Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2011
Authors
Inger MartinussenAbstract
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Abstract
On small dairy farms, high investment costs and lack of investment capital may delay the modernising of facilities. The aim of this study was to investigate the importance of economics of scale in building costs of barns compared to other sources of variation in costs. The study includes 44 farms with a mean herd size of 49.5 ± 15.1 cows, built between year 1999 and 2006 and with a mean total area in the barns of 896 ± 454 m2. Building cost data were obtained from farmers and merged with construction, mechanisation and layout data from the same barns. Construction costs decreased up to approximately 1250 m2 while mechanisation costs and total building costs decreased up to approximately 1000 m2. A further increase in building area had only limited effect on the building costs per m2. Models including explanatory variables showed that milking and service area was significantly more expensive than other areas. AMS-barns were all together not significantly more expensive than other barns, since the increased mechanisation cost is offset by a lower requirement for milking area. Farmers remodelling their barns were able to realise a modernised building for a certain herd size for a lower cost compared to a completely new building. The use of their own effort varied considerably between projects. In many cases, farmers would be able to find alternative income sources with a higher hourly rate than the value of their own effort suggested by the model.
Authors
Ragnhild Nærstad Arne Hermansen Vinh Hong Le Grete Lund Abdelhameed Elameen May Bente BrurbergAbstract
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Abstract
Wood exhibits a highly anisotropic mechanical behavior due to its heterogeneous microscopic structure and composition. Its microstructure is organized in a strictly hierarchical manner from a length scale of some nanometers, where the elementary constituents cellulose, hemicelluloses, lignin, and extractives are found, up to a length scale of some millimeters, where growth rings composed of earlywood and latewood are observed. To resolve the microscale origin of the mechanical response of the macro-homogeneous but micro-heterogeneous material wood, micromechanical modeling techniques were applied. They allow for prediction of clear wood stiffness (Hofstetter et al. 2005,2007, Bader et al. 2010a,b) from microstructural characteristics. Fungal decay causes changes in the wood microstructure, expressed by decomposition or degradation of its components (Côté 1965, Schwarze 2007). Consequently, macroscopic mechanical properties are decreasing (see e.g. Wilcox 1978). Thus, in the same manner as for clear wood, consideration of alterations of wood in a micromechanical model allows predicting changes in the macroscopic mechanical properties. This contribution covers results from an extensive experimental program, where changes in chemophysical properties and corresponding changes in the mechanical behavior were investigated. For this purpose, pine (Pinus sylvestris) sapwood samples were measured in the reference condition, as well as degraded by brown rot (G. loeophyllum trabeum) or white rot (Trametes. versicolor). Stiffness properties of the unaffected and the degraded material were not only measured in uniaxial tension tests in the longitudinal direction, but also in the three principal material directions by means of ultrasonic testing. The experiments revealed transversal stiffness properties to be much more sensitive to degradation than longitudinal stiffness properties. This is due to the degradation of the polymer matrix between the cellulose fibers, which has a strong effect on the transversal stiffness. On the contrary, longitudinal stiffness is mainly governed by cellulose, which is more stable with respect to degradation by fungi. Consequently, transversal stiffness properties or ratios of normal stiffness tensor components may constitute suitable durability indicators. Subsequently, simple micromechanical models, as well as a multiscale micromechanical model for wood stiffness, were applied for verification of hypotheses on degradation mechanisms and model validation.
Authors
Trygve D. Kjellsen Igor A. Yakovlev Carl Gunnar Fossdal Richard StrimbeckAbstract
Siberian spruce (Picea obovata) grows in the coldest forested environments on Earth, with average temperatures in midwinter months below -40 C and record lows below 60 C. Fully acclimated needles of this species survive immersion in liquid nitrogen at -196 C provided they are first cooled to an intermediate temperature of around -30 C. To investigate the role of dehydrins in extreme frost tolerance, we monitored frost tolerance, relative dehydrin concentration, and relative changes in dehydrin transcript levels in P. obovata needles over a full acclimation-deacclimation cycle.
Abstract
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Authors
Hanna Marika Silvennoinen Annelene Pengerud Christina Biasi Peter DörschAbstract
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No abstract has been registered