1,689 research outputs found

    How two business models respond to current chalenges of agrowood production: the case of Brandenburg, Germany

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    PosterThe agrowood acreage in Brandenburg has increased fifteen-fold since 2008 reaching in 2013 1819ha (Ministerium fĂĽr Infrastruktur und Landwirtschaft 2013) and therefore the leading position of all federal states in Germany. Despite of the constant rise and the chances associated with the production of agrowood, potential producers have to face a wide range of challenges: uncertainties about yields, high initial investments, a fixation of land for the 20 years` lifetime of an agrowood plantation and an irregular cash flow all 3 or 5 years. A non-transparent market in addition to lacking long term experiences and machinery available, affects the decision-making process of potential producers negatively. In Brandenburg this innovative crop, growing even under harsh conditions, matches the unfavorable agricultural conditions (Murach et al. 2008). Our subjects of investigation are the two prevailing business models in the agrowood sector in Brandenburg: comprehensive cooperation agreements and independent farming. They coexist and mutually interact with synergies as well as obstructions. We combine a qualitative method with guided interviews focusing on planting decision making processes with a modeling approach using different risk levels and yield expectations to analyze transaction and opportunity costs of those two models. Thereby the characteristics and effects of the business models are compared and analyzed. Our results show that cooperation agreements have effects on the actor`s decision by motivating farmers to decide in favor of agrowood. They also contribute to an expansion of agrowood acreage accounting for almost 40% of the total area in Brandenburg in 2012 (Ehm 2013). Furthermore cooperation agreements are affirmed by interviewees to overcome economic, trade and machinery related constraints of agrowood, secure long-term incomes and increase creditworthiness of producers. In contrast, independent producers are acknowledged to have the burden of higher risks, but may benefit from governmental support programs, which not apply for contract farmers

    Composition, volume, and aspect ratio dependence of the strain distribution, band lineups and electron effective masses in self-assembled pyramidal In1-xGaxAs/GaAs and SixGe1-x/Si quantum dots

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    We present a systematic investigation of the strain distribution of self-assembled pyramidal In1-xGaxAs/GaAs and SixGe1-x/Si quantum dots for the case of growth on a (001) substrate. The dependence of the biaxial and hydrostatic components of the strain on the quantum dot volume, aspect ratio, composition, and percentage of alloying x is studied using a method based on a Green's function technique. The dependence of the carriers' confining potentials and the electronic effective mass on the same parameters is then calculated in the framework of eight-band k .p theory. The results for which comparable published data are available are in good agreement with the theoretical values for strain profiles, confining potentials, and electronic effective mass. © 2002 American Institute of Physics

    Effect of deconfinement on resonant transport in quantum wires

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    The effect of deconfinement due to finite band offsets on transport through quantum wires with two constrictions is investigated. It is shown that the increase in resonance linewidth becomes increasingly important as the size is reduced and ultimately places an upper limit on the energy (temperature) scale for which resonances may be observed.Comment: 6 pages, 6 postscript files with figures; uses REVTe

    Changes in the electrical transport of ZnO under visible light

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    Complex impedance spectroscopy data in the frequency range 16Hz < f < 3 MHz at room temperature were acquired on pure ZnO single crystal and thin film. The measured impedance of the ZnO samples shows large changes with time after exposure to or covering them from visible light. At fixed times Cole-Cole-diagrams indicate the presence of a single relaxation process. A simple analysis of the impedance data allows us to obtain two main relaxation times. The behavior for both, ZnO crystal and thin film, is similar but the thin film shows shorter relaxation times. The analysis indicates the existence of two different photo-active defects with activation energies between ~0.8 eV and ~1.1 eV.Comment: 11 pages, 9 figures. Solid state communications, in pres
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