Different Degrees Of Compaction Research Articles

Further Development of Integer Programming in Earthwork Optimization

The objective of existing linear programming methods of earthwork‐system optimization in road construction has been either minimizing the cost or maximizing profit, generally without considering the project duration. This paper develops a linear programming model incorporating the project duration. The model attempts to optimize a comprehensive earthmoving system in road construction by comparing alternative fleets (from available fleets) to provide an optimum material distribution and appropriate plant fleets to complete a project within the specified time. The situations where different degrees of compaction, availability of various soil strata at cut sections and borrow pits, and selection of borrow/disposal sites are also incorporated. Among the possible extensions, equipment sharing between fleets and sequence of operations present at cut and fill sections are examined. The validity of the model is demonstrated by applying it to a numerical example, providing additional tools to the management such as the minimum project‐completion time, the cheapest project cost and corresponding duration achievable with available resources.

The effect of compaction of the arable layer in sandy soils on the growth of maize for silage. 1. Critical matric water potentials in relation to soil aeration and mechanical impedance.

A new approach in defining the range of soil structure for optimal maize production is proposed. The effect of different degrees of compaction of ploughed sandy soils on soil aeration and mechanical impedance and on root and shoot growth of maize was tested in 5 model field experiments in the eastern Netherlands. In this first paper the effects on soil aeration and penetration resistance are described. The narrower the range of matric water potentials which allow unimpeded root growth, the greater the potential risks for plant growth and the greater the need for a controlled supply of water. Soil structures which substantially impede root growth even at the most favourable water potential are classified as dangerous. (Abstract retrieved from CAB Abstracts by CABI’s permission)

A Method for Preparing Small Soil Samples with Specified Bulk Densities and Water Contents

AbstractA centrifugation procedure is described for producing different degrees of compaction in both wet and dry soils. To ensure uniform distribution of water in the test samples, appropriate quantities of crushed ice are mixed with the oven‐dry soils 24 h prior to the centrifugation step.

Infiltration Under Surge Irrigation

ABSTRACT RATE of advance and infiltration field data were used to develop a characterization of infiltration under surge irrigation. The potential benefits of surge irrigation were quantified, discussed and related to the infiltration phenomenon. The surge infiltration function appeared to undergo a step reduction from the time dependent rate to the basic rate after one complete wetting and dewatering cycle. This infiltration rate reduction led to reduced amounts of time and water necessary to complete advance when surged applications were used instead of continuous applications. The surge infiltration phenomenon also caused a reduction in advance time differences between successive irrigations as well as between furrows with different degrees of compaction..

Modifications of some erythrocyte parameters in hibernating vertebrates, revealed by cytofluorometric techniques

AbstractThe variations of the glycoconjugate concentrations (PAS‐positive material), with special reference to the membrane sialic component have been studied during the annual cycle in erythrocytes of three mammalian species (Erinaceus europaeus, Glis glis, Talpa europaea) and of one amphibian species (Rana esculenta). In R. esculenta the structural modifications of nuclear chromatin (different degree of compactness) have also been examined through the propidium iodide intercalation at different concentrations.The membrane sialic components during hibernation increase in Rana (457%), Glis (304%), and Erinaceus (244%), and decrease in Talpa (59%), not really a hibernating species. These data can be related with a slowing down of erythropoiesis and with the increase of the average length of erythrocyte life in the winter. Residual glycoconjugate components are also modified with a similar, but less evident, pattern. The changes in the fluorescence fading during the annual cycle show a substantial independence from the concentration index of the PAS‐positive material; this fact might be related to molecular modifications or heterogeneity of the substrate.The DNA‐propidium iodide intercalation in frog erythrocyte chromatin decreases during the hibernation, possibly related to a reduced functional activity of cells.

Effect of the degree of compactness of the cross section of soft interlayers

In practice it is often necessary to determine the mechanical properties (OT, aB) of nondetachable joints in the form of composites consisting of a strong metal base T and a soft interlayer M; these composites may have different degree of compactness of the cross section = S/B (e.g,, in laboratory tests of mechanically inhomogeneous welded specimens, specimens cut out of thick welded joints, etc.), Because of the difference in compactness of the section, the results of such tests are mutually not comparable [i]. The use of the dependences obtained in [2, 3] and other works for evaluating the effect of the compactness of the cross section on the mechanical properties of soft interlayers in composites leads to considerable errors, especially when there is only a small difference between the mechanical characteristics of the materials T and H (oTT/OT M, oBT/~I << 2),

Urea-induced unfolding of the alpha subunit of tryptophan synthase: evidence for a multistate process.

The urea-induced unfolding of the alpha subunit of tryptophan synthase from E. coli was monitored by optical spectroscopy and by urea-gradient gel electrophoresis. Three independent lines of evidence support the conclusion that one or more stable intermediates are present in this process: (i) Satisfactory fits of the equilibrium unfolding transitions obtained from difference spectroscopy at 286 nm and circular dichroism spectroscopy at 222 nm require a model which involves a stable intermediate in addition to the native and unfolded forms. (ii) Kinetic studies of the change in the extinction coefficient at 286 nm show that while the unfolding is well described by a single exponential change the refolding kinetics are complex. The nature of the dependence of the refolding kinetics on the initial concentration of urea supports the conclusion that at least one stable intermediate exists. (iii) The patterns obtained from urea-gradient gel electrophoresis experiments on the alpha subunit show that at least one and possibly two stable intermediates are involved; the intermediates have markedly different degrees of compactness. A kinetic model for the folding of the alpha subunit, consistent with all of these results, can be formulated.

A case study on the effect of soil compaction on potato growth in a loamy sand soil. 1. Physical measurements and rooting patterns.

An interdisciplinary field study, including consideration of soil tillage, soil physics, pedology and crop science was made to study the effect of soil compaction on potato growth in a young alluvial loamy sand soil in the very dry growing season of 1976. The treatments consisted of different degrees of compaction in or just below the arable layer and also consider the effect of irrigation. Compaction decreased soil pore vol. whereas the volumetric water content at any given pressure potential was increased or decreased depending on the degree of compaction. A high mechanical resistance encountered by the roots proved to be the primary factor affecting root elongation. Roots penetrated the compacted layers in all treatments but at very different rates. As a result the pressure potential at the rooting front was relatively low as long as roots were growing in the compacted layers. Moisture flow to the roots by capillary rise from the water table occurred during the entire growing season but varied significantly among treatments as a function of the distance above the water table and hydraulic conductivity of the various layers. Moderate compaction increased, but severe compaction decreased, the potential for capillary rise in the topsoil. The plough pan in the subsoil increased the potential for capillary rise. Critical groundwater levels at a given rooting depth were calculated for different steady upward fluxes for some of the treatments. (Abstract retrieved from CAB Abstracts by CABI’s permission)

SINKING RATES OF EUPHAUSIID FECAL PELLETS

Sinking rates of natural fecal pellets from freshly collected euphausiids (126–862 m/day) were, in general, two to three times higher than the sinking rates of pellets produced by the same animals maintained on a diet of Artemia and algae (53–411 m/day). The difference is attributed to different degrees of compaction as well as different food residues in the two types of pellets. Sinking rates of natural fecal pellets from euphausiids can account for the rapid descent of radionuclides. Euphausiid fecal pellets may be at least as important quantitatively as sinking carcasses in the downward transport of matter to deep water and sediments.

Biologically significant properties of submerged marine sands

Biologically significant properties of submerged marine sands

Energy required to pulverize soil at different degrees of compaction

Two new laboratory methods to determine the energy to pulverize natural soil are presented. Results for impact loads produced by a machine similar to the Charpy impact testing machine for metal and elastic products are compared to results obtained for a compression method of loading at a slow rate. Results are presented for different degrees of compaction and soil moisture content. Energy requirements increased when using the impact machine, after soil shrinkage during the drying process, for the finer degrees of pulverization and for compacting the soil. The energy results are compared to soil shear and soil impedance penetrometer parameters.

Soil physical conditions of winter and the growth of ryegrass plants: I. effects of compaction and puddling

Abstract Six pot trials with seedling plants of perennial ryegrass (Latium perenne L.) have been carried out to investigate the effects, on growth, of compaction and saturation of the topsoil. In each trial identical soil was packed, in 1 em layers, into a number of 17 em-diameter pots, treatments comprising different degrees of compaction or puddling in the surface 5 em of the soil. Seedling plants at the two-leaf stage were planted in holes 1 em in diameter and 1.2 em deep, their root systems being previously cut down to one root 1.2 em long. The pot soils were kept at high and constant moisture contents by sub-irrigation from shallow water tables, rain being excluded, and the trials were run at winter temperatures. Growth was related to measurements of physical properties of the surface 5 em of the soil. These comprised dry density, moisture content, volume of air pores, the diffusivity of oxygen gas through an extracted core of soil, and the current flowing to a platinum micro-electrode at a depth of ...