Failure sensing and protection circuit for converter networks Patent

Circuit design for failure sensing and protecting low voltage electric generator and power transmission network

Absence of orbital-selective Mott transition in Ca_2-xSr_xRuO4

Quasi-particle spectra of the layer perovskite Sr$_2$RuO$_4$ are calculated within Dynamical Mean Field Theory for increasing values of the on-site Coulomb energy $U$. At small $U$ the planar geometry splits the $t_{2g}$ bands near $E_F$ into a wide, two-dimensional $d_{xy}$ band and two narrow, nearly one-dimensional $d_{xz,yz}$ bands. At larger $U$, however, the spectral distribution of these states exhibit similar correlation features, suggesting a common metal-insulator transition for all $t_{2g}$ bands at the same critical $U$.Comment: 4 pages, 4 figure

1/z-renormalization of the mean-field behavior of the dipole-coupled singlet-singlet system HoF_3

The two main characteristics of the holmium ions in HoF_3 are that their local electronic properties are dominated by two singlet states lying well below the remaining 4f-levels, and that the classical dipole-coupling is an order of magnitude larger than any other two-ion interactions between the Ho-moments. This combination makes the system particularly suitable for testing refinements of the mean-field theory. There are four Ho-ions per unit cell and the hyperfine coupled electronic and nuclear moments on the Ho-ions order in a ferrimagnetic structure at T_C=0.53 K. The corrections to the mean-field behavior of holmium triflouride, both in the paramagnetic and ferrimagnetic phase, have been calculated to first order in the high-density 1/z-expansion. The effective medium theory, which includes the effects of the single-site fluctuations, leads to a substantially improved description of the magnetic properties of HoF_3, in comparison with that based on the mean-field approximation.Comment: 26pp, plain-TeX, JJ

Micro-mineral profile in different grassland species

The aim was to investigate the micro-mineral profile of herbage as affected by grassland species, cutting time and seasonality and in relation to dairy cow requirements. The different grassland species were grown and harvested in mixtures with one grass and one legume for two growing seasons. The species turned out to have very individual mineral profiles, not influenced by year. Among the legumes red clover (Trifolium pratense) had high concentrations of Co, Cu and Zn, white clover (Trifolium repens) of Mn and Fe, lucerne (Medicago sativa) of Se and lotus (Lotus corniculatus) of Co, Mn, Zn and Fe. Among the grasses perennial ryegrass (Lolium perenne) generally had the highest concentrations of all the micro-minerals. Hybrid ryegrass (Lolium hybridum) had slightly lower concentrations than perennial ryegrass for all minerals. Meadow fescue (Festuca pratensis) had lower concentrations still, and timothy (Phleum pratense) had, with the exception of Zn, the lowest concentrations. In general, the mineral concentrations were higher in summer than in spring growth. During the growth Cu, Zn and Fe concentrations decreased, whereas Co, Se and Mg were unaffected. It was concluded that a mixture of red clover and perennial ryegrass had the best profile of micro-minerals for cattle feeding

Vitamin and mineral content and feeding value of different legumes and grass species grown in seven legume-grass mixtures

The aim was to examine if including a range of grassland species could help to balance the diet on organic dairy farms compared with traditional mixtures. Four different grass species and four legume species were grown and harvested in mixtures with one grass and one legume for two growing seasons. The species turned out to have very individual mineral, vitamin and fiber profiles and organic matter digestibility, not influenced by year. Among the legumes red clover (Trifolium pratense) and white clover (Trifolium repens) had the highest feeding value and red clover had further a high content of Co, Cu and Zn. Lucerne (Medicago sativa) had as red clover a high growth potential in mixture but had in general a low content of macro and micro minerals with exception of Se. Lotus (Lotus corniculatus) had a low competitive strength, and the effect of the whole herbage was therefore limited even that the content of the vitamins were high. Among the grasses perennial ryegrass (Lolium perenne) generally had the highest feeding value, and a higher content of the macro and micro minerals and of vitamins as well than the other grasses (hybrid ryegrass (Lolium hybridum), meadow fescue (Festuca pratensis) and timothy (Phleum pratense)). The only exception was meadow fescue, which had a higher content of alfa-tocopherol

15Nitrogen uptake from shallow- versus deep-rooted plants in multi-species mixtures and monoculture grassland

Only few studies have explored the importance of functional diversity in temperate agricultural grasslands in relation to nitrogen (N) uptake. This study investigates the consequence of growing deep-rooted plants together with grass-clover mixtures in terms of N uptake efficiency from deep soil layers. The objective was to compare the N uptake of the shallow-rooted grassland species Lolium perenne and Trifolium repens; and the deep-rooted species Cichorium intybus and Medicago sativa in monocultures and mixtures. We hypothesized that growing deep-rooted plant species in mixture with shallow-rooted species increases the N uptake from deep soil layers partly through competition. A 15N tracer study was carried out with 15N enriched ammonium-sulphate placed at three different soil depths (40, 80 and 120 cm). To recover 15N, above-ground plant biomass was harvested after 10 days. We described the decline of 15N uptake with depth by using an exponential decay function. The studied plant communities showed the same relative decline in 15N uptake by increasing soil depths, but different capacities in total 15N uptake. Monoculture L. perenne foraged less 15N in all depths compared to the other four plant communities. The relative 15N uptake of individual plant species grown in mixture decreased stronger with depth than in monoculture. Thus, both findings rejected our hypothesis

15Nitrogen transfer from legumes to neighbouring plants in multi-species grassland

This study investigates the N transfer from legumes to neighbouring plants, grasses, legumes and herbs in a temperate grassland. In a field experiment white clover (Trifolium repens), red clover (Trifolium pratense) and lucerne (Medicago sativa) were leaf-labelled with 15N enriched urea. The 15N tracer was measured in above-ground plant tissue of eight neighbouring plants in two subsequent harvests in 2008. The three legumes donated 15N to all neighbouring plants, of which grasses, white and red clover were strong receivers. Results show that N transfer increases with N application and from the 1st to the 2nd cut

Low-density series expansions for directed percolation II: The square lattice with a wall

A new algorithm for the derivation of low-density expansions has been used to greatly extend the series for moments of the pair-connectedness on the directed square lattice near an impenetrable wall. Analysis of the series yields very accurate estimates for the critical point and exponents. In particular, the estimate for the exponent characterizing the average cluster length near the wall, $\tau_1=1.00014(2)$, appears to exclude the conjecture $\tau_1=1$. The critical point and the exponents $\nu_{\parallel}$ and $\nu_{\perp}$ have the same values as for the bulk problem.Comment: 8 pages, 1 figur

Low-density series expansions for directed percolation III. Some two-dimensional lattices

We use very efficient algorithms to calculate low-density series for bond and site percolation on the directed triangular, honeycomb, kagom\'e, and $(4.8^2)$ lattices. Analysis of the series yields accurate estimates of the critical point $p_c$ and various critical exponents. The exponent estimates differ only in the $5^{th}$ digit, thus providing strong numerical evidence for the expected universality of the critical exponents for directed percolation problems. In addition we also study the non-physical singularities of the series.Comment: 20 pages, 8 figure

FeederAnt - An autonomous mobile unit feeding outdoor pigs

Small robots and the concept of decentralized animal husbandry make it possible to renew the principles of organic agriculture. The farm animals will be able to use the same type of housing and are placed integrated with the fields. This is expected to achieve a better utilization of nutrients and a better survival rate for useful insects and micro organisms. The small fields are flexible and could fit to the variation in soil structure topography. This type of precision agriculture has the possibility of increasing biodiversity. The paper presents the concept of an autonomic feeding system for outdoor piglets. Initial results are presented using a remote controlled feeding unit (a prototype of the FeederAnt) to feed several pens with piglets. The FeederAnt drives into the grass paddocks twice a day and position itself in a new location for each feeding. This will help to distribute the manure from the animals evenly over the grass paddock to prevent point leaching of nutrients. The FeederAnt replaces many stationary feeding tables and reduce the amount of daily manual feeding routines. Further, it is expected that the problem with vermins will be solved since no feed residues will be left within the pens.