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A quasi-Newton procedure for identifying pilot-related parameters of the optimal control model

The development and application of a quasi-Newton gradient search procedure for identifying independent pilot related parameters of the optimal control model for pilot/vehicle systems is reported. A sensitivity analysis procedure which determines whether a given model parameter is required to match a specific experimental result, and which experimentally induced parameter changes are required to account for behavioral and performance differences, is described. Application of the identification scheme to training effects in a manual control task is described

Evaluation of display and control concepts for a terminal configured vehicle in final approach in a windshear environment

A revised treatment of nonrandom inputs was incorporated in the model. Response behavior was observed for two display configurations (a pictorial EADI presentation and a flight-director configuration requiring use of a panel-mounted airspeed indicator), two control configurations (attitude and velocity control wheel steering), and two shear environments, each of which contained a head-to-tail shear and a vertical component. In general, performance trends predicted by the model were confirmed experimentally. Experimental and analytical results both indicated superiority to the EADI display with respect to regulation of height and airspeed errors. Velocity steering allowed tighter regulation of height errors, but control parameters had little influence on airspeed regulation. Model analysis indicated that display-related differences could be ascribed to differences in the quality of speed-related information provided by the two displays

Some computational techniques for estimating human operator describing functions

Computational procedures for improving the reliability of human operator describing functions are described. Special attention is given to the estimation of standard errors associated with mean operator gain and phase shift as computed from an ensemble of experimental trials. This analysis pertains to experiments using sum-of-sines forcing functions. Both open-loop and closed-loop measurement environments are considered

Child labour and poverty linkages: A micro analysis from rural Malawian data

This study assesses the impact of income and asset poverty on child work using the rural sub-sample of the 2004 Malawi Integrated Household Survey. Instrumenting consumption expenditure with a location dummy variable and interacting consumption expenditure with household land-holding size in probit models, the likelihood of child labour is found to relate negatively with household consumption. On the other hand child labour relates positively with household land-holding size for consumption poor households only and when labour markets are imperfect. These findings do not discourage asset accumulation policies as a remedy against child labour but support policies that aim at increasing returns on the assets.Child labour, Poverty, Assets, Malawi

A control theory model for human decision making

The optimal control model for pilot-vehicle systems has been extended to handle certain types of human decision tasks. The model for decision making incorporates the observation noise, optimal estimation, and prediction concepts that form the basis of the model for control behavior. Experiments are described for the following task situations: (1) single decision tasks; (2) two decision tasks; and (3) simultaneous manual control and decision tasks. Using fixed values for model parameters, single-task and two-task decision performance scores to within an accuracy of 10 percent can be predicted. The experiment on simultaneous control and decision indicates the presence of task interference in this situation, but the results are not adequate to allow a conclusive test of the predictive capability of the model

The state of knowledge concerning the Kuiper belt

The arguments for and against the idea that most short-period comets originate in the Kuiper belt are discussed. Observational constraints on the distribution of mass in the Kuiper belt are reviewed as well as a model of the physical conditions that now exist. Finally, predictions from this model about the detectability of the Kuiper belt are compared to optical surveys

Use of Linear Perspective Scene Cues in a Simulated Height Regulation Task

As part of a long-term effort to quantify the effects of visual scene cuing and non-visual motion cuing in flight simulators, an experimental study of the pilot's use of linear perspective cues in a simulated height-regulation task was conducted. Six test subjects performed a fixed-base tracking task with a visual display consisting of a simulated horizon and a perspective view of a straight, infinitely-long roadway of constant width. Experimental parameters were (1) the central angle formed by the roadway perspective and (2) the display gain. The subject controlled only the pitch/height axis; airspeed, bank angle, and lateral track were fixed in the simulation. The average RMS height error score for the least effective display configuration was about 25% greater than the score for the most effective configuration. Overall, larger and more highly significant effects were observed for the pitch and control scores. Model analysis was performed with the optimal control pilot model to characterize the pilot's use of visual scene cues, with the goal of obtaining a consistent set of independent model parameters to account for display effects

An Oort cloud origin for the high-inclination, high-perihelion Centaurs

We analyse the origin of three Centaurs with perihelia in the range 15 AU to 30 AU, inclinations above 70 deg and semi-major axes shorter than 100 AU. Based on long-term numerical simulations we conclude that these objects most likely originate from the Oort cloud rather than the Kuiper Belt or Scattered Disc. We estimate that there are currently between 1 and 200 of these high-inclination, high-perihelion Centaurs with absolute magnitude H<8.Comment: Accepted for publication in MNRA

Seasonal bias in household vulnerability to poverty stimates: insights from a natural experiment

Using data from 260 households from the Hadejia-Nguru wetlands, the paper shows that vulnerability to poverty estimates are biased if the data used is seasonal. The seasonal bias in the consumption expenditure is less pronounced than in its variance. The paper further shows that the relative sizes of the seasonal bias in expected consumption expenditure and its variance determines the final magnitude of the bias. However, the bias in the expected consumption expenditure is sufficiently corrected by including seasonal dummy variables. We therefore encourage researchers to consider seasonality when they are modelling consumption expenditure with the aim of estimating vulnerability.Seasonal bias; vulnerability to poverty; natural experiment; Nigeria