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Abstract: Residential wood fence posts may be dug directly into the ground, secured to a metal spike that goes into the ground, or secured to a concrete footing with a metal boot. It was hypothesized that, by keeping wood posts out of the ground, both spikes and boot attachments would increase protection against decay and termites and extend the service life of the posts. After 9 years of exposure in Kincardine, Ontario, Canada, at a site with decay and subterranean termites, we found that elevated fence post footings were associated with less biodegradation than posts dug directly into the soil. The spike and boot installations were particularly effective in reducing the incidence of termite attack under the conditions of this study. Spike and boot footings may offer a way to remediate posts by reusing the top portion of posts that were initially dug into the ground following a groundline failure.
Keywords: decay, fence posts, MCA, red pine, reuse, termites
Published in DiRROS: 30.12.2025; Views: 332; Downloads: 105
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Abstract: We consider a single real scalar field in flat spacetime with a polynomial potential up to ϕ4, that has a local minimum, the false vacuum, and a deeper global minimum, the true vacuum. When the vacua are almost degenerate we are in the thin wall regime, while as their difference in potential energy increases, we approach the thick wall regime. We give explicit simple formulae for the decay rate of the false vacuum in 3 and 4 spacetime dimensions. Our results include a careful treatment both of the bounce action, which enters at the exponent of the decay rate, and of the functional determinant at one loop, which determines the prefactor. The bounce action is computed analytically as an expansion in the thin wall parameter in generic D dimensions. We find that truncating such an expansion at second order we obtain a remarkably accurate bounce action also deep into thick wall regimes. We calculate the functional determinant numerically in 3 and 4 dimensions and fit the results with simple polynomials of the same thin wall parameter. This allows us to write the complete one-loop decay rate as a compact expression, which works accurately from thin to thick wall regimes.
Keywords: metastable states, false vacuum, decay rates, thermal field theory, early Universe
Published in DiRROS: 04.12.2025; Views: 410; Downloads: 130
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Abstract: The main characteristics of the cooling phase of post-flashover compartment fires are studied using a simplified first-principles heat transfer approach to establish key limitations of more traditional methodologies (e.g., Eurocode). To this purpose, the boundary conditions during cooling are analysed. To illustrate the importance of a first-principles approach, a detailed review of the literature is presented followed by the presentation of a simplified numerical model. The model is constructed to calculate first-order thermal conditions during the cooling phase. The model is not intended to provide a precise calculation method but rather baseline estimates that incorporate all key thermal inputs and outputs. First, the thermal boundary conditions in the heating phase are approximated with a single (gas) temperature and the Eurocode parametric fire curves, to provide a consistent initial condition for the cooling phase and to be able to compare the traditional approach to the first- principles approach. After fuel burnout, the compartment gases become optically thin and temperatures decay to ambient values, while the compartment solid elements slowly cool down. For simplicity, convective cooling of the compartment linings is estimated using a constant convective heat transfer coefficient and all linings surfaces are assumed to have the same temperature (no net radiative heat exchange). All structural elements are assumed to be thermally thick. While these simplifications introduce quantitative errors, they enable an analytical solution for transient heat conduction in a semi-infinite solid that captures all key heat transfer processes. Comparisons between the results obtained using both approaches highlight how, even when considering the same fire energy input, the thermal boundary conditions according to the Eurocode parametric fire curves lead to an increase energy accumulated in the solid after fuel burnout and a delay in the onset of cooling. This is not physically correct, and it may lead to misrepresentation of the impact of post-flashover fires on structural behaviour.
Keywords: cooling phase, fire decay, fire dynamics, compartment fires, structural fire engineering, fire safety
Published in DiRROS: 15.04.2024; Views: 1500; Downloads: 734
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Abstract: Riparian forests are among the most diverse terrestrial ecosystems, yet their biodiversity is increasingly threatened by habitat degradation, climate change, river regulation and invasive species. We investigated deadwood, widely recognized as an indicator for forest biodiversity, in riparian forests of the Mura-Drava-Danube Transboundary Biosphere Reserve. The Biosphere Reserve is a conservation area that spans five countries and three rivers located in south-eastern Europe. In detail, we analyzed the drivers of lying deadwood volume, occurrence and decay related to floodplain type, silvicultural management, and climatic conditions using regression models. Lying deadwood occurrence and volume significantly decreased as distance from the river edge increased, indicating that river dynamics likely play a role in deadwood accumulation in riparian forests. Deadwood volume was also positively influenced by stand basal area, a parameter that can be directly addressed by silvicultural management. Deadwood decay was affected positively by temperature and negatively by precipitation, highlighting the importance of climatic conditions on decay progression. However, in order to draw more accurate conclusions about the drivers and dynamics of deadwood in riparian forests, further monitoring efforts that consider river flooding and flow regime, deadwood transport and saproxylic organism activity in addition to forest management and site conditions, are needed.
Keywords: alluvial forest, hardwood floodplain, deadwood decay, Mura-Drava-Danube transboundary biosphere, reserve, riparian area, softwood floodplain, UNESCO biosphere reserve, wetlands
Published in DiRROS: 18.07.2022; Views: 1650; Downloads: 1214
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Abstract: Eutypella parasitica R.W. Davidson & R.C. Lorenz is the causative agent of Eutypella canker of maple, a destructive disease of maples in Europe and North America. The fungus E. parasitica is known to cause wood stain and decay. However, it is not known how effectively it decomposes the wood of the most widespread maple species in Europe. Wood samples of Acer pseudoplatanus L., A. platanoides L., and A. campestre L. were exposed to four isolates of E. parasitica and nine other fungal species for comparison, according to the modified EN 113 standard. After 15 weeks of incubation, mass loss and microscopical analysis of samples showed evidence of colonization and different wood decay potentials among fungal species. A highly significant positive correlation was found between mass loss and moisture content for all fungal species. Similarly, the measured cell wall thickness correlated well with the calculated mass loss of the samples. On average, the fungal species caused the lowest mass loss in A. pseudoplatanus (10.0%) and the highest in A. campestre (12.6%) samples. Among the samples exposed to E. parasitica isolates, the highest mass loss was recorded in A. pseudoplatanus (6.6%). Statistical analysis showed significant differences in mass loss and moisture content between different E. parasitica isolates. Based on the results of staining, we discuss the type of decay caused by E. parasitica. Although E. parasitica isolates caused smaller mass loss of samples compared to other more effective decay species, we should not disregard its capability of degrading maple wood. Because E. parasitica usually infects the lower portion of the trunk, which is the largest and most valuable part of the tree, any damage can cause significant economic and resource loss.
Keywords: wood decay, mass loss, moisture content, mini-block test, decay test, Acer spp., Eutypella parasitica, fungi, light microscopy, scanning electron microscopy
Published in DiRROS: 13.07.2020; Views: 2927; Downloads: 2053
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