Computation of Electron Delocalization for Extended Cyclic Conjugated Molecules

2016 ◽  
Vol 69 (9) ◽  
pp. 999 ◽  
Author(s):  
Suhwan Song ◽  
Minwoo Han ◽  
Eunji Sim
Keyword(s):  
Structural Parameters ◽  
Quantitative Relationship ◽  
Structural Heterogeneity ◽  
Electron Delocalization ◽  
Strongly Correlated ◽  
Conjugated Molecules ◽  
Alkyl Groups ◽  
Out Of Plane ◽  
Two Parameters ◽  
Torsional Angles

Cyclic conjugated molecules have relatively planar conformations due to overlap of adjacent π-orbitals of delocalized electrons and which is strongly correlated with the degree of electron delocalization. We first demonstrate the quantitative relationship between structural heterogeneity and two structural parameters: out-of-plane distances of atoms and torsional angles between neighbouring aromatic moieties. The molecular characteristic-dependent trend of planarity is presented in terms of these two parameters for the number of unit moieties, type and distribution of linkers, and substituting alkyl groups. The method presented may provide a simple yet systematic guide for determining the degree of delocalization of cyclic conjugated molecules.

Elasticity of colloidal gels: structural heterogeneity, floppy modes, and rigidity

Soft Matter ◽  
2021 ◽  
Author(s):  
D. Zeb Rocklin ◽  
Lilian C Hsiao ◽  
Megan E Szakasits ◽  
Michael J Solomon ◽  
Xiaoming Mao
Keyword(s):  
Coordination Number ◽  
Volume Fraction ◽  
Structural Parameters ◽  
Structural Heterogeneity ◽  
Colloidal Gels ◽  
Shear Moduli ◽  
Rheological Measurements

Rheological measurements of model colloidal gels reveal that large variations in the shear moduli as colloidal volume-fraction changes are not reflected by simple structural parameters such as the coordination number,...

SOFTENING BRANCHES OF A TWO-DEGREE-OF-FREEDOM SYSTEM INDUCED BY SPATIAL BUCKLING

2006 ◽  
Vol 06 (04) ◽  
pp. 493-512 ◽  
Author(s):  
NOËL CHALLAMEL
Keyword(s):  
Structural Model ◽  
Structural Parameters ◽  
Degree Of Freedom ◽  
Lateral Loading ◽  
Load Parameter ◽  
Imperfection Sensitivity ◽  
Softening Effect ◽  
Out Of Plane ◽  
Secondary Bifurcation ◽  
Two Degree Of Freedom

The aim of this paper is to show how geometrical non-linearity may induce equivalent softening in a simple two-degree-of-freedom spatial elastic system. The generic structural model studied is a generalization of Augusti's spatial model, incorporating lateral loading. This model could be used as a teaching model to understand the softening effect induced by out-of-plane buckling. The lateral loading in the plane of maximal stiffness is considered as the varying load parameter, whereas the vertical load is perceived as a constant parameter. It is shown that a bifurcation occurs at the critical horizontal load. The fundamental path becomes unstable, beyond this critical value. However, two symmetrical bifurcate solutions appear, whose stability depend on the structural parameters value. No secondary bifurcation is observed for this system. The presented system possesses imperfection sensitivity, and imperfection insensitivity, depending on the values of the structural parameters. In any case, for sufficiently large rotations, collapse occurs with unstable softening branches induced by spatial buckling.

Factors Affecting the Stiffening Potential of Mineral Fillers

1998 ◽  
Vol 1638 (1) ◽  
pp. 94-100 ◽  
Author(s):  
Naga Shashidhar ◽  
Pedro Romero
Keyword(s):  
Average Particle Size ◽  
Asphalt Mixture ◽  
Quantitative Relationship ◽  
Packing Fraction ◽  
Complex Problem ◽  
Average Particle ◽  
Factors Affecting ◽  
And Performance ◽  
Two Parameters ◽  
Mineral Fillers

The workability and performance of bituminous mixes is known to be affected by the filler-asphalt mixture (or mastic) properties. The addition of fillers is known to stiffen asphalt. The degree of stiffening is a function of several filler and asphalt properties, which are not well understood. A fundamental approach to understanding the influence of such factors on the stiffening potential of filler in asphalt is discussed. This complex problem is simplified by introducing two intermediate measurable parameters, the maximum packing fraction, ϕ m, and the generalized Einstein coefficient, KE. This enables a better understanding of the influence of various factors such as average particle size, gradation, particle shape, presence of agglomerates, degree of dispersion, and the asphalt-filler interface on the stiffening potential of asphalt. First, the relationship between these two parameters and stiffening is thoroughly examined. The physical meaning of these parameters is discussed. Second, the influence of each factor on stiffening potential is addressed individually, supported by experimental data and relevent literature to derive a quantitative relationship. Finally, the relative advantages of the approach over the traditional treatment are discussed. It is further shown that, since the parameters φm and KE take into account the properties of an asphalt-filler system as a whole, they are likely to predict stiffening more accurately than Rigden’s fractional voids approach which is based on the properties of fillers alone.

A multivariate approach to structural heterogeneity of retinal ganglion cells

2011 ◽  
Vol 28 (6) ◽  
pp. 499-512 ◽  
Author(s):  
I.I. PUSHCHIN ◽  
T.A. PODUGOLNIKOVA ◽  
S.L. KONDRASHEV
Keyword(s):  
Functional Organization ◽  
Ganglion Cells ◽  
Structural Parameters ◽  
Clustering Algorithms ◽  
Cluster Structure ◽  
Structural Heterogeneity ◽  
Multivariate Techniques ◽  
Accessory Optic System ◽  
Neuronal Types

AbstractKnowing neuronal types is essential for understanding the structural and functional organization of the nervous system. It has long been recognized that neuronal types should be discovered and not defined. This can be done using cluster analysis (CA). Despite there being many studies using CA to classify neurons, only a few of them meet its formal prerequisites. In the present study, we provide an example of using CA in combination with other multivariate techniques for examining neuronal diversity. A special emphasis is put on formal prerequisites to the data and procedure. The data under scrutiny are a sample of ganglion cells projecting to the basal optic nucleus [accessory optic system-projecting ganglion cells (AOS GCs)] in the common frog. There is physiological evidence that these cells comprise at least two functional types but their structural heterogeneity has not been addressed. Cells were labeled with horseradish peroxidasein vivoand examined in whole-mounted retinae using light microscopy. A sample of well-stained cells was obtained and used to estimate 18 structural parameters. A variety of clustering algorithms were used to classify the cells. The joint polar distribution of dendrite mass was monomodal. CA did not reveal a statistically reliable cluster structure in the sample. The clusters were not cohesive and well isolated. ANOVA-on-Ranks revealed no significant between-cluster differences. Our formal conclusion is that functionally distinct frog AOS GCs do not differ in morphology or dendritic arbor orientation. The advantages and limitations of the adopted approach are discussed.

Study on Selvage Parameter Based on Silk Fabric Specifications Database

2012 ◽  
Vol 502 ◽  
pp. 159-163 ◽  
Author(s):  
Xi Yang ◽  
Xi Mei Liu ◽  
Xue Ke Sun ◽  
Cen Feng
Keyword(s):  
Theoretical Basis ◽  
Quantitative Relationship ◽  
Silk Fabric ◽  
Technological Parameters ◽  
Silk Fabrics ◽  
Two Parameters ◽  
Fabric Design ◽  
Relationship Of ◽  
Density Coefficient ◽  
Design And Production

Based on the silk fabric specifications database, the paper proposes two technological parameters of selvage tightness coefficient and selvage warp density coefficient, and realizes the quantitative relationship of corresponding parameters between selvage and fabric. By making use of thousands data of silk products in the silk fabric specifications database, corresponding programs are wrote to achieve the automated numeration of various selvage parameters .Then the paper discusses three typical silk fabrics which contains eleven subclasses and analyses the distribution of the two parameters, with the comparison of selvage parameters in sub-categories of the same categories. The conclusion can provide a theoretical basis for the silk fabric design and production.

Performance Analysis of a Hyperbolic Flexure Hinge Based on its Closed-Form Equations

2011 ◽  
Vol 421 ◽  
pp. 540-543 ◽  
Author(s):  
Jun Feng Hu ◽  
Pei Li ◽  
Xiang Fu Cui
Keyword(s):  
Closed Form ◽  
Size Range ◽  
Structural Parameters ◽  
Small Variation ◽  
Flexure Hinge ◽  
Small Range ◽  
Accuracy Analysis ◽  
Flexible Hinge ◽  
Sensitivity Equations ◽  
Out Of Plane

In order to the effects of structural sizes of a hyperbolic on its performance, sensitivity and accuracy analysis are performed in this paper. According to the structure feature and force exerted on the flexible hinge, the closed-form equations are formulated for compliances to characterize both the active rotation and all other in- and out-of-plane parasitic motions by using the Castigliano’s second theorem. Meanwhile, the accuracy equations are obtained using the Castigliano’s second theorem. According to the closed-form flexibility formulas, the effects of the four structural parameters, such as thickness, notch depth, length and width, on the flexibility of flexible hinge are analyzed, respectively. In order to study further the effects of the structural parameters on its flexibility, we derive the sensitivity equations, and the sensitivity analysis is carried out. Meanwhile, the accuracy analysis of the hyperbolic flexure hinge is performed. The analysis results have shown that the parameters have large influence on in-plane compliance, and have small effects on out-of-plane one. And the changes are larger within initial small range of parameters, while be small variation in larger size range. And the length has no effect of sensitivity.

scholarly journals The time delay between star formation quenching and morphological transformation of galaxies in clusters: a phase–space view of EDisCS

2019 ◽  
Vol 486 (1) ◽  
pp. 868-884 ◽  
Author(s):  
Kshitija Kelkar ◽  
Meghan E Gray ◽  
Alfonso Aragón-Salamanca ◽  
Gregory Rudnick ◽  
Yara L Jaffé ◽  
...  
Keyword(s):  
Star Formation ◽  
Phase Space ◽  
Structural Parameters ◽  
Imaging Data ◽  
Morphological Transformation ◽  
Star Forming ◽  
Cluster Environment ◽  
Cluster Cores ◽  
Two Parameters ◽  
Star Formation Histories

Abstract We explore the possible effect of cluster environments on the structure and star formation histories of galaxies by analysing the projected phase–space (PPS) of intermediate-redshift clusters (0.4 ≤ z ≤ 0.8). HST I−band imaging data from the ESO Distant Cluster Survey (EDisCS) allow us to measure deviations of the galaxies’ light distributions from symmetric and smooth profiles using two parameters, Ares (‘asymmetry’) and RFF (residual flux fraction or ‘roughness’). Combining these structural parameters with age-sensitive spectral indicators ($H_{\delta \rm {A}}$, $H_{\gamma \rm {A}}$, and Dn4000), we establish that in all environments younger star-forming galaxies of all morphologies are ‘rougher’ and more asymmetric than older, more quiescent ones. Combining a subset of the EDisCS clusters, we construct a stacked PPS diagram and find a significant correlation between the position of the galaxies on the PPS and their stellar ages, irrespective of their morphology. We also observe an increasing fraction of galaxies with older stellar populations towards the cluster core, while the galaxies’ structural parameters (Ares and RFF) do not seem to segregate strongly with PPS. These results may imply that, under the possible influence of their immediate cluster environment, galaxies have their star formation suppressed earlier, while their structural transformation happens on a longer time-scale as they accumulate and age in the cluster cores.

A Computational Study of the Conformational Behavior of 2,5-Dimethyl- 1,4-dithiane-2,5-diol and Analogous S and Se: DFT and NBO Study

2020 ◽  
Vol 17 (10) ◽  
pp. 749-759
Author(s):  
Elmira Danaie ◽  
Shiva Masoudi ◽  
Nasrin Masnabadi
Keyword(s):  
Thermodynamic Parameters ◽  
Computational Study ◽  
Structural Parameters ◽  
Nbo Analysis ◽  
Electron Delocalization ◽  
Stereoelectronic Effects ◽  
Conformational Properties ◽  
Molecular Reactivity ◽  
Stabilization Energies ◽  
The Stability

Conformational behaviors of 2,5-dimethyl-1,4-dithiane-2,5-diol (compound 1), 2,5- dimethyl-1,4-dithiane-2,5-dithiol (compound 2) and 2,5-dimethyl-1,4-dithiane-2,5-diselenol (compound 3) were investigated by the B3LYP/6-311+G **, the M06-2X/aug-ccpvdz levels of theory and natural bond orbital NBO analysis. The structures and the structural parameters of the mentioned molecules were optimized by the B3LYP and the M06-2X methods. We assessed the roles and contributions of the effective factors in the conformational properties of the mentioned compounds by means of the B3LYP and M06-2X levels of theory and the NBO interpretations. The stereoelectronic effects of the mentioned molecules were studied using the NBO analysis. The results showed that the stereoelectronic effects were in favor of the (ax,ax) conformers (the most stable conformations), from compound 1 to compound 3; therefore, these effects have impacts on the conformational properties of compounds 1-3, and stabilization energies associated with LP2X→ σ*S1-C2 electron delocalization, where [X= O, S, and Se], for 1-ax, ax conformer has the greatest value between all of the other conformers. Therefore, according to the calculated thermodynamic parameters, the stability of the 1-ax, ax compound was justified by the presence of LP2X→σ*S1-C2 electron delocalization. A molecular orbital explanation was conducted to investigate the correlations between the linear combinations of natural bond orbitals in the HOMOs, LUMOs and the molecular reactivity parameters. There is a direct relationship between the stereoelectronic effects, molecular reactivity and thermodynamic parameters of compounds 1 to 3 as the harder ax, ax conformations with the greater stereoelectronic effects and ΔG(eq-ax) values are more stable than their corresponding eq, eq conformers. Besides frontier molecular orbitals (FMOs), mapped molecular electrostatic potential (MEP) surfaces of conformations of compounds 1 to 3 were investigated.

Influence of Random Geometry on Effective Properties and Damage Formation In Composite Materials

1994 ◽  
Vol 116 (3) ◽  
pp. 384-391 ◽  
Author(s):  
M. Ostoja-Starzewski ◽  
P. Y. Sheng ◽  
I. Jasiuk
Keyword(s):  
Composite Materials ◽  
Effective Properties ◽  
Plane Elasticity ◽  
Brittle Behavior ◽  
Geometric Patterns ◽  
Composite Systems ◽  
Fine Mesh ◽  
Out Of Plane ◽  
Two Parameters

We study the effective moduli and damage formation in out-of-plane elasticity (i.e., two-dimensional conductivity) of matrix-inclusion composite materials with either randomly or periodically distributed inclusions (fibers). In this paper, we focus our attention on composites with isotropic phases, both of which have elastic-brittle response in damage. The elastic-brittle behavior is modeled with the help of a fine mesh finite-difference system, whereby damage evolution is simulated by sequentially removing/breaking bonds in this lattice in accordance with the state of stress/strain concentrations. The composite systems are specified by two parameters: stiffness ratio and strength ratio of both phases. In particular, we investigate the following aspects: basic classification of effective constitutive responses, geometric patterns of damage, varying degrees of randomness of the inclusions’ arrangements, and mesh resolutions of continuum phases.

scholarly journals Inserting Stress Analysis of Combined Hexagonal Aluminum Honeycombs

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Xiangcheng Li ◽  
Kang Li ◽  
Yuliang Lin ◽  
Rong Chen ◽  
Fangyun Lu
Keyword(s):  
Structural Parameters ◽  
Base Material ◽  
Peak Stress ◽  
Displacement Curve ◽  
Out Of Plane ◽  
Aluminum Honeycomb ◽  
The One ◽  
Absorbing Property ◽  
Crushing Behavior ◽  
Energy Absorbing

Two kinds of hexagonal aluminum honeycombs are tested to study their out-of-plane crushing behavior. In the tests, honeycomb samples, including single hexagonal aluminum honeycomb (SHAH) samples and two stack-up combined hexagonal aluminum honeycombs (CHAH) samples, are compressed at a fixed quasistatic loading rate. The results show that the inserting process of CHAH can erase the initial peak stress that occurred in SHAH. Meanwhile, energy-absorbing property of combined honeycomb samples is more beneficial than the one of single honeycomb sample with the same thickness if the two types of honeycomb samples are completely crushed. Then, the applicability of the existing theoretical model for single hexagonal honeycomb is discussed, and an area equivalent method is proposed to calculate the crushing stress for nearly regular hexagonal honeycombs. Furthermore, a semiempirical formula is proposed to calculate the inserting plateau stress of two stack-up CHAH, in which structural parameters and mechanics properties of base material are concerned. The results show that the predicted stresses of three kinds of two stack-up combined honeycombs are in good agreement with the experimental data. Based on this study, stress-displacement curve of aluminum honeycombs can be designed in detail, which is very beneficial to optimize the energy-absorbing structures in engineering fields.

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