Theoretical and experimnental studies of the critical line length for the interruption of short-line faults

1981 ◽  
Vol PAS-100 (7) ◽  
pp. 3545-3552 ◽  
Author(s):  
U. Habedank ◽  
R. Kugler
Keyword(s):  
Author(s):  
Sape A. Miedema

In Deep Sea Mining, material will be excavated at the sea floor and transported to the surface. This transport always consists of horizontal and vertical transport and can be carried out mechanically or hydraulically. If the transport is hydraulically, during the horizontal transport there is a danger of bed formation and plugging the line. This is similar to the horizontal transport in dredging with the difference that in deep-sea mining the line length is much smaller, but also the line speeds may be smaller. To avoid plugging the line, the line speed has to be higher than a certain critical line speed. In literature there are many theories about this critical line speed and about bed forming in the pipe, but these theories are usually empirical and cannot be applied under all circumstances. Different particles sizes, pipe diameters and line speeds require different equations, although a generic theory should cover everything. For the critical velocity different definitions exist. Some researchers use the definition that above the critical velocity no bed, either stationary or sliding, exits. This definition is also referred to as the limit deposit velocity. Others use the transition between a stationary bed and a sliding bed as the definition of the critical velocity. Whatever definition is used, the Moody friction factor on the bed always plays an important role. Since in literature no explicit formulation for this Moody friction factor exists, an attempt is made to find an explicit formulation for the Moody friction factor for the interface of the fluid flow and the bed, where this interface consists of sheet flow.


2019 ◽  
Author(s):  
◽  
Daniel William Pinder

Sperber and Wilson (1995:222) posit the term poetic effect for the peculiar effect of an utterance which achieves most of its relevance through a wide array of weak implicatures. Crucially, the input to pragmatic processing, which prompts the derivation of a poetic effect, is achieved via some stylistically pronounced linguistic feature: for example, a repeated lexical item, a peculiar syntactic form, a piece of alliteration, and so on. However, what has never been considered to any great depth from a relevancetheoretic perspective is how unusual elements of visuospatial form might also impact upon the reader’s basic understanding and wider interpretation of a given poetic text in ways that result in the derivation of specialised poetic effects. Therefore, the thesis posits a relevance-theoretic account of the cognitive-pragmatic effects of short linelength and line divisions, when employed and interpreted within complex forms of poetry. The account is split into two hypotheses relating to short line-length and line divisions respectively. Hypothesis 1 states that the use of short line-length leads to the majority of the text’s lexical material being perceived in a much slower, and therefore intense fashion, which consequently causes the lexical and encyclopaedic entries that such material links to within the mind to remain active for relatively longer periods of time. During such extended periods of lexical and encyclopaedic activation, literary readers are encouraged to inferentially process the text’s explicit-propositional content in relation to a range of further items of encyclopaedic-contextual material, which can give rise to arrays of additional contextual effects of a weakly implicit and therefore poetic nature. Hypothesis 2 states that line divisions are often intentionally utilised in poetic texts by writers in order to visuospatially separate integral syntactic units upon the page. This can encourage readers to pause and briefly consider, upon an anticipatoryhypothetical basis, the various possible pragmatic extensions of the text’s momentarily incomplete logical and propositional status, pre-line division as it were. The various pragmatic extensions may be formulated as arrays of weak explicatures, which for some readers may achieve poetic effects (in the specialised relevance-theoretic sense of the term). The process effectively constitutes the visuospatial equivalent of a deliberate ‘pause for effect’, which triggers a considerable degree of further inferential processing, and provides a distinct communicational ‘reward’ primarily at an explicit-propositional level.


Perception ◽  
1995 ◽  
Vol 24 (5) ◽  
pp. 513-524 ◽  
Author(s):  
Michael J Morgan ◽  
Andrew Medford ◽  
Philip Newsome

A line abutting two tilted flanks is apparently shifted towards the orientation orthogonal to the flanks and at the same time is reduced in its apparent length. It has been suggested that both effects are caused by band-pass spatial filtering, followed by location of the end points of the line at the peaks in the filtered image. Here implications of the filtering explanation of these effects are explored further. In the first experiment, it was predicted that orientation thresholds (as opposed to biases) would be increased for short line lengths, and would be further increased by abutting bars. The predictions were confirmed. It was shown in experiment 2 that the orientation shift was reduced by a small (4 min arc) gap between target lines and orthogonal flanks. In experiment 3 the threshold elevations and the orientation shift produced by orthogonal and tilted flanks were compared. Last, in experiment 4, the threshold elevations and orientation shift produced by orthogonal and tilted flanks, at different retinal eccentricities varying from 0 to 3.2 deg were compared, and the prediction that the magnitude of the orientation shift would decrease with line length and increase with eccentricity was confirmed. The connection is explored between the orientation shift and the Zöllner illusion, and demonstrations are presented of the Zöllner effect in which target and inducing lines are of opposite contrast on a gray background. It is concluded that the Judd and Zöllner illusions do not depend upon a single mechanism.


2004 ◽  
Vol 63 (3) ◽  
pp. 143-149 ◽  
Author(s):  
Fred W. Mast ◽  
Charles M. Oman

The role of top-down processing on the horizontal-vertical line length illusion was examined by means of an ambiguous room with dual visual verticals. In one of the test conditions, the subjects were cued to one of the two verticals and were instructed to cognitively reassign the apparent vertical to the cued orientation. When they have mentally adjusted their perception, two lines in a plus sign configuration appeared and the subjects had to evaluate which line was longer. The results showed that the line length appeared longer when it was aligned with the direction of the vertical currently perceived by the subject. This study provides a demonstration that top-down processing influences lower level visual processing mechanisms. In another test condition, the subjects had all perceptual cues available and the influence was even stronger.


2008 ◽  
Author(s):  
Clare K. Porac ◽  
Alan Searleman ◽  
Alicia Dunbar
Keyword(s):  

2020 ◽  
Author(s):  
Randolph C Grace ◽  
Nicola J. Morton ◽  
Matt Grice ◽  
Kate Stuart ◽  
Simon Kemp

Grace et al. (2018) developed an ‘artificial algebra’ task in which participants learn to make an analogue response based on a combination of non-symbolic magnitudes by feedback and without explicit instruction. Here we tested if participants could learn to add stimulus magnitudes in this task in accord with the properties of an algebraic group. Three pairs of experiments tested the group properties of commutativity (Experiments 1a-b), identity and inverse existence (Experiments 2a-b) and associativity (Experiments 3a-b), with both line length and brightness modalities. Transfer designs were used in which participants responded on trials with feedback based on sums of magnitudes and later were tested with novel stimulus configurations. In all experiments, correlations of average responses with magnitude sums were high on trials with feedback, r = .97 and .96 for Experiments 1a-b, r = .97 and .96 for Experiments 2a-b, and ranged between r = .97 and .99 for Experiment 3a and between r = .82 and .95 for Experiment 3b. Responding on transfer trials was accurate and provided strong support for commutativity, identity and inverse existence, and associativity with line length, and for commutativity and identity and inverse existence with brightness. Deviations from associativity in Experiment 3b suggested that participants were averaging rather than adding brightness magnitudes. Our results confirm that the artificial algebra task can be used to study implicit computation and suggest that representations of magnitudes may have a structure similar to an algebraic group.


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