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

Continuous Heavy Metal Removal from Palm Oil Mill Effluent Using Natural Ceiba pentandra Packed-Bed Column

2014 ◽  
Vol 625 ◽  
pp. 822-825 ◽  
Author(s):  
Muhammad Afzaal ◽  
Balasubramanian Periyasamy ◽  
Mohd Azmuddin Abdullah
Keyword(s):  
Heavy Metal ◽  
Flow Rate ◽  
Palm Oil ◽  
Packing Density ◽  
Metal Removal ◽  
Heavy Metal Removal ◽  
Packed Bed ◽  
Palm Oil Mill Effluent ◽  
Packed Bed Column ◽  
Palm Oil Mill

Packed bed column studies were carried out to evaluate the performance of naturalCeiba pentandra(L). Gaertn. (kapok) for the heavy metal removal from Palm Oil Mill Effluent (POME) under varying flow rate (5-10 ml/min) and packing density (0.04-0.08 g/cm3). A multilevel factorial design based on Packing density and flow rate of the influent was developed. Maximum metal reductions for Fe, Mn and Zn were 2.06 ppm, 0.081 ppm, and 0.064 ppm respectively obtained at 0.08 g/cm3packing density and 5 ml/min flow rate. The results suggest the suitability of raw kapok fiber for low-cost removal of heavy metals.

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 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 Experimental and Numerical Study on the Packing Densification of Metal Powder with Gaussian Distribution

Metals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1401
Author(s):  
Huadong Yang ◽  
Shiguang Li ◽  
Zhen Li ◽  
Fengchao Ji
Keyword(s):  
Numerical Simulation ◽  
Packing Density ◽  
Simulation Analysis ◽  
Numerical Study ◽  
Three Dimensional ◽  
Packed Bed ◽  
Element Model ◽  
Powder Particle Size ◽  
Metal Powders ◽  
Powder Packing

In the additive manufacturing of metal materials, powder bed fusion 3D laser printing is the most widely used processing method. The density of the packed bed is another important parameter that can affect the part quality; however, it is the least understood parameter and needs further study. Aiming at addressing the problem of the powder packing density in the powder tank before powder spreading, which is neglected in the existing research, a combination of numerical simulation and experimental research was used to analyze the powder particle size distribution, powder stiffness coefficient, and vibration condition. Considering the van der Waals forces between the powders, a discrete element model suitable for fine metal powders for 3D printing is proposed. At the same time, a mathematical model that takes into account the vibration state is proposed, and the factors affecting the density of the powder were analyzed. A self-designed and manufactured three-dimensional vibration test rig was used to conduct physical experiments on spherical metal powders with approximately Gaussian distributions to obtain the maximum densities. The results obtained by the numerical simulation analysis method proposed in this paper are in good agreement with the experimental results. The influence of the amplitude and vibration frequency on the powder packing density is the same; that is, it increases with an increase in amplitude or frequency, and then decreases with a further increase in amplitude or frequency after reaching the maximum. It is unreasonable to discuss the packing densification only relying on the vibration intensity. Therefore, it is necessary to combine the amplitude and frequency to analyze the factors that affect the packing density of powders.

scholarly journals Spherical codes, maximal local packing density, and the golden ratio

2010 ◽  
Vol 51 (4) ◽  
pp. 043302 ◽  
Author(s):  
Adam B. Hopkins ◽  
Frank H. Stillinger ◽  
Salvatore Torquato
Keyword(s):  
Packing Density ◽  
Golden Ratio ◽  
Spherical Codes ◽  
Local Packing Density

scholarly journals Dissecting the roles of local packing density and longer-range effects in protein sequence evolution

2015 ◽  
Author(s):  
Amir Shahmoradi ◽  
Claus O Wilke
Keyword(s):  
Packing Density ◽  
Solvent Accessibility ◽  
Voronoi Cell ◽  
Sequence Evolution ◽  
Relative Importance ◽  
Site Specific ◽  
Contact Number ◽  
Evolutionary Variation ◽  
Local Packing Density ◽  
Protein Sequence Evolution

What are the structural determinants of protein sequence evolution? A number of site-specific structural characteristics have been proposed, most of which are broadly related to either the density of contacts or the solvent accessibility of individual residues. Most importantly, there has been disagreement in the literature over the relative importance of solvent accessibility and local packing density for explaining site-specific sequence variability in proteins. We show here that this discussion has been confounded by the definition of local packing density. The most commonly used measures of local packing, such as the contact number and the weighted contact number, represent by definition the combined effects of local packing density and longer-range effects. As an alternative, we here propose a truly local measure of packing density around a single residue, based on the Voronoi cell volume. We show that the Voronoi cell volume, when calculated relative to the geometric center of amino-acid side chains, behaves nearly identically to the relative solvent accessibility, and both can explain, on average, approximately 34\% of the site-specific variation in evolutionary rate in a data set of 209 enzymes. An additional 10\% of variation can be explained by non-local effects that are captured in the weighted contact number. Consequently, evolutionary variation at a site is determined by the combined action of the immediate amino-acid neighbors of that site and of effects mediated by more distant amino acids. We conclude that instead of contrasting solvent accessibility and local packing density, future research should emphasize the relative importance of immediate contacts and longer-range effects on evolutionary variation.

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