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Most of Austria's organic farms are located in mountainous areas und produce minly milk und beef; whereas a low percentage of cash-crop fanns are organic. As a result, the demnd for organically grown crops cannot be fully met by domestic production. This paper investigates the barriers to adoption of organic agriculture by cash-crop farmers in Austria. In a written survey, 383 conventional farmers provided information on their perception of organic farming und rated the importance of potential barriers to adoption. Technical challenges in cropping und additional labor requirements were rated as the most important barriers, followed by fear of decreased income und marketing problems. Structural und social issues, such as farm size und lack of support from family members, were less important.

The atomic structure, electronic, and magnetic properties of thin Mn films epitaxially grown on Cu͑100͒ substrates have been investigated by ab initio density-functional studies. Because the local-density approximation leads to a rather poor description of the magnetostructural properties of bulk Mn, a detailed study of the effect of generalized gradient corrections ͑GGC͒ to the exchange-correlation functional on the structure and magnetism of Mn in three and two dimensions has been performed. For the bulk we find that the GGC's lift the almost-degeneracy between the competing magnetic configurations and lead to a large magnetovolume effect, in much better agreement with experiment. For free-standing Mn monolayers the effect of the GGC's is even more pronounced: the relative stability of square and hexagonal layers is inverted, antiferromagnetic ordering leads to a large increase of the equilibrium distances. Therefore all investigations of Mn films on Cu substrates have been performed in the generalized gradient approximation. The results demonstrate that homogeneous Mn overlayers are unstable against interdiffusion and the formation of ordered surface alloys. At a coverage of ⌰ϭ0.5 Mn monolayers, an ordered ferromagnetic c(2ϫ2) surface alloy is formed. The same atomic structure is assumed at a coverage of ⌰ϭ1 and leads to an antiferromagnetic coupling between the CuMn alloy layers. In both homogeneous alloy layers and in the surface alloys, Mn is in a high-spin state with a magnetic moment close to 4 B . The large atomic volume of magnetic Mn leads an outward relaxation of the Mn atoms and a pronounced buckling of the surface. Detailed comparisons of the calculated atomic structure with low-energy electron diffraction and photoelectron diffraction experiments and of the electronic structure with photoemission and inverse photoemission spectroscopies are reported.

This paper deals with a method for performance calculation of shuttle-based storage and retrieval systems (SBS/RS) with tier captive shuttles. A continuous time open queueing system with limited capacity approach is applied. The cycle times of shuttles and lifts can be used directly with their time distributions. These cycle times are determined by a discrete spatial value approach. The main novelty of this approach is the use of a time continuous queueing model to take the interactions between lifts and shuttles combined with a spatial discrete approach for the processes of lifts and shuttles into account. A comparison between the analytical approach and a discrete events simulation is presented to validate the developed model. The data used in this comparison to validate this approach was given by an European material handling provider. Finally, it will be outlined how the model can be used for designing SBS/RS, to meet given requirements.

This paper presents a method to determine the performance of shuttle-based storage and retrieval systems (SBS/RS) with tier captive single-aisle shuttles and multiple-deep storage. The basis of this calculation method is a continuous-time open queueing system with limited capacity. The cycle times of lifts and shuttles, determined by a spatial value approach, can be directly used in the presented method with their time distributions. To take the multiple storage into account, a probabilitybased approach is applied. The invented approach is validated by a comparison with a discrete event simulation. A European material handling provider had given the data used in this comparison. Finally, an example is presented to outline how this calculation model can be used for designing SBS/RS which fulfil the predefined requirements. The result of this example is that with an increase of the storage depth to a certain value, the throughput increases and the cost decreases up to the same storage depth. Keywords Automated warehouse • Shuttle-based storage and retrieval system • Multiple-deep storage • Analytical and numerical modeling • Performance analysis (2020) 107:859-873