Dynamic response and control of a jet-transport aircraft encountering a single-axis vortex

The dynamic responses of a jet-transport aircraft to two types of single-axis wind vortex encounters are studied. Aircraft attitude, flight path angle, and aerodynamic angle excursions are analyzed and dominating dynamic forcing effects are identified for each encounter. A simple departure-preventing LQR controller is designed to demonstrate the benefits of using automatic control to reduce the wind vortex hazard. A Proportional-Integral-Filter controller structure successfully regulates the critical parameters, roll angle, phi, and sideslip angle, beta, for the two different vortex encounters considered in this study

AN ERP INVESTIGATION OF REWARD SIGNALS FOR DIFFERING CLASSES OF REINFORCING STIMULI

In order to successfully traverse an actively complex environment, an agent is required to learn from the consequences of their actions. For over a century, models of behavior have been developed demonstrating these consequence-based learning systems. More recently, underlying biological systems have been found to adhere to these constructs of learning. The electroencephalographic signal known as the Reward Positivity (RewP) is thought to reflect a dopamine-dependent cortical signal specific to reward receipt. Importantly, this signal has been shown to adhere to an axiomatic (rule-like) positive reward prediction error, whereby it is evoked following outcomes that are better than expected. These features of the RewP make it a candidate marker for clinical populations, such as major depressive disorder, substance use disorder, and Parkinson’s disease. Although recent experimental endeavors have highlighted key characteristics of the generation and modulation of the RewP, a major understudied feature of the RewP in humans is the link between hedonic experiences and reward processes, and how these interact to modulate learning. This dissertation aims to probe this overlooked hedonic aspect of RewP generation through the use of emotionally evocative image rewards. The first aim addresses methodological issues relating to the use of complex, ecologically valid stimuli in EEG experimentation. The second aim investigated techniques for rectifying these methodological issues. Lastly, the third aim investigated the use of emotionally salient images as rewards in a reinforcement learning paradigm

Japanese Foreign Aid: Suggested Legislation to Guide Administrative Distribution of Foreign Aid

This Comment analyzes the need for guiding legislation in the Japanese foreign aid program. First, the Comment describes the Japanese aid program and its shortcomings. It then suggests guiding legislation and analyzes the improvements such legislation will effectuate

Gyrokinetic Landau collision operator in conservative form

A gyrokinetic linearized exact (not model) Landau collision operator is derived by transforming the symmetric and conservative Landau form. The formulation obtains the velocity-space flux density and preserves the operator's conservative form as the divergence of this flux density. The operator contains both test-particle and field-particle contributions, and finite Larmor radius effects are evaluated in either Bessel function series or gyrophase integrals. While equivalent to the gyrokinetic Fokker–Planck form with Rosenbluth potentials [B. Li and D. R. Ernst, Phys. Rev. Lett. 106, 195002 (2011)10.1103/PhysRevLett.106.195002], the gyrokinetic conservative Landau form explicitly preserves the symmetry between test-particle and field-particle contributions, which underlies the conservation laws and the H theorem, and enables discretization with a finite-volume or spectral method to preserve the conservation properties numerically, independent of resolution. The form of the exact linearized field-particle terms differs from those of widely used model operators. We show the finite Larmor radius corrections to the field-particle terms in the exact linearized operator involve Bessel functions of all orders, while present model field-particle terms involve only the first two Bessel functions. This new symmetric and conservative formulation enables the gyrokinetic exact linearized Landau operator to be implemented in gyrokinetic turbulence codes for comparison with present model operators using similar numerical methods.United States. Department of Energy (Contract DE-FC02-08ER54966

Automated quantification and evaluation of motion artifact on coronary CT angiography images

Abstract Purpose This study developed and validated a Motion Artifact Quantification algorithm to automatically quantify the severity of motion artifacts on coronary computed tomography angiography (CCTA) images. The algorithm was then used to develop a Motion IQ Decision method to automatically identify whether a CCTA dataset is of sufficient diagnostic image quality or requires further correction. Method The developed Motion Artifact Quantification algorithm includes steps to identify the right coronary artery (RCA) regions of interest (ROIs), segment vessel and shading artifacts, and to calculate the motion artifact score (MAS) metric. The segmentation algorithms were verified against ground‐truth manual segmentations. The segmentation algorithms were also verified by comparing and analyzing the MAS calculated from ground‐truth segmentations and the algorithm‐generated segmentations. The Motion IQ Decision algorithm first identifies slices with unsatisfactory image quality using a MAS threshold. The algorithm then uses an artifact‐length threshold to determine whether the degraded vessel segment is large enough to cause the dataset to be nondiagnostic. An observer study on 30 clinical CCTA datasets was performed to obtain the ground‐truth decisions of whether the datasets were of sufficient image quality. A five‐fold cross‐validation was used to identify the thresholds and to evaluate the Motion IQ Decision algorithm. Results The automated segmentation algorithms in the Motion Artifact Quantification algorithm resulted in Dice coefficients of 0.84 for the segmented vessel regions and 0.75 for the segmented shading artifact regions. The MAS calculated using the automated algorithm was within 10% of the values obtained using ground‐truth segmentations. The MAS threshold and artifact‐length thresholds were determined by the ROC analysis to be 0.6 and 6.25 mm by all folds. The Motion IQ Decision algorithm demonstrated 100% sensitivity, 66.7% ± 27.9% specificity, and a total accuracy of 86.7% ± 12.5% for identifying datasets in which the RCA required correction. The Motion IQ Decision algorithm demonstrated 91.3% sensitivity, 71.4% specificity, and a total accuracy of 86.7% for identifying CCTA datasets that need correction for any of the three main vessels. Conclusion The Motion Artifact Quantification algorithm calculated accurate

Momentum transport, radial electric field, and ion thermal energy confinement in very high temperature plasmas

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1998.Includes bibliographical references (p. 213-238).Darin R. Ernst.Ph.D