Dynamics of stable viscous displacement in porous media

We investigate the stabilization mechanisms of the invasion front in two-dimensional drainage displacement in porous media by using a network simulator. We focus on the process when the front stabilizes due to the viscous forces in the liquids. We find that the capillary pressure difference between two different points along the front varies almost linearly as function of height separation in the direction of the displacement. The numerical results support arguments that differ from those suggested earlier for viscous stabilization. Our arguments are based upon the observation that nonwetting fluid flows in loopless strands (paths) and we conclude that earlier suggested theories are not suitable to drainage when nonwetting strands dominate the displacement process. We also show that the arguments might influence the scaling behavior between the front width and the injection rate and compare some of our results to experimental work.Comment: The paper has been substantially revised. 12 papes, 10 figure

Local dynamics of a randomly pinned crack front: A numerical study

We investigate numerically the dynamics of crack propagation along a weak plane using a model consisting of fibers connecting a soft and a hard clamp. This bottom-up model has previously been shown to contain the competition of two crack propagation mechanisms: coalescence of damage with the front on small scales and pinned elastic line motion on large scales. We investigate the dynamical scaling properties of the model, both on small and large scale. The model results compare favorable with experimental results

DNA from Ancient Reindeer Antler as Marker for Transport Routes and Movement of Craftspeople, Raw Material and Products in Medieval Scandinavia

This pilot project is a joint venture between natural and cultural scientists that share a common interest in exploiting whether available DNA technology makes it possible to trace back archaeologically found reindeer antler from medieval urban comb production sites to its original provenance. The provenancing of reindeer antler, used in the production of combs and other personal accessories during the Middle Ages, may be a key factor in the study of the identity and the organization of medieval combmakers. Hereunder routes of transportation used by these craftspeople and their products are important. Provenancing will also enhance the understanding of the social and economic importance of the different reindeer mass trapping systems in medieval Scandinavia.publishedVersio

Logistics costs in Norway: comparing industry survey results against calculations based on a freight transport model

This paper presents estimates of logistics costs in Norway. Two different methodological approaches are taken: (i) use of the national freight transport model for Norway, in which logistics costs as a share of gross domestic product (GDP) are obtained from national freight flows between municipalities in Norway and from foreign trading partners and (ii) use of a survey of industry representatives, where the results are aggregated to the macro level and yield logistics costs as a share of GDP. The transport model includes detailed cost functions for transport and other logistics cost components along with a module for optimal shipment size, frequency and mode choice. Although the two approaches are quite different, we find almost identical estimates of transport costs. For the other logistics cost components (warehousing, capital costs, insurance, wastage, packaging and administration), the survey-based approach yielded slightly higher estimates, indicating that the freight transport model does not cover all logistics cost components.publishedVersio

Author index for volume 46

Background: Patient satisfaction is an important, but controversial part of health service evaluation. This study dealt with how acknowledgement of illness and treatment needs effected the distribution of positive, neutral and negative evaluations in a group of first time admitted patients to a psychiatric hospital. Method: The participants filled out a standardized user satisfaction form before discharge. The number of positive, neutral and negative evaluations for each participant was calculated and used as dependent variables in analyses (Classification Tree) where acknowledgement of illness (The Patients' Experience of Hospitalisation Questionnaire) and treatment needs (HoNOS) were used as explanatory variables in addition to a number of potential confounders. Results: Different constellations of variables explained the three dependent variables. The number of positive scores was a function of age and worry (PEH); neutral scores were explained by HoNOS rated social needs and GAF (functional scale), both at admission. Outcome (GAF functional scale) and age explained the number of negative scores. Conclusion: (1) Moderately high negative correlations between positive and neutral scores, and between positive and negative scores, together with a positive correlation between the number of negative and neutral ratings was interpreted to mean that neutral scores sometimes function as undercommunicated negative evaluations. These could better be studied by qualitative methods. (2) The worry subscale (PEH) was important in identifying the majority of patients with the highest numbers of positive scores (patients older than 27.5 yrs with high worry score at admission.). The most dissatisfied group was characterised by denial of both mental problems and need for treatment. (3) Patients with high scores on the HoNOS Social subscale had the highest number of neutral scores. To the extent that neutral evaluations have negative connotations, treatment should focus more effectively on the patients' social needs. (4) The smallest number of negative scores was found among older patients with high functional improvement (GAF F). (5) Increasing age consistently predicted higher satisfaction. A better understanding of why younger patients are more dissatisfied is needed

Onset of Localization in Heterogeneous Interfacial Failure

We study numerically the failure of an interface joining two elastic materials under load using a fiber bundle model connected to an elastic half space. We find that the breakdown process follows the equal load sharing fiber bundle model without any detectable spatial correlations between the positions of the failing fibers until localization sets in. The onset of localization is an instability, not a phase transition. Depending on the elastic constant describing the elastic half space, localization sets in before or after the critical load causing the interface to fail completely, is reached. There is a crossover between failure due to localization or failure without spatial correlations when tuning the elastic constant, not a phase transition. Contrary to earlier claims based on models different from ours, we find that a finite fraction of fibers must fail before the critical load is attained, even in the extreme localization regime, i.e.\ for very small elastic constant. We furthermore find that the critical load remains finite for all values of the elastic constant in the limit of an infinitely large system.Comment: 4 pages, 5 figure