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Different Blocks (different + block)

Distribution by Scientific Domains

Engineering	50%
Earth and Environmental Science	50%

Selected Abstracts

Automatic Palletizing of Concrete Pavement Blocks: An Algorithm for Near-Optimal Assembly

COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 3 2001
Shraga Shoval
Palletizing concrete pavement blocks is a labor-intensive task that requires high levels of workmanship, skill, and concentration. This article proposes an automatic system in which palettes with required design patterns are assembled automatically off-site and then shipped to the construction site. The efficiency of the assembly process can be improved by incorporating automatic equipment consisting of assembly heads and feeders. An algorithm was developed to determine the optimal layout of the feeders (of different blocks) around the palette and the exact assembly sequence of each layer of blocks. Experimental results show that the algorithm is near optimal and that the solutions provided by it reduce palletizing cycle time for various patterns and sizes of concrete block by 20 to 30 percent. [source]

Deformation history of the eclogite- and jadeitite-bearing mélange from North Motagua Fault Zone, Guatemala: insights in the processes of a fossil subduction channel

GEOLOGICAL JOURNAL, Issue 2 2009
Michele Marroni
Abstract In Guatemala, along the northern side of the Motagua Valley, a mélange consisting of blocks of eclogite and jadeitite set in a metaserpentinitic and metasedimentary matrix crops out. The metasedimentary rocks display a complex deformation history that includes four tectonic phases, from D1 to D4. The D1 phase occurs only as a relic and is characterized by a mineral assemblage developed under pressure temperature (P,T) conditions of 1.00,1.25,GPa and 206,263°C. The D2 phase, characterized by isoclinal folds, schistosity and mineral/stretching lineation, developed at P,T conditions of 0.70,1.20,GPa and 279,409°C. The following D3 and D4 phases show deformations developed at shallower structural levels. Whereas the D1 phase can be interpreted as the result of underplating of slices of oceanic lithosphere during an intraoceanic subduction, the following phases have been acquired by the mélange during its progressive exhumation through different mechanisms. The deformations related to the D2 and D3 phases can be regarded as acquired by extrusion of the mélange within a subduction channel during a stage of oblique subduction. In addition, the structural evidences indicate that the coupling and mixing of different blocks occurred during the D2 phase, as a result of flow reverse and upward trajectory in the subduction channel. By contrast, the D4 phase can be interpreted as related to extension at shallow structural levels. In this framework, the exhumation-related structures in the mélange indicate that this process, probably long-lived, developed through different mechanisms, active in the subduction channel through time. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Subsurface drainage for reversing degradation of waterlogged saline lands

LAND DEGRADATION AND DEVELOPMENT, Issue 6 2006
D. P. Sharma
Abstract In irrigated agriculture of arid and semiarid regions waterlogging coupled with salinity is a serious problem. Experimental evidence at several locations has led to the realization that subsurface drainage is an essential intervention to reverse the processes of land degradation responsible for the formation of waterlogged saline lands. This paper presents the results of a study conducted from 1995 to 2000 to evaluate the impacts of subsurface drainage on soil properties, groundwater-table behaviour and crop productivity in a waterlogged saline area of 2200,ha. A subsurface drainage system was installed at 1·6,m depth with 60,m drain spacing covering an area of 1200,ha (23 blocks) during 1997,99 and compared with an undrained block of 1000,ha. Subsurface drainage facilitated the reclamation of waterlogged saline lands and a decrease in the soil salinity (ECe, dS,m,1) that ranged from 16·0 to 66·3,per,cent in different blocks. On average, 35·7,per,cent decrease in salt content was observed when compared with the initial value. Provision of subsurface drainage controlled the water-table below the root zone during the monsoon season and helped in bringing the soil to optimum moisture content for the sowing of winter crops. In the drained area, the increase in yields of different crops ranged from 18·8 to 27·6,per,cent. However, in the undrained area the yield of different crops decreased due to the increased waterlogging and soil salinity problems. Overall the results indicated that investment in subsurface drainage is a viable option for reversing the land degradation of waterlogged saline lands in a monsoon climate. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Numerical analysis of electrically small structures embedded in a layered medium

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2009
Yongpin P. Chen
Abstract Accurate numerical analysis of electrically small structures embedded in a layered medium is presented in this letter. In our approach, the matrix-friendly layered medium Green's function is implemented for its elegant expression and singularity of lowest order. The current is decomposed into divergence-free part and nondivergence-free part according to quasi-Helmholtz decomposition when frequency tends to zero, to capture both capacitance and inductance physics. Frequency normalization is applied after analyzing frequency scaling properties of different blocks of the matrix system. Similar to the free space case, connection matrix is utilized to make the electro-quasi-static block amenable to iterative solvers. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1304,1308, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24302 [source]