Rheological Model for Wood

Wood as the most important natural and renewable building material plays an important role in the construction sector. Nevertheless, its hygroscopic character basically affects all related mechanical properties leading to degradation of material stiffness and strength over the service life. Accordingly, to attain reliable design of the timber structures, the influence of moisture evolution and the role of time- and moisture-dependent behaviors have to be taken into account. For this purpose, in the current study a 3D orthotropic elasto-plastic, visco-elastic, mechano-sorptive constitutive model for wood, with all material constants being defined as a function of moisture content, is presented. The corresponding numerical integration approach, with additive decomposition of the total strain is developed and implemented within the framework of the finite element method (FEM). Moreover to preserve a quadratic rate of asymptotic convergence the consistent tangent operator for the whole model is derived. Functionality and capability of the presented material model are evaluated by performing several numerical verification simulations of wood components under different combinations of mechanical loading and moisture variation. Additionally, the flexibility and universality of the introduced model to predict the mechanical behavior of different species are demonstrated by the analysis of a hybrid wood element. Furthermore, the proposed numerical approach is validated by comparisons of computational evaluations with experimental results.Comment: 37 pages, 13 figures, 10 table

Hierarchical Strategy of Model Partitioning for VLSI-Design Using an Improved Mixture of Experts Approach

The partitioning of complex processor models on the gate and register-transfer level for parallel functional simulation based on the clock-cycle algorithm is considered. We introduce a hierarchical partitioning scheme combining various partitioning algorithms in the frame of a competing strategy. Melting together different partitioning results within one level using superpositions we crossover to a mixture of experts one. This approach is improved applying genetic algorithms. In addition we present two new partitioning algorithms both of them taking cones as fundamental units for building partitions

Typology of streams in Germany based on benthic invertebrates: Ecoregions, zonation, geology and substrate

AbstractBased on 390 benthic invertebrate samples from near-natural streams in Germany we defined eight stream type groups by Non-metric multidimensional scaling (NMS). The taxa lists were restricted to Mollusca, Ephemeroptera, Odonata, Plecoptera, Coleoptera and Trichoptera species and evaluated on presence/absence level. At genus level, streams located in the lowlands differ from streams in lower mountainous areas and the Alps, while the two latter groups were undistinguishable. At species level, a clear separation of different stream size classes is visible in the lowlands; a second gradient is related to the bottom substrate. Streams in the Alps can be distinguished from streams in lower mountainous areas at species level. Within the lower mountainous regions a size gradient is detectable, a less obvious gradient indicates catchment geology. The resulting “bottom-up” stream typology is compared to other stream typological systems in Germany

Hierarchical Model Partitioning for Parallel VLSI-Simulation Using Evolutionary Algorithms improved bei superpositions of partitions

Parallelization of VLSI-simulation exploiting model-inherent parallelism is a promising way to accelerate verification processes for whole processor designs. Thereby partitioning of hardware models influences the effciency of following parallel simulations essentially. Based on a formal model of Parallel Cycle Simulation we introduce partition valuation combining communication and load balancing aspects. We choose a 2-level hierarchical partitioning scheme providing a framework for a mixture of experts strategy. Considering a complete model of a PowerPC 604 processor, we demonstrate that Evolutionary Algorithms can be applied successfully to our model partitioning problem on the second hierarchy level, supposing a reduced problem complexity after fast pre-partitioning on the first level. For the first time, we apply superpositions during execution of Evolutionary Algorithms, resulting in a faster decreasing fitness function and an acceleration of population handling

Growth, residence, and movement of juvenile Chinook salmon within restored and reference estuarine marsh channels in Salmon River, Oregon

Tidal wetland channels provide rearing habitat for juvenile Chinook salmon as they emigrate from freshwater habitat and prepare to enter the ocean. Widespread diking and drainage of estuarine marshes for agricultural and urban development may have contributed to a decline in salmon abundance in the Pacific Northwest, prompting efforts to restore estuarine salmon habitat in the region. I investigated the growth and residence patterns of age-0 Chinook salmon in two blind tidal channels in the Salmon River estuary, Oregon. One channel drained a natural high salt marsh in “reference” condition, and the other channel was in an adjacent salt marsh, restored to tidal inundation in 1996 after being diked and controlled by a tide gate for thirty five years. Recapture of individually marked fish indicated salmon growth rates were similar in the two channels, though growth rates varied more seasonally in the restored site. Average minimum residence times of individual fish were approximately ten days in each channel, and individual salmon were observed up to 79 and 117 days after initial marking in the reference and restored channels, respectively. To characterize movement of age-0 salmon within tidal channels, I tested the feasibility of stationary Passive Integrated Transponder (PIT) detection within a small (approximately 8m wide) tidal channel within the natural marsh system. I found that a stationary PIT detector was an effective tool for monitoring tagged fish movement in a brackish water channel network. Salmon movements in the channel were asymmetrical about high slack tide, with peak movement frequency occurring late during both flood and ebb tide periods. Most movements were in the direction of tidal currents, but 20% of individuals entered the channel against the ebbing tide. Individuals occupied the intertidal channel for a median 4.9 hours and as long as 8.9 hours per tidal cycle, and few were detected moving when water depth was <0.4m. Some individuals used the channel on multiple successive tidal cycles, and others entered intermittently over periods up to 109 days. This research used individual-based fish marking methods to quantify juvenile Chinook salmon behavior and performance within tidal marsh channels, assessing functional equivalence of natural and restored sites and demonstrating the value of such habitats for conservation and restoration of salmon populations

Vascular white matter lesions negatively correlate with brain metastases in malignant melanoma - results from a retrospective comparative analysis

Brain metastasis (BM) is a major complication of different cancers. There is increasing evidence for influence of vascular factors on BM in patients with non-small cell lung cancer (NSCLC). It is not known if the same is true for other tumors that might rely on different forms of vasculogenesis. The objective of this retrospective study was to evaluate a possible negative association of vascular white matter lesions and vascular risk factors (vasRF) with brain metastases in patients with melanoma

Simulation and Visualization of Medical Application to the Inner Ear of the Guinea Pig to Reduce Animal Experiments

We present a novel approach to simulate drug application to the inner ear of the guinea pig with the goal to reduce animal experiments and to increase the accuracy of measurements. The framework is based on a tetrahedral grid representing the individual compartments of the cochlea, associated with a finite element model used to simulate medical diffusion and clearance. In a first simulation scenario, we were able to compute transfer coefficients between the inner compartments of the ear, validating experiments from the literature, and to prove the existence of clearance at the inner scala tympani. In a second scenario, the cochlea was unwound to obtain a one-dimensional model for efficient simulation-based transfer coefficient identification. These coefficients are useful to predict the impact of novel medication application systems