2,951 research outputs found
Analysis of Shear Lag in Steel Angle Connectors
Previous research has found an empirically based method for calculating the effective net area defined by stress distributions created by tensile loads in steel connections. Based on the results from that method a theoretical alternative is explored to simplify the process of determining the effective net area
Applied Error Related Negativity: Single Electrode Electroencephalography in Complex Visual Stimuli
Error related negativity (ERN) is a pronounced negative evoked response potential (ERP) that follows a known error. This neural pattern has the potential to communicate user awareness of incorrect actions within milliseconds. While the implications for human-machine interface and augmented cognition are exciting, the ERN has historically been evoked only in the laboratory using complex equipment while presenting simple visual stimuli such as letters and symbols. To effectively harness the applied potential of the ERN, detection must be accomplished in complex environments using simple, preferably single-electrode, EEG systems feasible for integration into field and workplace-ready equipment. The present project attempted to use static photographs to evoke and successfully detect the ERN in a complex visual search task: motorcycle conspicuity. Drivers regularly fail to see motorcycles, with tragic results. To reproduce the issue in the lab, static pictures of traffic were presented, either including or not including motorcycles. A standard flanker letter task replicated from a classic ERN study (Gehring et al., 1993) was run alongside, with both studies requiring a binary response. Results showed that the ERN could be clearly detected in both tasks, even when limiting data to a single electrode in the absence of artifact correction. These results support the feasibility of applied ERN detection in complex visual search in static images. Implications and opportunities will be discussed, limitations of the study explained, and future directions explored
Estimation and uncertainty of reversible Markov models
Reversibility is a key concept in Markov models and Master-equation models of
molecular kinetics. The analysis and interpretation of the transition matrix
encoding the kinetic properties of the model relies heavily on the
reversibility property. The estimation of a reversible transition matrix from
simulation data is therefore crucial to the successful application of the
previously developed theory. In this work we discuss methods for the maximum
likelihood estimation of transition matrices from finite simulation data and
present a new algorithm for the estimation if reversibility with respect to a
given stationary vector is desired. We also develop new methods for the
Bayesian posterior inference of reversible transition matrices with and without
given stationary vector taking into account the need for a suitable prior
distribution preserving the meta- stable features of the observed process
during posterior inference. All algorithms here are implemented in the PyEMMA
software - http://pyemma.org - as of version 2.0
Microwave state transfer and adiabatic dynamics of magnetically trapped polar molecules
Cold and ultracold polar molecules with nonzero electronic angular momentum
are of great interest for studies in quantum chemistry and control,
investigations of novel quantum systems, and precision measurement. However, in
mixed electric and magnetic fields, these molecules are generically subject to
a large set of avoided crossings among their Zeeman sublevels; in magnetic
traps, these crossings lead to distorted potentials and trap loss from electric
bias fields. We have characterized these crossings in OH by
microwave-transferring trapped OH molecules from the upper |f; M = +3/2> parity
state to the lower |e; +3/2> state and observing their trap dynamics under an
applied electric bias field. Our observations are very well described by a
simple Landau-Zener model, yielding insight to the rich spectra and dynamics of
polar radicals in mixed external fields.Comment: 5 pages, 4 figures plus supplementary materia
Magneto-electrostatic trapping of ground state OH molecules
We report the magnetic confinement of neutral, ground state hydroxyl radicals
(OH) at a density of cm and temperature of 30
mK. An adjustable electric field of sufficient magnitude to polarize the OH is
superimposed on the trap in either a quadrupole or homogenous field geometry.
The OH is confined by an overall potential established via molecular state
mixing induced by the combined electric and magnetic fields acting on the
molecule's electric dipole and magnetic dipole moments, respectively. An
effective molecular Hamiltonian including Stark and Zeeman terms has been
constructed to describe single molecule dynamics inside the trap. Monte Carlo
simulation using this Hamiltonian accurately models the observed trap dynamics
in various trap configurations. Confinement of cold polar molecules in a
magnetic trap, leaving large, adjustable electric fields for control, is an
important step towards the study of low energy dipole-dipole collisions.Comment: 4 pages, 4 figure
Toward an Antiphony Framework for Dividing Tasks into Subtasks
Task analysis is a staple of ergonomics, neuroergonomics, human factors, and experimental psychology inquiry, and often benefits from granularity beyond the task level to the subtask level. The concept and challenge of identifying the subcomponents of tasks are neither new, nor solved. Practitioners routinely identify individually internally consistent and yet conflicting subdivisions. The challenge of producing reliable, valid subtask data across efforts recommends a unified framework for identifying consistent subtask divisions within tasks. A framework is here forwarded, based upon universal “antiphony” turn-taking behavior in human-human interaction, but adapted to address the highly scripted vocabulary of human-machine interaction. Practical application to a real-world vehicle interface is demonstrated, an example discussed in the light of research design, applied use, and future improvement
Effects of Signal Probability on Multitasking-Based Distraction in Driving, Cyberattack & Battlefield Simulation
Multitasking-based failures of perception and action are the focus of much research in driving, where they are attributed to distraction. Similar failures occur in contexts where the construct of distraction is little used. Such narrow application was attributed to methodology which cannot precisely account for experimental variables in time and space, limiting distraction\u27s conceptual portability to other contexts. An approach based upon vigilance methodology was forwarded as a solution, and highlighted a fundamental human performance question: Would increasing the signal probability (SP) of a secondary task increase associated performance, as is seen in the prevalence effect associated with vigilance tasks? Would it reduce associated performance, as is seen in driving distraction tasks? A series of experiments weighed these competing assumptions. In the first, a psychophysical task, analysis of accuracy and response data revealed an interaction between the number of concurrent tasks and SP of presented targets. The question was further tested in the applied contexts of driving, cyberattack and battlefield target decision-making. In line with previous prevalence effect inquiry, presentation of stimuli at higher SP led to higher accuracy. In line with existing distraction work, performance of higher numbers of concurrent tasks tended to elicit slower response times. In all experiments raising either number of concurrent tasks or SP of targets resulted in greater subjective workload, as measured by the NASA TLX, even when accompanied by improved accuracy. It would seem that distraction in previous experiments has been an aggregate effect including both delayed response time and prevalence-based accuracy effects. These findings support the view that superior experimental control of SP reveals nomothetic patterns of performance that allow better understanding and wider application of the distraction construct both within and in diverse contexts beyond driving
Low-energy molecular collisions in a permanent magnetic trap
Cold, neutral hydroxyl radicals are Stark decelerated and confined within a
magnetic trap consisting of two permanent ring magnets. The OH molecules are
trapped in the ro-vibrational ground state at a density of
cm and temperature of 70 mK. Collisions between the trapped OH sample
and supersonic beams of atomic He and molecular D are observed and
absolute collision cross sections measured. The He--OH and D--OH
center-of-mass collision energies are tuned from 60 cm to 230 cm
and 145 cm to 510 cm, respectively, yielding evidence of reduced
He--OH inelastic cross sections at energies below 84 cm, the OH ground
rotational level spacing.Comment: 4 pages, 4 figure
Panel: Interdisciplinary Paradigms for IS Education: The Information School
Education for the information profession is in a state of radical change and re-design. Academic units are being reorganized around new interdisciplinary paradigms, while new curriculums are being developed to address the needs of a growing and diverse information profession. Existing schools, which offer multiple information degrees and are based upon interdisciplinary models, such as Syracuse, Pittsburgh, Drexel and Rutgers universities have been or are now joined by others, such as the University of Michigan and the University of California at Berkeley. Plans are in place to create new “information schools” at Penn State, Indiana University, UNC Charlotte, and other universities. New information colleges are being considered from the University of Arizona to the University of Rhode Island - and many points between
OH hyperfine ground state: from precision measurement to molecular qubits
We perform precision microwave spectroscopy--aided by Stark deceleration--to
reveal the low magnetic field behavior of OH in its ^2\Pi_{3/2} ro-vibronic
ground state, identifying two field-insensitive hyperfine transitions suitable
as qubits and determining a differential Lande g-factor of
1.267(5)\times10^{-3} between opposite parity components of the
\Lambda-doublet. The data are successfully modeled with an effective hyperfine
Zeeman Hamiltonian, which we use to make a tenfold improvement of the
magnetically sensitive, astrophysically important \Delta F=\pm1 satellite-line
frequencies, yielding 1720529887(10) Hz and 1612230825(15) Hz.Comment: 4+ pages, 3 figure
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