scholarly journals Experiment on compaction of air-dried soil under drop shocks

PLoS ONE ◽  
2021 ◽  
Vol 16 (4) ◽  
pp. e0250076
Author(s):  
Jianbo Wang ◽  
Tiansheng Hong ◽  
Zhen Li ◽  
Xiuyun Xue ◽  
Shilei Lyu
Keyword(s):  
Shock Intensity ◽  
Packing Density ◽  
Soil Compaction ◽  
Local Density ◽  
Drop Height ◽  
Nursery Culture ◽  
Straight Line ◽  
Dimensional Distribution ◽  
Line Slope ◽  
Local Packing Density

For the requirement in container nursery culture that growing media should be achieved the appropriate degree compaction, this paper presents an experiment on the compaction dynamics of air-dried soil under repetitive drop shocks, as a preliminary step toward the mechanization of this compaction method. The drop height used to adjust the shock intensity included 2 mm, 4 mm, 5 mm and 6 mm. And the overall packing density of soil in a vertically stratified cylinder vessel and the local packing density in each layer were taken as indicators of soil compaction states. The stretched exponential function derived from KWW law than the empirical inverse-logarithmic function has been found to be more suitable for expressing the temporal evolution of soil compaction, according to the results of curve-fitting to test values of the overall and local density. It is inherent in this experimental configuration that the drop shock intensity even at a constant drop height varies with drop times, owing to the interaction between the soil packing itself and drop shocks caused by the combination of the packing and the container. But the function t/τf(t,H) is manifested as a straight line on the drop times t with the line slope related to the drop height H, so the soil compaction dynamics caused by its drop shocks and that under the condition with actively controlled intensity actually share the common relaxation law. In addition, the soil’s one-dimensional distribution of local packing density showed a slight positive gradient as similar as monodisperse particles did.

scholarly journals Properties of Galaxies in Low Density Regions

1983 ◽  
Vol 104 ◽  
pp. 207-209
Author(s):  
N. Brosch
Keyword(s):  
Emission Line ◽  
Local Density ◽  
Three Dimensional ◽  
Average Density ◽  
Active Galaxies ◽  
Nuclear Activity ◽  
Isolated Galaxies ◽  
Dimensional Distribution ◽  
Mass Profile ◽  
Emission Line Galaxies

Isolated galaxies seem to have more nuclear activity and less disk activity than nonisolated objects. This is interpreted as an expression of the mass-profile in their halos.The discovery of voids in the three-dimensional distribution of galaxies has rapidly been followed by claims that in at least one such void some objects, like Markarian and emission-line galaxies, are present. Why are only active galaxies found in these voids? Should we also expect the opposite to be true, namely that active galaxies ought to be found more often in voids, or in regions of the Universe with lower-than-average density? There are indications that this seems to be the case, as Gisler (1978) found that emission-line galaxies, Markarians and possibly Seyferts avoid environments of dense clusters. Differences between “field” and “cluster” populations are probably due more to the enhanced local density of galaxies than to the nature of the overall environment.

scholarly journals City Shape and the Fractality of Street Patterns

2012 ◽  
Vol 31 (2) ◽  
pp. 29-37 ◽  
Author(s):  
Nahid Mohajeri ◽  
Paul Longley ◽  
Michael Batty
Keyword(s):  
Fractal Dimension ◽  
Power Laws ◽  
Step Length ◽  
The Other ◽  
Main Street ◽  
Straight Line ◽  
Line Slope ◽  
Straight Lines ◽  
The City ◽  
Street Segments

City Shape and the Fractality of Street Patterns This paper discusses, first, the concepts of fractals and power laws in relation to the street patterns of the city of Dundee, East Scotland and, second, the results of the measurement of 6,004 street segments in the city. The trends of the street segments are presented through rose diagrams and show that there are two main street trends in the city: one is parallel with the coast, the other is roughly perpendicular to the coast. It is clear that the coastline largely regulates the street trend, because both the main street trends change along the city so as to be nearly coast-perpendicular and coast-parallel everywhere. The lengths of the street segments follow power laws. When presented on log-log plots, however, the result is not a single straight line but two straight lines. At the break in line slope, the fractal dimension changes from 0.88 to 2.20. The change occurs at the step length of about 100 m, indicating that the short streets belong to a population that is different from that of the longer streets.

scholarly journals Local Packing Density Is the Main Structural Determinant of the Rate of Protein Sequence Evolution at Site Level

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
So-Wei Yeh ◽  
Tsun-Tsao Huang ◽  
Jen-Wei Liu ◽  
Sung-Huan Yu ◽  
Chien-Hua Shih ◽  
...  
Keyword(s):  
Packing Density ◽  
Protein Sequence ◽  
Solvent Accessibility ◽  
Sequence Evolution ◽  
Relative Solvent Accessibility ◽  
Sequence Variability ◽  
Substitution Rates ◽  
Contact Number ◽  
Local Packing Density ◽  
Structural Determinant

Functional and biophysical constraints result in site-dependent patterns of protein sequence variability. It is commonly assumed that the key structural determinant of site-specific rates of evolution is the Relative Solvent Accessibility (RSA). However, a recent study found that amino acid substitution rates correlate better with two Local Packing Density (LPD) measures, the Weighted Contact Number (WCN) and the Contact Number (CN), than with RSA. This work aims at a more thorough assessment. To this end, in addition to substitution rates, we considered four other sequence variability scores, four measures of solvent accessibility (SA), and other CN measures. We compared all properties for each protein of a structurally and functionally diverse representative dataset of monomeric enzymes. We show that the best sequence variability measures take into account phylogenetic tree topology. More importantly, we show that both LPD measures (WCN and CN) correlate better than all of the SA measures, regardless of the sequence variability score used. Moreover, the independent contribution of the best LPD measure is approximately four times larger than that of the best SA measure. This study strongly supports the conclusion that a site’s packing density rather than its solvent accessibility is the main structural determinant of its rate of evolution.

scholarly journals A multi sensor data fusion approach for creating variable depth tillage zones

2017 ◽  
Vol 8 (2) ◽  
pp. 461-465 ◽  
Author(s):  
D. Whattoff ◽  
A. Mouazen ◽  
T. Waine
Keyword(s):  
Data Fusion ◽  
Packing Density ◽  
Soil Compaction ◽  
Soil Bulk Density ◽  
Sensor Data ◽  
Variable Depth ◽  
Multi Sensor Data Fusion ◽  
Electromagnetic Sensor ◽  
Density Values ◽  
Fusion Approach

In this research a multi-sensor and data fusion approach was developed to create variable depth tillage zones. Data collected with an electromagnetic sensor was fused with measurements taken with a hydraulic penetrometer and conventionally acquired soil bulk density (BD) and moisture content (MC) measurements. Packing density values were then calculated for eight soil layers to determine the need to cultivate or not. From the results 62% of the site required the deepest tillage at 38 cm, 16% required tillage at 33 cm and 22% required no tillage at all. The resultant maps of packing density were shown to be a useful approach to map layered soil compaction and guide VDT operations.

Variation in the local packing density near the wall of a randomly packed bed of equal spheres

1978 ◽  
Vol 20 (2) ◽  
pp. 257-260 ◽  
Author(s):  
Keishi Gotoh ◽  
W.S. Jodrey ◽  
E.M. Tory
Keyword(s):  
Packing Density ◽  
Packed Bed ◽  
Local Packing Density

scholarly journals Soil compaction as a consequence of utilization modes

2004 ◽  
Vol 49 (2) ◽  
pp. 179-185 ◽  
Author(s):  
Bosko Gajic ◽  
Goran Dugalic ◽  
Zorica Sredojevic
Keyword(s):  
Physical Properties ◽  
Bulk Density ◽  
Packing Density ◽  
Agricultural Production ◽  
Soil Compaction ◽  
Void Ratio ◽  
Total Porosity ◽  
Soil Particles ◽  
Agricultural Machines ◽  
Properties Of Soil

Long-standing utilization of agricultural machines in agricultural production leads to a significant increase of compaction in noncarbonate, slightly smonitza - like meadow black soils, in the Kolubara river valley. A substantial increase of compaction in the investigated soils was found in arable and subarable horizons down to the depth of 30 cm. The compaction increase induced negative changes in other most important physical properties of soil, like the increase of bulk density and packing density of soil particles, and the decrease of total porosity, content of pores > 30 mm and void ratio.

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