Zum Tragverhalten der selbstregulierenden interaktiven Membrangründung

On the load bearing behavior of the self‐regulating interactive membrane foundation system The paper reports on a new foundation system, the self‐regulating membrane foundation, for embankments on deep soft soil deposits, such as stockpiles or infrastructure embankments. The load bearing behavior of the system was analyzed by means of centrifuge model tests and comprehensive numerical simulations, such as global sensitivity analyses and parametric studies. The results of those analyses and the derived design approach are presented in the paper. The paper concludes with a validation of the design approach, by comparison with results of the numerical simulation.     

FLOW OF LIQUOR THROUGH WOOD CHIPS IN A MODEL DIGESTER

Electrical resistance tomography was used to evaluate liquid flow trough a 40 L model digester filled with wood chips. Tests were made with cooked and uncooked chips, both uncompressed and at two levels of chip compression (giving external liquid void fractions of 0.53, 0.43, and 0.33). The chips were stationary in all tests. Flow situations (symmetrical and asymmetrical liquid upflow, symmetrical liquid downflow) were studied with liquor recirculated through the downcomer-screen circulation loop. The creation of distinct liquor flow zones both above and below the screen section depended on the ratio of liquor flow in the downcomer-screen circuit to the axial liquor flow (either upflow or downflow) and did not depend on the level of chip compaction attained. Asymmetrical flows created by closing one-half of the screen set established nonuniform zones within the model digester. The significance of these findings for operating digesters is discussed.     

FLOW OF LIQUOR THROUGH WOOD CHIPS IN A MODEL DIGESTER

Electrical resistance tomography was used to evaluate liquid flow trough a 40 L model digester filled with wood chips. Tests were made with cooked and uncooked chips, both uncompressed and at two levels of chip compression (giving external liquid void fractions of 0.53, 0.43, and 0.33). The chips were stationary in all tests. Flow situations (symmetrical and asymmetrical liquid upflow, symmetrical liquid downflow) were studied with liquor recirculated through the downcomer-screen circulation loop. The creation of distinct liquor flow zones both above and below the screen section depended on the ratio of liquor flow in the downcomer-screen circuit to the axial liquor flow (either upflow or downflow) and did not depend on the level of chip compaction attained. Asymmetrical flows created by closing one-half of the screen set established nonuniform zones within the model digester. The significance of these findings for operating digesters is discussed.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Task planning for cooperating self-reconfigurable mobile fixtures

The work solves the problem of task and motion planning of a self-reconfigurable fixture system. A feasible solution is a key requirement for the viability of such systems, which have raised hopes of overcoming the deficiencies that more traditional fixtures are recognized to have in the dynamic conditions of modern manufacturing, with its increasing emphasis on flexibility, adaptability, and automation. The paper proposes an application-independent approach for the generation of a time-relevant action plan for the locomotion, reconfiguration, and positioning of two or more mobile robotic fixtures. The fixture agents need to provide local support for a large workpiece during machining. The path-planning problem is converted into a constraint satisfaction problem (CSP). The proposed approach is called Triple-CSP, as it applies an incremental state search to solve three hierarchical path-planning tasks for the three components of each mobile fixture agent: a supporting head, a mobile base, and a parallel manipulator. A final time-related trajectory (time scaling of actions) for the agents’ entire task execution is obtained. Thus, the planner takes into account all the relevant physical, geometrical, and time-related constraints.     

Numerical study of the atmospheric composition in Bulgaria

The present work aims at studying the local to regional atmospheric pollution transport and transformation processes over Bulgaria and at tracking and characterizing the main pathways and processes that lead to atmospheric composition formation in the region.The US EPA Models-3 system is chosen as a modeling tool. As the NCEP Global Analysis Data with 1 degree resolution is used as meteorological background, the MM5 and CMAQ nesting capabilities are applied for downscaling the simulations to a 9 km resolution over Balkans and 3 km over Bulgaria. The TNO emission inventory is used as emission input. Special pre-processing procedures are created for introducing temporal profiles and speciation of the emissions.The study is based on a large number of numerical simulations carried out day by day for the years 2000–2007 and four emission scenarios—with all the emissions and with biogenic emissions, emissions from energetics and road transport excluded. Results from the numerical simulations concerning the main features of the atmospheric composition in Bulgaria and the contribution of the different emission categories are demonstrated in the paper. Some results from the CMAQ “Integrated Process Rate Analysis” are also given.     

Influence of geometric and thermophysical properties of reaction layer on sulphur dioxide oxidation in transient conditions

The sulphur dioxide to sulphur trioxide oxidation process in a fixed bed catalytic reactor is simulated in the case of cyclic change in the direction of the reaction mixture feed. It is shown that, for transient condition, the amount of catalyst in the reactor may be substantially reduced by its partial substitution with inert material of suitable form, dimensions and thermophysical properties, at the end of the layer. This makes the direct regenerative heat transfer process in these zones controllable, producing the same conversion and overall height of the layer. The results are significant for sulphuric acid production from gases poor in sulphur dioxide.