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Search Results: 1 - 10 of 26247 matches for " Martin Hulman "
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Livestock policy and trade issues in SADC : policy and trade issues
B. Hulman
Onderstepoort Journal of Veterinary Research , 2010, DOI: 10.4102/ojvr.v76i1.79
Abstract: As from 2001, the Southern African Development Community (SADC) has embarked on a course to deepen regional integration through restructuring. Under the new structure SADC has centralised the coordination of its activities to the Secretariat in Gaborone. The former Sector Coordinating Units have been merged into four directorates, one of which is the Food, Agriculture and Natural Resources (FANR) Directorate, which comprises, amongst others, the Livestock Development Unit (LDU).
Electronic Transport in Composites of Graphite Oxide with Carbon Nanotubes
Viera Skakalova,Viliam Vretenar,Lubomir Kopera,Peter Kotrusz,Clemens Mangler,Marcel Mesko,Jannik C. Meyer,Martin Hulman
Physics , 2013,
Abstract: We show that the presence of electrically insulating graphite oxide (GO) within a single wall carbon nanotube network strongly enhances electrical conductivity, whereas reduced graphite oxide, even though electrically conductive, suppresses electrical conductivity within a composite network with single wall carbon nanotubes. Measurements of Young modulus and of Raman spectra strongly support our interpretation of the indirect role of the oxide groups, present in graphite oxide within the single wall carbon nanotubes/graphite oxide composite, through electronic doping of metallic single wall carbon nanotubes.
Superposition of Quantum and Classical Rotational Motions in Sc2C2@C84 Fullerite
K. H. Michel,B. Verberck,M. Hulman,H. Kuzmany,M. Krause
Physics , 2007, DOI: 10.1063/1.2434175
Abstract: The superposition of the quantum rotational motion (tunneling) of the encapsulated Sc2C2 complex with the classical rotational motion of the surrounding C84 molecule in a powder crystal of Sc2C2@C84 fullerite is investigated by theory. Since the quantum rotor is dragged along by the C84 molecule, any detection method which couples to the quantum rotor (in casu the C2 bond of the Sc2C2 complex also probes the thermally excited classical motion (uniaxial rotational diffusion and stochastic meroaxial jumps) of the surrounding fullerene. The dynamic rotation-rotation response functions in frequency space are obtained as convolutions of quantum and classical dynamic correlation functions. The corresponding Raman scattering laws are derived, the overall shape of the spectra and the width of the resonance lines are studied as functions of temperature. The results of the theory are confronted with experimental low-frequency Raman spectra on powder crystals of Sc2C2@C84 [M. Krause et al., Phys. Rev. Lett. 93, 137403 (2004)]. The agreement of theory with experiment is very satisfactory in a broad temperature range.
A Yield Mapping Procedure Based on Robust Fitting Paraboloid Cones on Moving Elliptical Neighborhoods and the Determination of Their Size Using a Robust Variogram  [PDF]
Martin Bachmaier
Positioning (POS) , 2010, DOI: 10.4236/pos.2010.11004
Abstract: The yield map is generated by fitting the yield surface shape of yield monitor data mainly using paraboloid cones on floating neighborhoods. Each yield map value is determined by the fit of such a cone on an elliptical neighborhood that is wider across the harvest tracks than it is along them. The coefficients of regression for modeling the paraboloid cones and the scale parameter are estimated using robust weighted M-estimators where the weights decrease quadratically from 1 in the middle to zero at the border of the selected neighborhood. The robust way of estimating the model parameters supersedes a procedure for detecting outliers. For a given neighborhood shape, this yield mapping method is implemented by the Fortran program paraboloidmapping.exe, which can be downloaded from the web. The size of the selected neighborhood is considered appropriate if the variance of the yield map values equals the variance of the true yields, which is the difference between the variance of the raw yield data and the error variance of the yield monitor. It is estimated using a robust variogram on data that have not had the trend removed.
Sources of inaccuracy when estimating economically optimum N fertilizer rates  [PDF]
Martin Bachmaier
Agricultural Sciences (AS) , 2012, DOI: 10.4236/as.2012.33037
Abstract: Nitrogen rate trials are often performed to determine the economically optimum N application rate. For this purpose, the yield is modeled as a function of the N application. The regression analysis provides an estimate of the modeled function and thus also an estimate of the economic optimum, Nopt. Obtaining the accuracy of such estimates by confidence intervals for Nopt is subject to the model assumptions. The dependence of these assumptions is a further source of inaccuracy. The Nopt estimate also strongly depends on the N level design, i.e., the area on which the model is fitted. A small area around the supposed Nopt diminishes the dependence of the model assumptions, but prolongs the confidence interval. The investigations of the impact of the mentioned sources on the inaccuracy of the Nopt estimate rely on N rate trials on the experimental field Sieblerfeld (Bavaria). The models applied are the quadratic and the linear-plus-plateau yield regression model.
Waiting for Redemption in The House of Asterion: A Stylistic Analysis  [PDF]
Martin Tilney
Open Journal of Modern Linguistics (OJML) , 2012, DOI: 10.4236/ojml.2012.22007
Abstract: The House of Asterion is a short story by Jorge Luis Borges that retells the classical myth of the Cretan Minotaur from an alternate perspective. The House of Asterion features the Minotaur, aka Asterion, who waits for “redemption” in his labyrinth. Many literary critics have suggested that the Borgesian labyrinth is a metaphor for human existence and the universe itself. Others have correctly interpreted Asterion’s ironic death at the hands of Theseus as his eagerly awaited redemption. Borges’ subversion of the reader’s expectations becomes the departure point for a systemic functional stylistic analysis of the story in one of its English translations, revealing how deeper-level meanings in the text are construed through its lexicogrammatical structure. A systemic functional stylistic reading suggests that on a higher level of reality, Asterion’s redemption is not only the freedom that death affords, but also a transformation that transcends his fictional universe. Asterion’s twofold redemption is brought about not only by the archetypal hero Theseus but also by the reader, who through the process of reading enables Asterion’s emancipation from the labyrinth.
A Macroeconomic Model of Biodiversity Protection  [PDF]
David Martin
Theoretical Economics Letters (TEL) , 2013, DOI: 10.4236/tel.2013.35A1006
Abstract:

Many biodiversity researchers have responded to the financial constraints faced by policy makers to develop models based upon the “Noah’s Ark” metaphor, implying that society can save only a limited amount of biodiversity. Unfortunately, as Herman Daly (Land Economics, 1991) pointed out, such microeconomic rules can allow an ark to sink albeit in some optimal fashion. So, I step back to look at the macroeconomic question, how big should the ark be? I start with Norgaard’s (Ecological Economics, 2010) framework, which is based upon the concept of a production possibility frontier combined with a sustainability criterion. I develop a model from that starting point by shifting to an isoquant framework while maintaining the strong sustainability criterion. I demonstrate how this model allows for identifying and addressing the key biodiversity protection policy criteria at the macroeconomic level. One key conclusion from this modeling is that Daly’s analysis remains remarkably prescient.

Analysis of the Navier-Stokes Equations  [PDF]
Helmut Martin
Journal of Applied Mathematics and Physics (JAMP) , 2014, DOI: 10.4236/jamp.2014.210106
Abstract: The Navier-Stokes equations for incompressible fluid flows with impervious boundary and free surface are analyzed by means of a perturbation procedure involving dimensionless variables and a dimensionless perturbation parameter which is composed of kinematic viscosity of fluid, the acceleration of gravity and a characteristic length. The new dimensionless variables are introduced into the equation system. In addition, the perturbation parameter is introduced into terms for deriving approximations systems of different orders. Such systems are obtained by equating coefficients of like powers of perturbation parameter for the successive coefficients in the series. In these systems several terms are analyzed with regards to size and significance. Based on those systems, suitable solutions of NS equations can be found for different boundary conditions. For example, a relation for stationary channel flow is obtained as approximation to the NS equations of the lowest order after transformation back to dimensional variables.
Accelerating Expansion in a Closed Universe  [PDF]
Martin Tamm
Journal of Modern Physics (JMP) , 2015, DOI: 10.4236/jmp.2015.63029
Abstract: In this paper, I suggest a possible explanation for the accelerating expansion of the universe. This model does not require any dark energy or quintessence. Rather, the idea is to suggest a different view on the origin of general relativity. Since it is very difficult to say something in general, I will mainly restrict myself to the case of very low curvature. The question about the underlying reasons for the acceleration is also closely related to the question whether the universe is a finite or infinite. It is part of the purpose of this paper to argue that a phase of accelerating expansion may be very well compatible with the idea of a closed universe.
Time’s Arrow in a Finite Universe  [PDF]
Martin Tamm
International Journal of Astronomy and Astrophysics (IJAA) , 2015, DOI: 10.4236/ijaa.2015.52010
Abstract: In this paper, a simple model for a closed multiverse as a finite probability space is analyzed. For each moment of time on a discrete time-scale, only a finite number of states are possible and hence each possible universe can be viewed as a path in a huge but finite graph. By considering very general statistical assumptions, essentially originating from Boltzmann, we make the set of all such paths (the multiverse) into a probability space, and argue that under certain assumptions, the probability for a monotonic behavior of the entropy is enormously much larger then for a behavior with low entropy at both ends. The methods used are just very simple combinatorial ones, but the conclusion suggests that we may live in a multiverse which from a global point of view is completely time-symmetric in the sense that universes with Time’s Arrow directed forwards and backwards are equally probable. However, for an observer confined to just one universe, time will still be asymmetric.
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