Browsing by Author "Pohl, Christian"

Inelastic neutron scattering with emphasis on low-lying modes as well as cold neutron leakage measurements were performed on four prospective advanced cold moderator materials. Employing the time-of-flight instrument SV29 and DNS at the Julich FRJ-2 reactor, spectra were obtained from synthetic methane clathrate, tetrahydro-furane (THF) clathrate, 1,3,5-trimethyl-benzene (mesitylene) and light water ice at several temperatures between 2 and 70 K. Excitations at +/- 1,+ 2 and + 3meV were observed with synthetic methane clathrate. In mesitylene a wealth of low lying excitations were found. In the quenched phase we detected lines at 4.7, 7.2, 9.6, 13.6, 15.4, 18.4, 19.0, 23.0, 29.5 and 34.3 meV, respectively. In the annealed phase, we observed significant shifts with the majority of lines. The lowest lying lines now located at 7.0, 8.5 and 10.5 meV, respectively. In ice at T=2K up to now unreported low-lying energy levels were found at 1.8 and 2.6 meV. An additional line at 10 meV was detected in THF clathrate. Mesitylene, synthetic methane clathrate and water ice, all at T=20K, were tested as moderators at the Julich spallation mock-up JESSICA. The expected gain in neutron leakage current at energies around 2meV as compared to liquid hydrogen moderators was observed for methane clathrate and mesitylene. (C) 2004 Elsevier B.V. All rights reserved.

As risk management has gained in importance it has become a focal issue in research, literature, and agricultural consulting. Existing concepts, however, more or less left aside the aspect of (monetary) risk-bearing capacity, that is to say the financial resilience of agricultural holdings although it clearly impacts the risk assessment as such and especially the selection of appropriate tools to effectively manage risks (and opportunities). This text links the traditional four-tier approach to systematize the process of risk management (risk identification, assessment, management, and control) to a method of defining (by oneself) the risk-bearing capacity that can be applied in agricultural practice by farm managers. Here, the usual way of presenting the risk portfolio is used. The method is based on concise figures taken from the annual accounts of the business. In this text 8 key indicators are discussed that provide reliable insight into the financial viability of a business enterprise from the risk perspective. These indicators are used in practice and take account of both business and private elements in family farms. The practicality of the concept is confirmed by a transregional analysis of case studies and is validated on the basis of the extensive database covering the network of test farms run by the Federal Ministry of Food and Agriculture (BMEL). Model calculations for one arable farm, one specialised pig fattening farm and one dairy farm plus one "Verbundbetrieb" (farm with standard contribution margin between 50 and 75 percent of the business branch) complete the picture. They also demonstrate practical solutions for risk management that are a useful complement to existing approaches to manage risks.