Independent Orbiter Assessment (IOA): Assessment of the displays and controls subsystem

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items Llist (CIL) are presented. The IOA effort first completed an analysis of the Displays and Control hardware, generating draft failure modes and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. The IOA results were than compared to the NASA FMEA/CIL baseline with proposed Post 51-L updates included. A resolution of each discrepancy is provided through additional analysis as required. The results of that comparison for the Orbiter D and C hardware are documented

Independent Orbiter Assessment (IOA): Analysis of the displays and controls subsystem

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine failure modes, criticality, and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. This report documents the independent analysis results corresponding to the Orbiter Displays and Controls (D and C) subsystem hardware. The function of the D and C hardware is to provide the crew with the monitor, command, and control capabilities required for management of all normal and contingency mission and flight operations. The D and C hardware for which failure modes analysis was performed consists of the following: Acceleration Indicator (G-METER); Head Up Display (HUD); Display Driver Unit (DDU); Alpha/Mach Indicator (AMI); Horizontal Situation Indicator (HSI); Attitude Director Indicator (ADI); Propellant Quantity Indicator (PQI); Surface Position Indicator (SPI); Altitude/Vertical Velocity Indicator (AVVI); Caution and Warning Assembly (CWA); Annunciator Control Assembly (ACA); Event Timer (ET); Mission Timer (MT); Interior Lighting; and Exterior Lighting. Each hardware item was evaluated and analyzed for possible failure modes and effects. Criticality was assigned based upon the severity of the effect for each failure mode

Equilibrium and Stability of Rectangular Liquid-filled Vessels

Here we focus on the stability characteristics of a rectangular liquid-filled vessel. The position vector of the center of gravity of the liquid volume is derived and used to express the equilibrium angles of the vessel. Analysis of the potential function determines the stability of these equilibria, and bifurcation diagrams are constructed to demonstrate the co-existence of several equilibrium configurations of the vessel. To validate the results, a vessel of rectangular cross-section was built. The results of the experiments agree well with the theoretical predictions

Time-Frequency Transform Techniques for Seabed and Buried Target Classification

An approach for processing sonar signals with the ultimate goal of ocean bottom sediment classification and underwater buried target classification is presented in this paper. Work reported for sediment classification is based on sonar data collected by one of the AN/AQS-20’s sonars. Synthetic data, simulating data acquired by parametric sonar, is employed for target classification. The technique is based on the Fractional Fourier Transform (FrFT), which is better suited for sonar applications because FrFT uses linear chirps as basis functions. In the first stage of the algorithm, FrFT requires finding the optimum order of the transform that can be estimated based on the properties of the transmitted signal. Then, the magnitude of the Fractional Fourier transform for optimal order applied to the backscattered signal is computed in order to approximate the magnitude of the bottom impulse response. Joint time-frequency representations of the signal offer the possibility to determine the timefrequency configuration of the signal as its characteristic features for classification purposes. The classification is based on singular value decomposition of the time-frequency distributions applied to the impulse response. A set of the largest singular values provides the discriminant features in a reduced dimensional space. Various discriminant functions are employed and the performance of the classifiers is evaluated. Of particular interest for underwater under-sediment classification applications are long targets such as cables of various diameters, which need to be identified as different from other strong reflectors or point targets. Synthetic test data are used to exemplify and evaluate the proposed technique for target classification. The synthetic data simulates the impulse response of cylindrical targets buried in the seafloor sediments. Results are presented that illustrate the processing procedure. An important characteristic of this method is that good classification accuracy of an unknown target is achieved having only the response of a known target in the free field. The algorithm shows an accurate way to classify buried objects under various scenarios, with high probability of correct classification

Sonar Signal Enhancement Using Fractional Fourier Transform

In this paper we present an approach for signal enhancement of sonar signals. Work reported is based on sonar data collected by the Volume Search Sonar (VSS), as well as VSS synthetic data. The Volume Search Sonar is a beamformed multibeam sonar system with 27 fore and 27 aft beams, covering almost the entire water volume (from above horizontal, through vertical, back to above horizontal). The processing of a data set of measurement in shallow water is performed using the Fractional Fourier Transform algorithm. The proposed technique will allow efficient determination of seafloor bottom characteristics and bottom type using the reverberation signal. A study is carried out to compare the performance of the presented method with conventional methods. Results are shown and future work and recommendations are presented

Acoustic Seabed Classification using Fractional Fourier Transform

In this paper we present a time-frequency approach for acoustic seabed classification. Work reported is based on sonar data collected by the Volume Search Sonar (VSS), one of the five sonar systems in the AN/AQS-20. The Volume Search Sonar is a beamformed multibeam sonar system with 27 fore and 27 aft beams, covering almost the entire water volume (from above horizontal, through vertical, back to above horizontal). The processing of a data set of measurement in shallow water is performed using the Fractional Fourier Transform algorithm in order to determine the impulse response of the sediment. The Fractional Fourier transform requires finding the optimum order of the transform that can be estimated based on the properties of the transmitted signal. Singular Value Decomposition and statistical properties of the Wigner and Choi-Williams distributions of the bottom impulse response are employed as features which are, in turn, used for classification. The Wigner distribution can be thought of as a signal energy distribution in joint time-frequency domain. Results of our study show that the proposed technique allows for accurate sediment classification of seafloor bottom data. Experimental results are shown and suggestions for future work are provided

The Phase Retrieval Problem and Its Applications in Optics

In this dissertation the various forms and applications of the phase retrieval problem in imaging are discussed. The phase retrieval problem in general refers to the estimation of the phase of a complex-valued function based on knowledge of its magnitude. Here the phase retrieval problem is applied to the estimation of the phase of an electromagnetic wave field based on knowledge of its magnitude. The magnitude (not the phase) can be measured using several devices as discussed. There are many applications of phase retrieval which have been explored where the mapping between the detected wave field magnitude and the light source is the Fourier transform. Within these applications phase retrieval solutions are used to estimate the phase of the Fourier transform so as to obtain the image or the shape of the light emitter. These solutions necessitate a model of the propagation of the wave field, a method of detecting the field’s magnitude, and a method of estimating the phase of the observed field. The first two considerations are discussed here historically and reference many significant scientific discoveries, namely the Huygens-Fresnel principle, the Van Cittert-Zernike theorem, and the Michelson interferometer. Within the field of interferometry where the Fourier transform is the mapping between the light source and observed wave field, most solutions utilize a discrete Fourier transform. The estimate of the light source takes the form of a two-dimensional pixelated image. These solutions have been explored for many years and have many variations for particular applications. Not many of these solution methods, however, have confronted the problem of measurement noise. Measurement noise here refers to noise in the quantification of the magnitude of the wave field at the observed locations. Within this dissertation the negative effects of noise are analyzed and a method of filtering the noise from the data is derived, tested, and shown to be effective. In a separate analysis the use of the discrete Fourier transform as opposed to the continuous Fourier transform is questioned. A phase solution is proposed which is capable of estimating the source of the observed wave field and takes discrete magnitude data and outputs a continuous image function formed from Gaussian bases. This method is beneficial from an analytical point-of-view since it is not an iterative solution. It also has an error metric which definitively determines whether the true solution has been found—unlike the traditional solution methods. The phase retrieval problem is also explored in the case where the Fourier transform is not the mapping between the image and the observed wave field. Particularly, the case of a small asteroid occulting a star is analyzed with the goal of characterizing the shape of the asteroid’s silhouette. A solution is formulated capable of resolving the asteroid silhouette based on time histories of the intensity of the wave field measured at multiple spatial locations. The solution is based on an analysis of the shadow that the occulter casts. The phase retrieval problem is present in many current fields of imaging and remains a prominent source of inquiry. Although many solution methods exist, there are still many improvements that can be made. This dissertation addresses some potential improvements to existing solutions and proposes new applications and formulations of the phase retrieval problem

Individual Differences and Stability of Dynamics among Self-Concept Clarity, Impatience, and Negative Affect

Self-concept clarity (SCC) is associated with behavioral and emotion regulation, although the nature of this link is unclear. SCC may serve as a self-regulatory resource or it may be a product of well-regulated behaviors and emotions. In two studies using experience sampling among undergraduates (n = 46 and n = 36), we investigate whether models representing relationships among SCC, impatience, and negative affect (NA) states conform to these theories, are similar across individuals, and are stable across a one-month period. Results reveal substantial variation between persons in these dynamic relationships, suggesting that multiple SCC-relevant regulatory processes exist. These patterns were not stable from one month to the next, but changes in them related to changes in stress, suggesting higher-order regulation of these dynamics

Extended Kalman Filter for Photographic Data from Impact Acceleration Tests

This paper presents the development of an Extended Kalman Filter (EKF) that optimally processes photographic data collected during short-duration impact acceleration tests. The system is modeled by a non-linear state-space representation using quaternions for rotational kinematics. Three cameras are used to photograph up to 14 fiducials mounted on a plate attached to the subject\u27s mouth. The filter yields the history of the rotational and translational kinematics of the origin of the mouth plate. Results from the EKF and analysis of the estimation error are presented

Reconciling Semiclassical and Bohmian Mechanics: II. Scattering states for discontinuous potentials

In a previous paper [J. Chem. Phys. 121 4501 (2004)] a unique bipolar decomposition, Psi = Psi1 + Psi2 was presented for stationary bound states Psi of the one-dimensional Schroedinger equation, such that the components Psi1 and Psi2 approach their semiclassical WKB analogs in the large action limit. Moreover, by applying the Madelung-Bohm ansatz to the components rather than to Psi itself, the resultant bipolar Bohmian mechanical formulation satisfies the correspondence principle. As a result, the bipolar quantum trajectories are classical-like and well-behaved, even when Psi has many nodes, or is wildly oscillatory. In this paper, the previous decomposition scheme is modified in order to achieve the same desirable properties for stationary scattering states. Discontinuous potential systems are considered (hard wall, step, square barrier/well), for which the bipolar quantum potential is found to be zero everywhere, except at the discontinuities. This approach leads to an exact numerical method for computing stationary scattering states of any desired boundary conditions, and reflection and transmission probabilities. The continuous potential case will be considered in a future publication.Comment: 18 pages, 8 figure