389 research outputs found
Applying the proto-theory of design to explain and modify the parameter analysis method of conceptual design
This article reports on the outcomes of applying the notions provided by the reconstructed proto-theory of design, based on Aristotle’s remarks, to the parameter analysis (PA) method of conceptual design. Two research questions are addressed: (1) What further clarification and explanation to the approach of PA is provided by the proto-theory? (2) Which conclusions can be drawn from the study of an empirically derived
design approach through the proto-theory regarding usefulness, validity and range of that theory? An overview of PA and an application example illustrate its present model and unique characteristics. Then, seven features of the proto-theory are explained and demonstrated through geometrical problem solving and analogies are drawn between these features and the corresponding ideas in modern design thinking.
Historical and current uses of the terms analysis and synthesis in design are also outlined and contrasted, showing that caution should be exercised when applying them. Consequences regarding the design moves, process and strategy of PA allow proposing modifications to its model, while demonstrating how the ancient method of analysis can contribute to better understanding of contemporary design-theoretic issues
Stochastic Line-Motion and Stochastic Conservation Laws for Non-Ideal Hydromagnetic Models. I. Incompressible Fluids and Isotropic Transport Coefficients
We prove that smooth solutions of non-ideal (viscous and resistive)
incompressible magnetohydrodynamic equations satisfy a stochastic law of flux
conservation. This property involves an ensemble of surfaces obtained from a
given, fixed surface by advecting it backward in time under the plasma velocity
perturbed with a random white-noise. It is shown that the magnetic flux through
the fixed surface is equal to the average of the magnetic fluxes through the
ensemble of surfaces at earlier times. This result is an analogue of the
well-known Alfven theorem of ideal MHD and is valid for any value of the
magnetic Prandtl number. A second stochastic conservation law is shown to hold
at unit Prandtl number, a random version of the generalized Kelvin theorem
derived by Bekenstein-Oron for ideal MHD. These stochastic conservation laws
are not only shown to be consequences of the non-ideal MHD equations, but are
proved in fact to be equivalent to those equations. We derive similar results
for two more refined hydromagnetic models, Hall magnetohydrodynamics and the
two-fluid plasma model, still assuming incompressible velocities and isotropic
transport coefficients. Finally, we use these results to discuss briefly the
infinite-Reynolds-number limit of hydromagnetic turbulence and to support the
conjecture that flux-conservation remains stochastic in that limit.Comment: 20 pages, no figures, submitted to J. Math. Phys
A nullstellensatz for sequences over F_p
Let p be a prime and let A=(a_1,...,a_l) be a sequence of nonzero elements in
F_p. In this paper, we study the set of all 0-1 solutions to the equation a_1
x_1 + ... + a_l x_l = 0. We prove that whenever l >= p, this set actually
characterizes A up to a nonzero multiplicative constant, which is no longer
true for l < p. The critical case l=p is of particular interest. In this
context, we prove that whenever l=p and A is nonconstant, the above equation
has at least p-1 minimal 0-1 solutions, thus refining a theorem of Olson. The
subcritical case l=p-1 is studied in detail also. Our approach is algebraic in
nature and relies on the Combinatorial Nullstellensatz as well as on a Vosper
type theorem.Comment: 23 page
Le traitement de l’entérite chronique hypertrophiante des Bovidés par les sulfones
Verge Jean, Goret Pierre, Cauchy Laurent. Le traitement de l’entérite chronique hypertrophiante. In: Bulletin de l'Académie Vétérinaire de France tome 104 n°2, 1951. pp. 97-99
Imaging-guided interventions modulating portal venous flow: Evidence and controversies
Portal hypertension is defined by an increase in the portosystemic venous gradient. In most cases, increased resistance to portal blood flow is the initial cause of elevated portal pressure. More than 90% of cases of portal hypertension are estimated to be due to advanced chronic liver disease or cirrhosis. Transjugular intrahepatic portosystemic shunts, a non-pharmacological treatment for portal hypertension, involve the placement of a stent between the portal vein and the hepatic vein or inferior vena cava which helps bypass hepatic resistance. Portal hypertension may also be a result of extrahepatic portal vein thrombosis or compression. In these cases, percutaneous portal vein recanalisation restores portal trunk patency, thus preventing portal hypertension-related complications. Any portal blood flow impairment leads to progressive parenchymal atrophy and triggers hepatic regeneration in preserved areas. This provides the rationale for using portal vein embolisation to modulate hepatic volume in preparation for extended hepatic resection. The aim of this paper is to provide a comprehensive evidence-based review of the rationale for, and outcomes associated with, the main imaging-guided interventions targeting the portal vein, as well as to discuss the main controversies around such approaches. (c) 2022 The Authors. Published by Elsevier B.V. on behalf of European Association for the Study of the Liver (EASL). This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/)
Stevin numbers and reality
We explore the potential of Simon Stevin's numbers, obscured by shifting
foundational biases and by 19th century developments in the arithmetisation of
analysis.Comment: 22 pages, 4 figures. arXiv admin note: text overlap with
arXiv:1104.0375, arXiv:1108.2885, arXiv:1108.420
Le traitement de l'entérite chronique hypertrophiante des Bovidés par la streptomycine
Cauchy Laurent, Goret Pierre, Mérieux Charles, Verge Jean. Le traitement de l’entérite chronique hyperthrophiante des Bovidés par la streptomycine. In: Bulletin de l'Académie Vétérinaire de France tome 104 n°2, 1951. pp. 93-95
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