The Sector-Shaped Pad

1956 ◽  
Vol 23 (4) ◽  
pp. 584-586
Author(s):  
C. F. Kettleborough
Keyword(s):  
Numerical Methods ◽  
Operating Characteristics ◽  
Simplifying Assumptions ◽  
Varying Viscosity

Abstract Boegli’s simplifying assumptions for the solution of the rectangular pad has been applied to the sector-shaped pad and extended to the case of varying viscosity. The process of obtaining the operating characteristics is very rapid and yields results comparable with those obtained by longer numerical methods.

Collaborative Search in a Mock Baggage Screening Task

2018 ◽  
Author(s):  
Alison Enright ◽  
Jason Scott McCarley
Keyword(s):  
Signal Detection ◽  
Information Integration ◽  
Hierarchical Modeling ◽  
Operating Characteristics ◽  
Bayesian Hierarchical ◽  
Equal Variance ◽  
Collaborative Search ◽  
Baggage Screening ◽  
Simplifying Assumptions ◽  
The Individual

Signal detection theory provides models of information integration that allow researchers to predict and benchmark collaborative performance in a visual search task. Naturalistic stimuli, however, may not conform to the simplifying assumptions—specifically, assumptions of equal-variance signal and noise distributions and stochastically independent observers—that are often made to make collaborative signal detection models tractable. Here, we used Bayesian hierarchical modeling of receiver operating characteristics to circumvent this difficulty. Participants (N = 28–32 per experiment) performed a simulated baggage x-ray screening task, working alone or in teams of two. Team performance was compared to the predictions of two versions of a uniform weighting model of information integration, one that assumed stochastically independent judgments from the two members of a team and one that allowed for correlated judgments. Across four experiments, teams fell short of the uncorrelated-judgment model’s predictions, but outperformed predictions based on the observed correlations in individual judgments. Results imply motivational effects that improve individual searchers’ effort under collaborative conditions, or collaborative strategies that effectively decorrelate the individual searchers’ judgments.

scholarly journals The equations of ferrohydrodynamics: Modeling and numerical methods

2016 ◽  
Vol 26 (13) ◽  
pp. 2393-2449 ◽  
Author(s):  
Ricardo H. Nochetto ◽  
Abner J. Salgado ◽  
Ignacio Tomas
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Numerical Methods ◽  
Boundary Conditions ◽  
Numerical Experiments ◽  
Numerical Scheme ◽  
Stability Estimate ◽  
Simplifying Assumptions ◽  
Energy Stable ◽  
Magnetizing Field

We discuss the equations describing the motion of ferrofluids subject to an external magnetic field. We concentrate on the model proposed by Rosensweig, provide an appropriate definition for the effective magnetizing field, and explain the simplifications behind this definition. We show that this system is formally energy stable, and devise a numerical scheme that mimics the same stability estimate. We prove that solutions of the numerical scheme always exist and, under further simplifying assumptions, that the discrete solutions converge. We also discuss alternative formulations proposed in pre-existing work, primarily involving a regularization of the magnetization equation and supply boundary conditions which lead to an energy stable system. We present a series of numerical experiments which illustrate the potential of the scheme in the context of real applications.

Rigorous Performance Prediction Without Drudgery.

1940 ◽  
Vol 44 (350) ◽  
pp. 176-194
Author(s):  
Elliott G. Reid
Keyword(s):  
Numerical Methods ◽  
Performance Prediction ◽  
Convenient Method ◽  
Graphical Method ◽  
Constant Speed ◽  
List Type ◽  
Type Number ◽  
Level Flight ◽  
Simplifying Assumptions ◽  
Power Curves

SummaryA new graphical method of predicting aeroplane performance has been evolved by utilising the unique properties of Eiffel's logarithmic propeller chart. Its substitution for rigorous numerical methods results in the saving of labour without sacrifice of accuracy. Particularly convenient when constant speed propellers are involved, this method yields performance characteristics for altitudes below, as well as above, the critical ones for supercharged engines.Although coupling of the word “ rigorous ” with any method of aeroplane performance prediction may be somewhat of a misnomer, the title of this paper is intended to identify a method which falls short of complete rigour only to the extent dictated by acceptance of the following simplifying assumptions :—(1)That the propeller thrust acts along the direction of the flight path, and(2)That lift is equal to weight in steady rectilinear flight.The amount of labour involved in predicting the performance of a modern aeroplane with even this degree of rigour is so great that methods which incorporate additional simplifying assumptions have come into common use—despite their sacrifice of accuracy to convenience—and the more laborious methods are now rarely employed except in studies of very painstaking character. The desirability of minimising the drudgery of rigorous prediction has long impressed the writer and it is the purpose of this paper to describe a graphical method of attaining that objective.The principal departure which characterises the new method is the adaptation of Eiffel's logarithmic propeller chart to the construction of available power curves. The use of “ indicated airspeed ” (σ1/2V) and the analogous quantity “ indicated power ” (σ1/2 h.p.) as co-ordinates causes a single curve to represent the power requirements for level flight at all altitudes. Other simplifications arising from the recognition of certain engine characteristics, utilisation of the unique properties of the Eiffel chart and development of a convenient method for evaluating the excess available power (from logarithmic curves) make it possible to eliminate a large portion of the labour previously required for rigorous performance prediction. The method is not only applicable to, but especially convenient in, the case of the constant speed propeller; moreover, it yields complete level flight and climb characteristics for altitudes below, as well as above, the critical altitudes of supercharged engines.

Numerical Methods

2019 ◽  
Author(s):  
Rajesh Kumar Gupta
Keyword(s):  
Numerical Methods

Kriteriumsbezogene Cut-Off-Werte für Tätigkeitsspielraum und Arbeitsintensität

Diagnostica ◽  
2019 ◽  
Vol 65 (3) ◽  
pp. 179-190 ◽  
Author(s):  
Vincent Mustapha ◽  
Renate Rau
Keyword(s):  
Receiver Operating Characteristics ◽  
Operating Characteristics ◽  
Receiver Operating

Zusammenfassung. Cut-Off-Werte ermöglichen eine ökonomische, binäre Beurteilung von Summenscores. Für Beanspruchungsfragebögen, die personenbezogene Merkmale erfragen, sind Cut-Off-Werte häufig vorhanden und in der klinischen Diagnostik unerlässlich. Für die Bewertung von Arbeitsmerkmalen sind Cut-Off-Werte ebenfalls wünschenswert. Bislang fehlen sie jedoch für die Beurteilung von Arbeitsmerkmalen wie Arbeitsintensität und Tätigkeitsspielraum. Zwischen 2006 und 2016 wurden daher in verschiedenen Branchen 801 objektive Arbeitsplatzanalysen durchgeführt, welche eine Unterteilung in gut und schlecht gestalteten Tätigkeitsspielraum sowie gut und schlecht gestaltete Arbeitsintensität nach DIN EN ISO 6385 (2016) ermöglichen. Anhand dieser Unterteilung wurden mit der Receiver-Operating-Characteristics-Analyse Cut-Off-Werte für den subjektiv-bedingungsbezogen Fragebogen zum Erleben von Arbeitsintensität und Tätigkeitsspielraum (FIT; Richter et al., 2000 ) ermittelt. Für den Tätigkeitsspielraum weisen Summenscores ≤ 22 und für die Arbeitsintensität Summenscores ≥ 15 auf eine schlechte Gestaltung des jeweiligen Arbeitsmerkmals hin. Anhand einer weiteren Stichprobe von 1 076 Arbeitenden konnte gezeigt werden, dass Arbeitende mit schlecht gestaltetem Tätigkeitspielraum vital erschöpfter sowie weniger engagiert sind und Arbeitende mit schlecht gestalteter Arbeitsintensität eine höhere Erholungsunfähigkeit sowie vitale Erschöpfung aufweisen.

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