Robot Trajectories Comparison: A Statistical Approach
Ansuategui, A.; Arruti, A.; Susperregi, L.; Yurramendi, Y.; Jauregi, E.; Lazkano, E.; Sierra, B.
2014-01-01
The task of planning a collision-free trajectory from a start to a goal position is fundamental for an autonomous mobile robot. Although path planning has been extensively investigated since the beginning of robotics, there is no agreement on how to measure the performance of a motion algorithm. This paper presents a new approach to perform robot trajectories comparison that could be applied to any kind of trajectories and in both simulated and real environments. Given an initial set of features, it automatically selects the most significant ones and performs a statistical comparison using them. Additionally, a graphical data visualization named polygraph which helps to better understand the obtained results is provided. The proposed method has been applied, as an example, to compare two different motion planners, FM2 and WaveFront, using different environments, robots, and local planners. PMID:25525618
Statistical Prediction of Ocean Circulation and Trajectories
2016-06-07
GOALS We seek to develop a probabilistic description of the evolution of ocean currents and tracer trajectories, in order to improve performance and...in particular the mean, which represents a “best guess”, and the dispersion, which gauges uncertainty. Such an approach has evident advantages over...functional, developing explicit expressions for entropy gradients. ! Simulation of ensembles of quasi-geostrophic flows, relating evolution of
Measures of trajectory ensemble disparity in nonequilibrium statistical dynamics
Crooks, Gavin; Sivak, David
2011-06-03
Many interesting divergence measures between conjugate ensembles of nonequilibrium trajectories can be experimentally determined from the work distribution of the process. Herein, we review the statistical and physical significance of several of these measures, in particular the relative entropy (dissipation), Jeffreys divergence (hysteresis), Jensen-Shannon divergence (time-asymmetry), Chernoff divergence (work cumulant generating function), and Renyi divergence.
Statistics of actin-propelled trajectories in noisy environments
NASA Astrophysics Data System (ADS)
Wen, Fu-Lai; Chen, Hsuan-Yi; Leung, Kwan-tai
2016-06-01
Actin polymerization is ubiquitously utilized to power the locomotion of eukaryotic cells and pathogenic bacteria in living systems. Inevitably, actin polymerization and depolymerization proceed in a fluctuating environment that renders the locomotion stochastic. Previously, we have introduced a deterministic model that manages to reproduce actin-propelled trajectories in experiments, but not to address fluctuations around them. To remedy this, here we supplement the deterministic model with noise terms. It enables us to compute the effects of fluctuating actin density and forces on the trajectories. Specifically, the mean-squared displacement (MSD) of the trajectories is computed and found to show a super-ballistic scaling with an exponent 3 in the early stage, followed by a crossover to a normal, diffusive scaling of exponent 1 in the late stage. For open-end trajectories such as straights and S-shaped curves, the time of crossover matches the decay time of orientational order of the velocities along trajectories, suggesting that it is the spreading of velocities that leads to the crossover. We show that the super-ballistic scaling of MSD arises from the initial, linearly increasing correlation of velocities, before time translational symmetry is established. When the spreading of velocities reaches a steady state in the long-time limit, short-range correlation then yields a diffusive scaling in MSD. In contrast, close-loop trajectories like circles exhibit localized periodic motion, which inhibits spreading. The initial super-ballistic scaling of MSD arises from velocity correlation that both linearly increases and oscillates in time. Finally, we find that the above statistical features of the trajectories transcend the nature of noises, be it additive or multiplicative, and generalize to other self-propelled systems that are not necessarily actin based.
Advanced methods of structural and trajectory analysis for transport aircraft
NASA Technical Reports Server (NTRS)
Ardema, Mark D.
1995-01-01
This report summarizes the efforts in two areas: (1) development of advanced methods of structural weight estimation, and (2) development of advanced methods of trajectory optimization. The majority of the effort was spent in the structural weight area. A draft of 'Analytical Fuselage and Wing Weight Estimation of Transport Aircraft', resulting from this research, is included as an appendix.
Estimated Accuracy of Three Common Trajectory Statistical Methods
NASA Technical Reports Server (NTRS)
Kabashnikov, Vitaliy P.; Chaikovsky, Anatoli P.; Kucsera, Tom L.; Metelskaya, Natalia S.
2011-01-01
Three well-known trajectory statistical methods (TSMs), namely concentration field (CF), concentration weighted trajectory (CWT), and potential source contribution function (PSCF) methods were tested using known sources and artificially generated data sets to determine the ability of TSMs to reproduce spatial distribution of the sources. In the works by other authors, the accuracy of the trajectory statistical methods was estimated for particular species and at specified receptor locations. We have obtained a more general statistical estimation of the accuracy of source reconstruction and have found optimum conditions to reconstruct source distributions of atmospheric trace substances. Only virtual pollutants of the primary type were considered. In real world experiments, TSMs are intended for application to a priori unknown sources. Therefore, the accuracy of TSMs has to be tested with all possible spatial distributions of sources. An ensemble of geographical distributions of virtual sources was generated. Spearman s rank order correlation coefficient between spatial distributions of the known virtual and the reconstructed sources was taken to be a quantitative measure of the accuracy. Statistical estimates of the mean correlation coefficient and a range of the most probable values of correlation coefficients were obtained. All the TSMs that were considered here showed similar close results. The maximum of the ratio of the mean correlation to the width of the correlation interval containing the most probable correlation values determines the optimum conditions for reconstruction. An optimal geographical domain roughly coincides with the area supplying most of the substance to the receptor. The optimal domain s size is dependent on the substance decay time. Under optimum reconstruction conditions, the mean correlation coefficients can reach 0.70 0.75. The boundaries of the interval with the most probable correlation values are 0.6 0.9 for the decay time of 240 h
NASA Technical Reports Server (NTRS)
Shields, W. E.
1973-01-01
Tests were conducted to provide flight conditions for qualifying the Viking Decelerator System in a simulated Mars environment. A balloon launched decelerator test (BLDT) vehicle which has an external shape similar to the actual Mars Viking Lander Capsule was used so that the decelerator would be deployed in the wake of a blunt body. An effort was made to simulate the BLDT vehicle flights from the time they were dropped from the balloon, through decelerator deployment, until stable decelerator conditions were reached. The procedure used to simulate these flights using the Statistical Trajectory Estimation Program (STEP) is discussed. Using primarily ground-based position radar and vehicle onboard rate gyro and accelerometer data, the STEP produces a minimum variance solution of the vehicle trajectory and calculates vehicle attitude histories. Using film from cameras in the vehicle along with a computer program, attitude histories for portions of the flight before and after decelerator deployment were calculated independent of the STEP simulation. With the assumption that the vehicle motions derived from camera data are accurate, a comparison reveals that STEP was able to simulate vehicle motions for all flights both before and after decelerator deployment.
Advanced launch system trajectory optimization using suboptimal control
NASA Technical Reports Server (NTRS)
Shaver, Douglas A.; Hull, David G.
1993-01-01
The maximum-final mass trajectory of a proposed configuration of the Advanced Launch System is presented. A model for the two-stage rocket is given; the optimal control problem is formulated as a parameter optimization problem; and the optimal trajectory is computed using a nonlinear programming code called VF02AD. Numerical results are presented for the controls (angle of attack and velocity roll angle) and the states. After the initial rotation, the angle of attack goes to a positive value to keep the trajectory as high as possible, returns to near zero to pass through the transonic regime and satisfy the dynamic pressure constraint, returns to a positive value to keep the trajectory high and to take advantage of minimum drag at positive angle of attack due to aerodynamic shading of the booster, and then rolls off to negative values to satisfy the constraints. Because the engines cannot be throttled, the maximum dynamic pressure occurs at a single point; there is no maximum dynamic pressure subarc. To test approximations for obtaining analytical solutions for guidance, two additional optimal trajectories are computed: one using untrimmed aerodynamics and one using no atmospheric effects except for the dynamic pressure constraint. It is concluded that untrimmed aerodynamics has a negligible effect on the optimal trajectory and that approximate optimal controls should be able to be obtained by treating atmospheric effects as perturbations.
Intermediate/Advanced Research Design and Statistics
NASA Technical Reports Server (NTRS)
Ploutz-Snyder, Robert
2009-01-01
The purpose of this module is To provide Institutional Researchers (IRs) with an understanding of the principles of advanced research design and the intermediate/advanced statistical procedures consistent with such designs
Modeling phenotypic plasticity in growth trajectories: a statistical framework.
Wang, Zhong; Pang, Xiaoming; Wu, Weimiao; Wang, Jianxin; Wang, Zuoheng; Wu, Rongling
2014-01-01
Phenotypic plasticity, that is multiple phenotypes produced by a single genotype in response to environmental change, has been thought to play an important role in evolution and speciation. Historically, knowledge about phenotypic plasticity has resulted from the analysis of static traits measured at a single time point. New insight into the adaptive nature of plasticity can be gained by an understanding of how organisms alter their developmental processes in a range of environments. Recent advances in statistical modeling of functional data and developmental genetics allow us to construct a dynamic framework of plastic response in developmental form and pattern. Under this framework, development, genetics, and evolution can be synthesized through statistical bridges to better address how evolution results from phenotypic variation in the process of development via genetic alterations.
Quantum Trajectories and Their Statistics for Remotely Entangled Quantum Bits
NASA Astrophysics Data System (ADS)
Chantasri, Areeya; Kimchi-Schwartz, Mollie E.; Roch, Nicolas; Siddiqi, Irfan; Jordan, Andrew N.
2016-10-01
We experimentally and theoretically investigate the quantum trajectories of jointly monitored transmon qubits embedded in spatially separated microwave cavities. Using nearly quantum-noise-limited superconducting amplifiers and an optimized setup to reduce signal loss between cavities, we can efficiently track measurement-induced entanglement generation as a continuous process for single realizations of the experiment. The quantum trajectories of transmon qubits naturally split into low and high entanglement classes. The distribution of concurrence is found at any given time, and we explore the dynamics of entanglement creation in the state space. The distribution exhibits a sharp cutoff in the high concurrence limit, defining a maximal concurrence boundary. The most-likely paths of the qubits' trajectories are also investigated, resulting in three probable paths, gradually projecting the system to two even subspaces and an odd subspace, conforming to a "half-parity" measurement. We also investigate the most-likely time for the individual trajectories to reach their most entangled state, and we find that there are two solutions for the local maximum, corresponding to the low and high entanglement routes. The theoretical predictions show excellent agreement with the experimental entangled-qubit trajectory data.
Advances in low-thrust trajectory optimization and flight mechanics
NASA Astrophysics Data System (ADS)
Gao, Yang
The dissertation presents advances in trajectory optimization and flight mechanics of low-thrust spacecraft. With the aid of the extended multiple-shooting techniques with state and costate nodes, the hybrid method and the direct-shooting method are systematically described and used to solve a variety of optimal orbit transfer problems. The optimization methods are demonstrated by presenting solutions for optimal Earth-orbit and interplanetary trajectory examples, and complex interplanetary missions using solar electric propulsion (such as Eros sample return and Pluto-flyby missions). Alternative formulations of equations of motion are discussed, which include inertial frame transformation in terms of three Euler angles and a modified set of equinoctial elements using non-dimensional angular momentum. Finally, a low-thrust Earth-capture guidance scheme is developed and presented, which makes novel use of Perkins' low-thrust universal solution and doesn't require a stored reference trajectory. The simplicity and performance of this new guidance design makes it a viable candidate for onboard implementation.
Sexual Dimorphism in White Matter Developmental Trajectories Using Tract-Based Spatial Statistics.
Seunarine, Kiran K; Clayden, Jonathan D; Jentschke, Sebastian; Muñoz, Monica; Cooper, Janine M; Chadwick, Martin J; Banks, Tina; Vargha-Khadem, Faraneh; Clark, Christopher A
2016-02-01
Increasing evidence is emerging for sexual dimorphism in the trajectory of white matter development in children assessed using volumetric magnetic resonance imaging (MRI) and more recently diffusion MRI. Recent studies using diffusion MRI have examined cohorts with a wide age range (typically between 5 and 30 years) showing focal regions of differential diffusivity and fractional anisotropy (FA) and have implicated puberty as a possible contributory factor. To further investigate possible dimorphic trajectories in a young cohort, presumably closer to the expected onset of puberty, we used tract-based spatial statistics to investigate diffusion metrics. The cohort consisted of 23 males and 30 females between the ages of 8 and 16 years. Differences in diffusion metrics were corrected for age, total brain volume, and full scale IQ. In contrast to previous studies showing focal differences between males and females, widespread sexually dimorphic trajectories in structural white matter development were observed. These differences were characterized by more advanced development in females compared to males indicated by lower mean diffusivity, radial and axial diffusivity, and higher FA in females. This difference appeared to be larger at lower ages (8-9 years) with diffusion measures from males and females tending to converge between 10 and 14 years of age. Males showed a steeper slope for age-diffusion metric correlations compared to females, who either did not correlate with age or correlated in fewer regions. Further studies are now warranted to determine the role of hormones on the observed differences, particularly in 8-9-year-old children.
Beam Optics Analysis - An Advanced 3D Trajectory Code
Ives, R. Lawrence; Bui, Thuc; Vogler, William; Neilson, Jeff; Read, Mike; Shephard, Mark; Bauer, Andrew; Datta, Dibyendu; Beal, Mark
2006-01-03
Calabazas Creek Research, Inc. has completed initial development of an advanced, 3D program for modeling electron trajectories in electromagnetic fields. The code is being used to design complex guns and collectors. Beam Optics Analysis (BOA) is a fully relativistic, charged particle code using adaptive, finite element meshing. Geometrical input is imported from CAD programs generating ACIS-formatted files. Parametric data is inputted using an intuitive, graphical user interface (GUI), which also provides control of convergence, accuracy, and post processing. The program includes a magnetic field solver, and magnetic information can be imported from Maxwell 2D/3D and other programs. The program supports thermionic emission and injected beams. Secondary electron emission is also supported, including multiple generations. Work on field emission is in progress as well as implementation of computer optimization of both the geometry and operating parameters. The principle features of the program and its capabilities are presented.
Gorobets, Yu I; Gorobets, O Yu
2015-01-01
The statistical model is proposed in this paper for description of orientation of trajectories of unicellular diamagnetic organisms in a magnetic field. The statistical parameter such as the effective energy is calculated on basis of this model. The resulting effective energy is the statistical characteristics of trajectories of diamagnetic microorganisms in a magnetic field connected with their metabolism. The statistical model is applicable for the case when the energy of the thermal motion of bacteria is negligible in comparison with their energy in a magnetic field and the bacteria manifest the significant "active random movement", i.e. there is the randomizing motion of the bacteria of non thermal nature, for example, movement of bacteria by means of flagellum. The energy of the randomizing active self-motion of bacteria is characterized by the new statistical parameter for biological objects. The parameter replaces the energy of the randomizing thermal motion in calculation of the statistical distribution.
NASA Astrophysics Data System (ADS)
Kassomenos, P.; Vardoulakis, S.; Borge, R.; Lumbreras, J.; Papaloukas, C.; Karakitsios, S.
2010-10-01
In this study, we used and compared three different statistical clustering methods: an hierarchical, a non-hierarchical (K-means) and an artificial neural network technique (self-organizing maps (SOM)). These classification methods were applied to a 4-year dataset of 5 days kinematic back trajectories of air masses arriving in Athens, Greece at 12.00 UTC, in three different heights, above the ground. The atmospheric back trajectories were simulated with the HYSPLIT Vesion 4.7 model of National Oceanic and Atmospheric Administration (NOAA). The meteorological data used for the computation of trajectories were obtained from NOAA reanalysis database. A comparison of the three statistical clustering methods through statistical indices was attempted. It was found that all three statistical methods seem to depend to the arrival height of the trajectories, but the degree of dependence differs substantially. Hierarchical clustering showed the highest level of dependence for fast-moving trajectories to the arrival height, followed by SOM. K-means was found to be the least depended clustering technique on the arrival height. The air quality management applications of these results in relation to PM10 concentrations recorded in Athens, Greece, were also discussed. Differences of PM10 concentrations, during certain clusters, were found statistically different (at 95% confidence level) indicating that these clusters appear to be associated with long-range transportation of particulates. This study can improve the interpretation of modelled atmospheric trajectories, leading to a more reliable analysis of synoptic weather circulation patterns and their impacts on urban air quality.
Konovalov, Aleksandr B; Vlasov, V V; Kalintsev, A G; Lyubimov, Vladimir V; Kravtsenyuk, Olga V
2006-11-30
The inverse problem of diffuse optical tomography (DOT) is reduced by the method of photon average trajectories (PAT) to the solution of the integral equation integrated along the conditional mean statistical photon trajectory. The PAT bending near the flat boundary of a scattering medium is estimated analytically. These estimates are used to determine the analytic statistical characteristics of photon trajectories for the flat layer geometry. The inverse DOT problem is solved by using the multiplicative algebraic algorithm modified to improve the convergence of the iteration reconstruction process. The numerical experiment shows that the modified PAT method permits the reconstruction of near-surface optical inhomogeneities virtually without distortions. (special issue devoted to multiple radiation scattering in random media)
The changing hope trajectory in patients with advanced-stage cancer: a nursing perspective.
Sanders, Judith Brown; Seda, Julie S; Kardinal, Carl G
2012-06-01
As patients with advanced-stage cancer move from the initial diagnosis through treatment, remission, recurrence, and advanced-stage disease, the hope trajectory undergoes a dynamic transformation. By identifying the hope trajectory, nurses can help patients focus on obtainable hope objects while balancing the need to present a realistic prognosis. This, in turn, may help patients find meaning and purpose in advanced-stage cancer and facilitate realistic hope when faced with a life-threatening illness.
Kim, Seokyeon; Jeong, Seongmin; Woo, Insoo; Jang, Yun; Maciejewski, Ross; Ebert, David
2017-02-08
Geographic visualization research has focused on a variety of techniques to represent and explore spatiotemporal data. The goal of those techniques is to enable users to explore events and interactions over space and time in order to facilitate the discovery of patterns, anomalies and relationships within the data. However, it is difficult to extract and visualize data flow patterns over time for non-directional statistical data without trajectory information. In this work, we develop a novel flow analysis technique to extract, represent, and analyze flow maps of non-directional spatiotemporal data unaccompanied by trajectory information. We estimate a continuous distribution of these events over space and time, and extract flow fields for spatial and temporal changes utilizing a gravity model. Then, we visualize the spatiotemporal patterns in the data by employing flow visualization techniques. The user is presented with temporal trends of geo-referenced discrete events on a map. As such, overall spatiotemporal data flow patterns help users analyze geo-referenced temporal events, such as disease outbreaks, crime patterns, etc. To validate our model, we discard the trajectory information in an origin-destination dataset and apply our technique to the data and compare the derived trajectories and the original. Finally, we present spatiotemporal trend analysis for statistical datasets including twitter data, maritime search and rescue events, and syndromic surveillance.
A statistical quasiclassical trajectory model for atom-diatom insertion reactions.
Aoiz, F J; Sáez Rábanos, V; González-Lezana, T; Manolopoulos, D E
2007-04-28
A statistical model based on the quasiclassical trajectory method is presented in this work for atom-diatom insertion reactions. The basic difference between this and the corresponding statistical quantum model (SQM) lies in the fact that trajectories instead of wave functions are propagated in the entrance and exit channels. Other than this the two formulations are entirely similar. In particular, it is shown that conservation of parity can be taken into account in a natural and precise way in the statistical quasiclassical trajectory (SQCT) model. Additionally, the SQCT model complies with the principle of detailed balance and overcomes the problem of the zero point energy in the products. As a test, the model is applied to the H3+ and H+D2 exchange reactions. The excellent agreement between the SQCT and SQM results, especially in the case of the differential cross sections, indicates that the effect of tunneling through the centrifugal barrier is negligible. The effect of ignoring quantum mechanical parity conservation is also investigated.
Ogihara, Yusuke; Yamamoto, Takeshi; Kato, Shigeki
2011-08-09
Triplet ketene exhibits a steplike structure in the experimentally observed dissociation rate, but its mechanism is still unclear despite many theoretical efforts. A previous surface-hopping simulation at the CASSCF level suggests that nonadiabatic transition from the S0 to T1 states creates the T1 species in a highly nonstatistical manner, which raises the question of whether the use of statistical rate theory is valid in itself for the T1 state. Here, we study this problem by performing ab initio trajectory simulation at the multireference second-order Möller-Plesset perturbation (MRMP) level of theory. Since the MRMP theory is too expensive for such a trajectory calculation, we first construct dual-level potential energy surfaces (PESs) for the S0 and T1 states by calibrating the PESs at the B3LYP level with a limited set of MRMP energies. We then introduce the assumption of vibrational equilibrium on the S0 surface and characterize the S0 → T1 crossing points using the conditional microcanonical distribution on the S0/T1 seam surface. The latter distribution is obtained by running a constrained trajectory on the seam surface by use of an efficient SHAKE-like method. Subsequently, we propagate a number of T1 trajectories from the seam surface to obtain the dissociation rate. The result shows that (i) the S0 → T1 crossing points are localized mainly in the T1 reactant region; (ii) the lifetime on the T1 surface is about 30 ps at the MRMP level, which is 2 orders of magnitude greater than the previous estimate obtained from the surface-hopping simulation at the CASSCF level (∼100 fs); and (iii) the calculated T1 dissociation rate agrees reasonably well with classical transition state theory. These results suggest that the T1 dissociation is rather statistical, given that the T1 trajectories are initiated from the conditional microcanonical distribution on the seam surface.
Deterministic and Advanced Statistical Modeling of Wind-Driven Sea
2015-07-06
COVERED (From - To) 01/09/2010-06/07/2015 4. TITLE AND SUBTITLE Deterministic and advanced statistical modeling of wind-driven sea 5a. CONTRACT...Technical Report Deterministic and advanced statistical modeling of wind-driven sea Vladimir Zakharov, Andrei Pushkarev Waves and Solitons LLC, 1719 W...Development of accurate and fast advanced statistical and dynamical nonlinear models of ocean surface waves, based on first physical principles, which will
Writing to Learn Statistics in an Advanced Placement Statistics Course
ERIC Educational Resources Information Center
Northrup, Christian Glenn
2012-01-01
This study investigated the use of writing in a statistics classroom to learn if writing provided a rich description of problem-solving processes of students as they solved problems. Through analysis of 329 written samples provided by students, it was determined that writing provided a rich description of problem-solving processes and enabled…
Deviation-angle and trajectory statistics for inertial particles in turbulence
NASA Astrophysics Data System (ADS)
Bhatnagar, Akshay; Gupta, Anupam; Mitra, Dhrubaditya; Perlekar, Prasad; Wilkinson, Michael; Pandit, Rahul
2016-12-01
Small particles in suspension in a turbulent fluid have trajectories that do not follow the pathlines of the flow exactly. We investigate the statistics of the angle of deviation ϕ between the particle and fluid velocities. We show that, when the effects of particle inertia are small, the probability distribution function (PDF) Pϕ of this deviation angle shows a power-law region in which Pϕ˜ϕ-4 . We also find that the PDFs of the trajectory curvature κ and modulus θ of the torsion ϑ have power-law tails that scale, respectively, as Pκ˜κ-5 /2 , as κ →∞ , and Pθ˜θ-3 , as θ →∞ : These exponents are in agreement with those previously observed for fluid pathlines. We propose a way to measure the complexity of heavy-particle trajectories by the number NI(t ,St ) of points (up until time t ) at which the torsion changes sign. We present numerical evidence that nI(St ) ≡limt→∞N/I(t ,St ) t ˜St-Δ for large St , with Δ ≃0.5 .
Trajectory-probed instability and statistics of desynchronization events in coupled chaotic systems
Oliveira, Gilson F. de Chevrollier, Martine; Oriá, Marcos; Passerat de Silans, Thierry; Souza Cavalcante, Hugo L. D. de
2015-11-15
Complex systems, such as financial markets, earthquakes, and neurological networks, exhibit extreme events whose mechanisms of formation are not still completely understood. These mechanisms may be identified and better studied in simpler systems with dynamical features similar to the ones encountered in the complex system of interest. For instance, sudden and brief departures from the synchronized state observed in coupled chaotic systems were shown to display non-normal statistical distributions similar to events observed in the complex systems cited above. The current hypothesis accepted is that these desynchronization events are influenced by the presence of unstable object(s) in the phase space of the system. Here, we present further evidence that the occurrence of large events is triggered by the visitation of the system's phase-space trajectory to the vicinity of these unstable objects. In the system studied here, this visitation is controlled by a single parameter, and we exploit this feature to observe the effect of the visitation rate in the overall instability of the synchronized state. We find that the probability of escapes from the synchronized state and the size of those desynchronization events are enhanced in attractors whose shapes permit the chaotic trajectories to approach the region of strong instability. This result shows that the occurrence of large events requires not only a large local instability to amplify noise, or to amplify the effect of parameter mismatch between the coupled subsystems, but also that the trajectories of the system wander close to this local instability.
Trajectory-probed instability and statistics of desynchronization events in coupled chaotic systems
NASA Astrophysics Data System (ADS)
de Oliveira, Gilson F.; Chevrollier, Martine; Passerat de Silans, Thierry; Oriá, Marcos; de Souza Cavalcante, Hugo L. D.
2015-11-01
Complex systems, such as financial markets, earthquakes, and neurological networks, exhibit extreme events whose mechanisms of formation are not still completely understood. These mechanisms may be identified and better studied in simpler systems with dynamical features similar to the ones encountered in the complex system of interest. For instance, sudden and brief departures from the synchronized state observed in coupled chaotic systems were shown to display non-normal statistical distributions similar to events observed in the complex systems cited above. The current hypothesis accepted is that these desynchronization events are influenced by the presence of unstable object(s) in the phase space of the system. Here, we present further evidence that the occurrence of large events is triggered by the visitation of the system's phase-space trajectory to the vicinity of these unstable objects. In the system studied here, this visitation is controlled by a single parameter, and we exploit this feature to observe the effect of the visitation rate in the overall instability of the synchronized state. We find that the probability of escapes from the synchronized state and the size of those desynchronization events are enhanced in attractors whose shapes permit the chaotic trajectories to approach the region of strong instability. This result shows that the occurrence of large events requires not only a large local instability to amplify noise, or to amplify the effect of parameter mismatch between the coupled subsystems, but also that the trajectories of the system wander close to this local instability.
Electron Trajectory Reconstruction for Advanced Compton Imaging of Gamma Rays
NASA Astrophysics Data System (ADS)
Plimley, Brian Christopher
Gamma-ray imaging is useful for detecting, characterizing, and localizing sources in a variety of fields, including nuclear physics, security, nuclear accident response, nuclear medicine, and astronomy. Compton imaging in particular provides sensitivity to weak sources and good angular resolution in a large field of view. However, the photon origin in a single event sequence is normally only limited to the surface of a cone. If the initial direction of the Compton-scattered electron can be measured, the cone can be reduced to a cone segment with width depending on the uncertainty in the direction measurement, providing a corresponding increase in imaging sensitivity. Measurement of the electron's initial direction in an efficient detection material requires very fine position resolution due to the electron's short range and tortuous path. A thick (650 mum), fully-depleted charge-coupled device (CCD) developed for infrared astronomy has 10.5-mum position resolution in two dimensions, enabling the initial trajectory measurement of electrons of energy as low as 100 keV. This is the first time the initial trajectories of electrons of such low energies have been measured in a solid material. In this work, the CCD's efficacy as a gamma-ray detector is demonstrated experimentally, using a reconstruction algorithm to measure the initial electron direction from the CCD track image. In addition, models of fast electron interaction physics, charge transport and readout were used to generate modeled tracks with known initial direction. These modeled tracks allowed the development and refinement of the reconstruction algorithm. The angular sensitivity of the reconstruction algorithm is evaluated extensively with models for tracks below 480 keV, showing a FWHM as low as 20° in the pixel plane, and 30° RMS sensitivity to the magnitude of the out-of-plane angle. The measurement of the trajectories of electrons with energies as low as 100 keV have the potential to make electron
NASA Astrophysics Data System (ADS)
Salvador, P.; Artíñano, B.; Pio, C. A.; Afonso, J.; Puxbaum, H.; Legrand, M.; Hammer, S.; Kaiser, A.
2009-04-01
During the last years, the analysis of a great number of back-trajectories from receptor sites has turned out to be a valuable tool to identify sources and sinks areas of atmospheric particulate matter (PM) or to reconstruct their average spatial distribution. A number of works have applied different trajectory statistical methods (TSM), which allow working simultaneously with back-trajectories computed from one or several receptor points and PM concentration values registered there. In spite of these methods have many limitations, they are simple and effective methods to detect the relevant source regions and the air flow regimes which are connected with regional and large-scale air pollution transport. In this study 5-day backward air trajectories arriving over 3 monitoring sites, were utilised and analysed simultaneously with the PM levels and chemical composition values registered there. These sites are located in the centre of Europe and can be classified into natural continental background (Schauinsland-SIL in Germany (1205 m asl), Puy de Dôme-PDD in France (1450 m asl) and Sonnblick-SBO in Austria (3106 m asl)). In the framework of the CARBOSOL European project, weekly aerosol samples were collected with High Volume Samplers (DIGITEL DH77) and PM10 (SIL and PDD) or PM2.5 (SBO) inlets, on quartz fibre filters. Filter samples were treated and analyzed for determining the levels of major organic fractions (OC, EC) and inorganic ions. Additionally, analyses for specific organic compounds were also carried out whenever was possible (Pio et al., 2007). For each day of the sampling period, four trajectories ending at 00:00, 06:00, 12:00 and 18:00 h UTC have been computed by the Norwegian Institute for Air Research NILU (SIL and PDD) and the Central Institute for Meteorology and Geophysics of Austria (SBO) using the FLEXTRA model (Stohl et al., 1995). In all, more than 8000 complete trajectories were available for analysis, each with 40 endpoints. Firstly air mass
Conceptualizing a Framework for Advanced Placement Statistics Teaching Knowledge
ERIC Educational Resources Information Center
Haines, Brenna
2015-01-01
The purpose of this article is to sketch a conceptualization of a framework for Advanced Placement (AP) Statistics Teaching Knowledge. Recent research continues to problematize the lack of knowledge and preparation among secondary level statistics teachers. The College Board's AP Statistics course continues to grow and gain popularity, but is a…
Advanced Algorithms and Statistics for MOS Surveys
NASA Astrophysics Data System (ADS)
Bolton, A. S.
2016-10-01
This paper presents an individual view on the current state of computational data processing and statistics for inference and discovery in multi-object spectroscopic surveys, supplemented by a historical perspective and a few present-day applications. It is more op-ed than review, and hopefully more readable as a result.
Advance Report of Final Mortality Statistics, 1985.
ERIC Educational Resources Information Center
Monthly Vital Statistics Report, 1987
1987-01-01
This document presents mortality statistics for 1985 for the entire United States. Data analysis and discussion of these factors is included: death and death rates; death rates by age, sex, and race; expectation of life at birth and at specified ages; causes of death; infant mortality; and maternal mortality. Highlights reported include: (1) the…
Recent advances in statistical energy analysis
NASA Technical Reports Server (NTRS)
Heron, K. H.
1992-01-01
Statistical Energy Analysis (SEA) has traditionally been developed using modal summation and averaging approach, and has led to the need for many restrictive SEA assumptions. The assumption of 'weak coupling' is particularly unacceptable when attempts are made to apply SEA to structural coupling. It is now believed that this assumption is more a function of the modal formulation rather than a necessary formulation of SEA. The present analysis ignores this restriction and describes a wave approach to the calculation of plate-plate coupling loss factors. Predictions based on this method are compared with results obtained from experiments using point excitation on one side of an irregular six-sided box structure. Conclusions show that the use and calculation of infinite transmission coefficients is the way forward for the development of a purely predictive SEA code.
Project T.E.A.M. (Technical Education Advancement Modules). Advanced Statistical Process Control.
ERIC Educational Resources Information Center
Dunlap, Dale
This instructional guide, one of a series developed by the Technical Education Advancement Modules (TEAM) project, is a 20-hour advanced statistical process control (SPC) and quality improvement course designed to develop the following competencies: (1) understanding quality systems; (2) knowing the process; (3) solving quality problems; and (4)…
Advances in Statistical Methods for Substance Abuse Prevention Research
MacKinnon, David P.; Lockwood, Chondra M.
2010-01-01
The paper describes advances in statistical methods for prevention research with a particular focus on substance abuse prevention. Standard analysis methods are extended to the typical research designs and characteristics of the data collected in prevention research. Prevention research often includes longitudinal measurement, clustering of data in units such as schools or clinics, missing data, and categorical as well as continuous outcome variables. Statistical methods to handle these features of prevention data are outlined. Developments in mediation, moderation, and implementation analysis allow for the extraction of more detailed information from a prevention study. Advancements in the interpretation of prevention research results include more widespread calculation of effect size and statistical power, the use of confidence intervals as well as hypothesis testing, detailed causal analysis of research findings, and meta-analysis. The increased availability of statistical software has contributed greatly to the use of new methods in prevention research. It is likely that the Internet will continue to stimulate the development and application of new methods. PMID:12940467
Enhanced bio-manufacturing through advanced multivariate statistical technologies.
Martin, E B; Morris, A J
2002-11-13
The paper describes the interrogation of data, from a reaction vessel producing an active pharmaceutical ingredient (API), using advanced multivariate statistical techniques. Due to the limited number of batches available, data augmentation was used to increase the number of batches thereby enabling the extraction of more subtle process behaviour from the data. A second methodology investigated was that of multi-group modelling. This allowed between cluster variability to be removed, thus allowing attention to focus on within process variability. The paper describes how the different approaches enabled the realisation of a better understanding of the factors causing the onset of an impurity formation to be obtained as well demonstrating the power of multivariate statistical data analysis techniques to provide an enhanced understanding of the process.
Statistical analysis of piloted simulation of real time trajectory optimization algorithms
NASA Technical Reports Server (NTRS)
Price, D. B.
1982-01-01
A simulation of time-optimal intercept algorithms for on-board computation of control commands is described. The effects of three different display modes and two different computation modes on the pilots' ability to intercept a moving target in minimum time were tested. Both computation modes employed singular perturbation theory to help simplify the two-point boundary value problem associated with trajectory optimization. Target intercept time was affected by both the display and computation modes chosen, but the display mode chosen was the only significant influence on the miss distance.
Wu, Hao; Mey, Antonia S J S; Rosta, Edina; Noé, Frank
2014-12-07
We propose a discrete transition-based reweighting analysis method (dTRAM) for analyzing configuration-space-discretized simulation trajectories produced at different thermodynamic states (temperatures, Hamiltonians, etc.) dTRAM provides maximum-likelihood estimates of stationary quantities (probabilities, free energies, expectation values) at any thermodynamic state. In contrast to the weighted histogram analysis method (WHAM), dTRAM does not require data to be sampled from global equilibrium, and can thus produce superior estimates for enhanced sampling data such as parallel/simulated tempering, replica exchange, umbrella sampling, or metadynamics. In addition, dTRAM provides optimal estimates of Markov state models (MSMs) from the discretized state-space trajectories at all thermodynamic states. Under suitable conditions, these MSMs can be used to calculate kinetic quantities (e.g., rates, timescales). In the limit of a single thermodynamic state, dTRAM estimates a maximum likelihood reversible MSM, while in the limit of uncorrelated sampling data, dTRAM is identical to WHAM. dTRAM is thus a generalization to both estimators.
A Hierarchical Statistic Methodology for Advanced Memory System Evaluation
Sun, X.-J.; He, D.; Cameron, K.W.; Luo, Y.
1999-04-12
Advances in technology have resulted in a widening of the gap between computing speed and memory access time. Data access time has become increasingly important for computer system design. Various hierarchical memory architectures have been developed. The performance of these advanced memory systems, however, varies with applications and problem sizes. How to reach an optimal cost/performance design eludes researchers still. In this study, the authors introduce an evaluation methodology for advanced memory systems. This methodology is based on statistical factorial analysis and performance scalability analysis. It is two fold: it first determines the impact of memory systems and application programs toward overall performance; it also identifies the bottleneck in a memory hierarchy and provides cost/performance comparisons via scalability analysis. Different memory systems can be compared in terms of mean performance or scalability over a range of codes and problem sizes. Experimental testing has been performed extensively on the Department of Energy's Accelerated Strategic Computing Initiative (ASCI) machines and benchmarks available at the Los Alamos National Laboratory to validate this newly proposed methodology. Experimental and analytical results show this methodology is simple and effective. It is a practical tool for memory system evaluation and design. Its extension to general architectural evaluation and parallel computer systems are possible and should be further explored.
Calderon, Christopher P
2016-05-01
Single particle tracking (SPT) can aid in understanding a variety of complex spatiotemporal processes. However, quantifying diffusivity and confinement forces from individual live cell trajectories is complicated by inter- and intratrajectory kinetic heterogeneity, thermal fluctuations, and (experimentally resolvable) statistical temporal dependence inherent to the underlying molecule's time correlated confined dynamics experienced in the cell. The problem is further complicated by experimental artifacts such as localization uncertainty and motion blur. The latter is caused by the tagged molecule emitting photons at different spatial positions during the exposure time of a single frame. The aforementioned experimental artifacts induce spurious time correlations in measured SPT time series that obscure the information of interest (e.g., confinement forces and diffusivity). We develop a maximum likelihood estimation (MLE) technique that decouples the above noise sources and systematically treats temporal correlation via time series methods. This ultimately permits a reliable algorithm for extracting diffusivity and effective forces in confined or unconfined environments. We illustrate how our approach avoids complications inherent to mean square displacement or autocorrelation techniques. Our algorithm modifies the established Kalman filter (which does not handle motion blur artifacts) to provide a likelihood based time series estimation procedure. The result extends A. J. Berglund's motion blur model [Phys. Rev. E 82, 011917 (2010)PLEEE81539-375510.1103/PhysRevE.82.011917] to handle confined dynamics. The approach can also systematically utilize (possibly time dependent) localization uncertainty estimates afforded by image analysis if available. This technique, which explicitly treats confinement and motion blur within a time domain MLE framework, uses an exact likelihood (time domain methods facilitate analyzing nonstationary signals). Our estimator is demonstrated
NASA Astrophysics Data System (ADS)
Calderon, Christopher P.
2016-05-01
Single particle tracking (SPT) can aid in understanding a variety of complex spatiotemporal processes. However, quantifying diffusivity and confinement forces from individual live cell trajectories is complicated by inter- and intratrajectory kinetic heterogeneity, thermal fluctuations, and (experimentally resolvable) statistical temporal dependence inherent to the underlying molecule's time correlated confined dynamics experienced in the cell. The problem is further complicated by experimental artifacts such as localization uncertainty and motion blur. The latter is caused by the tagged molecule emitting photons at different spatial positions during the exposure time of a single frame. The aforementioned experimental artifacts induce spurious time correlations in measured SPT time series that obscure the information of interest (e.g., confinement forces and diffusivity). We develop a maximum likelihood estimation (MLE) technique that decouples the above noise sources and systematically treats temporal correlation via time series methods. This ultimately permits a reliable algorithm for extracting diffusivity and effective forces in confined or unconfined environments. We illustrate how our approach avoids complications inherent to mean square displacement or autocorrelation techniques. Our algorithm modifies the established Kalman filter (which does not handle motion blur artifacts) to provide a likelihood based time series estimation procedure. The result extends A. J. Berglund's motion blur model [Phys. Rev. E 82, 011917 (2010), 10.1103/PhysRevE.82.011917] to handle confined dynamics. The approach can also systematically utilize (possibly time dependent) localization uncertainty estimates afforded by image analysis if available. This technique, which explicitly treats confinement and motion blur within a time domain MLE framework, uses an exact likelihood (time domain methods facilitate analyzing nonstationary signals). Our estimator is demonstrated to be
Aoiz, F J; González-Lezana, T; Sáez Rábanos, V
2007-11-07
A complete formulation of a statistical quasiclassical trajectory (SQCT) model is presented in this work along with a detailed comparison with results obtained with the statistical quantum mechanical (SQM) model for the H+ +D2 and H+ +H2 reactions. The basic difference between the SQCT and the SQM models lies in the fact that trajectories instead of wave functions are propagated in the entrance and exit channels. Other than this the two formulations are entirely similar and both comply with the principle of detailed balance and conservation of parity. Reaction probabilities, and integral and differential cross sections (DCS's) for these reactions at different levels of product's state resolution and from various initial states are shown and discussed. The agreement is in most cases excellent and indicates that the effect of tunneling through the centrifugal barrier is negligible. Some differences are found, however, between state resolved observables calculated by the SQCT and the SQM methods which makes use of the centrifugal sudden (coupled states) approximation (SQM-CS). When this approximation is removed and the full close coupling treatment is used in the SQM model (SQM-CC), an almost perfect agreement is achieved. This shows that the SQCT is sensitive enough to show the relatively small inaccuracies resulting from the decoupling inherent to the CS approximation. In addition, the effect of ignoring the parity conservation is thoroughly examined. This effect is in general minor except in particular cases such as the DCS from initial rotational state j=0. It is shown, however, that in order to reproduce the sharp forward and backward peaks the conservation of parity has to be taken into account.
Application of an advanced trajectory optimization method to ramjet propelled missiles
NASA Technical Reports Server (NTRS)
Paris, S. W.; Fink, L. E.; Joosten, B. K.
1980-01-01
The mission performance characteristics of ramjet-propelled missiles are highly dependent upon the trajectory flown. Integration of the trajectory profile with the ramjet propulsion system performance characteristics to achieve optimal missile performance is very complex. Past trajectory optimization methods have been extremely problem dependent and require a high degree of familiarity to achieve success. A general computer code (CTOP) has been applied to ramjet-powered missiles to compute open-loop optimal trajectories. CTOP employs Chebyshev polynomial representations of the states and controls. This allows a transformation of the continuous optimal control problem to one of parameter optimization. With this method, the trajectory boundary conditions are always satisfied. State dynamics and path constraints are enforced via penalty functions. The presented results include solutions to minimum fuel-to-climb, minimum time-to-climb, and minimum time-to-target intercept problems.
Statistics of reversible transitions in two-state trajectories in force-ramp spectroscopy
Diezemann, Gregor
2014-05-14
A possible way to extract information about the reversible dissociation of a molecular adhesion bond from force fluctuations observed in force ramp experiments is discussed. For small loading rates the system undergoes a limited number of unbinding and rebinding transitions observable in the so-called force versus extension (FE) curves. The statistics of these transient fluctuations can be utilized to estimate the parameters for the rebinding rate. This is relevant in the experimentally important situation where the direct observation of the reversed FE-curves is hampered, e.g., due to the presence of soft linkers. I generalize the stochastic theory of the kinetics in two-state models to the case of time-dependent kinetic rates and compute the relevant distributions of characteristic forces. While for irreversible systems there is an intrinsic relation between the rupture force distribution and the population of the free-energy well of the bound state, the situation is slightly more complex if reversible systems are considered. For a two-state model, a “stationary” rupture force distribution that is proportional to the population can be defined and allows to consistently discuss quantities averaged over the transient fluctuations. While irreversible systems are best analyzed in the soft spring limit of small pulling device stiffness and large loading rates, here I argue to use the stiffness of the pulling device as a control parameter in addition to the loading rate.
NASA Astrophysics Data System (ADS)
Vitali, Lina; Righini, Gaia; Piersanti, Antonio; Cremona, Giuseppe; Pace, Giandomenico; Ciancarella, Luisella
2016-11-01
Air backward trajectory calculations are commonly used in a variety of atmospheric analyses, in particular for source attribution evaluation. The accuracy of backward trajectory analysis is mainly determined by the quality and the spatial and temporal resolution of the underlying meteorological data set, especially in the cases of complex terrain. This work describes a new tool for the calculation and the statistical elaboration of backward trajectories. To take advantage of the high-resolution meteorological database of the Italian national air quality model MINNI, a dedicated set of procedures was implemented under the name of M-TraCE (MINNI module for Trajectories Calculation and statistical Elaboration) to calculate and process the backward trajectories of air masses reaching a site of interest. Some outcomes from the application of the developed methodology to the Italian Network of Special Purpose Monitoring Stations are shown to assess its strengths for the meteorological characterization of air quality monitoring stations. M-TraCE has demonstrated its capabilities to provide a detailed statistical assessment of transport patterns and region of influence of the site under investigation, which is fundamental for correctly interpreting pollutants measurements and ascertaining the official classification of the monitoring site based on meta-data information. Moreover, M-TraCE has shown its usefulness in supporting other assessments, i.e., spatial representativeness of a monitoring site, focussing specifically on the analysis of the effects due to meteorological variables.
Statistical inference to advance network models in epidemiology.
Welch, David; Bansal, Shweta; Hunter, David R
2011-03-01
Contact networks are playing an increasingly important role in the study of epidemiology. Most of the existing work in this area has focused on considering the effect of underlying network structure on epidemic dynamics by using tools from probability theory and computer simulation. This work has provided much insight on the role that heterogeneity in host contact patterns plays on infectious disease dynamics. Despite the important understanding afforded by the probability and simulation paradigm, this approach does not directly address important questions about the structure of contact networks such as what is the best network model for a particular mode of disease transmission, how parameter values of a given model should be estimated, or how precisely the data allow us to estimate these parameter values. We argue that these questions are best answered within a statistical framework and discuss the role of statistical inference in estimating contact networks from epidemiological data.
Integration of Advanced Statistical Analysis Tools and Geophysical Modeling
2010-12-01
later in this section. 2) San Luis Obispo . Extracted features were also provided for MTADS EM61, MTADS magnetics, EM61 cart, and TEMTADS data sets from...subsequent training of statistical classifiers using these features. Results of discrimination studies at Camp Sibert and San Luis Obispo have shown...Comparison of classification performance Figures 10 through 13 show receiver operating characteristics for data sets acquired at San Luis Obispo . Subplot
Development of Advanced Methods of Structural and Trajectory Analysis for Transport Aircraft
NASA Technical Reports Server (NTRS)
Ardema, Mark D.; Windhorst, Robert; Phillips, James
1998-01-01
This paper develops a near-optimal guidance law for generating minimum fuel, time, or cost fixed-range trajectories for supersonic transport aircraft. The approach uses a choice of new state variables along with singular perturbation techniques to time-scale decouple the dynamic equations into multiple equations of single order (second order for the fast dynamics). Application of the maximum principle to each of the decoupled equations, as opposed to application to the original coupled equations, avoids the two point boundary value problem and transforms the problem from one of a functional optimization to one of multiple function optimizations. It is shown that such an approach produces well known aircraft performance results such as minimizing the Brequet factor for minimum fuel consumption and the energy climb path. Furthermore, the new state variables produce a consistent calculation of flight path angle along the trajectory, eliminating one of the deficiencies in the traditional energy state approximation. In addition, jumps in the energy climb path are smoothed out by integration of the original dynamic equations at constant load factor. Numerical results performed for a supersonic transport design show that a pushover dive followed by a pullout at nominal load factors are sufficient maneuvers to smooth the jump.
Balucani, Nadia; Capozza, Giovanni; Segoloni, Enrico; Russo, Andrea; Bobbenkamp, Rolf; Casavecchia, Piergiorgio; Gonzalez-Lezana, Tomas; Rackham, Edward J; Bañares, Luis; Aoiz, F Javier
2005-06-15
In this paper we report a combined experimental and theoretical study on the dynamics of the insertion reaction C((1)D)+D(2) at 15.5 kJ mol(-1) collision energy. Product angular and velocity distributions have been obtained in crossed beam experiments and quasiclassical trajectory (QCT) and rigorous statistical calculations have been performed on the recent and accurate ab initio potential energy surface of Bussery-Honvault, Honvault, and Launay at the energy of the experiment. The molecular-beam results have been simulated using the theoretical calculations. Good agreement between experiment and both QCT and statistical predictions is found.
Claassen, Daniel O; Dobolyi, David G; Isaacs, David A; Roman, Olivia C; Herb, Joshua; Wylie, Scott A; Neimat, Joseph S; Donahue, Manus J; Hedera, Peter; Zald, David H; Landman, Bennett A; Bowman, Aaron B; Dawant, Benoit M; Rane, Swati
2016-05-01
Advancing age and disease duration both contribute to cortical thinning in Parkinson's disease (PD), but the pathological interactions between them are poorly described. This study aims to distinguish patterns of cortical decline determined by advancing age and disease duration in PD. A convenience cohort of 177 consecutive PD patients, identified at the Vanderbilt University Movement Disorders Clinic as part of a clinical evaluation for Deep Brain Stimulation (age: M= 62.0, SD 9.3), completed a standardized clinical assessment, along with structural brain Magnetic Resonance Imaging scan. Age and gender matched controls (n=53) were obtained from the Alzheimer Disease Neuroimaging Initiative and Progressive Parkinson's Marker Initiative (age: M= 63.4, SD 12.2). Estimated changes in cortical thickness were modeled with advancing age, disease duration, and their interaction. The best-fitting model, linear or curvilinear (2(nd), or 3(rd) order natural spline), was defined using the minimum Akaike Information Criterion, and illustrated on a 3-dimensional brain. Three curvilinear patterns of cortical thinning were identified: early decline, late decline, and early-stable-late. In contrast to healthy controls, the best-fit model for age related changes in PD is curvilinear (early decline), particularly in frontal and precuneus regions. With advancing disease duration, a curvilinear model depicts accelerating decline in the occipital cortex. A significant interaction between advancing age and disease duration is evident in frontal, motor, and posterior parietal areas. Study results support the hypothesis that advancing age and disease duration differentially affect regional cortical thickness and display regional dependent linear and curvilinear patterns of thinning.
The statistical multifragmentation model: Origins and recent advances
NASA Astrophysics Data System (ADS)
Donangelo, R.; Souza, S. R.
2016-07-01
We review the Statistical Multifragmentation Model (SMM) which considers a generalization of the liquid-drop model for hot nuclei and allows one to calculate thermodynamic quantities characterizing the nuclear ensemble at the disassembly stage. We show how to determine probabilities of definite partitions of finite nuclei and how to determine, through Monte Carlo calculations, observables such as the caloric curve, multiplicity distributions, heat capacity, among others. Some experimental measurements of the caloric curve confirmed the SMM predictions of over 10 years before, leading to a surge in the interest in the model. However, the experimental determination of the fragmentation temperatures relies on the yields of different isotopic species, which were not correctly calculated in the schematic, liquid-drop picture, employed in the SMM. This led to a series of improvements in the SMM, in particular to the more careful choice of nuclear masses and energy densities, specially for the lighter nuclei. With these improvements the SMM is able to make quantitative determinations of isotope production. We show the application of SMM to the production of exotic nuclei through multifragmentation. These preliminary calculations demonstrate the need for a careful choice of the system size and excitation energy to attain maximum yields.
NASA Astrophysics Data System (ADS)
Poddubny, V. A.; Nagovitsyna, E. S.
2013-07-01
The well-known method of the back trajectory statistics (BTS) is used to develop a new approach to estimating atmospheric pollution fields according to local measurements. On the basis of instrumental measurements at one or a few monitoring points and information on atmospheric dynamics (in this work, back trajectories of the motion of air particles), the BTS method makes it possible to estimate the spatial structure of fields of a measured quantity. Results from solving a simplified demonstration of estimating the spatial distribution of the volume concentration of a fine aerosol fraction are presented; these results were obtained on the basis of an analysis of photometric measurements in the period of 2004-2010 at six AERO-NET monitoring sites on the territory of Russia: Zvenigorod, Moscow, Yekaterinburg, Tomsk, Yakutsk, and Ussuriisk.
Callahan, Charles D; Griffen, David L
2003-08-01
Emergency medicine faces unique challenges in the effort to improve efficiency and effectiveness. Increased patient volumes, decreased emergency department (ED) supply, and an increased emphasis on the ED as a diagnostic center have contributed to poor customer satisfaction and process failures such as diversion/bypass. Statistical process control (SPC) techniques developed in industry offer an empirically based means to understand our work processes and manage by fact. Emphasizing that meaningful quality improvement can occur only when it is exercised by "front-line" providers, this primer presents robust yet accessible SPC concepts and techniques for use in today's ED.
Development of Advanced Methods of Structural and Trajectory Analysis for Transport Aircraft
NASA Technical Reports Server (NTRS)
Ardema, Mark D.
1996-01-01
In this report the author describes: (1) development of advanced methods of structural weight estimation, and (2) development of advanced methods of flight path optimization. A method of estimating the load-bearing fuselage weight and wing weight of transport aircraft based on fundamental structural principles has been developed. This method of weight estimation represents a compromise between the rapid assessment of component weight using empirical methods based on actual weights of existing aircraft and detailed, but time-consuming, analysis using the finite element method. The method was applied to eight existing subsonic transports for validation and correlation. Integration of the resulting computer program, PDCYL, has been made into the weights-calculating module of the AirCraft SYNThesis (ACSYNT) computer program. ACSYNT bas traditionally used only empirical weight estimation methods; PDCYL adds to ACSYNT a rapid, accurate means of assessing the fuselage and wing weights of unconventional aircraft. PDCYL also allows flexibility in the choice of structural concept, as well as a direct means of determining the impact of advanced materials on structural weight.
Goedert, Kelly M.; Boston, Raymond C.; Barrett, A. M.
2013-01-01
Valid research on neglect rehabilitation demands a statistical approach commensurate with the characteristics of neglect rehabilitation data: neglect arises from impairment in distinct brain networks leading to large between-subject variability in baseline symptoms and recovery trajectories. Studies enrolling medically ill, disabled patients, may suffer from missing, unbalanced data, and small sample sizes. Finally, assessment of rehabilitation requires a description of continuous recovery trajectories. Unfortunately, the statistical method currently employed in most studies of neglect treatment [repeated measures analysis of variance (ANOVA), rANOVA] does not well-address these issues. Here we review an alternative, mixed linear modeling (MLM), that is more appropriate for assessing change over time. MLM better accounts for between-subject heterogeneity in baseline neglect severity and in recovery trajectory. MLM does not require complete or balanced data, nor does it make strict assumptions regarding the data structure. Furthermore, because MLM better models between-subject heterogeneity it often results in increased power to observe treatment effects with smaller samples. After reviewing current practices in the field, and the assumptions of rANOVA, we provide an introduction to MLM. We review its assumptions, uses, advantages, and disadvantages. Using real and simulated data, we illustrate how MLM may improve the ability to detect effects of treatment over ANOVA, particularly with the small samples typical of neglect research. Furthermore, our simulation analyses result in recommendations for the design of future rehabilitation studies. Because between-subject heterogeneity is one important reason why studies of neglect treatments often yield conflicting results, employing statistical procedures that model this heterogeneity more accurately will increase the efficiency of our efforts to find treatments to improve the lives of individuals with neglect. PMID
Amblàs-Novellas, J; Murray, S A; Espaulella, J; Martinez-Muñoz, M; Blay, C; Gómez-Batiste, X
2016-01-01
Objectives 2 innovative concepts have lately been developed to radically improve the care of patients with advanced chronic conditions (PACC): early identification of palliative care (PC) needs and the 3 end-of-life trajectories in chronic illnesses (acute, intermittent and gradual dwindling). It is not clear (1) what indicators work best for this early identification and (2) if specific clinical indicators exist for each of these trajectories. The objectives of this study are to explore these 2 issues. Setting 3 primary care services, an acute care hospital, an intermediate care centre and 4 nursing homes in a mixed urban–rural district in Barcelona, Spain. Participants 782 patients (61.5% women) with a positive NECPAL CCOMS-ICO test, indicating they might benefit from a PC approach. Outcome measures The characteristics and distribution of the indicators of the NECPAL CCOMS-ICO tool are analysed with respect to the 3 trajectories and have been arranged by domain (functional, nutritional and cognitive status, emotional problems, geriatric syndromes, social vulnerability and others) and according to their static (severity) and dynamic (progression) properties. Results The common indicators associated with early end-of-life identification are functional (44.3%) and nutritional (30.7%) progression, emotional distress (21.9%) and geriatric syndromes (15.7% delirium, 11.2% falls). The rest of the indicators showed differences in the associations per illness trajectories (p<0.05). 48.2% of the total cohort was identified as advanced frailty patients with no advanced disease criteria. Conclusions Dynamic indicators are present in the 3 trajectories and are especially useful to identify PACC for a progressive PC approach purpose. Most of the other indicators are typically associated with a specific trajectory. These findings can help clinicians improve the identification of patients for a palliative approach. PMID:27645556
ERIC Educational Resources Information Center
McGrath, April L.; Ferns, Alyssa; Greiner, Leigh; Wanamaker, Kayla; Brown, Shelley
2015-01-01
In this study we assessed the usefulness of a multifaceted teaching framework in an advanced statistics course. We sought to expand on past findings by using this framework to assess changes in anxiety and self-efficacy, and we collected focus group data to ascertain whether students attribute such changes to a multifaceted teaching approach.…
ERIC Educational Resources Information Center
Hassan, Mahamood M.; Schwartz, Bill N.
2014-01-01
This paper discusses a student research project that is part of an advanced cost accounting class. The project emphasizes active learning, integrates cost accounting with macroeconomics and statistics by "learning by doing" using real world data. Students analyze sales data for a publicly listed company by focusing on the company's…
NASA Astrophysics Data System (ADS)
Chao, Zenas C.; Bakkum, Douglas J.; Potter, Steve M.
2007-09-01
Electrically interfaced cortical networks cultured in vitro can be used as a model for studying the network mechanisms of learning and memory. Lasting changes in functional connectivity have been difficult to detect with extracellular multi-electrode arrays using standard firing rate statistics. We used both simulated and living networks to compare the ability of various statistics to quantify functional plasticity at the network level. Using a simulated integrate-and-fire neural network, we compared five established statistical methods to one of our own design, called center of activity trajectory (CAT). CAT, which depicts dynamics of the location-weighted average of spatiotemporal patterns of action potentials across the physical space of the neuronal circuitry, was the most sensitive statistic for detecting tetanus-induced plasticity in both simulated and living networks. By reducing the dimensionality of multi-unit data while still including spatial information, CAT allows efficient real-time computation of spatiotemporal activity patterns. Thus, CAT will be useful for studies in vivo or in vitro in which the locations of recording sites on multi-electrode probes are important.
NASA Astrophysics Data System (ADS)
Szkop, Artur; Pietruczuk, Aleksander; Posyniak, Michał
2016-12-01
A cluster analysis is applied to the Aerosol Robotic Network (AERONET) data obtained at Belsk, Poland, as well as three nearby Central European stations (Leipzig, Minsk and Moldova) for estimation of atmospheric aerosol types. Absorption Ångstrom exponent (AAE), aerosol optical thickness (AOT) and extinction Ångstrom exponent (EAE) parameters are used. Clustering in both 2D (AOT, EAE) and 3D (AOT, EAE, AAE) is investigated. A method of air mass backward trajectory analysis is then proposed, with the receptor site at Belsk, to determine possible source regions for each cluster. Four dominant aerosol source regions are identified. The biomass burning aerosol source is localized in the vicinity of Belarusian-Ukrainian border. Slovakia and northern Hungary are found to be the source of urban/industrial pollutants. Western Poland and eastern Germany are the main sources of polluted continental aerosols. The most differentiated source region of Scandinavia, Baltic Sea and Northern Atlantic, associated with lowest values of AOT, corresponds to clean continental and possibly maritime type aerosols.
Jorfi, M; González-Lezana, T; Zanchet, A; Honvault, P; Bussery-Honvault, B
2013-03-07
We report quasiclassical trajectory dynamical calculations for the C((3)P) + OH(X(2)Π) → CO(a(3)Π) + H((2)S) using a recently developed ab initio potential energy surface for the first electronic state of HCO of 1(2)A″ symmetry. The dependence of integral cross sections on the collision energy was determined. Product energy and angular distributions have also been calculated. Integral cross sections show no energy threshold and decrease as the collision energy increases. The comparison with results obtained from a statistical quantum method seems to confirm that the reaction is mainly dominated by an indirect mechanism in which a long-lived intermediate complex is involved.
NASA Astrophysics Data System (ADS)
Boning, Duane S.; Chung, James E.
1998-11-01
Advanced process technology will require more detailed understanding and tighter control of variation in devices and interconnects. The purpose of statistical metrology is to provide methods to measure and characterize variation, to model systematic and random components of that variation, and to understand the impact of variation on both yield and performance of advanced circuits. Of particular concern are spatial or pattern-dependencies within individual chips; such systematic variation within the chip can have a much larger impact on performance than wafer-level random variation. Statistical metrology methods will play an important role in the creation of design rules for advanced technologies. For example, a key issue in multilayer interconnect is the uniformity of interlevel dielectric (ILD) thickness within the chip. For the case of ILD thickness, we describe phases of statistical metrology development and application to understanding and modeling thickness variation arising from chemical-mechanical polishing (CMP). These phases include screening experiments including design of test structures and test masks to gather electrical or optical data, techniques for statistical decomposition and analysis of the data, and approaches to calibrating empirical and physical variation models. These models can be integrated with circuit CAD tools to evaluate different process integration or design rule strategies. One focus for the generation of interconnect design rules are guidelines for the use of "dummy fill" or "metal fill" to improve the uniformity of underlying metal density and thus improve the uniformity of oxide thickness within the die. Trade-offs that can be evaluated via statistical metrology include the improvements to uniformity possible versus the effect of increased capacitance due to additional metal.
Accuracy Evaluation of a Mobile Mapping System with Advanced Statistical Methods
NASA Astrophysics Data System (ADS)
Toschi, I.; Rodríguez-Gonzálvez, P.; Remondino, F.; Minto, S.; Orlandini, S.; Fuller, A.
2015-02-01
This paper discusses a methodology to evaluate the precision and the accuracy of a commercial Mobile Mapping System (MMS) with advanced statistical methods. So far, the metric potentialities of this emerging mapping technology have been studied in few papers, where generally the assumption that errors follow a normal distribution is made. In fact, this hypothesis should be carefully verified in advance, in order to test how well the Gaussian classic statistics can adapt to datasets that are usually affected by asymmetrical gross errors. The workflow adopted in this study relies on a Gaussian assessment, followed by an outlier filtering process. Finally, non-parametric statistical models are applied, in order to achieve a robust estimation of the error dispersion. Among the different MMSs available on the market, the latest solution provided by RIEGL is here tested, i.e. the VMX-450 Mobile Laser Scanning System. The test-area is the historic city centre of Trento (Italy), selected in order to assess the system performance in dealing with a challenging and historic urban scenario. Reference measures are derived from photogrammetric and Terrestrial Laser Scanning (TLS) surveys. All datasets show a large lack of symmetry that leads to the conclusion that the standard normal parameters are not adequate to assess this type of data. The use of non-normal statistics gives thus a more appropriate description of the data and yields results that meet the quoted a-priori errors.
Pataky, Todd C; Robinson, Mark A; Vanrenterghem, Jos
2016-01-01
One-dimensional (1D) kinematic, force, and EMG trajectories are often analyzed using zero-dimensional (0D) metrics like local extrema. Recently whole-trajectory 1D methods have emerged in the literature as alternatives. Since 0D and 1D methods can yield qualitatively different results, the two approaches may appear to be theoretically distinct. The purposes of this paper were (a) to clarify that 0D and 1D approaches are actually just special cases of a more general region-of-interest (ROI) analysis framework, and (b) to demonstrate how ROIs can augment statistical power. We first simulated millions of smooth, random 1D datasets to validate theoretical predictions of the 0D, 1D and ROI approaches and to emphasize how ROIs provide a continuous bridge between 0D and 1D results. We then analyzed a variety of public datasets to demonstrate potential effects of ROIs on biomechanical conclusions. Results showed, first, that a priori ROI particulars can qualitatively affect the biomechanical conclusions that emerge from analyses and, second, that ROIs derived from exploratory/pilot analyses can detect smaller biomechanical effects than are detectable using full 1D methods. We recommend regarding ROIs, like data filtering particulars and Type I error rate, as parameters which can affect hypothesis testing results, and thus as sensitivity analysis tools to ensure arbitrary decisions do not influence scientific interpretations. Last, we describe open-source Python and MATLAB implementations of 1D ROI analysis for arbitrary experimental designs ranging from one-sample t tests to MANOVA.
Links to sources of cancer-related statistics, including the Surveillance, Epidemiology and End Results (SEER) Program, SEER-Medicare datasets, cancer survivor prevalence data, and the Cancer Trends Progress Report.
Source apportionment advances using polar plots of bivariate correlation and regression statistics
NASA Astrophysics Data System (ADS)
Grange, Stuart K.; Lewis, Alastair C.; Carslaw, David C.
2016-11-01
This paper outlines the development of enhanced bivariate polar plots that allow the concentrations of two pollutants to be compared using pair-wise statistics for exploring the sources of atmospheric pollutants. The new method combines bivariate polar plots, which provide source characteristic information, with pair-wise statistics that provide information on how two pollutants are related to one another. The pair-wise statistics implemented include weighted Pearson correlation and slope from two linear regression methods. The development uses a Gaussian kernel to locally weight the statistical calculations on a wind speed-direction surface together with variable-scaling. Example applications of the enhanced polar plots are presented by using routine air quality data for two monitoring sites in London, United Kingdom for a single year (2013). The London examples demonstrate that the combination of bivariate polar plots, correlation, and regression techniques can offer considerable insight into air pollution source characteristics, which would be missed if only scatter plots and mean polar plots were used for analysis. Specifically, using correlation and slopes as pair-wise statistics, long-range transport processes were isolated and black carbon (BC) contributions to PM2.5 for a kerbside monitoring location were quantified. Wider applications and future advancements are also discussed.
ERIC Educational Resources Information Center
Abi-Mershed, Osama, Ed.
2011-01-01
"Trajectories of Education in the Arab World" gives a broad yet detailed historical and geographical overview of education in Arab countries. Drawing on pre-modern and modern educational concepts, systems, and practices in the Arab world, this book examines the impact of Western cultural influence, the opportunities for reform and the…
Trajectory structures and transport
Vlad, Madalina; Spineanu, Florin
2004-11-01
The special problem of transport in two-dimensional divergence-free stochastic velocity fields is studied by developing a statistical approach, the nested subensemble method. The nonlinear process of trapping determined by such fields generates trajectory structures whose statistical characteristics are determined. These structures strongly influence the transport.
NASA Astrophysics Data System (ADS)
Tscherwenka, W.; Seibert, P.; Kasper, A.; Puxbaum, H.
Continuous sulfur dioxide (SO 2) measurements were performed at the Sonnblick Observatory (SBO), Austria (3106 m a.s.l.) for several weeks during summer, autumn and spring 1995/96. The average SO 2 concentration was 0.30 μg m -3 standard temperature and pressure (STP; 273 K, 1013 hPa) (105 pptv), the median 0.10 μg m -3 STP (35 pptv). For 80% of the time sulfur dioxide concentrations were at "clean levels" (<0.30 μg m -3) interrupted by "episodes" lasting up to two days. During the episodes SO 2 levels rose generally above 0.5 μg m -3 and reached up to 8.0 μg m -3 in spring. Sulfur dioxide concentrations showed a strong seasonal variation with very low concentrations during summer and fall (means 0.11 and 0.17 μg m -3) and elevated concentrations during spring (mean 0.70 μg m -3). An analysis of the diurnal variation indicated that upslope winds are not responsible for the elevated SO 2 levels observed during SO 2 episodes; rather cloud transport appears to be the predominant process for lifting SO 2 from the boundary layer to the mid troposphere. For air and cloud transport across Western European countries hydrogen peroxide (H 2O 2) is apparently in excess and most SO 2 is removed by oxidation leading to "clean conditions". For the less frequent air and cloud transport from the East and Southeast SO 2 appears to be in excess leading to the "SO 2 episodes" at the 3 km level. These results are substantiated by in-cloud observations of elevated levels of SO 2 at SBO ( Brantner et al., 1994) and trajectory statistics for the SO 2 data set from SBO and analysis of the meteorological conditions during transport.
Kilshaw, Lindsey; Sammut, Hannah; Asher, Rebecca; Williams, Peter; Saxena, Rema; Howse, Matthew
2016-01-01
Background Some patients with end-stage renal failure (ESRF) are unlikely to benefit from dialysis and conservative management (CM) is offered as a positive alternative. Understanding the trajectory of illness by health care professionals may improve end-of-life care. Methods We aimed to describe the trajectory of functional status within our CM population through a prospective, observational study using the objective Timed Up and Go (TUG) test and subjective Barthel Index (BI) and health-related quality of life (HRQoL) [EuroQol 5D-5L (EQ-5D-5L)] measurements and correlating them with demographic and laboratory data and with sentinel events. Results There was a significant increase in TUG scores over the 6 months prior to death {2.24 [95% confidence interval (CI) 1.16–4.32], P = 0.017} and a significant decrease in EQ-5D-5L [−0.19 (95% CI −0.33 to −0.06), P = 0.006]. The only significant associations with mortality were serum albumin [hazard ratio (HR) 0.81 (95% CI 0.67–0.97), P = 0.024] and male gender [HR 5.94 (95% CI 1.50–23.5), P = 0.011]. Conclusions We have shown there is a significant decline in functional status in the last 6 months before death in the CM population. Of interest, there was a significant relationship of lower serum albumin with functional decline and risk of death. We hope that with improved insight into disease trajectories we can improve our ability to identify and respond to the changes in needs of these patients, facilitate complex and sensitive end-of-life discussions and improve end-of-life care. PMID:27274835
2008-06-01
Formation Control and Trajectory Management Techniques for Multiple Micro UAV Applications ( Contrôle d’une formation autonome évoluée, et gestion des...EN-SCI-195 Advanced Autonomous Formation Control and Trajectory Management Techniques for Multiple Micro UAV Applications ( Contrôle d’une formation...autonome évoluée, et gestion des trajectoires. Techniques d’applications pour micro UAV multiples) The material in this publication was
Sikirzhytskaya, Aliaksandra; Sikirzhytski, Vitali; Lednev, Igor K
2014-01-01
Body fluids are a common and important type of forensic evidence. In particular, the identification of menstrual blood stains is often a key step during the investigation of rape cases. Here, we report on the application of near-infrared Raman microspectroscopy for differentiating menstrual blood from peripheral blood. We observed that the menstrual and peripheral blood samples have similar but distinct Raman spectra. Advanced statistical analysis of the multiple Raman spectra that were automatically (Raman mapping) acquired from the 40 dried blood stains (20 donors for each group) allowed us to build classification model with maximum (100%) sensitivity and specificity. We also demonstrated that despite certain common constituents, menstrual blood can be readily distinguished from vaginal fluid. All of the classification models were verified using cross-validation methods. The proposed method overcomes the problems associated with currently used biochemical methods, which are destructive, time consuming and expensive.
Monte Carlo Simulations in Statistical Physics -- From Basic Principles to Advanced Applications
NASA Astrophysics Data System (ADS)
Janke, Wolfhard
2013-08-01
This chapter starts with an overview of Monte Carlo computer simulation methodologies which are illustrated for the simple case of the Ising model. After reviewing importance sampling schemes based on Markov chains and standard local update rules (Metropolis, Glauber, heat-bath), nonlocal cluster-update algorithms are explained which drastically reduce the problem of critical slowing down at second-order phase transitions and thus improve the performance of simulations. How this can be quantified is explained in the section on statistical error analyses of simulation data including the effect of temporal correlations and autocorrelation times. Histogram reweighting methods are explained in the next section. Eventually, more advanced generalized ensemble methods (simulated and parallel tempering, multicanonical ensemble, Wang-Landau method) are discussed which are particularly important for simulations of first-order phase transitions and, in general, of systems with rare-event states. The setup of scaling and finite-size scaling analyses is the content of the following section. The chapter concludes with two advanced applications to complex physical systems. The first example deals with a quenched, diluted ferromagnet, and in the second application we consider the adsorption properties of macromolecules such as polymers and proteins to solid substrates. Such systems often require especially tailored algorithms for their efficient and successful simulation.
PREFACE: Advanced many-body and statistical methods in mesoscopic systems
NASA Astrophysics Data System (ADS)
Anghel, Dragos Victor; Sabin Delion, Doru; Sorin Paraoanu, Gheorghe
2012-02-01
It has increasingly been realized in recent times that the borders separating various subfields of physics are largely artificial. This is the case for nanoscale physics, physics of lower-dimensional systems and nuclear physics, where the advanced techniques of many-body theory developed in recent times could provide a unifying framework for these disciplines under the general name of mesoscopic physics. Other fields, such as quantum optics and quantum information, are increasingly using related methods. The 6-day conference 'Advanced many-body and statistical methods in mesoscopic systems' that took place in Constanta, Romania, between 27 June and 2 July 2011 was, we believe, a successful attempt at bridging an impressive list of topical research areas: foundations of quantum physics, equilibrium and non-equilibrium quantum statistics/fractional statistics, quantum transport, phases and phase transitions in mesoscopic systems/superfluidity and superconductivity, quantum electromechanical systems, quantum dissipation, dephasing, noise and decoherence, quantum information, spin systems and their dynamics, fundamental symmetries in mesoscopic systems, phase transitions, exactly solvable methods for mesoscopic systems, various extension of the random phase approximation, open quantum systems, clustering, decay and fission modes and systematic versus random behaviour of nuclear spectra. This event brought together participants from seventeen countries and five continents. Each of the participants brought considerable expertise in his/her field of research and, at the same time, was exposed to the newest results and methods coming from the other, seemingly remote, disciplines. The talks touched on subjects that are at the forefront of topical research areas and we hope that the resulting cross-fertilization of ideas will lead to new, interesting results from which everybody will benefit. We are grateful for the financial and organizational support from IFIN-HH, Ovidius
NASA Astrophysics Data System (ADS)
Andronov, I. L.; Chinarova, L. L.; Kudashkina, L. S.; Marsakova, V. I.; Tkachenko, M. G.
2016-06-01
We have elaborated a set of new algorithms and programs for advanced time series analysis of (generally) multi-component multi-channel observations with irregularly spaced times of observations, which is a common case for large photometric surveys. Previous self-review on these methods for periodogram, scalegram, wavelet, autocorrelation analysis as well as on "running" or "sub-interval" local approximations were self-reviewed in (2003ASPC..292..391A). For an approximation of the phase light curves of nearly-periodic pulsating stars, we use a Trigonometric Polynomial (TP) fit of the statistically optimal degree and initial period improvement using differential corrections (1994OAP.....7...49A). For the determination of parameters of "characteristic points" (minima, maxima, crossings of some constant value etc.) we use a set of methods self-reviewed in 2005ASPC..335...37A, Results of the analysis of the catalogs compiled using these programs are presented in 2014AASP....4....3A. For more complicated signals, we use "phenomenological approximations" with "special shapes" based on functions defined on sub-intervals rather on the complete interval. E. g. for the Algol-type stars we developed the NAV ("New Algol Variable") algorithm (2012Ap.....55..536A, 2012arXiv1212.6707A, 2015JASS...32..127A), which was compared to common methods of Trigonometric Polynomial Fit (TP) or local Algebraic Polynomial (A) fit of a fixed or (alternately) statistically optimal degree. The method allows determine the minimal set of parameters required for the "General Catalogue of Variable Stars", as well as an extended set of phenomenological and astrophysical parameters which may be used for the classification. Totally more that 1900 variable stars were studied in our group using these methods in a frame of the "Inter-Longitude Astronomy" campaign (2010OAP....23....8A) and the "Ukrainian Virtual Observatory" project (2012KPCB...28...85V).
Preserving correlations between trajectories for efficient path sampling
Gingrich, Todd R.; Geissler, Phillip L.
2015-06-21
Importance sampling of trajectories has proved a uniquely successful strategy for exploring rare dynamical behaviors of complex systems in an unbiased way. Carrying out this sampling, however, requires an ability to propose changes to dynamical pathways that are substantial, yet sufficiently modest to obtain reasonable acceptance rates. Satisfying this requirement becomes very challenging in the case of long trajectories, due to the characteristic divergences of chaotic dynamics. Here, we examine schemes for addressing this problem, which engineer correlation between a trial trajectory and its reference path, for instance using artificial forces. Our analysis is facilitated by a modern perspective on Markov chain Monte Carlo sampling, inspired by non-equilibrium statistical mechanics, which clarifies the types of sampling strategies that can scale to long trajectories. Viewed in this light, the most promising such strategy guides a trial trajectory by manipulating the sequence of random numbers that advance its stochastic time evolution, as done in a handful of existing methods. In cases where this “noise guidance” synchronizes trajectories effectively, as the Glauber dynamics of a two-dimensional Ising model, we show that efficient path sampling can be achieved for even very long trajectories.
ERIC Educational Resources Information Center
Potter, James Thomson, III
2012-01-01
Research into teaching practices and strategies has been performed separately in AP Statistics and in K-12 online learning (Garfield, 2002; Ferdig, DiPietro, Black & Dawson, 2009). This study seeks combine the two and build on the need for more investigation into online teaching and learning in specific content (Ferdig et al, 2009; DiPietro,…
Classification of human colonic tissues using FTIR spectra and advanced statistical techniques
NASA Astrophysics Data System (ADS)
Zwielly, A.; Argov, S.; Salman, A.; Bogomolny, E.; Mordechai, S.
2010-04-01
One of the major public health hazards is colon cancer. There is a great necessity to develop new methods for early detection of cancer. If colon cancer is detected and treated early, cure rate of more than 90% can be achieved. In this study we used FTIR microscopy (MSP), which has shown a good potential in the last 20 years in the fields of medical diagnostic and early detection of abnormal tissues. Large database of FTIR microscopic spectra was acquired from 230 human colonic biopsies. Five different subgroups were included in our database, normal and cancer tissues as well as three stages of benign colonic polyps, namely, mild, moderate and severe polyps which are precursors of carcinoma. In this study we applied advanced mathematical and statistical techniques including principal component analysis (PCA) and linear discriminant analysis (LDA), on human colonic FTIR spectra in order to differentiate among the mentioned subgroups' tissues. Good classification accuracy between normal, polyps and cancer groups was achieved with approximately 85% success rate. Our results showed that there is a great potential of developing FTIR-micro spectroscopy as a simple, reagent-free viable tool for early detection of colon cancer in particular the early stages of premalignancy among the benign colonic polyps.
trajectory and the transient trajectories from the steady-state path to the endpoints could be computed separately. The results using this method agreed well with the exact solution and gave a tremendous savings in computing time....described the motion of a body similar to the one under study. The nature of the REAC solutions suggested that the steady-state, or mid-path
ERIC Educational Resources Information Center
McCarthy, Christopher J.; Lambert, Richard G.; Crowe, Elizabeth W.; McCarthy, Colleen J.
2010-01-01
This study examined the relationship of teachers' perceptions of coping resources and demands to job satisfaction factors. Participants were 158 Advanced Placement Statistics high school teachers who completed measures of personal resources for stress prevention, classroom demands and resources, job satisfaction, and intention to leave the field…
"I am Not a Statistic": Identities of African American Males in Advanced Science Courses
NASA Astrophysics Data System (ADS)
Johnson, Diane Wynn
The United States Bureau of Labor Statistics (2010) expects new industries to generate approximately 2.7 million jobs in science and technology by the year 2018, and there is concern as to whether there will be enough trained individuals to fill these positions. A tremendous resource remains untapped, African American students, especially African American males (National Science Foundation, 2009). Historically, African American males have been omitted from the so called science pipeline. Fewer African American males pursue a science discipline due, in part; to limiting factors they experience in school and at home (Ogbu, 2004). This is a case study of African American males who are enrolled in advanced science courses at a predominantly African American (84%) urban high school. Guided by expectancy-value theory (EVT) of achievement related results (Eccles, 2009; Eccles et al., 1983), twelve African American male students in two advanced science courses were observed in their science classrooms weekly, participated in an in-depth interview, developed a presentation to share with students enrolled in a tenth grade science course, responded to an open-ended identity questionnaire, and were surveyed about their perceptions of school. Additionally, the students' teachers were interviewed, and seven of the students' parents. The interview data analyses highlighted the important role of supportive parents (key socializers) who had high expectations for their sons and who pushed them academically. The students clearly attributed their enrollment in advanced science courses to their high regard for their science teachers, which included positive relationships, hands-on learning in class, and an inviting and encouraging learning environment. Additionally, other family members and coaches played important roles in these young men's lives. Students' PowerPoint(c) presentations to younger high school students on why they should take advanced science courses highlighted these
Analyzing Planck and low redshift data sets with advanced statistical methods
NASA Astrophysics Data System (ADS)
Eifler, Tim
The recent ESA/NASA Planck mission has provided a key data set to constrain cosmology that is most sensitive to physics of the early Universe, such as inflation and primordial NonGaussianity (Planck 2015 results XIII). In combination with cosmological probes of the LargeScale Structure (LSS), the Planck data set is a powerful source of information to investigate late time phenomena (Planck 2015 results XIV), e.g. the accelerated expansion of the Universe, the impact of baryonic physics on the growth of structure, and the alignment of galaxies in their dark matter halos. It is the main objective of this proposal to re-analyze the archival Planck data, 1) with different, more recently developed statistical methods for cosmological parameter inference, and 2) to combine Planck and ground-based observations in an innovative way. We will make the corresponding analysis framework publicly available and believe that it will set a new standard for future CMB-LSS analyses. Advanced statistical methods, such as the Gibbs sampler (Jewell et al 2004, Wandelt et al 2004) have been critical in the analysis of Planck data. More recently, Approximate Bayesian Computation (ABC, see Weyant et al 2012, Akeret et al 2015, Ishida et al 2015, for cosmological applications) has matured to an interesting tool in cosmological likelihood analyses. It circumvents several assumptions that enter the standard Planck (and most LSS) likelihood analyses, most importantly, the assumption that the functional form of the likelihood of the CMB observables is a multivariate Gaussian. Beyond applying new statistical methods to Planck data in order to cross-check and validate existing constraints, we plan to combine Planck and DES data in a new and innovative way and run multi-probe likelihood analyses of CMB and LSS observables. The complexity of multiprobe likelihood analyses scale (non-linearly) with the level of correlations amongst the individual probes that are included. For the multi
Design and contents of an advanced distance-based statistics course for a PhD in nursing program.
Azuero, Andres; Wilbanks, Bryan; Pryor, Erica
2013-01-01
Doctoral nursing students and researchers are expected to understand, critique, and conduct research that uses advanced quantitative methodology. The authors describe the design and contents of a distance-based course in multivariate statistics for PhD students in nursing and health administration, compare the design to recommendations found in the literature for distance-based statistics education, and compare the course contents to a tabulation of the methodologies used in a sample of recently published quantitative dissertations in nursing. The authors conclude with a discussion based on these comparisons as well as with experiences in course implementation and directions for future course development.
NASA Technical Reports Server (NTRS)
Rehder, J. J.
1975-01-01
One candidate for a reusable upper stage to be carried by the space shuttle is an aeromaneuvering orbit-to-orbit shuttle (AMOOS). This concept uses the drag of the vehicle during a pass through the atmosphere rather than the propulsion system to slow the vehicle on a return from a high energy orbit. The nature and magnitude of the sensitivity of AMOOS to uncertainties in the properties of the atmosphere are shown. Various guidance schemes for correcting for the effects that the unpredictable variations in the atmosphere have on the trajectory are discussed. For the mission studied here, a payload retrieval from geosynchronous orbit with aerodynamic plane change, a linear feedback guidance scheme was developed. A relatively simple heuristic law was used to demonstrate the concept. Using optimal control theory a feedback law was developed analytically. Testing with a large number of different atmospheres showed this law to be a feasible means of controlling the AMOOS trajectory. Refinements to the technique offer promise of significant improvement, and these are discussed.
ERIC Educational Resources Information Center
Heaviside, Sheila; And Others
The "Survey of Advanced Telecommunications in U.S. Public Elementary and Secondary Schools, Fall 1996" collected information from 911 regular United States public elementary and secondary schools regarding the availability and use of advanced telecommunications, and in particular, access to the Internet, plans to obtain Internet access, use of…
Advanced statistical process control: controlling sub-0.18-μm lithography and other processes
NASA Astrophysics Data System (ADS)
Zeidler, Amit; Veenstra, Klaas-Jelle; Zavecz, Terrence E.
2001-08-01
Feed-forward, as a method to control the Lithography process for Critical Dimensions and Overlay, is well known in the semiconductors industry. However, the control provided by simple averaging feed-forward methodologies is not sufficient to support the complexity of a sub-0.18micrometers lithography process. Also, simple feed-forward techniques are not applicable for logics and ASIC production due to many different products, lithography chemistry combinations and the short memory of the averaging method. In the semiconductors industry, feed-forward control applications are generally called APC, Advanced Process Control applications. Today, there are as many APC methods as the number of engineers involved. To meet the stringent requirements of 0.18 micrometers production, we selected a method that is described in SPIE 3998-48 (March 2000) by Terrence Zavecz and Rene Blanquies from Yield Dynamics Inc. This method is called PPC, Predictive Process Control, and employs a methodology of collecting measurement results and the modeled bias attributes of expose tools, reticles and the incoming process in a signatures database. With PPC, before each lot exposure, the signatures of the lithography tool, the reticle and the incoming process are used to predict the setup of the lot process and the expected lot results. Benefits derived from such an implementation are very clear; there is no limitation of the number of products or lithography-chemistry combinations and the technique avoids the short memory of conventional APC techniques. ... and what's next? (Rob Morton, Philips assignee to International Sematech). The next part of the paper will try to answer this question. Observing that CMP and metal deposition significantly influence CD's and overlay results, and even Contact Etch can have a significant influence on Metal 5 overlay, we developed a more general PPC for lithography. Starting with the existing lithography PPC applications database, the authors extended the
NASA Technical Reports Server (NTRS)
Burke, Laura M.
2004-01-01
The Systems Analysis Branch performs trajectory and systems analysis for next-generation launch vehicle and space transportation technologies. Currently the branch is supporting the Project Prometheus with analysis of nuclear electric and nuclear thermal propulsion missions to a variety of destinations. Within Project Prometheus a proposed mission to Jupiter and three of the planet sized icy moons that orbit it is developing. The Jupiter Icy Moons Orbiter (JIMO) as the project is being called will enable detailed scientific investigation of Jupiter's moons Callisto, Ganymede, and Europa. These moons were choose to orbit for intensive study in particular because they are each believed to have water, energy, and organic material. The JIMO mission will utilize nuclear fission power and electric propulsion in order to allow the spacecraft to orbit the moons at close range for long durations of time. My assignment this summer was to assist in developing a trajectory analysis for the spacecraft system the Jupiter Icy Moons Orbiter by rewriting an inefficient Excel file into a more efficient FORTRAN program. This program has been created for use planning the trajectory of the Jupiter Icy Moons Orbiter Mission. The program uses a database of thousands of data points representing flight time, burn time, thrust, mass of the propellant used, final mass of the spacecraft, ratio of finals mass to initial mass, and change in velocity that a spacecraft experiences during each phase in the Jupiter Icy Moons Orbiter Mission. The trajectory program is capable of taking a specific user entered specific impulse (isp), final mass fraction, and thrust (P(sub J)/m0) and through the use of cubic splines to fit specific data curves, the program can locate the exact flight time linked to the user specified values of specific impulse and final over initial mass fraction. Currently, the database used by the program to calculate flight times for a given thrust is only for isps in the range of
Schaid, Daniel J
2010-01-01
Measures of genomic similarity are the basis of many statistical analytic methods. We review the mathematical and statistical basis of similarity methods, particularly based on kernel methods. A kernel function converts information for a pair of subjects to a quantitative value representing either similarity (larger values meaning more similar) or distance (smaller values meaning more similar), with the requirement that it must create a positive semidefinite matrix when applied to all pairs of subjects. This review emphasizes the wide range of statistical methods and software that can be used when similarity is based on kernel methods, such as nonparametric regression, linear mixed models and generalized linear mixed models, hierarchical models, score statistics, and support vector machines. The mathematical rigor for these methods is summarized, as is the mathematical framework for making kernels. This review provides a framework to move from intuitive and heuristic approaches to define genomic similarities to more rigorous methods that can take advantage of powerful statistical modeling and existing software. A companion paper reviews novel approaches to creating kernels that might be useful for genomic analyses, providing insights with examples [1].
Statistical analyses of the magnet data for the advanced photon source storage ring magnets
Kim, S.H.; Carnegie, D.W.; Doose, C.; Hogrefe, R.; Kim, K.; Merl, R.
1995-05-01
The statistics of the measured magnetic data of 80 dipole, 400 quadrupole, and 280 sextupole magnets of conventional resistive designs for the APS storage ring is summarized. In order to accommodate the vacuum chamber, the curved dipole has a C-type cross section and the quadrupole and sextupole cross sections have 180{degrees} and 120{degrees} symmetries, respectively. The data statistics include the integrated main fields, multipole coefficients, magnetic and mechanical axes, and roll angles of the main fields. The average and rms values of the measured magnet data meet the storage ring requirements.
ERIC Educational Resources Information Center
Touchton, Michael
2015-01-01
I administer a quasi-experiment using undergraduate political science majors in statistics classes to evaluate whether "flipping the classroom" (the treatment) alters students' applied problem-solving performance and satisfaction relative to students in a traditional classroom environment (the control). I also assess whether general…
Advanced statistical methods for improved data analysis of NASA astrophysics missions
NASA Technical Reports Server (NTRS)
Feigelson, Eric D.
1992-01-01
The investigators under this grant studied ways to improve the statistical analysis of astronomical data. They looked at existing techniques, the development of new techniques, and the production and distribution of specialized software to the astronomical community. Abstracts of nine papers that were produced are included, as well as brief descriptions of four software packages. The articles that are abstracted discuss analytical and Monte Carlo comparisons of six different linear least squares fits, a (second) paper on linear regression in astronomy, two reviews of public domain software for the astronomer, subsample and half-sample methods for estimating sampling distributions, a nonparametric estimation of survival functions under dependent competing risks, censoring in astronomical data due to nondetections, an astronomy survival analysis computer package called ASURV, and improving the statistical methodology of astronomical data analysis.
Blangero, John; Diego, Vincent P.; Dyer, Thomas D.; Almeida, Marcio; Peralta, Juan; Kent, Jack W.; Williams, Jeff T.; Almasy, Laura; Göring, Harald H. H.
2014-01-01
Statistical genetic analysis of quantitative traits in large pedigrees is a formidable computational task due to the necessity of taking the non-independence among relatives into account. With the growing awareness that rare sequence variants may be important in human quantitative variation, heritability and association study designs involving large pedigrees will increase in frequency due to the greater chance of observing multiple copies of rare variants amongst related individuals. Therefore, it is important to have statistical genetic test procedures that utilize all available information for extracting evidence regarding genetic association. Optimal testing for marker/phenotype association involves the exact calculation of the likelihood ratio statistic which requires the repeated inversion of potentially large matrices. In a whole genome sequence association context, such computation may be prohibitive. Toward this end, we have developed a rapid and efficient eigensimplification of the likelihood that makes analysis of family data commensurate with the analysis of a comparable sample of unrelated individuals. Our theoretical results which are based on a spectral representation of the likelihood yield simple exact expressions for the expected likelihood ratio test statistic (ELRT) for pedigrees of arbitrary size and complexity. For heritability, the ELRT is: −∑ln[1+ĥ2(λgi−1)], where ĥ2 and λgi are respectively the heritability and eigenvalues of the pedigree-derived genetic relationship kernel (GRK). For association analysis of sequence variants, the ELRT is given by ELRT[hq2>0:unrelateds]−(ELRT[ht2>0:pedigrees]−ELRT[hr2>0:pedigrees]), where ht2,hq2, and hr2 are the total, quantitative trait nucleotide, and residual heritabilities, respectively. Using these results, fast and accurate analytical power analyses are possible, eliminating the need for computer simulation. Additional benefits of eigensimplification include a simple method for
Live-site UXO classification studies using advanced EMI and statistical models
NASA Astrophysics Data System (ADS)
Shamatava, I.; Shubitidze, F.; Fernandez, J. P.; Bijamov, A.; Barrowes, B. E.; O'Neill, K.
2011-06-01
In this paper we present the inversion and classification performance of the advanced EMI inversion, processing and discrimination schemes developed by our group when applied to the ESTCP Live-Site UXO Discrimination Study carried out at the former Camp Butner in North Carolina. The advanced models combine: 1) the joint diagonalization (JD) algorithm to estimate the number of potential anomalies from the measured data without inversion, 2) the ortho-normalized volume magnetic source (ONVMS) to represent targets' EMI responses and extract their intrinsic "feature vectors," and 3) the Gaussian mixture algorithm to classify buried objects as targets of interest or not starting from the extracted discrimination features. The studies are conducted using cued datasets collected with the next-generation TEMTADS and MetalMapper (MM) sensor systems. For the cued TEMTADS datasets we first estimate the data quality and the number of targets contributing to each signal using the JD technique. Once we know the number of targets we proceed to invert the data using a standard non-linear optimization technique in order to determine intrinsic parameters such as the total ONVMS for each potential target. Finally we classify the targets using a library-matching technique. The MetalMapper data are all inverted as multi-target scenarios, and the resulting intrinsic parameters are grouped using an unsupervised Gaussian mixture approach. The potential targets of interest are a 37-mm projectile, an M48 fuze, and a 105-mm projectile. During the analysis we requested the ground truth for a few selected anomalies to assist in the classification task. Our results were scored independently by the Institute for Defense Analyses, who revealed that our advanced models produce superb classification when starting from either TEMTADS or MM cued datasets.
New advances in methodology for statistical tests useful in geostatistical studies
Borgman, L.E.
1988-05-01
Methodology for statistical procedures to perform tests of hypothesis pertaining to various aspects of geostatistical investigations has been slow in developing. The correlated nature of the data precludes most classical tests and makes the design of new tests difficult. Recent studies have led to modifications of the classical t test which allow for the intercorrelation. In addition, results for certain nonparametric tests have been obtained. The conclusions of these studies provide a variety of new tools for the geostatistician in deciding questions on significant differences and magnitudes.
2012-01-01
assume that the NSMS can be approximated by a series of expansion functions F m ( ) such that ( ) m F m ( ) m1 M (31) UXO...a receiver coil is the electromotive force given by the negative of the time derivative of the secondary magnetic flux through the coil. Since the...statistical signal processing MM-1572 Final Report Sky Research, Inc. January 2012 52 A support vector machine learns from data: when fed a series
Advances in statistical methods to map quantitative trait loci in outbred populations.
Hoeschele, I; Uimari, P; Grignola, F E; Zhang, Q; Gage, K M
1997-11-01
Statistical methods to map quantitative trait loci (QTL) in outbred populations are reviewed, extensions and applications to human and plant genetic data are indicated, and areas for further research are identified. Simple and computationally inexpensive methods include (multiple) linear regression of phenotype on marker genotypes and regression of squared phenotypic differences among relative pairs on estimated proportions of identity-by-descent at a locus. These methods are less suited for genetic parameter estimation in outbred populations but allow the determination of test statistic distributions via simulation or data permutation; however, further inferences including confidence intervals of QTL location require the use of Monte Carlo or bootstrap sampling techniques. A method which is intermediate in computational requirements is residual maximum likelihood (REML) with a covariance matrix of random QTL effects conditional on information from multiple linked markers. Testing for the number of QTLs on a chromosome is difficult in a classical framework. The computationally most demanding methods are maximum likelihood and Bayesian analysis, which take account of the distribution of multilocus marker-QTL genotypes on a pedigree and permit investigators to fit different models of variation at the QTL. The Bayesian analysis includes the number of QTLs on a chromosome as an unknown.
Improved Test Planning and Analysis Through the Use of Advanced Statistical Methods
NASA Technical Reports Server (NTRS)
Green, Lawrence L.; Maxwell, Katherine A.; Glass, David E.; Vaughn, Wallace L.; Barger, Weston; Cook, Mylan
2016-01-01
The goal of this work is, through computational simulations, to provide statistically-based evidence to convince the testing community that a distributed testing approach is superior to a clustered testing approach for most situations. For clustered testing, numerous, repeated test points are acquired at a limited number of test conditions. For distributed testing, only one or a few test points are requested at many different conditions. The statistical techniques of Analysis of Variance (ANOVA), Design of Experiments (DOE) and Response Surface Methods (RSM) are applied to enable distributed test planning, data analysis and test augmentation. The D-Optimal class of DOE is used to plan an optimally efficient single- and multi-factor test. The resulting simulated test data are analyzed via ANOVA and a parametric model is constructed using RSM. Finally, ANOVA can be used to plan a second round of testing to augment the existing data set with new data points. The use of these techniques is demonstrated through several illustrative examples. To date, many thousands of comparisons have been performed and the results strongly support the conclusion that the distributed testing approach outperforms the clustered testing approach.
Advances in Statistical Methods to Map Quantitative Trait Loci in Outbred Populations
Hoeschele, I.; Uimari, P.; Grignola, F. E.; Zhang, Q.; Gage, K. M.
1997-01-01
Statistical methods to map quantitative trait loci (QTL) in outbred populations are reviewed, extensions and applications to human and plant genetic data are indicated, and areas for further research are identified. Simple and computationally inexpensive methods include (multiple) linear regression of phenotype on marker genotypes and regression of squared phenotypic differences among relative pairs on estimated proportions of identity-by-descent at a locus. These methods are less suited for genetic parameter estimation in outbred populations but allow the determination of test statistic distributions via simulation or data permutation; however, further inferences including confidence intervals of QTL location require the use of Monte Carlo or bootstrap sampling techniques. A method which is intermediate in computational requirements is residual maximum likelihood (REML) with a covariance matrix of random QTL effects conditional on information from multiple linked markers. Testing for the number of QTLs on a chromosome is difficult in a classical framework. The computationally most demanding methods are maximum likelihood and Bayesian analysis, which take account of the distribution of multilocus marker-QTL genotypes on a pedigree and permit investigators to fit different models of variation at the QTL. The Bayesian analysis includes the number of QTLs on a chromosome as an unknown. PMID:9383084
NASA Astrophysics Data System (ADS)
Colin, T. A.
1995-07-01
This paper reviews advances in methods for estimating fluvial transport of suspended sediment and nutrients. Research from the past four years, mostly dealing with estimating monthly and annual loads, is emphasized. However, because this topic has not appeared in previous IUGG reports, some research prior to 1990 is included. The motivation for studying sediment transport has shifted during the past few decades. In addition to its role in filling reservoirs and channels, sediment is increasingly recognized as an important part of fluvial ecosystems and estuarine wetlands. Many groups want information about sediment transport [Bollman, 1992]: Scientists trying to understand benthic biology and catchment hydrology; citizens and policy-makers concerned about environmental impacts (e.g. impacts of logging [Beschta, 1978] or snow-fences [Sturges, 1992]); government regulators considering the effectiveness of programs to protect in-stream habitat and downstream waterbodies; and resource managers seeking to restore wetlands.
NASA Astrophysics Data System (ADS)
Fernández-González, Daniel; Martín-Duarte, Ramón; Ruiz-Bustinza, Íñigo; Mochón, Javier; González-Gasca, Carmen; Verdeja, Luis Felipe
2016-08-01
Blast furnace operators expect to get sinter with homogenous and regular properties (chemical and mechanical), necessary to ensure regular blast furnace operation. Blends for sintering also include several iron by-products and other wastes that are obtained in different processes inside the steelworks. Due to their source, the availability of such materials is not always consistent, but their total production should be consumed in the sintering process, to both save money and recycle wastes. The main scope of this paper is to obtain the least expensive iron ore blend for the sintering process, which will provide suitable chemical and mechanical features for the homogeneous and regular operation of the blast furnace. The systematic use of statistical tools was employed to analyze historical data, including linear and partial correlations applied to the data and fuzzy clustering based on the Sugeno Fuzzy Inference System to establish relationships among the available variables.
NASA Astrophysics Data System (ADS)
Li, Y.; Kirchengast, G.; Scherllin-Pirscher, B.; Norman, R.; Yuan, Y. B.; Fritzer, J.; Schwaerz, M.; Zhang, K.
2015-08-01
We introduce a new dynamic statistical optimization algorithm to initialize ionosphere-corrected bending angles of Global Navigation Satellite System (GNSS)-based radio occultation (RO) measurements. The new algorithm estimates background and observation error covariance matrices with geographically varying uncertainty profiles and realistic global-mean correlation matrices. The error covariance matrices estimated by the new approach are more accurate and realistic than in simplified existing approaches and can therefore be used in statistical optimization to provide optimal bending angle profiles for high-altitude initialization of the subsequent Abel transform retrieval of refractivity. The new algorithm is evaluated against the existing Wegener Center Occultation Processing System version 5.6 (OPSv5.6) algorithm, using simulated data on two test days from January and July 2008 and real observed CHAllenging Minisatellite Payload (CHAMP) and Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) measurements from the complete months of January and July 2008. The following is achieved for the new method's performance compared to OPSv5.6: (1) significant reduction of random errors (standard deviations) of optimized bending angles down to about half of their size or more; (2) reduction of the systematic differences in optimized bending angles for simulated MetOp data; (3) improved retrieval of refractivity and temperature profiles; and (4) realistically estimated global-mean correlation matrices and realistic uncertainty fields for the background and observations. Overall the results indicate high suitability for employing the new dynamic approach in the processing of long-term RO data into a reference climate record, leading to well-characterized and high-quality atmospheric profiles over the entire stratosphere.
NASA Astrophysics Data System (ADS)
Li, Y.; Kirchengast, G.; Scherllin-Pirscher, B.; Norman, R.; Yuan, Y. B.; Fritzer, J.; Schwaerz, M.; Zhang, K.
2015-01-01
We introduce a new dynamic statistical optimization algorithm to initialize ionosphere-corrected bending angles of Global Navigation Satellite System (GNSS) based radio occultation (RO) measurements. The new algorithm estimates background and observation error covariance matrices with geographically-varying uncertainty profiles and realistic global-mean correlation matrices. The error covariance matrices estimated by the new approach are more accurate and realistic than in simplified existing approaches and can therefore be used in statistical optimization to provide optimal bending angle profiles for high-altitude initialization of the subsequent Abel transform retrieval of refractivity. The new algorithm is evaluated against the existing Wegener Center Occultation Processing System version 5.6 (OPSv5.6) algorithm, using simulated data on two test days from January and July 2008 and real observed CHAMP and COSMIC measurements from the complete months of January and July 2008. The following is achieved for the new method's performance compared to OPSv5.6: (1) significant reduction in random errors (standard deviations) of optimized bending angles down to about two-thirds of their size or more; (2) reduction of the systematic differences in optimized bending angles for simulated MetOp data; (3) improved retrieval of refractivity and temperature profiles; (4) produces realistically estimated global-mean correlation matrices and realistic uncertainty fields for the background and observations. Overall the results indicate high suitability for employing the new dynamic approach in the processing of long-term RO data into a reference climate record, leading to well characterized and high-quality atmospheric profiles over the entire stratosphere.
ERIC Educational Resources Information Center
Connell, Arin M.; Frye, Alice A.
2006-01-01
Recent advances in statistical techniques for longitudinal data analysis have provided increased capabilities for elucidating individual differences in trajectories of change in child behaviours and abilities. However, most techniques still assume that there is a single underlying distribution with respect to changes over time, about which…
Murari, A; Gelfusa, M; Peluso, E; Gaudio, P; Mazon, D; Hawkes, N; Point, G; Alper, B; Eich, T
2014-12-01
In a Tokamak the configuration of the magnetic fields remains the key element to improve performance and to maximise the scientific exploitation of the device. On the other hand, the quality of the reconstructed fields depends crucially on the measurements available. Traditionally in the least square minimisation phase of the algorithms, used to obtain the magnetic field topology, all the diagnostics are given the same weights, a part from a corrective factor taking into account the error bars. This assumption unduly penalises complex diagnostics, such as polarimetry, which have a limited number of highly significant measurements. A completely new method to choose the weights, to be given to the internal measurements of the magnetic fields for improved equilibrium reconstructions, is presented in this paper. The approach is based on various statistical indicators applied to the residuals, the difference between the actual measurements and their estimates from the reconstructed equilibrium. The potential of the method is exemplified using the measurements of the Faraday rotation derived from JET polarimeter. The results indicate quite clearly that the weights have to be determined carefully, since the inappropriate choice can have significant repercussions on the quality of the magnetic reconstruction both in the edge and in the core. These results confirm the limitations of the assumption that all the diagnostics have to be given the same weight, irrespective of the number of measurements they provide and the region of the plasma they probe.
Abut, Fatih; Akay, Mehmet Fatih
2015-01-01
Maximal oxygen uptake (VO2max) indicates how many milliliters of oxygen the body can consume in a state of intense exercise per minute. VO2max plays an important role in both sport and medical sciences for different purposes, such as indicating the endurance capacity of athletes or serving as a metric in estimating the disease risk of a person. In general, the direct measurement of VO2max provides the most accurate assessment of aerobic power. However, despite a high level of accuracy, practical limitations associated with the direct measurement of VO2max, such as the requirement of expensive and sophisticated laboratory equipment or trained staff, have led to the development of various regression models for predicting VO2max. Consequently, a lot of studies have been conducted in the last years to predict VO2max of various target audiences, ranging from soccer athletes, nonexpert swimmers, cross-country skiers to healthy-fit adults, teenagers, and children. Numerous prediction models have been developed using different sets of predictor variables and a variety of machine learning and statistical methods, including support vector machine, multilayer perceptron, general regression neural network, and multiple linear regression. The purpose of this study is to give a detailed overview about the data-driven modeling studies for the prediction of VO2max conducted in recent years and to compare the performance of various VO2max prediction models reported in related literature in terms of two well-known metrics, namely, multiple correlation coefficient (R) and standard error of estimate. The survey results reveal that with respect to regression methods used to develop prediction models, support vector machine, in general, shows better performance than other methods, whereas multiple linear regression exhibits the worst performance. PMID:26346869
Abut, Fatih; Akay, Mehmet Fatih
2015-01-01
Maximal oxygen uptake (VO2max) indicates how many milliliters of oxygen the body can consume in a state of intense exercise per minute. VO2max plays an important role in both sport and medical sciences for different purposes, such as indicating the endurance capacity of athletes or serving as a metric in estimating the disease risk of a person. In general, the direct measurement of VO2max provides the most accurate assessment of aerobic power. However, despite a high level of accuracy, practical limitations associated with the direct measurement of VO2max, such as the requirement of expensive and sophisticated laboratory equipment or trained staff, have led to the development of various regression models for predicting VO2max. Consequently, a lot of studies have been conducted in the last years to predict VO2max of various target audiences, ranging from soccer athletes, nonexpert swimmers, cross-country skiers to healthy-fit adults, teenagers, and children. Numerous prediction models have been developed using different sets of predictor variables and a variety of machine learning and statistical methods, including support vector machine, multilayer perceptron, general regression neural network, and multiple linear regression. The purpose of this study is to give a detailed overview about the data-driven modeling studies for the prediction of VO2max conducted in recent years and to compare the performance of various VO2max prediction models reported in related literature in terms of two well-known metrics, namely, multiple correlation coefficient (R) and standard error of estimate. The survey results reveal that with respect to regression methods used to develop prediction models, support vector machine, in general, shows better performance than other methods, whereas multiple linear regression exhibits the worst performance.
MacDonald, R. Lee; Thomas, Christopher G.
2015-05-15
Purpose: To investigate potential improvement in external beam stereotactic radiation therapy plan quality for cranial cases using an optimized dynamic gantry and patient support couch motion trajectory, which could minimize exposure to sensitive healthy tissue. Methods: Anonymized patient anatomy and treatment plans of cranial cancer patients were used to quantify the geometric overlap between planning target volumes and organs-at-risk (OARs) based on their two-dimensional projection from source to a plane at isocenter as a function of gantry and couch angle. Published dose constraints were then used as weighting factors for the OARs to generate a map of couch-gantry coordinate space, indicating degree of overlap at each point in space. A couch-gantry collision space was generated by direct measurement on a linear accelerator and couch using an anthropomorphic solid-water phantom. A dynamic, fully customizable algorithm was written to generate a navigable ideal trajectory for the patient specific couch-gantry space. The advanced algorithm can be used to balance the implementation of absolute minimum values of overlap with the clinical practicality of large-scale couch motion and delivery time. Optimized cranial cancer treatment trajectories were compared to conventional treatment trajectories. Results: Comparison of optimized treatment trajectories with conventional treatment trajectories indicated an average decrease in mean dose to the OARs of 19% and an average decrease in maximum dose to the OARs of 12%. Degradation was seen for homogeneity index (6.14% ± 0.67%–5.48% ± 0.76%) and conformation number (0.82 ± 0.02–0.79 ± 0.02), but neither was statistically significant. Removal of OAR constraints from volumetric modulated arc therapy optimization reveals that reduction in dose to OARs is almost exclusively due to the optimized trajectory and not the OAR constraints. Conclusions: The authors’ study indicated that simultaneous couch and gantry motion
Trajectory structures in turbulent plasmas
Vlad, Madalina; Spineanu, Florin
2006-11-03
Particle stochastic advection in two dimensional divergence free velocity fields is studied. The special statistical properties of this process (non-Gaussian distribution, memory effects and quasi-coherent behavior) are determined using a new approach, the nested subensemble method. The effect of the statistics of trajectories on the evolution of drift turbulence in magnetized plasmas is studied. It essentialy consists in the tendency of structure formation.
Goddard trajectory determination subsystem: Mathematical specifications
NASA Technical Reports Server (NTRS)
Wagner, W. E. (Editor); Velez, C. E. (Editor)
1972-01-01
The mathematical specifications of the Goddard trajectory determination subsystem of the flight dynamics system are presented. These specifications include the mathematical description of the coordinate systems, dynamic and measurement model, numerical integration techniques, and statistical estimation concepts.
Trajectory generation of space telerobots
NASA Technical Reports Server (NTRS)
Lumia, R.; Wavering, A. J.
1989-01-01
The purpose is to review a variety of trajectory generation techniques which may be applied to space telerobots and to identify problems which need to be addressed in future telerobot motion control systems. As a starting point for the development of motion generation systems for space telerobots, the operation and limitations of traditional path-oriented trajectory generation approaches are discussed. This discussion leads to a description of more advanced techniques which have been demonstrated in research laboratories, and their potential applicability to space telerobots. Examples of this work include systems that incorporate sensory-interactive motion capability and optimal motion planning. Additional considerations which need to be addressed for motion control of a space telerobot are described, such as redundancy resolution and the description and generation of constrained and multi-armed cooperative motions. A task decomposition module for a hierarchical telerobot control system which will serve as a testbed for trajectory generation approaches which address these issues is also discussed briefly.
Saunders, Jessica M
2010-01-01
The group-based trajectory modeling approach is a systematic way of categorizing subjects into different groups based on their developmental trajectories using formal and objective statistical criteria. With the recent advancement in methods and statistical software, modeling possibilities are almost limitless; however, parallel advances in theory development have not kept pace. This paper examines some of the modeling options that are becoming more widespread and how they impact both empirical and theoretical findings. The key issue that is explored is the impact of adding random effects to the latent growth factors and how this alters the meaning of a group. The paper argues that technical specification should be guided by theory, and Moffitt's developmental taxonomy is used as an illustration of how modeling decisions can be matched to theory.
NASA Astrophysics Data System (ADS)
Salman, Ahmad; Lapidot, Itshak; Pomerantz, Ami; Tsror, Leah; Shufan, Elad; Moreh, Raymond; Mordechai, Shaul; Huleihel, Mahmoud
2012-01-01
The early diagnosis of phytopathogens is of a great importance; it could save large economical losses due to crops damaged by fungal diseases, and prevent unnecessary soil fumigation or the use of fungicides and bactericides and thus prevent considerable environmental pollution. In this study, 18 isolates of three different fungi genera were investigated; six isolates of Colletotrichum coccodes, six isolates of Verticillium dahliae and six isolates of Fusarium oxysporum. Our main goal was to differentiate these fungi samples on the level of isolates, based on their infrared absorption spectra obtained using the Fourier transform infrared-attenuated total reflection (FTIR-ATR) sampling technique. Advanced statistical and mathematical methods: principal component analysis (PCA), linear discriminant analysis (LDA), and k-means were applied to the spectra after manipulation. Our results showed significant spectral differences between the various fungi genera examined. The use of k-means enabled classification between the genera with a 94.5% accuracy, whereas the use of PCA [3 principal components (PCs)] and LDA has achieved a 99.7% success rate. However, on the level of isolates, the best differentiation results were obtained using PCA (9 PCs) and LDA for the lower wavenumber region (800-1775 cm-1), with identification success rates of 87%, 85.5%, and 94.5% for Colletotrichum, Fusarium, and Verticillium strains, respectively.
Salman, A; Shufan, E; Zeiri, L; Huleihel, M
2014-07-01
Herpes viruses are involved in a variety of human disorders. Herpes Simplex Virus type 1 (HSV-1) is the most common among the herpes viruses and is primarily involved in human cutaneous disorders. Although the symptoms of infection by this virus are usually minimal, in some cases HSV-1 might cause serious infections in the eyes and the brain leading to blindness and even death. A drug, acyclovir, is available to counter this virus. The drug is most effective when used during the early stages of the infection, which makes early detection and identification of these viral infections highly important for successful treatment. In the present study we evaluated the potential of Raman spectroscopy as a sensitive, rapid, and reliable method for the detection and identification of HSV-1 viral infections in cell cultures. Using Raman spectroscopy followed by advanced statistical methods enabled us, with sensitivity approaching 100%, to differentiate between a control group of Vero cells and another group of Vero cells that had been infected with HSV-1. Cell sites that were "rich in membrane" gave the best results in the differentiation between the two categories. The major changes were observed in the 1195-1726 cm(-1) range of the Raman spectrum. The features in this range are attributed mainly to proteins, lipids, and nucleic acids.
Trajectory selection for the Mariner Jupiter/Saturn 1977 project
NASA Technical Reports Server (NTRS)
Dyer, J. S.; Miles, R. F., Jr.
1974-01-01
The use of decision analysis to facilitate a group decision-making problem in the selection of trajectories for the two spacecraft of the Mariner Jupiter/Saturn 1977 Project. A set of 32 candidate trajectory pairs was developed. Cardinal utility function values were assigned to the trajectory pairs, and the data and statistics derived from collective choice rules were used in selecting the science-preferred trajectory pair.
NASA Astrophysics Data System (ADS)
Ruggles, Adam J.
2015-11-01
This paper presents improved statistical insight regarding the self-similar scalar mixing process of atmospheric hydrogen jets and the downstream region of under-expanded hydrogen jets. Quantitative planar laser Rayleigh scattering imaging is used to probe both jets. The self-similarity of statistical moments up to the sixth order (beyond the literature established second order) is documented in both cases. This is achieved using a novel self-similar normalization method that facilitated a degree of statistical convergence that is typically limited to continuous, point-based measurements. This demonstrates that image-based measurements of a limited number of samples can be used for self-similar scalar mixing studies. Both jets exhibit the same radial trends of these moments demonstrating that advanced atmospheric self-similarity can be applied in the analysis of under-expanded jets. Self-similar histograms away from the centerline are shown to be the combination of two distributions. The first is attributed to turbulent mixing. The second, a symmetric Poisson-type distribution centered on zero mass fraction, progressively becomes the dominant and eventually sole distribution at the edge of the jet. This distribution is attributed to shot noise-affected pure air measurements, rather than a diffusive superlayer at the jet boundary. This conclusion is reached after a rigorous measurement uncertainty analysis and inspection of pure air data collected with each hydrogen data set. A threshold based upon the measurement noise analysis is used to separate the turbulent and pure air data, and thusly estimate intermittency. Beta-distributions (four parameters) are used to accurately represent the turbulent distribution moments. This combination of measured intermittency and four-parameter beta-distributions constitutes a new, simple approach to model scalar mixing. Comparisons between global moments from the data and moments calculated using the proposed model show excellent
ERIC Educational Resources Information Center
Schoenborn, Charlotte A.
This report is based on data from the 1988 National Health Interview Survey on Alcohol (NHIS-Alcohol), part of the ongoing National Health Interview Survey conducted by the National Center for Health Statistics. Interviews for the NHIS are conducted in person by staff of the United States Bureau of the Census. Information is collected on each…
Ascent trajectory dispersion analysis
NASA Technical Reports Server (NTRS)
1982-01-01
The results of a Space Transportation System ascent trajectory dispersion analysis are documented. Critical trajectory parameter values useful for the definition of lightweight external tank insulation requirements are provided. This analysis was conducted using two of the critical missions specified for the Space Transportation System: a 28.5 deg inclination trajectory launched from the Eastern Test Range (ETR) and a Western Test Range (WTR) trajectory launched into a 104 deg orbital inclination.
Challenges in Achieving Trajectory-Based Operations
NASA Technical Reports Server (NTRS)
Cate, Karen Tung
2012-01-01
In the past few years much of the global ATM research community has proposed advanced systems based on Trajectory-Based Operations (TBO). The concept of TBO uses four-dimensional aircraft trajectories as the base information for managing safety and capacity. Both the US and European advanced ATM programs call for the sharing of trajectory data across different decision support tools for successful operations. However, the actual integration of TBO systems presents many challenges. Trajectory predictors are built to meet the specific needs of a particular system and are not always compatible with others. Two case studies are presented which examine the challenges of introducing a new concept into two legacy systems in regards to their trajectory prediction software. The first case describes the issues with integrating a new decision support tool with a legacy operational system which overlap in domain space. These tools perform similar functions but are driven by different requirements. The difference in the resulting trajectories can lead to conflicting advisories. The second case looks at integrating this same new tool with a legacy system originally developed as an integrated system, but diverged many years ago. Both cases illustrate how the lack of common architecture concepts for the trajectory predictors added cost and complexity to the integration efforts.
Advani, S.H.; Lee, J.K.
1983-01-01
A summary review of hydraulic fracture modeling is given. Advanced hydraulic fracture model formulations and simulation, using the finite element method, are presented. The numerical examples include the determination of fracture width, height, length, and stress intensity factors with the effects of frac fluid properties, layered strata, in situ stresses, and joints. Future model extensions are also recommended. 66 references, 23 figures.
Trajectory correction propulsion for TOPS
NASA Technical Reports Server (NTRS)
Long, H. R.; Bjorklund, R. A.
1972-01-01
A blowdown-pressurized hydrazine propulsion system was selected to provide trajectory correction impulse for outer planet flyby spacecraft as the result of cost/mass/reliability tradeoff analyses. Present hydrazine component and system technology and component designs were evaluated for application to the Thermoelectric Outer Planet Spacecraft (TOPS); while general hydrazine technology was adequate, component design changes were deemed necessary for TOPS-type missions. A prototype hydrazine propulsion system was fabricated and fired nine times for a total of 1600 s to demonstrate the operation and performance of the TOPS propulsion configuration. A flight-weight trajectory correction propulsion subsystem (TCPS) was designed for the TOPS based on actual and estimated advanced components.
EPOXI Trajectory and Maneuver Analyses
NASA Technical Reports Server (NTRS)
Chung, Min-Kun J.; Bhaskaran, Shyamkumar; Chesley, Steven R.; Halsell, C. Allen; Helfrich, Clifford E.; Jefferson, David C.; McElrath, Timothy P.; Rush, Brian P.; Wang, Tseng-Chan M.; Yen, Chen-wan L.
2011-01-01
The EPOXI mission is a NASA Discovery Mission of Opportunity combining two separate investigations: Extrasolar Planet Observation and Characterization (EPOCh) and Deep Impact eXtended Investigation (DIXI). Both investigations reused the DI instruments and spacecraft that successfully flew by the comet Tempel-1 (4 July 2005). For EPOCh, the goal was to find exoplanets with the high resolution imager, while for DIXI it was to fly by the comet Hartley 2 (4 Nov 2010). This paper documents the navigation experience of the earlier ma-neuver analyses critical for the EPOXI mission including statistical ?V analyses and other useful analyses in designing maneuvers. It also recounts the trajectory design leading up to the final reference trajectory to Hartley 2.
Trajectories of Martian Habitability
2014-01-01
Abstract Beginning from two plausible starting points—an uninhabited or inhabited Mars—this paper discusses the possible trajectories of martian habitability over time. On an uninhabited Mars, the trajectories follow paths determined by the abundance of uninhabitable environments and uninhabited habitats. On an inhabited Mars, the addition of a third environment type, inhabited habitats, results in other trajectories, including ones where the planet remains inhabited today or others where planetary-scale life extinction occurs. By identifying different trajectories of habitability, corresponding hypotheses can be described that allow for the various trajectories to be disentangled and ultimately a determination of which trajectory Mars has taken and the changing relative abundance of its constituent environments. Key Words: Mars—Habitability—Liquid water—Planetary science. Astrobiology 14, 182–203. PMID:24506485
Optimization Of Simulated Trajectories
NASA Technical Reports Server (NTRS)
Brauer, Garry L.; Olson, David W.; Stevenson, Robert
1989-01-01
Program To Optimize Simulated Trajectories (POST) provides ability to target and optimize trajectories of point-mass powered or unpowered vehicle operating at or near rotating planet. Used successfully to solve wide variety of problems in mechanics of atmospheric flight and transfer between orbits. Generality of program demonstrated by its capability to simulate up to 900 distinct trajectory phases, including generalized models of planets and vehicles. VAX version written in FORTRAN 77 and CDC version in FORTRAN V.
Sindhikara, Daniel J; Kim, Seonah; Voter, Arthur F; Roitberg, Adrian E
2009-06-09
Molecular dynamics simulations starting from different initial conditions are commonly used to mimic the behavior of an experimental ensemble. We show in this article that when a Langevin thermostat is used to maintain constant temperature during such simulations, extreme care must be taken when choosing the random number seeds to prevent statistical correlation among the MD trajectories. While recent studies have shown that stochastically thermostatted trajectories evolving within a single potential basin with identical random number seeds tend to synchronize, we show that there is a synchronization effect even for complex, biologically relevant systems. We demonstrate this effect in simulations of alanine trimer and pentamer and in a simulation of a temperature-jump experiment for peptide folding of a 14-residue peptide. Even in replica-exchange simulations, in which the trajectories are at different temperatures, we find partial synchronization occurring when the same random number seed is employed. We explain this by extending the recent derivation of the synchronization effect for two trajectories in a harmonic well to the case in which the trajectories are at two different temperatures. Our results suggest several ways in which mishandling selection of a pseudorandom number generator initial seed can lead to corruption of simulation data. Simulators can fall into this trap in simple situations such as neglecting to specifically indicate different random seeds in either parallel or sequential restart simulations, utilizing a simulation package with a weak pseudorandom number generator, or using an advanced simulation algorithm that has not been programmed to distribute initial seeds.
Group-based trajectory modeling: an overview.
Nagin, Daniel S
2014-01-01
This article provides an overview of a group-based statistical methodology for analyzing developmental trajectories - the evolution of an outcome over age or time. Across all application domains, this group-based statistical method lends itself to the presentation of findings in the form of easily understood graphical and tabular data summaries. In so doing, the method provides statistical researchers with a tool for figuratively painting a statistical portrait of the predictors and consequences of distinct trajectories of development. Data summaries of this form have the great advantage of being accessible to nontechnical audiences and quickly comprehensible to audiences that are technically sophisticated. Examples of the application of the method are provided. A detailed account of the statistical underpinnings of the method and a full range of applications are provided by the author in a previous study.
Perching aerodynamics and trajectory optimization
NASA Astrophysics Data System (ADS)
Wickenheiser, Adam; Garcia, Ephrahim
2007-04-01
Advances in smart materials, actuators, and control architecture have enabled new flight capabilities for aircraft. Perching is one such capability, described as a vertical landing maneuver using in-flight shape reconfiguration in lieu of high thrust generation. A morphing, perching aircraft design is presented that is capable of post stall flight and very slow landing on a vertical platform. A comprehensive model of the aircraft's aerodynamics, with special regard to nonlinear affects such as flow separation and dynamic stall, is discussed. Trajectory optimization using nonlinear programming techniques is employed to show the effects that morphing and nonlinear aerodynamics have on the maneuver. These effects are shown to decrease the initial height and distance required to initiate the maneuver, reduce the bounds on the trajectory, and decrease the required thrust for the maneuver. Perching trajectories comparing morphing versus fixed-configuration and stalled versus un-stalled aircraft are presented. It is demonstrated that a vertical landing is possible in the absence of high thrust if post-stall flight capabilities and vehicle reconfiguration are utilized.
Rintoul, Mark Daniel; Wilson, Andrew T.; Valicka, Christopher G.; Kegelmeyer, W. Philip; Shead, Timothy M.; Newton, Benjamin D.; Czuchlewski, Kristina Rodriguez
2015-09-01
We want to organize a body of trajectories in order to identify, search for, classify and predict behavior among objects such as aircraft and ships. Existing compari- son functions such as the Fr'echet distance are computationally expensive and yield counterintuitive results in some cases. We propose an approach using feature vectors whose components represent succinctly the salient information in trajectories. These features incorporate basic information such as total distance traveled and distance be- tween start/stop points as well as geometric features related to the properties of the convex hull, trajectory curvature and general distance geometry. Additionally, these features can generally be mapped easily to behaviors of interest to humans that are searching large databases. Most of these geometric features are invariant under rigid transformation. We demonstrate the use of different subsets of these features to iden- tify trajectories similar to an exemplar, cluster a database of several hundred thousand trajectories, predict destination and apply unsupervised machine learning algorithms.
NASA Astrophysics Data System (ADS)
Dvorská, A.; Lammel, G.; Holoubek, I.
We use air mass back trajectory analysis of persistent organic pollutant (POP) levels monitored at a regional background site, Košetice, Czech Republic, as a tool to study the effectiveness of emission reduction measures taken in the last decade in the region. The representativity of the chosen trajectory starting height for air sampling near ground was ensured by excluding trajectories starting at time of inversions lower than their starting height. As the relevant pollutant sources are exclusively located in the atmospheric boundary layer, trajectory segments above this layer were also excluded from the analysis. We used a linear time weight to account for the influence of dispersion and deposition on trace components abundances and to quantify the ground source loading, a continuous measure for the influence of surface emissions. Hexachlorocyclohexanes (HCHs), hexachlorobenzene (HCB), polychlorinated biphenyls (PCBs), DDT, and two time periods, the years 1997-1999 and 2004-2006, were studied. The pollutant levels transported to Košetice decreased for all substances except HCB. Except for lindane seasonal emissions were insignificant. Increasing emissions of HCB were at least partly linked to the 2002 floods in the Danube basin. Major emissions of 1997-1999 which decreased significantly were in France (lindane), western Poland, Hungary and northern ex-Yugoslavia (technical HCH), and the Czech Republic (DDT). Emissions remaining in 2004-2006 include HCB and DDT in the northern Czech Republic, HCB and PCBs in Germany. Besides changes in emission strength meteorological factors influence the level of transported pollutant concentrations. The prevailing air flow pattern limits the geographic coverage of this analysis to central Europe and parts of western Europe. However, no POP monitoring stations exist in areas suitable for a possible extension of the study area.
Scout trajectory error propagation computer program
NASA Technical Reports Server (NTRS)
Myler, T. R.
1982-01-01
Since 1969, flight experience has been used as the basis for predicting Scout orbital accuracy. The data used for calculating the accuracy consists of errors in the trajectory parameters (altitude, velocity, etc.) at stage burnout as observed on Scout flights. Approximately 50 sets of errors are used in Monte Carlo analysis to generate error statistics in the trajectory parameters. A covariance matrix is formed which may be propagated in time. The mechanization of this process resulted in computer program Scout Trajectory Error Propagation (STEP) and is described herein. Computer program STEP may be used in conjunction with the Statistical Orbital Analysis Routine to generate accuracy in the orbit parameters (apogee, perigee, inclination, etc.) based upon flight experience.
NASA Astrophysics Data System (ADS)
McCray, Wilmon Wil L., Jr.
The research was prompted by a need to conduct a study that assesses process improvement, quality management and analytical techniques taught to students in U.S. colleges and universities undergraduate and graduate systems engineering and the computing science discipline (e.g., software engineering, computer science, and information technology) degree programs during their academic training that can be applied to quantitatively manage processes for performance. Everyone involved in executing repeatable processes in the software and systems development lifecycle processes needs to become familiar with the concepts of quantitative management, statistical thinking, process improvement methods and how they relate to process-performance. Organizations are starting to embrace the de facto Software Engineering Institute (SEI) Capability Maturity Model Integration (CMMI RTM) Models as process improvement frameworks to improve business processes performance. High maturity process areas in the CMMI model imply the use of analytical, statistical, quantitative management techniques, and process performance modeling to identify and eliminate sources of variation, continually improve process-performance; reduce cost and predict future outcomes. The research study identifies and provides a detail discussion of the gap analysis findings of process improvement and quantitative analysis techniques taught in U.S. universities systems engineering and computing science degree programs, gaps that exist in the literature, and a comparison analysis which identifies the gaps that exist between the SEI's "healthy ingredients " of a process performance model and courses taught in U.S. universities degree program. The research also heightens awareness that academicians have conducted little research on applicable statistics and quantitative techniques that can be used to demonstrate high maturity as implied in the CMMI models. The research also includes a Monte Carlo simulation optimization
NASA Technical Reports Server (NTRS)
Foster, Cyrus; Jaroux, Belgacem A.
2012-01-01
The Trajectory Browser is a web-based tool developed at the NASA Ames Research Center to be used for the preliminary assessment of trajectories to small-bodies and planets and for providing relevant launch date, time-of-flight and V requirements. The site hosts a database of transfer trajectories from Earth to asteroids and planets for various types of missions such as rendezvous, sample return or flybys. A search engine allows the user to find trajectories meeting desired constraints on the launch window, mission duration and delta V capability, while a trajectory viewer tool allows the visualization of the heliocentric trajectory and the detailed mission itinerary. The anticipated user base of this tool consists primarily of scientists and engineers designing interplanetary missions in the context of pre-phase A studies, particularly for performing accessibility surveys to large populations of small-bodies. The educational potential of the website is also recognized for academia and the public with regards to trajectory design, a field that has generally been poorly understood by the public. The website is currently hosted on NASA-internal URL http://trajbrowser.arc.nasa.gov/ with plans for a public release as soon as development is complete.
Gene–Environment Interactions on Growth Trajectories
Wang, Shuang; Xiong, Wei; Ma, Weiping; Chanock, Stephen; Jedrychowski, Wieslaw; Wu, Rongling; Perera, Frederica P.
2012-01-01
It has been suggested that children with larger brains tend to perform better on IQ tests or cognitive function tests. Prenatal head growth and head growth in infancy are two crucial periods for subsequent intelligence. Studies have shown that environmental exposure to air pollutants during pregnancy is associated with fetal growth reduction, developmental delay, and reduced IQ. Meanwhile, genetic polymorphisms may modify the effect of environment on head growth. However, studies on gene–environment or gene–gene interactions on growth trajectories have been quite limited partly due to the difficulty to quantitatively measure interactions on growth trajectories. Moreover, it is known that assessing the significance of gene–environment or gene–gene interactions on cross-sectional outcomes empirically using the permutation procedures may bring substantial errors in the tests. We proposed a score that quantitatively measures interactions on growth trajectories and developed an algorithm with a parametric bootstrap procedure to empirically assess the significance of the interactions on growth trajectories under the likelihood framework. We also derived a Wald statistic to test for interactions on growth trajectories and compared it to the proposed parametric bootstrap procedure. Through extensive simulation studies, we demonstrated the feasibility and power of the proposed testing procedures. We applied our method to a real dataset with head circumference measures from birth to age 7 on a cohort currently being conducted by the Columbia Center for Children's Environmental Health (CCCEH) in Krakow, Poland, and identified several significant gene–environment interactions on head circumference growth trajectories. PMID:22311237
This movie shows the cruise trajectory of NASA's Mars Atmosphere and Volatile Evolution (MAVEN) mission, which was launched on Nov. 18, 2013. It will arrive at Mars on Sept. 21, 2014, to explore th...
Automated Cooperative Trajectories
NASA Technical Reports Server (NTRS)
Hanson, Curt; Pahle, Joseph; Brown, Nelson
2015-01-01
This presentation is an overview of the Automated Cooperative Trajectories project. An introduction to the phenomena of wake vortices is given, along with a summary of past research into the possibility of extracting energy from the wake by flying close parallel trajectories. Challenges and barriers to adoption of civilian automatic wake surfing technology are identified. A hardware-in-the-loop simulation is described that will support future research. Finally, a roadmap for future research and technology transition is proposed.
Dien, Joseph
2010-03-15
This article presents an open source Matlab program, the ERP PCA (EP) Toolkit, for facilitating the multivariate decomposition and analysis of event-related potential data. This program is intended to supplement existing ERP analysis programs by providing functions for conducting artifact correction, robust averaging, referencing and baseline correction, data editing and visualization, principal components analysis, and robust inferential statistical analysis. This program subserves three major goals: (1) optimizing analysis of noisy data, such as clinical or developmental; (2) facilitating the multivariate decomposition of ERP data into its constituent components; (3) increasing the transparency of analysis operations by providing direct visualization of the corresponding waveforms.
Optimum Three Impulse Trajectory Generator with Patched Conic Trajectory Model
NASA Technical Reports Server (NTRS)
Payne, M. H.; Pines, S.; Horsewood, J. L.
1972-01-01
Optimal multi-impulse trajectories were investigated as a nominal about which asymptotic expansion was used to obtain approximations of optimal low thrust trajectories. The work consisted of the analysis and description of an optimal 3-impulse trajectory program. A patched-conic trajectory model was specifically designed for compatibility with the subsequent addition of the low thrust expansion approximation.
Somerville, Richard
2013-08-22
The long-range goal of several past and current projects in our DOE-supported research has been the development of new and improved parameterizations of cloud-radiation effects and related processes, using ARM data, and the implementation and testing of these parameterizations in global models. The main objective of the present project being reported on here has been to develop and apply advanced statistical techniques, including Bayesian posterior estimates, to diagnose and evaluate features of both observed and simulated clouds. The research carried out under this project has been novel in two important ways. The first is that it is a key step in the development of practical stochastic cloud-radiation parameterizations, a new category of parameterizations that offers great promise for overcoming many shortcomings of conventional schemes. The second is that this work has brought powerful new tools to bear on the problem, because it has been a collaboration between a meteorologist with long experience in ARM research (Somerville) and a mathematician who is an expert on a class of advanced statistical techniques that are well-suited for diagnosing model cloud simulations using ARM observations (Shen).
Kossobokov, V.G.; Romashkova, L.L.; Keilis-Borok, V. I.; Healy, J.H.
1999-01-01
Algorithms M8 and MSc (i.e., the Mendocino Scenario) were used in a real-time intermediate-term research prediction of the strongest earthquakes in the Circum-Pacific seismic belt. Predictions are made by M8 first. Then, the areas of alarm are reduced by MSc at the cost that some earthquakes are missed in the second approximation of prediction. In 1992-1997, five earthquakes of magnitude 8 and above occurred in the test area: all of them were predicted by M8 and MSc identified correctly the locations of four of them. The space-time volume of the alarms is 36% and 18%, correspondingly, when estimated with a normalized product measure of empirical distribution of epicenters and uniform time. The statistical significance of the achieved results is beyond 99% both for M8 and MSc. For magnitude 7.5 + , 10 out of 19 earthquakes were predicted by M8 in 40% and five were predicted by M8-MSc in 13% of the total volume considered. This implies a significance level of 81% for M8 and 92% for M8-MSc. The lower significance levels might result from a global change in seismic regime in 1993-1996, when the rate of the largest events has doubled and all of them become exclusively normal or reversed faults. The predictions are fully reproducible; the algorithms M8 and MSc in complete formal definitions were published before we started our experiment [Keilis-Borok, V.I., Kossobokov, V.G., 1990. Premonitory activation of seismic flow: Algorithm M8, Phys. Earth and Planet. Inter. 61, 73-83; Kossobokov, V.G., Keilis-Borok, V.I., Smith, S.W., 1990. Localization of intermediate-term earthquake prediction, J. Geophys. Res., 95, 19763-19772; Healy, J.H., Kossobokov, V.G., Dewey, J.W., 1992. A test to evaluate the earthquake prediction algorithm, M8. U.S. Geol. Surv. OFR 92-401]. M8 is available from the IASPEI Software Library [Healy, J.H., Keilis-Borok, V.I., Lee, W.H.K. (Eds.), 1997. Algorithms for Earthquake Statistics and Prediction, Vol. 6. IASPEI Software Library]. ?? 1999 Elsevier
NASA Astrophysics Data System (ADS)
Romé, M.; Lepreti, F.; Maero, G.; Pozzoli, R.; Vecchio, A.; Carbone, V.
2013-03-01
Highly magnetized, pure electron plasmas confined in a Penning-Malmberg trap allow one to perform experiments on the two-dimensional (2D) fluid dynamics under conditions where non-ideal effects are almost negligible. Recent results on the freely decaying 2D turbulence obtained from experiments with electron plasmas performed in the Penning-Malmberg trap ELTRAP are presented. The analysis has been applied to experimental sequences with different types of initial density distributions. The dynamical properties of the system have been investigated by means of wavelet transforms and Proper Orthogonal Decomposition (POD). The wavelet analysis shows that most of the enstrophy is contained at spatial scales corresponding to the typical size of the persistent vortices in the 2D electron plasma flow. The POD analysis allows one to identify the coherent structures which give the dominant contribution to the plasma evolution. The statistical properties of the turbulence have been investigated by means of Probability Density Functions (PDFs) and structure functions of spatial vorticity increments. The analysis evidences how the shape and evolution of the dominant coherent structures and the intermittency properties of the turbulence strongly depend on the initial conditions for the electron density.
Analysis and prediction of stratospheric balloons trajectories
NASA Astrophysics Data System (ADS)
Cardillo, A.; Memmo, A.; Musso, I.; Ibba, R.; Spoto, D.
The first step to manage a balloon flight from a trajectory point of view is the definition of launch location and period. Analysis data are used to realize a statistical study of the trajectories that can be obtained. The goal is define the conditions able to maximize the probability to respect mission objectives and constrains. Ones started with operations the balloon control centre has to manage the flight respecting safety and science. To predict stratospheric balloon trajectories we must utilize data from different forecast models and real-time measurements of wind and other meteorological entities. These sources of information have to be merged along the simulation of the balloon flight. Great attention has be paid for long duration flight from Pole and Equator, where QBO plays an important role.
Adaptive Trajectory Prediction Algorithm for Climbing Flights
NASA Technical Reports Server (NTRS)
Schultz, Charles Alexander; Thipphavong, David P.; Erzberger, Heinz
2012-01-01
Aircraft climb trajectories are difficult to predict, and large errors in these predictions reduce the potential operational benefits of some advanced features for NextGen. The algorithm described in this paper improves climb trajectory prediction accuracy by adjusting trajectory predictions based on observed track data. It utilizes rate-of-climb and airspeed measurements derived from position data to dynamically adjust the aircraft weight modeled for trajectory predictions. In simulations with weight uncertainty, the algorithm is able to adapt to within 3 percent of the actual gross weight within two minutes of the initial adaptation. The root-mean-square of altitude errors for five-minute predictions was reduced by 73 percent. Conflict detection performance also improved, with a 15 percent reduction in missed alerts and a 10 percent reduction in false alerts. In a simulation with climb speed capture intent and weight uncertainty, the algorithm improved climb trajectory prediction accuracy by up to 30 percent and conflict detection performance, reducing missed and false alerts by up to 10 percent.
The fastest evolutionary trajectory
Traulsen, Arne; Iwasa, Yoh; Nowak, Martin A.
2008-01-01
Given two mutants, A and B, separated by n mutational steps, what is the evolutionary trajectory which allows a homogeneous population of A to reach B in the shortest time? We show that the optimum evolutionary trajectory (fitness landscape) has the property that the relative fitness increase between any two consecutive steps is constant. Hence, the optimum fitness landscape between A and B is given by an exponential function. Our result is precise for small mutation rates and excluding back mutations. We discuss deviations for large mutation rates and including back mutations. For very large mutation rates, the optimum fitness landscape is flat and has a single peak at type B. PMID:17900629
Aggio, Raphael B. M.; de Lacy Costello, Ben; White, Paul; Khalid, Tanzeela; Ratcliffe, Norman M.; Persad, Raj; Probert, Chris S. J.
2016-01-01
Prostate cancer is one of the most common cancers. Serum prostate-specific antigen (PSA) is used to aid the selection of men undergoing biopsies. Its use remains controversial. We propose a GC-sensor algorithm system for classifying urine samples from patients with urological symptoms. This pilot study includes 155 men presenting to urology clinics, 58 were diagnosed with prostate cancer, 24 with bladder cancer and 73 with haematuria and or poor stream, without cancer. Principal component analysis (PCA) was applied to assess the discrimination achieved, while linear discriminant analysis (LDA) and support vector machine (SVM) were used as statistical models for sample classification. Leave-one-out cross-validation (LOOCV), repeated 10-fold cross-validation (10FoldCV), repeated double cross-validation (DoubleCV) and Monte Carlo permutations were applied to assess performance. Significant separation was found between prostate cancer and control samples, bladder cancer and controls and between bladder and prostate cancer samples. For prostate cancer diagnosis, the GC/SVM system classified samples with 95% sensitivity and 96% specificity after LOOCV. For bladder cancer diagnosis, the SVM reported 96% sensitivity and 100% specificity after LOOCV, while the DoubleCV reported 87% sensitivity and 99% specificity, with SVM showing 78% and 98% sensitivity between prostate and bladder cancer samples. Evaluation of the results of the Monte Carlo permutation of class labels obtained chance-like accuracy values around 50% suggesting the observed results for bladder cancer and prostate cancer detection are not due to over fitting. The results of the pilot study presented here indicate that the GC system is able to successfully identify patterns that allow classification of urine samples from patients with urological cancers. An accurate diagnosis based on urine samples would reduce the number of negative prostate biopsies performed, and the frequency of surveillance cystoscopy
NASA Technical Reports Server (NTRS)
Park, Brooke Anderson; Wright, Henry
2012-01-01
PatCon code was developed to help mission designers run trade studies on launch and arrival times for any given planet. Initially developed in Fortran, the required inputs included launch date, arrival date, and other orbital parameters of the launch planet and arrival planets at the given dates. These parameters include the position of the planets, the eccentricity, semi-major axes, argument of periapsis, ascending node, and inclination of the planets. With these inputs, a patched conic approximation is used to determine the trajectory. The patched conic approximation divides the planetary mission into three parts: (1) the departure phase, in which the two relevant bodies are Earth and the spacecraft, and where the trajectory is a departure hyperbola with Earth at the focus; (2) the cruise phase, in which the two bodies are the Sun and the spacecraft, and where the trajectory is a transfer ellipse with the Sun at the focus; and (3) the arrival phase, in which the two bodies are the target planet and the spacecraft, where the trajectory is an arrival hyperbola with the planet as the focus.
Mission objectives and trajectories
NASA Technical Reports Server (NTRS)
1973-01-01
The present state of the knowledge of asteroids was assessed to identify mission and target priorities for planning asteroidal flights in the 1980's and beyond. Mission objectives, mission analysis, trajectory studies, and cost analysis are discussed. A bibliography of reports and technical memoranda is included.
NASA Astrophysics Data System (ADS)
Pollard, David; Chang, Won; Haran, Murali; Applegate, Patrick; DeConto, Robert
2016-05-01
A 3-D hybrid ice-sheet model is applied to the last deglacial retreat of the West Antarctic Ice Sheet over the last ˜ 20 000 yr. A large ensemble of 625 model runs is used to calibrate the model to modern and geologic data, including reconstructed grounding lines, relative sea-level records, elevation-age data and uplift rates, with an aggregate score computed for each run that measures overall model-data misfit. Two types of statistical methods are used to analyze the large-ensemble results: simple averaging weighted by the aggregate score, and more advanced Bayesian techniques involving Gaussian process-based emulation and calibration, and Markov chain Monte Carlo. The analyses provide sea-level-rise envelopes with well-defined parametric uncertainty bounds, but the simple averaging method only provides robust results with full-factorial parameter sampling in the large ensemble. Results for best-fit parameter ranges and envelopes of equivalent sea-level rise with the simple averaging method agree well with the more advanced techniques. Best-fit parameter ranges confirm earlier values expected from prior model tuning, including large basal sliding coefficients on modern ocean beds.
Group-based modeling of ecological trajectories in restored wetlands.
Matthews, Jeffrey W
2015-03-01
Repeated measures taken at the same restoration sites over time are used to describe restoration trajectories and identify sites that are trending toward unexpected outcomes. Analogously, social scientists use repeated measures of individuals to describe developmental trajectories of behaviors or other outcomes. Group-based trajectory modeling (GBTM) is one statistical method used in behavioral and health sciences for this purpose. I introduce the use of GBTM to identify clusters of similar restoration trajectories within a sample of sites. Data collected at 54 restored wetlands in Illinois for up to 15 years post-restoration were used to describe trajectories of six indicators: plant species richness, number of Carex (sedge) species, mean coefficient of conservatism (mean C), native plant cover, perennial plant cover, and planted species cover. For each indicator, I used GBTM to classify wetlands into three to four groups with distinct trajectories. In general, cover by native and planted species declined, while species richness and mean C increased over time or peaked then declined. Site context and management may explain trajectory group membership. Specifically, wetlands restored more recently and those restored within forested contexts were more likely to follow increasing trajectories. I show GBTM to be useful for identifying typical restoration trajectory patterns, developing hypotheses regarding factors driving those patterns and pinpointing critical times for intervention. Furthermore, GBTM might be applied more broadly in ecological research to identify common patterns of community assembly in large numbers of plots or sites.
Air breathing engine/rocket trajectory optimization
NASA Technical Reports Server (NTRS)
Smith, V. K., III
1979-01-01
This research has focused on improving the mathematical models of the air-breathing propulsion systems, which can be mated with the rocket engine model and incorporated in trajectory optimization codes. Improved engine simulations provided accurate representation of the complex cycles proposed for advanced launch vehicles, thereby increasing the confidence in propellant use and payload calculations. The versatile QNEP (Quick Navy Engine Program) was modified to allow treatment of advanced turboaccelerator cycles using hydrogen or hydrocarbon fuels and operating in the vehicle flow field.
Voter, A F; Sindhikara, Daniel J; Kim, Seonah; Roitberg, Adrian E
2009-01-01
Molecular dynamics simulations starting from different initial conditions are commonly used to mimic the behavior of an experimental ensemble. We show in this article that when a Langevin thermostat is used to maintain constant temperature during such simulations, extreme care must be taken when choosing the random number seeds used in order to prevent statistical correlation among the MD trajectories. While recent studies have shown that stochastically thermostatted trajectories evolving within a single potential basin with identical random number seeds tend to synchronize, we show that there is a synchronization effect even for complex, biologically relevant systems. We demonstrate this effect in simulations of Alanine trimer and pentamer and in a simulation of a temperature-jump experiment for peptide folding of a 14-residue peptide. Even in replica-exchange simulations, in which the trajectories are at different temperatures, we find partial synchronization occurring when the same random number seed is employed. We explain this by extending the recent derivation of the synchronization effect for two trajectories in a harmonic well to the case in which the trajectories are at two different temperatures. Our results suggest several ways in which mishandling selection of a pseudo random number generator initial seed can lead to corruption of simulation data. Simulators can fall into this trap in simple situations such as neglecting to specifically indicate different random seeds in either parallel or sequential restart simulations, utilizing a simulation package with a weak pseudorandom number generator, or using an advanced simulation algorithm that hasn't been programmed to distribute initial seeds.
TrackTable Trajectory Analysis
Wilson, Andrew T.
2014-08-25
Tracktable is designed for analysis and rendering of the trajectories of moving objects such as planes, trains, automobiles and ships. Its purpose is to operate on large sets of trajectories (millions) to help a user detect, analyze and display patterns. It will also be used to disseminate trajectory research results from Sandia's PANTHER Grand Challenge LDRD.
Poukey, J.W.
1988-01-01
The trajectory code TRAJ has been used extensively to study nonimmersed foilless electron diodes. The basic goal of the research is to design low-emittance injectors for electron linacs and propagation experiments. Systems studied during 1987 include Delphi, Recirc, and Troll. We also discuss a partly successful attempt to extend the same techniques to high currents (tens of kA). 7 refs., 30 figs.
Surrealistic Bohm Trajectories
NASA Astrophysics Data System (ADS)
Englert, Berthold-Georg; Scully, Marian O.; Süssmann, Georg; Walther, Herbert
1992-12-01
A study of interferometers with one-bit which-way detectors demonstrates that the trajectories, which David Bohm invented in his attempt at a realistic interpretation of quantum mechanics, are in fact surrealistic, because they may be macroscopically at variance with the observed track of the particle. We consider a two-slit interferometer and an incomplete Stern-Gerlach interferometer, and propose an experimentum crucis based on the latter.
Flight Trajectory Control Investigation
1981-03-01
control algorithms for four-dimensional guidance of a transport air- craft were investigated for feasibility. Cost function constraints on the ptimal...21 3.1.6 Solution Constraints .... ............. ... 25 3.1.7 Trajectory Generator Review .. ......... .. 25 3.2 OPTIMAl CONTROLLER ALGORITHM...value formulation to a six-degree-of-freedom point mass aircraft with all the structural, maneuver, and mission constraints accounted for by using pelalty
NASA Technical Reports Server (NTRS)
Ardema, Mark D.
1995-01-01
This report summarizes the work entitled 'Advances in Hypersonic Vehicle Synthesis with Application to Studies of Advanced Thermal Protection Systems.' The effort was in two areas: (1) development of advanced methods of trajectory and propulsion system optimization; and (2) development of advanced methods of structural weight estimation. The majority of the effort was spent in the trajectory area.
Complexity Science Applications to Dynamic Trajectory Management: Research Strategies
NASA Technical Reports Server (NTRS)
Sawhill, Bruce; Herriot, James; Holmes, Bruce J.; Alexandrov, Natalia
2009-01-01
The promise of the Next Generation Air Transportation System (NextGen) is strongly tied to the concept of trajectory-based operations in the national airspace system. Existing efforts to develop trajectory management concepts are largely focused on individual trajectories, optimized independently, then de-conflicted among each other, and individually re-optimized, as possible. The benefits in capacity, fuel, and time are valuable, though perhaps could be greater through alternative strategies. The concept of agent-based trajectories offers a strategy for automation of simultaneous multiple trajectory management. The anticipated result of the strategy would be dynamic management of multiple trajectories with interacting and interdependent outcomes that satisfy multiple, conflicting constraints. These constraints would include the business case for operators, the capacity case for the Air Navigation Service Provider (ANSP), and the environmental case for noise and emissions. The benefits in capacity, fuel, and time might be improved over those possible under individual trajectory management approaches. The proposed approach relies on computational agent-based modeling (ABM), combinatorial mathematics, as well as application of "traffic physics" concepts to the challenge, and modeling and simulation capabilities. The proposed strategy could support transforming air traffic control from managing individual aircraft behaviors to managing systemic behavior of air traffic in the NAS. A system built on the approach could provide the ability to know when regions of airspace approach being "full," that is, having non-viable local solution space for optimizing trajectories in advance.
Trajectory Optimization: OTIS 4
NASA Technical Reports Server (NTRS)
Riehl, John P.; Sjauw, Waldy K.; Falck, Robert D.; Paris, Stephen W.
2010-01-01
The latest release of the Optimal Trajectories by Implicit Simulation (OTIS4) allows users to simulate and optimize aerospace vehicle trajectories. With OTIS4, one can seamlessly generate optimal trajectories and parametric vehicle designs simultaneously. New features also allow OTIS4 to solve non-aerospace continuous time optimal control problems. The inputs and outputs of OTIS4 have been updated extensively from previous versions. Inputs now make use of objectoriented constructs, including one called a metastring. Metastrings use a greatly improved calculator and common nomenclature to reduce the user s workload. They allow for more flexibility in specifying vehicle physical models, boundary conditions, and path constraints. The OTIS4 calculator supports common mathematical functions, Boolean operations, and conditional statements. This allows users to define their own variables for use as outputs, constraints, or objective functions. The user-defined outputs can directly interface with other programs, such as spreadsheets, plotting packages, and visualization programs. Internally, OTIS4 has more explicit and implicit integration procedures, including high-order collocation methods, the pseudo-spectral method, and several variations of multiple shooting. Users may switch easily between the various methods. Several unique numerical techniques such as automated variable scaling and implicit integration grid refinement, support the integration methods. OTIS4 is also significantly more user friendly than previous versions. The installation process is nearly identical on various platforms, including Microsoft Windows, Apple OS X, and Linux operating systems. Cross-platform scripts also help make the execution of OTIS and post-processing of data easier. OTIS4 is supplied free by NASA and is subject to ITAR (International Traffic in Arms Regulations) restrictions. Users must have a Fortran compiler, and a Python interpreter is highly recommended.
Trajectories in parallel optics.
Klapp, Iftach; Sochen, Nir; Mendlovic, David
2011-10-01
In our previous work we showed the ability to improve the optical system's matrix condition by optical design, thereby improving its robustness to noise. It was shown that by using singular value decomposition, a target point-spread function (PSF) matrix can be defined for an auxiliary optical system, which works parallel to the original system to achieve such an improvement. In this paper, after briefly introducing the all optics implementation of the auxiliary system, we show a method to decompose the target PSF matrix. This is done through a series of shifted responses of auxiliary optics (named trajectories), where a complicated hardware filter is replaced by postprocessing. This process manipulates the pixel confined PSF response of simple auxiliary optics, which in turn creates an auxiliary system with the required PSF matrix. This method is simulated on two space variant systems and reduces their system condition number from 18,598 to 197 and from 87,640 to 5.75, respectively. We perform a study of the latter result and show significant improvement in image restoration performance, in comparison to a system without auxiliary optics and to other previously suggested hybrid solutions. Image restoration results show that in a range of low signal-to-noise ratio values, the trajectories method gives a significant advantage over alternative approaches. A third space invariant study case is explored only briefly, and we present a significant improvement in the matrix condition number from 1.9160e+013 to 34,526.
Periodic billiard trajectories in polygons: generating mechanisms
NASA Astrophysics Data System (ADS)
Vorobets, Ya B.; Gal'perin, G. A.; Stepin, Anatolii M.
1992-06-01
CONTENTSIntroduction §1. Billiard trajectories in a plane domain §2. Fagnano's problem. Mechanical interpretations of periodic trajectories in triangles §3. An extremal property of billiard trajectories. Birkhoff's theorem. The non-existence of a unified construction of periodic trajectories in obtuse triangles §4. 'Perpendicular' trajectories in obtuse triangles of special shape §5. 'Perpendicular' trajectories in rational polygons and polyhedra §6. Stable trajectories §7. Stable perpendicular trajectories §8. Isolated trajectories §9. Isolated trajectories in acute and obtuse triangles. The bifurcation diagram of isolated trajectories (a 'hang-glider' configuration) §10. The density of F-triangles in a neighbourhood of (0, 0) §11. Generalization of the construction of isolated trajectories in obtuse triangles §12. Stable and unstable billiard trajectories in plane Weyl chambers §13. A criterion for the stability of periodic trajectories in a regular hexagonConclusionReferences
Laser tracker TSPI uncertainty quantification via centrifuge trajectory
NASA Astrophysics Data System (ADS)
Romero, Edward; Paez, Thomas; Brown, Timothy; Miller, Timothy
2009-08-01
Sandia National Laboratories currently utilizes two laser tracking systems to provide time-space-position-information (TSPI) and high speed digital imaging of test units under flight. These laser trackers have been in operation for decades under the premise of theoretical accuracies based on system design and operator estimates. Advances in optical imaging and atmospheric tracking technology have enabled opportunities to provide more precise six degree of freedom measurements from these trackers. Applying these technologies to the laser trackers requires quantified understanding of their current errors and uncertainty. It was well understood that an assortment of variables contributed to laser tracker uncertainty but the magnitude of these contributions was not quantified and documented. A series of experiments was performed at Sandia National Laboratories large centrifuge complex to quantify TSPI uncertainties of Sandia National Laboratories laser tracker III. The centrifuge was used to provide repeatable and economical test unit trajectories of a test-unit to use for TSPI comparison and uncertainty analysis. On a centrifuge, testunits undergo a known trajectory continuously with a known angular velocity. Each revolution may represent an independent test, which may be repeated many times over for magnitudes of data practical for statistical analysis. Previously these tests were performed at Sandia's rocket sled track facility but were found to be costly with challenges in the measurement ground truth TSPI. The centrifuge along with on-board measurement equipment was used to provide known ground truth position of test units. This paper discusses the experimental design and techniques used to arrive at measures of laser tracker error and uncertainty.
Optimal helicopter trajectory planning for terrain following flight
NASA Technical Reports Server (NTRS)
Menon, P. K. A.
1990-01-01
Helicopters operating in high threat areas have to fly close to the earth surface to minimize the risk of being detected by the adversaries. Techniques are presented for low altitude helicopter trajectory planning. These methods are based on optimal control theory and appear to be implementable onboard in realtime. Second order necessary conditions are obtained to provide a criterion for finding the optimal trajectory when more than one extremal passes through a given point. A second trajectory planning method incorporating a quadratic performance index is also discussed. Trajectory planning problem is formulated as a differential game. The objective is to synthesize optimal trajectories in the presence of an actively maneuvering adversary. Numerical methods for obtaining solutions to these problems are outlined. As an alternative to numerical method, feedback linearizing transformations are combined with the linear quadratic game results to synthesize explicit nonlinear feedback strategies for helicopter pursuit-evasion. Some of the trajectories generated from this research are evaluated on a six-degree-of-freedom helicopter simulation incorporating an advanced autopilot. The optimal trajectory planning methods presented are also useful for autonomous land vehicle guidance.
Calculating Trajectories And Orbits
NASA Technical Reports Server (NTRS)
Alderson, Daniel J.; Brady, Franklyn H.; Breckheimer, Peter J.; Campbell, James K.; Christensen, Carl S.; Collier, James B.; Ekelund, John E.; Ellis, Jordan; Goltz, Gene L.; Hintz, Gerarld R.; Legerton, Victor N.; Mccreary, Faith A.; Mitchell, Robert T.; Mottinger, Neil A.; Moultrie, Benjamin A.; Moyer, Theodore D.; Rinker, Sheryl L.; Ryne, Mark S.; Stavert, L. Robert; Sunseri, Richard F.
1989-01-01
Double-Precision Trajectory Analysis Program, DPTRAJ, and Orbit Determination Program, ODP, developed and improved over years to provide highly reliable and accurate navigation capability for deep-space missions like Voyager. Each collection of programs working together to provide desired computational results. DPTRAJ, ODP, and supporting utility programs capable of handling massive amounts of data and performing various numerical calculations required for solving navigation problems associated with planetary fly-by and lander missions. Used extensively in support of NASA's Voyager project. DPTRAJ-ODP available in two machine versions. UNIVAC version, NPO-15586, written in FORTRAN V, SFTRAN, and ASSEMBLER. VAX/VMS version, NPO-17201, written in FORTRAN V, SFTRAN, PL/1 and ASSEMBLER.
Jettison Engineering Trajectory Tool
NASA Technical Reports Server (NTRS)
Zaczek, Mariusz; Walter, Patrick; Pascucci, Joseph; Armstrong, Phyllis; Hallbick, Patricia; Morgan, Randal; Cooney, James
2013-01-01
The Jettison Engineering Trajectory Tool (JETT) performs the jettison analysis function for any orbiting asset. It provides a method to compute the relative trajectories between an orbiting asset and any jettisoned item (intentional or unintentional) or sublimating particles generated by fluid dumps to assess whether an object is safe to jettison, or if there is a risk with an item that was inadvertently lost overboard. The main concern is the interaction and possible recontact of the jettisoned object with an asset. This supports the analysis that jettisoned items will safely clear the vehicle, ensuring no collisions. The software will reduce the jettison analysis task from one that could take days to complete to one that can be completed in hours, with an analysis that is more comprehensive than the previous method. It provides the ability to define the jettison operation relative to International Space Station (ISS) structure, and provides 2D and 3D plotting capability to allow an analyst to perform a subjective clearance assessment with ISS structures. The developers followed the SMP to create the code and all supporting documentation. The code makes extensive use of the object-oriented format of Java and, in addition, the Model-View-Controller architecture was used in the organization of the code, allowing each piece to be independent of updates to the other pieces. The model category is for maintaining data entered by the user and generated by the analysis. The view category provides capabilities for data entry and displaying all or a portion of the analysis data in tabular, 2D, and 3D representation. The controller category allows for handling events that affect the model or view(s). The JETT utilizes orbital mechanics with complex algorithms. Since JETT is written in JAVA, it is essentially platform-independent.
NASA Astrophysics Data System (ADS)
Inomata, Akira; Noda, Yoshiyuki
2016-09-01
This paper is concerned with an advanced transfer trajectory planning method of 2-Dimensional transfer machine with vibrational element such as an overhead traveling crane. In the 2-D transfer machine, it is required to reach the target position in a short time, avoid the obstacles, and suppress the vibration. In recent years, the authors have proposed the trajectory planning method using the optimization problem with considering input and state constraints in the transfer system, obstacle avoidance and vibration suppression. However in the previous approaches, it takes a long time to derive the reference trajectory because of many variables in the optimization. Therefore in this study, we propose the fast solution for optimizing the transfer trajectory by giving a feasible initial trajectory. And, it is discussed how to give the cost function in the trajectory optimization with reducing the fluctuating cart motion. Moreover, we discuss the practical case that the proposed approach is applied to the large transfer space. The effectiveness of the proposed transfer trajectory planning method is verified by simulations of the overhead traveling crane.
Trajectory of body shape across the lifespan and cancer risk.
Song, Mingyang; Willett, Walter C; Hu, Frank B; Spiegelman, Donna; Must, Aviva; Wu, Kana; Chan, Andrew T; Giovannucci, Edward L
2016-05-15
The influence of adiposity over life course on cancer risk remains poorly understood. We assessed trajectories of body shape from age 5 up to 60 using a group-based modeling approach among 73,581 women from the Nurses' Health Study and 32,632 men from the Health Professionals Follow-up Study. After a median of approximately 10 years of follow-up, we compared incidence of total and obesity-related cancers (cancers of the esophagus [adenocarcinoma only], colorectum, pancreas, breast [after menopause], endometrium, ovaries, prostate [advanced only], kidney, liver and gallbladder) between these trajectories. We identified five distinct trajectories of body shape: lean-stable, lean-moderate increase, lean-marked increase, medium-stable, and heavy-stable/increase. Compared with women in the lean-stable trajectory, those in the lean-marked increase and heavy-stable/increase trajectories had a higher cancer risk in the colorectum, esophagus, pancreas, kidney, and endometrium (relative risk [RR] ranged from 1.22 to 2.56). Early life adiposity was inversely while late life adiposity was positively associated with postmenopausal breast cancer risk. In men, increased body fatness at any life period was associated with a higher risk of esophageal adenocarcinoma and colorectal cancer (RR ranged from 1.23 to 3.01), and the heavy-stable/increase trajectory was associated with a higher risk of pancreatic cancer, but lower risk of advanced prostate cancer. The trajectory-cancer associations were generally stronger for non-smokers and women who did not use menopausal hormone therapy. In conclusion, trajectories of body shape throughout life were related to cancer risk with varied patterns by sex and organ, indicating a role for lifetime adiposity in carcinogenesis.
Ballistic projectile trajectory determining system
Karr, T.J.
1997-05-20
A computer controlled system determines the three-dimensional trajectory of a ballistic projectile. To initialize the system, predictions of state parameters for a ballistic projectile are received at an estimator. The estimator uses the predictions of the state parameters to estimate first trajectory characteristics of the ballistic projectile. A single stationary monocular sensor then observes the actual first trajectory characteristics of the ballistic projectile. A comparator generates an error value related to the predicted state parameters by comparing the estimated first trajectory characteristics of the ballistic projectile with the observed first trajectory characteristics of the ballistic projectile. If the error value is equal to or greater than a selected limit, the predictions of the state parameters are adjusted. New estimates for the trajectory characteristics of the ballistic projectile are made and are then compared with actual observed trajectory characteristics. This process is repeated until the error value is less than the selected limit. Once the error value is less than the selected limit, a calculator calculates trajectory characteristics such a the origin and destination of the ballistic projectile. 8 figs.
Ballistic projectile trajectory determining system
Karr, Thomas J.
1997-01-01
A computer controlled system determines the three-dimensional trajectory of a ballistic projectile. To initialize the system, predictions of state parameters for a ballistic projectile are received at an estimator. The estimator uses the predictions of the state parameters to estimate first trajectory characteristics of the ballistic projectile. A single stationary monocular sensor then observes the actual first trajectory characteristics of the ballistic projectile. A comparator generates an error value related to the predicted state parameters by comparing the estimated first trajectory characteristics of the ballistic projectile with the observed first trajectory characteristics of the ballistic projectile. If the error value is equal to or greater than a selected limit, the predictions of the state parameters are adjusted. New estimates for the trajectory characteristics of the ballistic projectile are made and are then compared with actual observed trajectory characteristics. This process is repeated until the error value is less than the selected limit. Once the error value is less than the selected limit, a calculator calculates trajectory characteristics such a the origin and destination of the ballistic projectile.
Video partitioning by segmenting moving object trajectories
NASA Astrophysics Data System (ADS)
Badal, Tapas; Nain, Neeta; Ahmed, Mushtaq
2015-02-01
Video partitioning may be involve in a number of applications and present solutions for monitoring and tracking particular person trajectory and also helps in to generate semantic analysis of single entity or of entire video. Many recent advances in object detection and tracking concern about motion structure and data association used to be assigned a label to trajectories and analyze them independently. In this work we propose an approach for video portioning and a structure is given to store motion structure of target set to monitor in video. Spatio-temporal tubes separate individual objects that help to generate semantic analysis report for each object individually. The semantic analysis system for video based on this framework provides not only efficient synopsis generation but also spatial collision where the temporal consistency can be resolved for representation of semantic knowledge of each object. For keeping low computational complexity trajectories are generated online and classification, knowledge representation and arrangement over spatial domain are suggested to perform in offline manner.
Lunar Cube Transfer Trajectory Options
NASA Technical Reports Server (NTRS)
Folta, David; Dichmann, Donald James; Clark, Pamela E.; Haapala, Amanda; Howell, Kathleen
2015-01-01
Numerous Earth-Moon trajectory and lunar orbit options are available for Cubesat missions. Given the limited Cubesat injection infrastructure, transfer trajectories are contingent upon the modification of an initial condition of the injected or deployed orbit. Additionally, these transfers can be restricted by the selection or designs of Cubesat subsystems such as propulsion or communication. Nonetheless, many trajectory options can b e considered which have a wide range of transfer duration, fuel requirements, and final destinations. Our investigation of potential trajectories highlights several options including deployment from low Earth orbit (LEO) geostationary transfer orbits (GTO) and higher energy direct lunar transfer and the use of longer duration Earth-Moon dynamical systems. For missions with an intended lunar orbit, much of the design process is spent optimizing a ballistic capture while other science locations such as Sun-Earth libration or heliocentric orbits may simply require a reduced Delta-V imparted at a convenient location along the trajectory.
Lunar Cube Transfer Trajectory Options
NASA Technical Reports Server (NTRS)
Folta, David; Dichmann, Donald J.; Clark, Pamela; Haapala, Amanda; Howell, Kathleen
2015-01-01
Numerous Earth-Moon trajectory and lunar orbit options are available for Cubesat missions. Given the limited Cubesat injection infrastructure, transfer trajectories are contingent upon the modification of an initial condition of the injected or deployed orbit. Additionally, these transfers can be restricted by the selection or designs of Cubesat subsystems such as propulsion or communication. Nonetheless, many trajectory options can be considered which have a wide range of transfer durations, fuel requirements, and final destinations. Our investigation of potential trajectories highlights several options including deployment from low Earth orbit (LEO), geostationary transfer orbits (GTO), and higher energy direct lunar transfers and the use of longer duration Earth-Moon dynamical systems. For missions with an intended lunar orbit, much of the design process is spent optimizing a ballistic capture while other science locations such as Sun-Earth libration or heliocentric orbits may simply require a reduced Delta-V imparted at a convenient location along the trajectory.
Optimal solar sail planetocentric trajectories
NASA Technical Reports Server (NTRS)
Sackett, L. L.
1977-01-01
The analysis of solar sail planetocentric optimal trajectory problem is described. A computer program was produced to calculate optimal trajectories for a limited performance analysis. A square sail model is included and some consideration is given to a heliogyro sail model. Orbit to a subescape point and orbit to orbit transfer are considered. Trajectories about the four inner planets can be calculated and shadowing, oblateness, and solar motion may be included. Equinoctial orbital elements are used to avoid the classical singularities, and the method of averaging is applied to increase computational speed. Solution of the two-point boundary value problem which arises from the application of optimization theory is accomplished with a Newton procedure. Time optimal trajectories are emphasized, but a penalty function has been considered to prevent trajectories which intersect a planet's surface.
Evolutionary trajectories in rugged fitness landscapes
NASA Astrophysics Data System (ADS)
Jain, Kavita; Krug, Joachim
2005-04-01
We consider the evolutionary trajectories traced out by an infinite population undergoing mutation-selection dynamics in static, uncorrelated random fitness landscapes. Starting from the population that consists of a single genotype, the most populated genotype jumps from one local fitness maximum to another and eventually reaches the global maximum. We use a strong selection limit, which reduces the dynamics beyond the first time step to the competition between independent mutant subpopulations, to study the dynamics of this model and of a simpler one-dimensional model which ignores the geometry of the sequence space. We find that the fit genotypes that appear along a trajectory are a subset of suitably defined fitness records, and exploit several results from the record theory for non-identically distributed random variables. The genotypes that contribute to the trajectory are those records that are not bypassed by superior records arising further away from the initial population. Several conjectures concerning the statistics of bypassing are extracted from numerical simulations. In particular, for the one-dimensional model, we propose a simple relation between the bypassing probability and the dynamic exponent which describes the scaling of the typical evolution time with genome size. The latter can be determined exactly in terms of the extremal properties of the fitness distribution.
US Decadal Survey Outer Solar System Missions: Trajectory Options
NASA Astrophysics Data System (ADS)
Spilker, T. R.; Atkinson, D. H.; Strange, N. J.; Landau, D.
2012-04-01
The report of the US Planetary Science Decadal Survey (PSDS), released in draft form March 7, 2011, identifies several mission concepts involving travel to high-priority outer solar system (OSS) destinations. These include missions to Europa and Jupiter, Saturn and two of its satellites, and Uranus. Because travel to the OSS involves much larger distances and larger excursions out of the sun's gravitational potential well than inner solar system (ISS) missions, transfer trajectories for OSS missions are stronger drivers of mission schedule and resource requirements than for ISS missions. Various characteristics of each planet system, such as obliquity, radiation belts, rings, deep gravity wells, etc., carry ramifications for approach trajectories or trajectories within the systems. The maturity of trajectory studies for each of these destinations varies significantly. Europa has been the focus of studies for well over a decade. Transfer trajectory options from Earth to Jupiter are well understood. Current studies focus on trajectories within the Jovian system that could reduce the total mission cost of a Europa orbiter mission. Three missions to the Saturn system received high priority ratings in the PSDS report: two flagship orbital missions, one to Titan and one to Enceladus, and a Saturn atmospheric entry probe mission for NASA's New Frontiers Program. The Titan Saturn System Mission (TSSM) studies of 2007-2009 advanced our understanding of trajectory options for transfers to Saturn, including solar electric propulsion (SEP) trajectories. But SEP trajectories depend more on details of spacecraft and propulsion system characteristics than chemical trajectories, and the maturity of SEP trajectory search tools has not yet caught up with chemical trajectory tools, so there is still more useful research to be done on Saturn transfers. The TSSM studies revealed much about Saturn-orbiting trajectories that yield efficient and timely delivery to Titan or Enceladus
Analysis and Interpretation of Superresolution Single-Particle Trajectories
Holcman, D.; Hoze, N.; Schuss, Z.
2015-01-01
A large number (tens of thousands) of single molecular trajectories on a cell membrane can now be collected by superresolution methods. The data contains information about the diffusive motion of molecule, proteins, or receptors and here we review methods for its recovery by statistical analysis of the data. The information includes the forces, organization of the membrane, the diffusion tensor, the long-time behavior of the trajectories, and more. To recover the long-time behavior and statistics of long trajectories, a stochastic model of their nonequilibrium motion is required. Modeling and data analysis serve extracting novel biophysical features at an unprecedented spatiotemporal resolution. The review presents data analysis, modeling, and stochastic simulations applied in particular on surface receptors evolving in neuronal cells. PMID:26536253
Comparison of Performance Predictions for New Low-Thrust Trajectory Tools
NASA Technical Reports Server (NTRS)
Polsgrove, Tara; Kos, Larry; Hopkins, Randall; Crane, Tracie
2006-01-01
Several low thrust trajectory optimization tools have been developed over the last 3% years by the Low Thrust Trajectory Tools development team. This toolset includes both low-medium fidelity and high fidelity tools which allow the analyst to quickly research a wide mission trade space and perform advanced mission design. These tools were tested using a set of reference trajectories that exercised each tool s unique capabilities. This paper compares the performance predictions of the various tools against several of the reference trajectories. The intent is to verify agreement between the high fidelity tools and to quantify the performance prediction differences between tools of different fidelity levels.
Flight test trajectory control analysis
NASA Technical Reports Server (NTRS)
Walker, R.; Gupta, N.
1983-01-01
Recent extensions to optimal control theory applied to meaningful linear models with sufficiently flexible software tools provide powerful techniques for designing flight test trajectory controllers (FTTCs). This report describes the principal steps for systematic development of flight trajectory controllers, which can be summarized as planning, modeling, designing, and validating a trajectory controller. The techniques have been kept as general as possible and should apply to a wide range of problems where quantities must be computed and displayed to a pilot to improve pilot effectiveness and to reduce workload and fatigue. To illustrate the approach, a detailed trajectory guidance law is developed and demonstrated for the F-15 aircraft flying the zoom-and-pushover maneuver.
Galileo's Trajectory with Mild Resistance
ERIC Educational Resources Information Center
Groetsch, C. W.
2012-01-01
An aspect of Galileo's classical trajectory that persists in a simple resistance model is noted. The resistive model provides a case study for the classroom analysis of limiting behaviour of an implicitly defined function. (Contains 1 note.)
Four-body trajectory optimization
NASA Technical Reports Server (NTRS)
Pu, C. L.; Edelbaum, T. N.
1973-01-01
A collection of typical three-body trajectories from the L1 libration point on the sun-earth line to the earth is presented. These trajectories in the sun-earth system are grouped into four distinct families which differ in transfer time and delta V requirements. Curves showing the variations of delta V with respect to transfer time, and typical two and three-impulse primer vector histories, are included. The development of a four-body trajectory optimization program to compute fuel optimal trajectories between the earth and a point in the sun-earth-moon system are also discussed. Methods for generating fuel optimal two-impulse trajectories which originate at the earth or a point in space, and fuel optimal three-impulse trajectories between two points in space, are presented. A brief qualitative comparison of these methods is given. An example of a four-body two-impulse transfer from the Li libration point to the earth is included.
Hermes emergency reentry trajectories consequences on the Ariane 5 trajectories
NASA Astrophysics Data System (ADS)
Delattre, Ph.; Wagner, A.
1990-06-01
Hermes emergency reentry trajectories occur in case of any failure during that part of the launch phase from jettisoning the burn-out solid propellant boosters till the ignition of the MPH. In that case the Crew Escape Module cannot be used because of high Mach numbers and very severe constraints that would result of its low lift coefficient. The maximum constraints on the Hermes space plane are obtained in the atmospheric reentry phase of the emergency trajectories. Their important level is due to the deep flight path angle attained during the ballistic arc of the trajectory. Their values are depending on the instant of launch abort. These maximum constraints are very depending on the launch trajectory. The maximum Hermes constraints were represented in the altitude-velocity plane as a maximum altitude boundary for the Ariane 5 launch trajectory. Unfortunately a performance loss is the result of the requirement for a reduction of the culmination altitude. This has lead to a launch trajectory optimization that will be detailed in this paper. As an out-come of this study two important decisions have been made by CNES: choice of a L6 for the Hermes propulsion module; and the choice of the boundary that constraints the launch trajectory. Important efforts were made on Hermes in order to reduce the maximum constraints, in the field of aerodynamics (moment coefficient reduction, increase of the maximum angle of attack), center of gravity location (in order to reduce control surfaces hinge-moments and temperatures) and elevon-body-flap differential deflection.
NASA Technical Reports Server (NTRS)
1994-01-01
Pocket Statistics is published for the use of NASA managers and their staff. Included herein is Administrative and Organizational information, summaries of Space Flight Activity including the NASA Major Launch Record, and NASA Procurement, Financial, and Manpower data. The NASA Major Launch Record includes all launches of Scout class and larger vehicles. Vehicle and spacecraft development flights are also included in the Major Launch Record. Shuttle missions are counted as one launch and one payload, where free flying payloads are not involved. Satellites deployed from the cargo bay of the Shuttle and placed in a separate orbit or trajectory are counted as an additional payload.
NASA Technical Reports Server (NTRS)
1995-01-01
NASA Pocket Statistics is published for the use of NASA managers and their staff. Included herein is Administrative and Organizational information, summaries of Space Flight Activity including the NASA Major Launch Record, and NASA Procurement, Financial, and Manpower data. The NASA Major Launch Record includes all launches of Scout class and larger vehicles. Vehicle and spacecraft development flights are also included in the Major Launch Record. Shuttle missions are counted as one launch and one payload, where free flying payloads are not involved. Satellites deployed from the cargo bay of the Shuttle and placed in a separate orbit or trajectory are counted as an additional payload.
NASA Technical Reports Server (NTRS)
1996-01-01
This booklet of pocket statistics includes the 1996 NASA Major Launch Record, NASA Procurement, Financial, and Workforce data. The NASA Major Launch Record includes all launches of Scout class and larger vehicles. Vehicle and spacecraft development flights are also included in the Major Luanch Record. Shuttle missions are counted as one launch and one payload, where free flying payloads are not involved. Satellites deployed from the cargo bay of the Shuttle and placed in a separate orbit or trajectory are counted as an additional payload.
Trajectory Design for a Single-String Impactor Concept
NASA Technical Reports Server (NTRS)
Dono Perez, Andres; Burton, Roland; Stupl, Jan; Mauro, David
2017-01-01
This paper introduces a trajectory design for a secondary spacecraft concept to augment science return in interplanetary missions. The concept consist of a single-string probe with a kinetic impactor on board that generates an artificial plume to perform in-situ sampling. The trajectory design was applied to a particular case study that samples ejecta particles from the Jovian moon Europa. Results were validated using statistical analysis. Details regarding the navigation, targeting and disposal challenges related to this concept are presented herein.
Trajectories in Operating a Handheld Tool
ERIC Educational Resources Information Center
Heuer, Herbert; Sulzenbruck, Sandra
2009-01-01
The authors studied the trajectories of the hand and of the tip of a handheld sliding first-order lever in aiming movements. With this kind of tool, straight trajectories of the hand are generally associated with curved trajectories of the tip of the lever and vice versa. Trajectories of the tip of the lever exhibited smaller deviations from…
Trajectory optimization for an asymmetric launch vehicle. M.S. Thesis - MIT
NASA Technical Reports Server (NTRS)
Sullivan, Jeanne Marie
1990-01-01
A numerical optimization technique is used to fully automate the trajectory design process for an symmetric configuration of the proposed Advanced Launch System (ALS). The objective of the ALS trajectory design process is the maximization of the vehicle mass when it reaches the desired orbit. The trajectories used were based on a simple shape that could be described by a small set of parameters. The use of a simple trajectory model can significantly reduce the computation time required for trajectory optimization. A predictive simulation was developed to determine the on-orbit mass given an initial vehicle state, wind information, and a set of trajectory parameters. This simulation utilizes an idealized control system to speed computation by increasing the integration time step. The conjugate gradient method is used for the numerical optimization of on-orbit mass. The method requires only the evaluation of the on-orbit mass function using the predictive simulation, and the gradient of the on-orbit mass function with respect to the trajectory parameters. The gradient is approximated with finite differencing. Prelaunch trajectory designs were carried out using the optimization procedure. The predictive simulation is used in flight to redesign the trajectory to account for trajectory deviations produced by off-nominal conditions, e.g., stronger than expected head winds.
Wada, Y; Kaneko, Y; Nakano, E; Osu, R; Kawato, M
2001-05-01
solution can be computed in a wide work space and can also be obtained in a short time compared with the previous methods. Finally, we perform supplementary examinations of the experiments by Nakano, Imamizu, Osu, Uno, Gomi, Yoshioka et al. (1999). Estimation of dynamic joint torques and trajectory formation from surface electromyography signals using a neural network model. Biological Cybernetics, 73, 291-300. Their experiments showed that the measured trajectory is the closest to the minimum commanded torque change trajectory by statistical examination of many point-to-point trajectories over a wide range in a horizontal and sagittal work space. We recalculated the minimum commanded torque change trajectory using the proposed method, and performed the same examinations as previous investigations. As a result, it could be reconfirmed that the measured trajectory is closest to the minimum commanded torque change trajectory previously reported.
TAOS. Trajectory Analysis and Optimization System
Salguero, D.E.
1995-12-09
TAOS is a general-purpose software tool capable of analyzing nearly any type of three degree-of-freedom point-mass, high-speed trajectory. Input files contain aerodynamic coefficients, propulsion data, and a trajectory description. The trajectory description divides the trajectory into segments, and within each segment, guidance rules provided by the user describe how the trajectory is computed. Output files contain tabulated trajectory information such as position, velocity, and acceleration. Parametric optimization provides a powerful method for satisfying mission-planning constraints, and trajectories involving more than one vehicle can be computed within a single problem.
ERIC Educational Resources Information Center
Longford, Nicholas T.
A case is presented for adjusting the scores for free response items in the Advanced Placement (AP) tests. Using information about the rating process from the reliability studies, administrations of the AP test for three subject areas, psychology, computer science, and English language and composition, are analyzed. In the reliability studies, 299…
Bonanno, George A.; Diminich, Erica D.
2012-01-01
Background Research on resilience in the aftermath of potentially traumatic life events is still evolving. For decades researchers have documented resilience in children exposed to corrosive early environments, such as poverty or chronic maltreatment. Relatively more recently the study of resilience has migrated to the investigation of isolated and potentially traumatic life events (PTE) in adults. Methods In this article we first consider some of the key differences in the conceptualization of resilience following chronic adversity versus resilience following single-incident traumas, and then describe some of the misunderstandings that have developed about these constructs. To organize our discussion we introduce the terms emergent resilience and minimal-impact resilience to represent trajectories positive adjustment in these two domains, respectively. Results We focused in particular on minimal-impact resilience, and reviewed recent advances in statistical modeling of latent trajectories that have informed the most recent research on minimal-impact resilience in both children and adults and the variables that predict it, including demographic variables, exposure, past and current stressors, resources, personality, positive emotion, coping and appraisal, and flexibility in coping and emotion regulation. Conclusions The research on minimal impact resilience is nascent. Further research is warranted with implications for a multiple levels of analysis approach to elucidate the processes that may mitigate or modify the impact of a PTE at different developmental stages. PMID:23215790
ERIC Educational Resources Information Center
Osler, James Edward, II
2015-01-01
This monograph provides an epistemological rational for the Accumulative Manifold Validation Analysis [also referred by the acronym "AMOVA"] statistical methodology designed to test psychometric instruments. This form of inquiry is a form of mathematical optimization in the discipline of linear stochastic modelling. AMOVA is an in-depth…
Nonequilibrium statistical mechanics of nanotube nucleation
NASA Astrophysics Data System (ADS)
Artyukhov, Vasilii I.; Yakobson, Boris I.
A key problem that advanced carbon nanotube applications face is the difficulty of producing pure single-helicity samples. As the elementary processes of nanotube growth are difficult to observe in situ, theoretical understanding of the process is especially important. Direct molecular dynamics simulations offer limited insight due to computational intractability of space- and time-scales involved. We formulated a theory that explains a class of helicity-selective growth experiments, based on classical nucleation theory and crystal growth kinetics.1 However, a general theory of nanotube growth must also include fast irreversible growth beyond the classical near-equilibrium assumption. Here we construct a coarse-grained model allowing us to rigorously investigate the statistical mechanics of nanotube nucleation and trace how helicity emerges from the global nucleation trajectory ensemble. Importantly, our model can handle the whole range of conditions from perfect reversibility driven by energetics to perfect irreversibility driven by configurational entropy of nanotube caps and edges. Our theory generalizes earlier models in a large advance towards ultimate understanding of helicity-selective synthesis. 1 V.I. Artyukhov, E.S. Penev, and B.I. Yakobson, Nat. Commun. 5, 4892 (2014)
Ion drive performance and trajectories
NASA Technical Reports Server (NTRS)
Yen, C. L.
1978-01-01
The use of Solar Electric Propulsion (SEP) for the Solar Probe Mission is addressed. The dependence of the payload mass on the site of the SEP and the flight time are described on the basis of preliminary data. The range of hardware expected to be available in the 1980's is summarized. There are several classes of optimal low-thrust trajectories for the Solar Probe Mission. These are trajectory types A, B, C corresponding to one, two, or three orbital revolutions, respectively. Plots of transfer trajectories corresponding to type-A, type-A with a Venus Swingby, type-B, and type-C with ab Icarus Rendezvous are shown. A summary of the SEP performance is given.
Two Paths Diverged: Exploring Trajectories, Protocols, and Dynamic Phases
NASA Astrophysics Data System (ADS)
Gingrich, Todd Robert
Using tools of statistical mechanics, it is routine to average over the distribution of microscopic configurations to obtain equilibrium free energies. These free energies teach us about the most likely molecular arrangements and the probability of observing deviations from the norm. Frequently, it is necessary to interrogate the probability not just of static arrangements, but of dynamical events, in which case analogous statistical mechanical tools may be applied to study the distribution of molecular trajectories. Numerical study of these trajectory spaces requires algorithms which efficiently sample the possible trajectories. We study in detail one such Monte Carlo algorithm, transition path sampling, and use a non- equilibrium statistical mechanical perspective to illuminate why the algorithm cannot easily be adapted to study some problems involving long-timescale dynamics. Algorithmically generating highly-correlated trajectories, a necessity for transition path sampling, grows exponentially more challenging for longer trajectories unless the dynamics is strongly-guided by the "noise history", the sequence of random numbers representing the noise terms in the stochastic dynamics. Langevin dynamics of Weeks-Chandler-Andersen (WCA) particles in two dimensions lacks this strong noise guidance, so it is challenging to use transition path sampling to study rare dynamical events in long trajectories of WCA particles. The spin flip dynamics of a two-dimensional Ising model, on the other hand, can be guided by the noise history to achieve efficient path sampling. For systems that can be efficiently sampled with path sampling, we show that it is possible to simultaneously sample both the paths and the (potentially vast) space of non-equilibrium protocols to efficiently learn how rate constants vary with protocols and to identify low-dissipation protocols. When high-dimensional molecular dynamics can be coarse-grained and represented by a simplified dynamics on a low
Survivors Versus Non-Survivors Postburn: Differences In Inflammatory and Hypermetabolic Trajectories
Jeschke, Marc G.; Gauglitz, Gerd G.; Finnerty, Celeste C.; Kraft, Robert; Mlcak, Ronald P.; Herndon, David N.
2013-01-01
Objective To evaluate whether a panel of common biomedical markers can be utilized as trajectories to determine survival in pediatric burn patients. Summary Background Data Despite major advances in clinical care, of the more than 1 million people burned in the United States each year, more than 4,500 die as a result of their burn injuries. The ability to predict patient outcome or anticipate clinical trajectories using plasma protein expression would allow personalization of clinical care to optimize the potential for patient survival. Methods Two-hundred thirty severely burned children with burns exceeding 30% of the total body surface, requiring at least one surgical procedure were enrolled in this prospective cohort study. Demographics, clinical outcomes, as well as inflammatory and acute-phase responses (serum cytokines, hormones, and proteins) were determined at admission and at 11 time points for up to 180 days postburn. Statistical analysis was performed using a one-way ANOVA, Student’s t-test, Chi-square, and Mann-Whitney tests where appropriate. Results Survivors and non-survivors exhibited profound differences in critical markers of inflammation and metabolism at each time point. Non-survivors had significantly higher serum levels of IL-6, IL-8, granulocyte colony-stimulating factor, monocyte chemoattractant protein-1, c-reactive protein, glucose, insulin, blood urea nitrogen, creatinine, and bilirubin (p<0.05). Furthermore, non-survivors exhibited a vastly increased hypermetabolic response that was associated with increases in organ dysfunction and sepsis when compared with survivors (p<0.05). Conclusions Non-survivors have different trajectories in inflammatory, metabolic, and acute phase responses allowing differentiation of non-survivors from survivors and now possibly allowing novel predictive models to improve and personalize burn outcomes. PMID:23579577
INNOCENTI, ALESSANDRO; MORI, FRANCESCO; MELITA, DARIO; DREASSI, EMANUELA; CIANCIO, FRANCESCO; INNOCENTI, MARCO
2017-01-01
Aim: Evaluation of long-term results after aponeurotic blepharoptosis correction with external levator muscle complex advancement. Patients and Methods: We carried out a retrospective study with medical record review of 20 patients (40 eyes) affected by bilateral aponeurotic moderate and severe ptosis who underwent primary surgery between January 2010 and December 2013. Criteria for outcome evaluations included 3-year postoperative follow-up of upper margin reflex index (uMRD) and symmetry. Results: 3-Year postoperative follow-up showed 17 (85%) cases of successful correction of ptosis and three cases (15%) showed partial success. Two eyes showed hypocorrection, while one eye was overcorrected. The symmetry was maintained in all patients except for the oldest. Conclusion: External superior levator advancement is an effective procedure for moderate and severe aponeurotic blepharoptosis correction, and establishes good long-term eyelid position and symmetry. PMID:28064228
Animal escapology II: escape trajectory case studies
Domenici, Paolo; Blagburn, Jonathan M.; Bacon, Jonathan P.
2011-01-01
Summary Escape trajectories (ETs; measured as the angle relative to the direction of the threat) have been studied in many taxa using a variety of methodologies and definitions. Here, we provide a review of methodological issues followed by a survey of ET studies across animal taxa, including insects, crustaceans, molluscs, lizards, fish, amphibians, birds and mammals. Variability in ETs is examined in terms of ecological significance and morpho-physiological constraints. The survey shows that certain escape strategies (single ETs and highly variable ETs within a limited angular sector) are found in most taxa reviewed here, suggesting that at least some of these ET distributions are the result of convergent evolution. High variability in ETs is found to be associated with multiple preferred trajectories in species from all taxa, and is suggested to provide unpredictability in the escape response. Random ETs are relatively rare and may be related to constraints in the manoeuvrability of the prey. Similarly, reports of the effect of refuges in the immediate environment are relatively uncommon, and mainly confined to lizards and mammals. This may be related to the fact that work on ETs carried out in laboratory settings has rarely provided shelters. Although there are a relatively large number of examples in the literature that suggest trends in the distribution of ETs, our understanding of animal escape strategies would benefit from a standardization of the analytical approach in the study of ETs, using circular statistics and related tests, in addition to the generation of large data sets. PMID:21753040
Ballute Aerocapture Trajectories at Neptune
NASA Technical Reports Server (NTRS)
Lyons, Daniel T.; Johnson, Wyatt
2004-01-01
Using an inflatable ballute system for aerocapture at planets and moons with atmospheres has the potential to provide significant performance benefits compared not only to traditional all propulsive capture, but also to aeroshell based aerocapture technologies. This paper discusses the characteristics of entry trajectories for ballute aerocapture at Neptune. These trajectories are the first steps in a larger systems analysis effort that is underway to characterize and optimize the performance of a ballute aerocapture system for future missions not only at Neptune, but also the other bodies with atmospheres.
Predicting Adult Offenders' Criminal Trajectories from Their Juvenile Criminal Trajectories.
ERIC Educational Resources Information Center
Day, David M.; Bevc, Irene; Rosenthal, Jeffrey S.; Duchesne, Thierry; Rossman, Lianne; Theodor, Frances
This study examined the relationship between adolescent (10-17 years) criminal offending and adult (18-33 years) offending. The sample comprised 378 Canadian male offenders whose criminal trajectory was tracked for an average of 12.1 years, from adolescence into adulthood. Their man age at the time of the most recent follow-up was 27.5 years. The…
Mining spatiotemporal patterns of urban dwellers from taxi trajectory data
NASA Astrophysics Data System (ADS)
Mao, Feng; Ji, Minhe; Liu, Ting
2016-06-01
With the widespread adoption of locationaware technology, obtaining long-sequence, massive and high-accuracy spatiotemporal trajectory data of individuals has become increasingly popular in various geographic studies. Trajectory data of taxis, one of the most widely used inner-city travel modes, contain rich information about both road network traffic and travel behavior of passengers. Such data can be used to study the microscopic activity patterns of individuals as well as the macro system of urban spatial structures. This paper focuses on trajectories obtained from GPS-enabled taxis and their applications for mining urban commuting patterns. A novel approach is proposed to discover spatiotemporal patterns of household travel from the taxi trajectory dataset with a large number of point locations. The approach involves three critical steps: spatial clustering of taxi origin-destination (OD) based on urban traffic grids to discover potentially meaningful places, identifying threshold values from statistics of the OD clusters to extract urban jobs-housing structures, and visualization of analytic results to understand the spatial distribution and temporal trends of the revealed urban structures and implied household commuting behavior. A case study with a taxi trajectory dataset in Shanghai, China is presented to demonstrate and evaluate the proposed method.
Shi, Runhua; McLarty, Jerry W
2009-10-01
In this article, we introduced basic concepts of statistics, type of distributions, and descriptive statistics. A few examples were also provided. The basic concepts presented herein are only a fraction of the concepts related to descriptive statistics. Also, there are many commonly used distributions not presented herein, such as Poisson distributions for rare events and exponential distributions, F distributions, and logistic distributions. More information can be found in many statistics books and publications.
ERIC Educational Resources Information Center
Callamaras, Peter
1983-01-01
This buyer's guide to seven major types of statistics software packages for microcomputers reviews Edu-Ware Statistics 3.0; Financial Planning; Speed Stat; Statistics with DAISY; Human Systems Dynamics package of Stats Plus, ANOVA II, and REGRESS II; Maxistat; and Moore-Barnes' MBC Test Construction and MBC Correlation. (MBR)
ERIC Educational Resources Information Center
Petocz, Peter; Sowey, Eric
2008-01-01
As a branch of knowledge, Statistics is ubiquitous and its applications can be found in (almost) every field of human endeavour. In this article, the authors track down the possible source of the link between the "Siren song" and applications of Statistics. Answers to their previous five questions and five new questions on Statistics are presented.
NASA Technical Reports Server (NTRS)
Manning, Robert M.
1986-01-01
A rain attenuation prediction model is described for use in calculating satellite communication link availability for any specific location in the world that is characterized by an extended record of rainfall. Such a formalism is necessary for the accurate assessment of such availability predictions in the case of the small user-terminal concept of the Advanced Communication Technology Satellite (ACTS) Project. The model employs the theory of extreme value statistics to generate the necessary statistical rainrate parameters from rain data in the form compiled by the National Weather Service. These location dependent rain statistics are then applied to a rain attenuation model to obtain a yearly prediction of the occurrence of attenuation on any satellite link at that location. The predictions of this model are compared to those of the Crane Two-Component Rain Model and some empirical data and found to be very good. The model is then used to calculate rain attenuation statistics at 59 locations in the United States (including Alaska and Hawaii) for the 20 GHz downlinks and 30 GHz uplinks of the proposed ACTS system. The flexibility of this modeling formalism is such that it allows a complete and unified treatment of the temporal aspects of rain attenuation that leads to the design of an optimum stochastic power control algorithm, the purpose of which is to efficiently counter such rain fades on a satellite link.
NASA Astrophysics Data System (ADS)
Zack, J. W.
2015-12-01
Predictions from Numerical Weather Prediction (NWP) models are the foundation for wind power forecasts for day-ahead and longer forecast horizons. The NWP models directly produce three-dimensional wind forecasts on their respective computational grids. These can be interpolated to the location and time of interest. However, these direct predictions typically contain significant systematic errors ("biases"). This is due to a variety of factors including the limited space-time resolution of the NWP models and shortcomings in the model's representation of physical processes. It has become common practice to attempt to improve the raw NWP forecasts by statistically adjusting them through a procedure that is widely known as Model Output Statistics (MOS). The challenge is to identify complex patterns of systematic errors and then use this knowledge to adjust the NWP predictions. The MOS-based improvements are the basis for much of the value added by commercial wind power forecast providers. There are an enormous number of statistical approaches that can be used to generate the MOS adjustments to the raw NWP forecasts. In order to obtain insight into the potential value of some of the newer and more sophisticated statistical techniques often referred to as "machine learning methods" a MOS-method comparison experiment has been performed for wind power generation facilities in 6 wind resource areas of California. The underlying NWP models that provided the raw forecasts were the two primary operational models of the US National Weather Service: the GFS and NAM models. The focus was on 1- and 2-day ahead forecasts of the hourly wind-based generation. The statistical methods evaluated included: (1) screening multiple linear regression, which served as a baseline method, (2) artificial neural networks, (3) a decision-tree approach called random forests, (4) gradient boosted regression based upon an decision-tree algorithm, (5) support vector regression and (6) analog ensemble
Distance Education: Educational Trajectory Control
ERIC Educational Resources Information Center
Isaev, Andrey; Kravets, Alla; Isaeva, Ludmila; Fomenkov, Sergey
2013-01-01
Distance education has become a rather popular form of education recently. The advantages of this form are obvious and well-known. They include asynchronous learning, individualized learning trajectories and convenient case technologies. However, the distance form of education is not able to form the trainee's hands-on experience, especially…
Visiting Vehicle Ground Trajectory Tool
NASA Technical Reports Server (NTRS)
Hamm, Dustin
2013-01-01
The International Space Station (ISS) Visiting Vehicle Group needed a targeting tool for vehicles that rendezvous with the ISS. The Visiting Vehicle Ground Trajectory targeting tool provides the ability to perform both realtime and planning operations for the Visiting Vehicle Group. This tool provides a highly reconfigurable base, which allows the Visiting Vehicle Group to perform their work. The application is composed of a telemetry processing function, a relative motion function, a targeting function, a vector view, and 2D/3D world map type graphics. The software tool provides the ability to plan a rendezvous trajectory for vehicles that visit the ISS. It models these relative trajectories using planned and realtime data from the vehicle. The tool monitors ongoing rendezvous trajectory relative motion, and ensures visiting vehicles stay within agreed corridors. The software provides the ability to update or re-plan a rendezvous to support contingency operations. Adding new parameters and incorporating them into the system was previously not available on-the-fly. If an unanticipated capability wasn't discovered until the vehicle was flying, there was no way to update things.
Classical Trajectories and Quantum Spectra
NASA Technical Reports Server (NTRS)
Mielnik, Bogdan; Reyes, Marco A.
1996-01-01
A classical model of the Schrodinger's wave packet is considered. The problem of finding the energy levels corresponds to a classical manipulation game. It leads to an approximate but non-perturbative method of finding the eigenvalues, exploring the bifurcations of classical trajectories. The role of squeezing turns out decisive in the generation of the discrete spectra.
Trajectory optimization using regularized variables
NASA Technical Reports Server (NTRS)
Lewallen, J. M.; Szebehely, V.; Tapley, B. D.
1969-01-01
Regularized equations for a particular optimal trajectory are compared with unregularized equations with respect to computational characteristics, using perturbation type numerical optimization. In the case of the three dimensional, low thrust, Earth-Jupiter rendezvous, the regularized equations yield a significant reduction in computer time.
Canonical Transformations of Kepler Trajectories
ERIC Educational Resources Information Center
Mostowski, Jan
2010-01-01
In this paper, canonical transformations generated by constants of motion in the case of the Kepler problem are discussed. It is shown that canonical transformations generated by angular momentum are rotations of the trajectory. Particular attention is paid to canonical transformations generated by the Runge-Lenz vector. It is shown that these…
Aircraft flight test trajectory control
NASA Technical Reports Server (NTRS)
Menon, P. K. A.; Walker, R. A.
1988-01-01
Two design techniques for linear flight test trajectory controllers (FTTCs) are described: Eigenstructure assignment and the minimum error excitation technique. The two techniques are used to design FTTCs for an F-15 aircraft model for eight different maneuvers at thirty different flight conditions. An evaluation of the FTTCs is presented.
Experimental nonlocal and surreal Bohmian trajectories
Mahler, Dylan H.; Rozema, Lee; Fisher, Kent; Vermeyden, Lydia; Resch, Kevin J.; Wiseman, Howard M.; Steinberg, Aephraim
2016-01-01
Weak measurement allows one to empirically determine a set of average trajectories for an ensemble of quantum particles. However, when two particles are entangled, the trajectories of the first particle can depend nonlocally on the position of the second particle. Moreover, the theory describing these trajectories, called Bohmian mechanics, predicts trajectories that were at first deemed “surreal” when the second particle is used to probe the position of the first particle. We entangle two photons and determine a set of Bohmian trajectories for one of them using weak measurements and postselection. We show that the trajectories seem surreal only if one ignores their manifest nonlocality. PMID:26989784
Available Instruments for Analyzing Molecular Dynamics Trajectories
Likhachev, I. V.; Balabaev, N. K.; Galzitskaya, O. V.
2016-01-01
Molecular dynamics trajectories are the result of molecular dynamics simulations. Trajectories are sequential snapshots of simulated molecular system which represents atomic coordinates at specific time periods. Based on the definition, in a text format trajectory files are characterized by their simplicity and uselessness. To obtain information from such files, special programs and information processing techniques are applied: from molecular dynamics animation to finding characteristics along the trajectory (versus time). In this review, we describe different programs for processing molecular dynamics trajectories. The performance of these programs, usefulness for analyses of molecular dynamics trajectories, strong and weak aspects are discussed. PMID:27053964
Some Concepts for Target Trajectory Predictions
1994-03-01
Threat Acceleration 2-1 3 STATE-BASED PREDICTORS 3-1 CV Trajectory 3-1 CA Trajectory 3-1 CTR Trajectory 3-1 EDTR Trajectory 3-2 Helical Trajectory 3-6...8 CONCLUSIONS 8-1 REFERENCES 9-1 V I I NSWCDD/TR-92/445 I U ILLUSTRATIONS I Figure Pa•e 3-1 Typical EDTR trajectory and asymptote 3-5 6-1 True and...predictors. The new state-based predictors include Constant Turning Rate (CTR), Exponentially Decreasing Turning Rate ( EDTR ), and Helical. The CTR
Space Shuttle Day-of-Launch Trajectory Design Operations
NASA Technical Reports Server (NTRS)
Harrington, Brian E.
2011-01-01
A top priority of any launch vehicle is to insert as much mass into the desired orbit as possible. This requirement must be traded against vehicle capability in terms of dynamic control, thermal constraints, and structural margins. The vehicle is certified to specific structural limits which will yield certain performance characteristics of mass to orbit. Some limits cannot be certified generically and must be checked with each mission design. The most sensitive limits require an assessment on the day-of-launch. To further minimize vehicle loads while maximizing vehicle performance, a day-of-launch trajectory can be designed. This design is optimized according to that day s wind and atmospheric conditions, which increase the probability of launch. The day-of-launch trajectory design and verification process is critical to the vehicle s safety. The Day-Of-Launch I-Load Update (DOLILU) is the process by which the National Aeronautics and Space Administration's (NASA) Space Shuttle Program tailors the vehicle steering commands to fit that day s environmental conditions and then rigorously verifies the integrated vehicle trajectory s loads, controls, and performance. This process has been successfully used for almost twenty years and shares many of the same elements with other launch vehicles that execute a day-of-launch trajectory design or day-of-launch trajectory verification. Weather balloon data is gathered at the launch site and transmitted to the Johnson Space Center s Mission Control. The vehicle s first stage trajectory is then adjusted to the measured wind and atmosphere data. The resultant trajectory must satisfy loads and controls constraints. Additionally, these assessments statistically protect for non-observed dispersions. One such dispersion is the change in the wind from the last measured balloon to launch time. This process is started in the hours before launch and is repeated several times as the launch count proceeds. Should the trajectory design
NASA Astrophysics Data System (ADS)
Balasis, G.; Papadimitriou, C.; Daglis, I. A.; Georgiou, M.; Giamini, S. A.
2013-12-01
In the past decade, a critical mass of high-quality scientific data on the electric and magnetic fields in the Earth's magnetosphere and topside ionosphere has been progressively collected. This data pool will be further enriched by the measurements of the upcoming ESA/Swarm mission, a constellation of three satellites in three different polar orbits between 400 and 550 km altitude, which is expected to be launched in November 2013. New analysis tools that can cope with measurements of various spacecraft at various regions of the magnetosphere and in the topside ionosphere as well as ground stations will effectively enhance the scientific exploitation of the accumulated data. Here, we report on a new suite of algorithms based on a combination of wavelet spectral methods and artificial neural network techniques and demonstrate the applicability of our recently developed analysis tools both for individual case studies and statistical studies of ultra-low frequency (ULF) waves. First, we provide evidence for a rare simultaneous observation of a ULF wave event in the Earth's magnetosphere, topside ionosphere and surface: we have found a specific time interval during the Halloween 2003 magnetic storm, when the Cluster and CHAMP spacecraft were in good local time (LT) conjunction, and have examined the ULF wave activity in the Pc3 (22-100 mHz) and Pc4-5 (1-22 mHz) bands using data from the Geotail, Cluster and CHAMP missions, as well as the CARISMA and GIMA magnetometer networks. Then, we perform a statistical study of Pc3 wave events observed by CHAMP for the full decade (2001-2010) of the satellite vector magnetic data: the creation of a database of such events enabled us to derive valuable statistics for many important physical properties relating to the spatio-temporal location of these waves, the wave power and frequency, as well as other parameters and their correlation with solar wind conditions, magnetospheric indices, electron density data, ring current decay
A Study of the Trajectories of Projectiles.
ERIC Educational Resources Information Center
Grant, A. Ruari
1990-01-01
Described is a procedure for studying the trajectories of projectiles using ball bearings and aluminum foil. Trajectories were measured with and without the effects of air resistance. Multiflash photography was used to determine the flight paths of all objects. (KR)
Trajectory Synthesis for Fisher Information Maximization
Wilson, Andrew D.; Schultz, Jarvis A.; Murphey, Todd D.
2015-01-01
Estimation of model parameters in a dynamic system can be significantly improved with the choice of experimental trajectory. For general nonlinear dynamic systems, finding globally “best” trajectories is typically not feasible; however, given an initial estimate of the model parameters and an initial trajectory, we present a continuous-time optimization method that produces a locally optimal trajectory for parameter estimation in the presence of measurement noise. The optimization algorithm is formulated to find system trajectories that improve a norm on the Fisher information matrix (FIM). A double-pendulum cart apparatus is used to numerically and experimentally validate this technique. In simulation, the optimized trajectory increases the minimum eigenvalue of the FIM by three orders of magnitude, compared with the initial trajectory. Experimental results show that this optimized trajectory translates to an order-of-magnitude improvement in the parameter estimate error in practice. PMID:25598763
The Trajectory Synthesizer Generalized Profile Interface
NASA Technical Reports Server (NTRS)
Lee, Alan G.; Bouyssounouse, Xavier; Murphy, James R.
2010-01-01
The Trajectory Synthesizer is a software program that generates aircraft predictions for Air Traffic Management decision support tools. The Trajectory Synthesizer being used by researchers at NASA Ames Research Center was restricted in the number of trajectory types that could be generated. This limitation was not sufficient to support the rapidly changing Air Traffic Management research requirements. The Generalized Profile Interface was developed to address this issue. It provides a flexible approach to describe the constraints applied to trajectory generation and may provide a method for interoperability between trajectory generators. It also supports the request and generation of new types of trajectory profiles not possible with the previous interface to the Trajectory Synthesizer. Other enhancements allow the Trajectory Synthesizer to meet the current and future needs of Air Traffic Management research.
NASA Astrophysics Data System (ADS)
Rodríguez, Nancy
2015-03-01
The use of mathematical tools has long proved to be useful in gaining understanding of complex systems in physics [1]. Recently, many researchers have realized that there is an analogy between emerging phenomena in complex social systems and complex physical or biological systems [4,5,12]. This realization has particularly benefited the modeling and understanding of crime, a ubiquitous phenomena that is far from being understood. In fact, when one is interested in the bulk behavior of patterns that emerge from small and seemingly unrelated interactions as well as decisions that occur at the individual level, the mathematical tools that have been developed in statistical physics, game theory, network theory, dynamical systems, and partial differential equations can be useful in shedding light into the dynamics of these patterns [2-4,6,12].
Trajectories of Autism Severity in Early Childhood
ERIC Educational Resources Information Center
Venker, Courtney E.; Ray-Subramanian, Corey E.; Bolt, Daniel M.; Weismer, Susan Ellis
2014-01-01
Relatively little is known about trajectories of autism severity using calibrated severity scores (CSS) from the Autism Diagnostic Observation Schedule, but characterizing these trajectories has important theoretical and clinical implications. This study examined CSS trajectories during early childhood. Participants were 129 children with autism…
ERIC Educational Resources Information Center
Petocz, Peter; Sowey, Eric
2008-01-01
In this article, the authors focus on hypothesis testing--that peculiarly statistical way of deciding things. Statistical methods for testing hypotheses were developed in the 1920s and 1930s by some of the most famous statisticians, in particular Ronald Fisher, Jerzy Neyman and Egon Pearson, who laid the foundations of almost all modern methods of…
Geometric diffusion of quantum trajectories
Yang, Fan; Liu, Ren-Bao
2015-01-01
A quantum object can acquire a geometric phase (such as Berry phases and Aharonov–Bohm phases) when evolving along a path in a parameter space with non-trivial gauge structures. Inherent to quantum evolutions of wavepackets, quantum diffusion occurs along quantum trajectories. Here we show that quantum diffusion can also be geometric as characterized by the imaginary part of a geometric phase. The geometric quantum diffusion results from interference between different instantaneous eigenstate pathways which have different geometric phases during the adiabatic evolution. As a specific example, we study the quantum trajectories of optically excited electron-hole pairs in time-reversal symmetric insulators, driven by an elliptically polarized terahertz field. The imaginary geometric phase manifests itself as elliptical polarization in the terahertz sideband generation. The geometric quantum diffusion adds a new dimension to geometric phases and may have applications in many fields of physics, e.g., transport in topological insulators and novel electro-optical effects. PMID:26178745
Hierarchical Control and Trajectory Planning
NASA Technical Reports Server (NTRS)
Martin, Clyde F.; Horn, P. W.
1994-01-01
Most of the time on this project was spent on the trajectory planning problem. The construction is equivalent to the classical spline construction in the case that the system matrix is nilpotent. If the dimension of the system is n then the spline of degree 2n-1 is constructed. This gives a new approach to the construction of splines that is more efficient than the usual construction and at the same time allows the construction of a much larger class of splines. All known classes of splines are reconstructed using the approach of linear control theory. As a numerical analysis tool control theory gives a very good tool for constructing splines. However, for the purposes of trajectory planning it is quite another story. Enclosed in this document are four reports done under this grant.
Fractional Trajectories: Decorrelation Versus Friction
2013-07-27
from the integration of fractional differential equations in time. In Section 2 we provide a general demonstration of the new perspective on fractional ...section we demonstrate the equivalence between a fractional trajectory that is the solution of a Caputo fractional differential equation , and the... fractional differential equation dα dtα V(t) = OV(t), (1) where 0 < α < 1 and O is an operator, either linear or nonlinear, acting on the vector V(t
Aircraft flight test trajectory control
NASA Technical Reports Server (NTRS)
Menon, P. K. A.; Walker, R. A.
1988-01-01
Two control law design techniques are compared and the performance of the resulting controllers evaluated. The design requirement is for a flight test trajectory controller (FTTC) capable of closed-loop, outer-loop control of an F-15 aircraft performing high-quality research flight test maneuvers. The maneuver modeling, linearization, and design methodologies utilized in this research, are detailed. The results of applying these FTTCs to a nonlinear F-15 simulation are presented.
Dynamic Scaling of Manipulator Trajectories.
1983-01-01
Manipulators Robotics Trajectory Planning Manipulator Dynamics 20. ABSTRACT (Conftnue wn reverse side ID neceeOor Oine Identlfy b? block nuemNer) A...receives a c factor for each b(i). ’lhus both terms change equally with differing movement speeds. This contradicts the normal assumption in the robotics ...as well since they share the same significance as the velocity terms, yet this is not done. In any case, future generations of robots will contain
Bohmian trajectories of Airy packets
Nassar, Antonio B.; Miret-Artés, Salvador
2014-09-15
The discovery of Berry and Balazs in 1979 that the free-particle Schrödinger equation allows a non-dispersive and accelerating Airy-packet solution has taken the folklore of quantum mechanics by surprise. Over the years, this intriguing class of wave packets has sparked enormous theoretical and experimental activities in related areas of optics and atom physics. Within the Bohmian mechanics framework, we present new features of Airy wave packet solutions to Schrödinger equation with time-dependent quadratic potentials. In particular, we provide some insights to the problem by calculating the corresponding Bohmian trajectories. It is shown that by using general space–time transformations, these trajectories can display a unique variety of cases depending upon the initial position of the individual particle in the Airy wave packet. Further, we report here a myriad of nontrivial Bohmian trajectories associated to the Airy wave packet. These new features are worth introducing to the subject’s theoretical folklore in light of the fact that the evolution of a quantum mechanical Airy wave packet governed by the Schrödinger equation is analogous to the propagation of a finite energy Airy beam satisfying the paraxial equation. Numerous experimental configurations of optics and atom physics have shown that the dynamics of Airy beams depends significantly on initial parameters and configurations of the experimental set-up.
Trajectory versus probability density entropy.
Bologna, M; Grigolini, P; Karagiorgis, M; Rosa, A
2001-07-01
We show that the widely accepted conviction that a connection can be established between the probability density entropy and the Kolmogorov-Sinai (KS) entropy is questionable. We adopt the definition of density entropy as a functional of a distribution density whose time evolution is determined by a transport equation, conceived as the only prescription to use for the calculation. Although the transport equation is built up for the purpose of affording a picture equivalent to that stemming from trajectory dynamics, no direct use of trajectory time evolution is allowed, once the transport equation is defined. With this definition in mind we prove that the detection of a time regime of increase of the density entropy with a rate identical to the KS entropy is possible only in a limited number of cases. The proposals made by some authors to establish a connection between the two entropies in general, violate our definition of density entropy and imply the concept of trajectory, which is foreign to that of density entropy.
Estimation of motility parameters from trajectory data. A condensate of our recent results
NASA Astrophysics Data System (ADS)
Vestergaard, C. L.; Pedersen, J. N.; Mortensen, K. I.; Flyvbjerg, H.
2015-07-01
Given a theoretical model for a self-propelled particle or micro-organism, how does one optimally determine the parameters of the model from experimental data in the form of a time-lapse recorded trajectory? For very long trajectories, one has very good statistics, and optimality may matter little. However, for biological micro-organisms, one may not control the duration of recordings, and then optimality can matter. This is especially the case if one is interested in individuality and hence cannot improve statistics by taking population averages over many trajectories. One can learn much about this problem by studying its simplest case, pure diffusion with no self-propagation. This is an interesting problem also in its own right for the very same reasons: interest in individuality and short trajectories. We summarize our recent results on this latter issue here and speculate about the extent to which similar results may be obtained also for self-propelled particles.
Designing Asteroid Impact Scenario Trajectories
NASA Astrophysics Data System (ADS)
Chodas, Paul
2016-05-01
In order to study some of the technical and geopolitical issues of dealing with an asteroid on impact trajectory, a number of hypothetical impact scenarios have been presented over the last ten years or so. These have been used, for example, at several of the Planetary Defense Conferences (PDCs), as well as in tabletop exercises with the Federal Emergency Management Agency (FEMA), along with other government agencies. The exercise at the 2015 PDC involved most of the attendees, consisted of seven distinct steps (“injects”), and with all the presentations and discussions, took up nearly 10 hours of conference time. The trajectory for the PDC15 scenario was entirely realistic, and was posted ahead of the meeting. It was made available in the NEO Program’s Horizons ephemeris service so that users could , for example, design their own deflection missions. The simulated asteroid and trajectory had to meet numerous very exacting requirements: becoming observable on the very first day of the conference, yet remaining very difficult to observe for the following 7 years, and far enough away from Earth that it was out of reach of radar until just before impact. It had to be undetectable in the past, and yet provide multiple perihelion opportunities for deflection in the future. It had to impact in a very specific region of the Earth, a specific number of years after discovery. When observations of the asteroid are simulated to generate an uncertainty region, that entire region must impact the Earth along an axis that cuts across specific regions of the Earth, the “risk corridor”. This is important because asteroid deflections generally move an asteroid impact point along this corridor. One scenario had a requirement that the asteroid pass through a keyhole several years before impact. The PDC15 scenario had an additional constraint that multiple simulated kinetic impactor missions altered the trajectory at a deflection point midway between discovery and impact
NASA Astrophysics Data System (ADS)
Pregowski, Piotr; Owadowska, Edyta; Pietrzak, Jan; Zwolenik, Slawomir
2005-09-01
The paper presents method of acquiring a new form of statistical information about the changes at scenery, overseen by thermal imaging camera in static configuration. This type of imagers reach uniquely high efficiency during nighttime surveillance and targeting. The technical issue we have solved, resulted from the problem: how to verify the hypothesis that small, nocturnal rodents, like bank voles, use common paths inside their range and that they form a common, rather stable system? Such research has been especially difficult because the mentioned mammals are secretive, move with various speed and due to low contrast to their natural surroundings - as leaves or grass - nearly impossible for other kind of observations from a few meters distance. The main advantage of the elaborated method showed to be both adequately filtered long thermal movies for manual analyses, as well as auto-creation of the synthetic images which present maps of invisible paths and activity of their usage. Additional file with logs describing objects and their dislocations as the ".txt" files allows various, more detailed studies of animal behavior. The obtained results proved that this original method delivers a new, non-invasive, powerful and dynamic concept of solving various ecological problems. Creation of networks consisted of uncooled thermal imagers - of significantly increased availability - with data transmissions to digital centers allows to investigate of moving - particularly heat generated - objects in complete darkness, much wider and much more efficiently than up today. Thus, although our system was elaborated for ecological studies, a similar one can be considered as a tool for chosen tasks in the optical security areas.
NASA Technical Reports Server (NTRS)
Feiveson, Alan H.; Foy, Millennia; Ploutz-Snyder, Robert; Fiedler, James
2014-01-01
Do you have elevated p-values? Is the data analysis process getting you down? Do you experience anxiety when you need to respond to criticism of statistical methods in your manuscript? You may be suffering from Insufficient Statistical Support Syndrome (ISSS). For symptomatic relief of ISSS, come for a free consultation with JSC biostatisticians at our help desk during the poster sessions at the HRP Investigators Workshop. Get answers to common questions about sample size, missing data, multiple testing, when to trust the results of your analyses and more. Side effects may include sudden loss of statistics anxiety, improved interpretation of your data, and increased confidence in your results.
NASA Astrophysics Data System (ADS)
Hinsen, Konrad; Kneller, Gerald R.
2016-10-01
Anomalous diffusion is characterized by its asymptotic behavior for t → ∞. This makes it difficult to detect and describe in particle trajectories from experiments or computer simulations, which are necessarily of finite length. We propose a new approach using Bayesian inference applied directly to the observed trajectories sampled at different time scales. We illustrate the performance of this approach using random trajectories with known statistical properties and then use it for analyzing the motion of lipid molecules in the plane of a lipid bilayer.
Optimal Output Trajectory Redesign for Invertible Systems
NASA Technical Reports Server (NTRS)
Devasia, Santosh
1996-01-01
Given a desired output trajectory, inversion-based techniques find input-state trajectories required to exactly track the output. These inversion-based techniques have been successfully applied to the endpoint tracking control of multi-joint flexible manipulators and to aircraft control. The specified output trajectory uniquely determines the required input and state trajectories that are found through inversion. These input-state trajectories exactly track the desired output; however, they might not meet acceptable performance requirements. For example, during slewing maneuvers of flexible structures, the structural deformations, which depend on the required state trajectories, may be unacceptably large. Further, the required inputs might cause actuator saturation during an exact tracking maneuver for example, in the flight control of conventional takeoff and landing aircraft. In such situations, a compromise is desired between the tracking requirement and other goals such as reduction of internal vibrations and prevention of actuator saturation; the desired output trajectory needs to be redesigned.
Rapid Design of Gravity Assist Trajectories
NASA Technical Reports Server (NTRS)
Carrico, J.; Hooper, H. L.; Roszman, L.; Gramling, C.
1991-01-01
Several International Solar Terrestrial Physics (ISTP) missions require the design of complex gravity assisted trajectories in order to investigate the interaction of the solar wind with the Earth's magnetic field. These trajectories present a formidable trajectory design and optimization problem. The philosophy and methodology that enable an analyst to design and analyse such trajectories are discussed. The so called 'floating end point' targeting, which allows the inherently nonlinear multiple body problem to be solved with simple linear techniques, is described. The combination of floating end point targeting with analytic approximations with a Newton method targeter to achieve trajectory design goals quickly, even for the very sensitive double lunar swingby trajectories used by the ISTP missions, is demonstrated. A multiconic orbit integration scheme allows fast and accurate orbit propagation. A prototype software tool, Swingby, built for trajectory design and launch window analysis, is described.
Applications of Trajectory Solid Angle for Probabilistic Safety Assessment
Wong, Po Kee; Wong, Adam E.; Wong, Anita
2002-07-01
In 1974, a well-known research problem in Statistical Mechanics entitled 'To determine and define the probability function P.sub.2 of a particle hitting a predetermined area, given all its parameters of generation and ejection' was openly solicited for its solution from research and development organizations in U.S.A. One of many proposed solutions of the problem, initiated at that time, is by means of the Trajectory Solid Angle (TSA). TSA is defined as the integral of the dot product of the unit tangent of the particle's trajectory to the vector area divided by the square of the position vector connecting between the point of ejection and that of the surface to be hit. The invention provides: (1) The precise and the unique solution of a previously unsolved P.sub.2 problem: (2) Impacts to the governmental NRC safety standards and DOD weapon systems and many activities in the Department of Energy; (3) Impacts to update the contents of text books of physics and mathematics of all levels; (4) Impacts to the scientific instruments with applications in high technologies. The importance of Trajectory Solid Angle can be quoted from a letter by the late Institute Professor P. M. Morse of MIT who reviewed the DOE proposal P7900450 (reference No. 7) in 1979 and addressed to the inventor. 'If the Trajectory Solid Angle is correct it will provide a revolutionary concept in physics'. (authors)
... population, or about 25 million Americans, has experienced tinnitus lasting at least five minutes in the past ... by NIDCD Epidemiology and Statistics Program staff: (1) tinnitus prevalence was obtained from the 2008 National Health ...
Remus, Jeremiah J.; Gottfried, Jennifer L.; Harmon, Russell S.; Draucker, Anne; Baron, Dirk; Yohe, Robert
2010-05-01
of the classifier setup considered in this study include the training/testing routine (a 27-fold leave-one-sample-out setup versus a simple split of the data into separate sets for training and evaluation), the number of latent variables used in the regression model, and whether PLSDA operating on the entire broadband LIBS spectrum is superior to that using only a selected subset of LIBS emission lines. The results point to the robustness of the PLSDA technique and suggest that LIBS analysis combined with the appropriate statistical signal processing has the potential to be a useful tool for chemical analysis of archaeological artifacts and geological specimens.
NASA Technical Reports Server (NTRS)
Manning, Robert M.
1991-01-01
The dynamic and composite nature of propagation impairments that are incurred on Earth-space communications links at frequencies in and above 30/20 GHz Ka band, i.e., rain attenuation, cloud and/or clear air scintillation, etc., combined with the need to counter such degradations after the small link margins have been exceeded, necessitate the use of dynamic statistical identification and prediction processing of the fading signal in order to optimally estimate and predict the levels of each of the deleterious attenuation components. Such requirements are being met in NASA's Advanced Communications Technology Satellite (ACTS) Project by the implementation of optimal processing schemes derived through the use of the Rain Attenuation Prediction Model and nonlinear Markov filtering theory.
Duchesne, Stéphane; Ratelle, Catherine F
2014-04-01
This longitudinal study investigated the links between adolescents' perceptions of attachment security in their relationships with their mothers and fathers and developmental trajectories of depressive symptoms in a community sample of 414 adolescents (45 % males). The participants were followed annually from age 11 (end of elementary school) to 16 (end of high school). Group-based trajectory modeling analyses conditional on risk and protective factors identified four trajectories of depressive symptoms across adolescence: moderate stable (MS; 54.57 % of the sample), low stable (LS; 27.16 %), moderate increasing (MI; 11.30 %), and high declining (HD; 6.97 %). Membership in the HD versus LS trajectory group was predicted by attachment security to both the mother and father at baseline (age 11), whereas attachment security to the mother increased the odds of belonging to the MS and MI groups. These relationships were statistically significant after controlling for gender, anxiety symptoms, and academic competence. The findings are discussed with respect to their contribution to attachment theory and the research on the complementary contributions of mothers and fathers to the prevention of depressive symptomatology during adolescence.
Lunar Cube Transfer Trajectory Options
NASA Technical Reports Server (NTRS)
Folta, David C.; Dichman, Don; Clark, Pamela; Haapala, Amanda; Howell, Kathleen
2014-01-01
Contingent upon the modification of an initial condition of the injected or deployed orbit. Additionally, these designs can be restricted by the selection of the Cubesat subsystem design such as propulsion or communication. Nonetheless, many trajectory options can be designed with have a wide range of transfer durations, fuel requirements, and final destinations. Our investigation of potential trajectories highlights several design options including deployment into low Earth orbit (LEO), geostationary transfer orbits (GTO), and higher energy direct lunar transfer orbits. In addition to direct transfer options from these initial orbits, we also investigate the use of longer duration Earth-Moon dynamical systems. For missions with an intended lunar orbit, much of the design process is spent optimizing a ballistic capture while other science locations such as Sun-Earth libration or heliocentric orbits may simply require a reduced Delta-V imparted at a convenient location along the trajectory. In this article we examine several design options that meet the above limited deployment and subsystem drivers. We study ways that both impulsive and low-thrust Solar Electric Propulsion (SEP) engines can be used to place the Cubesat first into a highly eccentric Earth orbit, enter the Moon's Sphere of Influence, and finally achieve a highly eccentric lunar orbit. We show that such low-thrust transfers are feasible with a realistic micro-thruster model, assuming that the Cubesat can generate sufficient power for the SEP. Two examples are shown here: (1) A Cubestat injected by Exploration Mission 1 (EM-1) then employing low thrust; and (2) a CubSat deployed in a GTO, then employing impulsive maneuvers. For the EM-1 injected initial design, we increase the EM-1 targeted lunar flyby distance to reduce the energy of the lunar flyby to match that of a typical lMoon system heteroclinic manifold. Figure 1 presents an option that encompasses the similar dynamics as that of the ARTEMIS
Quantum Tunneling and Complex Trajectories
NASA Astrophysics Data System (ADS)
Meynig, Max; Haggard, Hal
2017-01-01
In general, the semiclassical approximation of quantum mechanical tunneling fails to treat tunneling through barriers if real initial conditions and trajectories are used. By analytically continuing classical dynamics to the complex plane the problems encountered in the approximation can be resolved. While, the complex methods discussed here have been previously explored, no one has exhibited an analytically solvable case. The essential features of the complex method will be discussed in the context of a novel, analytically solvable problem. These methods could be useful in quantum gravity, with applications to the tunneling of spacetime geometries.
Trajectory constraints in qualitative simulation
Brajnik, G.; Clancy, D.J.
1996-12-31
We present a method for specifying temporal constraints on trajectories of dynamical systems and enforcing them during qualitative simulation. This capability can be used to focus a simulation, simulate non-autonomous and piecewise-continuous systems, reason about boundary condition problems and incorporate observations into the simulation. The method has been implemented in TeQSIM, a qualitative simulator that combines the expressive power of qualitative differential equations with temporal logic. It interleaves temporal logic model checking with the simulation to constrain and refine the resulting predicted behaviors and to inject discontinuous changes into the simulation.
Rocket Launch Trajectory Simulations Mechanism
NASA Technical Reports Server (NTRS)
Margasahayam, Ravi; Caimi, Raoul E.; Hauss, Sharon; Voska, N. (Technical Monitor)
2002-01-01
The design and development of a Trajectory Simulation Mechanism (TSM) for the Launch Systems Testbed (LST) is outlined. In addition to being one-of-a-kind facility in the world, TSM serves as a platform to study the interaction of rocket launch-induced environments and subsequent dynamic effects on the equipment and structures in the close vicinity of the launch pad. For the first time, researchers and academicians alike will be able to perform tests in a laboratory environment and assess the impact of vibroacoustic behavior of structures in a moving rocket scenario on ground equipment, launch vehicle, and its valuable payload or spacecraft.
Driving trajectories in chaotic scattering.
Macau, Elbert E N; Caldas, Iberê L
2002-02-01
In this work we introduce a general approach for targeting in chaotic scattering that can be used to find a transfer trajectory between any two points located inside the scattering region. We show that this method can be used in association with a control of chaos strategy to drive around and keep a particle inside the scattering region. As an illustration of how powerful this approach is, we use it in a case of practical interest in celestial mechanics in which it is desired to control the evolution of two satellites that evolve around a large central body.
Trajectories of depressive symptoms after hip fracture
Cristancho, P.; Lenze, E. J.; Avidan, M. S.; Rawson, K. S.
2016-01-01
Background Hip fracture is often complicated by depressive symptoms in older adults. We sought to characterize trajectories of depressive symptoms arising after hip fracture and examine their relationship with functional outcomes and walking ability. We also investigated clinical and psychosocial predictors of these trajectories. Method We enrolled 482 inpatients, aged ≥60 years, who were admitted for hip fracture repair at eight St Louis, MO area hospitals between 2008 and 2012. Participants with current depression diagnosis and/or notable cognitive impairment were excluded. Depressive symptoms and functional recovery were assessed with the Montgomery–Asberg Depression Rating Scale and Functional Recovery Score, respectively, for 52 weeks after fracture. Health, cognitive, and psychosocial variables were gathered at baseline. We modeled depressive symptoms using group-based trajectory analysis and subsequently identified correlates of trajectory group membership. Results Three trajectories emerged according to the course of depressive symptoms, which we termed ‘resilient’, ‘distressed’, and ‘depressed’. The depressed trajectory (10% of participants) experienced a persistently high level of depressive symptoms and a slower time to recover mobility than the other trajectory groups. Stressful life events prior to the fracture, current smoking, higher anxiety, less social support, antidepressant use, past depression, and type of implant predicted membership of the depressed trajectory. Conclusions Depressive symptoms arising after hip fracture are associated with poorer functional status. Clinical and psychosocial variables predicted membership of the depression trajectory. Early identification and intervention of patients in a depressive trajectory may improve functional outcomes after hip fracture. PMID:27032698
Relativistic statistical arbitrage
NASA Astrophysics Data System (ADS)
Wissner-Gross, A. D.; Freer, C. E.
2010-11-01
Recent advances in high-frequency financial trading have made light propagation delays between geographically separated exchanges relevant. Here we show that there exist optimal locations from which to coordinate the statistical arbitrage of pairs of spacelike separated securities, and calculate a representative map of such locations on Earth. Furthermore, trading local securities along chains of such intermediate locations results in a novel econophysical effect, in which the relativistic propagation of tradable information is effectively slowed or stopped by arbitrage.
Combining Simulation Tools for End-to-End Trajectory Optimization
NASA Technical Reports Server (NTRS)
Whitley, Ryan; Gutkowski, Jeffrey; Craig, Scott; Dawn, Tim; Williams, Jacobs; Stein, William B.; Litton, Daniel; Lugo, Rafael; Qu, Min
2015-01-01
Trajectory simulations with advanced optimization algorithms are invaluable tools in the process of designing spacecraft. Due to the need for complex models, simulations are often highly tailored to the needs of the particular program or mission. NASA's Orion and SLS programs are no exception. While independent analyses are valuable to assess individual spacecraft capabilities, a complete end-to-end trajectory from launch to splashdown maximizes potential performance and ensures a continuous solution. In order to obtain end-to-end capability, Orion's in-space tool (Copernicus) was made to interface directly with the SLS's ascent tool (POST2) and a new tool to optimize the full problem by operating both simulations simultaneously was born.
Fixed-range optimum trajectories for short-haul aircraft
NASA Technical Reports Server (NTRS)
Erzberger, H.; Mclean, J. D.; Barman, J. F.
1975-01-01
An algorithm, based on the energy-state method, is derived for calculating optimum trajectories with a range constraint. The basis of the algorithm is the assumption that optimum trajectories consist of, at most, three segments: an increasing energy segment (climb); a constant energy segment (cruise); and a decreasing energy segment (descent). This assumption allows energy to be used as the independent variable in the increasing and decreasing energy segments, thereby eliminating the integration of a separate adjoint differential equation and simplifying the calculus of variations problem to one requiring only pointwise extremization of algebraic functions. The algorithm is used to compute minimum fuel, minimum time, and minimum direct-operating-cost trajectories, with range as a parameter, for an in-service CTOL aircraft and for an advanced STOL aircraft. For the CTOL aircraft and the minimum-fuel performance function, the optimum controls, consisting of air-speed and engine power setting, are continuous functions of the energy in both climb and descent as well as near the maximum or cruise energy. This is also true for the STOL aircraft except in the descent where at one energy level a nearly constant energy dive segment occurs, yielding a discontinuity in the airspeed at that energy. The reason for this segment appears to be the relatively high fuel flow at idle power of the engines used by this STOL aircraft. Use of a simplified trajectory which eliminates the dive increases the fuel consumption of the total descent trajectory by about 10 percent and the time to fly the descent by about 19 percent compared to the optimum.
Retired Status and Older Adults’ 10-Year Drinking Trajectories*
Brennan, Penny L.; Schutte, Kathleen K.; Moos, Rudolf H.
2010-01-01
Objective: Little research has examined the role of retirement in shaping late-life drinking careers, and it has generally been limited to cross-sectional designs or short-term follow-ups that emphasize group-level comparisons of retirees and nonretirees. The purpose of this study was to determine the following: (a) the effect of retired status on older adults’ 10-year within-person drinking trajectories and (b) whether age, gender, income, health, and problem-drinker status account for or moderate this effect. Method: We first estimated older adults’ (baseline M= 62 years; n = 595) 10-year within-person drinking trajectories using three successively predictive multilevel regression models: unconditional growth, retired status alone, and retired status controlling for covariates. Next, we determined whether inclusion of Retired Status × Covariate interactions would improve prediction of the trajectories. Results: Participants’ drinking frequency declined moderately over the 10-year interval, and retired status hastened the decline. However, this effect disappeared once covariates were added to the model: Baseline poorer health, lower income, and current problem-drinker status predicted steeper decline in drinking frequency, whereas former problem-drinker status predicted slower decline. Lower income and current drinking problems also predicted steeper declines in amount of alcohol consumed. There were no statistically significant or uniquely contributive interactions between retired status and age, gender, health, income, or drinking problems for predicting late-life drinking trajectories. Conclusions: Baseline health, income, and problem-drinking history are more important than retired status for predicting older adults’ long-term within-person drinking trajectories. These factors—and recency of drinking problems—should be considered in future studies of retirement and late-life drinking patterns. PMID:20230712
Debt trajectories and mental health.
Hojman, Daniel A; Miranda, Álvaro; Ruiz-Tagle, Jaime
2016-10-01
In the last few decades, there was a marked increase in consumer debt in the United States, Latin America and other emerging countries, spurring a debate about the real costs and benefits of household credit. Using a unique longitudinal dataset with detailed health and balance sheet information from a large sample of 10,900 Chilean households we study the relationship between debt trajectories in a three-year time window and mental health. We find that depressive symptoms are higher for those who have been persistently over-indebted, followed by those who transit from moderate to high debt levels. We also find that those who transition from over-indebtedness to moderate debt levels have no additional depressive symptoms compared to those with trajectories of moderate debt throughout (never over-indebted). This suggests that the debt-related contribution to depressive symptoms vanishes as debt levels fall. The association between debt and depressive symptoms seems to be driven by non-mortgage debt -primarily consumer credit- or late mortgage payments; secured debt (secured by collateral) per se is not associated with depressive symptoms. Policy interventions to reduce the negative association of over-indebtedness on mental health are discussed.
TOPTRAC: Topical Trajectory Pattern Mining
Kim, Younghoon; Han, Jiawei; Yuan, Cangzhou
2015-01-01
With the increasing use of GPS-enabled mobile phones, geo-tagging, which refers to adding GPS information to media such as micro-blogging messages or photos, has seen a surge in popularity recently. This enables us to not only browse information based on locations, but also discover patterns in the location-based behaviors of users. Many techniques have been developed to find the patterns of people's movements using GPS data, but latent topics in text messages posted with local contexts have not been utilized effectively. In this paper, we present a latent topic-based clustering algorithm to discover patterns in the trajectories of geo-tagged text messages. We propose a novel probabilistic model to capture the semantic regions where people post messages with a coherent topic as well as the patterns of movement between the semantic regions. Based on the model, we develop an efficient inference algorithm to calculate model parameters. By exploiting the estimated model, we next devise a clustering algorithm to find the significant movement patterns that appear frequently in data. Our experiments on real-life data sets show that the proposed algorithm finds diverse and interesting trajectory patterns and identifies the semantic regions in a finer granularity than the traditional geographical clustering methods. PMID:26709365
Discrimination and identification of periodic motion trajectories.
Or, Charles C-F; Thabet, Michel; Wilkinson, Frances; Wilson, Hugh R
2011-07-12
Humans are extremely sensitive to radial deformations of static circular contours (F. Wilkinson, H. R. Wilson, & C. Habak, 1998). Here, we investigate detection and identification of periodic motion trajectories defined by these radial frequency (RF) patterns over a range of radial frequencies of 2-5 cycles. We showed that the average detection thresholds for RF trajectories range from 1 to 4 min of arc and performance improves as a power-law function of radial frequency. RF trajectories are also detected for a range of speeds. We also showed that spatiotemporal global processing is involved in trajectory detection, as improvement in detection performance with increasing radial deformation displayed cannot be accounted for by local probability summation. Finally, identification of RF trajectories is possible over this RF range. Overall thresholds are about 6 times higher than previously reported for static stimuli. These novel stimuli should be a useful tool to investigate motion trajectory learning and discrimination in humans and other primates.
Computer optimization of a linac injector trajectory
Sawyer, C.; Detch, J.L. Jr.
1984-01-01
One can determine a computer prediction of the beam radius as a function of axial distance for a linac beam by providing a set of inputs to the computer code, ZFIELD. The trajectory may be improved by varying the magnet current values in the code, but repeated trails may still not attain the best trajectory. Starting with a set of points containing the desired trajectory, one may work the problem backwards and obtain the necessary magnet currents required by the trajectory. In the examples given, a portion of the trajectory is chosen to be parabolic. The trajectory information is used with a differential equation involving beam radius and its derivatives to yield the magnetic field as a function of axial position. Matrix methods are used to obtain the magnet currents from the magnetic field. 4 references, 6 figures.
Stochastic and fractal analysis of fracture trajectories
NASA Technical Reports Server (NTRS)
Bessendorf, Michael H.
1987-01-01
Analyses of fracture trajectories are used to investigate structures that fall between 'micro' and 'macro' scales. It was shown that fracture trajectories belong to the class of nonstationary processes. It was also found that correlation distance, which may be related to a characteristic size of a fracture process, increases with crack length. An assemblage of crack trajectory processes may be considered as a diffusive process. Chudnovsky (1981-1985) introduced a 'crack diffusion coefficient' d which reflects the ability of the material to deviate the crack trajectory from the most energetically efficient path and thus links the material toughness to its structure. For the set of fracture trajectories in AISI 304 steel, d was found to be equal to 1.04 microns. The fractal dimension D for the same set of trajectories was found to be 1.133.
ERIC Educational Resources Information Center
Chicot, Katie; Holmes, Hilary
2012-01-01
The use, and misuse, of statistics is commonplace, yet in the printed format data representations can be either over simplified, supposedly for impact, or so complex as to lead to boredom, supposedly for completeness and accuracy. In this article the link to the video clip shows how dynamic visual representations can enliven and enhance the…
NASA Astrophysics Data System (ADS)
Khan, Shahjahan
Often scientific information on various data generating processes are presented in the from of numerical and categorical data. Except for some very rare occasions, generally such data represent a small part of the population, or selected outcomes of any data generating process. Although, valuable and useful information is lurking in the array of scientific data, generally, they are unavailable to the users. Appropriate statistical methods are essential to reveal the hidden "jewels" in the mess of the row data. Exploratory data analysis methods are used to uncover such valuable characteristics of the observed data. Statistical inference provides techniques to make valid conclusions about the unknown characteristics or parameters of the population from which scientifically drawn sample data are selected. Usually, statistical inference includes estimation of population parameters as well as performing test of hypotheses on the parameters. However, prediction of future responses and determining the prediction distributions are also part of statistical inference. Both Classical or Frequentists and Bayesian approaches are used in statistical inference. The commonly used Classical approach is based on the sample data alone. In contrast, increasingly popular Beyesian approach uses prior distribution on the parameters along with the sample data to make inferences. The non-parametric and robust methods are also being used in situations where commonly used model assumptions are unsupported. In this chapter,we cover the philosophical andmethodological aspects of both the Classical and Bayesian approaches.Moreover, some aspects of predictive inference are also included. In the absence of any evidence to support assumptions regarding the distribution of the underlying population, or if the variable is measured only in ordinal scale, non-parametric methods are used. Robust methods are employed to avoid any significant changes in the results due to deviations from the model
NASA Astrophysics Data System (ADS)
Khan, Shahjahan
Often scientific information on various data generating processes are presented in the from of numerical and categorical data. Except for some very rare occasions, generally such data represent a small part of the population, or selected outcomes of any data generating process. Although, valuable and useful information is lurking in the array of scientific data, generally, they are unavailable to the users. Appropriate statistical methods are essential to reveal the hidden “jewels” in the mess of the row data. Exploratory data analysis methods are used to uncover such valuable characteristics of the observed data. Statistical inference provides techniques to make valid conclusions about the unknown characteristics or parameters of the population from which scientifically drawn sample data are selected. Usually, statistical inference includes estimation of population parameters as well as performing test of hypotheses on the parameters. However, prediction of future responses and determining the prediction distributions are also part of statistical inference. Both Classical or Frequentists and Bayesian approaches are used in statistical inference. The commonly used Classical approach is based on the sample data alone. In contrast, increasingly popular Beyesian approach uses prior distribution on the parameters along with the sample data to make inferences. The non-parametric and robust methods are also being used in situations where commonly used model assumptions are unsupported. In this chapter,we cover the philosophical andmethodological aspects of both the Classical and Bayesian approaches.Moreover, some aspects of predictive inference are also included. In the absence of any evidence to support assumptions regarding the distribution of the underlying population, or if the variable is measured only in ordinal scale, non-parametric methods are used. Robust methods are employed to avoid any significant changes in the results due to deviations from the model
Numerical Study of Orbital Trajectories about Phobos
1988-12-01
COF NUMERICAL STUDY OF ORBITAL TRAJECTORIES ABOUT PHOBOS THESIS Robert B. Teets Captain, USAF AFIT/GS0/AA/8 8D- 16 ..................D TIC SELECTEh...ful em t%... . 9 ... 3 ...29 ...058_... AFIT/GSO/AA/88D-16 0 NUMERICAL STUDY OF ORBITAL TRAJECTORIES ABOUT PHOBOS THESIS Robert B. Teets Captain...ORBITAL TRAJECTORIES ABOUT PHOBOS THESIS Presented to the Faculty of the School of Engineering of the Air Force Institute of Technology Air University In
Anomaly Detection and Modeling of Trajectories
2012-08-01
unsupervised fashion using support vector machines (SVMs) and various spatial representations of trajectories. This thesis will also focus on...empirically to provide a rich analysis of trajectory datasets. 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT Same as...based on the rest of the dataset. This thesis develops a technique for detecting anoma- lous trajectories in a dataset in an unsupervised fashion using
The Jupiter Icy Moons Orbiter reference trajectory
NASA Technical Reports Server (NTRS)
Whiffen, Gregory J.; Lam, Try
2006-01-01
The proposed NASA Jupiter Icy Moons Orbiter (JIMO) mission would have used a single spacecraft to orbit Callisto, Ganymede, and Europa in succession. The enormous Delta-Velocity required for this mission (nearly [25 km/s]) would necessitate the use of very high efficiency electric propulsion. The trajectory created for the proposed baseline JIMO mission may be the most complex trajectory ever designed. This paper describes the current reference trajectory in detail and describes the processes that were used to construct it.
An Expert System-Driven Method for Parametric Trajectory Optimization During Conceptual Design
NASA Technical Reports Server (NTRS)
Dees, Patrick D.; Zwack, Mathew R.; Steffens, Michael; Edwards, Stephen; Diaz, Manuel J.; Holt, James B.
2015-01-01
During the early phases of engineering design, the costs committed are high, costs incurred are low, and the design freedom is high. It is well documented that decisions made in these early design phases drive the entire design's life cycle cost. In a traditional paradigm, key design decisions are made when little is known about the design. As the design matures, design changes become more difficult in both cost and schedule to enact. The current capability-based paradigm, which has emerged because of the constrained economic environment, calls for the infusion of knowledge usually acquired during later design phases into earlier design phases, i.e. bringing knowledge acquired during preliminary and detailed design into pre-conceptual and conceptual design. An area of critical importance to launch vehicle design is the optimization of its ascent trajectory, as the optimal trajectory will be able to take full advantage of the launch vehicle's capability to deliver a maximum amount of payload into orbit. Hence, the optimal ascent trajectory plays an important role in the vehicle's affordability posture yet little of the information required to successfully optimize a trajectory is known early in the design phase. Thus, the current paradigm of optimizing ascent trajectories involves generating point solutions for every change in a vehicle's design parameters. This is often a very tedious, manual, and time-consuming task for the analysts. Moreover, the trajectory design space is highly non-linear and multi-modal due to the interaction of various constraints. When these obstacles are coupled with the Program to Optimize Simulated Trajectories (POST), an industry standard program to optimize ascent trajectories that is difficult to use, expert trajectory analysts are required to effectively optimize a vehicle's ascent trajectory. Over the course of this paper, the authors discuss a methodology developed at NASA Marshall's Advanced Concepts Office to address these issues
Trajectory analysis of a soccer ball
NASA Astrophysics Data System (ADS)
Goff, John Eric; Carré, Matt J.
2009-11-01
We performed experiments in which a soccer ball was launched from a machine while two cameras recorded portions of its trajectory. Drag coefficients were obtained from range measurements for no-spin trajectories, for which the drag coefficient does not vary appreciably during the ball's flight. Lift coefficients were obtained from the trajectories immediately following the ball's launch, in which Reynolds number and spin parameter do not vary much. We obtain two values of the lift coefficient for spin parameters that had not been obtained previously. Our codes for analyzing the trajectories are freely available to educators and students.
NBODY - a multipurpose trajectory optimization computer program
NASA Technical Reports Server (NTRS)
Strack, W. C.
1974-01-01
Documentation of the NBODY trajectory optimization program is presented in the form of a mathematical development plus a user's manual. Optimal multistage-launch ascent trajectories may be determined by variational thrust steering during the upper phase. Optimal low-thrust interplanetary spacecraft trajectories may also be calculated with solar power or constant power, all-propulsion or embedded coast arcs, fixed or optimal thrust angles, and a variety of terminal end conditions. A hybrid iteration scheme solves the boundary-value problem, while either transversality conditions or a univariate search scheme optimize vehicle or trajectory parameters.
Trajectories of Posttraumatic Stress Among Urban Residents
Galea, Sandro; Uddin, Monica; Koenen, Karestan C.
2014-01-01
Urban residents experience a wide range of traumatic events and are at increased risk of assaultive violence. Although previous research has examined trajectories of posttraumatic stress (PTS) through latent class growth analysis (LCGA) among persons exposed to the same index events (e.g., a natural disaster), PTS trajectories have not been documented among urban residents. The aims of this study were to conduct LGCA with a sample of trauma survivors from Detroit, Michigan (N = 981), and to explore predictors of trajectory membership. Participants completed three annual telephone surveys, each of which included the posttraumatic stress disorder (PTSD) Check-list-Civilian Version. Four PTS trajectories were detected. Although the majority evidenced a trajectory of consistently few symptoms (Low: 72.5 %), 4.6 % were in a trajectory of chronic severe PTSD (High), and the remainder were in trajectories of consistently elevated, but generally subclinical, levels of PTS (Decreasing: 12.3 %; Increasing: 10.6 %). Socioeconomic disadvantage (e.g., lower income), more extensive trauma history (e.g., childhood abuse), and fewer social resources (e.g., lower social support) were associated with membership in higher PTS trajectories, relative to the Low trajectory. The results suggest that efforts to reduce PTS in urban areas need to attend to socioeconomic vulnerabilities in addition to trauma history and risk for ongoing trauma exposure. PMID:24469249
Global trajectory targeting via computer graphics
NASA Technical Reports Server (NTRS)
Mann, F. I.
1971-01-01
A technique is described in which the two-point boundary value problem (TPBVP) may be solved with the aid of interactive computer graphics. The particular TPBVP considered is the optimal electric propulsion space trajectory problem. An appropriate two-dimensional projection of the TPBVP mapping, or trajectory, is displayed on the computer's television screen, and a man-in-the-loop varies selected trajectory starting conditions in the fashion of a nonlinear walk until the viewed trajectory endpoint lies near a displayed target. Once global targeting is accomplished in this manner, program internal logic can easily handle local targeting to strongly solve the TPBVP.
Nonadiabatic Molecular Dynamics with Trajectories
NASA Astrophysics Data System (ADS)
Tavernelli, Ivano
2012-02-01
In the mixed quantum-classical description of molecular systems, only the quantum character of the electronic degrees of freedom is considered while the nuclear motion is treated at a classical level. In the adiabatic case, this picture corresponds to the Born-Oppenheimer limit where the nuclei move as point charges on the potential energy surface (PES) associated with a given electronic state. Despite the success of this approximation, many physical and chemical processes do not fall in the regime where nuclei and electrons can be considered decoupled. In particular, most photoreactions pass through regions of the PES in which electron-nuclear quantum interference effects are sizeable and often crucial for a correct description of the phenomena. Recently, we have developed a trajectory-based nonadiabatic molecular dynamics scheme that describes the nuclear wavepacket as an ensemble of particles following classical trajectories on PESs derived from time-dependent density functional theory (TDDFT) [1]. The method is based on Tully's fewest switches trajectories surface hopping (TSH) where the nonadiabatic coupling elements between the different potential energy surfaces are computed on-the-fly as functionals of the ground state electron density or, equivalently, of the corresponding Kohn-Sham orbitals [2]. Here, we present the theoretical fundamentals of our approach together with an extension that allows for the direct coupling of the dynamics to an external electromagnetic field [3] as well as to the external potential generated by the environment (solvent effects) [4]. The method is applied to the study of the photodissociation dynamics of simple molecules in gas phase and to the description of the fast excited state dynamics of molecules in solution (in particular Ruthenium (II) tris(bipyridine) in water). [4pt] [1] E. Tapavicza, I. Tavernelli, U. Rothlisberger, Phys. Rev. Lett., 98, (2007) 023001. [0pt] [2] Tavernelli I.; Tapavicza E.; Rothlisberger U., J. Chem
Ledonio, Charles G.; Hunt, Matthew A.; Siddiq, Farhan; Polly, David W.
2016-01-01
Background Technological advances, including navigation, have been made to improve safety and accuracy of pedicle screw fixation. We evaluated the accuracy of the virtual screw placement (Stealth projection) compared to actual screw placement (intra-operative O-Arm) and examined for differences based on the distance from the reference frame. Methods A retrospective evaluation of prospectively collected data was conducted from January 2013 to September 2013. We evaluated thoracic and lumbosacral pedicle screws placed using intraoperative O-arm and Stealth navigation by obtaining virtual screw projections and intraoperative O-arm images after screw placement. The screw trajectory angle to the midsagittal line and superior endplate was compared in the axial and sagittal views, respectively. Percent error and paired t-test statistics were then performed. Results Thirty-one patients with 240 pedicle screws were analyzed. The mean angular difference between the virtual and actual image in all screws was 2.17° ± 2.20° on axial images and 2.16° ± 2.24° on sagittal images. There was excellent agreement between actual and virtual pedicle screw trajectories in the axial and sagittal plane with ICC = 0.99 (95%CI: 0.992-0.995) (p<0.001) and ICC= 0.81 (95%CI: 0.759-0.855) (p<0.001) respectively. When comparing thoracic and lumbar screws, there was a significant difference in the sagittal angulation between the two distributions. No statistical differences were found distance from the reference frame. Conclusion The virtual projection view is clinically accurate compared to the actual placement on intra-operative CT in both the axial and sagittal views. There is slight imprecision (~2°) in the axial and sagittal planes and a minor difference in the sagittal thoracic and lumbar angulation, although these did not affect clinical outcomes. In general, we find that pedicle screw placement using intraoperative cone beam CT and navigation to be accurate and reliable, and as such
Chaiton, Michael; Contreras, Gisèle; Brunet, Jennifer; Sabiston, Catherine M.; O’Loughlin, Erin; Low, Nancy C. P.; Karp, Igor; Barnett, Tracie A.; O’Loughlin, Jennifer
2013-01-01
Objective: This study describes developmental trajectories of depressive symptoms in adolescents and examines the association between trajectory group and mental health outcomes in young adulthood. Methods: Depressive symptoms were self-reported every three months from grade seven through grade 11 by 1293 adolescents in the Nicotine Dependence in Teens (NDIT) study and followed in young adulthood (average age 20.4, SD=0.7, n=865). Semi-parametric growth modeling was used to identify sex-specific trajectories of depressive symptoms. Results: Three distinct trajectory groups were identified: 50% of boys and 29% of girls exhibited low, decreasing levels of depressive symptoms; 14% of boys and 28% of girls exhibited high and increasing levels; and 36% of boys and 43% of girls exhibited moderate levels with linear increase. Trajectory group was a statistically significant independent predictor of depression, stress, and self-rated mental health in young adulthood in boys and girls. Boys, but not girls, in the high trajectory group had a statistically significant increase in the likelihood of seeking psychiatric care. Conclusions: Substantial heterogeneity in changes in depressive symptoms over time was found. Because early depressive symptoms predict mental health problems in young adulthood, monitoring adolescents for depressive symptoms may help identify those most at risk and in need of intervention. PMID:23667355
Mapping concentrations of posttraumatic stress and depression trajectories following Hurricane Ike
Gruebner, Oliver; Lowe, Sarah R.; Tracy, Melissa; Joshi, Spruha; Cerdá, Magdalena; Norris, Fran H.; Subramanian, S. V.; Galea, Sandro
2016-01-01
We investigated geographic concentration in elevated risk for a range of postdisaster trajectories of chronic posttraumatic stress symptom (PTSS) and depression symptoms in a longitudinal study (N = 561) of a Hurricane Ike affected population in Galveston and Chambers counties, TX. Using an unadjusted spatial scan statistic, we detected clusters of elevated risk of PTSS trajectories, but not depression trajectories, on Galveston Island. We then tested for predictors of membership in each trajectory of PTSS and depression (e.g., demographic variables, trauma exposure, social support), not taking the geographic nature of the data into account. After adjusting for significant predictors in the spatial scan statistic, we noted that spatial clusters of PTSS persisted and additional clusters of depression trajectories emerged. This is the first study to show that longitudinal trajectories of postdisaster mental health problems may vary depending on the geographic location and the individual- and community-level factors present at these locations. Such knowledge is crucial to identifying vulnerable regions and populations within them, to provide guidance for early responders, and to mitigate mental health consequences through early detection of mental health needs in the population. As human-made disasters increase, our approach may be useful also in other regions in comparable settings worldwide. PMID:27558011
Low-thrust rocket trajectories
Keaton, P.W.
1986-01-01
The development of low-thrust propulsion systems to complement chemical propulsion systems will greatly enhance the evolution of future space programs. Two advantages of low-thrust rockets are stressed: first, in a strong gravitational field, such as occurs near the Earth, freighter missions with low-thrust engines require one-tenth as much propellant as do chemical engines. Second, in a weak gravitational field, such as occurs in the region between Venus and Mars, low-thrust rockets are faster than chemical rockets with comparable propellant mass. The purpose here is to address the physics of low-thrust trajectories and to interpret the results with two simple models. Analytic analyses are used where possible - otherwise, the results of numerical calculations are presented in graphs. The author has attempted to make this a self-contained report. 57 refs., 10 figs.
Low-thrust rocket trajectories
Keaton, P.W.
1987-03-01
The development of low-thrust propulsion systems to complement chemical propulsion systems will greatly enhance the evolution of future space programs. Two advantages of low-thrust rockets are stressed: first, in a strong gravitational field, such as occurs near the Earth, freighter missions with low-thrust engines require one-tenth as much propellant as do chemical engines. Second, in a weak gravitational field, such as occurs in the region between Venus and Mars, low-thrust rockets are faster than chemical rockets with comparable propellant mass. The purpose here is to address the physics of low-thrust trajectories and to interpret the results with two simple models. Analytic analyses are used where possible - otherwise, the results of numerical calculations are presented in graphs. The author has attempted to make this a self-contained report.
Baydar, Nazli; Akcinar, Berna
2017-02-18
Theoretical advances in the study of the development of aggressive behaviors indicate that parenting behaviors and child aggression mutually influence one another. This study contributes to the body of empirical research in this area by examining the development of child aggression, maternal responsiveness, and maternal harsh discipline, using 5-year longitudinal data from a nationally representative sample of Turkish children (n = 1009; 469 girls and 582 boys). Results indicated that: (i) maternal responsiveness and harsh discipline at age 3 were associated with the subsequent linear trajectory of aggression; (ii) reciprocally, aggressive behaviors at age 3 were associated with the subsequent linear trajectories of these two types of parenting behaviors; (iii) deviations from the linear trajectories of the child and mother behaviors tended to be short lived; and, (iv) the deviations of child behaviors from the linear trajectories were associated with the subsequent changes in mother behaviors after age 5. These findings are discussed in the cultural context of this study.
Rendón-Macías, Mario Enrique; Villasís-Keever, Miguel Ángel; Miranda-Novales, María Guadalupe
2016-01-01
Descriptive statistics is the branch of statistics that gives recommendations on how to summarize clearly and simply research data in tables, figures, charts, or graphs. Before performing a descriptive analysis it is paramount to summarize its goal or goals, and to identify the measurement scales of the different variables recorded in the study. Tables or charts aim to provide timely information on the results of an investigation. The graphs show trends and can be histograms, pie charts, "box and whiskers" plots, line graphs, or scatter plots. Images serve as examples to reinforce concepts or facts. The choice of a chart, graph, or image must be based on the study objectives. Usually it is not recommended to use more than seven in an article, also depending on its length.
Order Statistics and Nonparametric Statistics.
2014-09-26
Topics investigated include the following: Probability that a fuze will fire; moving order statistics; distribution theory and properties of the...problem posed by an Army Scientist: A fuze will fire when at least n-i (or n-2) of n detonators function within time span t. What is the probability of
NASA Astrophysics Data System (ADS)
Goodman, Joseph W.
2000-07-01
The Wiley Classics Library consists of selected books that have become recognized classics in their respective fields. With these new unabridged and inexpensive editions, Wiley hopes to extend the life of these important works by making them available to future generations of mathematicians and scientists. Currently available in the Series: T. W. Anderson The Statistical Analysis of Time Series T. S. Arthanari & Yadolah Dodge Mathematical Programming in Statistics Emil Artin Geometric Algebra Norman T. J. Bailey The Elements of Stochastic Processes with Applications to the Natural Sciences Robert G. Bartle The Elements of Integration and Lebesgue Measure George E. P. Box & Norman R. Draper Evolutionary Operation: A Statistical Method for Process Improvement George E. P. Box & George C. Tiao Bayesian Inference in Statistical Analysis R. W. Carter Finite Groups of Lie Type: Conjugacy Classes and Complex Characters R. W. Carter Simple Groups of Lie Type William G. Cochran & Gertrude M. Cox Experimental Designs, Second Edition Richard Courant Differential and Integral Calculus, Volume I RIchard Courant Differential and Integral Calculus, Volume II Richard Courant & D. Hilbert Methods of Mathematical Physics, Volume I Richard Courant & D. Hilbert Methods of Mathematical Physics, Volume II D. R. Cox Planning of Experiments Harold S. M. Coxeter Introduction to Geometry, Second Edition Charles W. Curtis & Irving Reiner Representation Theory of Finite Groups and Associative Algebras Charles W. Curtis & Irving Reiner Methods of Representation Theory with Applications to Finite Groups and Orders, Volume I Charles W. Curtis & Irving Reiner Methods of Representation Theory with Applications to Finite Groups and Orders, Volume II Cuthbert Daniel Fitting Equations to Data: Computer Analysis of Multifactor Data, Second Edition Bruno de Finetti Theory of Probability, Volume I Bruno de Finetti Theory of Probability, Volume 2 W. Edwards Deming Sample Design in Business Research
NASA Pocket Statistics: 1997 Edition
NASA Technical Reports Server (NTRS)
1997-01-01
POCKET STATISTICS is published by the NATIONAL AERONAUTICS AND SPACE ADMINISTRATION (NASA). Included in each edition is Administrative and Organizational information, summaries of Space Flight Activity including the NASA Major Launch Record, Aeronautics and Space Transportation and NASA Procurement, Financial and Workforce data. The NASA Major Launch Record includes all launches of Scout class and larger vehicles. Vehicle and spacecraft development flights are also included in the Major Launch Record. Shuttle missions are counted as one launch and one payload, where free flying payloads are not involved. All Satellites deployed from the cargo bay of the Shuttle and placed in a separate orbit or trajectory are counted as an additional payload.
Enabling Parametric Optimal Ascent Trajectory Modeling During Early Phases of Design
NASA Technical Reports Server (NTRS)
Holt, James B.; Dees, Patrick D.; Diaz, Manuel J.
2015-01-01
-modal due to the interaction of various constraints. Additionally, when these obstacles are coupled with The Program to Optimize Simulated Trajectories [1] (POST), an industry standard program to optimize ascent trajectories that is difficult to use, it requires expert trajectory analysts to effectively optimize a vehicle's ascent trajectory. As it has been pointed out, the paradigm of trajectory optimization is still a very manual one because using modern computational resources on POST is still a challenging problem. The nuances and difficulties involved in correctly utilizing, and therefore automating, the program presents a large problem. In order to address these issues, the authors will discuss a methodology that has been developed. The methodology is two-fold: first, a set of heuristics will be introduced and discussed that were captured while working with expert analysts to replicate the current state-of-the-art; secondly, leveraging the power of modern computing to evaluate multiple trajectories simultaneously, and therefore, enable the exploration of the trajectory's design space early during the pre-conceptual and conceptual phases of design. When this methodology is coupled with design of experiments in order to train surrogate models, the authors were able to visualize the trajectory design space, enabling parametric optimal ascent trajectory information to be introduced with other pre-conceptual and conceptual design tools. The potential impact of this methodology's success would be a fully automated POST evaluation suite for the purpose of conceptual and preliminary design trade studies. This will enable engineers to characterize the ascent trajectory's sensitivity to design changes in an arbitrary number of dimensions and for finding settings for trajectory specific variables, which result in optimal performance for a "dialed-in" launch vehicle design. The effort described in this paper was developed for the Advanced Concepts Office [2] at NASA Marshall
Wind models for the NSTS ascent trajectory biasing for wind load alleviation
NASA Technical Reports Server (NTRS)
Smith, O. E.; Adelfang, S. I.; Batts, G. W.
1990-01-01
New concepts are presented for aerospace vehicle ascent wind profile biasing. The purpose for wind biasing the ascent trajectory is to provide ascent wind loads relief and thus decrease the probability for launch delays due to wind loads exceeding critical limits. Wind biasing trajectories to the the profile of monthly mean winds have been widely used for this purpose. The wind profile models presented give additional alternatives for wind biased trajectories. They are derived from the properties of the bivariate normal probability function using the available wind statistical parameters for the launch site. The analytical expressions are presented to permit generalizations. Specific examples are given to illustrate the procedures. The wind profile models can be used to establish the ascent trajectory steering commands to guide the vehicle through the first stage. For the National Space Transportation System (NSTS) program these steering commands are called I-loads.
Wind models for the NSTS ascent trajectory biasing for wind load alleviation
NASA Technical Reports Server (NTRS)
Smith, O. E.; Adelfang, S. I.; Batts, G. W.; Hill, C. K.
1989-01-01
New concepts are presented for aerospace vehicle ascent wind profile biasing. The purpose for wind biasing the ascent trajectory is to provide ascent wind loads relief and thus decrease the probability for launch delays due to wind loads exceeding critical limits. Wind biasing trajectories to the profile of monthly mean winds have been widely used for this purpose. The wind profile models presented give additional alternatives for wind biased trajectories. They are derived from the properties of the bivariate normal probability function using the available wind statistical parameters for the launch site. The analytical expressions are presented to permit generalizations. Specific examples are given to illustrate the procedures. The wind profile models can be used to establish the ascent trajectory steering commands to guide the vehicle through the first stage. For the National Space Transportation System (NSTS) program these steering commands are called I-loads.
Trajectories of prediagnostic functioning in Parkinson's disease.
Darweesh, Sirwan K L; Verlinden, Vincentius J A; Stricker, Bruno H; Hofman, Albert; Koudstaal, Peter J; Ikram, M Arfan
2017-02-01
SEE BREEN AND LANG DOI101093/AWW321 FOR A SCIENTIFIC COMMENTARY ON THIS ARTICLE: At the time of clinical diagnosis, patients with Parkinson's disease already have a wide range of motor and non-motor features that affect their daily functioning. However, the temporal sequence of occurrence of these features remains largely unknown. We studied trajectories of daily functioning and motor and non-motor features in the 23 years preceding Parkinson's disease diagnosis by performing a nested case-control study within the prospective Rotterdam study. Between 1990 and 2013, we repeatedly performed standardized assessments of daily functioning (Stanford Health Assessment Questionnaire, Lawton Instrumental Activities of Daily Living Scale), potential prediagnostic motor (hypo- and bradykinesia, tremor, rigidity, postural imbalance, postural abnormalities) and non-motor features of Parkinson's disease, including cognition (Mini-Mental State Examination, Stroop Test, Letter-Digit-Substitution Test, Word Fluency Test), mood (Center for Epidemiological Studies-Depression Scale, Hamilton Anxiety and Depression Scale), and autonomic function (blood pressure, laxative use). In addition, the cohort was followed-up for the onset of clinical Parkinson's disease using several overlapping modalities, including repeated in-person examinations, as well as complete access to medical records and specialist letters of study participants. During follow-up, 109 individuals were diagnosed with Parkinson's disease, and each case was matched to 10 controls based on age and sex (total n = 1199). Subsequently, we compared prediagnostic trajectories of daily functioning and other features between Parkinson's disease cases and controls. From 7 years before diagnosis onwards, prediagnostic Parkinson's disease cases more commonly had problems in instrumental activities of daily functioning, and more frequently showed signs of movement poverty and slowness, tremor and subtle cognitive deficits. In the
Statistical Physics of Fracture
Alava, Mikko; Nukala, Phani K; Zapperi, Stefano
2006-05-01
Disorder and long-range interactions are two of the key components that make material failure an interesting playfield for the application of statistical mechanics. The cornerstone in this respect has been lattice models of the fracture in which a network of elastic beams, bonds, or electrical fuses with random failure thresholds are subject to an increasing external load. These models describe on a qualitative level the failure processes of real, brittle, or quasi-brittle materials. This has been particularly important in solving the classical engineering problems of material strength: the size dependence of maximum stress and its sample-to-sample statistical fluctuations. At the same time, lattice models pose many new fundamental questions in statistical physics, such as the relation between fracture and phase transitions. Experimental results point out to the existence of an intriguing crackling noise in the acoustic emission and of self-affine fractals in the crack surface morphology. Recent advances in computer power have enabled considerable progress in the understanding of such models. Among these partly still controversial issues, are the scaling and size-effects in material strength and accumulated damage, the statistics of avalanches or bursts of microfailures, and the morphology of the crack surface. Here we present an overview of the results obtained with lattice models for fracture, highlighting the relations with statistical physics theories and more conventional fracture mechanics approaches.
Challenges in Modeling and Measuring Learning Trajectories
ERIC Educational Resources Information Center
Confrey, Jere; Jones, R. Seth; Gianopulos, Garron
2015-01-01
Briggs and Peck make a compelling case for creating new, more intuitive measures of learning, based on creating vertical scales using learning trajectories (LT) in place of "domain sampling." We believe that the importance of creating measurement scales that coordinate recognizable landmarks in learning trajectories with interval scales…
Variation in Trajectories of Women's Marital Quality
James, Spencer L.
2014-01-01
I examine variation in trajectories of women's marital quality across the life course. The analysis improves upon earlier research in three ways: (1) the analysis uses a sequential cohort design and data from the first 35 years of marriage; (2) I analyze rich data from a national sample; (3) I examine multiple dimensions of marital quality. Latent class growth analyses estimated on data from women in the National Longitudinal Survey of Youth-1979 (N = 2604) suggest multiple trajectories for each of three dimensions of marital quality, including two trajectories of marital happiness, two trajectories of marital communication, and three trajectories of marital conflict. Socioeconomic and demographic covariates are then used to illustrate how factors such as income, cohabitation, and race-ethnicity set individuals at risk of poor marital quality throughout the life course by differentiating between high and low trajectories of marital quality. Women on low marital quality trajectories are, as expected, at much greater risk of divorce. Taken together, these findings show how fundamental socioeconomic and demographic characteristics contribute to subsequent marital outcomes via their influence on trajectories of marital quality as well as providing a better picture of the complexity in contemporary patterns of marital quality. PMID:25432600
Guidance trajectories for aeroassisted orbital transfer
NASA Technical Reports Server (NTRS)
Miele, A.
1990-01-01
Research on aerobraking guidance schemes is presented. The intent is to produce aerobraking guidance trajectories exhibiting many of the desirable characteristics of optimal aerobraking trajectories. Both one-control schemes and two-control schemes are studied. The research is in the interest of aeroassisted flight experiment vehicles (AFE) and aeroassisted orbital transfer (AOT) vehicles.
Projecting uncertainty onto marine megafauna trajectories
NASA Astrophysics Data System (ADS)
Robel, Alexander A.; Susan Lozier, M.; Gary, Stefan F.; Shillinger, George L.; Bailey, Helen; Bograd, Steven J.
2011-09-01
In this study, a method is proposed for estimating the uncertainty of a Lagrangian pathway calculated from an undersampled ocean surface velocity field. The primary motivation and application for this method is the differentiation between active and passive movements for sea turtles whose trajectories are observed with satellite telemetry. Synthetic trajectories are launched within a reconstructed surface velocity field and integrated forward in time to produce likely trajectories of an actual turtle or drifter. Uncertainties in both the initial conditions at launch and the velocity field along the trajectory are used to yield an envelope of possible synthetic trajectories for each actual trajectory. The juxtaposition of the actual trajectory with the resulting cloud of synthetic trajectories provides a means to distinguish between active and passive movements of the turtle. The uncertainty estimates provided by this model may lead to improvements in our understanding of where and when turtles are engaged in specific behaviors (i.e. migration vs. foraging)—for which potential management efforts may vary accordingly.
Soccer Ball Lift Coefficients via Trajectory Analysis
ERIC Educational Resources Information Center
Goff, John Eric; Carre, Matt J.
2010-01-01
We performed experiments in which a soccer ball was launched from a machine while two high-speed cameras recorded portions of the trajectory. Using the trajectory data and published drag coefficients, we extracted lift coefficients for a soccer ball. We determined lift coefficients for a wide range of spin parameters, including several spin…
Minimum jerk trajectory planning for robotic manipulators
NASA Technical Reports Server (NTRS)
Kyriakopoulos, K. J.; Saridis, G. N.
1991-01-01
It has been experimentally verified that the jerk of the desired trajectory adversely affects the performance of the tracking control algorithms for robotic manipulators. In this paper, the reasons behind this effect are investigated, and an optimization problem that minimizes joint jerk over a prespecified Cartesian space trajectory is stated. The necessary conditions are derived, and a numerical algorithm is presented.
Simulation of Airplane and Rocket Trajectories
NASA Technical Reports Server (NTRS)
Wahbah, Magdy M.; Berning, Michael J.; Choy, Tony S.
1987-01-01
Simulation and Optimization of Rocket Trajectories program (SORT) contains comprehensive mathematical models for simulating aircraft dynamics, freely falling objects, and many types of ballistic trajectories. Provides high-fidelity, three-degrees-of-freedom simulation for atmospheric and exoatmospheric flight. It numerically models vehicle subsystems and vehicle environment. Used for wide range of simulations. Written in machine-independent FORTRAN 77.
14 CFR 417.207 - Trajectory analysis.
Code of Federal Regulations, 2014 CFR
2014-01-01
... a programmed thrust termination. (3) For launch vehicles flown with a flight safety system, a... OF TRANSPORTATION LICENSING LAUNCH SAFETY Flight Safety Analysis § 417.207 Trajectory analysis. (a) General. A flight safety analysis must include a trajectory analysis that establishes: (1) For any...
14 CFR 417.207 - Trajectory analysis.
Code of Federal Regulations, 2013 CFR
2013-01-01
... a programmed thrust termination. (3) For launch vehicles flown with a flight safety system, a... OF TRANSPORTATION LICENSING LAUNCH SAFETY Flight Safety Analysis § 417.207 Trajectory analysis. (a) General. A flight safety analysis must include a trajectory analysis that establishes: (1) For any...
Variation in trajectories of women's marital quality.
James, Spencer L
2015-01-01
I examine variation in trajectories of women's marital quality across the life course. The analysis improves upon earlier research in three ways: (1) the analysis uses a sequential cohort design and data from the first 35years of marriage; (2) I analyze rich data from a national sample; (3) I examine multiple dimensions of marital quality. Latent class growth analyses estimated on data from women in the National Longitudinal Survey of Youth-1979 (N=2604) suggest multiple trajectories for each of three dimensions of marital quality, including two trajectories of marital happiness, two trajectories of marital communication, and three trajectories of marital conflict. Socioeconomic and demographic covariates are then used to illustrate how factors such as income, cohabitation, and race-ethnicity set individuals at risk of poor marital quality throughout the life course by differentiating between high and low trajectories of marital quality. Women on low marital quality trajectories are, as expected, at much greater risk of divorce. Taken together, these findings show how fundamental socioeconomic and demographic characteristics contribute to subsequent marital outcomes via their influence on trajectories of marital quality as well as providing a better picture of the complexity in contemporary patterns of marital quality.
Trajectories of Delinquency and Parenting Styles
ERIC Educational Resources Information Center
Hoeve, Machteld; Blokland, Arjan; Dubas, Judith Semon; Loeber, Rolf; Gerris, Jan R. M.; van der Laan, Peter H.
2008-01-01
We investigated trajectories of adolescent delinquent development using data from the Pittsburgh Youth Study and examined the extent to which these different trajectories are differentially predicted by childhood parenting styles. Based on self-reported and official delinquency seriousness, covering ages 10-19, we identified five distinct…
Application of Taylor's series to trajectory propagation
NASA Technical Reports Server (NTRS)
Stanford, R. H.; Berryman, K. W.; Breckheimer, P. J.
1986-01-01
This paper describes the propagation of trajectories by the application of the preprocessor ATOMCC which uses Taylor's series to solve initial value problems in ordinary differential equations. Comparison of the results obtained with those from other methods are presented. The current studies indicate that the ATOMCC preprocessor is an easy, yet fast and accurate method for generating trajectories.
What Are the Key Statistics about Gallbladder Cancer?
... Cancer About Gallbladder Cancer What Are the Key Statistics About Gallbladder Cancer? The American Cancer Society’s estimates ... advanced it is when it is found. For statistics on survival rates, see “ Survival statistics for gallbladder ...
Housing Trajectories of Forensic Psychiatric Patients.
Salem, Leila; Crocker, Anne G; Charette, Yanick; Earls, Christopher M; Nicholls, Tonia L; Seto, Michael C
2016-03-01
The objectives of this study were to describe the disposition and housing trajectories of individuals found Not Criminally Responsible on account of Mental Disorder (NCRMD), and the factors that predict different trajectories. To do so, disposition and housing status were coded for 934 NCRMD patients over a 36-month follow-up period. Sequential data analysis resulted in four distinct trajectories: detention in hospital, conditional discharge in supportive housing, conditional discharge in independent housing, and absolute discharge to unknown housing. The likelihood of a placement in supportive housing compared with detention significantly decreased for individuals with a higher index offense severity. Less restrictive trajectories were significantly predicted by clinical factors. The results revealed little change in the disposition and housing trajectories of NCRMD patients. Furthermore, decisions about disposition and housing placement reflect a knowledge-practice gap between risk factors known to be predictive of community resources use in the forensic population. Copyright © 2016 John Wiley & Sons, Ltd.
Copepod Trajectory Characteristics in Thin Layers of Toxic Algal Exudates
NASA Astrophysics Data System (ADS)
Webster, D. R.; True, A. C.; Weissburg, M. J.; Yen, J.
2013-11-01
Recently documented thin layers of toxic phytoplankton (``cryptic blooms'') are modeled in a custom flume system for copepod behavioral assays. Planar laser-induced fluorescence (LIF) measurements quantify the spatiotemporal structure of the chemical layers ensuring a close match to in situ bloom conditions and allowing for quantification of threshold dissolved toxin levels that induce behavioral responses. Assays with the copepods Acartia tonsa (hop-sinker) and Temora longicornis (cruiser) in thin layers of toxic exudates from the common dinoflagellate Karenia brevis (cell equivalent ~ 1 - 10,000 cells/mL) examine the effects of dissolved toxic compounds and copepod species on swimming trajectory characteristics. Computation of parameters such as swimming speed and the fractal dimension of the two-dimensional trajectory (F2D) allows for statistical evaluation of copepod behavioral responses to dissolved toxic compounds associated with harmful algal blooms (HABs). Changes in copepod swimming behavior caused by toxic compounds can significantly influence predator, prey, and mate encounter rates by altering the fracticality (``diffuseness'' or ``volume-fillingness'') of a copepod's trajectory. As trophic mediators linking primary producers and higher trophic levels, copepods can significantly influence HAB dynamics and modulate large scale ecological effects through their behavioral interactions with toxic blooms.
Characteristic functions based on a quantum jump trajectory
NASA Astrophysics Data System (ADS)
Liu, Fei; Xi, Jingyi
2016-12-01
Characteristic functions (CFs) provide a very efficient method for evaluating the probability density functions of stochastic thermodynamic quantities and investigating their statistical features in quantum master equations (QMEs). A conventional procedure for obtaining these functions is to resort to a first-principles approach; namely, the evolution equations of the CFs of the combined system and its environment are obtained and then projected into the degrees of freedom of the system. However, the QMEs can be unraveled by a quantum jump trajectory. Thermodynamic quantities such as the heat, work, and entropy production can be well defined along a trajectory. Hence, on the basis of the notion of a trajectory, can we straightforwardly derive these CFs, e.g., their evolution equations? This is essential to establish the self-contained stochastic thermodynamics of a QME. In this paper, we show that it is indeed plausible and also simple. Particularly, these equations are fully consistent with those obtained by the first-principles method. Our results have practical significance; they indicate that the quantum fluctuation relations could be verified by more realistic photocounting experiments.
Photodissociation dynamics of phenol: multistate trajectory simulations including tunneling.
Xu, Xuefei; Zheng, Jingjing; Yang, Ke R; Truhlar, Donald G
2014-11-19
We report multistate trajectory simulations, including coherence, decoherence, and multidimensional tunneling, of phenol photodissociation dynamics. The calculations are based on full-dimensional anchor-points reactive potential surfaces and state couplings fit to electronic structure calculations including dynamical correlation with an augmented correlation-consistent polarized valence double-ζ basis set. The calculations successfully reproduce the experimentally observed bimodal character of the total kinetic energy release spectra and confirm the interpretation of the most recent experiments that the photodissociation process is dominated by tunneling. Analysis of the trajectories uncovers an unexpected dissociation pathway for one quantum excitation of the O-H stretching mode of the S1 state, namely, tunneling in a coherent mixture of states starting in a smaller ROH (∼0.9-1.0 Å) region than has previously been invoked. The simulations also show that most trajectories do not pass close to the S1-S2 conical intersection (they have a minimum gap greater than 0.6 eV), they provide statistics on the out-of-plane angles at the locations of the minimum energy adiabatic gap, and they reveal information about which vibrational modes are most highly activated in the products.
Mixed Membership Trajectory Models of Cognitive Impairment in the Multicenter AIDS Cohort Study
Molsberry, Samantha A.; Lecci, Fabrizio; Kingsley, Lawrence; Junker, Brian; Reynolds, Sandra; Goodkin, Karl; Levine, Andrew J.; Martin, Eileen; Miller, Eric N.; Munro, Cynthia A.; Ragin, Ann; Sacktor, Ned; Becker, James T.
2016-01-01
Objective The longitudinal trajectories that individuals may take from a state of normal cognition to HIV-associated dementia are unknown. We applied a novel statistical methodology to identify trajectories to cognitive impairment, and factors that affected the “closeness” of an individual to one of the canonical trajectories. Design The Multicenter AIDS Cohort Study (MACS) is a four-site longitudinal study of the natural and treated history of HIV Disease among gay and bisexual men. Methods Using data from 3,892 men (both HIV-infected and uninfected) enrolled in the neuropsychology substudy of the MACS, a Mixed Membership Trajectory Model (MMTM) was applied to capture the pathways from normal cognitive function to mild impairment to severe impairment. MMTMs allow the data to identify canonical pathways and to model the effects of risk factors on an individual’s “closeness” to these trajectories. Results We identified three distinct trajectories to cognitive impairment – one “normal aging” (low probability of mild impairment until age 60), one “premature aging” (mild impairment starting at age 45–50), and one “unhealthy” (mild impairment in 20s and 30s) profile. Second, clinically defined AIDS and not simply HIV Disease, was associated with closeness to the premature aging trajectory. And, third, Hepatitis-C infection, Depression, Race, Recruitment Cohort and Confounding Conditions all affected individual’s closeness to these trajectories. Conclusions These results provide new insight into the natural history of cognitive dysfunction in HIV disease and provide evidence for a potential difference in the pathophysiology of the development of cognitive impairment based on trajectories to impairment. PMID:25565498
Augmenting Parametric Optimal Ascent Trajectory Modeling with Graph Theory
NASA Technical Reports Server (NTRS)
Dees, Patrick D.; Zwack, Matthew R.; Edwards, Stephen; Steffens, Michael
2016-01-01
into Conceptual and Pre-Conceptual design, knowledge of the effects originating from changes to the vehicle must be calculated. In order to do this, a model capable of quantitatively describing any vehicle within the entire design space under consideration must be constructed. This model must be based upon analysis of acceptable fidelity, which in this work comes from POST. Design space interrogation can be achieved with surrogate modeling, a parametric, polynomial equation representing a tool. A surrogate model must be informed by data from the tool with enough points to represent the solution space for the chosen number of variables with an acceptable level of error. Therefore, Design Of Experiments (DOE) is used to select points within the design space to maximize information gained on the design space while minimizing number of data points required. To represent a design space with a non-trivial number of variable parameters the number of points required still represent an amount of work which would take an inordinate amount of time via the current paradigm of manual analysis, and so an automated method was developed. The best practices of expert trajectory analysts working within NASA Marshall's Advanced Concepts Office (ACO) were implemented within a tool called multiPOST. These practices include how to use the output data from a previous run of POST to inform the next, determining whether a trajectory solution is feasible from a real-world perspective, and how to handle program execution errors. The tool was then augmented with multiprocessing capability to enable analysis on multiple trajectories simultaneously, allowing throughput to scale with available computational resources. In this update to the previous work the authors discuss issues with the method and solutions.
NASA Technical Reports Server (NTRS)
Hargraves, W. R.; Delulio, E. B.; Justus, C. G.
1977-01-01
The Global Reference Atmospheric Model is used along with the revised perturbation statistics to evaluate and computer graph various atmospheric statistics along a space shuttle reference mission and abort trajectory. The trajectory plots are height vs. ground range, with height from ground level to 155 km and ground range along the reentry trajectory. Cross sectional plots, height vs. latitude or longitude, are also generated for 80 deg longitude, with heights from 30 km to 90 km and latitude from -90 deg to +90 deg, and for 45 deg latitude, with heights from 30 km to 90 km and longitudes from 180 deg E to 180 deg W. The variables plotted are monthly average pressure, density, temperature, wind components, and wind speed and standard deviations and 99th inter-percentile range for each of these variables.
Trajectories of Attentional Development: An Exploration with the Master Activation Map Model
ERIC Educational Resources Information Center
Michael, George A.; Lete, Bernard; Ducrot, Stephanie
2013-01-01
The developmental trajectories of several attention components, such as orienting, inhibition, and the guidance of selection by relevance (i.e., advance knowledge relevant to the task) were investigated in 498 participants (ages 7, 8, 9, 10, 11, and 20). The paradigm was based on Michael et al.'s (2006) master activation map model and consisted of…
NASA Astrophysics Data System (ADS)
Paine, Gregory Harold
1982-03-01
The primary objective of the thesis is to explore the dynamical properties of small nerve networks by means of the methods of statistical mechanics. To this end, a general formalism is developed and applied to elementary groupings of model neurons which are driven by either constant (steady state) or nonconstant (nonsteady state) forces. Neuronal models described by a system of coupled, nonlinear, first-order, ordinary differential equations are considered. A linearized form of the neuronal equations is studied in detail. A Lagrange function corresponding to the linear neural network is constructed which, through a Legendre transformation, provides a constant of motion. By invoking the Maximum-Entropy Principle with the single integral of motion as a constraint, a probability distribution function for the network in a steady state can be obtained. The formalism is implemented for some simple networks driven by a constant force; accordingly, the analysis focuses on a study of fluctuations about the steady state. In particular, a network composed of N noninteracting neurons, termed Free Thinkers, is considered in detail, with a view to interpretation and numerical estimation of the Lagrange multiplier corresponding to the constant of motion. As an archetypical example of a net of interacting neurons, the classical neural oscillator, consisting of two mutually inhibitory neurons, is investigated. It is further shown that in the case of a network driven by a nonconstant force, the Maximum-Entropy Principle can be applied to determine a probability distribution functional describing the network in a nonsteady state. The above examples are reconsidered with nonconstant driving forces which produce small deviations from the steady state. Numerical studies are performed on simplified models of two physical systems: the starfish central nervous system and the mammalian olfactory bulb. Discussions are given as to how statistical neurodynamics can be used to gain a better
Radiation Damage in Nuclear Fuel for Advanced Burner Reactors: Modeling and Experimental Validation
Jensen, Niels Gronbech; Asta, Mark; Ozolins, Nigel Browning'Vidvuds; de Walle, Axel van; Wolverton, Christopher
2011-12-29
The consortium has completed its existence and we are here highlighting work and accomplishments. As outlined in the proposal, the objective of the work was to advance the theoretical understanding of advanced nuclear fuel materials (oxides) toward a comprehensive modeling strategy that incorporates the different relevant scales involved in radiation damage in oxide fuels. Approaching this we set out to investigate and develop a set of directions: 1) Fission fragment and ion trajectory studies through advanced molecular dynamics methods that allow for statistical multi-scale simulations. This work also includes an investigation of appropriate interatomic force fields useful for the energetic multi-scale phenomena of high energy collisions; 2) Studies of defect and gas bubble formation through electronic structure and Monte Carlo simulations; and 3) an experimental component for the characterization of materials such that comparisons can be obtained between theory and experiment.
Six Developmental Trajectories Characterize Children With Autism
Fountain, Christine; Winter, Alix S.
2012-01-01
OBJECTIVE: The goal of this study was to describe the typical longitudinal developmental trajectories of social and communication functioning in children with autism and to determine the correlates of these trajectories. METHODS: Children with autism who were born in California from 1992 through 2001 and enrolled with the California Department of Developmental Services were identified. Subjects with <4 evaluations present in the database were excluded, resulting in a sample of 6975 children aged 2 to 14 years. Score sequences were constructed based on 9 evaluative items for social, communication, and repetitive behavior functioning. Typical trajectories were identified by using group-based latent trajectory modeling, and multinomial logistic regression models were used to determine the odds of classification within each trajectory varied by individual and family-level factors. RESULTS: Six typical patterns of social, communication, and repetitive behavior functioning were identified. These trajectories displayed significant heterogeneity in developmental pathways, and children whose symptoms were least severe at first diagnosis tended to improve more rapidly than those severely affected. One group of ∼10% of children experienced rapid gains, moving from severely affected to high functioning. Socioeconomic factors were correlated with trajectory outcomes; children with non-Hispanic, white, well-educated mothers were more likely to be high functioning, and minority children with less-educated mothers or intellectual disabilities were very unlikely to experience rapid gains. CONCLUSIONS: Children with autism have heterogeneous developmental pathways. One group of children evidenced remarkable developmental change over time. Understanding what drives these outcomes is thus critical. PMID:22473372
Trajectory Based Behavior Analysis for User Verification
NASA Astrophysics Data System (ADS)
Pao, Hsing-Kuo; Lin, Hong-Yi; Chen, Kuan-Ta; Fadlil, Junaidillah
Many of our activities on computer need a verification step for authorized access. The goal of verification is to tell apart the true account owner from intruders. We propose a general approach for user verification based on user trajectory inputs. The approach is labor-free for users and is likely to avoid the possible copy or simulation from other non-authorized users or even automatic programs like bots. Our study focuses on finding the hidden patterns embedded in the trajectories produced by account users. We employ a Markov chain model with Gaussian distribution in its transitions to describe the behavior in the trajectory. To distinguish between two trajectories, we propose a novel dissimilarity measure combined with a manifold learnt tuning for catching the pairwise relationship. Based on the pairwise relationship, we plug-in any effective classification or clustering methods for the detection of unauthorized access. The method can also be applied for the task of recognition, predicting the trajectory type without pre-defined identity. Given a trajectory input, the results show that the proposed method can accurately verify the user identity, or suggest whom owns the trajectory if the input identity is not provided.
Hill, Terrence D.; Uchino, Bert N.; Eckhardt, Jessica L.; Angel, Jacqueline L.
2016-01-01
Although numerous studies of non-Hispanic whites and blacks show that social integration and social support tend to favor longevity, it is unclear whether this general pattern extends to the Mexican American population. Building on previous research, we employed seven waves of data from the Hispanic Established Populations for the Epidemiologic Study of the Elderly to examine the association between perceived social support trajectories and the all-cause mortality risk of older Mexican Americans. Growth mixture estimates revealed three latent classes of support trajectories: high, moderate, and low. Cox regression estimates indicated that older Mexican American men in the low support trajectory tend to exhibit a higher mortality risk than their counterparts in the high support trajectory. Social support trajectories were unrelated to the mortality risk of older Mexican American women. A statistically significant interaction term confirmed that social support was more strongly associated with the mortality risk of men. PMID:26966256
Hill, Terrence D; Uchino, Bert N; Eckhardt, Jessica L; Angel, Jacqueline L
2016-04-01
Although numerous studies of non-Hispanic Whites and Blacks show that social integration and social support tend to favor longevity, it is unclear whether this general pattern extends to the Mexican American population. Building on previous research, we employed seven waves of data from the Hispanic Established Populations for the Epidemiologic Study of the Elderly to examine the association between perceived social support trajectories and the all-cause mortality risk of older Mexican Americans. Growth mixture estimates revealed three latent classes of support trajectories: high, moderate, and low. Cox regression estimates indicated that older Mexican American men in the low support trajectory tend to exhibit a higher mortality risk than their counterparts in the high support trajectory. Social support trajectories were unrelated to the mortality risk of older Mexican American women. A statistically significant interaction term confirmed that social support was more strongly associated with the mortality risk of men.
Soccer ball lift coefficients via trajectory analysis
NASA Astrophysics Data System (ADS)
Goff, John Eric; Carré, Matt J.
2010-07-01
We performed experiments in which a soccer ball was launched from a machine while two high-speed cameras recorded portions of the trajectory. Using the trajectory data and published drag coefficients, we extracted lift coefficients for a soccer ball. We determined lift coefficients for a wide range of spin parameters, including several spin parameters that have not been obtained by today's wind tunnels. Our trajectory analysis technique is not only a valuable tool for professional sports scientists, it is also accessible to students with a background in undergraduate-level classical mechanics.
Helicopter trajectory planning using optimal control theory
NASA Technical Reports Server (NTRS)
Menon, P. K. A.; Cheng, V. H. L.; Kim, E.
1988-01-01
A methodology for optimal trajectory planning, useful in the nap-of-the-earth guidance of helicopters, is presented. This approach uses an adjoint-control transformation along with a one-dimensional search scheme for generating the optimal trajectories. In addition to being useful for helicopter nap-of-the-earth guidance, the trajectory planning solution is of interest in several other contexts, such as robotic vehicle guidance and terrain-following guidance for cruise missiles and aircraft. A distinguishing feature of the present research is that the terrain constraint and the threat envelopes are incorporated in the equations of motion. Second-order necessary conditions are examined.
Mars Ascent Propulsion Trades with Trajectory Analysis
Whitehead, J
2004-04-22
Optimized trajectories to a 500 km circular orbit are calculated for vehicles having a 100 kg Mars launch mass. Staging trades, thrust optimization, and the importance of vehicle shape for drag are all taken into consideration. The high acceleration of solid rockets requires a steep trajectory for drag avoidance, followed by a relatively large circularization burn, appropriate for a second stage. Liquid thrust reduces drag, resulting in less steep trajectories which have small circularization burns. Liquid propulsion requires less total {Delta}v, and offers options for multiple stages or just one. Graphs of payload mass versus stage propellant fractions are compared for liquid and solid propulsion.
An Examination of "The Martian" Trajectory
NASA Technical Reports Server (NTRS)
Burke, Laura
2015-01-01
This analysis was performed to support a request to examine the trajectory of the Hermes vehicle in the novel "The Martian" by Andy Weir. Weir developed his own tool to perform the analysis necessary to provide proper trajectory information for the novel. The Hermes vehicle is the interplanetary spacecraft that shuttles the crew to and from Mars. It is notionally a Nuclear powered vehicle utilizing VASIMR engines for propulsion. The intent of this analysis was the determine whether the trajectory as it was outlined in the novel is consistent with the rules of orbital mechanics.
Ascent trajectory dispersion analysis for WTR heads-up space shuttle trajectory
NASA Technical Reports Server (NTRS)
1986-01-01
The results of a Space Transportation System ascent trajectory dispersion analysis are discussed. The purpose is to provide critical trajectory parameter values for assessing the Space Shuttle in a heads-up configuration launched from the Western Test Range (STR). This analysis was conducted using a trajectory profile based on a launch from the WTR in December. The analysis consisted of the following steps: (1) nominal trajectories were simulated under the conditions as specified by baseline reference mission guidelines; (2) dispersion trajectories were simulated using predetermined parametric variations; (3) requirements for a system-related composite trajectory were determined by a root-sum-square (RSS) analysis of the positive deviations between values of the aerodynamic heating indicator (AHI) generated by the dispersion and nominal trajectories; (4) using the RSS assessment as a guideline, the system related composite trajectory was simulated by combinations of dispersion parameters which represented major contributors; (5) an assessment of environmental perturbations via a RSS analysis was made by the combination of plus or minus 2 sigma atmospheric density variation and 95% directional design wind dispersions; (6) maximum aerodynamic heating trajectories were simulated by variation of dispersion parameters which would emulate the summation of the system-related RSS and environmental RSS values of AHI. The maximum aerodynamic heating trajectories were simulated consistent with the directional winds used in the environmental analysis.
Analysis of flight trajectories of a ramjet-powered vehicle
NASA Astrophysics Data System (ADS)
Fomin, V. M.; Aulchenko, S. M.; Zvegintsev, V. I.; Ustinov, L. A.
2014-11-01
Based on numerical simulations of flight trajectories with ramjet-powered flying vehicles, it is found that all possible flight trajectories can be classified into three groups: ballistic trajectories, trajectories with a horizontal segment, and skipping trajectories. Trajectories of each group can be optimized, for instance, to ensure the maximum flight range under given initial conditions and constraints. Examples of optimal trajectories for a given amount of available fuel are presented as functions of the initial slope of the trajectory, angle of attack of the vehicle, instants of engine actuation, and engine operation time.
Thermodynamics of trajectories of open quantum systems, step by step
NASA Astrophysics Data System (ADS)
Pigeon, Simon; Xuereb, André
2016-06-01
Thermodynamics of trajectories promises to make possible the thorough analysis of the dynamical properties of an open quantum system, a sought-after goal in modern physics. Unfortunately, calculation of the relevant quantities presents severe challenges. Determining the large-deviation function that gives access to the full counting statistics associated with a dynamical order parameter is challenging, if not impossible, even for systems evolving in a restricted Liouville space. Acting on the realisation that the salient features of most dynamical systems are encoded in the first few moments of the counting statistics, in this article we present a method that gives sequential access to these moments. Our method allows for obtaining analytical result in several cases, as we illustrate, and allows using large deviation theory to reinterpret certain well-known results.
Robust flight design for an advanced launch system vehicle
NASA Technical Reports Server (NTRS)
Dhand, Sanjeev K.; Wong, Kelvin K.
1991-01-01
Current launch vehicle trajectory design philosophies are generally based on maximizing payload capability. This approach results in an expensive trajectory design process for each mission. Two concepts of robust flight design have been developed to significantly reduce this cost: Standardized Trajectories and Command Multiplier Steering (CMS). These concepts were analyzed for an Advanced Launch System (ALS) vehicle, although their applicability is not restricted to any particular vehicle. Preliminary analysis has demonstrated the feasibility of these concepts at minimal loss in payload capability.
Geometry of tracer trajectories in turbulent rotating convection
NASA Astrophysics Data System (ADS)
Alards, Kim; Rajaei, Hadi; Kunnen, Rudie; Toschi, Federico; Clercx, Herman
2016-11-01
In Rayleigh-Bénard convection rotation is known to cause transitions in flow structures and to change the level of anisotropy close to the horizontal plates. To analyze this effect of rotation, we collect curvature and torsion statistics of passive tracer trajectories in rotating Rayleigh-Bénard convection, using both experiments and direct numerical simulations. In previous studies, focusing on homogeneous isotropic turbulence (HIT), curvature and torsion PDFs are found to reveal pronounced power laws. In the center of the convection cell, where the flow is closest to HIT, we recover these power laws, regardless of the rotation rate. However, near the top plate, where we expect the flow to be anisotropic, the scaling of the PDFs deviates from the HIT prediction for lower rotation rates. This indicates that anisotropy clearly affects the geometry of tracer trajectories. Another effect of rotation is observed as a shift of curvature and torsion PDFs towards higher values. We expect this shift to be related to the length scale of typical flow structures. Using curvature and torsion statistics, we can characterize how these typical length scales evolve under rotation and moreover analyze the effect of rotation on more complicated flow characteristics, such as anisotropy.
Porter, Ben; Bonanno, George A; Frasco, Melissa A; Dursa, Erin K; Boyko, Edward J
2017-06-01
Post-traumatic stress disorder (PTSD) is a serious mental illness that affects current and former military service members at a disproportionately higher rate than the civilian population. Prior studies have shown that PTSD symptoms follow multiple trajectories in civilians and military personnel. The current study examines whether the trajectories of PTSD symptoms of veterans separated from the military are similar to continuously serving military personnel. The Millennium Cohort Study is a population-based study of military service members that commenced in 2001 with follow-up assessments occurring approximately every 3 years thereafter. PTSD symptoms were assessed at each time point using the PTSD Checklist. Latent growth mixture modeling was used to compare PTSD symptom trajectories between personnel who separated (veterans; n = 5292) and personnel who remained in military service (active duty; n = 16,788). Four distinct classes (resilient, delayed-onset, improving, and elevated-recovering) described PTSD symptoms trajectories in both veterans and active duty personnel. Trajectory shapes were qualitatively similar between active duty and veterans. However, within the resilient, improving, and elevated recovering classes, the shapes were statistically different. Although the low-symptom class was the most common in both groups (veterans: 82%; active duty: 87%), veterans were more likely to be classified in the other three classes (in all cases, p < 0.01). The shape of each trajectory was highly similar between the two groups despite differences in military and civilian life.
Action Recognition Using Rate-Invariant Analysis of Skeletal Shape Trajectories.
Ben Amor, Boulbaba; Su, Jingyong; Srivastava, Anuj
2016-01-01
We study the problem of classifying actions of human subjects using depth movies generated by Kinect or other depth sensors. Representing human body as dynamical skeletons, we study the evolution of their (skeletons’) shapes as trajectories on Kendall’s shape manifold. The action data is typically corrupted by large variability in execution rates within and across subjects and, thus, causing major problems in statistical analyses. To address that issue, we adopt a recently-developed framework of Su et al. [1], [2] to this problem domain. Here, the variable execution rates correspond to re-parameterizations of trajectories, and one uses a parameterization-invariant metric for aligning, comparing, averaging, and modeling trajectories. This is based on a combination of transported square-root vector fields (TSRVFs) of trajectories and the standard Euclidean norm, that allows computational efficiency. We develop a comprehensive suite of computational tools for this application domain: smoothing and denoising skeleton trajectories using median filtering, up- and down-sampling actions in time domain, simultaneous temporal-registration of multiple actions, and extracting invertible Euclidean representations of actions. Due to invertibility these Euclidean representations allow both discriminative and generative models for statistical analysis. For instance, they can be used in a SVM-based classification of original actions, as demonstrated here using MSR Action-3D, MSR Daily Activity and 3D Action Pairs datasets. Using only the skeletal information, we achieve state-of-the-art classification results on these datasets.
Algorithm for fuel conservative horizontal capture trajectories
NASA Technical Reports Server (NTRS)
Neuman, F.; Erzberger, H.
1981-01-01
A real time algorithm for computing constant altitude fuel-conservative approach trajectories for aircraft is described. The characteristics of the trajectory computed were chosen to approximate the extremal trajectories obtained from the optimal control solution to the problem and showed a fuel difference of only 0.5 to 2 percent for the real time algorithm in favor of the extremals. The trajectories may start at any initial position, heading, and speed and end at any other final position, heading, and speed. They consist of straight lines and a series of circular arcs of varying radius to approximate constant bank-angle decelerating turns. Throttle control is maximum thrust, nominal thrust, or zero thrust. Bank-angle control is either zero or aproximately 30 deg.
Trajectory of the index finger during grasping.
Friedman, Jason; Flash, Tamar
2009-07-01
The trajectory of the index finger during grasping movements was compared to the trajectories predicted by three optimization-based models. The three models consisted of minimizing the integral of the weighted squared joint derivatives along the path (inertia-like cost), minimizing torque change, and minimizing angular jerk. Of the three models, it was observed that the path of the fingertip and the joint trajectories, were best described by the minimum angular jerk model. This model, which does not take into account the dynamics of the finger, performed equally well when the inertia of the finger was altered by adding a 20 g weight to the medial phalange. Thus, for the finger, it appears that trajectories are planned based primarily on kinematic considerations at a joint level.
Trajectories of Alcohol Consumption Following Liver Transplantation
DiMartini, Andrea; Dew, Mary Amanda; Day, Nancy; Fitzgerald, Mary Grace; Jones, Bobby L.; deVera, Michael; Fontes, Paulo
2010-01-01
Any use of alcohol in the years following liver transplantation (LTX) approaches 50% of patients transplanted for alcoholic liver disease (ALD). We collected detailed prospective data on alcohol consumption following LTX for ALD to investigate ongoing patterns of use. Using trajectory modeling we identified four distinct alcohol use trajectories. One group had minimal use over time. Two other groups developed early onset moderate to heavy consumption and one group developed late onset moderate use. These trajectories demonstrate that alcohol use varies based on timing of onset, quantity, and duration. Using discriminant function analysis, we examine characteristics of recipient’s pre-LTX alcohol histories and early post-LTX psychological stressors to identify the profile of those at risk for these specific trajectories. We discuss the relevance of these findings to clinical care and preliminarily to outcomes. PMID:20726963
Algorithm for fixed-range optimal trajectories
NASA Technical Reports Server (NTRS)
Lee, H. Q.; Erzberger, H.
1980-01-01
An algorithm for synthesizing optimal aircraft trajectories for specified range was developed and implemented in a computer program written in FORTRAN IV. The algorithm, its computer implementation, and a set of example optimum trajectories for the Boeing 727-100 aircraft are described. The algorithm optimizes trajectories with respect to a cost function that is the weighted sum of fuel cost and time cost. The optimum trajectory consists at most of a three segments: climb, cruise, and descent. The climb and descent profiles are generated by integrating a simplified set of kinematic and dynamic equations wherein the total energy of the aircraft is the independent or time like variable. At each energy level the optimum airspeeds and thrust settings are obtained as the values that minimize the variational Hamiltonian. Although the emphasis is on an off-line, open-loop computation, eventually the most important application will be in an on-board flight management system.
Numerical Calculation of Model Rocket Trajectories.
ERIC Educational Resources Information Center
Keeports, David
1990-01-01
Discussed is the use of model rocketry to teach the principles of Newtonian mechanics. Included are forces involved; calculations for vertical launches; two-dimensional trajectories; and variations in mass, drag, and launch angle. (CW)
Trajectory tracking control for underactuated stratospheric airship
NASA Astrophysics Data System (ADS)
Zheng, Zewei; Huo, Wei; Wu, Zhe
2012-10-01
Stratospheric airship is a new kind of aerospace system which has attracted worldwide developing interests for its broad application prospects. Based on the trajectory linearization control (TLC) theory, a novel trajectory tracking control method for an underactuated stratospheric airship is presented in this paper. Firstly, the TLC theory is described sketchily, and the dynamic model of the stratospheric airship is introduced with kinematics and dynamics equations. Then, the trajectory tracking control strategy is deduced in detail. The designed control system possesses a cascaded structure which consists of desired attitude calculation, position control loop and attitude control loop. Two sub-loops are designed for the position and attitude control loops, respectively, including the kinematics control loop and dynamics control loop. Stability analysis shows that the controlled closed-loop system is exponentially stable. Finally, simulation results for the stratospheric airship to track typical trajectories are illustrated to verify effectiveness of the proposed approach.
The Trajectories of Saccadic Eye Movements.
ERIC Educational Resources Information Center
Bahill, A. Terry; Stark, Lawrence
1979-01-01
Investigates the trajectories of saccadic eye movements, the control signals of the eye, and nature of the mechanisms that generate them, using the techniques of bioengineering in collecting the data. (GA)
Belmonti, Vittorio; Cioni, Giovanni; Berthoz, Alain
2013-05-01
In goal-oriented locomotion, healthy adults generate highly stereotyped trajectories and a consistent anticipatory head orienting behaviour, both evidence of top-down, open-loop control. The aim of this study is to describe the typical development of anticipatory orienting strategies and trajectory formation. Our hypothesis is that full-blown anticipatory control requires advanced navigational skills. Twenty-six healthy subjects (14 children: 4-11 years; 6 adolescents: 13-17 years; 6 adults) were asked to walk freely towards one of the three visual targets, in a randomised order. Movement was captured via an optoelectronic system, with 15 body markers. The whole-body displacement, yaw orientation of head, trunk and pelvis, heading direction and foot placements were extracted. Head-heading anticipation, trajectory curvature, indexes of variability of trajectories, foot placements and kinematic profiles were studied. The mean head-heading anticipation time and trajectory curvature did not significantly differ among age groups. In children, however, head anticipation was more often lacking (χ2 = 9.55, p < 0.01), and there were significant intra- and inter-subject variations. Trajectory curvature was often very high in children, while it became consistently lower in adolescence (χ2 = 78.59, p < 10(-17)). The indexes of spatial and kinematic variability all followed a decreasing developmental trend (R (2) > 0.5, p < 0.0001). In conclusion, children under 11 do not perform curvilinear locomotor trajectories as adolescents and adults do. Anticipatory head orientation and trajectory formation develop in late childhood, well after gait maturation. Navigational skills, such as path planning and shifting from ego- to allocentric spatial reference frames, are proposed as necessary requisites for mature locomotor control.
Tellinghuisen, Joel
2008-01-01
The method of least squares is probably the most powerful data analysis tool available to scientists. Toward a fuller appreciation of that power, this work begins with an elementary review of statistics fundamentals, and then progressively increases in sophistication as the coverage is extended to the theory and practice of linear and nonlinear least squares. The results are illustrated in application to data analysis problems important in the life sciences. The review of fundamentals includes the role of sampling and its connection to probability distributions, the Central Limit Theorem, and the importance of finite variance. Linear least squares are presented using matrix notation, and the significance of the key probability distributions-Gaussian, chi-square, and t-is illustrated with Monte Carlo calculations. The meaning of correlation is discussed, including its role in the propagation of error. When the data themselves are correlated, special methods are needed for the fitting, as they are also when fitting with constraints. Nonlinear fitting gives rise to nonnormal parameter distributions, but the 10% Rule of Thumb suggests that such problems will be insignificant when the parameter is sufficiently well determined. Illustrations include calibration with linear and nonlinear response functions, the dangers inherent in fitting inverted data (e.g., Lineweaver-Burk equation), an analysis of the reliability of the van't Hoff analysis, the problem of correlated data in the Guggenheim method, and the optimization of isothermal titration calorimetry procedures using the variance-covariance matrix for experiment design. The work concludes with illustrations on assessing and presenting results.
Trajectory Browser: An Online Tool for Interplanetary Trajectory Analysis and Visualization
NASA Technical Reports Server (NTRS)
Foster, Cyrus James
2013-01-01
The trajectory browser is a web-based tool developed at the NASA Ames Research Center for finding preliminary trajectories to planetary bodies and for providing relevant launch date, time-of-flight and (Delta)V requirements. The site hosts a database of transfer trajectories from Earth to planets and small-bodies for various types of missions such as rendezvous, sample return or flybys. A search engine allows the user to find trajectories meeting desired constraints on the launch window, mission duration and (Delta)V capability, while a trajectory viewer tool allows the visualization of the heliocentric trajectory and the detailed mission itinerary. The anticipated user base of this tool consists primarily of scientists and engineers designing interplanetary missions in the context of pre-phase A studies, particularly for performing accessibility surveys to large populations of small-bodies.
Trajectory options for the DART mission
NASA Astrophysics Data System (ADS)
Atchison, Justin A.; Ozimek, Martin T.; Kantsiper, Brian L.; Cheng, Andrew F.
2016-06-01
This study presents interplanetary trajectory options for the Double Asteroid Redirection Test (DART) spacecraft to reach the near Earth object, Didymos binary system, during its 2022 Earth conjunction. DART represents a component of a joint NASA-ESA mission to study near Earth object kinetic impact deflection. The DART trajectory must satisfy mission objectives for arrival timing, geometry, and lighting while minimizing launch vehicle and spacecraft propellant requirements. Chemical propulsion trajectories are feasible from two candidate launch windows in late 2020 and 2021. The 2020 trajectories are highly perturbed by Earth's orbit, requiring post-launch deep space maneuvers to retarget the Didymos system. Within these windows, opportunities exist for flybys of additional near Earth objects: Orpheus in 2021 or 2007 YJ in 2022. A second impact attempt, in the event that the first impact is unsuccessful, can be added at the expense of a shorter launch window and increased (∼3x) spacecraft ΔV . However, the second impact arrival geometry has poor lighting, high Earth ranges, and would require additional degrees of freedom for solar panel and/or antenna gimbals. A low-thrust spacecraft configuration increases the trajectory flexibility. A solar electric propulsion spacecraft could be affordably launched as a secondary spacecraft in an Earth orbit and spiral out to target the requisite interplanetary departure condition. A sample solar electric trajectory was constructed from an Earth geostationary transfer using a representative 1.5 kW thruster. The trajectory requires 9 months to depart Earth's sphere of influence, after which its interplanetary trajectory includes a flyby of Orpheus and a second Didymos impact attempt. The solar electric spacecraft implementation would impose additional bus design constraints, including large solar arrays that could pose challenges for terminal guidance. On the basis of this study, there are many feasible options for DART to
Filtering Drifter Trajectories Sampled at Submesoscale Resolution
2015-05-11
40, NO. 3, JULY 2015 497 Filtering Drifter Trajectories Sampled at Submesoscale Resolution Max Yaremchuk and Emanuel F. Coelho Abstract—In this paper...accel- erations while keeping the difference between the filtered and ob- served trajectories within the error bars of the positioning noise...Mexico in 2012. Index Terms—Computers and information processing/data pro- cessing,mathematics/ filtering algorithms, optimization, smoothing methods
Optimizing Simulated Trajectories Of Rigid Bodies
NASA Technical Reports Server (NTRS)
Brauer, Garry L.; Olson, David W.; Stevenson, Robert
1989-01-01
6D POST is general-purpose, six-degree-of-freedom computer program for optimization of simulated trajectories of rigid bodies. Direct extension of three-degree-of-freedom POST program. 6D POST program models trajectory of powered or unpowered vehicle operating at or near rotating planet. Used to solve variety of performance, guidance, and flight-control problems for atmospheric and orbital vehicles. Written in FORTRAN 77 and FORTRAN V.
Systematic Disturbance Of Optimal Rotational Trajectory
NASA Technical Reports Server (NTRS)
Grunwald, Arthur J.; Kaiser, Mary K.
1992-01-01
Algorithm introduces systematic disturbance into otherwise optimal rotation of body from prescribed initial to prescribed final orientation. Disturbance introduced as deviation of actual axis of rotation from optimal one, like wobble of top. Algorithm effects rotational transformations and solves differential equations necessary to compute disturbed trajectory. Devised for use with motion-control program and three-dimensional computer-graphical display to study ability of observers to distinguish between optimal and suboptimal rotational trajectories.
Machine Learning for Biological Trajectory Classification Applications
NASA Technical Reports Server (NTRS)
Sbalzarini, Ivo F.; Theriot, Julie; Koumoutsakos, Petros
2002-01-01
Machine-learning techniques, including clustering algorithms, support vector machines and hidden Markov models, are applied to the task of classifying trajectories of moving keratocyte cells. The different algorithms axe compared to each other as well as to expert and non-expert test persons, using concepts from signal-detection theory. The algorithms performed very well as compared to humans, suggesting a robust tool for trajectory classification in biological applications.
Elements of Statistical Mechanics
NASA Astrophysics Data System (ADS)
Sachs, Ivo; Sen, Siddhartha; Sexton, James
2006-05-01
This textbook provides a concise introduction to the key concepts and tools of modern statistical mechanics. It also covers advanced topics such as non-relativistic quantum field theory and numerical methods. After introducing classical analytical techniques, such as cluster expansion and Landau theory, the authors present important numerical methods with applications to magnetic systems, Lennard-Jones fluids and biophysics. Quantum statistical mechanics is discussed in detail and applied to Bose-Einstein condensation and topics in astrophysics and cosmology. In order to describe emergent phenomena in interacting quantum systems, canonical non-relativistic quantum field theory is introduced and then reformulated in terms of Feynman integrals. Combining the authors' many years' experience of teaching courses in this area, this textbook is ideal for advanced undergraduate and graduate students in physics, chemistry and mathematics. Analytical and numerical techniques in one text, including sample codes and solved problems on the web at www.cambridge.org/0521841984 Covers a wide range of applications including magnetic systems, turbulence astrophysics, and biology Contains a concise introduction to Markov processes and molecular dynamics
"Mental retirement?" Trajectories of work engagement preceding retirement among older workers.
de Wind, Astrid; Leijten, Fenna Rm; Hoekstra, Trynke; Geuskens, Goedele A; Burdorf, Alex; van der Beek, Allard J
2017-01-01
Objectives Before actual retirement, employees may already distance themselves from work, which could be referred to as "mental retirement". However, trajectories of work motivation, ie, work engagement, have not been studied yet. The present study aimed to (i) identify different trajectories of work engagement among older workers approaching the retirement age, and (ii) examine their associations with actual retirement. Methods In total 3171 employees aged 55-62 years, who participated in the Dutch Study on Transitions in Employment, Ability and Motivation were included in this study. Participants completed questionnaires in 2010, 2011, 2012, and 2013. Latent class growth mixture modeling was performed to identify groups of employees with similar three-year trajectories in work engagement. Logistic regression analyses were performed to study whether trajectory membership was associated with retirement. Results Of the 3171 employees, 16.2% made a transition from work to (early) retirement (N=513). Four trajectories of work engagement were identified: steady high (76.3%), steady low (12.7%), decreasing (6.2%), and increasing (4.8%). A steady low work engagement trajectory was associated with retirement [odds ratio (OR) 1.46], compared to a steady high work engagement trajectory. Although not statistically significant, an increasing work engagement trajectory seemed to be associated with retirement as well (OR 1.60). Conclusions This study did not support the concept of mental retirement before actual retirement, ie, a decrease in work engagement among those facing retirement. However, as one in eight employees did experience steady low work engagement in the years before retirement, interventions promoting work motivation are recommended to support the employability of these employees.
Mars interplanetary trajectory design via Lagrangian points
NASA Astrophysics Data System (ADS)
Eapen, Roshan Thomas; Sharma, Ram Krishan
2014-09-01
With the increase in complexities of interplanetary missions, the main focus has shifted to reducing the total delta-V for the entire mission and hence increasing the payload capacity of the spacecraft. This paper develops a trajectory to Mars using the Lagrangian points of the Sun-Earth system and the Sun-Mars system. The whole trajectory can be broadly divided into three stages: (1) Trajectory from a near-Earth circular parking orbit to a halo orbit around Sun-Earth Lagrangian point L2. (2) Trajectory from Sun-Earth L2 halo orbit to Sun-Mars L1 halo orbit. (3) Sun-Mars L1 halo orbit to a circular orbit around Mars. The stable and unstable manifolds of the halo orbits are used for halo orbit insertion. The intermediate transfer arcs are designed using two-body Lambert's problem. The total delta-V for the whole trajectory is computed and found to be lesser than that for the conventional trajectories. For a 480 km Earth parking orbit, the total delta-V is found to be 4.6203 km/s. Another advantage in the present approach is that delta-V does not depend upon the synodic period of Earth with respect to Mars.
A method for balloon trajectory control
NASA Astrophysics Data System (ADS)
Aaron, K. M.; Heun, M. K.; Nock, K. T.
A balloon trajectory control system is discussed that is under development for use on NASA's Ultra Long Duration Balloon Project. The trajectory control system exploits the natural wind field variation with altitude to generate passive lateral control forces on a balloon using a tether-deployed aerodynamic surface below the balloon. A lifting device, such as a wing on end, is suspended on a tether well beneath the balloon to take advantage of this variation in wind velocity with altitude. The wing generates a horizontal lift force that can be directed over a wide range of angles. This force, transmitted to the balloon by a tether, alters the balloon's path providing a bias velocity of a few meters per second to the balloon drift rate. The trajectory control system enables the balloon to avoid hazards, reach targets, steer around avoidance countries and select convenient landing zones. No longer will balloons be totally at the mercy of the winds. Tests in April 1999 of a dynamically-scaled model of the trajectory control system were carried out by Global Aerospace Corporation in ground level winds up to 15 m/s. The size of the scale model was designed to simulate the behavior of the full scale trajectory control system operating at 20 km altitude. The model confirmed many aspects of trajectory control system performance and the results will be incorporated into future development.
A demonstration and evaluation of trajectory mapping
Morris, G.A.
1994-09-01
Problem of creating synoptic maps from asynoptically gathered data has prompted the development of a number schemes, the most notable being the Kalman filter, Salby-Fourier technique, and constituent reconstruction. This thesis presents a new technique, called trajectory mapping, which employs a simple model of air parcel motion to create synoptic maps from asynoptically gathered data. Four sources of trajectory mapping errors were analyzed; results showed that (1) the computational error is negligible; (2) measurement uncertainties can result in errors which grow with time scales of a week; (3) isentropic approximations lead to errors characterized by time scales of a week; and (4) wind field inaccuracies can cause significant errors in individual parcel trajectories in a matter of hours. All the studies, however, indicated that while individual trajectory errors can grow rapidly, constituent distributions, such as on trajectory maps, are much more robust, maintaining a high level of accuracy for periods on the order of several weeks. This technique was successfully applied to a variety of problems:(1) dynamical wave- breaking events; (2) satellite data validation for both instrument accuracy and precision; and (3) accuracy of meteorological wind fields. Such demonstrations imply that trajectory mapping will become an important tool in answering questions of global change, particularly the issue of ozone depletion.
A Study of Shuttlecock's Trajectory in Badminton.
Chen, Lung-Ming; Pan, Yi-Hsiang; Chen, Yung-Jen
2009-01-01
The main purpose of this study was to construct and validate a motion equation for the flight of the badminton and to find the relationship between the air resistance force and a shuttlecock's speed. This research method was based on motion laws of aerodynamics. It applied aerodynamic theories to construct motion equation of a shuttlecock's flying trajectory under the effects of gravitational force and air resistance force. The result showed that the motion equation of a shuttlecock's flight trajectory could be constructed by determining the terminal velocity. The predicted shuttlecock trajectory fitted the measured data fairly well. The results also revealed that the drag force was proportional to the square of a shuttlecock velocity. Furthermore, the angle and strength of a stroke could influence trajectory. Finally, this study suggested that we could use a scientific approach to measure a shuttlecock's velocity objectively when testing the quality of shuttlecocks. And could be used to replace the traditional subjective method of the Badminton World Federation based on players' striking shuttlecocks, as well as applying research findings to improve professional knowledge of badminton player training. Key pointsThe motion equation of a shuttlecock's flying trajectory could be constructed by determining the terminal velocity in aerodynamics.Air drag force is proportional to the square of a shuttlecock velocity. Furthermore, the angle and strength of a stroke could influence trajectory.
Optimizing interplanetary trajectories with deep space maneuvers
NASA Astrophysics Data System (ADS)
Navagh, John
1993-09-01
Analysis of interplanetary trajectories is a crucial area for both manned and unmanned missions of the Space Exploration Initiative. A deep space maneuver (DSM) can improve a trajectory in much the same way as a planetary swingby. However, instead of using a gravitational field to alter the trajectory, the on-board propulsion system of the spacecraft is used when the vehicle is not near a planet. The purpose is to develop an algorithm to determine where and when to use deep space maneuvers to reduce the cost of a trajectory. The approach taken to solve this problem uses primer vector theory in combination with a non-linear optimizing program to minimize Delta(V). A set of necessary conditions on the primer vector is shown to indicate whether a deep space maneuver will be beneficial. Deep space maneuvers are applied to a round trip mission to Mars to determine their effect on the launch opportunities. Other studies which were performed include cycler trajectories and Mars mission abort scenarios. It was found that the software developed was able to locate quickly DSM's which lower the total Delta(V) on these trajectories.
Mobbs, Ralph J
2013-02-01
An alternative pedicle trajectory for use at the superior end of a construct to limit dissection of the mobile superior facet joint and reduce incision length and muscle dissection, thus minimizing approach-related trauma during pedicle fixation, is reported. The medio-latero-superior trajectory technique involves a starting point on the medial aspect of the pars and angulation of the pedicle screw in a mediolateral and caudocranial direction. This approach takes advantage of a predominantly cortical trajectory to assist with bone fixation. Drawbacks of this new screw trajectory are discussed along with its potential benefits.
Optimal flight trajectories in the presence of windshear, 1984-86
NASA Technical Reports Server (NTRS)
Miele, A.
1986-01-01
Optimal flight trajectories were determined in the presence of windshear and guidance schemes were developed for near optimum flight in a windshear. This is a wind characterized by sharp change in intensity and direction over a relatively small region of space. This problem is important in the takeoff and landing of both civilian airplanes and military airplanes and is key to aircraft saftey. The topics covered in reference to takeoff problems are: equations of motion, problem formulation, algorithms, optimal flight trajectories, advanced guidance schemes, simplified guidance schemes, and piloting strategies.
Minimum noise impact aircraft trajectories
NASA Technical Reports Server (NTRS)
Jacobson, I. D.; Melton, R. G.
1981-01-01
Numerical optimization is used to compute the optimum flight paths, based upon a parametric form that implicitly includes some of the problem restrictions. The other constraints are formulated as penalties in the cost function. Various aircraft on multiple trajectores (landing and takeoff) can be considered. The modular design employed allows for the substitution of alternate models of the population distribution, aircraft noise, flight paths, and annoyance, or for the addition of other features (e.g., fuel consumption) in the cost function. A reduction in the required amount of searching over local minima was achieved through use of the presence of statistical lateral dispersion in the flight paths.
MONITOR- MONTE CARLO INVESTIGATION OF TRAJECTORY OPERATIONS AND REQUIREMENTS
NASA Technical Reports Server (NTRS)
Glass, A. B.
1994-01-01
The Monte Carlo Investigation of Trajectory Operations and Requirements (MONITOR) program was developed to perform spacecraft mission maneuver simulations for geosynchronous, single maneuver, and comet encounter type trajectories. MONITOR is a multifaceted program which enables the modeling of various orbital sequences and missions, the generation of Monte Carlo simulation statistics, and the parametric scanning of user requested variables over specified intervals. The MONITOR program has been used primarily to study geosynchronous missions and has the capability to model Space Shuttle deployed satellite trajectories. The ability to perform a Monte Carlo error analysis of user specified orbital parameters using predicted maneuver execution errors can make MONITOR a significant part of any mission planning and analysis system. The MONITOR program can be executed in four operational modes. In the first mode, analytic state covariance matrix propagation is performed using state transition matrices for the coasting and powered burn phases of the trajectory. A two-body central force field is assumed throughout the analysis. Histograms of the final orbital elements and other state dependent variables may be evaluated by a Monte Carlo analysis. In the second mode, geosynchronous missions can be simulated from parking orbit injection through station acquisition. A two-body central force field is assumed throughout the simulation. Nominal mission studies can be conducted; however, the main use of this mode lies in evaluating the behavior of pertinent orbital trajectory parameters by making use of a Monte Carlo analysis. In the third mode, MONITOR performs parametric scans of user-requested variables for a nominal mission. Various orbital sequences may be specified; however, primary use is devoted to geosynchronous missions. A maximum of five variables may be scanned at a time. The fourth mode simulates a mission from orbit injection through comet encounter with optional
The trajectory and impact circumstances of asteroid 2008 TC3
NASA Astrophysics Data System (ADS)
Chodas, Paul; Chesley, S.; Yeomans, D.
2010-05-01
On October 6, 2008, the small newly discovered near-Earth asteroid 2008 TC3 was found to be on an Earth-impacting trajectory, with impact less than 20 hours away. This was the first ever predicted impact of a near-Earth object. Fortunately, it was immediately clear that the object was only a few meters in size and would therefore almost certainly break up when it entered the Earth's atmosphere. We review the pre-impact orbit computations and predictions, the post-impact reconstructions of the trajectory, and the trajectory geometry. The first prediction of impact was made by the Minor Planet Center (MPC), which quickly made the discovery and subsequent follow-up observations available to the astronomical community and contacted us at the NASA/JPL Near-Earth Object Program Office. Our impact predictions indicated that the atmospheric entry would occur over northern Sudan around 02:46 UT on October 7. Over the course of the day, the number of observations sky-rocketed to several hundred, and the impact prediction uncertainty shrank to ±3 km. Topocentric parallax up to 15 degrees is present in the data and the rates of motion approached 13.4 arcsec/s prior to the object's disappearance into the Earth's umbra. Detections of the actual atmospheric impact event suggested that it was an airburst explosion at an altitude of 37 km with an energy equivalent of about one kiloton of TNT. The airburst occurred at 02:45:45 UT at about 32.2 East longitude and 20.8 North latitude, matching the final impact predictions to within 0.2 s in time and 1.5 km in position. We compute Monte Carlo clones of the final orbit to investigate possible source orbits. Trajectory dispersions remain fairly compact as far back as 1961 , when an Earth close approach at 0.18 ± 0.12 AU scatters the predictions. Only statistical characterizations of the earlier trajectory are possible.
... PRS GO PSN PSEN GRAFT Contact Us News Plastic Surgery Statistics Plastic surgery procedural statistics from the ... Plastic Surgery Statistics 2005 Plastic Surgery Statistics 2016 Plastic Surgery Statistics Stats Report 2016 National Clearinghouse of ...
Statistical Challenges of Astronomy
NASA Astrophysics Data System (ADS)
Feigelson, Eric D.; Babu, G. Jogesh
Digital sky surveys, data from orbiting telescopes, and advances in computation have increased the quantity and quality of astronomical data by several orders of magnitude in recent years. Making sense of this wealth of data requires sophisticated statistical and data analytic techniques. Fortunately, statistical methodologies have similarly made great strides in recent years. Powerful synergies thus emerge when astronomers and statisticians join in examining astrostatistical problems and approaches. The volume focuses on several themes: · The increasing power of Bayesian approaches to modeling astronomical data · The growth of enormous databases, leading an emerging federated Virtual Observatory, and their impact on modern astronomical research · Statistical modeling of critical datasets, such as galaxy clustering and fluctuations in the microwave background radiation, leading to a new era of precision cosmology · Methodologies for uncovering clusters and patterns in multivariate data · The characterization of multiscale patterns in imaging and time series data As in earlier volumes in this series, research contributions discussing topics in one field are joined with commentary from scholars in the other. Short contributed papers covering dozens of astrostatistical topics are also included.
Slator, Paddy J.; Cairo, Christopher W.; Burroughs, Nigel J.
2015-01-01
. Our methods allow significantly more information to be extracted from individual trajectories (ultimately limited by time resolution and time-series length), and allow statistical comparisons between trajectories thereby quantifying inter-trajectory heterogeneity. Such methods will be highly informative for the construction and fitting of molecule mobility models within membranes incorporating aggregation, binding to the cytoskeleton, or traversing membrane microdomains. PMID:26473352
Current trajectory options for a comet nucleus sample return mission
NASA Astrophysics Data System (ADS)
Sauer, Carl G., Jr.
1992-08-01
A summary of the current trajectory options available for the ESA comet nucleus sample return mission, Rosetta, is presented. These options include direct trajectories, delta-V-EGA trajectories using a Titan IV/Centaur launch vehicle with upgraded solid rocket motors, a trajectory involving a gravity assist of the earth (VEGA) prior to comet rendezvous, and one involving an additional gravity assist of the earth (VEEGA). Other propulsion options proposed and discussed are solar electric propulsion/ballistic trajectory modes and nuclear electric propulsion trajectory modes. Tables of performance data for each of these trajectory options are given.
Superdiffusive trajectories in Brownian motion.
Duplat, Jérôme; Kheifets, Simon; Li, Tongcang; Raizen, Mark G; Villermaux, Emmanuel
2013-02-01
The Brownian motion of a microscopic particle in a fluid is one of the cornerstones of statistical physics and the paradigm of a random process. One of the most powerful tools to quantify it was provided by Langevin, who explicitly accounted for a short-time correlated "thermal" force. The Langevin picture predicts ballistic motion,
Method and Apparatus for Generating Flight-Optimizing Trajectories
NASA Technical Reports Server (NTRS)
Ballin, Mark G. (Inventor); Wing, David J. (Inventor)
2015-01-01
An apparatus for generating flight-optimizing trajectories for a first aircraft includes a receiver capable of receiving second trajectory information associated with at least one second aircraft. The apparatus also includes a traffic aware planner (TAP) module operably connected to the receiver to receive the second trajectory information. The apparatus also includes at least one internal input device on board the first aircraft to receive first trajectory information associated with the first aircraft and a TAP application capable of calculating an optimal trajectory for the first aircraft based at least on the first trajectory information and the second trajectory information. The optimal trajectory at least avoids conflicts between the first trajectory information and the second trajectory information.
NASA Astrophysics Data System (ADS)
Bookstein, Fred L.
1995-08-01
Recent advances in computational geometry have greatly extended the range of neuroanatomical questions that can be approached by rigorous quantitative methods. One of the major current challenges in this area is to describe the variability of human cortical surface form and its implications for individual differences in neurophysiological functioning. Existing techniques for representation of stochastically invaginated surfaces do not conduce to the necessary parametric statistical summaries. In this paper, following a hint from David Van Essen and Heather Drury, I sketch a statistical method customized for the constraints of this complex data type. Cortical surface form is represented by its Riemannian metric tensor and averaged according to parameters of a smooth averaged surface. Sulci are represented by integral trajectories of the smaller principal strains of this metric, and their statistics follow the statistics of that relative metric. The diagrams visualizing this tensor analysis look like alligator leather but summarize all aspects of cortical surface form in between the principal sulci, the reliable ones; no flattening is required.
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.
2015-09-30
active sonar. Toward this goal, fundamental advances in the understanding of fish behavior , especially in aggregations, will be made under conditions...relevant to the echo statistics problem. OBJECTIVES To develop new models of behavior of fish aggregations, including the fission/fusion process...and to describe the echo statistics associated with the random fish behavior using existing formulations of echo statistics. APPROACH
EUROPA Multiple-Flyby Trajectory Design
NASA Technical Reports Server (NTRS)
Buffington, Brent; Campagnola, Stefano; Petropoulos, Anastassios
2012-01-01
As reinforced by the 2011 NRC Decadal Survey, Europa remains one of the most scientifically intriguing targets in planetary science due to its potential suitability for life. However, based on JEO cost estimates and current budgetary constraints, the Decadal Survey recommended-and later directed by NASA Headquarters-a more affordable pathway to Europa exploration be derived. In response, a flyby-only proof-of-concept trajectory has been developed to investigate Europa. The trajectory, enabled by employing a novel combination of new mission design techniques, successfully fulfills a set of Science Definition Team derived scientific objectives carried out by a notional payload including ice penetrating radar, topographic imaging, and short wavelength infrared observations, and ion neutral mass spectrometry in-situ measurements. The current baseline trajectory, referred to as 11-F5, consists of 34 Europa and 9 Ganymede flybys executed over the course of 2.4 years, reached a maximum inclination of 15 degrees, has a deterministic delta v of 157 m/s (post-PJR), and has a total ionizing dose of 2.06 Mrad (Si behind 100 mil Al, spherical shell). The 11-F5 trajectory and more generally speaking, flyby-only trajectories-exhibit a number of potential advantages over an Europa orbiter mission.
Handling Trajectory Uncertainties for Airborne Conflict Management
NASA Technical Reports Server (NTRS)
Barhydt, Richard; Doble, Nathan A.; Karr, David; Palmer, Michael T.
2005-01-01
Airborne conflict management is an enabling capability for NASA's Distributed Air-Ground Traffic Management (DAG-TM) concept. DAGTM has the goal of significantly increasing capacity within the National Airspace System, while maintaining or improving safety. Under DAG-TM, autonomous aircraft maintain separation from each other and from managed aircraft unequipped for autonomous flight. NASA Langley Research Center has developed the Autonomous Operations Planner (AOP), an onboard decision support system that provides airborne conflict management (ACM) and strategic flight planning support for autonomous aircraft pilots. The AOP performs conflict detection, prevention, and resolution from nearby traffic aircraft and area hazards. Traffic trajectory information is assumed to be provided by Automatic Dependent Surveillance Broadcast (ADS-B). Reliable trajectory prediction is a key capability for providing effective ACM functions. Trajectory uncertainties due to environmental effects, differences in aircraft systems and performance, and unknown intent information lead to prediction errors that can adversely affect AOP performance. To accommodate these uncertainties, the AOP has been enhanced to create cross-track, vertical, and along-track buffers along the predicted trajectories of both ownship and traffic aircraft. These buffers will be structured based on prediction errors noted from previous simulations such as a recent Joint Experiment between NASA Ames and Langley Research Centers and from other outside studies. Currently defined ADS-B parameters related to navigation capability, trajectory type, and path conformance will be used to support the algorithms that generate the buffers.
Cullati, Stéphane
2015-06-01
Do socioeconomic differences in health status increase as people age, reflecting cumulative advantage or disadvantage in health trajectories? Life course research hypothesises that cumulative advantage/disadvantage (CAD) is an important underlying social process that shape inequalities as people age. The objective of this study is to examine whether health trajectories are diverging as people age across socioeconomic positions (education, employment status and income). In a random sample of 3,665 respondents living in Switzerland (Swiss Household Panel 2004-2011), trajectories of self-rated health, body mass index, depression and medicated functioning were examined with multilevel regression models. The results showed that employment status and income were associated with diverging health trajectories among men; however, only a few associations supported the CAD hypothesis. Education was rarely associated with diverging health trajectories. In conclusion, little evidence was found to support the CAD model.
Eucb: A C++ program for molecular dynamics trajectory analysis
NASA Astrophysics Data System (ADS)
Tsoulos, Ioannis G.; Stavrakoudis, Athanassios
2011-03-01
Eucb is a standalone program for geometrical analysis of molecular dynamics trajectories of protein systems. The program is written in GNU C++ and it can be installed in any operating system running a C++ compiler. The program performs its analytical tasks based on user supplied keywords. The source code is freely available from http://stavrakoudis.econ.uoi.gr/eucb under LGPL 3 license. Program summaryProgram title:Eucb Catalogue identifier: AEIC_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEIC_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 31 169 No. of bytes in distributed program, including test data, etc.: 297 364 Distribution format: tar.gz Programming language: GNU C++ Computer: The tool is designed and tested on GNU/Linux systems Operating system: Unix/Linux systems RAM: 2 MB Supplementary material: Sample data files are available Classification: 3 Nature of problem: Analysis of molecular dynamics trajectories. Solution method: The program finds all possible interactions according to input files and the user instructions. Then it reads all the trajectory frames and finds those frames in which these interactions occur, under certain geometrical criteria. This is a blind search, without a priori knowledge if a certain interaction occurs or not. The program exports time series of these quantities (distance, angles, etc.) and appropriate descriptive statistics. Running time: Depends on the input data and the required options.
Trajectories of cortical surface area and cortical volume maturation in normal brain development
Ducharme, Simon; Albaugh, Matthew D.; Nguyen, Tuong-Vi; Hudziak, James J.; Mateos-Pérez, J.M.; Labbe, Aurelie; Evans, Alan C.; Karama, Sherif
2015-01-01
This is a report of developmental trajectories of cortical surface area and cortical volume in the NIH MRI Study of Normal Brain Development. The quality-controlled sample included 384 individual typically-developing subjects with repeated scanning (1–3 per subject, total scans n=753) from 4.9 to 22.3 years of age. The best-fit model (cubic, quadratic, or first-order linear) was identified at each vertex using mixed-effects models, with statistical correction for multiple comparisons using random field theory. Analyses were performed with and without controlling for total brain volume. These data are provided for reference and comparison with other databases. Further discussion and interpretation on cortical developmental trajectories can be found in the associated Ducharme et al.׳s article “Trajectories of cortical thickness maturation in normal brain development – the importance of quality control procedures” (Ducharme et al., 2015) [1]. PMID:26702424
Advances in robust flight design
NASA Technical Reports Server (NTRS)
Wong, Kelvin K.; Dhand, Sanjeev K.
1991-01-01
Current launch vehicle trajectory design philosophies, generally based on maximizing payload capability, result in an expensive and time-consuming iteration in trajectory design for each mission. However, for a launch system that is not performance-driven, a flight design that is robust to variations in missions and provides single-engine-out capability can be highly cost-effective. This philosophy has led to the development of two flight design concepts to reduce recurring costs: standard trajectories and command multiplier steering. Preliminary analyses of these two concepts had proven the feasibility and showed encouraging results in applications to an Advanced Launch System vehicle. Recent progress has demonstrated the effective and efficient integration of the two concepts with minimal payload penalty.
On complex, curved trajectories in microtubule gliding
NASA Astrophysics Data System (ADS)
Gosselin, Pierre; Mohrbach, Hervé; Kulić, Igor M.; Ziebert, Falko
2016-04-01
We study the dynamics of microtubules in gliding assays. These biofilaments are typically considered as purely semiflexible, hence their trajectories under the action of motors covering the substrate have been regarded so far as straight, modulo fluctuations. However, this is not always the case experimentally, where microtubules are known to move on large scale circles or spirals, or even display quite regular wavy trajectories and more complex dynamics. Incorporating recent experimental evidence for a (small) preferred curvature as well as the microtubules' well established lattice twist into a dynamic model for microtubule gliding, we could reproduce both types of trajectories. Interestingly, as a function of the microtubules' length we found length intervals of stable rings alternating with regions where wavy and more complex dynamics prevails. Finally, both types of dynamics (rings and waves) can be rationalized by considering simple limits of the full model.
Departure Trajectory Synthesis and the Intercept Problem
NASA Technical Reports Server (NTRS)
Bolender, Michael A.; Slater, G. L.
1997-01-01
Two areas of the departure problem in air traffic control are discussed. The first topic is the generation of climb-out trajectories to a fix. The trajectories would be utilized by a scheduling algorithm to allocate runways, sequence the proposed departures, and assign a departure time. The second area is concerned with finding horizontal trajectories to merge aircraft from the TRACON to an open slot in the en-route environment. Solutions are presented for the intercept problem for two cases: (1) the aircraft is traveling at the speed of the aircraft in the jetway; (2) the merging aircraft has to accelerate to reach the speed of the aircraft in the en-route stream. An algorithm is given regarding the computation of a solution for the latter case. For the former, a set of equations is given that allows us to numerically solve for the coordinate where the merge will occur.
3D Visualization of Cooperative Trajectories
NASA Technical Reports Server (NTRS)
Schaefer, John A.
2014-01-01
Aerodynamicists and biologists have long recognized the benefits of formation flight. When birds or aircraft fly in the upwash region of the vortex generated by leaders in a formation, induced drag is reduced for the trail bird or aircraft, and efficiency improves. The major consequence of this is that fuel consumption can be greatly reduced. When two aircraft are separated by a large enough longitudinal distance, the aircraft are said to be flying in a cooperative trajectory. A simulation has been developed to model autonomous cooperative trajectories of aircraft; however it does not provide any 3D representation of the multi-body system dynamics. The topic of this research is the development of an accurate visualization of the multi-body system observable in a 3D environment. This visualization includes two aircraft (lead and trail), a landscape for a static reference, and simplified models of the vortex dynamics and trajectories at several locations between the aircraft.
OPTIMAL AIRCRAFT TRAJECTORIES FOR SPECIFIED RANGE
NASA Technical Reports Server (NTRS)
Lee, H.
1994-01-01
For an aircraft operating over a fixed range, the operating costs are basically a sum of fuel cost and time cost. While minimum fuel and minimum time trajectories are relatively easy to calculate, the determination of a minimum cost trajectory can be a complex undertaking. This computer program was developed to optimize trajectories with respect to a cost function based on a weighted sum of fuel cost and time cost. As a research tool, the program could be used to study various characteristics of optimum trajectories and their comparison to standard trajectories. It might also be used to generate a model for the development of an airborne trajectory optimization system. The program could be incorporated into an airline flight planning system, with optimum flight plans determined at takeoff time for the prevailing flight conditions. The use of trajectory optimization could significantly reduce the cost for a given aircraft mission. The algorithm incorporated in the program assumes that a trajectory consists of climb, cruise, and descent segments. The optimization of each segment is not done independently, as in classical procedures, but is performed in a manner which accounts for interaction between the segments. This is accomplished by the application of optimal control theory. The climb and descent profiles are generated by integrating a set of kinematic and dynamic equations, where the total energy of the aircraft is the independent variable. At each energy level of the climb and descent profiles, the air speed and power setting necessary for an optimal trajectory are determined. The variational Hamiltonian of the problem consists of the rate of change of cost with respect to total energy and a term dependent on the adjoint variable, which is identical to the optimum cruise cost at a specified altitude. This variable uniquely specifies the optimal cruise energy, cruise altitude, cruise Mach number, and, indirectly, the climb and descent profiles. If the optimum
A new trajectory correction technique for linacs
Raubenheimer, T.O.; Ruth, R.D.
1990-06-01
In this paper, we describe a new trajectory correction technique for high energy linear accelerators. Current correction techniques force the beam trajectory to follow misalignments of the Beam Position Monitors. Since the particle bunch has a finite energy spread and particles with different energies are deflected differently, this causes chromatic'' dilution of the transverse beam emittance. The algorithm, which we describe in this paper, reduces the chromatic error by minimizing the energy dependence of the trajectory. To test the method we compare the effectiveness of our algorithm with a standard correction technique in simulations on a design linac for a Next Linear Collider. The simulations indicate that chromatic dilution would be debilitating in a future linear collider because of the very small beam sizes required to achieve the necessary luminosity. Thus, we feel that this technique will prove essential for future linear colliders. 3 refs., 6 figs., 2 tabs.
Developmental trajectories of bullying and associated factors.
Pepler, Debra; Jiang, Depeng; Craig, Wendy; Connolly, Jennifer
2008-01-01
Trajectories in bullying through adolescence were studied along with individual, family, and peer relationship factors. At the outset, participants' ages ranged from 10 to 14; 74% identified as European Canadian with the remainder from diverse backgrounds. With 8 waves of data over 7 years, 871 students (466 girls and 405 boys) were studied to reveal 4 trajectories: 9.9% reported consistently high levels of bullying, 13.4% reported early moderate levels desisting to almost no bullying at the end of high school, 35.1% reported consistently moderate levels, and 41.6% almost never reported bullying. Students who bullied had elevated risks in individual, parent, and peer relationship domains. Risk profiles and trajectories provide direction for interventions to curtail the development of power and aggression in relationships.
Romantic attraction and adolescent smoking trajectories.
Pollard, Michael S; Tucker, Joan S; Green, Harold D; Kennedy, David P; Go, Myong-Hyun
2011-12-01
Research on sexual orientation and substance use has established that lesbian, gay, and bisexual (LGB) individuals are more likely to smoke than heterosexuals. This analysis furthers the examination of smoking behaviors across sexual orientation groups by describing how same- and opposite-sex romantic attraction, and changes in romantic attraction, are associated with distinct six-year developmental trajectories of smoking. The National Longitudinal Study of Adolescent Health dataset is used to test our hypotheses. Multinomial logistic regressions predicting smoking trajectory membership as a function of romantic attraction were separately estimated for men and women. Romantic attraction effects were found only for women. The change from self-reported heterosexual attraction to lesbian or bisexual attraction was more predictive of higher smoking trajectories than was a consistent lesbian or bisexual attraction, with potentially important differences between the smoking patterns of these two groups.
Statistical ecology comes of age.
Gimenez, Olivier; Buckland, Stephen T; Morgan, Byron J T; Bez, Nicolas; Bertrand, Sophie; Choquet, Rémi; Dray, Stéphane; Etienne, Marie-Pierre; Fewster, Rachel; Gosselin, Frédéric; Mérigot, Bastien; Monestiez, Pascal; Morales, Juan M; Mortier, Frédéric; Munoz, François; Ovaskainen, Otso; Pavoine, Sandrine; Pradel, Roger; Schurr, Frank M; Thomas, Len; Thuiller, Wilfried; Trenkel, Verena; de Valpine, Perry; Rexstad, Eric
2014-12-01
The desire to predict the consequences of global environmental change has been the driver towards more realistic models embracing the variability and uncertainties inherent in ecology. Statistical ecology has gelled over the past decade as a discipline that moves away from describing patterns towards modelling the ecological processes that generate these patterns. Following the fourth International Statistical Ecology Conference (1-4 July 2014) in Montpellier, France, we analyse current trends in statistical ecology. Important advances in the analysis of individual movement, and in the modelling of population dynamics and species distributions, are made possible by the increasing use of hierarchical and hidden process models. Exciting research perspectives include the development of methods to interpret citizen science data and of efficient, flexible computational algorithms for model fitting. Statistical ecology has come of age: it now provides a general and mathematically rigorous framework linking ecological theory and empirical data.
Postfire regrowth trajectories of chamise chaparral based on multi-temporal Landsat imagery
NASA Astrophysics Data System (ADS)
Storey, Emanual A.
Assessments of postfire recovery outcomes for the chamise chaparral shrublands of southern California provide a basis for land managers and ecologists to identify long-term changes in this sensitive ecosystem. Postfire vegetation recovery assessments based on fieldplot vegetation sampling and aerial image analysis have proven to be limited in coverage and inefficient for large areas of this landscape type. This study evaluates the potential of remotely sensed regrowth trajectories based on multi-temporal Landsat 4, 5, 7, and 8 satellite image observations for the postfire recovery assessment of chamise. Methods included: 1) an a priori determination of postfire shrub fractional cover changes based on multi-date high spatial resolution orthoimagery, 2) statistical testing to assess the sensitivity of regrowth trajectories based on several spectral vegetation indices and applied metrics to the recovery outcomes, and 3) an examination of regrowth trajectories which extend 19-29 years postfire relative to field-based measurements from other studies. Results provide a basis for interpretations about the sensitivities of the postfire regrowth trajectories derived from Landsat surface reflectance data to changes in the shrub matrix at various spatial and temporal scales. A primary finding was that several measures, including the Regeneration Index and another proposed here which is termed the Scaled Recovery Metric, enhanced the signals of postfire recovery derived from the multi-temporal trajectories and increased their comparability. Findings indicate that several of the spectral vegetation indices (NDVI, NDMI, NBR, and NBR2) were sensitive to long-term postfire changes in chamise, and that these same indices were statistically significant indicators of postfire recovery outcomes when certain metrics were applied. This study provides an overview of some advantages, limitations, and technical considerations of deriving postfire regrowth trajectories from Landsat imagery
Properties of the ellipse-line-ellipse trajectory with asymmetrical variations
NASA Astrophysics Data System (ADS)
Guo, Zijia; Noo, Frédéric; Maier, Andreas; Lauritsch, Guenter
2016-03-01
Three-dimensional cone-beam (CB) imaging using a multi-axis floor-mounted (or ceiling-mounted) C-arm system has become an important tool in interventional radiology. This success motivates new developments to improve image quality. One direction in which advancement is sought is the data acquisition geometry and related CB artifacts. Currently, data acquisition is performed using the circular short-scan trajectory, which yields limited axial coverage and also provides incomplete data for accurate reconstruction. To improve the image quality, as well as to increase the coverage in the longitudinal direction of the patient, we recently introduced the ellipse- line-ellipse trajectory and showed that this trajectory provides full R-line coverage within the field-of-view, which is a key property for accurate reconstruction from truncated data. An R-line is any segment of line that connects two source positions. Here, we examine how the application of asymmetrical variations to the definition of the ELE trajectory impacts the R-line coverage. This question is significant to understand how much flexibility can be used in the implementation of the ELE trajectory, particularly to adapt the scan to patient anatomy and imaging task of interest. Two types of asymmetrical variations, called axial and angular variations, are investigated.
Trajectory Software With Upper Atmosphere Model
NASA Technical Reports Server (NTRS)
Barrett, Charles
2012-01-01
The Trajectory Software Applications 6.0 for the Dec Alpha platform has an implementation of the Jacchia-Lineberry Upper Atmosphere Density Model used in the Mission Control Center for International Space Station support. Previous trajectory software required an upper atmosphere to support atmosphere drag calculations in the Mission Control Center. The Functional operation will differ depending on the end-use of the module. In general, the calling routine will use function-calling arguments to specify input to the processor. The atmosphere model will then compute and return atmospheric density at the time of interest.
On air motion trajectories in cold fronts
NASA Technical Reports Server (NTRS)
Reeder, Michael J.; Smith, Roger K.
1988-01-01
This paper examines air parcel trajectories in the two-dimensional model for a cold front by Reeder and Smith (1987). These are found to be in close agreement with trajectories deduced from analyses of summertime 'cool changes' in southeastern Australia, adding further support to the applicability of the numerical model to this kind of cold front. The favorable comparison points also to the dynamical consistency of the conceptual model for the cool change, which has evolved from the analysis of data from observational experiments.
General Methodology for Designing Spacecraft Trajectories
NASA Technical Reports Server (NTRS)
Condon, Gerald; Ocampo, Cesar; Mathur, Ravishankar; Morcos, Fady; Senent, Juan; Williams, Jacob; Davis, Elizabeth C.
2012-01-01
A methodology for designing spacecraft trajectories in any gravitational environment within the solar system has been developed. The methodology facilitates modeling and optimization for problems ranging from that of a single spacecraft orbiting a single celestial body to that of a mission involving multiple spacecraft and multiple propulsion systems operating in gravitational fields of multiple celestial bodies. The methodology consolidates almost all spacecraft trajectory design and optimization problems into a single conceptual framework requiring solution of either a system of nonlinear equations or a parameter-optimization problem with equality and/or inequality constraints.
A simple model of quantum trajectories
NASA Astrophysics Data System (ADS)
Brun, Todd A.
2002-07-01
Quantum trajectory theory, developed largely in the quantum optics community to describe open quantum systems subjected to continuous monitoring, has applications in many areas of quantum physics. I present a simple model, using two-level quantum systems (q-bits), to illustrate the essential physics of quantum trajectories and how different monitoring schemes correspond to different "unravelings" of a mixed state master equation. I also comment briefly on the relationship of the theory to the consistent histories formalism and to spontaneous collapse models.
Trajectory surgical guide stent for implant placement.
Adrian, E D; Ivanhoe, J R; Krantz, W A
1992-05-01
This article describes a new implant placement surgical guide that gives both implant location and trajectory to the surgeon. Radiopaque markers are placed on diagnostic dentures and a lateral cephalometric radiograph is made that shows the osseous anatomy at the symphysis and the anterior tooth location. The ideal implant location and trajectory data are transferred to a surgical stent that programs the angle and location of the fixtures at time of surgery. The stent has the additional benefit of acting as an occlusion rim, a mouth prop, and tongue retractor. Use of this stent has resulted in consistently programming the placement of implant fixtures that are prosthodontically ideal.
Trajectories of Multi-lined Spatial Scans
NASA Astrophysics Data System (ADS)
McCullough, P.
2017-03-01
We compare multi-lined (a.k.a. boustrophedonic) spatial scans with numerical simulations of the trajectories using a simple physical model for HST's motions. For scan rates less than or equal to 0.5 arc sec s-1, the simulated trajectories match the observed ones within 0.5 arc sec, i.e. sufficiently well for planning purposes. We provide IDL procedures for the simulator in the Appendix. We identify an overall unexplained drift, primarily in the UVIS detector X direction, throughout the one HST orbit during visit 1 of program 14878.
Optimal trajectories for the aeroassisted flight experiment
NASA Technical Reports Server (NTRS)
Miele, A.; Wang, T.; Lee, W. Y.; Zhao, Z. G.
1989-01-01
The determination of optimal trajectories for the aeroassisted flight experiment (AFE) is discussed. The intent of this experiment is to simulate a GEO-to-LEO transfer, where GEO denotes a geosynchronous earth orbit and LEO denotes a low earth orbit. The trajectories of an AFE spacecraft are analyzed in a 3D-space, employing the full system of 6 ordinary differential equations (ODEs) describing the atmospheric pass. The atmospheric entry conditions are given, and the atmospheric exit conditions are adjusted. Two possible transfers are considered: (1) indirect ascent to a 178 NM perigee via a 197 NM apogee; and (2) direct ascent to a 178 NM apogee.
Snake trajectories in ultraclean graphene p-n junctions
NASA Astrophysics Data System (ADS)
Rickhaus, Peter; Makk, Péter; Liu, Ming-Hao; Tóvári, Endre; Weiss, Markus; Maurand, Romain; Richter, Klaus; Schönenberger, Christian
2015-03-01
Snake states are trajectories of charge carriers curving back and forth along an interface. There are two types of snake states, formed by either inverting the magnetic field direction or the charge carrier type at an interface. The former has been demonstrated in GaAs-AlGaAs heterostructures, whereas the latter has become conceivable only with the advance of ballistic graphene where a gap-less p-n interface governed by Klein tunnelling can be formed. Such snake states were hidden in previous experiments due to limited sample quality. Here we report on magneto-conductance oscillations due to snake states in a ballistic suspended graphene p-n junction, which occur already at a very small magnetic field of 20 mT. The visibility of 30% is enabled by Klein collimation. Our finding is firmly supported by quantum transport simulations. We demonstrate the high tunability of the device and operate it in different magnetic field regimes.
Revealing nonergodic dynamics in living cells from a single particle trajectory
NASA Astrophysics Data System (ADS)
Lanoiselée, Yann; Grebenkov, Denis S.
2016-05-01
We propose the improved ergodicity and mixing estimators to identify nonergodic dynamics from a single particle trajectory. The estimators are based on the time-averaged characteristic function of the increments and can thus capture additional information on the process as compared to the conventional time-averaged mean-square displacement. The estimators are first investigated and validated for several models of anomalous diffusion, such as ergodic fractional Brownian motion and diffusion on percolating clusters, and nonergodic continuous-time random walks and scaled Brownian motion. The estimators are then applied to two sets of earlier published trajectories of mRNA molecules inside live Escherichia coli cells and of Kv2.1 potassium channels in the plasma membrane. These statistical tests did not reveal nonergodic features in the former set, while some trajectories of the latter set could be classified as nonergodic. Time averages along such trajectories are thus not representative and may be strongly misleading. Since the estimators do not rely on ensemble averages, the nonergodic features can be revealed separately for each trajectory, providing a more flexible and reliable analysis of single-particle tracking experiments in microbiology.
Smith-Bynum, Mia A.; Lambert, Sharon F.; English, Devin; Ialongo, Nicholas S.
2014-01-01
Many African American adolescents experience racial discrimination, with adverse consequences; however, stability and change in these experiences over time have not been examined. We examined longitudinal patterns of perceived racial discrimination assessed in grades 7 – 10 and how these discrimination trajectories related to patterns of change in depressive and anxious symptoms and aggressive behaviors assessed over the same 4-year period. Growth mixture modeling performed on a community epidemiologically-defined sample of urban African American adolescents (n = 504) revealed three trajectories of discrimination: (1) increasing, (2) decreasing, and (3) stable low. As predicted, African American boys were more frequent targets for racial discrimination as they aged, and were more likely to be in the increasing group. Results of parallel process growth mixture modeling revealed that youth in the increasing racial discrimination group were four times more likely to be in an increasing depression trajectory than youth in the low stable discrimination trajectory. Though youth in the increasing racial discrimination group were nearly twice as likely to be in the high aggression trajectory, results were not statistically significant. These results indicate an association between variation in the growth of perceived racial discrimination and youth behavior and psychological well-being over the adolescent years. PMID:24955844
Step detection in single-molecule real time trajectories embedded in correlated noise.
Arunajadai, Srikesh G; Cheng, Wei
2013-01-01
Single-molecule real time trajectories are embedded in high noise. To extract kinetic or dynamic information of the molecules from these trajectories often requires idealization of the data in steps and dwells. One major premise behind the existing single-molecule data analysis algorithms is the gaussian 'white' noise, which displays no correlation in time and whose amplitude is independent on data sampling frequency. This so-called 'white' noise is widely assumed but its validity has not been critically evaluated. We show that correlated noise exists in single-molecule real time trajectories collected from optical tweezers. The assumption of white noise during analysis of these data can lead to serious over- or underestimation of the number of steps depending on the algorithms employed. We present a statistical method that quantitatively evaluates the structure of the underlying noise, takes the noise structure into account, and identifies steps and dwells in a single-molecule trajectory. Unlike existing data analysis algorithms, this method uses Generalized Least Squares (GLS) to detect steps and dwells. Under the GLS framework, the optimal number of steps is chosen using model selection criteria such as Bayesian Information Criterion (BIC). Comparison with existing step detection algorithms showed that this GLS method can detect step locations with highest accuracy in the presence of correlated noise. Because this method is automated, and directly works with high bandwidth data without pre-filtering or assumption of gaussian noise, it may be broadly useful for analysis of single-molecule real time trajectories.
Smith-Bynum, Mia A; Lambert, Sharon F; English, Devin; Ialongo, Nicholas S
2014-11-01
Many African American adolescents experience racial discrimination, with adverse consequences; however, stability and change in these experiences over time have not been examined. We examined longitudinal patterns of perceived racial discrimination assessed in Grades 7-10 and how these discrimination trajectories related to patterns of change in depressive and anxious symptoms and aggressive behaviors assessed over the same 4-year period. Growth mixture modeling performed on a community epidemiologically defined sample of urban African American adolescents (n = 504) revealed three trajectories of discrimination: increasing, decreasing, and stable low. As predicted, African American boys were more frequent targets for racial discrimination as they aged, and they were more likely to be in the increasing group. The results of parallel process growth mixture modeling revealed that youth in the increasing racial discrimination group were four times more likely to be in an increasing depression trajectory than were youth in the low stable discrimination trajectory. Though youth in the increasing racial discrimination group were nearly twice as likely to be in the high aggression trajectory, results were not statistically significant. These results indicate an association between variation in the growth of perceived racial discrimination and youth behavior and psychological well-being over the adolescent years.
Topology for statistical modeling of petascale data.
Pascucci, Valerio; Mascarenhas, Ajith Arthur; Rusek, Korben; Bennett, Janine Camille; Levine, Joshua; Pebay, Philippe Pierre; Gyulassy, Attila; Thompson, David C.; Rojas, Joseph Maurice
2011-07-01
This document presents current technical progress and dissemination of results for the Mathematics for Analysis of Petascale Data (MAPD) project titled 'Topology for Statistical Modeling of Petascale Data', funded by the Office of Science Advanced Scientific Computing Research (ASCR) Applied Math program. Many commonly used algorithms for mathematical analysis do not scale well enough to accommodate the size or complexity of petascale data produced by computational simulations. The primary goal of this project is thus to develop new mathematical tools that address both the petascale size and uncertain nature of current data. At a high level, our approach is based on the complementary techniques of combinatorial topology and statistical modeling. In particular, we use combinatorial topology to filter out spurious data that would otherwise skew statistical modeling techniques, and we employ advanced algorithms from algebraic statistics to efficiently find globally optimal fits to statistical models. This document summarizes the technical advances we have made to date that were made possible in whole or in part by MAPD funding. These technical contributions can be divided loosely into three categories: (1) advances in the field of combinatorial topology, (2) advances in statistical modeling, and (3) new integrated topological and statistical methods.
Yu, Zhaoyuan; Yuan, Linwang; Luo, Wen; Feng, Linyao; Lv, Guonian
2015-12-30
Passive infrared (PIR) motion detectors, which can support long-term continuous observation, are widely used for human motion analysis. Extracting all possible trajectories from the PIR sensor networks is important. Because the PIR sensor does not log location and individual information, none of the existing methods can generate all possible human motion trajectories that satisfy various spatio-temporal constraints from the sensor activation log data. In this paper, a geometric algebra (GA)-based approach is developed to generate all possible human trajectories from the PIR sensor network data. Firstly, the representation of the geographical network, sensor activation response sequences and the human motion are represented as algebraic elements using GA. The human motion status of each sensor activation are labeled using the GA-based trajectory tracking. Then, a matrix multiplication approach is developed to dynamically generate the human trajectories according to the sensor activation log and the spatio-temporal constraints. The method is tested with the MERL motion database. Experiments show that our method can flexibly extract the major statistical pattern of the human motion. Compared with direct statistical analysis and tracklet graph method, our method can effectively extract all possible trajectories of the human motion, which makes it more accurate. Our method is also likely to provides a new way to filter other passive sensor log data in sensor networks.
Yu, Zhaoyuan; Yuan, Linwang; Luo, Wen; Feng, Linyao; Lv, Guonian
2015-01-01
Passive infrared (PIR) motion detectors, which can support long-term continuous observation, are widely used for human motion analysis. Extracting all possible trajectories from the PIR sensor networks is important. Because the PIR sensor does not log location and individual information, none of the existing methods can generate all possible human motion trajectories that satisfy various spatio-temporal constraints from the sensor activation log data. In this paper, a geometric algebra (GA)-based approach is developed to generate all possible human trajectories from the PIR sensor network data. Firstly, the representation of the geographical network, sensor activation response sequences and the human motion are represented as algebraic elements using GA. The human motion status of each sensor activation are labeled using the GA-based trajectory tracking. Then, a matrix multiplication approach is developed to dynamically generate the human trajectories according to the sensor activation log and the spatio-temporal constraints. The method is tested with the MERL motion database. Experiments show that our method can flexibly extract the major statistical pattern of the human motion. Compared with direct statistical analysis and tracklet graph method, our method can effectively extract all possible trajectories of the human motion, which makes it more accurate. Our method is also likely to provides a new way to filter other passive sensor log data in sensor networks. PMID:26729123
... Standards Act and Program MQSA Insights MQSA National Statistics Share Tweet Linkedin Pin it More sharing options ... but should level off with time. Archived Scorecard Statistics 2017 Scorecard Statistics 2016 Scorecard Statistics (Archived) 2015 ...
Chopper Gun Trajectory Optimization for Spray Forming in Automotive Manufacturing
NASA Astrophysics Data System (ADS)
Chen, Heping; Xi, Ning; Sheng, Weihua; Chen, Yifan; Dahl, Jeffrey
2004-06-01
Automatic chopper gun trajectory generation for spray forming is highly desirable for today's automotive manufacturing. Generating chopper gun trajectories for free-form surfaces to satisfy thickness requirements is still highly challenging due to the complex geometry of free-form surfaces. A CAD-guided chopper gun trajectory generation system for free-form surfaces has been developed in our previous work. A complex surface has to be divided into several patches to satisfy the given constraints. Optimization algorithms are developed to integrate the trajectories of patches to form a trajectory for the free-form surface. A thickness verification method is also provided to verify the generated trajectories. The results of experiments and simulations have shown that the trajectory generation system achieves satisfactory performance. This trajectory generation method can also be applied in many other CAD-guided robot trajectory planning applications.
Trajectory Browser: An online tool for interplanetary trajectory analysis and visualization
NASA Astrophysics Data System (ADS)
Foster, C.
The Trajectory Browser is a web-based tool developed at the NASA Ames Research Center for finding preliminary trajectories to planetary bodies and for providing relevant launch date, time-of-flight and Δ V requirements. The site hosts a database of transfer trajectories from Earth to planets and small-bodies for various types of missions such as rendezvous, sample return or flybys. A search engine allows the user to find trajectories meeting desired constraints on the launch window, mission duration and Δ V capability, while a trajectory viewer tool allows the visualization of the heliocentric trajectory and the detailed mission itinerary. The anticipated user base of this tool consists primarily of scientists and engineers designing interplanetary missions in the context of pre-phase A studies, particularly for performing accessibility surveys to large populations of small-bodies. The educational potential of the website is also recognized for academia and the public with regards to trajectory design, a field that has generally been poorly understood by the public. The website is currently hosted on NASA-internal URL http://trajbrowser.arc.nasa.gov/ with plans for a public release in early 2013.
Temporal Correlations of the Running Maximum of a Brownian Trajectory
NASA Astrophysics Data System (ADS)
Bénichou, Olivier; Krapivsky, P. L.; Mejía-Monasterio, Carlos; Oshanin, Gleb
2016-08-01
We study the correlations between the maxima m and M of a Brownian motion (BM) on the time intervals [0 ,t1] and [0 ,t2], with t2>t1. We determine the exact forms of the distribution functions P (m ,M ) and P (G =M -m ), and calculate the moments E {(M-m ) k} and the cross-moments E {mlMk} with arbitrary integers l and k . We show that correlations between m and M decay as √{t1/t2 } when t2/t1→∞ , revealing strong memory effects in the statistics of the BM maxima. We also compute the Pearson correlation coefficient ρ (m ,M ) and the power spectrum of Mt, and we discuss a possibility of extracting the ensemble-averaged diffusion coefficient in single-trajectory experiments using a single realization of the maximum process.
NASA Astrophysics Data System (ADS)
Striepe, Scott Allen
The objectives of this research were to develop a reconstruction capability using the Program to Optimize Simulated Trajectories II (POST2), apply this capability to reconstruct the Huygens Titan probe entry, descent, and landing (EDL) trajectory, evaluate the newly developed POST2 reconstruction module, analyze the reconstructed trajectory, and assess the pre-flight simulation models used for Huygens EDL simulation. An extended Kalman filter (EKF) module was developed and integrated into POST2 to enable trajectory reconstruction (especially when using POST2-based mission specific simulations). Several validation cases, ranging from a single, constant parameter estimate to multivariable estimation cases similar to an actual mission flight, were executed to test the POST2 reconstruction module. Trajectory reconstruction of the Huygens entry probe at Titan was accomplished using accelerometer measurements taken during flight to adjust an estimated state (e.g., position, velocity, parachute drag, wind velocity, etc.) in a POST2-based simulation developed to support EDL analyses and design prior to entry. Although the main emphasis of the trajectory reconstruction was to evaluate models used in the NASA pre-entry trajectory simulation, the resulting reconstructed trajectory was also assessed to provide an independent evaluation of the ESA result. Major findings from this analysis include: Altitude profiles from this analysis agree well with other NASA and ESA results but not with Radar data, whereas a scale factor of about 0.93 would bring the radar measurements into compliance with these results; entry capsule aerodynamics predictions (axial component only) were well within 3-sigma bounds established pre-flight for most of the entry when compared to reconstructed values; Main parachute drag of 9% to 19% above ESA model was determined from the reconstructed trajectory; based on the tilt sensor and accelerometer data, the conclusion from this assessment was that the
Statistics used in current nursing research.
Zellner, Kathleen; Boerst, Connie J; Tabb, Wil
2007-02-01
Undergraduate nursing research courses should emphasize the statistics most commonly used in the nursing literature to strengthen students' and beginning researchers' understanding of them. To determine the most commonly used statistics, we reviewed all quantitative research articles published in 13 nursing journals in 2000. The findings supported Beitz's categorization of kinds of statistics. Ten primary statistics used in 80% of nursing research published in 2000 were identified. We recommend that the appropriate use of those top 10 statistics be emphasized in undergraduate nursing education and that the nursing profession continue to advocate for the use of methods (e.g., power analysis, odds ratio) that may contribute to the advancement of nursing research.
Atmospheric statistics for aerospace vehicle operations
NASA Technical Reports Server (NTRS)
Smith, O. E.; Batts, G. W.
1993-01-01
Statistical analysis of atmospheric variables was performed for the Shuttle Transportation System (STS) design trade studies and the establishment of launch commit criteria. Atmospheric constraint statistics have been developed for the NASP test flight, the Advanced Launch System, and the National Launch System. The concepts and analysis techniques discussed in the paper are applicable to the design and operations of any future aerospace vehicle.
Lough, Graham; Kyriazakis, Ilias; Bergmann, Silke; Lengeling, Andreas; Doeschl-Wilson, Andrea B.
2015-01-01
Resistance and tolerance are two alternative strategies hosts can adopt to survive infections. Both strategies may be genetically controlled. To date, the relative contribution of resistance and tolerance to infection outcome is poorly understood. Here, we use a bioluminescent Listeria monocytogenes (Lm) infection challenge model to study the genetic determination and dynamic contributions of host resistance and tolerance to listeriosis in four genetically diverse mouse strains. Using conventional statistical analyses, we detect significant genetic variation in both resistance and tolerance, but cannot capture the time-dependent relative importance of either host strategy. We overcome these limitations through the development of novel statistical tools to analyse individual infection trajectories portraying simultaneous changes in infection severity and health. Based on these tools, early expression of resistance followed by expression of tolerance emerge as important hallmarks for surviving Lm infections. Our trajectory analysis further reveals that survivors and non-survivors follow distinct infection paths (which are also genetically determined) and provides new survival thresholds as objective endpoints in infection experiments. Future studies may use trajectories as novel traits for mapping and identifying genes that control infection dynamics and outcome. A Matlab script for user-friendly trajectory analysis is provided. PMID:26582028
2014-09-30
had access to trajectories of male moths finding a pheromone-emitting female; our goal was to quantify the mate-seeking behavior of these male moths ...turbulent environmental flows might be statistically summarized are known from fluid physics. Using the moth dataset, we developed new biomimetic...of a simplified behavior: location of the source of an odorant plume in a turbulent flow. The top plot shows movement of a male moth seeking a
Bohmian quantum mechanics with quantum trajectories
NASA Astrophysics Data System (ADS)
Jeong, Yeuncheol
The quantum trajectory method in the hydrodynamical formulation of Madelung-Bohm-Takabayasi quantum mechanics is an example of showing the cognitive importance of scientific illustrations and metaphors, especially, in this case, in computational quantum chemistry and electrical engineering. The method involves several numerical schemes of solving a set of hydrodynamical equations of motion for probability density fluids, based on the propagation of those probability density trajectories. The quantum trajectory method gives rise to, for example, an authentic quantum electron transport theory of motion to, among others, classically-minded applied scientists who probably have less of a commitment to traditional quantum mechanics. They were not the usual audience of quantum mechanics and simply choose to use a non-Copenhagen type interpretation to their advantage. Thus, the metaphysical issues physicists had a trouble with are not the main concern of the scientists. With the advantages of a visual and illustrative trajectory, the quantum theory of motion by Bohm effectively bridges quantum and classical physics, especially, in the mesoscale domain. Without having an abrupt shift in actions and beliefs from the classical to the quantum world, scientists and engineers are able to enjoy human cognitive capacities extended into the quantum mechanical domain.
Establishing cycler trajectories between Earth and Mars
NASA Astrophysics Data System (ADS)
Rogers, Blake A.; Hughes, Kyle M.; Longuski, James M.; Aldrin, Buzz
2015-07-01
Several cycler concepts have been proposed to provide safe and comfortable quarters for astronauts traveling between the Earth and Mars. However, no literature has appeared to show how these massive vehicles might be placed into their cycler trajectories. In this paper, trajectories are designed that use either V∞ leveraging or low thrust to establish cycler vehicles in their desired orbits. In the cycler trajectory cases considered, the use of V∞ leveraging or low thrust substantially reduces the total propellant needed to achieve the cycler orbit compared to direct orbit insertion. In the case of the classic Aldrin cycler, the propellant savings due to V∞ leveraging can be as large as 24 metric tons for a cycler vehicle with a dry mass of 75 metric tons, and an additional 111 metric tons by instead using low thrust. The two-synodic period cyclers considered benefit less from V∞ leveraging, but have a smaller total propellant mass due to their lower approach velocities at Earth and Mars. It turns out that, for low-thrust establishment, the propellant required is approximately the same for each of the cycler trajectories. The cycler concept may provide a crucial enabling technology that is safe, economical, and sustainable for the continuous habitation of Mars.
14 CFR 417.207 - Trajectory analysis.
Code of Federal Regulations, 2012 CFR
2012-01-01
... the requirements of paragraph (a) of this section. (c) Wind effects. A trajectory analysis must account for all wind effects, including profiles of winds that are no less severe than the worst wind conditions under which flight might be attempted, and must account for uncertainty in the wind conditions....
14 CFR 417.207 - Trajectory analysis.
Code of Federal Regulations, 2011 CFR
2011-01-01
... the requirements of paragraph (a) of this section. (c) Wind effects. A trajectory analysis must account for all wind effects, including profiles of winds that are no less severe than the worst wind conditions under which flight might be attempted, and must account for uncertainty in the wind conditions....
14 CFR 417.207 - Trajectory analysis.
Code of Federal Regulations, 2010 CFR
2010-01-01
... the requirements of paragraph (a) of this section. (c) Wind effects. A trajectory analysis must account for all wind effects, including profiles of winds that are no less severe than the worst wind conditions under which flight might be attempted, and must account for uncertainty in the wind conditions....
Performance of Trajectory Models with Wind Uncertainty
NASA Technical Reports Server (NTRS)
Lee, Alan G.; Weygandt, Stephen S.; Schwartz, Barry; Murphy, James R.
2009-01-01
Typical aircraft trajectory predictors use wind forecasts but do not account for the forecast uncertainty. A method for generating estimates of wind prediction uncertainty is described and its effect on aircraft trajectory prediction uncertainty is investigated. The procedure for estimating the wind prediction uncertainty relies uses a time-lagged ensemble of weather model forecasts from the hourly updated Rapid Update Cycle (RUC) weather prediction system. Forecast uncertainty is estimated using measures of the spread amongst various RUC time-lagged ensemble forecasts. This proof of concept study illustrates the estimated uncertainty and the actual wind errors, and documents the validity of the assumed ensemble-forecast accuracy relationship. Aircraft trajectory predictions are made using RUC winds with provision for the estimated uncertainty. Results for a set of simulated flights indicate this simple approach effectively translates the wind uncertainty estimate into an aircraft trajectory uncertainty. A key strength of the method is the ability to relate uncertainty to specific weather phenomena (contained in the various ensemble members) allowing identification of regional variations in uncertainty.
Hyper-X Mach 10 Trajectory Reconstruction
NASA Technical Reports Server (NTRS)
Karlgaard, Christopher D.; Martin, John G.; Tartabini, Paul V.; Thornblom, Mark N.
2005-01-01
This paper discusses the formulation and development of a trajectory reconstruction tool for the NASA X-43A/Hyper-X high speed research vehicle, and its implementation for the reconstruction and analysis of flight test data. Extended Kalman filtering techniques are employed to reconstruct the trajectory of the vehicle, based upon numerical integration of inertial measurement data along with redundant measurements of the vehicle state. The equations of motion are formulated in order to include the effects of several systematic error sources, whose values may also be estimated by the filtering routines. Additionally, smoothing algorithms have been implemented in which the final value of the state (or an augmented state that includes other systematic error parameters to be estimated) and covariance are propagated back to the initial time to generate the best-estimated trajectory, based upon all available data. The methods are applied to the problem of reconstructing the trajectory of the Hyper-X vehicle from data obtained during the Mach 10 test flight, which occurred on November 16th 2004.
Graphical Method for Determining Projectile Trajectory
ERIC Educational Resources Information Center
Moore, J. C.; Baker, J. C.; Franzel, L.; McMahon, D.; Songer, D.
2010-01-01
We present a nontrigonometric graphical method for predicting the trajectory of a projectile when the angle and initial velocity are known. Students enrolled in a general education conceptual physics course typically have weak backgrounds in trigonometry, making inaccessible the standard analytical calculation of projectile range. Furthermore,…
Developmental Trajectories of Bullying and Associated Factors
ERIC Educational Resources Information Center
Pepler, Debra; Jiang, Depeng; Craig, Wendy; Connolly, Jennifer
2008-01-01
Trajectories in bullying through adolescence were studied along with individual, family, and peer relationship factors. At the outset, participants' ages ranged from 10 to 14; 74% identified as European Canadian with the remainder from diverse backgrounds. With 8 waves of data over 7 years, 871 students (466 girls and 405 boys) were studied to…
Causal Inferences with Group Based Trajectory Models
ERIC Educational Resources Information Center
Haviland, Amelia M.; Nagin, Daniel S.
2005-01-01
A central theme of research on human development and psychopathology is whether a therapeutic intervention or a turning-point event, such as a family break-up, alters the trajectory of the behavior under study. This paper lays out and applies a method for using observational longitudinal data to make more confident causal inferences about the…
Families of Ellipses and their Orthogonal Trajectories
ERIC Educational Resources Information Center
Ayoub, Ayoub B.
2004-01-01
The topic of orthogonal trajectories is taught as a geometric application of first order differential equations. Instructors usually elaborate on the concept of a family of curves to emphasize that they are different even if their members are of the same type. In this article the author considers five families of ellipses, discusses their…
Developmental Trajectories of Early Communication Skills
ERIC Educational Resources Information Center
Maatta, Sira; Laakso, Marja-Leena; Tolvanen, Asko; Ahonen, Timo; Aro, Tuija
2012-01-01
Purpose: This study focused on developmental trajectories of prelinguistic communication skills and their connections to later parent-reported language difficulties. Method: The participants represent a subset of a community-based sample of 508 children. Data include parent reports of prelinguistic communication skills at 12, 15, 18, and 21 months…
Trajectory optimization for the National aerospace plane
NASA Technical Reports Server (NTRS)
Lu, Ping
1993-01-01
While continuing the application of the inverse dynamics approach in obtaining the optimal numerical solutions, the research during the past six months has been focused on the formulation and derivation of closed-form solutions for constrained hypersonic flight trajectories. Since it was found in the research of the first year that a dominant portion of the optimal ascent trajectory of the aerospace plane is constrained by dynamic pressure and heating constraints, the application of the analytical solutions significantly enhances the efficiency in trajectory optimization, provides a better insight to understanding of the trajectory and conceivably has great potential in guidance of the vehicle. Work of this period has been reported in four technical papers. Two of the papers were presented in the AIAA Guidance, Navigation, and Control Conference (Hilton Head, SC, August, 1992) and Fourth International Aerospace Planes Conference (Orlando, FL, December, 1992). The other two papers have been accepted for publication by Journal of Guidance, Control, and Dynamics, and will appear in 1993. This report briefly summarizes the work done in the past six months and work currently underway.
Using Developmental Trajectories to Understand Developmental Disorders
ERIC Educational Resources Information Center
Thomas, Michael S. C.; Annaz, Dagmara; Ansari, Daniel; Scerif, Gaia; Jarrold, Chris; Karmiloff-Smith, Annette
2009-01-01
Purpose: In this article, the authors present a tutorial on the use of developmental trajectories for studying language and cognitive impairments in developmental disorders and compare this method with the use of matching. Method: The authors assess the strengths, limitations, and practical implications of each method. The contrast between the…
Nonlinear Optimal Trajectories Using Successive Linearization
1977-06-28
integral sign represents a penalty for the local vertical and passing through the vehicle deviations of the perturbed trajectory from the at time equals... integral sign represents the penalty for control variations about the nominal, and needs z s - sin y (14) to be weighted to ensure that the control does
Fractal aircraft trajectories and nonclassical turbulent exponents.
Lovejoy, S; Schertzer, D; Tuck, A F
2004-09-01
The dimension (D) of aircraft trajectories is fundamental in interpreting airborne data. To estimate D, we studied data from 18 trajectories of stratospheric aircraft flights 1600 km long taken during a "Mach cruise" (near constant Mach number) autopilot flight mode of the ER-2 research aircraft. Mach cruise implies correlated temperature and wind fluctuations so that DeltaZ approximately Deltax (H(z) ) where Z is the (fluctuating) vertical and x the horizontal coordinate of the aircraft. Over the range approximately 3-300 km , we found H(z) approximately 0.58+/-0.02 close to the theoretical 5/9=0.56 and implying D=1+ H(z) =14/9 , i.e., the trajectories are fractal. For distances <3 km aircraft inertia smooths the trajectories, for distances >300 km , D=1 again because of a rise of 1 m/km due to fuel consumption. In the fractal regime, the horizontal velocity and temperature exponents are close to the nonclassical value 1/2 (rather than 1/3 ). We discuss implications for aircraft measurements as well as for the structure of the atmosphere.
Equilibrium sampling by reweighting nonequilibrium simulation trajectories.
Yang, Cheng; Wan, Biao; Xu, Shun; Wang, Yanting; Zhou, Xin
2016-03-01
Based on equilibrium molecular simulations, it is usually difficult to efficiently visit the whole conformational space of complex systems, which are separated into some metastable regions by high free energy barriers. Nonequilibrium simulations could enhance transitions among these metastable regions and then be applied to sample equilibrium distributions in complex systems, since the associated nonequilibrium effects can be removed by employing the Jarzynski equality (JE). Here we present such a systematical method, named reweighted nonequilibrium ensemble dynamics (RNED), to efficiently sample equilibrium conformations. The RNED is a combination of the JE and our previous reweighted ensemble dynamics (RED) method. The original JE reproduces equilibrium from lots of nonequilibrium trajectories but requires that the initial distribution of these trajectories is equilibrium. The RED reweights many equilibrium trajectories from an arbitrary initial distribution to get the equilibrium distribution, whereas the RNED has both advantages of the two methods, reproducing equilibrium from lots of nonequilibrium simulation trajectories with an arbitrary initial conformational distribution. We illustrated the application of the RNED in a toy model and in a Lennard-Jones fluid to detect its liquid-solid phase coexistence. The results indicate that the RNED sufficiently extends the application of both the original JE and the RED in equilibrium sampling of complex systems.
Academic Trajectories of Newcomer Immigrant Youth
ERIC Educational Resources Information Center
Suarez-Orozco, Carola; Gaytan, Francisco X.; Bang, Hee Jin; Pakes, Juliana; O'Connor, Erin; Rhodes, Jean
2010-01-01
Immigration to the United States presents both challenges and opportunities that affect students' academic achievement. Using a 5-year longitudinal, mixed-methods approach, we identified varying academic trajectories of newcomer immigrant students from Central America, China, the Dominican Republic, Haiti, and Mexico. Latent class growth curve…
Are U-Shaped Developmental Trajectories Illusory?
ERIC Educational Resources Information Center
Vouloumanos, Athena
2011-01-01
Without criteria for what counts as a U/N-shaped developmental trajectory, it is not clear how many legitimate "Us" really exist. Many, if not all, "Us" may turn out to be illusions borne out of our sampling methods, task construal, and blurry lenses of description. (Contains 2 figures.)
Equilibrium sampling by reweighting nonequilibrium simulation trajectories
NASA Astrophysics Data System (ADS)
Yang, Cheng; Wan, Biao; Xu, Shun; Wang, Yanting; Zhou, Xin
2016-03-01
Based on equilibrium molecular simulations, it is usually difficult to efficiently visit the whole conformational space of complex systems, which are separated into some metastable regions by high free energy barriers. Nonequilibrium simulations could enhance transitions among these metastable regions and then be applied to sample equilibrium distributions in complex systems, since the associated nonequilibrium effects can be removed by employing the Jarzynski equality (JE). Here we present such a systematical method, named reweighted nonequilibrium ensemble dynamics (RNED), to efficiently sample equilibrium conformations. The RNED is a combination of the JE and our previous reweighted ensemble dynamics (RED) method. The original JE reproduces equilibrium from lots of nonequilibrium trajectories but requires that the initial distribution of these trajectories is equilibrium. The RED reweights many equilibrium trajectories from an arbitrary initial distribution to get the equilibrium distribution, whereas the RNED has both advantages of the two methods, reproducing equilibrium from lots of nonequilibrium simulation trajectories with an arbitrary initial conformational distribution. We illustrated the application of the RNED in a toy model and in a Lennard-Jones fluid to detect its liquid-solid phase coexistence. The results indicate that the RNED sufficiently extends the application of both the original JE and the RED in equilibrium sampling of complex systems.
Statcast and the Baseball Trajectory Calculator
NASA Astrophysics Data System (ADS)
Kagan, David; Nathan, Alan M.
2017-03-01
Baseball's flirtation with technology began in 2005 when PITCHf/x® by Sportvision started to be installed in major league ballparks. Every stadium had the system operational by 2007. Since then, the trajectories of over six million pitches have been measured to within about half an inch using three 60-Hz video cameras to track the position of the ball.
Confounded Statistical Analyses Hinder Interpretation of the NELP Report
ERIC Educational Resources Information Center
Paris, Scott G.; Luo, Serena Wenshu
2010-01-01
The National Early Literacy Panel (2008) report identified early predictors of reading achievement as good targets for instruction, and many of those skills are related to decoding. In this article, the authors suggest that the developmental trajectories of rapidly developing skills pose problems for traditional statistical analyses. Rapidly…
Lagrangian statistics in laboratory 2D turbulence
NASA Astrophysics Data System (ADS)
Xia, Hua; Francois, Nicolas; Punzmann, Horst; Shats, Michael
2014-05-01
Turbulent mixing in liquids and gases is ubiquitous in nature and industrial flows. Understanding statistical properties of Lagrangian trajectories in turbulence is crucial for a range of problems such as spreading of plankton in the ocean, transport of pollutants, etc. Oceanic data on trajectories of the free-drifting instruments, indicate that the trajectory statistics can often be described by a Lagrangian integral scale. Turbulence however is a state of a flow dominated by a hierarchy of scales, and it is not clear which of these scales mostly affect particle dispersion. Moreover, coherent structures often coexist with turbulence in laboratory experiments [1]. The effect of coherent structures on particle dispersion in turbulent flows is not well understood. Recent progress in scientific imaging and computational power made it possible to tackle this problem experimentally. In this talk, we report the analysis of the higher order Lagrangian statistics in laboratory two-dimensional turbulence. Our results show that fluid particle dispersion is diffusive and it is determined by a single measurable Lagrangian scale related to the forcing scale [2]. Higher order moments of the particle dispersion show strong self-similarity in fully developed turbulence [3]. Here we introduce a new dispersion law that describes single particle dispersion during the turbulence development [4]. These results offer a new way of predicting dispersion in turbulent flows in which one of the low energy scales are persistent. It may help better understanding of drifter Lagrangian statistics in the regions of the ocean where small scale coherent eddies are present [5]. Reference: 1. H. Xia, H. Punzmann, G. Falkovich and M. Shats, Physical Review Letters, 101, 194504 (2008) 2. H. Xia, N. Francois, H. Punzmann, and M. Shats, Nature Communications, 4, 2013 (2013) 3. R. Ferrari, A.J. Manfroi , W.R. Young, Physica D 154 111 (2001) 4. H. Xia, N. Francois, H. Punzmann and M. Shats, submitted (2014
Parallel Aircraft Trajectory Optimization with Analytic Derivatives
NASA Technical Reports Server (NTRS)
Falck, Robert D.; Gray, Justin S.; Naylor, Bret
2016-01-01
Trajectory optimization is an integral component for the design of aerospace vehicles, but emerging aircraft technologies have introduced new demands on trajectory analysis that current tools are not well suited to address. Designing aircraft with technologies such as hybrid electric propulsion and morphing wings requires consideration of the operational behavior as well as the physical design characteristics of the aircraft. The addition of operational variables can dramatically increase the number of design variables which motivates the use of gradient based optimization with analytic derivatives to solve the larger optimization problems. In this work we develop an aircraft trajectory analysis tool using a Legendre-Gauss-Lobatto based collocation scheme, providing analytic derivatives via the OpenMDAO multidisciplinary optimization framework. This collocation method uses an implicit time integration scheme that provides a high degree of sparsity and thus several potential options for parallelization. The performance of the new implementation was investigated via a series of single and multi-trajectory optimizations using a combination of parallel computing and constraint aggregation. The computational performance results show that in order to take full advantage of the sparsity in the problem it is vital to parallelize both the non-linear analysis evaluations and the derivative computations themselves. The constraint aggregation results showed a significant numerical challenge due to difficulty in achieving tight convergence tolerances. Overall, the results demonstrate the value of applying analytic derivatives to trajectory optimization problems and lay the foundation for future application of this collocation based method to the design of aircraft with where operational scheduling of technologies is key to achieving good performance.
Hayat, Matthew J; Schmiege, Sarah J; Cook, Paul F
2014-04-01
Statistics knowledge is essential for understanding the nursing and health care literature, as well as for applying rigorous science in nursing research. Statistical consultants providing services to faculty and students in an academic nursing program have the opportunity to identify gaps and challenges in statistics education for nursing students. This information may be useful to curriculum committees and statistics educators. This article aims to provide perspective on statistics education stemming from the experiences of three experienced statistics educators who regularly collaborate and consult with nurse investigators. The authors share their knowledge and express their views about data management, data screening and manipulation, statistical software, types of scientific investigation, and advanced statistical topics not covered in the usual coursework. The suggestions provided promote a call for data to study these topics. Relevant data about statistics education can assist educators in developing comprehensive statistics coursework for nursing students.
Querying databases of trajectories of differential equations: Data structures for trajectories
NASA Technical Reports Server (NTRS)
Grossman, Robert
1989-01-01
One approach to qualitative reasoning about dynamical systems is to extract qualitative information by searching or making queries on databases containing very large numbers of trajectories. The efficiency of such queries depends crucially upon finding an appropriate data structure for trajectories of dynamical systems. Suppose that a large number of parameterized trajectories gamma of a dynamical system evolving in R sup N are stored in a database. Let Eta is contained in set R sup N denote a parameterized path in Euclidean Space, and let the Euclidean Norm denote a norm on the space of paths. A data structure is defined to represent trajectories of dynamical systems, and an algorithm is sketched which answers queries.
Statistics Poker: Reinforcing Basic Statistical Concepts
ERIC Educational Resources Information Center
Leech, Nancy L.
2008-01-01
Learning basic statistical concepts does not need to be tedious or dry; it can be fun and interesting through cooperative learning in the small-group activity of Statistics Poker. This article describes a teaching approach for reinforcing basic statistical concepts that can help students who have high anxiety and makes learning and reinforcing…
Predict! Teaching Statistics Using Informational Statistical Inference
ERIC Educational Resources Information Center
Makar, Katie
2013-01-01
Statistics is one of the most widely used topics for everyday life in the school mathematics curriculum. Unfortunately, the statistics taught in schools focuses on calculations and procedures before students have a chance to see it as a useful and powerful tool. Researchers have found that a dominant view of statistics is as an assortment of tools…
Wu, Rongling; Ma, Chang-Xing; Littell, Ramon C; Wu, Sameul S; Yin, Tongmingyin; Huang, Minren; Wang, Mingxiu; Casella, George
2002-06-01
The logistic or S-shaped curve of growth is one of the few universal laws in biology. It is certain that there exist specific genes affecting growth curves, but, due to a lack of statistical models, it is unclear how these genes cause phenotypic differentiation in growth and developmental trajectories. In this paper we present a statistical model for detecting major genes responsible for growth trajectories. This model is incorporated with pervasive logistic growth curves under the maximum likelihood framework and, thus, is expected to improve over previous models in both parameter estimation and inference. The power of this model is demonstrated by an example using forest tree data, in which evidence of major genes affecting stem growth processes is successfully detected. The implications for this model and its extensions are discussed.
Identifying Patterns of FEES-Derived Swallowing Trajectories Using Group-Based Trajectory Model.
Baijens, Laura W J; Pilz, Walmari; Kremer, Bernd; Passos, Valeria Lima
2015-10-01
The present study delineates and visualizes swallowing trajectories along seven swallow trials in dysphagic patients using group-based trajectory modeling (GBTM). This model facilitates the recognition of swallowing functional categories, estimates their frequency of occurrence, and enhances the understanding of swallowing dynamics. Two hundred and five dysphagic patients underwent a standardized FEES examination protocol. Five ordinal variables were blindly assessed for each swallow by two observers independently. GBTM analysis was conducted to find and characterize trajectories of FEES responses. For most FEES outcome variables, trajectories were qualitatively distinct in degree and kind (level of impairment and how this changed over the seven swallow trials). Two FEES outcome variables-delayed initiation of the pharyngeal reflex and postswallow pyriform sinus pooling-showed the highest prevalence of severe swallowing impairment. Highly impaired categories were more stable throughout the different swallow trials. Intermediate trajectories, by contrast, were erratic, responding more sensitively to shifts in bolus consistency. GBTM can identify distinct developmental trajectories of measured FEES variables in patients with oropharyngeal dysphagia. In clinical practice, classification into distinct groups would help to identify the subgroup of dysphagic patients who may need specific medical attention.
Phang, T.L.; Neville, M.C.; Rudolph, M.; Hunter, L.
2008-01-01
Trajectory clustering is a novel and statistically well-founded method for clustering time series data from gene expression arrays. Trajectory clustering uses non-parametric statistics and is hence not sensitive to the particular distributions underlying gene expression data. Each cluster is clearly defined in terms of direction of change of expression for successive time points (its ‘trajectory’), and therefore has easily appreciated biological meaning. Applying the method to a dataset from mouse mammary gland development, we demonstrate that it produces different clusters than Hierarchical, K-means, and Jackknife clustering methods, even when those methods are applied to differences between successive time points. Compared to all of the other methods, trajectory clustering was better able to match a manual clustering by a domain expert, and was better able to cluster groups of genes with known related functions. PMID:12603041
2012-01-01
ocean currents at daily or higher frequency. These data are used for search and rescue and object drift applica- tions (Davidson et al. 2009) as well ...larger. In general, the model trajectory errors were similar. Note especially that SURCOUF consistently made the best estimates in the subregion as well ...found agreement well within statistical uncertainty. Hereinafter we will refer to these fields as UV5W. The empirical cumulative density function of
Trajectory of Cognitive Decline after Incident Stroke
Levine, Deborah A.; Galecki, Andrzej T.; Langa, Kenneth M.; Unverzagt, Frederick W.; Kabeto, Mohammed U.; Giordani, Bruno; Wadley, Virginia G.
2015-01-01
Importance Cognitive decline is a major cause of disability in stroke survivors. The magnitude of survivors’ cognitive changes after stroke is uncertain. Objective To measure changes in cognitive function among survivors of incident stroke, controlling for their prestroke cognitive trajectories. Design, Setting, and Participants Prospective study of 23,572 participants aged ≥45 years without baseline cognitive impairment from the Reasons for Geographic and Racial Differences in Stroke (REGARDS) cohort, residing in the continental United States, enrolled 2003–2007 and followed through March 31, 2013. Over a median follow-up of 6.1 years (25th–75th percentile: 5.0–7.1 years), 515 participants survived expert-adjudicated incident stroke and 23,057 remained stroke-free. Exposure Time-dependent incident stroke. Outcome Measures The primary outcome was change in global cognition (Six-Item Screener, SIS; range 0–6). Secondary outcomes were change in new learning (Consortium to Establish a Registry for Alzheimer’s Disease Word List Learning; range 0–30), verbal memory (Word List Delayed Recall; range 0–10), and executive function (Animal Fluency Test; range ≥0), and cognitive impairment (SIS<5/impaired vs. ≥5/unimpaired). For all tests, higher scores indicate better performance. Results Stroke was associated with acute decline in global cognition (0.10 points; 95% CI, 0.04–0.17), new learning (1.80 points; 95% CI, 0.73–2.86), and verbal memory (0.60 points; 95% CI, 0.13–1.07). Participants with stroke, compared to those without stroke, demonstrated faster declines in global cognition (0.06 points per year faster; 95% CI, 0.03–0.08) and executive function (0.63 points per year faster; 95% CI, 0.12–1.15), but not in new learning and verbal memory, compared to prestroke slopes. Among survivors, the difference in risk of cognitive impairment acutely after stroke was not statistically significant (odds ratio, 1.32; 95% CI, 0.95–1.83; P=0
Reentry trajectory optimization based on a multistage pseudospectral method.
Zhao, Jiang; Zhou, Rui; Jin, Xuelian
2014-01-01
Of the many direct numerical methods, the pseudospectral method serves as an effective tool to solve the reentry trajectory optimization for hypersonic vehicles. However, the traditional pseudospectral method is time-consuming due to large number of discretization points. For the purpose of autonomous and adaptive reentry guidance, the research herein presents a multistage trajectory control strategy based on the pseudospectral method, capable of dealing with the unexpected situations in reentry flight. The strategy typically includes two subproblems: the trajectory estimation and trajectory refining. In each processing stage, the proposed method generates a specified range of trajectory with the transition of the flight state. The full glide trajectory consists of several optimal trajectory sequences. The newly focused geographic constraints in actual flight are discussed thereafter. Numerical examples of free-space flight, target transition flight, and threat avoidance flight are used to show the feasible application of multistage pseudospectral method in reentry trajectory optimization.
Reentry Trajectory Optimization Based on a Multistage Pseudospectral Method
Zhou, Rui; Jin, Xuelian
2014-01-01
Of the many direct numerical methods, the pseudospectral method serves as an effective tool to solve the reentry trajectory optimization for hypersonic vehicles. However, the traditional pseudospectral method is time-consuming due to large number of discretization points. For the purpose of autonomous and adaptive reentry guidance, the research herein presents a multistage trajectory control strategy based on the pseudospectral method, capable of dealing with the unexpected situations in reentry flight. The strategy typically includes two subproblems: the trajectory estimation and trajectory refining. In each processing stage, the proposed method generates a specified range of trajectory with the transition of the flight state. The full glide trajectory consists of several optimal trajectory sequences. The newly focused geographic constraints in actual flight are discussed thereafter. Numerical examples of free-space flight, target transition flight, and threat avoidance flight are used to show the feasible application of multistage pseudospectral method in reentry trajectory optimization. PMID:24574929
Optimal trajectories for the aeroassisted flight experiment
NASA Astrophysics Data System (ADS)
Miele, A.; Wang, T.; Lee, W. Y.; Zhao, Z. G.
This paper deals with the determination of optimal trajectories for the aeroassisted flight experiment (AFE). The intent of this experiment is to simulate a GEO-to-LEO transfer, where GEO denotes a geosynchronous Earth orbit and LEO denotes a low Earth orbit. Specifically, the AFE spacecraft is released from the Space Shuttle and is accelerated by means of a solid rocket motor toward Earth, so as to achieve atmospheric entry conditions identical with those of a spacecraft returning from GEO. During the atmospheric pass, the angle of attack is kept constant, and the angle of bank is controlled in such a way that the following conditions are satisfied: (a) the atmospheric velocity depletion is such that, after exiting, the AFE spacecraft first ascends to a specified apogee and then descends to a specified perigee; and (b) the exit orbital plane is identical with the entry orbital plane. The final maneuver, not analyzed here, includes the rendezvous with and the capture by the Space Shuttle. In this paper, the trajectories of an AFE spacecraft are analyzed in a 3D space, employing the full system of 6 ODEs describing the atmospheric pass. The atmospheric entry conditions are given, and the atmospheric exit conditions are adjusted in such a way that requirements (a) and (b) are met, while simultaneously minimizing the total characteristic velocity, hence the propellant consumption required for orbital transfer. Two possible transfers are considered: indirect ascent (IA) to a 178 NM perigee via a 197 NM apogee; and direct ascent (DA) to a 178 NM apogee. For both transfers, two cases are investigated: (i) the bank angle is continuously variable; and (ii) the trajectory is divided into segments along which the bank angle is constant. For case (ii), the following subcases are studied; 2, 3, 4 and 5 segments; because the time duration of each segment is optimized, the above subcases involve 4, 6, 8 and 10 parameters, respectively. It is shown that the optimal trajectories
CISLUNAR program manual: A low-thrust trajectory determination model
NASA Technical Reports Server (NTRS)
1988-01-01
CISLUNAR is a stand-alone computer program designed to generate the trajectory of a low-thrust spacecraft travelling in Earth-Moon space. The program allows the creation of functional trajectories dependent on the supplied spacecraft characteristics. The trajectory generation is a user interactive process. The original intent was for the program user to modify the necessary control values until a staisfactory trajectory has been created.
Feasibility Study for Integrated Flight Trajectory Control (Fighter).
1979-11-01
ntamber) Flight Trajectory C.ntrol Control Law Development Profile Synthesis Tactical Situation Display Four -Dimensional Navigation Vertical Situation...realtime trajectory generation was developed as a vital part of the total solution. This trajectory, generator operates in four dimensions, X, Y...FLIGHT PROFILE SYNTHESIS 5-1 5.1 Four -Dimensional Trajectory Generator 5-1 5.1.1 Waypoint Parameters 5-1 5.1.2 Threat Avoidance 5-2 5.1.3 Horizontal Path
Statistical behaviour of adaptive multilevel splitting algorithms in simple models
NASA Astrophysics Data System (ADS)
Rolland, Joran; Simonnet, Eric
2015-02-01
Adaptive multilevel splitting algorithms have been introduced rather recently for estimating tail distributions in a fast and efficient way. In particular, they can be used for computing the so-called reactive trajectories corresponding to direct transitions from one metastable state to another. The algorithm is based on successive selection-mutation steps performed on the system in a controlled way. It has two intrinsic parameters, the number of particles/trajectories and the reaction coordinate used for discriminating good or bad trajectories. We investigate first the convergence in law of the algorithm as a function of the timestep for several simple stochastic models. Second, we consider the average duration of reactive trajectories for which no theoretical predictions exist. The most important aspect of this work concerns some systems with two degrees of freedom. They are studied in detail as a function of the reaction coordinate in the asymptotic regime where the number of trajectories goes to infinity. We show that during phase transitions, the statistics of the algorithm deviate significatively from known theoretical results when using non-optimal reaction coordinates. In this case, the variance of the algorithm is peaking at the transition and the convergence of the algorithm can be much slower than the usual expected central limit behaviour. The duration of trajectories is affected as well. Moreover, reactive trajectories do not correspond to the most probable ones. Such behaviour disappears when using the optimal reaction coordinate called committor as predicted by the theory. We finally investigate a three-state Markov chain which reproduces this phenomenon and show logarithmic convergence of the trajectory durations.
Statistical behaviour of adaptive multilevel splitting algorithms in simple models
Rolland, Joran Simonnet, Eric
2015-02-15
Adaptive multilevel splitting algorithms have been introduced rather recently for estimating tail distributions in a fast and efficient way. In particular, they can be used for computing the so-called reactive trajectories corresponding to direct transitions from one metastable state to another. The algorithm is based on successive selection–mutation steps performed on the system in a controlled way. It has two intrinsic parameters, the number of particles/trajectories and the reaction coordinate used for discriminating good or bad trajectories. We investigate first the convergence in law of the algorithm as a function of the timestep for several simple stochastic models. Second, we consider the average duration of reactive trajectories for which no theoretical predictions exist. The most important aspect of this work concerns some systems with two degrees of freedom. They are studied in detail as a function of the reaction coordinate in the asymptotic regime where the number of trajectories goes to infinity. We show that during phase transitions, the statistics of the algorithm deviate significatively from known theoretical results when using non-optimal reaction coordinates. In this case, the variance of the algorithm is peaking at the transition and the convergence of the algorithm can be much slower than the usual expected central limit behaviour. The duration of trajectories is affected as well. Moreover, reactive trajectories do not correspond to the most probable ones. Such behaviour disappears when using the optimal reaction coordinate called committor as predicted by the theory. We finally investigate a three-state Markov chain which reproduces this phenomenon and show logarithmic convergence of the trajectory durations.
Physics of epigenetic landscapes and statistical inference by cells
NASA Astrophysics Data System (ADS)
Lang, Alex H.
Biology is currently in the midst of a revolution. Great technological advances have led to unprecedented quantitative data at the whole genome level. However, new techniques are needed to deal with this deluge of high-dimensional data. Therefore, statistical physics has the potential to help develop systems biology level models that can incorporate complex data. Additionally, physicists have made great strides in understanding non-equilibrium thermodynamics. However, the consequences of these advances have yet to be fully incorporated into biology. There are three specific problems that I address in my dissertation. First, a common metaphor for describing development is a rugged "epigenetic landscape'' where cell fates are represented as attracting valleys resulting from a complex regulatory network. I introduce a framework for explicitly constructing epigenetic landscapes that combines genomic data with techniques from spin-glass physics. The model reproduces known reprogramming protocols and identifies candidate transcription factors for reprogramming to novel cell fates, suggesting epigenetic landscapes are a powerful paradigm for understanding cellular identity. Second, I examine the dynamics of cellular reprogramming. By reanalyzing all available time-series data, I show that gene expression dynamics during reprogramming follow a simple one-dimensional reaction coordinate that is independent of both the time and details of experimental protocol used. I show that such a reaction coordinate emerges naturally from epigenetic landscape models of cell identity where cellular reprogramming is viewed as a "barrier-crossing'' between the starting and ending cell fates. Overall, the analysis and model suggest that gene expression dynamics during reprogramming follow a canonical trajectory consistent with the idea of an ``optimal path'' in gene expression space for reprogramming. Third, an important task of cells is to perform complex computations in response to
Psychosocial Correlates of Smoking Trajectories Among Urban African American Adolescents
ERIC Educational Resources Information Center
Fergus, Stevenson; Zimmerman, Marc A.; Caldwell, Cleopatra H.
2005-01-01
Little is known of smoking trajectories or of the correlates of smoking trajectories among African American youth. Ninth-grade African American adolescents (n = 566) were interviewed in Year 1 and then were subsequently interviewed annually for 3 additional years. Five trajectories of cigarette smokers were identified: abstainers,…
Developmental Trajectories of Childhood Obesity and Risk Behaviors in Adolescence
ERIC Educational Resources Information Center
Huang, David Y. C.; Lanza, H. Isabella; Wright-Volel, Kynna; Anglin, M. Douglas
2013-01-01
Using group-based trajectory modeling, this study examined 5156 adolescents from the child sample of the 1979 National Longitudinal Survey of Youth to identify developmental trajectories of obesity from ages 6-18 and evaluate associations of such trajectories with risk behaviors and psychosocial health in adolescence. Four distinctive obesity…
ERIC Educational Resources Information Center
Peugh, James; Fan, Xitao
2012-01-01
Growth mixture modeling (GMM) has become a more popular statistical method for modeling population heterogeneity in longitudinal data, but the performance characteristics of GMM enumeration indexes in correctly identifying heterogeneous growth trajectories are largely unknown. Few empirical studies have addressed this issue. This study considered…
Robot trajectory planning via dynamic programming
Dohrmann, C.R.; Robinett, R.D.
1994-03-01
The method of dynamic programming is applied to three example problems dealing with robot trajectory planning. The first two examples involve end-effector tracking of a straight line with rest-to-rest motions of planar two-link and three-link rigid robots. These examples illustrate the usefulness of the method for producing smooth trajectories either in the presence or absence of joint redundancies. The last example demonstrates the use of the method for rest-to-rest maneuvers of a single-link manipulator with a flexible payload. Simulation results for this example display interesting symmetries that are characteristic of such maneuvers. Details concerning the implementation and computational aspects of the method are discussed.
Irregular trajectories in vakonomic mechanical systems
NASA Astrophysics Data System (ADS)
Avakov, E. R.; Oleinikov, V. G.
2016-10-01
In his works, V.V. Kozlov proposed a mathematical model for the dynamics of a mechanical system with nonintegrable constraints, which was called vakonomic. In contrast to the then conventional nonholonomic model, trajectories in the vakonomic model satisfy necessary conditions for a minimum in a variational problem with equality constraints. We consider the so-called irregular case of this variational problem, which was not covered by Kozlov, when the trajectory is a singular point of the constraints and the necessary minimum conditions based on the Lagrange principle make no sense. This situation is studied using the theory of abnormal problems developed by the first author. As a result, the classical necessary minimum conditions are strengthened and developed to this class of problems.
Phugoid oscillations in optimal reentry trajectories
NASA Astrophysics Data System (ADS)
Vinh, N. X.; Chern, J. S.; Lin, C. F.
A major problem with operations of lifting reentry vehicle having an aft center-of-gravity location due to large engine mass at the rear is the required hypersonic trim to fight the desired trajectory. This condition is most severe for lifting maneuvers. As a first step toward analyzing this problem, this paper considers the lift requirement for some basic maneuvers in the plane of a great circle. Considerations are given to optimal lift control for achieving the maximization of either the final altitude, speed or range. For the maximum-range problem, phugoid oscillation along an optimal trajectory is less severe as compared to a glide with maximum lift-to-drag ratio. An explicit formula for the number of oscillations for an entry from orbital speed is proposed.
Trajectory analysis for magnetic particle imaging.
Knopp, T; Biederer, S; Sattel, T; Weizenecker, J; Gleich, B; Borgert, J; Buzug, T M
2009-01-21
Recently a new imaging technique called magnetic particle imaging was proposed. The method uses the nonlinear response of magnetic nanoparticles when a time varying magnetic field is applied. Spatial encoding is achieved by moving a field-free point through an object of interest while the field strength in the vicinity of the point is high. A resolution in the submillimeter range is provided even for fast data acquisition sequences. In this paper, a simulation study is performed on different trajectories moving the field-free point through the field of view. The purpose is to provide mandatory information for the design of a magnetic particle imaging scanner. Trajectories are compared with respect to density, speed and image quality when applied in data acquisition. Since simulation of the involved physics is a time demanding task, moreover, an efficient implementation is presented utilizing caching techniques.
Semi-Automatic Determination of Rockfall Trajectories
Volkwein, Axel; Klette, Johannes
2014-01-01
In determining rockfall trajectories in the field, it is essential to calibrate and validate rockfall simulation software. This contribution presents an in situ device and a complementary Local Positioning System (LPS) that allow the determination of parts of the trajectory. An assembly of sensors (herein called rockfall sensor) is installed in the falling block recording the 3D accelerations and rotational velocities. The LPS automatically calculates the position of the block along the slope over time based on Wi-Fi signals emitted from the rockfall sensor. The velocity of the block over time is determined through post-processing. The setup of the rockfall sensor is presented followed by proposed calibration and validation procedures. The performance of the LPS is evaluated by means of different experiments. The results allow for a quality analysis of both the obtained field data and the usability of the rockfall sensor for future/further applications in the field. PMID:25268916
Developmental trajectories to male borderline personality disorder.
Goodman, Marianne; Patel, Uday; Oakes, Allison; Matho, Andrea; Triebwasser, Joseph
2013-12-01
Due to the higher diagnostic prevalence of borderline personality disorder (BPD) in females, there exists a dearth of literature on the manifestations of BPD in men and minimal information on male developmental trajectories to the disorder. To identify precursors of BPD in males, surveys were administered to parents about their BPD male offspring and non-BPD male siblings. Questions covered aspects of probands' lives from infancy to late adolescence. BPD offspring were identified through self-reported clinical diagnoses and standardized diagnostic criteria embedded within the survey. A total of 263 male offspring (97 meeting strict criteria for BPD and 166 non-BPD siblings) were studied. The authors found that parents describe the early emergence of a constellation of symptoms in their BPD sons that include separation anxiety starting in infancy, body image concerns in childhood, and impulsivity, emptiness, and odd thinking in adolescence. This trajectory differs from the developmental course found in females diagnosed with BPD.
Neuroendocrine Tumor: Statistics
... Tumor > Neuroendocrine Tumor: Statistics Request Permissions Neuroendocrine Tumor: Statistics Approved by the Cancer.Net Editorial Board , 11/ ... the body. It is important to remember that statistics on how many people survive this type of ...
Adrenal Gland Tumors: Statistics
... Gland Tumor: Statistics Request Permissions Adrenal Gland Tumor: Statistics Approved by the Cancer.Net Editorial Board , 03/ ... primary adrenal gland tumor is very uncommon. Exact statistics are not available for this type of tumor ...
Outcome Trajectories in Extremely Preterm Infants
Carlo, Waldemar A.; Tyson, Jon E.; Langer, John C.; Walsh, Michele C.; Parikh, Nehal A.; Das, Abhik; Van Meurs, Krisa P.; Shankaran, Seetha; Stoll, Barbara J.; Higgins, Rosemary D.
2012-01-01
OBJECTIVE: Methods are required to predict prognosis with changes in clinical course. Death or neurodevelopmental impairment in extremely premature neonates can be predicted at birth/admission to the ICU by considering gender, antenatal steroids, multiple birth, birth weight, and gestational age. Predictions may be improved by using additional information available later during the clinical course. Our objective was to develop serial predictions of outcome by using prognostic factors available over the course of NICU hospitalization. METHODS: Data on infants with birth weight ≤1.0 kg admitted to 18 large academic tertiary NICUs during 1998–2005 were used to develop multivariable regression models following stepwise variable selection. Models were developed by using all survivors at specific times during hospitalization (in delivery room [n = 8713], 7-day [n = 6996], 28-day [n = 6241], and 36-week postmenstrual age [n = 5118]) to predict death or death/neurodevelopmental impairment at 18 to 22 months. RESULTS: Prediction of death or neurodevelopmental impairment in extremely premature infants is improved by using information available later during the clinical course. The importance of birth weight declines, whereas the importance of respiratory illness severity increases with advancing postnatal age. The c-statistic in validation models ranged from 0.74 to 0.80 with misclassification rates ranging from 0.28 to 0.30. CONCLUSIONS: Dynamic models of the changing probability of individual outcome can improve outcome predictions in preterm infants. Various current and future scenarios can be modeled by input of different clinical possibilities to develop individual “outcome trajectories” and evaluate impact of possible morbidities on outcome. PMID:22689874
Hypersonic Flight Mechanics. [for atmospheric entry trajectories
NASA Technical Reports Server (NTRS)
Busemann, A.; Vinh, N. X.; Culp, R. D.
1976-01-01
The effects of aerodynamic forces on trajectories at orbital speeds are discussed in terms of atmospheric models. The assumptions for the model are spherical symmetry, nonrotating, and an exponential atmosphere. The equations of flight, and the performance in extra-atmospheric flight are discussed along with the return to the atmosphere, and the entry. Solutions of the exact equations using directly matched asymptotic expansions are presented.
Trajectory optimization for kinematically redundant arms
NASA Technical Reports Server (NTRS)
Carignan, Craig R.
1991-01-01
A review of local optimization methods for resolving joint configurations in underconstrained manipulation tasks is conducted. A new approach is developed for observing joint limits and avoiding obstacles during the trajectory planning. The methodology is used in a four-link arm example to avoid a workspace singularity and is compared with results using the extended Moore-Penrose technique. An alternative measure of arm 'manipulability' based directly on the rank of the Jacobian is also introduced.
Efficient Calculation of Earth Penetrating Projectile Trajectories
2006-09-01
seconds and stable trajectories are solved in less than three seconds. 15. NUMBER OF PAGES 119 14 . SUBJECT TERMS Ballistic, Penetration, Simulation...Bottom Half of Weapon from 2 Degree Angle of Attack ............... 14 Figure 9. Moment on Top Half of Weapon from a 2 Degree Angle of Attack... 14 Figure 10. Forces on Bottom Half of Weapon from 2 Degree Angle of Attack ...............15 Figure 11. Additional Areas of Stress Due to
JBoss Middleware for Spacecraft Trajectory Operations
NASA Technical Reports Server (NTRS)
Stensrud, Kjell; Srinivasan, Ravi; Hamm, Dustin
2008-01-01
This viewgraph presentation reviews the use of middleware for spacecraft trajectory planning. It reviews the following areas and questions: 1. Project Background - What is the environment where we are considering Open Source Middleware? 2. System Architecture - What technologies and design did we apply? 3. Testing overview - What are the quality scenarios and test points? 4. Project Conclusion - What did we learn about Open Source Middleware?
Developmental Trajectories of Adolescent Substance Use
ERIC Educational Resources Information Center
Yamada, Samantha; Pepler, Debra; Jiang, Depeng; Cappadocia, M. Catherine; Craig, Wendy; Connolly, Jennifer
2016-01-01
Longitudinal data from 746 adolescents in Toronto, Canada (54% females), was gathered in eight waves over seven years (1995 through 2001), beginning when the youths were 10 to 12 years old (mean age = 11.8, SD = 1.2 years). Five trajectories of substance use were identified: chronic-high, childhood onset-rapid high, childhood onset-moderate,…
Constrained Trajectory Optimization Using Pseudospectral Methods (Preprint)
2008-08-05
at itu de , d eg POST SPOCS Figure 5. Trajectory Comparison of Integration Method Comparison IV.B. Basic Optimization Comparison The second set of...1500 2000 2500 3000 20 30 40 50 60 70 80 90 100 110 120 Altitude Time, sec A lti tu de , k m POST SPOCS Figure 7. Altitude Comparison of the First...Coordinates Z , k m POST SPOCS Figure 8. Range Comparison of the First Optimization Comparison 13 of 33 American Institute of Aeronautics and
Academic trajectories of newcomer immigrant youth.
Suárez-Orozco, Carola; Gaytán, Francisco X; Bang, Hee Jin; Pakes, Juliana; O'Connor, Erin; Rhodes, Jean
2010-05-01
Immigration to the United States presents both challenges and opportunities that affect students' academic achievement. Using a 5-year longitudinal, mixed-methods approach, we identified varying academic trajectories of newcomer immigrant students from Central America, China, the Dominican Republic, Haiti, and Mexico. Latent class growth curve analysis revealed that although some newcomer students performed at high or improving levels over time, others showed diminishing performance. Multinomial logistic regressions identified significant group differences in academic trajectories, particularly between the high-achieving youth and the other groups. In keeping with ecological-developmental and stage-environment fit theories, School Characteristics (school segregation rate, school poverty rate, and student perceptions of school violence), Family Characteristics (maternal education, parental employment, and household structure), and Individual Characteristics (academic English proficiency, academic engagement, psychological symptoms, gender, and 2 age-related risk factors, number of school transitions and being overaged for grade placement) were associated with different trajectories of academic performance. A series of case studies triangulate many of the quantitative findings as well as illuminate patterns that were not detected in the quantitative data. Thus, the mixed-methods approach sheds light on the cumulative developmental challenges that immigrant students face as they adjust to their new educational settings.
Towards Assessing the Human Trajectory Planning Horizon
Nitsch, Verena; Meinzer, Dominik; Wollherr, Dirk
2016-01-01
Mobile robots are envisioned to cooperate closely with humans and to integrate seamlessly into a shared environment. For locomotion, these environments resemble traversable areas which are shared between multiple agents like humans and robots. The seamless integration of mobile robots into these environments requires accurate predictions of human locomotion. This work considers optimal control and model predictive control approaches for accurate trajectory prediction and proposes to integrate aspects of human behavior to improve their performance. Recently developed models are not able to reproduce accurately trajectories that result from sudden avoidance maneuvers. Particularly, the human locomotion behavior when handling disturbances from other agents poses a problem. The goal of this work is to investigate whether humans alter their trajectory planning horizon, in order to resolve abruptly emerging collision situations. By modeling humans as model predictive controllers, the influence of the planning horizon is investigated in simulations. Based on these results, an experiment is designed to identify, whether humans initiate a change in their locomotion planning behavior while moving in a complex environment. The results support the hypothesis, that humans employ a shorter planning horizon to avoid collisions that are triggered by unexpected disturbances. Observations presented in this work are expected to further improve the generalizability and accuracy of prediction methods based on dynamic models. PMID:27936015
Contextualized trajectory parsing with spatiotemporal graph.
Liu, Xiaobai; Lin, Liang; Jin, Hai
2013-12-01
This work investigates how to automatically parse object trajectories in surveillance videos, which aims at jointly solving three subproblems: 1) spatial segmentation, 2) temporal tracking, and 3) object categorization. We present a novel representation spatiotemporal graph (ST-Graph) in which: 1) Graph nodes express the motion primitives, each representing a short sequence of small-size patches over consecutive images, and 2) every two neighbor nodes are linked with either a positive edge or a negative edge to describe their collaborative or exclusive relationship of belonging to the same object trajectory. Phrasing the trajectory parsing as a graph multicoloring problem, we propose a unified probabilistic formulation to integrate various types of context knowledge as informative priors. An efficient composite cluster sampling algorithm is employed in search of the optimal solution by exploiting both the collaborative and the exclusive relationships between nodes. The proposed framework is evaluated over challenging videos from public datasets, and results show that it can achieve state-of-the-art tracking accuracy.
Lunar Ascent and Rendezvous Trajectory Design
NASA Technical Reports Server (NTRS)
Sostaric, Ronald R.; Merriam, Robert S.
2008-01-01
The Lunar Lander Ascent Module (LLAM) will leave the lunar surface and actively rendezvous in lunar orbit with the Crew Exploration Vehicle (CEV). For initial LLAM vehicle sizing efforts, a nominal trajectory, along with required delta-V and a few key sensitivities, is very useful. A nominal lunar ascent and rendezvous trajectory is shown, along with rationale and discussion of the trajectory shaping. Also included are ascent delta-V sensitivities to changes in target orbit and design thrust-to-weight of the vehicle. A sample launch window for a particular launch site has been completed and is included. The launch window shows that budgeting enough delta-V for two missed launch opportunities may be reasonable. A comparison between yaw steering and on-orbit plane change maneuvers is included. The comparison shows that for large plane changes, which are potentially necessary for an anytime return from mid-latitude locations, an on-orbit maneuver is much more efficient than ascent yaw steering. For a planned return, small amounts of yaw steering may be necessary during ascent and must be accounted for in the ascent delta-V budget. The delta-V cost of ascent yaw steering is shown, along with sensitivity to launch site latitude. Some discussion of off-nominal scenarios is also included. In particular, in the case of a failed Powered Descent Initiation burn, the requirements for subsequent rendezvous with the Orion vehicle are outlined.
Trajectories in Close Proximity to Asteroids
NASA Technical Reports Server (NTRS)
Scheeres, D. J.
2000-01-01
Spacecraft motion in close proximity to irregularly shaped, rotating bodies such as asteroids presents a unique dynamical environment as compared to most space missions. There are several fundamental novelties in this environment that spacecraft must deal with. These include the possibility of orbital instabilities that can act over very short time spans (on the order of hours for some systems), possible non-uniform rotation of the central gravity field, divergence of traditional gravity field representations when close to the asteroid surface, dominance of perturbing forces, an extremely large asteroid model parameter space that must be prepared for in the absence of reliable information, and the possibility of employing new and novel trajectory control techniques such as hovering and repeated landings on the asteroid surface. An overview of how these novelties impact the space of feasible close proximity operations and how different asteroid model properties will affect their implementation is given. In so doing, four fundamental types of close proximity operations will be defined. Listed in order of increasing technical difficulty these are: (1) close, stable orbits; (2) low-altitude flyovers; (3) landing trajectories; and (4) hovering trajectories. The feasibility and difficulty of implementing these operations will vary as a function of the asteroid shape, size, density, and rotation properties, and as a function of the spacecraft navigation capability. Additional information is contained in the original extended abstract.
Early predictors of boys’ antisocial trajectories
SHAW, DANIEL S.; HYDE, LUKE W.; BRENNAN, LAURETTA M.
2012-01-01
Despite the large number of studies tracing patterns of youth antisocial behavior (AB) during adolescence, few have prospective data on the developmental precursors of AB beginning during infancy. Using a cohort of 268 low-income boys first assessed at 18 months, the current study examined predictors of early- and late-starting trajectories of AB assessed during early childhood and early adolescence. Four trajectory groups were identified, including early- and late-starting groups, a low stable group, and a high decreasing group, characterized by multiple risk factors during early childhood and early adolescence. During early childhood, parenting and maternal depression discriminated two AB trajectory groups, an early-starting and a high decreasing group, who would go on to demonstrate a high preponderance of juvenile court involvement (60% to 79%) and elevated rates of clinical depression 13 to 15 years later. The results were discussed in reference to targeting malleable family risk factors during early childhood associated with patterns of AB and mental health disorders during adolescence. PMID:22781860
A New Maneuver for Escape Trajectories
NASA Technical Reports Server (NTRS)
Adams, Robert B.
2008-01-01
This presentation put forth a new maneuver for escape trajectories and specifically sought to find an analytical approximation for medium thrust trajectories. In most low thrust derivations the idea is that escape velocity is best achieved by accelerating along the velocity vector. The reason for this is that change in specific orbital energy is a function of velocity and acceleration. However, Levin (1952) suggested that while this is a locally optimal solution it might not be a globally optimal one. Turning acceleration inward would drop periapse giving a higher velocity later in the trajectory. Acceleration at that point would be dotted against a higher magnitude V giving a greater rate of change of mechanical energy. The author then hypothesized that decelerating from the initial orbit and then accelerating at periapse would not lead to a gain in greater specific orbital energy--however, the hypothesis was incorrect. After considerable derivation it was determined that this new maneuver outperforms a direct burn when the overall DeltaV budget exceeds the initial orbital velocity (the author has termed this the Heinlein maneuver). The author provides a physical explanation for this maneuver and presents optimization analyses.
Bullet trajectory reconstruction - Methods, accuracy and precision.
Mattijssen, Erwin J A T; Kerkhoff, Wim
2016-05-01
Based on the spatial relation between a primary and secondary bullet defect or on the shape and dimensions of the primary bullet defect, a bullet's trajectory prior to impact can be estimated for a shooting scene reconstruction. The accuracy and precision of the estimated trajectories will vary depending on variables such as, the applied method of reconstruction, the (true) angle of incidence, the properties of the target material and the properties of the bullet upon impact. This study focused on the accuracy and precision of estimated bullet trajectories when different variants of the probing method, ellipse method, and lead-in method are applied on bullet defects resulting from shots at various angles of incidence on drywall, MDF and sheet metal. The results show that in most situations the best performance (accuracy and precision) is seen when the probing method is applied. Only for the lowest angles of incidence the performance was better when either the ellipse or lead-in method was applied. The data provided in this paper can be used to select the appropriate method(s) for reconstruction and to correct for systematic errors (accuracy) and to provide a value of the precision, by means of a confidence interval of the specific measurement.
Unstable trajectories and the quantum mechanical uncertainty
Moser, Hans R.
2008-08-15
There is still an ongoing discussion about various seemingly contradictory aspects of classical particle motion and its quantum mechanical counterpart. One of the best accepted viewpoints that intend to bridge the gap is the so-called Copenhagen Interpretation. A major issue there is to regard wave functions as probability amplitudes (usually for the position of a particle). However, the literature also reports on approaches that claim a trajectory for any quantum mechanical particle, Bohmian mechanics probably being the most prominent one among these ideas. We introduce a way to calculate trajectories as well, but our crucial ingredient is their well controlled local (thus also momentaneous) degree of instability. By construction, at every moment their unpredictability, i.e., their local separation rates of neighboring trajectories, is governed by the local value of the given modulus square of a wave function. We present extensive numerical simulations of the H and He atom, and for some velocity-related quantities, namely angular momentum and total energy, we inspect their agreement with the values appearing in wave mechanics. Further, we interpret the archetypal double slit interference experiment in the spirit of our findings. We also discuss many-particle problems far beyond He, which guides us to a variety of possible applications.
Trajectories of adjustment to couple relationship separation.
Halford, W Kim; Sweeper, Susie
2013-06-01
To test a stress-diathesis model of adjustment to separation, the current study describes the trajectories of different aspects of separation adjustment in people formerly married or cohabiting, and moderators of those trajectories. A convenience sample of 303 recently separated individuals (169 women; 134 men) completed assessments of their emotional attachment to the former partner, loneliness, psychological distress, and coparenting conflict at two time points 6 months apart. Multilevel modeling of the overlapping multicohort design was used to estimate the trajectories of these different aspects of adjustment as a function of time since separation, marital status, gender, presence of children from the relationship, who initiated separation, social support, and anxious attachment. Attachment to the former partner, loneliness, and psychological distress were initially high but improved markedly across the 2 years after separation, but coparenting conflict was high and stable. Adjustment problems were similar in men and women, and in those formerly married or cohabiting, except that reported coparenting conflict was higher in men than women. Low social support and high anxious attachment predicted persistent attachment to the former partner, loneliness, and psychological distress. Coparenting conflict is a common, chronic problem for many separated individuals, and individuals with certain psychological vulnerabilities also experience chronic personal distress.
NASA Technical Reports Server (NTRS)
Manning, Robert M.
1987-01-01
A dynamic rain attenuation prediction model is developed for use in obtaining the temporal characteristics, on time scales of minutes or hours, of satellite communication link availability. Analagous to the associated static rain attenuation model, which yields yearly attenuation predictions, this dynamic model is applicable at any location in the world that is characterized by the static rain attenuation statistics peculiar to the geometry of the satellite link and the rain statistics of the location. Such statistics are calculated by employing the formalism of Part I of this report. In fact, the dynamic model presented here is an extension of the static model and reduces to the static model in the appropriate limit. By assuming that rain attenuation is dynamically described by a first-order stochastic differential equation in time and that this random attenuation process is a Markov process, an expression for the associated transition probability is obtained by solving the related forward Kolmogorov equation. This transition probability is then used to obtain such temporal rain attenuation statistics as attenuation durations and allowable attenuation margins versus control system delay.
STATISTICAL ANALYSIS, REPORTS), (*PROBABILITY, REPORTS), INFORMATION THEORY, DIFFERENTIAL EQUATIONS, STATISTICAL PROCESSES, STOCHASTIC PROCESSES, MULTIVARIATE ANALYSIS, DISTRIBUTION THEORY , DECISION THEORY, MEASURE THEORY, OPTIMIZATION
Monocular motion adaptation affects the perceived trajectory of stereomotion
NASA Technical Reports Server (NTRS)
Brooks, Kevin R.
2002-01-01
Perceived stereomotion trajectory was measured before and after adaptation to lateral motion in the dominant or nondominant eye to assess the relative contributions of 2 cues: changing disparity and interocular velocity difference. Perceived speed for monocular lateral motion and perceived binocular visual direction (BVD) was also assessed. Unlike stereomotion trajectory perception, the BVD of static targets showed an ocular dominance bias, even without adaptation. Adaptation caused equivalent biases in perceived trajectory and monocular motion speed, without significantly affecting perceived BVD. Predictions from monocular motion data closely match trajectory perception data, unlike those from BVD sources. The results suggest that the interocular velocity differences make a significant contribution to stereomotion trajectory perception.
Improved Propulsion Modeling for Low-Thrust Trajectory Optimization
NASA Technical Reports Server (NTRS)
Knittel, Jeremy M.; Englander, Jacob A.; Ozimek, Martin T.; Atchison, Justin A.; Gould, Julian J.
2017-01-01
Low-thrust trajectory design is tightly coupled with spacecraft systems design. In particular, the propulsion and power characteristics of a low-thrust spacecraft are major drivers in the design of the optimal trajectory. Accurate modeling of the power and propulsion behavior is essential for meaningful low-thrust trajectory optimization. In this work, we discuss new techniques to improve the accuracy of propulsion modeling in low-thrust trajectory optimization while maintaining the smooth derivatives that are necessary for a gradient-based optimizer. The resulting model is significantly more realistic than the industry standard and performs well inside an optimizer. A variety of deep-space trajectory examples are presented.
Optimization and guidance of trajectories for coplanar, aeroassisted orbital transfer
NASA Astrophysics Data System (ADS)
Miele, A.; Wang, T.; Lee, W. Y.
1990-09-01
Guidance trajectories for coplanar aeroassisted orbital transfer (AOT) from high earth orbit to LEO are presently optimized under the assumption of trajectory control during its endoatmospheric phase by alpha-dependent lift coefficient. Optimal trajectories are first computed by minimizing the total velocity impulse required for AOT; attention is then given to guidance trajectories capable of approximating such key properties of the optimal trajectories as minimum altitude, exit velocity, and exit path inclination, in real time. A switch is made from target-altitude guidance to target path inclination-guidance according to the velocity depletion required for optimum flight.
Deriving average delay of traffic flow around intersections from vehicle trajectory data
NASA Astrophysics Data System (ADS)
Zhao, Minyue; Li, Xiang
2013-03-01
Advances of positioning and wireless communication technologies make it possible to collect a large number of trajectory data of moving vehicles in a fast and convenient fashion. The data can be applied to various fields such as traffic study. In this paper, we attempt to derive average delay of traffic flow around intersections and verify the results with changes of time. The intersection zone is delineated first. Positioning points geographically located within this zone are selected, and then outliers are removed. Turn trips are extracted from selected trajectory data. Each trip, physically consisting of time-series positioning points, is identified with entry road segment and turning direction, i.e. target road segment. Turn trips are grouped into different categories according to their time attributes. Then, delay of each trip during a turn is calculated with its recorded speed. Delays of all trips in the same period of time are plotted to observe the change pattern of traffic conditions. Compared to conventional approaches, the proposed method can be applied to those intersections without fixed data collection devices such as loop detectors since a large number of trajectory data can always provide a more complete spatio-temporal picture of a road network. With respect to data availability, taxi trajectory data and an intersection in Shanghai are employed to test the proposed methodology. Results demonstrate its applicability.
Early life growth trajectories and future risk for overweight
Jones-Smith, J C; Neufeld, L M; Laraia, B; Ramakrishnan, U; Garcia-Guerra, A; Fernald, L C H
2013-01-01
Objective: Standard approaches have found that rapid growth during the first 2 years of life is a risk factor for overweight in later childhood. Our objective was to test whether growth velocity, independent of concurrent size, was associated with overweight using a nonlinear random-effects model that allows for enhanced specifications and estimations. Methods: Longitudinal data from a birth cohort in Mexico (n=586) were used to estimate growth trajectories over 0–24 months for body mass index (BMI), length and weight using the SuperImposition by Translation and Rotation (SITAR) models. The SITAR models use a nonlinear random-effects model to estimate an average growth curve for BMI, length and weight and each participant's deviation from this curve on three dimensions—size, velocity and timing of peak velocity. We used logistic regression to estimate the association between overweight status at 7–9 years and size, velocity and timing of BMI, length and weight trajectories during 0–24 months. We tested whether any association between velocity and overweight varied by relative size during 0–24 months or birth weight. Results: SITAR models explained the majority of the variance in BMI (73%), height (86%) and weight (85%) between 0–24 months. When analyzed individually, relative BMI/length/weight (size) and BMI/length/weight velocity during 0–24 months were each associated with increased odds of overweight in late childhood. Associations for timing of peak velocity varied by anthropometric measure. However, in the mutually adjusted models, only relative BMI/length/weight (size) remained statistically significant. We found no evidence that any association between velocity and overweight varied by size during 0–24 months or birth weight. Conclusions: After mutual adjustment, size during 0–24 months of life (as opposed to birth size), but not velocity or timing of peak velocity, was most consistently associated with overweight in later childhood. PMID
Trajectory optimization for a hypersonic vehicle with constraint
NASA Astrophysics Data System (ADS)
Morimoto, Hitoshi
A new approach was developed to solve fuel-optimal problems for a hypersonic vehicle over an entire flight trajectory. A realistic vehicle model was proposed. Although shooting methods are accurate if they converge, initial guesses for costate variables which make the calculation to converge are difficult to obtain. The proposed approach allowed to divide an entire flight trajectory into two segments by selecting a connecting point in the middle of the trajectory. From the connecting point, a maximum-glide problem was solved first. It was proved that when a certain boundary conditions are satisfied, the maximum-glide trajectory constitutes a fuel-optimal trajectory over an entire flight profile. Determination of the maximum-glide trajectory provides with some of the initial values of the costate variables which are needed to start integration backwards from the connecting point. Since shooting methods are very sensitive to the initial guesses of the costates, obtaining accurate initial values of some of the costates is a large advantage. By combining the maximum-glide trajectory and the trajectory obtained by backward integration from the connecting point, an entire flight trajectory was obtained. This trajectory, in general, does not satisfy all the boundary conditions imposed. However, by adjusting the connecting points, the resulting entire flight trajectory approached the final solution. Periodic optimal cruise control problems were also solved with inequality constraints.
Statistical mechanics of nucleosomes
NASA Astrophysics Data System (ADS)
Chereji, Razvan V.
Eukaryotic cells contain long DNA molecules (about two meters for a human cell) which are tightly packed inside the micrometric nuclei. Nucleosomes are the basic packaging unit of the DNA which allows this millionfold compactification. A longstanding puzzle is to understand the principles which allow cells to both organize their genomes into chromatin fibers in the crowded space of their nuclei, and also to keep the DNA accessible to many factors and enzymes. With the nucleosomes covering about three quarters of the DNA, their positions are essential because these influence which genes can be regulated by the transcription factors and which cannot. We study physical models which predict the genome-wide organization of the nucleosomes and also the relevant energies which dictate this organization. In the last five years, the study of chromatin knew many important advances. In particular, in the field of nucleosome positioning, new techniques of identifying nucleosomes and the competing DNA-binding factors appeared, as chemical mapping with hydroxyl radicals, ChIP-exo, among others, the resolution of the nucleosome maps increased by using paired-end sequencing, and the price of sequencing an entire genome decreased. We present a rigorous statistical mechanics model which is able to explain the recent experimental results by taking into account nucleosome unwrapping, competition between different DNA-binding proteins, and both the interaction between histones and DNA, and between neighboring histones. We show a series of predictions of our new model, all in agreement with the experimental observations.
Zheng, Xiujun; Chaudhari, Rahul; Wu, Chunhui; Mehbod, Amir A; Transfeldt, Ensor E
2010-01-01
Successful placement of cervical pedicle screws requires accurate identification of both entry point and trajectory. However, literature has not provided consistent recommendations regarding the direction of pedicle screw insertion and entry point location. The objective of this study was to define a guideline regarding the optimal entry point and trajectory in placing subaxial cervical pedicle screws and to evaluate the screw accuracy in cadaver cervical spines. The guideline for entry point and trajectory for each vertebra was established based on the recently published morphometric data. Six fresh frozen cervical spines (C3-C7) were used. There were two men and four women. After posterior exposure, the entry point was determined and the cortical bone of the entry point was removed using a 2-mm burr. Pilot holes were created with a cervical probe based on the guideline using fluoroscopy. After tapping, 3.5-mm screws with appropriate length were inserted. After screw insertion, every vertebra was dissected and inspected for pedicle breach. The pedicle width, height, pedicle transverse angulation and actual screw insertion angle were measured. A total of 60 pedicle screws were inserted. No statistical difference in pedicle width and height was found between the left and right sides for each level. The overall accuracy of pedicle screws was 83.3%. The remaining 13.3% screws had noncritical breach, and 3.3% had critical breach. The critical breach was not caused by the guideline. There was no statistical difference between the pedicle transverse angulation and the actual screw trajectory created using the guideline. There was statistical difference in pedicle width between the breach and non-breach screws. In conclusion, high success rate of subaxial cervical pedicle screw placement can be achieved using the recently proposed operative guideline and oblique views of fluoroscopy. However, careful preoperative planning and good surgical skills are still required to
Trajectory analysis and optimization system (TAOS) user`s manual
Salguero, D.E.
1995-12-01
The Trajectory Analysis and Optimization System (TAOS) is software that simulates point--mass trajectories for multiple vehicles. It expands upon the capabilities of the Trajectory Simulation and Analysis program (TAP) developed previously at Sandia National Laboratories. TAOS is designed to be a comprehensive analysis tool capable of analyzing nearly any type of three degree-of-freedom, point-mass trajectory. Trajectories are broken into segments, and within each segment, guidance rules provided by the user control how the trajectory is computed. Parametric optimization provides a powerful method for satisfying mission-planning constraints. Althrough TAOS is not interactive, its input and output files have been designed for ease of use. When compared to TAP, the capability to analyze trajectories for more than one vehicle is the primary enhancement, although numerous other small improvements have been made. This report documents the methods used in TAOS as well as the input and output file formats.
Ares I-X Best Estimated Trajectory Analysis and Results
NASA Technical Reports Server (NTRS)
Karlgaard, Christopher D.; Beck, Roger E.; Starr, Brett R.; Derry, Stephen D.; Brandon, Jay; Olds, Aaron D.
2011-01-01
The Ares I-X trajectory reconstruction produced best estimated trajectories of the flight test vehicle ascent through stage separation, and of the first and upper stage entries after separation. The trajectory reconstruction process combines on-board, ground-based, and atmospheric measurements to produce the trajectory estimates. The Ares I-X vehicle had a number of on-board and ground based sensors that were available, including inertial measurement units, radar, air-data, and weather balloons. However, due to problems with calibrations and/or data, not all of the sensor data were used. The trajectory estimate was generated using an Iterative Extended Kalman Filter algorithm, which is an industry standard processing algorithm for filtering and estimation applications. This paper describes the methodology and results of the trajectory reconstruction process, including flight data preprocessing and input uncertainties, trajectory estimation algorithms, output transformations, and comparisons with preflight predictions.
Matching trajectory optimization and nonlinear tracking control for HALE
NASA Astrophysics Data System (ADS)
Lee, Sangjong; Jang, Jieun; Ryu, Hyeok; Lee, Kyun Ho
2014-11-01
This paper concerns optimal trajectory generation and nonlinear tracking control for stratospheric airship platform of VIA-200. To compensate for the mismatch between the point-mass model of optimal trajectory and the 6-DOF model of the nonlinear tracking problem, a new matching trajectory optimization approach is proposed. The proposed idea reduces the dissimilarity of both problems and reduces the uncertainties in the nonlinear equations of motion for stratospheric airship. In addition, its refined optimal trajectories yield better results under jet stream conditions during flight. The resultant optimal trajectories of VIA-200 are full three-dimensional ascent flight trajectories reflecting the realistic constraints of flight conditions and airship performance with and without a jet stream. Finally, 6-DOF nonlinear equations of motion are derived, including a moving wind field, and the vectorial backstepping approach is applied. The desirable tracking performance is demonstrated that application of the proposed matching optimization method enables the smooth linkage of trajectory optimization to tracking control problems.
Downer, Brian; Estus, Steven; Katsumata, Yuriko; Fardo, David W.
2014-01-01
Background: Previous research indicates that total cholesterol levels increase with age during young adulthood and middle age and decline with age later in life. This is attributed to changes in diet, body composition, medication use, physical activity, and hormone levels. In the current study we utilized data from the Framingham Heart Study Original Cohort to determine if variations in apolipoprotein E (APOE), a gene involved in regulating cholesterol homeostasis, influence trajectories of total cholesterol, HDL cholesterol, and total: HDL cholesterol ratio from midlife through late life. Methods: Cholesterol trajectories from midlife through late life were modeled using generalized additive mixed models and mixed-effects regression models. Results: APOE e2+ subjects had lower total cholesterol levels, higher HDL cholesterol levels, and lower total: HDL cholesterol ratios from midlife to late life compared to APOE e3 and APOE e4+ subjects. Statistically significant differences in life span cholesterol trajectories according to gender and use of cholesterol-lowering medications were also detected. Conclusion: The findings from this research provide evidence that variations in APOE modify trajectories of serum cholesterol from midlife to late life. In order to efficiently modify cholesterol through the life span, it is important to take into account APOE allele status. PMID:25325355
NASA Astrophysics Data System (ADS)
Koo, Peter K.; Mochrie, Simon G. J.
2016-11-01
The stochastic motions of a diffusing particle contain information concerning the particle's interactions with binding partners and with its local environment. However, an accurate determination of the underlying diffusive properties, beyond normal diffusion, has remained challenging when analyzing particle trajectories on an individual basis. Here, we introduce the maximum-likelihood estimator (MLE) for confined diffusion and fractional Brownian motion. We demonstrate that this MLE yields improved estimation over traditional mean-square displacement analyses. We also introduce a model selection scheme (that we call mleBIC) that classifies individual trajectories to a given diffusion mode. We demonstrate the statistical limitations of classification via mleBIC using simulated data. To overcome these limitations, we introduce a version of perturbation expectation-maximization (pEMv2), which simultaneously analyzes a collection of particle trajectories to uncover the system of interactions that give rise to unique normal and/or non-normal diffusive states within the population. We test and evaluate the performance of pEMv2 on various sets of simulated particle trajectories, which transition among several modes of normal and non-normal diffusion, highlighting the key considerations for employing this analysis methodology.
Koracin, Darko; Vellore, Ramesh; Lowenthal, Douglas H; Watson, John G; Koracin, Julide; McCord, Travis; DuBois, David W; Chen, L W Antony; Kumar, Naresh; Knipping, Eladio M; Wheeler, Neil J M; Craig, Kenneth; Reid, Stephen
2011-06-01
The main objective of this study was to investigate the capabilities of the receptor-oriented inverse mode Lagrangian Stochastic Particle Dispersion Model (LSPDM) with the 12-km resolution Mesoscale Model 5 (MM5) wind field input for the assessment of source identification from seven regions impacting two receptors located in the eastern United States. The LSPDM analysis was compared with a standard version of the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) single-particle backward-trajectory analysis using inputs from MM5 and the Eta Data Assimilation System (EDAS) with horizontal grid resolutions of 12 and 80 km, respectively. The analysis included four 7-day summertime events in 2002; residence times in the modeling domain were computed from the inverse LSPDM runs and HYPSLIT-simulated backward trajectories started from receptor-source heights of 100, 500, 1000, 1500, and 3000 m. Statistics were derived using normalized values of LSPDM- and HYSPLIT-predicted residence times versus Community Multiscale Air Quality model-predicted sulfate concentrations used as baseline information. From 40 cases considered, the LSPDM identified first- and second-ranked emission region influences in 37 cases, whereas HYSPLIT-MM5 (HYSPLIT-EDAS) identified the sources in 21 (16) cases. The LSPDM produced a higher overall correlation coefficient (0.89) compared with HYSPLIT (0.55-0.62). The improvement of using the LSPDM is also seen in the overall normalized root mean square error values of 0.17 for LSPDM compared with 0.30-0.32 for HYSPLIT. The HYSPLIT backward trajectories generally tend to underestimate near-receptor sources because of a lack of stochastic dispersion of the backward trajectories and to overestimate distant sources because of a lack of treatment of dispersion. Additionally, the HYSPLIT backward trajectories showed a lack of consistency in the results obtained from different single vertical levels for starting the backward trajectories. To
Beyond experimentation: Five trajectories of cigarette smoking in a longitudinal sample of youth
Lisha, Nadra E.
2017-01-01
The first goal of this study was to identify the most appropriate measure of cigarette smoking for identifying unique smoking trajectories among adolescents; the second goal was to describe the resulting trajectories and their characteristics. Using 15 annual waves of smoking data in the National Longitudinal Survey of Youth 1997 (NLSY97), we conducted an exploratory latent class growth analysis to determine the best of four outcome variables for yearly smoking (cigarettes per day on days smoked, days smoked per month, mean cigarettes per day, and total cigarettes per month) among individuals aged 12 to 30 (n = 8,791). Days smoked per month was the best outcome variable for identifying unique longitudinal trajectories of smoking and characteristics of these trajectories that could be used to target different types of smokers for prevention and cessation. Objective statistics were used to identify four trajectories in addition to never smokers (34.1%): experimenters (13.6%), quitters (8.1%), early established smokers (39.0%), and late escalators (5.2%). We identified a quitter and late escalator class not identified in the only other comparable latent class growth analysis. Logistic regressions were used to identify the characteristics of individuals in each trajectory. Compared with never smokers, all trajectories except late escalators were less likely to be black; experimenters were more likely to be out of school and unemployed and drink alcohol in adolescence; quitters were more likely to have a mother with a high school degree/GED or higher (versus none) and to use substances in adolescence and less likely to have ever married as a young adult; early established smokers were more likely to have a mother with a high school diploma or GED, be out of school and unemployed, not live with both parents, have used substances, be depressed, and have peers who smoked in adolescence and to have children as young adults and less likely to be Hispanic and to have ever
Shearer, Dara M; Thomson, W Murray; Broadbent, Jonathan M; McLean, Rachael; Poulton, Richie; Mann, Jim
2016-01-01
Objective To describe the natural history of glycemia (as measured by glycated hemoglobin (HbA1c)) over 12 years using group-based trajectory modeling (GBTM), and to examine baseline predictors of trajectory. Research design and methods HbA1c data collected at ages 26, 32 and 38 in the long-running, prospective Dunedin Multidisciplinary Health and Development Study were used to assign study members (n=893) to trajectories applying GBTM. A generalization of the model allowed the statistical linking of baseline demographic, smoking and anthropometric characteristics to group membership probability. Results Mean HbA1c increased with age, as did prevalence of prediabetes, diabetes and dysglycemia. The greatest increase occurred between ages 26 and 32. Glycemic health status at age 26 predicted glycemic health status at age 38. 3 HbA1c trajectory groups were identified: ‘low’ (n=98, 11.0%); ‘medium’ (n=482, 54.0%); and ‘high’ (n=313, 35.0%) with mean HbA1c of 29.6, 34.1, and 38.7 mmol/mol, respectively, at age 38. High waist circumference (≥880 mm for women and ≥1020 mm for men), high waist-height ratio (≥0.50), and being a smoker at age 26 predicted membership of the least favorable trajectory over the next 12 years. High body mass index (≥30) at age 26 did not predict of trajectory. Conclusions Trajectories of HbA1c are established relatively early in adulthood. HbA1c levels, waist circumference, waist-height ratio, and smoking status at age 26 are valid clinical predictors for future dysglycemic risk. The identification of HbA1c trajectories and their predictors introduces the possibility of an individualized approach to prevention at an earlier stage than is currently done. PMID:27648291
Statistical Reference Datasets
National Institute of Standards and Technology Data Gateway
Statistical Reference Datasets (Web, free access) The Statistical Reference Datasets is also supported by the Standard Reference Data Program. The purpose of this project is to improve the accuracy of statistical software by providing reference datasets with certified computational results that enable the objective evaluation of statistical software.
Explorations in statistics: statistical facets of reproducibility.
Curran-Everett, Douglas
2016-06-01
Learning about statistics is a lot like learning about science: the learning is more meaningful if you can actively explore. This eleventh installment of Explorations in Statistics explores statistical facets of reproducibility. If we obtain an experimental result that is scientifically meaningful and statistically unusual, we would like to know that our result reflects a general biological phenomenon that another researcher could reproduce if (s)he repeated our experiment. But more often than not, we may learn this researcher cannot replicate our result. The National Institutes of Health and the Federation of American Societies for Experimental Biology have created training modules and outlined strategies to help improve the reproducibility of research. These particular approaches are necessary, but they are not sufficient. The principles of hypothesis testing and estimation are inherent to the notion of reproducibility in science. If we want to improve the reproducibility of our research, then we need to rethink how we apply fundamental concepts of statistics to our science.
NASA Technical Reports Server (NTRS)
Idris, Husni; Vivona, Robert A.; Al-Wakil, Tarek
2009-01-01
This document describes exploratory research on a distributed, trajectory oriented approach for traffic complexity management. The approach is to manage traffic complexity based on preserving trajectory flexibility and minimizing constraints. In particular, the document presents metrics for trajectory flexibility; a method for estimating these metrics based on discrete time and degree of freedom assumptions; a planning algorithm using these metrics to preserve flexibility; and preliminary experiments testing the impact of preserving trajectory flexibility on traffic complexity. The document also describes an early demonstration capability of the trajectory flexibility preservation function in the NASA Autonomous Operations Planner (AOP) platform.
On trajectory-based nonadiabatic dynamics: Bohmian dynamics versus trajectory surface hopping
NASA Astrophysics Data System (ADS)
Curchod, Basile F. E.; Tavernelli, Ivano
2013-05-01
In this work, we present a complete derivation of the NonAdiabatic Bohmian DYnamics (NABDY) equations of motion. This approach naturally emerges from a transformation of the molecular time-dependent Schrödinger equation in the adiabatic representation of the electronic states. The numerical implementation of the method is discussed while simple nonadiabatic models are employed to address the accuracy of NABDY and to reveal its ability to capture nuclear quantum effects that are missed in trajectory surface hopping (TSH) due to the independent trajectory approximation. A careful comparison of the correlated, NABDY, and the uncorrelated, TSH, propagation is also given together with a description of the main approximations and assumptions underlying the "derivation" of a nonadiabatic molecular dynamics scheme based on classical trajectories.
On trajectory-based nonadiabatic dynamics: Bohmian dynamics versus trajectory surface hopping.
Curchod, Basile F E; Tavernelli, Ivano
2013-05-14
In this work, we present a complete derivation of the NonAdiabatic Bohmian DYnamics (NABDY) equations of motion. This approach naturally emerges from a transformation of the molecular time-dependent Schrödinger equation in the adiabatic representation of the electronic states. The numerical implementation of the method is discussed while simple nonadiabatic models are employed to address the accuracy of NABDY and to reveal its ability to capture nuclear quantum effects that are missed in trajectory surface hopping (TSH) due to the independent trajectory approximation. A careful comparison of the correlated, NABDY, and the uncorrelated, TSH, propagation is also given together with a description of the main approximations and assumptions underlying the "derivation" of a nonadiabatic molecular dynamics scheme based on classical trajectories.
NASA Technical Reports Server (NTRS)
Lugo, Rafael A.; Shidner, Jeremy D.; Powell, Richard W.; Marsh, Steven M.; Hoffman, James A.; Litton, Daniel K.; Schmitt, Terri L.
2017-01-01
The Program to Optimize Simulated Trajectories II (POST2) has been continuously developed for over 40 years and has been used in many flight and research projects. Recently, there has been an effort to improve the POST2 architecture by promoting modularity, flexibility, and ability to support multiple simultaneous projects. The purpose of this paper is to provide insight into the development of trajectory simulation in POST2 by describing methods and examples of various improved models for a launch vehicle liftoff and ascent.
The ESA's Space Trajectory Analysis software suite
NASA Astrophysics Data System (ADS)
Ortega, Guillermo
The European Space Agency (ESA) initiated in 2005 an internal activity to develop an open source software suite involving university science departments and research institutions all over the world. This project is called the "Space Trajectory Analysis" or STA. This article describes the birth of STA and its present configuration. One of the STA aims is to promote the exchange of technical ideas, and raise knowledge and competence in the areas of applied mathematics, space engineering, and informatics at University level. Conceived as a research and education tool to support the analysis phase of a space mission, STA is able to visualize a wide range of space trajectories. These include among others ascent, re-entry, descent and landing trajectories, orbits around planets and moons, interplanetary trajectories, rendezvous trajectories, etc. The article explains that STA project is an original idea of the Technical Directorate of ESA. It was born in August 2005 to provide a framework in astrodynamics research at University level. As research and education software applicable to Academia, a number of Universities support this development by joining ESA in leading the development. ESA and Universities partnership are expressed in the STA Steering Board. Together with ESA, each University has a chair in the board whose tasks are develop, control, promote, maintain, and expand the software suite. The article describes that STA provides calculations in the fields of spacecraft tracking, attitude analysis, coverage and visibility analysis, orbit determination, position and velocity of solar system bodies, etc. STA implements the concept of "space scenario" composed of Solar system bodies, spacecraft, ground stations, pads, etc. It is able to propagate the orbit of a spacecraft where orbital propagators are included. STA is able to compute communication links between objects of a scenario (coverage, line of sight), and to represent the trajectory computations and
Quantum Estimation, meet Computational Statistics; Computational Statistics, meet Quantum Estimation
NASA Astrophysics Data System (ADS)
Ferrie, Chris; Granade, Chris; Combes, Joshua
2013-03-01
Quantum estimation, that is, post processing data to obtain classical descriptions of quantum states and processes, is an intractable problem--scaling exponentially with the number of interacting systems. Thankfully there is an entire field, Computational Statistics, devoted to designing algorithms to estimate probabilities for seemingly intractable problems. So, why not look to the most advanced machine learning algorithms for quantum estimation tasks? We did. I'll describe how we adapted and combined machine learning methodologies to obtain an online learning algorithm designed to estimate quantum states and processes.
Gestational weight gain trajectories in primary care
Piccinini-Vallis, Helena; Lee-Baggley, Dayna; Stewart, Moira; Ryan, Bridget
2016-01-01
Objective To identify gestational weight gain trajectories, stratified by prepregnancy body mass index (BMI), of women with singleton pregnancies who received prenatal care in a primary care setting, and to compare these trajectories with the 2009 Institute of Medicine gestational weight gain recommendations. Design Retrospective cohort study. Setting Halifax, NS. Participants Women who received prenatal care at the Dalhousie Family Medicine clinics in Halifax from 2009 to 2013. Main outcome measures For each prenatal visit, gestational age and weight measurements were obtained. Multilevel modeling was used to analyze the gestational weight gain trajectories. The upper limit of the guideline-recommended weekly gestational weight gain was compared with the 95% CI of the observed mean weekly gestational weight gain for each prepregnancy BMI category. Results A total of 280 women were included in the analyses. There was a significant interaction between prepregnancy BMI category and gestational weight gain over time (P < .001), with gestational weight gain being significantly lower among women with prepregnancy BMI of 30.0 kg/m2 or greater compared with those with BMI of 18.5 to less than 25.0 kg/m2 and 25.0 to less than 30.0 kg/m2. When comparing women’s weight gain with the recommendations, women with prepregnancy BMI of 25.0 to less than 30.0 kg/m2 had the most guideline discordance, deviating from the weight gain recommendations at 20 weeks’ gestation. Conclusion These results are relevant and of benefit to women and clinicians wishing to address excess gestational weight gain, and to researchers and policy makers developing interventions aimed at curbing gestational weight gain in primary care. Although our results showed women with prepregnancy BMI of 25.0 to less than 30.0 kg/m2 gained the most excess, guideline-discordant weight, interventions should target all women planning or experiencing a pregnancy.
Lagrangian Trajectory Modeling of Lunar Dust Particles
NASA Technical Reports Server (NTRS)
Lane, John E.; Metzger, Philip T.; Immer, Christopher D.
2008-01-01
Apollo landing videos shot from inside the right LEM window, provide a quantitative measure of the characteristics and dynamics of the ejecta spray of lunar regolith particles beneath the Lander during the final 10 [m] or so of descent. Photogrammetry analysis gives an estimate of the thickness of the dust layer and angle of trajectory. In addition, Apollo landing video analysis divulges valuable information on the regolith ejecta interactions with lunar surface topography. For example, dense dust streaks are seen to originate at the outer rims of craters within a critical radius of the Lander during descent. The primary intent of this work was to develop a mathematical model and software implementation for the trajectory simulation of lunar dust particles acted on by gas jets originating from the nozzle of a lunar Lander, where the particle sizes typically range from 10 micron to 500 micron. The high temperature, supersonic jet of gas that is exhausted from a rocket engine can propel dust, soil, gravel, as well as small rocks to high velocities. The lunar vacuum allows ejected particles to travel great distances unimpeded, and in the case of smaller particles, escape velocities may be reached. The particle size distributions and kinetic energies of ejected particles can lead to damage to the landing spacecraft or to other hardware that has previously been deployed in the vicinity. Thus the primary motivation behind this work is to seek a better understanding for the purpose of modeling and predicting the behavior of regolith dust particle trajectories during powered rocket descent and ascent.
The Trajectory of the Chelyabinsk Impactor
NASA Astrophysics Data System (ADS)
Chodas, Paul; Chesley, Steven R.
2014-05-01
On February 15, 2013, a small asteroid called 2012 DA14 was about to make a much anticipated extremely close flyby of the Earth, when an even smaller asteroid stole the show by impacting into the Earth's atmosphere near Chelyabinsk, Russia, releasing half a megaton of energy and creating a shock wave that reportedly injured more than a thousand people. The passage of a 40-meter asteroid within the ring of geosynchrounous satellites is rare, calculated to be a once-in-40-year event, and yet it was upstaged on the same day by an actual Earth impact of a previously unseen 20-meter asteroid, an event expected to occur only about once per century, on average. Infrasound-based estimates of the released energy from this impact lie in the range of from 450 to 700 kilotons, making the Chelyabinsk fireball the largest impact event since the Tunguska explosion over Siberia in 1908. We have analyzed the approach trajectory of the impactor using impact event data provide U.S. Government sensors. We compare our results with other more detailed analyses of the trajectory. All of the analyses indicate that the asteroid approached the Earth from within 20 degrees of the sunline. Clearly, this object could not have been detected on its final approach by any of the asteroid search programs, unlike the even smaller asteroid 2008 TC3, which was discovered as it approached the Earth from near the opposition point. It is also clear that the east-to-west trajectory of the Chelyabinsk impactor was very different from the south-to-north path of 2012 DA14, implying that the two asteroids were unrelated.
Trajectory Design Considerations for Exploration Mission 1
NASA Technical Reports Server (NTRS)
Dawn, Timothy F.; Gutkowski, Jeffrey P.; Batcha, Amelia L.
2017-01-01
Exploration Mission 1 (EM-1) will be the first mission to send an uncrewed Orion vehicle to cislunar space in 2018, targeted to a Distant Retrograde Orbit (DRO). Analysis of EM-1 DRO mission opportunities in 2018 help characterize mission parameters that are of interest to other subsystems (e.g., power, thermal, communications, flight operations, etc). Subsystems request mission design trades which include: landing lighting, addition of an Orion main engine checkout burn, and use of auxiliary thruster only cases. This paper examines the evolving trade studies that incorporate subsystem feedback and demonstrate the feasibility of these constrained mission trajectory designs and contingencies.
Design of Quiet Rotorcraft Approach Trajectories
NASA Technical Reports Server (NTRS)
Padula, Sharon L.; Burley, Casey L.; Boyd, D. Douglas, Jr.; Marcolini, Michael A.
2009-01-01
A optimization procedure for identifying quiet rotorcraft approach trajectories is proposed and demonstrated. The procedure employs a multi-objective genetic algorithm in order to reduce noise and create approach paths that will be acceptable to pilots and passengers. The concept is demonstrated by application to two different helicopters. The optimized paths are compared with one another and to a standard 6-deg approach path. The two demonstration cases validate the optimization procedure but highlight the need for improved noise prediction techniques and for additional rotorcraft acoustic data sets.
Flow Trajectories in Friction Stir Welding
NASA Technical Reports Server (NTRS)
Bernstein, Edward L.
1999-01-01
In the Friction Stir Welding (FSW) process, a rotating, shouldered tool with a threaded pin is inserted under pressure along the seam of two pieces of metal which are tightly clamped together, and secured against a rigid anvil underneath. The rotating pin travels along the seam and through a combination of pressure and friction heating produces a zone of plastic deformation around the pin within the workpiece on either side of the seam. As the pin is moved in the direction of welding, the plasticised material moves around the tool and bonds together behind it. The elements of the material flow behavior are a combination of three elements. There is a rotational transport of material being carried around the tool, extrusion of material being forced around the pin on both sides into the cavity created behind it, and a lifting and dropping of material as it is stirred and mixed by the rotating action of the pin. It was assumed that rotational motion of the plastic zone is the primary mechanism for transport of material around the welding tool. A kinematic mathematical model was used to compute trajectories of material movement for various distributions of rotational slip within the plastic zone. These trajectories were then compared with the results of an experiment that produced radiographs of markers embedded in a workpiece that was welded with the FSW process. It was assumed that the copper wire markers retained their original length as the aluminum material flowed around them. The kinematic model included a constraint so that the displacements were such that the total length of the wire markers did not increase after deformation. There was good agreement between the calculated trajectories for the case of localized slip at the outer surface of the plastic deformation zone and the radiographs of the copper wire markers. The trajectories differed markedly from the radiograph traces when a distributed slip zone was assumed. It was concluded that the flow field could
Meteor trajectory estimation from radio meteor observations
NASA Astrophysics Data System (ADS)
Kákona, J.
2016-01-01
Radio meteor observation techniques are generally accepted as meteor counting methods useful mainly for meteor flux detection. Due to the technical progress in radio engineering and electronics a construction of a radio meteor detection network with software defined receivers has become possible. These receivers could be precisely time synchronized and could obtain data which provide us with more information than just the meteor count. We present a technique which is able to compute a meteor trajectory from the data recorded by multiple radio stations.
Dynamical phase trajectories for relativistic nuclear collisions
Arsene, I. C.; Bravina, L. V.; Cassing, W.; Ivanov, Yu. B.; Russkikh, V. N.; Larionov, A.; Randrup, J.; Toneev, V. D.; Zeeb, G.; Zschiesche, D.
2007-03-15
Central collisions of gold nuclei are simulated by several existing models and the central net baryon density {rho} and the energy density {epsilon} are extracted at successive times for beam kinetic energies of 5-40 GeV/nucleon. The resulting trajectories in the ({rho},{epsilon}) phase plane are discussed from the perspective of experimentally exploring the expected first-order hadronization phase transition with the planned FAIR at GSI or in a low-energy campaign at the Relativistic Heavy Ion Collider.
Midcourse trajectory correction for solar sail starships
NASA Astrophysics Data System (ADS)
Matloff, Gregory L.
2016-10-01
Hyperthin solar sails deployed as close to the Sun as possible are the only currently feasible approach to extrasolar solar exploration and interstellar travel. This paper quantifies and investigates the effects of timing errors in the unfurlment (or inflation) of solar sails at the perihelion of parabolic solar orbits upon the spacecraft's trajectory direction. Methods of correcting such aim errors include on-board solar-, radioisotope-, or nuclear-electric thrusters, electromagnetic thrustless turning, application of electric or magnetic sails, and a new application of toroidal magnetic ion scoops.
An optimal trajectory design for debris deorbiting
NASA Astrophysics Data System (ADS)
Ouyang, Gaoxiang; Dong, Xin; Li, Xin; Zhang, Yang
2016-01-01
The problem of deorbiting debris is studied in this paper. As a feasible measure, a disposable satellite would be launched, attach to debris, and deorbit the space debris using a technology named electrodynamic tether (EDT). In order to deorbit multiple debris as many as possible, a suboptimal but feasible and efficient trajectory set has been designed to allow a deorbiter satellite tour the LEO small bodies per one mission. Finally a simulation given by this paper showed that a 600 kg satellite is capable of deorbiting 6 debris objects in about 230 days.
Trajectory optimization software for planetary mission design
NASA Technical Reports Server (NTRS)
D'Amario, Louis A.
1989-01-01
The development history and characteristics of the interactive trajectory-optimization programs MOSES (D'Amario et al., 1981) and PLATO (D'Amario et al., 1982) are briefly reviewed, with an emphasis on their application to the Galileo mission. The requirements imposed by a mission involving flybys of several planetary satellites or planets are discussed; the formulation of the parameter-optimization problem is outlined; and particular attention is given to the use of multiconic methods to model the gravitational attraction of Jupiter in MOSES. Diagrams and tables of numerical data are included.