7,875 research outputs found
The effects of estimation of censoring, truncation, transformation and partial data vectors
The purpose of this research was to attack statistical problems concerning the estimation of distributions for purposes of predicting and measuring assembly performance as it appears in biological and physical situations. Various statistical procedures were proposed to attack problems of this sort, that is, to produce the statistical distributions of the outcomes of biological and physical situations which, employ characteristics measured on constituent parts. The techniques are described
Tensor distributions on signature-changing space-times
Irregularities in the metric tensor of a signature-changing space-time
suggest that field equations on such space-times might be regarded as
distributional. We review the formalism of tensor distributions on
differentiable manifolds, and examine to what extent rigorous meaning can be
given to field equations in the presence of signature-change, in particular
those involving covariant derivatives. We find that, for both continuous and
discontinuous signature-change, covariant differentiation can be defined on a
class of tensor distributions wide enough to be physically interesting.Comment: 9 pages, LaTeX 2.0
Contact-Aided Invariant Extended Kalman Filtering for Legged Robot State Estimation
This paper derives a contact-aided inertial navigation observer for a 3D
bipedal robot using the theory of invariant observer design. Aided inertial
navigation is fundamentally a nonlinear observer design problem; thus, current
solutions are based on approximations of the system dynamics, such as an
Extended Kalman Filter (EKF), which uses a system's Jacobian linearization
along the current best estimate of its trajectory. On the basis of the theory
of invariant observer design by Barrau and Bonnabel, and in particular, the
Invariant EKF (InEKF), we show that the error dynamics of the point
contact-inertial system follows a log-linear autonomous differential equation;
hence, the observable state variables can be rendered convergent with a domain
of attraction that is independent of the system's trajectory. Due to the
log-linear form of the error dynamics, it is not necessary to perform a
nonlinear observability analysis to show that when using an Inertial
Measurement Unit (IMU) and contact sensors, the absolute position of the robot
and a rotation about the gravity vector (yaw) are unobservable. We further
augment the state of the developed InEKF with IMU biases, as the online
estimation of these parameters has a crucial impact on system performance. We
evaluate the convergence of the proposed system with the commonly used
quaternion-based EKF observer using a Monte-Carlo simulation. In addition, our
experimental evaluation using a Cassie-series bipedal robot shows that the
contact-aided InEKF provides better performance in comparison with the
quaternion-based EKF as a result of exploiting symmetries present in the system
dynamics.Comment: Published in the proceedings of Robotics: Science and Systems 201
Oral History Interview: W. Hartley Fulks
This interview is one of a series concerning workers in various West Virginia industries and businesses. Mr. Fulks is a retired butcher and grocery man from Huntington, West Virginia. At the time of the interview he was living on Greasey Ridge in Ohio. Mr. Fulks talks about farming and his business.https://mds.marshall.edu/oral_history/1093/thumbnail.jp
The Problem of Membership in International Organization
Membership problems plague international organizations of all types. All organizations are in some way exclusive, and there is a hierarchy of acceptable joiner-nations with the European nations leading the list. Each organization appears statistically to have a norm of membership toward which its number tends. If it falls short of the norm, it is under compulsion to expand. If it exceeds the norm, expulsions or boycotts are likely to ensue. The ideal condition of an organization, therefore, is normal membership, not necessarily total inclusion of all nations legally admissable. More is to be lost by too large an organization than by one too small. There is a superfluity of discrete national memberships in separate organizations, which necessitates amalgamation of organizations
Ground-level insolation in the UV-B spectral region : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Physics at Massey University
This thesis describes the design and construction of two instruments for use in isolating the ultraviolet parts of the Solar spectral irradiance at Earth's surface. The first was a total UVA Pyranometer, which was undertaken to make preliminary investigations in the techniques of monitoring ultraviolet irradiances, as well as to provide useful data. The main part of this thesis was the construction of a portable, easily operated, interference filter spectrophotometer to isolate the ultraviolet-B spectrum into five discrete 10 nm passbands. However, as further reading will describe, realisation of only the two longer wavelength passbands was made due to deviations from the ideal quasi-rectangular passbands of the interference filter spectral transmittance curves. Discussion of how these problems can be overcome is presented in the conclusion. An outline on how the incident spectral solar irradiance could be found, from the five passbands, is presented along with some preliminary data from the two operational channels. An overall accuracy of 15% was obtained for data obtained, with better accuracies, to 7%, attainable by stabilisation of the instrument power supplies and, therefore, output voltage
Stochastic compartmental analysis - Some applications and examples of estimation in a pulse labelled system
Stochastic compartmental analysis with examples of estimation in pulse labelled syste
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