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Search Results: 1 - 10 of 14079 matches for " Jan Sebestik "
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The Beytr ge at 200: Bolzano's quiet revolution in the philosophy of mathematics
Jan Sebestik,Paul Rusnock
Journal for the History of Analytical Philosophy , 2013, DOI: 10.4148/jhap.v1i8.1460
Abstract: This paper surveys Bolzano's Beytr ge zu einer begründeteren Darstellung der Mathematik (Contributions to a better-grounded presentation of mathematics) on the 200th anniversary of its publication. The first and only published issue presents a definition of mathematics, a classification of its subdisciplines, and an essay on mathematical method, or logic. Though underdeveloped in some areas (including,somewhat surprisingly, in logic), it is nonetheless a radically innovative work, where Bolzano presents a remarkably modern account of axiomatics and the epistemology of the formal sciences. We also discuss the second, unfinished and unpublished issue, where Bolzano develops his views on universal mathematics. Here we find the beginnings of his theory of collections, for him the most fundamental of the mathematical disciplines. Though not exactly the same as the later Cantorian set theory, Bolzano's theory of collections was used in very similar ways in mathematics, notably in analysis. In retrospect, Bolzano's debut in philosophy was a remarkably successful one, though its fruits would only become generally known much later.
A Longitudinal Analysis of the Stability of Household Money Demand  [PDF]
Jan Tin
Modern Economy (ME) , 2011, DOI: 10.4236/me.2011.23046
Abstract: Past aggregate time-series studies, conducted under the assumption of a representative economic agent, frequently show that the demand for narrowly defined M1, especially non-interest-yielding demand deposit, is unstable during periods of financial innovations. Whether this is longitudinally the case among life-cycle savers is unclear. This study utilizes longitudinal data to take another look and find that volatility in the demand for non-interest-earning checking accounts in the mid and late 1990s is attributable solely to the portion held for the transactions motive. When the conventional Baumol-Tobin model is extended to include human capital and family formation variables representing the life-cycle motive, equilibrium money demand is a stable function of both economic and demographic variables.
A Spectral Method in Time for Initial-Value Problems  [PDF]
Jan Scheffel
American Journal of Computational Mathematics (AJCM) , 2012, DOI: 10.4236/ajcm.2012.23023
Abstract: A time-spectral method for solution of initial value partial differential equations is outlined. Multivariate Chebyshev series are used to represent all temporal, spatial and physical parameter domains in this generalized weighted residual method (GWRM). The approximate solutions obtained are thus analytical, finite order multivariate polynomials. The method avoids time step limitations. To determine the spectral coefficients, a system of algebraic equations is solved iteratively. A root solver, with excellent global convergence properties, has been developed. Accuracy and efficiency are controlled by the number of included Chebyshev modes and by use of temporal and spatial subdomains. As examples of advanced application, stability problems within ideal and resistive magnetohydrodynamics (MHD) are solved. To introduce the method, solutions to a stiff ordinary differential equation are demonstrated and discussed. Subsequently, the GWRM is applied to the Burger and forced wave equations. Comparisons with the explicit Lax-Wendroff and implicit Crank-Nicolson finite difference methods show that the method is accurate and efficient. Thus the method shows potential for advanced initial value problems in fluid mechanics and MHD.
Operationalizing Sustainability Principles in the Engineering Profession  [PDF]
Jan Adamowski
Natural Resources (NR) , 2012, DOI: 10.4236/nr.2012.34024
Abstract: The engineering profession has responded to the issue of sustainable development in two main ways. It has responded through public policy statements that acknowledge the magnitude of the problem in addition to pledging to steer engineering towards a more sustainable future, and it has also responded more directly through technological innovation. In this paper, these two responses will be explored with respect to the debate on how to operationalize sustainability principles in practical terms. This paper also attempts to provide the rationale for a philosophy of engineering ethics grounded in the notion of sustainable development. It is hoped that this would lead to a revised “social contract” that would enable engineers to engage more actively in political, technical, economic and social discussions and processes.
Chaos in Planar, Circular, Restricted Three-Body Problem  [PDF]
Jan Vrbik
Applied Mathematics (AM) , 2013, DOI: 10.4236/am.2013.41008

In this article we analyze the motion of a test particle of a planar, circular, restricted three-body problem in resonance, using the Kustaanheimo-Stiefel formalism. We show that a good qualitative description of the motion can be reduced to three simple equations for semi-major axis, eccentricity and resonance angle. Studying these equations reveals the onset of chaos, and sheds a new light on its weak nature. The 7:4 resonance is used as an example.

Compound Means and Fast Computation of Radicals  [PDF]
Jan ?ustek
Applied Mathematics (AM) , 2014, DOI: 10.4236/am.2014.516241
Abstract: In last decades, several algorithms were developed for fast evaluation of some elementary functions with very large arguments, for example for multiplication of million-digit integers. The present paper introduces a new fast iterative method for computing values \"\" with high accuracy, for fixed \"\" and \"\". The method is based on compound means and Padé approximations.
Short Report: A Sponge Phantom Provides a Homogeneous k-Space Pattern at MRI  [PDF]
Jan Menke
Open Journal of Radiology (OJRad) , 2014, DOI: 10.4236/ojrad.2014.42026
Abstract: Background: The spectral coverage of magnetic resonance (MR) sequences can be well assessed in k-space. However, many objects do not provide high signal intensities in the peripheral k-space. Purpose: To experimentally find a phantom that provides a homogeneous spectral pattern also at the high spatial frequencies of the k-space periphery. Material and Methods: Different phantoms were imaged on a 1.5 Tesla magnet, and the resulting MR images were viewed in k-space after fast Fourier transform. Results: Firstly, phantoms with a homogeneous physical structure were studied with a T2-weighted MR sequence, but they provided an inhomogeneous k-space pattern with dominant central low-frequency components. Secondly, phantoms with an inhomogeneous physical structure were studied. In this group, a water-soaked sponge showed a relatively homogeneous k-space pattern also at high spatial frequencies, owing to the fine porous structure. This sponge phantom can also be soaked with Gadolinium chelates for T1-weighted MR imaging. Conclusion: A simple sponge phantom provides a homogeneous k-space pattern, owing to its fine porous structure. This could be utilized in MR sequence development and for viewing the spectral coverage of MR sequences in k-space.

Fully Integrated High-Voltage Generators with Optimized Power Efficiency  [PDF]
Doutreloigne Jan
Journal of Computer and Communications (JCC) , 2014, DOI: 10.4236/jcc.2014.213001

This paper describes how the power efficiency of fully integrated Dickson charge pumps in high- voltage IC technologies can be improved considerably by implementing charge recycling techniques, by replacing the normal PN junction diodes by pulse-driven active diodes, and by choosing an appropriate advanced smart power IC technology. A detailed analysis reveals that the combination of these 3 methods more than doubles the power efficiency compared to traditional Dickson charge pump designs.

Production of Methane Emissions from Ruminant Husbandry: A Review  [PDF]
Jan Broucek
Journal of Environmental Protection (JEP) , 2014, DOI: 10.4236/jep.2014.515141
Abstract: The aim of this review is to summarize the current knowledge of methane (CH4) production from ruminants. The objectives are to identify the factors affecting CH4 production. Methane is a potent greenhouse gas (GHG). Ruminant livestock constitute worldwide the most important source of anthropogenic emissions of methane. There are two main factors influencing global warming change, an increase in greenhouse gas emissions and depletion of the ozone layer. Methane is associated with both factors. Ruminants (dairy, beef, goats, and sheep) are the main contributors to CH4 production. Their CH4 production is a natural and inevitable outcome of rumen fermentation. Feed is converted into products such as milk and meat. Many factors influence ruminant CH4 production, including level of intake, type and quality of feeds, energy consumption, animal size, growth rate, level of production, and environmental temperature. The methane emissions in dairy cows represent values from 151 to 497 g·day-1. Lactating cows produced more CH4 (354 g·day-1) than dry cows (269 g·day-1) and heifers (223 g·day-1). Dairy ewe generates 8.4 kg·head-1 annually. Holstein produced more CH4 (299 g·day-1) than the Crossbred (264 g·day-1). Methane emission by heifers grazing on fertilized pasture was higher (223 g·day-1) than that of heifers on unfertilized pasture (179 g·day-1). The average CH4 emissions are from 161 g·day-1 to 323 g·day-1 in beef cattle. Mature beef cows emit CH4 approximately from 240 g·day-1 to 396 g·day-1. Suffolk sheep emit 22 - 25 g·day-1. The bison’s annual CH4 emissions per year were 72
Time Series Econometrics: A Critique  [PDF]
Jan Kmenta
Open Journal of Applied Sciences (OJAppS) , 2015, DOI: 10.4236/ojapps.2015.512081
Abstract: This is a critical note regarding the currently established econometrics of time series. The criticism involves commonly practiced mechanistic modeling and testing of relationships, taking econometrics away from economics. Among others, modeling economic trends as simple functions of time is extremely naive and testing for cointegration lacks a proper economic foundation.
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