14,131 research outputs found
Convergence Rates for Newton’s Method at Singular Points
If Newton’s method is employed to find a root of a map from a Banach space into itself and the derivative is singular at that root, the convergence of the Newton iterates to the root is linear rather than quadratic. In this paper we give a detailed analysis of the linear convergence rates for several types of singular problems. For some of these problems we describe modifications of Newton’s method which will restore quadratic convergence
Superconducting Surface Impedance under Radiofrequency Field
Based on BCS theory with moving Cooper pairs, the electron states
distribution at 0K and the probability of electron occupation with finite
temperature have been derived and applied to anomalous skin effect theory to
obtain the surface impedance of a superconductor under radiofrequency (RF)
field. We present the numerical results for Nb and compare these with
representative RF field-dependent effective surface resistance measurements
from a 1.5 GHz resonant structure
Using multiple sensors for printed circuit board insertion
As more and more activities are performed in space, there will be a greater demand placed on the information handling capacity of people who are to direct and accomplish these tasks. A promising alternative to full-time human involvement is the use of semi-autonomous, intelligent robot systems. To automate tasks such as assembly, disassembly, repair and maintenance, the issues presented by environmental uncertainties need to be addressed. These uncertainties are introduced by variations in the computed position of the robot at different locations in its work envelope, variations in part positioning, and tolerances of part dimensions. As a result, the robot system may not be able to accomplish the desired task without the help of sensor feedback. Measurements on the environment allow real time corrections to be made to the process. A design and implementation of an intelligent robot system which inserts printed circuit boards into a card cage are presented. Intelligent behavior is accomplished by coupling the task execution sequence with information derived from three different sensors: an overhead three-dimensional vision system, a fingertip infrared sensor, and a six degree of freedom wrist-mounted force/torque sensor
An evaluation of exercises for the development of word recognition and word meaning in grade five
Thesis (Ed.M.)--Boston Universit
An evaluation of exercises for the development of word recognition and word meaning in grade five
Thesis (Ed.M.)--Boston Universit
Thyroid Hormone Controls the Onset of Androgen Sensitivity in the Developing Larynx ofXenopus laevis
AbstractGonadal differentiation, the onset of androgen-stimulated laryngeal growth and the genesis of a sex difference in laryngeal innervation, all temporally coincide with thyroid hormone (TH)-induced metamorphosis inXenopus laevis.To explore the role TH plays in the ontogeny of theXenopusandrogen-sensitive vocal neuromuscular system, we examined gonadal and laryngeal development in tadpoles in which metamorphosis had been blocked by treatment with the thyroxine synthesis inhibitor propylthiouracil (PTU). PTU treatment did not arrest gonadal differentiation. Testes from PTU-treated male tadpoles had seminiferous tubules and advanced stage male germ cells, while in females stage 1 oocytes were present. In contrast to the gonads, PTU did block morphological development of the larynx. Tadpoles treated with PTU for 50 or 100 days had larynges which structurally resembled those of stage 54 control tadpoles. PTU-treated animals did not exhibit the extensive development of the laryngeal cartilage seen in untreated animals. Laryngeal cartilages of hypothyroid tadpoles exhibited low density and minimal patterning of chondrocytes; the complex lumen and marked expansion of the dilator muscles characteristic of 50- and 100-day untreated animals were absent. Laryngeal growth evoked by exposure to exogenous androgen (dihydrotestosterone) was entirely prevented by PTU treatment. Hypothyroid tadpoles did not exhibit the decline in laryngeal nerve axon number characteristic of age-matched controls, nor were laryngeal nerve axon numbers sexually dimorphic. PTU treatment also interfered with the myelination of laryngeal axons. We conclude that while gonadal differentiation is independent of TH, androgen sensitive laryngeal development and sexually dimorphic laryngeal innervation require exposure to secreted TH
Density of bulk trap states in organic semiconductor crystals: discrete levels induced by oxygen in rubrene
The density of trap states in the bandgap of semiconducting organic single
crystals has been measured quantitatively and with high energy resolution by
means of the experimental method of temperature-dependent
space-charge-limited-current spectroscopy (TD-SCLC). This spectroscopy has been
applied to study bulk rubrene single crystals, which are shown by this
technique to be of high chemical and structural quality. A density of deep trap
states as low as ~ 10^{15} cm^{-3} is measured in the purest crystals, and the
exponentially varying shallow trap density near the band edge could be
identified (1 decade in the density of states per ~25 meV). Furthermore, we
have induced and spectroscopically identified an oxygen related sharp hole bulk
trap state at 0.27 eV above the valence band.Comment: published in Phys. Rev. B, high quality figures:
http://www.cpfs.mpg.de/~krellner
Multi-Objective Gust Load Alleviation Control Designs for an Aeroelastic Wind Tunnel Demonstration Wing
This paper presents several control and gust disturbance estimation techniques applied to a mathematical model of a physical flexible wing wind tunnel model used in ongoing tests at the University of Washington Aeronautical Laboratory's Kirsten Wind Tunnel. Three methods of gust disturbance estimation are presented, followed by three control methods: LQG, Basic Multi-Objective (BMO), and a novel Multi-Objective Prediction Correction (MOPC) controller. The latter of which augments a multi-objective controller, and attempts to correct for errors in the disturbance estimate. A simplified linear simulation of the three controllers is performed and a simple MIMO stability and robustness assessment is performed. Then, the same controllers are simulated in a higher fidelity Simulink environment that captures sampling, saturation and noise effects. This preliminary analysis indicates that the BMO controller provides the best performance and largest stability margins
A Persistent Simulation Environment for Autonomous Systems
The age of Autonomous Unmanned Aircraft Systems (AUAS) is creating new challenges for the accreditation and certification requiring new standards, policies and procedures that sanction whether a UAS is safe to fly. Establishing a basis for certification of autonomous systems via research into trust and trustworthiness is the focus of Autonomy Teaming and TRAjectories for Complex Trusted Operational Reliability (ATTRACTOR), a new NASA Convergent Aeronautics Solution (CAS) project. Simulation Environments to test and evaluate AUAS decision making may be a low-cost solution to help certify that various AUAS systems are trustworthy enough to be allowed to fly in current general and commercial aviation airspace. NASA is working to build a peer-to-peer persistent simulation (P3 Sim) environment. The P3 Sim will be a Massively Multiplayer Online (MMO) environment were AUAS avatars can interact with a complex dynamic environment and each other. The focus of the effort is to provide AUAS researchers a low-cost intuitive testing environment that will aid training for and assessment of decisions made by autonomous systems such as AUAS. This presentation focuses on the design approach and challenges faced in development of the P3 Sim Environment is support of investigating trustworthiness of autonomous systems
Soft-Collinear Factorization and Zero-Bin Subtractions
We study the Sudakov form factor for a spontaneously broken gauge theory
using a (new) Delta -regulator. To be well-defined, the effective theory
requires zero-bin subtractions for the collinear sectors. The zero-bin
subtractions depend on the gauge boson mass M and are not scaleless. They have
both finite and 1/epsilon contributions, and are needed to give the correct
anomalous dimension and low-scale matching contributions. We also demonstrate
the necessity of zero-bin subtractions for soft-collinear factorization. We
find that after zero-bin subtractions the form factor is the sum of the
collinear contributions 'minus' a soft mass-mode contribution, in agreement
with a previous result of Idilbi and Mehen in QCD. This appears to conflict
with the method-of-regions approach, where one gets the sum of contributions
from different regions.Comment: 9 pages, 5 figures. V2:ref adde
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