An analytic interface dynamo over a shear layer of finite depth

Parker's analytic Cartesian interface dynamo is generalized to the case of a shear layer of finite thickness and low resistivity ("tachocline"), bounded by a perfect conductor ("radiative zone") on the one side, and by a highly diffusive medium ("convective zone") supporting an $\alpha$-effect on the other side. In the limit of high diffusivity contrast between the shear layer and the diffusive medium, thought to be relevant for the Sun, a pair of exact dispersion relations for the growth rate and frequency of dynamo modes is analytically derived. Graphic solution of the dispersion relations displays a somewhat unexpected, non-monotonic behaviour, the mathematical origin of which is elucidated. The dependence of the results on the parameter values (dynamo number and shear layer thickness) is investigated. The implications of this result for the solar dynamo problem are discussed.Comment: 11 pages, 4 figures Geophys. Astrophys. Fluid Dyn., in pres

Climate or rural development policy?

Being heavily energy dependent, it is not much of a surprise that Europe pays special attention to reducing the use of fossil fuels. Each one of the ten new member states is characterized by relatively low per capita energy consumption and relatively low energy efficiency, and the share of renewables in their energy mix tends to be low, too. The paper examines the problem when policy measures create a decrease in environmental capital instead of an increase. In this case it hardly seems justified to talk about environmental protection. The authors describe a case of a Hungarian rapeseed oil mill which would not be of too much interest on its own but given that almost all similar plants went bankrupt, there are some important lessons to learn from its survival. The enterprise the authors examined aimed at establishing a micro-regional network. They completed a brown-field development to establish a small plant on the premises of a former large agricultural cooperative. By partnering with the former employees and suppliers of the sometime cooperative, they enjoyed some benefits which all the other green-field businesses focusing on fuel production could not. The project improved food security, energy security and population retention as well

Happiness, environmental protection and market economy

The manufacturing sector is leaving the West for Asia’s low wages and good working culture. Europe would be better off keeping these manufacturing activities, slowing down wage inflation and what is more, letting a young, cheaper workforce from the East settle down within their borders. This would aid in preserving the diverse economic structure which has been characteristic for Europe.Beside the economic growth there are two more concepts which have turned into the “holy cows” of economics during the last fifty years. One is the need to constantly improve labor productivity and the other is increasing competitiveness of nations. The high labor productivity of some countries, induces severe unemployment in the globalized world. In the other hand it is high time we understood that it is not competition, but cooperation that brings more happiness to humanity.Should we still opt for “happiness” and “sanity”, it is quite obvious that we all should, in economists’ terms, define our individual welfare functions corresponding to our own set of values, staying free from the influence of media, advertisements and fashion. The cornerstone to all this is the intelligent citizen who prefers local goods and services

Performance Assessment of Mismatch Mitigation Methodologies Using Field Data in Solar Photovoltaic Systems

Partial shading and other non‐ideal conditions cause electrical mismatches that reduce the output power generated by a photovoltaic (PV) system. It affects the overall performance and efficiency of PV systems. Therefore, a model is developed in MATLAB, which analyses the performance of the PV systems under real irradiance profiles and temperatures for various available mismatch mitigation methodologies, i.e., bypass diode, DC power optimizer, and differential power processing (DPP). More specifically, this study will help to understand the best mismatch reduction methodologies for a solar PV system under different scenarios. The results also are validated by comparing them with a similar PV system installed in SolarTechLAB, which also operates under the same irradiance and temperature conditions under which these models are tested. This study also presents novel results, covering discussions on the reverse voltage distribution under mismatch scenarios among bypass diode, DC power optimizer, and DPP techniques

The effect of a meridional flow on Parker's interface dynamo

Parker's interface dynamo is generalized to the case when a homogeneous flow is present in the high-diffusivity (upper) layer in the lateral direction (i.e. perpendicular to the shear flow in the lower layer). This is probably a realistic first representation of the situation near the bottom of the solar convective zone, as the strongly subadiabatic stratification of the tachocline (lower layer in the interface dynamo) imposes a strong upper limit on the speed of any meridional flow there. Analytic solutions to the eigenvalue problem are presented for the cases of vanishing diffusivity contrast and infinite diffusivity contrast, respectively. Unlike the trivial case of a homogeneous system, the ability of the meridional flow to reverse the propagation of the dynamo wave is strongly reduced in the interface dynamo. In particular, in the limit of high diffusivity contrast relevant to the solar case it is found that a meridional flow of realistic amplitude cannot reverse the direction of propagation of the dynamo wave. The implications of this result for the solar dynamo problem are discussed.Comment: 5 pages, 3 figures; MNRAS, in pres

Practical Model for Improved Classification of Trace Chemical Residues on Surfaces in Active Spectroscopic Measurements

Trace chemical detection and classification in stand-off reflection-based spectro- scopic data is challenging due to the variability of measured data and the lack of physics-based models that can accurately predict spectra. Most available models assume that the chemical takes the form of spherical particles or uniform thin films. A more realistic chemical presentation that could be encountered is that of a nonuniform chemical film that is deposited after evaporation of the solvent that contained the chemical. We present an improved signature model for this type of solid film. The proposed model, called sparse transfer matrix, includes a log-normal distribution of film thicknesses and is found to reduce the root mean square error between simulated and measured data by about 25% when compared with either the particle or uniform thin film models. When applied to measured data, the sparse transfer matrix model provides a 10% to 28% increase in classification accuracy over traditional models

Parentage analysis in Hungarian grapevine cultivars of 'Seibel'-'Seyve-Villard' origin

Viticulture is worldwide endangered by powdery (Erysiphe necator) and downy mildew (Plasmopara viticola) fungal diseases. These pathogens derive from North America and got into Europe with infected grape cuttings in the 19th century. Because of the vulnerability of the traditional European grapevine cultivars an interspecific hybrid breeding program was started in France with crossing Vitis species originating from North America and V. vinifera L. varieties. The results of this activity pioneered by Albert Seibel, Bertille Seyve and Victor Villard were hybrids having good quality and carrying partial resistance against fungal pathogens. 'Seibel' and 'Seyve-Villard' grapes were applied in the resistance breeding programs in Hungary, too. We analyzed 22 out of these hybrids, their putative parents and international reference varieties (altogether  40 genotypes) with microsatellite  and ScORA7-760 resistance QTL-linked marker

Phenotyping under extreme weather conditions and microsatellite based genotyping of some Hungarian grape cultivars

Phenology is an indicator of plant response to the environment. In viticulture growth stages timing is important for site and cultivar selection, vineyard planning and cultural practices management. In the last years, autochthonous cultivars obtained an increased interest and, therefore, in this work we studied the phenological performances of Hungarian old varieties. The data recorded in 2012 were compared with the ones published 60 years ago. The examined genotypes were identified by SSR markers. Extremely high temperature and low precipitation occurred during the 2012 vintage. The uncommon weather conditions affected the length of the vegetation period less than expected. However, the time period between flowering and harvest decreased significantly. In general, minor varieties seem to be more sensitive to extreme conditions than international cultivars, according to their eno-carpological characteristics

Origin of 'Csillám', a promising source for black rot resistance

Resaerch Not

Marker assisted selection for berry colour in a ‘Nektár’ x ‘Jacquez’ grape progeny

Research Not