; Sabroux, J. C.; Vitter, G.; Le Pichon, A.; Landeau, B.; Lognonné, P.; Cohen, Y.; Vergniole, S.; Hulot, G.; Mandéa, M.; Pineau, J.-F.; Bézard, B.; Keller, H. U.; Titov, D.; Breuer, D.; Szego, K.; Ferencz, Cs.; Roos-Serote, M.; Korablev, O.; Linkin, V.; Rodrigo, R.; Taylor, F. W.; Harri, A.-M.

    Lavoisier mission is a joint effort of eight European countries and a technological challenge aimed at investigating the lower atmosphere and the surface of Venus. The mission consists of a descent probe and three balloons to be deployed below the cloud deck. Its main scientific objectives may be summarized as following : (i) composition of the deep atmosphere : noble gas (elemental/isotopic), molecular species (elemental/ isotopic), oxygen fugacity; vertical/horizontal/temporal variability; (ii) infrared spectroscopy and radiometry (molecular composition, radiative transfer); (iii) dynamics of the atmosphere : p, T, acceleration measurements, balloon localization through VLBI, meteorological events signed by acoustic waves, atmospheric mixing as imprinted on radioactive tracers; (iv) surface morphology and mineralogy through near infrared imaging on dayside, surface temperature through NIR imaging on nightside. Additional tentative objectives are search for (a) atmospheric electrical activity (optically, radioelectrically, acoustically), (b) crustal outgassing and/or volcanic activity : acoustic activity, horizontal/vertical distribution of radioactive tracers, (c) seismic activity : acoustic waves transmitted from crust to atmosphere, and (d) remanent and/or intrinsic magnetic field. Lavoisier was proposed to ESA in response to the F2/F3 mission Announcement of Opportunity at the beginning of 2000, but it was not selected for the assessment study. A wide international partnership was created for this occasion, including Finland (FMI), France (IPSL, MAGIE, Université Orsay, IPSN, INPG, CEA, IPGP, Obs. Paris-Meudon), Germany (MPAe, Univ. Muenster), Hungary (KFKI, Univ. Eotvos), Portugal (OAL), Russia (IKI), Spain (IAA), United Kingdom (Univ. Oxford).

  11. Entry, Descent, and Landing with Propulsive Deceleration: Supersonic Retropropulsion Wind Tunnel Testing and Shock Phenomena

    NASA Technical Reports Server (NTRS)

    Palaszewski, Bryan

    2013-01-01

    The future exploration of the Solar System will require innovations in transportation and the use of entry, descent, and landing (EDL) systems at many planetary landing sites. The cost of space missions has always been prohibitive, and using the natural planetary and planet's moon atmospheres for entry, and descent can reduce the cost, mass, and complexity of these missions. This paper will describe some of the EDL ideas for planetary entry and survey the overall technologies for EDL that may be attractive for future Solar System missions. Future EDL systems may include an inflatable decelerator for the initial atmospheric entry and an additional supersonic retro-propulsion (SRP) rocket system for the final soft landing. A three engine retro-propulsion configuration with a 2.5 inch diameter sphere-cone aeroshell model was tested in the NASA Glenn 1x1 Supersonic Wind Tunnel (SWT). The testing was conducted to identify potential blockage issues in the tunnel, and visualize the rocket flow and shock interactions during supersonic and hypersonic entry conditions. Earlier experimental testing of a 70 degree Viking-like (sphere-cone) aeroshell was conducted as a baseline for testing of a supersonic retro-propulsion system. This baseline testing defined the flow field around the aeroshell and from this comparative baseline data, retro-propulsion options will be assessed. Images and analyses from the SWT testing with 300- and 500-psia rocket engine chamber pressures are presented here. In addition, special topics of electromagnetic interference with retro-propulsion induced shock waves and retro-propulsion for Earth launched booster recovery are also addressed.

  12. Entry, Descent, and Landing With Propulsive Deceleration: Supersonic Retropropulsion Wind Tunnel Testing

    NASA Technical Reports Server (NTRS)

    Palaszewski, Bryan

    2012-01-01

    The future exploration of the Solar System will require innovations in transportation and the use of entry, descent, and landing (EDL) systems at many planetary landing sites. The cost of space missions has always been prohibitive, and using the natural planetary and planet s moons atmosphere for entry, descent, and landing can reduce the cost, mass, and complexity of these missions. This paper will describe some of the EDL ideas for planetary entry and survey the overall technologies for EDL that may be attractive for future Solar System missions. Future EDL systems may include an inflatable decelerator for the initial atmospheric entry and an additional supersonic retro-propulsion (SRP) rocket system for the final soft landing. As part of those efforts, NASA began to conduct experiments to gather the experimental data to make informed decisions on the "best" EDL options. A model of a three engine retro-propulsion configuration with a 2.5 in. diameter sphere-cone aeroshell model was tested in the NASA Glenn 1- by 1-Foot Supersonic Wind Tunnel (SWT). The testing was conducted to identify potential blockage issues in the tunnel, and visualize the rocket flow and shock interactions during supersonic and hypersonic entry conditions. Earlier experimental testing of a 70 Viking-like (sphere-cone) aeroshell was conducted as a baseline for testing of a supersonic retro-propulsion system. This baseline testing defined the flow field around the aeroshell and from this comparative baseline data, retro-propulsion options will be assessed. Images and analyses from the SWT testing with 300- and 500-psia rocket engine chamber pressures are presented here. The rocket engine flow was simulated with a non-combusting flow of air.

  13. Strategies for Choosing Descent Flight-Path Angles for Small Jets

    NASA Technical Reports Server (NTRS)

    Wu, Minghong Gilbert; Green, Steven M.

    2012-01-01

    Three candidate strategies for choosing the descent flight path angle (FPA) for small jets are proposed, analyzed, and compared for fuel efficiency under arrival metering conditions. The strategies vary in operational complexity from a universally fixed FPA, or FPA function that varies with descent speed for improved fuel efficiency, to the minimum-fuel FPA computed for each flight based on winds, route, and speed profile. Methodologies for selecting the parameter for the first two strategies are described. The differences in fuel burn are analyzed over a year s worth of arrival traffic and atmospheric conditions recorded for the Dallas/Fort Worth (DFW) Airport during 2011. The results show that the universally fixed FPA strategy (same FPA for all flights, all year) burns on average 26 lbs more fuel per flight as compared to the minimum-fuel solution. This FPA is adapted to the arrival gate (direction of entry to the terminal) and various timespans (season, month and day) to improve fuel efficiency. Compared to a typical FPA of approximately 3 degrees the adapted FPAs vary significantly, up to 1.3 from one arrival gate to another or up to 1.4 from one day to another. Adapting the universally fixed FPA strategy to the arrival gate or to each day reduces the extra fuel burn relative to the minimum-fuel solution by 27% and 34%, respectively. The adaptations to gate and time combined shows up to 57% reduction of the extra fuel burn. The second strategy, an FPA function, contributes a 17% reduction in the 26 lbs of extra fuel burn over the universally fixed FPA strategy. Compared to the corresponding adaptations of the universally fixed FPA, adaptations of the FPA function reduce the extra fuel burn anywhere from 15-23% depending on the extent of adaptation. The combined effect of the FPA function strategy with both directional and temporal adaptation recovers 67% of the extra fuel relative to the minimum-fuel solution.

  14. Mathematical modeling approaches in the study of glaucoma disparities among people of African and European descents

    PubMed Central

    Guidoboni, Giovanna; Harris, Alon; Arciero, Julia C.; Siesky, Brent A.; Amireskandari, Annahita; Gerber, Austin L.; Huck, Andrew H.; Kim, Nathaniel J.; Cassani, Simone; Carichino, Lucia

    2014-01-01

    Open angle glaucoma (OAG) is a severe ocular disease characterized by progressive and irreversible vision loss. While elevated intraocular pressure (IOP) is a well-established risk factor for OAG, the progression of OAG in many cases, despite IOP treatment, suggests that other risk factors must play significant roles in the development of the disease. For example, various structural properties of the eye, ocular blood flow properties, and systemic conditions have been identified as risk factors for OAG. Ethnicity has also been indicated as a relevant factor that affects the incidence and prevalence of OAG; in fact, OAG is the leading cause of blindness among people of African descent. Numerous clinical studies have been designed to examine the possible correlation and causation between OAG and these factors; however, these studies are met with the challenge of isolating the individual role of multiple interconnected factors. Over the last decade, various mathematical modeling approaches have been implemented in combination with clinical studies in order to provide a mechanical and hemodynamical description of the eye in relation to the entire human body and to assess the contribution of single risk factors to the development of OAG. This review provides a summary of the clinical evidence of ocular structural differences, ocular vascular differences and systemic vascular differences among people of African and European descent, describes the mathematical approaches that have been proposed to study ocular mechanics and hemodynamics while discussing how they could be used to investigate the relevance to OAG of racial disparities, and outlines possible new directions of research. PMID:24501718

  15. The Effects of the Diurnal Atmospheric Variability on Entry, Descent and Landing on Mars

    NASA Astrophysics Data System (ADS)

    Marceta, D.

    2014-12-01

    Landing on Mars is extremely challenging task due to the fact that the Martian atmosphere is the most hostile environment in the Solar system to perform the entry, descent and landing (EDL) process, because it is thick enough to create substantial heating of the entry vehicle but not thick enough to reduce its velocity to the one necessary for safe landing. Beside this, the atmosphere is very dynamic mainly due to high eccentricity of the Martian orbit, obliquity of the orbital to the equatorial plane and close alignment of the winter solstice and the orbital perihelion. Although seasonal variations of atmospheric parameters are significantly larger than the diurnal, it is very important to analyze diurnal cycles as they can significantly change vertical and horizontal atmospheric profiles in very short time intervals. This can present a serious threat to missions which have very precise timings and specific requirements such as the requirement for the daytime landing to enable ground images acquisition during the descent and landing phase. A 3-degrees-of-freedom trajectory integration routine was combined with the Mars Global Reference Atmospheric Model (Mars-GRAM) to identify the dependence of the EDL profiles on the diurnal cycles of atmospheric parameters throughout the Martian year. The obtained results show that the influence of the diurnal cycles is the largest at the equator and decreases relatively symmetrically towards the poles with a slightly stronger influence in the northern hemisphere. Also, there is a significant influence of the orbital position of Mars on the effect of diurnal atmospheric variations which causes that, around the orbital perihelion and winter solstice, there is some kind of inversion of the dependance of optimal entry timing on latitude of the landing site comparing to the rest of the Martian year.

  16. Differences in Ocular Blood Flow in Glaucoma Between Patients of African and European Descent

    PubMed Central

    Siesky, Brent; Harris, Alon; Racette, Lyne; Abassi, Rania; Chandrasekhar, Kaarthik; Tobe, Leslie A.; Behzadi, Jennifer; Eckert, George; Amireskandari, Annahita; Muchnik, Michael

    2014-01-01

    Purpose To investigate differences in ocular blood flow in individuals of African descent (AD) and European descent (ED) with open angle glaucoma (OAG). Patients and Methods A retrospective data analysis was performed on OAG patients of AD and ED who were previously examined for ocular blood flow within the Department of Ophthalmology at Indiana University School of Medicine. Data analysis included blood pressure, heart rate, visual fields, intraocular pressure, ocular perfusion pressure, and color Doppler imaging of retrobulbar vessels. Color Doppler imaging measurements were performed on ophthalmic, central retinal, and nasal and temporal short posterior ciliary arteries, with peak systolic (PSV) and end diastolic velocities (EDV) as well as the Pourcelot vascular resistive index calculated for each vessel. Two-sample t tests of unequal variance were performed with P values <0.05 considered statistically significant. Results OAG patients of AD had statistically significant lower retrobulbar blood flow values than patients of ED including lower ophthalmic artery PSV (P=0.0001), ophthalmic artery EDV (P=0.0008), central retinal artery PSV (P=0.01), temporal short posterior ciliary artery PSV (P=0.0037), and nasal short posterior ciliary artery PSV (P<0.0001). No significant differences were found in terms of intraocular pressure or visual field parameters. Conclusions Significantly lower blood flow values were identified in all retrobulbar blood vessels in AD compared with ED OAG patients. These findings suggest that the contribution of ocular blood flow to the disease process may be different in AD compared with ED OAG patients. PMID:23807346

  17. Icing Frequencies Experienced During Climb and Descent by Fighter-Interceptor Aircraft

    NASA Technical Reports Server (NTRS)

    Perkins, Porter J.

    1958-01-01

    Data and analyses are presented on the relative frequencies of occurrence and severity of icing cloud layers encountered by jet aircraft in the climb and descent phases of flights to high altitudes. Fighter-interceptor aircraft operated by the Air Defense Command (USAF) at bases in the Duluth and Seattle areas collected the data with icing meters installed for a l-year period. The project was part of an extensive program conducted by the NACA to collect Icing cloud data for evaluating the icing problem relevant to routine operations. The average frequency of occurrence of icing was found to be about 5 percent of the number of climbs and descents during 1 year of operations The icing encounters were predominantly in the low and middle cloud layers, decreasing above 15,000 feet to practically none above 25,000 feet. The greatest thickness of ice that would accumulate on any aircraft component (as indicated by the accretion on a small object) was measured with the icing meters. The ice thicknesses on a small sensing probe averaged less than 1/32 inch and did not exceed 1/2 inch. Such accumulations are relatively small when compared with those that can form during horizontal flight in icing clouds. The light accretions resulted from relatively steep angles of flight through generally thin cloud layers. Because of the limited statistical reliability of the results, an analysis was made using previous statistics on icing clouds below an altitude of 20,000 feet to determine the general icing severity probabilities. The calculations were made using adiabatic lifting as a basis to establish the liquid-water content. Probabilities of over-all ice accretions on a small object as a function of airspeed and rate of climb were computed from the derived water contents. These results were then combined with the probability of occurrence of icing in order to give the icing severity that can be expected for routine aircraft operations.

  18. Atmospheric Risk Assessment for the Mars Science Laboratory Entry, Descent, and Landing System

    NASA Technical Reports Server (NTRS)

    Chen, Allen; Vasavada, Ashwin; Cianciolo, Alicia; Barnes, Jeff; Tyler, Dan; Hinson, David; Lewis, Stephen

    2010-01-01

    In 2012, the Mars Science Laboratory (MSL) mission will pioneer the next generation of robotic Entry, Descent, and Landing (EDL) systems, by delivering the largest and most capable rover to date to the surface of Mars. As with previous Mars landers, atmospheric conditions during entry, descent, and landing directly impact the performance of MSL's EDL system. While the vehicle's novel guided entry system allows it to "fly out" a range of atmospheric uncertainties, its trajectory through the atmosphere creates a variety of atmospheric sensitivities not present on previous Mars entry systems and landers. Given the mission's stringent landing capability requirements, understanding the atmosphere state and spacecraft sensitivities takes on heightened importance. MSL's guided entry trajectory differs significantly from recent Mars landers and includes events that generate different atmospheric sensitivities than past missions. The existence of these sensitivities and general advancement in the state of Mars atmospheric knowledge has led the MSL team to employ new atmosphere modeling techniques in addition to past practices. A joint EDL engineering and Mars atmosphere science and modeling team has been created to identify the key system sensitivities, gather available atmospheric data sets, develop relevant atmosphere models, and formulate methods to integrate atmosphere information into EDL performance assessments. The team consists of EDL engineers, project science staff, and Mars atmospheric scientists from a variety of institutions. This paper provides an overview of the system performance sensitivities that have driven the atmosphere modeling approach, discusses the atmosphere data sets and models employed by the team as a result of the identified sensitivities, and introduces the tools used to translate atmospheric knowledge into quantitative EDL performance assessments.

  19. Entry, Descent, and Landing with Propulsive Deceleration: Supersonic Retropropulsion Wind Tunnel Testing and Shock Phenomena

    NASA Technical Reports Server (NTRS)

    Palaszewski, Bryan

    2014-01-01

    The future exploration of the Solar System will require innovations in transportation and the use of entry, descent, and landing (EDL) systems at many planetary landing sites. The cost of space missions has always been prohibitive, and using the natural planetary and planet's moon atmospheres for entry, and descent can reduce the cost, mass, and complexity of these missions. This paper will describe some of the EDL ideas for planetary entry and survey the overall technologies for EDL that may be attractive for future Solar System missions. Future EDL systems may include an inflatable decelerator for the initial atmospheric entry and an additional supersonic retropropulsion (SRP) rocket system for the final soft landing. A three engine retropropulsion configuration with a 2.5 in. diameter sphere-cone aeroshell model was tested in the NASA Glenn Research Center's 1- by 1-ft (1×1) Supersonic Wind Tunnel (SWT). The testing was conducted to identify potential blockage issues in the tunnel, and visualize the rocket flow and shock interactions during supersonic and hypersonic entry conditions. Earlier experimental testing of a 70deg Viking-like (sphere-cone) aeroshell was conducted as a baseline for testing of a SRP system. This baseline testing defined the flow field around the aeroshell and from this comparative baseline data, retropropulsion options will be assessed. Images and analyses from the SWT testing with 300- and 500-psia rocket engine chamber pressures are presented here. In addition, special topics of electromagnetic interference with retropropulsion induced shock waves and retropropulsion for Earth launched booster recovery are also addressed.

  20. Modeling of identity-by-descent processes along a chromosome between haplotypes and their genotyped ancestors.

    PubMed

    Druet, Tom; Farnir, Frederic Paul

    2011-06-01

    Identity-by-descent probabilities are important for many applications in genetics. Here we propose a method for modeling the transmission of the haplotypes from the closest genotyped relatives along an entire chromosome. The method relies on a hidden Markov model where hidden states correspond to the set of all possible origins of a haplotype within a given pedigree. Initial state probabilities are estimated from average genetic contribution of each origin to the modeled haplotype while transition probabilities are computed from recombination probabilities and pedigree relationships between the modeled haplotype and the various possible origins. The method was tested on three simulated scenarios based on real data sets from dairy cattle, Arabidopsis thaliana, and maize. The mean identity-by-descent probabilities estimated for the truly inherited parental chromosome ranged from 0.94 to 0.98 according to the design and the marker density. The lowest values were observed in regions close to crossing over or where the method was not able to discriminate between several origins due to their similarity. It is shown that the estimated probabilities were correctly calibrated. For marker imputation (or QTL allele prediction for fine mapping or genomic selection), the method was efficient, with 3.75% allelic imputation error rates on a dairy cattle data set with a low marker density map (1 SNP/Mb). The method should prove useful for situations we are facing now in experimental designs and in plant and animal breeding, where founders are genotyped with relatively high markers densities and last generation(s) genotyped with a lower-density panel.

  1. Planning fuel-conservative descents with or without time constraints using a small programmable calculator: Algorithm development and flight test results

    NASA Technical Reports Server (NTRS)

    Knox, C. E.

    1983-01-01

    A simplified flight-management descent algorithm, programmed on a small programmable calculator, was developed and flight tested. It was designed to aid the pilot in planning and executing a fuel-conservative descent to arrive at a metering fix at a time designated by the air traffic control system. The algorithm may also be used for planning fuel-conservative descents when time is not a consideration. The descent path was calculated for a constant Mach/airspeed schedule from linear approximations of airplane performance with considerations given for gross weight, wind, and nonstandard temperature effects. The flight-management descent algorithm is described. The results of flight tests flown with a T-39A (Sabreliner) airplane are presented.

  2. Evaluating the physical demands when using sled-type stair descent devices to evacuate mobility-limited occupants from high-rise buildings.

    PubMed

    Lavender, Steven A; Mehta, Jay P; Hedman, Glenn E; Park, Sanghyun; Reichelt, Paul A; Conrad, Karen M

    2015-09-01

    The physical demands on evacuators were investigated when using different types of sled-type stair descent devices designed for the emergency evacuation of high rise buildings. Twelve firefighters used six sled-type stair descent devices during simulated evacuations. The devices were evaluated under two staircase width conditions (1.12, and 1.32 m). Dependent measures included electromyographic (EMG) data, heart rates, Borg Scale ratings, and descent velocities. All stair descent speeds were below those reported during pedestrian egress trials. With the exception of the inflatable device, the devices operated by two evacuators had higher descent speeds than those operated by a single evacuator. High friction materials under the sleds facilitated control and reduced the muscle demands on stairs but increased physical demands on the landings. Usability assessments found devices with shorter overall lengths had fewer wall contacts on the landing, and handles integrated in the straps were preferred by the evacuators.

  3. Factors that Enable Women of South Asian and African Descent to Succeed in Leadership Positions in Higher Education

    ERIC Educational Resources Information Center

    Kamassah, Sharon

    2010-01-01

    This research study focused on the factors that enable women of South Asian and African descent to succeed as leaders in the college system. The findings were derived from online questionnaires and in-depth interviews of 16 racialized women from two Greater Toronto Area (GTA) colleges. Many factors and recommendations were shared. Some of the…

  4. Multiple Marginality and Urban Education: Community and School Socialization among Low-Income Mexican-Descent Youth

    ERIC Educational Resources Information Center

    Conchas, Gilberto Q.; Vigil, James Diego

    2010-01-01

    This article conceptualizes the crucial social and developmental features impacting Mexican-descent youth and adolescents in low-income communities in southern California. All youth in these neighborhoods must confront and come to grips with the many environmental, socioeconomic, racial, and cultural forces they confront. However, it is the…

  5. Family Relations and the Adjustment of Young Children of Mexican Descent: Do Family Cultural Values Moderate These Associations?

    ERIC Educational Resources Information Center

    Gamble, Wendy C.; Modry-Mandell, Kerri

    2008-01-01

    This study examined the role of family cultural values as moderators of the association between family relations and the adjustment of young children. Fifty-five families of Mexican descent with young children enrolled in Head Start programs in the Southwest participated. Mothers provided information about closeness of the mother-child…

  6. 'The full has never been told': building a theory of sexual health for heterosexual Black men of Caribbean descent.

    PubMed

    Crowell, Candice N; Delgado-Romero, Edward A; Mosley, Della V; Huynh, Sophia

    2016-08-01

    Research on Black sexual health often fails to represent the heterogeneity of Black ethnic groups. For people of Caribbean descent in the USA, ethnicity is a salient cultural factor that influences definitions and experiences of sexual health. Most research on people of Caribbean descent focuses on the relatively high rate of STIs, but sexual health is defined more broadly than STI prevalence. Psychological and emotional indicators and the voice of participants are important to consider when exploring the sexual health of a minority culture. The purpose of this study was to qualitatively explore how heterosexual Black men of Caribbean descent define and understand sexual health for themselves. Eleven men who self-identified as Black, Caribbean and heterosexual participated in three focus groups and were asked to define sexual health, critique behaviours expertly identified as healthy and address what encourages and discourages sexual health in their lives. Findings point to six dimensions of sexual health for heterosexual Black men of Caribbean descent. These include: heterosexually privileged, protective, contextual, interpersonal, cultural and pleasurable dimensions. There were some notable departures from current expert definitions of sexual health. Recommendations for further theory development are provided.

  7. Anticipatory kinematics and muscle activity preceding transitions from level-ground walking to stair ascent and descent.

    PubMed

    Peng, Joshua; Fey, Nicholas P; Kuiken, Todd A; Hargrove, Levi J

    2016-02-29

    The majority of fall-related accidents are during stair ambulation-occurring commonly at the top and bottom stairs of each flight, locations in which individuals are transitioning to stairs. Little is known about how individuals adjust their biomechanics in anticipation of walking-stair transitions. We identified the anticipatory stride mechanics of nine able-bodied individuals as they approached transitions from level ground walking to stair ascent and descent. Unlike prior investigations of stair ambulation, we analyzed two consecutive "anticipation" strides preceding the transitions strides to stairs, and tested a comprehensive set of kinematic and electromyographic (EMG) data from both the leading and trailing legs. Subjects completed ten trials of baseline overground walking and ten trials of walking to stair ascent and descent. Deviations relative to baseline were assessed. Significant changes in mechanics and EMG occurred in the earliest anticipation strides analyzed for both ascent and descent transitions. For stair descent, these changes were consistent with observed reductions in walking speed, which occurred in all anticipation strides tested. For stair ascent, subjects maintained their speed until the swing phase of the latest anticipation stride, and changes were found that would normally be observed for decreasing speed. Given the timing and nature of the observed changes, this study has implications for enhancing intent recognition systems and evaluating fall-prone or disabled individuals, by testing their abilities to sense upcoming transitions and decelerate during locomotion.

  8. "Key Interactions" as Agency and Empowerment: Providing a Sense of the Possible to Marginalized, Mexican-Descent Students

    ERIC Educational Resources Information Center

    Reyes, Reynaldo, III

    2009-01-01

    This article discusses how key interactions between community members, teachers, and Latino counselors and advisers were integral in providing support, knowledge, and agency to marginalized, Mexican-descent students in their 1st year of college. Findings show that particular types of discourse and narrative exchanged between integral adult figures…

  9. 14 CFR 121.333 - Supplemental oxygen for emergency descent and for first aid; turbine engine powered airplanes...

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 3 2013-01-01 2013-01-01 false Supplemental oxygen for emergency descent..., FLAG, AND SUPPLEMENTAL OPERATIONS Instrument and Equipment Requirements § 121.333 Supplemental oxygen... shall furnish oxygen and dispensing equipment to comply with paragraphs (b) through (e) of this...

  10. 14 CFR 121.333 - Supplemental oxygen for emergency descent and for first aid; turbine engine powered airplanes...

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 3 2012-01-01 2012-01-01 false Supplemental oxygen for emergency descent..., FLAG, AND SUPPLEMENTAL OPERATIONS Instrument and Equipment Requirements § 121.333 Supplemental oxygen... shall furnish oxygen and dispensing equipment to comply with paragraphs (b) through (e) of this...

  11. 14 CFR 121.333 - Supplemental oxygen for emergency descent and for first aid; turbine engine powered airplanes...

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 3 2011-01-01 2011-01-01 false Supplemental oxygen for emergency descent..., FLAG, AND SUPPLEMENTAL OPERATIONS Instrument and Equipment Requirements § 121.333 Supplemental oxygen... shall furnish oxygen and dispensing equipment to comply with paragraphs (b) through (e) of this...

  12. 14 CFR 121.333 - Supplemental oxygen for emergency descent and for first aid; turbine engine powered airplanes...

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 3 2010-01-01 2010-01-01 false Supplemental oxygen for emergency descent..., FLAG, AND SUPPLEMENTAL OPERATIONS Instrument and Equipment Requirements § 121.333 Supplemental oxygen... shall furnish oxygen and dispensing equipment to comply with paragraphs (b) through (e) of this...

  13. "Arubaito," or Short-Term Working Abroad in Japan: A Case Study of Brazilian University Students of Japanese Descent

    ERIC Educational Resources Information Center

    Sasaki, Lindsey

    2012-01-01

    International migration between Japan and Brazil dates back to 1908, when the first group of Japanese migrated to Brazil. However, in the 1980s, a reverse flow occurred, as thousands of Brazilians of Japanese descent traveled to Japan to work in manufacturing and construction factories ("dekasegi" workers). Japanese Brazilians up until the third…

  14. Annual variation of deseasonalized mean flow acceleration in the equatorial lower stratosphere

    NASA Technical Reports Server (NTRS)

    Dunkerton, Timothy J.

    1990-01-01

    The quasi-biennial oscillation (QBO) in the equatorial lower stratosphere appears to be influenced by the seasonal cycle, as phase transitions at 50 mb occur primarily in the northern spring/summer season (April-August). Descent of east wind regimes varies widely from one QBO cycle to another. Most of this variation occurs because easterly shears slow down or 'stall' in their descent sometime between July and February. Minimum mean flow accelerations at 50 mb occur in the northern winter season, slightly before the annual minimum in equatorial tropopause temperature. Although a weak effect of the semiannual oscillation can be detected near 10 mb, the seasonal effect over most of the QBO region is annual. The seasonal cycle apparently modulates the onset of QBO phases, and slightly enhances the ability to predict the QBO, but is of insufficient strength or consistency to exactly synchronize the quasi-biennial oscillation with the seasonal cycle.

  15. TURBULENT SHEAR ACCELERATION

    SciTech Connect

    Ohira, Yutaka

    2013-04-10

    We consider particle acceleration by large-scale incompressible turbulence with a length scale larger than the particle mean free path. We derive an ensemble-averaged transport equation of energetic charged particles from an extended transport equation that contains the shear acceleration. The ensemble-averaged transport equation describes particle acceleration by incompressible turbulence (turbulent shear acceleration). We find that for Kolmogorov turbulence, the turbulent shear acceleration becomes important on small scales. Moreover, using Monte Carlo simulations, we confirm that the ensemble-averaged transport equation describes the turbulent shear acceleration.

  16. The direction of acceleration

    NASA Astrophysics Data System (ADS)

    Wilhelm, Thomas; Burde, Jan-Philipp; Lück, Stephan

    2015-11-01

    Acceleration is a physical quantity that is difficult to understand and hence its complexity is often erroneously simplified. Many students think of acceleration as equivalent to velocity, a ˜ v. For others, acceleration is a scalar quantity, which describes the change in speed Δ|v| or Δ|v|/Δt (as opposed to the change in velocity). The main difficulty with the concept of acceleration therefore lies in developing a correct understanding of its direction. The free iOS app AccelVisu supports students in acquiring a correct conception of acceleration by showing acceleration arrows directly at moving objects.

  17. The Descent Imager/Spectral Radiometer (DISR) Experiment on the Huygens Entry Probe of Titan

    NASA Astrophysics Data System (ADS)

    Tomasko, M. G.; Buchhauser, D.; Bushroe, M.; Dafoe, L. E.; Doose, L. R.; Eibl, A.; Fellows, C.; Farlane, E. M.; Prout, G. M.; Pringle, M. J.; Rizk, B.; See, C.; Smith, P. H.; Tsetsenekos, K.

    2002-07-01

    The payload of the Huygens Probe into the atmosphere of Titan includes the Descent Imager/Spectral Radiometer (DISR). This instrument includes an integrated package of several optical instruments built around a silicon charge coupled device (CCD) detector, a pair of linear InGaAs array detectors, and several individual silicon detectors. Fiber optics are used extensively to feed these detectors with light collected from three frame imagers, an upward and downward-looking visible spectrometer, an upward and downward looking near-infrared spectrometer, upward and downward looking violet phtotometers, a four-channel solar aerole camera, and a sun sensor that determines the azimuth and zenith angle of the sun and measures the flux in the direct solar beam at 940 nm. An onboard optical calibration system uses a small lamp and fiber optics to track the relative sensitivity of the different optical instruments relative to each other during the seven year cruise to Titan. A 20 watt lamp and collimator are used to provide spectrally continuous illumination of the surface during the last 100 m of the descent for measurements of the reflection spectrum of the surface. The instrument contains software and hardware data compressors to permit measurements of upward and downward direct and diffuse solar flux between 350 and 1700 nm in some 330 spectral bands at approximately 2 km vertical resolution from an alititude of 160 km to the surface. The solar aureole camera measures the brightness of a 6° wide strip of the sky from 25 to 75° zenith angle near and opposite the azimuth of the sun in two passbands near 500 and 935 nm using vertical and horizontal polarizers in each spectral channel at a similar vertical resolution. The downward-looking spectrometers provide the reflection spectrum of the surface at a total of some 600 locations between 850 and 1700 nm and at more than 3000 locations between 480 and 960 nm. Some 500 individual images of the surface are expected which can

  18. The Descent Imager/Spectral Radiometer (DISR) Experiment on the Huygens Entry Probe of Titan

    NASA Astrophysics Data System (ADS)

    Tomasko, M. G.; Buchhauser, D.; Bushroe, M.; Dafoe, L. E.; Doose, L. R.; Eibl, A.; Fellows, C.; Farlane, E. M.; Prout, G. M.; Pringle, M. J.; Rizk, B.; See, C.; Smith, P. H.; Tsetsenekos, K.

    2002-07-01

    The payload of the Huygens Probe into the atmosphere of Titan includes the Descent Imager/Spectral Radiometer (DISR). This instrument includes an integrated package of several optical instruments built around a silicon charge coupled device (CCD) detector, a pair of linear InGaAs array detectors, and several individual silicon detectors. Fiber optics are used extensively to feed these detectors with light collected from three frame imagers, an upward and downward-looking visible spectrometer, an upward and downward looking near-infrared spectrometer, upward and downward looking violet phtotometers, a four-channel solar aerole camera, and a sun sensor that determines the azimuth and zenith angle of the sun and measures the flux in the direct solar beam at 940 nm. An onboard optical calibration system uses a small lamp and fiber optics to track the relative sensitivity of the different optical instruments relative to each other during the seven year cruise to Titan. A 20 watt lamp and collimator are used to provide spectrally continuous illumination of the surface during the last 100 m of the descent for measurements of the reflection spectrum of the surface. The instrument contains software and hardware data compressors to permit measurements of upward and downward direct and diffuse solar flux between 350 and 1700 nm in some 330 spectral bands at approximately 2 km vertical resolution from an alititude of 160 km to the surface. The solar aureole camera measures the brightness of a 6° wide strip of the sky from 25 to 75° zenith angle near and opposite the azimuth of the sun in two passbands near 500 and 935 nm using vertical and horizontal polarizers in each spectral channel at a similar vertical resolution. The downward-looking spectrometers provide the reflection spectrum of the surface at a total of some 600 locations between 850 and 1700 nm and at more than 3000 locations between 480 and 960 nm. Some 500 individual images of the surface are expected which can

  19. Runway Texture and Grid Pattern Effects on Rate-of-Descent Perception

    NASA Technical Reports Server (NTRS)

    Schroeder, J. A.; Dearing, M. G.; Sweet, B. T.; Kaiser, M. K.; Rutkowski, Mike (Technical Monitor)

    2001-01-01

    To date, perceptual errors occur in determining descent rate from a computer-generated image in flight simulation. Pilots tend to touch down twice as hard in simulation than in flight, and more training time is needed in simulation before reaching steady-state performance. Barnes suggested that recognition of range may be the culprit, and he cited that problems such as collimated objects, binocular vision, and poor resolution lead to poor estimation of the velocity vector. Brown's study essentially ruled out that the lack of binocular vision is the problem. Dorfel added specificity to the problem by showing that pilots underestimated range in simulated scenes by 50% when 800 ft from the runway threshold. Palmer and Petitt showed that pilots are able to distinguish between a 1.7 ft/sec and 2.9 ft/sec sink rate when passively observing sink rates in a night scene. Platform motion also plays a role, as previous research has shown that the addition of substantial platform motion improves pilot estimates of vertical velocity and results in simulated touchdown rates more closely resembling flight. This experiment examined how some specific variations in the visual scene properties affect a pilot's perception of sink rate. It extended another experiment that focused on the visual and motion cues necessary for helicopter autorotations. In that experiment, pilots performed steep approaches to a runway. The visual content of the runway and its surroundings varied in two ways: texture and rectangular grid spacing. Four textures, included a no-texture case, were evaluated. Three grid spacings, including a no-grid case, were evaluated. The results showed that pilot better controlled their vertical descent rates when good texture cues were present. No significant differences were found for the grid manipulation. Using those visual scenes a simple psychophysics, experiment was performed. The purpose was to determine if the variations in the visual scenes allowed pilots to better

  20. Spacecraft Trajectory Generation by Successive Approximation for Powered Descent and Cyclers

    NASA Astrophysics Data System (ADS)

    Casoliva, Jordi

    Methods for spacecraft trajectory generation must be reliable. Complex nonlinear dynamics and constraints impede straightforward approaches. The approach pursued in this dissertation is to use successive approximation, which entails solving a sequence of problems, each one of which can be solved reliably, leading to the solution of the problem of interest. First, contractive sequential convex programming (CSCP) is developed and then applied to the problem of optimal powered descent landing in the presence of complex constraints, aerodynamic force and nonlinear engine performance. Second, numerical continuation is applied to the generation of cycler (periodic) spacecraft trajectories in the Earth-Moon system, the challenge here being the multiple scales of the three-body dynamics. The first-order necessary conditions for minimum-fuel powered descent are derived and interpreted. Both a point-mass model with throttle and thrust angle control and a rigid-body model with throttle and angular velocity control are considered, with a more complete analysis of the rigid-body case than previously available in the literature. The effects of boundary conditions on the thrust direction and finite bounds on the angular velocities are analyzed for the rigid-body case. Minimum-fuel solutions, obtained numerically, illustrate the optimal strategies. The optimal powered descent landing problem considered in the development of CSCP has a convex cost function, nonlinear dynamics, convex state constraints and nonlinear non-convex control constraints. The non-convexity in the control constraints is handled with the lossless convexification technique which consists of a convex relaxation on the control constraints. The novelty of CSCP is the ability to account for nonlinear dynamics and nonlinear control bounds in the optimal control problem and the use of interior-point methods for second-order cone programs which are guaranteed to find the optimal solution. CSCP solves a convergent

  1. Reactive Sequencing for Autonomous Navigation Evolving from Phoenix Entry, Descent, and Landing

    NASA Technical Reports Server (NTRS)

    Grasso, Christopher A.; Riedel, Joseph E.; Vaughan, Andrew T.

    2010-01-01

    Virtual Machine Language (VML) is an award-winning advanced procedural sequencing language in use on NASA deep-space missions since 1997, and was used for the successful entry, descent, and landing (EDL) of the Phoenix spacecraft onto the surface of Mars. Phoenix EDL utilized a state-oriented operations architecture which executed within the constraints of the existing VML 2.0 flight capability, compatible with the linear "land or die" nature of the mission. The intricacies of Phoenix EDL included the planned discarding of portions of the vehicle, the complex communications management for relay through on-orbit assets, the presence of temporally indeterminate physical events, and the need to rapidly catch up four days of sequencing should a reboot of the spacecraft flight computer occur shortly before atmospheric entry. These formidable operational challenges led to new techniques for packaging and coordinating reusable sequences called blocks using one-way synchronization via VML sequencing global variable events. The coordinated blocks acted as an ensemble to land the spacecraft, while individually managing various elements in as simple a fashion as possible. This paper outlines prototype VML 2.1 flight capabilities that have evolved from the one-way synchronization techniques in order to implement even more ambitious autonomous mission capabilities. Target missions for these new capabilities include autonomous touch-and-go sampling of cometary and asteroidal bodies, lunar landing of robotic missions, and ultimately landing of crewed lunar vehicles. Close proximity guidance, navigation, and control operations, on-orbit rendezvous, and descent and landing events featured in these missions require elaborate abort capability, manifesting highly non-linear scenarios that are so complex as to overtax traditional sequencing, or even the sort of one-way coordinated sequencing used during EDL. Foreseeing advanced command and control needs for small body and lunar landing

  2. Accelerating Particles with Plasma

    SciTech Connect

    Litos, Michael; Hogan, Mark

    2014-11-05

    Researchers at SLAC explain how they use plasma wakefields to accelerate bunches of electrons to very high energies over only a short distance. Their experiments offer a possible path for the future of particle accelerators.

  3. Accelerator Technology Division

    NASA Astrophysics Data System (ADS)

    1992-04-01

    In fiscal year (FY) 1991, the Accelerator Technology (AT) division continued fulfilling its mission to pursue accelerator science and technology and to develop new accelerator concepts for application to research, defense, energy, industry, and other areas of national interest. This report discusses the following programs: The Ground Test Accelerator Program; APLE Free-Electron Laser Program; Accelerator Transmutation of Waste; JAERI, OMEGA Project, and Intense Neutron Source for Materials Testing; Advanced Free-Electron Laser Initiative; Superconducting Super Collider; The High-Power Microwave Program; (Phi) Factory Collaboration; Neutral Particle Beam Power System Highlights; Accelerator Physics and Special Projects; Magnetic Optics and Beam Diagnostics; Accelerator Design and Engineering; Radio-Frequency Technology; Free-Electron Laser Technology; Accelerator Controls and Automation; Very High-Power Microwave Sources and Effects; and GTA Installation, Commissioning, and Operations.

  4. Linear accelerator: A concept

    NASA Technical Reports Server (NTRS)

    Mutzberg, J.

    1972-01-01

    Design is proposed for inexpensive accelerometer which would work by applying pressure to fluid during acceleration. Pressure is used to move shuttle, and shuttle movement is sensed and calibrated to give acceleration readings.

  5. Improved plasma accelerator

    NASA Technical Reports Server (NTRS)

    Cheng, D. Y.

    1971-01-01

    Converging, coaxial accelerator electrode configuration operates in vacuum as plasma gun. Plasma forms by periodic injections of high pressure gas that is ionized by electrical discharges. Deflagration mode of discharge provides acceleration, and converging contours of plasma gun provide focusing.

  6. MEQALAC rf accelerating structure

    SciTech Connect

    Keane, J.; Brodowski, J.

    1981-01-01

    A prototype MEQALAC capable of replacing the Cockcroft Walton pre-injector at BNL is being fabricated. Ten milliamperes of H/sup -/ beam supplied from a source sitting at a potential of -40 kilovolt is to be accelerated to 750 keV. This energy gain is provided by a 200 Megahertz accelerating system rather than the normal dc acceleration. Substantial size and cost reduction would be realized by such a system over conventional pre-accelerator systems.

  7. Mars Sample Return Using Commercial Capabilities: Propulsive Entry, Descent, and Landing of a Capsule Form Vehicle

    NASA Technical Reports Server (NTRS)

    Gonzales, Andrew A.; Lemke, Lawrence G.; Huynh, Loc C.

    2014-01-01

    This paper describes a critical portion of the work that has been done at NASA, Ames Research Center regarding the use of the commercially developed Dragon capsule as a delivery vehicle for the elements of a high priority Mars Sample Return mission. The objective of the investigation was to determine entry and landed mass capabilities that cover anticipated mission conditions. The "Red Dragon", Mars configuration, uses supersonic retro-propulsion, with no required parachute system, to perform Entry, Descent, and Landing (EDL) maneuvers. The propulsive system proposed for use is the same system that will perform an abort, if necessary, for a human rated version of the Dragon capsule. Standard trajectory analysis tools are applied to publically available information about Dragon and other legacy capsule forms in order to perform the investigation. Trajectory simulation parameters include entry velocity, flight path angle, lift to drag Ratio (L/D), landing site elevation, atmosphere density, and total entry mass, in addition engineering assumptions for the performance of the propulsion system are stated. Mass estimates for major elements of the overall proposed architecture are coupled to this EDL analysis to close the overall architecture. Three synodic launch opportunities, beginning with the 2022 opportunity, define the arrival conditions. Results state the relations between the analysis parameters as well as sensitivities to those parameters. The EDL performance envelope includes landing altitudes between 0 and -4 km referenced to the Mars Orbiter Laser Altimeter datum as well as minimum and maximum atmosphere density. Total entry masses between 7 and 10 mt are considered with architecture closure occurring between 9.0 and 10 mt. Propellant mass fractions for each major phase of the EDL - Entry, Terminal Descent, and Hazard Avoidance - have been derived. An assessment of the effect of the entry conditions on the Thermal Protection System (TPS) currently in use for

  8. Acceleration gradient of a plasma wakefield accelerator

    SciTech Connect

    Uhm, Han S.

    2008-02-25

    The phase velocity of the wakefield waves is identical to the electron beam velocity. A theoretical analysis indicates that the acceleration gradient of the wakefield accelerator normalized by the wave breaking amplitude is K{sub 0}({xi})/K{sub 1}({xi}), where K{sub 0}({xi}) and K{sub 1}({xi}) are the modified Bessel functions of the second kind of order zero and one, respectively and {xi} is the beam parameter representing the beam intensity. It is also shown that the beam density must be considerably higher than the diffuse plasma density for the large radial velocity of plasma electrons that are required for a high acceleration gradient.

  9. Acceleration: It's Elementary

    ERIC Educational Resources Information Center

    Willis, Mariam

    2012-01-01

    Acceleration is one tool for providing high-ability students the opportunity to learn something new every day. Some people talk about acceleration as taking a student out of step. In actuality, what one is doing is putting a student in step with the right curriculum. Whole-grade acceleration, also called grade-skipping, usually happens between…

  10. Far field acceleration

    SciTech Connect

    Fernow, R.C.

    1995-07-01

    Far fields are propagating electromagnetic waves far from their source, boundary surfaces, and free charges. The general principles governing the acceleration of charged particles by far fields are reviewed. A survey of proposed field configurations is given. The two most important schemes, Inverse Cerenkov acceleration and Inverse free electron laser acceleration, are discussed in detail.

  11. Angular Acceleration without Torque?

    ERIC Educational Resources Information Center

    Kaufman, Richard D.

    2012-01-01

    Hardly. Just as Robert Johns qualitatively describes angular acceleration by an internal force in his article "Acceleration Without Force?" here we will extend the discussion to consider angular acceleration by an internal torque. As we will see, this internal torque is due to an internal force acting at a distance from an instantaneous center.

  12. Compact Plasma Accelerator

    NASA Technical Reports Server (NTRS)

    Foster, John E.

    2004-01-01

    A plasma accelerator has been conceived for both material-processing and spacecraft-propulsion applications. This accelerator generates and accelerates ions within a very small volume. Because of its compactness, this accelerator could be nearly ideal for primary or station-keeping propulsion for spacecraft having masses between 1 and 20 kg. Because this accelerator is designed to generate beams of ions having energies between 50 and 200 eV, it could also be used for surface modification or activation of thin films.

  13. Development of Thermal Protection Materials for Future Mars Entry, Descent and Landing Systems

    NASA Technical Reports Server (NTRS)

    Cassell, Alan M.; Beck, Robin A. S.; Arnold, James O.; Hwang, Helen; Wright, Michael J.; Szalai, Christine E.; Blosser, Max; Poteet, Carl C.

    2010-01-01

    Entry Systems will play a crucial role as NASA develops the technologies required for Human Mars Exploration. The Exploration Technology Development Program Office established the Entry, Descent and Landing (EDL) Technology Development Project to develop Thermal Protection System (TPS) materials for insertion into future Mars Entry Systems. An assessment of current entry system technologies identified significant opportunity to improve the current state of the art in thermal protection materials in order to enable landing of heavy mass (40 mT) payloads. To accomplish this goal, the EDL Project has outlined a framework to define, develop and model the thermal protection system material concepts required to allow for the human exploration of Mars via aerocapture followed by entry. Two primary classes of ablative materials are being developed: rigid and flexible. The rigid ablatives will be applied to the acreage of a 10x30 m rigid mid L/D Aeroshell to endure the dual pulse heating (peak approx.500 W/sq cm). Likewise, flexible ablative materials are being developed for 20-30 m diameter deployable aerodynamic decelerator entry systems that could endure dual pulse heating (peak aprrox.120 W/sq cm). A technology Roadmap is presented that will be used for facilitating the maturation of both the rigid and flexible ablative materials through application of decision metrics (requirements, key performance parameters, TRL definitions, and evaluation criteria) used to assess and advance the various candidate TPS material technologies.

  14. Guidance and Control Algorithms for the Mars Entry, Descent and Landing Systems Analysis

    NASA Technical Reports Server (NTRS)

    Davis, Jody L.; CwyerCianciolo, Alicia M.; Powell, Richard W.; Shidner, Jeremy D.; Garcia-Llama, Eduardo

    2010-01-01

    The purpose of the Mars Entry, Descent and Landing Systems Analysis (EDL-SA) study was to identify feasible technologies that will enable human exploration of Mars, specifically to deliver large payloads to the Martian surface. This paper focuses on the methods used to guide and control two of the contending technologies, a mid- lift-to-drag (L/D) rigid aeroshell and a hypersonic inflatable aerodynamic decelerator (HIAD), through the entry portion of the trajectory. The Program to Optimize Simulated Trajectories II (POST2) is used to simulate and analyze the trajectories of the contending technologies and guidance and control algorithms. Three guidance algorithms are discussed in this paper: EDL theoretical guidance, Numerical Predictor-Corrector (NPC) guidance and Analytical Predictor-Corrector (APC) guidance. EDL-SA also considered two forms of control: bank angle control, similar to that used by Apollo and the Space Shuttle, and a center-of-gravity (CG) offset control. This paper presents the performance comparison of these guidance algorithms and summarizes the results as they impact the technology recommendations for future study.

  15. The Mars Science Laboratory (MSL) Entry, Descent And Landing Instrumentation (MEDLI): Hardware Performance and Data Reconstruction

    NASA Technical Reports Server (NTRS)

    Little, Alan; Bose, Deepak; Karlgaard, Chris; Munk, Michelle; Kuhl, Chris; Schoenenberger, Mark; Antill, Chuck; Verhappen, Ron; Kutty, Prasad; White, Todd

    2013-01-01

    The Mars Science Laboratory (MSL) Entry, Descent and Landing Instrumentation (MEDLI) hardware was a first-of-its-kind sensor system that gathered temperature and pressure readings on the MSL heatshield during Mars entry on August 6, 2012. MEDLI began as challenging instrumentation problem, and has been a model of collaboration across multiple NASA organizations. After the culmination of almost 6 years of effort, the sensors performed extremely well, collecting data from before atmospheric interface through parachute deploy. This paper will summarize the history of the MEDLI project and hardware development, including key lessons learned that can apply to future instrumentation efforts. MEDLI returned an unprecedented amount of high-quality engineering data from a Mars entry vehicle. We will present the performance of the 3 sensor types: pressure, temperature, and isotherm tracking, as well as the performance of the custom-built sensor support electronics. A key component throughout the MEDLI project has been the ground testing and analysis effort required to understand the returned flight data. Although data analysis is ongoing through 2013, this paper will reveal some of the early findings on the aerothermodynamic environment that MSL encountered at Mars, the response of the heatshield material to that heating environment, and the aerodynamic performance of the entry vehicle. The MEDLI data results promise to challenge our engineering assumptions and revolutionize the way we account for margins in entry vehicle design.

  16. Multidisciplinary Tool for Systems Analysis of Planetary Entry, Descent, and Landing

    NASA Technical Reports Server (NTRS)

    Samareh, Jamshid A.

    2011-01-01

    Systems analysis of a planetary entry (SAPE), descent, and landing (EDL) is a multidisciplinary activity in nature. SAPE improves the performance of the systems analysis team by automating and streamlining the process, and this improvement can reduce the errors that stem from manual data transfer among discipline experts. SAPE is a multidisciplinary tool for systems analysis of planetary EDL for Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Titan. It performs EDL systems analysis for any planet, operates cross-platform (i.e., Windows, Mac, and Linux operating systems), uses existing software components and open-source software to avoid software licensing issues, performs low-fidelity systems analysis in one hour on a computer that is comparable to an average laptop, and keeps discipline experts in the analysis loop. SAPE uses Python, a platform-independent, open-source language, for integration and for the user interface. Development has relied heavily on the object-oriented programming capabilities that are available in Python. Modules are provided to interface with commercial and government off-the-shelf software components (e.g., thermal protection systems and finite-element analysis). SAPE currently includes the following analysis modules: geometry, trajectory, aerodynamics, aerothermal, thermal protection system, and interface for structural sizing.

  17. Neighborhood Hispanic composition and depressive symptoms among Mexican-descent residents of Texas City, Texas.

    PubMed

    Shell, Alyssa Marie; Peek, M Kristen; Eschbach, Karl

    2013-12-01

    Substantial research shows that increased Hispanic neighborhood concentration is associated with several beneficial health outcomes including lower adult mortality, better self-rated health, and fewer respiratory problems. Literature on the relationship of Hispanic composition and depressive symptoms is more equivocal. In addition, few studies have directly investigated hypothesized mechanisms of this relationship. This study uses data from a probability sample of 1238 Mexican-descent adults living in 48 neighborhoods in Texas City, Texas. Multilevel regression models investigate whether Hispanic neighborhood composition is associated with fewer depressive symptoms. This study also investigates whether social support, perceived discrimination, and perceived stress mediate or moderate the relationship, and whether results differ by primary language used at home. We find that individuals living in high Hispanic composition neighborhoods experience fewer depressive symptoms than individuals in low Hispanic composition neighborhoods. In addition, we find that these beneficial effects only apply to respondents who speak English. Social support, perceived discrimination, and perceived stress mediate the Hispanic composition-depressive symptoms relationship. In addition, discrimination and stress moderate the relationship between Hispanic composition and depressive symptoms. Our findings support theories linking higher neighborhood Hispanic composition and better mental health, and suggest that Spanish language use, social support, discrimination and stress may play important roles in the Hispanic composition-depressive symptoms relationship. PMID:24355471

  18. Final STS-35 Columbia descent BET products and results for LaRC OEX investigations

    NASA Technical Reports Server (NTRS)

    Oakes, Kevin F.; Findlay, John T.; Jasinski, Rachel A.; Wood, James S.

    1991-01-01

    Final STS-35 'Columbia' descent Best Estimate Trajectory (BET) products have been developed for Langley Research Center (LaRC) Orbiter Experiments (OEX) investigations. Included are the reconstructed inertial trajectory profile; the Extended BET, which combines the inertial data and, in this instance, the National Weather Service atmospheric information obtained via Johnson Space Center; and the Aerodynamic BET. The inertial BET utilized Inertial Measurement Unit 1 (IMU1) dynamic measurements for deterministic propagation during the ENTREE estimation process. The final estimate was based on the considerable ground based C-band tracking coverage available as well as Tracking Data and Relay Satellite System (TDRSS) Doppler data, a unique use of the latter for endo-atmospheric flight determinations. The actual estimate required simultaneous solutions for the spacecraft position and velocity, spacecraft attitude, and six IMU parameters - three gyro biases and three accelerometer scale factor correction terms. The anchor epoch for this analysis was 19,200 Greenwich Mean Time (GMT) seconds which corresponds to an initial Shuttle altitude of approximately 513 kft. The atmospheric data incorporated were evaluated based on Shuttle derived considerations as well as comparisons with other models. The AEROBET was developed based on the Extended BET, the measured spacecraft configuration information, final mass properties, and the final Orbiter preoperation databook. The latter was updated based on aerodynamic consensus incrementals derived by the latest published FAD. The rectified predictions were compared versus the flight computed values and the resultant differences were correlated versus ensemble results for twenty-two previous STS entry flights.

  19. Acculturation and drinking among people of Mexican descent in Mexico and the United States.

    PubMed

    Caetano, R; Mora, M E

    1988-09-01

    This article studies the relationships between acculturation and drinking and alcohol-related problems among people of Mexican descent in Mexico and the United States. Subjects in the United States were part of a national probability sample of the Hispanic household population 18 years of age and older. Subjects in Mexico were randomly selected from among adult residents of the city of Morelia and an adjoining rural county, Tarimbaro, both in the State of Michoacan. Both samples were interviewed using the same questionnaire. Response rates were 72% in the United States and 92% in Mexico. Results show that Mexican-American men drink more frequently than men in Michoacan, who, as a group, drink infrequently but consume more often five or more drinks at a sitting as compared with Mexican Americans. Mexican-American women have a lower rate of abstention and a higher rate of women who drink at least once a week and who consume five drinks at a sitting at least once a year than do women in Michoacan. Among men, changes in drinking seem to occur soon after coming to the United States--often within 5 years. Among women, drinking patterns are not related to length of residence in the United States. In spite of less drinking, respondents in Michoacan report more alcohol problems than do Mexican Americans.

  20. Primary Open-Angle Glaucoma in Individuals of African Descent: A Review of Risk Factors

    PubMed Central

    Salowe, Rebecca; Salinas, Julia; Farbman, Neil H; Mohammed, Aishat; Warren, Joshua Z; Rhodes, Allison; Brucker, Alexander; Regina, Meredith; Miller-Ellis, Eydie; Sankar, Prithvi S; Lehman, Amanda; O’Brien, Joan M

    2015-01-01

    Objective To identify the major risk factors for primary open-angle glaucoma (POAG) in individuals of African descent. Methods We searched PubMed for relevant articles, with results spanning April 1947 to present. All abstracts were reviewed and, where relevant to POAG and race, articles were catalogued and analyzed. Additional sources were identified through citations in articles returned by our search. Results Numerous potential POAG risk factors were identified and organized into categories by demographics (age, sex, and skin color), lifestyle choices (smoking, alcohol), comorbidities (hypertension, diabetes, and obesity), ophthalmic findings (eye structure, central corneal thickness, corneal hysteresis, elevated intraocular pressure, myopia, cataract, and vascular abnormalities), family history, socioeconomic status, and adherence. Older age, male sex, lower central corneal thickness, decreased corneal hysteresis, elevated intraocular pressure, myopia, vascular abnormalities, and positive family history were definitively associated with increased risk of POAG. Conclusions Individuals at greatest risk for POAG should be screened by an ophthalmologist to allow earlier detection and to slow disease progression. Further studies on the genetics of the disease will provide more insight into underlying pathologic mechanisms and could lead to improved therapeutic interventions. Continued research in urban areas with large populations of blacks is especially needed. PMID:26664770

  1. Rain, winds and haze during the Huygens probe's descent to Titan's surface.

    PubMed

    Tomasko, M G; Archinal, B; Becker, T; Bézard, B; Bushroe, M; Combes, M; Cook, D; Coustenis, A; de Bergh, C; Dafoe, L E; Doose, L; Douté, S; Eibl, A; Engel, S; Gliem, F; Grieger, B; Holso, K; Howington-Kraus, E; Karkoschka, E; Keller, H U; Kirk, R; Kramm, R; Küppers, M; Lanagan, P; Lellouch, E; Lemmon, M; Lunine, J; McFarlane, E; Moores, J; Prout, G M; Rizk, B; Rosiek, M; Rueffer, P; Schröder, S E; Schmitt, B; See, C; Smith, P; Soderblom, L; Thomas, N; West, R

    2005-12-01

    The irreversible conversion of methane into higher hydrocarbons in Titan's stratosphere implies a surface or subsurface methane reservoir. Recent measurements from the cameras aboard the Cassini orbiter fail to see a global reservoir, but the methane and smog in Titan's atmosphere impedes the search for hydrocarbons on the surface. Here we report spectra and high-resolution images obtained by the Huygens Probe Descent Imager/Spectral Radiometer instrument in Titan's atmosphere. Although these images do not show liquid hydrocarbon pools on the surface, they do reveal the traces of once flowing liquid. Surprisingly like Earth, the brighter highland regions show complex systems draining into flat, dark lowlands. Images taken after landing are of a dry riverbed. The infrared reflectance spectrum measured for the surface is unlike any other in the Solar System; there is a red slope in the optical range that is consistent with an organic material such as tholins, and absorption from water ice is seen. However, a blue slope in the near-infrared suggests another, unknown constituent. The number density of haze particles increases by a factor of just a few from an altitude of 150 km to the surface, with no clear space below the tropopause. The methane relative humidity near the surface is 50 per cent. PMID:16319829

  2. Genome-wide patterns of identity-by-descent sharing in the French Canadian founder population

    PubMed Central

    Gauvin, Héloïse; Moreau, Claudia; Lefebvre, Jean-François; Laprise, Catherine; Vézina, Hélène; Labuda, Damian; Roy-Gagnon, Marie-Hélène

    2014-01-01

    In genetics the ability to accurately describe the familial relationships among a group of individuals can be very useful. Recent statistical tools succeeded in assessing the degree of relatedness up to 6–7 generations with good power using dense genome-wide single-nucleotide polymorphism data to estimate the extent of identity-by-descent (IBD) sharing. It is therefore important to describe genome-wide patterns of IBD sharing for more remote and complex relatedness between individuals, such as that observed in a founder population like Quebec, Canada. Taking advantage of the extended genealogical records of the French Canadian founder population, we first compared different tools to identify regions of IBD in order to best describe genome-wide IBD sharing and its correlation with genealogical characteristics. Results showed that the extent of IBD sharing identified with FastIBD correlates best with relatedness measured using genealogical data. Total length of IBD sharing explained 85% of the genealogical kinship's variance. In addition, we observed significantly higher sharing in pairs of individuals with at least one inbred ancestor compared with those without any. Furthermore, patterns of IBD sharing and average sharing were different across regional populations, consistent with the settlement history of Quebec. Our results suggest that, as expected, the complex relatedness present in founder populations is reflected in patterns of IBD sharing. Using these patterns, it is thus possible to gain insight on the types of distant relationships in a sample from a founder population like Quebec. PMID:24129432

  3. Rain, winds and haze during the Huygens probe's descent to Titan's surface

    USGS Publications Warehouse

    Tomasko, M.G.; Archinal, B.; Becker, T.; Bezard, B.; Bushroe, M.; Combes, M.; Cook, D.; Coustenis, A.; De Bergh, C.; Dafoe, L.E.; Doose, L.; Doute, S.; Eibl, A.; Engel, S.; Gliem, F.; Grieger, B.; Holso, K.; Howington-Kraus, E.; Karkoschka, E.; Keller, H.U.; Kirk, R.; Kramm, R.; Kuppers, M.; Lanagan, P.; Lellouch, E.; Lemmon, M.; Lunine, J.; McFarlane, E.; Moores, J.; Prout, G.M.; Rizk, B.; Rosiek, M.; Rueffer, P.; Schroder, S.E.; Schmitt, B.; See, C.; Smith, P.; Soderblom, L.; Thomas, N.; West, R.

    2005-01-01

    The irreversible conversion of methane into higher hydrocarbons in Titan's stratosphere implies a surface or subsurface methane reservoir. Recent measurements from the cameras aboard the Cassini orbiter fail to see a global reservoir, but the methane and smog in Titan's atmosphere impedes the search for hydrocarbons on the surface. Here we report spectra and high-resolution images obtained by the Huygens Probe Descent Imager/Spectral Radiometer instrument in Titan's atmosphere. Although these images do not show liquid hydrocarbon pools on the surface, they do reveal the traces of once flowing liquid. Surprisingly like Earth, the brighter highland regions show complex systems draining into flat, dark lowlands. Images taken after landing are of a dry riverbed. The infrared reflectance spectrum measured for the surface is unlike any other in the Solar System; there is a red slope in the optical range that is consistent with an organic material such as tholins, and absorption from water ice is seen. However, a blue slope in the near-infrared suggests another, unknown constituent. The number density of haze particles increases by a factor of just a few from an altitude of 150 km to the surface, with no clear space below the tropopause. The methane relative humidity near the surface is 50 per cent. ?? 2005 Nature Publishing Group.

  4. Testicular descent, sperm maturation and capacitation. Lessons from our most distant relatives, the monotremes.

    PubMed

    Ecroyd, Heath; Nixon, Brett; Dacheux, Jean-Louis; Jones, Russell C

    2009-01-01

    The present review examines whether monotremes may help to resolve three questions relating to sperm production in mammals: why the testes descend into a scrotum in most mammals, why spermatozoa are infertile when they leave the testes and require a period of maturation in the specific milieu provided by the epididymides, and why ejaculated spermatozoa cannot immediately fertilise an ovum until they undergo capacitation within the female reproductive tract. Comparisons of monotremes with other mammals indicate that there is a need for considerable work on monotremes. It is hypothesised that testicular descent should be related to epididymal differentiation. Spermatozoa and ova from both groups share many of the proteins that are thought to be involved in gamete interaction, and although epididymal sperm maturation is significant it is probably less complex in monotremes than in other mammals. However, the monotreme epididymis is unique in forming spermatozoa into bundles of 100 with greatly enhanced motility compared with individual spermatozoa. Bundle formation involves a highly organised interaction with epididymal proteins, and the bundles persist during incubation in vitro, except in specialised medium, in which spermatozoa separate after 2-3 h incubation. It is suggested that this represents an early form of capacitation.

  5. Evaluation of an Airborne Spacing Concept to Support Continuous Descent Arrival Operations

    NASA Technical Reports Server (NTRS)

    Murdoch, Jennifer L.; Barmore, Bryan E.; Baxley, Brian T.; Capron, William R.; Abbott, Terence S.

    2009-01-01

    This paper describes a human-in-the-loop experiment of an airborne spacing concept designed to support Continuous Descent Arrival (CDA) operations. The use of CDAs with traditional air traffic control (ATC) techniques may actually reduce an airport's arrival throughput since ATC must provide more airspace around aircraft on CDAs due to the variances in the aircraft trajectories. The intent of airborne self-spacing, where ATC delegates the speed control to the aircraft, is to maintain or even enhance an airport s landing rate during CDA operations by precisely achieving the desired time interval between aircraft at the runway threshold. This paper describes the operational concept along with the supporting airborne spacing tool and the results of a piloted evaluation of this concept, with the focus of the evaluation on pilot acceptability of the concept during off-nominal events. The results of this evaluation show a pilot acceptance of this airborne spacing concept with little negative performance impact over conventional CDAs.

  6. En Route Descent Advisor Multi-Sector Planning Using Active and Provisional Controller Plans

    NASA Technical Reports Server (NTRS)

    Vivona, Robert; Green, Steven

    2003-01-01

    As decision support tools are developed to support controllers in complex air traffic control environments, new approaches to maintaining situation awareness and managing traffic planning must be developed to handle the ever-increasing amounts of alerting and advisory data. Within high-density metering and other environments where flight path changes are the rule, not the exception, and where interactions between these changes are required, current trial planning approaches are limited by potential increases in workload. The Enroute Descent Advisor (EDA) is a set of decision support tool capabilities for managing high-density en route traffic subject to metering restrictions. The EDA system s novel approach builds aircraft plans from combinations of user intent data and builds controller plans from combinations of aircraft plans to effectively maintain situation awareness during traffic planning. By maintaining both active (current) and provisional (proposed) controller plans, EDA supports controllers in coordinated traffic planning both within and between sectors. Ultimately, EDA s multi-sector planning approach will facilitate a transition from current sector-oriented operations to a new trajectory-oriented paradigm, enabling new levels of efficiency and collaboration in air traffic control.

  7. Tracking capability for entry, descent and landing and its support to NASA Mars Exploration Rovers

    NASA Technical Reports Server (NTRS)

    Pham, Timothy; Chang, Christine; Fort, David; Satorius, Edgar; Finley, Susan; White, Leslie; Estabrook, Polly

    2003-01-01

    This paper described a new capability recently deployed in the NASA Deep Space Network to support the entry, descent and landing of the two Mars Exploration Rovers - Spirit and Opportunity. This final segment of a 7-month journey was critical step in enabling successful mission operation. The EDL Data Analysis (EDA) equipment processed the open loop recording samples from the existing radio science receivers, extracted the MFSK-modulated tones, and provided information on the occurrence of associated events happened onboard spacecraft. The EDA software supported real-time as well as post pass processing. The design flexibility allowed the track to be divided into different segments, each could be processed with a configuration optimized for its signal conditions and uncertainties. The use of dynamic lock state concept enabled signal detection be done with minimum required computing power - less was spent when signal was steadily detected and more when signal fluctuated. With the server-client design, the EDA supported connections to different remote operation centers for monitor purpose. The paper also presented the field results from both Spirit and Opportunity landings. The detection were much better than anticipated. All critical event tones were seen in real time. Surprising detection of LCP signal was found with Spirit landing, resulted in a reconfiguration for Opportunity landing to maximize signal detection.

  8. Mars Global Surveyor's View of Gusev Crater During Spirit's Entry, Descent, and Landing

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site] Click on image for larger annotated version

    7 January 2004 When the Mars Exploration Rover (MER-A), Spirit, was landing on 4 January 2004 (3 January 2004, PST), Mars Global Surveyor (MGS) was in position above the region to receive the critical entry, descent, and landing data via ultra high frequency (UHF) radio transmission to the MGS Mars Relay (MR) system. Data from the MR antenna are stored in the Mars Orbiter Camera (MOC) computer until they are transmitted to Earth. The transmission from Spirit on 4 January 2004 occurred in real time, as the rover descended, bounced, and rolled to a stop.

    At the same time that MGS was receiving data during Spirit's landing, the MGS MOC obtained this oblique wide angle view looking east across the martian surface toward Gusev Crater, the site where the MER-A landed. The image on the right is labeled to show the location of Gusev Crater; the arrow points approximately to the place that Spirit touched down. The 165 km (103 mi) diameter Gusev Crater and the Spirit landing site are located near 14.7oS, 184. 6oW. In this view, sunlight is coming from the bottom (west).

  9. Neighborhood Hispanic composition and depressive symptoms among Mexican-descent residents of Texas City, Texas.

    PubMed

    Shell, Alyssa Marie; Peek, M Kristen; Eschbach, Karl

    2013-12-01

    Substantial research shows that increased Hispanic neighborhood concentration is associated with several beneficial health outcomes including lower adult mortality, better self-rated health, and fewer respiratory problems. Literature on the relationship of Hispanic composition and depressive symptoms is more equivocal. In addition, few studies have directly investigated hypothesized mechanisms of this relationship. This study uses data from a probability sample of 1238 Mexican-descent adults living in 48 neighborhoods in Texas City, Texas. Multilevel regression models investigate whether Hispanic neighborhood composition is associated with fewer depressive symptoms. This study also investigates whether social support, perceived discrimination, and perceived stress mediate or moderate the relationship, and whether results differ by primary language used at home. We find that individuals living in high Hispanic composition neighborhoods experience fewer depressive symptoms than individuals in low Hispanic composition neighborhoods. In addition, we find that these beneficial effects only apply to respondents who speak English. Social support, perceived discrimination, and perceived stress mediate the Hispanic composition-depressive symptoms relationship. In addition, discrimination and stress moderate the relationship between Hispanic composition and depressive symptoms. Our findings support theories linking higher neighborhood Hispanic composition and better mental health, and suggest that Spanish language use, social support, discrimination and stress may play important roles in the Hispanic composition-depressive symptoms relationship.

  10. Neocytolysis on descent from altitude: a newly recognized mechanism for the control of red cell mass

    NASA Technical Reports Server (NTRS)

    Rice, L.; Ruiz, W.; Driscoll, T.; Whitley, C. E.; Tapia, R.; Hachey, D. L.; Gonzales, G. F.; Alfrey, C. P.

    2001-01-01

    BACKGROUND: Studies of space-flight anemia have uncovered a physiologic process, neocytolysis, by which young red blood cells are selectively hemolyzed, allowing rapid adaptation when red cell mass is excessive for a new environment. OBJECTIVES: 1) To confirm that neocytolysis occurs in another situation of acute plethora-when high-altitude dwellers with polycythemia descend to sea level; and 2) to clarify the role of erythropoietin suppression. DESIGN: Prospective observational and interventional study. SETTING: Cerro de Pasco (4380 m) and Lima (sea level), Peru. PARTICIPANTS: Nine volunteers with polycythemia. INTERVENTIONS: Volunteers were transported to sea level; three received low-dose erythropoietin. MEASUREMENTS: Changes in red cell mass, hematocrit, hemoglobin concentration, reticulocyte count, ferritin level, serum erythropoietin, and enrichment of administered(13)C in heme. RESULTS: In six participants, red cell mass decreased by 7% to 10% within a few days of descent; this decrease was mirrored by a rapid increase in serum ferritin level. Reticulocyte production did not decrease, a finding that establishes a hemolytic mechanism.(13)C changes in circulating heme were consistent with hemolysis of young cells. Erythropoietin was suppressed, and administration of exogenous erythropoietin prevented the changes in red cell mass, serum ferritin level, and(13)C-heme. CONCLUSIONS: Neocytolysis and the role of erythropoietin are confirmed in persons with polycythemia who descend from high altitude. This may have implications that extend beyond space and altitude medicine to renal disease and other situations of erythropoietin suppression, hemolysis, and polycythemia.

  11. Atmosphere Assessment for MARS Science Laboratory Entry, Descent and Landing Operations

    NASA Technical Reports Server (NTRS)

    Cianciolo, Alicia D.; Cantor, Bruce; Barnes, Jeff; Tyler, Daniel, Jr.; Rafkin, Scot; Chen, Allen; Kass, David; Mischna, Michael; Vasavada, Ashwin R.

    2013-01-01

    On August 6, 2012, the Mars Science Laboratory rover, Curiosity, successfully landed on the surface of Mars. The Entry, Descent and Landing (EDL) sequence was designed using atmospheric conditions estimated from mesoscale numerical models. The models, developed by two independent organizations (Oregon State University and the Southwest Research Institute), were validated against observations at Mars from three prior years. In the weeks and days before entry, the MSL "Council of Atmospheres" (CoA), a group of atmospheric scientists and modelers, instrument experts and EDL simulation engineers, evaluated the latest Mars data from orbiting assets including the Mars Reconnaissance Orbiter's Mars Color Imager (MARCI) and Mars Climate Sounder (MCS), as well as Mars Odyssey's Thermal Emission Imaging System (THEMIS). The observations were compared to the mesoscale models developed for EDL performance simulation to determine if a spacecraft parameter update was necessary prior to entry. This paper summarizes the daily atmosphere observations and comparison to the performance simulation atmosphere models. Options to modify the atmosphere model in the simulation to compensate for atmosphere effects are also presented. Finally, a summary of the CoA decisions and recommendations to the MSL project in the days leading up to EDL is provided.

  12. A calibrated chronology of biochemistry reveals a stem line of descent responsible for planetary biodiversity

    PubMed Central

    Caetano-Anollés, Gustavo; Mittenthal, Jay E.; Caetano-Anollés, Derek; Kim, Kyung Mo

    2014-01-01

    Time-calibrated phylogenomic trees of protein domain structure produce powerful chronologies describing the evolution of biochemistry and life. These timetrees are built from a genomic census of millions of encoded proteins using models of nested accumulation of molecules in evolving proteomes. Here we show that a primordial stem line of descent, a propagating series of pluripotent cellular entities, populates the deeper branches of the timetrees. The stem line produced for the first time cellular grades ~2.9 billion years (Gy)-ago, which slowly turned into lineages of superkingdom Archaea. Prompted by the rise of planetary oxygen and aerobic metabolism, the stem line also produced bacterial and eukaryal lineages. Superkingdom-specific domain repertoires emerged ~2.1 Gy-ago delimiting fully diversified Bacteria. Repertoires specific to Eukarya and Archaea appeared 300 millions years later. Results reconcile reductive evolutionary processes leading to the early emergence of Archaea to superkingdom-specific innovations compatible with a tree of life rooted in Bacteria. PMID:25309572

  13. Clogging of Joule-Thomson Devices in Liquid Hydrogen-Lunar Lander Descent Stage Operating Regime

    NASA Astrophysics Data System (ADS)

    Jurns, J. M.

    2010-04-01

    Joule-Thomson (J-T) devices have been identified as critical components for future space exploration missions. The NASA Constellation Program lunar architecture considers LOX/LH2 propulsion for the lunar lander descent stage main engine an enabling technology, ensuring the cryogenic propellants are available at the correct conditions for engine operation. This cryogenic storage system may utilize a Thermodynamic Vent System (TVS) that includes J-T devices to maintain tank fluid pressure and temperature. Previous experimental investigations have indicated that J-T devices may become clogged when flowing LH2 while operating at a temperature range from 20.5 K to 24.4 K. It has been proposed that clogging is due to a trace amount of metastable, supercooled liquid neon in the regular LH2 supply. In time, flow blockage occurs from accretion of solid neon on the orifice. This clogging poses a realistic threat to spacecraft propulsion systems utilizing J-T devices in cryogenic pressure control systems. TVS failure due to J-T clogging would prevent removal of environmental heat from the propellant and potential loss of mission. This report describes J-T clogging tests performed with LH2. Tests were performed in the expected Lunar Lander operating regime, and several methods were evaluated to determine the optimum approach to mitigating the potential risk of J-T clogging.

  14. A parametric approach to kinship hypothesis testing using identity-by-descent parameters.

    PubMed

    García-Magariños, Manuel; Egeland, Thore; López-de-Ullibarri, Ignacio; Hjort, Nils L; Salas, Antonio

    2015-11-01

    There is a large number of applications where family relationships need to be determined from DNA data. In forensic science, competing ideas are in general verbally formulated as the two hypotheses of a test. For the most common paternity case, the null hypothesis states that the alleged father is the true father against the alternative hypothesis that the father is an unrelated man. A likelihood ratio is calculated to summarize the evidence. We propose an alternative framework whereby a model and the hypotheses are formulated in terms of parameters representing identity-by-descent probabilities. There are several advantages to this approach. Firstly, the alternative hypothesis can be completely general. Specifically, the alternative does not need to specify an unrelated man. Secondly, the parametric formulation corresponds to the approach used in most other applications of statistical hypothesis testing and so there is a large theory of classical statistics that can be applied. Theoretical properties of the test statistic under the null hypothesis are studied. An extension to trios of individuals has been carried out. The methods are exemplified using simulations and a real dataset of 27 Spanish Romani individuals. PMID:26509786

  15. A comparison between gradient descent and stochastic approaches for parameter optimization of a sea ice model

    NASA Astrophysics Data System (ADS)

    Sumata, H.; Kauker, F.; Gerdes, R.; Köberle, C.; Karcher, M.

    2013-07-01

    Two types of optimization methods were applied to a parameter optimization problem in a coupled ocean-sea ice model of the Arctic, and applicability and efficiency of the respective methods were examined. One optimization utilizes a finite difference (FD) method based on a traditional gradient descent approach, while the other adopts a micro-genetic algorithm (μGA) as an example of a stochastic approach. The optimizations were performed by minimizing a cost function composed of model-data misfit of ice concentration, ice drift velocity and ice thickness. A series of optimizations were conducted that differ in the model formulation ("smoothed code" versus standard code) with respect to the FD method and in the population size and number of possibilities with respect to the μGA method. The FD method fails to estimate optimal parameters due to the ill-shaped nature of the cost function caused by the strong non-linearity of the system, whereas the genetic algorithms can effectively estimate near optimal parameters. The results of the study indicate that the sophisticated stochastic approach (μGA) is of practical use for parameter optimization of a coupled ocean-sea ice model with a medium-sized horizontal resolution of 50 km × 50 km as used in this study.

  16. Joint Inference of Identity by Descent Along Multiple Chromosomes from Population Samples

    PubMed Central

    Zheng, Chaozhi; Kuhner, Mary K.

    2014-01-01

    Abstract There has been much interest in detecting genomic identity by descent (IBD) segments from modern dense genetic marker data and in using them to identify human disease susceptibility loci. Here we present a novel Bayesian framework using Markov chain Monte Carlo (MCMC) realizations to jointly infer IBD states among multiple individuals not known to be related, together with the allelic typing error rate and the IBD process parameters. The data are phased single nucleotide polymorphism (SNP) haplotypes. We model changes in latent IBD state along homologous chromosomes by a continuous time Markov model having the Ewens sampling formula as its stationary distribution. We show by simulation that this model for the IBD process fits quite well with the coalescent predictions. Using simulation data sets of 40 haplotypes over regions of 1 and 10 million base pairs (Mbp), we show that the jointly estimated IBD states are very close to the true values, although the presence of linkage disequilibrium decreases the accuracy. We also present comparisons with the ibd_haplo program, which estimates IBD among sets of four haplotypes. Our new IBD detection method focuses on the scale between genome-wide methods using simple IBD models and complex coalescent-based methods that are limited to short genome segments. At the scale of a few Mbp, our approach offers potentially more power for fine-scale IBD association mapping. PMID:24606562

  17. Identity by Descent: Variation in Meiosis, Across Genomes, and in Populations

    PubMed Central

    Thompson, Elizabeth A.

    2013-01-01

    Gene identity by descent (IBD) is a fundamental concept that underlies genetically mediated similarities among relatives. Gene IBD is traced through ancestral meioses and is defined relative to founders of a pedigree, or to some time point or mutational origin in the coalescent of a set of extant genes in a population. The random process underlying changes in the patterns of IBD across the genome is recombination, so the natural context for defining IBD is the ancestral recombination graph (ARG), which specifies the complete ancestry of a collection of chromosomes. The ARG determines both the sequence of coalescent ancestries across the chromosome and the extant segments of DNA descending unbroken by recombination from their most recent common ancestor (MRCA). DNA segments IBD from a recent common ancestor have high probability of being of the same allelic type. Non-IBD DNA is modeled as of independent allelic type, but the population frame of reference for defining allelic independence can vary. Whether of IBD, allelic similarity, or phenotypic covariance, comparisons may be made to other genomic regions of the same gametes, or to the same genomic regions in other sets of gametes or diploid individuals. In this review, I present IBD as the framework connecting evolutionary and coalescent theory with the analysis of genetic data observed on individuals. I focus on the high variance of the processes that determine IBD, its changes across the genome, and its impact on observable data. PMID:23733848

  18. Lasso logistic regression, GSoft and the cyclic coordinate descent algorithm: application to gene expression data.

    PubMed

    Garcia-Magariños, Manuel; Antoniadis, Anestis; Cao, Ricardo; Gonzãlez-Manteiga, Wenceslao

    2010-01-01

    Statistical methods generating sparse models are of great value in the gene expression field, where the number of covariates (genes) under study moves about the thousands while the sample sizes seldom reach a hundred of individuals. For phenotype classification, we propose different lasso logistic regression approaches with specific penalizations for each gene. These methods are based on a generalized soft-threshold (GSoft) estimator. We also show that a recent algorithm for convex optimization, namely, the cyclic coordinate descent (CCD) algorithm, provides with a way to solve the optimization problem significantly faster than with other competing methods. Viewing GSoft as an iterative thresholding procedure allows us to get the asymptotic properties of the resulting estimates in a straightforward manner. Results are obtained for simulated and real data. The leukemia and colon datasets are commonly used to evaluate new statistical approaches, so they come in useful to establish comparisons with similar methods. Furthermore, biological meaning is extracted from the leukemia results, and compared with previous studies. In summary, the approaches presented here give rise to sparse, interpretable models that are competitive with similar methods developed in the field.

  19. Memristor-based multilayer neural networks with online gradient descent training.

    PubMed

    Soudry, Daniel; Di Castro, Dotan; Gal, Asaf; Kolodny, Avinoam; Kvatinsky, Shahar

    2015-10-01

    Learning in multilayer neural networks (MNNs) relies on continuous updating of large matrices of synaptic weights by local rules. Such locality can be exploited for massive parallelism when implementing MNNs in hardware. However, these update rules require a multiply and accumulate operation for each synaptic weight, which is challenging to implement compactly using CMOS. In this paper, a method for performing these update operations simultaneously (incremental outer products) using memristor-based arrays is proposed. The method is based on the fact that, approximately, given a voltage pulse, the conductivity of a memristor will increment proportionally to the pulse duration multiplied by the pulse magnitude if the increment is sufficiently small. The proposed method uses a synaptic circuit composed of a small number of components per synapse: one memristor and two CMOS transistors. This circuit is expected to consume between 2% and 8% of the area and static power of previous CMOS-only hardware alternatives. Such a circuit can compactly implement hardware MNNs trainable by scalable algorithms based on online gradient descent (e.g., backpropagation). The utility and robustness of the proposed memristor-based circuit are demonstrated on standard supervised learning tasks.

  20. Low Cost Entry, Descent, and Landing (EDL) Instrumentation for Planetary Missions

    NASA Technical Reports Server (NTRS)

    Hwang, H. H.; Munk, M. M.; Dillman, R. A.; Mahzari, M.; Swanson, G. T.; White, T. R.

    2016-01-01

    Missions that involve traversing through a planetary atmosphere are unique opportunities that require elements of entry, descent, and landing (EDL). Many aspects of the EDL sequence are qualified using analysis and simulation due to the inability to conduct appropriate ground tests, however validating flight data are often lacking, especially for missions not involving Earth re-entry. NASA has made strategic decisions to collect EDL flight data in order to improve future mission designs. For example, MEDLI1 and EFT-1 gathered hypersonic pressure and in-depth temperature data in the thermal protection system (TPS). However, the ability to collect EDL flight data from the smaller competed missions, such as Discovery and New Frontiers, has been limited in part due to the Principal Investigator-managed cost-caps (PIMCC). The recent NASA decision to consider EDL instrumentation earlier in the mission design cycle led to the inclusion of a requirement in the Discovery 2014 Announcement of Opportunity which requires all missions that involve EDL to include an Engineering Science Investigation (ESI).2 The ESI would involve sensors for aerothermal environment and TPS; atmosphere, aerodynamics, and flight dynamics; atmospheric decelerator; and/or vehicle structure.3 The ESI activity would be funded outside of the PIMCC.

  1. Identification of 15 genetic loci associated with risk of major depression in individuals of European descent.

    PubMed

    Hyde, Craig L; Nagle, Michael W; Tian, Chao; Chen, Xing; Paciga, Sara A; Wendland, Jens R; Tung, Joyce Y; Hinds, David A; Perlis, Roy H; Winslow, Ashley R

    2016-09-01

    Despite strong evidence supporting the heritability of major depressive disorder (MDD), previous genome-wide studies were unable to identify risk loci among individuals of European descent. We used self-report data from 75,607 individuals reporting clinical diagnosis of depression and 231,747 individuals reporting no history of depression through 23andMe and carried out meta-analysis of these results with published MDD genome-wide association study results. We identified five independent variants from four regions associated with self-report of clinical diagnosis or treatment for depression. Loci with a P value <1.0 × 10(-5) in the meta-analysis were further analyzed in a replication data set (45,773 cases and 106,354 controls) from 23andMe. A total of 17 independent SNPs from 15 regions reached genome-wide significance after joint analysis over all three data sets. Some of these loci were also implicated in genome-wide association studies of related psychiatric traits. These studies provide evidence for large-scale consumer genomic data as a powerful and efficient complement to data collected from traditional means of ascertainment for neuropsychiatric disease genomics.

  2. Cognitive phylogenies, the Darwinian logic of descent, and the inadequacy of cladistic thinking.

    PubMed

    Theofanopoulou, Constantina; Boeckx, Cedric

    2015-01-01

    There has been a reappraisal of phylogenetic issues in cognitive science, as reconstructing cognitive phylogenies has been considered a key for unveiling the cognitive novelties that set the stage for what makes humans special. In our opinion, the studies made until now have approached cognitive phylogenies in a non-optimal way, and we wish to both highlight their problems, drawing on recent considerations in philosophy of biology. The inadequacy of current visions on cognitive phylogenies stems from the influence of the traditional "linear cladograms," according to which every seemingly new or more sophisticated feature of a cognitive mechanism, viewed as a novelty, is represented as a node on top of the old and shared elements. We claim that this kind of cladograms does not succeed in depicting the complexity with which traits are distributed across species and, furthermore, that the labels of the nodes of these traditional representational systems fail to capture the "tinkering" nature of evolution. We argue that if we are to conceive of cognitive mechanisms in a multi-dimensional, bottom-up perspective, in accordance with the Darwinian logic of descent, we should rather focus on decomposing these mechanisms into lower-level, generic functions, which have the additional advantage of being implementable in neural matter, which ultimately produces cognition. Doing so renders current constructions of cognitive phylogenies otiose.

  3. Cognitive phylogenies, the Darwinian logic of descent, and the inadequacy of cladistic thinking

    PubMed Central

    Theofanopoulou, Constantina; Boeckx, Cedric

    2015-01-01

    There has been a reappraisal of phylogenetic issues in cognitive science, as reconstructing cognitive phylogenies has been considered a key for unveiling the cognitive novelties that set the stage for what makes humans special. In our opinion, the studies made until now have approached cognitive phylogenies in a non-optimal way, and we wish to both highlight their problems, drawing on recent considerations in philosophy of biology. The inadequacy of current visions on cognitive phylogenies stems from the influence of the traditional “linear cladograms,” according to which every seemingly new or more sophisticated feature of a cognitive mechanism, viewed as a novelty, is represented as a node on top of the old and shared elements. We claim that this kind of cladograms does not succeed in depicting the complexity with which traits are distributed across species and, furthermore, that the labels of the nodes of these traditional representational systems fail to capture the “tinkering” nature of evolution. We argue that if we are to conceive of cognitive mechanisms in a multi-dimensional, bottom-up perspective, in accordance with the Darwinian logic of descent, we should rather focus on decomposing these mechanisms into lower-level, generic functions, which have the additional advantage of being implementable in neural matter, which ultimately produces cognition. Doing so renders current constructions of cognitive phylogenies otiose. PMID:26528479

  4. Altair Navigation During Trans-Lunar Cruise, Lunar Orbit, Descent and Landing

    NASA Technical Reports Server (NTRS)

    Ely, Todd A.; Heyne, Martin; Riedel, Joseph E.

    2010-01-01

    The Altair lunar lander navigation system is driven by a set of requirements that not only specify a need to land within 100 m of a designated spot on the Moon, but also be capable of a safe return to an orbiting Orion capsule in the event of loss of Earth ground support. These requirements lead to the need for a robust and capable on-board navigation system that works in conjunction with an Earth ground navigation system that uses primarily ground-based radiometric tracking. The resulting system relies heavily on combining a multiplicity of data types including navigation state updates from the ground based navigation system, passive optical imaging from a gimbaled camera, a stable inertial measurement unit, and a capable radar altimeter and velocimeter. The focus of this paper is on navigation performance during the trans-lunar cruise, lunar orbit, and descent/landing mission phases with the goal of characterizing knowledge and delivery errors to key mission events, bound the statistical delta V costs for executing the mission, as well as the determine the landing dispersions due to navigation. This study examines the nominal performance that can be obtained using the current best estimate of the vehicle, sensor, and environment models. Performance of the system under a variety sensor outages and parametric trades is also examined.

  5. The role of the gubernaculum in the descent and undescent of the testis

    PubMed Central

    Hutson, John M.; Nation, T.; Balic, A.; Southwell, B. R.

    2009-01-01

    Testicular descent to the scrotum involves complex anatomical rearrangements and hormonal regulation. The gubernaculum remains the key structure, undergoing the ‘swelling reaction’ in the transabdominal phase, and actively migrating out of the abdominal wall to the scrotum in the inguinoscrotal phase. Insulin-like hormone 3 (Insl3) is the primary regulator of the first phase, possibly augmented by Müllerian inhibiting substance/anitmüllerian hormone (MIS/AMH), and regression of the cranial suspensory ligament by testosterone. The inguinoscrotal phase is controlled by androgens acting both directly on the gubernaculum and indirectly via the genitofemoral nerve, and release of calcitonin gene-related peptide from its sensory fibres. Outgrowth of the gubernaculum and elongation to the scrotum has many similarities to an embryonic limb bud. Cryptorchidism occurs because of both failure of migration congenitally, and failure of elongation of the spermatic cord postnatally. Germ cell development postnatally is disturbed in congenital cryptorchidism, but our current understanding of germ cell biology suggests that early orchidopexy, around 6 months of age, should provide a significant improvement in prognosis compared with a previous generation. Hormone treatment is not currently recommended. Acquired cryptorchid testes may need orchidopexy once they no longer reach the scrotum, although this remains controversial. PMID:21789060

  6. Risk-Constrained Dynamic Programming for Optimal Mars Entry, Descent, and Landing

    NASA Technical Reports Server (NTRS)

    Ono, Masahiro; Kuwata, Yoshiaki

    2013-01-01

    A chance-constrained dynamic programming algorithm was developed that is capable of making optimal sequential decisions within a user-specified risk bound. This work handles stochastic uncertainties over multiple stages in the CEMAT (Combined EDL-Mobility Analyses Tool) framework. It was demonstrated by a simulation of Mars entry, descent, and landing (EDL) using real landscape data obtained from the Mars Reconnaissance Orbiter. Although standard dynamic programming (DP) provides a general framework for optimal sequential decisionmaking under uncertainty, it typically achieves risk aversion by imposing an arbitrary penalty on failure states. Such a penalty-based approach cannot explicitly bound the probability of mission failure. A key idea behind the new approach is called risk allocation, which decomposes a joint chance constraint into a set of individual chance constraints and distributes risk over them. The joint chance constraint was reformulated into a constraint on an expectation over a sum of an indicator function, which can be incorporated into the cost function by dualizing the optimization problem. As a result, the chance-constraint optimization problem can be turned into an unconstrained optimization over a Lagrangian, which can be solved efficiently using a standard DP approach.

  7. Assessment of environments for Mars Science Laboratory entry, descent, and surface operations

    USGS Publications Warehouse

    Vasavada, Ashwin R.; Chen, Allen; Barnes, Jeffrey R.; Burkhart, P. Daniel; Cantor, Bruce A.; Dwyer-Cianciolo, Alicia M.; Fergason, Robini L.; Hinson, David P.; Justh, Hilary L.; Kass, David M.; Lewis, Stephen R.; Mischna, Michael A.; Murphy, James R.; Rafkin, Scot C.R.; Tyler, Daniel; Withers, Paul G.

    2012-01-01

    The Mars Science Laboratory mission aims to land a car-sized rover on Mars' surface and operate it for at least one Mars year in order to assess whether its field area was ever capable of supporting microbial life. Here we describe the approach used to identify, characterize, and assess environmental risks to the landing and rover surface operations. Novel entry, descent, and landing approaches will be used to accurately deliver the 900-kg rover, including the ability to sense and "fly out" deviations from a best-estimate atmospheric state. A joint engineering and science team developed methods to estimate the range of potential atmospheric states at the time of arrival and to quantitatively assess the spacecraft's performance and risk given its particular sensitivities to atmospheric conditions. Numerical models are used to calculate the atmospheric parameters, with observations used to define model cases, tune model parameters, and validate results. This joint program has resulted in a spacecraft capable of accessing, with minimal risk, the four finalist sites chosen for their scientific merit. The capability to operate the landed rover over the latitude range of candidate landing sites, and for all seasons, was verified against an analysis of surface environmental conditions described here. These results, from orbital and model data sets, also drive engineering simulations of the rover's thermal state that are used to plan surface operations.

  8. PRIMUS: Rapid Reconstruction of Pedigrees from Genome-wide Estimates of Identity by Descent

    PubMed Central

    Staples, Jeffrey; Qiao, Dandi; Cho, Michael H.; Silverman, Edwin K.; Nickerson, Deborah A.; Below, Jennifer E.

    2014-01-01

    Understanding and correctly utilizing relatedness among samples is essential for genetic analysis; however, managing sample records and pedigrees can often be error prone and incomplete. Data sets ascertained by random sampling often harbor cryptic relatedness that can be leveraged in genetic analyses for maximizing power. We have developed a method that uses genome-wide estimates of pairwise identity by descent to identify families and quickly reconstruct and score all possible pedigrees that fit the genetic data by using up to third-degree relatives, and we have included it in the software package PRIMUS (Pedigree Reconstruction and Identification of the Maximally Unrelated Set). Here, we validate its performance on simulated, clinical, and HapMap pedigrees. Among these samples, we demonstrate that PRIMUS can verify reported pedigree structures and identify cryptic relationships. Finally, we show that PRIMUS reconstructed pedigrees, all of which were previously unknown, for 203 families from a cohort collected in Starr County, TX (1,890 samples). PMID:25439724

  9. PRIMUS: rapid reconstruction of pedigrees from genome-wide estimates of identity by descent.

    PubMed

    Staples, Jeffrey; Qiao, Dandi; Cho, Michael H; Silverman, Edwin K; Nickerson, Deborah A; Below, Jennifer E

    2014-11-01

    Understanding and correctly utilizing relatedness among samples is essential for genetic analysis; however, managing sample records and pedigrees can often be error prone and incomplete. Data sets ascertained by random sampling often harbor cryptic relatedness that can be leveraged in genetic analyses for maximizing power. We have developed a method that uses genome-wide estimates of pairwise identity by descent to identify families and quickly reconstruct and score all possible pedigrees that fit the genetic data by using up to third-degree relatives, and we have included it in the software package PRIMUS (Pedigree Reconstruction and Identification of the Maximally Unrelated Set). Here, we validate its performance on simulated, clinical, and HapMap pedigrees. Among these samples, we demonstrate that PRIMUS can verify reported pedigree structures and identify cryptic relationships. Finally, we show that PRIMUS reconstructed pedigrees, all of which were previously unknown, for 203 families from a cohort collected in Starr County, TX (1,890 samples). PMID:25439724

  10. Genome-wide patterns of identity-by-descent sharing in the French Canadian founder population.

    PubMed

    Gauvin, Héloïse; Moreau, Claudia; Lefebvre, Jean-François; Laprise, Catherine; Vézina, Hélène; Labuda, Damian; Roy-Gagnon, Marie-Hélène

    2014-06-01

    In genetics the ability to accurately describe the familial relationships among a group of individuals can be very useful. Recent statistical tools succeeded in assessing the degree of relatedness up to 6-7 generations with good power using dense genome-wide single-nucleotide polymorphism data to estimate the extent of identity-by-descent (IBD) sharing. It is therefore important to describe genome-wide patterns of IBD sharing for more remote and complex relatedness between individuals, such as that observed in a founder population like Quebec, Canada. Taking advantage of the extended genealogical records of the French Canadian founder population, we first compared different tools to identify regions of IBD in order to best describe genome-wide IBD sharing and its correlation with genealogical characteristics. Results showed that the extent of IBD sharing identified with FastIBD correlates best with relatedness measured using genealogical data. Total length of IBD sharing explained 85% of the genealogical kinship's variance. In addition, we observed significantly higher sharing in pairs of individuals with at least one inbred ancestor compared with those without any. Furthermore, patterns of IBD sharing and average sharing were different across regional populations, consistent with the settlement history of Quebec. Our results suggest that, as expected, the complex relatedness present in founder populations is reflected in patterns of IBD sharing. Using these patterns, it is thus possible to gain insight on the types of distant relationships in a sample from a founder population like Quebec.

  11. Entry, Descent, and Landing Operations Analysis for the Genesis Entry Capsule

    NASA Technical Reports Server (NTRS)

    Desai, Prasun N.; Lyons, Daniel T.

    2007-01-01

    On September 8, 2004, the Genesis spacecraft returned to Earth after spending 29 months about the sun-Earth libration point (L1) collecting solar wind particles. Four hours prior to Earth arrival, the sample return capsule containing the samples was released for entry and subsequent landing at the Utah Test and Training Range. This paper provides an overview of the entry, descent, and landing trajectory analysis that was performed during the mission operations phase leading up to final approach to Earth. The final orbit determination solution produced an inertial entry flight-path angle of -8.002 deg (which was the desired nominal value) with a 3-sigma error of +/-0.0274 deg (a third of the requirement). The operations effort accurately delivered the entry capsule to the desired landing site. The final landing location was 8.3 km from the target, and was well within the allowable landing area. Overall, the Earth approach operation procedures worked well and there were no issues (logistically or performance based) that arose. As a result, the process of targeting a capsule from deep space and accurately landing it on Earth was successfully demonstrated.

  12. Parachute Models Used in the Mars Science Laboratory Entry, Descent, and Landing Simulation

    NASA Technical Reports Server (NTRS)

    Cruz, Juan R.; Way, David W.; Shidner, Jeremy D.; Davis, Jody L.; Powell, Richard W.; Kipp, Devin M.; Adams, Douglas S.; Witkowski, Al; Kandis, Mike

    2013-01-01

    An end-to-end simulation of the Mars Science Laboratory (MSL) entry, descent, and landing (EDL) sequence was created at the NASA Langley Research Center using the Program to Optimize Simulated Trajectories II (POST2). This simulation is capable of providing numerous MSL system and flight software responses, including Monte Carlo-derived statistics of these responses. The MSL POST2 simulation includes models of EDL system elements, including those related to the parachute system. Among these there are models for the parachute geometry, mass properties, deployment, inflation, opening force, area oscillations, aerodynamic coefficients, apparent mass, interaction with the main landing engines, and off-loading. These models were kept as simple as possible, considering the overall objectives of the simulation. The main purpose of this paper is to describe these parachute system models to the extent necessary to understand how they work and some of their limitations. A list of lessons learned during the development of the models and simulation is provided. Future improvements to the parachute system models are proposed.

  13. A calibrated chronology of biochemistry reveals a stem line of descent responsible for planetary biodiversity.

    PubMed

    Caetano-Anollés, Gustavo; Mittenthal, Jay E; Caetano-Anollés, Derek; Kim, Kyung Mo

    2014-01-01

    Time-calibrated phylogenomic trees of protein domain structure produce powerful chronologies describing the evolution of biochemistry and life. These timetrees are built from a genomic census of millions of encoded proteins using models of nested accumulation of molecules in evolving proteomes. Here we show that a primordial stem line of descent, a propagating series of pluripotent cellular entities, populates the deeper branches of the timetrees. The stem line produced for the first time cellular grades ~2.9 billion years (Gy)-ago, which slowly turned into lineages of superkingdom Archaea. Prompted by the rise of planetary oxygen and aerobic metabolism, the stem line also produced bacterial and eukaryal lineages. Superkingdom-specific domain repertoires emerged ~2.1 Gy-ago delimiting fully diversified Bacteria. Repertoires specific to Eukarya and Archaea appeared 300 millions years later. Results reconcile reductive evolutionary processes leading to the early emergence of Archaea to superkingdom-specific innovations compatible with a tree of life rooted in Bacteria. PMID:25309572

  14. Identification of 15 genetic loci associated with risk of major depression in individuals of European descent.

    PubMed

    Hyde, Craig L; Nagle, Michael W; Tian, Chao; Chen, Xing; Paciga, Sara A; Wendland, Jens R; Tung, Joyce Y; Hinds, David A; Perlis, Roy H; Winslow, Ashley R

    2016-09-01

    Despite strong evidence supporting the heritability of major depressive disorder (MDD), previous genome-wide studies were unable to identify risk loci among individuals of European descent. We used self-report data from 75,607 individuals reporting clinical diagnosis of depression and 231,747 individuals reporting no history of depression through 23andMe and carried out meta-analysis of these results with published MDD genome-wide association study results. We identified five independent variants from four regions associated with self-report of clinical diagnosis or treatment for depression. Loci with a P value <1.0 × 10(-5) in the meta-analysis were further analyzed in a replication data set (45,773 cases and 106,354 controls) from 23andMe. A total of 17 independent SNPs from 15 regions reached genome-wide significance after joint analysis over all three data sets. Some of these loci were also implicated in genome-wide association studies of related psychiatric traits. These studies provide evidence for large-scale consumer genomic data as a powerful and efficient complement to data collected from traditional means of ascertainment for neuropsychiatric disease genomics. PMID:27479909

  15. High brightness electron accelerator

    DOEpatents

    Sheffield, Richard L.; Carlsten, Bruce E.; Young, Lloyd M.

    1994-01-01

    A compact high brightness linear accelerator is provided for use, e.g., in a free electron laser. The accelerator has a first plurality of acclerating cavities having end walls with four coupling slots for accelerating electrons to high velocities in the absence of quadrupole fields. A second plurality of cavities receives the high velocity electrons for further acceleration, where each of the second cavities has end walls with two coupling slots for acceleration in the absence of dipole fields. The accelerator also includes a first cavity with an extended length to provide for phase matching the electron beam along the accelerating cavities. A solenoid is provided about the photocathode that emits the electons, where the solenoid is configured to provide a substantially uniform magnetic field over the photocathode surface to minimize emittance of the electons as the electrons enter the first cavity.

  16. Fiber Accelerating Structures

    SciTech Connect

    Hammond, Andrew P.; /Reed Coll. /SLAC

    2010-08-25

    One of the options for future particle accelerators are photonic band gap (PBG) fiber accelerators. PBG fibers are specially designed optical fibers that use lasers to excite an electric field that is used to accelerate electrons. To improve PBG accelerators, the basic parameters of the fiber were tested to maximize defect size and acceleration. Using the program CUDOS, several accelerating modes were found that maximized these parameters for several wavelengths. The design of multiple defects, similar to having closely bound fibers, was studied to find possible coupling or the change of modes. The amount of coupling was found to be dependent on distance separated. For certain distances accelerating coupled modes were found and examined. In addition, several non-periodic fiber structures were examined using CUDOS. The non-periodic fibers produced several interesting results and promised more modes given time to study them in more detail.

  17. ACOG Committee Opinion No. 442: Preconception and prenatal carrier screening for genetic diseases in individuals of Eastern European Jewish descent.

    PubMed

    2009-10-01

    Certain autosomal recessive disease conditions are more prevalent in individuals of Eastern European Jewish (Ashkenazi) descent. Previously, the American College of Obstetricians and Gynecologists recommended that individuals of Eastern European Jewish ancestry be offered carrier screening for Tay-Sachs disease, Canavan disease, and cystic fibrosis as part of routine obstetric care. Based on the criteria used to justify offering carrier screening for Tay-Sachs disease, Canavan disease, and cystic fibrosis, the American College of Obstetricians and Gynecologists' Committee on Genetics recommends that couples of Ashkenazi Jewish ancestry also should be offered carrier screening for familial dysautonomia. Individuals of Ashkenazi Jewish descent may inquire about the availability of carrier screening for other disorders. Carrier screening is available for mucolipidosis IV, Niemann-Pick disease type A, Fanconi anemia group C, Bloom syndrome, and Gaucher disease. PMID:19888064

  18. Attitude Issues on the Huygens Probe: Balloon Dropped Mock up Role in Determining Reconstruction Strategies During Descent in Lower Atmosphere

    NASA Technical Reports Server (NTRS)

    Bettanini, C.; Angrilli, F.

    2005-01-01

    As part of the collaboration with Italian Space Agency on HASI instrument for Huygens mission, University of Padova has been conducting since 2001 scientific activity on Stratospheric Balloon Launches from the Trapani base in Sicily. The most recent boomerang flight in July 2003 has successfully flown a mock up of the Huygens probe hosting spares of flight scientific units and extra housekeeping and scientific sensors on a parachuted descent from 33 kilometre altitude. This work presents the studies conducted on attitude reconstruction of the probe, as well as the utilisation of iterative extended Kalman filtering in investigating vanes induced spin rate and in providing a baseline for the performance evaluation of Huygens accelerometers operations. Finally some possible contributions on the reconstruction of the lower part of Titan descent for Huygens probe are suggested based on the confrontation of sensor data for 2003 flight.

  19. Acceleration in astrophysics

    SciTech Connect

    Colgate, S.A.

    1993-12-31

    The origin of cosmic rays and applicable laboratory experiments are discussed. Some of the problems of shock acceleration for the production of cosmic rays are discussed in the context of astrophysical conditions. These are: The presumed unique explanation of the power law spectrum is shown instead to be a universal property of all lossy accelerators; the extraordinary isotropy of cosmic rays and the limited diffusion distances implied by supernova induced shock acceleration requires a more frequent and space-filling source than supernovae; the near perfect adiabaticity of strong hydromagnetic turbulence necessary for reflecting the accelerated particles each doubling in energy roughly 10{sup 5} to {sup 6} scatterings with negligible energy loss seems most unlikely; the evidence for acceleration due to quasi-parallel heliosphere shocks is weak. There is small evidence for the expected strong hydromagnetic turbulence, and instead, only a small number of particles accelerate after only a few shock traversals; the acceleration of electrons in the same collisionless shock that accelerates ions is difficult to reconcile with the theoretical picture of strong hydromagnetic turbulence that reflects the ions. The hydromagnetic turbulence will appear adiabatic to the electrons at their much higher Larmor frequency and so the electrons should not be scattered incoherently as they must be for acceleration. Therefore the electrons must be accelerated by a different mechanism. This is unsatisfactory, because wherever electrons are accelerated these sites, observed in radio emission, may accelerate ions more favorably. The acceleration is coherent provided the reconnection is coherent, in which case the total flux, as for example of collimated radio sources, predicts single charge accelerated energies much greater than observed.

  20. Identity-by-descent filtering of exome sequence data identifies PIGV mutations in hyperphosphatasia mental retardation syndrome.

    PubMed

    Krawitz, Peter M; Schweiger, Michal R; Rödelsperger, Christian; Marcelis, Carlo; Kölsch, Uwe; Meisel, Christian; Stephani, Friederike; Kinoshita, Taroh; Murakami, Yoshiko; Bauer, Sebastian; Isau, Melanie; Fischer, Axel; Dahl, Andreas; Kerick, Martin; Hecht, Jochen; Köhler, Sebastian; Jäger, Marten; Grünhagen, Johannes; de Condor, Birgit Jonske; Doelken, Sandra; Brunner, Han G; Meinecke, Peter; Passarge, Eberhard; Thompson, Miles D; Cole, David E; Horn, Denise; Roscioli, Tony; Mundlos, Stefan; Robinson, Peter N

    2010-10-01

    Hyperphosphatasia mental retardation (HPMR) syndrome is an autosomal recessive form of mental retardation with distinct facial features and elevated serum alkaline phosphatase. We performed whole-exome sequencing in three siblings of a nonconsanguineous union with HPMR and performed computational inference of regions identical by descent in all siblings to establish PIGV, encoding a member of the GPI-anchor biosynthesis pathway, as the gene mutated in HPMR. We identified homozygous or compound heterozygous mutations in PIGV in three additional families.

  1. Regolith-Derived Heat Shield for Planetary Body Entry and Descent System with In-Situ Fabrication

    NASA Technical Reports Server (NTRS)

    Hogue, Michael D.; Mueller, Robert P.; Sibille, Laurent; Hintze, Paul E.; Rasky, Daniel J.

    2012-01-01

    High-mass planetary surface access is one of NASA's Grand Challenges involving entry, descent, and landing (EDL). Heat shields fabricated in-situ can provide a thermal protection system for spacecraft that routinely enter a planetary atmosphere. Fabricating the heat shield from extraterrestrial regolith will avoid the costs of launching the heat shield mass from Earth. This project will investigate three methods to fabricate heat shield using extraterrestrial regolith.

  2. Regolith-Derived Heat Shield for Planetary Body Entry and Descent System with In-Situ Fabrication

    NASA Technical Reports Server (NTRS)

    Hogue, Michael D.; Mueller, Robert P.; Sibille, Laurent; Hintze, Paul E.; Rasky, Daniel J.

    2012-01-01

    High-mass planetary surface access is one of NASA's Grand Challenges involving entry, descent, and landing (EDL). Heat shields fabricated in-situ can provide a thermal protection system for spacecraft that routinely enter a planetary atmosphere. Fabricating the heat shield from extraterrestrial regolith will avoid the costs of launching the heat shield mass from Earth. This project investigated three methods to fabricate heat shield using extraterrestrial regolith and performed preliminary work on mission architectures.

  3. Computer program development and user's manual for program PARACH. [to investigate parachute spent solid rocket booster during terminal descent

    NASA Technical Reports Server (NTRS)

    Murphree, H. I.

    1979-01-01

    A user's manual is provided for program PARACH, a FORTRAN digital computer program operational on the Univac 1108. A description of the program and operating instructions for it are included. Program PARACH is used to study the interaction dynamics of a parachute and its payload during terminal descent. Operating instructions, required input data, program options and limitations, and output data are described. Subroutines used in this program are also listed and explained.

  4. Identity-by-descent filtering of exome sequence data identifies PIGV mutations in hyperphosphatasia mental retardation syndrome.

    PubMed

    Krawitz, Peter M; Schweiger, Michal R; Rödelsperger, Christian; Marcelis, Carlo; Kölsch, Uwe; Meisel, Christian; Stephani, Friederike; Kinoshita, Taroh; Murakami, Yoshiko; Bauer, Sebastian; Isau, Melanie; Fischer, Axel; Dahl, Andreas; Kerick, Martin; Hecht, Jochen; Köhler, Sebastian; Jäger, Marten; Grünhagen, Johannes; de Condor, Birgit Jonske; Doelken, Sandra; Brunner, Han G; Meinecke, Peter; Passarge, Eberhard; Thompson, Miles D; Cole, David E; Horn, Denise; Roscioli, Tony; Mundlos, Stefan; Robinson, Peter N

    2010-10-01

    Hyperphosphatasia mental retardation (HPMR) syndrome is an autosomal recessive form of mental retardation with distinct facial features and elevated serum alkaline phosphatase. We performed whole-exome sequencing in three siblings of a nonconsanguineous union with HPMR and performed computational inference of regions identical by descent in all siblings to establish PIGV, encoding a member of the GPI-anchor biosynthesis pathway, as the gene mutated in HPMR. We identified homozygous or compound heterozygous mutations in PIGV in three additional families. PMID:20802478

  5. "Curiously parallel": analogies of language and race in Darwin's Descent of man. A reply to Gregory Radick.

    PubMed

    Alter, Stephen G

    2008-09-01

    In the second chapter of The descent of man (1871), Charles Darwin interrupted his discussion of the evolutionary origins of language to describe ten ways in which the formation of languages and of biological species were 'curiously' similar. I argue that these comparisons served mainly as analogies in which linguistic processes stood for aspects of biological evolution. Darwin used these analogies to recapitulate themes from On the origin of species (1859), including common descent, genealogical classification, the struggle for existence, and natural selection, among others. Skeptical of this interpretation, Gregory Radick sees the naturalistic account of language formation in the Descent comparisons as reinforcing Darwin's idea that languages and the races of mankind have both undergone progressive development. (The opposite view was that modern-day primitive peoples had degenerated from an originally civilized condition.) Yet the details of Darwin's language-species comparisons, as well as the polemical context in which they appear, show that they were not aimed at so limited a function. Rather, they addressed issues related to species transmutation in general. PMID:18761287

  6. Development and preliminary evaluation of a behavioural HIV prevention program for teenage girls of Latino descent in the USA

    PubMed Central

    Davidson, Tatiana M.; Lopez, Cristina M.; Saulson, Raelle; Borkman, April L.; Soltis, Kathryn; Ruggiero, Kenneth J.; de Arellano, Michael; Wingood, Gina M.; DiClemente, Ralph J.; Danielson, Carla Kmett

    2014-01-01

    National data suggests that teenage girls of Latino descent in the USA are disproportionately affected by HIV with the rate of new infections being approximately 4 times higher compared to White women of comparable age (Centers for Disease Control and Prevention 2013). This paper highlights the need for an effective single-sex HIV prevention program for teenage girls of Latino descent and describes the development and preliminary evaluation of Chicas Healing, Informing, Living and Empowering (CHILE), a culturally-tailored, HIV prevention programme exclusively for teenage girls of Latino descent that was adapted from Sisters Informing, Healing, Living, and Empowering (SiHLE), an evidence-based HIV prevention program that is culturally tailored for African American young women. Theatre testing, a pre-testing methodology to assess consumer response to a demonstration of a product, was utilised to evaluate the relevance and utility of the HIV program as well as opportunities for the integration of cultural constructs. Future directions for the evaluation of CHILE are discussed. PMID:24697607

  7. Gender difference in older adult's utilization of gravitational and ground reaction force in regulation of angular momentum during stair descent.

    PubMed

    Singhal, Kunal; Kim, Jemin; Casebolt, Jeffrey; Lee, Sangwoo; Han, Ki-Hoon; Kwon, Young-Hoo

    2015-06-01

    Angular momentum of the body is a highly controlled quantity signifying stability, therefore, it is essential to understand its regulation during stair descent. The purpose of this study was to investigate how older adults use gravity and ground reaction force to regulate the angular momentum of the body during stair descent. A total of 28 participants (12 male and 16 female; 68.5 years and 69.0 years of mean age respectively) performed stair descent from a level walk in a step-over-step manner at a self-selected speed over a custom made three-step staircase with embedded force plates. Kinematic and force data were used to calculate angular momentum, gravitational moment, and ground reaction force moment about the stance foot center of pressure. Women show a significantly greater change in normalized angular momentum (0.92Nms/Kgm; p=.004) as compared to men (0.45Nms/Kgm). Women produce higher normalized GRF (p=.031) during the double support phase. The angular momentum changes show largest backward regulation for Step 0 and forward regulation for Step 2. This greater difference in overall change in the angular momentum in women may explain their increased risk of fall over the stairs.

  8. "Curiously parallel": analogies of language and race in Darwin's Descent of man. A reply to Gregory Radick.

    PubMed

    Alter, Stephen G

    2008-09-01

    In the second chapter of The descent of man (1871), Charles Darwin interrupted his discussion of the evolutionary origins of language to describe ten ways in which the formation of languages and of biological species were 'curiously' similar. I argue that these comparisons served mainly as analogies in which linguistic processes stood for aspects of biological evolution. Darwin used these analogies to recapitulate themes from On the origin of species (1859), including common descent, genealogical classification, the struggle for existence, and natural selection, among others. Skeptical of this interpretation, Gregory Radick sees the naturalistic account of language formation in the Descent comparisons as reinforcing Darwin's idea that languages and the races of mankind have both undergone progressive development. (The opposite view was that modern-day primitive peoples had degenerated from an originally civilized condition.) Yet the details of Darwin's language-species comparisons, as well as the polemical context in which they appear, show that they were not aimed at so limited a function. Rather, they addressed issues related to species transmutation in general.

  9. Design and simulation of a descent controller for strategic four-dimensional aircraft navigation. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Lax, F. M.

    1975-01-01

    A time-controlled navigation system applicable to the descent phase of flight for airline transport aircraft was developed and simulated. The design incorporates the linear discrete-time sampled-data version of the linearized continuous-time system describing the aircraft's aerodynamics. Using optimal linear quadratic control techniques, an optimal deterministic control regulator which is implementable on an airborne computer is designed. The navigation controller assists the pilot in complying with assigned times of arrival along a four-dimensional flight path in the presence of wind disturbances. The strategic air traffic control concept is also described, followed by the design of a strategic control descent path. A strategy for determining possible times of arrival at specified waypoints along the descent path and for generating the corresponding route-time profiles that are within the performance capabilities of the aircraft is presented. Using a mathematical model of the Boeing 707-320B aircraft along with a Boeing 707 cockpit simulator interfaced with an Adage AGT-30 digital computer, a real-time simulation of the complete aircraft aerodynamics was achieved. The strategic four-dimensional navigation controller for longitudinal dynamics was tested on the nonlinear aircraft model in the presence of 15, 30, and 45 knot head-winds. The results indicate that the controller preserved the desired accuracy and precision of a time-controlled aircraft navigation system.

  10. Development and test results of a flight management algorithm for fuel conservative descents in a time-based metered traffic environment

    NASA Technical Reports Server (NTRS)

    Knox, C. E.; Cannon, D. G.

    1980-01-01

    A simple flight management descent algorithm designed to improve the accuracy of delivering an airplane in a fuel-conservative manner to a metering fix at a time designated by air traffic control was developed and flight tested. This algorithm provides a three dimensional path with terminal area time constraints (four dimensional) for an airplane to make an idle thrust, clean configured (landing gear up, flaps zero, and speed brakes retracted) descent to arrive at the metering fix at a predetermined time, altitude, and airspeed. The descent path was calculated for a constant Mach/airspeed schedule from linear approximations of airplane performance with considerations given for gross weight, wind, and nonstandard pressure and temperature effects. The flight management descent algorithm is described. The results of the flight tests flown with the Terminal Configured Vehicle airplane are presented.

  11. A General Method for Solving Systems of Non-Linear Equations

    NASA Technical Reports Server (NTRS)

    Nachtsheim, Philip R.; Deiss, Ron (Technical Monitor)

    1995-01-01

    The method of steepest descent is modified so that accelerated convergence is achieved near a root. It is assumed that the function of interest can be approximated near a root by a quadratic form. An eigenvector of the quadratic form is found by evaluating the function and its gradient at an arbitrary point and another suitably selected point. The terminal point of the eigenvector is chosen to lie on the line segment joining the two points. The terminal point found lies on an axis of the quadratic form. The selection of a suitable step size at this point leads directly to the root in the direction of steepest descent in a single step. Newton's root finding method not infrequently diverges if the starting point is far from the root. However, the current method in these regions merely reverts to the method of steepest descent with an adaptive step size. The current method's performance should match that of the Levenberg-Marquardt root finding method since they both share the ability to converge from a starting point far from the root and both exhibit quadratic convergence near a root. The Levenberg-Marquardt method requires storage for coefficients of linear equations. The current method which does not require the solution of linear equations requires more time for additional function and gradient evaluations. The classic trade off of time for space separates the two methods.

  12. The Dielectric Wall Accelerator

    SciTech Connect

    Caporaso, George J.; Chen, Yu-Jiuan; Sampayan, Stephen E.

    2009-01-01

    The Dielectric Wall Accelerator (DWA), a class of induction accelerators, employs a novel insulating beam tube to impress a longitudinal electric field on a bunch of charged particles. The surface flashover characteristics of this tube may permit the attainment of accelerating gradients on the order of 100 MV/m for accelerating pulses on the order of a nanosecond in duration. A virtual traveling wave of excitation along the tube is produced at any desired speed by controlling the timing of pulse generating modules that supply a tangential electric field to the tube wall. Because of the ability to control the speed of this virtual wave, the accelerator is capable of handling any charge to mass ratio particle; hence it can be used for electrons, protons and any ion. The accelerator architectures, key technologies and development challenges will be described.

  13. Switched matrix accelerator

    SciTech Connect

    Whittum, David H.; Tantawi, Sami G.

    2001-01-01

    We describe a new concept for a microwave circuit functioning as a charged-particle accelerator at mm wavelengths, permitting an accelerating gradient higher than conventional passive circuits can withstand consistent with cyclic fatigue. The device provides acceleration for multiple bunches in parallel channels, and permits a short exposure time for the conducting surface of the accelerating cavities. Our analysis includes scalings based on a smooth transmission line model and a complementary treatment with a coupled-cavity simulation. We also provide an electromagnetic design for the accelerating structure, arriving at rough dimensions for a seven-cell accelerator matched to standard waveguide and suitable for bench tests at low power in air at 91.392 GHz. A critical element in the concept is a fast mm-wave switch suitable for operation at high power, and we present the considerations for implementation in an H-plane tee. We discuss the use of diamond as the photoconductor switch medium.

  14. Switched Matrix Accelerator

    SciTech Connect

    Whittum, David H

    2000-10-04

    We describe a new concept for a microwave circuit functioning as a charged-particle accelerator at mm-wavelengths, permitting an accelerating gradient higher than conventional passive circuits can withstand consistent with cyclic fatigue. The device provides acceleration for multiple bunches in parallel channels, and permits a short exposure time for the conducting surface of the accelerating cavities. Our analysis includes scalings based on a smooth transmission line model and a complementary treatment with a coupled-cavity simulation. We provide also an electromagnetic design for the accelerating structure, arriving at rough dimensions for a seven-cell accelerator matched to standard waveguide and suitable for bench tests at low power in air at 91.392. GHz. A critical element in the concept is a fast mm-wave switch suitable for operation at high-power, and we present the considerations for implementation in an H-plane tee. We discuss the use of diamond as the photoconductor switch medium.

  15. Descent of low-Bond-number liquid-metal diapirs with trailing conduits during core formation

    NASA Astrophysics Data System (ADS)

    Rains, C.; Weeraratne, D. S.

    2012-12-01

    Formation of the early Earth involved violent impacts and meteorite bombardment which partially or fully melted surface materials, facilitating separation of iron metal from silicates. Geochemical constraints on core formation times indicate that this liquid metal must have been transported to the center of the Earth within 30 Ma. Among the mechanisms that have been proposed, metal-silicate plumes resulting from Rayleigh-Taylor instabilities of a liquid-metal pond at the bottom of a magma ocean provide the fastest rates of delivery to the core. Recent studies have shown that these rapidly descending plumes develop trailing conduits that fill with the overlying melted silicate material. However, while large plumes descend quickly, they do not provide enough time or surface area for metal-silicate equilibration to be achieved throughout the mantle. Instead, small metal drops descending in the wake of larger diapirs or in conduits of their own making may have been crucial in the equilibration process that resulted in the excess siderophile mantle abundance. We investigate the instability and descent of liquid-metal drops through a highly viscous layer using three-component laboratory fluid experiments representing the Earth's proto-mantle (layer 2) covered by a magma ocean (layer 1), and a liquid iron pond (layer 3) initially resting at their interface. Silicate materials are represented by dehydrated (layer 2), or diluted (layer 1) glucose and salt solutions. Liquid gallium represents the iron metal phase. We scale our experiments to the Earth's mantle through the use of Bond numbers to characterize drops and diapirs, and a non-dimensional length scale λ, which we define as the ratio of radius to height, to characterize conduits. Previous laboratory work using liquid gallium has investigated high-Bond-number diapirs (B = 13 - 66) and conduits of λ ~ 0.2, analogous to large plumes in the Earth. Here, we focus on low Bond numbers (B ~ 4), and small λ ~ .05 to

  16. Aerodynamic and performance characterization of supersonic retropropulsion for application to planetary entry and descent

    NASA Astrophysics Data System (ADS)

    Korzun, Ashley M.

    The entry, descent, and landing (EDL) systems for the United States' six successful landings on Mars and the 2011 Mars Science Laboratory (MSL) have all relied heavily on extensions of technology developed for the Viking missions of the mid 1970s. Incremental improvements to these technologies, namely rigid 70-deg sphere-cone aeroshells, supersonic disk-gap-band parachutes, and subsonic propulsive terminal descent, have increased payload mass capability to 950 kg (MSL). However, MSL is believed to be near the upper limit for landed mass using a Viking-derived EDL system. To achieve NASA's long-term exploration goals at Mars, technologies are needed that enable more than an order of magnitude increase in landed mass (10s of metric tons), several orders of magnitude increase in landing accuracy (10s or 100s of meters), and landings at higher surface elevations (0+ km). Supersonic deceleration has been identified as a critical deficiency in extending Viking-heritage technologies to high-mass, high-ballistic coefficient systems. As the development and qualification of significantly larger supersonic parachutes is not a viable path forward to increase landed mass capability to 10+ metric tons, alternative approaches must be developed. Supersonic retropropulsion (SRP), or the use of retropropulsive thrust while an entry vehicle is traveling at supersonic conditions, is one such alternative approach. The concept originated in the 1960s, though only recently has interest in SRP resurfaced. While its presence in the historical literature lends some degree of credibility to the concept of using retropropulsion at supersonic conditions, the overall immaturity of supersonic retropropulsion requires additional evaluation of its potential as a decelerator technology for high-mass Mars entry systems, as well as its comparison with alternative decelerators. The supersonic retropropulsion flowfield is typically a complex interaction between highly under-expanded jet flow and the

  17. Anhydrous liquid line of descent of Yamato-980459 and evolution of Martian parental magmas

    NASA Astrophysics Data System (ADS)

    Rapp, Jennifer F.; Draper, David S.; Mercer, Cameron M.

    2013-10-01

    We report the results of nominally anhydrous equilibrium and fractional crystallization experiments on a synthetic Yamato-980459 (Y98) bulk composition at 0.5 GPa. These experiments allow us to test a suggested fractional crystallization model, calculated using MELTS by Symes et al. (), in which a Y98-like initial liquid yielded a magma closely resembling the bulk composition of QUE 94201. Although the two meteorites cannot be cogenetic owing to their age difference, they are thought to represent bona fide magmatic liquids rather than products of crystal accumulation, as are most Martian basaltic meteorites. Hence, understanding possible petrogenetic links between these types of liquids could be revealing about processes of melting and crystallization that formed the range of Martian basalts. We find that Y98 can, in fact, generate a residual liquid closely resembling QUE, but only after a very different crystallization process, and different degree of crystallization, than that modeled using MELTS. In addition, both the identity and sequence of crystallizing phases are very different between model and experiments. Our fractional crystallization experiments do not produce a QUE-like liquid, and the crystallizing phases are an even poorer match to the MELTS-calculated compositions than in the equilibrium runs. However, residual liquids from our experiments define a liquid line of descent that encompasses bulk compositions of parental melts calculated for several Martian basaltic meteorites, suggesting that the known Martian basaltic meteorites had their ultimate origin from the same or very similar source lithologies. These are, in turn, similar to source rocks modeled by previous studies as products of extensive crystallization of an initial Martian magma ocean.

  18. Descent toward the Icehouse: Eocene sea surface cooling inferred from GDGT distributions

    NASA Astrophysics Data System (ADS)

    Inglis, Gordon N.; Farnsworth, Alexander; Lunt, Daniel; Foster, Gavin L.; Hollis, Christopher J.; Pagani, Mark; Jardine, Phillip E.; Pearson, Paul N.; Markwick, Paul; Galsworthy, Amanda M. J.; Raynham, Lauren; Taylor, Kyle. W. R.; Pancost, Richard D.

    2015-07-01

    The TEX86 proxy, based on the distribution of marine isoprenoidal glycerol dialkyl glycerol tetraether lipids (GDGTs), is increasingly used to reconstruct sea surface temperature (SST) during the Eocene epoch (56.0-33.9 Ma). Here we compile published TEX86 records, critically reevaluate them in light of new understandings in TEX86 palaeothermometry, and supplement them with new data in order to evaluate long-term temperature trends in the Eocene. We investigate the effect of archaea other than marine Thaumarchaeota upon TEX86 values using the branched-to-isoprenoid tetraether index (BIT), the abundance of GDGT-0 relative to crenarchaeol (%GDGT-0), and the Methane Index (MI). We also introduce a new ratio, %GDGTRS, which may help identify Red Sea-type GDGT distributions in the geological record. Using the offset between TEX86H and TEX86L (ΔH-L) and the ratio between GDGT-2 and GDGT-3 ([2]/[3]), we evaluate different TEX86 calibrations and present the first integrated SST compilation for the Eocene (55 to 34 Ma). Although the available data are still sparse some geographic trends can now be resolved. In the high latitudes (>55°), there was substantial cooling during the Eocene (~6°C). Our compiled record also indicates tropical cooling of ~2.5°C during the same interval. Using an ensemble of climate model simulations that span the Eocene, our results indicate that only a small percentage (~10%) of the reconstructed temperature change can be ascribed to ocean gateway reorganization or paleogeographic change. Collectively, this indicates that atmospheric carbon dioxide (pCO2) was the likely driver of surface water cooling during the descent toward the icehouse.

  19. Inference of identity by descent in population isolates and optimal sequencing studies

    PubMed Central

    Glodzik, Dominik; Navarro, Pau; Vitart, Veronique; Hayward, Caroline; McQuillan, Ruth; Wild, Sarah H; Dunlop, Malcolm G; Rudan, Igor; Campbell, Harry; Haley, Chris; Wright, Alan F; Wilson, James F; McKeigue, Paul

    2013-01-01

    In an isolated population, individuals are likely to share large genetic regions inherited from common ancestors. Identity by descent (IBD) can be inferred from SNP genotypes, which is useful in a number of applications, including identifying genetic variants influencing complex disease risk, and planning efficient cohort-sequencing strategies. We present ANCHAP – a method for detecting IBD in isolated populations. We compare accuracy of the method against other long-range and local phasing methods, using parent–offspring trios. In our experiments, we show that ANCHAP performs similarly as the other long-range method, but requires an order-of-magnitude less computational resources. A local phasing model is able to achieve similar sensitivity, but only at the cost of higher false discovery rates. In some regions of the genome, the studied individuals share haplotypes particularly often, which hints at the history of the populations studied. We demonstrate the method using SNP genotypes from three isolated island populations, as well as in a cohort of unrelated individuals. In samples from three isolated populations of around 1000 individual each, an average individual shares a haplotype at a genetic locus with 9–12 other individuals, compared with only 1 individual within the non-isolated population. We describe an application of ANCHAP to optimally choose samples in resequencing studies. We find that with sample sizes of 1000 individuals from an isolated population genotyped using a dense SNP array, and with 20% of these individuals sequenced, 65% of sequences of the unsequenced subjects can be partially inferred. PMID:23361219

  20. Human neutrophil alloantigen genotype frequencies among blood donors with Turkish and German descent.

    PubMed

    Hauck, B; Philipp, A; Eckstein, R; Ott, S; Zimmermann, R; Dengler, T; Zingsem, J

    2011-12-01

    Antibodies against the human neutrophil antigens (HNA) are able to stimulate transfusion reactions, autoimmune and neonatal neutropenia. The aim of this study was to determine the HNA allele frequencies in the largest ethnic minority group in Germany in comparison with the German population for predicting the risk of alloimmunization and associated transfusion reactions, as well as the risk of developing neonatal neutropenia for the newborn of racial mixed couples. However, there exists no data about HNA genotype distribution in Turkish population. DNA was isolated from blood samples of 119 German and 118 Turkish blood donors and typed them for HNA-1, -3, -4, and -5 by using a commercial polymerase chain reaction kit with sequence-specific primers (SSP-PCR) and compared the HNA genotype distribution of both groups. In German blood donors, the gene frequencies for HNA-1a and HNA-1b were 0.391 and 0.601, for HNA-3a and -3b, 0.744 and 0.256, for HNA-4a and -4b, 0.908 and 0.092, and for HNA-5a and -5bw, 0.731 and 0.269. In Turkish blood donors, we observed 0.420/0.564, 0.737/0.263, 0.881/0.119, and 0.754/0.246 for HNA-1a/1b, -3a/3b, -4a/4b, and -5a/5bw. No statistic significant difference between genotypes in these populations was observed. This study is the first to report HNA gene frequencies in a Turkish population. It showed that there is no difference of HNA genotype in blood donors with Turkish descent in comparison with German blood donors. The alternating transfusion of blood and blood components is no increased risk for developing alloantibodies against HNA antigens. In pregnancy of mixed couples no special screening programs for HNA are necessary.