Determination of operating characteristics of cats using conditioned suppression.

Reports a method for assessing frequency discrimination in cats by analyzing conditioned suppression as a decision-making process. After establishing a steady baseline of responding (lick rate), 3 cats were trained to discriminate between tone bursts that differed in frequency. Suppression ratios were treated as a confidence rating response from which receiver operating characteristics and sensitivities were determined. Results indicate that conditioned suppression is a viable procedure to use in auditory frequency discrimination and that the suppression ratio does conform with the detection of auditory signals. (10 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Scaling Laws for Centrifuge Modeling of Capillary Rise in Sandy Soils

The application of geotechnical centrifuge modeling to environmental problems seems promising. In this paper, one aspect of similitude laws concerning the flow of water through soils is investigated. Within the Network of European Centrifuges for Environmental Geotechnic Research, several tests have been carried out to study similitude laws describing the capillary ascension in porous media at different levels of acceleration. The aim of this paper is to present the results obtained at Ruhr-Universit?t Bochum. A fine sand is used in the experiment. For the visualization of capillary height in the soil sample, image processing is used. Different boundary conditions (constant or variable water level) have been investigated and discussed. All these experiments confirm that capillary rise appears scaled by the factor N and time seems to be scaled with N2. Thus, these results support the possibility of extending the use of accelerated small-scale models to the capillary phenomenon in centrifuge and open the way to more complex investigations of flow and pollutant transport in unsaturated soils.     

Propane Reactions over Faujasite Structure Zeolites Type-X and USY: Effect of Zeolite Silica over Alumina Ratio, Strength of Acidity and Kind of Exchanged Metal Ion

In this work we prepared various zeolite-X and USY samples partially exchanged with copper, iron and platinum. These samples were characterized by XRD, Chemical Analysis, SEM-EDS, N₂-adsorption–desorption, ammonia-TPD, and tested as catalysts in high temperature (400 and 550 °C) propane transformation. The obtained results revealed the strong effect of Si/Al ratio in faujasite zeolite structure, the number and strength of acid sites and of the presence of different metal ions in countered ion sites, on the catalytic activity and selectivity of zeolite-X and USY. The highest propane dehydrogenation activity was achieved with the platinum-exchanged X zeolite (∼11.2% propylene yield, ∼31% selectivity). On the contrary USY zeolites showed high cracking capability and relatively low dehydrogenation activity excepting the platinum-exchanged sample which yielded notably high aromatization products.     

Fish catch and fishing practices in the Nam Theun 2 Reservoir and watershed (Lao PDR)

A fish catch and fishing practice monitoring survey were conducted from 2008 to 2014 in villages adjacent to the Nam Theun 2 Reservoir and its upstream tributaries. The reservoir fisheries exhibited – the three expected phases following impoundment (i.e. trophic upsurge, trophic depletion and stabilization, respectively). This study focused on assessing fish catches and fishing practices from communities living next to the reservoir, and those living upstream of the reservoir, over these phases, and to identify factors that could influence total fish catch. The fish catch appeared to be higher among communities located next to the reservoir, compared to communities living in upstream areas. Fish catches in the upstream tributaries remained relatively stable after impoundment, with a slight increase in the average catch. The reservoir exhibited a low fish yield, compared to similar reservoirs, which could be linked to its oligotrophic status. The majority of the total catch biomass of the reservoir was comprised primarily of two species (i.e. Oreochromis niloticus; Hampala macrolepidota) since a stabilization of the catches was observed. Reservoir fisheries appeared to be mainly driven by hydrological factors, specifically the influence of the rainy season peak. The results of this study indicated no over‐exploitation of fisheries occurred overall, although the fishery resource is still fragile. Fishing activities are known to occur in protected zones (productive areas with large inundated habitat areas), with higher annual total catch being observed during periods of poor enforcement of these zones. As fisheries have become an important income source for villagers living along the NT2 Reservoir, regulation and adequate management of the reservoir are recommended to maintain the reservoir fisheries as a sustainable activity.     

A finite-element mesh generator based on growing neural networks

A mesh generator for the production of high-quality finite-element meshes is being proposed. The mesh generator uses an artificial neural network, which grows during the training process in order to adapt itself to a prespecified probability distribution. The initial mesh is a constrained Delaunay triangulation of the domain to be triangulated. Two new algorithms to accelerate the location of the best matching unit are introduced. The mesh generator has been found able to produce meshes of high quality in a number of classic cases examined and is highly suited for problems where the mesh density vector can be calculated in advance.     

Mehrlagig mit Geogittern bewehrte Erdkörper über pfahlartigen Gründungselementen – Numerische Simulation des Verformungsverhaltens unter statischer und zyklischer Einwirkung

Numerical simulation of the deformation behaviour of multi‐layered geogrid‐reinforced embankments on pile foundations under static and cyclic loading. Embankments for traffic constructions above soft soil are often founded on piles and geogrids are inserted at the bottom of the embankment. In the framework of present design procedures the cyclic (dynamic) traffic loads are considered in a very simplified manner. They are replaced by a static load with a magnification factor. The established model perception for static loading is a redistribution of stress due to arches in the embankment and tensile stress in the geogrids. However it has to be expected that the load bearing and deformation behaviour of such soil structures will change during the life time of the structure (millions of cycles). The cycles cause an accumulation of deformations and changes of stresses in the soil. This may cause a large destruction of the arches and may lead to unexpected settlements. Numerical strategies and constitutive models for the investigation of the behaviour of soils under high‐cyclic loading using finite element method were recently developed. This paper presents the results of such calculations of multi‐layered geogrid‐reinforced embankments on soft soil for the 2D case. The results show that, depending on the position of the geogrids in the embankment, their contribution is unequally to the bearing behaviour and that the stress arches will actually be destroyed under cyclic loading.     

FE‐Prognose der Setzung von Flachgründungen auf Sand unter zyklischer Belastung

FE prediction of the settlement of shallow foundations on sand under cyclic loading. This paper deals with the FE prediction of settlements of shallow foundations under cyclic loading. First the re‐calculation of a centrifuge model test from the literature is presented. After that several parametric studies are shown. The influence of the state variables of the soil (density, lateral earth pressure coefficient, cyclic preloading), of the loading (average load, load amplitude) and the geometry of the foundation (dimensions, embedding, shape) is discussed. The results of the FE calculations are compared with model tests in the literature.     

Zum Kontaktverhalten zwischen suspensionsgestützten Ortbetonwänden und dem anstehenden Boden

Skin friction of cast-in-place walls. Analytical and numerical calculations of retaining structures require the wall friction angle as an input parameter. It is specified as the maximal shear strength of the concrete-soil interface due to normal effective load. For the design of diaphragm walls the national engineering standards recommend an angle of wall skin friction of |δ| ≤ ϕ/2. In the framework of present design numerical calculations are performed to determine the deformation behaviour of structures, so that the contact formulation becomes fundamental. Bentonite suspensions are used to support the sides of excavation for diaphragm walls and uncased cast-in-place piles. When concrete is cast by tremie methods the filter cake remains adhering on side walls and becomes part of the concrete-soil interface and influences the characteristics of wall skin friction. In-situ specimens of the filter cake were taken from a diaphragm wall and examinations reveal that the filter cake consists of bentonite and fine soil particles. Due to the excavation process fine particles from the soil are suspended into the supporting fluid due to the liquid limit of the bentonite slurry. Thus, the suspension, in a process of filtration into the surrounding soil, forms a filter cake with a certain shear strength caused by the fine soil particles. This paper presents the results of field and laboratory tests for the investigation of the effective contact behaviour between cast-in-place walls and the surrounding soil.     

Auswirkung der Herstellungsmethode auf den Gebrauchszustand von Schlitzwänden in weichen bindigen Böden

Consequences of the construction process on the service serviceability of diaphragm walls in soft soils. In order to prove the serviceability of retaining structures, the finite element method is frequently used. A conventional calculation neglects the construction process of the retaining wall and adopts the earth pressure at rest as initial condition. However, the presented FE‐calculations show, that this kind of approach underestimates wall deflections, surface ground settlements and strut forces in case of a diaphragm wall in soft clayey ground. The stepwise construction of the panels affects the stress distribution in the adjacent ground and evokes the partial mobilisation of the earth resistance in the upper third of the wall. In order to consider the influence of the diaphragm wall construction, a modified initial stress field depending on the fresh concrete pressure is proposed.