1,362 research outputs found
Generalized Philosophy of Alerting with Applications for Parallel Approach Collision Prevention
An alerting system is automation designed to reduce the likelihood of undesirable
outcomes that are due to rare failures in a human-controlled system. It accomplishes this
by monitoring the system, and issuing warning messages to the human operators when
thought necessary to head off a problem. On examination of existing and recently
proposed logics for alerting it appears that few commonly accepted principles guide the
design process. Different logics intended to address the same hazards may take disparate
forms and emphasize different aspects of performance, because each reflects the intuitive
priorities of a different designer. Because performance must be satisfactory to all users
of an alerting system (implying a universal meaning of acceptable performance) and not
just one designer, a proposed logic often undergoes significant piecemeal modification
before gaining general acceptance. This report is an initial attempt to clarify the common
performance goals by which an alerting system is ultimately judged. A better
understanding of these goals will hopefully allow designers to reach the final logic in a
quicker, more direct and repeatable manner. As a case study, this report compares three
alerting logics for collision prevention during independent approaches to parallel
runways, and outlines a fourth alternative incorporating elements of the first three, but
satisfying stated requirements.NASA grant NAG1-218
Hazard Avoidance Alerting With Markov Decision Processes
This thesis describes an approach to designing hazard avoidance alerting systems based on a
Markov decision process (MDP) model of the alerting process, and shows its benefits over
standard design methods. One benefit of the MDP method is that it accounts for future decision
opportunities when choosing whether or not to alert, or in determining resolution guidance.
Another benefit is that it provides a means of modeling uncertain state information, such as
knowledge about unmeasurable mode variables, so that decisions are more informed.
A mode variable is an index for distinct types of behavior that a system exhibits at different
times. For example, in many situations normal system behavior is safe, but rare deviations from
the normal increase the likelihood of a harmful incident. Accurate modeling of mode
information is needed to minimize alerting system errors such as unnecessary or late alerts.
The benefits of the method are illustrated with two alerting scenarios where a pair of aircraft
must avoid collisions when passing one another. The first scenario has a fully observable state
and the second includes an uncertain mode describing whether an intruder aircraft levels off
safely above the evader or is in a hazardous blunder mode.
In MDP theory, outcome preferences are described in terms of utilities of different state
trajectories. In keeping with this, alerting system requirements are stated in the form of a reward
function. This is then used with probabilistic dynamic and sensor models to compute an alerting
logic (policy) that maximizes expected utility. Performance comparisons are made between the
MDP-based logics and alternate logics generated with current methods. It is found that in terms
of traditional performance measures (incident rate and unnecessary alert rate), the MDP-based
logic can meet or exceed that of alternate logics
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Restorative justice ideology among High School teachers in Ghana: investigating the role of collectivism and personality
Studies on Restorative Justice (RJ) ideology in school settings have largely focused on Western societies, to the neglect of African societies. This means that variables relevant to the Ghanaian setting that might be associated with RJ ideology have not been examined. The current study investigates the association between High School teachers’ Collectivism, Openness to Experience (OE), and their idea of Restoration. Analysis of data from 191 (Male=128, Female=63) teachers in Accra indicated that Collectivism and OE both predicted the idea of Restoration. This suggests that both Collectivism and OE are important resources that may help teachers embrace the idea of restoring a student offender to morally acceptable behaviour. This and other findings are discussed
Hazard avoidance alerting with Markov decision processes
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2004.Includes bibliographical references (p. 123-125).(cont.) (incident rate and unnecessary alert rate), the MDP-based logic can meet or exceed that of alternate logics.This thesis describes an approach to designing hazard avoidance alerting systems based on a Markov decision process (MDP) model of the alerting process, and shows its benefits over standard design methods. One benefit of the MDP method is that it accounts for future decision opportunities when choosing whether or not to alert, or in determining resolution guidance. Another benefit is that it provides a means of modeling uncertain state information, such as unmeasurable mode variables, so that decisions are more informed. A mode variable is an index for distinct types of behavior that a system exhibits at different times. For example, in many situations normal system behavior tends to be safe, but rare deviations from the normal increase the likelihood of a harmful incident. Accurate modeling of mode information is needed to minimize alerting system errors such as unnecessary or late alerts. The benefits of the method are illustrated with two alerting scenarios where a pair of aircraft must avoid collisions when passing one another. The first scenario has a fully observable state and the second includes an uncertain mode describing whether an intruder aircraft levels off safely above the evader or is in a hazardous blunder mode. In MDP theory, outcome preferences are described in terms of utilities of different state trajectories. In keeping with this, alerting system requirements are stated in the form of a reward function. This is then used with probabilistic dynamic and sensor models to compute an alerting logic (policy) that maximizes expected utility. Performance comparisons are made between the MDP-based logics and alternate logics generated with current methods. It is found that in terms of traditional performance measuresby Lee F. Winder.Ph.D
Quantum Dynamics of the Slow Rollover Transition in the Linear Delta Expansion
We apply the linear delta expansion to the quantum mechanical version of the
slow rollover transition which is an important feature of inflationary models
of the early universe. The method, which goes beyond the Gaussian
approximation, gives results which stay close to the exact solution for longer
than previous methods. It provides a promising basis for extension to a full
field theoretic treatment.Comment: 12 pages, including 4 figure
Neuroanatomic Correlates of Female Sexual Dysfunction in Multiple Sclerosis
OBJECTIVE:
This study intended to determine associations between alterations of female sexual arousal as well as vaginal lubrication and the site of cerebral multiple sclerosis (MS) lesions.
METHODS:
In 44 women with MS (mean age: 36.5 ± 9.9 years), we assessed their medical history and evaluated sexual function using the Female Sexual Function Index scores for arousal and vaginal lubrication. We determined potential confounding factors of sexual dysfunction: age; disease duration; physical disability; depression; bladder or urinary dysfunction; and total volume of cerebral lesions. Arousal and lubrication scores were correlated with one another and with potential confounding factors. Cerebral MS lesions were recorded on imaging scans. A voxel-based lesion symptom mapping (VLSM) analysis adjusted for confounding variables was performed correlating cerebral sites of MS lesions with arousal and lubrication scores.
RESULTS:
Decreased arousal scores correlated with decreased lubrication scores; decreased lubrication scores were associated with bladder or urinary symptoms. Arousal and lubrication scores were not associated with any other variables. Multivariate VLSM analysis, including arousal and lubrication scores as covariables of interest, showed right occipital lesions associated with impaired arousal and left insular lesions associated with decreased lubrication. Impaired lubrication remained associated with left insular lesions after adjustment for bladder or urinary dysfunction.
INTERPRETATION:
Our data indicate that impaired female sexual arousal is associated with MS lesions in the occipital region, integrating visual information and modulating attention toward visual input. Impaired lubrication correlated with lesions in the left insular region, contributing to mapping and generating visceral arousal states
Transient optical studies of charge recombination dynamics in a polymer/fullerene composite at room temperature
The recombination kinetics of photogenerated charge carriers in a composite of poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1-4-phenylene vinylene], (MDMO–PPV) and the functionalised fullerene 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 are investigated at room temperature by transient absorption spectroscopy. The decay dynamics of positively charged MDMO–PPV polarons were found to be either monophasic or biphasic, depending upon the laser excitation density employed. The slower, power law, decay phase (100 ns–10 ms) is attributed to recombination dynamics of localized polarons, while the fast decay component (<20 ns) is attributed to recombination of relatively mobile polarons observed when the density of localized states is exceeded by the density of photogenerated polarons (~10^17 cm-3). The implications of these observations are discussed in relation to polymer/C60 photovoltaic cells
Aspects of Magnetic Field Configurations in Planar Nonlinear Electrodynamics
In the framework of three-dimensional Born-Infeld Electrodynamics, we pursue
an investigation of the consequences of the space-time dimensionality on the
existence of magnetostatic fields generated by electric charges at rest in an
inertial frame, which are present in its four-dimensional version. Our analysis
reveals interesting features of the model. In fact, a magnetostatic field
associated with an electric charge at rest does not appear in this case.
Interestingly, the addition of the topological term (Chern-Simons) to
Born-Infeld Electrodynamics yields the appearance of the magnetostatic field.
We also contemplate the fields associated to the would-be-magnetic monopole in
three dimensions.Comment: 8 page
Gender Disparities in Alcohol Use Disorder Treatment Among Privately Insured Patients with Alcohol‐Associated Cirrhosis
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147837/1/acer13944_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147837/2/acer13944.pd
Use of Native Grassland in Small-Scale Dairy Systems in the Highlands of Central Mexico. A Case Study
Small-scale dairy systems in Mexico comprise 78% of specialized dairy farms and provide 37% of national production. They are small farms with herds 3-35 cows plus replacements, and rely on family labour (Posadas-Domínguez et al., 2014).
In the highlands, many farms have native grasslands, grazed during the rainy season, and supplemented with other feeds as maize straw, maize grain and maize ears. Native grasslands have not been studied in this context. This is a case study on the use of native grassland in a small-scale dairy farm. The objective was to determine how native grasslands are integrated in feeding milking dairy cows, and the feeding costs involved
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